High-rate reactive magnetron sputter deposition and characterization of metal oxide films

Sammanfattning: Molybdenum oxide films with good electrochromic properties were produced by single- and dual-target sputtering. Dual-target deposition was shown to be able of yielding optically functional films at much higher rates than that for single-target depositions. Molybdenum oxide films, prepared by dual-target sputtering under conditions leading to films that were blue in the as deposited state, evolved good electrochromic properties after a few color/bleach cycles.Stoichiometric aluminum oxide (Al2O3) films were produced in a high-rate stable arc-free process by using a laboratory sputtering system. The success of the deposition strategy hinged on the use of suitable deposition system geometry, including a large enough target-to-substrate distance, and on theuse of sufficiently high operating pressure. Theoretical work was done in order to explain the process underlying this unexpected result. Already existing models of the sputtering process were used as a basis for further development.A similar approach was applied to an industrial large-area prototype inline sputtering system. A construction for increasing the target-to-substrate distance was designed. With the new geometry, it was possible to grow stoichiometric aluminum oxide (Al2O3) and titanium oxide (TiO2) films from the target in the metallic mode, to avoid composition gradients in the film and to keep the target surface arc-free. The choice of suitable operating pressure was crucial for the long-term stability of the process. For titanium oxide, it was established that post-deposition thermal annealing modifies the structure to a polycrystalline phase with a large interior surface area.The influence of the magnetron discharge current during reactive large-area sputtering of elements with relatively high atomic mass was studied. Tungsten oxide sputtering of optically functional films with sufficiently amorphous structure showed to be severely limited due to the effect of gas rarefaction at high power. It was possible to improve the sputtering conditions for growing electrochromic tungsten oxide films at relatively high target currents and stability by choosing appropriate processconditions from an investigation of aluminum oxide.