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微/纳制造工艺技术Micro & Nano Fabrication TechnologyLecture 8 Dry Etching主讲：乔大勇OutlineOverview of dry etchingFundamentals of plasmaReactive Ion Etching (RIE)Deep RIEWhy dry etchingSmallLargeUse of chemicalsAcceptable High Batch production High Low Tool price Acceptable ，controllable High ，Uncontrollable Selectivity Acceptable ，controllable High ，controllable Etch rate ControllableIsotropic or anisotropic Side wall profile Very small >3 micronEtching tolerance Dry etching Wet etching Etching type Overview of dry etchingWetCl 2AlCHF 3Silicon OxideCF 4Silicon Nitride SF 6Silicon, PolysiliconDryH 3PO4AlHF Silicon OxideH 3PO 4Silicon Nirtide KOH, TMAH,EDPSiliconChemical used Etching target ModeComparison of Dry and Wet etchingWhy dry etchingOverview of dry etchingOverview of dry etchingPlasma is generated by RF and DC excitation of source gases in a vacuum system. Take SF6as an example, plasma composed of equal numbers of positive (SF5+) and negative charges (F-and e) and a different number of unionized molecules and radicals (F).Positive ions are accelerated and strike substrate with high kinetic energy, leading to material removal (Highly anisotropic and low selectivity). Neutral radicals interact with substrate surface to form volatile products (Isotropic and high selectivity)Fundamentals of plasma90％states of matter in Universe is plasma. Lightning and polar light are natural plasma. All stars are combination of matters in plasma state.IceWaterSteamPlasma (Ionized gas)Cold Warm Hot HotterMolecules fixed in lattices Molecules free to move Molecules free to move, large space Ions and electrons move, large spaceFundamentals of plasmaMan made PlasmaFundamentals of plasmaFundamentals of plasmaMan made PlasmagasAre-Ar+Ar+Ar+ArSheath-V+Fundamentals of plasmaMan made PlasmaExcitation(激发）跃迁eA A e +→+*For CF 4，4.0eV energy is needed for excitation. Symbol * stands for excited atoms, which will go back to general state in 1/billion second~several seconds by relaxation procedure.Fundamentals of plasmaMan made Plasma)(*Photos h A A ν+→Relaxation (驰豫)Light emitted during relaxation. Different gas plasma emitted different color. For Argon plasma, the color is pink.Fundamentals of plasmaMan made PlasmaDissociation (分裂)For CF4，12.5eV is neede for dissociation 。
【面板制程刻蚀篇】史上最全Dry Etch 分类、工艺Dry Etch工序的目的广义而言，所谓的刻蚀技术，是将显影后所产生的光阻图案真实地转印到光阻下的材质上，形成由光刻技术定义的图形。
它包含了将材质整面均匀移除及图案选择性部分去除，可分为湿式刻蚀(wet etching)和干式刻蚀(dry etching)两种技术。
湿式刻蚀具有待刻蚀材料与光阻及下层材质良好的刻蚀选择比（selectivity）。
然而，由于化学反应没有方向性，因而湿式刻蚀是各向同性刻蚀。
当刻蚀溶液做纵向刻蚀时，侧向的刻蚀将同时发生，进而造成底切（Undercut）现象，导致图案线宽失真，如下图所示。
底切现象自1970年以来，元件制造首先开始采用电浆刻蚀技术（也叫等离子体刻蚀技术），人们对于电浆化学性的了解与认识也就越来越深。
在现今的半导体集成电路或面板制造过程中，要求精确地控制各种材料尺寸至次微米大小，而且还必须具有极高的再现性，电浆刻蚀是现今技术中唯一能极有效率地将此工作在高良率下完成的技术，因此电浆刻蚀便成为半导体制造以及TFT LCD Array制造中的主要技术之一。
干式刻蚀通常指利用辉光放电（glow discharge）方式，产生包含离子、电子等带电粒子以及具有高度化学活性的中性原子、分子及自由基的电浆，来进行图案转印（pattern transfer）的刻蚀技术。
干法刻蚀是亚微米尺寸下刻蚀器件的最主要方法，广泛应用于半导体或面板前段制程。
Dry Etch 的分类及工艺的基本原理蚀刻技术中的术语1.各向同性与各向异性蚀刻( Isotropic and Anisotropic Etching)不同的蚀刻机制将对蚀刻后的轮廓(Profile)产生直接的影响。
如下图所示，纯粹的化学蚀刻通常没有方向选择性，上下左右刻蚀速度相同，蚀刻后将形成圆弧的轮廓，并在遮罩(Mask)下形成底切(Undercut)，这种刻蚀被称为各向同性蚀刻。
