U.S. patent application number 14/359775 was filed with the patent office on 2014-11-13 for atomic layer deposition reactor for processing a batch of substrates and method thereof.
This patent application is currently assigned to PICOSUN OY. The applicant listed for this patent is Sven Lindfors, Pekka J Soininen. Invention is credited to Sven Lindfors, Pekka J Soininen.
Application Number | 20140335267 14/359775 |
Document ID | / |
Family ID | 48469186 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140335267 |
Kind Code |
A1 |
Lindfors; Sven ; et
al. |
November 13, 2014 |
ATOMIC LAYER DEPOSITION REACTOR FOR PROCESSING A BATCH OF
SUBSTRATES AND METHOD THEREOF
Abstract
The invention relates to a method that includes providing a
reaction chamber module of an atomic layer deposition reactor for
processing a batch of substrates by an atomic layer deposition
process, and loading the batch of substrates before processing into
the reaction chamber module via a different route than the batch of
substrates is unloaded after processing. The invention also relates
to a corresponding apparatus.
Inventors: |
Lindfors; Sven; (Espoo,
FI) ; Soininen; Pekka J; (Espoo, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lindfors; Sven
Soininen; Pekka J |
Espoo
Espoo |
|
FI
FI |
|
|
Assignee: |
PICOSUN OY
Espoo
FI
|
Family ID: |
48469186 |
Appl. No.: |
14/359775 |
Filed: |
November 22, 2011 |
PCT Filed: |
November 22, 2011 |
PCT NO: |
PCT/FI2011/051017 |
371 Date: |
May 21, 2014 |
Current U.S.
Class: |
427/126.4 ;
118/715; 118/719; 427/58 |
Current CPC
Class: |
C23C 30/00 20130101;
Y02E 10/50 20130101; C23C 16/45546 20130101; H01L 31/1876 20130101;
Y02P 70/50 20151101 |
Class at
Publication: |
427/126.4 ;
427/58; 118/715; 118/719 |
International
Class: |
C23C 30/00 20060101
C23C030/00 |
Claims
1. A method comprising: providing a reaction chamber module of an
atomic layer deposition reactor for processing a batch of
substrates by an atomic layer deposition process; and loading the
batch of substrates before processing into the reaction chamber
module via a different route than the batch of substrates is
unloaded after processing.
2. The method of claim 1, comprising: pre-processing the batch of
substrates in a pre-processing module of the atomic layer
deposition reactor; processing the pre-processed batch of
substrates by the atomic layer deposition process in the reaction
chamber module of the reactor; and post-processing the processed
batch of substrates in a post-processing module of the reactor,
where the pre-processing module, the reaction chamber module, and
the post-processing module are located in a row.
3. The method of claim 2, wherein said processing by an atomic
layer deposition process comprises depositing material on the batch
of substrates by sequential self-saturating surface reactions.
4. The method of claim 2, wherein said pre-processing module is a
pre-heating module and said pre-processing comprises pre-heating
the batch of substrates.
5. The method of claim 2, wherein said post-processing module is a
cooling module and said post-processing comprises cooling the batch
of substrates.
6. The method of claim 2, comprising transporting the batch of
substrates in one direction through the whole processing line, the
processing line comprising the pre-processing, reaction chamber and
post-processing modules.
7. The method of claim 2, wherein the pre-processing module is a
first load lock, and the method comprises pre-heating the batch of
substrates in a raised pressure in the first load lock by means of
heat transport.
8. The method claim 2, wherein the post-processing module is a
second load lock, and the method comprises cooling the batch of
substrates in a raised pressure in the second load lock by means of
heat transport.
9. The method of claim 1, comprising dividing the batch of
substrates into substrate subsets, and processing each of the
subsets simultaneously in the reaction chamber module, each subset
having its own gas flow inlet and gas flow outlet.
10. The method of claim 1, comprising depositing aluminum oxide on
solar cell structure.
11. An apparatus comprising: a reaction chamber module of an atomic
layer deposition reactor configured to process a batch of
substrates by an atomic layer deposition process; and a loading and
unloading arrangement allowing loading the batch of substrates
before processing into the reaction chamber module via a different
route than the batch of substrates is unloaded after
processing.
12. The apparatus of claim 11, comprising: a pre-processing module
of the atomic layer deposition reactor configured to pre-process
the batch of substrates; the reaction chamber module of the reactor
configured to process the pre-processed batch of substrates by the
atomic layer deposition process; and a post-processing module of
the reactor configured to post-process the processed batch of
substrates, where the pre-processing module, the reaction chamber
module, and the post-processing module are located in a row.
13. The apparatus of claim 12, wherein said processing by an atomic
layer deposition process comprises depositing material on the batch
of substrates by sequential self-saturating surface reactions.
