Reducing energy consumption of gas discharge chamber blowers

Abstract

A control device for a light source including a plurality of gas discharge chambers with a blower disposed within each gas discharge chamber, the control device including: a fault monitoring module configured to monitor one or more operational conditions of the light source for each period of use of the light source, and to identify, for each monitored operational condition, a fault condition and a fault type relating to which blower of the gas discharge chamber is affecting the monitored operational condition; and a control module configured to receive the identified fault condition and the identified fault type from the fault monitoring module, select at least one gas discharge chamber, and send instructions to the blower in the selected at least one gas discharge chamber, the instructions being based on the identified fault condition and the identified fault type.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 63 / 411,452, filed September 29, 2022, the entire contents of which are incorporated herein by reference.

[0002]

[0002] The disclosed subject matter relates to controlling a blower disposed within a gas discharge chamber of a light source, thereby reducing the energy consumed by the blower during operation of the light source. [Background technology]

[0003] One type of gas discharge light source used in photolithography is called an excimer light source, or excimer laser. Typically, excimer lasers use a combination of one or more noble gases, which may include argon, krypton, or xenon, and a reactive gas, which may include fluorine or chlorine. Under the appropriate conditions of electrical stimulation (energized) and high pressure (of the gas mixture), excimer lasers can form excimers, or pseudomolecules, that exist only in their energized state. The energized excimers produce amplified light in the ultraviolet range. An excimer light source can use a single gas discharge chamber or multiple gas discharge chambers. When operating, an excimer light source generates a deep ultraviolet (DUV) light beam. DUV light can include wavelengths from about 100 nanometers (nm) to about 400 nm, for example.

[0004]

[0004] The DUV light beam can be directed to a photolithography exposure tool or scanner, which is a machine that imparts a desired pattern onto a target portion of a substrate (such as a silicon wafer). The DUV light beam interacts with a projection optical system, which projects the DUV light beam through a mask onto the photoresist of the wafer. In this way, one or more layers of the chip design are patterned on the photoresist, after which the wafer is etched and cleaned. Summary of the Invention

[0005] In some general aspects, a controller is configured for a light source. The light source includes a plurality of gas discharge chambers with a blower disposed within each gas discharge chamber. The controller includes: a fault monitoring module configured to monitor one or more operating conditions of the light source and, for each monitored operating condition, identify a fault condition and a fault type associated with which blower of the gas discharge chambers affects the monitored operating condition; and a control module configured to receive the identified fault condition and the identified fault type from the fault monitoring module, select at least one gas discharge chamber, and send instructions to the blower in the selected at least one gas discharge chamber, the instructions based on the identified fault condition and the identified fault type.

[0006]

[0006] Implementations may include one or more of the following features. For example, the fault monitoring module may be configured to identify, for each monitored operating condition, a priority for the monitored operating condition, and the control module may be configured to select at least one gas discharge chamber based on the identified priority. The fault monitoring module may be configured to monitor one or more operating conditions of the light source for each interval of usage of the light source, and the control module may be configured to select at least one gas discharge chamber based on a gas discharge chamber selected by the control module during an immediately preceding usage interval. The multiple gas discharge chambers may include a master oscillator gas discharge chamber and a power amplifier gas discharge chamber optically in series with the master oscillator gas discharge chamber, and the fault type may be selected from a set of possible fault types including a power amplifier fault type, a master oscillator fault type, and a common fault type.

[0007] Each of the one or more operating states can be defined by a performance metric related to the light source or the light beam generated by the light source. The one or more performance metric can include a wavelength histogram associated with the light beam, an energy dose error associated with the light beam, an energy error associated with the light beam, a bandwidth error associated with the light beam, an operating point of a master oscillator gas discharge chamber, an operating point of a power amplifier gas discharge chamber, a spectral feature accuracy associated with the light beam, and an actuator operating point of the light source.

[0008] An identified fault condition for a monitored operating state may be flagged if a performance metric associated with the monitored operating state is not within a threshold range for that performance metric, or may be cleared if the performance metric associated with the monitored operating state is within a threshold range for that performance metric. The fault monitoring module may be configured to identify an overall fault condition based on the identified fault condition for each monitored operating state, and the control module configured to select at least one gas discharge chamber and send instructions to a blower in the selected at least one gas discharge chamber may include a control module that decodes the overall fault condition to analyze the identified fault condition for each monitored operating state.

[0009] A control module configured to select at least one gas discharge chamber and transmit commands to a blower in the selected at least one gas discharge chamber can include a control module configured to operate in an active mode if all identified fault conditions are cleared and to operate in a risk mode if any one of the identified fault conditions is flagged. In the active mode, the control module can be configured to transmit commands to decrease the operating speed of the blower in the selected at least one gas discharge chamber by a decrement speed increment, and in the risk mode, the control module can be configured to transmit commands to increase the operating speed of the blower in the selected at least one gas discharge chamber by an incremental speed increment that is greater than the decrement speed increment. The incremental speed increment can be 40 revolutions per minute (rpm) or less, and the decrement speed increment can be approximately ½, ⅓, ¼, or ⅕ of the incremental speed increment. In the active mode, the control module can be configured to select one of the gas discharge chambers and transmit a command to reduce the operating speed of a blower disposed in the selected gas discharge chamber to a reduced operating speed if the reduced operating speed is above the baseline speed. The control module can be configured to transmit a command to increase the operating speed of a blower disposed in the selected gas discharge chamber if the current operating speed of the blower disposed in the selected gas discharge chamber is below the baseline speed, and to maintain the operating speed of the blower disposed in the selected gas discharge chamber if the current operating speed of the blower disposed in the selected gas discharge chamber is the baseline speed. The control device can further include a baseline module configured to control the baseline speed of each blower in each gas discharge chamber, wherein control of the baseline speed of a particular blower is related to the age of the gas discharge chamber in which the blower is housed. The fault monitoring module can be configured to identify a fault priority for each monitored operating condition.In the risk mode, the control module can be configured to analyze the fault conditions of each monitored operating condition to determine which one or more fault conditions are flagged, select one of the flagged fault conditions based on the identified fault priority if multiple fault conditions are flagged, select the single flagged fault condition if a single fault condition is flagged, select a gas discharge chamber based on a fault type associated with the selected fault condition, and send a command to increase the operating speed of the blower of the selected gas discharge chamber. The fault type can be associated with a single gas discharge chamber or multiple gas discharge chambers. In the risk mode, the control module configured to select a gas discharge chamber based on the fault type associated with the selected fault condition can include either selecting the single gas discharge chamber associated with the fault type or selecting the gas discharge chamber from the multiple gas discharge chambers associated with the fault type. In the risk mode, after the operating speed of the blower of the selected gas discharge chamber is increased, the control module enters a hold state, and after the hold state ends, the control module can be configured to receive from the fault monitoring module the next identified fault condition and fault type for each monitored operating condition, analyze the fault conditions for each monitored operating condition to determine which one or more fault conditions are flagged, select one of the flagged fault conditions based on the identified fault priority if any of the one or more fault conditions are flagged, i.e., if multiple fault conditions are flagged, select the single flagged fault condition if a single fault condition is flagged, select the gas discharge chamber based on the fault type associated with the selected fault condition, send a command to increase the operating speed of the blower of the selected gas discharge chamber, and if none of the one or more fault conditions are flagged, exit the risk mode and wait for the next identified fault condition and fault type from the fault monitoring module.

[0010] The fault monitoring module can be configured to monitor one or more operating conditions of the light source for each fixed usage time of the light source, where the fixed usage time of the light source can be measured as a number of pulses generated by the light source. The fixed usage time can include a first fixed usage time and a second fixed usage time greater than the first fixed usage time. The fault monitoring module can be configured to operate using the second fixed usage time after both identifying a flagged fault condition using the first fixed usage time and subsequently identifying the absence of the flagged fault condition within a subsequent usage time.

[0011] In another general aspect, a method is configured to control a plurality of blowers, each blower disposed within a gas discharge chamber of a light source, the method including: monitoring one or more operating conditions of the light source for each fixed period of use of the light source; identifying, for each monitored operating condition, a fault condition and a fault type relating to which blowers in the gas discharge chambers affect the monitored operating condition; selecting at least one gas discharge chamber; and transmitting instructions to the blowers in the selected at least one gas discharge chamber, the instructions being based on the identified fault condition and the identified fault type.

[0012]

[0012] Implementations may include one or more of the following features. For example, the method may further include, for each monitored operating condition, identifying a priority for the monitored operating condition. The at least one gas discharge chamber may be selected by selecting the at least one gas discharge chamber based on the identified priority. The at least one gas discharge chamber may be selected by selecting the at least one gas discharge chamber based on a gas discharge chamber selected during a most recent preceding usage time. The identified fault condition for the monitored operating condition may be flagged if a performance metric associated with the monitored operating condition is not within a threshold range of the performance metric, or may be cleared if the performance metric associated with the monitored operating condition is within a threshold range of the performance metric. The method may also include identifying an overall fault condition based on the identified fault condition for each monitored operating condition. At least one gas discharge chamber may be selected, and a command may be sent to a blower in the selected at least one gas discharge chamber by decoding the overall fault condition to analyze the identified fault condition for each monitored operating condition.

