U.S. patent application number 09/496466 was filed with the patent office on 2001-12-13 for plasma processing apparatus.
Invention is credited to Nishikawa, Kazuyasu, Oomori, Tatsuo, Ootera, Hiroki.
Application Number | 20010050144 09/496466 |
Document ID | / |
Family ID | 16252437 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010050144 |
Kind Code |
A1 |
Nishikawa, Kazuyasu ; et
al. |
December 13, 2001 |
Plasma processing apparatus
Abstract
A plasma processing apparatus includes a processing chamber,
processing gas supply means for supplying one or more processing
gases into the processing chamber, plasma generating means for
generating a plasma, a mounting stage for mounting an object to be
processed, bias applying means for applying an electrical bias
voltage to the mounting stage, a gas storage chamber being disposed
in a position opposite to a face of the mounting stage and being
provided with a supply system for supplying neutral particles or
gases to generate the neutral particles, a partition plate for
separating the gas storage chamber from the processing chamber and
having jet holes for jetting the neutral particles into the
processing chamber, and an exhaust system.
Inventors: |
Nishikawa, Kazuyasu; (Tokyo,
JP) ; Ootera, Hiroki; (Tokyo, JP) ; Oomori,
Tatsuo; (Tokyo, JP) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW
SUITE 300
WASHINGTON
DC
20005-3960
US
|
Family ID: |
16252437 |
Appl. No.: |
09/496466 |
Filed: |
February 2, 2000 |
Current U.S.
Class: |
156/345.33 ;
118/723E; 156/345.29 |
Current CPC
Class: |
H01J 37/32458 20130101;
H01J 37/32009 20130101 |
Class at
Publication: |
156/345 ;
118/723.00E |
International
Class: |
H01L 021/3065 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 5, 1999 |
JP |
11-190103 |
Claims
What is claimed is:
1. A plasma processing apparatus comprising a processing chamber,
processing gas supply means for supplying one or more processing
gases into the processing chamber, plasma generating means for
changing the processing gases supplied into the processing chamber
to a plasma, a mounting stage for mounting an object to be
processed which is provided in the processing chamber, bias
applying means for applying an electrical bias voltage to the
mounting stage, a gas storage chamber which is placed at a position
opposite to a face of the mounting stage on which the object being
processed is mounted and which is provided with a supply system for
supplying neutral particles or gases to generate the neutral
particles, a partition plate which separates the gas storage
chamber from the processing chamber and having jet holes for
jetting the neutral particles into the processing chamber, and an
exhaust system.
2. The plasma processing apparatus according to claim 1, wherein
the partition plate is a counter electrode to the mounting
stage.
3. The plasma processing apparatus according to claim 2, wherein
the partition plate comprises a dielectric film formed on an
electric conductor.
4. The plasma processing apparatus according to claim 2, wherein
the partition plate is grounded.
5. The plasma processing apparatus according to claim 2, wherein
the partition plate is provided with a power supply for applying a
radio frequency or a DC bias voltage.
6. The plasma processing apparatus according to claim 1, wherein
each jet hole is in a shape of a nozzle having an enlarged size
toward the side of the processing chamber.
7. The plasma processing apparatus according to claim 1, wherein
the gas storage chamber is composed of a plurality of discrete gas
storage chambers and a plurality of partition plates.
8. The plasma processing apparatus according to claim 1, wherein
the gas storage chamber is provided with plasma generating
means.
9. The plasma processing apparatus according to claim 1, wherein
the gas storage chamber is provided with a radical source.
10. The plasma processing apparatus according to claim 1, wherein
the gas storage chamber is provided with an ion source.
11. The plasma processing apparatus according to claim 10, wherein
the ion source is provided with ion accelerating means.
12. The plasma processing apparatus according to claim 1, wherein
the diameter of the jet hole is smaller than the mean free path of
neutral particles in the gas storage chamber.
13. The plasma processing apparatus according to claim 1, wherein a
longitudinal length of the jet hole is longer than a mean free path
of the neutral particles in the gas storage chamber.
14. The plasma processing apparatus according to claim 1, wherein a
pressure within the processing chamber is lower than that of the
gas storage chamber.
15. The plasma processing apparatus according to claim 1, wherein a
distance between the mounting stage and the partition plate is not
longer than a mean free path of the neutral particles in the
processing chamber.
16. The plasma processing apparatus according to claim 1, wherein
the supply system is provided with pulse valve supply means.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor
manufacturing apparatus to be used for forming a thin film onto a
surface of a workpiece or for etching a surface of a workpiece, and
more particularly to a plasma processing apparatus for processing a
surface of a workpiece having a pattern of a deep groove or hole
which is very small in dimension and high in an aspect ratio.
[0003] 2. Description of the Related Art
[0004] Conventionally, a plasma processing apparatus utilizing a
plasma has often been used as a processing apparatus for forming a
thin film onto a fine pattern formed over a surface of an object to
be processed such as a workpiece, for example, a substrate or a
semiconductor wafer (hereinafter referred to as a "wafer") or for
performing fine processing of a surface of a workpiece. One or more
processing gases are introduced into a processing chamber of the
plasma processing apparatus, thereby generating plasma.
Consequently, some ions (reactive ions) and neutral particles
(neutral radicals) contributing to the reaction are generated in
the plasma. The ions are accelerated by the sheath on the surface
of the workpiece and reach the surface of the workpiece, thereby
contributing to the processing of the surface of the workpiece. The
neutral radicals are transported to the surface of the workpiece by
diffusion and deposit on the surface of the workpiece which
contribute to the surface processing of the workpiece by performing
a surface reaction or a reaction by the aid of the energy of ions
incident on the surface.
[0005] For a method for forming a thin film on a surface of a deep
groove or hole which is very small in dimension and high in an
aspect ratio, molecular structures of a raw material for CVD
(chemical vapor deposition) gas has been conventionally devised.