14. The apparatus of claim 12, wherein said pre-processing module
is a pre-heating module configured to pre-heat the batch of
substrates.
15. The apparatus of claim 12, wherein said post-processing module
is a cooling module configured to cool the batch of substrates.
16. The apparatus of claim 12, wherein the apparatus is configured
for transporting the batch of substrates in one direction through
the whole processing line, the processing line comprising the
pre-processing, reaction chamber and post-processing modules.
17. The apparatus of claim 12, wherein the pre-processing module is
a first load lock configured to pre-heat the batch of substrates in
a raised pressure by means of heat transport.
18. The apparatus of claim 12, wherein the post-processing module
is a second load lock configured to cool the batch of substrates in
a raised pressure by means of heat transport.
19. The apparatus of claim 11, wherein the reaction chamber module
comprises partition walls or is configured to receive partition
walls dividing the batch of substrates into substrate subsets, each
subset having its own gas flow inlet and gas flow outlet.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to deposition
reactors. More particularly, but not exclusively, the invention
relates to such deposition reactors in which material is deposited
on surfaces by sequential self-saturating surface reactions.
BACKGROUND OF THE INVENTION
[0002] Atomic Layer Epitaxy (ALE) method was invented by Dr. Tuomo
Suntola in the early 1970's. Another generic name for the method is
Atomic Layer Deposition (ALD) and it is nowadays used instead of
ALE. ALD is a special chemical deposition method based on the
sequential introduction of at least two reactive precursor species
to a substrate. The substrate is located within a reaction space.
The reaction space is typically heated. The basic growth mechanism
of ALD relies on the bond strength differences between chemical
adsorption (chemisorption) and physical adsorption (physisorption).
ALD utilizes chemisorption and eliminates physisorption during the
deposition process. During chemisorption a strong chemical bond is
formed between atom(s) of a solid phase surface and a molecule that
is arriving from the gas phase. Bonding by physisorption is much
weaker because only van der Waals forces are involved.
Physisorption bonds are easily broken by thermal energy when the
local temperature is above the condensation temperature of the
molecules.
[0003] The reaction space of an ALD reactor comprises all the
heated surfaces that can be exposed alternately and sequentially to
each of the ALD precursor used for the deposition of thin films. A
basic ALD deposition cycle consists of four sequential steps: pulse
A, purge A, pulse B and purge B. Pulse A typically consists of
metal precursor vapor and pulse B of non-metal precursor vapor,
especially nitrogen or oxygen precursor vapor. Inactive gas, such
as nitrogen or argon, and a vacuum pump are used for purging
gaseous reaction by-products and the residual reactant molecules
from the reaction space during purge A and purge B. A deposition
sequence comprises at least one deposition cycle. Deposition cycles
are repeated until the deposition sequence has produced a thin film
of desired thickness.
[0004] Precursor species form through chemisorption a chemical bond
to reactive sites of the heated surfaces. Conditions are typically
arranged in such a way that no more than a molecular monolayer of a
solid material forms on the surfaces during one precursor pulse.
The growth process is thus self-terminating or saturative. For
example, the first precursor can include ligands that remain
attached to the adsorbed species and saturate the surface, which
prevents further chemisorption. Reaction space temperature is
maintained above condensation temperatures and below thermal
decomposition temperatures of the utilized precursors such that the
precursor molecule species chemisorb on the substrate(s)
essentially intact. Essentially intact means that volatile ligands
may come off the precursor molecule when the precursor molecules
species chemisorb on the surface. The surface becomes essentially
saturated with the first type of reactive sites, i.e. adsorbed
species of the first precursor molecules. This chemisorption step
is typically followed by a first purge step (purge A) wherein the
excess first precursor and possible reaction by-products are
removed from the reaction space. Second precursor vapor is then
introduced into the reaction space. Second precursor molecules
typically react with the adsorbed species of the first precursor
molecules, thereby forming the desired thin film material. This
growth terminates once the entire amount of the adsorbed first
precursor has been consumed and the surface has essentially been
saturated with the second type of reactive sites. The excess of
second precursor vapor and possible reaction by-product vapors are
then removed by a second purge step (purge B). The cycle is then
repeated until the film has grown to a desired thickness.
Deposition cycles can also be more complex. For example, the cycles
can include three or more reactant vapor pulses separated by
purging steps. All these deposition cycles form a timed deposition
sequence that is controlled by a logic unit or a
microprocessor.
[0005] Thin films grown by ALD are dense, pinhole free and have
uniform thickness. For example, in an experiment aluminum oxide has
been grown by thermal ALD from trimethylaluminum
(CH.sub.3).sub.3Al, also referred to as TMA, and water at
250-300.degree. C. resulting in only about 1% non-uniformity over a
substrate wafer.
