Magnetic z-actuator and wafer holder comprising such actuator

Abstract

A magnetic Z-actuator for payload positioning, with gravity compensation, includes a stationary assembly and a mobile assembly configured to move relative to the stationary assembly. The stationary assembly includes a tubular magnetic yoke and at least one upper permanent magnet and at least one lower permanent magnet mounted against an inner wall of the magnetic yoke on top of each other. Each of the at least one upper and lower permanent magnets is either annular in shape, extending along the entire inner circumference of the magnetic yoke, or arcuate in shape, extending along a portion of the inner circumference. The at least one upper permanent magnet has a radial magnetization opposite to that of the at least one lower permanent magnet. The mobile assembly includes a magnetic yoke, at least one permanent magnet, which is either annular in shape and positioned around the magnetic yoke or arcuate in shape, covering a portion of the yoke's circumference, and at least one coil mounted around the magnetic yoke. The stationary and mobile assemblies are configured to hold the payload in a stable position by counteracting gravity. The at least one coil is arranged to be energized such that the mobile assembly is moved upwardly or downwardly relative to the stationary assembly. A wafer holder may include the magnetic Z-actuator, and a piece of semiconductor equipment may include such a wafer holder.

Dependencies are inferred from the claim text.