U.S. patent application number 13/044741 was filed with the patent office on 2011-09-15 for plasma etching method and plasma etching apparatus.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Masanobu Honda, Akitaka Shimizu, Hidetami Yaegashi.
Application Number | 20110220609 13/044741 |
Document ID | / |
Family ID | 44508116 |
Filed Date | 2011-09-15 |
United States Patent
Application |
20110220609 |
Kind Code |
A1 |
Yaegashi; Hidetami ; et
al. |
September 15, 2011 |
PLASMA ETCHING METHOD AND PLASMA ETCHING APPARATUS
Abstract
There are provided a plasma etching method and a plasma etching
apparatus capable of independently controlling distributions of
line widths and heights of lines in a surface of a wafer. The
plasma etching method for performing a plasma etching on a
substrate W by irradiating plasma containing charged particles and
neutral particles to the substrate W includes controlling a
distribution of reaction amounts between the substrate W and the
neutral particles in a surface of the substrate W by adjusting a
temperature distribution in the surface of the substrate W
supported by a support 105, and controlling a distribution of
irradiation amounts of the charged particles in the surface of the
substrate W by adjusting a gap between the substrate W supported by
the support 105 and an electrode 120 provided so as to face the
support 105.
Inventors: |
Yaegashi; Hidetami;
(Yamanashi, JP) ; Honda; Masanobu; (Yamanashi,
JP) ; Shimizu; Akitaka; (Yamanashi, JP) |
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
44508116 |
Appl. No.: |
13/044741 |
Filed: |
March 10, 2011 |
Current U.S.
Class: |
216/12 ;
156/345.43; 216/67 |
Current CPC
Class: |
H01L 21/32139 20130101;
H01L 21/31122 20130101; H01L 21/32137 20130101; H01J 37/32091
20130101; H01J 37/32568 20130101; H01L 21/6831 20130101; H01L
21/67109 20130101; H01L 21/67103 20130101; H01L 21/31116 20130101;
H01J 37/32165 20130101; H01L 21/3065 20130101 |
Class at
Publication: |
216/12 ; 216/67;
156/345.43 |
International
Class: |
C23F 1/08 20060101
C23F001/08; C23F 1/00 20060101 C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2010 |
JP |
2010-054828 |
Claims
1. A plasma etching method for performing a plasma etching on a
substrate by irradiating plasma containing charged particles and
neutral particles to the substrate, the method comprising:
controlling a distribution of reaction amounts between the
substrate and the neutral particles in a surface of the substrate
by adjusting a temperature distribution in the surface of the
substrate supported by a support; and controlling a distribution of
irradiation amounts of the charged particles in the surface of the
substrate by adjusting a gap between the substrate supported by the
support and an electrode provided so as to face the support.
2. The plasma etching method of claim 1, further comprising: an
etching process for forming lines including a mask film by etching
the mask film formed on the substrate by the irradiated plasma,
wherein, in the etching process, a distribution of line widths of
the lines in the surface of the substrate is controlled by
adjusting the distribution of reaction amounts, and a distribution
of heights of the lines in the surface of the substrate is
controlled by adjusting the distribution of irradiation
amounts.
3. The plasma etching method of claim 2, wherein the etching
process includes: a second mask film etching process for forming
the lines including a second mask film by irradiating first plasma
containing first charged particles and first neutral particles to
the substrate and etching the second mask film formed on the
substrate via a first mask film by the irradiated first plasma; and
a first mask film etching process for forming the lines including
the first mask film by irradiating second plasma containing second
charged particles and second neutral particles to the substrate on
which the lines including the second mask film are formed and
etching the first mask film by the irradiated second plasma,
wherein temperature dependency of a reaction amount between the
second mask film and the first neutral particles is lower than
temperature dependency of a reaction amount between the first mask
film and the second neutral particles.
4. The plasma etching method of claim 1, wherein the distribution
of reaction amounts in the surface of the substrate is controlled
by adjusting the temperature distribution and a distribution of a
supply amount or a composition ratio of a processing gas supplied
to the substrate.
5. The plasma etching method of claim 4, further comprising: an
etching process for forming first lines including the mask film and
spaced apart from each other at a first gap and second lines
including the mask film and spaced apart from each other at a
second gap greater than the first gap by etching the mask film
formed on the substrate by the irradiated plasma, wherein, in the
etching process, a distribution of line widths of the first lines
and the second lines in the surface of the substrate is controlled
by adjusting the distribution of reaction amounts, and a
distribution of heights of the first lines and the second lines in
the surface of the substrate is controlled by adjusting the
distribution of irradiation amounts, and temperature dependency of
a first reaction amount between the first lines and the neutral
particles is lower than temperature dependency of a second reaction
amount between the second lines and the neutral particles.
6. The plasma etching method of claim 5, wherein the etching
process includes: a second mask film etching process for forming
the first lines and the second lines each including a second mask
film by irradiating first plasma containing first charged particles
and first neutral particles to the substrate and etching the second
mask film formed on the substrate via a first mask film by the
irradiated first plasma; and a first mask film etching process for
forming the first lines and the second lines each including the
first mask film by irradiating second plasma containing second
charged particles and second neutral particles to the substrate on
which the first lines and the second lines each including the
second mask film are formed and etching the first mask film by the
irradiated second plasma, wherein temperature dependency of a
reaction amount between the second mask film and the first neutral
particles is lower than temperature dependency of a reaction amount
between the first mask film and the second neutral particles.
7. The plasma etching method of claim 3, wherein the first mask
film includes an inorganic film and the second mask film includes
an organic film, and the first neutral particles include oxygen
radicals and the second neutral particles include fluorine
radicals.
8. The plasma etching method of claim 6, wherein the first mask
film includes an inorganic film and the second mask film includes
an organic film, and the first neutral particles include oxygen
radicals and the second neutral particles include fluorine
radicals.
9. A plasma etching apparatus configured to perform a plasma
etching on a substrate by irradiating plasma containing charged
particles and neutral particles to the substrate, the apparatus
comprising: a support capable of supporting the substrate; an
electrode provided so as to face the support; a temperature
distribution adjusting unit capable of adjusting a temperature
distribution in a surface of the substrate supported by the
support; a gap adjusting unit capable of adjusting a gap between
the substrate supported by the support and the electrode; and a
controller capable of controlling a distribution of reaction
amounts between the substrate and the neutral particles in the
surface of the substrate by adjusting the temperature distribution
by the temperature distribution adjusting unit and capable of
controlling a distribution of irradiation amounts of the charged
particles in the surface of the substrate by adjusting the gap by
the gap adjusting unit.
10. The plasma etching apparatus of claim 9, wherein lines
including a mask film are formed by etching the mask film formed on
the substrate by the irradiated plasma, and when the lines are
formed, the controller controls a distribution of line widths of
the lines in the surface of the substrate by adjusting the
distribution of reaction amounts, and the controller controls a
distribution of heights of the lines in the surface of the
substrate by adjusting the distribution of irradiation amounts.
11. The plasma etching apparatus of claim 10, wherein the lines
including a second mask film are formed by irradiating first plasma
containing first charged particles and first neutral particles to
the substrate and etching the second mask film formed on the
substrate via a first mask film by the irradiated first plasma; and
the lines including the first mask film are formed by irradiating
second plasma containing second charged particles and second
neutral particles to the substrate on which the lines including the
second mask film are formed and etching the first mask film by the
irradiated second plasma, wherein temperature dependency of a
reaction amount between the second mask film and the first neutral
particles is lower than temperature dependency of a reaction amount
between the first mask film and the second neutral particles.
12. The plasma etching apparatus of claim 9, further comprising: a
supply amount distribution adjusting unit capable of adjusting a
distribution of a supply amount or a composition ratio of a
processing gas supplied to the substrate in the surface of the
substrate, wherein the controller controls the distribution of
reaction amounts by adjusting the temperature distribution by the
temperature distribution adjusting unit and by adjusting the
distribution of the supply amount or composition ratio in the
surface of the substrate by the supply amount distribution
adjusting unit.
13. The plasma etching apparatus of claim 12, wherein first lines
spaced apart from each other at a first gap and including the mask
film and second lines spaced apart from each other at a second gap
greater than the first gap and including the mask film are formed
by etching the mask film formed on the substrate by the irradiated
plasma, when the first lines and the second lines are formed, the
controller controls a distribution of line widths of the first
lines and the second lines in the surface of the substrate by
adjusting the distribution of reaction amounts, and the controller
controls a distribution of heights of the first lines and the
second lines in the surface of the substrate by adjusting the
distribution of irradiation amounts, and temperature dependency of
a first reaction amount between the first lines and the neutral
particles is lower than temperature dependency of a second reaction
amount between the second lines and the neutral particles.
14. The plasma etching apparatus of claim 13, wherein the first
lines and the second lines each including a second mask film are
formed by irradiating first plasma containing first charged
particles and first neutral particles to the substrate and etching
the second mask film formed on the substrate via a first mask film
by the irradiated first plasma; and the first lines and the second
lines each including the first mask film are formed by irradiating
second plasma containing second charged particles and second
neutral particles to the substrate on which the first lines and the
second lines each including the second mask film are formed and
etching the first mask film by the irradiated second plasma,
wherein temperature dependency of a reaction amount between the
second mask film and the first neutral particles is lower than
temperature dependency of a reaction amount between the first mask
film and the second neutral particles.
15. The plasma etching apparatus of claim 11, wherein the first
mask film includes an inorganic film and the second mask film
includes an organic film, and the first neutral particles include
oxygen radicals and the second neutral particles include fluorine
radicals.
16. The plasma etching apparatus of claim 14, wherein the first
mask film includes an inorganic film and the second mask film
includes an organic film, and the first neutral particles include
oxygen radicals and the second neutral particles include fluorine
radicals.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Japanese Patent
Application No. 2010-054828 filed on Mar. 11, 2010, the entire
disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present disclosure relates to a plasma etching method
and a plasma etching apparatus for performing a plasma etching on a
substrate.
BACKGROUND OF THE INVENTION
[0003] In manufacturing a semiconductor device, as an apparatus for
processing a substrate such as a semiconductor wafer (hereinafter,
referred to as "wafer"), there has been used a plasma etching
apparatus which performs an etching process on the wafer by
irradiating plasma to the wafer.
[0004] By way of example, a wafer yet to be processed in the
above-described plasma etching apparatus is formed of a silicon
substrate. On the wafer, a silicon dioxide (SiO.sub.2) film, an
etching target film formed of a polysilicon film, a mask film
formed of a single layer or multiple layers, a bottom
anti-reflective coating BARC, and a photoresist film (hereinafter,
referred to as "resist film") are formed in sequence from the
bottom. The resist film is exposed and developed in advance, and a
pattern having lines is formed on the resist film. By etching the
bottom anti-reflective coating, the mask film, the etching target
film in sequence, the pattern having lines is formed on the etching
target film. The above-described example in which the etching
target film is formed of a polysilicon film may be related to a
gate etching process in which an etching target film serves as a
gate electrode, for example.
[0005] However, recently, in manufacturing a semiconductor device,
a wafer becomes larger. As the wafer becomes larger, it becomes
difficult to obtain uniformity in line widths CD (critical
dimension) and a height of lines formed on the surface of the
wafer.
[0006] In the above-described etching process, a gas including
fluorine, chlorine, oxygen or the like is used as a processing gas.
When the wafer is etched, the fluorine, chlorine, oxygen or the
like included in the processing gas may be excited into plasma. The
plasma includes charged particles (hereinafter, referred to as
"ions") and neutral particles (hereinafter, referred to as
"radicals"). The surface of the wafer reacts with the plasma
including the ions and radicals, so that a reaction product is
generated and the reaction product is volatilized. In this way, the
etching process proceeds.
[0007] The reaction product generated by the reaction between the
surface of the wafer and the plasma may adhere to the lines formed
on the wafer again. Therefore, the line widths of the lines formed
by the etching process may vary depending on a probability that the
reaction product may adhere to the lines again (hereinafter,
referred to as "adhesion coefficient"). Since the adhesion
coefficient depends on a temperature of the wafer, the line widths
of the lines formed on the wafer may vary depending on the
temperature of the wafer. Accordingly, there has been suggested a
plasma etching apparatus that performs an etching process with high
uniformity in line widths of the lines formed on a wafer by
controlling a temperature distribution in a surface of the wafer
(see, for example, Patent Document 1).
[0008] The line widths of the lines formed by performing the
etching process may vary depending on a gap between adjacent lines
(pattern gap) in addition to the adhesion coefficient. That is, the
line widths of the lines formed on the wafer may vary depending on
both the temperature of the wafer and the pattern gap.
