RU2158324C1 - Method for manufacturing polycrystalline silicone in the form of large-area plates and chamber for silicone deposition - Google Patents

Abstract

FIELD: manufacture of semiconductor materials, possibly production of initial polycrystalline silicone by vapor deposition or by deposition of gas-vapor phase of silanes onto heated substrates. SUBSTANCE: method comprises steps of placing flat substrate in chamber, feeding vapor or gas-vapor flow along surface of flat substrate, heating flat substrate by passing electric current; depositing onto flat substrate silicone from vapor or gas-vapor mixture, extracting flat substrate out of chamber for its subsequent treatment. Flat substrate is made of material with specific resistance in range from 1x10^-3 Ohm/cm up to 50 Ohm/cm. Then silicone is removed from flat substrate by cutting off. Chamber includes housing, holders for flat substrates arranged in housing with possibility for placing substrates in horizontal rows; nozzle for supplying vapor or gas-vapor mixture between rows; union for discharging vapor or gas-vapor mixture. Holders are provided with electric current leads. Nozzles are mounted at side of housing wall turned to long side of flat substrate. There are at least two nozzles for each interval between horizontal rows of substrates. EFFECT: enhanced efficiency, lowered cost of process. 14 cl, 4 dwg, 6 ex

Description

 The invention relates to the field of production of semiconductor materials and can be used for the production of the initial polycrystalline silicon during its deposition from steam or vapor-gas phase on heated substrates.

 Various methods are known for obtaining the initial silicon, including placing the base in a chamber, heating the base with a passing current, supplying a steam-gas mixture along the surface of the base, depositing silicon on the base from the gas-vapor mixture, removing the base with silicon from the chamber (1, 2, 3).

 In these methods, silicon rods are used as the base for the deposition.

 A known method of manufacturing the initial polycrystalline silicon in the form of plates, including placing a flat base in the chamber, supplying a steam stream of monosilane or a gas-vapor mixture of trichlorosilane and hydrogen along the surface of the flat base, heating the flat base with a flowing current, depositing silicon on the flat base from steam or gas-vapor mixture, removing flat base with silicon from the chamber, subsequent processing (4).

 According to the method, the initial polycrystalline silicon is obtained by precipitation on heated silicon substrates during the hydrogen reduction of chlorosilanes or in the process of decomposition of monosilane. The bases are silicon wafers with a width of 3.0 to 10.0 cm, a length of 120 cm and a thickness of 0.1 to 0.5 cm. The advantage of this method compared to the previous ones is a slight increase in the deposition rate of silicon.

 The limitations of the method are: the difficulty of obtaining wide silicon wafers - flat substrates for conducting hydrogen reduction processes of silicon with high productivity, the need for starting heating of the substrates with high resistivity.

 The device used in this technical solution has silicon wafers, into the space between which, through a nozzle mounted on the narrow side of the flat substrates, a stream of steam or vapor-gas mixture is supplied. Such a device has low productivity, due mainly to the small area of the flat base.

 The closest device is a chamber containing a housing, holders for flat bases installed in the housing with the possibility of placing the flat bases in horizontal rows, nozzles for supplying the gas mixture into the space between the rows of flat bases, a fitting for discharging steam or gas mixture (5).

 However, this chamber is intended for epitaxial growth of a silicon layer and does not serve to produce polycrystalline silicon source. An external RF inductor is used to heat the flat substrates, and a number of nozzles are installed only on the side of the chamber body walls facing the short sides of the flat substrates. In addition, the camera has one electric motor for rotating the flat bases and another electric motor for rotating the nozzles, which complicates the design.

 The problem solved by the invention is to increase the productivity and profitability of the production of the initial polycrystalline silicon, reducing the cost and complexity of obtaining broad bases.

 The technical result that can be obtained by implementing the inventive method is to simplify the hydrogen reduction process, increase the width of the flat substrates and the amount of the obtained silicon source, as well as reduce the process time and reduce energy consumption.

 The technical result that can be obtained by performing the claimed device is the improvement of technical and operational characteristics and simplification of the design.

To solve the problem in a known method of manufacturing the initial polycrystalline silicon in the form of plates, including placing a flat base in a chamber, supplying a steam stream of monosilane or a gas-vapor mixture of trichlorosilane and hydrogen along the surface of a flat base, heating the flat base with a flowing current, deposition of silicon from steam on a flat base or gas-vapor mixture, removing a flat base with silicon from the chamber, subsequent processing, according to the invention, materials used are used as a flat base, chemical inert to steam or gas mixture, with resistivity in the range from 1 • 10 ^-3 Ohm • cm to 50 Ohm • cm, and subsequent processing is performed by cutting deposited silicon from a flat base.

