Ultraviolet absorption sensors for precursor delivery rate control for metalorganic chemical vapor deposition of multiple component oxide thin films

We report the development of sensors for measuring the concentration of 2,2,6,6-tetramethyl-3,5-heptanedionate (thd) complexes of yttrium and copper in-situ, in the gas delivery system of a metalorganic chemical vapor deposition (MOCVD) reactor. The gas delivery system was modified to incorporate dual-beam ultraviolet absorption sensors accessed remotely with fiber optics. Spectral data were acquired for individual precursors at 4 s intervals using spectrograph/photodiode arrays. The measured absorption for individual precursors was used to determine concentration in the gas stream. Using the measured concentration, feedback control of the yttrium and copper thd complex molar flow rates was demonstrated to be better than one-half of one percent of the desired molar flow rate. (C) 1998 Published by Elsevier Science B.V. All rights reserved.