Chiplet systems that stack heterogeneous dies via 2.5D/3D integration use JTAG-based test access ports (TAPs) to validate inter-die links and enable in-field diagnosis. However, these TAPs create a shared attack surface: penetrating a single die can potentially expose control of the entire stack. Current countermeasures involve embedding a complete cryptographic engine in each chiplet, which increases the area and locks the protocol at tape-out, leaving it susceptible to future unknown attacks. This paper proposes a Software-Defined Secure Island (SDSI) architecture that decouples security policies from hardwired logic while satisfying non-functional requirements. Each chiplet instantiates an ultra-lightweight Secure Island Controller (SIC) macro that performs only two XORs and two additions per handshake. Meanwhile, a centralized secure island runs heavyweight cryptography in firmware using the multi-round SASL-JTAG+ protocol. SDSI enables scalable, adaptable test access protection by decoupling security from hardware. An FPGA implementation shows that the SIC macro occupies 11% of the area of an AES- 128 core and 37% of a SHA256 core, yet it supports 256 - to 512-bit keys with negligible growth. A security analysis demonstrates immunity to replay attacks because the authentication data is refreshed with each session. All future upgrades, such as longer keys, stronger hashes, and additional rounds, are delivered via firmware, providing scalable, field-upgradable protection for heterogeneous chiplet systems.

In recent years, approximate computing has been widely adopted in error-tolerant applications. For approximate multipliers, several techniques have been proposed that truncate lower bits based on the magnitude of the operands. In testing approximate circuits, excluding acceptable faults that affect only within the allowable error range can reduce test costs. This paper proposes a test pattern generation method for approximate multipliers based on the Enhanced Static Segment Method. In the proposed method, a constraint circuit used only during the test pattern generation phase is designed to identify acceptable faults, which reside in the truncated region and do not affect the final computation result. Since some faults cannot be detected without detecting acceptable faults, the proposed method also inserts test points to detect such faults under the condition that acceptable faults remain undetected. As a result, the proposed method achieves approximately 32.7% reduction in the number of test patterns, demonstrating its effectiveness in improving test efficiency for approximate arithmetic circuits.

This paper proposes a novel Test Point Insertion (TPI) strategy to enhance the testability for multi-cycle Built-In Self-Test (BIST) for logic circuits. The approach leverages Multivariate Temporal-Spatial Graph Convolutional Neural Networks (MTS-GCN) and Reinforcement Learning to identify optimal Test Points (TPs). The proposed TPI method treats the testability information of a logic circuit as time-series data and employs Multivariate Time-Series Graph Neural Networks (MTGNN) to capture the relationship between the circuit's structural (spatial information) attributes and the temporal variability of signal line testability across capture cycles. A subsequent Multi-Layer Perceptron (MLP) computes the metric for each signal line to pinpoint potential TPs based on the extracted temporal-spatial features. Experimental evaluation based on benchmark circuits confirms the efficacy of the proposed model, which is trained with Deep Q-Networks (DQN), in improving the fault detection for multi-cycle logic BIST.

In recent years, approximate computing has been used in error-tolerant applications. Several approximation methods have been proposed for approximate multipliers by trun-cating the lower bits of the calculation result according to the positions of one-bits in the multiplier and the multiplicand. In testing approximation circuits, test cost reduction can be achieved by removing acceptable faults that affect only within the acceptable range of the calculation error. This paper proposes a test generation method for an approximate multiplier based on the static segment method. The method adds a circuit in the test generation phase such that the fault propagation to the lower bits of the output is restricted only when these bits are truncated. As a result, the proposed test generation can attain about a 5.2 % reduction in test patterns.

Resistive open defects may occur at interconnects between a printed circuit board and ICs in solder process. An enhanced test method in final tests and a built-in test circuit are proposed to detect resistive open defects of small resistance with relaxation oscillator embedded in ICs in this paper. It is examined by Spice simulations what resistive open defects can be detected. The results show that resistive open defects of 23.4 Ω and above are detected by the test method in a test speed of 1 MHz per an interconnect.

