U.S. patent application number 10/793886 was filed with the patent office on 2005-02-10 for apparatus and method for plasma etching.
Invention is credited to Edamura, Manabu, Miya, Go, Nishio, Ryoji, Yoshioka, Ken.
Application Number | 20050028934 10/793886 |
Document ID | / |
Family ID | 34113700 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050028934 |
Kind Code |
A1 |
Miya, Go ; et al. |
February 10, 2005 |
Apparatus and method for plasma etching
Abstract
A plasma etching apparatus capable of performing processing with
excellent in-plane uniformity on an object to be processed having a
large diameter is provided. The present invention provides a plasma
etching apparatus including a processing chamber 13 which performs
plasma processing on an object to be processed 1, a first
processing gas supply source 40, a second processing gas supply
source 50, a first gas inlet 65-1 which introduces a processing gas
into the processing chamber, second gas inlets 65-2 which introduce
the processing gas into the processing chamber, flow rate
regulators 42 and 53 which regulate the flow rate of the processing
gas and a gas shunt 60 which divides the first processing gas into
a plurality of portions, wherein at least two gas pipes branched by
the shunt 60 are provided with the first gas inlet 65-1 or second
gas inlets 65-2 and merging sections 63-1 and 63-2 are provided
between the shunt 60 and the first gas inlet 65-1 and between the
shunt 60 and the second gas inlets 65-2 for merging the second
processing gas.
Inventors: |
Miya, Go; (Ibaraki-ken,
JP) ; Edamura, Manabu; (Ibaraki-ken, JP) ;
Yoshioka, Ken; (Hikari-shi, JP) ; Nishio, Ryoji;
(Kudamatsu-shi, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-9889
US
|
Family ID: |
34113700 |
Appl. No.: |
10/793886 |
Filed: |
March 8, 2004 |
Current U.S.
Class: |
156/345.33 |
Current CPC
Class: |
H01J 37/3244 20130101;
H01L 21/67017 20130101; H01L 21/67069 20130101; H01J 37/32449
20130101 |
Class at
Publication: |
156/345.33 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2003 |
JP |
2003-206042 |
Claims
What is claimed is:
1. A plasma etching apparatus comprising: a processing chamber for
performing plasma etching on an object to be processed; a first gas
supply source for supplying a processing gas; a second gas supply
source provided separately from said first processing gas; a first
gas inlet for introducing the processing gas into said processing
chamber; a second gas inlet provided separately from said first gas
inlet; a flow rate regulator for regulating the flow rate of the
processing gas; and a gas shunt for dividing the processing gas
into a plurality of portions, wherein said second gas is supplied
between said gas shunt and at least one of said first and second
gas inlets.
2. The plasma etching apparatus according to claim 1, wherein gases
of different flow rates or compositions are introduced through said
first gas inlet and said second gas inlet.
3. The plasma etching apparatus according to claim 2, further
comprising: a measuring instrument for measuring the object to be
processed before etching or after etching; a database for storing
the result of said measurement; an analysis section for performing
an analysis based on the data stored in said database and
generating a control command; and a control section for generating
a control signal based on said control command.
4. The plasma etching apparatus according to claim 1 or claim 2,
further comprising: at least one photoreception section for
receiving plasma emission during etching; a spectroscopic section
for discomposing said plasma emission into a plurality of
wavelength components; a database for storing the result of said
spectroscopy; an analysis section for performing an analysis based
on the data stored in said database and generating a control
command; and a control section for generating a control signal
based on said control command.
5. The plasma etching apparatus according to claim 1 or claim 2,
further comprising: a photoreception section for receiving light
from the center portion of said quasi-cylindrical processing
chamber; a photoreception section placed in a different location
from that of said photoreception section of said quasi-cylindrical
processing chamber; a spectroscopic section for discomposing said
plasma emission into a plurality of wavelength components; a
database for storing the result of said spectroscopy; an analysis
section for performing an analysis based on the data stored in said
database and generating a control command; and a control section
for generating a control signal based on said control command.
6. A plasma etching apparatus comprising: a processing chamber for
performing plasma etching on an object to be processed; a first
processing gas supply source; a second processing gas supply
source; a first gas inlet for introducing a processing gas into the
processing chamber; a second gas inlet for introducing a processing
gas into the processing chamber; a flow rate regulator for
regulating the flow rate of the processing gas; and a gas shunt for
dividing the first processing gas into a plurality of portions,
wherein at least two gas pipes branched by the gas shunt are each
provided with a first gas inlet and a second gas inlet
respectively, and a merging section for merging the second
processing gas is provided between the gas shunt and the first gas
inlet and between the gas shunt and the second gas inlet.
7. The plasma etching apparatus according to claim 6, wherein
different flow rates or compositions are applied for the processing
gas supplied to the first gas inlet and the processing gas supplied
to the second gas inlet.
8. The plasma etching apparatus according to claim 6 or claim 7,
further comprising: a database for storing the result of
measurement of the object to be processed before etching or after
etching; an analysis section for performing an analysis based on
the data stored in the database and generating a control command;
and a control section for generating a control signal for changing
the flow rates or compositions of the processing gases supplied to
the first gas inlet and second gas inlet based on the control
command.
9. The plasma etching apparatus according to claim 6 or claim 7,
further comprising: at least one photoreception section for
receiving plasma emission during etching; a spectroscopic section
for discomposing said plasma emission into a plurality of
wavelength components; a database for storing the result of said
spectroscopy; an analysis section for performing an analysis based
on the data stored in said database and generates a control
command; and a control section for generating a control signal for
changing the flow rates or compositions of the processing gases
supplied to the first gas inlet and the second gas inlet based on
said control command.
10. The plasma etching apparatus according to claim 6 or claim 7,
further comprising: a photoreception section for receiving light
from the center portion of said quasi-cylindrical processing
chamber; a photoreception section placed in a different location
from that of said photoreception section of said quasi-cylindrical
processing chamber; a spectroscopic section for discomposing said
plasma emission into a plurality of wavelength components; a
database for storing the results of said spectroscopy; an analysis
section for performing an analysis based on the data stored in said
database and generating a control command; and a control section
for generating a control signal for changing the flow rates or
compositions of the processing gases supplied to the first gas
inlet and the second gas inlet based on said control command.
11. The plasma etching apparatus according to claim 6 or claim 7,
further comprising: a photoreception section for receiving light
from the center portion of said quasi-cylindrical processing
chamber; a photoreception section placed in a different location
from that of said photoreception section of said quasi-cylindrical
processing chamber; a spectroscopic section for discomposing said
plasma emission into a plurality of wavelength components; a
database for storing the result of said spectroscopy; an analysis
section for performing an analysis based on the data stored in said
database and generating a control command; and a control section
for generating a control signal for changing the flow rates or
compositions of the processing gases supplied to the first gas
inlet and the second gas inlet based on said control command.
12. A plasma etching method for a plasma etching apparatus
comprising: a processing chamber for performing plasma etching on
an object to be processed; a first gas supply source; a second gas
supply source; a first gas inlet for introducing a processing gas
into the processing chamber; a second gas inlet for introducing a
processing gas into the processing chamber; a flow rate regulator
for regulating the flow rate of the processing gas; and a gas shunt
for dividing the first processing gas into a plurality of portions,
wherein the second processing gas is merged with at least one part
between the gas shunt and the first gas inlet and between the gas
shunt and the second gas inlet.
