U.S. patent application number 09/407051 was filed with the patent office on 2002-03-07 for electrostatic chuck.
Invention is credited to YAMAGUCHI, SHINJI.
Application Number | 20020027762 09/407051 |
Document ID | / |
Family ID | 17542655 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020027762 |
Kind Code |
A1 |
YAMAGUCHI, SHINJI |
March 7, 2002 |
ELECTROSTATIC CHUCK
Abstract
An electrostatic chuck includes a substrate, inner electrode and
outer electrodes each made of a metal and concentrically buried in
the substrate, a plurality of embossed portions formed on a main
plane of the substrate, a projecting portion made of the same
material as that of said plurality of the embossed portions and
formed on substantially an entire outer peripheral portion on the
main plane of the substrate on which the embossed portions are
formed, wherein positive and negative potentials are to be applied
to the inner and outer electrode, respectively, or vice versa, an
object to be treated is to be supported by the embossed portions
and the projecting portion, and a sum of a total area of upper
surfaces of the embossed portions in an outer electrode-located
zone of the substrate and an area of an upper surface of the
projecting portion in the outer electrode-located zone of the
substrate is in a range of 0.7 to 1.3 of a total area of upper
surfaces of the embossed portions in an inner electrode-located
zone of the substrate.
Inventors: |
YAMAGUCHI, SHINJI; (AICHI
PREF, JP) |
Correspondence
Address: |
BURR & BROWN
PO BOX 7068
SYRACUSE
NY
13261-7068
US
|
Family ID: |
17542655 |
Appl. No.: |
09/407051 |
Filed: |
September 27, 1999 |
Current U.S.
Class: |
361/234 ;
279/128 |
Current CPC
Class: |
G03F 7/707 20130101;
H01L 21/6831 20130101; Y10T 279/23 20150115; G03F 7/70708
20130101 |
Class at
Publication: |
361/234 ;
279/128 |
International
Class: |
H02N 013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 1998 |
JP |
10-274.506 |
Claims
What is claimed is:
1. An electrostatic chuck comprising a substrate, an inner
electrode and an outer electrode each made of a metal and
concentrically buried in the substrate, a plurality of embossed
portions formed on a main plane of the substrate, a projecting
portion made of the same material as that of said plurality of the
embossed portions and formed on substantially an entire outer
peripheral portion on the main plane of the substrate on which said
plurality of the embossed portions are formed, wherein positive and
negative potentials are to be applied to the inner and outer
electrode, respectively, or vice versa, an object to be treated is
to be supported by said plurality of said embossed portions and the
projecting portion, and a sum of a total area of upper surfaces of
the embossed portions in a zone of the substrate in which the outer
electrode is located and an area of an upper surface of said
projecting portion in the zone of the substrate in which the outer
electrode is located is in a range of 0.7 to 1.3 of a total area of
upper surfaces of the embossed portions in a zone of the substrate
in which the inner electrode is located.
2. The electrostatic chuck set forth in claim 1, which further
comprises a means to flow a back side gas in a space defined by the
embossed portion, the projecting portion, the object to be treated,
and said main plane of the substrate.
3. The electrostatic chuck set forth in claim 1 or 2, wherein an
area of the zone of the substrate where the inner electrode is
located is equal to that of the zone of the substrate where the
outer electrode is located, and a density of the embossed portions
in the zone of the substrate where the inner electrode is located
is larger than that in the zone of the substrate where the outer
electrode is located.
4. The electrostatic chuck set forth in claim 1 or 2, wherein an
area of the zone of the substrate where the inner electrode is
located is larger than that in the zone of the substrate where the
outer electrode is located, and a density of the embossed portions
in the zone of the substrate where the inner electrode is located
is larger than that in the zone of the substrate where the outer
electrode is located.
