Geometrical definitions used for the description of the flow process with volume conservation. (a) Before molding of a spin-coated resist, (b) after demolding, (c) before molding of a dispensed resist, and (d) after demolding.
Mechanical properties of polymers dependent on temperature, molecular weight, and cross-linking, after Ref. 95 . Schematic for a polymer with a around for normal process conditions. Particularly important for thermal NIL are the large drops of at two temperatures, and . At the thermomechanical properties between stamp and polymer become sufficiently different for repeated molding. characterizes a point at which viscosity drops to practical values molding needed for fast imprint.
Zero shear viscosity for some standard resists for thermal NIL for different polymers, taken from different sources: PMMA with of 25 and 75 kg/mol, 14 PS with of 58 and 353 kg/mol 18 (PS 58k and PS 353k), and the commercial resists mr-I 7000E, 8000, 8000E, and mr-NIL6000. 101 These curves are presented for the temperature range characterizes above the viscous . A process window for imprint is limited by high viscosity where unwanted viscoelastic effects become dominant and molding slow. Lower viscosities than are often not useful because it is often achieved with too low or too high .
Possible mass fabrication process for NIL (schematic) in a tandem setup with intermediate polymer stamp production by thermal NIL (left side) and simultaneous thermal and UV process for resist patterning (right side), both imprinted with a polymer foil acting as a soft pressurized membrane; Obducat has included a similar process in a manufacturing tool (Ref. 170 ).
Demolding issues: (a) generation of vacuum voids, (b) elongation and ripping of single structures, (c) ripping of resist from substrate, (d) penetration of air into voids (inclined sidewalls), (e) shrinkage and generation of rims, and (f) relaxation of frozen-in-strain.
Nanoimprint lithography: patterning of a thin resist and pattern transfer.
Comparison of thermal NIL and UV-NIL.
Levels of dimensions and dimensional effects in NIL (with concepts and examples from experiments and simulations). Numbers in brackets denote references.
Hard and soft tool concepts and setup for NIL. Numbers in brackets denote references.
Specific NIL processes for optimized pattern transfer, combined (hybrid) processes, and pattern transfer processes. Numbers in brackets denote references.
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