Super-Resolution Patterning and Photolithography Based on Surface Plasmon Polaritons

Abstract

With the developments of the nanoscale science and technology, the demand for fabrication of nanoscale patterns has been significantly increased. Photolithography has still been the most widely used microfabrication technique because of its ease of repetition, effective cost, and suitability for large-area fabrication. The diffraction limit, however, restricts single-exposure resolution to features with periods no smaller than half wavelength of the illuminating sources. To achieve nanometer feature sizes within the regime of diffraction physics, one straightforward method is to reduce the working wavelength by employing light sources of higher photon energy, such as extreme ultraviolet light (EUV), soft X-rays, or atomic wave packet [1][2][3][4]. The main drawbacks, however, are the drastic increase of complexity and cost for instrumentation and processing, including the developments of new sources, photoresist, and the optical components. Several alternative techniques, such as electron beam lithography [5][6][7][8][9], focused ion beam lithography [10][11][12][13][14], dip-pen lithography [15][16][17][18], and nanoimprint lithography [19][20][21][22], can also achieve nanoscale feature sizes; however, these methods require the introduction of a new infrastructure of tools, materials, and processing technologies, which costs huge expenses.Recently, a new photolithographic scheme, which is based on the unique properties of surface evanescent waves [23][24][25][26] or surface plasmon polaritons (SPPs) [27][28][29][30][31][32][33][34][35][36][37] induced at the interface between a metal and a dielectric material, to achieve sub-diffraction-limit nanopatterns was proposed and demonstrated. The wave vector of SPPs can be significantly larger than that of the free-space illuminating light at the same frequency, which results in extraordinary "optical frequency but X-ray wavelength" property. As a result, the resolution of this surface plasmon nanolithography can go far beyond the free-space diffraction limit of the light. Different versions of the implementation of the SPPs-based super-resolution nanolithography have been proposed and conducted both theoretically and experimentally in recent years, which all demonstrate that SPPs-based nanolithography has the potential to satisfy the requirements of high resolution, low cost, and high throughput simultaneously.