Delineation of point defect state in Czochralski Si by modified background haze

Abstract

A novel haze technique for analyzing point-defect distribution in Czochralski Si (CZ-Si) wafers without intentional contamination by transition metals was proposed. Based on the background haze in high-temperature oxidation, a three-step oxidation process including two-step low-temperature precipitation and a single-step high-temperature wet oxidation process was designed. After the newly designed heat processing and preferential etching, surface haze was formed selectively on the interstitial-dominant region of the wafer. Through electron microscopy analysis, surface defects decorated with Ni were observed, which suggested that the surface accumulation of non-gettered Ni adsorbed from the furnace causes surface haze on the interstitial-dominated region. The widths of the hazes could be optimized by adjusting the processing times of the first two steps, which affected the Ni gettering ability in the vacancy-dominated regions of the wafers. Additionally, the second stage at 1000 °C was associated with precipitate growth, as well as with haze formation.