CN114318498B

CN114318498B - Shouldering method of zone-melting silicon single crystal

Info

Publication number: CN114318498B
Application number: CN202111638491.9A
Authority: CN
Inventors: 王永涛; 尚锐刚; 刘建涛; 李明飞
Original assignee: Youyan Semiconductor Silicon Materials Co ltd
Current assignee: Youyan Semiconductor Silicon Materials Co ltd
Priority date: 2021-12-29
Filing date: 2021-12-29
Publication date: 2022-12-02
Anticipated expiration: 2041-12-29
Also published as: CN114318498A

Abstract

The invention discloses a shouldering method of zone-melting silicon single crystal, which adopts flat-head polysilicon to shoulder, and the control mode of heating power and polycrystalline speed is as follows: (1) At the beginning of shouldering of the flat-head polycrystal, the heating power is 20% -30% higher than that of the beginning of shouldering of the cone-head polycrystal, and then the heating power is gradually reduced until the diameter of the silicon single crystal is 30-40mmmm, and the heating power is reduced to be the same as that of the beginning of shouldering of the cone-head polycrystal; the subsequent parameters are the same as the parameters of the conical head polycrystal shouldering; (2) When the diameter of the silicon single crystal is 60-70mm, the polycrystalline speed approaches the cone head polycrystalline shouldering parameter, and the subsequent parameters are the same as the cone head polycrystalline shouldering parameters. By adopting the method, the secondary cone grinding processing of the polycrystal after the primary crystal pulling failure can be avoided, the polycrystal loss is reduced, the production efficiency is improved, and the production cost is reduced.

Description

Shouldering method of zone-melting silicon single crystal

Technical Field

The invention discloses a shouldering method of zone-melting silicon single crystal, and relates to the technical field of silicon single crystal manufacturing.

Background

The zone-melting polycrystalline silicon is first subjected to cone grinding, grooving and corrosion processing before being pulled. The grinding process is similar to "pencil sharpening", wherein a polycrystalline head is ground into a cone with a specific angle (generally 120 °), so as to obtain a cone head polycrystalline (as shown in fig. 3 a), and then seeding, shouldering, isodiametric sizing and the like are performed. However, during the crystal pulling process, a shoulder clamp, an equal diameter clamp and the like are often placed to cause the crystal pulling failure, and at the moment, the head of the polycrystal is basically flat (as shown in fig. 3b, called flat-head polycrystal), and the polycrystal needs to be ground again, so that the polycrystal is wasted and the production efficiency is reduced.

Disclosure of Invention

Based on the prior art, the invention aims to provide a shouldering method for a zone-melting silicon single crystal, which is based on flat-end polycrystal to shoulder, namely, after one-time crystal pulling fails, a small cone at the head part when the polycrystal is broken is used for carrying out shouldering operation again, so that secondary cone grinding processing is avoided, and the production yield and efficiency are improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

a shouldering method for zone-melting silicon single crystal adopts flat-head polysilicon to shoulder, and the control mode of heating power and polycrystalline speed is as follows:

(1) In the aspect of heating power control, at the beginning of shouldering of the flat-head polycrystal, the heating power is 20-30% higher than that at the beginning of shouldering of the cone-head polycrystal, and then the heating power is gradually reduced until the diameter of the silicon single crystal is 30-40mmmm, and the heating power is reduced to be the same as that at the beginning of shouldering of the cone-head polycrystal; the subsequent parameters are the same as the parameters of the conical head polycrystal shouldering;

(2) In the aspect of polycrystalline speed control, in the initial shoulder-putting of flat-head polycrystal, the polycrystalline speed is 2-3 times of that of cone-head polycrystal, then the polycrystalline speed is rapidly and gradually reduced to the lowest when the diameter of a silicon single crystal is 20-30mm, then the polycrystalline speed is gradually increased along with the increase of the diameter of the silicon single crystal, when the diameter of the silicon single crystal is 60-70mm, the polycrystalline speed is close to the cone-head polycrystal shoulder-putting parameter, and the subsequent cone-head polycrystal shoulder-putting parameter is the same as the cone-head polycrystal shoulder-putting parameter.

