U.S. patent application number 09/749681 was filed with the patent office on 2001-07-12 for thin-film deposition apparatus.
Invention is credited to Takagi, Tomoko, Ueda, Masashi.
Application Number | 20010007246 09/749681 |
Document ID | / |
Family ID | 18503825 |
Filed Date | 2001-07-12 |
United States Patent
Application |
20010007246 |
Kind Code |
A1 |
Ueda, Masashi ; et
al. |
July 12, 2001 |
Thin-film deposition apparatus
Abstract
Object of the invention is to present a thin-film deposition
apparatus comprising a practical means of heating not by the
radiation heating, which is suitable for manufacture of solar
cells. To accomplish this object, a thin-film deposition apparatus
of the invention comprises a deposition chamber which is a vacuum
chamber where thin-film deposition is carried out on a substrate at
a deposition temperature higher than room temperature, a load lock
chamber which is a vacuum chamber where the substrate stays
temporarily while it is transferred from an atmosphere to the
deposition chamber, and a heat chamber which heats the substrate
under atmospheric pressure or a pressure higher than the
atmospheric pressure. The heat chamber, the load lock chamber and
the deposition chamber are connected directly or indirectly in this
order interposing a valve. The heat chamber has a mechanism to heat
the substrate supplying gas of a temperature higher than the room
temperature by forced convection. The heating mechanism heats the
substrate at a temperature higher than the deposition temperature.
A temperature-decrease prevention mechanism which prevents the
substrate temperature from decreasing lower than the deposition
temperature is provided in the load lock chamber.
Inventors: |
Ueda, Masashi; (Tokyo,
JP) ; Takagi, Tomoko; (Tokyo, JP) |
Correspondence
Address: |
KANESAKA AND TAKEUCHI
727 Twenty-Third Street South
Arlington
VA
22202
US
|
Family ID: |
18503825 |
Appl. No.: |
09/749681 |
Filed: |
December 28, 2000 |
Current U.S.
Class: |
118/724 |
Current CPC
Class: |
C23C 16/46 20130101;
C23C 16/509 20130101; C23C 16/54 20130101; C23C 16/4587
20130101 |
Class at
Publication: |
118/724 |
International
Class: |
C23C 016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 1999 |
JP |
11-374422 |
Claims
What is claimed is:
1. A thin-film deposition apparatus, comprising; a deposition
chamber which is a vacuum chamber where thin-film deposition is
carried out on a substrate at a deposition temperature higher than
room temperature; and a heat chamber connected directly or
indirectly with said deposition chamber; wherein said heat chamber
is one which heats said substrate under atmospheric pressure or a
pressure higher than said atmospheric pressure, and has a mechanism
to heat said substrate supplying gas of a temperature higher than
said room temperature by forced convection.
2. A thin-film deposition apparatus as claimed in claim 1, wherein;
said heating mechanism is one which heats said substrate at said
deposition temperature or a temperature higher than said deposition
temperature.
3. A thin-film deposition apparatus as claimed in claim 1 or claim
2, wherein; said substrate is used for manufacture of a solar
cell.
4. A thin-film deposition apparatus comprising; a deposition
chamber which is a vacuum chamber where thin-film deposition is
carried out on a substrate at a deposition temperature higher than
room temperature; a load lock chamber which is a vacuum chamber
where said substrate stays temporarily while said substrate is
transferred from an atmosphere to said deposition chamber; and a
heat chamber which heats said substrate under atmospheric pressure
or a pressure higher than said atmospheric pressure; wherein said
heat chamber, said load lock chamber and said deposition chamber
are connected directly or indirectly in this order interposing a
valve; and said heat chamber has a mechanism to heat said substrate
supplying gas of a temperature higher than said room temperature by
forced convection.
5. A thin-film deposition apparatus as claimed in claim 4, wherein;
said heating mechanism is one which heats said substrate at said
deposition temperature or a temperature higher than said deposition
temperature.
6. A thin-film deposition apparatus as claimed in claim 5, wherein;
a temperature-decrease prevention mechanism which prevents
temperature of said substrate from decreasing lower than said
deposition temperature is provided in said load lock chamber.
