Lithographic apparatus and device manufacturing method

Abstract

A method and apparatus make use of data representing changes in wavelength of a radiation source to provide control of focal plane position or to provide correction of sensor data. In the first aspect, the wavelength variation data is provided to control systems that control focus by moving apparatus components including, for example, the mask table, the substrate table or optical elements of the projection optical system. In the second aspect, variation data is used in correcting, e.g., focal plane position data measured by an inboard sensor, such as a transmitted image sensor. The two aspects may be combined in a single apparatus or may be used separately.

1 . A lithographic projection apparatus comprising:
 an illumination system configured to condition a radiation beam;   a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;   a substrate table constructed to hold a substrate;   a projection system configured to project the patterned radiation beam onto a target portion of the substrate;   a wavelength sensor, constructed and arranged to measure a wavelength variation of the radiation beam;   an inboard sensor system configured to determine an operating property of the lithographic apparatus; and   a processor coupled to the inboard sensor system and configured to receive wavelength variation data from the wavelength sensor.   
   
   
       2 . A lithographic projection apparatus according to  claim 1 , wherein the processor is configured to perform at least one of:
 correcting sensor operation in real time and   post-processing data collected from the wavelength sensor and the inboard sensor.   
   
   
       3 . A lithographic projection apparatus according to  claim 2 , wherein the inboard sensor is a transmitted image sensor (TIS). 
   
   
       4 . A lithographic projection apparatus according to  claim 3 , wherein the TIS is configured to perform a vertical scan and a horizontal scan, and wherein the processor is configured to apply a curve fitting procedure used to determine a peak position based on radiation intensity data collected during the horizontal scan. 
   
   
       5 . A lithographic projection apparatus according to  claim 4 , wherein the wavelength variation data corresponds to variation of a position of a focal plane over a series of radiation pulses, and wherein the processor is configured to apply the wavelength variation data to modify the curve fitting procedure, wherein determining the peak position is improved. 
   
   
       6 . A lithographic projection apparatus according to  claim 2 , wherein the inboard sensor is an integrated lens interferometer at scanner (ILIAS) that is configured to measure lens aberration of the lithographic projection apparatus.