Canet Acikgoz

Direct surface structuring of organometallic resists using nanoimprint lithography

The availability of suitable resist materials is essential for nanoimprint lithography (NIL). In this work, the application of poly(ferrocenylmethylphenylsilane) (PFMPS) as a new type of imprint resist is reported. As PFMPS contains iron and silicon in the main chain, it possesses a very high resistance to reactive ion etching. Polymer patterns formed after imprinting were transferred into silicon substrates owing to the high etch resistivity of PFMPS. The parameters for imprinting, such as polymer molar mass and initial film thickness, were investigated. A decrease in the initial film thickness facilitated the residual layer removal, as well as the pattern transfer. Only upon complete removal of the residual layer with argon plasma did pattern transfer result in aspect ratios up to 4:1 and less surface roughness.

3D ordered nanostructures fabricated by nanosphere lithography using an organometallic etch mask

A new approach for fabricating porous structures on silicon substrates and on polymer surfaces, using colloidal particle arrays with a polymer mask of a highly etch-resistant organometallic polymer, is demonstrated. Monolayers of silica particles, with diameters of 60 nm, 150 nm, 300 nm, or 500 nm, were deposited either on a silicon substrate or on a surface coated with polyethersulfone (PES), and the voids of the arrays were filled with poly(ferrocenylmethylphenylsilane) (PFMPS). Argon ion sputtering removed the excess PFMPS on the particles which enabled removal of the particles with HF. Further pattern transfer steps with reactive ion etching for different time intervals provided structures in silicon or in a PES layer. Free-standing PES membranes exhibiting regular arrays of circular holes with high porosity were fabricated by using cellulose acetate as a sacrificial layer. The pores obtained on silicon substrates after etching were used as molds for nanoimprint lithography (NIL). A combination of the techniques of nanosphere lithography (NSL) and NIL has resulted in 3D nanostructures with a hemispherical shape (inherited from the nanoparticles) which was obtained both in silicon and in PMMA.

Nanoscale patterning by UV nanoimprint lithography using an organometallic resist.

This paper presents the fabrication of poly(ferrocenylmethylphenylsilane) (PFMPS) patterns by step-and-flash imprint lithography for use as high-contrast etch masks in dry etch processes. PFMPS was spin-coated onto a resist template made by UV nanoimprint lithography to create a reactive ion etch resist layer with a thickness variation corresponding to the imprinted pattern. Etching back the excess of PFMPS by argon sputtering revealed the imprinted organic resist material, which was subsequently removed by oxygen plasma. PFMPS lines down to 30 nm were obtained after removal of the organic resist by oxygen plasma. Because PFMPS contains iron and silicon atoms in its main chain, it possesses a high resistance to oxygen reactive ion etching and, e.g., CHF(3)/O(2) or SF(6)/O(2) reactive ion etch processes. PFMPS patterns formed after imprinting were subsequently transferred into the underlying silicon substrate, and etch rates of 300 nm/min into Si and around 1 nm/min into the PFMPS layer were achieved, resulting in an etch contrast of approximately 300.