FOCUS MEASUREMENTS USING SCATTEROMETRY METROLOGY

摘要

Target designs and methods are provided, which relate to periodic structures having elements recurring with a first pitch in a first direction. The elements are periodic with a second pitch along a second direction that is perpendicular to the first direction and are characterized in the second direction by alternating, focus-sensitive and focus-insensitive patterns with the second pitch. In the produced targets, the first pitch may be about the device pitch and the second pitch may be several times larger. The first, focus-insensitive pattern may be produced to yield a first critical dimension and the second, focus-sensitive pattern may be produced to yield a second critical dimension that may be equal to the first critical dimension only when specified focus requirements are satisfied, or provide scatterometry measurements of zeroth as well as first diffraction orders, based on the longer pitch along the perpendicular direction.