New hot-carrier degradation mode in PMOSFETs with W gate electrodes |
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Authors: | Matsuhashi H. Hayashi T. Nishikawa S. |
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Affiliation: | Oki Electr. Ind. Co. Ltd., Tokyo; |
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Abstract: | Hot-carrier degradation of W gate PMOSFETs, which are surface-channel devices because of the work function of W, has been investigated in comparison with polycide (WSix/n+ poly-Si) ones. In W gate PMOSFETs, transconductance gm and threshold voltage Vth decrease on the drain avalanche hot-carrier (DAHC) stress, and Δgm /gm0 and ΔVth become minimum at VG≅VD/2. By using the charge-pumping technique, it is found that, after stressing at the same stress condition, the interface state density of W gate devices is about 10 times larger than that of polycide ones but the densities of trapped electrons are almost equal. These results indicate that the difference of hot-carrier degradation between W and polycide gate devices is mainly caused by the difference of the interface state density |
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