Al/Si contacting of ultra-shallow epitaxially grown Si and SiGe junctions

Ultra-shallow diodes have been fabricated by epitaxially growing thin layers of highly doped Si or strained SiGe on silicon substrate wafers and contacting with Al/1%Si. Ideal diode I-V characteristics were achieved for both n⁺p and p⁺n junctions as shallow as 20 nm. The formation of silicon precipitates on the contact surface as a result of alloying after metallization was found to be impeded by increasing the Ge content of the epitaxially grown layer. For a concentration of 27%, no precipitates were observed.