Lambda Physik Ag

Lambda Physik Gesellschaft Zur Herstellung Von Lasern Mbh

Other

Lamba Physik Gmbh

Dirk Basting

Sergei V Govorkov

Uwe Stamm

Igor Bragin

Frank Voss

Juergen Kleinschmidt

Ulrich Rebhan

Gerd Steinfuhrer

Peter Lokai

Wolfgang Zschocke

Rainer Paetzel

Matthias Kramer

Andreas Targsdorf

Hubertus Von Bergmann

Jurgen Kleinschmidt

Klaus Mann

A Meller

Thomas Schröeder

Christian Schramm

Holger Bald

Kai Schmidt

A Master Oscillator (MO)&#x2014;Power Amplifier (PA) configuration (MOPA) can be used advantageously in an excimer laser system for micro-lithography applications, where semiconductor manufacturers demand powers of 40 W or more in order to support the throughput requirements of advanced lithography scanner systems. The timing of discharges in discharge chambers of the MO and PA can be precisely controlled using a common pulser to drive the respective chambers. The timing of the discharges further can be controlled through the timing of the pre-ionization in the chambers, or through control of the reset current in the final compression stages of the pulser. A common pulser, or separate pulser circuits, also can be actively controlled in time using a feedback loop, with precision timing being achieved through control of the pre-ionization in each individual discharge chamber. Yet another system provides for real-time compensation of time delay jitter of discharge pulses in the chambers.

Excimer or molecular fluorine laser system with precision timing

A process for the determination and correction of laser induced damages of the optical and electronic components within the beam path of a monitor module of a 193 nm excimer lasers is provided herein. Especially state of the art detectors like CCD cameras degrade under UV radiation. With a special correction of the sensitivity of each camera pixel this problem can be solved.

Determination and correction for laser induced CCD camera degradation

A line-narrowing module for a laser includes a prism beam expander and a grating preferably attached to a heat sink. A pressure-controlled enclosure filled with an inert gas seals the grating and/or other elements of the line-narrowing module. The pressure in the enclosure is adjusted for tuning the wavelength. Preferably, the pressure is controlled by controlling the flow of an inert gas through the enclosure. A pump may be used, or an overpressure flow may be used. Alternatively, a prism of the beam expander or an etalon may be rotatable for tuning the wavelength.

Tunable laser with stabilized grating

A F -laser includes a discharge chamber filled with a gas mixture including molecular fluorine for generating a spectral emission in a wavelength range between 157 nm and 158 nm including a primary line and a secondary line, multiple electrodes coupled with a power supply circuit for producing a pulsed discharge to energize the molecular fluorine, a resonator including the discharge chamber and an interferometric device for generating a laser beam having a bandwidth of less than 1 pm, and a wavelength monitor coupled in a feedback loop with a processor for monitoring a spectral distribution of the laser beam. The processor controls an interferometric spectrum of the interferometric device based on the monitored spectral distribution such that sidebands within the spectral distribution are substantially minimized.

Wavelength and bandwidth monitor for excimer or molecular fluorine laser

A preionization device for a gas laser comprises an internal preionization electrode having a dielectric housing around it and an external preionization electrode displaced from the dielectric housing by a small gap. The dielectric housing includes two cylindrical regions of differing outer radii of curvature. An open end of the housing has a larger radius of curvature than the other end which is closed. The internal electrode connects to circuitry external to the discharge chamber via a conductive feedthrough which penetrates through the housing. The external circuitry prevents voltage oscillations caused by residual energy stored as capacitance in the dielectric housing. The external preionization electrode, which is connected electrically to one of the main discharge electrodes, is formed to shield the internal preionization electrode from the other main discharge electrode to prevent arcing therebetween. The external electrode is also formed to shield the outer gas volume and walls of the discharge chamber from the preionization unit. A semi-transparent external electrode prevents charged particles emanating from the main discharge area from settling on the housing and causing field distortion and discharge instabilities.

Preionization arrangement for gas laser

Preionization arrangement for a gas laser

A tunable laser is provided having a gain medium and a resonator for generating a laser beam, and an angular dispersion element. The laser further includes a beam expander with adjustable magnification for adjusting an angular dispersion provided by the dispersion element. The adjustable beam expander preferably includes one or two rotatable prisms. When two prisms are used, the prisms are preferably synchronously rotatable according to a preset ratio such that any changes in refraction angle due to the rotation of the first prism are automatically compensated by the rotation of the second prism. A single prism may serve both as a dispersion element and as a beam expansion element. A processor preferably monitors the linewidth and wavelength of the output beam and adjusts an orientation of the prism or prisms of the expansion unit, and the tilt of either a reflection grating or a highly reflective mirror of the resonator in a feedback loop.

Wavelength selector for laser with adjustable angular dispersion

An apparatus and method for testing the quality of a line narrowing and/or selection module that has been particularly assembled for use with a line-narrowed excimer or molecular fluorine laser is described. The method includes providing a test beam which has been previously line-narrowed using an installed line-narrowing and/or selection module. Then, the test beam is directed into the test module. Next, the one or more properties of the retroreflected beam are measured, i.e., after the beam has traversed the test module. The quality of the test module and one or more of its components may be determined based on the measurements. Such properties as wavefront distortions, excessive scattering, total reflectivity, total dispersion and aging of components of the test module may be measured for making this quality determination.

