Production method for composite oxide thin film and device therefor and composite oxide film produced thereby
View Patent ↗A method and an apparatus which permits making a composite oxide thin film excellent in crystallinity easily and at a low temperature, with the capability of controlling the basic unit cell structure as desired, and without the need for a post annealing, as well as a composite oxide thin film thereby, especially a Cu group high temperature superconducting thin film, are disclosed. A thin Cu group high temperature superconducting film, which is constituted of a charge supply block ( 1 ) and a superconducting block ( 2 ), is formed on a substrate by alternately sputtering from a sputtering target having a composition of the charge supply block ( 1 ) and a sputtering target having a composition of the superconducting block ( 2 ) and repeating such an alternate sputtering operation a number of times needed for the film to reach a desired thickness. The first sputtering target for the charge supply block has a charge supply block composition in which Cu atoms are partly substituted with atoms of an element having a structure stabilizing effect.
1. A method of making a thin film of a Cu group high temperature superconductor wherein the superconductor has a basic unit cell comprised of a charge supply block and a superconducting block, comprising:
heating, in a vacuum atmosphere, an oriented crystalline substrate to a surface diffusion temperature;
forming, in said vacuum atmosphere, a buffer layer on said heated substrate by sputtering from a target for the charge supply block in which Cu atoms are partially substituted with atoms capable of bringing about a chemical self-assembling effect; and then
introducing an oxidizing gas under a selected pressure into said vacuum atmosphere;
a) forming epitaxially a first block constituting said superconducting block by sputtering from a target for superconducting block until said first block being formed has its thickness determined for said superconducting block in said basic unit cell;
b) forming epitaxially a second block constituting said charge supply block on said first block by sputtering from the target for the charge supply block until said second block being formed has its thickness determined for said charge supply block in said basic unit cell;
repeating steps a) and b) to make a thin film of the Cu high temperature superconductor having a selected thickness on said buffer layer; and then
c) forming an insulating layer having a selected film thickness on said formed thin film of Cu high temperature superconductor by sputtering from a third target made of an insulating material; and then
repeating steps a) and b) or steps b) and a) to make a thin film of the Cu high temperature superconductor having a selected thickness;
wherein said buffer layer satisfies lattice matching condition for the orientated crystalline substrate and the first block.
2. A Cu group high temperature superconducting thin film making method as set forth in claim 1 , wherein said atoms which are substituted for Cu atoms are at least one element selected from the group consisting of Tl, Bi, Pb, In, Ga, Al, B, Sn, Ge, Si, C, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, W, Re, Ru and Os.
3. A Cu group high temperature superconducting thin film making method as set forth in claim 1 , characterized in that said oxidizing gas is O 2 , O 3 , N 2 O or NO 2 .