Thermal Technology LLC

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Chemical Vapor Deposition (CVD) &
Chemical Vapor Infilitration (CVI)

 
GENERAL DESCRIPTION
 
CVD and CVI furnaces are designed for chemical vapor deposition (CVD) and chemical vapor infiltration (CVI) of refractory ceramic and metallic coatings. Standard furnaces are rated for use to 1600°C, with an optional upgrade to 2200°C for pyrolytic graphite and other high temperature deposition processes.
 
Each vacuum furnace is supplied as a complete system including: vacuum chamber, hot zone, power supply, vacuum pump, and a programmable control system. Manual process controls are provided for two reactant gases and one inert blanket gas. Additional flow channels are optionally available, as well as fully automatic process and blanket gas control systems.
 
CVD Furnace Model 814G   CVD Furnace Model 1200-1836
Top Loader
(Model 814G)
 
Bottom Loader
(Model 1200-1836)

 
CHAMBER AND HOT ZONE
 
Thermal Technology's CVD and CVI vacuum furnace vessels are manufactured with stainless steel, including the chamber, water jacket, and all flanges. Process gas and vacuum pump manifolds are also made with stainless steel, as well as any additional piping which may come in contact with chlorinated or fluorinated gases. Nickel gaskets are used as vacuum seals on small diameter piping where practical, and Viton O-rings on larger diameter flanges such as the main door and vacuum pumping system ports.
 
Graphite hot zones are used on all CVC and CVI vacuum furnaces, including graphite resistance heating elements and low density fibrous graphite insulation. Internal graphite retorts are also supplied to provide a barrier between blanket and process gases, thereby containing reactive gases and effluents. A graphite exhaust tube directs effluent gases to the pumping system while a gas supply manifold brings reactants into the retort. Internal gas distribution manifolds are normally provided by the user, or custom designed to meet a specific application. 
 
 
VERTICAL CVD/CVI VACUUM FURNACES
 
GAS CONTROLS
 
CVD & CVI vacuum furnaces include a basic gas supply system that can be upgraded to meet individual requirements. The basic system includes two corrosion resistant rotometers with manual needle valve controls, a laser welded stainless steel diaphragm pressure gauge, and manual blanket gas controls. The blanket gas controls include a shut-off valve, rotometer flow indicator, and a needle valve to adjust the flow of protective inert gases which surround the retort.
 
Optional enhancements include mass flow controllers, automatic retort pressure control systems, and automatic blanket gas pressure control systems. (See schematic drawing below.)
 
The automatic retort downstream pressure control system includes an absolute pressure capacitance manometer, a proportional control valve on the retort exhaust manifold, and a pressure control panel for maintaining process gas pressure at a constant level.
 
The automatic blanket gas upstream pressure control system uses a differential pressure capacitance manometer to monitor the pressure difference between the inside and outside of the retort. A set-point control panel maintains a constant positive pressure differential outside the retort by adjusting a proportional valve which controls inert blanket gas flow.
 
CVD and CVI vacuum furnaces must be furnished with a combustible gas safety system if explosive concentrations of combustible gases will be present. This optional system includes a blow-off port, burn-off tower, and extensive safety interlocks. Blow off and pressure relief ports must be properly vented by the user.
CVD / CVI Vacumm furnace 
SPECIAL FEATURES
  • Corrosion resistant vacuum pump, gauges and fittings 
  • Complete stainless steel chamber construction

VACUUM PUMPS
 
CVD and CVI vacuum furnaces are supplied with corrosion resistant two stage mechanical vacuum pumps designed for operation with chlorinated and fluorinated gases. Standard pumps are sized for rapid chamber evacuation to less than 0.1 torr in approximately five minutes.
 
The chamber can then be backfilled for deposition near atmospheric pressure, or operated above one torr with moderate gas flows. Deposition at lower pressures or with high gas flows will require a larger pump or the addition of a mechanical booster pump.
 
All pumps are normally provided with high-grade hydrocarbon oil. Synthetic inert fluids can be optionally provided, as well as oil filtration systems, inlet traps, and mist eliminators.
 
POWER SUPPLY

Two different power supplies are available, depending on whether the furnace will be used to 1600°C or 2200°C. Each supply is generously sized with ample reserves for load heatup and compensation for heat zone aging. Furnace heatup time to full temperature is typically one to two hours or less. 
        
 
ADDITIONAL INSTRUMENTATION
 
Microprocessor based programmable controllers are provided for all furnaces. The standard controller is capable of storing ten ramp and ten soak segments as well as two process events such as pump-down or backfill. Controllers with more extensive capabilities are optionally available, as well as custom designed control systems to meet any requirement.
 
Temperature sensing is done with a tungsten- rhenium thermocouple, or optionally with an infrared pyrometer. Independent over-temperature control systems using either a thermocouple or power transducer are also available. Two thermocouple gauges measure vacuum and a PLC coordinates system functions and provides safety interlocks.

 
Typical control cabinet features include:
 
  •  Pyrometer or TC    • Ionization gauge  
   • TC gauges    • Programmable logic controller  
  •  Voltmeters    • Ammeters  
 
 
INSTALLATION
 
Thermal Technology can provide assistance in selecting and installing scrubbers, gas bubblers, gas cabinets, mass spectrometers, exhaust hoods, and related equipment. Changes will be based on actual engineering time involved, field personnel time and travel expenses, subcontractor payments, and equipment costs. 

CUSTOM FURNACE DESIGN

Our engineering team can design a custom vacuum  furnace system to meet your exact requirements. When your needs exceed the capabilities of our standard models, you can count on receiving the same quality and reliability in a customized system. Typical reasons for needing a customized system include larger work loads, specialized control requirements, and proprietary gas handling systems.
 
Extensive design, fabrication, and testing skills are available for use in developing furnaces built for a specific application. Our custom designed vacuum furnaces are located at national laboratories and major corporations around the world. When you need the best—call Thermal Technology.
  
Press Release - Sept 1999
 
All specifications are subject to change.  Final quotation will be the governing document in all cases.