JP2003523091A - Gas discharge laser with stabilized average pulse energy - Google Patents

Abstract

(57) Abstract: A method and apparatus for maintaining the output energy of an excimer or molecular fluorine laser within a desired energy tolerance and maintaining an input drive voltage within an optimal input drive voltage tolerance. Excimer or molecular fluorine lasers consist of a laser tube filled with a gas mixture, several electrodes inside the laser tube connected to a gas discharge circuit for activating the gas mixture, and a resonator for generating a laser beam. And The method and apparatus include activating a laser to emit a laser beam within the tolerance of the desired energy. Measure the energy of the laser beam. The input drive voltage is adjusted to maintain the energy of the laser beam within the tolerance of the desired energy. Determine the value of the input drive voltage. Adjusting the total pressure of the gas mixture in the laser tube to maintain the input drive voltage within the tolerance of the optimal input drive voltage.

Description

Detailed Description of the Invention

(Priority) This application is based on US Provisional Patent Application No. 60/182, filed on February 11, 2000.
Claims the benefit of priority to No. 083.

FIELD OF THE INVENTION The present invention relates to gas discharge laser systems, and more particularly to systems which provide an output beam having a stabilized average pulse energy and which operates near the optimum input high voltage for discharge.

[0003] (Conventional technology)   Excimer lasers such as KrF and ArF lasers, and molecular fluorine (F _Two ) Gas discharge laser systems, including lasers, laser tube and cavity optics
It works differently depending on the situation of the parts. For example, a virtually new laser tube, a new
The gas discharge laser, which has new optical components and has new optical components, is an old laser tube.
, Significantly different from lasers with old cavity parts and / or old gas mixtures
Shows the following performance conditions. However, the age of the laser tube, the optical parts of the laser cavity,
Or a laser, no matter how old the gas mixture is, an applied process that uses a laser
Output laser near the average pulse energy predetermined based on the specifications of
Expected to generate a pulse.

In industrial applications, it is advantageous to have an excimer laser or a molecular fluorine laser that can be operated continuously for long periods of time, ie with a minimum downtime. Have excimer or molecular lasers that can operate without downtime all year while maintaining constant output beam parameters, or at least minimize the number and duration of downtime for routine maintenance Is desirable. More than 98% service life, for example, requires precise control and stabilization of the output beam parameters and thus precise composition of the gas mixture.

Unfortunately, the aggressive nature of fluorine or chlorine in the gas mixture causes gas contamination during the operation of excimer or molecular fluorine lasers.
Halogen gas is highly reactive, and as it reacts, the concentration in the gas mixture decreases while leaving a trace amount of contaminants. The halogen gas reacts with the other gases in the mixture as well as the material of the discharge chamber or laser tube.
Furthermore, reactions occur and the gas mixture deteriorates whether or not the laser is operating (discharging). For a typical KrF laser, the passive gas life is about 1 week.

During operation of a KrF excimer laser, it has been observed that the concentration of contaminants such as HF, CF ₄ , COF ₂ , SiF ₄ etc. increases rapidly (GM.
Jurisch et al., Gas contamination effect in discharge pumped KrF laser (
Gas Contaminant Effects in Discharge-Excited KrF Lasers), Applied Optics, Vol. 31, No. 12, pp. 1975-1981 (April 20, 1992)). In a static, ie non-discharged KrF laser gas mixture,
Increasing concentrations of HF, O ₂ , CO ₂ and SiF ₄ have been observed (see Juri, supra).
sch et al.).

One way to effectively reduce this gas degradation is to reduce or eliminate contamination sources within the laser tube. With this in mind, an all-metal ceramic laser tube is disclosed (D. Basting et al., Laser tube for halogen-containing gas discharge laser (Laserrohr fur halogenhaltige Gasentladun.
gslaser), G 295 20 280.1, January 25, 1995/1996.
Apr. 18, (See, Lambda Physics Novatube, incorporated herein by reference). FIG. 1 shows that by using a tube containing a material more resistant to halogen corrosion (line B), compared to using a tube that is not resistant to halogen corrosion (line A). 1 is a qualitative illustration of how the decrease in F ₂ concentration in a gas mixture can be delayed. While the F ₂ concentration shown by the line A has decreased to about 60% of the initial value after about 70 million pulses,
The F ₂ concentration shown by line B has only decreased to about 80% of its initial value after the same number of pulses. Cryogenic gas filters and other gas purification systems (US Pat. Nos. 4,534,034, 5,136,605, 5,430,7 assigned to the assignee)
52, 5,111,473 and 5,001,721.
No. 4,534,034 and 5,586,134, assigned to the present assignee, both of which are incorporated herein by reference. Incorporation by reference) also extends the life of the KrF laser gas to 100 million shots before a fresh replenishment is warranted.

[0008] Typically, gas discharge lasers such as excimer and molecular fluorine lasers
It is made to have a discharge circuit capable of applying electrical pulses to the electrodes in the discharge chamber with an input voltage within a wide dynamic range. Thus, as the optics of the laser tube and / or laser cavity age, or the gas mixture ages, an output with the same predetermined average pulse energy as the laser with the new laser tube and / or optics. The input voltage may be increased in order to continuously emit pulses. Heretofore, it has been accepted that the discharge becomes unstable and the efficiency decreases when the laser is operated at the high end and the low end of the wide dynamic range of the electric discharge circuit.

When a gas discharge laser has a discharge chamber that is filled with a gas mixture having a certain gas composition and total gas pressure and that includes a set of main discharge electrodes that are separated by a distance, some insulation with respect to the gas mixture between the electrodes. There will be a breakdown voltage. There is also an optimum value for the high voltage applied to the electrodes that maximizes efficiency and discharge stability. For example, if the laser tube, the electrode and the gas mixture are new enough, or if the breakdown voltage is so low that it is substantially below the optimum value, the discharge becomes very unstable and the electrode is damaged, or Can suffer significant wear. Moreover, among other potentially many things, other output laser beam parameters such as time pulse width, laser efficiency and / or bandwidth also change as the operating voltage changes, which is undesirable. A gas discharge laser having a certain gas composition and including a set of main discharge electrodes that are separated by a certain distance, and maintains the breakdown voltage of the discharge circuit and the corresponding drive voltage to be kept within the optimum range. Therefore, a gas discharge laser that can generate an efficient and stable discharge is desired.

Conventionally, in order to maintain the average pulse energy or the energy input amount near a predetermined constant value, the average pulse energy or the energy input amount is monitored, and the driving voltage is adjusted in the feedback loop so that the average pulse energy or the energy input amount is adjusted. Alternatively, the amount of energy input is kept at this predetermined constant value. As mentioned above, this causes the drive voltage to deviate from the optimum drive voltage by an undesirable amount.

Currently, the gas replenishment algorithm has been improved and is described in US patent application Ser. No. 09/447.
, 882 and 09 / 734,459.
A small amount of gas treatment such as HI) is performed. These patents are assigned to the present assignee and are hereby incorporated by reference. This low volume gas treatment can be performed to more frequently replenish the laser-active constituent gases in the discharge chamber and generally change the high voltage over the low volume region between gas treatments (see '882). .

Even when the laser-active constituent gas has the optimum composition, the accumulation of contaminants during fresh replenishment leads to a reduction in efficiency. As described above, the driving voltage is increased by an undesired amount higher than the optimum driving voltage, or new replenishment is frequently performed so that the operating voltage does not exceed the optimum operating voltage by more than the undesired amount. The disadvantages of raising the operating voltage too high have been argued, and making new refills at short intervals would result in extra undesirable laser downtime. Furthermore, since it is desired to increase the repetition rate, the problem of contaminant generation occurring at a correspondingly fast rate and more frequent replenishment would lead to longer laser outage times.

The gas discharge laser system can be configured so that the driving or applied high voltage is much lower than the optimum voltage immediately after a new refill. With such a configuration, it is possible to obtain a system in which the driving voltage becomes higher than the optimum value and the usable time of the laser becomes long until it is appropriate to stop the laser and perform new replenishment. But,
Since the drive voltage is too low, in this case the problems of discharge instability and electrode wear are encountered. Therefore, a gas discharge laser, especially an excimer or molecular fluorine laser, which can be operated for a long time without new replenishment, in which the input driving voltage for discharge changes only within a small range, A laser is desired that avoids the problems caused by large changes in the operating voltage.

US Pat. No. 5,450,436 describes some gas replenishment methods, such as injecting fresh gas into the discharge chamber, the final step of which is to expel a certain amount of gas to cause pressure in the chamber. Describes how to return the pressure to the optimum pressure (eg 2.5 bar).
In another embodiment described in the '436 patent, the pressure in the chamber remains increased after gas injection, and the slight increase in output energy due to the increase in pressure results in a drive voltage as low as the pressure. Will not rise. However, the pressure increase due to halogen implantation does not result in a pressure increase in the laser chamber, which substantially affects the output energy of the laser beam and correspondingly the input drive voltage.

(Problem to be Solved by the Invention) An object of the present invention is to make the operating input high voltage range lower than that of the conventional system while maintaining or increasing the usable time of the laser until a new replenishment. It is to provide an excimer or molecular fluorine laser system configured as possible.

(Means for Solving the Problems) According to the above object, the output energy of the excimer or molecular fluorine laser is maintained within a desired energy allowable range, and the input driving voltage is set to the optimum input driving voltage allowable range. Provide a way to stay within. The excimer or molecular fluorine laser comprises a laser tube filled with a gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture, and a resonance for generating a laser beam. And a vessel. The method involves operating a laser to emit a laser beam within a desired energy tolerance. Measure the energy of the laser beam. The input drive voltage is adjusted to keep the laser beam energy within the desired energy tolerance. Calculate the value of the input drive voltage. The total pressure of the gas mixture in the laser tube is adjusted to maintain the input drive voltage within the acceptable range of the optimum input drive voltage.

Further in accordance with the above object, a laser tube filled with a gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture and a resonance for generating a laser beam. A method for stabilizing the energy of an excimer or molecular fluorine laser having a container is provided. The method includes activating a laser to emit a laser beam. The energy of the laser beam is measured as the first energy. Performing a step of determining if the first energy is within a desired energy tolerance range. If the measured first energy is determined to be outside the desired energy tolerance range, the pressure of the gas mixture in the laser tube is adjusted to adjust the energy of the laser beam.

Further in connection with the above problems, a laser tube filled with a gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture and a laser beam are generated. And a method for optimizing the performance of an excimer or molecular fluorine laser with a cavity for the purpose. The method includes setting an input drive voltage value within an input drive voltage range that includes a predetermined optimum drive voltage to provide optimum laser system performance. The gas mixture is newly replenished in the laser tube. The laser is activated by operating the laser at the set value of the input drive voltage. Measure the energy of the laser beam. Performing a step to determine if the measured energy is within a desired energy tolerance range. If the measured energy is determined to be outside the desired energy tolerance range, the pressure of the gas mixture in the laser tube is adjusted to adjust the energy of the laser beam.

