原田 哲男

The pellicle plays a crucial role in the EUV photolithography process and has garnered increased attention from advanced semiconductor manufacturers as they strive to advance development for smaller process nodes. Carbon nanotubes (CNTs) are highly promising for EUV pellicle applications due to their exceptional mechanical, thermal, and optical properties. It is necessary for the pellicle to be durable and robust enough to withstand extreme scanner conditions, which involve combinations of high temperatures and active hydrogen species generated by EUV light. In this study, we present test results conducted to simulate the environment of the next-generation 600 W scanner using the NewSUBARU synchrotron light source facility. Our investigation focused on evaluating the performance of CNT films, both with and without protective coating layers. Surprisingly, the results indicate that the CNT film without coating demonstrated the most promising characteristics for pellicle applications, showcasing superior performance in the demanding EUV scanner environment.

There has been growing interest among advanced semiconductor manufacturers in pellicles that can withstand conditions in extreme ultraviolet (EUV) photolithography. The pellicle must have high mechanical toughness, high transparency in EUV radiation, thermal stability, and chemical stability for ionized and atomic hydrogen. For the above expectations, our experience shows that the carbon nanotube (CNT) yields the most promising results due to its outstanding mechanical and thermal properties. We are developing thin, free-standing CNT films for EUV pellicle application using a liquid filtration manufacturing method. This method has the advantage of producing highly uniform films, allowing us to use a variety of CNT types while avoiding the use of harsh chemicals. To advance our hypothesis, we will examine and discuss EUV radiation durability results evaluated with the NewSUBARU synchrotron light facility.

Development of new EUV resists is required for next-generation EUV lithography. A resist in which a large amount of photoacid generator (PAG) is introduced into the polymer side chain has been reported as a high-resolution nonchemically amplified negative-Tone resist. In this study, we synthesized a new high-PAG loading-Type negative-Tone resist as a model resist, evaluated EUV sensitivity by flood exposure, and also performed carbon K-edge and sulfur Ledge X-ray absorption spectroscopy (XAS) analysis. The synthesized high-PAG loading bound resist had a 79 mol% PAG unit in the polymer side chain. After the EUV exposure, the resist behaved as a negative-Tone resist in the alkaline developer and a positive-Tone resist in the organic developer. From the results of the XAS analysis, the possible decomposition mechanisms of the PAG unit in the polymer were estimated.

It has been reported that the good correlation in sensitivity and resolution between EUV exposure and EB exposure because of the similar mechanism of the photochemical-reaction in photoresists during exposure. However, in the early stages of EUV resist development, there are problems on the points of the cost and time-consuming to evaluate all EUV resist materials by EB exposure. Therefore, we investigated the possibility of using KrF exposure as the initial screening of EUV resists. If the correlation between KrF exposure, EB exposure and EUV exposure can be found, it will be possible to evaluate photoresists in a step-by-step manner, such as screening with KrF exposure first, followed by EB exposure, and finally EUV exposure in the initial evaluation stage. In this paper, we report on our investigations in the case of novolac resists, PHS chemically amplified resists, acrylic chemically amplified resists, and EUV polymer resists.

In extreme ultraviolet lithography (EUVL), it is required to develop EUV resist which has low line width roughness (LWR) for the further miniaturization of circuit pattern. In order to reduce LWR, it is necessary to analyze and control the chemical-components spatial distribution in the resist thin film. We have reported that the measurement of chemical-components spatial distribution in the resist thin film coated on the Si3N4 membrane using the method of the transmission-mode resonant soft X-ray scattering (RSoXS). In this study, in order to analyze the chemical-structure-size distribution in the resist thin film on a Si wafer under similar condition adapted to the resist-coating actual process, we examined the grazing-incidence RSoXS (GI-RSoXS). A chemically amplified resist (CAR) and a non-CAR were spin-coated on silicon wafers, which had varied film thickness of 20, 50, and 100 nm. The scattering profile of each sample was measured at the incident photon energy of 280 and 296 eV. As a result, it is suggested that the chemical-structure-size distribution in the resist thin films depends on the resist film thickness. It is confirmed that the GI-RSoXS method is very effective to evaluate the chemical-structure-size distribution of resist thin films.

The R&D of basic technologies such as mask, resist, optical element, optics. have been carried out at NewSUBARU synchrotron light facility since 1996. EUV Lithography started use in production from 2019 for 7 nm node logic devices and from 2020 for 5 nm node logic devices. Current status and prospect of EUV and usage probability of BEUV will be reported. And the necessity of BEUV-FEL will be discussed.

Our previous studies focused on ways to measure simulation parameters for EUV resists, including development parameters, Dill's C parameter, the diffusion length of PAG-derived acids, and parameters for deprotection reactions. Through EUV resist simulations based on these parameters, we examined conditions for reducing LER and improving resolution. This paper presents the results of our investigations of methods for determining the refractive index n and extinction coefficient k of photoresists for EUV light (wavelength 13.5 nm), parameters generally considered difficult to measure, and for calculating an absorption parameter known as the Dill's B parameter. We investigated three types of photoresists: polymer decomposition type resist, chemically amplified resist, and EUV metal resist.

