U.S. patent application number 12/690802 was filed with the patent office on 2010-05-13 for etching method and apparatus.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Masaru Nishino, Shigeru Tahara.
Application Number | 20100116787 12/690802 |
Document ID | / |
Family ID | 37034148 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100116787 |
Kind Code |
A1 |
Tahara; Shigeru ; et
al. |
May 13, 2010 |
ETCHING METHOD AND APPARATUS
Abstract
When a substrate is etched by using a processing gas including a
first gas containing halogen and carbon and having a carbon number
of two or less per molecule, while supplying the processing gas
toward the substrate independently from a central and a peripheral
portion of a gas supply unit, which face the central and the
periphery part of the substrate respectively, the processing gas is
supplied such that a gas flow rate is greater in the central
portion than in the peripheral portion. When the substrate is
etched by using a processing gas including a second gas containing
halogen and carbon and having a carbon number of three or more per
molecule, the processing gas is supplied such that a gas flow rate
is greater in the peripheral portion than in the central
portion.
Inventors: |
Tahara; Shigeru;
(Nirasaki-shi, JP) ; Nishino; Masaru; (Beverly,
MA) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Minato-ku
JP
|
Family ID: |
37034148 |
Appl. No.: |
12/690802 |
Filed: |
January 20, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11389041 |
Mar 27, 2006 |
7674393 |
|
|
12690802 |
|
|
|
|
60666574 |
Mar 31, 2005 |
|
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|
Current U.S.
Class: |
216/58 ;
156/345.26 |
Current CPC
Class: |
H01L 21/30604 20130101;
H01L 21/31138 20130101; H01J 37/32935 20130101; H01L 21/31116
20130101 |
Class at
Publication: |
216/58 ;
156/345.26 |
International
Class: |
C23F 1/00 20060101
C23F001/00; C23F 1/08 20060101 C23F001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2005 |
JP |
2005-087889 |
Claims
1. An etching method of performing etching on an etching target
film of a substrate by using a processing gas including a gas
containing halogen and carbon and having a carbon number of two or
less per molecule, and a gas supply unit for supplying the
processing gas toward the substrate from a central portion and a
peripheral portion of the gas supply unit, independently, the
central and the peripheral portion respectively facing the central
and the periphery part of the substrate, the method comprising the
step of: performing etching on the etching target film of the
substrate while supplying the processing gas from the gas supply
unit such that a flow rate of the gas per unit area of a gas supply
surface of the gas supply unit is greater in the central portion
than in the peripheral portion.
2. The etching method of claim 1, wherein the step of supplying the
processing gas from the gas supply unit such that a supply amount
of the gas is greater in the central portion than in the peripheral
portion is performed by controlling at least one of a flow rate of
the gas and a dilution rate of the gas diluted with a dilution
gas.
3. The etching method of claim 1, wherein the gas is at least one
of CH.sub.2F.sub.2 gas, CHF.sub.3 gas, CF.sub.4 gas and
C.sub.2F.sub.6 gas.
4. An etching apparatus comprising: a processing chamber in which a
susceptor for mounting a substrate thereon is disposed; a gas
supply unit, disposed in the processing chamber to face the
susceptor and having a surface facing the susceptor serving as a
gas supply surface, for supplying a processing gas containing
carbon and halogen toward the substrate mounted on the susceptor
from a central portion and a peripheral portion of the gas supply
unit, independently, the central and the peripheral portion
respectively facing the central and the periphery part of the
substrate; means for controlling a pressure inside the processing
chamber; means for generating a plasma in the processing chamber;
means for controlling a flow rate of the processing gas supplied to
the gas supply unit; and a controller for controlling each of the
means to perform the steps of the method described in claim 1,
wherein an etching target film formed on the substrate is etched by
a plasma of the processing gas.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This document is a divisional of pending U.S. application
Ser. No. 11/389,041, filed on Mar. 27, 2006, which claims priority
to Japanese Patent Application No. 2005-087889, filed on Mar. 25,
2005, and U.S. Provisional Application No. 60/666,574, filed on
Mar. 31, 2005, the entire contents of which are hereby incorporated
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a technology for performing
an etching on an etching target film formed on a substrate such as
a semiconductor wafer by using a gas containing carbon and
halogen.
BACKGROUND OF THE INVENTION
[0003] In a manufacturing process of a semiconductor device or an
LCD substrate, an etching process is performed to form a pattern of
a thin film. As one of a variety of etching apparatuses, for
example, there is a parallel plate plasma etching apparatus,
wherein parallel plate electrodes including a pair of an upper and
a lower electrode are disposed in a chamber, and a high frequency
electric field is formed therebetween by applying a high frequency
power to either one of the electrodes while introducing a
processing gas into the chamber. Due to the high frequency electric
field, a plasma of the processing gas is generated, whereby an
etching process is performed on, e.g., a semiconductor wafer
(hereinafter, referred to as a "wafer") W.
[0004] For example, in the semiconductor device, a low dielectric
film (low-k film) is practically used or tested as an interlayer
insulating film, a gate insulating film or the like. As the low
dielectric film including silicon (Si) and oxygen (O), for example,
there are an SiOC film formed by adding carbon to an SiO film
serving as a base film and an SiOCH film formed by adding carbon
and hydrogen onto the SiO film. When etching those films, a gas
containing carbon (C) and halogen such as fluorine (F), chlorine
(Cl) and bromine (Br) is used as a processing gas.
[0005] In etching, a hole (recess) is formed by an etching action
of an etchant together with polymerization which forms polymer on a
sidewall of the hole to protect the sidewall. For example, when the
SiO-based film is etched by using a gas containing carbon and
fluorine (hereinafter, referred to as a "CF-based gas") as a
processing gas, active species of CF, which are produced when the
CF-based gas is converted into a plasma, cause both the etching and
the polymerization.
[0006] The CF-based gases such as CF.sub.4 gas, CHF.sub.3 gas,
C.sub.2F.sub.6 gas, C.sub.3F.sub.8 gas, C.sub.4F.sub.8 gas,
C.sub.4F.sub.6 gas, and C.sub.5F.sub.8 gas have different etching
action and polymerization. Therefore, although etching target films
are the same, the most suitable kind of gas is selected from the
CF-based gases depending on a film thickness ratio of the etching
target film to an underlying film or a resist film.
[0007] Further, in the conventional parallel plate plasma etching
apparatus, in order to improve uniformity of etching
characteristics (e.g., an etching rate and processing dimensions
after etching) on the surface of the wafer W, the processing gas is
supplied toward the wafer W from the upper electrode configured as
a shower head having a plurality of gas injection openings, for
instance, while varying gas flow rates supplied onto a center part
and a periphery part of the wafer W.
[0008] However, due to lack of a consistent and reliable method for
determining a flow rate ratio of gases supplied to the central and
the periphery part for respective CF-based gases, the flow rate
ratio is determined through many trials and errors to perform an
etching process with a high in-surface uniformity. Thus, a lot of
efforts and time are necessary to determine the flow rate
ratio.
[0009] Japanese Patent Laid-open Application No. 2002-184764
discloses a technology wherein when an etching process is performed
on TEOS and a resist by using a gaseous mixture including
C.sub.5F.sub.8 gas, gaseous mixtures having different flow rate
ratios are supplied from two gas injection openings of the shower
head which are concentrically formed such that an oxygen flow rate
is lower in the periphery part, thereby preventing an etching
selectivity (TEOS/resist) in the periphery part from being
deteriorated. Even in the aforementioned patent document, however,
there is not disclosed a consistent and reliable method for
determining a flow rate ratio of gases supplied to the central and
the periphery part of the wafer W when an etching is performed by
using the CF-based gas.
SUMMARY OF THE INVENTION
[0010] The present invention has been conceived from the above
problems; and it is, therefore, an object of the present invention
to provide a technology capable of improving in-surface uniformity
when an etching is performed on a substrate by using gas containing
carbon and halogen.
[0011] In accordance with one embodiment of the present invention,
there is provided an etching method of performing etching on an
etching target film of a substrate by using a processing gas
including a first gas containing halogen and carbon and having a
carbon number of two or less per molecule, and a gas supply unit
for supplying the processing gas toward the substrate from a
central portion and a peripheral portion of the gas supply unit,
independently, the central and the peripheral portion respectively
facing the central and the periphery part of the substrate, the
method including the step of performing etching on the etching
target film of the substrate while supplying the processing gas
from the gas supply unit such that a flow rate of the first gas per
unit area of a gas supply surface of the gas supply unit is greater
in the central portion than in the peripheral portion.
[0012] Further, in accordance with another embodiment of the
present invention, there is provided an etching method of
performing etching on an etching target film of a substrate by
using a processing gas including a second gas containing halogen
and carbon and having a carbon number of three or more per
molecule, and a gas supply unit for supplying the processing gas
toward the substrate from a central portion and a peripheral
portion of the gas supply unit, independently, the central and the
peripheral portion respectively facing the central and the
periphery part of the substrate, the method including the step of
performing etching on the etching target film of the substrate
while supplying the processing gas from the gas supply unit such
that a flow rate of the second gas per unit area of a gas supply
surface of the gas supply unit is greater in the peripheral portion
than in the central portion.
[0013] Further, in accordance with still another embodiment of the
present invention, there is provided an etching method of
performing etching on an etching target film of a substrate by
using a processing gas which is a gaseous mixture including a first
gas containing halogen and carbon and having a carbon number of two
or less per molecule and a second gas containing halogen and carbon
and having a carbon number of three or more per molecule, and a gas
supply unit for supplying the processing gas toward the substrate
from a central portion and a peripheral portion of the gas supply
unit, independently, the central and the peripheral portion
respectively facing the central and the periphery part of the
substrate, the method including the step of performing etching on
the etching target film of the substrate while supplying the
processing gas from the gas supply unit, wherein a mixing ratio of
the first gas to the second gas in the central portion is equal to
that in the peripheral portion; and if a total number of halogen
atoms supplied along with the first gas is greater than that of
halogen atoms supplied along with the second gas, the processing
gas is supplied such that a flow rate of the gaseous mixture per
unit area of a gas supply surface of the gas supply unit is greater
in the central portion than in the peripheral portion, and if the
total number of halogen atoms supplied along with the first gas is
smaller than that of halogen atoms supplied along with the second
gas, the processing gas is supplied such that a flow rate of the
gaseous mixture per unit area of a gas supply surface of the gas
supply unit is greater in the peripheral portion than in the
central portion. In the etching method, the step of supplying the
processing gas from the gas supply unit such that a supply amount
of the gaseous mixture including the first gas and the second gas
is greater or smaller in the central portion than in the peripheral
portion is performed by controlling at least one of a flow rate of
the processing gas and a dilution rate of the processing gas
diluted with the dilution gas.
