Degradation of Mechanical Strength at Si/SiO2 Interface on SOI Wafers under Cyclic Loading

Fatigue tests of silicon stepped cantilevers fabricated from silicon on insulator (SOI) wafers were conducted under the bending mode to evaluate the effect of cyclic loading on fractures occurring in silicon and Si/SiO₂ interfaces. The specimen in the quasi-static mode fractured at the stress concentration site on the silicon specimens. However, during the fatigue tests the cantilever broke after 10⁴ cycles with stress amplitude of nearly half of the bending strength at the fixed end comprising the Si/SiO₂ interface. The results demonstrated that the cyclic stress durability in the Si/SiO₂ interface is significantly lower than that of the silicon body.