Superconductor technology: apparatus – material – process – Processes of producing or treating high temperature... – Coating
Patent
1993-10-14
1995-12-19
Weisstuch, Aaron
Superconductor technology: apparatus, material, process
Processes of producing or treating high temperature...
Coating
20419213, 20419224, 20429803, 20429806, 20429807, 505476, 505731, 505816, H01L 3924, C23C 1454
Patent
active
054768381
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for producing thin layers by means of reactive cathode sputtering using a process chamber with gas inlet and a gas outlet, a process gas as a gas mixture, at least one target formed as a cathode and a substrate, and for control the pressure of the process gas is held constant while material is sputtered from the target and deposited on the substrate. The invention also relates to an apparatus for producing thin layers with the aid of a chamber suitable for reactive cathodic sputtering with a gas inlet and a gas outlet for the purpose of control of a process gas provided as a mixture.
BACKGROUND OF THE INVENTION
Following the discovery of the oxidic high temperature superconductors in the year 1986, efforts have been made to include this material in microelectronics. The oxidic high temperature superconductors are materials with a complex structure. In order to ensure production of the highest quality and, where possible, epitaxially grown layers, it is required in the fabrication of a thin film of such oxidic high temperature superconductors, to provide an optimum and temporally stable deposition process during the film deposition to the greatest possible extent.
One possible thin film fabrication method for such materials resides is the process of cathode sputtering. With corresponding technological cost, one can maintain most of the deposition parameters such as, for example, substrate temperature, target temperature, sputtering power, sputtering current, and process gas pressure constant.
The hitherto known cathode sputtering processes have been found, however, to be disadvantageous in that the deposited films of the oxidic high temperature superconductors do not grow perfectly monocrystalline, but rather have inhomogeneities in the film structure.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process of the aforedescribed kind that reduces the mentioned drawbacks and as a result yields a thin film, especially of an oxidic high temperature superconductor, with reduced inhomogeneities. It is further an object of the invention to provide an apparatus for producing such thin layers.
The objects of the invention are attained in a process in which the process gas is so fed into the chamber up to the plasma surrounding the target during the cathode deposition. In a region of the space around the target surface and in a cross section parallel to the target surface in the plasma, there is spectroscopically detectable, in situ, at least one emission line profile for the duration of the cathode sputtering. After setting a desired cross-sectional profile with the sputtering process startup, this cross-sectional profile is held constant over time by controlling the process gas mixing proportions.
At this point, it is worth mentioning that changes in the plasma with time can give rise to a movement therefrom such that potential changes in the vicinity of the plasma give rise to changes in the electric field and thus to changes in the plasma. The fluctuations with time of the plasma characteristics, can, by means of potential changes, for example charge transfer, effect transfer of ions out of the plasma onto the surfaces.
The changes with time in the plasma can, on the other hand, be effected by the presence of oxygen in the deposition of high temperature superconductors. The oxygen is incorporated in the layer constituted of the oxidic high temperature superconductive material (e.g. YBa.sub.2 Cu.sub.3 O.sub.7) and is therefore provided also in the process gas. The oxygen can therefore be liberated at the surfaces, especially also the target surface, or captured therein. As a consequence, oxygen in the deposition process is withdrawn or supplied. It has been found that, most of all, the oxygen content of the target surface plays a significant role in the changes with time of the plasma. Depending upon the oxygen content, various high temperature superconductors (HTSC) can have metallic or insulatin
REFERENCES:
patent: 4407709 (1983-10-01), Enjouji et al.
patent: 4704199 (1987-11-01), Yokokawa et al.
patent: 4894132 (1990-01-01), Tanaka
patent: 4895631 (1990-01-01), Wirz et al.
Kruger Ursus
Kutzner Rolf
Wordenweber Roger
Dubno Herbert
Forschungszentrum Julich
Myers Jonathan
Weisstuch Aaron
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