Cracking of titanium nitride films grown on polycarbonate

TiN films were deposited on polycarbonate substrates by cathodic vacuum arc using the plasma immersion ion implantation and deposition (PIII and D) method. Films deposited without high voltage bias were found to delaminate easily from the substrate due to a high level of intrinsic stress. Detailed investigations of film cracking were carried out using optical microscopy and scanning electron microscopy. It was found that the films cracked due to a large difference between the thermal expansion coefficient of TiN and the polymer. This mismatch gives rise to large stresses in the films. A model is presented that explains the debonding, buckling and cracking phenomena that are observed as the film thickness increases.