A Comparison of Thickness Values for Very Thin SiO2 Films by Using Ellipsometric, Capacitance-Voltage and HRTEM Measurements
James R. Ehrstein, Curt A. Richter, Deane Chandler-Horowitz, Eric M. Vogel, Chadwin Young, Shweta Shah, Dennis Maher, Brendan C. Foran, Alain C. Diebold
Abstract. A comparison study of very thin SiO2 film thickness values obtained from the three dominant measure-ment techniques used in the Integrated Circuit industry: ellipsometry, capacitance-voltage (C-V) measurements and transmission electron microscopy has been completed. This work is directed at evaluating the metrology capabilities that might support the development and certification of Reference Materials for very thin dielectric films. Particular care was taken in the design of the sample set to allow redundancy and enable estimates of oxide layer consistency. We used a variety of models of the film structure to analyze ellipsometry measurements, and used three different quantum-mechanical based algorithms to account for quantized states in the substrate and depletion effects in the polysilicon capacitor-electrode to analyze the C-V results. TEM measurements of two capacitor cross-sections were conducted by both phase contrast high resolution (HRTEM) and atomic number (Z) contrast high-angle annular darkfield scanning transmission electron microscopy (STEM). We found a range of thickness values with each of the methods, but there was an overlap of values among the three techniques. HRTEM and STEM values showed less consistency between wafers than did the C-V data for the capacitors used, and seemed to be influenced more by lo-cal variations such as interface non-uniformities. We present sources of variation and estimates of the primary com-ponents of uncertainty for the measurements employed and discuss the implications of these results for obtaining consistent and unified film thickness metrology and for possible reference standards
Journal of the Electrochemical Society
gate dielectrics, reference materials, silicon dioxide, thin film metrology
, Richter, C.
, Chandler-Horowitz, D.
, Vogel, E.
, Young, C.
, Shah, S.
, Maher, D.
, Foran, B.
and Diebold, A.
A Comparison of Thickness Values for Very Thin SiO2 Films by Using Ellipsometric, Capacitance-Voltage and HRTEM Measurements, Journal of the Electrochemical Society
(Accessed February 21, 2024)