System for controlling a dual mover assembly for an exposure apparatus

A precision assembly for moving a device along a movement axis, the precision assembly comprising:

• a stage that retains the device;
• a mover assembly coupled to the stage, the mover assembly including a first mover that moves the stage along the movement axis and a second mover that moves the device along the movement axis, the second mover being rigidly coupled to the first mover so that movement of the first mover results in movement of the second mover;
• a measurement system that measures a measured position along the movement axis;
• and
• a control system that controls the mover assembly utilizing the measured position, wherein the control of the first mover results in a first mover quantization error and the control of the second mover results in a second mover quantization error, and wherein the control system utilizes a quantization error feedforward loop that includes utilizing the first mover quantization error in the control of the second mover.

A precision assembly for moving a device along a movement axis, the precision assembly comprising:

• a stage that retains the device;
• a mover assembly coupled to the stage, the mover assembly including a coarse first mover that moves the stage along the movement axis and a fine second mover that moves the device along the movement axis, wherein the second mover is stacked on top of the first mover and the output of the mover assembly along the movement axis is equal to the sum of the movement of the first mover and the movement of the second mover;
• a measurement system that measures a measured position along the movement axis, wherein only measurement signal is provided for the control of the first mover and the second mover;
• and
• a control system that controls the mover assembly utilizing the measured position, the control system utilizing a first mover path to control the first mover, a second mover path to control the second mover, and a decoupled path that effectively decouples the control of the first mover from the control of the second mover by directing a decoupled gain derived at least in part from the properties of the second mover to the first mover path, the control system having an open-loop transfer function GOL that is expressed as follows:
• GOL=F K1P1+F K2P2+F K2CK1P1
• wherein (i) “F” represents a filter in the control system that reduces noise, (ii) “K1” represents a controller in the control system for the first mover, (iii) “P1” represents the hardware of the first mover, (iv) “C” represents decoupled gain, (v) “K2” represents a controller in the control system for the second mover, and (vi) “P2” represents the hardware of the second mover.