[0013] At least one gas discharge chamber can be selected, and a command can be sent to a blower in the selected at least one gas discharge chamber by operating in an active mode if all of the identified fault conditions are clear and operating in a risk mode if any one of the identified fault conditions is flagged. In the active mode, a command can be sent to the blower by sending a command to reduce the operating speed of the blower in the selected at least one gas discharge chamber by a decrement speed increment, and in the risk mode, a command can be sent to the blower by sending a command to increase the operating speed of the blower in the selected at least one gas discharge chamber by an increment speed increment that is greater than the decrement speed increment. In the active mode, at least one gas discharge chamber can be selected by selecting one of the gas discharge chambers, and a command can be sent to the blower by sending a command to reduce the operating speed of the blower located in the selected gas discharge chamber to the reduced operating speed if the reduced operating speed is above the baseline speed. If the current operating speed of the blower disposed in the selected gas discharge chamber is equal to or less than the baseline speed, a command can be sent to the blower by sending a command to increase the operating speed of the blower disposed in the selected gas discharge chamber.If the current operating speed of the blower disposed in the selected gas discharge chamber is within a baseline speed threshold, a command can be sent to the blower by sending a command to maintain the operating speed of the blower disposed in the selected gas discharge chamber.The method can further include controlling the baseline speed of each blower in each gas discharge chamber, where controlling the baseline speed of a particular blower is related to the age of the gas discharge chamber in which the blower is housed.The method can also include identifying a fault priority for each monitored operating condition.Then, operating in the risk mode can include analyzing the fault conditions for each monitored operating condition to determine which one or more fault conditions are flagged, selecting one of the flagged fault conditions based on the identified fault priority if multiple fault conditions are flagged, selecting the single flagged fault condition if a single fault condition is flagged, selecting a gas discharge chamber based on a fault type associated with the selected fault condition, and sending a command to increase the operating speed of a blower of the selected gas discharge chamber. The fault type can be associated with a single gas discharge chamber or multiple gas discharge chambers, and operating in the risk mode can include selecting a gas discharge chamber based on the fault type associated with the selected fault condition, including either selecting the single gas discharge chamber associated with the fault type or selecting a gas discharge chamber from the multiple gas discharge chambers associated with the fault type.

[0014]

[0014] Operating in risk mode may include entering a hold state after the operating speed of the blower of the selected gas discharge chamber is increased, and after the hold state ends, analyzing the identified next fault condition for each monitored operating condition to determine which one or more fault conditions are flagged, and if any of the one or more fault conditions are flagged, i.e., if multiple fault conditions are flagged, selecting one of the flagged fault conditions based on the identified fault priority, and if a single fault condition is flagged, selecting the single flagged fault condition, selecting a gas discharge chamber based on the fault type associated with the selected fault condition, sending a command to increase the operating speed of the blower of the selected gas discharge chamber, and if none of the one or more fault conditions are flagged, exiting risk mode and waiting for the identified next fault condition and fault type.

[0015] In another general aspect, a controller is configured for a light source including a first gas discharge chamber and a second gas discharge chamber optically in series with the first gas discharge chamber, the controller including: a fault monitoring module configured to periodically monitor one or more operating conditions of the light source and, for each monitored operating condition, identify a fault condition; and a control module configured to send a first command to a first blower in the first gas discharge chamber and a second command to a second blower in the second gas discharge chamber, the first command and the second command relating to the speeds of the first blower and the second blower, respectively, the first command and the second command being based on the identified fault condition. [Brief explanation of the drawings]

[0016] [Figure 1]

[0016] A block diagram of an ultraviolet light source that generates a light beam used by a lithography exposure apparatus, the ultraviolet light source including a light generating device having one or more gas discharge chambers, each gas discharge chamber including a blower, and a device configured to at least partially control the speed of the blower. [Figure 2]

[0017] 2 is a block diagram of an implementation of the device of FIG. 1 including a monitor module, a decrement module, an increment module, and optionally a baseline module. [Figure 3]

[0018] 3 is a schematic diagram illustrating how an overall fault condition of a light source is identified based on one or more operational states of the light source for use by the apparatus of FIGS. 1 and 2. FIG. [Figure 4A]

[0019] 10 is an exemplary graph showing how baseline rates for different discharge chambers change with discharge chamber age. [Figure 4B] 1 is an exemplary graph showing how baseline rates change with discharge chamber age for different discharge chambers. [Figure 4C]1 is an exemplary graph showing how baseline rates change with discharge chamber age for different discharge chambers. [Figure 5]

[0020] FIG. 1 is a diagram of a state machine representing an embodiment of an apparatus, the state machine including a monitoring state (performed by a monitoring module), a decrement state (performed by a decrement module), and an increment state (performed by an increment module). [Figure 6A]

[0021] 10 is a flowchart of the procedure performed by the decrement module while the state machine is in the decrement state. [Figure 6B]

[0022] 10 is a flowchart of the procedure performed by the monitor module while the state machine is in the monitor state. [Figure 6C]

[0023] 10 is a flowchart of the procedure performed by the baseline module while the state machine is in the baseline state. [Figure 6D]

[0024] 10 is a flowchart of the procedure performed by the increment module while the state machine is in the increment state. [Figure 7A]

[0025] 3 is a flow chart of a procedure performed by the apparatus for controlling the speed of a blower of the light source of FIGS. 1 and 2. [Figure 7B]

[0026] An additional step that can be included in the procedure of Figure 7A. [Figure 8]

[0027] FIG. 1 is a block diagram of an embodiment of a light source in which the light-generating device includes two gas discharge chambers in a master oscillator-power amplifier configuration. [Figure 9A]

[0028] 1 is a block diagram of an embodiment of a light source and an embodiment of a lithographic exposure apparatus in which the light-generating device includes multiple gas discharge chambers; [Figure 9B]

[0029] 9B is a block diagram of an embodiment of a projection optical system of the lithographic exposure apparatus of FIG. 9A. [Figure 10]

[0030] 2 is a block diagram of an embodiment of a light source including multiple gas discharge chambers and an embodiment of the apparatus of FIG. 1 for controlling the speed of each blower in each gas discharge chamber based on fault conditions and fault types. [Figure 11]

[0031] 1 is an exemplary table showing fault types and fault priorities for each performance metric monitored. [Figure 12]

[0032] 11 is a flowchart of a procedure performed by the apparatus of FIG. 10 for controlling a plurality of blowers, each blower being disposed within a gas discharge chamber of the light source of FIG. 10. [Figure 13]

[0033] 13 is a flow chart of an active procedure carried out by the device of FIG. 10 in conjunction with the procedure of FIG. 12. [Figure 14]

[0034] 13 is a flow chart of a risk procedure performed by the apparatus of FIG. 10 in conjunction with the procedure of FIG. 12. [Figure 15]

[0035] 11 is a graph showing the blower speed versus the usage of the light source of FIG. 10, and a graph showing the status of the device of FIG. 10 versus the usage of the light source of FIG. 10; DETAILED DESCRIPTION OF THE INVENTION

[0017]

[0036] Referring to FIG. 1 , ultraviolet light source 100 includes a light-generating apparatus 105 that includes one or more gas discharge chambers 104 and device 110. In the example of FIG. 1 , light-generating apparatus 105 includes one discharge chamber 104, but it may also include multiple discharge chambers 104 (as shown in FIGS. 8 and 9A ). Gas discharge chamber 104 is configured to hold a gas mixture 107 including a gain medium within an interior cavity 104i of gas discharge chamber 104 and to house energy source 106 configured to provide energy to gas mixture 107, thereby generating light beam 102. The gain medium in gas mixture 107 is configured to emit deep ultraviolet (DUV) light in response to a voltage signal applied to energy source 106. Energy source 106 may be configured to provide energy to gas mixture 107 in short (e.g., nanosecond) current pulses using a high-voltage discharge interspersed with periods of no energy. The gas mixture 107 generates pulses of the light beam 102 from a population inversion that occurs in the gain medium of the gas mixture 107 by stimulated emission when energy from the energy source 106 is provided to the gas mixture 107. Thus, the light beam 102 is a pulsed light beam that includes pulses of light centered at wavelengths in the deep ultraviolet range, including wavelengths of 248 nanometers (nm) or 193 nm. For a deep ultraviolet light source, the gas gain medium of the gas mixture 107 may include, for example, argon fluoride (ArF), krypton fluoride (KrF), or xenon chloride (XeCl). The light beam 102 is directed along a path toward a lithography exposure tool 101. The light beam 102 is used to pattern microelectronic features on a substrate or wafer received by the lithography exposure tool 101. The size of the microelectronic features patterned on the wafer depends on the wavelength of the pulsed light beam 102, with lower wavelengths resulting in smaller minimum feature sizes or critical dimensions. For example, if the wavelength of the pulsed light beam 102 is 248 nm or 193 nm, the minimum size of the microelectronic features may be, for example, 50 nm or less.

[0018]

[0037] Specifically, energy source 106 can include a cathode and an anode, with a potential difference between the cathode and the anode creating an electric field in gas mixture 107. The electric field provides energy to the gain medium in gas mixture 107, sufficient to cause population inversion and generate optical pulses by stimulated emission. Repeated creation of this potential difference creates a train of optical pulses that ultimately constitutes light beam 102. A "discharge event" is the application of a voltage that creates a potential difference sufficient to cause an electric discharge in the gain medium of gas mixture 107 and the emission of optical pulses.

