The finite element analysis study of the laser lift-off (LLO) of III-nitride compound

Abstract

ANSYS was used to simulate the temperature field of the nitride semiconductor compound in the laser lift-off (LLO) process. One-dimension thermal conduction model is formulated. When the fluence is 107mJ/cm 2, the InN temperature starts to rise up, coupled with a large temperature gradient across the InN film, to above 600 C for a region within 108nm below the irradiated InN/sapphire interface. The diameter of the beam spot is 300μm, but the diameter of the decomposed area is around 100μm for InN due to Gaussian beam shape. For GaN, LLO can be achieved by using either a single pulse of 350mJ/cm2 fluence or multiple pulses of fluence down to 95mJ/cm2. The result shows that when six successive 95mJ/cm 2 pulses are used, the thermal stress can be greatly reduced from 0.929GPa in the case of a single 350mJ/cm2 pulse to 0.332GPa. © 2013 Springer Science+Business Media New York.