Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MICRODEVICE WITH MOVABLE M1CROPLATFORM AND PROCESS FOR
MAKING THEREOF
FIELD OF THE INVENTION
The present invention relates to a microdevice and a process for making
thereof, but more particularly, to a microdevice equipped with a movable
microplatform and a process for making thereof.
BACKGROUND OF THE INVENTION
There are several examples of miniature electromechanical devices equipped
with movable microplatforms with lateral dimensions from a few micrometers
to several thousands of micrometers. The pivoting along one or multiple axis,
and vertical or horizontal displacement of these microplatforms is possible
due
to various types of hinge members including torsional and flexure hinge types.
The movement of the microplatforms is induced typically via electrostatic,
magnetic or thermal mechanisms.
The functions performed by these microdevices equipped with movable
microplatforms include phase and amplitude modulation of visible, UV or IR
radiation beams as well as mechanical protection with open and close
functions of specialty microsystems. In particular, the microdevices used for
radiation beam manipulation are often called micromirror devices and find
multiple applications in telecom for laser beam attenuation and switching as
well as in projection imagers as the spatial light modulators.
In optical applications in particular, it is extremely important to provide
movable microplatforms that are free of mechanical deformations and defects,
with a residual radius of curvature of many meters and surface roughness
better than )~/10, where 7~ is the wavelength of radiation used.
There are typically two methods used for manufacturing individual and arrays
of microdevices equipped with movable micropiatforms. The first most
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commonly used method makes use of a thin film technology developed for
manufacturing integrated circuits (ICs), while the second method typically
involves micromachining silicon wafers and epitaxial silicon films by a deep
etching technique.
Known in the art is US Patent 6,025,951 by N.R. Swart et al, which discloses
a micromirror device equipped with a flexure hinge permitting to tilt as well
as
to displace vertically a microplatform via the electrostatic interaction.
Methods
for forming individual or multiple microdevices are also described. These
methods make use of the thin film technology developed for manufacturing
ICs.
The biggest drawback of the microplatforms produced by the thin film
technology is a residual stress in the deposited thin films as well as a
mismatch between stresses in films made of different materials. This
produces deviations from the platform flatness required and thus adversely
affects the microdevice performance. Typically, the residual stress in thin
films
scales inversely with the film thickness. However, the thin film technology
yields a film with a thickness not exceeding a few micrometers and thus the
stress reduction is not sufficient. Thin films also have rough surfaces, which
contributes to unwanted scattering of radiation illuminating the
microplatform.
Also known in the art is US Patent 4,317,611 by K.E. Petersen, which
discloses a torsional-type optical ray deflection apparatus produced out of a
pair of etched plates, one of which is single crystal semiconductor material
such as silicon, and the other is a suitable insulating material such as
glass. A
pivoting microplatform equipped with torsionai hinges is made by anisotropic
etching through a silicon wafer. It is then bonded to a glass plate equipped
with suitable metal electrodes for electrostatic activation of the
microplatform.
Also known in the art is US Patent 6,044,705 by A.P. Neukermans et al, which
discloses a different approach to manufacturing of pivoting microplatform
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devices making use of a stress-free semiconductor layer of silicon. The
epitaxial silicon layer with a thickness ranging from less than one to tens of
micrometers is grown on the etch stop layer deposited on the Si wafer.
Also known in the art, there are US Patent Application 2001/0044165 A1 by
S.B. Lee et al. and US Patent 6,353,492 B2 by R.W. McClelland, which
disclose pivoting microplatform devices made entirely from monocrystalline
silicon wafers by the deep etching technique.
Application of silicon in the form of polished wafers or epitaxial layers
deposited on silicon wafers allows to alleviate some limitations associated
with the thin film technology. Silicon in this form is light, strong and
stiff,
yielding rigid microplatforms with low moment of inertia. It also yields a
wide
range of microplatform thicknesses from tens to hundreds of micrometers.
