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Researchers, based primarily on theoretical analysis of different coverage metric, have proposed the need to cover small delay defect (SDD). There is very little silicon data justifying the need to add SDD tests to the manufacturing flow. This paper attempts to fill this gap. A high volume manufacturing experiment to ascertain the added screening capability of defective parts and infant mortality...
Clock gating is widely used in modern integrated circuits as a means of reducing dynamic power consumption. In this paper we present a comprehensive analysis of the impact of clock gating during test. We then propose a new type of test point called Clock Gate Test Points. Similar to classic test point techniques, clock gate test points help in increasing the test coverage as well as reducing the number...
The usefulness of scan tests with multiple fault activation cycles to improve the coverage of transistor stuck-open faults is investigated. A recent work demonstrated that tests with more than one fault activation cycle can detect additional transition delay faults and inline resistance faults when compared to two-pattern tests applied using the broadside or skewed-load methods. We extend this work...
Small delay defect (SDD) testing is expected to become more prevalent as technology nodes continue to shrink and design frequencies continue to increase. In this paper, we critically examine previously published methods for evaluating SDD coverage and identify their shortcomings as an accurate and practical coverage metric. We propose an accurate method for measuring the coverage of small delay defects...
Shrinking feature size and increased wire density increase the likelihood of occurrence of bridge related defects. N- detect based pattern sets are used commonly to improve the detection of bridge defects. However, achieving high bridge coverage requires deterministic bridge sites extraction from physical layout and bridge fault pattern generation. In this paper, we present a comprehensive comparative...
Recent studies have shown that new tests are required for the detection of a large percentage of scan cell internal open faults which are not detected by the existing tests. However, the additional coverage due to the new tests drops significantly when opens with moderate resistances are considered. In this paper we propose to augment earlier test methods to detect internal scan chain opens with a...
Testing for small delay defects is critical to guarantee that the manufactured silicon is timing-related defect free and to reduce quality loss associated with delay defects. Commercial solutions available for testing of small delay defects result in very high pattern count and run time. In this paper, we present two effective approaches for generating timing-aware transition fault patterns that target...
Scan chains contain a high percentage of the transistors in logic parts of VLSI designs. Nevertheless, faults inside scan cells are not directly targeted by scan based tests currently used, and they are assumed to be detected by what are called flush tests. Recently we investigated the detectability of stuck-at, stuck-on and stuck-open faults internal to scan chains using existing tests. We also proposed...
Nearly half of the transistors in the logic parts of large VLSI designs typically reside inside scan cells. Faults in scan cells may affect functional operation if left undetected. Such undetected faults may also affect the long term reliability of shipped products. Nevertheless, current test generation procedures do not directly target faults internal to the scan cells. Typically it is assumed that...
In many designs asynchronous inputs are used to set and/or reset flip-flops. Considering a scan cell implementation used in an industrial design we show that stuck-open faults in some transistors driven by asynchronous inputs require two new flush tests. Such faults, if left undetected, cause functional failures. The two new tests increase the overall stuck-open fault coverage of each scan cell by...
The objective of using logic BIST for online and periodic testing is to identify defects, like opens, resulting from the wear and tear of the circuit. We have shown that existing test sets have a low coverage for open defects located in scan flip-flops, even though such defects may affect functional operation. Existing Logic BIST structures suffer from the same limitations. A novel Logic BIST architecture...
Scan chains contain approximately 50% of the logic transistors in large industrial designs. Yet, faults in the scan cells are not directly targeted by scan tests and assumed detected by flush tests. Reported results of targeting the scan cell internal faults using checking sequences show such tests to be about 4.5 times longer than scan stuck-at test sets and require a sequential test generator, even...
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