In situ optical monitoring for SiGe epitaxy

In situ spectroscopic ellipsometry (SE) has been used to monitor growth of SiGe/Si epitaxial layers with box or step-graded Ge composition profiles. R eal-time estimates of both Ge concentration and layer thickness have been m ade as a function of time. Estimates of Ge concentration are generally accu rate, but total thickness is often under-estimated when very thin increment al surface layers are analysed. Interface grading observed when gases are s witched into the reactor is shown to depend on the presence of hydrogen in the mixture. A new algorithm for analysis of real-time SE data, which allow s prior knowledge about the growth system to be used in process control, is described. (C) 2000 Published by Elsevier Science B.V. All rights reserved .