Silicon wafers can be polished to provide excellent surface quality (i.e. very
low roughness) and flatness. They will reflect radiation effectively when
covered with appropriate coatings. On the other hand, patterning of silicon
wafers may be a limiting factor in terms of minimum feature size or
geometrical form especially if the anisotropic wet etching technique is
applied.
Moreover, the microdevices equipped with movable monocrystalline silicon
microplatforms are typically of hybrid construction. They consist of at least
two
different parts, one comprising the microplatform and the other one performing
a function of the supporting base equipped with electrodes and contact pads
for actuation of the microplatform. Fully monolithic devices are difficult to
implement and are mostly formed by the competing thin film technology.
The following United States Patents disclose other devices suffering from the
same drawbacks as described above: 5,083,857 (L.J. Hornbeck); 5,212,582
(W.E. Nelson); 5,233,456 (W.E. Nelson); 5,312,513 (J.M. Florence et al.); and
5,789,264 (J.H. Chung).
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SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for making a
microdevice equipped with a movable microplatform that overcomes the
above-identified drawbacks of the prior art devices. In particular, a
preferred
microdevice according to the present invention can have improved
mechanical strength, rigidity, low deformation, and high planarity. The
microdevice may also be fully monolithic.
According to the present invention, there is provided a process for making a
microdevice, comprising the steps of:
a) providing a base member;
b) selectively electroforming at least one support member for
supporting a microplatform with respect to the base member;
c) selectively electroforming the microplatform; and
d) forming at least one flexible hinge member for hingedly connecting
the microplatform to said at least one support member and allowing relative
movement of the microplatform with respect to said at least one support
member.
According to another aspect of the present invention, there is provided a
microdevice comprising:
a base member;
at least one support member mountably connected to the base
member, said at least one support member being selectively electroformed
according to a selective electroforming process;
at least one hinge member mountably connected to said at least one
support member; and
a microplatform hingedly connected to said at least one hinge member
for allowing relative movement of the microplatform with respect to said at
least one support member, the microplatform being selectively electroformed
according to a selective electroforming process.
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Other objects, advantages and features of the present invention will become
more apparent upon reading of the following non-restrictive description of
preferred embodiments thereof, given by way of example only with reference
to the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1A is a side section view along line A-A' of a microdevice shown in
Figure 2, according to a preferred embodiment of the present invention.
Figure 1A1 is a top view of a micropiatform with hinge members attached
thereto, of the microdevice shown in Figure 2, according to a preferred
embodiment of the present invention.
Figures 1A2 is top view of a microplatform with hinge members of a
microdevice according to another preferred embodiment of the present
invention.
Figure 1 B is a side section view similar to the one shown in figure 1A, of a
microdevice according to another preferred embodiment of the present
invention.
Figures 1 B1, 1 B2 and 1 B3 are top views of microplatforms with hinge
members attached thereto according to different preferred embodiments of
the present invention.
Figure 1 C is a side section view similar to those shown in figures 1 A and 1
B,
of a microdevice according to another preferred embodiment of the present
invention.
Figure 1C1 is a top view of the microplatform and hinge members shown in
Figure 1 C.
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Figure 2 is a perspective view of the microdevice shown in Figure 1A.
Figures 3A to 3L are side section views of various layers showing the steps
involved in a first preferred process of making a microdevice, according to a
preferred embodiment of the present invention.
Figures 4A to 4L are side section views of various layers showing the steps
involved in a second alternate process of making a microdevice according to a
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1A, 1 B, 1 C and 2, there are shown different types of
preferred embodiments of microdevices 1 according to the present invention.
Each of the illustrated microdevices 1 includes a base member and at least
one support member 4 mountably connected to the base member. As will be
explained below, the support member 4 is selectively electroformed according
to a selective electroforming process and there are typically two support
members 4 that are mounted on the base member. The microdevice 1 also
includes at least one hinge member 3 mountably connected to the support
member 4 and a microplatform 2 hingedly connected to the hinge member 3
for allowing relative movement of the microplatform 2 with respect to the
support member 4. The microplatform 2 is also selectively electroformed
according to a selective electroforming process.
