JP2002299011A - Ceramic heater and wafer-heating device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater, capable of preventing generation of cracks in the connection part of an oxide film for coating an aluminum nitride sintered body, forming a heating board with thermal stress and a heating resistor, and capable of generating heat stably over a long period of time, even after repeated rapid temperature increase and rapid cool down. SOLUTION: In the ceramic heater 10, one main face of the heating board 2 made of an aluminum nitride sintered body with an oxide film including Al over the entire surface is a heating face 3, the heating resistor 5 is formed on the other main face of the heating board 2, and an insulation film 4 is attached to the other main face of the heating board 2, to cover the heating resistor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer heating apparatus used for heating a wafer such as a semiconductor wafer, a liquid crystal substrate or a circuit board, and a ceramic heater used for the same. It is suitable for forming a resist film by drying and baking a resist liquid generated or applied on a wafer.

[0002]

2. Description of the Related Art Conventionally, in a manufacturing process of a semiconductor device,
In various processing steps such as a semiconductor thin film forming process, an etching process, and a resist film baking process, a method called a batch method for processing a plurality of wafers collectively and a single wafer method for processing wafers one by one are called. In recent years, as the size of a wafer has increased from 8 inches to 12 inches, a single-wafer method has been used to increase processing accuracy.

However, in the single-wafer method, the number of wafers processed at one time is small, so that it is necessary to reduce the processing time of wafers.

In order to perform the above-described various processes, it is necessary to heat the wafer, and a wafer heating device is used as a heating means. Shortening of time and soaking at a predetermined temperature were required.

For example, Japanese Patent Application Laid-Open No. 2000-272985 discloses a wafer heating apparatus mainly used for drying a photosensitive resin applied to a semiconductor wafer, and its structure is shown in FIG. In addition, one main surface of a heating plate 42 made of an aluminum nitride sintered body and having an oxide film P made of alumina coated on the entire surface is used as a heating surface 43, and the other main surface of the heating plate 42 is used. A ceramic heater 50 having a heating resistor 44 formed by printing a metal paste on a metal casing 51 is installed in an opening of a metal casing 51. By heating the heating resistor 44 to heat the heating plate 42, the wafer W on the heating surface 43 is heated.

Further, the oxide film P is formed on the surface of the heating plate 42 made of an aluminum nitride sintered body because the aluminum nitride sintered body has excellent thermal conductivity as compared with other ceramics. Although it is advantageous as a material for forming the heating plate 42 because of its high insulating property, it reacts with moisture in the atmosphere when exposed to the atmosphere to generate ammonia gas, which adversely affects the photosensitive resin. so,
By forming the heating plate 42 from an aluminum nitride-based sintered body having an oxide film P formed on the surface, the wafer W can be uniformly heated without adversely affecting the photosensitive resin. There is an advantage that the adhesion to the heating resistor formed on the surface can be improved.

[0007]

By the way, in the wafer heating device 41 used to dry the photosensitive resin applied to the semiconductor wafer W, the ceramic heater 50 is set to one.
Heating is performed at a temperature of 00 to 300 ° C. The processing time per sheet is determined by the heating time and cooling time of the ceramic heater 50. And forced cooling is performed. When a thermal cycle is repeatedly applied under such severe conditions, the ceramic heater 50 is formed on the surface of the aluminum nitride sintered body. Cracks occur at the boundary between the formed oxide film P and the heating resistor 44, and the heat transfer characteristics vary between a crack-free portion and a cracked portion, so that the uniformization of the heating surface 43 is hindered. As a result, the wafer W cannot be heated uniformly, so that the thickness of the photosensitive resin becomes non-uniform. And for the aluminum nitride sintered body and react to generate ammonia gas and amine gas, the gas is a problem such an adverse effect on the photosensitive resin.

That is, the aluminum nitride sintered body forming the heating plate 42 has a coefficient of thermal expansion of 4.7 × 10 ⁻⁶ / ° C.
On the other hand, the thermal expansion coefficient of the oxide film P made of alumina formed on its surface is about 7.3 × 10 ⁻⁶ / ° C., and there is a large difference in thermal expansion between the two. Since a tensile stress is always applied to the inside of the oxide film P, a metal paste is applied on the oxide film P and the heating resistor 44 having a larger thermal expansion coefficient is formed by baking. Due to the thermal cycle repeatedly applied by heating and cooling, a large stress acts between the oxide film P and the heating resistor 44, and a crack occurs between the oxide film P and the heating resistor 44 due to the stress. Was.

