Radical beam ion beam etching (RBIBE): Reactor characterization and etching of yttrium barium copper oxide thin film superconductors

High quality thin films of high temperature superconductors can be deposited by a number of techniques. However, superconducting devices cannot be realized unless a suitable etching technique is also developed. In this work, dry etching of {dollar}rm Ysb1Basb2Cusb3Osb{lcub}x{rcub}{dollar} superconducting thin films was studied in a radical beam ion beam etching (RBIBE) reactor.; Etching using ionic, molecular, and radical beams (individually or in combination) was performed. The Ar{dollar}sp+{dollar} beam was characterized for ion energy distribution and flux. The Cl-radical beam was produced by dissociation of Cl{dollar}sb2{dollar} in a microwave-generated remote plasma. A combined theoretical/experimental analysis of the radical beam reactor was carried out to determine the radical flux impinging on the substrate. Models for the plasma (radical source) and the downstream section of the reactor were developed. The influence of reactor dimensions and operating conditions on the Cl-radical density and flux was determined. Model predictions were tested by optical emission actinometry and etching of heavily P-doped polysilicon. By using the wall recombination probability of radicals as the only adjustable parameter, good agreement between predicted and measured Cl-radical density in the plasma and at the reactor exit was obtained. The same methodology can be applied to remote plasma processing in general.; The sputtering yield of {dollar}rm Ysb1Basb2Cusb3Osb{lcub}x{rcub}{dollar}x under Ar{dollar}sp+{dollar} bombardment was determined. A damage-free lithographic process capable of exposing micron-size features was developed. {dollar}rm Ysb1Basb2Cusb3Osb{lcub}x{rcub}{dollar} microbridges were etched using Ar-ion milling to study the intrinsic as well as modified properties of the superconductor. The resolution limit of ion milling was found to be 1600 A.; Molecular chlorine did not etch the superconductor at temperatures up to 500{dollar}spcirc{dollar}C. In contrast, a Cl-radical beam was found to rapidly chlorinate the film, thereby destroying superconductivity in the exposed areas. Based on this finding, a new patterning technique was developed. Simultaneous exposure of the superconductor to an ion beam and a molecular or atomic beam resulted in an enhancement of the etch rate by up to 50% compared to the ion milling rate.; Finally, a novel technique involving gas sequencing alternating with ion bombardment was developed to etch Cu thin films anisotropically, an unsolved problem up until now.