U.S. patent application number 11/682382 was filed with the patent office on 2008-05-15 for plasma etching apparatus and plasma etching method.
Invention is credited to Hiroshi Akiyama, Naoshi Itabashi, Seiichiro Kanno, Go Miya, Kouhei Satou, Junichi Tanaka.
Application Number | 20080110569 11/682382 |
Document ID | / |
Family ID | 39368061 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080110569 |
Kind Code |
A1 |
Miya; Go ; et al. |
May 15, 2008 |
PLASMA ETCHING APPARATUS AND PLASMA ETCHING METHOD
Abstract
The invention provides a method and apparatus for performing
plasma etching to form a gate electrode on a large-scale substrate
while ensuring the in-plane uniformity of the CD shift of the gate
electrode. The present invention measures a radical density
distribution of plasma in the processing chamber, feeds processing
gases into the processing chamber through multiple locations and
controls either the flow rates or compositions of the respective
processing gases or the in-plane temperature distribution of a
stage on which the substrate is placed, or feeds processing gases
into the processing chamber through multiple locations and controls
both the flow rates or compositions of the processing gases and the
in-plane temperature distribution of the stage on which the
substrate is placed.
Inventors: |
Miya; Go; (Tokyo, JP)
; Tanaka; Junichi; (Tokyo, JP) ; Kanno;
Seiichiro; (Tokyo, JP) ; Itabashi; Naoshi;
(Tokyo, JP) ; Akiyama; Hiroshi; (Kudamatsu-shi,
JP) ; Satou; Kouhei; (Kudamatsu-shi, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
39368061 |
Appl. No.: |
11/682382 |
Filed: |
March 6, 2007 |
Current U.S.
Class: |
156/345.35 |
Current CPC
Class: |
H01J 37/32972 20130101;
H01J 37/32935 20130101; H01L 21/67069 20130101 |
Class at
Publication: |
156/345.35 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2006 |
JP |
2006-303470 |
Claims
1. A plasma etching apparatus comprising: a vacuum processing
chamber for subjecting a substrate to plasma processing: a
substrate stage disposed in the vacuum processing chamber having a
support surface for supporting the substrate; a gas inlet for
supplying processing gas into the vacuum processing chamber; an
electromagnetic wave supply means for supplying electromagnetic
waves into the vacuum processing chamber; a plurality of light
receiving units for receiving plasma emission near a surface of the
substrate from a side surface of the vacuum processing chamber,
wherein the light receiving units are disposed so that the lengths
of optical paths received by the respective light receiving units
vary; a plasma emission distribution measurement system disposed
separately from the plurality of light receiving units; and a means
for computing a radical distribution in the plasma based on at
least either the plasma emission distribution measurement system or
the plurality of light receiving units; wherein the plasma etching
apparatus further includes a process for performing a plasma
etching process in advance, a process for computing the radical
distribution in the plasma during the process using the means for
computing radical distribution and the plurality of light receiving
units, and a process for measuring a CD shift distribution of the
substrate subjected to plasma processing in the plasma etching
process and storing the result thereof in a database; a means for
computing the radical distribution in the plasma using the
plurality of light receiving units during a plasma etching process
performed subsequent to said plasma etching process performed in
advance; and a means for controlling the plasma etching process
conditions based on the data stored in the database.
2. The plasma etching apparatus according to claim 1, wherein an
object for controlling the processing condition during the plasma
etching process is either a composition and flow rate of the
processing gas supplied through the plurality of gas inlets or a
temperature distribution of the supporting surface of the substrate
holder, or both.
3. The plasma etching apparatus according to claim 1 or claim 2,
including a means for computing the radical distribution in the
plasma using the plurality of light receiving units during a plasma
etching process performed subsequent to said plasma etching process
performed in advance, and a means for controlling the plasma
etching process conditions based on the data stored in the
database; wherein the process for computing the radical
distribution in the plasma and the process for controlling the
plasma etching process conditions are performed at a timing
selected from the following; per lot, per processing of the
substrate, or per step of the plurality of etching steps; or the
plasma etching process conditions is controlled immediately based
on the computed result of the radical distribution in the plasma.
Description
[0001] The present application is based on and claims priority of
Japanese patent application No. 2006-303470 filed on Nov. 9, 2006,
the entire contents of which are hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the art of plasma etching,
and more specifically, relates to a plasma etching apparatus and a
plasma etching method for etching a substrate having superior
in-plane uniformity of CD shift distribution.
[0004] 2. Description of the Related Art
[0005] Japanese Patent Application Laid-Open Publication No.
2005-56914 (patent document 1) discloses a prior art plasma etching
apparatus in which a plurality of light receiving means for
receiving plasma emission is disposed in the radial direction at
the upper portion of the processing apparatus for measuring the
radical density in the plasma, and based on the results, gases
having different compositions are fed through a plurality of gas
inlets disposed in the radial direction so as to control the
radical density distribution in the plasma, and to thereby improve
the in-plane uniformity of the substrate.
[0006] However, recently in the art of gate etching in which a
processing accuracy in the order of nanometers is demanded
throughout the whole surface of the large-diameter substrate, it is
desirable to perform measurement at multiple points in the vacuum
processing chamber, and in order to do so, a large number of light
receiving units must be disposed. Such system requires a large
installation space, and it became evident that it is difficult to
apply such prior art teachings.
[0007] With respect to the problems mentioned above, the present
inventors have proposed in Japanese Patent Application No.
2005-136248 (patent document 2) an art of inserting a light
receiving unit in an area in which plasma exists in the vacuum
processing chamber, rotating the light receiving unit to receive
plasma emission, and obtaining the radical density distribution.
However, patent document 2 does not disclose a means for reflecting
the result of the density distribution data obtained from the
plasma emission to the etching process, and therefore, it is not
sufficient to overcome the prior art problems mentioned above.
SUMMARY OF THE INVENTION
[0008] The present invention aims at solving the problems of the
prior art, and provides a plasma etching apparatus and a plasma
etching method for accurately measuring the plasma emission
distribution within the vacuum processing chamber, and reflecting
the result thereof to the plasma etching process so as to realize a
uniform in-plane distribution of CD shift of the substrate.
[0009] The present invention applies the following means to solve
the prior art problems.
[0010] The object of the present invention is achieved by a plasma
etching apparatus comprising a vacuum processing chamber for
subjecting a substrate to plasma processing, gas inlets provided at
least at two locations for feeding processing gas into the vacuum
processing chamber, a substrate stage for holding the substrate and
having disposed therein a temperature control means for controlling
the temperature of at least two locations, an electromagnetic wave
supplying means for supplying electromagnetic waves into the vacuum
processing chamber, a plasma emission distribution measurement
system for measuring the distribution of plasma emission near a
surface of the substrate from a side direction, a means for
computing a radical distribution in the plasma based on the plasma
emission distribution measurement system, and a means for
controlling both a composition or a flow rate of the processing gas
fed through the gas inlets provided at two locations and the
temperature of at least two locations in the substrate stage of the
substrate based on the radical distribution computed in advance by
the means for computing radical distribution and the measurement
results of CD shift distribution.
[0011] Further, the present object is achieved by providing a
plasma etching apparatus further comprising a means for computing
the radical distribution in the plasma during the plasma etching
process, and controlling based on the computed radical distribution
either the respective compositions or flow rates of the processing
gases fed through the gas inlets provided at two locations, or the
temperature distribution of the substrate stage of the
substrate.
[0012] Further, the present object is achieved by providing a
plasma etching method for etching a substrate using the above
plasma etching apparatus, comprising the steps of measuring a
radical density distribution of at least one radical and a CD shift
distribution during the etching process by performing at least two
etching processes in advance with the flow rates of processing
gases varied, storing the conditions of the etching processes, the
radical density distribution and the CD shift distribution in a
database, computing a relational expression of the radical density
distribution for the at least one radical and the CD shift
distribution, computing a processing condition to realize a uniform
CD shift using the relational expression, and computing a control
parameter of the etching process so as to realize the processing
condition computed to realize a uniform CD shift, wherein the
etching process of the substrate is performed using the computed
control parameter.
[0013] Further, the present object is achieved by a plasma etching
method further comprising measuring the radical density
distribution of said at least one type of radical during the
etching process, and computing during the etching process the
control parameter of the etching process so as to realize the
processing condition computed to realize a uniform CD shift,
wherein the etching process of the substrate is performed using the
computed control parameter.
[0014] Moreover, the present object is achieved by a plasma etching
method wherein said control parameter for the etching process for
realizing the processing condition computed so a to realize a
uniform CD shift is at least either the compositions or flow rates
of the processing gases fed from at least two locations, or the set
temperatures of the temperature control means disposed at least at
two locations for controlling the temperature distribution of the
substrate.
