Reactively sputtered TiN as a diffusion barrier between Cu and Si

Abstract

The properties of 100-nm-thick Ti55N45 and Ti45N55 films as diffusion barriers between silicon substrates and thin Cu films were studied by sheet resistance measurements, Rutherford backscattering spectrometry, Auger electron spectroscopy, secondary-ion mass spectrometry, transmission electron microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffractometry, and diode leakage current measurements. For unpatterned Si/titanium nitride/Cu samples, all the layers were intact and there was no indication of interdiffusion by conventional depth profiling techniques up to 700 °C for Ti55N45 and 900 °C for Ti45N55 after 30 s rapid thermal anneal in N2, respectively. Leakage current measurements did not show deterioration of diode junction (with junction depth of 0.25 and 0.30 μm) up to 650 °C for Ti55N45 and 800 °C for Ti45N55. The improvement in failure temperature of the N-rich Ti45N55 diffusion barrier is a result of the lower defect density and a more stable feature furnished by nitrogen stuffed at the defects.