U.S. patent application number 11/456062 was filed with the patent office on 2006-11-23 for surface pre-treatment for enhancement of nucleation of high dielectric constant materials.
Invention is credited to Shixue Han, Shreyas S. Kher, Craig R. Metzner.
Application Number | 20060264067 11/456062 |
Document ID | / |
Family ID | 29739281 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060264067 |
Kind Code |
A1 |
Kher; Shreyas S. ; et
al. |
November 23, 2006 |
SURFACE PRE-TREATMENT FOR ENHANCEMENT OF NUCLEATION OF HIGH
DIELECTRIC CONSTANT MATERIALS
Abstract
Embodiments of the present invention relate to a surface
preparation treatment for the formation of thin films of high k
dielectric materials over substrates. One embodiment of a method of
forming a high k dielectric layer over a substrate includes
pre-cleaning a surface of a substrate to remove native oxides,
pre-treating the surface of the substrate with a hydroxylating
agent, and forming a high k dielectric layer over the surface of
the substrate. One embodiment of a method of forming a hafnium
containing layer over a substrate includes introducing an acid
solution to a surface of a substrate, introducing a hydrogen
containing gas and an oxygen containing gas to the surface of the
substrate, and forming a hafnium containing layer over the
substrate.
Inventors: |
Kher; Shreyas S.; (Campbell,
CA) ; Han; Shixue; (Milpitas, CA) ; Metzner;
Craig R.; (Fremont, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
29739281 |
Appl. No.: |
11/456062 |
Filed: |
July 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10302752 |
Nov 21, 2002 |
|
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11456062 |
Jul 6, 2006 |
|
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60388928 |
Jun 14, 2002 |
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Current U.S.
Class: |
438/785 ;
257/E21.274; 257/E21.279; 257/E21.281; 257/E21.29 |
Current CPC
Class: |
C23C 16/0227 20130101;
H01L 21/3162 20130101; H01L 21/31641 20130101; H01L 21/31683
20130101; H01L 21/31604 20130101; H01L 21/02312 20130101; C23C
16/56 20130101; H01L 21/31612 20130101; H01L 21/02304 20130101;
H01L 21/31645 20130101; H01L 21/02307 20130101; H01L 21/31637
20130101; H01L 21/02148 20130101; C23C 16/509 20130101; C23C
16/0218 20130101; C23C 16/405 20130101; H01L 21/02181 20130101 |
Class at
Publication: |
438/785 |
International
Class: |
H01L 21/31 20060101
H01L021/31 |
Claims
1. A method for forming a high dielectric constant layer on a
substrate, comprising: pre-cleaning a surface of the substrate to
remove native oxides; forming a hydroxylating gas by combining a
gas containing molecular hydrogen and another gas containing
molecular oxygen; exposing the substrate to the hydroxylating gas
to form a hydroxylated surface thereon; and forming a dielectric
material on the substrate, comprising: forming a hafnium oxide
layer during an atomic layer deposition process; and forming a
hafnium silicate layer on the hafnium oxide layer during another
atomic layer deposition process.
2. The method of claim 1, wherein the native oxides are removed by
exposing the surface of the substrate to hydrofluoric acid solution
during the pre-cleaning.
3. The method of claim 1, further comprising: exposing the
substrate to a non-reactive gas while forming the hydroxylating
surface thereon.
4. The method of claim 1, wherein a ratio of the gas containing
molecular oxygen to the gas containing molecular hydrogen is
between about 65:35 to about 99.9:0.1.
5. (canceled)
6. The method of claim 1, wherein the hafnium oxide layer and the
hafnium silicate layer comprise a different concentration of
hafnium.
7. (canceled)
8. A method of forming a high dielectric constant layer over a
substrate, comprising: pre-cleaning a surface of the substrate to
remove native oxides; forming a hydroxylating gas by combining a
gas containing molecular hydrogen and another gas containing
molecular oxygen or nitrous oxide; exposing the substrate to the
hydroxylating gas to form a hydroxylated surface thereon; and
forming a dielectric material on the substrate, comprising: forming
a plurality of hafnium silicate layers by atomic layer deposition,
where each hafnium silicate layer comprises different proportions
of hafnium, silicon, and oxygen atoms.
9. The method of claim 8, wherein the native oxides are removed by
exposing the surface of the substrate to a hydrofluoric acid
solution during the pre-cleaning.
10. The method of claim 8, further comprising: exposing the
substrate to a non-reactive gas while forming the hydroxylating
surface thereon.
11. The method of claim 8, wherein an upper hafnium silicate layer
comprises more silicon than a lower layer.
12. The method of claim 8, wherein each hafnium silicate layer
comprises a different concentration of hafnium.
13. A method of forming a high dielectric constant layer over a
substrate, comprising: pre-cleaning a surface of the substrate to
remove native oxides; forming a hydroxylating gas by combining a
gas containing molecular hydrogen and another gas containing
molecular oxygen or nitrous oxide; exposing the substrate to the
hydroxylating gas to form a hydroxylated surface thereon; and
forming a dielectric material on the substrate, comprising: forming
a plurality of hafnium silicate layers by atomic layer deposition,
wherein the plurality of hafnium silicate layers comprises a
combination of the same hafnium silicate layers and different
hafnium silicate layers.
14.-15. (canceled)
16. The method of claim 8, wherein each hafnium silicate layer
comprises a different concentration of silicon.