[0006] General information on ALD thin film processes and
precursors suitable for ALD thin film processes can be found in Dr.
Riikka Puurunen's review article, "Surface chemistry of atomic
layer deposition: a case study for the trimethylaluminum/water
process", Journal of Applied Physics, vol. 97, 121301 (2005), the
said review article being incorporated herein by reference.
[0007] Recently, there has been increased interest in batch ALD
reactors capable of increased deposition throughput.
SUMMARY
[0008] According to a first example aspect of the invention there
is provided a method comprising:
[0009] providing a reaction chamber module of an atomic layer
deposition reactor for processing a batch of substrates by an
atomic layer deposition process; and
[0010] loading the batch of substrates before processing into the
reaction chamber module via a different route than the batch of
substrates is unloaded after processing.
[0011] In certain embodiments, the substrates comprise silicon
wafers, glass plates, metal plates or polymer plates.
[0012] In certain embodiments, the batch of substrates (generally
at least one batch of substrates) is loaded from a different side
of the reaction chamber module than the at least one batch of
substrates is unloaded from the reaction chamber module. The
loading and unloading may be performed on opposite sides of the
reaction chamber module or reactor. The loading and unloading may
be performed horizontally.
[0013] In certain embodiments, the method comprises:
[0014] pre-processing the batch of substrates in a pre-processing
module of the atomic layer deposition reactor;
[0015] processing the pre-processed batch of substrates by the
atomic layer deposition process in the reaction chamber module of
the reactor; and
[0016] post-processing the processed batch of substrates in a
post-processing module of the reactor, where the pre-processing
module, the reaction chamber module, and the post-processing module
are located in a row.
[0017] In certain embodiment, the modules have been integrated into
a single device. In certain embodiments, there is a continuous
route through the modules. In certain embodiments, the profile of
each of the modules is the same.
[0018] In certain embodiments, said processing by an atomic layer
deposition process comprises depositing material on the batch of
substrates by sequential self-saturating surface reactions.
[0019] In certain embodiments, said pre-processing module is a
pre-heating module and said pre-processing comprises pre-heating
the batch of substrates.
[0020] In certain embodiments, said post-processing module is a
cooling module and said post-processing comprises cooling the batch
of substrates.
[0021] In certain embodiments, the method comprises transporting
the batch of substrates in one direction through the whole
processing line, the processing line comprising the pre-processing,
reaction chamber and post-processing modules.
[0022] In certain embodiment, the modules lie in a horizontal row.
The transport mechanism through the modules is one-way through each
of the modules.
[0023] In certain embodiment, pre-processed substrates are loaded
into the reaction chamber module from one side of the module and
the ALD processed substrates are unloaded from the module from the
opposite side of the module. In an embodiment, the shape of the
reaction chamber module is an elongated shape.
[0024] In certain embodiments, the pre-processing module is a first
load lock, and the method comprises pre-heating the batch of
substrates in a raised pressure in the first load lock by means of
heat transport.
[0025] The raised pressure may refer to a pressure higher than
vacuum pressure, such as room pressure. Heat transport comprises
thermal conduction, convection and electromagnetic radiation. At
low pressures heat is transported through the gas space mostly by
electromagnetic radiation which is typically infrared radiation. At
raised pressure heat transport is enhanced by the thermal
conduction through the gas and by convection of the gas. Convection
can be natural convection due to temperature differences or it can
be forced convection carried out by a gas pump or a fan. The batch
of substrates may be heated by heat transport with the aid of
inactive gas, such as nitrogen or similar. In certain embodiment,
inactive gas is guided into the pre-processing module and said
inactive gas is heated by at least one heater.
[0026] In certain embodiments, the post-processing module is a
second load lock, and the method comprises cooling the batch of
substrates in a raised pressure higher than vacuum pressure in the
second load lock by means of heat transport.
[0027] In certain embodiments, the method comprises dividing the
batch of substrates into substrate subsets, and processing each of
the subsets simultaneously in the reaction chamber module, each
subset having its own gas flow inlet and gas flow outlet.
[0028] In certain embodiments, each subset are processed in a
confined space formed be interior dividing walls.
[0029] In certain embodiments, the method comprises depositing
aluminum oxide on solar cell structure.
[0030] In certain embodiments, the method comprises depositing
Zn.sub.1-xMg.sub.xO or ZnO.sub.1-xS.sub.x buffer layer on solar
cell structure.
[0031] According to a second example aspect of the invention there
is provided an apparatus comprising:
[0032] a reaction chamber module of an atomic layer deposition
reactor configured to process a batch of substrates by an atomic
layer deposition process; and
[0033] a loading and unloading arrangement allowing loading the
batch of substrates before processing into the reaction chamber
module via a different route than the batch of substrates is
unloaded after processing.
[0034] The apparatus may be an atomic layer deposition reactor, an
ALD reactor.
[0035] In certain embodiments, the apparatus comprises:
[0036] a pre-processing module of the atomic layer deposition
reactor configured to pre-process the batch of substrates;
[0037] the reaction chamber module of the reactor configured to
process the pre-processed batch of substrates by the atomic layer
deposition process; and
[0038] a post-processing module of the reactor configured to
post-process the processed batch of substrates, where the
pre-processing module, the reaction chamber module, and the
post-processing module are located in a row.
[0039] In certain embodiments, said processing by an atomic layer
deposition process comprises depositing material on the batch of
substrates by sequential self-saturating surface reactions.
[0040] In certain embodiments, said pre-processing module is a
pre-heating module configured to pre-heat the batch of substrates
to a temperature above room temperature.
[0041] In certain embodiments, said post-processing module is a
cooling module configured to cool the batch of substrates to a
temperature below the ALD process temperature.
[0042] In certain embodiments, the apparatus is configured for
transporting the batch of substrates in one direction through the
whole processing line, the processing line comprising the
pre-processing, reaction chamber and post-processing modules.
[0043] In certain embodiments, the pre-processing module is a first
load lock configured to pre-heat the batch of substrates in a
raised pressure by means of heat transport.
[0044] In certain embodiments, the post-processing module is a
second load lock configured to cool the batch of substrates in a
raised pressure by means of heat transport.
[0045] In certain embodiments, the reaction chamber module
comprises partition walls or is configured to receive partition
walls dividing the batch of substrates into substrate subsets, each
subset having its own gas flow inlet and gas flow outlet.
[0046] According to a third example aspect of the invention there
is provided an apparatus comprising:
[0047] a reaction chamber module of an atomic layer deposition
reactor configured to process a batch of substrates by an atomic
layer deposition process; and
[0048] means for loading the batch of substrates before processing
into the reaction chamber module via a different route than the
batch of substrates is unloaded after processing.
[0049] Different non-binding example aspects and embodiments of the
present invention have been illustrated in the foregoing. The above
embodiments are used merely to explain selected aspects or steps
that may be utilized in implementations of the present invention.
Some embodiments may be presented only with reference to certain
example aspects of the invention. It should be appreciated that
corresponding embodiments may apply to other example aspects as
well. Any appropriate combinations of the embodiments may be
formed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The invention will now be described, by way of example only,
with reference to the accompanying drawings, in which:
[0051] FIGS. 1A-1J show a method of batch processing in a
deposition reactor in accordance with an example embodiment;
[0052] FIG. 2 shows a deposition reactor in accordance with an
example embodiment;
[0053] FIG. 3 shows a carriage in another example embodiment;
[0054] FIG. 4 shows placement of substrates in a batch in
accordance with an example embodiment;
[0055] FIGS. 5A-5B show gas flow directions in accordance example
embodiments; FIG. 6 shows a curved rectangular tube furnace in
accordance with an example embodiment;
[0056] FIG. 7 shows a curved rectangular tube furnace in accordance
with another example embodiment;
[0057] FIG. 8 shows a curved rectangular tube furnace in accordance
with yet another example embodiment;
[0058] FIG. 9 shows a rectangular tube furnace in accordance with
an example embodiment;
[0059] FIG. 10 shows a rectangular tube furnace in accordance with
another example embodiment;
[0060] FIG. 11 shows a rectangular tube furnace in accordance with
yet another example embodiment;
[0061] FIG. 12 shows a round tube furnace in accordance with an
example embodiment;
[0062] FIG. 13 shows a round tube furnace in accordance with
another example embodiment; and
[0063] FIGS. 14A-14D show a method of a single batch processing in
a deposition reactor in accordance with an example embodiment.
DETAILED DESCRIPTION
[0064] In the following description, Atomic Layer Deposition (ALD)
technology is used as an example. Unless specifically restricted by
the appended patent claims, the embodiments of the present
invention are not strictly limited to that technology and to an
equivalent technology, but certain embodiments may be applicable
also in methods and apparatus utilizing another comparable
atomic-scale deposition technology or technologies.
[0065] The basics of an ALD growth mechanism are known to a skilled
person. Details of ALD methods have also been described in the
introductory portion of this patent application. These details are
not repeated here but a reference is made to the introductory
portion with that respect.
[0066] FIGS. 1A-1J show a method of batch processing in a
deposition reactor in accordance with an example embodiment. The
deposition reactor comprises a horizontal reaction chamber module
110, a tube furnace, which may have a rectangular cross-section, a
curved rectangular cross-section, or a round cross-section as shown
in more detail with reference to FIGS. 6-13. In other embodiments,
the cross-section may be yet another cross-section shape suitable
for the purpose.
[0067] The reaction chamber module 110 comprises gates 111 and 112
at respective ends of the module 110 for loading and unloading a
carriage 115 carrying substrate holders each carrying a batch of
substrates 120. The gates 111 and 112 may open as shown in FIGS. 1A
and 1H. In alternative embodiments, the gates may be gate valves or
similar requiring very little space when opening and closing. In
those embodiments, for example, a fixed or mobile pre-processing
module can be attached to the module 110 on the side of gate 111.
Similarly, in alternative embodiment, a fixed or mobile
post-processing module can be attached to the module 110 on the
side of gate 112. This is in more detail described later in this
description in connection with FIG. 2.
[0068] Each batch of substrates may reside in its own semiconfined
space formed by flow guides or guide plates 121 which surround each
of the batches on the sides. Each semiconfined space therefore
forms a kind of a box that has at least partially open top and
bottom side allowing exposure of substrates in the box to process
gases and removal of process gases from the box. The flow guides
121 may form a permanent structure of the carriage 115. A substrate
holder carrying a batch of substrates can be transferred into such
a box by a loading robot or similar before processing.
Alternatively, the flow guides 121 may be integrated to a substrate
holder. In those embodiments, and in other embodiments, a robot or
similar may move a batch of substrates from a regular plastic wafer
carrier cassette or substrate holder into a substrate holder (made
of aluminum, stainless steel or silicon carbide, for example) which
can tolerate the processing temperatures and precursors of ALD.
These substrate holders, which may have the flow guides 121 forming
the box walls, are then loaded into the carriage 115.
[0069] The substrates 120 may be round substrate wafers as shown in
FIG. 1A or rectangular wafers, square in particular, as shown in
more detail later in this description in connection with FIGS.
3-14D. Each batch may consist of wafers placed adjacent to each
other to form a horizontal stack with open gaps between wafers as
shown in more detail later in this description in connection with
for example FIGS. 4-5B.
[0070] The reaction chamber module 110 shown in FIGS. 1A-1J
comprises precursor vapor in-feed lines 135 in an upper portion of
the module. There may be one in-feed line for each precursor vapor.
In the embodiment shown in FIGS. 1A-1J there are two in-feed lines
which are horizontally adjacent. In other embodiments, the in-feed
lines may be vertically adjacent. Some examples on the placement of
the in-feed lines have been shown in FIGS. 6-13. Precursor vapor is
fed to the in-feed line at least from one point. In other
embodiments, in large reactors the in-feed line may be so long that
it is advantageous to have more than one feed point of the
precursor vapor to the in-feed line, for example at both ends of
the in-feed line.
[0071] There may be inlet openings in the in-feed lines allowing
gases and vapors leave the in-feed lines and enter the reaction
chamber. In an embodiment, the in-feed lines therefore are
perforated pipelines. The position of the inlet openings depends on
the embodiment. They may be, for example, in an upper and/or lower
and/or side surface of the in-feed lines. The feedthrough of the
in-feed lines into the reaction chamber may be implemented in
various ways depending on the implementation. One possibility is to
implement at least one feedthrough for each in-feed line through
the ceiling of the reaction chamber. Another possibility is to
implement at least one feedthrough for each in-feed line through a
side wall of the reaction chamber.
[0072] The reaction chamber module 110 comprises an exhaust channel
136 below the support surface practically along the whole length of
the module 110. During processing, reaction by-products and surplus
reactant molecules are purged and/or pumped to a vacuum pump 137
via the exhaust channel 136.
[0073] In an embodiment, the reaction chamber module 110 comprises
at least one heater heating the inside of the reaction chamber,
that is, practically the reaction space. One possible heating
arrangement is shown later in this description in connection with
FIGS. 14A-14D. The at least one heater may be covered by a thermal
insulator layer in directions other than the one pointing towards
the reaction space.
[0074] The carriage 115 comprises wheels 117 or other moving means
so that the carriage 115 can move or slide into and inside the
module 110 along a track or rails 125 or along other support
surface. The support surface comprises recesses 127 or other
reception means for locking the carriage 115 into a right position
for processing. In the embodiment shown in FIGS. 1B and 1C the
wheels 117 are lowered into the recesses 127. The carriage 115 may
have lower guiding means or plates 122 in the area of each of the
boxes that fit into the space 132 formed in the connection or below
the support surface.
[0075] In FIG. 1D, the carriage 115 is in the processing position
inside the module 110. The in-feed lines 135 are in fluid
communication with the exhaust channel 136 and vacuum pump 137
through each of the boxes housing the substrate batches.
[0076] Initially, the reaction chamber is in room pressure. The
loading hatch or gate 111 which was opened during loading has been
closed after the reaction chamber has been loaded with the batches
of substrates 120. The reaction chamber is then pumped into vacuum
by the vacuum pump 137. The loaded batches may have been
pre-processed, for example, pre-heated into the processing
temperature range (meaning the actual processing temperature or at
least close to the processing temperature) in a fixed or mobile
pre-processing module. Alternatively, they may be heated in the
reaction chamber.
[0077] Inactive purge (carrier) gas, such as nitrogen or similar,
flows from the in-feed lines 135 into each of the boxes, as
depicted by arrows 145. The balance between the flow rate of
inactive purge (carrier) gas to the reaction chamber and the
pumping speed of gas out of the reaction chamber keeps the reaction
chamber pressure typically in the rage of about 0.1-10 hPa,
preferably about 0.5-2 hPa during the deposition process.
[0078] A deposition process consists of one or more consecutive
deposition cycles. Each deposition cycle (ALD cycle) may consist of
a first precursor pulse (or pulse period) followed by a first purge
step (or period), which is followed by a second precursor pulse (or
pulse period) followed by a second purge step (or period).
[0079] FIG. 1E shows the first precursor pulse period during which
the substrates are exposed to a first precursor vapor. The route of
gas flow is from the in-feed line 135 into the boxes housing the
substrate batches and via the exhaust channel 136 into the pump
137.
[0080] FIG. 1F shows the subsequent first purge period during which
inactive gas flows through the reaction chamber and pushes gaseous
reaction byproducts and surplus precursor vapor to the exhaust
channel 136 and further to the pump 137.
[0081] FIG. 1G shows the second precursor pulse period during which
the substrates are exposed to a second precursor vapor. The route
of gas flow is, again, from the in-feed line 135 into the boxes
housing the substrate batches and via the exhaust channel 136 into
the pump 137.
[0082] After a second purge period, the deposition cycle is
repeated as many times as needed to grow a material layer of
desired thickness onto the substrates 120.
[0083] In an example ALD deposition process, aluminum oxide
Al.sub.2O.sub.3 is grown on batches of substrates 120 using
trimethyl aluminum TMA as the first precursor and water H.sub.2O as
the second precursor. In an example embodiment, the substrates 120
comprise solar cell structures onto which aluminum oxide is grown.
In an example embodiment, the processing temperature is about
200.degree. C.
[0084] After processing, the reaction chamber module 110 is
reverted back into room pressure. The carriage 115 is raised from
the recesses 127 as shown in FIG. 1H. And the carriage 115 is moved
out of the reaction chamber module 110 via the opened gate 112 as
shown in FIG. 1J.
[0085] The embodiment shown in FIGS. 1A-1J thus illustrated a
method of ALD batch processing in which the batch(es) of substrates
were loaded before processing into the reaction chamber module via
a different route than the batch(es) of substrates were unloaded
from the reaction chamber module after processing.
[0086] In an alternative embodiment, the support surface (reference
numeral 125, FIG. 1A) may be omitted. Instead, there may be a mesh,
a perforated plate or a similar construction element in the
carriage below the boxes extending along the area of each of the
boxes so that the exhaust channel is formed below the carriage. In
this embodiment, the carriage can be moved, for example, directly
on the floor of the reaction chamber module. This embodiment is
shown in more detail later in the description in connection with
FIGS. 6-8.
[0087] In another alternative embodiment, the mesh can be attached
to the support surface part. In this embodiment, the carriage can
be moved on the support surface but the carriage would not
typically have the lower guiding means or plates.
[0088] The embodiments in which a mesh is present can be
implemented without forming the boxes at all. Instead the mesh can
be designed such that the gas flow in the reaction space is as
uniform as possible so that a uniform growth on each surface of the
substrates can be achieved. For example, the size of the openings
in the mesh can be different depending on the distance from a
feedthrough conduit to the vacuum pump.
[0089] FIG. 2 shows a deposition reactor in accordance with another
embodiment. However, what has been presented in the preceding in
the connection of FIGS. 1A-1F is by default applicable also to the
embodiment presented in FIG. 2.
[0090] FIG. 2 shows a reaction chamber, a tube furnace, with three
modules mechanically coupled to each other. The reaction chamber
module 110 may basically be similar to that shown in the previous
embodiments. In a first side of the reaction chamber module 110 the
reactor comprises a pre-processing module 251. It may be a load
lock that is mechanically coupled to the reaction chamber module
110 by the gate valve 111 or similar. After at least one batch of
substrates has been loaded into the pre-processing module 251 via a
hatch or gate 211 or similar, the at least one batch of substrates
can be pre-processed in that module 251. For example, the at least
one batch of substrates can be pre-heated in the pre-processing
module 251 into the processing temperature range by heat transport.
In an embodiment, inactive gas, such as nitrogen or similar, is
conducted into the pre-processing module 251 from an inactive gas
source. The inactive gas in the pre-processing module 251 is heated
by at least one heater 260 located in or in the outside of the
pre-processing module 251. The at least one batch of substrates in
the pre-processing module 251 is heated by the heated inactive gas
by heat transport.
[0091] After pre-processing, the pre-processing module 251 is
pumped into vacuum, the gate valve 111 is opened and the carriage
or substrate holder carrying the pre-processed at least one batch
of substrates is moved into the reaction chamber module 110 for ALD
processing.
[0092] In a second (opposite) side of the reaction chamber module
110 the reactor comprises a post-processing module 252. It may be a
load lock that is mechanically coupled to the reaction chamber
module 110 by the gate valve 112 or similar. After processing, the
gate valve 112 is opened and the carriage or substrate holder
carrying the ALD processed at least one batch of substrates is
moved into the post-processing module 252 for post-processing. For
example, the processed at least one batch of substrates can be
cooled in the post-processing module 252 by heat transport. In an
embodiment, inactive gas, such as nitrogen or similar, is conducted
into the post-processing module 252 from an inactive gas source.
The pressure of the post-processing module 252 can be raised (into
room pressure, for example) and the at least one batch of
substrates in the post-processing module 252 is cooled by heat
transport from the at least one batch of substrates comprising heat
conduction through the inactive gas and natural and/or forced
convection of the inactive gas. The walls of the post-processing
module can be cooled for example with water-cooled piping. Warmed
inactive gas can be conducted into an external heat exchange unit,
cooled in the external heat exchange unit and returned by pumping
to the post-processing module 252.
[0093] After post-processing, the hatch or gate 212 is opened and
the carriage or substrate holder carrying the post-processed at
least one batch of substrates is moved out of the post-processing
module 252.
[0094] The embodiment shown in FIG. 2 thus illustrated a modular
deposition reactor. In an alternative embodiment, either of the
pre- and post-processing modules is omitted. In an alternative
embodiment, there is therefore implemented a deposition reactor
substantially consisting of a pre-processing module and a reaction
chamber module. And, in yet another alternative embodiment, there
is implemented a deposition reactor substantially consisting of a
reaction chamber module and a post-processing module.
[0095] FIG. 3 shows the type of a carriage shown in FIGS. 1A-1J for
carrying batches of substrates in accordance with another example
embodiment. Instead of carrying batches of round wafers, the
carriage 115 shown in FIG. 3 is used to carry square shaped wafers.
As shown in the enlargement of FIG. 4, the substrates can form
horizontal stacks put both horizontally and vertically next to each
other. In the example shown in FIGS. 3 and 4, each batch of
substrates has a 3.times.3 horizontal stack structure in which
three horizontal stacks have been placed on top of each other and
three such columns horizontally next to each other. The precursor
vapor and purge gas flows along the surface of each substrate
vertically from top to bottom as shown in FIG. 5A. In embodiments
shown for example in FIGS. 9-11 the flow is a mainly horizontal
flow along the surface of each substrate from left to right or from
right to left depending on the viewing angle as shown in FIG.
5B.
[0096] FIGS. 6-11 show different design alternatives of the
deposition reactor and deposition reactor modules in accordance
with certain embodiments.
[0097] FIGS. 6-7 show side views of curved rectangular tube
furnaces. In the embodiment shown in FIG. 6 the reaction chamber
module 110 comprises horizontally adjacent precursor vapor in-feed
lines 135a, 135b, whereas in the embodiment shown in FIG. 7 the
horizontal in-feed lines 135a, 135b are vertically adjacent.
Because ALD precursors are typically reactive with each other, each
precursor vapor flows preferably along its dedicated in-feed line
to the reaction chamber to prevent thin film deposition inside the
in-feed line. A substrate holder 660 in the carriage 115 carries a
batch of square shaped substrates 120 one of which is shown in
FIGS. 6 and 7. The in-feed lines 135a, 135b have openings on their
upper surface via which precursor vapor and purge gas is deflected
via the curved ceiling so as to generate a uniform top-to-bottom
flow along substrate surfaces. The carriage 115 has the mesh
(reference numeral 675) attached to it the function of which has
been discussed in the foregoing.
