Plasma assisted metalorganic chemical vapor deposition (MOCVD) system
The present invention is a high-throughput, ultraviolet (UV) assisted metalorganic chemical vapor deposition (MOCVD) system for the manufacture of HTS-coated tapes. The UV-assisted MOCVD system of the present invention includes a UV source that irradiates the deposition zone and improves the thin film growth rate. The MOCVD system further enhances the excitation of the precursor vapors and utilizes an atmosphere of monatomic oxygen (O) rather than the more conventional diatomic oxygen (O 2 ) in order to optimize reaction kinetics and thereby increase the thin film growth rate. In an alternate embodiment, a microwave plasma injector is substituted for the UV source.
1. A process for the continuous high throughput preparation of high temperature superconducting tape utilizing metalorganic vapor deposition comprising:
providing single or multiple strands of a substrate, the substrate strands having a major surface and having a biaxial buffer layer deposited thereon;
threading the substrate strands through a MOCVD reactor;
providing a source of superconducting precursor composition in vapor form, the superconducting precursor composition including an organometallic precursor;
mixing the superconducting precursor composition in vapor form with an inert carrier gas;
combining the vaporized precursor composition and inert carrier gas mixture with nitrous oxide and diatomic oxygen;
translating the substrate strands through a deposition zone in the MOCVD chamber where the deposition zone is defined by the space between a showerhead and a substrate heater disposed below the showerhead, where the substrate strands translate over the substrate heater, the substrate heater heats the substrate to a temperature of from about 700° C. to about 950° C., and the major surface of the substrate strands face the showerhead;
providing an energy source separate from the substrate heater, and directing microwave energy into the deposition zone and parallel to the major surface of the substrate strands and parallel to the biaxial buffer layer, where the energy provided is at least 10 kW of power to cause the diatomic oxygen to react and form monoatomic oxygen and to excite the organometallic precursor molecules to a high energy state, where the energy source is disposed within the MOCVD reactor;
introducing the combined gases and vapors into the MOCVD reactor through the showerhead; and
reacting the precursor vapor in the deposition zone to form a superconducting composition overlying the biaxial buffer layer of the substrate.
2. The process of claim 1 where a single strand of substrate is provided and the single strand of substrate is slit into multiple strands after coating.
3. The process of claim 1 where the MOCVD reactor is a cold wall reactor.
4. The process of claim 1 where the pressure within the MOCVD reactor is in the range of 1 to 50 Torr.
5. The process of claim 1 where the substrates are metallic and have a biaxial buffer layer deposited upon them.
6. The process of claim 1 where the energy source produces radiation at a wavelength in the range of from about 2 to about 4 GHz.
7. A process for the continuous high throughput preparation of high temperature superconducting tape utilizing metalorganic vapor deposition comprising:
providing a single strand of a substrate, the substrate strand having a major surface and having a biaxial buffer layer deposited thereon;
threading the substrate strands through a MOCVD reactor;
providing a source of superconducting precursor composition in vapor form, the superconducting precursor composition including an organometallic precursor;
mixing the superconducting precursor composition in vapor form with an inert carrier gas;
combining the vaporized precursor composition and inert carrier gas mixture with nitrous oxide and diatomic oxygen;
translating the substrate strands through a deposition zone in the MOCVD chamber where the deposition zone is defined by the space between a showerhead and a substrate heater disposed below the showerhead, where the substrate strands translate over the substrate heater, the substrate heater heats the substrate to a temperature of from about 700° C. to about 950° C., and the major surface of the substrate strands face the showerhead;
providing an energy source separate from the substrate heater, and directing microwave energy into the deposition zone and parallel to the major surface of the substrate strands and parallel to the biaxial buffer layer, where the energy provided is at least 10 kW of power to cause the diatomic oxygen to react and form monoatomic oxygen and to excite the organometallic precursor molecules to a high energy state;
introducing the combined gases and vapors into the MOCVD reactor through the showerhead;
reacting the precursor vapor in the deposition zone to form a superconducting composition overlying the biaxial buffer layer of the substrate; and
slitting the single strand of substrate comprising the biaxial buffer layer and the superconducting composition into multiple strands.
8. The process of claim 7 where the energy source is disposed externally to the MOCVD reactor.
9. The process of claim 7 where the energy source is disposed within the MOCVD reactor.
10. The process of claim 7 where the MOCVD reactor is a cold wall reactor.
11. The process of claim 7 where the pressure within the MOCVD reactor is in the range of 1 to 50 Torr.
12. The process of claim 7 where the substrates are metallic and have a biaxial buffer layer deposited upon them.
13. The process of claim 7 where the energy source produces radiation at a wavelength in the range of from about 2 to about 4 GHz.