Search

In situ X-ray diffraction observation was done for neutron-irradiated and un-irradiated HOPG samples with synchrotron radiation to clarify the effect of irradiation-induced defects on the transformation to diamond under high-pressure and high-temperature treatment. At 16 GPa, no remarkable change appeared for the irradiated HOPG with increasing the temperature up to 800 °C. At temperatures of 1200 and 1400 °C, hexagonal diamond was formed, along with the formation of cubic diamond. This is probably due to annealing of the irradiation defects that led to partial restoration of the structure to the original HOPG and then enables the formation. On the other hand, in un-irradiated HOPG, hexagonal diamond was formed at 400 °C, which changed to cubic diamond at 1200 °C or higher. We guess that irradiation defects promote the nucleation of cubic diamond in the irradiated sample and then contribute to the formation of isotropic polycrystalline diamond or amorphous diamond.

The molecular orientation and partial density of states were evaluated using NewSUBARU by soft X-ray absorption spectroscopy (XAS) and soft X-ray emission spectroscopy measurements. The degree of molecular alignment was degraded by increasing mesh temperature in hot mesh deposition (HMD), in other words, was changed from pentacene (Pn) to 6,13-dihydropentacene (DHP). At a mesh temperature of 1450 °C, the different XAS was obtained due to the mixing effect of Pn and DHP, and presence of Pn oligomer. The HMD carbon film transformed into the graphite-like film and the graphene on the quartz substrate and the Ni/quartz substrate after soft X-ray irradiation, respectively. The HMD carbon film after soft X-ray irradiation showed the peaks due to terminal carbon such as CH n and COOH in comparison with the reported large graphene sheet. It indicates that the flake size of the graphene on the Ni/quartz substrate was small and had many edges.

The electronic structure of monolayer hexagonal boron nitride grown on Ni by the diffusion and precipitation method was studied by x-ray absorption spectroscopy, emission spectroscopy, x-ray photoelectron spectroscopy and micro-ultraviolet photoemission spectroscopy. No indication of hybridization between h-BN pi and Ni 3d orbitals was observed. That is, the monolayer h-BN was found to be in the quasi-free-standing state. These results are in striking contrast to those of previous studies in which h-BN was strongly bound to the Ni surface by the orbital hybridization. The absence of hybridization is attributed to absence of a Ni(111) surface in this study. The lattice-matched Ni(111) surface is considered to be essential to orbital hybridization between h-BN and Ni.

The inhibition of the contamination of Ru-capped Mo/Si multilayer mirrors was systematically investigated by introducing ethanol into a controlled vacuum that mainly consisted of water vapor. Water vapor was introduced at a pressure of up to 1.3×10-5 Pa, which is a typical pressure in extreme ultraviolet (EUV) lithography production tools. Additionally, ethanol was introduced at several partial pressures ranging from 1.0×10-7 to 3.8×10-5 Pa. At the lowest ethanol pressure, the same degree of reflectance degradation as in the water-only case was observed. However, reflectance degradation was suppressed at ethanol pressures higher than 2.0×10-6 Pa. As a result of surface analyses using X-ray photoelectron spectroscopy, we determined that the reflectance degradation was caused by oxidation. The inhibition of contamination may be caused by a mechanism of a self-limiting carbon layer from ethanol adsorption on a hydroxylated mirror surface. It was found that oxides at the mirror surface were deoxidized by introduced ethanol. Therefore, deoxidization of the Ru layer may be one of the mechanisms of the inhibition of contamination. The suppression of reflectance degradation was independent of the photon intensity and measured for up to 1200 J/mm2. This dose corresponds to about 3 months of operation for projection optics mirrors at the maximum power expected. Therefore, the introduction of ethanol was found to be a promising method for inhibiting the contamination of projection optics mirrors, which are irradiated by a wide range of EUV power.

A new contamination evaluation system that can irradiate high-flux extreme ultraviolet (EUV) and measure, in situ, the reflectivity of multilayer mirrors for EUV lithography (EUVL) projection optics was constructed to develop a contamination inhibition mechanism at the NewSUBARU synchrotron radiation (SR) facility. The vacuum chambers of the systems are all metal sealed. All automatic stages in the system are driven by motors set outside the chambers. The optimum pressure of the chamber was 2 ×10-7 Pa, two orders of magnitude higher than that in the system reported last year. The partial pressure of the hydrocarbon components was also two orders of magnitude smaller than that in the previously reported system. In the first experiment using the system, the lifetime of Si-capped Mo/Si multilayer mirrors was evaluated as a function of water vapor pressure. The system can also be used to measure and map X-ray absorption near-edge structure (XANES) spectra in the irradiated area, which is very important for the in situ evaluation of the contamination mechanism.

