U.S. patent application number 10/083546 was filed with the patent office on 2003-08-28 for plasma processing apparatus, protecting layer therefor and installation of protecting layer.
Invention is credited to Furuse, Muneo, Koroyasu, Kunihiko, Tamura, Tomoyuki.
Application Number | 20030159778 10/083546 |
Document ID | / |
Family ID | 27753314 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030159778 |
Kind Code |
A1 |
Koroyasu, Kunihiko ; et
al. |
August 28, 2003 |
Plasma processing apparatus, protecting layer therefor and
installation of protecting layer
Abstract
The following plasma processing apparatus can suppress the
production of contaminants from the plasma processing chamber of
the apparatus and an article in the plasma processing chamber which
are allowed to act as ground electrodes: a plasma processing
apparatus in which a workpiece is processed by creating a plasma in
the processing chamber, and one or more surfaces made of a grounded
metal electric conductor which come into contact with the plasma in
the plasma processing chamber are coated with a plasma-resistant
polymeric material having a relationship between relative
dielectric constant k.epsilon. and thickness t (.mu.m) of
t/k.epsilon.<300, or a protecting layer formed of a
plasma-resistant and water-absorbing resin material is adhered and
fixed to the outer surface of an article in the processing chamber
by its swelling and then shrinkage.
Inventors: |
Koroyasu, Kunihiko;
(Kudamatsu, JP) ; Furuse, Muneo; (Kudamatsu,
JP) ; Tamura, Tomoyuki; (Kudamatsu, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-9889
US
|
Family ID: |
27753314 |
Appl. No.: |
10/083546 |
Filed: |
February 27, 2002 |
Current U.S.
Class: |
156/345.3 ;
118/723R; 118/728; 156/345.1 |
Current CPC
Class: |
C23C 14/568 20130101;
H01J 37/32559 20130101 |
Class at
Publication: |
156/345.3 ;
156/345.1; 118/723.00R; 118/728 |
International
Class: |
C23F 001/00; C23C
016/00 |
Claims
What is claimed is:
1. In a plasma processing apparatus in which a workpiece is
processed by creating a plasma in a processing chamber, the
improvement wherein a protecting layer formed of a plasma-resistant
and water-absorbing resin material is adhered and fixed to the
outer surface of an article in said processing chamber by its
swelling and then shrinkage to prevent electrical insulation of
said plasma and said article from each other.
2. In a protecting layer for plasma processing apparatus formed on
the outer surface of an article in the processing chamber of a
plasma processing apparatus, the improvement wherein said
protecting layer is formed of a plasma-resistant and
water-absorbing resin material so as to have such a shape that the
protecting layer becomes larger than the external shape of said
article in the processing chamber when it absorbs water.
3. In a method for installing a protecting layer for plasma
processing apparatus to be provided on the outer surface of an
article in the processing chamber of a plasma processing apparatus,
the improvement wherein said protecting layer is formed of a
plasma-resistant and water-absorbing resin material and allowed to
absorb water to be swollen, and the article in the processing
chamber is inserted into the protecting layer, after which water is
evaporated from said protecting layer by heating to shrink said
protecting layer, whereby the protecting layer is fixed to said
article.
4. In a method for installing a protecting layer for plasma
processing apparatus to be provided on the outer surface of an
article in the processing chamber of a plasma processing apparatus,
the improvement wherein said protecting layer is formed of a
plasma-resistant and water-absorbing resin material and allowed to
absorb water to be swollen, and the article in the processing
chamber is inserted into the protecting layer, after which water
contained in said protecting layer is evaporated while keeping said
protecting layer at a pressure lower than atmospheric pressure, to
shrink the protecting layer, whereby the protecting layer is fixed
to said article.
5. In a plasma processing apparatus in which a workpiece is treated
by creating a plasma in a processing chamber, the improvement
wherein a protecting layer formed of a plasma-resistant and
water-absorbing resin material comprising a polymeric material
having a relationship between relative dielectric constant
k.epsilon. and thickness t (.mu.m) of t/k.epsilon.<300 is
adhered and fixed to the outer surface of an article in said
processing chamber by its swelling and then shrinkage to prevent
electrical insulation of the plasma and the article from each
other.
6. In a plasma processing apparatus in which the creation of a
plasma and the control of energy for the introduction of ions into
a workpiece are independently carried out, the improvement wherein
one or more surfaces made of a grounded metal electric conductor
which come into contact with said plasma in the plasma processing
chamber of the apparatus are coated with a plasma-resistant
polymeric material having a relationship between relative
dielectric constant k.epsilon. and thickness t (.mu.m) of
t/k.epsilon.<300.
7. A plasma processing apparatus according to claim 6, wherein said
plasma-resistant polymeric material is formed on the inner surface
of said plasma processing chamber by spraying or coating.
8. A plasma processing apparatus according to claim 6, wherein said
plasma-resistant polymeric material is formed into a cylindrical
liner whose outside diameter is larger than the inside diameter of
said plasma processing chamber.
9. A plasma processing apparatus according to claim 8, wherein a
silicone resin is located on the periphery surface of said
cylindrical liner, and said cylindrical liner is closely attached
to the inner surface of said plasma processing chamber through the
silicone resin.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a plasma processing apparatus for
processing a workpiece by applying a high-frequency bias voltage to
the workpiece by use of a plasma, a protecting layer for plasma
processing apparatus provided in the processing chamber of the
plasma processing apparatus, and a method for installing the
protecting layer.
