Quartz Heat Shield

The Quartz Heat Shield, made of milky white quartz, is an advanced thermal management component tailored for use in high-temperature SiC epitaxy systems. Compared to transparent quartz, this material provides superior insulation, improved process stability, and better cost-efficiency—making it ideal for thermal shielding in MOCVD and CVD reaction chambers.

Ⅰ. Material Composition & Key Physical Properties

● Material: Milky white quartz (synthetic fused silica with dispersed microbubbles and grain boundaries)

● Color & Appearance: Translucent white

● Thermal Conductivity: Lower than transparent quartz due to internal bubble structure

● Working Temperature: Stable up to 1700°C

● Thermal Expansion Coefficient: ~0.55 × 10⁻⁶ /K (same as transparent quartz)

● High Thermal Shock Resistance

● Excellent Chemical Purity: Trace impurities (e.g., Al, Na) maintained below 1 ppm

Ⅱ. Key Functions in SiC Epitaxy Applications

Milky white quartz is specifically selected for SiC epitaxial reactors due to the following critical advantages:

(1) Enhanced Thermal Insulation Performance

Infrared Radiation Scattering: The internal bubbles and grain boundaries scatter IR radiation multiple times, significantly reducing radiative heat transfer. Offers 30–50% better insulation than transparent quartz under 1500–1700°C conditions.

Low Thermal Conductivity: Microbubble distribution decreases conductive heat loss, optimizing overall thermal efficiency.

(2) High-Temperature Durability & Stability

Thermal Shock Resistance: While sharing the same expansion coefficient as clear quartz, its microstructure helps absorb localized thermal stress—ideal for fast ramp-up/ramp-down processes.

Crystallization Resistance: In high-temperature reducing atmospheres (e.g., H₂), milky quartz is more resistant to devitrification into α-cristobalite, minimizing fracture risk.

(3) Process Compatibility & Deposition Control

Reduced Parasitic Deposition: Its opacity mitigates local overheating, which prevents premature decomposition of precursors (e.g., SiH₄, C₃H₈) on shield surfaces.

Uniform Temperature Field: Scattering behavior promotes even temperature distribution across the reaction zone, crucial for achieving epitaxial layer uniformity in SiC power devices.

(4) Cost-Effectiveness

Lower Material Cost: Milky white quartz is typically more affordable than ultra-high-purity transparent quartz, making it suitable as a consumable thermal barrier component.

(5) Maintenance & Considerations

Purity Assurance: Ensure extremely low impurity levels (Al, Na < 1 ppm) to avoid contamination of the SiC epitaxial surface.

Lifecycle Management: After long-term use (typically >1000 hours), microbubble coalescence may degrade thermal performance—regular replacement is recommended.

Typical Applications

✔SiC MOCVD and CVD reactors

✔Epitaxial growth of SiC power semiconductors

✔High-temperature diffusion and deposition chambers

✔Thermal shielding in vacuum/inert gas environments