Showing papers on "Proximity effect (electron beam lithography) published in 2017"

Proximity effect correction in electron-beam lithography based on computation of critical-development time with swarm intelligence

Abstract: Electron-beam lithography (EBL) is an important technique in manufacturing high-resolution nanopatterns for broad applications. However, the proximity effect in EBL can degrade the pattern quality and, thus, impact the performance of the applications greatly. The conventional proximity effect correction (PEC) methods, which employ computationally intensive cell or path removal method for development simulation, are very computational lengthy, especially for complex and large-area patterns. Here, the authors propose a novel short-range PEC method by transforming the evaluation of pattern feasibility into the shortest path problem based on the concept of critical-development time. The authors combine this evaluation algorithm with the swarm intelligence which mimics the natural collective behavior of animals to optimize the design of electron dose distribution in EBL. The PEC algorithm is applied for pattern fabrication for U-shaped split-ring resonator and produces optimized exposure pattern that shows exc...

Proximity correction and resolution enhancement of plasmonic lens lithography far beyond the near field diffraction limit

Abstract: Near-field optical imaging methods have been suffering from the issue of a near field diffraction limit, i.e. imaging resolution and fidelity depend strongly on the distance away from objects, which occurs due to the great decay effect of evanescent waves. Recently, plasmonic cavity lens with off-axis light illumination was proposed as a method for going beyond the near field diffraction limit for imaging dense nanoline patterns. In this paper, this investigation was further extended to more general cases for isolated and discrete line patterns, by enhancing the resolution and correcting the proximity effect with assistant peripheral groove structures. Experiment results demonstrate that the width of single, double and multiple line patterns is well controlled and the uniformity is significantly improved in lithography with a 365 nm light wavelength and 120 nm working distance, being approximately ten times the air distance defined by the near field diffraction limit. The methods are believed to find applications in nanolithography, high density optical storage, scanning probe microscopy and so forth.

Quadrupole lens alignment with improved STIM and secondary electron imaging for Proton Beam Writing

Abstract: Minimal proximity effect coupled with uniform energy deposition in thin polymer layers make Proton Beam Writing (PBW) an intuitive direct-write lithographic technique. Feature sizes matching the focused beam spot size have been fabricated in photoresists down to 19 nm. Reproducible sub-10 nm beam focusing will make PBW a promising contender for sub-10 nm lithography. In this paper, we present beam size characterization by imaging a PBW resolution standard using transmitted/scattered ions and secondary electrons. Using Scanning Transmission Ion Microscopy (STIM) spectra for 1 and 2 MeV H 2 + beams, we experimentally measure the thickness of the resolution standard to be 0.9 ± 0.1 μm, applying two independent calibration methods, which match the original intended thickness during fabrication. Through bias optimization of a Micro-Channel Plate (MCP), we show a tuneable secondary electron detection per proton for imaging with a maximum of 75% e/p for a beam of 1 MeV H 2 + . Based on STIM mode beam size measurement, we discuss considerations for quadrupole system alignment in order to remove higher order translational and rotational misalignments critical to achieve sub-40 nm spot sizes. A spot size of 13 × 32 nm 2 (STIM) was achieved using a newly developed interface, capable of autofocusing ion beams and performing PBW.

Nanofabrication and characterization of high-line-density x-ray transmission gratings

Abstract: We report the nanofabrication and characterization of x-ray transmission gratings with a high aspect ratio and a feature size of down to 65 nm. Two nanofabrication methods, the combination of electron beam and optical lithography and the combination of electron beam, x-ray, and optical lithography, are presented in detail. In the former approach, the proximity effect of electron beam lithography based on a thin membrane of low-z material was investigated, and the x-ray transmission gratings with a line density of up to 6666 lines/mm were demonstrated. In the latter approach, which is suitable for low volume production, we investigated the x-ray mask pattern correction during the electron beam lithography process and the diffraction effect between the mask and wafer during the x-ray lithography process, and we demonstrated the precise control ability of line width and vertical side-wall profile. A large number of x-ray transmission gratings with a line density of 5000 lines/mm and Au absorber thickness of up to 580 nm were fabricated. The optical characterization results of the fabricated x-ray transmission gratings were given, suggesting that these two reliable approaches also promote the development of x-ray diffractive optical elements.