Further related to the above problems, a laser tube filled with the gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture and a laser beam are generated. And a method for optimizing the performance of an excimer or molecular fluorine laser with a cavity for the purpose. The method includes setting an input drive voltage value within an acceptable input drive voltage range that includes a predetermined optimum drive voltage to provide optimum laser system performance. The gas mixture is newly replenished in the laser tube. The laser is operated to emit a laser beam with the desired energy. The step of determining whether the input drive voltage applied to obtain the desired energy is within the input drive voltage range is performed. If the input drive voltage is determined to be outside the allowable input drive voltage range, the pressure of the gas mixture in the laser tube is adjusted to adjust the energy of the laser beam.

Further related to the above problems, a laser tube filled with the gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture,
A resonator for generating a laser beam with a desired energy, a gas exchange unit connected to the laser tube containing an auxiliary volume at a pressure lower than the pressure of the gas mixture in the laser tube, and a gas exchange unit and a laser. An excimer or molecular fluorine laser is provided that includes a processor that controls the gas flow to and from the tube. If it is determined that the driving voltage is lower than the allowable driving voltage range for obtaining the desired energy, the gas mixture is discharged to the auxiliary volume to reduce the pressure in the laser tube,
In order to increase the drive voltage applied to obtain the desired energy,
It constitutes a gas exchange unit and a processor.

Further related to the above problems, a laser tube filled with the gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture,
An excimer or molecular fluorine laser comprising a resonator for generating a laser beam at a desired energy, a gas exchange unit connected to the laser tube, and a processor controlling the gas flow between the gas exchange unit and the laser tube. provide.
When it is determined that the driving voltage is higher than the allowable driving voltage range for obtaining the desired energy, gas is added to the laser tube to increase the pressure inside the laser tube and lower the driving voltage applied to obtain the desired energy. The gas exchange unit and processor are configured so that

(Incorporation by Reference) The following is a list of references. In addition to the references cited above, other aspects of the elements or features of the preferred embodiments are disclosed which are not referred to in the following description, and thus are incorporated herein by reference. Each is incorporated into the detailed description of the preferred embodiments below. These documents, alone or in combination of two or more, will help to obtain variants of the preferred embodiment described in the detailed description below. In addition, patents, patent applications and non-patent documents are cited in the specification, which are also incorporated by reference into the preferred embodiment with the same effect as described with respect to the following documents. U.S. Pat. Nos. 4,997,573, 5,337,215 and 5,097,2
No. 91, No. 5,140,600, No. 5,450,436, No. 4,674,0
99, 5,463,650, 5,710,787, 6,084,8
97, 5,835,520, 5,978,406, 6,028,8
No. 80, No. 6,130,904, No. 6,151,350; U.S. Patent Application Nos. 09 / 418,052, 09 / 447,882, 09 /
583,037, 09 / 379,034, 09 / 447,882, 09 / 379,034, 09 / 484,818, 09 / 418,052.
No. 09 / 513,025, 09 / 734,459 and 09/58
8,561. These are each assigned to the same assignee as the present application; and Japanese Laid-Open Patent Publication No. 63-86593.

DETAILED DESCRIPTION OF THE INVENTION Excimer or molecular fluorine lasers and methods of operating them are provided below, according to preferred embodiments. The average pulse energy or energy input of the output pulses is monitored and, if the pulse energy or energy input fluctuates from a predetermined constant value, preferably in a feedback device including a processor, an energy detector and a gas control unit, in a laser tube. Adjusting the total pressure of the laser gas mixture to maintain the average energy or energy input of the output pulse near a predetermined, substantially constant value. In this way, the drive discharge voltage applied from the pulser module to the electrodes in the laser tube or laser discharge chamber is maintained within a predetermined voltage range that is smaller than in conventional laser systems. Further, the average pulse energy or energy input is preferably maintained near a predetermined constant average energy and / or energy input, preferably without shortening the interval of new replenishment, and more preferably actually increasing such interval. To do.

Here, the laser tube is the part of the laser system that is filled with a gas mixture that is excited to generate a laser beam, and the discharge chamber is the part of the laser tube that also includes a heat exchanger and a fan. Note that it refers to parts. However, wherever the terms laser tube and discharge chamber are used herein, these terms are meant to refer to the respective laser tube. Furthermore, it should be noted that when the term energy is used herein, it refers non-exhaustively to the average pulse energy for several pulses, the energy input at the workpiece, the pulse energy, the average power of the pulsed output laser beam.

Within a certain limit of the driving high voltage, that is, H for optimally operating the laser
According to a preferred embodiment together with a processor for controlling one or more special gas procedures, independent of the age of the optics of the laser tube and the laser cavity, for operating the laser near V (HV _opt ). Construct an excimer or molecular fluorine laser system. Such an algorithm involves adjusting the total pressure in the laser tube. Further, it comprises an algorithm that calculates the amount of pressure to be adjusted before performing the pressure adjustment and gives a more accurate pressure in the adjustment. Includes pressure adjustments in the energy control algorithm of the laser's expert system to determine if the output laser energy is out of tolerance, ie, greater than or less than the desired average pulse energy or energy input. And for a total pressure of the laser tube, in each case providing a further algorithm for pressure release or pressure application.

[0026] Regardless of the aging state of the laser tube or cavity optics, by adjusting the total gas pressure in the laser tube during and laser operation after a new refill, HV _{o pt} or electrode driving voltage near its The average pulse energy or energy input is preferably stabilized using a pulsar circuit of the laser configured to apply to. Therefore, application of HV _opt to laser discharge produces a laser beam with desired average pulse energy or energy near the desired energy input. Therefore, by adjusting other parameters of the laser system other than the input drive voltage, an excimer or molecular fluorine laser system can be obtained whose average pulse energy can be adjusted. This allows the input drive voltage to be operated within a narrower voltage range than conventional systems without shortening the new refill interval.

FIG. 2 is a schematic diagram of an excimer or molecular fluorine laser system according to a preferred embodiment. Suitable gas discharge laser systems are eg Ar
A DUV or VUV laser system, such as an excimer laser system such as F or KrF, or a molecular fluorine (F ₂ ) laser system for use with a deep ultraviolet (DUV) or vacuum ultraviolet (VUV) lithography system, is illustrated. Alternative configurations for laser systems for other industrial applications such as TFT annealing, photoablation and / or micromachining are similar to and / or variations on the system shown in FIG. 2 of the present application. Those of ordinary skill in the art will recognize that the above requirements have been met. Another DUV or VUV laser system and component arrangement for this purpose is described in US patent application Ser. No. 09 / 317,6.
95, 09 / 130,277, 09 / 244,554, 09/45
No. 2,353, No. 09 / 317,527, No. 09 / 343,333, No. 09
/ 512,417, 09 / 599,130, 60 / 162,735,
60/166, 952, 60/171, 172, 60/141, 67
No. 8, 60 / 173,993, 60 / 166,967, 60/147
, 219, 60 / 170,342, 60 / 162,735, 60 /
178,445, 60 / 166,277, 60 / 167,835, 60 / 171,919, 60 / 202,564, 60 / 204,095
No. 60 / 172,674, 09 / 574,921, 09/734,
459, No. 09 / 741,465, No. 09 / 686,483, No. 09/7
15,803 and 60 / 181,156, and US Pat. No. 6,005.
, No. 880, No. 6,061,382, No. 6,020,723, No. 5,946.
, 337, 6,014,206, 6,157,662, 6,154
, 470, No. 6,160,831, No. 6,160,832, No. 5,559
, 816, 4,611,270, 5,761,236. Each of these was assigned to the same assignee as this application and is hereby incorporated by reference.

The system shown in FIG. 2 generally comprises a laser chamber 2 (or a laser including a heat exchanger and a fan for circulating a gas mixture in the chamber 2 or laser tube) having a pair of main discharge electrodes 3 connected to a solid pulser module 4. Tube) and gas handling module. The gas handling module 6 is valved to the laser chamber 2 and contains halogen gas, noble gas, buffer gas and preferably gas additive for ArF and KrF excimer lasers, halogen gas for F ₂ lasers. , Buffer gas and optionally gas additives, preferably in premixed form (see US patent application Ser. No. 09 / 513,025, and US Pat. No. 4,977,573, assigned to the same assignee as the present application). Each of which is incorporated herein by reference). The solid pulser module 4 is powered by a high voltage power supply 8. The laser chamber 2 is surrounded by the optical component module 10 and the optical component module 12 and forms a resonator. Optics modules 10 and 12 may be controlled by an optics control module (not shown) or directly by a computer or processor 16 as shown.

The laser control processor 16 receives various inputs and controls various operating parameters of the system. The diagnostic module 18 preferably has pulse energy at the separation position of the main beam 20 through optics for deflecting a small portion of the beam towards the module 18, such as a beam separation module (not specifically shown), Receives and measures one or more parameters such as average energy and / or power and wavelength. Beam 20 is preferably a laser that is directed towards a workpiece (not shown) such as an imaging system (not shown) and ultimately lithographic applications, and may also be output directly to the application process. The laser control computer 16 communicates with the stepper / scanner computer, other control units and / or other external systems (not shown) via the interface 24.

The laser chamber 2 contains a laser gas mixture and includes a set of main discharge electrodes plus one or more preionization electrodes (not shown). Suitable main electrodes 3 are described in US patent application Ser. Nos. 09 / 453,670 and 60 / 184,705. These are assigned to the same assignee as the present application and are hereby incorporated by reference.
Other electrode configurations have been assigned to the same assignee as this application in US Pat.
565 and 4,860,300, alternate embodiments are U.S. Pat. Nos. 4,691,322, 5,535,233 and 5,557,6.
No. 29, all of which are incorporated herein by reference. Suitable preionization units are disclosed in U.S. patent application Ser.
87, an alternative embodiment is US Pat. No. 5,337,330,
No. 5,818,865 and No. 5,991,324, all of which are incorporated herein by reference.

The solid-state pulser module 4 and the high-voltage power supply device 8 supply electric energy to the pre-ionization and main electrode 3 in the laser chamber 2 by compressed electric pulse,
Activate the gas mixture. Suitable pulser modules and components for high voltage power supplies are described in US patent application Ser. Nos. 09 / 640,595, 60 / 198,058, 60 / 204,095, 09 / 432,348 and 09. / 390,1
46, and 60 / 204,095, and US Pat. No. 6,005,8.
80 and 6,020,723. Each of these was assigned to the same assignee as this application and is hereby incorporated by reference. Other alternative pulser modules are US Pat. Nos. 5,982,800 and 5,982.
795, No. 5,940,421, No. 5,914,974, No. 5,949,
No. 806, No. 5,936,988, No. 6,028,872, No. 6,151.
346 and 5,729,562. These are referenced and incorporated herein. Conventional pulser modules can generate electrical pulses greater than 1-3 Joules of power (see the '988 patent).

