U.S. patent application number 11/496440 was filed with the patent office on 2006-11-23 for substrate processing method and substrate processing apparatus.
This patent application is currently assigned to Tadahiro Ohmi. Invention is credited to Masaki Hirayama, Tadahiro Ohmi, Shigetoshi Sugawa.
Application Number | 20060261037 11/496440 |
Document ID | / |
Family ID | 19187190 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060261037 |
Kind Code |
A1 |
Ohmi; Tadahiro ; et
al. |
November 23, 2006 |
Substrate processing method and substrate processing apparatus
Abstract
In a substrate processing apparatus, a control electrode (131)
separates a process space (11C) including a substrate to be
processed and a plasma formation space (11B) not including the
substrate. The control electrode includes a conductive member
formed in a processing vessel and having a plurality of apertures
(131a) for passing plasma. A surface of the control electrode is
covered by an aluminum oxide or a conductive nitride. In the
substrate processing apparatus, a gas containing He and N.sub.2 is
supplied into the processing vessel. In the plasma formation space,
there is formed plasma under a condition in which atomic state
nitrogen N* are excited. The atomic state nitrogen N* are used to
nitride a surface of the substrate.
Inventors: |
Ohmi; Tadahiro; (Sendai-Shi,
JP) ; Sugawa; Shigetoshi; (Sendai-Shi, JP) ;
Hirayama; Masaki; (Sendai-Shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Tadahiro Ohmi
Tokyo Electron Limited
|
Family ID: |
19187190 |
Appl. No.: |
11/496440 |
Filed: |
August 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10467820 |
Aug 11, 2004 |
|
|
|
PCT/JP02/12926 |
Dec 10, 2002 |
|
|
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11496440 |
Aug 1, 2006 |
|
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Current U.S.
Class: |
216/67 ;
156/345.46; 156/345.49; 216/70; 257/E21.267; 257/E21.292;
438/710 |
Current CPC
Class: |
C23C 8/36 20130101; H01L
21/318 20130101; H01L 21/02247 20130101; H01L 21/02252 20130101;
H01L 21/3143 20130101; H01J 37/321 20130101; H01J 37/32357
20130101 |
Class at
Publication: |
216/067 ;
438/710; 216/070; 156/345.49; 156/345.46 |
International
Class: |
C23F 1/00 20060101
C23F001/00; H01L 21/302 20060101 H01L021/302; H01L 21/306 20060101
H01L021/306; C03C 25/68 20060101 C03C025/68 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2001 |
JP |
2001-380535 |
Claims
1-9. (canceled)
10. A substrate processing apparatus, comprising: a processing
vessel defined by an outer wall and having a stage for holding a
substrate to be processed thereon; an evacuation system coupled to
said processing vessel; a plasma gas supplying part supplying a
plasma excitation gas and a process gas into said processing
vessel; a microwave window provided on said processing vessel so as
to face said substrate to be processed; and a control electrode
provided between said substrate to be processed on said stage and
said plasma gas supplying part so as to face said substrate to be
processed, and separating a plasma excitation space containing said
microwave window and a process space containing said substrate to
be processed, said control electrode comprising a conductive member
having a plurality of apertures for passing plasma formed in said
processing vessel therethrough, and a surface of said control
electrode being covered by any of aluminum oxide or electrically
conductive nitride.
11. The substrate processing apparatus as claimed in claim 10,
characterized in that said control electrode has a lattice-shaped
form and is grounded.
12. The substrate processing apparatus as claimed in claim 10,
characterized in that said control electro has a form of a
lattice-like shape and said substrate processing apparatus
comprises a negative voltage source connected to said control
electrode.
13. The substrate processing apparatus as claimed in claim 10,
characterized in that an inner wall of said processing vessel is
covered with an insulation film in said plasma excitation
space.
14. The substrate processing apparatus as claimed in claim 10,
characterized by further comprising a microwave antenna coupled to
said microwave window at an outer side of said processing
vessel.
15. A substrate processing apparatus, characterized by: a
processing vessel defined by a wall of quartz glass and having a
stage for holding a substrate to be processed; an evacuation system
coupled to said processing vessel; a plasma gas supplying part
supplying a plasma excitation gas and a process gas to said
processing vessel; a control electrode provided so as to face said
substrate to be processed on said stage and dividing an interior of
said processing vessel into a process space containing said
substrate to be processed and a plasma excitation space; and an
induction coil provided outside said quartz glass wall in
correspondence to said plasma excitation space, said control
electrode comprising a conductive member having a plurality of
apertures passing therethrough formed in said processing vessel,
and a surface of said control electrode being covered with any of
aluminum oxide or electrically conductive nitride.
