rapidannealing

Rapid annealing, also called rapid thermal annealing (RTA), is a thermal processing technique that heats a material to a high temperature in a very short time and maintains a brief high-temperature exposure. The key feature is a high heating rate, typically hundreds of degrees Celsius per second, with dwell times ranging from a few seconds to a couple of minutes. This contrasts with conventional furnace annealing, which uses slower heating and longer dwell times. In some contexts, rapid annealing may also refer to laser or flash-annealing methods that deliver energy in very short pulses.

RTA is commonly implemented in semiconductor fabrication using lamp-based systems or laser sources. The sample is heated by intense infrared or visible light, achieving uniform surface heating or spot heating, often under inert gas or forming gas to control oxidation and contamination. Temperatures commonly range from about 600 to 1200°C, with process times from several seconds to a couple of minutes. After annealing, controlled cooling completes the cycle.

Applications include dopant activation after ion implantation, annealing of defects in silicon, polysilicon, and compound semiconductors, and crystallization or grain growth in metal oxide thin films. Rapid annealing reduces diffusion of dopants relative to longer annealing, enabling shallow junctions and reduced defect formation. It also minimizes unwanted reactions and impurity diffusion while delivering improved electrical or optical properties.

Limitations include nonuniform heating across large wafers, edge effects, and thermal stress. Equipment cost is high, and precise temperature measurement is critical due to the short processing times. The technique requires careful optimization of temperature profile, ambient gas, and film/substrate compatibility.