7. A thin-film deposition apparatus as claimed in claim 4, claim 5
or claim 6, wherein; said substrate is used for manufacture of a
solar cell.
Description
BACKGROUND OF THE INVENTION
[0001] The invention of this application relates to a thin-film
deposition apparatus suitably used for manufacture of solar cells.
Thin-film deposition apparatuses, which deposit a thin-film on a
substrate, are widely used for manufacture of electronic devices
such as LSIs (large-scale integrated circuits) and display devices
such as liquid crystal displays. In addition, thin-film deposition
apparatuses may be used for manufacture of solar cells.
[0002] Though solar cell technology has been made into practical
use in electronic calculators conventionally, now it is expected
very much as electric power generating technology under increase of
energy problems, as observed in the New Sunshine Program of the
MITI (Ministry of International Trade and Industry).
[0003] Solar cells are divided into two kinds. One is silicon solar
cell. The other one is compound semiconductor solar cell. Though
the silicon solar cell includes crystallized solar cells such as
single crystalline silicon solar cells and poly-crystalline silicon
solar sells, much effort has been done to make amorphous silicon
solar cell practical. This is because the semiconductor layers in
the amorphous silicon solar cell could be thinner because of its
higher light absorption coefficient, as well as its lower
manufacturing cost. In addition, the amorphous solar cell has no
worry of resource exhaustion since it utilizes gas sources,
contrarily the crystal silicon that is the resource of the crystal
silicon solar cell is limited since it is raw material.
[0004] In manufacture of the amorphous solar cell, it is necessary
to deposit a thin-film on a substrate made of glass, metals or
resin. Therefore, a thin-film deposition apparatus is used. In
manufacture of an amorphous silicon solar cell that is the typical
amorphous solar cell, technique of plasma enhanced chemical vapor
deposition (CVD) using gas mixture of silane and hydrogen is often
adopted. For example, a hydrogenated amorphous silicon film is
deposited on a substrate, by generating a HF discharge of the gas
mixture of silane and hydrogen and utilizing decomposition of
silane thereby.
[0005] In thin-film deposition apparatuses, temperature of a
substrate that is maintained at a specified value during
deposition, hereinafter called "deposition temperature", is often
higher than room temperature. In CVD, the deposition temperature is
set higher than the room temperature on purpose that the final
reaction could take place by thermal energy, or, the deposition
rate and the film quality could be enhanced. Therefore, process of
heating the substrate prior to the deposition is required.
[0006] A heat chamber in which radiation lamp-heaters are provided
is usually used for heating the substrate. The heat chamber is
connected airtightly with a deposition chamber interposing a valve.
The substrate is heated in the heat chamber up to the deposition
temperature in vacuum, and is transferred to the deposition chamber
for the film deposition. The reason why the radiation heating is
employed is that internal environment of the apparatus is often a
vacuum pressure of about 10 Pa or lower, where heat transfer by
conduction and convection cannot be expected.
[0007] A load lock chamber is often connected with the deposition
chamber so that the deposition chamber may not be opened directly
to the atmosphere. The load loch chamber is sometimes commonly used
as the heating chamber by providing radiation lamp-heaters in
it.
[0008] However, the above-described radiation heating has problems
as follows.
[0009] First of all, the radiation heating has a problem that the
running cost is high because heating efficiency of the radiation
heating is worse than other heating methods. In addition, when a
larger substrate is employed, which often happens in the solar cell
manufacture, increase of the apparatus cost becomes remarkable
because many longer radiation lamp-heaters must be provided.
Moreover, it is required to consider the matter of
energy-payback-time reduction, which means manufacturing a solar
cell using energy smaller enough than electric energy generated by
the solar cell itself. In this point, the radiation heating does
not satisfy this request because the energy consumption easily
increases in manufacturing.
[0010] In addition, the radiation heating has the problem of the
overshoot in case a feed-back-control of the substrate temperature
is carried out, because the substrate temperature rapidly rises up
when the substrate is begun to be irradiated. The substrate
temperature may settle down at a target value, after exceeding it
greatly. If the overshoot happens, much thermal stress is provided
to the substrate and at the worst the substrate might be deformed
or fractured, or stress might remain in the substrate.
