Crystal pulling method for czochralski single crystal based on Ta-W crucible

Abstract

The invention discloses a crystal pulling method for czochralski single crystal based on a Ta-W crucible. The method comprises the following steps: (1) using a Ta-W alloy crucible; (2) after a furnace platform is vacuumized, the total melt power is 300 kw melt, a melt crucible is turned to 1 turn, the argon flow is 100 slpm, and the furnace pressure is 15 Torr; during feeding, the silicon material is re-fed without waiting for full melting of the silicon liquid, the continuous feeding furnace pressure is 25 Torr, and the argon flow is 150 slpm; (3) changing the crucible rotation from 5 to 10, the furnace pressure being 15 Torr and the argon flow being 100 slpm during temperature-adjusting welding, and changing the process crucible rotation into 10 rotation while the argon flow and the furnace pressure being unchanged; (4) after single crystal pulling is completed, re-feeding is carried out according to the melt power of 300 kw, the crucible retention rate is smaller than 1%, and the pulling-out ratio is larger than or equal to 99%; and (5) pulling the crystal for 900 hours, stopping the furnace, pulling the silicon material to be dry before stopping the furnace, and disassembling the furnace after stopping the furnace for 10 hours. The method has the advantages that the crystal pulling efficiency is improved, the crystal pulling quality is improved, the crystal pulling cost is reduced, and the crystal pulling process window is widened.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal silicon manufacturing, and in particular to a crystal pulling method based on Ta-W crucible straight-pull single crystal. Background Art

[0002] In the solar monocrystalline silicon industry, with the development and iteration of technology over the years, the market has gradually eliminated backward production capacity. In the fierce market competition, product quality requirements are getting higher and higher. Improving crystal pulling efficiency and increasing the effective output of silicon materials have become the industry's breakthrough needs. The current crystal pulling uses quartz crucibles, which soften and deform under high temperature conditions, which greatly restricts the upward breakthrough of the material rate. The RCZ technology is also limited by its service life of less than 600h, and it cannot be continuously fed. In addition, it will precipitate a large amount of oxygen atoms at high temperatures, affecting product quality, and further affecting the formation of concentric circle defects in the battery process, resulting in quality waste. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of long crystal pulling time, short life of quartz crucible, high oxygen content of single crystal rough rod and narrow crystal pulling process window. A crystal pulling method based on Ta-W crucible direct pulling single crystal is provided, which can improve crystal pulling efficiency, improve crystal pulling quality, reduce crystal pulling cost and widen the crystal pulling process window.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A crystal pulling method based on Ta-W crucible Czochralski single crystal, comprising: (1) Replace the quartz crucible with a Ta-W alloy crucible. After the furnace is cleaned, place the Ta-W crucible on the hot field crucible support of the single crystal furnace; (2) After the furnace is evacuated, the total melting power is set to 300kw, the melting crucible is set to 1 turn, the argon flow rate is set to 100slpm, and the furnace pressure is set to 15Torr; when the barrel is charged, the silicon material is re-added without waiting for the silicon liquid to be fully melted, the barrel is continuously charged, the charging furnace pressure is set to 25Torr, and the argon flow rate is set to 150slpm; (3) In the temperature adjustment welding stage, the crucible rotation setting is changed from 5 to 10 crucible rotations, the furnace pressure is set to 15 Torr, the argon flow rate is set to 100 slpm, and the lead-in and release process settings are changed from crucible rotation to 10 crucible rotations, 100 slpm argon flow rate, and the furnace pressure remains unchanged at 15 Torr; (4) After a single crystal pulling is completed, the melt power is re-added at 300kw. The crucible retention rate for a single crystal pulling is set to be less than 1%, that is, the value of the remaining material weight / total material input, and the pulling ratio is ≥99%; (5) The furnace is shut down when the crystal pulling time reaches 900 hours. The silicon material must be pulled dry before stopping the furnace. The furnace is dismantled after the furnace has been shut down for 10 hours. The Ta-W crucible is placed on a special vehicle and sent to the cleaning workshop to knock off the crystalline silicon attached to the bottom of the crucible. The inner wall of the crucible is cleaned with reagents and then dried for the next use in the furnace.

