Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
VACUUM DEPOSITION APPARATUS AND METHOD AND SOLAR CELL
MATERIAL
Technical Field
The present invention relates to vacuum deposition
apparatus and method and solar cell material.
Background Art
Known as vacuum deposition apparatuses for heating
substrates to deposit thin films thereon are low pressure
CVD and plasma CVD apparatuses and the like, using the
technique of chemical vapor deposition (CVD), and vacuum
evaporation, spattering, ionization deposition apparatuses
and the like, using the technique of physical vapor
deposition (PVD).
In the CVD using apparatuses among these apparatuses,
substrates heated to a predetermined temperature are
retained in a deposition chamber kept at a vacuum, and
source gas including elements which constitute film
material is fed onto the substrates, whereby desired thin
films are deposited on the substrates due to CVD by
chemical reactions in the vapor phase and on the
substrates. In such CVD, temperature of the substrates
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for deposition often has closer relationship with film
property than PVD and reactions in higher temperature tend
to be required. Therefore, it is especially important in
CVD to uniformly and quickly elevate temperature of the
substrates.
Recently, in the plasma CVD among the CVD methods, to
deposit films on a number of large-area substrates has
increased importance in industrial applications. Above
all, to deposit films on glass substrates has occupied an
important position in applications. Glass substrates tend
to be readily damaged when the substrates have uneven in-
plane temperature distributions; to quickly and
inexpensively elevate temperature of large-area substrates
with such property involves technique with higher level of
difficulty.
Thus, conventional vacuum deposition apparatuses are
inefficient because of usually dealing with only one or
two substrates at once; to concurrently treat with three
or more substrates by such apparatuses would result in
extreme increase in size of the apparatuses.
In a conventionally proposed vacuum deposition
apparatus of this kind comprises, as shown for example in
JP 2001-187332 A, a heating chamber for heating substrates
above a deposition temperature, a load lock chamber and a
deposition chamber for depositing thin films on the
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substrates, the chambers being airtightly connected in the
order named via gate valves, the substrates being heated
by forced convection in the heating chamber, the gas
passing through the heat source being fed in a circulating
manner by an air blower, whereby hot gas is fed to the
substrates to heat the same.
Furthermore, as shown in JP Patent 3211356, an
inline-type plasma CVD apparatus may comprise an
atmospheric heating furnace for preliminarily heating a
substrate, a load chamber for heating in a vacuum the
substrate introduced from the atmospheric furnace to a
predetermined temperature, a reaction chamber for
depositing film on the substrate and an unload chamber for
cooling the substrate, the furnace and the chambers being
arranged in series.
According to the above-mentioned JP 2001-187332 A,
the plural large-area substrates can be concurrently dealt
with without increasing the size of the apparatus, thereby
substantially improving the productivity in the operation
of depositing films on the substrates.
However, in said JP 2001-187332 A, it is difficult to
heat the whole surfaces of the substrates to an uniform
temperature in a short time. More specifically, in JP
2001-187332 A, heated hot gas is fluidized between the
substrates to heat the substrates by forced convection,
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the hot gas flowing in laminar flow in parallel with the
surfaces of the substrates. Heating through such laminar
flow may eventually obtain substantially uniform
temperature in the direction of the surfaces when
elevation in temperature of the substrates is completed;
however, during the process of elevation in temperature,
substantial nonuniformity in temperature tends to occur.
During the process of elevation in temperature by heating
with laminar flow and at an upstream side of the gas flow,
heat of the gas flowing closer to the objects to be heated
is transmitted to the objects, whereby the objects to be
heated are heated and the gas is cooled. Thus cooled gas
remains to be the laminar flow and flows downstream along
the objects to be heated; during such movement, the gas
robs heat from the hot gas flowing at positions away from
the objects to be heated (that is, heat is replenished to
the gas) and is heated again. Thus re-heated gas raises
the temperature of the downstream objects to be heated.
For these reasons, the temperature of the gas closer to
the objects to be heated is gradually lowered as the gas
flows downstream. To this end, the heating by the
downstream laminar flow is slower in temperature elevation
than that by the upstream one. Therefore, when the
objects to be heated are made from material such as glass
fragile to temperature gradient, they may be damaged
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during temperature elevation due to thermal deformation.
