Origin,modeling and suppression of grinding marks in ultra precision grinding of silicon wafers

A phenomenon commonly encountered in grinding of silicon wafers is the grinding marks, which are difficult to remove by subsequent polishing process, and have been a great obstacle to the manufacture of silicon wafers with higher flatness. In this paper, the grinding marks formation mechanism was clarified, a grinding marks formation model and an angular wavelength model were developed, and a grinding marks suppression method was proposed. A series of grinding experiments were carried out to verify the developed models and investigate the effect of the wafer rotational speed, the wheel rotational speed, the infeed rate, the axial run out of the cup wheel and the spark out time. The results show that: (1) grinding marks are waviness generated on silicon wafers caused by non-uniform material removal circumferentially due to the axial run out of the cup wheel; (2) grinding marks present multiple angular wavelengths characteristics; (3) the angular wavelength of grinding marks is a one-variable function of the rotational speed ratio of the wheel to the wafer; and (4) grinding marks could be suppressed significantly by properly selecting the rotational speed ratio.