5. The electrostatic chuck set forth in claim 2, wherein an area of
the zone of the substrate where the outer electrode is located is
smaller than that in the zone of the substrate where the inner
electrode is located, a total area of the upper surfaces of the
embossed portions per a unit electrode area in the zone of the main
plane of the substrate where the outer electrode is located is
larger than a total area of the upper surfaces of the embossed
portions per a unit electrode area in the zone of the main plane of
the substrate where the inner electrode is located.
6. The electrostatic chuck set forth in any one of claims 1 to 5,
wherein the inner electrode has a negative potential, and the outer
electrode has a positive potential.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] The present invention relates to an electrostatic chuck, and
particularly to an electrostatic chuck favorably usable for holding
a wafer in a semiconductor-producing apparatus.
[0003] (2) Related Art Statement
[0004] At present, electrostatic chucks are used for attracting and
holding semiconductor wafers in finely working, e.g., transferring,
exposing, film-forming by CVD, washing, etching, and ding the
semiconductor wafers.
[0005] As disclosed in, for example, JP-A 8-55,900, such an
electrostatic chuck a discoid positive electrode 2 and a discoid
negative electrode 3 are buried in a substrate 1 made of a ceramic
material or the like as shown in FIGS. 1 and 2, and an object 7 to
be treated, such as a semiconductor wafer, is attracted onto a main
plane 1A of the substrate 1 through an electric field generated by
applying a given voltage between the electrodes from a DC power
source 6. FIG. 2 is a plane view of the electrostatic chuck of FIG.
1 as viewed from an upper side. In FIG. 2, the object 7 is omitted
for facilitating the explanation.
[0006] However, since the electrostatic chuck with such a
construction has a relatively large electrode gap 8 between the
positive and negative electrodes 2 and 3, the electric field
generated there is not enough with the result that attracting force
for the object 7 to be treated is not sufficient near the gap 8
between the electrodes.
[0007] For this reason, the object 7 does not fully contact the
main plane 1A of the substrate 1 at the gap between the electrodes,
so that heat is not fully conducted to the object 7 from the
substrate and consequently the entire object 7 cannot be uniformly
heated.
[0008] Further, since the attracting force may vary dependent upon
any different in a buried depth between the positive and negative
electrodes 2 and 3 and different polarities of the applied voltage,
the degree for the object 7 to contact the main plane 1A of the
substrate 1 differs between a zone where the positive electrode 2
is positioned and a zone where the negative electrode 3 is
positioned, which causes variations in the heat conductivity.
SUMMARY OF THE INVENTION
[0009] It is therefore an objective of the present invention to
provide an electrostatic chuck which can uniformly attract an
object to be treated and uniformly transfer the heat to the
object.
[0010] The present invention relates to the electrostatic chuck
comprising a substrate, an inner electrode and an outer electrode
each made of a metal and concentrically buried in the substrate, a
plurality of embossed portions formed on a main plane of the
substrate, a projecting portion made of the same material as that
of said plurality of the embossed portions and formed on
substantially an entire outer peripheral portion on the main plane
of the substrate on which said plurality of the embossed portions
are formed, wherein positive and negative potentials are to be
applied to the inner and outer electrode, respectively, or vice
versa, an object to be treated is to be supported by said plurality
of said embossed portions and the projecting portion, and a sum of
a total area of upper surfaces of the embossed portions in a zone
of the substrate in which the outer electrode is located and an
area of an upper surface of said projecting portion in the zone of
the substrate in which the outer electrode is located is in a range
of 0.7 to 1.3 of a total area of upper surfaces of the embossed
portions in a zone of the substrate in which the inner electrode is
located.
[0011] These and other objects, features and advantages of the
invention will be apparent from the reading of the following
description of the invention when taken in conjunction with the
attached drawings, with the understanding that some modifications,
variations and changes of the same could be easily made by the
skilled person in the art to which the invention pertains.
BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS
[0012] For a better understanding the invention, reference is made
to the attached drawings, wherein:
[0013] FIG. 1 is a sectional view of a conventional electrostatic
chuck;
[0014] FIG. 2 is a plane view of the conventional electrostatic
chuck;
[0015] FIG. 3(a) is a plane view of an embodiment of the
electrostatic chuck according to the present invention, FIG. 3(b)
being a cross sectional view of FIG. 3(a) along with a line
III(b)-III(b);
[0016] FIG. 4 is a plane view of another embodiment of the
electrostatic chuck according to the present invention; and
[0017] FIG. 5 is a further embodiment of the electrostatic chuck
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] FIG. 3 is a plane view of an embodiment of the electrostatic
chuck according to the present invention. FIG. 3 gives an outward
appearance of the electrostatic chuck as viewed from the upper side
as in FIG. 2. In FIG. 3, an object to be treated is omitted,
too.
[0019] As shown in FIG. 3, in the electrostatic chuck according to
the present invention, an inner electrode 12 and an outer electrode
13 are concentrically arranged in a substrate 11, and positive and
negative potentials are to be applied to the inner and outer
electrode, respectively, or vice versa, so that an electric field,
i.e., an attracting force, can be uniformly formed as viewed in a
circumferential direction.
[0020] Further, a plurality of embossed portions 14 are formed on a
main plane 11A of a substrate, a projecting portion 15 is formed of
the same material as that of said plurality of the embossed
portions on an entire outer peripheral portion on the main plane
11A of the substrate 11, a sum of a total area of upper surfaces
14B of the embossed portions 14 in a zone 18 of the substrate in
which the outer electrode 13 is located and an area of an upper
surface 15A of said projecting portion 15 in a zone of the
substrate in which the outer electrode is located (this zone being
a zone of the substrate outwardly defined by a dotted line DL 2) is
in a range from 0.7 to 1.3 of a total area of upper surfaces 14A of
the embossed portions 14 in a zone of the substrate in which the
inner electrode 12 is located (this zone being a zone 17 of the
substrate internally defined by a dotted line DL 1), and an object
to be treated is to be supported by said plurality of said embossed
portions and the projecting portion. Therefore, the attracting
force is exerted upon the object by the electrodes uniformly as
viewed in the circumferential direction of the object. Thus, the
object to be treated can be uniformly heated.
[0021] Further, a positively charged amount of the object to be
treated is equal to a negatively charged amount thereof, so that
they are offset with each other to prevent the object from being
charged. Therefore, electric breakdown due to discharging between
the object and a member near it can be prevented.
[0022] Furthermore, since the object is in an intermediate
potential for the applied positive and negative potentials, the
attracting force between the object and one of the electrodes is
equal to that between the object and the other.
[0023] As shown in FIG. 3, the wording "the total area of upper
surfaces of the embossed portions in a zone of the substrate in
which the inner electrode is located" means the total area of the
upper surfaces 14A of the embossed portions which exist inside the
zone 17 in which the inner electrode 12 is located, in other words,
this total area is a value obtained by subtracting the total area
of the upper surfaces 14c of the embossed portions (See black parts
of the upper surfaces of the embossed portions crossing the dotted
line DL1) from the total area of the upper faces 14A of the
embossed portions 14 overlapping with the zone 17.
[0024] Similarly, the wording "the total area of upper surfaces of
the embossed portions in a zone of the substrate in which the outer
electrode is located" means the total area of the upper surfaces
14B of the embossed portions 14 which overlap the zone 18 in which
the inner electrode 12 is located.
[0025] The term "upper surface of the embossed portion" used herein
means a contact surface of the embossed portion between an object
to be treated in the state that the object is placed on the
electrostatic chuck. Since the object is generally a planar object
such as a wafer, it is preferable that the upper surfaces of a
plurality of the embossed portions and that of the projecting
portion are substantially flat and in flush with one another. It is
preferable that the embossed portion has a pillar shape, for
example, a pillar shape with a polygonal section, a pillar shape
with a round section or a pillar shape with an elliptical
section.
