Spin-coated and PECVD low dielectric constant porous organosilicate films studied by 1D and 2D solid-state NMR

Abstract

In the research field of the sub-65 nm semiconductor industry, organosilicate SiOCH films with low dielectric constant (k < 2.4) need to be developed in order to improve the performance of integrated circuits [International Roadmap for Semiconductors (ITRS), San Jose, CA, 2004]. One way to produce SiOCH films of low dielectric constant is to introduce pores into the film. This is usually obtained in two steps. Firstly, co-deposition of a matrix precursor, with a sacrificial organic porogen, either by plasma enhanced chemical vapor deposition (PECVD) or spin-coating. Secondly, application of a specific thermal treatment to remove the porogen and create the porosity. This last step can be improved by adding to the thermal process a super-critical CO₂ treatment, an UV irradiation or an electronic bombardment (e-beam). In this study, the two deposition processes as well as the various treatments applied to eliminate the porogens were evaluated and compared using high-resolution solid-state NMR. For this purpose, hybrid (containing porogens) and porous films were extensively characterized on the basis of their ¹H, ¹³C and ²⁹Si high-resolution NMR spectra. Information was obtained concerning the crosslinking of the Si skeleton. Spectral features could be correlated to the processes used. Isotropic chemical shift analyses and 2D correlation NMR experiments were used to show the existence and nature of the interactions between the matrix precursor and the organic porogen.