U.S. patent application number 09/273293 was filed with the patent office on 2001-11-15 for method and apparatus for plasma etching.
Invention is credited to ITO, NATSUKO, MORIYA, TSUYOSHI, UESUGI, FUMIHIKO.
Application Number | 20010041449 09/273293 |
Document ID | / |
Family ID | 13488908 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010041449 |
Kind Code |
A1 |
ITO, NATSUKO ; et
al. |
November 15, 2001 |
METHOD AND APPARATUS FOR PLASMA ETCHING
Abstract
A plasma etching apparatus includes a processing chamber for
etch-processing a substrate, a lower electrode located within the
processing chamber for holding the substrate on an upper surface
thereof by an electrostatic attraction, and an upper electrode
located to face the lower electrode. A purge gas introducing port
is provided at a side wall of the processing chamber at a position
which is between the upper electrode and the lower electrode in
height and which opposes to the evacuation port in a plan view in
such a manner that the lower electrode is positioned between the
evacuation port and the purge gas introducing port in the plan
view. A plasma etching method includes the steps of holding the
substrate on the lower electrode in such a condition that a surface
to be etched of the substrate is faced upwards, then introducing a
process gas into the processing chamber, applying a high frequency
voltage between the lower electrode and the upper electrode to
generate a plasma gas in a low pressure so as to etch the
substrate, and thereafter, introducing a purge gas into the process
chamber at the time of completion of the processing. At the time of
completing the processing, the supplying of the process gas is
stopped and it starts to supply the purge gas into the processing
chamber, and thereafter, when a predetermined time has elapsed, the
application of the high frequency voltage is stopped.
Inventors: |
ITO, NATSUKO; (TOKYO,
JP) ; UESUGI, FUMIHIKO; (TOKYO, JP) ; MORIYA,
TSUYOSHI; (TOKYO, JP) |
Correspondence
Address: |
HUTCHINS, WHEELER & DITTMAR
101 FEDERAL STREET
BOSTON
MA
02110
US
|
Family ID: |
13488908 |
Appl. No.: |
09/273293 |
Filed: |
March 19, 1999 |
Current U.S.
Class: |
438/706 |
Current CPC
Class: |
C23F 4/00 20130101; H01J
37/32862 20130101 |
Class at
Publication: |
438/706 |
International
Class: |
H01L 021/302; H01L
021/461 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 20, 1998 |
JP |
10-72424 |
Claims
1. A plasma etching method which uses a plasma etching apparatus
including a processing chamber for etch-processing a substrate, a
lower electrode located within the processing chamber for holding
the substrate on an upper surface thereof by an electrostatic
attraction, and an upper electrode located to face the lower
electrode, and which includes the steps of holding the substrate on
the lower electrode in such a condition that a surface to be etched
of the substrate is faced upwards, then introducing a process gas
into the processing chamber, applying a high frequency voltage
between the lower electrode and the upper electrode to generate a
plasma gas in a low pressure so as to etch the substrate, and
thereafter, introducing a purge gas into the process chamber at the
time of completion of the processing, wherein at the time of
completing the processing, the supplying of the process gas is
stopped and it starts to supply the purge gas into the processing
chamber, and thereafter, when a predetermined time has elapsed, the
application of the high frequency voltage is stopped.
2. A plasma etching method claimed in claim 1 wherein the
predetermined time is a length of time until the particles floating
above the substrate are removed from a zone above the substrate by
a flow of the purge gas.
3. A plasma etching method claimed in claim 1 wherein the
predetermined time is on the order of a few seconds.
4. A plasma etching method which uses a plasma etching apparatus
including a processing chamber for etch-processing a substrate, a
lower electrode located within the processing chamber for holding
the substrate on an upper surface thereof by an electrostatic
attraction, and an upper electrode located to face the lower
electrode, and which includes the steps of holding the substrate on
the lower electrode in such a condition that a surface to be etched
of the substrate is faced upwards, then introducing a process gas
into the processing chamber, applying a high frequency voltage
between the lower electrode and the upper electrode to generate a
plasma gas in a low pressure so as to etch the substrate, and
thereafter, introducing a purge gas into the process chamber at the
time of completion of the processing, wherein at the time of
completing the processing, the application of the high frequency
voltage is stopped, and thereafter, when a predetermined time has
elapsed, the supplying of the process gas is stopped and
simultaneously it starts to supply the purge gas into the
processing chamber.
5. A plasma etching method claimed in claim 4 wherein the
predetermined time is a length of time sufficient for neutralizing
the remaining electric charge of the substrate after the
electrostatic attraction is canceled.
6. A plasma etching method claimed in claim 4 wherein the
predetermined time is on the order of a few seconds.
