Method and device for replacing gas mixture in gas discharge chamber

Abstract

A method of replacing a gas mixture in a gas discharge chamber in a light source includes determining a performance of the light source and / or the gas discharge chamber based on one or more light source and / or gas discharge chamber performance metrics; determining a next refill pressure based on the determined performance and a current operating pressure of the gas discharge chamber; removing the gas mixture from the gas discharge chamber; and filling the gas discharge chamber with the replacement gas mixture to the determined next refill pressure. An apparatus for replacing a gas mixture is also disclosed.

Description

Cross Reference to Related Applications

[0001] This application claims priority to U.S. Application No. 63 / 491,990, filed March 24, 2023, entitled “METHOD AND APPARATUS FOR REPLACING GAS MIXTURE IN A GAS DISCHARGE CHAMBER,” the entirety of which is incorporated by reference herein. TECHNICAL FIELD

[0002] The present disclosure relates to a method and apparatus for replacing a gas mixture in a gas discharge chamber in a deep ultraviolet (DUV) light source, such as a power- ring amplifier gas discharge chamber in a DUV light source. BACKGROUND

[0003] One type of gas discharge light source used in photolithography is called an excimer light source or laser. Generally, an excimer laser uses a mixture of one or more noble gases, which can include argon, krypton, or xenon, and a reactive gas, which can include fluorine or chlorine. An excimer can be created under the right electrical analog (energy supply) and high pressure (high pressure of the gas mixture) conditions, which only exist when energized. The excimer, when energized, generates and amplifies light in the ultraviolet range. An excimer light source for photolithography typically includes multiple gas discharge chambers. When the excimer light source is operating, the excimer light source produces a deep ultraviolet (DUV) light beam. The DUV light can include wavelengths of, for example, about 100 nanometers (nm) to about 400 nm.

[0004] The DUV light beam from the light source can be directed to a photolithography exposure apparatus, which is a machine used to produce a desired pattern on a target portion of a substrate, such as a photoresist layer on a semiconductor wafer. The DUV light beam interacts with a projection optical system, which projects the DUV light beam through a mask or other imaging device onto the photoresist on the wafer. In this way, one or more layers of chip design can be patterned on the photoresist and then on or into the wafer, or on or into the layers built on the wafer. SUMMARY

[0005] In some general aspects, a process to replace a gas mixture in a gas discharge chamber in a light source includes determining a performance of the light source and / or the gas discharge chamber based on one or more light source and / or gas discharge chamber performance metrics; determining a next refill pressure based on the determined performance and a current operating pressure of the gas discharge chamber; removing the gas mixture from the gas discharge chamber; and filling the gas discharge chamber with a replacement gas mixture to the determined next refill pressure. Implementations can include one or more of the following.

[0006] The process can also include decreasing the gas discharge chamber pressure from the previous refill pressure to a current operating pressure based on one or more performance metrics of the light source and / or the gas discharge chamber. The process can also include determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein the margin value is a first value when the determined performance indicates that the light source and / or the gas discharge chamber is stable, and the margin value is a second value greater than the first value when the determined performance indicates that the light source and / or the gas discharge chamber is not stable. The gas discharge chamber can be a power amplifier gas discharge chamber.

[0007] The process can also include determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein determining the margin value includes: comparing the one or more light source and / or gas discharge chamber performance metrics to respective limits; setting the margin value to a first value if any of the one or more light source and / or gas discharge chamber performance metrics is outside of its respective limit(s); and setting the margin value to a second value if each of the one or more light source and / or gas discharge chamber performance metrics is within its respective limit(s); wherein the second value is less than the first value.

[0008] The process can also include determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein the determined performance indicates a level of stability of the light source and / or the gas discharge chamber, and the determined margin value decreases as the indicated level of stability increases.

[0009] The process can also include determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein determining the margin value includes: comparing the one or more light source and / or gas discharge chamber performance metrics to respective limits; and setting the margin value to a relatively higher value when the one or more light source and / or gas discharge chamber performance metrics are close to exceeding or exceed their respective limits, and setting the margin value to a relatively lower value when the one or more light source and / or gas discharge chamber performance metrics are far from exceeding their respective limits.

[0010] Determining the next refill pressure can include: determining a margin value, the margin value being smaller when the determined performance indicates that the light source is more stable, and the margin value being larger when the determined performance indicates that the light source is less stable; and setting the next refill pressure to at least the current operating pressure plus the margin value. Determining the performance of the light source and / or the gas discharge chamber can include comparing the one or more light source and / or gas discharge chamber performance metrics to respective limits. Determining the performance of the light source and / or the gas discharge chamber can include collecting the one or more light source and / or gas discharge chamber performance metrics during standard operation of the light source.

[0011] The gas discharge vessel can be a power amplifier gas discharge vessel.