Consequently, step coverage on a pattern surface has been improved
and the formation of a thin film on a pattern having a high aspect
ratio has been implemented.
[0006] On the other hand, as a method for performing fine
processing of, for example, a deep groove or hole which is very
small in dimension and high in an aspect ratio, there is a method
for increasing energy of ions incident on the surface of a
workpiece. By this method, workability in the direction
perpendicular to the surface of the workpiece has been improved and
a pattern having a high aspect ratio has been formed.
[0007] However, as an aspect ratio of a pattern more increases, it
becomes more difficult to process the surface thereof according to
the conventional method.
[0008] In order to solve the above mentioned problem, several
methods were proposed, which prevent the reaction by ions incident
on a side wall of a pattern in plasma etching. For example, a
method for forming an inhibitor layer on the side wall of the
pattern, which layer protects the surface from the reactive
species, is described in "Extended Abstracts of Solid State Devices
and Materials, p 229 (1986)"; a method for reducing the temperature
of a workpiece is described in "Appl. Phys. Lett., 52, 616 (1988)";
and a method for decreasing a gas pressure is described in "Jpn. J.
Appl. Phys., 29, 792 (1990)".
[0009] However, even if these methods are used, an incident flux of
the neutral radicals into a pattern having a high aspect ratio
decreases during etching of the pattern having a high aspect ratio.
In some cases, therefore, the inhibitor layer formed on the side
wall of the pattern became thin, so that etching by ions incident
on the side wall of the pattern could not be prevented.
[0010] Moreover, Japanese Patent Kokai Publication No. 163465/1994
has proposed a method for supplying a sufficient amount of neutral
radicals to a pattern bottom by separating a processing chamber
from a plasma chamber, and keeping the gas pressure within the
plasma chamber higher than that of the processing chamber to
provide the neutral radicals and gas molecules with a kinetic
energy in the direction to the substrate and to enhance the
incident directivity of the neutral radicals being supplied.
[0011] According to the above mentioned method, a unit construction
is proposed to produce the pressure difference between the plasma
generating chamber and the processing chamber, wherein a porous
plate having holes of small diameters (which are not more than 3
mm) is provided and a plurality of turbo molecule pumps are
provided so that gas within the processing chamber is exhausted at
a total exhausting rate of 4000 litters/sec. However, in addition
to an increase in the size of the apparatus, it is difficult for
ions to transport to the processing chamber due to the small
diameters of the holes, and ions are confined within the plasma
generating chamber. Therefore, a plasma density within the
processing chamber or an incident ion flux onto the workpiece
becomes insufficient for processing the workpiece. In the case
where an oxide film etching of a pattern having a high aspect ratio
is carried out, there was a problem that an etch rate rapidly
decreases due to the insufficient incident ion flux, so that
through-put is reduced. In other words, although the neutral
radicals are easily incident on the bottom portion of the pattern
having a high aspect ratio by the porous plate provided to enhance
the incidence directivity of the neutral radicals, the ion flux
transported to the processing chamber decreases. As a result of the
decrease of the ion flux, ions contributing to the etching reaction
become poor so that the etch rate is depressed. The above mentioned
method may be considered to be effective in etching reaction of
silicon or organic materials in which neutral radicals mainly
contribute to the reaction, however it is not suitable for etching
of oxide film in which ions mainly contribute to the reaction.
Further, the neutral radicals pass through the porous plate more
easily than the ions since the formers are not affected by the
sheath, however, they have a limited lifetime since they easily
recombine with other molecules to be changed into other kinds of
molecules or readily deposit on the wall of an apparatus. According
to the above mentioned method, even if the neutral particles easily
reach the bottom portion of the pattern having a high aspect ratio,
most of the neutral radicals deposit on the surface of the plasma
generating chamber or the number thereof decreases within the
plasma generating chamber, so that the flux of the neutral radical
incident on the workpiece is not so large. Therefore, it was
difficult to enhance an etch rate even in which the neutral
radicals mainly contribute to the reaction.
SUMMARY OF THE INVENTION
[0012] In order to solve the above mentioned problems of the prior
art, it is an object of the present invention to provide a plasma
processing apparatus capable of forming a thin film over a groove
or hole which is very small in dimension and high in an aspect
ratio at a high rate or forming a pattern with high precision at a
high etch rate.
[0013] A first aspect of the present invention is directed to a
plasma processing apparatus which comprises a processing chamber,
processing gas supply means for supplying one or more processing
gases into the processing chamber, plasma generating means for
changing the processing gases supplied into the processing chamber
to a plasma, a mounting stage for mounting an object to be
processed which is provided in the processing chamber, bias
applying means for applying an electrical bias voltage to the
mounting stage, a gas storage chamber which is placed at a position
opposite to a face of the mounting stage (on which the object being
processed is mounting) and which is provided with a supply system
for supplying neutral particles or one or more gases to generate
the neutral particles, a partition plate which separates the gas
storage chamber from the processing chamber and having jet holes
for jetting the neutral particles into the processing chamber, and
an exhaust system.
[0014] A second aspect of the present invention is directed to the
plasma processing apparatus according to the first aspect of the
present invention, wherein the partition plate is a counter
electrode which is placed in a position opposite to a face of the
mounting stage.
[0015] A third aspect of the present invention is directed to the
plasma processing apparatus according to the second aspect of the
present invention, wherein the partition plate comprises a
dielectric film formed on an electric conductor.
[0016] A fourth aspect of the present invention is directed to the
plasma processing apparatus according to the second aspect of the
present invention wherein the partition plate is grounded.
[0017] A fifth aspect of the present invention is directed to the
plasma processing apparatus according to the second aspect of the
present invention wherein the partition plate is provided with a
power supply for applying a radio frequency or a DC bias
voltage.