[0002] Apparatus such as that disclosed in JP-A-2001-57361 have
been known as a plasma processing apparatus for processing a
workpiece by applying a high-frequency bias voltage to the
workpiece by use of a plasma. The apparatus disclosed in the above
reference is as follows.
[0003] An antenna capable of emitting electromagnetic waves is
provided in the upper part of a plasma processing chamber. A bottom
electrode for setting a wafer thereon as a workpiece is provided in
the lower part of the plasma processing chamber. A processing gas
introduced into the plasma processing chamber is made into plasma
by the interaction between electromagnetic waves emitted by the
antenna and a magnetic field created by a magnetic-field-creating
means. A wafer is subjected to etching treatment by controlling
ions and radicals in the plasma by adjusting a bias electric power
applied to the antenna and a bias electric power applied to the
bottom electrode. For the etching treatment, a mixed gas containing
a fluorocarbon type gas is used as the treating gas. Thus, a
silicon dioxide film is etched.
[0004] A 2-mm thick sidewall sleeve composed of a resin layer of a
polyether imide or the like is provided on the inner wall of the
plasma processing chamber so as to be removable. Thus,
contamination with a metal from a metal wall surface constituting
the plasma treating chamber is prevented, and carbon-containing
deposits are stably accumulated on the resin layer to suppress the
production of contaminants.
[0005] As another prior art using a resin in order to prevent the
contamination, that disclosed in the specification of U.S. Pat. No.
4,397,724 (JP-B-4-62170) can be exemplified. This reference
discloses that a wafer is subjected to etching treatment after
being mounted in a reactor at least some of the inner surfaces of
which have been coated with a polyarylate polymer, and that a
thickness of the coating of about one-sixteenth inch is
advantageous.
BRIEF SUMMARY OF THE INVENTION
[0006] A first object of the present invention is to provide a
plasma processing apparatus that permits easy replacement of a
layer for protecting the outer surface of an article in the
processing chamber of the apparatus.
[0007] A second object of the present invention is to provide a
protecting layer for plasma processing apparatus that can easily be
attached to the outer surface of an article in the processing
chamber of a plasma processing apparatus.
[0008] A third object of the present invention is to provide a
method for installing a protecting layer for plasma processing
apparatus which permits easy attachment of the protecting layer to
the outer surface of an article in the processing chamber of a
plasma processing apparatus.
[0009] A fourth object of the present invention is to provide a
plasma processing apparatus which permits protection of the outer
surface of an article in the processing chamber of the apparatus
without lessening the effect of the article in the processing
chamber as an electrical ground for plasma.
[0010] A fifth object of the present invention is to provide a
plasma processing apparatus which prevents contamination with a
metal from a plasma processing chamber functioning as an electrical
ground, and permits easy control of the temperatures of one or more
surfaces exposed to a plasma in the processing chamber.
[0011] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a vertical cross-sectional view showing a plasma
etching apparatus as one example of the plasma processing apparatus
of the present invention.
[0013] FIG. 2 is a vertical cross-sectional view showing the
details of the bottom electrode portion of the apparatus shown in
FIG. 1 and portions around the bottom electrode.
[0014] FIG. 3A and FIG. 3B are perspective cross-sectional views of
a bottom-electrode cover and a cylindrical liner, respectively.
[0015] FIG. 4 is a flow chart showing a method for attaching the
cylindrical liner to the bottom-electrode cover of the apparatus
shown in FIG. 2.
[0016] FIG. 5 is a perspective cross-sectional view showing a
combination of the bottom-electrode cover and cylindrical liner of
the apparatus shown in FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In a plasma etching apparatus, the production of
contaminants in a processing chamber by plasma irradiation should
be suppressed. In order to suppress the production of contaminants,
a protecting layer is formed on each of the inner wall surface of
the processing chamber and the surface of an article in the
processing chamber. On the inner wall surface of the processing
chamber, the production of contaminants can be suppressed by
providing a sidewall sleeve (a cylindrical liner) made of a resin
such as a polyether imide, on the inner wall surface as in the
former prior art (JP-A-2001-57361) described above. On the surface
of the article in the processing chamber, a plasma-resistant
coating film is generally formed. The plasma-resistance coating
film is formed by modification into a plasma-resistant material,
such as anodized aluminum, or coating with a plasma-resistant
polymeric material.
[0018] In the former prior art (JP-A-57361), the attachment of a
resin layer (a protecting layer) to the inner wall surface of the
processing chamber is taken into consideration, but grounding for
plasma and the attachment of a resin layer to the surface of an
article in the treating chamber are not sufficiently taken into
consideration.
[0019] A high-frequency bias electric power should be applied to a
bottom electrode in a process in which the introduction of
high-energy ions is indispensable, such as etching of silicon
dioxide film. On the other hand, in an apparatus in which the
creation of a plasma and energy for the introduction of ions in the
plasma into a wafer are independently controlled [e.g. an apparatus
having in its plasma processing chamber an antenna capable of
emitting electromagnetic waves of a high-frequency electric power,
such as the antenna described above, and a bottom electrode which
faces the antenna and to which a bias voltage is applied; or an
apparatus having in its plasma processing chamber a top electrode
to which a high-frequency electric power is supplied and a bottom
electrode which faces the top electrode and to which a bias voltage
is applied], the antenna or top electrode which faces the bottom
electrode functions as a ground electrode with respect to a
high-frequency electric power for bias applied to the bottom
electrode. However, also in an apparatus having such a structure,
the inner wall surface of the electrically grounded plasma
processing chamber is etched by a plasma. This fact indicates that
the antenna or top electrode which faces the bottom electrode does
not function as a perfect electrical ground for high-frequency
electric power. The fact also indicates that a sheath is formed
between electrically grounded plasma processing chamber and the
plasma, so that the plasma processing chamber also functions as an
ground electrode for high-frequency electric power.
