Material issues for nanoporous ultra low-k dielectrics

Using the molecularly designed porogen (pore generating agent) approach, novel nanoporous low-k materials with improved mechanical properties have been achieved based on poly(methylsilsesquioxane), PMSSQ, structure. Two different methods, microphase separation system and grafted porogen system, were adopted to realize nonporous ultra low-k dielectrics with superior mechanical properties. We found that the behavior of dielectric constant as well as thin film modulus depends on the molecular structure of a porogen. Within the decomposition temperature windows of grafted porogens, a low-k material with k < 2.2 and Young's modulus > 6 Gpa was achieved. These results indicate that it is possible to design and fabricate nanoporous thin films with balanced low dielectric constant and robust mechanical properties, which are highly desired for microelectronic industry.