[0014] Further, in accordance with still another embodiment of the
present invention, there is provided an etching method of
performing etching on an etching target film of a substrate by
using a processing gas which is a gaseous mixture including a first
gas containing halogen and carbon and having a carbon number of two
or less per molecule and a second gas containing halogen and carbon
and having a carbon number of three or more per molecule, and a gas
supply unit for supplying the processing gas toward the substrate
from a central portion and a peripheral portion of the gas supply
unit, independently, the central and the peripheral portion
respectively facing the central and the periphery part of the
substrate, the method including the step of performing etching on
the etching target film of the substrate while supplying the
processing gas from the gas supply unit, wherein a first processing
gas produced by mixing the first gas with the second gas at a first
mixing ratio is supplied to the central portion of the gas supply
unit, and a second processing gas produced by mixing the first gas
with the second gas at a second mixing ratio is supplied to the
peripheral portion of the gas supply unit; and if a total number of
halogen atoms supplied along with the first gas is greater than
that of halogen atoms supplied along with the second gas, the
processing gas is supplied such that a flow rate of the first
processing gas is greater than that of the second processing gas
per unit area of the gas supply surface of the gas supply unit, and
if the total number of halogen atoms supplied along with the first
gas is smaller than that of halogen atoms supplied along with the
second gas, the processing gas is supplied such that a flow rate of
the first processing gas is smaller than that of the second
processing gas per unit area of the gas supply surface of the gas
supply unit.
[0015] Further, in accordance with still another embodiment of the
present invention, there is provided an etching method of
performing etching on an etching target film of a substrate by
using a processing gas which is a gaseous mixture including a first
gas containing halogen and carbon and having a carbon number of two
or less per molecule and a second gas containing halogen and carbon
and having a carbon number of three or more per molecule, and a gas
supply unit for supplying the processing gas toward the substrate
from a central portion and a peripheral portion of the gas supply
unit, independently, the central and the peripheral portion
respectively facing the central and the periphery part of the
substrate, the method including the step of performing etching on
the etching target film of the substrate while supplying the
processing gas from the gas supply unit such that a flow rate of
the first gas per unit area of the gas supply surface of the gas
supply unit is greater in the central portion than in the
peripheral portion and a flow rate of the second gas per unit area
of the gas supply surface of the gas supply unit is greater in the
peripheral portion than in the central portion.
[0016] Further, in accordance with still another embodiment of the
present invention, there is provided an etching method of
performing etching on an etching target film of a substrate by
using a processing gas which is a gaseous mixture including a first
gas containing halogen and carbon and having a carbon number of two
or less per molecule and a second gas containing halogen and carbon
and having a carbon number of three or more per molecule, and a gas
supply unit for supplying the processing gas toward the substrate
from a central portion and a peripheral portion of the gas supply
unit, independently, the central and the peripheral portion
respectively facing the central and the periphery part of the
substrate, the method including the step of performing etching on
the etching target film of the substrate while supplying the
processing gas from the gas supply unit wherein if a supply amount
of the first gas in the central portion of the gas supply unit is
equal to that in the peripheral portion thereof, the processing gas
is supplied such that a flow rate of the second gas per unit area
of the gas supply surface of the gas supply unit is greater in the
peripheral portion than in the central portion, and if a supply
amount of the second gas in the central portion of the gas supply
unit is equal to that in the peripheral portion thereof, the
processing gas is supplied such that a flow rate of the first gas
per unit area of the gas supply surface of the gas supply unit is
greater in the central portion than in the peripheral portion.
[0017] In the etching method, the step of supplying the processing
gas from the gas supply unit such that a supply amount of the first
gas is greater in the central portion than in the peripheral
portion is performed by controlling at least one of a flow rate of
the first gas and a dilution rate of the first gas diluted with the
dilution gas. Further, the step of supplying the processing gas
from the gas supply unit such that a supply amount of the second
gas is greater in the peripheral portion than in the central
portion is performed by controlling at least one of a flow rate of
the second gas and a dilution rate of the second gas diluted with
the dilution gas.
[0018] Further, in accordance with still another embodiment of the
present invention, there is provided an etching method of
performing etching on an etching target film of a substrate by
using a processing gas which is a gaseous mixture including a first
gas containing halogen and carbon and having a carbon number of two
or less per molecule and a second gas containing halogen and carbon
and having a carbon number of three or more per molecule, and a gas
supply unit for supplying the processing gas toward the substrate
from a central portion and a peripheral portion of the gas supply
unit, independently, the central and the peripheral portion
respectively facing the central and the periphery part of the
substrate, the method including the step of setting a composition
and an amount of the processing gas supplied from the gas supply
unit, wherein if a total number of halogen atoms supplied along
with the first gas is greater than that of halogen atoms supplied
along with the second gas, the processing gas is set such that a
total number of halogen atoms per unit area of the gas supply
surface of the gas supply unit per unit time is greater in the
central portion than in the peripheral portion, and if the total
number of halogen atoms supplied along with the first gas is
smaller than that of halogen atoms supplied along with the second
gas, the processing gas is supplied such that the total number of
halogen atoms per unit area of the gas supply surface of the gas
supply unit per unit time is greater in the peripheral portion than
in the central portion.
[0019] In the etching method, at least one of CH.sub.2F.sub.2 gas,
CHF.sub.3 gas, CF.sub.4 gas and C.sub.2F.sub.6 gas may be used as
the first gas, and at least one of C.sub.3F.sub.8 gas,
C.sub.4F.sub.8 gas, C.sub.4F.sub.6 gas and C.sub.5F.sub.8 gas may
be used as the second gas.
[0020] Such an etching method is performed by an etching apparatus,
including a processing chamber in which a susceptor for mounting a
substrate thereon is disposed; a gas supply unit, disposed in the
processing chamber to face the susceptor and having a surface
facing the susceptor serving as a gas supply surface, for supplying
a processing gas containing carbon and halogen toward the substrate
mounted on the susceptor from a central portion and a peripheral
portion of the gas supply unit, independently, the central and the
peripheral portion respectively facing the central and the
periphery part of the substrate; a means for controlling a pressure
inside the processing chamber; a means for generating a plasma in
the processing chamber; a means for controlling a flow rate of the
processing gas supplied to the gas supply unit; and a controller
for controlling each of the means, wherein an etching target film
formed on the substrate is etched by a plasma of the processing
gas.
[0021] As described above, in accordance with the present
invention, when etching is performed on an etching target film
formed on a substrate by using a processing gas including a gas
containing carbon and halogen, a supply amount of the gas
containing carbon and halogen is controlled, according to the
carbon number of the gas containing carbon and halogen, in such a
manner that a greater flow rate is supplied to the central portion
of the gas supply surface than to the peripheral portion and vice
versa. Therefore, high in-surface uniformity of etching
characteristics such as an etching rate, processing accuracy after
etching can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The above and other objects and features of the present
invention will become apparent from the following description of
preferred embodiments given in conjunction with the accompanying
drawings, in which:
[0023] FIG. 1 is a vertical sectional view showing a plasma etching
apparatus in accordance with a preferred embodiment of the present
invention;
[0024] FIG. 2 shows a configuration of a gas supply system of the
plasma etching apparatus;
[0025] FIG. 3 shows a configuration of another example of a gas
supply system of the plasma etching apparatus;
[0026] FIG. 4 offers a characteristic graph showing simulation
results for in-surface uniformity of a gas flow speed;
[0027] FIG. 5 presents a characteristic graph showing simulation
results for in-surface uniformity of a pressure;
[0028] FIG. 6 depicts a characteristic graph showing in-surface
uniformity of a film formation speed;
[0029] FIGS. 7A and 7B are, respectively, characteristic graphs
showing in-surface uniformity of CF density and CF.sub.2 density in
Embodiment 1;
[0030] FIGS. 8A and 8B show in-surface uniformity of a residual
resist film, an etching depth, a top CD and a bowing position in
Embodiment 2;
[0031] FIGS. 9A and 9B are characteristic graphs showing in-surface
uniformity of absolute values of a top CD difference and a etching
depth, respectively, in Embodiment 3;
[0032] FIG. 10 shows in-surface uniformity of a residual resist
film, a top CD, a bottom CD and a recess in Embodiment 4;
[0033] FIGS. 11A and 11B present in-surface uniformity of a taper
angle .theta. in Embodiment 5;
[0034] FIG. 12 is a characteristic graph showing in-surface
uniformity of an absolute value of a top CD difference in
Embodiment 6;
[0035] FIG. 13 shows in-surface uniformity of a top CD and a bottom
CD in Embodiment 7;
[0036] FIGS. 14A and 14B depict characteristic graphs showing
in-surface uniformity of a CD shift value in Embodiment 8;
[0037] FIG. 15 shows in-surface uniformity of an etching rate, a
resist selectivity, a residual resist film and an etching depth in
Embodiment 9;
[0038] FIG. 16 offers a characteristic graph showing in-surface
uniformity of a CD shift value in Embodiment 10;
[0039] FIG. 17 is a characteristic graph showing in-surface
uniformity of a CD in Embodiment 11; and
[0040] FIG. 18 displays in-surface uniformity of an etching rate in
Embodiment 12.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] Above all, there will be briefly described an example of a
plasma etching apparatus for performing an etching method in
accordance with a first preferred embodiment of the present
invention with reference to FIG. 1. FIG. 1 shows a chamber 1 which
is, for example, a cylindrical processing vessel formed of, e.g.,
aluminum whose surface is alumite treated (anodic oxidized); and
the chamber 1 is grounded. Provided in a bottom portion of the
chamber 1 is an approximately cylindrical susceptor 2 for mounting
thereon a substrate such as a semiconductor wafer (hereinafter,
referred to as a "wafer"). Further, the susceptor 2 also serves as
a lower electrode and is connected to a high pass filter (HPF) 23.
Reference numerals 21 and 22 in FIG. 1 refer to an insulating plate
made of ceramic or the like and a susceptor support member,
respectively. A reference numeral 24 in FIG. 1 refer to a coolant
chamber to which a coolant such as liquid nitrogen is supplied to
be circulated therein, so that the susceptor can be maintained at a
desired temperature by heat conduction.
[0042] The susceptor 2 has an upper central portion of disk shape,
which protrudes higher than its peripheral portion, and an
electrostatic chuck 3 that is shaped substantially identical to the
wafer W is disposed on the upper central portion of the susceptor
2. Further, the electrostatic chuck 3 includes an electrode 31
therein. The wafer W is electrostatically adsorbed onto
electrostatic chuck 3 by Coulomb force generated by a DC voltage
of, for example, 1.5 kV applied to the electrode 31 from a DC power
supply 32. A reference numeral 33 in FIG. 1 refer to a gas channel
for supplying a heat transfer medium, e.g., a He gas, to a backside
surface of the wafer W supported on the susceptor 2, wherein heat
is transferred between the susceptor 2 and the wafer W through the
heat transfer medium, so that the wafer W can be maintained at a
predetermined temperature. A reference numeral 25 in FIG. 1 refer
to an annular focus ring disposed to surround the wafer W loaded on
the electrostatic chuck 3. The focus ring 25 is formed of an
electrically conductive material such as silicon and functions to
improve uniformity of etching.
[0043] A gas supply unit 4 also serving as an upper electrode of,
e.g., an approximately cylindrical shape is disposed above the
susceptor 2 to face it in parallel. The gas supply unit 4 includes
an electrode plate 42 forming a facing surface to the susceptor 2
and having a plurality of injection openings 41; and an electrode
support member 43 for supporting the electrode plate 42. Further,
the electrode support member 43 has a water cooling structure and
is formed of, for example, aluminum whose surface is alumite
treated.
