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上篇论文(XI)报告双极场引晶体管的电化电流理论,这篇论文(XII)报告飘移扩散理论.两篇都讨论了单栅双栅,纯基不纯基,薄基厚基的情形.两篇都用表面及内部电势作为参变量耦合电压方程和电流方程.在这飘移扩散理论中,有许多电流项,属飘移电流的用迁移率因子标识,属扩散电流的用扩散率因子标识.给出完备飘移扩散解析方程,用以计算四种常用MOS晶体管的直流电流电压特性.飘移电流有四项:一维体电荷漂移项,一维载子空间电荷漂移项,一维横向电场漂移项,二维漂移项.扩散电流有三项:一维体电荷扩散项,一维载子空间电荷扩散项,二维扩散项.现有的晶体管理论都没认识到一维横向电场漂移项.当基区几乎是纯基,这项贡献显著,约总电流的25 %.二维项来自纵向电场的纵向梯度,它随德拜长度对沟道长度比率的平方按比例变化.当沟道长度为25nm,几乎纯基时,(LD/L)2=106,杂质浓度1018cm-3时,(LD/L)2=10-2.
This paper (XII) reports the theory of drift diffusion, which is discussed in the last paper (XI) for the electrochemical theory of bipolar field-effect transistors. Both of them discuss the case of single-gate double-gate, pure impure base, thin base thick base. Both of them use the surface and internal potentials as a parameter to couple the voltage and current equations. In this drift diffusion theory, there are many current terms, which belong to the drift current, which are identified by the mobility factor and the diffusion current, which are identified by the diffusion factor. The complete drift diffusion analytical equation is given to calculate the DC current and voltage characteristics of four common MOS transistors.The drift current has four items: one-dimensional body charge drift term, one-dimensional carrier space charge drift term, one-dimensional transverse electric field drift term , Two-dimensional drift term.The diffusion current has three items: one-dimensional body charge diffusion term, one-dimensional carrier space charge diffusion term and two-dimensional diffusion term.The existing transistor theory does not recognize the one-dimensional transverse electric field drift term.When the base This contribution is significant, approximately 25% of the total current. The two-dimensional term is derived from the longitudinal gradient of the longitudinal electric field that varies proportionally with the square of the ratio of Debye length to channel length. When the channel length is 25 nm , Almost pure base, (LD / L) 2 = 1 06, (LD / L) 2 = 10-2 at an impurity concentration of 1018 cm-3.