An atomic layer deposition reactor for processing a batch of substrates and
method thereof.
FIELD OF THE INVENTION
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
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.
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.
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.
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
trimethylaluminunn (CH3)3AI, also referred to as TMA, and water at 250 - 300 °C
resulting in only about 1% non-uniformity over a substrate wafer.
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.
Recently, there has been increased interest in batch ALD reactors capable of
increased deposition throughput.
SUMMARY
According to a first example aspect of the invention there is provided 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.
In certain embodiments, the substrates comprise silicon wafers, glass plates,
metal plates or polymer plates.
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.
In certain embodiments, the method comprises:
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.
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.
In certain embodiments, said processing by an atomic layer deposition process
comprises depositing material on the batch of substrates by sequential selfsaturating
surface reactions.
In certain embodiments, said pre-processing module is a pre-heating module and
said pre-processing comprises pre-heating the batch of substrates.
In certain embodiments, said post-processing module is a cooling module and said
post-processing comprises cooling the batch of substrates.
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.
In certain embodiment, the modules lie in a horizontal row. The transport
mechanism through the modules is one-way through each of the modules.
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.
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.
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.
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.
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.
In certain embodiments, each subset are processed in a confined space formed
be interior dividing walls.
In certain embodiments, the method comprises depositing aluminum oxide on
solar cell structure.
In certain embodiments, the method comprises depositing Zni -xMgxO or ZnOi -xSx
buffer layer on solar cell structure.
According to a second example aspect of the invention there is provided 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.
The apparatus may be an atomic layer deposition reactor, an ALD reactor.
In certain embodiments, the apparatus comprises:
a pre-processing module of the atomic layer deposition reactor configured to preprocess
the batch of substrates;
the reaction chamber module of the reactor configured to process the preprocessed
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.
In certain embodiments, said processing by an atomic layer deposition process
comprises depositing material on the batch of substrates by sequential selfsaturating
surface reactions.
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.
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.
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.
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.
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.
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.
According to a third example aspect of the invention there is provided 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
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.
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
The invention will now be described, by way of example only, with reference to the
accompanying drawings, in which:
Figs. 1A - 1J show a method of batch processing in a deposition reactor in
accordance with an example embodiment;
Fig. 2 shows a deposition reactor in accordance with an example
embodiment;
Fig. 3 shows a carriage in another example embodiment;
Fig. 4 shows placement of substrates in a batch in accordance with an
example embodiment;
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;
Fig. 7 shows a curved rectangular tube furnace in accordance with
another example embodiment;
Fig. 8 shows a curved rectangular tube furnace in accordance with yet
another example embodiment;
Fig. 9 shows a rectangular tube furnace in accordance with an example
embodiment;
Fig. 10 shows a rectangular tube furnace in accordance with another
example embodiment;
Fig. 11 shows a rectangular tube furnace in accordance with yet another
example embodiment;
Fig. 12 shows a round tube furnace in accordance with an example
embodiment;
Fig. 13 shows a round tube furnace in accordance with another example
embodiment; and
Figs. 14A - 14D show a method of a single batch processing in a deposition
reactor in accordance with an example embodiment.
DETAILED DESCRIPTION
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.
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.
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 crosssection
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.
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 .
Each batch of substrates may reside in its own semiconfined space formed by flow
guides or guide plates 12 1 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 12 1 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 12 1 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 .
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. 3-1 4D. 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.
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 infeed
line for each precursor vapor. In the embodiment shown in Figs. 1A-1 J there
are two in-feed lines which are horizontally adjacent. In other embodiments, the infeed
lines may be vertically adjacent. Some examples on the placement of the infeed
lines have been shown in Figs. 6-1 3 . 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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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 infeed
line 135 into the boxes housing the substrate batches and via the exhaust
channel 136 into the pump 137.
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.
In an example ALD deposition process, aluminum oxide AI2O3 is grown on batches
of substrates 120 using trimethyl aluminum TMA as the first precursor and water
H2O 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 °C.
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.
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.
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.
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.
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.
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.
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 2 11 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.
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 preprocessed
at least one batch of substrates is moved into the reaction chamber
module 110 for ALD processing.
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.
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.
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.
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 x 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. 9-1 1 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.
Figs. 6-1 1 show different design alternatives of the deposition reactor and
deposition reactor modules in accordance with certain embodiments.
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.
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 .
Figs. 9-1 0 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. 9-1 0 . 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.
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.
Figs. 12-1 3 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.
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.
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 141 5 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.
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 141 5 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 141 5 via gate 112 .
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.
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.
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.
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.
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.
The method of claim 2 or 3, wherein said pre-processing module is a pre
heating module and said pre-processing comprises pre-heating the batch of
substrates.
The method of any preceding claim 2 - 4, wherein said post-processing
module is a cooling module and said post-processing comprises cooling the
batch of substrates.
6 . The method of any preceding claim 2 - 5, 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 any preceding claim 2 - 6, 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 of any preceding claim 2 - 7, 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 any preceding claim, 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 any preceding claim, 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 preprocessed
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 or 13, wherein said pre-processing module is a pre
heating module configured to pre-heat the batch of substrates.
15 .The apparatus of any preceding claim 12 - 14, wherein said post-processing
module is a cooling module configured to cool the batch of substrates.
16 .The apparatus of any preceding claim 12 - 15, 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 any preceding claim 12 - 16, 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 any preceding claim 12 - 17, 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 any preceding claim 11 - 18, 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.