Referring to Figures 3A to 4L, there is also illustrated a process for making
the
above microdevice 1. The process essentially involves the steps of:
a) providing a base member;
b) selectively electroforming at least one support member 4 for
supporting a microplatform 2 with respect to the base member;
c) selectively electroforming the microplatform 2; and
d) forming at least one flexible hinge member 3 for hingedly
connecting the microplatform 2 to the at least one support member 4 and
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allowing relative movement of the microplatform 2 with respect to the at least
one support member 4.
Referring now to Figures 3A to 3L, the process according to the present
invention is preferably realized according to a first embodiment, wherein;
step b) comprises the step of mountably connecting the at least one
support member 4 to the base member;
step d) is performed after step b) and before step c) and comprises the
step of mountably connecting the at least one hinge member 3 to the at least
one support member 4; and
step c) comprises the step of mountably connecting the micropiatform 2
to the at least one hinge member 3.
Referring to now Figures 4A to 4L, the process according to the present
invention is preferably realized according to a second alternate embodiment,
wherein:
step c) is performed before steps a), b) and d) and comprises the step
of selectively electroforming the microplatform 2 on a sacrificial substrate
20;
step d) is performed before steps a) and b) and comprises the step of
mountably connecting the at least one hinge member 3 to the micropiatform 2;
step b) is performed before step a) and comprises the steps of
mountably connecting the at least one support member 4 to the at least one
hinge member 3 and removing the sacrificial substrate 20; and
step a) comprises the step of mountably connecting the at least one
support member 4 to the base member.
The above first and second preferred processes will be explained in more
details herein below. Of course, several modifications may be effected thereto
as those skilled in the art will understand.
As explained above, the process according the present invention is based on
the selective electroforming technique (i.e, localized electroforming), which
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makes use of photolithographically patterned photo resist layers as precise
masks defining the regions on a given substrate where the materials are
electrolytically deposited. Generally, electroforming, as opposed to other
film
deposition techniques such as thermal evaporation or sputtering, offers
several advantages including: a broad range of deposited materials
(principally pure metals, metal alloys and organoceramic dielectrics), near
room temperature processing using relatively low-cost equipment and
facilities, high deposition rate and film thickness range from below 1 pm to
several hundred of micrometers, stress free films, and conformal or selective
deposition with excellent shape fidelity. The direct or pulse current
electroforming allows a precise control of the material properties, including
its
composition, crystallographic structure, texture and grain size. Moreover,
stacking of thin layers with different compositions can be obtained with
relative
ease. Typical list of electroformed materials include: Au, Cr, Cu, Ni, Zn, Ag,
Fe, Ni-Fe, In, PbSn, and organoceramics.
Modern photoresist materials offer selective photopatterning capabilities with
submicrometer resolution, and masking layer thicknesses from a fraction of 1
pm to over 100 pm. With respect to forming the microdevices 1 equipped with
movable microplatforms 2, the fabrication processes according to the present
invention offer a reliable manufacturing of mechanically solid supports for
the
microplatforms 2, as well as the manufacturing of these platforms with
thicknesses up to tens and even hundreds of micrometers which guarantees
their mechanics! strength, rigidity, low deformation, and high planarity. This
provides a unique opportunity for forming microdevices 1 with microplatforms
2 with lateral dimensions of hundreds or even thousands of micrometers and
a wide range of tilt angles (up to 90°) and displacements (several
micrometers). Moreover, the forming processes make possible the
manufacturing of microdevices being integrated parts of semiconductor
substrates equipped with integrated electronic circuits or microdevices which
can be in a hybrid fashion attached via soldering, gluing etc. to other
substrates made of glass, ceramic or semiconductor. This offers an enormous
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flexibility in designing functional devices optimized for particular
applications
and operational environment.
