Note: Descriptions are shown in the official language in which they were submitted.
2022~7~
ED-03 7 8
TITLE
OP~O-ELECTRONIC COMPONENT H.4VlNG A POSITIONED
OPTICAL FlBER ASSOCIATED THEREWITH
CROSS REI;ERENCE TO RELATED APPLICATION
Subject matter disclosed herein is disclosed and claimed
in copending application Serial Number 07/_,_, filed
contemporaneously he.rewith, titled "Apparatus For Positioning
The Center Of An Optical Fiber Along a Predetermined
Reference Axis".
BACKGROUND OFTHE INVENTION
Field Of The ~nvention The present invention relates to
an opto-electronic component having a positioning apparatus
for positioning the center of an optical fiber along a
predetermined reference axis of an opto-electronic device
independently of variations in the outside diameter of the
fiber.
Description 0f ThQPrior Art Devices are known for
positioning an optical fiber so that the axis of the fiber is
positioned with respect ts:; a reference axis. A typical expedient
used in such devices is a generally V-shaped groove that îs
formed in A substrate material and which serves as a cradle to
accept the fiber being positioned. Representative of such
devices is that shown in United States Patent 4,756,S9l
(Fischer et al.), wherein a V-groove is formed in a silicon
substrate and an elastomeric membeir is biased against the
fiber to hold it in the groove. The groove may be stepped to
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provlde a deeper groove segment to hold the jacket of the fiber
within the device.
United States Patent 4,756,591 (Sheem) discloses a
5 grooved silicon substrate having a pair of intersecting V-
grooves therein. A fiber to be positioned is disposed in one of
the grooves while a shim is disposed in the other of the
grooves. The shim may lake the form of a tapered or an
eccentric fiber, which when respectively slid or rota~ed under
10 the first fiber serves to lift the same to bring the axis thereof
into alignment with a reference axis. A cover may be
positioned above the substrate to assist in clamping the first
fiber into position.
I 5 United States Patent 4,802,727 (Stanley) also discloses a
positioning arrangement for optical components and
waveguides which utilizes a V-grooved structure. United
States Patent 4,826,272 (Pimpinella et al.) and United States
Patent 4,830,450 (Connell et al.) discloses arrangements for
20 positioning an optical fiber that utilize members having
frustoconical apertures therethrough.
It is believed that single crystalline silicon is the material
of choice of the devices above mentioned because of the
25 proclivity of crystalline silicon to be etched along precise
crystallographic planes, thus forming precise grooves or
structural features by photolithographic microfabrication
techniques. Etchants exist that act upon a selected
crystallographic plane to a differential degree than upon an
30 adjacent plane, permitting the needed precise control. V-
grooves, in particular, can be etched to a controlled width and
~runcated depth. Under some conditions V-grooves may be
etched in a self-limiting operation. The photolithographic
microfabrication process is generally described by Brodie and
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Muray, "The Physics of Microfabrication", Plenum Publishing,
New York ( 1982).
Optical fibers include an inner core having a
5 predelermined index of refraction surrounded by a cladding
layer of a lower Index. The inner core is the medium in which
the optical energy is guided, while the cladding layer defines
the index boundary with the core. The outer diameter of the
fiber may vary in dimension about a predetermined nominal
10 dimension. It has been seen, for example, that two nominally
identical fibers from the same manufacturer may vary in
outside diametrical dimension by as much as plus or minus
four (4) micrometers. This fiber to fiber variation in outer
diameter makes difficult the accura~e positioning of the axis of
15 ~he core of a fiber with respect to a predetermined reference
ax1s.
In view of lhe foregoing it is believed advantageous to
ma}ce use of the ability of microfabrication techniques to form
2 O accurate structures, channels and/or surfaces in a crystalline
material to construct a positioning apparatus that will
accurately position the center of the fiber, or of any other
elongated generally cylindrical member having small
dimensions (such as capillary tubing), with respect to a
2 5 predetermined reference axis. Moreover, it is believed
advantageous to provide a positioning apparatus that
consislently aligns the predetermined point on the fiber or
other cylindrical member with the reference axis without
requiring great technical skill, expensive apparatus, and
30 extensive alignment procedures.
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SUMMARY OF THE INVENTION
The present invention relates to a relates to an opto-
5 electronic component having a positioning apparatus for
positioning the center of an optical fiber along a predetermined
reference axis of an opto-electronic device independently of
variations in the outside diameter of the fiber. The opto-
electronic device can take the form of a solid state laser or a
10 solid state light responsive diode such as a photodiode. The
opto-electronic device can be an edge active or a surface active
device. The optical fiber can be a single-mode or a multi-mode
fiber.
The positioning apparatus includes a first and a second
arm, each of which has at least a first and a second sidewall
that cooperate to define a groove therein. The groove in each
arm is preferably a converging groove so that when the arms
are arranged in superimposed relationship the converging
2 O grooves cooperate to define a funnel-like channel over at least
a predetermined portion of its length. The channel has an inlet
end and an outlet end and a reference axis extending
therethrough. A fiber introduced into the inlet end of the
channel with its axis spaced from the reference axis is
25 displacable by contact with at least one of the sidewalls on one
of the arms to place a predetermined point on an end face of
the member into alignment with the reference axis where it is
there held by contact with the first and second arms. To guide
the fiber toward the inlet end of the channel each of the first
30 and the second arms includes a trough therein, each trough
being disposed on an arm a predetermined distance behind the
groove in that arm, so that in the closed position the troughs
cooperate to define a guideway.
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The arms having the converging grooves therein may, as
is preferred, be mova~le from a first, closed, position to a
second, centering, position. The superimposed arms are, in this
instance, moun~ed cantilevered fashion, to a foundatiom Means
5 is provided for biasing each of the arms wilh a substantially
equal and oppositely directed biasing force toward the first
position. In the preferred implementation the biasing means
comprises a reduced thickness portion in each of the first and
the second arms, the reduced thickness portion defining a
10 flexure in each arm which, when each arm is deflected by
contact with the cylindrical member, generates a force on each
arm to bias each arm toward the closed position.
It should be understood lhat so long as the arms are
15 movable and biased toward the closed position, it is not
required that the grooves formed therein are converging
grooves. Accordingly, other positioning apparatus in which the
arms are movable but in which the grooves in each of the arms
have a form other than a converging groove are to be
20 cons~rued as Iying within the contemplation of the invention.
Succinctly stated, the present invention encompasses any
positioning apparatus having arms that are movable whether
the groove in each arm take the forrn of a converging groove or
a groove of an alternate form. Alternately, the present
25 invention also encompasses any positioning apparatus in which
the groove in each arm is converging in form, whether the
arms are movable or fixed with respect to each other.
In whatever embodiment realized, it is preferred that the
30 positioning apparatus be fabricated from a crystalline material,
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such as single crystal silicon, using microfabrication techniques.
