Thermal stability of low dielectric constant porous silica films

Thermal stability of porous-silica-based low dielectric constant, k , material deposited by chemical vapor deposition has been investigated in a wide temperature range. The films as-deposited and after heat treatments up to 600 ° C have Si 1 O 1.6 C 1.4 H 2.3 composition, permittivity k ≈ 2.8 , and porosity h ≈ 0.25 . A skeleton of silicon dioxide and empty pores justifies the permittivity and porosity values. Permeation experiments with deuterated water vapor indicate that pores are interconnected. At 700 ° C , the film has Si 1 O 1.6 C 1.4 H 1.4 composition, k ≈ 2.4 , and h ≈ 0.21 . Bonds with lower polarizability could be responsible for the decrease of k . Above 800 ° C , carbon segregation and nanoclusters formation occur.