16. The substrate processing apparatus as claimed in claim 15,
characterized in that said quartz glass wall defines a dome-like
space.
17. The substrate processing apparatus as claimed in claim 15,
characterized in that said control electrode is grounded.
18. The substrate processing apparatus as claimed in claim 15,
characterized in that said control gate is connected to a negative
voltage source.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to plasma processing
apparatuses and more particularly to a microwave plasma processing
apparatus.
[0002] Plasma process and plasma processing apparatus constitute
indispensable technology for fabricating ultrafine semiconductor
devices such as the one called deep submicron device or deep
sub-quarter micron device having a gate length near 0.1 .mu.m or
less, or for fabricating high-resolution flat panel display device
including a liquid crystal display device.
[0003] Conventionally, various plasma excitation methods have been
employed in the plasma processing apparatus used for fabricating
semiconductor devices or liquid crystal display devices.
Particularly, high-frequency plasma apparatuses of parallel plate
type or induction-coupled type plasma apparatus are used commonly.
However, such a conventional plasma processing apparatuses suffers
from the problem of non-uniform plasma formation in that the region
in which high electron density is achieved is substantially
limited, and there has been a difficulty in conducting a uniform
processing over the entire surface of the substrate with a large
processing rate or throughput. This problem becomes particularly
serious in the case of processing a substrate of large diameter.
Further, such a conventional plasma processing apparatus has
inherent problems, associated with its high electron temperature,
in that damages are caused in the semiconductor devices formed on
the substrate. Further, severe metal contamination may be caused as
a result of sputtering of the chamber wall. Thus, it is becoming
difficult with conventional plasma processing apparatuses to
satisfy the stringent demand of further miniaturization and further
improvement of productivity of semiconductor devices or flat
display devices.
[0004] Meanwhile, there has been a proposal of a microwave plasma
processing apparatus that uses high-density plasma excited, not by
d.c. magnetic field, but by a microwave electric field. For
example, there is a proposal of a plasma processing apparatus that
excites plasma by emitting a microwave into a processing vessel
from a planar antenna (radial line slot antenna) having a number of
slots arranged so as to produce a uniform microwave, for emitting a
microwave into a processing vessel. In this plasma processing
apparatus, the microwave electric field induces plasma by causing
ionization in the gas in the vacuum vessel. Reference should be
made to Japanese Laid-Open Patent Application 9-63793. By using the
microwave plasma excited according to such a process, it becomes
possible to realize a high-plasma density over a wide area right
underneath the antenna, and uniform plasma processing becomes
possible with short time period. Further, the microwave plasma thus
excited has an advantageous feature of low electron temperature as
a result of excitation of the plasma by using a microwave, and it
becomes possible to avoid the problem of damages or metal
contamination caused in the substrate. Further, it becomes possible
to excite uniform plasma over a substrate of large area, and thus,
the plasma processing apparatus can easily handle the fabrication
of semiconductor devices on a large-diameter semiconductor wafer or
fabrication of large flat panel display devices.
BACKGROUND ART
[0005] FIG. 1 shows the schematic construction of a conventional
induction-coupled plasma processing apparatus 1.
[0006] Referring to FIG. 1, the plasma processing apparatus 1
includes a processing vessel 2 of a quartz dome evacuated by an
evacuation line 2A, and there is provided a stage 3 in a process
space 2B defined by the processing vessel 2 such that the stage 2
is rotated by a rotating mechanism 3A. Further, a substrate 4 is
held on the stage 3. Further, an inert gas such as Ar and a process
gas such as oxygen or nitrogen are supplied to the process space 2B
via a process gas supply line 2C. Further, there is provided a coil
5 around the top part of the processing vessel 2 at the outside
thereof, and high-density plasma 2D is inducted at the top part of
the process space 2B by driving the coil 5 by a d.c. power
source.
[0007] In the plasma processing apparatus 1 of FIG. 1, the radicals
of the process gas formed with the high-density plasma 2D reach the
surface of the substrate 4 and the substrate processing such as
oxidation or nitridation is achieved.
