JPS6327287B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for pre-cleaning a reactor for producing polycrystalline silicon.

The most common manufacturing method for polycrystalline silicon currently practiced industrially is to heat the polycrystalline silicon to 1000°C to 1200°C in a metal reactor with a cooled exterior.
A mixed gas of halogenated silane and hydrogen is passed over the carrier held by the carrier, and polycrystalline silicon is deposited on the carrier by thermal decomposition of the halogenated silane and hydrogen reduction reaction.

When polycrystalline silicon is produced by this method, a polymer of high-boiling halogenated silane, which is produced as a by-product during thermal decomposition and hydrogen reduction reactions, is deposited on the relatively low-temperature portion of the inner wall of the reactor.

Since a part of this polymer has a high boiling point, it is difficult to completely remove it when replacing the halogenated silane atmosphere with an inert gas atmosphere after the reaction is completed. It is necessary to remove this as a pretreatment before proceeding to the reaction.

This pretreatment method combines cleaning the reactor inner wall with a hydrogen fluoride (HF) aqueous solution or sodium hydroxide (NaOH) aqueous solution and pure water, and gas etching the reactor inner wall with a chlorine gas. However, it has the disadvantage that it requires a large amount of equipment cost and requires a long processing time.

The present invention seeks to eliminate this drawback and to reliably clean the interior of the furnace without the use of cleaning agents as described above.

As mentioned above, when the high boiling point halogenated silane polymer produced as a by-product during the reaction is exposed to the atmosphere, it is hydrolyzed by moisture in the atmosphere to produce SiO ₂ and adheres to the reactor wall along with HCl produced at the same time. remain.
The generated HCl condenses as an aqueous HCl solution together with water vapor in the atmosphere, corroding the inner wall of the reactor, shortening the life of the equipment, and causing contamination due to corrosion of the furnace material. Also, it was formed at the same time and adhered to the reactor wall.
When the next reaction continues, SiO ₂ separates from the furnace wall during the reaction and adheres to the crystal growth surface, causing abnormal crystal growth and O ₂ contamination. Therefore, complete pre-cleaning of the furnace inner wall is an essential step in order to move on to the next reaction.On the other hand, the inventors believe that HCl maintained at a temperature above the acid dew point is less corrosive. By heating the reactor wall in advance and bringing water vapor-containing air or inert gas into contact with the reactor wall (the heating temperature of the reactor wall, the amount of water vapor contained in the air or inert gas) and its flow rate) to sufficiently hydrolyze the halogenated silane polymer adhering to the reactor wall, and release the HCl in the product out of the reactor as it is while keeping it in a non-condensing state. HCl above by
First, the problems associated with this are solved, and then a high-velocity jet stream of inert gas is injected onto the inner wall of the reverberatory furnace to remove the solid SiO ₂ in the hydrolysis product from the wall and crush it to the outside of the reverberatory furnace. Solving the problems related to SiO ₂ attached to the furnace wall by discharging it,
This makes it possible to reliably and effectively perform precleaning without using liquid phase cleaning or gas etching, which were originally described as conventional precleaning methods. This makes it possible to reduce the time required for preliminary cleaning to 1/2 to 1/3.

The method for pre-cleaning a reactor for producing polycrystalline silicon according to the present invention will be explained in more detail below based on examples thereof.

The drawings are explanatory diagrams for explaining an embodiment of the method of the present invention. Figure 1 shows the state of hydrolysis treatment using air containing water vapor or inert gas, and Figure 2 shows the state of separation and pulverization using a high-speed jet flow of inert gas. Each indicates the processing status.

1 is a reactor configured with double walls, 2 is a reactor 1
3 is a supply port for a mixed gas of halogenated silane and hydrogen, 4 is an outlet thereof, and (5) is a separately provided suction port 6 connected to a suction device (not shown). This is a reactor pedestal equipped with a

Example After completing the process of depositing polycrystalline silicon on the carrier 2 by thermal decomposition of halogenated silane and hydrogen reduction reaction and replacing the atmosphere in the reactor 1 with an inert gas atmosphere, the double wall of the reactor 1 was removed. Supply port 7 in the cavity
Steam was supplied to heat the inner wall 8 of the reactor 1, and the temperature of the inner wall 8 of the reactor 1 reached approximately 70° C. about 5 minutes later. Thereafter, while maintaining the heated state, a supply port 9 provided at the top of the reactor 1 supplies N ₂ gas which has been humidified to a relative humidity of around 70% by a humidifier (not shown).
The water was fed for 30 minutes at a flow rate of approximately 3000/min.
When the reactor 1 was opened and the HCl concentration in the gas inside the reactor was measured, the concentration was 1 ppm or less.