The laser cavity surrounding the laser chamber 2 containing the laser gas mixture preferably comprises an optics module 10 containing narrowing optics for a narrow line excimer or molecular fluorine laser. If narrowing is not desired, narrowing is done in the pre-optics module 12, using a spectral filter outside the resonator, or a laser system with narrowing optics in front of the high reflector. In, the optical component module can be replaced with a high reflectance (HR) mirror or the like to narrow the bandwidth of the output beam.

The laser chamber 2 is closed by a window that is transparent to the wavelength of the emitted laser light 20. This window may be a Brewster window or it may be tilted at another angle to the optical path of the resonant beam, for example at an angle of 5 °. Also, one of the windows may serve the beam outcoupling.

A portion of output beam 20 is an outcoupler of optics module 12.
After passing through, its output portion preferably impinges on a beam splitting module (not shown). The beam splitting module continues the main part of the beam 20 as the output beam 20 of the laser system, while deflecting a part of the beam towards the diagnostic module 18 or a small part of the externally coupled beam to the diagnostic module. Includes optics to allow access (US patent applications 60 / 177,809, 09 / 598,552 and 60/166, assigned to the same assignee as the present invention.
See 952, and U.S. Pat. No. 4,611,270. Incorporated herein by reference to each of these). Suitable optics include beam splitters or otherwise partially reflective surface optics. The optical component may include a mirror or a beam splitter as the second reflective component. More than one beam splitter and / or HR mirror and / or diagnostic mirror may be used to direct a portion of the beam to a component of diagnostic module 18. Holographic beam sampler, transmission grating, partially transmissive reflection diffraction grating, grism, prism or other reflective, dispersive and / or transmissive 1
Using one or more optics, only a small portion of the main beam 20 is detected for detection by the diagnostic module 18, while allowing the majority of the main beam 20 to reach the application process either directly or through an imaging system or otherwise. The beams may be separated.

The output beam 20 may pass through the beam splitting module while the reflected beam portion is directed at the diagnostic module 18. Or, a small part is transparent and diagnostic module 1
While reaching 8, the main beam 20 may be reflected. The externally coupled beam portion that successively passes through the beam splitter is the output beam 20 of the laser, which expands towards industrial or experimental applications such as imaging systems and workpieces for photolithographic applications.

Particularly for molecular fluorine laser systems and ArF laser systems, the beam path may be enclosed by an enclosure (not shown), such as to keep the beam path free of light absorbing species. A smaller enclosure may provide a seal between the chamber 2 and the optics modules 10 and 12, as well as between the beam splitter (not shown; see above) and the diagnostic module 18. A suitable enclosure is US patent application Ser. Nos. 09 / 343,333, 09/598, assigned to the same assignee and incorporated herein by reference.
552, 09 / 594,892 and 9 / 131,580, and US Pat. Nos. 5,559,584, 5,221,82, which are incorporated herein by reference.
3, No. 5,763,855, No. 5,811,753 and No. 4,616.
No. 908 for further details.

The diagnostic module 18 preferably includes at least one energy detector.
This detector measures the total energy in the beam section which directly corresponds to the energy of the output beam 20 (US Pat. No. 4,611,270 and US patent application Ser. No. 09 /
See 379,034. Each of which was assigned to the present assignee and is incorporated herein by reference). Optical structures such as optical attenuators, eg flat or coated optical attenuators, or other optical components are formed on or near the detector or beam splitting module 21 to determine the intensity of the emission impinging on the detector, the spectral distribution and And / or controlling other parameters (US patent application Ser. Nos. 09 / 172,805, 60 / 172,749, 60 / 166,952, 60 / 177,809).
No. 60 / 178,620. Each of these was assigned to the same assignee as the present application and is hereby incorporated by reference).

Another component of diagnostic module 18 is preferably a wavelength and / or bandwidth detection component such as a monitor etalon or grating spectrometer (US patent application Ser. No. 09 / assigned to the same assignee as this application). 416, 344, 60 / 186,003
No. 60 / 158,808, 60 / 186,096, 60/186,
096 and 60 / 186,096 and 60 / 202,564, and U.S. Patents 4,905,243, 5,978,391 and 5,45.
0,207, 4,926,428, 5,748,346, 5,02
See 5,445, and 5,978,394. All wavelength and / or bandwidth detection and monitoring components mentioned above are incorporated herein by reference.

For gas control and / or output beam energy stabilization, or by monitoring the amount of amplified spontaneous emission (ASE) in the beam as described in detail below, the ASE is below a predetermined level. Other components of the diagnostic module, such as for confirmation, are each assigned to the same assignee as the present application and are incorporated by reference into US patent application Ser. Nos. 09 / 484,818 and 09 / 418,052. It may also include a pulse shape detector or an ASE detector, each of which is described in. There may be, for example, a beam alignment monitor as described in US Pat. No. 6,014,206, or a beam profile monitor of US patent application 60 / 181,156 assigned to the same assignee. Each of these patent documents is referenced and incorporated herein.

The processor or control computer 16 determines the pulse shape, energy, ASE, among other input and output parameters of the laser system and output beam.
Energy stability, energy overshoot for burst mode operation, wavelength,
It receives and processes several values of spectral purity and / or bandwidth. The processor 16 also controls the narrow line module to adjust wavelength and / or bandwidth or spectral purity and to control the power supply and pulser modules 4 and 8, preferably moving average pulse power and energy. Then, the amount of energy input to the workpiece is stabilized near a desired value. In addition, the computer 16 controls the gas handling module 6 which includes gas supply valves connected to various gas sources. Further functions of the processor 16, such as overshoot control, energy stability control and / or monitoring input energy for discharge, are assigned to the assignee of the present application and in US patent application Ser. No. 09 / 588,561 incorporated herein by reference. Described in detail.

As shown in FIG. 2, the processor includes a solid-state pulser module 4 and an HV power supply device 8.
And separately or in combination, the gas handling module 6, the optical component module 1
0 and / or 12, preferably in communication with diagnostic module 18 and interface 24. The processor also controls an auxiliary volume 26 which is preferably connected to a vacuum pump 28 to expel gas from the laser tube 2 to reduce the total pressure in the tube 2 in accordance with the preferred embodiment detailed below. In this way, the processor receives pulse energy and / or beam output data from the diagnostic module 18 and preferably discharges in a feedback control loop according to one or more algorithms described below with reference to FIGS. The input voltage 30 and the total laser tube pressure 32 are controlled to control the average energy or energy input in the laser beam 20 output by the laser.

The laser gas mixture is first filled into the laser chamber 2 by a process referred to herein as “new fill”. In this process, the laser gas and contaminants in the laser tube are evacuated and replenished with fresh gas of optimum gas composition.
The highly stable gas composition for excimer or molecular fluorine lasers according to the preferred embodiment uses helium or neon or a mixture of helium and neon as buffer gas. Suitable gas compositions are each assigned to the present assignee and are incorporated herein by reference US Pat. No. 4,393,405, 6,157,16.
2 and 4,977,573 and US patent application Ser. No. 09 / 513,02.
5, No. 09 / 447,882, No. 09 / 418,052 and No. 09/5
88,561. The concentration of fluorine in the gas mixture is 0.003%
To 1.00%, preferably around 0.1%. Additional gas additives such as noble gases may be added to increase energy stability, overshoot control, and / or as an attenuator as described in the 09 / 513,025 application incorporated by reference above. . In particular, xenon, krypton and / or argon may be added to the F ₂ laser. The concentration of xenon or argon in the mixture ranges from 0.0001% to 0.1%. Xenon or krypton, which also has a concentration of 0.0001% to 0.1%, may be added to the ArF laser. Xenon or argon, which also has a concentration of 0.0001% to 0.1%, may be added to the KrF laser.

The gas handling module 6, which preferably comprises a vacuum pump, a valve network and one or more gas compartments, is used to carry out the halogen and noble gas injection, total pressure regulation and gas exchange processes. The gas handling module 6 receives gas via gas lines connected to gas containers, tanks, cans and / or bottles. Some suitable and alternative gas handling and / or replenishment procedures other than those specifically described herein (see below) are US Pat. Nos. 4,977,573 and 5 assigned to the same assignee as this application. , 396,514 and U.S. Patent Applications Nos. 09 / 447,882, 09 / 418,052, 09 / 379,034, 09 / 734,4.
59, 09 / 513,025 and 09 / 588,561, and U.S. Patents 5,978,406, 6,014,398 and 6,028,8.
No. 80 is explained. All of these are incorporated herein by reference. '0 above
According to the 25th application, xenon gas is internally supplied to the laser system, or
Alternatively, it may be supplied externally.

The total pressure adjustment in the form of gas release or total pressure reduction in the laser tube 2 is preferably carried out using the auxiliary volume 26. A valve is opened between the auxiliary volume 26 and the laser tube 2 when the auxiliary volume 26 has a lower pressure than the laser tube 2, preferably by means of a vacuum pump connected to the auxiliary volume before or during the pressure release. Even if the total pressure is adjusted by using the valve of the gas handling unit 6 and injecting a plurality of buffer gases such as helium, neon or a combination thereof in a single combination or by injecting them singly. Good. For example, when it is determined that the desired partial pressure of the halogen gas is in the laser tube 2 after the total pressure adjustment, the gas composition adjustment may be performed after the total pressure adjustment. Further, the total pressure may be adjusted after the gas is replenished, or may be combined with the adjustment of the discharge driving pressure which is smaller than the case where the pressure adjustment is not combined.

An auxiliary volume 26 is connected to the laser tube 2 to emit gas from the laser tube 2 into the volume 26 based on a control signal received from the processor 11. The processor 11 regulates the gas released to the auxiliary volume 26 via the valve assembly and also delivers the gas or gas mixture to the laser tube 2 via the valve assembly or valve system associated with the gas handling unit 6. adjust.

Preferably, the auxiliary volume has a known volume and preferably comprises a reserve chamber or compartment with a pressure gauge attached to measure the pressure in the auxiliary volume. Instead of or in combination with a pressure gauge, the flow rate controller allows the processor to control the flow rate of gas from the tube 2 to the auxiliary volume 26, and how much gas is being discharged by the processor or It can be precisely controlled and / or measured if it has been released. The laser tube and external volume 26 also have means for measuring the temperature of the gas in the volume 26 and tube 2, such as a thermocouple array, respectively. Compartment 7
The volume may be several to several thousand cm ³ (preferably, the laser tube 2 has a volume of 42
3,000 cm ³ ).

At least one valve is included to control the flow of gas between the laser tube 2 and the auxiliary volume 26. A valve may be further included between them. Also, the vacuum pump 2
8 and auxiliary volume 26, another valve is included to provide vacuum pump 28 and auxiliary volume 26.
You may control the access to and from. Further, one or more valves are provided between the vacuum pump 28 and the external volume 26 and / or between the laser tube 2 and the external volume 26 to control the atmosphere in the pipe between them. An additional pump or the same vacuum pump 28 is used to evacuate the tubing between the laser tube and the auxiliary volume either directly or via the auxiliary volume.