[0011] In addition, it is important to improve accuracy of the
temperature control of the substrate during the heating for
securing the film quality and the reproducibility. However, it is
difficult to control the substrate temperature with high accuracy
in the radiation heating. For a high-accuracy control, it is
preferable to measure the substrate temperature by a radiation
thermometer because of its high-performance. Contrarily, it is
difficult to measure the substrate temperature by the radiation
thermometer during the radiation heating, because infrared rays
reflect on the substrate surface, other than radiant rays proper to
the substrate temperature.
[0012] It is also possible to measure the substrate temperature by
a thermocouple. However, in many cases, it is impossible to make
the thermocouple contact with the substrate. The thermocouple is
not suitable for high-accuracy temperature measurement. Especially,
when the substrate is placed in a vacuum, the measurement accuracy
of the thermocouple decreases, resulting from that temperature
difference may occur at the contact points of the substrate and the
thermocouple because the atmospheric temperature equalization by
the convection cannot be expected.
[0013] In addition, the radiation heating has an essential problem
in the solar cell manufacturing. In structure of solar cells, at
least one side of a photovoltaic layer needs an optical transparent
electrode. For example, in the manufacture of amorphous silicon
solar cells, the amorphous silicon film is often deposited on a TCO
(Transparent Conductive Oxide) film formed on the substrate. Here,
what is problem is that the TCO film has a characteristic of high
infrared-ray reflectivity. Therefore, it is essentially impossible
to heat the substrate having the TCO film on it by means of the
radiation heating with enough efficiency.
[0014] Other than the radiation heating, there is a method
utilizing the heat conduction. In this method, a plate with high
thermal conductivity is made contact with the substrate at its
backside. This plate is hereinafter called "backing plate". When
the backing plate is heated, the substrate is heated through heat
transfer by the conduction from the backing plate to the substrate.
However, this method cannot be employed in case the backing plate
is not used considering the energy-payback-time reduction. In
addition, it is difficult to make the baking plate contact with the
substrate sufficiently and uniformly. This brings disadvantage that
highly efficient and uniform heating is impossible to the backing
plate method.
[0015] In addition, by the backing plate method, the substrate is
heated only from its backside. As a result, temperature difference
in the direction along the substrate thickness easily occurs with
thick substrates. Worse, the substrate may suffer a thermal
deformation before it is heated up to a required temperature.
[0016] There may be another method where the substrate is heated
from both sides by radiation. Even if this method is adopted, it is
difficult to keep a balance of heating from both sides because the
TCO film that hardly absorbs infrared rays exists on one side of
the substrate. Particularly, if this method is carried out placing
the substrate under a vacuum pressure, it is almost impossible to
heat the substrate from both sides because heat transfer by the
convection and the conduction cannot be expected.
SUMMARY OF THE INVENTION
[0017] Object of this invention is to solve problems described
above.
[0018] To accomplish this object, the invention presents a
thin-film deposition apparatus, comprising; a deposition chamber
which is a vacuum chamber where thin-film deposition is carried out
on a substrate at a deposition temperature higher than room
temperature, and a heat chamber connected directly or indirectly
with the deposition chamber, wherein the heat chamber is one which
heats the substrate under the atmospheric pressure or a pressure
higher than the atmospheric pressure, and has a mechanism to heat
the substrate supplying gas of a temperature higher than the room
temperature by forced convection.
[0019] To accomplish this object, the invention also presents a
thin-film deposition apparatus, comprising; a deposition chamber
which is a vacuum chamber where thin-film deposition is carried out
on a substrate at a deposition temperature higher than room
temperature, a load lock chamber which is a vacuum chamber where
the substrate stays temporarily while the substrate is transferred
from the atmosphere to the deposition chamber, and a heat chamber
which heats the substrate under the atmospheric pressure or a
pressure higher than the atmospheric pressure, wherein the heat
chamber, the load lock chamber and the deposition chamber are
connected directly or indirectly in this order interposing a valve,
and the heat chamber has a mechanism to heat the substrate
supplying gas of a temperature higher than the room temperature by
forced convection.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 shows a front sectional view of a thin-film
deposition apparatus that is an embodiment of the invention.
