Alumina films by sputter deposition with Ar/O2: Preparation and characterization

Abstract

rf bias sputtered alumina thin films were produced under a variety of sputter conditions and analyzed for composition, thickness, density, and dielectric strength (breakdown field) in order to assess the affect of the inclusion of oxygen in the sputter gas on these films. All of the Al:O ratios for these films, as determined by Rutherford backscattering spectrometry, were lower than or equal to the ratio expected from stoichiometric considerations (0.67). In general, higher partial pressures of oxygen in the sputter system produced oxygen rich films. The Al:O ratios were found to vary from a high of 0.66 to a low of 0.54. These were found to correlate with the breakdown field measurements, with the oxygen rich films proving to be better insulators. Sputter bias was found to have the second greatest influence on dielectric strength. A sputter bias of −40 V in our sputtering system produced the best insulating films both in the presence and absence of oxygen in the sputter gas, with breakdown fields dropping off at lower and higher biases.