Enhanced process control of pitch split double patterning by use of CD-SEM critical dimension uniformity and local overlay metrics

A Critical Dimension-Scanning Electron Microscopy (CD-SEM) technique for determination of both the CD width and the local overlay between individual pitch split layer 1 and layer 2 is employed for measurement on electrical device test structures and nearby in-die metrology sites. Measured overlay correlation studies by varying radial distances of in-die overlay metrology sites to the electrical test structures within the field show distance threshold effects. The lack of overlay vector correlation above a distance threshold is confirmed by examining the correlation of the electrically measured capacitance difference between the pitch split layers and the measured overlay at different in-die site locations. This methodology is applied to examine pitch split process improvements.