As cars become increasingly computerized and their safety functions evolve rapidly, the number of complex safety-critical components deployed in advanced driver assistance systems or autonomous vehicles is rising dramatically with high-end models containing hundreds of embedded microcontrollers. These integrated circuits must adhere to stringent requirements for high quality and long-term reliability driven by functional safety standards. This requires test solutions that address challenges posed by automotive systems. This article presents a scan-based test scheme optimizing test time and area overhead during manufacturing and in-system test of automotive electronics. The proposed scheme deploys observation test points that capture the faulty effects in every shift cycle into separate observation scan chains. To reduce area overhead, the scheme enables the sharing of flip-flops among control points. It is also shown how test points enhance test coverage (TC) in the presence of cascaded clock gaters. Finally, processing challenges when fault simulating every scan shift cycle to determine TC are addressed. Experimental results obtained for contemporary automotive designs and reported herein show significant improvements in test quality over traditional solutions.

Logic built-in self-test (LBIST) is now increasingly used with on-chip test compression as a complementary solution for in-system test, where high quality, low power, low silicon area, and most importantly short test application time are key factors affecting ICs targeted for safety-critical systems. Test points, common in LBIST-ready designs, can help to reduce test time and the overall silicon overhead so that one can get desired test coverage with the minimal number of patterns. Typically, LBIST test points are dysfunctional when enabled in an ATPG-based test compression mode. Similarly, test points used to reduce ATPG pattern counts (PCs) cannot guarantee desired random testability. In this paper, we present a hybrid test point technology designed to reduce deterministic PCs and to improve fault detection likelihood by means of the same minimal set of test points. The hybrid test points are subsequently deployed in a scan-based LBIST scheme addressing stringent test requirements of certain application domains such as the automotive electronics market. These requirements, largely driven by safety standards, are met by significantly reducing test application time while preserving the high fault coverage. The new scheme is a combination of pseudorandom test patterns delivered in a test-per-clock fashion through conventional scan chains and per-cycle-driven hybrid observation test points that capture faulty effects every shift cycle into dedicated scan chains. Their content is gradually shifted into a compactor shared with the remaining chains that deliver responses once a test pattern has been shifted-in. Experimental results obtained for industrial designs confirm feasibility of the new schemes, and they are reported herein.

As cars become increasingly computerized and their safety functions are evolving rapidly, the number of complex safety-critical components deployed in advanced driver assistance systems or autonomous vehicles is progressively rising with high-end models containing more than a hundred embedded microcontrollers. These integrated circuits must adhere to stringent requirements for high quality and long-term reliability driven by functional safety standards. This requires test solutions that address challenges posed by automotive electronics. The paper presents a scan-based LBIST scheme optimizing test time and area overhead during in-system test applications for automotive ICs. It ensures highly reliable operations of ICs for the duration of their lifespan. The proposed scheme works with observation test points that capture faulty effects every shift cycle into separate observation scan chains. To reduce area overhead, the scheme takes advantage of a procedure allowing one to share flip-flops among control points. It is also shown how test points can enhance test coverage in the presence of cascaded clock gaters. Finally, processing challenges when fault simulating every scan shift cycle to determine observed faults are addressed. Experimental results obtained for contemporary automotive designs and reported herein show significant improvements in quality of test over traditional BIST schemes.

Growing reverse-engineering attempts to steal or violate a design intellectual property (IP), or to identify the device technology in order to counterfeit integrated circuits (ICs), raise serious concerns in the IC design community. As the information derived from these practices can be used in a number of malicious ways, various active techniques have been proposed and deployed to protect IP, of which logic locking is a vital part. It allows inserting certain gates in a circuit’s data path to lock outputs to fixed logic values, if a wrong unlocking key is applied. This paper demonstrates that test points—industry-proven design-for-test technology used primarily to enhance the overall design testability–can also be reused in the mission mode to lock the circuit, and thus to improve the hardware security against IP piracy. In particular, it is shown that test points can facilitate the hiding of design functionality from adversaries. As a result, not only is the overall design testability improved, but also effective protection against piracy through unauthorized excess production and other forms of IP theft is ensured. Experimental results on industrial designs with test points demonstrate that the proposed scheme is effective in achieving a desired degree of hardware obfuscation.

