High-resolution energy-dispersive x-ray spectroscopic analysis of ultrathin ion diffusion barriers using microcalorimetry

Abstract

The advent of microcalorimetry for x-ray detectors holds the promise for high-resolution compositional microanalysis applicable to nanometer-scale devices and structures. To demonstrate this capability, microcalorimeter-based energy dispersive x-ray spectroscopy (EDS) has been used to analyze ultrathin TaSiN films under development as ion diffusion barriers in sub-0.1 μm integrated circuit interconnect structures. Microanalysis of TaSiN films has been carried out using microcalorimetry-based EDS for comparison with similar data acquired using conventional Si(Li) EDS detectors. The elimination of elemental peak overlaps provided by the improved energy resolution of the microcalorimeter x-ray detector is demonstrated for TaSiN EDS spectra from films as thin as 3.5 nm. In addition, variation of the electron probe beam energy is examined to reduce the x-ray generation volume relative to the TaSiN film thickness. It is shown that microcalorimetery-based EDS is a potentially powerful technique for the characterization/metrology of ultrathin barrier films used for microelectronics, with x-ray energy-resolving capabilities similar to techniques such as wavelength dispersive spectroscopy.