Study on Boron–Hydrogen Pairs in Bare and Passivated Float-Zone Silicon Wafers

Abstract

This study deals with the dynamics of the formation and dissociation of boron–hydrogen (BH) pairs in crystalline silicon during a rapid high-temperature treatment and subsequent dark annealing between 200 and 300 °C. Highly accurate resistivity measurements are used to detect BH pairs in chemically polished B-doped float-zone silicon. It is found that an unexpecteded high amount of hydrogen is present in the as-purchased wafers. Hydrogen is initially mostly paired to boron but can be dissolved by a short high-temperature firing step. If a firing step (530 °C) is applied to bare, unpassivated Si wafers, most of the initial BH pairs are dissolved, and hydrogen dimers ((Formula presented.)) form. With increasing peak temperature, an increasing amount of hydrogen leaves the (Formula presented.) system, while the proportion of BH increases. Additional hydrogen can be introduced by firing a wafer passivated with plasma-enhanced chemical vapor deposition (PECVD) (Formula presented.) H. A three-state model shows a good agreement with the measured data for both bare and coated samples as well as for different annealing temperatures. With increasing dark annealing temperatures, the BH dynamics accelerates, whereas the maximum BH concentration reached decreases. For temperatures above 280 °C, significant changes in the reaction dynamics are observed.