Mechanical Impact on Non-silicon Devices: Stress Effects on Technology

MINDSET addressed a reliability challenge for future semiconductor technologies: how local mechanical stress affects emerging non-silicon transistors when it acts alone or together with electrical and thermal stress. This is increasingly important for back-end-of-line-compatible devices, monolithic three-dimensional integration and advanced packaging, where fabrication, integration and local heating can generate stress close to active devices. The project focused on oxide-semiconductor IGZO thin-film transistors and two-dimensional WS2 field-effect transistors. Its objective was to establish an experimental and modelling pathway that links controlled local loading to changes in threshold voltage, leakage, mobility and bias-temperature instability. By enabling stress-aware reliability assessment, the project supports the development of more dependable next-generation electronic devices and strengthens European expertise in semiconductor research and advanced manufacturing.

The project established a reproducible nanoindenter-based in-situ electrical characterization workflow. Local mechanical loading was synchronized with electrical measurements, and finite-element modelling was used to convert applied force into device-level stress distributions. Systematic experiments were performed on 300 mm wafer-fabricated IGZO and WS2 devices during loading and unloading. The work compared mechanical-stress-only, electrical-stress-only and combined mechanical-plus-electrical-stress conditions, and evaluated threshold-voltage shift, subthreshold behaviour, on-current, leakage, positive-bias-temperature-instability degradation and recovery. A local Pt microheater was also integrated with IGZO test structures, enabling localized thermal control and combined electro-thermo-mechanical experiments. The experimental results were interpreted using FEM, density-functional-theory-supported analysis for IGZO, and TCAD-assisted analysis for WS2. The project produced first-author peer-reviewed publications, conference presentations, internal technical dissemination and knowledge transfer through training on the nanoindenter methodology.

MINDSET advanced beyond the state of the art by demonstrating a combined experimental and simulation framework for localized GPa-level stress in emerging semiconductor devices. In IGZO TFTs, compressive mechanical stress produced a positive threshold-voltage shift of about 100 mV, while transfer characteristics recovered after unloading. Combined mechanical and electrical stress enhanced PBTI degradation, consistent with stress-assisted carrier trapping. In WS2 FETs, local mechanical stress produced a fully recoverable gate-leakage response in one study, while vertical compression in another reduced on-current by up to approximately 74%, with mobility reduction identified as the dominant mechanism. The local-heater platform achieved localized temperature control of about 85 °C and extended the method to simultaneous thermal, mechanical and electrical assessment. The results provide a basis for stress-aware design and reliability qualification of IGZO-based memory and logic, two-dimensional devices, BEOL-compatible transistors and monolithic 3D technologies. Further uptake can build on continued device-level validation, expanded thermal-mechanical studies and translation of the methodology into future qualification workflows.

Periodic Reporting for period 1 - MINDSET (Mechanical Impact on Non-silicon Devices: Stress Effects on Technology)

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