Abstract: An excimer laser system with a real time fluorine monitor and an automatic fluorine control system to permit precise control of the fluorine concentration within the laser chamber. Cleaned laser gas is extracted from the laser chamber and directed through an F2 sample cell prior to returning to the chamber through one of the chamber window housings. A UV light beam is directed through the F2 sample cell and the amount of absorption of the light is measured. In preferred embodiments the absorption is measured by detecting with a photo detector the amount of light which passes through the cell. The photo detector provides a feedback signal which is used by a laser controller to automatically control fluorine concentration in the chamber to within desired ranges. In another preferred embodiment an acoustic detector detects acoustic signals resulting from absorbed light pulses. This invention provides a substantially real time measurement of fluorine concentration.

Abstract: A high pulse rate pulse power source for supplying controlled high energy electrical pulses at rates of 2000 Hz or greater. The source includes a pulse generating circuit including a charging capacitor, a solid state switch and a current limiting inductor. Pulses generated in the pulse generating circuit are compressed in at least two pulse compression circuits and a step-up pulse transformer increases peak voltage to at least 12,000 volts. A very fast regulated power supply is provided for charging the charging capacitor in less than 400 microseconds and a pulse control system including a programmed processor controls the charging of the charging capacitor to an accuracy of less than about one percent at a rate of at least 4000 charges per second. In a preferred embodiment capable of operating at pulse rates of 2000 to 4000 Hz or greater, water cooling of the saturable inductors is provided.

Abstract: A laser lithography system in which two or more lasers provide laser illumination for two or more lithography exposure tools through a laser beam multiplexer. The mulitplexer contain several mirror devices each having a multi-reflectance mirror with surfaces of different reflectance and an adjusting mechanism for positioning one of the surfaces to intersect a laser beam from at least one of the lasers and direct a portion of it to at least one of the exposure tools.

Abstract: A smart laser having automatic computer control of pulse energy, wavelength and bandwidth using feedback signals from a wavemeter. Pulse energy is controlled by controlling discharge voltage, wavelength by controlling the position of an RMAX mirror in a line narrowing module and bandwidth is controller by adjusting the curvature of a grating in the line narrowing module. Preferred embodiments include automatic feedback control of horizontal and vertical beam profile by automatic adjustment of a prism plate on which beam expander prisms are located and automatic adjustment of the RMAX tilt.

Abstract: A feedthrough structure of a gas discharge laser chamber conducts electric power through the wall of a sealed gas enclosure to a single piece electrode inside the enclosure. The feedthrough structure includes a single piece integrated main insulator larger than the electrode. The main insulator is compressed between the electrode and the wall of the enclosure. The surfaces forming interfaces between the electrode and the single piece insulator are the insulator and the wall are all very smooth to permit the parts to expand and contract as the chamber temperature varies. The feedthrough structure also provides mechanical support and alignment for the electrode and includes seals to prevent gas leakage around the feedthrough structure.

Abstract: A smart laser having automatic computer control of pulse energy, wavelength and bandwidth using feedback signals from a wavemeter. Pulse energy is controlled by controlling discharge voltage. Wavelength is controlled by very fine and rapid positioning of an RMAX mirror in a line narrowing module. Bandwidth is controller by adjusting the curvature of a grating in the line narrowing module. Preferred embodiments include automatic feedback control of horizontal and vertical beam profile by automatic adjustment of a prism plate on which beam expander prisms are located and automatic adjustment of the RMAX tilt. Other preferred embodiments include automatic adjustment of the horizontal position of the laser chamber within the resonance cavity. In preferred embodiments, feedback signals from a wavelength monitor are used to position the RMAX mirror. In other preferred embodiments a separate laser beam reflected off the RMAX mirror on to a photodiode array is used to position the mirror.

Abstract: A support bar member for supporting an electrode member of a pulsed laser system is described. The support bar member includes an aerodynamic nose configured to reduce an aerodynamic load applied against a blower assembly of the laser system by the support bar member. The nose provides an aerodynamic cut-off region on the support bar member such that, when the blower assembly is operating, the blower assembly does not vibrate significantly.