Periodic Mo/B4C multilayer films (MLs) for extreme ultraviolet mirrors were deposited by an rf-enhanced plasma magnetron sputtering system with changing the sputtering Ar pressure and layer thickness ratio. Internal stresses in the entire film were measured by Newton's rings method. Microscopic internal stresses in Mo crystallites in Mo/B4C MLs and in Mo single layer film were also determined by wide-angle X-ray diffraction from which lattice spacing in Mo (110) planes was measured. The internal stresses changed from a compressive value of about 1.1 GPa to a tensile value of about 0.6 GPa with increasing Ar pressure from 1.3 to 6.0 mTorr. The transition point of changing the stress from compressive to tensile shifted to lower Ar pressure with increasing the Mo layer thickness ratio. From atomic force microscope observation, the surface roughness of Mo/B4C multilayer films was found to increase monotonically from 0.11 to 0.23 nm (rms) with increasing Ar pressure. We examined the effect of the storage conditions of the films under vacuum, in low-humidity air and in air saturated with water vapor. Deterioration of film quality in Mo/B4C MLs was observed within a few weeks in the samples stored in open air with high humidity.

We have investigated the generation of electrical damage in n-GaN films following treatment in a CF4 plasma, employing capacitance–voltage and steady-state photocapacitance spectroscopy techniques. The effective carrier concentration at depths of 50–150 nm from the GaN surface decreases, probably owing to Ga vacancies (VGa) diffusing into the bulk after being introduced at the surface by ion bombardment. These vacancies consequently form acceptor-type hydrogenated VGa with optical onsets at ~1.79 and ~3.23 eV below the conduction band. In particular, the dominant 3.23 eV level is most likely attributed to (VGa–H2)− species, because the VGa concentration at depth is very low.

The generation behavior of deep-level defects in Ar+-irradiated GaN has been investigated by photoluminescence, capacitance–voltage, and photocapacitance techniques. Ar+ irradiation induces a significant increase in near-band edge emission peak intensity due to donor-bound excitons, in agreement with the largely increased effective carrier concentration in a shallow-lying region near the surface. More interestingly, with increasing irradiation time, the carrier concentration tends to decrease in a deep-lying region, compared with that in the inner bulk region, which is considered to stem from carrier trapping and/or carrier compensation via the diffusion and formation of acceptor-type deep-level defects, such as Ga vacancies and residual C.

Amorphous carbon nanorods were synthesized from hollow multiwalled carbon nanotubes (MWCNTs) by low-energy Ar ion irradiation at room temperature. The obtained nanorods were investigated by Raman spectroscopy, transmission electron microscopy (TEM), soft X-ray photoelectron spectroscopy (XPS), and soft X-ray absorption spectroscopy (XAS). It was found that the diameter of the MWCNTs significantly increased with increasing the fluence. Finally, the original hollow structure and the graphite (002) TEM diffraction spots of MWCNTs completely disappeared and a broadening of Raman spectra occurred, indicating the amorphization of MWCNTs. The increase in the diameter by the irradiation can be explained by the bending and the randomization of the broken carbon hexagonal networks, and the accumulation of knocked-on atoms. The XPS and XAS measurements also support the formation of amorphous carbon nanorods.

Structural analysis by the measurement of carbon K-edge near-edge X-ray absorption fine structure (NEXAFS) using synchrotron radiation was performed on 23 types of silicon-containing diamond-like carbon (Si-DLC) film fabricated by various synthesis methods. In addition, elementary composition in the Si-DLC films was determined by the combination of Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA) using an electrostatic accelerator. In the C K-edge NEXAFS spectra of Si-DLC films, the σ* band shrunk and shifted to the lower-energy side, and the π* peak broadened with increasing silicon content in the Si-DLC film. The observed NEXAFS spectra of Si-DLC films were classified into four types.

