Power devices are now ubiquitous and integral in control of systems across various sectors of the economy. Silicon-based power devices still dominate in most of the applications although new materials and device architectures are becoming common in the next generation of devices. While several techniques to characterize the overall device properties are necessary, the fundamentals in several of these power devices such as Insulated Gate Bipolar Transistors (IGBTs) still rely on healthy junctions for optimal device performance. The technique of Electron Beam Induced Current (EBIC) is used to examine the depletion zones of the p/n junctions between drift and body regions of the device. Simple sample preparation methods such as cleaving the device allows quick cross-section evaluation of the device structure and electrical characterization using EBIC yields good data. The role of acceleration potential on depletion zone thickness is considered during the analysis of intact die and cross-sections. While low voltage EBIC provides images of the p/n junctions in cross-sections, it is found that high voltage (30 kV) EBIC images can also be used to image these same p/n junctions and therefore may point to a very quick line monitor or means for early failure analysis of these devices.

In prior work, it was demonstrated that information about device turn-on can be obtained in a nanoprobing setup which involves no applied bias across the channel. This was performed on nFET logic devices in 7 nm technology and attributed to the Seebeck effect, or heating from the SEM beam. In this work, the experiments are continued to both nFET and pFET devices and on both 22 nm and 5 nm devices. Further discussion about the opportunities and evidence for Seebeck effect in nanoprobing are discussed.

An experimental study was undertaken to determine the minimum level of leakage or shorting current that could be detected by electron-beam induced resistance change (EBIRCH) analysis. A 22-nm SRAM array was overstressed with a series of gradually increasing voltage biases followed by EBIRCH scans at 1 V and 2-kV SEM imaging until fins were observed. It was found that the fins of a pulldown device could be imaged by EBIRCH at just 12 nA of shorting current, representative of a soft failure. Stressing the sample at higher voltages eventually created an ohmic short, which upon further investigation, strongly suggested that the Seebeck effect plays a significant role in EBIRCH analysis.

Using a compact nanoprobing setup comprising eight probe tips attached to piezo-driven micromanipulators, various techniques for fault isolation are performed on 28 nm samples inside an SEM. The recently implemented Current Imaging technique is used to quickly image large arrays of contacts providing a means of locating faults.

The advances on IC technology have made defect localization extremely challenging. “Soft” failures (resistive vias and contacts) are typically difficult to localize using commonly available failure analysis (FA) techniques such as emission microscopy (EMMI) and scanning optical microscopy (SOM), and often cannot be observed by two-dimensional inspections using layer by layer removal. The article describes the Resistive Contrast Imaging (RCI) defect localization technique (also known as Electron Beam Absorbed Current (EBAC), instrumentations, and case studies on test structures or process control monitors especially designed to detect “soft” open failures on advanced (28nm and below) technology devices. It also lists the key SEM parameters critical for effective FA using the RCI nano-probing system.