Incorporating Time-Domain Reflectometry in Chip-Level Failure Analysis Workflow: Case Studies

 Liao, Joy Y., Khanh Giang, Timothy Pham, and Howard Lee Marks. "Incorporating time-domain reflectometry in chip-level failure analysis workflow: case studies." In International Symposium for Testing and Failure Analysis, vol. 84741, pp. 145-150. ASM International, 2023.

Abstract

Non-destructive electrical fault isolation (FI) techniques such as emission- and laser-based techniques have been utilized widely for chip-level failure analysis (FA). However, these techniques by themselves can sometimes be inadequate for certain failure modes. In this paper, we present six FA case studies using Time-domain Reflectometry (Electro-optical terahertz pulse reflectometry, EOTPR) in combination with the traditional FI techniques. We also present continuing development in making EOTPR accessible to the semiconductor process and packaging communities.

see https://dl.asminternational.org/istfa/proceedings-abstract/ISTFA2023/84741/145/28577

Recent Developments in EOTPR Towards a Fully Automated Tool for High Volume Failure Analysis

White, Tom, Jesse Alton, Brett Gibson, Martin Igarashi, Joy Liao, Timothy Pham, and Howard Marks. "Recent Developments in EOTPR Towards a Fully Automated Tool for High Volume Failure Analysis." In 2025 IEEE International Reliability Physics Symposium (IRPS), pp. 1-5. IEEE, 2025.

Abstract

Developments in backside power delivery (BPD) technology will become increasingly important for advanced semiconductors, but will present new challenges for failure analysis (FA) labs. Electro-Optical TeraHertz Pulsed Reflectometry (EOTPR) is a well-established electrical FA technique for package level open and leakage faults, but has comparatively little use for detecting die-level faults. Here, two case studies are presented that demonstrate how EOTPR can be used to localize faults within a die, highlighting how EOTPR could be utilized for BPD devices. Recent and future key developments in EOTPR are also presented.

see https://ieeexplore.ieee.org/abstract/document/10983830

Reduction in Reflection Signal Losses in Complex Terahertz Optical Elements Through Tailored Oil Application

 Kaluza, Mateusz, Adrianna Nieradka, Mateusz Surma, Wojciech Krauze, and Agnieszka Siemion. "Reduction in Reflection Signal Losses in Complex Terahertz Optical Elements Through Tailored Oil Application." Applied Sciences 15, no. 20 (2025): 11167.

Abstract

In complex terahertz (THz) systems, multiple optical elements are often combined to achieve advanced functionalities. However, unwanted Fresnel reflections at their interfaces and between components lead to parasitic interference effects and signal losses. This study presents oil-based refractive-index-matching fillers integrated with additively manufactured assemblies to suppress Fresnel reflections and enhance overall optical system performance. The optical properties of 20 plant-based, synthetic, and mineral oils were investigated using terahertz time-domain spectroscopy (THz TDS). Furthermore, a multilayer structure was designed and experimentally verified, fabricated via fused deposition modeling (FDM) using highly transparent cyclic olefin copolymer (COC). The results demonstrate that the use of tailored oils reduces Fresnel reflection signal losses and also mitigates parasitic interference within the system, thereby improving the effective efficiency of the optical system. Additionally, THz TDS measurements on multilayer structures revealed that, in imaging configurations, the application of refractive-index-matched oils increases the signal gain by 2.33 times. These findings highlight the potential of oil-based index-matching fillers for imaging multilayered objects and mitigating delamination effects in optical elements.

see https://www.mdpi.com/2076-3417/15/20/11167

The first annual Showcase of the EPSRC NetworkPlus in Terahertz System

 📣 We are pleased to announce that the first annual Showcase of the EPSRC NetworkPlus in Terahertz Systems will take place in Leeds on 21st and 22nd April 2026 📣

The Showcase will bring together academics and representatives working in industry and non-academic research organisations for two days of engaging discussions on future prioritisation areas for THz science and technology across the UK and Europe. We will also provide information on our Flexible Fund, which will support researchers in exploring some of these opportunities through seedcorn projects. There will be plenty of opportunities for networking – including a poster session and conference dinner – and for helping to shape the future of the NetworkPlus.

For further details and to register your interest in attending the meeting, please see below 👇 The deadline for EOIs is Friday 30th January.

Using density changes to monitor blending with magnesium stearate by terahertz time-domain spectroscopy

Anuschek, Moritz, Thea Nilsson, Anne Linnet Skelbæk-Lorenzen, Thomas Kvistgaard Vilhelmsen, J. Axel Zeitler, and Jukka Rantanen. "Using density changes to monitor blending with magnesium stearate by terahertz time-domain spectroscopy." International Journal of Pharmaceutics 672 (2025): 125303.

Abstract

Magnesium stearate (MgSt) is among the most common excipients and the most common lubricant in solid oral products. It is primarily added to tablet formulations to ease ejection during tablet compression. While commonly present in low concentrations, the addition of MgSt substantially affects the final tablet properties. Its impact is further not only concentration dependent but also varies with exposure of the formulation to shear, which worst-case results in over-lubrication. The presented study investigated the applicability of terahertz time-domain spectroscopy (THz-TDS) to monitor the shear-induced blend densification of microcrystalline cellulose blended with MgSt over a range of concentrations (0.3, 0.7, and 1.0 %). The effect of shear was investigated by variation of blending times (5 – 20 min) in a diffusion blender. THz-TDS measurements of the powder blends were acquired in transmission by measuring directly through the mixing container. The refractive index at terahertz frequencies was found to be sufficiently sensitive to resolve the densification of the blend with increased blending times. Thus, THz-TDS blend density measurements can be used as a surrogate parameter to evaluate the total shear exposure of a blend. Considerations regarding implementation are discussed. In the context the approach was integrated with the well-described THz-TDS-based tablet porosity analysis into a unified model to monitor and predict the tensile strength. Including the THz-TDS measurement on the blend allowed for a more accurate description of the tensile strength, reducing the root mean squared error by over 40 % (0.33 MPa). The possibility of monitoring the density changes of a blend non-invasively makes THz-TDS a promising process analytical technology approach for controlling the total shear impact on lubricated blends and tablet quality.

see https://www.sciencedirect.com/science/article/pii/S0378517325001395