17. A method for forming a high dielectric constant layer on a
substrate, comprising: pre-cleaning a surface of the substrate to
remove native oxides; forming a hydroxylating gas by combining a
gas containing molecular hydrogen and another gas containing
oxygen; exposing the substrate to the hydroxylating gas to form a
hydroxylated surface thereon; and forming the high dielectric
constant material on the substrate, further comprising: forming a
plurality of hafnium containing layers by atomic layer
deposition.
18. The method of claim 17, wherein an upper hafnium containing
layer comprises more silicon than a lower layer.
19. The method of claim 17, wherein each hafnium containing layer
comprises a different concentration of hafnium.
20. The method of claim 17, wherein each hafnium containing layer
comprises a different composition.
21. The method of claim 17, wherein the plurality of hafnium
containing layers comprises a combination of the same hafnium
containing layers and different hafnium containing layers.
22. The method of claim 17, wherein the plurality of hafnium
containing layers comprise hafnium silicate layers.
23. The method of claim 22, wherein each hafnium silicate layer
comprises a different concentration of hafnium.
24. The method of claim 22, wherein each hafnium silicate layer
comprises a different concentration of silicon.
25. The method of claim 17, wherein the oxygen containing gas
comprises molecular oxygen or nitrous oxide.
26. A method for forming a high dielectric constant layer on a
substrate, comprising: pre-cleaning a surface of the substrate to
remove native oxides; forming a hydroxylating gas by combining a
gas containing molecular hydrogen and another gas containing
molecular oxygen; exposing the substrate to the hydroxylating gas
to form a hydroxylated surface thereon; and forming a dielectric
material on the substrate, comprising: forming a plurality of
hafnium containing layers by plasma enhanced vapor deposition.
27. The method of claim 26, wherein an upper hafnium containing
layer comprises more silicon than a lower layer.
28. The method of claim 26, wherein each hafnium containing layer
comprises a different concentration of hafnium.
29. The method of claim 26, wherein each hafnium containing layer
comprises a different concentration.
30. The method of claim 26, wherein the plurality of hafnium
containing layers comprises a combination of the same hafnium
containing layers and different hafnium containing layers.
31. The method of claim 26, wherein the plurality of hafnium
containing layers comprise hafnium silicate layers.
32. The method of claim 31, wherein each hafnium silicate layer
comprises a different concentration of hafnium.
33. The method of claim 31, wherein each hafnium silicate layer
comprises a different concentration of silicon.
34. The method of claim 26, wherein the plasma enhanced vapor
deposition is an atomic layer deposition process.
35. The method of claim 26, wherein the plasma enhanced vapor
deposition is a chemical vapor deposition process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/302,752 (APPM/006174.02.Y1), filed Nov. 21,
2002, which application claims benefit of U.S. Provisional Patent
Application Ser. No. 60/388,928 (APPM/006412L), filed Jun. 14,
2002, both of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention relate to the formation
of thin films of high k dielectric materials over substrates for
use in manufacturing semiconductor devices, flat-panel display
devices, and other electronic devices. More particularly,
embodiments of the present invention relate to a surface
preparation treatment for the formation of thin films of high
dielectric constant materials over substrates.
[0004] 2. Description of the Related Art
[0005] In the field of semiconductor processing, flat-panel display
processing or other electronic device processing, chemical vapor
deposition has played an important role in forming films on
substrates. As the geometries of electronic devices continue to
shrink and the density of devices continues to increase, the size
and aspect ratio of the features are becoming more aggressive,
e.g., feature sizes of 0.07 microns and aspect ratios of 10 or
greater are being considered. Accordingly, conformal deposition of
materials to form these devices is becoming increasingly
important.
[0006] High dielectric constant materials, such as metal oxides,
are one type of thin film being formed over substrates. Problems
with current methods of forming metal oxide films over substrates
include high surface roughness, high crystallinity, and/or poor
nucleation of the formed metal oxide film.
[0007] Therefore, there is a need for improved processes and
apparatuses for forming high k dielectric materials over
substrates.
SUMMARY OF THE INVENTION
[0008] Embodiments of the present invention relate to a surface
preparation treatment for the formation of thin films of high k
dielectric materials over substrates. One embodiment of a method of
forming a high k dielectric layer over a substrate includes
pre-cleaning a surface of a substrate to remove native oxides,
pre-treating the surface of the substrate with a hydroxylating
agent, and forming a high k dielectric layer over the surface of
the substrate. One embodiment of a method of forming a hafnium
containing layer over a substrate includes introducing an acid
solution to a surface of a substrate, introducing a hydrogen
containing gas and an oxygen containing gas to the surface of the
substrate, and forming a hafnium containing layer over the
substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] So that the manner in which the above recited features,
advantages and objects of the present invention are attained and
can be understood in detail, a more particular description of the
invention, briefly summarized above, may be had by reference to the
embodiments thereof which are illustrated in the appended
drawings.
[0010] It is to be noted, however, that the appended drawings
illustrate only typical embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
[0011] FIG. 1 is a flow chart of one embodiment of a method of
forming a high k dielectric layer over a substrate.
[0012] FIGS. 2A-C are schematic cross-sectional views of one
embodiment of a substrate at certain stages in the method of FIG.
1.
