U.S. patent application number 12/120713 was filed with the patent office on 2008-11-20 for plasma processing apparatus and plasma processing method.
Invention is credited to Takeharu MOTOKAWA.
Application Number | 20080283500 12/120713 |
Document ID | / |
Family ID | 40026452 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080283500 |
Kind Code |
A1 |
MOTOKAWA; Takeharu |
November 20, 2008 |
PLASMA PROCESSING APPARATUS AND PLASMA PROCESSING METHOD
Abstract
A plasma processing apparatus includes a processing chamber
which has a dielectric wall partly formed of a dielectric substance
and in which a to-be-processed substrate is subjected to a plasma
process, an induction coil which is arranged to face the dielectric
wall and generates an induction electric field to generate plasma
in the processing chamber, a Faraday shield which is provided to
partially have openings between the dielectric wall and the
induction coil to shield an electrostatic field component and pass
an electromagnetic field component, and a drive mechanism which
moves the Faraday shield.
Inventors: |
MOTOKAWA; Takeharu;
(Zushi-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
40026452 |
Appl. No.: |
12/120713 |
Filed: |
May 15, 2008 |
Current U.S.
Class: |
216/68 ;
156/345.48 |
Current CPC
Class: |
H01J 37/321 20130101;
H01J 37/32697 20130101; H01J 37/32633 20130101; H05H 1/46
20130101 |
Class at
Publication: |
216/68 ;
156/345.48 |
International
Class: |
C23F 1/02 20060101
C23F001/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2007 |
JP |
2007-132918 |
Claims
1. A plasma processing apparatus comprising: a processing chamber
which has a dielectric wall partly formed of a dielectric substance
and in which a to-be-processed substrate is subjected to a plasma
process, an induction coil which is arranged to face the dielectric
wall and generates an induction electric field to generate plasma
in the processing chamber, a Faraday shield which is provided to
partially have openings between the dielectric wall and the
induction coil to shield an electrostatic field component and pass
an electromagnetic field component, and a drive mechanism which
moves the Faraday shield.
2. The plasma processing apparatus according to claim 1, wherein
the dielectric wall is cylindrical, the Faraday shield is arranged
to cover an outer peripheral surface of the dielectric wall and the
openings of the Faraday shield are arranged in a circumferential
direction of the dielectric wall at regular intervals.
3. The plasma processing apparatus according to claim 2, wherein
the Faraday shield is configured by arranging strip-form metal
plates in an outer peripheral direction of the dielectric wall at
regular intervals.
4. The plasma processing apparatus according to claim 2, wherein
the drive mechanism causes the Faraday shield to make one of a
rotational movement and a reciprocal rotational movement along the
outer peripheral surface of the dielectric wall.
5. The plasma processing apparatus according to claim 1, wherein
the Faraday shield includes a plurality of Faraday shields
coaxially overlapped in plural stages and each stage is provided to
be independently moved.
6. The plasma processing apparatus according to claim 4, wherein a
total numerical aperture of the Faraday shield is controlled by
changing an overlapping state of the Faraday shields of the plural
stages.
7. The plasma processing apparatus according to claim 1, wherein a
lower portion of the processing chamber is formed of metal and an
upper portion thereof is formed of the dielectric substance.
8. The plasma processing apparatus according to claim 1, wherein
the processing chamber is formed to be cylindrical.
9. The plasma processing apparatus according to claim 1, wherein a
gas inlet port which introduces gas used for a plasma process is
provided in an upper portion of the processing chamber and a gas
outlet port which discharges the gas is provided in a lower portion
thereof.
10. The plasma processing apparatus according to claim 1, wherein a
dielectric substance forming the dielectric wall is quartz.
11. The plasma processing apparatus according to claim 1, wherein
the dielectric wall is formed in a cylindrical form to cover an
upper surface of the processing chamber, the Faraday shield is
arranged above the dielectric wall and the Faraday shield has
shielding portions and opening portions alternately arranged in a
circumferential direction.