Further, the damage of the ceramic heater 50 due to such thermal stress also occurs in a film forming process and an etching process which are used by heating to a higher temperature.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention relates to a heating plate made of an aluminum nitride sintered body and having an oxide film containing Al over its entire surface. A ceramic heater is formed by forming a heating resistor on the other main surface of the heating plate and applying an insulating film on the other main surface of the heating plate so as to cover the heating resistor. It is characterized by.

As the insulating film, a heat-resistant resin is used.
The film thickness is set to 5 to 100 μm, or an oxide ceramic or glass is used, and the film thickness is set to 5 to 3 μm.
It is preferably set to 00 μm.

Further, the present invention is arranged such that an outer peripheral portion of a heating plate constituting the ceramic heater is installed so as to cover an opening of a metal casing having a bottomed cylindrical body, and the ceramic heater is supported by the metal casing. Thus, a wafer heating device is constituted.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing an example of a wafer heating apparatus provided with a ceramic heater according to the present invention. The wafer heating apparatus 1 has a metal casing 21 having a bottomed cylindrical body.
And the ceramic heater 10 provided on the metal casing 21 and provided so as to cover the opening.

The ceramic heater 10 is made of an aluminum nitride sintered body, and has an upper surface of a disk-shaped heating plate 2 having an oxide film Q containing Al on the entire surface thereof.
A heating resistor 5 made of, for example, a metal material and glass is formed in the center of the lower surface of the heating plate 2 so as to have a spiral pattern shape. And a heating resistor 5 made of glass
Are formed in a spiral pattern. The heating resistor 5 is provided with a power supply portion 6 for extracting electric power from a current-carrying terminal 7, and the lower surface of the heating plate 2 is provided with the power supply portion 6. The insulating film 4 is applied so as to cover the heating resistor 5 except for the above.

On the heating surface 3 of the heating plate 2, a plurality of support pins 8 are arranged concentrically at equal intervals, and the wafer W is supported by placing the wafer W on the top surface of the support pins 8. It has become.

Further, as means for fixing the ceramic heater 10 on the metal casing 21, as shown in an enlarged view in FIG. 2, the outer peripheral portion of the heating plate 2 constituting the ceramic heater 10 penetrates the upper and lower surfaces. A glass layer 2 is provided around the through hole on the upper and lower surfaces of the heating plate 2.
7 is formed. And the through-hole 2a of this heating plate 2
And a flange portion 22 provided at an end of the metal casing 21
The heating plate 2 is aligned with the through hole 22a
The bolt 23 is inserted into the through hole 2a on the side via a spring, an elastic member 24 such as elastic rubber, and the nut 25 is tightened on the flange portion 22 side, so that the heating plate 2 is pressed by the elastic member 24. The metal casing 21 is pressed and fixedly supported. In addition, 26
Are washers disposed between the nut 25 and the flange portion 22, between the heating plate 2 and the flange portion 22, and between the heating plate 2 and the elastic member 24.

As described above, if the glass layer 27 is formed around the through hole 2a of the heating plate 2, the metal casing 21
Even if friction occurs due to a difference in thermal expansion between the heating plate 2 and the heating plate 2, the frictional force is small because the surface is smooth, and wear can be minimized. Can be prevented from being worn out or peeled off.

An intermediate plate 27 having a through hole 27a is provided at the center of the metal casing 21.
The current-carrying terminal 7 is inserted into the through hole 27a of the middle plate 27, and an elastic member 28 such as a spring or elastic rubber is arranged between the middle plate 27 and the flange portion 7a provided at the center of the outer periphery of the current-carrying terminal 7. Then, the pressing force of the elastic member 28 presses the energizing terminal 7 against the power supply section 6 provided in the heating resistor 5, electrically connects the terminal 7, and looks at the cross section of the heating plate 2.
The central part of the heating surface 3 has a smooth convex shape slightly projecting from the outer peripheral part. Reference numeral 9 denotes a thermocouple for measuring the temperature of the ceramic heater 10.

