Stage system or device

A stage device or system comprising an electrostatic chuck portion having a substrate-mounted face made of ceramics, a support block continuous from the bottom of the electrostatic chuck portion and made integral to it, an insulating section for electrically insulating the electrostatic chuck portion from other members, at least an electrode embedded in the electrostatic chuck portion and serving to generate charge on the substrate-mounted face, when DC voltage is applied to it, to attract and hold a substrate on the face, and oxide or resistibility reducing materials added to the ceramics to reduce resistibility of the ceramics forming the electrostatic chuck portion to remove charge from the substrate-mounted face when the substrate is to be released from the face, wherein the amount of oxide or conductive particles contained in the ceramics becomes gradually smaller as it comes from the electrode nearer to the support block.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a stage device or system provided with an 
electrostatic chuck to suck and hold a substrate such as the LCD one and 
semiconductor wafer when the system is incorporated in the etching or CVD 
(chemical vapor deposition) apparatus. 2. Description of the Related Art 
When the semiconductor wafer or LCD substrate is to be film-forming- or 
etching-processed by the CVD film-forming or plasma-etching apparatus, it 
is usually mounted on a horizontal stage. The horizontal stage has an 
electrostatic chuck to attract and hold the wafer or LCD substrate on the 
stage by electrostatic attraction (or Coulomb force). 
This electrostatic chuck generates electrostatic charge in such a way that 
both faces of a disk-like thin plate electrode is coated by thin 
insulating film and that high DC voltage is applied to it. Polyimide resin 
has been used as the insulating film for the electrostatic chuck. However, 
its durability is low and its life is relatively short when it is used 
under severe process conditions such as plasma discharged. 
Recently, therefore, ceramic material, more excellent in durability, is 
used instead of polyimide resin. The electrostatic chuck made of ceramics 
comprises embedding the copper-made and disk-like thin plate electrode in 
the ceramic material and bonding it by insulating adhesive. A DC power 
source is connected to the copper-made electrode and when DC power is 
applied to the electrode, positive or negative charge is caused on a 
ceramics-made and substrate-mounted face of the electrostatic chuck to 
thereby suck the substrate on the face. 
When the wafer W is to be carried out of the process chamber, however, 
charge must be removed from the substrate-mounted face, on which the wafer 
W is sucked and held, to quickly release the wafer W from the face. In the 
case of the conventional stage system, however, charge remains on the 
ceramic material even after the DC power source is turned OFF. The wafer W 
is thus left sucked on the substrate-mounted face to thereby make it 
difficult to release the wafer W from the stage. 
When an insulating section of the electrostatic chuck portion is made 
conductive to make it easy to remove charge from the substrate-mounted 
face, leak current 15b is caused, not passing through the substrate W but 
leaking from a plus-side electrode to another minus-side one, in the case 
of the electrostatic chuck portion of the bi-polar type. The 
substrate-sucking and holding force is thus reduced. 
Further, when an adhesive having a high bonding strength is used to bond 
the copper electrode to the ceramic material, the ceramic material may be 
broken by the difference of linear expansibility of the ceramic material 
relative to the copper electrode during the thermal cycle process. When 
another adhesive having a low bonding strength is used, however, it 
becomes quickly useless during the thermal cycle process, thereby causing 
the stage to be made short in life. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a stage device or system 
capable of more quickly removing electrostatic charge from the 
substrate-mounted face, without causing any leak current, to more easily 
release the substrate from the face. 
Another object of the present invention is to provide a stage device or 
system, less in deterioration but more excellent in durability and longer 
in life, even when it is used for a long time. 
The inventor of the present invention has tried to add and mix 
resistibility reducing materials in that section of the ceramic material 
which is in the vicinity of the substrate-mounted face and make the face a 
little conductive to remove remaining charge from the face. As the result, 
it has been found that carbon, silicon and tungsten particles are more 
suitable for the conductive ones. To add more, however, it is preferable 
that the diameter of each resistibility reducing material is in a range of 
0.01-10 .mu.m. 
It has also been found that ceramics of the alumina group are more suitable 
for the substrate-mounted portion. The reason resides in that the 
substrate-mounted face made of alumina (Al.sub.2 O.sub.3) has an inherent 
contact resistance rate (.OMEGA..cm), so large, relative to the wafer W as 
to gain a predetermined electrostatic attraction even under a condition 
that resistibility reducing materials are contained in the face. 
