Optimization of demolding temperature for throughput improvement of nanoimprint lithography

Abstract

Annealing effects onto the reflow of imprinted resist patterns have been investigated on 250 nm dense line arrays printed with standard hot embossing lithography and thermoplastic polymer. Atomic force microscopy measurements were performed to point out the annealing temperature and time effects, respectively. The reflow velocity with respect to annealing temperature has been determined. Its variation is ascribed to both resist dynamic viscosity and surface free energy. Our approach demonstrated that imprint cycle time could be significantly reduced by saving cooling down time.

Nanoimprint Lithography and the Role of Viscoelasticity in the Generation of Residual Stress in Model Polystyrene Patterns

“…Attempts have been made to achieve high throughput in thermal embossing NIL, by directly demolding at high temperatures without the cooling process after the imprinting. [16] Clearly, our study suggests that if high molar mass is utilized, significant reduction or lateral instability of the patterns might occur. Thermal ''reflow'' by heating the patterns above the T g of the polymers to reduce the line-edge roughness also has been demonstrated by Chou et al in the case of a commercial unentangled polymer resist.…”

“…This difficulty becomes greater for small and closely packed structures with a high aspect ratio. To obtain faithful description of the pattern shape, special tips (such as flare tips) have to be used [16]. In this study, the purpose of AFM analysis is only limited to extracting the pattern height, not the full pattern profile.…”

“…There is recent interest in roll-to-roll thermal imprint processes where imprint times would be substantially shorter and the mold would be separated from the roll at high temperatures. [16] Under this circumstance, stress generation and pattern relaxation may be highly problematic for imprinting pattern stability. An alternative to extending t imp is to relax the imprint-induced stress is to raise the imprinting temperature (T imp ).…”

“…However, the stability of these ''as-imprinted'' structures then becomes a central concern in the development of this process. [16,17] Although low temperature patterning of glassy polymers has been demonstrated, most thermal-embossing NIL is performed at temperatures above the glass-transition temperature (T g ) of the polymer. [18] The patterning resolution is determined by the viscoelastic deformation of thin polymer films under applied pressure.…”

Wafer-scale selective area growth of GaN hexagonal prismatic nanostructures on c-sapphire substrate

“…The imprint process was done at 110 1C using a contact force of 10 kN in a EVG s 520HE nanoimprint equipment (see experimental details in Ref. [19]). The residual resist layer at the bottom of the holes was removed by a short oxygen plasma treatment to reach the Si 3 N 4 surface (see Fig.…”