U.S. patent application number 09/944376 was filed with the patent office on 2002-09-19 for plasma treatment apparatus and method of producing semiconductor device using the apparatus.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Goto, Yasunori, Itabashi, Naoshi, Kofuji, Naoyuki.
Application Number | 20020129904 09/944376 |
Document ID | / |
Family ID | 18934185 |
Filed Date | 2002-09-19 |
United States Patent
Application |
20020129904 |
Kind Code |
A1 |
Itabashi, Naoshi ; et
al. |
September 19, 2002 |
Plasma treatment apparatus and method of producing semiconductor
device using the apparatus
Abstract
To provide a stable and continuous plasma generation
characteristic while maintaining uniformity of large diameter with
a wide range of gas seeds, pressure and density so as to provide a
plasma treatment apparatus with a wide application range and with
high production efficiency, and a method of producing semiconductor
device using it. The plasma treatment apparatus which introduces
electromagnetic waves from a dielectric window into a chamber
evacuated to low pressure has a part of controlling standing wave
provided in the the periphery part of the dielectric window with
the portions other than the entrance thereof being surrounded by
conductor, having quality of material to fill up therein being made
appropriate, and having shape and size thereof equivalent to depth
d=l/4+l/2.times.(n-l).+-.l/8: (n=positive integer, l=c(light
velocity)/f/{square root}{square root over (.di-elect cons.)}) in
terms of the characteristic length.
Inventors: |
Itabashi, Naoshi; (Hachioji,
JP) ; Kofuji, Naoyuki; (Tama, JP) ; Goto,
Yasunori; (Kudamatsu, JP) |
Correspondence
Address: |
Miles & Stockbridge P.C.
1751 Pinnacle Drive, Suite 500
McLean
VA
22102-3833
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
18934185 |
Appl. No.: |
09/944376 |
Filed: |
September 4, 2001 |
Current U.S.
Class: |
156/345.48 ;
118/723AN; 257/E21.312 |
Current CPC
Class: |
H01L 21/32137 20130101;
H01J 37/32192 20130101; H01J 37/32284 20130101 |
Class at
Publication: |
156/345.48 ;
118/723.0AN |
International
Class: |
C23F 001/02; C23C
016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 2001 |
JP |
2001-077423 |
Claims
What is claimed is:
1. A plasma treatment apparatus comprising in a chamber feasible to
be evacuated to low pressure a wafer stage for an object for
processing to be disposed thereon, a dielectric window, that faces
said object for processing, for introducing electromagnetic waves,
a high-frequency power source with frequency=f to generate
electromagnetic wave for making a predetermined gas to be
introduced into inside said chamber evacuated to low pressure into
plasma, and a part of controlling standing wave provided in the
vicinity of the periphery part of said dielectric window, filled
with vacuum, air, or a dielectric with dielectric constant
.di-elect cons., and with the portions other than the entrance
thereof being surrounded by conductor, having depth thereof falling
within the range of the characteristic length of
d=l/4+l/2.times.(n-1).+-.l/8: (n=positive integer, l=c(light
velocity)/f/{square root}{square root over (.di-elect cons.)}).
2. The plasma treatment apparatus according to claim 1, wherein
intensity of standing wave electric field formed inside said
dielectric window reaches a maximum in a radial location same as
inner diameter of said chamber.
3. The plasma treatment apparatus according to claim 1, wherein
intensity of standing wave electric field formed in the side of the
plasma just below said dielectric window material reaches a minimum
in a radial location same as inner diameter of said chamber.
4. The plasma treatment apparatus according to claim 1, wherein
radius of said dielectric window only is increased by sizes
equivalent to the case where said part of controlling standing wave
is provided in the direction of side of said dielectric window in
terms of characteristic length of electromagnetic wave, and said
dielectric window and said part of controlling standing wave in the
vicinity thereof are integrated.
5. The plasma treatment apparatus according to claim 1, wherein
said part of controlling standing wave is provided upward or
downward in the periphery part of said dielectric window, and
shapes and sizes thereof are made equivalent to the case where said
part of controlling standing wave is provided in the direction of
side of said dielectric window in terms of characteristic length of
electromagnetic wave.
6. The plasma treatment apparatus according to claim 1, wherein
said part of controlling standing wave is provided upward, sideward
or downward in the periphery part of said dielectric window, and
while maintaining equivalency in terms of characteristic length of
electromagnetic wave, and shapes thereof are caused to undergo
further bending, or to changes in width or curvature.
7. The plasma treatment apparatus according to claim 1, wherein
said part of controlling standing wave is provided upward or
downward in said dielectric window, and while maintaining
equivalency in terms of characteristic length of electromagnetic
wave, the part is disposed inward than an end part of said
dielectric window.
8. The plasma treatment apparatus according to claim 1 comprising
an antenna made of conductor or semiconductor in an atmosphere side
or a vacuum side of said dielectric window.
9. The plasma treatment apparatus according to claim 1 comprising a
mechanism capable of changing sizes of said part of controlling
standing wave.
10. The plasma treatment apparatus according to claim 1, wherein a
dielectric used inside said dielectric window as well as said part
of controlling standing wave is constructed by any of alumina
(Al.sub.2O.sub.3) and quartz (SiO.sub.2) or by compound hereof.
11. The plasma treatment apparatus according to claim 1 having a
plurality of reactors on a base frame, wherein each of which
reactors comprises inside a chamber feasible to be evacuated to low
pressure a wafer stage for an object for processing to be disposed
thereon, a dielectric window, that faces said object for
processing, for introducing electromagnetic waves, a high-frequency
power source with frequency=f to generate electromagnetic wave for
making a predetermined gas to be introduced into said chamber
evacuated to low pressure into plasma, and a part of controlling
standing wave provided in the vicinity of the periphery part of
said dielectric window, filled with vacuum, air, or a dielectric
with dielectric constant a, and with the portions other than the
entrance thereof being surrounded by conductor, having depth
thereof falling within the range of the characteristic length of
d=l/4+l/2.times.(n-1).+-- .l/8: (n=positive integer, l=c(light
velocity)/f/{square root}{square root over (.di-elect cons.)}).
12. A plasma treatment apparatus comprising a chamber feasible to
be evacuated to low pressure, a wafer stage for an object for
processing located inside said chamber to be disposed thereon, an
antenna as well as a dielectric window provided at a location
facing said object for processing, a high-frequency power source
with frequency=f to generate electromagnetic wave for making a
predetermined gas to be introduced into said chamber into plasma,
and a part of controlling standing wave for making the standing
wave electric field distribution provided in the vicinity of the
periphery part of said dielectric window proper.
13. The plasma treatment apparatus according to claim 12, wherein
said part of controlling standing wave is provided in the periphery
part of said dielectric window in a ring form.
14. A method of producing a semiconductor device using a plasma
treatment apparatus comprising a chamber feasible to be evacuated
to low pressure, a wafer stage for a wafer located inside said
chamber to be mounted thereon, an antenna as well as a dielectric
window provided in a location facing said wafer, a high-frequency
power source with frequency=f to generate electromagnetic wave for
making a predetermined gas to be introduced into said chamber into
plasma, and a part of controlling standing wave for making the
standing wave electric field distribution provided in the vicinity
of the periphery part of said dielectric window proper, comprising:
a step of forming a first film on a main surface of the wafer; a
step of forming a mask making a predetermined pattern shape on said
first film; and a step of mounting the wafer in which said mask is
formed onto the wafer stage of said plasma treatment apparatus and
causing a part of said first film in which said mask is not formed
to undergo etching processing.
15. The method of producing a semiconductor device according to
claim 14, wherein said first film is made of polysilicon.
16. A method of producing a semiconductor device using a plasma
treatment apparatus comprising of a chamber feasible to be
evacuated to low pressure, a wafer stage for a wafer located inside
said chamber to be mounted thereon, an antenna as well as a
dielectric window provided in a location facing said wafer, a
high-frequency power source with a predetermined frequency to
generate electromagnetic wave for making a predetermined gas to be
introduced into said chamber into plasma, and a part of controlling
standing wave for making the standing wave electric field
distribution provided in the vicinity of the periphery part of said
dielectric window proper, comprising: a step of forming a first
film on a main surface of the wafer; a step of forming a second
film on said first film, a step of forming a third film on said
second film; a step of forming a mask making a predetermined
pattern shape on said third film; and a step of mounting the wafer
in which said mask is formed onto the wafer stage of said plasma
treatment apparatus, causing a part of said third film in which
said mask is not formed to undergo etching processing, and copying
the pattern of said mask onto the third, the second and the first
films.
17. The method of producing a semiconductor device according to
claim 16, wherein said first film is a conductor film formed for
MOS gate, said second film is an insulating film, said third film
is an anti-reflective film and said mask is a photoresist mask.
18. The method of producing a semiconductor device according to
claim 16, wherein in said (5) step, after the third and the second
films undergo etching processing selectively with said plasma
treatment apparatus, a first film undergoes etching processing
selectively using said second film etched selectively with said
plasma treatment apparatus.
19. The method of producing a semiconductor device according to
claim 16, wherein prior to said (1) step, a step of forming
trenches for element isolation onto the main surface of said wafer
with said plasma treatment apparatus and a step of embedding an
insulating film inside trenches thereof are included.