[0019]

[0038] When a light pulse is generated from the gas mixture 107 near the energy source 106, there is a period of time during which the molecules in the gas mixture 107 recover. This recovery time is longer than the time between pulses of the energy source 106. Furthermore, if another pulse of energy is supplied to the recovering gas mixture 107 residing closest to the energy source 106, it will degrade the output quality of the light pulse in the resulting light beam 102 and may cause damage to the light-generating device 105. To solve this problem, the gas discharge chamber 104 carries a blower 108 fixed to the walls 103A, 103B of the gas discharge chamber 104. In various embodiments, the blower 108 can include a rotating structure such as a fan. See, for example, U.S. Patent No. 6,765,946, issued July 20, 2004, in the names of inventors Partlo, et al., which is incorporated herein by reference in its entirety. The blower 108 is configured to move the recovering portion of the gas mixture 107 within the gas discharge chamber 104 away from the energy source 106 at regular intervals to allow fresh gas mixture 107 to interact with the energy source 106 before the next pulse of the energy source 106 is generated. If the speed of the blower 108 is too slow, arcing, dropouts, and inefficiencies may occur within the gas discharge chamber 104, and the gas discharge chamber 104 may fail if the blower 108 is unable to sufficiently remove the recovering portion of the gas mixture 107. Another consideration is that the rotation or movement of the blower 108 may create vibrations within the gas discharge chamber 104 that may affect one or more spectral characteristics of the light beam 102 and the dosing performance of the light beam 102 in the lithography exposure apparatus 101.

[0020]

[0039] During operation of the light source 100, the operating speed of the blower 108 (which is the speed or rate at which the blower 108 rotates about its axis of rotation) can be maintained constant at a preset speed. Specifically, the operating speed of the blower 108 can be maintained at a maximum blower speed so that the operating speed of the blower 108 does not change over time as the light source 100 operates. Under such conditions, the blower 108 may consume a nearly constant amount of energy over time, or in other words, require constant power as the light source 100 operates, which may be costly and ineffective at the very least. Therefore, as described herein, the operating speed of the blower 108 is varied or adjusted over time (as the light source 100 operates) by the device 110 based on a fault condition of one or more operational states of the light source 100 and the baseline speed of the blower 108 (which is the minimum allowable speed of the blower 108). The operating speed of the blower 108 is varied or adjusted by adjusting the operating speed setpoint of the blower 108. In this manner, the device 110 functions as a blower controller that controls the operating speed of the blower 108 by adjusting the operating speed between a minimum blower speed and a maximum blower speed, which together define a safe blower speed range for the blower 108 during operation of the light source 100. In other words, when the light source 100 is operating, the device 110 adjusts the operating speed of the blower 108 to be within a safe blower speed range that will not cause any faults and / or problems within the light source 100, and also adjusts the operating speed of the blower 108 so that more energy is saved by the blower 108, and, as a result, less energy is consumed by the light source 100. The device 110 will now be described in more detail. The device 110 performs an analysis every certain number of hours of operation of the light source 100 and sends instructions regarding the operating speed of the blower 108. The usage time can be based on the number of pulses of the light beam 102 generated by the light-generating device 105. Thus, for example, the device 110 can perform an analysis and send instructions every 5 million pulses of the light beam 102. At any particular time, depending on the current state of performance of the light source 100, the usage time can be increased to, for example, 10 million pulses of the light beam 102.

[0021]

[0040] Referring to FIG. 2, device 110 (ie, a blower controller) includes a monitor module 112 and a control module 115, which includes a decrement module 114 and an increment module .

[0022]

[0041] Generally, the monitoring module 112 is configured to monitor for fault conditions associated with one or more operational states of the light source 100. For example, each of the one or more operational states may be defined by performance metrics associated with the light source 100 or the light beam 102 generated by the light source 100. A fault condition may be considered flagged if at least one of the associated performance metrics is not within a threshold range for that performance metric, and a fault condition may be considered cleared if all of the associated performance metrics are within their respective threshold ranges. Thus, as the light source 100 operates, the monitoring module 112 may monitor one or more operational states of the light source 100 by monitoring one or more associated performance metrics.

[0023]

[0042] Generally, the decrement module 114 is configured to decrease the operating speed of the blower 108 if a fault condition related to one or more operational states of the light source 100 is clear and if the decreased operating speed is equal to or greater than the baseline speed of the blower 108 (which is the minimum allowable speed of the blower 108). For example, the decrement module 114 may be configured to decrease the operating speed of the blower 108 by a decrement speed increment.

[0024]

[0043] Generally, the increment module 116 is configured to increase the operating speed of the blower 108 when a fault condition in one or more operational conditions of the light source 100 is flagged. The increment module 116 can be configured to increase the operating speed of the blower 108 by an increment speed increment. In one example, the increment speed increment can be, for example, 25 revolutions per minute (rpm) or less. In this example, the increment speed increment can be greater than the decrement speed increment, and the decrement speed increment can be approximately one-half, one-third, one-quarter, or one-fifth the increment speed increment. In some implementations, the increment speed increment can be, for example, 40 rpm or less.

[0025]

[0044] The apparatus 110 may also include a baseline module 118 configured to increase the operating speed of the blower 108 if the operating speed of the blower 108 is below the baseline speed.

[0026]

[0045] When light source 100 operates, the operating speed of blower 108 is adjusted by increment and decrement modules 114, 116 and baseline module 118 to within a blower speed range defined by a minimum blower speed and a maximum blower speed. The blower speed range is a safe range within which light source 100 operates properly without problems and / or failures. In this manner, device 110 controls the operating speed of blower 108 by adjusting the operating speed within the safe blower speed range so that minimal energy is consumed by blower 108 and the energy consumed by light source 100 is reduced.

[0027]

[0046] The modules 112, 114, 116, 118 of the apparatus 110 can be implemented in a control system that communicates with and thereby controls the blower 108. Thus, the control system of the blower controller 108 is configured to monitor a fault condition for one or more operational conditions of the light source 100, reduce the operating speed of the blower 108 in a decrement state if the fault condition for one or more operational conditions of the light source 100 is clear and if the reduced operating speed is equal to or greater than the baseline speed, and increase the operating speed of the blower 108 in an increment state if a fault condition for one or more operational conditions of the light source 100 is flagged. The control system of the blower controller 110 can also be configured to increase the operating speed of the blower 108 in an increment state if the reduced operating speed of the blower 108 is below the baseline speed.

[0028]

[0047] The device 110 may also include a computer-readable memory module and one or more electronic processors coupled to the computer-readable memory module. Each of the modules 112, 114, 116, and 118 may be in communication with the memory module and controlled by one or more electronic processors. For example, each of the modules 112, 114, 116, and 118 may include or have access to one or more programmable processors, each capable of executing a program of instructions that performs a desired function by operating on input data and generating appropriate output. Each of the modules 112, 114, 116, and 118 may be implemented in digital electronic circuitry, computer hardware, firmware, or software. In further embodiments, each module 112, 114, 116, 118 accesses memory in a memory module that is also configured to store information output from one or more of the modules 112, 114, 116, 118, information from the discharge chamber 104, or information about other aspects of the light-generating device 105, which is available for various uses by the modules 112, 114, 116, 118 during operation of the device 110. The memory in the memory module may be read-only memory and / or random-access memory and may provide storage devices suitable for tangibly embodying computer program instructions and data. The device 110 may also include one or more input devices (e.g., a keyboard, a touch-enabled device, an audio input device, etc.) and one or more output devices, such as audio or video output.

[0029]

[0048] In an example where device 110 functions as a blower controller, fault conditions for one or more operational states may be defined (by the control system) using a binary system. Specifically, a fault condition may be assigned a value of zero (0) if the fault condition is clear and a value of one (1) if the fault condition is flagged. The following provides details of fault conditions for one or more operational states of light source 100:

[0030]

[0049] 3, an overall fault condition 327 for light source 100 is identified by device 110 in each iteration based on one or more operational states of light source 100. Each of the one or more operational states is defined by performance metrics 320_1-320_N related to light source 100 or the light beam 102 generated by light source 100. The fault condition 327 used by device 110 to control blower 108 should be based on system parameters, metrics, and signals that are significantly affected by changes in the speed of blower 108.

[0031]

[0050] In the example of FIG. 3 , the one or more performance metrics 320_1-320_N include a spectral feature accuracy associated with the light beam 102, an energy dose error associated with the light beam 102, an energy error associated with the light beam 102, an actuator operating point of the light generating device 105 in the light source 100, and a dropout rate of the gas discharge chamber.

[0032]

[0051] Spectral feature accuracy represents the stability and precision of the spectral features (such as wavelength) of the light beam 102 generated by the light source 100. Specifically, the spectral feature accuracy with respect to wavelength is based on the mean and standard deviation of the error in the wavelength of the light beam 102 calculated over a moving window of M pulses of the light beam 102 (M is an integer equal to or greater than 1). The value of the spectral feature accuracy can be measured / calculated directly or can be estimated from other measurement data.

[0033]

[0052] Energy dose error represents the difference between the desired or target dose at the wafer and the actual dose at the wafer received by the lithography exposure tool 107. The dose at the wafer is the amount of light energy per unit area or a specific number of pulses at the wafer that the light beam 102 delivers over the exposure time. While the energy dose error may be measured / calculated directly, the energy dose error may alternatively be estimated from other measurement data.

[0034]

[0053] The energy error represents the standard deviation of the measured energy of the light beam 102. In particular, the energy error can be considered as the difference between the amount of energy in a pulse of the light beam 102 and a target energy. While the energy error may be measured directly, the energy error may alternatively be estimated from other data.

