Characterization and Elimination of Defects in Oxide Layers Grown on Czochralski Silicon Substrates

Smal l defects in Czochralski silicon substrates are responsible for defect generation in oxide layers grown thermally on the substrates. The relationship between the defect density D and the thickness to • of as-grown oxides is shown to be D = A. tox. exp (-B 9 tox), where A and B are constants. Good agreement is obtained between these equations and experimental data. We show that the implantation of ions straight through the oxide layers eliminates oxide defects at implantation doses above i0 ~4 cm-2. This suggests that oxide defects are associated with structures that are destroyed by the ion implantation, during wh ich their Constituent a toms are randomly displaced. In addition, we show that pour ing deionized water on a rotating wafer wi th an oxide layer eliminates oxide defects. Electrostatic measurement reveals that negative charges are produced during the rotation. We propose a mode l in wh ich electrons produced through friction between the water and the SiO2 surface induce a high electric field, and an oxide defect is selectively subjected to excessive electron conduct ion fol lowed by local joule-heating, wh ich changes the chemical state of the defect. The formation of oxide defects on Czochralski silicon (CZ-Si) substrates was first observed 1-3 using the copper decoration method. It was also shown 15 that the oxide de-fect density reaches a peak in oxide layers about 50 n