[0026] Further, as shown in FIGS. 3(a) and 3(b), the wording "an
area of an upper surface of said projecting portion in a zone of
the substrate in which the outer electrode is located" means the
area of the upper surface 15A of the projecting portion which
overlaps with the zone 18 in which the outer electrode 13 is
located, in other words, it means the area of the upper surface
part 15B (See a network pattern surface portion) of the projecting
portion outside the zone 18 in which the outer electrode is
positioned from the area of the upper surface 15A of the projecting
portion 15.
[0027] In the present invention, assuming that the total area of
the upper surfaces of the embossed portions formed in the zone of
the main plane of the substrate where the inner electrode is
located is taken as 1, the sum between the total area of upper
surfaces of the embossed portions in a zone of the main plane of
the substrate in which the outer electrode is located and the area
of the upper surface of the projecting portion in the zone of the
substrate in which the outer electrode is located is in a range of
0.7 to 1.3. In other words, the above means the following
inequalities. 1 0.7 V I - V W V w - V o 1.3
[0028] in which V.sub.I is a potential applied to the inner
electrode, V.sub.W is a potential generated in the object placed on
the electrostatic chuck for treatment, and V.sub.O is a potential
applied to the outer electrode.
[0029] The present invention will be explained in more detail based
on preferred embodiments of the present invention with reference to
the drawings.
[0030] A first preferred embodiment of the electrostatic chuck
according to the present invention has a plane view as shown in
FIG. 3(a). In this embodiment, the area of the zone 17 of the
substrate in which the inner electrode 12 is located is
substantially in a range of 0.7 to 1.3 that of the zone 18 of the
substrate in which the outer electrode 13 is located. The density
of the embossed portions on the main plane 11A of the substrate 11
in the zone 17 in which the inner electrode 12 is located is larger
than that of the embossed portions on the main plane 11A of the
substrate 11 in the zone 18 in which the outer electrode 13 is
located.
[0031] By so constructing, since the object is more closely contact
the inner side of the electrostatic chuck, the heat conductivity in
the inner side can be made larger. For this reason, when a high
frequency voltage is applied between the inner electrode 12 and the
outer electrode 13, the outer side of the object can be prevented
from being heated to a high temperature with the heat of
plasma.
[0032] However, the above construction is not necessarily
indispensable to attain the objective of the present invention, and
any other construction may be employed so long as the requirement s
of the present invention are satisfied.
[0033] In this embodiment, a negative potential is applied to the
inner electrode 12, whereas a positive potential is applied to the
outer electrode 13. However, the inner electrode 12 and the outer
electrode 13 only have to be concentrically formed so as to attain
the objective of the present invention. Therefore, it may be that a
positive potential is applied to the inner electrode 12, whereas a
negative potential is applied to the outer electrode 13.
[0034] If the negative and positive potentials are applied to the
inner and outer electrodes 12, 13, respectively, the density of
lines of the electric force can be increased, to more firmly
attract the object to the substrate, although the reason has not
been clarified.
[0035] The size of a gap between the electrodes is not particularly
limited so long as the inner electrode 12 can be electrically
insulated from the outer electrode. However, the electrodes are so
arranged that the width D of the gap may be generally 2 to 10
mm.
[0036] The configuration of the embossed portions 14 is not
particularly limited so long as the total areas of the upper
surfaces 14A and 14B satisfy the above-mentioned requirement. Any
shape such as a cylindrical shape as well as a rectangular-section
shape such as a parallelopiped shape may be employed so long as the
upper faces of the embossed portions are flat.
[0037] With respect to the projecting portion 15 formed on the
outer peripheral portion of the main plane 11A of the substrate 11,
any shape may be employed so long as the area of the upper face 15A
satisfies the above requirement.
