Solid precursor feed system for thin film depositions
A dry powder MOCVD vapor source system is disclosed that utilizes a gravimetric powder feeder, a feed rate measurement and feeder control system, an evaporator and a load lock system for continuous operation for thin film production, particularly of REBCO type high temperature superconductor (HTS) tapes.
1. A precursor powder feed system for deposition of thin films, the system comprising:
a powder vessel maintained under vacuum for housing a precursor powder;
a load lock assembly located outside the powder vessel and comprising a pressure isolated chamber for reloading the powder vessel, wherein a plurality of gas control valves and a gate valve pressure isolate the load lock assembly from the powder vessel to provide for addition of powder precursor while the feed system operates continuously, and a flow control orifice to equalize pressure between the load lock assembly and powder vessel;
a scale coupled to the powder vessel and configured to provide continuous mass data of precursor powder in the powder vessel;
a mechanically driven powder feeder coupled to the powder vessel and configured to receive powder from the powder vessel; and
an evaporator configured to receive the powder from the powder feeder and evaporate the powder.
2. The system of claim 1 , further comprising a motor driven agitator located within the powder vessel and configured to provide powder mixing and distribution.
3. The system of claim 1 , wherein the evaporator further comprises an outlet screen.
4. The system of claim 1 , wherein the powder feeder is a feed screw.
5. The system of claim 1 , further configured for injection of an inert carrier gas.
6. The system of claim 1 , further comprising a control system having a PID controller with a data processor configured to control the powder feeder to deliver a target precursor powder feed rate to the evaporator based on the continuous mass data from the scale.
7. The system of claim 1 , further comprising a control system having a PID controller with a data processor configured to control at least one of the plurality of gas control valves of the load lock assembly.
8. The system of claim 1 , further comprising a control system having a PID controller with a data processor configured to control at least one of the plurality of gas control valves of the load lock assembly and the powder feeder to deliver a target precursor powder feed rate to the evaporator based on the continuous mass data from the scale.
9. The system of claim 1 , wherein the precursor powder is comprised of more than one thin film component.