U.S. patent application number 09/749329 was filed with the patent office on 2001-08-16 for apparatus for growing thin films.
Invention is credited to Kilpi, Vaino, Soininen, Pekka T..
Application Number | 20010013312 09/749329 |
Document ID | / |
Family ID | 8555822 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013312 |
Kind Code |
A1 |
Soininen, Pekka T. ; et
al. |
August 16, 2001 |
Apparatus for growing thin films
Abstract
The invention relates to an apparatus for growing thin films
onto the surface of a substrate by exposing the substrate to
alternately repeated surface reactions of vapor-phase reactants.
The apparatus comprises at least one process chamber having a
tightly sealable structure, at least one reaction chamber having a
structure suitable for adapting into the interior of said process
chamber and comprising a reaction space of which at least a portion
is movable, infeed means connectable to said reaction space for
feeding said reactants into said reaction space, and outfeed means
connectable to said reaction space for discharging excess reactants
and reaction gases from said reaction space, and at least one
substrate adapted into said reaction space. At least one loading
chamber is arranged to cooperate with said process chamber so as to
permit said reaction space or a portion thereof to be moved into
said process chamber and away from said process chamber and,
further, the operating pressure of the loading chamber is arranged
to be controllable independently from said pressure chamber.
Inventors: |
Soininen, Pekka T.;
(Helsinki, FI) ; Kilpi, Vaino; (Espoo,
FI) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
8555822 |
Appl. No.: |
09/749329 |
Filed: |
December 27, 2000 |
Current U.S.
Class: |
117/86 |
Current CPC
Class: |
C30B 25/14 20130101;
Y10T 117/10 20150115; C30B 25/08 20130101; Y10S 117/90 20130101;
C23C 16/45525 20130101; C23C 16/54 20130101; C23C 16/45544
20130101 |
Class at
Publication: |
117/86 |
International
Class: |
C30B 023/00; C30B
025/00; C30B 028/12; C30B 028/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 1999 |
FI |
19992798 |
Claims
What is claimed is:
1. An apparatus for growing thin films onto the surface of a
substrate by exposing the substrate to alternate surface reactions
of vapor-phase reactants, the apparatus comprising: at least one
process chamber having a substantially sealed structure; at least
one reaction chamber comprising a reaction space of which at least
a portion is movable, an inlet connectable to said reaction space
for feeding said reactants into said reaction space, and outlet
connectable to said reaction space for discharging excess reactants
and reaction gases from said reaction space; at least one substrate
located within said reaction space; and at least one loading
chamber which is in selective communication with said process
chamber so as to permit said reaction space or a portion thereof to
be moved from said loading chamber into said process chamber and
from said process chamber to said loading chamber.
2. The apparatus according to claim 1, where an operation pressure
within said at least one loading chamber can be controlled
independently from an operation pressure within said process
chamber.
3. The apparatus according to claim 1, wherein a door separates
said process chamber from said loading chamber, said door being
adapted to be movable in the interior of said loading chamber in a
direction substantially perpendicular to a backing surface of said
door.
4. The apparatus according to claim 3, wherein the door includes
supports that face said process chamber and are adapted to be moved
in the vertical direction so as to be capable of transferring said
reaction space or a portion thereof from said loading chamber to
said process chamber.
5. The apparatus according to claim 1, wherein the process chamber
and said loading chamber are separated from each other by a gate
valve.
6. The apparatus according to claim 1, wherein said outlet is
permanently mounted in said process chamber.
7. The apparatus according to claim 1, wherein said inlet is
moveable with said reaction space from said loading chamber to said
process chamber.
8. The apparatus according to claim 1, further including electrical
actuators configured to actuate movement of said reaction space,
said electrical actuators being located on an exterior side of said
process chamber and said loading chamber.
9. The apparatus according to claim 1, wherein said loading chamber
is adapted to operate a cooling station for said reaction
space.
10. The apparatus according to claim 1, wherein said loading
chamber is adapted to operate as a preheating station for said
reaction space.
11. The apparatus according to claim 1, wherein said loading
chamber is in selective communication with a plurality of process
chambers that are adapted to produce thin-film structures of
different types.
12. The apparatus according to claim 1, wherein said loading
chamber is in selective communication with a plurality of process
chambers that are adapted to produce thin-film structures of a same
type.
