Study on Lapping Paste of 6H–SiC Single-Crystal Substrate in Tribochemical Mechanical Lapping

Abstract

To improve the efficiency and surface quality in tribochemical mechanical lapping of 6H–SiC single-crystal substrate, the effects of oxidant type, content and abrasive size on the material removal rate (MRR) and surface roughness were studied in this paper. The results show that different oxidants have their maximum of material removal rate at their respective optimum content, namely 1768 nm/min for 10% wt sodium hydroxide, 1382 nm/min for 5% wt potassium permanganate and 1271 nm/min for 5% wt dichromium trioxide, respectively. However, the types and contents of oxidants have little effect on the surface roughness of SiC after lapping. Therefore, 10% wt NaOH was chosen as the oxidant of tribochemical mechanical lapping paste for lapping 6H–SiC single-crystal substrate. The abrasive size had a great influence on the material removal rate in lapping 6H–SiC single-crystal substrate. When the abrasive size is 28 µm in diameter, the material removal rate reaches the maximum value, but the surface roughness also is the maximum value after lapping. Then, the composition of optimized lapping paste was obtained. Research results show that the larger the abrasive using in lapping paste is, the larger the MRR and surface roughness are in certain range. The tribochemical reactions on the surface of SiC will occur and oxides of SiO2 or Si(OH)4 or Na2SiO3 or the compound of SiO2, Na2SiO3 and Si(OH)4 produced on the surface of SiC will be removed by the abrasives.