Optical digital profilometry (ODP) feasibility studies for CD control in lithography applications

Abstract

A series of experiments were performed to determine if Tokyo Electron's (TEL) Optical Digital Profilometry (ODP) scatterometry technology could meet the requirements for CD (Critical Dimension) control in lithography applications. ODP technology, using broadband optical spectra taken from grating structures, is non-destructive, and in addition to CD, provides sidewall angle (SWA), profile and film thickness information in a single measurement. ODP's output was compared to CD-SEM (Critical Dimension-Scanning Electron Microscopy) to develop the correlation of different metrology techniques. ODP was able to demonstrate excellent correlation to CD-SEM and provide robust uniformity measurement with high repeatability. ODP measurements were also used to optimize within-wafer CD uniformity by controlling the scanner process parameters. The high resolution of CD and SWA data taken by ODP demonstrated high sensitivity to scanner process control and a significant reduction in CD variation. From the experimental results, the ODP technology was well qualified for CD control in lithography applications.