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