Enhancing radiation hardness of microelectronics through stress-relief milling

Single event effects (SEE) in microelectronic devices are predominantly studied from the perspective of electrical charge generation and collection. This study introduces a multi-physics concept by investigating the impact of highly localized mechanical stress in electrically sensitive regions, such as the gate in a transistor. Our hypothesis is that reducing mechanical stress beneath the gate will decrease voltage transients caused by SEE by limiting charge generation and diffusion. To explore this electro-mechanical coupling in relation to SEE, we milled a microscale trench in the substrate beneath a transistor of the LM124 operational amplifier using a focused ion beam, thereby alleviating mechanical stress in the vicinity of the trench. We then perform pulsed laser SEE testing on the stress-relieved transistor and a control specimen without a micro-trench modification. Our experimental results demonstrate a significant decrease in single event transient peak amplitude and collected charge in the stress-relieved device compared to its pristine counterpart under identical pulsed laser conditions. These findings support our hypothesis and suggest that mitigating mechanical stress localizations could inform the design and fabrication of radiation-hardened electronics.