Wafer bow of substrate transfer process for GaNLED on Si 8 inch

This paper investigates the wafer bow induced during the substrate transfer process for GaN LED on Si (111) 8 inch wafers. The substrate transfer process is to transfer the thin GaN LED device layer to a carrier wafer using a CuSnCu permanent bonding layer. The process generates tensile bow on a wafer due to the high tensile stress of the Cu or the Cu_xSn_y intermetallic layer after bonding. Understanding the wafer bow evolution during the substrate transfer is very important to get a good control of the process. The high wafer bow value may cause problems for some automatic handling tools in the production line or affect process quality such as in lithography. The influence of substrate thickness and Cu metallization thickness on the wafer bow has been studied. A bow compensation layer can be used to compensate the tensile bow, thus minimizing the wafer bow after the substrate transfer process.