WO2016049947A1

WO2016049947A1 - Method for growing large diameter float zone silicon monocrystal

Info

Publication number: WO2016049947A1
Application number: PCT/CN2014/088600
Authority: WO
Inventors: 沈浩平; 王彦君; 张雪囡; 靳立辉; 高树良; 刘嘉; 王遵义; 刘铮; 赵宏波; 刘琨; 郝大维; 吴峰; 楚占宾
Original assignee: 天津市环欧半导体材料技术有限公司
Priority date: 2014-09-30
Filing date: 2014-10-15
Publication date: 2016-04-07
Also published as: CN104328482A

Abstract

The present invention provides a method for growing a large diameter float zone silicon monocrystal. The method comprises: furnace charging, evacuating, inflating, preheating, material melting, seeding, narrow neck growing, shoulder expanding, maintaining, equal diameter growing, ending, cooling, and furnace removal and cleaning. By means of a method for controlling the generator output power, the polycrystal material descending speed and other parameters, the problem of easy stacking caused by difficulty in melting of the large diameter polycrystal material, and the problem of a low crystal forming rate caused by poor process repeatability, dislocation in the shoulder expanding process and the like under the conditions of the existing process and method are solved, the crystal forming rate and the qualification rate of the large diameter float zone silicon monocrystal are increased, the labor intensity is reduced, and the repeatability and the reproducibility are good.

Description

Method for growing large diameter region molten silicon single crystal

Technical field

The invention relates to a method for growing a large diameter region molten silicon single crystal.

Background technique

The suspension zone melting method includes several steps of removing the furnace, preheating, chemical material, seeding, pulling the neck, expanding the shoulder, turning the shoulder, holding, closing, and stopping the furnace. The existing method is mainly controlled by the operator. The output power of the high-frequency generator and the descending speed of the polycrystalline material control the growth of the silicon single crystal. After the furnace is removed, the preheating, the material, the seeding, and the neck are pulled, the operator constantly adjusts the height. The output power of the frequency generator and the downstream speed of the polycrystalline material play the role of controlling the process of expanding the shoulder, and artificially changing the output power and the descending speed of the polycrystalline material to complete the steps of turning shoulder, holding and closing. With the existing method, the human operation factor is too much, the process repeatability is poor, the operator is labor intensive, and the crystal pulling failure is easily caused by personal operation errors.

Summary of the invention

The invention overcomes the deficiencies of the prior art and provides a method for growing a large-diameter molten silicon single crystal, which can effectively improve the problem that the process repeatability is poor and the dislocation is easy to occur during the shoulder expansion process.

In order to solve the above technical problem, the technical solution adopted by the present invention is: a method for growing a large-diameter region molten silicon single crystal, which is characterized in that the following operations are performed by using a zone melting single crystal furnace:

(1) Loading furnace: loading the cleaned polycrystalline bar material into the crystal holder in the zone melting furnace, and loading the seed crystal into the seed crystal fixing chuck;

(2) Evacuation, aeration, preheating: Place the preheating ring under the polycrystalline bar material, above the zone melting coil, close the furnace door to evacuate, and then flush into the argon gas. When the pressure in the furnace reaches 2.6-6.5 bar, Stop rapid inflation, use slow inflation, open the exhaust valve for argon flow; after inflation, preheat the polycrystalline bar;

(3) Chemical material and seeding: the preheating ring is withdrawn, and the chemical material is melted. After the polycrystalline material is melted, the seed crystal and the molten silicon are welded, and after welding, the melting zone is shaped and seeded;

(4) Growing the neck: After the end of the seeding, the neck is grown, the diameter of the neck is 2-6 mm, and the length is 30-60 mm;

(5) Expanding the shoulder: the process of expanding the shoulder, adjusting the output power of the high-frequency generator and the descending speed of the polycrystalline material through the actually measured single crystal diameter;

(6) Maintaining, equal diameter growth: When the diameter of the shoulder is larger than the required diameter, the single crystal is maintained and the equal diameter growth begins. During the growth of the single crystal diameter, the rotation speed of the polycrystalline material is 0.1-1 rpm. The growth rate of the single crystal is 1.5-2.5 mm/min, and the rotation speed of the single crystal is 6-25 rpm.