Extreme ultraviolet (EUV) lithography has recently been utilized as a high-volume manufacturing technology for advanced semiconductors. An EUV mirror can be easily contaminated in the existence of a residual hydrocarbon vapor gas inside an exposure chamber in a vacuum environment, which reduces the reflectance of the Mo/Si multilayer coating. To reduce this carbon contamination, hydrogen gas is introduced at a pressure of a few pascals in the EUV scanner. However, during this process, the multilayer may be damaged by hydrogen. In addition, the multilayer surface can become oxidized by residual water vapor in the vacuum chamber. Therefore, an EUV irradiation tool in hydrogen and water vapor atmospheres was developed and installed at BL-09 of the NewSUBARU synchrotron light facility to evaluate the cleaning effect and irradiation durability of the Mo/Si multilayer. The EUV irradiation intensity increased up to 6 W cm(-2), and the hydrogen pressure reached 70 Pa.

Using a newly developed edge-support heat treatment method of polyimide, self-standing graphite thin films (GTFs) with a frame were prepared. The graphite basal plane in the GTF was oriented in the direction of the film surface, resulting in GTFs with high quality, large area, and a uniform thickness of 50-120 nm. The thickness distribution (3s) with an area of 25 mm x 25 mm and a thickness of 54 nm sample was 5.17 nm (measurement area 7.8 mm x 10.4 mm). The electric conductivity of a similarly prepared sample was 1.81 x 10(4) S/cm. The Young's modulus and ultimate tensile strength of a 60-nm-thick GTF were 1.02 x 10(2) and 5.34 GPa, respectively. Approximately 50 nm thick GTF samples were thinned by reactive ion etching using oxygen to fabricate a thickness between 10 and 20 nm. A film with an area of 10 mm x 10 mm and thickness of 16.7 nm exhibited a 3 sigma value of 1.80 nm which means that the thickness difference corresponds to 5 layers of graphite. The conductivity of a 16.2-nm-thick GTF was 1.79 x 10(4) S/cm. These results indicate that the etching proceeded uniformly. The proposed top-down method is an industrially superior method that overcomes the drawbacks of conventional bottom-up methods. (C) 2021 Elsevier Ltd. All rights reserved.

This article presents a prototype 22.4 mu m pixel pitch global shutter (GS) wide dynamic range (WDR) soft X-ray CMOS image sensor (sxCMOS). Backside-illuminated (BSI) pinned photodiodes with a 45-mu m thick Si substrate were introduced for low noise and high radiation hardness to high energy photons. Two-stage lateral overflow integration capacitor (LOFIC) and voltage domain memory bankwith high-densitySi trench capacitorswere introduced for WDR and for GS. The developed sxCMOS achieved maximum 21.9 Me- full well capacity with a single exposure 129 dB dynamic range by GS operation. Over 70% quantum efficiency (QE) toward soft X-ray was successfully achieved. The developed prototype sxCMOS is a step forward toward a 4 M pixel detector system to be utilized in next-generation synchrotron radiation facilities and X-ray free-electron lasers.

In 2019, EUV lithography technology with a wavelength of 13.5 nm was used for the mass production of semiconductor logic devices with 7 nm node. As with small feature size of electronic circuits in semiconductor device will be required in the future, beyond EUV (BEUV) lithography with exposure wavelength around 6.7 nm is a candidate for the next generation lithography. In BEUV, the developments of high-reflective multilayers, high-sensitive resists, and high-power light sources are critical issues. Thus, we have developed BEUV evaluation tools in NewSUBARU synchrotron light facility. Accurate BEUV reflectometry is significant for the development of high-reflective BEUV multilayer. For the accurate reflectometry, higher-diffraction-order generated from a monochromator should be suppressed. At the BL10 beamline at NewSUBARU, the components of second and third-diffraction-order light are 7% mixed into the BEUV measurement light. Mo transmission filter with a 200-nm-thick was previously used to suppress the higher-order light to 1/10, which was insufficient for target accuracy of 0.1%. We have developed a high-order-light cutting unit consisting of two mirrors with TiO2 coating, which suppressed the high-order light to 1/100.

At EUV lithography, an EUV mirror can be easily contaminated with carbon. This carbon contamination causes the reflectance drop of the Mo/Si multilayer mirror. For the carbon-contamination cleaning, hydrogen gas is introduced at a pressure of a few Pascal in the EUV exposure tool. However, during this process, the hydrogen damage would be caused on a Mo/Si multilayer, which would decrease EUV reflectance of the multilayer. The cleaning rate and damage threshold of hydrogen pressure and EUV dose were not well known. Therefore, an EUV irradiation tool in hydrogen atmosphere is developed and installed at the BL09 beamline of the NewSUBARU synchrotron light facility to evaluate the irradiation durability and cleaning effect of the Mo/Si multilayer under these conditions. The EUV-irradiation intensity was up to 6 W/cm2, and hydrogen pressure was up to 70 Pa. The contamination was occurred at the low-hydrogen-pressure conditions from 0 to 5 Pa. The contamination was not occurred at the high-hydrogen-pressure condition of 20 and 68 Pa. In addition, the sample with many particles on the surface was damaged by the EUV-induced plasma.

