Real-time spatial-phase-locked electron-beam lithography

Abstract

The ability of electron-beam lithography (EBL) to create sub-10-nm features with arbitrary geometry makes it a critical tool in many important applications in nanoscale science and technology. The conventional EBL system is limited by its poor absolute-placement accuracy, often worse than its resolution. Spatial-phase-locked electron-Beam lithography (SPLEBL) improves the placement accuracy of EBL tools to the nanometer level by directly referencing the beam position via a global-fiducial grid placed on the substrate, and providing feedback corrections to the beam position. SPLEBL has several different modes of operation, and it can be applied to both scanning electron-beam lithography (SEBL) and variable-shaped-beam lithography. This research focuses primarily on implementing real-time SPLEBL in SEBL systems. Real-time SPLEBL consists of three major components: a fiducial-reference grid, a beam-position detection algorithm and a partial-beam blanker. Several types of fiducial grids and their fabrication processes were developed and evaluated for their signal-to-noise ratio and ease of usage. An algorithm for detecting the beam position based on Fourier techniques was implemented, and -1 nm placement accuracy achieved. Finally, various approaches to partial-beam blanking were examined, and one based on an electrostatic quadrupole lens was shown to provide the best performance.