Measurements of Size, Morphology, and Spatial Distribution of Oxygen Precipitates in Si Wafers Using RIE

Abstract

A new technique for detecting oxygen precipitates in Si wafers, which utilizes a reactive ion etching (RIE) process with a Si/ etching rate ratio of about 200, has been applied to measurements of the size, morphology, and distribution of oxygen precipitates. The detectable precipitate size limit of the technique, which detects oxygen precipitates as needle-shaped Si cones formed under the precipitates, was estimated to be 8 nm. When the RIE depth was shallow, the size and morphology of oxygen precipitates were revealed by TEM observation of the top of Si cones. Also, the plane and depth distributions of oxygen precipitates were successfully obtained by measuring the position and height of Si cones regardless of the depth position of the precipitates and the RIE depth. Furthermore, effect of oxygen precipitates on gate oxide integrity (GOI) yield was examined using the technique, and it was shown that small-sized (15-40 nm) oxygen precipitates strongly degrade GOI yield.