Dip-In Photoresist for Photoinhibited Two-Photon Lithography to Realize High-Precision Direct Laser Writing on Wafer

Abstract

For decades, photoinhibited two-photon lithography (PI-TPL) has been continually developed and applied into versatile nanofabrication. However, ultrahigh precision fabrication on wafer by PI-TPL remains challenging, due to the lack of a refractive index (n) matched photoresist (Rim-P) with effective photoinhibition capacity for dip-in mode. In this paper, various Rim-P are developed and then screened for their applications in PI-TPL. In addition, different lithography methods (in terms of oil-mode and dip-in mode) are analyzed by use of optical simulations combined with experiments. Remarkably, one type of Rim-P (n = 1.518) shows effective photoinhibition capacity, which represents an outstanding breakthrough in the field of PI-TPL. In contrast to photoresist with an unsuitable refractive index, optical aberrations are almost completely eliminated in the dip-in mode by using the Rim-P. Consequently, features with a minimum critical dimension as small as 39 nm are successfully achieved on wafer by dip-in PI-TPL, which paves the way for subdiffraction silicon-based chip manufacturing by PI-TPL. Moreover, through a combination of the Rim-P and dip-in mode, the ability to achieve tall and high-precision three-dimensional nanostructures is no longer problematic.

Two‐Photon Polymerization Lithography for Optics and Photonics: Fundamentals, Materials, Technologies, and Applications

“…[432] As aforementioned, diffusion-assisted high-resolution TPL approaches and STED have been proposed and the printing resolution can be pushed down to 9 nm (Figure 7a and b). [325,[433][434][435][436] These methods requires complex setup modification and precise beam alignment between writing beam and inhibition beam. Leveraging on the high collimation enabled by extraordinary ENZ metamaterial features-a nanocavity in metal/insulator/metal/insulator (MIMI) configuration (Figure 7c and d), ultrathin dielectric hyper-resolution nanostructures are realized with a size reduction of 89% in height and 50% in width respectively, compared with the standard printing method.…”

Low-Fluorescence Starter for Optical 3D Lithography of Sub-40 nm Structures

“…19 Typical structure sizes achieved so far are in the range of 50 nm both in the lateral 10,20,21 and axial direction. 4 Lateral feature sizes below 40 nm were reported recently, 15,22,23 but no improvements in axial feature sizes were attempted in these studies.…”

Direct laser writing breaking diffraction barrier based on two-focus parallel peripheral-photoinhibition lithography

“…A formulation containing 0.5 g of 7-diethylamino-3-thenoylcoumarin, 8.6 g of tricyclodecane dimethanol diacrylate, 0.7 g of ethoxylated bisphenyl fluorene diacrylate, and 0.7 g of o-phenyl phenoxyethyl acrylate was used as the sample photoresist. 49 The exposed samples were developed in propylene glycol 1-monomethyl ether 2-acetate for 15 min, followed by rinsing in isopropanol for 5 min. A 2-nm-thick gold layer was evaporated on the samples prior to topography observation.…”