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Research Papers

Hierarchical Analysis of the Release Step in a Nanofabrication Process Using an Adhesion/Atomistic Friction Surface Interaction Model

[+] Author and Article Information
E. D. Reedy

e-mail: edreedy@sandia.gov

J. V. Cox

Sandia National Laboratories,
Albuquerque, NM 87185

Contributed by the Materials Division of ASME for publication in the Journal of Engineering Materials and Technology. Manuscript received November 5, 2012; final manuscript received November 10, 2012; published online January 23, 2013. Assoc. Editor: Thomas Siegmund.

J. Eng. Mater. Technol 135(1), 011008 (Jan 23, 2013) (9 pages) Paper No: MATS-12-1091; doi: 10.1115/1.4023042 History: Received May 11, 2012; Revised October 11, 2012

Finite element analysis techniques were used to study the release step in a nanofabrication process. These calculations employed a novel adhesion/atomistic friction surface interaction model to define how the glassy polymer interacts with the hard mold. This model is applicable to solids that interact via relatively weak, van der Waals forces and is applicable to intentionally weakened interfaces (e.g., when a mold release is used). The goal of this effort is to simulate the entire separation process. The release step was studied by performing unit cell calculations for a pattern composed of identical, parallel channels. The interface between the mold and the glassy polymer did not unzip in a continuous, quasi-static manner in these simulations. Instead, there was a complex failure sequence that included multiple dynamic separations and arrest events as well as adhesive reattachment. The sensitivity of the release process to interface and bulk material properties, polymer shrinkage, and feature geometry was then quantified by examining variations from a baseline configuration. Finally, the feasibility of a hierarchical analysis that represents the nanometer-scale pattern by a pattern traction–separation (T–U) relationship, which is defined by a unit cell analysis, was demonstrated.

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Figures

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Fig. 3

Release process includes multiple dynamic separation and arrest events as well as adhesive reattachment: 1-2, 2-3, reattach 2-4, 4-2

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Fig. 2

Unit cell geometry used in the release calculations

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Fig. 1

(a) Adhesion and (b) atomistic friction portions of Ad/AF surface interaction model, where τ* opposes frictional slip δt

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Fig. 4

Pattern T–U relationship for the BL calculation

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Fig. 5

Effect of mesh refinement and an increase in mold thickness on calculated pattern T–U relationship

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Fig. 9

Effect of mass proportional damping on the pattern T–U relationship, (a) no damping and (b) (mdΓ/σ*)/(E/ρ)1/2 varied

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Fig. 11

Effect of L1/(Γ/σ*) on the pattern T–U relationship (L1 and Γ varied in calculation)

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Fig. 10

Effect of L1/(Γ/σ*) on the pattern T–U relationship (Γ varied in calculation)

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Fig. 6

Effect of polymer shrinkage εo on the pattern T–U relationship

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Fig. 7

Effect of τ*/σ* on the pattern T–U relationship

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Fig. 8

Effect of σ*/E on the pattern T–U relationship

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Fig. 12

Models used in hierarchical analysis. (a) 60-channel model and (b) unit cell model.

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Fig. 13

Calculated pattern T–U relationship as determined from the unit cell analysis

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Fig. 14

Calculated average applied traction versus the average applied displacement as determined by an analysis that explicitly models the 60-channel pattern is compared to hierarchical analysis result

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Fig. 15

Models used in hierarchical analysis. (a) 20-pillar model and (b) unit cell model.

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Fig. 16

Calculated pattern T–U relationship as determined from the unit cell analysis

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Fig. 17

Calculated average applied traction versus the average applied displacement as determined by an analysis that explicitly models the 20-pillar pattern is compared to hierarchical analysis result

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