Transcript Soft Lithography - University of California, Santa Cruz

CHEM 146C_Experiment #7
Soft Lithography: Patterning
Yat Li
Department of Chemistry & Biochemistry
University of California, Santa Cruz
Objective
In this laboratory experiment, we will learn:
1. The principle of soft lithography and the fabrication of
poly(dimethylsiloxane) (PDMS) stamp
2. Microcontact printing technique to create patterned metal electrodes
(or interesting features) on a substrate
Micro- and nanofabrication
Microfabrication, through its role in microelectronics and optoelectronics, is
an indispensable contributor to information technology.
Photolithoghaphy: ~ 1 micrometer (resolution limited by diffraction of light)
E-beam lithography: < 50 nm
Photo or
E-beam resists
lithography
Develop
Lift-off
Metal
evaporation
Drawback: expensive, time consuming (e-beam), poorly suited for patterning
nonplanar surface
Soft lithography
Soft lithography represents a nonphotolithographic strategy based on self
assembly and replica molding for carrying
out micro- and nanofabrication
1. Generate patterns and structures with
feature sizes ranging from 30 nm to
100 mm
2. Convenient, effective, and low-cost
Xia, Y. N. and Whitesides, G. M. “Soft Lithography”.
Annu. Rev. Mater. Sci. 28, 153-184 (1998)
Poly(dimethylsiloxane) (PDMS)
Poly(dimethylsiloxanes):
1. A unique combination of properties resulting
from the presence of an inorganic siloxane
backbone and organic methyl groups attached
to silicon.
2. Very low glass transition temperatures and
hence are fluids at room temperature.
3. Can be readily converted into solid elastomers
by cross-linking.
PDMS:
SYLGARD® 184 SILICONE ELASTOMER KIT
base
cure
Mechanism of cross-linking
Dean J. Campbell, Katie J. Beckman
Preparation of PDMS elastomeric block
Xia, Y. N. and Whitesides, G. M. “Soft Lithography”.
Annu. Rev. Mater. Sci. 28, 153-184 (1998)
Dean J. Campbell, Katie J. Beckman
Microcontact printing
The concept of microcontact printing is use the relief pattern on the surface
of a PDMS stamp to form patterns of SAMs on the surfaces of substrates by
contact. For example, alkylthiol on Au and Ag surfaces.
Simple and suitable for non-planar substrates!
Xia, Y. N. and Whitesides, G. M. “Soft Lithography”. Annu. Rev. Mater. Sci. 28, 153-184 (1998)
Making metal thin films
Typical methods to make
high quality metal films:
Sputtering
Tollens process:
[Ag(NH3)2]+ + reducing agent
Solution A: a mixture of AgNO3 and NH4NO3
Solution B: NaOH
Solution C: Glucose (C6H12O6)
Evaporation
Ag film
Making metal electrodes by microcontact printing
Gerber, R. W. and Oliver-Hoyo, M. T. “Selective Etching via Soft Lithography of Conductive Multilayered Gold
Films with Analysis of Electrolyte Solutions”. Journal of Chemical Education 85, 1108-1111 (2008)