U.S. patent application number 14/519348 was filed with the patent office on 2015-03-12 for etching method of multilayer film.
The applicant listed for this patent is Tokyo Electron Limited. Invention is credited to Shinji Himori, Hiroaki Ishizuka, Etsuji Ito, Shu Kusano, Kazuya Nagaseki, Akihiro Yokota.
Application Number | 20150072534 14/519348 |
Document ID | / |
Family ID | 51191100 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150072534 |
Kind Code |
A1 |
Himori; Shinji ; et
al. |
March 12, 2015 |
ETCHING METHOD OF MULTILAYER FILM
Abstract
A plasma processing apparatus for performing a plasma process on
a substrate includes: a mounting table configured to mount thereon
the substrate; an electromagnet including a core member and a
plurality of coils; a current source connected to both ends of the
coils for supplying currents to the coils; and a control unit
configured to control the current source to start or stop and to
control a current value of the current source. The core member is
made of a magnetic material and has a structure including a
column-shaped member, multiple cylindrical members, and a base
member. The plurality of coils are accommodated in grooves and
wound around an outer peripheral surface of the column-shaped
member and the cylindrical members, and the grooves are formed
between the column-shaped member and one of the cylindrical members
and between the cylindrical members.
Inventors: |
Himori; Shinji;
(Kurokawa-gun, JP) ; Ito; Etsuji; (Kurokawa-gun,
JP) ; Yokota; Akihiro; (Kurokawa-gun, JP) ;
Kusano; Shu; (Kurokawa-gun, JP) ; Ishizuka;
Hiroaki; (Kurokawa-gun, JP) ; Nagaseki; Kazuya;
(Kurokawa-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited |
Tokyo |
|
JP |
|
|
Family ID: |
51191100 |
Appl. No.: |
14/519348 |
Filed: |
October 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14158981 |
Jan 20, 2014 |
8895454 |
|
|
14519348 |
|
|
|
|
61758340 |
Jan 30, 2013 |
|
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Current U.S.
Class: |
438/725 |
Current CPC
Class: |
H01J 37/3266 20130101;
H01L 21/31138 20130101; H01L 21/3081 20130101; H01J 37/32669
20130101; H01J 37/32165 20130101; H01L 21/31116 20130101 |
Class at
Publication: |
438/725 |
International
Class: |
H01L 21/311 20060101
H01L021/311; H01L 21/308 20060101 H01L021/308 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2013 |
JP |
2013-008504 |
Mar 27, 2013 |
JP |
2013-066464 |
Claims
1. (canceled)
2. A plasma processing apparatus for performing a plasma process on
a substrate in a processing chamber, the apparatus comprising: a
mounting table configured to mount thereon the substrate; an
electromagnet comprising: a core member made of a magnetic material
and having a structure including a column-shaped member, multiple
cylindrical members, and a base member, wherein the column-shaped
member is provided such that a central axis line thereof coincides
with a substrate central axis line vertically passing through a
center of the substrate, wherein each of the multiple cylindrical
members is extended in a direction of the substrate central axis
line, and is arranged on each of multiple concentric circles around
the substrate central axis line, wherein at least one of the
cylindrical members is positioned outside of an edge of the
substrate in a radial direction, and wherein the base member has a
substantially disc shape and is provided such that a central axis
line thereof coincides with the substrate central axis line; and a
plurality of coils accommodated in grooves and wound around an
outer peripheral surface of the column-shaped member and the
cylindrical members, wherein the grooves are formed between the
column-shaped member and one of the cylindrical members and between
the cylindrical members; a current source connected to both ends of
the coils for supplying currents to the coils; and a control unit
configured to control the current source to start or stop and to
control a current value of the current source.
3. The plasma processing apparatus of claim 2, wherein the control
unit is further configured to control the current source to start
or stop for each film of a multilayer film including a first oxide
film, a second oxide film, and an organic film formed between the
first oxide film and the second oxide film.
4. The plasma processing apparatus of claim 3, further comprising:
a high frequency power supply for plasma generation configured to
apply a high frequency power to one of an upper electrode and the
mounting table serving as a lower electrode.
5. The plasma processing apparatus of claim 4, wherein the high
frequency power supply for plasma generation is further configured
to apply the high frequency power in an etching of the organic film
that is set to be higher than the high frequency power in an
etching of the first oxide film and the high frequency power in an
etching of the second oxide film.
6. The plasma processing apparatus of claim 2, further comprising:
a high frequency power supply for ion attraction configured to
apply a high frequency bias power to the mounting table serving as
a lower electrode.
7. The plasma processing apparatus of claim 6, wherein the high
frequency power supply for ion attraction is further configured to
apply the high frequency bias power in an etching of the first
oxide film and the high frequency bias power in an etching of the
second oxide film that are set to be higher than the high frequency
bias power in an etching of the organic film.
8. The plasma processing apparatus of claim 7, wherein the control
unit is further configured to generate a magnetic field such that
horizontal magnetic field components in the radial direction with
respect to the substrate central axis line have an intensity
distribution having a peak value at a position far from the
substrate central axis line by controlling the current source.
9. The plasma processing apparatus of claim 8, wherein the control
unit is further configured to generate a magnetic field such that a
position of the peak value of the horizontal magnetic field
components in the etching of the organic film is closer to the
substrate central axis line than a position of the peak value of
the horizontal magnetic field components in the etching of the
first oxide film and a position of the peak value of the horizontal
magnetic field components in the etching of the second oxide
film.
10. The plasma processing apparatus of claim 9, wherein the high
frequency power supply is further configured to apply the high
frequency bias power in the etching of the second film that is set
to be higher than the high frequency power in the etching of a
first oxide film, and the control unit is further configured to
generate the magnetic field such that intensity of the horizontal
magnetic field components in the etching of the second oxide film
is higher than intensity of the horizontal magnetic field
components in the etching of the first oxide film when a thickness
of the second oxide film is greater than a thickness of the first
oxide film.
11. The plasma processing apparatus of claim 9, the control unit is
further configured to generate the magnetic field such that, in the
etching of the organic film, a position of a peak intensity of the
horizontal magnetic field components is an intermediate position
between a center of the substrate and an edge of the substrate in
the radial direction.
12. The plasma processing apparatus of claim 9, the control unit is
further configured to generate the magnetic field such that, in the
etching of the first oxide film and the etching of the second oxide
film, a position of a peak intensity of the horizontal magnetic
field components is an outer position of an edge of the substrate
in the radial direction
13. The plasma processing apparatus of claim 2, wherein the control
unit is further configured to control the current source to start
or stop for each film of a multilayer film including a first oxide
film and a second oxide film.
14. The plasma processing apparatus of claim 13, further
comprising: a high frequency power supply for plasma generation
configured to apply a high frequency power to one of an upper
electrode and the mounting table serving as a lower electrode.
15. The plasma processing apparatus of claim 14, wherein the high
frequency power supply for plasma generation is further configured
to apply the high frequency power in an etching of the second film
that is set to be higher than the high frequency power in an
etching of the first oxide film.
16. The plasma processing apparatus of claim 13, further
comprising: a high frequency power supply for ion attraction
configured to apply a high frequency bias power to the mounting
table serving as a lower electrode.
17. The plasma processing apparatus of claim 16, wherein the high
frequency power supply for ion attraction is further configured to
apply the high frequency bias power in an etching of the first
oxide film that is set to be higher than the high frequency bias
power in an etching of the second oxide film.
18. The plasma processing apparatus of claim 17, wherein the
control unit is further configured to generate a magnetic field
such that horizontal magnetic field components in the radial
direction with respect to the substrate central axis line have an
intensity distribution having a peak value at a position far from
the substrate central axis line by controlling the current source,
and wherein the control unit is further configured to generate a
magnetic field such that a position of the peak value of the
horizontal magnetic field components in the etching of the second
oxide film is closer to the substrate central axis line than a
position of the peak value of the horizontal magnetic field
components in the etching of the first oxide film.
19. The plasma processing apparatus of claim 18, wherein the
control unit is further configured to generate a magnetic field
such that, in the etching of the second film, a position of a peak
intensity of the horizontal magnetic field components is an
intermediate position between a center of the substrate and an edge
of the substrate in the radial direction.
20. The plasma processing apparatus of claim 18, wherein the
control unit is further configured to generate a magnetic field
such that, in the etching of the first film, a position of a peak
intensity of the horizontal magnetic field components is an outer
position of an edge of the substrate in the radial direction.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application of U.S. patent application
Ser. No. 14/158,981 filed on Jan. 20, 2014, which claims the
benefit of Japanese Patent Application Nos. 2013-008504 and
2013-066465 filed on Jan. 21, 2013 and Mar. 27, 2013, respectively,
and U.S. Provisional Application Ser. No. 61/758,340 filed on Jan.
30, 2013, the entire disclosures of which are incorporated herein
by reference.
TECHNICAL FIELD
[0002] The embodiments described herein pertain generally to an
etching method of a multilayer film.
