This paper describes process optimization of UV curing for ultra Low-k SiOC (ULK-SiOC, k=2.65) and High stress silicon nitride (HS-SiN) liner. We have investigated the impact of UV curing using different UV bulbs (UV-X and UV-Y) on BEOL process damages to the ULK-SiOC. The k-value variations of ULK-SiOC modified with UV-X with higher photon energy than UV-Y are greater than those of the pristine ULK-SiOC and the ULK-SiOC modified with UV-Y. These results are consistent with the previously reported FT-IR and NMR analyses that the UV-X generates 3-fold Si-O ring defects and Si-H bonds in the ULK-SiOC. In order to discuss the pore structure in UV-modified ULK-SiOC, the solvent diffusion of toluene and ethanol in ULK-SiOC were measured. The solvent diffusion of the UV-modified ULK-SiOC with UV-X is faster than that of the UV-modified ULK-SiOC with UV-Y. This result indicates that the pore size of UV-modified ULK-SiOC with UV-X is larger than that of UV- modified ULK-SiOC with UV-Y. The dependence of the stress increase in HS-SiN liner on different UV bulbs (UV-X and UV-Y) has been investigated by using stress measurement and FT-IR. The UV-modified HS-SiN liner with UV-Y achieves higher tensile stress, compared to the UV-X. FT-IR results have revealed that UV-Y is more effective for the dehydrogenation and SiN crosslinking, resulting in the greater increase in the tensile stress. In conclusion, UV-Y bulb with medium photon energy yields the desired UV modifications for ULK-SiOC and HS-SiN applications.