Requirements for metallization: 1. Low electrical resistivity 2. Electrical contact with device(Ohmic or Schottky) methods(can it be etched?) 5. Thermal and mechanical stability 6. Reliability in service, e.g. electro-migration. Next week (beside metallization inter-metal dielectrics are equally important ll/703 3.155J6.l52J l. Resistivity, why low Crudely: I=I cm/ Fringe field factor TL-RC-1.8K. -_1I T2=36K Local interconnects L F r2=10-7sec Global interconnects A few m Chip area(mm-) ll/703 3.155J6.l52JRequirements for metallization: 1. Low electrical resistivity 2. Electrical contact with device (Ohmic or Schottky) 3. Step coverage 4. Patterning methods (can it be etched?) 5. Thermal and mechanical stability 6. Reliability in service, e.g. electro-migration. Next week (beside metallization, inter-metal dielectrics are equally important …) 11/17/03 3.155J/6.152J 3 ox ≈ Fmin oxe0r ËHxox s WL ¯ Ë Fmin ¯ k 4 ox t L ª10-17 10-8 t L = RCª1.8k e0rL2 Á ˜ + H,Ls, xox t L ª 3.6k Á ˜ t gate ª10-11 min = 0.25 microns WSi2 W Al Cu for F Poly Si Local interconnects L Fmin sec Delay Global interconnects L A few mm t L ª10-9 sec time (sec) Inductive effects 2 -3 orders smaller; t ind = (LC) 10-12 1 10 100 Chip area (mm2 ) 11/17/03 3.155J/6.152J 4 Crudely: t = 1 cm/c = 10-8 sec but if e > e 0, t = 1 cm (eµ) > 10-8 sec Compared to gate times of order 10-11 sec L WL R = r C = koxe0 WH xox Fringe field factor Ê 1 1 HL + koxe0 L 1. Resistivity, why low? CI Cs R L H Ls W s ˆ 2 ˆ Ê L 2