BACKGROUND
[0003] A plasma etching technique for a target object is important
in manufacturing devices. In the plasma etching technique, a plasma
density distribution in a processing space needs to be controlled
to adjust an etching rate distribution of a target object. As a
technique of controlling a plasma density distribution, there has
been known a technique of controlling a plasma density distribution
by generating a magnetic field in a processing space where an
electric field is formed. Such a technique is described in, for
example, Patent Document 1.
[0004] A plasma processing apparatus described in Patent Document 1
is a parallel-plate type plasma processing apparatus including an
upper electrode and a lower electrode. This plasma processing
apparatus generates a magnetic field which is symmetric in a radial
direction with respect to a central axis line of a target object,
i.e. a wafer, in a processing space. To be specific, in the plasma
processing apparatus described in Patent Document 1, a mounting
table serving as the lower electrode is provided in the processing
space and the wafer is mounted on the mounting table. A ceiling
portion of a processing chamber, which partitions the processing
space, serves as the upper electrode, and multiple permanent
magnets are provided on an upper surface of the ceiling portion.
The multiple permanent magnets are arranged along multiple
concentric circles around the central axis line of the wafer and
also arranged in the radial direction with respect to the central
axis line. In the plasma processing apparatus, a vertical electric
field is generated in the processing chamber, and by setting
directions of magnetic poles of the multiple permanent magnets at
the processing space side, a magnetic field distributed in a radial
shape is generated in the processing space. Thus, electrons in
plasma are subject to Lorentz force, and perform a drift motion to
be revolved around the central axis line of the wafer. A speed of
the drift motion is inversely proportion to intensity of horizontal
magnetic field components in a radial direction with respect to the
central axis line of the wafer. Therefore, in an area where the
drift motion is performed at a low speed, a staying time of the
electrons becomes long. In an area where a staying time of the
electrons is long, dissociation of a processing gas becomes
accelerated. As a result, a plasma density distribution in the
processing space can be adjusted.
[0005] Patent Document 1: Japanese Patent Publication No.
4107518
[0006] Meanwhile, when etching a multilayer film formed of multiple
films different from each other in a kind of a film and a thickness
of a film, a high frequency power for plasma generation to be
applied to an upper electrode or a lower electrode and/or a high
frequency bias power for ion attraction to be applied to the lower
electrode may be changed depending on a kind of a film and a
thickness of a film. If the high frequency power and/or the high
frequency bias power are changed, the plasma density distribution
in the processing space is also changed.
[0007] However, in the plasma processing apparatus described in
Patent Document 1, since the positions of the multiple permanent
magnets are fixed, an intensity distribution of the horizontal
magnetic field components cannot be adjusted. Therefore, in the
multilayer film formed of multiple films different from each other
in a kind of a film and a thickness of a film, when each of the
multiple films is etched, a plasma density distribution cannot be
adjusted. As a result, an etching rate of each film may be
non-uniform in a radial direction from the center.
[0008] Under these circumstances, in this technical field, it has
been demanded to suppress non-uniformity of an etching rate
depending on a position when etching each film of a multilayer
film.
SUMMARY
[0009] In one example embodiment, an etching method of a multilayer
film is provided. This etching method is to etch the multilayer
film including a first oxide film, a second oxide film, and an
organic film formed between the first oxide film and the second
oxide film in a plasma processing apparatus. In this etching
method, a target object having the multilayer film and a resist
mask formed on the first oxide film is accommodated in a processing
space of the plasma processing apparatus. This etching method
includes etching the first oxide film by generating plasma of a
first processing gas in the processing space; etching the organic
film by generating plasma of a second processing gas in the
processing space after the etching of the first oxide film; and;
and etching the second oxide film by generating plasma of a third
processing gas in the processing space after the etching of the
organic film. Here, each of the plasma of the first processing gas,
the plasma of the second processing gas, and the plasma of the
third processing gas is generated by applying a high frequency
power to one of a lower electrode serving as a mounting table
configured to mount thereon the target object and an upper
electrode provided above the lower electrode. Further, in each of
the etching of the first oxide film, the etching of the organic
film, and the etching of the second oxide film, a high frequency
bias power is applied to the lower electrode.
[0010] Since an underlying film of the organic film is the second
oxide film, it is necessary to reduce damage to the second oxide
film caused by the etching of the organic film. In order to reduce
the damage to the second oxide film, the organic film may not be
etched with ions having high energy, i.e. the organic film needs to
be etched with a large amount of active species such as radicals
while suppressing ions from being attracted toward the target
object as far as possible. Meanwhile, when the first oxide film and
the second oxide film are etched, it is desirable to accelerate the
etching of the first oxide film and the etching of the second oxide
film by ion attraction effect. Therefore, in the etching method,
the high frequency power in the etching of the organic film is set
to be higher than the high frequency power in the etching of the
first oxide film and the high frequency power in the etching of the
second oxide film. Further, in the etching method, the high
frequency bias power in the etching of the first oxide film and the
high frequency bias power in the etching of the second oxide film
are set to be higher than the high frequency bias power in the
etching of the organic film. Thus, in the etching of the organic
film, since the high frequency power is high, a large amount of
radicals are generated, and since the high frequency bias power is
low, the organic film can be etched with low energy. Therefore, it
is possible to suppress damage to the second oxide film. Further,
since the high frequency bias power in the etching of the first
oxide film and the high frequency bias power in the etching of the
second oxide film are relatively high, it is possible to accelerate
the etching of the first oxide film and the etching of the second
oxide film by ion attraction effect.
[0011] Typically, a density of plasma generated by generating a
high frequency electric field between the upper electrode and the
lower electrode tends to be increased in an area closer to the
central axis line of the target object. That is, there is formed a
plasma density distribution having a gradient in which a plasma
density is decreased as farther from the central axis line. As the
high frequency power is increased, the gradient becomes steeper.
Therefore, in the etching method, in the etching of the first oxide
film, the etching of the organic film, and the etching of the
second oxide film, a magnetic field is generated such that the
horizontal magnetic field components in a radial direction with
respect to the central axis line of the target object have an
intensity distribution having a peak value at a position far from
the central axis line. Further, in the etching method, in the
etching of the organic film, a magnetic field is generated such
that a position of the peak value of the horizontal magnetic field
components is closer to the central axis line than a position of
the peak value of the horizontal magnetic field components in the
etching of the first oxide film and a position of the peak value of
the horizontal magnetic field components in the etching of the
second oxide film. As described above, in the etching method, in
the etching of the first oxide film, the etching of the organic
film and the etching of the second oxide film, since the magnetic
field is generated such that the horizontal magnetic field
components have an intensity distribution having a peak value at a
position far from the central axis line, it is possible to decrease
the gradient of the plasma density distribution. Further, a
position of the peak value of the horizontal magnetic field
components in the etching of the organic film is closer to the
central axis line than a position of the peak value of the
horizontal magnetic field components in the etching of the first
oxide film and a position of the peak value of the horizontal
magnetic field components in the etching of the second oxide film.
Therefore, it is possible to decrease a steeper gradient of the
plasma density distribution which can be generated in the etching
of the organic film if such a magnetic field is not generated.
Therefore, in the etching method, in the etching of the first oxide
film, the etching of the organic film and the etching of the second
oxide film, by reducing non-uniformity of the plasma density
distribution, it is possible to suppress non-uniformity of an
etching rate depending on a position when each film of the
multilayer film is etched.
[0012] In the etching of the organic film, a position of a peak
intensity of the horizontal magnetic field components may be an
intermediate position between a center of the target object and an
edge of the target object in the radial direction. Further, in the
etching of the first oxide film and the etching of the second oxide
film, a position of a peak intensity of the horizontal magnetic
field components may be an outer position of an edge of the target
object in the radial direction.
[0013] A thickness of the second oxide film may be greater than a
thickness of the first oxide film, and the high frequency bias
power in the etching of the second oxide film may be higher than
the high frequency bias power in the etching of the first oxide
film. Further, intensity of the horizontal magnetic field
components in the etching of the second oxide film may be higher
than intensity of the horizontal magnetic field components in the
etching of the first oxide film. With this configuration, it is
possible to suppress non-uniformity of an etching rate depending on
a position when etching each film of the multilayer film, and also
possible to increase an etching rate of the second oxide film
having a greater thickness by ion attraction effect.
[0014] In another example embodiment, an etching method of a
multilayer film is provided. In another example embodiment, the
multilayer film includes at least a first film and a second film.
Further, the etching method includes etching the first film by
generating plasma of a processing gas in a processing space of a
plasma processing apparatus in which a target object having the
multilayer film is accommodated; and etching the second film by
generating plasma of a processing gas in the processing space. Each
of the plasma of the processing gas generated in the etching of the
first film and the plasma of the processing gas generated in the
etching of the second film is generated by applying a high
frequency power to one of a lower electrode serving as a mounting
table configured to mount thereon the target object and an upper
electrode provided above the lower electrode, and the high
frequency power in the etching of the second film is set to be
higher than the high frequency power in the etching of the first
film. Further, in each of the etching of the first film and the
etching of the second film, a high frequency bias power is applied
to the lower electrode, and the high frequency bias power in the
etching of the first film is set to be higher than the high
frequency bias power in the etching of the second film.