[0038] Each of the embossed portions 14 and the projection 15 is
not particularly limited in size, and may be formed in an arbitrary
depending up a use of the electrostatic chuck. If cylindrical
embossed portions and an annular projecting portion are employed as
shown in FIG. 3, it is preferable that the diameter "r" of the
embossed portion is 1 to 8 mm, and the thickness "d" of the annular
projecting portion is 1 to 8 mm. The height of each of the embossed
portions and the annular portion is preferably 5 to 50 .mu.m.
[0039] Further, the number of the embossed portions 14 is not
particularly limited. In order to disperse the pressure at which
the object to be treated is supported, uniformly holding the
object, and more effectively attain the objective of the present
invention, it is preferable that the rate of the embossed portions
14 is 2 to 4/cm.sup.2 in the concentric area 17 in which the inner
electrode is located and 1 to 2/cm.sup.2 in the concentric area 18
in which the outer electrode is located.
[0040] In the electrostatic chuck having the construction as shown
in FIG. 3, each of the total area of the upper surfaces 14A of the
embossed portions 14 in the zone 17 of the substrate in which the
inner electrode is located and the sum of the total area of upper
surfaces 14B of the embossed portions in the zone of the substrate
in which the outer electrode is located and the area of the upper
surface 15A of said projecting portion 15 in the zone of the
substrate in which the outer electrode is located is set at 20 to
200 cm.sup.2 for the plane having the diameter of 200 mm so that
the object to be treated can be firmly supported.
[0041] Although the embossed portions 14 and the projecting portion
15 need to be formed of the same material. The material is not
particularly limited to any material, so long as the object can be
uniformly supported. For example, AlN or Al.sub.2O.sub.3 may be
used as such a material.
[0042] The embossed portions 14 and the projecting portion 15 is
formed on the main plane 11A of the substrate by blast working or
CVD.
[0043] As the substrate 11, a known ceramic material usable in the
electrostatic chucks, such as AlN or Al.sub.2O.sub.3 may be used.
As the inner electrode 12 and the outer electrode 13, a known
metallic electrode material such as Mo or W may be used.
[0044] The substrate 11 may be produced by a known method, for
example, by forming a molded body of a ceramic material particles
in a given shape, placing the inner electrode 12 and the outer
electrode 13 on the molded body, charging the ceramic particles on
it, molding the particles, and firing the resulting assembly,
thereby realizing a state in which the inner electrode 12 and the
outer electrode 13 are buried in the fired body.
[0045] FIG. 4 shows a plane view showing another electrostatic
chuck according to the present invention. In FIG. 4, a zone 27 in
which an inner electrode 22 is located, i.e., the area of the inner
electrode 22 is larger than a zone 28 where an outer electrode 23
is located, i.e., the area of the outer electrode 23, whereas the
density of the embossed portions 24 on the zone 27 on the main
plane 11A of the substrate 11 where the inner electrode 22 is
located is equal to that of the embossed portions 24 on the main
plane 11A of the substrate where the outer electrode 23 is
located.
[0046] By employing such a construction, the contacting density
between the electrostatic chuck and the object to be treated is
uniform over the inner and outer portions, heat can be conducted
from the electrostatic chuck to the object, so that the object can
be uniformly heated.
[0047] In such a case, the objective of the present invention can
be realized so long as the requirements according to the present
invention, such as that imposed upon the total area of the upper
surfaces 24A of the embossed portions 24 in the zone where the
inner electrode is located, are satisfied.
[0048] In FIG. 4, a negative potential and a positive potential are
applied to the inner and outer electrodes 22 and 23, respectively.
However, this is not particularly restrictive, so long as these
electrodes are concentrically arranged. That is, a positive
potential and a negative potential may be applied to the inner and
outer electrodes 22 and 23, respectively. However, it is preferable
for the same reason as in FIG. 3 that the negative potential and
the positive potential are applied to the inner and outer
electrodes 22 and 23, respectively.
