Temperature Measurement in Rapid Thermal Annealing

Microelectronics Industry and consequently semiconductor research have developed into pillars of modern technology. Industrial demands for short process times at low cost are steadily increasing. Considerable attention is thereby drawn to ultra-short annealing cycles on the order of just a few milliseconds.
One major application for thermal annealers is to anneal damage caused by ion implantation. For this purpose temperatures above 600 °C are preferred, although a high diffusion rate of the dopants ought to be avoided. Therefore, short heating periods with steep ramp rates are desired.
This is where Flash Lamp Annealing comes into play. It allows for directed thermal treatment of surfaces within just a few milliseconds without or with drastically reduced thermal stress of the bulk material. Due to the selected wavelength range in the visible and near infrared region the lightpulse is absorbed by the near-surface layers and diffusion into the bulk is limited by the ultra-short time span. Thereby temperatures up to 2000°C are achieved dependent on the energy of the lightpulse and the optical properties of the sample. Cooling takes place by heat conduction into the bulk.
The applications are numerous, especially in thermal treatment of semiconductor surfaces where doping concentrations far beyond the solubility limit are desired, e.g. for ultra shallow implantation profiles. Similarily, highly doped layers are required when studying small scale effects like superconductivity brought about by the implanted dopant.
Due to the high energy density on the sample even high melting points can be achieved for defect annealing during recrystallization of the melt.
The response of various materials to subsecond thermal treatment, however, is not well understood for most cases, especially the temperature dependence of many material parameters is unknown to a large extent. Clearly, for deeper investigation into the subject a real-time temperature measurement with a high temperature resolution (ΔT << 5K), is crucial and is regarded as a key component in order to achieve rapid and reliable processing.
For this purpose traditional means of temperature measurement, e.g. thermocouples, must be excluded. Not only do they lead to wafer contamination but their long response time contradicts the ultra-fast annealing time of the Flash Lamp Device.
In the framework of the presentation previous non-contact approaches to rapid temperature measurement will be discussed with special regard to temperature resolution and industrial mass production.