Study On Copper Nitride Thin Films Prepared By Magnetron Sputtering

The effects of different deposition conditions by direct current(DC)magnetron sputtering on the structure and properties of copper nitride (Cu₃N) thin films have been investigated systemically in this paper. And the effects of doping Al, Fe, La on the structure and properties of Cu₃N films have also been studied. We have made these conclusions:(1) Copper nitride thin films were deposited on glass substrates by reactive direct current(DC)magnetron sputtering at various N₂-gas partial pressures and room temperature. X-ray diffraction measurements show that the films are composed of Cu₃N crystallites and exhibit preferential orientation of the [111] direction at low N₂ partial pressure. The film growth prefers to the [111] and the [100] direction at high N₂ partial pressure. The resistivity of Cu₃N films increases sharply with increasing N₂ partial pressure. At low N₂ partial pressure, the Cu₃N films show the metallic conduction mechanism through the Cu path, and at high N₂ partial pressure, the conductivity of Cu₃N films shows the semiconductor conduction mechanism. Such preferential film growth is interpreted as being due to the variation of Cu nitrification rate with N₂.(2) Copper nitride thin films were deposited on glass substrates by reactive DC magnetron sputtering at various N₂-gas flow rates. We made a conclusion that at the low N₂-gas flow rate, the films exhibit preferential orientation of the [111] direction, but exhibit preferential orientation of the [100] direction at high N₂-gas flow rate. The N₂-gas flow rate not only affects the crystal structures of the films but also the deposition rate, the resistivity and the microhardness of the Cu₃N films. But the high N₂-gas flow rate not always has advantages to the deposition. Generally speaking, we can control the N₂-gas flow rate 10～15sccm at the high N₂ partial pressure.(3) The different substrate temperatures (Ts) on the structures and properties of copper nitride thin films have been investigated by reactive DC magnetron sputtering. When the Ts< 100oC, the crystal level of films increases with the increasing of Ts. When the Ts>100 oC, the crystal level of films decreases with the increasing of Ts, and when the Ts=200 oC, it is very low in so far as the films can not form Cu₃N crystal. The results also indicate that in order to prepare the fine crystal Cu₃N films, the best Ts is 100 oC more or less.(4) Copper nitride thin films were deposited on glass substrates by reactive DC magnetron sputtering at room temperature and Ts =100 oC. All the samples have been sintered at various temperatures; the effects of different anneal temperature (Ta) on the properties and stability of films has been researched in this chapter. The XRD patterns indicate that the prepared films begin to decompose when the Ta>200 oC, and much decomposed phenomena has been observed at the Ta=300 oC, the films decompose entirety when the Ta>350 oC. There are small differences of stability between the samples prepared at Ts=100 oC and room temperature, we found that the samples which were prepared at room temperature are more stable than that were prepared at Ts=100 oC.(5) Copper nitride thin films were deposited on glass substrates by reactive DC magnetron sputtering at different DC powers. The intensity of the preferred crystalline orientation of the films and the grain size increased with the increasing DC power. The DC power not only affects the crystal structure of the Cu₃N films but also affects its resistivity. In our experimental condition, the resistivity of Cu₃N films decreased sharply with increasing the DC power and reached a value as low as 1. 33Ωcm. From this work, we find the optimum DC sputtering power for producing high-quality and well [111]-oriented Cu₃N films on glass substrates is 80W, while 0.8Pa N₂-gas partial pressure and 100oC substrate temperature at our experimental apparatus.(6) Cu₃N film and Al_xCu₃N films were prepared with reactive magnetron sputtering method. The two films were deposited on glass substrates at 0.8Pa N₂ partial pressure and 100oC substrate temperature by using a pure Cu and Al target, respectively. X-ray diffraction (XRD) measurements show that the un-doped film was composed of Cu₃N crystallites with anti-ReO₃ structure and adopted [111] preferred orientation. XRD shows that the growth of the Al-doped copper nitride films (Al_xCu₃N) was affected strongly by doping Al, the intensity of [111] peak decreases with the increasing concentration of Al and the high concentration of Al could prevent the Cu₃N from crystallization. The doping threshold of Al is 8.07%. Compared with the Cu₃N films, the resistivities of the Al-doped copper nitride films (Al_xCu₃N) have been reduced, and the microhardness has been enhanced. Al-doped copper nitride films (Al_xCu₃N) have been changed the structure and the electric properties of Cu₃N films, and the quality has been enhanced.(7) By reactive magnetron sputtering of a pure Cu and a pure La target, the copper nitride film (Cu₃N) and the La-doped copper nitride films (La_xCu₃N) were prepared on glass respectively. X-ray diffraction (XRD) measurements show that the non-doping La film was composed of Cu₃N crystallites with anti-ReO3 structure and prefers to be [111]-oriented. XRD shows that the crystal growth of the La_xCu₃N films is affected strongly by La, the peak intensity of preferred crystalline [111]-orientation decreases with the increased concentration of La and the high concentration of La could prevent the Cu₃N from crystallization. From this result we can assume that there exists a limit of content of La influencing the growth of Cu₃N crystalline, this limit may be below 5.87%. Compared with the Cu₃N films, the resistivities of the La_xCu₃N films have been decreased.Moreover, on the same condition (Ts=100oC, N₂-gas partial pressures=0.8Pa, DC power =50 W), we prepared Al or La doped Cu₃N, and the similitude results have been observed.(8) By reactive magnetron sputtering of a pure Cu and a pure Al, Fe, La target,Cu₃N film and Cu-Al-N, Cu-Fe-N, Cu-La-N films were prepared on glass, respectively, at 0.5 Pa N₂ partial pressure and 100 oC substrate temperature. X-ray diffraction measurements showed that Cu₃N film was composed of Cu₃N crystallites with anti-ReO3 structure and prefer to be [111]-oriented. The Al-doped copper nitride film (Cu-Al-N) with very weak diffraction peak preferred to being [111]-oriented, too. XRD showed that the Fe-doped copper nitride film (Cu-Fe-N) and the La-doped copper nitride film (Cu-La-N) were amorphous. The resistivities of Cu-X-N films (X=Al, Fe and La) were higher than that of Cu₃N film.With the systemically research on the magnetron sputtering, we can make a conclusion: the best prepare condition is the Ts=100 oC, N₂-gas partial pressures=0.8Pa, DC power =50 W, the gas flow rate can not be too high, the total gas flow rate is 5～15sccm, and the N₂ flow rate can be chose 10～15sccm or 2～5sccm by the high or low N₂ partial pressure.This paper has also investigated the effects of doped some metals (La, Al, Fe) on the structure and properties of Cu₃N films on the same experiment condition (Ts=100oC, N₂-gas partial pressures=0.8Pa, DC power= 50W). The results behave similar phenomena: the crystal level decreased with the increasing doping level x. And the doping level would reach a different limit related to the different doped metal. The resistivity of the samples can be reduced with the increased doping level x.On the side, we prepared some doped metal Cu₃N on the changed preparing condition (Ts=100oC, N₂-gas partial pressures=0.5Pa, DC power= 50 W), the structure and electronic properties of Cu₃N different with the samples which prepared on the condition (Ts=100 oC, N₂-gas partial pressures=0.8Pa, DC power =50W). This indicated the importance of the preparing condition and the complexity of the metal doped Cu₃N by magnetron sputtering.