[0035]

[0054] The actuator operating point of a light-generating device 105 characterizes where, within a range of possible settings, values, or conditions, an actuator within the light-generating device 105 is operating. In some embodiments, as described below with respect to FIG. 8 , the actuator can be a timing module coupled to a first stage including a first discharge chamber 804A (the first stage comprising a master oscillator) and a second stage including a second discharge chamber 804B (the second stage comprising a power amplifier) ​​of the light-generating device 805. Such a timing module controls the relative timing between a first trigger signal sent to a first energy source 806A of the first discharge chamber 804A and a second trigger signal sent to a second energy source 806B of the second discharge chamber 804B. This relative timing can be referred to as differential timing. In these embodiments, the actuator operating point metric of the light-generating device 805 can quantify the deviation of the actual relative timing from the peak efficient differential timing (Tpeak), which is the relative timing value at which the light-generating device 805 (via energy sources 806A, 806B) produces the light beam 802 having the maximum energy at a particular input energy applied to the light-generating device 805. This actuator operating point metric can be calculated or estimated based on the voltage or energy supplied to the energy sources 806A, 806B, the output energy of the light beam 802, and the differential timing.

[0036]

[0055] The gas discharge chamber dropout rate quantifies a failure mechanism in which the blower 108 is unable to remove a sufficient portion of the recovering gas mixture 107, causing the gas mixture to not move quickly enough through the gas discharge chamber 104, resulting in arcing and energy loss within the gas discharge chamber 104.

[0037]

[0056] In some embodiments, as described above, one or more of performance metrics 320_1-320_N for light source 100 may not be available at a particular moment in operation or within a particular system, and device 110 may estimate the value of the unavailable performance metric based on other available data to identify fault condition 327. To calculate overall fault condition 327, device 110 receives performance metrics 320_1, 320_2, ... 320_N.

[0038]

[0057] Each of the one or more performance metrics 320_1-320_N is associated with a respective value 321_1-321_N that is passed through a respective filter 322_1-322_N to remove noise effects or temporary performance problems that may occur during operation. For example, each of the filters 322_1-322_N can be a low-pass filter or a weighted sum filter, and as a result, a fault condition 327 related to one or more operating states 320_1-320_N of the light source 100 is identified using the filters 322_1-322_N (including the low-pass filter or the weighted sum filter). Additionally, each of the filters 322_1-322_N can have a configurable transfer function for filtering the values ​​321_1-321_N of the performance metrics 320_1-320_N.

[0039]

[0058] A filtered value 323_1-323_N of the performance metric 320_1-320_N is output from each of the respective filters 322_1-322_N. Each of the filtered values ​​323_1-323_N is compared to a respective threshold range 324_1-324_N associated with that respective performance metric 320_1-320_N to identify a respective fault condition 325_1-325_N associated with that respective performance metric 320_1-320_N (and thus an operational state). If it is determined that the respective performance metric 320_1-320_N is not within the threshold range 324_1-324_N of that performance metric 320_1-320_N, then the fault condition 325_1-325_N of that performance metric 320_1-320_N is flagged. If a respective performance metric 320_1-320_N is determined to be within the threshold range 324_1-324_N for that performance metric 320_1-320_N, then the fault status 325_1-325_N for that performance metric 320_1-320_N is clear. As noted above, the fault status 325_1-325_N may be assigned a value of zero (0) if the fault status 325_1-325_N is clear, or a value of one if the fault status 325_1-325_N is flagged.

[0040]

[0059] Each fault status 325_1-325_N is input to a fault status module 326 (which may be a controller) that determines an overall fault status 327 for the light source 100 based on the fault statuses 325_1-325_N of the performance metrics 320_1-320_N for the light source 100. For example, in some embodiments, if any one of the fault statuses 325_1-325_N is flagged (i.e., given a value of 1), the overall fault status 327 for the light source 100 is flagged (i.e., given a value of 1). And, if all of the fault statuses 325_1-325_N are clear (i.e., have a value of 0), the overall fault status 327 for the light source 100 is clear (i.e., has a value of 0). In this manner, the overall fault status 327 for the light source 100 can be determined, and the apparatus 110 can control the blower 108 based on the fault status 327 for the light source 100, thereby reducing energy consumption by the blower 108 during operation. In other embodiments, the fault condition module 326 may be configured to flag the entire fault condition 325 only if multiple fault conditions 325_1-325_N are flagged.

[0041]

[0060] Next, the baseline speed of the blower 108 is detailed.

[0042]

[0061] 4A-4C, the baseline speed of blower 108 can be related to the age of gas discharge chamber 104. In the examples of FIGS. 4A-4C, the baseline speed changes as gas discharge chamber 104 ages over time. In other words, the baseline speed changes as the number of pulses of light beam 102 generated by gas discharge chamber 104 increases over time (and as gas discharge chamber 104 ages). In these examples, apparatus 110 adjusts the baseline speed of blower 108 between a minimum baseline speed bmin and a maximum baseline speed bmax. Any of modules 114, 116, 118 or another module of apparatus 110 can perform this adjustment. Generally, the baseline speed of blower 108 needs to increase as gas discharge chamber 104 ages and performance failures, problems, and / or errors occur more frequently in the aging light source 100 (and gas discharge chamber 104). By increasing the baseline velocity of the gas discharge chamber 104 as the discharge chamber 104 ages, performance impairments, performance problems, and / or performance errors that may occur within the aging light source 100 are reduced or mitigated.

[0043]

[0062] 4A , apparatus 110 adjusts the baseline speed from a maximum baseline speed bmax to a minimum baseline speed bmin at time t1a. At this time, apparatus 110 begins gradually increasing the baseline speed at time t1a. The baseline speed of blower 108 is incremented at a constant rate 429a (i.e., slope) as gas discharge chamber 104 ages over time (or as pulses of light beam 102 are generated by gas discharge chamber 104). The baseline speed of blower 108 is increased or incremented from the minimum baseline speed bmin to the maximum baseline speed bmax so that the baseline speed reaches the maximum baseline speed bmax at time t2a, which is the end of the life of gas discharge chamber 104.

[0044]

[0063] 4B, apparatus 110 adjusts the baseline speed from a maximum baseline speed bmax to a minimum baseline speed bmin at time tlb. While gas discharge chamber 104 is new for a period of time dL between time tlb and time t2b, the baseline speed of blower 108 does not change and remains constant at the minimum baseline speed bmin. Because gas discharge chamber 104 is new between time tlb and time t2b, no increase in the baseline speed is necessary to mitigate or alleviate the performance problem in light source 100 in this example.

[0045]

[0064] At time t2b, apparatus 110 begins to increase or increment the baseline speed. The baseline speed of blower 108 is incremented at a constant rate 429b (i.e., slope) as gas discharge chamber 104 ages and deteriorates (and as pulses of light beam 102 are generated by gas discharge chamber 104). The baseline speed of blower 108 is increased or incremented from a minimum baseline speed bmin to a maximum baseline speed bmax such that at time t3b, which is the end of the life of gas discharge chamber 104, the baseline speed reaches the maximum baseline speed bmax.

[0046]

[0065] 4C is similar to the example of FIG. 4B, except that the baseline speed of blower 108 remains constant for a shorter time dS and is incremented at a slower rate 429c than rate 429b. After decrementing the baseline speed to a minimum baseline speed bmin at time tlc and maintaining this minimum baseline speed bmin for time dS, at time t2c the baseline speed is increased at a constant rate 429c as gas discharge chamber 104 ages and deteriorates over time until the baseline speed of blower 108 reaches a maximum baseline speed bmax at time t3c, which is the end of the life of gas discharge chamber 104.

[0047]

[0066] 5, apparatus 110 (FIG. 2) is represented as a state machine 510 for light source 100. In this diagram of state machine 510, monitor module 112 is represented by monitor state 512, decrement module 114 is represented by decrement state 514, and increment module 116 is represented by increment state 516. State machine 510 may also include a baseline state 518, which represents baseline module 118 (FIG. 2). Also, in this embodiment, state machine 510 includes a passive state 511 in which there are no commands or instructions from state machine 510 to change or adjust the operating speed of blower 108.

[0048]

[0067] The state machine 510 transitions from the passive state 511 to the decrement state 514 when the number of pulses in the light beam 102 produced from the gas discharge chamber 104 exceeds a threshold value or after the state machine 510 has been in the passive state 511 for a threshold period of time (T(PD)). Generally, the decrement state 514 is configured to reduce the operating speed of the blower 108 when the fault condition 327 for one or more operating conditions of the light source 100 is clear and when the reduced operating speed is equal to or greater than the baseline speed.

[0049]

[0068] 6A, in the decrement state 514, the decrement module 114 determines (532) whether the fault status 327 of the light source 100 is clear (e.g., is 0). If the fault status 327 is not clear (and thus is flagged or has a value of 1) (532), the decrement module 114 exits the decrement state 514 and the state machine 510 transitions (T(DI)) from the decrement state 514 to the increment state 516 such that the operating speed of the blower 108 is incremented to a safe operating speed at which no problems and / or faults will occur within the light source 100.

[0050]

[0069] If the fault condition is clear (i.e., has a value of 0) 532, the decrement module 114 determines whether the operating speed of the blower 108 is greater than the baseline speed 533. If the operating speed of the blower 108 is not greater than the baseline speed (which means that the operating speed of the blower 108 is at or below the baseline speed of the blower 108), the decrement module 114 exits the decrement state 514 and the state machine 510 transitions (T(DB)) from the decrement state 514 to the baseline state 518 such that the operating speed of the blower 108 is incremented to a safe operating speed above the baseline speed where no problems and / or faults will occur within the light source 100.

