Heating device, method of manufacturing the same, and processing apparatus using the same

A heating device is formed by a heating plate formed of silica and having a heating surface for heating an object to be heated, a heating element having a predetermined pattern and fixed to a surface opposing the heating surface of the heating plate, and a reflecting plate formed of silica and brought into tight contact with the surface of the heating plate on which the heating element is formed. This heating device is arranged in a processing vessel in a CVD apparatus, and a semiconductor wafer is placed on the heating device. A process gas is supplied into the processing vessel while the semiconductor wafer is heated, thereby forming a predetermined film on the semiconductor wafer.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a heating device suitable for the process 
of manufacturing a semiconductor device, a method of manufacturing the 
heating device, and a processing apparatus using the heating device. 
2. Description of the Related Art 
In the process of manufacturing a semiconductor device, when surface 
processing for a semiconductor wafer on which devices are formed, for 
example, etching processing or CVD processing, is to be performed, a 
semiconductor wafer serving as an object to be processed is placed on a 
susceptor arranged in a processing vessel designed to have airtightness, 
and the processing vessel is evacuated to a predetermined low-pressure 
atmosphere. A predetermined process gas is supplied into the processing 
vessel. In this manner, predetermined processing is performed. 
In this case, heating a semiconductor wafer to a predetermined temperature 
to perform predetermined processing has been conventionally used. A 
heating device for heating a semiconductor wafer is generally incorporated 
in the susceptor. A conventional heating device comprises a heating plate 
formed of a ceramic material such as Al.sub.2 O.sub.3 or AlN and a heating 
element formed of tungsten, and has a structure in which the heating 
element is simply inserted in a groove formed in a ceramic material in 
correspondence with the pattern of the heating element. 
However, in the conventional heating device, Al.sub.2 O.sub.3 or AlN 
constituting the heating plate tends to form particles, so that 
contamination may occur in a processing vessel or on a semiconductor 
wafer. Since the inner surface of the processing vessel is exposed to 
various etching gas atmospheres, corrosion must be considered. However, 
the above ceramic material does not necessarily have a satisfactory 
resistance to corrosion. In addition, since the ceramic material has a low 
thermal shock resistance, the ceramic material cannot be abruptly 
increased or decreased in temperature, and must be used in a steady state. 
Since the heating device has the heating element simply inserted into the 
patterned groove, the heating element may be cluttered in the patterned 
groove, and particles may be formed by the cluttered heating element. 
A degree of vacuum in the processing vessel is set to be high, for example, 
1 Torr or less. At the high degree of vacuum, the dielectric breakdown 
level of a gas, i.e., a discharge start voltage level, is lowered, and 
discharge tends to occur. For this reason, there is no power supply method 
effective in the processing vessel, and a power supply path extending 
through the susceptor from the atmospheric side of the processing vessel 
must be formed. Therefore, this power supply path poses a problem on 
design for the heating device and maintenance. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a heating device, for 
heating an object such as a semiconductor wafer, which is excellent in 
resistance to corrosion, does not form particles which cause 
contamination, and can abruptly increase or decrease a temperature. 
It is another object of the present invention to provide a heating device 
in which an effective supply of power from the atmospheric side can be 
performed. 
It is still another object of the present invention to provide a method of 
manufacturing the heating device. 
It is still another object of the present invention to provide a processing 
apparatus in which the heating device is incorporated. 
According to the first aspect of the present invention, there is provided a 
heating device comprising: 
a heating plate formed of silica and having a heating surface for heating 
an object to be heated; and 
a heating element having a predetermined pattern and fixed to a surface of 
the heating plate which opposes the heating surface. 
According to the second aspect of the present invention, there is provided 
a heating device comprising: 
a heating plate formed of silica and having a heating surface for heating 
an object to be heated; 
a heating element having a predetermined pattern and fixed to a surface of 
the heating plate which opposes the heating surface; and 
a reflecting plate formed of silica and brought into tight contact with the 
surface of the heating plate on which the heating element is formed. 