7. A plasma etching method which uses a plasma etching apparatus
including a processing chamber for etch-processing a substrate, a
lower electrode located within the processing chamber for holding
the substrate on an upper surface thereof by an electrostatic
attraction, and an upper electrode located to face the lower
electrode, and which includes the steps of holding the substrate on
the lower electrode in such a condition that a surface to be etched
of the substrate is faced upwards, then introducing a process gas
into the processing chamber, applying a high frequency voltage
between the lower electrode and the upper electrode to generate a
plasma gas in a low pressure so as to etch the substrate, and
thereafter, introducing a purge gas into the process chamber at the
time of completion of the processing, wherein at the time of
completing the processing, it starts to supply the purge gas into
the processing chamber, and thereafter, when a predetermined time
has elapsed, the application of the high frequency voltage and the
supplying of the process gas are stopped.
8. A plasma etching method claimed in claim 7 wherein the
predetermined time is a length of time until the particles floating
above the substrate are removed from a zone above the substrate by
a flow of the purge gas.
9. A plasma etching method claimed in claim 7 wherein the
predetermined time is on the order of a few seconds.
10. A plasma etching method which uses a plasma etching apparatus
including a processing chamber for etch-processing a substrate, a
lower electrode located within the processing chamber for holding
the substrate on an upper surface thereof by an electrostatic
attraction, and an upper electrode located to face the lower
electrode, and which includes the steps of holding the substrate on
the lower electrode in such a condition that a surface to be etched
of the substrate is faced upwards, then introducing a process gas
into the processing chamber, applying a high frequency voltage
between the lower electrode and the upper electrode to generate a
plasma gas in a low pressure so as to etch the substrate, and
thereafter, introducing a purge gas into the process chamber at the
time of completion of the processing, wherein at the time of
completing the processing, the application of the high frequency
voltage is stopped and simultaneously it starts to supply the purge
gas into the processing chamber, and thereafter, when a
predetermined time has elapsed, the supplying of the process gas is
stopped.
11. A plasma etching method claimed in claim 10 wherein the
predetermined time is a length of time sufficient for neutralizing
remaining electric charge of the substrate after the electrostatic
attraction is canceled.
12. A plasma etching method claimed in claim 10 wherein the
predetermined time is on the order of a few seconds.
13. A plasma etching apparatus including a processing chamber
having an evacuation port, a lower electrode located within the
processing chamber for holding the substrate on an upper surface
thereof by an electrostatic attraction in such a condition that a
surface to be etched of the substrate is faced upwards, and an
upper electrode located to face the lower electrode, wherein a
purge gas introducing port is provided at a side wall of the
processing chamber at a position which is between the upper
electrode and the lower electrode in height and which opposes to
the evacuation port in a plan view in such a manner that the lower
electrode is positioned between the evacuation port and the purge
gas introducing port in the plan view.
14. A plasma etching apparatus claimed in claim 13, further
including a sensor for detecting the flow rate of the purge gas,
and a controller receiving a detection signal from the sensor, for
determining the timing for stopping the application of the high
frequency voltage and for actually stopping the application of the
high frequency voltage.
15. A plasma etching apparatus claimed in claim 13, further
including a sensor for detecting the stop of the application of the
high frequency voltage, and a controller receiving a detection
signal from the sensor, for determining the timing for stopping the
supplying of the process gas and for actually stopping the
supplying of the process gas.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a plasma etching method and
a plasma etching apparatus, and more specifically to a plasma
etching method and a plasma etching apparatus, for preventing
particles generated in an etching, from depositing on a
substrate.
[0003] 2. Description of Related Art
[0004] In manufacturing a semiconductor device, it is in many cases
that a plasma etching apparatus is used for the purpose of
executing a dry etching by use of a reactive plasma gas under a low
pressure. In the following, an example of a prior art plasma
etching apparatus will be described with reference to the drawings.
FIG. 6 is a diagrammatic sectional view for illustrating a plasma
etching apparatus generally used in a semiconductor device
manufacturing factory The plasma etching apparatus generally
indicated with Reference Numeral 10 includes a processing chamber
12 for processing a substrate by an etching, a lower electrode 16
located within the processing chamber 12 for holding a substrate 11
put on an upper surface thereof, and an upper electrode 18 located
to face the lower electrode 16 and having a discharge surface for
generating an electric discharge between the upper electrode 16 and
the substrate held on the lower electrode 16.
[0005] The lower electrode 16 includes an electrostatically
attracting electrode 15 for holding the substrate 11 by action of
an electrostatic attraction, an insulating plate 24 provided under
the electrode 15, and a lower electrode body 17 provided under the
insulating plate 24. The electrostatically attracting electrode 15
is connected to a DC voltage supply 26, and the lower electrode
body 17 is connected to a high frequency voltage supply 28. The
upper electrode 18 has a gas introducing path 22 for introducing a
process gas and a purge gas, and gas nozzles 22 provided in a lower
surface of the upper electrode 16 and over a region positioned just
above the substrate. This upper electrode 18 is connected to
ground.
