This article describes a novel method for improving image resolution achieved using time-resolved photon emission techniques. Instead of directly generating images from photon counting, all detected photons are displayed as a point cloud in 3D space and a new higher-resolution image is generated based on probability density functions associated with photon distributions. Unsupervised learning algorithms identify photon distribution patterns as well as fainter emission sources.

This article provides a high-level review of the tools and techniques used for backside analysis. It discusses the use of laser scanning and conventional microscopy, liquid and solid immersion lenses, photon emission microscopy (PEM), and laser-based fault isolation methods with emphasis on light-induced voltage alteration (LIVA). It explains how laser voltage probing is used for backside waveform acquisition and describes backside sample preparation and deprocessing techniques including parallel polishing and milling, laser chemical etching, and FIB circuit edit and modification.

Photon emission microscopy (PEM) has proven to be a powerful tool for fault isolation and has adapted well to ongoing changes in technology and emerging needs. In this tutorial, the authors describe the fundamentals of photon emission, the essential elements of a typical PEM system, and the procedures involved in diagnosing various types of failures. They also classify a wide range of photon-emitting defects and explain how PEM is used for backside analysis of flip-chip packaged devices and for timing diagnostics.

This article discusses some of the early uses of emission microscopy in semiconductor device failure analysis and the challenges that were overcome to make it the invaluable tool it is today. One of the impediments early on was a misconception that silicon cannot emit light when, in fact, it has several light emission mechanisms that have proven useful in electron microscopy. One such mechanism, avalanche luminescence, occurs in junctions during reverse breakdown and is useful for resolving low breakdown voltage and problems with ESD protection circuits. Other light emission mechanisms discussed in the article include forward bias emission, MOS transistor saturation, and dielectric luminescence, which is used to examine oxide test structures and detect oxide defects.

IDDQ testing is normally the key to isolating state-dependent defects in dense ICs. In the case study presented here, however, the functionally failing ICs did not fail the static IDDQ test nor did they draw significant current when biased into a static state on the lab bench. After extensive testing and analysis, including ATE IDDQ scanning, ATE-interfaced photo-emission microscopy, FIB assisted mechanical microprobing, and scanning capacitance microscopy, the defect was found to be p-type counterdoping of the n-active regions caused by a contaminated solvent tank used during wafer fabrication.

This is a case study of an illumination-sensitive failure. Due to the unavailability of a scanning optical microscope, fault isolation was performed using a different approach based on available equipment. Through a combination of emission microscopy, FIB isolation, mechanical probing, and in-depth circuit analysis, the root cause and failure mechanism were determined.