Micromachining and dicing of sapphire, gallium nitride and micro-LED devices with a UV copper vapour laser

Gallium nitride and sapphire are important materials for fabricating novel photonic devices such as high brightness light emitting diodes (LEDs), photo detectors and laser diodes. These materials are strongly resistant to wet chemical etching and also, low etch rates and limited etch selectivity restrict the use of dry etching. Thus, to develop alternative high resolution processing and machining techniques for these materials is important to the further development of the photonic devices. In this work, a repetitively pulsed UV copper vapour laser (255nm) has been used to machine and dice gallium nitride, sapphire and micro LED devices. Machining parameters were optimised so as to achieve controllable machining and high resolution. For sapphire, well-defined grooves 30 micron wide and 450 micron deep were machined. For gallium nitride, precision features such as holes on a tens of micron length scale have been fabricated. By using this technique, compact micro LED array chips with a small die space (100 micron) and 450 micron thick sapphire substrate have been successfully diced. Measurements show that the performances of LED devices are not influenced by the UV laser machining. Our results demonstrate that the pulsed UV copper vapour laser is a powerful tool for micromachining and fabrication of photonic materials and devices.