[0044] The electrode support member 43 includes a gas introduction
chamber formed therein, which is divided into two inner and outer
parts which are, respectively, a first gas chamber (first gas
introduction chamber) 45 facing a center part of the wafer W and a
second gas chamber (second gas introduction chamber) 46 facing a
periphery part of the wafer W by a partition wall 44 of, e.g., a
ring shape. Thus, bottom surfaces of the first gas chamber 45 and
the second gas chamber 46 are formed with the electrode plate 42
having the injection openings 41 and serving as a gas supply
surface.
[0045] Further, for instance, as shown in FIG. 2, the first gas
chamber 45 is connected to a processing gas supply system 53 via a
first gas introduction line 51 provided with a flow rate control
unit F1; and the second gas chamber 46 is connected to the
processing gas supply system 53 via a second gas introduction line
52 provided with a flow rate control unit F2. A reference numeral
47 in FIG. 1 refer to an insulation member; reference numeral 48, a
high frequency absorbing member; and reference numeral 49, an
insulation member for supporting the gas supply unit 4 in the
chamber 1. Further, the susceptor 2 and the gas supply unit 4 are
spaced from each other by, for example, about 10.about.60 mm.
[0046] A low dielectric film (low-k film) described above such as
an SiOC film, an SiOCH film, an SiO.sub.2 film, an SiOF film, an
SiO.sub.2 film containing Si--H, a HydrogenSilses-Quioxane (HSQ)
film, a porous silica film, a SiO.sub.2 film containing a methyl
group, a MethylSilses-Quioxane (MSQ) film, a porous MSQ film or the
like can be used as an etching object film. As for the processing
gas, a gas containing carbon and a halogen atom such as fluorine,
bromine and chlorine is used as a main etching gas. As examples of
a CF-based gas containing carbon and fluorine employed as a main
etching gas, there are a first gas having a carbon number of 2 or
less (e.g., CF.sub.4 gas, CHF.sub.3 gas, and C.sub.2H.sub.6 gas),
and a second gas having a carbon number of 3 or more (e.g.,
C.sub.3F.sub.8 gas, C.sub.4F.sub.6 gas, C.sub.4F.sub.8 gas, and
C.sub.5F.sub.8 gas). Moreover, as the processing gas, it is
possible to use a gaseous mixture obtained by mixing the CF-based
gas with a rare gas or a dilution gas such as, N.sub.2 gas, H.sub.2
gas, O.sub.2 gas, CO gas and CO.sub.2 gas without containing
halogen atom, or a combination of a plurality of the CF-based
gases.
[0047] The processing gas supply system 53, for example, includes a
first gas supply source 54 for supplying the first gas, a second
gas supply source 55 for supplying the second gas and a dilution
gas supply source 56 for supplying the dilution gas, which are
connected to the first gas introduction line 51 and the second gas
introduction line 52 via a supply line 57 equipped with respective
flow rate control units F3 to F5. The flow rate control units F1 to
F5 for regulating a supply amount of the processing gas include a
valve and a mass flow controller, and their operations are
controlled by a controller 6. Thus, the first gas, the second gas
and the dilution gas are mixed to make the processing gas, and the
mixed processing gas is supplied to the first gas introduction
chamber 45 and the second gas introduction chamber 46 at specified
flow rates, respectively.
[0048] A vacuum pump 12 such as a turbo molecular pump for
controlling the pressure in the chamber 1 is connected to a bottom
portion of the chamber 1 via a gas exhaust pipe 11. Thus, the
inside of the chamber 1 can be evacuated to form therein a
depressurized atmosphere having, e.g., a predetermined pressure of
1 Pa or less. Further, a gate valve 13 is installed on a sidewall
of the chamber 1. The wafer W is transferred between the chamber 1
and an adjacent load-lock chamber (not shown) while the gate valve
13 is opened.
[0049] The gas supply unit 4 serving as the upper electrode is
connected to a first high frequency power supply 61 serving as a
plasma generation means through a matching unit 62 and a power feed
rod 63, and, further, coupled to a low pass filter (LPF) 64. The
first high frequency power supply 61 has a frequency of 27 MHz or
more. By applying a high frequency power in such a range, a
high-density plasma in a desirable dissociation state can be
generated in the chamber 1, which makes it possible to perform a
plasma processing under a low pressure. In this example, the
frequency of the first high frequency power supply 61 is chosen to
be 60 MHz.
[0050] The susceptor 2 serving as the lower electrode is connected
to a second high frequency power supply 65 through a matching unit
66 installed in a feeder line. The second high frequency power
supply 65 has a frequency ranging from 100 kHz to 10 MHz. By
applying a power of a frequency in such a range, a proper ionic
action can be facilitated without causing any damage on the wafer
W. In this example, the frequency of the first high frequency power
supply 65 is chosen to be 2 MHz.
[0051] Hereinafter, there will be described an etching method
performed by using the plasma etching apparatus in accordance with
the present invention. First, in the plasma etching apparatus,
after the gate valve 13 is opened, the wafer W, i.e., a substrate,
is loaded from the load-lock chamber (not shown) into the chamber 1
to be mounted on the electrostatic chuck 3. Then, the wafer W is
electrostatically adsorbed onto the electrostatic chuck 3 by
applying a DC voltage from the high voltage DC power supply
thereto. Next, the gate valve 13 is closed, and the inside of the
chamber 1 is evacuated to a predetermined vacuum level by using the
vacuum pump 12.
[0052] Subsequently, the processing gases from the processing gas
supply system 53 are introduced into the first gas chamber 45 and
the second gas chamber 46 of the gas supply unit 4 through the
first gas introduction line 51 and the second gas introduction line
52 while supply amounts are controlled by the flow rate control
units F1, F2, respectively. Accordingly, the processing gas is
supplied to the center part of the wafer W from the first gas
chamber 45 while, at the same time, being supplied to the periphery
part of the wafer W from the second gas chamber 46, and the
pressure in the chamber 1 is maintained at a predetermined
value.
[0053] Afterwards, a high frequency of 27 MHz or more, e.g., 60
MHz, is applied to the gas supply unit 4 from the first high
frequency power supply 61. Thus, high frequency electric field is
generated between the gas supply unit 4 and the susceptor 2, so
that the processing gas is dissociated to be converted into a
plasma and the wafer W is etched by the plasma.
[0054] Meanwhile, a high frequency of 100 kHz.about.10 MHz, for
example, 2 MHz, is applied to the susceptor 2 from the second high
frequency power supply 65. Accordingly, ions in the plasma are
attracted into the susceptor 2, so that ion assist improves
anisotropy of the etching. The wafer W on which the predetermined
etching process has been performed as described above is
transferred to the outside from the chamber 1, proceeding to a next
step.
[0055] In the etching method of the present invention, when a
SiO-based film such as SiOC film is etched by a gas containing
CF-based gas serving as the main etching gas, a larger amount of
the CF-based gas is supplied to the center part of the wafer W than
the periphery part and vice versa depending on the carbon number of
the CF-based gas. Detailed description thereof will be offered
below.
[0056] First, there will be described a case where the CF-based gas
and the dilution gas are mixed before being supplied to the plasma
etching apparatus. In such a case, the processing gases supplied to
the first gas chamber 45 and the second gas chamber 46 of the gas
supply unit 4 in the plasma etching apparatus have a same
composition. Thus, flow rates of the processing gases supplied to
the first and the second gas chamber 45 and 46 are controlled,
whereby the amounts of the CF-based gases included in the
processing gases can be controlled to be supplied toward the
central and the periphery part.
[0057] Specifically, first, there will be described a case of using
one kind of the CF-based gas. When the first gas whose carbon
number is 2 or less is used as the main etching gas, the processing
gases are introduced into the gas supply unit 4 such that per unit
area of the gas supply surface of the gas supply unit 4 per unit
time, an amount of the first gas supplied to a central portion of
the gas supply surface is greater than that supplied to a
peripheral portion thereof.
[0058] That is, flow rates of the first gas and the dilution gas
are controlled to be specified values by the flow rate control
units F3 and F5 to thereby produce a processing gas wherein the
first gas and the dilution gas are mixed at a predetermined mixing
ratio. Then, the processing gases are introduced into the first and
the second gas chamber 45 and 46 through the first and the second
gas introduction line 51 and 52 at respective flow rates by the
flow rate control units F1 and F2 such that the amount of the
processing gas supplied into the first gas chamber 45 is greater
than that supplied into the second gas chamber 46. Consequently,
the central portion of the gas supply surface is supplied with a
greater amount of the first gas than the peripheral portion
thereof.
[0059] Here, "the supply amount of the first gas" used in the
present invention means a supply amount thereof per unit area of
the gas supply surface per unit time. Further, "the central portion
of the gas supply surface is supplied with a greater amount of the
first gas than the peripheral portion thereof" means that the
number of moles of the first gas supplied to the central portion is
greater than that of the first gas supplied to the peripheral
portion.
[0060] Further, when the second gas having the carbon number of 3
or more is used as the main etching gas, the processing gases are
introduced into the gas supply unit 4 such that per unit area of
the gas supply surface of the gas supply unit 4 per unit time, an
amount of the second gas supplied to the peripheral portion of the
gas supply surface is greater than that supplied to the central
portion thereof.
[0061] That is, flow rates of the second gas and the dilution gas
are controlled to be specified values by the flow rate control
units F4 and F5 to thereby produce a processing gas wherein the
second gas and the dilution gas are mixed at a predetermined mixing
ratio. Then, the processing gases are introduced into the first and
the second gas chamber 45 and 46 through the first and the second
gas introduction line 51 and 52 at respective flow rates by the
flow rate control units F1 and F2 such that the amount of the
processing gas supplied into the second gas chamber 46 is greater
than that supplied into the first gas chamber 45. Therefore, the
peripheral portion of the gas supply surface is supplied with a
greater amount of the first gas than the central portion
thereof.
[0062] Here, "the central portion of the gas supply surface" means
the gas supply surface of the first gas chamber 45, facing the
center part of the wafer W occupying about seven-tenths (square
root of a half) of its radius. "The peripheral portion of the gas
supply surface" means the gas supply surface of the second gas
chamber 46, facing a periphery part of the wafer W surrounding the
center part thereof. Further, areas of the central portion and the
peripheral portion are designed to be approximately equal to each
other. In the plasma etching apparatus, the gas supply surface of
the gas supply unit 4 faces the wafer W, and it is configured such
that the processing gases are supplied from the first and the
second gas chamber 45 and 46 of the gas supply unit 4 toward the
central and the periphery part of the wafer W, respectively.
Therefore, when the amount of the first gas supplied to the central
portion of the gas supply surface is set to be greater than that
supplied to the peripheral portion thereof, the amount of the first
gas supplied to the center part of the wafer W becomes greater than
that supplied to the periphery part thereof. On the other hand,
when the amount of the second gas supplied to the peripheral
portion of the gas supply surface is set to be greater than that
supplied to the central portion thereof, the amount of the second
gas supplied to the periphery part of the wafer W becomes greater
than that supplied to the center part thereof.
