High-Frequency Small-Signal and Noise Characterization for Advanced MOSFETs Considering Temperature Dependence

• Main Authors: Wang, Sheng-Chun, 王生圳
• Other Authors: Su, Pin
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/91845434978315698583

博士 === 國立交通大學 === 電子研究所 === 99 === This dissertation provides a comprehensive high-frequency small-signal and noise characterization and modeling for various kinds of modern planar MOSFET devices, including the bulk MOSFET, silicon-on-insulator (SOI) MOSFET, partially-depleted SOI dynamic threshold voltage (DT) MOSFET, and strained MOSFET. The traditional RF small-signal equivalent circuit for the bulk MOFET will be modified to include existing parasitic components present in each kind of MOSFETs. Based on each tailored small-signal model, the corresponding high-frequency noise model can be built by adding the noise sources in place. For the first time, the temperature dependence of the high-frequency performance will also be discussed. The SOI MOSFET has the inherent neutral-body effect, which will be found to influence the output characteristic even in GHz applications. The channel noise Sid has been shown to have a negative temperature coefficient for both the bulk and SOI MOSFETs due to the lowered channel conductance at high temperature. Besides, the self-heating effect (SHE) and the floating-body effect (FBE) of the SOI MOSFET would make its noise factor higher than the bulk MOSFET. It shows that the FBE, which dominates at low VGS regime, can be suppressed by elevating the ambient temperature, while the SHE, obvious at high VGS, would be partly counterbalanced by the lowered channel conductance at high temperature. The body-related parasitics and the series resistance of the SOI DT MOSFET are found to have more impact on fmax (maximum oscillation frequency) than ft (cut-off frequency). Besides, in the normal bias condition - low gate and drain voltage (low VDD) regime, both ft and fmax have positive temperature coefficients due to the increased gm (trans-conductance) at high temperature. We also show that the DT MOSFET would get a negative temperature coefficient for equivalent noise resistance Rn towards the weaker inversion region due to the much higher gm2 than Sid with increasing temperature. Furthermore, our research results show the noise arising from the body resistance Rb can degrade the minimum noise figure NFmin, and the larger Rb encountered in the low VDD regime would have less impact on the temperature dependence of NFmin. The tensile-strained nMOSFET presents larger Sid than the control device due to its enhanced mobility and nearly the same saturation voltage for a given bias point, and has the same temperature dependence of Sid as the control device. However, our measured data indicates that the enhanced carrier trans-conductance in the tensile nMOSFET would contribute to better ft, fmax, NFmin and Rn than the control device for a given DC power consumption. Finally, for the emerging millimeter-wave applications, we examine the millimeter wave noise behavior of 65nm MOSFETs. The experimental results show that the continually increasing Sid makes it play a more and more important role in the millimeter-wave noise modeling and characterization. Besides, compared to the substrate resistance, the gate resistance has more impact on the noise parameters in the millimeter-wave frequency.