[0051]

[0070] If the operating speed of the blower 108 is greater than the baseline speed (533), the decrement module 114 determines (534) whether the proposed new blower speed is greater than the baseline speed. The proposed new blower speed is the operating speed of the blower 108 minus the decrement speed step size. If the proposed new speed of the blower 108 is not greater than the baseline speed (i.e., the proposed new blower speed is at or less than the baseline speed) (534), the decrement module 114 exits the decrement state 514 and the state machine 510 transitions (T(DM)) from the decrement state 514 to the monitor state 512 so that the state machine 510 can monitor one or more operating conditions of the light source 100 and the operating speed of the blower 108.

[0052]

[0071] On the other hand, if the proposed new blower speed is greater than the baseline speed (534), the decrement module 114 determines whether the number of pulses in the light beam 102 generated by the gas discharge chamber 104 since the last time the blower speed was changed is greater than a threshold number of pulses (541). The threshold number of pulses can be preset to a positive integer to reduce the frequency at which the blower speed is changed. For example, the frequency at which the blower speed is changed can be set to ensure that the light-generating device 105, and even performance metrics, have sufficient time to adjust to the effects of the blower speed change. It is also possible to operate in the decrement state 514 without performing this step 541.

[0053]

[0072] If the number of pulses of the light beam 102 produced by the gas discharge chamber 104 is not greater than the threshold number of pulses (thus, the number of pulses is less than or equal to the threshold number of pulses) (541), the decrement module 114 returns to step 532 and repeats steps 532, 533, and 534. If the number of pulses of the light beam 102 produced by the gas discharge chamber 104 is greater than the threshold number of pulses (541), the decrement module 114 instructs the blower 108 to decrease or decrement its operating speed (542). For example, the decrement state 514 may decrement the operating speed of the blower 108 by the decrement speed increment.

[0054]

[0073] After reducing (542) the operating speed of the blower 108 in the decrement state 514, the decrement module 114 returns to querying (532) whether the fault status 327 for one or more operating conditions of the light source 100 is clear (e.g., has a value of 0).

[0055]

[0074] Thus, in summary, decrement module 114 reduces (524) the speed of blower 108 if there is no fault (532), if the speed of blower 108 is greater than the baseline speed (533), if the proposed new blower speed is greater than the baseline speed (534), and if a certain number of pulses of light beam 102 have been generated since the last change in blower speed (541). In this way, the energy consumed by blower 108 is significantly reduced, especially early in the life of light source 100 and gas discharge chamber 104.

[0056]

[0075] Referring again to FIG. 5, as described above with reference to FIG. 6A, if the proposed new speed of the blower 108 is not greater than the baseline speed (i.e., the proposed new blower speed is at or less than the baseline speed) (534), the decrement module 114 exits the decrement state 514 and the state machine 510 transitions from the decrement state 514 to the monitor state 512 (T(DM)) so that one or more operating conditions of the light source 100 and the operating speed of the blower 108 can be monitored.

[0057]

[0076] Generally, in the monitoring state 512, the monitoring module 112 is configured to monitor the exit criteria and remain in the monitoring state 512 while there are no faults, the blower speed is greater than the baseline speed, and no exit criteria events occur. Referring to FIG. 6B , in the monitoring state 512, the monitoring module 112 determines (537) whether the fault condition 327 for one or more operational conditions of the light source 100 is clear (e.g., has a value of 0). If the fault condition 327 is not clear (and thus flagged) (537), the state machine 510 transitions from the monitoring state 512 to the increment state 516 (T(MI)) so that the operating speed of the blower 108 is increased to a safe operating speed at which no problems and / or faults will occur within the light source 100.

[0058]

[0077] If the fault condition is clear (i.e., has a value of 0) (537), the monitor module 112 determines (538) whether the operating speed of the blower 108 is greater than the baseline speed. If the operating speed of the blower 108 is less than the baseline speed, i.e., falls below the baseline speed (538), the state machine 510 transitions from the monitor state 512 to the baseline state 518 so that the operating speed of the blower 108 is increased to a safe operating speed (T(MB)) at which no problems and / or faults will occur within the light source 100. If the operating speed of the blower 108 is greater than the baseline speed (538), the monitor module 112 determines (536) whether one or more termination criteria are met. For example, the termination criteria can be based on one or more of the baseline speed, the number of pulses of the light beam 102 generated by the light source 100, and an event that results in an improvement in the performance of the light source 100. If the termination criteria are met, the state machine 510 transitions from the monitor state 512 to the decrement state 514 (T(MD)) (because it is determined that the light source 100 is in a safe state to reduce the operating speed of the blower 108). If the termination criteria are not met, the monitor module 112 returns to determining (537) whether the fault condition 327 for one or more operating conditions of the light source 100 is clear (e.g., has a value of 0). One possible termination criterion that can be evaluated in step 536 is a determination of whether the speed of the blower 108 is greater than the baseline speed plus a lower threshold (e.g., 200 rpm). In this case, it may be more appropriate to reduce the blower speed (via the decrement state 514). Another possible termination criterion that can be evaluated in step 536 is determining whether the number of pulses of the light beam 102 currently being generated is greater than a predetermined threshold, such as 100 million pulses. Alternatively, instead of evaluating the set of termination criteria in step 536 based on the number of pulses of the generated light beam 102, the monitoring module 112 can evaluate whether a particular performance-improving event has occurred. For example, the performance-improving event can be a gas refill or gas injection in which the gas mixture 107 is at least partially or completely replaced. Such an event can result in an improvement in the performance of the light source 100.

[0059]

[0078] 5, as described above with reference to FIG. 6A, if the operating speed of the blower 108 is less than or equal to the baseline speed (533), the decrement module 114 exits the decrement state 514 and the state machine 510 transitions from the decrement state 514 to the baseline state 518 (T(DB)) such that the operating speed of the blower 108 is incremented to a safe operating speed above the baseline speed at which no problems and / or faults will occur within the light source 100. The baseline state 518 is described with reference to FIG. 6C. Generally, the baseline state 518 is configured to increase the operating speed of the blower 108 if the operating speed of the blower 108 is less than or equal to the baseline speed. The baseline module 118 determines (539) whether the fault status 327 of the light source 100 is clear (e.g., equal to 0). If the fault condition 327 is not clear (and therefore flagged or has a value of 1) (539), the state machine 510 transitions from the baseline state 518 to the increment state 516 so that the operating speed of the blower 108 is incremented to a safe operating speed at which no problems and / or faults will occur within the light source 100 (T(BI)).

[0060]

[0079] If the fault condition is clear (i.e., has a value of 0) (539), the baseline module 118 determines whether the operating speed of the blower 108 is less than the baseline speed (540). If the operating speed of the blower 108 is equal to or greater than the baseline speed (540), the state machine 510 transitions (T(BM)) from the baseline state 518 to the monitoring state 512 (because there is no need to increase the operating speed). On the other hand, if the operating speed of the blower 108 is less than the baseline speed (540), the baseline module 118 determines whether the number of pulses in the light beam 102 generated by the gas discharge chamber 104 since the last time the blower speed was changed is greater than a threshold number of pulses (548). As described above, the threshold number of pulses can be preset to a positive integer to reduce the frequency at which the blower speed is changed. If the number of pulses in the light beam 102 generated by the gas discharge chamber 104 is less than or equal to the threshold number of pulses (548), the baseline module 118 continues to query whether the number of pulses in the light beam 102 generated by the gas discharge chamber 104 since the last time the blower speed was changed is greater than the threshold number of pulses (548).

[0061]

[0080] If the number of pulses of the light beam 102 generated by the gas discharge chamber 104 is greater than the threshold number of pulses (548), the baseline module 118 increases or increments (549) the operating speed of the blower 108. For example, the baseline module 118 may increment the operating speed of the blower 108 by an increment speed step size. By way of example, the increment speed step size may be approximately 5 revolutions per minute (rpm). After increasing the operating speed of the blower 108, the baseline module 118 returns to step 439 again to determine whether the fault status 327 of the light source 100 is clear (e.g., equal to 0).

[0062]

[0081] 5, as described above with reference to FIGS. 6A-6C, the state machine 510 can transition to the increment state 516 from any one of the decrement state 514, the monitor state 512, and the baseline state 518. For example, if while in the decrement state 514, the fault condition 327 is not clear (and thus is flagged or has a value of 1) (532), the decrement module 114 exits the decrement state 514, and the state machine 510 transitions (T(DI)) from the decrement state 514 to the increment state 516. Generally, in the increment state 516, the operating speed of the blower 108 is incremented to a safe operating speed at which no problems and / or faults will occur within the light source 100. The increment state 516 will now be described with reference to the embodiment shown in FIG. 6D.

[0063]

[0082] Specifically, in the increment state 516, the increment module 116 determines (544) whether the fault status 327 of the light source 100 is clear (e.g., 0). If the fault status 327 is not clear (e.g., the fault status is 1) (544), the increment module 116 sets (545) a new target speed for the blower 108. The new target speed for the blower 108 may be equal to the operating speed of the blower 108 plus a large increment of the increment speed (e.g., 100 rpm). The idea is to significantly increase the speed of the blower 108 when a fault occurs. After the new target speed for the blower 108 is set (545), or after the increment module 116 determines (544) that the fault status is clear (e.g., the fault status is 0), the increment module 116 determines (535) whether the operating speed of the blower 108 is less than the new target speed. If the operating speed of the blower 108 is not less than the new target speed (535), meaning that the operating speed of the blower 108 is greater than or equal to the new target speed (535), the state machine 510 transitions from the increment state 516 to the monitor state 512 (T(IM)).