[0063] In this case, in the plasma etching apparatus, if the number
of the injection openings 41 formed on the bottom surface of the
first chamber 45 (injection openings for supplying a gas to the
center part of the wafer W) is equal to that of the injection
openings 41 formed on the bottom surface of the second chamber 46
(injection openings for supplying a gas to the periphery part of
the wafer W) and a gas flow rate ratio of the central portion to
the peripheral portion of the gas supply surface is set at 5:5, a
gas flow rate from each of the injection openings 41 is constant.
However, if the number of the injection openings 41 formed on the
bottom surface of the first chamber 45 is different from that of
the injection openings 41 formed on the bottom surface of the
second chamber 46 or if conductance to the injection openings 41
formed on the bottom surface of the first chamber 45 is different
from that to the injection openings 41 formed on the bottom surface
of the first chamber 46, adjustment therefor needs to be carried
out.
[0064] For example, a case where the ratio of the number of the
injection openings 41 formed on the bottom surface of the first gas
chamber 45 versus that of the injection openings 41 formed on the
bottom surface of the second gas chamber 46 is set to be 2:1, if
the processing gases are supplied to the center part and the
periphery part at a flow rate ratio of 1:2, has a substantially
same effect as the case where the processing gases are supplied to
the center part and the periphery part at a flow rate ratio of 5:5
in the plasma etching apparatus. Therefore, when, for example,
C.sub.4F.sub.8 gas is used as the main processing gas, it is
preferable that two thirds of the entire processing gas or larger
is supplied to the periphery part.
[0065] Next, there will be described a case of using two or more
kinds of CF-based gas. For example, when the combination of the
first gas and the second gas is used, the first gas, the second gas
and the dilution gas are mixed at a predetermined mixing ratio by
the flow rate control units F3 to F5 to produce the processing gas.
The total number of halogen atoms introduced by each of the first
and the second gas is calculated. The flow rates are determined
depending on the kind of CF-based gas having the greater total
number. This is because the etching efficiency is dominated by the
number of halogen atoms, and thus the uniformity is dominated by a
gas having a greater number of halogen atoms.
[0066] For example, in case that the first gas of CF.sub.4 gas and
the second gas of C.sub.4F.sub.8 gas are mixed at a mixing ratio of
15:6 (CF.sub.4:C.sub.4F.sub.8) to make the processing gas, the
total number of F introduced by CF.sub.4 gas is 4.times.15=60, and
the total number of F introduced by C.sub.4F.sub.8 is 8.times.6=48.
Namely, the total introduction number of F in the CF.sub.4 is
greater than C.sub.4F.sub.8. Thus, the flow rates are determined by
the CF.sub.4 gas. A greater amount of the processing gas is
introduced to the first gas introduction chamber 45 than to the
second gas introduction chamber 46 by controlling the flow rate
control units F1, F2 such that the amount of the processing gas
supplied to the central portion of the gas supply surface is
greater than that supplied to the peripheral portion thereof.
[0067] Similarly, in case that the total number of halogen atoms
supplied along with the first gas is smaller than that supplied
along with the second gas, the amount of the processing gas
introduced to the second gas chamber 46 is greater than that
introduced to the first gas chamber 45 by controlling the flow rate
control units F1 and F2 such that the amount of the processing gas
supplied to the peripheral portion of the gas supply surface is
greater than that supplied to the central portion thereof.
[0068] Hereinafter, there will be described a second preferred
embodiment of the present invention. In this embodiment, the
compositions of processing gases supplied to the central portion
and the peripheral portion of the gas supply surface of the gas
supply unit 4 are controlled independently, which is realized by,
e.g., a plasma etching apparatus shown in FIG. 3. In the plasma
etching apparatus shown apparatus, for example, the first gas
introduction line 51 provided with the flow rate control unit F1 is
connected to a first gas supply source 161 for supplying the first
gas, a second gas supply source 162 for supplying the second gas
and a dilution gas supply source 163 for supplying the dilution gas
via supply lines equipped with flow rate control units F6, F7 and
F8, respectively. Further, the second gas introduction line 52
provided with the flow rate control unit F2 is connected to a first
gas supply source 164 for supplying the first gas, a second gas
supply source 165 for supplying the second gas and a dilution gas
supply source 166 for supplying the dilution gas via a supply lines
equipped with the flow rate control units F9, F10 and F11.
[0069] The flow rate control units F1, F2, F6 to F11 are controlled
by the controller 6, and thus the processing gases having different
mixing ratios of the first gas, the second gas and the dilution gas
(different dilution rates) can be supplied to the first gas chamber
45 and the second gas chamber 46 through the first gas introduction
line 51 and the second gas introduction line 52, respectively. And
the other configuration is same as the plasma etching apparatus
shown in FIG. 1.
[0070] In this embodiment, in case that the processing gases have
the same composition or that a CF-based gas is only supplied, the
flow rates of the processing gases supplied to the first gas
chamber 45 and the second gas chamber 46 is controlled, thereby
controlling the total number of fluorine atoms (halogen atoms)
supplied to the central portion of the gas supply surface and that
supplied to the peripheral portion thereof. Besides, the processing
gases having the different compositions can be supplied to the
plasma etching apparatus. Accordingly, by varying compositions of
the processing gases, that is, dilution rates of the CF-based
gases, while flow rates of the processing gases supplied to the
first gas chamber 45 and the second gas chamber 46 are kept to be
equal, the total number of fluorine atoms (halogen atoms) supplied
to the central portion of the gas supply surface and that supplied
to the peripheral portion thereof may be controlled.
[0071] At this time, in case the first gas having the carbon number
of 2 or less is used as the main etching gas, the amount of the
first gas supplied to the first gas chamber 45 and that supplied to
the second gas chamber 46 are controlled such that the total number
of fluorine atoms supplied to the central portion of the gas supply
surface is greater than that of fluorine atoms supplied to the
peripheral portion thereof.
[0072] For example, in case that CF.sub.4 gas is used as the first
gas and the dilution gas is not used, the flow rate of CF.sub.4 gas
supplied to the first gas chamber 45 is set at 100 sccm by the flow
rate control units F1 and F6; and the flow rate of CF.sub.4 gas
supplied to the second gas chamber 46 is set at 50 sccm by the flow
rate control units F2 and F9. In other words, the gas flow rate
supplied to the central portion of the gas supply surface is 100
sccm; and the gas flow rate supplied to the peripheral portion
thereof is 50 sccm, so that the total number of fluorine atoms
supplied to central portion of the gas supply surface is greater
that supplied to the peripheral portion thereof. In this case, a
single flow rate control unit may be provided between the first gas
chamber 45 and the first gas supply source 161 or between the first
gas chamber 45 and the second gas supply source 162. Further, it is
possible to provide only one flow rate control unit between the
second gas chamber 46 and the first gas gas supply source 164 or
between the second gas chamber 46 and the second gas supply source
165.
[0073] Further, for example, in case that the first gas of CF.sub.4
gas and the dilution gas of Ar gas are employed while varying the
dilution rates of the first gases supplied to the central portion
and the peripheral portion of the gas supply surface, the first gas
having a flow rate of 50 sccm and the dilution gas having a flow
rate of 100 sccm are supplied to first gas introduction line 51 via
the flow rate control units F6 and F8 while, at the same time, the
first gas having a flow rate of 50 sccm and the dilution gas having
a flow rate of 300 sccm are supplied to the second gas introduction
line 52 via the flow rate control units F9 and F11. Then, by
controlling the flow rate control units F1 and F2, processing gases
of the same flow rate are supplied to the first gas chamber 45 and
the second gas chamber 46 from the first gas introduction line 51
and the second gas introduction line 52, respectively.
[0074] As described above, by supplying the processing gases at a
same flow rate to the first gas chamber 45 and the second gas
chamber 46; and making the dilution rate of the first gas diluted
with the dilution gas greater in the processing gas supplied to the
second gas chamber 46 than in the processing gas supplied to the
first gas chamber 45, the total number of fluorine atoms supplied
to the central portion of the gas supply surface can be controlled
to be greater than that of fluorine atoms supplied to the
peripheral portion thereof.
[0075] Similarly, in case of using the second gas having the carbon
number of 3 or more as the main etching gas, amounts of the second
gases supplied to the central portion and the peripheral portion of
the gas supply surface are controlled such that the total number of
fluorine atoms in the second gas supplied to the central portion of
the gas supply surface is smaller than that of the halogen atoms of
the second gas supplied to the peripheral portion thereof.
[0076] In the same way as in the case of using the first gas, in
case that the processing gases have the same composition or that a
CF-based gas is only supplied, the larger amount of the second gas
is supplied to the second gas chamber 46 that the first gas chamber
45, so that it can be controlled that the total number of fluorine
atoms supplied to the peripheral portion of the gas supply surface
is greater than that of fluorine atoms supplied to the central
portion thereof. Besides, by varying compositions of the processing
gases, that is, dilution rates of the second gases, while the
amounts of the processing gases supplied to the first gas chamber
45 and the second gas chamber 46 are kept to be equal, it can be
controlled that the total number of fluorine atoms supplied to the
peripheral portion of the gas supply surface is greater than that
supplied to the central portion thereof may be controlled.
[0077] Further, in case the first gas having the carbon number of 2
or less and the second gas having a carbon number of 3 or more are
mixed, the total number of halogen atoms introduced by each
CF-based gas is calculated, and then it is determined whether more
halogen atoms are supplied to the central portion or the peripheral
portion of the gas supply surface by the CF-based gas having a
greater number of halogen atoms.
[0078] When the processing gases having different mixing ratios of
the first gas to the second gas are respectively supplied to the
first gas chamber 45 and the second gas chamber 46, for example,
when a first processing gas having a first mixing ratio of the
first gas to the second gas is supplied to the first gas chamber 45
and a second processing gas having a second mixing ratio of the
first gas to the second gas is supplied to the second gas chamber
46, after calculating the total number of halogen atoms introduced
by each CF-based gas in the entire processing gas including the
first and the second processing gas, the amount of the first gas
supplied to the first gas chamber 45 and the amount of the second
gas supplied to the second gas chamber 46 are determined by the
CF-based gas having a greater number of halogen atoms.
[0079] That is, in case the number of fluorine atoms introduced by
the first gas is greater than that introduced by the second gas,
the flow rates of the first processing gas and the second
processing gas are controlled by the flow rate control units F1 and
F2 such that the amount of the first processing gas supplied to the
first gas chamber 45 is greater than that of the second processing
gas supplied to the second gas chamber 46.
[0080] On the other hand, in case the number of fluorine atoms
introduced by the second gas is greater than that introduced by the
first gas, the flow rates of the first processing gas and the
second processing gas are controlled by the flow rate control units
F1 and F2 such that the amount of the first processing gas supplied
to the first gas chamber 45 is smaller than that of the second
processing gas supplied to the second gas chamber 46.
