Feedback control of MOCVD growth of submicron compound semiconductor films

The problem of controlling the growth of submicron compound semiconductor films using metalorganic chemical vapor deposition (MOCVD) is considered. This is a new control application aimed at one of the key processes in the compound semiconductor manufacturing industry. This paper begins by introducing epitaxy, the MOCVD process, and spectroscopic ellipsometry in an effort to clearly understand the control problem. Distinguishing between design and implementation issues, a systematic approach toward controller design is then proposed that accommodates the nonlinearity and uncertainty inherent in this process. The key idea is that structure in the process model can be exploited through a change of coordinates to facilitate the use of linear design methodologies. Finally, experimental results are presented, demonstrating composition control of Al_xGa_1-x As and thickness control of GaAs