In practice, the SiN stripes or pads are periodically patterned on silicon, so the spacing effect on dislocation injection from sharp features deserves attention. As in Figure 1, the SiN stripes with residue stress , of width L and thickness h, are periodically patterned with spacing S. In the numerical calculation, we take shear modulus and Poisson’s ratio of Si3N4 to be 54.3 GPa and 0.27, and those of silicon 68.1GPa and 0.22, the same as in Ref.[1].

The normalized stress intensity factor is plotted in Figure 2 as a function of the ratio of spacing to thickness of the stripe for different aspect ratios L/h=2 and 20. The effect of spacing is quite small for both the large stripe pattern (L/h=20) and the small one (L/h=2), except that the spacing becomes too small, say . But the effect of aspect ratio (L/h) is quite obvious, as shown by the difference between two curves in Figure 2, which is consistent with the conclusion in Ref.[1].

Ref.[1]. Z. Zhang, J Yoon, and Z. Suo, APL 89 in press (2006). Preprint is available on http://imechanica.org/node/434 .

The results is in the attachment.