Impact of molecular weight of polymers and shear rate effects for nanoimprint lithography

Schulz, H.; Wissen, M.; Bogdanski, N.; Scheer, Hella-Christin; Mattes, K.; Friedrich, Chr.

doi:10.1016/j.mee.2005.07.090

Cited by 60 publications

(58 citation statements)

References 35 publications

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“…In comparison to PS18.7k, the PS96.9k is more susceptible to the shear thinning, which is normal behavior for higher molar mass polymers. [31,32] For PS1510k, the t KWW increases only moderately with the imprinting temperature. As T imp increases from T g þ 20 8C to T g þ 80 8C, the average relaxation time, t KWW increases from approximately 18 min to 87 min for the 430 nm pitch pattern and 34 min to 61 min for the 850 nm pitch pattern.…”

Section: Nil Processmentioning

confidence: 97%

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

Ding

Alvine

et al. 2008

Adv Funct Materials

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Understanding polymer deformation during the nanoimprinting process is key to achieving robust polymer nanostructures. Information regarding this process can be extracted from monitoring the decay of the imprinted polymer patterns during thermal annealing. In the present work, the effect of both the molar mass and the imprinting temperature on the pattern decay behavior during thermal annealing is investigated. Previously, it was found that the decay rate is fastest for a highly entangled polymer due to the elastic recovery caused by the residual stress created during the imprinting process. The present paper demonstrates that this residual stress level can be modified through control of the imprinting temperature. These results are contrasted with those for an unentangled polymer over a similar range of imprinting temperatures, where it is found that the pattern decay is controlled by simple Newtonian flow. In particular, the pattern decay is well described by surface‐tension‐driven viscous flow, and no imprinting‐temperature effect is observed during thermal annealing. It is shown that the stability of the film against pattern decay can be optimized for moderately entangled polymer films. This effect is attributed to the competition between the effect of increased viscosity with increasing molar mass and increased residual stresses with entanglements. These observations provide guidance for the optimization of imprinting process in terms of selection of molar mass and processing temperatures.

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Section: Nil Processmentioning

confidence: 97%

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

Ding

Alvine

et al. 2008

Adv Funct Materials

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“…The plastic deformation can also vary from point to point, ranging from shear in some regions to extensional flow in others. [20] Simulations suggest that when the residual layer of resist between the pattern and the supporting substrate is thicker than the width of penetrating protrusions in the mold, shear flow will dominate the mold filling. [21] The molds and thicknesses of the films imprinted here are consistent with this shear-flow-dominated regime.…”

mentioning

confidence: 99%

“…It has been suggested that the shear rates during the imprinting process approach the shearthinning regime, especially for higher-molecular-mass polymers. [20,22] Therefore, comparing the time scale for structural relaxations in the bulk polymer to the duration of the imprint process provides some insight into the mold-filling physics. [23] This is done below just for the PS patterns, given the abundant literature on the rheological properties of PS for a range of molecular masses.…”

mentioning

confidence: 99%

Polymer Viscoelasticity and Residual Stress Effects on Nanoimprint Lithography

et al. 2007

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The decay kinetics of polystyrene (PS) gratings are monitored by tracking the intensity of the first‐order laser diffraction peak as a function of annealing time. For low‐molecular‐mass PS (24 kg mol–1, blue circles), an exponential response suggests that the pattern decay is a surface‐tension‐ driven viscous flow. In high‐molecular‐mass PS (1007 kg mol–1, green circles) a complicated response includes a rapid elastic recovery, a power‐law creep, and a viscouslike flow (see figure).

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“…At first sight, NIL processes involve multidisciplinary concepts (fluidics, chemistry, mechanics, thermal considerations, surface science) that are not yet fully integrated in a single and validated simulation tool. In the second place, the dedicated and available tools, like the one proposed by Schulz et al [10] based on nanoimprint experiments with polystyrene, have a limited range of applications. The main reason is that the mechanical behavior of the thin and ultra-thin polymeric films, which is considered as input of simulation tool, are not yet well-established.…”

Section: Introductionmentioning

confidence: 99%

Influence of thermal diffusion and shear thinning during the leveling of nanoimprinted patterns in a polystyrene thin film

et al. 2015

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Science Arts & Métiers (SAM)is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Abstract. When capillary forces prevail, the leveling of the free surface of a fluid film is a natural phenomenon that has already found applicative interest either with brushmarks for paint coatings or for rheology on polymeric thin films. Among many parameters, the material behavior influences notably this phenomenon and its characterization still arouses curiosity at the nanoscale. In this article the nanoscale properties of a polystyrene film are derived from the leveling rate of nanoimprinted patterns and are compared to bulk values obtained with a parallel plate rheometer. In particular the focus is made on the isothermal assumption during the process and the consequences of an anisothermal state on the material behavior. Both points are investigated by using numerical simulations based on the natural element method. First we demonstrate experimentally that the leveling rate is influenced by the heat exchange at the air-polymer interface and that thermal diffusion should be taken into account within the film and its underlying substrate. Then we numerically investigate the influence of thermal diffusion and shear-thinning on the leveling rate. Finally we show that the bulk properties can represent particularly closely the behavior of the polymer at the nanoscale if adequate thermal boundary conditions are used and if shear-thinning is taken into account. This agreement postulates a decrease by 7• C of the mean temperature of the polystyrene film coated on silicon when experiments are carried out on a hotplate at 100• C in a cleanroom environment.

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Impact of molecular weight of polymers and shear rate effects for nanoimprint lithography

Cited by 60 publications

References 35 publications

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

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

Polymer Viscoelasticity and Residual Stress Effects on Nanoimprint Lithography

Influence of thermal diffusion and shear thinning during the leveling of nanoimprinted patterns in a polystyrene thin film

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