Extreme-low k porous pSiCOH dielectrics prepared by PECVD

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A novel extreme low-k (ELK) porous SiCOH (pSiCOH) dielectric has been developed by adding a third carbosilane precursor to the diethoxymethylsilane and bicycloheptadiene precursors used in the plasma enhanced chemical vapor deposition fabrication process of ultralow-k pSiCOH interconnect dielectrics. By adjusting the plasma parameters, the dielectric constant (k) has been lowered to k < 2.1. The k value of the ELK dielectric has been further reduced to 1.8 by extracting the porogen from the as-deposited films before subjecting them to ultraviolet cure using hydrogen radicals. It was found that the carbon concentration and the porosity of the ELK film can be tuned with different porogen extraction times in order to control the final k value of the dielectric.