Materials
Fused Quartz Glass
High-purity amorphous silicon dioxide glass with exceptional thermal stability and ultra-low thermal expansion — the core material for semiconductor process components.
What Is Fused Quartz Glass?
Fused quartz glass — also called fused silica — is an amorphous (non-crystalline) form of silicon dioxide (SiO₂) produced by melting high-purity quartz crystal or synthetic silicon compounds at temperatures exceeding 1700°C. Unlike borosilicate glass, fused quartz contains virtually no metallic oxides, giving it a unique combination of properties:
- Extreme thermal stability — softening point above 1683°C
- Negligible thermal expansion — CTE of only 0.55 × 10⁻⁶/°C, roughly 15× lower than stainless steel
- Excellent UV transparency — transmits from 150 nm to 3500 nm
- Superior chemical resistance — resistant to almost all acids except HF and hot phosphoric acid
- Ultra-low metallic contamination — critical for preventing wafer contamination in semiconductor processes
Material Grades Available
Tuguan Semiconductor stocks and machines three primary fused quartz grades, each suited to different purity and performance requirements:
Grade 1 · Natural Fused Quartz
| Property | Value |
|---|---|
| SiO₂ Purity | ≥ 99.99% |
| OH Content | < 30 ppm |
| Total Metallic Impurities | < 20 ppm |
| Max Use Temperature | 1150°C continuous / 1400°C short-term |
| Thermal Expansion Coefficient | 0.55 × 10⁻⁶/°C |
| Softening Point | 1683°C |
| Annealing Point | 1120°C |
| Refractive Index (589 nm) | 1.4585 |
| Density | 2.20 g/cm³ |
Best for: Standard diffusion tubes, furnace liners, wafer boats for temperatures up to 1150°C. Equivalent to Momentive GE-124 / Heraeus F300 / Tosoh ES grades.
Grade 2 · Synthetic Fused Silica (High Purity)
| Property | Value |
|---|---|
| SiO₂ Purity | ≥ 99.9999% |
| OH Content | 800–1200 ppm (standard wet) / < 1 ppm (dry grade) |
| Total Metallic Impurities | < 50 ppb |
| Max Use Temperature | 1200°C continuous |
| Key Advantage | Ultra-low trace metal contamination |
Best for: CVD chambers, wet-etching components, cleaning tanks, and any application where trace metal contamination at the ppb level cannot be tolerated. Equivalent to Momentive HPFS 7980 / Heraeus Suprasil grades.
Grade 3 · Opaque (Milky) Fused Quartz
| Property | Value |
|---|---|
| SiO₂ Purity | ≥ 99.9% |
| Appearance | Translucent / milky white |
| IR Reflectivity | > 90% |
| Max Use Temperature | 1100°C |
Best for: Thermal shields, boat holders, and insulation components where high infrared reflectivity is needed rather than optical transparency.
Physical & Optical Properties
| Property | Value | Test Standard |
|---|---|---|
| Density | 2.20 g/cm³ | ISO 1183 |
| Vickers Hardness | ~600 HV | ISO 6507 |
| Young’s Modulus | 73 GPa | — |
| Poisson’s Ratio | 0.17 | — |
| Thermal Conductivity | 1.38 W/(m·K) at 20°C | — |
| Dielectric Constant | 3.75 at 1 MHz | — |
| UV Transmission (200 nm) | > 90% (2 mm thickness) | — |
| Birefringence | < 5 nm/cm (annealed) | — |
Why Fused Quartz for Semiconductor Manufacturing?
Semiconductor wafer fabrication imposes severe requirements on process components:
- Thermal cycling resistance — Diffusion furnaces ramp from room temperature to 1000–1200°C repeatedly; the ultra-low CTE of quartz prevents cracking from thermal shock.
- Metallic purity — Even ppb-level contamination from process tube materials can introduce lifetime-killing traps in silicon. Natural fused quartz offers < 20 ppm total metals; synthetic silica achieves < 50 ppb.
- Chemical inertness — Process gases (O₂, N₂, Cl₂, HCl) and cleaning chemicals (HF, H₂SO₄, HCl) do not react with SiO₂ under normal process conditions.
- Dimensional stability — At 1000°C continuous operation, quartz maintains dimensional integrity far better than metals or polymers.
Our Machining Capabilities on Fused Quartz
Tuguan Semiconductor applies the following processes to fused quartz billets and tubing:
| Process | Achievable Specification |
|---|---|
| CNC cylindrical grinding | OD/ID tolerance ±0.01 mm |
| Face grinding & lapping | Flatness < 0.002 mm |
| Precision cutting (diamond wire) | Thickness ±0.02 mm |
| CNC drilling | Hole diameter ±0.01 mm, position ±0.02 mm |
| Optical polishing | Ra < 0.05 μm, surface form λ/4 |
| Fusion welding | He leak rate < 1×10⁻⁹ mbar·L/s |
| Flame bending / flaring | Wall uniformity ±10% |
| Annealing | Birefringence < 5 nm/cm |
Typical Products Machined from Fused Quartz
- Diffusion tubes & furnace liners — straight-bore, flanged, or bell-end configurations
- Wafer boats — horizontal and vertical, 4”–12” wafer compatibility
- Focus rings & etch rings — tight-tolerance plasma-facing components
- Bell jars & domes — CVD and epitaxy reactor enclosures
- Observation windows & viewports — optically polished flat or curved surfaces
- Cleaning tanks — HF/SC-1/SC-2 compatible wet cleaning vessels
- Gas injectors & showerheads — precision multi-hole gas distribution
Certifications & Documentation
Every fused quartz component ships with:
- Material certificate including XRF/ICP-OES purity data
- Dimensional inspection report traceable to calibrated CMM
- Surface condition report (roughness + cleanliness)
Certificates of conformance for ISO 9001, RoHS, and REACH available upon request.