JPS60258917A - Manufacture of sic-si heat equalizing tube for manufacturing gas impermeable semiconductor - Google Patents

Abstract

PURPOSE:To reduce the contents of copper and an alkali metal in a heat equalizing tube to an allowable concentration by selectively removing the copper and the alkali metal by heat treatment in the atmosphere mainly consisting of a halogen gas. CONSTITUTION:Silicon nitride, silicon carbide, etc. for industrial use are used and these raw materials' powder or the burned products made from them are treated in the atmosphere of a halogen gas such as chlorine, hydrogen chloride, freon, silicon tetrachloride maintained at a temperature of 900-1,400 deg.C and impurities of copper and an alkali metal are made halogenides such as copper chloride, alkali metal chloride, etc. having a low boiling point, volatilized and removed. The content of copper can be made 20ppm or less and the content of alkali metal can be made 100ppm or less only by heat treatment in the halogen gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a gas-impermeable 5iC-8i soaking tube for semiconductor manufacturing, which prevents contamination of semiconductor materials.

[Technical background of the invention and its problems] In general, a soaking tube for semiconductor manufacturing is installed in a diffusion furnace for semiconductor manufacturing, and the heat in the diffusion furnace is transferred to a quartz tube as a bare tube loaded inside the soaking tube. This is a member that uniformly irradiates the semiconductor material inside the quartz tube and uniformly fires the semiconductor material inside the quartz tube.

By the way, oxide sintered tubes made of alumina, mullite, etc. have been used as conventional heat soaking tubes, but these heat soaking tubes have low heat conductivity and spalling resistance, so their temperature rise and fall rates are slow. This hindered semiconductor manufacturing efficiency. In addition, since these soaking tubes have a high porosity, during operation, alkaline substances that evaporate from the furnace wall due to high temperatures easily pass through the heat soaking tubes and devitrify the quartz tube inside. However, it has the disadvantage that it partially passes through quartz and contaminates semiconductor materials.

For this reason, recrystallized silicon carbide tubes have recently been considered as soaking tubes. This soaking tube has high thermal conductivity and excellent spalling properties, so it can stably heat the semiconductor material, and has the advantage of being able to efficiently manufacture semiconductors with fast temperature rise and fall rates. are doing. However, on the other hand, since it has an apparent porosity of around 20%, it still has the same problem as the above-mentioned oxide sintered tube in that it is easy for alkaline substances vaporized during operation to pass through.

On the other hand, in order to improve this drawback, the recrystallized silicon carbide tube is impregnated with molten metal silicon to lower the air permeability.
-SiC-Sl based soaking tubes have been proposed. However, this soaking tube has high temperatures during operation because impurities such as copper are mixed in during the process of recrystallizing the sintered silicon carbide and impregnating the metal silicon, especially during the process of impregnating the metal silicon. Copper evaporates from the soaking tube itself, passes through the quartz tube inside the soaking tube and contaminates the semiconductor material, resulting in a short lifetime and the generation of many etch pit crystal dislocations, making it possible to obtain only a conductor. There wasn't. The occurrence of these etch pits has been a fatal defect 1 particularly in the production of bipolar, linear, etc. junction semiconductors.

One way to prevent this is to use high-purity metal silicon in the process of impregnating the recrystallized silicon carbide body with metal silicon. An improvement in body purity is observed.

However, this still does not fully meet the requirements.

In view of these various problems, the present inventors have attempted to manufacture an STC-ST system soaking tube that will not cause copper to volatilize from the SiC-St system and contaminate semiconductor materials even under high temperatures during operation. and conducted extensive research. As a result, stc −
The volatilization of copper from the ST-type soaking tube is of course related to the content of hooks in the tube, but even if the content is minute, volatilization may proceed depending on the conditions. It was assumed that the presence of other impurities in the soaking tube was involved in the volatilization of copper. After various investigations into other impurities in the soaking tube, it was determined that it was the alkali metals mixed in that promoted the volatilization of copper.

