Scanning electron microscope imaging by selective e-beaming using photoelectron beams from semiconductor photocathodes

Nishitani, T.; Arakawa, Yuta; Noda, Shotaro; Koizumi, Akira; Shikano, Haruka; Iijima, H.; Honda, Yoshio; Amano, Hiroshi

doi:10.1116/6.0002111

Cited by 7 publications

(9 citation statements)

References 10 publications

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“…We experimentally confirmed 𝑟 p = 10 nm and 𝐼 p = 13 nA using SEM equipped with a photocathode electron gun with 𝐼 e = 15 µA. 15 This probe current is 10 times higher than FE. Further improvement of 𝐼 p is expected by optimizing the SEM column design for the photocathode.…”

Section: Sem Probe Current Estimation From a Photocathodementioning

confidence: 52%

“…2(a)). 15 The system consists of a laser system, an electron gun chamber, an electron gun controller, and a power supply. A schematic of the electron gun system is shown in Fig.…”

Section: High-beam Current With Small Transverse Energy 21 Photocatho...mentioning

confidence: 99%

“…Figure 2. Key parameters of photocathode electron gun: (a) photo of a photocathode electron gun,15 (b) schematic of a photocathode electron gun. A laser beam is introduced into the electron gun through an optical window and focused onto the back surface of the photocathode to generate an electron beam.…”

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confidence: 99%

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Novel electron beam technology using InGaN photocathode for high-throughput scanning electron microscope imaging

Koizumi

Shikano

Noda

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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An InGaN photocathode with a negative electron affinity (NEA) surface is suitable for industrial use because of features such as a long quantum efficiency lifetime, availability with a visible laser as an excitation light source, and the presence of a transmission-type structure. The first objective is the development of an InGaN photocathode electron gun that can be mounted on a scanning electron microscope (SEM) and the evaluation of the electron beam size at the emission point, maximum emission current, and transverse energy of the electron beam, which are important factors for realizing a high probe current in the SEM. The second objective is the evaluation of emission current stability, while the third objective is the generation of a pulsed electron beam and multi-electron beam from the InGaN photocathode. The parameters of the electron beam from the photocathode electron gun were an emission beam radius of 1 μm, transverse energy of 44 meV, and an emission current of up to 110 μA. Using a high beam current with low transverse energy from the photocathode, a 13 nA probe current with 10 nm SEM resolution was observed with 15 μA emission. At 15 μA, the continuous electron beam emission for 1300 h was confirmed; at 30 μA, the cycle time between the NEA surface reactivations was confirmed to be 90 h with 0.043% stability. Moreover, a 4.4 ns pulsed e-beam with a 4.7 mA beam current was generated, and a 5 × 5 multielectron beam with 12% uniformity was then obtained. The advantages of the InGaN photocathode, such as high electron beam current, low transverse energy, long quantum efficiency lifetime, pulsed electron beam, and multi-electron beam, are useful in industries including semiconductor device inspection tools.

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Section: Sem Probe Current Estimation From a Photocathodementioning

confidence: 52%

“…2(a)). 15 The system consists of a laser system, an electron gun chamber, an electron gun controller, and a power supply. A schematic of the electron gun system is shown in Fig.…”

Section: High-beam Current With Small Transverse Energy 21 Photocatho...mentioning

confidence: 99%

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Novel electron beam technology using InGaN photocathode for high-throughput scanning electron microscope imaging

Koizumi

Shikano

Noda

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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“…2), the probe current can be selectively changed within one field of view of the SEM image. [1][2][3] This technology is called Digital Selective e-Beaming (DSeB). DSeB is implemented by synchronizing the laser output signal that irradiates the photocathode with the SEM scan signal (Fig.…”

Section: Vc Change Of Nmos Due To Selective E-beam Irradiationmentioning

confidence: 99%

Local voltage contrast changes in MOSFET using scanning electron microscopy with photoelectron beam technology

Sato,

Arakawa,

Niimi

et al. 2024

Metrology, Inspection, and Process Control XXXVIII

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Scanning electron microscopy (SEM) is used for metrology and inspection in semiconductor manufacturing. In addition, electrical defects such as short circuits and unintentional insulation appear as contrast differences called voltage contrast (VC) in SEM under low acceleration voltage conditions. Moreover, by using pulsed electron beams from a photocathode, the probe current can be arbitrarily changed by pixel in the SEM image. Using this technology, we succeeded in observing the change in the VC of the drain in the metal-oxide-semiconductor field effect transistor (MOSFET) by changing in electron beam irradiation on the gate only. In this study, to estimate the threshold voltage of n-type MOSFET (nMOS) from VC, we investigated quantitative changes in the specimen current of the drain (Id) and the gate (Ig) due to gate e-beam irradiation ON/OFF during SEM imaging. The landing energy of the electron beam was set to 0.8 keV, the probe current was 6.3 pA, and the e-beam was irradiated onto only the gate and drain electrodes. Id and Ig, which showed a positive value at the beginning, decreased with time, and saturated at negative values. When the electron beam irradiation to the gate was turned OFF, the Id decreased further and reached saturation. When the gate e-beam irradiation was turned ON again, Ig recovered to a positive and then saturated again to a negative value. On the other hand, the drain Id increased when the gate irradiation was turned ON and returned to the same value as before it was turned OFF.

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“…In this study, as an application of the GaN-based semiconductor photocathode electron beam source to SEM technology, an electron gun equipped with an InGaN semiconductor photocathode was mounted on a commercial-based SEM system to obtain SEM images using the pulse electron beam characteristics from semiconductor photocathodes. SEM imaging using the pulsed electron beam characteristics from the semiconductor photocathode was performed by selective electron beam irradiation 10 , in which the scanning signal of the SEM system was synchronized with the laser for photocathode excitation to irradiate arbitrary regions in the SEM image at arbitrary intensity.…”

Section: Introductionmentioning

confidence: 99%

Photoelectron beam technology for SEM imaging with pixel-specific control of irradiation beam current

Nishitani

Arakawa

Noda

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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The scanning electron microscope (SEM) with photocathode technology was launched by retrofitting the photocathode electron gun to a commercial-based SEM system. In this SEM system, the excitation laser for photoelectron generation from the photocathode is synchronized to the scanning signal. SEM images were obtained by high-speed modulation of the photoelectron beam current using the photocathode SEM, where the location in the field of view and its irradiation current were arbitrarily selected on a pixel-by-pixel basis (Selective e-Beaming technology). As a demonstration experiment contributing to non-contact electrical inspection, low-voltage SEM imaging of MOS-FET structures in 3D-NAND flash memory was performed using this selective e-beam technology. As a result, changes in the voltage contrast of the drain electrode were observed in response to on/off selective electron beam irradiation to the gate electrode in the MOS-FET structure. As an extension of the selective electron beaming technology, a Yield Controlled e-beaming (YCeB) technology was invented to control the secondary electron yield generated in the entire field of view of the SEM image by feedback control of the laser power irradiating the photocathode to the intensity of each pixel in the SEM image. The YCeB image, in which the laser power intensity corresponding to the probe intensity is modulated so that the secondary electron yield generated in the entire field of view of the SEM image is constant, is a clearer image with less noise than the original SEM image.

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Scanning electron microscope imaging by selective e-beaming using photoelectron beams from semiconductor photocathodes

Cited by 7 publications

References 10 publications

Novel electron beam technology using InGaN photocathode for high-throughput scanning electron microscope imaging

Novel electron beam technology using InGaN photocathode for high-throughput scanning electron microscope imaging

Local voltage contrast changes in MOSFET using scanning electron microscopy with photoelectron beam technology

Photoelectron beam technology for SEM imaging with pixel-specific control of irradiation beam current

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