Abstract: A method is described for estimating a spectral feature of a pulsed light beam produced by an optical source and directed toward a wafer of a lithography apparatus. The method includes receiving a set of N optical spectra of pulses of the light beam; saving the received N optical spectra to a saved set; transforming the optical spectra in the saved set to form a set of transformed optical spectra; averaging the transformed optical spectra to form an averaged spectrum; and estimating a spectral feature of the pulsed light beam based on the averaged spectrum.

Abstract: Apparatus for and method of temperature compensating a focusing system in having at least one transmissive optical element with a thermal lens. A reflective optical element is introduced having a thermal lens complementary to the thermal lens of the transmissive optical element so that the combined optical characteristics of the two optical elements are substantially temperature independent. Provision can also be made for a change in the absorption of the transmissive optical element over time. The focusing system is especially applicable to systems for generating EUV light for use in semiconductor photolithography.

Abstract: A pulsed light beam emitted from an optical source is received, the pulsed light beam being associated with a temporal repetition rate; a frequency of a disturbance in the optical source is determined, the frequency being an aliased frequency that varies with the temporal repetition rate of the pulsed light beam; a correction waveform is generated based on the aliased frequency; and the disturbance in the optical source is compensated by modifying a characteristic of the pulsed light beam based on the generated correction waveform.

Abstract: Corrosion resistant electrodes are formed of brass that has been doped with phosphorus. The electrodes are formed of brass that contains about 100 ppm to about 1,000 ppm of phosphorus, and the brass has no visible microporosity at a magnification of 400×. The brass may be cartridge brass that contains about 30 weight percent of zinc and the balance copper. Corrosion resistant electrodes also may be formed by subjecting brass to severe plastic deformation to increase the resistance of the brass to plasma corrosion. The corrosion resistant electrodes can be used in laser systems to generate laser light.

Abstract: A method and system for performing injects of halogen gas into the chambers of a two chamber gas discharge laser such as a MOPA excimer laser for allowing operation of the laser within acceptable parameters and compensating for ageing effects without the necessity of performing refills is described. A parameter reflecting efficiency of the laser is measured, and the change in the parameter with respect to the length of laser operation is estimated. The change in the parameter with respect to the pressure in one of the chambers is also measured. At a given time, the total change in the value of the parameter is estimated, and from this change in pressure that is needed to reverse the change in the value of the parameter is calculated. The pressure in the chamber is then changed to correct for the amount of time that the laser has been in operation.

Abstract: A spectral feature of a pulsed light beam produced by an optical source is estimated by modifying the wavelength of the pulsed light beam based on a predefined repeating pattern having a pattern period including a plurality of steps, the modification including shifting the wavelength of the pulsed light beam by a wavelength offset from a baseline wavelength for each step in the pattern period; measuring the wavelength of the light beam for each step in the pattern period as the wavelength is modified across the pattern; and estimating a spectral feature of the pulsed light beam over an evaluation window that includes all of the steps within the pattern period based at least in part on the measured wavelength of the light beam for each step in the pattern period.

Abstract: Extreme ultraviolet light (EUV) is produced in a laser-produced plasma (LPP) EUV light source when laser light strikes a target. Measuring reflected light from the target by a Return Beam Diagnostics (RBD) module provides data on EUV production, including but not limited to target position, target focus, target shape, and target profile. In a RBD module, a controller sequences an optical switch to direct the reflected light between a blocking element and a sensing device, providing greater flexibility in measuring the reflected light during different aspects of the EUV generation process, such as different power levels and duty cycles of the laser light striking the target.

Abstract: A system and method for automatically performing gas optimization after a refill in the chambers of a two chamber gas discharge laser is disclosed. The laser is fired at low power, and the gas in the amplifier laser chamber bled if necessary until the discharge voltage meets or exceeds a minimum value without dropping the pressure below a minimum value. The power output is increased to a burst pattern that approximates the expected operation of the laser, and the amplifier chamber gas bled again if necessary until the voltage and an output energy meet or exceed minimum values, or until the pressure is less than a minimum value. The gas in the master oscillator chamber is then bled if necessary until the output energy of the master oscillator meets or falls below a maximum value, again without dropping the pressure in the chamber below the minimum value. While the pressure is adjusted, bandwidth is also measured and adjusted to stay within a desired range.

Abstract: A system for producing EUV light using a drive laser beam to irradiate a stream of material droplets. There is included a monitoring system for monitoring at least one of drive laser beam reflection from the drive laser beam and EUV radiation pulses and producing a detector signal, the detector signal being a pulse train. There is also included an arrangement for analyzing the detector signal to ascertain whether there exists at least one satellite droplet in the stream of material droplets.

Abstract: In master oscillator-power amplifier (MOPA) systems for generating laser light, a fluorine concentration in each of the master oscillator and power amplifier chambers is maintained. While sensors at the chambers can measure certain values of some variables, the sensors do not directly measure fluorine concentration. As a further complication, the values received from the sensors are known to be affected by various specified variables. To estimate the effect on the received values, an RLS algorithm and covariance matrix are used. To ensure that the RLS algorithm is responsive to recent changes in a specified variable, portions of the covariance matrix are reset to more quickly and more heavily weight the more recent values.

Abstract: A device and method are disclosed in which gas is caused to flow parallel to a flow of source material to form a gas shroud. The gas shroud may protect flow of source material from being disrupted by a cross flow of gas. The gas shroud may also limit heating of a physical shroud through which the source material passes and limit accumulation of source material on the physical shroud by deforming a plasma bubble formed during irradiation of the source material so that the plasma bubble does not come too near the physical shroud. A device and method are also disclosed for establishing an additional transverse flow of gas so that the gas shroud does not cause source material contamination of an optic used to collect light generated during irradiation of the source material.