Referring now to Figures 1A to 2, there are schematically shown different
typical embodiments of microdevices 1 equipped with movable microplatforms
2. Figure 1A shows a microdevice 1 equipped with a pivoting microplatform 2
and torsion hinge members 3 (shown in Figures 1A1 and 1A2) supporting this
microplatform 2. Figure 1 B shows a microdevice 1 equipped with the
cantilever type microplatform 2 and flexure hinge members 3 (shown also in
Figures 1 B1, 1 B2 and 1 B3). Figure 1 C shows a microdevice 1 equipped with
the piston-like microplatform 2 and flexure hinge members 3 (also shown in
Figure 1 C1 ). Figure 2 shows a perspective view of the microdevice
illustrated
in Figure 1A and equipped wiih the pivoting microplatform 2. Each of the
microdevices 1 shown in Figures 1A, 1 B, 1 C and 2 comprises the following
basic parts: a movable microplatform 2, at least one hinge member 3
providing a suspension to the microplatform 2 as well as the restoring torque
for its movement, at least one support member 4 providing a support to the
microplatform 2 and the hinge members 3, and a base member. The base
member includes a substrate 5 providing a base for the at least one electrode
6 and contact pad 8 placed on the substrate 5 and supplying the electrical
field for the microdevices 1 making use of the electrostatic actuation. The
microdevice 1 also has a cavity 7 separating the microplatform 2 from the
substrate 5.
Referring to Figure 3A to 3L, there is illustrated a first preferred
embodiment
of a manufacturing process for making the monolithic microdevice 1 equipped
with a movable microplatform 2 that is depicted in Figure 2.
Figure 3A shows the rnicrodevice substrate 5 equipped with electrodes 6 and
metallic contact pads 8. This substrate 5 is typically a glass or ceramic
plate
or a semiconductor wafer equipped with an integrated electronic circuit for
control and powering of the microdevice 1. This substrate 5 is covered with a
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thin (typically below 1 pm) protective layer 9 typically made of Si02 or
Si3N4.
Openings 10 are provided in the protective layer 9 for accessing the metallic
(typically AI, Au) contact pads 8.
5 Figure 3B shows the manufacturing step of covering the substrate 5 with a
first metal seed layer 11. This seed layer 11 has typically a thickness of 0.1
to
0.15 prn and is made of metals such as Cu or Zn. This seed layer 11 is
typically deposited by thermal evaporation, sputtering or electroforming. The
seed layer 11 permits to apply electrical potential to the substrate 5 to
start the
10 electroforming process. Additional layers made of Ti or Cr with a thickness
below 0.1 pm may also be used with the other materials as the adherence
increasing layers.
Figure 3C shows the step of covering the substrate 5 with the first
photoresist
layer 12 and patterning of this layer 12 using the photolithographic
technique.
Various commercially available photoresist materials compatible with standard
electroplating baths such as Shipley 1800 series, SU-8, AZ 4562 and BPR
100 can be used. Thickness of this photoresist layer 12 will define the height
of cavity 7 underneath the microplatform 2, as shown in Figure 2. This height
may vary from 1 pm to hundreds of micrometers. In the photofithographic
patterning process, openings 13 are produced in the first photoresist layer
12.
Figure 3D illustrates the selective electroforming of the support members 4 in
the openings 13 of the first photoresist layer 12. These support members 4
are in electrical contact with the contact pads 8 of the substrate 5. The
preferred materials for the support members 4 are typically Ni and Ni-Fe
alloys. Typically, low internal stress and very uniform Ni deposits can be
obtained from nickel sulfamate baths continuously agitated and filtered to
less
than 3 ym. Commercial wafer electroplating stations, known in the art,
equipped with stationary or rotating cathodes with proper baffle arrangements
will allow to achieve such high quality nickel deposits. Typical applied
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currents, bath temperatures and pH levels are in the range 0.5-30 Adm-Z, 32-
60°C and 3.5-5 respectively.