[0015] The present invention having the arrangements mentioned
above provides a plasma etching apparatus and a plasma etching
method capable of measuring the density distribution of various
radicals in the plasma, and based on the measured results,
controlling either the compositions or flow rates of processing
gases fed through gas inlets disposed at two locations or the
temperature distribution of the substrate stage so as to control
the radical distribution in the plasma, and realizing a uniform
in-plane CD shift distribution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a configuration diagram of the plasma etching
apparatus used in the first embodiment of the present
invention;
[0017] FIG. 2 is a flowchart showing the flow of the process
according to the first embodiment of the present invention;
[0018] FIG. 3 is a density distribution diagram of O radicals and
SiCl.sub.x radicals which is optimized by applying the first
embodiment of the present invention and which is not optimized by
applying the first embodiment of the present invention;
[0019] FIG. 4 is a CD shift distribution diagram which is not
optimized by applying the first embodiment of the present invention
and which is not optimized by applying the first embodiment of the
present invention;
[0020] FIG. 5 is a configuration diagram of the plasma etching
apparatus used in the second embodiment of the present
invention;
[0021] FIG. 6 is a flowchart showing the flow of the process
according to the second embodiment of the present invention;
[0022] FIG. 7 is a configuration diagram of the plasma etching
apparatus used in the third embodiment of the present
invention;
[0023] FIG. 8 is a flowchart showing the flow of the process
according to the third embodiment of the present invention;
[0024] FIG. 9 is an enlarged view of the portion near the light
receiving unit of the plasma emission distribution measurement
system used in the fourth embodiment of the present invention;
[0025] FIG. 10 is an enlarged view of the portion near the light
receiving unit of the plasma emission distribution measurement
system used in the fifth embodiment of the present invention;
[0026] FIG. 11 is a top view of the plasma etching apparatus used
in the sixth embodiment of the present invention; and
[0027] FIG. 12(a) is a density distribution diagram of O radicals
obtained by applying the sixth embodiment of the present invention,
and FIG. 12(b) is an emission peak intensity distribution of O
radicals.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
[0028] Now, a first embodiment in which the present invention is
applied to an etching process for forming a gate electrode
(hereinafter referred to as gate etching) is described with
reference to FIGS. 1 through 4. FIG. 1 is a cross-sectional view
showing the structure of a UHF-ECR (ultra high frequency-electron
cyclotron resonance) plasma etching apparatus to which the first
embodiment of the present invention is applied. In FIG. 1, a
processing chamber lid 22 is disposed on top of a substantially
cylindrical processing chamber side wall 20 by which a vacuum
processing chamber 26 is defined, and in the vacuum processing
chamber 26 is disposed a substrate stage 28 for holding a substrate
1. Two lines of processing gasses composed of a center-side gas
line 70-1 and a circumference-side gas line 70-2 are introduced to
the vacuum processing chamber 26. Each gas line is composed for
example of a gas supply means such as a gas cylinder (not shown), a
flow rate control means (not shown) for controlling the flow rate
of each gas, and a valve (not shown) for outputting or stopping the
flow of each gas, and the lines are capable of outputting the
desired gas at a desirable flow rate or stopping the same.
[0029] A first processing gas 36-1 led to a first gas feed pipe
30-1 via the center-side gas line 70-1 is supplied to a center-side
space 32-1 formed between the processing chamber lid 22 and a
shower head plate 24. A center-side gas feed area 34-1 composed of
multiple holes is formed at the center of the shower head plate 24
disposed at a position opposing to the substrate 1, through which
the first processing gas 36-1 is fed into the vacuum processing
chamber 26. Similarly, a second processing gas 36-2 guided via the
second gas feed pipe 30-2 is supplied to a circumference-side space
32-2 formed between the processing chamber lid 22 and the shower
head plate 24. A circumference-side gas feed area 34-2 composed of
multiple holes is formed at the outer side of the center-side gas
feed area 34-1 on the shower head plate 24, through which the
second processing gas 36-2 is fed into the vacuum processing
chamber 26.
[0030] Moreover, a circumferential projection 22-1 is formed on the
lower surface of the processing chamber lid 22, which adheres
tightly to the upper surface of the shower head plate 24 and
separates the center-side space 32-1 from the circumference-side
space 32-2, so as to prevent the first processing gas 36-1 and the
second processing gas 36-2 from mixing before being fed into the
vacuum processing chamber 26.
[0031] By the above arrangement, the first processing gas 36-1 and
the second processing gas 36-2 having different flow rates and
different compositions (if the gas is a mixed gas composed of a
plurality of gases, the flow rate of each gas) are fed respectively
into the vacuum processing chamber 26 through the center-side gas
feed area 34-1 and the circumference-side gas feed area 34-2. A
substrate stage 28 is disposed in the vacuum processing chamber 26,
on which a substrate 1 to be processed is attached via
electrostatic chuck. Multiple lines of fluid passages 62 are formed
at various radial positions within the substrate stage 28, and by
controlling the temperature of the fluid circulated therethrough
via a circulator 64, it becomes possible to control the temperature
of the substrate 1.
[0032] A portion of the first processing gas 36-1 and the second
processing gas 36-2 and volatile products generated by the reaction
during the plasma etching process are evacuated through an exhaust
port 40. A vacuum pump (not shown) is connected to the end of the
exhaust port 40, by which the pressure within the vacuum processing
chamber 26 is reduced to approximately 1 Pa (Pascal).
[0033] An antenna 52 is disposed above the processing chamber lid
22, through which electromagnetic waves are fed from an UHF power
supply 54 through the processing chamber lid 22 and the shower head
plate 24 formed of insulating material into the vacuum processing
chamber 26 so as to generate plasma 38.
[0034] In addition, a plasma emission distribution measurement
system is equipped to the plasma etching apparatus illustrated in
the present embodiment. The plasma emission distribution
measurement system is composed of a motor 140, a rotation
transmitting shaft 142, a light receiving unit 144, a rotation
feed-through 146, an optical fiber 148, a spectroscope 150 and a
computer 154. We will now describe the plasma emission distribution
measurement system. The driving mechanism of the plasma emission
distribution measurement system is composed of the motor 140 and
the rotation transmitting shaft 142, and a light receiving unit 144
is connected to the rotation transmitting shaft 142. The rotation
transmitting shaft 142 and the light receiving unit 144 are rotated
by driving the motor 140. Furthermore, by disposing an angle sensor
on the rotation shaft of the motor 140, the light receiving
direction can be obtained accurately.
[0035] As shown in FIG. 1, the rotation transmitting shaft 142 is
inserted through the rotation feed-through 146 to the vacuum
processing chamber 26, so that the plasma emission distribution
measurement system can be installed and driven while maintaining a
decompressed pressure in the vacuum processing chamber 26. Further,
an optical fiber 148 is connected to the light receiving unit 144
for conducting the emission of plasma 38 received by the light
receiving unit 144 to the spectroscope 150. The emission of plasma
38 introduced to the spectroscope 150 has the intensity of each
wavelength converted into emission spectral data in the
spectroscope 150 and output therefrom. The output emission spectral
data 152 is transmitted to the computer 154. The emission spectral
data 152 is transmitted to the computer 154 and stored. The
computer 154 outputs a drive signal 156 to the motor 140, by which
the rotation of the motor 140 is controlled.
[0036] Furthermore, upon storing the emission spectral data 152 in
the computer 154, the data is associated with the rotary position
of the motor 140 so that the emission spectral data 152 is
associated with the light receiving direction of the light
receiving unit 144, by which the plasma emission distribution in
the vacuum processing chamber 26 is obtained. Furthermore, the
emission intensity of the desired radical can be obtained by
extracting only the light existing in a predetermined wavelength
region of the plasma emission spectrum by the computer 154.
[0037] The emission intensity distribution thus obtained is an
integration value of plasma emission within the line of sight
observed from the light receiving unit, so the value must be
converted into spatial distribution of emission intensity in the
computer. The plasma is in a substantially axisymmetric
distribution in the processing apparatus, so it is preferable to
utilize Abel inversion for the above-mentioned conversion. If it is
not possible to achieve a symmetric property in the processing
apparatus, it is preferable to dispose light receiving units at
multiple locations and to perform a computer-tomography calculation
of the emission data obtained from the multiple light receiving
units.
[0038] The spatial distribution of radical emission obtained by the
conversion is not directly equal to radical density distribution,
since it is influenced by the electron density distribution and
electron temperature distribution in the plasma It is possible to
perform process control without removing the influence of the
electron density and electron temperature distribution, but in
order to perform a more accurate process control, it is preferable
to suppress the influence of electron density and electron
temperature distribution as much as possible. Therefore, an
actinometry is performed to normalize the desired radical emission
of each spatial position using the emission of inert gas such as
Ar, He, Ne, Kr and Xe.
[0039] Moreover, the computer 154 sends a control data 158 to a
control computer 160 of the plasma etching apparatus based on the
achieved density distribution of each radical. Thereafter, the
control computer 160 sends control signals 162 to the center-side
gas system 70-1 and the circumference-side gas system 70-2, based
on which the flow rate control means and valves of the systems are
controlled, according to which the compositions and flow rates of
the first processing gas 36-1 and the second processing gas 36-2
are controlled.