[0008] In such a conventional induction-coupled plasma processing
apparatus 1, on the other hand, there exists a drawback in that the
high-density plasma 2D is localized at the top part of the
processing vessel and there appears an extremely non-uniform
distribution in the radicals that are formed with the plasma.
Particularly, the non-uniformity of the radical concentration in
the radial direction of the substrate is not resolved even when the
stage 3 is rotated by the rotating mechanism 3A.
[0009] Thus, in the conventional induction-coupled plasma
processing apparatus 1, the plasma processing apparatus was
designed such that the substrate 4 is separated from the region in
which the high-density plasma 2D is formed with a large distance
for realizing as uniform radical concentration distribution as
possible at the surface of the substrate 4. As a result of such a
construction, on the other hand, the overall size of the substrate
processing apparatus 1 is increased inevitably. Further, the amount
of the radicals reaching the substrate 4 is reduced. These problems
become particularly serious in the technology of current trend of
processing a large-diameter substrate.
[0010] On the other hand, there is a proposal of a microwave plasma
processing apparatus that uses high-density plasma induced, not by
an induction magnetic field but by a microwave electric field. For
example, there is proposed a plasma processing apparatus that uses
a planar antenna (radial line slot antenna) having a large number
of slots arranged so as to produce a uniform microwave, for
emitting a microwave into a processing vessel. In this apparatus,
the microwave electric field thus induced is used to excite plasma
by causing ionization in the gas in the vacuum vessel. Reference
should be made to Japanese Laid-Open Patent Application 9-63793. By
using the microwave plasma excited according to such a process, it
becomes possible to realize a high-plasma density over a wide area
right underneath the antenna, and uniform plasma processing becomes
possible with short time period. Further, the microwave plasma thus
excited has an advantageous feature of low electron temperature as
a result of excitation of the plasma by using a microwave, and it
becomes possible to avoid the problem of damages or metal
contamination caused in the substrate. Further, it becomes possible
to excite uniform plasma over a substrate of large area, and thus,
the plasma processing apparatus can easily handle the fabrication
of semiconductor devices on a large-diameter semiconductor wafer or
fabrication of large flat panel display devices.
[0011] FIG. 2 shows the construction of a microwave plasma
processing apparatus 10 that uses such a radial line slot antenna
as proposed before by the inventor of the present invention.
[0012] Referring to FIG. 2, the microwave plasma processing
apparatus 10 includes a processing chamber 11 evacuated at a
plurality of evacuation ports 11a, and there is provided a stage 13
inside the processing chamber 11 for supporting a substrate 12 to
be processed. In order to achieve uniform evacuation of the
processing chamber 11, there is provided a ring-shaped space 11A
around the stage 13, and the processing chamber 11 is evacuated
uniformly via the space 11A and further via the evacuation ports
11a by arranging the evacuation ports 11a communicating with the
space 11A in axial symmetry with respect to the substrate.
[0013] On the processing chamber 11, there is provided a plate-like
shower plate 14 formed of a low-loss dielectric such as
Al.sub.2O.sub.3 or SiO.sub.2 as a part of the outer wall of the
processing chamber 11 at a location facing the substrate 12 held on
the stage 13, wherein the shower plate 14 is provided via a seal
ring not illustrated and includes a number of apertures 14A.
Further, a cover plate 15 also of a low-loss dielectric such as
Al.sub.2O.sub.3 or SiO.sub.2 is provided at the outer side of the
shower plate 14 via another seal ring not illustrated.
[0014] The shower plate 14 is provided with a gas passage 14B at a
top surface thereof, and each of the apertures 14A are provided so
as to communicate with the gas passage 14B. Further, there is
provided a gas supply passage 14C in the interior of the shower
plate 14 in communication with a gas supply port 11p provided at an
outer wall of the processing vessel 11. Thus, the plasma-excitation
gas such as Ar or Kr supplied to the gas supply port 11p is
forwarded to the apertures 11A via the supply passage 14C and
further via the passage 14B and is released to the process space
11B right underneath the shower plate 14 inside the processing
vessel 11 from the foregoing apertures 14A.
[0015] On the processing vessel 11, there is further provided a
radial line slot antenna 20 at the outer side of the cover plate 15
with a separation of 4-5 mm from the cover plate 15. The radial
line slot antenna 20 is connected to an external microwave source
(not illustrated) via a coaxial waveguide 21 and causes excitation
of the plasma-excitation gas released into the process space 11B by
the microwave from the microwave source. It should be noted that
the cover plate 15 and the radiation surface of the radial line
slot antenna are contacted closely, and there is provided a cooling
block 19 on the antenna 20 for cooling the antenna. The cooling
block 19 includes a cooling water passage 19A.