In order to heat the wafer W using the wafer heating apparatus 1, the wafer W is placed on the support pins 8 and the power supply terminal 7 is energized to cause the heating resistor 5 to generate heat so that the heating plate 2 is heated. Heat. At this time, since the outer periphery of the heating plate 2 is in contact with the metal casing 21, the temperature of the outer peripheral portion of the heating surface 2 tends to be lower than that of the central portion due to heat shrinkage. By making the calorific value larger than the calorific value of the heating resistor 5 at the center, the heating plate 2 is made of an aluminum nitride sintered body having excellent thermal conductivity, and the heating surface 3 is smooth. Since the wafer W is formed in a convex shape and the wafer W is held by the support pins 8, it is possible to prevent the wafer W from coming into contact with the heating plate 2. When heating the wafer W, the entire surface of the wafer W can be uniformly heated without unevenness.

The wafer heating apparatus 1 applies a large amount of electric power to the ceramic heater 10 to rapidly heat the ceramic heater 10 to a predetermined temperature.
A thermal cycle of blowing air to the surface on the side opposite to the heating surface 3 to forcibly cool is applied. However, the ceramic heater 10 of the present invention has an oxide film Q containing Al.
Since the insulating film 4 is applied to the lower surface of the heating plate 2 made of an aluminum nitride sintered body provided with Since direct exposure can be prevented and rapid cooling can be suppressed, thermal stress acting on the joint between the oxide film Q and the heating resistor 5 is reduced, and cracks occur at the joint. Therefore, even if rapid cooling and rapid heating are repeated, heat can be stably generated for a long period of time.

The material for forming the insulating film 4 has a volume resistivity value of 10 ⁸ Ω · c in order to prevent the patterns of the heating resistors 5 from being short-circuited and disconnected.
m, heat-resistant resin, oxide ceramics,
Alternatively, in the case of using a heat-resistant resin formed of glass, for example, it is preferable to use polyimide, polyamide, polyimide amide, or the like that preferably has a heat-resistant temperature of 300 ° C. or higher.

Since these heat-resistant resins have a lower thermal conductivity than the heat-generating resistor 5 made of a metal material, even if air is blown during cooling, the heat-generating resistor 5 is rapidly cooled. Can be prevented, the thermal stress acting due to the difference in thermal expansion between the heating resistor 5 and the oxide film Q can be suppressed, and the thermal shock can be alleviated. Cracks can be effectively prevented from occurring at the joint between the body 5 and the oxide film Q.

Moreover, the insulating film 4 made of a heat-resistant resin is
Since the thermal conductivity is lower by at least one order of magnitude than the aluminum nitride sintered body forming the heating plate 2, heat radiation from the surface of the heating resistor 5 can be suppressed, and heat can be efficiently transmitted to the heating surface 3 side. .

However, when a heat-resistant resin is used as the insulating film 4, its thickness is preferably 5 to 100 μm. The reason is that when the film thickness is less than 5 μm, the effect of suppressing the transmission of heat to the heating resistor 5 is small, and when rapid cooling is repeated, the heating resistor 5 and the oxide film Q can be used for a short time.
When the thickness exceeds 100 μm, bubbles are generated in the resin in the drying step of the heat-resistant resin paste applied for film formation. If the insulating film 4 is used, the bubbles may move to the surface of the heat-resistant resin and break when the ceramic heater 10 is repeatedly heated, and the bubbles may cause particles. Preferably, the film thickness is 10 to 50 μm.

In the case where the insulating film 4 is formed of a heat-resistant resin, the operating temperature is limited,
It is difficult to use a heat-resistant resin as the insulating film 4 in applications exceeding ℃.

In such a case, if oxide-based ceramics or glass is used for the insulating film 4, the operating temperature is 400 ° C.
C. or higher can be suitably used.

Here, when the insulating film 4 is formed of ceramics, oxide-based ceramics are used because they are relatively stable even when used in an air atmosphere or an oxygen atmosphere. However, there is a problem in that the volume specific resistance value is small, and the patterns of the spirally formed heating resistors 5 are short-circuited to each other to cause disconnection.
Further, in the case of the nitride ceramics, it reacts with the moisture in the atmosphere to generate ammonia gas and amine gas, and the wettability with the glass forming the heating resistor 5 is extremely poor. This is because it cannot be directly applied.