[0012] In other general aspects, there is provided a gas mixture replacement device associated with a gas discharge vessel within a light source, the device comprising (1) a monitoring and control system connected to the light source and configured to (a) determine a current operating pressure value of the gas discharge vessel; (b) determine one or more performance metrics of the light source and / or the gas discharge vessel; and (c) determine a next refill pressure value for the gas discharge vessel based on the one or more performance metrics and the current operating pressure value of the gas discharge vessel; (2) a gas mixture removal system configured to remove a gas mixture from the gas discharge vessel; and (3) a gas mixture resupply system connected to the monitoring and control system and configured to fill the gas discharge vessel with a replacement gas mixture to the determined refill pressure value. Implementations can include one or more of the following.

[0013] The gas discharge vessel can be a power amplifier gas discharge vessel. The power amplifier gas discharge vessel can be a power ring amplifier gas discharge vessel. The light source can be a multi-stage light source, and one stage of the multi-stage light source can be a power amplifier stage comprising the gas discharge vessel and a circulating ring-shaped light path through the gas discharge vessel. The gas mixture can comprise argon fluoride (ArF). The gas mixture can comprise argon fluoride (ArF).

[0014] The monitoring and control system can be further configured to determine a margin value for increasing the next refill pressure relative to the current operating pressure by comparing the one or more performance metrics of the light source and / or the gas discharge vessel to respective limits, and setting the margin value to a first value if any of the one or more light source and / or gas discharge vessel performance metrics is outside of its respective limit(s), and setting the margin value to a second value if each of the one or more light source and / or gas discharge vessel performance metrics is within its respective limit(s), wherein the second value is less than the first value.

[0015] The monitoring and control system can be further configured to determine a margin value for increasing the next refill pressure relative to the current operating pressure by comparing the one or more performance metrics of the light source and / or the gas discharge vessel to respective limits, and setting the margin value to a first value if any of the one or more light source and / or gas discharge vessel performance metrics is outside of its respective limit(s), and setting the margin value to a second value if each of the one or more light source and / or gas discharge vessel performance metrics is within its respective limit(s), wherein the second value is less than the first value.

[0016] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a block diagram of a gas control device and related gas discharge chamber and light source providing an amplified light beam to an output device;

[0018] Figure 2 is a flowchart of a method of the present disclosure;

[0019] Figure 2A is a flowchart of a method that can be used Figure 2 ;

[0020] Figure 2B is a flowchart of a method that can be used Figure 2 ;

[0021] Figure 3 is a block diagram of an implementation of an output device of Figure 1 ;

[0022] Figure 4 is a block diagram of an implementation of a gas control device and related gas discharge chamber and light source of Figure 1 , showing a two-stage light source;

[0023] Figure 5 is a graph showing a trajectory representing the pressure of a gas mixture in a gas discharge chamber 150 as a function of time, illustrating aspects of the present disclosure;

[0024] Figure 6 is a block diagram showing one aspect of a method of the present disclosure; and

[0025] Figure 7 is a block diagram showing another aspect of a method of the present disclosure. DETAILED DESCRIPTION

[0026] Referring to Figure 1 , a gas control device 100 is associated with a gas discharge chamber 150 of a light source 160. The light source 160 is configured as part of an optical system (including optical feedback not shown in Figure 1 ) that provides an amplified light beam 165 (at least partially generated by an output light beam 153 of the gas discharge chamber 150) to an output device 180. The output device 180 can be, for example, a lithography exposure device that patterns microelectronic features on a substrate such as a wafer. The gas discharge chamber 150 can be configured as part of a gas discharge stage 155, which can be a power amplifier or power amplifier stage, and the light source 160 can contain one or more additional stages such as a master oscillator (MO) stage (Figure 1 not shown, see below Figure 4 ).

[0027] The gas control apparatus 100 includes a monitoring system 140, a gas supply system 170, and a control system 105. The control system 105 includes a gas control module 110 that can be configured to perform a gas fill process, a gas exchange process, and a pressure regulation process on the gas discharge chamber 150. The gas fill process can be an initial fill of the gas discharge chamber 150 with a gas mixture 151 to prepare the gas discharge chamber 150 and / or the light source 160 for initial operation or initial testing. The gas exchange process can be performed after the monitoring system 140 and / or the control system 105 determines that a gas exchange is required to restore the operational performance of the gas discharge chamber 150 and / or the light source 160 to standard (or improved) operational performance, to exchange the gas mixture 151 in the gas discharge chamber 150 with a new (fresh) exchange gas mixture 151. The pressure regulation process is performed after the gas fill process or the gas exchange process to optimize and / or restore the performance of the gas discharge chamber 150 and / or the light source 160.

[0028] In a gas exchange as understood herein, all or substantially all of the gas mixture 151 within the gas discharge chamber 150 is exchanged, for example, by first evacuating the gas discharge chamber 150 via the gas mixture removal system 114, for example by venting the old gas mixture 151 to a gas exhaust (not shown), or even evacuating the chamber 150 with a vacuum pump (not shown), or purging the chamber with a purge gas (not shown), or a combination thereof, and then refilling the gas discharge chamber 150 with fresh gas mixture 151 from the gas supply system 170.