[0018] A sixth aspect of the present invention is directed to the
plasma processing apparatus according to the first aspect of the
present invention wherein each jet hole is in a shape of a nozzle
having an enlarged size (or diameter) toward the side of the
processing chamber.
[0019] A seventh aspect of the present invention is directed to the
plasma processing apparatus according to the first aspect of the
present invention wherein the gas storage chamber is composed of a
plurality of discrete gas storage chambers and a plurality of
partition plates.
[0020] An eighth aspect of the present invention is directed to the
plasma processing apparatus according to the first aspect of the
present invention wherein the gas storage chamber is provided with
plasma generating means.
[0021] A ninth aspect of the present invention is directed to the
plasma processing apparatus according to the first aspect of the
present invention wherein the gas storage chamber is provided with
a radical source.
[0022] A tenth aspect of the present invention is directed to the
plasma processing apparatus according to the first aspect of the
present invention wherein the gas storage chamber is provided with
an ion source.
[0023] An eleventh aspect of the present invention is directed to
the plasma processing apparatus according to the tenth aspect of
the present invention wherein the ion source is provided with ion
accelerating means.
[0024] A twelfth aspect of the present invention is directed to the
plasma processing apparatus according to the first aspect of the
present invention wherein a diameter of the jet hole is smaller
than a mean free path of neutral particles in the gas storage
chamber.
[0025] A thirteenth aspect of the present invention is directed to
the plasma processing apparatus according to the first aspect of
the present invention wherein a longitudinal length of the jet hole
is longer than a mean free path of the neutral particles in the gas
storage chamber.
[0026] A fourteenth aspect of the present invention is directed to
the plasma processing apparatus according to the first aspect of
the present invention wherein a pressure within the processing
chamber is lower than that of the gas storage chamber.
[0027] A fifteenth aspect of the present invention is directed to
the plasma processing apparatus according to the first aspect of
the present invention wherein a distance between the mounting stage
and the partition plate is not longer than a mean free path of the
neutral particles in the processing chamber.
[0028] A sixteenth aspect of the present invention is directed to
the plasma processing apparatus according to the first aspect of
the present invention wherein the supply system is provided with
pulse valve supply means.
[0029] According to the first aspect of the present invention as
described above, since the plasma processing apparatus comprises
the processing chamber, the processing gas supply means for
supplying the processing gases into the processing chamber, the
plasma generating means for changing the processing gases supplied
into the processing chamber to the plasma, the mounting stage for
mounting an object to be processed which is provided in the
processing chamber, bias applying means for applying the electrical
bias to the mounting stage, the gas storage chamber which is placed
at a position opposite to the face of the mounting stage for
mounting the object being processed and which is provided with the
supply system for supplying the neutral particles or the gases to
generate the neutral particles, the partition plate which separates
the gas storage chamber from the processing chamber and having the
jet holes for jetting the neutral particles into the processing
chamber, and the exhaust system, it is possible to perform, at a
high processing rate, the surface processing of the workpiece
having the patterns which includes a deep groove and/or hole which
is very small in dimension and high in an aspect ratio.
[0030] According to the second aspect of the present invention
wherein the partition plate is arranged to be the counter electrode
to the mounting stage in the first aspect, the processing for the
workpiece can be uniformly performed.
[0031] According to the third aspect of the present invention
wherein the partition plate comprises the dielectric film formed on
the electric conductive material in the second aspect, it is
possible to obtain an effect that deterioration in the partition
plate is prevented.
[0032] According to the fourth aspect of the present invention
wherein the partition plate is grounded in the second aspect, a
uniform processing of the workpiece can be carried out.
[0033] According to the fifth aspect of the present invention
wherein the partition plate includes the power supply for applying
the radio frequency or the DC bias voltage in the second aspect,
the density of particular particles in the processing chamber can
be adjusted by the selection of the material of the partition plate
and/or the control of the electric potential of the partition
plate. As a result, the processing conditions can be flexible.
[0034] According to the sixth aspect of the present invention,
wherein each jet hole or port is formed in the shape of a nozzle
having the enlarged diameter at the side of the processing chamber
in the first aspect, the particles in the gas storage chamber can
be jetted into the processing chamber without reducing a transport
speed thereof during the passage through the jet hole.
[0035] According to the seventh aspect of the present invention
wherein the gas storage chamber is constituted by a plurality of
gas storage chambers and a plurality of partition plates in the
first aspect, particle flows can be uniformly supplied to the
workpiece and the processing for the workpiece can be uniformly
carried out. Moreover, it is also possible to vary the processing
of the workpiece in its face by changing the particles to be
introduced.
[0036] According to the eighth aspect of-the present invention
wherein the gas storage chamber includes the plasma generating
means in the first aspect, the plasma can be generated at a lower
pressure than in the conventional case, and the ions and/or neutral
particles can be incident on the workpiece without collision or
with a few collisions, and thus, anisotropy for processed profile
can be enhanced. Moreover, a particular kind of the neutral
radicals can be introduced into the processing chamber in a large
number by adjusting the operating pressure and/or the source power
of the plasma generating means which are provided in the gas
storage chamber. As a result, the neutral radicals suitable for the
intended processing can be supplied to the workpiece and the
processing can be improved.
[0037] According to the ninth aspect of the present invention
wherein the gas storage chamber includes the radical source in the
first aspect, a large number of the neutral radicals suitable for
the intended processing can be introduced into the processing
chamber, so that the processing performance can be enhanced.
[0038] According to the tenth aspect of the present invention
wherein the gas storage chamber includes the ion source in the
first aspect, a large number of ions suitable for the intended
processing can be supplied into the processing chamber, so that the
processing performance can be enhanced.
