JPH02102185A - Granular raw material feeder of single crystal pulling-up machine - Google Patents

Abstract

PURPOSE:To surely and stably feed a granular raw material and to prevent admixture of impurities by forming a cylinder in such a way that the cylinder covers the lower half of a screw from a bottom opening part of a hopper to a granular raw material sending side. CONSTITUTION:A screw 14 is rotated through a coupling 18, a magnetic sealing unit 19 and bevel gears 20 and 16 by an adjustable speed motor 17, a granular raw material 12 fed from a bottom opening part 11a of a hopper 11 to a cylinder 13 is transported to the right-hand side in the figure and the granular raw material 12 is dropped from the right end of the cylinder 13 to a feed opening 23 of a raw material introduction part 22. In the operation, when clearance between an inner wall of the cylinder 13 and a thread of a screw 14 is 1.5-2 times as long as the maximum particle diameter of the granular raw material 13 capable of being adjusted to <=a fixed granule by a sieve, the granular raw material 12 will not be caught between the inner wall of the cylinder 13 and the thread of the screw 14 by revolution of the screw 14 and an amount of the granular raw material corresponding to rotation of the screw 14 can be transported.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a single crystal pulling machine, and particularly to a device for feeding granular raw material into a crucible.

(Prior art) For example, a silicon single crystal pulling machine using the Czochralski method melts polycrystalline silicon that has been set in a crucible in advance, and the thickness of the single crystal to be pulled depends on the size of the crucible. It was determined by capacity.

(Problem to be solved by the invention) In the above-mentioned pulling machine, in order to obtain a large single crystal, the capacity of the crucible must be increased.However, as the capacity of the crucible is increased, heating It is necessary to increase the capacity of the section, and the overall size of the equipment also increases, and the capacity of various equipment such as the pressure reduction device, inert gas supply device, and cooling device for the outside wall of the equipment must be increased. It is desirable to gradually feed the raw material to the crucible, but for example, polycrystalline silicon, which is a raw material, generally has an amorphous shape and a variable thickness, so it is not possible to feed the raw material using a screw, which is used in various other fields. Even if an attempt was made to apply the entire device as is, the screws and cylinders would wear out, making it extremely difficult to put it into use.

The present invention uses a method of charging the raw material into the crucible while pulling the single crystal, uses a granular raw material, and uses a screw to supply the granular raw material completely reliably and stably, and the single crystal does not contain any impurities. The purpose is to provide a complete drawing machine granular raw material feeding equipment.

[Structure of the invention]

(Means for Solving the Problems) To achieve the above object, the present invention includes a hopper for storing granular raw materials, a cylinder arranged approximately horizontally and connected to the lower end opening of the hopper, and a cylinder connected to the lower end opening of the hopper. A granular raw material supply device for a single crystal pulling machine, comprising a screw that is provided and rotationally driven, and a raw material introduction part that receives the granular raw material sent out by the screw and has an input port for guiding it to a crucible, The cylinder is formed to cover at least the lower half of the screw at the lower end opening of the hopper on the delivery side of the granular raw material, and the gap between the inner wall of the cylinder and the crest of the screw is 1.5 of the maximum particle size of the entire granular raw material. ~2
It has been doubled.

In addition, since the raw material introduction part is generally directed to a crucible in a reduced pressure inert gas atmosphere, the part leading to the inlet must be able to be depressurized, but in this case, the hopper, cylinder, screw, and inlet is preferably installed in an atmosphere that is at least partially isolated from the atmosphere by a transparent partition so that the state of raw material supply can be monitored. Further, in this case, it is preferable to provide an auxiliary tank outside the above atmosphere that can be opened and closed with a lid via the pulp.