On the other hand, that portion of the support block which does not form 
the substrate-mounted face must have a high insulation to prevent high 
bias frequency from being leaked. The inventor, therefore, has found that 
aluminum nitride (AlN) is more suitable as ceramics for this portion of 
the support block when high insulation and heat conductivity are taken 
into consideration. 
As the size of wafer becomes larger to 8 and 12 inches, the diameter of 
stage must also be made larger. That section of the electrostatic chuck 
portion which is bonded to the support block becomes a trouble in this 
case. Instead of adhesive, the inventor attached the rim of the 
electrostatic chuck portion to the support block by screws. However, 
thermal expansion difference is caused between the screwed rim area of the 
chuck portion and the not-screwed center area thereof to thereby cause the 
electrostatic chuck portion to be broken. He, therefore, has earnestly 
studied on such a structure of the chuck portion that causes no thermal 
expansion difference. As the result, he has made the electrostatic chuck 
portion integral to the support block. 
A stage device or system according to the present invention comprises an 
electro-static chuck portion having a substrate-mounted face made of 
ceramics; a support block continuous from the bottom of the electrostatic 
chuck portion and made integral to the electrostatic chuck portion; an 
insulating section for electrically insulating the electrostatic chuck 
portion from other members; at least one of an electrode embedded in the 
electro-static chuck portion and serving to generate charge on the 
substrate-mounted face, when DC voltage is applied to the substrate, to 
attract and hold a substrate on the substrate-mounted face; and 
resistibility reducing material added to the ceramics to reduce 
resistibility of the ceramics forming the electrostatic chuck portion to 
remove charge from the substrate-mounted face when the substrate is to be 
released from the face; wherein an amount of the resistibility reducing 
material contained in the ceramics becomes gradually smaller as the amount 
of resistibility reducing material comes from the electrode nearer to the 
support block. 
According to the stage system of the present invention, the amount of 
resistibility reducing materials contained in that section of the 
electrostatic chuck portion which is in the vicinity of the 
substrate-mounted face is large. When the power source is turned OFF, 
therefore, charge can be eliminated from the electro- static chuck portion 
to release the substrate from the substrate-mounted face at once. 
Further, ceramics of the alumina group is selected as insulating material 
for the face-near section of the chuck portion even in the case of the one 
of the bipolar type. This can prevent leak current 15b (or current passing 
through not the substrate but the electrostatic chuck portion) from 
flowing from the plus electrode to the minus one. 
On the other hand, the amount of resistibility reducing materials contained 
is made gradually smaller as it comes from the electrostatic chuck portion 
nearer to the support block. Insulation relative to high frequency can be 
thus fully guaranteed and power loss can be reduced. 
As the above resistibility reducing material, there may used one kind or 
two or more kinds of semiconductors selected from a group of C, Si, W, and 
Wo, or metallic particles. Or, there may be used one kind or two or more 
kinds of oxide selected from a group of Y.sub.2 O.sub.3, CaO, MgO, 
Cr.sub.2 O.sub.3, and SiO.sub.2. 
The following will explain the principle why resistibility of the ceramics 
is reduced by added oxide materials. 
First, in a case where the ceramics forming the electrostatic chuck portion 
is AlN, oxygen of oxide is combined with Al of the matrix so as to newly 
produce Al.sub.2 O.sub.3 if the above oxide is added to matrix AlN. If the 
produced Al.sub.2 O.sub.3 is solubilized in matrix AlN, a crystal 
dislocation is generated in the AlN matrix. By the presence of the crystal 
dislocation, electrical resistibility of the AlN matrix is reduced. 
Next, in a case where the ceramics forming the electrostatic chuck portion 
is Al.sub.2 O.sub.3, the density of a particle lump of Al.sub.2 O.sub.3 is 
lowered if the above oxide is added to matrix Al.sub.2 O.sub.3. Since leak 
current flows to bypass such a rough particle lump of Al.sub.2 O.sub.3, 
electrical resistibility of Al.sub.2 O.sub.3 matrix is reduced. 
Still further, the electrostatic chuck portion and the support block are 
made as a unit. Local stress concentration, therefore, cannot be caused 
even under the thermal cycle condition to thereby prevent the 
electrostatic chuck portion from being broken. 