 Thus, flat silicon substrates are made by cutting wafers from deposited polysilicon, and substrates for multiple silicon deposition without starting heating are made in the form of flat wafers or strips of the required width from materials chemically neutral to the gas mixture, which can be applied over 10 or more times.

There are additional options for implementing the method, in which it is advisable that:
- graphite was used as a flat base;
- as a flat base used compressed and sintered carbon composite material consisting of 60-80% weight. fine graphite powder with the addition of 20-40% weight. silica;
- cermet, a sintered composite material consisting of 70-90% weight, was used as a flat base. alumina (Al ₂ O ₃ ) and 10-30% by weight. iron or nickel;
- as a flat base used conductive quartz glass, consisting of 90 - 70% weight. silicon dioxide and 10-30% by weight. iron oxides;
- carbon fabric was used as a flat base;
- as a flat base used silica fabric with pyrocarbon or pyrographic coating;
- when placing the flat base in the chamber, it was arranged in rows with the long side horizontally, and steam or gas mixture along the surface of the flat base would be supplied with at least two streams for each gap of the row from the side of the chamber wall facing the long side of the flat base;
- steam or gas mixture along the surface of the flat base was supplied with at least two streams for each gap of the row from the side of the chamber walls facing the short sides of the flat base;
- before placing the flat base in the chamber, it was annealed at a temperature higher than the heating temperature of the flat base during deposition;
- cutting the deposited silicon from a flat base was carried out while maintaining a layer of deposited silicon on it with a thickness of at least 2 mm, after which the cutting surfaces would be cleaned by grinding, etching and washing in deionized water.

 To solve the problem with the achievement of the specified technical result in a known chamber containing a housing, holders for flat bases installed in the housing with the possibility of placing flat bases in horizontal rows, nozzles for supplying steam or gas mixture in the space between the rows of flat bases, fitting for outputting steam or gas-vapor mixture, according to the invention, current leads connected to the holders are introduced, nozzles for supplying steam or gas-vapor mixture are installed on the side of the casing wall facing towards the other side of the flat base, with the number of nozzles selected at least two for each gap between the horizontal rows.

Additional camera embodiments are possible, in which it is advisable that:
- a mesh was introduced, installed in the housing in front of the nozzle exits;
- additional nozzles installed from the side of the casing walls facing the short sides of the flat base would be introduced, while the number of additional nozzles would be selected at least two for each gap between the horizontal rows.

 These advantages, as well as features of the present invention are illustrated by options for its implementation with reference to the accompanying figures.

FIG. 1 shows a chamber structure (schematically), a longitudinal section;
FIG. 2 is the same as FIG. 1, a top view of FIG. 1 without cover;
FIG. 3 - a base with precipitated silicon, a longitudinal section;
FIG. 4 is the same as FIG. 3, cross section.

 The camera (Fig. 1, 2) has a housing 1, holders 2 for flat bases 3, mounted in the housing 1 with the possibility of placing the flat bases 3 in horizontal rows. The chamber also contains nozzles 4 for supplying steam or vapor-gas mixture into the space between the rows of flat bases 3 and a fitting 5 for outputting steam or vapor-gas mixture. The current leads 6 are connected to the holders 2. The nozzles 4 are installed on the side of the wall of the housing 1 facing the long side of the flat base 3. The number of nozzles 4 is selected at least two for each gap between the horizontal rows. The figure 1 also schematically shows the lid 7 of the chamber and the window 8 made therein, a pipe 9 for supplying steam or gas-vapor mixture to the nozzles 4.

 A mesh 10 (FIG. 1) may be introduced into the housing 1, which is installed in front of the nozzle exits 4 to disperse the flows of steam or gas-vapor mixture.

 Additional nozzles 11 mounted on the side of the walls of the housing 1 facing the short sides of the flat base 3 can be introduced into the design. The number of additional nozzles 11 can be selected at least two for each gap between the horizontal rows. From additional nozzles 11, 20 to 40% by weight can be supplied. of the total amount of steam or vapor-gas mixture to improve their mixing conditions.

 The device operates as follows.