Furthermore, in each of the etching of the first film and the
etching of the second film, a magnetic field is generated such that
horizontal magnetic field components in a radial direction with
respect to a central axis line of the target object have an
intensity distribution having a peak value at a position far from
the central axis line, and a position of the peak value of the
horizontal magnetic field components in the etching of the second
film is closer to the central axis line than a position of the peak
value of the horizontal magnetic field components in the etching of
the first film.
[0015] In the etching method in accordance with another example
embodiment, in the etching of the second film, a relatively higher
high frequency power is used to generate plasma, and the second
film is etched with a large amount of active species such as
radicals. Meanwhile, in the etching of the first film, since a
relatively lower high frequency power is used to generate plasma
and a relatively higher high frequency bias power is used to
attract ions toward the target object, the etching of the first
film is accelerated. A plasma density distribution in the etching
of the first film and a plasma density distribution in the etching
of the second film have gradients in which a plasma density is
decreased as farther from the central axis line, but since the high
frequency power in the etching of the second film is relatively
high, a gradient of the plasma density distribution in the etching
of the second film is steeper than a gradient of the plasma density
distribution in the etching of the first film. For this reason, in
the etching method in accordance with another example embodiment,
the magnetic field is generated such that a position of the peak
value of the horizontal magnetic field components in the etching of
the second film is closer to the central axis line than a position
of the peak value of the horizontal magnetic field components in
the etching of the first film. Thus, it is possible to decrease the
gradient of the plasma density distribution. As a result, it is
possible to suppress non-uniformity of an etching rate depending on
a position when each film of the multilayer film is etched.
[0016] In the etching of the second film, a position of a peak
intensity of the horizontal magnetic field components may be an
intermediate position between a center of the target object and an
edge of the target object in the radial direction. Further, in the
etching of the first film, a position of a peak intensity of the
horizontal magnetic field components may be an outer position of an
edge of the target object in the radial direction.
[0017] As explained above, in accordance with the example
embodiments, it is possible to suppress non-uniformity of an
etching rate depending on a position when each film of the
multilayer film is etched. The foregoing summary is illustrative
only and is not intended to be in any way limiting. In addition to
the illustrative aspects, embodiments, and features described
above, further aspects, embodiments, and features will become
apparent by reference to the drawings and the following detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In the detailed description that follows, embodiments are
described as illustrations only since various changes and
modifications will become apparent from the following detailed
description. The use of the same reference numbers in different
figures indicates similar or identical items.
[0019] FIG. 1 is a schematic cross sectional view of a plasma
processing apparatus in accordance with an example embodiment;
[0020] FIG. 2 illustrates a gas supply system of the plasma
processing apparatus in accordance with the example embodiment;
[0021] FIG. 3 is a plane view of the plasma processing apparatus of
FIG. 1 when viewed from the top;
[0022] FIGS. 4A and 4B are drawings to explain a drift motion of an
electron caused by an electric field and a magnetic field generated
in the plasma processing apparatus of FIG. 1;
[0023] FIG. 5 is a flow chart illustrating an etching method of a
multilayer film in accordance with the example embodiment;
[0024] FIG. 6 is a cross sectional view of an example of a wafer
including a multilayer film;
[0025] FIG. 7 illustrates high frequency powers and high frequency
bias powers when etching each film of the multilayer film is
etched;
[0026] FIG. 8 illustrates a correlation between a high frequency
power and a plasma density distribution;
[0027] FIGS. 9A to 9C are cross sectional views illustrating
statuses of a wafer after each block of the method illustrated in
FIG. 5;
[0028] FIGS. 10A and 10B illustrate magnetic fields generated at
block S1 and block S3;
[0029] FIGS. 11A and 11B illustrate a magnetic field generated at
block S2;
[0030] FIG. 12 is a schematic cross sectional view of a plasma
processing apparatus in accordance with a second example
embodiment;
[0031] FIG. 13 is a plane view of an electromagnet when viewed from
a processing space;
[0032] FIGS. 14A to 14D illustrate examples of a magnetic field
generated by the electromagnet;
[0033] FIG. 15 illustrates results of an experimental example 1 and
a comparative experimental example 1;
[0034] FIG. 16 illustrates results of an experimental example 2 and
a comparative experimental example 2;
[0035] FIG. 17 illustrates results of an experimental example 3 and
a comparative experimental example 3;
[0036] FIGS. 18A and 18B illustrate electric field intensity
distributions in the processing space;
[0037] FIG. 19 is a schematic cross sectional view of a plasma
processing apparatus in accordance with a third example embodiment;
and
[0038] FIG. 20 is a schematic cross sectional view of a plasma
processing apparatus in accordance with a fourth example
embodiment.
DETAILED DESCRIPTION
[0039] In the following detailed description, reference is made to
the accompanying drawings, which form a part of the description. In
the drawings, similar symbols typically identify similar
components, unless context dictates otherwise. Furthermore, unless
otherwise noted, the description of each successive drawing may
reference features from one or more of the previous drawings to
provide clearer context and a more substantive explanation of the
current example. Still, the examples described in the detailed
description, drawings, and claims are not meant to be limiting.
Other embodiments may be utilized, and other changes may be made,
without departing from the spirit or scope of the subject matter
presented herein. It will be readily understood that the aspects of
the present disclosure, as generally described herein and
illustrated in the drawings, may be arranged, substituted,
combined, separated, and designed in a wide variety of different
configurations, all of which are explicitly contemplated
herein.
[0040] A plasma processing apparatus in which an etching method of
a multilayer film in accordance with an example embodiment is
performed will be explained first. FIG. 1 is a schematic cross
sectional view of a plasma processing apparatus in accordance with
the example embodiment. A plasma processing apparatus 10 depicted
in FIG. 1 includes a processing chamber 12, a mounting table 14, an
upper electrode 16, a first high frequency power supply 18, and a
second high frequency power supply 20.
[0041] The processing chamber 12 has a substantially cylindrical
shape and forms a processing space S therein. The processing space
S is depressurizable by an exhaust device. In the processing space
S, the mounting table 14 is provided. The mounting table 14
includes a base member 14a and an electrostatic chuck 14b. The base
member 14a is made of a conductive material, for example, aluminum
and has a substantially disc shape.
[0042] On an upper peripheral region of the base member 14a, a
focus ring 26 is provided to surround an edge of a wafer W.
Further, on an upper central region of the base member 14a, the
electrostatic chuck 14b is provided. The electrostatic chuck 14b
includes, for example, an electrode film interposed between
insulating films and has a substantially disc shape. At the
electrostatic chuck 14b, an electrostatic force is generated by a
DC voltage applied to the electrode film from a DC power supply via
a switch, and, thus, a target object W (hereinafter, referred to as
"wafer W") is attracted and held. When the wafer W is mounted on
the electrostatic chuck 14b, a central axis line Z vertically
passing through a center of the wafer W substantially coincides
with central axis lines of the base member 14a and the
electrostatic chuck 14b. Further, the wafer W may have a diameter
of, for example, about 300 mm.
[0043] The base member 14a serves as a lower electrode. The base
member 14a is connected via a first matching unit 22 to the high
frequency power supply 18 configured to generate a high frequency
power for plasma generation. The high frequency power supply 18
generates a high frequency power having a frequency of, for
example, about 100 MHz. Further, the first matching unit 22
includes a circuit capable of matching output impedance of the
first matching unit 22 with input impedance of a load side (lower
electrode side). Furthermore, the high frequency power supply 18
may be connected to the upper electrode 16. The base member 14a is
connected via a second matching unit 24 to the high frequency power
supply 20 configured to generate a high frequency power for ion
attraction. The high frequency power supply 20 generates a high
frequency power having a frequency of, for example, about 3.2 MHz.
Further, the second matching unit 24 includes a circuit capable of
matching output impedance of the second matching unit 24 with input
impedance of a load side (lower electrode side).
[0044] Above the base member 14a, i.e. the lower electrode, the
upper electrode 16 is provided to face the lower electrode via the
processing space S. The upper electrode 16 partitions an upper
portion of the processing space S and has a substantially disc
shape. The upper electrode 16 is provided such that a central axis
line thereof substantially coincides with the central axis line of
the mounting table 14. The upper electrode 16 serves as a shower
head. In accordance with the example embodiment, a buffer room 16a,
a gas line 16b, and multiple gas holes 16c are formed in the upper
electrode 16. The buffer room 16a is connected to an end of the gas
line 16b. Further, the buffer room 16a is connected to the multiple
gas holes 16c, and the gas holes 16c are extended downwardly and
opened toward the processing space S.
[0045] FIG. 2 illustrates a gas supply system of the plasma
processing apparatus in accordance with the example embodiment. The
plasma processing apparatus 10 may further include a gas supply
system GS depicted in FIG. 2. The gas supply system GS includes
multiple gas sources GS1, GS2, GS3, GS4, GS5, and GS6. The gas
source GS1 is a source of a CHF.sub.3 gas, the gas source GS2 is a
source of an O.sub.2 gas, the gas source GS3 is a source of a
CH.sub.4 gas, the gas source GS4 is a source of a N.sub.2 gas, the
gas source GS5 is a source of a C.sub.4F.sub.8 gas, and the gas
source GS6 is a source of an Ar gas.
