Lapping is next, in this step the Ingots have now become rough cut Silicon wafers with saw marks and other defects on both sides of the wafer. Also at this point the wafer is much thicker than it will be when it is finished. Lapping the wafers accomplishes several things, it removes saw marks and surface defects from the front and backside of the wafers, it thins the wafer and relieves a lot of the stress accumulated in the wafer from the sawing process. Both before and after the lapping process many in-process checks will be done on the Silicon wafers and more fall-out will occur (good news for the people that need coin roll for test wafers). At the LEFT you can see a drawing of the "business end" of a typical lapping machine. After lapping the wafers go thru several cleaning /etching steps using sodium hydroxide or acetic and nitric acids to remove microscopic cracks and surface damage caused by the lapping process, this is followed by followed by deionized water rinses.

Edge grinding or rounding is an important part of the wafer manufacturing process, it is normally done before or after lapping, this rounding of the edge of the wafer is very important! If it is not done the wafers will be more susceptible to breakage in the remaining steps of the wafer manufacturing process and the device manufacturing processes to come. If you look at the edge of a finished wafer you will see the edge rounding even in the notch area of 200mm and 300mm wafers. On the best Prime wafers the edges are also highly polished, this can improve cleaning results on wafers and reduce breakage up to 400%. Process Specialties has seen a notable yield differential between poorly and perfectly edge rounded material