Refractive Indexes of Porous Thin Films Prepared From Organic-templated Polymethylsilsesquioxanes

Abstract

The rapidly developing microelectronics industry has shown a strong demand for high performance materials to improve device performance [1,2]. Nanoporous silicate thin films are considered as important materials for advanced electronics. The formation of air-filled nanopores is a key technology for preparing insulating materials [3-12]. Polymethylsilsesquioxane (PMSSQ), with the empirical formula of (CH3-SiO1.5)n, is a potential candidate for low dielectric spin-on glass [13]. It has the characteristics of low dielectric constant ranging from 2.7 to 2.9, high thermal stability, low moisture uptake, good adhesion to metal, and excellent mechanical properties [11,14]. In addition, star-shaped macromolecules, such as hyperbranched poly(ecaprolactone) (PCL), are generally used as an organic template to generate nanometer-sized pores in the matrix polymer [11,15]. The organic templates dispersed in the polymer matrix are required to completely decompose at a relatively low temperature range (200°C ~ 400°C), and after the thermal calcination process, the derived nanopores need to be well distributed as a closedcell structure in the polymer matrix. The air-filled nanopores in a thin film can be generated by a method that disperses organic templates into an insulating matrix material, and decomposes them at elevated temperature. The mechanical strength of an insulating material will undoubtedly decrease, and the size and distribution of the as-made pores cannot be uniform, due to the organic templates, which leave pores behind from the thermal decomposition. Moreover, if the pores agglomerate, the insulating material may break down at low voltage. Therefore, the thermal decomposition and dispersibility of the organic templates in matrix polymers, and control of the nanopore generation, should be suitably considered for the structural design of organic templates. In order to effectively generate and thoroughly distribute nanopores in the whole matrix film, the organic templates should be completely dispersed in matrix polymers, and the miJung-Soo Kim and Dae-Geun Nam Energy Component and Material R&BD Group, Korea Institute of Industrial Technology, Busan 618-757, Korea