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 may need optical transmission, thermal-cycling resistance, and sealing performance depending on the process and mounting design.

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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	Common Review Range	Custom
OD	Reviewed by forming route	Per drawing
Height	Reviewed by drawing	Per drawing
Wall thickness	Reviewed by application	Per drawing
Flange OD	Reviewed by sealing design	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 — stress-relief annealing reviewed by geometry and optical requirements
5. Final machining — flange face and OD/ID requirements finished to the agreed drawing
6. Leak testing — arranged for welded or vacuum-relevant assemblies when specified

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Quality Inspection

• Visual inspection under high-intensity illumination
• Helium leak testing for relevant welded or vacuum assemblies when specified
• Flange flatness verification according to agreed sealing requirements
• Wall thickness review where required by drawing
• Birefringence measurement where optical stress requirements are specified