[0020] However, in the former prior art, the sidewall sleeve
provided on the inner wall surface of the processing chamber is as
thick as 2 mm. Therefore, the sidewall sleeve becomes a resistor
between the processing chamber and a plasma to a high-frequency
electric power, so that the processing chamber becomes ineffective
as a ground electrode. As a result, the surface of the sidewall
sleeve is covered with deposits composed of the components of a
processing gas used in a plasma process, resulting in causing a
problem of production of contaminants by the deposits.
[0021] In the former prior art, the outside diameter of the
sidewall sleeve is made smaller than the inside diameter of inner
wall of the processing chamber by about 0.1 mm to facilitate the
installation of sidewall sleeve in the processing chamber. During
plasma processing, the sidewall sleeve is swollen by heat
introduced from a plasma, to adhere to the inner wall of the
processing chamber. Thus, the conduction of heat between the
sidewall sleeve and the inner wall of the processing chamber is
improved. Such a sidewall sleeve, however, cannot be used on the
outer surface of an article such as that in the processing chamber
because it is thermally swollen during plasma processing.
[0022] On the other hand, in the method in which a plasma-resistant
coating film is formed on the surface of an article in the
processing chamber, the coating film is consumed by the sputtering
action of ions from a plasma, so that the time of maintenance of
the inhibitory effect on contaminants is determined by the
thickness of the coating film. In addition, the thickness of the
coating film is limited by a method for forming the coating film
and hence cannot be increased without a limitation. If the coating
film is consumed by repeated plasma processing operations, the
coating film should be reformed. In such maintenance, the timing of
reformation of the coating film and the cost of the reformation are
important. Moreover, depending on the thickness of the coating film
formed, the coating film becomes a resistor between a plasma and an
article in the grounded processing chamber to lessen the effect of
the article as an electrical ground.
[0023] Also in the latter prior art (the specification of U.S. Pat.
No. 4,397,724 (JP-B-4-62170)) described above, an electrical ground
for plasma is not sufficiently taken into consideration. When the
inner wall of a plasma processing chamber is coated with a
polyarylate polymer layer of about one-sixteenth inch in thickness
as in the latter prior art, the inner wall does not function as an
electrical ground for plasma. Therefore, a plasma diffuses in
search of an electrical ground, so that it is used for etching as a
low-density plasma. Moreover, since the ground potential is not
determined, a plasma created in the plasma processing chamber
diffuses, so that the plasma density on a wafer to be subjected to
etching process is decreased. Accordingly, the etching rate of the
wafer is decreased.
[0024] The present invention was made in order to solve the
problems in the above prior arts.
[0025] The above first object of the present invention can be
achieved as follow: in a plasma processing apparatus in which a
workpiece is treated by creating a plasma in a processing chamber,
a protecting layer formed of a plasma-resistant and water-absorbing
resin material is adhered and fixed to the outer surface of an
article in the processing chamber by its swelling and then
shrinkage to prevent electrical insulation of the plasma and the
article from each other.
[0026] The above second object can be achieved by forming a
protecting layer on the outer surface of an article in the
processing chamber of a plasma processing apparatus as follows: the
protecting layer is formed of a plasma-resistant and
water-absorbing resin material so as to have such a shape that the
protecting layer becomes larger than the external shape of the
article in the processing chamber when it absorbs water.
[0027] The above third object can be achieved as follows: in a
method for installing a protecting layer to be provided on the
outer surface of an article in the processing chamber of a plasma
processing apparatus, the protecting layer is formed of a
plasma-resistant and water-absorbing resin material and allowed to
absorb water to be swollen, and the article in the processing
chamber is inserted into the protecting layer, after which water is
evaporated from the protecting layer by heating to shrink the
protecting layer, whereby the protecting layer is fixed to the
article in the processing chamber.
[0028] In addition, the above third object can be achieved as
follows: in a method for installing a protecting layer to be
provided on the outer surface of an article in the processing
chamber of a plasma processing apparatus, said protecting layer is
formed of a plasma-resistant and water-absorbing resin material and
allowed to absorb water to be swollen, and the article in the
processing chamber is inserted into the protecting layer, after
which water contained in said protecting layer is evaporated while
keeping said protecting layer at a pressure lower than atmospheric
pressure, to shrink the protecting layer, whereby the protecting
layer is fixed to said article.
[0029] The above fourth object can be achieved as follows: in a
plasma processing apparatus in which a workpiece is processed by
creating a plasma in a processing chamber, a protecting layer
formed of a plasma-resistant and water-absorbing resin material
comprising a polymeric material having a relationship between
relative dielectric constant k.epsilon. and thickness t (.mu.m) of
t/k.epsilon.<300 is adhered and fixed to the outer surface of an
article in the processing chamber by its swelling and then
shrinkage to prevent electrical insulation of the plasma and the
article from each other.
[0030] The above fifth object can be achieved as follows: in a
plasma processing apparatus in which the creation of a plasma and
the control of energy for the introduction of ions into a workpiece
are independently carried out, one or more surfaces made of a
grounded metal electric conductor which come into contact with the
plasma in a plasma processing chamber are coated with a
plasma-resistant polymeric material having a relationship between
relative dielectric constant k.epsilon. and thickness t (.mu.m) of
t/k.epsilon.<300.
