U.S. patent application number 12/702747 was filed with the patent office on 2010-07-08 for method and apparatus for modulation of precursor exposure during a pulsed deposition process.
This patent application is currently assigned to NOVELLUS SYSTEMS INC.. Invention is credited to Dennis Hausmann, Francisco Juarez, Bunsen Nie, Teresa Pong, Adrianne Tipton, Patrick Van Cleemput.
Application Number | 20100173074 12/702747 |
Document ID | / |
Family ID | 42103156 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100173074 |
Kind Code |
A1 |
Juarez; Francisco ; et
al. |
July 8, 2010 |
METHOD AND APPARATUS FOR MODULATION OF PRECURSOR EXPOSURE DURING A
PULSED DEPOSITION PROCESS
Abstract
A method of depositing material on a substrate comprises
providing a reactor with a reaction chamber having a first volume,
and contacting a surface of a substrate in the reaction chamber
with a first precursor at the first chamber volume to react with
and deposit a first layer on the substrate. The method further
includes enlarging the reaction chamber to a second, larger volume
and removing undeposited first precursor and any excess reaction
product to end reaction of the first precursor with the
substrate.
Inventors: |
Juarez; Francisco; (Fremont,
CA) ; Hausmann; Dennis; (Los Gatos, CA) ; Nie;
Bunsen; (Fremont, CA) ; Pong; Teresa; (Dublin,
CA) ; Tipton; Adrianne; (Pleasanton, CA) ; Van
Cleemput; Patrick; (Stockton, CA) |
Correspondence
Address: |
LAW OFFICE OF DELIO & PETERSON, LLC.
121 WHITNEY AVENUE, 3RD FLLOR
NEW HAVEN
CT
06510
US
|
Assignee: |
NOVELLUS SYSTEMS INC.
San Jose
CA
|
Family ID: |
42103156 |
Appl. No.: |
12/702747 |
Filed: |
February 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10821092 |
Apr 8, 2004 |
7700155 |
|
|
12702747 |
|
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Current U.S.
Class: |
427/255.28 ;
118/728; 427/248.1 |
Current CPC
Class: |
C23C 16/45589 20130101;
C23C 16/45523 20130101 |
Class at
Publication: |
427/255.28 ;
427/248.1; 118/728 |
International
Class: |
C23C 16/458 20060101
C23C016/458; C23C 16/44 20060101 C23C016/44; C23C 16/00 20060101
C23C016/00 |
Claims
1. A method of depositing material on a substrate comprising:
providing a reactor with a reaction chamber having a first volume;
contacting a surface of a substrate in the reaction chamber with a
first precursor at the first chamber volume to react with and
deposit a first layer on the substrate; and enlarging the reaction
chamber to a second, larger volume and removing undeposited first
precursor and any excess reaction product to end reaction of the
first precursor with the substrate.
2. The method of claim 1 further including: reducing the reaction
chamber to the first chamber volume; contacting the first layer in
the reaction chamber with a second precursor at the first chamber
volume to react with and deposit a second layer on the first layer,
thereby forming a film; and enlarging the reaction chamber to the
second volume and removing undeposited second precursor and any
excess reaction product to end reaction of the second
precursor.
3. The method of claim 1 wherein removing undeposited first
precursor and any excess reaction product is by purging the
reaction chamber at the second volume with a gas.
4. The method of claim 1 wherein removing undeposited first
precursor and any excess reaction product is by exposing the
reaction chamber at the second volume to a vacuum.
5. The method of claim 1 wherein the reaction chamber includes a
pedestal adapted to secure the substrate during the deposition and
movable between first and second positions, a first chamber section
above the pedestal in the first position defining the first chamber
volume, and a second chamber section outside the first chamber
section; and wherein the reaction chamber is enlarged to the
second, larger volume by moving the pedestal to the second position
such that the first and second chamber sections together with the
pedestal in the second position define the second chamber
volume.
6. The method of claim 1 wherein the second chamber section is on
one or more sides of the pedestal.
7. The method of claim 1 wherein the second chamber section is
below the pedestal.
8. A method of depositing a film on a substrate comprising:
providing a reactor with a reaction chamber having a first volume;
contacting a surface of a substrate in the reaction chamber with a
first precursor at the first chamber volume to react with and
deposit a first layer on the substrate; enlarging the reaction
chamber to a second, larger volume and removing undeposited first
precursor and any excess reaction product to end reaction of the
first precursor with the substrate; reducing the reaction chamber
to the first chamber volume; contacting the first layer in the
reaction chamber with a second precursor at the first chamber
volume to react with and deposit a second layer on the first layer,
thereby forming a film; and enlarging the reaction chamber to the
second volume and removing undeposited second precursor and any
excess reaction product to end reaction of the second
precursor.