[0006] Ordinarily, one evacuation port 23 is provided in a bottom
of the processing chamber 12, and a feeding port 30 is provided a
side wall of the processing chamber 12 for feeding the substrate
11.
[0007] FIG. 7 is a graph for illustrating an operating condition of
the plasma etching apparatus 10 at the time of etching the
substrate in the plasma etching apparatus 10, corresponding to one
cycle of the substrate processing. In the plasma etching apparatus
10, a highly reactive process gas such as chlorine is introduced
through the gas nozzles 22 of the upper electrode 18 into the
processing chamber, and when a pressure has reached a predetermined
constant pressure, a high frequency voltage is applied between the
upper and lower electrodes to bring the process gas into a plasma
condition, with the result that an etching is carried out. If the
etching is completed, the application of the high frequency voltage
and the supplying of the process gas are simultaneously stopped,
and after a few seconds, a less reactive halogen gas is introduced
as a purge gas.
[0008] However, in an LSI manufacturing process, in particular, in
a process for etching a metal film by a plasma gas, generated
particles have become a large cause for lowering the yield of
production and the operating efficiency of the apparatus. A main
cause of generation of the particles is that reaction products
deposited on an inside of the plasma etching apparatus peel off and
drop on the substrate. Accordingly, it is difficult to completely
prevent the generated particles from depositing on the substrate.
Under this circumstance, a method for causing the generated
particles not to deposit on the substrate, or an apparatus having a
function of causing the generated particles not to deposit on the
substrate, have been developed. These method and apparatus are
disclosed in Japanese Patent Application Pre-examination
Publication Nos. JP-A-59-119839, JP-A-60-195937, JP-A-04-250621,
JP-A-05-029272, JP-A-05-267234, JP-A-07-058033, JP-A-08-115903 and
JP-A-06-122978 (an English abstract of these Japanese patent
publications is available and the content of the English abstract
of is incorporated by reference in its entirety into this
application).
[0009] JP-A-59-119839 and JP-A-60-195937 propose to hold the
substrate to be processed, downward or vertically, so that the
particles falling by gravity is prevented from depositing on the
substrate. JP-A-04-250621 propose to provide a cover on an
electrode moving part and a periphery of a metal sealing, in order
to prevent the falling particles from spreading in the inside of
the vacuum chamber. JP-A-05-029272 proposes to mount a cover for
covering the substrate just after the completion of the processing,
so as to prevent the particles from falling on the substrate. These
Japanese patent publications prevent the particles from falling on
the substrate.
[0010] On the other hand, JP-A-05-267234 and JP-A-08-115903 propose
a means for positively moving the particles thereby to prevent the
particles from depositing on the substrate. JP-A-05-267234
electrostatically removes the particles by means of a dust
collecting electrode. JP-A-08-115903 provides a means for
preventing the flow of process gas from being directed from the
working electrode to the substrate, thereby to prevent the
particles included in the gas from reaching the substrate.
[0011] As combination of the above mentioned methods,
JP-A-07-058033 proposes to provide an electric precipitator and a
cover for covering the substrate just after the completion of the
processing, so as to prevent the particles from reaching the
substrate.
[0012] JP-A-06-122978 proposes to introduce the purge gas between
the substrate and the high frequency electrode after the
application of the high frequency voltage is stopped, and to cause
the particles to reach the surface of the substrate with a few
seconds, whereby the particles are prevented from depositing on the
substrate surface after the film deposition.
[0013] However, the prior art methods and apparatuses disclosed in
the above referred Japanese patent publications need to modify the
machine or to add parts, so that the mechanism of the machine
becomes complicated. In addition, the machine cost becomes high.
This problem will be discussed in the following.
[0014] In order to change the substrate holding direction, it is
necessary to mount heavy parts such as a feeding mechanism, a
working electrode and a wafer holding mechanism, on an upper
portion of the apparatus, or to hold these parts vertically. As a
result, a new problem occurs in connection with a stable operation
of the apparatus. Furthermore, since it is necessary to strongly
make a frame for supporting these heavy parts, the apparatus
becomes large in size. Moreover, the substrate feeding mechanism
becomes complicated. In addition, after completion of the process,
in order to cover the substrate with a cover or in order to
electrostatically attract the particle, it is necessary to provide
a moving mechanism near to the substrate within the apparatus.
Because of this, there is possibility that the particles are
generated by the moving mechanism. Furthermore, provision of these
mechanisms results in a further enlarged size of the apparatus.
