半导体材料ppt课件

,Semiconductor materials,Lecturer: Aimin Liu & Weifeng Liu,1,半导体材料及器件工艺技术（四）,1 喷雾热解成膜技术 2 CVD成膜技术 低压CVD、常压CVD、离子增强型CVD、MOCVD 3 扩散及阳极氧化技术,2,超声喷雾热分解装置示意图,3,4,5,6,CVD薄膜生长,7,CVD 炉体设计,8,CVD SYSTEM,9,10,11,Gas Flow Control,Regulator Flow meter Mass flow controller,12,CVD 爐管內的氣流,13,CVD化学反应,Disproportionation irreversible AsCl3(g) 3Ga(s) 3GaCl(g) 1/4 As4(g) 3GaCl(g) 1/2 As4(g) 2GaAs(s) GaCl3(g) Disadvantages: multizone furnace low gas flow low reaction efficiency (66%) system contamination (hot wall),14,CVD化学反应,Pyrolysis irreversible Hydride reaction, SiH4(g) Si(s) 2H2(g) Metal-organic reaction MOCVD (CH3)3Ga(g) AsH3(g) GaAs(s) 3CH4(g) Advantages: low growth temperature cold wall reactor Disadvantage: chemical purity and cost,15,16,气体的扩散及表面反应,17,18,19,Low-Pressure CVD System,20,Plasma-Enhanced CVD,21,以不同法成長Si3N4之比較,22,PECVD、LPCVD、APCVD 之比較,23,24,25,26,The MOVD growth system,27,Vacuum and Exhaust system,Gas handle system,Computer Control,Reactor,MOCVD Growth System,28,Reactor-1,29,Aixtron Model-2400 reactor,30,Vapor pressure of most common MO compounds,Logp(torr)=B-A/T,31,Horizontal MOVPE Reactor,32,MOVPE Reactor,33,34,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 Structure of graphite crucible,36,37,Schematic diagram of Anodic Oxidation equipment,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。 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,40,Dry Etching,Dry etching methods Glow discharge methods Dry physical etching (Sputter etching) Plasma assisted etching Dry chemical etching (Plasma etching) Reactive ion etching (RIE) Ion beam methods Ion milling Reactive ion beam etching Chemical assisted ion milling Common materials to dry etch Si, SiO2, Si3N4, Al, W, Ti, TiN, TiSi2, Photoresist Difficult materials to dry etch Fe, Ni, Co, Cu, Al2O3, LiNbO3, etc.,41,RF-powered plasma etch system,RF-powered plasma etch system,42,Barrel plasma system,43,44,45,46,Etchants and etch products,47,Plasma assisted etching,Plasma assisted etching sequence Take a molecular gas CF4 Establish a glow discharge CF4+e CF3 + F + e Radicals react with solid films to form volatile product Si + 4F SiF4 Pump away volatile product (SiF4 ),48,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 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 plasma,sputtering,SILICON VLSI TECHNOLOGY Fundamentals, Practice and Modeling By Plummer, Deal & Griffin, 2000 by Prentice Hall Upper Saddle River NJ,49,50,Chemical vs. chemical/physical etching,Purely chemical etching (using only reactive neutral species) Isotropic etching,Chemical + physical etching (using reactive neutral species and ionic species) Anisotropic etching,51, Many different mechanisms proposed for this synergistic etching between physical and chemical components. Two mechanisms are shown above. Ion bombardment can enhance etch process (such as by damaging the surface to increase reaction, or by removing etch byproducts), or can remove inhibitor that is an indirect byproduct of etch process (such as polymer formation from carbon in gas or from photoresist). Whatever the exact mechanism (multiple mechanisms may occur at the same time): need both components for etching to occur. get anisotropic etching and little undercutting because of directed ion flux. get selectivity due to chemical component and chemical