Novel Silicon-Elastomers for Advanced Soft Lithography
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0947-A03-26
Novel Silicon-Elastomers for Advanced Soft Lithography Kyung Choi Bell Labs, Murray Hill, NJ, 07974 High resolution pattern transfers in the nano-scale regime have been considerable challenges in ‘soft lithography’ to achieve nanodevices with enhanced performances. In this technology, the resolution of pattern integrations is significantly rely on the materials’ properties of polydimethylsiloxane (PDMS) stamps. Since commercial PDMS stamps have shown limitations in nano-scale resolution soft lithography due to their low physical toughness and high thermal expansion coefficients, we developed stiffer, photocured PDMS silicon elastomers designed, specifically for nano-sized soft lithography and photopatternable nanofabrications.
INTRODUCTION Integration of nanopatterns fabricated using diverse organic functionalities enables to develop novel devices, which could achieve multiple tasks. Since optimization of such hybrid device functions ultimately depends upon the precise positioning of the functionally distinct materials, chemists and materials scientists play an important role to synthesize new materials to achieve high performances in devices.1-9 Recent studies in developing new materials for nanotechnology purposes have emphasized that this is a challenge, owing to the lack of well-developed nano-scale materials and fabrication techniques in this area. In nano-fabrication, ‘soft lithography technique’ has been widely used in replicating and fabricating small features. It is a low cost alternative to photolithography by transferring small features from masters to substrates using elastomeric materials such as highly stretchable silicon elastomers. This technique significantly relies on the performance of polydimethylsiloxane (PDMS) stamp materials. However, commercial PDMS stamp materials have shown a lot of limitations due to their low physical toughness and high thermal expansion coefficients, which often fail to meet the set of our requirements to use this for nano-scaled soft lithography. To achieve high performance in molding and microprinting, we designed a new version of stiffer, photocured PDMS silicon elastomers. We then demonstrated its unique capabilities on nano-resolution soft lithography using a master with features of 300 nm line-widths and 600 nm narrow and tall heights of photoresistor, which is one of the most challenging ‘nano-patterning’ tasks in submicron scale soft lithography with other commercially available elastomers.
Figure 1 illustrates a chemical structure of the photocurable silicon elastomers described in our earlier publications.3 In structural design of new PDMS stamp materials, surface
wetting property is partially reliant on both flexibility and physical toughness, which are required especially for the ‘microcontact printing’ process printing features on the gold surfaces.
CH3 CH3 Si O CH3
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CH3 Si O CH3 Si a CH3
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CH3 3 CH3 O Si O Si O (R ) CH3 C H 3b CH3 CH3
Si
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CH3 Si O H 3C
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