Novel micro patterning techniques have been developed for the patterning of
volatile functional materials which cannot be conducted by conventional
photolithography. First, in order to create micro patterns of volatile materials (such as
bio-molecules and organic materials), micro-contact printing and shadow mask methods
are investigated. A novel micro-contact printing technique was developed to generate
micro patterns of volatile materials with variable size and density. A PDMS (Polydimethylsiloxane)
stamp with 2-dimensional pyramidal tip arrays has been fabricated by
anisotropic silicon etching and PDMS molding. The variable size of patterns was
achieved by different external pressures on the PDMS stamp. A novel inking process
was developed to enhance the uniformity and repeatability in micro-contact printing.
The variable density of patterns could be obtained by alignment using x-y transitional
stage and multiple stamping with a z-directional moving part.
Second, for direct patterning of small molecule organic materials (e.g. pentacene),
a novel shadow mask method has been developed with a simple and accurate alignment
system. To make accurate dimensions of patterning windows, a silicon wafer was used for the shadow mask since a conventional semiconductor process gives a great
advantage for accurate and repeatable fabrication processes. A sphere ball alignment
system was developed for the accurate alignment between the shadow mask and the
silicon substrate. In this alignment system, four matching pyramidal cavities were
fabricated on each side of the shadow mask and silicon wafer substrate using an
anisotropic silicon bulk etching. By placing four steel spheres in between the matching
cavities, the self-alignment system could be demonstrated with 2-3um alignment
accuracy in x-y directions. For OTFT (Organic thin film transistor) application, an
organic semiconducting layer was directly deposited and patterned on the substrate using
the developed shadow mask method.
On the other hand, novel embedding techniques were developed for enabling
conventional semiconductor processes including photolithography to be applied on the
small substrate. The polymer embedding method was developed to provide an extended
processing area as well as easy handling of the small substrate. As an application, post
CMOS (Complementary metal-oxide-semiconductor) integration of a relatively large
microstructure which might be even larger than the substrate was demonstrated on a
VCO (Voltage-controlled oscillator) chip. In addition, micro patterning on the optical
fiber was demonstrated by using a silicon wafer holder designed to surround and hold
the optical fiber. The micro Fresnel lens could be successfully patterned and integrated
on the optical fiber end.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-791 |
| Date | 2009 May 1900 |
| Creators | Hong, Jung M. |
| Contributors | Zou, Jun |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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