13. The plasma etching method according to claim 12, wherein
different flow rates or compositions are applied for the processing
gas supplied to said first gas inlet and the processing gas
supplied to said second gas inlet.
14. The plasma etching method according to claim 12 or claim 13,
further comprising the steps of: measuring the object to be
processed before etching or after etching; storing the result of
said measurement in a database; performing an analysis based on the
data stored in the database and generating a control command; and
changing the flow rates or compositions of the processing gases
supplied to the first gas inlet and the second gas inlet based on
the control command.
15. The plasma etching method according to claim 12 or claim 13,
further comprising the steps of: receiving plasma emission during
etching; discomposing said plasma emission into a plurality of
wavelength components; storing the result of said spectroscopy in a
database; performing an analysis based on the data stored in said
database and generating a control command; and changing the flow
rates or compositions of the processing gases supplied to the first
gas inlet and the second gas inlet based on said control command.
Description
[0001] The present application claims priority from Japanese
application JP2003-206042 filed on Aug. 5, 2003, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a plasma etching apparatus
for processing an object to be processed such as a semiconductor
wafer, and a plasma etching method using the plasma etching
apparatus.
[0004] 2. Description of the Related Art
[0005] In a semiconductor chip manufacturing process, a plasma
etching apparatus using reactive plasma to process an object to be
processed such as a semiconductor wafer is conventionally used.
[0006] Here, with reference to across-sectional view of an object
to be processed shown in FIG. 13, etching for forming a
poly-silicon (Poly-Si) gate electrode of an MOS (Metal Oxide
Semiconductor) transistor (hereinafter referred to as "gate
etching") will be explained as one example of a plasma etching
process. As shown in FIG. 13(a), an object to be processed 1 prior
to etching is formed of a silicon dioxide (SiO.sub.2) film 3,
poly-silicon film 4 and photoresist mask 5 deposited on the surface
of a silicon (Si) substrate 2 in the named order. This photoresist
mask 5 is formed via a photolithography process by applying a
photoresist, projecting the same pattern onto one or a plurality of
chips for exposure to light using a mask called a "reticule"
through a reduced projection photolithography apparatus, and
developing the same. The dimension of this photoresist mask 5, that
is, a photoresist mask width 7, greatly affects the width of a gate
electrode which will be described later, and is therefore subject
to strict control.
[0007] Gate etching is a process for removing the poly-silicon film
4 in an area not covered with the photoresist mask 5 by exposing
the object to be processed 1 to reactive plasma, and by this
process, a gate electrode 6 is formed as shown in FIG. 13(b). Since
a gate width 8 at the bottom of the gate electrode 6 greatly
affects the performance of the electronic device, it is subject to
strict control as most important CD (critical dimension). For this
reason, a target completion dimension is preset for the gate width
8.
[0008] Furthermore, a value obtained by subtracting the gate width
8 after etching from the photoresist mask width 7 before etching is
called a "CD shift", and constitutes an important index for
expressing the quality of gate etching.
[0009] A conventional example of a plasma etching apparatus which
carries out the above described gate etching will be explained with
reference to FIG. 14. A processing chamber cover 12 is placed on a
quasi-cylindrical processing chamber side wall 11, and a processing
chamber 13 defined by the above parts is provided with a substrate
holder 14.
[0010] A processing gas 21 is introduced into the processing
chamber 13 through an inlet 22 provided in the central part of the
processing chamber cover 12 to generate plasma 25. Plasma etching
is performed by exposing the object to be processed 1 to this
plasma 25. The processing gas 21 and a volatile substance generated
by the reaction in the plasma etching processing are exhausted from
the outlet 30. A vacuum pump (not shown here) is connected to the
tip of the outlet 30 and the pressure in the processing chamber 13
is thereby reduced to approximately 1 Pa (Pascal).
[0011] Gate etching is performed using the plasma etching apparatus
as described above, but with the recent increase in the diameter of
the object to be processed 1, it is becoming more difficult to
secure the in-plane uniformity of etching rates or the in-plane
uniformity of the gate width 8 over a wide area of the object to be
processed 1. Likewise, along with the recent miniaturization of
semiconductor devices, demands are increasing for more severe
dimensional control of the gate width 8.
[0012] Next, adhesion and deposition of reaction products onto the
side of a gate electrode, which is one of influences on the
dimension of the gate width 8, will be explained. A plurality of
gases such as chlorine (Cl.sub.2), hydrogen bromide (HBr) and
oxygen (O.sub.2) are conventionally used for processing of gate
etching. During etching, these gases are in a plasma state to
perform etching on the poly-silicon film 4, but during the process,
chlorine, hydrogen bromide and oxygen contained in the processing
gas 21 are dissociated, and the thus-produced ions and radicals of
Cl (chlorine), H (hydrogen), Br (bromine) and O (oxygen) react with
silicon deriving from the poly-silicon film 4, producing reaction
products. Of these reaction products, volatile ones are exhausted
from the outlet 30, but non-volatile products are adhered or
deposited onto the inner side (vacuum side) of the processing
chamber side wall 11, the processing chamber cover 12 and the sides
of the poly-silicon film 4 and photoresist mask 5. When the
reaction products are deposited on the sides of the poly-silicon
film 4 and photoresist mask 5, they serve as a mask for etching,
which often increases the gate width 8.
[0013] Especially when a compound SiBr.sub.x (x=1, 2, 3) of silicon
and bromine or compound SiCl.sub.x (x=1, 2, 3) of silicon and
chlorine reacts with oxygen (O), Si.sub.xBr.sub.yO.sub.z (x, y, z:
natural number) or Si.sub.xCl.sub.yO.sub.z (x, y, z: natural
number) which are non-volatile and have high deposition
characteristic is produced, and adhesion or deposition of these
products to the poly-silicon film 4 and photoresist film 5 may
cause an increase of the gate width 8.
[0014] The increase of the gate width 8 may occur nonuniformly
within the plane of the object to be processed 1. That is,
nonuniform CD shifts may occur within the plane of the object to be
processed 1. For example, in an area with a high etching rate, the
concentration of reaction products including silicon deriving from
the poly-silicon film 4 becomes higher than in areas with a low
etching rate, which may cause in-plane nonuniformity of CD
shifts.
[0015] Furthermore, in the central part of the object to be
processed 1, all surrounding areas are subject to etching, whereas
outside the outermost region of the wafer, there is no area subject
to etching. For this reason, even if an etching rate is uniform
within the plane of the object to be processed 1, the concentration
of reaction products including silicon deriving from the
poly-silicon film 4 is high in the center portion and low in the
outer regions. This may also cause in-plane nonuniformity of CD
shifts.
[0016] Furthermore, as described above, reaction products are
deposited on the processing chamber side wall 11 or inner side
(vacuum side) of the processing chamber cover 12 through plasma
etching processing, but during plasma etching, radicals and ions of
chlorine, hydrogen, bromine, oxygen and these compounds maybe
dissociated from these depositions and discharged into the plasma
25. In this case, the concentration of the radicals and ions
discharged from the reaction products is likely to increase in the
outer regions of the object to be processed 1. This is because the
processing chamber cover 12 is placed parallel to the object to be
processed 1 as shown in FIG. 14, and radicals and ions discharged
from the deposited reaction products are likely to disperse over
the whole object to be processed 1, while the processing chamber
side wall 11 is located to surround the outer regions of the object
to be processed 1 and radicals and ions discharged from the
reaction products deposited thereto are likely to cause an increase
of concentration in the outer regions of the object to be processed
1. The radicals and ions discharged from the reaction products as
described above may cause deterioration of in-plane uniformity of
CD shifts on the surface of the object to be processed 1.
