High-power Excimer Laser Research Articles

Development of a high-power ultra-short pulse excimer laser in the Max-Planck-Institut.

Development of a high-power ultra-short pulse excimer laser in the Max-Planck-Institut.

Laser plasma as X-ray source for lithographic imaging of submicron structures onto experimental X-ray resist

We present experimental work on laser plasma based X-ray lithography, which is aimed at the development of a compact lithographic work-station for VLSI pattern transfer. Results presented are obtained with the frequency doubled output of a low repetition rate, high power Nd:YAG/Glass laser. The power density in the laser focus was 3×10 12 W/cm 2. This source was used to image Si X-ray masks with submicron Au absorber profiles. Experimental X-ray photoresist, RAY-PF (Hoechst), was used to record the structures and analysed for imaging and recording properties. For the exposure, 80 lasershots sufficed to faithfully reproduce 0.5 μm mask structures onto the photoresist, which is equivalent to a sensitivity of better than 50 mJ/cm 2. It is possible to predict source improvements, obtainable with a high power excimer laser for this application. The higher repetition rate at which excimer lasers can be operated reduces the exposure time of the photoresist to several seconds, enabling an industrial throughput of 27 6″-wafers/hour in one work-station.

A high-power long pulse excimer laser

Excimer lasers operating at high average powers are becoming important for materials-processing applications. A long-pulse excimer laser with automatic spark preionization which provides a pulse energy of 1 J with an optical pulse length of 200 ns full-width half-maximum for XeCl is described. Successful scaling of the repetition rate to 220 p.p.s. is discussed along with requirements for gas flow. >

1-ns high-power high-repetitive excimer laser oscillator

A 1-ns high-power high-repetitive excimer laser oscillator has been developed for which the peak power obtained was more than 1 MW with 1-ns pulse width for both XeCl and KrF gas mixtures. The characteristic output power per unit active volume is calculated to be more than 2 GW/L, which is nearly one order larger than that extracted from usual discharge devices. It is inferred that the gain depletion in the active medium under such an extremely large output power condition has led to successful pulse shortening. The device can be operated at a repetition frequency of at least 500 Hz without a gas circulation system. The beam divergence was reduced to near the diffraction limit, although the oscillated-pulse width is only 1 ns.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pulsed Laser Cleaning of Antimony Single Crystal &lt;111&gt; Surface

ABSTRACTThe&lt;111&gt; face of an antimony single crystal was irradiated under ultra-high-vacuum conditions by the 193 rn radiation of a high-power excimer laser. The effects of the laser beam on the sample as a function of the light Energy Density (ED) and of theannealing Repetition Number are presented.Surface studies by Auger electron spectroscopy, scanning electron microscopy and low energy electron diffraction show that an atomically clean and well ordered surface can be produced by t is method. A strong chemical reduction is induced by pulsed aser annealing above 100 to 130 mI/cm2. Surface analysis shows that, for an ED less than 500 mJ/cm2 the surface evaporates without melting deeper than 200 rim. Evidences for oxide modification and for organic molecule desorption were observed even after irradiations with an ED as low as 45 mJ/cm2.The surface reduction is described by a thermal model involving surface heating and subsequent evaporation of the oxide layer. The desorption and diffusion processes may involve both thermal and photolytic mechanisms.

Optical fiber transmission of high power excimer laser radiation

An experimental investigation of optical fiber transmission of high power excimer laser radiation is presented. Different types of commercially available UV fiber have been tested, measuring energy handling capabilities and transmission losses of short samples at the XeCl (308-nm) and KrF (249-nm) wavelengths by using a standard excimer laser. A power density dependent damage process has been observed over 1 GW/cm(2). Fiber losses due to different radii of curvature are also reported. Experimental results have been examined to evaluate the effectiveness of excimer laser transmission through optical fibers for such medical uses as laser angioplasty, including also a comparison between the use of KrF or XeCl emission lines for this purpose. Finally, optimum excimer laser characteristics to increase the energy coupling in fibers are discussed.

Electro-optic voltage measurement in a high-power excimer laser

A novel electro-optic technique for measuring the voltage between the discharge electrodes of a high peak power excimer laser is described. The accurate measurement of this rapidly varying (&amp;gt;100 MHz) high voltage (&amp;gt;20 kV) in the immediate vicinity of very large rates of change of currents (&amp;gt;1012 A/s) is of importance in laser research but presents considerable difficulties when using conventional measuring techniques.

High-power excimer lasers and new sources of coherent radiation in the vacuum ultraviolet

1. Introduction 1031 2. Generation of powerful ultrashort pulses of ultraviolet radiation with excimer lasers 1032 3. Generation of high harmonics and nonlinear frequency mixing in atomic and molecular gases 1034 4. Multiphoton pumping of atoms and molecules with subsequent stimulated emission in the vacuum ultraviolet region 1036 5. Lasers based on anti-Stokes Raman scattering 1037 6. Conclusions 1039 7. References 1040

Tunable oscillation of a high-power argon excimer laser in the vacuum-ultraviolet spectral region

Successful oscillation of a tunable, high-power argon excimer laser is reported. The wavelength was tuned from 124.5 to 127.5 nm with a spectral width of 0.3 nm. The output power of 2.2 MW, obtained at the line center, is 3 orders of magnitude larger than the value reported previously by Wrobel et al. [Appl. Phys. Lett. 36, 113 (1980)]. The possibility of frequency conversion of the argon excimer laser radiation to other wavelengths by a stimulated Raman scattering process is discussed.

