Cracking due to multiple indentations in silicon: effect of indentation spacing and relative orientations

The issue of multiple cracks in materials and their interaction is central in understanding the overall fracture behavior of materials. In the case of materials used in the microelectronics industry, indentation cracking has been extensively used for the measurement of fracture toughness due to its small sample size requirements as well as a relatively good correlation with values obtained from traditional fracture mechanics tests. The majority of these studies have focused on the fracture behavior of a single indent. The present study was aimed at understanding the effect of interaction between the cracks generated on Si from a pair of sequential indents as well as a set of four sequential indents placed at the corners of a square. The distance between the indents was varied from a level comparable to the crack size to a level where interaction could be ignored. This paper discusses the changes in the nature as well as the sizes of cracks due to interaction between the stress fields of the indents.