JPH0135774B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing semiconductor polycrystalline silicon, and more particularly to a method for utilizing waste generated in a manufacturing process for semiconductor polycrystalline silicon.

The method proposed below eliminates the unreacted chlorosilane, hydrogen and chloride present in methods for producing semiconductors from the gas phase, for example in the growth of epitaxial structures or in the production of large size single and polycrystalline semiconductor materials. Applicable for regeneration and utilization of effluent steam/gas mixtures consisting of hydrogen.

Various methods are known in the art for regenerating unreacted chlorosilane and hydrogen in semiconductor polycrystalline silicon manufacturing processes.

For example, when the vapor/gas mixture to be regenerated consisting of unreacted chlorosilane and hydrogen chloride is subjected to multiple recirculation into a hydrogen reduction unit, chlorosilane is
Semiconductor polycrystalline silicon is produced by reduction in either stages or closed cycles. In this case, most of the unreacted chlorosilane and hydrogen are recycled in the semiconductor polycrystalline silicon manufacturing process, while another part of the vapor/gas mixture is entrained in the waste gas by the hydrogen stream or is not contaminated with harmful contaminants. Eject from the still of the device along with other objects. The recycled steam/gas mixture is systematically subjected to regeneration and purification from harmful contaminants. Regeneration of the vapor/gas mixture is carried out by condensing the chlorosilanes and purifying them (eg distillation). Hydrogen regeneration is
It is carried out by freezing hydrogen chloride.

A method for producing high-purity semiconducting polycrystalline silicon by hydrogen reduction of chlorosilane on a substrate in two facilities connected in series in a cycle sealed for chlorosilane and semi-closed for hydrogen is in the art. It is known that Each of these facilities includes a chlorosilane evaporator, a reactor,
Consists of a condensation system, and a distillation column. This conventional method is implemented as follows. Purified trichlorosilane and hydrogen are mixed in an evaporator and put into the reactor of the first equipment to carry out the reduction of chlorosilane.

The reaction products, namely tetrachlorosilane, polymeric chlorosilane and hydrogen chloride, and the unused raw materials, namely trichlorosilane and hydrogen, are treated at -80 DEG C. in the condensate system of the facility. As a result,
Two streams of product result. The first of these streams, consisting of liquid chlorosilane and a portion of dissolved hydrogen chloride, is treated in a distillation column for purification from the polymeric chlorosilane and then fed to the evaporator and reactor of the second facility for re-treatment. used. A second stream containing mainly hydrogen is fed to the reactor of the second facility and reused for reduction. The gas containing the vapor/gas mixture leaving the reactor of the second installation is treated in its condensing system as in the first installation. The liquid chlorosilane thus obtained is reused in the reduction reactor and the mixture of hydrogen and hydrogen chloride is discharged from the process and directed to combustion.

The process is characterized by poor utilization of the effluent hydrogen and the initial loss of chlorosilane, especially dichlorosilane, together with the gas mixture stream exiting for combustion and the polymeric chlorosilane stream exiting the distillation column. A disadvantage is that the extraction of silicon from chlorosilane is low. Said extraction of silicon is carried out only once in a second installation (GDR Patent No. 48582).

Processes for the production of semiconducting polycrystalline silicon are known in the art, involving the low temperature condensation of chlorosilane at −20° C. and separation of the effluent vapor/gas mixture at elevated pressures of 20 to 30 atmospheres.

Regeneration of the vapor/gas mixture discharged after reduction and containing chlorosilane, hydrogen chloride and hydrogen is carried out by compressing it in a compressor, condensing the chlorosilane in multiple stages and separating it by distillation. The vapor/gas mixture separated after condensation and containing mainly hydrogen is passed through an adsorption column with activated carbon, where hydrogen chloride is adsorbed, and the hydrogen is passed through the column and recycled to the process for producing semiconductor crystalline silicon. let After the activated carbon is saturated with hydrogen chloride, the adsorption tower is heated to +200℃ with hot gas.
Heating to a temperature of +300°C and utilizing the released hydrogen chloride.

This method has the disadvantages that the process equipment design is complicated, the degree of condensation of chlorosilane is not high enough (chlorosilane is deposited on the active surface of carbon and reduces its adsorption capacity, and the operation of the adsorption column is It is disadvantageous in that it makes it extremely complicated. Regenerated hydrogen is inevitably contaminated with adsorbed substances,
Therefore, this hydrogen cannot be introduced into the semiconductor polycrystalline silicon manufacturing process without additional purification.

When the adsorption device is subjected to cleaning, polymeric chlorosilane is easily ignited. This is often accompanied by local explosions. In addition to the above, the need for periodic regeneration of the adsorbent requires considerable power and effort (GB 1144855).