[0015] On the other hand, the provision of the cover for preventing
the falling particles from spreading in the inside of the vacuum
chamber, and the control of the direction of the flow of process
gas, cannot sufficiently prevent the particles (dust) peeled off
from the upper electrode, from falling and depositing on the
substrate.
[0016] Under the above mentioned circumstances, there are demanded
a plasma etching method for effectively preventing the particles
generated in the plasma etching apparatus, from reaching and
depositing on the substrate, by adding a simple mechanism without
enlarging the size of the processing apparatus, and a plasma
etching apparatus capable of carrying out the method.
SUMMARY OF THE INVENTION
[0017] Accordingly, it is an object of the present invention to
provide a plasma etching method and a plasma etching apparatus
which have overcome the above mentioned defect of the conventional
one.
[0018] Another object of the present invention is to provide a
plasma etching method and a plasma etching apparatus, capable of
effectively preventing the particles generated in the plasma
etching apparatus, from depositing on the substrate, by adding only
a simple modification without enlarging the size of the processing
apparatus.
[0019] The co-inventors of the present invention measured a
relation between the lapse of time and the number of particles
generated in the operating course when the substrate is etched in
the prior art plasma etching apparatus 10. FIG. 8 is a graph
illustrating the result of this measurement. In FIG. 8, the number
of particles is indicated by small ovals. The number of particles
was measured by introducing a laser light into the processing
chamber to pass through a zone confined above the substrate, and by
detecting scattering lights from the particles contained in the
confined zone, by a CCD camera, so as to count the number of
particles. In parallel to the counting of the number of particles,
a signal indicative of the operating condition of the etching
apparatus was picked up. FIG. 8 shows the accumulated value after
25 wafers have been processed.
[0020] In the following, the change of the particle number with the
lapse of time in the etching process carried out in the plasma
etching apparatus 10 will be described. In order to carry out the
etching in the plasma etching apparatus 10, the substrate is fed
into the processing chamber through the feeding port, and then, the
process gas is supplied. When the pressure within the processing
chamber reaches a predetermined value, the substrate is
electrostatically attracted, and simultaneously, the high frequency
voltage is applied so that a plasma is generated to start the
etching of the substrate. After the etching is completed, the
application of the high frequency voltage, the supplying of the
process gas and the electrostatic attraction of the substrate are
simultaneously stopped.
[0021] With a few seconds from the stopping, in order to quickly
exhausting the process gas, an inert gas having no contribution to
the etching is supplied as a purge gas for a constant time, so that
the pressure in the processing chamber is elevated. The substrate
thus etched is fed out from the processing chamber through the
feeding port.
[0022] It would be understood from FIG. 8 that there is a clear
relation between the amount of particles generated in the etching
and the operating condition of the apparatus. Namely, almost no
particle is generated in the etching processing, but after the
completion of the etching, many particles are generated. In
particular, the amount of particles generated is at maximum when
the purge gas is introduced.
[0023] Carefully investigating the image of the scattering light
from the particles, the flying course of the particles is apt to go
towards the substrate at the time of the completion of the etching,
but to go towards the evacuation port when the purge gas is
introduced
[0024] Based on the above mentioned result of measurement, the
co-inventors of the present invention reached the following
conclusion: If the application of the high frequency voltage and
the supplying of the process gas are stopped at the time of the
completion of the etching, since the flow rate of the process gas
evacuated through the evacuation port by action of a vacuum suction
is not so high, the particles, which had floated in the etching
process, cannot be exhausted together with the process gas towards
the evacuation port, with the result that the particles fall down
and move towards the substrate from which the electric charge has
not yet completely neutralized. If the purge gas is introduced with
a few seconds from the completion of the etching, the particles are
exhausted together with the purge gas towards the evacuation
port.
[0025] Therefore, the co-inventors of the present invention studied
to maintain the flow of gas within the processing chamber when the
application of the high frequency voltage is stopped, thereby to
cause the generated particles to move towards the evacuation port,
so that the particles are prevented from depositing on the
substrate. As a result, the co-inventors reached the present
invention.
[0026] In order to achieve the above and other objects of the
present invention, there is provided a first method of the plasma
etching method in accordance with the present invention which uses
a plasma etching apparatus including a processing chamber for
etch-processing a substrate, a lower electrode located within the
processing chamber for holding the substrate on an upper surface
thereof by an electrostatic attraction, and an upper electrode
located to face the lower electrode, and which includes the steps
of holding the substrate on the lower electrode in such a condition
that a surface to be etched of the substrate is faced upwards, then
introducing a process gas into the processing chamber, applying a
high frequency voltage between the lower electrode and the upper
electrode to generate a plasma gas in a low pressure so as to etch
the substrate, and thereafter, introducing a purge gas into the
process chamber at the time of completion of the processing,
wherein at the time of completing the processing, the supplying of
the process gas is stopped and it starts to supply the purge gas
into the processing chamber, and thereafter, when a predetermined
time has elapsed, the application of the high frequency voltage is
stopped.