[0029] The pressure regulation process is performed to optimize the gas pressure within the gas discharge chamber 150 in order to establish standard operation after an initial fill of the gas mixture, or to restore or reestablish standard operating conditions after an exchange of the gas mixture. During the standard mode of operation of the gas discharge chamber 150 after the pressure regulation process, the light beam 165 is generated in accordance with the requirements of the output device 180. In various implementations, the light beam 165 can be generated in accordance with instructions from or under the control of the output device 180.

[0030] During the pressure regulation process, after the gas discharge chamber 150 is supplied with the initial or fresh replacement gas mixture 151, the gas control module 110 signals the energy source actuator 154 to supply energy to the energy source 152 of the gas discharge chamber 150, thereby generating a discharge or light beam (output light beam) 153 from the gas discharge chamber 150. The discharge or light beam 153 can correspond to the amplified light beam 165, or the amplified light beam 165 can be generated from the discharge or light beam 153 prior to exiting the light source 160. The gas control module 110 then analyzes the performance of the gas discharge chamber 150 and / or the light source 160 against a set of performance metrics and thresholds or limits specific to the pressure regulation process. The gas control module 110 can perform this analysis by accessing the performance parameters tracked or monitored by the monitoring system 140. For example, performance parameters that can be monitored include variations in the energy of the light beam 153 output by the gas discharge chamber 150 and / or the light source 160, the high voltage setting, variations in the wavelength of the light beam 153 output from the gas discharge chamber 150 and / or the power source 160, and the wavelength or bandwidth of the light beam 153 output from the gas discharge chamber 150 and / or the light source 160.

[0031] If the gas control module 110 determines that the discharge chamber 150 and / or the light source 160 is not operating within the performance thresholds specific to the pressure regulation process, the gas control module 110 can signal the gas supply system 170 to iteratively vent (fresh) gas mixture 151 from the gas discharge chamber 150 (or multiple gas discharge chambers within the light source 160, if multiple chambers are undergoing the pressure regulation process) until one or more conditions are met. For example, the iterative pressure reduction can continue until one or more performance metrics required for standard operation are met, such as performance metrics for power output, wavelength, wavelength bandwidth, etc., or until one or more thresholds or limits at which standard operation begins are reached, such as a minimum pressure or a maximum voltage, etc. These thresholds or limits can sometimes be referred to as recovery settings or gas recovery settings or limits. Once one or more conditions (of either type) are met or reached, standard operation of the gas discharge chamber 150 and the light source 160 can begin, or can begin again, with the light source 160 supplying the amplified light beam 165 to the output device 180.

[0032] In existing gas control methods and apparatuses for gas discharge chambers (such as gas discharge chamber 150), particularly when gas discharge chamber 150 is a power amplifier gas discharge chamber, when gas mixture 151 is initially supplied to gas discharge chamber 150 or replaced, the fresh gas mixture supplied to gas discharge chamber 150 is supplied to a pre-specified initial refill pressure or a pre-specified replacement refill pressure, such as 300 kPa or higher, to achieve a relatively wide (downward) pressure regulation range during the pressure regulation process. Once completed, the pressure regulation process generates an operating pressure (which may be referred to as the "current operating pressure") in gas discharge chamber 150, which is set or optimized by the pressure regulation process to achieve standard operation of the light source. The current operating pressure thus set can fall within a relatively wide range, such as 220 to 300 kPa, so in this example, a refill pressure of at least 300 kPa is required. However, such a high refill pressure is not required in all cases. While such a relatively high pressure may be required for initial filling and some refills, lower refill pressures can be used under appropriate conditions, as described below. Using a lower refill pressure under appropriate conditions during gas mixture replacement can save resources and costs because the amount of gas required for gas mixture replacement is reduced.

[0033] Based on all aspects of this disclosure and with reference to Figure 2 Additional References Figure 1 Show and discuss replacing the light source (such as Figure 1 The gas discharge chamber (such as the light source 160) in the light source 160) Figure 1 The gas mixture (such as gas discharge chamber 150) in the gas discharge chamber 150 Figure 1 The process 220 involves a gas mixture 151. Figure 2 As shown, process 220 includes determining the performance of light source 160 and / or gas discharge chamber 150 based on one or more light source and / or gas discharge chamber performance metrics (222); determining the next refill pressure based on the determined performance and the current operating pressure of gas discharge chamber 150 (223); removing gas mixture 151 from gas discharge chamber 150 (224); and filling gas discharge chamber 150 to the determined next refill pressure with a replacement gas mixture (225). In implementation, the gas discharge chamber and / or light source performance metrics may be measured by monitoring system 140 and may include metrics such as wavelength, wavelength variability, bandwidth, power, power variability, etc., of the light beam 153 generated by gas discharge chamber 150 and / or the light beam 165 generated by light source 160, as well as the operating voltage and other operating conditions of gas discharge chamber 150. Implementation may also include one or more of the following.

[0034] Process 220 may include determining the current operating pressure from the previous refill pressure reduction using one or more performance metrics based on the light source 160 and / or the gas discharge chamber 150, these performance metrics being specific to the above-mentioned... Figure 1 The pressure regulation process discussed.