[0039] According to the eleventh aspect of the present invention
wherein the ion source is provided with the ion accelerating means
in the tenth aspect, the neutral particles having an energy
suitable for the intended processing can be supplied into the
processing chamber in a large number, so that the processing
performance can be enhanced.
[0040] According to the twelfth aspect of the present invention
wherein the diameter of the jet hole is smaller than the mean free
path of neutral particles in the gas storage chamber in the first
aspect, a neutral particle flow which has a particular ratio of a
temperature in a vertical direction to a temperature in a
horizontal direction with respect to the workpiece face can be
supplied to the workpiece.
[0041] According to the thirteenth aspect of the present invention
wherein the length of the jet hole is greater than the mean free
path of the neutral particles in the gas storage chamber in the
first aspect, a neutral particle flow which has a particular ratio
of a temperature in a vertical direction to a temperature in a
horizontal direction with respect to the workpiece face can be
supplied to the workpiece.
[0042] According to the fourteenth aspect of the present invention
wherein the pressure of the processing chamber is lower than that
of the gas storage chamber in the first aspect, when the neutral
particles are to be jetted from the gas storage chamber to the
processing chamber through the jet holes, a kinetic energy is given
to the particles in the direction perpendicular to the workpiece
face, so that the temperature in the direction perpendicular to the
workpiece face can be raised. Thus, the temperature of the neutral
particles in the direction perpendicular to the workpiece face
becomes higher than the temperature in the horizontal direction,
the neutral particles can easily be supplied to the bottom portion
of the pattern having a high aspect ratio.
[0043] According to the fifteenth aspect of the present invention
wherein the distance between the mounting stage and the partition
plate is not longer than the mean free path of the neutral
particles in the processing chamber in the first aspect, the
neutral particles jetted from the gas storage chamber can be
supplied to the surface of the workpiece without rescattering in
the processing chamber.
[0044] According to the sixteenth aspect of the present invention
wherein the supply system is provided with pulse valve supply means
in the first aspect, the difference in the pressure between the gas
storage chamber and the processing chamber greatly increases.
Accordingly, the neutral particles or ions can be sufficiently
supplied to the bottom portion of the pattern having a high aspect
ratio.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a schematic cross-sectional view of a plasma
processing apparatus according to a first embodiment of the present
invention;
[0046] FIG. 2 is a graph showing an amount of flux of neutral
particles into the bottom of a hole;
[0047] FIGS. 3a and 3b are charts showing an amount of the incident
flux of the neutral particles into a hole having a high aspect
ratio;
[0048] FIG. 4 is a schematic cross-sectional view of a plasma
processing apparatus according to a second embodiment of the
present invention;
[0049] FIG. 5 is a schematic cross-sectional view of a plasma
processing apparatus according to a third embodiment of the present
invention;
[0050] FIG. 6 is a schematic cross-sectional view of a plasma
processing apparatus according to a fourth embodiment of the
present invention;
[0051] FIG. 7 is a schematic cross-sectional view of a plasma
processing apparatus according to a fifth embodiment of the present
invention;
[0052] FIG. 8 is a schematic cross-sectional view of a plasma
processing apparatus according to a sixth embodiment of the present
invention; and
[0053] FIG. 9 is a schematic cross-sectional view of a plasma
processing apparatus according to a seventh embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0054] Preferred embodiments of the present invention will be
described below with reference to FIGS. 1 to 9.
[0055] Embodiment 1
[0056] FIG. 1 is a schematic cross-sectional view of the plasma
processing apparatus according to the first embodiment of the
present invention. The plasma etching processing apparatus shown in
FIG. 1 has a processing container 1 formed of an electric conductor
such as aluminum. A predetermined etching processing is carried out
in a processing chamber 2 formed in the processing container 1. In
addition, the wall of the processing container 1 is optionally
protected by a coating, which is formed for example by an alumina
or insert of a quartz plate between the processing container and
plasma since the wall of the processing container 1 may be
sputtered with a plasma generated in the processing chamber 2
depending on the kind of processing gases or the wall of the
processing container 1 may be etched by a chemical reaction.
Further, the inner wall of the processing chamber 2 may be heated
to prevent reaction products or the like from depositing to the
wall of the processing container.
[0057] The processing container 1 is grounded. The inside of the
processing container 1 is provided with a mounting stage 4 for
mounting a workpiece 5 thereon for example made of a semiconductor
wafer (hereinafter, also referred to as a wafer) on an insulating
plate 3 made of for example ceramic. A gas storage chamber 6 is
provided in a position opposite to a face of the mounting stage 4
where the wafer 5 is mounted, and is airtightly connected to the
processing container 1. The processing chamber 2 and the gas
storage chamber 6 are partitioned by a partition plate 7. The gas
storage chamber 6 is provided with a supply system for supplying
one or more gases through a gas line 12a, and neutral particles
(neutral radicals) which contribute to a reaction are generated in
the gas storage chamber 6 by plasma generating means and radical
generating means which are not shown in FIG. 1, for example, radio
frequency discharge means or heating means. Alternatively, an
arrangement may be selected wherein the neutral particles are
generated in the other reaction vessels, passed through the line
12a and stored within the gas storage chamber 6.
[0058] The partition plate 7 is provided with a plurality of jet
holes or ports 8 each of which is formed in a shape of a nozzle
having an enlarged diameter at the side of the processing chamber.
Through the jet holes 8, the neutral particles within the gas
storage chamber 6 are jetted into the processing chamber 2 without
reducing transport speed thereof.
[0059] Moreover, the partition plate 7 is a porous plate having a
plurality of jet holes, which arrangement allows the particles to
be supplied to the workpiece in a uniform flow, so that uniform
processing of the workpiece is achieved.
