JP2779052B2 - Multilayer ceramic heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multilayer ceramic heater, particularly a high-purity ceramic heater which does not scatter metal impurities even under high temperature and high vacuum. The present invention relates to a multilayer ceramic heater suitable for the space industry.

[Prior Art] With the recent technological progress, a large number of heating processes are required in the industrial world, especially in the semiconductor industry, so that the required characteristics of heaters in various heating processes are becoming strict.

In other words, the heating heater used in the semiconductor industry may adversely affect the device due to metal impurities scattered from the heater during heating, or may cause a disadvantage that the degree of vacuum is reduced. Is alumina, aluminum nitride,
A wire or foil of a high-melting-point metal such as molybdenum or tungsten is wound as a heater or bonded to a sintered body such as zirconia or quartz as a heater.

[Problems to be Solved by the Invention] However, these heaters are disadvantageous in that metal impurities from a sintered binder and carbon due to insufficient degreasing are mixed into the sintered body, and the heating is also difficult. The heater is complicated to assemble, and it is difficult to control the temperature precisely because the heater cannot directly contact the object to be heated.Furthermore, since the heater is made of metal, deformation and embrittlement due to heat are apt to occur, shortening and sparking There is a drawback that such troubles often occur.

Therefore, for this type of heater, a film of pyrolytic carbon (hereinafter abbreviated as PG) is deposited on a pyrolytic boron nitride (hereinafter abbreviated as PBN) molded body, and this PG portion is cut and processed. Although a heater circuit has been developed, this is a high-purity product, but it requires a long time for the reaction because PG is made by the pyrolysis method. Since it is performed by cutting, it is extremely expensive, and there is a disadvantage that a product having a complicated shape cannot be manufactured.

[Means for Solving the Problems] The present invention relates to a multilayer ceramic heater which solves such disadvantages, and applies a synthetic organic compound to a high-purity ceramic so as to form a circuit pattern. It is characterized in that the compound is fired at a temperature higher than its decomposition temperature to form a carbon film heater.

In other words, the present inventors have conducted various studies to develop a heater that is free from impurity contamination from the heater, has little deformation and embrittlement, and is compact and inexpensive, and can also handle complicated shapes. If the compound is applied to a desired circuit pattern and then fired at a temperature equal to or higher than its decomposition temperature, this organic compound becomes a carbon film heater, and a multilayer ceramic in which the carbon film heater is firmly bonded on a ceramic substrate・ Besides finding out that the heater can be obtained, it is of high purity, so there is no contamination by impurities from the heater, and it is not deformed or embrittled. Therefore, molecular beam epitaxy (MBE), MOCVD, plasma Heating heaters for which precise temperature control is required, such as CVD, sputtering, and electron beam irradiation (EB) equipment The present invention has been completed by confirming that it is useful as a heater for heating which degasses and disperses impurities under high vacuum.

 This will be described in more detail below.

[Function] The present invention relates to a multilayer ceramic heater in which a carbon film heater is attached to high-purity ceramics.

The ceramic base constituting the multilayer ceramic heater of the present invention is made of insulating high-purity ceramic.

As the ceramic substrate, alumina, zirconia, silicon dioxide, magnesia, beryllia, titania,
Examples include aluminum nitride, silicon nitride, boron nitride, titanium nitride or a composite thereof.If this contains a large amount of metal impurities, these impurities may be scattered during use under high temperature and high vacuum. It is necessary to use a high-purity metal impurity having a metal impurity content of 10 ppm or less, since it may be mixed into the object to be processed. Therefore, this ceramic substrate is preferably made by chemical vapor deposition (CVD), which has good heat resistance and heat shock properties, and has no degassing pyrolytic boron nitride (PBN). ).

The carbon film heater constituting the multilayer ceramic heater is made by firing a synthetic organic compound. This is because when this organic compound is natural, the content of impurities is extremely large, and it is necessary to chemically synthesize the organic compound. Examples thereof include thermoplastic resins such as polystyrene and polyethylene, and thermosetting resins such as phenol resins, furfural resins, epoxy resins, and polyester resins.

