Elastic and fracture properties of free-standing amorphous ALD Al₂O₃thin films measured with bulge test

Abstract

We have measured mechanical and fracture properties of amorphous Al2O3 thin films deposited by atomic layer deposition with bulge test technique using a free-standing thin film membrane. Elastic modulus was determined to be 115 GPa for a 50-nm thick film and 170 GPa for a 15-nm thick film. Residual stress was 142 MPa in the 50-nm film while it was 116 MPa in the 15-nm film. XRR density was 3.11 g/cm 3 for the 50-nm film and 3.28 g/cm 3 for the 15-nm film. Fracture strength of the 15-nm film was 4.21 GPa while the 50-nm film had only 1.72 GPa at a 100 hPa/s pressure ramp rate. Fracture strength was observed to be positively strain-rate dependent. The effective volume of a circular film in bulge test was determined from a FEM model enabling comparison of fracture strength data between different techniques.

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