Patent ID: 8248578
Filing Date: 2012-08-21
Classification: G03F

Abstract:
1. A projection exposure method comprising: generating primary radiation having a center wavelength λ; guiding the primary radiation through an illumination system along an illumination path to generate illumination radiation incident in an illumination field on a mask bearing a pattern; projecting an image of the pattern onto an image field on a radiation-sensitive substrate through a projection objective with projection radiation along a projection path; varying the center wavelength within a wavelength variation range Δλ having a lower limit λ wherein, within the wavelength variation range, a specific absorption coefficient k(λ) of at least one gaseous absorbent species, selected from the group consisting of oxygen (O controlling a concentration of the absorbent species within the gas-filled space such that an overall absorption variation effected by the absorbent species for all rays running along differing ray paths towards the image field is maintained below a predetermined absorption variation threshold value.