[0016] The radial line slot antenna 20 is formed of a flat,
disk-shaped antenna body 17 connected to an outer waveguide tube
21A of the coaxial waveguide 21 and a radiation plate 16 provided
at the opening of the antenna body 17, wherein the radiation plate
16 is formed with a number of slots and a retardation plate of a
dielectric plate having a constant thickness is interposed between
the antenna body 17 and the radiation plate 16.
[0017] In the radial line slot antenna 20 having such a
construction, the microwave fed thereto from the coaxial waveguide
21 propagates along a path between the disk-shaped antenna body 17
and the radiation plate 16 in the radial direction, wherein the
microwave thus propagating undergoes compression of wavelength as a
result of the existence of the retardation plate 18. Thus, by
forming the slots concentrically in correspondence to the
wavelength of the microwave thus propagating in the radial
direction, and by forming the slots so as to form a perpendicular
angle with each other, it becomes possible to emit a plane wave
having a circular polarization from the radial line slot antenna 20
in the direction substantially perpendicular to the radiation plate
16.
[0018] By using such a radial line slot antenna 20, there is formed
uniform high-density plasma in the process space 11B right
underneath the shower plate 14. The high-density plasma thus formed
has a feature of low electron temperature and the occurrence of
damages in the substrate 12 to be processed is avoided. Further,
there occurs no metal contamination caused by sputtering of the
chamber wall of the processing vessel 11.
[0019] Thus, by supplying a process gas, such as an O.sub.2 gas, an
NH.sub.3 gas, or a mixed gas of an N.sub.2 gas and an H.sub.2 gas,
to the gas inlet port 11p of the substrate processing apparatus 10
of FIG. 2 in addition to the plasma-excitation gas such as Ar or
Kr, there is caused an excitation of active species such as atomic
state oxygen O* or hydrogen nitride radicals NH* in the process
space 11B by the high-density plasma, and it becomes possible to
conduct oxidation processing, nitridation processing or
oxynitridation processing on the surface of the substrate 12.
[0020] Further, there is proposed a substrate processing apparatus
10A shown in FIG. 3 having a construction similar to the substrate
processing apparatus 10 of FIG. 2 except that there is provided a
lower shower plate 31 at the lower side of the shower plate 14. The
lower shower plate 31 is provided with a process gas passage 31A
communicating with a process gas inlet port 11r formed at the
surface of the processing vessel 1 and a large number of process
gas inlet nozzle openings 31B are formed in communication with the
process gas passage 31A. Further, the lower shower plate 31 is
provided with large apertures for passing the process gas radicals
formed in the space 11B.
[0021] Thus, in the substrate processing apparatus 10A of FIG. 3,
there is defined another process space 11C underneath the lower
shower plate 31. By forming the lower shower plate 31 by a
conductive material such as a stainless steel having a passivation
surface by aluminum oxide (Al.sub.2O.sub.3) in such an apparatus,
it becomes possible to block the penetration of microwave to the
process space 11C. Thereby, the excitation of plasma is limited in
the process space 11B right underneath the upper shower plate 14,
and the radicals Kr* of Kr or Ar* of Ar penetrate into the process
space 11C through the large apertures formed in the shower plate 31
after excitation in the space 11B. The radicals Kr* or Ar* thus
penetrated into the process space 11C cause activation of the
process gas released from the nozzle apertures 31B, and the
processing of the substrate 12 is achieved by the process gas
radicals thus activated.
[0022] In the substrate processing apparatus 10A of FIG. 3, it
should be noted that the microwave is expelled from the process
space 11C by forming the lower shower plate 31 by a conductive
material, and the damaging of the substrate by microwave is
avoided.
[0023] In the substrate processing apparatus 10A of FIG. 3, it is
also possible to conduct a plasma CVD process by introducing a CVD
source gas from the lower shower plate 31. Further, it is possible
to conduct a dry etching process by introducing a dry etching gas
from the lower shower plate 31 and applying a high-frequency bias
to the stage 13.
