Abstract
Displacement Talbot lithography (DTL) is a new technique for patterning large areas with sub-micron periodic features with low cost. It has applications in fields that cannot justify the cost of deep-UV photolithography, such as plasmonics, photonic crystals, and metamaterials and competes with techniques, such as nanoimprint and laser interference lithography. It is based on the interference of coherent light through a periodically patterned photomask. However, the factors affecting the technique's resolution limit are unknown. Through computer simulations, we show the mask parameter's impact on the features' size that can be achieved and describe the separate figures of merit that should be optimized for successful patterning. Both amplitude and phase masks are considered for hexagonal and square arrays of mask openings. For large pitches, amplitude masks are shown to give the best resolution; whereas, for small pitches, phase masks are superior because the required exposure time is shorter. We also show how small changes in the mask pitch can dramatically affect the resolution achievable. As a result, this study provides important information for choosing new masks for DTL for targeted applications.
Highlights
Periodic organisations of structures are useful for the creation of devices in many different fields such as plasmonics [1], photonic structures [2] or metamaterials [3]
It has applications in fields that cannot justify the cost of deep-UV photolithography, such as plasmonics, photonic crystals, and metamaterials and competes with techniques, such as nanoimprint and laser interference lithography
Deep-ultraviolet immersion lithography using a 193 nm excimer laser is widely used in industry and is capable of achieving a resolution of 14 nm [4], and extreme ultraviolet (EUV) sources with a wavelength of 13.2 nm are on the horizon to further decrease the minimum feature sizes [5]
Summary
Periodic organisations of structures are useful for the creation of devices in many different fields such as plasmonics [1], photonic structures [2] or metamaterials [3]. The main drawback is the lifetime of the 3D master mould Another approach is to use interference lithography, in which coherent sources of electrons [8] or photons [9] interfere, creating a periodic array of intensity. Displacement Talbot lithography is a recently developed technique for patterning large areas with sub-micron periodic features [10]. It is an extension of Talbot lithography, which uses the three-dimensional interference pattern created when monochromatic light diffracts through a periodic mask. Introducing a displacement during a photolithography exposure along the axis perpendicular to the mask integrates the optical field and solves these problems This technique is called Displacement Talbot Lithography (DTL) and has the advantage of a theoretical infinite depth of field [10]. Thanks to this comparison between experiment and modelling, the conditions required to optimize the resolution will be discussed
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