Machining processes for sapphire wafers: a literature review

Abstract

Sapphire wafers are widely used as the substrates for fabricating GaN light-emitting diodes (LEDs). The quality of LEDs depends directly on the quality of the sapphire wafers. A series of machining processes is required to turn sapphire barstock into wafers with the desired geometry and surface quality. This paper reviews the literature on various machining processes for sapphire wafers: slicing (including outer diameter cut-off grinding, inner diameter cut-off grinding, loose abrasive multi-wire sawing, fixed abrasive slicing, and fixed abrasive multi-wire sawing), flattening (including lapping and grinding), and surface finishing (including mechanical polishing and chemical mechanical polishing). New machining technologies are also introduced.

Comparison between sapphire lapping processes using 2-body and 3-body modes as a function of diamond abrasive size

“…Furthermore, it is widely used in other fields, such as laser diodes and laser sources for storage and optical media [4][5][6][7][8][9], due to its combination of high chemical resistance and mechanical characteristics as well as its transparency [10][11][12]. Generally, abrasion processing of sapphire material is composed of slicing, lapping, and surface finishing, which follows the fabrication of the substrate after the growth of the ingot [13], as shown in Fig. 1 [13][14][15].…”

“…Generally, abrasion processing of sapphire material is composed of slicing, lapping, and surface finishing, which follows the fabrication of the substrate after the growth of the ingot [13], as shown in Fig. 1 [13][14][15].…”

“…Machining process flow for sapphire wafers[13][14][15]. (a) Slicing (b) Edge profiling (c) Flattening (lapping) and (d) Surface finishing Fig.…”

Propagation of focused ultrashort pulse laser during micromachining of sapphire

“…However, it's difficult to machine sapphire due to the fact that its Mohs hardness is as high as 9. Although sapphire is able to be cut by diamond wire 3 , the diamond wire is abraded during machining. In contrast, laser micromachining is noncontact, flexible and precise 4 .…”

Mirror surface grinding of sapphire by coarse grain size diamond wheels

“…Sapphire is used in the manufacture of LEDs substrates or optical components for liquid crystal projectors because it has outstanding mechanical characteristics, optical characteristics, and thermal resistance (Ambacher, 1998;Duboz, 1999;Park and Chan, 2002;Li et al, 2011).…”