Article
Uniform Pressing Mechanism in Large-Area Roll-to-Roll
Nanoimprint Lithography Process
Ga Eul Kim
1,2,†
, Hyuntae Kim
1,†
, Kyoohee Woo
1
, Yousung Kang
2
, Seung-Hyun Lee
1
, Yongho Jeon
2
,
Moon G. Lee
2,
* and Sin Kwon
1,
*
Citation: Kim, G.E.; Kim, H.; Woo,
K.; Kang, Y.; Lee, S.-H.; Jeon, Y.; Lee,
M.G.; Kwon, S. Uniform Pressing
Mechanism in Large-Area
Roll-to-Roll Nanoimprint
Lithography Process. Appl. Sci. 2021,
11, 9571. https://doi.org/10.3390/
app11209571
Academic Editor: Arkadiusz Gola
Received: 17 September 2021
Accepted: 7 October 2021
Published: 14 October 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1
Department of Printed Electronics, Nano-Convergence Manufacturing Systems Research Division,
Korea Institute Machinery Materials (KIMM), Daejeon-si 34103, Korea; autumn@kimm.re.kr (G.E.K.);
kht1682@kimm.re.kr (H.K.); khwoo@kimm.re.kr (K.W.); shlee79@kimm.re.kr (S.-H.L.)
2
Department of Mechanical Engineering, Ajou University, Suwon-si 16499, Korea; gidalim89@ajou.ac.kr (Y.K.);
princaps@ajou.ac.kr (Y.J.)
* Correspondence: moongulee@ajou.ac.kr (M.G.L.); skwon@kimm.re.kr (S.K.); Tel.: +82-219-2338 (M.G.L.);
+82-42-868-7219 (S.K.)
† These authors contributed equally to this work.
Abstract:
We aimed to increase the processing area of the roll-to-roll (R2R) nanoimprint lithography
(NIL) process for high productivity, using a long roller. It is common for a long roller to have bending
deformation, geometric errors and misalignment. This causes the non-uniformity of contact pressure
between the rollers, which leads to defects such as non-uniform patterning. The non-uniformity of
the contact pressure of the conventional R2R NIL system was investigated through finite element (FE)
analysis and experiments in the conventional system. To solve the problem, a new large-area R2R
NIL uniform pressing system with five multi-backup rollers was proposed and manufactured instead
of the conventional system. As a preliminary experiment, the possibility of uniform contact pressure
was confirmed by using only the pressure at both ends and one backup roller in the center. A more
even contact pressure was achieved by using all five backup rollers and applying an appropriate
pushing force to each backup roller. Machine learning techniques were applied to find the optimal
combination of the pushing forces. In the conventional pressing process, it was confirmed that
pressure deviation of the contact area occurred at a level of 44%; when the improved system was
applied, pressure deviation dropped to 5%.
Keywords:
roller bending; contact pressure; roll-to-roll process; nanoimprint lithography; high pro-
ductivity
1. Introduction
Nanoimprint lithography (NIL), which was introduced by Chou in 1995, has been
regarded as a promising technology with outstanding advantages. Based on the mechan-
ical deformation of a curable resist, NIL is a fabrication method in which a substrate is
coated and a desired pattern is pressed into the coating to replicate an inverse pattern [
1
].
Because it makes it possible to easily replicate patterns using molds with fine patterns,
NIL technology is highly applicable to the manufacturing process of functional optical
devices, semiconductors or display devices; it can reproduce not only micro-scale patterns
but also nano-scale patterns. Recently, the fabrication of a pattern with a size of 10 nm or
less by applying a nanoimprint process has been announced [
2
,
3
]. Because it has potential
to pattern on a large area by the application of a step-and-repeat process, NIL is considered
a next-generation patterning process that can replace photolithography [3–6].
When NIL was first introduced, an imprinted pattern was fabricated by pressing a
flat mold with the pattern onto a flat substrate. However, with this method it is difficult to
increase the pattern area, so it is difficult to improve productivity. To improve productivity,
a new process with a long imprinting (pressing) roller with the pattern has been proposed.
Appl. Sci. 2021, 11, 9571. https://doi.org/10.3390/app11209571 https://www.mdpi.com/journal/applsci