[0009] In this case, it is difficult to independently control the
line widths of the lines in an area of a large pattern gap
(hereinafter, referred to as "sparse area") and an area of a small
pattern gap (hereinafter, referred to as "dense area") only by
adjusting the temperature of the wafer. However, it may be possible
to independently control the line widths of the lines in the sparse
area and the dense area only by adjusting a supply amount or
composition ratio of a processing gas. Accordingly, there has been
suggested a plasma etching apparatus that independently controls
the line widths of the lines in a sparse area and a dense area by
adjusting a temperature distribution in a surface of a wafer and a
supply amount or composition ratio of a processing gas (see, for
example, Patent Document 2). [0010] Patent Document 1: Japanese
Translation of PCT Application No. 2008-532324 [0011] Patent
Document 2: Japanese Patent Laid-open Publication No.
2007-081216
[0012] However, in case of using the above-described plasma etching
apparatuses to perform a plasma etching process, there are some
problems as follows.
[0013] In the example disclosed in Patent Document 1, if a uniform
pattern having only a dense area is required to be formed, it is
possible to perform an etching process with high uniformity in line
widths of the lines formed on a wafer. However, as described above,
when a pattern having both a sparse area and a dense area is
required, it is impossible to perform an etching process with high
uniformity in line widths of the lines formed on a wafer.
[0014] In the example disclosed in Patent Document 2, even when a
pattern having a sparse area and a dense area is formed, it is
possible to perform an etching process with high uniformity in line
widths of lines formed on a wafer. However, if a supply amount of a
processing gas as well as a composition ratio thereof is adjusted,
there is a change in both a supply amount of radicals and a supply
amount of ions. The ions move straightforward and mainly contribute
to an etching rate. Thus, it is difficult to control the etching
rate to a required level by controlling the supply amount or
composition ratio of the processing gas. Consequently, line widths
and heights of the lines in the surface of the wafer cannot be
uniformed and cross sections of the lines cannot be uniformed.
[0015] By way of example, if the mask film includes an organic
film, as a processing gas for etching the organic film, it may be
possible to use a processing gas such as an oxygen gas (O.sub.2)
having a low adhesion coefficient or a low reaction rate between
the radicals and the mask film. In case of using the processing gas
having the radicals of the low reaction rate, even if the
temperature of the wafer and the supply amount or composition ratio
of the processing gas are adjusted within a typical variable range,
an amount of reacted radicals is hardly changed and the line widths
of the lines cannot be controlled.
BRIEF SUMMARY OF THE INVENTION
[0016] In view of the foregoing, the present disclosure provides a
plasma etching method and a plasma etching apparatus that
independently control distributions of line widths and heights of
lines in a surface of a wafer and performs an etching process with
high uniformity in cross sectional shapes of lines when the lines
are formed by etching a layered mask film including an inorganic
film and an organic film or when multiple kinds of line groups
having various gaps between adjacent lines are formed by etching a
mask film.
[0017] In order to solve the above-described problems, the present
disclosure provides the following features.
[0018] In accordance with one aspect of the present disclosure,
there is provided a plasma etching method for performing a plasma
etching on a substrate by irradiating plasma containing charged
particles and neutral particles to the substrate. The plasma
etching method includes controlling a distribution of reaction
amounts between the substrate and the neutral particles in a
surface of the substrate by adjusting a temperature distribution in
the surface of the substrate supported by a support; and
controlling a distribution of irradiation amounts of the charged
particles in the surface of the substrate by adjusting a gap
between the substrate supported by the support and an electrode
provided so as to face the support.
[0019] In accordance with another aspect of the present disclosure,
there is provided a plasma etching apparatus configured to perform
a plasma etching on a substrate by irradiating plasma containing
charged particles and neutral particles to the substrate. The
plasma etching apparatus includes a support capable of supporting
the substrate; an electrode provided so as to face the support; a
temperature distribution adjusting unit capable of adjusting a
temperature distribution in a surface of the substrate supported by
the support; a gap adjusting unit capable of adjusting a gap
between the substrate supported by the support and the electrode;
and a controller capable of controlling a distribution of reaction
amounts between the substrate and the neutral particles in the
surface of the substrate by adjusting the temperature distribution
by the temperature distribution adjusting unit and capable of
controlling a distribution of irradiation amounts of the charged
particles in the surface of the substrate by adjusting the gap by
the gap adjusting unit.
[0020] In accordance with the present disclosure, it is possible to
independently control distributions of widths and heights of lines
in a surface of a wafer and it is also possible to perform an
etching process with high uniformity in cross sectional shapes of
lines when the lines are formed by etching a layered mask film
including an inorganic film and an organic film or when multiple
kinds of line groups having various gaps between adjacent lines are
formed by etching a mask film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Non-limiting and non-exhaustive embodiments will be
described in conjunction with the accompanying drawings.
Understanding that these drawings depict only several embodiments
in accordance with the disclosure and are, therefore, not to be
intended to limit its scope, the disclosure will be described with
specificity and detail through use of the accompanying drawings, in
which:
[0022] FIG. 1 is a cross sectional view showing a schematic
configuration of a plasma etching apparatus in accordance with a
first embodiment and showing a status of an upper electrode located
at a retreat position;
[0023] FIG. 2 is a cross sectional view showing a schematic
configuration of the plasma etching apparatus in accordance with
the first embodiment and showing a status of the upper electrode
located at a process position;
[0024] FIGS. 3A and 3B provide explanatory diagrams simply showing
an upper electrode driving unit;
[0025] FIG. 4 is a transversal cross-sectional view of the upper
electrode;
[0026] FIG. 5 is a diagram for explaining a schematic configuration
of a gas supply apparatus;
[0027] FIG. 6 is a flowchart for explaining a sequence of processes
of a plasma etching method in accordance with the first
embodiment;
[0028] FIGS. 7A to 7E are cross sectional views schematically
showing wafer states in each process of the plasma etching method
in accordance with the first embodiment;
[0029] FIGS. 8A to 8C are graphs showing distributions of etching
rates ER in a longitudinal direction on a surface of a wafer when a
gap G is adjusted;
[0030] FIGS. 9A to 9D are graphs schematically showing temperature
dependency of line widths CD of line groups and gap dependency of
an etching rate ER in a longitudinal direction during a second mask
film etching process;
[0031] FIGS. 10A to 10D are graphs schematically showing
temperature dependency of line widths CD of line groups and gap
dependency of an etching rate ER in a longitudinal direction during
a first mask film etching process;
[0032] FIG. 11 is a cross sectional view showing a schematic
configuration of a plasma etching apparatus in accordance with a
second embodiment and showing a status of an upper electrode
located at a retreat position;
[0033] FIG. 12 is a cross sectional view showing a schematic
configuration of the plasma etching apparatus in accordance with
the second embodiment and showing a status of the upper electrode
located at a process position;
[0034] FIGS. 13A and 13B provide explanatory diagrams simply
showing an upper electrode driving unit;
[0035] FIG. 14 is a transversal cross sectional view of the upper
electrode;
[0036] FIG. 15 is a diagram for explaining a schematic
configuration of a gas supply apparatus;
[0037] FIG. 16 is a flowchart for explaining a sequence of
processes of a plasma etching method in accordance with the second
embodiment;
[0038] FIGS. 17A to 17E are cross sectional views schematically
showing statuses of a wafer in each process of the plasma etching
method in accordance with the second embodiment; and
[0039] FIGS. 18A to 18C are graphs schematically showing
temperature dependency of line widths CD of line groups and gap
dependency of an etching rate ER in a longitudinal direction in the
second embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Hereinafter, embodiments of the present disclosure will be
described with reference to the accompanying drawings.
First Embodiment
[0041] Referring to FIGS. 1 to 10D, a plasma etching method and a
plasma etching apparatus in accordance with a first embodiment of
the present disclosure will be explained.
[0042] First of all, referring to FIGS. 1 and 2, a plasma etching
apparatus in accordance with the present embodiment will be
explained. FIGS. 1 and 2 are cross sectional views showing
schematic configurations of the plasma etching apparatus in
accordance with the present embodiment. FIG. 1 shows a
configuration in which an upper electrode is located at a retreat
position, and FIG. 2 shows a configuration in which the upper
electrode is located at a process position.
[0043] A plasma etching apparatus 100 in accordance with the
present embodiment is configured as a parallel plate type plasma
etching apparatus, for example.
[0044] The plasma etching apparatus 100 includes a cylindrical
chamber (processing vessel) 102 made of, for example, aluminum of
which surface is anodically oxidized (alumite treated). The chamber
102 is grounded.
[0045] A susceptor support 104 formed in a substantially columnar
shape is provided at a bottom of the chamber 102 via an insulating
plate 103 made of ceramic. Further, provided on the susceptor
support 104 is a susceptor 105 serving as a lower electrode. The
susceptor 105 is connected with a high pass filter HPF 105a.
[0046] The susceptor 105 is formed to have a protruded circular
plate shape in an upper central area thereof, and an electrostatic
chuck 111 having substantially the same size as a wafer W is
provided on the susceptor 105. The electrostatic chuck 111 is
formed of an insulating member having an electrostatic electrode
112 embedded therein. The electrostatic chuck 111 is made of a
circular plate-shaped ceramic material, and the electrostatic
electrode 112 is connected with a DC power supply 113. If a
positive DC voltage is applied to the electrostatic electrode 112,
a negative potential is generated at a surface of the wafer W on
the electrostatic chuck 111's side (hereinafter, referred to as
"rear surface"), so that there is generated a potential difference
between the electrostatic electrode 112 and the rear surface of the
wafer W. The wafer W is attracted to and held on the electrostatic
chuck 111 by Coulomb force or Johnsen-Rahbek force caused by the
potential difference. By way of example, a DC voltage of about 1.5
kV is applied to the electrostatic chuck 111 from the DC power
supply 113 connected with the electrostatic electrode 112. Thus,
the wafer W is electrostatically attracted to the electrostatic
chuck 111.
[0047] Further, the susceptor support 104 and the susceptor 105
serve as a supporting member of the present disclosure.
[0048] The susceptor 105 is connected with a first high frequency
power supply 114 via a first matching unit 115 and a second high
frequency power supply 116 via a second matching unit 117. The
first high frequency power supply 114 applies a bias power, which
is a high frequency power having a relatively low frequency of, for
example, about 13.6 MHz, to the susceptor 105. The second high
frequency power supply 116 applies a power for plasma generation,
which is a high frequency power having a relatively high frequency
of, for example, about 40 MHz, to the susceptor 105. The susceptor
105 applies the power for plasma generation to the inside of the
chamber 102.
[0049] Furthermore, provided through the insulating plate 103, the
susceptor support 104, the susceptor 105, and the electrostatic
chuck 111 is a gas passage 118 for supplying a heat transfer medium
(for example, a backside gas such as a He gas) to the rear surface
of the wafer W as a target object to be processed. Heat is
transferred between the susceptor 105 and the wafer W through this
heat transfer medium, so that the wafer W is maintained at a
predetermined temperature.
[0050] An annular focus ring 119 is provided at an upper periphery
of the susceptor 105 so as to surround the wafer W supported on the
electrostatic chuck 111. The focus ring 119 is made of a dielectric
material such as ceramic or quartz or a conductive material such as
single crystalline silicon which is the same as a material of the
wafer W. Therefore, a distribution region of the plasma is extended
from the wafer W to the focus ring 119, so that plasma density
above an outer peripheral area of the wafer W can be maintained at
substantially the same level as plasma density above a central area
of the wafer W. Thus, plasma etching uniformity in the surface of
the wafer W can be improved.
[0051] There will be explained a temperature distribution adjusting
unit 106 which adjusts a temperature distribution in the surface of
the wafer W supported on the susceptor 105. The temperature
distribution adjusting unit 106 includes heaters 106a and 106b,
heater power supplies 106c and 106d, thermometers 106e and 106f,
and coolant paths 107a and 107b.
[0052] Within the susceptor support 104, the central heater 106a is
provided at a central area and the outer peripheral heater 106b is
provided at an outer peripheral area. The central heater 106a is
connected with the central heater power supply 106c and the outer
peripheral heater 106b is connected with the outer peripheral
heater power supply 106d. Each of the central heater power supply
106c and the outer peripheral heater power supply 106d
independently controls a power applied to the central heater 106a
and the outer peripheral heater 106b, so that it is possible to
control a temperature distribution of the susceptor support 104 and
the susceptor 105 in a radial direction. Thus, it is possible to
control a temperature distribution of the wafer W in a radial
direction.
[0053] Further, within the susceptor support 104, the central
thermometer 106e and the outer peripheral thermometer 106f are
provided. The central thermometer 106e and the outer peripheral
thermometer 106f measure temperatures of the central area and the
outer peripheral area of the susceptor support 104. Thus,
temperatures at a central area and an outer peripheral area of the
wafer W can be calculated. The temperatures measured by the central
thermometer 106e and the outer peripheral thermometer 106f are
transmitted to an apparatus controller 190. The apparatus
controller 190 adjusts output of the central heater power supply
106c and the outer peripheral heater power supply 106d such that
the wafer W's temperature calculated from the measured temperatures
becomes a target temperature.
