Efficient moisture barrier of nitrogen-doped amorphous-carbon layer by room temperature fabrication for copper metallization

To enhance the humidity reliability of copper (Cu) metallization used in memory LSIs, nitrogen (N)-doped amorphous-carbon (a-C:N) deposited by sputtering on the Cu surface is proposed. Since the preparation of a-C:N film can be achieved at room temperature, the process temperature is compatible with LSIs fabrication. After the higherature/humidity storage test, the a-C:N layer was found to be an excellent barrier to protect the Cu surface from oxidation and avoid the increase of Cu sheet resistance. Depth profiles imply no oxidation occurs on the underlying Cu surface. An appropriate concentration of N-doping is considered to prevent the penetration of moisture with the effects of the repulsive force between both N and O atoms. The proposed method is promising as a practical method to improve the reliability of Cu metallization for long-term storage.