JP2948357B2 - Multilayer ceramic heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for heating a multilayer ceramic heater, especially for a silicon wafer for semiconductors, and for heating a substrate when forming a thin film by a chemical vapor deposition method or a sputtering method. The present invention relates to a multilayer ceramic heater to be used.

[0002]

2. Description of the Related Art Conventionally, as a heater used in a semiconductor process, a wire or foil of a refractory metal such as molybdenum or tungsten is wound as a heating element on a support made of sintered ceramics such as alumina, aluminum nitride, and zirconia. Or, what is adhered has been used. Further, as this improved product, a product in which a heat generating layer made of conductive ceramics is provided on a support base material made of electrically insulating ceramics has also been developed.

[0003]

However, since the heating element is made of a metal, the above-mentioned known heater is liable to be deformed or embrittled, and therefore has a short life and is difficult to assemble. Is also complicated.
In addition, this improved product has the advantage that it has a long life because the heating element is made of ceramics and is easy to assemble because the heating element is integrated with the supporting base material. Since there is only one surface of the base material, there is no portion that absorbs the difference in thermal expansion between the two.Therefore, when the temperature changes, the heater is deformed. There is a defect that the temperature becomes uniform and the temperature uniformity is impaired.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a multilayer ceramic heater which has solved such disadvantages.
This is pyrolytic boron nitride or chemical vapor deposited silicon nitride
Pyrolytic graphite or chemical on both sides of the supporting substrate is
It is characterized in that a heat generating layer made of vapor deposited silicon carbide is provided.

That is, the present inventors have conducted various studies to develop a multilayer ceramic heater which has solved the conventional disadvantages. As a result, the heating layers of conductive ceramics are provided on both surfaces of a support base made of electrically insulating ceramics. For example, the deformation due to the difference in thermal expansion between the supporting base material and the heat generating layer is counteracted by the conductive ceramics on the back surface, so that even when the temperature changes, the deformation of the heater does not occur. It has been found that the uniformity of temperature is not impaired even when used for heating, and this conductive ceramic may be other ceramics having substantially the same thermal expansion coefficient, Young's modulus, and Poisson's ratio as this. After confirming that, the present invention was completed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a laminated ceramic heater, which comprises conductive ceramics on both surfaces of a support substrate in order to cancel deformation due to a difference in thermal expansion coefficient between the support substrate and the heating layer. It is provided with a heating layer.

The multilayer ceramic heater according to the present invention is provided with conductive ceramics as heat generating layers on both sides of a support base made of electrically insulating ceramics. The electrically insulating ceramics constituting the support base is thermally decomposed and nitrided. Boron
Or chemical vapor deposition silicon nitride, and the conductive ceramic of the heating layer is made of pyrolytic graphite or chemical vapor deposition carbonization.
It should be silicon .

However, in this type of multilayer ceramic heater, if the heating layer adhering to the surface of the supporting substrate is sufficiently thin, heating the heating layer causes a change in the temperature of the supporting substrate. The following equation between the material and the surface layer: σ = Et (1-vt) · (αt−αs) · ΔT (where σ: thermal stress, Et: Young's modulus of the surface layer, vt:
Poisson's ratio of the surface layer, αt: coefficient of thermal expansion of the surface layer, α
s: thermal expansion coefficient of the substrate, ΔT: temperature change), and the magnitude of this thermal stress is determined by its thermal expansion coefficient, Young's modulus, and Poisson's ratio, as can be seen from this equation. Therefore, in the conventionally known multilayer ceramic heater, the coefficient of thermal expansion, Young's modulus, of the ceramics forming the supporting base material and the ceramics forming the heat generating layer,
Due to the difference in Poisson's ratio, thermal stress is generated during heating, which deforms the heater.

[0009] The multilayer ceramic heater of the present invention comprises a support base material, and heat generating layers provided on both surfaces of the support base material.
Since a heat generation layer of the same type as the front surface heat generation layer is provided on the back surface of the support base material, when this is heated, thermal stress is also generated between the support base material and the heat generation layer on the back surface, This thermal stress occurs between the supporting base material and the heat generating layer on the surface.
Since the balance is made at the same value as above, the deformation of the heater is prevented.

[0010] In this case, the heat generating layer provided on the back surface of the supporting substrate is are those of conductive ceramic and the same kind of heat-generating layer provided on the surface of the supporting substrate, the supporting substrate and the surface As long as the same thermal stress as that generated between the heat generating layer and the heat generating layer is generated, the conductive ceramic layer of the heat generating layer provided on the back surface of the supporting base material has the same thermal expansion as the ceramic layer on the front surface. rate, Young's modulus, it is not always necessary to those of the same kind as long as it has a Poisson's ratio.

The supporting substrate of the multilayer ceramic heater according to the present invention is made of the above ceramics, and is composed of pyrolytic boron nitride or silicon nitride manufactured by a chemical vapor deposition method.
As compared with the one manufactured by the sintering method, there is no impurity caused by the binder and the like, so that an effect of high purity can be obtained.

