Patent ID: 8411356
Filing Date: 2013-04-02
Classification: G02B,G03F

Abstract:
1. A projection objective having an object surface and an image surface, the projection objective comprising: a plurality of optical elements arranged along an optical axis and configured so that during operation the projection objective images a pattern arranged in the object surface onto the image surface, the optical elements comprising: a concave mirror; a first deflecting mirror tilted relative to the optical axis by a first tilt angle, t a second deflecting mirror tilted relative to the optical axis by a second tilt angle, t wherein for a pattern comprising a grating having a line width of 45 nm and a pitch, p, the projection objective images the pattern to the image surface such that for a first orientation of the pattern and a second orientation of the pattern a difference, ΔHV, between the imaged line width is 1.2 nm or less for 100 nm<p<1,000 nm, where the grating lines in the first orientation are orthogonal to the grating lines in the second orientation.