On the Fracture Toughness Measurement of Thin Film Coated Silicon Wafers

This paper reports on the effect of residual stress on the microcrack propagation of thin-film coated silicon wafers and the fracture toughness measurement using the micro indentation technique. Two types of silicon nitride films with different stress states, a high tensile vs. a low compressive stress, deposited by a LPCVD method were studied. It is found that a high tensile residual stress in the film leads to longer microcracks and a lower fracture toughness of silicon, while a compressive stress depresses the microcrack propagation and increases the toughness of silicon. To improve the mechanical performance of silicon devices, a slightly compressive stress in the film is suggested.