This section summarizes basic elements of all three steps. Defect modeling Modeling of spot defects generates basic features of the defect, i. Defect locations are usually modeled by random number generators using a unifor. The density of the defects is also determined from test waters fabricated with the appropriate test structures.

It has to be stressed that the experimental procedure that is used to determine defiect characteristics is very important. Thus, the identification of the spot defect characteristics is a main step in the modeling of spot defects. The most critical step is the identification of the defect size distribution. The common feature of defect size distributions is that i4 ;3 Zi the smaller the size of the spot defect the more often it occurs. This z5 relation is very strong and explains the fact that the majority of Figure Extra active region a introduces a parasitic spot defects observed in the actual IC are comparable in size with tramistor and a short to the Vdd line b.

The the minimum feature size in the IC layout. Analysis of IC topology -- deformation Analysis of the deformations that are introduced into the IC structure by a spot defect is a main step in the realistic fhult performed function. There exists a couple of approaches that can be used for The above two examples lead to the conclusion that: this purpose. All of topology deformations and associated probabilities in an analytical them support the above observations. Therefore, one can generalize manner. Essentially, all of the methods mentioned above are performed by: paper IO.

Placing the spot defect in one of the layers of the analyzed IC; 2.

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Analyzing the vertical structure of the region affected by the spot defect to determine the type of the created device connection, isolation, transistor, etc. Analyzing the vertical structures in the neighborhood of the spot defect to find the type of devices connected to the device created by the spot defect; These three steps are illustrated in the drawing shown in Fig. Gate d region expanded by R, c and d , and critical areas for two different values of R, e and f.

The critical area for a short of two regions, can be computed as the intersection of these regions expanded by R, where R is the radius of the defect. The critical area computations are, however, rather complicated and can be applied for very regular structures only.

### VLSI Fault Modeling and Testing Techniques (Book)

Hence, the last topology deformation step in the realistic fault simulation is the analysis of the electrical behavior of the deformed circuit and its logic or switch level Location of the defects and defect size are determined by the representation. Such an analysis should determine the defects defect model. For each layer the occurrence can be computed from the probabilities of defects appropriate density of defects is used.

After defect placement each newly created region is analyzed and its vertical structure is interpreted. See Fig. This The above goal can be achieved through the comparison of the interpretation is performed through the matching of combinations of defect free circuit diagram with the diagram deformed by the defect.

## Digital Circuits and Stuck at Fault Model

Each entry on the list has its electrical stuck-at or bridging faults. The parasitic active devices can also be equivalent. This way each region in the area affected by the spot detected but, of course, their impact on the circuit behavior should defect can be properly identified. Finally, the same kind of be determined by means of simulation.

At the end of this process the electrical diagram of the terms of deformations of the switch level description of the circuit affected area can be created. There are some differences between various approaches to the fault modeling technique, as far as specific algorithms are concerned.

Applications In fully automated methods such as implemented in VLASIC and The fault modeling technique described in the previous section also implemented by Ferguson, computations are performed in a has been used to Monte Carlo fashion. Probabilities of fault occurrences are 1. Investigate electrical consequences of spot defects in the estimated by the frequences of fault occurrences.

The critical area associated with the short of two polysilicon gates extracted from the example discussed in the previous section is 3.

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Generate list of faults that may occur in a memory shown in Fig. A certain point belongs to the critical area if a celr Estimate the range of fault probabilities in a PLA Compute a ranked list of faults for a 4 x 4 multiplier cellz3. Paper Galiay, Y. Crouzet and M. One can expect, however, that logical fault models MOS LSI circuits: Impact on th ir accurate probability computations will be rather expensive. C, June , p6 Conclusions The fault simulation technique that and complete list of faults that may occur in the Tamir and C. C, No. It requires that the spot defect Sequin and Y. Fichtner and M.

Acknowledgments The author would like to acknowledge the Ferguson and Dr. The November , pp. EE Trans. CAD-4, No. Maly, M. Thomas, J. Chinn, and M. Series, Maly, J. Ferguson and J. Maly, A. Strojwas, and S. Conference , Philadelphia, October , pp. Shen, W. Maly and F. Doi, W. Maly, and M. Walker and S.

Gangatir:kar, R. Presson, and L. ROSIN, Stapper, R. Amstrong and K. W, Maly, B, Trifilo, R. Hughes, and A. Maly and J. Related Papers. By Tracy Larrabee and Joel Ferguson. A CMOS fault extractor for inductive fault analysis.

## Basics of testing CMOS

Hierarchical defect-oriented fault simulation for digital circuits. By Witold A. Pleskacz and W. Defect-oriented fault simulation and test generation in digital circuits. By Witold Pleskacz. By Tracy Larrabee. Download pdf. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Embed Size px. Start on.

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