12. The plasma processing apparatus according to claim 11, wherein
the processing chamber is formed in a cylindrical form and the
dielectric wall is provided to cover an opening of an upper-side
portion of the processing chamber.
13. The plasma processing apparatus according to claim 11, wherein
the Faraday shield is obtained by radially arranging fan-shaped
metal plates used as the shielding portions at regular
intervals.
14. The plasma processing apparatus according to claim 11, wherein
the drive mechanism causes the Faraday shield to move coaxially
with the rotation of the dielectric wall.
15. A plasma processing method comprising: preparing a plasma
processing apparatus having a dielectric wall formed of a
dielectric substance and partly disposed in a processing chamber
used for a plasma process and a Faraday shield which is provided to
partially have openings between the dielectric wall and an
induction coil to shield an electrostatic field component and pass
an electromagnetic field component, generating plasma in the
processing chamber by supplying gas into the processing chamber and
generating an induction electric field in the processing chamber by
use of the induction coil, and changing a positional relation of
the openings of the Faraday shield with respect to the dielectric
wall by moving the Faraday shield during the plasma process by use
of the plasma or moving the Faraday shield after elapse of a preset
processing period of time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2007-132918,
filed May 18, 2007, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a plasma processing apparatus used
for semiconductor etching and formation of thin films, and more
particularly to a plasma processing apparatus having a Faraday
shield, and further relates to a plasma processing method using the
above apparatus.
[0004] 2. Description of the Related Art
[0005] In a plasma processing apparatus used for semiconductor
etching and formation of thin films, electromagnetic waves are
applied to gas filled in a plasma processing chamber as one means
for generating plasma in the plasma processing chamber. In this
case, as representative means for generation of electromagnetic
waves, an induction coil is used.
[0006] In the plasma generation process using the induction coil,
the inner wall of the processing chamber wall (dielectric wall)
that faces the induction coil is exposed to a strong
electromagnetic field. Such a strong electromagnetic field damages
the dielectric wall surface. In order to reduce the damage, a
measure of disposing a Faraday shield between the induction coil
and the dielectric wall is taken. The Faraday shield is arranged
not to cover the entire surface of the dielectric wall that faces
the induction coil but to cover a portion thereof. Specifically,
the Faraday shield is configured by arranging metal plates around
the dielectric wall at regular intervals and alternately arranging
areas (shielding portions) in which the metal plates are placed and
areas (opening portions) in which the metal plates are not placed.
This is because electromagnetic waves cannot be introduced into the
plasma processing chamber if the entire surface of the dielectric
wall that faces the induction coil is covered with the shielding
portion.
[0007] As documents in which the effect of the Faraday shield is
explained, "IEEE Trans. Plasma Sci. PS-13 (1985) 569, 2" and "Study
of Nuclear Fusion, Vol. 58, No. 1 (July, 1987), Plasma Wave Heating
Antenna and Analysis of Electromagnetic Field, pp 13 to 25" are
known. As given in the above documents, and also realized by the
present invention, the following three effects are provided by a
Faraday shield.
[0008] (Effect 1): Component of electric field in antenna axial
direction is smoothly distributed
[0009] (Effect 2): Component of electric field perpendicular to
antenna is shielded
[0010] (Effect 3): Component of electrostatic field is shielded
[0011] It is understood based on (Effect 1) that provision of the
Faraday shield itself contributes to a reduction in the damage to
the dielectric wall surface. However, (Effects 2 and 3) are
different in the opening portion and shielding portion of the
Faraday shield. The above difference results in the generation of
local damage to the dielectric wall surface. When such local damage
continues, particles are generated from the dielectric wall
surface.
[0012] Thus, in the conventional plasma processing apparatus, the
dielectric wall surface is subjected to local damage due to the
presence of the Faraday shield disposed between the induction coil
and the dielectric wall, which causes a problem that particles may
be generated.