[0046] In the gas supply system GS, the gas source GS1 is connected
to a gas line CL via a valve V11, a flow rate controller FC1, and a
valve V12; the gas source GS2 is connected to the gas line CL via a
valve V21, a flow rate controller FC2, and a valve V22; the gas
source GS3 is connected to the gas line CL via a valve V31, a flow
rate controller FC3, and a valve V32; the gas source GS4 is
connected to the gas line CL via a valve V41, a flow rate
controller FC4, and a valve V42; the gas source GS5 is connected to
the gas line CL via a valve V51, a flow rate controller FC5, and a
valve V52; and the gas source GS6 is connected to the gas line CL
via a valve V61, a flow rate controller FC6, and a valve V62. The
gas line CL is connected to the other end of the gas line 16b
depicted in FIG. 1.
[0047] In the plasma processing apparatus 10, a processing gas from
the gas supply system GS is supplied to the processing space S
through the upper electrode 16 serving as the shower head, and a
high frequency power from the high frequency power supply 18 is
applied to the lower electrode to generate a high frequency
electric field between the upper electrode 16 and the lower
electrode. Thus, plasma of the processing gas is generated in the
processing space S. Further, the wafer W can be processed with
active species of molecules or atoms, which constitute the
dissociated processing gas, in the plasma. Furthermore, an amount
of attracted ions can be controlled by adjusting a high frequency
bias power applied to the lower electrode from the high frequency
power supply 20.
[0048] Further, the plasma processing apparatus 10 further includes
multiple electromagnets 30. The multiple electromagnets 30 are
provided on the upper electrode 16, i.e. on a ceiling portion of
the processing chamber 12. Each of the multiple electromagnets 30
includes a yoke 30a formed of a rod-shaped magnetic material and a
coil 30b. The coil 30b is wound around an outer peripheral surface
of the yoke 30a. Since both ends of the coil 30b are connected to a
current source, a value and a direction of a current supplied into
the coil 30b can be controlled.
[0049] FIG. 3 is a plane view of the plasma processing apparatus of
FIG. 1 when viewed from the top. As depicted in FIG. 3, the
multiple electromagnets 30 are arranged in a radial direction with
respect to the central axis line Z that passes through the center
of the wafer W and is vertically extended. Further, the multiple
electromagnets 30 are arranged along multiple concentric circles
around the central axis line Z.
[0050] In accordance with the example embodiment, as depicted in
FIG. 3, the multiple electromagnets 30 are divided into a first
group 31, a second group 32, a third group 33, a fourth group 34,
and a fifth group 35, and each group includes several
electromagnets 30. The first group 31 may include one or more
electromagnets 30 provided on or near the central axis line Z. In
an example depicted in FIG. 3, the first group 31 includes one
electromagnet 30, and the yoke 30a of the electromagnet 30 is
provided along the central axis line Z.
[0051] Further, in the example depicted in FIG. 3, each of the
second group 32, the third group 33, the fourth group 34, and the
fifth group 35 includes 24 electromagnets 30. In FIG. 3, each
number in parentheses next to the reference numeral 30 is a
reference numeral of each group. The electromagnets 30 of the
second group 32 are arranged on a circle C2 having a radius L2 such
that the yokes 30a are extended substantially parallel to the
central axis line Z. The radius L2 is about 75 mm in the plasma
processing apparatus that processes the wafer W having a diameter
of about 300 mm. The electromagnets 30 of the third group 33 are
arranged on a circle C3 having a radius L3 such that the yokes 30a
are extended substantially parallel to the central axis line Z. The
radius L3 is greater than the radius L2, and the radius L3 is about
125 mm in the plasma processing apparatus that processes the wafer
W having a diameter of about 300 mm. The electromagnets 30 of the
fourth group 34 are arranged on a circle C4 having a radius L4 such
that the yokes 30a are extended substantially parallel to the
central axis line Z. The radius L4 is greater than the radius L3,
and the radius L4 is about 175 mm in the plasma processing
apparatus that processes the wafer W having a diameter of about 300
mm. Further, the electromagnets 30 of the fifth group 35 are
arranged on a circle C5 having a radius L5 such that the yokes 30a
are extended substantially parallel to the central axis line Z. The
radius L5 is greater than the radius L4, and the radius L5 is about
225 mm in the plasma processing apparatus that processes the wafer
W having a diameter of about 300 mm.
[0052] Further, as depicted in FIG. 1, the plasma processing
apparatus 10 may further include a control unit Cnt. The control
unit Cnt may be a computer device. The control unit Cnt is
configured to set a magnitude of a high frequency power generated
from the first high frequency power supply 18, a magnitude of a
high frequency power generated from the second high frequency power
supply 20, an exhaust amount of the exhaust device, gases supplied
from the gas supply system GS and flow rates thereof, and a value
and a direction of a current supplied into the coil 30b of each
electromagnet 30 of the first group 31, the second group 32, the
third group 33, the fourth group 34, and the fifth group 35. For
this reason, the control unit Cnt may output a control signal to
the first high frequency power supply 18, the second high frequency
power supply 20, the exhaust device, each component of the gas
supply system GS, and the current source connected to the
electromagnets 30 in response to a recipe stored in a memory
thereof or input through an input device.
[0053] In the plasma processing apparatus 10, by setting a
direction of a current to be supplied into the coil 30b of each
electromagnet 30 of the first group 31, the second group 32, the
third group 33, the fourth group 34, and the fifth group 35, it is
possible to set a magnetic pole of each electromagnet 30 of the
first group 31, the second group 32, the third group 33, the fourth
group 34, and the fifth group 35 at the processing space S side to
be an N pole or an S pole. Thus, it is possible to generate a
magnetic field having horizontal magnetic field components in a
radial direction with respect to the central axis line Z in the
processing space S.
[0054] FIGS. 4A and 4B are drawings to explain a drift motion of an
electron caused by an electric field and a magnetic field generated
in the plasma processing apparatus of FIG. 1. FIG. 4A is a cross
sectional view of the plasma processing apparatus 10, and FIG. 4B
is a plane view of the plasma processing apparatus 10 when viewed
from the top. As depicted in FIGS. 4A and 4B, there is generated an
electric field E toward the lower electrode (base member 14a) from
the upper electrode 16 within the processing space S while plasma
is generated. Further, as depicted in FIGS. 4A and 4B, for example,
if a magnetic pole of the electromagnet 30 of the first group 31 at
the processing space S side is set to be an N pole by adjusting a
direction of a current supplied into the coil 30b of the
electromagnet 30 of the first group 31 and each magnetic pole of
the electromagnets 30 of the fifth group 35 at the processing space
S side is set to be an S pole by adjusting a direction of a current
supplied into the coils 30b of the electromagnets 30 of the fifth
group 35, there is generated a magnetic field B toward the magnetic
pole of the electromagnets 30 of the fifth group 35 at the
processing space S side from the magnetic pole of the electromagnet
30 of the first group 31 at the processing space S side. As
depicted in FIG. 4B, the magnetic field B includes horizontal
magnetic field components B.sub.H in a radial direction with
respect to the axis line Z.
[0055] As described above, the electric field E and the magnetic
field B having the horizontal magnetic field components B.sub.H are
generated within the processing space S, and electrons within the
processing space S are subject to Lorentz force caused by the
electric field and the horizontal magnetic field components
B.sub.H, and perform the drift motion. To be specific, the
electrons are accelerated in a tangent direction of a circumference
around the central axis line Z and revolved on the central axis
line Z along a circular electron trajectory D according to the
Fleming's left-hand rule.
[0056] However, a velocity V.sub.gE of the electron performing the
drift motion caused by the electric field E and the horizontal
magnetic field components B.sub.H is expressed by the following
Equation (1).
VgE=E/B.sub.H (1)
[0057] According to Equation (1), when the intensity of the
electric field E is constant, the velocity of the electron
performing the drift motion is decreased as the intensity of the
horizontal magnetic field components B.sub.H (magnetic field
intensity) is increased. When the velocity of the electron
performing the drift motion is decreased, a staying time in which
electrons stay at a specific location is increased and, thus, an
electron density at the corresponding location is increased. As a
result, a possibility of collision between the electrons and
molecules or atoms of the processing gas is increased, so that a
plasma density at the corresponding location is increased. That is,
by increasing the intensity of the horizontal magnetic field
components B.sub.H at a certain location by the electromagnets 30,
the plasma density at the corresponding location can be
increased.