[0060] Since the gas storage chamber is provided in the position
opposite to the face of the workpiece, the neutral particles jetted
from the jet holes in the direction toward the workpiece can reach
the surface of the workpiece through the shortest distance.
Therefore, the neutral particles having a directivity in the
direction toward the workpiece (a direction perpendicular to the
surface of the workpiece) are sufficiently supplied to the bottom
portion of a pattern having a high aspect ratio and a processing
rate can be enhanced.
[0061] In this embodiment, when the pressure in the gas storage
chamber 6 is set higher than that of the processing chamber 2, the
particles jetted from the gas storage chamber 6 have a more
improved directivity toward the wafer 5 (a vertical component of
the transport speed is relatively higher than a horizontal
component thereof), so that the particle rarely collide with other
particle in the processing chamber 2 and reach the surface of the
wafer 5.
[0062] Besides, a difference in the pressure between the gas
storage chamber 6 and the processing chamber 2 greatly increases by
high speed exhaust means or pulse-driven gas supply means using a
pulse valve for a gas supply system. When the difference in the
pressure satisfies a supersonic free jet condition, the neutral
particles introduced into the gas storage chamber 6 are jetted in a
supersonic free jet through the jet holes 8. Consequently, the
neutral particles can be fully supplied to the bottom portion of
the pattern having a high aspect ratio.
[0063] Moreover, the particles can be prevented from collision in
the processing chamber 2 by providing the mounting stage 4 at a
distance which is almost equal to or shorter than the length of the
mean free path of the jetted neutral particle flow. Thus, the
particles can be fully supplied to the bottom portion of the
pattern having a high aspect ratio.
[0064] By setting the diameter of the jet holes 8 smaller than the
mean free path of the neutral particles in the gas storage chamber
6 or setting the length of the jet holes 8 longer than the mean
free path of the neutral particles in the gas storage chamber 6,
the neutral particles collide with the wall of the jet holes 8
twice or more times upon passing through the nozzle-shaped jet
holes 8 and are transported to the processing chamber 2 to form a
neutral particle flow having a particular uniform temperature in
the vertical direction of the workpiece. As a result, a neutral
particle flow which has a temperature in a vertical direction
relatively higher than a temperature in a horizontal direction is
supplied to the wafer 5. Therefore, the neutral particles can be
fully supplied to the bottom portion of the pattern having a high
aspect ratio.
[0065] In order to prevent the deposition of a film which causes
the generation of dust, the wall of the gas storage chamber 6 and
the partition plate 7 may be coated or heated by a heater. In the
case where the gas storage chamber 6 and the partition plate 7 are
heated by the heater, neutral particles can also be generated from
the gases through heat dissociation by setting the temperature of
the heater not less than the dissociating temperature of the
gases.
[0066] The processing gases are supplied from a gas cylinder (not
shown) into the processing chamber 2 through a gas line 12b. The
plasma processing apparatus shown in FIG. 1 comprises, in the
processing chamber 2, a radio frequency antenna 9 of a conductor,
for example made of carbon in a spiral, a coil or a loop form and
the antenna is often covered with dielectric materials, for example
made of ceramic and/or quartz. A radio frequency power supply 11a
is connected to the radio frequency antenna 9 through a matching
unit 10a. When a radio frequency power is applied to the radio
frequency antenna 9, electromagnetic waves are radiated from the
radio frequency antenna so that a radio frequency electric field is
formed in the processing chamber 2. The plasma processing apparatus
is arranged to generate a plasma by causing electrons present in
then electromagnetic field space collide with the processing gases
supplied into the processing chamber 2, and ionizing the processing
gases.
[0067] Consequently, ions are generated by plasma generating means
provided in the processing chamber 2. As a result, a sufficient
amount of ion flux can be supplied to the surface of the workpiece,
thereby a high processing rate can be achieved.
[0068] While ions and neutral particles are generated by the plasma
generating means provided within the processing chamber 2, the
density of the neutral particles in the processing chamber can be
controlled because the neutral particles are transported from the
gas storage chamber 6 into the processing chamber 2 through the jet
holes 8 in addition to the neutral particles generated in the
processing chamber 2.
[0069] In FIG. 1, the plasma processing apparatus comprises the
plasma generating means using the radio frequency antenna, however
other plasma generating means may also be used.
[0070] In FIG. 1, although the gas line 12b is positioned on one
side of the processing chamber 2, it may be constituted such that
the gases are uniformly supplied with respect to the wafer 5.
[0071] In order to prevent metal contamination in an embodiment
when the antenna is not covered with some suitable materials, for
example ceramic or quartz, carbon, silicon or silicon carbide (SiC)
may be used as the material of the radio frequency antenna 9 which
is inserted in the processing chamber 2 through the partition plate
7.
[0072] Further, the mounting stage 4 is provided with wafer holding
means and wafer cooling means which are not shown, and is connected
to a radio frequency power supply 11b through the matching unit
10b. Therefore, ions in a plasma generated in the processing
chamber 2 are accelerated by a radio frequency bias voltage which
is independently applied to the mounting stage 4, for example, a
radio frequency of 800 kHz, and such irons strike the wafer 5
mounted on the mounting stage 4. Thus, an etching process is
carried out.
[0073] Moreover, the partition plate 7 is made of an electric
conductor, for example, a silicon plate, and functions also as a
counter electrode to the mounting stage 4 to which an electrical
bias voltage is applied in the construction of the present
invention. In the preset embodiment, the partition plate 7 is
grounded. Consequently, the partition plate 7 is equivalent to an
electrode which is provided in the position opposite to the
mounting stage 4 and is grounded, so that the bias electric field
to be applied to the mounting stage 4 can be uniformly applied to
the workpiece. As a result, the workpiece can be uniformly
processed. Moreover, the radio frequency electric field is applied
between the mounting stage 4 and the partition plate 7. Therefore,
the radio frequency electric field can be prevented from being
applied to metal parts provided around the mounting stage. Thus,
abnormal discharge such as arching can be effectively
prevented.