[0035] about Figure 2 The process involves receiving a signal indicating the need to replace the gas mixture at some point before removing the gas mixture 151 (224) from the gas discharge chamber 150. The need for refilling can depend on several complex and often unpredictable variables, including the light source ignition mode and energy, the lifespan of the light source module, and other variables and parameters familiar to those skilled in the art. Refilling can be performed according to a scheduled timetable if necessary, ensuring that light source operation is never unexpectedly interrupted due to the light source reaching its operating limits. In implementation, the relative timing of receiving the signal indicating the need for refilling or gas replacement can be at various locations before the start of gas mixture removal, including... Figure 2 The positions A, B, and C shown are relative timing positions.

[0036] refer to Figure 2A Procedure 223a can be executed, which is used to determine the next refill pressure based on the determined performance and the current operating pressure. Figure 2 (223). Process 223a includes determining a margin value for increasing the next refill pressure relative to the current operating pressure (226a and 216a). When the determined performance indicator light source is stable (the "yes" branch of 227), the margin value is set to a first value (228a), and when the determined performance indicator light source is unstable (the "no" branch of 227), the margin is set to a second value greater than the first value (229a). The gas discharge chamber 150 of process 223a may be a power amplifier gas discharge chamber (i.e., the gas discharge chamber of the power amplifier of the light source, including the gas discharge chamber of the power loop amplifier).

[0037] refer to Figure 2B In other implementations, procedure 223b can be executed, which is used to determine the next refill pressure based on the determined performance and current operating pressure. Figure 2The process 223b includes determining a margin value to increase the next refill pressure relative to the current operating pressure (226b and 216b) by: comparing the one or more performance metrics to respective limits (217), setting the margin value to a first value if any of the one or more performance metrics is outside of its respective limit(s) (the "No" branch of 218), setting the margin value to a second value greater than the first value if none of the one or more performance metrics is outside of its respective limit(s) (the "Yes" branch of 218).

[0038] In other implementations, the process 220 can also include determining a margin value to increase the next refill pressure relative to the current operating pressure, where (1) the determined performance indicates a level of stability of the light source 160 and / or the gas discharge chamber 150, and (2) the determined margin value decreases as the indicated level of stability increases. The process 220 can also include determining a margin value to increase the next refill pressure relative to the current operating pressure, where determining the margin value includes: (1) comparing the one or more performance metrics to respective limits, and (2) setting the margin value to a relatively lower value when the one or more performance metrics is far from exceeding its respective limit(s), and setting the margin value to a relatively higher value when the one or more performance metrics is relatively close to exceeding or exceeding its respective limit(s). The process 220 can also include: determining the margin value, the margin value being smaller when the determined performance indicates that the light source 160 and / or the gas discharge chamber 150 is more stable, and the margin value being larger when the determined performance indicates that the light source 160 and / or the gas discharge chamber 150 is less stable; and setting the next refill pressure to the current operating pressure plus the margin value, or at least to the current operating pressure plus the margin value. Determining the performance of the light source 160 and / or the discharge chamber 150 can include collecting the one or more performance metrics during standard operation of the light source 160. The one or more performance metrics can also be compared to their respective targets during standard operation of the light source 160. If desired, the next refill pressure can also be determined and re-determined continuously or even nearly continuously during standard operation of the light source 160. As mentioned above, the gas discharge chamber 150 of the process 220 can be a power ring amplifier gas discharge chamber.

[0039] Referring again to Figure 1 , the gas control device 100 includes a performance monitoring module 115 that can be configured to continuously analyze one or more performance parameters of the light source 160 and / or the gas discharge chamber 150 during standard operation of the light source 160. The performance analysis can be performed by a performance analyzer PA , as described above. The performance analyzer PA, the performance monitoring module 115 can continuously update the margin value based on the analysis and store the updated margin value within the control system 105, such as in memory M In implementations, the performance monitoring module 115 can continuously update the next refill pressure itself and store it in memory M The performance monitoring module 115 can continuously record performance data, such as in memory M The margin value (and next refill pressure) can be used by or stored in the control system 105 for setting the next refill pressure relative to the current operating pressure the next time the gas control module 110 performs a gas mixture changeover process, or the next refill pressure value itself can be used by or already stored in the control system 105. Thus, there is no need for manual adjustment of the margin value or related next refill pressure.

[0040] In implementations, the memory M may be located outside of the gas control module 110, such as generally within the control system 105. The memory M may be accessible by one or more of the modules 110, 115 within the control system 105, as well as other modules not shown. The memory M may be read only memory and / or random access memory, and can provide storage suitable for tangibly embodying computer program instructions and data. The memory M may be configured to store information output from each module and / or received from the monitoring system 140 for use by the various modules of the control system 105 during operation of the control system 105.

[0041] In implementations, the control system 105 also includes one or more input and / or output devices 109 (such as a keyboard, touch-enabled device, audio input device as input, and audio or video for output) and one or more processors 108. Communication between the modules 110, 115 and any of the other modules and the memory M may be through direct or physical connections (e.g., wired) or wireless connections.