Each structural element of the positioning apparatus (viz., each
of the arms and each foundation) is fabricated in mass on a
wafer of silicon. The finished wafer are aligned, superimposed,
and bonded, and each of the resulting positioning apparatus
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BRIEI~ DESCRIPTION OF THE DRAWINQS
~he invenlion wi~l be more fully understood from the
5 following detailed description thereof, taken in connection with
the accompanying drawings, which form a part of this
application, and in which:
Figure 1 is a perspective, exploded view of a positioning
10 apparatus in accordance with the preferred embodiment of the
presenl inven~ion for positioning lhe center point on the end
face of an optical fiber with respect to a predetermined
reference axis;
Figure 2 is a perspective view of the positioning
apparatus of Figure 1 in the fully assembled condition;
Figure 3 is a front elevation view of the assembled
positioning apparatus of Figures I and 2, taken along view lines
20 3-3 in Figure 2;
Figure 4 is a sectional view, in elevation, of the assembled
positioning apparatus of Figure 2, taken along section lines 4-4
in that Figure illustrating ~he truncated V-groove therein;
Figure 4A is a view generally similar to Figure 4 in which
a full V-groove is formed in the positioning apparatus while
Figure 4B is a view generally similar to Figure 4 in which both
a full V-groove and a truncated V-groove are formed;
Figure 5 is a plan view one of the arms of the positioning
apparatus of Figure 1 illustrating the relationships of the axes
of the groove and the guideway therein;
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Figures 6A and 6B, 7A and 7B, and 8A and 8B are
diagrammatic eleva~ional and end views of the action of the
clips disposed on the arms of the positioning apparatus shown
in Figures I and 2 in response to the introduction of a fiber
5 thereinto;
Figures 9 and 10 are exploded and assembled perspective
views, generally similar to Figures I and 2, of another alternate
embodiment of a positioning device in accordance with the
10 present invention in which the arms have nonconverging
grooves therein and in which the arms are articulably movable
with respect to each other along one axis only;
- Figures 11 are 12 are sectional views taken along section
15 lines 11-11 and 12-12 in Figure 10;
Figures 13 and 14 are exploded and assembled
perspective views, generally similar to Figures I and 2, of
another alternate embodiment of a positioning device in
20 accordance with the present invention in which only one of the
arms has a nonconverging groove therein and in which both of
the arms are articulably movable with respect to each other;
Figures I S are 16 are sectional views taken along section
25 lines 15-15 and 16-16 in Figure 14;
Figures 17 and 18 are exploded and assembled
perspective views, generally similar to Pigures I and 2, of an
alternate embodiment of a positioning device in accordance
30 with the present invention in which the arms have converging
grooves therein and in which the arms are fixed with respect lo
each other;
Figure 19 is an end view taken along view lines 19-19 in
35 Figure 18;
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Figure 20 is a side sec~ional view, taken along view lines
20-20 in Figure 18, illustrating the posilion of the fiber within
the channel of the a positioning apparatus in accordance with
5 the alternate embodiment of the invention shown therein;
Figure 21 is an exploded isometris view of a pair of
positioning apparatus as shown in Figure 1 used to form a
fiber-to-fiber connector in accordance with the present
10 invention while Figure 22 is an isometric view of the fully
assembled connector of Figure 21;
Figures 23 and 24 are, respectively, a top view in seceion
and a side elevation section view of a pair of positioning
15 apparatus in accordance the embodiment of the invention as
shown in Figure 17 used to form a fiber-to-fiber connector in
accordance with the present invention;
Figures 25 and 26 are isometric views of a housing used
20 for the fiber-to-fiber connector shown in Figures 21 and 22 in
the open and in the partially closed positions, respectively,
while Figure 27 is a section view of the housing of Figure 25 in .
the fully closed position taken along section lines 27-27 of
Figure 26;
Figure 28 is a section view generally similar to Figure 27
of a housing used for the fiber-to-fiber connector shown in
Figure 24;
Figure 29 is a isomelric view of an alternate housing for a
fiber-to-fiber connector formed of a pair of positioning
apparatu s;
.
Figures 3~ and 31 are isometric exploded and assembled
views, respectively, illustrating lhe use of a positioning
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apparatus in accordance with the present invention to position
an optical fiber with respect to the axis of an edge emitting
active device, in which the device is surface mounted;
Figure 31 A is a side elevational view generally similar to
Figure 31 showing a positioning apparatus in accordance with
the present invention positioning a lens with respec~ to an
opto-electronic component,
Figures 32 and 33 are isometric exploded and assembled
views, respectively, generally similar to Pigures 30 and 31,
illustrating the use of a positioning apparatus in in accordance
with the present invention to position an optical fiber with
respect to the axis of a device having active surface device, in
which the device is edge mounted;
Figure 34 is a perspective view of a wafer used used to
fabricate a plurality of arms or foundations used in a
positioning apparatus in accordance with the present invenlion;
Figure 35 is a perspective view of a mask used in the
photolithographic process forming a plurality of arms or
foundations for a positioning apparatus in accordance with the
present invention;
Figure 36 is an enlarged view of a portion of the mask
used for creating a plurality of arms on the wafer 34;
Figures 37A through 37E are schematic representatians
of the process steps effected during fabrication of the wafer;
Figure 38 is is an enlarged view of a portion of the mask
used for creating solder masks on lhe wafer;
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1 1
Figure 39 is an enlarged view of a portion of the mask
used for crea~ing foundations on the wafer;
Figures 40A through 40D are schematic representations
5 of the sleps used to form a plurality of fiber-to-fiber
connectors from superimposed wafers having lhe arms and
foundations thereon;
~igure 41 is a definitional drawing illustrating the
10 characterislics of a converging groove as that term is used in
this application; and
Figures 42A through 42F are end views showing
alternate arrangements of movable arms each holding a
15 cylindrical member along at least three contact points in
accordance with the present invention.
DETAll~ED DESCRlPTlON OF THE INVENTION
Throughout the following detailed description similar
reference numerals refer to similar elements in all Figures of
the drawings.
With reference to Figures I and 2 a posi~ioning apparatus
2 5 generally by reference character 20 in accordance with the
present invention is shown in an exploded and in a fully
assembled condition. As will be developed herein, in the
preferred instance Ihe positioning apparatus 20 is
microfabricated from single crystal silicon or another
differentially etchable single crystal material. These materials
are preferred because they permit the accurate formation of
the structural features of the apparatus 20 using the process of
differenlial etching.
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12
The positioning appara~us 20 is useful in accurately
positioning a predelermined point on the end face of a
cylindrical member, typically a point on the central axis of the
member, along a reference axis. Typically this reference axis is
5 itself collinearly aligned with respect to anoIher axis, as an
operative axis of a device operably associable with the
cylindrical member. Throughout this application the
description of the cylindrical member is cast in terms of an
optical fiber, but it is to be understood that the present
10 invention may be effectively utilized with any other member
having ~he form of small diameler cylindrical object. By way of
example and not limitation, the positioning apparatus invention
may be used lo position a point on the end face of a length of
microtubing or capillary tubing. By small diameter it is
15 generally meant less than 0.04 inch (one (1) millimeter), but
usually less than 0.020 inch. Moreover, it should be further
understood that ~he term cylindrical is not to be strictly limited
to an object having a completely circular outer configuration,
but would apply to any object whose outer contour is
20 symmetrical to its central axis. Thus, again by way of further
example and not limitation, the positioning apparatus of the
present invention may be used to position a point on the end
face of a polygonal shaped member or an elliptical member.
2 5 As noted, the cylindrical member preferably takes the
form of an optical fiber. The positioning apparatus of the
present invention is particularly adap~ed to place a
predetermined point P on the end face E of an optical fiber F
along a predetermined Teference axis R. In practice the point P
is the geometric center and lies on Ihe axis A of Ihe core C
(Figures 6A and ~Bj of lhe fiber F. The core C is ilself
surrounded by an ouler cladding layer L. A jacket J is
provided about the cladding layer L bul is stripped from the
fiber F prior to the insertion of the fiber inlo the positioning
apparatus 20. The jacket may comprise n-ore Ihan one layer.
12
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13
As discussed previously, the dimension of the outer diameter D
of the cladding layer I, of the fiber F may vary from fiber to
fiber. Typically this diametrical variation from fiber to fiber is
on the order of th~ee (3) micrometers. This situation makes
5 difficult the positioning of the point P along the reference axis
R using the positioning devices of the prior art. The fiber may
be a single-mode or a multi-mode fiber. As will be seen from
the following the positioning capability of the positioning
apparatus 20 is especially adapted for posilioning the point P
1 0 of a single mode fiber within the precise tolerances required to
effectively couple light emana~ing from the single mode fiber
into another fiber or to position the fiber with respect to an
optical device.
With reference to Figures 1 and 2 it is seen that the
positioning apparatus 20 includes a first and a second arm 22A,
22B, respectively. Preferably, each of the arms 22A, 22B is
identically formed in a manner to be discussed, so the
structural details of only one of the arms, e. g., the arm 22A,
20 will be discussed. It should be apparent, however, that each
structural detail of the arm 22A finds a counterpart in the
other arm 22B. Accordingly, corresponding reference numerals
with the appropriate alphabet suffix will denote corresponding
structural details on the arm 22B. If the arms are not
2 5 substantially identical (as, for example, in the embodiments of
Figures 13 through 16 and Figure 42) adjustments must be
made to provide the requisite biasing forces to maintain the
point P on the ~eference axis R
The arm 22A includes a base porlion 24A having a first
major surface 26A and a second, opposed, major surface 28A.
The base portion 24A extends along the full length o~ the arm
22A and the dimension of the central region 25A of the base
portion 24A defines the basic dimension of the arm 22A. A
3~ clip generally indicated by the reference characler 30A is
13
14
defirled at a first end of the arm 22A. The clip 30A is formed
in a relatively thicker abutment portion 32A that lies on the
first surface 26A of the arm 22A. The abutment 32A has a
planar surface 34A thereon that preferably lies parallel to the
5 first major surface 26A. To provide some feeling for the
physical dimensions involved, the arm 22A has an overall
length dimension on the order of twenty eight hundred (2800)
micrometers and a width on the order of three hundred fifty
(350) micrometers. In the central region 25A the arm 22A has
1 0 a thickness dimension on the order of fifty (S0) micrometers,
while the remaining portion of lhe arm 22A has a thickness
dimension on the order of one hundred twenty five (125)
micrometers .
