12 June 2003 Enhanced processing: sub-50 nm features with 0.8-μm DOF using a binary reticle
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Abstract
With the ever-increasing demand for reducing the size of devices on a chip, one frequently meets the lithographic challenge of printing very small lines on a wafer. The rapidly shrinking process latitudes, especially the depth-of-focus (DOF), really become a burden when trying to print sub-80nm resist lines on a wafer with 193nm lithography. In this paper, we report on a method that is capable of enlarging the process windows for printing small lines, while also reducing a line collapse issue, by using an enhanced resist processing procedure. In this procedure, the PEB time duration, in combination with the exposure dose, is used as a tuning process parameter. It is shown that, by using this procedure, a significant increase in DOF is obtained for printing small (down to 40nm) isolated and semi-dense lines, while the pitch is not scaled down. While using a binary mask and annular 193nm illumination with a NA of 0.63 and s of 0.87/0.57, we show that it is possible to print 50nm lines on a 240nm pitch with 0.8 micron DOF, whereas the standard process, using the vendor recommended PEB, can only print 80nm lines with a comparable DOF. The large process enhancement, among which the reduced curvature in the Bossung plots, is explained by the more efficient use of the acid and quencher present in the photoresist, as well as by the peculiarities of acid diffusion near regions where quencher is remaining. The results obtained are explained by a compact resist model in which acid-quencher reaction-diffusion is incorporated.
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David Van Steenwinckel, David Van Steenwinckel, Jeroen Lammers, Jeroen Lammers, "Enhanced processing: sub-50 nm features with 0.8-μm DOF using a binary reticle", Proc. SPIE 5039, Advances in Resist Technology and Processing XX, (12 June 2003); doi: 10.1117/12.485202; https://doi.org/10.1117/12.485202
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