Patent ID: 8098364
Filing Date: 2012-01-17
Classification: G03F

Abstract:
1. An apparatus, comprising: a radiation source, operable to provide a radiation beam to expose a semiconductor substrate; a level sensor for identifying a height of a feature on the substrate and providing an indication of a first height and an indication of a second height to a controller, wherein the first and second height are in a single exposure field of the substrate; a variable focusing device, wherein the variable focusing device comprises a membrane and is configured to provide a first focus length when a first electric field is applied to the membrane and provide a second focus length with a second electric field is applied to the membrane; the controller operably coupled to the variable focusing device and configured to control the variable focusing device by providing both the first electric field and the second electric field separately while exposing a single exposure field of the substrate, during a step-and-scan process, wherein the first electric field is provided in response to the indication of the first height from the level sensor and the second electric field is provided in response to the indication of the second height from the level sensor; and a substrate stage providing for positioning the semiconductor substrate for a step-and-scan process.