[0024] Thus, in the substrate processing apparatus of FIG. 2 of
FIG. 3, Kr radicals (Kr*) of intermediate excitation state having
an energy of about 10 eV are excited at the time of conducting an
oxidation processing, by introducing a Kr gas and an oxygen gas
into the process space 11B. The Kr radicals thus excited cause
efficient excitation of atomic state oxygen O* according to the
reaction O.sub.2.fwdarw.O*+O*, while the atomic state oxygen O*
thus excited cause the desired oxidation of the surface of the
substrate 12.
[0025] In the case of conducting a nitridation processing of the
substrate 12, a Kr gas and an ammonia gas, or a Kr gas and a
nitrogen gas and a hydrogen gas are introduced. In this case, the
excited Kr radicals (Kr*) or Ar radicals (Ar*) cause the excitation
of hydrogen nitride radicals NH* according to the reaction
NH.sub.3.fwdarw.NH*+2H*+e.sup.-, or N.sub.2+H.sub.2.fwdarw.NH*+NH*,
wherein the hydrogen nitride radicals thus excited cause the
desired nitridation processing of the substrate of the surface
12.
[0026] Meanwhile, there are cases in which it is preferable to use
atomic state nitrogen (N*), free from hydrogen and having a strong
nitriding power, at the time of the nitridation processing of the
substrate. The atomic state nitrogen N* are formed according to the
reaction N.sub.2.fwdarw.N*+N*, wherein it should be noted that such
a reaction requires the energy of 23-25 eV. This means that it is
not possible to excite the atomic state nitrogen N* according to
the foregoing reaction, as long as Kr or Ar plasma is used. As
noted previously, the energy of the Kr radicals or Ar radicals
obtained by the Kr or Ar plasma is merely in the order of 10
eV.
[0027] Thus, even when there is made an attempt to supply a
nitrogen gas in the substrate processing apparatus of FIG. 2 or
FIG. 3 in place of the Kr gas or the Ar gas, merely the reaction
N.sub.2.fwdarw.N.sub.2.sup.++e.sup.-, is obtained, and there is
caused no desired atomic state oxygen N*.
[0028] FIG. 4 shows the relationship between the state density of
the Kr plasma and the excitation energy of the atomic state
nitrogen N*, hydrogen nitride radicals NH* and nitrogen atoms
N.sub.2.sup.+.
[0029] Referring to FIG. 4, it can be seen that the state density
of the Kr plasma is large at the low energy side, while the state
density shows a rapid decrease with increase of the energy. Such a
plasma cannot achieve efficient excitation of the desired nitrogen
radicals.
DISCLOSURE OF THE INVENTION
[0030] Accordingly, it is a general object of the present invention
to provide a novel and useful substrate processing apparatus
wherein the foregoing problems are eliminated.
[0031] Another and more specific object of the present invention is
to provide a substrate processing method and apparatus capable of
forming nitrogen radicals N* efficiently.
[0032] Another object of the present invention is to provide a
method of processing a substrate by using a substrate processing
apparatus which has such a construction that a process space, in
which a substrate to be processed is contained, is separated from a
plasma formation space, in which the substrate to be processed is
not contained, by a control electrode in a processing vessel,
characterized by the steps of:
[0033] supplying a gas containing He and N.sub.2 to said processing
vessel;
[0034] forming plasma in said plasma formation space under a
condition such that there is caused excitation of atomic state
nitrogen N* in said plasma; and
[0035] nitriding a surface of the substrate to be processed by said
atomic state nitrogen N* in said process space.
[0036] Another object of the present invention is to provide a
substrate processing apparatus, comprising:
[0037] a processing vessel defined by an outer wall and having a
stage for holding a substrate to be processed thereon;
[0038] an evacuation system coupled to said processing vessel;
[0039] a plasma gas supplying part supplying a plasma excitation
gas and a process gas into said processing vessel;
[0040] a microwave window provided on said processing vessel so as
to face said substrate to be processed; and
[0041] a control electrode provided between said substrate to be
processed on said stage and said plasma gas supplying part so as to
face said substrate to be processed and separating a plasma
excitation space containing said microwave window and a process
space containing said substrate to be processed,
[0042] said control electrode comprising a conductive member having
a plurality of apertures for passing plasma formed in said
processing vessel therethrough, and
[0043] a surface of said control electrode being covered by any of
aluminum oxide or electrically conductive nitride.