reactions. There are many applications in etching today.,Ion-Enhanced Etching,Chemical component selectivity Physical component anisotropy,volatility of byproducts,Roles of ions:Adsorption, Reaction, Formation of byproducts, removal,SILICON VLSI TECHNOLOGY Fundamentals, Practice and Modeling By Plummer, Deal & Griffin, 2000 by Prentice Hall Upper Saddle River NJ,52,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,53,54,55,56,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,57,课程总结,半导体材料与工艺课程内容共分为五部分,58,半导体材料及器件工艺技术（一）,1发光器件材料及工艺技术 2光伏器件材料及工艺技术,59,1发光器件材料及工艺技术,60,61,典型的量子阱激光器波导结构示意图,62,63,2光伏器件材料及工艺技术,64,在织构化硅衬底上制备的HIT太阳电池（Heterojunction With Intrinsic Thin Layer）,65,半导体材料及器件工艺技术（二）,1光刻技术 2真空镀膜 3晶体制备及液相外延 4磁控溅射,66,溅射（sputtering）又叫阴极溅射（cathodic sputtering）。溅射镀膜是一个PVD过程。通过用由稀有气体在低真空下放电获得的正离子轰击置于阴极的固体表面（靶），使固体原子（或分子）从表面射出，进而以一定能量淀积在基片上，形成薄膜。与蒸发薄膜相比，由于溅射中的靶材料无相变，化合物不易分解，合金不易分馏，因此使用的膜材更为广泛。在微米/纳米技术中有广泛的用途。如用于制备金属膜、合金膜、半导体膜、氧化物、绝缘介质膜、化合物半导体膜、碳化物及氮化物，以及超导薄膜等。,溅射镀膜,67,射频溅射镀膜法 在靶阴极上的电位是相对0电位的基片的是一叠加在4000V负高压上作射频变化的电压。特点：淀积速率高，质量较好，几乎适于所有材料。,磁控溅射镀膜法 在电场的垂直方向加一磁场，电子在正交电磁场的空间里作摆线运动，大大提高离子流的密度，从而提高溅射效率。是一种理想的方法，已获广泛应用。,+,-,68,溅射阀值 溅射阀值是指使靶原子发生溅射的入射离子所必须具有的最小能量。能量较小的荷电正离子并不能立即阴极材料中轰出原子。而只能使它们在其平衡位置加速振动。只有当获得的能量超过其结合能，才可能从表面被溅射出来。溅射阈值取决于靶材料对于同一周期的元素，溅射阀值随原子序数增加而减小。对绝大多数金属来说，该值为1030eV,69,半导体材料及器件工艺技术（三）,1离子镀成膜技术 2分子束外延技术,70,离子成膜法,离子镀膜法是美国Sandia公司的D.M.Mattox于1963年首先提出来的，它是在真空条件下，靠直流电场引起放电，阳极兼作蒸发源，基片放在阴极上，在气体离子和蒸发物质的轰击下，将蒸发物质或其反应物镀在基电底上。 由于使用离子轰击基片，可以获得附着性更好，膜的硬度更高，厚更厚的薄膜。,1-5kV,原子,离子,71,蒸发离子镀,离子镀是在真空条件下，利用气体放电使气体或 被蒸发物部分离化，产生离子轰击效应，最终将 蒸发物或反应物沉积在基片上。离子镀集气体辉 光放电、等离子体技术、真空蒸发技术于一身， 大大改善了薄膜的性能。优点是： 1、兼有真空蒸发镀膜和溅射的优点； 2、所镀薄膜与基片结合好； 3、到达基片的沉积粒子绕射性好； 4、可用于镀膜的材料广泛； 5、沉积率高； 6、镀膜前对镀件清洗工序简单且对环境无污染。,72,成膜原理,在离子镀的过程中，存在两种反的过程 其一，淀积作用,：淀积速率（m/min） ：薄膜密度 g/cm3 M：淀积物质的摩尔质量 NA：质量阿佛伽德罗常数,其二，剥离作用,j：入射离子形成的电流密度（mA/cm2）,镀膜条件：n nj,73,半导体材料及器件工艺技术（四）,1 喷雾热解成膜技术 2 CVD成膜技术 低压CVD、常压CVD、离子增强型CVD、MOCVD 3 扩散及阳极氧化技术,74,CVD薄膜生长,75,CVD化学反应,Pyrolysis irreversible Hydride reaction, SiH4(g) Si(s) 2H2(g) Metal-organic reaction MOCVD (CH3)3Ga(g) AsH3(g) GaAs(s) 3CH4(g) Advantages: low growth temperature cold wall reactor Disadvantage: chemical purity and cost,76,CVD化学反应,Disproportionation irreversible AsCl3(g) 3Ga(s) 3GaCl(g) 1/4 As4(g) 3GaCl(g) 1/2 As4(g) 2GaAs(s) GaCl3(g) Disadvantages: multizone furnace low gas flow low reaction efficiency (66%) system contamination (hot wall),77,Plasma-Enhanced CVD,78,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,79,RF-powered plasma etch system,RF-powered plasma etch system,80,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 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 plasma,sputtering,SILICON VLSI TECHNOLOGY Fundamentals, Practice and Modeling By Plummer, Deal & Griffin, 2000 by Prentice Hall Upper Saddle River NJ,81,Etchants and etch products,82,Plasma assisted etching,Plasma assisted etching sequence Take a molecular gas CF4 Establish a glow discharge CF4+e CF3 + F + e Radicals react with solid films to form volatile product Si + 4F SiF4 Pump away volatile product (SiF4 ),83,（六）代表性的几种半导体材料特性 及表征技术,Elemental semiconductor-Si, Ge Compound semiconductor IV-IV-Si SiC III-V-GaAs,GaSb,InP,InAs, II-VI -ZnO,ZnS,ZnSe Alloys Binary-Si1-xGex Tenary-AlGaAs,AlInAs, Quaternary-AlGaAsSb,84,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,85,