[0058] As described above, the plasma processing apparatus 10 can
set a direction and a value of a current supplied into the coils
30b of the multiple electromagnets 30 for each of the first group
31, the second group 32, the third group 33, the fourth group 34,
and the fifth group 35. Therefore, in the plasma processing
apparatus 10, by adjusting a direction of a current supplied into
the coils 30b of the electromagnets 30 of each of the first group
31, the second group 32, the third group 33, the fourth group 34,
and the fifth group 35, an intensity distribution of the horizontal
magnetic field components B.sub.H in a radial direction with
respect to the axis line Z can be adjusted. Further, by adjusting a
magnitude (value) of the current supplied into the coils 30b of the
electromagnets 30 of each of the first group 31, the second group
32, the third group 33, the fourth group 34, and the fifth group
35, intensity of the horizontal magnetic field components B.sub.H
in a radial direction with respect to the axis line Z can be
adjusted.
[0059] Hereinafter, there will be explained an etching method of a
multilayer film in accordance with the example embodiment, which
can be performed in the plasma processing apparatus 10. FIG. 5 is a
flow chart illustrating the etching method of the multilayer film
in accordance with the example embodiment. The method illustrated
in FIG. 5 can be performed to etch a multilayer film ML of a wafer
W depicted in FIG. 6. Further, FIG. 6 is a cross sectional view of
an enlarged part of the wafer W.
[0060] The wafer W depicted in FIG. 6 includes a resist mask PRM, a
first oxide film OXF1, an organic film OR, a second oxide film
OXF2, and an etching target layer EL. The etching target layer EL
is a layer to be etched by using a mask formed by etching the
second oxide film OXF2, and is, for example, a silicon layer. On
the etching target layer EL, the second oxide film OXF2 is formed.
The second oxide film OXF2 is a silicon oxide layer and has a
relatively great film thickness which can endure the etching of the
etching target layer EL having a great film thickness. The
thickness of the second oxide film OXF2 is, for example, about 2000
nm.
[0061] On the second oxide film OXF2, the organic film OR is
formed. The organic film OR serves as a mask to be used in etching
the second oxide film OXF2. A thickness of the organic film OR is,
for example, about 300 nm.
[0062] On the organic film OR, the first oxide film OXF1 is formed.
The first oxide film OXF1 serves as a mask to be used in etching
the organic film OR. The first oxide film OXF1 is, for example, a
silicon oxide layer. The first oxide film OXF1 has a thickness
smaller than that of the second oxide film OXF2. A thickness of the
first oxide film OXF1 is, for example, 45 nm.
[0063] On the first oxide film OXF1, the resist mask PRM is formed.
The resist mask PRM can be formed by coating a resist material on
the first oxide film OXF1, and then, exposing/developing the resist
material.
[0064] As described above, the wafer W includes the multilayer film
ML having a stacked structure of multiple films different from each
other in a kind of a film and/or a thickness of a film. As plasma
generation conditions during the etching of each film of the
multilayer film ML, various conditions are employed depending on a
kind of a film and/or a thickness of a film. FIG. 7 illustrates
high frequency powers and high frequency bias powers when etching
each film of the multilayer film. In FIG. 7, a horizontal axis
represents a high frequency bias power LF for ion attraction, and a
longitudinal axis represents a high frequency power HF for plasma
generation.
[0065] In the wafer W, the second oxide film OXF2 is formed as an
underlying film of the organic film OR. The second oxide film OXF2
serves as a mask for etching the etching target layer EL.
Therefore, when the organic film OR is etched, it is necessary to
reduce damage to the second oxide film OXF2. Therefore, the organic
film OR is etched with a large amount of active species, such as
radicals, generated by dissociation of molecules and/or atoms in
the processing gas with a relatively higher high frequency power HF
(for example, about 2400 W). Further, the organic film OR is etched
with low energy by using a relatively lower high frequency bias
power LF (for example, about 200 W). Thus, it is possible to reduce
damage to the second oxide film OXF2. Hereinafter, a value of the
high frequency power and a value of the high frequency bias power
during the etching of the organic film OR will be referred to as
HF3 and LF3, respectively.
[0066] Meanwhile, the first oxide film OXF1 and the second oxide
film OXF2 are etched by attracting a large amount of active
species, such as ions, generated by dissociation of molecules
and/or atoms in the processing gas toward the wafer W. For this
reason, when the first oxide film OXF1 and the second oxide film
OXF2 are etched, the high frequency power HF for plasma generation
is set to be a lower value (for example, about 1000 W) and the high
frequency bias power LF for ion attraction is set to be a higher
value. Herein, a value of the high frequency power HF during the
etching of the first oxide film OXF1 will be referred to as HF1, a
value of the high frequency power HF during the etching of the
second oxide film OXF2 will be referred to as HF2. Further, a value
of the high frequency bias power LF during the etching of the first
oxide film OXF1 will be referred to as LF1, and a value of the high
frequency bias power LF during etching of the second oxide film
OXF2 will be referred to as LF2. In this case, these values have
conditions as follows: HF3>HF1, HF3>HF2, LF1>LF3, and
LF2>LF3.
[0067] Further, in the example embodiment, a thickness of the
second oxide film OXF2 is greater than that of the first oxide film
OXF1. Therefore, when the second oxide film OXF2 is etched, it is
desirable to increase an etching rate of the second oxide film OXF2
by attracting ions having higher energy toward the wafer W.
Therefore, in the example embodiment, LF2 and LF1 have a condition
as follows: LF2>LF1.
[0068] In the above-described plasma processing apparatus 10, if
plasma is generated with the set high frequency powers for etching
each of the first oxide film OXF1, the second oxide film OXF2, and
the organic film OR without generating a magnetic field by the
electromagnets 30, a plasma density distribution within the
processing space S becomes non-uniform in a radial direction with
respect to the axis line Z. FIG. 8 illustrates a correlation
between a high frequency power and a plasma density distribution.
In FIG. 8, a horizontal axis represents a position in a radial
direction from the central axis line Z, and a position of the
central axis line Z is set to be about 0 mm. Further, in FIG. 8, a
longitudinal axis represents a normalized value of an electron
density (Ne) by a maximum value (NeMax) of the electron density,
and indicates a value reflecting a plasma density. Furthermore, in
FIG. 8, a plasma density distribution shown in a dotted line shows
a density distribution of plasma generated by the high frequency
power having the value HF1 for etching the first oxide film OXF1
and the high frequency power having the value HF2 for etching the
second oxide film OXF2. Meanwhile, a plasma density distribution
shown in a solid line shows a density distribution of plasma
generated by the high frequency power having the value HF3 for
etching the organic film OR.
[0069] As depicted in FIG. 8, even if any one of the high frequency
powers for etching the first oxide film OXF1, the second oxide film
OXF2, and the organic film OR is used, a plasma density
distribution has a gradient in which a plasma density is high near
the central axis line Z and becomes decreased as farther from the
central axis line Z. Further, when using the high frequency power
having the value HF3 for etching the organic film OR, this gradient
tends to be remarkable. That is, when plasma for etching the
organic film OR is generated, the high frequency power having the
high value HF3 is used. Therefore, a plasma density distribution
obtained when etching the organic film OR has a gradient in which a
plasma density difference between when using the high frequency
power of HF3 and when using the high frequency power of HF1 or when
using the high frequency power of HF2 is larger at a position
closer to the central axis line Z.
[0070] According to the method illustrated in FIG. 5,
non-uniformity of the plasma density distribution can be reduced by
using electromagnets. Hereinafter, referring to FIG. 5 and FIGS. 9A
to 9C, the method will be described. FIGS. 9A to 9C are cross
sectional views illustrating a status of a wafer W after performing
each block of the method illustrated in FIG. 5. According to the
method illustrated in FIG. 5, before block S1 (Etch First Oxide
Film), the wafer W depicted in FIG. 6 is accommodated into the
processing space S and mounted on the electrostatic chuck 14b of
the mounting table 14. Then, at block S1, the first oxide film OXF1
is etched. At block S1, as a first processing gas, a processing gas
including a fluorocarbon gas and/or a fluorohydrocarbon gas is
supplied into the processing space S. By way of example, at block
S1, a processing gas including a CHF.sub.3 gas of the gas source
GS1 and an O.sub.2 gas of the gas source GS2 is supplied into the
processing space S. Further, at block S1, the high frequency power
having the value HF1 and the high frequency bias power having the
value LF1 are applied to the lower electrode. The high frequency
power may be applied to the upper electrode 16.
[0071] As described above, if a magnetic field is not generated by
the electromagnets, a density of plasma generated by applying the
high frequency power having the value HF1 to the electrode has a
distribution as shown in the dotted line in FIG. 8. Therefore, in
the example embodiment, at block S1, the magnetic field B is formed
such that a position of a peak intensity of the horizontal magnetic
field components B.sub.H is farther from the central axis line Z
than a position of a peak intensity of the horizontal magnetic
field components B.sub.H at block S2 to be described later.
[0072] FIGS. 10A and 10B illustrate magnetic fields generated at
block S1 and block S3. FIG. 10A is a cross sectional view of the
plasma processing apparatus 10, and FIGS. 10A and 10B show an
intensity distribution of the horizontal magnetic field components
B.sub.H (magnetic flux density distribution). As depicted in FIG.