9. The method of claim 8 wherein the reaction chamber includes a
pedestal adapted to secure the substrate during the deposition and
movable between first and second positions, a first chamber section
above the pedestal in the first position defining the first chamber
volume, and a second chamber section outside the first chamber
section; and wherein the reaction chamber is enlarged to the
second, larger volume by moving the pedestal to the second position
such that the first and second chamber sections together with the
pedestal in the second position define the second chamber
volume.
10. The method of claim 1 wherein the second chamber section is on
the side of and below the pedestal.
11. An apparatus for depositing a film on a substrate comprising: a
reactor having a variable volume reaction chamber for reacting one
or more precursors with the substrate to deposit a film thereon; a
pedestal in the reaction chamber adapted to secure the substrate
during the deposition, the pedestal being movable between first and
second positions; a first chamber section above the pedestal in the
first position; a second chamber section outside the first chamber
section, wherein volume of the reaction chamber may be varied by
moving the pedestal between the first position, where the first
chamber section together with the pedestal in the first position
define a first chamber volume, and the second position, where the
first and second chamber sections together with the pedestal in the
second position define a second, larger chamber volume.
12. The apparatus of claim 11 wherein the pedestal is movable
upwards to the first position and downwards to the second
position.
13. The apparatus of claim 11 wherein the second chamber section is
on one or more sides of the pedestal.
14. The apparatus of claim 11 wherein the second chamber section is
below the pedestal.
15. The apparatus of claim 11 further including a perforated plate
above the pedestal in the first chamber section, the perforated
plate being adapted to diffuse the precursors.
16. The apparatus of claim 11 further including an environmental
control for maintaining the first chamber section at a different
temperature than the second chamber section.
17. An apparatus for depositing a film on a substrate comprising: a
reactor having a variable volume reaction chamber for reacting one
or more precursors with the substrate to deposit a film thereon; a
pedestal in the reaction chamber adapted to secure the substrate
during the deposition, the pedestal being movable between an upper
position and a lower position; a first chamber section above the
pedestal in the upper position; a second chamber section along side
or below the first chamber section, wherein volume of the reaction
chamber may be varied by moving the pedestal between the upper
position, where the first chamber section together with the
pedestal in the first position define a first chamber volume, and
the lower position, where the first and second chamber sections
together with the pedestal in the lower position define a second,
larger chamber volume.
19. The apparatus of claim 11 further including a perforated plate
above the pedestal in the first chamber section, the perforated
plate being adapted to diffuse the precursors.
20. The apparatus of claim 11 further including an environmental
control for maintaining the first chamber section at a different
temperature than the second chamber section.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/821,092 entitled "Method And Apparatus For Modulation
of Precursor Exposure During A Pulsed Deposition", filed on Apr. 8,
2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to reactors used in the
semiconductor manufacturing industry and, in particular, to a
reactor for pulsed layer deposition of thin films in the
fabrication of integrated circuits.
[0004] 2. Description of Related Art
[0005] A primary goal of the semiconductor manufacturing industry
is to reduce the size of integrated circuits in order to them to
perform more operations in a shorter time. As integrated circuit
device features become smaller, several technical difficulties are
presented. One such problem is depositing conformal thin films in
holes or trenches having a small diameter or a small width-to-depth
ratio. One standard technique for depositing such thin films has
been chemical vapor deposition (CVD), which works well for feature
sizes on the order of 120 nm and smaller. However, CVD may not be
extendable to high aspect ratio features at these dimensions.
Pulsed layer deposition (PLD) has been seen as a likely replacement
for film deposition and holes below 120 nm in width and for the
high aspect ratio features.
[0006] PLD is useful for depositing thin films having two
components. The process generally consists of four steps, which may
be repeated to produce films of desired thickness. The steps are
normally conducted in a reactor with a controlled environment. The
first step consists of saturating a surface with the first
precursor or reactant needed to create the film, followed by
removing the excess byproducts of the first reaction and any
unreacted precursor from the reactor. The next step consists of
saturating the surface with a second precursor or reactant in order
to form the desired film. The last step is to remove unwanted
excess byproducts from the third step and any unreacted
precursor.
[0007] The precursor exposure steps of PLD are said to be
self-limiting, that is, the amount of material deposited on the
surface stops depositing after a relatively short period of time.