20. The method of producing a semiconductor device according to
claim 19, wherein said step of embedding an insulating film inside
the trenches comprises a step of depositing an insulating film on
the main surface of the wafer in which trenches are formed and a
step of removing that deposited insulating film on the main surface
of the wafer by way of chemical mechanical polishing.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to plasma treatment technology
for making a source gas into a plasma and carrying out treatments
such as etching, ashing, film deposition, and sputtering etc. on a
surface of a solid material such as a semiconductor with physical
or chemical mutual reaction of activated particles. In particular,
the present invention relates to a plasma treatment apparatus
effective for etching gate or metal during the course of
manufacturing a semiconductor device (semiconductor integrated
circuit device).
RELATED ART
[0002] Conventionally, with regard to a plasma treatment apparatus,
for the purpose of improving uniformity or stability of plasma for
treatment on the surface of a semiconductor material, the following
construction is known.
[0003] (a) A plasma treatment apparatus which comprises a
dielectric window for introduction of electromagnetic wave into
inside a chamber evacuated to low pressure, and for which size and
shape of an opening of dielectric window to the side of the chamber
evacuated to low pressure, that is, size and shape of the chamber
evacuated to low pressure immediately below the dielectric window
is stipulated.
[0004] For example, JP-A-11-111696 specification discloses the
relationship between size and shape of an opening of a rectangular
dielectric window to the side of the chamber evacuated to low
pressure and frequency of electromagnetic wave. In addition,
JP-A-10-199699 specification discloses the relationship between
size and shape of an opening of a circular dielectric window to the
side of the chamber evacuated to low pressure and frequency of
electromagnetic wave.
[0005] (b) A plasma treatment apparatus which comprises a
dielectric window for introduction of electromagnetic wave into
inside a chamber evacuated to low pressure and an antenna of a disk
type, a ring type, and a slot type etc. toward the atmosphere side
of the dielectric window, and for which size and shape of the
antenna is stipulated.
[0006] For example, JP-A-2000-164392 specification discloses the
relationship between size and shape of an antenna of a ring type
comprised in the atmosphere side of the dielectric window and
frequency of electromagnetic wave. In addition, JP-A-2000-223298
specification discloses the relationship between size and shape of
an antenna of a slot type comprised in the atmosphere side of the
dielectric window and frequency of electromagnetic wave.
[0007] In addition, JP-A-2000-77384 specification, for example,
discloses a plasma treatment apparatus related to both of the above
described (a) and (b), and control of uniformity of plasma by way
of ratio of size and shape of an antenna of a circular type
comprised in the atmosphere side of the dielectric window to size
and shape of an opening of a circular dielectric window to the side
of the chamber evacuated to low pressure.
[0008] (c) A plasma treatment method which comprises inside a
chamber evacuated to low pressure an antenna for introduction of
electromagnetic wave into inside the chamber evacuated to low
pressure, and for which size and shape of the antenna is
stipulated. For example, JP-A-2000-268994 specification discloses
the relationship between size and shape of an antenna comprised
inside a chamber evacuated to low pressure and frequency of
electromagnetic wave. In addition, JP-A-10-134995 specification
discloses the relationship between size and shape of an antenna
comprised inside a chamber evacuated to low pressure, which
includes the case where walls of a chamber evacuated to low
pressure are regarded as a part of an antenna and frequency of
electromagnetic wave.
[0009] (d) A plasma treatment apparatus for which size and shape of
a periphery part of a dielectric window for introduction of
electromagnetic wave into inside a chamber evacuated to low
pressure or structure and material quality thereof is
stipulated.
[0010] For example, JP-A-3-68771 specification discloses a plasma
treatment apparatus in which a microwave absorber is caused to be
equipped in the final end of a microwave transmission line.
[0011] Moreover, JP-A-11-354502 specification, for example,
discloses a plasma treatment apparatus related to both of the above
described (c) and (d), and relationship between the end of the
antenna and shape/size of a grounding part with respect to function
of the periphery part of the antenna comprised inside the chamber
evacuated to low pressure. In addition, JP-A-2000-357683
specification discloses relationship between the end of the antenna
and shape/size of a electromagnetic wave corrector made of metal or
dielectric with respect to function of the periphery part of the
antenna comprised inside the chamber evacuated to low pressure.
[0012] In recent years, improvement in uniform treatment
performance inside semiconductor wafers with large diameter (300
mm.phi. or more) is demanded in plasma treatment utilized for
manufacturing semiconductor integrated circuit apparatus, so-called
LSI (Large Scale Integrated Circuit). In addition, a wide range of
application to the following processing steps in an LSI
manufacturing process are demanded.
[0013] (1) An application to an etching step that can go with
micronization with high anisotropy and selectivity, targeting
processing of a gate electrode, a metal film or an insulating
film.
[0014] (2) An application to an anti-reflective film processing
step such as BARC (Bottom Anti-Reflective Coating) etc. prior to
the above described etching step and a processing step of a hard
mask made of film oxide or film nitride etc.
[0015] (3) An application to a trimming step for controlling size
of a mask prior to the above described etching step.
[0016] (4) An application to a step of processing a trench for
device split or a gate side wall spacer that is regarded to require
a wide range of controllability on such as angle of shape or
roundness, etc.
[0017] (5) An application to film deposition step that is regarded
to require a wide range of condition setting such as pressure range
etc.
[0018] (6) An application to a step (post-treatment step) to remove
resist and etching remains (etching residue) as well as damage
layer after etching treatment.
[0019] (7) An application to sputtering.
[0020] In particular, just the etching step (etching step including
primary gate processing as well as before and after that
processing) related to forming of a gate of an MOS transistor may
include a lot of steps covering the above described trench
processing, anti-reflective film processing, mask processing,
processing of making a trimmed mask accompanied hereby, processing
of the gate itself, and spacer processing thereafter and an
apparatus that has all-round ability enabling to carry out all of
them is being demanded.
[0021] In addition, due to recent demand for small-amount
multi-species production, and also from necessity of application to
an LSI such as a system LSI in which a plurality of device
structures are mounted in a mixed fashion on the same wafer,
extremely highly uniform plasma generation is regarded necessary
for processing a wafer with large diameter within a wide condition
ranges of 0.1 Pa to 10 Pa in terms of processing pressure, 0.3 to 3
mA/cm.sup.2 in terms of ion incident current flux to a wafer with
respect to various gas seeds.
[0022] The present inventors made it clear what are the problems
with the existing plasma treatment apparatus prior to the present
invention. Those problems will be described below with reference to
FIG. 17 and FIG. 18.
[0023] FIG. 17 is a schematic view of a plasma treatment apparatus
that the inventors considered. This plasma treatment apparatus
comprises a chamber evacuated to low pressure (chamber) 206 shaped
a cylinder on which an object for processing is disposed. FIG. 17
shows a right half sectional view in the radius direction from the
center to the outer periphery of this chamber 206.
[0024] According to this plasma treatment apparatus, a dielectric
window consisting of a quartz plate 202 and a quartz shower plate
203 is provided in a position facing a wafer stage 201 inside the
chamber evacuated to low pressure 206. In addition, the quartz
plate 202 and the quartz shower plate 203 are fixed to the chamber
evacuated to low pressure 206 with a vacuum seal material 204. In
order to generate plasma 205, a gas is introduced into inside the
chamber evacuated to low pressure 206, and as for frequency of a
high-frequency power source to generate electromagnetic wave for
making this gas into plasma, 450 MHz was used. The radius of the
quartz glass is designed larger than the radius of the internal
wall surface of the chamber evacuated to low pressure 206 by around
23 mm. Here, 23 mm is a size fallen off from a range of
characteristic length of d=l/4+l/2.times.(n-1).+-.l/8: (n: a
positive integer, l=c(light velocity)/f/{square root}{square root
over (.di-elect cons.)}), .di-elect cons.: dielectric constant. A
gap 207 with a thin air layer is provided on the rear face of the
quartz plate 202. An antenna 208 and an antenna spacer 209 made of
alumina (Al.sub.2O.sub.3) is provided in the upper part of the
quartz plate 202.
[0025] An electric field distribution inside the chamber 206 is
shown in FIG. 18. This electric field distribution has been got by
calculation.
[0026] (a) For a plasma density being not more than
2.8.times.10.sup.10 cm.sup.-3 (equivalent to 1.0 mA/cm.sup.2 in
terms of incident ion current flux (ICF)), a portion with an
intensive electric field intensiveness appears in a region slightly
get biased to the center part of the space located above the wafer
stage. The plasma is initially generated in this intensive electric
field portion, and that plasma spreads outward due to diffusion so
that a uniform ion current is incident onto a wafer. However, as
the plasma density is made to increase to (b) 4.0.times.10.sup.10
cm.sup.-3 (equivalent to 1.4 mA/cm.sup.2 in terms of ICF), or (c)
8.0.times.10.sup.10 cm.sup.-3 (equivalent to 2.8 mA/cm.sup.2 in
terms of ICF), as shown by a circle 210, a portion with the
electric field intensiveness being intensive appears gradually in
the periphery part of the chamber evacuated to low pressure, and as
shown by a circle 211, will get larger. This made the density
increase in the periphery part (in the vicinity of the internal
walls of the chamber) inside the chamber evacuated to low pressure
206, and spoiled uniformity.
