Characterization of near-field holography grating masks for optoelectronics fabricated by electron beam lithography

Abstract

Direct write e-beam lithography and reactive ion etching was used to fabricate square-wave gratings in quartz substrates which serve as pure phase masks in the near-field holographic printing of gratings. This method of fabricating these masks extends the flexibility of the printing technique by allowing both abrupt phase shifts as well as multiple grating pitches to be simultaneously printed from a single contact mask. Grating masks with periods in the 235–250 nm range have been produced and measured to be within 0.15 nm of the design period. Transmitted and diffracted beam powers have also been measured for various duty cycles and etch depths and are shown to be important parameters for ‘‘balancing’’ these interfering beams. Simple scalar diffraction modeling is used to qualitatively examine the dependence of diffraction on grating parameters, but the need for a more comprehensive modeling is illustrated. Prototype masks have been used to produce grating patterns on InP substrates using two different ultraviolet illumination sources: an argon ion laser and a conventional mercury lamp.