Silicon wafer thinning is mostly performed by the method of
self-rotating grinding. In grinding, the grinding force is a crucial factor of
affecting the grinding performance, form accuracy and surface/subsurface
thinning quality. To control the thinning quality of ground wafer, grinding
force is the most essential factor need to be controlled. However, no
theoretical model is developed to correlate grinding parameters to grinding
force yet. In this article, a theoretical model is established based on the
removal behavior of silicon, including cutting and sliding. For the first time,
the effects of processing parameters, wafer radial distance and crystal
orientation on grinding force are quantitatively described in a theoretical
model. Excess grinding force causes local damage of wafer in the form of
subsurface cracks, as a determinant factor on the quality of wafer. Therefore,
nine sets of self-rotating grinding experiments with variable processing
parameters are performed, and the depth of subsurface cracks h are
measured to evaluate the damage of ground wafer. Based on the scratching theory
of single abrasive grain, the relationship between h and the normal
grinding force Fnt is found, which is also validated by the
experimental results. Finally, an optimized two-stage process is proposed to
control subsurface cracks and improve material removal rate simultaneously,
according to the predictive model of grinding force.
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