An Overview of Recent Advances in Chemical Mechanical Polishing (CMP) of Sapphire Substrates

Abstract

Nowadays, sapphire substrates are widely employed for GaN light emitting diodes (LEDs) due to their comparatively low cost, large diameter, high quality, optical transparency, and high temperature stability etc. However, in spite of its commercial importance and extended history, the machining of sapphire remains a challenge. In the manufacture of sapphire, chemical mechanical polishing (CMP) has been widely used to obtain a mirror surface on the sapphire substrate and minimize the subsurface damages. In this paper, published literature in the past decade on CMP of sapphire substrates is summarized. Recent investigations into material removal mechanism of CMP of sapphire substrates are introduced and advances in experimental studies are reviewed in terms of abrasives, sapphire crystal orientations, pad materials, and other process parameters (such as polishing pressure, pad rotational speed, and temperature etc.). Possible topics for future research are also discussed.

A Substrate-Reclamation Technology for GaN-Based Lighting-Emitting Diodes Wafer

“…Thus, reclaiming the sapphire substrate for GaN-based LED wafers can significantly reduce the manufacturing cost of LED chips. A chemical mechanical polishing (CMP) method is currently used universally to reclaim substrates [8][9][10]. However, the disadvantages of CMP include process complexity, surface scrapes, and thinning of the sapphire substrate.…”

Analysis of sapphire- chemical mechanical polishing using digital image processing

“…In the recent years, the demand for light emitting diodes (LEDs) continue to rise because LEDs can reduce energy consumption when compared with conventional light sources. In the fabrication process of LEDs, sapphire material is an ideal material because of its relatively low cost, large attainable diameter, chemical compatibility, optical transparency and high temperature stability (Yu-Nong Zhang, et al, 2013). In addition, sapphire crystal structure is preferable for LED lights efficiency in order to have a wider beam angle and a structure similar to that of gallium nitride (GaN).…”

Effects of Surfactants on the Chemical Mechanical Polishing Performance of a-Plane Sapphire Substrates

“…3 Many efforts have been carried out to improve the polishing performance of sapphire CMP. [4][5][6][7] Shi et al 8 compared the polishing effect of alumina abrasives and silica abrasives during the sapphire CMP process. The results indicated that soft spherical silica abrasive particles could achieve good surface quality.…”