According to the third aspect of the present invention, there is provided a 
method of manufacturing a heating device, comprising the steps of: 
preparing a heating plate formed of silica and having a heating surface for 
heating an object to be heated; 
forming a recessed portion corresponding to a pattern of a heating element 
in the surface of the heating plate which opposes the heating surface; 
filling a paste containing a heat generating component in the recessed 
portion; and 
sintering the paste to form the heating element. 
According to the fourth aspect of the present invention, there is provided 
a method of manufacturing a heating device, comprising the steps of: 
preparing a heating plate formed of silica and having a heating surface for 
heating an object to be heated; 
applying a paste containing a heat element component to a surface of the 
heating plate which opposes the heating surface, in correspondence with a 
heating element pattern; and 
sintering the paste to form the heating element. 
According to the fifth aspect of the present invention, there is provided a 
processing apparatus comprising: 
a processing vessel for processing an object to be processed in a 
predetermined low-pressure atmosphere; 
a heating device, arranged in the processing vessel, for heating the 
object; and 
process gas supply means for supplying a process gas for processing the 
object into the processing vessel, 
wherein the heating device includes a heating plate formed of silica and 
having a heating surface for heating the object, and a heating element 
having a predetermined pattern and fixed to a surface of the heating plate 
which opposes the heating surface. 
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 
A heating device according to the present invention comprises a heating 
plate for heating an object to be heated, and a heating element arranged 
on the heating plate. The heating plate formed of silica (SiO.sub.2) and 
has a heating surface for heating the object. The heating element has a 
predetermined pattern, and is fixed to the surface of the heating plate 
which opposes the heating surface. 
Since the heating plate formed of silica as described above, the heating 
plate has a corrosion resistance higher than that of a conventional 
ceramic material of AlN and Al.sub.2 O.sub.3 and rarely forms particles 
which cause contamination. In addition, since silica has a small thermal 
expansion coefficient and a high thermal shock resistance, the heating 
plate can be abruptly heated or cooled. Since the heating element is fixed 
to the heating plate, unlike a conventional heating element, the heating 
element is not cluttered in a groove. 
Silica used to form the heating plate preferably has impurities of 10 ppm 
or less and low alkali metal content in consideration using a 
semiconductor manufacturing apparatus. The silica constituting the heating 
plate may be obtained by melting a high-purity silica powder and then 
cooling it, or may be synthesized from gases. Furthermore, the silica may 
be glassy, or may partially or entirely have a crystalline state such as 
quartz. 
The heating plate is preferably transparent. Due to this, an object to be 
heated can be efficiently heated. 
A reflecting plate formed of silica as in the heating plate is preferably 
arranged on the surface of the heating plate which opposes the heating 
surface with the heating element interposed therebetween. The presence of 
the reflecting plate suppresses the external heat dissipation from the 
heating element, and heat reflected by the reflecting plate contributes to 
heating. For this reason, the object can be more efficiently heated. In 
this case, the reflecting plate is arranged in tight contact with the 
heating plate. 
As the material of the heating element, for example, platinum (Pt), nickel 
(Ni), or carbon (C) is available. As the pattern of the heating element, 
for example, a two-dimensional spherical pattern, a concentrically 
circular pattern, or a checkerboard pattern for uniform heating is 
available. This heating element generally generates heat by receiving 
power is from a power supply. 
In order to fix the heating element to the heating plate, a groove 
corresponding to the pattern of the heating element may be formed in the 
surface of the heating plate and then filled with the heating element, or 
the heating element may be bonded to the surface of the heating plate by a 
proper means. In this case, the heating element can be formed on the 
surface of the heating plate as a thick-film pattern by screen printing or 
the like. 
Preferred embodiments of the heating device described above will be 
described below. 
FIG. 1 is a perspective view showing the outer appearance of a heating 
device according to the first embodiment of the present invention, FIG. 2 
is a plan view showing the heating device in FIG. 1, and FIG. 3 is a 
sectional view showing the heating device along a III-III' line in FIG. 2. 