In a typical selective electroforming operation, the substrate 5 or
sacrificial
substrate 20 are placed in a holder which allows electrical contact through
the
seed layers 11 or 21. This holder is then dipped in the electroplating bath so
that the substrate faces the anode consisting of the metal to be plated or a
platinized grid. A constant or pulsed current is then applied between the
anode and stationary or rotating cathode so that the electrochemical reduction
and consequently metal deposition can take place. The electroforming time is
proportional to the thickness of deposited metal. The wafer is then rinsed and
dried prior to subsequent processing steps.
Figure 3E shows deposition of a second metallic seed layer 14 similar to the
first seed layer 11. The second seed layer 14 required for electroforming of
the hinge members 3 material typically consist of the same material as the
first seed layer 11, i.e. Cu, Zn or AI and it is deposited using the thermal
evaporation and sputtering techniques. Its thickness is typically smaller than
the thickness of the first seed layer 11, i.e. below 0.1 pm. Figure 3E also
shows deposition usually by a spin coating method of a second photoresist
layer 15 and the photolithographic patterning of this second photoresist layer
15 in order to define the shape of the hinge members 3. Openings 16 in this
second photoresist layer 15 down to the second seed layer 14 will permit
electroforming of the hinge members 3.
Figure 3F shows the electroforming of the hinge members 3. The hinge
members 3 are typically made of materials having low Young's modulus and
high yield strength and relatively low stiffness such as Au in order to allow
free
movements of the microplatform attached to them. For electrolytic gold
plating, commercial cyanide-containing formulations used in the
microelectronics industry can be employed. Typical applied currents, bath
temperatures and pH levels are in the range 0.05-0.3 Adm-2, 43-60°C and
5.5-
7 respectively. It is preferable and most advantageous that the hinge
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members 3 be also selectively electroformed. However, those skilled in the art
will understand that the hinge members may be formed by using other
techniques such as the inorganic and organic thin film technology combined
with the etching technique.
Figure 3G shows removal of the second photoresist layer 15 and deposition
and patterning of the third photoresist layer 17 which will be used as a mask
for a selective electroforming of the microplatform 2. The second seed layer
14 protects the first photoresist layer 12 during removal, typically by
stripping
in a proper solution or by oxygen plasma ashing of the second photoresist
layer 15. The opening 18 in the third photoresist layer 17 will define the
shape
of the microplatform 2 while the thickness of the third photoresist layer 17
will
define the thickness of this microplatform 2.
Figure 3H shows the selective electroforming of the microplatform 2. This
microplatform 2 has to be stiff in order to maintain an undeformed shape.
Materials exhibiting high Young's modulus and low density such as Ni and Ni-
Fe alloys are selected for manufacturing of the microplatform 2. Thickness of
this microplatform 2 has to be properly selected taking into account its
lateral
dimensions and the requirements for undeformed shape and low residual
stress as well as low surface roughness. This thickness may vary from few to
several tens of micrometers, typically. The metallic microplatform 2 is in the
electrical contact with the contact pads 8 via the conducting support members
4 and the hinge members 3. At this stage, a deposition and patterning of an
additional highly reflective optical layer on the upper surface 19 of the
microplatform 2 can optionally be performed (not shown in Figure 3H).
Moreover, manufacturing of an additional particular functional element such
as a diffraction grating can also be performed at this stage.
Figure 31 shows an optional step of polishing the upper surface 19 of the
microplatform 2 to reduce its rugosity and thus to increase its reflectivity
of
radiation. This manufacturing step may be necessary if very thick
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microplatforms are produced (over 50 pm) and the microdevice application
requires efficient and low-loss reflection of electromagnetic radiation from
the
movable microplatform.
Figure 3J shows the step of removal of the third photoresist layer 17 by the
wet stripping or oxygen plasma ashing techniques.
