U.S. patent application number 11/456531 was filed with the patent office on 2007-09-06 for method for forming silicon oxynitride materials.
Invention is credited to THAI CHENG CHUA.
Application Number | 20070207628 11/456531 |
Document ID | / |
Family ID | 38471974 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070207628 |
Kind Code |
A1 |
CHUA; THAI CHENG |
September 6, 2007 |
METHOD FOR FORMING SILICON OXYNITRIDE MATERIALS
Abstract
Embodiments of the invention provide methods for forming silicon
oxynitride materials on a substrate. In one embodiment, a method
for forming a dielectric material on a substrate is provided which
includes positioning a substrate containing a native oxide surface
within a processing system containing a plurality of process
chambers, and removing the native oxide surface to form a substrate
surface free of native oxide during a clean process. The method
further provides exposing the substrate to a first
nitrogen-containing plasma to form a silicon nitride layer from the
substrate surface during a first nitridation process, exposing the
substrate to an oxygen source to form a silicon oxynitride layer
from the silicon nitride layer during a thermal oxidation process,
exposing the substrate to a second nitrogen-containing plasma
during a second nitridation process, and exposing the substrate to
an annealing process.
Inventors: |
CHUA; THAI CHENG;
(Cupertino, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
38471974 |
Appl. No.: |
11/456531 |
Filed: |
July 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11367882 |
Mar 2, 2006 |
|
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11456531 |
Jul 10, 2006 |
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Current U.S.
Class: |
438/769 ;
257/E21.268 |
Current CPC
Class: |
H01L 21/02337 20130101;
H01L 21/28202 20130101; H01L 21/0214 20130101; H01L 21/02247
20130101; H01L 21/02323 20130101; H01L 21/3144 20130101; H01L
21/02252 20130101 |
Class at
Publication: |
438/769 |
International
Class: |
H01L 21/31 20060101
H01L021/31 |
Claims
1. A method for forming a dielectric material on a substrate,
comprising: positioning a substrate containing a native oxide
surface within a processing system comprising a plurality of
process chambers; removing the native oxide surface to form a
substrate surface free of native oxide during a cleaning process;
exposing the substrate to a first nitrogen-containing plasma to
form a silicon nitride layer from the substrate surface during a
first nitridation process; exposing the substrate to an oxygen
source to form a silicon oxynitride layer from the silicon nitride
layer during a thermal oxidation process; exposing the substrate to
a second nitrogen-containing plasma during a second nitridation
process; and exposing the substrate to an annealing process.
2. The method of claim 1, wherein the substrate is maintained
within the processing system during the cleaning process, the first
nitridation process, the thermal oxidation process, the second
nitridation process, and the annealing process.
3. The method of claim 1, wherein the cleaning process comprises
exposing the substrate to a wet clean solution.
4. The method of claim 3, wherein the cleaning process comprises
exposing the substrate to a hydrofluoric acid solution.
5. The method of claim 1, wherein the first nitrogen-containing
plasma comprises nitrogen and the second nitrogen-containing plasma
comprises a reagent selected from the group consisting of nitrogen,
oxygen, nitric oxide, nitrous oxide, derivatives thereof, and
combinations thereof.
6. The method of claim 1, wherein the oxygen source comprises a
reagent selected from the group consisting of oxygen, nitric oxide,
nitrous oxide, water, derivatives thereof, and combinations
thereof.
7. The method of claim 1, wherein the oxygen source comprises water
vapor formed by combining hydrogen gas, nitrogen gas, and oxygen
gas or hydrogen gas, nitrogen gas, and nitrous oxide gas.
8. A method for forming a dielectric material on a substrate,
comprising: positioning a substrate containing a native oxide
surface within a processing system comprising a plurality of
process chambers; removing the native oxide surface to form a
substrate surface free of native oxide during a cleaning process;
exposing the substrate to a plasma comprising nitrogen and oxygen
to form a silicon oxynitride layer from the substrate surface
during a plasma process; exposing the substrate to an oxygen source
during a thermal oxidation process; exposing the substrate to a
nitrogen-containing plasma during a nitridation process; and
exposing the substrate to an annealing process.
