As the urgency of energy conversati

As the urgency of energy conversation and the development of
optoelectronics device, single crystal substrates such as sapphire and
SiC have attracted more and more attention [1–4]. As we known,
sapphire is the most common substrate for light emitting diode
(LED), due to the excellent crystalline growth technology. Based on
the demands of high power and high brightness LED, SiC single
crystalline will be the mostly applied material in future. Any microdefects
on the substrate surface could influence GaN epilayer growth
quality in LED fabrication, thus planarization of substrate wafer is
very crucial for high performance LED devices. Currently, chemical
mechanical polishing (CMP) is still one method of the most effective
technology to achieve global planarization [5–7]. However, owing to
the super-high hardness and super-strong chemical innerness, CMP
removal of sapphire and SiC wafer is very difficult [8–16]. Moreover,
the relative research on CMP characteristics of sapphire and SiC
wafer is very few, especially CMP mechanism.