In-situ monitoring of temperature and alloy composition of Hg1-xCdxTe using FTIR spectroscopic techniques

Optical real-time in-situ sensors play a very important role in the process ing of semiconductor devices because of their noncontact remote nature and excellent compatibility with UHV systems. In this work, we report on progre ss in developing an in-situ temperature sensor for HgCdTe structures grown by molecular beam epitaxy (MBE). Based on the Fourier transform infrared (F TIR) spectrometer, this sensor is capable of continuous real-time monitorin g of the surface temperature, thickness and alloy composition of HgCdTe epi layers, The accuracy and sensitivity of this FTIR technique were studied in all temperature ranges of interest. Also compared are two different method s of temperature determination obtained from the normalized spectral radian ce. The influence of stray radiation and of sample holder rotation on the m easurement accuracy have been studied, Reflectivity spectra for HgCdTe/CdZn Te(211) and HgCdTe/ CdTe(211)/Si(211) structures have been analyzed in real time in order to determine the layer thickness and alloy composition for g rowing layers. Also discussed is a multilayer-structure optical model devel oped to solve the problem of composition determination at early stages of g rowth. The application of this model for fitting the transmission spectra i s demonstrated.