9. The method of claim 8, wherein the substrate is maintained
within the processing system during the cleaning process, the
plasma process, the thermal oxidation process, the nitridation
process, and the annealing process.
10. The method of claim 8, wherein the cleaning process comprises
exposing the substrate to a wet clean solution.
11. The method of claim 10, wherein the cleaning process comprises
exposing the substrate to a hydrofluoric acid solution.
12. The method of claim 8, wherein the plasma comprising nitrogen
and oxygen comprises a reagent selected from the group consisting
of nitrogen, oxygen, nitric oxide, nitrous oxide, derivatives
thereof, and combinations thereof.
13. The method of claim 8, wherein the oxygen source comprises a
reagent selected from the group consisting of oxygen, nitric oxide,
nitrous oxide, water, derivatives thereof, and combinations
thereof.
14. The method of claim 8, wherein the oxygen source comprises
water vapor formed by combining hydrogen gas, nitrogen gas, and
oxygen gas or hydrogen gas, nitrogen gas, and nitrous oxide
gas.
15. A method for forming a dielectric material on a substrate,
comprising: positioning a substrate containing a native oxide
surface within a processing system comprising a plurality of
process chambers; removing the native oxide surface to form a
substrate surface free of native oxide during a cleaning process;
exposing the substrate to a nitrogen-containing plasma to form a
silicon nitride layer from the substrate surface during a
nitridation process; exposing the substrate to an oxygen source to
form a silicon oxynitride layer during a thermal oxidation process;
exposing the substrate to a plasma comprising nitrogen and oxygen
during a plasma process; and exposing the substrate to an annealing
process.
16. The method of claim 15, wherein the substrate is maintained
within the processing system during the cleaning process, the
nitridation process, the thermal oxidation process, the plasma
process, and the annealing process.
17. The method of claim 15, wherein the cleaning process comprises
exposing the substrate to a hydrofluoric acid solution.
18. The method of claim 15, wherein the plasma comprising nitrogen
and oxygen comprises a reagent selected from the group consisting
of nitrogen, oxygen, nitric oxide, nitrous oxide, derivatives
thereof, and combinations thereof.
19. The method of claim 15, wherein the oxygen source comprises a
reagent selected from the group consisting of oxygen, nitric oxide,
nitrous oxide, water, derivatives thereof, and combinations
thereof.
20. The method of claim 15, wherein the oxygen source comprises
water vapor formed by combining hydrogen gas, nitrogen gas, and
oxygen gas or hydrogen gas, nitrogen gas, and nitrous oxide gas.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. Ser.
No. 11/367,882 (APPM/009696), filed Mar. 2, 2006, which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention generally relate to a
method for forming a dielectric material. More particularly,
embodiments of the invention relate to a method for forming a
silicon oxynitride (SiO.sub.xN.sub.y) dielectric material.
[0004] 2. Description of the Related Art
[0005] As integrated circuit sizes and the sizes of the transistors
thereon decrease, the drive current required to increase the speed
of the transistor has increased. The drive current increases as the
capacitance increases, and capacitance=kA/d, wherein k is the
dielectric constant, d is the dielectric thickness, and A is the
area of the device. Decreasing the dielectric thickness and
increasing the dielectric constant of the gate dielectric are
methods of increasing the gate capacitance and the drive
current.
[0006] Attempts have been made to reduce the thickness of
dielectrics, such as silicon oxide (SiO.sub.x) dielectrics, below
20 .ANG.. However, the use of silicon oxide dielectrics with
thicknesses below 20 .ANG. often results in undesirable performance
and durability. For example, boron from a boron doped electrode can
penetrate through a thin silicon oxide dielectric into the
underlying silicon substrate. Also, there is typically an increase
in gate leakage current, i.e., tunneling current, with thin
dielectrics that increases the amount of power consumed by the
gate. Thin silicon oxide gate dielectrics may be susceptible to
negative-channel metal-oxide semiconductor (NMOS) hot carrier
degradation, in which high energy carriers traveling across the
dielectric can damage or destroy the channel. Thin silicon oxide
gate dielectrics may also be susceptible to positive channel metal
oxide semiconductor (PMOS) negative bias temperature instability
(NBTI), wherein the threshold voltage or drive current drifts with
operation of the gate.
[0007] A method of forming a dielectric layer suitable for use as
the gate dielectric layer in a MOSFET (metal oxide semiconductor
field effect transistor) includes nitriding a thin silicon oxide
film in a nitrogen-containing plasma. Increasing the net nitrogen
content in the gate oxide to increase the dielectric constant is
desirable for several reasons. For example, the bulk of the oxide
dielectric may be lightly incorporated with nitrogen during the
plasma nitridation process, which reduces the equivalent oxide
thickness (EOT) over the starting oxide. This may result in a gate
leakage reduction, due to tunneling during the operation of a field
effect transistor, at the same EOT as the oxide dielectric that is
not nitrided. At the same time, increased nitrogen content may also
reduce damage induced by Fowler-Nordheim (F-N) tunneling currents
during additional processing operations, provided that the
thickness of the dielectric is in the F-N range. Another benefit of
increasing the net nitrogen content of the gate oxide is that the
nitrided gate dielectric is more resistant to the problem of gate
etch undercut, which in turn reduces defect states and current
leakage at the gate edge.
[0008] U.S. Pat. No. 6,610,615 discloses nitrogen profiles in a
silicon oxide film for both thermal and plasma nitridation process.
The nitrided oxide films are disposed on a silicon substrate.
Testing of the thermal nitrided oxide films nitrogen profiles in
the crystalline silicon beneath the oxide film shows a first
concentration of nitrogen at a top surface of an oxide layer, a
generally declining concentration of nitrogen deeper in the oxide,
an interfacial accumulation of nitrogen at the oxide-silicon
interface, and finally, a nitrogen concentration gradient that is
generally declining with distance into the substrate. In contrast,
it may be shown that the plasma nitridation process produces a
nitrogen profile that is essentially monotonically decreasing from
the top surface of the oxide layer through the oxide-silicon
interface and into the substrate. The undesirable interfacial
accumulation of nitrogen observed with a thermal nitridation
process does not occur with the ionic bombardment of the nitrogen
plasma. Furthermore, the nitrogen concentration in the substrate is
lower, at all depths, than is achieved with the thermal nitridation
process.
[0009] A benefit of increasing nitrogen concentration at the gate
electrode-gate oxide interface is that dopant diffusion with
dopants, such as boron, from polysilicon gate electrodes into or
through the gate oxide is reduced. This improves device reliability
by reducing defects in the bulk of the gate oxide caused by, for
example, in-diffused boron from a boron doped polysilicon gate
electrode. Another benefit of reducing nitrogen content at the gate
oxide-silicon channel interface is the reduction of fixed charge
and interface state density. This improves channel mobility and
transconductance.
[0010] A nitrogen containing silicon oxide dielectric material that
may be used with a physical thickness that is effective to reduce
current leakage density and provide high gate capacitance is
needed. The nitrogen containing silicon oxide dielectric material
must have a dielectric constant that is higher than that of silicon
dioxide. Typically, the thickness of such a dielectric material
layer is expressed in terms of the equivalent oxide thickness
(EOT). Thus, the EOT of a dielectric layer is the thickness that
the dielectric layer would have if its dielectric constant were
that of silicon dioxide.
[0011] A silicon oxynitride (SiO.sub.xN.sub.y) dielectric material
may be formed by incorporating nitrogen into a silicon oxide
(SiO.sub.2 or SiO.sub.x) layer or forming a silicon nitride layer
on a silicon substrate and incorporating oxygen into the layer by
an oxidation process involving oxygen or precursor gases that
contain nitrogen and oxygen.
[0012] However, as device geometries continue to shrink, there
remains a need for an improved method of depositing silicon
oxynitride dielectrics that have lower EOT than conventionally
deposited silicon oxynitride films.
SUMMARY OF THE INVENTION
[0013] In one embodiment, a method for depositing a dielectric film
is provided which includes forming silicon nitride on the surface
of the substrate, oxidizing the silicon nitride on the surface of
the substrate, exposing the surface of the substrate to a
hydrogen-free nitrogen source, and annealing the substrate.
[0014] In another embodiment, a method for the deposition of a
dielectric film is provided which includes forming silicon nitride
on the surface of the substrate, oxidizing the silicon nitride on
the surface of the substrate, including exposing the surface of the
substrate to a gas selected from the group of oxygen, nitric oxide,
and nitrous oxide, and exposing the surface of the substrate to a
hydrogen-free nitrogen source, wherein the hydrogen-free nitrogen
source is a gas such as nitrogen, nitric oxide, or nitrous
oxide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] So that the manner in which the above recited features of
the invention can be understood in detail, a more particular
description of the invention, briefly summarized above, may be had
by reference to embodiments, some of which are illustrated in the
appended drawings. 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.
[0016] FIG. 1 is a flow chart depicting a process flow of one
embodiment of the invention.
[0017] FIGS. 2A to 2D are schematic sectional views of a substrate
illustrating process steps of one embodiment of the invention
performed on the substrate.
DETAILED DESCRIPTION
[0018] The present invention provides a method of forming a silicon
oxynitride film with lower hydrogen content than those films formed
using a plasma nitridation process that provides plasma with
ammonia or other hydrogen containing precursors. The resulting
silicon oxynitride films with low hydrogen content have a higher
dielectric constant and thinner equivalent oxide thickness than
silicon oxynitride films with higher hydrogen content. Preferably,
the silicon oxynitride films have a hydrogen content of about 5% or
less.
[0019] FIG. 1 is a flow diagram illustrating one embodiment of a
process 100. Films formed using processes described herein may be
used, for example, in a device such as field effect transistors,
for example, complementary metal oxide semiconductor structures
(CMOS) field effect transistors. Process 100 begins by introducing
a substrate into a process chamber that is part of an integrated
tool containing multiple process chambers connected by a common,
shared chamber during start step 102. Next, during native oxide
removal step 104, the substrate is moved to a cleaning process
chamber to remove native silicon oxide that forms across the
substrate surface during substrate transport and storage. After the
native silicon oxide is removed from the substrate surface, the
substrate is moved to a chamber for exposure to a nitrogen
containing plasma to form silicon oxynitride during plasma
nitration step 106. Then, the substrate is exposed to an oxygen
containing precursor and annealed during thermal oxidation step
108. Next, the substrate is again exposed to a plasma formed with a
nitrogen containing, hydrogen free precursor during plasma
nitridation step 110. The substrate is annealed during thermal
anneal step 112, and then forwarded on to additional processing
steps during end step 114.
[0020] FIGS. 2A-2D are sectional views of a substrate illustrating
the process and resulting changes in film composition as the steps
of process 100 are performed. Initially, a substrate 200 is
positioned in a processing chamber during the start step 102. One
example of a processing chamber that may be used to perform
processes described herein is a decoupled plasma nitridation
process chamber described in commonly assigned U.S. Ser. No.
10/819,392, filed Apr. 6, 2004, and published as US 2004-0242021,
which is herein incorporated by reference in its entirety. One
suitable decoupled plasma nitridation (DPN) chamber is the DPN
CENTURA.RTM. chamber, which is commercially available from Applied
Materials, Inc., of Santa Clara, Calif. An example of an integrated
processing system that may be used is the Gate Stack CENTURA.RTM.
system, available from Applied Materials, Inc., of Santa Clara,
Calif. Process 100 may be performed on various substrates, such as
200 mm diameter or 300 mm diameter substrates or other medium
suitable for semiconductor or flat panel display processing.
[0021] A native oxide layer 204 is often present on the surface of
the substrate 200. Native oxide layer 204 may be removed using a
wet clean method. During native silicon oxide removal step 104,
native oxide layer 204 may be removed using a hydrofluoric acid
solution containing hydrogen fluoride (HF) and deionized (Dl)
water. The solution has a concentration within a range from about
0.1 wt % (weight percent) to about 10.0 wt % of HF and a
temperature within a range from about 20.degree. C. to about
30.degree. C. In a preferred embodiment, the solution has about 0.5
wt % of HF and a temperature of about 25.degree. C. A brief
exposure of the substrate 200 to the solution may be followed by a
rinse step in de-ionized water. The removal step 104 may be
performed in either a single substrate or batch system. The removal
step 104 may be performed in an ultra-sonically enhanced bath. Upon
completion of oxide removal step 104, substrate 200 is placed in a
vacuum load lock or nitrogen purged environment for transport on to
the next processing chamber for plasma nitriding.
[0022] During the plasma nitridation step 106, substrate 200 is
exposed to nitrogen-containing plasma. FIG. 2B illustrates layer
206, containing a silicon nitride material or a silicon oxynitride
material, grown on substrate 200 as a product of the plasma
nitridation step 106. Generally, layer 206 may have a thickness
within a range from about 2 .ANG. to about 12 .ANG.. In one
embodiment, layer 206 has a thickness within a range from about 6
.ANG. to about 10 .ANG.. The chamber for the plasma nitration step
is a RADIANCE.RTM. reactor or RTP XE+.TM. reactor. RADIANCE.RTM. or
RTP XE+.TM. reactors are available from Applied Materials, Inc., of
Santa Clara, Calif. In one embodiment, the plasma of step 106
contains at least one of nitrogen, as well as one or more optional
noble gases such as argon and helium. Step 106 may be performed
using a decoupled plasma nitridation (DPN) plasma reactor of an
integrated processing system. A sub-layer of nitrogen containing
film 205 has a typical thickness within a range from about 1 .ANG.
to about 12 .ANG., preferably, from about 3 .ANG. to about 6
.ANG..
[0023] In one embodiment, the plasma may contain nitrogen, as well
as one or more oxidizing gas such as oxygen (O.sub.2), nitric oxide
(NO), and nitrous oxide (N.sub.2O). The plasma may contain one or
more optional noble gases such as argon or helium. In an
alternative embodiment, the plasma contains at least one of ammonia
(NH.sub.3), as well as one or more optional noble gases such as
argon or helium. In one embodiment, the layer 206 may be formed in
a DPN reactor by providing nitrogen at a flow rate within a range
from about 10 sccm to about 2,000 sccm, a substrate support
temperature within a range from about 20.degree. C. to about
500.degree. C., and a pressure in the reaction chamber within a
range from about 5 mTorr to about 1,000 mTorr. The radio-frequency
(RF) plasma is energized at 13.56 MHz using either a continuous
wave (CW) or pulsed plasma power source within a range from about 3
kW to about 5 kW. During pulsing, peak RF power, frequency, and a
duty cycle are within ranges from about 10 W to about 3,000 W from
about 2 kHz to about 100 kHz, and from about 2% to about 50%.
Pulsing may be performed for a duration within a range from about 1
second to about 180 seconds. In one embodiment, N.sub.2 is provided
at about 200 W and about 1,000 W of peak RF power is pulsed at
about 10 kHz with a duty cycle of about 5% applied to an inductive
plasma source, at a temperature of about 25.degree. C. and a
pressure of about 40 mTorr to about 80 mTorr, for about 15 seconds
to about 60 seconds.
[0024] Illustrated by FIG. 2C, plasma nitridation step 106 may form
a silicon oxynitride layer 206 with sublayers 205, 207, and 208, in
one embodiment. The sublayers 205, 207, 208 vary in nitrogen,
hydrogen, and oxygen concentration within the layer 206. In one
example, the upper sublayer 205 has the highest nitrogen
concentration of the three sublayers and sublayer 208 has the
lowest concentration of nitrogen. This concentration gradient
provides layer 206 with a more desirable interface between the
substrate 200 (that contains minimal nitrogen) and the sublayer 208
with a lower nitrogen content than the rest of the layer 206.
