Influence of Quartz Window on Bistability of the Silicon Wafer in Lamp-Based Reactor

The effect of a quartz plate (window) on the silicon wafer temperature is studied in the conditions of the combined thermal transfer in a lamp-based chamber for the rapid thermal treatment (RTP) set up. The quartz window influence, as a rule, is considered by restriction of the spectral interval for the heater emission in the spectral range from 0.4 to 4.0 µm. The chamber for RTP is simulated by a radiative-closed thermal system including the influence of quartz window as a spectral filter of lamp emission and a source of emitted thermal radiation. Energy equations for thermal fluxes involved in the heat input and output from the working wafer and quartz window are solved in spectral approximation. The model of the chamber composed of the three plates with different spectral ranges of the heater radiation can be considered as two limiting cases of the chamber model including the quartz window. The transfer characteristics that are defined by the temperature dependences of the silicon wafer and the quartz window on the temperature of the heater are accounted. It is shown that temperature bistability in the silicon wafer initiates induced bistability into the quartz window that does not reveal bistable behaviour because of the linear temperature dependence of its total optical characteristics. The width and the locations of the loops are exactly in accordance with the same parameters for the silicon wafer transfer characteristics. A possibility for simulation of the quartz window by spectral restriction of the heater radiation is confirmed. The availability of the weak bistable effect in the mode of zero effective heat exchange coefficient of a non-radiative component of the thermal flux removed from the working wafer has been obtained. In this case, the efficiency of the radiative heat removal from the silicon wafer in the low-temperature state is insufficient that the wafer is maintained in the stationary state.