After turning on the current through the current leads 6, the flat substrates 3 are heated to temperatures from 1050 to 1200 ^o C. After being fed into the housing 1 through nozzles 4, and also if they are available through additional nozzles 11, trichlorosilane (SiHCl ₃ ) and hydrogen (H ₂ ) silicon is precipitated from the vapor-gas phase onto flat bases 3 by the reaction: SiHCl ₃ + H ₂ = Si + 3HCl. The placement of the nozzles 4 from the side of the wall of the housing 1, facing the long side of the flat base 3, allows you to increase the speed and amount of deposited silicon. The deposition of silicon from monosilane vapor is produced on a heated flat base 3 without the participation of hydrogen.

 As chemically neutral and conductive materials for the manufacture of flat substrates 3, carbon and composite materials based on high-temperature oxides with the addition of carbon and metals can be used. The necessary conductivity in the materials is created by changing the composition and sintering temperature of the composites. The choice of a suitable conductivity value is necessary for the proper organization of heating the base to the required temperature.

 With a large conductivity and a wide width of the flat substrates 3, the current for their electric heating can be limited to the necessary limits only by using thin flat substrates 3, the strength of which may be insufficient. In addition, it is necessary to sequentially incorporate the flat bases 3 into the electric circuit, which can lead to an undesirable change in cos φ between the phases. Large currents also require the use of large cross-sections of current leads 6 and secondary windings of transformers. Complicated switching and regulation systems.

To carry out the deposition processes without introducing any impurities into the deposited material, flat bases made of carbon and composite materials are preliminarily annealed for one hour in vacuum at temperatures up to 1800 ^o C.

 At the end of the hydrogen reduction process, 3 obtained material is removed from the flat bases. First, the deposited silicon 12 is cut from the sides of the flat base 3 (Fig. 3, 4) to create the base planes necessary for installing the flat base 3 before the subsequent cutting of silicon from wide sides. Then, the deposited material is cut from the wide side of the flat base 3, leaving a layer of at least 2 mm thick contaminated with diffusion. The cut lines are shown in FIG. 3.4 dotted line.

 Preparation for reloading the flat bases 3 into the chamber ends with grinding of the cut planes, etching and washing with deionized water.

The cut material is subjected to the same treatment, after which it can be used as wide flat silicon bases, as well as for remelting as lumpy or measured loads. For the manufacture of flat substrates 3, various materials can be used that are chemically neutral to steam or gas mixture, with a specific resistance of 1 • 10 ^-3 Ohm • cm (10 Ohm mm ² / m) to 50 Ohm • cm (2.5 • 10 ⁵ Ohm mm ² / m).

 Example 1. In the hydrogen reduction chamber receive the original polycrystalline silicon in an amount of about 400 kg The deposition is carried out in the process of hydrogen reduction of silicon on 12 heated flat substrates 3 (Fig. 2 schematically shows six flat substrates 3) made of highly pure graphite grade GMZ OSCH (or GMZ - MT OSCH) with a length of 130 cm and a width of 15 cm and a thickness of 0.5 cm. The length of the working part of the plates on which the deposition occurs is 120 cm.

The specific resistance of graphite is ρ = 1 • 10 ^-3 Ohm • cm. With such a low resistance, the bases are sequentially turned on with their total resistance of about 0.18 ohms. The minimum thickness of the flat base 3 is selected at the lower tensile strength of the material. In the process of heating flat substrates 3 to reduction temperatures of 1100 - 1150 ^o C and deposition of silicon on them, the resistance decreases. As a result, the heating current rises to almost 2000 A.

 Before starting the recovery process, open the cover 7 of the housing 1 (Fig. 1) and fix the flat base 3 of graphite in the holders 2 of the current leads 6 (Fig. 1, 2) in a horizontal position in parallel and at a distance of 8.0 cm from each other. This creates favorable conditions for the mutual heating of the flat base 3 and achieve significant energy savings.

After loading, the housing 1 is sealed with a lid 7, vacuum to a residual pressure of (1-2) • 10 ^-2 Torr, a mixture of hydrogen with steam of trichlorosilane (TCS) is introduced and the working volume is blown for 10 minutes. The recovery process begins at a mixture overpressure of about 100 Torr and a base temperature of 1050 - 1100 ^o C. During the deposition process, the temperature is increased by 80 - 100 ^o C. TCS is supplied in an amount up to 8.0 kg per 1.0 kg of precipitated silicon. Hydrogen is supplied in an amount of 4-5 m ³ per 1 m ³ TCS.