[0031] The plasma-resistant polymeric material is formed into a
cylindrical liner whose outside diameter is larger than the inside
diameter of the plasma processing chamber.
[0032] Silicone resin is located on the periphery surface of the
cylindrical liner, and the cylindrical liner is closely attached to
the inner surface of the plasma processing chamber through the
silicone resin.
[0033] Alternatively, the plasma-resistant polymeric material is
formed on the inner surface of the plasma processing chamber by
spraying or coating.
[0034] Another embodiment is as follows: in a plasma processing
apparatus for oxide film in which the creation of a plasma and the
control of energy for the introduction of ions into a workpiece are
independently carried out, the inner wall surface of a plasma
processing chamber which is made of a grounded metal electric
conductor and in which the plasma is created is coated with a
plasma-resistant polymeric material having a relationship between
relative dielectric constant k.epsilon. and thickness t (.mu.m) of
t/k.epsilon.<300.
[0035] Further another embodiment is as follows: in a plasma
processing apparatus equipped with a plasma processing chamber in
which at least one surface to be exposed to plasma is made of a
grounded metal; a plasma-creating means for creating a plasma with
a plasma density of 1.times.10.sup.3/cm.sup.3 (charged
particles/cm.sup.3) or more in the plasma processing chamber; a
workpiece holder provided in the plasma treating chamber in order
to set a workpiece thereon; and a high-frequency bias power source
connected to the workpiece holder and capable of giving an energy
sufficient to introduce ions in the plasma into the workpiece, the
RF output of said high-frequency bias power source being 1 KW or
more, the inner wall surface of metal portion of the plasma
processing chamber is coated with a plasma-resistant polymeric
material having a grounding function with respect to the RF
output.
[0036] Still another embodiment is as follows: in a plasma
processing apparatus in which the creation of a plasma and the
control of energy for the introduction of ions into a workpiece are
independently carried out, one or more surfaces made of a grounded
metal electric conductor which come into contact with the plasma in
a plasma processing chamber are coated with a plasma-resistant
polymeric material containing one or more electroconductive
materials.
[0037] The protecting layer formed on the inner wall of a plasma
processing chamber should have the following properties: it does
not cause contamination of a wafer owing to plasma processing such
as etching or does not scatter contaminants or the like on a wafer,
and the processing chamber functions as a ground electrode for
giving a reference potential to a plasma. Therefore, as a material
for the protecting layer, there is used a material which does not
become a cause of the contamination or a source of contaminants,
for example, a member made of a plasma-resistant polymeric material
composed of elements which constitute a gas used in an etching
process and a material to be etched. In addition, a material and a
structure which have a low electrical resistance value are used so
that the plasma processing chamber may act as an electrical
ground.
[0038] As a method for locating a plasma-resistant polymeric
material on the inner wall surface of a plasma processing chamber,
there are a method of forming the plasma-resistant polymeric
material into a cylindrical liner having an outside diameter larger
than the inside diameter of the plasma processing chamber, and
adhering and fixing the cylindrical liner to the inner wall surface
of the plasma processing chamber by utilizing the tension of the
material itself, and a method of providing the material on the
inner wall surface by spraying or applying the material on the
inner wall surface. In both methods, a metal constituting the
plasma processing chamber, i.e., a vacuum chamber is not directly
exposed to a plasma, so that the metal or the like is not scattered
from the wall. Thus, floating contaminants are not deposited on the
surface of a wafer for a semiconductor device and hence does not
cause an undesirable wiring failure. Furthermore, since the
plasma-resistant polymeric material is provided on the inner wall
surface of the plasma processing chamber so as to adhere thereto
closely, the conduction of heat from the inner wall of the plasma
treating chamber is improved by temperature controlling of the
plasma processing chamber and the surface which comes into contact
with a plasma can be thermostated with good controllability even in
a narrow temperature range (temperature region), so that it becomes
possible to prevent the adhesion of deposits easily.
[0039] As to a protecting layer formed on the surface of an article
to be exposed to a plasma in the plasma processing chamber, the
timing of reformation of the protecting layer and the cost of the
reformation are important. Moreover, depending on the thickness of
the protecting layer formed, the protecting layer becomes a
resistor between a plasma and the protected article to lessen the
effect of the article as an electrically grounded ground electrode.
Therefore, it is effective to attach a polymeric material as
plasma-resistant protecting member to the article in the processing
chamber in the form of a liner whose thickness can be freely set.
The liner should be closely adhered to the periphery surface of the
article so as not to get out of position, in order to protect the
article against the plasma while allowing the article in the
processing chamber to function as a ground electrode (i.e. as an
electrical ground), by utilizing the liner made of the
plasma-resistant polymeric material. A method for attaching the
liner is as follows. For example, when the periphery surface of a
cylindrical article such as a bottom-electrode cover is protected,
a cylindrical liner having an inside diameter a little smaller than
the outside diameter of the article is formed of a water-absorbing
plasma-resistant material such as a polyimide at first. Then, the
liner is allowed to absorb water and the article is inserted into
the liner swollen by the water absorption. The integrated body of
the cylindrical article and the liner is heated or placed in a
vacuum atmosphere, to evaporate the water contained in the liner
and shrink the liner. Thus, the plasma-resistant liner can be
strongly fixed even to the article in the processing chamber, such
as the cylindrical article.