SUMMARY OF THE INVENTION
[0027] The present invention has been completed based on
recognition of the above described problems of the inventors.
[0028] An objective of the present invention is to introduce gases
and electromagnetic waves into inside a chamber evacuated to low
pressure to form plasma and alleviate change in a standing wave
distribution in a plasma treatment apparatus for treatment of the
object for processing.
[0029] Another objective of the present invention is to provide a
plasma treatment apparatus that can give a stable and continuous
plasma generation characteristic while maintaining uniformity of
large diameter with a wide range of gas seeds, density and
pressure.
[0030] Another objective of the present invention is to provide a
method of manufacturing a semiconductor device that can be planned
to improve throughput.
[0031] Among inventions disclosed in the present application,
summary of representative ones will be described as follows.
[0032] The plasma treatment apparatus of the present invention
consists of a chamber feasible to be evacuated to low pressure
(chamber), a wafer stage for an object for processing located
inside the above described chamber to be disposed thereon, an
antenna as well as a dielectric window provided at a location
facing the above described object for processing, a high-frequency
power source with frequency=f to generate electromagnetic wave for
making a predetermined gas to be introduced into inside the above
described chamber into plasma, and a part of controlling standing
wave for making the standing wave electric field distribution
provided in the vicinity of the periphery part of the above
described dielectric window proper.
[0033] The basic construction of the part of controlling standing
wave is a ring structure with the portions other than the entrance
thereof being surrounded by conductor and with a mode of a cavity
having the final end being sealed with conductor, and inside the
cavity is filled with any one of vacuum, air, or a dielectric with
dielectric constant .di-elect cons..
[0034] In addition, with the radial depth of the chamber (the
distance from the entrance to the internal end part of the
conductor) d being set equivalent to l/4+l/2.times.(n-1): (n:
positive integer, t=c(light velocity)/f/{square root}{square root
over (.di-elect cons.)}) in terms of characteristic length of
electromagnetic wave or in the vicinity thereof, the standing wave
electric field distribution formed inside the dielectric window is
made to reach a maximum (that is, a maximum amplitude position of
the standing wave) in terms of radial position of an entrance of
the part for controlling standing wave. Incidentally, the radial
position of an entrance of the part for controlling standing wave
refers to a position of the periphery end part of the dielectric
window where the part for controlling standing wave is mounted and
a position equivalent to the internal wall surfaces of the
chamber.
[0035] If quality constants of plasma for high frequency, which are
described in technical literature on high-frequency plasma, for
example, M. A. Lieberman and A. J. Lichtenberg: Principles of
Plasma Discharges and Materials Processing, (John Wiley and Sons,
Inc.) pp.93-96,pp.108-110), are expressed by a dielectric constant,
they will be expressed by a real number part giving a negative
value and an imaginary number part expressing loss in the plasma. A
negative dielectric constant means an inductive medium. According
hereto, for example, with quality constants of plasma in, for
example, a plasma of chloride of 0.4 Pa under plasma density being
2.8.times.10.sup.10 cm.sup.-3 (equivalent to 1.0 mA/cm.sup.2 in
terms of an incident ion current flux (ICF: Ion Current Flux)),
4.0.times.10.sup.10 cm.sup.31 3 (equivalent to 1.4 mA/cm.sup.2 in
terms of ICF), and 8.0.times.10.sup.10 cm.sup.-3 (equivalent to 2.8
mA/cm.sup.2 in terms of ICF), the dielectric constant of the plasma
medium can be expressed as .di-elect cons.(2.8.times.10.sup.10
cm.sup.-3)=-10.1+j0.0816, .di-elect cons.(4.0.times.10.sup.10
cm.sup.-3)=-14.9+j0.117, and .di-elect cons.(8.0.times.10.sup.10
cm.sup.-3)=-30.8+j0.233. With these, propagation of electromagnetic
waves in a plasma can be analyzed. When an electromagnetic wave
comes from a dielectric window into inside a plasma expressed by
the above described quality constants, a change in medium serves to
inverse relationship between a maximum amplitude position of and a
minimum amplitude position of the standing wave electric field
distribution in a location equivalent to wall surfaces inside a
chamber. Accordingly, distribution of standing wave electric field
formed in the plasma just below the dielectric window material will
reach a minimum (that is, a minimum amplitude position of the
standing wave) in a location equivalent to wall surfaces inside a
chamber. If an entrance of the part for controlling standing wave
is narrow to a certain extent, plasma will not extend its
influence. Therefore, the wavelength of standing wave electric
field to be formed inside the part of controlling standing wave
will hardly be influenced by kinds of gases to be made into plasma
and changes in density and pressure.
[0036] Accordingly, even if the quality constants of the plasma
medium change, for a chamber comprising a part of controlling
standing wave regulated to have the above described depth, in the
radial position that is the same as the inner diameter of the above
described chamber evacuated to low pressure, the standing wave
electric field distribution formed in the side of the plasma just
below the above described dielectric window material will always be
a minimum (that is, a minimum amplitude position of the standing
wave). This can regulate the electric field in the vicinity of wall
surfaces in the side of plasma just below the above described
dielectric window material, and the power of the electromagnetic
waves is introduced into an effective space region having a
constant span with an expected destination above the wafer stage
where an object for processing is always disposed.
[0037] That is, according to the present invention, the depth of
the part of controlling standing wave will become effective in the
case of falling within the range of d=l/4+l/2.times.(n-1).+-.l/8
(n=positive integer, l=c(light velocity)/f/{square root}{square
root over (.di-elect cons.)}). Accordingly, under a wide range of
conditions, a plasma treatment apparatus that has high uniformity
as well as linearity of plasma density for electromagnetic wave
invested power and stable and continuous characteristic can be
provided.
[0038] The part of controlling standing wave of the present
invention is filled with vacuum, air, and a dielectric almost
lacking loss inside itself, and is to make the electric field in
the vicinity of the internal walls of the chamber proper with
device in terms of size and shape, and therefore will not give rise
to bad influences such as loss of power and excess heating in that
portion.
[0039] In addition, since designing that disposition takes place
outside the vacuum in the periphery part of the dielectric window
is easily feasible, there is no necessity that a ring made of metal
material is inserted inside the chamber evacuated to low pressure
directly, either.
[0040] Moreover, the wavelength of standing wave electric field
formed inside the part of controlling standing wave is
approximately constant irrespective of conditions of plasma, there
is no need to change the structure mode from time to time during
wafer processing with some moving mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIGS. 1A and 1B are schematic views of a plasma treatment
apparatus related to Embodiment 1 of the present invention;
[0042] FIG. 2 is a schematic view of a plasma treatment apparatus
related to Embodiment 2 of the present invention;
[0043] FIG. 3 is a schematic view showing an electric field
distribution inside a chamber of a plasma treatment apparatus
related to Embodiment 2 of the present invention;
[0044] FIGS. 4A, 4B and 4C are plasma characteristic graphs showing
a comparison between a plasma treatment apparatus shown in FIG. 17
and a plasma treatment apparatus related to Embodiment 2 of the
present invention;
[0045] FIG. 5 is a schematic view of a plasma treatment apparatus
related to Embodiment 3 of the present invention;
[0046] FIG. 6 is a schematic view of a plasma treatment apparatus
related to Embodiment 4 of the present invention;
[0047] FIG. 7 is a schematic view of a plasma treatment apparatus
related to Embodiment 5 of the present invention;
[0048] FIG. 8 is a partial schematic view of a plasma treatment
apparatus related to Embodiment 6 of the present invention;
[0049] FIG. 9 is a plasma characteristic graph of a plasma
treatment apparatus related to Embodiment 6 of the present
invention;
[0050] FIG. 10 is a schematic view showing an entire construction
of a plasma treatment apparatus related to Embodiment 6 of the
present invention;
[0051] FIG. 11 is a plan view showing a base frame in its entirety
related to Embodiment 6 of the present invention;
[0052] FIG. 12 is a plasma characteristic graph showing a
comparison between a plasma treatment apparatus shown in FIG. 17
and a plasma treatment apparatus related to Embodiment 6 of the
present invention;
[0053] FIG. 13 is a schematic view showing a plasma treatment
apparatus (insulating film etcher) that the present inventors have
considered prior to completion of the present invention;
[0054] FIG. 14 is a schematic view showing a plasma treatment
apparatus (insulating film etcher) related to Embodiment 7 of the
present invention;
[0055] FIG. 15 is a sectional view showing a manufacturing process
of a semiconductor device related to Embodiment 9 of the present
invention;
[0056] FIG. 16 is a sectional view showing a manufacturing process
of a semiconductor device related to Embodiment 9 of the present
invention;
[0057] FIG. 17 is a schematic view showing a plasma treatment
apparatus (etcher for gate processing) that the present inventors
have considered prior to completion of the present invention;
and
[0058] FIGS. 18A, 18B and 18C are schematic views showing electric
field distributions inside a chamber of a plasma treatment
apparatus having been shown in FIG. 17.
