Effects of annealing on the properties of a structure made of copper (Cu) and low dielectric constant (low-k) plasma polymer films were investigated. Low-k plasma polymer films used in the experiment were deposited using a mixture of decahydronaphthalene (C10H18: DHN) and tetraethylorthosilicate (Si-(O-C2H5)(4): TEOS) as the precursors and were referred to as PPDHN:TEOS films. In current-voltage measurements of Cu/PPDHN:TEOS/Si/Al structures for which Cu/PPDHN:TEOS/Si were annealed before the Al back-contact deposition, 400 and 450 degreesC annealed samples showed lower leakage current than the not-annealed sample possibly due to improvement of the Cu/PPDHN:TEOS interface. 500 and 580 degreesC annealed samples showed slightly and significantly higher leakage currents, respectively, than 400 and 450 degreesC annealed samples. Secondary ion mass spectroscopy analysis of Cu/PPDHN:TEOS structures and Fourier transform infrared absorption spectroscopy analysis of the PPDHN:TEOS films suggested that the increase of leakage current of Cu/PPDHN:TEOS/Si/Al structures after 500 and 580 degreesC annealing is caused by the compositional and structural change of the PPDHN:TEOS films, rather than by the diffusion of Cu into the PPDHN:TEOS films