BRIEF SUMMARY OF THE INVENTION
[0013] According to a first aspect of the present invention, there
is provided a plasma processing apparatus including a processing
chamber which has a dielectric wall partly formed of a dielectric
substance and in which a to-be-processed substrate is subjected to
a plasma process, an induction coil which is arranged to face the
dielectric wall and generates an induction electric field to
generate plasma in the processing chamber, a Faraday shield which
is provided to partially have openings between the dielectric wall
and the induction coil to shield an electrostatic field component
and pass an electromagnetic field component, and a drive mechanism
which moves the Faraday shield.
[0014] According to a second aspect of the present invention, there
is provided a plasma processing method which includes preparing a
plasma processing apparatus having a dielectric wall formed of a
dielectric substance and partly disposed in a processing chamber
used for a plasma process and a Faraday shield that is provided to
partially have openings between the dielectric wall and an
induction coil to shield an electrostatic field component and pass
an electromagnetic field component, generating plasma in the
processing chamber by supplying gas into the processing chamber and
generating an induction electric field in the processing chamber by
use of the induction coil, and changing a positional relation of
the openings of the Faraday shield with respect to the dielectric
wall by moving the Faraday shield during the plasma process by use
of the plasma or moving the Faraday shield after elapse of a preset
processing period of time.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0015] FIG. 1 is a schematic configuration view showing a plasma
processing apparatus according to a first embodiment of this
invention.
[0016] FIG. 2 is a perspective view showing an installation example
of a Faraday shield in the first embodiment.
[0017] FIGS. 3A and 3B are cross-sectional views each showing the
Faraday shield as viewed from above, for illustrating the plasma
processing apparatus according to the first embodiment.
[0018] FIGS. 4A and 4B are cross-sectional views each showing a
Faraday shield as viewed from above, for illustrating a plasma
processing apparatus according to a second embodiment of this
invention.
[0019] FIG. 5 is a schematic configuration view showing a plasma
processing apparatus according to a third embodiment of this
invention.
[0020] FIG. 6 is a plan view showing an installation example of a
Faraday shield in the third embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Embodiments of the present invention will be described below
with reference to the accompanying drawings.
First Embodiment
[0022] FIG. 1 is a schematic configuration view showing a plasma
processing apparatus according to a first embodiment of this
invention. The apparatus is a cylinder type ICP (Inductive Coupling
Plasma) etching apparatus having a Faraday shield.
[0023] A reference symbol 10 in FIG. 1 is a metal processing
chamber and a conductive stage 21 on which a to-be-processed
substrate 20 is placed, which is disposed in the processing chamber
10. The stage 21 is fixed above a platform 11 that is fixed on the
bottom portion of the processing chamber 21 with an insulating body
22 disposed therebetween. An RF power source 24 provided outside
the processing chamber 21 is connected to the stage 21.
[0024] A gas inlet port 12 is formed in the upper wall portion of
the processing chamber 10 and a vacuum pump drawing passage (gas
outlet port) 13 is provided in a lower portion of the processing
chamber 10, lower than the stage 21. Gas used for plasma etching is
introduced via the gas inlet port 12 and discharged from the gas
outlet port 13.
[0025] The upper portion of the processing chamber 10 is formed
with a large inside diameter and a cylindrical dielectric wall 15
is provided in a portion in which the inside diameter of the
processing chamber is increased. The dielectric wall 15 is formed
of a dielectric substance such as ceramic or quartz and the inside
diameter is set to be substantially the same as the inside diameter
of the lower portion of the processing chamber 10.
[0026] An induction coil 31 is disposed on the upper portion in
which the inside diameter of the processing chamber 10 is increased
to surround the outer peripheral surface of the dielectric wall 15.
The induction coil 31 applies an induction electric field for
plasma generation to an inside portion of the processing chamber 10
and is connected to an RF power source 32 provided outside the
processing chamber 10. Thus, plasma is generated in an area 34
shown in FIG. 1 by supplying gas into the processing chamber 10 and
applying the induction electric field by use of the induction coil
31.