DESCRIPTION OF THE SYMBOLS
[0059] 101 . . . Chamber evacuated to low pressure
[0060] 102 . . . Wafer stage
[0061] 103 . . . Dielectric window
[0062] 104 . . . Electromagnetic wave
[0063] 105 . . . High-frequency power source with frequency=f
[0064] 106 . . . Part of controlling standing wave
[0065] 107 . . . Region behind the dielectric window
[0066] 108 . . . Entrance of the part for controlling standing
wave
[0067] 109 . . . Part of controlling standing wave
[0068] 100 . . . Wafer
[0069] 110 . . . Standing wave electric field distribution formed
in the dielectric window material
[0070] 111 . . . Maximum amplitude position of the standing
wave
[0071] 112 . . . Plasma
[0072] 113 . . . Minimum amplitude position of the standing
wave
[0073] 201 . . . Wafer stage
[0074] 202 . . . Quartz plate
[0075] 203 . . . Quartz shower plate
[0076] 204 . . . Vacuum seal material
[0077] 205 . . . Plasma
[0078] 206 . . . Chamber evacuated to low pressure
[0079] 207 . . . Gap of air layer
[0080] 208 . . . Antenna
[0081] 209 . . . Antenna spacer
[0082] 210 . . . Electric field (medium) in the periphery part of
the chamber evacuated to low pressure
[0083] 211 . . . Electric field (intensive) in the periphery part
of the chamber evacuated to low pressure
[0084] 300 . . . Wafer
[0085] 301 . . . Quartz plate
[0086] 302 . . . Gap of air layer
[0087] 303 . . . Plasma
[0088] 304 . . . Vacuum seal material
[0089] 305 . . . Chamber evacuated to low pressure
[0090] 306 . . . Wafer stage
[0091] 307 . . . Quartz shower plate
[0092] 308 . . . Antenna
[0093] 309 . . . Antenna spacer
[0094] 310 . . . Electric field (weak) in the periphery part of the
chamber evacuated to low pressure
[0095] 311 . . . Electric field (weak) in the periphery part of the
chamber evacuated to low pressure
[0096] 401 . . . Uniformity of ICF in the case where a construction
in FIG. 2 is used
[0097] 402 . . . Uniformity of ICF in the case where a construction
in FIG. 3 is used
[0098] 403 . . . Electromagnetic wave power dependency of ICF in
the case where constructions in FIG. 2 and FIG. 3 are used
[0099] 404 . . . Electromagnetic wave power dependency of ICF in
the case where a construction in FIG. 2 is used
[0100] 405 . . . Electromagnetic wave power dependency of ICF in
the case where a construction in FIG. 3 is used
[0101] 501 . . . Part of controlling standing wave
[0102] 502 . . . Chamber evacuated to low pressure
[0103] 503 . . . Plasma
[0104] 504 . . . Wafer stage
[0105] 505 . . . Quartz plate
[0106] 506 . . . Quartz shower plate
[0107] 507 . . . Vacuum seal material
[0108] 508 . . . Gap of air layer
[0109] 509 . . . Antenna
[0110] 510 . . . Antenna spacer
[0111] 511 . . . Part of controlling standing wave
[0112] 512 . . . Part of controlling standing wave
[0113] 513 . . . Antenna spacer
[0114] 601 . . . Part of controlling standing wave
[0115] 602 . . . Quartz plate
[0116] 603 . . . Chamber evacuated to low pressure
[0117] 604 . . . Plasma
[0118] 605 . . . Wafer stage
[0119] 606 . . . Quartz shower plate
[0120] 607 . . . Vacuum seal material
[0121] 608 . . . Antenna
[0122] 609 . . . Antenna spacer
[0123] 610 . . . Gap of air layer
[0124] 611 . . . Length of an L-shaped conductor part
[0125] 612 . . . Dependency of ICF linearity for electromagnetic
wave power toward length of an L-shaped conductor part
[0126] 701 . . . Reactor for plasma etching
[0127] 702 . . . High-frequency power source with f=450 MHz for
plasma
[0128] 703 . . . Tuner for plasma
[0129] 704 . . . Solenoid coil for generating and controlling the
magnetic field
[0130] 705 . . . Base frame
[0131] 706 . . . Wafer stage
[0132] 707 . . . Wafer (300 mm.phi.)
[0133] 708 . . . Power source of f=400 kHz for wafer biasing
[0134] 709 . . . Matching box for wafer biasing
[0135] 710 . . . Reactor for plasma etching
[0136] 711 . . . Reactor for plasma ashing
[0137] 712 . . . Wafer cassette loading spot
[0138] 713 . . . Wafer conveyor robot
[0139] 801 . . . Etching rate uniformity in the case where a
construction in FIG. 2 is used
[0140] 802 . . . Etching rate uniformity in the case where a
construction in FIG. 3 is used
[0141] 803 . Etching rate uniformity under 360 W of electromagnetic
wave power according to a construction in FIG.
[0142] 804 . . . Etching rate uniformity under 720 W of
electromagnetic wave power according to a construction in FIG.
[0143] 805 . . . Etching rate uniformity under 360 W of
electromagnetic wave power according to a construction in FIG.
[0144] 806 . . . Etching rate uniformity under 720 W of
electromagnetic wave power according to a construction in FIG.
[0145] 900 . . . Wafer (300 mm.phi.)
[0146] 901 . . . Wafer stage
[0147] 902 . . . Quartz plate
[0148] 903 . . . Circular shower antenna
[0149] 904 . . . Antenna spacer
[0150] 905 . . . Part of controlling standing wave.
PREFERRED EMBODIMENTS OF THE INVENTION
Embodiment 1
[0151] Embodiment 1 of the present invention will be described
below with reference to FIG. 1 to FIG. 4.
[0152] FIG. 1A is a sectional view showing main parts of a plasma
treatment apparatus in which a part of controlling standing wave
has been provided.
[0153] This plasma treatment apparatus consists of a chamber
feasible to be evacuated to low pressure (chamber evacuated to low
pressure) 101, a wafer stage 102 for an object for processing
(semiconductor wafer 101) located inside the chamber 101, a
disk-shaped dielectric window 103 facing the above described object
for processing, a high-frequency power source with frequency=f 105
to generate electromagnetic wave 104 for making a predetermined gas
to be introduced into inside the above described chamber into
plasma, and a part of controlling standing wave for making the
standing wave electric field distribution 106 mounted in the
vicinity of the periphery part of the above described dielectric
window proper. In addition, although FIG. 1 does not show, an
antenna is located in a region 107 behind the dielectric window 103
so as to be sectioned from a plasma (plasma generating region) 112
of the internal part 112 of the chamber. For this antenna, antenna
systems in variety of shapes and waveguide systems in variety of
shapes are selected corresponding with necessity.
[0154] The part of controlling standing wave 106 has, as shown in
FIG. 1B, portions other than the entrance 108 brought into contact
with the dielectric window 103 have cavity part 106 surrounded by a
conductor. That is, the part of controlling standing wave 106 is
constructed in the side wall of the dielectric window 103 to have a
ceiling plate 106a, a bottom plate 106b, a side plate 106c closing
the final ends of these plates 106a and 106b, and an entrance 108
located in the opposite direction against the side plate 106c and
brought into contact with the dielectric window 103, and an
internal part of the cavity part 106 partitioned by these plates
106a, 106b and 106c is filled with a vacuum, air or a dielectric
with dielectric constant .di-elect cons.. In addition, this part of
controlling standing wave 106 constitutes a ring structure
surrounding a disk-shaped dielectric window 103. The cavity part
106 is filled with any one of a vacuum, air or a dielectric of the
dielectric constant .di-elect cons.. Making the depth d of the
cavity part 106 (distance from the entrance end 108 to the internal
wall of the side plate 106c) equivalent to l/4+l/2.times.(n-1):
(n=positive integer, l=c(light velocity)/f/{square root}{square
root over (.di-elect cons.)}) in terms of characteristic length of
electromagnetic wave, the location of entrance of the part for
controlling standing wave 108 (that is, in this basic construction,
a location of the end of the periphery of the dielectric window
where this part of controlling standing wave is disposed, and a
radial position equivalent to internal wall surfaces of the chamber
evacuated to low pressure) the standing wave electric field
distribution 110 formed inside the dielectric window will become
maximum (that is, a maximum amplitude position of the standing wave
111).
[0155] On the other hand, as described above, if quality constants
of plasma for high frequency, are expressed by a dielectric
constant, they will be expressed by a real number part giving a
negative value and an imaginary number part expressing loss in the
plasma. A negative dielectric constant means an inductive medium.
