Description
Furnace & diffusion tubes are fused-quartz process-chamber tubes used inside diffusion, oxidation and related high-temperature furnaces for semiconductor and solar-cell wafer processing. Unlike general straight quartz tubing, the critical product parameters are the chamber end geometry, gas inlet and exhaust arrangement, flange interface, heated-zone length and wafer-boat clearance.
The base OD, ID, wall-thickness and fabrication range follows the general Fused Quartz Tubes specification. This page focuses on the dimensions and interfaces that determine furnace fit and process-chamber function.
Process Tube Geometry
| Parameter | Furnace Tube Specification |
|---|---|
| OD | 25–300 mm standard; custom process tubes up to 500 mm |
| ID / Wall Thickness | Selected from the general quartz tube dimensional and tolerance range according to required chamber clearance and structural load |
| Length | Matched to heater-zone length, wafer-boat travel and load / unload clearance |
| Cross-Section | Round process chamber |
| End Geometry | Open end, closed end, flanged end and ported closed-end configurations |
Heated Zone & Boat Clearance
Hot Zone Length — The usable chamber length is matched to the furnace heater zone and the loaded wafer-boat length so the process load remains within the controlled thermal region.
Boat Clearance — Tube ID is selected around the wafer-boat OD, carrier geometry and required running clearance. This is particularly important on horizontal systems where the boat is cantilever-loaded through the open end of the process tube.
| Design Input | Controls |
|---|---|
| Heater-zone length | Required hot-zone / usable chamber length |
| Wafer-boat OD | Minimum process-tube ID and running clearance |
| Boat load length | Required heated process length |
| Load / unload travel | Overall tube length and open-end clearance |
| Door / seal position | Flange position and end-interface geometry |
End & Port Designs
Standard Diffusion Tube — One end open for wafer-boat loading and one end closed with a center gas inlet.
Open-End Flange — The loading end can be formed or welded with a quartz flange to increase sealing area and match the furnace door or O-ring interface.
Single Gas Inlet — Central or offset rear inlet for controlled process-gas delivery.
Double Gas Inlet — Dual-port configuration for separate gas feeds or process-gas distribution.
Rear Exhaust / Scavenger Port — Additional outlet geometry for systems using dedicated exhaust or scavenger flow paths.
Thermocouple Well — Integrated quartz well or branch tube for temperature sensing where the furnace assembly requires an isolated probe position.
Furnace Fit
| Furnace Type | Typical Tube Configuration | Fit-Control Parameters |
|---|---|---|
| Horizontal Furnace | Open-ended or single-flanged process tube with cantilever-loaded wafer boat | Tube ID, hot-zone position, boat running clearance, flange face and gas-port location |
| Vertical Furnace | Liner / process tube with flange assembly; wafer boat loaded through flange opening | Flange OD, opening ID, vertical chamber length, liner position and port arrangement |
| OEM Replacement Tube | Replacement chamber matched to existing furnace hardware | Door interface, O-ring land, flange profile, total length, inlet / exhaust positions and mating dimensions |
Flange and end-interface geometry can be matched to the existing furnace door and sealing hardware used on SVG-, Thermco- and Kokusai-type systems when the mating dimensions are supplied.
Material Options
| Material | Use | Selection Driver |
|---|---|---|
| Type I Electrically Fused Quartz | Standard furnace and diffusion-tube material | High-temperature process chamber use and general semiconductor furnace service |
| GE214-Equivalent Quartz | General semiconductor process tubes | Standard electrically fused quartz specification |
| Low-Alkali GE224-Equivalent Quartz | Contamination-sensitive furnace processes | Reduced alkali contamination requirement |
Related Fabrication
Flange Forming & Welding — Single-end flanges, welded quartz flanges and furnace-door mating interfaces.
Branch-Port Welding — Gas inlet, exhaust and thermocouple-well ports welded to the process tube body.
Closed-End Forming — Rounded, formed or welded closed ends with integrated gas inlet geometry.
Cutting & Grinding — Finished tube length, flange-face cleanup and end preparation before welding or furnace fit-up.
Post-Weld Annealing — Flame or furnace annealing applied where required after major welded assemblies.
What to Specify for a Furnace Tube
| Required Input | What It Defines |
|---|---|
| Furnace make / model or mating drawing | Door, flange, seal and port interface |
| Tube OD / ID or wall thickness | Base chamber size |
| Total tube length | Installation and loading envelope |
| Heated-zone length | Usable process chamber |
| Wafer-boat OD and load length | Internal clearance and hot-zone fit |
| Gas inlet / exhaust positions | Port quantity, diameter and location |
| Flange dimensions | Door / O-ring mating interface |
| Quartz grade | Material / contamination requirement |