Next, as shown in FIG. 2, the reactor 1 is transferred onto a reactor pedestal 5, and a
While suctioning to about 100mmAq, hand hole 10
Insert nozzle 11 from
A jet flow of N ₂ gas of m/s was sprayed over the entire inner wall 8 of the reactor 1, so that it adhered to the inner wall 8.
SiO ₂ was separated and pulverized from the inner wall 8 and discharged to the outside of the reactor 1 from the suction port 6.

After preliminary cleaning by the method of the present invention described above,
The properties of polycrystalline silicon precipitated by the following thermal decomposition and hydrogen reduction reactions were: Specific resistance (ρN) - 2000 Ωcm Lifetime (τ) - 1000 μsec O ₂ concentration - 0.6 × 10 ¹⁶ atoms/cm ³ .

Example As in the example, steam is supplied to the double-wall cavity of the reactor 1 after the atmosphere has been replaced with an inert gas atmosphere to heat the inner wall 8 of the reactor 1, and after about 5 minutes, the temperature of the inner wall 8 of the reactor 1 reaches approximately The temperature reached 70℃. Thereafter, while maintaining the heated state, normal air (normal atmospheric pressure,
The air purifier installed at the supply port 9 at the top of the reactor 1 as shown in Figure 3 has a flow rate of 6 m ³ /min when converting outside air (temperature and humidity) to 1 atm and standard conditions of 0°C. It was inhaled through filter 12 for about 1 hour. When the reactor 1 was opened and the HCl concentration in the gas inside the reactor was measured, the concentration was 1 ppm or less.

Next, the reactor 1 is equipped with a gas injection nozzle unit 13 that can cover all directions as shown in FIG.
and a suction port 6.
While suctioning to about -100mmAq from the suction port 6 of the frame 5', the initial velocity is applied from the gas injection nozzle unit 13.
A jet flow of _N2 gas of 250 m/sec to 300 m/sec is applied at a flow rate of 6500/min to 10000/min for 10
The SiO 2 adhering to the inner wall 8 of the reactor 1 was blown onto the inner wall 8 for a minute to separate and crush it from the inner wall 8, and the SiO ₂ was discharged from the suction port 6 to the outside of the reactor 1.

After preliminary cleaning by the method of the present invention described above,
The properties of polycrystalline silicon precipitated by the following thermal decomposition and hydrogen reduction reaction were as follows: Specific resistance (ρN) - 2500 Ωcm Lifetime (τ) - 800 μsec O ₂ concentration - 0.5 × 10 ¹⁶ atoms/cm ³ .

[Brief explanation of drawings]

The drawings are explanatory diagrams for explaining examples of the method of the present invention, and FIGS. 1 and 2 are explanatory diagrams (front views) showing the states of hydrolysis treatment and separation and pulverization treatment of SiO ₂ in the examples, respectively. It is. 3 and 4 are explanatory partial views showing the air cleaning filter 12 and the gas injection nozzle unit 13, respectively, in the embodiment. Explanation of the symbols in the drawings below: 1: Reactor, 2: Support, 3: Supply port for mixed gas of halogenated silane and hydrogen, 4: Exhaust port, 5, 5': Reactor frame, 6: Reactor pedestal 5,
7: Steam supply port in the double wall cavity of the reactor 1, 8: Inner wall of the reaction 1, 9: Supply port provided at the top of the reactor 1, 10: Steam supply port provided at the top of the reactor 1. Hand hole, 11: Nozzle, 12: Air cleaning filter, 13: Gas injection nozzle unit.

Claims (1)

[Claims] 1 A mixed gas of halogenated silane and hydrogen is passed over a carrier maintained at 1000°C to 1200°C by electrical heating in a metal reactor whose outside is cooled to thermally decompose the halogenated silane and In a reactor for producing polycrystalline silicon, in which polycrystalline silicon is deposited on a carrier by a hydrogen reduction reaction, air or inert gas containing water vapor is fed into the furnace while heating the furnace wall to generate heat. The polymerized halogenated silane that is produced as a by-product during the decomposition and reduction reactions and adheres to the furnace wall is hydrolyzed, and the HCl produced by the hydrolysis is released outside the furnace while being kept in a non-condensing state. Polycrystalline silicon characterized by injecting a high-speed jet stream of inert gas onto the furnace wall to separate and crush the remaining solid content (SiO ₂ ) in the hydrolysis product from the furnace wall and discharge it outside the furnace. Preliminary cleaning method for manufacturing reactors.