The effect of CVD W/TiW metallization on very shallow CoSi/sub 2/ junctions

The effect of Al/CVD W deposition on shallow junctions below CoSi/sub 2/ using 450-1800-AA sputtered TiW as a barrier/glue layer is investigated. The thermal stability of the Al/CVD W/TiW/CoSi/sub 2/ structure is studied by comparing the reverse bias current of the initial diodes with that after annealing the structure. The results for the deeper n/sup +/(P)/p diodes approximately 1000 AA below approximately 700-AA CoSi/sub 2/ are different from those for the p/sup +/(BF/sub 2/)/n diodes approximately 500 AA below CoSi/sub 2/. When the TiW is >450 AA thick, Al/CVD W does not degrade the n/sup +//p diodes. The reverse bias current is <10 nA/cm/sup 2/ when the Al/CVD W/900-AA TiW is annealed at up to 450 degrees C for 60 min. The n/sup +//p diode sport population increases when CVD W is deposited on 450-AA TiW. The diodes are severely degraded after 3000-AA Al is sputtered at 300 degrees C. The temperature of CVD W deposition affected the degradation of the p/sup +//n diodes. Higher-temperature depositions at approximately 500 degrees C degraded these diodes less than depositions at approximately 300 degrees C. However, annealing the Al/CVD W/900-AA TiW/CoSi/sub 2/ p/sup +//n structures at 400 degrees C for 30 min degrades the diodes independently of the CVD W temperature where 300>