[0044] Another object of the present invention is to provide a
substrate processing apparatus, characterized by:
[0045] a processing vessel defined by a wall of quartz glass and
having a stage for holding a substrate to be processed;
[0046] an evacuation system coupled to said processing vessel;
[0047] a plasma gas supplying part supplying a plasma excitation
gas and a process gas to said processing vessel;
[0048] a control electrode provided so as to face said substrate to
be processed on said stage and dividing an interior of said
processing vessel into a process space containing said substrate to
be processed and a plasma excitation space; and
[0049] an induction coil provided outside said quartz glass wall in
correspondence to said plasma excitation space,
[0050] said control electrode comprising a conductive member having
a plurality of apertures passing therethrough plasma formed in said
processing vessel, and
[0051] a surface of said control electrode being covered with any
of aluminum oxide or electrically conductive nitride.
[0052] According to the present invention, it becomes possible to
form plasma having the energy sufficient for causing excitation of
atomic state nitrogen N* in the substrate processing apparatus by
using He for the plasma excitation gas, and it becomes possible to
conduct an efficient nitridation of the substrate by using the
atomic state nitrogen N* thus excited. By separating the plasma
excitation space in which the high-density plasma is excited from
the process space in which the substrate is included by means of
the control electrode, it becomes possible to reduce the plasma
energy in the process space to the level suitable for substrate
processing. Further, it becomes possible to trap the positive ions
formed in the plasma excitation space. In the case of applying the
present invention to the substrate processing apparatus that uses
microwave-excited plasma, it becomes possible to avoid excessive
increase of the plasma energy by conducting the plasma excitation
by using a microwave having the frequency of about 28 GHz or
more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 is a diagram showing the construction of a
conventional induction coupled plasma processing apparatus;
[0054] FIG. 2 is a diagram showing the construction of a previously
proposed microwave substrate processing apparatus;
[0055] FIG. 3 is a diagram showing the construction of another
previously proposed microwave substrate processing apparatus;
[0056] FIG. 4 is a diagram explaining the characteristics of plasma
excitation in the microwave substrate processing apparatus of FIG.
2 or FIG. 3;
[0057] FIG. 5 is a diagram showing the construction of a microwave
substrate processing apparatus according to a first embodiment of
the present invention;
[0058] FIG. 6 is a diagram showing a part of the microwave
substrate processing apparatus of FIG. 5;
[0059] FIG. 7 is a diagram showing the characteristics of plasma
excitation in the microwave substrate processing apparatus of FIG.
5;
[0060] FIG. 8 is a diagram showing a modification of the microwave
plasma processing apparatus of FIG. 5;
[0061] FIG. 9 is a diagram showing the construction of a microwave
plasma processing apparatus according to a second embodiment of the
present invention; and
[0062] FIG. 10 is a diagram showing the construction of an
induction coupled plasma processing apparatus according to a third
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0063] FIG. 5 shows the construction of a substrate processing
apparatus 100 according to a first embodiment of the present
invention. In FIG. 5, those parts corresponding to the parts
described previously are designated by the same reference numerals
and the description thereof will be omitted.
[0064] Referring to FIG. 5, the shower plate 14 is mounted on the
processing vessel 11 via a seal 11s, and the cover plate 15 is
mounted on the shower plate 14 via a seal 11t. Further, the radial
line slot antenna 20 is mounted on the processing vessel 11 via a
seal 11u.
[0065] Further, in the substrate processing apparatus 100 of FIG.
5, the interface between the emission plate 16 and the cover plate
15 is evacuated via a ring-shaped groove 11g formed at the top part
of the processing vessel 11 in the region where the processing
vessel makes an engagement with the emission plate and further via
an evacuation port 11G communicating with the ring-shaped groove
11g. After evacuation, a He gas is introduced into the foregoing
interface with a pressure of about 0.8 atmospheres as a thermal
conducting medium. The He gas thus introduced is confined therein
by closing the valve 11V.
[0066] In the substrate processing apparatus 100 of FIG. 5, it
should be noted that the lower shower plate 31 used in the
substrate processing apparatus 10A of FIG. 3 is removed and a
control electrode 131 of a conductive member is formed, wherein the
control electrode 31 has a lattice shape as represented in FIG. 6
and is formed so as to separate the plasma excitation space 11B and
the process space 11C.
[0067] Referring to FIG. 6, the lattice-shaped control electrode
131 is formed with large number of apertures 132 having a size set
such that there occurs free passage of the radicals excited in the
plasma excitation spate 11B, and thus, the plasma excited in the
plasma excitation space 11B cause diffusion freely into the process
space 11C through the control electrode 131.
