Abstract
The thermal stability of COSi2 for thermal budgets suitable for a self-aligned P+ gate MOSFET process using rapid thermal processing was studied. The substrate underlying the suicide has a major impact on suicide degradation. Suicides formed on as-deposited amorphous silicon films and on single crystal Si were found to be stable at least up to 1000°C, whereas suicides formed on as-deposited polysilicon (i.e. conventional polycide) began to degrade at annealing temperatures greater than 800°C. BF2-implant dosages of 1×1015 cm-2 to 2×1016 cm-2 at 20keV in the suicide were found to affect the conventional polycide significantly. With higher implant dosages, the degradation of the conventional polycide is retarded for a 900°C anneal. However, for thermally stable suicides i.e., suicides formed on as-deposited amorphous Si and on single crystal Si, a high dose 2×1016 cm-2 implant increases the sheet resistance slightly from 1.4 Ω/square to 1.6 Ω/square for suicides on as-deposited amorphous Si substrate, and from 1.3 Ω/square to 1.6 Ω/square for suicides on single crystal substrates. A model which involves spheroidization of the suicide, silicon incursion, and indiffusion of Co into polysilicon is proposed to explain the degradation behavior.
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Chen, W., Lin, J., Banerjee, S. et al. Thermal Stability of Cobalt Disilicide for Self-Aligned Silicide Applications. MRS Online Proceedings Library 260, 163–167 (1992). https://doi.org/10.1557/PROC-260-163
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DOI: https://doi.org/10.1557/PROC-260-163