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 o f 2,2,6,6-tetramethyl-3,5-heptanedionate (thd) complexes of yttrium an d copper in-situ, in the gas delivery system of a metalorganic chemica l vapor deposition (MOCVD) reactor. The gas delivery system was modifi ed to incorporate dual-beam ultraviolet absorption sensors accessed re motely with fiber optics. Spectral data were acquired for individual p recursors at 4 s intervals using spectrograph/photodiode arrays. The m easured absorption for individual precursors was used to determine con centration in the gas stream. Using the measured concentration, feedba ck 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 right s reserved.