半导体器件原理2

CarrierTransportPhenomenamobilityresistivityRecombinationprocesses—mobilityVd=E-迁移率，表示单位场强下电子的平均漂移速度（cm2/V·s)I=-nqVd1sJ=-nqVd=-nqESi:n=1350cm2/V·s,p=500cm2/V·s—mobilityGe,Si:声学波散射（晶格振动）和电离杂质散射声学波散射：电离杂质散射：总迁移率：23252352114)(~)(38TmkTmECqdsl2312112312213232)(~])12(1ln[)2(64TNmNqkTmqNkTIIsIsi1)11(il—mobilityIII-V族：除共价键外，还有离子键成分，长纵光学波有重要的散射作用2123)(~Tm—resistivityJ=E=nqnE+pqpE)(11pnqpn—Recombinationprocessesnpni2（注入、抽取）np=ni2非平衡载流子非平衡载流子的复合：（1）直接复合：电子在导带和价带之间的直接跃迁，引起电子和空穴的直接复合（2）间接复合：电子和空穴通过禁带的能级(复合中心）进行复合—Recombinationprocesses直接复合—Recombinationprocesses间接复合的四个过程甲-俘获电子；乙-发射电子；丙-俘获空穴；丁-发射空穴。（a)过程前(b)过程后—RecombinationprocessesrecombinationrateU(cm-3/s,单位时间、单位体积复合掉的电子-空穴对数):lifetime（小注入）)()(112ppnnnnpUnpipnnppU0SiGeHBTtechnologyforcircuitapplicationSemiconductorFabricationSiGeHBTTheSiGeHBTsusedwerefabricatedbyIBM,andaretypicaloffirst-generationSiGetechnology.Aschematiccross-sectionisshowninFigure.TheSiGeHBThasaplanar,self-alignedstructurewithaconventionalpolyemittercontact,silicidedextrinsicbase,anddeep-andshallow-trenchisolation.TheSiGebasewasgrownusingUHV/CVD.Thep-typesubstrateandthen-p-nlayersoftheintrinsictransistorforman-p-n-pmulti-layerstructure,thep-typesubstrateisusuallybiasedatthelowestpotential(5.2Vhere)forisolation.BipolarMOSFETMOSFETMOSFETcircuittechnologyhasdramaticallychangedoverthelastthreedecades.Startingwithaten-micronpMOSprocesswithanaluminumgateandasinglemetallizationlayeraround1970,thetechnologyhasevolvedintoatenth-micronself-aligned-gateCMOSprocesswithuptofivemetallizationlevels.Thetransitionfromdopantdiffusiontoionimplantation,fromthermaloxidationtooxidedeposition,fromametalgatetoapoly-silicongate,fromwetchemicaletchingtodryetchingandmorerecentlyfromaluminum(with2%copper)wiringtocopperwiringhasprovidedvastlysuperioranaloganddigitalCMOScircuits.Figure:Cross-sectionalviewofaself-alignedpoly-silicongatetransistorwithLOCOSisolation0.25mCMOS工艺工艺1工艺2Technology晶体生长与外延氧化与薄膜淀积扩散与离子注入光刻—图形曝光与刻蚀Technology晶体生长与外延—从熔体中生长单晶：直拉法(Si)和布里奇曼法(GaAs)原材料：石英砂SiC(固体)+SiO2(固体)Si(固体)+SiO(气体)+CO(气体)冶金级硅电子级硅（ppb量级）硅片成形:前处理切片双面研磨抛光—介质淀积常压化学气相淀积（APCVD)低压化学气相淀积（LPCVD)等离子增强化学气相淀积(PECVD)：(因素：衬底温度、淀积速率和膜的均匀性、表面形貌、电学和机械性能，以及介质膜的化学组分）其中PECVD温度低：亚微米以下,低温淀积就变得更为重要，以减少热扩散，驰豫扩散与离子注入(用可控制数量的杂质掺入半导体)退火光刻—图形曝光与刻蚀—0.1m以内仍采用光学光刻技术—短波长的射线：1nm波长软X射线、13nm波长极紫外线、电子束Transferofapatterntoaphotosensitivemateriala)Patterndefinitioninpositiveresist,b)Patterndefinitioninnegativeresista)Patterntransferfrompatternedphotoresisttounderlyinglayerbyetching,b)Patterntransferfrompatternedphotoresisttooverlyinglayerbylift-off.各种光刻技术的优势及面临的技术挑战157nm光学光刻技术下一代光刻（NGL）技术EUVL（极紫外光刻）XRL（X射线光刻）SCALPEL（限散射角电子束光刻）基本原理157nmF2激光投影光学光刻4倍缩小扫描投影，约80层Mo-Si结构多层膜，激光等离子体光源，波长范围1113nm1倍X射线接近式投影光刻，1X掩膜4倍缩小电子束投影，钨（W）散射掩膜前景分辨率：80nm应用领域：ULSI分辨率:100nm延伸至30nm以下应用领域：ULSI分辨率:100nm延伸至40nm应用领域：ULSI、GaAsIC、纳米加工、MEMS100nm延伸至50nm应用领域：ULSI、MEMS重大课题掩膜，薄膜，光刻胶，透镜成本，环境无缺陷反射式掩膜、沾污控制；光学问题包括多层膜、光源（功率、寿命），设备成本占用率，真空环境1X掩膜空间电荷效应、硅片表面热效应BasicEquationforSemiconductor-DeviceOperation—BasicEquations:MaxwellEquations:如（）其中tDJH),,(zyxD0)(xdxdE0BEJHB0ED0tBECurrent-densityEquations:One-dimensional:nqDEnqJnnnpqDEpqJpppxnqDEnqJnnnxpqDEpqJpppContinuityEquations:由于电流，单位时间单位体积积累的空穴数：三维：whereG–electronandholegenerationrate,causedbyexternalinfluencesuchasopticalexcitationorimpactionization.(小注入）xJqp)(1pJq1nnnJqUGtn1pppJqUGtp1pnnppU0problem1.Ap+-njunctionisformedinanntypesubstratewithND=1015cm-3.Ifthejunctioncontains1015cm-3generation-recombinationcenterslocated0.02eVabovetheintrinsicFermilevelofsiliconwithn=p=10-15cm2(Vth107cm/s),calculatethegenerationandrecombinationcurrentat–0.5V.2.Findthedepletion-layerwidthandthemaximumfieldatthermalequilibrationforthep+-n1-n2structure.