Presentation slides for the ISTFA 2024 Tutorial session “Advanced FIB/SEM Sample Preparation and Analysis Techniques (2024 Update).”

We demonstrate the effectiveness of combining top-down and cross-sectional electron beam induced current (EBIC) imaging with SEM nanoprobe analysis to identify subtle front-end defects in advanced FinFET technology. Our approach successfully localized a novel fin nanocrack defect that had previously eluded detection through conventional TEM imaging. This systematic resistive pMOS failure, observable only in memory arrays at 150°C, exemplifies the power of EBIC as an alternative to scanning capacitance microscopy for detecting dopant anomalies and subtle defects. The sample preparation and EBIC methodologies presented here are broadly applicable across CMOS technologies, offering a versatile approach to defect analysis.

In the field of failure analysis (FA) for semiconductor devices, the transmission electron microscope (TEM) as an analytical tool is integral to finding visible evidence of defects and their root cause. Especially as device features shrink, imaging and analyzing increasingly subtle defects requires detailed elemental analysis. In this work, elemental analysis using an aberration-corrected TEM at different accelerating voltages (200 kV and 80 kV) is discussed. The impact of accelerating voltage on elemental analysis with regards to Electron Energy Loss Spectroscopy (EELS) and Energy Dispersive X-Ray Spectroscopy (EDS) is of central focus. Two case studies involving TEM samples of different thicknesses are presented that clearly indicate important differences in the analytical data collected at different accelerating voltages. The work revealed that for elemental analysis of thick TEM samples (100 nm and over) 200 kV is preferred, and for thin samples, 80 kV provides superior signal in EDS and EELS.

As integrated circuit (IC) feature dimensions have shrunk, the need for precise and repeatable sample preparation techniques has increased. In this work, the process of preparation of ultrathin planar-to-cross-section conversion transmission electron microscopy (TEM) samples using a gallium dual-column focused ion beam (FIB)/scanning electron microscope (SEM) system is examined. Sample preparation technique in this paper is aimed at repeatably isolating features in the 5-30 nm range, while limiting common issues such as amorphization, lamella warpage, and the curtain effect (or “curtaining”). This can be achieved through careful selection of FIB parameters including ion beam energy, ion beam current, stage tilt, and deposited protective layer materials and thicknesses, which are all discussed in this work.

In this work, we present three case studies that highlight the novelty and effectiveness of using multiple plasma FIB trenches to simultaneously access multiple metal layers for nanoprobing failure analysis. Multilayer access enabled otherwise impossible two-tip current imaging techniques and allowed us to fully characterize suspect logic gate transistors by exposing internal nodes, while preserving higher metal inputs and outputs. The presented case studies focus on late node planar and established FinFET technologies. The delayering techniques used are not necessarily technology dependent, but highly scaled and advanced processes generally require smaller trench areas for multilayer access. The minimum trench dimensions are limited by ion beam imaging resolution and trench-nanoprobe tip geometry.

Presentation slides for the ISTFA 2023 Tutorial session “TEM Techniques for Semiconductor Failure Analysis.”

Presentation slides for the ISTFA 2023 Tutorial session “Advanced FIB/SEM Sample Preparation and Analysis Techniques.”