Since 2019, EUV lithography has started to be used for the mass production of 7-nm-node-logic devices. However, many significant issues on EUV lithography still remain in the fabrication of future devices. The technical issues are the development technologies of resist, mask, and EUV light source. Therefore, many significant fundamental researches have been carried out at our facility. Here the EUV mask technologies is highlighted. It is described the fundamental research activities on EUV lithography at NewSUBARU synchrotron light facility, which is related with EUV mask technologies.

An extreme ultraviolet (EUV) light with a wavelength of 13.5 nm has been introduced to 7 nm FinFET technology. Optical elements such as Mo/Si multilayer mirror in lithography equipment are contaminated with hydrocarbon during the EUV light irradiation. The reflectance of the mirrors is decreased by carbon contamination. Therefore, the removal method of the carbon contamination is required for reduction of maintenance cost. The surface treatment using atomic hydrogen generated by a heated tungsten mesh, called as atomic hydrogen annealing (AHA), have been investigated for cleaning of the optical elements used in the synchrotron facility. The Au/Cr/Si substrate, Ni mirror and Ni diffraction grating with carbon contamination were cleaned and the reflectance of the mirrors was recovered by AHA. In addition, the AHA conditions could be optimized for cleaning of Mo/Si multilayer mirrors from the relationship between the treatment conditions and degradation. Furthermore, to clarify the reaction of atomic hydrogen with not only C-C bond but also C-O bond, the graphene oxide (GO) film was also treated by AHA. The C-O-C bonds in the GO films were preferentially reduced by AHA. It is found that the surface contamination consisting of hydrocarbon and/or C-O bond on the optical elements is removed without damage. The ability of atomic hydrogen to clean the optical elements had been confirmed. The findings are useful for the advanced lithography technology using EUV light.

Up to now, we have been researching methods for measuring the simulation parameters of EUV resist. These parameters include the development parameter, the Dill C parameter, the diffusion length of acid generated from PAG, and the deprotection reaction parameter. By using these parameters, we have attempted to simulate EUV resist. As a result, we could investigate the conditions for reducing LER and for enhancing resolution. We hereby report on the methods of calculating the refractive index n and k values of photoresist with EUV light (13.5 nm), which has been difficult to measure until now, and the Dill B parameter, which is an absorption parameter. The three types of photoresists we investigated are the main chain scission type resist, chemically amplified resist, and metal resist.

Extreme ultraviolet lithography was started to use for the production of 7-nm node-logic-semiconductor devices in 2019. And it was adapted to use for high volume manufacturing (HVM) of 5-nm logic devices in 2020. EUVL is required to be extended to use in 1.5-nm-node-device fabrications. However, it still has many technical issues. Especially, for EUV resists, simultaneous achievement of high sensitivity and low line edge width are required. To solve the EUV resist issue, the fundamental work using synchrotron in soft X-ray region is necessary. The fundamental evaluation study of EUV resist at NewSUBARU synchrotron light facility is described in this paper.

In extreme ultraviolet (EUV) lithography development, the reduction of line width roughness (LWR) is a one of the significant issues. It has been reported that the LWR of photoacid generator (PAG) bounded resist is lower than that of PAG blended resist. It is considered that the chemical composition distribution of PAG bounded resist is more uniform than PAG blended resist. However, it has not been evaluated systematically and experimentally. In this study, we introduced the contact angle measurement method for the evaluation of the chemical composition distribution between PAG blended resist and PAG bounded resist. It is clarified that the resist thin film has a different chemical composition distribution from the center to the outside of wafer regardless of the type of resists. In particular, the chemical composition distribution of the bounded resist showed the opposite behavior to that the blended one.

A prototype 22.4μm pixel pitch global shutter wide dynamic range soft X-ray CMOS image sensor (sxCMOS) is presented. The sxCMOS employs backside-illuminated (BSI) pinned photodiode with a 45μm-thick Si substrate for low noise and high light resistance to high energy photons, two-stage LOFIC for wide dynamic range and voltage domain memory bank with high density capacitors for global shutter. The developed chip successfully demonstrated a high quantum efficiency (QE) toward soft X-ray with a single exposure 129dB dynamic range by global shutter.

The recent EUVL activities of resists, masks, and optics at NewSUBARU Synchrotron Light Facility are introduced. In addition, the capabilities of the shortening the wavelength to 6.75 nm with high-power EUV source are also discussed.

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. An essential element of sub-15 nm nanoimprint lithography is to create fine patterns on a template. However, it is challenging to create sub-15 nm half-pitch patterns on a template by direct drawing with a resist, owing to poor resolution and low sensitivity. We are currently researching the development of sub-15 nm half-pitch patterns by applying self-aligned double patterning on a template. The defect density of the template has not yet reached a high-volume manufacturing level. The aim of our study is to achieve a defect density of less than 1 pcs/cm2 for sub-15 nm templates. To achieve this, we need to overcome stochastics-induced resist defects. We aim to determine the mechanism of defect formation by observing the details of the defects. We challenged resist-pattern inspections using a grazing-incidence coherent scatterometry microscope, which illuminated an extreme ultraviolet light to the resist pattern and detected the diffraction signal from the pattern. This study was conducted in collaboration with University of Hyogo and Kioxia Corporation. In this paper, we present the results of damage evaluations and resist-pattern inspections.

