Porous ultra low k deposited by PECVD: From deposition to material properties

A new challenge for semiconductor industry is to reach low permittivity (k < 2.4) required for advanced microelectronic interconnections. Porosity introduction in SiOCH matrix is the main research field investigated. Several synthesis ways can be used to deposit these nanoporous SiOCH layers. In this work, plasma enhanced chemical vapor deposition (PECVD) of this material using three different concepts (porogen approach, cyclic precursor, foaming) is studied and compared to spin-coated films. It is shown that the porogen approach, which consists in the co-deposition of a matrix precursor and a sacrificial organic porogen followed by a post-treatment to remove the organic porogen phase, allows to create porosity in a thin SiOCH film. The impact of deposition process and curing on basic film properties such as dielectric constant, porosity and elastic properties are studied. Foaming appears as another attractive way to deposit nanoporous SiOCH using PECVD.