Formation of irregular micro- or nano-structure with features of varying size by spatial fine-modulation of electric field

Electrically induced patterning is a process for fabricating micro- or nano-structures where a voltage is applied between a conductive template and a polymer-coated substrate, sandwiching an air gap. In the structure-forming process, the polymer film is pulled upwards non-uniformly to the template under the influence of an electric field spatially modulated by protrusions and cavities of the template pattern, being deformed into a structure positive to the template pattern. This paper explores applicability of the electrically induced patterning process in duplicating an irregular structure with features of significantly varying size from a template onto the polymer, and shows that irregular structures, such as the one composed of features with a linewidth varying from 2 μm to 20 μm, as in our experiment and numerical simulation, can be formed on the polymer by a spatially fine-modulated electric field. A ratio of modified most unstable wavelength on the characteristic length and a mass parameter are proposed in terms of the major process variables to define the regimes of spatial modulation by the electric field, i.e. under-modulation, fine-modulation and over-modulation. In addition, an experiment is also performed to duplicate clusters of cylindrical pillars and square prisms sized from 5 μm to 40 μm by tuning the process into a regime of fine-modulation. The experimental results have shown an applicability of the ratio of the modified most unstable wavelength on the characteristic length and the mass parameter in characterizing this structuring method.