Wafer Lapping And Polishing

 

The silicon crystal cylinder is cut into individual wafers using a water-lubricated single-bladed diamond saw. The sliced wafers are then mechanically lapped using a counter-rotating lapping machine and an aluminum oxide slurry. This flattens the wafer surfaces, makes them parallel and reduces mechanical defects like saw markings.

 

Known as lapping, it is a comparatively a gentle procedure which requires some applied pressure with some fine abrasives particles in suspension, which rolls between the wafer and the lapping plate. Each sliced wafer is as thick as 3 sheets of newspapers. The individual pieces of wafer are subsequently polished into a mirror-like finish. A 9-micron grit size as lapping abrasive normally used. Apart from lapping, grinding by comparison is an aggressive machining process for the same purpose.