Round‐robin test of medium‐energy ion scattering for quantitative depth profiling of ultrathin HfO₂/SiO₂/Si films

Abstract

Medium‐energy ion scattering (MEIS) has been used for quantitative depth profiling with single atomic layer resolution to determine the composition, thickness, and interface structure of ultrathin films and nanoparticles. To assure the consistency of the MEIS analysis, an international round‐robin test (RRT) with nominally 1‐, 3‐, 5‐, and 7‐nm thick HfO2 films was conducted among 12 institutions. The measurements were performed at each participating laboratory under their own conditions, and the collected data were analyzed. For the data analysis, the Moliere potential, the stopping and range of ions in matter (SRIM) 95 and new fitted electronic stopping power and the Chu straggling were used. For analyzing the MEIS data from the magnetic sector and electrostatic analyzers, the neutralization corrections of Marion and Young for 100‐keV H+ and He+ ions and of Armstrong for 400‐ to 500‐keV He+ ions were used. The standard deviations were 5.3% for the composition, 15.3% for the thickness, and 13.3% for the Hf content, and they were improved to 7.3%, 4.5%, and 7.0% by using refitted electronic stopping powers based on the experimental data. Hence, this study suggests that correct electronic stopping powers are critical for quantitative MEIS analysis.

Determination of Dimension and Conformal Arsenic Doping Profile of a Fin Field Effect Transistors by Time-of-Flight Medium Energy Ion Scattering

“…The error also could arise from the incorrect scattering cross sections and multiple scattering effect of the MEIS analysis or the matrix effect of SIMS. In this report, a Moliere potential was used for calculating the scattering cross section, which is one of the widely used screened potential in MEIS analysis , including the ISO standard . Nevertheless, the cross section by this potential could have some errors within standard deviation, resulting in some difference in quantity.…”

“…The Chu model was used to account for straggling. This follows the analysis process used at the round robin test (RRT) of HfO 2 ultrathin film for developing an ISO standard for quantitative MEIS analysis with an addition that we used a 3D model for the FinFETs. The 3D model consisted of voxels instead of the uniform layers used in planar samples, which were described by the number fraction of elements present, density, stopping power, and straggling information.…”

Traceable thickness measurement of ultra-thin HfO2 films by medium-energy ion scattering spectroscopy

“…In the analysis, the Andersen cross section [18] and Chu straggling [19] were used. For the stopping power, fitted values based on the experimental data [20] were used following recent MEIS round robin test results [21]. The simulations took into account the solid angle of the detector, and the kinematic broadening of each element was reliably applied.…”

Recent advances in MEIS

“…With the development of diverse MEIS instruments as well as the increased number of MEIS systems being in use in various research areas, questions have been raised as to whether MEIS analysis results are consistent with each other and reliable as we expected. To assess the reliability of MEIS analysis results, recently, an international round robin test (RRT) of MEIS in quantitative depth profiling of ultrathin HfO 2 /SiO 2 /Si films was performed involving most of the major MEIS users and experts with various MEIS instruments including TEA, magnetic, and TOF energy analyzers . According to the recent report on the international MEIS RRT, MEIS analysis results can be consistent within 8% with the use of corrected electronic stopping power based on experimental data from the IAEA database .…”

“…In addition to the system complexity, MEIS spectra can be used for rough but reliable composition estimation, but for quantitative compositional depth profiling, extensive repeated simulations are required to fit the obtained MEIS spectra. For most of the present MEIS analysis conditions using He ions, there seems to be significant contribution from multiple scattering . Programs to simulate multiple scattering such as PowerMEIS, TRBS, and Corteo are currently available, but their automatic use is still limited.…”