Method for obtaining improved feedforward data, a lithographic apparatus for carrying out the method and a device manufacturing method

A method of obtaining improved feedforward data for a feedforward control system to move a component through a setpoint profile, said setpoint profile comprising a plurality of target states of said component each to be substantially attained at one of a corresponding sequence of target times, said method comprising:

• a) moving said component with the feedforward control system according to the setpoint profile using a first set of feedforward data;
• b) measuring a state of said component at a plurality of times during said moving;
• c) comparing the measured states with corresponding target states defined by said setpoint profile to obtain a set of errors;
• d) filtering said set of errors with a non-linear filter;
• and
• e) generating improved feedforward data based on the filtered errors, said improved feedforward data being usable by said feedforward control system during a subsequent moving of said component more accurately through the setpoint profile,
• wherein said set of errors is represented by an array of data points ey(i), where 0≦i≦n, n is the number of samples in the set, said filter is represented by an amplitude-dependent filter matrix Φ(ey(i)), and step (d) corresponds to a multiplication of Φ(ey(i)) by ey(i).

A lithographic projection apparatus arranged to project a pattern from a patterning device onto a substrate, comprising:

• (a) a movable support configured to support a component;
• and
• (b) a system configured to move said movable support through a setpoint profile comprising a plurality of target states of said movable support, each to be substantially attained at one of a corresponding sequence of target times, said system comprising:
• (i) a displacement device configured to move said movable support according to said setpoint profile;
• (ii) a feedforward control system configured to control said displacement device using a first set of feedforward data;
• (iii) a measuring system configured to measure the state of said component at a plurality of times during movement of said movable support;
• (iv) a comparison device configured to compare the measured states with corresponding target states to obtain a set of errors, said set of errors being compared to a threshold to determine if the set of errors or a subset of the set of errors are above the threshold;
• (v) a dead zone non-linear filter configured to filter said set of errors if the set of errors or a subset of the set of errors are above the threshold;
• (vi) a feedforward data generating device arranged to generate modified feedforward data based on the filtered set of errors, said modified feedforward data being usable by said feedforward control system during a subsequent moving of the movable support to control said displacement device to more accurately move said movable support through the setpoint profile, said system being configured to iteratively use the most recently obtained modified feedforward data instead of the first set of feedforward data to determine improved feedforward data until it is determined that the set of errors or the subset of the set of errors obtained by the comparison device are below the threshold.

A device manufacturing method, comprising:

• (a) projecting a pattern from a patterning device onto a substrate;
• (b) supporting a component with a movable support;
• (c) moving the movable support with a feedforward control system through a setpoint profile using a first set of feedforward data, said setpoint profile comprising a plurality of target states of said movable support, each to be substantially attained at one of a corresponding sequence of target times;
• (d) measuring a state of the component at a plurality of times during said moving;
• (e) comparing the measured states with corresponding target states to obtain a set of errors;
• (f) comparing the set of errors to a threshold and determining if the set of errors or a subset of the set of errors are above the threshold;
• (g) filtering the set of errors with a dead zone non-linear filter if the set of errors or a subset of the set of errors are above the threshold;
• (h) generating improved feedforward data based on the filtered set of errors;
• (i) moving the movable support through the setpoint profile using the improved feedforward data;
• (j) repeating steps (c) to (h) iteratively, using the most recently obtained improved feedforward data instead of the first set of feedforward data, until it is determined that the set of errors or subset of the set of errors obtained in step (e) are below the threshold.