 After entering the housing 1, heavy trichlorosilane vapors usually form an increased concentration in the lower part of the chamber. With the lower location of the flat bases 3, the gas-vapor mixture is more uniformly fed to their surfaces using vertically arranged nozzles 4 and is better mixed. The contact time of the mixture with heated flat substrates 3 increases, and the resulting hydrogen chloride rises up together with hydrogen and is removed from the chamber body 1 through the nozzle 5.

Upon receipt of 400 kg of silicon on each flat base 3 precipitated 33.5 kg of material. At the end of the deposition process, the width of the flat substrates 3 reaches 21 cm. With an average deposition surface on both sides of the flat substrate 3 of about 5040 cm ² and a specific deposition rate of polysilicon of 0.1 g / cm ² • h, the deposition time of a given amount of silicon is 33500: (5040 • 0.1) = 66.5 hours or 2.8 days. 400 / 2.8 = 142.8 kg are obtained per day; per hour - 5.9 kg.

 Due to a slight change in the productivity of the process with a small change in the surface of the flat substrates 3, the ratio of the components of the vapor-gas mixture during the deposition process is not changed. This greatly simplifies the technology.

The weight of 1 m ³ pair of TCS is 6 kg. Therefore, 1.35 m ³ • 5.9 kg = 8.0 m ^{3 of} TCS steam and about 35.0 m ^{3 of} hydrogen are supplied per hour. Compared with the known method, the main technical and operational indicators of production are improved by 1.5-2.0 times.

 At the end of the process, the power supply is first stopped, and then the steam or gas-vapor mixture is supplied. After this, the chamber is evacuated, air is admitted and its discharge is carried out.

 Precipitated silicon is removed from the flat base 3 by longitudinal cutting, for example, with diamond saws. In this case, silicon is first cut from the sides of the flat substrates 3, and then from the wide, leaving at least 2 mm of deposited material on each side. Before reloading from the cutting surfaces of the flat substrates 3, 1.0 mm of silicon is ground each, and then etched and washed in deionized water. The cut material is subjected to the same treatment, and then crushed into pieces before loading into the crucible. Measured loads are pre-cut and then ground, etched and washed.

Example 2. In the same device receive 400 kg of the original polycrystalline silicon. To reduce conductivity, the deposition is carried out on a flat base 3 of a carbon composite material consisting of 60-80% by weight. from a pure powder of fine-grained graphite with the addition of 20-40% weight. pure silicon dioxide, pressed and sintered at 1600 ^o C. Dimensions of flat bases 3: 120 x 30 x 0.6 cm. Specific resistance of the material of flat bases 3: 0.1-0.3 Ohm • cm. This is 200 times higher than in example 1, which allowed to significantly increase the width and thickness of the flat base 3. Moreover, the productivity of the process for producing silicon increased by almost 1.8 times. Pre-treatment of flat substrates 3 and the silicon reduction process are carried out analogously to example 1.

Example 3. In the same device receive 400 kg of the original polycrystalline silicon. As flat bases 3 use plates made of cermet - a composite material consisting of 70-90% weight. from pure alumina (Al ₂ O ₃ ) and 10 to 30% by weight. iron or nickel, sintered at 1700 ^o C. Apply flat bases 3 with a length of 120 cm, a width of 30 cm and a thickness of 0.6 cm. The specific resistance of the material of flat bases 3: 0.1-0.3 Ohm • see Preparation of flat bases 3, the process of obtaining silicon and its results are similar to example 1.

 Example 4. In the same device receive 400 kg of polycrystalline silicon using as flat bases 3 plates of conductive quartz glass. Apply flat bases 3 with a length of 120 cm, a width of 40 cm and a thickness of 0.4 cm with a specific resistance of 0.1 to 25 Ohm • cm. Glass composition from 90 to 70% weight. silicon dioxide and 10-30% by weight. iron oxides are obtained by extrusion from a melt by conventional technology to obtain technical glasses. The preparation of silicon is carried out analogously to example 1. With a width of flat bases 3 of about 40 cm, the productivity of the process for producing silicon, compared with that shown in example 1, increased by 2.3 times and amounts to (when deposited on 6 flat bases 3) about 6.0 kg / hour or about 160 kg / day.