[0017] As described above, nonuniformity of concentration of
reaction products is caused on locations within the plane of the
object to be processed 1, but this nonuniformity varies from moment
to moment according to the condition in the processing chamber 13.
That is, even if the total amount and composition of the processing
gas 21 or process input conditions such as the pressure in the
processing chamber 13 are the same when plasma etching is
performed, CD shifts fluctuate. This is because the adhesion
condition of reaction products deposited on the processing chamber
cover 12 and processing chamber side wall 11 varies from moment to
moment as the plasma etching processing advances as described
above.
[0018] In addition to the advance of the above described plasma
etching processing, the condition in the processing chamber also
changes through a process called "cleaning." Every time the
aforementioned plasma etching process is carried out, the amount of
reaction products deposited on the inner side (vacuum side) of the
processing chamber side wall 11 and the processing chamber cover 12
increases. When these depositions fall off and attach to the
surface of the object to be processed 1, the yield of volume
production of semiconductor devices is deteriorated. To prevent
this, plasma cleaning using reactive plasma is carried out
periodically to remove the aforementioned depositions. Furthermore,
depositions which cannot be removed by plasma cleaning are removed
by operations called "wet cleaning" or "manual cleaning" which are
manually performed by the operator with the processing chamber 13
left open to the atmosphere. These two types of cleaning processes
reduce the amount of depositions stuck to the processing chamber
cover 12 and processing chamber side wall 11. As shown above, since
the condition in the processing chamber 13 varies from moment to
moment, distributions of radicals and ions on the surface of the
object to be processed 1 also change accordingly.
[0019] In the plasma etching apparatus of the conventional example
(prior art) shown in FIG. 14, the processing gas is only introduced
from the inlet 22 provided above the central part of the object to
be processed 1, and therefore the concentration of radicals of gas
components contained in the processing gas or ions resulting from
dissociation is often high in the central part and low in the outer
regions of the object to be processed 1.
[0020] One art intended to improve in-plane uniformity of ions and
radicals in plasma is an art of introducing a processing gas from a
plurality of parts of the processing chamber. This art relates to a
reactive ions etching apparatus provided with a flow rate
controller capable of introducing the processing gas into the
processing chamber through a plurality of inlets and controlling
the flow rate of the processing gas for each inlet independently
(e.g., see Patent Document 1). This art is capable of changing the
in-plane uniformity of the etching rate, but since the processing
gas introduced from the respective inlets has the same composition,
it cannot sufficiently adjust the in-plane uniformity of ions and
radicals.
[0021] There is another art of introducing a reaction product gas
into the processing chamber for the purpose of improving the
concentration distribution of reaction products on the surface of
the object to be processed 1. This art relates to a method of dry
etching which provides two gas inlets, introduces a reactive gas
from one inlet and introduces a reaction product gas generated by
an etching reaction from the other inlet as a reaction inhibition
gas for the purpose of equalizing the etching rate on an object to
be processed (e.g., see Patent Document 2). The use of this method
can adjust the in-plane uniformity of ions and radicals and improve
in-plane uniformity of the etching rate.
[0022] However, since the position of introducing the reaction
product gas as the reaction inhibition gas is limited to one inlet,
this structure has constraints on the improvement of in-plane
uniformity of the etching rate. For example, when the etching rate
in the central part of the object to be processed is greater than
the etching rate in the outer regions, it is possible to improve
the in-plane uniformity of the etching rate by introducing a
reaction product gas into the central part as the reaction
inhibition gas. However, on the contrary, when the etching rate in
the outer regions of the object to be processed is greater than the
etching rate in the central part, this structure requires gas pipes
to be replaced, so it is unable to respond to the demand quickly.
It also has the disadvantage that a supply source of the reaction
product gas and piping system need to be added in addition to the
gas used for normal etching to the apparatus.
[0023] In view of the above described problems, it is an object of
the present invention to provide a plasma etching apparatus and
plasma etching method capable of carrying out processing with
excellent in-plane uniformity on an object to be processed having a
large diameter.
[0024] [Patent Document 1]
[0025] Japanese Patent Application Laid-Open No. 62-290885
[0026] [Patent Document 2]
[0027] Japanese Patent Application Laid-Open No. 5-190506
[0028] [Patent Document 3]
[0029] Specification of U.S.P. No. 6418954
BRIEF SUMMARY OF THE INVENTION
[0030] In order to solve the problems of the above described prior
arts, the present invention provides a plurality of inlets 65 for
introducing a processing gas 21 into a processing chamber 13 and
uses the respective inlets 22 to adjust the flow rate or
composition of the processing gas 21. The processing gas (first
processing gas) from a common gas system at that time is divided
into a plurality of portions, a gas from an additional gas system
(second processing gas) is mixed with the respective piping systems
after the division to thereby adjust the composition and/or flow
rate of the processing gas introduced from the plurality of inlets
provided in the processing chamber 13.
[0031] Furthermore, the present invention measures the size of a
photoresist mask width 7 formed in a photolithography process
before plasma etching and makes an analysis using the measurement
result to thereby adjust the composition and/or flow rate of the
processing gas 21 introduced through the plurality of inlets.
[0032] Furthermore, the present invention measures the gate width 8
after etching and makes an analysis using the measurement result to
thereby adjust the composition and/or flow rate of the processing
gas 21 introduced through the plurality of inlets.
[0033] Furthermore, the present invention calculates the amount of
deposition in the processing chamber 13 from the photoreception
result of plasma emission, estimates the amount of generated ions
and radicals from the calculation result to thereby adjust the
composition and/or flow rate of the processing gas 21 introduced
from the plurality of inlets.
[0034] Furthermore, the present invention provides a plurality of
plasma emission photoreception sections above the object to be
processed 1, calculates distributions of ions and radicals from the
plasma photoreception result and adjusts the composition and/or
flow rate of the processing gas 21 introduced from the plurality of
inlets using the result.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 illustrates a gas piping system of a first embodiment
of the present invention;
[0036] FIG. 2 is a top view of a processing chamber cover used in
the first embodiment of the present invention;
[0037] FIG. 3 is a sectional side view of a processing chamber used
for the first embodiment of the present invention;
[0038] FIG. 4 is a table showing a set flow rate of the processing
gas used in the first embodiment of the present invention and flow
rate of each gas;
[0039] FIG. 5 is a graph showing an oxygen concentration
distribution and a table showing a gate width, which shows a
comparison between results obtained from the first embodiment of
the present invention and results obtained from the conventional
example;
[0040] FIG. 6 illustrates the gas system of the first embodiment of
the present invention, which shows a structure different from that
in FIG. 1;
[0041] FIG. 7 is a sectional side view of a processing chamber used
in a second embodiment of the present invention;
[0042] FIG. 8 is a top view of a showerhead plate used for the
second embodiment of the present invention;
[0043] FIG. 9 illustrates a gas piping system and control system
according to a third embodiment of the present invention;
[0044] FIG. 10 is a sectional side view of an object to be
processed before and after etching of the third embodiment of the
present invention;
[0045] FIG. 11 illustrates a gas piping system and control system
according to a fourth embodiment of the present invention;
[0046] FIG. 12 illustrates a gas piping system and control system
according to a fifth embodiment of the present invention;
[0047] FIG. 13 is a sectional side view of an object to be
processed before and after gate etching processing; and
[0048] FIG. 14 is a sectional side view of a processing chamber
showing a conventional example of a plasma etching apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] [First Embodiment]
[0050] With reference to FIG. 1 through FIG. 6, a first embodiment
of the present invention will be described in detail below. FIG. 1
illustrates a gas piping system of a plasma etching apparatus to
which the first embodiment of the present invention is applied.