[0042] Although the control system 105 is represented as a box in which all components appear to be juxtaposed, the control system 105 can also consist of components that are physically far apart from each other, such as modules 110, 115, and others not shown. Each of modules 110, 115, and others not shown can be a dedicated processing system for receiving and analyzing data, or one or more modules can be combined into a single processing system. Each module may include or have access to one or more programmable processors 108, and each module can execute instructions to perform a desired function by manipulating input data and generating appropriate output. Modules 110, 115, and others can be implemented using any of digital electronic circuitry, computer hardware, firmware, or software.

[0043] refer to Figure 3 In some implementations, the output device 180 is a photolithography exposure apparatus 380. The exposure apparatus 380 includes an optical arrangement comprising an illuminator system 381 having, for example, one or more condenser lenses, a mask, and an objective lens arrangement through which a light beam 165 is guided to a substrate (wafer) 382. The mask can be moved along one or more directions, such as along the axis of the light beam 165 or in a plane perpendicular to the axis of the light beam 165. The objective lens arrangement includes, for example, a projection lens and enables an image to be transferred from the mask to a photoresist on the wafer 382. The illuminator system 381 adjusts the angular range of the light beam 165 illuminating the mask. Among other features, the exposure apparatus 380 may include a photolithography controller 383 that controls how layers are patterned on the wafer 382. The photolithography controller 383 can communicate with the control system 105.

[0044] As mentioned above, the light source 160 can be a multi-stage system. In Figure 4 In the illustrated implementation, light source 160 is a two-stage light source 460. Light source 460 includes a master oscillator 461A as its first stage and a power amplifier 461B as its second stage. The master oscillator 461A includes a master oscillator gas discharge chamber 450A, and the power amplifier 461B includes a power amplifier gas discharge chamber 450B. The master oscillator gas discharge chamber 450A includes two elongated electrodes serving as an energy source 452A, which provide pulsed energy to the gas mixture 451A within chamber 450A. The power amplifier gas discharge chamber 450B includes two elongated electrodes serving as an energy source 452B, which provide pulsed energy to the gas mixture 451B within chamber 450B.

[0045] The master oscillator 461A provides a pulsed amplified beam (referred to as a seed beam) 462 to the power amplifier 461B. The master oscillator gas discharge chamber 450A contains a gas mixture 451A, which includes a gain medium in which amplification occurs, and the master oscillator 461A includes an optical feedback mechanism such as an optical resonator. The optical resonator is formed between a spectral optics system 463A on one side of the master oscillator gas discharge chamber 450A and an output coupler 464A on the second side of the master oscillator gas discharge chamber 450A. The power amplifier gas discharge chamber 450B contains a gas mixture 451B, which includes a gain medium in which amplification occurs when the seed beam 462 is seeded from the master oscillator 461A. If the power amplifier 461B is designed as a regenerative ring resonator, it is described as a power ring amplifier, and in this case, sufficient optical feedback can be provided from the ring design. The power amplifier 461B may also include a beam returner (such as a reflector) 463B and an output coupler 464B, the beam returner returning the beam (e.g., via reflection) into the power amplifier gas discharge chamber 452B to form a loop path (where the input of the loop amplifier intersects with the output of the loop amplifier), the output coupler for inputting a seed beam 462 and outputting an amplified beam 465. Beam 153 may correspond to either the seed beam 462 or the amplified beam 465.

[0046] The gas mixtures used in the respective discharge chambers 450A and 450B (e.g., gas mixtures 451A and 451B) may be combinations of suitable gases for generating a magnified beam with the desired wavelength, bandwidth, and energy. For example, gas mixtures 451A and 451B may include argon fluoride (ArF) emitting light with a wavelength of about 193 nm, or krypton fluoride (KrF) emitting light with a wavelength of about 248 nm.

[0047] Figure 5 Figure 590, showing an arbitrary scale and proportion, illustrates the pressure of the gas mixture 151 within the gas discharge chamber 150. P The solid line trajectory 591 is used as time. t The function. Trajectory 591 shows a cycle 592 (its time range is indicated by brackets marked 592). Cycle 592 extends from the completion of the initial gas mixture filling 593, indicated by the vertical dashed line 593 marked with completion time, or the immediate preceding gas mixture replacement 593, to the completion of the next gas mixture replacement 594, indicated by the vertical dashed line 594 marked with completion time (not shown before the next pressure regulation process).

[0048] Continue to refer to Figure 5After the initial gas mixture fill or the fill completion immediately preceding a preceding gas mixture change 593, a pressure adjustment process 595 (indicated by the decreasing pressure increment in trace 591 and by the bracket labeled 595) incrementally decreases the pressure in the gas discharge chamber 150 until a desired performance level is reached. When the desired performance level is reached, the pressure adjustment process stops at a current operating pressure 596. The gas discharge chamber 151 then enters a normal operation period 597.