13. The apparatus according to claim 1, wherein said reaction
chamber is supported said process chamber with supports that are
adapted to substantially with a center point of said outlet.
14. A method for growing thin films onto the surface of a substrate
comprising: placing at least one reaction chamber into a loading
chamber; lowering the pressure in said loading chamber; moving said
at least one reaction chamber into a process chamber; exposing the
reaction chamber to alternating pulses of vapor-phase reactants
such that a substrate located within said reaction space is exposed
to alternating surface reactions of said vapor-phase reactants.
15. The method of claim 14, further comprising: placing an inlet to
said at least one reaction chamber into said loading chamber;
moving said inlet with said at least one reaction chamber into said
process chamber.
16. The method of claim 14, wherein moving said at least one
reaction chamber into said process chamber further includes placing
said at least one reaction chamber on an outlet of said reaction
space.
17. The method of claim 14, further comprising: removing said at
least one reaction chamber from said process chamber and placing
said at least one reaction chamber into said loading chamber;
pressurizing said loading chamber; removing said at least one
reaction chamber from said loading chamber.
Description
PRIORITY INFORMATION
[0001] This application claims the priority benefit under 35 U.S.C.
.sctn.119 to Finnish Patent Application No. 19992798, filed Dec.
28, 1999, the entire content of which is hereby expressly
incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an apparatus according for
growing thin films on a surface of a substrate. More particularly,
the present invention relates to an apparatus for producing thin
films on the surface of a substrate by subjecting the substrate to
alternately repeated surface reactions of vapor-phase
reactants.
Discussion of Related Art and Summary of the Invention
[0003] Conventionally, thin-films are grown using vacuum
evaporation deposition, the Molecular Beam Epitaxy (MBE) and other
similar vacuum deposition methods, different variants of the
Chemical Vapor Deposition (CVD) method (including low-pressure and
organometallic CVD and plasma-enhanced CVD) or a deposition method
of alternately repeated surface reactions called the Atomic Layer
Epitaxy (ALE) method or Atomic Layer Deposition (ALD).
[0004] In MBE and CVD methods, the thin film growth rate is
determined by the concentrations of the provided starting material
in addition to other process variable. To achieve a uniform
thickness of the layers deposited by these methods, the
concentrations and reactivities of starting materials must be
carefully kept constant on different surface areas of the
substrate. If the different starting materials are allowed to mix
with each other prior to reaching the substrate surface, as is the
case in the CVD method, for instance, a chance of their mutual
reaction arises. Then, a risk of microparticle formation already
within the infeed channels of the gaseous reactants is imminent.
Such microparticles generally have a deteriorating effect on the
quality of the deposited thin film. Therefore, the possibility of
premature reactions in MBE and CVD reactors, for instance, is
avoided by heating the starting materials not earlier than at the
substrate surfaces. In addition to heating, the desired reaction
can be initiated using, e.g., a plasma discharge or other similar
activating means.
[0005] In the MBE and CVD processes, the growth of thin films is
primarily adjusted by controlling the infeed rates of starting
materials impinging on the substrate. In contrast, the growth rate
in the ALE process is controlled by the substrate surface
qualities, rather than the starting material concentrations or flow
variables. The only prerequisite in the ALE process is that the
starting material is available in sufficient concentration to
saturate the surface of the substrate. The ALE method is described,
e.g., in FI patent publications 52,359 and 57,975 and in U.S.
patent publications 4,058,430 and 4,389,973. Furthermore, equipment
constructions suited to implement this method are disclosed in
patent publications U.S. 5,855,680 and FI 100,409. Apparatuses for
growing thin films are also described in the following
publications: Material Science Report 4(7) (1989), p. 261, and
Tyhjiotekniikka (Finnish publication for vacuum techniques), ISBN
951-794-422-5, pp. 253-261. These references are incorporated
herein by reference.
[0006] In the ALE growth method described in FI Pat. No. 57,975,
the reactant atoms or molecules are arranged to sweep over the
substrates, thus impinging on their surface until a fully saturated
molecular layer is formed thereon. Next, the excess reactant and
the gaseous reaction products are removed from the substrates with
the help of inert gas pulses passed over the substrates or,
alternatively, by pumping the reaction space to a vacuum before the
next gaseous pulse of a different reactant is admitted. The
succession of the different gaseous reactant pulses and the
diffusion barriers formed by the separating inert gas pulses or
cycles of vacuum pumping result in a thin film growth controlled by
the individual surface-chemical reactions of all these components.