For total pressure release, according to the algorithm of the preferred embodiment described herein,
A quantity of the gas mixture in the tube 2 is preferably discharged from the laser tube 2 into the auxiliary volume 26. For example, the same auxiliary volume may be used for the partial, minor or trace gas displacement operations described in the 09 / 734,459 application incorporated by reference above. As an example, a gas handling unit 6 connected to the laser tube 2 directly or via an additional valve assembly, such as one that includes a small compartment controlling the amount of injected gas (see the '459 application), is a KrF laser. On the other hand, it includes a gas pipe for injecting the premix A containing 1% F ₂ : 99% Ne and another pipe for injecting the premix B containing 1% Kr: 99% Ne. Premix B has Ar instead of Kr for ArF laser and Premix B for F ₂ laser
Not used. Therefore, by injecting the premix A and the premix B into the tube 2 via the valve assembly, it is possible to replenish the fluorine and krypton concentrations (for KrF laser, for example) in the laser tube, respectively. Then, a certain amount of gas is released corresponding to the injected amount. Auxiliary gas lines and / or valves may be used to inject the auxiliary gas mixture. A gas injection procedure, such as a new refill, partial and low volume gas replacement, enrichment and normal micro halogen injection, and any other gas replenishment actions are initiated and controlled by the processor 11. The processor 11 controls the valve assembly of the gas handling unit 6, the laser tube 2, the auxiliary volume 26 and the vacuum pump 28 based on various input information in the feedback loop.

An example of the method according to the invention for the precise and precise release of gas from the laser tube 2 into the auxiliary volume 26 will now be described. Similar procedures for replenishing the gas accurately and accurately, including injection into the laser tube 2, are preferably used for small gas injections, so that there is no significant distribution of the output beam parameters with each gas injection. Please note that. For example, when the processor 16 monitoring the parameter indicating the fluorine concentration in the laser tube 2 determines that it is time to increase the halogen concentration in the gas mixture in the laser tube 2, the processor 16 injects a trace amount of halogen (μHI). May be initiated (further description of suitable gas replenishment practices can be found in the '459 application).

For the preferred total pressure release according to this preferred embodiment, the processor 16 determines the timing of the pressure release. The processor 16 then sends a signal to open the valve between the tube 2 and the volume 26 until a predetermined pressure is reached in the auxiliary volume 26, or according to a known flow rate and when the valve should be opened. To allow gas to flow from volume 26. Then close the valve. Preferably, the pressure in the pipe 2 after the discharge is measured by a pressure gauge of the pipe 2 or calculated by using a known gas discharge amount and the gas amount in the pipe 2 before the discharge. The valve between the vacuum pump and the auxiliary volume is then preferably opened to evacuate the volume 26 of gas.

When the pressure in the pipe before discharge is 3 bar, the pressure in the pipe is 42,000 cm ³ , and the pressure in the auxiliary capacity after discharge rises, for example, around 3 bar,
0.5 × [(volume of the auxiliary volume 26) / 42,000] bar results in a reduced pressure in the tube 2 as a result of the discharge. Specific total pressure release or additional algorithm,
This will be described below with reference to FIGS.

The above calculation is performed by the processor 16 to more accurately determine the amount of gas released or the amount of gas before release, and based on the information received by the processor 16 and / or pre-programmed criteria, the processor 16 The pressure in the auxiliary volume 26 may be set according to the calculated amount of gas to be released. Preferably, the auxiliary volume is evacuated so that the pressure measured by the gauge measuring the pressure inside volume 26 is substantially zero and very low. Also, the temperature difference between the gas in the tube 2 and the auxiliary volume 26 can be corrected very accurately by the processor 16, or the temperature in the auxiliary volume can be preset to the temperature in the laser tube 2, for example. Good.

There may be a plurality of auxiliary capacitors such as the above-mentioned auxiliary capacitor 26, and each may have different characteristics such as volume space. For example, there may be two compartments, one for the gas replacement procedure and the other for the total pressure release. There may be more than two compartments and the amount of gas released may be varied or the drive voltage range corresponding to different gas actuation algorithms adjusted (see the '459 application).

A general description of the narrowing features of some embodiments of the invention will now be given,
High spectral purity or bandwidth (eg, 1
Listed are patents and patent applications incorporated by reference, with variations and features that can result in an output beam having less than pm, preferably less than or equal to 0.6 pm. Examples of narrowing optics housed in the optics module 10 include a beam expander, a selective interference device such as an etalon, and a diffraction grating. This grating produces a relatively high degree of scattering for narrow band lasers such as those used with catadioptric or catadioptric photolithography imaging systems. As mentioned above, the front optics module may also include line narrowing optics (09 / 715,803, 60/173).
See applications 993, 60 / 170,919 and 60 / 166,967. Each of these has been assigned to the assignee and is hereby incorporated by reference).

For semi-narrow band lasers such as those used with total internal reflection imaging systems, the grating may be replaced with a high reflectivity mirror and the scattering prisms cause slight scattering. Semi-narrowband lasers typically have an output beam linewidth of greater than 1 pm and can be as high as 100 pm in some laser systems, depending on the laser's characteristic wide bandwidth.

The beam expander of the exemplary narrowing optics of the optics module 10 preferably includes one or more prisms. The beam expander may include lens assemblies or other beam expanding optics such as converging / diverging lens pairs. The grating or high-reflectance mirror is preferably rotatable and the wavelengths reflected within the acceptance angle of the resonator can be selected or tuned. Alternatively, the pressure of the grating, other components or optical components, or the entire narrowing module is assigned to the present assignee and is incorporated herein by reference, 60 / 178,445 and 09 / 317,527 It may be adjusted according to the description of the application. A grating may be used to scatter the beam to achieve a narrow bandwidth, and preferably to retroreflect the beam on the laser tube. Alternatively, a high-reflectance mirror that receives the reflection from the grating and bounces the beam on the grating having the Littman configuration may be arranged behind the grating, or the grating may be a transmission grating. One or more scattering prisms can also be used and more than one etalon can be used.

There are many alternative optical configurations that can be used, depending on the type and degree of narrowing and / or the desired selection and adjustment, as well as the particular laser incorporating the narrowing optics. To this end, the references set forth below are incorporated herein by reference. U.S. Pat. Nos. 4,399,540, 4,905 assigned to the same assignee as the present application
, 243, 5,226,050, 5,559,816, 5,659
, 419, 5,663,973, 5,761,236, 6,081
, 542, 6,061,382 and 5,946,337, and U.S. Patent Applications Nos. 09 / 317,695, 09 / 130,277, 09 /
244,554, 09 / 317,527, 09 / 073,070, 09 / 452,353, 09 / 602,184, 09 / 629,256
No. 09 / 599,130, 60 / 170,342, 60/172,
749, 60 / 178,620, 60 / 173,993, 60/1
66,277, 60 / 177,967, 60 / 167,835, 6
0 / 170,919, 60 / 186,096. US Pat. No. 5,095,4
No. 92, No. 5,684,822, No. 5,835,520, No. 5,852,6
No. 27, No. 5,856,991, No. 5,898,725, No. 5,901,1
63, 5,917,849, 5,970,082, 5,404,3
66, 4,975,919, 5,142,543, 5,596,5
96, No. 5,802,094, No. 4,856,018, No. 5,970,0
No. 82, No. 5,978,409, No. 5,999,318, No. 5,150,3
70 and 4,829,536 and German Patent DE 298 2.
No.2090.3.

The optics module 12 preferably includes means for outcoupling the beam 20, such as a partially reflective resonant reflector. Otherwise, the beam 20 may be outcoupled, such as by a partially reflecting surface of an intracavity beam splitter or other optical element, in which case the optics module 12 comprises a high reflector. Optics control module 14 controls optics modules 10 and 12, preferably by receiving and decoding signals from processor 16 and initiating reconditioning or reconfiguration procedures (see '353, supra).
, '695,' 277, '554, and' 527 applications).

The preferred embodiment is an excimer and molecular device configured to adjust the average pulse energy of the output beam of the laser system by using a gas handling procedure that involves adjusting the total pressure of the gas mixture in the laser tube 2. Specially related to fluorine laser system. The desired average pulse energy corresponds to the input drive voltage within a high voltage tolerance around HV _opt to avoid operating lasers with new laser tubes and optics at optimum drive voltage levels, ie below HV _opt Until then, the total gas pressure after fresh replenishment is advantageously reduced by total pressure release as described above with reference to FIG.

During the laser operation, a gas replenishment procedure for the KrF and ArF excimer lasers to replenish the amounts of halogen, noble gas and buffer gas in the laser tube, and for molecular fluorine lasers to replenish the halogen and buffer gas. Keep the halogen and noble gas concentrations constant by means of and keep these gases after the new replenishment procedure in the same predetermined ratio as in the laser tube 2. As mentioned above, the resulting reduction in the total pressure in the tube 2 is achieved by venting the gas from the tube 2 through the auxiliary volume 26. Gas injection operations such as μHI, as understood from the aforementioned '459 application, are advantageously modified for microgas replacement procedures to reduce the total pressure to compensate for the increased energy of the output laser beam. In contrast, or in the alternative, conventional laser systems reduce the input drive voltage to bring the energy of the output beam to a predetermined desired energy. In this way, the exchange rate of the gas mixture or the laser tube 2
Such as by controlling the gas flow velocity through the gas procedure is supplemented with a gas, and while maintaining the average pulse energy or energy input, keeps the driving voltage within a narrow range around HV _{op t.}

Further stabilization by increasing the average pulse energy during laser operation can advantageously be carried out by raising the total pressure of the gas mixture in the laser tube to P _max . If the gas injection is not compensated by outgassing after injection, the increase in total pressure will occur automatically. Or, it is caused by the positive rise of the total gas pressure in the laser tube 2. This total pressure increase does not depend on any gas replenishment procedure, or adjusting the gas composition to the desired composition, or controlling the increase in average pulse energy due to the total pressure increase. Advantageously, the gas procedure described herein allows the laser system to operate within a very narrow range near the HV _opt while providing average pulse energy control and gas replenishment.

A laser system having a discharge chamber or laser tube 2 with the same gas mixture, total gas pressure, constant electrode distance and constant charge rise time of the laser peak capacitor of the pulsar module 4 has a constant discharge breakdown. Have a voltage. In the operation of the laser, there is an optimum driving voltage HV _{opt in} which the laser beam is most efficiently generated and the discharge is stable.