For example, with quality constants of plasma in, for example, a
plasma of chloride of 0.4 Pa under plasma density being
2.8.times.10.sup.10 cm.sup.-3 (equivalent to 1.0 mA/cm.sup.2 in
terms of an incident ion current flux (ICF: Ion Current Flux)),
4.0.times.10.sup.10 cm.sup.-3 (equivalent to 1.4 mA/cm.sup.2 in
terms of ICF), and 8.0.times.10.sup.10 cm.sup.-3 (equivalent to 2.8
mA/cm.sup.2 in terms of ICF), the dielectric constant of the plasma
medium can be expressed as .di-elect cons. (2.8.times.10.sup.10
cm.sup.-3)=-10.1+j0.0816, .di-elect cons. (4.0.times.10.sup.10
cm.sup.-3)=-14.9+j0.117, and .di-elect cons. (8.0.times.10.sup.10
cm.sup.-3)=-30.8+j0.233. With these, propagation of electromagnetic
waves in a plasma can be analyzed. When an electromagnetic wave
comes from a dielectric window 103 into inside a plasma 112
expressed by the above described quality constants, a change in
medium serves to inverse relationship between a maximum amplitude
position of and a minimum amplitude position of the standing wave
electric field distribution in a location equivalent to wall
surfaces inside a chamber. Accordingly, distribution of standing
wave electric field formed in the plasma just below the dielectric
window material 103 will reach a minimum (that is, a minimum
amplitude position of the standing wave 113) in a location
equivalent to wall surfaces inside a chamber.
[0156] An entrance 108 of the part for controlling standing wave
106 is made narrow so as not to be influenced by the plasma 112.
Therefore, the wavelength of standing wave electric field to be
formed inside the part of controlling standing wave will become
hardly influenced by kinds of gases to be made into plasma and
changes in density and pressure. Therefore, even if the quality
constants of the plasma medium change, for a chamber comprising a
part of controlling standing wave regulated to have the above
described depth, in the position that is the same as the inner
diameter of the above described chamber, the standing wave electric
field distribution formed in the side of the plasma just below the
above described dielectric window material will always be a minimum
(that is, a minimum amplitude position 113 of the standing wave).
This can regulate the electric field in the vicinity of wall
surfaces in the side of plasma just below the above described
dielectric window material, and the power of the electromagnetic
waves is introduced into an effective space region having a
constant span above the wafer stage 102 where an object for
processing (semiconductor wafer) is always disposed. Thus, under a
wide range of conditions, a plasma treatment apparatus that has
high uniformity as well as linearity of plasma density for
electromagnetic wave invested power and stable and continuous
characteristic can be provided.
[0157] Incidentally, according to the present embodiment, the depth
of the part of controlling standing wave within the range of
.+-.1/8 gives rise to effect, but if it departs therefrom, a plasma
characteristic that does not provide uniformity within only a
constant narrow range as in the case where a part of controlling
standing wave is not comprised will be reinstated. Accordingly, the
depth of the part of controlling standing wave will become
effective in the case of falling within the range of
d=l/4+l/2.times.(n-1).+-.l/8 (n=positive integer, l=c(light
velocity)/f/{square root}{square root over (.di-elect cons.)}).
[0158] The part of controlling standing wave of the present
embodiment is filled with vacuum, air, and a dielectric almost
lacking loss inside itself, and is to make the electric field in
the vicinity of the internal walls of the chamber proper with
device in terms of size and shape, and therefore will not give rise
to bad influences such as loss of power and excess heating in that
portion.
[0159] In addition, since designing that disposition takes place
outside the vacuum in the periphery part of the dielectric window
is easily feasible, there is no necessity that a ring made of metal
material is inserted inside the chamber evacuated to low pressure
directly, either.
[0160] Moreover, the wavelength of standing wave electric field
formed inside the part of controlling standing wave is
approximately constant irrespective of conditions of plasma, there
is no need to change the structure mode during wafer processing
with a certain moving mechanism.
Embodiment 2
[0161] Embodiment 2 of the present invention will be described
below with reference to FIG. 2, FIGS. 3A, 3B and 3C.
[0162] The present Embodiment 2 is constructed to have as shown in
FIG. 2 a part of controlling standing wave in which a quartz plate
301 and a thin air layer (gap) 302 are extended for a portion
equivalent to the characteristic length of the part of controlling
standing wave 106 having been added in the above described
Embodiment 1.
[0163] In the plasma treatment apparatus shown in FIG. 17, the
designed size of balance between the radius of the quartz plate 202
and the inner diameter of the chamber was around 23 mm. On the
other hand, in the present Embodiment 2, the designed size of
balance between the radius of the quartz plate 301 and the inner
diameter of the chamber 305 suitable for sealing the chamber 305
with a vacuum seal material 304 is larger than the designed size in
FIG. 2. That is, the radius of the quartz plate 301 is designed to
be larger than the inner diameter of the chamber 305 by
approximately 108 mm. Incidentally, for a wafer stage 306, a quartz
shower plate 307, an antenna 308 and an antenna spacer 309, those
being same as those shown in FIG. 2 were used.
[0164] Generation of the plasma 303 according to this construction
will be described below with reference to FIGS. 3A, 3B and 3C.
[0165] The above described designed size 108 mm falls within the
range of the characteristic length of d=l/4+l/2.times.(n-1).+-.l/8:
(n=positive integer, and here n=1, l=c(light velocity)/f/{square
root}{square root over (.di-elect cons.)}), being calculated on the
assumption of substance (dielectric constant .di-elect cons.:
around 3.3 to 3.6) with the dielectric constant being slightly low
than quartz (dielectric constant of 3.5 to 3.8), taking influence
of a thin air layer gap 302 provided behind the quartz plate 301
into consideration as well. The calculated results of electric
field distribution at this time by calculation are shown in FIGS.
3A, 3B and 3C. Increase in plasma density as in (a)
2.8.times.10.sup.10 cm.sup.-3, (b) 4.0.times.10.sup.10 cm.sup.-3
and (c) 8.0.times.10.sup.10 cm.sup.-3 does not present phenomena
that as shown in a circle 310 as well as a circle 311 electric
field increases in the vicinity of the internal walls of the
chamber (the periphery part inside the chamber). At this time, even
if the power of power source to be introduced to the chamber 305
for generating electromagnetic wave is made to increase and the
plasma density is made to increase, a space region where the power
is introduced will not get biased to the periphery part, but under
any power conditions, highly uniform ion currents are incident onto
a wafer. In this construction, on the assumption that the gas seed
or pressure is changed a lot, with the constant expressing the
quality of the plasma medium being made to change further widely,
no phenomena that electric field of the periphery part of the
chamber continues to increase were observed.
[0166] Comparison between the plasma treatment apparatus shown in
FIG. 17 and the construction of the present Embodiment 2 in terms
of the plasma characteristics obtainable is shown in FIGS. 4A, 4B
and 4C. FIG. 4A shows a plasma characteristic in the construction
of the plasma treatment apparatus shown in FIG. 2. In addition,
FIG. 4B shows a plasma characteristic in the construction of the
present Embodiment 2. These plasma characteristics show uniformity
of ICF in the case where chloride is used as gas and the pressure
is set at 0.4 Pa. In addition, FIG. 4C is the plasma characteristic
showing linearity to the power of electromagnetic wave in the both
parties.
[0167] As for the plasma characteristic 401 of the plasma treatment
apparatus shown in FIG. 17, as shown in FIG. 4A, when the power of
electromagnetic wave is increased from 360 W to 500W, the ICF
distribution being approximately uniform with the center part being
slightly higher changes into the ICF distribution with the
periphery parts being slightly higher, and an increase to 1000 W
has provided the ICF distribution with the periphery parts being
rather higher.
[0168] On the other hand, as for the plasma characteristic 402 of
the present Embodiment 2, as shown in FIG. 4B, nearly flat ICF
distribution is given for the range from 360 W to 1000 W, falling
within a range of .+-.5% (3.sigma.: .sigma. is a standard
deviation) as a result under all the power conditions. In addition,
although it is not depicted, the construction of FIG. 17 could not
maintain plasma in a stable fashion with 250 W or less. However,
the present Embodiment 2 was found to be capable of maintaining
plasma in a stable fashion with the power even lowered to reach 50
W.
[0169] In addition, in order to confirm linearity of ICF for powers
in the both parties, a plasma characteristic 403 in which power is
plotted on the horizontal axis and average value of ICF inside the
300 mm.phi. plane of wafer is plotted on the vertical axis is shown
in FIG. 4C.
[0170] For the plasma treatment apparatus (405) shown in FIG. 17,
the ICF showed a tendency toward saturation with 500 W or more. On
the other hand, in the present Embodiment 2 (404), all the dots to
reach 1000 W were resulted in tracing an approximately straight
line.
[0171] Incidentally, in order to confirming that the plasma
characteristic of the construction according to the present
Embodiment 2 (FIG. 2) in which the dielectric window of the quartz
itself was extended outward is equivalent in principle to the one
shown in the basic construction of FIG. 1, such a part that is the
dielectric window 301 shown in FIG. 2 being split immediately
outside a vacuum seal material 304 was produced and the
experimental comparison was carried out, but the case involving
split and the case involving no split have give rise to exactly the
same characteristic.
[0172] In addition, it goes without saying that the effect in the
present Embodiment 2 can be given likewise with a material having
different dielectric constant such as alumina in instead of the
dielectric window consisting of a quartz plate and a quartz shower
plate. In addition, even if the shower plate is removed so that the
method for introducing gas is changed, the essence of the invention
will not be influenced at all, which is as described in Embodiment
1 with reference to FIG. 1.
Embodiment 3
[0173] As Embodiment 3 of the present invention, a variation of
disposition of the part of controlling standing wave will be
described below with reference to FIG. 5.
