Thin oxide reliability and gettering efficiency in advanced silicon substrates

Various substrates are compared for both bulk defect formation and thin oxide reliability. Wafers were subjected to a complete device fabrication process, and the formation of the denuded zone was monitored by SPV measurements of carrier lifetime. Oxide reliability tests were carried out by exponentially ramped current stress and constant current stress measurements. Oxides with different thicknesses (70, 150 and 300 Å) were tested, in order to detect both gettering effects (expected to be most effective in the thinnest oxides) and defectivity related to vacancy clusters (reported to be most apparent in 200–500 Å thick oxides). The detrimental effect of vacancy clusters and oxygen-related defects is demonstrated by comparing Czochralski grown wafers with different densities of such defects and epitaxial p/p+ material. In Czochralski material, the usual denuding and precipitation thermal cycle is compared to the recently proposed method to control oxygen precipitation through the concentration of intrinsic point defects.