[0013] FIG. 3 is a schematic cross-section view of one embodiment
of a single-substrate clean chamber.
[0014] FIG. 4 is a schematic view of one embodiment of an apparatus
adapted for rapid thermal processing.
[0015] FIG. 5 is a flow chart of one embodiment of an in-situ steam
generation process.
[0016] FIG. 6 is a schematic cross-sectional view of one embodiment
of a chamber capable of depositing a high k dielectric layer by
chemical vapor deposition.
[0017] FIG. 7 is a general chemical structure for one embodiment of
a hafnium metal organic precursor.
[0018] FIG. 8 is a schematic top view of one embodiment of an
integrated processing system.
[0019] FIGS. 9A-9B are schematic cross-sectional views of
embodiments of a hafnium containing layer comprising a plurality of
layers formed over a substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Embodiments of the present invention relate to the formation
of high k dielectric materials over substrates. High k dielectric
materials include hafnium containing materials, aluminum oxides,
zirconium oxides, lanthanum oxides, yttrium oxides, tantalum
oxides, other suitable materials, composites thereof, or
combinations thereof. Hafnium containing high k dielectric
materials include hafnium oxides (e.g., HfO.sub.2), hafnium
silicates (e.g., HfSiO), hafnium nitrides (e.g., HfN), other
suitable materials, composites thereof, or combinations thereof.
The high k dielectric material preferably comprises hafnium oxides,
hafnium silicates, composites thereof, or combinations thereof.
Substrates include semiconductor wafers or glass substrates and may
include materials formed thereover, such as dielectric materials,
conductive materials, silicon layers, metal layers, etc.
[0021] FIG. 1 is a flow chart of one embodiment of a method 100 of
forming a high k dielectric layer over a substrate. In step 110,
the surface of a substrate is pre-cleaned to remove native oxides
which may have formed over the surface of the substrate. In step
120, the surface of the substrate is pre-treated with a
hydroxylating agent to perform a controlled hydroxylation of the
substrate. In step 130, a high k dielectric layer is formed
thereover.
[0022] Not wishing to be bound by theory unless explicitly set
forth in the claims, FIGS. 2A-C are schematic cross-sectional views
of one embodiment of a silicon substrate 200 at certain stages in
the method 100 of FIG. 1. For clarity of description, the method
100 will be described in reference to formation of a high k
dielectric layer comprising a hafnium containing layer.
[0023] FIG. 2A shows the substrate 200 after the surface of the
substrate is pre-cleaned to remove native oxides which may have
formed over the substrate surface. It is believed that the
pre-clean leaves the surface of a substrate with a silicon-hydrogen
(Si--H) surface 212. FIG. 2B shows the substrate 200 after the
surface of the substrate is pre-treated with a hydroxylating agent.
It is believed that the hydroxylating agent converts the Si--H
surface 212 of FIG. 2A into a silicon-hydroxy (Si--O--H) surface
214. FIG. 2C shows the substrate 200 after a hafnium containing
layer 216, such as a hafnium oxide layer, has been formed over the
surface of the substrate.
[0024] The hafnium containing layer 216 can comprise a single layer
or a plurality of layers. If the hafnium containing layer 216 is
made of a plurality of layers, each layer may be a different type
of hafnium containing material, the same type of hafnium containing
material, or combinations thereof. For example, FIG. 9A is a
schematic cross-sectional view of one embodiment of a hafnium
containing layer comprising a hafnium silicate material layer
formed over a hafnium oxide material layer. In another example,
FIG. 9B is a schematic cross-sectional view of one embodiment of a
hafnium containing layer comprising a plurality of hafnium silicate
layers. Each hafnium silicate layer may comprise the same or
different proportions of hafnium, silicon, and oxygen atoms.
[0025] In reference to FIGS. 2A-C, it is believed that during
formation of the hafnium containing layer 216 an interfacial layer
215 comprising hafnium silicates is formed between the hafnium
containing layer 216 and the substrate 200. It is believed that in
formation of the hafnium containing layer 216, less energy is
required to break the bonds of the Si--O--H surface 214 of FIG. 2B
to form the hafnium containing layer 216 than directly breaking the
bonds of the Si--H surface 212 of FIG. 2A. In addition, the extent
of hydroxylation of the surface of the substrate can be controlled,
as opposed to hydroxylation by the atmosphere (native oxides), and
the thickness of the interfacial layer 215 can be reduced.
[0026] It has been observed that a hafnium containing layer formed
by the methods disclosed herein has improved film characteristics.
The formed hafnium containing layer is amorphous and may be formed
over a substrate with minimal formation of an interfacial layer
215, such as an interfacial layer having a thickness about 13 .ANG.
or less, more preferably about 6 .ANG. or less. In addition, the
formed hafnium containing layer has improved nucleation (fewer
islands) over a substrate surface. In certain embodiments, a
hafnium containing layer may be formed to a surface roughness (Rms)
of less than about 4 .ANG., preferably less than about 3 .ANG., and
more preferably about 2.55 .ANG. or less.
Pre-Clean
[0027] Referring to step 110 of FIG. 1, pre-cleaning of a substrate
surface may be performed by contacting the substrate surface with a
cleaning solution in a batch clean system, in a single-substrate
clean system, or any other suitable clean system. One example of a
single-substrate clean system is an OASIS CLEAN.TM. system
available from Applied Materials, Inc. of Santa Clara, Calif. The
cleaning solution may be an RCA-type cleaning solution or any other
suitable cleaning solution which removes native oxides, which may
have formed over the substrate surface, and may involve single-step
chemistry or multi-step chemistries. The substrate surface may be
contacted with the cleaning solution for a specified time
period.
