Double-side exposure UV-LED CNC lithography for fine 3D microfabrication

Abstract

This paper presents a double-side-exposure scheme based on computer-numerical-controlled (CNC) UVLED lithography for fine 3-D microfabrication. The CNC UV-LED lithography manipulates the exposure angle of the UV light where the system comprises a switchable, movable UV-LED array as a light source, a motorized tilt-rotational sample holder, and a computer-control unit. The double-sided exposure scheme utilizes an additional photomask on top of the photoresist-bearing photomask/substrate. The CNC UV-LED apparatus programmably introduces tilt-rotational UV light through the two photomasks via sequential exposure of each side by use of a synchronized switchable UV light source. This creates user-definable 3-D light traces, which are transferred into the photosensitive resist. This approach enables the fabrication of new 3-D structures that have previously been impossible to implement using single-side exposure lithography. Sample fabricated 3D microstructures include a micro spear, a micro golf club, a micro folder, and a micro bird. Arrays of micro ‘y’ and micro mushroom structures are demonstrated as batch fabrications.