Thermal Oxidation — Wet and Dry
Related parts: Quartz tubes, quartz boats, MFCs (O2, H2), heater assemblies, temperature controllers
Thermal Oxidation — Wet and Dry
Category: Thermal
Process Overview
Thermal oxidation is a critical semiconductor manufacturing process used to grow high-purity silicon dioxide (SiO₂) layers on silicon wafers. It is fundamental for creating insulating layers, gate dielectrics, and surface passivation in devices like CMOS transistors and MEMS sensors. The process occurs in high-temperature furnaces, where silicon reacts with oxygen (dry oxidation) or water vapor (wet oxidation). Wet oxidation, which uses steam, produces faster growth rates (1–5 nm/hr) compared to dry oxidation (0.1–0.5 nm/hr), making it ideal for thicker oxides. In data center chip manufacturing, thermal oxidation ensures reliability in high-performance logic and memory devices by enabling precise dielectric layers.
The process is performed in quartz-lined furnaces to prevent contamination, with strict control over temperature, gas flow, and pressure. Industry standards like SEMI E142-0707 (Thermal Processing Equipment) and ISO 14644-1 (Cleanroom Classification) govern chamber design and environmental conditions to ensure uniformity and safety.
Key Process Parameters
| Parameter | Typical Range | Unit |
|----------------------|--------------------------------|----------|
| Temperature | 900–1200°C | °C |
| Pressure | 1 atm (atmospheric) | atm |
| O₂ Flow (dry) | 100–500 sccm | sccm |
| H₂/O₂ Ratio (wet) | 1:1–2:1 (for steam generation) | — |
| Oxide Growth Rate | 0.1–0.5 nm/hr (dry); 1–5 nm/hr (wet) | nm/hr |
| Heater Power | 10–50 kW | kW |
Equipment & Parts Required
- Quartz Tubes & Boats: High-purity quartz contains the high-temperature environment and prevents contamination. Quartz boats hold wafers during processing. Caladan’s fused silica quartz components are engineered for thermal stability up to 1600°C.
- Mass Flow Controllers (MFCs): Precisely regulate O₂ and H₂ flows to generate consistent steam (wet oxidation) or control dry O₂ partial pressure. Caladan’s MFCs offer ±1% accuracy for repeatable results.
- Heater Assemblies: Resistive heaters (typically silicon carbide or graphite) achieve and maintain process temperatures. Caladan’s modular heater designs allow rapid zone-specific temperature adjustments.
- Temperature Controllers: PID controllers ensure ±1°C stability, critical for uniform oxide thickness. Caladan’s controllers integrate with SEMI E142-compliant furnace systems.
Common Issues & Troubleshooting
- Non-Uniform Oxide Thickness: Often caused by temperature gradients. Fix: Calibrate heater zones and inspect thermocouples. Replace faulty heater elements if temperature deviations exceed ±3°C.
- Contamination in Quartz Tubes: Particulates or outgassing degrade oxide quality. Fix: Replace quartz tubes with Caladan’s high-purity, low-defect alternatives and perform post-process cleaning.
- Gas Flow Instability: Inconsistent MFC readings lead to fluctuating steam/O₂ ratios. Fix: Recalibrate MFCs or replace with Caladan’s fail-safe models featuring built-in diagnostics.
- Quartz Boat Deformation: Thermal stress or prolonged high-temperature use warps boats. Fix: Replace with Caladan’s reinforced quartz boats rated for >10,000 process cycles.
Frequently Asked Questions
Q1: What is the primary difference between wet and dry oxidation?
“Wet oxidation uses steam to grow oxide faster (1–5 nm/hr), while dry oxidation employs O₂ for slower, denser layers (0.1–0.5 nm/hr). Wet is preferred for thicker oxides, dry for high-quality gate dielectrics.”
Q2: What temperature range is required for thermal oxidation?
“The process typically occurs between 900°C and 1200°C, depending on oxide thickness and uniformity requirements.”
Q3: Why are quartz tubes essential for this process?
“Quartz is chemically inert and thermally stable up to 1600°C, preventing contamination and ensuring consistent oxide quality.”
Q4: How do I ensure gas flow safety during wet oxidation?
“Always use SEMI S23-compliant gas delivery systems with redundant shut-off valves. Caladan’s MFCs include H₂ leak detection for real-time safety monitoring.”
Q5: What industry standards govern thermal oxidation equipment?
“SEMI E142-0707 defines thermal processing equipment requirements, while ISO 14644-1 ensures cleanroom particulate control during oxide growth.”
Parts for This Process
Looking for parts to support this process? Caladan Semi stocks used and refurbished components including: Quartz tubes, quartz boats, MFCs (O2, H2), heater assemblies, temperature controllers.
Parts for This Process
Caladan stocks used and refurbished parts for thermal oxidation — wet and dry equipment — tested, inspected, and ready to ship.