bluuebunny/crossref_metadata_2025 huggingface dataset:
In-vivo Pharmacokinetics of δ-ALA induced PPIX during Photodynamic Therapy on mice tumor model
Authors: Parmeswaran D. , Aruna P. , Gupta P.K. , Ganesan S.
Published: February 2023

In the recent years δ-aminolevulinic acid (δ-ALA) a precursor for the endogenous production of protoporphyrin IX (PPIX) has gained importance in the Photodynamic Therapy (PDT) of superficial and early-stage cancers. Though δ-ALA is present naturally in the cells, systemic administration of exogenous δ-ALA leads to the production of intracellular endogenous PP IX in both the tumor and the normal cells, but with varying concentration. However, the PPIX is accumulated more in the tumor tissues as the fast growing tumor cells take up the administered δ-ALA more than the normal cells. As the therapeutic efficacy of PDT is dependent on the post δ-ALA incubation time, at which the tumor to normal ratio of the PPIX concentration is high, the concentration of the PPIX in the normal and the tumor site were estimated using fluorescence spectroscopy. However, the estimation of the PPIX concentration during/after PDT is mandatory, as the PDT dosimetry is dependent on the sensitizer concentration at the target of interest. The observed variation in the concentration of PPIX in the tumor site with respect to the unexposed normal surrounding tissues, may be attributed to the diffusion of PPIX from the surrounding normal tissues to the tumor site, across the concentration gradient. Based on this a mathematical model has been proposed, to estimate the rate parameter for the diffusion of PPIX from the surrounding normal tissues in to the tumor tissue (Km), due to photobleaching during PDT at two different fluence. The Km value at two different fluences, 57.6 and 36 J/cm2 are estimated as 5.444 ± 1.186 and 3.221 ± 0.957, respectively. Further, the rate parameter for the cleavage and efflux of δ-ALA (Kl), and the rate parameter for the evasion of the PPIX from the tumor tissues during PDT (Kt), were also estimated by fitting the experimental data to the developed mathematical model. The estimated parameters will be utilized to estimate the exact concentration of PPIX in the tumor tissues for a better PDT efficacy.
Laser generated micro- and nanoeffects: inactivation of proteins coupled to gold nanoparticles with nano- and picosecond pulses
Authors: Radt Benno , Serbin Jesper , Lange Björn I. , Birngruber Reginald , Hüttmann Gereon
Published: February 2023

Background: Protein denaturation in the fs-ns time regime is of fundamental interest for high precision applications in laser tissue interaction. Conjugates of colloidal gold coupled to proteins are presented as a model system for investigating ultrafast protein denaturation. It is expected that irradiation of such conjugates in tissue using pico-up to nanosecond laser pulses could result in effects with a spatial confinement in the regime of single macromolecules up to organelles.

Materials and Methods: Experiments were done with bovine intestinal alkaline phosphatase (aP) coupled to 15 nm colloidal Gold. This complex was irradiated at 527 nm/ 532 nm with a variable number of pico- and nanosecond pulses. The radiant exposure per pulse was varied from 2 to 50 mJ/cm2 in the case of the picosecond pulses and 10 to 500 mJ/cm2 in the case of the nanosecond pulses. Denaturation was detected as a loss of protein function with the help of the fluorescence substrate 4MUP.

Results and Discussion: Irradiation did result in a steady decrease of the aP activity with increasing radiant exposures and increasing number of pulses. Inactivations up to 80% using 35 ps pulses at 527 nm with 50 mJ/cm2 and a complete inactivation induced by 16 ns pulses at 450 mJ/cm2 are discussed. The induced temperature in the particles and the surrounding water was calculated using Mie’s formulas for the absorption of the nanometer gold particles and an analytical solution of the for heat diffusion. The calculated temperatures suggest that picosecond pulses heat a molecular scaled area whereas nanosecond pulses could be used for targeting larger cellular compartiments.

It is difficult to identify one of the possible damage mechanisms, i.e. thermal denaturation or formation of micro bubbles, from the dependance of the inactivation on pulse energy and number of applied pulses. Therefore experiments are needed to further elucidate the damage mechanisms. The observed inactivation dependencies on applied energy and radiant power can not be explained with one or two photon photochemistry.

In conclusion, denaturing proteins irreversibly via nanoabsorbers using pico-/ nanosecond laser pulses is possible. The expected confinement of the heat to the nanoabsorbers suggests that denaturation of proteins with nanometer precision could be possible with this approach. However, the mechanism of protein inactivation, which is part of present investigations, is crucial for the precision of such nanoeffects.
Photodynamic action on some pathogenic microorganisms of oral cavity
Authors: Ovchinnikov Ilya S. , Tuchin Valery V.
Published: February 2023

The work is devoted to an analysis of pre-clinical and clinical experiments on photodynamic action of HeNe laser radiation in aggregate with a cation thiazinium dye Methylene Blue (MB) on a mix of pathogenic and conditionally pathogenic aerobic bacteria being activators of pyoinflammatory diseases of oral cavity. Concentration of photosensitizes at which there is no own bactericidal influence on dying microflora, and parameters of influence at which the efficiency of irradiated microflora defeat reaches 99 % are determined.
Diode laser osteoperforation and its application to osteomyelitis treatment
Authors: Privalov Valery A. , Krochek Igor V. , Lappa Alexander V.
Published: February 2023

Laser osteoperforation, previously studied in experiment in rabbits at treatment for acute purulent osteomyelitis (Privalov V. et.al., SPIE Proc., v.3565., pp. 72-79), was applied in clinic to 36 patients with chronic purulent osteomyelitis and to 6 patients (children) with acute haematogenic osteomyelitis. Diode lasers of 805 and 980 nm wavelength were used. There was achieved full recovery in all acute cases, and stable remission in chronic cases during all the observation period (1 – 2.5 years).
CN violet -band emission as a time-resolved optical probe of transient temperature, induced by laser ablation of type I collagen from bovine Achilles tendon
Authors: Kompitsas M. , Theodossiou T.
Published: February 2023

The B 2Σ+→X 2Σ+ violet band emission spectrum of CN following laser ablation of type I collagen was exploited for the estimation of the transient temperature of the plasma plume and consequently of the sample surface considering thermodynamic equilibrium. The temperature dependence upon experimental parameters, such as laser intensity and wavelength as well as delay of gated detection was obtained. The temperature was found to increase with increasing laser intensity and decrease with increasing gated time delay and laser wavelength.
Comparison between the traditional and the laser bleaching treatment
Authors: Cesar Ilene C. R. , Redígolo Marcela L. , Liporoni Priscila C. S. , Munin Egberto
Published: February 2023

Fifteen human embedded third molars were used in this in vitro study to evaluate the effects of two bleaching products associated or not with Argon laser application. The samples received a cervical-apical cut and were longitudinally cut into 4 parts resulting in 75 specimens. These parts were divided at random into 5 groups and submitted to the traditional power bleaching procedure for enamel. Group 1 was separated as a control group. Group 2 was exposed to 37 % carbamide peroxide bleaching solution and developed with an Argon laser application. The same solution was used in Group 3 but the bleaching was developed with an halogen lamp irradiation. 35 % carbamide peroxide were used in Groups 4 and 5. One was developed as Group 2 and the other as Group 3. The samples were analyzed under a photoreflectance experiment. We observed that Group 2 presented more white spectra than Group 3. However, Groups 4 and 5 showed the same results independent of the use of the laser or the halogen lamp for the light curing. Comparing both bleaching products, the 35 % carbamide peroxide was more efficient on its purposes than the other one.
PUVB-mediated prevention of luminal narrowing after arterial wall injury: modulation of mechanical arterial properties as a putative mechanism of action
Authors: Perrée Jop , Kerindongo Raphaela P.A. , van Leeuwen Ton G.
Published: February 2023

In a previous study we have found that the photodynamic modality PUVB (8-methoxy-Psoralen + UVB) reduces luminal narrowing after arterial endovascular injury. We hypothesized that PUVB may modulate the arterial mechanical properties and tested this hypothesis by measuring the stress as a function of the strain in segments of carotid artery. Furthermore, we have investigated the potential for PUVB-induced cross-linking of extracellular matrix proteins by gel electrophoresis. It was found that both techniques were suitable for testing our hypotheses as evidenced by a statistically significant difference for the positive control. However, no differences between A) control, B) sensitizer only, C) light only and D) PUVB-treated smaples could be found with respect to macro- and micro-mechanical properties. Therefore, the hypothesis that PUVB mediates its luminal narrowing reduction effect by directly changing the arterial mechanical properties should be rejected.
Interstitial Laser Photocoagulation of Breast Tumours
Authors: Pickard David C. O. , Bown Stephen G. , Briggs Gavin M. , Hall-Craggs Margaret
Published: February 2023

Interstitial Laser Photocoagulation (ILP) is a method of destroying lesions in the center of solid organs without the need for open surgery. Under image guidance, up to four needles are inserted percutaneously into the tumor through which thin optic fibers are passed into the target lesion. Low power laser light from a semiconductor laser is delivered to gently coagulate the tissue. This ‘dead tissue’ is subsequently resorbed by the body’s normal healing processes. Follow up is achieved with ultrasound imaging. One study is described for assessing ILP for benign fibroadenomas. Fibroadenomas were treated to assess how laser treated breast tissue healed in the long term and we have shown that the necrosed tissue is resorbed without complications over a period of months. Nevertheless, by following treated fibroadenomas (up to 35mm diameter) with ultrasound measurement at 3, 6 and 12 months, in 14 patients, only one lesion was still detectable 12 months after ILP. In appropriate cases, ILP could be an attractive option, as it leaves no scars and should not change the shape or size of the breast. If the present studies are successful, the plan is for a multi-center trial of minimally invasive, thermal ablation of breast cancers.
Effects of Low-intensity Laser Irradiation on Animal Antioxidant System
Authors: Tsiunchyck O.S. , Khomich T.I. , Preobrazhensky D.V.
Published: February 2023

The effects of laser irradiation on human and animal organisms have been intensively studied, but the mechanism of this effect is not well understood and discussed on the level of hypothesis. The effect of low-intensity laser irradiation (LILI) depends both on its physical parameters (wavelength, power density, time etc.) and on optical properites of irradiated tissues. The biological response on LILI started from the resonance absorption of irradiation by specific acceptors-enzymes, pigments and other biochemical structures containing in most cases chromophores. At the same time, distribution of absorbed energy between oscillated-excited states of atomic groups of macromolecules with following energy migration takes place too. Such effects induced changes in intensity of lipid peroxidation (LPO) and transitions of cell membrane confirmations with following changes of membrane enzyme activity (adenilate cyclase, ATPase) and ion permeability of membranes [1-3].
Numerical Simulation of Optical Breakdown for Cellular Surgery at Nanosecond to Femtosecond Time Scales
Authors: Vogel Alfred , Noack Joachim
Published: February 2023

We have shown by experimental investigations that cellular surgery (microdissection, optoporation, and optoinjection) with Nd:YAG laser pulses of 1064 nm and 532 nm wavelength relies on nonlinear absorption leading to optical breakdown and plasma formation at the laser focus. The present study explores possibilities of refining the breakdown effects by employing shorter pulse durations and irradiances that generate plasmas below the threshold for shock wave and bubble formation. Optical breakdown in water at NA = 0.9 and NA = 1.3 was simulated numerically for wavelengths of 1064 nm, 532 nm and 355 nm, and pulse durations of 6 ns, 30 ps and 100 fs. We used a rate model that allows the calculation of the temporal evolution of the free electron density
ρ
during breakdown,
ρ (t)
could be followed separately for the free electrons generated by multiphoton ionization and avalanche ionization. We obtained excellent agreement between the calculated and measured threshold values for breakdown with 6-ns pulses. The simulations predict that the energy threshold for cellular surgery can be reduced by a factor of 350-2600 (depending on wavelength) when the pulse duration is reduced from 6 ns to 100 fs. The calculated breakdown energies for 100 fs pulses focused by an objective with NA = 1.3 are 0.6 nJ at 355 nm, 1.6 nJ at 532 nm, and 3.9 nJ at 1064 nm. With ns-pulses at 1064 nm, the breakdown threshold is very sharp, i. e. there is either no effect at all, or a dense plasma is formed causing a micro-explosion. With shorter wavelengths and pulse durations, the threshold is smoother, and electron densities may be produced that stay below the threshold for explosive vaporization and bubble formation. This creates the possibility of achieving highly localized plasma-mediated chemical or thermal changes in the cell. We conclude that both the reduced energy threshold and the smoother breakdown process with fs pulses bear a large potential for the refinement of intracellular surgery.
Interferometric Detection of Laser Induced Microbubbles in the Retinal Pigment Epithelium
Authors: Neumann Jörg , Brinkmann Ralf
Published: February 2023

We developed an interferometric technique in order to detect microbubble formation within porcine retinal pigment epithelial (RPE) cells ex vivo after short pulsed laser exposure (527 nm, 350ns). The irradiated surface of the RPE tissue samples was monitored by a Michelson interferometer. The obtained interferometric transients revealed bubble dynamics and were compared to optoacoustic transients recorded simultaneously. This interferometric technique might be useful for in vivo dosimetry during selective RPE-treatment.
Optical Tracing of Q-switched mid-IR Laser Induced Bubble Formation
Authors: Brendel Tobias , Brinkmann Ralf
Published: February 2023

Q-switched TEM00 thulium laser (λ = 2.01µm, 300 ns FWHM) induced bubble dynamics at a silica-water interface were investigated. In particular, bubble dynamics far above the Threshold Radiant Exposure (TRE) for bubble formation were studied. At this, different silica surfaces (all of standard optical quality) were used, at which particular TREs were measured. Irradiation parameters like pulse duration or beam diameter were kept constant. As reported recently,1 every silica surface provides different nucleation sites for bubble formation and thus shows a specific TRE. By means of a sensitive optical detection device bubble lifetimes at the interface were monitored as a function of radiant exposure. Measurements were performed with maximum radiant exposures of 330 mJ/mm2 on four different silica surfaces. The TREs of the surfaces were preliminarily determined to lie between 38 mJ/mm2 and 95 mJ/mm2. Above 150 mJ/mm2, bubble lifetimes were measured to be independent of the surface used and its particular TRE. An explanation for this behavior was found by fast flash photographs of the onset of bubble formation, revealing vanishing differences in the heterogeneous nucleation with increasing radiant exposure.
Irradiation with a diode at 820 nm induces changes in circular dichroism spectra (250–780 nm) of living cells
Authors: Karu Tiina I. , Kolyakov Sergei F. , Pyatibrat Ludmila V. , Mikhailov Evgenii L. , Kompanets Oleg N.
Published: February 2023

A sensitive method for measuring the circular dichroism (CD) of living cells in visible-near IR region is developed. The changes in CD spectra from 250 to 780 nm of HeLa cell suspension after the first and second irradiation at 820 nm in dose 9 J/cm2 are investigated. The CD spectrum of the intact cells is well structured and characterized by a positive signal in the UV (250-290 nm) and visible-near IR (500-780 nm) regions as well as by a negative signal in 300-450 nm region. Distinct maxima in the visible-near IR region are recorded at 566, 634, 680, 712, and 741 nm. As a rule, the peak circular dichroism signals decrease in the irradiated cells except of the area 750-770 nm. Peak positions (exception: the peak at 680 nm) shift as a rule to the long-wavelength direction. The most remarkable changes in peak positions as well as in CD signals are recorded in the region 750-770 nm: an appearance of the new peak at 767 nm after the first irradiation and its shift to 752 nm after the second irradiation. The peaks at 712 and 741 nm disappear after the irradiation. A new peak appears at 601 nm. It is assumed that the changes in the degree of oxidation of the chromophores of cytochrome c oxidase caused by the irradiation are accompanied by conformational changes in their vicinity. It can be suggested that these changes are occurring in CuB environment.
A Shack-Hartmann-Sensor based Aberrometer for Ophthalmic Diagnostics
Authors: Weidner Frank , Schröder Eckhard
Published: February 2023

Wavefront analysis as tool for quality control of optical systems is known for more than 100 years. With the availability of high quality Shack-Hartmann-Sensors at moderate cost, aberrometers became of interest for ophthalmic diagnostics. Customized corneal ablation guided by wavefront analysis of visual performance opens the opportunity for further improvement of the refractive surgical outcome.
Real Time Atomic Force Fluorescence-Microscopy on Living Cells
Authors: Struckmeier Jens , Klopp Erk , Born Matthias , Hofmann Martin , Rink Damaris , Jones David B. , Ecke Stefan , Butt Hans-Jürgen
Published: February 2023

The reaction of bone cells after mechanical stimulation is a key issue in understanding the origins of osteoporosis. We investigate mechanical stimulation of osteoblasts and their reaction with a new combination of an atomic force apparatus with a fluorescence microscope. First measurements on the mechanically induced calcium response of osteoblasts are presented. The average threshold force for stimulation is 300nN and the dynamics of the calcium response is in the several tens of seconds range.
Near-field Mie scattering in optical trap nanometry
Authors: Ganic Djenan , Gan Xisaosong , Gu Min
Published: February 2023

A mathematical model for understanding near-field Mie scattering, as used in optical trap nanomery for single molecule detection, is developed. Both perpendicular and parallel polarization states of incident electromagnetic waves have been considered. Simulations under different incident angles, and refractive indices of trapped particle have been investigated. Half-space signal strength is studied on the base of the calculated three-dimensional scattered electromagnetic field.
Biomedical applications of coherent-optical methods for the analysis of lymph flow in microvessels
Authors: Solov'eva Anastasiya V. , Brill Grigory E. , Galanzha Ekateryna I. , Ulyanov Sergey S. , Tuchin Valery V. , Stepanova Tatiana V. , Sedykh Alexey V.
Published: February 2023

In the present study the characteristics of lymph microcirculation are investigated. The lymph microcirculation was studied on small intestine mesentery during NG-nitro-L-arginine (L-NNA) application on intact microvessels and after stress. The direct measurement of lymph flow velocity (parameter V) in individual microvessels was based on the technique of light intravital videomicroscopy. The first spectral moments of Doppler signal characterizing the mean velocities of lymph flow in microvessels (parameters Ml) were measured by the laser-speckle method. Simultaneously, diameters of lymph microvessels as well as parameters of phasic contractions and valve functioning were registered.
Bacteria cell ultra structure three-dimensional image
Authors: Volkov Uryi P. , Konnov Nikolai P. , Novikova Olga V.
Published: February 2023

The vast majority information about cells and cell organellae structure were obtained by means of transmission electron microscopy investigation of cells serial thin sections. However often it is very difficult to derive information about 3-D structure of specimens from such electron micrographs. A new program restoring 3-D image of cells from the serial thin sections micrographs have been developed in our lab. The program makes it possible to visualize a 3-D image of cell and obtain image of inner cell structure in arbitrary plane. The plague bacteria and anthrax cells with spore were visualized with resolution about 70 nm by means of the program.
Dynamic light scattering and natural fluorescence measurements of the corneal tissue
Authors: Pollonini Luca , Rovati Luigi , Ansari Rafat R.
Published: February 2023

Dynamic light scattering (DLS) and autofluorescence (AF) are non-invasive diagnostic techniques that can monitor changes at the molecular level in ocular tissues. In the present study, we demonstrate as simultaneous measurements of autofluorescence and dynamic light scattering on the corneal tissues can be performed using a novel specifically designed instrument. The integrated instrument takes advantage of the singular techniques by improving the measurement quality and the reliability of the diagnosis. Preliminary tests on volunteers show promise in relation to possible use in the clinical practice.
High speed 3-D imaging using photorefractive holography with novel low coherence interferometers
Authors: Gu Y. , Ansari Z. , Siegel J. , Dunsby C. , Itoh M. , Parsons-Karavassilis D. , Tziraki M. , Jones R. , Dowling K. , French P. M. W. , Nolte D.D. , Headley W. , Melloch M.R.
Published: February 2023

We report high speed (~ 470 frames/s) 3-D imaging using photorefractive holography with sources of diverse temporal and spatial coherence and discuss design considerations for real-world high bit-rate imaging systems. We also propose a new real-time optical sectioning technique based on structured illumination with photorefractive holography to detect fluorescence.
Characterisation of layered scattering media using the spatial distribution of polarized light
Authors: Stockford I. M. , Morgan S. P. , Chang P. C. Y. , Walker J. G.
Published: February 2023

The scattering of polarized light from a multilayered scattering medium is investigated using Monte Carlo simulations. The polarization and spatial properties of the emerging light are used to perform tissue localisation in order to extract the physical and optical properties of the layered medium. The polarization technique is enhanced using linearly and circularly polarized illumination to probe different depths. Absorption and layer thickness is varied and it is demonstrated that the determination of these values is aided by the inclusion of polarization information to allow localisation of different volumes within the sample. Potential applications of these techniques are burn depth and melanoma thickness measurement.
Optoacoustic tomography using a two dimensional optical pressure transducer and two different reconstruction algorithms
Authors: Frauchiger D. , Köstli K.P. , Paltauf G. , Frenz M. , Weber H.P.
Published: February 2023

Optoacoustic pressure waves were generated by irradiating blood vessels embedded into calf cartilage with 5 ns long pulses from an optical parametric oscillator (OPO). A two dimensional pressure transducer consisting of a glass prism and a liquid layer was used to measure the laser-induced pressure waves. The pressure dependent changes of reflection at the prism-liquid interface were recorded with a time-gated CCD-camera. On the basis of the 2D pressure measurements the spatial distribution of the blood vessels was reconstructed using two different algorithms, one based on radial back projection and one using Fourier transformation. High lateral (100 μm) and depth resolution (20 μm) was achieved.
Measurement of photoacoustic signals from skin: Potential application to burn depth estimation
Authors: Sato Shunichi , Shimada Tomoaki , Arai Tsunenori , Kikuchi Makoto , Obara Minoru , Ashida Hiroshi
Published: February 2023

We propose a new method of burn depth estimation based on the measurement of photoacoustic signal from the skin, where the acoustic waves originated from the light absorption by blood are detected with a piezoelectric transducer put on the skin surface. Because vascular occlusion takes place in the thermally-damaged tissue layer, the propagating time of the blood-originated signals would have the depth information of injury. To investigate the validity of the proposed diagnosis, experiment using rat burn model was performed. The results showed that deep burn (DB), deep dermal burn (DDB), and control (healthy skin) can be well differentiated by the photoacoustic signals. Quantitative information relating to the depth of injury can be also obtained from the signals.
A Modular, Multiwavelength, Wideband, Intensity Modulated Optical Spectrometer for Localised Near Infrared Spectroscopy
Authors: Tullis Iain D. C. , Cope Mark , Delpy David T.
Published: February 2023

We describe the development of a modular, multiwavelength, wideband intensity-modulated near infrared spectrometer (100MHz – 1GHz) capable of simultaneous measurement of three parameters – the dc intensity, the ac intensity and the phase shift of light transmitted through tissue at a high sampling rate. The intended purpose of this instrument is the detection of fast dynamic changes in the reduced scattering coefficient of tissue due to cellular depolarisation. The instrument requires sensitivity to small changes in optical pathlength and absorption in small volumes of tissue.
EUV Lithography Cost of Ownership Analysis
Authors: Hawryluk Andrew M. , Ceglio Natale M.
Published: February 2023

The cost of fabricating state-of-the-art integrated circuits (ICs) has been increasing and it will likely be economic rather than technical factors that ultimately limit the progress of ICs toward smaller devices. It is estimated that lithography currently accounts for approximately one-third the total cost of fabricating modern ICs(1). It is expected that this factor will be fairly stable for the forseeable future, and as a result, any lithographic process must be cost-effective before it can be considered for production. Additionally, the capital equipment cost for a new fabrication facility is growing at an exponential rate(2); it will soon require a multibillion dollar investment in capital equipment alone to build a manufacturing facility.
Performance of a Two Mirror, Four Reflection, Ring Field Imaging System
Authors: Sommargren Gary E.
Published: February 2023

The surface figure of the individual mirrors of a two mirror, four reflection, ring field imaging system has been measured after each phase of the construction process: substrate fabrication, coating and potting. Contributions to the final system wavefront error and performance of the system in terms of the modulation transfer function and initial imaging tests are discussed.
Investigation of Image Defects in EUV Lithography Experiments
Authors: Sweatt W. C. , Chow W. W.
Published: February 2023

Physical-optics modeling of EUVL imaging is done with accurate descriptions of the illumination. Two EUVL optical systems are described in this paper: (1) a Schwarzchild camera, illuminated with a laser-plasma source (LPS) and a simple illuminator, and (2) a ring-field camera, illuminated with an LPS and a high-efficiency condenser.
Limitations to Silylated Resist Technology
Authors: Taylor Gary N. , Hutton Richard S. , Stein Susan M. , Boyce Craig H. , LaFontaine Bruno , MacDowell Alastair , Wheeler David R.
Published: February 2023

Silylated, dry-developed resists have demonstrated superior resolution performance beyond that of their solution-developed resist counterparts. However, the implementation of plasma-developed resists in the manufacture of integrated circuit devices has only been realized in pilot line fabrication despite the fact that silylated resists additionally avoid other imaging pitfalls including thickness variations over topography, limited depth of focus and reflection-induced exposure variations. This is exemplified most dramatically with deep-UV lithography at 248 nm. Silylated resists have printed 0.2 μm features with a 0.53 NA exposure tool at this wavelength without any benefit from optical "tricks". The implementation of silylation technology is not considered seriously yet because of the conviction that solution-developed resists will meet the specifications for fabricating 0.25 μm design rule devices in the near term. But will the actual yields be high enough and the processing and materials costs be low enough? For silylated resists, on the other hand, the difficulties and challenges revolve around the availability of production worthy equipment, the complex nature of the dry processing, yields which may be adversely affected by particles produced in the plasma development environment and cost.
Validation of Modeling Hoechst AZ PN114 for EUV Projection Lithography and Investigation of Diffusion Effects
Authors: Lum Bernice M. , Neureuther Andrew R. , La Fontaine Bruno , MacDowell Alastair A. , Wood Obert R.
Published: February 2023

A dissolution rate model for Hoechst AZ PN114 for extreme ultraviolet (EUV) exposure is described and experimental results of effects of processing conditions on 0.1 μm imaging are presented. The dissolution model is based on volumetric energy deposited in the resist in J/cm3 and uses a standard molecular weight increase. It is derived from published electron-beam [2] and EUV [3] data along with new experiments at EUV wavelengths and was implemented in the SAMPLE lithography program by adding a new development rate Comparisons made between SEM cross-sections and simulations using proto-typical aberrations show similar undercutting shapes characteristic at these wavelengths but did not fully describe the top corner rounding. An extensive matrix of experiments of post exposure bake (PEB) time ranging from 2 1/2 minutes to 15 minutes and PEB temperature from 95°C to 115°C and exposure dose from 1.5 mJ/cm2 to 10 mJ/cm2 was carried out at Brookhaven National Laboratory in conjunction with AT & T Bell Laboratories to explore sensitivity tradeoffs and possible diffusion effects. Nominal conditions for 0.1 μm imaging were exposure at 3 mJ/cm2 and post exposure bake for 5 minutes at 105°C. In general, an increase of 5°C requires a dose decrease of 1.5 mJ/cm2 and every 5 minute increase in bake time leads to a decrease of 1.2 mJ/cm2 to obtain similar sized features. It was observed that the AZ PN114 resist shows little diffusion except at high PEB temperatures of about 115°C. Debris or image imperfections seemed to be more noticeable at long PEB times.
Imaging of EUV Lithographic Masks with Programmed Substrate Defects
Authors: Nguyen K. B. , Attwood D. T. , Mizota T. , Haga T. , Kinoshita H.
Published: February 2023

Extreme ultraviolet lithographic masks with programmed defects on the mask substrates have been imaged to study substrate defects printability. Imaging was performed with a 2-aspherical-mirror system operating at 14 nm wavelength. Results showed that 25 nm thick substrate defects caused observable distortions of resist patterns. Defects of sizes approximately half the minimum resolvable features resulted in 15%-20% variations in resist linewidths. However, since the imaging system was operating at a reduced resolution due to misalignments of the optics, the effect of the defects may have been partially concealed by the phase front distortions caused by mirror misalignments.
EUV Reticle Pattern Repair Experiments using 10 KeV Neon Ions
Authors: Hawryluk A. M. , Kania D. R. , Celliers P. , DaSilva L. , Stith A. , Stewart D. , Mrowka S.
Published: February 2023

Any potential lithography must demonstrate an industrially-compatable reticle pattern repair process before the lithographic process can be seriously considered for production. Repair of clear defects on EUV reticles (i.e., regions on the mask which are reflective and should be non-reflective) requires the deposition of a thin layer of absorbing material. This process has been demonstrated in commercially available tools which were originally developed to repair proximity-print x-ray lithography masks. However, the repair of opaque defects (i.e., the recovery of reflectivity from regions on the reticle covered with an absorber) is more difficult. Opaque defect repair requires the removal of the absorber layer without damaging the underlying multilayer, a process which could degrade the mirror reflectivity. While opaque defect repair processes have been demonstrated in a research environment(1,2), these processes may not be commercially suitable. We are developing reticle repair processes that will be consistent with a commercially available repair tool. In this paper, we report on our first results.
Recovery of EUV Lithography Substrates
Authors: Vernon S. P. , Baker S. L.
Published: February 2023

Mo/Si multilayers were removed from superpolished zerodur and fused silica substrates with a dry etching process that, under suitable processing conditions, produces negligible change in either the substrate surface figure or surface roughness. Full recovery of the initial normal incidence extreme ultra-violet (EUV) reflectance response has been demonstrated on reprocessed substrates.
High Average Power Solid-State Laser for EUV Lithography
Authors: Hermann Mark , Honig John , Hackel Lloyd
Published: February 2023

A diode-pumped, solid-state laser has recently been activated in the Extreme Ultraviolet Lithography (EUVL) facility at Lawrence Livermore National Laboratory. The purpose of this report is to document the design, operation, current laser operating points, and future upgrades of the EUVL laser system.
Advanced Source Studies on Laser Produced Plasmas for EUV Lithography
Authors: Spitzer R. C. , Gaines D. P.
Published: February 2023

Laser-produced plasmas are source candidates for EUV lithography. The radiation angular distribution for several target materials is investigated and source debris is characterized.
Detailed EUV Characterization of Laser-Plasma Sources for EUV Lithography*
Authors: Rockett Paul D. , Hunter John A. , Kubiak Glenn D. , Krenz Kevin , Shields Harry , Powers Michael
Published: February 2023

Emission characteristics for laser-driven EUV lithographic plasma sources have been studied exhaustively for the last four years. While debris issues now dominate research in this area, final details are being concluded on our understanding of material spectra and radiation transport of 13 nm light in laser-plasmas. Spectra of Sn, Cu, Xe, and Au were studied in the 2-20 nm region with transmission grating spectroscopy using 248 nm illumination. Additionally, conclusive results were obtained with 308 nm light, showing the pulselength threshold below which plumes no longer limit the transmission of (and thus the conversion efficiency to) 13 nm radiation.
Performance Criteria of Mass-Limited Ice Laser Plasma Targets for EUV Lithography
Authors: Richardson Martin , Jin Feng
Published: February 2023

The operation of a laser plasma source in a demonstration production-line EUV lithography system will have to meet strict cost and operation criteria. We examine current approaches, especially the mass-limited ice target concept, and compare their anticipated performance with that demanded by accepted system cost scenarios.
Debris Free, Electron Beam Driven, Lithography Source at 130Å
Authors: Fulton R. D. , Abdallah J. , Goldstein J. C. , Jones M. E. , Kilcrease D. P. , Kinross-Wright J. M. , Kong S. H. , Nguyen D. C.
Published: February 2023

Most of the proposed Extreme Ultraviolet Lithography (EUVL) sources utilize the interaction of some high energy density source, i.e. a laser, electron beam, or arc discharge, with a solid target. EUV can be efficiently generated by these techniques, but debris from the interaction region impacting on the reflective optics can substantially degrade the performance of the condenser system. Los Alamos and Grumman are cooperatively investigating a debris free source1,2 for EUV lithography. This source utilizes the predicted anomalous energy loss3,4 of a short pulse electron beam in a preformed plasma to heat and ionize the ions to a charge state where efficient radiation at 130Å occurs. Accelerators5 developed for the free electron laser program at Los Alamos are used as the electron bunch source. These accelerators use a laser driven photocathode to produce 15 psec electron bunches containing 4 nC of charge with an energy of 15.5 MeV. These micropulses are produced at a repetition rate of 108 MHz and continue for the length of the rf macropulse energizing the accelerator cavities, typically 1-10 μsec. The weakly ionized preformed plasma is created by purely classical collisional ionization caused by the initial few electron micropulses within the macropulse. When a critical electron density is reached, n
e
≅ 1.6x1015/τ2cm-3, where τ is the FWHM, in psec, of the electron bunch, the plasma responds collectively to the electron micropulse generating a large amplitude plasma wave. The plasma wave efficiently slows the high energy electron beam while heating the background plasma electrons. The initial electron population rapidly heats and then equilibrates with the bulk ion and electron populations in a few 10's of picoseconds. With neon as the dominant ionic species, an efficient filamentary radiator of line radiation near 130Å is created.
Electron-Gun-Driven EUV Lithography System
Authors: Todd Alan M. M. , Lehrman Ira S. , Krishnaswamy Jayaram , Calia Vincent , Gutowski Robert
Published: February 2023

The interaction of a high-brightness electron beam with a gas target has been proposed as a "granular" source of radiation that could generate sufficient power for extreme ultra-violet lithography (EUVL) applications. A system based on this concept that seeks to achieve writing rates in excess of 3 cm2 sec-1 at a wavelength around 130 Å is described. The potential advantage of a gas target system is the minimization of particulate debris and optics contamination. This electron-gun-driven lithography source consists of three basic components: a high-brightness, high-duty factor photocathode electron gun; a steady-state supersonic neon jet and gas collection subsystem; and output optics, imaging and exposure components. The overall systems aspects of such a EUVL source, together with the status and recent progress in the development of the electron gun and gas subsystems, are addressed. It is shown that the projected level of EUV radiation can reach the thermal limits of existing optical system designs for these wavelengths.
Scalar Wave Diffraction from a Circular Aperture
Authors: Cerjan C.
Published: February 2023

The scalar wave theory is used to evaluate the expected diffraction patterns from a circular aperture. The standard far-field Kirchhoff approximation is compared to the exact result expressed in terms of oblate spheroidal harmonics. Deviations from an expanding spherical wave are calculated for both cases as a function of the circular aperture radius and the incident beam wavelength using suggested values for a recently proposed point diffraction interferometer. The Kirchhoff approximation is increasingly reliable in the far-field limit as the aperture radius is increased, although significant errors in amplitude and phase persist.
EUV Metrology of Multilayer Optics
Authors: Ray-Chaudhuri A. K. , Stulen R. H. , Ng W. , Cerrina F. , Spector S. , Tan Z. , Bjorkholm J. , Tennant D.
Published: February 2023

EUV metrology is central to the successful commercialization of EUV projection lithography. Metrology carried out at the EUV wavelength of 13 nm enables a gain of ~50 in precision when translated from visible light wavelengths. It also uniquely measuring wavefront errors due to lateral variations in the inherent phase shift upon reflection from the multilayer coating. We present the development of two metrology techniques: EUV Foucault and Ronchi tests.
Real-time, Sub-Micron Fluorescence Imaging of Extreme Ultraviolet Aerial Images
Authors: La Fontaine B. , MacDowell A. A. , Tan Z. , Taylor G. N. , White D. L. , Tennant D. M. , Wood O. R.
Published: February 2023

A new technique using single crystal phosphors has been used to observe, in real time, soft x-ray images with features as small as 100 nm. This fluorescence imaging scheme takes advantage of the high fluorescence yield, high index of refraction, short absorption depth of extreme ultraviolet (EUV) light (λ~139Å) and excellent optical properties of single crystals activated with rare earth ions.
Characterization of mass-limited ice droplet laser plasmas
Authors: Torres D. , Jin F. , Richardson M. , DePriest C.
Published: February 2023

The ice droplet laser plasma can meet the strict cost and operation
criteria for a demonstration production-line EUV lithography system.
We have begun a systematic theoretical and experimental
characterization of the source emission, plasma dynamics and the
radiation physics, of the mass-limited ice droplet plasma. We discuss
our initial findings.
Feasibility of Various Discharge Configurations for High Intensity Lithium Vapor Discharge Source at 13.5 nm for EUVL
Authors: Klosner M.A. , Silfvast W.T.
Published: February 2023

This study examines the possibility for two different discharge
configurations to achieve the plasma conditions required for a lithium
vapor discharge source operating at 13.5 nm. Due to the difficulties
of working with a pure lithium vapor system, the experiments were
carried out using noble gases. The results suggest that a lithium
vapor capillary discharge could be a suitable configuration for an
EUVL lamp.
Development of Extreme Ultraviolet Lithography along the European route
Authors: Bijkerk F.
Published: February 2023

We survey several research themes and experimental results of an initial collaborative development programme in Europe on Extreme Ultraviolet Lithography (EUVL).
Progress in the Development of EUV Imaging Systems
Authors: Tichenor D. A. , Ray-Chaudhuri A. K. , Kubiak G. D. , Nguyen K. B. , Haney S. J. , Berger K. W. , Nissen R. P. , Perras Y. E. , Jin P. S. , Weingarten L. I. , Keifer P. N. , Stulen R. H. , Shagam R. N. , Sweatt W. C. , Smith T. G. , Wood O. R. , MacDowell A. A. , Bjorkholm J. E. , Jewell T. E. , Zernike F. , Fix B. L. , Hauschildt H. W.
Published: February 2023

An extreme ultraviolet (EUV) ring-field camera, comprised of 3 aspheric mirrors, has been fabricated and evaluated using visible light. The wavefront error (WFE) within a 1 mm × 25 mm field of view is 2.5 nm RMS. In a 10x Schwarzschild optic, having a 0.4 mm diameter field of view, an optically measured WFE of 1 nm RMS has been achieved. EUV images recorded in resist using the Schwarzschild camera are shown. The integration of this camera into a laboratory tool for device fabrication experiments is described.
Far-field Radiation From a Cleaved Cylindrical Dielectric Waveguide
Authors: Cerjan C.
Published: February 2023

A determination of the angular spread in the far-field radiation pattern of a cleaved dielectric waveguide is made from the modal structure at the surface of the waveguide using the Smythe vector integral formulation. The essential features are the following. First, a mode exists in the fiber that has no wavelength cutoff - the so-called HEn mode. This mode arises when non-azimuthal angular dependence of the incoming radiation is present. Second, the energy flow from this hybrid mode fills the fiber face and is not annularly shaped as opposed to the symmetric TE and TM modes. Third, the HE11 mode is not polarization dependent in contrast to the TE and TM modes. Fourth, for small differences in the indices of refraction between the core and cladding regions only the HE11 mode will be supported until the next modes appear around 3.33λ. At this point, three new modes can propagate and the modal structure of the radiation becomes more complicated. Fifth, the far-field radiation pattern will have negligibly small angular dependence in the phases of the vector fields when only the lowest mode is present; the amplitude has an overall angular dependent form factor. Furthermore, when other modes are present (above 3.33λ), the phase of the vector fields will acquire an angular dependence.
Projection Lithography with Ail-Reflecting Optics
Authors: Wood O.R. , Bjorkholm J. E. , MacDowell A.A. , Vaidya S. , Shafer D.R.
Published: February 2023

Recent efforts to design a high-numerical aperture (NA), all-reflecting, vacuum-ultraviolet (VUV) imaging system for projection lithography are described.
Reticle blanks for extreme ultraviolet lithography: ion beam sputter deposition of low defect density Mo/Si multilayers
Authors: Vernon S.P. , Kania D.R. , Kearney P.A. , Levesque R.A. , Hayes A.V. , Druz B. , Osten E. , Rajan R. , Hedge H.
Published: February 2023

We report on the growth of low defect density Mo/Si multilayer (ML)
coatings. The coatings were grown in a deposition system specifically
designed for EUVL reticle blank fabrication. Complete, 81 layer, high
reflectance Mo/Si ML coatings were deposited on 150 mm diameter (100)
oriented Si wafer substrates using ion beam sputter deposition (IBSD).
Added defects, measured by optical scattering correspond to defect
densities of 2x10-2/cm2. This represents a
reduction in defect density of Mo/Si ML coatings by a factor of
105.
At-wavelength inspection of EUVL mask defects with a 1X Offner ring-field system
Authors: Nguyen K. B. , MacDowell A. , Fujii K. , Tennant D. M. , Fetter L. A.
Published: February 2023

At-wavelength inspection of EUV masks containing programmed defects was performed with an EUV 1X Offner ring-field system. At-wavelength inspection was sensitive to thin substrate defects. The sensitivity of the detection was limited by the resolution of the imaging system. At-wavelength inspection also revealed defects that are not detectable by other inspection techniques.
EUVL Reticle Factory Model and Reticle Cost Analysis
Authors: Hawryluk Andrew M. , Shelden Gilbert , Troccolo Patrick
Published: February 2023

The key issues in reticle manufacturing are cost and delivery time,
both of which are dependent upon the yield of the process line. To
estimate the cost and delivery time for EUVL reticles in commercial
manufacturing, we have developed the first model for an EUV reticle
factory which includes all the tools required for a presumed EUVL
reticle fabrication process. This model includes the building, support
tools and sufficient “in-line” process tools for the manufacture of
(more than) 2500 reticles per year. Industry specifications for the
tool performance are used to determine the number of tools required
per process step and the average number of reticles fabricated per
year. Building and capital equipment depreciation costs, tool
installation costs, tool maintenance costs, labor, clean room costs,
process times and process yields are estimated and used to calculate
the yearly operating cost of the reticle factory and the average
reticle fabrication cost. We estimate the sales price of an EUV
reticle to be $60K for non-critical levels and $120K for
“leading-edge. The average reticle fabrication time is calculated for
three different process-line yields.