1 5 As may be better seen with reference to Figures 3 and 4
a generally converging V-shaped groove 36A is defined in the
abutment 32A of the clip 30A by generally planar first and
second sidewalls 38A, 40A, respectively, and the forward end
region of the first surface 26A of the base 24A. The sidewall
20 38A has an upper edge 39A (Figure 1) thereon while the
sidewall 40A has an upper edge 41 A thereon. It should be
understood that the term "planar" is meant to encompass a
surface formed in a single crystal material by etching in which
microscopic steps are of necessity produced owing ~o the lattice
2 5 structure of the crystal .
With reference now to the definitional drawing of Figure
41, the meaning of the term "converging" when applied to a
groove (using the reference characters of Figures I and 2) may
30 be made more clear. As used herein, a "converging" groove is a
groove 36 derlned from at least two planar sidewalls 38, 40
and has an enlarged inlet end 42A and a narrower outlet end
43A. The respective upper edges 39, 41 of the sidewalls 38, 40
of the groove 36 lie in a reference plane RP having a reference
35 axis R Iying therein. The planar surfaces 34 also lie in the
14
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reference plane RP. The reference axis R extends in the
reference plane RP from the inlet end 42 to the the outlet end
43 of the groove 36. Each point on the reference axis R is
spaced in the reference plane RP an equal distance from the
5 respeetive upper edges 39, 41 of the sidewalls 38, 40. The
distance belween the upper edges of the sidewalls decreases
from the inlet end 42 to the outlet end 43 of the groove 36.
The surfaces of the sidewalls 38, 40 are equally and
10 oppositely inclined with respect to the reference plane at an
angle A greater than zero and less than ninety degrees. The
angle of inclination A is determined by the lattice structure of
the crystal, and in the case of (100) silicon, is 54.74 degrees.
The projections of the sidewalls 38, 40 intersect in a line L that
15 itself intersects the reference axis R forwardly past the outlet
end 43 of the groove 36. The line L is inclined wilh respect to
the reference plane RP at an angle B that is greater than zero
degrees but less than ninety degrees. In the reference plane
RP the upper edges 39, 41 of the sidewalls 38, 40 each
20 converge toward the reference axis R at an angle C that is on
the order of two and one-half to five degrees (2.5 ~o 5) degrees,
and most preferably at about three (3) degrees. The angle B is
dependent upon the values of the angles A and C and typically
the angle B lies in the range from about four (4) to five (S)
25 degrees. As used herein a "fully funnel-like" channel is a
channel that is defined by the cooperative association of at
least two converging grooves. A "partially funnel-like" channel
is a channel that is defined by one converging groove and a
surface .
From the foregoing it may be readily understood that a
"uniform width" groove is one in which each point on the
reference axis R is spaced in the reference plane RP a uniform
distance fron~ lhe edges 39, 41 of the sidewalls 38, 40 as one
35 progresses from the inlet end 42 to the outlet end 43 of the
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16
groove 36. The sidewalls of a uniform width groove may be
inc]ined with respect to reference plane RP, or lhey may extend
perpendicularly to it, as desired. A channel formed from one
or two uniform widlh groove(s) is termed a "uniform width"
5 channel. Such a channel may have a rectangular cross section
in a plane perpendicular both to the reference plane and to the
reference axis, assuming no inclination of the sidewalls of ~he
groove.
A tapering groove is one in which the planar sidewalls
are perpendicular to the reference plane bul the distance in the
reference plane between the reference axis and the edges of
the sidewalls decreases as one progresses from the inlet to the
outlet of the groove such that the extensions of the planar
15 sidewalls intersect in a line that itself intersects
perpendicularly with the reference axis.
In the preferred embodiment seen in Figures 3 and 4 the
groove 36 is a converging groove, and more preferably, is a V-
20 groove truncated by the presence of a third sidewall definedby a portion of the major surface 26 of the arm 22 in which it
is disposed. The truncated V-groove has the same depth
throughout its length, when measured along a dimension line
erected perpendicuial to lhe surface 34A of the abutment 32A
2 5 in a direclion extending toward ~he major surface 26A.
It should be understood thal the V-shape of the groove
36A may ~ake alternate forms and remain within the
contemplation o~ the invention. For example, as seen in Figure
30 4A, the groove 36A may be defined by only the first and
second sidewalls 38A, 40A, respectively, in which event the
groove 36A appears as a full V-shape throughout its lenglh.
The apex 42A of the groove 36A thus appears throughout the
full length of the groove 36A.
16
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17
Figure 4B shows another alternative arrangement in
which a truncated V-groove (defined by the first and second
sidewalls 3~A, 40A, respectively, and the portion of the major .
surface 26A) extends for some predetermined axial distance
5 while a full V-groove (defined by the first and second sidewalis
38A, 40A, respectively) extends for some second
predetermined distance. Thus, as seen in Figure 4B, when
measured along a dimension line erected perpendicular to the
surface 34A of the abutment 32A in a direction extending
10 toward the major surface 26A the depth that the groove 36A
extends into tlle abutment 3~A is greater at its inlet end 42 (as
indicated by the dimension arrow 44A) than it is at its outlet
end 43 (as indicated by the dimension arrow 46A).
The fully truncated V-groove shown in Figure 4 is
preferred. For purposes of ease of manufacturability, as will be
made clear herein, it is also preferred that the groove 36A does
not converge throughout the full axial distance through the
abutment 32A. Owing to the provision of tabs 48A, 48B
20 (Figures 1 and S) formed near the ends of the abutments 32A,
32B, the sidewalls 38A, 40A defining the groove 36A do not
converge throughout the full length of the groove, but define a
short uniform wid~h portion just pas~ the converging portion of
the groove 36A. The overall axial leng~h of the groove 36
25 ~including both the converging and the uniform width portions)
is on the order of three tenths (0.3) of a millime~er, while the
uniform width por~ion of the groove occupies an axial length of
one tenth (0.1) of a millimeter. As is believed best seen in
Figure 5 the converging and nonconverging portions of the
30 groove 36A have a common axis 50A associated therewith.
Again with reference to Figure 2, an extended
enlargement region 54A having a planar surface 56A lies on
lhe base portion 24A of the arm 22A spaced a predetermined
35 axial distance 58A behind the abutment 32A. The distance
17
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58A is on the order of one (I) millimeler. The surface 56A is
coplanar with Ihe surface 34A. The enlargement 54A is
provided wilh a nonconverging, uniform width, truncated V-
shaped trough 60A defined by inclined planar sidewalls 62A,
5 64A, respectively, and by a portion of the major surface 26A of
the base porlion 24A near the second end thereof. In the
embodiment shown in Figures 1 and 2 the trough 60A is
uniform in depth along ils axial length, as measured with
respect to a dimension line erected perpendicular to the
1 0 surface 56A toward the major surface 26A. The trough 60A
communicates with a converging lead-in 68A. If desired, the
walls 62A, 64A may be inclined with respect to each other so
that the trough 60A may be a full V-shape or a partial V-
shape, similar to the situation illustrated in connection with
15 Figures 4A and 4B for the groove 36A. Alternatively, the walls
62A, 64A defining the troughs 60A, 60B may be parallel or
otherwise conveniently oriented with respect to each other. As
is believed best seen in Figure 5 the trough 6VA and the lead-
in 68A have a common axis 70A. The length of the trough 60A
20 and associated lead-in 68A is on the order of 1.59 millimeter.
Figure 5 is a plan view of one of the arms 22A. In the
preferred implementation the axes 50A, 70A (respectively
through the groove 36A and the trough/lead-in 60A/68A) are
25 offset a predetermined distance 72 in the reference plane RP
(the plane of Figure 5). Preferably, the offset 72 is at least
one-half the difference between the diameters of the
anticipated largest and smallest fibers to be positioned. As will
become clearer herein offsetting the axes SOA, 70A of the
30 structures 36A, 60A/68A facilitates the centering action of the
positioning apparatus 20 by insuring that a fiber, as it is
introduced into the apparalus 20, is biased to strike one of the
sidewalls 38A, 40A forming the groove 36A (and analogously,
the sidewalls 38B, 40B forming the groove 36B). This insures
35 wall contact with the fiber at at least two spaced locations.
