Single plane orthogonally movable drive system

A system for positioning wafers with high precision, high speed and short settling times relative to the optical axis in a step and repeat system comprising:

• a flat table surface normal to and encompassing the optical axis;
• a platform disposed above the flat table surface and including air bearing means providing low friction support on the platform, the platform having its center of gravity in a plane close to the table surface and the air bearing means including a number of air bearing pads spaced apart about the center of gravity;
• linear motor means coupling the table surface to the platform, the linear motor means including winding means and permanent magnet means, with one being mounted on the platform facing the table surface and closely positioned relative to the plane of the center of gravity and the other being embedded in the table surface, the winding means comprising an array of orthogonally disposed linear active lengths of windings disposed such that forces generated by inductive reaction between active lengths of the same orthogonal direction and the permanent magnet means are exerted symmetrically relative to the plane of the center of gravity in the platform and are symmetrical and substantially perpendicular to an axis normal thereto;
• means for sensing the position of the platform relative to the table;
• and
• means for separately energizing the active lengths in each orthogonal direction in response to sensed position to provide controlled thrust on the platform.

A system for positioning a semiconductor wafer precisely in X and Y directions within a given horizontal plane comprising:

• a planar member having a flat upper surface including a plurality of embedded square outline permanent magnet elements disposed in rows and columns along X and Y axes, and a plurality of square outline non-magnetic separators disposed therebetween in alternating fashion in the rows and columns, the permanent magnet elements in individual columns and rows being of like polarity but the polarities of the elements in successive columns and rows alternating;
• a platform including air bearing means maintaining the platform at a predetermined height above the upper surface of the planar member, the platform having a predetermined center of gravity;
• four coil sets mounted in quadrants symmetrically about the center of gravity of the platform on the underside of the platform, the coil sets of one diagonally opposed pair having active linear lengths of turns disposed substantially along the X axis, and the coil sets of the other diagonally opposed pair having active lengths of turns disposed substantially along the Y axis, each coil set having multiple parallel subsets of turns and a square outline covering a predetermined number of magnetic elements and non-magnetic elements;
• means for sensing the position of the platform;
• means providing driving signals for the X and Y directions;
• and
• means responsive to the sensed position of the platform and the driving signals for commutating the driving signals in appropriate senses to the subsets of the turns of the coil sets to provide desired thrusts in the X and Y directions.

A system for positioning a platform precisely in horizontal plane comprising:

• a planar member having a flat upper surface lying in a horizontal plane, the planar member including a plurality of permanent magnet elements in a rectangular array, the elements being spaced apart and being of like polarity along the lines of the array, with polarity alternating along successive lines, the planar member including non-magnetic spacers between the permanent magnet elements;
• a platform member including support means movably maintaining the platform member above the planar member at a selected spacing, the platform member including a number of coil sets disposed about the vertical axis of the center of gravity thereof, the coil sets having windings with active turns disposed only in one of two orthogonal, horizontal directions, the coil sets and permanent magnet elements having areas and spacings such that the active turns of the coil sets concurrently span like areas of oppositely poled permanent magnet elements;
• and
• means coupled to the coil sets for energizing the coil sets to generate forces on the platform member to provide movement in any direction in the horizontal plane.

A system for positioning a platform precisely on a horizontal plane comprising:

• a planar member having a plurality of windings in first and second sets with the active lengths of each set being disposed in only one of two orthogonal directions in a horizontal plane, the windings of the first and second sets intersecting throughout an area in which the platform is to be positioned;
• platform means disposed and movable above the horizontal plane and including a number of permanent magnet elements in a preselected pattern of opposite polarities adjacent the horizontal plane that is substantially aligned with the two orthogonal directions;
• and
• means for energizing the first and second sets of windings to exert thrusts on the platform means to the permanent magnet elements by interaction between the active lengths of the sets of windings and the permanent magnet elements.