Quartz Viewport Window

Quartz & Sapphire Viewport Windows

Viewport windows allow optical access to semiconductor process chambers for endpoint detection, optical emission spectroscopy (OES), pyrometry, laser heating, and visual inspection — without compromising chamber vacuum or gas purity.

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Window Material Selection

Property	Fused Quartz	Synthetic Fused Silica	Sapphire
Transmission range	150 nm – 3.5 μm	150 nm – 3.5 μm	140 nm – 6 μm
Max use temperature	1200°C	1200°C	1900°C
Chemical resistance (plasma)	Excellent	Excellent	Superior
Purity (trace metals)	< 20 ppm	< 50 ppb	N/A (single crystal)
Achievable Ra	< 0.5 nm	< 0.5 nm	< 0.1 nm
Best use case	General monitoring	High-purity CVD	Plasma + high-temp

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Unmounted Windows (Blanks)

Polished window blanks without flanges — for customer-integration into existing viewport assemblies.

Specification	Standard	Precision
Diameter tolerance	±0.05 mm	±0.02 mm
Thickness tolerance	±0.05 mm	±0.02 mm
Surface roughness (both faces)	Ra 0.5–2 nm	Ra < 0.5 nm
Flatness (surface form)	λ/4	λ/10
Parallelism	< 3 arc-min	< 1 arc-min
Edge chamfer	0.3–0.5 mm × 45°	0.1–0.3 mm × 45°
Clear aperture	≥ 85% of diameter	≥ 90% of diameter

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Flanged Viewport Assemblies

Complete viewport assemblies with metal flanges for direct bolt-on installation to chamber walls.

Flange Type	Description	Leak Rate
CF (ConFlat) flange	UHV-rated metal knife-edge seal	< 1×10⁻¹⁰ mbar·L/s
ISO-KF flange	Quick-release O-ring seal	< 1×10⁻⁸ mbar·L/s
Custom bolt-pattern flange	Per customer drawing	Per spec

Window-to-flange attachment methods: optical contact bonding, metallic indium seal, or brazed (sapphire only).

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Anti-Reflection Coatings

AR coatings are available for specific wavelength applications:

Coating	Wavelength	Reflectance	Application
Single-layer MgF₂	Broadband VIS	< 1% per face	General monitoring
V-coat	193 nm (ArF)	< 0.5% per face	DUV lithography monitoring
V-coat	248 nm (KrF)	< 0.5% per face	KrF process monitoring
V-coat	532 / 1064 nm	< 0.2% per face	Laser pyrometry
Dual-band	355 + 1064 nm	< 0.5% per face	Multi-wavelength systems

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Typical Applications

• OES endpoint detection — plasma etch process control
• Pyrometry windows — temperature measurement via IR transmission
• Laser heating observation ports — RTP, annealing
• In-situ reflectometry — CVD film thickness monitoring
• UV process monitoring — DUV lamp-based cleaning/curing systems