Stable stoichiometric copper nitride thin films via reactive sputtering

Cu3N films were deposited by reactive sputtering of copper in a nitrogen/argon gas mixture at different combinations of substrate temperatures and nitrogen/argon gas ratios. The films were studied by SEM, EDS, XRD, spectrophotometry, and resistivity measurements to evaluate the deposition technique as a flexible low-cost fabrication method for potential applications. The results showed that the films were polycrystalline with a preferential crystalline orientation that varies with the deposition temperature when a Si substrate is used. The film's crystalline orientation does not change with substrate temperature in the case of glass substrates. The optical band gap values obtained from spectrophotometry measurements show a considerable variation with substrate temperature and nitrogen gas fraction, ranging from 1.66 to 1.85 eV. The resistivity of the film material also varies substantially as a function of both the substrate temperature and the nitrogen gas fraction, changing by more than one order of magnitude from several hundred to thousands of omega cm. All samples except those deposited at a substrate temperature of 100 degrees C were found to become an order of magnitude less resistive after aging for one year. Substrate deposition temperature of 100 degrees C and a high nitrogen fraction in the sputtering gas mixture (0.71) led to a stable material with a chemical composition that is very close to the stoichiometric copper-to-nitrogen ratio of 3.

Automated summary

The Cu3N films were deposited through reactive sputtering of copper in a nitrogen/argon gas mixture, with the resulting films exhibiting polycrystalline structure and variable crystalline orientation depending on substrate temperature. The optical band gap values and resistivity of the film material showed significant variations with substrate temperature and nitrogen gas fraction, with different characteristics observed for films deposited on Si and glass substrates.