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1、半导体材料半导体材料66-772半导体材料及器件工艺技术（四）1 喷雾热解成膜技术喷雾热解成膜技术n2 CVD成膜技术成膜技术n低压低压CVD、常压、常压CVD、离子增强型离子增强型CVD、MOCVDn3 扩散及阳极氧化技术扩散及阳极氧化技术9CVD SYSTEM101112Gas Flow ControlnRegulatornFlow meternMass flow controller13CVD CVD 爐管內的氣流14CVDCVD化学反应Disproportionation irreversibleAsCl3(g) 3Ga(s) 3GaCl(g) 1/4 As4(g)3GaCl(g) 1
2、/2 As4(g) 2GaAs(s) GaCl3(g)Disadvantages: multizone furnacelow gas flowlow reaction efficiency (66%)system contamination (hot wall)15CVDCVD化学反应Pyrolysis irreversibleHydride reaction, SiH4(g) Si(s) 2H2(g)Metal-organic reaction MOCVD(CH3)3Ga(g) AsH3(g) GaAs(s) 3CH4(g)Advantages: low growth temperature
3、cold wall reactorDisadvantage: chemical purity and cost1617气体的扩散及表面反应181920Low-Pressure CVD System21Plasma-Enhanced CVD22以不同法成長SiSi3 3N N4 4之比較23PECVDPECVD、LPCVDLPCVD、APCVDAPCVD 之比較24252627The MOVD growth system 28Vacuum andExhaust systemGas handle systemComputerControlReactorMOCVD Growth System29Re
4、actor-130Aixtron Model-2400 reactor31Vapor pressure of most common MO compounds Compound P at 298 K(torr)A B Melt point (oC)(Al(CH3)3)2TMAl14.2278010.4815Al(C2H5)3 TEAl0.041 362510.78-52.5Ga(CH3)3 TMGa238 18258.50-15.8Ga(C2H5)3 TEGa4.79 25309.19-82.5In(CH3)3 TMIn1.7528309.7488In(C2H5)3 TEIn0.3128158
5、.94-32Zn(C2H5)2 DEZn8.5321908.28-28Mg(C5H5)2 Cp2Mg0.05355610.56175Logp(torr)=B-A/T 32Horizontal MOVPE Reactor33MOVPE Reactor3435 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36石墨扩散舟结构图Structure of graphite crucible3738Schematic diagram of Anodic Oxidation equipment GaSb做阳极，铂片做阴极，电解液
6、是酒石酸与乙烯乙二醇混合后的一种水溶液 n阳极氧化39n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。H2OH+ +OH-阴极 6H+ 6e3H2阳极 6OH- 6e3H2O 3O 2M 3O 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
7、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。40半导体材料及器件工艺技术（五）n1 刻蚀技术刻蚀技术n化学刻蚀、化学刻蚀、离子刻蚀、反应离子刻蚀离子刻蚀、反应离子刻蚀n2 半导体材料及器件的测试半导体材料及器件的测试41Dry EtchingnDry etching methodsGlow discharge methodsnDry physical etching (Sputter etching)nPlasma assisted etchingDry chemical etching (Plasma etching)Reactive ion
8、etching (RIE)Ion beam methodsnIon millingnReactive ion beam etchingnChemical assisted ion millingnCommon materials to dry etchSi, SiO2, Si3N4, Al, W, Ti, TiN, TiSi2, PhotoresistnDifficult materials to dry etchFe, Ni, Co, Cu, Al2O3, LiNbO3, etc.42RF-powered plasma etch systemRF-powered plasma etch sy
9、stem43Barrel plasma system44454647Etchants and etch productsSolidEtch gasEtch productSi, SiO2, Si3N4PSG, and BPSGCF4, SF6, and NF3SiF4SiCl2 and CCl2F2SiCl2 and SiCl4AlBCl3, CCl4, Cl2Al2Cl6 and AlCl3Organic solidsPhotoresists, etc.O2O2 + CF4CO, CO2, H2OCO, CO2, HFRefractory metals(W, Ta, Ti, Mo, etc.
10、)CF4WF6 .GaAs, InPCl2 and CCl2F2GaCl3, AsCl5, .48Plasma assisted etchingnPlasma assisted etching sequenceTake a molecular gas nCF4Establish a glow dischargenCF4+e CF3 + F + e Radicals react with solid films to form volatile productnSi + 4F SiF4 Pump away volatile product (SiF4 ) 49MaskMaskFilmFilm+
11、+ +Ionic speciesIonic species+ + + + + + +Physical Etching Not very selective since all materials sputter at about the same rate. Physical sputtering can cause damage to surface, with extent and amount of damage a direct function of ion energy (not ion density).Ion Enhanced Etching The chemical and
12、physical components of plasma etching do not always act independently - both in terms of net etch rate and in resulting etch profile. Figure shows etch rate of silicon as XeF2 gas (not plasma) and Ar+ ions are introduced to the silicon surface. Only when both are present does appreciable etching occur. Etch profiles can be very anisotopic, and selectivity can be good. No plasmasputteringSILICON VLSI TECHNOLOGYFundamentals, Practice and ModelingBy Plummer, Deal & Griffin 2000 by Prentice HallUpper Saddle River NJ