Study On The Removal Technology Of Contaminants On Solar Polysilicon Slice

The photovoltaic (PV) industry in China has got rapid development recently. From 2007 to now, China was the world leader in solar cell production and module assembling. Currently, crystalline silicon solar cell accounted for 80% of commercial solar cells, and polysilicon solar cells occupied more than 90% of the crystalline silicon solar cell. The cleanliness of polysilicon slice has a significant influence on the subsequent manufacturing process of solar cell, which can directly impact the properties and production yield of solar cell. Traditional wafer cleaning technology is based on the RCA cleaning technology developed by Radio Corporation of America. The RCA cleaning technology, however, consumes large amount of strong acid, alkali and oxidizer, has high cost, pollute the environment, therefore, it only be used in the cleaning of electronic grade wafer. Based on the RCA cleaning principles, we have designed a high efficient and low cost detergent was considering characteristics of different multi-silicon slice's surface. The aqueous detergent consists of high efficient surfactants, alkali, chelating agent and water et al.In this paper, first we investigated the oil removal efficiency of different alkali and surfactants. The relationship between the cleaning performance and surface tension of different detergents were considered. Six surfactants with comprehensive properties have been chosen as excellent components for the detergents, among a lot of different anionic surfactants and nonionic surfactants. Then we formulated a lot of detergents using the selected surfactants and different additives. Finally, we optimized the components by alkali A, nonionic surfactant B, anionic surfactant C as main constituents in the detergent (MT).Through orthogonal experiment, we studied the influence of oil removal efficiency by the main constituents, and got their optimal combination proportion, the final formulation (MT). Then, we examined the influence of the oil removal efficiency of the detergent by cleaning temperature, time, and the concentration of detergent. Finally, we got the best oil removal cleaning process with the detergent is 60℃,3min,3%(wt.).Adopting ultrasonic cleaning process, we examined the influence of the cleaned wafer's contact angle with different ultrasonic power, cleaning temperature, time and the concentration of the detergent, and we got the optimal ultrasonic cleaning process is 80W,60℃,5min, 10%(wt.). With comparison to RCA cleaning agent, our detergent could get a better surface condition, smaller contact angle, and lower roughness on the wafer. Furthermore, we investigated the polysilicon's surface composition by XRF and TEM test, and we found that the surface of the cleaned wafer were without organic and metal residue.