Using Gray-Based Taguchi Method to Construct Multi-Objective Optimal Model in Super-Resolution Near-Field Photolithography


  • Ching-Been Yang,

    Corresponding author
    • Department of Mechanical Engineering, Taoyuan Innovation Institute of Technology, Chung Li City, Taiwan, Republic of China
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  • Hsiu-Lu Chiang

Address for reprints: Ching-Been Yang, Department of Mechanical Engineering, Taoyuan Innovation Institute of Technology, 414 Chung Shang E. Road, Section 3, Chung Li City, Taiwan, R. O. C. E-mail:


This study integrated thermally induced super-resolution into near-field photolithography and conducted simulation and analysis on line segment fabrication. This technique involves passing a laser beam through an aluminum-plated optical fiber probe onto a thin film of indium (approximately 10 nm thick). The indium film opens a melted aperture narrower than the width of the laser beam, creating a melted region and a crystalline region. The difference in penetration rate between the two regions leads to the generation of thermally induced super-resolution. This paper proposes a combination of Taguchi method with gray relational analysis, in which S/N ratios obtained using the Taguchi method are converted into gray relational grades to identify an optimal combination of parameters capable of meeting multiple quality objectives. This optimal combination includes a probe aperture of 100 nm (A1), exposure energyinline image of 0.002nJinline image (B2), development time of 60 s (C3), and indium film with a thickness of 7 nm (D1). The optimal parameters were (A1B2C3D1) for the gray relational analysis and (A1B1C1D1) for the Taguchi method. Results showed a negative improvement of –14.3% in line width from 126.2 (Taguchi method) to 144.2 nm (gray relational analysis). Working depth, however, showed a significantly improvement of 140.4% from 5.7 (Taguchi method) to 13.7 nm (gray relational analysis). The proposed approach resolves the conflicts that commonly occur among factor levels in Taguchi analysis under the requirements of multiple quality requirements. SCANNING 35:47-58, 2013. © 2012 Wiley Periodicals, Inc.