[0064]

[0083] If the operating speed of the blower 108 is less than the target speed (535), the increment module 116 determines whether the number of pulses of the light beam 102 generated by the gas discharge chamber 104 is greater than a threshold number of pulses (546). If the number of pulses of the light beam 102 generated by the gas discharge chamber 104 is less than or equal to the threshold number of pulses, the increment module 116 continues to query whether the number of pulses of the light beam 102 generated by the gas discharge chamber 104 is greater than the threshold number of pulses (546). If the number of pulses of the light beam 102 generated by the gas discharge chamber 104 is greater than the threshold number of pulses, the increment module 116 increases or increments the operating speed of the blower 108 by a specified amount (547). For example, the increment module 116 may increment the operating speed of the blower 108 by an increment speed step size, for example, 25 rpm. After increasing 547 the operating speed of the blower 108, the increment module 116 returns to step 535 to determine 535 whether the increased operating speed of the blower 108 is less than the target speed.

[0065]

[0084] More generally, with reference to Figure 7A, apparatus 110 performs procedure 760 for controlling blower 108. Procedure 760 may be performed for light source 100 (Figure 1) including apparatus 110 (Figure 2) and blower 108 in gas discharge chamber 104. Procedure 760 may also be performed for state machine 510 (Figure 5). Procedure 760 is described below with respect to light source 100 including blower 108.

[0066]

[0085] Procedure 760 includes monitoring 761 one or more operational state fault conditions of the light source. For example, as described above with reference to FIG. 6B, the monitoring module 112 monitors 537 one or more operational state fault conditions 327 (FIG. 3) of the light source 100.

[0067]

[0086] Next, the apparatus 110 decrements (763) the operating speed of the blower 108 if the fault condition for one or more operational states of the light source 100 is clear and if the reduced operating speed is equal to or greater than the baseline speed. For example, with reference to FIG. 6A , if the fault condition 327 for one or more operational states of the light source 100 is clear (532) and if the reduced operating speed of the blower 108 is greater than the baseline speed (534), the decrement module 114 decrements (542) the operating speed of the blower 108. Decrementing the operating speed of the blower 108 may include decreasing the operating speed of the blower 108 by the decrement speed increment. Decrementing the operating speed of the blower 108 may also include reducing the amount of vibration within the light source 100 caused by movement of the blower 108.

[0068]

[0087] 7, the apparatus 110 increments (765) the operating speed of the blower 108 if a fault condition is flagged for one or more operational conditions of the light source. For example, referring to FIG. 6D, if a fault condition 327 is flagged for the light source 100, the increment module 116 increments (547) the operating speed of the blower 108. Incrementing the operating speed of the blower 108 may include increasing the operating speed of the blower 108 by an increment speed step size. In this manner, the increment module 116 prevents the blower 108 from operating at an operating speed that may cause problems and / or faults within the light source 100.

[0069]

[0088] 7B, procedure 760 can further include incrementing (767) the operating speed of the blower if the reduced operating speed of the blower is below the baseline speed. For example, with reference to FIG. 6C, if baseline module 118 determines (540) that the reduced operating speed of blower 108 (which decrement module 114 reduced) is below the baseline speed, baseline module 118 increases or increments (549) the operating speed of blower 108. Thus, similar to increment module 116, baseline module 118 prevents blower 108 from operating at an operating speed that may cause problems and / or failures within light source 100.

[0070]

[0089] In one example, decrementing and incrementing the operating speed of the blower 108 may include adjusting the operating speed of the blower 108 within a blower speed range defined by a minimum blower speed and a maximum blower speed. In other words, the operating speed of the blower 108 is adjusted between the minimum and maximum blower speeds by the increment and decrement modules 114, 116 (and also the baseline module 118). As described above, the blower speed range is a safe range within which the light source 100 operates properly without problems and / or failures. Therefore, the device 110 may control the operating speed of the blower 108 by adjusting the operating speed within the safe blower speed range so that minimal energy is consumed by the blower 108 and the energy consumed by the light source 100 is reduced.

[0071]

[0090] In some implementations, procedure 760 further includes determining increment and decrement speed increments for the blower 108, where each speed increment depends on the fault condition 327 for one or more operational states of the light source 100. Specifically, for example, a user may perform one or more studies of the light source 100 by determining the largest increment and decrement speed increments that maintain the stability of the light source 100 and do not adversely affect the performance of the light source 100 (so that the fault condition 327 for the light source 100 remains clear). Additionally, procedure 760 may further include determining a blower speed range for the blower 108, where the blower speed range depends on the fault condition 327 for one or more operational states of the light source 100. Similarly, for example, a user can perform one or more studies of the light source 100 by determining a minimum and maximum blower speed (and thus a blower speed range) such that the performance of the light source 100 is not adversely affected when the blower 108 is operating within the blower speed range (so that the fault condition 327 of the light source 100 remains clear).

[0072]

[0091] 3, in some embodiments, at least one of the operating states (associated with a respective performance metric 320_1-320_N) of light source 100 is active and at least one of the operating states is reactive or risk-responsive. Specifically, in an active operating state, the operating speed of blower 108 is adjusted (e.g., by increment module 116 or decrement module 114) before the value 323_1-323_N of the associated performance metric 320_1-320_N falls outside the threshold range 324_1-324_N of the performance metric 320_1-320_N. In a reactive operating state, the operating speed of the blower 108 is adjusted (e.g., by the increment module 116 or the decrement module 114) after the value 323_1-323_N of the associated performance metric 320_1-320_N falls outside the threshold range 324_1-324_N of the performance metric 320_1-320_N. Additionally, in some embodiments, each active operating state is associated with a limited threshold range that is narrower than the actual threshold range 324_1-324_N of the performance metric 320_1-320_N, and the operating speed of the blower 108 is adjusted (e.g., by the increment module 116 or the decrement module 114) before the value 323_1-323_N of the associated performance metric 320_1-320_N falls outside the actual threshold range 324_1-324_N by identifying a fault condition 325_1-325_N of the active operating state based on the limited threshold range.

[0073]

[0092] 8, an embodiment 800 of light source 100 (FIG. 1) includes a light-generating apparatus 805 that includes two gas discharge chambers 804A, 804B to generate a pulsed output light beam 802 that is directed to a lithography exposure tool 801. The pulsed output light beam 802 has a wavelength in the ultraviolet range (e.g., in the deep ultraviolet range) that is used by the lithography exposure tool 801 to pattern a semiconductor substrate or wafer 870. In the example of FIG. 8, gas discharge chamber 804A is part of a master oscillator configured to generate a seed light beam 802s, and gas discharge chamber 804B is part of a power amplifier configured to generate an output light beam 802 from the seed light beam 802s. Each of the discharge chambers 804A, 804B includes a respective blower 808A, 808B configured to move a respective gas mixture 807A, 807B containing the gain medium from a respective energy source 806A, 806B through the respective gas discharge chamber 804A, 804B. In the example of Figure 8, the apparatus 110 is configured as an apparatus 810 configured to control the operating speed of the two blowers 807A, 807B. Specifically, the apparatus 810 controls the blowers 807A, 807B to consume a minimal amount of energy or power during operation of the light source 800 while ensuring that problems and / or failures within the light source 800 are not encountered (or are at least mitigated). Other implementations of the light source 800 are possible.

[0074]

[0093] Each discharge chamber 804A, 804B is configured to hold a respective gas mixture 807A, 807B within a respective internal cavity 873A, 873B. The gas mixture 807A, 807B used in each discharge chamber 804A, 804B can be a combination of gases suitable for generating a respective light beam 802s, 802 centered around a desired wavelength, bandwidth, and energy. For example, the gas mixture 807A, 807B can include argon fluoride (ArF), which emits light at a wavelength of approximately 193 nm. Each discharge chamber 804A, 804B is defined by a respective blower 808A, 808B and respective chamber walls 803A_1, 803A_2, 803B_1, 803B_2 configured to hold, in this embodiment, a respective optical component 875A, 876A, 877A, 875B, 876B, 877B. Each discharge chamber 804A, 804B houses a respective energy source 806A, 806B configured to provide energy to a gas mixture 807A, 807B within each internal cavity 873A, 873B. For example, each energy source 806A, 806B may include a pair of electrodes that create a potential difference to excite a gain medium in the gas mixture 807A, 807B during operation.

[0075]

[0094] Each discharge chamber 804A, 804B can include one or more optical components. For example, discharge chamber 804A includes optical components 875A, 876A associated with internal cavity 873A of discharge chamber 804A. Optical components 875A, 876A can include windows that allow a light beam to enter and exit internal cavity 873A of discharge chamber 804A. Optical component 875A can be a partially reflective / partially transmissive optical coupler that allows seed light beam 802s to exit discharge chamber 804A. Light source 800 can also include other optical components external to discharge chamber 804A, such as optical component 877A corresponding to a spectral feature selection module that selects the wavelength and / or bandwidth of seed light beam 802s output from discharge chamber 804A. For example, spectral feature selection module 877A can include one or more of a beam expansion prism or a beam splitter. In this example, optical component 875A is held within chamber wall 803A_1 and optical component 876A is held within chamber wall 803A_2.

[0076]

[0095] Discharge chamber 804B includes optical components 875B and 876B associated with internal cavity 873B of discharge chamber 804B. Optical components 875B and 876B may include windows that allow light beams (such as seed light beam 802s and light beam 802) to enter and exit internal cavity 873B of discharge chamber 804B. Light source 800 may also include other optical components external to discharge chamber 804B, such as optical component 877B corresponding to a beam reverser or rotator configured to direct light beam 802 back through discharge chamber 804B. In the example of FIG. 8 , optical component 875B is held within chamber wall 803B_1, and optical component 876B is held within chamber wall 803B_2.

