On-mask CD and overlay test structures for alternating aperture phase shift lithography

Atomic force and scanning electron microscope measurements of electrical structures for the measurement of critical dimension on alternating aperture phase shifting masks are presented. These have been used to explain anomalies that were observed in previously reported work. In addition, the development of a new capacitance test structure which can measure the alignment between the chrome blocking layer and the phase shifting areas etched into the quartz mask substrate is presented. A progressional offset array technique enables the use of this test structure without calibration and this is demonstrated by simulation and measurements.