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As the semiconductor industry continues to push to smaller critical dimensions, pattern collapse during lithographic
processing caused by unbalanced capillary forces during the final rinse and drying process has become an important
problem that can limit the practical resolution of a resist material to feature sizes larger than its intrinsic resolution limit.
One of the primary modes of pattern collapse is via elastoplastic pattern deformation which is strongly related to the
mechanical properties of the resist. One approach to mitigating such collapse problems is to enhance the mechanical
properties of the resist features. Since such modification of resist physical properties for pattern collapse purposes is
difficult to achieve through modified formulation of the resist itself (i.e. due to the complex set of requirements that a
resist must satisfy and the complex set of physical and chemical phenomena that underlie the imaging processing itself),
we have pursued an alternative strategy for improving the resist mechanical properties after features are developed in the
film but before they are rinsed and dried. The family of techniques being developed in this work function through the
use of aqueous compatible reactive rinse solutions that can be applied to developed resist features while they are wet
during normal rinse processing on a track system. By applying these techniques during the rinse process, the resist
features can be strengthened before they are subjected to significant capillary forces during the final drying step. In this
work, the use of diamine compounds to reactively crosslink the surface of resists containing carboxylic acid groups
through formation of amide bonds using carbodiimide chemistry has been explored. One advantage of this approach is
that it is an aqueous process that should be easily compatible with high volume, track-based lithographic processes.
Contact angle studies and x-ray photoelectron spectroscopy (XPS) were used to characterize the surface crosslinking
reaction using such diamine surface rinse treatments. Pattern collapse test structures were fabricated and analyzed to
measure the amount of mechanical property improvement imparted by such treatments. Application of such amine
reactive rinses was found to clearly result in an improvement in the resistance of resists to pattern collapse as observed
by SEM. A comparison of the critical stress at the point of pattern collapse as a function of resist feature size also
clearly shows a significant improvement in mechanical resilience of resist samples processed with the reactive rinse
treatment.
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