Magnetically induced pulser laser excitation

A novel excitation scheme has been developed for excimer discharge lasers. The technique uses pulse transformer technology to induce a fast, high voltage pulse directly onto a ground potential laser electrode resulting in the breakdown of the laser gas mix. Saturation of the pulse transformer core inductance then permits efficient energy transfer from the main energy storage circuit into the discharge. When this excitation technique was used in a XeCl laser an output energy density of 2.5 J/l and an overall electrical to optical efficiency of 2% were obtained. The technique appears promising for the development of high energy, high average power excimer lasers.

High Repetition-Rate, High Power Excimer Laser

High Repetition-Rate, High Power Excimer Laser

Moshchnye eksimernye lazery i novye istochniki kogerentnogo izlucheniya v vakuumnom ul'trafiolete

Moshchnye eksimernye lazery i novye istochniki kogerentnogo izlucheniya v vakuumnom ul'trafiolete

High-power argon excimer laser at 126 nm pumped by an electron beam

A high-power argon excimer laser has been developed with an output power exceeding 2 MW in the VUV region at 126 nm. As an alternative to a conventional Al/MgF(2)-coated mirror, which was susceptible to damage, an uncoated quartz plate was successfully used as a reflector for reproducible high-power operation of the argon excimer laser without any mirror damage. Observation of the temporal behavior of the laser pulse in relation to that of the gain coefficient is discussed.

Investigation of dye lasers excited by high-power KrF laser radiation

An investigation was made of the lasing characteristics of ethanol solutions of the dyes rhodamine 6G (R6G), coumarin 47 (C47), p-terphenyl (PTP), and POPOP pumped by high-power KrF laser radiation (λ = 248 nm) pulses of up to 10 J energy and 80 nsec duration. A laser output energy of 1.1 J at an efficiency of 14% was obtained from the R6G and C47 solutions. The optical strength of the R6G and C 47 solutions at the pump radiation wavelength was determined. The construction of dye lasers pumped by high-power excimer laser radiation was considered.

Saturation of resonant third-harmonic generation due to self-defocusing and a redistribution of the population densities

Using a high-power excimer laser, pumped dye laser third-harmonic generation in strontium was investigated around several two-photon resonances for input intensities which are well above the onset of saturation. The dominant role of self-defocusing and of the time-dependent redistribution of the population densities is demonstrated. Strong stimulated emission on several transitions branching off from the excited state of the two-photon resonance and several competing parametric processes have been observed. Good agreement is obtained with a theoretical model which accounts for the redistribution of the population densities and which shows the importance of the ac Stark effect for the central structure of the high-intensity conversion profiles.

Injection-locking unstable resonator excimer lasers

We review the basic criteria for effective and efficient injection locking of high-power excimer lasers, and enumerate the various parameters of practical concern for experimental implementation. Various injection schemes are compared and the fundamental limitations of the process are covered. Corroborative experimental results are also reviewed, and applications made possible by injection locking are discussed.

Plasma-surface interaction studies using laser resonance scattering

Results of systematic plasma-surface interaction studies by laser resonance scattering are presented. Conventional laser sources have been used to obtain improvements in metallic atom detection of (i) absolute calibration of the optical system, (ii) velocity-distribution function measurements, and (iii) angular distribution measurement of sputtered atoms by ion-beam bombardment. In addition, wide-range (from vacuum UV to visible) tunable sources have been developed based on a high-power excimer laser. Single-shot velocity-distribution function measurements are also described using a fast-frequency scan dye laser.

Deep uv submicron lithography by using a pulsed high-power excimer laser

Deep uv lithography by using a pulsed high-power excimer laser is demonstrated, in which submicron patterns with high resolutions were fabricated on PMMA (polymethyle methacrylate) photoresists by laser irradiation for 20 ns.

Effective deep ultraviolet photoetching of polymethyl methacrylate by an excimer laser

Photoetching of polymethyl methacrylate (PMMA) for pulsed high power UV light is demonstrated. As a high power UV light source, a KrF excimer laser was used. Etching depth obtained by deep UV light irradiation has not only energy dependence, but also power dependence. It increased abruptly by increasing the exposed power density for the same exposed energy density.These experimental results show that high power excimer lasers are the effective light source for UV photoetching of PMMA.

Ultrafast deep UV Lithography with excimer lasers

The use of high-power pulsed excimer lasers for photolithography is described for the first time. Short exposure times, high resolution and absence of speckle are experimentally demonstrated. Using a XeCl laser at 308 nm and a KrF laser at 248 nm, excellent quality images are obtained by contact printing in two positive photoresists. Resolution down to 1000 line-pairs/mm is demonstrated. These images are comparable to state-of-the-art lithography done with conventional lamps; the major difference is that the excimer laser technique is ∼ 2 orders of magnitude faster. Preliminary results on reciprocity behavior in several resists are also presented.