[0021] FIG. 2 shows a side schematic view of a transfer mechanism
5.
[0022] FIG. 3 shows a side schematic view of a deposition chamber
1.
[0023] FIG. 4 shows a side schematic view of a heat chamber 3.
[0024] FIG. 5 shows a side schematic view of a load lock chamber
2.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0025] Preferred embodiments of this invention are described as
follows.
[0026] FIG. 1 shows a front sectional view of a thin-film
deposition apparatus as a preferred embodiment of this invention.
The apparatus shown in FIG. 1 comprises a deposition chamber 1
where a thin-film deposition is carried out on substrates 9 at a
deposition temperature higher than room temperature, a couple of
load lock chamber 2 and unload rock chamber 20 where substrates 9
stay temporarily while substrates 9 are transferred between
deposition chamber 1 and an atmosphere, a heat chamber 3 which
heats substrates 9 under a pressure higher than the atmospheric
pressure. Heat chamber 3, load lock chamber 2, deposition chamber 1
and unload rock chamber 20 are connected airtightly in this order
interposing valves 4. A transfer mechanism 5 which transfers
substrates 9 between the atmosphere and chambers 3, 2, 1, 20 is
provided.
[0027] Valves 4 open and close the openings provided at each
boundary between chambers 3, 2, 1, 20 for transferring substrates
9. As valves 4, a gate-valve is suitable. The gate-valve is the
valve used at a linear vacuum path and can make the path clear with
no obstacle remaining when the valve is opened.
[0028] Deposition chamber 1, load lock chamber 2 and unload rock
chamber 20 are vacuum chambers, which comprise a pumping system 11,
21, and 201, respectively. Though heat chamber 3 is an airtight
chamber, it has no pumping system.
[0029] The composition of transfer mechanism 5 is described using
FIG. 1 and FIG. 2. FIG. 2 shows a side schematic view of transfer
mechanism 5. Transfer mechanisms 5 is a kind of rack-and-pinion
mechanism. Transfer mechanism 5 is mainly composed of a rack board
51 provided horizontally with rack 50 underneath it and pinion
mechanism 52 that transfer rack board 51 to a horizontal direction,
i.e., vertical to the paper of FIG. 2. Each pinion mechanism 52 is
composed of a number of pinions 521 engaged with rack 50 and motors
522 that rotate each pinion 521 to move rack board 51 horizontally.
Linear guides 54 guiding the movement of rack board 51 are
provided.
[0030] As shown in FIG. 1 and FIG. 2, supports 53 are provided
uprightly on rack board 51. Each support 53 has hooks (not shown)
holding substrates 9. A number of pinions 521 are placed at certain
intervals along the transfer direction. As shown in FIG. 1, pinion
mechanisms 52 are provided at one side of the atmosphere, inside of
heat chamber 3, inside of load lock chamber 2, inside of deposition
chamber 1, inside of unload rock chamber 20 and the other side of
the atmosphere. Each pinion mechanism 52 is operated in order so
that rack board 51 can be transferred from one side of the
atmosphere to the other side through heat chamber 3, load lock
chamber 2, deposition chamber 1 and unload rock chamber 20.
[0031] As understood from FIG. 1 and FIG. 2, rack board 51 has a
rectangular shape, which length direction is in the transfer
direction. Substrates 9 also have a rectangular shape. Substrates 9
are held by supports 53, making its surface vertical and its length
direction along the transfer direction. As shown in FIG. 2, six
substrates 9 are arranged and held with one rack board 51 in this
embodiment. When rack board 51 is moved, six substrates 9 held by
supports 53 are transferred at the same time.
[0032] A part of transfer mechanism 5 may be provided outside
chambers 1,2,3,20. For example, a mechanism magnetically coupling
through a wall of chambers 1,2,3,20 can be adopted. An actuator
provided at the atmosphere drives a mechanism holding substrates 9
in chambers 1,2,3,20. This composition is preferable because
mechanisms that are easy to produce dusts or contaminant can be
provided outside chambers 1,2,3,20.