As mentioned above, heat transfer from the gas at
positions away from the objects to be heated to the gas
closer thereto has a great role in the heating through the
laminar flow. However, heat transfer in a direction
perpendicular to the gas flow in the laminar flow is
governed by diffusion and therefore is slow in velocity.
As a result, the rate of temperature elevation downstream
of the objects to be heated tends to be further lowered.
When the hot gas wide in width (or in the form of
slit) is fluidized along the substrates to heat the same,
deviation in gas flow rate in widthwise direction tends to
occur, which disadvantageously prolongs the time period
necessary for temperature elevation of the whole object to
be heated to the required temperature; if the temperature
gradient is remarkable during temperature elevation,
thermal deformation may disadvantageously damage the
objects to be heated.
In said JP Patent 3211356, the substrate is heated in
the vacuum to the predetermined temperature through
radiant heating using lamp heaters, so that it is
insufficient in heating efficiency and takes much time for
heating. Moreover, movement of the substrate is effected
by a stainless chain conveyor so that concurrent heating
of the plural substrates is difficult to carry out and
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fundamentally it can be heated only one by one, leading to
very poor productivity.
In said JP 2001-187332 A, the heating is effected at
atmospheric pressure so that usable as heat source is city
gas, kerosene or the like which has lower cost per unit
calorific value and which has lower amount of carbon
dioxide generated per unit calorific value; by contrast,
JP Patent 3211356 has to use electric energy because of
heating in the vacuum and therefore may be said to be a
heating method with greater environmental burden.
In the heating by the lamp heaters shown in JP Patent
3211356, used is near infrared radiation with high energy
density emitted from high-temperature heat source. When
such heat source with high energy density is used and
thermal capacity of the object to be heated differs
largely and locally, there is a possibility of greater
temperature nonuniformity in the direction of surface upon
completion of temperature elevation. For example, when
the thermal capacity of a holder holding the object to be
heated is small and the object to be heated has larger
thermal capacity, the temperature of the holder may be
abnormally increased when the object to be heated is
raised in temperature to a desired temperature. Moreover,
as generally known, radiating and reflectance ratios to
near infrared radiation substantially vary depending upon
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kind of material and upon surface status. Therefore, when
there is difference or change in surface status to
infrared radiation within the surface of the object itself
to be heated or between the object to be heated and the
holder, uniform heating with good repeatability cannot be
expected.
In view of the above, some embodiments of the invention have
as their object to carry out in a short period of time and with
high efficiency heating of substrates as pretreatment of vacuum
deposition formation thereon; uniform surface temperature
is retained during thermal elevation and after completion
of heating; moreover, the plural substrates are
concurrently heated to enhance productivity of solar cell
material or the like.
Summary of The Invention
Some embodiments of the invention are directed to a vacuum
deposition apparatus wherein substrates heated by a substrate
heater are introduced to a deposition chamber for film deposition,
said substrate heater comprising a heating chamber,
flattened plate nozzles arranged in the heating chamber so
as to be spaced apart from surfaces of the substrates
introduced into said heating chamber by required spacing,
each of said plate nozzles being provided with a gas
intake, and a heating gas induction device for guiding
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heating gas to the gas intakes of said plate nozzles, a
face plate of each of said plate nozzles facing the
corresponding substrate being formed with a plurality of
gas spout holes so as to heat the substrate through
impinging jet of the heating gas.
Thus, according to an embodiment of the invention, the
heating gas is discharged through the gas spout holes on the
plate nozzles so as to heat the substrates through the impinging
jet, whereby heating efficiency is enhanced to shorten
heating time for the substrates.
Generally speaking, when there is no target object
for impingement, gas jet flow conditions may be classified,
in the order of proximity to gas spout holes, into
potential core, transition and developed regions.
Depending upon to which region the substrate to be heated
is located, heat transfer rate thereof may vary. By
arranging the substrate up to the developed region near
the transition region, higher heat transfer rate may be
obtained. To the contrary, when the substrate is
positioned far away from gas spout holes, no higher heat
transfer rate may be obtained. The gas jet flow
conditions may be also related with size of gas spout
holes on the plate nozzle. The gas spout holes referred
to herein are openings through which heating gas jets
toward the substrate.
