Two step post-deposition treatment of ild layer for a lower dielectric constant and improved mechanical properties

Abstract

A method of lowering the dielectric constant of an organosilicon low k dielectric layer while improving the hardness and thermal stability is provided. A deposited layer of carbon doped oxide, HSQ, or MSQ is cured and treated with a He plasma which improves hardness for a subsequent CMP step and lowers the dielectric constant. There is no loss of HO or CHduring the He treatment. The low k dielectric layer is then treated with a Hplasma which converts some of the Si—O and Si—CHbonds near the surface to Si—H bonds, thereby further lowering the dielectric constant and increasing thermal stability that improves breakdown resistance. Moisture uptake is also reduced. The method is especially useful for interconnect schemes with deep sub-micron ground rules. Surprisingly, the k value obtained from two different plasma treatments is lower than when two He treatments or two Htreatment are performed.