Degradation of ZrN films at high temperature under controlled atmosphere

The degradation of ZrN films deposited onto Si substrates by unbalanced magnetron sputtering was investigated over temperatures of 300–1200°C in different atmospheres by analyzing changes in color and appearance, as well as microstructures. The atmospheres contained air, nitrogen, and forming gas (N2∕H2=9), which exhibited drastically different oxygen/nitrogen partial pressure ratios. The resultant degradation included mainly color changes and formation of blisters on the film surface. Color change was associated with the oxidation of the nitride film, which was analyzed by looking into the Gibbs free-energy changes at various temperatures and oxygen partial pressures. Two types of blisters occurred at different temperature ranges. Several large round blisters, denoted as A-type blisters, occurring at low temperatures originated from the large residual stress in the films. Many small irregular blisters, denoted as B-type blisters, appearing at relatively high temperatures resulted from the oxidation of the film.