Use of Graphite Cap to Reduce Unwanted Post-Implantation Annealing Effects in SiC
| Periodical | Materials Science Forum (Volumes 556 - 557) |
|---|---|
| Main Theme | Silicon Carbide and Related Materials 2006 |
| Edited by | N. Wright, C.M. Johnson, K. Vassilevski, I. Nikitina and A. Horsfall |
| Pages | 611-614 |
| DOI | 10.4028/www.scientific.net/MSF.556-557.611 |
| Citation | Erwan Oliviero et al., 2007, Materials Science Forum, 556-557, 611 |
| Online since | September, 2007 |
| Authors | Erwan Oliviero, Mihai Lazar, Heu Vang, Christiane Dubois, Pierre Cremillieu, Jean Louis Leclercq, Jacques Dazord, Dominique Planson |
| Keywords | Diffusion, Dopant, Graphite Cap, Ion Implantation, Post Implantation Annealing |
| Price | US$ 28,- |
6H and 4H–SiC epilayers were Al-implanted at room temperature with multiple energies (ranging from 25 to 300 keV) in order to form p-type layers with an Al plateau concentration of 4.5×1019 cm-3 and 9×1019 cm-3. Post-implantation annealing were performed at 1700 or 1800 °C up to 30 min in Ar ambient. During this process, some samples were encapsulated with a graphite (C) cap obtained by thermal conversion of a spin-coated AZ5214E photoresist. From Atomic Force Microscope measurements, the roughness is found to increase drastically with annealing temperature for unprotected samples while the C capped samples show a preservation of their surface states even for the highest annealing temperature. After 1800°C/30 min annealing, the RMS roughness is 0.46 nm for the lower fluence implanted samples, slightly higher than for unimplanted samples (0.31 nm). Secondary Ion Mass Spectroscopy measurements confirm that the C cap was totally removed from the SiC surface. The total Al-implanted fluence is preserved during postimplantation annealing. A redistribution of the Al dopants is observed at the surface which might be attributed to Si vacancy-enhanced diffusion. An accumulation peak is also observed after annealing at 0.29 9m, depth corresponding to the amorphous/crystalline interface that was determined on the as-implanted samples by Rutherford Backscattering Spectroscopy in channeling mode. The redistribution of the dopants has an impact on their electrical activation. A lower sheet resistance (Rsh= 8 k) is obtained for samples annealed without capping than for samples annealed with C capping (Rsh= 15 k ).
