METHODS FOR CONTROLLING LITHOGRAPHIC APPARATUS, LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD

摘要

A lithographic apparatus uses a height sensor (LS) to obtain height sensor data (722) representing a topographical variation across a substrate (718). The height sensor data is used (730) to control focusing of a device pattern at multiple locations across the substrate. A controller identifies one or more first areas (A) where height sensor data is judged to be reliable and one or more second areas (B, C) where the height sensor data is judged to be less reliable. Substitute height data is calculated (724) for the second areas using height sensor data for the first areas together with prior knowledge (712) of expected device-specific topography. The focusing of the lithographic apparatus is controlled using a combination of the height data from the sensor and the substitute height data.