If necessary, the effect of the vacuum pumping cycle may be
augmented by the inert gas flow. For the function of the process,
it is typically irrelevant whether the gaseous reactants or the
substrates are kept in motion; it only matters to keep the
different reactants of the successive reactions separate from each
other and to have them sweep successively over the substrate.
[0007] Most vacuum evaporators operate on the so-called
"single-shot" principle. In such an arrangement, a vaporized atom
or molecule can impinge on the substrate only once. If no reaction
with the substrate surface occurs, the atom/molecule rebounds or is
revaporized so as to hit the apparatus walls or the vacuum pump,
undergoing condensation therein. In hot-walled reactors, an atom or
molecule that collides with the process chamber wall or the
substrate can undergo revaporization and, hence, repeated
impingements on the substrate. When applied to ALE process
chambers, this "multi-shot" principle can offer a number of
benefits including improved efficiency of material consumption.
[0008] ALE reactions operating on the "multi-shot" principle
generally are designed for the use of a cassette unit in which a
plurality of substrates can be taken simultaneously into the
process chamber. In a modified arrangement, the substrates can be
placed unmountedly into the process space formed by a pressure
vessel, whereby the process space also serves as the reaction
chamber wherein the vapor-phase reactants are reacted with the
substrate surface in order to grow thin film structures. If a
cassette unit designed for holding several substrates is employed,
the reaction chamber is formed in the interior of the cassette
unit. Use of a cassette unit shortens the growth time per substrate
in respect to single-substrate cycling, whereby a higher production
throughput is attained. Furthermore, a cassette unit arranged to be
movable into and out from the process chamber can be dismantled and
cleaned without interrupting the production flow because one
cassette unit can be used in the process chamber while another one
is being cleaned.
[0009] Batch processing is preferred in conventional ALE thin film
processes because of the relatively slow production pace of the ALE
method relative to other thin film growth techniques. The overall
growth time per substrate of a thin film structure can be reduced
in a batch process to a more competitive level. For the same
reason, larger substrate sizes are also preferred.
[0010] In the deposition of thin films, the goal is to keep the
process chambers continually running under controlled process
conditions as to the temperature, pressure and other process
parameters so that particulate matter of the ambient air and other
chemical impurities cannot reach the substrates. Additionally, this
arrangement eliminates the heating/cooling cycles that impair the
reliability of process chambers and are time-consuming. Generally,
a separate loading chamber is employed that is continually kept
under a vacuum and to which the reactors are connected. Substrate
loading thereto and unloading therefrom is accomplished by taking
both the process chamber and the loading chamber to a vacuum, after
which a valve between both chambers is opened and a robotic arm
adapted into the loading chamber removes the processed substrate
and loads a new substrate into the process chamber. Subsequently,
the valve is closed and the process may be started after the
substrate and the process chamber have attained the proper process
conditions. Next, the processed substrate is moved via another
controllable valve from the loading chamber to an air lock pumped
to a vacuum, after which the valve is closed. Subsequently, the air
lock can be pressurized, whereby the substrate can be removed from
the system via a third valve opening into the ambient space. The
new substrate to be processed is taken in the same fashion via the
loading chamber into the process chamber.
[0011] Currently, process apparatuses equipped with this type of a
loading chamber are available for single substrates only and they
are not suited for accommodating heavy substrate cassette units.
Depending on the batch and substrate size, such cassette units may
weigh up to 200 kg, whereby devices designed for their handling
must have a sturdy construction. Moreover, the lubrication of
bearings and other similar components of the transfer means is
problematic, because the lubricant required herein may affect the
structure of the thin film to be grown.
[0012] The large cassette units used in conventional ALE deposition
processes are assembled outside the process apparatus, after which
the process chamber is opened and the cassette units are
transferred as assembled entities into the process chamber. In the
process chamber, the cassette unit is heated typically for 1-4
hours, processed for 2-4 hours and cooled up to ten hours depending
on the cassette unit size. Furthermore, the assembly/disassembly of
the cassette unit is a time-consuming operation. The ratio of the
processing time vs. the work time required for other operations
becomes even more disadvantageous when thin films of extremely
shallow thickness (e.g., in the range 1-50 nm) are to be grown and
the growth period may take from one minute to a few minutes. Under
these circumstances, a major portion of the overall process cycle
time in regard to the actual thin film growth period is lost in
heating/cooling the reaction chamber structures, pressurizing the
reactor, disassembling and reassembling the reaction chamber,
pumping to a vacuum and reheating the system.
[0013] It is therefore an object of the present invention to
provide an novel type of ALE apparatus that reduces the amount of
time lost in heating/cooling the reaction chamber structures,
pressurizing the reactor, disassembling and reassembling the
reaction chamber, pumping to a vacuum and reheating the system.
[0014] Accordingly, one aspect of the invention involves equipping
the process chamber with a separate loading chamber that can be
pressurized independently from the process chamber so that the
loading of the cassette unit into the process chamber can be
carried out under a vacuum or a low-pressure inert gas atmosphere.
The loading chamber can be complemented with preheating/cooling
stations to shorten the overall processing cycle time. In a
modified arrangement, a plurality of process chambers can be
connected to each loading chamber. For moving the cassette unit,
the reactor is provided with a transfer mechanism capable of
accurately and sealably placing the cassette unit into its proper
position in the process chamber and removing the same
therefrom.
[0015] More specifically, the invention relates an apparatus that
comprises at least one process chamber having a tightly sealable
construction, at least one into the interior of said process
chamber adaptable reaction chamber including a reaction space of
which at least a portion is movable, infeed means connected to the
reaction space for feeding reactants into the reaction space and
outfeed means connected to the reaction space for discharging
excess reactants and reaction gases from the reaction space, and at
least one substrate adapted into said reaction space. The apparatus
further includes at least one loading chamber in which the reaction
space can be moved into and away from the process chamber and whose
operating pressure can be controlled independently from said
process chamber.
[0016] The invention offers significant benefits. For example, with
the help of the loading chamber, the cassette unit can be moved
into the process chamber and out therefrom so that the process
chamber is at all times kept under stabilized process conditions.
Hence, the steps of heating, pressurizing and pumping to a vacuum
need not be carried out for the entire process chamber, but
instead, for the substrates only, thus improving the efficiency of
process chamber vastly. Owing to the use of the loading chamber,
the interior parts of the process chamber are isolated from a
direct connection to the ambient air, whereby the number of
detrimental particles in the process chamber is reduced. The
transfer mechanism employed in the embodiment of the invention is
capable of moving relatively heavy cassette unit constructions and
locating them accurately in a desired position within the process
chamber. In another modified arrangement, a single loading chamber
can be connected to a plurality of process chambers adapted to
produce different kinds of thin film structures so that a plurality
of thin-film layers can be grown without the need for intermediate
transfer of the cassette units to ambient air atmosphere. This
reduces the risk of possible contamination and the required number
of thermal cycles.
[0017] It should be noted that certain objects and advantages of
the invention have been described above for the purpose of
describing the invention and the advantages achieved over the prior
art. Of course, it is to be understood that not necessarily all
such objects or advantages may be achieved in accordance with any
particular embodiment of the invention. Thus, for example, those
skilled in the art will recognize that the invention may be
embodied or carried out in a manner that achieves or optimizes one
advantage or group of advantages as taught herein without
necessarily achieving other objects or advantages as may be taught
or suggested herein.
[0018] It should also be noted that all of these embodiments are
intended to be within the scope of the invention herein disclosed.
These and other embodiments of the present invention will become
readily apparent to those skilled in the art from the following
detailed description of the preferred embodiments having reference
to the attached figures, the invention not being limited to any
particular preferred embodiment(s) disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In the following, the invention will be described in greater
detail with the help of exemplifying embodiments illustrated in the
appended drawings, in which
[0020] FIG. 1 is a partially sectional view of an embodiment of the
apparatus according to the invention; and
[0021] FIG. 2 is a layout diagram of another embodiment of the
apparatus according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] In the context of the present invention, the term "reactant"
refers to a gas or a vaporizable solid or liquid starting material
capable of reacting with the surface of the substrate. The ALE
method conventionally uses reactants selected from two separate
groups. The term "metallic reactants" is used of metallic compounds
which may even be elemental metals. Suitable metallic reactants are
the halogenides of metals including chlorides and bromides, for
instance, and organometallic compounds such as the thd complex
compounds. As examples of such metallic reactants are Zn,
ZnCl.sub.2, Ca(thd).sub.2, (CH.sub.3).sub.3Al and Cp.sub.2Mg. The
term "nonmetallic reactants" is used for compounds and elements
capable of reacting with metallic compounds. The latter group is
appropriately represented by water, sulfur, hydrogen sulfide and
ammonia.
[0023] In the present context, the term "protective gas" is used
when reference is made to a gas which is admitted into the reaction
space and is capable of preventing undesired reactions related to
the reactants and, correspondingly, the substrate. Such reactions
include e.g. the reactions of reactants and the substrate with
possible impurities. The protective gas also serves to prevent
reactions between substances of different reactant groups in, e.g.,
the infeed piping. In the method according to the invention, the
protective gas is also advantageously used as the carrier gas of
the vapor-phase pulses of the reactants. According to a preferred
embodiment, in which reactants of different reactant groups are
admitted via separate infeed manifolds into the reaction pace, the
vapor-phase reactant pulse is admitted from one infeed channel
while the protective gas is admitted from another infeed channel
thus preventing admitted reactants from entering the reactant
infeed channel of another reactant group. Examples of suitable
protective gases are inert gases such as nitrogen and noble gases,
e.g., argon. The protective gas may also be an inherently reactive
gas such as hydrogen gas selected to prevent undesirable reactions
(e.g., oxidization reactions) from occurring on the substrate
surface.
[0024] According to the invention, the term "reaction chamber"
includes both the reaction space in which the substrate is located
and in which the vapor-phase reactants are allowed to react with
the substrate in order to grow thin films as well as the gas
infeed/outfeed channels communicating immediately with the reaction
space. The channels serve to admit the reactants into the reaction
space (infeed channels) or to remove the gaseous reaction products
and excess reactants of the thin-film growth process from the
reaction space (outfeed channels). A substrate located in this kind
of reaction chamber is subjected to alternately repeated surface
reactions of at least two different reactants used for producing a
thin film. The vapor-phase reactants are admitted repetitively and
alternatingly, each reactant being fed separately from its own
source into the reaction chamber, where they are allowed to react
with the substrate surface for the purpose of forming a solid-state
thin film product on the substrate. Reaction products which have
not adhered onto the substrate and any possible excess reactant are
removed from the reaction chamber in the vapor phase.
[0025] Herein, the term "substrate surface" is used to denote that
surface of the substrate onto which the vapor-phase reactant
flowing into the reaction chamber impinges. In practice, said
surface, during the first cycle of the thin-film growing process is
constituted by the surface of a substrate such as glass, for
instance, or some other starting surface; during the second cycle
the surface is constituted by the layer formed during the first
cycle and comprising the solid-state reaction product which is
deposited by the reaction between the reactants and is adhered to
the substrate, etc.
[0026] The term "process chamber" is used when reference is made to
the space in which the thin film growth process is carried out and
which is isolated from its environment in a tightly sealable
manner. The reaction chamber is located in the process chamber and,
further, a single process chamber may incorporate a plurality of
reaction chambers.
[0027] Now referring to FIG. 1, an apparatus having certain
features and advantages according to the present invention is
illustrated. The apparatus construction includes a loading chamber
1, which also serves as a loading gate, whose wall is partially
sectioned in the Figure to elucidate the interior of the chamber 1.
The illustrated apparatus also includes a cold-walled process
chamber 2, which is illustrated with one wall partially sectioned
to elucidate the interior of the chamber. A cassette unit 3, which
contains substrates and acts as the process space, is shown resting
on supports, such as, for example, forks 4, which are preferably
mounted on a door 5 that, as will be explained below, separates the
loading chamber 1 from the process chamber 2. Above the cassette
unit 3 is adapted a sprayhead 16, which contains the reactant
infeed channels. In the process chamber 2 is a suction box 12,
which is preferably permanently mounted. The cassette unit 3 and
the sprayhead 16 can be mounted above the suction box 12. The
illustrated suction box 12 preferably houses the outfeed means of
reaction gases and excess reactants. The cassette unit 3, the
sprayhead 16 and the suction box 12 together form the reaction
chamber.
