The double-side lapping of SiC wafers with semifixed abrasives and resin–combined plates

Abstract

SiC crystal has been widely used in semiconductor substrates because of its excellent physical, chemical, and photoelectric properties. As a semiconductor substrate, the SiC wafer not only needs good surface quality but also requires surface shape accuracy. In the present study, a novel lapping plate was designed for SiC wafers to improve their surface quality and shape accuracy. In the novel lapping plate, epoxy resin and a soft gel body containing diamond abrasives are combined to form a hard honeycomb structure. The cellular structure is used to support the lapping pressure to reduce the deformation of the lapping plate and improve the surface shape accuracy. The cellular structure is filled with soft gel with diamond abrasives which play the role of semifixed lapping to obtain good surface quality. Two crystalline forms of silicon carbide (4H-SiC and 6H-SiC) were selected to carry out double-sided lapping experiments with the novel lapping plate. The experimental results show that the lapped wafers have good surface quality with low surface roughness, some small scratches, and acceptable cracks. In addition, the surface shape accuracy is improved; the values of bow, warp, and total thickness variation (TTV) are all reduced after lapping. Under the same lapping conditions, the 6H-SiC has a smaller surface roughness than 4H-SiC, and for a specific crystalline form, the surface roughness of the C face is smaller than that of the Si face. The bow and warp of 4H-SiC are smaller, but the TTV is larger. The material removal rate is basically the same for 4H-SiC and 6H-SiC.