Publication

Abstract : Low-kfilms with k of 2.5–2.9 were deposited under different conditions of pressures and temperatures using a plasma-enhanced chemical vapor deposition(PECVD) system. These films were prepared using a new liquid precursor, tetravinyltetramethylcyclotetrasiloxane (TVTMCTS) and H2H2 carrier gas. The rf power was kept as low as possible to maintain the original ring structure in the films. The as-deposited films were annealed and the dielectric and optical properties were investigated. Identification of the absorption bands in the IR spectra for as-deposited films reveals a broadband around 950–1200 cm−1cm−1 arising from the Si–O stretching mode of the ring (1065 cm−1)cm−1) and chain structure (1000 cm−1),cm−1), respectively; a band at 750–900 cm−1cm−1 due to Si–O bending (790 cm−1);cm−1); Si–CH3Si–CH3 rocking mode (760 cm−1);cm−1); a sharp band centered at 1260 cm−1cm−1 due to a Si–CH3Si–CH3 bending mode; and a broadband at 2800–3000 cm−1cm−1 due to the CH group. A comparison of the IR spectra of the PECVDfilm and TVTMCTS liquid reveals that vinyl vibrations (Si–CH=CH2)(Si–CH=CH2) at 960, 1410, and 3030–3095 cm−1cm−1 for CH2CH2 and at 1598 cm−1cm−1 for C=C present in the liquid were not detected in the CVDfilms. Hence C=C bonds were broken in the plasma polymerization process. As the pressure and the depositiontemperature(TD)(TD) increased, the intensity of the Si–O vibration arising from the ring structure increased and decreased, respectively. Thus by tuning the pressure and TDTD we can control the structure of the film. There is a good correlation found between the Si–CH3Si–CH3 and Si–O ring intensities and k values; the increasing Si–CH3Si–CH3 and Si–O ring is accompanied by decreasing k. The films were thermally stable up to 400 °C400 °Cannealingtemperature.