Abstract: The present invention provides a very narrow band pulse excimer laser capable of producing pulses at a rate in the range of about 500 to 2000 Hz with enhanced energy dose control and reproducibility. Very small quantities of a stablizing additive consisting of oxygen or a heavy noble gas (xenon or radon for KrF lasers, or krypton, xenon or radon for ArF lasers), are added to the gas mixture. Tests performed show substantial improvements in energy stability with the addition of about 30 ppm of xenon to a KrF laser. Tests show improved performance for the ArF lasers with the addition of about 6-10 ppm of Xe or 40 ppm of Kr. In a preferred embodiment very narrow bandwidth is achieved on a KrF laser by reducing fluorine partial pressure to less than 0.10 percent and by increasing the reflectance of the output coupler to greater than 25 percent. In a preferred embodiment, prior art fused silica beam expansion prisms used in the prior art line-narrowing module were replaced with calcium fluoride prisms.

Abstract: A line narrowed ultraviolet laser having a line narrowing system which includes a grating and an all reflective beam expander. In a preferred embodiment, the beam expander consists of a relatively small circular cylindrical mirror and relatively larger elliptical cylindrical mirror and the grating is an eschelle grating mounted in a Littrow configuration.

Abstract: An overcoat protected diffraction grating. A replica grating having a thin aluminum reflective grating surface is produced by replication of a master grating or a submaster grating. The thin aluminum reflective surface may be cracked or have relatively thick grain boundaries containing oxides and hydroxides of aluminum and typically is also naturally coated with an aluminum oxide film. The grating is subsequently recoated in a vacuum chamber with a thin, pure, dense aluminum overcoat and then also in the vacuum the aluminum overcoat is coated with a thin film of MgF.sub.2. The grating is especially suited for use for wavelength selection in an ArF laser operating producing an ultraviolet laser beam at a wavelength of about 193 nm. The oxygen free aluminum overcoat prevents the ultraviolet light from causing damage by stimulating chemical reactions in grating materials under the aluminum grating surface or in the aluminum oxide film. The MgF.sub.

Abstract: An excimer laser system with an automatic fluorine control system to permit precise control of the fluorine concentration within an F.sub.2 "sweet spot" in a gas discharge laser chamber. This is done with a computer control system which monitors laser parameters, determines .DELTA.E/.DELTA.V, the change of pulse energy with voltage, and automatically and precisely controls the fluorine concentration based on .DELTA.E/.DELTA.V without the need to actually measure the fluorine concentration.

Abstract: A high pulse rate pulse power source for supplying controlled high energy electrical pulses at rates of 2000 Hz or greater. The source includes a pulse generating circuit including a charging capacitor, a solid state switch and a current limiting inductor. Pulses generated in the pulse generating circuit are compressed in at least two pulse compression circuits and a step-up pulse transformer increases peak voltage to at least 12,000 volts. A very fast regulated power supply is provided for charging the charging capacitor in less than 400 microseconds and a pulse control system including a programmed processor controls the charging of the charging capacitor to an accuracy of less than about one percent at a rate of at least 2000 charges per second.

Abstract: A tangential fan and cutoff assembly for recirculating a lasing gas mixture has blade members, which vary in circumferential position stepwise from end to end, and/or a tapered anode assembly. The number of blade members can be constant or variable between ends. The circumferential position of blade members can shift monotonically or reversibly between ends. Blade members are stiffened by optimally selecting the number and placement of hub members to control the natural vibration frequency of the fan. Methods of forming tangential fans include casting, and machining from a solid block. Monolithic structures can be joined, typically by electron-beam welding. Casting, welding, and machining processes introduce no additional contaminants. Tangential fans produced have mechanical rigidity, accurate tolerances, and low contaminant concentrations. Blade members can be formed into air foil shapes.

Abstract: The present invention provides a reliable modular production quality excimer laser capable of producing 10 mJ laser pulses at 2000 Hz with a full width half, maximum bandwidth of about 0.6 pm or less. Replaceable modules include a laser chamber; a pulse power system comprised of three modules; an optical resonator comprised of a line narrowing module and an output coupler module; a wavemeter module, an electrical control module, a cooling water module and a gas control module. Improvements in the laser chamber permitting the higher pulse rates and improved bandwidth performance include a single upstream preionizer tube and a high efficiency chamber. The chamber is designed for operation at lower fluorine concentration. Important improvements have been provided in the pulse power unit to produce faster rise time and improved pulse energy control.

