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Manufacturing defects in FinFET SRAMs can cause hard-to-detect faults such as Random Read Faults (RRFs). Detection of RRFs is not trivial, as they may not lead to incorrect outputs. Undetected RRFs become test escapes, which might lead to no-trouble-found devices and early in-field failures. Therefore, the detection of RRFs is of utmost importance. This paper proposes test solutions to detect RRFs and reduce test escapes. To achieve this, we first statistically analyze the failure rate due to RRFs, followed by an experimental study of stress conditions’ (SCs) impact on detecting RRFs, such as test algorithms, supply voltage, and temperature. Based on the results, we propose a new Design-For-Testability (DFT) scheme for FinFET SRAMs to detect such faults using SCs that improve the detection rate of RRFs. This scheme introduces a negligible area and test time overhead while significantly enhancing RRF detection. Hence, using the proposed DFT leads to reduced test escapes and, consequently, higher-quality FinFET SRAMs., Computer Engineering, Quantum & Computer Engineering

One of the most challenging aspects in nowadays microelectronics industry is production test and verification of mixed-signal circuits. In order to cope with some of the drawbacks encountered in this scenario, researchers have found alternate test as a promising solution in achieving such endeavor. This work prospects the possibilities of using space tessellations along multiple directions in order to improve the test decision boundary definition in the alternate measure space. The proposed method is able to reduce false positive test outcomes, i.e. test escapes, with acceptable penalty in test yield loss metric. The key idea presented in this work is to use an ensemble of octrees, each of them tessellating the plane along different directions. Such tessellations create a refinement in the non linear test decision boundaries without the need of including extra circuit samples. The tree ensemble, together with a strict test decision criterion, serve as a classifier during the production testing phase. The proposed multi-directional ensemble tessellation strategy has been applied to test a band-pass Biquad filter affected by parametric variations. The proposed method has reported promising simulation results in lowering the test escapes metric as compared to a single octree classifier. The computational overhead of evaluating several octrees is insignificant since 2n-tree data structures are traversed efficiently. The octree ensemble technique has also been compared against a classic specification guard-banding technique reporting better test yield loss metrics for the same test escape target., Peer Reviewed, Postprint (author's final draft)

Testing analog and mixed-signal circuits is a costly task due to the required test time targets and high end technical resources. Indirect testing methods partially address these issues providing an efficient solution using easy to measure CUT information that correlates with circuit performances. In this work, a multiple specification band guarding technique is proposed as a method to achieve a test target of misclassified circuits. The acceptance/rejection test regions are encoded using octrees in the measurement space, where the band guarding factors precisely tune the test decision boundary according to the required test yield targets. The generated octree data structure serves to cluster the forthcoming circuits in the production testing phase by solely relying on indirect measurements. The combined use of octree based encoding and multiple specification band guarding makes the testing procedure fast, efficient and highly tunable. The proposed band guarding methodology has been applied to test a band-pass Butterworth filter under parametric variations. Promising simulation results are reported showing remarkable improvements when the multiple specification band guarding criterion is used., Peer Reviewed, Postprint (author's final draft)

Intragate open defects are responsible for a significant percentage of defects in present technologies. A majority of these defects causes the logic gate to become stuck open, and this is why they are traditionally modeled as stuck-open faults (SOFs). The classical approach to detect the SOFs is based on a two-vector sequence, and has been proved effective for a wide range of technologies. However, factors typically neglected in past technologies have become a major concern in nanometer technologies, i.e., leakage currents and downstream parasitic capacitances. Some recent works have examined the influence of leakage currents. However, to the best of our knowledge, no one has considered the influence of downstream parasitic capacitances. In this paper, the influence of both factors is investigated and experimentally measured with a test chip built on a 65-nm technology. An analysis based on the electrical simulations is performed to quantify the number of test escapes in the presence of SOFs. Test recommendations are derived from the analysis results to maximize the detectability of these faults in present and future technologies., Peer Reviewed, Postprint (published version)

Testing M-S circuits is a difficult task demanding high amount of resources. To overcome these drawbacks, indirect testing methods have been adopted as an efficient solution to perform specification based tests using easy to measure metrics. In this work, a testing technique using octrees in the measure space is presented. Octrees have been used in computer graphics with successful results for rendering, image processing and space clustering applications. In this paper are used to encode the test acceptance region with arbitrary precision after an statistical training phase. Such representation allows an efficient way to test a candidate circuit in terms of test application time. The method is applied to test a Biquad filter with encouraging results. Test escapes and test yield loss caused by parametric variations have been estimated., Postprint (published version)