Integrated magnetic levitation and rotation system

An integrated magnetic motor and suspension system that rotates a mass about a vertical z-axis that is mutually orthoganal with x and y axes, comprising,

• a cylindrical wall,
• a ring-like rotor formed of a ferromagnetic material with a pair of flanges that each project radially and are mutually spaced along said vertical z-axis,
• a stator assembly that extends generally in said x-y plane and surrounds the rotor in a closely spaced relationship, said stator assembly having
• (i) upper and lower pole pieces that are each vertically aligned with one of said rotor flanges in said spacing with said cylindrical wall interposed,
• (ii) a permanent magnet coupled between said upper and lower pole pieces to produce a DC magnetic flux field across said spacing and through said wall that (a) passively reluctance centers the rotor along the z-axis and in an orientation generally orthogonal to the z-axis, (b) provides a radial bias force on the rotor, and (c) induces a DC flux field at said rotor,
• (iii) windings mounted on said pole pieces to drive the rotor to rotate about the z-axis through an interaction with said DC flux field at said rotor, said driving occurring across said spacing and though said cylindrical wall, and
• (iv) a plurality of position control coils equiangularly spaced around said stator assembly which produce a magnetic flux that adds and subtracts from the flux field of said DC permanent magnetic field to radically center said rotor with respect to said stator assembly and to supplement the passive tilt control of said permanent magnetic,
• means for sensing at least the actual radial position of the rotor and producing an electrical signal indicative of the sensed radial position, and
• means for producing position control currents in each of said plurality of position control coils in response to said electrical signal that produce said magnetic flux adding and subtracting.

An integrated magnetic support and rotational drive for processing semiconductor wafers in a sealable chamber, that includes a cylindrical side wall comprising,

• a rotor with plural poles formed of a ferromagnetic material located in the chamber and adapted to support the wafer in the chamber and rotate it about a vertical z-axis while it extends in an x-y plane orthogonal to said vertical z-axis, said rotor being formed of a ferromagnetic material with a high magnetic permeability and with a pair of vertically spaced flanges,
• a stator located outside said chamber and surrounding said rotor in a closely spaced relationship having,
• (i) a permanent magnet whose DC flux, acting across said spacing and through said cylindrical side wall, levitates said rotor, radially biases the position of said rotor, and induces a DC flux field in said rotor,
• (ii) upper and lower stator plates aligned with said pair of flanges that sandwich said permanent magnet and are each divided into plural equiangularly-spaced pole segments,
• (a) a polyphase winding wound on said stator that surrounds said rotor and produces a rotating electromagnetic field that interacts with said induced DC flux in said rotor to rotate said rotor and the wafer supported on said rotor about said z-axis in said x-y plane,
• (b) a plurality of position control coils wound on each of said stator plate segments,
• rotor position sensing means that determine at least the radial and vertical positions of said rotor, and
• a feedback control circuit responsive to said position sensing means that said position control coils to center said rotor radially and against tilt out of said x-y plane by modulating the DC flux of said permanent magnet acting on said rotor.