Furnace anneal uses batch processing in a diffusion furnace for longer-duration thermal treatments including dopant diffusion, activation, and oxide growth. Temperature: Typically 800-1100 C. Lower temperatures for gentle annealing, higher for significant diffusion. Duration: Minutes to hours depending on process requirements. Much longer than RTA (seconds). Batch processing: 50-200 wafers processed simultaneously in horizontal or vertical tube furnaces. High throughput. Ramp rates: Slow temperature ramps (5-15 C/min) to avoid thermal stress and wafer warping. Contrast with RTA (50-200 C/sec). Applications: Drive-in diffusion of implanted dopants, thermal oxidation (dry and wet), LPCVD film deposition, densification anneals, stress relief. Diffusion profiles: Long anneal times produce broad, Gaussian diffusion profiles. Good for deep wells and isolation structures. Thermal budget: Significant thermal budget affects all previously formed junctions and structures. Must account for total thermal history. Atmosphere: N2, O2, H2/N2 (forming gas), or specific process gases depending on application. Equipment: Horizontal or vertical tube furnaces with quartz tubes. Kokusai, TEL, ASM, Tempress. Uniformity: Excellent temperature uniformity across batch. Temperature profiling along tube compensates for gas depletion effects. Limitation: High thermal budget unacceptable for advanced nodes requiring ultra-shallow junctions. RTA/spike/laser anneal preferred.