《MOS二极管》PPT课件.ppt

2019/8/4,1,半导体器件物理 刘艳红,2019/8/4,2,教材,MOS器件原理 纳米CMOS器件 甘学温 黄如 刘晓彦 张兴 编著 科学出版社 2004,2019/8/4,3,成绩,平时小考试：30 平时作业：20 期末考试：50 授课方式 每周4学时课。讲3学时。写作业或小考试1个学时 请上课带教材，课上研读教材,2019/8/4,4,一、硅基MOS集成电路仍将是微电子技术的主流,信息产业的产值已超过机械制造等传统产业成为第一大产业 无论从发展速度还是从对人类社会的影响，都是其它产业无法比拟的。 难以取代 新材料方面取得的进展，不具有成为主流技术的条件 巨大投入形成的产业无法抛弃 对硅及其衍生物的了解劝是其它材料代替不了的。知识的积累非常宝贵,2019/8/4,5,一、硅基MOS集成电路仍将是微电子技术的主流,微电子技术发展空间大 加工工艺水平 设计水平 系统结构 应用领域扩展 系统芯片 MEMS DNA生物芯片,保证产业继续发展到2030年进入成熟期，形成朝阳产业 发现在的汽车业、航空业,2019/8/4,6,MOS二极管,2019/8/4,7,SiO2,metal,semiconductor,SiO2,d,Ohmic contact,The MOS 二极管在半导体器件物理中相当重要，在半导体表面的理论与实验研究中是应用最为广泛的工具,The MOS 二极管,参数？,2019/8/4,8,能带及能带图,能带图是研究半导体材料及器件电学特性的有力工具。要深刻理解它、灵活运用它，至少也要能看懂它,2019/8/4,9,2019/8/4,10,2019/8/4,11,2019/8/4,12,Ec,Ev,Eg,Ei,EFn,EFp,2019/8/4,13,电场,电势,电子能量,以半导体体内为零电势,2019/8/4,14,利用能带图研究金属半导体接触,2019/8/4,15,2019/8/4,16,2019/8/4,17,铯的功函数最低，1.93eV， 铂的最高5.65eV,2019/8/4,18,The Ideal MOS Diode,qs,费米势,2019/8/4,19,理想 MOS 二极管,a) 零偏置条件下,金属半导体功函数差为零,任何偏置条件下二极管中的电荷只存在在半导体表面及金属上，且二者符号相反，电量相同。氧化层中不存在电荷,在直流偏置条件下，氧化层中没有电流通过，也就是说氧化层电阻无限大。,d) 界面态电荷密度为零,2019/8/4,20,改变栅压，半导体表面状态随之变化,2019/8/4,21,MOS在外加电压作用下，达到平衡的判据：,2019/8/4,22,Accumulation:,Qm,QS,-d,x,Charge Distribution,x,E(X),Electric Field,2019/8/4,23,EF,Vg0,EF,Ev,Ec,Ei,Charge Distribution,Electric Field,depletion:,2019/8/4,24,inversion,EF,Vg0,EF,Ev,Ec,Ei,Strong Inversion:,2019/8/4,25,Strong Inversion:,x,wm,Qm,-d,Qn,Qsc,Charge Distribution,Electric Field,x,E(x),Once strong inversion occurs, a very small increase in band bending corresponding to a very small increase in depletion-layer width results in a large increase in the Qn in the inversion layer, so the surface depletion-layer with reaches a maximum, Wm.,2019/8/4,26,is the band bending with boundary conditions,in the bulk and,EF,Ei,Semiconductor surface,EC,Ev,Eg,Oxide,x,P-type silicon,2019/8/4,27,表面载流子密度,P型半导体表面状态,空穴积累 (bands bend upward),平带,空穴耗尽 (bands bend downward),反型,强反型,2019/8/4,28,表面空间电荷区中表面势函数 分布,耗尽近似,表面势,1,2,3,2019/8/4,29,强反型判据,最大耗尽层宽度,表面电荷,4,5,6,2019/8/4,30,阈值电压,2019/8/4,31,Surface Charge vs. Surface Potential,2019/8/4,32,The relationship between Wm and the impurity concentration for silicon and gallium arsenide, where NB is equal to NA for P-type and ND for n-type semiconductor.,Dielectric constant Si:11.7 GaAs:12.9,2019/8/4,33,Capacitance at Low Frequency or quasi-static,2019/8/4,34,Capacitance in a MOS capacitor,小信号电容,MOS capacitance is defined as small signal capacitance and is measured by applying a small ac voltage on the top of a dc bias,理想MOS电容器,2019/8/4,35,单位面积的微分电容 微分电容C与外加偏压VG 的关系称为MOS系统的电容电压特性。 若令,2019/8/4,36,则 = 绝缘层单位面积上的电容， = 半导体表面空间电荷区单位面积电容。 称为系统的归一化电容。,2019/8/4,37,P-type subst rate,Accumulation,2019/8/4,38,积累区（ 0） MOS系统的电容C基本上等于绝缘体电容 。当负偏压的数值逐渐减少时，空间电荷区积累的空穴数随之减少，并且 随 的变化也逐渐减慢， 变小。总电容C也就变小。 平带情况（ =0） 平带电容由掺杂浓度和氧化层厚度确定,德拜长度,2019/8/4,39,Depletion,请推导此表达式,2019/8/4,40,耗尽区（ 0）,归一化电容 随着外加偏压 的增加而减小.,W,2019/8/4,41,Inversion,wdm,Once the inversion layer forms, the capacitance starts to increase, since csi is now given by the variation of the inversion charge with respect to,which is much large than the depletion capacitance,2019/8/4,42,反型区（ 0）,2019/8/4,43,In low frequency, the generation-recombination rates in the surface depletion region are equal to or faster than the voltage variation, then the electron concentration (minority) can follow the alternating current (ac) signal and lead to charge exchange with the inversion layer in step with the measurement signal.,The incremental charges appears at the edge of the depletion region in high measurement frequency.,2019/8/4,44,C-V Curves,Deep depletion,2019/8/4,45,Frequency Effect,The frequency of ac signal play an im