Patent ID: 8520186

Claim:
A method of controlling a spectral property of a light beam, the method comprising: directing a light beam generated by an optical source to a lithography exposure apparatus configured to create a pattern on a wafer; receiving information representative of a spectral property of the light beam from one or more of the optical source and a beam analysis module in the path of the directed light beam; receiving information representative of an optical imaging condition relating to an optical property of one or more components within the lithography exposure apparatus from the lithography exposure apparatus; approximating the spectrum of the light beam by calculating a metric that includes both the received spectral property information and the received optical imaging condition information; estimating a characteristic value of the light beam based on the calculated metric; determining whether the estimated light beam characteristic value matches a target light beam characteristic value; and if it is determined that the estimated light beam characteristic value does not match the target light beam characteristic value, adjusting the spectral property of the light beam.