It was recalled that recent studies had suggested that a possible source of poor oxide integrity was the incorporation of native defects from the Si substrate during oxide growth. The main candidates were D defects which existed largely within the central region of float-zone crystals. The use of N doping eliminated D defects, as detected by conventional means, and improved the integrity of the oxide. The present results indicated a prevalence of micro-defects in the central region of p-type N-doped float-zone material by using the Li+ drift method in an electric field. A model was developed which was based upon Li interactions in Si and which described the Li precipitation mechanism. This showed that vacancies were the most likely Li precipitation sites. The results were considered with regard to the breakdown mode patterns of polished float-zone wafers after gate oxide tests.

W.B.Knowlton, J.T.Walton, J.S.Lee, Y.K.Wong, E.E.Haller, W.Ammon, W.Zulehner: Materials Science Forum, 1995, 196-201, 1761-6