[0040] When a polymeric material (relative dielectric constant
k.epsilon.: about 2.1 to about 4.2) such as a polyamide-imide,
polyether ether ketone, polyimde, polyether imide,
polytetrafluoroethylene, polybenzoimidazole or the like is used as
a material for the plasma contact surface in the plasma processing
chamber, metals such as iron, chromium and nickel and metal
compounds such as aluminum fluoride are not released from the
plasma contact surface.
[0041] Furthermore, a grounding function can be imparted to the
plasma processing chamber by setting the thickness of the
plasma-resistant polymeric material attached to each of the inner
wall surface of the plasma processing chamber and the periphery
surface of an article in the processing chamber to a thickness
smaller than a predetermined thickness. In prior art, a plasma
cover is located on the inner wall of a plasma processing chamber
and the thickness of the cover is specified, but physical property
values of a material for the cover are not taken into
consideration. Whether the inner wall of the plasma processing
chamber serves as an electrical ground for a plasma or not is
determined by the thickness and relative dielectric constant of the
material, and it was found that the value of the relationship
between relative dielectric constant k.epsilon. and thickness t
(.mu.m) (t/k.epsilon.) is important. It was also found that the
specification of values of the above relative dielectric constant
k.epsilon. and thickness t (.mu.m) is important particularly in the
case of a polymeric material because the relative dielectric
constant changes depending on starting materials to be mixed, the
sequence state and temperature.
[0042] It is also possible to allow a plasma-resistant material to
function as an electrical ground for plasma, by incorporating one
or more electroconductive materials such as silicon, carbon, etc.
into the plasma-resistant material. In this case, a protecting
layer for the wall contains the electroconductive material(s) and
acts as an electrical ground, so that a plasma does not diffuse
widely in the plasma processing chamber. Since the silicon and/or
carbon incorporated into the plasma-resistant material is the same
as in the case of an element and a resist material, a wafer is not
contaminated therewith.
[0043] Moreover, since a plasma-resistant material composed of the
above-exemplified polymeric material is composed mainly of elements
such as carbon, oxygen and hydrogen which are the same as the
components of a resist, it has no undesirable influence on the
processing of a wafer.
[0044] Thus, the amount of contaminants on a wafer to be subjected
to plasma processing and the degree of contamination of the wafer
can be reduced, so that the fraction defective of the wafers
subjected to plasma processing can be reduced. Therefore, the
productivity of the plasma processing apparatus itself can be
improved by locating the plasma-resistant material according to the
present invention on the plasma contact surface in the plasma
processing chamber of the apparatus.
[0045] Examples of the present invention are explained below with
reference to FIGS. 1 to 5.
[0046] FIG. 1 shows a plasma etching apparatus to which the present
invention has been applied. In detail, FIG. 1 shows an ECR type
plasma etching apparatus in which an antenna emits electromagnetic
waves and a plasma is created by the interaction between the
electromagnetic waves and a magnetic field. The temperature of the
inner wall surface of a plasma processing chamber, i.e., an etching
chamber 1 in this case can be adjusted in a temperature range of 20
to 100.degree. C. by a thermostating means not shown. An antenna 3
is located in the upper part of the etching chamber 1 in this case
through a dielectric 2. A high-frequency power source 6 capable of
generating UHF electromagnetic waves in this case is connected to
the antenna 3 through a coaxial line 4 and a matching box 5. The
dielectric 2 provided between the etching chamber 1 and the antenna
3 can transmit electromagnetic waves. A magnetic-field coil 7 for
forming a magnetic field in the etching chamber 1 is provided
around the periphery of the etching chamber 1. A bottom electrode
10 as a workpiece holder for setting a wafer 9 thereon as a
workpiece is provided under the antenna 3 in the etching chamber 1.
To the bottom electrode 10 are connected a high-frequency bias
power source 11 for giving energy for introduction into the wafer 9
to ions in a plasma and a DC power source 12 for adsorbing the
wafer 9 electrostatically on the bottom electrode 10. Numeral 8
denotes a gas feeder for feeding a processing gas into the etching
chamber 1.
[0047] The etching chamber 1 is made of a metal and is grounded.
The inner wall surface of the etching chamber 1 is coated with a
resin layer 14 composed of a plasma-resistant polymeric material.
In this case, the resin layer 14 is a 630-.mu.m thick cylindrical
liner made of a polytetrafluoroethylene. The outside diameter of
the resin layer 14 is made larger than the inside diameter of the
etching chamber 1 by about 0.2 to about 0.3 mm so that the resin
layer 14 may be closely adhered to the inner wall of the etching
chamber 1 when set in the etching chamber 1. In this case, the
adhesion is further improved when the resin layer 14 is set in the
etching chamber 1 after locating flexible silicone resin with a
high thermal conductivity on the outer surface of the resin layer
14 or thinly coating a silicone resin on outer surface of the resin
layer 14. Thus, the difference between the temperatures of the
resin layer 14 and the inner wall of the etching chamber 1 is
narrowed down. The frequency of reformation of the resin layer 14
is preferably reduced by increasing the thickness of the resin
layer 14. Therefore, a plasma-resistant polymeric material having
as high a relative dielectric constant k.epsilon. as possible is
preferably used.
[0048] When the resin layer 14 is too thin to be formed into a
cylindrical liner, the resin layer 14 can be formed in the etching
chamber 1 by dissolving the resin in a solvent, spraying the
resulting solution, and controlling the thickness of the resin
layer 14 by adjusting, for example, the number of spraying
operations. In this case, the thermal conductivity is further
improved because the resin layer is completely adhered to the inner
wall surface of the etching chamber 1.