Therefore, we further explored various relationships between the content ratios of copper and alkali metals, and found that when the copper content exceeds 20 ppm, the volatilization of copper from the soaking tube progresses regardless of the presence of alkali metals. It has been found that even if the alkali metal content is 20 ppm or less, copper volatilization progresses when the alkali metal content exceeds 100 ppm. Note that the influence of alkali metals is the greatest in promoting the movement of copper ions, and in the case of iron, aluminum, etc., the influence is relatively small, so there is no need to consider their presence when the copper content is low.

Moreover, even if only the content of copper is limited, volatilization of copper cannot be prevented. That is, since the alkali metal promotes the movement of copper ions as described above, when the alkali metal is in excess, the volatilization of copper from the soaking tube progresses even if the copper content is small. Therefore, by limiting both copper and alkali metal, volatilization of copper from the soaking tube can be prevented for the first time.

In this way, by limiting the copper content to 20 ppm or less and the alkali metal content to 100 ppm or less in the gas-impermeable 5tc-st soaking tube, It has been found that the volatilization of copper is prevented, and it is possible to produce a semiconductor with an extremely long lifetime and no generation of etch pits, and it is also possible to prevent devitrification and cracking of the quartz tube inside the soaking tube.

However, according to the conventional manufacturing method, as mentioned above, it is difficult to manufacture such high-purity 5IC-8i soaking tubes because copper and other substances are mixed in during the impregnation process of metal silicon into recrystallized silicon carbide. be.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a method for producing a 5TC-ST soaked tube in which the refining process is improved so as to obtain a 5IC-81 soaked tube in which copper and alkali metals are reduced to the above-mentioned allowable concentrations. It is.

[Summary of the invention]

That is, 81C for gas impermeable semiconductor manufacturing according to the present invention.
-8i type soaking tubes are manufactured by selectively removing copper and alkali metals by heat treatment in an atmosphere mainly consisting of Halon 6-1 series, and reducing the copper content in the soaking tubes. of 20 ppm or less, and the alkali metal content is 100 ppm or less.

[Embodiments of the invention]

The method for manufacturing a gas-impermeable 5-inch-81 type soaking tube according to the present invention will be described below with reference to Examples, but it is needless to say that the method is not limited to this method.

Conventionally, in order to manufacture a 5-inch-8-ton soaking tube, first, a binder such as tar pitch is added to and mixed with powder mainly composed of high-purity silicon carbide, and then molded into a mother tube shape using a normal molding machine. After molding, the binder in this molded body is fired and carbonized at a temperature of about 800° C. to produce a fired body.

Then, this fired body is embedded in a filling powder mainly made of high-purity silicon nitride, and heat-treated at a high temperature of about 2000°C. In this high-temperature heat treatment step, silicon nitride decomposes and generates silicon gas. This silicon gas silicides the carbon in the fired body to produce silicon carbide, and at the same time, silicon gas permeates and deposits into the pores in the fired body. Gas-impermeable 8IC
-81 series soaking tube can be obtained. However, in such a method, it is necessary to use raw materials of extremely high purity, which increases the cost significantly. Furthermore, there is a risk of contamination during the manufacturing process such as powder manufacturing, so it is not possible to achieve the desired purity at a low cost. I can't get what I want.

This invention uses usually commercially available industrial silicon nitride, silicon carbide, etc. 1-1 These raw material powders or the fired bodies made from them are heated with chlorine, hydrogen chloride, etc. maintained at a temperature of 900 to 1400°C, for example. Halogens such as freon and silicon tetrachloride are treated in a gas atmosphere for a certain period of time, for example, about 2 hours, to reduce the boiling point of copper and alkali metal impurities into halides such as copper chloride and alkali chloride, respectively, and volatilize and remove them. , a 5iC-8t soaking tube with extremely low content of copper and alkali metals is obtained. According to this method, a gas-impermeable semiconductor with a copper content of 20 ppm or less and an alkali metal content of 1009 pm or less can be manufactured by simply performing heat treatment in a halogen-based gas. 5tc-st soaking tube can be easily manufactured.

