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Influence of TiNx sublayer on determination of structural characteristics of dielectric and conducting layers of crystals of integrated circuits

Keywords:

S.A. Sokolov ‒ Post-graduate Student, Lomonosov Moscow State University
E-mail:sokolovsa48@gmail.com
R.A. Milovanov ‒ Ph.D. (Eng.), Head of Department, Moscow Technological University (MIREA)
E-mail: milovanov_r@inbox.ru
L.N. Sidorov ‒ Dr.Sc. (Chem.), Professor, Lomonosov Moscow State University
E-mail: sidorov@thermo.chem.msu.ru
V.I. Shishkin ‒ Ph.D. (Chem.), Associate Professor, Moscow Technological University (MIREA)
E-mail: shishkin@mirea.ru


The influence of the titanium nitride TiNx sublayer on the determination of structural characteristics of dielectric (for example, SiO2) and conductive (for example Al) layers of integrated circuit (IC) dice by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) are described. The methods based on SEM and EDXA make it possible determination the composition of the analyzed film, and due to the direct dependence of the region of generation of the characteristic X-ray radiation on the density and thickness of the analyzed film, it is possible to determine all the basic structural characteristics of the film under analysis. It is suggested to use the modified Anderson-Hessler equation for approximation the experimental results. The modeling of the region of generation of the characteristic X-ray radiation by the Monte Carlo method was used for determination the values of the constants K1 and K2 in the modified Anderson-Hessler equation. A characteristic feature of the region of generation of the characteristic X-ray radiation in the SiO2/TiNx/Al and Al/TiNx/SiO2 structures was revealed based on the simulation results, as compared to the structures SiO2/Al and Al/SiO2  the presence of regions with an abnormally high intensity of the characteristic X-ray radiation. The presence of such regions is associated with an increase in the fraction of backscattered electrons from the TiNx layer, which has a significantly higher density (5.40 g/cm3 for TiNx compared to 2.00 and 2.70 g/cm3 for SiO2 and Al, respectively). Comparison of the obtained experimental calibration dependences for the SiO2/TiNx/Al and Al/TiNx/SiO2 structures with the results of the simulation of the region of generation of the characteristic X-ray radiation by the Monte Carlo method showed that the presence of the undetectable sublayer from titanium nitride TiNx leads to a significant change in the coefficients K1 and K2 in the modified Anderson-Hessler equation. The values of the SiO2 and Al densities determined from the experimental data were 1.96 and 2.55 g/cm3, respectively. Calculated on the basis of the calibration direct values of the thicknesses of the SiO2 and Al layers on the IC crystal differ from the actual obtained values by no more than 15 %.

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June 24, 2020
May 29, 2020

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