Patent ID: 6977135

Claim:
An apparatus, comprising: a thin layer of material for attaching to a semiconductor wafer surface, the thin layer having a first surface and a second surface substantially parallel to the first surface, and wherein a first light beam of wavelength λ and a second light beam of wavelength λ entering the thin layer of material have different transmission coefficients when propagating through the thin layer of material in the same propagation direction, the propagation direction having an angle α between 35 degrees and 85 degrees with respect to the normal to the first surface, wherein the first light beam is linearly polarized parallel with the first surface and the second light beam has polarization orthogonal to the first light beam, and wherein the first light beam exposes an unexposed photoresist material attached to the semiconductor wafer surface with sufficient dose for forming a pattern on the semiconductor wafer, and wherein the second light beam exposes the unexposed photoresist material with insufficient dose for forming a pattern on the semiconductor wafer.