However, in order for the deposition reactions of steps one and
three to go to completion, the surface must receive a high exposure
of the precursor. This is achieved if the precursor is allowed to
remain for a long period above the surface or if the concentration
of the precursor above the wafer is high. Provided the precursor
exposures are high and the purging performed during the second and
third steps are sufficient, there results a thin film consisting of
the reaction product of the two components. The purging steps are
sufficient if concentrations of the un-reacted precursors and
reaction byproducts are low enough to minimize or eliminate one
precursor or its byproducts from contacting, and possibly reacting
with, the second precursor or its byproducts.
[0008] In addition to the steps outlined above, there are
additional practical requirements. First, each step should be as
short as possible to fulfill the requirement that the thin film be
formed as fast as possible to make the entire process commercially
viable for ultra large scale integration (ULSI) of the circuits.
Second, the smallest possible amount of precursor should be used
because precursor costs must be minimized to make the process
commercially viable, and un-reacted precursor and byproducts must
be minimized to reduce the need for abatement of environmentally
harmful substances. Accordingly, the requirements for a rapid
process and use of minimum amount of precursor, coupled with the
requirements of high exposure and sufficient purging, necessitate
trade offs to be made in the PLD process.
SUMMARY OF THE INVENTION
[0009] Bearing in mind the problems and deficiencies of the prior
art, it is therefore an object of the present invention to provide
a method and apparatus for depositing films in a pulsed layer
deposition process.
[0010] It is another object of the present invention to provide a
method and apparatus for controlling exposure of precursors or
reactants to a substrate during a pulsed layer deposition
process.
[0011] A further object of the present invention is to provide a
method and apparatus which reduces the amount of precursor or
reactant needed to deposit a film in a pulsed layer deposition
process.
[0012] It is yet another object of the present invention to provide
a method and apparatus that reduces the amount of excess byproduct
and unreacted precursor or reactant in a pulsed layer deposition
process.
[0013] Still other objects and advantages of the invention will in
part be obvious and will in part be apparent from the
specification.
[0014] The above and other objects, which will be apparent to those
skilled in art, are achieved in the present invention which is
directed to a method of depositing material on a substrate
comprising providing a reactor with a reaction chamber having a
first volume, and contacting a surface of a substrate in the
reaction chamber with a first precursor at the first chamber volume
to react with and deposit a first layer on the substrate. The
method further includes enlarging the reaction chamber to a second,
larger volume and removing undeposited first precursor and any
excess reaction product to end reaction of the first precursor with
the substrate.
[0015] The method may further include reducing the reaction chamber
to the first chamber volume, and contacting the first layer in the
reaction chamber with a second precursor at the first chamber
volume to react with and deposit a second layer on the first layer,
thereby forming a film. The method then includes enlarging the
reaction chamber to the second volume and removing undeposited
second precursor and any excess reaction product to end reaction of
the second precursor.
[0016] The removal of undeposited first precursor and any excess
reaction product may be by purging the reaction chamber at the
second volume with a gas, and/or by exposing the reaction chamber
at the second volume to a vacuum.
[0017] The reaction chamber preferably includes a pedestal adapted
to secure the substrate during the deposition and which is movable
between first and second positions. A first chamber section is
above the pedestal in the first position and defines the first
chamber volume. A second chamber section is outside the first
chamber section. The reaction chamber is enlarged to the second,
larger volume by moving the pedestal to the second position such
that the first and second chamber sections together with the
pedestal in the second position define the second chamber
volume.
[0018] In another aspect, the present invention is directed to an
apparatus for depositing a film on a substrate comprising a reactor
having a variable volume reaction chamber for reacting one or more
precursors with the substrate to deposit a film thereon, and a
pedestal in the reaction chamber adapted to secure the substrate
during the deposition. The pedestal is movable between first and
second positions, so that a first chamber section is above the
pedestal in the first position, and a second chamber section is
outside the first chamber section. Volume of the reaction chamber
may be varied by moving the pedestal between the first position,
where the first chamber section together with the pedestal in the
first position define a first chamber volume, and the second
position, where the first and second chamber sections together with
the pedestal in the second position define a second, larger chamber
volume.
