Super-resolution laser probing of integrated circuits using algorithmic methods

Abstract

Laser probing remains invaluable to the semiconductor industry for isolating and diagnosing defects in silicon transistors in integrated circuits during electrical stress tests. However, continuous device miniaturization below the 20 nm technology node has crammed multiple transistors within the focal spot of the laser beam, resulting in signal crosstalk, poor beam positioning accuracy and degraded fault isolation capabilities. The challenge is analogous to focusing attention to a single speaker in a crowd despite the multiple simultaneous conversations in the background. Through algorithms introduced in this patented work, consisting of cross-correlations, clustering, and our previously developed combinational logic analysis, we achieved beam positioning accuracy to better than 10 nm, extracted electrooptic waveforms from a node of a group of transistors (~18 times beyond the optical resolution limit), and applied this to isolate and identify an actual fault on a defective device. While problems associated with probing with shorter wavelength lasers continue to be addressed, our approach enhances and enables the continued probing of ICs using sub-bandgap photon energies without hardware modification to existing technology at semiconductor technology nodes below 10 nm.