Atomic layer deposition of transition metal chalcogenide TaSx using Ta[N(CH3)2]3[NC(CH3)3] precursor and H2S plasma

As a transition metal chalcogenide, tantalum sulfide (TaSx) is of interest for semiconductor device applications, for example, as a diffusion barrier in Cu interconnects. For deposition of ultrathin nanolayers in such demanding 3D structures, a synthesis method with optimal control is required, and therefore, an atomic layer deposition (ALD) process for TaSx was developed. ALD using (tert)-butylimidotris(dimethylamido)tantalum (Ta[N(CH3)2]3[NC(CH3)3]) as the precursor and an H2S-based plasma as the coreactant results in linear growth of TaSx films as a function of the number of cycles for all temperatures in the range 150–400 °C with growth per cycle values between 1.17±0.03 Å and 0.87±0.08 Å. Saturation of the precursor and plasma dose times, established at 300 °C, was reached after 20 and 10 s, respectively. Variation of the table temperature or the plasma composition offers the possibility to tune the film properties. At 300 °C, amorphous TaS3 films were grown, while addition of H2 to the plasma led to polycrystalline TaS2 films. The difference in sulfur content in the films correlates to a change in resistivity, where the least resistive film had the lowest S content.