2VLSI Test Principles and Architectureson a feature size of less than 100 nanometers (100 nm). The reduction in feature sizehas also resulted in increased operating frequencies and clock speeds; for example,in 1971, the first microprocessor ran at a clock frequency of 108 KHz, while currentcommercially available microprocessors commonly run at several gigahertz.The reduction in feature size increases the probability that a manufacturingdefectin the IC will result in a faulty chip. A very small defect can easily result in afaulty transistor or interconnecting wire when the feature size is less than 100 nm.Furthermore, it takes only one faulty transistor or wire to make the entire chip failto function properly or at the required operating frequency. Yet, defects createdduring the manufacturing process are unavoidable, and, as a result, some numberof ICs is expected to be faulty; therefore, testing is required to guarantee fault-
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