[0028] FIG. 3 is a schematic cross-section view of one embodiment
of a single-substrate clean chamber 300 which may be part of a
multi-chamber system. The chamber 300 includes a platter 308 with a
plurality of acoustic or sonic transducers 302 located thereon. The
transducers 302 are attached to the bottom surface of platter 308.
The transducers 302 create acoustic or sonic waves directed towards
the surface of a substrate 306.
[0029] The substrate 306 is held at a distance above the top
surface of platter 308. The substrate 306 is clamped by a plurality
of clamps 310 face up and can rotate or spin substrate 306 about
the substrate's central axis. In chamber 300, the clamps 310 and
substrate 306 are rotated during use whereas platter 308 remains in
a fixed position. Additionally, in chamber 300, substrate 306 is
placed face up and the backside of the substrate faces platter 308,
i.e., the side of the substrate with patterns or features faces
towards one or more nozzles 351 which spray cleaning or etching
chemicals thereon.
[0030] During use, deionized water (DI water) is fed through a feed
through channel 328 and platter 308 and fills the gap between the
backside of substrate 306 and platter 308 to provide a water filled
gap 318 through which acoustic waves generated by transducers 302
can travel to substrate 306.
[0031] Additionally during use, cleaning solutions such as SC-1 and
SC-2, etchants such as diluted hydrofluoric acid or buffered
hydrofluoric acid, and rinsing water such as deionized water are
fed through a plurality of nozzles 351 to the top surface of the
substrate 306 while the substrate 306 is spun. Tanks 323 containing
wet processing chemicals such as diluted hydrofluoric acid,
de-ionized water, and cleaning solutions are coupled by conduit 354
to nozzles 351.
[0032] Other aspects and embodiments of a single-substrate clean
system are disclosed in U.S. patent application Ser. No.
09/891,849, entitled "Method and Apparatus for Wafer Cleaning,
filed Jun. 25, 2001 and in U.S. patent application Ser. No.
09/891,791, entitled "Wafer Spray Configurations for a Single Wafer
Processing Apparatus," filed Jun. 25, 2001, both of which are
herein incorporated by reference in their entirety to the extent
not inconsistent with the present disclosure.
[0033] One embodiment of the step 110 (FIG. 1) of pre-cleaning the
substrate surface, which may be performed in the apparatus as
described in reference to FIG. 3 or may be performed in other batch
clean systems or single-substrate clean systems, comprises
introducing a dilute hydrofluoric acid solution onto the substrate
surface for a suitable time period, such as between about 5 seconds
and about 1 hour or more, preferably between about 1 minute and
about 15 minutes, more preferably about 2 minutes. Any suitable
concentration of hydrofluoric acid may be used, preferably between
about 1 weight percent and about 49 weight percent hydrofluoric
acid, more preferably about 2 weight percent hydrofluoric acid.
After introduction of a hydrofluoric acid solution to the
substrate, the substrate surface is referred to a HF-last
surface.
Pre-Treatment
[0034] Referring to FIG. 1, one embodiment of step 120 of
pre-treating the substrate surface with a hydroxylating agent
comprises contacting the surface of the substrate with water vapor
generated in a flash in-situ steam generation (ISSG) process. In
other embodiments, the hydroxylating agent may be other suitable
compounds. The pre-treatment of the present invention can be
carried out in a rapid thermal heating apparatus, such as, but not
limited to, the RTP XE chamber, available from Applied Materials,
Inc. of Santa Clara, Calif. One embodiment of a rapid thermal
heating apparatus is disclosed in U.S. Pat. No. 6,037,273, entitled
"Method and Apparatus for In situ Vapor Generation," assigned to
Applied Materials, Inc. of Santa Clara, Calif., which is a
Continuation-In-Part Application to U.S. patent application Ser.
No. 08/893,774, both of which are incorporated by reference in
their entirety to the extent not inconsistent with the present
disclosure. Another suitable rapid thermal heating apparatus and
its method of operation is set forth in U.S. Pat. No. 5,155,336,
entitled "Rapid Thermal Heating Apparatus and Method," filed Oct.
24, 1991, which is herein incorporated by reference in its entirety
to the extent not inconsistent with the present disclosure.
Additionally, other types of thermal reactors may be utilized such
as the Epi or Poly Centura single wafer "cold wall" reactor by
Applied Materials, Inc. of Santa Clara, Calif.
[0035] FIG. 4 is a schematic view of one embodiment of an apparatus
400 adapted for rapid thermal processing. The apparatus 400
includes an evacuated process chamber 413 enclosed by a sidewall
414 and a bottom wall 415. A radiant energy light pipe assembly 418
is positioned over and coupled to window assembly 417. The radiant
energy light pipe assembly 418 includes a plurality of tungsten
halogen lamps 419 each mounted into a light pipe 421. Lamps 419 are
positioned to adequately cover the entire surface area of substrate
461. A window assembly 417 may be disposed below the light pipe
assembly 418.