[0077]

[0096] During operation of light source 800, apparatus 110 controls the operating speed of each of two blowers 808A, 808B. In some embodiments, control of the operating speed of blower 807A can be independent of control of the operating speed of blower 807B. In some embodiments, each blower 808A, 808B is independently controlled by a dedicated apparatus (810A, 810B). Apparatus 810B can also be designed differently from apparatus 810A to account for differences in how discharge chambers 804A, 804B affect the parameters of the output light beam. Additionally, in these embodiments, control of blowers 808A, 808B is not coupled, but simultaneous control by apparatus 810A, 810B can be coupled in performance differently than controlling only one blower due to the different manner in which each blower 808A, 808B drives vibrations within the frame of chambers 804A, 804B.

[0078]

[0097] In other embodiments, control of the operating speed of blower 807A and / or blower 807B may depend on a performance metric associated with light-generating device 805, and thus control of the two blowers 807A, 807B may be coupled.

[0079]

[0098] In some implementations, it is possible to have a single device 810 configured to control the blower 810A of the first discharge chamber 804A, but not use a device 810 to control the blower 810B of the second discharge chamber 804B.

[0080]

[0099] 8, apparatus 810 includes a monitoring module (such as monitoring module 112 of apparatus 110 of FIG. 2) configured to monitor a fault condition for one or more operational states of light source 800. Additionally, apparatus 810 includes a decrement module (such as decrement module 114 of apparatus 110 of FIG. 2) configured to reduce the operating speed of the appropriate blower 808A, 808B when the fault condition for one or more operational states of light source 800 is clear and when the reduced operating speed of the respective blower 808A, 808B is equal to or greater than the baseline speed. Apparatus 810 also includes an increment module (such as increment module 116 of apparatus 110 of FIG. 2) configured to increase the operating speed of the appropriate blower 808A, 808B when a fault condition for one or more operational states of light source 800 is flagged. In this manner, the device 810 controls the blowers 808A, 808B to consume a minimal amount of energy or power during operation of the light source 800, such that problems and / or faults within the light source 800 are mitigated or mitigated based on the fault condition of the light source 800 and the baseline speed of the blowers 808A, 808B.

[0081]

[0100] 9A, an embodiment 900 of light source 100 (FIG. 1) includes a light-generating device 905 that includes a plurality of optical oscillators 909-1 to 909-N, each including a respective gas discharge chamber 904-1 to 904-N, and that generates a pulsed light beam 902 that is directed to a lithography exposure tool 901, and a control system 950. Light source 900 is configured to generate an output light beam 902, for example, in the ultraviolet range, that is used by lithography exposure tool 901 to pattern a semiconductor substrate or wafer 970. Specifically, lithography exposure tool 901 exposes wafer 970 with a shaped exposure beam 902′ that is formed by passing light beam 902 (which is an exposure beam in this example) through a projection optical system 995. 9A, light-generating apparatus 905 includes N optical oscillators 909-1 to 909-N and thus N gas discharge chambers 904-1 to 904-N, where N is an integer greater than 1. Each of gas discharge chambers 904-1 to 904-N is configured to emit a respective light beam 978-1 to 978-N toward beam combiner 993. In the illustrated example, control system 950 is connected to light-generating apparatus 905 and lithography exposure apparatus 901. Other implementations of light source 900 are possible.

[0082]

[0101] Each of gas discharge chambers 904-1 through 904-N includes a respective blower 908-1 through 908-N, which is configured to move a respective gas mixture 907-1 through 907-N containing a gain medium from a respective energy source 906-1 through 906-N through each of gas discharge chambers 904-1 through 904-N. In the example of FIG. 9A , apparatus 910 (an embodiment of apparatus 110) is included as part of control system 950. As a blower controller, apparatus 910 is configured to control the operating speed of blowers 908-1 through 908-N. Specifically, apparatus 910 controls each blower 908-1 through 908-N to consume a minimal amount of energy or power during operation of light source 900 while ensuring that problems and / or failures within light source 900 are not encountered (or are at least mitigated).

[0083]

[0102] Details of optical oscillator 909-1 are provided below. The other N-1 optical oscillators in light-generating device 905 include the same or similar features.

[0084]

[0103] Optical oscillator 909-1 includes a gas discharge chamber 904-1 that houses an energy source 906-1, which may include, for example, a cathode and an anode, and a blower 908-1. Discharge chamber 904-1 also houses a gas mixture 907-1 that includes a gain medium. A resonator is formed between a spectral feature selection module 977-1 on one side of discharge chamber 904-1 and an output coupler 980-1 on a second side of discharge chamber 904-1. Spectral feature selection module 977-1 can include a diffractive optical element, such as a grating and / or a prism, that fine-tunes the spectral output of discharge chamber 904-1. In some implementations, spectral feature selection module 977-1 includes multiple diffractive optical elements. For example, spectral feature selection module 977-1 can include four prisms, some of which are configured to control the center wavelength of light beam 978-1 and others of which are configured to control the spectral bandwidth of light beam 978-1.

[0085]

[0104] In some implementations, the spectral feature selection module 977-1 can include or communicate with a spectral feature control system configured to control, for example, various components within the spectral feature selection module 977-1. In these implementations, the apparatus 910 includes a decrement module (similar to the decrement module 114) and an increment module (similar to the increment module 116). Together, the decrement module and the increment module of the apparatus 910 can be configured to avoid interfering blower operating speeds in which aliased frequencies of the second harmonics of the blower 908-1 interfere with the spectral feature control system associated with the light source 900. For example, the interfering blower operating speeds can depend on the repetition rate at which the light source 900 generates the light beam (including the light beam 902 or the exposure beam 902′ in this example).

[0086]

[0105] Optical oscillator 909-1 also includes a line center analysis module 981-1 that receives the output optical beam from output coupler 980-1. Line center analysis module 981-1 is a measurement system that can be used to measure or monitor the wavelength of optical beam 978-1. Line center analysis module 981-1 can provide data to control system 950, which can determine metrics related to optical beam 978-1 based on the data from line center analysis module 981-1. For example, control system 950 can determine beam quality metrics or spectral bandwidth based on the data measured by line center analysis module 981-1.

[0087]

[0106] The light-generating device 905 also includes a gas supply system 990 fluidly coupled to the interior of the discharge chamber 904-1 via a fluid conduit 998. The fluid conduit 998 is any conduit capable of transporting a gas or other fluid without or with minimal loss of the fluid. For example, the fluid conduit 998 can be a pipe made of or coated with a material that does not react with one or more fluids transported within the conduit 998. The gas supply system 990 includes a chamber 991 configured to contain and / or receive a supply of one or more gases used in the gas mixture 907-1. The gas supply system 990 also includes devices (pumps, valves, and / or fluidic switches) that allow the gas supply system 990 to remove or inject gases from or into the discharge chamber 904-1. The gas supply system 990 is coupled to a control system 950. The gas supply system 990 can be controlled by the control system 950 to, for example, perform a refill procedure.

[0088]

[0107] The other N-1 optical oscillators are similar to optical oscillator 904-1 and have similar or identical components and subsystems. For example, optical oscillators 909-1 through 909-N each include an energy source similar to energy source 906-1, a spectral feature selection module similar to spectral feature selection module 977-1, and an output coupler similar to output coupler 980-1. Optical oscillators 909-1 through 909-N can be tuned or configured so that optical beams 978-1 through 978-N all have the same characteristics, or optical oscillators 909-1 through 909-N can be tuned or configured so that at least some optical oscillators have at least some characteristics that are different from the other optical oscillators. For example, optical beams 978-1 through 978-N can all have the same center wavelength, or the center wavelength of each optical beam 978-1 through 978-N can be different. The center wavelength generated by a particular one of the optical oscillators 909-1 through 909-N can be set using the respective spectral feature selection module.

[0089]

[0108] The light generating device 905 also includes a beam controller 992 and a beam combiner 993. The beam controller 992 is located between the gas mixtures of the optical oscillators 909-1 through 909-N and the beam combiner 993. The beam controller 992 determines which of the optical beams 978-1 through 978-N are incident on the beam combiner 993. The beam combiner 993 forms the exposure beam 902 from one or more optical beams incident on the beam combiner 993. In the illustrated example, the beam controller 992 is represented as a single element. However, the beam controller 992 can be implemented as a collection of individual beam controllers. For example, the beam controller 992 can include a collection of shutters, one shutter associated with each optical oscillator 909-1 through 909-N.

[0090]

[0109] The light-generating device 905 may include other components and systems. For example, the light-generating device 905 may include a beam preparation system 994 that includes a bandwidth analysis module that measures various characteristics (such as bandwidth or wavelength) of the light beam. The beam preparation system 994 may also include a pulse stretcher (not shown), which stretches in time each pulse that interacts with the pulse stretcher. The beam preparation system 994 may also include other components that can affect light, such as reflective and / or refractive optical elements (e.g., lenses and mirrors, etc.) and / or filters. In the illustrated example, the beam preparation system 994 is positioned in the path of the exposure beam 902. However, the beam preparation system 994 may be located elsewhere within the light source 900. Other implementations are also possible. For example, the light-generating device 905 may include N instances of the beam preparation system 994, each positioned to interact with one of the light beams 978-1 through 978-N. In another example, light generating device 905 may include optical elements (such as mirrors) that direct light beams 978-1 through 978-N toward beam combiner 993.

