Devices and methods for compensating for tilting of a leveling table in a microlithography apparatus

In an exposure apparatus including a wafer stage movable at least in X- and Y-directions, a leveling table tiltable relative to a Z-axis that is perpendicular to the X-and Y-directions, and a reticle stage movable at least in the X- and Y-directions, a control system for compensating for lateral shift of the leveling table caused by a tilt (θ) of the leveling table, the control system comprising:

• a reticle-stage-position loop servo configured to actuate movement of the reticle stage in response to a reticle-position command;
• a leveling-table tilt-position loop servo configured to apply a tilting torque to the leveling table in response to a leveling command;
• and
• a first feed-forward loop from the leveling-table tilt-position loop servo to the reticle-stage-position loop servo, the first feed-forward loop being configured to convert a torque-control signal for the leveling table to a linear-acceleration-control signal for the reticle stage, the linear-acceleration-control signal causing the reticle stage to move laterally to compensate for the lateral shift of the leveling table accompanying a change in tilt of the leveling table.

An exposure apparatus, comprising:

• a projection-optical system having an optical axis parallel to a Z-axis;
• a wafer stage situated downstream of the projection-optical system and being movable at least in the X- and Y-axis directions;
• a leveling table situated do stream of the projection-optical system and being tiltable relative to the Z-axis;
• a wafer-stage-position loop servo connected to the wafer stage and configured to actuate movement of the wafer stage in response to a wafer-position command;
• a leveling-table tilt-position loop servo connected to the leveling table and configured to apply a tilting torque to the leveling table in response to a leveling command;
• and
• a control system for compensating for lateral shift of the leveling table caused by a tilt (θ) of the leveling table, the control system comprising a feed-forward loop from the leveling-table tilt-position loop servo to the wafer-stage-position loop servo, the feed-forward loop being (a) configured to convert a torque-control signal for the leveling table to a linear-acceleration-control signal for the wafer-stage, the linear-acceleration-control signal causing the wafer stage to move laterally in a manner that compensates for the lateral shift of the leveling table accompanying a change in tilt of the leveling table;
• and (b) represented by a block diagram comprising:
• a coordinate converter connected to the leveling-table tilt-position loop servo and configured to convert an angular-acceleration (θ″) command from the leveling-table tilt-position loop servo to a corresponding linear-acceleration command output from the coordinate converter;
• a controller connected downstream of the coordinate converter and configured to apply a factor ms to the linear-acceleration command output of the coordinate converter, wherein ms is a combined mass of the wafer stage and leveling table, thereby producing a first force command;
• and
• an adder situated and configured to add the first force command to a second force command produced by the wafer-stage-position loop servo, so as to produce an output routed to a wafer-stage actuator.

An exposure apparatus, comprising:

• a projection-optical system having an optical axis parallel to a Z-axis;
• a leveling table situated downstream of the projection-optical system and being tiltable relative to the Z-axis;
• a reticle stage situated upstream of the projection-optical system and being movable at least in X- and Y-directions;
• a leveling-table tilt-position loop servo connected to the leveling table and being configured to apply a tilting torque to the leveling table in response to a leveling command;
• a reticle-stage-position loop servo connected to the reticle stage and being configured to actuate movement of the reticle stage in response to a reticle-position command;
• and
• a control system for compensating for lateral shift of the leveling table caused by a tilt (θ) of the leveling table, the control system comprising a first feed-forward loop from the leveling-table tilt-position loop servo to the reticle-stage-position loop servo, the first feed-forward loop being configured to convert a torque-control signal for the leveling table to a linear-acceleration-control signal for the reticle stage, the linear-acceleration-control signal causing the reticle stage to move laterally to compensate for the lateral shift of the leveling table accompanying a change in tilt of the leveling table.

In an exposure method in which a substrate, mounted on a wafer stage movable at least in mutually perpendicular X- and Y-axis directions, is exposed to a pattern defined by a reticle, a method for maintaining an alignment of the substrate for exposure, the method comprising:

• mounting the substrate on leveling table that is tiltable relative to a Z-axis perpendicular to the X- and Y-axis directions, the leveling table being mounted on the wafer stage and being controlled by a leveling-table tilt-position loop servo that applies a tilting torque to the leveling table as required in response to a leveling command corresponding to a torque-control signal, and the wafer stage being controlled by a wafer-stage-position loop servo that actuates movement of the wafer stage at least in the X- and Y-axis directions as required in response to a wafer-position command;
• in association with tilting of the leveling table in response to the tilting command, feeding forward the torque-control signal from the leveling-table tilt-position loop servo to the wafer-stage-position loop servo such that the torque-control signal is converted to an acceleration-control signal for the wafer stage, the acceleration-control signal causing the wafer stage to move laterally to compensate for a lateral shift of the leveling table caused by tilting of the leveling table;
• mounting the reticle in a reticle stage movable at least in the X- and Y-axis directions and controlled by a reticle-stage-position loop servo that actuates movement of the reticle stage in response to a reticle-position command;
• and
• in association with tilting of the leveling table in response to the tilting command, (i) feeding forward the torque-control signal from the leveling-table tilt-position loop servo to the reticle-stage-position loop servo, (ii) converting the fed-forward torque-control signal to a linear-acceleration-control signal for the reticle stage, and (iii) applying the linear-acceleration-control signal to the reticle stage to cause the reticle stage to move laterally to compensate for a lateral shift of the leveling table accompanying a change in tilt of the leveling table.

