U.S. patent application number 12/647902 was filed with the patent office on 2010-04-22 for method for forming insulation film.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Seiji Matsuyama, Genji Nakamura, Toshio Nakanishi, Shigenori Ozaki, Masaru Sasaki, Takuya Sugawara, Yoshihide Tada.
Application Number | 20100096707 12/647902 |
Document ID | / |
Family ID | 28671932 |
Filed Date | 2010-04-22 |
United States Patent
Application |
20100096707 |
Kind Code |
A1 |
Sugawara; Takuya ; et
al. |
April 22, 2010 |
Method for Forming Insulation Film
Abstract
In a process involving the formation of an insulating film on a
substrate for an electronic device, the insulating film is formed
on the substrate surface by carrying out two or more steps for
regulating the characteristic of the insulating film involved in
the process under the same operation principle. The formation of an
insulating film having a high level of cleanness can be realized by
carrying out treatment such as cleaning, oxidation, nitriding, and
a film thickness reduction while avoiding exposure to the air.
Further, carrying out various steps regarding the formation of an
insulating film under the same operation principle can realize
simplification of the form of an apparatus and can form an
insulating film having excellent property with a high
efficiency.
Inventors: |
Sugawara; Takuya;
(Nirasaki-shi, JP) ; Tada; Yoshihide;
(Nirasaki-shi, JP) ; Nakamura; Genji;
(Nirasaki-shi, JP) ; Ozaki; Shigenori;
(Amagasaki-shi, JP) ; Nakanishi; Toshio;
(Amagasaki-shi, JP) ; Sasaki; Masaru;
(Amagasaki-shi, JP) ; Matsuyama; Seiji;
(Amagasaki-shi, JP) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
28671932 |
Appl. No.: |
12/647902 |
Filed: |
December 28, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12145971 |
Jun 25, 2008 |
7662236 |
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12647902 |
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10509370 |
Sep 28, 2004 |
7446052 |
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PCT/JP2003/004091 |
Mar 31, 2003 |
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12145971 |
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Current U.S.
Class: |
257/411 ;
257/E21.192; 257/E29.255; 438/585 |
Current CPC
Class: |
H01L 21/3105 20130101;
H01L 21/022 20130101; H01L 21/02329 20130101; H01L 21/0214
20130101; H01L 21/3165 20130101; Y10T 428/12806 20150115; H01L
21/02164 20130101; H01L 21/3185 20130101; H01L 21/02326 20130101;
Y10T 428/12736 20150115; H01L 21/0234 20130101 |
Class at
Publication: |
257/411 ;
438/585; 257/E21.192; 257/E29.255 |
International
Class: |
H01L 29/78 20060101
H01L029/78; H01L 21/28 20060101 H01L021/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2002 |
JP |
2002-097906 |
Claims
1. An electronic device including a substrate, manufactured by a
process for forming an insulating film on the surface of the
substrate, comprising the steps of: cleaning the substrate with
plasma based on a cleaning gas comprising a rare gas; oxidizing the
substrate with plasma based on an oxidizing gas comprising a rare
gas and oxygen, to thereby form an oxide film thereon; nitriding
the oxide film with plasma based on a nitriding gas comprising a
rare gas and nitrogen, to thereby form an oxynitride film thereon;
treating the oxynitride film with plasma based on a treating gas
comprising hydrogen after the nitriding to recover defects in the
oxynitride film; forming an electrode on the oxynitride film; and,
wherein the cleaning and oxidizing are conducted under the same
operation principle; and, the cleaning and oxidizing are conducted
in the same vessel without exposure of the substrate to air.
2. An electronic device according to claim 1, wherein the substrate
is subjected to wet cleaning prior to the cleaning with plasma.
3. An electronic device according to claim 1, wherein the electrode
comprises polysilicon.
4. An electronic device including a substrate, manufactured by a
process for forming an insulating film on the surface of the
substrate, comprising the steps of: cleaning the substrate with
plasma based on a cleaning gas comprising a rare gas; oxidizing the
substrate with plasma based on an oxidizing gas comprising a rare
gas and oxygen, to thereby form an oxide film thereon; treating the
oxide film with plasma based on a treating gas comprising hydrogen
after the oxidizing to recover defects in the oxide film; forming a
High-k film on the oxide film after the treating; forming an
electrode on the High-k film; and, wherein the cleaning and
oxidizing are conducted under the same operation principle; and,
the cleaning and oxidizing are conducted in the same vessel without
exposure of the substrate to air.
5. An electronic device according to claim 4, wherein the High-k
film comprises one material selected from the group consisting of
Al.sub.20.sub.3, Zr0.sub.2, Hf0.sub.2, and Ta.sub.20.sub.5, ZrSiO,
HfSiO and ZrA10.
6. An electronic device according to claim 4, wherein the process
comprises nitriding the oxide film with plasma based on a nitriding
gas comprising a rare gas and nitrogen after the oxidizing.
7. An electronic device according to claim 4, wherein the electrode
comprises one material selected from the group consisting of
polysilicon, silicon germanium and metal.
8. An electronic device according to claim 4, wherein the treating
gas consists of rare gas and hydrogen.
9. An electronic device according to claim 4, wherein the substrate
is subjected to wet cleaning prior to the cleaning with plasma.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S.
application Ser. No. 12/145,971, filed Jun. 25, 2008, which is a
continuation application of U.S. application Ser. No. 10/509,370,
filed Sep. 28, 2004, which is a National Phase of
PCT/JP2003/004091, filed Mar. 31, 2003 and which claims priority
under 35 U.S.C. .sctn.119 to Japanese Patent Application No.
2002-097906, filed Mar. 29, 2002, the entire disclosures of which
are herein expressly incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a process for forming an
insulating film having various excellent characteristics (for
example, control of very small film thickness and a high level of
cleanness) with a high efficiency (for example, small footprint
provided by conducting various steps in a single reaction chamber,
or simplification of operationality and prevention of
cross-contamination between apparatuses realized by conducting
various steps in separate reaction chambers under the same
principle of operation). The process for forming an electronic
device material according to the present invention is suitably
usable for the formation of a material, for example, for a
semiconductor or a semiconductor device (for example, one having an
MOS-type semiconductor structure with a gate insulating film having
an excellent characteristic).
BACKGROUND ART
[0003] The present invention is generally and widely applicable to
the formation of electronic device materials, for example, for
semiconductors or semiconductor devices and liquid crystal devices.
Herein, for the convenience of explanation, the background art
relating to semiconductor devices will be explained as an
example.
[0004] Substrates for semiconductor. or electronic device materials
including silicon are subjected to various types of treatment such
as formation of insulating films including oxide films, formation
of films by CVD or the like, and etching.
[0005] It is not too much to say that an improvement in the
performance of semiconductor devices in recent years has been
achieved by virtue of techniques for microfabrication of the
devices including transistors. Even today, an effort is still being
made to further improve the transistor microfabrication techniques
for higher performance. A demand for a higher level of
microfabrication and higher performance of semiconductor devices in
recent years has led to ever-increasing needs for insulating films
with higher performance, for example, in terms of leakage current.
The reason for this is that, in recent microfabricated, highly
integrated and/or higher-performance devices, even a low level of
leakage current may possibly cause severe problems, although such a
leakage current does not pose substantially no problem in the case
of conventional relatively low-integrated devices. In particular,
low-power consumption devices are indispensable to the development
of portable electronic devices in the so-called ubiquitous society
(information-oriented society using as a medium electronic devices
which can be connected to networks anywhere at any time) which has
begun in recent years, and, to this end, a reduction in leakage
current is very important.
[0006] Typically, for example, in the development of a
next-generation or advanced MOS transistor, with the advancement of
the above microfabrication technique, the possible thickness
reduction of gate insulating films has approached to its limit,
and, consequently, a severe problem to be overcome has appeared.
More specifically, according to process technology, the thickness
of a silicon oxide (SiO.sub.2) film, which is currently used as a
gate insulating film, can be reduced to the maximum (level of 1 to
2 atomic layers). However, when the film thickness is reduced to 2
nm or less, the leakage current due to a direct tunnel by quantum
effect is increased exponentially, so as to increased the power
consumption disadvantageously.
[0007] At the present time, IT (information technology) markets are
being transformed from stationary electronic devices typified, for
example, by desktop personal computers and home telephones (devices
in which electric power is supplied from a receptacle) to
"ubiquitous network society" in which electronic devices are
accessible to the Internet and the like anywhere at any time.
Therefore, in the very near future, portable terminals such as
portable telephones (cellular phones) and car navigation systems
are considered to be mainly used. Such portable terminals per se
are required to be a high performance device. At the same time,
requirements for small size, lightweight, and functions capable of
withstanding use for a long period of time should be satisfied,
although such requirements are not very important to the above
stationary devices. Therefore, in portable terminals, reducing
power consumption while improving performance is very
important.
[0008] Typically, for example, in the development of
next-generation MOS transistors, enhancing the level of
microfabrication of high-performance silicon LSI poses problems of
increased leakage current and increased power consumption. In order
to reduce the power consumption while enhancing the performance,
the characteristics of MOS transistors should be improved without
increasing gate leakage current in the transistors.
[0009] The formation of a good-quality and thin (for example, a
film thickness of not more than about 15 A (angstroms)) insulating
film is indispensable for simultaneously achieving an enhancement
in the level of microfabrication and an improvement in
characteristics.
[0010] However, the formation of a good-quality and thin insulating
film is very difficult. For example, an insulating film formed by
conventional thermal oxidation or CVD (chemical vapor deposition
method) is unsatisfactory in any one of characteristics, i.e.,
either film quality or film thickness.
DISCLOSURE OF INVENTION
[0011] An object of the present invention is to solve the drawbacks
encountered in the prior art and to provide a process for forming a
thin insulating film on a substrate for an electronic device.
[0012] Another object of the present invention is to provide a
process for forming a thin insulating film on the surface of a
substrate for an electronic device, which can suitably carry out
post-treatment (for example, formation of films by CVD or the like
and etching) and can provide an insulating film excellent in both
film quality and film thickness.
[0013] A further object of the present invention is to carry out
various steps involved in the formation of an insulating film under
the same principle of operation, thereby simplifying the apparatus
form and efficiently forming an insulating film having an excellent
characteristic. As a result of earnest study, the present inventors
have found that the formation of an insulating film by a method
which enables not only the practice of one step in one apparatus as
in the prior art but also the practice of various steps in a single
apparatus is very effective for attaining the above objects.
[0014] The process or forming an insulating film formation on the
surface of a substrate for an electronic device according to the
present invention is based on the above discovery. More
specifically the process comprises: at least two steps of
regulating the characteristic-of the insulating film, wherein the
at least two steps of regulating the characteristic of the
insulating film are conducted under the same operation principle.
For example, the present invention may include some embodiments
wherein the application of plasma to a substrate for an electronic
device using a process gas comprising at least a rare gas can
provide a cleaning effect, the incorporation of oxygen or nitrogen
in the same plasma causes oxidation or nitridation, or the
application of the same plasma containing at least hydrogen to an
oxygen atom-containing insulating film including an oxide film can
reduce the thickness of the insulating film.
[0015] In the process for forming an insulating film according to
the present invention having the above constitution, for example,
an insulating film having any desired thickness can easily be
formed by forming a film having a desired thickness with attention
focused on film quality and then reducing the film thickness by a
specific plasma treatment.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a schematic sectional view showing one embodiment
of an MOS structure which can be formed according to the present
invention.
[0017] FIG. 2 is a partial schematic sectional view showing one
embodiment of a semiconductor production device usable in the
process for forming an insulating film according to the present
invention.
[0018] FIG. 3 is a schematic vertical sectional view showing one
embodiment of a plane antenna member (RLSA; also referred to as
slot plane antenna or SPA) plasma processing unit usable in the
process for forming an insulating film according to the present
invention.
[0019] FIG. 4 is a schematic plan view showing one embodiment of
RLSA usable in a apparatus for producing an electronic device
material according to the present invention.
[0020] FIG. 5 is a graph showing a leakage characteristic of an
oxide film in a case where the oxide film has been subjected to a
pre-oxidation plasma treatment, and the oxide film has not been
subjected to a pre-oxidation plasma treatment. In this figure, the
abscissa denotes the electrical film thickness and the ordinate
denotes the leakage current value for the gate oxide film at a gate
voltage Vfb -0.4 V.
[0021] FIG. 6 is a diagram showing a flatband characteristic of a
similar film. In this figure, the abscissa denotes the electrical
film thickness and the ordinate denotes the flatband voltage.
[0022] FIG. 7a is a diagram showing a change in the electrical film
thickness of a gate oxynitride film using a plurality of steps
(multi-process) in the present invention with the elapse of time
(i.e., a change in the electrical film thickness in each step). In
this figure, the abscissa denotes the treatment time, and the
ordinate denotes the electrical film thickness.
[0023] FIG. 7b is a diagram showing a change in the electrical film
thickness of a film similar to that of FIG. 6 with the elapse of
time (i.e., a change in the electrical film thickness in each
step). In this figure, the abscissa denotes the treatment time, and
the ordinate denotes the electrical film thickness.
[0024] FIG. 8 is a diagram showing the results of SIMS analysis for
the concentration of oxygen in a film similar to that of FIG. 6, In
this figure, the abscissa denotes the etching time in the analysis,
and the ordinate denotes the oxygen signal intensity.
[0025] FIG. 9 is a schematic sectional view showing one embodiment
of the surface of a silicon substrate on which a gate oxide film
and a gate insulating film are to be formed.
[0026] FIG. 10 is a schematic sectional view showing one embodiment
of plasma treatment to be effected on the surface of a
substrate.
[0027] FIG. 11 is a schematic sectional view showing one embodiment
of the formation of an SiO.sub.2 film on a substrate using plasma,
nitriding, and hydrogen plasma treatment.
[0028] FIG. 12 is a schematic sectional view showing one embodiment
of the formation of a film using a Hi-k material.
[0029] FIG. 13 is a schematic sectional view showing one embodiment
of the formation of a gate electrode on a Hi-k material film.
[0030] FIG. 14 is a schematic sectional view showing one embodiment
of the formation of an MOS capacitor.
[0031] FIG. 15 is a schematic sectional view showing one embodiment
of the formation of a source and a drain by ion implantation.
[0032] FIG. 16 is a schematic sectional view showing one embodiment
of an MOS transistor structure provided by the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0033] Hereinbelow, the present invention will be described in
detail with reference to the accompanying drawings as desired. In
the following description, "%" and "part(s)" representing a
quantitative proportion or ratio are those based on mass, unless
otherwise specifically noted.
(Process for Forming Insulating Film)
[0034] In the present invention, a very thin (not more than 15 A)
insulating film can be formed by adopting a desired combination of
two or more steps, e.g., a step of applying plasma to a substrate
for an electronic device using a process gas comprising at least a
rare gas to attain a cleaning effect, a step of incorporating
oxygen or nitrogen in the same plasma for oxidation or nitridation,
and a step of applying the same plasma containing at least hydrogen
to an oxygen atom-containing insulating film including an oxide
film to reduce the thickness of the insulating film. The process
for forming an insulating film according to the present invention
can be applied to any object without particular limitation. For
example, the present invention can provide a thin insulating film
having a surface particularly suitable for the formation of a film
of a high-dielectric constant (high-k) material sensitive to the
film-forming conditions and the like.
(Insulating Film to be Formed)
[0035] The composition, thickness, production process, and
properties of an insulating film formable by the present invention
are as follows. Composition: oxide film, oxynitride film, and
nitride film Production process: a process in which, in a single
vessel using plasma comprising at least a rare gas, one or at least
two of a step of cleaning, a step of oxidation, a step of
nitriding, and a step of film thickness reduction is carried out on
an electronic substrate; or a process in which plasma comprising at
least a rare gas is produced within a plurality of vessels under
the same principle of operation and a step of cleaning, a step of
oxidation, a step of nitriding, or a step of film thick reduction
is carried out on an electronic substrate. Thickness: physical thin
film 5 A to 20 A
(Evaluation of Film Quality and Film Thickness)
[0036] The level of the film quality and the level of the film
thickness of the thin insulating film, which has been formed
according to the present invention, can be suitably evaluated, for
example, by actually forming a film of a high-k material on the
surface of the thin film. In this case, whether or not a
high-quality high-k material film has been formed can be evaluated,
by a method wherein a standard MOS semiconductor structure as
described in a publication (see, Masanori Kishino and Mitsumasa
Koyanagi, "VLSI Device no Butsuri (Physics of VLSI Devices)", pp.
62-63, published by Maruzen) is fabricated and the evaluation of
the characteristic of the thus fabricated MOS can be used as the
evaluation of the characteristic of the insulating film itself.
This is because, in such a standard MOS structure, the
characteristic of the insulating film constituting the MOS
structure has much effect on the MOS characteristic.
[0037] Regarding the formation of this MOS structure, for example,
an MOS capacitor comprising a high-k material film can be formed
under conditions of Example 1 appearing hereinafter. In the
formation of an MOS capacitor comprising a high-k material film
under conditions of Example 1, according to the present invention,
it is preferred that (1) flatband characteristic or (2) leak
characteristic (more preferably, both of these) as described below
are provided.
[0038] (1) Preferred flatband characteristic: Within .+-.50 mV as
compared with thermally grown oxide film
[0039] (2) Leak characteristic: Reduction by one figure (or digit)
as compared with thermally grown oxide film, or less
(Combination with Post-Treatment)
[0040] A thin insulating film formed by the process for forming an
insulating film according to the present invention is suitable for
the subsequent various types of treatment. The "post-treatment" is
not particularly limited and may be various types of treatment such
as formation of an oxide film, formation of film by CVD or the
like, and etching. The process for forming an insulating film
according to the present invention can be carried out at a low
temperature. Therefore, regarding the subsequent treatment as well,
a combination with treatment under relatively low (preferably
600.degree. C. or below, more preferably 500.degree. C. or below)
temperature conditions is particularly effective. The reason for
this is that, since the use of the present invention enables the
formation of an oxide film, i.e., one of the steps requiring the
highest temperature in the device preparation process, to be
carried out at a low temperature, a device can be prepared while
avoiding a high-temperature heat history.
(Substrate for Electronic Device)
[0041] The substrate for an electronic device usable in the present
invention is not particularly limited, and one or a combination of
two or more of conventional substrates for an electronic device may
be properly selected and used. Examples of such substrates for an
electronic device may include semiconductor materials and liquid
crystal device materials. Examples of semiconductor materials may
include materials mainly comprising single-crystal silicon and
materials mainly comprising silicon germanium.
(Process Gas)
[0042] Any process gas may be used in the present invention without
particular limitation, as long as the gas contains at least a rare
gas, and one or a combination of two or more of conventional
process gases usable in the
[0043] production of electronic devices may be properly selected
and used. Examples of such process gases (rare gas) may include: Ar
(argon), He (helium), Kr (krypton), Xe (xenon), Ne (neon), O.sub.2
(oxygen), N.sub.2 (nitrogen), H.sub.2 (hydrogen), and NH.sub.3
(ammonia).
(Treatment Conditions)
[0044] In the formation of an insulating film according to the
present invention, the following conditions are suitably usable
from the viewpoint of the property of the thin insulating film to
be formed.
[0045] Rare gas (for example, Kr, Ar, He, Xe, or Ne): 500 to 3000
sccm, more preferably 1000 to 2000 sccm.
[0046] In a step of cleaning, a process gas comprising at least a
rare gas may be used, and a hydrogen gas may further be added. The
flow rate of the hydrogen gas H.sub.2 may be 0 to 100 sccm, more
preferably 0 to 50 sccm. In a step of oxidation, a process gas
comprising at least a rare gas and oxygen may be used, and the flow
rate of the oxygen gas O.sub.2 may be 10 to 500 sccm, more
preferably 10 to 200 sccm.
[0047] In a step of nitriding, a process gas comprising at least a
rare gas and nitrogen may be used, and the flow rate of the
nitrogen gas N.sub.2 may be 3 to 300 sccm, more preferably 20 to
200 sccm.
[0048] In a step of etching, a process gas comprising at least a
rare gas and hydrogen may be used, and the flow rate of the
hydrogen gas H.sub.2 is 0 to 100 sccm, more 5 preferably 0 to 50
sccm.
[0049] Temperature: room temperature 25.degree. C. to 500.degree.
C., more preferably 250 to 500.degree. C., particularly preferably
250 to 400.degree. C.
[0050] Pressure: 3 to 500 Pa, more preferably 7 to 260 Pa
[0051] Microwave: 1 to 5 W/cm.sup.2, more preferably 2 to 4
W/cm.sup.2, particularly preferably 2 to 3 W/cm.sup.2
[0052] In the present invention, any plasma may be used without
particular limitation. It is preferred to use plasma with a
relatively low electron temperature and a high density, from the
viewpoint of easiness on uniform film thickness reduction.
(Suitable Plasma)
[0053] The property of plasma which is suitably used in the present
invention is as follows.
[0054] Electron temperature: 0.5 to 2.0 eV
[0055] Density: 1E10 to 5E12/cm.sup.3
[0056] Uniformity of plasma density: .+-.10%
(Plane Antenna Member)
[0057] In the process for forming an insulating film according to
the present invention, it is preferred that plasma with a low
electron temperature and a high density is formed by the
application of microwaves through a plane antenna member provided
with a plurality of slots. In the present invention, since an
oxynitride film is formed using plasma having such an excellent
property, a low-plasma damage, low-temperature, and highly reactive
process can be realized. Further, in the present invention, as
compared with the use of conventional plasma, the application of
microwaves through the plane antenna member is advantageous in that
an insulating film, the thickness of which has been more suitably
reduced can easily be formed.
[0058] According to the present invention, an insulating film with
a reduced film thickness can be formed. Therefore, a semiconductor
device structure having an excellent characteristic can easily be
formed by forming another layer (for example, another insulating
layer) on the insulating film with a reduced film thickness. The
insulating film with a thickness reduced by the present invention
is particularly suitable for the formation of a high-k material
film on the surface of the insulating film with a reduced film
thickness.
(High-k Material)
[0059] The high-k material usable in the present invention is not
particularly limited. The value of the k (specific dielectric
constant) may preferably be not less than 7, more preferably, not
less than 10, from the viewpoint of increasing the physical film
thickness.
[0060] Preferred examples of the high-k material may be one or at
least two high-k materials selected from the group consisting of:
A1.sub.2O.sub.3r ZrO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5, and
silicates such as ZrSiO, HfSiO; aluminates such as ZrAlO.
(Treatment in the Same Vessel)
[0061] The expression "in the same vessel" which will be described
below means that, after a certain step, the substrate to be treated
is subjected to a subsequent treatment without passage through the
wall of the vessel. In the case of the use of the so-called
"cluster" structure using a combination of a plurality of vessels,
when the transfer of the substrate between different vessels
constituting the cluster is carried out, this treatment is not
treatment "in the same vessel" referred to in the present
invention.
[0062] In this way, in the present invention, "in the same vessel"
without the exposure of the substrate to be formed (such as a
silicon substrate) to the air, a plurality of steps can be
successively carried out in a reaction chamber under the same
principle. For example, a reduction in footprint can be realized by
conducting all steps in a single reaction chamber. Further, also
when the individual steps are carried out in respective separate
reaction chambers, since reaction chambers identical to each other
in the principle of operation are arranged, the same gas piping and
operation panel can be used, to thereby realize an excellent
maintenance and operationality. Further, the same apparatus is
used, there is no significant fear of cross-contamination between
the apparatuses. Even when a cluster construction using a plurality
of reaction chambers is adopted, the processing order can be
changed in various ways. A gate insulating film having various
characteristics can be prepared by this method.
[0063] The oxide film or oxynitride film formed according to the
present invention as such may be used as a gate insulating film.
Alternatively, a process may be adopted which comprises forming a
very thin (about 10 A (angstroms)) oxide film or oxynitride film
according to the present invention and forming thereon a film of a
material a having high dielectric constant such as a high-k
material. According to this method, a stacked gate insulating film
structure (gate stack structure) having a higher level of
interfacial characteristic (such as a higher level of transistor
carrier mobility) than the gate insulating film formed using a
high-k material only.
(Suitable Characteristic of MOS Semiconductor Structure)
[0064] The very thin and good-quality insulating film formable on
the substrate cleaned by the present invention is particularly
suitable for the utilization as an insulating film in a
semiconductor device (particularly, a gate insulating film in an
MOS semiconductor structure).
[0065] According to the present invention, as described below, an
MOS semiconductor structure having suitable characteristic can
easily be produced. The characteristic of the oxynitride film
formed by the present invention can be evaluated, by a method
wherein a standard MOS semiconductor structure as described in a
publication (see, Masanori Kishino and Mitsumasa Koyanagi, "Physics
of VLSI Devices", pp. 62-63, published by Maruzen) is fabricated
and the evaluation of the characteristic of the thus fabricated MOS
can be used as the evaluation of the characteristic of the
oxynitride film itself. This is because, in such a standard MOS
structure, the characteristic of the oxynitride film constituting
the MOS structure has much effect on the MOS characteristic.
(One Embodiment of Production Apparatus)
[0066] A preferred embodiment of the production process according
to the present invention will be described.
[0067] At the outset, regarding one embodiment of the structure of
a semiconductor device which can be produced by the production
process of an electronic device material according to the present
invention, a semiconductor device having an MOS structure provided
with a gate insulating film as an insulating film will be described
with reference to FIG. 1.
[0068] In FIG. 1 (a), reference numeral 1 designates a silicon
substrate, numeral 11 a field oxide film, numeral 2 a gate
insulating film, and numeral 13 a gate electrode. As described
above, in the production process according to the present
invention, a very thin and good-quality gate insulating film 2 can
be formed. As shown in FIG. 1 (b), this gate insulating film 2
comprises a high-quality insulating film formed at the interface of
the silicon substrate 1. For example, the gate insulating film 2
comprises an about 2 nm-thick oxide film or oxynitride film.
[0069] In this embodiment, it is preferred that this high-quality
oxide film 2 comprises a silicon oxynitride film (hereinafter
referred to as "SiON film") formed using plasma produced on the
surface of an object substrate mainly comprising silicon (Si) by
applying microwave through a plane antenna member provided with a
plurality of slots to the substrate in the presence of a process
gas containing O.sub.2, N.sub.2 and rare gas. When this SiON 2 film
is used, as described below, advantageously, the interphase
interfacial quality (for example, interfacial level) is good, and,
in the form of an MOS structure, good gate leak characteristic can
easily be provided. In the embodiment shown in FIG. 1, a gate
electrode 13 mainly comprising silicon (polysilicon or amorphous
silicon) is further provided on the surface of the silicon
oxynitride film.
(One Embodiment of Production Process)
[0070] A process for forming of the above silicon oxynitride film
will be described.
[0071] FIG. 2 is schematic view (schematic plan view) showing an
example of the total arrangement of a semiconductor manufacturing
equipment 30 for conducting the process for producing an electronic
device material according to the present invention.
[0072] As shown in FIG. 2, in a substantially central portion of
the semiconductor manufacturing equipment 30, there is disposed a
transportation chamber 31 for transporting a wafer W (FIG. 3).
Around the transportation chamber 31, there are disposed: plasma
processing units 32 and 33 for conducting various treatments on the
wafer, two load lock units 34 and 35 for conducting the
communication/cutoff between the respective processing chambers, a
heating unit 36 for operating various heating treatments, and a
heating reaction furnace 47 for conducting various heating
treatments on the wafer. These units are disposed so as to surround
the transportation chamber 31.
[0073] On the side of the load lock units 34 and 35, a preliminary
cooling unit 45 and a cooling unit 46 for conducting various kinds
of preliminary cooling and cooling treatments are disposed.
[0074] In the inside of transportation chamber 31, transportation
arms 37 and 38 are disposed, so as to transport the wafer W (FIG.
2) between the above-mentioned respective units 32-36.
[0075] On the foreground side of the load lock units 34 and 35 in
this figure, loader arms 41 and 42 are disposed. These loader arms
41 and 42 can put wafer W in and out with respect to four cassettes
44 which are set on the cassette stage 43, which is disposed on the
foreground side of the loader arms 41 and 42.
[0076] In FIG. 2, as the plasma processing units 32 and 33, two
plasma processing units of the same type are disposed in
parallel.
[0077] Further, it is possible to exchange both of the plasma
processing units 32 and 33 with a single-chamber type CVD process
unit. It is possible to set one or two of such a single-chamber
type CVD process unit in the position of the plasma processing
units 32 and 33.
[0078] When two plasma processing units 32 and 33 are used, it is
possible that an SiO.sub.2 film is formed in the plasma processing
unit 32, and then the SiO.sub.2 film is subjected to surface
nitridation in the plasma processing unit 33. Alternatively, it is
also possible an SiO.sub.2 film is formed, and the SiO.sub.2 film
is surface-nitrided in parallel, in the plasma processing units 32
and 33.
(One Embodiment of Plasma Processing Apparatus)
[0079] FIG. 3 is a schematic sectional view in the vertical
direction showing the plasma processing unit 32 (or 33) which is
usable in the film formation of the gate insulator 2.
[0080] Referring to FIG. 3, reference numeral 50 denotes a vacuum
container made of, e.g., aluminum. In the upper portion of the
vacuum container 50, an opening portion 51 is formed so that the
opening portion 51 is larger than a substrate (for example, wafer
W). A top plate 54 in a flat cylindrical shape made of a dielectric
such as quartz and aluminum oxide so as to cover the opening
portion 51. In the side wall of the upper portion of vacuum
container 50 which is below the top plate 54, gas feed pipes 72 are
disposed in the 16 positions, which are arranged along the
circumferential direction so as to provide equal intervals
therebetween. A process gas comprising at least one kind of gas
selected from O.sub.2, inert gas, N.sub.2, H.sub.2, etc., can be
supplied into the vicinity of the plasma region P in the vacuum
container 50 from the gas feed pipes 72 evenly and uniformly.
[0081] On the outside of the top plate 54, there is provided a
radio-frequency power source, via a plane antenna member 60 having
a plurality of slots, which comprises a plane antenna (RLSA) made
from a copper plate, for example. As the radio-frequency power
source, a waveguide 63 is disposed on the top plate 54, and the
waveguide 63 is connected to a microwave power supply 61 for
generating microwave of 2.45 GHz, for example. The waveguide 63
comprises a combination of: a flat circular waveguide 63A, of which
lower end is connected to the RLSA 60; a circular waveguide 63B,
one end of which is connected to the upper surface side of the
circular waveguide 63A; a coaxial waveguide converter 63C connected
to the upper surface side of the circular waveguide 63B; and a
rectangular waveguide 63D, one end of which is connected to the
side surface of the coaxial waveguide converter 63C so as to
provide a right angle therebetween, and the other end of which is
connected to the microwave power supply 61.
[0082] In the inside of the above-mentioned circular waveguide 63B,
an axial portion 62 of an electroconductive material is coaxially
provided, so that one end of the axial portion 62 is connected to
the central (or nearly central) portion of the RLSA 60 upper
surface, and the other end of the axial portion 62 is connected to
the upper surface of the circular waveguide 63B, whereby the
circular waveguide 63B constitutes a coaxial structure. As a
result, the circular waveguide 63B is constituted so as to function
as a coaxial waveguide.
[0083] In addition, in the vacuum container 50, a stage 52 for
carrying the wafer W is provided so that the stage 52 is disposed
opposite to the top plate 54. The stage 52 contains a temperature
control unit (not shown) disposed therein, so that the stage can
function as a hot plate. Further, one end of an exhaust pipe 53 is
connected to the bottom portion of the vacuum container 50, and the
other end of the exhaust pipe 53 is connected to a vacuum pump
55.
(One Embodiment of RLSA)
[0084] FIG. 4 is a schematic plan view showing an example of RLSA
60 which is usable in an apparatus for producing an electronic
device material according to the present invention.
[0085] As shown in this FIG. 4, on the surface of the RLSA 60, a
plurality of slots 60a, 60a, . . . are provided in the form of
concentric circles. Each slot 60a is a substantially square
penetration-type groove. The adjacent slots are disposed
perpendicularly to each other and arranged so as to form a shape of
alphabetical "T"-type character. The length and the interval of the
slot 60a arrangement are determined in accordance with the
wavelength of the microwave supplied from the microwave power
supply unit 61.
(Embodiment of Plasma Processing)
[0086] Next, there is described an embodiment of the process
processing to be used in the present invention.
[0087] A gate valve (not shown) provided at the side wall of the
vacuum container 50 in the plasma processing unit 32 (FIG. 2) is
opened, and the above-mentioned wafer W comprising the silicon
substrate 1, and the field oxide film 11 formed on the surface of
the silicon substrate 1 is placed on the stage 52 (FIG. 3) by means
of transportation arms 37 and 38.
[0088] Next, the gate valve was closed so as to seal the inside of
the vacuum container 50, and then the inner atmosphere therein is
exhausted by the vacuum pump 55 through the exhaust pipe 53 so as
to evacuate the vacuum container 50 to a predetermined degree of
vacuum and a predetermined pressure in the container 50 is
maintained. On the other hand, microwave (e.g., of 1.80 GHz and
2200 W) is generated by the microwave power supply 61, and the
microwave is guided by the waveguide so that the microwave is
introduced into the vacuum container 50 via the RLSA 60 and the top
plate 54, whereby radio-frequency plasma is generated in the plasma
region P of an upper portion in the vacuum container 50.
[0089] Herein, the microwave is transmitted in the rectangular
waveguide 63D in a rectangular mode, and is converted from the
rectangular mode into a circular mode by the coaxial waveguide
converter 63C. The microwave is then transmitted in the cylindrical
coaxial waveguide 63B in the circular mode, and transmitted in the
circular waveguide 63A in the expanded state, and is emitted from
the slots 60a of the RLSA 60, and penetrates the plate 54 and is
introduced into the vacuum container 50. In this case, microwave is
used, and accordingly a high-density and low-electron temperature
plasma can be generated. Further, the microwave is emitted from a
large number of slots 60a of the RLSA 60, and accordingly the
plasma is caused to have a uniform distribution.
[0090] When an oxide film is formed, the wafer W is introduced into
the reaction chamber 50 (FIG. 3) prior to the induction of
microwave, and a process gas comprising a rare gas (such as krypton
and argon) and oxygen gas as a gas for forming an oxide film, is
introduced at flow rates of 2000 sccm and 200 sccm, respectively,
into the reaction chamber from the gas feed pipe 52, while heating
the wafer with the stage 52. The pressure of the reaction chamber
is maintained at 133 Pa and microwave is introduced thereinto at 2
W/cm.sup.2 so as to generate plasma, and oxygen radicals are caused
to react on the substrate W surface, to thereby form a silicon
oxide film. In the case of pre-oxidation treatment, it is preferred
to use a rare gas only, or a rare gas and hydrogen gas as the
process gas. In the case of nitridation treatment, it is preferred
to use a rare gas and nitrogen-containing gas as the process
gas.
[0091] Hereinbelow, the present invention will be described in more
detail with reference to Examples.
EXAMPLES
Example 1
[0092] A device (N-type MOS capacitor) for carrying out various
evaluations was formed by the following method.
[0093] (1): Substrate (FIG. 9)
[0094] As shown in FIG. 9, a P-type silicon substrate having a
specific resistance of 8 to 12 .OMEGA.cm and plane orientation
(100) was used as a substrate. The surface of the silicon substrate
had a sacrificial oxide film with a thickness of 500 A (angstrom)
previously formed by thermal oxidation.
[0095] (2): Cleaning Before Gate Oxidation
[0096] The sacrificial oxide film and contamination elements
(metals and organic matter, particles) were removed by RCA cleaning
using a combination of APM (a mixed liquid composed of ammonia,
aqueous hydrogen peroxide, and pure water) with HPM (a mixed liquid
composed of hydrochloric acid, aqueous hydrogen peroxide, and pure
water) and DHF (a mixed liquid composed of hydrofluoric acid and
pure water).
[0097] (3): Plasma Treatment Before Oxidation (FIG. 10)
[0098] After the treatment in the above step (2), RLSA plasma
treatment was carried out on the substrate (FIG. 10) under the
following conditions. A wafer was transferred to a reaction chamber
indicated by 32 in FIG. 2 and FIG. 3 under vacuum (back pressure:
not more than 1.times.10.sup.-4 Pa), and the conditions were then
held in the following manner: substrate temperature of 400.degree.
C., rare gas (for example, Ar gas) of 1000 sccm, and pressure of 7
Pa to 133 Pa (50 mTorr to 1 Torr). A microwave was applied at 2 to
3 W/cm.sup.2 to this atmosphere through a plane antenna member
(RLSA) having a plurality of slots to generate rare gas plasma for
plasma treatment on the substrate surface (FIG. 10). As desired,
hydrogen (5 to 30 sccm) may be contained in the rare gas for
hydrogen pre-oxidation plasma treatment.
[0099] (4): Plasma Oxidation Process (FIG. 11)
[0100] An oxide film was formed by the following method on the
silicon substrate treated in the step (3). While avoiding the
exposure of the silicon substrate treated in the step (3) to the
air, the silicon substrate is subjected to treatment by the
following process (for example, treatment in an identical reaction
chamber 32, or treatment using a vacuum transfer system in other
reaction chamber 33 while avoiding exposure to the air). According
to this method, oxidation treatment can be carried out while
optimally maintaining the organic contaminant removing effect and
the spontaneous oxide film removing effect attained by the
treatment in the step (3). More specifically, rare gas and oxygen
were allowed to flow respectively 25 to 500 sccm over the silicon
and the pressure was held at to 1000 mTorr). A microwave to this
atmosphere through a at 1000 to 2000 sccm and 50 substrate heated
at 400.degree. C., 13 Pa to 133 Pa (100 mTorr was applied at 2 to 3
W/cm.sup.2 plane antenna member (RLSA) having a plurality of slots
to generate plasma containing oxygen and rare gas, and this plasma
was used for the formation of an SiO.sub.2 film on the substrate
treated in the step (3) (FIG. 11). Further, the film thickness was
regulated by varying treatment conditions including treatment
time.
[0101] (5): Plasma Nitriding Process (FIG. 11)
[0102] Nitriding was carried out by the following method on the
oxide film formed in the step (4). While avoiding the exposure of
the oxide film formed in the step (4) to the air, the oxide film is
subjected to treatment by the following process (for example,
treatment in an identical reaction chamber 32, or treatment using a
vacuum transfer system in other reaction chamber 33 while avoiding
exposure to the air). According to this method, nitriding treatment
can be carried out while suppressing organic matter contamination
and an increase in spontaneous oxide film on the upper part of the
oxide film formed in the treatment in the step (4). More
specifically, rare gas and nitrogen were allowed to flow
respectively at 500 to 2000 sccm and 4 to 500 sccm over the silicon
substrate heated at 400.degree. C., and the pressure was held at 3
Pa to 133 Pa (20 mTorr to 1000 mTorr). A microwave was applied at 3
W/cm.sup.2 to this atmosphere through a plane antenna member (RLSA)
having a plurality of slots to generate plasma containing nitrogen
and rare gas, and this plasma was used for the formation of an
oxynitride film (SiON film) on the substrate (FIG. 11).
[0103] (6): Film Thickness Reduction and Recovery of Vfb Shift by
Hydrogen Plasma (FIG. 11)
[0104] Annealing treatment with hydrogen plasma was carried out on
the oxynitride film formed in the treatment in the step (5) by the
following method. While avoiding the exposure of the oxynitride
film formed in the treatment in the step (5) to the air, the
oxynitride film is subjected to treatment by the following process
(for example, treatment in an identical reaction chamber 32, or
treatment using a vacuum transfer system in other reaction chamber.
33 while avoiding exposure to the air). According to this method,
hydrogen plasma annealing treatment can be carried out while
suppressing organic matter contamination and an increase in
spontaneous oxide film on the upper part of the oxynitride film
formed in the treatment in the step (5). More specifically, rare
gas and hydrogen were allowed to flow respectively at 500 to 2000
sccm and 4 to 500 sccm over the silicon substrate heated at
400.degree. C., and the pressure was held at 3 Pa to 133 Pa (20
mTorr to 1000 mTorr). A microwave was applied at 2 to 3 W/cm.sup.2
to this atmosphere through a plane antenna member (RLSA) having a
plurality of slots to generate plasma containing hydrogen and rare
gas, and this plasma was used for hydrogen plasma annealing
treatment on the oxynitride film (FIG. 11). In FIG. 11, for the
SIMS analysis sample, the treatment was stopped in this step, and
the analysis was carried out.
[0105] (7): Formation of Polysilicon Film for Gate Electrode
[0106] A polysilicon film was formed as a gate electrode by CVD on
the oxynitride film formed through the treatment in the steps (3)
to (6). The silicon substrate with an oxynitride film formed
thereon was heated at 630.degree. C., and silane gas (250 sccm) was
supplied under a pressure of 33 Pa over the substrate, followed by
holding for 30 min to form a 3000 A-thick polysilicon film for an
electrode on the SiO.sub.2 film.
[0107] (8): Doping of P (phosphorus) Into Polysilicon
[0108] The silicon substrate prepared in the step (7) was heated to
875.degree. C., and POCl.sub.3 gas, oxygen and nitrogen were
supplied respectively at 350 sccm, 200 sccm, and 20000 sccm under
the atmospheric pressure over the substrate, followed by holding
for 24 min. to dope phosphorus into the polysilicon.
[0109] (9): Patterning and Gate Etching
[0110] Patterning was carried out by lithography on the silicon
substrate prepared in the step (8), and the silicon substrate was
then immersed in a liquid chemical of HF:HNO.sub.3:H.sub.2O=1:60:60
for 3 min. to dissolve polysilicon in its parts remaining
unpatterned. Thus, an MOS capacitor was prepared.
Example 2
[0111] The measurement of the MOS capacitor prepared in Example 1
was carried out by the following methods. The capacitor having a
gate electrode area of 10,000 (m2 was evaluated for CV and IV
characteristic. The CV characteristic were determined by sweeping
the gate voltage from +1 V to about -3 V at a frequency of 100 kHz
and evaluating the capacitance at each voltage. The electrical film
thicknesses and Vfb (flatband voltage) were calculated from the CV
characteristic. The IV characteristic were determined by sweeping
the gate voltage from 0 V to about -5 V and evaluating the value of
current which flows at each voltage (leakage current value). The
leakage current value at a gate electrode voltage obtained by
subtracting -0.4 V from Vfb determined from the CV measurement was
calculated from the IV characteristic.
[0112] FIG. 5 is a diagram showing a comparison of leakage
characteristic of an oxide film subjected to previous plasma
treatment with leakage characteristic of an oxide film not
subjected to previous plasma treatment. In this connection, it
should be noted that, for illustrating only the effect of the
previous plasma treatment, the oxide film used here have not been
subjected to nitriding and post-hydrogen treatment. The electrical
film thickness determined from the CV characteristic is plotted as
abscissa against leakage current value at a gate voltage Vfb -0.4 V
(about -1.2 V because Vfb is about -0.8 V) as ordinate. As can be
seen from FIG. 5, the previous plasma treatment could reduce the
leakage current value of the oxide film.
[0113] FIG. 6 is a diagram showing a comparison of flatband
characteristic of RLSA plasma an oxide film subjected to previous
plasma treatment with flatband. characteristic of thermally grown
an oxide film currently commonly used in devices. The electrical
film thickness determined from the CV characteristic is plotted as
abscissa against flatband voltage determined from the CV
characteristic as ordinate. It is known that, when defects and the
like, which serve as traps of carriers, are present in the film and
interface, the flatband voltage is greatly shifted in a negative
direction. However, for the film subjected to previous plasma
treatment, the flatband value was similar to that of the thermally
grown oxide film (about -0.8 V), and a deterioration in flatband
characteristic in this step was not observed.
[0114] FIG. 7a shows a change in the electrical film thickness of
gate oxynitride film using a plurality of steps (multi-process) in
the present invention with the elapse of time (a change in the
electrical film thickness for each step). The process time is
plotted as abscissa against electrical film thickness as ordinate.
The electrical film thickness could be successfully reduced by 1 to
3.5 A by nitriding. Further, a further film thickness reduction
could be realized by post-hydrogen treatment.
[0115] FIG. 7b is a diagram showing a change in flatband voltage of
the same film as shown in FIG. 9 with the elapse of time (a change
in flatband voltage for each step). The process time is plotted as
abscissa against flatband voltage as ordinate. It is known that,
when detects and the like, which serve as traps of carriers, are
present in the film and interface, the flatband voltage is greatly
shifted in a negative direction. However, for the film subjected to
post-plasma hydrogen treatment, recovery of the flatband shift is
observed, indicating that the film characteristic deteriorated by
nitriding could be recovered.
[0116] As can be seen from FIG. 8, upon hydrogen treatment, the
film thickness (the thickness of the oxygen-containing layer) is
reduced. This is attributable to reduction by a hydrogen reaction
species. Control (etching) of a film thickness reduction in a
region where the control of film thickness reduction is difficult
(around 10 A) can be realized by effectively utilizing this
step.
[0117] As can be seen from FIGS. 7a and 7b, according to the
present invention, a plurality of steps can be successively carried
out in a reaction chamber under the same principle while avoiding
the exposure of a silicon substrate to the air. For example, a
reduction in footprint can be realized by conducting all steps in a
single reaction chamber. Further, also when the individual steps
are carried out in respective separate reaction chambers, since
reaction chambers identical to each other in principle of operation
are arranged, identical gas piping and operation panel can be used,
leading to the realization of excellent maintenance and
operationality. Further, since identical apparatuses are used,
there is no significant fear of cross-contamination between the
apparatuses. Even when a cluster construction using a plurality of
reaction chambers is adopted, the processing order can be varied.
Gate insulating film having various characteristic can be prepared
by this method.
[0118] Further, in the above example, the oxynitride film prepared
according to the present invention as such is used as a gate
insulating film. Alternatively, a process may be adopted which
comprises forming a very thin (about 10 A (angstroms)) oxynitride
film according to the present invention and forming thereon a film
of a material a having high dielectric constant such as a high-k
material. According to this method, a stacked gate insulating film
structure (gate stack structure) having a higher level of
interfacial characteristic, for example, a higher level of
transistor carrier mobility, than a gate insulating film formed
using a high-k material only.
Example 3
[0119] The production process of a logic device in this embodiment
is roughly carried out in the following order: "element isolation R
preparation of MOS transistor R capacitance preparation R formation
of interlayer insulating film and wiring". Among steps before the
preparation of an MOS transistor including the process according to
the present invention, particularly the preparation of an MOS
structure deeply associated with the present invention will be
explained through a typical example.
[0120] (1): Substrate
[0121] A P-type or N-type silicon substrate having a specific
resistance of 1 to 30 .OMEGA.cm and plane orientation (100) is used
as a substrate. A process for the preparation of an NHOS transistor
using a P-type silicon substrate will be explained.
[0122] A step of element isolation such as STI or LOCOS and channel
implantation have been carried out on the silicon substrate
according to the purpose, and the surface of the silicon substrate,
on which a gate oxide film and a gate insulating film are to be
formed, has a sacrificial oxide film thereon (FIG. 9).
[0123] (2): Cleaning Before Gate Oxide Film (Gate Insulating Film)
Formation
[0124] In general, the sacrificial oxide film and contamination
elements (metals and organic matter, particles) are removed by RCA
cleaning using a combination of APM (a mixed liquid composed of
ammonia, aqueous hydrogen peroxide, and pure water) with HPM (a
mixed liquid composed of hydrochloric acid, aqueous hydrogen
peroxide, and pure water) and DHF (a mixed liquid composed of
hydrofluoric acid and pure water). As desired, SPM (a mixed liquid
composed of sulfuric acid and aqueous hydrogen peroxide), aqueous
ozone, FPM (a mixed liquid composed of hydrofluoric acid, aqueous
hydrogen peroxide, and pure water), aqueous hydrochloric acid (a
mixed liquid composed of hydrochloric acid and pure water), and
organic alkalis and the like are sometimes used.
[0125] (3): Plasma Treatment Before Base Oxidation
[0126] After the treatment in the step (2), RLSA plasma treatment
is carried out on the substrate as a step before base oxide film
formation. Possible treatment conditions may be, for example, as
follows. A wafer is transferred to a vacuum (back pressure: not
more than 1.times.10.sup.-4 Pa) reaction chamber 32, and conditions
of substrate temperature 400.degree. C., rare gas (for example, Ar
gas) 1000 sccm, and pressure 7 Pa to 133 Pa (50 mTorr to 1000
mTorr) are then held. A microwave is applied at 2 to 3 W/cm.sup.2
to this atmosphere through a plane antenna member (RLSA) having a
plurality of slots to generate rare gas plasma for plasma treatment
on the substrate surface. As desired, hydrogen (5 to 30 sccm) may
be contained in the mixed gas for hydrogen pre-oxidation plasma
treatment (FIG. 10).
[0127] (4): Formation of Base Oxide Film
[0128] An oxide film is formed by the following method on the
silicon substrate treated in the step (3). While avoiding the
exposure of the silicon substrate treated in the step (3) to the
air, the silicon substrate is subjected to treatment by the
following process (for example, treatment in an identical reaction
chamber 32). According to this method, oxidation treatment can be
carried out while optimally maintaining the organic contaminant
removing effect and the spontaneous oxide film removing effect
attained by the treatment in the step (3). More specifically, rare
gas and oxygen are allowed to flow respectively at 1000 to 2000
sccm and 50 to 500 sccm over the silicon substrate heated at
400.degree. C., and the pressure is held at 13 Pa to 133 Pa (100
mTorr to 1000 mTorr). A microwave is applied at 2 to 3 W/cm.sup.2
to this atmosphere through a plane antenna member (RLSA) having a
plurality of slots to generate plasma containing oxygen and rare
gas, and this plasma is used for the formation of an SiO.sub.2 film
on the substrate treated in the step (3). Further, the film
thickness can be regulated by varying treatment conditions
including treatment (process) time (FIG. 11).
[0129] (5): Plasma Nitriding Process
[0130] Nitriding is carried out by the following method on the
oxide film formed in the step (4). While avoiding the exposure of
the oxide film formed in the step (4) to the air, the oxide film is
subjected to treatment by the following process (for example,
treatment in an identical reaction chamber 32, or treatment using a
vacuum transfer system in other reaction chamber 33 while avoiding
exposure to the air). According to this method, nitriding treatment
can be carried out while suppressing organic matter contamination
and an increase in spontaneous oxide film on the upper part of the
oxide film formed in the treatment in the step (4). More
specifically, rare gas and nitrogen are allowed to flow
respectively at 500 to 2000 sccm and 4 to 500 sccm over the silicon
substrate heated at 400.degree. C., and the pressure is held at 3
Pa to 133 Pa (20 mTorr to 1000 mTorr). A microwave is applied at 2
to 3 W/cm.sup.2 to this atmosphere through a plane antenna member
(RLSA) having a plurality of slots to generate plasma containing
nitrogen and rare gas, and this plasma is used for the formation of
an oxynitride film (SiON film) on the substrate (FIG. 11).
[0131] (6): Film Thickness Reduction and Recovery of Vfb Shift by
Hydrogen Plasma
[0132] Annealing treatment with hydrogen plasma is carried out on
the oxynitride film formed in the treatment in the step (5) by the
following method. While avoiding the exposure of the oxynitride
film formed in the treatment in the step (5) to the air, the
oxynitride film is subjected to treatment by the following process
(for example, treatment in an identical reaction chamber 32, or
treatment using a vacuum transfer system in other reaction chamber
33 while avoiding exposure to the air). According to this method,
hydrogen plasma annealing treatment can be carried out while
suppressing organic matter contamination and an increase in
spontaneous oxide film on the upper part of the oxynitride film
formed in the treatment in the step (5). More specifically, rare
gas and hydrogen are allowed to flow respectively at 500 to 2000
sccm and 4 to 500 sccm over the silicon substrate heated at
400.degree. C., and the pressure is held at 3 Pa to 133 Pa (20
mTorr to 1000 mTorr). A microwave was applied at 2 to 3 W/cm.sup.2
to this atmosphere through a plane antenna member (RLSA) having a
plurality of slots to generate plasma containing hydrogen and rare
gas, and this plasma is used for hydrogen plasma annealing
treatment on the oxynitride film (FIG. 11).
[0133] (7): Formation of High-k Gate Insulating Film
[0134] A film of a high-k material is formed on the base oxynitride
film formed in the step (6). Methods for high-k gate insulating
film formation are classified roughly into a process using CVD and
a process using PVD. Here the formation of a gate insulating film
by CVD will be mainly described. In the formation of a gate
insulating film by CVD, raw material gases (for example, HTB: Hf
(OC.sub.2H.sub.5).sub.4 and SiH.sub.4) are supplied onto the above
silicon substrate heated at a temperature falling within the range
of 200.degree. C. to 1000.degree. C., and thermally produced
reaction species (for example, Hf radicals, Si radicals, and 0
radicals) are allowed to react with each other on the surface of
the film and consequently to form a film (for example, HfSiO). The
reaction species are sometimes produced by plasma. The physical
film thickness of the gate insulating film may generally be 1 nm to
10 nm (FIG. 12).
[0135] (8): Formation of Polysilicon Film for Gate Electrode
[0136] A film of polysilicon (including amorphous silicon) is
formed, as a gate electrode for an MOS transistor, by CVD on the
high-k gate insulating film (including the base gate oxide film)
formed in the step (7). The silicon substrate with the gate
insulating film formed thereon is heated to a temperature falling
within the range of 500.degree. C. to 650.degree. C., and a
silicon-containing gas (for example, silane, disilane, etc.) is
supplied over the substrate under a pressure of 10 to 100 Pa to
form a 50 nm to 500 nm-thick polysilicon film for an electrode on
the gate insulating film. In the gate electrode, silicon germanium
and metals (for example, W (tungsten), Ru (ruthenium), TiN
(titanium nitride), Ta (tantalum), and Mo (molybdenum)) are
sometimes used as an alternative to polysilicon (FIG. 13).
[0137] Thereafter, patterning of the gate and selective etching are
carried out to form an MOS capacitor (FIG. 14), and ion
implantation is carried out to form a source and a drain (FIG. 15).
Thereafter, annealing is carried out to activate the dopant
(phosphorus (P), arsenic (As), boron (B) or the like implanted into
the channel, the source, and the drain). Subsequently, a step of
wiring by combining formation of an interlayer insulating film,
patterning, selective etching, and formation of a metal film is
carried out as a post-process to prepare an MOS transistor involved
in this embodiment (FIG. 16). Finally, a step of wiring is carried
out on the. upper part of the transistor in various patterns to
prepare a circuit and thus to complete a logic device.
[0138] In this Example, a film of Hf silicate (HfSiO film) was
formed as the insulating film. However, an insulating film having
other composition may also be formed. The gate insulating film may
be one or at least two film selected from the group consisting of
film of conventional low-dielectric constant SiO.sub.2 and SiON,
and relatively high-dielectric constant SiN, high-dielectric
constant Al.sub.2O.sub.3r ZrO.sub.2, HfO.sub.2r and Ta.sub.2O.sub.5
called high-k materials, and silicates such as ZrSiO and HfSiO and
aluminates such as ZrAlO.
[0139] Further, in this Example, the formation of a base gate
oxynitride film is intended. Alternatively, the base gate
oxynitride film as such may be used as the gate insulating film
without the formation of a film of a high-k material. In this case,
the thickness of the base oxide film should be regulated.
[0140] Furthermore, an oxide film not subjected to nitriding may
also be used as the base film, and the oxide film per se may also
be used as the gate insulating film.
[0141] Further, as desired, the treatment before oxidation and the
post-hydrogen treatment may also be omitted, and the order of
treatment may also be changed.
[0142] Examples of the order of treatment according to the purposes
are as follows.
[0143] 1: Formation of Gate Oxide Film
[0144] Treatment before oxidation.fwdarw.oxidation
treatment.fwdarw.formation of poly film
[0145] 2: Formation of Gate Oxynitride Film-1
[0146] Treatment before oxidation.fwdarw.oxidation
treatment.fwdarw.nitriding.fwdarw.post-hydrogen
treatment.fwdarw.formation of poly film
[0147] 3: Formation of Gate Oxynitride Film-2
[0148] Treatment before oxidation.fwdarw.nitriding.fwdarw.oxidation
treatment.fwdarw.post-hydrogen treatment.fwdarw.formation of poly
film
[0149] 4: Formation of High-k Base Oxide Film
[0150] Treatment before oxidation.fwdarw.oxidation
treatment.fwdarw.film thickness reduction by post-hydrogen
treatment.fwdarw.formation of high-k film.fwdarw.formation of poly
film
[0151] 5: Formation of High-k Base Nitride Film
[0152] Treatment before nitriding (same as treatment before
oxidation).fwdarw.nitriding.fwdarw.post-hydrogen
treatment.fwdarw.formation of high-k film.fwdarw.formation of poly
film
[0153] The above embodiments are merely examples of embodiments of
the present invention. In addition to the above embodiments, other
various treatment methods can be carried out in an identical
apparatus construction.
[0154] As described above, according to the present invention, a
plurality of steps can be successively carried out in a reaction
chamber(s) under the same principle while avoiding the exposure of
a silicon substrate to the air. For example, a reduction in
footprint can be realized by conducting a plurality of steps of
cleaning, oxidation, nitriding, and etching in a single reaction
chamber. Further, also when the individual steps are carried out in
respective separate reaction chambers, since reaction chambers
identical to each other in principle of operation are arranged,
identical gas piping and operation panel can be used, leading to
the realization of excellent maintenance and operationality.
Further, since identical apparatuses are used, there is no
significant fear of cross-contamination between the apparatuses.
Even when a cluster construction using a plurality of reaction
chambers is adopted, the processing order can be varied. Gate
insulating film having various characteristic can be prepared by
this method.
INDUSTRIAL APPLICABILITY
[0155] As described above, according to the present invention, an
insulating film having various excellent characteristic (for
example, control of very small film thickness and a high level of
cleanness) can be produced with a high efficiency (for example,
small footprint provided by conducting a plurality of steps of
cleaning, oxidation, nitriding, and etching in a single reaction
chamber, or simplification of operationality and prevention of
cross-contamination between apparatuses realized by conducting
various steps in reaction chambers under the same principle of
operation).
* * * * *