[0054] Furthermore, within the susceptor support 104, the central
coolant path 107a may be provided at the central area and the outer
peripheral coolant path 107b may be provided at the outer
peripheral area. By way of example, cooling water and
fluorocarbon-based coolant having different temperatures from each
other may be circulated in the coolant paths 107a and 107b,
respectively. In this case, a coolant is introduced to the central
coolant path 107a through a central inlet line 108a; circulated in
the central coolant path 107a; and then discharged through a
central outlet line 109a. Meanwhile, a coolant is introduced to the
outer peripheral coolant path 107b through an outer peripheral
inlet line 108b; circulated in the outer peripheral coolant path
107b; and then discharged through an outer peripheral outlet line
109b.
[0055] A temperature of the susceptor 105 is adjusted by heating by
the heaters 106a and 106b and cooling by the coolants. Therefore,
the wafer W is adjusted to a preset temperature by a heat transfer
from the susceptor 105 as well as a radiation heat transfer from
the plasma or irradiation of the ions contained in the plasma. In
the present embodiment, the susceptor support 104 includes the
central heater 106a and the central coolant path 107a at the
central area and the outer peripheral heater 106b and the outer
peripheral coolant path 107b at the outer peripheral area.
Therefore, the temperatures at the central area and the outer
peripheral area of the wafer W can be adjusted independently, and
the temperature distribution in the surface of the wafer W can be
adjusted.
[0056] There may be a non-illustrated space between the central
heater 106a and the outer peripheral heater 106b or between the
central coolant path 107a and the outer peripheral coolant path
107b, and the space may serve as a heat insulating layer. The heat
insulating layer thermally isolates the central heater 106a from
the outer peripheral heater 106b or the central coolant path 107a
from the outer peripheral coolant path 107b so that it is easy to
make a great temperature difference between the central area of the
wafer W and the outer peripheral area of the wafer W.
[0057] An upper electrode 120 facing the susceptor 105 in parallel
is provided above the susceptor 105. The upper electrode 120 can be
moved in one direction, for example, in a vertical direction, by an
upper electrode driving unit 200. Since the upper electrode 120 can
be moved in the vertical direction, a thickness of a space between
the upper electrode 120 and the susceptor 105, i.e., a distance G
(hereinafter, referred to as "gap") between the upper electrode 120
and the susceptor 105 can be adjusted. By adjusting the gap G,
plasma can be distributed appropriately in the space between the
upper electrode 120 and the susceptor 105 in the chamber 102 as
described below. Further, it is possible to adjust a distribution
of a plasma irradiation amount to the surface of the wafer W
supported on the susceptor 105.
[0058] A maximum value of a vertical moving amount of the upper
electrode 120 driven by the upper electrode driving unit 200 can be
set to be, for example, about 70 mm. In this case, the gap G can be
adjusted within a range of about 20 mm to about 90 mm.
[0059] The plasma etching apparatus may have a configuration
rotated 90 degrees from the configurations illustrated in FIGS. 1
and 2 or may have an upside-down configuration thereof. Further,
the upper electrode 120 serves as an electrode of the present
disclosure. The upper electrode driving unit 200 serves as a gap
adjusting unit of the present disclosure.
[0060] The upper electrode 120 is supported by an upper inner wall
of the chamber 102 via a bellows 122. The bellows 122 is fixed to
the upper inner wall of the chamber 102 via an annular upper flange
122a by a fixing member such as a bolt and fixed to a surface of
the upper electrode 120 via an annular lower flange 122b by a
fixing member such as a bolt.
[0061] The upper electrode 120 is connected with a DC power supply
123. Further, the upper electrode 120 is connected with a low pass
filter LPF 124.
[0062] A bottom area of the chamber 102 is connected with a gas
exhaust pipe 131 and the gas exhaust pipe 131 is connected with a
gas exhaust unit 135. The gas exhaust unit 135 includes a vacuum
pump such as a turbo-molecular pump and adjusts the internal
pressure of the chamber 102 to a preset depressurized atmosphere
(for example, about 0.67 Pa or less). Further, a gate valve 132 is
installed at a sidewall of the chamber 102. By opening the gate
valve 132, the wafer W can be loaded into the chamber 102 and
unloaded from the chamber 102. Furthermore, by way of example, when
the wafer W is transferred, a transfer arm may be used.
[0063] Hereinafter, a configuration of the upper electrode driving
unit 200 will be explained in detail with reference to FIGS. 3A and
3B. FIGS. 3A and 3B provide explanatory diagrams simply showing the
upper electrode driving unit. To be specific, FIG. 3A shows the
upper electrode driving unit located at a retreat position, and
FIG. 3B shows the upper electrode driving unit located at a process
position.
[0064] The upper electrode driving unit 200 includes a
substantially cylindrical support member 204 which supports the
upper electrode 120. The support member 204 is fixed at an
approximate center of the top of the upper electrode 120 by a bolt
or the like.
[0065] The support member 204 is installed so as to be allowed to
enter a hole 102a formed at an approximate center of an upper wall
of the chamber 102. To be specific, an outer surface of the support
member 204 is supported at an inner wall of the hole 102a of the
chamber 102 via a slide mechanism 210.
[0066] By way of example, the slide mechanism 210 includes a guide
member 216 fixed to a vertical part of a fixing member 214 having
an L-shaped cross section at an upper area of the chamber 102; and
a rail 212 provided on the outer surface of the support member 204
in one direction (vertical direction in the present embodiment) and
supported by the guide member 216 so as to be slidably moved.
[0067] The fixing member 214 that fixes the guide member 216 of the
slide mechanism 210 has a horizontal part which is fixed at the
upper area of the chamber 102 via an annular horizontal position
adjusting plate 218. The horizontal position adjusting plate 218 is
configured to adjust a horizontal position of the upper electrode
120. By way of example, the horizontal position adjusting plate 218
is fixed to the chamber 102 by a multiple number of bolts arranged
at a same interval in a circumferential direction of the horizontal
position adjusting plate 218, and an inclination of the horizontal
position adjusting plate 218 with respect to a horizontal direction
may be adjusted by a protruded height of the bolts. By adjusting
the inclination of the horizontal position adjusting plate 218 with
respect to the horizontal direction, an inclination of the guide
member 216 of the slide mechanism 210 with respect to a vertical
direction can be adjusted. Therefore, an inclination of the upper
electrode 120 supported via the guide member 216 with respect to a
horizontal direction can be adjusted. Consequently, a horizontal
position of the upper electrode 120 can be maintained all the time
by a simple manipulation.
[0068] A pneumatic cylinder 220 for driving the upper electrode 120
is provided above the chamber 102 via a cylindrical body 201. A
lower end of the cylindrical body 201 is airtightly sealed so as to
cover the hole 102a of the chamber 102 and an upper end of the
cylindrical body 201 is airtightly sealed with a lower end of the
pneumatic cylinder 220.
[0069] The pneumatic cylinder 220 includes a rod 202 which can be
moved in one direction. A lower end of the rod 202 is connected
with an approximate center of the top of the support member 204 by
a bolt or the like. By driving the rod 202 of the pneumatic
cylinder 220, the upper electrode 120 is moved by the support
member 204 in one direction along with the slide mechanism 210. The
rod 202 is formed in a cylinder shape and an inner space of the rod
202 communicates with a center hole formed at an approximate center
of the support member 204 so as to be opened to the atmosphere.
Therefore, a line for grounding the upper electrode 120 via the low
pass filter LPF 124 and a power supply line for applying a DC
voltage from the DC power supply 123 to the upper electrode 120 may
be connected with the upper electrode 120 via the inner space of
the rod 202 and the center hole of the support member 204.
[0070] By way of example, provided at a side area of the pneumatic
cylinder 220 is a linear encoder 205 as a position detection unit
for detecting a position of the upper electrode 120. Meanwhile,
provided at an upper end of the rod 202 of the pneumatic cylinder
220 is an upper end member 207 having an extended part 207a
extended from the rod 202 in a lateral direction. The extended part
207a of the upper end member 207 is in contact with a detector 205a
of the linear encoder 205. Since the upper end member 207 is moved
along with the upper electrode 120, a position of the upper
electrode 120 can be detected by the linear encoder 205.
[0071] The pneumatic cylinder 220 includes a cylinder main body 222
between an upper support plate 224 and a lower support plate 226.
Provided on an outer surface of the rod 202 is an annular partition
member 208 which divides the inside of the pneumatic cylinder 220
into an upper space 232 and a lower space 234.
[0072] As depicted in FIGS. 3A and 3B, compressed air is introduced
from an upper port 236 of the upper support plate 224 into the
upper space 232 of the pneumatic cylinder 220. Further, compressed
air is introduced from a lower port 238 of the lower support plate
226 into the lower space 234 of the pneumatic cylinder 220. By
controlling an amount of the air introduced from the upper port 236
and the lower port 238 into the upper space 232 and the lower space
234, respectively, it is possible to control the rod 202 to be
moved in one direction (vertical direction in this embodiment). The
amount of the air introduced to the pneumatic cylinder 220 is
controlled by a pneumatic circuit 300 provided in the vicinity of
the pneumatic cylinder 220.
[0073] The upper electrode driving unit 200 includes a controller
290 and the controller 290 is connected with the apparatus
controller 190. A control signal from the apparatus controller 190
is transmitted to the controller 290 and each component of the
upper electrode driving unit 200 is controlled by the controller
290.
[0074] Hereinafter, there will be explained a supply amount
distribution adjusting unit 130 that adjusts a distribution of a
supply amount of a plasma gas supplied to the wafer W supported on
the susceptor 105. The supply amount distribution adjusting unit
130 includes a shower head 140 configured as one body with the
upper electrode 120, and a gas supply apparatus 150.
[0075] Referring to FIGS. 1, 2 and 4, a configuration of the shower
head 140 will be explained. FIG. 4 is a transversal cross sectional
view of the upper electrode.
[0076] The shower head 140 is configured to supply a mixed gas onto
the wafer W supported on the susceptor 105. The shower head 140
includes a circular electrode plate 141 (upper electrode 120)
having a multiple number of gas discharge holes 141a and an
electrode support body 142 which supports an upper surface of the
electrode plate 141 and is detachable therefrom. The electrode
support body 142 is formed in a circular plate shape having the
same diameter as the electrode plate 141 and includes a circular
buffer room 143 therein. By way of example, as depicted in FIG. 4,
in the buffer room 143, an annular partition wall member 145 formed
of an O-ring is installed and divides the buffer room 143 into a
first buffer room 143a on a central side and a second buffer room
143b on an outer peripheral side. The first buffer room 143a faces
a central area of the wafer W on the susceptor 105 and the second
buffer room 143b faces an outer peripheral area of the wafer W on
the susceptor 105. Bottom surfaces of the respective buffer rooms
143a and 143b communicate with the gas discharge holes 141a, and
the mixed gas may be discharged from the first buffer room 143a
toward the central area of the wafer W and from the second buffer
room 143b toward the outer peripheral area of the wafer W. Further,
the mixed gas is supplied to the buffer rooms 143a and 143b by the
gas supply apparatus 150.
[0077] Hereinafter, referring to FIGS. 1, 2 and 5, the gas supply
apparatus 150 will be explained. FIG. 5 is a diagram for explaining
a schematic configuration of the gas supply apparatus.
[0078] As depicted in FIG. 5, the gas supply apparatus 150 includes
a first gas box 161 which accommodates a multiple number of, for
example, three gas supply sources 160a, 160b, and 160c and a second
gas box 163 which accommodates a multiple number of, for example,
two additional gas supply sources 162a and 162b. In the present
embodiment, by way of example, a fluorocarbon-based fluorine
compound as a processing gas, for example, C.sub.XF.sub.Y such as
CF.sub.4, C.sub.4F.sub.6, C.sub.4F.sub.8, and C.sub.5F.sub.8 is
sealed in the gas supply source 160a. Further, by way of example,
an oxygen (O.sub.2) gas as a gas for controlling adhesion of a
CF-based reaction product is sealed in the gas supply source 160b.
A rare gas as a carrier gas, for example, an Ar gas is sealed in
the gas supply source 160c. By way of example, a C.sub.XF.sub.Y gas
capable of promoting an etching process is sealed in the additional
gas supply source 162a, and an oxygen (O.sub.2) gas capable of
controlling adhesion of a CF-based reaction product is sealed in
the additional gas supply source 162b.
[0079] Each of the gas supply sources 160a to 160c of the first gas
box 161 is connected with a mixing line 170 where various gases
from each of the gas supply sources 160a to 160c are joined and
mixed together. In the mixing line 170, a mass flow controller 171
for adjusting a flow rate of a gas from each of the gas supply
sources 160a to 160c is provided for each gas supply source. The
mixing line 170 is connected with a first branch line 172 and a
second branch line 173 which divide the mixed gas mixed at the
mixing line 170. The first branch line 172 is connected with the
first buffer room 143a of the shower head 140. The second branch
line 173 is connected with the second buffer room 143b of the
shower head 140.