[0005] Furthermore, in the step (1), the crucible is installed without a crucible side.

[0006] Furthermore, the single-stage crystal pulling crucible retention rate is less than the total material input amount*1.

[0007] Furthermore, the temperature-adjusting crucible rotation number is changed by 5, the crucible rotation number used in the whole crystal pulling process is ≥10 crucible rotations, the furnace pressure is ≥15 Torr, and the operation time reaches >900h of crystal pulling.

[0008] In the present invention, a Ta-W crucible is used to achieve high-temperature silicon melting: (1) the melting power is increased from the current 200kw to 300kw; (2) the silicon melt will not react with the Ta-W crucible, and the crucible will not precipitate oxygen atoms during the crystal pulling process, thereby reducing the oxygen content of the crystal rod head and improving the core competitiveness of the product; (3) the Ta-W crucible operates at a high temperature of 2000°C for a long time without material deformation, which can eliminate the crucible guards currently used, save crystal pulling costs, extend crystal pulling time, and provide favorable support for RCZ technology; (4) a large crucible is used during crystal pulling, and high furnace pressure is used to widen the process window and improve crystal formation.

[0009] Compared with the prior art, the advantages of the technical solution of the present invention are: (1) The present invention adopts Ta-W material, because its melting point is greater than 2000°C and it is not easy to deform under high temperature conditions, so it can be well applied to the field of crystal pulling crucibles, widen the crystal pulling process window, and improve the crystal pulling efficiency; (2) The monthly crystal pulling efficiency and output of a single furnace increased by 30kg / d; (3) Reduce the oxygen content at the head of the crystal rod to less than 5ppma, and the proportion of oxygen return at the head of the crystal rod will be reduced to 0%; (4) The present invention breaks the limitation of the traditional quartz crucible operation of less than 600 hours and achieves 900 hours of operation. Compared with the current disassembly and assembly twice a month, it is changed to disassembly and assembly once every two months, which realizes the effective utilization of working hours and reduces the non-silicon cost of crystal pulling; (5) The crucible of the present invention has no crucible guard, which reduces the thermal field cost; (6) The crucible of the present invention can be heated directly without heat transfer loss due to the crucible side, thus reducing the power consumption of crystal pulling; (7) With the same crystal pulling heat field, the crucible diameter can be directly increased by 1 inch, and the feeding amount can be increased; (8) Compared with conventional quartz crucibles, the bottom thickness of the Ta-W crucible of the present invention can be consistent with the side wall without being thickened, and the feeding amount can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the structure of a quartz crucible with a crucible side installed in the prior art; Figure 2 It is a schematic diagram of the structure of the Ta-W crucible without a crucible rim of the present invention. DETAILED DESCRIPTION Example

