Real-time composition control of InAlAs grown on InP using spectroscopic ellipsometry

Spectroscopic ellipsometry (SE) was shown to be an accurate in situ method for determining the composition and thickness of III-V semiconductor layers during growth. In order to fully exploit the potential of SE for real-time in situ control, one needs to acquire a database of optical constants. In this article, we present the acquisition and parameterization (both composi tion and temperature) of a fully dynamic database and its use in the real-t ime composition control of InAlAs grown on InP. This is accomplished by acq uiring SE data from growing films of different compositions, while the temp erature is controlled using feedback from band-gap thermometry. The layer c ompositions are assessed by fitting high-resolution x-ray diffraction patte rns with a simulation based on dynamical diffraction theory. In order to im prove the stability during real-time control, the database was parameterize d using a transfer function model. The parameterized database was then used , in real time, during growth to control the InxAl1-xAs film composition (x ) to within +/-0.003. (C) 2000 American Vacuum Society [S0734-211X(00)05803 -0].