As briefly mentioned above, operating a laser with an input drive voltage well below the HV _opt can create undesired situations for conventional laser tubes. Such low drive voltages are outside the drive voltage range for operating the laser of the preferred embodiment. When operating the laser at this low discharge voltage, the discharge is not stable and the electrodes of conventional laser systems can quickly corrode or burn violently. To avoid operating a laser with new laser tube and optics at a voltage below HV _opt , a new The total gas pressure in the laser tube 2 after replenishment is advantageously reduced according to the preferred embodiment. In this way, the desired average pulse energy is achieved and at most only the deviations from the optimum drive voltage HV _opt are dealt with. For example, conventional lasers typically operate at 1.5 kV or normal total laser tube pressure at the lower end of the conventional range, while preferred embodiment lasers near 1.7 kV, or near the optimum input drive voltage. In operation, the laser tube pressure is reduced to, for example, a low pressure around the minimum allowable pressure P _min .

The first preferred algorithm according to this procedure is shown in the flow diagram of FIG. Referring to FIG. 3, _E s in S31 step, to set parameters including the _{U s, ΔE s, ΔP} and _{P mi n.} Where E _s corresponds to the desired average output pulse energy of the laser oscillation, preferably around 10 mJ, and U _s corresponds to the desired drive voltage for laser operation with the average pulse energy E _s , preferably It is around _{HV opt} or may, as described above, _{HV o pt} and _{U s} correspondingly is preferably around 1.7 kV, Delta] E _s is the desired average pulse energy by the laser operating in the driving voltage _{U s} Corresponding to the tolerance range, preferably around 0.5 mJ or less, ΔP is a given amount of the released gas mixture, eg about 100 mbar, is released during the step, and P _min is the total gas pressure in the laser tube 2. Corresponding to the predetermined minimum allowable value of 2200
And 2800 mbar, the minimum pressure P _min depends on the gas mixture of the laser system and therefore varies.

In step S32, a new replenishment is performed as described above and / or as understood by one of ordinary skill in the art. In step S33, the laser is operated at a constant or substantially constant drive voltage U _s and a duty cycle of 100%. Next, in step S34, the output average pulse energy E is measured by the energy detector. The energy measured here is preferably the processor 16 of FIG.
Send to.

The processor 16 then determines if the measured energy E is not greater than the acceptable range, ie E> E _s + ΔE _s . If the processor 16 determines in step S35 that the energy E is larger than the allowable limit E _s + ΔE _s , then step S3
In 6 steps, pressure discharge of ΔP is performed from the laser tube 2. Next, when it is determined in step S37 that the pressure P in the pipe 2 after the pressure release is greater than P _min ,
The procedure is returned to step S33. However, if it is determined in step S38 that the pressure P in the pipe 2 after pressure release is equal to or lower than P _min , the gas optimization procedure ends in step SF. After the energy measurement in step S34, the processor 16 terminates the gas optimization procedure in step SF if the measured energy E is within or below the acceptable range, ie E <E _s + ΔE _s and step S39 is determined. .

[0067]   A second preferred algorithm according to the gas optimization procedure of the preferred embodiment is shown in FIG.
Shown in the raw diagram. Referring to FIG. 4, in step S41, E_s, U_s, ΔE _s , Q and P_minSet parameters including. here,   E_sCorresponds to the desired average output pulse energy of the laser oscillation,   U_sIs the average pulse energy E_sDrive power for laser operation with
Equivalent to pressure, preferably HV_optOr near it,   ΔE_sIs the drive voltage U_sOf average pulse energy by laser operation in
Corresponds to the desired tolerance,   Q is the desired reduction in average laser pulse energy and the discharge pressure of the gas mixture.
Corresponding to a factor determined based on the relationship with the required value, usually between 2 and 4,
and   P_minCorresponds to a predetermined minimum permissible value of the total gas pressure in the laser tube 2. these
Some suitable values for the amount of

In step S42, new replenishment is performed as described above and / or as understood by one of ordinary skill in the art. In step S43, the laser is operated at a constant or substantially constant drive voltage U _s and a duty cycle of 100%. Next, in step S44, the output average pulse energy E is measured by the energy detector. The energy measured here is preferably the processor 16 of FIG.
Send to.

The processor 16 then determines if the measured energy E is not greater than the acceptable range, ie E> E _s + ΔE _s . If the processor 16 determines in step S45 that the energy E is greater than the allowable limit E _s + ΔE _s , then step S4
In step 6, the processor 16 calculates the amount of pressure ΔP to be released. S46
In step, the energy difference δE is calculated as δE = (E−E _s ) / E. Next, the pressure difference δP is calculated as δP = δE / Q. Then, the pressure release amount ΔP is calculated as ΔP = P × δP = P × (E−E _s ) / (Q × E). Where P is the pressure in the tube before the pressure release ΔP.

Next, in step S47, pressure discharge of the amount ΔP calculated from the laser tube 2 is performed. After that, in step S48, when it is determined that the pressure P in the pipe 2 after the pressure release is higher than P _min , the procedure is returned to step S43. However, if it is determined in step S49 that the pressure P in the pipe 2 after pressure release is equal to or lower than P _min , the gas optimization procedure ends in step SF. After the energy measurement in step S44,
If the measured energy E is within or below the acceptable range, ie E ≦ E _s + ΔE _s , the processor 16 determines that the gas optimization procedure is S
It ends in F step.

FIG. 4 shows in FIG. 3 that the adjustment of the average pulse energy by lowering the total gas pressure in the laser tube is carried out by the pressure release in the amount calculated in the step S46 before the release in the step S47. It is an alternative algorithm to the algorithm. Figure 3
In contrast to the algorithm shown in (1), the pressure release amount ΔP is obtained first.

FIG. 5 refers to the above, the average laser output energy versus the same when the Q factor used to determine the amount of pressure to be released in step S46 of the algorithm of FIG. 4 is various values. Fig. 5 represents a diagram of pressure relief which is the discharge pressure of a quantity. The graph in Figure 5 is
When operating the laser with a Q factor of Q = 2, the average output pulse energy is about 2 m
If the J is reduced, while the same amount of pressure relief is done with a laser operating at Q = 9, the average output pulse energy is reduced by only about 0.4 mJ. Q factor is Q = 3 and Q =
For lasers operating between 8 and 8, the reduction in average output pulse energy varies between 2 and 0.4 mJ for the same pressure release. Thus, FIG. 5 clearly shows that for the same pressure release, the average pulse energy decreases by an amount that depends on the Q factor of the laser system. Next, in order to reduce the output energy by the same amount of energy for lasers operating at different Q values,
According to the algorithm, the pressure release amount is advantageously changed as shown in the calculation step S46 in which the calculation amount depends on the q factor. The accuracy of the method of reducing the average pulse energy to the desired pulse energy, and the number of such procedures, is improved according to the algorithm of FIG.

A third preferred algorithm according to the gas optimization procedure of the preferred embodiment is shown in the flow diagram of FIG. Referring to FIG. 6, in step S61, E _s , U _s , Δ
Set parameters including E _s , Q, P _min and P _max . Where E _s corresponds to the desired average output pulse energy of the laser oscillation, U _s corresponds to the desired drive voltage for laser operation with the average pulse energy E _s , preferably at or near HV _opt. , ΔE _s corresponds to the desired tolerance of the average pulse energy due to laser actuation at the drive voltage U _s , and Q is the relationship between the desired reduction of the average laser pulse energy and the required value of the discharge pressure of the gas mixture. P _min corresponds to a predetermined minimum permissible value of the total gas pressure in the laser tube 2, and P _max corresponds to a predetermined maximum permissible value of the total gas pressure in the laser tube 2. Usually 3b
greater than ar.

In step S62, a new replenishment is performed as described above and / or as understood by one of ordinary skill in the art. In step S63, the laser is operated at a constant or substantially constant drive voltage U _s and a duty cycle of 100%. Next, in step S64, the output average pulse energy E is measured by the energy detector. The energy measured here is preferably sent to the processor 16 of FIG.

The processor 16 then determines if the measured energy E is not greater than the acceptable range, ie E> E _s + ΔE _s . If the processor 16 determines in step S65 that the energy E is larger than the allowable limit E _s + ΔE _s , step S6 is performed.
The amount of pressure ΔP to be released is calculated by the processor 16 in six steps. S66
In step, the energy difference δE is calculated as δE = (E−E _s ) / E. Next, the pressure difference δP is calculated as δP = δE / Q. Then, the pressure release amount ΔP is calculated as ΔP = P × δP = P × (E−E _s ) / (Q × E). Where P is the pressure in the tube before the pressure release ΔP.

Next, in step S67, the pressure ΔP calculated from the laser tube 2 is discharged. After that, in step S68, when it is determined that the pressure P in the pipe 2 after the pressure release is higher than P _min , the procedure is returned to step S64. However, if it is determined in step S69 that the pressure P in the pipe 2 after the pressure release is equal to or lower than P _min , the gas optimization procedure ends in step SF.

After the energy measurement in step S64, the processor 16 adds the measured energy E into the laser tube 2 if the measured energy E is within the allowable range or smaller, that is, E ≦ E _s + ΔE _s , in step S70. The pressure amount ΔP is calculated by the processor 16
Calculate by In step S71, the energy difference δE is calculated as δE = (E−E _s ).
Calculate as / E. Next, the pressure difference δP is calculated as δP = δE / Q. Then, the pressure application amount ΔP is calculated as ΔP = P × δP = P × (E−E _s ) / (Q × E). Here, P is the pressure in the pipe before the pressure application ΔP.

Next, in step S72, the calculated amount ΔP of pressure is applied to the laser tube 2. When it is determined in step S73 that the pressure P in the pipe 2 after the pressure is applied is smaller than P _max , the procedure is returned to step S64. However, if it is determined in step S74 that the pressure P in the pipe 2 after the pressure is applied is equal to or higher than P _max , the gas optimization procedure ends in step SF.

FIG. 6 shows that the adjustment of the average pulse energy by lowering the total gas pressure in the laser tube is performed in step S6 before the emission or addition in step S47 or step S72.
6 is an alternative algorithm to the algorithm shown in FIGS. 3 and 4, performed by pressure release or pressure application, respectively, with the amount calculated in step 6 or step S71. In contrast to the algorithm shown in FIG. 3, the pressure release amount ΔP is obtained first. Also,
The pressure application step is absent in either algorithm of FIG. 3 or 4.

FIG. 7 shows an algorithm that incorporates all pressure adjustments except immediately after a new refill into the average pulse energy control algorithm. Conventional average pulse energy control algorithms are known to those skilled in the art, and the steps involved in these procedures preferably combined with the steps of the algorithm shown in FIG. 7 are not shown or described here. Nos. 09 / 588,561 and 09 incorporated herein by reference above
/ 734,459 application discloses a burst overshoot control (
See especially the '561 application), and an energy control algorithm including an average pulse energy controller of a suitable algorithm that can be combined with the algorithm of FIG. 7 including pressure regulation to control the average pulse energy. ing.

