TRADITIONALLY, EACH MANUFACTURED instance of an integrated circuit (IC) is subjected to several testing steps before it is sent to customer. (See Section II for description of a typical industrial test flow.) All of these testing steps are to maintain a high quality of chips shipped since customer returns not only require new chips to be shipped to replace the defective ones, but too many of them can also result in poor reputation, loss of business, and sometimes even legal actions. Hence one of the primary functions of each testing step is to minimize defective chips from being shipped (also known as test escapes). However, each testing step also adds significant cost to an IC. Therefore, it is desirable to eliminate any unnecessary test. In fact, if an entire testing step can be skipped without loss of IC quality, that would provide significant cost reduction not only from removing the test application cost associated with that step, but also from eliminating any infrastructure required to carry out that test in an industrial environment.
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