Scanning proximal probe lithography for sub-10 nm resolution on calix[4]resorcinarene

Abstract

Influence of the development process on ultimate resolution electron beam lithography, using ultrathin hydrogen silsesquioxane resist layersThe use of molecular resist in scanning proximal probe lithography (SPPL) offers a novel and promising maskless lithographic method with sub-10 nm resolution. Here, the authors present their investigation of the patterning capabilities of C-Methylcalix[4]resorcinarene at ambient conditions using SPPL. The STM-based setup operates in constant-current Fowler-Nordheim regime and results in positive-tone self-developing phenomena. The lithographic operation is performed at currents in the range of pico-ampere, writing speeds of 1-10 lm=s, and bias voltages ranging from 20 up to 70 V. Currently, the authors have achieved feature sizes from 7 nm to micrometers depending on the applied exposure parameters. The direct patterning process shows high reproducibility and reliability over this large feature range.

Scanning probes in nanostructure fabrication

“…A more detailed description of the line-width dependencies from bias voltage, exposure dose and tip is provided elsewhere. 6,7 In summary, the self-developing EF-CC-SPL scheme offers a high resolution mask-less patterning method (sub-5 nm lines 12 ) applicable for a closed loop SPL strategy. Herein, we have recently demonstrated the promising combination of EF-CC-SPL with electron beam lithography (also extreme ultraviolet lithography is possible instead) in a mix-and-match approach, 12 increasing both the process window and the throughput of the EF-CC-SPL method.…”

“…21,38 Recently, we have demonstrated the positive-tone, developmentless, so called "self-development" patterning of calixarene molecular glass resists using highly confined electric field, current-controlled scanning probe lithography (EF-CC-SPL) scheme. 6,7,38,39 Herein, an electric field is applied between scanning probe and sample, resulting in a current flux of low energy electrons (<50 eV), which is regulated by the lithography current feedback loop. This current flux in turn penetrates the molecular resist material below the nanoprobe, leading to a highly localized removal process used for patterning of nanofeatures.…”

“…Tip/sample interactions can result in a highly confined oxidation, heating, electron exposure, or chemical modification leading to patterning at the nanoscale. 6,7 For example, one approach is to use an electrical bias on the scanning probe tip to generate field emission electrons. 8 The resulting localized electron beam exposes a resist covered sample, like in standard electron beam lithography, but without complex electron beam optics.…”

Review Article: Active scanning probes: A versatile toolkit for fast imaging and emerging nanofabrication

“…In frame of our research on FE-SPL, we demonstrated: (1) a closed-loop lithography for generation of lithographic features in positive, negative as well as in dual tone; 12,18,50 (2) a novel self-development mode, wherein the resist material is directly removed, which avoids development-related problems; 17,18,48,49 (3) sub-10 nm lithographic resolution capabilities; 17,18 (4) step-and-repeat, multistep, and multilayer lithography by incorporation of probe-based high accuracy alignment; 18,19 (5) applicability of novel molecular glass resists and coevaporated resist material systems; 51,52 (6) patterning of 2D-materials, e.g., MoS 2 nanoribbons with 15 nm lateral confinement; (7) pattern transfer capability of FE-SPL defined features by plasma etching at cryogenic temperatures. 29,53 As a main result, the developed technology chain has demonstrated its capability by successful fabrication of roomtemperature single electron transistor (SET) devices showing effective quantum dot sizes of less than 2 nm.…”

“…Due to the low electron energies, typically 50 eV, which are close to the binding energies of the resist molecules, the lithographic process is efficient and proximity effects are circumvented. 48,49 Lithographic processes, which are spatially confined to the sub-10 nm scale are yielded by the highly localized electric field and the use of tip-sample distances well below 100 nm. Based on the thermomechanically actuated, piezoresistive, so called active cantilever technology 14,50 a scanning probe lithography 06G101-7 Rangelow et al: Active scanning probes 06G101-7 platform 18,50 able to image, inspect, align and pattern features at the single-digit nanoregime was developed.…”