[0049] When the resin layer 14 have a thickness of more than about
500 .mu.m, it can be formed into a cylindrical liner. When the
resin layer 14 is formed by the spraying method, it can be formed
in a thickness of upto about 500 .mu.m. In addition, when the
spraying method is adopted, the resin layer 14 can be formed in a
thickness of about 800 .mu.m or more by incorporating one or more
electroconductive materials such as a silicon, carbon, etc. into
the resin layer 14.
[0050] FIG. 2 is a detail view of the bottom electrode 10. A
grounded electrode cover 104 is provided at the periphery of an
electrode 101 through an insulating material 102. A cylindrical
liner 105, i.e., a cylindrical protective member molded from a
polyimide in this case is adhered and fixed to the periphery
surface of the electrode cover 104. The purpose of grounding the
electrode cover 104 is to prevent the diffusion of a plasma 13
caused when the plasma 13 misses the ground potential. Numeral 103
denotes an insulating cover covering the periphery of the wafer 9
on the electrode 101.
[0051] In the apparatus constructed in the manner described above,
UHF electromagnetic waves outputted from the high-frequency power
source 6 are supplied to the etching chamber 1 from the antenna 3
through the matching box 5, the coaxial line 4 and the dielectric
2. On the other hand, a magnetic field is formed in the etching
chamber 1 by the solenoid coil 7 around the etching chamber 1. An
etching gas introduced into the etching chamber 1 is efficiently
made into plasma by the interaction of the electric field due to
electromagnetic waves and the magnetic field due to the solenoid
coil. Using this plasma 13, the wafer 9 on the bottom electrode 10
is subjected to a predetermined etching process. As the plasma used
for such a process, a plasma having a density of about
1.times.10.sup.10/cm.sup.3 or more is used. In the etching process,
energy for the introduction of ions in the plasma into the wafer 9
is set so as to give a desirable etched shape, by controlling the
energy by use of the high-frequency bias power source 11. In a
process requiring a high bias voltage, such as the etching process
of an insulating film typified by a silicon dioxide film, the RF
output from the high-frequency bias power source 11 should be 1 kW
or more.
[0052] On the other hand, electric circuits are formed among an
electrical ground, the high-frequency bias power source 11, the
bottom electrode 10, the plasma 13 and the antenna 3 and between
the etching chamber 1 and an electrical ground, respectively. In
this case, an ion sheath is formed also between the etching chamber
1 and the plasma 13, so that ions in the plasma 13 are introduced
into the inner wall of the etching chamber 1. In the vicinity of
the bottom electrode 10, an ion sheath is formed also between the
grounded electrode cover 104 and the plasma 13, so that ions in the
plasma 13 are introduced also into the outer wall of the electrode
cover 104.
[0053] In this case, a grounding function can be imparted to the
plasma-resistant protecting layer (the cylindrical liner 105)
attached to the surface of the electrode cover 104, in the plasma
processing chamber (the etching chamber 1) by setting the thickness
of the protecting layer at a thickness not larger than a
predetermined thickness.
[0054] A sheath of plasma is present in the vicinity of the inner
wall surface of the plasma processing chamber in which a plasma has
been created and in the vicinity of the outer surface (the outer
wall surface) of an article in the processing chamber. When the
plasma is used for etching, the thickness of the sheath is
determined by the plasma density. The plasma density is determined
by the composition of a gas used and an RF output employed. For
example, when the density of the plasma created is about
1.times.10.sup.10/cm.sup.3, the thickness of the sheath is about
600 .mu.m. The relative dielectric constant k.epsilon. in the
sheath is about 1.0, and the sheath resistance between the plasma
and the wall can be considered to be 600/1.0=600. When a resistor
made of a resin or Alumilite is inserted between the sheath and the
wall, it was experimentally found that the wall can be regarded as
an electrical ground for the plasma even if such a resistor having
a resistance about one-half (about 300) as high as the sheath
resistance is inserted.
[0055] Therefore, under conditions which satisfy the condition
t/k.epsilon.<300 wherein k.epsilon. is the relative dielectric
constant of the resistor inserted between the sheath and the wall
and t (mm) is the thickness of the resistor, the wall covered with
the resistor acts as an electrical ground for the plasma. According
to this fact, the thickness of the resistor can be about 1065 .mu.m
or less when a polyimide resin (relative dielectric constant: 3.55)
is used as the resistor. The thickness of the resistor can be about
630 .mu.m or less when a polytetrafluoroethylene (relative
dielectric constant: 2.1) is used as the resistor.
[0056] For example, when a silicon dioxide film is etched with a CF
type gas (C.sub.4F.sub.8, C.sub.5F.sub.8 or the like), CxFy ions
are produced in the plasma 13 and are drawn toward the etching
chamber 1. In this case, the CxFy ions are introduced into the
resin layer 14 because the resin layer 14 is provided on the inner
wall surface of the etching chamber 1. Since the resin layer 14 of
a polymeric material is composed of a CHF type compound and hence
has the same components as the ion components in the plasma,
reaction products produced by the reaction of ions in the plasma
with the resin layer 14 and the components of the resin layer 14
subjected to sputtering by the ions are also CF type compounds.
Therefore, their undesirable influences on the etching process can
be prevented. Thus, the resin layer 14 according to the present
example is effective in a process in which a CF type gas is used as
a processing gas.