In the case where an oxide-based ceramic is used as the insulating film 4, for example, alumina, mullite or magnesia spinel can be used. In the case where glass is used, a material having a heat-resistant temperature of 400 ° C. or more may be used.

Since these oxide-based ceramics or glass have a lower thermal conductivity than the heating resistor 5 made of a metal material, the heating resistor 5 is rapidly cooled even if air is blown during cooling. Therefore, thermal stress acting due to a difference in thermal expansion between the heat generating resistor 5 and the oxide film Q can be suppressed, and the aluminum nitride sintered body forming the heating plate 2 can be prevented. Since the thermal expansion difference is small, the heating resistor 5 having a large thermal expansion coefficient is sandwiched between the heating plate 2 and the insulating film 4 to reduce the thermal stress acting on the joint between the heating resistor 5 and the oxide film Q. Therefore, even if the temperature is rapidly cooled from a temperature of 400 ° C. or more, it is possible to effectively prevent cracks from being generated at the junction between the heating resistor 5 and the oxide film Q.

However, when an oxide-based ceramic or glass is used as the insulating film 4, its thickness is 5 to 30.
Preferably, the thickness is 0 μm. Because the film thickness is 5μ
m, the effect of suppressing the transfer of heat to the heating resistor 5 is small, and the effect of suppressing the expansion of the heating resistor 5 by the insulating film 4 is also small. This causes cracks to occur at the joint between the heating resistor 5 and the oxide film Q.
If the thickness exceeds 0 μm, the heat capacity of the insulating film 4 becomes too large, so that the time required for heating and cooling becomes long. Preferably, the film thickness is 10 to 200 μm.

In order to deposit an oxide ceramic as the insulating film 4, an ion plating method, a CVD method,
The film may be formed by a known film forming means such as a PVD method, a thermal spraying method, or the like. In order to apply glass as the insulating film 4, a glass paste obtained by mixing an organic solvent with glass powder is applied. What is necessary is just to form by baking.

In the present invention, the film thickness of the insulating film 4 refers to the average thickness of the insulating film 4 applied on the main surface (the widest surface) of the heating resistor 5 and may be, for example, any thickness. What is necessary is just to take the average of the thickness of 10 places measured in this way.

On the other hand, the heating resistor 5 formed on the lower surface of the heating plate 2 is made of at least one of Au, Ag, Pd, Pt, Rh and Ir, or an alloy thereof, with Zn,
It is preferable to use a glass containing at least one of B and Si.

At this time, as the glass contained in the heating resistor 5, it is preferable to use a glass whose transition point is higher than the film forming temperature of the insulating film 4.
It is possible to prevent the glass component from softening and deforming due to the heat history at the time of applying the insulating film 4, thereby preventing the resistance value of the heating resistor 5 from varying.

Further, as the glass used for the heating resistor 5,
Has Zn inside_TwoSiO_Four, Zn _ThreeB_TwoO₆, Zn_Three(B
O_Three)_Two, Zn (BO_Three)_Two, SiO_TwoAt least one of
It is preferable to use one containing crystals. these
Crystal has a small coefficient of thermal expansion.
This has the effect of lowering the expansion coefficient and
Even if cracks occur, the above crystal suppresses the progress of cracks.
Conventionally, heat of 50 to 350 ° C.
Disconnect after about 2,000 cycles in cycle test
Extend the life of the heating resistor 5 to 20,000 cycles
And provide a long-life ceramic heater 10
can do.

In particular, when a needle-shaped crystal structure is used, elongated crystals are present in a state of being entangled in the glass, so that the strength of the heating resistor 5 can be improved, which is effective.

The glass of the heating resistor 5 contains Zn ₂ Si
O ₄ , Zn ₃ B ₂ O ₆ , Zn ₃ (BO ₃ ) ₂ , Zn (B
As a method for containing at least one kind of crystal of O ₃ ) ₂ and SiO ₂ , it is sufficient to crystallize in glass or disperse in glass.

