One embodiment of the present invention concerns a test assembly for testing product circuitry of a product die. In one embodiment, the test assembly includes at test die and an interconnection substrate for electrically coupling the test die to a host controller that communicates with the test die. The test die may be designed according to a design methodology that includes the step of concurrently designing test circuitry and a product circuitry in a unified design. The test circuitry can be designed to provide a high degree of fault coverage for the corresponding product circuitry generally without regard to the amount of silicon area that will be required by the test circuitry. The design methodology then partitions the unified design into the test die and the product die. The test die includes the test circuitry and the product die includes the product circuitry. The product and test die may then be fabricated on separate semiconductor wafers. By partitioning the product circuitry and test circuitry into separate die, embedded test circuitry can be either eliminated or minimized on the product die. This will tend to decrease the size of the product die and decrease the cost of manufacturing the product die while maintaining a high degree of test coverage of the product circuits within the product die. The test die can be used to test multiple product die on one or more wafers.

Test assembly including a test die for testing a semiconductor product die

Today's computers must perform with increasing reliability, which in turn depends on the problem of determining whether a circuit has been manufactured properly or behaves correctly. However, the greater circuit density of VLSI circuits and systems has made testing more difficult and costly. This book notes that one solution is to develop faster and more efficient algorithms to generate test patterns or use design techniques to enhance testability - that is, "design for testability." Design for testability techniques offer one approach toward alleviating this situation by adding enough extra circuitry to a circuit or chip to reduce the complexity of testing. Because the cost of hardware is decreasing as the cost of testing rises, there is now a growing interest in these techniques for VLSI circuits.The first half of the book focuses on the problem of testing: test generation, fault simulation, and complexity of testing. The second half takes up the problem of design for testability: design techniques to minimize test application and/or test generation cost, scan design for sequential logic circuits, compact testing, built-in testing, and various design techniques for testable systems.Hideo Fujiwara is an associate professor in the Department of Electronics and Communication, Meiji University. Logic Testing and Design for Testability is included in the Computer Systems Series, edited by Herb Schwetman.

Logic testing and design for testability

In this brief, a cobweb-based redundant through-silicon-via (TSV) design is proposed with efficient hardware as well as high repair rate to repair clustered faulty TSVs (FTSVs). The experimental simulation results demonstrate that for highly clustered faults, the repair rate of the proposed RTSV method is 48.59% and 1.75% higher than that of the ring-based and router-based RTSV methods, respectively. Furthermore, the proposed design can achieve 63.93% and 16.34% hardware reductions compared with the router-based and the ring-based design, respectively.

Architecture of Cobweb-Based Redundant TSV for Clustered Faults

A method and system to automate scan synthesis at register-transfer level (RTL). The method and system will produce scan HDL code modeled at RTL for an integrated circuit modeled at RTL. The method and system comprise computer-implemented steps of performing RTL testability analysis, clock-domain minimization, scan selection, test point selection, scan repair and test point insertion, scan replacement and scan stitching, scan extraction, interactive scan debug, interactive scan repair, and flush/random test bench generation. In addition, the present invention further comprises a method and system for hierarchical scan synthesis by performing scan synthesis module-by-module and then stitching these scanned modules together at top-level. The present invention further comprises integrating and verifying the scan HDL code with other design-for-test (DFT) HDL code, including boundary-scan and logic BIST (built-in self-test).

Computer-aided design system to automate scan synthesis at register-transfer level

Three-dimensional integrated circuits (3-D-ICs) that employ the through-silicon vias (TSVs) vertically stacking multiple dies provide many benefits, such as high density, high bandwidth, and low power. However, the fabrication and bonding of TSVs may fail because of many factors, such as the winding level of the thinned wafers, the surface roughness and cleanness of silicon dies, and bonding technology. To improve the yield of 3-D-ICs, many redundant TSV (RTSV) architectures were proposed to repair 3-D-ICs with faulty TSVs. These methods reroute the signals of faulty TSVs to other regular TSV or RTSV. In practice, the faulty TSVs may cluster because of imperfect bonding technology. To resolve the problem of clustered TSV faults, router-based RTSV architecture was the first proposed to pay attention to it. Their method enables faulty TSVs to be repaired by RTSVs that are farther apart. However, to repair some rarely occurring defective patterns, their method requires too much area. In this paper, we propose a ring-based RTSV architecture to utilize the area more efficiently as well as to maintain high yield. Assume that the size of the TSVs is 1 $\mu \text{m}$ . Simulation results show that for a given number of TSVs ( $8 \times 8$ ) and TSV failure rate (1%), our design achieves 58.9% area reduction of MUXes per signal, 54.6% total area reduction per signal, and 50.54% total wire length reduction while the yield of our ring-based RTSV architectures can still maintain 98.47%–99% as compared with the router-based design. Furthermore, the shifting length of our ring-based RTSV architecture is at most 1, which guarantees at most one MUX-delay timing overhead of each signal.

