Adaptive Methods for Machine Learning-Based Testing of Integrated Circuits and Boards
The relentless growth in information technology and artificial intelligence (AI) is placing demands on integrated circuits and boards for high performance, added functionality, and low power consumption. As a result, design complexity and integration continue to increase, and emerging devices are being explored. However, these new trends lead to high test cost and challenges associated with semiconductor test.
Machine learning has emerged as a powerful enabler in various application domains, and it provides an opportunity to overcome the challenges associated with expert-based test. Taking the advantages of powerful machine-learning techniques, useful information can be extracted from history testing data, and this information helps facilitate the testing process for both chips and boards.
Moreover, to attain test cost reduction with no test quality degradation, adaptive methods for testing are now being advocated. In conventional testing methods, variations among different chips and different boards are ignored. As a result, the same test items are applied to all chips; online testing is carried out after every fixed interval; immutable fault-diagnosis models are used for all boards. In contrast, adaptive methods observe changes in the distribution of testing data and dynamically adjust the testing process, and hence reduce the test cost. In this dissertation, we study solutions for both chip-level test and board-level test. Our objective is to design the most proper solutions for adapting machine-learning techniques to testing area.
For chip-level test, the dissertation first presents machine learning-based adaptive testing to drop unnecessary test items and reduce the test cost in high-volume chip manufacturing. The proposed testing framework uses the parametric test results from circuit probing test to train a quality-prediction model, partitions chips into different groups based on the predicted quality, and selects the different important test items for each group of chips. To achieve the same defect level as in prior work on adaptive testing, the proposed fine-grained adaptive testing method significantly reduces test cost.
Besides CMOS-based chips, emerging devices (e.g., resistive random access memory (ReRAM)) are being explored to implement AI chips with high energy efficiency. Due to the immature fabrication process, ReRAMs are vulnerable to dynamic faults. Instead of periodically interrupting the computing process and carrying out the testing process, the dissertation presents an efficient method to detect the occurrence of dynamic faults in ReRAM crossbars. This method monitors an indirect measure of the dynamic power consumption of each ReRAM crossbar, determines the occurrence of faults when a changepoint is detected in the monitored power-consumption time series. This model also estimates the percentage of faulty cells in a ReRAM crossbar by training a machine learning-based predictive model. In this way, the time-consuming fault localization and error recovery steps are only carried out when a high defect rate is estimated, and hence the test time is considerably reduced.
For board-level test, the cost associated with the diagnosis and repair due to board-level failures is one of the highest contributors to board manufacturing cost. To reduce the cost associated with fault diagnosis, a machine learning-based diagnosis workflow has been developed to support board-level functional fault identification in the dissertation. In a production environment, the large volume of manufacturing data comes in a streaming format and may exhibit a time-dependent concept drift. In order to process streaming data and adapt to concept drifts, instead of using an immutable diagnosis model, this dissertation also presents the method that uses an online learning algorithm to incrementally update the identification model. Experimental results show that, with the help of online learning, the diagnosis accuracy is improved, and the training time is significantly reduced.
The machine learning-based diagnosis workflow can identify board-level functional faults with high accuracy. However, the prediction accuracy is low when a new board has a limited amount of fail data and repair records. The dissertation presents a diagnosis system that can utilize domain-adaptation algorithms to transfer the knowledge learned from a mature board to a new board. Domain adaptation significantly reduces the requirement for the number of repair records from the new board, while achieving a relatively high diagnostic accuracy in the early stage of manufacturing a new product. The proposed domain adaptation workflow designs a metric to evaluate the similarity between two types of boards. Based on the calculated similarity value, different domain-adaptation algorithms are selected to transfer knowledge and train a diagnosis model.
In summary, this dissertation tackles important problems related to the testing of integrated circuits and boards. By considering variations among different chips or boards, machine learning-based adaptive methods enable the reduction of test cost. The proposed machine learning-based testing methods are expected to contribute to quality assurance and manufacturing-cost reduction in the semiconductor industry.
online fault detection
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