[0019] The pedestal is preferably movable upwards to the first
position and downwards to the second position. The second chamber
section may be on one or more sides of the pedestal, or below the
pedestal. The apparatus may further include a perforated plate,
above the pedestal in the first chamber section, which is adapted
to diffuse the precursors. It may also include an environmental
control for maintaining the first chamber section at a different
temperature than the second chamber section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The features of the invention believed to be novel and the
elements characteristic of the invention are set forth with
particularity in the appended claims. The figures are for
illustration purposes only and are not drawn to scale. The
invention itself, however, both as to organization and method of
operation, may best be understood by reference to the detailed
description which follows taken in conjunction with the
accompanying drawings in which:
[0021] FIG. 1 is a cross-sectional elevational view of the
preferred reactor apparatus of the present invention, with the
pedestal in the raised position providing a smaller reaction
chamber volume.
[0022] FIG. 2 is a cross-sectional elevational view of the
preferred reactor apparatus of FIG. 1, showing the pedestal in the
lowered position providing a larger purging reactor chamber
volume.
[0023] FIG. 3 is a flow chart showing the preferred method of
practicing the process of the present invention.
[0024] FIG. 4 is a cross-sectional elevational view of an alternate
embodiment of the reactor apparatus of FIG. 1, with the pedestal in
the raised position.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0025] In describing the preferred embodiment of the present
invention, reference will be made herein to FIGS. 1-4 of the
drawings in which like numerals refer to like features of the
invention.
[0026] The invention is a reactor apparatus and method for pulsed
layer deposition of thin films that meets the requirements of high
exposure of precursor and sufficient purging while maintaining low
precursor usage and fast process time. The reactor consists of an
isolated chamber with a pedestal for holding a wafer, a feed
through for uniformly introducing precursor and purging fluid over
the wafer surface, and a drain or vacuum source to permit the
precursor, byproducts and purging fluids egress. The reactor has
two zones, a small volume zone, and a large volume zone. The
pedestal and wafer is placed in the small volume zone during
precursor exposure, and then moved to the high volume zone,
maintained at a lower pressure, to allow un-reacted precursor and
byproduct an exit. Concurrently with moving the pedestal to the
purge position, or immediately following, the purge fluid is turned
on so un-reacted precursor and byproducts are both drawn out by the
vacuum source and pushed out by the purge fluid.
[0027] The preferred reactor apparatus for practicing the present
is depicted in FIGS. 1 and 2. Reactor 10 comprises a reaction
chamber housing 100 having internal reactor chamber sections 103,
104. The reactor chamber interior, particularly chamber section
104, communicates with a passageway 106 leading to a high vacuum
source (not shown), with a shut off valve 107 controlling
communication therewith. Process fluids enter from a source (not
shown) through control valve 108 and passageway 111 into reaction
chamber 103. This source may hold solid, liquid or gaseous
compounds, which are then processed by conventional means to
provide the precursor in gaseous form through passageway 111.
Perforated diffusion plates 109 and 110 extend across the upper
portions of chamber section 103 below passageway 111, and have
different size openings therein in order to diffuse the flow of
process fluids evenly into the reaction chamber.
[0028] Below reactor chamber section 103 is disposed a moveable
circular pedestal 102 for securing a wafer substrate 105 on which
the film is to be deposited. Pedestal 102 is moveable between an
upper position as shown in FIG. 1, and a lower position as shown in
FIG. 2. A columnar pedestal base 115, on which the pedestal 102 is
secured, is slideable in conjunction with a flexible, pleated metal
housing section 114 to move between the two positions, while
maintaining a sealed environment within the reaction chamber.
[0029] In the upper position (FIG. 1), an initial, relatively small
reactor chamber volume is defined by the upper and side walls 117
of chamber section 103 and the surface of pedestal 102. In this
embodiment, pedestal 102 is of a diameter that is slightly smaller
than the spacing between opposite reactor side walls 117, so that
the pedestal may move upward to a position above the lower portion
of walls 117. Reactor chamber section 104 is located below and on
at least one side of, preferably completely around, pedestal 102.
When the pedestal is moved down to its lowered position (FIG. 2), a
subsequent larger reactor chamber volume is defined by the combined
volume of both chamber sections 103 and 104, as well as pedestal
102. Pedestal 102 may also be moveable to secure wafer 105 in any
intermediate position between the upper and lower positions
depicted.
[0030] In order to control the temperature of reactor chamber
section 103 at a temperature different from the remainder of the
reactor chamber, there are provided heating elements 112 along side
the sidewalls of chamber section 103, and cooling coils 113
containing a re-circulating fluid in the overhead wall of chamber
section 103. These electric heaters 112 and cooling coil 113
provide environmental controls for heating or cooling the wafer
while in the smaller reactor chamber volume.
