Composite TiSi2/n + poly-Si low-resistivity gate electrode and interconnect for VLSI device technology

• Published in: IEEE transactions on electron devices 1982-04, Vol.29 (4), p.547-553
• Main Authors: Wang, K.L., Holloway, T.C., Pinizzotto, R.F., Sobczak, Z.P., Hunter, W.R., Tasch, A.F.
• Format: Article
• Language: English
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/T-ED.1982.20741

A composite polycide structure consisting of refractory metal silicide film on top of polysilicon has been considered as a replacement for polysilicon as a gate electrode and interconnect line in MOSFET integrated circuits. This paper presents fine-line patterning techniques and device characteristics of MOSFET's with a TiSi 2 polycide gate. A coevaporated TiSi 2 polycide gate was chosen for this study because it had 2 to 5 times lower resistivity as compared to other silicides. Polycide formation by electron-beam coevaporation is chosen in preference to sputtered TiSi 2 because of lower oxygen contamination. The coevaporation technique to form TiSi 2 polycide with a sheet resistivity of 1 Ω/square (bulk resistivity of 21 µΩ.cm) is described. Anisotropic etching of nominally 1-µm lines with a 15:1 etch selectivity against oxide is reported. Measurements of metal-semiconductor work function, fixed oxide charge density, dielectric strength, oxide defect density, mobile-ion contamination, threshold voltage, and mobility have been made on polycide structures with 25-nm gate oxides. These MOS parameters correspond very closely to those obtained for n+ poly-Si gates. In addition, the specific contact resistivity between Al and TiSi 2 polycide is lower than the contact resistivity between Al and polysilicon by one order of magnitude.