Fluid and solid mechanics in the step and flash imprint lithography process
Abstract
Step and Flash Imprint Lithography (SFIL) has become a promising technology to
bring integrated circuit feature sizes to the nanometer scale. It is a molding process in
which liquid monomer is imprinted by a patterned template, with a UV cure to
polymerize the monomer into its patterned form. The success of the process depends
heavily on fluid management issues presented in this study. Important insights are
obtained by detailed analysis of the physics of the fluid and solid mechanics, making it
possible to manipulate issues including imprint time and pressure, template deformation,
and feature filling in order to drive the process to becoming a successful and efficient
manufacturing technique.
The fluid mechanics are simulated using lubrication theory. The solid mechanics
governing elastic deformation of the template are simulated using thin plate theory. The
solution of this coupled fluid-solid mechanics problem provides a dynamic simulation of
the elastic deformation of the template and the time evolution of the fluid flow and
pressure. The interplay of elastic, viscous, and capillary forces govern the behavior of
the fluid and solid mechanics. In order to avoid extreme viscous or capillary pressures
that lead to elastic deformation, it is found that an exact balance of the viscous and
capillary forces throughout the imprint yields negligible deformation. The imprint time
can be reduced using multiple drops and apportioning drop volume appropriately.
A study of feature filling in both the lateral and vertical directions is presented,
and it is found that the aspect ratio and geometry of the feature determine its ability to
fill. A vertical study of the fluid-air interface as it moves into a template feature provides
new understanding of the mechanics of contact line motion and interface reconfiguration.
A modified pressure boundary condition in the lubrication code handles fluid motion
through template features in the lateral direction. Both studies determined that high
aspect ratio features are more difficult to fill, either trapping air due to interface
stretching or requiring a lag time before fluid moves into the feature. This study provides
a better understanding of these fluid issues and presents insights into the details of the
process that can be controlled to make the process a viable technology in the future of
imprint lithography.
Department
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