Oxygen precipitate studies in silicon for gettering in solar cell applications

Abstract

Oxygen precipitates in silicon can be used (in a process called internal gettering) as sites of heterogeneous nucleation of precipitates of iron and other transition metal that are harmful to solar cell device operation. Oxygen precipitate densities in p- (10¹⁴ boron atoms/cm³) wafers were quantified using chemical etch techniques. The precipitate densities were then used to estimate times to getter iron based on a diffusion limited precipitation model. Oxygen precipitate densities in p++ (10¹⁹ boron atoms/cm³) wafers were quantified using chemical etch techniques. High levels of boron in p++ wafers make quantifying precipitate densities particularly difficult, via etching, or other methods because precipitate densities in highly doped wafers are very high and the size of precipitates small.