[0033] Next, the composition of deposition chamber 1 is described
using FIG. 1 and FIG. 3. FIG. 3 shows a side schematic view of
deposition chamber 1. This embodiment has a composition where an
amorphous silicon film is deposited in deposition chamber 1 by the
HF plasma CVD method. Here, frequencies between LF (Low Frequency)
and UHF (Ultra-High Frequency) are defined as HF (High Efficiency).
Specifically, deposition chamber 1 comprises HF electrodes 12
provided in deposition chamber 1, HF power supplies 13 which apply
HF power to HF electrodes 12 and a gas introduction system 14 which
introduces the gas mixture of silane and hydrogen into deposition
chamber 1.
[0034] HF electrodes 12 are elongated downward from the upper wall
of deposition chamber 1. HF electrodes 12 are antenna-like. Each HF
electrode 12 is a U-shaped metal rod. Both ends of each HF
electrode 12 are fixed airtightly with insulation block 15 provided
at the upper wall of deposition chamber 1. Both ends of HF
electrodes 12 are connected to HF power supplies 13.
[0035] When HF power supplies 13 apply the HF power to HF
electrodes 12 in state of the gas mixture of silane and hydrogen
introduced by gas introduction system 14, HF discharges are
generated in the gas mixture to form plasmas. Silane decomposes in
the plasmas, resulting in that the hydrogenated amorphous silicon
film is deposited on the surface of the substrate 9 placed on both
sides of HF electrodes 12.
[0036] Points greatly characterizing this embodiment are in the
composition of heat chamber 3. These points are described as
follows using FIG. 4. FIG. 4 shows a side schematic view of heat
chamber 3.
[0037] One point greatly characterizing this embodiment is that the
means of heating is provided not in load lock chamber 2 but in
separately provided heat chamber 3. The means of heating in this
embodiment is a heating mechanism 31 provided in heat chamber 3.
Another point greatly characterizing this embodiment is that
substrates 9 are heated at a pressure higher than the atmospheric
pressure utilizing forced convection.
[0038] Specifically, heat chamber 3 comprises valves 4 at each
boundary to the atmosphere and to load lock chamber 2. Pressurizing
gas supply system 32 that supplies compressed air or dry air into
heat chamber 3 to pressurize it is provided. Heating mechanism 31
in heat chamber 3 is composed mainly of heat source 311, baffle
plates 312, 313, 314, 315 that form an air flow path, and air
blower 316 blowing air through the air flow path for circulating
inside heat chamber 3.
[0039] Heat source 311 has high energy efficiency such as
combustion equipment used with a boiler. Heat source 311 produces
heat of 4000 joule/second, i.e., 6000 Kcal/hour, using City gas as
fuel. Instead of City gas, liquefied petroleum gas (LPG) may be
used as fuel. A centrifugal turbo fan is used as air blower 316.
Baffle plate 312 (hereinafter called the first baffle plate 312)
separates the region at which substrates 9 are placed and the
region at which heat source 311 is provided. Heat source 311 is put
between baffle plate 312 and baffle plate 313 (hereinafter called
the second baffle plate 313). Baffle plate 314 (hereinafter called
the third baffle plate 314) shuts the space between the upper end
of the first baffle plate 312 and the upper end of the second
baffle plate 313. Baffle plate 315 (hereinafter called the fourth
baffle plate 315) shuts the space between the bottom end of the
second baffle plate 313 and the wall of heat chamber 3.
[0040] Second baffle plate 313 is provided with a circulation hole
317. Air blower 316 is fixed on the sidewall of heat chamber 3 at
the same height as circulation hole 317. When air blower 316 is
operated, air heated by heat source 311 is inhaled into the upper
space through circulation hole 317.
[0041] Filter 33 is provided above the region where substrates 9
are placed. Filter 33 is flush with the third baffle plate 314 at
its bottom end. Filter 33 traverses the air flow path. Heated air
blowing from air blower 316 flows between the third baffle plate
314 and the upper wall of heat chamber 3, and reaches to the space
above filter 33. The heated air flows to substrates 9 through
filter 33 knocking on the wall of heat chamber 3, resulting in that
substrates 9 are heated.