In an exposure method in which a substrate, mounted on a wafer stage movable at least in mutually perpendicular X- and Y-axis directions, is exposed to a pattern defined by a reticle mounted on a reticle stage, a method for maintaining an alignment of the substrate for exposure, the method comprising:

• mounting the substrate on a leveling table that is tiltable relative to a Z-axis that is perpendicular to the X- and Y-axis directions, the leveling table being mounted on the wafer stage and being controlled by a leveling-table tilt-position loop servo that applies a tilting torque to the leveling table as required in response to a leveling command corresponding to a torque-control signal;
• mounting the reticle in a reticle stage movable at least in the X- and Y-axis directions and controlled by a reticle-stage-position loop servo that actuates movement of the reticle stage in response to a reticle-position command;
• and
• in association with tilting of the leveling table in response to the tilting command, (i) feeding forward the torque-control signal from the leveling-table tilt-position loop servo toward the reticle-stage-position loop servo, (ii) converting the fed-forward torque-control signal to an acceleration-control signal for the reticle stage, and (iii) applying the acceleration-control signal to the reticle stage to cause the reticle stage to move laterally to compensate for a lateral shift of the leveling table accompanying a change in tilt of the leveling table.

A positioning apparatus for positioning a substrate, comprising:

• a first stage movable at least in a first direction;
• a second stage mounted on the first stage, the second stage being configured to retain a substrate and being tiltable relative to the first stage;
• and
• a control system connected to the first stage and the second stage, the control system comprising a first-stage-position loop for the first stage, a second-stage-position loop for the second stage, and a feed-forward loop connected to the first-stage-position loop and the second-stage-position loop;
• wherein the first-stage-position loop actuates movement of the first stage by utilizing a first-stage control signal;
• the second-stage-position loop actuates a tilting motion of the second stage by utilizing a second-stage control signal;
• the feed-forward loop converts the second-stage control signal to the first-stage control signal;
• and
• the first-stage control signal causes the first stage to move in a manner that compensates for the lateral shift of the substrate accompanying a change in tilt of the second stage.

A positioning apparatus that positions a substrate, comprising:

• a first stage that is movable at least in a first direction;
• a second stage mounted on the first stage, the second stage being configured to retain the substrate and be tiltable relative to the first stage;
• a third stage that is movable at least in the first direction, the third stage being configured to move synchronously with the substrate moved by the first stage;
• and
• a control system connected to the first, second, and third stages, the control system comprising a second-stage-position loop for the second stage, a third-stage-position loop for the third stage, and a first feed-forward loop connected to the second-stage-position loop and the third-stage-position loop;
• wherein the second-stage-position loop actuates a tilting motion of the second stage by utilizing a second-stage control signal;
• the third-stage-position loop actuates movement of the third stage by utilizing a third-stage control signal;
• the first feed-forward loop converts the second-stage control signal to the third-stage control signal;
• and
• the third-stage control signal causes the third stage to move in a manner that compensates for alignment errors between the third stage and the substrate accompanying a change in tilt of the second stage.

In an exposure apparatus including a reticle stage movable at least in X- and Y-directions, a wafer stage movable at least in X- and Y-directions, a leveling table associated with the wafer stage and tiltable relative to a Z-axis that is perpendicular to the X- and Y-directions, and a control system that compensates for lateral shift of the leveling table caused by a tilt (θ) of the leveling table, the control system comprising:

• a wafer-stage-position loop servo configured to actuate movement of the wafer stage in response to a positional command;
• a leveling-table tilt-position loop servo configured to apply a tilting torque to the leveling table in response to a leveling command;
• a feed-forward loop from he leveling-table tilt-position loop servo to the wafer-stage-position loop servo, the feed-forward loop being configured to convert a torque-control signal for the leveling table to a linear-acceleration-control signal for the wafer stage, the linear-acceleration-control signal causing the wafer stage to move laterally in a manner that compensates for the lateral shift of the leveling table accompanying a change in tilt of the leveling table;
• and
• a reticle-stage-position loop servo configured to actuate movement of the reticle stage in response to a reticle-position command, the control system further comprising a second feed-forward loop from the leveling-table tilt-position loop servo to the reticle-stage-position loop servo, the second feed-forward loop being configured to convert a positional signal for the leveling table to a position-control signal for the reticle stage, the position-control signal causing the reticle stage to move laterally to compensate, at least in part, for the lateral shift of the leveling table accompanying a change in tilt of the leveling table.

An exposure apparatus, comprising:

• a projection-optical system having an optical axis parallel to a Z-axis;
• a wafer stage situated do stream of the projection-optical system and being movable at least in the X- and Y-axis directions;
• a leveling table situated downstream of the projection-optical system and being tiltable relative to the Z-axis;
• a wafer-stage-position loop servo connected to the wafer stage and configured to actuate movement of the wafer stage in response to a wafer-position command;
• a leveling-table tilt-position loop servo connected to the leveling table and configured to apply a tilting torque to the leveling table in response to a leveling command;
• a control system for compensating for lateral shift of the leveling table caused by a tilt (θ) of the leveling table, the control system comprising a feed-forward loop from the leveling-table tilt-position loop servo to the wafer-stage-position loop servo, the feed-forward loop being configured to convert a torque-control signal for the leveling table to a linear-acceleration-control signal for the wafer-stage, the linear-acceleration-control signal causing the wafer stage to move laterally in a manner that compensates for the lateral shift of the leveling table accompanying a change in tilt of the leveling table;
• a reticle stage situated upstream of the projection-optical system and being movable at least in the X- and Y-directions;
• a reticle-stage-position loop servo connected to the reticle stage and being configured to actuate movement of the reticle stage in response to a reticle-position command, wherein the control system further comprises second feed-forward loop from the leveling-table tilt-position loop servo to the reticle-stage-position loop servo, the second feed-forward loop being configured to convert a positional signal for the leveling table to a position-control signal for the reticle stage, the position-control signal causing the reticle stage to move laterally to compensate, at least in part, for the lateral shift of the leveling table accompanying a change in tilt of the leveling table.