Quartz Bell Jar & Dome

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.

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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

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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

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Manufacturing Process

Bell jars are formed by:

1. Blank preparation — cylindrical quartz tube or blown preform machined to near-net shape
2. Flame forming — dome/hemispherical closed top formed by controlled oxy-hydrogen flame working
3. Flange attachment — precision-machined flange fusion-welded to open end
4. Annealing — full stress-relief anneal; birefringence verified < 10 nm/cm
5. Final machining — flange face ground flat (< 0.05 mm); OD/ID ground to tolerance
6. He leak test — 100% on all weld seams

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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)