[0098] In the embodiment shown in FIG. 8, the reaction chamber
module 110 comprises additional inactive gas in-feed lines 835 in
the top corners of the module 110 to enhance purging of the
reaction chamber. Flow rate of inactive gas along the additional
inactive gas in-feed lines 835 can vary during the deposition
process. For example, during the precursor pulse time the flow rate
is low in inactive in-feed lines 835 to minimize inert gas
shielding of the upper corners of the substrates and during the
purge time between the precursor pulses the flow rate is high in
inactive in-feed lines 835 to enhance purging of the reaction
chamber. Nitrogen or argon can be used as the inactive gas in most
cases. The in-feed lines 835 may be perforated pipelines having
openings on their upper surface so that inactive gas initially
flows in the direction(s) shown in FIG. 8.
[0099] FIGS. 9-10 show side views of rectangular tube furnaces. A
substrate holder or carriage 960 which can be horizontally moved
within the reaction chamber module 110 carries a batch of square
shaped substrates 120 one of which is shown in FIGS. 9-10. In the
embodiment shown in FIG. 9 the reaction chamber module 110
comprises horizontally adjacent precursor vapor in-feed lines 135a,
135b for producing horizontal precursor vapor flow along substrate
surfaces. The in-feed lines 135a, 135b have openings on their side
surface via which precursor vapor and purge gas is deflected via a
side wall 980 of the module 110. In this way a uniform horizontal
(left-to-right) flow along substrate surfaces is generated. The gas
flow finally passes via a vertical mesh 975 into an exhaust channel
936.
[0100] In the embodiment shown in FIG. 10 the reaction chamber
module 110 comprises additional inactive gas in-feed lines 1035 in
the corners of the side wall 980 to enhance purging of the reaction
chamber. The in-feed lines 1035 may be perforated pipelines having
openings on their surfaces so that inactive gas initially flows in
the direction(s) shown in FIG. 11, that is, towards the
corners.
[0101] FIGS. 12-13 show cross-sectional views of round tube
furnaces. A substrate holder or carriage 1260 which can be
horizontally moved within the reaction chamber module 110 carries a
batch of square shaped substrates 120. In the embodiment shown in
FIG. 12 the reaction chamber module 110 comprises vertically
adjacent horizontal precursor vapor in-feed lines 135a, 135b. The
in-feed lines 135a, 135b have openings on their upper surface via
which precursor vapor and purge gas is deflected via the round
ceiling so as to generate a uniform top-to-bottom flow along
substrate surfaces. The module 110 has the mesh (reference numeral
1275) on the bottom. The volume below the mesh 1275 forms an
exhaust channel 1236.
[0102] In the embodiment shown in FIG. 13, the reaction chamber
module 110 comprises additional inactive gas in-feed lines 1335
near the ceiling of the module 110 to enhance purging of the
reaction chamber.
[0103] FIGS. 14A-14D show a method of batch processing in a
deposition reactor in accordance with another example embodiment.
The method shown in FIGS. 14A-14D basically corresponds to the
method shown with reference to FIGS. 1A-1J in the foregoing. The
difference is that instead of processing a plurality of batches at
the same time, in the current embodiment only a single batch is
processed at the time. However, in the side direction, the batch on
the carriage 1415 may be fairly long enabling hundreds or even
thousands of substrates to be processed simultaneously. The
processing capacity can be increased by setting horizontal stacks
of substrates in rows and columns as shown in FIG. 14A (and in
FIGS. 3 and 4 in the foregoing). Visible are also the at least one
heater (reference numeral 1461) heating the reaction space of the
reaction chamber module 110 and the thermal insulation layer
(reference numeral 1462) covering the at least one heater 1461 in
directions other than the one pointing towards the reaction
space.
[0104] Otherwise the reference numbering and the operations in
FIGS. 14A-14D corresponds to those used in FIGS. 1A-1J. FIG. 14A
shows the loading of the carriage 1415 into the reaction chamber
module 110 via gate 111. FIGS. 14B and 14C shows the lowering of
the wheels of the carriage 117 into the recesses 127 and the
gaseous flow into the confined box housing the substrates during
processing. FIGS. 14D shows the unloading of the processed batch of
substrates on the carriage 1415 via gate 112.
[0105] The foregoing description has provided by way of
non-limiting examples of particular implementations and embodiments
of the invention a full and informative description of the best
mode presently contemplated by the inventors for carrying out the
invention. It is however clear to a person skilled in the art that
the invention is not restricted to details of the embodiments
presented above, but that it can be implemented in other
embodiments using equivalent means without deviating from the
characteristics of the invention.
[0106] Furthermore, some of the features of the above-disclosed
embodiments of this invention may be used to advantage without the
corresponding use of other features. As such, the foregoing
description should be considered as merely illustrative of the
principles of the present invention, and not in limitation thereof.
Hence, the scope of the invention is only restricted by the
appended patent claims.
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