[0028] As mentioned above, the door 5 that also serves as the gate
valve between the loading chamber 1 and the process chamber 2. An
actuator mechanism 7 is adapted to move the door 5 within the
loading chamber 1. A lateral transfer mechanism 6 is located above
the cassette unit 3. In the illustrated arrangement, the later
transfer mechanism is adapted to grip the cassette unit 3 during
the lifting thereof by means of hooks. Both the actuator mechanism
7 and the top-side lateral transfer mechanism 6 of the door 5 can
use an eccentric cam 8 for actuating the lift movement and a ball
screw 9 for actuating the horizontal movement. One advantage of
these arrangements is a reliably tightly sealed implementation of
rotary motion feedthroughs 10. The electrical actuators 11 of the
transfer means 6, 7, 8, 9 can be located outside the loading
chamber 1 and the process chambers 2. Such an arrangement can avoid
subjecting the electrical actuators 11 to breakthrough problems
that may occur under a vacuum. Moreover, this arrangement makes the
maintenance of the actuators 11 easier.
[0029] In use, the cassette unit 3 with the substrates placed
therein and the sprayhead 16 are transferred via a door 15 into the
loading chamber 1. The door 15 is then closed. As the steps of the
ALE process are typically carried out at a pressure of about 0.1-30
mbar, the loading chamber 1 after the door 15 is closed is
preferably pumped to a pressure lower than the process pressure.
For this purpose, the loading chamber 1 is preferably equipped with
a separate vacuum pump dedicated to this task. After vacuum
pumping, the door 5 separating the loading chamber 1 from the
process chamber 2 is preferably opened with the help of the door
actuator mechanism 7. The door 5 preferably is arranged to move in
the interior of the loading chamber in a direction essentially
orthogonal to its seal surface. The lateral transfer mechanism 6,
which is preferably locked to the top of the cassette unit 3 by
means of hooks, transfers the cassette unit 3 with the sprayhead 16
onto vertically movable lift, such as, for example forks 4 mounted
on the side of the door 5 facing the process chamber 2.
Subsequently, the lateral transfer mechanism 6 is detached from the
cassette unit 3. The door can then be moved towards the process
chamber 2 and the cassette unit 3 with the sprayhead 16, which are
resting on the forks 4, can be lowered onto the suction box 12.
Preferably, the cassette unit 3 is lowered onto the suction box
when the door 5 is approximately 10-20 mm from a closed position of
the door 5. In such an arrangement, the forks 4 mounted on the door
5 are released before the end of the downward motion as the
cassette unit 3 rests on the suction box 12. This arrangement
relieves the door 5 from the additional load of the cassette unit 3
when it is closed. This makes it easier for the door 5 to mate with
its seat surface and thus impose a uniform linear pressure on the
seal 13 as required for an efficient seal. The seating step can be
further facilitated by providing a pivoting mount 14 for the door
5.
[0030] In the illustrated arrangement, the cassette unit 3, the
sprayhead 16 and the suction box 12 form a reaction chamber wherein
the vapor-phase reactants are allowed to react with the substrate
in order to grow thin films. The infeed channels in the sprayerhead
16 serve to admit the reactants into the reaction space between the
substrates and outfeed channels in the suction box 12 serve to
remove the gaseous reaction products and excess reactants of the
thin-film growth process from the reaction space . The substrates
located are preferably subjected to alternately repeated surface
reactions of at least two different reactants used for producing a
thin film. The vapor-phase reactants are admitted repetitively and
altematingly, each reactant preferably being fed separately from
its own source into the reaction chamber, where they are allowed to
react with the substrate surface for the purpose of forming a
solid-state thin film product on the substrate. Reaction products
which have not adhered onto the substrate and any possible excess
reactant are removed from the reaction chamber in the vapor phase.
Of course, to perform the above-described processes, the
illustrated apparatus preferably includes a suitably configured
controller.
[0031] After the processing steps are completed, the cassette unit
3 with the above-lying sprayhead 16 is preferably lifted off from
above the suction box 12 by means of the forks 4. Next, the door 5
is opened and the cassette unit 3 is moved on the forks 4 into the
loading chamber 1. The lateral transfer mechanism 6 grips the
cassette unit 3, preferably at its top, and transfers the cassette
unit 3 with the above-lying sprayhead 16 from the forks 4 to in
front of the door 15 of the loading chamber 1. After the door 5 is
closed, the loading chamber 1 can be pressurized and the cassette
unit 3 removed from the loading chamber 1. Removal of the cassette
unit 3 from the loading chamber 1 and loading of a new cassette
unit into the loading chamber 1 can be performed using, e.g., a
carriage equipped with a fork lift mechanism.
