1. MEMS Fabrication By Thomas Szychowski

2. MEMS overview • Micron level mechanical parts • Made from transistor materials and metals • Van Der Waals forces • Intermolecular bonding • Plays an important part in design

3. Fabrication Techniques • Mask Lithography • Injection molding • Microstereolithography • Silicon Surface Micromachining • Silicon Bulk Micromachining

4. Mask Lithography • Use of photo resist • Positive • Dissolves under light • Negative • Hardens under light • Both get covered with desired material, then photo resist is dissolved by a solvent • Multiple layers – Multiple steps

5. Mask Lithography

6. Injection Molding • Starts with mask lithography • Metal poured over resist • Resist gets dissolved • Metal form is left for plastic injection molding

7. Injection Molding

8. Microstereolithography • Similar principal to mask lithography, but for 3D pieces • Uses an “active mask” • Not a physical mask • Utilizes a photo-reactive acrylic resin • Each layer image projected through a DMD(digital mirror device) • Projected into the resin • Uses lenses • Resin that is illuminated, Cross-links and hardens • Piece is then covered in a hardened layer

9. Microstereolithography • Dimensional capabilities • Lateral and Vertical resolution: 10μm • Maximum field size: 10.24mm x 7.68mm • Structural height: up to 5mm

10. Microstereolithography

11. Microstereolithography

12. Silicon Surface Micromachining • Uses the same process as IC fabrication • Needs multiple layers to create structures • Cheapest form of Micromachining • Similar to lithography • Sacrificial material • Structural material • When sacrificial material is removed, only whole structures are left

13. Silicon Surface Micromachining

14. Silicon Surface Micromachining

15. Silicon Surface Micromachining

16. Silicon Bulk Micromachining • Done with Crystalline silicon • Constructed using etch stop planes • Chemical process • Anisotropic Etching • Speed dependent – Directional • etch in different crystallographic directions at different rates • Slower directions create and etch stop plane

17. Deep Reactive Ion Etching (DRIE) • Uses photo resist and a mask to create structures

18. Sapphire Etching • Metal Mask • 100µm etch depth • .28µm/min etch rate • Chlorine etching

19. Pressure Sensor Etching • Used on silicon • Metal mask • .81µm etch depth • Utilizes Fluorine

20. High-Speed Etching • Silicon material • 1µm/min etch rate • W-Si Mask

21. Whacky Neato Pictures

22. Questions ?

23. References • http://home.earthlink.net/~trimmerw/mems/tour.html • http://home.earthlink.net/~trimmerw/mems/BM_bulk.html • http://www.samcointl.com/apps/mems.html • http://www.cmf.rl.ac.uk/latest/msl.html • http://www.chemguide.co.uk/atoms/bonding/vdw.html • “Micromachining for Optical and Optoelectronic Systems”. MING C. WU