The influence of point defect on the behavior of oxygen precipitation in CZ-Si wafers

Cz-Silicon Produced from Solar Grade and Recycled Materials. Part I: Bulk Properties and Formation of As-Grown Defects

“…Oxidation . [24] By this procedure, incorporated interstitial oxygen [O i ] experienced a super-saturated state and nucleated preferentially at efficient sites of increased surface potential such as surface and crystal defects. White contrast ring patterns were revealed in radial direction after this procedure, as shown in Figures 6(a) and (b).…”

Comprehensive Model for Charge Carrier Recombination in Czochralski‐Grown Silicon Due to Oxygen Precipitation in Industrial Solar Cell Manufacturing

“…[ 16,17 ] The requirements for nucleation are a sufficient oxygen concentration, the existence of lattice defects, especially vacancies acting as nucleation sites, and a specific thermal history of the material, providing the energy to form the nuclei. [ 16–18 ] The first two conditions are fulfilled along most of the Cz‐Si ingots. Due to the reaction between the silicon melt and the crucible, the crystallized silicon is saturated with interstitial oxygen (O i ).…”

“…The investigated 750 mm‐long ingot was pulled with a relatively slow speed of 36 mm h −1 , leading to a cooling rate of about 100 K h −1 at temperatures above 1300 °C. [ 20 ] However, in current Cz‐Si manufacturing (especially for photovoltaics) the pulling rate is much higher (≥60 mm h −1 ), [ 18,21 ] leading to high cooling rates (≫100 K h −1 ) at high temperatures where the temperature–time profile flattens out as room temperature is approached. [ 20,21 ] Nielsen et al [ 5 ] recently even introduced active cooling near the melt/crystal interface in industrial ingot manufacturing to increase throughput.…”

“…Another impact on oxygen precipitation is the gas atmosphere during the HT processes, which is known to influence the nucleation rate. [ 16,18,28 ] During oxidation, silicon self‐interstitials are emitted into the bulk, reducing the number of vacancies and thus nucleation sites. Therefore, in inert gas atmosphere (e.g., nitrogen) nucleation is found to be enhanced in comparison with an oxidizing ambient.…”

“…[ 31 ] After the transformation, the OPs are strained and thus become visible after preferential etching. [ 16,18,32 ] According to Murphy et al, OPs then act as strong recombination centers, whereas the recombination at unstrained precipitates is weak. [ 33 ] The recombination activity of OPs scales with the surface area of strained precipitates.…”