[0080] A pressure adjusting unit 174 is installed on the first
branch line 172. In the same manner, a pressure adjusting unit 175
is installed on the second branch line 173. The pressure adjusting
unit 174 includes a pressure gauge 174a and a valve 174b. Likewise,
the pressure adjusting unit 175 includes a pressure gauge 175a and
a valve 175b. A measurement result measured by the pressure gauge
174a of the pressure adjusting unit 174 and a measurement result
measured by the pressure gauge 175a of the pressure control unit
175 may be outputted to a pressure control apparatus 176. The
pressure control apparatus 176 adjusts an opening/closing degree of
each valve 174b or 175b based on the measurement results of the
pressure gauges 174a and 175a and controls a pressure ratio, i.e.,
a flow rate ratio of the mixed gas in the first branch line 172 and
the second branch line 173. Further, when setting a supplied gas,
the pressure control apparatus 176 may adjusts the pressure ratio
of the mixed gas flowing through the first branch line 172 and the
second branch line 173 to a preset target pressure ratio in a state
where an additional gas is not supplied from the second gas box
163, which will be described later, to the second branch line 173
and the pressure control apparatus 176 may set opening/closing
degrees of the valves 174b and 175b in that state.
[0081] Each additional gas supply source 162a or 162b of the second
gas box 163 is connected with an additional gas supply line 180
communicating with, for example, the second branch line 173. By way
of example, the additional gas supply line 180 is connected with
each additional gas supply source 162a or 162b and the additional
gas supply line 180 is connected with the second branch line 173 on
the way. The additional gas supply line 180 is connected with a
downstream side of the pressure adjusting unit 175. On the
additional gas supply line 180, a mass flow controller 181 for
controlling a flow rate of an additional gas from each additional
gas supply source 162a or 162b is provided for each additional gas
supply source. With this configuration, the additional gases from
the second gas box 163 may be selected and mixed together to be
supplied to the second branch line 173.
[0082] Operations of the mass flow controller 171 in the first gas
box 161 and the mass flow controller 181 in the second gas box 163
are controlled by, for example, the apparatus controller 190, which
will be described later, of the plasma etching apparatus 100.
Accordingly, the apparatus controller 190 may control a start and a
stop of supply of various gases from the first gas box 161 and the
second gas box 163, and control supply amounts of various
gases.
[0083] Further, the second gas box 163 and the additional gas
supply line 180 may be omitted from the gas supply apparatus
150.
[0084] The plasma etching apparatus 100 includes the apparatus
controller 190. The apparatus controller 190 includes a
non-illustrated operation processing unit such as a CPU and a
non-illustrated storage medium such as a hard disk. The apparatus
controller 190 controls an operation of each component such as the
first high frequency power supply 114, the second high frequency
power supply 116, the temperature distribution adjusting unit 106,
the upper electrode driving unit 200, or the supply amount
distribution adjusting unit 130. Further, by way of example, when
the apparatus controller 190 controls the operation of each
component, the CPU of the apparatus controller 190 controls the
operation of each component according to a program corresponding to
each etching process which is stored in, for example, the hard disk
of the apparatus controller 190.
[0085] The apparatus controller 190 serves as a controller of the
present disclosure.
[0086] Hereinafter, referring to FIG. 6 and FIGS. 7A to 7E, there
will be explained a plasma etching method using the plasma etching
apparatus 100. FIG. 6 is a flowchart for explaining a sequence of
processes of a plasma etching method in accordance with the present
embodiment. FIGS. 7A to 7E are cross sectional views schematically
showing statuses of a wafer in each process of the plasma etching
method in accordance with the present embodiment.
[0087] As depicted in FIG. 6, the plasma etching method in
accordance with the present embodiment includes a resist pattern
forming process (step S11), an anti-reflective coating etching
process (step S12), a second mask film etching process (step S13),
a first mask film etching process (step S14), and an etching target
film etching process (step S15).
[0088] Further, the second mask film etching process (step S13) and
the first mask film etching process (step S14) are included in an
etching process of the present disclosure.
[0089] Above all, the resist pattern forming process (step S11) is
performed. In the resist pattern forming process (step S11), a
resist pattern having line groups 16a and 16b formed of a resist
film 16 is formed on a surface of a wafer W on which a second mask
film 14 is already formed via a first mask film 13. FIG. 7A shows a
wafer state in the resist pattern forming process (step S11).
[0090] Herein, a line group is a structure extended in a certain
direction and spaced apart from an adjacent line group in a
direction orthogonal to the extended direction when viewed from the
top.
[0091] There is prepared in advance a substrate in which an
insulating film 11, an etching target film 12, a first mask film
13, a second mask film 14, and an anti-reflective coating 15 are
formed in sequence from the surface of a wafer 10 made of, for
example, a silicon.
[0092] The etching target film 12 is a film to be etched finally in
the plasma etching method in accordance with the present
embodiment. By way of example, the insulating film may be a silicon
oxide (SiO.sub.2) film made of, e.g., tetraethoxysilane (TEOS)
serving as a gate insulating film, and the etching target film 12
after an etching process may be a polysilicon film serving as a
gate electrode.
[0093] The first mask film 13, to which a shape of the second mask
film 14 as an upper layer is transferred, serves as a hard mask
when the etching target film 12 as a lower layer is etched. The
first mask film 13 may have a high selectivity as compared to the
etching target film 12 when the etching target film 12 is etched.
That is, a ratio of an etching rate of the etching target film 12
to an etching rate of the first mask film 13 may be high. For
example, as the first mask film 13, it may be possible to use an
inorganic film such as a SiN film and a SiON film. A thickness of
the first mask film 13 may be set to be, for example, about 200
nm.
[0094] The second mask film 14, to which a resist pattern shape of
the resist film 16 as an upper layer is transferred, serves as a
mask when the first mask film 13 as a lower layer is etched. The
second mask film 14 has a high selectivity as compared to the first
mask film 13 when the first mask film 13 is etched. That is, a
ratio of the etching rate of the first mask film 13 to an etching
rate of the second mask film 14 is high. By way of example, as the
second mask film 14, it may be possible to use an organic film made
of a variety of organic materials such as amorphous carbon formed
by chemical vapor deposition CVD, polyphenol formed by spin-on
techniques or a photoresist such as a i-line resist. A thickness of
the second mask film 14 may be set to be, for example, about 280
nm.
[0095] The anti-reflective coating 15 serves as an antireflection
film when a photolithography process is performed on the resist
film 16 formed on the anti-reflective coating 15. For example, as
the anti-reflective coating 15, it is possible to use a film made
of C.sub.xH.sub.yO.sub.z referred to as an organic BARC. A
thickness of the anti-reflective coating 15 may be set to be, for
example, 80 nm.
[0096] The resist film 16 is formed on the wafer 10 on which the
above-described films from the insulating film 11 to the
anti-reflective coating 15 are layered. A pattern of the formed
resist film 16 is exposed to lights and developed, so that the
resist pattern having the line groups 16a and 16b formed of the
resist film 16 is formed. As depicted in FIG. 7A, a resist pattern
formed of the resist film 16 has lines of line widths CD and
heights H. On the left of FIG. 7A, there is formed an area A1
(hereinafter, referred to as "dense area") where the lines 16a are
arranged at a relatively small distance D1 and on the right of FIG.
7A, there is formed an area A2 (hereinafter, referred to as "sparse
area") where the lines 16b are arranged at a relatively large
distance D2 (larger than the distance D1). The line groups 16a and
16b serve as a mask when the anti-reflective coating 15 and the
second mask film 14 are etched. As the resist film 16, it may be
possible to use, for example, an ArF resist. Further, a thickness
of the resist film 16 may be set to be, for example, about 170
nm.
[0097] Herein, a line width CD is a width of a line in a direction
orthogonal to an extended direction of the line.
[0098] The line in the dense area A1 serves as a first line of the
present disclosure. Further, a line in the sparse area A2 serves as
a second line of the present disclosure.
[0099] After the resist pattern forming process (step S11) and
before the anti-reflective coating etching process (step S12), a
slimming process or a trimming process may be performed, so that a
line width adjusting process for reducing line widths CD of the
line groups 16a and 16b of the resist film 16 may be performed. If
the line width adjusting process is performed, a line width CD
indicates a width of the line after the line width adjusting
process.
[0100] Then, the anti-reflective coating etching process (step S12)
is performed. In the anti-reflective coating etching process (step
S12), plasma is irradiated onto the wafer 10 and the
anti-reflective coating 15 is etched by the irradiated plasma by
using the line groups 16a and 16b formed of the resist film 16 as a
mask. FIG. 7B shows a status of a wafer in the anti-reflective
coating etching process (step S12).
[0101] In response to a control signal from the apparatus
controller 190, the upper electrode driving unit 200 is moved in a
vertical direction and a distance between the susceptor 105 and the
upper electrode 120 is set to be a preset gap G. Thereafter, in
response to a control signal from the apparatus controller 190, a
predetermined supply amount FLI of a processing gas is supplied to
the central area of the wafer W supported on the susceptor 105 in
the chamber 102 from the gas supply apparatus 150 via the first
branch line 172 and the first buffer room 143a of the shower head
140. Further, in response to a control signal from the apparatus
controller 190, a predetermined supply amount FLO of a processing
gas is supplied to the outer peripheral area of the wafer W
supported on the susceptor 105 in the chamber 102 from the gas
supply apparatus 150 via the second branch line 173 and the second
buffer room 143b of the shower head 140. Then, in response to a
control signal from the apparatus controller 190, a first high
frequency power is applied from the first high frequency power
supply 114 and a second high frequency power is applied from the
second high frequency power supply 116. The processing gas
introduced into the chamber 102 is excited into plasma by the high
frequency power applied into the chamber 102 from the first high
frequency power supply 114 and the second high frequency power
supply 116 which are connected with the susceptor 105.
[0102] The excited plasma contains ions, electrons, and radicals.
The ions are attracted toward the wafer 10 supported on the
susceptor 105 by a bias voltage generated between the upper
electrode 120 and the susceptor 105 and react with the surface of
the wafer 10, so that the wafer 10 is etched. Meanwhile, the
radicals are not attracted by a bias potential but diffuse to the
surface of the wafer 10 and react with the surface of the wafer 10,
so that the wafer 10 is etched. Consequently, the anti-reflective
coating 15 is etched using the line groups 16a and 16b formed of
the resist film 16 as a mask.
[0103] Further, the ions serve as charged particles of the present
disclosure and the radicals serve as neutral particles of the
present disclosure.
[0104] In the anti-reflective coating etching process (step S12),
as the processing gas, it may be possible to use a mixed gas of a
CF-based gas such as CF.sub.4, C.sub.4F.sub.8, CHF.sub.3,
CH.sub.3F, and CH.sub.2F.sub.2 with an Ar gas, or the mixed gas
further including an oxygen gas if necessary.
[0105] Subsequently, the second mask film etching process (steps
S13) is performed. In the second mask film etching process (steps
S13), the second mask film 14 is etched by plasma irradiated to the
wafer 10 using line groups 15a and 15b formed of the resist film 16
and the anti-reflective coating 15 as a mask, so that line groups
14a and 14b including the second mask film 14 are formed. FIG. 7C
shows a wafer state in the second mask film etching process (step
S13).
[0106] In the second mask film etching process (step S13), a
temperature distribution in the surface of the wafer 10 supported
on the susceptor 105 is adjusted and a distribution of a supply
amount of the processing gas supplied to the wafer 10 in the
surface of the wafer 10 is adjusted. By these adjustments, a
distribution of a reaction amount between the radicals of the
plasma in the surface of the wafer 10 and the surface of the wafer
10 is controlled. By controlling the distribution of the reaction
amounts it is possible to control a distribution of line widths CD
of the line groups 14a and 14b in the surface of the wafer 10.
[0107] In response to a control signal from the apparatus
controller 190 to the temperature distribution adjusting unit 106,
temperatures of the central and outer peripheral thermometers 106e
and 106f are adjusted to predetermined temperatures TI and TO,
respectively. Further, in response to the control signal from the
apparatus controller 190 to the temperature distribution adjusting
unit 106, the central heater 106a and the outer peripheral heater
106b are controlled independently. Consequently, it is possible to
set the temperature TI at the central area of the wafer 10 to be
different from the temperature TO at the outer peripheral area of
the wafer 10, and, thus, the temperature distribution in the
surface of the wafer 10 can be adjusted.
