Low-temperature phosphorus gettering diffusion process based on removal of metal impurities in polycrystalline silicon

A technology of metal impurity and diffusion process, which is applied in the direction of diffusion/doping, crystal growth, sustainable manufacturing/processing, etc. It can solve the problems of reduced minority carrier lifetime, high impurity content, and reduced solar cell efficiency, and achieve crystal Improvement of microstructural defects, improvement of silicon wafer quality, effect of process temperature and time optimization

Inactive Publication Date: 2012-10-03
TIANWEI NEW ENERGY HLDG +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The purpose of the present invention is to overcome the deficiencies of the current technology, provide a low-temperature phosphorus gettering diffusion process based on the removal of metal impurities in polysilicon, and solve the problem that the life of minority carriers is reduced due to the high impurity content of polysilicon cast in the existing process , which leads to a decrease in the efficiency of the solar cell

Method used

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  • Low-temperature phosphorus gettering diffusion process based on removal of metal impurities in polycrystalline silicon
  • Low-temperature phosphorus gettering diffusion process based on removal of metal impurities in polycrystalline silicon

Examples

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Embodiment 1

[0023] A low-temperature phosphorus gettering and diffusion process based on the removal of metal impurities in polysilicon, including the following steps:

[0024] (1) Entering the boat: Start the diffusion furnace, and when the temperature in the furnace tube reaches 780°C, place the silicon wafer to be processed on the quartz boat, and then slowly put the quartz boat into the furnace tube;

[0025] (2) Stable temperature rise: After closing the furnace door, the temperature in the furnace tube is stabilized at 780°C, the atmosphere in the furnace is a nitrogen atmosphere, and the flow rate is 5L / min;

[0026] (3) Oxidation: At a temperature of 780°C, pass O into the furnace tube 2 , the time is 20min, a layer of oxide film is formed on the surface of the silicon wafer to protect the surface of the silicon wafer and increase the uniformity of diffusion;

[0027] (4) The first step of deposition: at a temperature of 780 ° C, 1000 sccmN is passed into the furnace tube 2 POCl...

Embodiment 2

[0034] A low-temperature phosphorus gettering and diffusion process based on the removal of metal impurities in polysilicon, including the following steps:

[0035] (1) Entering the boat: start the diffusion furnace, and when the temperature in the furnace tube reaches 800°C, place the silicon wafer to be processed on the quartz boat, and then slowly put the quartz boat into the furnace tube;

[0036] (2) Stable temperature rise: After closing the furnace door, the temperature in the furnace tube is stabilized at 800°C, the atmosphere in the furnace is a nitrogen atmosphere, and the flow rate is 15L / min;

[0037] (3) Oxidation: At a temperature of 800°C, pass O into the furnace tube 2 , the time is 10min, a layer of oxide film is formed on the surface of the silicon wafer to protect the surface of the silicon wafer and increase the uniformity of diffusion;

[0038] (4) The first step of deposition: at a temperature of 800 ° C, 800 sccmN is passed into the furnace tube 2 POCl...

Embodiment 3

[0045] A low-temperature phosphorus gettering and diffusion process based on the removal of metal impurities in polysilicon, including the following steps:

[0046] (1) Entering the boat: start the diffusion furnace, and when the temperature in the furnace tube reaches 790°C, place the silicon wafer to be processed on the quartz boat, and then slowly put the quartz boat into the furnace tube;

[0047] (2) Stable temperature rise: After closing the furnace door, the temperature in the furnace tube is stabilized at 790°C, the atmosphere in the furnace is a nitrogen atmosphere, and the flow rate is 10L / min;

[0048] (3) Oxidation: At a temperature of 790°C, pass O into the furnace tube 2 , and the time is 15 minutes, forming an oxide film on the surface of the silicon wafer to protect the surface of the silicon wafer and increase the uniformity of diffusion;

[0049] (4) The first step of deposition: at a temperature of 790 ° C, 500 sccmN is passed into the furnace tube 2 POCl ...

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Abstract

The invention discloses a low-temperature phosphorus gettering diffusion process based on removal of metal impurities in polycrystalline silicon. The method mainly comprises the following steps of: (1) feeding into a boat; (2) stably heating; (3) performing first-step deposition; (4) performing second-step deposition; (5) propelling; (6) absorbing impurities; (7) propelling once again at a low temperature; and (8) cooling, annealing and discharging out of the boat. Through innovation of a polycrystalline silicon diffusion process in a solar industrial production process, the removal of metal ions in a type B polycrystalline silicon wafer with short minority carrier lifetime and improvement on the structure of a silicon wafer crystal are realized, the photoelectric conversion efficiency of a solar cell produced by using the type B wafer with short minority carrier lifetime is increased, the average value of the minority carrier lifetime of the type silicon wafer is not less than 12mus, and the efficiency of a battery produced by using the type silicon wafer is 0.2 percent higher than that of a battery produced by using a normal process.

Description

technical field [0001] The invention relates to a polysilicon diffusion process, in particular to a low-temperature phosphorus gettering diffusion process based on the removal of metal impurities in polysilicon. Background technique [0002] Cast polysilicon has become the most important raw material for solar cells due to its high cost performance. However, compared with single crystal silicon, it has a higher density of structural defects and a high content of impurities, especially heavy metal impurities such as Fe, Cu and Ni, which generate energy levels in the middle of the forbidden band and act as recombination centers and traps. The lifetime of the minority carriers is reduced, which leads to a reduction in the efficiency of the solar cell. [0003] During the production process of cast polycrystalline silicon, due to the limitations of the casting process, the top and bottom parts of the entire silicon ingot have more structural defects and higher content of metal...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C30B31/06H01L31/18
CPCY02P70/50
Inventor 姜丽丽路忠林盛雯婷张凤鸣
Owner TIANWEI NEW ENERGY HLDG
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