The effect of plasma damage on the material composition and electrical performance of different generations of SiOC(H) low k films

The degradation of SiOC(H) low-k films upon plasma treatments has been investigated. Different generations of SiOC(H) low-k dielectrics (k=3.0 and k=2.6) were used. The low-k materials have been exposed to N /sub 2/O, NH/sub 3/, O/sub 2/, H/sub 2/, He, Ar and N/sub 2/ based plasmas, representing the most commonly-used plasmas during interconnect integration. Some of the experiment points were also carried out on a highly porous SiOC material (k=2.3), for additional comparison. For all plasma-treated samples, an increase in k-value and decrease in breakdown voltage was observed. These observations could be attributed to chemical degradation, in particular to carbon depletion and OH-bond formation. The latter leads to moisture adsorption, which was confirmed by contact angle measurements and FTIR spectra. The N/sub 2/O plasma treatment was found Io be the most aggressive for all low-k dielectrics studied. It drastically increases the k-value and the leakage current and results in complete carbon removal on the top-surface. This effect is most pronounced on the most porous material. On the other hand, an in-situ helium plasma shortly after low-k deposition enhances the resistance to chemical degradation upon exposure to other plasmas, even for the most aggressive ones. For the argon and reactive pre-clean plasmas, only small compositional changes were observed. In conclusion, it can be said that not only the plasma treatments have to be tuned in accordance with the low k integration requirements, but also attention has to be paid to limit moisture absorption during integration.