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19
However, the presence of the offset 72 necessitates additional
manufacturing considerations, as will be discussed. It should
be noted that the force resulting from biasing the fiber in the
manner just discussed (or the force on the fiber due to gravity)
5 is much smaller in magnitude than the biasing force of the
arms which serves to center the fiber on the reference axis.
In the assembled condition the arms 22A~ 22B are
disposed in superimposed relationship one above the other,
1 0 wilh the groove 36A, the trough 60A and the lead-in 68A on
the one arm 22A registering wilh the corresponding groove
36B, trough 60B and lead-in 68B on the other arm 22B. The
registered converging grooves 36A, 36B in ~he abutments 32A,
32B cooperate to define a generally fully funnel-shaped
1 5 channel 92 having an input end 94 (Figure 4) and an output
end 96 (Figures 4 and 5). (Nole that if the tabs 48-are
provided, the channel 92 so defined has a uniform width
portion just preceding the outlet end 96 thereof.) The
reference axis R extends centrally and axially through the
20 channel 92. Preferably, the reference axis R lies on the
intersection of the reference plane RP (which contains the
conjoined surfaces 34A, 34B) with the plane containing the
axes 50A, 50B of the converging grooves 36A, 36B.
The registered troughs 60 and lead-ins 68 coopera~e to
define a guideway 98 (Figure 2). Similarly, the axis R' through
the guideway 98 lies on the intersection of the plane containing
the conjoined surfaces 56A, 56B of the enlargements 54A, 54B
(which is the reference plane in the preferred case) with the
plane containing the axes 70A, 70B (Figure 5) of the
trough/lead-in 60At68A, 60B/68B. The axes R and R' both lie
in the reference plane RP (the plane of the surfaces 34A, 34B,
56A, 56B) allhough the axes R and R' are laterally offset with
respect to each other in this reference plane by a
19
` 2~22~t~
predetermined offset distance 100. For a fiber the offset
distance 100 is typically on the order of five (5) micrometers.
The inlet end 94 of the fully funnel-like channel 92 (best
5 seen ;n Figures 4 and 5) is sized to sircumscribe and thereby to
accommoda~e a fiber F whose cladding layer L (or outside
surface) has the largest e~pected outer diameter dimension.
The outlet end 96 of ~he channel 92 (best seen in Figure 3) is
sized to circumscribe and thereby to accommodate a fiber F
10 whose cladding layer L (or outside surface) has a dimension
somewhat smaller than the minimum expected outer diameler
dimension of the fiber F. In practice, to position an optical
fiber having a nominal outer diameter dimension of one
hundred twenty five (125) micrometers, the largest expected
15 outer diameter dimension is on the order of one hundred
twenty nine (129) micrometers while the smallest expected
outer diameter dimension is on lhe order of one hundred
twenty one ( 121 ) micrometers.
The dimension of each of the troughs 60A, 60B is such
that the guideway 98 so formed by the registered troughs 60A,
60B is sized to accommodate a fiber F whose cladding layer L
has the largest expected outer diame~er dimension. Despile its
dimension with respect to the fiber, the guideway 98 assists in
the insertion of a fiber into the positioning apparatus 20 and is
advantageous in this regard.
In the embodiment shown in Figures I through 5 the
surfaces 34A, 34B on the respective arms 22A, 22B,
respectively, are, when in a first, closed, posilion, either in
contact with each olher or, if desired, wilhin a predetermined
close distance to each other. For oplical fibers ~he
predetermined close distance is typically on lhe order of five
(5) to twenty-five (25) micrometers. In lhis embodiment the
planar surfaces 34A, 34B on the abutments 32A, 32B of the
- ''
.
`` 2a22~7~
21
clips 30A, 30B are not secured to each other and may move to
a second, cenlering, position, as will be described. The planar
surfaces 56A, 56B on the respective arms 22A, 22B are secured
to each other by any convenient means of attachment, as by
5 fusing or soldering. It should be understood tha~ any other
mechanical securing expedien~ may be used to attach or
otherwise hold together the surfaces 56A, 56B tv each other.
The positioning apparatus 20 further includes, in the
10 preferred instance, a mounting foundation 74 (Figures I and 2).
The mounting foundation 74 is provided with a planar
attachment surface 76 lhereon. A step 78 in the mounting
foundalion 74 serves to space lhe attachment surface 76 a
predetermined clearance distance 80 from a second surface 82.
1~ The opposite major surface, e.g., the surface 28A, of the arm
22A is secured, as by fusing or soldering, to the planar
attachment surface 76 on the foundation 74. Of course, it
should be again understood that any alternative mechanical
attachment expedient may be used to attach or otherwise hold
20 together the second major surface of the arm to the foundation
74.
Although Ihe second surface 82 of the foundation is
shown in the Figures as being generally planar in the preferred
2 ~ case, it should be understood that this surface 82 may take any
desired configuration. As will be more fully appreciated
herein, so long as the opposile surface 28A of the arm 22A
affixed to the ioundation 74 is, at least in the region of the clips
30A, spaced at least a predetermined clearance distance 80
30 from the second surface 82 ~assuming lhe surface 82 is parallel
to the surface 76), the movement o`f the clip on the arm 22A
attached to the foundation (in the drawings, Ihe clip 30A) to be
described will not be impeded.
21
--`` 2~2~7~
22
When assembled, the clips 30A, 30B disposed at the ends
of the arms 22A, 22B, respectively, are supported in a
cantilevered fashion from the conjoined enlargements 54A, 54
at the opposite ends of the arms. The arms 22A, 22B are rigid
in x-z plane, as defined by the coordinate axes shown in Figure
1. Moreover, the relatively thin dimension of the central
region 25A, 25B of the base portion 24A, 24B of the arms 22A,
22B axially intermediate the respec~ive abutments 32A, 32B
and the enlargemenls 54A, 54B acts as a flexure and permits
1 0 each arm 22 to flex, springboard fashion, in the directions of
the arrows ~8 in the y-z plane. As used herein it should thus
be appreciated that a f~exure is a spring member that is rigid in
one plane and is constrained to flex in the orthogonal plane.
It should further be appreciated that when a clip 30A,
1 5 30B is def1ected in its corresponding respective direction 88A,
88B, the resiliency of the Ihinner central region 25A, 25B of the
base 24A, 24B, acting as a flexure, defines means for biasing
the clips 30A, 30B toward the first, closed, position. The
biasing force acts on the clip 30A, 30B in a direction shown by
20 the arrows 90A, 90B, counter to the direction of motion 88A,
88B of the arms. The biasing forces must be substantially
e4ual and in opposite directions. In general, whatever the
number of arms used in the positioning apparatus, the force on
each arm passes lhrough the reference axis and the sum of
25 forces when in the centering position position substantially
equals zero. Biasing means employing the thinner central
region of the base 24 as a flexure (as shown in the Figures 1 to
4) is preferred, because when implemented in a single crystal
material using a microfabrication techni4ue precise control of
30 the biasing forces is able to be attained. Typically the bias
force on each arm is on the order of five (5) grams.
It should be understood th.ll any other convenient
mechanism may be used to define lhe means for biasillg the
22
.
`` 202247~
23
arms and the clips 30 thereon toward the closed position so
long as the force on each arm passes through the reference axis
and the sum of forces on the arms when they are in the
centering position is substantially equal to zero. Whatever
5 form of biasing means is selected the bias force must increase
with deflection of the arm.
-o-O-o-
1 0 Having defined the structure of the positioning apparatus
20, the operation thereof in positioning a point P on the end
face E of an optical fiber F along a predetermined reference
axis R may be readily understood in connection with Figures 5
through 7.5
ln operation the fiber F is inserted into the positioning
apparatus 20 in the direction of the arrow 102 (Figure 6A).
The lead-in portions 68A, 68B (Figure 1) cooperate to guide the
fiber F into the guideway 98 (Figure 2) defined by the
20 registered troughs 60A, 60B in the enlargements 54A, 54B
(Figure 1). Because the axis R' of the passage 98 is offset from
the axis R of the fully funnel shaped channel 92 the guideway
98 serves to guide the face E of the fiber F toward the inlet end
94 of the channel 92 at a predetermined azimuth with respect
25 to the axis R.
As a result the end face E of the fiber F enters the
channel 92 and is initially displaced through contact with at
least one of the sidewalls 38A or 38B, 40A or 40B (or porlionS
30 of the major surface 26A, 26B, if these are llsed ~o define the
grooves 36A, 36B, as in Figure 4) on one of lhe clips 30A, 30B,
respectively, to the extent necessary lo place a predetermilled
point P on an end face E of the fiber F into alignmellt with the
reference axis R.
