New test pattern generation units for NPSF oriented memory built-in self test

Testing for delay and CMOS stuck-open faults requires two pattern tests and test sets are usually large. Built-in self-test (BIST) schemes are attractive for such comprehensive testing. The BIST test pattern generators (TPGs) for such testing should be designed to ensure high pattern-pair coverage. In this paper, necessary and sufficient conditions to ensure complete/maximal pattern-pair coverage for linear feedback shift register (LFSR) and cellular automata (CA) have been derived. The theory developed here identifies all LFSR/CA TPGs which maximize pattern-pair coverage under any given TPG size constraints. It is shown that LFSRs with primitive feedback polynomials with large number of terms are better for two-pattern testing. Also, CA are shown to be better TPGs than LFSRs for two-pattern testing. Results derived in this paper provide practical algorithms for the design of optimal TPGs for two-pattern testing. Experiments on some benchmark circuits indicate the TPGs designed using the procedures outlined in this paper provide much higher delay fault coverage than other TPGs. >

This paper presents three built-in self-test (BIST) schemes for robust testing of stuck-open faults in combinational FCMOS complex cells of arbitrary structure. The first method shows that all single stuck-open faults can be robustly tested by applying a universal sequence of 5/spl times/2/sup n/ vectors to the modified circuit under test (CUT), and counting the number of 1's in the output response. The second method uses the same test pattern generator (TPG), but faults are detected by a self comparison technique without the need of storing a signature. Finally, we propose a new adaptive BIST technique, where the TPG is driven by the past outputs of the CUT itself In all the cases, the TPG is universal, i.e., if does not depend on the functionality and the structure of the CUT, but does ensure robust testing. Neither any test vector, nor any fault dictionary, is required. These approaches provide simplicity, less testing time and test data, and compare favorably with earlier BIST designs for CMOS circuits.

A new technique called input reduction is proposed for built-in self test (BIST) test pattern generator (TPG) design and test set compaction. This technique analyzes the circuit function and identifies sets of compatible and inversely compatible inputs; inputs in each set can be combined into a test signal in the test mode without sacrificing fault coverage, even if they belong to the same circuit cone. The test signals are used to design BIST TPGs that guarantee the detection of all detectable stuck-at faults in practical test lengths. A deterministic test set generated for the reduced circuit obtained by combining inputs into test signals is usually more compact than that generated for the original circuit. Experimental results show that BIST TPGs based on input reduction achieve complete stuck-at fault coverage in practical test lengths (/spl les/2/sup 30/) for many benchmark circuits. These are achieved with low area overhead and performance penalty to the circuit under test. Results also show that the memory storage and test application time for external testing using deterministic test sets can be reduced by as much as 85%.

In this research, a BIST (built in self test) architecture for testing crosstalk effects in highly dense Through Silicon Via (TSV) placed in structured array form, in 3DICs (Three Dimensional integrated circuits), designed and simulated using the Xilinx ISE tool and the VHDL language. A novel methodology is proposed, and simulated, to observe the test responses of the victim TSVs in the chosen group simultaneously. Boundary-scan cell structures are modified, created for the purpose of operating in different modes such as shift, update and capture in either conventional serial shift mode as well as in proposed parallel broadcasting mode. Output Response Analyzers (ORA), or signature analyzers that have been simulation-verified. In this study, we suggested a novel encoder-based signature generator to locate faulty TSVs in the parallel-observed TSVs. This paper discusses the whole BIST architecture, the BIST controller built on an algorithmic state machine, the design of TPG (Test Pattern Generator), and the faulty TSV signature generator. Comparing the BIST architecture, to serial shift based interconnect tests done by IEEE 1149.1 (JTAG) such as EXTEST and IEEE 1838 standards, the test’s time complexity of BIST is relatively very low. The entire TSV array test is completed in just 32 clock cycles. The design is adaptable and can be used to broadcast test patterns to a group or to transmit test patterns serially using IEEE 1838 or 1149.1.

A novel design of a test pattern generator (TPG) for built-in self-testing (BIST) of path delay faults, is proposed. For an n-input CUT, the TPG generates a sequence of length (n.2/sup n/+1), that includes all n.2/sup n/ single-input-change (SIC) test pairs, and hence optimal. The generation of such a sequence of minimum length (i.e., n.2/sup n/+1) was an open problem. A simple iterative circuit of the TPG is then constructed. This provides minimum test application time for testing path delay faults, and compares favorably with the earlier BIST designs.

