The effects of several growth parameters on the formation behavior of point defects in Czochralski-grown silicon crystals

Abstract

Variation of growth parameters such as the crystal rotation rate, the crucible rotation rate and the configuration of cusp magnetic fields results in the increase or the decrease of critical growth rate V*, transition from interstitial to vacancy, of Czochralski (CZ)-grown silicon crystals. It can also make axially asymmetric distributions of grown-in microdefect regions. V* is remarkably increased in some range of the crystal rotation rate and the crucible rotation rate, which are likely to depend on crucible shape, size and melt volume. The crystal rotation rate as well as the crucible rotation rate affects the incorporation of point defects into the growing crystal through modification of the melt convection. Variation of the configuration of cusp magnet also can increase V* since it affects the melt temperature field. Significant results of interstitial-rich region at crystal center and vacancy-rich region at crystal edge are given in the minority carrier life-time map. These effects are directly caused by the change of heat flow in the melt, controlled with the crystal rotation rate, the crucible rotation rate and the magnetic configuration. The axial temperature gradient in the crystal near the crystal-melt interface is indirectly affected by heat flow through the crystal-melt interface. In addition, the novel technique, the unbalanced magnetic technique, is proposed to control heat transfer and oxygen transfer separately. (c) 2006 Elsevier B.V. All rights reserved.