A method also utilizes the effluent vapor/gas mixture containing unreacted chlorosilane and hydrogen chloride by freezing the chlorosilane at a temperature of -120°C and freezing the hydrogen chloride at a temperature of -150°C to -186°C. known (FRG Patent No. 1129937).

This method is disadvantageous in that it requires complete purification of the regenerated product, the power required for heating and freezing is high, and the process equipment is complex.

Methods of producing semiconductor polycrystalline silicon by isolation from the gas phase are known in the art. According to this method, chlorosilane and unreacted portions of chlorosilane produced in the process are regenerated and recycled to the process. Regenerated chlorosilane is introduced into the silicon reduction device in such a proportion that the ratio of chlorosilane at the device outlet relative to the initial chlorosilane should be constant (FRG Patent No. 12918066).

This method has the disadvantage that the utilization of the starting materials (hydrogen and chlorosilane) is not high enough and that the sterillity of the process is relatively low.

It is also known to regenerate the vapor/gas mixture consisting of chlorosilane, hydrogen chloride and hydrogen, which occurs in the production process of semiconductor polycrystalline silicon, by pyrolysis of chlorosilane.

This method has the disadvantage that the degree of condensation of the steam/gas mixture to be regenerated is relatively low (FRG Patent No. 2918060).

It is also known to regenerate the vapor/gas mixture produced in the manufacturing process of semiconductor polycrystalline silicon by freezing the vapor/gas mixture at a temperature equal to or below the melting temperature of hydrogen chloride. The frozen material containing chlorosilane and hydrogen chloride is heated to evaporate the hydrogen chloride. Recirculating chlorosilane into the semiconductor polycrystalline silicon manufacturing process. In order to remove contaminants, the chlorosilane can be previously subjected to distillation (FRG Patent No. 2918078).

This method is disadvantageous in that the process is not sufficiently safe and requires considerable effort and power.

The main objectives of the present invention are to make more complete use of the initial material by modification of the process technology, to increase the degree of extraction of silicon, to simplify the process, to increase the degree of condensation of chlorosilane, and to improve the sterility of the process. An object of the present invention is to provide a method for regenerating unreacted chlorosilane and hydrogen in a manufacturing process of semiconductor polycrystalline silicon that increases the production of semiconductor polycrystalline silicon.

The purpose is to regenerate unreacted chlorosilane and hydrogen in a semiconductor polycrystalline silicon manufacturing process by condensing and freezing the chlorosilane and hydrogen chloride and then recycling it into the semiconductor polycrystalline silicon manufacturing process. The condensation of is carried out in multiple stages in the temperature range from -15 °C to -90 °C (the number of stages is at least 4, and the temperature in each condensation stage is constant),
Hydrogen is then regenerated by freezing chlorosilane and hydrogen chloride in at least three stages (the freezing temperature in the first stage is -120°C to -125°C).
, the freezing temperature in the second stage is from -150°C to -165°C, and the freezing process of the substance is carried out in the third stage at a temperature equal to or higher than the evaporation temperature of liquid nitrogen). This is accomplished by providing a method for regenerating unreacted chlorosilane and hydrogen in a crystalline silicon production process.

In order to ensure production safety, reduce power and improve the quality of chlorosilane, the condensation in each stage is fractional.

In order to obtain high quality hydrogen, freezing of chlorosilane and hydrogen chloride in each stage is fractional.

In order to obtain high quality silicon, the contaminated chlorosilane is purified from harmful contaminants by additional distillation before the fourth condensation stage.

For the removal of polysilane chloride from the initial chlorosilane, it is advantageous to cool the vapor/gas mixture before the first stage condensation.

This method differs significantly from methods currently in use.

The method offers high condensation of chlorosilane (more than 44%), simplicity of process equipment and operation in each stage, ease of automation, better protection of workers and improved safety of the process, power and labor savings. It is characterized by savings, increased sterility of production, and more complete utilization of raw materials (chlorosilane and hydrogen).

A high degree of condensation of chlorosilane is obtained by stepwise cooling of the vapor/gas mixture, stepwise freezing of hydrogen chloride improves the quality of the hydrogen recycled to the process, while stepwise condensation of chlorosilane is obtained by stepwise cooling of the vapor/gas mixture. Improve their quality at each stage. The combination of all these factors is
Provides more complete utilization of raw materials (chlorosilane and hydrogen), increases worker protection and process safety, increases process sterility, and reduces the labor and Reduce power.

Simplicity of process equipment and operation, improved worker protection and labor savings are due to the mechanization and partial automation of the processes involved, as well as the installation of a large number of standard equipment into the process cycle, integrated special equipment and obtained by the use of chemical engineering machines.

The major power supply savings are made through cooling regeneration. For example, the cooled vapor/gas mixture from the third stage of condensation is used to cool the vapor/gas mixture in the second stage of condensation, and the cooled vapor/gas mixture from the second stage of condensation is used to cool the vapor/gas mixture in the second stage of condensation. used to cool vapor/gas mixtures in condensation.

