Phase-Shift Reticle for Characterizing a Beam

摘要

Methods and apparatus for characterizing a beam parameter associated with an electromagnetic beam of a light source. The light source exposes a phase-shifted target through a set of focal distances relative to a focal plane of a substrate. At each focal distance of the set, registration values are measured and used to determine one or more registration slopes as a function of focal distance. The registration slopes are compared with baseline registration slopes to characterize the current relative state of the beam parameter in question. Beam parameters that may be characterized in this manner include degree of polarization and polarization rotation relative to an initial polarization direction. Phase shift test patterns advantageously used for beam characterization are described.

主权项

1. A photomask structure for characterizing a beam parameter of an electromagnetic beam, the electromagnetic beam characterized by a wavelength, the photomask structure comprising:
a. a substrate, having a planar surface, substantially transparent to the electromagnetic beam, and having a characteristic optical depth at the wavelength of the electromagnetic beam; and b. a plurality of linear segments of material opaque to the electromagnetic beam formed into a plurality of polygons upon the planar surface of the substrate, wherein each of the plurality of polygons encloses an enclosed region having an enclosed optical depth, different from the characteristic optical depth of the substrate, by a fraction less than one wavelength of the electromagnetic beam; and wherein any intersection, between closed polygons enclosing two enclosed regions characterized by an identical enclosed optical depth, occurs at no more than two points.