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Shape of the gas spout holes such as square or circle
may be selected depending upon design requirements;
provided that a representative size of the spout holes is
B, in some embodiments there is a relationship of H/B <
20 between this B and spacing (distance) H between the
respective gas spout holes to each other. The
representative size B is, for example, a side of a square
when openings with square shape are selected; it is a
diameter when round openings are selected. More generally,
the representative size is a size employed when Reynolds
number is determined which governs flow of the gas spout
holes.
When the ratio H/B is less than 20, then a heating
rate can be obtained which is industrially substantially
higher.
In heating using impinging jet, effected is local
heating around a stagnation point at a front of the gas
spout hole. Local heat input is moderated by lateral heat
transfer on the substrate, resulting in temperature
increase of the substrate as a whole and thermal
equalization of the substrate. With material such as
glass which may be damaged due to steep local increase of
temperature, great care is to be taken in this respect
when heating is made through impinging jet. Provided that
glass has enough thickness, then its in-plane heat
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transfer is substantially great so that nonuniformity in
glass in-plane temperature becomes smaller; alternatively,
increasing number density of the gas spout holes may
reduce nonuniformity.
In order to prevent the glass from being damaged,
provided that the substrate is glass with thickness t and
the distance between the respective gas spout holes to
each other is r, then some embodiments have the
relationship r/t < 20.
Moreover, face plates on both sides of the plate
nozzle may have gas spout parts, substrates being arranged
to face the face plates on both sides of the plate nozzle.
Furthermore, plate nozzles arranged oppositely to each
other with the substrate between may have gas intakes at
positions such that non-uniformity in gas spout amount due
to pressure gradients in each of the plate nozzles may be
balanced out. The plate nozzles may be comb-type nozzles
which are arranged in plural in the form of comb with the
substrates being arranged therebetween. The substrates
may be introduced while supported by a carriage, the
heating gas from the plate nozzles being introduced
through said carriage into the heating gas induction
device.
Since the plate nozzles are arranged oppositely to
each other with the substrate between and are provided
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with gas intakes at positions such that nonuniformity in
gas spout amount generated in each of the plate nozzles
due to pressure gradient may be balanced out, the
substrate can be heated by more uniform surface
temperature.
Since the heating gas is circulated through the
carriage to the heating gas induction device after it have
heated the substrate, stabilized are fluidization of the
heating gas and heating of the substrate.
A further aspect of the invention is a vacuum
deposition method which comprises arranging a substrate
heater to be connected to a deposition chamber,
introducing substrates into the substrate heater,
injecting heating gas from gas spout holes on face plates
of plate nozzles which are spaced apart from the
substrates by required spacing, heating the substrates by
jet heating, and introducing the substrates into the
deposition chamber for film deposition after the
substrates are heated to a uniform temperature.
The deposition method may be a plasma CVD method.
A still further aspect of the invention is solar cell
material produced by the above.
Thus, according to an embodiment of the invention, the
heating gas is introduced by the gas spout holes formed on the
plate nozzles and the substrates are heated by the impinging jet,
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so that heating efficiency can be enhanced to shorten heating time for the
substrates.
Accordingly, solar cell material may be produced highly efficiently.
In one particular aspect of the invention, there is provided a vacuum
deposition apparatus wherein substrates heated by a substrate heater are
introduced into a deposition chamber for film deposition, said substrate
heater
comprising a heating chamber, flattened plate nozzles arranged in the heating
chamber so as to be spaced apart from surfaces of the substrates introduced
into
said heating chamber by required spacing, each of said plate nozzles being
provided with a gas intake, and a heating gas induction device for guiding
heating
gas to the gas intakes of the plate nozzles, the substrates being arranged to
face
the opposite face plates of each of said plate nozzles, each of said face
plates
being formed with a plurality of gas spout holes for heating the substrates
through
impinging jet of the heating gas.