[0074] The partition plate 7 may be constituted by forming a
dielectric film on an electric conductor. Thus, a deterioration of
the partition plate can be prevented.
[0075] Since the plasma processing apparatus according to the
present embodiment has the above mentioned features, the neutral
particles having a particular directivity to the face of the wafer
5 are incident on the face of the wafer 5. Usually, the neutral
particles heated by the plasma or the like have a temperature on
the order of about 500 K. According to the above mentioned feature,
the neutral particles having the directivity to the face of the
wafer 5 are jetted into the processing chamber 2. Then, the neutral
particles rarely cause collision and reach the surface of the wafer
5, and get incident on the pattern on the surface of the wafer 5.
The neutral particles incident in the pattern is affected by the
side wall of a pattern, and may deposit on the side wall of the
pattern or may be reflected. Since the kinetic energy of the
neutral particles is about 0.05 eV, which is usually lower than
that of incident ions, a time for interaction of the neutral
particles with a pattern wall is longer than that of ions.
Accordingly, the neutral particles diffuse while performing random
reflection (diffusive reflection) on the pattern wall. In the
embodiment according to the present invention, as described above,
the temperature, in a vertical direction of the face of the wafer
5, of the neutral particles jetted from the jet holes 8 of the
partition plate 7 is relatively higher than that in a horizontal
direction thereof. Therefore, the position where the neutral
particles first collide with the side wall tends to shift more
deeply on the side wall as compared with the neutral particles
which have equivalent temperatures in all direction. When a pattern
having a high aspect ratio is processed, it may be considered that
an amount of the flux reaching the bottom portion of the pattern
(incident flux) increases. Such a mechanism will be described below
with reference to FIG. 2.
[0076] FIG. 2 shows a result of calculation of the amount of the
incident flux of the neutral particles at the bottom of the hole
when a relation of a temperature of the neutral particles entering
the hole in a longitudinal direction (axial direction) of the hole
(T .perp.) and a temperature thereof in a direction perpendicular
to the axis (vertical direction) of the hole (T .parallel.) is
varied wherein a trajectory calculation of the neutral particles is
executed by using the Monte Carlo method. In FIG. 2, the axis of
ordinates represents a normalized flux of the neutral particles and
the axis of abscissa represents an aspect ratio of the hole. As
shown in FIG. 2, as the aspect ratio increases, the amount of the
flux of the neutral particles decreases. However, the amount of the
flux of the neutral particles into the bottom of the hole can
increase by raising a temperature, that is, a kinetic energy of the
neutral particles in the axial direction of the hole. Consequently,
a deterioration of the processing rate due to the lack of the
neutral particles contributing to the etching reaction may be
prevented.
[0077] FIG. 3 shows an amount of the flux in a hole having a high
aspect ratio. In FIG. 3, the result of calculation with an aspect
ratio of 10 is shown. FIG. 3(a) shows the result of a conventional
example and FIG. 3(b) shows the result of the present embodiment.
It is shown from FIGS. 3(a) and (b) that the amount of the flux of
the neutral particles not only at the bottom of the hole, but also
at a deep position of the side wall which is just close to the
bottom, which particles have a relatively higher temperature in the
axial direction of the hole according to the present embodiment is
larger than that of the neutral particles having an equivalent
temperatures in all direction in the conventional case.
[0078] In a conventional apparatus in which the gas storage chamber
6 and the plasma generating means of the processing chamber 2 are
integrally constituted, for example, the neutral particles which
deposit onto a surface and have a function of preventing etching
are supplied to the bottom of a pattern. However, in the apparatus
according to the present embodiment in which the gas storage
chamber 6 is separated from the processing chamber 2 having the
plasma generating means, it is an advantage that only specific kind
of neutral particles may be supplied to the bottom portion of the
pattern in a large amount.
[0079] As in the conventional apparatus, when the diameter of the
holes is reduced in order to increase a difference of pressure
between a plasma chamber and a workpiece processing chamber, the
plasma tends to be confined in the plasma chamber. Consequently,
only a small amount of ions are transported to the processing
chamber. On the other hand, the plasma generating means is provided
within the processing chamber 2 in the present embodiment.
Therefore, it is possible to generate a high plasma density in the
processing chamber 2, thereby enhancing a processing rate.
Moreover, it is also possible to generate a large area plasma by
devising the shape and arrangement of the partition plate 7 and the
radio frequency antenna 9. For example, the jet holes 8 are formed
between every two turns of the radio frequency antenna 9.
[0080] Furthermore, since the partition plate 7 is grounded and is
arranged at a position opposite to the wafer 5, the bias electric
field can be uniformly applied to the wafer 5. As a result, the
process can be uniformly carried out.
[0081] The constitution of the apparatus according to the present
embodiment, as described above, allows a uniform processing of the
wafer 5 having a pattern with a high aspect ratio at a high
processing rate.
[0082] The present embodiment has been described mainly about the
plasma etching processing apparatus, however, the same is also
applicable to a plasma CVD processing apparatus. In particular,
when a thin film is deposited on a pattern having a high aspect
ratio, a larger amount of the neutral particles which act as
precursors of the thin film can reach the bottom of the pattern
having the high aspect ratio by such an apparatus according to the
present invention. Further, since a bias electric field can be
uniformly applied to the wafer 5, ions can be uniformly drawn into
the wafer 5. Consequently, the pattern having the high aspect ratio
can be covered with such a thin film through an ion assist
deposition reaction, so that a uniform processing can be performed.