(Function) The granular raw material stored in the hopper is transferred from the lower end opening of the hopper to the cylinder and the screw by controlling the rotation of the screw to match the amount of melt that is pulled up and reduced in the crucible. The raw material is gradually fed out, enters the input port, and is supplied to the raw material introduction part into the Eril crucible. The granular raw material supplied into the crucible enters the melt inside the crucible, is melted, and is sequentially pulled up. This makes it possible to pull single crystals with a large capacity without increasing the capacity of the crucible too much, and also without cooling the crucible by cutting off the heating section that includes the crucible from the pulling section that pulls the single crystal. Once a single crystal is extracted, it can be pulled several times in succession. At this time, the gap between the inner wall of the cylinder and the crest of the screw is set to 1.
By setting the value to 5 or more, the granular raw material is not trapped, and the granular raw material can be fed without completely damaging the cylinder or screw, thereby preventing the mixing of impurities. Note that if the gap is too large, the feed rate will decrease and become unstable, so it is preferable to keep the gap to about twice the particle size.

In addition, if installed in an atmosphere that is isolated from the atmosphere by the hopper, cylinder, screw, and all bulkheads of the inlet,
The supply section such as a hopper leading to the input port can be easily and reliably placed under reduced pressure, and maintenance is easy.
By making at least a portion of the partition completely transparent, the interior can be monitored. Furthermore, if an auxiliary hopper is provided in the above atmosphere via a valve, granular raw materials can be supplied to the hopper without opening the partition wall.

(Example) Hereinafter, a description will be given of FIGS. 1 and 2 showing an example of the present invention. In FIG. 1, a hopper 11 is placed on a pedestal 10.
is installed. It is preferable that the hopper 1 is formed entirely or partially from a transparent member such as acrylic resin so that the amount of granular raw material 12 stored therein can be seen at a glance. A cylinder 13 made of stainless steel, for example, is connected to the lower end opening 113 of the hopper 11 and is arranged substantially horizontally to receive the granular raw material 12 in the hopper 11 . For example, a screw 14 also made of stainless steel is fitted into the cylinder 13.

The screw 14 is rotatably attached to the cylinder 13 by means of two bearings 15 at its base on the left end side in FIG. A bevel gear 16 is attached to the base end of the screw 14, and is rotated by a bevel gear 20 that is rotated by a variable speed motor 17 attached to the pedestal 10 via a turnip puller 18 and a magnetic seal unit 19 that passes through the pedestal 10t. It is now possible to

A gap δ is provided between the inner wall of the cylinder 13 and the crest of the screw 14, as shown in FIG. This gap δ is set to be 1.5 to 2 times the maximum particle size of the granular raw material 12 that has been passed through a sieve and has a particle size of less than one particle.

In FIG. 1, the left end side of the space between the cylinder 13 and the screw 14 is closed by a ring 21.
The right end side is open. On the pedestal 10, a raw material introduction part 22 is located below the right end of the cylinder 13.
An input port 23 is installed. The lower introduction pipe 24 of the raw material introduction section 22 is airtightly attached to the lower surface of the pedestal 10, placed in a heating chamber (not shown) capable of reducing pressure, and supplies the granular raw material 12 to a crucible 25, which is tentatively shown in FIG. It is designed to guide you. Inside the crucible 25, an annular partition wall 2 is provided.
6 is provided, and the lower introduction pipe 2 is connected to the outside of this partition wall 26.
4 to guide the granular raw material 12. Note that 27 is a pulled single crystal, and 28 is a melt.

The pedestal 10 has a magnetic seal unit 1 located thereon.
Upper part of 9, bevel gear +6.20. Hopper 11° cylinder 1
3. It is preferable that all or part of the screw 14 and the input port 23 be surrounded by metal, and a partition wall 29 made of a transparent plate material such as acrylic resin is installed in the seal 30 in an airtight manner, and the upper part is covered with a seal 31. It is hermetically closed by an upper plate 32 through which the inner space 33 is connected to a pressure reducing device and an inert gas supply device (not shown), so as to create the same reduced pressure inert gas atmosphere as in the aforementioned heating chamber (not shown).