[0036] A substrate (wafer) 461 is supported inside chamber 413 by a
support ring 462 which engages the substrate near its edge. Support
ring 462 is mounted on a rotatable quartz cylinder 463. By rotating
quartz cylinder 463, support ring 462 and wafer 461 can be caused
to rotate.
[0037] The bottom wall 415 of apparatus 400 includes a coated top
surface 411 for reflecting energy onto the backside of wafer 461.
Additionally, rapid thermal heating apparatus 400 includes a
plurality of fiber optic probes 470 positioned through the bottom
wall 415 of apparatus 400 in order to detect the temperature of
substrate 461 at a plurality of locations across its bottom
surface.
[0038] Rapid thermal heating apparatus 400 includes a gas inlet 469
formed through sidewall 414 for injecting process gas into chamber
413 to allow various processing steps to be carried out in chamber
413. Coupled to gas inlet 469 are one or more gas sources (not
shown). Positioned on the opposite side from gas inlet 469, in
sidewall 414, is a gas outlet 468. Gas outlet 468 is coupled to a
vacuum source (not shown), such as a pump, to exhaust process gas
from chamber 413 and to reduce the pressure in chamber 413. The
vacuum source maintains a desired pressure while process gas is fed
into the chamber during processing.
[0039] FIG. 5 is a flow chart of one embodiment of an ISSG process
500. The ISSG process may be performed in any suitable chamber. For
clarity of description, the ISSG process 500 will be described in
reference to substrate processing apparatus 400 as described in
FIG. 4 and will be described in reference to a 200 mm diameter
substrate. The process conditions may vary depending on the
apparatus used and the size of the substrate.
[0040] In step 510 of the process 500, the substrate 461 is moved
into the chamber 413. The substrate 461 is generally transferred
into the chamber 413 having a non-reactive gas ambient, such as a
nitrogen (N.sub.2) ambient, at a transfer pressure between about 1
mtorr and about 100 torr, preferably between about 1 torr and about
10 torr. Chamber 413 is then sealed. The chamber 413 may be
evacuated to a pressure to remove the nitrogen ambient.
[0041] In step 520, the substrate 461 is heated or is ramped to a
process temperature by applying power to lamps 419. The process
temperature may be any suitable temperature, such as between about
400.degree. C. and about 1250.degree. C., preferably between about
700.degree. C. and about 900.degree. C., more preferably between
about 775.degree. C. and about 825.degree. C. During at least a
portion of step 520, a non-reactive gas, such as helium gas or
nitrogen gas, may be introduced into the chamber. It is believed
that the non-reactive gas acts as a thermal conductor and helps to
improve temperature uniformity. Preferably, the non-reactive gas
which is used is helium gas introduced at a flow rate between about
0.1 slm and about 10 slm, preferably about 1 slm. Not wishing to be
bound by theory unless explicitly set forth in the claims, it is
believed that helium is a better thermal conductor than N.sub.2. In
addition or alternatively, one or more process gases may be
introduced during the ramp. Preferably, a hydrogen containing gas
is introduced, such as hydrogen (H.sub.2) gas, at a flow rate
between about 1 sccm and 20 sccm, preferably about 5 sccm.
[0042] In step 530, at the desired process temperature, a hydrogen
containing gas and an oxygen containing gas are introduced to the
chamber 413. The hydrogen containing gas and the oxygen containing
gas are introduced to be reacted together to form water vapor
(H.sub.2O) at the desired process temperature. The hydrogen
containing gas is preferably hydrogen gas (H.sub.2), but may be
other hydrogen containing gases such as, but not limited to,
ammonia (NH.sub.3), deuterium, and hydrocarbons, such as methane
(CH.sub.4). The oxygen containing gas is preferably nitrous oxide
(N.sub.2O), but may be other types of oxygen containing gases such
as but not limited to oxygen gas (O.sub.2). It is believed that
N.sub.2O provides a more controlled hydroxylation of the substrate
surface in comparison to the use of O.sub.2 which is more reactive
than N.sub.2O. A non-reactive gas, such as helium gas, nitrogen
gas, or other non-reactive gases, may be introduced during step
530. It is believed that the non-reactive gas acts as a thermal
conductor to help improve temperature uniformity. In addition or
alternatively, it is believed that a non-reactive acts to catalyze
the in-situ steam generation process by isolating reaction
fragments. A helium non-reactive gas is preferred over a nitrogen
non-reactive gas because it is believed that the helium
non-reactive gas is a better thermal conductor and better at
catalyzing the ISSG process.
[0043] The hydrogen containing gas and the oxygen containing gas
may be introduced at any suitable chamber pressure, such as between
about 0.1 Torr and about 200 Torr, preferably between about 1 Torr
and about 20 Torr. Any concentration ratio of hydrogen containing
gas and oxygen containing gas may be used. Preferably, a high ratio
of oxygen containing gas to hydrogen containing gas is used. For
example, a process gas mixture comprising a ratio of oxygen
containing gas to hydrogen containing gas is preferably between
about 65:35 and about 99.9:0.1, preferably about 99.5:0.5.
[0044] The desired process temperature causes the hydrogen
containing gas and oxygen containing gas to react to form moisture
or steam (H.sub.2O). Since rapid thermal heating apparatus 400 is a
"cold wall" reactor, the only sufficiently hot surfaces in chamber
413 to initiate the reaction are the substrate 461 and support ring
462. As such, the moisture generating reaction occurs near the
surface of substrate 461. Since it is the temperature of the
substrate (and support ring) which initiates or turns "on" the
moisture generation reaction, the reaction is said to be thermally
controlled by the temperature of wafer 461 (and support ring 462).