Figure 3K shows the step of selective removal of part of the second seed
layer 14 not protected by the hinge member 3 material and the microplatform
2 material. A wet isotropic etching is typically performed and the etching
solution should not attack the materials of the hinge members 3 and the
microplatform 2. Figure 3K also shows, after removal of the second seed layer
14, the removal of the first photoresist layer 12. This processing step is
carried
out in a proper solution not attacking the other materials of the microdevice
1
or by the plasma ashing in the oxygen containing atmosphere.
Figure 3L shows the final step of removal of the first seed layer 11 from the
surface of the substrate 5 as well as the residue of the second seed layer 14
from the microplatform 2 and the hinge members 3. This completes the
liberation of the microplatform 2, the hinge member 3, and the support
members 4. The etching solution for removal of the seed layers 11 and 14
should not attack other materials of the microdevice 1. This final step also
fully
defines the height of the cavity 7 below the microplatform 2 allowing a free
movement of this microplatform 2 supported by the hinges 3 and the support
members 4.
Referring to Figures 4A to 4L, there is shown a second preferred embodiment
of a manufacturing process for making hybrid microdevices 1 equipped with
movable microplatforms 2.
Figure 4A shows a temporary or sacrificial substrate 20 covered with the first
seed layer 21 and the first photoresist layer 22. The preferred materials for
the
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sacrificial substrate 20 are glass and semiconductor wafers such as Si. The
preferred materials for the first seed layer 21 are Cu, Zn, and Al layers
typically having a thickness 0.1 -- 0.5 pm. Additional layers made of Ti or Cr
with a thickness below 0.1 pm may also be used with the other materials as
the adherence increasing layers. Ali these layers are typically deposited by
the thermal evaporation or sputtering techniques. The sacrificial substrate 20
is used to build a partial microdevice equipped with a movable microplatform 2
before transferring this partial microdevice and attaching it to a permanent
substrate 5 so that it becomes the final microdevice 1. The first seed layer
21
is used to achieve the electroforming of the microplatform 2. It is also used
as
a sacrificial layer for attaching the partial microdevice during build-up to
the
temporary substrate 20. The first photoresist layer 22 is patterned to define
the shape of the microplatform to be electroformed in the opening 23 in the
first photoresist layer 22. Rugosity of the upper surface 24 of the temporary
substrate 20 will define the surface quality of the microplatform 2 to be
built on
the temporary substrate 20. An optional step (not shown) of deposition and
patterning of an additional highly reflective optical layer potentially having
grating or other optical structures can be performed at this stage, on the
first
seed layer 21 and prior to deposition of the first photoresist layer 22.
Figure 4B shows the step of electroforming of the microplatform 2. This
microplatform 2 may have the same specifications as the one described with
reference to Figure 3H.
Figure 4C shows the deposition of the second seed layer 25 as well as
deposition and patterning of the second photoresist layer 26. The openings 27
in the second photoresist layer 26 will define the shape of hinge members.
Figure 4D shows electroforming of the hinge members 3 which may have the
same specifications as the hinge members 3 described with reference to
Figure 3F.
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Figure 4E shows the removal of the second photoresist layer 26 by the wet
stripping or oxygen plasma ashing as well as deposition and patterning of the
third photoresist layer 28. The openings 29 in this third photoresist layer 28
will define the shape of the support members 4.
5
Figure 4F shows the step of electroforming of the support members 4. The
support members 4 are not completely filling the openings 29 in the third
photoresist layer 28 thus permitting a subsequent selective electroforming of
other materials. The support members 4 may have the same specifications as
10 the support members 4 described with reference to Figure 3D. If the
fabricated microplatform 2 thickness can be kept significantly below 10 pm,
forming of the second seed layer 25 would not be necessary. In this case, the
first photoresist layer 22 could be removed after the electroforming of the
microplatform 2, then the photolithographic steps as well as the
electroforming
15 steps for manufacturing of the hinge members 3 and then the support
members 4 could be performed using the first seed layer 21. For thick
microplatforms 2, a non-uniform distribution of spinned photoresist could
appear if the planarizing first photoresist layer 22 is removed.