10A, in accordance with the example embodiment, at block S1, a
magnetic pole of the electromagnets 30 of the first group 31 to the
fourth group 34 at the processing space S side is set to be an N
pole, and a magnetic pole of the electromagnets 30 of the fifth
group 35 at the processing space S side is set to be an S pole.
Thus, in the processing space S, a magnetic field B depicted in
FIG. 10A is generated. When the wafer W having a diameter of about
300 mm is processed, as depicted in FIG. 10B, the horizontal
magnetic field components B.sub.H in this magnetic field B have the
peak intensity at an outer position (for example, about 225 mm away
from the central axis line Z) of an edge of the wafer W in a radial
direction. Since the magnetic field B having the horizontal
magnetic field components B.sub.H is generated, a plasma density is
increased in an upper outer region of the edge of the wafer W. As a
result, non-uniformity of a plasma density distribution having a
relatively gentle gradient is reduced. Therefore, at block S1,
non-uniformity of the plasma density distribution in a radial
direction with respect to the central axis line Z is reduced.
[0073] At block S1, as depicted in FIG. 9A, the first oxide film
OXF1 is etched and a pattern of the resist mask PRM is transcribed
into the first oxide film OXF1. Further, since non-uniformity of
the plasma density distribution in a radial direction with respect
to the central axis line Z is reduced, non-uniformity of the
etching rate depending on a position in a diametric direction of
the first oxide film OXF1 is reduced. Here, the diametric direction
implies a direction parallel to the radial direction. Processing
may proceed from block S1 to block S2.
[0074] Hereinafter, according to the method illustrated in FIG. 5,
at block S2 (Etch Organic Film), the organic film OR is etched. At
block S2, as a second processing gas, a processing gas including
oxygen is supplied into the processing space S. By way of example,
at block S2, the processing gas including an O.sub.2 gas of the gas
source GS2, a CH.sub.4 gas of the gas source GS3, and a N.sub.2 gas
of the gas source GS4 is supplied into the processing space S.
Further, at block S2, the high frequency power having the value HF3
and the high frequency bias power having the value LF3 are applied
to the lower electrode. The high frequency power may be applied to
the upper electrode 16.
[0075] As described above, if a magnetic field is not generated by
the electromagnets 30, a density of plasma generated by applying
the high frequency power having the value HF3 to the electrode has
a distribution as shown in the solid line in FIG. 8. Therefore, in
the example embodiment, at block S2, the magnetic field B is formed
such that a position of the peak intensity of the horizontal
magnetic field components B.sub.H is closer to the central axis
line Z than a position of the peak intensity of the horizontal
magnetic field components B.sub.H at block 51 and block S3.
[0076] FIGS. 11A and 11B illustrate a magnetic field generated at
block S2. FIG. 11A is a cross sectional view of the plasma
processing apparatus 10, and FIG. 11B shows an intensity
distribution of the horizontal magnetic field components B.sub.H
(magnetic flux density distribution). As depicted in FIG. 11A, in
accordance with the example embodiment, at block S2, a magnetic
pole of the electromagnets 30 of the first group 31 and the second
group 32 at the processing space S side is set to be an N pole, and
a magnetic pole of the electromagnets 30 of the third group 33 to
the fifth group 35 at the processing space S side is set to be an S
pole. Thus, in the processing space S, a magnetic field B depicted
in FIG. 11A is generated. When the wafer W having a diameter of
about 300 mm is processed, as depicted in FIG. 11B, the horizontal
magnetic field components B.sub.H in this magnetic field B have the
peak intensity at an intermediate position (for example, about 100
mm away from the central axis line Z) between the edge and the
center of the wafer W in a radial direction. Since the magnetic
field B having the horizontal magnetic field components B.sub.H is
generated, a plasma density is increased in an upper region of the
intermediate position between the edge and the center of the wafer
W. As a result, non-uniformity of a plasma density distribution
having a steep gradient in which a plasma density is decreased at a
position close to the central axis line Z is reduced. Therefore, at
block S2, non-uniformity of the plasma density distribution in a
radial direction with respect to the central axis line Z is
reduced.
[0077] At block S2, as depicted in FIG. 9B, the organic film OR is
etched and a pattern of the first oxide film OXF1 is transcribed
into the organic film OR. Further, at block S2, since the
oxygen-based gas is used, the resist mask PRM made of an organic
material like the organic film OR is removed. Furthermore, as
described above, since non-uniformity of the plasma density
distribution in a radial direction with respect to the central axis
line Z is reduced, non-uniformity of the etching rate depending on
a position in a diametric direction of the organic film OR is
reduced at block S2. Processing may proceed from block S2 to block
S3.
[0078] Hereinafter, in the method illustrated in FIG. 5, at block
S3 (Etch Second Oxide Film), the second oxide film OXF2 is etched.
At block S3, as a third processing gas, a processing gas including
a fluorocarbon gas and/or a fluorohydrocarbon gas is supplied into
the processing space S. By way of example, at block S3, the
processing gas including a C.sub.4F.sub.8 gas of the gas source
GS5, an O.sub.2 gas of the gas source GS2, and an Ar gas of the gas
source GS6 is supplied into the processing space S. Further, at
block S3, the high frequency power having the value HF2 and the
high frequency bias power having the value LF2 are applied to the
lower electrode. The high frequency power may be applied to the
upper electrode 16.
[0079] As described above, if a magnetic field is not generated by
the electromagnets 30, a density of plasma generated by applying
the high frequency power having the value HF2 to the electrode has
a distribution as shown in the dotted line in FIG. 8. That is, a
density distribution of plasma generated with the high frequency
power having the value HF2 and the high frequency bias power having
the value LF2 for block S3 has a gradient similar to that of a
density distribution of plasma generated with the high frequency
power having the value HF1 and the high frequency bias power having
the value LF1 for block S1. Therefore, in the example embodiment,
at block S3, the magnetic field B is formed such that a position of
the peak intensity of the horizontal magnetic field components
B.sub.H is farther from the central axis line Z than a position of
the peak intensity of the horizontal magnetic field components
B.sub.H at block S2. That is, at block S3, as depicted in FIGS. 10A
and 10B, there is formed the magnetic field having the same
intensity distribution of the horizontal magnetic field components
B.sub.H as shown at block S1. However, the magnetic field formed at
block S3 is formed such that an intensity value of the horizontal
magnetic field components B.sub.H is higher than an intensity value
of the horizontal magnetic field components B.sub.H at block S1.
Further, an intensity value of the horizontal magnetic field
components B.sub.H can be controlled by adjusting values of
currents supplied into the coils of the electromagnets 30 of the
first to fifth groups 31 to 35. As described above, at block S3,
non-uniformity of the plasma density distribution in a radial
direction with respect to the central axis line Z is reduced.
[0080] At block S3, as depicted in FIG. 9C, the second oxide film
OXF2 is etched and a pattern of the organic film OR is transcribed
into the second oxide film OXF2. Further, the first oxide film OXF1
made of a material similar to that of the second oxide film is
removed at block S3. Furthermore, since non-uniformity of the
plasma density distribution in a radial direction with respect to
the central axis line Z is reduced, non-uniformity of the etching
rate depending on a position in a diametric direction of the second
oxide film OXF2 is reduced.
[0081] Hereinafter, another plasma processing apparatus in which
the method illustrated in FIG. 5 is performed will be explained.
FIG. 12 is a schematic cross sectional view of a plasma processing
apparatus in accordance with a second example embodiment. The
plasma processing apparatus 10A depicted in FIG. 12 is different
from the plasma processing apparatus 10 in that the plasma
processing apparatus 10A includes an electromagnet 30A instead of
the electromagnets 30. Hereinafter, referring to FIG. 12 and FIG.
13, the electromagnet 30A will be explained. FIG. 13 is a plane
view of the electromagnet 30A when viewed from the processing space
S.
[0082] As depicted in FIG. 12 and FIG. 13, the electromagnet 30A
includes a core member 50 and coils 61 to 64. The core member 50
has a structure including a column-shaped member 51, multiple
cylindrical members 52 to 55, and a base member 56, which are
integrally formed with each other, and is made of a magnetic
material. The base member 56 has a substantially disc shape and is
provided such that a central axis line thereof coincides with the
central axis line Z. From a bottom surface of the base member 56,
the column-shaped member 51 and the multiple cylindrical members 52
to 55 are extended downwardly. The column-shaped member 51 has a
substantially column shape and is provided such that a central axis
line thereof coincides with the central axis line Z. A radius L1 of
the column-shaped member 51 is, for example, about 30 mm.
[0083] Each of the cylindrical members 52 to 55 has a cylindrical
shape extended in a direction of the central axis line Z. The
cylindrical members 52 to 55 are respectively arranged along
multiple concentric circles C2 to C5 around the central axis line
Z. To be specific, the cylindrical member 52 is extended along the
concentric circle C2 having a radius L2 greater than the radius L1;
the cylindrical member 53 is extended along the concentric circle
C3 having a radius L3 greater than the radius L2; the cylindrical
member 54 is extended along the concentric circle C4 having a
radius L4 greater than the radius L3; and the cylindrical member 55
is extended along the concentric circle C5 having a radius L5
greater than the radius L4. In the example, the radiuses L2, L3,
L4, and L5 are about 76 mm, about 127 mm, about 178 mm, and about
229 mm, respectively.
[0084] Between the column-shaped member 51 and the cylindrical
member 52, a groove is formed. In this groove, a coil 61 wound
around an outer peripheral surface of the column-shaped member 51
is accommodated. Between the cylindrical member 52 and the
cylindrical member 53, a groove is formed, and in this groove, a
coil 62 wound around an outer peripheral surface of the cylindrical
member 52 is accommodated. Further, between the cylindrical member
53 and the cylindrical member 54, a groove is formed, and in this
groove, a coil 63 wound around an outer peripheral surface of the
cylindrical member 53 is accommodated. Furthermore, between the
cylindrical member 54 and the cylindrical member 55, a groove is
formed, and in this groove, a coil 64 wound around an outer
peripheral surface of the cylindrical member 54 is accommodated.
Both ends of each of the coils 61 to 64 are connected to current
sources. Start or stop of the supply of a current to each of the
coils 61 to 64, and a current value can be controlled in response
to a control signal from the control unit Cnt.
[0085] In the electromagnet 30A, by supplying a current into one or
more of the coils 61 to 64, a magnetic field B having horizontal
magnetic field components B.sub.H in a radial direction with
respect to the central axis line Z can be generated within the
processing space S. FIGS. 14A to 14D illustrate examples of a
magnetic field generated by the electromagnet 30A. FIG. 14A
illustrates a magnetic field B when a current is supplied to the
coil 62 and a cross section of the electromagnet 30A in a half
plane with respect to the central axis line Z, and FIG. 14B
illustrates an intensity distribution of the horizontal magnetic
field components B.sub.H when a current is supplied to the coil 62.
Further, FIG. 14C illustrates a magnetic field B when a current is
supplied to the coil 64 and a cross section of the electromagnet
30A in a half plane with respect to the central axis line Z, and
FIG. 14D illustrates an intensity distribution of the horizontal
magnetic field components B.sub.H when a current is supplied to the
coil 64. In the graphs shown in FIGS. 14B and 14D, horizontal axes
represent positions in a radial direction from the central axis
line Z when a position of the central axis line Z is set to be
about 0 mm, and longitudinal axes represent intensities (magnetic
flux densities) of the horizontal magnetic field components
B.sub.H.
[0086] When a current is supplied to the coil 62 of the
electromagnet 30A, the magnetic field B as shown in FIG. 14A is
generated. That is, there is generated the magnetic field B toward
end portions of the cylindrical members 53 to 55 at the processing
space S side from end portions of the column-shaped member 51 and
the cylindrical member 52 at the processing space S side. An
intensity distribution of the horizontal magnetic field components
B.sub.H in a radial direction of the magnetic field B has a peak
value under a center of the coil 62 as shown in FIG. 14B. In an
example, a position of the center of the coil 62 is about 100 mm
away from the central axis line Z. When the wafer W having a
diameter of about 300 mm is processed, the position of the center
of the coil 62 is an intermediate position between a center and an
edge of a wafer W in a radial direction. Therefore, the magnetic
field B generated by supplying a current to the coil 62 can be used
at block S2.
[0087] Further, if a current is supplied to the coil 64 of the
electromagnet 30A, the magnetic field B as shown in FIG. 14C is
generated. That is, there is generated the magnetic field B toward
an end portion of the cylindrical member 55 at the processing space
S side from end portions of the column-shaped member 51 and the
cylindrical members 52 to 54 at the processing space S side. An
intensity distribution of the horizontal magnetic field components
B.sub.H in a radial direction of the magnetic field B has a peak
value under a center of the coil 64 as shown in FIG. 14D. In an
example, a position of the center of the coil 64 is about 200 mm
away from the axis line Z. When the wafer W having a diameter of
about 300 mm is processed, the position of the center of the coil
64 is an outer position of an edge of a wafer W in a radial
direction. Therefore, the magnetic field B generated by supplying a
current to the coil 64 can be used at blocks S1 and S3.
Experimental Examples 1 to 3 and Comparative Experimental Examples
1 to 3
[0088] Hereinafter, there will be explained experimental examples 1
to 3 and comparative experimental examples 1 to 3 carried out by
using the plasma processing apparatus 10A. In the experimental
example 1, at block S1, an oxide film uniformly formed on a
substrate having a diameter of about 300 mm is etched in the plasma
processing apparatus 10A. Conditions of the experimental example 1
are as follows.
[0089] (Conditions of Experimental Example 1)
[0090] High frequency power: 100 MHz, 1000 W
[0091] High frequency bias power: 3.2 MHz, 300 W
[0092] Pressure in processing space: 15 mTorr (2 Pa)
[0093] Processing gas: CHF.sub.3 (500 sccm), O.sub.2 (10 sccm)
[0094] Coil to which current is supplied: coil 64
[0095] Further, for comparison, there is performed the comparative
experimental example 1 which is different from the experimental
example 1 in that a magnetic field is not generated by the
electromagnet 30A.
[0096] In the experimental example 2, at block S2, an organic film
uniformly formed on a substrate having a diameter of 300 mm is
etched in the plasma processing apparatus 10A. Conditions of the
experimental example 2 are as follows.
[0097] (Conditions of Experimental Example 2)
[0098] High frequency power: 100 MHz, 2400 W
[0099] High frequency bias power: 3.2 MHz, 200 W
[0100] Pressure in processing space: 30 mTorr (4 Pa)
[0101] Processing gas: N.sub.2 (45 sccm), O.sub.2 (22 sccm),
CH.sub.4 (180 sccm)
[0102] Coil to which current is supplied: coil 62
[0103] Moreover, for comparison, there is performed the comparative
experimental example 2 which is different from the experimental
example 2 in that a magnetic field is not generated by the
electromagnet 30A.
[0104] In the experimental example 3, at block S3, an oxide film
uniformly formed on a substrate having a diameter of 300 mm is
etched in the plasma processing apparatus 10A. Conditions of the
experimental example 3 are as follows. A value of a current
supplied to the coil 64 in the experimental example 3 is set to be
higher than a value of a current supplied to the coil 64 in the
experimental example 1.
[0105] (Conditions of Experimental Example 3)
[0106] High frequency power: 100 MHz, 1000 W
[0107] High frequency bias power: 3.2 MHz, 5800 W
[0108] Pressure in processing space: 15 mTorr (2 Pa)
[0109] Processing gas: C.sub.4F.sub.8 (130 sccm), Ar (100 sccm),
O.sub.2 (40 sccm)
[0110] Coil to which current is supplied: coil 64
[0111] Further, for comparison, there is performed the comparative
experimental example 3 which is different from the experimental
example 3 in that a magnetic field is not generated by the
electromagnet 30A.
[0112] In the experimental example 1 and the comparative
experimental example 1, film thicknesses of the oxide films before
and after performing the processes are measured at multiple
positions in a radius of the substrate, and etching rates at the
multiple positions are obtained, respectively. Further, in the
experimental example 2 and the comparative experimental example 2,
film thicknesses of the organic films before and after performing
the processes are measured at multiple positions in a radius of the
substrate, and etching rates at the multiple positions are
obtained, respectively. Furthermore, in the experimental example 3
and the comparative experimental example 3, film thicknesses of the
oxide films before and after performing the processes are measured
at multiple positions in a radius of the substrate, and etching
rates at the multiple positions are obtained, respectively. A
distribution of the etching rates obtained in each of the
experimental example 1 and the comparative experimental example 1
is shown in FIG. 15; a distribution of the etching rates obtained
in each of the experimental example 2 and the comparative
experimental example 2 is shown in FIG. 16; and a distribution of
the etching rates obtained in each of the experimental example 3
and the comparative experimental example 3 is shown in FIG. 17. In
FIG. 15 to FIG. 17, horizontal axes represent positions in a radius
of the substrate when a center location of the substrate is set to
be about 0 mm. Further, longitudinal axes on the left represent
etching rates, and longitudinal axes on the right represent
intensities (magnetic flux densities) of horizontal magnetic field
components B.sub.H. In FIG. 15 to FIG. 17, intensity distributions
of horizontal magnetic field components B.sub.H obtained by
simulating the experimental examples 1 to 3 are also shown.
[0113] As shown in FIG. 15, in the comparative experimental example
1, a magnetic field is not generated by the electromagnet 30A.
Therefore, it is observed that the etching rate of the oxide film
tends to be decreased as closer to the edge of the substrate due to
the effect of the plasma density distribution. That is, in the
comparative experimental example 1, non-uniformity of the etching
rate distribution of the oxide film in a diametric direction is
observed. Meanwhile, in the experimental example 1, i.e. when a
magnetic field having horizontal magnetic field components, which
have a peak intensity at an outer position of the edge of the
substrate in a radial direction, is generated by supplying a
current to the coil 64, the non-uniformity of the etching rate
distribution of the oxide film in a diametric direction is
reduced.
[0114] Further, as shown in FIG. 16, in the comparative
experimental example 2, a magnetic field is not generated by the
electromagnet 30A. Therefore, it is observed that an etching rate
of the organic film tends to be decreased as closer to the edge of
the substrate due to the effect of the plasma density distribution.
That is, in the comparative experimental example 2, non-uniformity
of the etching rate distribution of the organic film in a diametric
direction is observed. Meanwhile, in the experimental example 2,
i.e. when a magnetic field having horizontal magnetic field
components, which have a peak intensity at an intermediate position
between the center and the edge of the substrate in a radial
direction, is generated by supplying a current to the coil 62, the
non-uniformity of the etching rate distribution of the organic film
in a diametric direction is reduced.
[0115] Furthermore, as shown in FIG. 17, in the comparative
experimental example 3, a magnetic field is not generated by the
electromagnet 30A. Therefore, it is observed that the etching rate
of the oxide film tends to be decreased as closer to the edge of
the substrate due to the effect of the plasma density distribution.
That is, in the comparative experimental example 3, non-uniformity
of an etching rate distribution of the oxide film in a diametric
direction is observed. Meanwhile, in the experimental example 3,
i.e. when a magnetic field having horizontal magnetic field
components, which have a peak intensity at an outer position of the
edge of the substrate in a radial direction, is generated by
supplying a current greater than the current of the experimental
example 1 to the coil 64, the non-uniformity of an etching rate
distribution of the oxide film in a diametric direction is
reduced.
[0116] Although various example embodiments and experimental
examples thereof have been explained, the present disclosure is not
limited to the above-described example embodiments and various
modifications can be made. By way of example, although the method
in accordance with the above-described example embodiments is an
etching method of the multilayer film including the first oxide
film, the organic film, and the second oxide film, the concept of
the present disclosure can be applied to an etching method of a
multilayer film including at least a first film and a second film.
The first film and the second film may be films layered
continuously to each other and may be films having different kinds
from each other. Further, any one of the first film and the second
film may be an upper layer. That is, any one of the first film and
the second film may be etched first. According to the concept of
the present disclosure, in a process of etching the first film,
plasma is generated by using a high frequency power having a
relatively lower value, and in a process of etching the second
film, plasma is generated by using a high frequency power having a
relatively higher value. Further, in the process of etching the
first film and the process of etching the second film, a magnetic
field is generated such that horizontal magnetic field components
in a radial direction with respect to the central axis line Z have
an intensity distribution having a peak value at a position far
from the central axis line Z. Furthermore, in the process of
etching the second film, a magnetic field is generated such that a
position of the peak value of horizontal magnetic field components
is closer to the central axis line Z than a position of the peak
value of horizontal magnetic field components in the process of the
etching the first film. By way of example, in the process of
etching the second film, a magnetic field having horizontal
magnetic field components, which have a peak intensity at an
intermediate position between the center and the edge of the wafer
W in a radial direction is generated. Moreover, in the process of
etching the first film, a magnetic field having horizontal magnetic
field components, which have a peak intensity at an outer position
of an edge of the wafer W in a radial direction, is generated.
Therefore, it is possible to decrease a gradient of the plasma
density distribution in the process of etching the first film and
also possible to reduce a gradient of the plasma density
distribution in the process of etching the second film. Thus, it is
possible to suppress non-uniformity of the etching rate depending
on a position when etching each film.
[0117] Further, in the above, a frequency of about 100 MHz is
provided as an example of a frequency of the high frequency power
for plasma generation from the high frequency power supply 18, but
a frequency of the high frequency power for plasma generation can
be set to be a certain value. By way of example, a frequency of
about 40 MHz or more may be set as a frequency of the high
frequency power for plasma generation.
[0118] Herein, an electric field intensity distribution within the
processing space S when a magnetic field is not generated by the
electromagnets 30 or 30A and when a high frequency power is applied
to any one of the disc-shaped upper electrode and the lower
electrode is expressed by the following equation (2) using a
zero-order Bessel function (equation (3)), and the electric field
intensity distribution expressed by equation (2) reflects a plasma
density distribution.
( Equation 2 ) E = E 0 j .omega. t J 0 ( .omega. r c ) ( 2 ) (
Equation 3 ) J 0 ( x ) = 1 - 1 1 ( x 2 ) 2 + 1 ( 2 ) 2 ( x 2 ) 4 -
1 ( 3 ) 2 ( x 2 ) 6 + ( 3 ) ##EQU00001##
[0119] Herein, E represents an electric field intensity
distribution, r represents a distance from the central axis line Z
in a radial direction, c represents a speed of light, .omega.
represents an angular frequency of a high frequency power, and
E.sub.0 represents a certain value of electric field intensity.
[0120] The electric field intensity distribution within the
processing space S expressed by equation (2) is shown in FIGS. 18A
and 18B. In FIGS. 18A and 18B, an electric field intensity
distribution in each case where a frequency of the high frequency
power is about 3 MHz, about 10 MHz, about 30 MHz, about 100 MHz, or
about 300 MHz is expressed as a function of the distance from the
central axis line Z in a radial direction. In FIGS. 18A and 18B,
horizontal axes represent distances when a position of the central
axis line Z is set to be about 0 mm, and longitudinal axes
represent electric field intensity. Further, FIG. 18A illustrates
an electric field intensity distribution in a range of about 0.15 m
from the central axis line Z, and FIG. 18B illustrates an electric
field intensity distribution in a range of about 1.5 m from the
central axis line Z.
[0121] As shown in FIGS. 18A and 18B, there is a difference in the
electric field intensity distributions from the central axis line Z
in a radial direction within the processing space S depending on a
frequency of the high frequency power for plasma generation.
However, regardless of a frequency of the high frequency power for
plasma generation, the electric field intensity distribution has a
gradient in which the electric field intensity is high at the
central axis line Z and is decreased as farther from the central
axis line Z. Therefore, the effect of reducing non-uniformity of
the plasma density distribution by generating a magnetic field
having horizontal magnetic field components within the processing
space S in accordance with the example embodiments can be achieved
regardless of a frequency of the high frequency power for plasma
generation. In other words, a frequency of the high frequency power
for plasma generation used in the above-described example
embodiments is not limited.
[0122] Further, in the above, a diameter of about 300 mm is
provided as an example of a diameter of the wafer W, but a diameter
of the wafer W may be smaller or greater than 300 mm. By way of
example, the above-described example embodiments can be applied to
a wafer W having a diameter of about 450 mm.
[0123] Herein, as can be seen clearly from the electric field
intensity distributions shown in FIGS. 18A and 18B, even when a
high frequency power for plasma generation having a relatively low
frequency of about 30 MHz is used, if the wafer W has a greater
diameter of about 450 mm, non-uniformity of a plasma density
distribution is not ignorable. That is, if a diameter of the wafer
W is increased, even when a high frequency power for plasma
generation having a relatively low frequency is used, a difference
between a plasma density right above the center of the wafer W and
a plasma density right above the edge of the wafer W is not
ignorable. Therefore, the effect of reducing non-uniformity of the
plasma density distribution by generating a magnetic field having
horizontal magnetic field components within the processing space in
accordance with the example embodiments can be achieved regardless
of a diameter of the wafer W. In other words, a diameter of the
wafer W to which the above-described example embodiments can be
applied is not limited.
[0124] Furthermore, in the above-described example embodiments, the
electromagnet is used to generate a magnetic field, but a permanent
magnet may be used instead of the electromagnet. Moreover, in the
above-described example embodiments, the electromagnet is provided
on the upper electrode 16, but the electromagnet may be arranged at
any position as long as it can generate a magnetic field having the
above-described horizontal magnetic field components within the
processing space S.
[0125] By way of example, in the example embodiments shown in FIG.
12, the electromagnet 30A is provided on the upper electrode 16.
However, as depicted in FIG. 19, an electromagnet 30B which is the
same as the electromagnet 30A may be provided within the base
member 14a. Further, in a plasma processing apparatus 10B depicted
in FIG. 19, a direction of the electromagnet 30B is reversed from
the direction of the electromagnet 30A such that the column-shaped
member 51 and the cylindrical members 52 to 55 of the electromagnet
30B are positioned on the base member 56.
[0126] Further, by way of example, as depicted in FIG. 20, multiple
electromagnets each of which is the same as the electromagnet 30A
may be provided. In a plasma processing apparatus 10C depicted in
FIG. 20, the electromagnet 30A is provided on the upper electrode
16 and the electromagnet 30B is provided within the base member
14a. Positions of electromagnets and the number of the
electromagnets can be optionally selected. Further, the upper
electrode 16 or the base member 14a can be made of aluminum. The
upper electrode or the base member 14a scarcely affects a magnetic
field generated by the electromagnets.
[0127] From the foregoing, it will be appreciated that various
embodiments of the present disclosure have been described herein
for purposes of illustration, and that various modifications may be
made without departing from the scope and spirit of the present
disclosure. Accordingly, the various embodiments disclosed herein
are not intended to be limiting, with the true scope and spirit
being indicated by the following claims.
* * * * *