Recently, silicon wafer production processes are diversified according to increase of product types.  Consequently, effective control of intermediate products is required highly for upholding and improving product quality.

In the mirror-finished-surface polishing process, if thickness of wafers set to the polisher is uneven, defects such as cracking may occur and also unnecessary removal is made. 

Since P/N type and thickness are varied generally in the reclaim wafer process, unless they are classified in an orderly way beforehand, processing becomes complicated and much time is used until completion. 

For effective production, wafer sorting is indispensable.