In addition, since the radio frequency antenna 9 is arranged within
the processing chamber 2 in the constitution shown in FIG. 1, it is
effective for the deposition of an electrically conductive film as
compared with the case where the radio frequency antenna 9 is
arranged outside. Furthermore, when the radio frequency antenna 9
is made of a material containing a component of the deposited film,
metal contamination can be prevented and plasma characteristics can
also be prevented from being changed by the deposited film.
[0083] Embodiment 2
[0084] FIG. 4 is a schematic cross-sectional view of a plasma
processing apparatus according to the second embodiment of the
present invention. The apparatus according to the second embodiment
is similar to that of the first embodiment except that both the gas
storage chamber 6 and the dielectric window 13 are provided in a
position opposite to a face of the mounting stage 4 where the wafer
5 is mounted and are airtightly connected to the processing
container 1, and that the radio frequency antenna 9 is arranged
outside the dielectric window 13, by which arrangement a plasma may
be generated by applying a radio frequency power to the radio
frequency antenna 9 and injecting a radio frequency electric field
into the processing chamber 2 through the dielectric window 13.
[0085] According to the second embodiment of the present invention,
since the radio frequency antenna 9 is arranged outside the plasma
processing apparatus, the radio frequency antenna 9 is not
sputtered by the plasma and thus the generation of dust can be
prevented.
[0086] Embodiment 3
[0087] FIG. 5 is a schematic cross-sectional view of a plasma
processing apparatus according to the third embodiment of the
present invention. In the apparatus according to the third
embodiment, both the gas storage chamber 6 and the dielectric
window 13 are provided in a position opposite to a face of the
mounting stage 4 where the wafer 5 is mounted and are airtightly
connected to the processing container 1, and the gas storage
chamber 6 and the processing chamber 2 are partitioned by the
partition plate 7. A wave guide 14 in a ring form is provided
outside the dielectric window 13 for introducing microwaves. The
microwaves transmitted through the wave guide 14 are injected into
the processing chamber 2 through the dielectric window 13, thereby
generating a plasma.
[0088] According to the third embodiment of the present invention,
the microwaves are also transmitted as surface waves to the central
portion of the processing chamber 2 through the portion between the
partition plate 7 and the plasma sheath. Therefore, a large area
plasma can be generated and processing can be uniformly carried
out.
[0089] Embodiment 4
[0090] FIG. 6 is a schematic cross-sectional view of a plasma
processing apparatus according to the fourth embodiment of the
present invention. The apparatus according to the present
embodiment is the same as that of the first embodiment except that
a radio frequency power supply 11c is connected to the partition
plate 7 through a matching unit 10c.
[0091] In the apparatus having the above mentioned constitution,
for example, when a fluorocarbon-based gas is introduced as the
processing gas, fluorine radicals are present in a processing
chamber 2, which are generated by plasma generating means. However,
there may be a case wherein the density of the fluorine radicals is
too high depending on the processing conditions, so that an
anisotropic etched profile may not be obtained. In such a case, use
of silicon as the material of the partition plate 7 makes it
possible that the generation of the fluorine radicals is decreased
to some extent by causing a reaction between the silicon of the
partition plate 7 and the fluorine radicals.
[0092] Moreover, application of the electrical bias voltage to the
partition plate 7 makes it possible to draw not only the fluorine
radicals but also ions into the partition plate 7, thereby
decreasing the density of ions in the processing chamber 2.
Furthermore, when the partition plate 7 is made of carbon, carbon
can be supplied into the processing chamber 2 by utilizing the
sputtering of the partition plate 7. As described above, the
density of specific particles in the processing chamber 2 can be
adjusted by the selection of the material of the partition plate 7
and/or the control of the electric potential of the partition plate
7. As a result, the processing conditions can be flexible.
[0093] The power supply for applying power to the partition plate 7
may be a DC power supply.
[0094] Embodiment 5
[0095] FIG. 7 is a schematic cross-sectional view of a plasma
processing apparatus according to the fifth embodiment of the
present invention. In the same manner as in the fourth embodiment,
the apparatus according to the fifth embodiment has such a
constitution that a radio frequency power supply 11c is connected
to a partition plate 7 through a matching unit 10c. The
constitution of the fifth embodiment is the same as that of the
fourth embodiment except that a grounding plate 15 is arranged at a
position opposite to the partition plate 7 in the gas storage
chamber 2.
[0096] In the fifth embodiment, application of a radio frequency to
the partition plate 7 makes it possible to change the gases
introduced into the gas storage chamber 6 through the gas line 12a
into a plasma. Consequently, the plasma of the gases which is
introduced into the gas storage chamber 6 can be generated and the
dissociated species of the gases can be generated. Then, the ions
and electrons are jetted into the processing chamber 2 through the
jet holes 8. By using them as seeds for discharge, a plasma can be
generated in the processing chamber 2 at a lower pressure as
compared with the conventional case. As a result, the ions and
neutral particles can strike the wafer 5 accompanying few
collisions, so that the anisotropy for processed profile can be
enhanced. Furthermore, the dissociated species generated in the gas
storage chamber 6 are also jetted into the processing chamber 2
through the jet holes 8. Accordingly, a large number of a
particular kind of neutral radicals can be introduced into the
processing chamber 2 by adjusting the operating pressure and/or
electric power of the plasma generating means provided in the gas
storage chamber 6. As a result, the neutral radicals suitable for
the intended processing can be supplied to the workpiece and the
processing can be improved.
[0097] In the same manner as in the above mentioned fourth
embodiment, the density of specific particles in the processing
chamber 2 can be adjusted by the selection of the material of the
partition plate 7 and/or the regulation of the electric potential
of the partition plate 7. As a result, the processing conditions
can be flexible.
[0098] It is preferable that the frequency of the radio frequency
power to be applied to the partition plate 7 is selected to have a
phase difference or a frequency difference from the other frequency
in order to avoid cohesion of the radio frequency waves.