[0011] To make the present invention more clear, a crystal pulling method based on Ta-W crucible straight-pull single crystal of the present invention is further described below in conjunction with the accompanying drawings. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0012] A crystal pulling method based on Ta-W crucible Czochralski single crystal, characterized by: (1) Replace the traditional quartz crucible material with Ta-W alloy material to widen the crystal pulling window and reduce energy consumption; (2) After the furnace is cleaned, the Ta-W crucible is placed on the crucible support in the hot field of the single crystal furnace without installing the crucible side. After the furnace is evacuated, the total melting power is set to 300kw, the melting crucible speed is set to 1 turn, the argon flow rate is set to 100slpm, and the furnace pressure is set to 15Torr; when adding materials to the barrel, there is no need to wait for the silicon liquid to be fully melted, and the barrel is continuously added. The feeding furnace pressure is set to 25Torr and the argon flow rate is 150slpm; (3) During the temperature adjustment welding stage, the crucible rotation setting is changed from 5 to 10 crucible rotations, the furnace pressure is set to 15 Torr, the argon flow rate is set to 100 slpm, and the process settings of the lead-out and release are 10 crucible rotations, 100 slpm argon flow, and 15 Torr furnace pressure remains unchanged. After a single crystal pulling is completed, the melt power is re-added at 300 kW. The crucible retention rate for a single crystal pulling is set to be less than 1% of the remaining material weight / total material input, and the pulling ratio is ≥99%; (4) The furnace is shut down when the pulling time reaches 900h, of which 900h is not the service life of the crucible, and 900h is the service life of the bottom electrode sheath. The silicon material must be pulled dry before stopping the furnace. The furnace is dismantled after the furnace is stopped for 10h. The Ta-W crucible is placed on a special vehicle and sent to the cleaning workshop to knock off the crystalline silicon attached to the bottom of the crucible. The inner wall of the crucible is cleaned with reagents and then dried for the next use in the furnace.

[0013] In the present invention, the Ta-W crucible can be reused after cleaning. Figure 1 FIG. 1 is a schematic diagram of a structure in which a conventional quartz crucible 1 is equipped with a crucible side 2 in the prior art, while the present invention does not use a crucible side when installing a Ta-W crucible 3. Figure 2 As shown in the figure, Ta-W material can be well applied in the field of crystal pulling crucibles because of its melting point > 2000℃ and its non-deformation property under high temperature conditions, thus widening the crystal pulling process window and improving the crystal pulling efficiency.

[0014] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for pulling a single crystal based on a Ta-W crucible, characterized in that: (1) Replace the quartz crucible with a Ta-W alloy crucible. After the furnace is cleaned, place the Ta-W crucible on the hot field crucible support of the single crystal furnace; (2) After the furnace is evacuated, the total melting power is set to 300kw, the melting crucible is set to 1 turn, the argon flow rate is set to 100slpm, and the furnace pressure is set to 15Torr; when the barrel is charged, the silicon material is re-added without waiting for the silicon liquid to be fully melted, the barrel is continuously charged, the charging furnace pressure is set to 25Torr, and the argon flow rate is set to 150slpm; (3) In the temperature adjustment welding stage, the crucible rotation setting is changed from 5 to 10 crucible rotations, the furnace pressure is set to 15 Torr, the argon flow rate is set to 100 slpm, and the lead-in and release process settings are changed from crucible rotation to 10 crucible rotations, 100 slpm argon flow rate, and the furnace pressure remains unchanged at 15 Torr; (4) After a single crystal pulling is completed, the melt power is re-added at 300kw. The crucible retention rate for a single crystal pulling is set to be less than 1%, that is, the value of the remaining material weight / total material input, and the pulling ratio is ≥99%; (5) The furnace is shut down when the crystal pulling time reaches 900 hours. The silicon material must be pulled dry before stopping the furnace. The furnace is dismantled after the furnace has been shut down for 10 hours. The Ta-W crucible is placed on a special vehicle and sent to the cleaning workshop to knock off the crystalline silicon attached to the bottom of the crucible. The inner wall of the crucible is cleaned with reagents and then dried for the next use in the furnace.

2. The crystal pulling method based on Ta-W crucible Czochralski single crystal according to claim 1, characterized in that: In the step (1), the crucible is installed without a crucible side.

3. The crystal pulling method based on Ta-W crucible Czochralski single crystal according to claim 1 or 2, characterized in that: The single-stage crystal pulling crucible retention rate is less than the total material input amount*1.

4. The crystal pulling method based on Ta-W crucible Czochralski single crystal according to claim 1 or 2, characterized in that: The temperature-adjusting crucible rotation number is changed by 5 times, the crucible rotation number used in the whole crystal pulling process is ≥10 crucible rotations, the furnace pressure is ≥15 Torr, and the operation time reaches >900h of crystal pulling.

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