As is apparent from FIGS. 1 to 3, a heating device 1 has a disk-like shape 
as a whole, and includes a heating plate 11 and a reflecting plate 21 
having almost the same two-dimensional shape. The heating device 1 is 
constituted such that the surfaces of the heating plate 11 and the 
reflecting plate 21 are tightly joined to each other. 
The heating plate 11 is formed of transparent silica (SiO.sub.2), and has a 
recessed portion 12 for placing an object to be heated, for example, a 
semiconductor wafer having a diameter of 8 inches, thereon is formed in 
the upper surface of the heating plate 11. The upper surface of the 
recessed portion 12 serves as a heating surface for heating the 
semiconductor wafer. Radially extended portions 13 and 14 are formed on 
the circumferential surface of the heating plate 11, and the extended 
portions 13 and 14 are symmetrically located. These extended portions 13 
and 14 are formed of the same material as that of the heating plate 11, 
i.e., silica (SiO.sub.2). 
A groove 15 corresponding to the pattern of a heating element is formed in 
the lower surface of the heating plate 11, and a heating element 31 is 
filled in the groove 15. 
The reflecting plate 21 located on the lower side is formed of opaque 
silica (SiO.sub.2) as a whole. The reflecting plate 21 reflects radiant 
heat from the heating element 31 airtightly sealed when the reflecting 
plate 21 is joined to the heating device 1 to the heating plate 11. The 
reflecting plate 21 conducts heat generated by the heating element 31 to 
the semiconductor wafer without any loss. 
The heating element 31 is formed of platinum and constitutes a so-called 
heat-generating electrode. When the heating element 31 receives power from 
external power supply, the heating element 31 generates heat and has a 
temperature about 1,000.degree. C. 
Note that extended portions 22 and 23 corresponding to the extended 
portions 13 and 14 and having the same two-dimensional shape as that of 
the extended portions 13 and 14 are arranged on the peripheral surface of 
the reflecting plate 21, and these extended portions 22 and 23 are tightly 
joined to the extended portions 13 and 14, respectively. 
A method of manufacturing the heating device 1 arranged as described above 
will be described below. 
As shown in FIGS. 4 and 5, a groove 15 corresponding to the heating element 
pattern and having a predetermined depth is formed in the lower surface of 
the heating plate 11. The groove 15 can be formed by using, for example, 
etching. During formation of the groove 15, through holes 16 and 17 
vertically extending through the heating plate 11 are formed in the groove 
15 portions of the extended portions 13 and 14. 
As shown in FIG. 6, a paste 31a for forming the heating element 31, for 
example, a platinum paste is filled in the groove 15 corresponding to the 
heating device pattern. At this time, when the paste 31a is filled in the 
groove 15 while being properly pressed such that the paste-like heat 
generation material or paste 31a extends to every corner in the groove 15. 
In addition, the paste 31a is filled in the through holes 16 and 17. 
However, the through holes 16 and 17 need not be filled with the paste 
31a, and the through holes 16 and 17 may be filled with a general 
conductive material later. 
After the paste 31a is filled, the heating plate 11 is burned to evaporate 
a solvent or the like in the paste 31a, and the paste 11 is sintered to 
obtain a heating element 31. As described above, since the heating plate 
11 is formed of silica (SiO.sub.2), a burning temperature is set to be 
lower than the softening point (1,650.degree. C.) of silica (SiO.sub.2), 
preferably 1100 to 1300.degree. C. 
After the burning, as shown in FIG. 7, the upper and lower surfaces of the 
heating plate 11 are ground by, for example, a surface grinding machine or 
the like and polished to remove an unnecessary heating element 31, thereby 
increasing the degree of flatness. In this manner, the heating element 31 
is filled and stored in the groove 15 corresponding to the heating element 
pattern of the heating plate 11. The through holes 16 and 17 are filled 
with platinum, thereby constituting conductive potions 16a and 17a 
connected to the heating element 31. 
The reflecting plate 21 which is prepared in advance and has surfaces 
machined to a predetermined degree of flatness is brought into tight 
contact with the lower surface of the heating plate 11, and the resultant 
structure is heated to about 1,200.degree. C. in, for example, an electric 
furnace. In this state, the structure is pressed as shown in FIG. 8 to 
join the heating plate 11 and the reflecting plate 21 to each other by 
welding (electrodeposition). 
Finally, as shown in FIG. 3, when the recessed portion 12 for storing a 
semiconductor wafer is formed in the upper surface of the heating plate 
11, and the outer shape is adjusted, the heating device 1 is completed. 
An example wherein the heating device 1 arranged as described above is 
applied to a CVD apparatus to perform film formation processing for a 
surface of a semiconductor wafer will be described below. 
FIG. 9 is a sectional view showing a CVD apparatus to which the heating 
device 1 is applied, and FIG. 10 is an enlarged sectional view showing the 
main part of the CVD apparatus. This CVD apparatus has an almost 
cylindrical airtight processing vessel 41. The processing vessel 41 is 
formed of aluminum which is entirely anodized, and is constituted by a 
shower head 42 serving as the upper portion of the processing vessel 41, a 
peripheral wall 43, and a bottom wall 44 to have an airtight structure. 
The above heating device 1, on which a semiconductor wafer W serving as an 
object to be processed is placed, for heating the semiconductor wafer W is 
arranged in the processing vessel 41. The semiconductor wafer W is placed 
on the recessed portion 12 formed in the upper surface of the heating 
plate 11 of the heating device 1 described above. 
The shower head 42 has a hollow disk-like shape. A process gas supply unit 
45 is formed in an upper wall 42a of the shower head 42, a large number of 
gas discharge holes 48 are formed in a lower wall 42b of the shower head 
42, and a space 42c is present between the upper wall 42a and the lower 
wall 42b. A process gas source 47 is connected to the process gas supply 
unit 45 through a process gas supply pipe 46. A gas mixture of, for 
example, SiH.sub.4 (silane) and H.sub.2, is supplied as a process gas from 
the process gas source 47 to the shower head 42, and the gas mixture is 
uniformly discharged from the gas discharge holes 48 toward the 
semiconductor wafer W placed on the heating device 1. 
An exhaust hole 49 is formed near the bottom portion of the peripheral wall 
43 of the processing vessel 41. An exhaust unit 50 is connected to the 
exhaust hole 49 through an exhaust pipe 49a. The exhaust unit 50 can keep 
the inside of the processing vessel 41 to a predetermined degree of 
vacuum, for example, 10.sup.-6 Torr. 
An annular extended portion 43a extended inward is formed on the lower end 
of the peripheral wall 43 of the processing vessel 41, and the heating 
device 1 is arranged on the extended portion 43a. That is, the heating 
device 1 is mounted on the extended portion 43a such that the reflecting 
plate 21 faces downward. Therefore, the extended portion 43a of the 
peripheral wall 43 is in contact with the reflecting plate 21. 
An annular coolant path 51 is formed in the extended portion 43a, and a 
coolant source 53 is connected to the coolant path 51 through a coolant 
supply pipe 52. For example, cooling water serving as a coolant is 
supplied from the coolant source 53 into the coolant path 51 through the 
coolant supply pipe 52, and is circulated therethrough. This cooling water 
can cool the peripheral portions of the conductive potions 16a and 17a of 
the heating device 1 to about 200.degree. C. 
Power supply pins 54 are connected to the upper surfaces of the conductive 
potions 16a and 17a of the heating device 1, respectively. Cylindrical 
insulating members 55 are arranged to enclose the power supply pins 54, 
respectively. The lower end faces of the insulating members 55 are 
airtightly pressed against the peripheral portions of the conductive 
potions 16a and 17a of the heating plate 11 through O-rings 56. The upper 
end faces of the insulating members 55 are airtightly pressed against the 
lower wall 42b of the shower head 42 through O-rings 57. 
An AC power supply 58 arranged outside the processing vessel 41 is 
connected to the two power supply pins 54. When a predetermined current 
flows from the AC power supply 58 to the heating element 31 through the 
power supply pins 54, the heating element 31 generates heat to increase 
the temperature of the heating device to about 1,000.degree. C. The 
semiconductor wafer W placed in the recessed portion 12 on the heating 
plate 11 is heated to have a predetermined temperature. 