[0081] With reference to FIG. 7, _E s in accordance with the algorithm, _{U s,} Delta] E _{s, Q,} parameters including _{P mi n} and _{P max} has already been set, in accordance with the algorithm described in FIG. 7 You may adjust. Where E _s corresponds to the desired average output pulse energy of the laser oscillation, U _s corresponds to the desired drive voltage for laser operation with the average pulse energy E _s , preferably at or near HV _opt. , ΔE _s corresponds to the desired tolerance of the average pulse energy due to laser actuation at the drive voltage U _s , and Q is the relationship between the desired reduction of the average laser pulse energy and the required value of the discharge pressure of the gas mixture. P _min corresponds to a predetermined minimum permissible value of the total gas pressure in the laser tube 2, and P _max corresponds to a predetermined maximum permissible value of the total gas pressure in the laser tube 2. To do.

In step S163, the laser is operated at a constant or substantially constant drive voltage U _s and a duty cycle of 100%. Next, in step S164, the output average pulse energy E is measured by the energy detector. The energy measured here is preferably sent to the processor 16 of FIG. The processor 16 may, and preferably does, have other procedures that make it possible to control the average pulse energy during the measurement in step S164, such as gas replenishment. However, the algorithm in FIG.
It shows how the processor 16 regulates energy at the beginning of pressure regulation.

The processor 16 determines whether the measured energy E is not greater than the acceptable range, ie E> E _s + ΔE _s , or the measured energy E is not less than the acceptable range, ie E <E _s −. Determine if it is not ΔE _s . When the processor 16 determines that the energy E is larger than the allowable limit E _s + ΔE _{s in} step S165, the pressure amount ΔP to be released is calculated by the processor 16 in step S166. In step S166, the energy difference δE is calculated as δE = (E−E _s ) /
Calculate as E. Next, the pressure difference δP is calculated as δP = δE / Q. Then, the pressure release amount ΔP is calculated as ΔP = P × δP = P × (E−E _s ) / (Q × E). Where P is the pressure in the tube before the pressure release ΔP. Alternatively, the pressure amount ΔP may be obtained first, as described above with reference to the algorithm shown in FIG.

Next, in step S167, pressure discharge of the amount ΔP calculated from the laser tube 2 is performed. Then, if it is determined in step S168 that the pressure P in the pipe 2 after the pressure release is higher than P _min , the procedure is returned to step S164. However, S169
If the pressure P in the tube 2 after the pressure release is determined to be less P _min in step, until a pressure of at least the tube 2 is greater than P _min later, the pressure release option one o'clock in SD1 step Invalidated. Such an increase in the total pressure P can be achieved, for example, when a gas injection is performed without a corresponding pressure relief, or with other gas treatments or with a positive pressure application in combination with the operation described in steps S170-S172. Occurs when

After the energy is measured in step S164, the processor 16 determines that the measured energy E is smaller than the allowable range, that is, E <E _s −ΔE _s, and the amount of pressure applied to the laser tube 2 is determined in step S170. Calculate ΔP by the processor 16. In step S171, the energy difference δE is calculated as δE = (E−E _s ) / E. Next, the pressure difference δP is calculated as δP = δE / Q. And
The pressure application amount ΔP is calculated as ΔP = P × δP = P × (E−E _s ) / (Q × E). Here, P is the pressure in the pipe before the pressure application ΔP. Alternatively, the above-described pressure amount ΔP may be determined first with reference to the algorithm shown in FIG.

Next, in step S172, the calculated amount ΔP of pressure is applied to the laser tube 2. Then, when it is determined in step S173 that the pressure P in the pipe 2 after the pressure is applied is smaller than P _max , the procedure is returned to step S164. However, S174
If it is determined that the pressure P in the pipe 2 after the pressure application is equal to or higher than P _max in the step, the pressure application option is temporarily set in the SD2 step at least until the pressure in the pipe 2 is reduced to less than P later. Disable it. Such a decrease in the total pressure P occurs, for example, when the positive pressure release is performed in combination with the operation described in steps S165 to S167.

It has to be noted here that the method described above can be modified. For example,
By adjusting the input drive voltage, the energy of the laser beam can be continuously maintained within an acceptable range around the desired energy. The input drive voltage may then be monitored. When the input drive voltage is higher or lower than the optimum drive voltage HV _opt by a predetermined amount or a calculated amount, the total drive pressure is applied or released to set the input drive voltage close to HV _opt or within the allowable range of the input drive voltage. Adjust the amount of. The total pressure applied or released is a predetermined amount of the calculated amount as described above. In this case, the desired change in the input drive voltage is then determined corresponding to the change in energy compensated by the calculated or predetermined amount of gas addition or release. Similar formulas may be used for the above.

By incorporating pressure regulation into the average pulse energy control algorithm according to the preferred embodiment, the range of drive voltages applied for discharge is advantageously reduced. Therefore, even if the gas mixture becomes old, the driving voltage applied for discharging does not greatly change from the optimum driving voltage HV _opt without shortening the interval of new replenishment. Another advantage realized by itself or in combination with the reduction of the drive voltage fluctuation range is that gas pressure such as halogen injection and gas replenishment described below is applied to increase output energy (when operating at low pressure). When used in combination with the method, the interval between new refills is extended. 8 and 9 illustrate the advantageous features of the latter according to the preferred embodiment.

Referring to FIG. 8, some drive voltage levels (HV _i ) are shown for which a particular gas treatment is predetermined. The processor 16 monitors the drive voltage and operates on the basis of the value of the drive voltage or on the basis of parameters such as time, number of pulses and / or total input electrical energy for discharge (x-axis in FIG. 8). Depending on which setting range (left-hand y-axis in FIG. 8) the driving voltage being applied falls into the gas supply unit to varying degrees, partial and small amount gas displacement to varying degrees, and varying degrees or Perform a constant total pressure adjustment. (See the above '561 application).

[0090]   Next, an example relating to the present invention will be described with reference to FIG. HV laser system _min And HV_maxIt is configured so that it can be operated with a drive voltage between and. Actual operation
HV with minimum and maximum drive voltage indicated by dashed vertical axis₁And HV₇Very narrow between
Set to a range The advantage of this preferred embodiment is that the HV₁To HV₇Range up to
The drive current changes significantly during laser operation as it reduces itself to a very small window.
There is no point. This operating range itself is HV_minAnd HV_maxBetween
In this case, for example, a gas mixture that attenuates the output energy (see the above '025 application)
Adjust) or an extra-cavity attenuator (assigned to the assignee, see here
No. 60 / 178,620, incorporated by reference herein).
Adjust the actual voltage range (volts) corresponding to the
And extend the life of the optics of the laser tube. Also, advantageously, HV₁And HV₇With
Reduce the operating drive voltage range between laser tube, optics and
And / or maintain or extend the life of the gas mixture while
HV_optThe fluctuation of the driving voltage becomes smaller than that.

The right vertical axis shows the total pressure in the laser tube 2 during the life of the gas mixture (new refill interval) and corresponds to the drive voltage level shown on the left vertical axis. At the lowest drive voltage used in the system, namely HV ₁ , the pressure is preferably as low as P _min . For example, by having the lowest allowable voltage in the tube when a new replenishment has recently been made, the same desired average pulse energy can be obtained while the drive voltage level HV ₁ is increased compared to a system operating at a constant total pressure. It can be higher (and closer to the HV _opt ).

At the highest drive voltage used in the system, ie HV ₇ , the pressure in tube 2 is preferably as high as P _max . Driven as compared to a system operating at constant total pressure while obtaining the same desired average pulse energy by maximally allowing the pressure in the tube when the gas mixture has reached the end of its life before a new refill, for example. The voltage level HV ₇ can be lower (and closer to HV _opt ). Alternatively, the driving voltage range can be expanded to extend the life of the gas. Preferably, the total pressure is increased with the driving voltage range used as the gas mixture ages, extending the useful life of each driving voltage range.

The coordinate axes of FIG. 8 show the gas treatments that can be performed based on one or more cumulative parameters when the drive voltage is within each interval. In addition, as the gas mixture ages, or as the system progresses from left to right on the coordinate axes, it is also preferably pressurized, as evidenced by the increase in total laser tube pressure shown on the right vertical axis. The usual sequence of gas treatments is left to right as the gas mixture ages. However, when performing each gas procedure, look at the drive voltage and the next gas procedure that may be performed corresponds to the same drive voltage range, or to different drive voltage ranges represented to the left or right of that range. You may. For example, after performing a PGR (if the drive voltage is determined to be higher than HV ₅ ), lower the drive voltage between HV ₂ and HV ₃ to allow the system to return to normal μHI and MGR ₁ gas controlled operation. You can Further, when performing the pressurization, the drive voltage range can be reduced from the high voltage to the low voltage range according to the state of the system after the pressurization.

Within the working range between HV ₁ and HV ₇ , some other ranges are defined. For example, if the drive voltage HV is between HV ₁ and HV ₂ (ie, HV ₁ <HV <HV ₂ ) and the total tube pressure is between P _min and P ₁ , then sufficient in the gas mixture. No gas treatment is performed because there is a sufficient amount of halogen. If the drive voltage is between HV ₂ and HV ₃ (ie HV ₂ <HV <HV ₃ ) and the total tube pressure is between P ₁ and P ₂ , then the cumulative parameter (ie due to discharge Input electrical energy, time and / or pulse count, etc. of MGR ₁ and regular μHI periodically. This is the normal range of operation of the system according to the preferred embodiment.

When the driving voltage was between HV ₃ and HV ₄ (ie HV ₃ >HV> HV ₄ ) and the total tube pressure was between P ₂ and P ₃ , gas release was supported. Increase one or both injection doses of μHI and MGR. In this example, only μHI is increased.
Therefore, the range between HV ₃ and HV ₄ in FIG.
The range is to carry out enhanced μHI which is a halogen injection of a larger amount or a shorter period than the above, and keeps the same MGR amount as in the range between HV ₂ and HV ₃ .

Clearly, enhanced μHI differs from normal μHI in one or two ways. First, the injection amount may be increased. Secondly, the interval between consecutive μHIs may be shortened.

The range between HV ₄ and HV ₅ (ie, HV ₄ <HV <HV ₅ ) and the range between total tube pressures P ₃ and P ₄ correspond to μHI and MGR corresponding to outgassing. Represents a new range in which one or both doses are increased (or the interval between successive movements is decreased) In this example, only MGR is increased compared to the range from HV ₃ to HV ₄ .
Therefore, when the drive voltage is in the range between HV ₄ and HV ₅ , a normal amount of MG
Inject an enhanced amount of halogen gas between R ₁ and each MGR ₂ (with corresponding outgassing). Alternatively, or in combination with a large amount of gas replacement, a small amount of gas replacement MGR ₂ is performed at intervals that are shorter than the intervals at which MGR ₁ is performed. Preferred and alternative M
In each of the GR ₂ procedures, the intervals in the discharge chamber are shorter than those in the MGR ₁ procedure in which the contaminants in the discharge chamber are in the lower drive voltage range between HV ₃ and HV ₄ (among other things, for example, accumulated input energy for discharge). , Pulse count and / or time). Also, preferably μHI is performed periodically in this range to recondition the gas mixture. It should be noted here that the adjustment range of the amount injected between one or both of μHI and MGR may be defined corresponding to a predetermined drive voltage range. Also, the injection volume may be adjusted for each injection, as described above in connection with monitoring pressure (and optionally temperature) within the accumulator (and optionally laser tube).

