Wafer temperature measurement in conduction-based RTP systems

In conduction-based RTP systems the heating relies on the conduction of energy through a thin gas layer of gas between the wafer and the surrounding chamber walls. In most of these types of systems a gas flow is used to control the heating ambient. It turns out that the pressure drop in the system is a direct measure of the wafer temperature. This principle is used to determine the wafer temperature in the Levitor system. With this method, temperature measurements can be carried out in the range 200–1100°C. The absolute accuracy and repeatability in steady state (i.e. long processing times) is 4°C and 1.5°C (1σ), respectively. The time resolution is in the ms range. Transient phenomena that influence the measurements in short anneal processes are discussed in detail, and procedures are given to correct for such effects.