INSITU ELLIPSOMETRY FOR REAL-TIME FEEDBACK-CONTROL OF OXIDATION FURNACES

A real-time control system is presented which has been developed in order to enhance accuracy and repeatability of layer processing in horizontal or vertical furnaces. The measurement system consists of an in situ ellipsometer and prism-based lightguiding optics for polarized light. Routines have been implemented for convenient alignment and real-time calculation of layer thickness taking into account the optical properties at high temperatures. Statistical data illustrate the improvement of reproducibility of thermal oxidation by end-point detection and end-point prediction. Feasibility of process integrity control and closed-loop control is demonstrated.