[0108] Further, in response to a control signal from the apparatus
controller 190 to the supply amount distribution adjusting unit
130, a gas from the first gas box 161 is supplied to the first
buffer room 143a and the second buffer room 143b of the shower head
140 via each of the first branch line 172 and the second branch
line 173. Since the flow rates in the first branch line 172 and the
second branch line 173 are adjusted by the pressure adjusting units
174 and 175, the flow rate FLI of the processing gas supplied to
the central area of the wafer 10 can be set to be different from
the flow rate FLO of the processing gas supplied to the outer
peripheral area of the wafer 10. Consequently, it is possible to
adjust the distribution of supply amounts of the processing gas in
the surface of the wafer 10.
[0109] As described above, by adjusting the temperature
distribution and the distribution of supply amounts of the
processing gas in the surface of the wafer 10, it is possible to
control the distribution of line widths CD of the line groups 14a
and 14b formed of the second mask film 14 in the surface of the
wafer 10.
[0110] In the second mask film etching process (step S13), in
response to a control signal from the apparatus controller 190 to
the upper electrode driving unit 200, a gap G between the wafer 10
supported on the susceptor 105 and the upper electrode 120 facing
the wafer 10 is adjusted. By adjusting the gap G, it is possible to
control a distribution of irradiation amounts of ions in the
surface of the wafer 10 and a distribution of etching rates ER in a
longitudinal direction (depth direction). Further, by controlling
the distribution of etching rates ER in the longitudinal direction
(depth direction), it is possible to control a distribution of
heights H of the line groups 14a and 14b in the surface of the
wafer 10.
[0111] In the second mask film etching process (step S13), it may
be possible to use an oxygen (O.sub.2) gas as the processing
gas.
[0112] Thereafter, the first mask film etching process (step S14)
is performed. In the first mask film etching process (step S14),
the first mask film 13 is etched by plasma irradiated to the wafer
10 using the line groups 14a and 14b formed of the second mask film
14 as a mask, so that line groups 13a and 13b including the first
mask film 13 are formed. FIG. 7D shows a status of a wafer in the
first mask film etching process (step S14).
[0113] In the first mask film etching process (step S14), a
temperature distribution in the surface of the wafer 10 supported
on the susceptor 105 is adjusted and a distribution of supply
amounts of the processing gas supplied to the wafer 10 in the
surface of the wafer 10 is adjusted. By these adjustments, a
distribution of reaction amounts between the radicals of the plasma
in the surface of the wafer 10 and the surface of the wafer 10 is
controlled. By controlling the distribution of reaction amounts, it
is possible to control a distribution of line widths CD of the line
groups 13a and 13b in the surface of the wafer 10.
[0114] Further, in the first mask film etching process (step S14),
in response to a control signal from the apparatus controller 190
to the upper electrode driving unit 200, a gap G between the wafer
10 supported on the susceptor 105 and the upper electrode 120
provided so as to face the wafer 10 is adjusted. By adjusting the
gap G, it is possible to control a distribution of irradiation
amounts of ions in the surface of the wafer 10 and a distribution
of etching rates ER in a longitudinal direction (depth direction).
Further, by controlling the distribution of etching rates ER in the
longitudinal direction (depth direction), it is possible to control
a distribution of heights H of the line groups 13a and 13b in the
surface of the wafer 10.
[0115] In the first mask film etching process (step S14), as the
processing gas, it may be possible to use a mixed gas of a CF-based
gas such as CF.sub.4, C.sub.4F.sub.8, CHF.sub.3, CH.sub.3F, and
CH.sub.2F.sub.2 with an Ar gas, or the mixed gas further including
an oxygen (O.sub.2) gas if necessary.
[0116] There may be a following relationship between the second
mask film etching process (step S13) and the first mask film
etching process (step S14). That is, temperature dependency of a
reaction amount between the radicals and a surface of the first
mask film 13 in the first mask film etching process (step S14) may
be greater than temperature dependency of a reaction amount between
the radicals and a surface of the second mask film 14 in the second
mask film etching process (step S13). That is because, as described
below, if the relationship is satisfied, it is impossible to
independently control a distribution of line widths CD of the line
groups and a distribution of heights H of the line groups in the
surface of the wafer 10 in the conventional method.
[0117] Then, the etching target film etching process (step S15) is
performed. In the etching target film etching process (step S15),
the etching target film 12 is etched by plasma irradiated to the
wafer 10 using the line groups 13a and 13b formed of the first mask
film 13 as a mask, so that line groups 12a and 12b including the
etching target film 12 are formed. FIG. 7E shows a status of a
wafer in the etching target film etching process (step S15).
[0118] In the etching target film etching process (step S15), such
control as performed in the first mask film etching process (step
S14) may be performed. That is, by adjusting the temperature
distribution and the distribution of supply amounts of the
processing gas in the surface of the wafer 10, it is possible to
control a distribution of line widths CD of the line groups 12a and
12b in the surface of the wafer 10, and by adjusting the gap G
between the upper electrode 120 and the wafer 10, it is possible to
control a distribution of heights H of the line groups 12a and 12b
in the surface of the wafer 10.
[0119] In the etching target film etching process (step S15), as
the processing gas, it may be possible to use a mixed gas of a
CF-based gas such as CF.sub.4, C.sub.4F.sub.8, CHF.sub.3,
CH.sub.3F, and CH.sub.2F.sub.2 with an Ar gas, or the mixed gas
further including an oxygen (O.sub.2) gas if necessary.
[0120] Hereinafter, there will be explained a case where a
distribution of line widths CD of lines and a distribution of
heights H of the lines in a surface of a wafer are independently
controlled and an etching process can be performed with high
uniformity in cross sectional shapes of lines when the etching
process is performed on the wafer using the plasma etching method
in accordance with the present embodiment.
[0121] As described above, the plasma of the processing gas
contains the ions and the radicals. Since the ions are accelerated
by the bias voltage generated between the upper electrode 120 and
the susceptor 105 and irradiated to the wafer, an anisotropic
etching process is mainly performed on the wafer. Therefore, the
lines to be formed are mainly etched in a longitudinal direction
(depth direction). Meanwhile, the radicals are not accelerated by
the bias voltage, and, thus, an isotropic etching process is mainly
performed on the wafer. Therefore, the lines to be formed are
mainly etched in a width direction. Further, a reaction product
generated by a reaction between a surface of the wafer and the
plasma may adhere to the lines again. Here, a line width CD of the
lines may vary depending on an adhesion coefficient which indicates
a probability that the reaction product adheres to the line again.
Since the adhesion coefficient depends on a temperature of the
wafer, the line width CD of the lines may vary depending on the
temperature of the wafer.
[0122] As described above, in the plasma etching process, an
etching condition (parameter) controlling an etching rate ER in a
vertical direction (longitudinal direction) is different from an
etching condition (parameter) controlling a line width CD of the
lines in the surface of the wafer.
[0123] When plasma is irradiated to the wafer, the parameter
controlling the etching rate ER in the longitudinal direction
includes an amount of ions (ion flux) approximately vertically
incident to a surface of the wafer per unit time; energy of ions;
and an adsorption amount of radicals adsorbed to the surface of the
wafer. When the radicals are supplied sufficiently, the most
dominant parameter in controlling the etching rate ER in the
longitudinal direction is the ion flux. In order to control a
distribution of line widths CD of lines formed by an etching
process in the surface of the wafer, it is necessary to
independently control a distribution of the ion flux and a
distribution of reaction amounts of the radicals.
[0124] Herein, a method of controlling a distribution of an ion
flux in the surface of the wafer may include the following three
methods: a method of adjusting a distribution of a magnetic field
by using a permanent magnet or an electromagnet; a method of
adjusting a distribution of an electric field by dividing an
electrode and adjusting impedance; and a method of forming
protrusions or recesses in the upper electrode or adjusting a
distance (gap) between the upper electrode and the lower
electrode.
[0125] Among these three methods of controlling the distribution of
the ion flux, in accordance with the method of adjusting the
distribution of the magnetic field, the distribution of the ion
flux cannot be controlled stably. Especially, a magnetic field
exists near the wafer, and, thus, arcing may occur easily. Further,
in accordance with the method of adjusting the distribution of the
electric field by dividing an electrode and adjusting impedance,
the distribution of the ion flux cannot be made substantially
uniform.
[0126] Meanwhile, in accordance with the method of adjusting the
gap G, the ion flux may be adjusted in a wide range. By adjusting
the ion flux, it is possible to control the distribution of etching
rates ER in the longitudinal direction in the surface of the
wafer.
[0127] Hereinafter, referring to FIGS. 8A to 8C, gap dependency of
an etching rate ER in a longitudinal direction will be explained.
FIGS. 8A to 8C are graphs showing distributions of etching rates ER
in a longitudinal direction in a surface of a wafer when a gap G is
adjusted. The gaps G in FIGS. 8A, 8B, and 8C are 30 mm, 50 mm, and
90 mm, respectively. In FIGS. 8A to 8C, a horizontal axis
represents a distance X from a center in a radial direction and a
vertical axis represents an etching rate ER in a longitudinal
direction. Further, a wafer of 300 mmO is used.
[0128] As depicted in FIG. 8A, when a gap G is about 30 mm, an
etching rate ER in a longitudinal direction is maximized at a
central area of the wafer and gradually decreased toward an outer
peripheral area of the wafer and after reaching a minimum value,
the etching rate ER is slightly increased at the outer peripheral
area. Thus, a distribution of etching rates ER is not uniform in a
surface of the wafer. In this case, an average of the etching rates
ER in the longitudinal direction is about 178.4 nm/min and a
deviation is about 14.9%.
[0129] Meanwhile, as depicted in FIG. 8B, when a gap G is about 50
mm, an etching rate ER becomes more uniform in the surface of the
wafer although an etching rate ER in a longitudinal direction is
increased at the outer peripheral area of the wafer as compared to
that in the central area of the wafer. In this case, an average of
the etching rates ER in the longitudinal direction is about 208.3
nm/min and a deviation is about 12.6%.
[0130] Further, as depicted in FIG. 8C, when a gap G is about 90
mm, an etching rate ER in a longitudinal direction becomes much
more uniform in the surface of the wafer. In this case, an average
of the etching rates ER in the longitudinal direction is about
164.5 nm/min and a deviation is about 7.3%.
[0131] As described above, by adjusting a gap G, it is possible to
control a distribution of ion flux.
[0132] When the plasma is irradiated to the wafer, the ions
contained in the plasma are substantially vertically incident to
the surface of the wafer and scarcely irradiated to sidewalls of
the lines. Therefore, parameters controlling line widths CD of
lines to be formed may include an amount of a polymer film formed
on a surface of the sidewall of the line due to adhesion of the
radicals to the sidewall and an etching amount of the surface of
the sidewall of the line due to a reaction between the radicals and
the sidewall of the line.
[0133] Herein, a method of controlling a reaction amount of the
radicals in the surface of the wafer may include the following
three methods: a method of adjusting a distribution of a supply
amount of a processing gas supplied to generate the radicals; a
method of adjusting a distribution of a composition ratio of the
processing gas supplied as a mixed gas; and a method of adjusting a
temperature distribution in the surface of the wafer in order to
adjust a reaction rate.
[0134] Among these three methods of controlling the distribution of
reaction amounts of the radicals, in accordance with the method of
adjusting the distribution of the supply amount of the processing
gas and the method of adjusting the distribution of the composition
ratio of the processing gas, it is impossible to locally adjust the
supply amount and the composition ratio of the processing gas in
the surface of the wafer. For this reason, it is also impossible to
locally adjust the distribution of the reaction amount of the
radicals.
[0135] Meanwhile, in accordance with the method of adjusting the
temperature distribution of the wafer, even if various processing
gases and various radicals are used, it is possible to locally
adjust the distribution of reaction amounts of the radicals. Thus,
it is possible to locally control the distribution of line widths
CD of the lines in the surface of the wafer.
[0136] To be specific, referring to Table 1, there will be
explained a method of independently controlling a distribution of
an ion flux and a distribution of a reaction amount of radicals by
using the method of adjusting the gap G and the method of adjusting
the temperature distribution of the wafer. Herein, as described
below, the gap G and the temperature distribution of the wafer are
adjusted under conditions (A) and (B), and a deviation of line
widths CD in the surface of the wafer is calculated.
(A) Second Mask Film Etching Process (Step S13)
[0137] Material of second mask film: naphthalene (or
polystyrene)
[0138] Thickness of second mask film: 280 nm
[0139] Internal pressure of film forming apparatus: 20 mTorr
[0140] High frequency power (40 mHz/13 MHz): 500/0 W
[0141] Potential of upper electrode: 0 V
[0142] Flow rate of processing gas: O.sub.2=750 sccm
[0143] Processing time: 60 seconds
(B) First Mask Film Etching Process (Step S14)
[0144] Material of first mask film: silicon nitride (SiN)
[0145] Thickness of first mask film: 280 nm
[0146] Internal pressure of film forming apparatus: 75 mTorr
[0147] High frequency power (40 mHz/13 MHz): 500/0 W
[0148] Potential of upper electrode: 300 V
[0149] Flow rate of processing gas:
CF.sub.3/CF.sub.4/Ar/O.sub.2=125/225/600/60 sccm (here,
CH.sub.2F.sub.2 of about 20 sccm may be added to outer peripheral
area)
[0150] Processing time: 60 seconds
[0151] In the conditions (A) and (B), a flow rate of the processing
gas is used to adjust a supply amount of the processing gas, for
example. However, it may be also possible to change a supply time
of the processing gas by opening/closing a valve so as to adjust
the supply amount of the processing gas without changing the flow
rate of the processing gas.
