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Pattern Classification for Small-Sized Defects Using Multi-Head CNN in Semiconductor Manufacturing
Yunseon Byun,Jun-Geol Baek 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.10
To improve the quality of semiconductor manufacturing, defects need to be detected and their root causes controlled. Because the root causes can vary depending on defect patterns, classifying the patterns accurately is important. Several recent studies have investigated automatic defect classification using a convolutional neural network (CNN) with wafer map images. CNNs are excellent tools for classifying images of different shapes and sizes. However, the detection of small-sized defects that have small clusters and linear patterns is difficult. Therefore, this study focuses on patterns that are difficult to detect. We propose three steps for pattern classification. First, modified median filtering is used to preserve the original shapes of patterns. Second, a rotated defects (RoD) transform is performed by applying the rotational properties of wafer maps. The RoD transform augments the defect proportion and improves the detection of small-sized defects. Third, a multi-head CNN is used to extract and combine the features from the original and transformed maps. The combined features are then used to classify the defect patterns. Overall classification performance of defects can be improved by accurately classifying small clusters and linear patterns. The proposed model was evaluated using WM-811K wafer maps, and small-sized defects were accurately classified. Such an accurate defect classification model will enable effective root cause analysis and quality improvement in semiconductor manufacturing.
Yunseon Choe,Hoseung Lee,Sangyoel Han,Taekyun Kim,Kyuwon Sim 강원대학교 산림과학연구소 2016 Journal of Forest Science Vol.32 No.2
This study examined the recognition differences between local residents and national park managers on the adjustment of national parks which are conducted every ten years for the purpose of providing basic information for the park management, according to the Natural Parks Act. Both local residents and national park managers positively perceived the adjustment of national parks, but park managers showed concern towards the damage of natural resources resulting from the cancellation and adjustment of restricted development districts in Korean national parks. Local residents are more likely than park managers to recommend boundary adjustment in other national parks regarding the influence of parks adjustment on local change. While local residents recognized that the boundary adjustment of national parks improves the level of community management, park managers focused on damages on the local environment and the park landscape adjacent to the areas. The result shows the recognition differences of local residents and park managers. Further research into adjustment of national parks is necessary to diminish perception gaps among stakeholders and develop prediction indicators of cancellation effect in response to the future cancellation areas of national parks through the characteristics of cancellation communities, revitalization of local economy, and environmental change of local community.
Helical tomotherapy for spine oligometastases from gastrointestinal malignancies
Yunseon Choi,Jun Won Kim,Ik Jae Lee,Hee Ji Han,Jonggeal Baek,Jinsil Seong 대한방사선종양학회 2011 Radiation Oncology Journal Vol.29 No.4
Purpose: This study evaluated the treatment effectiveness and proper radiation dose of helical tomotherapy (HT) in spine oligometastases from gastrointestinal cancers. Materials and Methods: From 2006 to 2010, 20 gastrointestinal cancer patients were treated with HT for spine oligometastases (31 spine lesions). The gross tumor volume (GTV) was the tumor evident from magnetic resonance imaging images fused with simulation computed tomography images. Clinical target volume (CTV) encompassed involved vertebral bodies or dorsal elements. We assumed that the planning target volume was equal to the CTV. We assessed local control rate after HT for 31 spine metastases. Pain response was scored by using a numeric pain intensity scale (NPIS, from 0 to 10). Results: Spine metastatic lesions were treated with median dose of 40 Gy (range, 24 to 51 Gy) and median 5 Gy per fraction (range, 2.5 to 8 Gy) to GTV with median 8 fractions (range, 3 to 20 fraction). Median biologically equivalent dose (BED, α/β = 10 Gy) was 52 Gy₁₀ (range, 37.5 to 76.8 Gy₁₀) to GTV. Six month local control rate for spine metastasis was 90.3%. Overall infield failure rate was 15% and outfield failure rate was 75%. Most patients showed pain relief after HT (93.8%). Median local recurrence free survival was 3 months. BED over 57 Gy₁₀ and oligometastases were identified as prognostic factors associated with improved local progression free survival (p = 0.012, p = 0.041). Conclusion: HT was capable of delivering higher BED to metastatic lesions in close proximity of the spinal cord. Spine metastases from gastrointestinal tumors were sensitive to high dose radiation, and BED (α/β = 10 Gy) higher than 57 Gy₁₀ could improve local control.