We have investigated characteristics of anatase TiO2 thin film surfaces etched by a capacitively coupled radio frequency N2 plasma from the viewpoint of both an experiment and a simulation. The result obtained with use of the N2 plasma is compared with that obtained with use of the He plasma. The experimental O/Ti ratio at the surface etched by the N2 plasma increases as a function of etching time. The increase in the experimental O/Ti ratio is independent of a change in gas pressure. The above-mentioned experimental results agree with the simulation result that the Ti atoms at the surface are preferentially removed by N2+ ions. The experimental O/Ti ratio at the surface etched by the He plasma also increases, which does not agree with the simulation result that the O atoms are preferentially removed by He+ ions. The O-1s XPS spectra of the surface etched by the He plasma show the peak associated with oxygen and water adsorbed by the surface. In the case where the component of the adsorbed oxygen and water in each spectrum is subtracted, the experimental O/Ti ratio at the surface etched by the He plasma shows a decrease. This is consistent with the simulation result. The adsorption of oxygen and water seems to be caused by ambient air. Morphology of the surface etched by the N2 plasma is almost similar to that of the as-grown surface regardless of the changes both in etching time and in gas pressure. In contrast, morphology of the surface etched by the He plasma changes as the etching time increases. This result is independent of the gas pressure.

Mechanically-hard hydrogenated amorphous silicon carbide (a-SiCx:H) films were formed from the decomposition of Si(CH3)4 using the electron-cyclotron resonance plasma flow of Ar. An external radio-frequency (RF) voltage was applied to the substrate with the negative self-bias voltage (−VRF) of 0–100 V. Compositional analysis was made with a combination of Rutherford backscattering and elastic recoil detection analysis. The C/Si ratios of films were 2.2–2.7. Film hardness was measured with a nano-indentation testing equipment. Chemical bonding was analyzed using carbon-K near edge X-ray absorption fine structure (C-K NEXAFS) spectroscopy using an accelerator NewSUBARU. The peak-fitting analysis of the C-K NEXAFS spectra yielded the sp2/(sp2+sp3) ratios, being fully correlated with film hardness. With supported by the IR and Raman spectroscopic measurements, the change of the chemical structure induced by −VRF was discussed.

Damage characteristics of p-GaN surfaces etched by capacitively coupled radio frequency Ar plasma at various gas pressures have been studied in terms of the ultraviolet (UV) light irradiation effect. The UV light corresponding to Ar II is emitted from the plasma at high gas pressures from 50 to 100 mTorr, whereas no UV light is emitted at a low gas pressure of 10 mTorr. The result of the etched p-GaN surface is compared with that of the etched n-GaN surface. The difference between the results of the p- and n-GaN surfaces depends strongly on the gas pressure. Both the experimental N/Ga ratios at the p- and n-GaN surfaces etched at the low gas pressure decrease with increasing etching time. The decreases in the experimental N/Ga ratios agree with the simulation results that N atoms at the p- and n-GaN surfaces are preferentially removed by Ar+ ions. The morphologies of the p- and n-GaN surfaces etched at the low gas pressure are similar to those of the as-grown surfaces. The damage characteristic of the p-GaN surface induced in the absence of the UV light irradiation also appears at the high gas pressures, although the p-GaN surfaces etched at the high gas pressures are irradiated with the emitted UV light. In contrast, both the experimental N/Ga ratios and morphologies of the n-GaN surfaces etched at the high gas pressures change with increasing etching time. The changes in the n-GaN surfaces probably result from the UV light irradiation.

An extreme ultraviolet (EUV) irradiation experiment with the use of single-bunch synchrotron radiation (SR) was carried out to evaluate the optics lifetime for EUV lithography due to contaminations. The sequential change in the reflectivity of Ru-capped Mo/Si multilayer mirrors was measured during EUV irradiation in the presence of hydrocarbon gas or water vapor vacuum environment. The EUV dose dependence of decreases in reflectivity for single-bunch SR was almost the same as that for light-attenuated multibunch SR. From the results, there was no marked difference in the dependence of decrease in reflectivity on pulse structure in the frequency range of 2.5 to 500 MHz.

In order to investigate the analyzing depth of N-K absorption spectra measured using the TEY and TFY methods, the spectra of Si3N4 crystals covered with Cr thin films were measured. The thicknesses of Cr films were 1 – 100 nm. The N-K absorption intensity of Si3N4 measured using the TEY method was observed at Cr thickness of less than 3 nm, while that measured with the TFY method was observed for more than 100 nm. The decrease in the TFY peak intensity was explained by the transmittance of Cr film. The results were applied to estimate the damage depth of plasma-etched GaN crystal. The deformation of the crystal structure in n-GaN etched by Ar plasma was restricted in a shallow region of less than 3 nm from the surface.

