Resistance repeatability study of ion-beam deposited vanadium oxide thin films

Ion Beam Sputter Deposition (IBSD) is a versatile technique particularly suited to applications requiring high quality, high performance layer materials as it allows independent and accurate control of the process parameters. Vanadium oxides, used for example in the fabrication of microbolometers, optical switches or optical storage, exhibit interesting properties such as a high Temperature Coefficient of Resistance (TCR), relatively low 1/f noise and a semiconductormetal phase transition close to room temperature. However, it is very challenging to control the stoichiometry of the deposited film as there are at least 25 different oxidation states of vanadium, few of which display the required electrical characteristics. In the present study, vanadium oxide thin layers were deposited by IBSD using an Oxford Ionfab300+ and analyzed with regard to their electrical properties. The impact of the system parameters on the resistance repeatability, wafer-to-wafer and batch-to-batch, was thoroughly investigated to provide the end user with a clear understanding of the factors affecting film resistivity while ensuring at the same time a steep variation of resistance with temperature, as notably required for uncooled bolometers. These parameters were balanced to also achieve a good deposition rate, throughput and uniformity over large device areas, compatible with the requirements of industrial applications.