[0068] In the construction of FIG. 5, it should be noted that the
lattice-shaped control electrode 131 is grounded, and thus, the
microwave introduced into the plasma excitation space 11B from the
radial line slot antenna 11B is reflected by the lattice shaped
control electrode 131, and there is caused no invasion of the
microwave into the process space 11C. Thus, the problem of the
microwave causing damages in the substrate 12 is not caused in the
substrate processing apparatus 100 of FIG. 5.
[0069] It should be noted that the lattice-shaped control electrode
131 can be formed by W, Ti, or the like, wherein it is possible to
increase the resistance against plasma irradiation by forming a
layer 131a of a conductive nitride such as WN or TiN on the surface
thereof. Further, it is possible to form such a lattice-shaped
control electrode 131 by using a quartz glass and provide the
conductive nitride layer 131a on the surface thereof. Further, in
the substrate processing apparatus 100, it should be noted that the
sidewall surface of the processing vessel 11 is covered by a quartz
liner 11D for the part corresponding to the plasma excitation space
11B
[0070] In the substrate processing apparatus 100 of FIG. 5, a He
gas and an N.sub.2 gas are introduced to the process gas inlet port
11p, and a microwave of about 28 GHz is supplied to the radial line
slot antenna. Typically, the process pressure in the processing
vessel 11 is set to the range of 66.5-266 Pa (0.5-2 Torr), and
nitridation processing or oxynitridation processing of the
substrate 12 is conducted in the temperature range of
200-500.degree. C.
[0071] FIG. 7 shows the state density of the plasma excited in the
substrate processing apparatus 100 of FIG. 5 for the case He is
used for the plasma gas.
[0072] Referring to FIG. 7, it should be noted that the use of He
having a characteristically small collision cross-section for the
plasma gas causes significant acceleration in the excited He
radicals He* with the microwave electric field, and as a result,
there is caused significant increase of plasma energy to the level
suitable for excitation of the atomic state nitrogen N*. On the
other hand, it can be seen that the efficiency of excitation of the
hydrogen nitride radicals NH* or nitrogen ions N.sub.2.sup.+, which
are excited efficiently in the case Kr is used for the plasma gas,
is reduced significantly.
[0073] Thus, in the present invention, efficient excitation of the
atomic state nitrogen N* is achieved in the substrate processing
apparatus 100 at the high plasma energy of 23-25 eV by using He for
the plasma gas. In order to avoid excessive increase of the
electron temperature in the plasma, the present invention uses a
microwave source 22 that produce a microwave of the frequency
higher than the previously proposed frequency, such as about 28 GHz
or more, for driving the radial line slot antenna 20. Thereby, it
is possible to select the frequency of the microwave source from
the frequencies such as about 2.4 GHz or about 8.3 GHz. Further, by
separating the plasma excitation space 11B and the process space
11C by the control electrode 131, it is possible to reduce the
electron temperature and the plasma energy to a level suitable for
substrate processing.
[0074] Particularly, it should be noted that the control electrode
is protected effectively from the high-energy plasma by forming a
conductive nitride such as an Al.sub.2O.sub.3 passivation film on
the surface of the control electrode 131 as explained already.
Further, the problem of sputtering of the inner wall of the
processing vessel by the high-energy plasma and the associated
problem of contamination of the substrate are avoided by covering
the inner wall of the processing vessel 11 by a quartz liner 11D
for the part corresponding to the plasma excitation region 11B.
[0075] FIG. 8 shows the construction of a substrate processing
apparatus 100A according to a modification of the present
embodiment.
[0076] Referring to FIG. 8, it becomes possible in the substrate
processing apparatus 100A to capture the nitrogen ions
N.sub.2.sup.+ excited in the plasma excitation space 11B with the
positive electric charge, by controlling the potential of the
control electrode 31 to a suitable negative potential value.
Thereby, penetration of the nitrogen ions N.sub.2.sup.+ into the
process space 11C is avoided.
[0077] In the substrate processing apparatus 100 or 100A of the
present embodiment, it is possible to conduct an oxynitridation
processing of the substrate 12 by supplying a He gas, an N.sub.2
gas and an O.sub.2 gas to the plasma gas supply port 11p.
Second Embodiment
[0078] FIG. 9 shows the construction of a substrate processing
apparatus 200 according to a second embodiment of the present
invention. In FIG. 9, those parts corresponding to the parts
described previously are designated by the same reference numerals
and the description thereof will be omitted.
