半导体材料66-77课件

Semiconductormaterials

Lecturer:AiminLiu&WeifengLiu刘爱民刘维峰

1半导体材料及器件工艺技术（四）1喷雾热解成膜技术2CVD成膜技术低压CVD、常压CVD、离子增强型CVD、MOCVD3扩散及阳极氧化技术2超声喷雾热分解装置示意图

35（a）UndopedZnOfilmsurfaceandcrosssection100nm100nm(b)N-IncodopedZnOfilmsurfaceandcrosssection100nm100nm6CVD薄膜生长7CVDSYSTEM91011CVD爐管內的氣流13CVD化学反应Disproportionation

irreversibleAsCl3(g)＋3Ga(s)3GaCl(g)＋1/4As4(g)3GaCl(g)＋1/2As4(g)2GaAs(s)＋GaCl3(g)Disadvantages: multizonefurnace lowgasflow lowreactionefficiency(<66%) systemcontamination(hotwall)14CVD化学反应Pyrolysis

irreversibleHydridereaction,SiH4(g)Si(s)＋2H2(g)Metal-organicreaction

MOCVD(CH3)3Ga(g)＋AsH3(g)GaAs(s)＋3CH4(g)Advantages: lowgrowthtemperature coldwallreactorDisadvantage: chemicalpurityandcost15气体的扩散及表面反应171819Plasma-EnhancedCVD21以不同法成長Si3N4之比較22PECVD、LPCVD、APCVD

之比較232526TheMOVDgrowthsystem27Reactor-129AixtronModel-2400reactor30VaporpressureofmostcommonMOcompoundsCompoundPat298K(torr)ABMeltpoint(oC)(Al(CH3)3)2TMAl14.2278010.4815Al(C2H5)3

TEAl0.041362510.78-52.5Ga(CH3)3

TMGa23818258.50-15.8Ga(C2H5)3

TEGa4.7925309.19-82.5In(CH3)3

TMIn1.7528309.7488In(C2H5)3

TEIn0.3128158.94-32Zn(C2H5)2

DEZn8.5321908.28-28Mg(C5H5)2

Cp2Mg0.05355610.56175Log[p(torr)]=B-A/T

31HorizontalMOVPEReactor32MOVPEReactor

3334

扩散系统示意框图1.氢气入口；2.氢气出口；3.石墨舟；4.加入炉管；5.抽气口；6.分子泵；7.机械泵。

扩散系统示意框图35石墨扩散舟结构图Structureofgraphitecrucible3637SchematicdiagramofAnodicOxidationequipment

GaSb做阳极，铂片做阴极，电解液是酒石酸与乙烯乙二醇混合后的一种水溶液

阳极氧化38阳极氧化膜的形成机理:电极反应：金属（M）的阳极氧化，首先是电解水。在电解液中，通电后在电流作用下发生水解，同时在阴极放出氢气。H2O→H++OH-阴极6H+6e→3H2↑阳极6OH--6e→3H2O3[O]2M3[O]→M2O3阳极氧化膜的生长过程是在膜的增厚和溶解这一矛盾过程中展开的。通电瞬间，由于氧和M的亲和力特别强，在M表面迅速生成一层致密无孔的氧化膜，它具有很高的绝缘电阻，称之为阻挡层。由于在形成氧化M时体积要膨胀，使得阻挡层变得凹凸不平，在膜层较薄的地方，氧化膜首先被电解液溶解并形成空穴，接着电解液变通过空穴到达M基体表面，使电化学反应能够继续进行，孔隙越来越深，阻挡层便逐渐向M基体方向扩展，即得到了多孔状的氧化膜。39半导体材料及器件工艺技术（五）1刻蚀技术化学刻蚀、离子刻蚀、反应离子刻蚀2半导体材料及器件的测试40DryEtchingDryetchingmethodsGlowdischargemethodsDryphysicaletching(Sputteretching)PlasmaassistedetchingDrychemicaletching(Plasmaetching)Reactiveionetching(RIE)IonbeammethodsIonmillingReactiveionbeametchingChemicalassistedionmillingCommonmaterialstodryetchSi,SiO2,Si3N4,Al,W,Ti,TiN,TiSi2,PhotoresistDifficultmaterialstodryetchFe,Ni,Co,Cu,Al2O3,LiNbO3,etc.41RF-poweredplasmaetchsystemRF-poweredplasmaetchsystem42Barrelplasmasystem43444546Etchantsandetchproducts47PlasmaassistedetchingPlasmaassistedetchingsequenceTakeamoleculargasCF4EstablishaglowdischargeCF4+eCF3+

F+e RadicalsreactwithsolidfilmstoformvolatileproductSi+4F

SiF4Pumpawayvolatileproduct(SiF4)48PhysicalEtching•Notveryselectivesinceallmaterialssputterataboutthesamerate.•Physicalsputteringcancausedamagetosurface,withextentandamountofdamageadirectfunctionofionenergy(notiondensity).IonEnhancedEtching•Thechemicalandphysicalcomponentsofplasmaetchingdonotalwaysactindependently-bothintermsofnetetchrateandinresultingetchprofile.•FigureshowsetchrateofsiliconasXeF2gas(notplasma)andAr+ionsareintroducedtothesiliconsurface.Onlywhenbotharepresentdoesappreciableetchingoccur.•Etchprofilescanbeveryanisotop