Recent reverse-engineering attempts to steal a competitive design intellectual property (IP) or to identify the device technology in order to counterfeit integrated circuits (ICs) have raised serious concerns in the IC design community. This paper demonstrates that test points - industry-proven design-for-test technology used to enhance the overall design testability - can also be deployed in the mission mode to obfuscate the circuit's structure, and thus to improve the hardware security against reverse engineering, IC cloning, and IP theft. In particular, it is shown how test points can facilitate the hiding of design functionality from adversaries. As a result, not only the overall design testability is improved, but also effective protection against reverse engineering and other forms of attacks is ensured.

Logic built-in self-test (LBIST), originally introduced for board, system, and in-field tests, is now being increasingly used with on-chip test compression. This hybrid approach allows LBIST to become a complementary solution for in-system test, where high quality, low power, low silicon area, and most importantly short test application time are key factors affecting ICs that are targeted for safety-critical and automotive systems. Test points are common in BIST-ready designs where they play a key role in reducing both test application time given a test coverage goal and the overall silicon overhead so that one can get a desired coverage with the minimal number of patterns. Unfortunately, these test points are typically dysfunctional when enabled in an ATPG-based test compression mode. Similarly, test points used to reduce ATPG-based test pattern counts cannot guarantee desired random testability. Incompatibility of both types of test points has motivated research presented in this paper. We present a novel hybrid test point technology designed to both reduce deterministic pattern counts and improve fault detection likelihood by means of the same minimal set of test points. Experimental results obtained for large industrial designs illustrate feasibility of the proposed hybrid test points and are reported herein.

Test points are known to improve the fault coverage in BIST applications. This article discusses a new class of test points used to improve the ATPG pattern count in designs that employ embedded deterministic test.

Conflict-aware test points, introduced recently, facilitate significant reductions in deterministic test pattern counts. However, dedicated flip-flops driving control points increase test logic area. This paper presents a method to minimize silicon area needed to implement conflict-aware test points by reusing functional flip-flops as drivers of control points. Conflict analysis is applied during the test point selection process, and ATPG verification is run for every potential candidate. Experimental results show that functional flip-flops can be reused as drivers for more than 90% of the control points with the average of 5% penalty in pattern count increase as compared to methods using only dedicated flip-flops. After replacing dedicated flip-flops with functional flip-flops, conflict-aware test points can still achieve remarkable pattern count reductions.

This paper introduces a novel test data compression scheme, which is primarily devised for low-power test applications. It is based on a fundamental observation that in addition to low test cube fill rates, a very few specified bits, necessary to detect a fault, are actually irreplaceable, whereas the remaining ones can be placed in alternative locations (scan cells). The former assignments are used to create residual test cubes and, subsequently, test templates. They control a power-aware decompressor and guide automatic test pattern generation to produce highly compressible test patterns through finding alternative assignments. The proposed approach reduces, in a user-controlled manner, scan shift-in switching rates with minimal hardware modifications. It also elevates compression ratios to values typically unachievable through conventional low-power reseeding-based solutions. Experimental results obtained for large industrial designs illustrate feasibility of the proposed test scheme and are reported herein.

This paper presents a new method to design digital circuits for low pattern counts, one of the key factors shaping cost-effective VLSI test schemes. The method identifies the largest conflicts between internal signals that prevent efficient test compaction in ATPG. These locations are modified by inserting conflict-reducing test points (CRTP) to significantly reduce the ATPG-produced pattern counts. Experimental results obtained for large industrial designs with on-chip test compression demonstrate, on average, 3x - 4x reduction in stuck-at and transition patterns and 3x shorter ATPG times.

