title: A new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage.
abstract: Next-generation lithography requires a high precision stage, which is compatible with a high vacuum condition. A magnetic levitation stage with six degrees-of-freedom is considered state-of-the-art technology for a high vacuum condition. The noncontact characteristic of magnetic levitation enables high precision positioning as well as no particle generation. To position the stage against gravity, z-directional electromagnetic levitation mechanisms are widely used. However, if electromagnetic actuators for levitation are used, heat is inevitably generated, which deforms the structures and degrades accuracy of the stage. Thus, a gravity compensator is required. In this paper, we propose a new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage. The novel Halbach magnetic bearing exerts a force four times larger than a conventional magnetic bearing with the same volume. We also discuss the complementary characteristics of the two magnetic bearings. By modifying the height of the center magnet in a Halbach magnetic bearing, a performance compromise between levitating force density and force uniformity is obtained. The Halbach linear active magnetic bearing can be a good solution for magnetic levitation stages because of its large and uniform levitation force.
authors.affiliation: Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Kusung-Dong, Yusong-Gu, Daejon 305-701, Republic of Korea.
authors.forename: Young-Man
authors.initials: YM
authors.lastname: Choi
authors.forename: Moon G
authors.initials: MG
authors.lastname: Lee
authors.forename: Dae-Gab
authors.initials: DG
authors.lastname: Gweon
authors.forename: Jaehwa
authors.initials: J
authors.lastname: Jeong