Nanofabrication by Electron Beam

Abstract: Electron beam lithography is the most important and also the most versatile nanofabrication technique. Electrons work very much like photons for nanofabrication. They carry energy and transfer the energy into the energy-sensitive polymer materials called electron resists. The resists exposed by electron beam are developed into surface relief patterns which act as masks for subsequent transfer into the substrate materials.

Nanofabrication of 10-nm T-shaped gates using a double patterning process with electron beam lithography and dry etch

Abstract: A process to fabricate T-shaped gates with the footprint scaling down to 10 nm using a double patterning procedure is reported. One of the keys in this process is to separate the definition of the footprint from that for the gate-head so that the proximity effect originated from electron forward scattering in the resist is significantly minimized, enabling us to achieve as narrow as 10-nm foot width. Furthermore, in contrast to the reported technique for 10-nm T-shaped profile in resist, this process utilizes a metallic film with a nanoslit as an etch mask to form a well-defined 10-nm-wide foot in a SiNx layer by reactive ion etch. Such a double patterning process has demonstrated enhanced reliability. The detailed process is comprehensively described, and its advantages and limitations are discussed. Nanofabrication of InP-based high-electron-mobility transistors using the developed process for 10- to 20-nm T-shaped gates is currently under the way.

A comprehensive model for sub-10 nm electron-beam patterning through the short-time and cold development.

Abstract: In this study, we propose a set of single-spot experiment to construct a comprehensive model of electron-beam lithography to describe the relation among the incident electrons, resist, and the development conditions such as durations and temperatures. Through the experiments, small feature can be achieved by performing a short-time development due to the high acceleration voltage and large depth of focus of electron-beam system. The singular point in the beginning of the development is also observed in our model and supported by the experimental data. In addition, we verify the characteristic region of each incident spot induced by the point spread function of the electron-beam system. We further fabricate the single line with narrow groove width by utilizing the results from single-spot experiment at low developing temperatures. The line is formed by arranging a series of incident points with a distance close to the characteristic radius. This method can eliminate the proximity effect effectively and thus the groove width is scaled down to 8 nm. By adopting the successful experience in the single line formation, dense array with narrow linewidth is also demonstrated under well suppression of the proximity effect. The minimum groove width of 9 nm with 30 nm pitch is achieved with 5 s development time at -10 °C. Finally, the exceptional capability of pattern transfer is presented due to the high aspect ratio of the resist.

Dataset for Helium Ion Beam Lithography on Fullerene Molecular Resists for Sub-10 nm Patterning

Abstract: Dataset supporting: Shi, Xiaoqing et al (2016) Helium ion beam lithography on fullerene molecular resists for sub-10 nm patterning. Microelectronic Engineering.Helium ion beam lithography (HIBL) is an emerging technique that uses a sub-nanometre focused beam of helium ions generated in the helium ion microscope to expose resist. It benefits from high resolution, high sensitivity and a low proximity effect. Here we present an investigation into HIBL on a novel, negative tone fullerene-derivative molecular resist. Analysis of large area exposures reveals a sensitivity of ~40 ?C/cm2 with a 30 keV helium beam which is almost three orders of magnitude higher than the sensitivity of this resist to a 30 keV electron beam. Sparse line features with line widths of 7.3 nm are achieved on the ~10 nm thick resist. The fabrication of 8.5 half-pitched lines with good feature separation and 6 nm half-pitched lines with inferior but still resolvable separation are also shown in this study. Thus, sub-10 nm patterning with small proximity effect is demonstrated using HIBL using standard processing conditions, establishing its potential as an alternative to EBL for rapid prototyping of beyond CMOS devices.Funded by Single Nanometer Manufacturing for beyond CMOS devices (SNM, 318804), 2013 to 2016.