[0174] As shown in FIG. 5, above a quartz plate 505, a part of
controlling standing wave 501 of quartz (dielectric constant of 3.5
to 3.8) made by being brought into connection with that quartz
plate is mounted. A wafer stage 504, the quartz plate 505 and the
quartz shower plate 506 mounted in a position faxing this, a vacuum
seal material 507 as well as a thin air layer gap 508, and an
antenna 509 mounted on the upper part thereof are exactly the same
as those shown in FIG. 17. In addition, from necessity to provide
the part of controlling standing wave 501 upward, the antenna
spacer 510 and the conductor member covering it from outside were
designed to have a radius smaller by approximately 40 mm.
[0175] The size of the part of controlling standing wave 501 with
width of entrance being 35 mm was considered by calculation
technique same as that in the above described Embodiment 1. As a
result thereof, with a construction comprising a quartz plate 505,
a part of controlling standing wave 501 and a thin air layer 508,
the thin air layer 508 being sandwiched between the upper plane of
the quartz plate 505 and the part of controlling standing wave 501,
if the height of the part of controlling standing wave 501 is 70
mm, the calculation results of standing wave electric field
distribution with plasma density of 2.8.times.10.sup.10 cm.sup.-3
(equivalent to 1.0 mA/cm.sup.2 in terms of ICF),
4.0.times.10.sup.10 cm.sup.-3 (equivalent to 1.4 mA/cm.sup.2 in
terms of ICF), and 8.0.times.10.sup.10 cm.sup.-3 (equivalent to 2.8
mA/cm.sup.2 in terms of ICF) were found to correspond to the result
(FIG. 3) given by the construction shown in FIG. 2. That is, as in
the present Embodiment 3, also with a construction in which the
direction is changed by 90 degree, it became obvious that a shape
and size to become equivalent as the characteristic length of
electromagnetic wave could be found out. This is an effective
knowledge on design of an apparatus that the protrusion in the
horizontal direction avoids interfering with any other parts.
Embodiment 4
[0176] As Embodiment 4 of the present invention, another variation
of disposition of the part of controlling standing wave will be
described below with reference to FIG. 6.
[0177] According to the present Embodiment 4, in order to plan
further enhancement in compactness on shapes and sizes of a part of
controlling standing wave, alumina (with dielectric constant of
9.8) with higher dielectric constant was adopted as constructing
material of the part of controlling standing wave in the above
described Embodiment 3. In addition, an optimum shapes and sizes
were considered by a similar calculation technique.
[0178] As shown in FIG. 6, the width of the entrance of the part of
controlling standing wave 511 was set to 25 mm and the other
constructions were made same as that shown in FIG. 5.
[0179] According to the present Embodiment 4, in the case where the
height of the part of controlling standing wave was set to 50 mm,
the calculation results of the standing wave electric field
distribution with plasma density of 2.8.times.10.sup.10 cm.sup.-3
(equivalent to 1.0 mA/cm.sup.2 in terms of ICF),
4.0.times.10.sup.10 cm.sup.-3 (equivalent to 1.4 mA/cm.sup.2 in
terms of ICF), 8.0.times.10.sup.10 cm.sup.-3 (equivalent to 2.8
mA/cm.sup.2 in terms of ICF), obviously corresponded to the results
given by Embodiment 2 (FIG. 3) and Embodiment 3 (FIG. 5). This can
serve to plan further enhancement in compactness in shapes and
sizes with making the dielectric constant of the material to fill
out the part of controlling standing wave higher.
[0180] As a dielectric to be used in the part of controlling
standing wave, quartz and alumina etc. are selected due to cost
issues, but materials with further higher dielectric constant, for
example, any one of zirconia (ZrO.sub.2), titania (TiO.sub.2), and
YAG ceramics (Y.sub.3Al.sub.5O.sub.12) may be used so that further
enhancement in compactness becomes available.
Embodiment 5
[0181] As Embodiment 5 of the present invention, a variation of
disposition of the part of controlling standing wave will be
described below with reference to FIG. 7.
[0182] The present Embodiment 5 is structured to have the part of
controlling standing wave of Embodiment 4 that was further bent to
constitute a right angle inward in order to plan further
enhancement in compactness of the part of controlling standing
wave. As shown in FIG. 7, the part of controlling standing wave 512
is filled with alumina inside and is shaped by being bent inward.
In addition, the entrance width and the internal width are
respectively 30 mm. For securing space, an antenna spacer 513 is
made a little small, and the other constructions are the same as
those of FIG. 5 and FIG. 6.
[0183] Consideration was proceeded with calculation technique
similar to that in the above described Embodiment 2. As a result
thereof, the calculation results of the standing wave electric
field distribution with shapes and sizes shown in FIG. 5 and with
plasma density of 2.8.times.10.sup.10 cm.sup.-3 (equivalent to 1.0
mA/cm.sup.2 in terms of ICF), 4.0.times.10.sup.10 cm.sup.-3
(equivalent to 1.4 MA/cm.sup.2 in terms of ICF),
8.0.times.10.sup.10 cm.sup.-3 (equivalent to 2.8 mA/cm.sup.2 in
terms of ICF), obviously corresponded to the results given by
respective constructions of Embodiment 2 (FIG. 3), Embodiment 3
(FIG. 5) and Embodiment 4 (FIG. 6).
[0184] This made clear that the part of controlling standing wave
can be appropriately bent according to convenience of designing so
that enhancement in compactness can be planned, and that the shape
and sizes of the present Embodiment 5 are equivalent to Embodiment
2, Embodiment 3 and Embodiment 4 in terms of characteristic length
of electromagnetic wave. As a result of consideration on the plasma
characteristics respectively in Embodiment 3, Embodiment 4, and
Embodiment 5 under the same experimental conditions as in
Embodiment 2, well corresponding characteristics in terms of
uniformity of ICF in each power of electromagnetic waves as shown
in FIG. 4B and FIG. 4C and linearity of ICF toward the power of the
electromagnetic waves were confirmed to appear.
[0185] In Embodiments 3, 4 and 5, variations in which the part of
controlling standing wave was mounted on the periphery part of the
dielectric window or that was bent were respectively described, but
with a construction that it is extended in the side direction and
is bent downward in the atmosphere side, or the parts other than
the entrance are surrounded by conductor in the downward vacuum
side or with changes in thickness of curvature, adjustment in
design of shape and size to make the characteristic length
equivalent is possible.
Embodiment 6
[0186] As Embodiment 6 of the present invention, another variation
in disposition of the part of controlling standing wave will be
described below with reference to FIG. 8.
[0187] The present Embodiment 6 is a construction of a part of
controlling standing wave that realized further enhancement in
compactness. As shown in FIG. 6, the part of controlling standing
wave 601 is mounted in the location inward from the end part of a
quartz plate 602. A wafer stage 605, a quartz plate 602 mounted on
the location facing this, and a quartz shower plate 606, a vacuum
seal material 607 and an antenna 608 mounted thereon are exactly
the same as Embodiment 3 (FIG. 5).
[0188] The shape and size of the antenna spacer 609 was made to be
slightly smaller than in FIG. 5(c) for convenience that the part of
controlling standing wave 601 is biased to inward. In addition, the
shape of the thin air layer gap 610 also undergoes slight
changes.
[0189] The entrance of the part for controlling standing wave 601
is above the quartz plate 602, and is disposed 17 mm inward from
the outside end part of the a quartz plate 602. In addition,
thickness of alumina filling the part of controlling standing wave
601 is made 7 mm thin compared with the construction shown in FIG.
5, and moreover the width of the entrance of the part for
controlling standing wave is narrow with 9.5 mm. Due to such a
design, the construction is made to house all in the same space as
in the plasma treatment apparatus shown in FIG. 17.
[0190] With a calculation technique similar to that in Embodiment
2, the depth of the part of controlling standing wave was
considered. As a result thereof, with a design of depth of depth
shown in FIG. 6 and length 611 of an L-type conductor part
surrounding the part of controlling standing wave, the calculation
results of standing wave electric field distribution with plasma
density of 2.8.times.10.sup.10 cm.sup.-3 (equivalent to 1.0
mA/cm.sup.2 in terms of ICF), 4.0.times.10.sup.10 cm.sup.-3
(equivalent to 1.4 mA/cm.sup.2 in terms of ICF), and 8.0'10.sup.10
cm.sup.-3 (equivalent to 2.8 mA/cm.sup.2 in terms of ICF) were
found to correspond to the result given by Embodiment 2.
[0191] Strictly speaking, it looks like that the present Embodiment
6 is constructed to involve two branched routes of electromagnetic
wave that is reflected by the end part of the quartz dielectric
window and returns and electromagnetic wave that enter the part of
controlling standing wave and reaches the innermost part and
returns subject to reflection, but in the end, multiplexing them
well, the effect similar to effects having been described so far
can be given.
[0192] Thus, even with constructions involve branching of routes of
electromagnetic wave, and bending direction or width of the
entrance of the part of controlling standing wave etc. that change
in lapse of time, if only characteristic of electromagnetic wave is
designed to be same, it became obviously possible to give effects
equivalent to Embodiments 2, 3, 4 and 5.
[0193] Embodiment 6 is housed into the most compact design among
embodiments that have been described so far. With the construction
such as Embodiment 6 as a base, under central condition of size and
shape shown in FIG. 8, experiments to cause the characteristic
length of the part of controlling standing wave to be changed were
carried out. In the experiment, the length 611 of the L-type
conductor part was changed so that the effective depth of the part
of controlling standing wave was changed.
