Influence of low-k dry etch chemistries on the properties of copper and a Ta-based diffusion barrier

In this study, the film properties of Cu and a Ta-based diffusion barrier deposited on organic polymer and SSQ-based low-k materials with subtractive porosity were investigated. Emphasis was put on the effects of exposure of the low-k materials to the dry etch plasmas prior to metal deposition. The metal film properties were influenced by the type of the dry etch plasma chemistry used and by the porosity of the low-k material. Thermal desorption spectra (TDS) obtained during annealing of these metal films revealed an increased amount of species with m/e 44, attributed to CO2, and H2O desorbing from the Cu film at high temperatures. The TDS data for the Ta film did not contain such high temperature desorption peaks for these species mentioned. Surface morphology of the Cu and Ta films observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) also showed a poor wetting of the metal films on the porous low-k materials that have been dry etch plasma treated.