A novel fixed abrasive process: chemo-mechanical grinding technology

As finishing techniques for Si wafers, the free abrasive processes like lapping and polishing are able to offer a better surface roughness when finer abrasives are applied, but fall short of maintaining profile accuracy when the wafer size increases. On the other hand, the fixed abrasive process or grinding is known as a promising solution to improve accuracy of profile geometry, but always introduces subsurface damages. In order to simultaneously achieve both surface quality and geometry accuracy, this research has proposed a novel chemo-mechanical-grinding (CMG) process by effective use of chemical reaction in the grinding process. CMG wheels which contain chemically active abrasives and additives have been developed, characterised and applied into grinding of ø300 mm bare Si wafers. The ground wafers are examined on both surface and subsurface. The results show no subsurface damage produced due to machining. A defect-free surface so far only achievable by polishing has been realised by the fixed abrasive process. A discussion is also made to understand the mechanism and chemical reaction involved in the process.