As the critical dimensions of integrated circuit features decrease toward 0.18 um, feature width measurements with nanometer level accuracy will become increasingly important to the semiconductor processing industry. Atomic force microscopy (AFM) offers the promise of being able to perform such measurements. The apparent width of a feature in an AFM image is generally least affected by probe geometry near the top of the feature. Therefore, we have initially focused on this type measurement, which we call the top width. A sample of preferentially etched lines in Si was prepared for our top width measurement. The NIST calibrated atomic force microscope (C-AFM), an AFM with metrology traceable to the wavelength of light in all three axes, was used for this experiment. To achieve the smallest possible uncertainties, it is necessary to characterize the geometry of the tip and to correct the measurements of top width for the finite size of the probe. We used samples of mica with nanometer sized colloidal particles deposited on them to obtain these characterizations, and thus determined the corrected top width of the lines on the Si sample. Comparisons of these results with cross-sectional TEM measurements yielded good with uncertainties below the level of 30 nm (2sd).
Proceedings Title: Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography X, Susan K. Jones, Editor
Conference Dates: March 11, 1996
Conference Location: Santa Clara, CA
Conference Title: Scanning Probe Metrology
Pub Type: Conferences
AFM, CD, metrology, SPM, standards, tip characterization