Effects of High-Temperature Porogens on Materials Properties of Novel 2-Pahse Low-k Dielectrics

A solid-first scheme was employed for making ultra low-k materials (k < 2.5) based on methylsilsesquioxane (MSQ) and high-temperature porogens in order to circumvent the reliability issues related to as-deposited porous dielectric. Based on thermal stability data, the MSQ/poly(styrene-b-4- vinylpyridine) material system was recommended to be cured at 300 {degree sign}C for subsequent backend processes, and the porogen to be removed at 400 {degree sign}C for 2 hours after CMP step. The mechanical properties of ultra-low-k films used in different integration schemes were further investigated using nano-indentation and FT-IR for various porogen loading. The moduli of 2-phase films were higher than their porous films, and even better than dense MSQ, for porogen loading below a critical level (~50%), which could be attributed to their enhanced degree of crosslinking in MSQ. In addition, MSQ/porogen films cured at 300 {degree sign}C possessed good elastic modulus (> 4.0 GPa) to pass CMP test.