Polarization Camera based Fringe Locking Control of a Writing Head for Scanning Beam Interference Lithography

This paper presents the modeling, identification, and controller design for a novel lithography writing head for Scanning Beam Interference Lithography (SBIL), a high-precision technique for the efficient fabrication of periodic structures through a parallelized writing process. To attain the requisite nanometer precision for the fabrication of high-quality gratings, the writing head is designed to operate within a nanopositioning and nanomeasuring machine. The positioning accuracy is enhanced by a novel fringe locking controller which utilizes an additional piezo-actuated mirror. The fringe locking controller is designed to concurrently regulate both stage positioning errors and thermal drifts inside the beam paths, based on a polarization camera. The effectiveness of this controller is validated by experimental testing.