Broadband UV-assisted thermal annealing of low-k silicon carbonitride films using a C-rich silazane precursor

Low-k dielectric silicon carbonitride (SiC_xN_y) films are deposited by plasma-enhanced chemical vapor deposition using a carbon-rich silazane precursor, N-methyl-aza-2,2,4-trimethylsilacyclopentane (SiC₇NH₁₇), at 100 °C. The post-treatments of SiC_xN_y films are carried out by thermal annealing and a broadband UV-assisted thermal annealing (UV-annealing) at 400 °C for 5 min. Compared to the thermal annealing treatment, UV-annealing can improve both dielectric and mechanical properties of low-k SiC_xN_y films. Under thermal annealing, SiC_xN_y films show great thermal stability, but little structural change. In contrast, upon UV-annealing, most of the Si-H and N-H bonds are broken up, which induces more Si-N cross-linking and converts Si-C matrix into Si-N matrix. The ethylene bridges in Si-(CH₂)₂-Si also remain intact, but the unbridged hydrocarbons in Si-(CH₂)₂-N and Si-CH₂-CH₃ bonds decompose completely during the UV-annealing process. These account for the reduced dielectric constant to k = 3.2 from 3.6 and a 21% enhancement of Young's modulus to 7.4 GPa in the SiC_xN_y films after UV-annealing. Broadband UV-annealing shows promise as a post-treatment method for enhancing the properties of low-k dielectric barrier, SiC_xN_y films.