Mems fabrication

Mems Fabrication

1. MEMS Fabrication
Mr.S.S.Gurav
SITCOE

2. MEMS overview
Micron level mechanical parts
Made from transistor materials and
metals

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
Si Mask