THESIS
1998
58 leaves : ill. ; 30 cm
Abstract
Silicides have been widely used to reduce the parasitic resistances in silicon-based VLSI circuits, and as the novel self-aligned-silicide (salicide) technology in MOS devices. Nickel and Cobalt silicides (Nisi and CoSi
2) are two of the most promising silicides.
2 2 2...[
Read more ]
Silicides have been widely used to reduce the parasitic resistances in silicon-based VLSI circuits, and as the novel self-aligned-silicide (salicide) technology in MOS devices. Nickel and Cobalt silicides (Nisi and CoSi
2) are two of the most promising silicides.
In the first part of the work, stability of Co and Ni silicides on crystalline Si (c-Si), polycrystalline Si (poly-Si) and amorphous Si (a-Si) substrates have been studied. CoSi
2 shows low resistivity ([spacing tide]15[mu omega]-cm) on c-Si, poly-Si and a-Si after 650-900℃/30-60min long time anneal in N
2 or forming gas. Nisi has lo resistivity ([spacing tide]15[mu omega]-cm) on c-Si and poly-Si after 350-700℃/30- 60min anneal. On a-Si, however, Nisi has increasing resistivities and mixes with Nisi
2 and a-Si even at 400℃.
In the second part, stability of Ti, Co, Ni and Ti/Co silicides on poly-Si gate lines have been studied. On P-doped poly-Si, TiSi
2, CoSi
2 and Nisi lines show low resistivity ([spacing tide]15[mu omega]-cm) after 850, 800 and 700℃/lhour long time anneal respectively. The low resistivity is stable down to linewidths of around 0.43, 0.50 and 0.15 pm. 200Å of Ti-capping layer on Co has also been tested. The Ti cap layer seems to improve the resistivity stability of CoSi
2 down to around 0. lμm after 800℃/l hour anneal.
Finally, a new pure Nisi gate has been studied. The pure gate is found to maintain low resistivity ([spacing tide]15[mu omega]-cm) even after 900℃/lmin rapid thermal anneal. It is also stable on gate oxide as thin as 130Å after 700℃/lmin rapid thermal anneal. Using the pure gate, symmetrical threshold voltages have been obtained on both n-channel and p-channel MOS devices. The new dual gate technology can greatly help to improve the CMOS process and device performance.
Post a Comment