A four-point bend technique (4PBT) was employed to characterize adhesion strength of nanoporous silica (SiCOH-based low-κ) to a hard mask layer (TEOS). Adhesion energy was analyzed as a function of low-κ porogen loading (3, 6, 9, and 11%). Effect of an adhesion promoter (AP) layer would also be discussed. Low fracture energies (< 5 J/m 2 ) confirm the weak mechanical properties of such highly porous materials. Fracture energy decreases as the porosity increases for samples without AP. However it becomes slightly higher and independent on the porosity when AP is applied. Low-κ/TEOS interface is the main delamination path for samples without AP. On the other hand, AP/TEOS interface becomes the interface that controls the adhesion for samples with AP hence it becomes independent on the low-κ porosity.