Additionally, the vapor generation reaction is said to be "surface
catalyzed" because the heated surface of the substrate is necessary
for the reaction to occur.
[0045] The hydrogen containing gas and the oxygen containing gas
are introduced at a process temperature for a sufficient period of
time to enable the water vapor generated from the reaction of the
hydrogen containing gas and the oxygen containing gas to
hydroxylate the substrate surface. The substrate 461 will typically
be held at process temperature for a time period between about 1
minute and about 1 second or less, preferably for a time period of
about 10 seconds or less. Process time and temperature are
generally dictated by amount of hydroxylation desired and the type
and concentrations of the process gases.
[0046] In step 540, power to lamps 419 is reduced or turned off to
reduce or ramp down the temperature of substrate 461.
Simultaneously, a purge gas, such as nitrogen gas (N.sub.2), is fed
into the chamber 413 to remove residual process gases. Then, the
substrate 461 may be removed from the chamber 413.
[0047] Although the present invention has been described with
respect to in-situ generation of a vapor of a specific reactive
species, water, it is to be appreciated that the teachings of the
present invention can be applied to other processes where the
temperature of a substrate is used to initiate or catalyze the
reaction of reactant gases to form a vapor of a reactive species
near the wafer surface. The reactive species vapor can then be
reacted with the wafer or with films formed thereon to carry out
processes such as film growth. For example, a reactant gas mixture
comprising ammonia (NH.sub.3) and oxygen (O.sub.2) can be fed into
a chamber and then caused to react by heating a wafer to a
sufficient temperature to initiate a reaction of the gases to form
an oxy-nitride surface.
High K Dielectric Layer Formation
[0048] Referring to step 130 of FIG. 1, a high k dielectric layer
may be formed by chemical vapor deposition (including metal-organic
chemical vapor deposition (MOCVD), low pressure chemical vapor
deposition, plasma-enhanced chemical vapor deposition), atomic
layer deposition (ALD), physical vapor deposition, vapor phase
epitaxy (VPE), other suitable deposition techniques, and
combination of deposition techniques.
[0049] One embodiment of a chamber capable of depositing a high k
dielectric layer by MOCVD is disclosed in commonly assigned U.S.
patent application Ser. No. 09/179,921, which is incorporated by
reference in its entirety to the extent not inconsistent with the
present disclosure.
[0050] FIG. 6 is a schematic cross sectional view of one embodiment
of a chamber 600 capable of depositing a high k dielectric layer,
such as hafnium containing layer, by MOCVD. Chamber body 610 and
heated chamber lid 605, which is hingedly connected to chamber body
610, together form a processing region 602 bounded by showerhead
640, substrate support 650, and the walls of chamber body 610.
Substrate support 650 (shown in the raised position for processing)
extends through the bottom of chamber body 610. A slit valve 615
allows substrates to be transferred to and from the processing
region 602.
[0051] Imbedded within substrate support 650 is a resistive heater.
A thermocouple in thermal contact with substrate support 650 may
sense the temperature of substrate support 650 to allow for
temperature control of heated substrate support 650. Substrate 601
is supported by the upper surface of support 650 and is heated by
the resistive heaters within substrate support 650 to processing
temperatures.
[0052] Turning now to gas delivery features of chamber 600, process
gases are introduced via conduit 673, through central bore 630 and
flow through blocker plate 637 and showerhead 640 into processing
region 602. Pumping passage 603 and outlet port 660 formed within
chamber body 610 remove process gas and by-products of processing
operations conducted within processing region 602.
[0053] For illustration purposes, deposition of a high k dielectric
layer will be described in reference to MOCVD of a hafnium oxide
layer. Metal-organic CVD of hafnium oxide comprises introducing a
hafnium organic precursor and introducing an oxygen containing
compound to the chamber, such as chamber 600 of FIG. 6. Examples of
a hafnium organic precursor include the compound having the
structure of Hf(NRR').sub.4 shown in FIG. 7, wherein at least one
of R and R' are as follows: [0054] R.dbd.H, CH.sub.3,
C.sub.2H.sub.5, C.sub.3H.sub.7, CO, NCO, alkyl or aryl and [0055]
R'.dbd.H, CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, CO, NCO, alkyl
or aryl. R and R' may or may not be the same. Preferably, both R
and R' are an alkyl group having one to four carbon atoms, and more
preferably are the same alkyl group. Examples of preferred hafnium
organic precursors include tetrakis(diethylamido)hafnium (TDEAH)
and tetrakis (dimethylamido)hafnium, and most preferably is TDEAH.
Examples of an oxygen containing compound include oxygen gas
(O.sub.2). Other oxygen containing compounds may also be used, such
as ozone, H.sub.2O, N.sub.2O, and atomic oxygen (i.e. oxygen
plasma).
[0056] One embodiment of a process for depositing hafnium oxide by
MOCVD will be described in reference to a 200 mm diameter
substrate. The process conditions may vary depending on the
apparatus used and the size of the substrate. One embodiment of
depositing hafnium oxide comprises flowing TDEAH onto the substrate
surface at a rate between about 1 mg/min and about 50 mg/min,
preferably about 7 mg/min, O.sub.2 is flowed onto the wafer surface
between about 30 sccm and about 3,000 sccm, preferably 1,000 sccm,
and N.sub.2 is flowed onto the wafer surface at a rate between
about 30 sccm and about 3,000 sccm, preferably about 1,500 sccm.