23
2(32~7~
24
At some point on the path of axial insertion of the fiber
into the channel 92, as the end ~ of the fiber F moves toward
the outlet end 96, the outer diameter of the cladding layer L of
the fiber F exceeds the dimension of the channel 92. The arms
5 22A, 22B respond to a force in the directions 88A, 88B imposed
thereon by the fiber F by moving against the biasing force from
the first, closed, position, shown in Figures 7A, 7B, toward a
second, centering, position showing in Figures 8A, 8B. In the
centering position the clips 30A, 30B open against the bias
10 force acting in the directions 90A, 90B generated by the flexing
of the arms 22A, 22B, to separate the surfaces 34A, 34B
thereon. However, this movement of the arms 22A, 22B from
the first toward the second position maintains the point P on
the end face E of the fiber F on the reference axis R. The end
15 face E of the fiber F thus exits through the outlet end 96 of the
fully funnel shaped channel 92 with the point P precisely
aligned with (i.e., within one micrometer of) the reference axis
R, as is shown in Figures 8A, 8B. The fiber F is held in this
position by contact with the sidewalls 38A, 3~B, 40A, and 40B.
If the tabs 48A, 48B are formed on the abutments 32A,
32B these tabs cooperate to define a passage of uniform width
along its axial length that communicates with the ou~let of the
funnel-like channel. The fiber F passes lhrough and emerges
25 from such a conduit with the point P on the end face of the
fiber still along the reference axis R.
It should be noted that the movement of the arms could
be other Ihan the flexing thereof as described heretofore. It
30 therefore lies withi~ the contemplation of this invention to
have the arms move in any other manner, as, for example, by
any form of pinned or joinled (articulaled) motion.
-o-O-o^
24
2(~22~7~
With reference now to Figures 9 lhrough 12 an alternate
embodiment of the positioning apparatus 20' in accordance
with lhe present invention is shown. In this embodiment the
arms 22' are, similar to the embodiment earlier discussed,
5 articl~lably rnovable in cantilevered fashion with respect to
each ~ther against the bias of the riexure defined by the central
portion 25' lhereof. l~owever, the grooves 36' formed in the
arms 22' are not converging grooves, but are uniform width
grooves. Accordingly the channel 92' formed by the
10 cooperative association of lhe arms 22' when superimposed one
on the other is a uniform widlh channel. The maximum
dimension of such a channel 92' in the plane perpendicular to
the reference R is less than the outside diameter of the smallest
anticipated fiber F.
A further modification to the positioning apparatus 20'
may be seen from Figure 12. It is first noted that the planar
walls 62', 64' of the troughs 60' are parallel, rather than
inclined with respect to each other. Moreover, the offset l O0'
20 between the axes R and R' lies in Ihe vertical plane, that is, in
the plane containing the axes 70' of the troughs 60', as opposed
to being offset laterally (i.e., in the plane containing the
surfaces ~6'). The lead-in portions 68'A, 68'B are ommitted
here but may be provided.
In operation, a fiber F is inserted inlo lhe posi~ioning
apparatus 20' and guided by the passage 98' defined by the
registered troughs 6~'A, 60'B. Because the axis R' of the
passage 98' is vertically offset from lhe axis R of the channel
30 92' the surface 26'B of the arm 22'B bounding lhe passage 98'
serves to guide the fiber F toward the inlet end 94' of the
channel 92'. The fiber F enters the channel 92' and contacts
with the edges of the sidewalls 38'A, 38'B, 40'A and 40'B. Due
lo the sizing of the grooves 36'A, 36'B the fiber F does nol
3 5 touch the major surface 26'A, 26'B of the arms 22'A, 22'B,
`-` 2~2~
26
respectively. The fiber may be chamfered or ~apered or a
mechailical device may be used to facilitate insertion of the
fiber into the channel 92'.
Since the fiber F exceeds the dimension of the channel 92'
the clips 30'A, 30'B are displaced from the first, closed, position
toward a second, centering, position. This movement of the
clips 30'A, 30'B mainlains tlle point P on lhe end face E of the
fiber F on the reference axis R. The end face E of the fiber F
10 thus exits through the outlet end 96' of ~he channel 92' with
the point P precisely aligned on the reference axis R. The 'iber
F is held in this position by contact with the edges of the
sidewalls 38'A, 38'B, 40'A, and 40'B, as indicated by the
character LC.
The embodiment of Figures 9 to l 2 can be further
modified, as seen in Figures 13 to 16. In this modification, the
arm 22"B differs from those shown earlier in that no groove is
provided therein. In this embodiment, if the groove is a
20 converging groove, a partially funnel-like channel is defined.
The fiber F is guided by contact against the major surface 26"B
and held in position on the reference axis R by contact with the
major surface 26"B and the edges of the sidewalls 38'A, 38'B,
agnin as indicated by the character LC.
-o-O-o-
Figures 17 and 18 are exploded and assembled
perspective views, generally similar to Figures I and 2, of
30 another alternate embodimenl of a positioning npparatus 20"'
in accordance with the presenl invention wllile Figure l 9
shows the end view Ihereof. In Ihis embodiment, instead of
the arms being articulnbly mov.lble as described earlier, the
arms are fixed relalive to each olher. Each of the arms 22"'A
35 and 22"'B has a convergillg groove thereill and the ch;lllllel 92"'
' - ' ''
... . . ,~
,
~ ' ,
2al224~
27
formed by the cooperative association of the arms 22"' when
superimposed one on ~he other is fully funnel-like in forrn.
The channel 92"' defines a minimum dimension in the plane
perpendicular to the reîerence R that is, near its outlet end, less
5 than the outside diameter of the smallest anticipated fiber F.
In operation, a fiber F is inserted into the positioning
apparatus 20"' and guided through the passage 98"' toward the
inlet end 94"' of the channel 92"'. The fiber F enters the
1 0 funnel-like channel 92"' and is guided by contact with one or
more of the sidewalls 38'A, 38'B, 40'A and 40'B and/or major
surfaces 26"'A, 26"'B to place the point P of the fiber F on the
axis R. However, since the arms 22"' are fixed with respect to
each other, lhe fiber F can only advance within the channel 92"'
15 to the axial location where the outer diameter of the fiber F
equals the local dimension of the channel 92"'. At this axial
location within the channel the fiber is held in position by a
minimum of four point contacts ~indicated by the characters
PC) between the fiber F and each of the sidewalls 38'A, 38'B,
20 40'A, and 40'B. The dimension of the channel is such that the
fiber is not able to contact the major surfaces of the arms 22"'
when it is held along the reference axis R. Figure 20 illustrates
the fiber as the same is held within the channel 92"'. The axial
spacing 104 between the end face E of the fiber F and the
25 outlet end 96"' of the channel 92"' varies, dependent upon the
outer diameter dimension of the fiber F.
-o-O-o-
The positioning apparatus in accordance with any of the
above-described embodiments of lhe invention may be used in
a variety of applica~ions which require the precise positioning
of a point P on the end face E of a fiber F along a reference axis
R.
27
'
-
.
.
.. .
-- 2~22~7~
28
In Figures 21 and 22, a pair of positioning apparatus 20-
1,
20-2 (corresponding ~o the embodiment shown in Figures 1
and 2) are arranged to define a fiber-to-fiber connector
5 generally indicated by the reference character 120. In this
arrangement the apparatus 20- 1, 20-2 are confrontationally
disposed wilh respect to the other so that the outlet ends 96 of
the respective channels 92 therein are spaced a predetermined
distance 122 with the respective reference axes R therethrough
1 0 being collinear. To effect such an arrangement the foundation
74 is extended in an axial direction and each axial end thereof
is provided with a planar attachment surface 76. Each
positioning apparatus 20- 1, 20-2 is mounted to its respective
attachment surface 76.
The fibers F- I and F-2 to be connected are inserted into
the lead-ins 68 of the respective positioning apparatus 20-1,
20-2. Each positioning apparatus 20-1, 20-2, acting in the
manner described above, serves to place the point P on the end
20 face E, of the respective fiber F-l or F-2 along the collinearly
disposed axes R'. The fibers F-l, F-2 are inserted in to the
respective apparatus 20-l, 20-2 until the end faces E, E' abut.