[0194] As a result hereof, as shown in FIG. 9, whether the length
of L part should be made longer or shorter than the center size
(L=31.5 mm), the characteristics are deteriorated likewise. It has
become obvious that, for example, with shortage of 18 mm, linearity
of ICF toward the power of electromagnetic wave is deteriorated to
reach a level of characteristic similar to that in the case where
the part of controlling standing wave is not comprised. That is,
the part of controlling standing wave was found out to extend
effects within a range having a certain width from the center size
of the length of the L part of the L-type conductor part (L-type
metal fittings) 611. The electromagnetic wave at first propagates
outward inside the dielectric window and returns at the tip part of
the L part and enters the part of controlling standing wave. Taking
this into account, the change of 18 mm of L-part length can be said
to be equivalent to change in propagation route of the
electromagnetic wave for reciprocal routes of 18 mm. Estimates
based hereon, the part of controlling standing wave was found out
to extend its effects when it falls within a region of at least
.+-.1/8 from the center size compared with a case where this is not
used. In order to carry out reconfirmation with a simple experiment
system, as a result of changing the radii within a range of .+-.1/8
in a construction in which the radii of the quartz plate and thin
air layer gap are changed shown in FIG. 2, the effect of the
present embodiment is provided within the range of .+-.1/8, but
when to deviate from it, deterioration is reconfirmed to take
place, as in the characteristic without the part of controlling
standing wave.
[0195] FIG. 10 is a schematic view showing the whole construction
of the plasma treatment apparatus (gate processing etcher or metal
processing etcher) in the present Embodiment 6. Functions of this
plasma treatment apparatus will be described below.
[0196] In FIG. 10, the electromagnetic waves generated in a
high-frequency power source with f=450 MHz for plasma 702 are
introduced into inside the reactor for plasma etching 701 via the
tuner for plasma 703.
[0197] Plasma is made highly efficiently by applying the magnetic
field generated by a solenoid coil for generating and controlling
the magnetic field 704. A plasma etching reactor 701 and a solenoid
coil for generating and controlling the magnetic field 704 are
mounted on a base frame 705 having pumping equipment. A gas supply
tube is buried as shown in the drawing in this base frame 705. The
gas is introduced into the gap between the quartz plate 602 and the
quartz shower plate 606, and introduced into the reactor 701 via a
plurality of pores provided in the quartz shower plate. On the
other hand, on the wafer stage 706 having ascending/descending
mechanism, for example, a wafer 707 with diameter of 300 mm is
loaded, and high-frequency wave generated by a power source of
f=400 kHz for wafer biasing 708 is applied to that wafer 707 via a
matching box for wafer biasing 709. And the surface of the wafer
707 undergoes etching treatment.
[0198] FIG. 11 is a plan view showing a base frame in its entirety.
The plasma etching reactor 710 shown in FIG. 10 is mounted onto the
base frame 705. The construction having two plasma etching reactors
710 will enable parallel treatment with good efficiency in case of
mass production. For the present Embodiment 6, one of these was
used to assess etching. In addition, on the same base frame 705,
two plasma ashing reactors 711 are mounted to constitute a
construction enabling resist mask and removal of surface polymer
subject to etching. In addition, in the wafer cassette loading spot
712, there is provided a waiting site for a wafer prior to etching
and a waiting site for a wafer subject to etching, and the wafer is
structured to be conveyed to respective places with a wafer
conveyor robot 713.
[0199] That is, the basic construction of the embodiment shown in
FIG. 11 has a plurality of reactors on the base frame, each of
which reactors is characterized by comprising in a chamber feasible
to be evacuated to low pressure a wafer stage for an object for
processing to be disposed thereon, a dielectric window, that faces
the above described object for processing, for introducing
electromagnetic waves, a high-frequency power source with
frequency=f to generate electromagnetic wave for making a
predetermined gas to be introduced into the above described chamber
evacuated to low pressure into plasma, and a part of controlling
standing wave provided in the vicinity of the periphery part of the
above described dielectric window, filled with vacuum, air, or a
dielectric with dielectric constant a, and with the portions other
than the entrance thereof being surrounded by conductor, having
depth thereof falling within the range of the characteristic length
of d=l/4+l/2.times.(n-1).+-- .l/8: (n=positive integer, l=c(light
velocity)/f/{square root}{square root over ()}).
[0200] In FIG. 12A, plasma characteristic 801 related to uniformity
in the plasma treatment apparatus in FIG. 17 is shown and in FIG.
12B, plasma characteristic 802 related to uniformity in the present
Embodiment 6 is shown respectively. For respective apparatuses,
chlorine is used as gas and the pressure is set at 0.4 Pa. In
addition, uniformity in polysilicon etching in the case where 360 W
and 720 W were-used as the power of electromagnetic wave was
assessed.
[0201] As shown in FIG. 12A, the plasma treatment apparatus of FIG.
17 deteriorates in its uniformity through transition from the
characteristic 803 to the characteristic 804 changing power of
electromagnetic wave.
[0202] On the other hand, as shown in FIG. 12B, the present
Embodiment 6 scarcely shows change in uniformity in the
characteristic 805 and the characteristic 806 despite changes in
power of electromagnetic wave. That is, according to the present
Embodiment 6, uniformity was not deteriorated and good results were
provided.
[0203] Incidentally, under similar conditions, uniformity of the
same polysilicon was confirmed on Embodiments 2, 3, 4 and 5
respectively, but results well corresponding to the plasma
characteristic shown in FIG. 12B were provided.
[0204] With the plasma treatment apparatus of the present
Embodiment 6, uniformity of treatment performance on various steps
and various film seeds in manufacturing course of LSI was
confirmed. As an example, consistent treatment on etching related
to gate forming with a single chamber was considered. As an
experiment, etching treatment in the following manufacturing steps
of LSI was carried out.
[0205] (a) BARC processing step of STI (Shallow Trench Isolation)
pattern with CF.sub.4 as a base: electromagnetic power 400 W.
[0206] (b) Top round processing step of STI with CF.sub.4 as a
base: electromagnetic power 350 W.
[0207] (c) Taper processing step of STI with HBr as a base:
electromagnetic power 800 W.
[0208] (d) Bottom round processing step of STI with added gas:
electromagnetic power 350 W.
[0209] (e) Step of trimming of gate mask pattern with O.sub.2 and
halogen mixed system: electromagnetic power 400 W.
[0210] (f) BARC processing step of gate pattern with CF.sub.4 as a
base: electromagnetic power 600 W.
[0211] (g) SiN mask processing step of gate pattern with CF.sub.4
as a base: electromagnetic power 700 W.
[0212] (h) Perpendicular processing step polysilicon gate with
Cl.sub.2 as a base: electromagnetic power 450 W.
[0213] (i) Overetching step of polysilicon gate with HBr as a base:
electromagnetic power 450 W.
[0214] For these steps of (a) to (i), uniformity on patternless
wafers (300 mm.phi.) and uniformity on microprocessing in patterned
wafers (300 mm.phi.) were confirmed.
[0215] As a result thereof, for all steps of (a) to (i), with
patternless wafers, uniform treatment falling within a range of
.+-.3% (3.sigma.) was able to be confirmed, and with patterned
wafers, etching processing including etching angle, roundness,
residual amount of pattern mask etc. without shape differences and
size differences between the center part and the periphery part
within the wafer plane was be able to be carried out with a single
chamber evacuated to low pressure of the present invention.
Compared with the case where a series of processing is carried out
by dedicated apparatus of respective steps giving and taking wafers
from an apparatus to an apparatus or the case where it is carried
out in an apparatus having a plurality of dedicated chambers
evacuated to low pressure, extra time for conveying wafers into and
out from respective dedicated apparatus or chambers evacuated to
low pressure can be saved and in total the time could be curtailed
to not more than 50% and throughput was increased twice and more.
Thus, construction with a single chamber evacuated to low pressure
will make is possible to cope with various process conditions in
wide ranges, and is ranked extremely high in terms of improvement
in mass production efficiency. It goes without saying that the
system using the present invention can show uniform treatment
performance under a wide range of conditions for other
semiconductor treatment such as film forming CVD or sputtering etc.
utilizing physical and chemical action of seeds created by plasma,
and it works likewise in other various steps that coverage of a
wide range of characteristics by a single plasma apparatus gives
rise to an effect to improve production efficiency.
[0216] Incidentally, in the present Embodiment 6, application of
magnetic field to the made plasma can not only enhance plasma
making efficiency but also tune in uniformity of treatment inside
the wafer surface exactly to a further higher extent.
[0217] In addition, the design of the chamber used in the present
Embodiment 6 can be designed under any wavelength of
electromagnetic waves in principle. For the design of an actual
apparatus, there is a limit with which the space should comply in
the case where frequency is made low and wavelength is made long,
but utilization of enhancement in heightening dielectric constant
of material with which the part of controlling standing wave is
filled up inside and a structure involving multiple bending enabled
design for low frequency to reach 10 MHz. On the other hand, as the
frequency increases, the wavelength gets shorter, a tiny step
structure of the chamber could make standing waves to exist
locally, and thus, attention is needed to be paid to the shape of
boundary shape of the chamber other than the part of controlling
standing wave, but with the design in which attention is paid to
relief from corner to corner of the chamber can provide design that
can cope with high frequency to reach 3 GHz.
