Multiple input multiple output controller design to match chamber performance in plasma etching for semiconductor manufacturing
In semiconductor manufacturing, multiple chambers utilized for the same process step often experience performance variation. This chamber to chamber performance variation has affected the yield of wafers, but there are no standard procedures to reduce them in semiconductor manufacturing. This paper introduces chamber matching in plasma etching as one of the core issues in semiconductor manufacturing and suggests a step-by-step procedure to address chamber matching issues. A brief review of two approaches, fault detection and classification and equipment control, is given and a step-by-step procedure of the equipment control approach is introduced. To design a multiple input-multiple output controller, a decomposed etch rate map makes it possible to analyze etch rate performance between chambers and to define controlled variables. Optimum variable selection techniques, such as singular value analysis and relative gain array methods, and dynamic optimization with constraints are suggested in this paper. In addition, a performance matching index (PMI) is introduced to calculate performance of chambers in terms of both etch rate and wafer yield to verify the matching capability of our approach. PMI is a quantitative index, which calculates performance of two chambers and lower value is better. By applying our approach, the performance of a worst chamber reaches to that of a golden chamber, resulting in PMI improvement from 100.7 to 31.6. The methodology of chamber matching introduced in this paper should be useful to semiconductor manufacturers impacted by chamber matching issues.
Kye Hyun Baek, Kyounghoon P. Han, Gilheyun Choi, Ho-Kyu Kang, Eun Seung Jung et al.
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