[0031] Operation of the apparatus is depicted in the process steps
as shown in FIG. 3. At the start of the process 20, the pedestal is
moved to the desired wafer loading position, and the wafer secured
to the top of pedestal 102. The reactor is then pressurized to its
base pressure, 22. The pedestal is then moved upward to the reactor
top, compacted position, 24, and the first precursor or reactant is
flowed into chamber section 103 through valve 108 and passageway
111. The temperature in reactor vessel 103 is also adjusted by
environmental controls 112, 113. While in the smaller chamber
volume, the wafer surface 105 receives a high exposure of the first
precursor. Because of the limited volume, smaller amounts of
gaseous precursor may achieve higher desired concentration for
reaction. Once the desired reaction is achieved along a layer of
the wafer surface, the pedestal is moved to the bottom, expanded
position 26, and the chambers are evacuated through valve 107 and
simultaneously purged with a reaction-limiting purge gas through
valve 108. The higher volume within combined reaction chamber
sections 103 and 104 rapidly reduces the overpressure and
concentration of the first precursor, and limits the reaction on
the wafer surface. Once the initial precursor and excess byproducts
are removed from the reaction chamber above the wafer substrate
105, the pedestal is again moved to the top position, 28, and the
second precursor is flowed into the smaller initial chamber volume
103 as described in step 24. Again, once the reaction with the
second precursor is achieved, and a desired film thickness is
deposited on wafer 105 surface, the pedestal is moved to the bottom
position, 30, and vacuum and purge gas flow is again initiated in
order to stop the reaction and remove excess second precursor and
unwanted reaction byproducts from the larger volume reaction
chamber.
[0032] Process steps 24-30 may be repeated as necessary to achieve
the desired thickness of the deposited layer on the surface of
wafer substrate 105. Once the film deposition is completed, the
pedestal is moved back to the desired wafer loading position, 32,
and the reaction chamber is pumped to the wafer transfer pressure.
A reactor isolation valve (not shown) is then opened and the wafer
may be removed from the reaction chamber.
[0033] An example of pulse layer deposition utilizing the method
and apparatus of the present invention is described below.
[0034] With the reactor in the compacted position, trimethyl
aluminum at a pressure of 12 torr is introduced into the chamber by
opening valve 108 for approximately 1 sec, to deposit an
approximately monoatomic layer of aluminum oxide on to the wafer
surface. The wafer pedestal is then lowered to the reactor expanded
position, and an inert purge gas such as nitrogen is introduced at
a high rate by opening valve 108 to purge the remaining precursor
and reactant gases over the wafer. Simultaneously, valve 107 is
opened to evacuate the expanded chamber. Subsequently, the pedestal
is moved up, to the reactor compacted position, and a silanol
precursor, such as tris-t-pentoxysilanol, is introduced into the
chamber by opening valve 108. The silanol gas is at a pressure of
about 1 Torr and the valve is opened for about 5 to 20 seconds,
until the polymerization reaction at the wafer surface results in a
silicon dioxide layer of about 100-150 angstroms thickness. The
aluminum oxide layer serves to catalyze the reaction that deposits
the silicon dioxide. The pedestal is then lowered to expand the
reaction chamber, and the purge gas is again introduced to stop the
reaction and evacuate the chamber.
[0035] FIG. 4 depicts an alternate embodiment of the reactor
apparatus of FIG. 1, with the pedestal in the raised position. In
this embodiment, pedestal 102 has a diameter larger than the
spacing between side walls 117. Pedestal 102 has chamfered edges
116 that correspond with the lower chamfered corners 118 of reactor
walls 117. If film builds up on the reactor walls, the space
between the pedestal and walls as in FIG. 1 will not become sealed,
and the pedestal will not bind to the walls, even if the pedestal
contacts chamfered corners 118.
[0036] Accordingly, the present invention provides an improved
method and apparatus for a pulsed layer deposition in the
fabrication of microelectronic circuits. The variable reactor
chamber volume makes the process partially viable for ULSI
processing. Additionally, the variable reaction chamber volume
reduces the amount of precursors used while enabling high
concentrations and fast reaction times to be achieved.
[0037] While the present invention has been particularly described,
in conjunction with a specific preferred embodiment, it is evident
that many alternatives, modifications and variations will be
apparent to those skilled in the art in light of the foregoing
description. It is therefore contemplated that the appended claims
will embrace any such alternatives, modifications and variations as
falling within the true scope and spirit of the present
invention.
* * * * *