[0027] A Faraday shield 41 that shields an electrostatic field
component and permits an electromagnetic field component to pass
therethrough is provided between the induction coil 31 and the
dielectric wall 15. The Faraday shield 41 has openings partly
formed therein and arranged along the outer peripheral surface of
the dielectric wall 15.
[0028] FIG. 2 is a perspective view showing the arrangement
relation between the dielectric wall 15 and the Faraday shield 41.
Strip-form metal plates 41a (shielding portions) forming the
Faraday shield 41 are arranged around the outer peripheral surface
of the cylindrical dielectric wall 15 in a circumferential
direction at regular intervals. The metal plate 41a has high
conductivity and is formed by coating silver on the surface of a
copper plate, for example. Further, the length of the metal plate
41a in the lengthwise direction is set to be equal to the height of
the cylindrical dielectric wall 15.
[0029] The regular arrangement interval of the metal plates 41a
makes a configuration in which areas (shielding portions) 41a in
which the metal plates are present and areas (opening portions) 41b
in which the metal plates are not present are alternately arranged
in a circumferential direction of the dielectric wall 15. That is,
in the Faraday shield 41, the shielding portions 41a and the
opening portions 41b are alternately arranged in the
circumferential direction of the dielectric wall 15. In this case,
the width of the shielding portion 41a (the length of the
dielectric wall 15 in the circumferential direction) may be set to
be the same as or different from the width of the opening portion
41b. The shielding amount of the electrostatic field component and
the passage amount of the electromagnetic field component can be
adjusted by changing the dimensional relation between the width of
the shielding portion 41a and the width of the opening portion
41b.
[0030] The bottom portion of the Faraday shield 41, that is, the
bottom portion of each metal plate 41a formed in a strip form is
linked with a ring-form Faraday shield base 42. The Faraday shield
base 42 can be rotated by a motor or actuator (not shown) and the
Faraday shield 41 can also be rotated by rotating the Faraday
shield base 42. The arrangement relation between the shielding
portions 41a and the opening portions 41b of the Faraday shield 41
can be changed by rotating the Faraday shield base 42.
[0031] Next, the plasma processing method using the present
apparatus is explained. First, the basic process of the plasma
process by use of an ICP etching apparatus is explained.
[0032] First, gas used for plasma etching is introduced into the
processing chamber 10 via the gas inlet port 12 and filled in the
plasma generation area 34. Then, the pressure of the area 34 in
which plasma is generated is controlled by controlling the
cross-sectional area of the vacuum pump drawing passage 13.
[0033] After this, the RF power sources 24, 32 are activated to
output RF powers so as to generate plasma in the processing chamber
10. The to-be-processed substrate 20 on the stage 21 is etched by
use of the thus generated plasma. In this way, the plasma process
is performed by the ICP etching apparatus.
[0034] Next, the arrangement relation and the operation of the
Faraday shield 41, which are the features of the preset embodiment,
are explained.
[0035] FIGS. 3A and 3B are cross-sectional views each showing the
Faraday shield 41 shown in FIG. 2 as viewed from above. In FIGS.
3A, 3B, the Faraday shield 41 is moved to rotate around the central
axis of the cylindrical dielectric wall 15. When the position shown
in FIG. 3A is set as a reference, the Faraday shield 41 is moved to
rotate by 15 degrees in FIG. 3B. As a result, an opening area A of
FIG. 3A becomes an opening area B in FIG. 3B and an area which is
an opening area in FIG. 3A becomes a shield area in FIG. 3B. When
the Faraday shield base 42 is thus rotated, the arrangement of the
shielding portions 41a and the opening portions 41b of the Faraday
shield 41 can be shifted. As a result, damage to the dielectric
wall 15 can be prevented, and generation of particles due to any
irregularities in the dielectric wall 15 can be prevented.
