MECH466-Lecture-17 - 1 MECH 466 Microelectromechanical...

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Unformatted text preview: 1 MECH 466 Microelectromechanical Systems University of Victoria Dept. of Mechanical Engineering Lecture 17: Microfabrication Technologies July 9th, 2007 Mech 466, N. Dechev, UVic 2 Detailed look at Bulk Micromachining Detailed look at Surface Micromachining MUMPs Micromachining SUMMiT Micromachining Overview Mech 466, N. Dechev, UVic 3 Microfabrication using Bulk Micromachining Bulk Micromachining is based on the etching and bonding of thick sheets of material such as silicon oxides and crystalline silicon. There are three main types of methods for Bulk Micromachining: Anisotropic Wet Etching Isotropic Wet Etching (Silicon & Glass) Dry Etching - Gas and Plasma Etching- Reactive Ion Etching- Deep Reactive Ion Etching Mech 466, N. Dechev, UVic Fig 10.1 Definition of isotropic and anisotropic etching [Foundations of MEMS, Chang Liu] 4 Anisotropic (directional) etching along crystal planes. A liquid Wet etchant is used to remove the bulk material. Mech 466, N. Dechev, UVic Anisotropic Wet Etching Silicon Crystal Orientations, [Chang Liu] 3 Microfabrication using Bulk Micromachining Bulk Micromachining is based on the etching and bonding of thick sheets of material such as silicon oxides and crystalline silicon. There are three main types of methods for Bulk Micromachining: Anisotropic Wet Etching Isotropic Wet Etching (Silicon & Glass) Dry Etching - Gas and Plasma Etching- Reactive Ion Etching- Deep Reactive Ion Etching Mech 466, N. Dechev, UVic Fig 10.1 Definition of isotropic and anisotropic etching [Foundations of MEMS, Chang Liu] 4 Anisotropic (directional) etching along crystal planes. A liquid Wet etchant is used to remove the bulk material. Mech 466, N. Dechev, UVic Anisotropic Wet Etching Silicon Crystal Orientations, [Chang Liu] 5 Anisotropic Wet Etching Silicon Substrate Wafer inserted into High Temp Furnace with oxygen gas, to grow oxide layer Mech 466, N. Dechev, UVic 6 Silicon Substrate HF Acid Etch Oxide is patterned with photolithography (Not Shown) Oxide Mech 466, N. Dechev, UVic Anisotropic Wet Etching 7 Silicon Substrate Wet Silicon Etchant Mech 466, N. Dechev, UVic Anisotropic Wet Etching 8 Silicon Substrate 54.7 <100> <111> Mech 466, N. Dechev, UVic Anisotropic Wet Etching 9 EDP (Ethylene diamine pyrocatechol) @ 90 o C- Etch rate ratio for <100> and <111> is as high as 35:1 or higher [Petersen]- Etch rate for silicon nitride and silicon oxide is almost negligible.- Native oxide becomes important in processing- Highly directional selective, allows cheap oxide as mask. Disadvantage: Expensive; chemically unstable.- Aging: etch rate and color changes with time after exposure to oxygen. KOH (Potassium hydroxide) @ 75-90 o C- Various concentrations can be used, 20-40 wt % is common....
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This note was uploaded on 02/02/2010 for the course MECH 466 taught by Professor Dechev during the Summer '07 term at University of Victoria.

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MECH466-Lecture-17 - 1 MECH 466 Microelectromechanical...

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