When the driving voltage is higher than HV ₅ (that is, HV ₅ <HV <HV ₆ ), PGR with more gas replacement is performed. PGR can be used to replace up to 10% or more of the gas mixture. If, for example, the laser is being tuned, certain safety measures are used here to prevent the occurrence of unwanted gas treatments. One is to energize for some time after the HV ₅ level is exceeded and before the gas treatment is performed to ensure that the drive voltage actually increases due to degradation of the gas mixture. When the driving voltage becomes higher than HV ₆ , it is time to refill the laser tube. Here, it should be noted that the size of the drive voltage range shown in FIG. 8 is not necessarily drawn at a constant ratio.

FIG. 9 shows normal and enhanced μH according to the preferred embodiment and example described in FIG.
3 is a flow diagram implementing I, MGR and PGR. The procedure begins with a new refill, filling the discharge chamber with the optimum gas mixture. The laser can then be run for industrial use, idle, or shut down altogether. After measuring the current drive voltage (HV), a drive voltage check (HV check) is performed.

[0100]   Measure the drive voltage (HV) to the specified value HV₁~ HV₇Compare with. HV is HV ₁ And HV_TwoBetween (ie HV₁<HV <HV_Two) Whether the process
Judged by Sasser and returned to the previous step along the route (1) without gas treatment.
You Although not shown, HV is HV₁If smaller, some laser gas
Release and / or inject some buffer gas into / from the laser tube
By taking steps to reduce the halogen gas concentration in the laser tube.
Good. Or the total pressure is P_minIn the following cases, write in any of the above-mentioned FIGS.
Pressure release may be performed according to the algorithm described.

If the processor determines that the HV is between HV ₂ and HV ₃ , then the system is within normal operating drive range. If within normal working width, along path (2), normal μHI and MGR ₁ are input, preferably for a predetermined time by an expert system based on operating conditions, input electrical energy and / or pulse for discharge. Implement based on the number of intervals. Further, as described above, each gas treatment may be adjusted by the calculated partial pressure or the number of halogen molecules in the laser tube.

ΜHI and MGR ₁ performed along route (2) are determined in relation to any of the methods described in previously incorporated US patent application Ser. No. 09 / 588,561. If the HV is not within the normal working width, it is determined whether the HV is smaller than HV ₂ (that is, HV <HV ₂ ). If HV is less than HV ₂ , then route (2
), And no gas treatment.

If the HV is between HV ₃ and HV ₄ (ie HV ₃ <HV <HV ₄ ), then along Path (3) and using enhanced μHI and MGR ₁ with time, pulse count and / or The operation is performed again based on the electric energy applied to the discharge counter. The exact amount and composition of the gas to be injected and the exact amount and composition of the gas to be released are determined, preferably using an expert system and by operating conditions.

If the HV is between HV ₄ and HV ₅ (ie HV ₄ <HV <HV ₅ ), then along route (4) and enhanced μHI and MGR ₂ are performed by examination of the counter values. May be. Also, the exact amount and composition of the gas to be injected and the exact amount and composition of the gas to be released, preferably using an expert system,
And it depends on the operating conditions.

If the HV is between HV ₅ and HV ₆ (ie, HV ₅ <HV <HV ₆ ), then PGR is performed. If HV is higher than HV ₆ (ie, HV ₆ <HV), a new recruitment is performed.

Along the route (2)-(5), after carrying out the corresponding gas treatment and, preferably after a certain stabilization time, the operating mode of the laser is determined and the HV is measured and determined. Return to the step of comparing with the HV levels HV _{1 to} HV ₇ .

All of these different drive voltages and total laser tube pressure levels, the time, the electrical energy applied for the discharge and / or the number of pulse schedules are set individually or for different operating situations. It can be compared to a stored computer controlled database. Operation of the laser at different HV levels under different operating conditions such as continuous pulse or burst mode may be taken into account.

Also in connection with the preferred embodiment, a partial new replenishment procedure may be implemented as shown in FIG. As shown in FIG. 8, an additional HV range that is higher than the PGR range 5 and lower than the drive voltage threshold value HV ₇ is defined. If the processor determines that the high voltage is higher than HV ₆ , then a new or partial new refill is performed. If the high voltage is below HV ₇ ,
Partial new replenishment is performed, and if HV is greater than ₇ , complete new replenishment is performed. Or, if the total pressure added by SD2 step of FIG. 7 is invalid, the total pressure is if Ikere lower than P _max, the total pressure to extend the operation of the laser by performing a pressure to reach the P _max.

When performing a completely new replenishment, almost 100% of the gas mixture is evacuated from the discharge chamber and an entirely new gas mixture is introduced into the laser chamber. However, when performing a partial fresh replenishment, only a portion of the total gas mixture (eg 5% to 70% or about 0.1%).
Emits 5 bar to 2 bar). More specifically, the preferred amounts are 20% and 50%
And between 0.6 bar and 1.5 bar. A particularly suitable amount would be about 1 bar or about 30% gas mixture. Experiments have shown that performing a partial new replenishment procedure with 1 bar exchange increases gas life by a factor of 5 over that without the procedure.

The amount that can be released is substantially determined by the time it takes to pump the gas, which is greater than 50% and substantially less than a complete fresh refill. Therefore, the partial fresh replenishment procedure is advantageous in that it exchanges large amounts of old gas for new gas in a short time, thus increasing wafer throughput, for example when using lasers for lithographic applications.

Here, referring to FIG. 9, when the processor determines that the high voltage is higher than HV _6, it determines whether the high voltage is HV ₇ or lower. If the answer is yes, i.e. the high voltage is below HV ₇ , a partial fresh replenishment is initiated to remove substantially less than 100% of the gas mixture from the discharge chamber and replace it with fresh gas. Advantageously, this system has less downtime compared to performing a completely new replenishment. If the answer is no, that is, the high voltage is higher than HV ₇ , then a new refill is performed. As noted above, experiments have shown that the partial new replenishment procedure improves gas life by a factor of 5 before reaching the new replenishment range.

It should be appreciated that a system without all of ranges 1-6 and range 6 new replenishment / partial new replenishment may be advantageously implemented. For example, in FIG. 8, a system using only one range with partial new replenishment and a new replenishment is used to improve gas life. After removing some ranges, the partial new refill range may be moved to a lower threshold high voltage. Further, the pressure range may be used more than once for the drive voltage ranges HV _{1 to} HV ₇ using a range that is lower or higher than the total pressure range shown. For example, using one range or the entire range of total pressure during less than the entire drive voltage range, _reusing the entire pressure range of P _{min to} P _{max at} a higher drive voltage range, and so on. It is preferred to use the full range and corresponding gas treatment for optimum laser system performance.

All combinations of these different gas control and replenishment mechanisms are involved in the coordination of many elements and variants. In combination with an expert system and a database, the processor-controlled laser system of the preferred embodiment extends the gas life before a new refill is required. In principle, it is possible to completely prevent the shutdown of the laser system for new replenishment. The life of the laser system is determined by the periodic maintenance intervals determined by other laser components, such as for replacement of laser tube windows or other optical components. Further, as described above, even if the lifespan of the laser tube and the resonator component is increased, the interval between the stop periods is increased.

[0114]   During the laser operation, the concentration ratio of the gas components of the gas mixture is changed to ArF, KrF and F. _Two It is important to keep constant at the desired ratio described above using a laser system as an example.
Is. Halogen injection is preferably F during laser operation._TwoNot only wear but also
Compensate for static deterioration of the gas mixture in the laser tube and any deterioration of the optical components
.

If the fluorine level is not monitored and kept at the desired level, ie about 0.1%, the average energy is compensated by the deterioration of the optics and the laser tube and the accumulation of contaminants in the laser tube 2. Is at the desired level, but the gas mixture has more fluorine than desired. In this case, various lasing parameters may change from desired values as a result of increased fluorine concentration during laser operation,
And gas life and laser tube life can be shortened. Therefore, it is desirable to keep the fluorine concentration constant at the desired value and to vary the total pressure and drive voltage within the limits of the preferred embodiment. In particular, it is preferable to keep the halogen and rare gas concentrations for ArF and KrF lasers and the halogen concentration for F ₂ lasers constant during laser operation, and to replenish the halogen, rare gas and preferably buffer gas in the laser tube 2. Keep the amount in the same proportion as immediately after the new replenishment procedure.

When a pressure release is performed, a reduction of the total gas pressure in the laser tube 2 is achieved, preferably by discharging via the auxiliary volume 26 (see FIG. 2). This auxiliary volume 26 is preferred because the emission of the gas mixture is very small and therefore it is desirable to more accurately determine the emission compared to the emission from the laser tube 2 during, for example, a new refill or a partial new refill. Uses.

Many variations on the preferred embodiment are possible, and many alternative embodiments will be understood by those skilled in the art. As mentioned above, the microhalogen injection can advantageously be exchanged for a micro or constant replacement of the gas mixture, ie the pressure release can be carried out in connection with the halogen injection. In this case, the gas procedure involves working with a single parameter, namely the rate of exchanging the gas mixture or the gas flow rate through the laser tube 2.

This gas flow velocity can be set to a constant value. This value can preferably be large enough to extend the life of the gas mixture. Further, the gas flow rate is set to be dependent on the time, the number of pulses, the input energy for discharge, etc.
The flow rate may be increased as one or more of these parameters progress. It is also possible to make the gas flow rate dependent on the duty cycle of the laser, for example increasing the flow rate at higher duty cycles.

Further, the total pressure increase during laser operation may be performed according to the gas flow rate, and the pressure may be increased when the gas flow rate for microgas displacement exceeds a threshold value. Further, as shown in FIG. 8, the increase of the total gas pressure in the laser tube 2 may depend on the high voltage of the laser operation. The total pressure increase can be started at the beginning of the laser operation, for example after a new refill, or at a certain time, pulse number or input energy for discharge after a new refill. In addition, the time at which the pressure increase starts, the number of pulses, or the input energy for discharging may depend on the duty cycle. Preferably, the total gas pressure increase itself increases at a constant value from the start and again depends on the time, the number of pulses or the total input energy for the discharge at the start of the laser operation or the start of the pressure increase or on the duty cycle. Or may depend on the drive voltage level or operating range of the laser system.

While illustrative and specific embodiments of the present invention have been illustrated and illustrated, it should be understood that the scope of the present invention should not be limited to the particular embodiments discussed.
Therefore, the embodiments should be considered as illustrative rather than limiting, and modifications of these embodiments can be made by those skilled in the art without departing from the scope of the invention as claimed and equivalents thereof. I want you to understand.