© 2020 SPST. The surface treatment using atomic hydrogen genareted by a heated tungsten mesh was investigated for the cleaning of the optical elements used in the synchrotron facility. We call the surface-tretament by the atomic hydrogen annealing (AHA). The Au and Ni mirors and Ni and Mo diffraction gratings with carbon contamination were cleaned by the chemical reaction and thermal effect due to the recombination of the atomic hydrogens during AHA. The carbon contamination was removed and the reflactance of the Au and Ni mirrors was recovered by AHA. The AHA conditions could be optimaized for cleaning of Mo/Si multilayer mirrors from the relationship between the treatment condition and degradation. In addition, to clarify the removal reaction of the carbon contamination, the two-types of amorphous carbon (a-C) films were used. The etching rate of the a-C film by AHA was strongly related to the hydrogen content, atomic density and sp2/sp3 component of a-C film.

© 2020SPST. EUV lithography is started to use in high volume manufacturing of 7-nm node semiconductor devices for smart phones. However, a resist development is still remained significant critical issue in EUV lithography. The EUV resist has to be achieved high resolution, high sensitivity, and low line-width roughness (LWR), simultaneously. Especially, the resist is required low LWR performance for a fine patterning. To reduce LWR, it is significant to control and reduce the stochastic behavior of the resist chemical contents such as the functional groups, photo reactive compound (photoacid generators：PAG), additives such as amines and so on. However, there is no method to measure the chemical contents spatial distribution. Therefore, the resonant soft X-ray scattering (RSoXS) method is applied to evaluate the chemical contents spatial distribution. Around the carbon absorption edge, the resonant absorption peaks are specific to the chemical contents of carbon. In RSoXS method, the soft X-ray scattering intensity from the resist is recorded by a CCD camera, which the incident photon energy irradiate to the resist sample is varied around the carbon absorption K-edge of 284 eV. If these chemical contents have large dispersion, the stochastic becomes worth. In this way, the chemical contents spatial distribution in photoresists is measured by RSoXS method, and this method is significant for development of low LWR resist.

© 2019 The Japan Society of Applied Physics. We develop a high-quantum-efficiency, high-exposure-durability backside-illuminated CMOS image sensor for soft-X-ray detection. The backside fabrication process is optimized to reduce the dead-layer thickness, and the Si-layer thickness is increased to 9.5 μm to reduce radiation damage. Our sensor demonstrates a high quantum efficiency of >90% in the photon-energy range of 80-1000 eV. Further, its EUV-regime efficiency is ∼100% because the dead-layer thickness is only 5 nm. The readout noise is as low as 2.5 e- rms and the frame rate as high as 48 fps, which makes the device practical for general soft X-ray experiments.

© 2019 The Japan Society of Applied Physics. We recently developed a backside-illuminated CMOS image sensor for soft X-ray detection based on a commercial CMOS sensor. This sensor demonstrated a high quantum efficiency, low readout noise of 2.6 e- rms, and high frame rate of 48 fps. This sensor also showed an energy resolution of 80 eV to 1,000 eV photon. We demonstrated fluorescence detection from highly-oriented graphite and a polymethyl methacrylate film using a simple setup, where the samples faced a CMOS sensor without a monochromator. This energy-resolving performance and high frame rate will facilitate new applications for soft X-ray and EUV experiments.

© 2019 Author(s). In synchrotron radiation (SR) optical devices coated with oxidation-prone metal, such as Ni and Cr, the UV-O3 ashing method cannot be used for removal of the contaminated carbon film deposited during use in the beamline. We have demonstrated that surface treatment technology using atomic hydrogen is effective as a new contaminated carbon film removal technology. Hydrogen gas was flowed into contact with a tungsten mesh (catalyst) heated to 1700°C to obtain atomic hydrogen. By flowing this atomic hydrogen on the surface of the SR mirror, deposited contaminants could be almost completely removed. The reflectance of the mirror recovered from about 14% to about 70% at the C-K absorption region. The reflectance also increased by about 20% at a photon energy greater than 300 eV because of the removal of carbon film and the reduction of native oxide at the mirror surface.

© 2019 SPIE. We develop the monochromator and reflectometer to evaluate optical properties of an EUV optics and EUV resist at the BL3 beamline in NewSUBARU synchrotron light facility. This system supports from the EUV to out-of-band (OoB) energy region which corresponds at the wavelength region from 10 to 300 nm. This monochromator design is collimatedplane- grating monochromator with the constant-line-spaced grating of 1,000 lines/mm. The deviation angles are 150° for EUV region and 120° for the OoB region. The absorption edges of Si, Al and Mg filters are clearly observed using this system. The beam size on a sample position is 0.6(H) × 0.3(V) mm2. We measured the EUV and OoB reflectance of a Mo/Si multilayer, an absorber TaN on the multilayer, and glass substrate which is used as a substrate of the black border on an EUV mask. The OoB reflectance of glass substrate was over 20%, which would affect to the EUV imaging performance in an EUV exposure tool. In addition, the OoB reflectance of the Mo/Si multilayer was quite different from that in calculation. Thus, it is important for evaluate the actual OoB reflectance of an EUV optics.