A material analysis beamline which is designed to useable in the wide energy range, 50~4000 eV for the various industrial demands, was constructed at BL05 in NewSUBARU for industrial companies' use in cooperation with the Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo and well-informed researchers in the industrial world. BL05 consists of two branch lines, which is mounted with a double crystal monochromator at BL05A and grating monochromator at BL05B. XAFS measurements in the total electron yield mode and partial fluorescence yield mode using a silicon drift detector can be performed at the both branch lines. In addition, the photoelectron spectra can be measured at BL05B. The maintenance and management of BL05 are performed by Synchrotron Analysis LLC (SALLC), which is a consortium of user companies of BL05, under the supervision of the LASTI staff. If industrial users want help with measurements at BL05, operators of SALLC can assist them.

We have investigated the effects of bias voltage and substrate temperature on the growth process of RF-magnetron-sputtered BN films. When the negative bias voltage was higher than 80 V, films including the sp3-BN phase grew even if the substrate temperature was RT. When the substrate temperature and the negative bias voltage were 600 °C and >100 V, respectively, films containing more than 90% sp3-BN phase were grown. The growth process of films deposited at 150 and 600 °C under a constant bias voltage of -100 V was studied by Near edge X-ray absorption fine structure (NEXAFS) measurements. These films consisted of two layers: an sp2-BN phase underlayer and an sp3-BN phase top layer. The sp2-BN underlayer had a preferential orientation of the c-axis parallel to the film surface. The thickness of the sp2-BN underlayer decreased with increasing substrate temperature. High substrate temperatures assisted the nucleation and growth of the sp3-BN phase.

To understand the details of etching-induced damage on a GaN surface, n-GaN crystals were plasma-etched with He and N2 gases. The etched surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) methods. The composition of the surface etched with He plasma changed significantly to being Ga-rich with the N/Ga ratio nearly equaling 0.4–0.5. The ratio of the surface etched with N2 plasma was about 0.6. The shape of the near-edge X-ray absorption fine structure (NEXAFS) of the N-K edge deformed with increasing gas pressure and processing time. The deformation can be explained by the increase in the band widths of a number of peaks in the NEXAFS spectra owing to the increase in the degree of structural disorder in the crystal. The increase in band width for the surface etched with N2 plasma was larger than that for the surface etched with He plasma. The above results can be explained with the model of the elastic energy transfer ratio of He+ and N2 + ions incident on the solid surface.

Controlling defect structure in multiwalled carbon nanotube (MWCNT) is essential to realization of MWCNT devices. Here, we show that the diagram of the Raman intensity ratio of the G to D peaks and the G peak width can reveal two damaging stages of MWCNT films. In a transition period, additional peaks appeared in the X-ray absorption spectra, thereby indicating some significant change in the electronic structure. Also, a remarkable increase occurred in the diameter of the MWCNTs in the latter stage, suggesting the formation of dislocation dipoles which may relate to the change in the properties of field-emission devices.

The characteristics of TiO2 thin film surfaces treated with He and air dielectric barrier discharge (DBD) plasmas at different gas pressures are investigated. There is a difference between the two DBD plasma characteristics: for He-DBD, which is an atmospheric pressure glow discharge (APGD), the breakdown voltage and discharge current hardly change with increasing gas pressure, whereas for air-DBD, which is basically a filamentary discharge, they increase with increasing gas pressure. There is also a difference between the characteristics of TiO2 surfaces treated with the two DBDs. The surface roughness for He-DBD is lower than the roughness of the as-grown surface, whereas that for air-DBD is higher. The surface hydrophilicity for He-DBD is more enhanced than the hydrophilicity of the as-grown surface regardless of UV irradiation. The hydrophilicity for air-DBD is dependent on UV irradiation. It is more enhanced with UV irradiation; it is not improved adequately without UV irradiation.

Diamond like carbon film containing tungsten (W-DLC) was fabricated by focused-ion-beam chemical-vapor deposition (FIB-CVD), and its thermal durability was investigated using near the carbon K-edge X-ray absorption fine structure (C-K NEXAFS) spectroscopy and a combination of Rutherford backscattering and elastic recoil detection analysis, in comparison with those of commercial DLC and W-DLC films. The concentration of W in the films did not decrease when the annealing temperature was increased, while the concentration of H did. The sp2/(sp2+sp3) ratio of carbon atoms in the films increased with annealing temperature. The W-DLC film fabricated by FIB-CVD unchanged after annealing for 32 h at 873 K in vacuum. Its thermal durability was comparable to that of commercially available films.

