Major Polysilicon Suppliers Weigh in on New SEMI PV Standard for Silicon Feedstock
By James Amano, Senior Director, International Standards and EHS, SEMI
Two new PV standards to specify silicon feedstock and to address nitric acid chemical quality were approved during the Spring 2011 Photovoltaic Standards committee meetings in Berlin, Germany, and San Jose, California. These two new standards bring the total of published SEMI Standards to 17, and there are over 25 additional PV standardization efforts are underway.
The increasing number of players in the market for PV silicon feedstock materials has introduced a wide variety of material grades. This wide variety requires considerable efforts from both suppliers and end users to achieve a common understanding of the material specifications, as well as the impacts of the different materials on the quality and performance of the resulting PV product.
The SEMI Standards PV Silicon Materials Task Force was established in 2009 to develop this standardized specification for solar grade feedstock materials, which will allow manufacturers to produce consistent silicon solar cells. The specification received input from major polysilicon suppliers through three rounds of balloting, and was approved by the PV Standards Committee during their meeting at the PV Fab Managers Forum in Berlin.
By using this specification, polysilicon and cell manufacturers can specify chemical (donor concentration), dimensional (chunk, rod, bricks), and packaging characteristics on their purchase order for feedstock materials. The purchase order form will also include test methods to validate specified characteristics.
SEMI PV17-0611 covers virgin silicon feedstock materials produced by CVD processes, metallurgical refining processes or other processes. CVD processes include the so-called Siemens process, fluidized bed processes, powder processes and other processes using distilled silane or halosilane compounds. These specified materials are intended for growing of single crystalline ingots and casting or other methods of growing multicrystalline Si, used for producing Si wafers for solar cells.