[0040] The above-mentioned arrangement is used to feed a first
processing gas 36-1 and a second processing gas 36-2 having
different compositions to the vacuum processing chamber 26. For
example, when utilizing a mixed gas composed of chlorine
(Cl.sub.2), hydrogen bromide (HBr) and oxygen (O.sub.2), the
density of oxygen radicals can be set higher at the circumferential
portion than at the center portion on the surface of the substrate
1 by reducing the flow rate of oxygen in the first processing gas
36-1 fed through the center-side gas feed area 34-1 than the flow
rate of oxygen in the second processing gas 36-2 fed through the
circumference-side gas feed area 34-2. Conversely, the density of
oxygen radicals can be set lower at the circumference portion than
at the center portion on the surface of the substrate 1 by
increasing the flow rate of oxygen in the first processing gas 36-1
than the flow rate of oxygen in the second processing gas 36-2.
[0041] Similarly, the density distribution of chlorine radicals can
be controlled by controlling the flow rates of chlorine in the
first processing gas 36-1 and the second processing gas 36-2, and
in addition, when a processing gas such as CF.sub.4 (carbon
tetrafluoride) is used, the density distribution of
fluorocarbon-based radicals can be controlled by controlling the
flow rates of the first processing gas 36-1 and the second
processing gas 36-2 in a similar manner.
[0042] During gate etching, Cl (chlorine), Br (bromine) and O
(oxygen) radicals generated by dissociating processing gas react
with the polysilicon film, by which silicon-based reaction products
are generated. The volatile reaction products are taken away
through the exhaust port 40, but a portion of the nonvolatile
reaction products stick to and deposit on the polysilicon film and
photoresist mask, functioning as a side-wall protection film
against etching caused by radicals of etchant such as chlorine.
Therefore, if the amount of deposits on the side walls of the gate
electrode is small, isotropic etching of the side walls of the gate
electrode is performed by the etchant radicals, and as a result,
the width of the gate electrode (gate width) after the etching
process is often reduced. On the other hand, if the amount of
deposits on the side walls of the gate electrode is large, the
deposits constitute a mask against etching, and as a result, the
gate width after the etching process is often large. Furthermore,
the value obtained by subtracting the mask dimension prior to
processing from the width of the gate electrode after the etching
(also referred to as CD or critical dimension) is called a CD
shift, which is an important indicator representing the quality of
the etching process, and a target value thereof is set in
advance.
[0043] Further, it is known that the deposition property of
reaction products becomes stronger when silicon-based reaction
products are bound with oxygen radicals. Therefore, if the density
of oxygen radicals is increased at a certain area, the amount of
deposits on the side walls of the gate electrode is increased
compared to the area where the density is low, and as a result, the
gate width can be increased, that is, the CD shift can be
increased. Moreover, when fluorocarbon gas such as CF.sub.4 (carbon
tetrafluoride) is used as the processing gas, carbon-based radicals
having a strong deposition property are generated and are deposited
on the side walls of the gate electrode, so that if the density of
carbon-based radicals is increased similarly at a certain area, the
CD shift can be increased compared to other areas where the density
is low. Furthermore, if the density of chlorine radicals is
increased in a certain area, the amount of isotropic etching of the
side walls of the gate electrode in that area is increased compared
to other areas having a low density, and the CD shift can be
reduced. Thus, by controlling the amount of oxygen, fluorocarbon
gas or chlorine contained in the first and second processing gases
36-1 and 36-2, it becomes possible to control the in-plane CD shift
distribution on the surface of the substrate 1.
[0044] Moreover, the above-mentioned plasma emission distribution
measurement system can be used to measure the emission intensity of
the desired radicals in a desired direction. The data on the
emission intensity of each radicals and the light receiving
direction of the light receiving unit 144 are processed via Abel
inversion so as to compute the radial direction distribution of the
radical emission intensity, and thus, the density distribution of
respective radicals can be obtained.
[0045] Furthermore, it is important that the range of rotation of
the light receiving unit 144 is wide enough to obtain the radical
density distribution of the area including at least the whole
diameter of the substrate 1. Furthermore, since the radical density
distribution of the area near the surface of the substrate 1 is
closely related, it is desirable that the light receiving height of
the light receiving unit 144 is higher than the substrate 1 but as
close as possible to the surface of the substrate 1.
[0046] The flowchart shown in FIG. 2 is referred to in describing
the actual process for determining the plasma etching conditions of
the present embodiment. In FIG. 2, the gate etching process of the
substrate 1 is performed in advance for N times with the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2 varied, and the radical density distribution in
the plasma 38 at that time is measured by the aforementioned plasma
emission distribution measurement system. Further, the CD shift
distribution of each process is measured, and the data is obtained
(step 170). For example, the process is performed under a condition
in which the first processing gas 36-1 is composed of HBr,
Cl.sub.2, O.sub.2 and Ar mixed in the amount of 50 sccm, 50 sccm, 5
sccm and 10 sccm and the second processing gas 36-2 is composed of
the same gases mixed in the same amounts (hereinafter called
condition A), and the density distribution of the radical species
and the CD shift distribution are obtained. This constitutes one of
the data obtained by the etching performed in advance for N times
(at least two times). It is desirable to measure the density
distribution of a plurality of radical species during measurement
by the plasma emission distribution measurement system. For
example, it is preferable to measure the density distribution of
respective radical species such as H, Br, Cl and O generated by the
dissociation of the processing gas, radical species such as SiBr,
Si, SiCl and SiCl.sub.2 generated by the etching of Poly-Si, and Ar
contained in the processing gas. In order to perform the
aforementioned actinometry, it is preferable to add Ar or other
inert gas to the processing gas for performing processing
regardless of whether it is necessary for the etching reaction.
[0047] Furthermore, in step 170, in order to clarify the
relationship between the compositions and flow rates of the first
and second processing gases 36-1 and 36-2 and the CD shift
distribution, it is preferable to set the processing conditions
other than the compositions and flow rates of the first and second
processing gases 36-1 and 36-2, such as the temperature
distribution of the substrate 1, the processing pressure and the
UHF power applied to the antenna 52, to the same values during the
gate etching process performed for N times.
[0048] The data on the CD shift distribution achieved as the result
of the gate etching process performed for N times in advance, the
processing conditions during each of the processes such as the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2, the temperature distribution of the substrate
1, the processing pressure and the UHF power applied to the antenna
52, and the data on the density distribution of radicals are stored
in the database in the control computer 160 (step 172).
[0049] Next, the control computer 160 computes the relational
expression of the density distribution of the respective radicals
and the CD shift distribution (step 174).
[0050] Next, the control computer 160 computes the density
distribution of the respective radicals for realizing a uniform CD
shift distribution within the plane of the substrate 1 based on the
relational expression of the density distribution of respective
radicals and the CD shift distribution obtained in step 174 (step
176).
[0051] Next, the compositions and flow rates of the first and
second processing gases 36-1 and 36-2 are computed in order to
realize the density distribution of the respective radicals
computed in step 176 (step 178).
[0052] Next, the etching process is performed utilizing the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2 computed in step 178 (step 180). At this time,
the etching process is performed so that the processing conditions
other than the compositions and flow rates of the first and second
processing gases 36-1 and 36-2 are the same as those in the etching
performed for N times in step 170. Further, since the etching
process of step 180 is performed under a condition optimized so
that the in-plane CD shift distribution becomes uniform, it is not
necessary to measure the radical density distribution during the
etching process using the plasma emission distribution measurement
system.
[0053] However, when the etching apparatus is used for a long
period of time, the radical distribution within the vacuum
processing chamber 26 may vary with time. In this case, it is
effective to measure the plasma emission during the etching process
using the plasma emission distribution measurement system and
perform a real-time control of the processing conditions while
performing the etching process. In this case, at first, the density
distribution of the respective radicals is measured using the
plasma emission distribution measurement system, and the density
distribution data of the respective radicals is sent to the control
computer 160 (step 182). Next, the data is compared with the
computation results of the density distribution of the respective
radicals for realizing a uniform in-plane CD shift distribution of
the substrate 1 computed in step 176 (step 184), and as a result,
the computer 154 computes the parameters for realizing the most
appropriate density distribution of the respective radicals (step
178), which is reflected on the plasma etching conditions for
performing the process (step 180). If steps 182, 184, 178 and 180
are performed once in two seconds during the etching process, for
example, the radical density distribution can be controlled in real
time during etching.
