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Introduction to Microfabrication
Nick FerrellBiomedical Engineering
Basics of Microfabrication
• Developed by microelectronics industry• Adapted for silicon MEMS• Refined for nanoscale fabrication• Extended to polymer micro/nanofabrication
Basic Processing-Photolithography
Coating and Exposure
Latent Image Formation
Develop-Positive Tone Develop-Negative Tone
Limits of Photolithography
Minimum Features Size α Exposure Wavelength
Spectrum for Hg Arc Lamp (365 and 436 nm)
http://www.cairnweb.com/tech/tech_lamp2.html
Nanofabrication
Excimer Lasers: KrF (248 nm) ArF (193 nm)
F2 (157 nm)
X-rays, EUV (10-40 nm)E-beam: (.0037 nm @ 100kV)
X-ray (70 nm) E-beam (43 nm)Ito, Okazaki, Nature 408 (2000), 1027-1031.
Polymer Micro/Nanofabrication
Polymer Properties•Wide range of physical and chemical properties• Biocompatible• Cheap
Techniques• Hot Embossing• Injection Molding• Soft Lithography
- Microtransfer Molding- Microcontact Printing- Micromolding in Capillaries- Sacrificial Layer Micromolding
Hot Embossing
J. Narasimhan, I. Papautsky, J. Micromech. Microeng. 14(2004), 85-105
Soft Lithography
Figure 2. Chemical structure of PDMS.
-Cheap-Easy-Quick-Robust
RapidPrototyping
Y. Xia, G.M. Whitesides, Soft Lithography, Angew. Chem Int. Ed. 37(1998), 550-575.
Y. Xia, G.M. Whitesides, Soft Lithography, Angew. Chem Int. Ed. 37(1998), 550-575.
Soft Lithography
Microcontact Printing
Sacrificial Layer Micromolding
Multi-layer Patterning
HEAT (110° C)
SU8
PDMS
PPMA
PDMS
OH OH OH
CH3 CH3
CH3 CH3CH3
CH3 CH3
O2 Plasma
CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3CH3
OH OH
OH OH OH
OH OH
OH OH OH OH OH OH OH OH OH
Si
OSi
Si
OSi
Si
OSi
Si
OSi
PDMS Bonding