In the semiconductor manufacturing, which consists of significantly precise and diverse unit processes, minute defects can cause significantly large risk, which is directly related to the yield. Through fault detection and classification (FDC), the equipment status is monitored, and the potential causes of faults can be investigated. In the mass production process, unbalanced data problems are also important, including preprocessing methods for data analysis in real time. This study proposes a stepwise FDC method with a process fault detection (FD) and faulty equipment part classification. Fault detection (FD) is proposed using a one-class support vector machine (OC-SVM) to determine anomalies that occur during a process, and fault classification (FC) is followed by the importance between variables that determine whether a fault exists is extracted using extreme gradient boosting (XGBoost). Variables whose importance has been confirmed, are reclassified to a part-level based on the variable name, and defects are notified to the part-level level. An empirical study to validate the proposed data-based framework for fault detection and diagnosis was performed under the scenario of unexpected failure of two ${\mathbf {\mathrm {SF}}}_{\mathbf {6}}/{\mathbf {\mathrm {O}}}_{\mathbf {2}}$ mass flow controllers (MFCs). The experimental results confirmed that the application-oriented proposed framework performed well in FDC operations and showed that it can provide part-level notification to engineers.

Semiconductor manufacturing comprises hundreds of consecutive unit processes. A single misprocess could jeopardize the whole manufacturing process. In current manufacturing environments, data monitoring of equipment condition, wafer metrology, and inspection, etc., are used to probe any anomaly during the manufacturing process that could affect the final chip performance and quality. The purpose of investigation is fault detection and classification (FDC). Various methods, such as statistical or data mining methods with machine learning algorithms, have been employed for FDC. In this paper, we propose an artificial immune system (AIS), which is a biologically inspired computing algorithm, for FDC regarding semiconductor equipment. Process shifts caused by parts and modules aging over time are main processes of failure cause. We employ state variable identification (SVID) data, which contain current equipment operating condition, and optical emission spectroscopy (OES) data, which represent plasma process information obtained from faulty process scenario with intentional modification of the gas flow rate in a semiconductor fabrication process. We achieved a modeling prediction accuracy of modeling of 94.69% with selected SVID and OES and an accuracy of 93.68% with OES data alone. To conclude, the possibility of using an AIS in the field of semiconductor process decision making is proposed.

This study practiced virtual metrology (VM) for the etch profile and depth in the deep silicon trench etching with SF ₆ /O ₂ /Ar plasma. Machine learning-based VM models constitute the classification models of etch profile and the prediction models of etch depth from the silicon trench etch. Machine learning algorithms of random forest and Xgboost were used for classifying etch profiles by employing recipe-based equipment status variable identification (SVID) data. Predictive etch depth models constructed with neural network models employed both equipment SVID data and optical emission spectroscopy (OES) data, which provide chemistry information of the plasma during the etch process. Plasma VM model, augmenting OES data to SVID data presented improved accuracy in predicting etch profile. The augmented phenomenological plasma information during the etch process helped to establish a more accurate VM model in the plasma process. The importance of variables was identified through the permutation importance of each model. Additionally, the actual process results of the variables with high importance were analyzed with the etching reaction of SF ₆ /O ₂ /Ar plasma.

This research proposes an application of generative adversarial networks (GANs) to solve the class imbalance problem in the fault detection and classification study of a plasma etching process. Small changes in the equipment part condition of the plasma equipment may cause an equipment fault, resulting in a process anomaly. Thus, fault detection in the semiconductor process is essential for success in advanced process control. Two datasets that assume faults of the mass flow controller (MFC) in equipment components were acquired using optical emission spectroscopy (OES) in the plasma etching process of a silicon trench: The abnormal process changed by the MFC is assumed to be faults, and the minority class of Case 1 is the normal class, and that of Case 2 is the abnormal class. In each case, additional minority class data were generated using GANs to compensate for the degradation of model training due to class-imbalanced data. Comparisons of five existing fault detection algorithms with the augmented datasets showed improved modeling performances. Generating a dataset for the minority group using GANs is beneficial for class imbalance problems of OES datasets in fault detection for the semiconductor plasma equipment.

Plasma-based semiconductor processing is highly sensitive, thus even minor changes in the procedure can have serious consequences. The monitoring and classification of these equipment anomalies can be performed using fault detection and classification (FDC). However, class imbalance in semiconductor process data poses a significant obstacle to the introduction of FDC into semiconductor equipment. Overfitting can occur in machine learning due to the diversity and imbalance of datasets for normal and abnormal. In this study, we suggest a suitable preprocessing method to address the issue of class imbalance in semiconductor process data. We compare existing oversampling models to reduce class imbalance, and then we suggest an appropriate sampling strategy. In order to improve the FC performance of plasma-based semiconductor process data, it was confirmed that the SMOTE-based model using an undersampling technique such as Tomek link is effective. SMOTE-TOMEK, which removes multiple classes and makes the boundary clear, is suitable for FDC to classify minute changes in plasma-based semiconductor equipment data.

Semiconductor industry is experiencing a rising demand for environmentally friendly processes with the emphasis on green policies and worldwide environmental sustainability. Nitrogen trifluoride (NF3), the most common plasma chamber cleaning agent gas, poses a significant concern as a potent greenhouse gas since it has global warming potential (GWP), 740 times and 6 times higher than that CO2 and N2O. This study investigated the exhaust gas using quadrupole mass spectroscopy (QMS) and analyzed the change in cleaning speed and the type of exhaust gas through plasma monitoring using optical mass spectroscopy (OES). The objective is to lower the use of the amount of NF3 gas in chamber cleaning process to partially contribute the environmental sustainability in the point of semiconductor manufacturing. When a small amount of N2 was added to NF3 whose ratio of 7:23, the cleaning efficiency reached to 90 % compared to NF3 gas alone. Addition of N2 positively affected electron density and temperature to increase the F-radical in remote plasma system. In conclusion, 18 % of NF3 usage amount was reduced during the SiO2 deposition chamber cleaning process.