[0054] Next, the effects of the present embodiment will be
described. FIG. 3(a) shows an in-plane distribution 190 of O
radicals on the surface of the substrate 1 when etching is
performed under the aforementioned condition A, and an in-plane
distribution 192 of O radicals computed in step 176 so as to
realize a uniform CD shift. The respective in-plane distributions
are composed of data corresponding to 100 positional points on the
surface of the substrate 1 having a diameter of 300 mm. According
to condition A, as shown by the in-plane distribution 190 of O
radicals, the density at the circumference portion is lower than
that of the in-plane distribution 192. In order to correct the
same, the oxygen flow rate of the second processing gas 36-2 is
increased by 3 sccm than condition A, that is, to 8 sccm. Since the
circumference-side gas feed area 32-2 through which the second
processing gas 36-2 is introduced is disposed toward the outer
circumference than the center-side gas feed area 32-1, the density
of O radicals at the circumference portion near the surface of the
substrate 1 is increased by the influence of the second processing
gas 36-2. If the oxygen flowrate of the second processing gas 36-2
is increased in the above manner, the density at the circumference
portion becomes higher than at the center portion of the substrate
1, however, the density at the center portion is also increased by
the influence of the second processing gas 36-2, according to which
a distribution as shown by in-plane distribution 191 occurs. In
order to correct the same, the present embodiment reduces the
oxygen flow rate of the first processing gas 36-1 by 2 sccm than
condition A, that is, to 3 sccm, so as to realize an in-plane
distribution 192 in which the O radical density is equal to
condition A at the center portion and higher at the outer
circumference portion.
[0055] Furthermore, with respect to FIG. 3(a), the reason why the
in-plane CD shift is more uniform according to the O-radical
in-plane distribution 192 having a higher density at the outer
circumference portion than according to the O-radical in-plane
distribution 190 having a flatter distribution is because, as
mentioned above, the tendency of the CD shift being smaller at the
outer circumference portion than at the center portion of the
substrate 1 is cancelled and corrected by the O radical density
being increased at the outer circumference portion to thereby
enhance the deposition property of reaction products and increase
the CD shift.
[0056] Moreover, FIG. 3(b) shows an in-plane distribution of
SiCl.sub.x (x=2, 3) radicals on the surface of the substrate 1. The
distribution obtained by performing etching under condition A is
shown in in-plane distribution 190', and the distribution realized
by applying the present invention to control the oxygen flow rate
is shown in in-plane distribution 192'. In the in-plane
distribution 192', the density of SiClx radicals at the outer
circumference portion of the substrate 1 is slightly reduced
compared to condition A. This is considered to be caused by the
application of the present invention increasing the O radical
density at the outer circumference portion, which lead to the
increase of the amount of deposition of reaction products forming a
protection film against etching.
[0057] As described, by comprehending not only the in-plane
distribution of O radicals shown in FIG. 3(a) but also the in-plane
distribution of SiClx radicals, it becomes possible to comprehend
the status of the plasma 38 in detail. Thus, the control accuracy
of the in-plane distribution of the CD shift of the substrate 1 is
improved.
[0058] Next, FIG. 4 shows a CD shift distribution 194 according to
condition A and a CD shift distribution 196 in which the present
invention is applied to perform control. According to the CD shift
distribution 196, the CD shift in the radial position of 100 mm and
smaller became greater compared to the CD shift 194 of condition A,
and thus, a uniform in-plane distribution was achieved.
[0059] Moreover, according to the present embodiment, the density
distributions of O radicals and SiCl.sub.x radicals are computed in
order to control the flow rate of oxygen in the first and second
processing gases 36-1 and 36-2, but the present invention is not
restricted thereto, and it is also possible to compute the density
distributions of other radicals and to control the corresponding
flow rates or compositions of the processing gases. For example, it
is possible to compute the density distribution of Cl radicals
which are etchant radicals in order to control the flow rates of
chlorine in the first and second processing gases 36-1 and
36-2.
[0060] According further to the present embodiment, processing
gases are fed through two gas feed areas, the center-side gas feed
area 34-1 and the circumference-side gas feed area 34-2, but the
number of gas feed areas is not restricted to two, and it is
possible to provide three or more gas feed areas.
Embodiment 2
[0061] Next, the second embodiment of the present invention will be
described with reference to FIGS. 5 and 6. In the present
embodiment, the temperature distribution of the substrate 1 is
controlled based on the radical density distribution obtained by
the plasma emission distribution measurement system, so as to
control and uniformize the in-plane distribution of CD shift of the
substrate 1. The following describes the differences of the present
embodiment from the first embodiment.
[0062] In the plasma etching apparatus of FIG. 5, the processing
gas is fed through a single gas feed area 42. Multiple lines of
temperature control means are provided at various radial positions
within the substrate stage 28, and the radial-direction temperature
distribution of the substrate 1 is controlled by controlling the
temperatures of the temperature control means. According to the
present embodiment, an inner circumference-side fluid passage 62-1
and an outer circumference-side fluid passage 62-2 are provided as
temperature control means, which are respectively connected to an
inner circumference-side circulator 64-1 and an outer
circumference-side circulator 64-2, and the set temperature of the
fluids circulated through the inner circumference-side fluid
passage 62-1 and the outer circumference-side fluid passage 62-2
are controlled so as to control the radial-direction temperature
distribution of the substrate 1 to be processed.
[0063] In the present embodiment, a control signal 162 is output
from the control computer 160 to the inner and outer
circumference-side circulators 64-1 and 64-2 so as to control the
set temperatures respectively. Furthermore, the relationship
between the set temperatures of the inner and outer
circumference-side circulators 64-1 and 64-2 and the in-plane
temperature distribution in the radial direction of the substrate 1
is computed in advance by tests or numerical simulations.
[0064] As described, the deposition of reaction products on the
side walls of the gate electrode influence the CD shift, and in
general, the reaction products tend to deposit more easily when the
temperature becomes lower. Therefore, the CD shift distribution can
be controlled by controlling the temperature distribution of the
substrate 1. The actual process for determining the plasma etching
conditions according to the present embodiment will be described
with reference to the flowchart of FIG. 6. In FIG. 6, similar to
the first embodiment, gate etching of the substrate 1 is performed
in advance for N times with the compositions and flow rates of the
processing gases varied, and the radical density distributions in
the plasma 38 and the CD shift distributions according to the
respective processes are measured to obtain data (step 170'). For
example, the data on the radical density distribution in the plasma
38 and the CD shift distribution is obtained by using a processing
gas composed of 50 sccm of HBr, 50 sccm of Cl.sub.2, 5 sccm of
O.sub.2 and 10 sccm of Ar, and the set temperatures of the inner
and outer circumference-side circulators 64-1 and 64-2 respectively
set to 40.degree. C. and 25.degree. C. (hereinafter referred to as
condition B), and the data constitutes one of the data of the
etching process performed in advance for N times. At this time, in
order to clarify the relationship between the density distributions
of the respective radicals and the CD shift distribution, if the
composition or the flow rate of the processing gas is varied, it is
preferable that the other processing conditions are the same during
the etching process performed for N times.
[0065] The data on the CD shift distribution obtained as a result
of the gate etching process performed in advance for N times, the
processing conditions of each process and the density distribution
of radicals are stored in the database of the control computer 160
(step 172').
[0066] Next, the control computer 160 computes the relational
expression of the density distribution of the respective radicals,
the set temperatures of the inner and outer circumference-side
circulators 64-1 and 64-2 and the CD shift distribution (step
174'). For example, if the density of O radicals is reduced at the
outer circumference portion of the substrate 1 compared to the O
radical distribution of the CD shift distribution that realizes a
uniform in-plane distribution of the substrate 1, the CD shift at
the outer circumference portion tends to be smaller than at the
center portion. In order to prevent this drawback, the set
temperature of the outer circumference-side circulator 64-2 is
lowered so as to allow the reaction products to be attached more
easily to the side walls of the gate electrode, by which the CD
shift at the outer circumference portion is increased and the CD
shift distribution is controlled to be more uniform.
[0067] Furthermore, in order to control the CD shift distribution,
it is necessary to obtain in advance a relational expression
representing the influence of the density distribution of a certain
radical on the CD shift distribution and the influence of the set
temperatures of the inner and outer circumference-side circulators
64-1 and 64-2 on the CD shift distribution, and to quantify the
same. Based on the processing condition of step 170', the density
distributions of respective radicals measured by the plasma
emission distribution measurement system and the CD shift
measurement results, and from the data stored in the database of
the control computer 160 in step 172', step 174' computes the
relational expression of the density distributions of the
respective radicals and the set temperatures of the inner and outer
circumference-side circulators 64-1 and 64-2, the in-plane
temperature distribution in the radial direction of the substrate 1
computed based on the set temperature of the circulators, and the
CD shift distribution.
[0068] Next, the control computer 160 computes, based on the
relational expression of the density distributions of the
respective radicals, the set temperatures of the respective
circulators and the CD shift distribution obtained in step 174',
the set temperatures of the respective circulators for realizing a
uniform CD shift distribution within the plane of the substrate 1
(step 176'). For example, according to the present embodiment, if
it is determined in step 174' that the density distribution of O
radicals is lower by 20% at the outer circumference portion of the
substrate 1 compared to the case in which the in-plane CD shift is
uniform, which results in the CD shift at the outer circumference
portion being narrowed by 3 nm than the center portion, it is
necessary to widen the CD shift by 3 nm at the outer circumference
portion so as to realize a uniform CD shift distribution. The set
temperatures of the inner and outer circumference-side circulators
64-1 and 64-2 for realizing the same are analyzed. For example, the
present embodiment computes that the set temperature of the outer
circumference-side circulator 64-2 should be reduced by 5.degree.
C. from the 25.degree. C. of condition B to 20.degree. C., and
since when the set temperature of the outer circumference-side
circulator 64-2 is reduced by 5.degree. C., the temperature of the
inner circumference-side of the substrate 1 on the chucked surface
is also lowered due to the thermal conductance of the substrate
stage, the set temperature of the inner circumference-side
circulator 64-1 should be raised by 2.degree. C. from the
40.degree. C. of condition B to 42.degree. C., so as to realize a
uniform in-plane distribution of the CD shift.
[0069] Next, plasma etching is performed using the set temperatures
of the inner and outer circumference-side circulators 64-1 and 64-2
for realizing a uniform CD shift distribution computed in step 176'
(step 180'). Further, the etching in step 180' is performed under a
condition optimized so as to realize a uniform in-plane CD shift
distribution, so it is not necessary to measure the radical density
distribution using the plasma emission distribution measurement
system during the process.
[0070] However, when the etching device is used for a long period
of time, the radical distribution within the vacuum processing
chamber 26 may vary with time. In this case, it is effective to
measure the plasma emission during etching using the plasma
emission distribution measurement system and to perform a real-time
control of the processing conditions. In such case, at first, the
density distribution of the respective radicals during etching is
measured by the plasma emission distribution measurement system,
and the density distribution data of the respective radicals thus
obtained is stored in the control computer 160 (step 182'). Next,
the density distribution data of the respective radicals is
substituted in the relational expression of the density
distribution of the respective radicals, the set temperatures of
the respective circulators and the CD shift distribution obtained
in step 174' (step 184'). Then, the set temperatures of the
respective circulators for realizing a uniform CD shift
distribution in the plane of the substrate 1 are computed (step
176'), and the result is reflected on the etching conditions. If
steps 182', 184' and 176' are performed once in two seconds during
the etching process, for example, it becomes possible to control
the temperature distribution of the substrate 1 in real time during
etching, and a uniform CD shift distribution can be realized.
[0071] By applying the present embodiment described above, it
becomes possible to utilize the plasma emission distribution
measurement system to measure the radical density distribution in
the plasma, to predict the CD shift distribution, to control the
temperature of the substrate based on the predicted value, and to
uniformize the CD shift distribution.
[0072] The set temperatures of two lines of circulators are
controlled to adjust the temperature distribution of the substrate
1 according to the present embodiment, but the number of lines of
temperature control is not restricted to two lines, and a greater
number of lines can be used. If a greater number of lines is used,
it becomes possible to control the temperature distribution in
further detail in the radial direction of the substrate 1.
According further to the present embodiment, circulators are used
as a means for controlling the temperature distribution of the
substrate 1, but the present invention is not restricted thereto,
and it is also possible to control the temperature distribution of
the substrate 1 by providing two lines of heaters, an inner
circumference-side heater and an outer circumference-side heater,
in the substrate stage 28, and to control the heating performed
thereby. Using heaters are more advantageous than using circulators
since it has better response property of temperature control of the
substrate 1. Of course, even when using heaters as the temperature
control means, the temperature distribution can be controlled in
further detail in the radial direction of the substrate 1 if a
greater number of lines is provided.
Embodiment 3
[0073] Next, the third embodiment of the present invention will be
described with reference to FIGS. 7 and 8. The present embodiment
controls the in-plane distribution of CD shift using both the means
for controlling the flow rates and compositions of processing gases
fed through two or more different gas feed areas and the multiple
lines of temperature control means disposed within the substrate
stage 28, based on the radical density distribution obtained using
the plasma emission distribution measurement system. The following
describes the differences between the present embodiment and the
aforementioned first and second embodiments.
[0074] In the plasma etching apparatus of FIG. 7, the in-plane
distribution of the CD shift of substrate 1 is controlled by
adjusting the compositions or flow rates of the first and second
processing gases 36-1 and 36-2 and the temperatures of the fluid
circulated through the inner and outer circumference-side fluid
passages 62-1 and 62-2 formed on the substrate stage 28.
[0075] The actual process for determining the gate etching
conditions according to the present embodiment will be described
with reference to the flowchart of FIG. 8. In FIG. 8, similar to
the description of the first embodiment, gate etching of the
substrate 1 is performed in advance for N times with the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2 varied, and the density distributions of
radicals in the plasma 38 are measured using the plasma emission
distribution measurement system, and further, the CD shift
distributions of the respective processes are measured to obtain
data (step 170''). For example, the data on the density
distributions of radical species and the CD shift distribution is
obtained under a condition using a first processing gas 36-1
composed of 50 sccm of HBr, 50 sccm of Cl.sub.2, 5 sccm of O.sub.2
and 10 sccm of Ar, a second processing gas 36-2 composed of 50 sccm
of HBr, 50 sccm of Cl.sub.2, 5 sccm of O.sub.2 and 10 sccm of Ar,
and setting the respective temperatures of the inner and outer
circumference-side circulators 64-1 and 64-2 to 40.degree. C. and
25.degree. C. (hereinafter referred to as condition C), the data
constituting one of the data of the etching performed in advance
for N times. At this time, in order to clarify the compositions and
flow rates of the first and second processing gases 36-1 and 36-2,
the set temperatures of the inner and outer circumference-side
circulators 64-1 and 64-2 and the CD shift distribution, if the
compositions or flow rates of the first and second processing gases
36-1 and 36-2 are varied, it is preferable that the other
processing conditions are maintained the same during the etching
process performed for N times.
[0076] The data on the CD shift distribution obtained as a result
of the gate etching process performed in advance for N times, the
processing conditions of each process and the density distribution
of radicals are stored in the data base of the control computer 160
(step 172'').
[0077] Next, the control computer 160 computes the relational
expression of the density distributions of the respective radicals,
the set temperatures of the inner and outer circumference-side
circulators 64-1 and 64-2 and the CD shift distribution (step
174''). For example, if the density of 0 radicals is reduced at the
outer circumference portion of the substrate 1 compared to the O
radical distribution when the in-plane CD shift distribution of the
substrate 1 is uniform, the CD shift at the outer circumference
portion tends to be smaller than the center portion. In order to
prevent this drawback, the set temperature of the outer
circumference-side circulator 64-2 is reduced so as to allow the
reaction products to be stuck more easily to the side walls of the
gate electrode, and the flowrate of oxygen in the second processing
gas 36-2 is increased, by which the CD shift at the outer
circumference portion is controlled to be increased. Furthermore,
in order to control the CD shift distribution, it is necessary to
obtain in advance a relational expression representing the
influence of the density distribution of a certain radical on the
CD shift distribution and the influence of the set temperatures of
the inner and outer circumference-side circulators 64-1 and 64-2 on
the CD shift distribution, and to quantify the same. Based on the
processing condition of step 170'', the density distribution of
respective radicals measured by the plasma emission distribution
measurement system and the CD shift measurement results, and by the
data stored in the database of the control computer 160 in step
172'', step 174'' computes the relational expression of the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2, the density distribution of the respective
radicals, the set temperatures of the inner and outer
circumference-side circulators 64-1 and 64-2, the in-plane
temperature distribution in the radial direction of the substrate 1
computed based on the set temperatures of the circulators, and the
CD shift distribution.
[0078] Next, the control computer 160 computes, based on the
relational expression of the density distributions of the
respective radicals, the set temperatures of the respective
circulators and the CD shift distribution obtained in step 174'',
the flow rates and compositions of the respective processing gases
and the set temperatures of the respective circulators for
realizing a uniform CD shift distribution within the plane of the
substrate 1 (step 176''). For example, according to the present
embodiment, if it is determined in step 174'' that compared to the
case in which the in-plane CD shift is uniform, the density
distribution of O radicals is lower by 20% at the outer
circumference portion of the substrate 1, which results in the CD
shift at the outer circumference portion being narrowed by 3 nm
than at the center portion, it is necessary to widen the CD shift
by 3 nm at the outer circumference portion so as to realize a
uniform CD shift distribution. The set temperatures of the inner
and outer circumference-side circulators 64-1 and 64-2 and the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2 for realizing the same are analyzed. For
example, the present embodiment computes that a uniform in-plane CD
shift distribution can be realized by reducing the oxygen flow rate
of the first processing gas 36-1 by 1 sccm to 4 sccm and increasing
the oxygen flow rate of the second processing gas 36-2 by 1.5 sccm
to 6.5 sccm, increasing the set temperature of the inner
circumference-side circulator 64-1 by 1.degree. C. to 41.degree. C.
and reducing the set temperature of the outer circumference-side
circulator 64-2 by 2.5.degree. C. to 22.5.degree. C. compared to
condition C.