[0042] Filter 33 is used to prevent substrates 9 from
contamination. A HEPA filter (High-Efficiency Particle Air filter)
with heat-resistance up to about 250.degree. C. is preferably used
as filter 33. A heat insulator is provided at the wall of heat
chamber 3 if necessary.
[0043] As designated by arrows in FIG. 4, the heated air heats
substrates 9, when it flows down from the upper space to the bottom
space. Then, the air reaches between the first baffle plate 312 and
the second baffle plate 313, knocking on the bottom wall of heat
chamber 3. Consequently, the air is heated again by heat source 311
and blows out from air blower 316. Rack board 51 and pinion
mechanism 52 are designed to pass the heated air sufficiently.
[0044] Substrates 9 are heated higher than the deposition
temperature by heating mechanism 31 as described. Showing an
example, in case the amorphous silicon film is deposited, the
deposition temperature is about 200.degree. C. In this case,
substrates 9 must be heated in heating chamber 3 up to about
230.degree. C. Heating mechanism 31 is designed so that the
temperature of the heated air can become about 250.degree. C. and
the flow rate of the heated air can be maintained at about 100
m.sup.3 per minute. With this composition, substrates 9 are heated
up to about 230.degree. C. within ten to fifteen minutes.
[0045] On the other hand, in this embodiment, a
temperature-decrease prevention mechanism 22 is provided in load
lock chamber 2. Temperature-decrease prevention mechanism 22
prevents the substrate temperature from decreasing lower than the
deposition temperature. This point is described using FIG. 1 and
FIG. 5. FIG. 5 shows a side schematic view of load lock chamber
2.
[0046] Radiation lamp-heaters 221 are employed as
temperature-decrease prevention mechanism 22 in this embodiment.
Radiation lamp-heaters 221 are rod-shaped filament lamps such as
halogen lamps. Radiation lamp-heaters 221 are posed horizontally
and aligned vertically. Radiation lamp-heaters 221 are held at both
ends together with holders 222 in which a feeding line is provided.
Units of radiation lamp-heaters 221 and a couple of holder 222 are
arranged between two substrates 9 and between a substrate 9 and the
wall of load lock chamber 2.
[0047] When the infrared absorption coefficient of substrates 9 is
poor such as in the case substrates 9 have a TCO film as described,
it is difficult to heat substrates 9 by radiation lamp-heaters 221.
However, in this embodiment, the heating in load lock chamber 2 is
supplementary because heating mechanism 31 in heat chamber 3 heats
substrate 9 higher than the deposition temperature. In other words,
heating is enough if the substrate temperature does not become
lower than the deposition temperature while substrates 9 stay in
load lock chamber 2. Considering this point, radiation lamp-heaters
221 are employed as temperature-decrease prevention mechanism 22 in
this embodiment.
[0048] Showing a more-detailed example, about fifteen lamps of
about 1 kW are used for each substrate 9 as temperature-decrease
prevention mechanism 22, in case that substrates 9 are heated up to
about 230.degree. C. in heat chamber 3, the deposition temperature
is 200.degree. C., and substrates 9 are placed in load lock chamber
2 for about nine minutes. In this example, the pressure in load
lock chamber 2 is about 1 Pa.
[0049] Heating quantity of radiation lamp-heaters 221 is decided
according to how high temperature substrates 9 are heated to in
heat chamber 3. In addition, it should be considered how much the
substrate temperature decreases by heat dissipation while
substrates 9 are transferred from heat chamber 3 to deposition
chamber 1, and how much heat substrates 9 receive from radiation
lamp-heaters 221 of temperature-decrease prevention mechanism 22 in
load lock chamber 2. It is preferable that the substrate
temperature is just the same as the deposition temperature when
substrates 9 reach deposition chamber 1.
[0050] Next, whole operation of the apparatus of this embodiment is
described.