Wherein, in the initial stage of shouldering the flat head polycrystal, the heating power is 20-30% higher, which is the first key factor of success or failure of shouldering, so that the shape and position of the polycrystal influence the initial heating power because the zone melting crystal pulling heating mode is high-frequency induction heating. The heating power can not be given by the diameter of the polycrystal, the area of the flat-end polycrystal required to be induced is larger, and the root part of the small cone has an area mutation, so that the temperature stability of crystal growth is ensured, and the temperature gradient required by the crystal growth can be met only by controlling the heating power in a nonlinear control mode.

As a preferable scheme of the invention, at the beginning of shouldering the flat-head polycrystal, the heating power is 55kW; and the power is reduced to 40kW when the diameter of the silicon single crystal is 30-40 mmmm.

In the aspect of polycrystalline speed control, the flat-head polycrystalline shouldering is initial, because the small cone head diameter of the flat-head polycrystalline is far smaller than the large cone head diameter of the cone-head polycrystalline, the polycrystalline speed is 2-3 times of the polycrystalline speed of the cone-head polycrystalline shouldering initial to ensure the polycrystalline volume required by single crystal shouldering, when the small cone head below the flat head is about to be completely melted, the polycrystalline speed is rapidly and gradually reduced to be the lowest when the diameter is 20-30mm, and the second key factor is whether the shouldering is successful or not. The polycrystal speed is gradually increased along with the increase of the diameter, and the flat head polycrystal speed is close to the cone head polycrystal speed when the diameter is 60-70mm, at the moment, the cone head polycrystal cone head part is completely melted and is converted into a single crystal part, so that the flat head shoulder-putting subsequent parameter is the same as the cone head polycrystal shoulder-putting parameter.

As a preferable scheme of the invention, the polycrystalline speed is controlled to be 3.3mm/min at the beginning of shouldering the flat-head polycrystalline; reducing the diameter of the silicon single crystal to 0.1-0.2mm/min when the diameter of the silicon single crystal is 20-30 mm.

The invention has the beneficial effects that:

by adopting the shouldering method of the zone-melting silicon single crystal, the small cone at the head part when the polycrystal is broken is utilized to carry out shouldering operation again after one-time crystal pulling fails, so that secondary cone grinding processing is avoided, and the production yield and efficiency are improved.

Drawings

FIG. 1 is a graph showing the heating power and the polycrystal speed during the shouldering process of the cone head polycrystal in the comparative example.

FIG. 2 is a graph showing the heating power and the polycrystal speed during the shouldering process of the flat head polycrystal in the example.

FIG. 3 is a structural comparison between a cone polycrystal and a flat polycrystal, in which FIG. 3a shows the cone polycrystal and FIG. 3b shows the flat polycrystal.

Detailed Description

The present invention is further illustrated by the following specific examples, which are not intended to limit the scope of the invention.

Comparison example (conical head polycrystal shouldering)

In this comparative example, the tapered polysilicon of the structure shown in FIG. 3a was used for shouldering, and the changes in heating power and polycrystalline speed are shown in FIG. 1. The heating power was 45kW at the beginning of shouldering, and was gradually reduced to 40kW until the diameter of the silicon single crystal became 30mm, and then the heating power was gradually increased as shown in FIG. 1. At the beginning of shouldering, the polycrystalline speed was 1.5mm/min, the polycrystalline speed started to decrease until the diameter of the silicon single crystal was 40mm, and the polycrystalline speed started to decrease until the diameter of the silicon single crystal was 70mm to 1mm/min, and then the polycrystalline speed was gradually increased as shown in FIG. 1.

The shouldering operation of 6 batches of the zone-melting silicon single crystals was carried out by the above method, and the shouldering data of the cone-head polycrystal is shown in table 1.

Table 1: cone head polycrystal shouldering data

As can be seen from the data in the table, the

polycrystal numbers

1, 4 and 5 form crystals once, which shows that the shoulder-laying once succeeds, and the float-zone silicon single crystal is obtained in the equal diameter stage smoothly. And when the primary shouldering of the polycrystal

serial numbers

2, 3 and 6 fails, the polycrystal needs to be subjected to cone grinding again, so that corresponding head loss and secondary cone grinding loss are generated, corresponding working hours are consumed, and the yield and the production efficiency are reduced.