An auxiliary hopper 34 is attached to the upper plate 32. The auxiliary hopper 34 is hermetically closed by a lid 35 that can be opened and closed at the upper end, and the space 34 is closed by a pressure reducing device and an inert gas supply device (not shown).
It is now possible to create the same atmosphere. Auxiliary hopper 3
The lower end of 4 extends into the space 33 via a valve 36 that can be closed airtight, so that the granular material 12 in the auxiliary hopper 34 can be fed to the hopper 11 without removing the upper plate 32.

Next, the operation of this device will be explained. First, pulp 3
6 is closed, the lid 35 is opened, and the granular raw material 12 is put into the auxiliary hopper 34. Next, the lid 35 is closed, the inside of the auxiliary hopper 34 is made into a reduced pressure inert gas atmosphere, the pulp 36 is opened, and the granular raw material 12 in the auxiliary hopper 34 is charged into the hopper 11. Granular raw material from this auxiliary hopper 34 to the hopper 11! The replenishment of the granular raw material 2 is carried out as appropriate depending on the remaining amount of the granular raw material 12 in the hopper 11.

The space 33 around the hopper 11 is maintained in the same reduced pressure inert gas atmosphere as the inside of the heating chamber, so it is communicated with the inside of the heating chamber through the raw material introduction part 22. It will not completely inhibit it.

The granular raw material 12 in the hopper 11 is controlled by monitoring the melt level position in the crucible 25 with a laser level gauge (not shown), or by operating the variable speed motor 17 according to the decrease in the melt level. Alternatively, the variable speed motor 17 may be operated at all speeds depending on the pulling speed of the single crystal 27. By means of the variable speed motor 17 operated in this manner, the screw 14 is connected to the turnip puller I8, the magnetic seal unit 19. It rotates via the bevel gear 20.16' and sends the granular raw material 12 entering the cylinder 13 from the lower end opening +18 of the hopper 11 to the right in FIG. The granular raw material 12 is dropped into the input port 23.

At this time, the gap δ between the inner wall of the cylinder 13 and the crest of the screw 14 is set to 1.5 of the maximum particle size of the granular raw material 12, which has been sieved to a certain particle size or less as described above.
If it is more than doubled, cylinder 1 will be rotated by the rotation of screw 4.
The granular raw material 12 can be fed in an amount corresponding to the rotation of the screw 14 without being caught between the inner wall of the screw 12 and the crest of the screw 14.

FIG. 3 shows the experimental results of the relationship between the rotational speed of the screw 14 and the supply amount of the granular raw material 2. The granular raw material 12 used in this experiment is polycrystalline silicon that has been passed through a 2-square mesh sieve to a certain particle size or less.
The inner diameter Dl (see Fig. 142) is 3 lran, and the thread diameter D2 of the screw 14 is 25 lran.

The root diameter D3 was 19 mm, and the lead L of the screw 14 was 15 mm.

As is clear from Fig. 3, even if the gap δ is set as large as above, the screw still remains. A supply amount almost proportional to the number of rotations of the cylinder 13 and the screw 14 was obtained, and there was no occurrence of jamming or damage to the cylinder 13 and screw 14, and there was no problem of contamination with impurities.

Note that, if the gap δ is too large, the supply amount will decrease and become unstable, so it is preferable to limit the gap to about twice the maximum particle size of the granular raw material 12.

The granular raw material 12 that has fallen into the input port 23 is transferred to the lower introduction pipe 24.
is supplied inside the crucible 25 and outside the annular partition wall 26, is melted within the crucible 25 by a heater (not shown) provided outside the crucible 25, and is pulled up as a single crystal 27.

Therefore, a single crystal 27 with a large capacity is pulled from the crucible 25. Furthermore, after pulling one single crystal 27, the single crystal 27 can be taken out of the machine without cooling the crucible 25 by opening a gate valve (not shown) between the heating chamber and the pulling chamber above it. , if the next pulling is performed, it becomes possible to pull several times in succession even if the amount of impurities remaining in the crucible due to the pulling is taken into account.

