Machine Learning-based Defect Coverage Boosting of Analog Circuits under Measurement Variations

Safety-critical and mission-critical systems, such as airplanes or (semi-)autonomous cars, are relying on an ever-increasing number of embedded integrated circuits. Consequently, there is a need for complete defect coverage during the testing of these circuits to guarantee their functionality in the field. In this context, reducing the escape rate of defects during production testing is crucial, and significant progress has been made to this end. However, production testing using automatic test equipment is subject to various measurement parasitic variations, which may have a negative impact on the testing procedure and therefore limit the final defect coverage. To tackle this issue, this article proposes an improved test flow targeting increased analog defect coverage, both at the system and block levels, by analyzing and improving the coverage of typical functional and structural tests under these measurement variations. To illustrate the flow, the technique of inserting a pseudo-random signal at available circuit nodes and applying machine learning techniques to its response is presented. A DC-DC converter, derived from an industrial product, is used as a case study to validate the flow. In short, results show that system-level tests for the converter suffer strongly from the measurement variations and are limited to just under 80% coverage, even when applying the proposed test flow. Block-level testing, however, can achieve only 70% fault coverage without improvements but is able to consistently achieve 98% of fault coverage at a cost of at most 2% yield loss with the proposed machine learning–based boosting technique.