Title :
Reducing arsenic to germanium cross contamination with isotopically enriched SDS 72GeF4
Author :
Rendon, Michael J. ; Locke, Jason ; Brown, Bob ; Kamenitsa, Dennis
Author_Institution :
APRDL, Motorola Inc., Austin, TX, USA
Abstract :
Pre-amorphization (PA) implants are becoming increasingly popular in CMOS processing as junction depths decrease. As an isoelectric species, germanium has demonstrated a capability for performing such implants into silicon. The gaseous vapor of liquid GeF4 is a common source of germanium for ion beams. The isotope with the atomic mass 74 is usually chosen for implantation because of its high natural abundance. However, cross contamination issues exist with similar mass dopants such as arsenic. The use of isotopically enriched 72Ge to more than 50% abundance improves the available beam current and reduces potential cross contamination. The use of the isotopically enriched 72Ge safe delivery system (SDS) source has been evaluated in a high current implanter. The mass resolution of this high current implanter is demonstrated. The surface and energetic cross contamination levels using both natural abundance GeF4 and a SDS GeF4 enriched source are compared using SIMS. The effectiveness of a between species purge, when using different implants, to reduce the energetic arsenic contaminant is presented
Keywords :
arsenic; doping profiles; elemental semiconductors; germanium; ion implantation; secondary ion mass spectra; silicon; surface contamination; As; CMOS processing; GeF4; SDS GeF4 enriched source; SIMS; Si:Ge; arsenic to germanium cross contamination; beam current; energetic arsenic contaminant; energetic cross contamination levels; isotopically enriched 72Ge safe delivery system source; isotopically enriched SDS 72GeF4; junction depth; mass resolution; natural abundance GeF4; pre-amorphization implants; surface cross contamination levels; Amorphous materials; CMOS process; CMOS technology; Contamination; Germanium; Implants; Ion beams; Ion sources; Isotopes; Silicon;
Conference_Titel :
Ion Implantation Technology, 2000. Conference on
Conference_Location :
Alpbach
Print_ISBN :
0-7803-6462-7
DOI :
10.1109/.2000.924251