Photoresist passivation structures for laser lifted-off light emitting diodes

摘要

SU-8 photoresist passivation structures were used to protect vertical structure GaN-based light emitting diodes from explosive forces produced during the laser lift-off (LLO) process of a sapphire substrate. The soft bake time of SU-8, which determines the solvent content, was varied to measure the mechanical properties of SU-8 at different dilution ratios. The SU-8 attained a sufficient hardness of 0.23 GPa and a Young's modulus greater than 4.0 GPa, regardless of soft bake time and dilution ratio. The SU-8 passivation structures with good damping properties showed excellent protection of the weak GaN-based layers from the LLO process.