Mechanism behind the Crack Formation in Hydrogen Doping Cz-Si Crystal Growth

Abstract

In this study, {100} cracks were found in Czochralski (Cz) silicon wafers grown in the atmosphere including hydrogen under the condition of a low V_c/G_c (V_c, growth rate; and G_c, temperature gradient) although the {100} plane is not a cleavage plane of silicon crystals. It was also found that dislocation clusters were associated with the as-grown defects. To reveal the mechanism behind the crack formation, the process of introducing interstitial and hydrogen atoms into a Cz-Si crystal upon solidification was imitated by applying ion irradiation into Cz silicon wafers under three different conditions: silicon ions and hydrogen ions, silicon ions only, and hydrogen ions only. In this case, {100} cracks were only found in the wafer irradiated with both silicon and hydrogen ions. This suggests that the existence of dislocations in silicon is necessary for crack formation. Density functional theory calculations showed that the cleavage energy was decreased by the arrangement of hydrogen atoms on a {100} plane of a silicon crystal, which can explain the formation of {100} cracks during solidification.

Fig. 3 Cross-sectional TEM images of wafers after ion irradiation with (a) silicon dose of 1 × 10¹⁵ atoms/cm² and a hydrogen dose of 5 × 10¹⁶ atoms/cm², (b) silicon dose of 1 × 10¹⁵ atoms/cm² and (c) hydrogen dose of 5 × 10¹⁶ atoms/cm², and (d), (e), and (f) enlarged images of the areas surrounded by rectangles in (a), (b), and (c), respectively.