The formation of the carbon film heater with this synthetic organic compound
After the synthetic organic compound is applied on the above-mentioned ceramic substrate so as to form a desired circuit pattern, it is baked at a temperature not lower than its thermal decomposition temperature and carbonized. It is desirable that the synthetic organic compound be made of a thermosetting resin, since it is desirable that there is no occurrence of the deformation and deformation of the formation pattern. Further, the carbon film heater thus formed needs to be firmly bonded to the ceramic substrate. It is important to select the firing atmosphere and the firing temperature. An inert gas atmosphere such as high-purity argon or helium may be used, and the calcination temperature is such that the carbonization of the organic compound is performed at about 800 to 1,500 ° C., and at 1,500 ° C. or higher, graphitization starts, and up to 2,200 ° C. As the temperature increases, the hardness increases and the electrical resistance decreases,
When the temperature exceeds 2,200 ° C, decomposition of the carbon film starts,
The temperature may be in the range of 00 to 2,200 ° C. If this carbon film also contains a large amount of metal impurities, the impurities coming out of the heater will cause a defect in the object to be processed. Therefore, it is necessary that the metal impurities be 50 ppm or less. The thickness of the carbon film is 100 μm or less, preferably 50 μm to avoid peeling due to a heat cycle or the like.
The following may be used.

The multilayer ceramic heater of the present invention has a two-layer structure in which a carbon film heater produced by firing a synthetic organic compound on a high-purity ceramic substrate is formed.
This may be a three-layer structure in which high-purity ceramics are bonded on the carbon film heater as necessary, or a multi-layer structure in which the two-layer structure is combined in multiple stages. According to this, there is provided an advantage that a high-purity multilayer ceramic heater can be easily and inexpensively obtained.

[Examples] Next, examples of the present invention and comparative examples will be described.

EXAMPLE Boron trichloride and ammonia were combined under reduced pressure
Perform a chemical vapor deposition reaction at a temperature of 900 ° C for 15 hours, and
When a pyrolytic boron nitride (PBN) molded body having a diameter of 1 mm and a thickness of 1 mm was produced, the amount of metallic impurities in the PBN was 8 ppm.

Then, an epoxy resin-Epicoat 815 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) is applied on the PBN molded body by screen printing in a spiral circuit pattern having a width of 3 mm, and heated to 800 ° C. in an argon gas atmosphere. Is heated at a rate of 150 ° C / min, heated to 1,900 ° C at a rate of 250 ° C / min, baked at this temperature for 5 hours, and then cooled. Since a vortex formed at 2.0 μm was obtained, molybdenum electrodes were attached to both ends of the vortex of the carbon film with carbon screws to produce a multilayer ceramic heater.

Next, a GaAs film was formed using this as a substrate heating device of a molecular beam epitaxy (MBE) device, and the film was heated at 20 ° C.
When the electron mobility was measured at 8,400 cm ² / V
c, which is the theoretical value of 8,500 cm ² / V
・ Excellent high purity GaAs because it is close to sec
It was confirmed that a film was obtained.

Comparative Example After washing with methanol, the boron nitride sintered body (BN) was purified to a high purity by heat treatment at 2,000 ° C. for 50 hours.
When a disk having a thickness of 5 mm was manufactured, the amount of metallic impurities was 35 ppm.

Next, a spiral carbon film was formed on the BN molded body in the same manner as in Example 1 using a purified natural rubber solution (metal impurity amount: 700 ppm), and electrodes were provided in the same manner as in Example 1 to form a multi-layer. We made a multilayer ceramic heater.

Next, this was used as a substrate heating device for the MBE
When a film of s was formed and the electron mobility of the film was measured, it was 2,000 cm ² / V · sec, which was a defective product.

[Effects of the Invention] The present invention relates to a multilayer ceramic heater, in which a synthetic organic compound is applied to a high-purity ceramic in a desired circuit pattern as described above, and the organic compound is heated to the decomposition temperature or higher. It is characterized in that it is baked at a temperature of 2 to become a carbon film heater. According to this, the carbon film heater is firmly bonded to the ceramics, and the ceramics and carbon film heater are of high purity. When used as a heating heater, there is no contamination by impurities from the heater, and it is not deformed or embrittled by heating, so it can be used for molecular beam epitaxy (MBE), MOCVD, plasma CVD, sputtering, electron beam irradiation It is useful as a heater for heating (BE) equipment and as a heater that avoids degassing and scattering of impurities under high temperature and high vacuum. Advantage that is given.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 41/87 H05B 3/14

Claims (4)

(57) [Claims] 1. A multilayer film comprising a high purity ceramic coated with a synthetic organic compound so as to form a desired circuit pattern, and firing the organic compound at a temperature not lower than its decomposition temperature to form a carbon film heater. Ceramic heater. 2. The multi-layer ceramic heater according to claim 1, wherein the high-purity ceramic is pyrolytic boron nitride having a metal impurity amount of 10 ppm or less, formed by a chemical vapor deposition method. 3. The multilayer ceramic heater according to claim 1, wherein the synthetic organic compound is a thermosetting resin having a metal impurity of 50 ppm or less. 4. The multilayer ceramic according to claim 1, wherein the firing of the synthetic organic compound is performed at a temperature of 800 to 2,200 ° C.
heater.