By analyzing the fault behaviors of conventional flash memory fault models, two new concise fault types are proposed: the 1-safe fault and the 0-safe fault. For a 1(0)-safe fault, if logic 1(0) is programmed into the faulty cell, the effect of the fault can be masked. Data shaping (DS) and the page address remapping (PAR) techniques are used to increase the masking probability. DS manipulates the data patterns so that they can be written into the flash pages safely. PAR scrambles the logical-to-physical address mapping for data words and buffer words. Since the effect of a fault is masked for a large proportion of faulty cells, the burden on the error-correction code (ECC) is reduced, as is the number of incorporated redundancies. A novel test-and-repair flow is proposed that uses DS and PAR and corresponding hardware architectures are also developed. A simulator is used to evaluate the hardware overhead, the repair rate, the yield, and the reliability. The experimental results show that these measures are significantly improved with an almost negligible hardware overhead.

With the high integration of integrated circuits, small delay faults have occurred as the cause of a circuit failure. We have proposed a method for testing small delay faults using a boundary scan circuit with embedded TDC (TDCBS). In this method, delay faults are detected by using the number of stages in which a transition signal has propagated through a delay line. However, there exists delay variation in a delay line. This paper investigated delay variation by measuring transition delay for different paths in the delay line. In addition, to calibrate delay variation, we investigated a calibration method for considering the variation of wire length and delay in a delay line in TDCBS. Measurement results for an experimental chip show that the method can compensate the variations in the delay line.

A boundary scan design with embedded time-to-digital converter (TDCBS) has been proposed for testing small delay faults. In this paper, the TDCBS is applied for testing TSVs in 3D IC. To reduce test application time of the TDCBS, we propose a modified TAP controller that utilizes the bypass mode for reducing unnecessary scan shifts during observation of the captured results. The simulation for an experimental circuit is shown to evaluate the effectiveness of the proposed method.

Non-scan based test generation is required to reduce test cost and improve security. However, sequential test generation consumes a lot of time to identify untestable faults. Therefore, it is important to identify untestable faults in the preprocessing of the test generation. In this paper, an unreachable state identification method, which identifies whether states on a few flip-flops can be justified using SAT, and an untestable fault identification method using the unreachable states are proposed. Experimental results show that our proposed method was effective compared with conventional methods.

We propose a supply current test method with a built-in sensor for detecting open defects on signal lines in CMOS logic circuits. The test method is based on an appearance time of dynamic supply current that flows when a test input vector is provided to a device under test. In addition, we propose a test pattern generation algorithm for the test method. An IC embedding the sensor is prototyped to examine the testability of the test method. We show by SPICE simulation and by some experiments with the IC that open defects that is undetectable by delay tests can be detected by the test method.

Based on the fault behaviors of conventional fault models, the 1-safe and 0-safe fault types are derived in this paper. We can try to store the safe value of a flash cell such that the fault effects can be masked. To boost the masking probability, both the data inversion (DI) and the page address remapping (PAR) techniques are also proposed. DI tries to complement the data bits to be programmed if their values derivate from the safe values of the corresponding faulty flash cells. PAR manipulates the logical-to-physical mapping of data words and the buffer words such that faulty cells can be programmed with their safe values. Since most of the fault effects are masked, we can reduce the strength of the adopted ECC or the amount of incorporated redundancies. The corresponding hardware architectures are also developed. A simulator is developed to evaluate the hardware overhead, repair rate, and reliability. According to experimental results, these measures can be improved significantly with negligible hardware overhead.

A testable design method for electrical testing is proposed in this paper to detect open defects occurring at interconnects between dies in a 3D IC and locate the defective interconnects. An IEEE 1149.1 test circuit is utilized to provide a test input vector to a targeted interconnect in the electrical tests. Feasibility of the electrical tests is evaluated by Spice simulation and some experiments with a prototyping IC. It is shown by the experiments that an open defect can be detected at a test speed of 1MHz.