© 2019 The Japan Society of Applied Physics. We have developed an EUV interference lithographic exposure tool to evaluate a resist. The target patterning size of this system is 10 nm and below in half pitch. Transmission grating fabrication is a key technology in EUV interference lithography. To replicate a 10-nm-line-and-space (L/S) resist pattern on a wafer, a 20-nm-L/S pattern is required for the transmission grating. The pitch size of the interference fringes is half the size of the absorber pattern of the transmission grating. For the chemically amplified positive tone resist process, instead of alkali development, organic development can be adopted to convert to a negative-tone chemical amplification resist process, and pattern collapse can be suppressed. In addition to this process, a dry development rinse (DDR) process is used. The DDR process with dry development successfully prevents pattern collapse at a high aspect pattern because there is no surface tension in the dry development of the DDR process. The EUV diffraction efficiencies of the fabricated gratings were measured to be 14%, 11% and 4% for 40, 30 and 20-nm-L/S pattern grating, respectively. Using these gratings, 20, 15 and 10 nm resist pattern might be replicated on a resist. And the diffraction efficiency was sufficient for interferometric exposure using synchrotron radiation.

© 2019 SPST. The resist development is a critical issue in EUV lithography for high volume manufacturing of semiconductor devices. Especially, the resist should have low line-width roughness (LWR) performance in fine patterning. To reduce the LWR, it is significant to control and reduce the stochastic behavior in the resist material. We employed the resonant soft X-ray scattering (RSoXS) method to evaluate the non-uniformity of the resist material components such as base polymer, functional group, and photo-acid generator and so on. In RSoXS method, the soft X-ray scattering intensity from the resist is recorded by a CCD camera, which the incident photon energy irradiated to the resist sample was varied around the carbon absorption K-edge of 284 eV. Around the carbon absorption edge, the absorption spectrum had resonant absorption peaks that depended on the chemical bonding structure of carbon. The scattering signal profile of a commercial chemical-amplified resist was different at each absorption peaks, which indicated non-uniformity of resist material. Thus, the non-uniformity of the resist material was measured by RSoXS method, which was important for development of low LWR resist.

© 2019 SPST. In the advanced lithography, the pattern collapse is significant issue. Since the resist pattern collapse origin to the surface force of the rinse solvent such as ultra-pure deionized water, pattern strip and pattern collapse occur easily when the resist aspect ratio exceeds two. The pattern strip and pattern collapse occur near or at the bottom layer and of a resist inside the resist film, respectively. Thus, the layer analysis inside the resist is significant. The layer separation analysis inside the resist film is very difficult by the X-ray reflectivity method because the layer separation contrast is very small using hard X-ray. Therefore, the resonant soft X-ray reflectivity (RSoXR) method was utilized for the layer separation of the resist film. A commercial chemical-amplifier resist was employed as a sample to in this study. Around carbon absorption edge region of 284 eV, optical index will depend on chemical-bonding structure of the resist strongly. The separated-layer structure was clearly analyzed at 287.1 eV. The resist had 5 nm and 6 nm separated layer at the top and the bottom position.

© 2018 Wiley Periodicals, Inc. For evaluation of defects on extreme ultraviolet (EUV) masks at the blank state of manufacturing, we developed a microcoherent EUV scatterometry microscope (micro-CSM). The illumination source is coherent EUV light with a 140-nm focus diameter on the defect using a Fresnel zoneplate. This system directly observes the reflection and diffraction signals from a phase defect. The phase and the intensity image of the defect is reconstructed with the diffraction images using ptychography, which is an algorithm of the coherent diffraction imaging. We observed programmed phase defect on a blank EUV mask. Phase distributions of these programmed defects were well reconstructed quantitatively. We also observed actual defects which were inspected by the ABI tool. Actual amplitude defect and phase defect images were reconstructed with intensity and phase contrast. The reconstructed image indicated the defect type of these defect. The micro-CSM is very powerful tool to evaluate an EUV phase defect.

To improve EUV resist sensitivity, studies have sought to enhance EUV light absorption by adding metals characterized by high EUV light absorption to the resist polymer. This approach is intended to increase secondary electron emission, thereby enhancing PAG reactivity and improving acid generation efficiency([1-3)]. As reported in our previous report, to determine whether adding metals characterized by high EUV light absorption actually enhances sensitivity, we performed transmittance measurements and sensitivity evaluations of resist samples doped with ZrO2 or TeO2 nanoparticles, which have low and high EUV light absorption, respectively, in molar quantities of 0-2 relative to PAG. The samples were subjected to EUV exposure at the NewSUBARU synchrotron radiation facility. The results of transmittance measurements and sensitivity evaluations showed that, while the ZrO2-doped resist showed no changes in absorption or sensitivity, the TeO2-doped resist showed enhancement in both properties. Based on these results, we confirmed that adding metals characterized by high EUV light absorption to the EUV resist enhances its EUV light absorption and increases secondary electron emission, thereby enhancing PAG reactivity and improving acid generation efficiency([4-5]). In the efforts discussed in the present report, we examined whether adding metals directly to PAG could further enhance sensitivity by increasing the EUV light absorption of PAG itself, thereby efficiently heightening the effect of the secondary electron emission on PAG.

Copyright © 2018 SPIE. We have developed the reflectometer to evaluate EUV mirrors and masks at BL-10 beamline of NewSUBARU synchrotron light facility. This reflectometer usually measures s-polarized reflectance. Reflectance of an EUV mirror is strongly depends on polarization state of incident light, if angle of incidence to the sample is not normal. The center radiation from a bending source of a synchrotron source is almost horizontally polarized. However, there was several percent of vertical polarized component at the center radiation on NewSUBARU. For accurate reflectometry, a horizontal-polarization control unit (PCU) has been developed to remove the unnecessary vertically-polarized EUV component. This unit consisted of two reflection polarizer mirrors coated with aperiodic Mo/Si broadband multilayer, which multilayer was coated in our laboratory. Using this unit, degree of horizontal polarization was improved to be 1.00. In addition, vertical-PCU has been developed for p-polarized reflectance measurement. There is vertical polarized light component on off-axis radiation from the bending source. This vertical-PCU also generated the fully-verticalpolarized light. As the results, the reflectometer measures accurate s- and p-polarized reflectance without setup change of the sample stage and the detector stage.

Copyright © 2018 SPIE. The resist thickness of EUV lithography is thin less than 50 nm. Since the most photon is not absorbed by the resist, the EUV chemical reaction is not occurred sufficiently. In order to increase chemical reaction, a resist should have a highabsorption material compounds for the EUV photons. Many high-absorbing material has been studied such as hafnium, zinc, tin oxide, and tellurium. Resist performance improvements are expected in sensitivity and reduction of line-edgeroughness. For the development of the high-absorbing resist materials, it is significant to measure the EUV absorption coefficient accurately. For measurement of absorption, it is necessary to measure both transmittance and thickness of resist accurately. We have developed an absorption-coefficient-measurement method of the EUV resist at BL-10 beamline of NewSUBARU synchrotron light facility. The resist is coated on a detector photodiode directly, and EUV transmittance and thickness are measured. We measured an absorption coefficient of PMMA resist, which has very simple chemical composition and ZEP520A resist which is copolymer. The transmittance uniformity on the photodiode was less than 0.6%. This result indicates that the resist sample was coated with good uniformity on the surface of the photodiode. The result of PMMA well corresponded to the calculated value. Thus, it is practicable to measure the absorption coefficient accurately.

© 2018, Tokai University. All rights reserved. EUV lithography will be used as high volume manufacturing of semiconductor devices after 2020, where the half pitch of the devices is 10 nm. EUV interference lithography (EUV-IL) has been developed for the EUV resist evaluation with 10-nm and below patterning. The transmission grating is a key component for EUV-IL. The pitch size of the interference fringes are half size of the absorber pattern of the transmission grating. In this paper, diffraction grating pattern with 20-nm line-and-space pattern with very high aspect of 90-nm carbon layer was fabricated using the dry development rinse (DDR) process with spin-on-carbon under-layer. The diffraction efficiency of the grating is expected to be 6%, which is enough for EUV-IL. In the DDR process, the DDR material replaced the exposed and developed part. The DDR process with dry development is to prevent pattern collapse perfectly because there is no surface tension at the dry development process. As the results, 20-nm L/S pattern with high-aspect-ratio of 5.9 was fabricated, which can be applied for the 10-nm EUV resist evaluation by EUV-IL.

© 2017 The Japan Society of Applied Physics. In extreme-ultraviolet (EUV) lithography, the development of a review apparatus for the EUV mask pattern at an exposure wavelength of 13.5nm is required. The EUV mask is composed of an absorber pattern and a Mo/Si multilayer on a glass substrate. This mask pattern has a threedimensional (3D) structure. The 3D structure would modulate the EUV reflection phase, which would cause focus and pattern shifts. Thus, the review of the EUV phase image is also important. We have developed a coherent EUV scatterometry microscope (CSM), which is a simple microscope without objective optics. The EUV phase and intensity images were reconstructed with diffraction images by ptychography. For a standalone mask review, the high-harmonic-generation (HHG) EUV source was employed. In this study, we updated the sample stage, pump-laser reduction system, and gas-pressure control system to reconstruct the image. As a result, an 88nm line-and-space pattern and a cross-line pattern were reconstructed. In addition, a particle defect of 2 μm diameter was well reconstructed. This demonstrated the high capability of the standalone CSM, which can hence be used in factories, such as mask shops and semiconductor fabrication plants.

<p>For evaluation of defects on extreme ultraviolet (EUV) masks at the blank state of manufacturing, we developed a micro coherent EUV scatterometry microscope (micro-CSM). The illumination source is coherent EUV light with a 140-nm focus diameter on the defect using a Fresnel zoneplate. This system directly observes the reflection and diffraction signals from a phase defect. The phase and the intensity image of the defect is reconstructed with the diffraction images using ptychography, which is an algorithm of the coherent diffraction imaging. We observed programmed phase defect on a blank EUV mask. Phase distributions of these programmed defect were well reconstructed quantitatively. We also observed actual defects which was inspected by the ABI tool. Actual amplitude defect and phase defect images were reconstructed with intensity and phase contrast. The reconstructed image indicated the defect type of these defect. The micro-CSM is very powerful tool to evaluate an EUV phase defect.</p>

© 2017 SPIE. Studies have been carried out on developing a method for improving EUV resist sensitivity by enhancing EUV light absorption through the addition of metals having high EUV light absorption to the resist polymer in order to increase secondary electron emission, thereby enhancing PAG reactivity and improving acid generation efficiency[1-3]. To confirm whether the addition of metals having high EUV light absorption actually does enhance sensitivity, study efforts included transmittance measurements and sensitivity evaluations of resist samples doped with ZrO2 or TeO2 nanoparticles, which have low and high EUV light absorption, respectively, in molar quantities of 0-2 relative to PAG. The samples were subjected to EUV exposure at the NewSUBARU synchrotron radiation facility. While the ZrO2-doped resist showed no evident enhancement of sensitivity or transmittance, the TeO2-doped resist showed enhancement in both properties. Based on these results, we confirmed that the addition of metals having high EUV light absorption to the EUV resist enhances its EUV light absorption and increases secondary electron emission, thereby enhancing PAG reactivity and improving acid generation efficiency.

© 2017 SPST. The technical issues of EUV resist are high resolution, high sensitivity, low line edge roughness (LER), and low outgas. Between these, there is a trade-off relationship, and the most significant point in these issues is the simultaneous achievement of high sensitivity and low LER. In order to efficiently develop high-performance EUV resist, it is necessary to understand the chemical reaction of EUV resist. Thus, we have studied the EUV chemical reaction using the soft X-ray absorption spectroscopy. In this method, the absorption spectra had a lot of absorption peak which could not be assigned to the chemical bonding. For analysis of these unknown peaks, the molecular orbital (MO) calculation using the first principle, so-called "ab initio", is expected to be an effective support computation method. Since the chemical-structural-optimization is necessary for the first-principle calculation, we introduced the MO calculation software Conflex that can search the position of reactive active molecules in the conformational space, optimize resist chemical structure, and create a resist molecular model. Based on this optimized molecular model, the MO calculation software Gaussian was performed to calculate IR spectrum. By comparing the IR spectra obtained by an experiment and the calculation, some IR peaks was assigned to a chemical group, and chemical-bond transformation was suggested. From these results, it was confirmed that MO calculation had an ability for analyze the chemical reaction of resist material. Thus, MO calculation can accelerate the development of high-performance resist material, which will help a breakthrough of semiconductor devices for “the internet of things”.

© 2017SPST. Since the resist thickness in EUV lithography of which base material mainly consists of an organic material is thin, the EUV photon energy is not be used efficiently for the EUV chemical reaction. In order to increase chemical reaction incidence in the EUV photon energy, a resist having a high-absorption material compounds for the EUV photons has been developed. It has been studied to increase the absorption including high-absorption materials such as hafnium and zinc, tin oxide, tellurium. For the development of the next-generation high sensitive resist materials, since it is significant to measure the EUV absorption coefficient accurately, it is necessary to measure the transmittance and resist thickness to obtain the absorption coefficient accurately. Thus, we have developed to evaluate the absorption coefficient of the EUV resist at BL 10 beamline of NewSUBARU synchrotron hlight facility. In the previous paper, we measured the EUV resist transmittance on a freestanding membrane. However, since it was very difficult to coat resist on a membrane with high uniformity, the transmittance could not be measured accurately. Thus, we have developed the precise transmittance measurement method by coating resist on a photodiode directly, and the resist thickness on a photodiode was measured by XRR accurately instead on conventional method. Finally, the accurate measurement of EUV resist absorption coefficient was achieved.

© 2017SPST. In DSA pattern observation of hp 5 nm and below, the pattern observation method for physical and chemical structures is necessary. Scattering measurement of hard X-rays is one method which can quantitatively evaluate the physical structure of materials. However, when many components such as polymer materials are mixed, it can observe the averaged physical structure, and it is difficult to evaluate the structure of the individual chemical components. Thus, we developed a scattering measurement method using soft X-rays near the carbon absorption edge. Since the absorption spectrum varies in the near carbon absorption edge for each polymer molecule, the individual physical structures can be observed from the scattering profile with different photon energy. In this study, both the physical and chemical structures of the triblock terpolymers such as poly[isoprene-block-styrene-block-(2-vinylpyridine)] which consists of polyisoprene, polystyrene, and poly(2-vinylpyridine) were observed. The physical structure of the triblock polymer observed two types of the packed cylinder structures such as the tetragonal and hexagonal packed structures. The film thickness of this triblock polymer was 400 nm. By varying the photon energy of the scattering measurement, the scattering light intensity changed greatly, and the signal from each polymer could be evaluated. The soft X-ray scattering measurement at the near absorption edge can be measured the molecular structure of a composite material such as a blended polymer individually and can be utilized in material development.

© 2017 SPIE. In extreme ultraviolet (EUV) lithography, development of review tools for EUV mask pattern and phase defect at working wavelength of 13.5 nm is required. The EUV mask is composed of an absorber pattern (50 - 70 nm thick) and Mo/Si multilayer (280 nm thick) on a glass substrate. This mask pattern seems three-dimensional (3D) structure. This 3D structure would modulate EUV reflection phase, which would cause focus and pattern shifts. Thus, EUV phase imaging is important to evaluate this phase modulation. We have developed coherent EUV scatterometry microscope (CSM), which is a simple microscope without objective optics. EUV phase and intensity image are reconstructed with diffraction images by ptychography with coherent EUV illumination. The high-harmonic-generation (HHG) EUV source was employed for standalone CSM system. In this study, we updated HHG system of pump-laser reduction and gas-pressure control. Two types of EUV mask absorber patterns were observed. An 88-nm lines-and-spaces and a cross-line patterns were clearly reconstructed by ptychography. In addition, a natural defect with 2-μm diameter on the cross-line was well reconstructed. This demonstrated the high capability of the standalone CSM, which system will be used in the factories, such as mask shops and semiconductor fabrication plants.

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. In this paper, we designed the synthesis of negative-Type molecular resist materials for EB and EUVL exposure tools, and their properties were examined. The resist materials for EUVL have been required showing higher sensitivity for high throughput in the lithographic process, and expecting lower shot noise to improve a roughness. In EUVL process, the resist materials must be ionized by absorbing EUV to emit more secondary electrons. The EUV absorption of the synthesized resist materials was measured using their thin films on the silicon wafer, and it was observed that the ratio of EUV absorption of the synthesized resist was higher than in the comparison of that of PHS as a reference., i.e., 2.4 times higher absorption was shown. Furthermore, we examined the relationship between the ratios of EUV absorptions and functional groups of the resist materials. As the result, the sensitivity of resist materials under EUV exposure tool was consistent with their structures.

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. To improve EUV resist sensitivity, studies have sought to enhance EUV light absorption by adding metals characterized by high EUV light absorption to the resist polymer. This approach is intended to increase secondary electron emission, thereby enhancing PAG reactivity and improving acid generation efficiency [1-3]. As reported in our previous report, to determine whether adding metals characterized by high EUV light absorption actually enhances sensitivity, we performed transmittance measurements and sensitivity evaluations of resist samples doped with ZrO2 or TeO2 nanoparticles, which have low and high EUV light absorption, respectively, in molar quantities of 0-2 relative to PAG. The samples were subjected to EUV exposure at the NewSUBARU synchrotron radiation facility. The results of transmittance measurements and sensitivity evaluations showed that, while the ZrO2-doped resist showed no changes in absorption or sensitivity, the TeO2-doped resist showed enhancement in both properties. Based on these results, we confirmed that adding metals characterized by high EUV light absorption to the EUV resist enhances its EUV light absorption and increases secondary electron emission, thereby enhancing PAG reactivity and improving acid generation efficiency [4-5]. In the efforts discussed in the present report, we examined whether adding metals directly to PAG could further enhance sensitivity by increasing the EUV light absorption of PAG itself, thereby efficiently heightening the effect of the secondary electron emission on PAG.

© 2016 The Japan Society of Applied Physics. In extreme-ultraviolet (EUV) lithography, the development of high-power EUV sources is one of the critical issues. The EUV output power directly depends on the collector mirror performance. Furthermore, mirrors with large diameters are necessary to achieve high collecting performance and take sufficient distance to prevent heat and debris from a radiation point of the source. Thus collector mirror development with accurate reflectometer is important. We have developed a large reflectometer at BL-10 beamline of the NewSUBARU synchrotron facility that can be used for mirrors with diameters, thicknesses, and weights of up to 800 mm, 250mm, and 50 kg, respectively. This reflectometer can measure reflectivity with fully s-polarized EUV light. In this study, we measured the reflectance of a 412-mm-diameter EUV collector mirror using a maximum incident angle of 36°. We obtained the peak reflectance, center wavelength and reflection bandwidth results and compared our results with Physikalisch-Technische Bundesanstalt results.

© 2016 Society of Photo-Optical Instrumentation Engineers (SPIE). To evaluate defects on extreme ultraviolet (EUV) masks at the blank state of manufacturing, we developed a micro-coherent EUV scatterometry microscope (micro-CSM). The illumination source is coherent EUV light with a 140 nm focus diameter on the defect using a Fresnel zone plate. This system directly observes the reflection and diffraction signals from a phase defect. The phase and the intensity image of the defect are reconstructed with the diffraction images using ptychography, which is an algorithm of the coherent diffraction imaging. We observed programmed phase defect on a blank EUV mask. Phase distributions of these programmed defects were well reconstructed quantitatively. The micro-CSM is a very powerful tool to review an EUV phase defect.