There is also provided a vacuum deposition method, comprising
arranging a substrate heater and connecting said heater to a deposition
chamber,
introducing substrates into the substrate heater to face the opposite face
plates of
each of the plate nozzles, injecting heating gas from gas spout holes on face
plates of plate nozzles which are spaced apart from the substrates by required
spacing, heating the substrates by impinging jet, and introducing the
substrates
into the deposition chamber for film deposition after the substrates are
heated to a
uniform temperature.
Solar cell material produced by such a method is also provided.
Brief Description of Drawings
Fig. 1 is a schematic plan view showing an overall layout of a
vacuum deposition apparatus according to an embodiment of the invention;
Fig. 2 is a sectional front view showing an embodiment of a
substrate heater in the vacuum deposition apparatus according to an embodiment
of the invention;
Fig. 3 is a side view of a carriage;
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Fig. 4 is a perspective view partly showing the carriage and rails;
Fig. 5 is an enlarged sectional view showing a part of a plate nozzle
shown in Fig. 2;
Fig. 6 is a perspective view for explanation of gas spout holes
formed on a face plate of the plate nozzle;
Fig. 7 is a partial sectional view showing a further embodiment of the
plate nozzles for heating the substrates;
Fig. 8 is a partial sectional view showing a still further embodiment of
the plate nozzles for heating the substrates;
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Fig. 9 is a sectional plan view showing the plate
nozzles which are arranged oppositely to each other with a
substrate between and have gas intakes formed on opposite
ends thereof; and
Fig. 10 is a diagram showing relationship of passage
of time with change of temperature of substrate in a
comparison between heating of substrate by impinging jet
according to an embodiment of the invention and heating of
substrate by conventional laminar flow.
Best Mode for Carrying Out the Invention
Embodiments of the invention will be described in
conjunction with the drawings.
Fig. 1 is a schematic plan view showing an overall
layout of a plasma CVD apparatus which is an embodiment of
the vacuum deposition apparatus according to the invention.
The plasma CVD apparatus comprises a substrate applied
part 1, a substrate heater 3 with plate nozzles 33, a load
lock chamber 6 with heat equalizers 4 and an evacuation
device 5, a deposition chamber 11 with inductive coupling
electrodes 7, an evacuation device 8, a source gas feeder
9 and a temperature controller 10, an unload lock chamber
13 with an ambient-air intake 2 and an evacuation device
12 and a substrate discharge part 14. Reference numerals
15a, 15b,'15c, 15d and 15e denote gate valves closable for
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airtightness; and 16, a carriage adapted to be moved while
vertically supporting a plurality of substrates 17.
A deposition operation on the substrates 17 supported
by the carriage 16 is carried out in the following manner.
The substrates 17 are vertically supported on the carriage
16 in the substrate applied part 1. In the embodiment
shown in Fig. 1, six substrates 17 are supported on the
carriage 16.
The carriage 16 with the substrates 17 supported is
admitted into the heater 3 with the gate valve 15a being
opened. Then, the gate valve 15a is closed and the
substrates 17 are uniformly heated to a predetermined
temperature by the action of the plate nozzles 33.
Then, the gate valve 15b is opened, and the carriage
16 is moved to the load lock chamber 6. Then, the gate
valve 15b is closed, and the load lock chamber 6 is
evacuated by the evacuation device 5 to a negative
pressure same as that of the deposition chamber 11, the
temperature of the substrates 17 being maintained to the
above-mentioned predetermined temperature by the heat
equalizer 4.
Thereafter, the gate valve 15c is opened and the
substrates 17 are moved to the deposition chamber 11.
Then, the gate valve 15c is closed and the source gas is
supplied by the source gas feeder 9 to deposit silicon
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films on the substrates 17 by the action of the inductive
coupling electrodes 7, the predetermined negative pressure
being maintained by the evacuation device 8 and the
temperature of the substrates 17 being maintained to said
predetermined temperature by the temperature controller 10.
After completion of the film deposition on the
substrates 17, the gate valve 15d is opened and the
substrates 17 are moved to the unload lock chamber 13 the
interior of which has been evacuated by the evacuation
device 12 to the negative pressure same as that of the
deposition chamber 11. After the substrates 17 are
discharged out to the unload lock chamber 13, the gate
valve 15d is closed.