A temperature sensor 59 for measuring the temperature of a predetermined 
portion of the heating plate 11 is buried in the heating device 1, and the 
temperature sensor 59 is connected to a controller 60 through a 
measurement unit 59a. The measurement unit 59a sequentially measures 
temperatures on the basis of detection signals from the temperature sensor 
59, and signals from the temperature sensor 59 are input to the controller 
60. On the basis of these signals, control signals are output from the 
controller 60 to the AC power supply 58 and the coolant source 53 to 
adjust an output from the heating element 31 and the flow rate of the 
cooling water, thereby controlling the temperature of the semiconductor 
wafer. 
In this CVD apparatus, although not shown, lift pins for lifting the 
semiconductor wafer in conveyance of the semiconductor wafer W are 
arranged extendibly from the surface of the heating device 1. 
In the CVD apparatus arranged as described above, when the AC power supply 
58 is turned on, the heating element 31 generates heat to heat the 
semiconductor wafer W on the heating plate 11. The exhaust unit 50 
evacuates the processing vessel 41 to a predetermined degree of vacuum, 
for example, 1 Torr, and a predetermined process gas, for example, a 
silane-based gas is supplied into the processing vessel 41. In this 
manner, a predetermined film, for example, a polysilicon film, is formed 
on the surface of the semiconductor wafer W. 
In this case, since cooling water is circulated in the coolant path 51, a 
temperature gradient in the heating plate 11 is shown in FIG. 11. More 
specifically, although the portion of the semiconductor wafer W (the right 
portion with respect to c in FIGS. 10 and 11) is heated by the heating 
element 31 to about 900.degree. C., the connection portion between the 
conductive potion 16a and the power supply pin 54 and a portion around 
O-rings 56 (the portion between a and b in FIGS. 10 and 11) are cooled to 
about 200.degree. C. 
More specifically, on the heating plate 11, a short-distance portion (the 
portion between b and c in FIGS. 10 and 11) has a very high temperature 
gradient. Since the connection portion between the conductive potion 16a 
and the power supply pin 54 and the O-ring 56 portion have a temperature 
of about 200.degree. C., the O-rings 56 are not thermally deformed at all, 
and the inside of the insulating member 55 is kept at a predetermined 
airtight state. Therefore, even if the outside of the insulating member 55 
has a high degree of vacuum, of 1 Torr, the inside of the insulating 
member 55, i.e., the connection portion between the power supply pin 54 
and the conductive potion 16a can be kept in an atmospheric state. For 
this reason, a power can be supplied to the heating element 31 of the 
heating device 1 arranged in a state having a high degree of vacuum 
without any trouble. 
As shown in the graph of FIG. 11, the portion on which the semiconductor 
wafer W is placed is kept at 900.degree. C. which is a predetermined 
heating temperature. In a practical apparatus, the distance between the 
inner O-ring 56 and the edge of the semiconductor wafer W (the portion 
between b and c in FIGS. 10 and 11) is about several cm at most. Although 
the distance is short as described above, a high temperature gradient is 
obtained because silica (SiO.sub.2) is used as the material of the heating 
plate 11. 
As described above, when the power supply system with the above arrangement 
is used, a power can be supplied from the power supply in an atmospheric 
state to the heating device 1 arranged in a high degree of vacuum. In 
addition, since airtightness is secured by the O-rings, the insulating 
members 55 can be easily removed from the heating plate 11, and 
maintenance can be easily performed. 
Furthermore, since the semiconductor wafer W is placed on the recessed 
portion 12 of the heating plate 11, a heat loss is small, and the planar 
uniformity of the temperature of the semiconductor wafer W is high. For 
this reason, processing can be uniformed. Since silica has a small thermal 
expansion coefficient and a high thermal shock resistance, the heating 
plate is not substantially damaged even if a temperature sharply increases 
or decreases as described above. Therefore, processing having a large 
difference in temperature can be continuously performed, and the 
throughput can be increased. 
The second embodiment of the present invention will be described below. 
