Use of TRIDYN and medium energy ion scattering to calibrate an industrial arsenic plasma doping process

Abstract

Plasma doping ion implantation (PLAD) is becoming increasingly important for enabling the manufacture of advanced semiconductor devices. In this study, a VIISTA PLAD implanter was used to implant planar 300 mm Si wafers with As/7 keV from an arsine containing plasma with a total ion fluence of 1 × 1016 ions/cm2. The wafers then underwent a wet chemical clean and anneal to mimic a full industrial process flow. The effects of each process step were measured using cross-sectional TEM images, TEM/energy dispersive spectroscopy measurements, and medium energy ion scattering (MEIS). The PLAD implantation process was modeled using dynamic trim (TRIDYN), a dynamic, binary collision approximation model that accounted for the interactions between wafers and the ions and neutrals produced by the PLAD implanter. MEIS spectra were analyzed to extract elemental concentration depth profiles using POWERMEIS guided by the outputs of the TRIDYN model. The input fluxes of the TRIDYN model were calibrated such that the predicted TRIDYN and MEIS profiles were self-consistent. Combining the different analysis techniques and considering elemental concentrations alongside a TRIDYN model enabled magnitudes of ion and neutral fluxes of Si, As, and H to be proposed, and the relative importance of direct implantation and ion beam mixing during the PLAD implant to be revealed. This, in turn, led to proposals for the sources of the ion and neutral species, the importance of Si neutrals originating from the plasma chamber over those originating from the Si bulk in the “deposited” layer being of particular interest. Following the evolution of the as-implanted profiles through the wet clean and anneal steps gave insights into how the PLAD implant affected the results of the full process flow.