This paper presents a design-for-testability method for detecting delay faults. In order to observe the effect of small delay defects, we present modified boundary scan cells in which a time-to-digital converter (TDC) is embedded. In our boundary scan cells, flip-flops are utilized for both making a scan path and capturing circuit response. The architecture of the boundary scan design is proposed to detect delay from the other cores or chips or its interconnects. The basic operation of the design is evaluated by simulation and by experimental ICs. Experimental results show that the measurement of the transition delay can be achieved by the boundary scan design with the time-to-digital converter.

In this paper, a method for reducing test data volume of BIST-aided scan test (BAST) is proposed. In our BAST method, scan chains are ordered using compatible flip-flops to reduce the conflicting bits between ATPG pattern and random pattern obtained by LFSR. The inverter block in BIST-aided scan architecture is modified for shifting inverter code such that the random pattern produced by LFSR has less conflicting bits with ATPG patterns when providing the test pattern to the scan chains. The experimental results show the method can reduce the test data volume than the previous method.

We propose a testable design method of level shifters inside a liquid crystal display driver IC. The design method enables us to detect open defects in level shifters by supply current testing that are difficult to be tested by voltage testing. Also, we show by circuit simulation that more resistive open defects may be detected by supply current testing than voltage testing, if the level shifter is designed by using the proposed DFT method.

Under the open fault model with considering the effects of adjacent lines, the open fault excitation is depended on the tests. Therefore, the layout information is needed to generate a test for an open fault. However, it is not easy to extract accurate circuit parameters of a deep sub-micron LSI. We have already proposed an open fault model without using the accurate circuit parameters. In this paper, we propose a new class of the pair of tests for the open fault called Ordered Pair of Tests (OPT). OPT is generated based on the fault excitation function as a threshold function of the adjacent lines. Also we propose a method for generating OPTs from the given stuck-at fault test set. The proposed method generates OPTs using only information about adjacent lines of the target open fault. Experimental results show that the proposed method can generate the OPTs for the open faults with high fault coverage.

In this paper, a DFT method of resistor string digital-to-analog converters (DACs) is proposed so as to be tested fully by supply current testing. Targeted defects are opens and shorts in the DACs. Testability of a testable designed DAC is examined experimentally. The results show that shorts and opens in a testable designed DAC will be detected with a smaller number of test vectors by supply current testing.

Under the modern manufacturing technologies, the open defect is one of the significant issues to maintain the reliability of DSM circuits. However, the modeling and techniques for test and diagnosis for open faults have not been established yet. In this paper, we give an important clue for modeling an open fault with considering the affects of adjacent lines. Firstly, we use computer simulations to analyze the defective behaviors of a line with the open defect. From the simulation results, we propose a new open fault model that is excited depending on the logic values at the adjacent lines assigned by a test. Next, we propose a diagnosis method that uses the pass/fail information to deduce the candidate open fault. Finally, experimental results show that the proposed method is able to diagnose the open faults with good resolution. It takes about 6 minutes to diagnose the open fault on the large circuit (2M gates).

A built-in-current sensor (BIC sensor) is proposed whose IDDQ limit is able to be adjusted in each IC test. IDDQ tests of identical IDDQ limit can be realized with the current sensor, even if process variation occurs in the sensor. Also, an IDDQ test method is proposed for ICs, in each of which the BIC sensor is implemented. It is shown by some experiments that IDDQ limit of 10mu A will be able to be set and IDDQ test results based on the limit will be obtained by adjusting the limit for each IC if size variation of MOSs in the BIC sensor is less than 50%

An I/sub DDQ/ test method is proposed in this paper, which is applicable even if supply current measurement is impaired by noise. Wavelet transformation is used for noise elimination in the test method. In this paper, it is shown by some experiments that bridging faults will be detected by using the proposed test method. Since expert knowledge on filter design is not needed in noise elimination of the I/sub DDQ/ test method, it is expected that the test method will be used in many I/sub DDQ/ tests.

In this paper, an I/sub DDQ/ test time reduction method is proposed which is suitable for BIST approaches. Also, a BIST circuit for I/sub DDQ/ tests, based on the method, is proposed. The layout of a CMOS logic circuit having the BIST circuit is designed and the performance is evaluated by SPICE simulation. The results show us that I/sub DDQ/ test time can be reduced by using this test circuit.

