Approach to CD SEM metrology utilizing the full waveform signal

Critical dimension scanning electron microscope metrology attempts to relate the electron intensity signal of the SEM tool to the actual size and shape of the feature measured. This intensity signal is frequently visualized and manipulated as a profile or waveform. A measurement of the size of a feature involves the extraction of edge positions from this waveform. Traditional line width metrology ignores much of the effect of the variation of the shape of che feature measured on the waveform to be analyzed. Deducing the shape of a feature from the waveform requires interpretation of the shape of the waveform. Analysis of the CD SEM intensity signal allows one to not only measure the specific width of a feature but it also allows a better estimate as to the actual shape of the feature. Both photo and etch production process drift can be monitored, resulting in improved process and quality control before gross failures in metrology occur.