Processflow


Boron Texturing

Boron Texturing

Process Purpose

▪ Removing surface contaminations and saw damage layers

▪ Reducing light reflection and increasing light absorption

Process methods

▪ Anisotropic etching occurs in a hot alkaline solution to form micron pyramid texture

Diffusion

Diffusion

Process Purpose

▪ Preparing uniform PN junctions to from a built-in electric field, which separates photo-generated carriers

Process methods

▪ The BCl3 source is introduced into the high temperature diffusion furnace for a period of time, and P + doping layer is formed on the surface of n-type silicon wafer

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BSG Removal and Back Side Polish

Process Purpose

▪ Removing BSG layer on the back

▪ Back Side Polish 

Process methods

▪ BSG Removal:Using a certain concentration of acid solutions  to chemically react with the back of the silicon wafer, so as to etch the BSG on the back side.

▪ Alkali etching: using  the etching effect of alkali to polish the back of the silicon waferetching.

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Low Pressure Chemical Vapor Deposition

Process Purpose

▪ Providing a tunneling oxide layer to selectively pass electrons.

▪ The amorphous silicon layer is formed, and the passivation film layer is constructed together with the oxide layer.

Process methods

▪ SiO2 is formed through the reaction of oxygen and silicon under low pressure and high temperature process condition.

▪ SiH4 is thermally decomposed into Si and H2 under low pressure and high temperature, and the amorphous silicon layer is formed.

 

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Phosphorus Diffusion

Process Purpose

▪ Polysilicon formation through high temperation crystallization process of amorphous silicon.

▪ At the same time, the polysilicon is doped with phosphorus to form N+ layer,Phosphorus doping in Poly to form good ohmic contact with back electrode.

Process methods

▪ POCl3 source is diffused at high temperature for a period of time to conduct phosphorus doping on Poly-Si.

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PSG

Process Purpose

▪ PSG, Removing wrapped-around PSG layer on the front side of silicon wafer.

▪ Poly-Si,Removing the Poly-Si on the front side of the silicon wafer.

▪ PSG, Removing the BSG on the front side and the PSG on the back side.

Process methods

▪ PSG Removal : Using a certain concentration of acid solutions to chemically react with the back of the silicon wafer, so as to etch off the edge junction.

▪ Alkali etching: Using the etching effect of alkali to remove polycrystalline silicon film on the front surface

 

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ALD AlOx

Process Purpose

▪ The field effect passivation of AlOx film is used to reduce the minority carrier recombination on silicon wafer surface

Process methods

▪ TMA and ozone are fed into the furnace tube, and AIOx film is grown by the method of ALD(atomic layer deposition)

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Front side / Back side SiNx coating

Process Purpose

▪ Depositing SiNx anti- reflective thin film to reduce light reflection.

Process methods

▪ SiNx thin film is deposited using PECVD method through ionized  decomposition of SiH4 and NH3 gas.

 

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Screen Printing & Firing

Process Purpose

▪ Ag paste is printed on the surface of the silicon wafer and fired to form a conductive electrode, in order to collecting and exporting current

Process methods

▪ Printing back busbar and drying

▪ Printing back finger and drying

▪ Printing front busbar and drying

▪ Printing front finger

▪ Firing

▪ Light injection

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Testing

Process Purpose

▪ According to the test sorting standards, the solar cells are classified by appearance, EL and electrical performance.

Process methods

▪ Automatic Optical Inspection

▪ Electroluminescent test

▪ IV test

▪ Packing