Enhancing the reliability of n⁺-p junction diodes using plasma treated tantalum barrier film

The properties of Ta barrier films treated with various plasma nitridations have been investigated by Cu/barrier/Si. An amorphous layer is formed on Ta barrier film after plasma treatments. The thickness of the amorphous layer is about 3 nm. Plasma treated Ta films possess better barrier performance than sputtered Ta and TaN films. It is attributed to the formation of a new amorphous layer on Ta surface after the plasma treatment. Cu/Ta(N,H)/Ta (10 nm)/Si remained stable after annealing at 750 °C. Ta(N,H)/Ta possesses the best thermal stability and excellent electrical properties. Cu/Ta/n⁺-p and Cu/Ta(N,O)/Ta/n⁺-p diodes resulted in large reverse-bias junction leakage current after annealing at 500 °C and 600 °C, respectively. On the other hand, Ta(N,H)/Ta and Ta(N)/Ta diffusion barriers improve the thermal stability of junction diodes to 650 °C. Ta(N,H)/Ta barrier film possesses lowest resistivity among Ta, Ta(N,O)/Ta, and Ta(N)/Ta films. Hydrogen plays an important role in enhancement of barrier properties. It is believed that hydrogen not only induces amorphization on Ta, but also eliminates the oxygen in the film. It is believed that the enhancement of ability against the copper diffusion is due to the combined effects of the hydrogen reaction and nitridation.