Low temperature wet etching using various etchants was investigated to reveal sub-surface damage in sapphire wafer induced during lapping. Surface scratches during wafer preparation is conveniently observed using optical or atomic force microscopy whereas sub-surface damage to crystal requires techniques such as X-ray diffraction, Raman spectroscopy etc. In this study, sub-surface damage in sapphire was revealed as shallow scratches by etching in H2SO4 at temperatures similar to 125 degrees C and 3:1 H2SO4-H3PO4 at temperatures similar to 75 degrees C. These etching conditions showed no measurable etch rate of sapphire and also did not affect the pristine sapphire surface. The heavily damaged and sub-surface damaged layer was determined to be 1.6 +/- 0.1 and 2.2 +/- 0.1 mu m deep by repeated chemical mechanical polishing and etching of sapphire wafer lapped with 1 mu m diamond abrasive. (C) 2013 Elsevier B. V. All rights reserved.