Polycrystalline silicon ingot casting process based on boron nitride coating

A technology of polysilicon ingot casting furnace and boron nitride, which is applied in the direction of polycrystalline material growth, crystal growth, chemical instruments and methods, etc., can solve the problem that the annealing effect affects the stress distribution of the finished ingot, the quality of the finished polysilicon ingot is greatly affected, The quality of the finished ingot is greatly affected, and the coating process is easy to control, the drying structure design is reasonable, and the cost is low.

Inactive Publication Date: 2017-01-04
XIAN HUAJING ELECTRONICS TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, in the solar polysilicon ingot casting process, the crucible spraying process used is Si 3 N 4 material as a spray material, but due to Si 3 N 4 The poor thermal conductivity and instability of the material itself make it easy to form hard spots during the ingot casting process, and the oxygen content at the bottom of the finished ingot is relatively high, which has a great impact on the quality of the product
At the same time, Si 3 N 4 Although the material can effectively isolate the reaction between the silicon liquid and the crucible, the Si 3 N 4 After reacting with silicon liquid, a red zone is formed, which is easy to introduce impurity Si 3 N 4 And form a hard point, which has a great influence on the quality of the finished ingot
[0004] In addition, annealing is an extremely important process step in the process of polysilicon ingot casting. Poor annealing effect directly affects the stress distribution state inside the finished ingot, and has a great impact on the quality of the finished polysilicon ingot.
At present, when annealing polysilicon ingots, there is no unified, standard and standardized method to follow. In actual processing, there are inevitably problems such as relatively random operations, long time-consuming, and poor annealing effects. Therefore, the existing The annealing process also has a great influence on the quality of the finished ingot

Method used

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  • Polycrystalline silicon ingot casting process based on boron nitride coating
  • Polycrystalline silicon ingot casting process based on boron nitride coating
  • Polycrystalline silicon ingot casting process based on boron nitride coating

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0054] like figure 1 A kind of polysilicon ingot technology based on boron nitride coating as shown, comprises the following steps:

[0055] Step 1, preparation of the coating on the bottom of the crucible, the process is as follows:

[0056] Step 101, preparation of coating spraying liquid: uniformly mixing organic binder, deionized water and boron nitride at a mass ratio of 1:2.2:1 to obtain coating spraying liquid;

[0057] Step 102, spraying: use spraying equipment to evenly spray the coating spray liquid described in step 101 on the inner bottom surface of the crucible 1, and the inner bottom surface of the crucible 1 is 1 m 2 The mass of boron nitride contained in the coating spray liquid sprayed in the area is 100g-150g;

[0058] The crucible 1 is a quartz crucible for a polysilicon ingot furnace;

[0059] Step 103, drying: place the crucible 1 in step 102 horizontally in the drying equipment, and use the drying equipment to spray the coating sprayed on the inner bot...

Embodiment 2

[0107] In this embodiment, the difference from Embodiment 1 is: during the preheating process in step 202, the heating power of the ingot furnace is gradually increased to P1, where P1=50kW~100kW; After all the silicon material is melted, the heating power variation of the ingot furnace is observed, and the melting process is completed after the heating power of the ingot furnace drops to P2 and keeps P2 constant for a duration of t; Among them, P2=25kW~45kW.

[0108] And, when melting in step 203, the process is as follows:

[0109] Step 1, heat preservation: control the heating temperature of the polysilicon ingot casting furnace at T1, and keep heat for 0.4h to 0.6h;

[0110] Step 2 to Step 5, heating and pressurization: gradually increase the heating temperature of the polysilicon ingot furnace from T1 to T6 in four steps from first to last, and the heating time is 0.4h to 0.6h; The polysilicon ingot casting furnace is filled with inert gas and the air pressure of the po...

Embodiment 3

[0155] In this example, the difference from Example 2 is: in step 202, the preheating time is 4 hours and T1=1285°C, P1=100kW; in step 203, T2=1560°C, t=20min, P1=45kW, Q2=650mbar ; In the first step, the holding time is 0.4h; in the second step to the fifth step, T6=1325°C, and the heating time is 0.4h; in the sixth step, T7=1460°C, and the heating time is 3.5h; in the seventh step, T8 =1510°C and the heating time is 3.5h; the heating time in the 8th step is 3.5h; the holding time in the 9th step is 3.5h; the holding time in the 10th step is 4h;

[0156] In the present embodiment, when heating up and pressurizing in the 2nd step to the 5th step, the process is as follows:

[0157] The second step, the first step of raising: the heating temperature of the polysilicon ingot casting furnace is raised from 1285°C to 1290°C, and the heating time is 5 minutes.

[0158] The third step and the second step of raising: raise the heating temperature of the polysilicon ingot casting fur...

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Abstract

The invention discloses a polycrystalline silicon ingot casting process based on a boron nitride coating. The process includes the first step of preparing a coating at the bottom of a crucible and the second step of conducting polycrystalline silicon ingot casting, wherein filling, preheating, melting, nucleating, and annealing and cooling are conducted in sequence, and the annealing and cooling step includes the substeps of primary annealing, wherein the heating temperature of a polycrystalline silicon ingot casting furnace is lowered to T4 and the temperature is kept for 2-3 h, and T4 is 1250-1280 DEG C; secondary annealing, wherein the heating temperature of the polycrystalline silicon ingot casting furnace is lowered to T5 from T4 and the temperature is kept for 2-3 h, and T5 is 900-950 DEG C; cooling. The process is simple in step, reasonable in design, easy and convenient to implement and good in use effect; by coating the bottom of the crucible with a layer of bottom coating with boron nitride as the main raw material, the oxygen content of the bottom of the crucible can be effectively reduced, the hard point of a finished ingot casting product can be effectively reduced, the annealing process is adjusted, and the quality of the finished ingot casting product can be improved.

Description

technical field [0001] The invention belongs to the technical field of polysilicon ingot casting, and in particular relates to a polysilicon ingot casting process based on a boron nitride coating. Background technique [0002] Photovoltaic power generation is one of the most important clean energy sources with great development potential. The key factors restricting the development of photovoltaic industry are low photoelectric conversion efficiency on the one hand and high cost on the other hand. Photovoltaic silicon wafers are the basic material for the production of solar cells and components. The purity of polysilicon used to produce photovoltaic silicon wafers must be above 6N (that is, the total content of non-silicon impurities is below 1ppm), otherwise the performance of photovoltaic cells will be greatly negative Influence. In recent years, the production technology of polycrystalline silicon wafers has made remarkable progress, and the polycrystalline ingot casti...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C30B28/06C30B29/06C30B33/02C03C17/00
CPCC30B28/06C03C17/006C30B29/06C30B33/02
Inventor 刘波波贺鹏蔺文吴增伟
Owner XIAN HUAJING ELECTRONICS TECH
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