[0081] In this case, the mixing ratio of the first gas to the
second gas in the first processing gas is controlled by the flow
rate control units F6 and F7, while the mixing ratio of the first
gas to the second gas in the second processing gas is controlled by
the flow rate control units F9 and F10. Then, the amounts of the
first and the second processing gas to be supplied to the first gas
chamber 45 and the second gas chamber 46 are controlled by the flow
rate control units F1 and F2, respectively.
[0082] Further, in case the first gas having the carbon number of 2
or less and the second gas having the carbon number of 3 or more
are mixed, the amounts of the first gas and the second gas
respectively supplied to the first gas chamber 45 and the second
gas chamber 46 may be controlled such that a greater amount of the
first gas is supplied to the central portion than to the peripheral
portion and that a greater amount of the second gas is supplied to
the peripheral portion than to the central portion.
[0083] Specifically, for example, in case CF.sub.4 gas is used as
the first gas and C.sub.4F.sub.8 is used as the second gas,
C.sub.4F.sub.8 gas having a flow rate of 2 sccm and CF.sub.4 gas
having a flow rate of 10 sccm are supplied to the first gas chamber
45, while C.sub.4F.sub.8 having a flow rate of 4 sccm and CF.sub.4
gas having a flow rate of 5 sccm are supplied to the second gas
chamber 46. By doing so, the processing gas in the central portion
of the gas supply surface has a greater amount of the first gas and
a smaller mixing ratio of the second gas to the first gas than the
processing gas in the peripheral portion. Further, the processing
gas in the peripheral portion has a greater amount of the second
gas and a greater mixing ratio of the second gas to the first gas
than the processing gas in the central portion. Therefore, the flow
rate of the first gas is controlled in such a manner that a greater
amount of fluorine atoms is supplied to the central portion than to
the peripheral portion of the gas supply surface, while the flow
rate of the second gas is controlled in such a manner that a
greater amount of fluorine atoms is supplied to the peripheral
portion than to the central portion.
[0084] In this case, the amount of the first gas supplied to the
first gas chamber 45 is controlled by the flow rate control unit F1
or F6, while the amount of the first gas supplied to the second gas
chamber 46 is controlled by the flow rate control unit F2 or F9.
Further, the amount of the second gas supplied to the first gas
chamber 45 is controlled by the flow rate control unit F1 or F7,
while the amount of the second gas supplied to the second gas
chamber 46 is controlled by the flow rate control unit F2 or F10.
Accordingly, in this embodiment, only one flow rate control unit
may be installed between the first gas chamber 45 and the first gas
supply source 161; between the first gas chamber 45 and the second
gas supply source 162; between the second gas chamber 46 and the
first gas supply source 164; or between the second gas chamber 46
and the second gas supply source 165.
[0085] Further, in case the first gas having carbon number of two
or less and the second gas having a carbon number of three or more
are mixed with each other as described above, if the amount of the
processing gas supplied to the first gas chamber 45 is equal to
that supplied to the second gas chamber 46, the ratio of the first
gas to the processing gas is set to be greater in the central
portion than in the peripheral portion of the gas supply surface,
while the ratio second gas to the processing gas is set to be
greater in the peripheral portion than in the central portion of
the gas supply surface.
[0086] Further, in case the first gas having a carbon number of two
or less and the second gas having a carbon number of three or more
are mixed with each other, the flow rate of the first gas may be
controlled such that the same amount of the first gas is supplied
to the first gas chamber 45 and the second gas chamber 46, whereas
the flow rate of the second gas may be controlled such that a
greater amount of the second gas is supplied to the second gas
chamber 46 than to the first gas chamber 45 to thereby supply it to
the peripheral portion than to the central portion of the gas
supply surface. For example, the first gas chamber 45 is supplied
with a gaseous mixture containing C.sub.4F.sub.8 gas having a flow
rate of 2 sccm and CF.sub.4 gas having a flow rate of 10 sccm,
while the second gas chamber 46 is supplied with a gaseous mixture
containing C.sub.4F.sub.8 gas having a flow rate of 4 sccm and
CF.sub.4 gas having a flow rate of 10 sccm.
[0087] At this time, by maintaining the flow rates of the
processing gases supplied to the first gas chamber 45 and the
second gas chamber 46 to be equal, and at the same time, making the
ratio of the first gas to the processing gas in the first gas
chamber 45 equal to that in the second gas chamber 46, it is
possible to set the ratio of the second gas to the processing gas
to be greater in the peripheral portion than in the central portion
of the gas supply surface.
[0088] Further, the flow rate of the second gas may be controlled
such that the same amount of the second gas is supplied to the
first gas chamber 45 and the second gas chamber 46, whereas the
flow rate of the first gas may be controlled such that a greater
amount of the first gas is supplied to the first gas chamber 45
than to the second gas chamber 46 to thereby supply it to the
central portion than to the peripheral portion of the gas supply
surface. For example, the first gas chamber 45 is supplied with a
gaseous mixture containing C.sub.4F.sub.8 gas having a flow rate of
2 sccm and CF.sub.4 gas having a flow rate of 10 sccm, while the
second gas chamber 46 is supplied with a gaseous mixture containing
C.sub.4F.sub.8 gas having a flow rate of 2 sccm and CF.sub.4 gas
having a flow rate of 5 sccm.
[0089] At this time, by maintaining the flow rates of the
processing gases supplied to the first gas chamber 45 and the
second gas chamber 46 to be equal, and at the same time, making the
ratio of the second gas to the processing gas in the first gas
chamber 45 equal to that in the second gas chamber 46, it is
possible to set the ratio of the first gas to the processing gas to
be greater in the central portion than in the peripheral portion of
the gas supply surface.
[0090] By doing so, the processing gas in the central portion of
the gas supply surface has a smaller mixing ratio of the second gas
to the first gas than the processing gas in the peripheral portion.
Further, the processing gas in the peripheral portion has a greater
mixing ratio of the second gas to the first gas than the processing
gas in the central portion. Therefore, the flow rate of the first
gas is controlled in such a manner that a greater amount of
fluorine atoms is supplied to the central portion than to the
peripheral portion of the gas supply surface, while the flow rate
of the second gas is controlled in such a manner that a greater
amount of fluorine atoms is supplied to the peripheral portion than
to the central portion.
[0091] Also in this case, the amount of the first gas supplied to
the first gas chamber 45 is controlled by the flow rate control
unit F1 or F6, while the amount of the first gas supplied to the
second gas chamber 46 is controlled by the flow rate control unit
F2 or F9. Further, the amount of the second gas supplied to the
first gas chamber 45 is controlled by the flow rate control unit F1
or F7, while the amount of the second gas supplied to the second
gas chamber 46 is controlled by the flow rate control unit F2 or
F10. Accordingly, a single flow rate control unit may be installed
between the first gas chamber 45 and the first gas supply source
161; between the first gas chamber 45 and the second gas supply
source 162; between the second gas chamber 46 and the first gas
supply source 164; or between the second gas chamber 46 and the
second gas supply source 165.
[0092] Further, in accordance with the present invention, in case
the total number of halogen atoms supplied along with the first gas
is greater than that of supplied along with the second gas, the
composition of the processing gas or the supply amount of the
processing gas may be controlled in such a manner that the total
number of halogen atoms per unit area of the gas supply surface per
unit time is greater in the central portion than in the peripheral
portion. In such a case, the number of halogen atoms supplied along
with the first gas and the second gas is greater in the central
portion than in the peripheral portion of the gas supply
surface.
[0093] At this time, in case the total number of halogen atoms
supplied along with the first gas is smaller than that supplied
along with the second gas, the composition of the processing gas or
the supply amount of the processing gas may be set in such a manner
that the total number of halogen atoms per unit area of the gas
supply surface per unit time is greater in the peripheral portion
than in the central portion. In such a case, the number of halogen
atoms supplied along with the first gas and the second gas is
greater in the peripheral portion than in the central portion of
the gas supply surface.
[0094] In the above-mentioned methods, according to the carbon
number of the CF-based gas, the amount of CF-based gas supplied to
the central portion is controlled to be greater or smaller than
that supplied to the peripheral portion of the gas supply surface.
Therefore, as will be clear in embodiments to be described later,
it is possible to secure the in-surface uniformity of etching
characteristics, such as an etching rate or processing accuracy
after etching, such as a top CD, a bottom CD, an etching residual
film, an etching depth and a hole shape.
[0095] At this time, it has been determined in advance, depending
on the carbon number in CF-based gas, which of the central portion
and the peripheral portion of the gas supply surface is supplied
with more halogen atoms. Therefore, it narrows down the scope of
parameters used in determining the most appropriate condition for
the flow rates and compositions of the processing gases supplied to
the central portion and the peripheral portion of the gas supply
surface and the like, readily setting the condition.
Embodiments
[0096] Hereinafter, an evaluation method of the present invention
will be described. From various data obtained from the experiments,
the inventors of the present invention found that a greater amount
of the first gas having the carbon number of two or less is
supplied to the central portion than to the peripheral portion of
the gas supply surface, and a greater amount of the second gas
having the carbon number of three or more is supplied to the
peripheral portion than to the central portion of the gas supply
surface in order to increase the in-surface uniformity of the
etching characteristics such as the etching rate or processing
accuracy after etching.
[0097] First, a description will be offered on experiment examples
conducted to prove the mechanism of the present invention.
[0098] FIG. 4 provides simulation results of gas flow speed
distribution near the surface of the wafer W when the amounts of
CF-based gases supplied to the central portion and the peripheral
portion of the gas supply surface are changed by changing the flow
rate ratio of the processing gas supplied to the first gas chamber
45 (the central portion of the gas supply surface) versus the
processing gas supplied to the second gas chamber 46 (the
peripheral portion of the gas supply surface) in the
above-described plasma etching apparatus, wherein it was assumed
that the CF-based gas was C.sub.4F.sub.8. In FIG. 4, the vertical
axis represents the gas flow speed and the horizontal axis
represents the distance from the center of the wafer W. Further, a
flow rate ratio C/E is a flow rate in the central portion (C) to a
flow rate in the peripheral portion (E) of the gas supply surface,
wherein a dashed dotted line indicates a case of C/E=3/7; a solid
line, a case of C/E=5/5; and a dashed double-dotted line, a case of
C/E=7/3. Further, the flow rate ratio C/E of 3/7 means that
three-tenths of the flow rate of the entire processing gas is
supplied to the central portion of the gas supply surface, while
seven-tenths of the flow rate of the entire processing gas is
supplied to the peripheral portion.
[0099] As a result, it is known that when a greater amount of the
processing gas is supplied to the central portion than to the
peripheral portion of the gas supply surface, the gas flow speed is
the highest, and when a greater amount of the processing gas is
supplied to the peripheral portion than to the central portion, the
gas flow speed is the lowest. When a greater amount of the
processing gas is supplied to the central portion than to the
peripheral portion, since the acceleration of the gas flow speed is
greater compared to the case of supplying a greater amount of the
processing gas to the peripheral portion, it is inferred that the
gas flows quickly from the center of the wafer W to the edge
thereof.