[0049] Further, with respect to each of the embossed portions 24
and the projecting portion 25, the same size and the same shape as
in FIG. 3 may be employed, and the embossed portions and the
projecting portion may be formed, on a main plane 21A of a
substrate 21, of the same material in the same manner as in FIG.
3.
[0050] FIG. 5 shows a case where an inner electrode terminal 39 for
an inner electrode is formed in an outer electrode 33 in an
electrostatic chuck as shown in FIG. 3. When the inner electrode
terminal 39 is formed in the electrode portion of the substrate 31
like this, a voltage applying part such as a wire needs not be
arranged near the center of the substrate, so that a positional
limitation in attaching the device can be diminished. For example,
this is effective, since the number of parts interrupting light is
decreased in heating the electrostatic chuck with a lamp.
[0051] In this way, the objective of the present invention can be
realized in a case where the outer electrode 33 is interrupted and
discontinued in its circumferential direction by the provision of
the inner electrode terminal 39, so long as the requirements
according to the present invention are satisfied.
[0052] The other matters may be effected in the same manner as in
FIG. 3, including the materials usable for the embossed portions
34, etc. and their producing processes.
[0053] In the electrostatic chucks shown in FIGS. 3 to 5, a back
side gas may be introduced into a space between the embossed
portions 14, the object to be treated, and the projecting portion
15 through a line (not shown) arranged at a rear surface of the
electrostatic chuck.
[0054] By so doing, the heat conductivity from the main plane of
the substrate to the object to be treated can be enhanced, so that
the object can be more uniformly heated.
[0055] As the back side gas, known He gas, Ar gas or the like may
be used.
[0056] In general, since the above introducing line is formed at a
central portion of the substrate, the back side gas is introduced
into a central portion of the above space.
[0057] After the object to be treated is attracted to the
electrostatic chuck, the back side gas is introduced, and
simultaneously the object begins to be heated to actuate a
film-forming process.
[0058] Therefore, as the area of the substrate constituting the
electrostatic chuck becomes relatively large, it need take a
relatively long time for the back side gas to reach an edge portion
of the space defined by the embossed portions, the projecting
portion and the object to be treated. Owing to this, the
temperature of the object to be treated may be non-uniform
depending upon this non-uniformity of the back side gas immediately
after the film-forming process is started, which causes variations
in various film characteristics.
[0059] In such a way, as shown in FIG. 4, when the area of the
inner electrode is larger than that of the outer electrode, that
is, the area of the outer electrode is smaller than that of the
inner electrode, and the total area of the upper surfaces of a
plurality of the embossed portions per a unit area of the electrode
in the zone where the outer electrode is located is larger than the
total area of the upper surfaces of a plurality of the embossed
portions per a unit area of the electrode in the zone where the
inner electrode is located, a rate at which a portion of the object
located at an edge portion of the above space is directly heated by
the embossed portions increases.
[0060] Therefore, the object can be uniformly treated from the
beginning of the film-forming process, while compensating the
non-uniformity of the back side gas. Further, since the requirement
for the area of the embossed portions are satisfied, the objective
of the present invention can be also effectively accomplished.
[0061] The total area of the upper surfaces of a plurality of the
embossed portions in the zone where each of the inner and outer
electrodes is located can be increased or decreased by varying the
density of the embossed portions in the zone where the electrode is
located or by varying the diameter of the embossed portions.
EXAMPLE
[0062] The present invention will be more concretely explained
based on an example.
[0063] In this example, electrostatic chucks in which the area of
the inner electrode was equal to that of the outer electrode, and a
positive potential and a negative potential were applied to the
inner and outer electrodes as shown in FIG. 3, respectively.
