Energy dispersive x-ray analysis (EDS) is used for non-destructive measurement of photoresist thickness on integrated circuit geometries as small as 2 microns. The technique is based on the principle that the characteristic x-ray emission intensity from the underlying material varies with the photoresist coating thickness. Calibration curves are used to relate this intensity to the photoresist thickness. The method is applied to I. C .structures to acquire data which was inaccessable to optical methods and which previously would have required destructive SEM cross-sections. Data can be collected from any location on a wafer, making this a technique attractive for process development. Mathematical estimates of the electron-solid interactions are used to investigate the ultimate resolution of the technique. The validity of the method is demonstrated by comparison to SEM cross-sections. Both test structures and real integrated circuit device patterns are examined. The test structure results include measurements on small aluminum lines over 1 and 2 micron high steps. Real device results include resist thickness on the severe toography found on the second level metal layer in a double layer metal interconnect structure.

Date Published: 15 October 1984
PDF: 8 pages
Proc. SPIE 0480, Integrated Circuit Metrology II, (15 October 1984); doi: 10.1117/12.943043

Published in SPIE Proceedings Vol. 0480:
Integrated Circuit Metrology II
Diana Nyyssonen, Editor(s)