Proximity effect (electron beam lithography)

About: Proximity effect (electron beam lithography) is a research topic. Over the lifetime, 940 publications have been published within this topic receiving 8508 citations.

Proximity Effect Correction for 20nm dimension patterning

Abstract: Electron Beam Direct Writing (EBDW) has been applied to various applications such as prototyping or small amount production of electronic devices. Originally, proximity effect in EBDW is considered as the problem of the background energy difference caused by the pattern density distribution. However, the critical dimensions of target patterns are getting smaller, we cannot ignore influences of the forward scattering. Theoretically, when the critical dimension is close to 3 or 4 times of forward scattering range, influence cannot be ignored. For example, in case ofthat corresponds, fabricating 20 nm dimension patterns by Nano Imprint Lithography (NIL) which is significant candidate of next generation lithography technology. Because it requires original dimension (1:1) mold. Therefore proximity effect correction (PEC) system which considers the forward scattering must be important. We developed simulation-based proximity effect correction system combined with data format conversion, works on Linux PC cluster. And we exposed the patterns which are dose compensated by this system. Firstly, we have speculated parameters about backward scattering parameters by exposing 100 nm line and space patterns. We got following parameters, beta (backward scattering range) = 32 urn, eta (backward scattering coefficient) = 2.5. Secondary, we have exposed Line and Space patterns whose dimensions are from 20 nm to 100 nm. We found that smaller and dense patterns have trend to be over exposed and bigger. Experimental specification is following, EB Direct Writing system is JBX-9300FS (lOOkeV ace. Voltage) by JEOL co.ltd, (Japan) , resist is HSQ (FOx 12) by Dow Coming co. (United States), substrate is Si.

40-100nm contact-hole processes of ZEP520A e-beam resist on PCM prototyping applications

Abstract: ZEP520A e-beam processes for 40-100nm contact holes were studied for application of phase change memory (PCM) device prototyping. Resist baking, e-beam and development process parameters were investigated on the isolated and semi-dense (1:3) contact holes. PAB temperature for minimum exposure dose-to-size (E SIZE ) is 70°C. E SIZE of 200°C PAB is 250 μC/cm 2 while that of 70°C is 120 μC/cm 2 for 100nm contact hole. E SIZE of contact hole increases very quickly as the CD gets smaller than 60nm. CDs with beam currents of 100pA and 200pA are nearly the same while that with 2nA differs much. Sidewall profiles of contact holes exposed by 100pA and 200pA are near 90° while that exposed with 2nA is tapered. E SIZE decreases with development time. Bottom of contact hole is broadened for prolonged development time. CDs after PDB are not changed. There is little difference in CD between isolated and semi-dense patterns. CD uniformity on the corner and center of contact-hole array are around 5% (+/-3σ), showing a very weak proximity effect. Inter-layer mix-and-match processes were applied to PCM manufacturing. Cross-shaped alignment marks results in the strongest signal waveform on TiW bottom electrode than oxide and TiN/Ti. Mix-and-match PCM device structure was, for the first time, ever demonstrated.

Quantification of electron-beam proximity effects using a virtual direct write environment

Abstract: An e-beam exposure module has been developed for an existing lithography simulator, covering aspects of e-beam inter-action with the stack, exposure of the resist by the e-beam as well as development of the resist. The goal of the simulation is to complement experimental data with insights that are difficult or impossible to obtain experimentally and to provide advanced capabilities for process optimization. Simulations are performed for an iso-dense pattern to show that in the case of 5kV acceleration voltage, a standard dose correction works well for tight beams with 5nm blur but is very challenging for 30nm beam blur. Geometric corrections will most likely be needed for a wide beam blur.

Optimal Design for Nonperiodic Fine Grating Structure Controlled by Proximity Correction with Electron-Beam Lithography

Abstract: We describe a method for designing nonperiodic fine grating structures such as a small F-number diffractive cylindrical lens, to be fabricated by direct-writing electron-beam lithography. The design is based on a resist development simulator for estimating a proximity effect of electron dose and the finite difference time domain (FDTD) method for simulating an electromagnetic field. The surface profile and electron dose distribution are simultaneously optimized to obtain the high diffraction efficiency. For the design of a diffractive lens of 50 µm width and 25 µm focal length, the calculated diffraction efficiency is 49% for 650-nm-wavelength light, which is slightly lower than that of a diffractive lens profile optimized by electromagnetic analysis without restrictions on fabrication limits.

Helium ion beam lithography

Abstract: As nanoelectronic device design pushes towards ever smaller feature sizes, there is an increasing need for new lithographic patterning techniques and resists. Helium ion beam lithography (HIBL), an emerging technique that uses a high-intensity, sub-nanometer focused beam of helium ions generated in the helium ion microscope (HIM) to expose resist, promises to drive nano-patterning beyond the capabilities of conventional electron beam lithography (EBL). In this work, an investigation on HIBL in direct comparison with EBL using both conventional EBL resist PMMA and a novel fullerene-based molecular resist is described. Analysis of large area exposures reveals a sensitivity of 2 μC/cm2 on PMMA and 40 μC/cm2 on fullerene derivative resist with 30-keV helium ion beam, which are 60 times and 500 times higher than those with an electron beam for the same resists respectively. This improved resist sensitivity in HIBL demonstrates the potential for faster pattern definition and therefore high throughput. The proximity effect, caused by the backscattered primary particles and known to limit the performance of EBL, was then quantitatively studied using a “doughnut” method on 20-nm-thick PMMA resist on silicon with 30 keV HIBL and EBL. The lithographic results were fitted to the proximity function and the backscattered electrons/ions range were found out to be ~3.26 μm and ~0.067 μm, revealing a 60 times proximity effect reduction in HIBL compared to EBL. This suggests that the negligible proximity effect in HIBL enables high-density pattern definition, whilst avoiding the inadvertent exposure of surrounding material. Finally, to demonstrate the benefit of the smaller spot size and the reduced proximity effect in HIBL, line dose optimisation was carried out with high-resolution single-pixel line arrays on both resists. Linewidth of ~11.7 nm was achieved in 20-nm PMMA with pitches down to 30 nm. In 10-nm fullerene resist, line widths of 7.2 nm were achieved in sparse line arrays. The fabrication of 8.5 nm half-pitched lines with good feature separation and 6 nm half-pitched lines with inferior but still resolvable separation is also shown in this resist. Thus, sub-10 nm patterning with high resist sensitivity and small proximity effect is demonstrated using HIBL with standard processing conditions, establishing its potential as an alternative to EBL for rapid prototyping of beyond CMOS devices.