Papers by Author: Yoshihiro Okamoto

Abstract: The damage induced at the cut surface of SiC crystal by slicing were investigated by Raman scattering method and transmission electron microscopy. Electric discharge machining (EDM) predominately forms cracks, silicon, carbon and 3C-SiC by 6H-SiC pyrolysis and wiresawing with loose abrasive (WSLA) induces triangular crystal disordered area, stacking faults and dislocation loop bundles by stressing at the cut surfaces of SiC crystal.

Abstract: Electron beam induced current (EBIC) observations have been carried out to investigate the influence of mechanical polishing (MP) direction on the dislocations formation at the Si-face c(0001) of 4H-SiC epitaxial layers. Two opposite MP directions (defined by polish pad moving direction) have been compared, which are [11-20] off-cut directions along step-up and step-down, respectively. It has been found that high density of dislocations have been formed along the polish paths for the 8o off samples with polishing pad moved in step-up direction. By contrast, step-down polishing samples have shown no significant dislocation increase although shallow polish scratches were observed. Similar experiments have also been carried out for 4o off samples, showing step-up MPs introduced more dislocations than step-down ones. The results are discussed in terms of forces along the slip plane [11-20](0001) effectively exerted by the abrasive particles on the steps.

Abstract: Shallow defects, which were induced by mechanical treatment, on 4H-SiC wafers were investigated. The density and the distribution in depth of shallow defects on the wafers were depended on wafer venders. Most of serious defects such as dislocation array (DA), triangular stacking fault (TRSF) and triangular defect (TRD) in epitaxial film were demonstrated to be caused by shallow dislocations on the surface of the wafers. Revised mechanical polish can reduce the densities of DA, TRSF and TRD in epitaxial film.