Properties of sputtered Cr–O and reactively sputtered Cr–N–O as passivation layers against copper oxidation

Abstract

Passivation layers of 200 Å sputtered Cr–O as well as reactive sputtered Cr–N–O were studied with respect to the passivation capability against thermal oxidation of Cu in flowing nitrogen and flowing oxygen ambients. In a flowing N2 ambient, both Cr–O and Cr–N–O passivation layers were able to prohibit oxidation of Cu at temperatures up to 700 °C. In an O2 ambient, the passivation capability of Cr–N–O layer was found to be 500 °C, which is 150 °C higher than that of Cr–O layer. The superiority of the passivation capability of the Cr–N–O layer is presumably due to decoration of the surface defects and grain boundaries with nitrogen, which provide fast paths for oxygen and copper diffusion.