[0152] Table 1 shows a deviation CD1.sigma. of line widths in a
dense area A1 when a gap G, a temperature TI at a central area of
the wafer, and a temperature TO at an outer peripheral area of the
wafer are adjusted. Further, Table 1 shows an example where a ratio
between a flow rate FLI of the processing gas at the central area
and a flow rate FLO of the processing gas at the outer peripheral
area is optimized in advance to 50:50.
TABLE-US-00001 TABLE 1 Gap G (mm) 30 50 90 50 Central area 40 40 40
50 temperature TI (.degree. C.) Outer peripheral area 40 40 40 40
temperature TO (.degree. C.) Flow rate ratio between 50:50 50:50
50:50 50:50 central flow rate FLI and outer peripheral flow rate
FLO Deviation CD1.sigma. (nm) 7.5 3.8 1.9 1.5 of line width CD at
dense area A1 Deviation CD2.sigma. (nm) 36.5 7.2 7.7 2.9 of line
widths CD at sparse area A2
[0153] As shown in Table 1, under the condition that the gap G is
about 30 mm, the temperature TI at the central area is about
40.degree. C., and the temperature TO at the outer peripheral area
is about 40.degree. C., the deviation CD1.sigma. becomes as great
as about 7.5 nm. Further, the deviation CD1.sigma. is decreased to
about 3.8 nm and about 1.9 nm by adjusting the gap G to about 50 mm
and about 90 mm, respectively, without changing the condition that
the temperature TI at the central area is about 40.degree. C. and
the temperature TO at the outer peripheral area is about 40.degree.
C.
[0154] Furthermore, by adjusting the temperature TI at the central
area and the temperature TO at the outer peripheral area as well as
the gap G, the deviation CD1.sigma. can be decreased to about 1.5
nm under the condition that the gap G is about 50 mm, the
temperature TI at the central area is about 50.degree. C., and the
temperature TO at the outer peripheral area is about 40.degree.
C.
[0155] That is, the present inventors have found that it is
desirable to use the method of adjusting the gap G and the method
of adjusting the temperature distribution of the wafer together in
order to independently control the distribution of ion flux and the
distribution of reaction amount of the radicals with low cost and
high effect.
[0156] The line width CD of the line formed by an etching process
may vary depending on a gap of adjacent lines (pattern gap) in
addition to the adhesion coefficient.
[0157] Therefore, the line width CD of the line formed on the wafer
may vary depending on the temperature of the wafer and the pattern
gap.
[0158] However, as described above, if there are areas having
different pattern gaps in the surface of the wafer, it is difficult
to independently control a line width CD of a line in the dense
area A1 and a line width CD of a line in the sparse area A2 by
adjusting only the temperature of the wafer. In this case, it may
be possible to independently control the line widths CD of the
lines in the dense area A1 and the sparse area A2 by adjusting the
supply amount or composition ratio of the processing gas.
[0159] Further, Table 1 shows the deviation CD2.sigma. of the line
widths in the sparse area A2. As described above, the ratio between
the flow rate FLI of the processing gas at the central area and the
flow rate FLO of the processing gas at the outer peripheral area is
optimized in advance to 50:50. For this reason, by adjusting the
gap G, the temperature TI at the central area, and the temperature
TO at the outer peripheral area, the deviation CD2.sigma. in the
sparse area A2 can be decreased to about 2.9 nm under the condition
that the gap G is about 50 mm, the temperature TI at the central
area is about 50.degree. C., and the temperature TO at the outer
peripheral is about 40.degree. C.
[0160] Hereinafter, referring to FIGS. 9A to 10D, there will be
explained an example where distributions of line widths CD and
heights H of lines in the surface of the wafer can be controlled
independently.
[0161] FIGS. 9A to 9D are graphs schematically showing temperature
dependency of line widths CD of the line groups and gap dependency
of etching rates ER in a longitudinal direction during the second
mask film etching process. In each of FIGS. 9A to 9D, the
temperature dependency of line widths CD in the dense area A1, the
temperature dependency of line widths CD in the sparse area A2 and
the gap dependency of the etching rates ER in the longitudinal
direction are shown in sequence from the left.
[0162] FIGS. 10A to 10D are graphs schematically showing
temperature dependency of line widths CD of the line groups and gap
dependency of etching rates ER in a longitudinal direction during
the first mask film etching process. In each of FIGS. 10A to 10D,
the temperature dependency of line widths CD in the dense area A1,
the temperature dependency of line widths CD in the sparse area A2
and the gap dependency of the etching rates ER in the longitudinal
direction are shown in sequence from the left.
[0163] Referring to FIGS. 10A to 10D, there will be explained an
example where in the first mask film etching process (step S14), it
is possible to independently control the distribution of line
widths CD and heights H of the line groups in the surface of the
wafer and possible to perform an etching process with high
uniformity in cross sectional shapes of the line groups.
[0164] FIG. 10A shows each dependency before a temperature
distribution, a distribution of a supply amount, and a gap G are
adjusted. In FIG. 10A, a flow rate FLI at the central area is set
to be FLI0 and a flow rate FLO at the outer peripheral area is set
to be FLO0. FIG. 10A shows an example where line widths CD both in
the dense area A1 and in the sparse area A2 have different
temperature dependency at the central area and the outer peripheral
area of the wafer. Further, in the example shown in FIG. 10A, the
temperature dependency of the line widths CD in the dense area A1
has a tendency opposite to a tendency of the temperature dependency
of the line widths CD in the sparse area A2. Furthermore, in the
example shown in FIG. 10A, etching rates ER in the longitudinal
direction have different gap dependency at the central area and the
outer peripheral area of the wafer. Here, the gap G is set to be G0
where a difference between the etching rates ER in the longitudinal
direction at the central area and the outer peripheral area is
small.
[0165] In the example shown in FIG. 10A, when the temperature TI at
the central area of the wafer and the temperature TO at the outer
peripheral area of the wafer are set to be same as a temperature
T0, a line width CDI1 at the central area in the dense area A1
cannot be the same as a line width CDO1 at the outer peripheral
area in the dense area A1. Further, a line width CDI12 at the
central area in the sparse area A2 cannot be the same as a line
width CDO2 at the outer peripheral area in the sparse area A2.
[0166] FIG. 10B shows each dependency after the temperature
distribution is adjusted. As depicted in FIG. 10B, the temperature
TI at the central area is set to be T1 lower than TO, and the
temperature TO at the outer peripheral area is set to be T2 higher
than T0. In this way, by adjusting the temperature distribution in
the surface of the wafer, a difference between the line width CDI1
at the central area in the dense area A1 and the line width CDO1 at
the outer peripheral area in the dense area A1 can be further
reduced. However, since the temperature dependency of the line
widths CD in the dense area A1 has a tendency opposite to a
tendency of the temperature dependency of the line widths CD in the
sparse area A2, a difference between the line width CDI2 at the
central area in the sparse area A2 and the line width CDO2 at the
outer peripheral area in the sparse area A2 may not be reduced.
[0167] FIG. 10C shows each dependency after the distribution of the
supply amount of the processing gas is adjusted. As depicted in
FIG. 10C, the flow rate at the central area is set to be FLI1 lower
than FLI0 and the flow rate at the outer peripheral area is set to
be FLO1 higher than FLO0. In this way, by adjusting the
distribution of the gas supply amount in the surface of the wafer,
the reaction amount of the radicals at the central area is
decreased in the dense area A1 and in the sparse area A2, and,
thus, a straight line that represents the temperature dependency of
the line width CD moves downward. Meanwhile, the reaction amount of
the radicals at the outer peripheral area is increased, and, thus,
a straight line that represents the temperature dependency of the
line width CD moves upward.
[0168] Further, the lines 13b in the sparse area A2 are more likely
to be in contact and react with the radicals than the lines 13a in
the dense area A1. For this reason, when the gas supply amount is
changed, the line widths CD of the lines 13b in the sparse area A2
may be greatly changed as compared to the line widths CD of the
lines 13a in the dense area A1. That is, the gas supply amount
dependency of the reaction amount between the lines 13a in the
dense area A1 and the radicals may be less than the gas supply
amount dependency of the reaction amount between the lines 13b in
the sparse area A2 and the radicals.
[0169] Therefore, by adjusting the distribution of the gas supply
amount, the line widths CD can be greatly changed in the sparse
area A2 as compared to those in the dense area A1. Further, as
depicted in FIG. 10C, the line width CDI1 at the central area in
the dense area A1 may be set to be substantially the same as the
line width CDO1 at the outer peripheral area in the dense area A1,
and the line width CDI12 at the central area in the sparse area A2
may be set to be substantially the same as the line width CDO2 at
the outer peripheral area in the sparse area A2.
[0170] However, if the gas supply amount is changed, an ion flux
may be changed. Thus, as depicted in FIG. 10C, an etching rate ER
in the longitudinal direction may be also changed. The ion flux at
the central area is decreased and the ion flux at the outer
peripheral area is increased. Thus, when the gap is G0, a
difference between an etching rate ERI in the longitudinal
direction at the central area and an etching rate ERO in the
longitudinal direction at the outer peripheral area becomes
increased as compared to a difference in the case before the
temperature distribution and the gas supply amount in the wafer
surface are adjusted.
[0171] In the first mask film etching process (step S14), by
adjusting the gap G, the difference between the etching rate ERI in
the longitudinal direction at the central area and the etching rate
ERO in the longitudinal direction at the outer peripheral area may
be decreased.
[0172] FIG. 10D shows each dependency after the gap G is adjusted.
In the example shown in FIG. 10D, the gap is set to be G1 smaller
than G0. Thus, the difference between the etching rate ERI in the
longitudinal direction at the central area and the etching rate ERO
in the longitudinal direction at the outer peripheral area can be
decreased. Therefore, after the distribution of the reaction amount
of the radicals in the wafer surface is adjusted, the etching rate
ER in the longitudinal direction in the wafer surface may be
adjusted.
[0173] As described above, in the first mask film etching process
(step S14), by adjusting the gap G in addition to controlling the
temperature distribution and the supply amount or composition ratio
of the processing gas, it is possible to independently control the
distribution of line widths CD of the line groups and the
distribution of etching rates ER in the longitudinal direction.
Consequently, the line widths CD and the heights H in the surface
of the wafer can be uniformed and cross sections of the line groups
may also be uniformed.
[0174] Hereinafter, there will be explained an example where it is
possible to independently control the distribution of line widths
CD and heights H of line groups in a surface of a wafer and to
perform an etching process with high uniformity in cross sectional
shapes of lines in the second mask film etching process (step S13)
shown in FIGS. 9A to 9D.
[0175] FIG. 9A shows each dependency before a temperature
distribution, a distribution of a supply amount, and a gap G are
adjusted. In FIG. 9A, a flow rate FLI at a central area is set to
be FLI0 and a flow rate FLO at an outer peripheral area is set to
be FLO0. FIG. 9A shows an example where line widths CD both in a
dense area A1 and in a sparse area A2 have little temperature
dependency at the central area and the outer peripheral area of the
wafer. Further, in the example shown in FIG. 9A, etching rates ER
in the longitudinal direction have different gap dependency at the
central area and the outer peripheral area of the wafer. Here, the
gap G is set to be G0 where a difference between the etching rates
ER in the longitudinal direction at the central area and the outer
peripheral area is small.
[0176] That is, temperature dependency of a reaction amount between
radicals and the surface of the second mask film 14 in the second
mask film etching process (step S13) may be smaller than
temperature dependency of a reaction amount between radicals and
the surface of the first mask film 13 in the first mask film
etching process (step S14). The radicals in the second mask film
etching process (step S13) serve as first neutral particles of the
present disclosure. Further, the radicals in the first mask film
etching process (step S14) serve as second neutral particles of the
present disclosure.
[0177] In the example shown in FIG. 9A, when a temperature TI at
the central area of the wafer and a temperature TO at the outer
peripheral area of the wafer are set to be same as a temperature
T0, a line width CDI1 at the central area in the dense area A1
cannot be the same as a line width CDO1 at the outer peripheral
area in the dense area A1. Further, a line width CD12 at the
central area in the sparse area A2 cannot be the same as a line
width CDO2 at the outer peripheral area in the sparse area A2.
