Ceramic heating jig

Details Ceramic heating jig Ceramic heating jig

2000-12-04

2002-05-07

Paik, Sang (Department: 3742)

Electric heating

Heating devices

Combined with container, enclosure, or support for material...

C219S548000, C118S725000

Reexamination Certificate

active

06384383

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ceramic heating jig, more specifically to a ceramic heating jig suitably used for a heat treatment process in a process for producing a semiconductor device or an optical device.
2. Description of the Related Art
As a general resistance heating heater used for a process for producing a semiconductor device or the like, there has been conventionally used a heater wherein a wire or a foil made of metal having high melting point such as molybdenum, tungsten (W) or the like is wound around or adhered on a base material made of sintered ceramics such as alumina, aluminum nitride, zirconia, boron nitride, or the like, on which a electrical insulating ceramic plate is placed. As improvement thereof, there have been developed a resistance heating ceramic heater wherein an exothermic layer made of conductive ceramics is provided on an electrical insulating ceramic base material, on which electrical insulating ceramic is coated, and a resistance heating ceramic heater wherein a conductive heating element such as W or the like is buried in electrical insulating ceramic, and is molded integrally. They are improved in insulating property and corrosion resistance.
As a ceramic base material, there is generally used a sintered body wherein a sintering additive is added to a raw material powder, which is then sintered. In such a ceramic base material, damage is caused by thermal stress generated due to a difference of thermal expansion coefficient from heterogeneous material such as a heating element. For example, when semiconductor wafer or the like is placed and heated on a ceramic heater base consisting of heterogeneous material such as a ceramic base material and a heating element, a failure of surface close contact with the wafer may be occurred due to the above-mentioned damage, which may cause disorder of temperature distribution.
As a method for suppressing such damage, there have been proposed, a method of increasing stiffness by increasing thickness of ceramic base material, and a method of reinforcing fixing with a table. However, if a damage is suppressed by methods described above, thermal stress may be concentrated inside of ceramic base material, and on an interface between a ceramic base material and a heating element. Accordingly, if temperature is increased and decreased repeatedly, problems such as breakage at sintered grain boundary or an interface between a ceramic base material and a heating element may be caused.
Furthermore, if thickness of a ceramic base material is increased, thermal capacity is increased, and thus there may be caused a problem that it takes long time to raise and lower a temperature.
In order to solve the problem, there have been developed a multi-layer resistance heating ceramic heater that is an integral type wherein a heater pattern consisting of pyrolytic graphite film formed by thermal chemical vapor deposition method (thermal CVD method) is joined on a surface of a supporting substrate consisting of pyrolytic boron nitride film formed by thermal CVD method, and the heater pattern is covered with a close layered protective film made of the same material as that of the supporting substrate, namely pyrolytic boron nitride.
The multi-layer resistance heating ceramic heater has a high purity and is chemically stable and strong to thermal shock. Accordingly, it has been used in various fields that requires rapid raising and lowering of temperature. For example, it has been used in a field of production of a semiconductor wafer. Specifically, it is used widely at a continuous process wherein a semiconductor wafer or the like is treated in a single wafer processing method, and temperature is changed in phase. Since the multi-layer ceramic heater is totally manufactured by a CVD method as described above, there is no grain boundary, and thus there is no de-gassing, so that there is no harmful influence to the process when heating is conducted in a vacuum process. Accordingly, it has been used in a wider field.
However, pyrolytic boron nitride constituting the above-mentioned multi-layer ceramic heater has a small Young's modulus, a warp is caused during heating due to thermal stress remaining in the substrate during production. If a wafer or the like is placed and heated directly thereon, failure of surface close contact may be caused, which may cause disorder in temperature distribution. Accordingly, it is necessary that susceptor made of material that has large Young's modulus and is excellent in heat resistance is located on the ceramic heater, and the wafer is placed thereon to be heated.
A susceptor has a thermal capacity corresponding to size, and a rate of raising and lowering temperature of a wafer in the case that a wafer is heated on the susceptor depends on thermal capacity of the susceptor. The rate of raising and lowering temperature can be increased by decreasing thermal capacity of a susceptor. In that case, it is necessary to decrease thermal capacity by decreasing thickness of the susceptor, since it is necessary to make an area of upper surface thereof the same or more as the wafer. If a thin susceptor is used, thermal capacity can be decreased, and a rate of raising and lowering temperature is raised. However, if it is too thin, there may be caused a warp during processing of the susceptor and thermal deformation during raising and lowering temperature, which may lead to disorder of temperature distribution due to failure of surface close contact with a wafer.
In the case that a susceptor is fixed to the ceramic heater or the like by fastening tightly with a screw or a bolt, stress generated around the fixed part when it is fasten, or thermal stress generated during heating may cause swell of the susceptor, which may lead to breakage thereof. As described above, deformation or breakage due to fixing with a screw or a bolt is not only a problem in the susceptor, but also a problem in a part that is especially heated, such as a ceramic heater, a heat shielding plate used for shielding heat of a ceramic heater or the like.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above-mentioned problems, and an object of the present invention is to provide a ceramic heating jig wherein defects such as thermal deformation, breakage or the like of susceptor or the like are hardly caused, temperature can be raised or lowered rapidly, and flatness of a susceptor can be kept even at high temperature.
To solve the above-mentioned problems, the present invention relates to a ceramic heating jig consisting of a susceptor on which a work to be heated is placed, a ceramic heater for heating the susceptor and at least one heat shielding plate for shielding heat of the ceramic heater wherein the susceptor and the heat shielding plate are located so that each of them is located across the ceramic heater each leaving a certain space therefrom, a thickness of the susceptor is 0.5 mm to 5 mm, a thickness of the ceramic heater is 0.5 mm to 3 mm, a thickness of the heat shielding plate is 0.5 mm to 3 mm.
As described above, in a ceramic heating jig wherein the susceptor having a certain thickness and at least one heat shielding plate are located so that each of them is located across the ceramic heater each leaving a certain space therefrom, a thickness of the susceptor and the ceramic heater is not too thin, so that strength is sufficient, swell or the like is never caused on the upper surface of the susceptor. They are not too thick either, so that they have small thermal capacity, and can raising and lowering a temperature rapidly.
In that case, it is further preferable that an interval between the susceptor and the ceramic heater, and an interval between the heat shielding plate and the ceramic heater are 0.5 mm to 10 mm.
If the susceptor, the ceramic heater and the heat shielding plate are located leaving such an interval, the intervals between them are not too narrow nor too wide, the heat of the ceramic heater can be conduct

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