FIG. 12 is a perspective view showing the schematic arrangement of a 
heating device according to the second embodiment of the present 
invention, FIG. 13 is a longitudinal sectional view showing the heating 
device. Like the heating device 1 of the first embodiment, a heating 
device 61 according to the second embodiment has an almost circular shape 
as a whole. The heating device 61 has a basic arrangement in which a 
heating plate 71, a reflecting plate 81, and a cooling member 91 which 
have almost the same two-dimensional shape are stacked downward. 
The heating plate 71 is formed of transparent silica (SiO.sub.2), and 
extended portions 72 and 73 formed of the same material as that of the 
heating plate 71, i.e., silica (SiO.sub.2), are arranged on the 
circumferential surface of the heating plate 71 such that the extended 
portions 72 and 73 oppose with respect to the center of the heating plate 
71. 
As shown in FIG. 14, a heating element 74 formed of platinum (Pt) is bonded 
to the lower surface of the heating plate 71 to have a thickness of about 
10 .mu.m and an almost C shape as a two-dimensional shape, and end 
portions 74a and 74b of the heating element 74 are bonded to the extended 
portion 73. This heating element 74 is formed by, for example, a 
thick-film pattern, and is designed to generate heat when the heating 
element 74 receives an AC current from an AC power supply 75. 
Around the heating element 74, a temperature measuring resistor 76 formed 
of platinum (Pt) is joined to the lower surface of the heating plate 71 
such that the resistor 76 does not cross the heating element 74 and has a 
shape similar to the pattern of the heating element 74. End portions 76a 
and 76b constituting the terminals of the resistor 76 are located at the 
extended portion 73. 
A signal current source 77 for outputting a current having a predetermined 
value is connected across the end portions 76a and 76b of the resistor 76, 
and a voltmeter 78 for measuring the voltage of the resistor 76 is 
connected across the end portions 76a and 76b. 
As described above, the reflecting plate 81 with a recessed portion 81a 
having a depth enough to store the heating element 74 and the temperature 
measuring resistor 76 is airtightly joined to the lower surface of the 
heating plate 71 having the heating element 74 and the temperature 
measuring resistor 76 formed on the lower surface of the heating plate 71, 
and extended portions 82 and 83 of the reflecting plate 81 and a 
peripheral portion 81b thereof correspond to the extended portions 72 and 
73 and peripheral portion of the heating plate 71, respectively. This 
reflecting plate 81 is formed of whitish, opaque silica, and has a 
function of reflecting radiant heat from the heat generator 74 to the 
heating plate 71. 
Note that the depth of the recessed portion 81a of the reflecting plate 81 
is set to form a gap having, for example, about 100 .mu.m, between the 
lower surface of the heating element 74 and the bottom surface of the 
recessed portion 81a. In this manner, when the small gap is formed, 
diffusion of heat conducted from the heating element 74 can be suppressed, 
thereby improving heating efficiency. 
The cooling member 91 airtightly joined to the lower surface of the 
reflecting plate 81 has extended portions 92 and 93 arranged to correspond 
to the extended portions 82 and 83, and is formed of silica like the 
heating plate 71 and the reflecting plate 81. A groove 94 constituting a 
flow path for a cooling gas is formed in the upper surface of the cooling 
member 91, and both end portions 94a and 94b of the groove 94 are open to 
the lower surface of the cooling member 91. 
More specifically, as shown in FIG. 15, the groove 94 has a pattern such 
that the end portions 94a and 94b spirally extend toward the center of the 
cooling member 91 to be connected to each other at the central portion, 
and the groove 94 has no cross portion halfway and is not eccentric with 
respect to the reflecting plate 81. Therefore, when a cooling gas such as 
N.sub.2 gas (nitrogen gas) flows in the groove 94, the gas is brought into 
contact with the lower surface of the reflecting plate 81, and heat 
exchange is performed at the contact portion, thereby cooling the 
reflecting plate 81. 
