JP2013035741A - Silicon carbide heating element for raw material gas supply - Google Patents

Abstract

Disclosed is a silicon carbide heating element for supplying a raw material gas having good air permeability.
A gas permeable heating member 2 made of silicon carbide that generates heat when energized and an end member 3 that energizes the gas permeable heating member 2 have a pipe shape with one end closed. A silicon carbide heating element 1 for supplying raw material gas, wherein the gas permeable heating member has a porosity of 20% or more and less than 35% and a gas permeability of 0.04 slpm · cm / torr · cm ² or more. A silicon carbide heating element 1 for supplying a raw material gas.
[Selection] Figure 1

Description

  The present invention relates to a silicon carbide heating element for supplying a source gas for an electric furnace. More specifically, a silicon carbide heating element for supplying a raw material gas capable of supplying a gas from the surface of the heating portion while supplying a semiconductor raw material from one end of a pipe-like silicon carbide heating element and heating it to heat it into a high temperature gas. It is about.

  The supply of the source gas in the step of forming a semiconductor film on a substrate such as a solar cell is generally called an injector and has a double pipe structure. The inner pipe is provided with a raw material gas outlet, and the outer pipe is provided with a slit or a round hole on the side facing the outlet of the inner pipe. A space between the inner pipe and the outer pipe serves as a buffer so that the source gas flows out from the outer pipe at a uniform flow rate (Patent Document 1: Japanese Patent Application Laid-Open No. 2007-63575).

  Further, Patent Document 2: Japanese Patent No. 3504613 discloses that an inner pipe is energized using a gas-permeable silicon carbide heating element and heated to discharge the raw material gas to the outer pipe.

However, in general, a silicon carbide heating element is used as a heat source of an electric furnace, and is deteriorated by the equation (1), so that the porosity is required to be as small as possible for the purpose of preventing oxygen diffusion into the heating element. Usually, the porosity of a silicon carbide heating element is about 25%. (Non-Patent Document 1)
(1) SiC + 2O ₂ → SiO ₂ + CO ₂
If the porosity of the silicon carbide heating element is about 25%, in order to release the source gas from the inner diameter, the pressure loss is large and a pressure difference occurs between one end and the other end, and the source gas cannot be released uniformly. there were.

The gas permeability required for the silicon carbide heating element for heating and supplying the raw material gas is 0.04 slpm · cm / torr · cm ² or more, preferably 0.07 slpm · cm / torr · cm ² or more. When the porosity of the silicon carbide heating element is about 25%, the gas permeability is 0.01 to 0.02 slpm · cm / torr · cm ² , and the gas permeability is low.

  Further, an exhaust gas purifying honeycomb heater (for example, Patent Document 3: Japanese Patent Application Laid-Open No. 2010-106735) has been proposed as a silicon carbide heating element that transmits gas. However, this honeycomb heater has a porosity of 90% or more, a small current capacity per unit cross-sectional area, and thus a small calorific value (kW), so it cannot be a heating element for supplying a raw material gas for an electric furnace. .

JP 2007-63575 A Japanese Patent No. 3504613 JP 2010-106735 A

New edition industrial furnace handbook (Japan Industrial Furnace Association) p707-p709

  The problem to be solved by the invention is to provide a silicon carbide heating element for supplying a raw material gas having good air permeability.

The gist of the present invention is as follows.
(1) For supplying a raw material gas having a pipe shape having a structure in which one end is made of silicon carbide, which includes a gas permeable heating member that generates heat by energization and an end member that energizes the gas permeable heating member. A raw material gas characterized by being a silicon carbide heating element, wherein the porosity of the gas permeable heating member is 20% or more and less than 35% and the gas permeability is 0.04 slpm · cm / torr · cm ² or more. Silicon carbide heating element for supply.
(2) The silicon carbide heating element for supplying a source gas as described in the item (1), wherein the gas permeability is 0.07 slpm · cm / torr · cm ² or more.
(3) Mixing silicon carbide raw material powder with 0.5 to 7% by weight of silicon dioxide powder having an average particle size of 50 to 150 microns, and forming and firing into a pipe shape to produce a gas permeable heating member. The method for producing a gas-permeable silicon carbide heating member according to item (1) or (2), wherein end members are joined.
(4) The method for producing a gas-permeable silicon carbide heating member according to item (3), further comprising mixing 20 to 60% by weight of carbonaceous powder with respect to the silicon dioxide powder.
(5) Mixing silicon carbide raw material powder with acrylic resin spherical fine particles having an average particle size of 80 to 150 microns, forming and firing into a pipe shape to produce a gas permeable heating member, and joining end members A method for producing a gas-permeable silicon carbide heating member as described in (1) or (2).