In the above embodiment, the cylinder 13 and the screw 14 were made of stainless steel.
A hard wear-resistant coating layer or single crystal 27 on the surface that contacts 2.
The entire wear-resistant coating layer may be formed without causing any harm to the formation of the wear-resistant coating. Further, when the granular raw material 12 fed through the cylinder 13 by the screw 14 leaves the lower end opening +13 of the hopper 11 to a certain extent toward the right delivery side in FIG.
Since most of the screws are present only in the lower half of the cylinder 13, and there is space above, the delivery side of the cylinder 13 does not necessarily have a complete cylindrical shape, and even if it covers approximately the lower half of the screw 14, the work can be done. stomach. Furthermore, the auxiliary hopper 34
is suitable for supplying the granular raw material 12 to the hopper 11 during pulling;
Step 21: If no replenishment is required or if the supply from the hopper 11 to the crucible 25 can be temporarily stopped during lifting, this auxiliary hopper 34 is unnecessary, and the granular raw material 12 is directly fed into the hopper 11 by opening and closing the upper plate 32. In this case, for example, it is preferable to provide the pulp 36 and four rods of pulp at the bottom of the inlet 23.

〔Effect of the invention〕

As described above, according to the present invention, the granular raw material that is the raw material for single crystals can be reliably and stably supplied into the crucible during the entire pulling process, and no impurities are mixed in. In addition, it is possible to pull large single crystals without increasing the capacity of the Eril crucible too much, and it is also possible to pull several times in succession without cooling the crucible.
The effect of greatly improving the pulling efficiency can be obtained.

In addition, the hobba, cylinder, screw, and inlet are
If it is installed in an atmosphere where at least a portion of the material is isolated from the atmosphere by a transparent partition wall, there is no need to seal the moving parts, so the pressure can be reduced easily and reliably, and maintenance is easy. The supply status can be monitored from the outside.

Furthermore, if an auxiliary hopper that can be opened and closed on the lid via the pulp is provided, there is no need to open the partition wall, so it is possible to reliably obtain reduced pressure. This has the effect of replenishing granular raw materials.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a crucible temporarily combined with an embodiment of the granular raw material supply device for a single crystal pulling machine according to the present invention, Fig. 2 is a partially enlarged sectional view of a shilling and screw, and Fig. 3 is It is a figure which shows the experimental result of the relationship between the rotation speed of a screw and the supply amount of granular raw material. O... Frame, 11... Hopper, 12... Granular raw material, 13... Cylinder, 14...
...Screw, 17...Variable speed motor, 9...
Magnetic seal unit, 22...raw material introduction section, 23.
...Input port, 25...Crucible, 27...Single crystal,
29... Partition wall, 23... Upper plate, 34...
Auxiliary hopper, 35...Lid, 36...Pulp.

Claims (1)

[Claims] 1. A hopper for storing granular raw materials, a cylinder connected to the lower end opening of the hopper in a substantially horizontal manner, a screw provided in the cylinder and driven to rotate, and the screw. A granular raw material supply device for a single crystal pulling machine includes a raw material introduction section having an input port for receiving the granular raw material sent out by the hopper and guiding it to the crucible, the cylinder is configured to collect the granular raw material from the lower end opening of the hopper. The cylinder is formed to cover at least the lower half of the screw on the delivery side, and the gap between the inner wall of the cylinder and the crest of the screw is 1.5 to 2 times the maximum particle diameter of the granular raw material. Granular raw material supply device for crystal pulling machine. 2. The granular raw material supply device for a single crystal pulling machine according to claim 1, wherein the hopper, cylinder, screw, and input port are installed in an atmosphere where at least a portion of the hopper is isolated from the atmosphere by a transparent partition wall. 3. Claim 2 characterized in that an auxiliary hopper having an openable and closable lid provided outside the atmosphere and separated from the atmosphere by a partition wall, and a pulp provided at a lower end opening of the auxiliary hopper are provided. Granular raw material feeding device for single crystal pulling machine.