Design for low power testing is primary concern in modern VLSI circuits. In this paper a novel test pattern generator (TPG) is proposed which is more suitable for built in self test (BIST) architecture, used for testing of VLSI circuits. The objective of the BIST is to reduce power consumption during testing of VLSI circuits. In CMOS devices 80% of power consumption is due to switching activity occurred during operation. The proposed TPG is based on read only memory (ROM) which is carefully designed to store the test vectors with minimum area over the conventional ROM. This reduces the number of CMOS transistors significantly when compared to that of LFSR/counter TPG. The proposed TPG is more suitable for deterministic pattern testing and the fault coverage is improved over the LFSR. Low power reordered test patterns also can also be stored in the same order to reduce the test power in circuit under test (CUT). The TPG is designed and implemented for benchmark circuits ISCAS 85 and 89. Experimental results shows that a considerable reduction in number of CMOS devices and test power is achieved over the LFSR-TPG

Existing built-in self test (BIST) strategies require the use of specialized test pattern generation hardware which introduces significant area overhead and performance degradation. In this paper, we propose a novel method for implementing test pattern generators based on adders widely available in data-path architectures and digital signal processing circuits. Test patterns are generated by continuously accumulating a constant value and their quality is evaluated in terms of the pseudo-exhaustive state coverage on subspaces of contiguous bits. This new test generation scheme, along with the recently introduced accumulator-based compaction scheme facilitates a BIST strategy for high performance datapath architectures that uses the functionality of existing hardware, is entirely integrated with the circuit under test, and results in at-speed testing with no performance degradation and area overhead.

When using Built-In Self Test (BIST) for testing VLSI circuits, a major concern is the generation of proper test patterns that detect the faults of interest. Usually a linear feedback shift register (LFSR) is used to generate test patterns. We first analyze the probability that an arbitrary pseudo-random test sequence of short length detects all faults. The term short is relative to the probability of detecting the fault having the fewest test patterns. We then show how to guide the search for an initial state (seed) for a LFSR with a given primitive feedback polynomial so that all the faults of interest are detected by a minimum length test sequence. Our algorithm is based on finding the location of test patterns in the sequence generated by this LPSR. This is accomplished using, the theory of discrete logarithms. We then select the shortest subsequence that includes test patterns for all the faults of interest, hence resulting in 100% fault coverage. >

This paper presents a Built In Self Test (BIST) scheme for very high parallelism memory testing to be done on a BIST Board with DC stimuli. A BIST scheme with ten algorithms was implemented on a 256Meg, 4 banks, X32 SDRAM. Self Test operation is synchronized by an on chip oscillator which also generates internal timing signals needed for memory testing. Various ways to test the functionality of BIST circuitry as well as some engineering and debug features are also included.

This paper proposes a low power efficient Built in Self Test (BIST) with Test Pattern Generation (TPG) technique, which reduces power dissipation during testing. In general, the correlations between the consecutive test patterns are higher during normal mode than during testing mode. The proposed approach uses the concept of reducing the transitions in the test patterns generated by conventional Linear Feedback Shift Register (LFSR) . The transitions are reduced by increasing the correlation between the successive bits in the test pattern, which is done with the help of modified LFSR. This approach eliminates the need for an external tester. The simulation result shows that the power dissipated during testing is reduced in modified LFSR than in conventional LFSR.

This paper introduces a test pattern generator (TPG) in order to use in built-in self-test(BIST). MSIC TPG generates multiple single input change (MSIC) vectors in a pattern, i.e., each vector applied to a scan chain is an SIC vector. With the help of reconfigurable Johnson counter and a scalable SIC counter its easy to generate a class of minimum transition sequences. The proposed TPG is flexible to test-per-scan schemes. A theory is developed to represent and analyze the sequences and to extract a class of MSIC sequences. Analysis results show that the produced MSIC sequences have the favorable features of uniform distribution, minimum transitions, and low input transition density. The Performances of the designed MSIC TPG and the circuit under test are evaluated. Simulation results shows that it can save delay time and power. It also achieves the target fault coverage without increasing the test length.

Many Built-in Self Test (BIST) pattern generators use Linear Feedback Shift Registers (LFSR) to generate test sequences. In this paper, we address the generation of deterministic pairs of patterns for delay faults testing with LFSRs. A new synthesis procedure for a n-size LFSR is given and guarantees that a deterministic set of n precomputed test pairs is embedded in the maximal length pseudo-random test sequence of the LFSR. Sufficient and necessary conditions for the synthesis of this pseudo-deterministic LFSR are provided and show that at-speed delay faults testing becomes a reality without any additional cost for the LFSR. Moreover, since the theoretical properties of LFSRs are preserved, our method could be beneficially used in conjunction with any other technique proposed so far.

