Optimization Research Of Polysilicon Cleaning Process

As the upstream of PV industry,the demand of polysilicon is increasing largely with the development of PV industry.But there will bring out some refractory polysilicon and polysilicon with carbon during the production process.In order to reduce production cost,improve product quality,improve the level of production management and enhance enterprise competition ability,it is necessary to clean the refractory and carbon materiel.In recent years,more and more attention has been put on the cleaning process of polysilicon.The cleaning process and method for refractory polysilicon was studied in this paper.Some factors affecting the appearance and the quality of the refractory polysilicon were investigation such as concentration of lye,ratio of mixed acid,washing times by water,ultrasonic time and drying time and so on.The results show that the appearance of the refractory polysilicon is the same with the qualified polysilicon after cleaning by this process.And the cleaning process include immersion in lye concentrations of 40%for 3 minutes,corrosion in mixed acid of hydrofluoric acid and nitric acid?volume ratio is 1:6?for 120 seconds,washing by 18M?water for 6 times,ultrasonic for 120 seconds and then drying for 60 seconds.The scale metal content of the cleaned refractory polysilicon is 70.92 ppb.Ingot experiment using the cleaned refractory polysilicon indicates that it is able to meet the requirements of the ingot industry.Meanwhile,the cleaning process and method for polysilicon with carbon was studied in this paper.Affecting factors on the cleaning quality including mixed acid kinds and ratio,corrosion time,washing times and ultrasonic time were studied.Cleaning process for different type polysilicon with carbon was comparative studied.The study results show that the significant interface between graphite and silicon was obtained in the polysilicon with carbon sample 1 and sample 2 which were pretreatment by mixed acid?HNO₃:H₂SO₄?.Then the pretreatment sample 1 and sample 2 were immersion in mixed acid?HF-HNO₃?for 240 seconds and 120 seconds respectively,the graphite and silicon carbide on the surface were removed completely.The yield was 89%and 96%respectively.Finally,after washing by water for 8 times and ultrasonic for 140 seconds,the scale metal content of the cleaned polysilicon with carbon is 74.94 ppb.Ingot experiment using the cleaned polysilicon with carbon indicates that it is able to meet the requirements of the ingot industry also.In short,the cause of the refractory polysilicon and polysilicon with carbon was investigated in this paper,and then the cleaning process was studied respectively.Ingot experiment was carried out using the cleaned polysilicon.