[0100] On the other hand, when a greater amount of the processing
gas is supplied to the peripheral portion than to the central
portion, since the gas flow speed is low in the center part of the
wafer W and becomes high suddenly in the periphery part thereof, it
is inferred that the gas is stagnant in the center part, so that
there are a large number of molecules whose residence time is long
in the center part.
[0101] As for a CF-based gas whose molecule has a small carbon
number of two or less, an etching action is strong due to a high
ratio of F/C and the in-surface uniformity of etching rate is
depended on the residence time of the gas. Therefore, when a
greater amount of the gas is supplied to the peripheral portion,
the residence time of the gas in the center part becomes long,
resulting in an excessive etching compared to the periphery part,
thereby deteriorating the in-surface uniformity. Contrarily, when a
greater amount of the gas is supplied to the central portion, since
the gas flows quickly from the center to the edge of the wafer W,
it is inferred that the residence time of the gas within the wafer
W is more likely to be uniform, thus showing a high in-surface
uniformity of the etching rate. Further, as for a CF-based gas
whose molecule has a large carbon number of three or more,
polymerization action is high due to a low ratio of F/C, and it is
inferred that in-surface uniformity of the etching characteristics
is more affected by distribution of active species than by the
residence time of the gas.
[0102] Therefore, as shown in FIG. 5, simulation was performed to
obtain pressure distribution near the surface of the wafer W when
the flow rate ratio of the processing gas supplied to the central
portion and the processing gas supplied to the peripheral portion
of the gas supply surface is changed, wherein it was assumed that
the CF-based gas was C.sub.4F.sub.8. In FIG. 5, the vertical axis
represents the pressure, while the horizontal axis represents the
distance from the center of the wafer W. Further, a dashed
double-dotted line indicates a case of C/E=3/7; a solid line, a
case of C/E=5/5; and a dashed dotted line, a case of C/E=7/3.
[0103] As a result, it was known that when a greater amount of the
processing gas is supplied to the peripheral portion than to the
central portion of the gas supply surface, the most uniform
pressure distribution within the surface of the wafer W is
achieved. The uniform pressure distribution means that the density
of molecules in the processing gas and the density of active
species present within the surface of the wafer W become uniform.
As described above, in case of the CF-based gas having the carbon
number of three or more, it is inferred that, when a greater amount
of the processing gas is supplied to the peripheral portion than to
the central portion, active species are more likely to exist
uniformly throughout the surface of the wafer W, thus increasing
the in-surface uniformity of the etching.
[0104] Further, to support this, a film forming process was
performed on a bare silicon by plasma of the processing gas under
the following processing condition in the plasma etching apparatus
shown in FIG. 1 while varying the flow rates of the processing
gases supplied to the central portion and the peripheral portion of
the gas supply surface, wherein C.sub.5F.sub.8 was used as CF-based
gas, and Ar gas and O.sub.2 gas are used as the dilution gas. Then,
the in-surface uniformity of the film forming speed was
measured.
[0105] <Processing Condition> [0106] Flow rate ratio of
C.sub.5F.sub.8 gas, Ar gas and O.sub.2 gas;
C.sub.5F.sub.8:Ar:O.sub.2=15:380:19 sccm [0107] Processing
pressure; 1.995 Pa (15 mTorr) [0108] Processing temperature;
20.degree. C. [0109] Frequency and power of the first high
frequency power supply 61; 60 MHz, 2170 W [0110] Frequency and
power of the second high frequency power supply 65; 2 MHz, 0 W
[0111] Results are shown in FIG. 6, wherein the vertical axis
represents the film forming speed, while the horizontal axis
represents the distance from the center of the wafer W. Further,
.quadrature. indicates a case of the flow rate ratio C/E=7/3;
.largecircle. represents a case of C/E=5/5; and .box-solid.
represents a case of C/E=3/7. From these results, it is proved that
when the flow rate ratio C/E is 3/7, the film forming speed is the
most uniform throughout the surface of the wafer W. Therefore, it
is confirmed that when the flow rate supplied to the peripheral
portion is greater than that supplied to the central portion, the
pressure distribution becomes uniform, so that the density of
active species becomes uniform throughout the surface of the wafer
W.
[0112] Hereinafter, respective embodiments will be described.
Embodiment 1
[0113] After the processing gas was produced in advance by mixing
CHF.sub.3 gas employed as the CF-based gas; and Ar gas and N.sub.2
gas employed as the dilution gas, an etching process was performed
on a resist layer (formed on an entire surface of the wafer W
without patterns formed thereon) formed on the wafer W under the
following processing condition by introducing the processing gas
into the plasma etching apparatus shown in FIG. 1 while varying the
amounts of the processing gases supplied to the central portion and
the peripheral portion of the gas supply surface. Then, the
in-surface uniformity of CF density and CF.sub.2 density on the
wafer W was measured by utilizing an LIF (laser induced
fluorescence) technology. The flow rate ratios C/E of the
processing gases were set to be 0/10, 3/7, 5/5, 7/3 and 10/0.
Further, the flow rate ratio C/E of 0/10 means a case where the
processing gas is supplied only to the peripheral portion of the
gas supply surface.
[0114] <Processing Condition> [0115] Flow rate ratio of
CHF.sub.3 gas, Ar gas and N.sub.2 gas;
CHF.sub.3:Ar:N.sub.2=40:1000:80 sccm [0116] Processing pressure;
6.65 Pa (50 mTorr) [0117] Frequency and power of the first high
frequency power supply 61; 60 MHz, 1200 W [0118] Frequency and
power of the second high frequency power supply 65; 2 MHz, 1700
W
[0119] FIG. 7A shows the in-surface uniformity of CF density, and
FIG. 7B presents the in-surface uniformity of CF.sub.2 density. In
FIGS. 7A and 7B, the vertical axis represents CF density and
CF.sub.2 density, respectively, while the horizontal axis
represents the distance from the center of the wafer W. Further,
.tangle-solidup. indicates a case of the flow rate ratio C/E=0/10;
.box-solid. indicates a case of C/E=7/3; .largecircle. represents a
case of C/E=5/5; .quadrature. represents a case of C/E=3/7; and
.DELTA. represents a case of C/E=10/0.
[0120] From these results, it is known that both CF density and
CF.sub.2 density are more uniform within the surface of the wafer W
when the flow rate is higher in the central portion of the gas
supply surface than that in the peripheral portion. At this time,
when the flow rate is higher in the peripheral portion, CF density
is high in the center part of the wafer W, while it is low in the
periphery part of the wafer W. Thus, it is inferred that gas
stagnation occurs in the center part of the wafer W as described
above. Contrarily, when the flow rate is higher in the central
portion, the density is low in the center part of the wafer W and
is almost uniform on the surface of the wafer W. Thus, it is
inferred that the high in-surface uniformity of the gas flow speed
distribution as described above helps, for example, CF density
become uniform within the surface of the wafer W.
[0121] As described above, in case of the first gas having the
carbon number of two or less, it is inferred that when the flow
rate of the central portion is higher, the amount of active species
of CF or CF.sub.2, active species of CF-based gas, becomes uniform
within the surface of the wafer W, so that the etching rate
throughout the surface of the wafer W becomes uniform. Further, the
inventors of the present invention conducted a same experiment by
using C.sub.4F.sub.8 gas as that conducted by using CHF.sub.3 gas,
but since measurement values of LIF were small and less reliable,
the measurement data are not presented.
Embodiment 2
[0122] After the processing gas was produced in advance by mixing
CHF.sub.3 gas employed as the CF-based gas; and Ar gas and N.sub.2
gas employed as the dilution gas, an etching process was performed
on an etching target film (SiOC film) formed on the wafer W under
the following processing condition by introducing the processing
gas into the plasma etching apparatus shown in FIG. 1 while varying
the flow rates of the processing gases supplied to the central
portion and the peripheral portion of the gas supply surface. Then,
the in-surface uniformity of a residual resist film, an etching
depth, a top CD and a bowing position was evaluated. Here, the flow
rate ratios C/E of the processing gases supplied to the central
portion and the peripheral portion of the gas supply surface were
set to be 1/9, 5/5 and 9/1.
[0123] In FIG. 8A, a reference numeral 71 refers to the SiOC film
serving as the etching target film; and a reference numeral 72
refers to a resist film formed on the surface of the SiOC film. The
residual resist film is represented by a distance A; the etching
depth, a distance B; the bowing position, a distance C from the top
surface of the SiOC film to the greatest diameter portion of a hole
(recessed portion) 73 formed in the SiOC film; and the top CD, a
top diameter D of the hole (recessed portion) 73 formed in the SiOC
film.
[0124] Further, the distances A, B, C and the diameter D were
measured in the center part and the periphery part of the wafer W
by using a cross-sectional SEM (scanning electronic microscope)
image of films after etching, and in-surface uniformity thereof was
evaluated in such a manner that the smaller a difference between
values in the center part and the periphery part is, the better the
in-surface uniformity gets. The center part of the wafer W means a
rotational center of the wafer W and the periphery part of the
wafer W means a position 5 mm away from the outer periphery of the
wafer W. The definitions of the residual resist film, the etching
depth, the bowing position and the top CD, the data measurement
method and the method of evaluating the in-surface uniformity based
on the difference between data values in the center part and the
periphery part of the wafer W are the same also in the following
embodiments.
[0125] <Processing Condition> [0126] Flow rate ratio of
CHF.sub.3 gas, Ar gas and N.sub.2 gas;
CHF.sub.3:Ar:N.sub.2=40:1000:80 sccm [0127] Processing pressure;
6.65 Pa (50 mTorr) [0128] Frequency and power of the first high
frequency power supply 61; 60 MHz, 1200 W [0129] Frequency and
power of the second high frequency power supply 65; 2 MHz, 1700
W
[0130] The results are tabled in FIG. 8B. In case of CHF.sub.3 gas,
for the residual resist film, the etching depth, the top CD, and
the bowing position, the difference (absolute value) between values
in the center part and the periphery part of the wafer W was
smaller when a greater flow rate is supplied to the central portion
than to the peripheral portion. Also from this embodiment, it is
understood that in case of CF-based gas having the carbon number of
two or less, when a greater flow rate is supplied to the central
portion than to the peripheral portion, the etching rate becomes
more uniform within the surface of the wafer W, thus improving the
in-surface uniformity of the etching characteristics of the
residual resist film, the etching depth, the top CD, the bowing
position.
Embodiment 3
[0131] After the processing gas was produced in advance by mixing
CHF.sub.3 gas employed as the CF-based gas; and Ar gas, N.sub.2 gas
and O.sub.2 gas employed as the dilution gas, an etching process
was performed on an etching target film (SiOCH film) formed on the
wafer W under the following processing condition by introducing the
processing gas into the plasma etching apparatus shown in FIG. 1
while varying the flow rates of the processing gases supplied to
the central portion and the peripheral portion of the gas supply
surface. Then, the in-surface uniformity of the top CD and the
etching depth formed by etching was evaluated.
[0132] <Processing Condition> [0133] Processing pressure;
6.65 Pa (50 mTorr) [0134] Frequency and power of the first high
frequency power supply 61; 60 MHz, 1500 W [0135] Frequency and
power of the second high frequency power supply 65; 2 MHz, 2800
W
[0136] FIGS. 9A and 9B show the in-surface uniformity of the top CD
and the in-surface uniformity of the etching depth, respectively.