For example, when produced by crystallization,
The glass containing at least one of Zn, B, and Si, which is a component of the crystal, is heated and melted, and the molten glass is maintained at about the crystal nucleation temperature for about one hour to sufficiently generate crystal nuclei. After that, the temperature may be raised to the crystal growth temperature to form crystallized glass in the glass.

In addition to crystallization, Zn ₂ SiO ₄ , Zn ₃ B ₂ O ₆ , Zn ₃ (BO ₃ ) ₂ ,
With Zn (BO _{3) 2,} the SiO ₂ paste mixed with at least one powder may be caused to coexist in the glass by baking.

The crystal phase contained in the glass of the heating resistor 5 can be identified by X-ray diffraction (manufactured by Rigaku Denki), and the transition point of the glass forming the heating resistor 5 can be identified. Is measured by using a differential scanning calorimeter, measuring the flow of heat while increasing the temperature, and determining the intersection of the asymptote of the first endothermic shift portion of the baseline as the transition point of the glass.

Further, Au, Ag, Pd, Pt, Rh, and Ir can be used as the metal forming the heating resistor 5, and among these, Pt, Au, or an alloy thereof causes migration. It is difficult to prevent the heating resistor 5 from deteriorating.
t and Au are excellent in oxidation resistance.
The life in the thermal cycle test at 0 ° C. can be extended up to 250,000 cycles.

In obtaining the heating resistor 5, the mixing ratio of glass and metal is preferably 40:60 to 80:20 by weight. This is because if the mixing ratio of glass is less than 40 (if the mixing ratio of metal is more than 60), the amount of glass becomes too small.
On the contrary, when the mixing ratio of glass is more than 80 (when the mixing ratio of metal is less than 20), the content of metal is too small, and the volume specific resistance value is partially reduced. This is because variations occur, and the heating surface 3 of the heating plate 2 cannot be uniformly heated, and the disconnection of the heating resistor 5 easily occurs.

On the other hand, as the aluminum nitride sintered body forming the heating plate 2, it is preferable to use one having a high thermal conductivity.
As sintering aids, Y ₂ O ₃ , Er ₂ O ₃ , Ce ₂ O ₃ , Yb ₂
When a compound containing a rare earth element compound such as O _{3 in} a range of 1 to 9% by weight is used, a thermal conductivity of 100 W / m · K or more, further 150 W / m · K or more can be obtained. 2 can be suitably used.

As a means for forming an Al oxide film Q on the surface of the aluminum nitride sintered body forming the heating plate 2, an aluminum nitride sintered body is prepared by heating an aluminum nitride sintered body in an oxidizing atmosphere at 850 to 1200 ° C. Heat treatment may be performed at a temperature for about 1 to 10 hours.

Here, the heat treatment temperature is 850 to 1200 ° C.
The reason is that if the temperature exceeds 1200 ° C., the generation rate of the oxide film becomes too fast, and cracks are easily generated in the oxide film Q. Conversely, if the temperature is lower than 850 ° C., the generation of the oxide film Q is poor. This is because the entire surface of the aluminum nitride sintered body cannot be covered with the oxide film Q.

The thickness T of the oxide film Q formed on the surface of the aluminum nitride sintered body is 0.05 to 5 μm.
And the thickness T of the oxide film Q is 0.05 μm.
If it is less than m, it is difficult to completely cover the entire surface of the aluminum nitride-based sintered body by oxidation, so that the aluminum nitride-based sintered body reacts with moisture in the air to generate an ammonia gas or an amine-based gas, If the film thickness T of the oxide film Q exceeds 5 μm, the properties of the photosensitive resin formed on the wafer W are deteriorated. Since the contraction of the film Q is larger than that of the aluminum nitride sintered body forming the heating plate 2 (the coefficient of thermal expansion of the aluminum nitride sintered body: 4.7 × 10
^-6 / ° C. (20 to 400 ° C.), coefficient of thermal expansion of oxide film Q made of alumina: 7.3 × 10 ^-6 / ° C. (20 to 400 ° C.)
° C)), a tensile stress always acts on the oxide film Q due to the difference in shrinkage. In this state, if a thermal shock is applied due to the temperature rise of the heating resistor 5 and forced air cooling, cracks are generated in the heating resistor 5. Because it occurs. In addition, preferably 0.1 to
It is preferable to cover the oxide film Q in a range of 2 μm.

