Structural Studies of Copper Sulfide Film Growth: Influence of Humidity

Copper is a critical material in electrical components and is subject to atmospheric sulfidation. This study characterized the product formed when Cu is exposed to a dilute (50-200ppb) H2S atmosphere at low (0.5%) to high (80%) relative humidity (RH). An important observation was that the Cu2S growth rate for long times is significantly higher for sulfides formed at low RH compared to high RH. In addition, it was found that for both low and high RH sulfidation, copper reacts to form the low chalcocite phase (Cu2S) as identified by x-ray and electron diffraction. Cross-section and plan-view TEM revealed that the Cu2S grains formed at high RH are 20-50 nm in size with a large amount of porosity, whereas the grains formed at low RH are 75-150+ nm and appear to undergo grain growth with little porosity as the film thickens.