Sub-100nm, Maskless Deep-UV Zone-Plate Array Lithography

摘要

Semiconductor lithography is at a crossroads. With mask set costs in excess of $1M, long mask-turn-around times, and tools that are characterized by their inflexibility and skyrocketing costs (in excess of $20M), there is need for a new paradigm in lithography. Zone-Plate-Array Lithography (ZPAL) bypasses some of the most pressing problems of current lithography equipment by offering a maskless lithography tool that is scalable, flexible and low cost. 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 report covers 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 and are extendable to the limits of the lithography process. As a result, ZPAL represents the most promising approach to low cost maskless lithography for the semiconductor industry and other areas of nanoscale science and engineering.