[0178] The line widths CD have little temperature dependency when
the processing gas has a small reaction rate between radicals and
sidewalls of lines or the radicals adhering to the sidewalls of the
lines has a low adhesion coefficient. As described above, in the
second mask film etching process (step S13), an oxygen (O.sub.2)
gas is used as the processing gas, but oxygen radicals (O*)
contained in plasma may have a low reaction coefficient and a low
adhesion coefficient.
[0179] FIG. 9B shows each dependency after the temperature
dependency is changed. As depicted in FIG. 9B, originally, the line
widths CD have little temperature dependency both in the dense area
A1 and the sparse area A2. Therefore, even if the temperature TI at
the central area is set to be T1 lower than T0 and the temperature
TO at the outer peripheral area is set to be T2 higher than T0, a
difference between the line width CDI1 at the central area in the
dense area A1 and the line width CDO1 at the outer peripheral area
in the dense area A1 may not be decreased. Further, a difference
between the line width CDI2 at the central area in the sparse area
A2 and the line width CDO2 at the outer peripheral area in the
sparse area A2 may not be decreased.
[0180] FIG. 9C shows each dependency after the distribution of the
supply amount of the processing gas is adjusted. As depicted in
FIG. 9C, the flow rate at the central area is set to be FLI1 lower
than FLI0 and the flow rate at the outer peripheral area is set to
be FLO1 higher than FLO0. In this way, by adjusting the
distribution of the gas supply amount in the surface of the wafer,
the reaction amount of the radicals at the central area is
decreased in the dense area A1 and in the sparse area A2, and,
thus, a straight line that represents the temperature dependency of
the line width CD moves downward. Meanwhile, the reaction amount of
the radicals at the outer peripheral area is increased, and, thus,
a straight line that represents the temperature dependency of the
line width CD moves upward.
[0181] In the same manner as the first mask film, etching process
(step S14), by way of example, the lines 14b in the sparse area A2
are more likely to be in contact and react with the radicals than
the lines 14a in the dense area A1. For this reason, when the gas
supply amount is changed, the line widths CD of the lines 14b in
the sparse area A2 may be greatly changed as compared to the line
widths CD of the lines 14a in the dense area A1. That is, the gas
supply amount dependency of the reaction amount between the lines
14a in the dense area A1 and the radicals may be less than the gas
supply amount dependency of the reaction amount between the lines
14b in the sparse area A2 and the radicals.
[0182] Therefore, by adjusting the distribution of the gas supply
amount, the line widths CD can be greatly changed in the sparse
area A2 as compared to those in the dense area A1. Further, as
depicted in FIG. 9C, the line width CDI1 at the central area in the
dense area A1 may be set to be substantially the same as the line
width CDO1 at the outer peripheral area in the dense area A1, and
the line width CDI12 at the central area in the sparse area A2 may
be set to be substantially the same as the line width CDO2 at the
outer peripheral area in the sparse area A2.
[0183] However, in the same manner as the example shown in FIGS.
10A to 10D, if the gas supply amount is changed, an ion flux as
well as the supply amount of the radicals may be changed. Thus, as
depicted in FIG. 9C, an etching rate ER in the longitudinal
direction may be changed. The ion flux at the central area is
decreased and the ion flux at the outer peripheral area is
increased. Thus, when the gap is G0, a difference between an
etching rate ERI in the longitudinal direction at the central area
and an etching rate ERO in the longitudinal direction at the outer
peripheral area becomes increased as compared to a difference in
the case before the temperature distribution and the gas supply
amount in the wafer surface are adjusted.
[0184] In the second mask film etching process (step S13), by
adjusting the gap G, the difference between the etching rate ERI in
the longitudinal direction at the central area and the etching rate
ERO in the longitudinal direction at the outer peripheral area may
be decreased.
[0185] FIG. 9D shows each dependency after the gap G is adjusted.
In the example shown in FIG. 9D, the gap is set to be G1 smaller
than G0. Thus, the difference between the etching rate ERI in the
longitudinal direction at the central area and the etching rate ERO
in the longitudinal direction at the outer peripheral area can be
decreased. Therefore, after the distribution of the reaction amount
of the radicals in the wafer surface is adjusted, the etching rate
ER in the longitudinal direction in the wafer surface may be
adjusted.
[0186] As described above, in the second mask film etching process
(step S13), the processing gas having a low reaction rate or
adhesion coefficient of the radicals is used, and, thus, even if
the temperature of the wafer and the supply amount or composition
ratio of the processing gas are adjusted, it is impossible to
control the line widths CD of the lines. However, by adjusting the
gap G in addition to controlling the temperature distribution and
the supply amount or composition ratio of the processing gas, it is
possible to independently control the distribution of line widths
CD of the line groups and the distribution of etching rates ER in
the longitudinal direction. Consequently, the line widths CD and
the heights H in the surface of the wafer can be uniformed and
uniform cross sectional shape can be achieved.
[0187] In the example described with reference to FIGS. 9A to 10D,
for the simplicity of explanation, it has been explained that the
temperature distribution in the wafer surface is first adjusted;
the distribution of the gas supply amount in the wafer surface is
then adjusted; and then the gap G is finally adjusted. However, the
sequence of adjusting the temperature distribution, the
distribution of gas supply amounts, and the gap G is not limited
thereto, and their adjustments can be carried out in any
sequence.
[0188] Further, it may be possible to prepare in advance data of
line widths CD and etching rates ER in a longitudinal direction in
the dense area A1 and the sparse area A2, which are obtained under
respective conditions of the temperatures TI and TO at the central
area and the outer peripheral area, the flow rates FLI and FLO at
the central area and the outer peripheral area, and the gap G. In
this case, each condition may be optimized such that the
distributions of line widths CD and etching rates ER in the wafer
surface can be uniformed based on the data prepared in advance. The
optimization of each condition can be carried out by the apparatus
controller 190.
[0189] Further, when selecting a mask film and a processing gas for
etching the mask film, it is desirable to control a distribution of
shapes of lines in the wafer surface while achieving selectivity in
etching rates between an upper film and a lower film when the mask
film is etched. Therefore, in accordance with the present
embodiment, it may be possible to use a mask film including
inorganic and organic films capable of increasing selectivity in
etching rates for each processing gas when the processing gas is
varied. Thus, it may be possible to transfer a shape of a resist
pattern onto an etching target film with high accuracy and also
possible to uniform a distribution of shapes of lines formed of the
etching target film in the wafer surface.
[0190] The present embodiment has been explained for the example
where the mask film is composed of the upper mask film including
the organic film and the lower mask film including the inorganic
film. However, the present embodiment can also be applied to a case
where a mask film includes only a single film and in this case, it
is also possible to uniform a distribution of shapes of lines
formed of an etching target film in a wafer surface.
Modification Example of First Embodiment
[0191] Hereinafter, a plasma etching method and a plasma etching
apparatus in accordance with a modification example of the first
embodiment will be explained.
[0192] The present modification example is different from the first
embodiment in that when an organic film is etched, a processing gas
having a high adhesion coefficient and having radicals of a high
reaction rate is used in a second mask film etching process.
[0193] In the present modification example, the plasma etching
apparatus explained with reference to FIGS. 1 to 5 may be used, as
in the first embodiment. Further, as the first embodiment, a plasma
etching method in accordance with the present modification example
also includes a resist pattern forming process (step S11), an
anti-reflective coating etching process (step S12), a second mask
film etching process (step S13), a first mask film etching process
(step S14), and an etching target film etching process (step S15)
explained with reference to FIG. 6. Furthermore, a wafer state in
each process is the same as illustrated in FIGS. 7A to 7E.
[0194] Meanwhile, in the present modification example, in the
second mask film etching process (step S13), it may be possible to
use a mixed gas including a nitrogen (N.sub.2) gas/a hydrogen
(H.sub.2) gas instead of an oxygen (O.sub.2) gas as a processing
gas. When a temperature distribution, a distribution of a supply
amount, and a gap G are adjusted in the second mask film etching
process (step S13), example processing conditions other than the
processing gas are as follows.
(C) Second Mask Film Etching Process (Step S13)
[0195] Material of second mask film: naphthalene (or
polystyrene)
[0196] Thickness of second mask film: 280 nm
[0197] Internal pressure of film forming apparatus: 100 mTorr
[0198] High frequency power (40 mHz/13 MHz): 700/0 W
[0199] Potential of upper electrode: 0 V
[0200] Flow rate of processing gas: N.sub.2/H.sub.2=160/480
sccm
[0201] Processing time: 60 seconds
[0202] When the second mask film 14 is etched by using the mixed
gas including the nitrogen (N.sub.2) gas/the hydrogen (H.sub.2)
gas, line widths CD may be observed to have temperature dependency
and gas supply amount dependency and an etching rate ER in a
longitudinal direction may have gap dependency in the same way as
described in the first embodiment in FIGS. 10A to 10D. Therefore,
the temperature distribution, the distribution of the supply
amount, and the gap G can be adjusted in the same manner as the
first mask film etching process (step S14) in the first
embodiment.
[0203] That is, as depicted in FIG. 10A, a line width CD has
different temperature dependency at a central area and an outer
peripheral area of a wafer. For this reason, as depicted in FIG.
10B, by adjusting only the temperature distribution in the wafer
surface, it is possible to decrease a difference between a line
width CDI1 at the central area in a dense area A1 and a line width
CDO1 at the outer peripheral area in the dense area A1 but it is
impossible to decrease a difference between a line width CDI2 at
the central area in a sparse area A2 and a line width CDO2 at the
outer peripheral area in the sparse area A2. Further, as depicted
in FIG. 100, by adjusting flow rates FLI and FLO of the processing
gas at the central area and the outer peripheral area, it is
possible to make the line width CDI1 at the central area in the
dense area A1 substantially the same as the line width CDO1 at the
outer peripheral area in the dense area A1 and also possible to
make the line width CDI2 at the central area in the sparse area A2
substantially the same as the line width CDO2 at the outer
peripheral area in the sparse area A2. Here, since the ion flux is
also changed, by adjusting the gap G, it is possible to decrease a
difference between the etching rate ERI in the longitudinal
direction at the central area and the etching rate ERO in the
longitudinal direction at the outer peripheral area as depicted in
FIG. 10D.
[0204] Therefore, in accordance with the present embodiment, it may
be possible to use a mask film including inorganic and organic
films capable of increasing selectivity in etching rates for each
processing gas when the processing gas is varied. Thus, it may be
possible to transfer a shape of a resist pattern onto an etching
target film with high accuracy and also possible to uniform a
distribution of shapes of lines formed of the etching target film
in the wafer surface.
[0205] Further, the present modification example can also be
applied to a case where a mask film is composed of a film including
either an organic film or an inorganic film and in such a case, it
is possible to uniform a distribution of shapes of lines formed of
an etching target film in a wafer surface.
Second Embodiment
[0206] Hereinafter, referring to FIGS. 11 to 15, a plasma etching
method and a plasma etching apparatus in accordance with a second
embodiment of the present disclosure will be explained.
[0207] The present embodiment is different from the first
embodiment in that a distribution of a gas supply amount in a wafer
surface is not adjusted and a pattern to be formed does not have a
sparse area but only has a dense area.
[0208] Referring to FIGS. 11 to 15, the plasma etching apparatus in
accordance with the present embodiment will be elaborated. FIGS. 11
and 12 are cross sectional views showing a schematic configuration
of the plasma etching apparatus in accordance with the present
embodiment. To be specific, FIG. 11 shows a configuration in which
an upper electrode is located at a retreat position, and FIG. 12
shows a configuration in which the upper electrode is located at a
process position. FIGS. 13a and 13b provide explanatory diagrams
simply showing an upper electrode driving unit. To be specific,
FIG. 13A shows a configuration in which the upper electrode is
located at the retreat position and FIG. 13B shows a configuration
in which the upper electrode is located at the process
position.
[0209] As depicted in FIGS. 11 to 13B, a plasma etching apparatus
100a has the same components as those of the plasma etching
apparatus 100 explained with reference to FIGS. 1 to 3B except for
a shower head 140a (upper electrode 120a) and a gas supply
apparatus 150a, and the same components are assigned with same
reference numerals as those of the plasma etching apparatus 100 and
explanation thereof will be omitted.
[0210] The shower head 140a is configured to supply a mixed gas
onto the wafer W supported on a susceptor 105. The shower head 140a
includes a circular electrode plate 141 (upper electrode 120a)
having a multiple number of gas discharge holes 141a and an
electrode support body 142 which supports the surface of the
electrode plate 141 and is detachable therefrom as explained in the
first embodiment. Further, the electrode support 142 and a buffer
room 143c are configured in the same manner as the first
embodiment.
[0211] Meanwhile, in the present embodiment, an annular partition
wall member 145 formed of an O-ring is not installed in the buffer
room 143c and the buffer room is not divided into plural sections.
