COMPARISON OF LATCHUP IMMUNITY FOR SILICIDED SOURCE DRAIN AT DIFFERENT N(+) IMPLANT ENERGY/

The effect of titanium disilicide (TiSi2) on latchup immunity for diff erent n(+) source/drain (s/d) junction depth is investigated. Highly l atchup immune 0.25 mu m CMOS devices have been fabricated with a 50 An gstrom gate oxide, retrograde twin-well and titanium silicided shallow s/d. The trigger current (I-trig) more than doubled from 14 to 32 mA, while the current gain of the npn parasitic BJT (beta) is reduced fro m 4.9 to 2.5. These improvements are observed when comparing between n on-silicided and silicided s/d with shallow junction (at 30 keV). Howe ver, when the s/d junction is deep (at 40 keV), the improvement in lat chup immunity of silicided s/d over non-silicided s/d decreases. In ad dition, silicided wafers with shallow junction are more latchup immune than those with deep junction. The above observations are attributed to the reduction of the emitter width and the dopant consumption durin g TiSi2 formation, enhanced hole injection due to thinner interfacial oxide, and larger contact area of the silicide and silicon (Si). (C) 1 998 Elsevier Science Ltd. All rights reserved.