Effects of surface oxide layer on fatigue crack propagation properties of submicrometre-thick freestanding copper films

To investigate the effects of oxide layer on fatigue crack propagation properties, fatigue tests in about 500-nm-thick copper films with a thickness-controlled oxide layer and without an oxide layer were conducted. Specimens with native oxide layer with a thickness of about 2 nm, those with thermal oxide layer with a thickness of about 20 nm and those without oxide layer were prepared. The results showed that fatigue crack propagation rate (da/dN) of specimens with thermal oxide layer was faster than of specimens with native oxide layer and without an oxide layer in higher ΔK and was smaller in lower ΔK.