Still further, it is desirable that a thin film layer of substantially pure 
ceramics in which no resistibility reducing material is contained is 
formed on the top of the electrostatic chuck portion. This pure ceramic 
thin film layer enables the chuck portion to be more highly insulated from 
plasma discharged, without disturbing the removal of remaining charge from 
the face. 
Still further, the mixing rate of ceramics and metal contained is gradually 
changed as it comes from the support block nearer to the metal-made and 
cooling jacket-provided portion. These portions can be thus made as a unit 
and their manufacturing process and structure can also be made simpler. 
It is noted that the metal-made and cooling jacket-provided portion is 
preferably made of metal having a high melting point such as Cu, W, Mo. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Some preferred embodiments of the present invention will be described with 
reference to the accompanying drawings. 
The load lock system provided with the stage system according to a first 
embodiment of the present invention will be described firstly with 
reference to FIGS. 1 through 4. 
As shown in FIG. 1, a stage system 10 is arranged in a chamber 2 of the 
load lock system. The load lock chamber 2 is made of metal material such 
as aluminum alloy and stainless steel and it is earthed or grounded. 
Exhaust passages 5 extend from its bottom while a gas supply passage 2 
from its top. It can be thus exhausted through the exhaust passages 5 
while gases such as nitrogen and others of the non-oxide group are 
supplied into it through the gas supply passage 6. 
Openings 3 are formed in both sides of the chamber 2 and a gate valve 4 is 
attached to each of the openings 3. When the gate valve 4 is opened, a 
semiconductor wafer W is carried into the chamber 2 through the opening 3 
by the arm mechanism (not shown) and mounted on the stage system 10. 
The stage system 10 has a main portion comprising a support block 12 and an 
electrostatic chuck portion 13 and the support block 12 is supported by 
and fixed to the bottom of the chamber 2 through an insulating member 11. 
The electrostatic chuck portion 13 is formed on the support block 12 and 
the top serves as a face on which the wafer W is mounted. The 
electrostatic chuck portion 13 and the support block 12 are formed as a 
unit. 
A pair of electrodes 14A and 14B each being a thin film like tungsten foil 
or Ag--Pd sintered sheet are embedded in the electrostatic chuck portion 
13. One 14A of them is connected to the plus side of a DC power source 18A 
of a circuit 16 via a lead 17A and a switch 19A. The other 14B is 
connected to the minus side B of a DC power source 18B of the circuit 16 
via a lead 17B and a switch 19B. When both of the switches 19A and 19B are 
turned ON, positive charge is caused by the electrode 14A while negative 
one by the other electrode 14B. When the wafer W is positioned above these 
electrodes 14A and 14B, current 15a flows between them through the wafer 
W, which can be thus sucked by and held on the wafer-mounted face 13a of 
the electrostatic chuck portion 13. 
The electrostatic chuck portion 13 and the support block 12 are made as a 
unit by sintered alumina. To make a little conductive that insulation area 
of the electrostatic portion 13 which is in the vicinity of the 
wafer-mounted face 13a, an adequate amount of carbon particles 71 is mixed 
in ceramics of the alumina group in the electrostatic chuck portion 13. 
This conductivity in the insulation area may be such that can prevent the 
occurrence of remaining charge. When it is too much, power loss becomes 
large. The resistibility reducing materials 71 include nonmetallic ones 
such as silicon and carbon as well as metallic ones such as tungsten. 
Moreover, as the resistibility reducing material 71, there may be used one 
kind or two or more kinds of oxide selected from a group of Y.sub.2 
O.sub.3, CaO, MgO, Cr.sub.2 O.sub.3, and SiO.sub.2. The following will 
explain the case that the matrix is AlN and the case that the matrix is 
Al.sub.2 O.sub.3. 
If oxide is added to the matrix AlN, oxygen of oxide is combined with Al of 
the matrix so that Al.sub.2 O.sub.3 is newly produced. If the produced 
Al.sub.2 O.sub.3 is solubilized in matrix AlN, the crystal dislocation is 
generated in the AlN matrix. By the presence of the crystal dislocation, 
electrical resistibility of the AlN matrix is reduced. 