In FIG. 9A, the vertical axis represents an absolute value of
difference of the top CD between the center part and the periphery
part. In FIG. 9B, the vertical axis represents an absolute value of
difference of the etching depth between the center part and the
periphery part. Further, in FIGS. 9A and 9B, the horizontal axis
represents the flow rate ratio C/E of gases supplied to the central
portion and the peripheral portion. For example, the flow rate
ratio 50% means that the flow rate ratio C/E is 5/5, and the flow
rate 90% means that the flow rate ratio C/E is 9/1.
[0137] From these results, it is proved that when the flow rate
supplied to the central portion of the gas supply surface is
greater, the difference of the top CD and the etching depth between
the center part and the periphery part of the wafer W is smaller,
showing higher in-surface uniformity. Therefore, also from this
embodiment, it is understood that in case of the first gas having
the carbon number of two or less, when a greater flow rate is
supplied to the central portion than to the peripheral portion, the
etching rate becomes more uniform within the surface of the wafer
W.
Embodiment 4
[0138] After the processing gas was produced in advance by mixing
CH.sub.2F.sub.2 gas employed as the CF-based gas; and O.sub.2 gas
employed as the dilution gas, an etching process was performed on
an etching target film (laminated film consisting of SiO film and
SiOCH film) formed on the wafer W under the following processing
condition by introducing the processing gas into the plasma etching
apparatus shown in FIG. 1 while varying the flow rates of the
processing gases supplied to the central portion and the peripheral
portion of the gas supply surface. Then, the in-surface uniformity
of the residual resist film, the top CD, the bottom CD and the
recess was evaluated. Here, the flow rate ratios C/E of the
processing gases supplied to the central portion and the peripheral
portion were set to be 1/9, 5/5 and 9/1.
[0139] <Processing Condition> [0140] Flow rate ratio of
CH.sub.2F.sub.2 gas, and O.sub.2 gas; CH.sub.2F.sub.2:O.sub.2=40:20
sccm [0141] Processing pressure; 7.98 Pa (60 mTorr) [0142]
Frequency and power of the first high frequency power supply 61; 60
MHz, 700 W [0143] Frequency and power of the second high frequency
power supply 65; 2 MHz, 300 W
[0144] The bottom CD is represented by a diameter E of a bottom
portion of the hole 73 formed in the etching target film (SiOC
film) 71 shown in FIG. 8A, and the recess means an etching amount
of an underlying film of the etching target film. Further, data on
the evaluation items were measured in the center part and the
periphery part of the wafer W by using a cross-sectional SEM image
of films after etching, and in-surface uniformity thereof was
evaluated in such a manner that the smaller a difference between
values in the center part and the periphery part is, the better the
in-surface uniformity gets. The definitions of the bottom CD, the
recess, the data measurement method and the method of evaluating
the in-surface uniformity based on the difference between data
values in the center part and the periphery part of the wafer W are
the same also in the following embodiments.
[0145] From results shown in FIG. 10, it is proved that when the
flow rate ratio C/E is 9/1, the difference of the top CD, the
bottom CD and the recess between the center part and the periphery
part of the wafer W is smaller, showing higher in-surface
uniformity. Therefore, also from this embodiment, it is understood
that in case of the first gas having the carbon number of two or
less, when a greater flow rate is supplied to the central portion
than to the peripheral portion, the etching rate becomes more
uniform within the surface of the wafer W.
Embodiment 5
[0146] After the processing gas was produced in advance by mixing
C.sub.4F.sub.8 gas employed as the CF-based gas; and Ar gas and
N.sub.2 gas employed as the dilution gas, an etching process was
performed on an etching target film (laminated film formed by
laminating a tetraethyl orthosilicate (TEOS) film having the
thickness of 50 nm and an bottom anti-reflection coating (BARC)
having the thickness of 100 nm on a SiOC film) formed on the wafer
W under the following processing condition by introducing the
processing gas into the plasma etching apparatus shown in FIG. 1
while varying the flow rates of the processing gases supplied to
the central portion and the peripheral portion of the gas supply
surface. Then, a shape of a hole formed by etching was evaluated.
Here, the flow rate ratios C/E of the processing gases supplied to
the central portion and the peripheral portion were set to be 1/9,
5/5 and 9/1.
[0147] <Processing Condition> [0148] Flow rate ratio of
C.sub.4F.sub.8 gas, Ar gas and N.sub.2 gas;
C.sub.4F.sub.8:Ar:N.sub.2=5:1000:150 sccm [0149] Processing
pressure; 6.65 Pa (50 mTorr) [0150] Frequency and power of the
first high frequency power supply 61; 60 MHz, 500 W [0151]
Frequency and power of the second high frequency power supply 65; 2
MHz, 2000 W
[0152] The hole shape was evaluated by measuring a taper angle
.theta. formed between an outer surface 74 of a sidewall of the
hole 73 and an extension line 75 from a bottom surface of the hole,
and calculating the difference of the taper angle .theta. of the
hole between the center part and the periphery part. The smaller
difference means the better in-surface uniformity of the hole
shape.
[0153] These results are shown in FIG. 11B. In FIG. 11B, the
vertical axis represents the taper angle .theta., while the
horizontal axis represents the position on the wafer W. Further,
.diamond. indicates a case of the flow rate ratio C/E=1/9;
.quadrature., a case of C/E=5/5; and .DELTA., a case of C/E=9/1.
From the results, it is proved that when the flow rate ratio C/E is
1/9, the difference of the taper angle .theta. between the center
part and the periphery part is the smallest, thus showing good
in-surface uniformity of the hole shape. Therefore, it is
understood that in case of the second gas having the carbon number
of three or more, when a greater flow rate is supplied to the
peripheral portion than to the central portion, the holes have more
uniform shapes are within the surface of the wafer W.
Embodiment 6
[0154] After the processing gas was produced in advance by mixing
C.sub.4F.sub.8 gas and CF.sub.4 gas employed as the CF-based gas
without the dilution gas, an etching process was performed on an
etching target film (SiOCH film) formed on the wafer W under the
following processing condition by introducing the processing gas
into the plasma etching apparatus shown in FIG. 1 while varying the
flow rates of the processing gases supplied to the central portion
and the peripheral portion of the gas supply surface. Then, the
in-surface uniformity of the top CD was evaluated as described
above.
[0155] <Processing Condition> [0156] Flow rate ratio of
C.sub.4F.sub.8 gas and CF.sub.4 gas; C.sub.4F.sub.8:CF.sub.4=5:200
sccm [0157] Frequency of the first high frequency power supply 61;
60 MHz [0158] Frequency of the second high frequency power supply
65; 2 MHz
[0159] Results are displayed in FIG. 12. In FIG. 12, the vertical
axis represents an absolute value of difference of the top CD
between the center part and the periphery part, while the
horizontal axis represents the flow rate ratio C/E of processing
gases supplied to the central portion and the peripheral portion.
From these results, it is proved that when the flow rate ratio C/E
is 7/3, the top CD difference is the smallest, showing high
in-surface uniformity of the top CD.
[0160] In this embodiment, the flow rate ratio of C.sub.4F.sub.8
gas and CF.sub.4 gas is 5:200 sccm. Thus, the number of fluorine
atoms supplied along with the CF.sub.4 gas is greater than that of
fluorine atoms supplied along with the C.sub.4F.sub.8 gas. In this
case, it is understood that a greater flow rate is supplied to the
central portion of the gas supply surface than to the peripheral
portion in accordance with the CF.sub.4 gas to secure the
in-surface uniformity of the top CD.
Embodiment 7
[0161] After a first etching process was performed by introducing
the processing gas, which was produced in advance by mixing
C.sub.4F.sub.8 gas and CF.sub.4 gas employed as the CF-based gas;
and N.sub.2 gas and O.sub.2 gas employed as the dilution gas, into
the chamber, a second etching process was performed by introducing
the processing gas, which was produced in advance by mixing
C.sub.4F.sub.8 gas employed as the CF-based gas; and Ar gas and
N.sub.2 gas employed as the dilution gas, into the chamber. In this
case, the in-surface uniformity of the top CD and the bottom CD was
evaluated as described above. Further, the etching process was
performed on an etching target film (laminated film formed by
laminating a TEOS film having the thickness of 50 nm and an bottom
anti-reflection coating (BARC) having the thickness of 65 nm on a
SiOCH film) formed the wafer W by using the plasma etching
apparatus shown in FIG. 1 under the following processing condition
while changing the flow rates of the processing gas supplied to the
central portion and the peripheral portion of the gas supply
surface. The evaluation was conducted for a case of the flow rate
ratio C/E=5/5 in both the first and the second etching process, and
a case of C/E=9/1 in the first etching process and C/E=1/9 in the
second etching process.
[0162] <First Etching Processing Condition> [0163] Flow rate
ratio of C.sub.4F.sub.8 gas, CF.sub.4 gas, N.sub.2 gas and O.sub.2
gas; C.sub.4F.sub.8:CF.sub.4:N.sub.2:O.sub.2=6:15:120:10 sccm
[0164] Processing pressure; 6.65 Pa (50 mTorr) [0165] Frequency and
power of the first high frequency power supply 61; 60 MHz, 800 W
[0166] Frequency and power of the second high frequency power
supply 65; 2 MHz, 1400 W
[0167] <Second Etching Processing Condition> [0168] Flow rate
ratio of C.sub.4F.sub.8 gas, Ar gas and N.sub.2 gas;
C.sub.4F.sub.8:Ar:N.sub.2=8:50:1000 sccm [0169] Processing
pressure; 3.325 Pa (25 mTorr) [0170] Frequency and power of the
first high frequency power supply 61; 60 MHz, 1000 W [0171]
Frequency and power of the second high frequency power supply 65; 2
MHz, 3000 W
[0172] Results are shown in FIG. 13. From these results, it is
proved that when a greater amount of the processing gas is supplied
to the central portion in the first etching process and to the
peripheral portion in the second etching process, the difference
(absolute value) between data of the top CD and the bottom CD in
the center part and the periphery part of the wafer W is smaller,
showing higher in-surface uniformity of the CD.
[0173] Also in case that the first etching process and then the
second etching process were performed while changing kinds of the
CF-based gas, as described above, it is proved that the etching
process can be performed with the high in-surface uniformity by
controlling the flow rates of the processing gases supplied to the
central portion and the peripheral portion in accordance with the
carbon number of each CF-based gas.
[0174] At this time, in the first etching process, the flow rate
ratio of C.sub.4F.sub.8 gas to CF.sub.4 gas is
C.sub.4F.sub.8:CF.sub.4=6 sccm:15 sccm, and thus the number of
fluorine atoms supplied along with the CF.sub.4 gas is greater than
that of the fluorine atoms supplied along with the C.sub.4F.sub.8
gas. Therefore, it is understood that when a greater flow rate is
supplied to the central portion in accordance with the CF.sub.4
gas, the top CD and the bottom CD are more uniform within the
surface of the wafer W. Further, in the second etching process,
since C.sub.4F.sub.8 gas is used, the top CD and the bottom CD are
more uniform within the surface of the wafer W when a greater flow
rate is supplied to the peripheral portion.