  The silicon carbide heating element for supplying source gas according to the present invention is suitable for heating and supplying source gas in a step of forming a semiconductor film on a substrate such as a solar cell.

It is a front view of the heat generating body for source gas supply of this invention. It is sectional drawing of the heat generating body for source gas supply of this invention.

  1 and 2 are views showing a configuration of a silicon carbide heating element for supplying a source gas according to an embodiment of the present invention. FIG. 1 is a front view and FIG. 2 is a cross-sectional view.

  In FIG. 1, a silicon carbide heating element 1 for supplying a source gas has a pipe shape, and one end thereof is closed as is apparent from FIG.

  The silicon carbide heating member 2 located at the center in the longitudinal direction of the raw material gas supply silicon carbide heating element 1 is gas permeable.

  End members 3 for energizing the gas permeable silicon carbide heating member 2 are located at both ends in the longitudinal direction of the raw material gas supply silicon carbide heating element 1.

  The source gas supplied from the open end of the pipe-shaped silicon carbide heating element 1 for supplying source gas passes through the gas-permeable heating member and is supplied by heating.

The gas permeable heating member has a porosity of 20% or more and less than 35% and a gas permeability of 0.04 slpm · cm / torr · cm ² or more, preferably 0.07 slpm · cm / torr · cm ² or more.

If the porosity of the gas permeable heat generating member is less than 20%, the gas permeability is 0.01 slpm · cm / torr · cm ² or less, which is not preferable. If the porosity exceeds 35%, the strength of the heat generating part This is not preferable because of a decrease in the quality of the system and a problem in handling.

Further, if the gas permeability of the gas permeable heating member is less than 0.04 slpm · cm / torr · cm ² , the pressure loss becomes large and the raw material gas cannot be supplied uniformly, which is not preferable.

In order to produce a gas permeable heating member having a porosity of 20% or more and less than 35% and a gas permeability of 0.04 slpm · cm / torr · cm ² or more, the average particle size of the recrystallized silicon carbide raw material powder is Either mix and mold 0.5 to 7% by weight of silicon dioxide powder of 50 to 150 microns, or mix and form acrylic resin spherical fine particles with an average particle size of 80 to 150 microns in silicon carbide raw material powder for recrystallization. That's fine.

  In the method of manufacturing a gas permeable heating member by blending silicon dioxide powder, if the average particle size of the silicon dioxide powder is less than 50 microns, the pore diameter formed in the gas permeable silicon carbide heating member And the effect of improving the gas permeability is reduced, and the average particle diameter is more than 150 microns. This is not preferable because the pore diameter increases and the strength of the heat generating part decreases greatly.

  Further, if the addition rate of silicon dioxide powder is less than 0.5% by weight, the effect of improving gas permeability is reduced, which is not preferable. If the addition rate exceeds 7% by weight, the strength reduction of the heat generating portion increases. Therefore, it is not preferable.

  In forming the gas permeable heat generating member, a binder may be blended, and the binder may be one used for ordinary ceramic molding, such as PVA or cellulose organic binder.

  For the purpose of improving the strength of the gas permeable heating element, carbonaceous powder may be added to the silicon dioxide powder when the gas permeable heating element is molded.

  The compounding quantity of carbonaceous powder is 20 to 60 weight% with respect to silicon dioxide powder. When the blending amount of the carbonaceous powder is less than 20% by weight, no improvement in the strength of the gas permeable heating element is observed, and even if the blending exceeds 60% by weight, only carbon remains.

  In the case of a method for producing a gas-permeable heating member by blending silicon dioxide powder, the firing after molding may be performed within a range of 2200 to 2600 ° C.

  The method for producing a gas-permeable heat generating member by blending acrylic resin spherical fine particles is that acrylic resin spherical fine particles disappear due to calcination or firing because acrylic resin spherical fine particles have a perfect spherical shape. The shape of the holes formed is also a perfect sphere. That is, the gas permeability of the gas permeable silicon carbide heating member becomes uniform.