[0099] Embodiment 6
[0100] FIG. 8 is a schematic cross-sectional view of a plasma
processing apparatus according to the sixth embodiment of the
present invention. The apparatus according to the present
embodiment has such a constitution that the partition plate 7 is
grounded as in the first embodiment. The constitution of this
embodiment is the same as that of the first embodiment except that
an electrode 16 is arranged at a position opposite to the partition
plate 7 in the gas storage chamber 6.
[0101] According to the above mentioned constitution, the gases
introduced into the gas storage chamber 6 through a gas line 12a
can be changed into a plasma by applying a radio frequency bias
voltage to the electrode 16. In the same manner as in the fifth
embodiment, consequently, the plasma of the gases introduced into
the gas storage chamber 6 can be generated and the dissociated
species of the gases can be generated. Then, the ions and electrons
are jetted into the processing chamber 2 through jet holes 8. By
using them as seeds for discharge, a plasma can be generated in the
processing chamber 2 at a lower pressure than in the conventional
apparatus. As a result, the ions and neutral particles can strike
the wafer 5 accompanying few collisions, so that the anisotropy for
processed profile can be enhanced. Furthermore, the dissociated
species generated in the gas storage chamber 6 are also jetted into
the processing chamber 2 through the jet holes 8.
[0102] Accordingly, by regulating the operating pressure and/or
electric power of the plasma generating means provided in the gas
storage chamber 6, a large number of a certain kind of neutral
radicals can be introduced into the processing chamber 2. As a
result, the neutral radicals suitable for the processing can be
supplied to the workpiece. Thus, the processing can be
enhanced.
[0103] Moreover, since the partition plate 7 is grounded, it is
possible to prevent the radio frequency waves applied to the
electrode 16 from being propagated into the processing chamber
2.
[0104] In the present embodiment, a radio frequency discharge is
employed as a the plasma generating mean which is provided in the
gas storage chamber 6, other discharging means may be used.
[0105] It is preferable that the frequency of the radio frequency
power to be applied to the partition plate 7 is selected to have a
phase difference or a frequency difference from the other radio
frequency wave in order to avoid cohesion of the radio frequency
waves.
[0106] Embodiment 7
[0107] FIG. 9 is a schematic cross-sectional view of a plasma
processing apparatus according to the seventh embodiment of the
present invention. The constitution of this embodiment is the same
as that of the third embodiment except that a plurality of gas
storage chambers 6 and a plurality of partition plates 7 are used
and are arranged at a position opposite to the face of the
workpiece in the apparatus, and that each gas storage chamber 6
includes an ion source 17 and an ion accelerator 18. Since a
plurality of the gas storage chambers 6 and a plurality of the
partition plates 7 are arranged at a position opposite to the face
of the workpiece, particle flows can be uniformly supplied to the
workpiece and the workpiece can be uniformly processed. Moreover,
the processing for the workpiece can also be varied in the face by
changing particles to be introduced into each gas storage chamber
6.
[0108] Furthermore, the ions generated by the ion source 17 which
is provided within the gas storage chamber 6 are accelerated by the
ion accelerator 18 and reach the gas storage chamber 6. The gases
and the ions which are introduced into the gas storage chamber 6
collide with each other so that the ions are changed into neutral
particles by charge transfer and are transported to the processing
chamber 2 through the jet holes 8 to reach the wafer 5.
[0109] According to the above mentioned constitution, the ions
having a desired energy can be changed into the neutral particles
by charge exchange. Therefore, high-speed neutral particles can be
supplied to the wafer 5. For example, the neutral particles heated
by a plasma have a temperature of about 500 degrees K which is
equivalent to about 0.05 eV. On the other hand, the accelerated
ions lose some energy by the collision in the gas storage chamber
6. However, accelerating the ions to about 100 eV by the ion
accelerator, the neutral particles having energy of about several
tens of electron volts (eV) can be supplied to the wafer 5.
Moreover, although the moving direction of the ions is not always
perpendicular to the face of the wafer 5 due to the collision of
the ions with the gases in the gas storage chamber 6, the neutral
particles collimated to some extent can be supplied to the face of
the wafer 5 by adjusting the size, length and shape of the jet
holes 8. As a result, processing of the pattern having the high
aspect ratio can be achieved.
[0110] Although the seventh embodiment is illustrated about an
apparatus having a plurality of the gas storage chambers 6, the
apparatus may have only one gas storage chambers 6. In addition,
the constitution having a plurality of the gas storage chambers 6
which are arranged at a position opposite to the face of the
workpiece as in the seventh embodiment may be applied to any of the
constitution selected from the first to sixth embodiments.
[0111] Although the gas storage chambers 6 is provided with the
plasma generating means in the fifth and sixth embodiments, and the
gas storage chambers 6 is provided with the ion source 17 and the
ion accelerator 18 in the seventh embodiment, the gas storage
chamber 6 may be provided with a radical source. Such a
constitution makes it possible to introduce a particular kind of a
neutral radical, which is suitable for the intended processing, in
a large amount into the processing chamber 2. As a result, the
neutral radical suitable for the processing can be supplied to the
workpiece so that processing performance can be enhanced.
[0112] Moreover, the gas storage chamber 6 can be provided with an
ion source. Consequently, a large number of ions suitable for the
processing can be supplied to the processing chamber 2. Thus, the
processing performance can be enhanced.
[0113] The materials and shapes described in the above mentioned
first to seventh embodiments are presented only for explanation,
and they may be changed, are not restricted thereto and can be
properly changed if necessary.
[0114] It should be understood by those skilled in the art that the
materials and shapes described in the above mentioned first to
seventh embodiments are not limited to the specific details and
representative embodiments but presented for explanation only, and
various modifications thereof are contemplated as necessary within
the scope of the invention.
* * * * *