The conductive ceramic of the heat generating layer is also made of silicon carbide produced by a chemical vapor deposition method, like the supporting substrate.
Pyrolytic carbon or pyrolytic obtained by thermal decomposition such as methane
Graphite . According to this, the heat generation layer can be made of high purity.

Further, the multilayer ceramic heater of the present invention thus manufactured is suitable for heating a semiconductor wafer in a semiconductor process, since the heater is of high purity and has no deformation. When this is used in a III / V compound semiconductor process, pyrolytic boron nitride, which is a homologous compound, is used as the supporting base material, and the heat generating layer and the compensation layer are formed of heat having good adhesion to the pyrolytic boron nitride. The use of pyrolytic carbon and the entire coating with pyrolytic boron nitride has the advantage that contamination by group IV elements, alkali metals, heavy metals, etc. can be prevented, and is supported when used in silicon semiconductor processes. Substrate is made of chemical vapor deposited silicon nitride containing no group III metal element, and the heat generating layer and compensation layer are made of chemical vapor deposited by group IV compound. Garbled have a homo or pyrolytic carbon the group III metal element or an alkali metal, it is possible to prevent contamination by heavy metals.

[0014]

Next, examples of the present invention and comparative examples will be described. Example 1 and Comparative Example 1 Ammonia and boron trichloride were reacted at 2,000 ° C. under a vacuum of 10 Torr to obtain a diameter of 80 mm and a thickness of 1 mm.
The pyrolytic boron nitride inner plate is made, and pyrolytic carbon obtained by heating methane gas to 2,200 ° C. under a vacuum of 5 torr at 2,200 ° C. is adhered on both surfaces to a thickness of 10 μm. This heater pattern was processed to produce a multilayer ceramic heater.

Next, a diameter of 3
Inch gallium arsenide wafer from room temperature to 1,000 ° C
When heated, the disk-shaped heater did not show any deformation, and the temperature uniformity of the wafer was good as ± 2 ° C. However, in the same manner except that no heat-generating layer was provided on the back surface for comparison. When a similar test was performed using the manufactured heater, the heater was warped by 0.4 mm.
The temperature uniformity of the wafer was also poor at ± 9 ° C.

Example 2, Comparative Example 2 Ammonia and silicon tetrachloride were added under vacuum of 5 torr,
The reaction was carried out at 400 ° C. to produce a chemical vapor deposited silicon nitride disk having a diameter of 110 mmφ and a thickness of 1 mm.
A chemical vapor deposited silicon carbide layer obtained by reacting at 0 ° C. was provided with a thickness of 5 μm, and a heater pattern was processed on both sides to produce a multilayer ceramic heater.

Next, a diameter of 4
When an inch silicon wafer was heated from room temperature to 1,000 ° C., no deformation was observed in the disk-shaped heater, and the temperature uniformity of the wafer was as good as ± 1 ° C. When a similar test was performed using a heater manufactured in the same manner except that no heat generating layer was provided, the heater was warped by 0.5 mm, and the temperature uniformity of the wafer was poor at ± 10 ° C. .

Example 3, Comparative Example 3 Ammonia and silicon tetrachloride were added under vacuum of 5 torr,
The reaction was carried out at 400 ° C. to produce a disk made of chemical vapor deposited silicon nitride having a diameter of 110 mm and a thickness of 1 mm, and then pyrolysis obtained by heating methane gas on both sides to 1,700 ° C. under a vacuum of 8 Torr. A carbon layer was provided with a thickness of 12 μm, and a heater pattern was processed on both sides to produce a multilayer ceramic heater as a heating layer.

Next, using this disk-shaped heater,
When an inch silicon wafer was heated from room temperature to 1,000 ° C., no deformation was observed in the disk-shaped heater, and the temperature uniformity of the wafer was as good as ± 1 ° C. When a similar test was performed using a heater manufactured in the same manner except that no heat generating layer was provided, the heater was warped by 0.5 mm, and the temperature uniformity of the wafer was poor at ± 10 ° C. .

[0020]

According to the present invention, the table on the back surface of the supporting substrate
Since the same heat generation layer as the surface is provided, the same heat stress as the heat stress generated between the support substrate and the heat generation layer on the front surface when the heater is heated causes the heat generation layer on the support substrate and the heat generation layer on the back surface. also occurs between this because two thermal stress is balanced without heater is deformed, the wafer temperature uniformity better of when using this to heat treatment of the semiconductor process wafer, also support Base material and heat generating layer with high purity
The effect that becomes becomes .

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Kubota 2-13-1 Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Chemical Co., Ltd.Precision Functional Materials Laboratory (72) Inventor Imada Harada Isobe, Annaka-shi, Gunma Prefecture No. 2-13-1 Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Laboratory (58) Field surveyed (Int. Cl. ⁶ , DB name) H05B 3/14 C04B 41/87

Claims (1)

(57) [Claims] 1. Pyrolytic boron nitride or chemical vapor deposition nitriding
Pyrolytic graphite or both sides of a silicon support substrate
Is a multi-layer ceramic heater characterized by having a heating layer made of chemical vapor deposited silicon carbide .