Fracture toughness measurement of thin-film silicon

The fracture toughness of single-crystal silicon thin films oriented to (100) and (110) was investigated by tensile testing under both < 100 > and < 110 > loading conditions. The specimen was fabricated from a p-type Czochralski (CZ)-grown wafer and passed through a thermal process during the fabrication of the test device. The measured fracture toughness is dependent on the loading direction in the tensile test and independent of the specimen surface orientation. The test results were 1.94 MPa root m in the < 100 > direction and 1.17 MPa root m in the < 110 >. In these tests, no longitudinal size effect on the fracture stress or fracture toughness was observed. The SEM photographs obtained from the fracture specimens after the tensile test show that the crack initiated from the notch tip and propagated straight in the across-the-width direction on the (110) or (111) cleavage plane.