O.sub.2, N.sub.2 and TDEAH are introduced onto the wafer surface
either simultaneously, sequentially, or a combination thereof.
[0057] The hafnium oxide layer is formed at temperatures in the
range between about 225.degree. C. and about 700.degree. C.
Preferably, the hafnium oxide layer is formed at about 485.degree.
C. The pressure in the deposition chamber is in the range between
about 1.5 Torr and about 8 Torr, preferably about 4 Torr. The
process may be performed for a specified time period, preferably
about 60 seconds or less. Preferably, the hafnium oxide layer
formed has a thickness between about 20 .ANG. and about 50 .ANG.,
preferably about 40 .ANG. or less.
Processing System
[0058] The processes in the formation of a high k dielectric layer
as disclosed herein may be carried out in one or more single
chamber systems, one or more mainframe systems having a plurality
of chambers, or combinations thereof. The processes may be
performed in separate processing systems or an integrated
processing system.
[0059] FIG. 8 is a schematic top view of one embodiment of an
integrated system 800 capable of performing the processes disclosed
herein. The integrated system 800 comprises a cleaning module 810
and a thermal processing/deposition mainframe system 830. As shown
in the figure, the cleaning module 810 is an OASIS CLEAN.TM.
system, available from Applied Materials, Inc., located in Santa
Clara, Calif. The thermal processing/deposition mainframe system
830 is a CENTURA.RTM. system and is also commercially available
from Applied Materials, Inc., located in Santa Clara, Calif. The
particular embodiment of the system to perform the process as
disclosed herein is provided to illustrate the invention and should
not be used to limit the scope of the invention unless otherwise
set forth in the claims.
[0060] The cleaning module 810 generally includes one or more
substrate cassettes 812, one or more transfer robots 814 disposed
in a substrate transfer region, and one or more single-substrate
clean chambers 816. The single-substrate clean chambers 816 may be
similar to chamber described in reference to FIG. 3.
[0061] The thermal processing/deposition mainframe system 830
generally includes load lock chambers 832, a transfer chamber 834,
and processing chambers 836A, 836B, 836C, 836D. The load lock
chambers 832 allow for the transfer of substrates into and out from
the thermal processing/deposition mainframe system 830 while the
transfer chamber 834 remains under a low pressure non-reactive
environment. The transfer chamber includes a robot 840 having one
or more blades which transfers the substrates between the load lock
chambers 832 and processing chambers 836A, 836B, 836C, 836D. Any of
the processing chambers 836A, 836B, 836C, 836D may be removed from
the thermal processing/deposition mainframe system 830 if not
necessary for the particular process to be performed by the system
830. The transfer region is preferably between 1 mtorr to about 100
torr and preferably comprises a non-reactive gas ambient, such as
an N.sub.2 ambient.
[0062] It is believed that it is advantageous to perform the
pre-treatment step 120 (FIG. 1) and the high k dielectric layer
formation 130 (FIG. 1) on a mainframe system to reduce the
formation of native oxides and/or contamination of the pre-treated
surface of a substrate prior to formation of the high k dielectric
layer. Exposing the substrate to air between the pre-treatment step
120 and the high k dielectric layer formation 130 may reduce the
effectiveness of nucleation thereover of high k dielectric
materials. It is optional to have the cleaning module 810 coupled
with mainframe system 830 as shown in FIG. 8 to further reduce the
formation of native oxides over and/or contamination of substrates
between cleaning steps and other processing steps. Of course, in
other embodiments, cleaning steps may be performed in a cleaning
module separate from the thermal processing/deposition mainframe
system.
[0063] One embodiment of the integrated system 800 configured to
form a high k dielectric layer comprises processing chamber 836B
adapted to perform an ISSG process as described above and a
processing chamber 836C, such as a chemical vapor deposition
chamber or an atomic layer deposition chamber, adapted to deposit a
high dielectric constant material, such as a hafnium containing
layer. Other embodiments of the system 800 are within the scope of
the present invention. For example, the position of a particular
processing chamber on the system may be altered.
EXAMPLES
[0064] Various samples of silicon substrates were processed. Each
silicon substrate comprised 200 mm diameter wafers.
Comparative Example 1
[0065] Sample 1 was pre-cleaned using a hydrofluoric acid solution
to form an HF-last surface. A layer of hafnium oxide was deposited
by MOCVD to a thickness of about 40 .ANG. over the substrate
surface at a temperature of about 325.degree. C. The roughness of
the hafnium oxide surface of Sample 1 was measured to have an Rms
(nm) of 0.580, an Ra (nm) of 0.45 and an Rmax (nm) of 10.01.
