U.S. patent application number 11/674895 was filed with the patent office on 2007-06-14 for methods for producing silicon nitride films and silicon oxynitride films by thermal chemical vapor deposition.
Invention is credited to Christian DUSSARRAT, Jean-Marc Girard, Takako Kimura, Yuusuke Sato, Naoki Tamaoki.
Application Number | 20070134433 11/674895 |
Document ID | / |
Family ID | 32040471 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070134433 |
Kind Code |
A1 |
DUSSARRAT; Christian ; et
al. |
June 14, 2007 |
METHODS FOR PRODUCING SILICON NITRIDE FILMS AND SILICON OXYNITRIDE
FILMS BY THERMAL CHEMICAL VAPOR DEPOSITION
Abstract
Silicon nitride film is formed on substrate (112) by feeding
trisilylamine and ammonia into a CVD reaction chamber (11) that
contains a substrate (112). The ammonia gas/trisilylamine gas flow
rate ratio is set to a value of at least about 10 and/or the
thermal CVD reaction is run at a temperature no greater than about
600.degree. C. Silicon oxynitride is obtained by introducing an
oxygen source gas into the CVD reaction chamber (11). This method
avoids the production of ammonium chloride and/or the incorporation
of carbonaceous contaminants which are detrimental to the quality
of the deposited film.
Inventors: |
DUSSARRAT; Christian;
(Tsukuba, JP) ; Girard; Jean-Marc; (Paris, FR)
; Kimura; Takako; (Tsukuba, JP) ; Tamaoki;
Naoki; (Tokyo, JP) ; Sato; Yuusuke; (Tokyo,
JP) |
Correspondence
Address: |
AIR LIQUIDE
2700 POST OAK BOULEVARD, SUITE 1800
HOUSTON
TX
77056
US
|
Family ID: |
32040471 |
Appl. No.: |
11/674895 |
Filed: |
February 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10669623 |
Sep 24, 2003 |
7192626 |
|
|
11674895 |
Feb 14, 2007 |
|
|
|
Current U.S.
Class: |
427/446 ;
257/E21.269; 427/248.1 |
Current CPC
Class: |
H01L 21/3145 20130101;
H01L 21/0214 20130101; H01L 21/3185 20130101; H01L 21/0217
20130101; H01L 21/02271 20130101; C23C 16/308 20130101; C23C 16/345
20130101; H01L 21/02219 20130101 |
Class at
Publication: |
427/446 ;
427/248.1 |
International
Class: |
B05D 1/08 20060101
B05D001/08; C23C 16/00 20060101 C23C016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2002 |
JP |
2002-279880 |
Claims
1. A method for producing silicon oxynitride films by thermal
chemical vapor deposition comprising: a) feeding a trisilylamine
gas, an ammonia gas, and an oxygen-containing gas into a chemical
vapor deposition reaction chamber that contains at least one
substrate; and b) forming a silicon oxynitride film on said at
least one substrate by reacting said gases under predetermined
temperature and pressure conditions, wherein the predetermined
temperature is equal to or lower than 600.degree. C.
2. The method of claim 1, wherein said oxygen-containing gas is at
least one component selected from the group consisting of: O.sub.2,
O.sub.3, H.sub.2O, H.sub.2O.sub.2, NO, NO.sub.2, and N.sub.2O.
3. A method for producing silicon oxynitride films by thermal
chemical vapor deposition, comprising: a) feeding a trisilylamine
gas and at least one additional gas containing both oxygen and
nitrogen into a chemical vapor deposition reaction chamber that
contains at least one substrate; and b) forming a silicon
oxynitride film on said at least one substrate by reacting said
gases under predetermined temperature and pressure conditions,
wherein the predetermined temperature is equal to or lower than
600.degree. C.
4. The method of claim 3, wherein said oxygen and nitrogen gas is
at least one component selected from the group consisting of NO,
NO.sub.2, and N.sub.2O.
5. A method for producing silicon oxynitride films by thermal
chemical vapor deposition comprising: a) feeding at least one
trisilylamine gas, at least one ammonia gas, and at least one
oxygen-containing gas into a chemical vapor deposition reaction
chamber that contains at least one substrate; and b) forming at
least one silicon oxynitride film on said at least one substrate by
reacting said gases under predetermined temperature and pressure
conditions, wherein the predetermined temperature is equal to or
lower than 600.degree. C.
6. The method of claim 5, wherein said oxygen-containing gas is at
least one component selected from the group consisting of: O.sub.2,
O.sub.3, H.sub.2O, H.sub.2O.sub.2, NO, NO.sub.2, and N.sub.2O.
7. A method for producing silicon oxynitride films by thermal
chemical vapor deposition, comprising: a) feeding at least one
trisilylamine gas and at least one additional gas containing both
oxygen and nitrogen into a chemical vapor deposition reaction
chamber that contains at least one substrate; and b) forming at
least one silicon oxynitride film on said at least one substrate by
reacting said gases under predetermined temperature and pressure
conditions, wherein the predetermined temperature is equal to or
lower than 600.degree. C.
8. The method of claim 7, wherein said oxygen and nitrogen gas is
at least one component selected from the group consisting of NO,
NO.sub.2, and N.sub.2O.
9. A method for producing silicon oxynitride-containing film by
thermal chemical vapor deposition comprising: a) feeding a
trisilylamine-containing gas, an ammonia-containing gas, and an
oxygen-containing gas into a chemical vapor deposition reaction
chamber that contains at least one substrate; and b) forming a
silicon oxynitride-containing film on said at least one substrate
by reacting said gases under predetermined temperature and pressure
conditions, wherein the predetermined temperature is equal to or
lower than 600.degree. C.
10. The method of claim 9, wherein said oxygen-containing gas is at
least one component selected from the group consisting of; O.sub.2,
O.sub.3, H.sub.2O, H.sub.2O.sub.2, NO, NO.sub.2, and N.sub.2O.
11. A method for producing silicon oxynitride-containing films by
thermal chemical vapor deposition, comprising: a) feeding a
trisilylamine-containing gas and at least one additional gas
containing both oxygen and nitrogen into a chemical vapor
deposition reaction chamber that contains at least one substrate;
and b) forming a silicon oxynitride-containing film on said at
least one substrate by reacting said gases under predetermined
temperature and pressure conditions, wherein the predetermined
temperature is equal to or lower than 600.degree. C.
12. The method of claim 11, wherein said oxygen-containing and
nitrogen-containing gas is at least one component selected from the
group consisting of NO, NO.sub.2, and N.sub.2O.
13. A method for producing silicon oxynitride-containing films by
thermal chemical vapor deposition comprising: a) feeding at least
one trisilylamine-containing gas, at least one ammonia-containing
gas, and at least one oxygen-containing gas into a chemical vapor
deposition reaction chamber that contains at least one substrate;
and b) forming at least one silicon oxynitride-containing film on
said at least one substrate by reacting said gases under
predetermined temperature and pressure conditions.
14. The method of claim 13, wherein said oxygen-containing gas is
at least one component selected from the group consisting of:
O.sub.2, O.sub.3, H.sub.2O, H.sub.2O.sub.2, NO, NO.sub.2, and
N.sub.2O.
15. A method for producing silicon oxynitride-containing films by
thermal chemical vapor deposition, comprising: a) feeding at least
one trisilylamine-containing gas and at least one additional gas
containing both oxygen and nitrogen into a chemical vapor
deposition reaction chamber that contains at least one substrate;
and b) forming at least one silicon oxynitride-containing film on
said at least one substrate by reacting said gases under
predetermined temperature and pressure conditions, wherein the
predetermined temperature is equal to or lower than 600.degree.
C.
16. The method of claim 15, wherein said oxygen-containing and
nitrogen-containing gas is at least one component selected from the
group consisting of NO, NO.sub.2, and N.sub.2O.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn.119(a) and (b) to U.S. application Ser. No.
10/669,623, filed Sep. 24, 2003, the entire contents of which are
incorporated herein by reference.
BACKGROUND
[0002] This invention relates to methods for producing silicon
nitride films and silicon oxynitride films. More particularly, this
invention relates to methods for producing silicon nitride films
and silicon oxynitride films by thermal chemical vapor deposition
(thermal CVD).
[0003] Silicon nitride films have excellent barrier properties and
an excellent oxidation resistance and as a consequence are used in
the fabrication of semiconductor devices, for example, as an
etch-stop layer, barrier layer, or gate dielectric layer, and in
oxide/nitride stacks.
[0004] Plasma-enhanced CVD (PECVD) and low-pressure CVD (LPCVD) are
the methods primarily used at the present time to form silicon
nitride films.
[0005] PECVD is typically carried out by introducing a silicon
source (typically silane) and a nitrogen source (typically ammonia,
but more recently nitrogen) between a pair of parallel plate
electrodes and applying high-frequency energy across the electrodes
at low temperatures (about 300.degree. C.) and low pressures (1
mtorr to 1 torr) in order to induce the generation of a plasma from
the silicon source and nitrogen source. The active silicon species
and active nitrogen species in the resulting plasma react with each
other to produce a silicon nitride film. The silicon nitride films
formed in this manner by PECVD typically do not have a
stoichiometric composition and are also hydrogen rich and
accordingly exhibit a low film density, a poor step coverage, a
fast etching rate, and a poor thermal stability.
[0006] LPCVD uses low pressures (0.1 to 2 torr) and high
temperatures (700.degree. C. to 900.degree. C.) and produces
silicon nitride films with a quality superior to that of the
silicon nitride films produced by PECVD. At the present time
silicon nitride is typically produced by LPCVD by the reaction of
dichlorosilane and gaseous ammonia. However, ammonium chloride is
produced as a by-product in the reaction of dichlorosilane and
gaseous ammonia in this LPCVD procedure: this ammonium chloride
accumulates in and clogs the reactor exhaust lines and also
deposits on the wafer.
[0007] Methods using chlorine-free silicon nitride precursors,
i.e., alkylsilanes, aminosilanes, have been proposed in order to
solve the aforementioned problems. All of these precursors,
however, contain carbon. In accordance with the present invention,
the inventors have discovered that the use of these precursors,
either alone or in combination with ammonia, results in the
incorporation of silicon carbide and/or free carbon in the
resulting silicon nitride film and a deterioration in the
insulating characteristics of this film.
[0008] This problem also occurs when the aforementioned prior art
precursors are used to produce silicon oxynitride films (with the
same precursors, nitrogen containing gases plus an oxygen
containing gas, which are films that have the same properties and
applications as silicon nitride films.
[0009] The formation of silicon nitride on a silicon oxide film by
the reaction of ammonia and trisilylamine (TSA) at 720-740.degree.
C. and an ammonia (TSA partial pressure ratio of 5:1; TSA partial
pressure=5.times.10.sub.-2 torr) has been reported very recently
(M. Copel et al., Applied Physics Letters, Vol. 74, Number 13,
1999). However, this article does not go beyond reporting on the
silicon nitride growth mechanism, nor does it provide any
evaluation of the properties of the produced silicon nitride films.
Moreover, this article is silent on the formation of silicon
oxynitride films using TSA.
[0010] Accordingly, there is a need to day to provide a CVD-based
method that can produce silicon nitride films and silicon
oxynitride films with improved film characteristics without the
accompanying generation of ammonium chloride and without
incorporation of carbonaceous contaminants into the films.
SUMMARY
[0011] As the result of extensive investigations directed to
addressing the issues described hereabove, the present inventors
found that trisilylamine, aside from its lack of chlorine and
carbon, reacts with ammonia to produce high-quality silicon nitride
and reacts with ammonia and an oxygen-containing gas to produce
high-quality silicon oxynitride. These reactions are also not
accompanied by the appearance of reaction by-products downstream
from the reaction chamber. The inventors also discovered that the
ammonia: trisilylamine feed flow rate ratio into the reaction
chamber during the production of silicon nitride film by the
reaction of trisilylamine with ammonia influences the compositional
stability of the resulting silicon nitride film. The inventors
further discovered that the reaction temperature (film formation
temperature) during the production of silicon nitride film by the
reaction of trisilylamine with ammonia influences the step coverage
afforded by the silicon nitride film product. The present invention
is based on these discoveries.
[0012] According to a first aspect of this invention there is
provided a method for producing silicon nitride films by thermal
chemical vapor deposition, comprising the steps of feeding a
trisilylamine gas and an ammonia gas into a chemical vapor
deposition reaction chamber that holds at least one substrate,
forming a silicon nitride film on said at least a substrate by
reacting the two gases under predetermined temperature and pressure
conditions, said method further comprising the step of providing a
flow rate ratio of the ammonia gas to trisilylamine gas fed into
said reaction chamber equal to or greater than 10.
[0013] Preferably, the predetermined temperature conditions of the
reaction between the aforesaid trisilylamine and ammonia gas is set
at a temperature which is equal to or lower than 600.degree. C.
[0014] According to a second aspect of this invention, there is
provided a method for producing silicon nitride films by thermal
chemical vapor deposition, comprising the steps of feeding a
trisilylamine gas and an ammonia gas into a chemical vapor
deposition reaction chamber that holds at least one substrate,
forming a silicon nitride film on said at least one substrate by
reacting the two gases afore mentioned under predetermined
temperature and pressure conditions, said method further comprising
the step of setting the predetermined temperature of the reaction
between the aforesaid trisilylamine and ammonia gas is set at a
value equal to or lower than 600.degree. C.
[0015] According to another aspect of this invention, there is
provided a method for producing silicon oxynitride films by thermal
chemical vapor deposition, said method comprising the steps of:
[0016] feeding a trisilylamine gas, an ammonia gas, and an
oxygen-containing gas into a chemical vapor deposition reaction
chamber that holds at least one substrate; and [0017] forming a
silicon oxynitride film on said at least one substrate by reacting
these gases, under predetermined temperature and pressure
conditions.
[0018] Preferably, the aforesaid oxygen-containing gas is selected
from the group essentially consisting of O.sub.2, O.sub.3,
H.sub.2O, H.sub.2O.sub.2, NO, NO.sub.2, and/or N.sub.2O or any
mixture thereof.
[0019] According to still another aspect of this invention, there
is provided a method for producing silicon oxynitride films by
thermal chemical vapor deposition, comprising the steps of: [0020]
feeding at least one trisilylamine gas and at least one gas
containing both oxygen and nitrogen as constituent elements into a
chemical vapor deposition reaction chamber that holds at least one
substrate; and [0021] forming a silicon oxynitride film on said at
least one substrate by reacting the two gases under predetermined
temperature and pressure conditions.
[0022] Preferably, the aforesaid gas containing both oxygen and
nitrogen as constituent elements is selected from the group
consisting of NO, NO.sub.2, and/or N.sub.2O or any mixture
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 contains a block diagram that illustrates an example
of an apparatus for producing silicon(oxy)nitride films.
[0024] FIG. 2 contains a block diagram that illustrates another
example of an apparatus for producing silicon(oxy)nitride
films.
[0025] FIG. 3 contains a graph that reports the relationship
between the ammonia gas/trisilylamine gas flow rate ratio and the
compositional variation rate of silicon nitride films.
[0026] FIG. 4 contains a graph that reports the relationship
between the CVD reaction temperature and the step coverage ratio
afforded by silicon nitride films.
[0027] FIG. 5 contains a graph that reports the relationship
between the trisilylamine decomposition rate and temperature.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] This invention relates to methods for forming silicon
nitride films and silicon oxynitride films (referred to as
silicon(oxy)nitride films hereinbelow) on substrates by thermal CVD
and uses trisilylamine (TSA) as a precursor for silicon(oxy)nitride
films.
[0029] The methods for producing silicon nitride films will be
considered first. A silicon nitride film is formed on substrate in
this case by feeding TSA gas, ammonia gas, and an optional dilution
gas into a chemical vapor deposition reaction chamber (abbreviated
below as the CVD reaction chamber) that holds at least 1 substrate
(particularly a semiconductor substrate such as a silicon
substrate) and reacting the TSA gas with the ammonia gas. The
substrate may already be provided with an oxide film, such as a
silicon oxide film.
[0030] The pressure in the CVD reaction chamber during this
reaction between TSA gas and ammonia gas can be maintained at from
0.1 torr to 1 atmosphere. This reaction (silicon nitride film
formation) can generally be run at temperatures
.ltoreq.1,000.degree. C. However, since almost no production of
silicon nitride occurs at temperatures below 300.degree. C., the
reaction between TSA gas and ammonia gas will generally be run at
300.degree. C. to 1,000.degree. C. The ammonia gas and TSA gas will
generally be fed into the CVD reaction chamber at an NH.sub.3/TSA
flow rate ratio of at least 4. While silicon nitride can also be
produced at NH.sub.3/TSA flow rate ratios above 500, such
NH.sub.3/TSA flow rate ratios above 500 are uneconomical.
[0031] The inert dilution gas introduced on an optional basis into
the CVD reaction chamber can be an inert gas, for example, nitrogen
or a rare gas such as argon.
[0032] Since TSA contains neither carbon nor chlorine, its reaction
with ammonia does not generate the ammonium chloride by-product
that has heretofore been a problem and the silicon nitride film
product does not become contaminated with carbonaceous
material.
[0033] It has been discovered, in accordance with the first aspect
of this invention, that the compositional stability of the silicon
nitride film product is significantly improved by the use of an
NH.sub.3/TSA flow rate ratio of at least 10 during reaction of the
TSA gas and ammonia gas as described above to produce silicon
nitride film. In other words, silicon nitride film is produced by
reacting ammonia gas and TSA gas under the aforementioned pressure
and reaction temperature conditions using, according to the first
aspect of this invention, a value of at least 10 for the feed flow
ratio of the ammonia gas to the TSA gas that are fed into the CVD
reaction chamber. This use of a value of at least 10 for the
NH.sub.3/TSA flow rate ratio enables the production of silicon
nitride for which the compositional variation of the silicon
nitride film within the plane of the semiconductor substrate due to
flow rate ratio fluctuations is restrained to very small variation
rates of no more than 8%. An almost constant silicon nitride film
composition is obtained at NH.sub.3/TSA flow rate ratios
.gtoreq.20.
[0034] It has also been discovered, in accordance with the second
aspect of this invention, that the step coverage performance of the
silicon oxynitride film product is significantly improved by the
use of a value no greater than 600.degree. C. for the ammonia
gas/TSA gas reaction temperature during reaction of the TSA gas and
ammonia gas as described above to produce silicon nitride film. In
other words, silicon nitride film is produced by reacting ammonia
gas and TSA gas under the aforementioned pressure and NH.sub.3/TSA
flow rate ratio conditions using, according to the second aspect of
this invention, an ammonia gas/TSA gas reaction temperature no
greater than 600.degree. C.
[0035] As used herein, the reaction temperature generally denotes
the temperature of or near the substrate on which the silicon
nitride is formed. While this invention is not limited to the
following means, the temperature of the substrate can be measured
using a radiation thermometer, which converts the intensity of the
radiation from the substrate directly into temperature, or using a
thermocouple disposed in the vicinity of the substrate. When a
thermocouple is employed, it will generally be disposed within the
susceptor that supports the substrate or in the gas region near the
substrate, but other locations can be used as long as they enable
estimation of the temperature of the substrate.
[0036] The step coverage performance can be evaluated using the
step coverage ratio as an index. This step coverage ratio can be
defined as the value afforded by dividing the minimum film
thickness at a step feature by the film thickness in a flat or
planar region. The reaction of ammonia gas with TSA gas at a
temperature no greater than 600.degree. C. in accordance with the
second aspect of this invention can achieve step coverage ratios of
about 0.9 even for apertures with an aspect ratio of 10.
[0037] As the preceding description makes clear, for the purpose of
producing silicon nitride film with a uniform composition and an
excellent step coverage ratio it will be desirable to use an
NH.sub.3/TSA flow rate ratio of at least 10 in combination with a
reaction temperature no greater than 600.degree. C.
[0038] Silicon oxynitride films can be formed on substrates in
accordance with the present invention by introducing at least 1
oxygen-containing gas into the CVD reaction chamber in addition to
the TSA, nitrogenous gas, and optional dilution gas described above
in connection with the formation of silicon nitride films. This
oxygen-containing gas is preferably free of carbon and chlorine and
can be an oxygen-containing gas selected from the group consisting
of oxygen (O.sub.2), ozone (O.sub.3), water vapor (H.sub.2O),
hydrogen peroxide (H.sub.2O.sub.2), nitric oxide (NO), nitrogen
dioxide (NO.sub.2), and nitrous oxide (N.sub.2O).
[0039] A silicon oxynitride film can be formed on substrate by
reacting TSA, ammonia gas, and an oxygen source gas under the
pressure, temperature, and gas flow rate ratio conditions described
in connection with the production of silicon nitride films.
[0040] Ammonia gas need not be separately introduced when the
oxygen source gas is a gas that contains both oxygen and nitrogen
as constituent elements (referred to hereinbelow as
(oxygen+nitrogen)-containing gas). The (oxygen+nitrogen)-containing
gas can be selected from the group consisting of nitric oxide (NO),
nitrogen dioxide (NO.sub.2), and nitrous oxide (N.sub.2O).
[0041] The oxygen source gas can be introduced into the CVD
reaction chamber at an oxygen source gas/TSA gas flow rate ratio of
0.1 to 100.
[0042] The TSA gas used here can be prepared in advance and stored
in, for example, a sealed container, but it can also be synthesized
onsite and the TSA gas thus synthesized can be introduced directly
into the CVD reaction chamber. TSA gas can be synthesized onsite by
introducing ammonia gas and a halosilane that will react with
ammonia to produce TSA, for example, dichlorosilane (DCS), into a
synthesis chamber. At this point, an inert dilution gas, such as
the inert dilution gas that may be introduced into the reaction
chamber, can also be introduced into the synthesis chamber along
with the aforementioned reaction gases. With regard to the
conditions during introduction of the ammonia (NH.sub.3) gas and
DCS gas into the synthesis chamber, the pressure in the synthesis
chamber should be maintained at 300 to 400 torr and the NH.sub.3
gas/DCS flow rate ratio should be 2.5 to 3. The two gases can be
reacted at 50 to 300.degree. C. This reaction produces TSA gas.
While ammonium chloride is produced in this case, it can be removed
using a filter or trap prior to introduction into the CVD reaction
chamber. The resulting TSA gas freed of ammonium chloride can be
introduced into the CVD reaction chamber after its pressure has
been adjusted using a pressure regulator.
[0043] FIG. 1 contains a block diagram that illustrates an example
of an apparatus for producing silicon(oxy)nitride films that is
suitable for implementing the inventive method for producing
silicon(oxy)nitride films. The apparatus illustrated in FIG. 1 uses
a TSA gas source that contains already prepared TSA gas.
[0044] As used on FIG. 1 and the following figures, the reference
symbols used on these drawings have the following meaning:
REFERENCE SYMBOLS
[0045] 10, 20--silicon(oxy)nitride film production apparatus [0046]
11--CVD reaction chamber [0047] 12--trisilylamine gas source [0048]
13--ammonia gas source [0049] 14--inert dilution gas source [0050]
15--oxygen source gas source [0051] 16--waste gas treatment
facility [0052] 21--TSA synthesis chamber [0053] 22--halosilane gas
source [0054] 23--powder trap [0055] 11--susceptor [0056]
112--substrate [0057] 113, 211--heater [0058] L1-L5, L21-L24 --gas
feed line [0059] V1-V4, V21-V23--shutoff valve [0060] PG--pressure
sensor [0061] MFC1-MFC4, MFC21-MFC23--mass flow controller [0062]
BV1, BV2--butterfly valve [0063] PM--vacuum pump
[0064] The production apparatus 10 illustrated in FIG. 1 is
provided with a CVD reaction chamber 11, a TSA gas source 12, an
ammonia gas source 13, and a source 14 of the inert dilution gas
that is introduced on an optional basis. When the production of
silicon oxynitride films is desired, the production apparatus 10
can also be provided with an oxygen source gas source 15. In other
words, an oxygen source gas feed system (the oxygen source gas
source 15 and its attendant features (supply lines, etc.)) is
unnecessary when the production of silicon nitride films is being
pursued.
[0065] A susceptor 111 is disposed within the CVD reaction chamber
11, and a semiconductor substrate 112, such as a silicon substrate,
is mounted on the susceptor 111 (a single semiconductor substrate
is mounted on the susceptor 111 since the apparatus illustrated in
FIG. 1 is a single-wafer apparatus). A heater 113 is provided
within the susceptor 111 in order to heat the semiconductor
substrate 112 to the prescribed CVD reaction temperature. From
several semiconductor substrates to 250 semiconductor substrates
may be held in the CVD reaction chamber in the case of a batch
apparatus. The heater used in a batch apparatus can have a
different structure from the heater used in a single-wafer
apparatus.
[0066] The TSA gas source 12 comprises a sealed container that
holds liquefied TSA. The TSA gas is introduced from its source 12
through the TSA gas feed line L1 and into the CVD reaction chamber
11. There are disposed in this line L1 a shut-off valve V1 and,
downstream therefrom, a flow rate controller such as, for example,
a mass flow controller MFC1. The TSA gas is subjected to control to
a prescribed flow rate by the mass flow controller MFC1 and is
introduced into the CVD reaction chamber 11.
[0067] The ammonia gas source 13 comprises a sealed container that
holds liquefied ammonia. The ammonia gas is introduced from its
source 13 through the ammonia gas feed line L2 and into the CVD
reaction chamber 11. There are disposed in this line L2 a shut-off
valve V2 and, downstream therefrom, a flow rate controller such as,
for example, a mass flow controller MFC2. The ammonia gas is
subjected to control to a prescribed flow rate by the mass flow
controller MFC2 and is introduced into the CVD reaction chamber
11.
[0068] The inert dilution gas source 14 comprises a sealed
container that holds the inert dilution gas. As necessary or
desired, the inert dilution gas is introduced from its source 14
and into the CVD reaction chamber 11 through the inert dilution gas
feed line L3. As shown in FIG. 1, the inert dilution gas feed line
L3 can be joined with the TSA gas feed line L1 and the inert
dilution gas can thereby be introduced into the CVD reaction
chamber 11 in combination with the TSA gas. There are disposed in
this line L3 a shut-off valve V3 and, downstream therefrom, a flow
rate controller such as, for example, a mass flow controller MFC3.
The inert gas is subjected to control to a prescribed flow rate by
the mass flow controller MFC3 and is introduced into the CVD
reaction chamber 11.
[0069] The oxygen source gas source 15 used during the production
of silicon oxynitride films comprises a sealed container that holds
the oxygen source gas. The oxygen source gas is introduced from its
source 15 and into the CVD reaction chamber 11 through the oxygen
source gas feed line L4. There are disposed in this line L4 a
shut-off valve V4 and, downstream therefrom, a flow rate controller
such as, for example, a mass flow controller MFC4. The oxygen
source gas is subjected to control to a prescribed flow rate by the
mass flow controller MFC4 and is introduced into the CVD reaction
chamber 11.
[0070] The outlet from the CVD reaction chamber 11 is connected to
a waste gas treatment facility 16 by the line L5. This waste gas
treatment facility 16 removes, for example, by-products and
unreacted material, and the gas purified by the waste gas treatment
facility 16 is discharged from the system. There are disposed in
the line L5 a pressure sensor PG, a pressure regulator such as a
butterfly valve BV1, and a vacuum pump PM. The introduction of each
gas into the CVD reaction chamber 11 is carried out by the
respective mass flow controllers, while the pressure within the CVD
reaction chamber 11 is monitored by the pressure sensor PG and is
established at a prescribed pressure value by operation of the pump
PM and control of the aperture of the butterfly valve BV1.
[0071] When an (oxygen+nitrogen)-containing gas is used as the
oxygen source gas during the production of silicon oxynitride
films, silicon oxynitride film production can be carried out, as is
clear from the preceding discussion, without the installation of
the ammonia gas feed system (the ammonia gas source 13 and its
attendant features (the valve V2, MFC2, and line L2)).
[0072] FIG. 2 contains a block diagram that illustrates one example
of an apparatus for producing silicon(oxy)nitride films that
contains an onsite facility for producing TSA gas. Those
constituent elements in FIG. 2 that are the same as in FIG. 1 are
assigned the same reference symbol and their detailed explanation
has been omitted.
[0073] The production apparatus 20 illustrated in FIG. 2, in
addition to having the same type of CVD reaction chamber 11 as the
one illustrated in FIG. 1, contains a synthesis chamber 21 for the
onsite synthesis of TSA gas. A heater 211 is disposed on the
circumference of this synthesis chamber 21 for the purpose of
heating the interior of the synthesis chamber 21 to the prescribed
reaction temperature.
[0074] The production apparatus 20 illustrated in FIG. 2 lacks the
TSA gas source 12 shown in FIG. 1 and contains a source 22 of a
halosilane gas, such as dichlorosilane, that will react with
ammonia to produce TSA. The halosilane gas source 22 comprises a
sealed container that holds halosilane gas. Halosilane gas is
introduced from this source 22 through the feed line L21 and into
the synthesis chamber 21. There are disposed in the line L21 a
shut-off valve V21 and, downstream therefrom, a flow rate
controller such as, for example, a mass flow controller MFC21. The
halosilane gas is subjected to control to a prescribed flow rate by
the mass flow controller MFC21 and is introduced into the synthesis
chamber 21.
[0075] The ammonia gas source 13 is provided with a feed line L22
to the synthesis chamber 21 in addition to the feed line L2 to the
CVD reaction chamber 11. There are disposed in this feed line L22 a
shut-off valve V22 and, downstream therefrom, a flow rate
controller such as, for example, a mass flow controller MFC22. The
ammonia gas is subjected to control to a prescribed flow rate by
the mass flow controller MFC22 and is introduced into the synthesis
chamber 21.
[0076] The inert dilution gas source 14 is provided with a feed
line L23 to the synthesis chamber 21 in addition to the feed line
L3 to the CVD reaction chamber 11. There are disposed in this feed
line L23 a shut-off valve V23 and, downstream therefrom, a flow
rate controller such as, for example, a mass flow controller MFC23.
The inert dilution gas is subjected to control to a prescribed flow
rate by the mass flow controller MFC23 and is introduced into the
synthesis chamber 21. The line L3 in the apparatus in FIG. 2 is
directly connected to the CVD reaction chamber 11.
[0077] The outlet from the synthesis chamber 21 is connected by the
line L24 to the CVD reaction chamber 11. There are disposed in the
line L24 a powder trap 23 and, downstream therefrom, a pressure
regulator, for example, a butterfly valve BV2. The purpose of the
powder trap 23 is to remove silazane solids and particulate
ammonium chloride generated as by-products in the synthesis chamber
21. The TSA gas afforded by the synthesis chamber 21 is subjected
to removal of the solid silazane and ammonium chloride by-products
by the powder trap 23 and is introduced into the CVD reaction
chamber 11 after the pressure has been adjusted by the butterfly
valve BV2 as appropriate for introduction into the CVD reaction
chamber 11.
EXAMPLES
[0078] This invention will be described in additional detail by
working examples as follows, but this invention is not limited to
these working examples.
Example 1
[0079] A production apparatus as illustrated in FIG. 1 (lacking,
however, an oxygen source gas feed system) was used in this
example. Ammonia gas and TSA gas were introduced into a CVD
reaction chamber holding a silicon substrate and a silicon nitride
film was formed on this silicon substrate under the following
conditions. [0080] ammonia gas flow rate: 40 sccm [0081] TSA gas
flow rate: 0.5 sccm [0082] pressure within the CVD reaction
chamber: 1 torr [0083] reaction temperature: 640.degree. C.
[0084] The resulting silicon nitride film was confirmed by Auger
spectroscopy to have the composition Si.sub.0.81N. The deposition
(growth) rate of this silicon nitride film was 17 .ANG./min. The
NH.sub.3/TSA flow rate ratio in this example was 80, and a stable
film composition was achieved.
Example 2
[0085] A production apparatus as illustrated in FIG. 1 (lacking,
however, an oxygen source gas feed system) was used in this
example. Ammonia gas and TSA gas were introduced into a CVD
reaction chamber holding a silicon substrate and a silicon nitride
film was formed on this silicon substrate under the following
conditions. [0086] ammonia gas flow rate: 40 sccm [0087] TSA gas
flow rate: 4 sccm [0088] pressure within the CVD reaction chamber:
1 torr [0089] reaction temperature: 560.degree. C.
[0090] The resulting silicon nitride film was confirmed by Auger
spectroscopy to have the composition Si.sub.1.04N. The deposition
(growth) rate of this silicon nitride film was 6 .ANG./min. The
NH.sub.3/TSA flow rate ratio in this example was 10, and a stable
film composition was achieved.
Example 3
[0091] A production apparatus as illustrated in FIG. 1 (lacking,
however, an oxygen source gas feed system) was used in this
example. Ammonia gas and TSA gas were introduced into a CVD
reaction chamber holding a silicon substrate, and a silicon nitride
film was formed on this silicon substrate using a pressure within
the CVD reaction chamber of 1 torr and a reaction temperature of
600.degree. C. Silicon nitride film formation was carried out at
different NH.sub.3/TSA flow rate ratios over the range from 0 to
80. Auger spectroscopy was used to analyze the composition of the
silicon nitride films obtained at the different NH.sub.3/TSA flow
rate ratios, and the compositional variation rate was calculated
from the equation compositional variation rate=-d(Si/N)dX wherein X
is the NH.sub.3/TSA flow rate ratio. The results are reported in
FIG. 3.
[0092] The results reported in FIG. 3 show that the film
compositional variation rate due to changes in the flow rate ratio
assumed very small values when the NH.sub.3/TSA flow rate ratio was
at least 10 and more particularly that the film compositional
variation rate became approximately 0 when the NH.sub.3/TSA flow
rate ratio was at least 20.
Example 4
[0093] (A) Using a production apparatus with the structure shown in
FIG. 1 (lacking, however, an oxygen source gas feed system),
silicon nitride films were formed at different reaction
temperatures in a CVD reaction chamber holding a silicon substrate
on which trenches (diameter: 0.6 .mu.m) with an aspect ratio
(depth/diameter) of 10 had been formed. Ammonia gas was introduced
at a flow rate of 40 sccm; TSA gas was introduced at a flow rate of
0.5 sccm; and a pressure of 1 torr was established in the CVD
reaction chamber. The step coverage ratios of the silicon nitride
films obtained at the different temperatures were measured by
scanning electron microscopy (SEM), and the results are reported in
FIG. 4.
[0094] The results in FIG. 4 show that the step coverage
performance of the produced silicon nitride films was improved up
to about 0.9 through the use of a reaction temperature no greater
than 600.degree. C.
[0095] (B) The thermal stability of TSA was also evaluated. The TSA
concentration at the CVD reaction chamber outlet was measured with
a mass spectrometer at different temperatures within the CVD
reaction chamber. TSA gas was introduced into the CVD reaction
chamber during these experiments at a flow rate of 0.12 sccm and
ammonia gas was introduced at a flow rate of 10 sccm. The ratio of
the TSA concentration at the outlet from the CVD reaction chamber
to the TSA concentration at the inlet was calculated and is
reported in FIG. 5.
[0096] The results in FIG. 5 show that the TSA outlet
concentration/TSA inlet concentration undergoes a sharp decline
above 600.degree. C., or in other words that the TSA decomposition
rate undergoes a sharp increase above 600.degree. C.
[0097] These results show that the step coverage performance of
silicon nitride films formed by the reaction of ammonia and TSA is
closely related to the TSA decomposition temperature and is
significantly better (a step coverage ratio of about 0.9 is reached
at temperatures .ltoreq.600.degree. C.) at temperatures no greater
than 600.degree. C. where TSA decomposition substantially does not
occur. It is thought that reaction intermediates produced by the
vapor-phase decomposition reaction of TSA cause a deterioration in
the step coverage performance.
Example 5
[0098] A production apparatus with the structure illustrated in
FIG. 2 (lacking, however, an oxygen source gas feed system) was
used in this example. DCS gas was introduced at a flow rate of 20
sccm, ammonia gas was introduced at a flow rate of 54 sccm, and
nitrogen gas (inert dilution gas) was introduced at a flow rate of
20 sccm while the pressure within the synthesis chamber was
maintained at 300-400 torr and the temperature was maintained at
200.degree. C. The composition of the synthesis chamber effluent
gas was analyzed by gas chromatography at the synthesis chamber
outlet downstream from the powder trap. The composition was
determined to be 5 volume % TSA with the remainder being mainly
nitrogen. This effluent gas was directly introduced into the CVD
reaction chamber after adjustment of its pressure. Ammonia gas was
also introduced into the CVD reaction chamber. The following
conditions were used. [0099] ammonia gas flow rate: 20 sccm [0100]
effluent gas flow rate: approximately 20 sccm [0101] pressure
within the CVD reaction chamber: 1 torr [0102] reaction
temperature: 635.degree. C.
[0103] The resulting silicon nitride film was confirmed by Auger
spectroscopy to have the composition Si.sub.0.9N. The deposition
(growth) rate of this silicon nitride film was 18 .ANG./min.
Neither carbon nor chlorine was detected by Auger spectroscopy in
the silicon nitride film product.
Example 6
[0104] The production apparatus illustrated in FIG. 1 was used in
this example. Silicon oxynitride film was formed on a silicon
substrate under the following conditions by admitting ammonia gas
and nitrogen-diluted TSA gas (5 volume % TSA) into a CVD reaction
chamber holding a silicon substrate. [0105] ammonia gas flow rate:
17 sccm [0106] flow rate of nitrogen-diluted TSA gas: 2.5 sccm
[0107] oxygen flow rate: 0.5 sccm [0108] pressure within the CVD
reaction chamber: 10 torr [0109] reaction temperature: 600.degree.
C.
[0110] The resulting silicon oxynitride film was confirmed by Auger
spectroscopy to have the composition Si.sub.0.78N.sub.1O.sub.0.1.
The deposition (growth) rate of this silicon oxynitride film was
15.5 .ANG./min.
[0111] This invention has been described hereinabove through
various embodiments and working examples, but this invention is not
limited thereto. The various embodiments described above can be
combined as appropriate.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0112] As has been described hereinabove, the inventive methods
enable the production of silicon nitride films and silicon
oxynitride films without the accompanying production of ammonium
chloride and without incorporation of carbonaceous contaminants in
the film. More particularly, the use of an ammonia
gas/trisilylamine gas flow rate ratio of at least 10 during the CVD
reaction enables the production of silicon nitride films that have
small compositional variation rates. Moreover, the use of a CVD
reaction temperature no greater than 600.degree. C. enables the
production of silicon nitride films that exhibit an excellent step
coverage performance.
[0113] Of course, the invention described in the present
specification comprises also the introduction of one or several
trisilylamine containing gases, one or several ammonia containing
gases and one or several oxygen containing gases in the
reactor.
[0114] It Will be understood that many additional changes in the
details, materials, steps and arrangement of parts, which have been
herein described in order to explain the nature of the invention,
may be made by those skilled in the art within the principle and
scope of the invention as expressed in the appended claims. Thus,
the present invention is not intended to be limited to the specific
embodiments in the examples given above.
* * * * *