Axial uniformity is achieved using multi-zone heaters.
Quartz hardware allows operation at temperatures in excess of 1000 C, although at very high temperatures migration of sodium through the furnace tube becomes a concern for MOS device fabrication. Transient temperature control is much more challenging. Modern reactors employ model-based temperature control to minimize heatup and cooldown ramp times. Radial film uniformity Radial uniformity is excellent if pressure is low and surface reaction rate slow. Wide variations can occur depending on loading conditions, operating temperature, gas flow rates, and injection scheme.