| Summary: | 博士 === 國立交通大學 === 材料科學與工程學系 === 100 === This work examines the structure-property relationship of porous low-k dielectrics such as novel MSQ/high-temperature porogen hybrid materials and nano-clustering materials, and explores their integration feasibility for future technology node. Specifically, the effect of porogen structure on the structure-property relationship in MSQ/porogen hybrid films and their corresponding porous films by using a post-integration porogen removal scheme is investigated. Poly(styrene-b-4-vinylpyridine) containing di-block structure and pyridine polar group possesses higher moisture uptake and k-value in the hybrid films as compared to poly(styrene-block-butadiene-block-styrene) with symmetrical structure and non-polar groups. Moreover, the moisture uptake behavior in both as-prepared hybrid films is in physical sorption mode based on their reversible adsorption-desorption curve measured by quartz-crystal-microbalance. After porogen removal, the k-values of porous films are favorably not influenced by porogen structures. The k-value decreases from 2.89 to 2.44 when a porosity of 40.1 vol% is introduced into a dense MSQ matrix.
Furthermore, the moduli of the hybrid films were found to be higher than their porous forms, and even better than the dense MSQ film, for porogen loading below a critical level (~69.5 vol%). This could be attributed to their enhanced degree of crosslinking in MSQ as evidenced by the network/cage structural ratios. Besides, high-temperature porogen plays different roles during the crosslinking of MSQ depending on its loadings. In our study, with immediate loading at 16.7 vol%, PS-b-P4VP can serve as plasticizer to enhance the degree of crosslinking, but at a large loading >16.7 vol%, it becomes a steric hindrance reducing the degree of crosslinking.
On the other hand, a methyltrimethoxysilane (MTMS) modified silica zeolite (MSZ) film was prepared using a high ratio of MTMS/tetraethyl orthosilicate (TEOS) to study the structure-property relationship. The study investigated the effect of MTMS addition on the low-k matrix structure, elastic modulus, and pore geometry. High MTMS loading reduced the k-value of MSZ film down to 2.0, but yielded a lower elastic modulus, 2.7 GPa. Based on grazing-incidence small-angle X-ray scattering (GISAXS) analysis, the pore geometry of the MSZ film was found to be small but elliptical (Rin-plane ~3.75 nm; Rout-of-plane ~3.04 nm). The elliptical pore shape was formed by a collapse of film structure at 150–160°C as a result of ~32% thickness shrinkage due to the decomposition of tetra-n-propylammonium hydroxide (TPAOH), a structure directing catalyst, and due to a large degree of crosslinking reaction in the silica matrix. Combining GISAXS, 29Si-NMR, and FT-IR results, we propose that the lower elastic modulus was caused by the incorporation of a large amount of methyl groups from the MTMS precursor and the elliptic pores.
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