Comparative Study of Trimethyl Silane and Tetramethylcyclotetrasiloxane-Based Low-k Films

Abstract

In this work, chemical vapor deposited low- films using trimethylsilane (3MS) as the linear precursors and tetramethylcyclotetra siloxanes (TMCTS) as the cyclic precursors are studied. There are four processes studied: , process and , process for 3MS and TMCTS precursors, respectively. Films deposited by the 3MS and TMCTS processes displayed similarities in the relationship between the Fourier transform infrared spectroscopy peak ratios, dielectric constants, refractive indexes, hardness, and modulus. The dielectric constant was found to have a linear relationship with hardness and modulus and inversely proportional with the peak ratio for both precursors. It is believed that the introduction of a methyl group in the film has reduced the covalency of the Si-O bond thus reducing its dielectric constant in comparison with silica. In this work, the 3MS based low- films appear to have slightly wider process windows compared to the TMCTS based low- films. The linear precursors (3MS) in both and process and cyclic precursors (TMCTS) in both and processes yielded similar hardness and modulus values for the same range of dielectric constants. In terms of the films electrical properties and stability, all films indicate mild stress where the 3MS system showed lower values of stress, good thermal stability, breakdown voltage, and leakage current values that are comparable to silica.