The heating device 61 with the above arrangement is manufactured as 
follows. The pattern of the heating element 74 and the pattern of the 
temperature measuring resistor 76 are formed on a screen printing plate in 
advance. A platinum powder for forming the heating element 74 and the 
resistor 76, an organic binder, and an organic solvent are mixed with each 
other to form a paste. This paste is screen-printed on the lower surface 
of the heating plate 71 using the screen printing plate. More 
specifically, the paste-like heating element 74 and the paste-like 
resistor 76 are simultaneously formed on the lower surface of the heating 
plate 71 by a thick-film printing method. When these films are 
simultaneously sintered, the heating element 74 having the predetermined 
pattern and the temperature measuring resistor 76 having the predetermined 
pattern are formed to be bonded to the lower surface of the heating plate 
71. 
Thereafter, the reflecting plate 81 is brought into tight contact with the 
heating plate 71, and the cooling member 91 is brought into contact with 
the plate 81, and simultaneously pressed and heated to be integrated. As a 
matter of course, after the reflecting plate 81 and the heating plate 71 
are brought into tight contact with each other, pressed, and heated, the 
cooling member 91 may be brought into tight contact with the resultant 
structure, pressed, and heated. As described above, the heating device 61 
can be easily manufactured at a high speed. 
According to the heating device 61 having the above arrangement, since the 
heating plate 71, the reflecting plate 81, and the cooling member 91 are 
formed of silica, they have a corrosion resistance higher than that of a 
conventional ceramic material, and particles which cause contamination are 
rarely formed. The presence of the reflecting plate 81 makes the heating 
efficiency are formed by the heating element 74 high. In addition, since 
the heating plate 71 and the reflecting plate 81 consist of silica, they 
have a small thermal expansion coefficient and a high thermal shock 
resistance, and can be abruptly heated or cooled. Therefore, when 
semiconductor wafers are to be heated, the throughput of the semiconductor 
wafers can be increased. Since the reflecting plate 81 is cooled by the 
cooling member 91, such an abrupt increase/decrease in temperature can be 
easily realized. 
In a heating device of this type, a temperature must be always measured to 
control the temperature. Conventionally, a sheath-like thermocouple is 
generally inserted in a hole formed in, for example, a heating plate. 
However, according to the measurement method described above, a 
countermeasure against particles formed by the thermocouple is cumbersome, 
and the manufacture and processing of the heating plate itself are 
cumbersome. In addition, since the measurement method uses one 
representative measurement point, a plurality of thermocouples are 
required to measure the average temperature of the entire heating plate. 
With respect to this point, in the heating device 61 according to the 
second embodiment, the temperature measuring resistor 76 is arranged 
around the heating element 74. When the voltage obtained by the signal 
current source 77 is always measured, the average temperature of the 
entire heating plate 71 can be measured. More specifically, by using a 
change in resistance of the resistor 76 caused by a change in temperature, 
the temperature of the heating plate 71 can be calculated on the basis of 
the prepared temperature-resistance correlation data of the resistor 76 
and a change in resistance calculated on the basis of a change in voltage. 
Furthermore, since the resistor 76 is arranged in correspondence with the 
pattern of the heating element 74, the average temperature of the entire 
heating plate 71 based on the temperature of the heating element 74 can be 
measured. 
When the temperature measuring resistor 76 is to be formed on the heating 
plate 71, the resistor 76 and the heating element 74 can be simultaneously 
formed by screen printing. For this reason, the resistor 76 can be easily 
formed, and the heating plate 71 itself need not be processed. 
In the heating device 61, the heating element 74 and the temperature 
measuring resistor 76 are arranged not to cross each other. However, when 
a thin insulating film is formed on the lower surface of, for example, the 
heating element 74, and the resistor 76 is formed on the lower surface of 
the insulating film, the temperature measuring resistor 76 can be formed 
to have an arbitrary pattern suitable for a temperature measuring 
operation. 
An object to be heated need not be placed on a heating plate, and the 
object may be located at a position where the object can be heated by the 
heating surface of the heating plate. In addition, a processing apparatus 
to which the heating device according to the present invention is applied 
is not limited to a CVD apparatus, and the heating device may be applied 
to another apparatus such as an apparatus for performing oxidation and 
diffusion. 
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, representative devices, and illustrated examples 
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.