Electron Beam Induced Current Observation of Dislocations in 4H-SiC Introduced by Mechanical Polishing

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 8 degrees 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 4 degrees off samples, showing step-up MPs introduced more dislocations than step-down ones. The results are discussed in terms of forces effectively exerted in [11-20] direction along the (0001) slip planes by the abrasive particles on the steps.