FUSED QUARTZ
Quartz Bell Jar & Dome
Blown and formed fused quartz bell jars and domes for CVD, epitaxy, and sputtering reactor enclosures — up to 500 mm diameter with hermetic weld flanges.
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Quartz Bell Jars & Domes
Bell jars and domes provide the primary reactor enclosure in CVD, epitaxy, and PVD systems. The quartz envelope must transmit radiant energy from heating lamps, withstand cyclic thermal stress from process heating, and maintain vacuum-grade hermeticity.
Configurations
Standard Bell Jar
Cylindrical body with hemispherical or flat-bottom closed top, open flanged bottom for mounting to the base plate.
| Dimension | Standard Range | Custom |
|---|---|---|
| OD | 100–500 mm | Up to 600 mm |
| Height | 100–800 mm | Per drawing |
| Wall thickness | 3–8 mm | Per drawing |
| Flange OD | OD + 30–50 mm | Per drawing |
Reactor Dome (Low-Profile)
Shallow dome geometry for rapid thermal processing (RTP) and single-wafer reactors — minimizes internal volume for faster purge and pump-down.
| Diameter | Profile Height | Wall | Application |
|---|---|---|---|
| 200–250 mm | 50–80 mm | 3–5 mm | 8” wafer RTP |
| 300–350 mm | 60–100 mm | 4–6 mm | 12” wafer RTP |
| Custom | Per spec | Per spec | CVD/epitaxy |
Manufacturing Process
Bell jars are formed by:
- Blank preparation — cylindrical quartz tube or blown preform machined to near-net shape
- Flame forming — dome/hemispherical closed top formed by controlled oxy-hydrogen flame working
- Flange attachment — precision-machined flange fusion-welded to open end
- Annealing — full stress-relief anneal; birefringence verified < 10 nm/cm
- Final machining — flange face ground flat (< 0.05 mm); OD/ID ground to tolerance
- He leak test — 100% on all weld seams
Quality Inspection
- Visual inspection under high-intensity illumination (bubble, cord, inclusion mapping)
- He mass spectrometer leak test at all weld joints
- Flange flatness CMM verification
- Wall thickness measurement (ultrasonic) at 12 points
- Birefringence measurement (polariscope)