Embodiment 7
[0218] As Embodiment 7 of the present invention, a variation in
disposition of the antenna will be described below with reference
to FIG. 13 and FIG. 14.
[0219] The embodiments having been described so far are constructed
to have an antenna mounted outside the dielectric window effective
in particular for gate etching or metal etching.
[0220] However, the present invention introduces the waveguide for
electromagnetic waves into the chamber by way of piercing through
the dielectric window and is applicable to a construction having an
antenna mounted inside the chamber as well. In particular, this
construction is applied to etching of insulating film (oxide film
etc.).
[0221] In order to confirm effects of a part of controlling
standing wave, a construction without a part of controlling
standing wave as shown in FIG. 13 and a construction (the present
Embodiment 7) comprising a part of controlling standing wave as
shown in FIG. 14 were used for comparison and study on uniformity
of ICF inside surface of a wafer (300 mm.phi.) and uniformity of
etching.
[0222] At first, FIG. 13 shows a construction of a plasma treatment
apparatus consisting of only an antenna spacer 904 without using
the part of controlling standing wave. For a wafer stage 901, the
same specification as that for Embodiments so far was used and for
a quartz plate 902, a waveguide for electromagnetic waves was
caused to pierce through the center part. In addition, the quartz
shower plate so far is taken off, and replacing it, a circular
shower antenna 903 is fixed onto the quartz plate 902. In addition,
a wafer 900 is mounted onto the wafer stage 901.
[0223] On the other hand, FIG. 14 shows a construction of a plasma
treatment apparatus using a part of controlling standing wave 905
approximately the same as the part of controlling standing wave
having been described in Embodiment 6. For a wafer stage 901, the
same specification as that for Embodiments so far was used and for
a quartz plate 902, a waveguide for electromagnetic waves was
caused to pierce through the center part. In addition, a circular
shower antenna 903 is fixed onto the quartz plate 902. A wafer 900
is mounted onto the wafer stage 901.
[0224] At first, uniformity of ICF was considered. Under a
condition involving an Ar base to which a small amount of CF system
gas and 02 gas were added, the cases of powers of electromagnetic
wave being 400 W and 900 W were compared. As a result thereof,
large difference was not observed in both the parties for this
construction with high power of electromagnetic wave being 900 W,
but under condition of this construction with low power of
electromagnetic wave being 400 W, for a construction without using
a part of controlling standing wave, another plasma mode was given
rise to with ICF to be caused to heighten locally only in the
center part. In addition, as a result of investigation in detail,
there was a transition point of mode just around 500 W and in the
vicinity thereof the plasma state became unstable. On the other
hand, for the construction using the part of controlling standing
wave, also with 400 W, the ICF distribution similar to the case
with 900 W was given in a stable fashion, and no unstable state was
admitted around 500 W.
[0225] In the case where an antenna is mounted inside a chamber
evacuated to low pressure, there are two kinds, that is,
electromagnetic wave introduced into the plasma directly from the
antenna and the component introduced into the plasma subject to
propagation around the antenna and inside the dielectric window on
the rear face thereof. The component introduced directly into the
plasma from the former antenna is deemed to be introduced almost
irrespective of the part of controlling standing wave of the
present invention, but as for the latter component that propagates
in the horizontal direction inside the dielectric, the standing
wave electric field distribution was made appropriate in the
periphery thereof with the part of controlling standing wave,
contributing to mode transfer and elimination of instability.
Embodiment 8
[0226] The L-type metal fitting having been described in Embodiment
6 is mounted in the atmosphere side and is in the ground potential,
and therefore can be made a movable system easily. Metal
contamination will not have to be concerned about as in the case
where a movable part is provided inside the chamber, and difficulty
on designing will not be given rise to as in the case where an
antenna directly to which an electromagnetic wave power is applied
is made movable. In order to comply with mass production, it is
desirable that such a mechanism that moves wafer one by one
mechanically is avoided as much as possible, but the present
invention shows an effect that can maintain uniformity under a wide
range of process conditions also with structure being fixed, and
therefore, it goes without saying that it operates movable
mechanism on each process condition. However, in the case where
wafers themselves are remarkably different, for example in the case
where a wafer with special quality being not a silicon wafer
undergoes etching, or in the case where reaction products are
abundant, fine tuning of the movable part can execute adjustment to
an extremely highly uniform treatment condition. In addition, being
mounted in the atmosphere side, and being in ground potential, the
movable parts will not be incapable of undergoing adjustment on
each wafer according to cases.
Embodiment 9
[0227] The basic construction of the plasma treatment apparatus
having been described in Embodiment 6 consists of a chamber
feasible to be evacuated to low pressure, a wafer stage for a wafer
located inside the above described chamber to be mounted thereon,
an antenna as well as a dielectric window provided in a location
facing the above described wafer, a high-frequency power source
with frequency=f to generate electromagnetic wave for making a
predetermined gas to be introduced into the above described chamber
into plasma, and a part of controlling standing wave for making the
standing wave electric field distribution provided in the vicinity
of the periphery part of the above described dielectric window
proper.
[0228] With this plasma treatment apparatus, a manufacturing method
of a semiconductor device (for example, MOSLSI) will be described
below with reference to FIG. 15 and FIG. 16.
[0229] (1) STI Forming Step
[0230] In FIG. 15, at first with the above described plasma
treatment apparatus, the main surface of a semiconductor substrate
(wafer) 1001 is masked with an SiN film (not shown) and trenches
are formed selectively. In addition, after formation of trenches,
(b), (c) and (d) having been described in Embodiment 6 are
executed. Subsequently, an insulating film (SiO.sub.2) is deposited
on the main surface of the wafer 1001 where trenches have been
formed. Subsequently, the insulating film on the wafer main surface
is polished by way of a chemical machining polishing method (CMP)
so that a region of shallow trench isolation (STI) 1002 in which
insulating film is embedded into trenches is formed.
[0231] (2) Step of Forming a Conductor Film for MOS Gate
[0232] In FIG. 15, after gate oxide film (not shown) is formed on a
plane surface of an element forming region surrounded by the region
of shallow trench isolation (STI) 1002, the conductor film (first
film) for MOS gate 1003 is formed. This conductor film for MOS gate
1003 is made of for example polysilicon or polymetal. Subsequently,
onto this conductor film for MOS gate 1003, SiO.sub.2 or SiN film
is formed as a hard mask (second film) 1004. This hard mask is used
for taking sufficient selection ratio at the time of gate
processing. The present Embodiment 9 adopts an SiN film as the hard
mask. Subsequently, an anti-reflective film (third film) 1005
called as BARC is formed onto this hard mask 1004. In addition, a
photoresist mask 1006 is formed into a predetermined pattern onto
the anti-reflective film 1005 by way of normally-applied
photo-lithography technology. FIG. 15 is a sectional view when the
photoresist mask 1006 was formed into a pattern.
[0233] Step of Processing Conductor Film for MOS Gate
[0234] In FIG. 15 and FIG. 16, the above described mask pattern
1006 is copied onto the above described anti-reflective film 1005,
the hard mask 1004 and the conductor film for MOS gate 1003
respectively subject to dry etching processing on the above
described anti-reflective film 1005, the hard mask 1004 and the
conductor film for MOS gate 1003 sequentially with the above
described plasma treatment apparatus. At this time, subject to
selective etching on the above described anti-reflective film 1005
and the hard mask 1004 with the mask pattern 1006, the resist mask
1004 as well as the anti-reflective film 1005 are removed so that a
pattern for the conductor film for MOS gate 1003 is formed with the
hard mask 1004. In this step, (e) to (i) having been described in
Embodiment 6 are carried out.
[0235] Hereafter, a source as well as a drain with the gate
(electrode) 1003 as a mask will be formed. In addition, moreover,
on the sidewall of the gate (electrode) 1003, a sidewall (SiN)
spacer will be formed. The above described plasma treatment
apparatus is also applied to anisotropy etching at the time when
this sidewall spacer is formed.
[0236] After all, according to the present Embodiment, use of
plasma treatment apparatus for general purpose enables a plan of
improvement in throughput as well as improvement in yield.
[0237] According to a plasma treatment apparatus using high
frequency of the present invention, a part of controlling standing
wave is comprised in a location in the vicinity of the periphery
part of a dielectric window, and the standing wave electric field
distribution given rise to inside the dielectric window material is
made appropriate when electromagnetic waves are introduced into a
chamber evacuated to low pressure from the dielectric window. This
can serve to process a test sample uniformly under conditions of a
wide range of gas seeds, pressure and density. In addition,
applying a single chamber evacuated to low pressure to a number of
steps under a wide range of conditions in a consistent fashion, a
plasma treatment apparatus with high production efficiency can be
provided.
[0238] In addition, applying the plasma treatment apparatus in
which high frequency of the present invention was used to a step of
manufacturing an LSI, uniform microprocessing is carried out inside
a wafer surface and an LSI with high yield can be achieved.
* * * * *