Structure to improve adhesion between top CVD low-k dielectric and dielectric capping layer

A method of forming an interconnect structure comprising:

• forming an adhesion transition layer on a surface of a diffusion barrier capping dielectric, including elements of C, Si and H, said adhesion transition layer comprising a lower SiOx- or SiON-containing region and an upper C graded region, said forming the adhesion layer comprises (i) subjecting the barrier diffusion capping dielectric to an oxygen plasma process at an operation pressure from 0.05 to 20 torr for a period of time from about 5 to about 60 seconds to convert a top surface region of the diffusion barrier capping dielectric into a SiO-containing layer, said oxygen plasma process further includes generating an oxygen plasma from an oxygen gas that is admixed with an inert gas utilizing an RF power source, and (ii) performing an argon plasma pretreatment process during an initial stage of a subsequent step of forming of a low-k dielectric material that includes atoms of Si, C, O and H, said argon pretreatment process is performed at an operation pressure from 0.05 to 20 torr for a period of time from about 5 to about 20 second utilizing an argon plasma generated from Ar gas that is admixed with N, He, Xe or Kr utilizing an RF power source;
• and
• forming said low-k dielectric having a dielectric constant of less than 4.0 atop the adhesion transition layer, wherein an interface of said low-k dielectric is in contact with the upper C graded region of the adhesion transition layer.