[0032] Thermal expansion of the suction box 12 and the cassette
unit 3 may impose thermal stresses on the suction box 12 if it is
supported to the process chamber 2 by. for example, its edges. The
magnitude of such thermal expansion may mount up to several
millimeters. These dimensional changes may complicate some process
steps, such as, for example, the positioning of the cassette unit 3
in the process chamber 2 during the automated unload/load steps.
Hence, the suction box 12 is preferably supported to the wall
structures of the process chamber 2 so that the center of the
support point coincides at least substantially with the center
point of the suction box 12. This provides the suction box 12 with
a greater degree of freedom to expand outward from its support
point and the positioning accuracy of the cassette unit 3 is
improved.
[0033] A modified arrangement of the present invention is
illustrated schematically in FIG. 2. In this arrangement, the
loading chamber 1 is made wider in its lateral dimension so as to
provide the loading chamber 1 with additional cassette unload sites
by extending the reach of the lateral transfer mechanism 6. Thus, a
single loading chamber 1 can be connected to a plurality of process
chambers 2. In such an arrangement, the process chambers 2 can be
adapted to produce, for example, different types of thin-film
structures or to run the different steps of a given thin-film
growth process. The use of the expanded loading chamber 1 offers a
shorter processing time per substrate and other salient
benefits.
[0034] In addition to those described above, the invention may have
additional modified arrangements. For example, a single process
chamber 2 may be adapted to house a plurality of reaction chambers.
Furthermore, the loading chamber 1 may be complemented with an
intermediate station serving to heat the cassette unit 3 prior to
its transfer into the process chamber 2 and/or to cool the cassette
unit 3 prior to its transfer of out from loading chamber 1. Such an
arrangement can improve the throughput capacity of the process
chamber 2. In another modified arrangement, the cassette unit 3 can
be transferred from the ambient air atmosphere into loading
chambers 1 having a plurality of unload positions for cassette
units 3 and respectively removed via separate pressurizing
chambers. In such an arrangement, there is no need for pressurizing
the large-volume loading chamber 1 in conjunction with the transfer
of the cassette unit 3.
[0035] In yet another modified arrangement, a gate valve can be
used in addition to or instead of a door 4 for sealing the process
chamber 2 from the loading chamber 1. In still yet another modified
arrangement, the cassette unit 3 need not have a construction that
must be moved as an entity. For example, the interior of the
cassette unit 3 may be provided with a holder into which the
substrates are placed. The holder can then moved from the loading
chamber 1 into the process chamber 2 and then away from the process
chamber 2.
[0036] It should be noted that certain objects and advantages of
the invention have been described above for the purpose of
describing the invention and the advantages achieved over the prior
art. Of course, it is to be understood that not necessarily all
such objects or advantages may be achieved in accordance with any
particular embodiment of the invention. Thus, for example, those
skilled in the art will recognize that the invention may be
embodied or carried out in a manner that achieves or optimizes one
advantage or group of advantages as taught herein without
necessarily achieving other objects or advantages as may be taught
or suggested herein.
[0037] Moreover, although this invention has been disclosed in the
context of certain preferred embodiments and examples, it will be
understood by those skilled in the art that the present invention
extends beyond the specifically disclosed embodiments to other
alternative embodiments and/or uses of the invention and obvious
modifications and equivalents thereof. In addition, while a number
of variations of the invention have been shown and described in
detail, other modifications, which are within the scope of this
invention, will be readily apparent to those of skill in the art
based upon this disclosure. For example, it is contemplated that
various combination or subcombinations of the specific features and
aspects of the embodiments may be made and still fall within the
scope of the invention. Accordingly, it should be understood that
various features and aspects of the disclosed embodiments can be
combined with or substituted for one another in order to form
varying modes of the disclosed invention. Thus, it is intended that
the scope of the present invention herein disclosed should not be
limited by the particular disclosed embodiments described above,
but should be determined only by a fair reading of the claims that
follow.
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