[0051] Furthermore, a top view of a processing chamber cover 12 in
this embodiment is shown in FIG. 2. As shown in FIG. 2, a first gas
inlet 65-1 is set in the center portion of the processing chamber
cover 12 and eight second gas inlets 65-2 are set in a circular
form around the first gas inlet 65-1.
[0052] As shown in FIG. 1, this plasma etching apparatus is
constructed of a processing chamber 13 having a processing chamber
cover 12, a substrate holder 14 provided in the processing chamber,
a first gas inlet 65-1 and second gas inlets 65-2 provided in the
processing chamber cover 12, a common gas system 40 which is a
first processing gas supply source, an additional gas system 50
which is a second processing gas supply source, a shunt 60 which
shunts a first processing gas from the common gas system 40 into a
plurality of parts, a merging section 63-1 provided at a position
of a pipe between a first shunt outlet 62-1 of the shunt 60 and the
first gas inlet 65-1 for merging a second processing gas and a
merging section 63-2 provided at a position of a pipe between a
second shunt outlet 62-2 of the shunt 60 and the second gas inlet
65-2 for merging the second processing gas.
[0053] The common gas system 40 is constructed of gas cylinders
41-1 and 41-2 as gas supply sources, flow rate regulators 42-1 and
42-2 which regulate the flow rates of the respective gases, valves
43-1 and 43-2 which let pass or stop the respective gases and a
merging section 44 which merges the respective gases of the common
gas system 40.
[0054] In this embodiment, the gas cylinder 41-1 is filled with
hydrogen bromide (HBr) and the gas cylinder 41-2 is filled with
chlorine (Cl.sub.2) as common gases.
[0055] The common gases which have merged at the merging section 44
are guided to the gas shunt 60 located downstream. The gas shunt 60
is a device having the function of shunting an arbitrary gas which
has entered a gas shunt inlet 61 into a plurality of shunt outlets
at an arbitrary flow rate ratio. This gas shunt 60 shunts a
processing gas into two shunt outlets, and one shunt outlet thereof
is provided with a flow meter which measures the flow rate of the
processing gas and a restrictor which restricts or regulates the
flow of the processing gas, and the other shunt outlet is provided
with a mass flow controller which can let flow the processing gas
at a set flow rate. A flow rate set value is sent from this flow
meter to a mass flow controller, which makes it possible to shunt
the processing gas entering the inlet into two shunt outlets at an
arbitrary flow rate ratio (e.g., see Patent Document 3).
[0056] In this embodiment, a mixed gas of hydrogen bromide and
chlorine is shunt into two outlets by this gas shunt 60; shunt
outlet 62-1 and shunt outlet 62-2, at a flow rate ratio of 8:2.
[0057] The additional gas system 50 is constructed of a gas
cylinder 51 as a gas supply source, a branch 52 for branching the
gas into plural portions (2 portions in this embodiment), flow rate
regulators 53-1 and 53-2 which regulate the flow rates of the
respective gases, and valves 54-1 and 54-2 for letting flow or
stopping the gas. In this embodiment, oxygen (O.sub.2) is put in a
gas cylinder 51 as an additional gas.
[0058] The common gas (a mixed gas of hydrogen bromide and chlorine
in this embodiment) output from the shunt outlet 62-1 merges with
the additional gas (oxygen in this embodiment) which has passed
through the valve 54-1 at the merging section 63-1, and the mixed
gas of common gas and additional gas is guided to the first gas
inlet 65-1 provided in the center of the processing chamber cover
12.
[0059] Likewise, the common gas (a mixed gas of hydrogen bromide
and chlorine in this embodiment) output from the shunt outlet 62-2
merges with the additional gas (oxygen in this embodiment) which
has passed through the valve 54-2 at the merging section 63-2, and
the mixed gas of common gas and additional gas is guided to the
second gas inlets 65-2 provided in the outer regions of the
processing chamber cover 12.
[0060] Using the above described structure and by regulating the
set flow rates of the flow rate regulators 42-1, 42-2, 53-1 and
53-2 and the flow rate ratio between the shunt outlet 62-1 and
shunt outlet 62-2 of the shunt 60, processing gases having
different flow rates and compositions are introduced through the
first gas inlet 65-1 and second gas inlets 65-2.
[0061] Then, the plasma etching apparatus of this embodiment will
be explained with reference to FIG. 3. The processing chamber cover
12 is placed on the processing chamber side wall 11 and in the
processing chamber 13 formed of these parts, the substrate holder
14 is placed. A circular groove is formed in the top end face of
the processing chamber side wall 11 and an O-ring 15 is filled in
this groove. This O-ring 15 keeps the processing chamber 13
airtight.
[0062] A chucking electrode 16 is buried in the substrate holder
14, and an electrostatic force is produced between the chucking
electrode 16 and object to be processed 1 by a DC power supply 17
connected to the chucking electrode 16, whereby the object to be
processed 1 is attracted to the substrate holder 14. Furthermore, a
switch 18 is provided between the chucking electrode 16 and DC
power supply 17 for turning ON/OFF a DC voltage to be applied.
[0063] The processing gas 21-1 which has passed through the merging
section 63-1 and the processing gas 21-2 which has passed through
the merging section 63-2 are introduced into the processing chamber
13 through the first inlet 65-1 and the second inlets 65-2,
respectively. These first inlet 65-1 and second inlets 65-2 are
formed of pipes penetrating the processing chamber cover 12.
High-frequency coils 23 are placed on the processing chamber cover
12 and when a high-frequency power supply 24 applies high frequency
to the high-frequency coils 23, the processing gas 21 is
transformed into plasma 25. A switch 26 is provided between the
high-frequency coils 23 and high-frequency power supply 24 for
turning ON/OFF a high-frequency voltage to be applied.
[0064] Plasma etching process is performed by exposing the object
to be processed 1 to the plasma 25. A high-frequency application
electrode 27 for applying a high-frequency voltage is buried in the
substrate holder 14, and when the high-frequency voltage is applied
by a high-frequency power supply 28 connected thereto, the
high-frequency application electrode 27 produces a bias potential,
attracts ions produced in the plasma 25 into the object to be
processed 1 and performs anisotropic etching. A switch 29 is
provided between the high-frequency application electrode 27 and
the high-frequency power supply 28 for turning ON/OFF the
high-frequency voltage to be applied.
[0065] The processing gas 21 and volatile substances produced by a
reaction in the plasma etching processing are exhausted through an
outlet 30. A vacuum pump (not shown here) is connected to the tip
of the outlet 30 to reduce the pressure in the processing chamber
13 to approximately 1 Pa (Pascal). Furthermore, a pressure
regulating valve 31 is provided between the outlet 30 and the
vacuum pump to regulate the pressure in the processing chamber 13
by regulating the opening of the pressure regulating valve 31.
