Photon effect on radiative properties of silicon during rapid thermal processing

Abstract

Emissivity is a critical parameter in the rapid thermal processing (RTP) of semiconductors for temperature control and thermal modeling. It is often considered as a material property that depends on the sample temperature and surface finishing. For a silicon wafer placed in a radiation environment such as a RTP chamber, however, the ambient photons emitted from lamps create electron-hole pairs in the wafer. These electrons and holes participate in the thermal emission from the wafer and change its radiative properties. This work studies this photon effect on the radiative properties of silicon and demonstrates, through modeling and experiment, that radiative properties of a silicon wafer may depend on the temperature of the lamps due to free-carrier excitation. Such an photon effect imposes a limit on the accuracy of temperature measurement by the infrared pyrometry method in a RTP environment. It is also an important factor to consider in the measurement of the temperature dependence of silicon’s optical properties and in the thermal modeling of the RTP.