[0027] Here, the electrostatic attraction is a holding method for
attracting the substrate by action of the electrostatic force. The
purge gas is a gas having no contribution to the etching even if
the high frequency voltage is applied. For example, the purge gas
is composed of an inert gas
[0028] In this first method of the plasma etching method in
accordance with the present invention, the predetermined time is a
length of time until the particles floating above the substrate are
removed from a zone above the substrate by a flow of the purge gas.
Ordinarily, the predetermined time is on the order of a few
seconds.
[0029] According to a second aspect of the present invention, there
is provided a second method of the plasma etching method in
accordance with the present invention which uses a plasma etching
apparatus including a processing chamber for etch-processing a
substrate, a lower electrode located within the processing chamber
for holding the substrate on an upper surface thereof by an
electrostatic attraction, and an upper electrode located to face
the lower electrode, and which includes the steps of holding the
substrate on the lower electrode in such a condition that a surface
to be etched of the substrate is faced upwards, then introducing a
process gas into the processing chamber, applying a high frequency
voltage between the lower electrode and the upper electrode to
generate a plasma gas in a low pressure so as to etch the
substrate, and thereafter, introducing a purge gas into the process
chamber at the time of completion of the processing, wherein at the
time of completing the processing, the application of the high
frequency voltage is stopped, and thereafter, when a predetermined
time has elapsed, the supplying of the process gas is stopped and
simultaneously it starts to supply the purge gas into the
processing chamber.
[0030] In this second method of the plasma etching method in
accordance with the present invention, the predetermined time is a
length of time until the particles floating above the substrate are
removed from a zone above the substrate by a flow of the process
gas. Ordinarily, the predetermined time is on the order of a few
seconds
[0031] According to a third aspect of the present invention, there
is provided a third method of the plasma etching method in
accordance with the present invention which uses a plasma etching
apparatus including a processing chamber for etch-processing a
substrate, a lower electrode located within the processing chamber
for holding the substrate on an upper surface thereof by an
electrostatic attraction, and an upper electrode located to face
the lower electrode, and which includes the steps of holding the
substrate on the lower electrode in such a condition that a surface
to be etched of the substrate is faced upwards, then introducing a
process gas into the processing chamber, applying a high frequency
voltage between the lower electrode and the upper electrode to
generate a plasma gas in a low pressure so as to etch the
substrate, and thereafter, introducing a purge gas into the process
chamber at the time of completion of the processing, wherein at the
time of completing the processing, it starts to supply the purge
gas into the processing chamber, and thereafter, when a
predetermined time has elapsed, the application of the high
frequency voltage and the supplying of the process gas are
stopped.
[0032] Here, the predetermined time in this third method of the
plasma etching method in accordance with the present invention is
the same as the predetermined time in the first method of the
plasma etching method in accordance with the present invention.
[0033] According to a fourth aspect of the present invention, there
is provided a fourth method of the plasma etching method in
accordance with the present invention which uses a plasma etching
apparatus including a processing chamber for etch-processing a
substrate, a lower electrode located within the processing chamber
for holding the substrate on an upper surface thereof by an
electrostatic attraction, and an upper electrode located to face
the lower electrode, and which includes the steps of holding the
substrate on the lower electrode in such a condition that a surface
to be etched of the substrate is faced upwards, then introducing a
process gas into the processing chamber, applying a high frequency
voltage between the lower electrode and the upper electrode to
generate a plasma gas in a low pressure so as to etch the
substrate, and thereafter, introducing a purge gas into the process
chamber at the time of completion of the processing, wherein at the
time of completing the processing, the application of the high
frequency voltage is stopped and simultaneously it starts to supply
the purge gas into the processing chamber, and thereafter, when a
predetermined time has elapsed, the supplying of the process gas is
stopped.
[0034] Here, the predetermined time in this fourth method of the
plasma etching method in accordance with the present invention is
the same as the predetermined time in the second method of the
plasma etching method in accordance with the present invention.
[0035] According to a fifth aspect of the present invention, there
is provided a plasma etching apparatus for carrying out the above
mentioned first to fourth methods of the plasma etching method in
accordance with the present invention, including a processing
chamber having an evacuation port, a lower electrode located within
the processing chamber for holding the substrate on an upper
surface thereof by an electrostatic attraction in such a condition
that a surface to be etched of the substrate is faced upwards, and
an upper electrode located to face the lower electrode, wherein a
purge gas introducing port is provided at a side wall of the
processing chamber at a position which is between the upper
electrode and the lower electrode in height and which opposes to
the evacuation port in a plan view in such a manner that the lower
electrode is positioned between the evacuation port and the purge
gas introducing port in the plan view.