Abstract: A system for providing support for the movement of a laser chamber of a laser system during the installation and removal of the laser chamber from the laser system housing. The system includes a rail assembly that is retractable and extendible from the laser system housing and provides support for moving the laser chamber between an operating position within the housing and a position outside of the housing for removal. The rail assembly is retractable to reside within the housing when not in use. The system may also include at least one actuator for controlling the movement of the laser chamber in a direction having a vertical component. Actuator types that may be used include rotary, piston cylinder, hydraulic, pneumatic, and/or electrical mechanical. One type of rail assembly includes opposing rail structures that retract and extend by moving laterally out from the housing or by pivoting out from the housing. The system may be implemented with a gas laser system such as an excimer laser system.

Abstract: A chamber/optics support structure for a laser having a laser chamber with a vibration source. The chamber and the laser resonance cavity optical elements are supported on a platform. The chamber is supported by a plurality of wheels which in turn rests on two tracks on track supports mounted on the platform. A flexible clamp flexibly clamps the chamber in a horizontal position to align it with the resonance cavity optical elements and to substantially decouple vibration between the chamber vibration source to the optical elements in a frequency range of concern.The invention is especially useful for positioning the heavy laser chamber of a narrow band excimer laser and for decoupling vibrations resulting from its blower from the lasers line narrowing module and output coupler. In a preferred embodiment the plurality of wheels is three wheels, two of which rest in a V-groove track and one of which rests on a flat track.

Abstract: The present invention provides an electric discharge gas laser having a laser cavity in which is contained a laser gas and a fan for circulating the laser gas. The fan is supported by an active radial magnetic bearing system and driven by a brushless DC motor in which the rotor of the motor and the rotors of at least two radial bearings are sealed within the gas environment of the laser cavity and the motor stator and the coils of the bearing magnets are located outside the gas environment. No thrust bearing is provided. Axial positioning of the shaft is provided by reluctance centering produced by the at least two radial magnetic bearings and the brushless DC motor. In a preferred embodiment the motor stator is larger in the axial direction than the rotor to increase the magnetic centering effect.

Abstract: A bidirectional bandwidth controlled grating assembly. A spring housing is connected to one of two end plates extending away from the lined surface of the grating. An adjustment rod threaded through the other end plate extends into the spring housing. Inside the spring housing in a preferred embodiment are two compression springs mounted between pressure surfaces in the housing and a piston which is fixed on the adjustment rod. The lined surface of the grating can be made more concave (or less convex) by screwing the rod in a direction into the spring housing compressing one of the springs to push the end plates apart and the surface can be made more convex (or less concave) by screwing the rod in a direction out of the spring housing compressing the other spring to pull the end plates toward each other.

Abstract: An excimer laser with optical pulse multiplication. A pulse multiplier optical system receives the laser output beam and produces a multiplier output beam having a larger number of pulses, each with substantially reduced intensity values as compared to the laser output beam. The present invention is particularly important as an improvement to the ArF excimer laser to reduce two-photon absorption damage to optical equipment in lithography machines. For damage mechanisms involving two-photon processes, such as the compaction and solarization of fused silica in the DUV spectral region, a factor of 4 reduction in peak power decreases the quantity of two photon absorption damage done by the synthesized 4-pulse burst by a factor of about 16 compared to delivering all of the energy in the single pulse emitted by the laser.

Abstract: A laser-illuminated wafer-exposing system such as a stepper or scanner having a first light intensity detector located within the exposing system near a mask and second light intensity detector located near the output of the laser. A feedback control system controls the output of the laser based on signals detected by at least one of the detectors. The feedback control system includes a processor programmed with an algorithm which is used to control the laser discharge voltage in order to provide light pulses having desired intensity at the mask with the laser operating in a burst mode. The algorithm utilizes at least the following parameters; a previously measured pulse energy, a calculated energy error, a calculated dose error, a value for the rate of change of pulse energy with voltage, and at least one reference voltage.