[0025] Following plasma nitridation, thermal oxidation is performed
on the substrate at step 108 using a thermal annealing chamber,
such as a RADIANCE.RTM. reactor or RTP XE+.TM. reactor,
commercially available from Applied Materials, Inc., of Santa
Clara, Calif. Thermal oxidation improves the chemical composition
and chemical binding structure of the silicon oxynitride layer 206
by increasing the oxygen content of sublayers 205, 207, and 208,
providing increased electron mobility in the dielectric sublayers.
Step 108 also improves the crystalline structure and chemical
composition of the interface between layer 206 and substrate 200 by
tuning the oxygen and silicon concentration profiles at the
interface. This improved crystalline structure and chemical
composition at the interface improves the reliability of the
interface.
[0026] In one embodiment, the thermal oxidation may be performed by
exposing the substrate to oxygen having a flow rate within a range
from about 2 sccm to about 5,000 sccm or to nitric oxide having a
flow rate within a range from about 100 sccm to about 5,000 sccm or
both gases at the same time and flow rates. In a preferred process,
the flow rate of oxygen gas may be at about 500 sccm. Either gas
may be optionally mixed with nitrogen. The substrate surface
temperature is within a range from about 800.degree. C. to about
1,100.degree. C., and a chamber pressure is within a range from
about 0.1 Torr to about 50 Torr. The process may be performed for a
duration within a range from about 5 seconds to about 180 seconds.
In one embodiment, oxygen is provided at about 500 sccm while
maintaining the chamber at about 1,000.degree. C. and a pressure of
about 0.1 Torr, for about 15 seconds. In another embodiment, nitric
oxide is provided at about 500 sccm at a substrate temperature of
about 1,000.degree. C. and a pressure of about 0.5 Torr for about
15 seconds.
[0027] In another embodiment, the thermal oxidation may be
performed by providing a wet oxidation environment, such as by an
in situ steam generation (ISSG) process, is commercially available
from Applied Materials, Inc., of Santa Clara, Calif. The ISSG
process includes heating the substrate surface to a temperature
within a range from about 700.degree. C. to about 1,000.degree. C.,
while in a process chamber pressurized at a pressure within a range
from about 0.5 Torr to about 18 Torr. The substrate is exposed to
oxygen having a flow rate within a range from about 500 sccm to
about 5,000 sccm and to hydrogen having a flow rate within a range
from about 10 sccm to about 1,000 sccm. Preferably, hydrogen is
less than 20% of the total gas flow of the mixture of oxygen and
hydrogen. The period of exposure to the gas mixture is within a
range from about 5 seconds to about 180 seconds. In one example,
oxygen is provided at about 980 sccm, hydrogen is provided at about
20 sccm, the substrate surface temperature is about 800.degree. C.,
the chamber pressure is about 7.5 Torr, and the period of exposure
is about 15 seconds. The process may be performed in a
RADIANCE.RTM. reactor or an RTP XE.TM. reactor, commercially
available from Applied Materials, Inc., of Santa Clara, Calif.
[0028] After thermal oxidation, the substrate is exposed to a
hydrogen free nitrogen containing precursor during plasma
nitridation step 110. The layer 206 is treated with nitrogen plasma
to enhance the amount of nitrogen in the layer 206, especially to
increase the nitrogen content of the upper sublayers 205 and 207 of
FIG. 2C to form a nitrogen enhanced sublayer. FIG. 2D illustrates a
nitrogen enhanced, hydrogen free sublayer 210 that forms on the top
surface of the dielectric layer during plasma nitridation step 110.