[0079] Referring to FIG. 9, it should be noted that the shower
plate 14 is removed in the present embodiment, and in place of
this, there are provided a plurality of process gas inlet ports 11P
on the processing vessel 11 such that the process gas inlet ports
11P are disposed with a symmetric relationship with respect to the
substrate 12. As a result, therefore, the cover plate 15
constituting the dielectric window is exposed at the top part of
the plasma excitation space 11B. Further, the sidewall surface of
the processing vessel is covered by the quartz liner 11D for the
part corresponding to the plasma excitation space 11B similarly to
the previous embodiment.
[0080] According to the present embodiment, the construction of the
substrate processing apparatus 11 is simplified, and it becomes
possible to conduct the nitridation processing of the substrate 12
efficiently with low cost by using the atomic state nitrogen N*, by
supplying a He gas and an N.sub.2 gas to the plasma gas supplying
port 11p and by supplying the microwave of about 28 GHz to the
radial line slot antenna 20. Further, it is possible to conduct an
oxynitridation processing by supplying a He gas, an N.sub.2 gas and
an O.sub.2 gas to the plasma gas supplying port 11p.
Third Embodiment
[0081] FIG. 10 shows the construction of a substrate processing
apparatus 300 according to a third embodiment of the present
invention. In FIG. 10, those parts corresponding to the parts
described previously are designated by the same reference numerals
and the description thereof will be omitted.
[0082] Referring to FIG. 10, the substrate processing apparatus 300
has a construction similar to the substrate processing apparatus 1
explained before with reference to FIG. 1, except that a control
electrode 6 similar to the control electrode 31 is provided in the
quartz vessel 2, and the space inside the quartz vessel 2 is
divided by the control electrode 6 into a plasma excitation space
2B1 in which the high-density plasma 2D is excited and a process
space 2B2 that includes the substrate 4 to be processed.
[0083] In the present embodiment, a He gas and an N.sub.2 gas are
introduced into the plasma excitation space 2B1 via the process gas
supply line 2C, and there is formed high-density plasma 2D having a
high electron temperature and plasma energy sufficient for exciting
atomic state nitrogen N* in the plasma excitation space 2B1.
[0084] The atomic state nitrogen N* thus formed cause diffusion
into the process space 2C through the control electrode 6, and the
surface of the substrate 4 undergoes nitridation. In such a
construction, it should be noted that the plasma has a very high
electron temperature and energy in the plasma excitation space 2B1,
while the electron temperature and the energy of the plasma are
reduced to the level suitable for processing the substrate 4 in the
process space 2B2.
[0085] In the present embodiment, too, it becomes possible to
remove the low energy positive ions such as N.sub.2.sup.+ formed in
the plasma excitation space 2B1 from the process space 2B2 by
trapping the same, by controlling the potential of the control
electrode 6 by the voltage source 6A. Further, it becomes possible
to control the state of the high-density plasma 2D in the plasma
excitation space 2B1 by controlling the potential of the control
electrode 6.
[0086] In the substrate processing apparatus 200 of the present
embodiment, it is also possible to conduct an oxynitridation
processing of the substrate 4 in the process space 2B.sub.2 by
introducing a He gas and an N.sub.2 gas and an O.sub.2 gas from the
process gas supply line 2C.
[0087] Further, the present invention is not limited to the
specific preferred embodiments described heretofore, but various
variations and modifications may be made without departing from the
scope of the invention recited in the claims.
INDUSTRIAL APPLICABILITY
[0088] According to the present invention, it becomes possible to
form plasma having the energy sufficient for causing excitation of
atomic state nitrogen N* in the substrate processing apparatus by
using He for the plasma excitation gas, and it becomes possible to
conduct an efficient nitridation of the substrate by using the
atomic state nitrogen N* thus excited. By separating the plasma
excitation space in which the high-density plasma is excited from
the process space in which the substrate is included by means of
the control electrode, it becomes possible to reduce the plasma
energy in the process space to the level suitable for substrate
processing. Further, it becomes possible to trap the positive ions
formed in the plasma excitation space. In the case of applying the
present invention to the substrate processing apparatus that uses
microwave-excited plasma, it becomes possible to avoid excessive
increase of the plasma energy by conducting the plasma excitation
by using a microwave having the frequency of about 28 GHz or
more.
* * * * *