用图神经网络预测半导体制造中的异常,提前50步预警。
Unsupervised Anomaly Prediction with N-BEATS and Graph Neural Network in Multi-variate Semiconductor Process Time Series
- 用GNN捕捉多变量间依赖关系,比独立建模更准确。
- 可提前50步预测异常,且在20步内预测误差小。
- 模型参数少、算力低,适合工业场景实时部署。
半导体制造过程复杂精密,涉及成千上万相互关联的参数,来自多种设备与工序。多变量时间序列分析已成为实现实时监控与故障检测的关键。然而,半导体制造中的异常预测面临高维数据、真实故障稀少导致的严重类别不平衡,以及变量间复杂依赖关系带来的挑战。本文提出两种新方法,将异常检测推进至异常预测,以支持实时工艺修正与主动预防。框架包含两个阶段:(a) 在假设无异常的数据集上训练预测模型;(b) 对未见时间序列进行预测,并与训练信号对比,偏差超过阈值即标记为异常。两种方法区别在于预测模型:第一种采用N-BEATS进行单变量独立预测;第二种使用图神经网络(GNN)建模变量间关系。两者在20步预测范围内表现优异,异常预测稳定达50步。GNN持续优于N-BEATS,同时显著减少可训练参数与计算开销。结果表明,GNN是工业环境中在线异常预测的有力候选方案。
原文摘要 · Abstract (English)
Semiconductor manufacturing is an extremely complex and precision-driven process, characterized by thousands of interdependent parameters collected across diverse tools and process steps. Multi-variate time-series analysis has emerged as a critical field for real-time monitoring and fault detection in such environments. However, anomaly prediction in semiconductor fabrication presents several critical challenges, including high dimensionality of sensor data and severe class imbalance due to the rarity of true faults. Furthermore, the complex interdependencies between variables complicate both anomaly prediction and root-cause-analysis. This paper proposes two novel approaches to advance the field from anomaly detection to anomaly prediction, an essential step toward enabling real-time process correction and proactive fault prevention. The proposed anomaly prediction framework contains two main stages: (a) training a forecasting model on a dataset assumed to contain no anomalies, and (b) performing forecast on unseen time series data. The forecast is compared with the forecast of the trained signal. Deviations beyond a predefined threshold are flagged as anomalies. The two approaches differ in the forecasting model employed. The first assumes independence between variables by utilizing the N-BEATS model for univariate time series forecasting. The second lifts this assumption by utilizing a Graph Neural Network (GNN) to capture inter-variable relationships. Both models demonstrate strong forecasting performance up to a horizon of 20 time points and maintain stable anomaly prediction up to 50 time points. The GNN consistently outperforms the N-BEATS model while requiring significantly fewer trainable parameters and lower computational cost. These results position the GNN as promising solution for online anomaly forecasting to be deployed in manufacturing environments.
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