Nickel Germanesilicide Contacts Formed on Heavily Boron Doped Si{sub}(1-x)Ge{sub}x Source/Drain Junctions for Nanoscale CMOS

摘要

Formation of source/drain junctions with a small parasitic series resistance is one of the key challenges for CMOS technology nodes beyond 100 nm. A new source/drain technology based on selective deposition of heavily in situ doped Si{sub}(1-x)Ge{sub}x layers was recently developed in this laboratory. This paper presents formation and structural characterization of self-aligned nickel ger-nianosilicide contacts formed on heavily boron doped Si{sub}(1-x)Ge{sub}x alloys. The results show that thin NiSi{sub}(1-x)Ge{sub}x contacts with a resistivity of ～25 /μΩ-cm can be formed on Si{sub}(1-x)Ge{sub}x alloys at temperatures as low as 350℃. However, the low resistivity and the structural integrity of the NiSi{sub}(1-x)Ge{sub}x films can be maintained up to a maximum temperature of 450℃. At higher temperatures, Ge out-diffusion from NiSi{sub}(1-x)Ge{sub}x grains results in interface roughening and NiSi spikes. If the maximum processing temperature is kept within 400℃, p{sup}+ - n junctions with excellent leakage behavior can be formed. A minimum contact resistivity of 2 × 10{sup}(-8) Ω-cm{sup}2 is demonstrated for Ge concentrations above ～40%, which can be linked to the smaller semiconductor bandgap and high boron activation under the metal contact. The results suggest that NiSi{sub}(1-x)Ge{sub}x contacts formed on Si{sub}(1-x)Ge{sub}x junctions have the potential to satisfy the contact resistivity requirements of future CMOS technology nodes.