Example (Flat head polycrystal shouldering)

In this example, the flat-headed polysilicon of the structure shown in FIG. 3b was used for shouldering, and the change of the heating power and the polysilicon rate was as shown in FIG. 2. The heating power was gradually decreased at 55kW at the beginning of shouldering, and 40kW at the time of shouldering to a diameter of 30mm, followed by gradually increasing the heating power as shown in FIG. 2, and the subsequent heating power control was performed in the same manner as in the comparative example. The polycrystal velocity at the beginning of shouldering was 3.3mm/min, and the polycrystal velocity at the beginning of shouldering to a diameter of 30mm was reduced to 0.2mm/min, and then the polycrystal velocity was gradually increased as shown in FIG. 2, and when shouldering to a diameter of 70mm, the polycrystal velocity was the same as that in comparative example, and the polycrystal velocity control was the same as that in comparative example 1 thereafter.

The shouldering operation of 6 batches of the zone-melting silicon single crystals was carried out by the above method, and the shouldering data of the flat-head polycrystal is shown in Table 2.

TABLE 2 Flat head polycrystal shouldering data

Number of polycrystal	Loss (kg)	Man-hour (h)	Yield (kg)	Charging (kg)	Yield of	Efficiency (kg/h)
							1	0	16	36.5	52	70.2％	2.3
2	1	20	35.2	50.5	69.7％	1.8
							3	0.8	16	29.5	43.2	68.3％	1.8
4	0	17	37.5	53.1	70.6％	2.2
							5	2.1	16	29.5	43	68.6％	1.8
6	3.2	21	34.6	51	67.8％	1.6
							Total up to	7.1	106	202.8	292.8	69.3％	1.9

As can be seen from the data in the table, the

polycrystal numbers

1 and 4 are crystallized once, which shows that the shoulder-laying is successful once, and the float-zone silicon single crystal is obtained successfully in the equal-diameter stage. Although the single shouldering process in the polycrystal

serial numbers

2, 3, 5 and 6 is not successful, compared with the single shouldering failure of cone head polycrystal, the single shouldering process does not need to be carried out again, the influence on shouldering operation, yield and yield is not large, and the accumulative yield and production efficiency can be greatly improved.

According to the method, the cone does not need to be ground again after the crystal pulling fails, the accumulated yield is improved by 6 percent within 3 months by using the flat-head polycrystalline shouldering process, and the production efficiency is improved by more than 10 percent.

Claims

1. A shouldering method of zone-melting silicon single crystal is characterized in that flat-head polycrystalline silicon is adopted for shouldering, and the control mode of heating power and polycrystalline speed is as follows:

(1) In the aspect of heating power control, at the beginning of shouldering of the flat-head polycrystal, the heating power is 20% -30% higher than that at the beginning of shouldering of the cone-head polycrystal, and then the heating power is gradually reduced until the diameter of the silicon single crystal is 30-40mm, and the heating power is reduced to be the same as that at the beginning of shouldering of the cone-head polycrystal; the subsequent parameters are the same as the parameters of the conical head polycrystal shouldering;

(2) In the aspect of polycrystalline speed control, in the initial shoulder-putting of flat-head polycrystal, the polycrystalline speed is 2-3 times of that of cone-head polycrystal, then the polycrystalline speed is rapidly and gradually reduced to the lowest when the diameter of the silicon single crystal is 20-30mm, then the polycrystalline speed is gradually increased along with the increase of the diameter of the silicon single crystal, when the diameter of the silicon single crystal is 60-70mm, the polycrystalline speed is the same as the cone-head polycrystalline speed, and the subsequent shoulder-putting parameter is the same as the cone-head polycrystalline speed.

2. The method of shouldering a float-zone silicon single crystal according to claim 1, wherein the heating power is 55kW at the start of shouldering of the flat-head polycrystal; and when the diameter of the silicon single crystal is 30-40mm, the power is reduced to 40kW.

3. The shouldering method of a float-zone silicon single crystal according to claim 2, wherein the polycrystal speed is controlled to be 3.3mm/min at the beginning of shouldering of the flat-headed polycrystal; reducing the diameter of the silicon single crystal to 0.1-0.2mm/min when the diameter of the silicon single crystal is 20-30 mm.