Noncontact handling of semiconductor wafers

Semiconductor wafer manufacturing involves many processing steps. During manufacturing, the wafer is transferred from one processing chamber to another by wafer handling equipment. Also the environment encountered by the wafer can vary from high vacuum to high temperature and high corrosion. At the same time, the wafer must be kept free of stresses and contaminants. This project proposes a noncontact wafer handling system to alleviate the contamination problems of single wafer processing. Robotic end-effectors are developed for transporting the wafer, without introducing undesirable contact, stresses or contaminants to the wafer. Two different approaches are considered: gas bearing levitation and magnetic levitation. In gas bearing levitation, a stable cushion of gas is pumped underneath the wafer from a platform. The wafer is supported by pressure differentials rather than solid to solid contact. To avoid turbulence, vacuum is used to suck up the gas produced by the platform. By moving the platform and controlling its tilt, the wafer is transported from position to position without any contact with material surfaces. A control system is developed to move the platform and control the wafer position relative to the platform during wafer transportation. By making the underside of a wafer conductive, magnetic levitation is used to float the wafer above a platform that has an alternating magnetic field. The levitation is inherently stable. The wafer is moved using the system developed for the gas bearing levitation.