Pneumatic Servo Bearing Actuator with Multiple Bearing Pads for Ultraprecise Positioning

Abstract

With the increase in demand for semiconductor products, ultrafine linear patterning technologies for Large-Scale Integrations (LSIs) have been making progress. The requested positioning accuracy in such ultraprecise apparatuses is of nanometer order. To meet such specific needs, the research and development of a variety of actuators has been necessary. Our laboratory has developed a ‘Pneumatic Servo Bearing Actuator (PSBA),’ a novel actuator that uses pneumatic servo technology for ultraprecise positioning. Our past studies have showed that the minimum resolution of PSBA was almost 6 nm, even under open loop control; thus, we concluded that the PSBA was a promising actuator in advanced ultraprecise positioning systems. However, the stroke of the PSBA was comparatively short. To expand the stroke of the actuator, we proposed and developed a new PSBA with multiple thin thrust-bearing pads. The main purpose in this study is to investigate the positioning properties of the new PSBA with multiple thrust bearing pads. The obtained characteristics of the PSBA can be enumerated as follows. (1) The PSBA with multiple bearing pads achieves a longer stroke than the PSBA with a single pad. (2) The difference in the thickness of the bearing pads affects the dynamic characteristics of the actuator. (3) The minimum positioning resolution of the developed PSBA with twenty-nine bearing pads is about 2 – 4 nm with feedback control.