Dimensional Metrology with the NIST Calibrated Atomic Force Microscope
Ronald G. Dixson, R Koning, V W. Tsai, Joseph Fu, Theodore V. Vorburger
Atomic force microscopes (AFMs) are increasingly used in the semiconductor industry as tools for submicrometer dimensional metrology. The scales of an AFM must be calibrated in order to perform accurate measurements. We have designed and developed the calibrated AFM (C-AFM) to calibrate standards using an AFM. Specifically, our primary calibrations are expected to be of combined pitch/height, or three dimensional magnification standards for AFM. The C-AFM has metrology traceable to the SI unit of length for all three axes. This is accomplished through the integration of a flexure x-y translation stage, heterodyne laser interferometers, and a z-axis piezoelectric actuator with an integrated capacitance sensor. Our first pitch measurements for an outside customer were recently completed, in which we were able to report combined expanded uncertainties (k=2) as low as 1%, including sample non-uniformity which dominates the larger uncertainties, on submicrometer pitches. Four samples were measured for this customer -- two with grid patterns and two with orthogonal linear scales. The results as reported to the customer are included in this paper. We have also recently made considerable improvements in our uncertainty budget for step height measurements. For example, we recently achieved 0.2 nm expanded uncertainty (k=2) on a 20 nm step. We also participated in the recently completed first round of the NIST linewidth correlation project, in which linewidth measurements obtained from different methods (including the C-AFM) are compared. In this paper, we will report on the current status of the C-AFM, and on our plans for further development.
Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography XIII, Bhanwar Singh, Editor
, Koning, R.
, Tsai, V.
, Fu, J.
and Vorburger, T.
Dimensional Metrology with the NIST Calibrated Atomic Force Microscope, Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography XIII, Bhanwar Singh, Editor, Santa Clara, CA
(Accessed June 3, 2023)