Wafer stage assembly, servo control system, and method for operating the same

A method for determining a position of a table relative to a projection optical assembly in a semiconductor substrate manufacturing device, the table being supported by a stage and a stage base, comprising the steps of:

• determining a position of the stage base relative to the projection optical assembly;
• determining a position of the stage relative to the stage base;
• and
• determining a position of the table relative to the stage.

A table servo control system of a stage assembly having a stage base for supporting a stage and positioning a semiconductor substrate, a table connected to the stage for supporting the substrate, comprising:

• a first sensor controller to generate a first position signal of an exposure point on the table relative to a projection optical assembly, wherein the first sensor controller comprises:
• a first sub-sensor to generate a first sub-position signal of the stage base relative to the projection optical assembly;
• a first input controller to input a first input position signal of the stage relative to the stage base;
• a second sub-sensor controller to generate a second sub-position signal of the table relative to the stage;
• and
• a second input controller to generate a second input position signal of the exposure point relative to the table;
• a second sensor controller to generate a second position signal of a focal point of the projection optical assembly relative to the exposure point;
• and
• a table controller to determine a correction force corresponding to the first and second position signals, the correction force being exerted on the table to bring the exposure point to substantially coincide with the focal point.

A method for operating a table servo control system of a stage assembly, comprising the steps of:

• creating a first loop to generate a first position signal of an exposure point on a table relative a projection optical system, wherein the step of creating a first loop comprises:
• generating a first position signal of a stage base relative to the projection optical system;
• generating a second position signal of a stage relative to the stage base;
• generating a third position signal of a table relative to the stage;
• and
• generating a fourth position signal of the exposure point relative to the table;
• creating a second loop to generate a second position signal of a focal point of the projection optical system relative to the exposure point;
• and
• exerting a correction force, in response to the first and second position signals, onto the table to bring the exposure point to substantially coincide with the focal point.