There is no common agreement on the definition of Rapid Thermal Annealing. Usually Rapid Thermal Annealing is understood to be:
• Single wafer processing
• Processing with shorter processing times in comparison to conventional batch furnaces
• Processing with fast heating and cooling rates
• Wafer is thermally isolated from processing chamber
• Cold wall and controlled ambient processing
• Processing with control of thermally driven surface reactions
The most important difference between conventional batch thermal annealing and Rapid Thermal Annealing is the fact that in an RTA system the processed wafer is never in thermal equilibrium with the surrounding environment.
The word “rapid” was used the first time in the Detailed Description section of the Mammels Patent “Method of Heat Treatment of Workpieces” filed in 1968. On a side note,
there was a lot of jockeying for semantic position – Varian was pushing the term Isothermal Annealing, and AG Associates pushing “Heat Pulse Annealing”, and academics using terms such as “Blink Furnace Annealing”. As time passed Rapid Thermal Annealing and Rapid Thermal Processing became the common term; a lot better than Rapid Isothermal Processing – whose acronym (RIP) didn’t seem particularly auspicious. In reality, Rapid Thermal Annealing (RTA) is one of the most complex segments of semiconductor manufacturing
involving the quantum and solid state physics, optics, and engineering. However, the basic principle is very simple. This simple basic principle of Rapid Thermal Annealing (RTA) leads many people to believe that any “garage operation” can build an Rapid Thermal Annealing (RTA) system. There was a time when 14 companies offered rapid thermal processing systems. A lot of people learned the lesson the hard way, many times paying a high price for mistakes made. In such situations it is human nature that people remember the historical development from their point of view.
Rapid Thermal Annealing (RTA) may be seen as a success or a failure, depending on what you want to see and if you are user or manufacturer of Rapid Thermal Annealing (RTA) equipment. The reason for many failures of Rapid Thermal Annealing (RTA) in the past is so called “mind conditioning”. Mind conditioning is basically an addiction by being constantly told that some things are good and others are bad.
Regardless of the past RTA slowly gained acceptance for implant anneals and processes where chamber ambient needs to be well controlled. Very likely, as the trend towards
single wafer processing continues, Rapid Thermal Annealing (RTA) will gradually play a more important role in thermal processing of semiconductors. There is common belief that Rapid Thermal
Processing of semiconductors was a continuation of the laser processing of semiconductors. However, incoherent lamp based systems were developed and used much
earlier than laser processing techniques. Unfortunately, several excellent ideas were invented too early when no market and application existed. This is probably the
reason why Rapid Thermal Processing of semiconductors instead of going through a thorough and systematic scientific development followed a chaotic and spontaneous road of partial improvements. In the past the Rapid Thermal Annealing (RTA) market was so small that it never attracted large companies with resources to solve serious Rapid Thermal Annealing (RTA) technical challenges. The conventional batch furnace has proven to be a reliable, low cost technology. Traditional lamp basedRapid Thermal Annealing (RTA) systems still have many problems in a manufacturing environment. As long as a working alternative to the processing is available it is very difficult to significantly penetrate the market with a new unproved technology.
