US Patent 7276328 Lithography mask utilizing asymmetric light source

A method of reflective lithography includes directing an asymmetric radiation (light) beam onto a reticle of a reflective lithography system. The asymmetry in the shape of the radiation beam may be used to compensate for a non-zero (non-normal) angle of incidence of the incident radiation. The radiation source shape may be configured to produce a substantially-symmetric output from the reticle. The shape of the radiation source may be configurable by any of a variety of suitable methods, for example by use of a configurable reflective device such as a fly's eye mirror, or by use of one or more suitable mirrors, lenses, and/or slits.