第二讲半导体物理及器件基础案例.ppt

第二讲半导体物理及器件基础,贵州大学电子科学系贵州省微纳电子与软件技术重点实验室半导体功率器件可靠性教育部工程研究中心马奎博士/副教授2016-03-08,目录,固体能带结构半导体物理基础PN结双极型晶体管MOS晶体管几种大功率器件,1/50,固体能带结构,HerbertKroemersLemma-QuotedfromtheNobelLecture,December8,2000,If,indiscussingasemiconductorproblem,youcannotdrawanEnergyBandDiagram,thisshowsthatyoudontknowwhatyouaretalkingabout.Ifyoucandrawone,butdont,thenyouraudiencewontknowwhatyouaretalkingabout.,在讨论半导体问题时，如果不能画出能带图，这说明，你自己也不知所云。你能画出能带图，但是不能理解能带图的含义，那么，听众不知道你在讲什么。,2/50,固体能带结构,3/50,固体能带结构,4/50,固体能带结构,5/50,固体能带结构,6/50,半导体物理基础,半导体中的电子|空穴对,7/50,半导体物理基础,半导体中的电子|空穴对,8/50,半导体物理基础,半导体中施主和受主,9/50,半导体物理基础,FD统计分布和费米能级,10/50,半导体物理基础,本征半导体,Ec,Ev,Ei,N型半导体,Ec,Ev,Ei,P型半导体,Ec,Ev,Ei,Ef,Ef,三种半导体的费米能级分布,11/50,半导体物理基础,平衡态半导体的载流子浓度方程,12/50,半导体物理基础,扩散运动由浓度梯度引起的载流子的运动。漂移运动由外加”场”的作用引起的载流子的运动。散射载流子运动过程中运动方向或速度改变的现象。晶格散射、杂质和缺陷散射、表面和界面散射，或者是由周期性势场引起的散射。,13/50,PN结,N,P,14/50,PN结,PN结形成的微观过程,N-Si,P-Si,15/50,PN结,PN结形成的微观过程,接触,N-Si,P-Si,16/50,PN结,PN结形成的微观过程,扩散,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,N-Si,P-Si,扩散电流,17/50,PN结,PN结形成的微观过程,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,N-Si,P-Si,扩散电流,复合,18/50,自建电场,PN结,PN结形成的微观过程,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,N-Si,P-Si,漂移电流,19/50,PN结,平衡,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,+,N-Si,P-Si,空间电荷区,PN结形成的微观过程,20/50,PN结,XM,Ebi,Vbi,载流子数量极少。高阻区。耗尽区,XN,XP,XNXPXM,NDXNNAXP,根据电中性：,自建场,自建势,空间电荷区,21/50,PN结,PN结的偏置,N,P,VD,N,P,V,正向偏置,NSi：低电位PSi：高电位,反向偏置,NSi：高电位PSi：低电位,22/50,PN结,EC,EV,EC,EV,PN结形成之前,EC,EV,EC,EV,PN结形成之后,qVbi,XM,PN结的能带,23/50,PN结,EC,EV,EC,EV,q（VbiVD）,XM,正偏状态,EC,EV,EC,EV,q（VbiVR）,XM,反偏状态,PN结的能带,qVD,qVR,24/50,PN结,PN结的IV特性,V,I,(1)V=VB:雪崩击穿；(2)VBVbi：势垒消失，电流随偏压增加而迅速增大。