The composition of the soaking tube produced by the method of the present invention is usually 70 to 95% by weight of silicon carbide and 30 to 5% by weight of free silicon, and the porosity varies depending on the state of the pores at the time of production of the silicon carbide body. Although it cannot be absolutely limited, in the case of unconnected vents, gas impermeability can be sufficiently maintained if the porosity is set to 3 cm or less.

In addition, if a large amount of impurities other than copper and alkali metals such as iron, manganese, chromium, etc. are mixed into the soaking tube and have an adverse effect on semiconductor materials, it is desirable to suppress the mixing of these impurities, especially other impurities. The amount of iron mixed in as an impurity is 20
It is desirable to suppress it to 0.00 ppm or less.

Next, one embodiment of this invention will be described.

91 Example 1 First, commercially available silicon nitride powder (particle size 1 to 3 vm) was
Processed in a chlorine gas atmosphere maintained at a temperature of 0°C to selectively reduce copper and sodium, silicon nitride powder (containing copper IPP'% sodium 10 Ppnl) was prepared as a filling powder.
prepared. Next, silicon carbide powder (containing copper 5P"% sodium 40 ppm) and lamp black (containing copper 4pP"% sodium 20 ppm) were purified in the same manner.
After adding phenol resin and kneading, it is granulated and dried, and then molded using a rubber press to form an outer diameter of 1.
A molded body with a length of 20 m, an inner diameter of 105 mm, and a length of 1500 mm was made. Subsequently, after firing this molded body at 800°C,
Furthermore, it is embedded in the silicon nitride powder and
It was heated and recrystallized at a temperature of 00°C to obtain a SiC-83 soaking tube. This soaking tube contained 6.3% by weight of free silicon, had a porosity of 0.5 inch, and was gas impermeable.

In addition, the content of copper in this soaking tube was 16 ppm, sodium was 50 ppm; iron was 2000 ppm, and 10
- That's it.

Example 2 The fired body used in Example 1 was treated with cyclochlorine gas in the same manner as in Example 1 to form a mixed powder (containing 2 pP"% copper and 10 ppm sodium) of high-purity silica powder and returned powder. ) and heated to a temperature of 1,500 to 2,050°C to recrystallize it.It contains 4.2% by weight of free silicon from K and has a gas permeability of 5ic-st recrystallized material (copper) with a porosity of 11.6%. 3 pP"% sodium content (containing 55 ppm) was obtained. Next, this recrystallized product was mixed with silicon powder (containing 42 ppm copper, 400 ppm sodium) with a particle size of 1 to 5 m+.
The tube was filled with carbon and heated to 2000 to 2100° C., and the pores were impregnated with silicon to obtain a SiC-Si soaking tube. This soaking tube contained 12.1% by weight of free silicon, had a porosity of 0.54, and was impermeable to gas. Still, the content of copper in this soaking tube is 7 ppm%, and the content of sodium is 95 ppm.
pm and 1000 ppm of iron.

Example 3 Silicon carbide powder (copper 3
Phenol resin was mixed with lamp black (containing 4 ppm of copper and 20 ppm of sodium) and lamp black (containing 4 ppm of copper and 20 ppm of sodium), and then the obtained calcined body was heated with chlorine at 1200°C for 2 hours in the same manner as in Example 1. After gas treatment, high-purity metal silicon (copper IPP"% sodium 1 ppm or less) was brought into contact at a high temperature of 1500°C to impregnate the pores to obtain an 81C-8L soaking tube.

This soaking tube contained 13.5% by weight of free silicon, had a porosity of 0.5%, and was gas impermeable. In addition, the copper content in this soaking tube is 2 ppm%, and the sodium content is 5 ppm%.
ppm% iron was 200 ppm.

Next, three types of experimental examples conducted as comparative examples with respect to the above-mentioned examples will be explained.