[0051] To begin with, substrates 9 are set to rack board 51 at a
platform (not shown). Each support 53 holds substrates 9. After the
valve 4 on the atmosphere side of heat chamber 3 is opened,
transfer mechanism 5 is operated to transfer substrates 9 into heat
chamber 3. The pressure in heat chamber 3 is always maintained a
little higher than the atmospheric pressure by pressurizing gas
supply system 32.
[0052] After closing the valve 4, air blower 316 is operated to
cause the forced convection, thereby heating substrates 9. Heat
source 311 is operated all the time while the apparatus is
available. Air blower 316 may be operated all the time as well.
[0053] After heating substrates 9 up to a specified temperature, a
valve on pressurizing gas supply system 32 is closed. Substrates 9
are transferred to load lock chamber 2 after valve 4 between heat
chamber 3 and load lock chamber 2 is opened. After closing the
valve 4, load lock chamber 2 is pumped by pumping system 21 to a
specified vacuum pressure. Substrates 9 are transferred to
deposition chamber 1 after valve 4 between load lock chamber 2 and
deposition chamber 1 is opened.
[0054] Next, after the valve 4 is closed the deposition onto
substrates 9 is carried out in deposition chamber 1 as described.
Substrates 9 are transferred out to the atmosphere via unload lock
chamber 20 after the deposition. Substrates 9 are taken out from
each support 53 on rack board 51 at another platform (not
shown)
[0055] The apparatus of this embodiment described above brings a
merit that the energy efficiency is higher and the running cost is
cheaper because heating mechanism 31 provided in heat chamber 3
heats substrates 9 not by the radiation but by the forced
convection. Particularly, the apparatus of this embodiment is
suitable for the manufacture of solar cells for power supply
because it requires the energy-payback-time reduction.
[0056] Substrates 9 are heated sufficiently even if those infrared
ray absorption coefficients are poor as in case of the substrate
with the TCO film, because substrates 9 are heated not by the
radiation but by the forced convection. This point is another
reason why this embodiment is suitable for the manufacture of solar
cells.
[0057] Problems of the overshoot and the thermal deformation of
substrates 9 do not arise in this embodiment, because substrates 9
are not heated rapidly as in case of the radiation heating. In
addition, it is possible to measure the substrate temperature with
high accuracy by a radiation thermometer. Therefore, the
temperature control of substrates 9 can be carried out with high
accuracy.
[0058] The composition where substrates 9 are heated to a
temperature higher than the deposition temperature also contributes
to enhancing energy efficiency. It is possible to heat substrates 9
at a temperature lower than the deposition temperature in heat
chamber 3 and thereinafter heat substrates 9 up to the deposition
temperature in load lock chamber 2 or deposition chamber 1.
However, it is difficult to heat substrates 9 efficiently in load
lock chamber 2 or deposition chamber 1 because those are vacuum
chambers where the convection heating cannot be utilized.
Therefore, heating in load lock chamber 2 or deposition chamber 1
must be the radiation heating. As described, the radiation heating
has the low energy efficiency. The radiation heating of the
substrate with the TCO film is essentially impossible. Contrarily,
when substrates 9 are heated higher than the deposition temperature
in heat chamber 3 as in this embodiment, the radiation heating of
the low efficiency is not required. Therefore, even the substrate
with the TCO film can be heated sufficiently.
[0059] The merit of film quality improvement is brought from the
composition that substrates 9 are transferred to deposition chamber
1 via load lock chamber 2 after substrates 9 are heated to a
temperature higher than the deposition temperature in heat chamber
3. To heat substrates 9 in heat chamber 3 brings the significance
that adsorbed gas can be released sufficiently from substrates 9.
Gas such as water is adsorbed to the surface of substrates 9. If
the deposition is carried out in state that adsorbed gas such as
water has not been well released, adsorbed gas would be released
rapidly to contaminate the deposited film or to cause a structural
defect such as forming bubbles within it. When substrates 9 are
heated prior to the deposition, these problems are prevented since
adsorbed gas is well released in advance.
