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UBC Theses and Dissertations

On multiple intermediate signature analysis for built-in self-test Wu, Yuejian


Built-in Self-Test (BIST) is becoming a widely accepted means for testing VLSI circuits. BIST usually consists of two major functions known as on chip test pattern generation and test response evaluation. There are two major difficulties regarding test response evaluation. The first is reducing the error escape rate or aliasing while still maintaining reasonably small hardware requirements. The other is accurately assessing the impact of aliasing on the overall test quality of a BIST scheme. This dissertation addresses these two difficulties by developing a group of techniques known as multiple intermediate signature analysis. Compared to the conventional single signature analysis, multiple intermediate signature analysis has many advantages, e.g., smaller aliasing, easier exact fault coverage computation, shorter average test time, and increased fault diagnosability. Based on the investigation of an aliasing model, this dissertation develops a comprehensive fault coverage model for predicting the fault coverage performance with multiple intermediate signature analysis. In addition to the parameters used in the aliasing model, such as the number of intermediate signatures and the length of each signature, the proposed model also includes information on the scheduling of intermediate signatures. In addition to the studies on the conventional multiple intermediate signature analysis, referred to as CMS schemes, this dissertation also describes two novel multiple intermediate signature analysis techniques. The first is a fuzzy multiple intermediate signature analysis, or simply called the FMS scheme. Unlike the CMS schemes, where each checked signature must correspond to a specific reference on a one-to-one basis for a circuit under test (CUT) to be declared good, the FMS scheme declares a CUT good if each checked signature maps to any element of the same set of references. In comparison, the FMS scheme is very simple and easy to implement. A complete theory for the aliasing performance and hardware requirement prediction with the FMS scheme is derived. The second novel multiple intermediate signature analysis proposed in this dissertation is single reference multiple intermediate signature analysis, simply referred to as the SMS scheme. Conventionally, checking n signatures requires n references. With the SMS scheme, however, regardless of the number of checked signatures, only one single reference is needed. The SMS scheme requires minimal hardware for multiple intermediate signature analysis, i.e., essentially the same amount of hardware as for conventional single signature analysis. To efficiently implement the SMS scheme, a systematic approach is developed based on the discovery of some identical signature properties. This implementation approach of the SMS scheme does not require any circuit modification of the CUTs. The cost for implementing the SMS scheme is a non-recurring CPU time overhead in the design phase. In return, the SMS scheme yields significantly recurring silicon area savings as well as reduced aliasing. With the algorithms provided in this dissertation, The CPU time overhead for implementing the SMS scheme is very small. For example, if the SMS scheme is used to check two 16-bit signatures, which yields 65,536 times smaller aliasing at no extra hardware cost compared to conventional single signature schemes, the total CPU time overhead required for implementing the SMS scheme is less than 4 seconds on a Sun Sparc 2 workstation for a test length of 220, independently of the size of CUTs.

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