Mixed-level identification of fault redundancy in microprocessors

A new high-level implementation independent functional fault model for control faults in microprocessors is introduced. The fault model is based on the instruction set, and is specified as a set of data constraints to be satisfied by test data generation. We show that the high-level test, which satisfies these data constraints, will be sufficient to guarantee the detection of all non-redundant low level faults. The paper proposes a simple and fast simulation based method of generating test data, which satisfy the constraints prescribed by the proposed fault model, and a method of evaluating the high-level control fault coverage for the proposed fault model and for the given test. A method is presented for identification of the high-level redundant faults, and it is shown that a test, which provides 100% coverage of non-redundant high-level faults, will also guarantee 100% non-redundant SAF coverage, whereas all gate-level SAF not covered by the test are identified as redundant. Experimental results of test generation for the execution part of a microprocessor support the results presented in the paper.Comment: 2019 IEEE Latin American Test Symposium (LATS

On NBTI-induced Aging Analysis in IEEE 1687 Reconfigurable Scan Networks

The Negative Bias Temperature Instability (NBTI) phenomenon is one of the main reliability issues in today’s nanoelectronic systems. It causes increase in threshold voltage of pMOS transistors, thus degrading signal propagation delay in logic paths between flip-flops. Recently, IEEE published a new standard IEEE 1687 for Reconfigurable Scan Networks (RSN) to facilitate access to embedded instrumentation within an integrated circuit. In the field, the RSN infrastructure is often exploited for fault-management in failure-sensitive critical parts of the system. Therefore, the severity level of a fault in the RSN itself is very high, thus, amplifying the impact of the reliability issues caused by the aforementioned effect. To the best of the authors’ knowledge, no approach has been proposed to investigate or address this issue so far. In this paper, we analyze the effect of NBTI-induced aging in RSNs from architectural and operational (functional) perspectives and present a novel technique to mitigate the degradation. The methodology is demonstrated on a case-study example and the effectiveness of our approach is evaluated on a sub-set of ITC2016 benchmark RSN designs

On BTI Aging Rejuvenation in Memory Address Decoders

Memory designs require timing margins to compensate for aging and fabrication process variations. With technology downscaling, aging mechanisms became more apparent, and larger margins are considered necessary. This, in return, means a larger area requirement and lower performance for the memory. Bias Temperature Instability (BTI) is one of the main contributors to aging, which slows down transistors and ultimately causes permanent faults. In this paper, first, we propose a low-cost aging mitigation scheme, which can be applied to existing hardware to mitigate aging on memory address decoder logic. We mitigate the BTI effect on critical transistors by applying a rejuvenation workload to the memory. Such an auxiliary workload is executed periodically to rejuvenate transistors that are located on critical paths of the address decoder. Second, we analyze workloads' efficiency to optimize the mitigation scheme. Experimental results performed with realistic benchmarks demonstrate several-times lifetime extension with a negligible execution overhead.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work publicComputer EngineeringQuantum & Computer Engineerin

Modeling Soft-Error Reliability Under Variability

The Soft-Error (SE) reliability and the effects of Negative Bias Temperature Instability (NBTI) in deep submicron technologies are characterized as the major critical issues of high-performance integrated circuits. The previous scientific research studies provide a comprehensive description that the soft-error vulnerability becomes more severe as the circuit performance degrades with aging. The main reason is the reduction of cell-level critical charge in an aging environment. However, such increased soft-error generation does not necessarily contribute towards circuits' critical functional failures. The proposal of this paper is the experimental investigation of soft error propagation at the aged gate-level by considering the different derating factors like Electrical Derating (EDR), Temporal Derating (TDR), Logical Derating (LDR), and Functional Derating (FDR). As contrary to the previous studies, the results of this work prove that SEU fault propagation probability is reducing in critical paths as time advances while the propagation probability of SET faults is neither reducing nor increasing, but the spot of generation of failure enhancing SETs is shifting within the clock period.Computer EngineeringQuantum & Computer Engineerin

A DFT Scheme to Improve Coverage of Hard-to-Detect Faults in FinFET SRAMs

Manufacturing defects can cause faults in FinFET SRAMs. Of them, easy-to-detect (ETD) faults always cause incorrect behavior, and therefore are easily detected by applying sequences of write and read operations. However, hard-to-detect (HTD) faults may not cause incorrect behavior, only parametric deviations. Detection of these faults is of major importance as they may lead to test escapes. This paper proposes a new design-for-testability (DFT) scheme for FinFET SRAMs to detect such faults by creating a mismatch in the sense amplifier (SA). This mismatch, combined with the defect in the cell, will incorrectly bias the SA and cause incorrect read outputs. Furthermore, post-silicon calibration schemes can be used to avoid over-testing or test escapes caused by process variation effects. Compared to the state of the art, this scheme introduces negligible overheads in area and test time while it significantly improves fault coverage and reduces the number of test escapes.Computer EngineeringQuantum & Computer Engineerin

A DFT Scheme to Improve Coverage of Hard-to-Detect Faults in FinFET SRAMs

Manufacturing defects can cause faults in FinFET SRAMs. Of them, easy-to-detect (ETD) faults always cause incorrect behavior, and therefore are easily detected by applying sequences of write and read operations. However, hard-to-detect (HTD) faults may not cause incorrect behavior, only parametric deviations. Detection of these faults is of major importance as they may lead to test escapes. This paper proposes a new design-for-testability (DFT) scheme for FinFET SRAMs to detect such faults by creating a mismatch in the sense amplifier (SA). This mismatch, combined with the defect in the cell, will incorrectly bias the SA and cause incorrect read outputs. Furthermore, post-silicon calibration schemes can be used to avoid over-testing or test escapes caused by process variation effects. Compared to the state of the art, this scheme introduces negligible overheads in area and test time while it significantly improves fault coverage and reduces the number of test escapes.</p