The ends E of the fibers F 1, F-2 are secured due to the above-
described holding action of the positioning apparatus. If
2 5 desired an suitable index matching adhesive, such as an
ultraviolet curing adhesive such that rnanufactured and sold by
Electro-Lite Corporation, Danbury, Connecticut as number
82001 ELC4480, may be used.
The fiber-to-fiber connector may be implemented using
any of the above-discussed allernative embodiments of the
positioning apparatus. In the event a pair positioning
apparatus as shown in Figure 17 is used (see Figures 23 and
24), the confronting ends of the positioning apparatus 20"'-1,
20"'-2 are preferably abutted and secured, or the pair of
28
,. . ~ . : ~ , '
:
.
. ~' :.
.
20224~
29
positioning apparatus formed integrally with each other. The
spacing 122 between the end faces E of the fibers
F-l, F-2 is, in this embodiment, defined by the sum of the
distances 104-1, 104-2. The spacing 122 is filled with an index
5 malching material, such as lhe adhesive defined above. To this
end, an access port 124 is provided to permit the introduction.
of the index matching material into the region between the
confronting end face of the fibers F-l, F-2.
Prior to insertion into the positioning app~ratus (of
whatever form) it should be understood that the jacket J
(Figure 29) of the fiber F is stripped in its entirety a
predetermined distance from the free end thereof. The
exposed portion of the fiber is cleaned with alcohol. The fiber
is cleaved to form the end face E. If desired the end face E may
be ground into a convex shape to yield a point or be lensed.
-o-O-o
If desired the fiber-to-fiber conneclor 120 may be
disposed in a suitable housing 130 (figure 2~. The preferred
form of the housing 130 is generally similar to that disclosed in
United States Patent 4,784,4S6 (Smith), assigned to the
assignee of the present invention. This patent is hereby
incorporated by reference herein. The housing 130 includes a
base 132 and a cover 134. The base 132 is, in all cases,
provided with a recess 136 that is sized to closely receive the
connector 120. If the conneclor 120 is realized using any form
of the positioning app~ratus that articulales, the cover 134
must bè provided with a corresponding recess 138 located so
as to permit the articulating molion of the arms of positioning
apparatus used to form the connector. lf the connector 120 is
realized using the form of the positioning apparatus shown in
Figures 23 and 24, the recess 138 need not be provided. Such
a housing 130 is shown in Figure 28.
29
2822i.~7~ ~
The cover 134 is segmented into three sections, 140A,
140B, 140C, each which is hinged to the base 132. The base
132 has, adjacent to each end of the recess 136, V-shaped
5 grooved regions 142A, 142B. The top end sections 140A, 140B
each contain respective generally tapered lands 143A, 143B.
Each of the lands has serrations 145A, 145B respectively
thereon.
In use a connector is inserted in the recess 136 of the
housing 130. It is there held in place by friction but may be
otherwise secured if desired. The central section 140C of the
cover may then be closed, if desired. An optical fiber having a
predetermined length of its jacket J stripped and cleaned, is
1 5 inserted through one of the V-shaped grooved regions 142A,
142B to dispose the stripped end of the fiber into the connector
120. The grooved region serves to properly orient and position
the fiber with respect to the connector 120 in the recess 136.
The associated top end section 140A, 140B, as the case may be,
20 is then closed and latched to the corresponding portion of the
base 132 (Figure 25, with the fiber ommitted for clarity).
When the top is secured to the base the serrations 145 act
against the jacket of the fiber to urge, or to bias, the fiber
toward the connector. A second fiber is correspondingly
25 introduced into the housing and connector in an analagous
manner. If not already done so, the central section 140C of the
cover is lhen closed. The housing 130 is preferably formed by
injection moldlng.
As seen in F~igure 29, in another form the housing 130
may be implernented using a mass 160 of index matching
material, such as ~hat identified above. The mass 160 extends
over both the connector 12() (to embed the same therein) and
some predeterrnined portion of the jackets J of the fibers F-l,
F-2.
-
.
2~2247~
31
-o-O-o-
The reference axis R on which the point P of the fiber F is
5 positioned may itself extend collinearly with the axis X of any
of a variety of devices. Accordingly, a positioning apparatus 20
may be used lo accurately posilion the point P on the end face
E of lhe fiber F with respect to the axis X of a particular device
170. Figures 30, 31 and Figures 32, 33 illustrate several
I O examples of the use of a positioning apparatus 20 to locate a
fiber F along an axis X of a device 170. The device 170 may,
for example, be realized by any active optical component, such
as a solid state laser, a photodiode, a light emitting diode,
whether these devices are edge active devices or surface active
I 5 devices. Although in the discussion that follows the reference
characteT 20 is used to indicate the positioning apparatus, it
should be understood that any one of the embodiments of the
positioning apparatus heretofore described may used.
When used in connection with an edge active device 170
the arrangement in Figures 30 and 31 is preferred. In this
arrangement lhe foundation 74 is axially extended to define a
pedestal 174 at the axial end thereof. The upper surface 176
of the pedestal 174 defines a planar attachment surface. The
surface 176 is spaced a predetermined distance above the
attachment surface 76 or otherwise located such that when the
active optical component 170 is mounted the surface 176 the
axis X of the device 170 and the reference axis R are collinear.
With the axes R and X collinear, the positioning of the point P
on the fiber F along the a~is R wi~l automatically position that
point P in the same relationship with the axis X. The device
170 must be accurately mounted on the surface 176 so that its
axis X is collinearly aligned with the axis R.
31
- ~ . .
`
2~2~
32
To mount lhe device 170 the surface 176 may be
provided with a layer of solder layer, SUCIl as a gold/tin solder.
The device 170 may have a corresponding layer of the same
material. The device 170 is positioned on ~he surface 176
5 using a sui~able micropositioning apparalus, such as a vacuum
probe. The device is aligned to the edge, heated above the
melting point of (he solder and cooled, so that the solder forms
a bond.
When used with a surface active device, as seen in
Figures 32 and 33, the active surface of the device 170 is
secured to the front surface 178 of the pedestal 174. Attaching
the device to the front surface 178 is believed to provide
sufficient bonding area lo secure the device 170 to the
15 positioning apparatus 20. The surface 176 of the pedestal 174
is relieved to avoid obstruction between the active region of
the device 170 and the end face E of the fiber F.
lt should also be appreciated, as is illustrated in Figure
20 31A, that the positioning apparatus in accord;snce with any one
of the embodiments heretofore described may be configured to
accurately posi~ion a lens, such as a ball or a rod lens L, with
respect to the axis X of the device 170 (whether the same is an
edge active or a surface active device). The positioning
25 apparatus would be modified to provide a seat 31S in the clips
30 thereof sized to accept the lens L.
-o-O-o-
.. . .
2~22~75
33
The photolithographic microfabrication technique used to
manufacture a positioning appara~us 20 may be understood
from the following discussion taken in connection with Figures
34 to 40. Although the discussion is cast in terms of the
5 manufacture of a fiber-to-fiber connector 120 using the
preferred embodiment of the positioning device 20, as shown
in Figure 22, the teachings are readily extendable to the
manufacture of any of the embodiments of the positioning
apparatus heretofore described, including their use in the
10 various other applications previously sel forth.
A silicon wafer 200 having an appropriate predetermined
crystallographic orientation is the ~tarting point for fabrication
of the arms 22 of a positioning apparatus 20 in accordance with
15 the present invention. It should be understood that other
single crystalline substrate materials, such as germanium, may
be used provided appropriate alternative etchants and
materials compatible with the selected alternative substrate
are used. The wafer 200 is polished on at least one surface.
20 Suilable silicon wafers are available from SEH America, Inc., a
subsidiary of Shin-~tsu Handotai Co. Ltd., Tokyo, Japan, located
at Sparta, New Jersey. It should be understood that the wafer
200 can be of the "p-type", "n-type" or intrinsic silicon.
The substrate material is preferably (100) surface silicon
because this material can be elched by anisotropic etchants
which readily act upon the (100) crystallographic plane but
substantially do not etch the ( 1 1 1 ) plane. As a result the
preferred truncated V-shaped grooves 36A, 36B, the troughs
60A, 60B, the lead-ins 68A, 68B and the central region 25A,
25B of the arms 22A, 22B between the abulments 32A, 32B
and the enlargements 54A, 54B are easily formed. The width
and depth of such features are dependent upon the preselected
widlh of the opening in the photolithograpllic mas}; being used
and the time during which the elchanls are permitted to act.