Architecture of Ring-Based Redundant TSV for Clustered Faults

A 3D stacked network-on-chip (NOC) promises the integration of a large number of cores in a many-core system-on-chip (SOC). The NOC can be used to test the embedded cores in such SOCs, whereby the added cost of dedicated test-access hardware can be avoided. However, a potential problem associated with 3D NOC-based test access is the emergence of hotspots due to stacking and the high toggle rates associated with structural test patterns used for manufacturing test. High temperatures and hotspots can lead to the failure of good parts, resulting in yield loss. We describe a unicast-based multicast approach and a thermal-driven test scheduling method to avoid hotspots, whereby the full NOC bandwidth is used to deliver test packets. Test delivery is carried out using a new unicast-based multicast scheme. Experimental results highlight the effectiveness of the proposed method in reducing test time under thermal constraints.

Multicast-Based Testing and Thermal-Aware Test Scheduling for 3D ICs with a Stacked Network-on-Chip

A 3D stacked network-on-chip (NOC) promises the integration of a large number of cores in a many-core system-on-chip (SOC). The NOC can be used to test the embedded cores in such SOCs, whereby the added cost of dedicated test-access hardware can be avoided. However, a potential problem associated with a 3D NOC-based test access is the emergence of hotspots due to stacking and the high toggle rates associated with structural test patterns used for manufacturing test. High temperatures and hotspots can lead to the failure of good parts, resulting in yield loss. We describe a thermal-driven test scheduling method to avoid hotspots, whereby the full NOC bandwidth is used to deliver test packets. Test delivery is carried out using a new unicast-based multicast scheme. Experimental results highlight the effectiveness of the proposed method in reducing test time under thermal constraints.

Thermal-aware test scheduling for NOC-based 3D integrated circuits

The invention provides a method of design for testability at RTL which can guarantee high fault coverage and a method of test sequence generation for easily generating test sequences for an RTL circuit which is designed to be easily testable by the method of design for testability. In the RTL circuit, scannable registers are selected so that the RTL circuit can attain an easily testable circuit structure such as an acyclic structure. This RTL circuit is timeframe expanded on the basis of a predetermined evaluation function and logically synthesized, so as to generate a timeframe expanded combinational circuit, that is, a gate level timeframe expanded circuit, as a circuit for test sequence generation. For the timeframe expanded combinational circuit, test patterns for multiple stuck-at faults are generated, the test patterns are transformed into test sequences on the basis of data on timeframes including primary inputs and pseudo-primary inputs, and the test sequences are transformed into scanning test sequences in view of a scan shift operation.

Method of design for testability and method of test sequence generation

We present a unified test technique that targets faults in links, routers, and cores of a network-on-chip design based on test sessions. We call an entire procedure, that delivers test packets to the subset of routers/cores, a test session. Test delivery for router/core testing is formulated as two fault-tolerant multicast algorithms. Test packet delivery for routers is implemented as a fault-tolerant unicast-based multicast scheme via the fault-free links and routers that were identified in the previous test sessions to avoid packet corruption. A new fault-tolerant routing algorithm is also proposed for the unicast-based multicast core test delivery in the whole network. Identical cores share the same test set, and they are tested within the same test session. Simulation results highlight the effectiveness of the proposed method in reducing test time.

Fault-Tolerant Unicast-Based Multicast for Reliable Network-on-Chip Testing

We present a unified test technique that targets all the components of a network-on-chip design. The proposed technique targets faults in links, routers, and cores. Link faults are first located using built-in self-test hardware inserted in the routers. Test packets for routers are delivered to the routers via the fault-free links and routers identified in the previous steps. A test packet can be corrupted by faulty links or routers, therefore, it is delivered across only previously identified fault-free routers/links. Test packet delivery for routers is implemented as a fault-tolerant unicast-based multicast scheme within the tested part of the network-on-chip. After all faulty routers are identified, a new fault-tolerant unicast-based multicast routing technique is proposed to deliver test packets for the cores. Identical cores share the same test set, and they are tested within the same test session. Simulation results highlight the effectiveness of the proposed method in reducing test time.

Hideo Fujiwara

Papers

Multicast-Based Testing and Thermal-Aware Test Scheduling for 3D ICs with a Stacked Network-on-Chip

Thermal-aware test scheduling for NOC-based 3D integrated circuits

Method of design for testability and method of test sequence generation

Fault-Tolerant Unicast-Based Multicast for Reliable Network-on-Chip Testing

A unified test and fault-tolerant multicast solution for network-on-chip designs