Damage Detection Research On The Surface Layer Of The Lapped SiC Wafer

With the development of SiC crystal growth technology, the SiC wafer is gradually increased in size. New lapping and polishing technology with high efficiency, high precision and low damage is being paid more and more attention. However, lapping process would inevitably bring about surface layer damage, which will severely affect the wafer processing efficiency and cost. Owing to the high hardness and the strong chemical stability, it is very difficult to process and etch the SiC wafers, and detect the subsurface damage. Currently, studies on the damage detection of SiC wafer surface layer are extremely rare. Therefore, the research on the SiC wafer surface layer damage measuring methods has an important significance to realize the machining of the SiC wafer with high efficiency, precision, undamaged and ultra-smooth surface.Based on surface layer damage form of the lapped SiC wafer, several common crystal surface damage detection technology are studied, through the detailed experimental study,this artical determines the suitable surface damage detection technology and experimental scheme of the lapped SiC wafer, contrast analyses the surface layer damage form and forming-reason about free abrasive lapped SiC wafers and fixed abrasive lapped SiC wafers, the results show that the SiC wafer with fixed abrasive lapping has smaller damage and higher machining accuracy.By using the Cross-sectional microscopy method and microscopic Raman spectra method, the surface layer damage depth distribution of the SiC wafer with fixed abrasive lapping, the influential rule of process parameters and the surface residual stress are studied. The research results are listed as:The micro-cracks configurations of the lapped SiC wafer are vertical, oblique line, hooked, fork, dendritic, herringbone and horizontal lines. The damage depth of (0001) Si face and (0001) C face are basically same, along the different crystal orientation, the damage depths are basically same. The SSD is not uniform, on the same crystal face, the damage depth on edges is bigger than central part, and the value is about0.6μm-1μm. In the case of other lapping parameters unchanged, as the grit size and lapping pressure gradually increase. the SSD increases too, and the influence of grit size is stronger. With the grit size of W7, the main residual stress of fixed abrasive lapped SiC wafer exists compressive residual stress and the stress value is small. When the grit size increases to W14and W28, the main residual stress of fixed abrasive lapped SiC wafers exists tensile stress and with a larger fluctuation.