Chuck System for Integrated IR-Based Temperature Measurement in Rotational Grinding of Sapphire Wafers

Single crystalline sapphire wafers are used as a substrate for semiconductor and optoelectronic applications like gallium nitride-based LED light sources. In the optimization of the manufacturing chain, rotational grinding plays a mayor role by substituting the conventional lapping process in order to reduce cost intensive efforts in downstream polishing steps. Due the material properties of the sapphire and in particular its hardness of 9 on the Mohs Scale however, it is difficult to establish a stable finishing process. For this reason, the detection of in-process variables like the grinding temperature distribution in the contact zone between the wafer and the grinding wheel are of significant interest. On the one hand, the acquired data increase process understanding, enhancing grinding wheel and process development. On the other hand, real-time processing of the measurement data enables direct control of the process in order to achieve optimum stability. Within this paper, a novel chuck system for the measurement of contact zone temperatures is presented. The general behaviour of the realized system is examined in preliminary calibration tests and grinding tests are performed to prove the feasibility of the chuck system under common machining conditions.