[0057] When the relative dielectric constant k.epsilon. of the
resin layer 14 is taken as 2.1, the thickness of the resin layer 14
having a relationship of t/k.epsilon.<300 is 630 .mu.m. When the
material according to the present example, i.e., a cylindrical
liner of polytetrafluoroethylene is used, the etching chamber 1 can
be allowed to act as an electrical ground. Therefore, the potential
of the plasma 13 can be stabilized, so that a desirable etching
process can be carried out by applying a necessary bias voltage to
the wafer 9 by use of the high-frequency bias power source 11.
[0058] In a process in which the application of a high bias voltage
to the wafer 9 is unnecessary in etching process of a silicon
dioxide film or the like, the sheath voltage between the etching
chamber 1 and the plasma 13 is low, so that the thickness of the
resin layer 14 should be reduced.
[0059] FIG. 3A shows a schematic perspective section of the
electrode cover 104. FIG. 3B shows a schematic perspective section
of the cylindrical liner 5 made of a polyimide which is a
protecting layer. FIG. 4 shows a flow chart in the case of
attaching the cylindrical liner 105 to the electrode cover 104.
[0060] At first, the cylindrical liner 105 as a polyimide
protective member for the electrode cover 104 is formed so that its
inside diameter may become larger than the outside diameter of the
electrode cover 104 when the cylindrical liner 105 absorbs water to
swell. That is, the inside diameter of the cylindrical liner 105 is
set at a size a little smaller than the outside diameter of the
electrode cover 104 in view of the expansion coefficient of the
cylindrical liner 105 at the time of water absorption (shown in
step 31 in FIG. 4). Although the thickness of the cylindrical liner
105 can be freely set, it should be set according to the output of
high-frequency electric power so that the cylindrical liner 105 may
become an electrical ground for a high-frequency voltage applied to
the bottom electrode 10.
[0061] Then, the cylindrical liner 105 formed in the manner
described above is allowed to absorb water by its immersion in a
vessel containing pure water at ordinary temperature, to be swollen
(shown in step 32 in FIG. 4). In this case, the inside diameter of
the cylindrical liner 105 becomes a little larger than the outside
diameter of the electrode cover 104. Although pure water at
ordinary temperature is absorbed above, employment of warm water is
also effective. Or, in place of immersing in the pure water tank,
the pure water can be sprayed for water absorption, or there may be
used in place of the pure water an alcohol or the like, which the
liner absorbs to swell. Thereafter, as shown in FIG. 5, the
electrode cover 104 is inserted into the water-absorbed swelled
cylindrical liner 105 (shown in step 33 in FIG. 4). Next, the
cylindrical liner 105 having the electrode cover 104 inserted
thereinto is heated in a baking furnace to evaporate water and
shrink the liner (shown in step 34 in FIG. 4). In this case, the
heating temperature is set at a temperature that deteriorates
neither the electrode cover 104 nor the cylindrical liner 105.
Owing to the shrinkage, the cylindrical liner 105 as a protective
member is adhered and fixed to the electrode cover 104 (shown in
step 35 in FIG. 4). As a method for evaporating water, there may be
adopted a method of maintaining the cylindrical liner 105 having
the electrode cover 104 inserted thereinto, at a pressure lower
than atmospheric pressure, or a combination of this method and
heating may be employed.
[0062] As described above, according to the present example, the
protecting layer as a plasma-resistant protective member is adhered
and fixed to each of the inner wall surface of the plasma
processing chamber and an article in the plasma processing chamber,
whereby contamination with metals from the inner wall surface and
the article surface can be prevented. Moreover, by optimizing a
material for covering the inner wall surface and the article
surface and the thickness of the layer, a grounding function can be
imparted to these surfaces.
[0063] In addition, in the present example, the plasma creation and
the control of energy for the introduction of ions into the wafer
are independently carried out, so that a plasma having a necessary
density can be stably created without any influence of the control
of energy for the introduction of ions. In such an etching
processing apparatus, the etching chamber can be regarded as an
electrical ground by coating the grounded inner wall surface of the
etching chamber with a plasma-resistant polymeric material having a
relationship between relative dielectric constant k.epsilon. and
thickness t (.mu.m) of t/k.epsilon.<300, so that a stable plasma
potential can be given.
[0064] Although a polyimide is used as a material for the
protective member of plasma-resistant polymeric material in the
example, there may be used other plasma-resistant and
water-absorbing polymeric materials such as polyamide-imides,
polyether ether ketones, polyether imides,
polytetrafluoro-ethylenes, polybenzoimidazoles, etc.
[0065] According to the present example, in the case of etching a
wafer into a desirable shape by applying a bias voltage obtained at
a high-frequency output of 1 kW or more to the bottom electrode
which etching requires a high energy for the introduction of ions
in a plasma into the wafer, the following advantages can be
obtained. Even if the inner wall surface of the etching chamber and
an article in this processing chamber are etched by their reaction
and sputtering, contamination with metals from the etching chamber
and the article in this processing chamber can be prevented because
the inner wall surface of the etching chamber and the surface of
the article in this processing chamber are protected with the
plasma-resistant polymeric material containing the same components
as those of a processing gas system. Moreover, the reaction
products and sputtered layer produced by the inner wall surface
have no undesirable influence on the process because they have the
same components as those of the processing gas system. Thus, the
fraction defective of wafers subjected to the etching process can
be reduced, so that the productivity of the etching apparatus can
be improved. Furthermore, since the inner wall surface of the
etching chamber 8 is coated with the plasma-resistant polymeric
material, the heat of the thermostated etching chamber is
efficiently transmitted to the plasma-resistant polymeric material,
so that the temperatures of one or more surfaces to be exposed to
the plasma can easily be controlled.
