Oxygen Precipitation Related Stress-Modified Crack Propagation in High Growth Rate Czochralski Silicon Wafers

Abstract

We report on crack propagation in 200 mm diameter Czochralski (CZ) grown silicon wafers produced for photovoltaic (PV) applications at elevated growth rates. Enhanced thermal gradients and point defectimpurity distributions associated with rapid growth produces large localized stresses in the wafer core, which influences the direction of propagating cracks, which originate at the wafer edge. The stress modified crack behavior deviates considerably from the initial energetically favorable Si110(111) system, enabling scenarios that behave like a ductile fracture following a radial path. Preferential etch pit measurements confirmed the presence of oxygen precipitate (OP) rings, which influence stress dependent energy transfer processes at the propagating crack-tip, thereby dramatically modifying the crack path. Raman spectroscopy was used to quantify local stress profiles associated with radial oxygen precipitate bands, whereas micro-FTIR spectroscopic measurements determined the distribution and shape of OPs indicating their dominant role in crack path deviation. © 2011 The Electrochemical Society.