,Vbi,VB,-Is,25/50,PN结,P衬底,N+,P+,PN结在集成电路中的剖面图及电路符号,Anode,Cathode,26/50,双极型晶体管,基本结构和分类,三层结构,NPN晶体管,PNP晶体管,BJT:BipolarJunctionTransistor,27/50,双极型晶体管,发射区,集电区,基区,集电结,发射极,集电极,基极,发射结,Emitter,Base,Collector,（1）两个PN结：发射结、集电结（2）三个区：发射区、基区、集电区（3）杂质浓度：发射区基区集电区（4）窄基区：小于数微米,NPN晶体管,28/50,双极型晶体管,发射结（B-E结）：正偏集电结（B-C结）：反偏,输入,输出,发射区,集电区,基区,集电结,发射极,集电极,基极,发射结,共发射极接法,29/50,双极型晶体管,发射区,集电区,基区,发射极,集电极,基极,Ie,Ib,载流子输运情况,30/50,双极型晶体管,发射区,集电区,基区,发射极,集电极,自建场方向,Ie,基极,Ib,载流子输运情况,31/50,双极型晶体管,发射区,集电区,基区,发射极,集电极,基极,Ie,Ib,电流增益：通过基区的电流与在基区复合的电流之比。,Ic,载流子输运情况,32/50,双极型晶体管,Vcev.s.Ic,Vbe,Vce,e,c,b,Vce,Ic,Ib=0,截止区,晶体管特性曲线,Vbe0Vce较小：eb结和cb结均正偏，Ic随Vce增加而增加。Vce较大：eb结正偏而cb结反偏，IcIb。,截止区,放大区,34/50,双极型晶体管,NPN晶体管在集成电路中的剖面图及电路符号,N+,N+,P衬底,P,N,C,B,E,c,b,e,35/50,MOS晶体管,NMOSFET,PMOSFET,N+,P,Sourse源极,N+,Gate栅极,Drain漏极,P+,N,Sourse源极,P+,Gate栅极,Drain漏极,Metal-Oxide-SemiconductorFieldEffectTransistor,金属氧化物半导体场效应晶体管,基本结构和分类,36/50,MOS晶体管,NMOS的共源极接法,源极,N+,P,N+,栅极,漏极,漏结,源结,沟道Channel,37/50,MOS晶体管,NMOS电容,源极,N+,P,N+,栅极,漏极,VGS=0,VDS=0,VS=0,38/50,MOS晶体管,空间电荷区（耗尽区）,源极,N+,P,N+,栅极,漏极,VGS0（小）,VDS=0,VGS0（小）:栅氧化层下出现空间电荷区（耗尽区）,VS=0,NMOS电容,39/50,MOS晶体管,耗尽区,反型层,源极,N+,P,N+,栅极,漏极,VGS,VDS0,VGS增加：空间电荷向下扩展，栅氧化层下的半导体表面出现多余自由电子，相当于在表面形成一层导电类型相反的半导体层，称为反型层。此时的VGS称为阈值电压VT(0.5V-1.0V)。,VS=0,NMOS电容,40/50,MOS晶体管,VGSVT:表面反型程度进一步加深，半导体表面积累更多的电子，同时反型层的屏蔽作用使得耗尽区停止扩展。,耗尽区,反型层,源极,N+,P,N+,栅极,漏极,VGSVT,VDS0,VS=0,NMOS电容,41/50,MOS晶体管,阈值电压计算公式,NPN：,PNP：,42/50,MOS晶体管,NMOS共源极接法的工作机理,VGS0:漏结耗尽区扩展，使得栅极下方耗尽区宽度从源到漏逐渐增加，晶体管截止，IDS0。,源极,N+,P,N+,栅极,漏极,VGS0,IDS,43/50,MOS晶体管,VGSVT,VDS0（小）:栅极下方耗尽区宽度从源到漏逐渐增加，而反型层宽度从源到漏逐渐减小，ID随VDS增加而线性增加。,源极,N+,P,N+,栅极,漏极,VGSVT,VDS,ID,VDS0(小),IDS,NMOS共源极接法的工作机理,44/50,MOS晶体管,NMOS共源极接法的工作机理,VGSVT,VDS=Vsat:漏结附近反型层宽度减小到零，ID达到最大值。Vsat称为饱和电压,ID称为饱和电流。,源极,N+,P,N+,栅极,漏极,VGSVT,ID,VDSVsat,IDS,Vsat=VGS-VT,Vsat=VGS-VT,Isat,VDS,45/50,MOS晶体管,源极,N+,P,N+,栅极,漏极,VGSVT,VDS,ID,VDSVsat,IDS,Vsat=VGS-VT,Isat,NMOS共源极接法的工作机理,VGSVT，VDSVsat:沟道被夹断，随着VD的增加有效沟道长度减小，ID饱和。,46/50,MOS晶体管,VDS,有效沟道长度,IDS,高阻区长度,IDS,IDS不变(饱和),NMOS共源极接法的工作机理,47/50,MOS晶体管,线性区,VSD,ID,饱和区,截止区,线性区：,饱和区：,NMOS的I-V特性曲线,48/50,MOS晶体管,P衬底,N+,P,N+,N,N+,P+,P+,P+,G