Reticle optimization algorithms and optimal target design

摘要

Metrology target designs on the reticle and on the wafer, and target design and processing methods are provided. Target designs comprise coarse pitched periodic structures having fine pitched sub-elements, which vary in sub-element CD and/or height, an orthogonal periodic structure, perpendicular to the measurement direction, with an orthogonal unresolved pitch among periodically recurring bars, which provide a calibration parameter for achieving well-printed targets. Orthogonal periodic structures may be designed on the reticle and be unresolved, or be applied in cut patterns on the process layer, with relatively low sensitivity to the cut layer overlay. Designed targets may be used for overlay metrology as well as for measuring process parameters such as scanner aberrations and pitch walk.