Grinding Marks in Back Grinding of Wafer with Outer Rim

Back Grinding of Wafer with Outer Rim (BGWOR) is a new method for carrier-less thinning of silicon wafers. In this paper, the simulation model of grinding marks of wafer in BGWOR was developed. With the model, the relationship between process parameters, including wheel rotational speed, wafer rotational speed, wheel infeed rate, spark out time and the protruding height of the abrasive grains in the grinding wheel, and grinding marks was discussed. Reasonable grinding parameters to control the grinding marks were also proposed. The model was verified by the experiments of BGWOR. The results showed that: (1) The pattern of the grinding marks of the wafers in BGWOR was depended on the grinding wheel rotational speed, the wafer rotational speed, the wheel infeed rate, the spark out time and the protruding height of the abrasive grains on the grinding wheel; (2) The angle between two adjacent grinding marks changes as the variation of the wheel rotational speed and wafer rotational speed; (3) The grinding marks density can be controlled by selecting the proper ratio of wheel speed to wafer speed. The depth of grinding marks can be reduced by increasing the spark out time and reducing the protruding height of the abrasive grains.