[0036] Specifically, any differences between the damage of the
dielectric wall 15 that faces the opening portions 41b and the
damage of the dielectric wall 15 that faces the shielding portions
41a can be controlled by changing the arrangement relation of the
opening portions 41b of the Faraday shield 41 with respect to the
dielectric wall 15. In practice, when the damage difference has
reached a certain reference level, the damage difference is
gradually decreased by reversely setting the positions of the
opening portions 41b and shielding portions 41a. That is, it is
understood that it is effective to change the arrangement of the
opening portions 41b of the Faraday shield 41 in order to prevent
occurrence of local damage of the dielectric wall 15 that is the
problem of the Faraday shield 41.
[0037] The rotation operation of the Faraday shield 41 may be
performed at the same time as the plasma process or may be
performed a preset period of time after the plasma process was
performed. When the rotation operation of the Faraday shield 41 is
performed at the same time as the plasma process, the Faraday
shield may be rotated at an extremely slow speed (for example, at a
speed of one rotation/hour) during the plasma process. When the
rotation operation of the Faraday shield 41 is periodically
performed, for example, the relation between the plasma process
accumulation time and a desired number of particles with respect to
the processing chamber in which the plasma process is performed is
previously acquired and time at which the arrangement of the
opening portions is changed may be determined based on the thus
acquired relation. That is, it is important to make uniform any
local damage caused by the opening portions of the Faraday shield
41 without allowing any specific local damage to worsen.
[0038] Thus, according to the present embodiment, irregularities in
the damage to the dielectric wall 15 can be eliminated by rotating
the Faraday shield 41 a preset period of time after the plasma
process or during the process. Therefore, generation of particles
due to irregularity in damage can be prevented. That is, generation
of particles can be prevented by eliminating damage irregularities
and controlling the damage amount. This leads to enhancement of the
reliability of the plasma process and thus an extremely useful
effect can be attained.
Second Embodiment
[0039] FIGS. 4A and 4B are cross-sectional views each showing a
Faraday shield as viewed from above, for illustrating a plasma
processing apparatus according to a second embodiment of this
invention. Portions which are the same as those of FIGS. 3A and 3B
are denoted by the same reference symbols and a detailed
explanation thereof is omitted.
[0040] The present embodiment also relates to a cylinder type ICP
(Inductive Coupling Plasma) etching apparatus as in the first
embodiment, and the basic apparatus configuration is substantially
the same as that of the first embodiment. The differences are in
the following three items.
[0041] (1) Faraday shields are coaxially arranged in multiple
stages (in two stages in this example).
[0042] (2) Respective Faraday shield bases can be independently
rotated.
[0043] (3) The positional relation between the Faraday shield and
the Faraday shield base can be changed.
[0044] The present embodiment is an example in which the numerical
aperture of the Faraday shield is controlled by using the function
(3). Two-stage Faraday shields 51, 52 are provided to surround the
outer peripheral surface of a dielectric wall 15. The inner Faraday
shield 51 is obtained by arranging strip-form metal plates
(shielding portions) 51a at regular intervals in the
circumferential direction of the dielectric wall 15. In this case,
however, unlike the first embodiment, two types of opening portions
are provided, with small opening portions and large opening
portions alternately arranged. The outer Faraday shield 52 is
obtained by arranging strip-form metal plates 52a at regular
intervals in the circumferential direction of the dielectric wall
15. The size of the opening portions of the outer Faraday shield 52
is the same as that of the large opening portions of the inner
Faraday shield 51 and the arrangement interval is set to twice that
of the inner Faraday shield 51.
[0045] The Faraday shields 51, 52 are connected to a Faraday shield
base (not shown) and rotated by rotating the Faraday shield base.
Further, the positional relations of the Faraday shields 51, 52
with respect to the Faraday shield base can be independently
changed.
[0046] As shown in FIG. 4A, in the initial condition, it is
supposed that the large opening portions of the inner Faraday
shield 51 are overlapped with the opening portions of the outer
Faraday shield 52. At this time, if the large opening portion of
the inner Faraday shield 51 is set to the same size as the opening
portion 41b of the Faraday shield 41 of FIG. 3A, the numerical
aperture in the initial state is set to the same value as that of
FIG. 3A. Therefore, the arrangement relation of the opening
portions with respect to the dielectric wall 15 can be changed, as
in the first embodiment, by rotating both of the Faraday shields
51, 52 in the same direction by driving the Faraday shield base in
this state.
