Channel length and width dependence of hot-carrier hardness in fluorinated MOSFETs

Abstract

A study of the interface degradation caused by channel-hot-electron (CHE) and substrate-hot-electron (SHE) injection in fluorinated MOSFETs and in unfluorinated control over a wide range of channel lengths and widths is discussed. In all cases, the fluorinated MOSFETs are more resistant to hot-electron-induced interface damage, although the beneficial effect of fluoride becomes less significant for submicrometer devices. For nonfluorinated control devices, a significant gate-size dependence of the transconductance degradation is observed after either CHE or SHE injection. In contrast, the fluorinated devices exhibit almost no gate-length dependence in the range of 0.6-10.0 mu m or gate-width dependence in the range of 1.6-10.0 mu m after SHE injection, in which the injected hot electrons assume much better areal uniformity than in CHE injection. However, significant gate-size dependence was observed in fluorinated devices after CHE injection, primarily due to the spatial nonuniformity of the CHE damage. The beneficial effect of F and its influence on the gate-size dependence in response to SHE injection may be attributed to the local strain relaxation near the SiO/sub 2//Si interface where F is incorporated in the Si-O network. These results also suggest that the development of local-strain relaxed isolation technology will be important for deep-submicrometer MOSFETs. >