[23p-E307-1~20] 13.5 Semiconductor devices/ Interconnect/ Integration technologies

▼ [23p-E307-16] Substrate Impurity Concentration Dependence of Sub-threshold Swing of Si n-channel MOSFETs at Cryogenic Temperature

〇(D)Minsoo Kang¹, Hiroshi Oka², Takahiro Mori², Mitsuru Takenaka¹, Kasidit Toprasertpong¹, Shinichi Takagi¹ (1.The Univ. of Tokyo, 2.National Inst. of AIST)

Keywords:Cryogenic Temperature, Sub-threshold Swing, Substrate Impurity Concentration

The sub-threshold swing (SS) of Si nMOSFETs at cryogenic temperature has been reported to have the following characteristics: 1) saturation of SS with decreasing temperature, 2) increased inward bending (inflection) of SS as a function of the drain current (I_D). To explain these two phenomena, Beckers et al.[1] have proposed models of band tail states and localized interface states near the band edge with a Gaussian distribution as Fig. 1. The Gaussian distribution has an amplitude N₀ and a standard deviation W₀/2, while the band tail has a characteristic tail of W_t. We have succeeded in representing experimental SS of Si nMOSFETs with a substrate impurity concentration of 2.0×10¹⁶ cm^-3 in wide ranges of temperature and I_D by assuming these band tail states and localized interface states [2]. However, the influence of the substrate impurity concentration (N_A) on SS has not been studied so far. In this study, we have evaluated SS of nMOSFETs with different substrate impurity concentrations at 300 to 4 K and examined if the present model can quantitatively represent experimental SS.