Si, Ge, GaAs and InP single crystals are four kinds of important electronic semiconductors used in microelectronic devices. Owing to different loading conditions and anisotropy of the single crystals, the materials usually exhibit different deformation and cracking behaviors and in-plane anisotropic strength and fracture toughness. Investigation of these mechanical properties and understanding of the corresponding mechanisms are of both practical and theoretical significance for improving the reliability of microelectronic devices.
Four kinds of typical semiconductor single crystals with [001] out-of-plane direction, Si, Ge, GaAs and InP, were selected in this study. Micro-indentation and three-point-bending testing combined with microscopic observations and statistics analysis were used to systemically investigate deformation and cracking behavior, in-plane anisotropy of strength and fracture toughness, the relation between the characteristics of dynamic fracture and the loading rate of the single crystals. The experimental results are summarized below:
1. Under indentation loading, the deformation of Si and Ge was dominated by the formation of shear faults, while that of GaAs and InP was accommodated by the activation of slip systems.
2. The hardness, elastic modulus, fracture toughness of the [001]-oriented Si, Ge, GaAs and InP crystals showed the different extent of in-plane anisotropy. The minimum value of Si appeared in the in-plane <011>-direction and the maximum value in the in-plane <001>-direction. Comparatively, the maximum value of GaAs and InP happened in the in-plane <011>-direction and the minimum value in the in-plane <001>-direction. No anisotropic values occurred in Ge.
3. The order of the decrease of the elastic modulus (E), the hardness (H) and the fracture toughness of four kinds of the crystals is Si>Ge>GaAs>InP. The maximum value of H/E of four kinds of the crystals appeared in the in-plane <001>-direction and the minimum value in the in-plane <011>-direction. The value of H/E of Si is larger than that of Ge, GaAs, InP in all in-plane direction.
4. There exists a linear relationship between the indentation-induced crack length and the indent size of the single crystals. Compared with GaAs and InP, Si and Ge had the smaller critical indent size and the linear fitting slope. Such a variation tend is consistent with the change in the hardness and fracture toughness.
5. Dynamic fracture experiments showed that a ratio of the length of the mirror zone to that of the hackle zone at low loading rate was higher than that at high loading rate. At the same loading rate, the ratio of Ge crystal was higher than that of Si. While at the high loading rate, the ratio of InP was close to that of GaAs, but the ratio of GaAs is higher than InP at the low loading rate.
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