Apparatus and Methods for Low K Dielectric Layers

Methods and apparatus for a low k dielectric layer of porous SiCOH. A method includes placing a semiconductor substrate into a vapor deposition chamber; introducing reactive gases into the vapor deposition chamber to form a dielectric film comprising SiCOH and a decomposable porogen; depositing the dielectric film to have a ratio of Si-CH3 to SiOnetwork bonds of less than or equal to 0.25; and performing a cure for a cure time to remove substantially all of the porogen from the dielectric film. In one embodiment the porogen comprises a cyclic hydrocarbon. The porogen may be UV curable. In embodiments, different lowered Si-CH3 to SiOnetwork ratios for the deposition of the dielectric film are disclosed. An apparatus of a semiconductor device including the low k dielectric layers is disclosed.