Methods and apparatus for positioning a substrate relative to a support stage

1. A pushing device, comprising:

a pusher adapted to:

extend toward an edge of a substrate that is supported by a stage;

contact the edge of the substrate while the substrate is supported by the stage; and

continue extending so as to cause the substrate to translate relative to the stage toward one or more stops until the substrate contacts the one or more stops;

wherein the pushing device further comprises a biasing device coupled to the pusher of the pushing device and adapted to move the pusher toward the edge of the substrate; and

wherein the pushing device further comprises a retracting device coupled to the pusher of the pushing device and adapted to counteract the biasing device so as to move the pusher away from the edge of the substrate.

2. The pushing device of claim 1 further comprising:

a biasing device adapted to apply a biasing force to the pusher; and

a bias-defeating device adapted to apply a retracting force to the pusher so as to counteract the biasing force of the biasing device.

3. The pushing device of claim 2 further comprising a common frame coupled to the biasing device and the bias-defeating device.

4. The pushing device of claim 3 wherein the common frame is adapted to restrict motion of the pusher so as to prevent impact between the pusher and the stage.

5. The pushing device of claim 2 further comprising a pusher support coupled to the pusher.

6. The pushing device of claim 5 further comprising a guideshaft adapted to support and guide the pusher support.

7. The pushing device of claim 6 further comprising a sensor adapted to generate a signal corresponding to at least one of a speed of rotation of the guideshaft and a rotational position of the guideshaft.

8. The pushing device of claim 7 further comprising a controller adapted to:

receive the signal from the sensor; and

determine a position of the pusher relative to the stage based on the signal.

9. A method of adjusting a position of a substrate relative to a stage that supports the substrate, comprising:

providing a plurality of pushers and stops in a spaced relation around a stage that is adapted to support a substrate;

causing each pusher to extend toward an edge of the substrate;

causing each pusher to contact the edge of the substrate; and

causing each pusher to continue extending so as to cause the substrate to translate relative to the stage toward one or more of the stops until the substrate contacts the one or more stops;

wherein each pushing device further comprises a biasing device coupled to the pusher of the pushing device and adapted to move the pusher toward the edge of the substrate; and

wherein each pushing device further comprises a retracting device coupled to the pusher of the pushing device and adapted to counteract the biasing device so as to move the pusher away from the edge of the substrate.

10. The method of claim 9 wherein causing each pusher to extend toward an edge of the substrate includes causing a biasing force applied to each pusher to dominate a retracting force applied to each pusher.

11. The method of claim 9 wherein causing each pusher to continue extending so as to cause the substrate to translate relative to the stage toward one or more of the stops until the substrate contacts the one or more stops includes causing the position of the substrate relative to the stage to be calibrated to an x-y coordinate system of the stage.

12. The method of claim 9 further comprising causing one or more of the plurality of pushers to retract.

13. The method of claim 9 further comprising loading a substrate on the support.

14. The method of claim 13 wherein the substrate is misaligned with the stage.

15. The method of claim 14 further comprising:

permitting sliding communication between each pusher and the edge of the substrate; and

permitting sliding communication between each stop and the edge of the substrate.

16. A computer program product comprising:

a medium readable by a computer, the computer readable medium having computer program code adapted to:

cause a plurality of pushers to extend toward an edge of a substrate, wherein the plurality of pushers and a plurality of stops are provided in a spaced relation around a stage that is adapted to support the substrate;

cause each pusher to extend toward the edge of the substrate;

cause each pusher to contact the edge of the substrate; and

cause each pusher to continue extending so as to cause the substrate to translate relative to the stage toward one or more of the stops until the substrate contacts the one or more stops;

wherein each pushing device further comprises a biasing device coupled to the pusher of the pushing device and adapted to move the pusher toward the edge of the substrate; and

wherein each pushing device further comprises a retracting device coupled to the pusher of the pushing device and adapted to counteract the biasing device so as to move the pusher away from the edge of the substrate.

17. The computer program product of claim 16 wherein the computer program code is further adapted to cause a biasing force applied to each pusher to dominate a retracting force applied to each pusher by reducing the retracting force.

18. The computer program product of claim 17 wherein the computer program code is further adapted to cause the position of the substrate relative to the stage to become calibrated to an x-y coordinate system of the stage.

19. The computer program product of claim 17 wherein the computer program code is further adapted to cause one or more of the plurality of pushers to retract by increasing the retracting force.