摘要
The considerably high carrier mobility of Ge makes Ge-based channels a promising candidate for enhancing the performance of next-generation devices. The n-type metal-oxide semiconductor field-effect transistor (nMOSFET) is fabricated by introducing the epitaxial growth of high-quality Ge-rich Ge <sub>1 - x</sub> Si <sub>x</sub> alloys in source/drain (S/D) regions. However, the short channel effect is rarely considered in the performance analysis of Ge-based devices. In this study, the gate-width dependence of a 20 nm Ge-based nMOSFET on electron mobility is investigated. This investigation uses simulated fabrication procedures combined with the relationship of the interaction between stress components and piezoresistive coefficients at high-order terms. Ge <sub>1 - x</sub> Si <sub>x</sub> alloys, namely, Ge <sub>0.96</sub> Si <sub>0.04</sub> , Ge <sub>0.93</sub> Si <sub>0.07</sub> , and Ge <sub>0.86</sub> Si <sub>0.14</sub> , are individually tested and embedded into the S/D region of the proposed device layout and are used in the model of stress estimation. Moreover, a 1.0 GPa tensile contact etching stop layer (CESL) is induced to explore the effect of bi-axial stress on device geometry and subsequent mobility variation. Gate widths ranging from 30 nm to 4 μm are examined. Results show a significant change in stress when the width is <300 nm. This phenomenon becomes notable when the Si in the Ge <sub>1 - x</sub> Si <sub>x</sub> alloy is increased. The stress contours of the Ge channel confirm the high stress components induced by the Ge <sub>0.86</sub> Si <sub>0.14</sub> stressor within the device channel. Furthermore, the stresses (S <sub>yy</sub> ) of the channel in the transverse direction become tensile when CESL is introduced. Furthermore, when pure S/D Ge <sub>1 - x</sub> Si <sub>x</sub> alloys are used, a maximum mobility gain of 28.6% occurs with an ∼ 70 nm gate width. A 58.4% increase in mobility gain is obtained when a 1.0 GPa CESL is loaded. However, results indicate that gate width is extended to 200 nm at this point.