CD metrology of binary and phase shift masks using scatterometry

In this paper, we report on a Scatterometry based metrology system that provides line width and thickness measurements on binary, APSM, EPSM masks both on FCCD (final check CD) and DCCD (develop check CD), fabricated on 193nm process. Measurements were made with scatterometer in DUV to visual wavelength range. Calculation of profile information was performed by a library-based analysis software. We characterized the CD uniformity, linearity, trench depth uniformity. Results show that linearity measured from fixed-pitch, varying line/space ratio targets show good correlation to top-down CD-SEM, meanwhile linearity from wide range of different pitch generally does not correlate well and therefore post-measurement calibration is needed. Depth measurements from APSM show that scatterometer makes good correlations to AFM. The effect of optical properties of the film layers on metrology performance is discussed. The data show that Scatterometry provides a nondestructive of monitoring basic etch profile combined with relatively little time loss from CD measurement step.