 Example 5. In the same device receive the same amount of silicon. The deposition is carried out on carbon fabric (type UTM-8) with a specific resistance of 0.1-10 Ohm • cm, a width of 70 cm. The working length of the flat substrates 3 is 120 cm. The preparation of the material for deposition and the deposition of reduced silicon are carried out analogously to example 1. The deposition is carried out on six flat bases 3, included two in each phase of the three-phase current. The surface area of the six bases, in this case, is almost 2 times larger than the surface area of the 12 bases (in Example 1). Therefore, to obtain 400 kg of silicon, 34 hours with a capacity of about 12 kg / hour are enough.

 Example 6. In the same device receive 400 kg of the original polycrystalline silicon. For this, silica fabric with a pyrocarbon or pyrographite coating 50 cm wide and with a resistivity of 25 Ohm • cm to 50 Ohm • cm is used as flat bases 3.

 The dimensions of each of the six flat bases 3 are 120 x 50 x 0.08 cm.

 In this case, the productivity increases by 1.45 times compared with example 1 and a given amount of silicon is obtained in less than two days. Productivity ≅ 200 kg / day or 8.6 kg / hour.

 The most successfully claimed method and camera can be used to obtain the original polycrystalline silicon in the form of plates with a large surface area.

Sources of information:
1. The patent of Germany N 2854707, publ. 1978

 2. Japan Patent N 52-21453, publ. 1977

 3. US patent N 4125643, publ. 1978

 4. Patent of Germany N 2541284, C 30 V 25/02, publ. 1977

 5. Application of Great Britain N 1560982, C 30 V 25/00, publ. 1980 year

Claims (14)

1. A method of manufacturing an initial polycrystalline silicon in the form of plates, comprising placing a flat base, supplying a steam stream of monosilane or a gas-vapor mixture of trichlorosilane and hydrogen along the surface of a flat base, heating the flat base with a flowing current, depositing silicon on a flat base from steam or a vapor-gas mixture, removing the flat bases with silicon from the chamber, subsequent processing, characterized in that as a flat base materials are used that are chemically inert to steam or to a gas-vapor mixture, with specific resistance in the range of 1 • 10 ^-3 - 50 ohm • cm, and subsequent treatment of the precipitated silica produced by cutting a flat base.  2. The method according to claim 1, characterized in that graphite is used as a flat base.  3. The method according to claim 1, characterized in that as a flat base, a pressed and sintered carbon composite material is used, consisting of 60 to 80 wt.% Fine graphite powder with the addition of 20 to 40 wt.% Silicon dioxide. 4. The method according to claim 1, characterized in that as a flat base use cermet-sintered composite material consisting of 70 - 90 wt.% Aluminum oxide Al ₂ O ₃ and 10 - 30 wt.% Iron or nickel.  5. The method according to claim 1, characterized in that the conductive silica glass consisting of 90 - 70 wt.% Silicon dioxide and 10 - 30 wt.% Iron oxide is used as a flat base.  6. The method according to claim 1, characterized in that as a flat base using carbon fabric.  7. The method according to claim 1, characterized in that as a flat base using silica fabric with pyrocarbon or pyrographic coating.  8. The method according to claim 1, characterized in that when placing the flat base in the chamber, it is arranged in rows with long side horizontally, and steam or gas mixture along the surface of the flat base is produced by at least two streams for each row row from the side of the wall camera facing the long side of a flat base.  9. The method according to claim 8, characterized in that the steam or gas mixture along the surface of the flat base is produced by at least two streams for each gap of the row from the side of the chamber walls facing the short sides of the flat base.  10. The method according to claim 1, characterized in that before placing the flat base in the chamber, it is annealed at a temperature higher than the heating temperature of the flat base during deposition.  11. The method according to claim 11, characterized in that the deposition of deposited silicon from a flat base is performed while maintaining a layer of deposited silicon on it with a thickness of at least 2 mm, after which the surface of the cut is cleaned by grinding, etching and washing in deionized water.  12. A chamber containing a housing, holders for flat bases installed in the housing with the possibility of placing the flat bases in horizontal rows, nozzles for supplying steam or gas mixture into the space between the rows of flat bases, a fitting for outputting steam or gas mixture, characterized in that introduced current leads connected to the holders, nozzles for supplying steam or gas mixture are installed on the side of the casing wall facing the long side of the flat base, while the number of nozzles is selected at least two for each spacing between horizontal rows.  13. The camera according to item 12, wherein the introduced mesh installed in the housing in front of the nozzle exits.  14. The chamber according to claim 12, characterized in that additional nozzles are installed mounted on the side of the housing walls facing the short sides of the flat base, while the number of additional nozzles is selected at least two for each gap between the horizontal rows.

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