Technical processes are easy to control. The design of the equipment ensures reliable operation of all units, allows almost complete condensation of high-boiling and low-boiling chlorosilanes, and allows the chlorosilanes after a certain stage of condensation to be fed to provide additional Enables reuse without refining.

An important advantage of this method is that, after appropriate process improvements, the vapor/
A wide range of application possibilities for the regeneration and utilization of gas mixtures.

The application of the inventive method for regenerating chlorosilane and hydrogen opens wide prospects for complete mechanization and automation of the industrial production process of polycrystalline silicon.

The above advantages characterize the method as an innovative technology that meets modern engineering requirements.

Use of the present method eliminates the disadvantages of the conventional method.

The invention is carried out as follows.

The starting materials, namely chlorosilane and hydrogen (molar ratio 5-10:1), are fed to the reduction apparatus. In this device cooling of the silicon takes place on a heated surface (for example on a silicon substrate) to a temperature of 1000-1200°C. The charged chlorosilane is previously subjected to distillation or purification in order to greatly cool the silicon and remove heavy metal contaminants. The vapor/gas mixture effluent from the reduction unit and containing 5-15% by volume of chlorosilane, 1-5% by volume of hydrogen chloride and 80-85% by volume of hydrogen is subjected to a first stage of condensation precooling, and the effluent vapor/gas mixture is As a result of contact with the liquid chlorosilane coming from the second stage condensation, a portion of the harmful contaminants (eg Cu, Fe, Al) are transferred from the gas phase to the liquid phase. In other words, a partial purification of the steam/gas mixture takes place. Liquid chlorosilane also scavenges chilled hydrogen chloride.

Furthermore, the liquid chlorosilane stream in which the cooled polymeric chlorosilane (polysilane chloride) has been effectively captured is continuously discharged from the first stage condensation device and utilized.

Pure hydrogen is introduced into the first stage condensing precooler to compensate for losses in the process and for additional purification.

further subjecting the vapor/gas mixture containing chlorosilane, hydrogen chloride and hydrogen to a second stage of condensation;
There, at temperatures of -30 DEG C. to -45 DEG C., condensation of high-boiling chlorosilanes (mainly residues of SiCl ₄ and polysilane chloride) takes place. The condensed chlorosilane together with the contaminants is discharged from the closed system and used in another technological process. Furthermore, the vapor/gas mixture is passed into a third stage condensation cooler, where condensation of the most valuable chlorosilanes (SiHCI ₃ and a portion of SiH ₂ Cl ₂ ) takes place at temperatures of -65°C to -70°C.

The condensed chlorosilane travels along a pipeline to the distillation column still and is recycled to the process after purification.

The remaining vapor/gas mixture from the third stage condensation is subjected to a fourth stage condensation, where complete condensation of the chlorosilane occurs at a temperature of -80°C to -90°C, and the isolated chlorosilane is subjected to a purification stage. It can be introduced into the manufacturing process of semiconductor polycrystalline silicon without going through the process.

The remaining vapor/gas mixture containing traces of chlorosilane, hydrogen chloride and hydrogen is then subjected to a first stage freezing at a temperature of -115°C to -125°C to freeze traces of chlorosilane and partially of hydrogen chloride. After warming the frozen chlorosilane and hydrogen chloride to a temperature of -30°C to -40°C, they are flushed out with gaseous nitrogen and ready for utilization.

The non-condensable gas containing a mixture of hydrogen and hydrogen chloride is subjected to a second freezing stage where it is heated from -155°C to -
Freezing of hydrogen chloride occurs at a temperature of 165°C.
After warming the frozen hydrogen chloride to -50°C or -60°C, it is evacuated with gaseous nitrogen and made available for use.

Furthermore, the hydrogen is subjected to a final stage of freezing. The regenerated hydrogen is recycled by a compressor along the pipeline to the semiconductor polycrystalline silicon manufacturing process.

Example 1 To manufacture semiconductor polycrystalline silicon, 10:
Highly purified chlorosilane and hydrogen in a molar ratio of 1 are fed to the reactor. As a result of the reaction at temperatures of 1000-1200°C, silicon is deposited on silicon rods.

Flowing from the reduction device and hydrogen chloride 3.5% by volume,
A first stage condensation is carried out by passing a vapor/gas mixture containing 8% by volume of chlorosilane and 88.5% by volume of hydrogen into a bed of liquid chlorosilane at a rate of 330 Nm ³ /h. In the first stage, a temperature of -15°C is maintained. In the first stage of condensation, high-boiling chlorosilane, ie polysilane chloride, condenses. These are continuously discharged from the device together with the tetrachlorosilane in an amount of 6% by weight of the total amount of chlorosilane.