[0036] With this arrangement, the purge gas is flowed substantially
in parallel to the substrate. Therefore, when the purge gas is
introduced into the processing chamber, the particles floating in a
zone above the substrate are effectively transported towards the
evacuation port to be exhausted through the evacuation port. As a
result, the amount of particles falling on the substrate can be
greatly reduced.
[0037] In order to carry out the above mentioned first and third
methods of the plasma etching method in accordance with the present
invention, the plasma etching apparatus preferably includes a
sensor for detecting the flow rate of the purge gas, and a
controller receiving a detection signal from the sensor, for
determining the timing for stopping the application of the high
frequency voltage and for actually stopping the application of the
high frequency voltage.
[0038] In order to carry out the above mentioned second and fourth
methods of the plasma etching method in accordance with the present
invention, the plasma etching apparatus preferably includes a
sensor for detecting the stop of the application of the high
frequency voltage, and a controller receiving a detection signal
from the sensor, for determining the timing for stopping the
supplying of the process gas and for actually stopping the
supplying of the process gas.
[0039] The above and other objects, features and advantages of the
present invention will be apparent from the following description
of preferred embodiments of the invention with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a graph showing an operating condition of the
plasma etching apparatus, for illustrating a first embodiment of
the plasma etching method in accordance with the present
invention;
[0041] FIG. 2 is a graph showing an operating condition of the
plasma etching apparatus, for illustrating a second embodiment of
the plasma etching method in accordance with the present
invention;
[0042] FIG. 3 is a graph showing an operating condition of the
plasma etching apparatus, for illustrating a third embodiment of
the plasma etching method in accordance with the present
invention;
[0043] FIG. 4 is a graph showing an operating condition of the
plasma etching apparatus, for illustrating a fourth embodiment of
the plasma etching method in accordance with the present
invention;
[0044] FIG. 5 is a diagrammatic sectional view for illustrating an
embodiment of the plasma etching apparatus in accordance with the
present invention;
[0045] FIG. 6 is a diagrammatic sectional view for illustrating a
prior art plasma etching apparatus generally used in a
semiconductor device manufacturing factory;
[0046] FIG. 7 is a graph for illustrating an operating condition at
the time of etching the substrate in the prior art plasma etching
apparatus; and
[0047] FIG. 8 is a graph for illustrating the relation between the
lapse of time and the number of particles generated in the
operating course when the substrate is etched in the prior art
plasma etching apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] Now, the present invention will be described with reference
to the drawings.
Embodiment 1
[0049] Referring to FIG. 1, there is shown a graph showing an
operating condition of the plasma etching apparatus, for
illustrating a first embodiment of the plasma etching method in
accordance with the present invention, corresponding to one cycle
of the substrate processing, when a substrate is etched in the
plasma etching apparatus 10 shown in FIG. 6.
[0050] In this embodiment, when the etching processing is
completed, the supplying of the process gas is stopped, and
simultaneously, it starts to supply the purge gas into the
processing chamber, similarly to the prior art method. However,
when a few seconds have elapsed from the start of the supplying of
the purge gas, the application of the high frequency voltage is
stopped, differently from the prior art method. Here, the time from
the start of the supplying of the purge gas to the stopping of the
application of the high frequency voltage corresponds to the time
until the particles floating above the substrate are removed from a
zone above the substrate by a flow of the purge gas.
[0051] With this arrangement, a number of particles which start to
fall down from the atmosphere within the chamber, are transported
and exhausted by the flow of the purge gas (which is ordinarily of
an inert gas), so that the particles are prevented from reaching
and depositing on the substrate.
[0052] In this case, this embodiment can be carried out by using a
plasma etching apparatus having a controller for automatically
executing the etching process in accordance with the process shown
in FIG. 1. In addition, if a plasma etching apparatus shown in FIG.
5, which will be described hereinafter, is used, this embodiment
can be carried out more advantageously.
Embodiment 2
[0053] Referring to FIG. 2, there is shown a graph showing an
operating condition of the plasma etching apparatus, for
illustrating a second embodiment of the plasma etching method in
accordance with the present invention, corresponding to one cycle
of the substrate processing, when a substrate is etched by using
the plasma etching apparatus 10 shown in FIG. 6.
