| The deposition of Si, Nb, Mo, and W oxides by reactive dc-magnetron sputtering from high temperature metallic Si, Nb, Mo, and W targets in Ar/O 2 atmospheres has been studied. It is shown that the oxides formed on Si targets above 1500 K, on Nb above 2310 K, on Mo above 1700 K, and on W above 1900 K evaporate, leaving the target surface free of the solid oxide coatings which induce hysteresis, voltage instability and arc breakdown in conventional reactive sputtering. Also, the deposition rate can be much higher because the target surface is coating-free and because sublimed oxides, SiO(g) for Si, a mixture of NbO(g)+NbO2(g) for Nb, a mixture of MoO 2(g)+MoO3(g) for Mo, and a mixture of WO(g)+WO2(g)+WO 3(g) for W, contribute significantly to the deposit: The deposition rate of SiO2 is three times higher than for a conventional process with the same power, for Nb2O5, it is seven times higher, for MoO3, it is 23 times higher, and for WO3, it is 15 times higher. Thermionic emission can be an important process in the hot target sputtering of a metal target. In Nb hot target sputtering, thermionic emission constitutes more than half of the total discharge current and significantly reduces the Nb sputter rate. On the other hand, in W hot target sputtering, thermionic emission constitutes about 10% of the total discharge current and has no significant effect on the W sputter rate. |
