Dopant characterization round-robin study performed on two-dimensional test structures fabricated at Texas Instruments

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Abstract
The lack of a two-dimensional (2D) dopant standard and hence a priori knowledge of dopant distribution makes it impossible to unambiguously judge accuracy of any experimental or theoretical effort to characterize silicon doping in two-dimensions. Recently a strong progress has been made in quantitative scanning capacitance microscopy (SCM), scanning spreading resistance microscopy (SSRM), secondary electron (SE) and transmission electron microscopy (TEM) doping profiling. Several research groups have claimed an ability of quantitative 2D dopant characterization. A round-robin study involving various analytical techniques and comprehensive numerical simulations should help to evaluate an accuracy of available quantitative techniques and set some helpful standard for further development. We report on a world-wide round-robin study performed on CMOS 2D test structures fabricated at Texas Instruments (TI). Seven research groups, which represent an advanced SCM, SSRM and TEM dopant profiling, participated in the study. Related process information and 1D dopant profiles measured by secondary ion mass-spectroscopy (SIMS) were released to the sites. Process simulator TSUPREM4 tuned using SIMS and inverse electrical modeling was employed to simulate 2D dopant distributions for both PMOS and NMOS test structures. Method-to-method variations in pn-junction position are noticeably higher than 10 nm, the spatial resolution requested by TCAD. The statistical scatter in pn-junction position varies from 10 to 30%. Although interpretation of the data is still a challenging problem, controlled and reproducible surface preparation is an important step, which may help to reduce the observed diversity of dopant characterization results. A round-robin study on test structure capable of electrical characterization should link round-robin results to device performance and hence is necessary.

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