[0079] Next, a plasma etching process is performed using the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2 and the set temperatures of the inner and outer
circumference-side circulators 64-1 and 64-2 computed in step 176''
(step 180''). Further, the etching in step 180'' is performed under
a condition optimized so as to realize a uniform in-plane CD shift
distribution, so it is not necessary to measure the radical density
distribution using the plasma emission distribution measurement
system during the process.
[0080] However, when the etching apparatus is used for a long
period of time, the radical distribution within the vacuum
processing chamber 26 may vary with time. In this case, it is
effective to measure the plasma emission during etching using the
plasma emission distribution measurement system and to perform a
real-time control of the processing conditions. In such case, at
first, the density distribution of the respective radicals during
etching is measured using the plasma emission distribution
measurement system, and the density distribution data of the
respective radicals thus obtained is stored in the control computer
160 (step 182''). Next, the density distribution data of the
respective radicals is substituted in the relational expression of
the density distribution of the respective radicals, the set
temperatures of the respective circulators and the CD shift
distribution obtained in step 174'' (step 184''). Then, the
compositions and flow rates of the first and second processing
gases 36-1 and 36-2 and the set temperatures of the respective
circulators for realizing a uniform CD shift distribution of the
substrate 1 obtained instep 176'' is computed, and the result is
reflected on the conditions for the etching process (step 180'').
If steps 182'', 184'' and 180'' are performed once in two seconds
during the etching process, for example, real-time control of
processing conditions during etching is performed, and a uniform CD
shift distribution can be realized.
[0081] According to the above embodiment, it becomes possible to
use the plasma emission distribution measurement system to measure
the radical density distribution in the plasma, to predict the CD
shift distribution, to control the flow rates and compositions of
the processing gases and the temperature distribution of the
substrate 1 based on the predicted value, and to uniformize the CD
shift distribution. As described in the present embodiment, by
utilizing both the control means of the first and second
embodiments, the amount of control of CD shift can be increased
compared to the case in which each control means is used by itself,
and it becomes possible to correspond to a wide range of etching
conditions. Moreover, the CD shift distribution can be controlled
with better response property compared to the case in which each
control means is used by itself.
Embodiment 4
[0082] Next, the fourth embodiment of the present invention will be
described with reference to FIG. 9. In the first through third
embodiments, the light receiving unit 144 and the rotation
transmitting shaft 142 of the plasma emission distribution
measurement system were directly exposed to plasma 38. It is
possible to use materials such as polyimide to form these members
so that they have resistance to corrosion from the plasma 38, but
if they are to be used for a long period of time, it is necessary
that they are protected by a cover or the like. In FIG. 9, a cover
170 made of quartz is arranged to cover the light receiving unit
144 and the rotation transmitting shaft 142 of the plasma emission
distribution measurement system illustrated in embodiments 1
through 3. Furthermore, by designing the light receiving unit 144
and the rotation transmitting shaft 142 to be rotated within the
cover, it becomes possible to change the direction of the light
receiving unit 144 while receiving the light emitted from the
plasma 38, so that the density distribution of various radicals in
the plasma 38 can be measured. According to the present embodiment,
it becomes possible to measure the radical density distribution in
the plasma 38 for a long period of time.
Embodiment 5
[0083] Next, the fifth embodiment of the present invention will be
described with reference to FIG. 10. Similar to the fourth
embodiment, the present embodiment considers long-term use of the
plasma emission distribution measurement system, wherein a quartz
window 172 is embedded in the wall 20 of the processing chamber,
and the light receiving unit 144 of the plasma emission
distribution measurement system is provided on the outer side (on
the atmospheric side) of the window 172. By enabling the light
receiving unit 144 to be rotated, it becomes possible to change the
direction of the light receiving unit 144 while receiving the light
emitted from the plasma 38, so that the density distribution of
various radicals in the plasma 38 can be measured. According to the
present embodiment, it becomes possible to measure the radical
density distribution of the plasma 38 for a long period of
time.
Embodiment 6
[0084] Next, the sixth embodiment of the present invention will be
described with reference to FIGS. 11 and 12. The present embodiment
disposes a plurality of light receiving units in the direction of
observation suitable for extracting the radical density
distribution in the processing chamber, and computes in real time
during the etching process the radical and plasma distribution in
the chamber based on the plurality of observation data obtained by
the plurality of light receiving units as compared with the
database prepared in advance. The present embodiment considers
long-term use of the plasma emission distribution measurement
system, and in addition, simplifies the structure of the
distribution measurement means. As shown in FIG. 11, in order to
observe the area on the surface of the substrate 1 ranging from the
center to the outer circumference thereof in the direction parallel
to the surface of the substrate 1, a plurality of (four in the
present drawing) windows 201-1 through 201-4 are arranged at even
intervals on the wall of the processing chamber, and light
receiving units 200-1 through 200-4 are arranged to face the
windows, by which the plasma generated in the vacuum processing
chamber 26 is observed. According to this arrangement, the light
receiving units 200-1 through 200-4 must be arranged at observation
directions suitable for extracting the radical density distribution
in the plasma. In the present embodiment, the light receiving units
are arranged so that a length of the path through which each light
receiving unit observes the plasma in the transverse direction
(hereinafter referred to as optical path) differs for each light
receiving unit, and at the same time, is parallel with the optical
paths of other units. Furthermore, the plasma emission received by
the light receiving units is the integration value of plasma
emission existing in the optical path passing transversely across
the processing chamber 26, as illustrated by the dotted arrowed
lines of FIG. 11. Furthermore, when receiving light using the light
receiving units 200-1 through 200-4, it is important that the light
receiving unit 144 of the plasma emission distribution measurement
system is arranged so as not to interfere with the optical paths.
The actual method of use of the present system will be described in
detail below.
[0085] At first, upon performing etching for N times in advance and
acquiring data on the correlation of the radical density
distribution and the CD shift distribution using the plasma
emission distribution measurement system as illustrated in the
first to third embodiments, the light emitted from the plasma (not
shown) is received by the plurality of light receiving units 200-1
through 200-4 illustrated in FIG. 11. Each light receiving unit
200-1 through 200-4 has an optical fiber 148-1 through 148-4
connected respectively thereto, and the received plasma emission is
transmitted to a spectroscope 150. The intensities of respective
wavelengths of the plasma emission transmitted to the spectroscope
150 are converted into emission spectral data at the spectroscope
150, and sent to the computer 154. The computer 154 identifies the
radical species and computes the emission peak intensity of each
radical species. Further, the radial position thereof is computed
based on the set positions of the light receiving units 200-1
through 200-4, the result of which is combined with the emission
peak intensity of each radical. In this case, a path
perpendicularly crossing the optical paths of the light receiving
units and passing the center of the processing chamber 26 is set as
an axis, and the coordinates on the axis show the radial positions.
At this time, by rotating the light receiving unit 144 of the
plasma emission distribution measurement system, and based on the
method shown in the first to third embodiments, it becomes possible
to achieve the radical density distribution. Further, the CD shift
by the etching process is measured. According to the above process,
similar to the first to third embodiments, during the plurality (N
times) of processes performed in advance before the actual etching
process, the peak intensity of each radical at multiple radial
positions, the density distribution of each radical and the CD
shift distribution are acquired, the data of which are correlated
and stored in the database of the control computer 160.
[0086] After acquiring these data, even if the light receiving unit
144 of the plasma emission distribution measurement system is
removed, the actual radical density distribution 190 during etching
can be computed in real time by using only the light receiving
units 200-1 through 200-4. At this time, an example of the O
radical density distribution measured by the light receiving unit
144 during the plurality (N times) of processes performed in
advance is shown in FIG. 12(a), and an example of the emission peak
intensity distribution of O radicals measured using the light
receiving units 200-1 through 200-4 is shown in FIG. 12(b). The O
radical density distribution 202a shows a substantially uniform
distribution throughout the plane. The emission peak intensity
distribution of O radicals measured using the light receiving units
200-1 through 200-4 during the process is shown in 204-1a through
204-4a. The reason why the O radical density distribution 202a is
substantially uniform whereas according to the emission peak
intensity distribution 204-1a through 204-4a the intensity is
reduced toward the outer radial position is that the integration
value of O radical emission reduces as the position becomes close
to the outer side and the optical path length becomes shorter.
