Single-digit 6-nm multilevel patterns by electron beam grayscale lithography

Abstract

We report on the fabrication of very high-resolution discrete four-resist-level grayscale patterns in poly(methyl methacrylate) with just 6-nm step height and down to 32-nm step width using dose-modulated, grayscale electron beam lithography and a low-contrast resist-developer system. This direct pattern writing is important for replication in high-volume manufacturing of diffractive optics. An innovative concept of unexposed auxiliary spacers helped to enhance the discrete character of the multi-level patterns. For pattern step widths between 100 and 32 nm, a transformation toward blazed gratings with increasingly continuous-slope character was obtained. All high-resolution patterns were prepared in a single exposure and development process from an initially about 30-nm thin film. The pattern roughness due to a relatively large polymer molecular weight was reduced using selective thermal annealing with only minimally affecting the global pattern shape by reflow. The results will enable further approaches toward single-digit vertical and prospectively single-digit lateral resolution grayscale patterns.

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials

“…In this case too, the electrons in contact with the resist are modifying its solubility, permitting the selective removal of the exposed or non-exposed regions of the resist by subsequent etching in a solvent. The main advantage of this method relies on the maskless fabrication of sub-20 nm patterns in the horizontal plane [ 63 ] and of sub-10 nm patterns in the vertical plane [ 64 ] by employing a computer software that guides a finely focused beam of electrons over the patternable surface. Nonetheless, the best contrast and sensitivity of the material has to be considered when choosing the appropriate resist for high-aspect ratio patterns [ 65 ] and when aiming at sub-20 nm resolution on both positive and negative tones resists [ 66 ].…”

Anisotropic Etching of Pyramidal Silica Reliefs with Metal Masks and Hydrofluoric Acid

“…To achieve comparable patterns, high‐resolution grayscale lithography along with sophisticated pattern transfer would be required. [ 18–20,21 ]…”

“…To achieve comparable patterns, high-resolution grayscale lithography along with sophisticated pattern transfer would be required. [18][19][20]21] Of course, different shapes of initial patterns are conceivable but this work concentrates on rectilinear shapes ( Figure S1, Supporting Information) to obtain pyramidal structures with rectilinear base. The respective metal patterns are obtained via lift-off processing of electron beam evaporated thin gold, platinum, or chromium films with and without titanium adhesion layers.…”

Smart Origination and Functional Replication: Thermal Reflow and Innovative 3D Structures

“…Usually, a lower contrast is more suitable for GEBL due to higher resilience against dose variations [12]. However, high-resolution patterns [13] demanded minimal dark erosion for the unexposed patterns, especially in this relative low M w resist, and thus, required IPA to be used as co-solvent.…”

“…3). For laterally high-resolution steps, a quasi-continuous pattern might be obtained due to the non-negligible lateral development and thus an effective merging of neighboring steps [13]. Due to the variation of the GEBL dose, the M w, and thus, the T g varies significantly [10].…”