Abstract: Focus of a laser optical system can be corrected using a variable radius mirror having a focusing cavity and a separate cooling cavity. Pressure of a focusing material at a sufficiently low mass flow in the focusing cavity deforms a reflective surface mounted to the focusing cavity, changing its radius. Cooling material provided to the cooling cavity cools the variable radius mirror. A laser beam is reflected by the deformed reflecting surface to focusing optics, focusing the reflected laser beam on an EUV-emitting target, and minimizing a laser focus error by one or more of: maximizing a measured EUV power or minimizing a measured laser beam divergence. Providing focusing material at a deformation pressure and at a sufficiently low mass flow, and providing a separate cooling cavity, avoids perturbations in the reflective surface which would otherwise affect laser beam focus.

Abstract: In master oscillator-power amplifier (MOPA) systems for generating laser light, a fluorine concentration in each of the master oscillator and power amplifier chambers is maintained. While sensors at the chambers can measure certain values of some variables, the sensors do not directly measure fluorine concentration. As a further complication, the values received from the sensors are known to be affected by various specified variables. To estimate the effect on the received values, an RLS algorithm and covariance matrix are used. To ensure that the RLS algorithm is responsive to recent changes in a specified variable, portions of the covariance matrix are reset to more quickly and more heavily weight the more recent values.

Abstract: An apparatus and method of operation for a high power broad band elongated thin beam laser annealing light source, which may comprise a gas discharge seed laser oscillator having a resonance cavity, providing a seed laser output pulse; a gas discharge amplifier laser amplifying the seed laser output pulse to provide an amplified seed laser pulse output; a divergence correcting multi-optical element optical assembly intermediate the seed laser and the amplifier laser. The divergence correcting optical assembly may adjust the size and/or shape of the seed laser output pulse within a discharge region of the amplifier laser in order to adjust an output parameter of the amplified seed laser pulse output. The divergence correcting optical assembly may comprise a telescope with an adjustable focus. The adjustable telescope may comprise an active feedback-controlled actuator based upon a sensed parameter of the amplified seed laser output from the amplifier laser.

Abstract: A method and apparatus for creating and utilizing dual laser curtains from a single laser source in a laser produced plasma (LPP) extreme ultraviolet (EUV) light system is disclosed. A polarizing beam splitter creates two beams of orthogonal polarization from a single laser, and the beams are used to generate two laser curtains. Sensors detect flashes from droplets of target material as they pass through the curtains. One sensor may detect the position of the droplets relative to a desired trajectory to the irradiation site so that the orientation of a droplet generator may be adjusted to direct subsequent droplets to the irradiation site, as in the prior art. A second sensor may detect each droplet as it passes through a curtain to determine when a source laser should generate a pulse so that the pulse will arrive at the irradiation site at the same time as the droplet, so that a signal may be sent to the source laser to fire at the correct time.

Abstract: An aspect of the disclosed subject matter includes a method of reducing the laser absorption of a beam reverser prism consisting of at least one of the following: increasing a first distance between a first incident point and a chamfered corner, wherein the first incident point is on a first reflective surface of the prism and the chamfered corner is formed between the first reflective surface and a second reflective surface of the prism, wherein the chamfered corner has a chamfered surface; increasing a second distance between a second incident point and the chamfered corner, wherein the second incident point is on the second reflective surface of the prism; and increasing a reflectivity of the chamfered surface of the chamfered corner of the prism. A method of determining a prime cut for an optical component is also disclosed. A laser including at least one prime cut optical component is also disclosed.

Abstract: Apparatus for and method of temperature compensating a focusing system in having at least one transmissive optical element with a thermal lens. A reflective optical element is introduced having a thermal lens complementary to the thermal lens of the transmissive optical element so that the combined optical characteristics of the two optical elements are substantially temperature independent. Provision can also be made for a change in the absorption of the transmissive optical element over time. The focusing system is especially applicable to systems for generating EUV light for use in semiconductor photolithography.

Abstract: Extreme ultraviolet light (EUV) is produced in a laser-produced plasma (LPP) EUV light source when laser light strikes a target. Measuring reflected light from the target by a Return Beam Diagnostics (RBD) module provides data on EUV production, including but not limited to target position, target focus, target shape, and target profile. In a RBD module, a controller sequences an optical switch to direct the reflected light between a blocking element and a sensing device, providing greater flexibility in measuring the reflected light during different aspects of the EUV generation process, such as different power levels and duty cycles of the laser light striking the target.

Abstract: A method and apparatus may comprise a line narrowed pulsed excimer or molecular fluorine gas discharge laser system which may comprise a seed laser oscillator producing an output comprising a laser output light beam of pulses which may comprise a first gas discharge excimer or molecular fluorine laser chamber; a line narrowing module within a first oscillator cavity; a laser amplification stage containing an amplifying gain medium in a second gas discharge excimer or molecular fluorine laser chamber receiving the output of the seed laser oscillator and amplifying the output of the seed laser oscillator to form a laser system output comprising a laser output light beam of pulses, which may comprise a ring power amplification stage.

Abstract: A laser includes a regenerative ring resonator that includes a discharge chamber having electrodes and a gain medium between the electrodes for producing a laser beam; a partially-reflective optical coupler, and a beam modification optical system in the path of the laser beam. The beam modification optical system transversely expands a profile of the laser beam such that the near field laser beam profile uniformly fills each aperture within the laser and such that the regenerative ring resonator remains either conditionally stable or marginally unstable when operating the laser at powers that induce thermal lenses in optical elements inside the regenerative ring resonator.