The introduction of FinFET technology has accelerated the adoption of patterns that target cell internal defects such as cell-aware tests. Even though cell-aware tests can replace stuck-at and transition patterns from the screening point of view, we have to address the increase in test data volume. This combined with the growing gate counts enabled by new technology nodes is driving the need for even greater compression levels. In this paper, we present a novel test points technology designed to reduce deterministic pattern counts for cell-aware tests. The technology is based on identification and resolution of conflicts across internal signals allowing ATPG to significantly increase the number of faults targeted by a single pattern. Experimental results on a number of industrial designs with test compression demonstrate that the proposed test points are effective in achieving, on average, a 3×–4× multiplicative increase in compression for 1-cycle and 2-cycle cell-aware patterns.

The paper presents a novel test data compression scheme. The invention follows from a fundamental observation that in a typical test cube only a small portion of the specified positions are necessary to detect a fault, and most of the remaining ones have many alternatives. The necessary assignments are used to form test templates which both control a decompressor to guarantee the necessary assignments and guide ATPG to find alternative assignments to produce highly compressible test cubes. The proposed approach synergistically elevates compression ratios to values typically unachievable through conventional reseeding-based solutions. It also reduces, in a user-controlled manner, switching rates in scan chains with minimal hardware modification. Experimental results obtained for large industrial designs illustrate feasibility of the proposed test scheme and are reported herein.

With the ever increasing integration capability of semiconductor technology, today’s large integrated circuits require an increasing amount of data to test them which increases test time and elevated requirements of tester memory. At the same time, as VLSI design sizes and their operating frequencies continue to increase, timing-related defects are high proportion of the total chip defects and atspeed test is crucial. DFT techniques are widely used in order to improve the testability of a design. While DFT techniques facilitate generation and application of tests, they may cause the test vectors to contain non-functional states which result in higher switching activities compared to the functional mode of operation. Excessive switching activity causes higher power dissipation as well as higher peak supply currents. Excessive power dissipation may cause hot spots that could cause damage the circuit. Excessive peak supply currents may cause higher IR drops which increase signal propagation delays during test causing yield loss. Several methods have been proposed to reduce the switching activity in the circuit under test during shift and capture cycles. While these methods reduce switching activity during test and eliminate the abnormal IR drop, circuits may now operate faster on the tester than they would in the actual system. For speed related and high resistance defect mechanisms, this type of undertesting means that the device could be rejected by the systems integrator or by the end consumer and thus increasing the DPPM of the devices. Therefore, it is critical to ensure that the peak switching activity generated during the two functional clock cycles of an at-speed test is as close as possible to the functional switching activity levels specified for the device. The first part of this dissertation proposes a new method to generate test vectors that mimic functional operation from the switching activity point of view. It uses states obtained by applying a number of functional clock cycles starting from the scan-in state

Growing test data volume and excessive test power consumption in scan testing are both serious concerns for the semiconductor industry. This paper presents a method to simultaneously reduce test data volume and test power utilizing clock gating. This is achieved through not clocking a high proportion of scan chains during both scan shift and test response capture. Reducing the number of scan chains shifted during scan load can be expected to permit higher scan shift frequency thus reducing the test time. Reduced test data volume can be expected to permit fewer tester channels for testing which can increase the number of chips tested in parallel. Experimental results presented for industrial circuits demonstrate that on average a factor of 1.98 and 4 reductions in test data volume and test power, respectively is achievable using the proposed method.

Growing test data volume and excessive test power consumption in at-speed scan testing are both serious concerns for the semiconductor industry. This paper presents a method to simultaneously reduce test data volume and test power in atspeeddelay test utilizing clock gating. This is achieved through not clocking a high proportion of scan chains during both scan shift and test response capture. Reducing the number of scan chains shifted during scan load can be expected to permit higher scan shift frequency thus reducing the test time. Reduced test data volume can be expected to permit fewer tester channels for testing which can increase the number of chips tested in parallel. Experimental results for a set of industrial circuits show that the proposed method, on average, reduces test data volume by a factor 2.7, switching activity during scan shift by a factor of 5 and peak switching activity during test response capture by a factor of 2.