IR-Based Temperature Measurement in Rotational Grinding of Sapphire Wafers

Single crystalline sapphire wafers are used as a substrate for semiconductor applications like gallium nitride-based white LEDs. In the optimization of the manufacturing chain, rotational grinding can play a mayor role by substituting the conventional lapping process and reducing cost intensive efforts in downstream polishing steps. Due the material properties and in particular the hardness of sapphire, however, grinding process development is difficult. For this reason, the measurement of in-process variables like contact zone temperatures is of significant interest. In this paper, a concept and experimental setup for IRbased temperature measurement that utilizes the optical properties of sapphire is presented. The system behavior of the realized test setup is examined in calibration tests. The results of successfully performed grinding tests are presented to prove the feasibility of the measurement concept.