(7) Closing: When the single crystal is pulled to the tail of the polycrystalline material, the finishing of the tail is started, and the diameter of the silicon single crystal is gradually reduced. When the diameter of the single crystal reaches the required value, the melting zone is pulled apart, and the lower shaft of the melting furnace of the time zone is pulled. The single crystal continues to move downward, the upper shaft is moved upward with the polycrystalline material, and the argon gas is turned off;

(8) Cooling and dismantling the furnace: Slowly cool the crystal until the red tail turns black in the tail of the crystal, and then remove the furnace.

Preferably, the polycrystalline bar in the step (1) has a diameter of 145-175 mm.

Further, the output frequency of the high frequency generator in the furnace in the step (2) is 2-4 MHz.

Further, in the step (5) of expanding the shoulder, the relationship between the single crystal diameter and the output power of the high frequency generator and the descending speed of the polycrystalline material is: single crystal diameter = [(polycrystalline material diameter ² × polycrystalline material downstream speed) ) / single crystal down speed] ^1/2 ; high frequency generator output power is linear with the single crystal diameter.

Further, when the diameter of the shoulder is greater than 8 inches in the step (6), the single crystal is maintained and the equal diameter growth is started. The cooling time in the step (8) is 50-90 min.

The invention has the advantages and positive effects: by controlling the output power of the generator and the descending speed of the polycrystalline material, the method of the original process and the method is overcome, and the large-diameter polycrystalline material is difficult to be melted, which is easy to cause the stacking. Problems, poor process repeatability, low crystal formation rate caused by problems such as dislocations in the process of expanding the shoulder, improving the crystallization rate and yield of the large-diameter molten silicon single crystal, reducing the labor intensity and repeatability of the personnel. Reproducible.

DRAWINGS

Figure 1 is a graph showing the relationship between the output power of a high frequency generator and the diameter of a single crystal.

Fig. 2 is a graph showing the relationship between the diameter of the single crystal and the descending speed of the polycrystalline material and the descending speed of the single crystal.

detailed description

Example 1

A method for growing a single-hole molten silicon single crystal in an 8-inch zone, using the zone melting single crystal furnace to perform the following operations: (1) loading the furnace: loading the cleaned polycrystalline bar material into the crystal holder in the zone melting furnace, The seed crystal is loaded into the seed crystal holding chuck; the diameter of the polycrystalline bar material is 145-175 mm.

(2) Evacuation, inflation, preheating: Place the preheating ring under the polycrystalline bar, above the zone fuse, and close The furnace door is evacuated, and then argon gas is flushed. When the pressure in the furnace reaches 2.6-6.5 bar, the rapid inflation is stopped, and the slow inflation is used, and the exhaust valve is opened to carry out argon flow; after the inflation is completed, the polycrystalline bar is performed. Preheating; the area melting coil has a diameter range of 280-350mm, and has multiple steps and bevel designs above the pinhole coil, and has 2-5 auxiliary openings with a length of 20-150mm. The thickness of the pinhole coil ranges from 20-35mm. The output frequency of the high frequency generator is 2-4 MHz.

(5) Expanding the shoulder: the process of expanding the shoulder, adjusting the output power of the high-frequency generator and the descending speed of the polycrystalline material through the actually measured single crystal diameter; as shown in Fig. 1, 2, the diameter of the single crystal = [( The crystal material diameter is ² × polycrystalline material descending speed) / single crystal down speed] ^1/2 ; the high frequency generator output power is linear with the single crystal diameter.

(6) Maintaining, equal diameter growth: when the diameter of the shoulder is greater than 8 inches, the single crystal is maintained and the equal diameter growth begins. During the growth of the single crystal diameter, the rotation speed of the polycrystalline material is 0.1-1 rpm, and the single crystal The growth rate is 1.5-2.5 mm/min, and the single crystal rotation speed is 6-25 rpm.

