FRACTURE STRENGTH MEASUREMENT OF SILICON CHIPS

In this study, a three point bending test is used to determine how the susceptivity of large chips to brittle fracture correlates with chip thickness and backend process quality. Four sets of wafer backend proc esses, including the commonly used mechanical grinding, were used in t his experimental work. In the mechanical grinding process, chip streng th was more significantly influenced by the geometry of the machine ma rk than by the depth of the scratched groove. This experimental result indicates that a limitation exists in the enhancement of the mechanic al stability of Si chips by the control of chip thickness because crac ks in chips have a tendency to seek out deep scratches rather than typ ical flaws. Therefore, the mechanical instability associated with incr easing chip size should be compensated for by optimization of the back lap process.