[0054] In this embodiment, when the etching processing is
completed, the application of the high frequency voltage is
stopped, and thereafter, when a few seconds have elapsed from the
stop of the application of the high frequency voltage, the
supplying of the process gas is stopped and simultaneously it
starts to supply the purge gas into the processing chamber. Here,
the time from the stop of the application of the high frequency
voltage to the stop of the supplying of the process gas, is a time
sufficient for neutralizing the remaining electric charge of the
substrate after the electrostatic attraction is canceled. For
example, this time is on the order of 3 seconds to 5 seconds.
[0055] Thus, an advantage similar to that obtained in the first
embodiment can be obtained. In this case, if the plasma etching
apparatus shown in FIG. 5, which will be described hereinafter, is
used, this embodiment can be carried out more advantageously.
Embodiment 3
[0056] Referring to FIG. 3, there is shown a graph showing an
operating condition of the plasma etching apparatus, for
illustrating a third embodiment of the plasma etching method in
accordance with the present invention, corresponding to one cycle
of the substrate processing, when a substrate is etched by using
the plasma etching apparatus 10 shown in FIG. 5.
[0057] In this embodiment, when the etching processing is
completed, the purge gas such as an inert gas having no
contribution to the etching is supplied into the chamber, and
thereafter, when a few seconds have elapsed from the start of the
supplying of the purge gas, the application of the high frequency
voltage and the supplying of the process gas are stopped. Here, the
time from the start of the supplying of the purge gas to the
stopping of the application of the high frequency voltage
corresponds to the time until the particles floating above the
substrate are removed from a zone above the substrate by a flow of
the purge gas. In this case, after the start of the supplying of
the purge gas until the stopping of the application of the high
frequency voltage, the etching of the substrate continues.
Therefore, by considering this time as an over-etching time, the
actual etching time is suitably adjusted.
[0058] Thus, an advantage similar to that obtained in the first
embodiment can be obtained. In this case, if the plasma etching
apparatus shown in FIG. 5, which will be described hereinafter, is
used, this embodiment can be carried out more advantageously.
Embodiment 4
[0059] Referring to FIG. 4, there is shown a graph showing an
operating condition of the plasma etching apparatus, for
illustrating a fourth embodiment of the plasma etching method in
accordance with the present invention, corresponding to one cycle
of the substrate processing, when a substrate is etched by using
the plasma etching apparatus 10 shown in FIG. 5.
[0060] In this embodiment, when the etching processing is
completed, the application of the high frequency voltage is
stopped, and simultaneously, it starts to supply the purge gas into
the chamber, and thereafter, when a few seconds have elapsed from
the start of the supplying of the purge gas, the supplying of the
process gas is stopped. Here, the time from the stop of the
application of the high frequency voltage to the stop of the
supplying of the process gas, is a time sufficient for neutralizing
the remaining electric charge of the substrate after the
electrostatic attraction is canceled.
[0061] Thus, an advantage similar to that obtained in the first
embodiment can be obtained. In this case, if the plasma etching
apparatus shown in FIG. 5, which will be described hereinafter, is
used, this embodiment can be carried out more advantageously.
Embodiment 5
[0062] Referring to FIG. 5, there is shown a diagrammatic sectional
view for illustrating an embodiment of the plasma etching apparatus
in accordance with the present invention. In FIG. 5, elements
similar to those shown in FIG. 5 are given the same Reference
Numerals, and explanation will be omitted.
[0063] This embodiment of the plasma etching apparatus, generally
designated with Reference Numeral 34, includes a purge gas
introducing port 36 formed in a side wall of the processing chamber
12, different from the prior art example shown in FIG. 6. This
purge gas introducing port 36 is positioned between the upper
electrode 18 and the lower electrode 16 in height, and formed in a
wall portion opposing to a wall portion nearest to the evacuation
port 23 in a plan view in such a manner that the lower electrode 16
is positioned between the evacuation port 23 and the purge gas
introducing port 36 in a diameter direction of the lower electrode
16.
[0064] In this plasma etching apparatus 34, the purge gas is flowed
from the purge gas introducing port 36 to the evacuation port 23
substantially in parallel to the substrate. Therefore, a
disturbance in the gas flow above the substrate is remarkably small
in comparison with the prior art example. Therefore, when the purge
gas is introduced into the processing chamber, the particles
floating in a zone above the substrate are effectively transported
towards the evacuation port to be exhausted through the evacuation
port. As a result, the amount of particles falling on the substrate
can be greatly reduced.
[0065] In the prior art plasma etching apparatus 10 shown in FIG.
6, it was a general practice to supply both the process gas and the
purge gas from a position directly above the substrate, and on the
other hand, one evacuation port 23 is provided in only one place of
the bottom of the processing chamber 12. In this construction, in a
zone 32 most remote from the evacuation port 23, a disturbance
occurs in the gas flow, so that a disturbance also occurs in the
gas flow in a portion near to the zone 32, of the zone above the
substrate. Therefore, there was possibility that the particles
falls down on the substrate. However, the possibility that the
particles falls down on the substrate, has been greatly reduced by
the plasma etching apparatus 34.
