Relation of Dielectric Constants and Chemical Structures of Low Dielectric Constant SiCOH Films Deposited by Using Octamethylcyclotetrasiloxane and Tetraethylorthosilicate Precursors

In case of the conventional SiCOH films, a post-deposition process was used to make pores by vaporization of porogen (e.g., hydrocarbon) for decreasing the dielectric constant. However, the authors intended the deposition of the SiCOH films, which does not need the post-deposition process to form the pores by using the dual precursors having different structures. The octamethylcy-clotetrasiloxane (OMCTS) and tetraethylorthosilicate (TEOS) have different structures which were of the ring shape and the linear shape, respectively. The OMCTS and TEOS were used to fabricate the plasma polymerized low dielectric constant SiCOH film by using the plasma enhanced chemical vapor deposition system in this work. A ratio of OMCTS and TEOS was adjusted by controlling flow rates of precursor carrier gases into the process chamber. The SiCOH films, which were deposited with dual precursors, showed the very low dielectric constants (relative dielectric constant k 2.06 and 2.09) at plasma power of 10 W. All the fabricated SiCOH films showed the proper leakage current densities below 10⁻⁶ A/cm⁻² at 1 MV/cm as the intermetallic dielectric material. The SiCOH films were investigated to study the relations between dielectric constants and chemical structures by using Fourier transform infrared spectroscopy. The formation of pores inside the SiCOH films was studied through the relation between Si–O–Si peaks, including network, suboxide and cage peaks, and the dielectric constant.