1. 1 Microfabrication Technologies Luiz Otávio Saraiva Ferreira LNLS lotavio@lnls.br

2. 2 OUTLINE Lithography Transfer of Patterns Bulk Silicon Micromachinning Surface Micromachinning LIGA technique

3. 3 Litography - Evolution France, 1822 Graphic arts. Printed circuit board- 1940-1945. – 0.1mm wide lines. –(It may be used for microfluidics). Integrated circuit - 1961. –5um wide lines. Wide evolution on electronics industry. Microsystems require progress on 3D lithography.

4. 4 Stencil UV LIGHT GLASS OR QUARTZ PHOTORESIST SUBSTRATE LIGHT ABSORBER (800A Cr) 1:1 IMAGE Light Field Dark Field Lithographic Masks

5. 5 PHOTORESIST Si SUBSTRATE SiO 2 Photoresist processing Spinning Most used substrate: Si/SiO 2 Si Oxidation –Wet or dry. –Between 900 and 1150 o C. SiO 2 masks the substrate in the following processing steps.

6. 6 Transfer of Patterns Si SiO 2 Photoresist Radiation Glass Metal Unexposed Photoresist 1 6 4 2 3 5

7. 7 Karl Suss MA4 Mask Aligner

8. 8 Ultra Violet or X-Ray Source Mask Before ExposureExposure After Development 3D Lithography Techniques Thornell & Johansson, J. Micromech. Microeng. (1998) 251-262

9. 9 Bulk Silicon Micromachining Wet or Dry Etch AB ISOTROPIC Isotropic Anisotropic Selective ANISOTROPIC Sci. Am. April 1983 pp. 39

10. 10 Back and Front Side Bulk Micromachining Suspense devices Membrane Back Side Etch Front Side Etch Cantilever

11. 11 Problems of Bulk Micromachining

12. 12 Corner Compensation No compensationBeginning etch Mid etchEnd of etch

13. 13 Surface Micromachining Etch Before etch After etch CantileverBridge

14. 14 Example of Surface Micromachining Sandia

15. Germany - 80’s Resist Base Plate IRRADIATION Base Plate Resist structure DEVELOPMENT ELECTROFORMING Metal Resist Structure Base Plate MOLD FABRICATION Mold Insert Mold Cavity Synchrotron Radiation Mask membrane Absorber structure MOLD FILLING Mold Insert Mold Material Gate Plate Injection Hole DEMOLDING Plastic Microstructure PLASTIC MOLDING Mold Insert Mold Material Plastic Structure (Lost Mold) DEMOLDING SLURRY CASTING Ceramic Slurry Plastic Structure (Lost Mold) FIRING Ceramic Micro- structure ELECTROFORMING Metal Gate Plate Injection Hole Metallic Micro- structure FINISHING Plastic Structure LIGA Technology 15

16. X-Ray Be Filter (125um) Al Filter 100um thick SU-8 film Si substrate Au absorber (1.8um)20um SU-8 Kapton mask Plating Base (0.2um Au) 5 - 15 keV spectrum after filtering Deep X-ray Lithography 16

17. PMMA (polymethylmetacrylate) the most used. High resolution. Low sensitivity (2.5 kJ/cm 3 minimum dose). Long exposure times. Up to 100µm thick  1-3 keV energy. From 100µm to 500µm thick  3 - 7 keV energy. SU-8 (epoxy based) a promising material Good resolution. High sensitivity. Short exposure times. Difficult processing. Resists for deep X-ray Lithography 17

18. 20µm thick UV- LIGA process. Deep UV lithography on SU-8. Au platting. Frame 25µm thick Kapton Membrane Plating Base 2µm Au 20µm SU-8 Kapton Mask 18

19. UV Cheap Non-vertical sidewalls - border diffraction effect. RX Expensive Vertical sidewalls - negligible border diffraction. Deep UV lithography  Deep X-ray lithography 19