Experimental study of laser dicing sapphire substrate by green DPSS laser

Abstract

Sapphire is an important material for fabricating photonic devices such as light emitting diode (LED). The matter is strongly resistant to wet and dry chemical etching because of its unique physical property. Moreover, there also exist some problems like chipping and edge crack by diamond dicing. Thereby, lots of emerging laser-based techniques have been invented, including various lasers at different wavelength and different technologies, which have gradually become the alternative powerful and efficient methods to dicing this material. Most of investigations on laser dicing sapphire are conducted by UV and ultra-short pulse laser, few by green laser with wavelength of 532nm. So a green laser with wavelength of 532nm and high repetition frequency is employed to dice sapphire substrate. The effects of machining parameters as laser power, repetition frequency, scanning velocity and number of scans on kerf width, kerf depth and aspect ratio are analyzed. Kerf width and depth are measured by optical microscope (OM) and micro-morphology of sapphire is observed by scanning electron microscopy (SEM). Results indicate that narrower kerf, higher aspect ratio and better surface quality can be obtained under the combined processing parameters of medium laser power, lower repetition frequency, medium scanning velocity and multiple scans, which proves green laser to be an effective tool to dice sapphire substrate.