《半导体材料》PPT课件.ppt

1、1,Semiconductor materials,Lecturer: Aimin Liu & Weifeng Liu,刘爱民 刘维峰,2,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,3,超声喷雾热分解装置示意图,4,5,6,7,CVD薄膜生长,8,CVD 炉体设计,9,CVD SYSTEM,10,11,12,Gas Flow Control,Regulator Flow meter Mass flow controller,13,CVD 爐管內的氣流,14,CVD化学反应,Dispro

2、portionation 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),15,CVD化学反应,Pyrolysis irreversible Hydride reaction, SiH4(g) Si(s) 2H2(g) Metal-organic react

3、ion MOCVD (CH3)3Ga(g) AsH3(g) GaAs(s) 3CH4(g) Advantages: low growth temperature cold wall reactor Disadvantage: chemical purity and cost,16,17,气体的扩散及表面反应,18,19,20,Low-Pressure CVD System,21,Plasma-Enhanced CVD,22,以不同法成長Si3N4之比較,23,PECVD、LPCVD、APCVD 之比較,24,25,26,27,The MOVD growth system,28,Vacuum a

4、nd Exhaust system,Gas handle system,Computer Control,Reactor,MOCVD Growth System,29,Reactor-1,30,Aixtron Model-2400 reactor,31,Vapor pressure of most common MO compounds,Logp(torr)=B-A/T,32,Horizontal MOVPE Reactor,33,MOVPE Reactor,34,35,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

5、框图,36,石墨扩散舟结构图 Structure of graphite crucible,37,38,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,39,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

6、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。,40,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,41,Dry Etching,Dry etching methods Glow discharge methods Dry phys

7、ical 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 mate

8、rials to dry etch Fe, Ni, Co, Cu, Al2O3, LiNbO3, etc.,42,RF-powered plasma etch system,RF-powered plasma etch system,43,Barrel plasma system,44,45,46,47,Etchants and etch products,48,Plasma assisted etching,Plasma assisted etching sequence Take a molecular gas CF4 Establish a glow discharge CF4+e CF

9、3 + F + e Radicals react with solid films to form volatile product Si + 4F SiF4 Pump away volatile product (SiF4 ),49,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 fu

10、nction 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 c