[0049] During normal operation 597, the current operating pressure 596 typically only varies slightly, and the performance of the gas discharge chamber 150 and / or the light source 160 (see Figure 1 and Figure 4 ) that is part thereof is monitored. In addition, during normal operation 597, performance metrics are detected and / or calculated and recorded or otherwise stored, and the performance of the gas discharge chamber 150 and / or the light source 160 is evaluated or assessed. As described above, a margin value MV determined from the performance of the gas discharge chamber 150 and / or the light source 160

[0050] At the end of the normal operation period 597, when a gas mixture change is signaled or otherwise required, the gas mixture 151 in the gas discharge chamber 150 is evacuated and / or purged, indicated by the decreasing pressure 598. Then, a fresh gas mixture flows into the gas discharge chamber, indicated by the increasing pressure 599a or 599b, until a next refill pressure determined by the current operating pressure 596 plus the margin value MV is reached. NRP As described above, the margin value MV is determined by evaluating the performance of the gas discharge chamber 150 and / or the light source 160 during normal operation 597.

[0051] In implementations, this evaluation can be based on the entire normal operation period 597, or only a time period close to the end of the normal operation period, or a weighted evaluation that sets greater or lesser weight to later times of the operation period 597. In implementations, trends and / or variability at the entire or any point of the normal operation period 597 can also be used in the evaluation metric. If the light source 160 and / or the discharge chamber 150 is (or has been) evaluated to be relatively more stable during normal operation, a relatively more aggressive gas saving is achieved in the gas mixture change process by setting the margin value MV to a relatively smaller margin value MVa that, when added to the current operating pressure 596, determines a relatively lower next refill pressure value NRPa. At least the relatively lower next refill pressure value NRPa is less than 300 kPa, or less than the initial fill pressure of the discharge chamber 150, and can save gas compared to filling to the initial fill pressure. If the light source operation is evaluated as relatively unstable, a relatively larger margin value MVb is added to the current operating pressure 596 to determine a relatively higher next refill pressure value for the next gas mixture change NRPb . In implementations, the relatively higher next refill pressure is also less than 300 kPa, or less than the initial fill pressure of the discharge chamber 150, and produces a gas saving compared to the initial fill pressure, just not as much as the refill pressure NRPa case.

[0052] the relatively larger margin value MVb and the associated relatively higher next refill pressure value NRPb provides a larger pressure range, i.e., a larger operating window, for the next pressure regulation process (not shown) to find the next current operating pressure according to the recovery settings or gas recovery settings or limits (not shown) for the next successive normal operating period (not shown). It should be noted that the graph 590 is illustrative only, not quantitative, and has substantially arbitrary scales and proportions, as described above. (For example, the increased pressures represented at 599a and 599b of trace 591 need not have different slopes - the separation of the lines shown at 599a and 599b is used to better illustrate the principles of the present disclosure. Likewise, in practice, the pressure change over time during a gas mixture change is not linear everywhere.)

[0053] As described above, the determination of the margin value MV can have a substantially binary outcome or a more continuous outcome. This is illustrated in Figure 6 and Figure 7 . With reference to Figure 6 , the performance analyzer 630 (such as the performance analyzer 430) can determine the margin value Figure 1The performance analyzer (PA) within the gas controller 110 receives a signal 631 instructing the replacement of the gas mixture 151 in the gas discharge chamber 150, and one or more performance metrics 632 of the gas discharge chamber 150 and / or the light source 160. If the analyzed performance is relatively low, the performance analyzer PA triggers a conservative gas-saving mode 633 (upper alternative), in which the next refill pressure is set (634) to the current operating pressure plus a relatively large (conservative) margin. If the analyzed performance is relatively high, the performance analyzer PA triggers an aggressive gas-saving mode 635 (lower alternative), in which the next refill pressure is set (636) to the current operating pressure plus a relatively small (aggressive) margin to achieve greater gas savings in the next gas change.

[0054] refer to Figure 7 Performance Analyzer 730 (such as Figure 1 Performance analyzer within the gas controller 110 PA The system receives a signal 731 instructing the replacement of the gas mixture 151 in the gas discharge chamber 150, and one or more performance metrics 732 for the gas discharge chamber 150 and / or the light source 160. A margin value (737) is set such that a higher performance result in a lower (more aggressive) margin value. The next refill pressure (738) is set based on the current operating pressure and the margin value to achieve greater gas savings during the next gas mixture replacement when the performance of the gas discharge chamber 150 and / or the light source 160 is more stable.

