Interfacial Interactions during Demolding in Nanoimprint Lithography

Abstract

Nanoimprint lithography (NIL) is a useful technique for the fabrication of nano/micro-structured materials. This article reviews NIL in the field of demolding processes and is divided into four parts. The first part introduces the NIL technologies for pattern replication with polymer resists (e.g., thermal and UV-NIL). The second part reviews the process simulation during resist filling and demolding. The third and fourth parts discuss in detail the difficulties in demolding, particularly interfacial forces between mold (template) and resist, during NIL which limit its capability for practical commercial applications. The origins of large demolding forces (adhesion and friction forces), such as differences in the thermal expansion coefficients (CTEs) between the template and the imprinted resist, or volumetric shrinkage of the UV-curable polymer during curing, are also illustrated accordingly. The plausible solutions for easing interfacial interactions and optimizing demolding procedures, including exploring new resist materials, employing imprint mold surface modifications (e.g., ALD-assisted conformal layer covering imprint mold), and finetuning NIL process conditions, are presented. These approaches effectively reduce the interfacial demolding forces and thus lead to a lower defect rate of pattern transfer. The objective of this review is to provide insights to alleviate difficulties in demolding and to meet the stringent requirements regarding defect control for industrial manufacturing while at the same time maximizing the throughput of the nanoimprint technique.

Micropatterned Amorphous Zr-Based Alloys Coated with Silica Nanoparticles as Superhydrophobic Surfaces against Abrasion

“…The PDMS prepolymer was poured onto the micropatterned silicon substrate, followed by degassing at ∼0.1 atm in a desiccator and curing for 2 h at 85 °C on a hot plate. After detaching from the silicon template, the micropatterns were transferred to a resist by UV imprint. , An appropriate amount of UV-curable resist (DUV DW-3360-6, China) was manually dispensed on the PDMS mold. A polycarbonate (PC) film with a thickness of 1 mm was laid over the uncured resist.…”

Silicon Metalens Fabrication from Electron Beam to UV-Nanoimprint Lithography

“…Thus, a key feature of the process flow is connected with the realization of the master template [ 42 ]. Although there are several studies based on the nanoimprint process, the issues regarding the defect mechanism have not been completely solved [ 43 , 44 ]. The common defect mechanism that appears in the NIL processes is connected with the demolding step, in which the stamp has to be detached from the cured resist.…”

“…Still, the defects generated by the polymer sticking on the stamp surface are present due to the interfacial forces (adhesion and friction forces) between the resist and the stamp material. The interfacial forces are strongly linked to the quality of the stamp (design, roughness, antisticking layer and material), meaning by the quality of the master, resist material but also by the mechanical characteristics of the used UV-NIL tool [ 43 ]. In addition, these forces are dependent on the residual stress that appears during the UV irradiation due to the shrinkage of the resist that makes the stamp to adhere more to the resist surface [ 44 ].…”

Burger Model as the Best Option for Modeling of Viscoelastic Behavior of Resists for Nanoimprint Lithography

“…Decreasing adhesion and understanding the interfacial phenomena are of constant research focus. Approaches to these problems include exploring new pairs of materials, mold surface modifications, and finetuning parameters of NIL [5] and new investigation methods [6].…”