The influence of abrasive size on high-pressure chemical mechanical polishing of sapphire wafer

Abstract

Demand for sapphire wafer has increased with growth of LED market. Chemical mechanical polishing (CMP) comprises a large part of wafering cost since the CMP process requires approximately 3–6 hours. For longer polishing times, the cost of consumables (COC) in CMP increases the total wafering cost; hence, considerable efforts have been made to decrease the polishing time of sapphire wafers to reduce the COC. There are two main approaches to reduce polishing time: controlling the chemical factor and adjusting the mechanical factor. Controlling the chemical factor is a common approach to manipulating the removal rate and roughness. However, it is hard to control the chemical factor. Instead, this study investigates the effects of various mechanical factors. This paper focuses on the effect of high-pressure CMP on the material removal performance; the maximum applied pressure is ∼800 g/cm2. The removal rate increases linearly with gradual increase of CMP pressure to 800 g/cm2. Finally, the effect of high pressure on the removal rate of, and frictional force on, sapphire wafer during CMP using different sized abrasives is investigated; the effect of the abrasives on the removal rate is likewise analyzed at different pressures.