[0055] Implementations of the present invention may be further described in the following numbered clauses: 1. A method for replacing a gas mixture in a gas discharge chamber of a light source, the method comprising: The performance of the light source and / or gas discharge chamber is determined based on one or more performance metrics of the light source and / or gas discharge chamber. The next refill pressure is determined based on the established performance and the current operating pressure of the gas discharge chamber. Removing the gas mixture from the gas discharge chamber; and The gas discharge chamber is filled to the determined next refill pressure using a replacement gas mixture. 2. The method according to Clause 1 further includes reducing the gas discharge chamber pressure from the previous refill pressure to the current operating pressure based on one or more performance metrics of the light source and / or the gas discharge chamber. 3. The method of clause 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein the margin value is a first value when the determined performance indicates that the light source and / or the gas discharge cell is stable, and the margin value is a second value greater than the first value when the determined performance indicates that the light source and / or the gas discharge cell is not stable. 4. The method of clause 3, wherein the gas discharge cell is a power amplifier gas discharge cell. 5. The method of clause 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein determining the margin value comprises: comparing one or more light source and / or gas discharge cell performance metrics to respective limits; setting the margin value to a first value if any of the one or more light source and / or gas discharge cell performance metrics is outside of its respective limit or limits; and setting the margin value to a second value if each of the one or more light source and / or gas discharge cell performance metrics is within its respective limit or limits; wherein the second value is less than the first value. 6. The method of clause 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein the determined performance indicates a level of stability of the light source and / or the gas discharge cell, and the determined margin value decreases as the indicated level of stability increases. 7. The method of clause 6, wherein the gas discharge cell is a power amplifier gas discharge cell. 8. The method of clause 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein determining the margin value comprises: comparing one or more light source and / or gas discharge cell performance metrics to respective limits; and setting the margin value to a relatively higher value when the one or more light source and / or gas discharge cell performance metrics are close to exceeding or exceed their respective limits, and setting the margin value to a relatively lower value when the one or more light source and / or gas discharge cell performance metrics are far from exceeding their respective limits. 9. The method of clause 1, wherein determining the next refill pressure comprises: determining a margin value, the margin value being smaller when the determined performance indicates that the light source is more stable, and the margin value being larger when the determined performance indicates that the light source is less stable; and setting the next refill pressure to at least the current operating pressure plus the margin value. 10. The method of clause 1, wherein determining the next refill pressure comprises: determining a margin value, the margin value being smaller when the determined performance indicates that the light source is more stable and the margin value being larger when the determined performance indicates that the light source is less stable; and setting the next refill pressure to the current operating pressure plus the margin value. 11. The method of clause 1, wherein determining the performance of the light source and / or the gas discharge cell comprises comparing one or more light source and / or gas discharge cell performance metrics to respective limits. 12. The method of clause 1, wherein determining the performance of the light source and / or the gas discharge cell comprises collecting one or more light source and / or gas discharge cell performance metrics during standard operation of the light source. 13. The method of clause 1, wherein the gas discharge cell is a power ring amplifier gas discharge cell. 14. A gas mixture replacement device associated with a gas discharge cell within a light source, the device comprising: a monitoring and control system connected to the light source and configured to determine a current operating pressure value of the gas discharge cell; determine one or more performance metrics of the light source and / or the gas discharge cell; and determine a next refill pressure value of the gas discharge cell based on the one or more performance metrics and the current operating pressure value of the gas discharge cell; a gas mixture removal system configured to remove a gas mixture from the gas discharge cell; and a gas mixture resupply system connected to the monitoring and control system and configured to fill the gas discharge cell with a replacement gas mixture to the determined refill pressure value. 15. The device of clause 14, wherein the gas discharge cell is a power amplifier gas discharge cell. 16. The device of clause 15, wherein the power amplifier gas discharge cell is a power ring amplifier gas discharge cell. 17. The device of clause 15, wherein the light source is a multi-stage light source. 18. The device of clause 15, wherein the light source is a multi-stage light source, and one stage of the multi-stage light source is a power amplifier stage, the power amplifier stage comprising the gas discharge cell and a circulating ring-shaped light path through the gas discharge cell, and wherein the gas mixture comprises argon fluoride (ArF). 19. The apparatus of clause 15, wherein the monitoring and control system is further configured to determine the margin value for the next refill pressure increase relative to the current operating pressure by comparing one or more performance metrics of the light source and / or the gas discharge chamber to respective limits, and setting the margin value to a first value if any of the one or more light source and / or gas discharge chamber performance metrics is outside of its respective limit or limits, and setting the margin value to a second value if each of the one or more light source and / or gas discharge chamber performance metrics is within its respective limit or limits, wherein the second value is less than the first value. 20. The apparatus of clause 15, wherein the monitoring and control system is further configured to determine the margin value for the next refill pressure increase relative to the current operating pressure by comparing the one or more light source and / or gas discharge chamber performance metrics to respective limits, and setting the margin value to a relatively higher value when the one or more light source and / or gas discharge chamber performance metrics are close to exceeding or exceed their respective limits, and setting the margin value to a relatively lower value when the one or more light source and / or gas discharge chamber performance metrics are far from exceeding their respective limits.

[0056] The above implementations and other implementations are within the scope of the following claims.

Claims

1. A method of replacing a gas mixture in a gas discharge chamber in a light source, the method comprising: determining a performance of the light source and / or gas discharge chamber based on one or more light source and / or gas discharge chamber performance metrics; determining a next refill pressure based on the determined performance and a current operating pressure of the gas discharge chamber; removing the gas mixture from the gas discharge chamber; and filling the gas discharge chamber with a replacement gas mixture to the determined next refill pressure.

2. The method of claim 1, further comprising reducing a gas discharge chamber pressure from a previous refill pressure to a current operating pressure based on one or more performance metrics of the light source and / or the gas discharge chamber.

