The effects of arsenic drain profile on submicrometer silicide MOSFETs

The performance and reliability tradeoffs with source-drain implant energy were examined on n-channel MOSFETs with 0.5-μm physical gate lengths and fully silicided sources, drains, and gates. Platinum silicide was used over structures with self-aligned arsenic source-drain implants with energies ranging from 40 to 220 keV at a constant dose of 1×10¹⁴ cm². Shallow implants showed low diode reverse breakdowns due to depletion layer interactions, but yielded low series resistance and underdiffusion (ΔL) values, and high device gains. Deeper implants (>70 keV) showed improved diode characteristics, but devices exhibited increased series resistance, ΔL, and reduced gains. Only minor short-channel effects were noted on threshold voltage and subthreshold swings for channel devices with L=0.5 μm over the range of implants examined, although the higher-energy implants did show more severe drain modulation effects. Significantly improved immunity to hot-carrier degradation was noted with the deeper implants. The drains implanted at 145 keV showed the best immunity to hot-electron degradation, small gain, and short-channel effects, giving a good balance between device performance and reliability