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Molybdenum as a Gate Electrode for Deep Sub-Micron CMOS Technology

Published online by Cambridge University Press:  14 March 2011

Pushkar Ranade ,
Yee-Chia Yeo ,
Qiang Lu ,
Hideki Takeuchi ,
Tsu-Jae King  and
Chenming Hu
Pushkar Ranade
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA 94720
Yee-Chia Yeo
Affiliation:
Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA 94720
Qiang Lu
Affiliation:
Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA 94720
Hideki Takeuchi
Affiliation:
Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA 94720
Tsu-Jae King
Affiliation:
Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA 94720
Chenming Hu
Affiliation:
Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA 94720
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Abstract

Molybdenum has several properties that make it attractive as a CMOS gate electrode material. The high melting point (∼2610°C) and low coefficient of thermal expansion (5×10−6/°C, at 20 °C) are well suited to withstand the thermal processing budgets normally encountered in a CMOS fabrication process. Mo is among the most conductive refractory metals and provides a significant reduction in gate resistance as compared with doped polysilicon. Mo is also stable in contact with SiO2 at elevated temperatures. In order to minimize short-channel effects in bulk CMOS devices, the gate electrodes must have work functions that correspond to Ec (NMOS) and Ev (PMOS) in Si. This would normally require the use of two metals with work functions differing by about 1V on the same wafer and introduce complexities associated with selective deposition and/or etching. In this paper, the dependence of the work function of Mo on deposition and annealing conditions is investigated. Preliminary results indicate that the work function of Mo can be varied over the range of 4.0-5.0V by a combination of suitable post-deposition implantation and annealing schemes. Mo is thus a promising candidate to replace polysilicon gates in deep sub-micron CMOS technology. Processing sequences which might allow the work function of Mo to be stabilized on either end of the Si energy band gap are explored.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 611: Symposium C – Gate Stack & Silicide Issues in Silicon Processing , 2000 , C3.2.1
Copyright
Copyright © Materials Research Society 2000

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References

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