3. The method of claim 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein the margin value is a first value when the determined performance indicates that the light source and / or the gas discharge chamber is stable, and the margin value is a second value greater than the first value when the determined performance indicates that the light source and / or the gas discharge chamber is unstable.

4. The method of claim 3, wherein the gas discharge chamber is a power amplifier gas discharge chamber.

5. The method of claim 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein determining the margin value comprises: comparing the one or more light source and / or gas discharge chamber performance metrics to respective limits; setting the margin value to a first value if any of the one or more light source and / or gas discharge chamber performance metrics is outside of a respective one or more limits for the any light source and / or gas discharge chamber performance metric; and setting the margin value to a second value if each of the one or more light source and / or gas discharge chamber performance metrics is within a respective one or more limits for the each light source and / or gas discharge chamber performance metric; wherein the second value is less than the first value.

6. The method of claim 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein the determined performance indicates a level of stability of the light source and / or the gas discharge chamber, and the determined margin value decreases as the indicated level of stability increases.

7. The method of claim 6, wherein the gas discharge chamber is a power amplifier gas discharge chamber.

8. The method of claim 1, further comprising determining a margin value to increase the next refill pressure relative to the current operating pressure, wherein determining the margin value comprises: comparing the one or more light source and / or gas discharge chamber performance metrics to respective limits; and The margin value is set to a relatively higher value when the one or more light source and / or gas discharge cell performance metrics are close to exceeding or exceed a respective limit of the one or more light source and / or gas discharge cell performance metrics, and is set to a relatively lower value when the one or more light source and / or gas discharge cell performance metrics are far from exceeding a respective limit of the one or more light source and / or gas discharge cell performance metrics.

9. The method of claim 1, wherein determining the next refill pressure comprises: determining a margin value, the margin value being smaller when the determined performance indicates that the light source is more stable, and the margin value being larger when the determined performance indicates that the light source is less stable; and setting the next refill pressure to at least the current operating pressure plus the margin value.

10. The method of claim 1, wherein determining the next refill pressure comprises: determining a margin value, the margin value being smaller when the determined performance indicates that the light source is more stable, and the margin value being larger when the determined performance indicates that the light source is less stable; and setting the next refill pressure to the current operating pressure plus the margin value.

11. The method of claim 1, wherein determining the performance of the light source and / or gas discharge cell comprises comparing one or more light source and / or gas discharge cell performance metrics to respective limits.

12. The method of claim 1, wherein determining the performance of the light source and / or gas discharge cell comprises collecting the one or more light source and / or gas discharge cell performance metrics during standard operation of the light source.

13. The method of claim 1, wherein the gas discharge cell is a power ring amplifier gas discharge cell.

14. A gas mixture replacement apparatus associated with a gas discharge cell within a light source, the apparatus comprising: a monitoring and control system connected to the light source and configured to determine a current operating pressure value of the gas discharge cell; determine one or more performance metrics of the light source and / or the gas discharge cell; and determine a next refill pressure value of the gas discharge cell based on the one or more performance metrics and the current operating pressure value of the gas discharge cell; a gas mixture removal system configured to remove the gas mixture from the gas discharge cell; and a gas mixture resupply system connected to the monitoring and control system and configured to fill the gas discharge cell to the determined refill pressure value with a replacement gas mixture.

15. The apparatus of claim 14, wherein the gas discharge cell is a power amplifier gas discharge cell.

16. The apparatus of claim 15, wherein the power amplifier gas discharge cell is a power ring amplifier gas discharge cell.

17. The apparatus of claim 15, wherein the light source is a multi-stage light source.

18. The apparatus of claim 15, wherein the light source is a multi-stage light source, and one stage of the multi-stage light source is a power amplifier stage, the power amplifier stage including the gas discharge chamber and a circulating toroidal light path through the gas discharge chamber, and wherein the gas mixture includes argon fluoride (ArF).

19. The apparatus of claim 15, wherein the monitoring and control system is further configured to determine a margin value for increasing the next refill pressure relative to the current operating pressure by comparing the one or more performance metrics of the light source and / or the gas discharge chamber to respective limits, and setting the margin value to a first value if any of the one or more light source and / or gas discharge chamber performance metrics is outside of the respective one or more limits for the any light source and / or gas discharge chamber performance metric, and setting the margin value to a second value if each of the one or more light source and / or gas discharge chamber performance metrics is within the respective one or more limits for the each light source and / or gas discharge chamber performance metric, wherein the second value is less than the first value.

20. The apparatus of claim 15, wherein the monitoring and control system is further configured to determine a margin value for increasing the next refill pressure relative to the current operating pressure by comparing the one or more light source and / or gas discharge chamber performance metrics to respective limits, and setting the margin value to a relatively higher value when the one or more light source and / or gas discharge chamber performance metrics are close to exceeding or exceed the respective limits for the one or more light source and / or gas discharge chamber performance metrics, and setting the margin value to a relatively lower value when the one or more light source and / or gas discharge chamber performance metrics are far from exceeding the respective limits for the one or more light source and / or gas discharge chamber performance metrics.

Images