R. Dugnani, Exponent Failure Analysis Associates, Menlo Park, CA; M. Wu, Edwards Lifesciences, Irvine, CA

Summary: The recent increase in utilization of bare silicon integrated circuits (ICs) is largely due to the booming in the consumer markets of digital devices such as MP3 players, cellular phones, digital cameras, PDAs, etc. Due to continuous effort in miniaturizing these devices, silicon dice are often mounted on boards without encapsulation. In addition, silicon die commonly need to be mechanically thinned in order to fit into compact devices. The thinning of the wafers is normally carried out by mechanical grinding, a process that naturally weakens the silicon by introducing micro-cracks at its surface. The utilization of thin silicon die in combination with the lack of mechanical protection has makes of bare dice a typical failure mechanism in the IC industry. The current work presents results from strength characterization of silicon chips using a miniaturized four-point bending test fixtureAs expected, the strength is affected by grinding direction on silicon chip’s surface. Three distinctive fracture mechanisms associated with grinding angles were observed. Modeling of the expected fracture strength based on flaw-size SEM survey was found to correlate well with data from testing.