In this paper, a new method for reducing scan shifts is presented. Scan design is one of the most popular design for test technologies for sequential circuits. However, it requires much test application time and test data when applied to circuits with many flip-flops. The new scan method utilizes two configurations of scan chains, a folding scan tree and a fully compatible scan tree. A test pattern including many don't care values is used to configure a fully compatible scan tree in order to reduce the scan shift without degrading fault coverage. And then a folding scan tree is configured to reduce the length of the scan chain and thus reduce the scan shift. Experimental results for benchmark circuits shows this scan method can reduce many scan shifts.

In this paper, test time reduction for I/sub DDQ/ testing is discussed. Although I/sub DDQ/ testing is known to be effective in detecting faults in CMOS circuits, the test time of I/sub DDQ/ testing is larger than that of logic testing. It is shown that the test time of I/sub DDQ/ test mostly depends on the switching current. To reduce the test time of I/sub DDQ/ testing, a procedure to arrange test vectors such that the switching current quickly disappears is proposed for combinational circuits. The procedure utilizes a unit delay model to estimate the time of the last transition of logic values from low to high in a circuit. Experimental results for benchmark circuits show the effectiveness of the procedure.

In this paper, a new test method is proposed for detecting open defects in CMOS ICs. The method is based on supply current of ICs generated by applying time-variable supply voltage and electric field from the outside of the ICs. The feasibility of the test is examined by some experiments. The empirical results show that, by using the method, open defects in CMOS ICs can be detected. Also, the test input vectors for the test method are proposed and it is shown that they can be generated more easily than functional test methods based on stuck-at fault models.

In this paper, a useful technique is proposed for realizing high speed IDDQ tests. By using the technique, load capacitors of the CMOS logic gates can be charged quickly, where the output logic level changes L to H by applying a test input vector to a circuit under test. The technique is applied to built-in I/sub DDQ/ sensor design and external I/sub DDQ/ sensor design. It is shown experimentally that high speed I/sub DDQ/ tests can be realized by using the technique.

In this paper, a procedure to reduce sequential circuits by removing undetectable faults in sequential circuits is proposed. To identify whether an undetectable fault is removable or not, strongly unreachable states, which are the states with no incoming transitions, are utilized. It is proved that part of undetectable faults related to strongly unreachable states can be removed from a circuit. Test generation method is used to find undetectable faults related to two or more strongly, unreachable states. Experimental results for ISCAS benchmark circuits are shown.

In this paper, a new test method is proposed for detecting open defects in CMOS ICs. The method is based on supply current of ICs generated by applying time-variable electric field from the outside of the ICs. The feasibility of the test is examined by some experiments. The empirical results promised that, by using the method, open defects in CMOS ICs can be detected by measuring supply current which flows when time-variable electric field is applied.

A new high speed IDDQ test method is proposed. It is based on charge current for load capacitances of gates whose output logic values are changed from L to H by test input vector application. In this paper, the testability of the test method is examined for some process variations generated in CMOS IC production.

When a feedback bridging fault occurs in a combinational circuit and it is activated, logical oscillation may be generated in the circuit. In this paper, the necessary conditions are presented for feedback bridging faults to generate logical oscillation. Also, a method is proposed to identify such faults in feedback bridging ones. It is based on piecewise-linearized models obtained from input/output characteristics of logic gates and does not require circuit simulation of large size of circuits to identify them. In the experiments for evaluating the method, all of the feedback bridging faults to generate logical oscillation are identified by using the method.

We present a procedure to reduce sequential circuits by removing undetectable faults based on unreachable states. Procedures for obtaining unreachable stares and for identifying undetectable faults which can be the target of fault removal are presented. Experimental results for ISCAS benchmark circuits are shown.

This paper presents a retiming and redundancy removal method for a sequential circuit with a specified initial state so that the resynthesized circuit has a state corresponding to the initial state and gives same behavior for any input sequences of the original circuit. Experimental results show the proposed method can optimize circuits as well as the method which does not consider the specified initial state.