Dimensionally controlled complex 3D sub-micron pattern fabrication by single step dual diffuser lithography (DDL)

• A single step fabrication of complex 3D sub-micron structures.
• Diffusion of collimated UV light at wider angles by dual diffuser.
• Dimensional control over patterns by change in exposure energy.
• Demonstrated fabrication of sub-micron microlens and nm size microtips.

This article presents a facile single step fabrication method of complex 3D microstructures like microtips, microlenses, microtrapezoids, etc. with controlled dimensions which has been the main focus of researchers over the decades. Each type of above mentioned microstructures individually requires a large number of expensive and complex fabrication processes e.g. plasma RIE, stereo lithography, UV micro stamping and so on. In this study, we have proposed a simple, convenient, cost effective and commercially applicable one step dual diffuser lithography (DDL) method for the fabrication of such complex 3D microstructures by adding a pair of diffusers in conventional photolithography, which diffused the incident beam of ultraviolet (UV) light at wide angles. A conventionally used positive photoresist AZP 4620 was exposed to the diffused light at various exposure energies and the effect of change in exposure energy on the fabricated patterns was studied. Patterns with sub-micron dimensions and microtips with ∼200 nm tip size were also fabricated using the proposed DDL process. The morphology of the fabricated patterns was analyzed using the field-emission scanning electron microscope (FE-SEM) images and 3-dimensional (3D) profiler data.

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