Xe capillary target for laser-plasma extreme ultraviolet source

A cryogenic Xe jet system with an annular nozzle has been developed in order to continuously fast supply a Xe capillary target for generating a laser-plasma extreme ultraviolet (EUV) source. The cooling power of the system was evaluated to be 54 W, and the temperature stability was +/-0.5 K at a cooling temperature of about 180 K. We investigated experimentally the influence of pressure loss inside an annular nozzle on target formation by shortening the nozzle length. Spraying caused by cavitation was mostly suppressed by mitigating the pressure loss, and a focused jet was formed. Around a liquid-solid boundary, a solid-Xe capillary target (10070 microm phi) was formed with a velocity of < or =0.01 ms. Laser-plasma EUV generation was tested by focusing a Nd:YAG laser beam on the target. The results suggested that an even thinner-walled capillary target is required to realize the inertial confinement effect.     

长春光机所软X射线-极紫外波段光学研究

综述了我所软X射线-极紫外波段关键技术的研究进展。描述了软X射线-极紫外波段光源技术,研制了工作波段为6~22 nm的微流靶激光等离子体光源;介绍了光子计数成像探测器技术,研制出了有效直径为25 mm,等效像元分辨率为0.3 mm的极紫外波段探测器;开展了超光滑表面加工、检测技术的研究,研制了超光滑表面抛光机,加工出高面形精度的超光滑表面,面形精度为6 nm(RMS值),表面粗糙度达0.6 nm(RMS值);进行了软X射线-极紫外波段多层膜技术的研究,研制出13 nm处反射率为60%的多层膜反射镜,150 mm口径反射镜的反射率均匀性优于±2.5%;最后,讨论了软X射线-极紫外波段测量技术研究,研制出该波段反射率计,其测量范围为5~50 nm,光谱分辨率好于0.2 nm,测量重复性好于±1%。在上述关键技术研究基础上,研制出了极紫外波段成像仪和空间极紫外波段太阳望远镜,这些仪器在我国空间科学研究项目中发挥了作用。     

使用感应电荷位敏阳极的极紫外单光子计数成像系统

研制了用于月基极紫外成像相机的二维极紫外位敏阳极光子计数成像探测器原型样机,该探测器系统主要由工作在脉冲计数模式下的微通道板堆、楔条形感应位敏阳极及相关的模拟和数据处理电路组成。设计和制备了周期为1.5mm,有效直径为47 mm的三电极楔条形位敏阳极,研制了最高计数率为200 kHz的前端模拟和数字电路。测量了探测器的暗计数率、脉冲高度分布、增益、线性及空间分辨率等工作特性。测量结果表明,探测器的空间分辨率为7.13 lp/mm(即0.14 mm),满足月基极紫外相机对空间分辨率的要求。     

Present Status of EUV Interferometer Development at the Research Center for Soft X-ray Microscopy

A new interferometer for extreme ultraviolet (EUV) radiation with a laser produced plasma (LPP) laboratory source is under construction. The LPP source is operated with a Sn solid rod target on which pulsed YAG laser is focused to produce high temperature plasma emitting EUV radiation. The source is equipped with a newly designed debris stopper protecting a condenser multilayer mirror from the particle debris of the target. The condenser mirror focuses the light onto an EUV beam - splitter to form transmitted and reflected paths for producing interference fringes of a sharing type. The optical configuration is of a common path based on a triangular path type with a focusing at the beam- splitter, which is enabled to produce fringes by a low coherence radiation with a standard optical quality beam - splitter. The fringes are recorded by an imaging plate with pixels as small as 25μm. The dynamic range of linearity in detection of the EUV light was found to be more than 10^4 with sensitivity of 10^4 photo ns/pixel, enough for the purpose of interferogram recording possibly with one laser shot.     

Xe液体微滴靶激光等离子体光源实验

基于Xe的惰性和在13~14 nm波段高的辐射强度,Xe被认为是极紫外投影光刻(EUVL)潜在的靶材,为此设计和研制了一台液体微滴喷射靶激光等离子体(LPP)极紫外光源。详细地研究了Xe液体微滴喷射靶的光谱辐射特性、在13.4 nm的激光-EUV转换效率、辐射稳定性及碎屑产生状况。实验结果表明,Xe在13.4 nm的最高转换效率可以达到0.75%/2πsr/2%bw,辐射稳定性±4%(1σ),在激光打靶10⁵次后无碎屑产生。     

A 9 keV electron-impact liquid-gallium-jet x-ray source

We demonstrate a high-brightness compact 9 keV electron-impact microfocus x-ray source based on a liquid-gallium-jet anode. A approximately 30 W, 50 kV electron gun is focused onto the approximately 20 ms, 30 mum diameter liquid-gallium-jet anode to produce an approximately 10 microm full width at half maximum x-ray spot. The peak spectral brightness is >2 x 10(10) photons(s mm(2) mrad(2)x0.1% BW). Calculation and experiments show potential for increasing this brightness by approximately three orders of magnitude, making the source suitable for laboratory-scale x-ray crystallography and hard x-ray microscopy.     

极紫外波段空间相机的辐射定标

考虑极紫外波段空间相机尚无合适的辐射定标方法和装置,本文提出了适用于该波段的小目标成像辐射定标方法并基于该方法在实验室建立了辐射定标装置。提出的标定方法首先使用标准传递探测器标定小目标的辐射亮度;然后,用待定标相机中心视场对该小目标成像,获得中心视场部分的辐射强度响应度;最后,通过调整转动结构使不同视场对该小目标成像,得到不同区域的辐射强度响应度。构建的辐射定标装置由光源系统、标准传递探测器、真空罐及四维运动转台等组成。光源系统包括空心阴极光源、极紫外掠入射单色仪、准直反射镜,能够出射工作波段的准直光束;标准传递探测器标定出光束照度并计算得到小目标的辐射强度;运动平台使相机能够以不同视场角对小目标成像,测得不同视场的辐射强度响应度。利用该装置对一台极紫外相机进行了辐射定标实验,并进行了误差源分析。实验结果表明该装置的定标精度优于15%,能够实现整机状态下的辐射定标。     

小型的高精度软X射线-极紫外反射率计

针对探月二期工程中的有效载荷之一极紫外相机中的多层膜光学元件高精度反射率测量的需要,建立了一台使用液体靶激光等离子体光源的小型软X射线-极紫外波段反射率计。该反射率计主要由激光等离子体光源、Mcpherson 247动狭缝掠入射单色仪及相关的数据采集系统组成。单色仪波段范围1-125nm,光谱分辨率小于0.08nm。无碎屑的液体靶激光等离子体光源的使用避免了光学元件的损坏,而动狭缝掠入射单色仪的使用则提高了光谱分辨率和波段范围。使用该反射率计实测了工作波长为13.5nm和30.4nm的Mo/Si多层膜的反射率,测量结果表明测量重复性优于±0.5%。     

Z(eff) measurement using extreme ultraviolet bremsstrahlung emission in LHD

Radial profile measurement of Z(eff) using visible bremsstrahlung (5300 A?) in the Large Helical Device (LHD) has often encountered difficulties because the intensity profile was largely deformed by the nonuniform visible bremsstrahlung emissions from the edge ergodic layer surrounding the core plasma. A space-resolved flat-field extreme ultraviolet (EUV) spectrometer has been newly adopted to measure the Z(eff) profile using the EUV bremsstrahlung continuum in the wavelength range of 70-75 A?. The EUV bremsstrahlung intensity profiles have been measured and checked for all the magnetic configurations with totally different magnetic field structures in the ergodic layer of LHD. It is found that the nonuniform bremsstrahlung emission from the thick ergodic layer can be entirely eliminated by use of the EUV emission with relatively high photon energy of 170 eV. As a result, the Z(eff) profile can be successfully measured for most of discharges regardless of magnetic field structures of the ergodic layer. The Z(eff) profiles measured in the EUV range are compared with those measured in the visible range at a magnetic configuration with the thinnest ergodic layer thickness. The result verifies that the use of the EUV bremsstrahlung continuum is an alternative way for the Z(eff) measurement in toroidal plasmas with nonuniform bremsstrahlung emissions at the edge. Typical results from the EUV bremsstrahlung measurement are presented showing a fairly flat Z(eff) profile with error bars of ±14%.     

Experimental investigation of laser-produced-plasma EUV source based on liquid target

1Introduction LPPsourcesholdgreatpromiseasbright sourcesofextreme ultraviolet(EUV)andsoft X rayradiationforapplicationssuchasprojec tionlithography[12],microscopy[3].However,withLPPsource,theapplicabilityisrestricted duetotheemissionsofdebris,whichmaydam agesensitivemetrologycomponentsclosetoLPP source.Toreducethedebris,methodsconcen tratingontwoaspectshavebeenappliedbefore theappearanceofgasandliquidtargets.Oneas pectistoreducetheamountofdebris,theother istointerdictthedebrisfromreaching…     

CO2 laser pulse shortening by laser ablation of a metal target

A repeatable and flexible technique for pulse shortening of laser pulses has been applied to transversely excited atmospheric (TEA) CO(2) laser pulses. The technique involves focusing the laser output onto a highly reflective metal target so that plasma is formed, which then operates as a shutter due to strong laser absorption and scattering. Precise control of the focused laser intensity allows for timing of the shutter so that different temporal portions of the pulse can be reflected from the target surface before plasma formation occurs. This type of shutter enables one to reduce the pulse duration down to ~2 ns and to remove the low power, long duration tails that are present in TEA CO(2) pulses. The transmitted energy is reduced as the pulse duration is decreased but the reflected power is ~10 MW for all pulse durations. A simple laser heating model verifies that the pulse shortening depends directly on the plasma formation time, which in turn is dependent on the applied laser intensity. It is envisaged that this plasma shutter will be used as a tool for pulse shaping in the search for laser pulse conditions to optimize conversion efficiency from laser energy to useable extreme ultraviolet (EUV) radiation for EUV source development.     

A stand‐alone compact EUV microscope based on gas‐puff target source

We report on a very compact desk‐top transmission extreme ultraviolet (EUV) microscope based on a laser‐plasma source with a double stream gas‐puff target, capable of acquiring magnified images of objects with a spatial (half‐pitch) resolution of sub‐50 nm. A multilayer ellipsoidal condenser is used to focus and spectrally narrow the radiation from the plasma, producing a quasi‐monochromatic EUV radiation (λ = 13.8 nm) illuminating the object, whereas a Fresnel zone plate objective forms the image. Design details, development, characterization and optimization of the EUV source and the microscope are described and discussed. Test object and other samples were imaged to demonstrate superior resolution compared to visible light microscopy.     

XUV laser-plasma source based on solid Ar filament

We present a laser driven soft x-ray source based on a novel solid argon filament. The continuously flowing micron-sized filament (diameter approximately 56 microm, flow speed approximately 5 mms) was used as a laser target in order to generate a plasma source of high brightness in the "water window" (2.2-4.4 nm) spectral range. The emission properties of the source were characterized in detail with respect to crucial parameters such as positional and energy stability using an extreme ultraviolet (XUV) sensitive pinhole camera and an XUV spectrometer. The results are compared with an argon plasma based on a gas puff target operated under the same experimental conditions showing an increase of the brilliance by a factor of 84. By changing the capillary geometry from a constant diameter to a convergent shape the flow speed of the filament was significantly increased up to 250 mms, facilitating the operation at higher repetition rates.     

Spectroscopic comparison between 1200 grooves/mm ruled and holographic gratings of a flat-field spectrometer and its absolute sensitivity calibration using bremsstrahlung continuum

A flat-field extreme ultraviolet (EUV) spectrometer with a varied line spacing groove grating (1200 grooves/mm at grating center) has been developed to study the emission spectra from highly ionized medium Z impurities in large helical device (LHD). It covers a wavelength range of 50-500 A using a mechanically ruled grating, which was later replaced by a newly developed laminar-type holographic grating for comparative studies. Differences in spectral resolution, intensities of higher order spectra, and sensitivities of the spectrometer were studied between the two gratings by observing the emission spectra of LHD plasmas. Although the achieved resolution was alike between them, i.e., deltalambda approximately 0.24 A at 200 A, the holographic grating was much superior in suppressing the higher order light than the ruled grating. The relative sensitivity between the two gratings was evaluated using continuum radiation from LHD plasmas. As a result, it was found that the holographic grating has a flat response in the full wavelength range, but the sensitivity of the ruled grating drops sharply below 200 A. A new technique for the absolute calibration of the EUV holographic grating spectrometer was tried by combining the continuum radiation with a branching ratio of C IV lines (3p-3s: 5800 A/3p-2s: 312 A), and an accurate absolute sensitivity has been successfully obtained.     

采用多层膜偏光器的EUV实验室Farady旋光测量装置

开发了用于实验室的ＥＵＶ（５０～７０ｅＶ）波段的Ｆａｒａｄａｙ 旋光测量装置。其中光源采用了激光等离子体光源。起偏器和检偏器均采用了入射角为准Ｂｒｅｗ ｓｔｅｒ角的反射式Ａｌ／ＹＢ６多层膜。利用４ 块Ｓｍ －Ｃｏ 永久磁铁在被测样品处生成了０．８２Ｔ的磁场。对强磁材料Ｎｉ的Ｍ２,３吸收端进行了Ｆａｒａｄａｙ 旋光测量,测量结果在６５．３ｅＶ处为－ ２．７°／２１ｎｍ 。该结果与我们在同步辐射光源上测量的结果相符合。这是ＥＵＶ 波段首次利用激光等离子体光源成功进行的磁光效应测量实验。     

Laser scanning confocal microscopy characterization of water repellent distribution in a sandstone pore network

In the present work, we propose the use of the Laser Scanning Confocal Microscopy (LSCM) to determine the effect of water repellents on rock's pore-network configuration and interconnection. The rocks studied are sandstones of Miocene age, a building material that is commonly found in the architectural heritage of Tunisia. The porosity quantitative data of treated and untreated samples, obtained by mercury porosimetry tests, were compared. The results show a slight decrease in total porosity with the water repellent treatment, which reduced both microporosity and macroporosity. This reduction produced a modification in pore size distribution and a shift of the pore access size mode interval toward smaller pore diameters (from the 30-40 microm to the 20-30 microm intervals). The water repellent was observed in SEM images as a continuous film coating grain surfaces; moreover, it was easily visualized in LSCM, by staining the water repellent with Epodye fluorochrome, and the coating thickness was straightforwardly measured (1.5-2 microm). In fact, the combination of mercury intrusion porosimetry data and LSCM observations suggests that the porosity reduction and the shift of the pore diameter mode were mainly due to the general reduction of pore diameters, but also to the plugging of the smallest pores (less than 3-4 microm in diameter) by the water repellent film. Finally, the LSCM technique enabled the reconstruction of 3D views of the water repellent coating film in the pore network, indicating that its distribution was uniform and continuous over the 100 microm thick sample. The LSCM imaging facilitates the integration and interpretation of mercury porosimetry and SEM data.     

Efficient Kalpha x-ray source from submillijoule femtosecond laser pulses operated at kilohertz repetition rate

We report an efficient Cu K(alpha) x-ray source produced by focusing submillijoule, 120 fs Ti:sapphire laser pulses on a solid copper target to a spot diameter of few microns. The experimental results show strong emission of K(alpha) x-rays from solid targets from microplasmas created by p-polarized 0.2-0.3 mJ laser pulses at 1 kHz repetition rate. We have demonstrated K(alpha) x-ray point source emission rates of 6.7 x 10(9) photonss into 2 pi sr at 1 kHz repetition rate. The source has an x-ray conversion efficiency into Cu K(alpha) line emission of 3.2 x 10(-5). The source has a measured size of approximately 8 microm. Such a high repetition rate K(alpha) x-ray source can be very useful for time resolved x-ray diffraction and radiographic applications.     

Development of Debris-free Laser Plasma Sources for EUV Lithography in CIOMP

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｌａｓｅｒ - ｐｒｏｄｕｃｅｄｐｌａｓｍａ (ＬＰＰ)ｉｓａｎａｔｔｒａｃ ｔｉｖｅｔａｂｌｅｔｏｐＥＵＶｓｏｕｒｃｅｆｏｒａｐｐｌｉｃａｔｉｏｎｉｎＥＵＶｌｉｔｈｏｇｒａｐｈｙｄｕｅｔｏｉｔｓｓｍａｌｌｓｉｚｅ ,ｈｉｇｈｐｅａｋｐｏｗｅｒａｎｄｓｐａｔｉａｌｓｔａｂｉｌｉｔｙ .Ｈｏｗｅｖｅｒ,ｔｈｅｃｏｎｖｅｎｔｉｏｎａｌＬＰＰｓｏｕｒｃｅｗｉｔｈｍｅｔａｌｔａｒｇｅｔｈａｓａｓｅｒｉｏｕｓｄｉｓａｄ ｖａｎｔａｇｅｏｆｅｊｅｃｔｉｎｇｈｉｇｈ -ｔｅｍｐｅｒａｔｕｒｅａ…     

Absolute intensity calibration of flat-field space-resolved extreme ultraviolet spectrometer using radial profiles of visible and extreme ultraviolet bremsstrahlung continuum emitted from high-density plasmas in Large Helical Device

A precise absolute intensity calibration of a flat-field space-resolved extreme ultraviolet (EUV) spectrometer working in wavelength range of 60-400 ? is carried out using a new calibration technique based on radial profile measurement of the bremsstrahlung continuum in Large Helical Device. A peaked vertical profile of the EUV bremsstrahlung continuum has been successfully observed in high-density plasmas (n(e) ≥ 10(14) cm(-3)) with hydrogen ice pellet injection. The absolute calibration can be done by comparing the EUV bremsstrahlung profile with the visible bremsstrahlung profile of which the absolute value has been already calibrated using a standard lamp. The line-integrated profile of measured visible bremsstrahlung continuum is firstly converted into the local emissivity profile by considering a magnetic surface distortion due to the plasma pressure, and the local emissivity profile of EUV bremsstrahlung is secondly calculated by taking into account the electron temperature profile and free-free gaunt factor. The line-integrated profile of the EUV bremsstrahlung continuum is finally calculated from the local emissivity profile in order to compare with measured EUV bremsstrahlung profile. The absolute intensity calibration can be done by comparing measured and calculated EUV bremsstrahlung profiles. The calibration factor is thus obtained as a function of wavelength with excellent accuracy. It is also found in the profile analysis that the grating reflectivity of EUV emissions is constant along the direction perpendicular to the wavelength dispersion. Uncertainties on the calibration factor determined with the present method are discussed including charge-coupled device operation modes.