Further, the O radical density distribution in the process
performed according to a different processing condition is 202b,
and the emission peak intensity distribution of O radicals measured
during the process using the light receiving units 200-1 through
200-4 is shown in 204-1b through 204-4b. As described, since the
radical density distribution and the radical peak intensity at
multiple radial positions are mutually correlated and stored in the
database, even if the light receiving unit 144 of the plasma
emission distribution measurement system disposed in the processing
chamber 26 is removed after the N times of etching processes
performed in advance, it becomes possible to use the radical
emission peak intensity obtained by the light receiving units 200-1
through 200-4 to refer to the database and acquire a detailed
radical density distribution. In addition, since according to the
present system there is no need to dispose the light receiving unit
144 in the processing chamber 26 after completing the etching
performed in advance for N times, the stability of long-term
operation of the etching process is enhanced. Furthermore, since it
is possible to achieve the detailed radical density distribution
without mechanically rotating the light receiving unit 144, and
since it is not necessary to perform computing processes such as
the Abel inversion which is mathematically advanced, it becomes
possible to achieve the radical density distribution at high speed.
This is advantageous in performing control of the processing
conditions based on the measurement results of the radical density
distribution.
[0087] For example, in the etching process performed after the
etching process performed in advance for N times, the emission peak
intensity distribution of O radicals measured using the plurality
of light receiving units 200-1 through 200-4 shows a distribution
as shown in 204-1b through 204-4b by influences such as the time
variation of the etching apparatus, it is possible to refer to the
database in the control computer to discover that the O radical
density distribution will be similar to 202b of FIG. 12(a). If
according to the etching process performed in advance for N times,
the in-plane distribution of CD shift becomes uniform when the O
radical density distribution is as shown in 202a, the CD shift will
become smaller at the outer circumference portion of the substrate
1 according to a processing condition in which the emission peak
intensity distribution of O radicals is as shown in 204-1b through
204-4b. In order to prevent this problem, the oxygen flow rate of
the processing gas supplied through the outer circumference-side
gas feed region 34-2 can be increased (by 2 sccm, for example) as
shown in embodiment 1, so as to control the O radical emission peak
intensity distribution to become equal to 204-1a through 204-4a.
According to such control, by referring to a database, it can be
seen that the O radical density distribution will be similar to the
O radical density distribution 202a, and that the CD shift will be
uniform throughout the plane. As described, based on the radical
emission peak intensity obtained through light receiving units
200-1 through 200-4, it becomes possible to control the processing
conditions so as to improve the in-plane uniformity of CD
shift.
[0088] The timing for performing such control of the processing
conditions can be selected freely by the user of the present
invention. For example, in the current semiconductor fabrication,
the processing of the substrates is performed in units called lots
(for example, one lot includes 25 substrates), so that the radical
emission peak intensity obtained through light receiving units
200-1 through 200-4 in the etching process of a certain lot can be
used to control the processing conditions of the subsequent lot so
as to improve the in-plane uniformity of CD shift. Furthermore, the
radical emission peak intensity obtained through light receiving
units 200-1 through 200-4 during the processing of a certain
substrate can be used to control the processing conditions for the
subsequent substrate so as to improve the in-plane uniformity of CD
shift. Moreover, if the etching process is composed of multiple
steps, it is possible to measure the radical emission peak
intensity using light receiving units 200-1 through 200-4 in a
certain step, refer to the database, and if it is detected that the
in-plane uniformity of CD shift is likely to be deteriorated,
control the processing conditions in the subsequent step so as to
realize a uniform CD shift by the process. Further, in case the
processing conditions are to be controlled per each step, it is
necessary to adjust the processing conditions for each step during
the N times of etching performed in advance, and to store the
radical density distribution, the radical emission peak intensity
measured by the plural light receiving units and the CD shift
distribution after the etching process in the database. Further, it
is also possible to immediately control the processing conditions
based on the radical emission peak intensity during etching to
perform a real-time control of processing conditions, so as to
improve the in-plane uniformity of CD shift.
[0089] As described, if the processing conditions for the
subsequent step is to be controlled or if real-time control of
processing conditions is to be performed based on the radical
emission peak intensity acquired in a certain step, if the control
object is the temperature distribution of the substrate 1, it is
preferable that the response of control is quick, that is, the
control for realizing a target temperature is quick. In this case,
it is possible to provide two lines of heaters, an inner
circumference-side heater and an outer-circumference side heater,
in the substrate stage 28, and to control the respective heating
thereof so as to control with high response the temperature
distribution of the substrate 1.
[0090] If the present embodiment is not applied and the plasma
emission is measured using only the light receiving units arranged
at four locations without acquiring in advance the detailed radical
density distribution, only the radical emission peak intensities
204-1a through 204-4a at four points are acquired, and the density
distribution at locations between the measurement points cannot be
acquired. For example, the density distribution of radicals at
locations between measurement points can be estimated through
techniques such as polynomial approximation or spline
interpolation, but it cannot be guaranteed that the estimated
distribution corresponds with the actual radical density
distribution. As mentioned, the in-plane CD shift dispersion in the
order of nanometers creates a problem in the current semiconductor
mass production, so it is not sufficient to only obtain the radical
density distribution of a few locations, and it is important to
obtain a highly accurate radical density distribution throughout
the area covering the radius of the substrate 1.
[0091] Furthermore, it is important that a plurality of light
receiving units are arranged in the observation direction suitable
for extracting the radical density distribution in the processing
chamber, and according to the present embodiment, four light
receiving units 200-1 through 200-4 are arranged at even intervals
on the processing chamber wall so as to measure the region from the
center to the outer circumference on the surface of the substrate
1. However, the locations of the light receiving units are not
restricted thereto. For example, it is possible to arrange the
plurality of light receiving units on the upper portion of the
processing chamber 26 so that they are at different radial
positions facing the substrate 1. However, if the distance in the
height of the plasma 38, that is, the distance between the
center-side gas feed area 34-1 and the substrate 1 is long, the
influence from the radical emission in the area other than near the
surface of the substrate 1 becomes strong. Since the radicals near
the surface of the substrate 1 strongly influence the etching
process, the SN ratio may be deteriorated in the above case.
Further according to the present embodiment, the light receiving
units are arranged so that the optical path lengths of plasma
differ for each light receiving unit. This is because the radical
density distribution in the plasma is axisymmetric since the
processing chamber 38 has a substantially cylindrical shape. If the
light receiving units are arranged so that the optical path length
of plasma received by the light receiving units are all equal, the
radical emission peak intensity obtained through the light
receiving units become equal and the in-plane distribution cannot
be obtained. Therefore, it is preferable to arrange the light
receiving units so that the optical path lengths of plasma differ
for each light receiving unit, as described in the present
embodiment. Moreover, the light receiving units in the present
embodiment are arranged so that the optical path of plasma received
by each unit is parallel with the other paths, but if the optical
path length of plasma of the units are varied, effects similar to
those of the present embodiment can be achieved even if the optical
paths are not parallel. Further, there are four light receiving
units disposed on the processing chamber wall according to the
present embodiment, but the number is not restricted thereto. The
spatial resolution performance of the plasma emission distribution
in the processing chamber 26 is improved as the number is
increased, but if the number is too large, there are drawbacks such
as the necessity of a large installation space and the complexity
of structure. According to the studies performed by the present
inventors, it has been discovered that the appropriate number of
light receiving units ranges from 3 to 10, and in the present
embodiment, the number is four.
[0092] According to the present embodiment, there are four light
receiving units 200-1 through 200-4 arranged at even intervals from
the center of the substrate 1 toward the outer circumference
thereof, but the present invention is not restricted to this
example, and the interval can be uneven. For example, in an etching
apparatus utilizing ICP (inductively-coupled plasma), the plasma
density tends to be higher near the inductive coupling coil. In
correspondence thereto, the light receiving unit should be disposed
at the peak radial position near the inductive coupling coil where
the density becomes highest to measure the radical emission peak
intensity, which is combined with the emission peak intensity data
from other light receiving units and referred to the database to
obtain a detailed radical density distribution.
[0093] According further to the present embodiment, light receiving
units 200-1 through 200-4 are disposed so as to receive emission
through windows formed on the processing chamber wall, but during
long-term operation, deposits may adhere on the inner side (vacuum
side) of the window, or the window may be etched by the plasma and
tarnished, by which the received intensity may be weakened. In that
case, the influence can be reduced by setting the emission peak
intensity of a certain radical (such as argon) as reference, and
utilizing a ratio thereof with the emission peak intensity of the
target radical (such as O). The radical used as reference for the
emission peak should preferably be an inert gas that is less
subject to influence from radical density distribution since it
does not react with other radicals.
[0094] Further according to the present embodiment, the method for
controlling the processing conditions controlled the flow rates and
compositions of the processing gases supplied through two or more
gas feed areas similar to the first embodiment, but it is not
restricted thereto, and it is possible to control the temperatures
of the plural lines of temperature control means formed in the
substrate stage 28 similar to the second embodiment, or to control
both the means for controlling the flow rates and compositions of
the processing gases fed from two or more gas feed areas and the
plural lines of temperature control means formed in the substrate
stage 28 similar to the third embodiment.
