Microfabrication of Sapphire by Laser-Induced Plasma-Assisted Ablation (LIPAA)

Crack-free microfabrication of sapphire with little debris deposition and little swelling around ablated regions by laser-induced plasma-assisted ablation (LIPAA) using a second harmonic of Q-switched Nd:YAG laser is described. LIPAA process has been originally developed by ourselves in which merely a single conventional pulsed laser is used. In this process, the wavelength of laser beam must be transparent to the substrate, so that the laser beam goes through the substrate first and is then absorbed by a metal target placed behind. For laser fluence above ablation threshold for the target and below damage threshold for the substrate, the laser-induced plasma is generated from the metal target and then the species fly towards the rear surface of the substrates with very high speed. Due to the interaction of the laser beam and the plasma, ablation takes place at the rear surface of the substrate. Dependence of ablation depth and width of ablated grooves on scanning speed and target-substrate distance are investigated. Based on the obtained results, LIPAA process is applied for scribing of sapphire substrates. Double scan of laser beam with a shift of the focal point shows a great potential of high-quality scribing of sapphire substrates.