Hydrogen free nitrogen containing precursors for this plasma
nitridation step 110 include nitrogen, nitrous oxide, and nitric
oxide. The process may be performed using a DPN reactor by
providing nitrogen gas having a flow rate within a range from about
10 sccm to about 2,000 sccm, a substrate support temperature within
a range from about 20.degree. C. to about 500.degree. C., and a
reaction chamber pressure within a range from about 5 mTorr to
about 1,000 mTorr. The radio-frequency (RF) plasma is at 13.56 MHz,
with a continuous wave (CW) or pulsed plasma power source within a
range from about 3 kW to about 5 kW. During pulsing, peak RF power,
frequency and duty cycle are typically within a range from about 10
W to about 3,000 W, from about 2 kHz to about 100 kHz, and from
about 2% to about 50%. Plasma nitridation may be performed for
about 1 second to about 180 seconds. In one example, nitrogen is
provided at about 200 sccm, and about 1,000 W RF power is pulsed at
about 10 kHz with a duty cycle of about 5% applied to an inductive
plasma source, at a temperature of about 25.degree. C., at a
pressure within a range from about 100 mTorr to about 80 mTorr, and
for a duration within a range from about 15 seconds to about 180
seconds. The plasma may be produced using a quasi-remote plasma
source, an inductive plasma source, a radial line slotted antenna
(RLSA) source, or other plasma sources. In alternate embodiments,
sources of CW or pulsed microwave power may be used to form the
layer 210.
[0029] After thermal oxidation step 108 and plasma nitration step
110, the nitrogen and oxygen concentration gradient in the
sublayers 210, 207, and 208 illustrated by FIG. 2C progresses from
sublayer 210 that is nitrogen rich and hydrogen free and thus has a
higher dielectric constant than comparable oxynitride films to
sublayer 208 that has been tailored to provide an improved
interface between the dielectric and substrate 200. During thermal
anneal step 112, the dielectric layers and substrate 200 are
annealed. Thermal anneal step 112 improves reliability of the
resulting gate dielectric by reducing leakage current in the layers
210, 207, and 208 and increasing the charge carrier mobility of the
upper sublayers of substrate 200. Thermal anneal step 112 may be
performed using an annealing chamber, such as the RADIANCE.RTM.
reactor or RTP XE+.TM. reactor of an integrated processing system
available from Applied Materials, Inc., of Santa Clara, Calif.
Alternatively, the anneal step may not be performed.
[0030] In one embodiment, the annealing process may be performed by
exposing the substrate to oxygen having a flow rate within a range
from about 2 sccm to about 5,000 sccm or to nitric oxide having a
flow rate within a range from about 100 sccm to about 5,000 sccm.
Additionally, the two gases may be introduced to the chamber at the
same time. The oxygen and/or nitric oxide may be optionally mixed
with nitrogen, while maintaining the substrate temperature within a
range from about 800.degree. C. to about 1,100.degree. C. and the
chamber pressure within a range from about 0.1 Torr to about 50.0
Torr. The process may be performed for a duration within a range
from about 5 seconds to about 180 seconds. In one example, oxygen
is provided at about 500 sccm, the substrate is heated to about
1,000.degree. C., the chamber pressure is about 0.1 Torr, and the
time of exposure is about 15 seconds. In another example, nitric
oxide is provided at about 500 sccm, the substrate is heated to
about 1,000.degree. C., the chamber pressure is about 0.5 Torr, and
the time of exposure is about 15 seconds.
[0031] Upon completion of end step 114, process 100 is completed
and the substrate is moved to an additional chamber or integrated
tool for further processing during end step 114.
[0032] The absence of hydrogen in the final plasma nitridation and
anneal steps yields a film with improved properties. The film has a
higher dielectric constant than a silicon oxide film with a similar
thickness. The effective oxide thickness (EOT) is within a range
from about 7 .ANG. to about 12 .ANG.. The channel integrity and the
negative bias temperature instability (NBTI) are improved. The
concentration gradient formed in the film increases the dielectric
constant while also providing an improved interface between the
dielectric and substrate.
[0033] While the foregoing is directed to embodiments of the
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.
* * * * *