oxidation furnace

An oxidation furnace is a specialized diffusion furnace designed to grow thermal silicon dioxide by exposing silicon wafers to an oxidizing ambient at high temperature. **Process**: Si + O2 -> SiO2 (dry) or Si + 2H2O -> SiO2 + 2H2 (wet/steam). Silicon is consumed as oxide grows. **Dry oxidation**: Pure O2 ambient. Slow growth rate but highest quality oxide. Used for gate oxides and thin critical oxides. **Wet oxidation**: Steam (H2O) ambient. Much faster growth rate (5-10x dry). Used for thick field oxides, isolation, and pad oxides. **Temperature**: 800-1200 C. Higher temperature = faster oxidation rate. **Deal-Grove model**: Mathematical model predicting oxide thickness vs time. Linear regime (thin oxide, surface-reaction limited) and parabolic regime (thick oxide, diffusion limited). **Furnace design**: Horizontal or vertical quartz tube with controlled gas delivery. Pyrogenic steam generation (H2 + O2 torch) for wet oxidation. **Thickness control**: Controlled by temperature, time, and ambient. Reproducibility within angstroms for gate oxide. **Si consumption**: Approximately 44% of final oxide thickness comes from consumed silicon. Important for dimensional control. **Chlorine addition**: Small amounts of HCl or TCA added to getter metallic contamination and improve oxide quality. **Equipment**: Same furnace platforms as diffusion (Kokusai, TEL). Dedicated tubes for oxidation to prevent cross-contamination.