Optical device and method for line-narrowed excimer or molecular fluorine laser

A molecular fluorine (F ) laser is provided wherein the gas mixture comprises molecular fluorine for generating a spectral emission including two or three closely spaced lines around 157 nm. An etalon provides line selection such that the output beam only includes one of these lines. The etalon may also serve to outcouple the beam and/or narrow the selected line. Alternatively, a prism provides the line selection and the etalon narrows the selected line. The etalon may be a resonator reflector which also selects a line, while another element outcouples the beam. The etalon plates comprise a material that is substantially transparent at 157 nm, such as CaF , MgF , LiF , BaF , LiF, SrF , quartz and fluorine doped quartz. The etalon plates are separated by spacers comprising a material having a low thermal expansion constant, such as invar, zerodur&reg;, ultra low expansion glass, and quartz. A beam expander is preferably provided before the etalon for expanding the beam before the beam is incident on the etalon. The beam expander is preferably configured to reduce the divergence of the beam.

Molecular fluorine (F2) laser with narrow spectral linewidth

A molecular fluorine (F.sub.2) laser is provided wherein the gas mixture comprises molecular fluorine for generating a spectral emission including two or three closely spaced lines around 157 nm. An etalon provides line selection such that the output beam only includes one of these lines. The etalon may also serve to outcouple the beam and/or narrow the selected line. Alternatively, a prism provides the line selection and the etalon narrows the selected line. The etalon may be a resonator reflector which also selects a line, while another element outcouples the beam. The etalon plates, preferably uncoated, comprise a material that is transparent at 157 nm, such as CaF.sub.2, MgF.sub.2, LiF.sub.2, BaF.sub.2, SrF.sub.2, quartz and fluorine doped quartz. The etalon plates are separated by spacers comprising a material having a low thermal expansion constant, such as invar, zerodur.RTM., ultra low expansion glass, and quartz. A gas such as helium or a solid such as CaF.sub.2 that does not absorb radiation 157 nm fills the gap between the etalon plates, or the gap is evacuated. The gas mixture preferably further includes neon as a buffer gas. Another etalon may be used for line narrowing. One or more of a highly reflective mirror, a high finesse etalon or a prism with a highly reflective back surface may serve as a highly reflective resonator reflector. Any of one or more etalons, a prism, a brewster plate and a highly or partially reflective mirror may seal the laser discharge chamber.

Molecular fluorine (F.sub.2) laser with narrow spectral linewidth

A laser system, and method of operating the same, that includes a resonant cavity that terminates at one end with a mirror and at the other end with a dispersive wavelength selector, a gain medium disposed in the resonant cavity, and a power supply that excites the gain medium to generate a laser beam that oscillates along an optical axis of the resonant cavity. The dispersive wavelength selector disperses the laser beam at different angles in a critical plane as a function of wavelength so that only a particular range of wavelengths in the beam are aligned to the optical axis and oscillate in the resonant cavity. The critical plane is parallel to the laser beam. The resonant cavity further includes a wavefront curvature compensating lens that is selectively rotatable about an axis of rotation that is perpendicular to the critical plane. The compensating lens is oriented about the axis of rotation to alter a wavefront curvature of the laser beam in the critical plane so that the wavefront curvature of the beam incident upon the wavelength selector matches the shape of the wavelength selector in the critical plane, thus minimizing a spectral linewidth of the particular range of wavelengths.

Laser system and method for narrow spectral linewidth through wavefront

The present invention is an apparatus and method for stabilization of laser output beam characteristics by automatically adjusting the angular and the lateral positions of the output beam. A component of the output beam is detected at a far field location and also at a near field location along an optical path of the component. Both the angular and the lateral positions of the output beam are determined, as well as characteristics of the output beam, after the component is detected at both the near and the far field locations. Both the angular position and the lateral position of the output beam are automatically adjusted to optimize the output beam. The adjustment of both the angular position and the lateral position are made possible by using a beam steering device preferably including two mirrors.

Stabilization of angular and lateral laser beam position

An apparatus and method for providing accurate sub-nanosecond timing control between the voltage outputs of branches of an excitation circuit which are driven by a common switch. This invention allows for the introduction of variable timing delays between the branches of the circuit, and eliminates relative timing jitter. Using saturable inductors with variable bias in the high-voltage excitation circuit, this invention provides a continuously tuneable delay on the subnanosecond time scale between two or more excitation circuit branches.

Precision variable delay using saturable inductors

A narrow-band laser apparatus comprises an optical resonator including first and second reflectors for reflecting radiation, a laser medium for amplifying radiation in said resonator and an etalon for selecting a given wavelength component from said radiation. A polarizing beam splitter is provided for linearly polarizing said radiation and also for acting as an output coupler. In order to obtain very narrow bandwidth radiation of high intensity, a Faraday rotator is provided for rotating the plane of polarization while maintaining the linear polarization thereby allowing a second wavelength selection element (such as a grating) to be efficiently employed to further narrow the output of the laser.

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Fort Lauderdale, FL, United States of America

Dirk Basting