Controlling resist thickness and etch depth for fabrication of 3D structures in electron-beam grayscale lithography

• Published in: Microelectronic engineering 2007-12, Vol.84 (12), p.2859-2864
• Main Authors: Kim, J., Joy, D.C., Lee, S.-Y.
• Format: Article
• Language: English
• Subjects: Applied sciences; Dose Control; E-beam lithography; Electronics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Gratings; Grayscale lithography; Micro- and nanoelectromechanical devices (mems/nems); Microelectronic fabrication (materials and surfaces technology); Nanoscale; Optical elements, devices, and systems; Optics; Optoelectronic devices; Physics; Reactive ion etching; Remaining resist profile; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Three-dimensional structures
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2007.02.015

In many applications such as optoelectronic devices, three-dimensional (3D) structures are required. Examples include photonic band gap (PBG) crystals, diffractive optical elements, blazed gratings, MEMS, NEMS, etc. It is known that the performance characteristics of such structures are highly sensitive to their dimensional fidelity. Therefore, it is essential to have a fabrication process by which such 3D structures can be realized with high dimensional accuracy. In this paper, practical methods to control thickness of the remaining resist and etch depth, which may be employed for fabrication of such 3D structures using grayscale electron-beam lithography, are described. Through experiments, explicit control of the remaining resist thickness and etch depth at the resolution of 20 nm for the feature sizes of 0.5 μm and 1 μm has been successfully demonstrated. Also, the 1:1 ratio of silicon to resist etching rates was achieved for transferring the remaining resist profile onto the silicon substrate.