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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.
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