  Furthermore, since it disappears at a relatively low temperature of 200 to 400 ° C., no gas that inhibits firing is generated near the firing temperature, and thus firing is facilitated.

  The acrylic resin-based spherical fine particles in the present invention are resins mainly composed of polymethyl methacrylate (PMMA), polyacrylonitrile (PAN) or the like. There are cross-linked PMMA fine particles, polyacrylonitrile fine particles, etc., and they are used as matting agents and fluidity improvers for paints and inks. In particular, PMMA has a spherical shape and high water dispersibility.

  For example, “Tough Tick AR650” series manufactured by Toyobo Co., Ltd. can be mentioned.

  When the average particle diameter of the acrylic resin-based spherical fine particles to be blended is less than 80 microns, the pore diameter formed in the gas-permeable silicon carbide heating member is reduced, and the effect of improving gas permeability is reduced. If the average particle diameter of the resin-based spherical fine particles exceeds 150 μm, the pore diameter increases and the strength of the heat generating part decreases greatly, which is not preferable.

  The acrylic resin spherical fine particles may be blended in an amount of 1 to 7% by weight with respect to the silicon carbide raw material powder.

  When the blending amount of the acrylic resin-based spherical fine particles is less than 1% by weight, it is not preferable that the addition rate is less than 1% by weight because the effect of improving gas permeability is reduced, and when it exceeds 7% by weight, heat is generated. This is not preferable because the strength of the part is greatly reduced.

  In the case of a method for producing a gas-permeable heat generating member by blending acrylic resin spherical fine particles, firing after molding may be performed at 2200 to 2600 ° C.

  Moreover, you may calcine before baking.

  The terminal member of the present invention is a normal silicon carbide described in Non-Patent Document 1, such as a reaction sintered silicon carbide (composite material of silicon carbide and silicon) or a recrystallized silicon carbide impregnated with silicon. What is necessary is just the end member quality of a heat generating body.

  In order to form a silicon carbide heating element for supplying a raw material gas using silicon dioxide, a predetermined amount of silicon dioxide, carbon and an organic binder are added to a silicon carbide raw material powder for recrystallization, followed by dry mixing, and then an appropriate amount. Add water and knead. Thereafter, it is formed into a pipe shape by extrusion and dried. The dried molded body can be fired at 2200 ° C. to 2600 ° C. in a non-oxidizing atmosphere to form a recrystallized silicon carbide heating portion, that is, a gas permeable heating member. The added silicon dioxide disappears upon firing.

  As physical properties suitable for the gas permeable heating member, the specific resistance is 0.06 to 0.12 Ωcm, and the bending strength is 20 MPa or more, preferably 30 MPa or more.

  By cutting the recrystallized silicon carbide heating part (gas permeable heating member) to a predetermined length and welding the ends, a silicon carbide heating element for supplying raw material gas can be obtained.

Example 1
1% by weight of silicon dioxide powder with an average particle diameter of 80 microns and 2.5% by weight of organic binder are added to the recrystallized silicon carbide raw material powder for recrystallization and dry-mixed. In addition, after kneading, it was formed into a pipe shape having an outer diameter of 50 mm and an inner diameter of 33 mm.

  The molded body was dried and then fired at 2400 ° C. to prepare a gas-permeable silicon carbide heating member as a recrystallized silicon carbide heating element. The specific resistance of the heat generating member was 0.08 Ωcm.

  Further, as shown in FIG. 2, silicon carbide heating elements 50 × 1200 × 350 (outer diameter × heat generation section length) for supplying a raw material gas are bonded to silicon carbide / silicon end portions having the same outer diameter and inner diameter. X end length). The 1,000 ° C rating of this silicon carbide heating element for supplying raw material gas was 146V, 186A.

  For the evaluation, the porosity, bending strength, appearance (presence or absence of cracks) of the heat generating portion and the gas permeability test of the silicon carbide heating element for supplying the raw material gas were conducted. The results are shown in Table 1.

Example 2
A silicon carbide heating element for supplying a raw material gas was prepared in the same manner as in Example 1 except that the amount of silicon dioxide added was 7% by weight.

Comparative Example 1
A silicon carbide heating element for supplying a raw material gas was prepared in the same manner as in Example 1 without adding silicon dioxide.

Comparative Example 2
A silicon carbide heating element for supplying a raw material gas was prepared in the same manner as in Example 1 except that the amount of silicon dioxide added was 10% by weight.

