Vacuum table and method for clamping warped substrates

A method of clamping a substrate to a vacuum table, the method comprising:

• positioning the substrate on a top surface of the vacuum table, the top surface being provided with at least two pressure zones, each pressure zone connected to a respective vacuum connector for providing a reduced pressure, at least one of the pressure zones being provided with grooves extending like fingers from a corresponding circular groove in radial direction across the top surface, and wherein at least one of the fingers has at least one end unconnected to any other groove;
• applying a first reduced pressure to a first pressure zone until a first threshold has been met indicating that the substrate is clamped to the top surface within the first pressure zone;
• and
• applying a second reduced pressure to a second pressure zone until a second threshold has been met indicating that the substrate is clamped to the top surface within the second pressure zone.