Martin L. Villafana

Experiments and analysis to characterize logic state retention limitations in 28nm process node

Mobile devices spend most of the time in standby mode. Supported features and functionalities are increasing in each newer model. With the wide spread adaptation of multitasking in mobile devices, retaining current status and data for all active tasks is critical for user satisfaction. Extending battery life in portable mobile devices necessitates the use of minimum possible energy in standby mode while retaining present states for all active tasks. This paper for the first time, explains the low voltage data-retention failure mechanism in flops. It analyzes the impact of design and process parameters on the data retention failure. Statistical nature of data retention failure is established and validated with extensive Monte-Carlo simulations across various process corners. Finally, silicon measurement from several 28nm industrial mobile chips is presented showing good correlation of retention failure prediction from simulation.

Reliability of via and its diagnosis by e-beam probing

A stress-related intermittent via failure was investigated in an unstable digital circuit of a mixed signal device by novel use of an e-beam probing technique. The failed via structure was traced and identified by an e-beam prober connected to an ATE tester. FIB, SEM, and TEM analysis of the failed via structure showed voids and an anomalous thin layer under the Ti/TiN adhesion layer at the interface of tungsten plug and AlCu alloy.