Embodiment 8
[0175] Etching processes were performed on an etching target film
formed on the wafer W under the same etching condition as that in
Embodiment 7, and an in-surface CD distribution was evaluated by
CD-SEM (electron microscope which allows an inspection from the top
surface of the wafer W without breaking the wafer W). FIG. 14A
shows results obtained in case of the flow rate ratio C/E=9/1 in
the first etching process and C/E=1/9 in the second etching
process. FIG. 14B shows results obtained in case of the flow rate
ratio C/E=5/5 in both the first and the second etching process.
Further, in FIGS. 14A and 14B, the vertical axis represents a CD
shift value; the horizontal axis, the position on the wafer;
.diamond., X-axis data; and .largecircle., Y-axis data. The CD
shift value in this embodiment means a difference of a diameter of
a hole in a mask before and after etching.
[0176] From these results, it is proved that when a greater flow
rate is supplied to the central portion in the first etching
process and a greater flow rate is supplied to the peripheral
portion in the second etching process, the CD shift values of the
X-axis data and the Y-axis data are small, showing the good
uniformity of the in-surface CD distribution.
Embodiment 9
[0177] After producing the processing gas in advance by mixing
C.sub.5F.sub.8 gas employed as the CF-based gas; and Ar gas and
O.sub.2 gas employed as the dilution gas, the etching process was
performed by introducing the processing gas into the chamber. Then,
uniformity of an etching rate, resist selectivity, a residual
resist film and an etching depth was evaluated. At this time, the
etching process was performed on a resist formed on the wafer W
under the following processing condition by using the plasma
etching apparatus shown in FIG. 1, while varying the flow rates of
the processing gas supplied to the central portion and the
peripheral portion of the gas supply surface. The etching rate, the
resist selectivity, the residual resist film and the etching depth
were evaluated for a case where a flow rate supplied to the central
portion was 208 sccm and a flow rate supplied to the peripheral
portion was 208 sccm, and a case where a flow rate supplied to the
central portion was 208 sccm and a flow rate supplied to the
peripheral portion was 312 sccm. Here, the etching selectivity is
calculated by a ratio of an etching amount of SiO.sub.2 film to a
thickness reduction amount of a resist mask film. The values of the
etching rate and the resist selectivity in the center part and the
periphery part of the wafer W were obtained by using a
cross-sectional SEM (scanning electronic microscope) image of films
after etching, and in-surface uniformity thereof was evaluated in
such a manner that the smaller a difference between the values in
the center part and the periphery part is, the better the
in-surface uniformity gets.
[0178] <Processing Condition> [0179] Flow rate ratio of
C.sub.5F.sub.8 gas, Ar gas, and O.sub.2 gas;
C.sub.5F.sub.8:Ar:O.sub.2=16:380:20 sccm [0180] Processing
pressure; 3.325 Pa (25 mTorr) [0181] Frequency and power of the
first high frequency power supply 61; 60 MHz, 1000 W [0182]
Frequency and power of the second high frequency power supply 65; 2
MHz, 3000 W
[0183] Results are shown in FIG. 15. From these results, it is
proved that when a greater flow rate is supplied to the peripheral
central portion than to central portion of the gas supply surface,
the difference of the etching rate, the etching selectivity and
etching depth between the center part and the periphery part is
small, showing high in-surface uniformity thereof.
[0184] Further, the flow rate supplied to the peripheral portion
was changed without changing the flow rate supplied to the central
portion in this embodiment, and it is confirmed that although the
flow rate supplied to the peripheral portion is changed, if the
flow rate supplied to the central portion is not changed, the
etching characteristics in the central portion of the wafer W are
not changed. Therefore, after setting the total flow rate of the
processing gas and the flow rates supplied to the central portion
and the peripheral portion, by increasing the flow rate supplied to
the peripheral portion without any change in the flow rate supplied
to the central portion, it is understood that the etching
characteristics in the periphery part can be changed while
maintaining the etching characteristics in the center part, thus
improving the in-surface uniformity of the etching
characteristics.
Embodiment 10
[0185] The etching process was performed by using the processing
gas produced by mixing C.sub.4F.sub.8 gas employed as the CF-based
gas; and CO gas, N.sub.2 gas and O.sub.2 gas employed as the
dilution gas, and uniformity of the CD shift value was evaluated.
At this time, the etching process was performed on an etching
target film (SiOC film) formed on the wafer W under the following
processing condition by using the plasma etching apparatus shown in
FIG. 1, while varying the flow rates of the processing gas supplied
to the central portion and the peripheral portion of the gas supply
surface. The evaluation was made for cases where flow rate ratios
C/E were 2/4, 2/2, 2/6, respectively.
[0186] <Processing Condition> [0187] Processing pressure;
6.65 Pa (50 mTorr) [0188] Frequency and power of the first high
frequency power supply 61; 60 MHz, 800 W [0189] Frequency and power
of the second high frequency power supply 65; 2 MHz, 1400 W
[0190] Results are shown in FIG. 16. From these results, it is
proved that the CD shift value is greatly changed in the periphery
part by changing the flow rate of C.sub.4F.sub.8 gas supplied the
peripheral portion, and the in-surface uniformity of the CD shift
is improved by supplying a greater flow rate of C.sub.4F.sub.8 gas
to the peripheral portion than to the central portion.
[0191] Therefore, it is understood that the etching process can be
performed with high in-surface uniformity by changing a mixing
ratio of the first gas to the second gas in the processing gas
supplied to the central portion and the peripheral portion.
Embodiment 11
[0192] After a first etching process was performed by using the
processing gas obtained by mixing CHF.sub.3 gas and CF.sub.4 gas
employed as the CF-based gas; and Ar gas and N.sub.2 gas employed
as the dilution gas, a second etching process was performed by
using the processing gas obtained by mixing C.sub.4F.sub.8 gas
employed as the CF-based gas; and Ar gas and N.sub.2 gas employed
as the dilution gas. In this case, the in-surface uniformity of the
top CD was evaluated as described above. At this time, the etching
process was performed on a resist formed on the wafer W by
introducing the processing gas, which had been mixed at a
predetermined ratio, into the plasma etching apparatus shown in
FIG. 1 under the following processing conditions while changing the
flow rates of the processing gases supplied to the central portion
and the peripheral portion.
[0193] <First Etching Processing Condition> [0194] Flow rate
ratio of CHF.sub.3 gas, CF.sub.4 gas, Ar gas and N.sub.2 gas;
CHF.sub.3:CF.sub.4:Ar:N.sub.2=15:15:500:80 sccm [0195] Processing
pressure; 6.65 Pa (50 mTorr) [0196] Frequency and power of the
first high frequency power supply 61; 60 MHz, 800 W [0197]
Frequency and power of the second high frequency power supply 65; 2
MHz, 1700 W
[0198] <Second Etching Processing Condition> [0199] Flow rate
ratio of C.sub.4F.sub.8 gas, Ar gas and N.sub.2 gas;
C.sub.4F.sub.8:Ar:N.sub.2=7:950:120 sccm [0200] Processing
pressure; 6.65 Pa (50 mTorr) [0201] Frequency and power of the
first high frequency power supply 61; 60 MHz, 1200 W [0202]
Frequency and power of the second high frequency power supply 65; 2
MHz, 1700 W
[0203] Further, the evaluation was conducted over a case where the
flow rate ratio C/E was 50/50 in both the first etching process and
the second etching process, and a case where the flow rate ratio
C/E was 95/5 in the first etching process and 5/95 in the second
etching process.
[0204] Results are shown in FIG. 17. From these results, it is
proved that when a greater flow rate of the processing gas is
supplied to the central portion in the first etching process and a
greater flow rate of the processing gas is supplied to the
peripheral portion in the second etching process, the difference of
the top CD between the center part and the periphery part is small,
showing the good in-surface uniformity of the CD.
[0205] As described above, it is proved that when the first etching
process was performed by using the processing gas produced by
mixing CHF.sub.3 gas, CF.sub.4 gas, Ar gas and N.sub.2 gas, a
greater flow rate of the processing gas is supplied to the central
portion in accordance with the first gas having the carbon number
of two or less, and the second etching process was performed by
using the processing gas produced by mixing C.sub.4F.sub.8 gas, Ar
gas and N.sub.2 gas, a greater flow rate of the processing gas is
supplied to the peripheral portion in accordance with the second
gas having the carbon number of three or more, by supplying a
greater amount of the processing gas to the peripheral portion,
thus achieving the good etching characteristics.
Embodiment 12
[0206] The etching process was performed by using the processing
gas produced in advance by mixing C.sub.4F.sub.8 gas and CF.sub.4
gas employed as the CF-based gas; and N.sub.2 gas and O.sub.2 gas
employed as the dilution gas. Then, in-surface uniformity of an
etching rate was evaluated. At this time, the etching process was
performed on a resist formed on the wafer W under the following
processing condition by using the plasma etching apparatus shown in
FIG. 1, while varying the flow rates of the processing gas supplied
to the central portion and the peripheral portion of the gas supply
surface.
[0207] <Processing Condition> [0208] Flow rate ratio of
C.sub.4F.sub.8 gas, CF.sub.4 gas, N.sub.2 gas and O.sub.2 gas;
C.sub.4F.sub.8:CF.sub.4:N.sub.2:O.sub.2=6:15:120:10 sccm [0209]
Processing pressure; 6.65 Pa (50 mTorr) [0210] Frequency and power
of the first high frequency power supply 61; 60 MHz, 800 W [0211]
Frequency and power of the second high frequency power supply 65; 2
MHz, 1400 W
[0212] Further, the evaluation was conducted for a case of the flow
rate ratio C/E=5/5, and a case of C/E=9/1.
[0213] Results are shown in FIG. 18. From these results, it is
proved that when a greater flow rate of the processing gas is
supplied to the central portion, the difference of the etching rate
between the center part and the periphery part is small, showing
the high in-surface uniformity of the etching rate.
[0214] Further, in case of supplying a gaseous mixture of the first
gas and the second gas, it is proved that when the number of
fluorine atoms supplied along with CF.sub.4 gas is greater than
that of fluorine atoms supplied along with C.sub.4F.sub.8, flow
rates of the processing gases supplied the central portion and the
peripheral portion are controlled in accordance with the CF.sub.4
gas to thereby obtain the good etching characteristics.
[0215] The present invention may be applied to a glass substrate
employed in a flat display panel, such as an LCD and a PDP glass
substrate, as well as the semiconductor wafer W. Further, the
plasma etching apparatus used in the present invention may be of an
RIE (reactive ion etching) type, an ICP (inductive coupled plasma)
type, an ECR (electron cyclotron resonance) type, a helicon wave
plasma type or the like, all using magnetic field, instead of a
parallel plate type plasma etching apparatus.
[0216] While the invention has been shown and described with
respect to the preferred embodiments, it will be understood by
those skilled in the art that various changes and modifications may
be made without departing from the spirit and scope of the
invention as defined in the following claims.
* * * * *