Surface integrity of silicon wafers in ultra precision machining

Silicon wafers are the most extensively used material for integrated circuit (IC) substrates. Before taking the form of a wafer, a single crystal silicon ingot must go through a series of machining processes, including slicing, lapping, surface grinding, edge profiling, and polishing. A key requirement of the processes is to produce extremely flat surfaces on work pieces up to 350 mm in diameter. A total thickness variation (TTV) of less than 15 μm is strictly demanded by the industry for an 0.18 μm IC process. Furthermore, the surfaces should be smooth (Ra