Maskless nanolithography and imaging with diffractive optical arrays

Abstract

Semiconductor lithography is at a crossroads. With mask set costs in excess of one million dollars, long mask turn-around times, and tools that are characterized by their inflexibility and skyrocketing costs, there is a need for a new paradigm in lithography. The work presented in this thesis, Zone-Plate-Array Lithography (ZPAL), bypasses some of the most pressing problems of current lithography equipment by developing a maskless lithography tool that will be scalable, flexible and cost-effective. It is the departure from a century-old tradition of refractive optics, in combination with the use of advanced micromechanics and fast computing, that enables ZPAL to open up a new application space in lithography. This thesis addresses in detail all levels of the ZPAL system, from the micromechanics, to the diffractive optics, to the control system. Special emphasis is placed on the design, fabrication and characterization of high-numerical-aperture diffractive optical elements for lithography and imaging. The results achieved provide conclusive evidence that diffractive optics in general, and zone plates in particular, are capable of state-of-the-art lithography.