[0066] This plasma etching apparatus 34 can be controlled by a
controller 40, which controls a switch 42 for on-off controlling
the application of the DC voltage supply 26 to the
electrostatically attracting electrode 15, and another switch 44
for on-off controlling the application of the high frequency
voltage supply 28 to the lower electrode body 17. The controller 40
is connected to receive a detection signal from a flow sensor 46
for detecting the flow rate of the process gas, and to supply a
control signal to a valve 48 for on-off controlling the supplying
of the process gas. Furthermore, the controller 40 is connected to
receive a detection signal from a flow sensor 50 for detecting the
flow rate of the purge gas, and to supply a control signal to a
valve 53 for on-off controlling the supplying of the purge gas.
[0067] Therefore, in order to carry out the above mentioned first
and third methods of the plasma etching method in accordance with
the present invention, the controller 40 receives a detection
signal from the sensor 50 for detecting the flow rate of the purge
gas, and if the start of the supplying of the purge gas is
detected, when the predetermined time has elapsed from the start of
the supplying of the purge gas, the controller 40 determines the
timing for stopping the application of the high frequency voltage
and turns off the switches 42 and 44 for actually stopping the
application of the DC voltage and the high frequency voltage. When
the first method is carried out, the controller 40 closes the valve
48 at the same time as the start of the supplying of the purge gas
is detected. When the third method is carried out, the controller
40 closes the valve 48 at the same time as the time of turning off
the switch 44.
[0068] On the other hand, in order to carry out the above mentioned
second and fourth methods of the plasma etching method in
accordance with the present invention, the controller 40 uses a
control signal for on-off controlling the switch 44, as a detection
signal of a sensor for detecting the stop of the application of the
high frequency voltage. If the stop of the application of the high
frequency voltage is detected, when the predetermined time has
elapsed from the stop of the application of the high frequency
voltage, the controller 40 determines the timing for stopping the
supplying of the process gas, and closes the valve 48 for actually
stopping the supplying of the process gas. When the second method
is carried out, the controller 40 opens the valve 52 at the same
time as the time of closing the valve 48. When the fourth method is
carried out, the controller 40 closes the valve 48 at the same time
as the time of turning off the switch 44.
[0069] As mentioned above, according to the plasma etching method
in accordance with the present invention, when the etching
processing is completed, (1) the supplying of the process gas is
stopped, and simultaneously, it starts to supply the purge gas into
the processing chamber, and thereafter, when a predetermined time
has elapsed from the start of the supplying of the purge gas, the
application of the high frequency voltage is stopped, or (2) the
application of the high frequency voltage is stopped, and
thereafter, when a predetermined time has elapsed from the stop of
the application of the high frequency voltage, the supplying of the
process gas is stopped and simultaneously it starts to supply the
purge gas into the processing chamber, or (3) the purge gas such as
an inert gas having no contribution to the etching is supplied into
the chamber, and thereafter, when a predetermined time has elapsed
from the start of the supplying of the purge gas, the application
of the high frequency voltage and the supplying of the process gas
are stopped, or (4) the application of the high frequency voltage
is stopped, and simultaneously, it starts to supply the purge gas
into the chamber, and thereafter, when a predetermined time has
elapsed from the start of the supplying of the purge gas, the
supplying of the process gas is stopped. Accordingly, with a slight
modification of the operating condition such as the timing of the
stopping of the application of the high frequency voltage, the
timing of the supplying of the purge gas, it is possible to
effectively minimize the amount of particles falling down on the
substrate. Namely, it is possible to effectively minimize the
amount of particles depositing on the substrate by a very simple
method.
[0070] On the other hand, according to the plasma etching apparatus
in accordance with the present invention, a purge gas introducing
port is provided at a side wall of the processing chamber at a
position which is between the upper electrode and the lower
electrode in height and which opposes to a side wall portion
nearest to the evacuation port in a plan view in such a manner that
the lower electrode is positioned between the evacuation port and
the purge gas introducing port in the plan view.
[0071] Therefore, with a minimum modification by newly providing
only the purge gas introducing port, it is possible to realize the
plasma etching apparatus capable of minimizing the amount of
particles falling on the substrate. Namely, the amount of particles
falling on the substrate can be greatly reduced without enlarging
the size of the plasma etching apparatus and with modification
which can be realized with a less number of parts newly added.
[0072] The invention has thus been shown and described with
reference to the specific embodiments. However, it should be noted
that the present invention is in no way limited to the details of
the illustrated structures but changes and modifications may be
made within the scope of the appended claims.
* * * * *