On the other hand, if oxide is added to the matrix Al.sub.2 O.sub.3, the 
density of a particle lump of Al.sub.2 O.sub.3 is lowered. Since the leak 
current flows to bypass such a rough particle lump of Al.sub.2 O.sub.3, 
electrical resistibility of Al.sub.2 O.sub.3 matrix is reduced. 
The support block and electrostatic chuck portions 12 and 13 will be 
described referring to FIGS. 2 through 4. 
FIG. 2 shows how resistibility reducing materials are contained and 
distributed in the support block and electrostatic chuck portions 12 and 
13. A certain amount of resistibility reducing materials 71 is contained 
in that section of them which is between the substrate-mounted face 13a 
and the electrodes 14A, 14B. On the other hand, the amount of 
resistibility reducing materials 71 contained in that section of them 
which is below the electrodes 14A, 14B reduces gradually as shown by a 
curve E. When it is so arranged, a higher electrostatic suction can be 
achieved in a case the system is under operation and no remaining charge 
can be caused in another case it is not operated. In addition, power loss 
can be more effectively prevented. 
The support block and electrostatic chuck portions 12 and 13 are made, as a 
unit, of ceramic material of the alumina group and their distinction is 
not clear but obscure. To make it easy to distinct them, however, the 
electrostatic chuck portion 13 has a thickness L1 of about 0.5-2.0 mm and 
the electrode 14 has a thickness of about 10-100 .mu.m. A depth L2 
extending from the substrate-mounted face 13a to that level in the support 
block portion where resistibility reducing materials 71 becomes zero is 
about 0.5-5 mm. When the amount of resistibility reducing materials 71 
contained is changed little by little, as described above, the occurrence 
of large thermal stress can be prevented in the portions 12 and 13. 
Referring to FIG. 3, it will be described how the support block and 
electrostatic chuck portions 12 and 13 are made. 
Plural thin film ceramic sheets (or green sheets) 70 are laminated and the 
tungsten foil electrodes 14A and 14B are sandwiched between them. Each of 
them has a thickness L3 of 10-100 .mu.m. This laminated matter is pressed 
and then sintered under a temperature of 1200.degree.-1900.degree. C. 
The amount of resistibility reducing materials 71 contained is certain in 
those ceramic sheets 70 which are above the electrodes 14A, 14B. To make 
it zero at the depth L2 which is 1 mm from the substrate-mounted face 13a 
in this case, twenty ceramic sheets 70 each having a thickness of about 50 
.mu.m may be laminated. Conductive particles 71 contained and distributed 
can be therefore adjusted by changing the number of sheets 70 laminated or 
the amount of resistibility reducing materials 71 contained in each of the 
sheets 70. 
Further, that section of the portion 12 which is below that level thereof 
where the amount of resistibility reducing materials 71 contained becomes 
zero may be made by ceramic sheets each of which is thicker than the sheet 
70. 
Furthermore, Al.sub.2 O.sub.3 or AlN can be used as insulating material for 
the members 12 and 13. Or a combination of these ceramic materials may be 
used for this purpose. For example, Al.sub.2 O.sub.3 which is more 
excellent particularly in durability can be used as ceramic material for 
that section of the portions 12, 13 which is above the electrode 14, while 
AlN which is more excellent in heat conductivity can be used for that 
section thereof which is below the electrode 14. 
Still further, when both of Al.sub.2 O.sub.3 and AlN are used as the 
insulating material, it is desirable that their mixture is used in the 
border of one of them relative to the other, not causing the one to 
quickly switch over to the other. 
A thin film layer 72 of pure ceramics may be formed on the top surface (or 
substrate-mounted face) of the electrostatic chuck portion 13, as shown in 
FIG. 4. This pure ceramic thin film layer 72 is extremely thin, having a 
thickness of 10-50 .mu.m, and it is made of substantially pure ceramics in 
which few resistibility reducing materials 71 are contained. 
It is preferable in this case that the amount of resistibility reducing 
materials 71 contained in the insulating (or ceramic) material which is 
between the pure ceramic thin film layer 72 and the electrode 14 increases 
quickly more and more as it comes from the pure ceramic thin film layer 72 
nearer to the electrode 14. The pure ceramic layer 72 is extremely thin, 
so that thermal stress caused in it can be made extremely small. As the 
result, the amount of resistibility reducing materials 71 contained and 
distributed in that section of the portions 12, 13 which is in the 
vicinity of the thin film layer 72 may change gently as shown by a curve 
F1 or may be same as shown by a line F2. 
When the pure ceramic thin film layer 72 is formed, as described above, on 
the top of the portions 12, 13, electrostatic suction can be kept 
unchanged even when the system is under operation. In addition, no charge 
remains on the substrate-mounted face 13a when the system is left 
inoperative. This can effectively prevent film from being stuck and formed 
on that rim portion 13b of the substrate-mounted face which is not 
overlapped by the wafer W. 
In the case of the electrostatic chuck portion 13 shown in FIG. 2, the 
chuck surface (or substrate-mounted face) 13a has quite small 
conductivity. When high frequency is applied to it, therefore, power loss 
is caused at the rim portion 13b, while forming a DC circuit coupled with 
discharge plasma. Further, the drawing of active species and plasma toward 
the rim portion 13b becomes so strong that density film such as SiO.sub.2 
can be stuck and formed on the rim portion 13b. This density SiO.sub.2 
film cannot be removed by usual cleaning operation. 
A second embodiment of the present invention will be described with 
reference to FIGS. 5 through 8. A stage device or system of the plasma CVD 
apparatus will be described as the second embodiment in this case. Same 
components as those of the first embodiment will be mentioned only when 
needed. 
As shown in FIG. 5, a chamber 22 of the plasma CVD apparatus 24 has a 
ceiling, side walls and a bottom made of conductive matter such as 
aluminum alloy, for example. An upper electrode 84 and a lower electrode 
(or stage system) 26 are opposed to each other in it. The stage system 26 
has a substrate-mounted face made of heat-conductive ceramics. Its 
electrostatic chuck and support block portions 58 and 60 are made as a 
unit. It is mounted on a member 62, which is provided with a cooling 
jacket 88, through O-rings 81. Heat-conductive gas such as helium is 
supplied into a clearance between the support block 60 and the member 62 
to keep their heat conductivity excellent. An insulating member 28 is 
interposed between the cooling-jacket-provided member 62 and the chamber 
22. 
The electrostatic chuck portion 58 is formed at the top of the stage system 
26. It is of the single-pole type, having an electrode 14, which is 
connected to DC and high frequency power sources 18 and 20. The high 
frequency power source 20 serves to apply bias voltage to the electrode 14 
to effectively draw active species from discharge plasma. 
A plasma-creating high frequency power source 22 is connected to the upper 
electrode 84, which is supported in the upper portion of the chamber 22 by 
an insulating support member 30. A feeder line 32 extending from the upper 
electrode 84 is connected to the high frequency power source 22 of 13.5 
MHz through a matching circuit 34. 
A gate valve 34 is formed in a side wall of the chamber 22 and the wafer W 
is carried into and out of the chamber 22 through the gate valve 34. Two 
nozzles 36 and 38 are passed through another opposite side wall of the 
chamber 22. The first nozzle 36 is communicated with a gas supply source 
46 by a pipe 40 through a mass flow controller 42 and a switch valve 44. 
Plasma-generating gas such as argon is contained in the gas supply source 
46. The second nozzle 38 is communicated with a gas supply source 54 by a 
pipe 48 through a mass flow controller 50 and a switch valve 52. Process 
gas is contained in the gas supply source 54. The chamber 22 is exhausted 
through plural exhausting openings 56 in the bottom thereof. 
The electrode 14 made of tungsten foil is embedded in the electrostatic 
chuck portion 58. A lead 64 extending from the electrode 14 is connected 
to the high frequency bias power source 20 through a matching box 66. The 
other branching lead 64 is connected to the DC power source 18, which 
serves for the electrostatic chuck, through a low-pass filter 67 and a 
change-over switch 68. 
The electrostatic chuck and support block portions 58 and 60 are formed as 
a unit and resistibility reducing materials 71 such as carbon and silicon 
are mixed in the ceramic material, of which the electrostatic chuck 
portion 58 is made, to make the portion 58 a little conductive. 
The amount of resistibility reducing materials 71 contained and distributed 
in the case of the second stage system 26 is substantially same as that in 
the first one. 
