Development of a Compact and Contactless Stage Capable of Levitating/Rotating Wafer Functioning as an Ultrasonically Virtual Hand

This article presents a compact and contactless stage capable of levitating/rotating the wafer via hybrid excitation of standing waves (SWs) and traveling waves (TWs). The stage incorporates two concentrically- arranged irradiators, where the inner one sends out powerful SW to accomplish the levitation while the outer one generates the TW whose intensity and direction are modulatable to achieve the rotation. Interestingly, the stage is regarded as an ultrasonically virtual hand with the holding and plucking functions. Initially, the SW- and TW- irradiators’ configurations are designed to tune the resonance frequency of each component and enhance the air pressure. Subsequently, through acousto-structural analysis, the levitation force and propulsion torque are estimated to numerically discuss the acoustic properties of the air gap between the stage and the wafer. Finally, a stage prototype 220 mm in diameter and 390 mm in height is fabricated to assess its performance. At 20.3 kHz working frequency and 400 V voltage, the stage yielded the maximal levitation height of ∼1 mm. Meanwhile, the maximal rotation speeds reach 0.15 and 0.16 rad/s in the clockwise and counter-clockwise directions, respectively. These results validate the effectiveness of our proposal and demonstrate the stage's potential for the semi-conductor manufacturing industry.