SIMULTANEOUS MEASUREMENT OF MULTIPLE OVERLAY ERRORS USING DIFFRACTION BASED OVERLAY

摘要

A plurality of overlay errors in a structure is determined using a target that includes a plurality of diffraction based overlay pads. Each diffraction based overlay pad has the same number of periodic patterns as the structure under test. Additionally, each diffraction based overlay pad includes a programmed shift between each pair of periodic patterns. The pads are illuminated and the resulting light is detected and used to simultaneously determine the plurality of overlay errors in the structure based on the programmed shifts. The overlay errors may be determined using a subset of elements of the Mueller matrix or by using the resulting spectra from the pads.

主权项

1. A method of simultaneously measuring n overlay errors in a structure with a number m of periodic patterns, where n≧2 and m=n+1, the method comprising:
illuminating a target with incident radiation, the target having a plurality of diffraction based overlay pads, each diffraction based overlay pad having the same number m of periodic patterns as the structure and wherein each diffraction based overlay pad includes a programmed shift between each pair of periodic patterns; detecting radiation from the target after the incident radiation interacts with the plurality of diffraction based pads; and using the detected radiation from each of the plurality of diffraction based overlay pads to simultaneously determine the n overlay errors based on the programmed shift between each pair of periodic patterns.