[0047] Next, as shown in FIG. 4B, the outer Faraday shield 52 is
rotated in the circumferential direction to set and overlap the
small opening portions of the inner Faraday shield 51 with the
opening portions of the outer Faraday shield 52 by using the
function (3). As a result, for example, the numerical aperture of
33% in the case of FIG. 4A can be reduced to 11% in the case of
FIG. 4B. Thus, the arrangement relation of the opening portions
with respect to the dielectric wall 15 can be changed, as in the
first embodiment, by rotating both of the Faraday shields 51, 52 in
the same direction by driving the Faraday shield base in this
state. Additionally, the state of the small numerical aperture can
be maintained.
[0048] According to this embodiment, the Faraday shields are
provided in two stages and the sizes of the opening portions
determined by overlapping of the two Faraday shields 51, 52 can be
changed. Therefore, it is of course possible to attain the same
effect as that of the first embodiment and freely adjust the
passage amount of the electromagnetic field component and the
shielding amount of the electrostatic field component determined by
the numerical aperture of the Faraday shield. This means that the
optimum numerical aperture of the Faraday shield can be selected
based on a combination of the damage to the dielectric wall 15 and
the strength of the electromagnetic field applied within the
processing chamber 10.
Third Embodiment
[0049] FIG. 5 is a schematic configuration view showing a plasma
processing apparatus according to a third embodiment of this
invention. Portions which are the same as those of FIG. 1 are
denoted by the same reference symbols and a detailed explanation
thereof is omitted.
[0050] The present embodiment is different from the first
embodiment explained before in that the induction coil 31 is not
disposed on the side wall surface of the processing chamber 10 but
arranged above the processing chamber 10.
[0051] The upper wall portion of the processing chamber 10 is
formed of a disk-like dielectric wall 17 and the induction coil 31
is arranged above the dielectric wall 17. A Faraday shield 61 is
movably provided between the induction coil 31 and the dielectric
wall 17. As shown in FIG. 6, the Faraday shield 61 is formed by
radially arranging fan-shaped metal plates (shielding portions) 61a
at regular intervals. That is, the Faraday shield 61 is formed by
alternately arranging the shielding portions 61a and opening
portions 61b in the circumferential direction.
[0052] The outer peripheral portion of the Faraday shield 61, that
is, the outer peripheral surface of each metal plate 61a is
connected to a ring-form Faraday shield base 62. The Faraday shield
base 62 can be rotated by use of a motor or actuator (not shown).
Therefore, the Faraday shield 61 is rotated by rotating the Faraday
shield base 62 to change the position of the opening portions of
the Faraday shield 61.
[0053] With the above configuration, any irregularities in the
damage of the dielectric wall 15 can be eliminated by rotating the
Faraday shield base 62 to rotate the Faraday shield 61 a preset
period of time after the plasma process or during the process.
Therefore, the same effect as that of the first embodiment can be
attained.
Modification
[0054] This invention is not limited to the above embodiments. In
the first and second embodiments, the Faraday shield is configured
by a plurality of strip-form metal plates and the shielding
portions and opening portions are alternately arranged. However,
this invention is not limited to this case and the Faraday shield
can be configured by forming openings in a cylindrical metal plate
at regular intervals. Further, the material and numerical aperture
of the Faraday shield can be appropriately changed according to the
specification. Also, the driving mechanism of the Faraday shield is
not limited to the motor or actuator and can be provided by use of
a hydraulic or pneumatic apparatus. In addition, the rotation
direction of the Faraday shield is not limited to one direction and
may be within a range of preset angles.
[0055] Further, the apparatus of the embodiments is explained as an
example of the etching apparatus, but the apparatus can be used as
a film formation apparatus by replacing the introduced gas. In
addition, the apparatus is not limited to the etching apparatus or
film formation apparatus and can be applied to various types of
plasma processing apparatuses.
[0056] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *