Abstract: A circuit comprises a plurality of scan chains configured to perform scan shifting in two opposite directions and a register configured to store a first signal. The first signal determines whether the plurality of scan chains operate in a first mode or a second mode. The plurality of scan chains operating in the first mode is configured to perform, based on a second signal, either scan shifting in a first direction in the two opposite directions or scan capturing during a test; the plurality of scan chains operating in the second mode is configured to perform, based on the second signal, scan shifting in the first direction or a second direction in the two opposite directions.

Abstract: A system and method for performing scan chain testing is disclosed. Scan cells, in the form of scan chains, may be inserted into circuit designs for testing those circuit designs. Because the scan chains themselves may be defective, the integrity of scan chains may be checked first before testing the circuit under test. In order to do so, various scan chain patterns, including one or both of U-turn and Z-turn patterns, may be used in order to generate scan chain test data. The scan chain test data may then be analyzed in order to identify one or both of a type of defect (e.g., a timing fault, stuck-at fault, etc.) or a location of the defect. Further, the scan chain testing may be performed using chain patterns with adaptive length.

Abstract: Various aspects of the disclosed technology relate to techniques of logic diagnosis based on cell-aware diagnostic pattern generation. A first diagnosis process is performed on a failed integrated circuit based on a first fail log to generate a first set of defect suspects. The first fail log is generated by applying the first set of test patterns to the failed integrated circuit in a first scan-based test. A second set of test patterns are generated using fault models for internal defects in one or more cells included in the first set of defect suspects. The second set of test patterns are applied to the failure integrated circuit to generate a second fail log. A second diagnosis process is performed on the failure integrated circuit based on the second fail log.

Abstract: A computing system may include a model training engine configured to train a supervised learning model with a training set comprising training probability distributions computed for training dies through a local phase of a volume diagnosis procedure. The computing system may also include a volume diagnosis adjustment engine configured to access a diagnosis report for a given circuit die that has failed scan testing and compute, through the local phase of the volume diagnosis procedure, a probability distribution for the given circuit die from the diagnosis report. The volume diagnosis adjustment engine may also adjust the probability distribution into an adjusted probability distribution using the supervised learning model and provide the adjusted probability distribution for the given circuit die as an input to a global phase of the volume diagnosis procedure to determine a global root cause distribution for multiple circuit dies that have failed the scan testing.

Abstract: A test pattern is shifted into scan chains in a circuit in a first direction. The scan cells on each of the scan chains are further coupled to corresponding scan cells on two other scan chains in the scan chains such that data bits stored in the scan cells can be shifted circularly in a second direction orthogonal to the first direction based on a control signal. The loaded test pattern is then shifted in the second direction for a number of clock cycles equal to the number of the scan chains. The test pattern is then shifted in the first direction out of the scan chains to generate a chain test result.

Abstract: Logic diagnosis is performed on failing reports of defective integrated circuits to derive a diagnosis report for each of the failing reports which comprise information of suspects. The suspects comprise cell internal suspects and interconnect suspects. A probability distribution of root causes for causing the defective integrated circuits is determined to maximize a likelihood of observing the diagnosis reports based on a probability for each of the suspects given each of the root causes and a probability for each of the diagnosis reports given each of the suspects. The probability for each of the diagnosis reports given each of the cell internal suspects is weighted higher than the probability for each of the diagnosis reports given each of the interconnect suspects.

Abstract: Aspects of the invention relate to yield analysis techniques for generating root cause candidates for yield analysis. With various implementations of the invention, points of interest are first identified in a layout design. Next, regions of interest are determined for the identified points of interest. Next, one or more properties are extracted from the regions of interest. Based at least on the one or more properties, diagnosis reports of failing devices fabricated according to the layout design are analyzed to identify probable root causes.

Abstract: One or more machine-learning models are trained and employed to predict test coverage and test data volume. Input features for the one or more machine-learning models comprise the test configuration features and the design complexity features. The training data are prepared by performing test pattern generation and circuit design analysis. The design complexity features may comprise testability, X-profiling, clock domains, power domains, design-rule-checking warnings, or any combination thereof.

Abstract: Various aspects of the disclosed technology relate to techniques of selecting scan cells from state elements for partial scan designs. Signal probability values for logic gates in a circuit design are first determined. Based on the signal probability values, next-state capture probability values for state elements in the circuit design are computed. Based on the next-state capture probability values, scan cells are selected from the state elements. Scan cells may be further selected based on continuously-updated control weight values and observation weight values associated with the state elements.

Abstract: Various aspects of the disclosed technology relate to machine learning-based chain diagnosis. Faults are injected into scan chains in a circuit design. Simulations are performed on the fault-injected circuit design to determine observed failing bit patterns. Bit-reduction is performed on the observed failing bit patterns to construct first training samples. Using the first training samples, first-level machine-learning models are trained. Affine scan cell groups are identified. Second training samples are prepared for each of the affine scan cell groups by performing bit-filtering on a subset of the observed failing bit patterns associated with the faults being injected at scan cells in the each of the affine scan cell groups. Using the second training samples, second-level machine-learning models are trained. The first-level and second-level machine learning models can be applied in a multi-stage machine learning-based chain diagnosis process.

Abstract: Various aspects of the disclosed technology relate to machine learning-based chain diagnosis. Faults are injected into scan chains in a circuit design. Simulations are performed on the fault-injected circuit design to determine test response patterns in response to the test patterns which are captured by the scan chains. Observed failing bit patterns are determined by comparing the unloaded test response patterns with corresponding good-machine test response patterns. Bit-reduction is performed on the observed failing bit patterns to construct training samples. Using the training samples, machine-learning models for faulty scan cell identification are trained. The bit reduction comprises pattern-based bit compression for good scan chains or cycle-based bit compression for the good scan chains. The bit reduction may further comprise bit-filtering. The bit-filtering may comprises keeping only sensitive bits on faulty scan chains for the training samples construction.

Abstract: An integrated circuit for on-chip speed grading comprises test circuitry comprising scan chains and a test controller; and wide-range clock signal generation circuitry comprising phase-locked loop circuitry and frequency divider circuitry. The wide-range clock signal generation circuitry is configured to generate a wide-range test clock signal for the test circuitry to conduct a structural delay test for on-chip speed grading. The wide-range test clock signal is generated based on a test clock signal associated with the test circuitry, a frequency range selection signal and a frequency setting signal.

Abstract: Various aspects of the disclosed technology relate to circuit defect diagnosis based on sink cell fault models. Defect candidates are determined based on path-tracing from failing bits into the circuit design. Based on the defect candidates and one or more conventional fault models, failing test pattern simulations are performed to determine initial defect suspects. Initial defective sink cell suspects are then determined by comparing driving strengths for fan-out cells of the initial defect suspects with driving strengths for corresponding driver cells. Defective sink cell suspects may be identified in the initial defective sink cell suspects based on fault effect propagations and passing test pattern simulations.

Abstract: Aspects of the disclosed technology relate to techniques of test pattern generation based on the cell transition fault model. An assignment for two consecutive clock cycles at inputs of a complex cell in a circuit design is determined based on a gate-level representation of the circuit design. The assignment includes a first transition at one of the inputs which is sensitized by remaining part of the assignment to cause a second transition at an output of the complex cell. A test pattern that generates the assignment at the inputs and propagates a value at the output corresponding to the second clock cycle of the two consecutive clock cycles from the output to an observation point is then derived based on the gate-level representation.

Abstract: Disclosed herein are exemplary embodiments of a so-called “X-press” test response compactor. Certain embodiments of the disclosed compactor comprise an overdrive section and scan chain selection logic. Certain embodiments of the disclosed technology offer compaction ratios on the order of 1000×. Exemplary embodiments of the disclosed compactor can maintain about the same coverage and about the same diagnostic resolution as that of conventional scan-based test scenarios. Some embodiments of a scan chain selection scheme can significantly reduce or entirely eliminate unknown states occurring in test responses that enter the compactor. Also disclosed herein are embodiments of on-chip comparator circuits and methods for generating control circuitry for masking selection circuits.

Abstract: Various aspects of the disclosed technology relate to techniques of logic diagnosis based on cell-aware diagnostic pattern generation. A first diagnosis process is performed on a failed integrated circuit based on a first fail log to generate a first set of defect suspects. The first fail log is generated by applying the first set of test patterns to the failed integrated circuit in a first scan-based test. A second set of test patterns are generated using fault models for internal defects in one or more cells included in the first set of defect suspects. The second set of test patterns are applied to the failure integrated circuit to generate a second fail log. A second diagnosis process is performed on the failure integrated circuit based on the second fail log.

Abstract: Various aspects of the present disclosed technology relate to techniques of locating defective memory cells based on scan chain diagnosis. Chain pattern responses of a circuit are first analyzed and at least one or more chain segment defect candidates on one faulty scan chain in the circuit and a fault model associated with the one faulty scan chain are determined. Here, each of the one or more chain segment defect candidates is a counter-based scan chain unit derived from a part or a whole of a memory array. Scan pattern responses are then analyzed to determine one or more memory cell defect candidates in the one or more chain segment defect candidates based on the information of the part or the whole of the memory array and the fault model.

Abstract: Disclosed herein are exemplary embodiments of a so-called “X-press” test response compactor. Certain embodiments of the disclosed compactor comprise an overdrive section and scan chain selection logic. Certain embodiments of the disclosed technology offer compaction ratios on the order of 1000×. Exemplary embodiments of the disclosed compactor can maintain about the same coverage and about the same diagnostic resolution as that of conventional scan-based test scenarios. Some embodiments of a scan chain selection scheme can significantly reduce or entirely eliminate unknown states occurring in test responses that enter the compactor. Also disclosed herein are embodiments of on-chip comparator circuits and methods for generating control circuitry for masking selection circuits.

Abstract: Embodiments of the disclosed technology comprise software-based techniques that can be used to improve scan chain test pattern generation and scan chain failure diagnosis resolution. For example, certain embodiments can be used to generate high quality chain diagnosis test patterns that are able to isolate a scan chain defect to a single scan cell. Such embodiments can be used to generate a “complete” test set—that is, a set of chain diagnosis test patterns that is able to isolate any scan chain defect in a faulty scan chain to a single scan cell.

Abstract: Various aspects of the disclosed techniques relate to channel sharing techniques for testing circuits having non-identical cores. Compressed test patterns for a plurality of circuit blocks are generated for channel sharing. Each of the plurality of circuit blocks comprises a decompressor configured to decompress the compressed test patterns. Test data input channels are thus shared by the decompressors. Control data input channels are usually not shared by non-identical circuit blocks in the plurality of circuit blocks.