Poly-Si_(1-x)Ge_x栅应变SiN型金属-氧化物-半导体场效应管栅耗尽模型研究

Study of gate depletion effect in strained Si NMOSFET with polycrystalline silicon germanium gate

基于对Poly-Si_(1-x)Ge_x栅功函数的分析,通过求解Poisson方程,获得了Poly-Si_(1-x)Ge_x栅应变SiN型金属-氧化物-半导体场效应器件(NMOSFET)垂直电势与电场分布模型.在此基础上,建立了考虑栅耗尽的Poly-Si_(1-x)Ge_x栅应变Si NMOSFET的阈值电压模型和栅耗尽宽度及其归一化模型,并利用该模型,对器件几何结构参数、物理参数尤其是Ge组分对Poly-Si_(1-x)Ge_x栅耗尽层宽度的影响,以及栅耗尽层宽度对器件阈值电压的影响进行了模拟分析.结果表明:多晶耗尽随Ge组分和栅掺杂浓度的增加而减弱,随衬底掺杂浓度的增加而增强;此外,多晶耗尽程度的增强使得器件阈值电压增大.所得结论能够为应变Si器件的设计提供理论依据.

Abstract Based on the analysis of Poly-Si1-χGeχ gate work function and by solving Poisson equation, the models of vertical electric field and potential distribution in strained Si NMOSFET with Poly-Si1-χGeχ gate are obtained; threshold voltage model and the gate depletion thickness and it＇s normalization model are established in strained Si NMOSFET based on the above results, with the gate depletion effect of Poly-Si1-χGeχ taken into account. Then the influences of device geometrical and physical parameters of device especially the Ge fraction on Poly-Sil_xGe~ gate depletion thickness are investigated. Furthermore, the effect of gate depletion thickness on threshold voltage is analyzed. It shows that the poly depletion thickness decreases with the increases of Ge fraction and gate doping concentration, while it increases with the increase of substrate doping concentration. Furthermore, the threshold voltage increases with the increase of gate depletion thickness. The results can provide theoretical references to the design of strained Si devices.