Pressure sensor Surface Micromachining Deposit sacrificial layer Si PSG By HF Poly by XeF2 Pattern anchors Deposit/pattern structural layer Etch sacrificial layer Surface micromachining Structure sacrificial etchant Polysilicon Silicon dioxide HF SiNx PSG HF Silicon dioxide polysilicon XeF2 SiNx polysilicon XeF2 Aluminum photoresist oxygen plasma Residual stress gradients More tensile on top More compressive on top Just right! Clean Room Gowning with bunny suit Class,, 0 Class of clean rooms Class means one speckle of 0.5 µ partical in one ft 3. Class, 0, 00 HEPA filter, AHU A salt grain on a chip 6
Air Filters HEPA (High Efficiency Particulate Air) filters High efficiency, low p, good loading characteristics Glass fibers in a paper like medium 97% retainment of incident particles of 0.3 µm or larger Class Class of clean rooms,000,000 0 0.5 µ particle,000,000 0 Temp tolerance 3 o F 2 o F o F 0.5 o F 0.3 o F RH tolerance 3% 2% $/ft 2 $250-300 $350-400 $200 $3500 $,000 Particles class 0.µ 35 350 0 00 0.2µ 7.5 75 750 0.3µ 3 30 300 0.5µ 0 00 5.0µ 7 Toxicity TLV (Threshold Limit Value) Upper limit material concentration that an average healthy person can be exposed without adverse effects, ppm or mg/m 3 Notorious Poisons CO (0 ppm), CO 2 (5000 ppm), HCN ( ppm), H 2 S ( ppm) SO 2 (5 ppm), NH 3 (50 ppm) Arsenic trioxide AS 2 O 3 (0.g fatal) Hg (0. ppm via skin contact) All material are toxic in sufficient quantity, 5g caffein is fatal. Federal Standard 209; Number of particles per cubic foot MEMS Applications Market Leader R.& D. Issues Display Technologies OLED FED CRT Flat CRT PDP CRT R-TV R-TV 20 40 60 80 HT Poly DLP LT Poly Screen Size 0 300 inch HDTV for 60 ~ 80 Home Theater Digital Presentation for 0 ~ 300 Projector Key Factor : Brightness 7
Brightness of Projection Displays 995 CRT : ~300 : ~300 lm lm : ~600 : ~600 lm lm AMA? :: ~2000 lm lm st Optical MEMS device TM & DLP PROJECTOR lux = lumen / m 2 DMD Optical Switching Principle DMD Cell Structure 2 DMD Mirror on/off ± o Texas Instruments s Technical Journal: Vol. 5, No. 3, July-Sept. 998. Texas Instruments s Technical Journal: Vol. 5, No. 3, July-Sept. 998. Light Modulation of Thinfilm Micromirror Array Light Projection Lens Black 50 µm Light Source No No Modulation Stop Max. Max. Increase of tilting angle Source Stop Mirror White 8
Mirror Via contact to MOS Pixel Architecture Post contact to actuator Mirror Top Electrode Actuation vs DMD DMD TM (Texas Instrument) Electrostatic TM (Daewoo Electronics) Piezoelectric Actuator PZT Bottom Electrode 0 o ~ 3 o Angle - o, 0 o, + o (continuous) Common Electrode Supporting Layer Gray Scale Control On/Off Complex Linear Simple MOS Drain Pad Gate Line Source Line Anchor Drawbacks Fatigue Sticking High Cost Uniformity Micromirror Arrays Mirror Flatness (VGA) XGA 24 X 768 786,432 pixels MLE = ε f ε r ε m = 0.8 ε m MLE = Module Light Efficiency ε f = Fill Factor = 90% ε r = Reflectvity = 90% ε m = Mirror Flatness ε m = 50% MLE = 43% Human Hair VGA 640 X 480 307,200 pixels 50 µm (97µm 97µm mirror) ε m = 83% MLE = 70% Coupled Natures of Thin Film Processes Evolution of Pixels Forward coupling Step coverage, confromality Backward coupling Temperature dependent microstructural degradation Over/under etch, etch stop control Side attack, Passivation breakage Optical Efficiency(%) 24 20 6 2 8 st st 2nd 2nd 3rd 3rd 4 95 96 97 98 99 Year 9
Piezoelectric Amplifiers MIT Bow-actuator Nick Conway, MS 2003 Bottom PZT Top End effector Released Design of nanopipette (2): In-line array of nanopipettes Massive Parallel Nanopipette Array by Inplane Scanning Probe Systems Integration with Microfluidic channels Integration of nanopipettes in AFM in an 0 x 0 array 4-bar linkage design Fixed substrate Single nanopipette Photonic crystal modeling Microcavity waveguide finite-difference time-domain mesh Photonic band gap microcavity waveguide processing design matrix of various geometries: defect lengths, waveguide width, d/a, number of holes SiO 2 Si E x,r max Nanofabrication: SiN x mask /w electron-beam Proximity pattern transfer to resist 30 nm minimum features 0 µm input pulse a a d w 0 Hard mask from Cr lift-off 2 Optimized Si RIE PMMA on Si a d Q = 80 min Cr lift-off mask 300 nm 200 nm J. Ferrera, NanoStructures Laboratory, MIT. 2 J. Foresi, Kimerling group, MIT. Design Domains Design is a mapping process From What to How Small scale systems design What How 2.008-spring-2002 N. P. Suh, Axiomatic Design, Oxford