The introduction of porosity in dielectrics is desirable to reduce the dielectric constant; but it causes integration problems such as CVD/ALD precursor penetration for barrier layer/seed layer deposition. CVD Parylene-N has been shown to work as a pore sealant for porous low-kappa materials but penetrates itself slightly into porous dielectric. The depth profile of Parylene-N in porous MSQ can be obtained using the Nuclear Reaction Analysis (NRA) of C-12. The penetration of Parylene-N can be controlled by deposition at higher pressure where the deposition rate is also high. High deposition rate can also be attained by adding a carrier gas which also shows low Parylene-N penetration. The experimentally measured dielectric constants, after pore sealing, are compared to those calculated using the NRA data of Parylene-N penetration. (c) 2005 American Vacuum Society.