[0095] Based on the density distribution of the respective radicals
obtained as above, and by applying the method and control
illustrated in embodiments 1 through 3, the density distribution of
various radicals during etching can be obtained at high speed using
the light receiving units 200-1 through 200-4 disposed at multiple
locations, and plasma etching can be performed by performing
control so as to realize a uniform in-plane distribution of the CD
shift. By applying these methods, plasma etching can be performed
with superior long-term operability to realize a uniform in-plane
CD shift distribution advantageously in the mass production of
semiconductor devices.
[0096] Further, the density distributions of radicals in the plasma
are measured according to the first through sixth embodiments of
the present invention, but the present invention is not restricted
thereto, and it is possible to measure the density distribution of
plasma itself.
[0097] The first through sixth embodiments of the present invention
are described with respect to a gate etching process for forming
Poly-Si gates, but the present invention is not restricted thereto,
and can be applied to etching of other materials. Furthermore, in
the case of a plasma CVD, since the radical density distribution
and the temperature distribution of the substrate 1 influences the
in-plane uniformity of the deposition rate or the in-plane
uniformity of the film quality, a superior plasma CVD process is
enabled by applying the present invention.
[0098] The first through sixth embodiments of the present invention
are described with respect to a UHF-ECR apparatus, but the plasma
source is not restricted to UHF-ECR, and the present invention can
be applied to processing apparatuses utilizing other plasma sources
such as ICP (inductively-coupled plasma) and CCP
(capacitively-coupled plasma).
[0099] By utilizing the plasma etching apparatus of the present
invention, the following plasma etching apparatuses and plasma
etching methods are realized. [0100] 1. A plasma etching apparatus
comprising:
[0101] a vacuum processing chamber for subjecting a substrate to
plasma processing:
[0102] a substrate stage disposed in the vacuum processing chamber
having a support surface for supporting the substrate;
[0103] a gas inlet for supplying processing gas into the vacuum
processing chamber;
[0104] an electromagnetic wave supply means for supplying
electromagnetic wave into the vacuum processing chamber;
[0105] a plurality of light receiving units for receiving plasma
emission near a surface of the substrate from a side surface of the
vacuum processing chamber, wherein the light receiving units are
disposed so that the lengths of optical paths received by the
respective light receiving units vary;
[0106] a plasma emission distribution measurement system disposed
separately from the plurality of light receiving units; and
[0107] a means for computing a radical distribution in the plasma
based on at least either the plasma emission distribution
measurement system or the plurality of light receiving units;
wherein
[0108] the plasma etching apparatus further includes a process for
performing a plasma etching process in advance, a process for
computing the radical distribution in the plasma during the process
using the means for computing radical distribution and the
plurality of light receiving units, and a process for measuring a
CD shift distribution of the substrate subjected to plasma
processing in the plasma etching process and storing the result
thereof in a database;
[0109] a means for computing the radical distribution in the plasma
using the plurality of light receiving units during a plasma
etching process performed subsequent to said plasma etching process
performed in advance; and
[0110] a means for controlling the plasma etching process
conditions based on the data stored in the database. [0111] 2. The
plasma etching apparatus according to aspect 1, wherein
[0112] an object for controlling the processing condition during
the plasma etching process is either a composition and flow rate of
the processing gas supplied through the plurality of gas inlets or
a temperature distribution of the supporting surface of the
substrate holder, or both. [0113] 3. The plasma etching apparatus
according to aspect 1 or aspect 2, including a means for computing
the radical distribution in the plasma using the plurality of light
receiving units during a plasma etching process performed
subsequent to said plasma etching process performed in advance, and
a means for controlling the plasma etching process conditions based
on the data stored in the database; wherein
[0114] the process for computing the radical distribution in the
plasma and the process for controlling the plasma etching process
conditions are performed at a timing selected from the following;
per lot, per processing of the substrate, or per step of the
plurality of etching steps; or the plasma etching process
conditions is controlled immediately based on the computed result
of the radical distribution in the plasma. [0115] 4. A plasma
etching method for etching a substrate using a plasma etching
apparatus comprising a vacuum processing chamber for subjecting the
substrate to plasma processing; at least two gas supply sources for
supplying processing gases to the vacuum processing chamber; gas
inlets located at least at two locations for feeding processing gas
to the vacuum processing chamber; an electromagnetic wave supplying
means for supplying electromagnetic waves to the vacuum processing
chamber; a plasma emission distribution measurement system for
measuring the distribution of plasma emission near the surface of
the substrate from a side surface; a means for computing the
radical distribution in the plasma by the plasma emission
distribution measurement system; and a means for controlling either
a composition or a flow rate of processing gases fed through the
two gas inlets based on the radical distribution computed in
advance by the radical distribution computing means and the
measurement result of the CD shift distribution; the method
comprising the steps of
[0116] measuring a radical density distribution of at least one
radical and a CD shift distribution during the etching process by
performing at least two etching processes in advance with the flow
rates of processing gases varied;
[0117] storing the conditions of the etching processes, the radical
density distribution and the CD shift distribution in a
database;
[0118] computing a relational expression of the radical density
distribution for the at least one radical and the CD shift
distribution;
[0119] computing a processing condition to realize a uniform CD
shift using the relational expression; and
[0120] computing a control parameter of the etching process so as
to realize the processing condition computed to realize a uniform
CD shift;
[0121] wherein the etching process of the substrate is performed
using the computed control parameter. [0122] 5. A plasma etching
method for etching a substrate using a plasma etching apparatus
comprising a vacuum processing chamber for subjecting the substrate
to plasma processing; a substrate stage disposed in the vacuum
processing chamber for holding the substrate and having formed
therein a temperature control means for controlling the temperature
of at least two locations; an electromagnetic wave supplying means
for supplying electromagnetic waves to the vacuum processing
chamber; a plasma emission distribution measurement system for
measuring the distribution of plasma emission near the surface of
the substrate from the side direction; a means for computing the
radical distribution in the plasma by the plasma emission
distribution measurement system; and a means for controlling the
temperature of at least two locations of the substrate stage for
the substrate based on the radical distribution computed in advance
by the radical distribution computing means and the measurement
result of the CD shift distribution; the method comprising the
steps of
[0123] measuring a radical density distribution of at least one
radical and a CD shift distribution during the etching process by
performing at least two etching processes in advance with the flow
rates of processing gases varied;
[0124] storing the conditions of the etching processes, the radical
density distribution and the CD shift distribution in a
database;
[0125] computing a relational expression of the radical density
distribution for the at least one radical and the CD shift
distribution;
[0126] computing a processing condition to realize a uniform CD
shift using the relational expression; and
[0127] computing a control parameter of the etching process so as
to realize the processing condition computed to realize a uniform
CD shift;
[0128] wherein the etching process of the substrate is performed
using the computed control parameter. [0129] 6. A plasma etching
method for etching a substrate using a plasma etching apparatus
comprising a vacuum processing chamber for subjecting the substrate
to plasma processing; gas inlets located at least at two locations
for feeding processing gas into the vacuum processing chamber; a
substrate stage disposed in the vacuum processing chamber for
holding the substrate and having embedded therein a temperature
control means for controlling the temperature of at least two
locations; an electromagnetic wave supplying means for supplying
electromagnetic waves to the vacuum processing chamber; a plasma
emission distribution measurement system for measuring the
distribution of plasma emission near the surface of the substrate
from a side surface; a means for computing the radical distribution
in the plasma by the plasma emission distribution measurement
system; and a means for controlling a composition or a flow rate of
processing gases fed through the two gas inlets and the temperature
of at least two locations of the substrate stage for the substrate
based on the radical distribution computed in advance by the
radical distribution computing means and the measurement result of
the CD shift distribution; the method comprising the steps of
[0130] measuring a radical density distribution of at least one
radical and a CD shift distribution during the etching process by
performing at least two etching processes in advance with the flow
rates of processing gases varied;
[0131] storing the conditions of the etching processes, the radical
density distribution and the CD shift distribution in a
database;
[0132] computing a relational expression of the radical density
distribution for the at least one radical and the CD shift
distribution;
[0133] computing a processing condition to realize a uniform CD
shift using the relational expression; and
[0134] computing a control parameter of the etching process so as
to realize the processing condition computed to realize a uniform
CD shift;
[0135] wherein the etching process of the substrate is performed
using the computed control parameter. [0136] 7. The plasma etching
method according to any one of the aforementioned 4 through 6,
further comprising
[0137] measuring the radical density distribution of said at least
one radical during the etching process; and
[0138] computing during the etching process the control parameter
of the etching process so as to realize the processing condition
computed to realize a uniform CD shift;
[0139] wherein the etching process of the substrate is performed
using the computed control parameter. [0140] 8. The plasma etching
method according to any one of the aforementioned 4 through 7,
wherein
[0141] said control parameter for the etching process for realizing
the processing condition computed so a to realize a uniform CD
shift is at least either the compositions or flow rates of the
processing gases fed from at least two locations, or the set
temperatures of the temperature control means disposed at least at
two locations for controlling the temperature distribution of the
substrate.
* * * * *