Furthermore, in the method claims, the operations are arranged in the selected printing order. However, except for claims which are selected and arranged in this manner for the sake of printing convenience, and in which a particular sequence of steps is explicitly stated or understood as necessary by one of ordinary skill in the art,
It is not intended to indicate any particular order in which the operations may be performed.

[Brief description of drawings]

FIG. 1 is a plot of halogen concentration versus pulse number for laser systems with different quality laser tubes.

FIG. 2 is a schematic diagram of an excimer or molecular fluorine laser system according to a preferred embodiment.

FIG. 3 shows a gas reaction algorithm including a pressure release step according to a first preferred embodiment.

FIG. 4 shows a gas reaction algorithm including a pressure release step according to a second preferred embodiment.

FIG. 5 is a diagram showing points that characterize laser performance for different values of the quality factor Q.

FIG. 6 shows a gas reaction algorithm including pressure release and pressure application steps according to a third preferred embodiment.

FIG. 7 shows a gas reaction algorithm including pressure release and pressure application steps according to a fourth preferred embodiment.

FIG. 8: Pulse number, time and / or pulse for a system according to a preferred embodiment.
Or a qualitative graph showing drive voltage and total laser tube pressure versus input energy for discharge, showing regular halogen injection, minor gas replacement and partial gas replacement.

FIG. 9 is a flow diagram for performing halogen injection, minor gas replacement, partial gas replacement, and total pressure adjustment for the preferred embodiment.

Claims (35)

[Claims] 1. A method of maintaining the output energy of an excimer or a molecular fluorine laser within a desired energy tolerance range and maintaining an input drive voltage within an optimum input drive voltage tolerance range. Molecular fluorine laser
The method comprises a laser tube filled with a gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture, and a resonator for generating a laser beam. Activating the laser to emit a laser beam within the allowable range of the desired energy, measuring the energy of the laser beam, adjusting the input drive voltage to adjust the energy of the laser beam to the desired energy Maintaining within an acceptable range, determining the value of the input drive voltage, and adjusting the total pressure of the gas mixture in the laser tube to maintain the input drive voltage within the acceptable range of the optimum input drive voltage. How to include. 2. The method of claim 1, wherein the total pressure adjustment step comprises releasing a predetermined amount of the gas mixture from a laser tube. 3. The method of claim 1, wherein the total pressure adjustment step comprises adding a predetermined amount of gas to the gas mixture in the laser tube. 4. The total pressure adjusting step calculates the amount of gas mixture to be emitted from the laser tube to adjust the input drive voltage to a desired value, and the calculated amount of gas mixture is emitted from the laser tube. The method of claim 1, comprising the step of releasing. 5. The total pressure adjusting step calculates the amount of gas to be added to the gas mixture to adjust the input drive voltage to a desired value, and the calculated amount of gas is added to the gas mixture in the laser tube. The method according to claim 1, further comprising the step of: 6. The adjusting step comprises: calculating an amount of a gas mixture to be emitted from the laser tube to adjust the energy to a desired value; and emitting the calculated amount of the gas mixture from the laser tube, The method of claim 1, comprising: 7. The adjusting step comprises: calculating the amount of gas to be added to the gas mixture to adjust the energy to a desired value; and adding the calculated amount of gas to the gas mixture in the laser tube. The method of claim 1, comprising: 8. Applying an input voltage to the electrodes to excite a gas mixture having a first pressure to generate a beam at a first energy, and applying substantially the same input voltage to the electrodes. The method of claim 1, further comprising: exciting a gas mixture having a second pressure to generate a beam at a conditioning energy different from the first energy. 9. Applying a first input voltage to the electrodes to excite a gas mixture having a first pressure to produce a beam at a desired energy, and applying a second input voltage to the electrodes, The method of claim 1, further comprising exciting the gas mixture having a second pressure to produce a beam at substantially the same desired energy. 10. The method of claim 1, further comprising replenishing the gas mixture to further maintain the input drive voltage within the optimum drive voltage tolerance and to maintain the energy within the desired energy tolerance. the method of. 11. A laser tube filled with a gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture, and a resonator for generating a laser beam. An energy stabilization method for an excimer or molecular fluorine laser, the method comprising the steps of operating a laser to emit a laser beam, measuring the energy of the laser beam as the first energy, wherein the first energy is the desired energy The energy of the laser beam when it is determined that the measured first energy is out of the desired energy tolerance range by adjusting the pressure of the gas mixture in the laser tube. Adjusting. 12. The method of claim 11, wherein said conditioning step comprises releasing a predetermined amount of gas mixture from a laser tube. 13. The method of claim 11, wherein the conditioning step comprises adding a predetermined amount of gas to the gas mixture in the laser tube. 14. The adjusting step calculates the amount of gas mixture to be emitted from the laser tube to adjust the input drive voltage to a desired value, and emits the calculated amount of gas mixture from the laser tube. 12. A process comprising:
The method described. 15. The adjusting step calculates the amount of gas to be added to the gas mixture to adjust the input drive voltage to a desired value, and adding the calculated amount of gas to the gas mixture in the laser tube. The method according to claim 11, further comprising: 16. The adjusting step comprises: calculating the amount of gas mixture to be emitted from the laser tube to adjust the energy to a desired value; and releasing the calculated amount of gas mixture from the laser tube, 11. Including
The method described. 17. The step of adjusting comprises: calculating the amount of gas to be added to the gas mixture to adjust the energy to the desired value; and adding the calculated amount of gas to the gas mixture in the laser tube. The method of claim 11, comprising: 18. A step of applying an input voltage to the electrodes to excite a gas mixture having a first pressure to generate a beam at a first energy, and applying substantially the same input voltage to the electrodes. 12. The method of claim 11, further comprising: exciting a gas mixture having a second pressure to produce a beam at a conditioning energy that is different than the first energy. 19. A step of applying a first input voltage to an electrode to excite a gas mixture having a first pressure to generate a beam at a desired energy, and applying a second input voltage to the electrode, 12. The method of claim 11, further comprising exciting the gas mixture having a second pressure to produce a beam at substantially the same desired energy. 20. The method of claim 11, further comprising replenishing the gas mixture to further maintain the energy within the desired energy tolerance range. 21. A laser tube filled with a gas mixture; a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture; and a resonator for generating a laser beam. A method for optimizing the performance of an excimer or molecular fluorine laser, wherein the method sets the value of the input drive voltage within an input drive voltage range that includes a predetermined optimum drive voltage for optimum laser system performance. The step of replenishing the gas mixture in the laser tube, the step of operating the laser at the input driving voltage value to emit the laser beam, the step of measuring the energy of the laser beam, and the pressure of the gas mixture in the laser tube Is adjusted to determine that the measured first energy is outside the allowable range of the desired energy, the laser beam energy is adjusted. Comprising the step, of adjusting the Energy. 22. The method of claim 21, wherein the conditioning step comprises releasing a predetermined amount of the gas mixture from the laser tube if the measured energy is determined to be above a desired energy tolerance range. 23. The method of claim 21, wherein the adjusting step comprises adding a predetermined amount of gas to the gas mixture in the laser tube if the measured energy is determined to be below the desired energy tolerance range. Method. 24. The adjusting step comprises the steps of: calculating the amount of gas mixture to be emitted from the laser tube to reduce the energy to the desired value; and emitting the calculated amount of gas mixture from the laser tube. 22. including
The method described. 25. The adjusting step comprises the steps of: calculating the amount of gas to be added to the gas mixture to increase the energy to the desired value; and adding the calculated amount of gas to the gas mixture in the laser tube, 22. The method of claim 21, comprising: 26. A laser tube filled with a gas mixture, a plurality of electrodes in the laser tube connected to a gas discharge circuit for activating the gas mixture, and a resonator for generating a laser beam. A method for optimizing the performance of an excimer or molecular fluorine laser, wherein the method provides an input drive voltage value within an allowable input drive voltage range that includes a predetermined optimum drive voltage for optimum laser system performance. Setting step, new replenishment of gas mixture in laser tube, step of operating laser to emit laser beam with desired energy, input drive voltage applied to obtain desired energy is within input drive voltage range To determine whether the input drive voltage is equal to the input drive voltage by adjusting the pressure of the gas mixture in the laser tube. Comprising the step, of adjusting the input drive voltage applied to obtain the desired energy when outside to have been determined. 27. The method of claim 26, wherein the adjusting step comprises releasing a predetermined amount of the gas mixture from the laser tube if the input drive voltage is determined to be below an acceptable input drive voltage range. 28. The method of claim 26, wherein the adjusting step comprises adding a predetermined amount of gas to the gas mixture in the laser tube if the input drive voltage is determined to be above the allowable input drive voltage range. . 29. The adjusting step calculates the amount of gas mixture to be emitted from the laser tube to increase the input drive voltage applied to bring the desired energy to the desired value, and the calculated amount of 27. Emitting the gas mixture from the laser tube.
The method described. 30. The adjusting step calculates the amount of gas to be added to the gas mixture to reduce the input drive voltage applied to bring the desired energy to the desired value, and the calculated amount of gas. 27. The method of claim 26, including the step of: adding to the gas mixture in the laser tube. 31. An excimer or molecular fluorine laser system, the system comprising a laser tube filled with a gas mixture, in the laser tube, a power supply circuit for applying a driving voltage to the electrodes to activate the gas mixture. A plurality of electrodes connected to the resonator, a resonator for generating a laser beam at a desired energy, a gas exchange unit connected to the laser tube and including an auxiliary volume at a pressure lower than the pressure of the gas mixture in the laser tube, and gas exchange A processor for controlling the gas flow between the unit and the laser tube,
When the driving voltage is determined to be lower than the allowable driving voltage for obtaining the desired energy, the gas mixture is discharged to the auxiliary capacity to reduce the pressure in the laser tube and applied to obtain the desired energy. A laser system in which the gas exchange unit and the processor are configured to increase the drive voltage to operate. 32. The processor is configured to calculate the amount of gas mixture to be emitted from the laser tube to increase the input drive voltage applied so that the desired energy is the desired amount. Laser system described. 33. The laser system of claim 31, further comprising a pump connected to the auxiliary volume to reduce the pressure within the auxiliary volume. 34. An excimer or molecular fluorine laser system, the system comprising a laser tube filled with a gas mixture, in the laser tube, a power supply circuit for applying a driving voltage to the electrodes to activate the gas mixture. A plurality of electrodes connected to the resonator, a resonator for generating a laser beam at a desired energy, a gas exchange unit connected to the laser tube, and a processor for controlling the gas flow between the gas exchange unit and the laser tube. ,
When the driving voltage is determined to be higher than the allowable driving voltage for obtaining the desired energy, gas is added to the laser tube to increase the pressure in the laser tube and then applied to obtain the desired energy. A laser system in which the gas exchange unit and the processor are configured to reduce the drive voltage. 35. The processor is configured to calculate the amount of gas mixture to be added to the laser tube to reduce the input drive voltage applied to achieve the desired amount of desired energy. Laser system described.