The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment of the present invention, and may be modified or modified without departing from the gist of the present invention. Needless to say, it's good.

[0049]

(Example 1) Here, a wafer heating device provided with a ceramic heater of the present invention and a wafer heating device provided with a conventional ceramic heater were prepared, and the heating resistor after a heat cycle test was performed. An experiment was conducted to examine the change in resistance and the presence or absence of cracks in the oxide film.

[0050] Upon this experiment, heating plate constituting the ceramic heater of 5% by weight relative to AlN powder Y ₂ O ₃
, And further kneaded and dried by adding an appropriate amount of a binder and a solvent to produce a granulated powder. The granulated powder is filled in a mold, and pressed at a molding pressure of 100 MPa.
By sintering using a hot press method of sintering at a temperature of 800 to 1900 ° C., a plate-shaped aluminum nitride sintered body having a thermal conductivity of about 120 W / m · K is manufactured, and further cut and polished. 230m outside diameter after processing
m, a disk having a thickness of 3 mm, and then heat-treated under the condition of 1000 ° C. × 3 hours.
It was manufactured by coating an oxide film made of thick alumina.

In forming the heating resistor constituting the ceramic heater, Au (30% by weight) and Pt were used.
(10% by weight) of metal powder and Zn ₂ Si
O ₄ , Zn ₃ B ₂ O ₆ , Zn ₃ (BO ₃ ) ₂ , Zn (B
A heat-generating resistor paste containing 60% by weight of glass that generates one or more types of crystal particles of O ₂ ) ₂ and SiO ₂ (quartz) was used.

In manufacturing the ceramic heater of the present invention, the heating resistor paste is printed on the surface opposite to the heating surface of the heating plate and baked at a temperature of 800 to 900 ° C. to form the heating resistor. After that, an Au paste is printed on the end of the heating resistor, and 700 to 750 is printed.
Forming a power supply part by baking at ℃,
It was manufactured by applying an insulating film to the surface of the heating plate opposite to the heating surface so as to cover the heating resistor except for the power supply portion.

When a heat-resistant resin made of polyimide, polyamide or polyimide amide is used as the insulating film covering the heating resistor, printing and drying of each resin paste are performed on the surface of the heating plate opposite to the heating surface. By repeatedly coating and baking at a temperature of 350 to 450 ° C,
When an insulating film made of a heat-resistant resin is applied and glass is used as the insulating film covering the heating resistor, a glass paste is printed on the surface of the heating plate opposite to the heated surface,
By baking at 0 ° C., an insulating film made of glass is deposited, and when alumina and silicon oxide are used as the insulating film covering the heating resistor, the heating surface of the heating plate is opposite to the heating surface using a plasma CVD method. An insulating film made of alumina and an insulating film made of silicon oxide were applied to the surface on the side. In forming the insulating film made of alumina, AlH ₃ was used as a film forming gas, and H ₂ was used as a carrier gas.
In forming an insulating film made of silicon oxide, SiH ₄ was used as a film forming gas and H ₂ was used as a carrier gas.

On the other hand, in manufacturing a conventional ceramic heater, the heating resistor paste was printed on the surface of the heating plate opposite to the heating surface and baked at a temperature of 800 to 900 ° C.

Then, each of the obtained ceramic heaters was installed in an opening of a metal casing having a bottomed cylindrical body to manufacture a wafer heating apparatus.

Then, a current is applied to the heating resistor of each of the obtained ceramic heaters, the temperature of the wafer placed on the heating surface is raised to 300 ° C. in 90 seconds, and the wafer is heated to 300 ° C. by forced air cooling.
Thermal cycle test to cool to 50 ° C or less in 10,000 seconds
Cycling was performed, and a change in resistance value of the heating resistor before and after the heat cycle test was confirmed. The temperature of the wafer was measured using a resistance temperature element installed on the wafer.

Further, a portion of the heating plate after the heat cycle test was cut out, and the presence or absence of cracks in the oxide film Q was confirmed by an electron microscope.

The results are as shown in Table 1.

[0059]

[Table 1]

As a result, the sample No. As shown in No. 22, in the conventional ceramic heater having no insulating film, cracks were observed in the oxide film after the heat cycle test. In addition, a large change was observed in the resistance value of the heating resistor before and after the heat cycle test.

