In-situ gas cleaning technology of hot-wall batch-type reactor for (Ba,Sr)TiO/sub 3/

We present a novel approach to gas cleaning technology for Ba/sub x/Sr/sub (1-x)/TiO/sub 2/ (BST) residual coating in hot wall CVD reactors. It consists of two step continuous process. In the first step we use Cl/sub 2/ gas at 800 deg. C to remove Ba and Sr which have low vapor pressure. Second step consists of using ClF/sub 3/ gas to remove Ti at relatively low temperature. Vapor pressures of the chlorine compounds of Ba and Sr are considerably higher than those of their other existing compounds, thus by chlorination, Ba and Sr turn volatile and are easily etched off.