Process control system
AssigneeAvco Corporation
InventorsHarold E. DeBolt, Joseph Morrissey, Raymond J. Suplinskas
Life of this patent
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Abstract
This invention relates to a process control system and method of controlling a chemical vapor deposition (CVD) process where a coating is deposited on a substrate heated by passing a current through the substrate to create a heating zone. The control system relies on detecting a signal induced on the coated substrate outside of the heating zone and using the induced signal to control one or more process parameters.
Claims12
In a CVD reactor system for depositing a coating on a filament substrate in a heating zone within a reaction chamber to make a continuous filament, said substrate being heated by passing an electric current through the filament thereby defining a heating zone, the improvement comprising:
- a process control system having a pair of electrodes, at least one of which is outside the heating zone;
- voltage detection means coupled to said pair of electrodes for detecting a voltage induced between the electrodes;
- means for generating a control voltage in response to said induced voltage coupled to the voltage detection means;
- and
- means responsive to said control means for controlling a process parameter.
In a CVD reactor system for depositing a coating on a filament substrate moving through a heating zone within a reaction chamber to make a continuous filament, said substrate being heated by passing an electric current through the filament thereby defining a heating zone, the improvement comprising:
- means for supplying boron-forming feedstock to said reactor to deposit boron on said substrate;
- means for blending a hydrocarbon and hydrogen with said boron-forming feedstock for depositing B.sub.4 C on said boron;
- a process control system having a pair of electrodes, at least one of which is outside the heating zone,
- voltage detection means coupled to said pair of electrodes for detecting an induced voltage developed between the electrodes;
- means for generating a control voltage in response to said induced voltage;
- and
- means responsive to said control means for controlling the flow of hydrocarbon and/or hydrogen to said heating zone.
In a CVD process for depositing a coating in a heating zone defined by an electrically-heated filament through which a heating current is supplied by a pair of spaced-apart electrodes, a process control method comprising:
- sensing voltage changes induced between two points on the filament where one of said points does not carry heating current;
- generating a control signal in response to said voltage changes;
- and
- using the control signal to control a process parameter.
In a process for depositing B.sub.4 C on an electrically-heated boron filament moving through a heating zone by adding a hydrocarbon, a boron-forming feedstock, and hydrogen to the reaction zone, a method of controlling the process comprising:
- sensing a voltage induced in said filament outside of the heating zone forming a control voltage responsive to the magnitude of the induced voltage;
- and
- using said control voltage to control the flow of the hydrocarbon and/or hydrogen to said reaction zone.
Dependencies are inferred from the claim text.