Abstract:
In order to maintain the reliability of structural materials such as ceramics, it is important to nondestructively evaluate micrometer-order surface defects that reduce the strength of materials. The standard defects are needed whose size and shape are precisely defined, but only a Vickers and Knoop indentation crack can be used traditionally. However, since indentation cracks are created stochastically, it is difficult to precisely define the size and shape. Alternatively creation of standard defects on Si(100) wafers was attempted by using the focused ion beam (FIB) machining process, and three grooves of 3-(mu)m depth and 50-, 100-, and 200-(mu)m length were made by a 90-nm-diam Ga ion beam on a Si surface. Iodine gas was used for making fine edges. Then these defects were evaluated by using the phase velocity scanning (PVS) method which generates excellently directive surface acoustic waves (SAWs). A 60-MHz SAW generated by the PVS method was used and the distances from detects to the probe of SAW were about 4 mm. The reflection coefficients of 200-, 100-, and 50-(mu)m defects were evaluated to be about 9.6%, 3.5%, and 1%, respectively, and the usefulness of these standard defects was confirmed.