Example 2
[0066] Samples 2-5 were pre-cleaned using a hydrofluoric acid
solution to form an HF-last surface. Thereafter, Samples 2-5 were
pre-treated with a rapid thermal oxidation (RTO) process in an
O.sub.2 ambient. Sample 2 was pre-treated with an RTO process at a
temperature of about 900.degree. C. for a time period of about 10
seconds. Sample 3 was pre-treated with an RTO process at a
temperature of about 900.degree. C. for a time period of about 5
seconds. Sample 4 was pre-treated with an RTO process at a
temperature of about 850.degree. C. for a time period of about 10
seconds. Sample 5 was pre-treated with an RTO process at a
temperature of about 850.degree. C. for a time period of about 5
seconds. A layer of hafnium oxide was deposited by MOCVD over the
substrate surface to a thickness of about 40 .ANG. at a temperature
of about 325.degree. C. over each of the Samples 2-5. The
roughnesses of the hafnium oxide surfaces of Samples 2-5 were
measured and are shown below in Table 1. Samples 2-5 had lower
surface roughness in comparison to Sample 1. TABLE-US-00001 TABLE 1
Rms (nm) Ra (nm) Rmax (nm) Sample 2 0.386 0.306 3.724 Sample 3
0.387 0.307 3.812 Sample 4 0.394 0.313 3.678 Sample 5 0.393 0.311
3.882
Example 3
[0067] Sample 6 was pre-cleaned using a hydrofluoric acid solution
to form an HF-last surface. Thereafter, Sample 6 was pre-treated
with an oxygen (O.sub.2) soak. A layer of hafnium oxide was
deposited by MOCVD to a thickness of about 40 .ANG. over the
substrate surface at a temperature of about 325.degree. C. The
roughness of the hafnium oxide surface of Sample 6 was measured to
have an Rms (nm) of 0.714, an Ra (nm) of 0.567, and an Rmax (nm) of
6.618. Sample 6 had a higher surface roughness in comparison to
Sample 1.
Example 4
[0068] Samples 7-9 were pre-treated with a high dose decoupled
plasma nitridation. Thereafter, for Sample 7, a layer of hafnium
oxide was deposited by MOCVD to a thickness of about 40 .ANG. over
the substrate surface at a temperature of about 325.degree. C.
Sample 8 was cleaned using a hydrofluoric acid solution to form an
HF-last surface and a layer of hafnium oxide was deposited by MOCVD
to a thickness of about 40 .ANG. over the substrate surface at a
temperature of about 325.degree. C. Sample 9 was cleaned using a
hydrofluoric acid solution to form an HF-last surface and treated
with a rapid thermal oxidation process at a temperature about
900.degree. C. The roughnesses of the surfaces of the Samples 7-9
were measured and are shown in Table 2. Note that a layer of
hafnium oxide was not deposited over Sample 9. Sample 7 had a
slightly higher surface roughness in comparison to Sample 1 while
Sample 8 had a slightly lower surface roughness in comparison to
Sample 1. TABLE-US-00002 TABLE 2 Rms (nm) Ra (nm) Rmax (nm) Sample
7 0.611 0.483 5.439 Sample 8 0.539 0.425 4.899 Sample 9 0.265 0.209
2.680
Example 5
[0069] Samples 10-12 were pre-treated with a low dose decoupled
plasma nitridation process. Thereafter, for Sample 10, a layer of
hafnium oxide was deposited by MOCVD to a thickness of about 40
.ANG. over the substrate surface at a temperature of about
325.degree. C. Sample 11 was cleaned using a hydrofluoric acid
solution and a layer of hafnium oxide was deposited by MOCVD to a
thickness of about 40 .ANG. at a temperature of about 325.degree.
C. Sample 12 was pre-cleaned using a hydrofluoric acid solution to
form an HF-last surface and treated with a rapid thermal oxidation
process at a temperature of about 900.degree. C. Then, for Sample
12, a layer of hafnium oxide was deposited by MOCVD to a thickness
of about 40 .ANG. over the substrate surface at a temperature of
about 325.degree. C. The roughnesses of the hafnium oxide surface
of Samples 10-12 were measured and are shown below in Table 3.
Sample 10 had a slightly higher surface roughness in comparison to
Sample 1 while Sample 11 had a slightly lower surface roughness in
comparison to Sample 1 and while Sample 12 had a lower surface
roughness in comparison to Sample 1. TABLE-US-00003 TABLE 3 Rms
(nm) Ra (nm) Rmax (nm) Sample 10 0.593 0.470 5.521 Sample 11 0.573
4.455 4.971 Sample 12 0.266 0.210 2.773
Example 6
[0070] Samples 13-15 were pre-cleaned using a hydrofluoric acid
solution to form an HF-last surface. Thereafter, Samples 13-15 were
pre-treated with an ISSG process utilizing H.sub.2 gas and N.sub.2O
gas. Sample 13 was pre-treated in the ISSG process for a time
period of about 4 seconds. Sample 14 was pre-treated in the ISSG
process for a time period of about 6 seconds. Sample 15 was
pre-treated in the ISSG process for a time period of about 8
seconds. A layer of hafnium oxide was deposited by MOCVD over the
substrate surface to a thickness of about 40 .ANG. at a temperature
of about 325.degree. C. over each of the Samples 13-15. The
roughnesses of the hafnium oxide surface of Samples 13-15 were
measured and are shown below in Table 4. Samples 13-15 had much
lower surface roughnesses in comparison to Sample 1. TABLE-US-00004
TABLE 4 Rms (nm) Ra (nm) Rmax (nm) Sample 13 0.255 0.201 2.688
Sample 14 0.262 0.206 2.654 Sample 15 0.260 0.204 2.498
[0071] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *