[Show abstract][Hide abstract] ABSTRACT: Abstract. Actinic mask defect inspection and metrology requires high-brightness extreme-ultraviolet (EUV) sources. The self-absorption of radiation limits the in-band EUV radiance of the source plasma and makes it difficult to attain the necessary brightness and power from a conventional single unit EUV source. One possible solution is through multiplexing of multiple low etendue sources. NANO-UV is delivering a new generation of EUV light source, the CYCLOPS, in which a micro-plasma-pulsed discharge source is integrated to a photon collector based on an in situ active plasma structure. The source module is characterized by high brightness, low etendue, and high irradiance at moderate output power without the use of external physical optics. Such a source could form the basic building block of EUV source through spatial-temporal multiplexing of several units to deliver the brightness and power required for actinic mask metrology. We report on the EUV source development including the extensive numerical modeling, which provided the basic parameters required for high irradiance operating regimes. A new Sn-alloy cathode material enhances the output. Based upon the multiplexing concept, a family of specially configured multiplexed source structures, the HYDRA design, is being introduced to address the mask metrology needs.
Full-text · Article · Apr 2012 · Journal of Micro/ Nanolithography, MEMS, and MOEMS
[Show abstract][Hide abstract] ABSTRACT: Soft x-ray microscopy is an attractive tool for the study of biological
samples in-vitro, due to the penetrating nature of x-rays and the
natural contrast which can be achieved in hydrated samples. There has
been a roadblock to the commercialisation and rollout of small,
laboratory scale, x-ray microscopes for use in the wider community, as
high resolution x-ray microscopy requires tuneable, high brightness
x-ray sources. NANO-UV has engaged in a product development programme to
introduce the first affordable stand-alone compact soft x-ray microscope
for in-vitro studies, known as McXI. The initial specification of McXI
is to provide 100 nm resolution on in-vitro specimens, with a unique
wavelength selection mechanism in the 2.3-4.4 nm region.
[Show abstract][Hide abstract] ABSTRACT: The roll out of EUV lithography for HVM, including the associated tools for actinic mask and mask blank defect inspection, require reliable and powerful EUV radiation sources. NANO-UV has developed a unique EUV/soft X-ray source, the CYCLOPSTM, based on a fast, micro-plasma pulsed discharge, incorporating the i-SoCoMoTM technology; an intrinsic plasma structure to provide photon collection and delivery. We report on the EUV light source development, including the extensive numerical modelling which provided the basic parameters required for high power or high irradiance operating regimes. Without using external physical optics, a peak irradiance exceeding 1018 ph/cm2/s, in a 3 nm bandwidth around 13.5nm, has been recorded at a distance 74 cm downstream from the source, which was operating at 1 kHz in a He:N2:Xe gas admixture at up to 0.5J per pulse operation. A new Sn-alloy cathode material has enhanced the output by a factor of 1.5 with the power now delivered in a sub-cm size spot being greater than 20W in 3nm band, with a typical étendue below 10-2 mm2•sr. NANO-UV can meet the HVM source requirements with its HYDRATM spatial/temporal multiplexed source development. A multiplex of 12 units form HYDRATM -12P having the potential of reaching 240W (within 3 nm EUV band) at IF demonstrates multiplexing principle.
No preview · Article · Mar 2011 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: EUV sources for actinic mask metrology, particularly for defect inspection, require extremely high brightness. The selfabsorption of radiation limits the in-band EUV radiance of the source plasma and makes it difficult to attain the necessary brightness and power from a conventional single unit EUV source. One possible solution is through multiplexing of multiple low etendue sources. NANO-UV is delivering a new generation of EUV light source with an intrinsic photon collector, the i-SoCoMo™ concept, where a micro plasma pulsed discharge source is integrated to a photon collector based on an in situ active plasma structure. The source is characterized by high brightness, low etendue and very high irradiance, at moderate output power, without the use of external physical optics. Such a source could form the basic building block, through multiplexing of several units, to satisfy the very high brightness and moderate power requirement of the EUV sources required for actinic mask metrology. Based upon this multiplexing concept, a family of specially configured multiplexed source structures, the HYDRA™ design, is being introduced to address the mask metrology needs.
No preview · Article · Mar 2010 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: EUVL solution for HVM at the 22 nm node requires a high power long-term EUV source operation with hundreds of watts at the intermediate focus output. EUV mask blank and mask defects inspections require at-wavelength tools with high brightness. Theoretical analysis with a 2-D radiation MHD code Z* has been performed to address key issues in EUV plasma sources with radiation transfer. The study shows that self-absorption defines the limiting brightness of a single EUV source, which cannot meet the requirements of the HVM tool with high efficiency and is not sufficient for critical metrology applications, given the limiting etendue of the optics. It is shown that the required irradiance can be achieved by spatial multiplexing, using multiple small sources. We present here details of the study, as well as experimental results from a novel EUV light source with an intrinsic photon collector demonstrating high brightness, the i-SoCoMo concept, where an impulse micro discharge plasma source is integrated to a photon collector based on an active plasma structure. The small physical size and low etendue properties of the i-SoCoMo unit allows a large number of such sources to be put together in one physical package and be operated in a multiplexed fashion to meet necessary power requirements.
[Show abstract][Hide abstract] ABSTRACT: A new technique capable of obtaining quantitative values of the rotation angle of the polarization vector by using holography is presented. This is a two-stage holographic process; during the recording stage a hologram of the object of interest is obtained. The reference beam is composed of two beams that form a small angle between them and keep their polarization states at right angles to each other. In the reconstruction stage of the hologram, two images from the hologram are obtained along two different angles. As a result of the interference between these two images, a set of parallel fringes is formed at the image plane. The fringe contrast on the reconstruction is related to the angle of the polarization vector of the light at each position on the image plane. Measurements of the rotation of the polarization angle of a fraction of a degree were obtained. The main application of this technique is in the study of transient phenomena, where single-shot measurements are the only means of obtaining reliable data.
[Show abstract][Hide abstract] ABSTRACT: Experiments with two different configurations of dense z‐pinches have been carried out on the Llampüdkeñ
generator with the objective of investigating the time evolution of the discharges. These configurations were studied with refractive optical measurements using the second harmonic of a Nd:YAG laser (10 ns FWHM, λ=532 nm). The Llampüdkeñ
generator delivered a pulse current of 450 kA with a 260 ns rise time. Refractive optical measurements with schlieren
diagnostics were made using an optical system which provided two frames per discharge. The original beam was split into two separate beams with perpendicular polarizations using a polarizer
beam splitter and an extra path length was introduced into one of the beams delaying it with respect to the other. The path through the discharge chamber was equal for both beams therefore providing identical views of the plasma at two different times. The images were recorded on 35mm cameras using suitably orientated polarizers to select the corresponding beam. As a complementary diagnostic technique, MCP cameras with exposure time of 2 ns were used to obtain VUV images of the loads. Preliminary results of these experiments will be presented and discussed.
[Show abstract][Hide abstract] ABSTRACT: An experimental study of the effect of the initial radius on the formation of hollow gas embedded z-pinches is presented. These hollow pinches are formed using a ring precursor plasma generated by focussing a 10ns, 0.2J, 1064nm, Nd:YAG laser pulse onto the cathode surface. The laser pulse is focussed into a ring shape, by using a combination of a converging lens and an axicon. Ring radius variation give place to different initial radius of hollow z-pinches. The experiments were carried out on the Gepopu generator at 110kA, 50ns rise time using flat electrodes. The anode had a central hole, allowing the laser to be focussed onto the cathode surface. Experiments were performed in hydrogen at 1/3 of atmosphere. Schlieren and interferometry are the main plasma diagnostics using the second harmonic of the same laser. Comparison between initial radius of 2 and 3mm are presented, where electron densities on the order of 1018 cm-3 were measured in both cases. Temperature estimates using Bennett relation are of 185 eV and 75 eV respectively. Pinch effect was observed for current density ~ 5MA/cm2.
[Show abstract][Hide abstract] ABSTRACT: The Plasma Physics Group at Pontificia Universidad Católica de Chile (PUCC) has been investigating z‐pinch like plasmas for the last twenty years. Here we present experimental observations on a variety of z‐pinch like plasmas, using a range of very small to medium size pulse power drivers. The experiments include low and high current capillary discharge,
plasma focus pinch, hollow gas embedded z‐pinch, x‐pinch and wire‐array pinch. Different diagnostics are used to characterize the plasma dynamics and radiation properties of the different z‐pinch plasma, as well as the emission of plasma jets and ion beams.
[Show abstract][Hide abstract] ABSTRACT: A method to produce ring plasmas on a metal surface is presented. The ring plasma is produced by focusing a laser pulse into an annular shape. This is achieved by using a combination of a converging lens and an axicon. The axicon is a rotationally symmetric prism. The radius of the focused ring is determined by the base angle of the axicon, and the focal length of the converging lens. The experiments are performed on a titanium surface, using a 0.18 J, 10 ns, 1064 nm pulsed, from a Nd:YAG laser. The background gas is hydrogen, at pressures in the atmospheric range. The ring structure was measured using schlieren imaging and Mach Zehnder interferometry. The expansion velocities of the laser-produced plasma in the background gas were measured in two directions; parallel and perpendicular to the metallic surface. Characteristic values are 5-9.103 m/s, for the ring radius expansion, parallel to the surface, and 1.0-1.7.104 m/s, perpendicular to the surface. Characteristic electron densities of the order of 1018 cm-3 were measured, with hollow radial profiles. The temperature of the plasma was estimated to be between 0.1 and 0.4 eV. This ring plasma is used as precursor plasma to achieve a hollow gas embedded z-pinch.
[Show abstract][Hide abstract] ABSTRACT: A new technique is presented for the formation of annular plasmas on a metal surface with a high-power laser using a combination of axicon and converging lenses. The annular plasma formed on a titanium target in a chamber of hydrogen gas was investigated using schlieren imaging and Mach Zehnder interferometry. Expansion of the plasma was shown to be anisotropic with velocities of ∼ 103–104 m/s. Electron densities of 1018 cm−3 were measured with radial profiles that confirm the presence of a hollow structure. The interferometric observations also show the presence of an inward shock wave traveling to the center of the annular plasma, which compresses the background neutrals, reaching a density around 18 times initial gas density, at 95 ns after the initial annular plasma is produced.
Full-text · Article · Jun 2006 · Review of Scientific Instruments
[Show abstract][Hide abstract] ABSTRACT: We report observations of the formation of a metallic plasma in a high aspect ratio z-pinch confined within a ceramic capillary. A series of experiments on different capillary geometries was undertaken in which titanium metal rings were used to promote the formation of a titanium plasma through preferential ablation. In an initial vacuum a titanium seed plasma is formed in the hollow cathode (HC) volume by a low energy laser spark. This pre-ionizing plasma is assisted in its expansion into the z-pinch volume by the electron beams generated by a pre-ionizing discharge in the capillary, due to the HC effect. Further intense e-beam activity occurs on applying the main driver current to the capillary electrodes before the discharge impedance abruptly drops to give rise to an ensuing high current z-pinch. A segmented titanium ring structure within the capillary promotes metal ablation. The discharges are performed in tubes of 60 to 110 mm length and 3 and 5 mm effective internal diameter. The main discharge current is provided from a small pulsed power switched coaxial line, at up to 150 kA. The generator may be configured to deliver two different rates of current rise and this is found to have a significant effect on the plasma dynamics. The plasma properties are obtained from observations of the axial x-ray emission. The diagnostics used are filtered Si diodes, filtered time-resolved multi-pinhole camera images and the time resolved soft x-ray spectrum from 3 to 20 nm. While a single species metal plasma is not obtained, a very significant proportion of Ti is achieved in the higher rate of current rise configuration. The fraction of Ti diminishes for the longest length discharges and for the larger diameter tube diameter, as does the observed z-pinch uniformity. There is a weak dependance of the electron temperature with tube geometry, but the plasma density falls substantially in the longer discharges. This coincides with diminished effectiveness of the transient HC.
No preview · Article · Jun 2006 · Plasma Sources Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Fast Fourier transform and wavelet analysis methods were used to denoise electrical signals by a soft thresholding technique. A neutron pulse of 14 MeV is sent over a sample; as a consequence of the interaction between the sample and the neutrons, multi-spectral gamma rays are emitted by the sample. The gamma-rays were measured using three photo multiplier tubes, which detect optical signals coming from three filtered detectors made of plastic scintillator material. Applying wavelet analysis was possible to realize that the signal can be divided into three different regions. Each region has different thresholds; therefore, different frequency components can be used independently in each region. Comparisons of this method with the fast Fourier transform are presented. In this particular application, it was found that the wavelet transform produces a much better way of denoising the signals in terms of keeping the characteristic high frequency at the start of the signals; this feature allows the differential classification of the signals and the consequent identification of the component of the sample. The preliminary results presented here are the first attempt to identify the chemical composition of samples using this method.
No preview · Article · Feb 2006 · Measurement Science and Technology
[Show abstract][Hide abstract] ABSTRACT: The development of a pulsed corona discharge ionization source and its use in ion mobility spectrometry (IMS) is presented. In a point-plane electrode geometry, an electrical pulse up to 12 kV, 150 ns rise time and 500 ns pulse width was used to generate a corona discharge in air. A single positive high voltage pulse was able to generate about 1.6×1010 ions at energy consumption of 22 μJ. Since the temporal distribution of ions is in a pulsed form, the possibility of removal the ion gate has been investigated. By purposely arranging the interface between discharge field and drift field, nearly 107 positive ions were drawn into the drift region with absence of the ion gate after every single discharge. The positive spectrum of acetone dimer (working at room temperature) was obtained with a resolving power of 20 by using this configuration. The advantages of this new scheme are the low power consumption compared with the dc method as well as the simplicity of the IMS cell structure.
[Show abstract][Hide abstract] ABSTRACT: Results obtained from aluminium wire x-pinch experiments at a current level of ~400 kA, 260 ns risetime, are presented. The x-pinches were made from two 125 µm diameter wires. The x-pinches typically emitted 15 J of K-shell x-rays in nanosecond duration pulses from hot spots of diameters of ~10 µm or less. Frequently several hot spots were formed in a single discharge. Spectroscopic measurements estimate an electron temperature of about 600 eV. Spatial resolution of typically 10 µm was obtained in radiographic images. Details of the dynamics of the pinch were obtained from time resolved soft x-ray frames, showing formation of the plasma jet due to the coalescence of the expanding corona plasmas from the x-pinch limbs and ejection of plasma in the direction perpendicular to the x-pinch axis when hot spots were formed.
Full-text · Article · May 2005 · Plasma Sources Science and Technology
[Show abstract][Hide abstract] ABSTRACT: The results from a series of experiments are presented whose purpose is to explore different schemes which may lead to the formation of pure metal plasmas in a capillary discharge with parameters appropriate for X ray lasing. The experiments were performed in ceramic wall capillary discharges at currents of up to 120 kA, with an available ID of between 3 and 8 mm and with lengths from 60 to 100 mm. Initial plasma conditions in the capillary exploit transient hollow cathode effects in a preionizing discharge. A laser focused onto the back surface of the cathode initiates both beam activity in the capillary volume and plasma injection. To promote metal ablation into the pinch channel of elements other than the ceramic wall material, a number of graded ring schemes have been tried. The plasma is observed axially using both time and energy resolved soft X-ray pin hole images as well as from time resolved soft X-ray spectra. By varying the rate of rise of the current of the main discharge, and the preionizing conditions the diameter and the stability of the Z-pinch column are seen to be affected. The ratio of the species from the ablated wall material to the plasma formed from the graded ring structure is found to depend both on the capillary dimensions as well as the other operating conditions.
[Show abstract][Hide abstract] ABSTRACT: Results of new optical method of generating a precursor plasma for a shell gas embedded Z-pinch are presented. Experiments were performed on a pulse power generator using a peak current up to 150 kA with a rise time of 70 ns, 120 ns pulse length. The optical precursor plasma was generated by using a Nd-Y AG laser, 200 ml, 8 ns at 1.06 µm. Two different optical schemes were used, one consists of a combination of lenses capable of producing a hollow beam; while the other uses an axicon to generate the hollow beam. In both cases the hollow beam was focused at the cathode surface where metallic ring plasma, of either 2 or 6 mm diameter, is created. The annular preionization is created immediately before or during the first 30 ns after the line voltage is applied. The discharge was carried out in a chamber filled with hydrogen gas at 1/3 atm. Flat electrodes were used with 10 mm separation. The anode has a 6 mm diameter central hole to allow the passage of the preionizing laser. Optical diagnostics (schlieren, shadowgraphy and interferometry) were performed using the second harmonics of the same laser used to preionize. Preionizing using an axicon results in better formed hollow discharges.
[Show abstract][Hide abstract] ABSTRACT: Llampüdken~  is a pulsed power generator designed to deliver a 1 MA, 250 ns risetime current pulse into a dense plasma load. The main novel feature of this generator is the two auxiliary transmission lines which transmit the energy not absorbed by the load, reflect it at the open end of the line and deliver it to the load when the energy from the main lines is decreasing. With the auxiliary lines an increase of 30% on the current as well as a decrease of the voltage at the load is obtained. To date Llampüdken~ has been operated up to the 400 kA level, into both short circuit and plasma loads. Details of actual performance of the pulse power generator are presented and compared with simulations.
[Show abstract][Hide abstract] ABSTRACT: A small pulsed power generator, 150 kA and 120 ns, is used to form
a plasma in a 5-mm diameter alumina ceramic tube. A hollow cathode
geometry is used and a preionized plasma is formed in an initial vacuum
background by focussing a pulsed Nd:YAG laser onto a metallic target in
the hollow cathode volume. The evolution of the preionizing plasma and
its expansion into the main discharge volume may be assisted by applying
a current of order Amps for a variable time before the main discharge
current is applied. Strong electron beams are observed both during the
preionizing stage and during the start of the main current. The plasma
species and temporal evolution during the main discharge is observed
using X-ray spectroscopy and X-ray pinhole imaging. On varying the rate
of rise of the current in the pinching phase, the transient hollow
cathode effect was found to be significant at early times in the
discharge in the case of the lower value of dI/dt. Both the pinch
temperature and diameter depend on varying the dI/dt from 1.5 to 3
× 10<sup>12</sup> A/s. The implications of plasma injection for
metal vapor capillary discharges are discussed
Full-text · Article · Mar 2002 · IEEE Transactions on Plasma Science