Plasmonic Interference Lithography for Low-Cost Fabrication of Dense Lines with Sub-50 nm Half-Pitch

Limited by the cost and complexity, a sub-50 nm lithography node is hard to achieve through the traditional interference lithography. In this paper, the dense lines with half-pitch of 32 nm (∼λ/11) and 22 nm (∼λ/16) are first achieved at the wavelength of 365 nm by simple plasmonic interference lithography. Through selecting the high spatial frequency plasmonic modes in Al/Photoresist (Pr)/Al waveguide and allowing interference with each other, the deep subwavelength plasmonic interference field could be obtained in Pr film. Moreover, the lithography structure is separated from the mask, so etch transfer process from Pr to substrate after lithography is easy to attain, and the mask with high cost could be used multiple times. Meanwhile, a near-field lithography setup was developed, and we experimentally realized the comparatively distinct lithography fringes with the half-pitch of 32 and 22 nm when there is an air gap smaller than ∼20 nm between mask and the lithography films. Compared with the imaging lithography with 1:1 ratio, the plasmonic interference lithography could achieve the demagnified patterns with a 2:1 ratio, which reduces the difficulty and cost of the mask fabrication. It is believed that this method will supply the simple and low-cost nanofabrication scenario in the near future.