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

摘要

This study deals with the dynamics of the formation and dissociation ofboron–hydrogen (BH) pairs in crystalline silicon during a rapid high-temperaturetreatment and subsequent dark annealing between 200 and 300 °C. Highlyaccurate resistivity measurements are used to detect BH pairs in chemicallypolished B-doped float-zone silicon. It is found that an unexpecteded high amountof hydrogen is present in the as-purchased wafers. Hydrogen is initially mostlypaired to boron but can be dissolved by a short high-temperature firing step. If afiring step (530 °C) is applied to bare, unpassivated Si wafers, most of the initial BHpairs are dissolved, and hydrogen dimers (H_2) form. With increasing peak temperature,an increasing amount of hydrogen leaves the H_2 ⇌ BH system, while theproportion of BH increases. Additional hydrogen can be introduced by firing awafer passivated with plasma-enhanced chemical vapor deposition (PECVD)SiNx:H. A three-state model shows a good agreement with the measured data forboth bare and coated samples as well as for different annealing temperatures.Withincreasing dark annealing temperatures, the BH dynamics accelerates, whereas themaximum BH concentration reached decreases. For temperatures above 280 °C,significant changes in the reaction dynamics are observed.