Then, the ambient-air intake 2 is opened to raise the
pressure of the unload lock chamber 13 to the atmospheric
pressure and the gate valve 15e is opened to guide the
carriage 16 outside. The carriage 16 is moved to the
substrate discharge part 14 and the substrates 17 with
films deposited thereon and supported by the carriage 16
are taken out.
According to the vacuum deposition apparatus shown in
Fig. 1, heating of the substrates 17 and silicon
deposition on the heated substrates 17 can be conducted
substantially in sequence, so that productivity can be
enhanced and the plural substrates 17 supported on the
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carriage 16 can be concurrently heated and deposited with
silicon films, thereby attaining further enhanced
productivity.
In the above-mentioned plasma CVD apparatus of Fig. 1,
particulars of the substrate heater 3 will be described
which heats the substrates 17 to a predetermined
temperature in a short period of time and so as to have
uniform surface temperature.
First of all, before referring to the substrate
heater 3, the carriage 16 will be described. The carriage
16 comprises, as shown in Figs. 2-4, a rectangular support
base 20 movable via wheels 19 on rails 18a and 18b
arranged on an inner bottom of a heating chamber 23 which
constitutes the substrate heater 3. Front and rear sides
in the travel direction of the support base 20 have five
support posts 21 and 21', respectively, spaced apart from
each other by a required spacing in a lateral direction,
the posts 21 and 21' extending vertically and being fixed
oppositely to each other. The front and rear posts 21 and
21' leftmost in Fig. 4 and the posts 21 and 21' second-
leftmost in Fig. 4 support at their right and left side
surfaces, respectively, the substrates 17 via supports 22,
the two substrates 17 being arranged oppositely.
Similarly, the front and rear posts 21 and 21' third- and
fourth-leftmost and the front and rear posts 21 and 21'
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fifth- and sixth-leftmost have two of the substrates 17 in
opposed relationship, respectively. Thus, on the carriage
16, the opposing three pairs of or six substrates 17 are
arranged vertically.
The support base 20 has a longitudinally extending
rack 24 on its lower surface, said rack 24 being in mesh
with a pinion 25 carried by a shaft 26 which extends
through the heating chamber 23 to be connected to an outer
drive 27. Thus, the drive 27 is driven to rotate the
pinion 25 which in turn can move the carriage 16 via the
rack 24 along the rails 18a and 18b. Since the rails 18a
and 18b are cut off for arrangement of the gate valves 15a,
15b, 15c, 15d and 15e, the drive 27 and pinion 25 are
arranged for each of the chambers 6, 11 and 13 and the
carriage 16 has the plural wheels 19 so as to run over the
cuts of the rails 18a and 18b.
As shown in Fig. 2, the heating chamber 23 has in its
interior an upper partition plate 28 which divides off the
upper part of the carriage 16 and a side partition plate
29 which divides off one side (right side) in the travel
direction of the carriage 16, the side partition plate 29
being fixed at its upper end to the upper partition plate
28 and extending at its lower end adjacent to the support
base 20. The right rail 18b is in the form of laid-down
ladder as shown in Fig. 4 so as to provide openings 30 for
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gas distribution. The support base 20 of the carriage 16
which supports the substrates 17 is formed with gas
passages 36 so as to allow the heating gas, which flows
down between the substrates 17, to flow through downwardly.
Thus, in the heating chamber 23, a gas circulation passage
31 is provided which communicates between the substrates
17 on the carriage 16, below the carriage 16, right-lower
side of the side partition plate 29 and right-upper side
of the upper partition plates 28 and which constitutes a
part of a heating gas induction device 32.
Fixed to a bottom of the upper partition plate 28 at
positions between the oppositely supported substrates 17
on the carriage 16 are upper ends of plate nozzles 33 each
with a rectangular flat shape larger in area than each of
the substrates 17 and in parallel with the substrates 17,
the upper ends of the plate nozzles 33 constituting gas
intakes 34 for communication between the gas circulation
passage 31 above the upper partition plate 28 and
interiors of the plate nozzles 33. Thus, the plate
nozzles 33 are in the form of flat bags with the gas
intakes 34 being provided at their tops. In Fig. 2, the
three plate nozzles 33 are arranged in comb-like formation
on the upper partition plate 28 so as to correspond to
gaps each between each of the three pairs of opposing
substrates 17.