Recent trends in IC technology have given rise to a new requirement, that of low power dissipation during testing, that Built‐In Self‐Test (BIST) structures must target along with the traditional requirements. To this end, by exploiting the inherent properties of Carry Save, Carry Propagate and modified Booth multipliers, in this paper we propose new power‐efficient BIST structures for them. The proposed BIST schemes are derived by: (a) properly assigning the Test Pattern Generator (TPG) outputs to the multiplier inputs, (b) modifying the TPG circuits and (c) reducing the test set length. Our results indicate that the total power dissipated during testing can be reduced from 29.3% to 54.9%, while the average power per test vector applied can be reduced from 5.8% to 36.5% and the peak power dissipation can be reduced from 15.5% to 50.2% depending on the implementation of the basic cells and the size of the multiplier. The test application time is also significantly reduced, while the introduced BIST schemes implementation area is small.

Integration of diagnostics with a memory built-in self-test (BIST) allowing both an effective and efficient manufacturing test as well as an effective diagnostic capability is detailed. Detection of failures within a memory are the primary objective of an embedded memory BIST. Inclusion of comprehensive diagnostics, to isolate faults incurred during the manufacturing or design process, are an extension to the memory BISI, further utilizing the existing circuitry and functionality. Detection and diagnosis of failures within an embedded memory can be realized throughout the entire manufacturing process.

The benefits of the continued progress in integrated circuit manufacturing have been numerous, most notably in the explosion of computing power in devices ranging from cell phones to cars. Key to this success has been strategies to identify, manage, and mitigate yield loss. One such strategy is the use of test structures to identify sources of yield loss early in the development of a new manufacturing process. However, the aggressive scaling of feature dimensions, the integration of new materials, and the increase in structural complexity in modern technologies has challenged the capabilities of conventional test structures. To help address these challenges, a new logic test chip, called the Carnegie Mellon Logic Characterization Vehicle (CM-LCV), has been developed. The CM-LCV utilizes a two- dimensional array of functional unit blocks (FUBs) that each implement an innovative functionality. Properties including fault coverage, logical and physical design features, and fault distinguishability are shown to be composable within the FUB array; that is, they exist regardless of the size and composition of the FUB array. A synthesis ow that leverages this composability to adapt the FUB array to a wide range of test chip design requirements is presented. The connection between the innovative FUB functionality and orthogonal Latin squares is identified and used to analyze the universe of possible FUB functions. Two additional variants to the FUB array are also developed: heterogenous FUB arrays utilize multiple FUB functions to improve the synthesis ow performance, while pipelined FUB arrays incorporate sequential circuit elements (e.g., ip- ops and latches) that are absent from the original combinational FUB array. In addition to the design of the CM-LCV, methods for testing it are presented. Techniques to create minimal sets of test patterns that exhaustively exercise each FUB within the FUB array are developed. Additional constraints are described for the heterogenous and pipelined FUB arrays that allow these techniques to be applied for both variant FUB arrays. Furthermore, a simple built-in self test (BIST) scheme is described and applied to a reference design, resulting in a 88.0% reduction in the number of test cycles required without loss in fault coverage. A hierarchical FUB array diagnosis methodology (HFAD) is also presented for the CM- LCV that leverages its unique properties to improve performance for multiple defects. Experiments demonstrate that this HFAD methodology is capable of perfect accuracy in 93.1% of simulations with two injected faults, an improvement on the state-of-the-art commercial diagnosis. Additionally, silicon fail data was collected from a CM-LCV manufactured using a 14nm process by an industry partner. A comparison of the diagnosis results for the 1,375 fail logs examined shows that the HFAD methodology discovers additional defects during multiple defect diagnosis that the commercial tool misses for 40 of the diagnosed fail logs. Examination of these cases shows that the additional defects found by the HFAD methodology can result in improved diagnosis confidence and more precise descriptions of the defect behavior(s). The contributions of this dissertation can thus be summarized as the description of the design, test, and diagnosis of a new logic test chip for use in yield learning during process development. This CM-LCV can be adapted to meet a wide range of test chip requirements, can be efficiently and rigorously tested, and exhibits properties that can be used to improve diagnosis outcomes. All of these claims are validated through both simulated experiments and silicon data.