Fabrication of DFB laser gratings using synchrotron radiation proximity lithography

Abstract

First and second order gratings for 1.55 μm distributed feed-back lasers (DFB) have been fabricated in InP using synchrotron radiation proximity lithography. High resolution X-ray masks with 1 st and 2 nd order DFB laser gratings were fabricated by Electron Beam Lithography (EBL) using a single-level resist process and gold electroplating. The resulting 0.23 μm and 0.46 μm period structures were used to transfer a grating image into InP, using synchrotron radiation (SR). A 5μm mask to wafer gap was used. Both positive and negative X-ray resists were used to define the images on InP, and subsequently, were transferred into InP by dry etching process. Issues related to the fidelity of the image transfer process and the control of the line to space ratio on the mask are also discussed.