A bottom surface of the buffer room 140c communicates with gas
discharge holes 141a, and the mixed gas can be discharged toward
the wafer W. Further, the mixed gas is supplied to the buffer room
143c by a gas supply apparatus 150a.
[0212] As depicted in FIGS. 13A and 13B, a detail configuration of
the upper electrode driving unit 200 is the same as explained in
the first embodiment. However, in the present embodiment, as
described below, a mixing line 170 for supplying a gas into the
buffer room 143c of the upper electrode 120a is not divided and is
configured as a single line. For this reason, a diameter of the
bellows 122 may be smaller as compared to that in the first
embodiment.
[0213] Hereinafter, referring to FIGS. 11, 12, 14 and 15, the gas
supply apparatus 150a will be explained. FIG. 14 is transversal
cross sectional view of an upper electrode. FIG. 15 is a diagram
for explaining a schematic configuration of a gas supply
apparatus.
[0214] The gas supply apparatus 150a includes a gas box 161 which
accommodates a multiple number of, for example, three, gas supply
sources 160a, 160b, and 160c. By way of example, a C.sub.XF.sub.Y
gas such as CF.sub.4, C.sub.4F.sub.6, C.sub.4F.sub.8, and
C.sub.5F.sub.8 is sealed in a gas supply source 160a, an oxygen
(O.sub.2) gas is sealed in a gas supply source 160b, and an Ar gas
is sealed in a gas supply source 160c.
[0215] Each of the gas supply sources 160a to 160c is connected
with the mixing line 170 via a mass flow controller 171. Further,
the mixing line 170 is not divided and is connected with the buffer
room 143c of the shower head 140a.
[0216] A pressure adjusting unit 174 is installed on a part of the
mixing line 170, and the pressure adjusting unit 174 includes a
pressure gauge 174a and a valve 174b. A measurement result measured
by the pressure gauge 174a of the pressure adjusting unit 174 may
be outputted by a pressure control apparatus 176. The pressure
control apparatus 176 adjusts an opening/closing degree of the
valve 174b based on the measurement result of the pressure gauge
174a and controls a flow rate of the processing gas flowing through
the mixing line 170.
[0217] An operation of the mass flow controller 171 of the gas box
161 is controlled by, for example, an apparatus controller 190 of
the plasma etching apparatus 100a. Therefore, the apparatus
controller 190 may control a start and a stop of supply of various
gases from the gas box 161 and control a supply amount of the
various gases.
[0218] Hereinafter, referring to FIGS. 16 to 17E, a plasma etching
method using the plasma etching apparatus 100a will be explained.
FIG. 16 is a flowchart for explaining a process sequence of a
plasma etching method in accordance with the present embodiment.
FIGS. 17A to 17E are cross sectional views schematically showing
wafer states in each process of the plasma etching method in
accordance with the present embodiment.
[0219] The plasma etching method in accordance with the present
embodiment, as depicted in FIG. 16, includes a resist pattern
forming process (step S21), an anti-reflective coating etching
process (step S22), a second mask film etching process (step S23),
a first mask film etching process (step S24), and an etching target
film etching process (step S25).
[0220] First, the resist pattern forming process (step S21) is
performed. The resist pattern forming process (step S21) may be
performed in the same manner as the resist pattern forming process
(step S11) of the first embodiment. FIG. 17A shows a wafer state in
the resist pattern forming process (step S21). However, as depicted
in FIG. 17a, in the present embodiment, only an area (dense area)
A1 in which lines 16a are arranged at a distance D1 is formed and a
sparse area is not formed.
[0221] Then, the anti-reflective coating etching process (step S22)
is performed. The anti-reflective coating etching process (step
S22) may be performed in the same manner as the anti-reflective
coating etching process (step S12) of the first embodiment. FIG.
17B shows a wafer state in the anti-reflective coating etching
process (step S22).
[0222] Subsequently, the second mask film etching process (step
S23) is performed. In the second mask film etching process (step
S23), a second mask film 14 is etched by plasma irradiated to a
wafer 10 using lines 15a formed of a resist film 16 and an
anti-reflective coating 15, so that lines 14a including the second
mask film 14 are formed. FIG. 17C shows a wafer state in the second
mask film etching process (step S23).
[0223] In the second mask film etching process (step S23), a
temperature distribution in the surface of the wafer 10 supported
on the susceptor 105 is adjusted. By this adjustment, a
distribution of reaction amounts between the radicals of the plasma
in the surface of the wafer 10 and the surface of the wafer 10 is
controlled. By controlling the distribution of the reaction
amounts, it is possible to control a distribution of line widths CD
of the lines 14a in the surface of the wafer 10.
[0224] In response to a control signal from an apparatus controller
190 to a temperature distribution adjusting unit 106, temperatures
of central and outer peripheral thermometers 106e and 106f are
adjusted to predetermined temperatures TI and TO, respectively.
Further, in response to a control signal from the apparatus
controller 190 to the temperature distribution adjusting unit 106,
a central heater 106a and an outer peripheral heater 106b are
controlled independently. Consequently, it is possible to set the
temperature TI at the central area of the wafer 10 to be different
from the temperature TO at the outer peripheral area of the wafer
10, and, thus, a temperature distribution in the surface of the
wafer 10 can be adjusted.
[0225] As described above, by adjusting the temperature
distribution in the surface of the wafer 10, it is possible to
control the distribution of the line widths CD of the lines 14a
formed of the second mask film 14 in the surface of the wafer
10.
[0226] In the second mask film etching process (step S23), in
response to a control signal from the apparatus controller 190 to
an upper electrode driving unit 200, a gap G between the wafer 10
supported on the susceptor 105 and the upper electrode 120a
provided so as to face the wafer 10 is adjusted. By adjusting the
gap G, it is possible to control a distribution of irradiation
amounts of ions in the surface of the wafer 10 and a distribution
of etching rates ER in a longitudinal direction (depth direction).
Further, by controlling the distribution of the etching rates ER in
the longitudinal direction (depth direction), it is possible to
control a distribution of heights H of the lines 14a in the surface
of the wafer 10.
[0227] In the second mask film etching process (step S23), it may
be possible to use an oxygen (O.sub.2) gas as the processing
gas.
[0228] Thereafter, the first mask film etching process (step S24)
is performed. In the first mask film etching process (step S24),
the first mask film 13 is etched by plasma irradiated to the wafer
10 using the lines 14a formed of the second mask film 14 as a mask,
so that lines 13a including the first mask film 13 are formed. FIG.
17D shows a wafer state in the first mask film etching process
(step S24).
[0229] In the first mask film etching process (step S24), a
temperature distribution in the surface of the wafer 10 supported
on the susceptor 105 is adjusted. By this adjustment, the
distribution of the reaction amounts between the radicals of the
plasma in the surface of the wafer 10 and the surface of the wafer
10 is controlled. By controlling the distribution of the reaction
amounts, it is possible to control a distribution of the line
widths CD of the lines 13a in the surface of the wafer 10.
[0230] Further, in the first mask film etching process (step S24),
in response to a control signal from the apparatus controller 190
to the upper electrode driving unit 200, a gap G between the wafer
10 supported on the susceptor 105 and the upper electrode 120a
provided so as to face the wafer 10 is adjusted. By adjusting the
gap G, it is possible to control a distribution of irradiation
amounts of ions in the surface of the wafer 10 and a distribution
of etching rates ER in a longitudinal direction (depth direction).
Further, by controlling the distribution of the etching rates ER in
the longitudinal direction (depth direction), it is possible to
control a distribution of heights H of the lines 13a in the surface
of the wafer 10.
[0231] In the first mask film etching process (step S24), as the
processing gas, it may be possible to use a mixed gas of a CF-based
gas such as CF.sub.4, C.sub.4F.sub.8, CHF.sub.3, CH.sub.3F, and
CH.sub.2F.sub.2 with an Ar gas, or the mixed gas further including
an oxygen (O.sub.2) gas if necessary.
[0232] Thereafter, the etching target film etching process (step
S25) is performed in the same manner as the etching target film
etching process (step S15) of the first embodiment. FIG. 17E shows
a status of a wafer in the etching target film etching process
(step S25).
[0233] Hereinafter, there will be explained a case where a
distribution of line widths CD of lines and a distribution of
heights H of the lines in a surface of a wafer are independently
controlled and an etching process can be performed with high
uniformity in cross sectional shapes of lines when the etching
process is performed on the wafer using the plasma etching method
in accordance with the present embodiment.
[0234] In the present embodiment, it is possible to independently
control a distribution of ion fluxes and a distribution of reaction
amounts of radicals by using a method of controlling the
distribution of ion fluxes by adjusting a gap G and a method of
controlling the distribution of the reaction amounts of the
radicals by adjusting a temperature distribution in a wafer.
[0235] Herein, referring to FIGS. 18A to 18C, there will be
explained an example where distributions of line widths CD of lines
and the distribution of heights H of lines in the surface of the
wafer can be independently controlled.
[0236] FIGS. 18A to 18C are graphs schematically showing
temperature dependency of line widths CD of lines and gap
dependency of etching rates ER in a longitudinal direction in the
present embodiment. In each of FIGS. 18A to 18C, the temperature
dependency of line widths CD and the gap dependency of the etching
rates ER in the longitudinal direction are shown in sequence from
the left.
[0237] Further, when a temperature distribution, a distribution of
a supply amount, and a gap G are adjusted in the second mask film
etching process (step S23) and the first mask film etching process
(step S24), example processing conditions other than the processing
gas are as follows.
(D) Second Mask Film Etching Process (Step S23)
[0238] Material of second mask film: naphthalene (or
polystyrene)
[0239] Thickness of second mask film: 280 nm
[0240] Internal pressure of film forming apparatus: 100 mTorr
[0241] High frequency power (40 mHz/13 MHz): 700/0 W
[0242] Potential of upper electrode: 0 V
[0243] Flow rate of processing gas: N.sub.2/H.sub.2=160/480
sccm
[0244] Processing time: 60 seconds
(E) First Mask Film Etching Process (Step S24)
[0245] Material of first mask film: TEOS-SiO.sub.2
[0246] Thickness of first mask film: 280 nm
[0247] Internal pressure of film forming apparatus: 75 mTorr
[0248] High frequency power (40 mHz/13 MHz): 500/0 W
[0249] Potential of upper electrode: 300 V
[0250] Flow rate of processing gas:
CHF.sub.3/CF.sub.4/Ar/O.sub.2=125/225/600/60 sccm (here,
CH.sub.2F.sub.2 of 20 sccm may be added to outer peripheral
area)
[0251] Processing time: 60 seconds
[0252] In the present embodiment, when the organic film is etched,
a processing gas having a high adhesion coefficient and having
radicals of a high reaction rate is used as in the modification
example of the first embodiment. Therefore, the second mask film
etching process (step S23) and the first mask film etching process
(step S24) can be explained with reference to FIGS. 18A to 18C.
[0253] FIG. 18A shows each dependency before a temperature
distribution and a gap G are adjusted. FIG. 18A shows an example
where line widths CD have different temperature dependency at the
central area of the wafer and the outer peripheral area of the
wafer. Further, in the example shown in FIG. 18A, the etching rates
ER in the longitudinal direction have different gap dependency at
the central area of the wafer and the outer peripheral area of the
wafer.
[0254] FIG. 18B shows each dependency after the temperature
distribution is adjusted. As depicted in FIG. 18B, the temperature
TI at the central area is set to be T1 lower than T0 and the
temperature TO at the outer peripheral area is set to be T2 higher
than T0. In this way, by adjusting the temperature distribution in
the surface of the wafer, a difference between the line width CDI
at the central area and the line width CDO at the outer peripheral
area can be further reduced.
[0255] FIG. 18C shows each dependency after the gap G is adjusted.
In the example shown in FIG. 18C, the gap is set to be G1 greater
than G0. Thus, a difference between the etching rate ERI in the
longitudinal direction at the central area and the etching rate ERO
in the longitudinal direction at the outer peripheral area can be
further reduced. Therefore, after the distribution of the reaction
amount of the radicals in the wafer surface is adjusted, the
etching rate ER in the longitudinal direction in the wafer surface
may be adjusted.
[0256] In the present embodiment, it may be possible to use a mask
film including inorganic and organic films capable of increasing
selectivity in etching rates for each processing gas when the
processing gas is varied. Thus, it may be possible to transfer a
shape of a resist pattern onto an etching target film with high
accuracy and also possible to uniform a distribution of shapes of
lines formed of the etching target film in the wafer surface.
[0257] Further, the present embodiment can be applied to a case
where a mask film includes only a single film and in this case, it
is also possible to uniform a distribution of shapes of lines
formed of an etching target film in a wafer surface.
[0258] As described above, there have been explained embodiments of
the present disclosure, but the present invention is not limited to
the above-described embodiments and can be modified and changed in
various ways within a scope of the following claims.
* * * * *