An improved approach for the lapping of sapphire

The slurry containing large grain size boron carbide abrasives (B4C slurry) is usually used in double-sided lapping of sapphire to fast flatten sapphire substrate. However, this can induce severe damage on the wafer surface that needs more time to remove in next processing. Experiments to lap sapphire by using the slurry of small size diamonds (diamond slurry), the slurry composed of small size diamonds and silicon dioxide abrasives (mixed abrasives slurry), and the mixed abrasives slurry together with the assistance of ultrasonic vibration of the 304 stainless steel lapping tool were conducted and analyzed in this paper. Based on their lapping characteristics three-stages lapping strategy is proposed. The diamond slurry is taken at the beginning of lapping for an hour. It is followed by the use of the mixed abrasives slurry. Finally the ultrasonic vibration assistance with the mixed abrasives slurry is applied for the final half an hour of lapping. The proposed approach is verified by two hours lapping of sapphire. It is found that a uniform with rarely damage lapped surface is created while a satisfactory material removal rate of 85% of that by using the B4C slurry is achieved. Comparing with the use of diamond slurry, the material removal rate is increased by 94%, and the surface roughness Sa is improved by 44%. ? ISAAT 2017.All right reserved.