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Each face plate 33a of the flat bag-shaped plate
nozzle 33 facing the corresponding substrate 17 is formed
with, as shown in Figs. 2, 5 and 6, a plurality of gas
spout holes 35 for injecting and impinging the heating gas
vertically against a surface of the substrate 17, thereby
providing a gas spout part A. Any arrangement of the gas
spout holes 35 in this gas spout part A will do provided
that temperature distribution of the substrates 17 becomes
practically uniform; therefore, the gas spout holes may be
regularly arranged to have for example rectangular or
staggered arrangement; alternatively, they may be
irregularly arranged to have constant area density.
The heating gas induction device 32 has a partition
37 intermediately of the gas circulation passage 31. The
partition 37 is formed with an opening into which a
circular fan 39 driven by a drive 38 extend. Furthermore,
arranged between the partition 37 and the rail 18b with
the openings 30 in the gas circulation passage 31 are gas
heaters 40 for heating of the gas. Each of the gas
heaters 40 shown in Fig. 2 comprises a heat transfer tube
41 arranged in the gas circulation passage 31 below the
circulation fan 39, said heat transfer tube 41 being fed
via a control valve 42 with hot fluid so as to heat the
gas through heat exchange. In place of heating the gas
through the heat transfer tubes 41, for example,
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combustion cylinders may be arranged in the gas
circulation passage 31 so as to heat the gas through
combustion of fuel in the combustion cylinders; in this
case, fuel flow rate is controlled by the control valve 42.
Above the upper partition plate 28, there is provided a
filter 43 for high-temperature.
A temperature detector 44 is arranged to sense gas
temperature in the heating chamber 23 or preferably gas
temperature just above the upper partition plate 28. Also
arranged is a temperature controller 45 which receives
input from the temperature detector 44 to control the
control valve 42 so that the detected temperature may be
maintained to a predetermined constant value, whereby
heating of the gas by the gas heaters 40 may be controlled.
In Figs. 2 and 5, the face plates 33a on both sides
of the plate nozzle 33 are formed with the gas spout parts
A including the gas spout holes 35, and the substrates 17
are arranged to face the gas spout parts A, whereby only
one surface of each of the substrates 17 may be heated;
alternatively, as shown in Fig. 7, the gas spout part A is
provided only one of the face plates 33a of the plate
nozzle 33, whereby only one surface of each of the
substrates 17 may be heated. Alternatively, as shown in
Fig. 8, the gas spout part A is provided on the face
plates 33a on both sides of the plate nozzle 33, whereby
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the heating gas is injected from the gas spout holes 35 to
concurrently heat both the surfaces of the substrate 17.
As shown in Fig. 9 which is the sectional plan view,
in the plate nozzles 33 arranged oppositely to each other
with the substrate 17 between and having the gas spout
parts A at their surfaces facing the substrate 17, it is
preferable that the plate nozzles 33 have gas intakes 34
at positions such that nonuniformity in gas spout amounts
due to the pressure gradients in the respective plate
nozzles 33 may be balanced out. More specifically, the
plate nozzles 33 arranged oppositely to each other with
the substrate 17 between may have the gas intakes 34 which
are arranged at mutually (vertically or laterally)
opposite ends. In Fig. 9, (left) one of the plate nozzles
33 has the gas intake 34 top on the paper or figure while
the other (right) plate nozzle 33 has the gas intake 34
bottom on the paper or figure. Thus, the heat gas
introduced from the one gas intake 34 into the one plate
nozzle 33 and that introduced from the other gas intake 34
into the other plate nozzle 33 are mutually oppositely
fluidized to be injected through the respective gas spout
holes 35.
Mode of operation of the above embodiments will be
described.
In the structure of Fig. 2, the circulation fan 39 is
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driven by the drive 38 to fluidize the gas in the gas
circulation passage 31 from below to above while hot fluid
is fed to the heat transfer tubes 41 of the gas heaters 40
to heat the gas. The hot gas heated by the gas heaters 40
is fed by the circulation fan 39 to the filter 43 for
purification, and then is introduced via the gas intakes
34 into the respective plate nozzles 33 where it is blown
perpendicularly against the surfaces of the substrates 17
in an impinging manner via the plural gas spout holes 35
of the gas spouts A on the face plates 33a of the plate
nozzles 33. Thus, the substrates 17 are heated.