[0064] As illustrated in the above embodiments of the present
invention, a molded body was formed by molding AlN ceramic powder
to be used as a substrate 11 in a given shape, metallic electrodes
made of Mo were placed on the molded body, the above ceramic powder
was applied onto the resulting molded body and molded again to form
a final molded body in which the metallic electrodes were buried,
and then this molded body was sintered in a nitrogen atmosphere to
produce a substrate in a diameter of 200 mm in which an inner
electrode 12 and an outer electrode 13 were buried.
[0065] By employing the same method as explained in the embodiment
according to the present invention, embossed portions 14 each
having a diameter of 3 mm and a height of 20 were formed of AlN on
the above substrate 11 at a ratio of 3 embossed portions/cm.sup.2
in the zone 17 of the main plane 11A of the substrate 11 where the
inner electrode 12 is located and at a ratio of 1/cm.sup.3 in the
zone 17 where the outer electrode 12 is locate.
[0066] A projecting portion 15 made of AlN was formed at an outer
edge portion with a width of 2 mm.
[0067] At that time, each of the total area of the upper surfaces
14A of the embossed portions 14 in the zone 17 where the inner
electrode was located and a sum of the total area of the upper
surfaces 14B of the embossed portions 14 in the zone 18 where the
outer electrode was located and the area of the upper surface 15A
of the projecting portion 15 was 63 cm.sup.2. A gap 16 between the
inner electrode 12 and the outer electrode 13 was 4 mm in width
D.
[0068] An Si wafer in a diameter of 200 mm as an object to be
treated was placed on the embossed portions 14 and the projecting
portion 15 of the thus produced electrostatic chuck, and an
electric field was formed by applying a DC voltage between the
inner electrode 12 and the outer electrode 13, so that the Si wafer
was attracted onto the electrostatic chuck in this Example.
[0069] Then, a back side gas of Ar gas was fed and uniformly
charged into the space defined between the Si wafer and the
substrate 11 through a line not shown, and the Si wafer was heated
to 350.degree. C. by heating the substrate 11.
[0070] At that time, the temperature distribution of the surface of
the Si wafer was examined by TC (Thermo Couple), which revealed
that the variation in the temperature over the entire surface of
the wafer was .+-.3.degree.C. for the above 350.degree. C.
COMPARATIVE EXAMPLE
[0071] In this Comparative Example, a conventional electrostatic
chuck in which D-shaped electrodes were buried as shown in FIGS. 1
and 2 was produced.
[0072] By using the same ceramic material and the same metallic
electrode material as in Example, an electrostatic chuck was
completed by forming a substrate 1, in the same manner as in
Example, in which a positive electrode 2 and a negative electrode 3
each having a diameter of 200 mm were buried.
[0073] An Si wafer identical with that in Example as an object to
be treated was placed on this electrostatic chuck, a DC voltage was
applied between the positive electrode 2 and the negative electrode
3 through terminals 4 and 5, respectively, from a DC power source
6, and the above Si wafer was attracted onto the electrostatic
chuck in this Comparative Example.
[0074] Next, the same back side gas as in Example was charged in a
space between the Si wafer and the substrate through a line not
shown, the Si wafer was heated to 350.degree. C. as in Example by
heating the substrate 1.
[0075] Examination of the temperature distribution of the surface
of the Si wafer in the same manner as in Example 1 revealed that
the variation was .+-.10.degree. C. for the above 350.degree.
C.
[0076] As is clear from Example and Comparative Example, the
electrostatic chuck according to the present invention can
uniformly attract the object to be treated, even if the gap between
the electrodes is set at a relatively wide distance, and has
extremely small variations in the temperature distribution at the
surface of the object on heating it so that the object can be
uniformly heated.
[0077] Although the present invention has been explained based on
the above embodiments, the invention is not limited to these
embodiments and can be changed and modified in various ways within
a range not falling outside the scope of the invention.
[0078] In summary, the electrostatic chuck according to the present
invention can extremely uniformly attract the object to be treated
and therefore can uniformly heat the object with small variations
in the temperature distribution of the surface of the object.
* * * * *