Organosilicate Spin-on Glasses II. Effect of Physical Modification on Mechanical Properties

Porous copolymer films were synthesized from a methylsilsequioxane:1,2-bis(trimethoxysilyl)ethane (MSSQ:BTMSE) matrix and either an aromatic-core or aliphatic-core porogen at 10, 20, or 30 wt % porogen loading. Films were characterized using scanning electron microscopy (SEM), IR spectroscopy, and ellipsometry. Depth-sensing indentation experiments were performed to measure apparent film modulus, E, and hardness, H. Indentation load-displacement traces and SEM images were used to determine the threshold load for cracking, Pc. The aliphatic-core porogen produced a greater porosity film than the aromatic-core porogen for 10 wt % loading and smaller porosity films for 20 and 30 wt % loadings. IR spectra, normalized for film thickness and density, indicated decreased O-Si-O networking in porous MSSQ:BTMSE films. The combination of increased porosity and decreased O-Si-O networking led to a decreased apparent E and H relative to the unmodified MSSQ:BTMSE film. However, low-porosity (approximately 7%), aliphatic-porogen MSSQ:BTMSE films are optimized relative to unmodified MSSQ with smaller dielectric constant and greater E and H.This work is supported by the Korean Collaborative Project for Excellence in Basic System IC Technology (System IC 2010: 98- B4-C0-00-01-00-02). Financial support from the Ministry of Science and Technology (MOST) and the Korean Ministry of Education through the National Research Laboratory Fund and the Brain Korea 21 Program, respectively, is also greatly acknowledged