The heating gas blown to the substrates 17 to heat
the same flows down between the confronting substrates 17
and flows downstream through the gas passages 36 of the
support base 20, and introduced again into the gas heater
40 via the openings 30 of the rail 18b.
The temperature controller 45 to which the detected
temperature by the detector 44 above the upper partition
plate 28 is inputted controls the flow rate of the hot
fluid by the control valves 42, thereby controlling the
temperature of the heating gas introduced into the plate
nozzles 33 to be always to a predetermined constant value;
thus, the substrates 17 are always and surely heated to
the targeted or predetermined temperature. In place of
controlling the flow rate of the hot fluid fed to the gas
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heaters 40, the circulated amount of the heating gas
through the circulation fan 39 may be controlled to
control the heating temperature of the substrates 17.
As shown in Figs. 5, 7 and 8, the plate nozzles 33
blow the heating gas vertically against the surfaces of
the substrates 17 in an impinging manner through the
respective gas spout holes 35 of the gas spouts A, so that
the substrates 17 are heated with high efficiency through
the impinging jet produced by the impinge of the heating
gas.
Fig. 10 shows relationship of passage of time with
change in temperature of the substrate in a comparison
between a case (solid line) where, as shown in Figs. 5, 7
and 8, the heating gas is vertically blown against the
surface of the substrate 17 in an impinging manner to
thereby heat the substrate through the impinging jet and a
case (dotted line) where the substrate is heated by the
heating gas in creeping or laminar flow in parallel with
the substrate as in the prior art shown in said JP 2001-
187332 A. In Fig. 10, temperature change of the substrate
17 is qualitatively shown when the substrate is heated to
a target range, using the same heating gas flow rate.
As is clear from Fig. 10, in order to attain the
target temperature range, the heating (dotted line) in the
laminar flow will require longer time than the heating
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(solid line) by the impinging jet according to the
invention. Therefore, when the heating time is to be
shortened in heating in the laminar flow, supply of the
heating gas must be increased substantially, leading to
increase in running cost. Moreover, flowing of such great
amount of heating gas along the substrate 17 makes it
further difficult to adjust uniform widthwise flow rate of
the substrate 17, disadvantageously resulting in further
tendency toward nonuniform surface temperature of the
substrates 17.
As mentioned above, the gas spout holes 35 of the gas
spout parts A on the face plates 33a of the plate nozzles
33 blow the heating gas perpendicularly against the
surfaces of the substrates 17 in the impinging manner so
that the substrates 17 are heated by the impinging jet,
whereby the substrates 17 can be heated in a short time
period and with high efficiency.
Moreover, the gas spout holes 35 of the gas spouts A
on the face plates 33a are in an arrangement suitable for
uniform heating of the substrate 17 in its surface
direction so that the surface temperature of the
substrates 17 can be uniformly controlled with high degree
of accuracy.
In the embodiments of the invention, the gas spout
holes 35 are round. Moreover, as main conditions of the
CA 02524487 2005-11-01
experiments, their diameter B was set to be 3 mm and the
spacing H between the face plate 33a and the substrate 17
was set to 30 mm. While the diameter B was constant, the
spacing H was changed in a range of 15 mm to 150 mm so as
to measure the rate in temperature rise of the substrate
17. As a result, no substantial change was seen with the
spacing of 15 mm to 20 mm. With the spacing of 15 mm to
mm, once the rate of temperature rise was increased to
have a maximum vale; then with the spacing of more than 30
mm, temperature rising rate was lowered. With the spacing
of 60 mm, the temperature rising rate was lowered to 60%
of the maximum. Similar experiments were carried out with
the diameter of the gas spout holes 35 being 2 mm; then,
with the spacing of more than 40 mm, temperature rising
rate was violently lowered.
