Development of Technique of Creation of Small-Scale Crack and its Application to Micro Strength Test

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In recent years, the phenomenon treated by the mechanical engineering has reached the micro domain. In the field of fracture mechanics, the detailed analysis of the small-scale crack and the defect conventionally dealt with as if it was fully small has increased importance. Moreover, if progress of remarkable semiconductor process technology is used, it is also possible creating such a small-scale defect with highly controlled shape and so it is considered to become possible to make crack geometry, not passively but actively. The purpose of this research is the establishment of experimental method of fracture mechanics using the small-scale crack with high accuracy. Specifically, we investigated the manufacturing method of small-scale cracks using the semiconductor process technology together with the measurement technique of the evaluation of degradation resulting from the introduced small-scale crack. Examining various methods for creation of small-scale cracks on the single crystal … More silicone, it was shown that the combination of ICP etching and the Ta as the mask material shows the best performance. It was enabled to create a small-scale crack with 20μμ width and 45μμ depth. Three points bending test under small load was conducted using the manufactured specimen and the bending strength was investigated. The results showed that the strength decreases by about 230MPa by introduction of small-scale cracks. The stress analysis was conducted using finite element method and the stress concentration factor was shown to be about 5 and thus the maximum stress at the bottom of the created slit is supposed to be about 902MPa which exceeds the bending strength *00MPa for silicon specimen without slit. The distribution of the strength was plotted on the Weibull probability paper and the data were plotted on the straight line which shows the brittle property of the material as was expected. Scale effect was performed using Weibull parameters evaluated from the probability paper for the specimen without a slit. It was expected that the strength of specimen with slit will decrease since the area of the bottom part of the slit is smaller than the cut area of the specimen without slit. However, the decrease of strength could not be explained only by the scale effect and so it is supposed that the some effects that is specific to the micro-structure exist. These are left unsolved. Less