[0066] Here, set flow rates of the respective processing gases and
the numbers of flow rate regulators which regulate the respective
flow rates used in the conventional example and this embodiment are
shown in FIG. 4(a), and the flow rate ratio of the gas shunt 60 and
the flow rates of the processing gases introduced through first
inlet 65-1 and second inlets 65-2 are shown in FIG. 4(b). In FIG.
4(b), when the shunt ratio of the gas shunt 60, that is, the ratio
of the flow rate from the shunt outlet 62-1 to the flow rate from
the shunt outlets 62-2 is 100:0 and the set flow rate of the flow
rate regulator 53-2 is 0 sccm, the processing gas is introduced
only through the gas inlet 65-1 placed in the center of the
processing chamber cover 12, which is equivalent to the processing
in the conventional example, and therefore described as the
conventional example.
[0067] In the case of the condition shown in FIG. 4, while the flow
rate ratio of hydrogen bromide, chlorine and oxygen of the
processing gas introduced through the first inlet 65-1 in the
conventional example and this embodiment is 20:10:1, the flow rate
ratio of hydrogen bromide, chlorine and oxygen of the processing
gas introduced through the second inlets 65-2 of this embodiment is
20:10:2. That is, in this embodiment, the processing gas of higher
oxygen concentration is introduced through the second inlets 65-2
than through the first inlet 65-1.
[0068] Next, FIG. 5(a) shows a comparison of the oxygen
concentration distribution on the surface of the object to be
processed 1 having a diameter of 300 mm between the conventional
example and the present embodiment. As opposed to the conventional
example where the oxygen concentration is lower in the outer
regions than in the center portion of the object to be processed,
it is evident in this embodiment that the reduction of oxygen
concentration in the outer regions is suppressed and that the
in-plane uniformity is improved. Furthermore, FIG. 5(b) shows the
measurement result of the gate width 8 of the object to be
processed 1. As shown in this figure, while there is a large
difference of the gate width 8 between the center portion and outer
region of the prior art, the difference is reduced in this
embodiment. This is because the processing gas of higher oxygen
concentration is introduced into the outer regions than the center
portion, non-volatile reaction products Si.sub.xBr.sub.yO.sub.z (x,
y, z: natural number) or Si.sub.xCl.sub.yO.sub.z (x, y, z: natural
number) are deposited more on the sides of the poly-silicon film 4
and photoresist film 5 in the outer regions than the center portion
and the gate width 8 is increased compared to the conventional
example. Thus, by introducing processing gases having different
mixing ratios through a plurality of gas inlets 65, it is possible
to improve the in-plane uniformity of CD shifts of the object to be
processed 1 and realize gate etching whereby the gate width 8
becomes more uniform within the plane.
[0069] According further to this embodiment, when the processing
gases are introduced into a plurality of gas inlets 65 as shown in
FIG. 1, a common gas which is commonly introduced into the
plurality of gas inlets 65 (hydrogen bromide and chlorine in this
embodiment) is shunted by the gas shunt 60 at an arbitrary flow
rate ratio and the additional gases (oxygen in this embodiment)
with different flow rates are introduced at places downstream from
the respective shunt outlets 62-1 and 62-2. This makes it possible
to introduce processing gases having different flow rates and
compositions from the plurality of gas inlets 65 with a simple
structure.
[0070] This embodiment uses hydrogen bromide and chlorine as common
gases, but common gases are not limited to them and other gases can
also be used.
[0071] Furthermore, this embodiment uses oxygen as an additional
gas. However, the additional gas is not limited to oxygen, and it
is possible to use other gases for generating depositional reaction
products as additional gases. Furthermore, on the contrary, it is
also possible to use gases which inhibit the generation of
depositional reaction products as additional gases, regulate their
concentration distributions within the plane of the object to be
processed 1 to thereby improve the in-plane uniformity of the gate
width 8.
[0072] Furthermore, this embodiment uses two types of gases of
hydrogen bromide and chlorine as common gases, but common gases are
not limited to these. It is also possible to use a single gas, or
three or more types of gases as the common gas.
[0073] Furthermore, this embodiment only uses oxygen as an
additional gas, but the additional gas is not limited to one type
of gas, and a plurality of gases can also be used. FIG. 6 shows an
example of using a plurality of additional gases. In this case, it
is possible to provide a first additional gas system 50-1
consisting of a gas cylinder 51-1 filled with a first additional
gas, a branch 52-1, flow rate regulators 53-1 and 53-2 and valves
54-1 and 54-2, and a second additional gas system 50-2 consisting
of a gas cylinder 51-2 filled with a second additional gas, a
branch 52-2, flow rate regulators 53-3 and 53-4 and valves 54-3 and
54-4. The common gases output from the gas shunt outlets 62-1 and
62-2 are mixed with the first additional gas and second additional
gas at the sections 63-1 and 63-2, respectively, and the processing
gases with different flow rates and compositions are introduced
into the gas inlets 65-1 and 65-2.
[0074] Furthermore, this embodiment uses a smaller total flow rate
of the processing gas 21-2 introduced from the gas inlets 65-2
placed in the outer regions of the processing chamber cover 12 than
a total flow rate of the processing gas 21-1 introduced from the
gas inlet 65-1 placed in the center portion, but the present
invention is not limited to this embodiment. The implementer of the
present invention can freely decide the flow rates of the
processing gases introduced from the respective inlets to realize
optimal plasma etching. Therefore, if a greater total flow rate of
the processing gas 21-2 should be introduced from the gas inlets
65-2 than a total flow rate of the processing gas 21-1 introduced
from the gas inlet 65-1 to achieve a better etching result, such
setting is also acceptable.
[0075] Furthermore, this embodiment assigns a greater value to the
ratio of the oxygen flow rate to the total flow rate of the
processing gas 21-2 introduced through the gas inlets 65-2 than the
ratio of the oxygen flow rate to the total flow rate of the
processing gas 21-1 introduced through the gas inlet 65-1, but the
present invention is not limited to this embodiment. For example,
when the gate width 8 in the outer regions is greater than a target
completion size and the gate width 8 in the center portion is
smaller than the target product size, it is possible to reduce the
ratio of the oxygen flow rate to the total flow rate of the
processing gas 21-2 introduced through the gas inlets 65-2 and
increase the oxygen flow rate to the total flow rate of the
processing gas 21-1 introduced thruogh the gas inlet 65-1 to
thereby approximate the gate widths 8 at the respective positions
to the target completion size.
[0076] Furthermore, this embodiment uses the gas shunt 60 described
in Patent Document 3, but the present invention is not limited to
this embodiment. It is possible to use a device having a different
structure to shunt the processing gas into a plurality of parts.
Furthermore, this embodiment provides the merging section 63-1 for
merging the second processing gas on the pipe between the first
shunt outlet 62-1 of the shunt 60 which shunts the first processing
gas from the common gas system 40 into a plurality of portions and
the first gas inlet 65-1, and the merging section 63-2 for merging
the second processing gas on the pipe between the second shunt
outlet 62-2 of the shunt 60 and the second gas inlet 65-2, but it
is also possible to adopt a structure having at least one of the
merging sections 63-1 and 63-2 for merging the second processing
gas.
[0077] [Second Embodiment]
[0078] Then, a second embodiment of the present invention will be
explained using FIG. 7 and FIG. 8. While the first embodiment makes
a plurality of holes in the processing chamber cover 12 to provide
the second gas inlets 65-2, this embodiment places below the
processing chamber cover 12 a plate called a "showerhead plate" in
which a plurality of holes are formed, and forms second gas inlets
65-2 using the holes in the showerhead plate 19 as shown in FIG. 7.
Furthermore, the same piping system as that explained in the first
embodiment will be used to introduce processing gases into a
processing chamber 13.
[0079] A processing gas 21-1 which has passed through a merging
section 63-1 is introduced into the processing chamber 13 through a
first gas inlet 65-1 formed of a pipe penetrating the processing
chamber cover 12 and showerhead plate 19. On the other hand, a
processing gas 21-2 which has passed through a merging section 63-2
is introduced between the processing chamber cover 12 and
showerhead plate 19 through a gas introduction pipe 22 and then
introduced into the processing chamber 13 through second inlets
65-2 formed on the showerhead plate. Furthermore, the processing
gas 21-1 introduced through the first inlet 65-1 and the processing
gas 21-2 introduced through the gas introduction pipe 22 are
prevented from mixing with each other in the space between the
processing chamber cover 12 and the showerhead plate 19.
Furthermore, an O-ring 15' placed beneath the showerhead plate 19
maintains air tightness.
[0080] FIG. 8 shows a top view of the showerhead plate 19. A hole
for passing through the pipe forming the first inlet 65-1 is formed
in the center of the showerhead plate 19, and the second gas inlets
65-2 are formed in a circular form around the first inlet 65-1.
[0081] The conductance between the processing chamber cover 12 and
the showerhead plate 19 is designed to be sufficiently larger than
the conductance of each of the second gas inlets 65-2, and the
processing gas 21-2 introduced through the gas introduction pipe 22
is introduced into the processing chamber 13 from the respective
second gas inlets 65-2 at the same flow rate.
[0082] This embodiment makes it possible to form the second gas
inlets 65-2 with a simpler structure than that of the first
embodiment shown in FIG. 2 and FIG. 3. Moreover, using the
structure explained in the first embodiment allows effects similar
to those of the first embodiment to be achieved.
[0083] [Third Embodiment]
[0084] Then, a third embodiment of the present invention will be
explained with reference to FIG. 9. This embodiment adds a
measuring instrument 70, a database 72, an analysis section 74 and
a control section 76 to the structure explained in the first
embodiment that allows processing gases with different flow rates
and compositions to be introduced through a plurality of gas inlets
65.
[0085] The measuring instrument 70 is intended to measure an object
to be processed 1 before etching or after etching, and a length
measuring SEM (Scanning Electron Microscope) and measuring
instrument called a "CD-SEM" are examples of this measuring
instrument. This irradiates the surface of the object to be
processed 1 with electron beams and acquires information on
projections and depressions on the surface of the object to be
processed 1 using secondary electrons emitted from the irradiated
locations, which allows to measure a photoresist mask width 7
before etching and gate width 8 after etching. Moreover, in
addition to this, a so-called "OCD (Optical-CD) measuring
instrument" can also be used which irradiates the surface of the
object to be processed 1 with light rays and acquires information
on projections and depressions on the surface of the object to be
processed 1 using the reflected light. In addition, a so-called
"AFM (Atomic Force Microscope)" can also be used as the measuring
instrument 70, which scans the surface of the object to be
processed 1 using a lever provided with a small probe called a
"cantilever" at one end and acquires information on projections and
depressions on the surface of the object to be processed 1. This
OCD measuring instrument or AFM also allows measurement of the
photoresist mask width 7 before etching and gate width 8 after
etching.
[0086] Measured data 71 obtained by this measuring instrument 70 at
a plurality of positions of the object to be processed 1 is sent to
and stored in the database 72.
[0087] Data 73 stored in the database 72 is sent to the analysis
section 74. The analysis section 74 carries out an analysis based
on the data 73, and a control command 75 is sent to the control
section 76. Based on the control command 75, the control section 76
sends a control signal 77 to flow rate regulators 42-1, 42-2, 53-1,
53-2 and valves 43-1, 43-2, 54-1, 54-2 and gas shunts 60 and
pressure regulating valve 31. These devices perform control based
on the received control signal 77.
[0088] As described above, by adding the measuring instrument 70,
database 72, analysis section 74 and control section 76 to the
first embodiment, this embodiment can cope with differences in the
photo resist mask width 7 between the center portion and the outer
regions of the object to be processed 1. It can further cope with
variations in the etching result which varies from one etching
process to another. Hereinafter, an example of the processing
method using this structure will be explained more
specifically.
[0089] First, a case where the photoresist mask width 7 of the
object to be processed 1 is measured before etching will be
explained. The photoresist mask width 7 on the surface of the
object to be processed 1 is measured using the measuring instrument
70 such as CD-SEM, OCD measuring instrument or AFM first, and then
the measured data 71 is sent to the database 72. This measured data
71 includes data indicating measured locations in the object to be
processed 1 and data of the photoresist mask width 7 before
etching. Furthermore, when a plurality of objects to be processed
are processed successively in mass production, the measured data 71
also includes data for identifying each of the plurality of objects
to be processed.
[0090] When the photoresist mask width 7 is measured at a plurality
of locations within the plane of the object to be processed 1 and
its in-plane distribution is calculated, it is important to measure
the same positions in a plurality of chips formed on the surface of
the object to be processed 1. This is because complicated patterns
are formed in a chip and the photoresist mask width 7 is not always
identical in all patterns in the chip. Moreover, to suppress
variations in the performance among chips formed on the object to
be processed 1, it is important to suppress variations in the
photoresist mask width 7 at the same position in the chip from one
chip to another.
[0091] The data 73 stored in the database 72 is sent to the
analysis section 74 at appropriate timings. The analysis section 74
analyzes the in-plane distribution of the photoresist mask width 7
on the surface of the object to be processed 1 based on the data
73. For example, as shown in FIG. 10, when the photoresist mask
width 7-1 of a chip in the center portion of the object to be
processed 1 is large, while the photoresist mask width 7-2 of a
chip in the outer region is small, it is possible to regulate the
gas condition so that the CD shift becomes greater in the center
than in the outer regions, and thereby approximate the gate width
8-1 of the chip in the center portion to the gate width 8-2 in the
chip in the outer regions. In this case, it is possible to
introduce a processing gas with higher oxygen concentration from
the second gas inlets 65-2 placed in the outer regions than from
the first gas inlet 65-1 placed in the center of the processing
chamber cover 12. The analysis section 74 calculates the necessary
flow rate ratios, flow rates and processing pressures of the
respective processing gases introduced through the first and second
gas inlets 65 to realize this condition. That is, the set flow rate
values of the flow rate regulators 42-1, 42-2, 53-1 and 53-2, the
set shunt ratio values of the gas shunt 60 and set value of the
opening of the pressure regulating valve 31 to realize the set
processing pressure are calculated.
[0092] The above described analysis is performed by the analysis
section 74, the control command 75 reflecting the analysis result
is sent to the control section 76 and the control signal 77 is sent
from the control section 76 to the devices of the gas piping
system. That is, the control signal 77 including the set flow rate
value is sent to the respective flow rate regulators 42-1, 42-2,
53-1 and 53-2, valve ON/OFF control signal 77 is sent to the
respective valves 43-1, 43-2, 54-1 and 54-2, the control signal 77
including the set shunt ratio value is sent to the gas shunt 60 and
the control signal 77 including the set value of the opening to
realize the set processing pressure is sent to the pressure
regulating valve 31.
[0093] As shown above, based on the measurement result of the
photoresist mask width 7 obtained by the measuring instrument 70,
it is possible to approximate the gate width 8-1 of the chip in the
center of the object to be processed 1 to the gate width 8-2 of the
chip in the outer regions.
[0094] Next, a case where the gate width 8 of the object to be
processed 1 is measured after etching will be explained. First, the
gate width 8 is measured at a plurality of locations on the surface
of the object to be processed 1 using measuring instrument 70 such
as a CD-SEM, OCD measuring instrument or AFM, and the measured data
71 is sent to the database 72. This measured data 71 includes data
indicating the measurement locations in the object to be processed
1, and data of the gate width 8 after etching. Furthermore, when a
plurality of objects to be processed is processed continuously in
mass production, the measured data 71 also includes data for
identifying data of each of the plurality of objects to be
processed. As with the measurement of the photoresist mask width 7,
the gate width 8 is measured at the same locations in a plurality
of chips formed on the surface of the object to be processed 1, and
an in-plane distribution of the object to be processed 1 of the
gate width 8 is calculated.
[0095] The data 73 stored in the database 72 is sent to the
analysis section 74 at appropriate timings. The analysis section 74
analyzes the in-plane distribution of the gate width 8 on the
surface of the object to be processed 1 based on the data 73. For
example, when the gate width 8-1 of the chip in the center portion
of the object to be processed 1 is larger than the target
completion size and the gate width 8-2 of the chip in the outer
regions is smaller than the target completion size, by regulating
the gas condition so that the gate width 8-1 becomes smaller in the
chip in the center portion and the gate width 8-2 becomes larger in
the chip in the outer regions, it is possible to approximate the
gate width 8-1 of the chip in the center portion and the gate width
8-2 of the chip in the outer regions to the target completion size
of the gate width 8. In this case, it is possible to reduce the
oxygen concentration of the processing gas 21-1 introduced through
the first gas inlet 65-1 placed in the center of the processing
chamber cover 12 and increase the oxygen concentration of the
processing gas 21-2 introduced through the second gas inlet 65-2
placed in the outer regions. The flow rate ratios, flow rates and
processing pressures of the processing gases introduced through the
first and second gas inlets 65 necessary to realize this condition
are calculated by the analysis section 74. That is, the set flow
rate values of the flow rate regulators 42-1, 42-2, 53-1 and 53-2,
the shunt ratio set value of the gas shunt 60 and the set value of
the opening of the pressure regulating valve 31 to realize the set
processing pressure are calculated.
[0096] The above described analysis is performed by the analysis
section 74, the control command 75 reflecting the analysis result
is sent to the control section 76 and the control signal 77 is sent
from the control section 76 to the devices of the gas piping
system. That is, the control signal 77 including the set flow rate
value is sent to the respective flow rate regulators 42-1, 42-2,
53-1 and 53-2, valve ON/OFF control signal 77 is sent to the
respective valves 43-1, 43-2, 54-1 and 54-2, the control signal 77
including the shunt ratio set value is sent to the gas shunt 60,
and the control signal 77 including the set value of the opening to
realize the set processing pressure is sent to the pressure
regulating valve 31.
[0097] As shown above, through feedback control of the etching
processing condition based on the measurement result of the gate
width 8 obtained by the measuring instrument 70, it is possible to
approximate the gate width 8-1 of the chip in the center portion of
the object to be processed 1 and the gate width 8-2 of the chip in
the outer regions to the target completion size.
[0098] The target of the feedback control applied to the etching
processing condition based on the measurement result of the gate
width 8 may also be a processing of another object to be processed
carried out immediately after the measurement of the object to be
processed or may be processing of the object to be processed
carried out after a processing of two or more objects. Furthermore,
a group of objects to be processed are handled in a unit called a
"lot" in mass production, and the aforementioned feedback control
target may also be a processing carried out one lot or more after
the processing of the measured object to be processed. Since
measurement using the measuring instrument 70 may take a long time,
it is also possible to carry out feedback control on the processing
carried out 1 lot or more after the processing of the measured
object to be processed based on the measurement result.
Furthermore, when processing for manufacturing multiple types of
electronic devices is carried out using the same plasma etching
apparatus, processing conditions which vary from one type of
product to another are often used. For this reason, the target of
feedback control is preferably the processing of electronic devices
of the same type.
[0099] This embodiment uses the processing chamber 13 having the
gas inlets 65 formed in the processing chamber cover 12 as shown in
the first embodiment, but the present invention is not limited to
this embodiment. It is also possible to use the processing chamber
13 using the showerhead plate 19 as shown in the second
embodiment.
[0100] [Fourth Embodiment]
[0101] The fourth embodiment of the present invention will now be
explained with reference to FIG. 11. This embodiment adds a
photoreception window 80, an optical fiber 81, a spectroscopic
section 82, a database 72, an analysis section 74 and a control
section 76 to the structure explained in the first embodiment that
allows processing gases with different flow rates and compositions
to be introduced through a plurality of gas inlets 65.
[0102] The photoreception window 80 is provided in a processing
chamber wall 11 to allow emission of plasma 25 to be received, and
the plasma emission received by the photoreception window 80 is
guided to the spectroscopic section 82 through the optical fiber
81. The plasma light is dispersed into a spectrum at the
spectroscopic section 82, further converted to multi-channel
signals (e.g., signals of 1024 channels in a wavelength range of
200 nm to 800 nm in this embodiment) at certain sampling intervals
(e.g., 1 second) periodically every certain wavelength by a CCD
(charge-coupled device) incorporated in the spectroscopic section
82. Plasma emission data 83 consisting of multi-channel signals is
sent to the database 72. Data 73 stored in the database 72 is sent
to the analysis section 74 at appropriate timings, and the analysis
section 74 analyzes the plasma 25 from the data 73.
[0103] When etching process is performed as described above,
reaction products are deposited on the inner surfaces of the
processing chamber side wall 11 and processing chamber cover 12.
This deposition is also deposited on the inner side of the
photoreception window 80, which causes a reduction in the amount of
photoreception of the plasma 25 by the optical fiber 81. If the
composition and film quality of the deposition on the inner side of
the photoreception window 80 are the same, the reduction in the
amount of photoreception increases as the thickness of the
deposition increases. Furthermore, the reduction in the amount of
photoreception at each wavelength varies depending on the
wavelength. On the other hand, as shown above, the reaction
products deposited on the inner sides of the processing chamber
side wall 11 and processing chamber cover 12 are dissociated by the
plasma 25, producing ions of silicon and bromine, etc., which may
affect the etching of the object to be processed 1 and provoke a
variation of the gate width 8. Thus, there is a correlation between
the amount of photoreception of the plasma 25 at each wavelength
and variation in the gate width 8.
[0104] This embodiment calculates in advance a polynomial showing a
relationship between the data 73 indicating plasma emission and the
gate width 8, and carries out an analysis through the analysis
section 74 using this polynomial. Assuming that the gate width 8 at
the chip in the center portion of the object to be processed 1 is
Gc and the i-th channel signal of the multi-channel signals
obtained through the spectroscopic section 82 is Ii, Gc and signal
I of each channel are expressed by the following Formula (1) where
f.sub.1 indicates that Gc is a function of I.
[0105] [Formula 1]
Gc=f.sub.1(I.sub.1, I.sub.2, . . . ., I.sub.1024) (1)
[0106] Likewise, assuming that the gate width 8 at the chip in the
outer regions of the object to be processed 1 is Go and the i-th
channel signal of the multi-channel signals obtained through the
spectroscopic section 82 is Ii, Go and signal I of each channel are
expressed by the following Formula (2) where f.sub.2 indicates that
Go is a function of I.
[0107] [Formula 2]
Go=f.sub.1(I.sub.1, I.sub.2, . . . ., I.sub.1024) (2)
[0108] According to these polynomials, the gate width 8 of the
chips in the center portion and outer region of the object to be
processed 1 is calculated and its in-plane distribution is
analyzed. For example, if the analysis result shows that the gate
width 8 at the chip in the central part of the object to be
processed 1 is larger than a target completion size and the gate
width 8 at the chip in the outer region is smaller than the target
completion size, by regulating the gas condition so that the gate
width 8 at the chip in the center portion becomes smaller and the
gate width 8 at the chip in the outer region becomes greater, it is
possible to approximate the gate widths 8 at the chips in the
center portion and in the outer region to the target completion
size. In this case, it is possible to reduce the oxygen
concentration of the processing gas 21-1 introduced from the first
gas inlet 65-1 placed in the center of the processing chamber cover
12 and increase the oxygen concentration of the processing gas 21-2
introduced from the second gas inlet 65-2 placed in the outer
region. It is possible to improve the in-plane distribution of the
gate width 8 of the object to be processed 1 and approximate it to
the target completion size using these analysis results and by
carrying out control similar to that in the third embodiment.
[0109] As shown above, by controlling the etching processing
condition in real time based on the light emission measurement
result of the plasma 25 obtained by the spectroscopic section 82,
it is possible to approximate the gate width 8-1 in the center
portion and the gate width 8-2 in the outer regions of the object
to be processed 1 to their respective target completion sizes.
[0110] Here, multi-channel signals obtained by the spectroscopic
section 82 are used as variables making up the f.sub.1 or f.sub.2
function used to calculate the gate width 8, but the number of
channels is not particularly limited. This embodiment uses signals
I of all 1024 channels, but it is also possible to use signals I of
several channels or one channel out of the multi-channel signals
obtained.
[0111] [Fifth Embodiment]
[0112] A fifth embodiment of the present invention will be
explained using FIG. 12. This embodiment adds one additional set of
photoreception window 80 and optical fiber 81 to the configuration
explained in the fourth embodiment. It also provides two
photoreception windows 80 in the center portion and outer regions
of the processing chamber cover 12, analyzes concentrations of
radicals and ions in the center portion and outer regions in the
processing chamber 13 to regulate flow rates and compositions of
processing gases 21 introduced from a plurality of locations. A
specific method of implementing this embodiment will be explained
below.
[0113] To allow reception of emission of plasma 25, a first
photoreception window 80-1 is provided in the center portion of the
processing chamber cover 12 and a second photoreception window 80-2
is provided in the outer regions. Emissions of the plasma 25
received by the respective photoreception windows 80 are guided to
a spectroscopic section 82 through an optical fiber 81-1 and an
optical fiber 81-2. The respective plasma emissions are dispersed
into a spectrum at the spectroscopic section 82, further converted
to multi-channel signals (e.g., signals of 1024 channels in a
wavelength range of 200 nm to 800 nm in this embodiment) at certain
sampling intervals (e.g., 1 second) periodically every certain
wavelength by a CCD incorporated in the spectroscopic section 82.
Plasma emission data 83 consisting of multi-channel signals is sent
to a database 72. Data 73 stored in the database 72 is sent to an
analysis section 74 at appropriate timings, and the analysis
section 74 analyzes the plasma 25 based on the data 73.
[0114] Ions and radicals in the plasma 25 emit light having a
wavelength specific to each component. For example, 288 nm or the
like for Si, 827 nm or the like for Br, 617 nm or the like for O
and503.5 nm or the like for SiBr. Thus, by analyzing the plasma
emission data 83 obtained from the first photoreception window 80-1
placed in the center portion and the second photoreception window
80-2 placed in the outer regions of the processing chamber cover
12, it is possible to compare concentrations of ions and radicals
in the center portion and outer regions of the object to be
processed 1.
[0115] Thus, if an analysis result shows that, for example, the
SiBr concentration in the center portion is relatively similar to
that in the outer regions and the 0 concentration is lower in the
outer regions than in the center portion, it is possible to
introduce a processing gas 21-2 with higher oxygen concentration
from the second gas inlet 65-2 placed in the outer regions rather
than the processing gas 21-1 introduced from the first gas inlet
65-1 placed in the center portion of the processing chamber cover
12. As a result, it is possible to control the concentration
distribution of oxygen in the processing chamber 13 uniformly and
approximate the gate width 8 at the chip in the center portion of
the object to be processed 1 to the gate width 8 at the chip in the
outer regions. The analysis section 74 calculates the flow rate
ratios, flow rates and processing pressures of the respective
processing gases introduced from the first and second gas inlets 65
necessary to realize this condition. That is, the set flow rate
values of the flow rate regulators 42-1, 42-2, 53-1 and 53-2, set
shunt ratio value of the gas shunt 60 and set value of the opening
of the pressure regulating valve 31 to realize the set processing
pressure are calculated.
[0116] The above described analysis is performed by the analysis
section 74, the control command 75 reflecting the analysis result
is sent to the control section 76 and the control signal 77 is sent
to the devices of the gas piping system from the control section
76. That is, the control signal 77 including the set flow rate
value is sent to the respective flow rate regulators 42-1, 42-2,
53-1 and 53-2, the valve ON/OFF control signal 77 is sent to the
respective valves 43-1, 43-2, 54-1 and 54-2, the control signal 77
including the set shunt ratio value is sent to the gas shunt 60 and
the control signal 77 including the set value of the opening of the
valve to realize the set processing pressure is sent to the
pressure regulating valve 31.
[0117] As shown above, by controlling the etching processing
condition in real time based on emissions of the plasma 25 received
through the first photoreception window 80-1 placed in the center
portion of the processing chamber cover 12 and the second
photoreception window 80-2 placed in the outer regions, it is
possible to approximate the gate width 8 at the chip in the center
portion of the object to be processed 1 to the gate width 8 of the
chip in the outer regions and improve the in-plane uniformity of
the gate width 8.
[0118] The embodiments of the present invention have been explained
using gate etching as an example, but application of the present
invention is not limited to gate etching. It goes without saying
that the present invention is also applicable to a plasma etching
apparatus and plasma etching method targeted at metal such as
aluminum (Al), or silicon dioxide (SiO.sub.2) and ferroelectric
material or the like.
[0119] As described above, the present invention provides a plasma
etching processing apparatus and plasma etching processing method
which perform processing with excellent in-plane uniformity on an
object to be processed having a large diameter.
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