It is generally said that when heating is effected by
impinging jet, heat transfer coefficient is complexly
varied depending upon spacing H, diameter B, flow rate and
the like so that heat transfer coefficient cannot be
uniformly described. However, these experiments revealed
that when industrially applicable conditions such as flow
rate are added and the ratio H/B is retained below 20,
then the substrates 17 can be speedy elevated in
temperature.
Moreover, according to the present embodiments,
CA 02524487 2005-11-01
26
experiments were effected with the gas spout holes 35
having the pitch r of 35 mm and arranged in square
arrangement, glass with thickness of 4 mm being used as
substrates 17. Temperature difference was measured
between the stagnation point at the front of the gas spout
hole 35 and point farthest from the gas spout hole 35.
When the heating was carried out with the main conditions
of the experiments, the maximum temperature difference
between the respective points became 30 C during
temperature rising. It has been empirically known that
glass substrate has higher probability of being damaged
when in-plane temperature difference thereof exceeds 50 C.
Thus, it was confirmed that there is substantially no
probability of being damaged in the present embodiments.
However, it was found out that when the pitch of the gas
spout holes 35 is increased to more than 60 mm, then the
glass substrates will be damaged due to glass in-plane
temperature difference. Moreover, it was also deduced
that when thickness of the glass substrate is reduced to
less than 2 mm, then in-plane thermal transfer of the
glass substrate slows, resulting in damage of the glass
substrates.
With respect to the heating gas introduced into the
plate nozzle from the gas intake 34 at the upper end of
the bag-shaped plate nozzle 33, because of pressure
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27
variation between the upper and lower parts, the heating
gas amount injected from the lower gas spout holes 35 may
be small relative to the heating gas amount from the upper
gas spout holes 35; as a result, there may be a
possibility of temperature rise deviation between the top
and bottom of the substrate 17. However, in fact, it was
found out that such temperature deviation can be
substantially prevented. More specifically, in order to
make substantially equal the gas spout amount of the upper
gas spout holes 35 and that of the lower gas spout holes
35, it is effective to minimize pressure difference
between upstream and downstream sides of the plate nozzle
33; to this end, by designing the plate nozzle 33 to have
greater space volume, the gas spout amounts of the
upstream and downstream sides are made substantially equal,
thereby substantially removing the temperature deviation.
As shown in Fig. 9, when the plate nozzles 33
arranged oppositely to each other with the substrate 17
between have gas intakes 34 which are arranged mutually
opposite ends thereof, the pressure gradients in the plate
nozzles 33 are mutually reversely oriented and are
balanced out, so that sum of the heating gas spout amounts
from the left and right plate nozzles 33 arranged
oppositely to each other with the substrate 17 between is
uniform longitudinally (vertically in Fig. 9), whereby the
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substrates can be heated to uniform temperature.
The substrates 17 heated to the predetermined and
uniform surface temperature by the substrate heater 3 as
mentioned above are introduced to the load lock chamber 6
in Fig. 1 where its temperature is maintained by the heat
equalizer 4. Then, the substrates 17 are introduced into
the deposition chamber 11 for deposition of silicon films
while the substrates 17 are maintained to said
predetermined temperature by the temperature controller 10
in the deposition chamber 11. Thus, the silicon films are
deposited on the substrates 17 with their uniform surface
temperature being maintained, so that silicon films of
good quality are deposited on the substrates 17.
Thus, according to the above-mentioned vacuum
deposition apparatus, solar cell material of good quality
can be produced with high efficiency.
It is to be understood that the invention is not
limited to the above embodiments and that various changes
and modifications may be made without departing from the
scope of the invention. For example, it may be applicable
to any vacuum deposition apparatuses other than the plasma
CVD apparatus such as spattering apparatus, vacuum
evaporation apparatus or ionization deposition apparatus
which require heating of the substrates. Shape of the
plate nozzles may be varied variously. Any heating gas
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29
induction device other than that shown in the above-
mentioned embodiment may be employed.
Industrial Applicability
Heating of substrates, which is effected as
pretreatment of vacuum deposition treatment on the
substrates, can be effected in a short time period and
with high efficiency; during the temperature rising and
after completion of heating, uniform surface temperature
can be obtained; moreover, the plural substrates can be
heated concurrently, whereby a product such as solar cell
material of good quality can be produced with high
efficiency.