(8) Cooling and demolition furnace: The crystal is slowly cooled down, and the temperature is reduced from 50 to 90 minutes. After the red tail turns black, the furnace is removed.

In the implementation process of this patent, the original method and process conditions are effectively solved, the large-diameter polycrystalline material is difficult to melt, and it is easy to cause the problem of stockpiling. The process repeatability is poor, the dislocation is easy to generate dislocation during the process of extending the shoulder, and the process is maintained. Easy to crack and other issues. Under the original process conditions, the polycrystalline material with a diameter exceeding 135mm cannot be smoothly melted and flows down from the zone melting coil, and the single crystal cannot be drawn. The proportion of the single crystal in the process of expanding the shoulder causes the crystal pulling failure to account for 92% of the total number of failures, after using the growth method of the present invention, the ratio was reduced to 57%, which greatly reduced the proportion of dislocation failure caused by the occurrence of dislocations during the extension process.

The embodiments of the present invention have been described in detail above, but are not intended to limit the scope of the present invention. All changes and improvements made in accordance with the scope of the present application should still fall within the scope of the patents of the present invention.

Claims

A method for growing a large diameter region molten silicon single crystal, characterized in that the following operation is performed by using a zone melting single crystal furnace:

(1) Loading furnace: loading the cleaned polycrystalline bar material into the crystal holder in the zone melting furnace, and loading the seed crystal into the seed crystal fixing chuck;

(2) Evacuation, aeration, preheating: Place the preheating ring under the polycrystalline bar material, above the zone melting coil, close the furnace door to evacuate, and then flush into the argon gas. When the pressure in the furnace reaches 2.6-6.5 bar, Stop rapid inflation, use slow inflation, open the exhaust valve for argon flow; after inflation, preheat the polycrystalline bar;

(3) Chemical material and seeding: the preheating ring is withdrawn, and the chemical material is melted. After the polycrystalline material is melted, the seed crystal and the molten silicon are welded, and after welding, the melting zone is shaped and seeded;

(4) Growing the neck: After the end of the seeding, the neck is grown, the diameter of the neck is 2-6 mm, and the length is 30-60 mm;

(5) Expanding the shoulder: the process of expanding the shoulder, adjusting the output power of the high-frequency generator and the descending speed of the polycrystalline material through the actually measured single crystal diameter;

(6) Maintaining, equal diameter growth: When the diameter of the shoulder is larger than the required diameter, the single crystal is maintained and the equal diameter growth begins. During the growth of the single crystal diameter, the rotation speed of the polycrystalline material is 0.1-1 rpm. The growth rate of the single crystal is 1.5-2.5 mm/min, and the rotation speed of the single crystal is 6-25 rpm.

(7) Closing: When the single crystal is pulled to the tail of the polycrystalline material, the finishing of the tail is started, and the diameter of the silicon single crystal is gradually reduced. When the diameter of the single crystal reaches the required value, the melting zone is pulled apart, and the lower shaft of the melting furnace of the time zone is pulled. The single crystal continues to move downward, the upper shaft is moved upward with the polycrystalline material, and the argon gas is turned off;

(8) Cooling and dismantling the furnace: Slowly cool the crystal until the red tail turns black in the tail of the crystal, and then remove the furnace.
The growth method according to claim 1, wherein the polycrystalline bar in the step (1) has a diameter of 145 to 175 mm.
The growth method according to claim 1, wherein the output frequency of the high frequency generator in the furnace in the step (2) is 2-4 MHz.
The growth method according to claim 1, wherein in the step (5) of expanding the shoulder, the relationship between the diameter of the single crystal and the output power of the high-frequency generator and the descending speed of the polycrystalline material is: single crystal diameter = [ (polycrystalline material diameter 2 × polycrystalline material descending speed) / single crystal down speed] 1/2 ; high frequency generator output power is linear with single crystal diameter.
The growth method according to claim 1, wherein when the diameter of the shoulder is greater than 8 inches in the step (6), the single crystal is maintained and the equal diameter growth is started.
The growth method according to claim 1, characterized in that the temperature-lowering duration in the step (8) is 50-90 min.