Example 3
Example 1 is the same as in Example 1 except that the addition amount of silicon dioxide was 0.6% by weight and the carbonaceous powder was added by 50% by weight to silicon dioxide (0.3% by weight with respect to silicon carbide). Similarly, a silicon carbide heating element for supplying raw material gas was prepared.

Examples 4 and 5 and Comparative Examples 3 and 4
A silicon carbide heating element for supplying a raw material gas was prepared in the same manner as in Example 1 except that the composition of silicon dioxide and carbon was changed to Table 1.

Examples 1, 2, 3, 4, and 5 have a gas permeability of 0.04 slpm · cm / torr · cm ² or more and a porosity of 20 to 35%, which is suitable as a silicon carbide heating member for supplying raw material gas. It was something.

  Comparative Examples 1 and 3 had low gas permeability and were not suitable as silicon carbide heating elements for supplying raw material gas.

  In Comparative Examples 2 and 4, the gas permeability was high, but the gas leaked through the crack, the bending strength was low, and it was unbearable for use in an electric furnace.

Example 6
7% by weight of acrylic resin spherical fine particles with an average particle size of 80 microns and 2.5% by weight of organic binder are added to dry-crystallized silicon carbide raw material powder by a conventional method and dry-mixed. % And kneaded, and formed into a pipe shape having an outer diameter of 50 mm and an inner diameter of 33 mm.

The molded body was dried and then fired at 2350 ° C. to prepare a gas-permeable silicon carbide heating member as a recrystallized silicon carbide heating element. The specific resistance of the heat generating member was 0.09 Ωcm.
Other than that, a silicon carbide heating element for supplying a source gas was prepared in the same manner as in Example 1. The 1,000 ° C rating of this silicon carbide heating element for supplying raw material gas was 146V, 173A.

  In addition, when the smoke test was visually performed using the sample of Example 6 and the sample of Example 5 having substantially the same gas permeability values, the boundary of the heat generating portion on the side where Example 6 was sealed at one end Smoke erupted uniformly to near.

Example 7
A silicon carbide heating element for supplying a raw material gas was prepared in the same manner as in Example 6 except that 3% by weight of acrylic resin spherical fine particles having an average particle size of 100 microns was added and 7.6% of added water was used.

Example 8
A silicon carbide heating element for supplying a raw material gas was prepared in the same manner as in Example 6 except that acrylic resin spherical fine particles having an average particle size of 160 microns were 1% by weight, added water was 8.0%, and calcined at 500 ° C. Created.

In Examples 6, 7, and 8, the gas permeability was 0.04 slpm · cm / torr · cm ² or more and the porosity was 20 to 35%, which was suitable as a silicon carbide heating member for supplying raw material gas.

  In addition, firing was possible at a temperature lower than that of addition of silicon dioxide, and gas permeation was uniform.

  A silicon carbide heating element for supplying a source gas suitable for supplying a source gas in a step of forming a semiconductor film on a substrate such as a solar cell can be provided.

DESCRIPTION OF SYMBOLS 1 Heating element for source gas supply 2 Gas-permeable silicon carbide heating member 3 End member

Claims (5)

A silicon carbide for supplying a raw material gas having a pipe shape having a structure in which one end is closed, comprising a gas permeable heating member made of silicon carbide and generating heat by energization and an end member for energizing the gas permeable heating member Carbonization for supplying raw material gas, characterized in that the gas permeable heating member has a porosity of 20% to less than 35% and gas permeability of 0.04 slpm · cm / torr · cm ² or more. Silicon heating element. ^{2. The} silicon carbide heating element for supplying a raw material gas according to claim 1, wherein the gas permeability is 0.07 slpm · cm / torr · cm ² or more.   3. The silicon carbide raw material powder is mixed with 0.5 to 7% by weight of silicon dioxide powder having an average particle size of 50 to 150 microns, and molded and fired into a pipe shape. Of manufacturing a gas-permeable silicon carbide heating member.   The method for producing a gas-permeable silicon carbide heating member according to claim 3, further comprising mixing 20 to 60% by weight of carbonaceous powder with respect to the silicon dioxide powder.   3. The gas permeable silicon carbide according to claim 1, wherein acrylic resin-based spherical fine particles having an average particle size of 80 to 150 microns are mixed with silicon carbide raw material powder, and are molded and fired into a pipe shape. A method for producing an elementary heating member.

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