As shown by a line M in FIG. 6, the amount of AlN contained is increased in 
the support block 60 as it comes remoter from the substrate-mounted face 
13a. On the other hand, the amount of Al.sub.2 O.sub.3 contained is 
gradually reduced in the support block 60, as shown by a line C in FIG. 7, 
as it comes remoter from the substrate-mounted face 13a. 
It will be described how the second stage system is operated. 
The semiconductor wafer W is carried into the process chamber 22 through 
the gate valve 34 by a carrier arm (not shown) and it is mounted on the 
substrate-mounted face of the electrostatic chuck portion 58 while moving 
a lifter pin (not shown) up and down. DC voltage is applied to the 
electrode 14 to generate charge in the substrate-mounted face of the 
electrostatic chuck portion 58, thereby enabling the wafer W to be sucked 
and held on the substrate-mounted face. 
A predetermined process pressure is kept in the process chamber 22 while 
introducing argon and process gases into it. High frequency voltage is 
applied to the upper electrode 84 at the same time to generate plasma in a 
process space 22a, so that the wafer W can be CVD-processed. 
When these steps are repeated, the stage system 26 is subjected to thermal 
cycle. No concentration of a large local stress, however, is caused in the 
electrostatic chuck and support block portions 58 and 60. This can 
effectively prevent them from being broken. 
Further, that section of the electrostatic chuck and support block portions 
58 and 60 in which resistibility reducing materials 71 are contained has a 
thickness of 0.5-5 mm. The insulation of the whole support block 60 from 
high frequency can be thus fully guaranteed, thereby preventing power loss 
from becoming large. 
When the electrostatic chuck and support block portions 58 and 60 are made 
as a unit by two kinds of ceramic material, their mixing rate is gradually 
changed in the border of one of them relative to the other. When it is so 
arranged, internal stress can be more reduced. 
When the electrostatic chuck and support block portions 58 and 60 are 
formed as a unit, the stage system can be made simpler in structure and 
the number of parts or components used can be made smaller. 
As shown in FIG. 8, the support block 60 and the cooling jacket 62 may be 
formed as a unit. The cooling jacket 62 is made, in this case, of copper 
(Cu) instead of aluminum. In addition, the mixing rate of ceramics and 
copper is more gradually changed when it comes from the support block 60 
nearer to the cooling jacket 62 in the thickness direction of the unit. 
When it is so arranged, the number of components used can be still further 
reduced. Heat resistance can also be made smaller in the thickness 
direction of the unit. The efficiency of cooling the wafer W can be thus 
increased. 
Metal material is not limited to copper but any metal materials which are 
more or less durable against the temperature (or about 1200.degree. C.), 
under which the ceramics are sintered, can be used. 
If the cooling jacket 62 is made of metal which may fail to withstand the 
plasma, it is desirable that the jacket 62 be coated with a thing film of 
Al.sub.2 O.sub.3 or AlN. 
The insulating material for the electrostatic chuck portion and others is 
not limited to Al.sub.2 O.sub.3 and AlN but other ceramics such as SiN may 
be used. 
Although the above-described second embodiment has been applied to the 
plasma CVD apparatus, it may also be applied to other plasma process 
apparatus such as plasma etching and ashing ones. 
According to the present invention, the electrostatic chuck portion and the 
support block can be formed as a unit. Internal stress which is caused by 
the thermal expansion difference of one component relative to the other 
can be thus reduced, thereby enabling the durability of the stage system 
to be increased to a greater extent. In addition, the number of components 
used can be made smaller when both of the electrostatic chuck portion and 
the support block are formed as a unit. 
Further, the amount of resistibility reducing materials contained in the 
ceramics is changed little by little in the thick direction of the unit. 
Electrostatic suction can be thus kept unchanged and charge can be more 
quickly removed from the substrate-mounted face of the unit after the 
power is turned OFF. 
Still further, the insulation of the substrate-mounted face can be 
increased not to cause the face to be coupled with plasma, when the pure 
ceramic thin film layer is formed to serve as the substrate-mounted face. 
Power loss can be thus reduced and the adhering of product, so dense as 
not to be removed by the usual cleaning operation, to the face can be 
prevented. 
Still further, when the cooling jacket portion is also made integral to the 
support block, the stage system can be made simpler in construction and 
the whole of it can be made by a single process. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept as defined by 
the appended claims and their equivalents.