On the other hand, the sample No. As shown in Nos. 1 to 21, each of the ceramic heaters of the present invention in which an insulating film was applied so as to cover the surface of the heating resistor had no cracks in the oxide film after the heat cycle test, and had good durability. showed that.

However, when the insulating film is formed of a heat-resistant resin, the sample No. When the film thickness of the insulating film is smaller than 5 μm as in the case of Sample No. 14, the resistance value of the heating resistor changes greatly because the effect of the insulating film as a protective film is small. As in 19, the thickness of the insulating film is 100
If it exceeds μm, bubbles were generated in the heat-resistant resin forming the insulating film.

As a result, when a heat-resistant resin is used as the insulating film, it is preferable that the film thickness be 5 to 100 μm.
It can be seen that it is better to apply in the range of １００100 μm.

In the case where the insulating film was formed of oxide ceramics or glass, the sample No. When the thickness of the insulating film is less than 5 μm as in Examples 1 and 4, the effect of the insulating film as a protective film is small, and the change in the resistance value of the thermal resistor is large. If the thickness of the insulating film exceeds 300 μm as in 13, the heat capacity of the insulating film becomes too large, and there is a disadvantage that the electric power required for heating to a predetermined temperature becomes too large.

As a result, when an oxide ceramic or glass is used as the insulating film, the thickness of the film is 5 to 300 μm.
It turns out that it is good to set it to m.

[0066]

As described above, according to the present invention, one main surface of a heating plate made of an aluminum nitride sintered body and having an oxide film containing Al on the entire surface is used as a heating surface. A heating resistor is formed on the other main surface of the heating plate, and an insulating film is applied to the other main surface of the heating plate so as to cover the heating resistor, thereby forming a ceramic heater. Even if severe conditions such as temperature rise and rapid cooling are repeated, cracks do not occur at the junction between the oxide film covering the aluminum nitride sintered body forming the heating plate and the heating resistor, and heat is not generated. Since the characteristics of the resistor are not deteriorated, a ceramic heater having excellent durability can be provided.

Further, the top surface of a metal casing having a bottomed cylindrical body is brought into contact with the outer periphery of a heating plate constituting the ceramic heater, and the ceramic heater is supported by the metal casing to constitute a wafer heating apparatus. By
It is possible to provide a wafer heating apparatus that has a short tact time and does not adversely affect the resin when drying the photosensitive resin.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a wafer heating apparatus using a ceramic heater according to the present invention.

FIG. 2 is an enlarged partial cross-sectional view of a fixing structure of a heating plate of a ceramic heater and a metal casing constituting the wafer heating apparatus of the present invention.

FIG. 3 is a sectional view showing a conventional wafer heating apparatus.

[Explanation of symbols]

 1: Wafer heating device 2: Heating plate 3: Placement surface 4: Insulating film 5: Heating resistor 6: Power supply unit 7: Conductive terminal 8: Support pin 9: Thermocouple 10: Ceramic heater 21: Metal casing 22: Flange Part 23: Bolt 24: Elastic member 25: Nut 26: Washer 27: Glass layer 41: Wafer heating device 42: Heating plate 43: Heating surface 44: Heating resistor 35: Conductive terminal 50: Ceramic heater 51: Metal casing P: Oxide film Q: Oxide film W: Wafer

Claims (4)

[Claims] 1. A heating plate made of an aluminum nitride sintered body and having an oxide film containing Al over its entire surface is used as a heating surface, and heat is generated on the other main surface of the heating plate. A ceramic heater, wherein a resistor is formed, and an insulating film is applied to the other main surface of the heating plate so as to cover the heating resistor. 2. The method according to claim 1, wherein said insulating film is made of a heat-resistant resin, and has a thickness of 5 to 100 μm.
The ceramic heater according to 1. 3. The ceramic heater according to claim 1, wherein said insulating film is made of an oxide ceramic or glass, and has a thickness of 5 to 300 μm. 4. An outer peripheral portion of a heating plate constituting the ceramic heater according to any one of claims 1 to 3, is disposed at an opening of a metal casing having a bottomed cylindrical body, and is provided by the metal casing. A wafer heating device supporting the ceramic heater.