Aging effects in digital circuits change the switching characteristics of their transistors, resulting in timing violations that can lead to functional errors at the system level. In particular, bias temperature instability (BTI) is a degradation effect that changes the threshold voltage of transistors. Its effect is more prevalent as the scaling of transistor dimensions progresses. In this work, we present a method to enable defect-centric long-term modeling of BTI degradation that takes into account the effects of concrete workloads at the processor data path level. Based on this study, we propose a novel design flow to link the impact of BTI degradation at the transistor ( ${\Delta {}V_{\text {th}}}$ ), processor data path (e.g., maximum frequency) and application-functionality levels. This flow may be used to improve system correctness over the entire device lifetime, avoiding unsafe working points, or to achieve a graceful degradation of system characteristics. Our design flow is applicable to all types of digital circuits, including high-performance processors. However, in this specific work we focus on the domain of biosignal processing applications for wireless body sensor networks (WBSNs), the pseudoperiodic nature of which interacts with the partially recoverable nature of BTI. Our results in this domain show, for a 32-nm implementation, a variation of up to 54.6 mV in the threshold voltage of the circuit transistors after one year of continuous operation, with an impact of 8.4% in the maximum safe operating frequency. Such effects are expected to strongly worsen for longer lifetimes and more scaled technology nodes.

中文翻译：

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超低功耗处理器中长期依赖于工作负载的 BTI 降级产生的功能错误分析

数字电路中的老化效应会改变其晶体管的开关特性，导致时序违规，从而导致系统级功能错误。特别是，偏置温度不稳定性 (BTI) 是一种退化效应，它会改变晶体管的阈值电压。随着晶体管尺寸的缩小，其影响更为普遍。在这项工作中，我们提出了一种方法来启用以缺陷为中心的 BTI 退化长期建模，该方法考虑了处理器数据路径级别的具体工作负载的影响。基于这项研究，我们提出了一种新颖的设计流程，将 BTI 退化对晶体管 (${\Delta {}V_{\text {th}}}$)、处理器数据路径（例如，最大频率）和应用程序功能级别。此流程可用于在整个设备生命周期内提高系统正确性，避免不安全的工作点，或实现系统特性的优雅降级。我们的设计流程适用于所有类型的数字电路，包括高性能处理器。然而，在这项具体工作中，我们专注于无线身体传感器网络 (WBSN) 的生物信号处理应用领域，其伪周期性质与 BTI 的部分可恢复性质相互作用。我们在该领域的结果表明，对于 32 纳米实施，连续运行一年后，电路晶体管的阈值电压变化高达 54.6 mV，对最大安全工作频率的影响为 8.4%。对于更长的寿命和更大规模的技术节点，这种影响预计会严重恶化。