Varun is currently the applications engineering manager for Candela group at KLA Corporation. During his 6 years at KLA, his main focus area has been defect inspection on compound semiconductor wafers like GaN, SiC, GaAs, InP, etc. being used for Power Device, LED, Communications and Sensing markets. Before joining KLA, he received his MSc in Photonics from Cochin University of Science and Technology, India and PhD in the field of Laser Spectroscopy from University of Basel, Switzerland.
Due to its higher power efficiency, GaN is heir apparent to silicon for 5G RF applications. GaN-based 5G power amplifiers can efficiently handle higher voltage in a much smaller area than comparable laterally diffused MOSFET (LDMOS) devices. Another factor which makes GaN attractive is its ability to power a much wider range of mmWave 5G frequencies than standard silicon. However, growing GaN epitaxial wafers has unique challenges. The quality of substrate wafer or non-optimal metal organic chemical vapor deposition (MOCVD) reactor conditions may impact device yield or reliability due to the presence of killer defects on the epitaxial layer. When there is a mismatch between the lattice constant and the thermal expansion coefficient of the epitaxial and substrate materials, high lattice stress may also lead to cracking and/or slip lines. We will discuss how multiple complementary inspection and metrology techniques can be used to detect critical defects on GaN wafers. We will also discuss how feedback from inspection & metrology systems can be used effectively to improve device yield.