[0066] According to the present example, a resin layer can be
provided on the inner wall surface of the etching chamber so as to
be closely adhered to the inner wall surface. Therefore, the
temperature of the inner surface of the resin layer can be
equalized with the temperature of the thermostated etching chamber,
and reaction products produced during the etching process of a
silicon dioxide film can be prevented from depositing on the inner
wall surface of the etching chamber, by adjusting the wall surface
temperature of the etching chamber to about 80.degree. C. or
higher.
[0067] According to the present example, the resin layer can be
provided on the inner wall surface of the etching chamber so as to
be closely adhered to the inner wall surface. Therefore, the
temperature of the inner surface of the resin layer can be
equalized with the temperature of the thermostated etching chamber,
and reaction products produced during the etching process of a
silicon dioxide film can be deposited on the inner wall surface of
the etching chamber so as to be strongly adhered to the inner wall
surface, by adjusting the wall surface temperature of the etching
chamber to about 40.degree. C. or lower. Accordingly, peeling of
the adhered deposits can be prevented, so that the adhesion of
contaminants derived from the reaction products to the wafer by
their scattering can be prevented.
[0068] According to the present example, the plasma-resistant
polymer protecting layer can easily be attached also to the outer
surface of an article as in the case of the surface of an article
in the etching chamber by forming the protecting layer into a
cylindrical liner and swelling the liner by water absorption. The
liner can easily be closely adhered to the article by evaporating
(removing) water from the liner attached to the article.
[0069] Although a method for attaching the cylindrical liner to the
cylindrical article is described in the present example, the
present invention can be conducted in the same manner as above not
only in the case of a cylindrical article but also in the case of
an article having, for example, a polygonal shape or the like.
[0070] In addition, although the plasma etching apparatus is
described in the present example, an article in a processing
chamber can be protected by the same means as above also in other
plasma processing apparatus.
[0071] When one or more electroconductive materials are
incorporated into the plasma-resistant polymeric material, the
resin layer itself tends to be thinned by a plasma. However, since
the resin layer has electroconductivity, a grounding function can
be imparted to the resin layer even when the thickness of the resin
layer is increased. Moreover, the thickness of the resin layer can
easily be increased. Therefore, such a resin layer is effectively
used in an apparatus in which a process using a low bias voltage is
employed.
[0072] The present example have the following other
characteristics.
[0073] (1) A plasma processing apparatus for oxide film in which
the creation of a plasma and the control of energy for the
introduction of ions into a workpiece are independently carried
out, said apparatus being characterized in that the inner wall
surface of a plasma processing chamber which is made of a grounded
metal electric conductor and in which the plasma is created is
coated with a plasma-resistant polymeric material having a
relationship between relative dielectric constant k.epsilon. and
thickness t (.mu.m) of t/k.epsilon.<300.
[0074] (2) A plasma processing apparatus equipped with a plasma
processing chamber in which at least one surface to be exposed to
plasma is made of a grounded metal; a plasma-creating means for
creating a plasma with a plasma density of
1.times.10.sup.10/cm.sup.3 or more in said plasma processing
chamber; a workpiece holder provided in said plasma processing
chamber in order to set a workpiece thereon; and a high-frequency
bias power source connected to said workpiece holder and capable of
giving an energy sufficient to introduce ions in said plasma into
said workpiece, the RF output of said high-frequency bias power
source being 1 KW or more, which apparatus is characterized in that
the inner wall surface of metal portion of said plasma processing
chamber is coated with a plasma-resistant polymeric material having
grounding function with respect to said RF output.
[0075] (3) A plasma processing apparatus in which the creation of a
plasma and the control of energy for the introduction of ions into
a workpiece are independently carried out, said apparatus being
characterized in that one or more surfaces made of a grounded metal
electric conductor which come into contact with said plasma in a
plasma processing chamber are coated with a plasma-resistant
polymeric material containing one or more electroconductive
materials.
[0076] According to the present invention described above, the
following effect can be obtained: a protecting layer member can
easily be attached to the outer surface of an article in the
processing chamber of a plasma processing apparatus, so that the
protecting layer can easily be replaced.
[0077] According to the present invention, the following effect can
also be obtained: there can be provided a method for attaching a
protecting layer for plasma processing apparatus which permits easy
attachment of the protecting layer to the outer surface of an
article in the processing chamber of a plasma processing
apparatus.
[0078] In addition, according to the present invention, the
following effect can also be obtained: there can be provided a
plasma processing apparatus which permits protection of the outer
surface of an article in the processing chamber of the apparatus
without lessening the effect of the article in the processing
chamber as an electrical ground for plasma.
[0079] Furthermore, according to the present invention, the inner
surface of a plasma processing chamber can be made into an
electrical ground for plasma by setting the thickness of a material
covering the inner wall surface of the plasma processing chamber
and an article in the processing chamber at such a thickness that
the relationship between the relative dielectric constant
k.epsilon. and thickness t (.mu.m) of the material is
t/k.epsilon.<300. It is also possible to prevent contamination
with metals from the plasma processing chamber and an article in
the processing chamber which are allowed to act as ground
electrodes. The present invention has such an effect that a
protecting layer can be installed so as to be closely adhered and
that the temperatures of one or more surfaces exposed to a plasma
can easily be controlled.
[0080] It should be further understood by those skilled in the art
that the foregoing description has been made on embodiments of the
invention and that various changes and modifications may be made in
the invention without departing from the spirit of the invention
and scope of the appended claims.
* * * * *