Showing papers on "Proximity effect (electron beam lithography) published in 2019"

Influence of the dose assignment and fracturing type on patterns exposed by a variable shaped e-beam writer: simulation vs experiment

Abstract: The result of electron beam lithography is influenced by many effects: forward and backward scattering, formation of secondary electrons, re-scattering of electrons, chemicals diffusion in the resist material, wafer stack, etc. To achieve high resolution all these effects should be taken into account. Commonly, the electron energy distribution in the exposed matter is described by the Point Spread Function (PSF). This is a simple approach which takes into account large portion of phenomena using few parameters. PSF function is a Gauss or multiple Gauss function, which is determined experimentally by the calibration procedure. Each resist material with corresponding stack is characterised by its own PSF, in case of double Gaussian, with the following parameters: α, β and η. In the current work the PSF parameters were systematically varied to study their influence on the dose assignment and resulting pattern. This gives a broader understanding of the correction mechanism using PSF. Furthermore, the resulting shape of the structure is influenced not only by the PSF parameters and dose assignment, but by the fracturing type as well. All these effects were studied using experimental and simulation approaches.

Method for processing silicon nano cylinder by electron beam lithography

Abstract: The invention provides a method for processing a silicon nano cylinder by electron beam lithography, comprising a silicon wafer coating step of coating the surface of a silicon wafer with an electron beam photoresist; an electron beam exposure and development step of direct writing exposing the silicon wafer coated with the electron beam photoresist twice and developing the silicon wafer to obtain at least two rectangular patterns vertically overlapping each other; a thermal reflow step of heating the developed silicon wafer; and an etching step of etching the thermally reflowed silicon wafer. The method converts nano cylinder fabrication into grating direct writting by an electron beam exposure proximity effect and the thermal reflow method, shortens the time of direct writing a pattern of 1 mm2 to 20 minutes which is 1/80 of the original time, and greatly improves the pattern direct writing efficiency.

Optimization of electron beam lithography and lift-off process for nanofabrication of sub-50 NM gold nanostructures

Abstract: Since the demonstration of the first integrated circuit in the late 1950s, the microelectronics industry has witnessed a vast transformation with transistor densities doubling roughly every two years as a result of continuous scaling down of device dimensions, referred to as miniaturization. The fundamental concept of miniaturization has not only been employed for the realization of ultra large scale integrated (ULSI) circuits with reduced manufacturing costs, lower power consumption, higher speed and computational power; but also, for developing novel transducer elements and energy storage devices by harnessing the unique physical effects that arise at micro/nanoscales such as higher surface-to-volume ratios. One of the most important technologies in micro/nano device fabrication, if not the single most important, is lithography. The broad range of lithographic techniques ranging from conventional optical lithography methods (e.g. ultraviolet-UV, deep ultraviolet-DUV, extreme ultraviolet-EUV) to unconventional ones (e.g. electron beam lithography, x-ray lithography, ion-beam lithography, stereolithography, scanning probe lithography, nanoimprint lithography, directed self-assembly) can be used to create features with microns to tens of nanometer resolution and below. Among these, electron beam lithography (EBL) stands out as a powerful direct-write tool offering nanometer scale patterning capability and is especially useful in low volume R&D prototyping. However, patterning with EBL requires careful balance of process parameters which need to be considered in conjunction with the pattern transfer technology that can be either etching or lift-off specifically for the case metallic layers. Accordingly, this thesis provides a systematic study to address the gap in process optimization of lift-off process based on EBL patterning of sub-50 nm metallic nanostructures using a lower cost PMMA/PMMA positive tone bilayer resist spin approach. The governing parameters in EBL including exposure dose, bake temperature, develop time, developer solution, substrate effect, proximity effect (PE) are experimentally studied and their effects on nanopatterning are characterized by field emission scanning electron microscopy (FE-SEM) of fabricated nanostructures