Extreme Ultraviolet Lighting Using Carbon Nanotube-Based Cold Cathode Electron Beam

Abstract

Laser-based plasma studies that apply photons to extreme ultraviolet (EUV) generation are actively being conducted, and studies by direct electron irradiation on Sn for EUV lighting have rarely been attempted. Here, we demonstrate a novel method of EUV generation by irradiating Sn with electrons emitted from a carbon nanotube (CNT)-based cold cathode electron beam (C-beam). Unlike a single laser source, electrons emitted from about 12,700 CNT emitters irradiated the Sn surface to generate EUV and control its intensity. EUV light generated by direct irradiation of electrons was verified using a photodiode equipped with a 150 nm thick Zr filter and patterning of polymethyl methacrylate (PMMA) photoresist. EUV generated with an input power of 6 W is sufficient to react the PMMA with exposure of 30 s. EUV intensity changes according to the anode voltage, current, and electron incident angle. The area reaching the Sn and penetration depth of electrons are easily adjusted. This method could be the cornerstone for advanced lithography for semiconductor fabrication and high-resolution photonics.

Enhanced extreme ultraviolet lighting using carbon nanotube-based cold cathode electron beam irradiation

“…When I photo is 4 μA, the usable time without melting Sn is 506 s. Additionally, in our previous study, it was confirmed that a PMMA photoresist that reacts to an EUV dose of 25 mJ cm −2 can be sufficiently reacted with C-beam based EUV light with I photo of 4 μA in 30 s of exposure. 24,32) When irradiating one C-beam, the usable time without melting Sn and I photo are in a trade-off relationship. The usage time is shorter to use enhanced EUV lighting.…”

“…The intensity of EUV light generated by the C-beam varies with anode voltage and electron incident angle as well as anode current. 24) Sn has a low melting point of about 232 °C, so it cannot withstand high-energy electron bombardment. EUV intensity increases in proportion to the electron impact power of the C-beam, 24) but as Sn melts, vaporized Sn particles act as debris and can contaminate the inside of the EUV system.…”

“…24) Sn has a low melting point of about 232 °C, so it cannot withstand high-energy electron bombardment. EUV intensity increases in proportion to the electron impact power of the C-beam, 24) but as Sn melts, vaporized Sn particles act as debris and can contaminate the inside of the EUV system. 2,5,30,31) It is necessary to identify the point where Sn does not melt, and as shown in Fig.…”

“…We reported in a previous study that EUV generation by irradiating Sn with electrons emitted from the C-beam and that the generated EUV could react with polymethyl methacrylate (PMMA) photoresist. 24) In this study, enhanced EUV lighting was studied by optimizing the technique of irradiating Sn with electrons emitted from the C-beam. We identified the conditions under which Sn does not melt to minimize the occurrence of debris, and propose a multiple C-beam irradiation technique to improve EUV intensity.…”

Boosting the Electron Beam Transmittance of Field Emission Cathode Using a Self-Charging Gate

“…We believe that this high-efficiency, long-term stable cathode has great potential for using in neutralizers, solar sails and tethered satellites in the long-term space missions.Carbon nanotubes (CNTs) present numerous advantages as the field emission cathodes (FEC), such as its ultralow turn on voltage (>0.4 V/μm) 1, 2 resulting from the low work function (~5 eV), [3][4][5] exceptional chemical and physical stabilities, 6 as well as high electrical and thermal conductivity 7, 8 attributed to the C-C covalent bond, seamless hexagonal network architecture and one-dimension carbon nanostructures. 9, 10 These unique characteristics render FEC an ideal electron source for various applications, including field emission scanning electron microscopy (FESEM), 11 field emission display (FED), 12 electron-beam (E-beam) lithography (EBL) 13,14 and X-ray tube. 15 In modern space technologies, 16,17 FEC often severs as the cathode for electric propulsion (EP) system, providing electrons to neutralize the positive ions or positively charged droplets to avoid charging of the spacecraft.…”