33
34
Etchants operate on 100 surface silicon in an essentially self-
limiling manner which property is useful in forming a full
V-groove. One of skill in the art will recognize that if other
cross-section configurations are required, other predetermined
5 cryslallographic orientations of the silicon may be used. For
example, if square cross-section features are riesired, (110)
surfaces silicon wafers can be used. Other cross sectional
configurations for the features are, however, significantly more
expensive and, as will be seen later, would require a more
1 0 complicated configuration to obtain the fiber centering action
equivalent to that inherent in a V-groove.
Figure 34 is a plan view of the wafer 200. The wafer 200
has peripheral flats 201 and 202, as specified by the SEMI
1 5 Standard. The fiats 201, 202 primarily indicate orientation of
the crystallographic structure of the silicon and are also used
for wafer identification and mask alignment. The longer flat
201 indicates the direction of crystallographic plane (110).
The shorter flat 202 is placed a predetermined angular amount
20 on the periphery of the wafer with respect to the flat 201, the
magnitude of the angle depending upon the doping of the
crystal .
As will be developed, the peripheral regions 203 of the
25 wafer 200, when prepared, carry alignment grooves, while the
central region 204 of the wafer 200 has ~he structural features
of the arm or foundation, as the case may be, of the posilioning
apparatus formed thereon.
Figure 35 shows a mask 210 with a patlerns 212 of
orthogonal alignment grooves thereon. The grooves in each
pattern 212 are graduated in size to accommodate various
sized (diameter) quartz alignment fibers. The grooves 212
have a V-shaped cross section to accepl fibers ranging in width
from about 0.004825 inches (0.123 mm) to 0.005000 inches
34
-` 2a!22~7~
(0.127 mm) in 0.039370 inch (0.1 mm) sleps, five grooves 212
having been illustrated. The groove width (at the open top of
the groove) is larger than the diameter of the fiber so that the
cente]r of the fiber is substantially coplanar with the surface of
5 the ~afer w11en the fiber is disposed in its associated groove.
Accordingly, for a 0.123 mm fiber, a groove 0.1506 mn~ is
provided. Similarly, for a 0.124 mm fiber, the open top
dimension of the groove is 0.1518 mm. For a 0.125 mm fiber,
the open top dimension of the groove is 0.1531 mm; for a 0.126
10 mm fiber the open top dimension of the groove is 0.1543 mm.;
and for a 0.127 mm fiber, the open top dimension of the groove
is 0.1555 mm.
A central area 214 of the mask 210 has provided thereon
15 a repetitive pattern 220 (one of which is shown in Figure 36)
containing to a predetermined number of structural features
(i.e., arms or foundations) of the positioning apparatus 20 being
formed. Since the typical wafer 200 is about 3.9381 inches
(101.028 mm) in diameter and a typical connector 120
20 measures about three hundred fif~y (350) micrometers at the
widest location and is about two thousand eight hundred
(2800) micrometers in length, the structural features for
approximately one thousand (1000) connectors 120 may be
formed from the central region 204 of the wafer 200.
Figure 36 is an enlarged view of a portion 220 of the
pattern provided on the central region 214 of the mask 210.
In Figure 36, the paltern illustraled is thal used to form a
plurality of conjoined arms 22 used in a connector 120 (Figure
30 22). The pattern 220 is formed on the surface of the central
region 214 of the mask 210 using a well-known step and
repeat process to cover the entire area.
The repetitive pattern 22V shown in Figure 36 is
35 comprised of a plurality of columns 224 which are defined
2~22~75
36
be~ween an array of adjacent parallel scribe lines 226 and a
firs~ and a second separation line 227A and 227B. Each column
224 contains ten (10) discrete zones 22BA through 228E that
are symmetrical within the column 224 about a cutting line
5 230.
Seen between two next adjacent scribe lines 226 is the
configuration of two arms 22 joined front end to front end.
Seen between three next adjacent scribe lines 226 is the
1 0 configuration of two arms 22 joined lengthwise side to side.
The zone 228A corresponds to features defining the region of
the lead in 68A of an arm 22A. The zone 228B corresponds to
features defining the region of the trough 60A of the arm 22A.
Similarly, zone 228C corresponds to the central portion 25A of
1 5 the arm 22A, while the zone 228D corresponds to features
defining the region of the converging groove 36A on the arm
22A. The axis 50A of the converging groove 36A is offset from
the axis 70A of the trough 60A by the offset distance 100.
Finally, if provided, the zone 228E corresponds to features
20 defining the region of the tabs 48A of an arm 22A. Note that in
the mask illustrated in Figure 36 the position of the offset 100
on one side of the cutting line 230 is reversed from the position
of the offset 100 on the opposite side of the cutting line,
although this arrangement is not necessarily required.
The repetitive pattern for a mask of the arm 22B will be
similar to that shown in Figure 36 except that the direction of
the offset distances 100 for the arm 22B will be the mirror
image of the paltern for the arm 22A. As will be come clearer
30 herein, this mirror image relationship belween the offsets is
necessary so that so that features on the resulting arms 22A,
22B will register with each other when one is inverted and
superimposed on the other. Of course if the offset 100 is
eliminated, masks for the arms 22A and 22B will be identical.
36
-` 2~22~ o~3
37
The cross-hatched areas shown in Figure 36 preferably
correspond to those areas of the cen~ral region of the wafer
200 Ihat will be protected by a layer of resist material (as will
be d~scribed) while the areas shown without hatching will be
5 left unpro~ected during subsequent etching steps. A negative
resist is employed but it should be apparent that the location of
~he ha~ched and clear areas of Figure 36 may be reversed if
desired. This would alter somewhat subsequent steps, but in a
manner known to those in the art.
Figures 37A through 37E illustrate the process steps
whereby a wafer 200 of crystalline silicon may be formed into
an array of arms 22A corresponding to the array shown on the
mask of Figures 35 and 36. As seen in Figure 37A the wafer
15 200 is preliminarily covered with a layer 232 of a ma~erial that
acts in a manner similar to a mask. Silicon nitride (Si3N4) is
preferred, and is surfaced onto the polished operative surface
200S of the silicon wafer 200 by thermally growing the silicon
nitride layer in an oxygen atmosphere at elevated temperature
20 (circa seven hundred fifty (750) degrees Celsius), as is known.
As indicated, silicon nitride is used because available etchants
that attack silicon will also attack known photoresists but will
not affect silicon nitride. A suitable nitride layer is grown onto
the wafer by CVD Systems and Services, Incorporated,
25 Quakertown, Pennsylvania.
The layer of silicon nitride 232 is then covered with a
photoresist 234. Preferred is a positive resist, such as the
mixture of 2-ethoxyethyl acetate, N-bu~yl acetate and xylene
30 sold by Shipley Company, Incorporated of Newton,
Massachusetts, as "Microposit Photoresist" 1400-37. The resist
is spun onto the surface of the silica nitride in accordance with
instructions set forth in the Shipley Microelectronic Products
Brochure ( 1984) using standard apparatus such as that
2~22'~7~
38
available from Headway Research Incorporated of Garland,
Texas under model number ECR485.
The mask 210 is mounted atop the wafer 200 and is
5 aligned with Tespecl to lhe flats 201, 202 of the wafer 200
using alignment bars 235. Thus, in a finished wafer the
alignment grooves 212 are precisely positioned with respect to
~he flats on the wafer through the use of alignment bars 213 on
the mask. The wafer 200 is exposed to ultraviolet light
lO through the mask 210 and subsequently developed.
Since a positive resist is used the unexposed areas of the
resist are washed away using de-ionized water, leaving the
Iayered arrangement of exposed, hardened resist 234, silica
1 5 nitride 232 and wafer 200, as shown in Figure 37B.
Next the pattern of the mask 210 is etched into ~he silica
layer 232. Phosphoric acid (H3PO4) is preferred. This step
results in the arrangement shown in Figure 37C. Those skilled
20 in the art wi~l recognize that process variables such as, for
example, concentration, time and temperature are all adjusted
appropriately to optimize results in all of the wet processing
steps described.
Thereafter, a second, differential, etching step is
performed to etch the silicon to form the features of the arms
22A. Preferably using an anisotropic etchant such as ethylene
diamine ("ED~) pyrocatechol ("P") and water. A mix of 750 ml
ED, 120 gm P and 240 ml water is preferred. A two-step etch
using potassium hydroxide (KOH) may also be used if desi~ed.
This etching produces the structural feature in the surface of
the silicon illustrated schematically in Figure 37D by reference
character 236. The depth of the feature 236 is controlled by
controlling the etching time, as is well known. Of course,
38
. .
,. ~ .
