MEMS课件 Chapter2 MEMS Fabrication Review.ppt

Other lithography techniques? Laser direct write X ray Electron beam (E-beam) lithography Interference lithography Scanning probe lithography (Dip-pen) Soft lithography Electric lithography Nanoimprint lithography Plasma lithography … AME/ABE 488/588: Fabrication techniques Etching AME/ABE 488/588: Fabrication techniques Methods of Dry Etching Physical Etching: (e.g. sputtering etch) -mechanical/physical interaction -positive ions are accelerated and strike (physical) (chemical) (physical chemical) substrate with high kinetic energy, some energy is then transferred to surface atoms, which leads to material removal -negative ions cannot reach the wafer and therefore plays no role in the etching Chemical Etching: -neutral or/and ionized species interact with the material’s surface to form volatile products -High product volatility is important so that the reaction product would not coat the surface and prevent further etching Combinations of Chemical and Physical Etching -Anisotropic profile, reasonably good selectivity, and moderate bombardment-induced damage. AME/ABE 488/588: Fabrication techniques Types of Etching Methods Geometry Selectivity Excitation Energy Pressure Gas/vapor Etching Chemical Isotropic Very high none High (760-1torr) Plasma Etching Chemical Isotropic High 10s to100s of Watts Medium (100mtorr) Reactive ion Etching Chemical Physical Directional Fair 100s of Watts Low (10-100mtorr) SputteringEtching Physical Directional Low 100s to 1000s of Watts Low (~10mtorr) Types of Dry Etching Processes ( 1 torr = 1 mmHg) AME/ABE 488/588: Fabrication techniques HNA(HF+ HNO3+AceA ticacid) Alkali-OH (e.g.,( KOH) EDP(ethylene didiaminei pyrochatechol) TMAH (t(tetramethyl-tthl ammonium hydroxide) XeF2 SF6 PlPlasma DRIE (D(Deep reactiveion etch) Etchtype wet wet wet wet dry dry Dry Anisotropic? no yes yes yes no varies Yes Sietchrate 1to3 ?m/min 1to2 1to30 ~1 1to3 ~1 1 SiRoughness low low low variable high variable Low Nitridee