Top surface imaging (TSI) techniques using vapor or liquid phase silylation have been investigated extensively as
alternatives to conventional resist processing. However, earlier imaging schemes such as diffusion enhanced silylated
resist (DESIRE) and digital top surface imaging showed several difficulties limiting the successful application of such
TSI approaches. In the case of DESIRE, additional CF4 plasma descum process was required to remove the thin layer of
Si incorporated into the cross-linked regions, as some of the Si remained even in the unexposed regions. Also, difference
in the cross-linking density and subsequent amount of silicon incorporation across the width of an optically projection
printed feature led to non-uniform silylation profiles resulting the difficulty with critical dimension (CD) control of the
feature and increased the LER of the overall process. In the case of digital TSI, even though it was developed to
overcome these problems with the cross-linking-based silylation process, the concentration of active sites in the exposed
polymer varies across the feature width due to the non-uniform energy deposition profile across a feature which results
from the non-ideal aerial image produced using optical projection tools.
In this study, we have used a diazoketo-functionalized polymer as the platform for the immobilization of amine-functionalized
poly(dimethyl siloxane) (amine-PDMS). The diazoketo functional groups undergo Wolff rearrangement
to generate carboxylic acid groups upon UV light exposure. This chemistry is exploited to create alternate
hydrophilic/hydrophobic patterned regions by selective UV light exposure. The hydrophilic regions that contain
carboxylic acid groups predominantly are further used to immobilize amine-PDMS by amide bond formation using
carbodiimide coupling chemistry. Due to the high silicon content, the immobilized PDMS acts as the etch barrier for the
subsequent oxygen plasma reactive ion etching (O2-RIE) process. Thus, a negative-tone pattern has been successfully
generated using O2-RIE process. An amine-PDMS with a molecular weight of 900 was used in this study. Auger electron
spectroscopy was employed to characterize the immobilization of amine-PDMS onto UV light exposed regions of
diazoketo-functionalized polymer surface. Atomic force microscopy was used to study the surface smoothness after O2-RIE process. Scanning electron microscopy was used to image the pattern profiles formed after O2-RIE process. High
resolution pattern profiles are obtained using the TSI process reported in this study.
A simple lithographic process in conjunction with a novel biocompatible nonchemically amplified photoresist material
was successfully used for the patterning of biomolecules such as cells and proteins. UV light irradiation on selected
regions of the nonchemically amplified resist film renders the exposed regions hydrophilic by the formation of
carboxylic groups. Mouse fibroblast cells were found to be preferentially aligned and proliferated on the UV light
exposed regions of the nonchemically amplified resist film, where carboxylic groups were present. For streptavidin
patterning, amine-terminated biotin was linked to the carboxylic groups of the UV light exposed regions, which was
further used to bind streptavidin to the UV light exposed regions.
A novel monomer containing a diazoketo functional group was designed and synthesized. Polymers were synthesized
using the diazoketo-functionalized monomer and their physical properties were evaluated. The polymers were
synthesized by radical copolymerization of cholic acid 3-diazo-3-ethoxycarbonyl-2-oxo-propyl ester methacrylate,
methyl methacrylate, and γ-butyrolacton-2-yl methacrylate. These polymers showed 0.7 &mgr;m line and space patterns using
a mercury-xenon lamp in a contact printing mode.
Negative working nanomolecular resists based on fully epoxy-protected tetra-Cmethylcalixresorcinarene (epoxy C-4-R) and oxetanyl-protected tetra-methylcalixresocinarene (oxetanyl C-4-R) have been developed. They were prepared by the reaction of C-4-R with epichlorohydrin or in the presence of trimethylamine. They can be coated on the silicon wafer by spin-coating method. A clear film cast from a 20 wt% epoxy C-4-R solution in chloroform showed high transparency to UV above 300 nm. A fine negative image featuring 0.8 μm of minimum line and space patterns was observed on the film of the photoresist exposed to 40 mJ/ cm2 of Near UV-light by the contact mode.
A novel nanomolecular resist based on POSS substituted with diazodiketo-functionalized cholate derivatives was successfully synthesized as a candidate for 193-nm lithography. The diazodiketo group was introduced into the cholate derivatives to provide the solubility change and to eliminate the problems of chemically amplified resists. The decomposition temperature of the resist was found to be 130°C. The initial lithographic studies showed the feasibility of the resist to be used as a candidate for 193-nm lithography.