[0060] Now, how much quantity of adsorbed gas is released depends
on how high temperature substrates 9 are heated and how long the
temperature is kept. In this embodiment, substrates 9 are heated
higher than the deposition temperature in heating chamber 3 and
transferred to deposition chamber 1 via load lock chamber 2,
keeping almost the same temperature. Therefore, adsorbed gas is
well released from substrates 9 by the time when substrates 9
arrive at deposition chamber 1. Contrarily, if the adsorbed gas
release is carried out only by the heating in load lock chamber 2,
gas release is insufficient because high-temperature keeping time
gets shorter. In this case, substrates 9 need to stay longer in
load lock chamber 2 so that adsorbed gas can be well released,
resulting in that the productivity decreases and the running cost
increases. Therefore, this composition is not preferable.
[0061] Another merit that substrates 9 are not required to be
heated at so high temperature in heat chamber 3 is brought from the
composition that temperature-decrease prevention mechanism 22 is
provided in load lock chamber 2. If temperature-decrease prevention
mechanism 22 is not provided, there arises necessity to heat
substrates 9 at so high temperature calculating the temperature
decrease in load lock chamber 2. In this composition, it would take
longer time to heat substrates 9 in heat chamber 3. Otherwise,
heating mechanism 31 would be required to be larger size. The cost
of providing temperature-decrease prevention mechanism 22 and the
running cost in this embodiment possibly would be cheaper rather
than that.
[0062] Moreover, another merit that substrates 9 can be restrained
from contamination while those are transferred from heat chamber 3
to deposition chamber 1 is brought form the composition that heat
chamber 3 is a part of the apparatus, i.e., heat chamber 3 and
deposition chamber 1 are connected airtightly. If substrates 9 are
temporarily taken out from the apparatus while those are
transferred from heat chamber 3 to deposition chamber 1, substrates
9 may suffer from contamination such as adhesion of contaminants.
The possibility of contamination is low when heat chamber 3 is
connected with deposition chamber 1 directly or indirectly as shown
in this embodiment.
[0063] It is possible to employ a chamber layout of the
cluster-tool types where load lock chamber 2, heat chamber 3 and
deposition chamber 1 are provided around a transfer chamber in
which a transfer robot is provided.
[0064] It is also possible to employ the composition where
substrates 9 are heated just at the deposition temperature, though
those are heated higher than the deposition temperature in this
embodiment. The pressure in heat chamber 3 may be the same as the
atmospheric pressure. Still, the pressure higher than the
atmospheric pressure brings the advantage that contaminants would
not be introduced into heat chamber 3. Inert gas such as nitrogen
may be supplied into heat chamber 3 instead of compressed air or
dry air at a pressure higher than the atmospheric pressure.
[0065] A ceramic heater may be used as temperature-decrease
prevention mechanism 22 instead of radiation lamp-heaters 221. The
heating in load lock chamber 2 can be abolished by heating
substrates 9 in heat chamber 3 at a temperature higher enough than
the deposition temperature. A specified heat-insulation mechanism
may be used as temperature-decrease prevention mechanism 22 in load
loch chamber 2.
[0066] Other than the hydrogenated amorphous silicon film
deposition as described, the apparatus of the invention can carry
out another amorphous silicon film deposition such as amorphous
silicon fluoride film deposition, amorphous silicon carbide film
deposition, amorphous silicon germanium firm deposition and the
like. Phosphorus doped films or boron doped films also can be
deposited by the apparatus of the invention.
[0067] The apparatus of the invention can be used for manufacture
of liquid crystal displays or information storage disks other than
solar cells. For example, the composition of the heating in this
invention can be used for a thin-film deposition for a driver
electrode in a LCD. Especially, sufficient gas release is required
when an indium-tin-Oxide (ITO) film is deposited by sputtering on a
substrate with a color filter formed on it, because the color
filter involves much water. Therefore, the apparatus of the
invention that can carry out the gas release efficiently is
suitable.
[0068] The composition of deposition chamber 1 is optimized
according to a kind of deposition process. For example, a CVD not
by an inductive coupled plasma but by a capacitive coupled plasma
may be adopted. Physical depositions such as sputtering or ion-beam
deposition can be adopted as well.
* * * * *