The surfaces of single-crystal wafers of sapphire and silicon carbide with microelectronic-grade high polish were exposed to a gas-cluster ion beam (GCIB) and significant reductions in roughness were observed. Atomic-force microscopy revealed that the typical initial surfaces consisted of a fine but small random roughness together with relatively large and sharp asperities. The latter were removed efficiently and GCIB smoothing process improvements are reported. The SiC wafers also have a high density of shallow scratch marks and these too were removed, with the average roughness R_a falling below 4 angstrom after the best process. Analysis of the SiC by Rutherford backscattering spectroscopy in channeling mode revealed that when the GCIB process was adjusted so that asperities and scratch marks were removed, there was no increase in near- and at-surface damage. In particular, no lattice damage was observed of the sort typically caused by ion implantation prior to annealing. Significantly, it was found that oxygen gas cluster ion beams provided superior results with SiC as compared with argon GCIB. Surface smoothing mechanisms are proposed to explain these results.

Date Published: 27 December 2001
PDF: 8 pages
Proc. SPIE 4468, Engineering Thin Films with Ion Beams, Nanoscale Diagnostics, and Molecular Manufacturing, (27 December 2001); doi: 10.1117/12.452556

Published in SPIE Proceedings Vol. 4468:
Engineering Thin Films with Ion Beams, Nanoscale Diagnostics, and Molecular Manufacturing
Emile J. Knystautas; Wiley P. Kirk; Valerie Browning, Editor(s)