JP3589429B2 - Pyrolytic boron nitride-coated multilayer molded article and method for producing the same - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a pyrolytic boron nitride-coated multilayer molded article excellent in heat resistance, corrosion resistance, and chemical stability, and a method for producing the same.
[0002]
[Prior art]
Pyrolytic boron nitride (hereinafter abbreviated as PBN) has advantageous properties such as heat resistance, corrosion resistance, chemical stability, and high purity, and can be used as a graphite layer, Al ₂ O ₃ , Si ₃ N ₄ , SiC, Various application products have been developed which cover the multilayer molded body made of a ceramic substrate such as BN or PBN and make use of its characteristics. For example, Japanese Utility Model Application No. 3-030393 discloses a PBN coating of a ceramic heater in which a pyrolytic graphite (PG) layer is formed on a PBN substrate, and Japanese Patent Application Laid-Open No. 5-105557 discloses a PG heat absorbing layer formed on a PBN container. There is one coated with a PBN coating layer.
[0003]
[Problems to be solved by the invention]
However, when coating the outermost surface of the multilayer molded body with PBN, if there are irregularities on the surface of the multilayer molded body, internal stress is generated in the PBN coating layer at the corner, and cracks and peeling are likely to occur. There were drawbacks. In addition, when used as a contact heating type ceramic heater, temperature variation occurs, and when used as an electrostatic chuck, the electrostatic attraction force is reduced.
SUMMARY OF THE INVENTION The present invention is directed to a pyrolytic boron nitride-coated multi-layered molded product which solves such a drawback, and in particular, the multi-layered molded product comprises an insulating ceramic substrate and a PG layer multi-layered molded product, and a PBN coating layer is formed on the outermost surface thereof. TECHNICAL FIELD The present invention relates to a ceramic heater, an electrostatic chuck, a heat shield plate, a heat shield cylinder, a container with a heat absorbing band, and a method for manufacturing the same.
[0004]
[Means for Solving the Problems]
The present inventors have investigated the causes of cracks and peeling phenomena that occur in the PBN coating layer in order to solve such problems, and as a result, the internal stress is concentrated on the portions of the ceramic substrate-PG layer multilayer molded body where the surface irregularities are significant. The present invention has been completed by examining this stress dispersion method, and the gist of the invention is that the outermost surface of a multilayer molded body in which a PG layer is provided on the surface of a substrate made of ceramic is heated. In forming the decomposed boron nitride layer, after forming the same groove portion as the pattern in advance on the base material, forming the PG layer, removing the convex portion, and polishing, the surface irregularity difference is set to 100 μm or less, and The present invention relates to a method for producing a PBN-coated multilayer molded article characterized by forming a PBN layer, and a PBN-coated multilayer molded article produced by this method, which comprises a ceramic heater, an electrostatic chuck, and a heat shield plate. , Shield It was found to have excellent quality as a cylinder and a container with heat absorption band.
Hereinafter, the present invention will be described in detail.
[0005]
[Action]
When the causes of cracks and peeling phenomena occurring in the PBN coating layer were investigated, it was found that internal stress was concentrated on the portions of the ceramic substrate-PG layer multilayer molded body having large irregularities.
This internal stress is generated at the corners of the uneven portion and is due to the thermal anisotropy of PBN and PG. The magnitude of the stress is 1) large anisotropy, 2) coating It was found that the film was thicker and 3) the larger the irregularities in the corners, the larger the film.
In general, the thermal expansion coefficients of PBN and PG are anisotropic, and the thermal expansion coefficient in the growth direction during the deposition of PBN and PG shows a value about 10 times that in the direction perpendicular to the growth direction. If the substrate surface is perpendicular to the growth direction, the coefficients of thermal expansion of the substrate and the coating match, but if the substrate surface is parallel to the growth direction, a difference of 10 times occurs in the coefficient of thermal expansion, As a result, the substrate surface length increases, and the stress generated here increases. For example, as shown in FIG. 3, in the cross section of the PBN-PG multilayer molded body, stress is generated due to a temperature difference when cooled from a PBN deposition temperature to a normal temperature on a vertical surface of a groove cut for pattern processing. become. For these reasons, these stresses can be reduced by minimizing the unevenness of the PBN-coated surface. Therefore, as this stress dispersion method, a PG layer is formed after forming a concave pattern on a substrate made of insulating ceramics in advance, the convex portion is removed, and the unevenness of the surface of the molded body is reduced to 100 μm or less, preferably 50 μm. The problem was solved by polishing and polishing as described above. This has also been found to be effective, especially when it is necessary to thicken the PG film.
Further, this contributes to improvement of the uniformity in the case of the ceramic heater and improvement of the electrostatic force in the case of the electrostatic chuck.
[0006]
If the surface unevenness exceeds 100 μm, the stress relaxation effect is lost, so it is necessary to set the thickness to 100 μm or less. Similar effects can be obtained by depositing a PG layer on a flat insulating substrate, setting the thickness of the PG layer to 100 μm or less, and setting the PG pattern processing to a step of 100 μm.
[0007]
Next, an example of the production method of the present invention will be described.
For example, in the case of a ceramic heater, a conventional processing method is to deposit a PG layer serving as a heating resistor on an insulating plate to a uniform thickness by a CVD method, and then cut and remove the PG layer along a heater pattern shown in FIG. , On which a PBN layer was coated. When this cutting is performed by ordinary end milling, this cross-sectional shape has irregularities with a groove depth d = 200 μm or more, and when the PBN layer is covered (FIG. 3), cracks enter the PBN layer 3 from the corners 4. , Peeling occurs. As the ceramic heater is repeatedly heated and lowered several times, cracks occur in the entire PBN coating layer, and the ceramic heater becomes unusable.
In the manufacturing method of the present invention, as shown in the vertical sectional view of FIG. 1, first, a groove having the same shape as the heater pattern is formed by cutting the insulating ceramic substrate to a depth of, for example, 200 to 300 μm (FIG. 1A). Then, a PG layer is formed on the surface by CVD to fill the grooves (FIG. 1B). The PG layer is cut and removed by milling until a boundary of the heater pattern appears, and a heater pattern is formed. Is polished to make the difference in unevenness 100 μm or less, preferably 50 μm or less (FIG. 1C). By coating PBN on the surface of the multilayer molded body produced by this method by the CVD method, a good PBN coating layer free from cracks and peeling can be obtained.
[0008]
【Example】
Hereinafter, embodiments of the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.
(Example)
A PBN substrate having a diameter of 100 mm and a thickness of 1.2 mm was formed with a groove having the same shape as that of the heater pattern shown in FIG. 3 to a depth of 200 μm using a square end mill (FIG. 1A). It was put into a CVD apparatus, the temperature was raised to 1900 ° C., 5 SLM of high-purity propane gas and 20 SLM of hydrogen were introduced, the pressure was maintained at 12.5 Torr, and the reaction was carried out for 15 hours to obtain a 150 μm PG sedimentary layer (FIG. b)). Next, a heater pattern was formed by cutting and removing an excess PG layer of the convex portion by a grinder, and then polished with abrasive grains to reduce the surface irregularity difference to 10 μm or less (FIG. 1C). Next, this was put into the CVD apparatus again, the temperature was raised to 1800 ° C., BCl ₃ , NH ₃ , and H ₂ were introduced at 1 SLM, 5 SLM, and 20 SLM, respectively, and the reaction was performed for 6 hours while maintaining the pressure at 8.7 Torr and 50 μm. (FIG. 1 (d)). This heater was energized in a vacuum vessel and the heating and cooling at 0 to 1000 ° C. were repeated 20 times, but the PBN layer did not crack or peel.
[0009]
(Comparative example)
Using the same flat PBN base material as in the example, a PG layer was formed thereon to a thickness of 150 μm under the same conditions as in the example, and cut to a depth d = 300 μm using a normal square end mill. Was formed under the same conditions as in the example to prepare a heater having a PBN coating layer having a thickness of 50 μm. Next, when the heater was energized in a vacuum vessel and heated and cooled at 0 to 1000 ° C., the PBN coating was peeled off the first time.
[0010]
【The invention's effect】
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PBN-coated multilayer molded body in which defects such as cracks and peeling caused by internal stress generated during PBN film formation have been eliminated, and a method for producing the same. It is an object of the present invention to provide a PBN-coated multilayer molded article having excellent durability, such as a hot plate, a heat shield cylinder, and a container with a heat absorbing band.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of a processing method according to the present invention.
(A) A step of forming a groove on a PBN substrate surface by an end mill.
(B) Step of forming a PG layer.
(C) A step of cutting and removing an excess PG layer and polishing.
(D) forming a PBN layer on the PG layer;
FIG. 2 is a top view showing the structure of the ceramic heater.
FIG. 3 is a vertical cross-sectional view showing a stress generating portion.
[Explanation of symbols]
1 base 2 PG layer 3 PBN coating layer

Claims (7)

In a method for producing a pyrolytic boron nitride-coated multilayer molded body comprising forming a pyrolytic boron nitride layer on the surface of a multilayer molded body having a pyrolytic graphite layer provided on the surface of a substrate made of an insulating ceramic, A groove having the same pattern as that of the pyrolytic graphite layer is formed on the surface of the base made of the conductive ceramic, a pyrolytic graphite layer is formed thereon, and then the surface is cut and removed and polished to reduce the surface irregularity to 100 μm or less. A method for producing a pyrolytic boron nitride-coated multilayer molded body, comprising: forming a pyrolytic graphite layer pattern surface; and forming a pyrolytic boron nitride layer on the outermost surface by a CVD method. A substrate comprising the insulating ceramic according to claim 1, wherein the substrate comprises one or more ceramics selected from boron nitride, pyrolytic boron nitride, silicon nitride, aluminum nitride, silica, and alumina. A method for producing a multilayer molded body coated with pyrolytic boron nitride. A method for producing a pyrolytic boron nitride-coated multilayer molded body, wherein the substrate made of the insulating ceramic according to claim 2 is made of pyrolytic boron nitride. In a multi-layer molded body coated with a pyrolytic boron nitride formed by forming a pyrolytic boron nitride layer on the surface of a multi-layer molded body formed by forming a pyrolytic graphite layer on the surface of a substrate made of insulating ceramics, Embedded in a surface of a substrate made of an insulating ceramic, and the surface of the substrate has an irregularity of 100 μm or less. A substrate comprising the insulating ceramic according to claim 4, wherein the substrate comprises one or more ceramics selected from the group consisting of boron nitride, pyrolytic boron nitride, silicon nitride, aluminum nitride, silica and alumina. Pyrolytic boron nitride coated multilayer molded body. A multi-layer molded body coated with pyrolytic boron nitride, wherein the substrate made of the insulating ceramic according to claim 5 is made of pyrolytic boron nitride. Pyrolytic boron nitride coating multilayer molded article, characterized in that pyrolytic boron nitride coating multilayer molded article according is ceramic heater to claim 4.

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