Figure 4G shows the selective electroforming of the soldering material 30
such as PbSn alloys or In the openings 29 thus completely filling these
openings 29. This soldering material 30 will be used for a permanent
attachment of the microdevice 1 to its permanent substrate 5. For tin-lead
solder electroplating, commercial methane sulfonic acid bath chemistries are
preferred due to their enhanced stability, high deposition rate, lower cost
and
environmental compatibility. Other commercial lead-free tin based plating
chemistries such as those used in wafer bump plating can also be employed.
Typical applied currents, bath temperatures and pH levels for eutectic
Pb37%Sn63% are in the range 5-12 Adm-2, 30-50°C and less than 2
respectively. Indium solder plating is best performed from an indium sulfamate
bath. Typical applied currents, bath temperatures and pH are in the range 1-5
Adm~2, 20-25°C and 1.5-2 respectively.
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Figure 4H shows the removal of the third photoresist layer 28 by the wet
stripping or oxygen plasma ashing down to the second seed layer 25.
Figure 41 shows the selective partial removal of the second seed layer 25 not
protected by the support members 4 and the hinge members 3 materials.
Figure 4J shows the removal of the first photoresist layer 22 by the wet
stripping or oxygen plasma ashing techniques.
Figure 4K shows the separation by wet etching of the microdevice 1 from the
sacrificial substrate 20. This separation is achieved by removal by wet
etching
of the first seed layer 21. At the same time the residue of the second seed
layer 25 now exposed is also removed in the same etching solution. This
precludes that the etching solution used is attacking both the second seed
layer 25 and the first seed layer 21 but not attacking other materials
present.
Figure 4L shows the final step of attaching the freestanding partial
microdevice to the permanent substrate 5 by making use, for example, of the
soldering material 30. The soldering material 30 is subjected to a reflow and
then brought in thermal and mechanical contact with the contact and soldering
pads 8 of the substrate 5 covered with the protective layer 9. Surface tension
of the molten soldering material 30 during the soldering of the partial
microdevice to the substrate 5 will help to align the support members 4 with
respect to the contact pads 8 of the substrate 5. Other methods for
attachment of the microdevice 1 to the permanent substrate 5 can also be
used including gluing or thermal bonding.
There is a possibility that the separation step illustrated in Figure 4K can
be
performed after completion of the attachment step shown in Figure 4L. This
may be quite suitable especially in the case when individual miniature devices
or partial microdevices are being manipulated in order to perform their
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attachment to the permanent substrate 5. This may not be the case when a
large array of partial microdevices having a form of a substantial
freestanding
pellicle is being manipulated for attachment.
As mentioned above, the microdevices 1 that are formed according to the
process of the present invention can provide mechanically solid support
members 4 and microplatforms 2, with thicknesses up to tens and even
hundreds of micrometers. These microdevices 1, when compared to the prior
art devices, have improved mechanical strength, rigidity, low deformation, and
high planarity. This provides a unique opportunity for forming microdevices 1
with microplatforms 2 with lateral dimensions of hundreds or even thousands
of micrometers and a wide range of tilt angles (up to 90°) and
displacements
(several micrometers). Moreover, tl-a proposed forming processes make
possible the manufacturing of microdevices 1 being integrated parts of
semiconductor substrates equipped with integrated electronic circuits or
microdevices which can be in a hybrid fashion attached via soldering, gluing
etc. to other substrates made of glass, ceramic or semiconductor. This offers
an enormous flexibility in designing functional devices optimized for
particular
applications and operational environment,
Although preferred embodiments of the present invention have been
described in the context of manufacturing a single microdevice equipped with
a movable microplatforrn, the same embodiments can be applied to
manufacturing in a single process of arrays of several microdevices at the
same time. Moreover, it is to be understood that the invention described in
detail herein and illustrated in the accompanying drawings is not limited to
these precise embodiments and that various changes and modifications may
be effected therein without departing from the scope or spirit of the present
invention.
