Characterization and Integration Performance of Methyl Silsesquioxane-Based Nano Porous Low-k Dielectric Films

We evaluated three kinds of methyl silsesquioxane-based porous spin-on materials with target k values at or below 2.25, prepared under ideal baking and curing conditions. Analysis was carried out to determine the thickness, refractive index, uniformity, chemical signature, k value and mechanical properties (hardness and modulus) of the prepared films. In order to improve the adhesion at the chemical vapor deposited capping layer and porous low-k film interface, plasma treatments were utilized, and modified edge lift-off and chemical mechanical polishing tests were performed to confirm its effectiveness. 1LM integration tests were also carried out to determine metal line resistance, leakage current and breakdown field strength. While the metal line resistance and leakage characteristics were similar, the breakdown field strengths of low k dielectrics were higher than those of nano-porous low-k dielectrics. The evaluation of two kinds of methyl silsesquioxane-based porous low-k dielectrics were achieved with regards to unit processes such as spin coating, etch and chemical mechanical processing, and integration. Adhesion between the porous low-k films and the capping layer was improved by applying CO2 plasma treatment on the low-k material surface before deposition of the capping layer.