The surface of an n-GaN crystal etched with an Ar, Kr, or Xe plasma was analyzed by nitrogen K near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS spectroscopy was carried out with the total electron yield (TEY) method in a sample current mode and the total fluorescence yield (TFY) method by measuring the amount of fluorescence using a photodiode. The shapes of the spectra of Ar plasma-etched samples obtained by the TEY method became smooth (blunt) with increasing Ar pressure from 10 to 200 mTorr. However, those obtained by the TFY method did not change with pressure. These results indicate that the etching damage was restricted in the shallow region of less than a few nm from the surface. A change in the NEXAFS spectral shape of Kr or Xe plasma-etched samples was not observed even when measured by the TEY method. This result indicates that the surface damage in Kr or Xe plasma-etched samples was less pronounced than that in Ar plasma-etched samples.

Damage characteristics of TiO2 thin film surfaces etched by capacitively coupled RF He plasmas are found to be dependent on gas pressure and etch time. At a low gas pressure (10 mTorr), the morphology of TiO2 surface etched for 5 min is smooth like the as-grown surface. When the etch time lengthens to 60 min, the surface morphology is smoother. However, the atomic O concentration at the surface is lower than that of the as-grown surface. On the other hand, at a high gas pressure (50–100 mTorr), the He plasma etch causes a rough surface morphology (surface defects) when the etch time lengthens to 60 min.

The effects of thermal annealing of W incorporated diamond-like carbon (W-DLC) films fabricated with focused ion beam chemical vapor deposition (FIB-CVD) were investigated using X-ray absorption fine structure near the carbon K-edge (C-K NEXAFS) and the combination of Rutherford backscattering (RBS) and elastic recoil detection analysis (ERDA). W-DLC films were annealed for 32 h at temperatures, T a, between 673 and 1073 K. Comparing the T a dependences of Ga and H contents obtained from RBS-ERDA and the sp2/(sp2 + sp3) ratios from C-K NEXAFS, it was found that even a trace amount of W incorporation into DLC films fabricated by Ga+ FIB-CVD may cause a significant sp3 →sp2 structural change.

To estimate the optics lifetime of an extreme ultraviolet lithography (EUVL) system with a contaminated mirror surface, it is indispensable to carry out an acceleration test using high-flux EUV irradiation. In this study, Mo/Si multilayer mirrors were irradiated in various vacuum environments using a contamination evaluation system with an undulator light source, and changes in their reflectivity were evaluated. The dependence of the decrease in reflectivity per unit dose on the EUV irradiance was observed in high-flux irradiation experiments in vacuum with water vapor or n-decane gas introduction at pressures lower than about 10-5 Pa. The irradiance dependence disappeared when the pressures were increased for both water vapor and decane gas. A reflectivity distribution with a doughnut shape, namely, high at the irradiation center, low in the surrounding area, and high in the non-irradiated area, was observed in the irradiation experiments during the simultaneous introduction of water vapor and decane gas. These results can be generally explained by the mechanism of the supply-controlled limit.

Surface treatment effect on TiO2 thin films with the anatase phase by dielectric barrier discharge (DBD) air plasmas has been investigated for a variety of gas pressures and treatment times. At a low gas pressure (100 hPa) at which a glow-like discharge plasma occurs, hydrophilicities of TiO2 thin films treated at 5 and 30 min are enhanced compared with that of the as-grown thin film. For the 5 min treatment, this trend is more pronounced probably due to oxygen absorbed on the surface from the air plasma. For the 30 min treatment, the enhanced hydrophilicity is probably due to oxygen vacancy created on the surface by a high fluence of the plasma. When the gas pressure increases to 400 hPa at which a streamer discharge plasma occurs, the hydrophilicity is more weakened than that of the as-grown thin film: the plasma-induced damage occurs regardless of the treatment time. This result would probably result from the higher discharge current and UV light intensity caused by the higher breakdown voltage based on Paschen's law.

