Logic Verification And Test Generation For Vlsi Circuits

Logic Verification and Test Generation for VLSI Circuits

IDDQ Testing of VLSI Circuits

Power supply current monitoring to detect CMOS IC defects during production testing quietly laid down its roots in the mid-1970s. Both Sandia Labs and RCA in the United States and Philips Labs in the Netherlands practiced this procedure on their CMOS ICs. At that time, this practice stemmed simply from an intuitive sense that CMOS ICs showing abnormal quiescent power supply current (IDDQ) contained defects. Later, this intuition was supported by data and analysis in the 1980s by Levi (RACD, Malaiya and Su (SUNY-Binghamton), Soden and Hawkins (Sandia Labs and the University of New Mexico), Jacomino and co-workers (Laboratoire d'Automatique de Grenoble), and Maly and co-workers (Carnegie Mellon University). Interest in IDDQ testing has advanced beyond the data reported in the 1980s and is now focused on applications and evaluations involving larger volumes of ICs that improve quality beyond what can be achieved by previous conventional means. In the conventional style of testing one attempts to propagate the logic states of the suspended nodes to primary outputs. This is done for all or most nodes of the circuit. For sequential circuits, in particular, the complexity of finding suitable tests is very high. In comparison, the IDDQ test does not observe the logic states, but measures the integrated current that leaks through all gates. In other words, it is like measuring a patient's temperature to determine the state of health. Despite perceived advantages, during the years that followed its initial announcements, skepticism about the practicality of IDDQ testing prevailed. The idea, however, provided a great opportunity to researchers. New results on test generation, fault simulation, design for testability, built-in self-test, and diagnosis for this style of testing have since been reported. After a decade of research, we are definitely closer to practice.

Testing and Diagnosis of VLSI and ULSI

This volume contains a collection of papers presented at the NATO Advanced Study Institute on ·Testing and Diagnosis of VLSI and ULSI" held at Villa Olmo, Como (Italy) June 22 -July 3,1987. High Density technologies such as Very-Large Scale Integration (VLSI), Wafer Scale Integration (WSI) and the not-so-far promises of Ultra-Large Scale Integration (ULSI), have exasperated the problema associated with the testing and diagnosis of these devices and systema. Traditional techniques are fast becoming obsolete due to unique requirements such as limited controllability and observability, increasing execution complexity for test vector generation and high cost of fault simulation, to mention just a few. New approaches are imperative to achieve the highly sought goal of the • three months· turn around cycle time for a state-of-the-art computer chip. The importance of testing and diagnostic processes is of primary importance if costs must be kept at acceptable levels. The objective of this NATO-ASI was to present, analyze and discuss the various facets of testing and diagnosis with respect to both theory and practice. The contents of this volume reflect the diversity of approaches currently available to reduce test and diagnosis time. These approaches are described in a concise, yet clear way by renowned experts of the field. Their contributions are aimed at a wide readership: the uninitiated researcher will find the tutorial chapters very rewarding. The expert wiII be introduced to advanced techniques in a very comprehensive manner.