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1、 Semiconductor materials Lecturer: Aimin Liu & Weifeng Liu刘爱民 刘维峰 12Chemical vs. chemical/physical etchingPurely chemical etching(using only reactiveneutral species)Isotropic etchingChemical + physical etching(using reactive neutral speciesand ionic species)Anisotropic etching3Effect of the inhibito
2、r w/o inhibitor= Isotropicw/ inhibitor= Anisotropic5Plasma assisted etchingnDry chemical etching (Plasma etching)RF energy is applied to a separate electrode with the substrates grounded. Material is removed from the substrate by chemical means.Purely chemical etchingGlow discharge is used to produc
3、e chemically reactive species (atoms, radicals, or ions)nReactive-ion Etching (RIE)If RF energy is applied to the substrates in a low pressure halogen-rich environment, material can be removed by both chemical means and ion bombardment of the substrate surface. Greater control over line widths and e
4、dge profiles is possible with oxides, nitrides, polysilicon and aluminum.A combination of physical/chemical etchingAccomplished by replacing the neutral gas in a r.f. sputtering system by one or more chemical speciesGlow discharge is used to produce chemically reactive species (atoms, radicals, or i
5、ons) and chemically inert ionsHighly anisotropic etching6溅射离子刻蚀原理及斜面刻蚀分析 1. 刻面效应 2. 再沉积效应 3. 阴影效应 78910 表征方法 1. 霍尔效应测试 2. X射线衍射方法（XRD） 3. 光致发光谱（PL） 4. X射线光电子能谱（XPS） 5.其他测试方法：扫描电子显微镜（SEM）、采用PMT 920光电倍增 、 DF4810型晶体管特性图示仪、KEITHLEY 4200 I-V测试系统 11 课程总结n半导体材料与工艺课程内容共分为五部分12半导体材料及器件工艺技术（一）n1发光器件材料及工艺技术n2光
6、伏器件材料及工艺技术13l nj27半导体材料及器件工艺技术（四）1 喷雾热解成膜技术n2 CVD成膜技术n低压CVD、常压CVD、离子增强型CVD、MOCVDn3 扩散及阳极氧化技术28CVD薄膜生长29CVD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 temperaturecold wall reactorDisadvantage: ch
7、emical purity and cost30CVD化学反应Disproportionation irreversibleAsCl3(g) 3Ga(s) 3GaCl(g) 1/4 As4(g)3GaCl(g) 1/2 As4(g) 2GaAs(s) GaCl3(g)Disadvantages: multizone furnacelow gas flowlow reaction efficiency (66%)system contamination (hot wall)31Plasma-Enhanced CVD32半导体材料及器件工艺技术（五）n1 刻蚀技术n化学刻蚀、离子刻蚀、反应离子刻蚀
8、n2 半导体材料及器件的测试33RF-powered plasma etch systemRF-powered plasma etch system34Physical 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
9、Enhanced Etching The chemical and 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 pr
10、esent 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 NJ35Etchants and etch products36Plasma assisted etc
11、hingnPlasma 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 ) 37（六）代表性的几种半导体材料特性 及表征技术nElemental semiconductor-Si, GenCompound semiconductorIV-IV-Si SiCIII-V-GaAs,GaSb,InP,InAs,II-VI -ZnO,ZnS,ZnSenAlloysBinary-Si1-xGexTenary-AlGaAs,AlInAs,Quaternary-AlGaAsSb38 表征方法 1. 霍尔效应测试 2. X射线衍射方法（XRD） 3. 光致发光谱（PL） 4. X射线光电子能谱（XPS） 5.其他测试方法：扫描电子显微镜（SEM）、采用PMT 920光电倍增 、 DF4810型晶体管特性图示仪、KEITHLEY 4200 I-V测试系统 39