2O22L.~ 7~
39
differential etching is self-limiting for the inside angles of the
struclure, if left to proceed.
The silicon nilride layer 232 is ~hen removed by etching
5 wilh phosphoric acid and a layer of silica, i.e., silicon dioxide, is
grown on the surface. Next, resist is deposited on lhe surface
of the wafer and is imaged through a mask, as shown Figure
38. This results in a layer 238 of hardened resist being formed
on Ihose predetermined portions of the wafer that are to be
10 bonded (corresponding to zones 228C through 228E and to
troughs 60 (see Figure 36)).
The silicon layer is then etched from areas that are not to
be bonded (See, Fgiure 37E) using hydrofluoric acid (HF). The
15 resist layer 238 is s~ripped using acetone, leaving a finished
wafer ready for bonding.
This completes the fabrication of the first wafer 200
having the array of arms 22A thereon.
-o-O-o-
As noted earlier, since the axis of the guideway 98A is
offset from the axis of the groove 92A, the mask for the arrns
25 22B is not identical with the mask used to form the arms 22A.
Accordingly, a second wafer having an array of arms 22B
thereon must be prepared in accordance with the method steps
illustrated in Figure 37. The finished second wafer (not
specifically illustrated but hereinafter referred lo by character
30 200') is similar in aJI respects excepl in location of the offset
100.
A thi;rd wafer 200" is prepared using a foundation mask,
a portion of which is shown in Figure 39. Figure 39 is an
35 enlarged view of a portion of the pa~lern 220' provided on the
39
2 ~ 7 ~
central region of lhe foundation mask (analagous to the paltern
of thle arm mask shown in Figure 36). The repetitive pattern
220' is comprised of a plurality of columns 244 which are
defined between an array of adjacent parallel scribe lines 246
5 and a first and a second separation line 248A and 248~. Each
column 244 contains four (4) discrete zones 250 that are
symmetrical within the column 244 about a center line 252.
The zones 250A define mounting surface 76 on a foundation
74. The zones 250B correspond to the surfaces 82 provided on
1 0 the foundation. The wafer 200" containing the foundations 74
is exposed in a manner analagous to that shown in Figure 37,
with the exception that the exception that the solder mask
exposure is not carried out. However, the layer of silica is
removed from the surface of the wafer 200".
Having prepared wafers for the arms 22A (the wafer
200), the aTms 22B (the wafer 200') and the foundations 74
(the wafer 200"), the final assembly of the connector 120 may
be made as is shown in Figure 40.
The wafer 200' is placed on top of the wafer 200. The
registration of the features on the wafer 200' to those on the
wafer 200 is effected using at least two and preferably four
lengths of a stripped optical fiber and ~he corresponding
25 appropriate one of the alignment grooves in each array 212 of
grooves. The diameter of each length of the optical fiber is
measured by micrometer, accurate to plus or minus 0.5
micrometers. Each of the fibers is placed in groove in the
groove array 212 that most closely corresponds to the
30 measured diameler. Each alignment fiber thus sits in the
selected alignment groove such that lhe axis of the alignment
fiber lies in the plane of the surface of the wafer 200 with the
remaining portion of each fiber protrudes above that surface.
` 2~2~
41
The wafer 200' is inverted and placed atop lhe wafer
200, with the corresponding grooves in the wafer 200'
recei ving the prolruding portions of the alignment fibers
there'by to precisely align the pattern of the two wafers. Since
5 the alignment grooves on each wafer are formed
simultaneously with the formation of the features on the wafer,
and since the mask for each wafer is formed optically one from
the other, precise alignment between the wafers is achieved. It
is noted in Figures 40A and 40B only one of the fibers 254 and
10 grooves 121 is shown, for clarity of illuslration.
The assembly of superimposed wafers 200, 200' shown in
Figure 40A is bonded in a wet controlled atmosphere furnace
according to methods described in the paper by Shimbo et al.,
15 "Silicon-to-silicon direct bonding method" published 10/86 in
the Journal of Applied Physics, and in the paper by Lasky et al.,
"Silicon on Insulator (SOI) By Bonding and Etchback", IEDM 85.
As seen in Figure 40B the exterior surface 256' of the wafer
200' is lapped to reduce its thickness from it original thickness
20 (typically approximately seventeen (17) micrometers) to a final
thickness of five (5) micrometers.
The resulting bonded slructure is inverted and the
exterior surface 256' of the wafer 200' is mounted atop the
25 wafer 200". l'he alignmenl Or these wafers is effected using a
fixture employing quartz blocks 26û abutting against the flats
201, 202 of the wafer 200. The wafer 200' is then bonded to
the wafer 200". It is to be underslood that other bonding
techniques, such as those discussed in the paper by
30 Wallis and Pomerantz "Field Assisted Glass-Metal Sealing"
published 9/69 in the Journal of Applied Physics may be used
to bond the wafers. Still other a3ternate bonding techniques
would include metallic or glass solder bonding.
41
- 2~2'~7~
42
The exlerior surface 256 of the wafer 200 is then lapped
until the dimension of the wafer 200 is that of the wafer 200'.
Thus, the substantial equality of lhe biasing forces imposed by
the flexure is provided.
The resultant three wafer bonded stack shown in Figure
40D may lhen be cut. Only the top two wafers 200, 200' of the
bonded stack (containing ~he arms 22-1 B, 22-2B and the arms
22-lA, 22-2A, respectively, Figure 22) are first cut along the
1 0 lines in the wafers corresponding lo the cutting lines 230, 230'
on the arm masks (Figure 36). This cut is made using a blade
that is on the order of 0.003 inches to create the distance 122
in F;igure 22. The bonded stack is thereafter cut, using a blade
that is 0.015 inches thick, along lhe lines in the wafers
1 5 corresponding to the separation lines 227A, 227B on the wafer
200, the separation lines 227A', 227B' on ~he wafer 200', and
the separation lines 248A, 248B on the wafer 200", as well
along the scribe lines 226, 226' and 246 (on the respective
wafers 200, 200' and 200") all of which are registered with
20 each other~ thereby to yield from the bonded stack about one
thousand of ~he fiber-to-fiber connectors 120.
. ~
-o-O-o-
Those skilled in ~he art, having the benefits of the
teachings of the present invention as hereinabove set forth,
may impart numerous modificalions thereto.
For example, as seen in Figure 42, in addition to the
~arious embodiments of the two-armed configuralions for the
positioning apparaius of the presen~ invenlion previously
disclosed, it lies within the conlemplation of this invention for a
positioning apparatus to exhibit more than two arms 22. In
this regard Figures 42A to 42C illus~rale a positioning
apparatus having three arms 22A, 22E~ and 22C while Figures
42
.
- 2~2~7~
43
42D through 42F illustrale a positioning appara~us having four
arms 22A, 22B, 22C and 22D. The extension to even greater
number of arms would be readily apparent to those skilled in
the art.
In Figure 42A each the arms are configured similar to the
form of the arms discussed above. The arms may, if desired
carry a groove, altllough il should be understood that such is
not required. In Figures 42B and 42E the arms are configured
from rods. Although lhe rods shown as round in cross section .
it should be underslood that they can have any desired
alternate cross section. In Figures 42C and 42F the arms are
configured in a general Iy planar bar form. In Figure 42D the
four arms may be formed by sawing the upper and lower arms
(indicated by the characters 22A, 22B in Figures I to 4) along
a cut line ex~ending perpendicular to the major suraces 26 and
28 of each of the arms.
However configured the arms are shown in Figures 42A
through 42F as angularly juxtaposed in a surrounding
relationship to the channel 92 defined their cooperative
association. Similar lo the situation described heretofore the
resiliency of the arms defines lhe biasing means which urge
the arms toward lhe closed position. However~ it should be
understood that the biasing means may be otherewise defined,
f so long as the force on eacll arm passes through the reference
axis and Ihe sum of forces on the arms when they are in the
centering position is substan~ially equ.ll lo zero. Whatever
form of biasing means is selected lhe bias force must increase
wilh defleclion of the arln. The arms acl ag;linsl tlle fiber F
inserled into the channel alolIg the various lines of contact LC
illustrated in Figure 42 lo main~.lin ~he predelerlIlined poin~ on
the fiber on the reference axis R.
43
.. . .. , . , , .. ~ .. ... . . . . . . . . .
44
It should be understood that such modifications as herein
preented and any others are to be construed as Iying within
lhe contemplation of the present invention, as defined by the
appended claims.
WHAT IS CLAIMED IS:
44