Furthermore, the vapor/gas mixture is fed to a second device for condensation. There, a predominant condensation of tetrachlorosilane (90% by weight SiCl ₄ , 10% by weight SiHCl ₃ ) occurs at temperatures of -35° C. to -45° C. Numerous harmful contaminants (Cu, Au, Ag, Al, Ba, Be, Ga, Cd,
Co, Fe, K, Na, Li, Mg, Mn, Ni, Pt, Rt,
Tetrachlorosilane contaminated with chlorides of Rb, Sr, Te, Ti, U, Zn, Zr) is continuously discharged in an amount of 10% by weight of the total amount of chlorosilane. Then,
Regenerated chlorosilane is continuously discharged from the process and directed to another manufacturing process.

The vapor/gas mixture is then passed into a third condensing device, where the main part of the chlorosilane (50% by weight of the total amount of chlorides) is condensed (75% by weight _{of SiCl4} , _SiHCl3 24% by weight, _{SiH2Cl2 1} % by weight). The condensed chlorosilane is then distilled. The low boiling contaminants, hydrogen chloride and a portion of chlorosilane (15% by weight) are then discharged from the process at the top of the column and the purified chlorosilane is recycled to the semiconductor polycrystalline silicon production process.

The remaining vapor/gas mixture enters the fourth stage cooler, where the most complete isolation of chlorosilane (30% by weight of the total amount of chlorosilane) occurs at a temperature of -80 °C to -90 °C (SiCl ₄ 45% by weight) %,
_SiHCl3 52% by weight, _{SiH2Cl2 3} % by weight). The isolated chlorosilane is then introduced into the semiconductor polycrystalline silicon manufacturing process without going through a purification step.

The vapor/gas mixture is then transferred to a heat exchanger where complete freezing of the chlorosilane occurs together with some amount of dissolved hydrogen chloride at a temperature of -115°C to -125°C.

Hydrogen chloride 1% by weight, SiCl ₄ 25% by weight, SiHCl ₃ 70
Frozen chlorosilane and hydrogen chloride of 3% by weight of the total amount of chlorosilane containing 5% by weight and 5% by weight of SiH ₂ Cl ₂ are blown off with gaseous nitrogen after warming to a temperature of −30° C. to −40° C., and towards use. The non-condensable gas containing 97.5% by volume hydrogen and 2.5% by volume hydrogen chloride is fed at a rate of 300Nm ³ /h into the second stage freezing device where it is heated from −155°C to −165°C.
Hydrogen chloride was frozen at a temperature of (0.001% by volume). Furthermore, the hydrogen is subjected to a final stage of freezing at temperatures higher than -195.6°C, where the hydrogen chloride content in the hydrogen is reduced to 0.00005-0.0001% by volume and the contaminant content of harmful substances is reduced to 1×10 ^-4 ~1×
It was reduced to 10 ^-5 % by volume.

The regenerated hydrogen is recycled by a compressor along the pipeline to the semiconductor polycrystalline silicon manufacturing process.

The yield of high quality semiconductor polycrystalline silicon is
Higher than 70%. The electrophysical parameters of high quality polycrystalline silicon are as follows.

(a) Resistance to the donor 300 ohm cm (b) Resistance to the acceptor 3000 ohm cm Example 2 Semiconducting polycrystalline silicon is produced under the same conditions as in example 1, but the main part of the chlorosilane from the third device of condensation is purified. It is directly recycled into the semiconductor polycrystalline silicon manufacturing process without being subjected to any stage (in the form of distillation).

In this case, the yield of high quality semiconductor polycrystalline silicon is 2.5-3 times lower.

Claims (1)

[Claims] 1. Regenerating unreacted chlorosilane and hydrogen in a semiconductor polycrystalline silicon manufacturing process by condensing and freezing the chlorosilane and hydrogen chloride, and then recycling them into the semiconductor polycrystalline silicon manufacturing process. For this, the condensation of chlorosilane is carried out in multiple stages in the temperature range from -15°C to -90°C (the number of stages is at least 4, and the temperature in each condensation stage is constant), and then chlorosilane and hydrogen chloride are Hydrogen is regenerated by freezing in the first stage (the freezing temperature in the first stage is -120°C to -125°C,
The freezing temperature in the second stage is from -150°C to -165°C, and in the third stage the freezing process of the material is carried out at a temperature above the evaporation temperature of liquid nitrogen. A method for regenerating unreacted chlorosilane and hydrogen in the manufacturing process. 2. The method according to claim 1, wherein the condensation of chlorosilane in each stage is fractional. 3. The method according to claim 1, wherein freezing of chlorosilane and hydrogen chloride in each stage is fractional. 4. Process according to claim 1, characterized in that the condensed chlorosilane from the third stage condensation is directed to distillation. 5. Process according to claim 1, characterized in that the vapor/gas mixture is precooled before the first stage of condensation.