The desorption processes of H and Ga from diamond-like carbon (DLC) film synthesized by focused-ion-beam chemical vapor deposition (FIB-CVD) were investigated by elementary analysis and local structure analysis after heat treatment under various conditions. The elementary composition of FIB-CVD DLC film was determined using a combination of Rutherford backscattering spectra and elastic recoil detection analysis spectra. Local structure analysis was performed by the measurement of near-edge X-ray absorption fine structure using synchrotron radiation. Desorption of H from FIB-CVD DLC film by heat treatment was found to comprise two types of process. One is the local graphitization along paths, where residual Ga atoms move by annealing. In this process, Ga acts as a catalyst for the graphitization of DLC. The other process is derived from the graphitization of the whole DLC film by heat, regardless of Ga. In this process, the sp2 content increases considerably.

A high-intensity extreme ultraviolet (EUV) irradiation and reflectivity measurement system was developed in order to add a contamination inhibition mechanism to Mo/Si multilayer mirrors for EUV lithography. The system can irradiate EUV light at a high flux density of 500 mW/mm2, and it can measure the reflectivity change in situ. As a first experiment using this equipment, irradiation on a Si-capped multilayer was carried out. In this experiment, the water vapor pressure was changed, and changes in the reflectivity were examined. As a result, the decrease in reflectivity increased with an increase in the water vapor pressure. In the meantime, it was indicated that the decrease in reflectivity at an equal dose reversed when the irradiation intensity was lowered using a filter. As a result of surface analysis, the Si-capping layer was oxidized in the irradiation area, and there was deposition of C in the outer part of the irradiation area.

We chose Cr and Ta metals as new absorbing materials for extreme ultraviolet lithography (EUVL) reflection masks. The transmittances of EUV light for these metals were calculated to be nearly equal to those for W metal at the wavelength of 13.5 nm. Reflection masks were successfully fabricated from Ta metal films by dry-etching and from Cr metal films by the lift-off technique. The mask contrast was measured using an EUV reflectometer system with a synchrotron radiation source. For the Cr absorber mask, measured peak reflectivities at the reflecting and the absorbing part of the processed patterns were 59% and 4.9%, respectively, and the contrast was about 12. The peak reflectivities at the reflecting and absorbing parts of the processed patterns for the Ta absorber mask were 50% and 0.48%, respectively, and the contrast was about 105. The masks, prepared about one year before the reflectivity measurements and stored in air, exhibited no significant degradation of reflectivity or surface quality. However, a 4% reduction in reflectivity was observed after two years' storage in air, even though the top layer of the Mo/Si multilayer for the masks was Si, which has been reported to prevent oxidation.

The demagnifying optics for extreme ultra-violet lithography (EUVL), which consists of three aspherical mirrors and one plane mirror, is proposed. A resolution of 0.1 µ m can be achieved on a ring field of 26 mm×1 mm in size and the blur size owing to the distortion is small. The assembly tolerance such as decentration tolerance and tilt tolerance is investigated for each of the aspherical mirrors. It is clarified that the assembly accuracy requires 0.0015 degree for the proposed optics.

Mirrors for the imaging optics of extreme ultra-violet lithography (EUVL) systems require highly precise figure processing. We have examined a method of fabricating the aspherical surfaces by deposition. A film of graded thickness is deposited on a spherical substrate using an RF-plasma-enhanced magnetron sputtering system with a deposition mask. The distribution in thickness of the deposited film is close to the designed value, and the method was shown to be feasible for figuring aspherical surfaces. The deposition films for the method are required to have little surface roughness and low residual stress. We have compared the roughnesses and residual stresses in Mo single layer films and Mo/Si multilayer films used in mirrors for soft X-rays. Both values for Mo/Si multilayers were about one order of magnitude smaller than those for Mo single layer films. The roughness of Mo/Si multilayer films almost satisfies the required value for EUVL optics; however, further study is necessary to diminish the residual stress.

The control of polarization of soft X-ray lasers is presented. Double-pass amplification in a soft X-ray laser with a half-cavity comprising a multilayer polarizer and a normal incidence reflector has been tested. Successful results have been obtained using a curved-slab target for the lasing line at 19.6 nm due to the J=0–1 transition of the collisional-excitation neonlike germanium soft X-ray laser.

We investigated the effect of soft X-ray multilayer mirrors on the characteristics of image formation and determined that the phase shift of the X-ray on the mirror plays an important role in image formation as well as reflectivity. Under such a condition that the effect on the characteristics of image formation can be neglected, we designed an optical system that has a resolution of 0.18 µm and 0.25 µm at the wavelength of 5 nm and 13 nm, respectively, and distortion of less than 0.01 µm in a whole exposure field of 20×40 mm2. The necessary surface accuracy of mirrors and tolerance of setting mirrors are discussed.