Comparative Examples 1 to 3 Commercially available silicon nitride powder (18 ppm copper) IJum 70
After adding and mixing phenol resin to lamp black (containing 4 ppm of copper and 20 ppm of sodium), the mixture was molded and fired in the same manner as in Example 1 to obtain a sintered body. Next, this sintered body was mixed with a mixed powder of silica powder and returned powder (copper 10 ppm, sodium 30 ppm).
The porosity is 15, containing 3.0% by weight of free silicon.
Gas permeability 5iC-81 recrystallized material (copper 16.5
ppm.

This recrystallized product was then converted into a silicon powder containing 20 ppm of copper and 400 ppm of sodium (Comparative Example 1), 40 ppm of copper, (Na) IJ.
Embedded in silicon powder containing 200 ppm of copper (Comparative Example 2) and silicon powder containing 60 ppm of copper and 600 ppm of sodium (Comparative Example 3) of 1500 to 2100 ppm, respectively.
℃ to impregnate silicon into the pores of the pores to form a material containing 15.7% by weight of free silicon and a porosity of 0.7 cm.
A seed 5iC-8L soaking tube was obtained. The content of copper and IJum in these soaking tubes is as follows: Comparative Example 1 has copper 19
．． 5ppms sodium 125ppm content, comparative example 2
13- Contains 22 ppm of copper and 90 ppm of sodium, and Comparative Example 3 contains 26 ppm of copper and 151 ppm of sodium.
Met.

Now, the following tests were conducted on the six types of 5ic-si soaking tubes obtained in Examples 1, 2.3 and Comparative Examples 1 to 3. That is, first, these 810-8i type soaking tubes were attached to a diffusion furnace, and then a quartz tube with a bipolar material inside was inserted into these soaking tubes. And 1
The operation of manufacturing semiconductors by heating them to 250°C was continued for one year, and the condition of each quartz tube and the occurrence of etch pits in the manufactured semiconductors were observed. These results are shown in the table below.

14- As is clear from the table above, the SiC-Si soaked tube (Example 1.2.3) containing 20 ppm or less of copper and 100 ppm or less of alkali metal does not work as well as a quartz glass tube even after one year of use. was not colored, and the manufactured semiconductor had a long lifetime and was of extremely high quality with no etch pit crystal transition. On the other hand, even if copper is 20 ppm or less, alkali metals are 100 ppm or less.
The 5iC-8i soaking tube (comparative example 1) with ppm or more is 1
After being used for ~3 months, the quartz glass tube became colored red, and the obtained semiconductor had many etch pits, the lifetime was short, and pulse noise defects occurred frequently.

Also, even if the alkali metal content is 1100 pp or less, copper is 20 pp.
5iC-8T containing pm or more [Effects of the Invention] As detailed above, the 5tc-st soaking tube for semiconductor manufacturing manufactured according to the present invention has a particularly low concentration of impurities such as copper and alkali metals. Even if the temperature is high during operation, copper will not volatilize from the soaking tube itself, unlike in the conventional method.

As a result, the quartz glass tubes inside these soaking tubes do not devitrify, and the semiconductors manufactured here have a long lifetime and are of extremely high quality with no etch pits. It shows a remarkable effect on the production of junction semiconductors such as I-La and linear. Furthermore, conventional SI
Since high thermal conductivity and high heat resistance similar to C-81 type soaking tubes are ensured, semiconductor manufacturing efficiency is also good. Moreover, since the method of the present invention only requires heat treatment in an atmosphere mainly containing a halodane gas, it can be carried out extremely easily.

Applicant's agent: Patent attorney Suzue Takehiko 17-

Claims (1)

[Claims] A silicon compound is heated in an atmosphere mainly containing halogen gas to selectively reduce copper and alkali metals, so that the copper content is 20 ppm or less and the alkali metal content is 100 ppm or less. A method for producing a 5IC-8i soaking tube for producing gas-impermeable semiconductors made of silicon carbide and free silicon, characterized in that: