Microlens array imaging system for photolithography

A micro-optical system is proposed that uses a stack of four microlens arrays for 1:1 imaging of extended object planes. The system is based on the concept of multiple-aperture imaging. A compact system is presented that is remarkable in that it provides a diffraction-limited resolution of 3 m for unlimited object and image areas. Resolution of 5 m has been demonstrated for an area of 2020 mm 2 in an experimental setup using melting resist microlens arrays (190-m lens diameter). The investigated imaging system was developed in connection with a new contactless photolithographic technique called microlens lithography. This new lithographic imaging technique provides an increased depth of focus (50 m) at a larger working distance (1 mm) than with customary proximity printing. Potential applications are photolithography for large print areas (flat panel displays, color filters), for thick photoresist layers (micromechanics), on curved surfaces (or substrates with poor planarity), in V grooves, etc.