[0091]

[0110] Lithography exposure apparatus 901 can be an immersion system or a dry system. Lithography exposure apparatus 901 includes a projection optical system 995, through which exposure beam 902 passes before reaching wafer 970, and a sensor system or metrology system 997. Wafer 970 is held or received on wafer holder 996. Referring again to FIG. 9B , projection optical system 995 includes a projection objective including slit 995a, mask 995b, and lens system 995c. Lens system 995c includes one or more optical elements. Exposure beam 902 enters lithography exposure apparatus 901 and impinges on slit 995a, with at least a portion of beam 902 passing through slit 995a to form shaped exposure beam 902′. 9A and 9B, slit 995a is rectangular and shapes exposure beam 902 into an elongated, rectangular shaped light beam, which is shaped exposure beam 902'. Mask 995b contains a pattern that determines which portions of the shaped light beam are transmitted and which portions are blocked by mask 995b. Microelectronic features are formed on wafer 970 by exposing a layer of radiation-sensitive photoresist material on wafer 970 to exposure beam 902'. The design of the pattern on the mask is determined by the particular microelectronic circuit characteristics desired.

[0092]

[0111] As described above with reference to FIGS. 8 and 9A, apparatus 810 / 910 is configured to cooperate with a respective light-generating device 805 / 905 of a respective light source 800 / 900. Referring to FIG. 10, an embodiment 1010 of apparatus 810 or 910 is shown with light-generating device 1005 of light source 1000, which generates light beam 1002, a pulsed light beam. Light source 1000 may correspond to light source 800, which includes light-generating device 805, or light source 900, which includes light-generating device 905. Light-generating device 1005 includes a plurality of gas discharge chambers 1004i, where i is a set of integers from 1 to an integer greater than 1. For example, gas discharge chamber 1004i may correspond to gas discharge chambers 804A and 804B of light-generating device 805, or gas discharge chamber 1004i may correspond to gas discharge chambers 904-1 through 904-N of light-generating device 905. Each gas discharge chamber 1004i contains or holds a blower 1008i.

[0093]

[0112] The apparatus 1010 includes a fault monitoring module 1012 and a control module 1015. The fault monitoring module 1012 is similar in some general aspects to the monitoring module 112, and the control module 1015 is similar in some general aspects to the control module 115. Additionally, the fault monitoring module 1012 and the control module 1015 have several additional features that further improve how the apparatus 1010 controls, adjusts, or varies the operating speed of the blower 1008i.

[0094]

[0113] The fault monitoring module 1012 is configured to monitor one or more operational conditions 1030k of the light source 1000 for each fixed period of use of the light source 1005, where k is either 1 (if one operational condition is monitored) or a set of integers from 1 to an integer greater than 1. For each monitored operational condition 1030k, the fault monitoring module 1012 is configured to identify a fault condition 1025 and a fault type 1055 related to which blower 1008i of one of the gas discharge chambers 1004i in the light source 1000 affects the monitored operational condition 1030k. The fault monitoring module 1012 can also be configured to identify, for each monitored operational condition 1030k, a fault priority 1056 associated with or related to the monitored operational condition 1030k. The fault priority 1056 indicates the importance or urgency associated with resolving a flagged fault condition for the particular monitored operational condition 1030k. Some monitored operating conditions 1030k have a higher priority with respect to clearing any flagged faults than other monitored operating conditions 1030k. The control module 1015 receives the identified fault condition 1025 and the identified fault type 1055 from the fault monitoring module 1012. The control module 1015 is configured to select at least one of the gas discharge chambers 1004i. The control module 1015 is configured to send instructions 1031 to the blower 1008i in the selected gas discharge chamber 1004i. The instructions 1031 are based on the identified fault condition 1025 and the identified fault type 1055.

[0095]

[0114] As described above, each of the one or more operating states 1030k of the light source 1000 is defined by a performance metric 1020k (where again, k is a set of integers from 1 to greater than 1), which performance metric 1020k relates to the light source 1005 or the light beam 1002 it generates. The performance metric 1020k may be affected by the speed of one or more blowers 1008i associated with each gas discharge chamber 1004i. For example, with reference to FIG. 8 , the performance metric 1020k related to the wavelength performance of the light beam 1002 is likely to be affected by the speed of the blower 808A in the gas discharge chamber 804A. As another example, the performance metric 1020k related to the bandwidth performance of the light beam 1002 is likely to be affected by the speed of the blower 808A in the gas discharge chamber 804A. On the other hand, beam parameters (parameters of light beam 1002) are likely to be affected by the speed of blower 808B in gas discharge chamber 804B. As a further example, parameters associated with energy performance in light beam 1002 are likely to be affected by the speeds of both blowers 808A, 808B in both gas discharge chambers 804A, 804B. Similar to apparatus 110, apparatus 1010 adjusts or varies the operating speed of one or more blowers 1008i based on one or more fault conditions 1025 of these one or more operating states 1030k. Moreover, apparatus 1010 also adjusts or varies the operating speed of one or more blowers 1008i based on the fact that a fault in a particular operating state 1030k is affected by a particular gas discharge chamber 1004i. Apparatus 1010 can select which blowers 1008i to adjust or maintain by considering the fault type 1055 of each fault.

[0096]

[0115] 11, in the example of light source 800 of FIG. 8, where there are two gas discharge chambers 804A, 804B, there are three fault types 1155 associated with each fault condition 1025 in each operating state 1030i defined by performance metrics 1120k. Additionally, as described below, each fault condition 1025 may have an associated fault priority 1156 indicating the importance of resolving any associated flagged fault condition 1025. In this example, the three fault types 1155 may be the master oscillator (or MO) of the first gas discharge chamber 804A, the power amplifier (PA) of the second gas discharge chamber 804B, and a common (Comm.) fault for faults affected by both gas discharge chambers 804A, 804B. Table 1180 also shows examples of performance metrics 1120k that can be monitored by apparatus 1010. The listed performance metrics 1120k are PADropout, MODropout, EnergySigmaMax, EnergyDoseMax, EnergyDoseMin, WLHistoMax, WLHistoMin, BWFault, and H / VDivergence. For example, as described above, the dropout performance metric 1120k (PADropout or MODropout) corresponds to a dropout rate, which quantifies a failure mechanism in which the gas discharge chamber blower fails to sufficiently remove the portion of the gas mixture being recovered, causing the gas mixture to not move through the gas discharge chamber fast enough, resulting in arcing and energy loss within the gas discharge chamber. The EnergySigmaMax performance metric 1120k corresponds to the maximum standard deviation of the energy in the light beam 1002. The EnergyDoseMax / Min performance metric 1120k corresponds to the maximum / minimum running average of the error in the energy of the light beam 1002. The WLHistoMax / Min performance metric 1120k corresponds to the average value of the wavelength ±3σ (respectively) of the light beam 1002. The BWFault performance metric 1120k corresponds to the bandwidth of the light beam 1002 that is out of range. The H / VDivergence performance metric 1120k is a measure of the divergence of the light beam 1002.

[0097]

[0116] 11 , the flagged fault condition 1025 associated with the PADropout performance metric 1120k has a fault type 1155 PA. Therefore, assuming that only one fault condition 1025 exists within the current usage time, the device 1010 selects PA (gas discharge chamber 804B), and any speed-related commands are sent to the blower 808B of the gas discharge chamber 804B. Meanwhile, the device 1010 does not change the speed of the blower 808A of the gas discharge chamber 804A (MO chamber) because the fault type 1155 associated with the PADropout performance metric 1120k is not an MO fault type. For comparison, the flagged fault condition 1025 associated with the MODropout performance metric 1120k has a fault type 1155 MO. Thus, assuming there is only one fault condition 1025 within the current usage time, the device 1010 selects MO (gas discharge chamber 804A) and any speed instructions 1031 are sent by the control module 1015 to the blower 808A of the gas discharge chamber 804A (while the speed of the blower 808B remains unchanged). As a further example, the flagged fault condition 1025 associated with the EnergyDoseMax metric 1120k has a (common) fault type 1155 Comm. This means that the fault associated with EnergyDoseMax is affected by both gas discharge chambers 804A and 804B.

[0098]

[0117] In this manner, the apparatus 1010 can manage the blower speeds of multiple gas discharge chambers by considering not only the fault condition 1025 but also the fault type 1155 .

[0099]

[0118] Additionally, referring again to FIG. 10 , the apparatus 1010 may also consider a fault priority 1056 associated with a monitored operating condition 1030k. The fault priority 1056 may be considered and analyzed each time a fault condition 1025 is flagged for multiple operating conditions 1030k within the current time of use. In this example, the fault monitoring module 1012 is configured to identify, for each monitored operating condition 1030k, a fault priority 1056 for the monitored operating condition 1030k. The control module 1015 receives the fault priority 1056 and further selects the gas discharge chamber 1004i based on the fault priority 1056. In this manner, the apparatus 1010 determines instructions to select at least one of the gas discharge chambers 1004k during the current time of use based on the fault condition 1025, the fault type 1055, and the fault priority 1056. If two or more operating conditions have flagged fault conditions 1025 during the current usage time, the device 1010 can compare the fault priorities 1056 for each of these (flagged) fault conditions 1025 and select the gas discharge chamber 1004i associated with the performance metric 1120k having the higher fault priority 1056 (and send an instruction 1031 to the blower 1008i of that selected gas discharge chamber 1004i).

[0100]

[0119] 11 , a failure priority 1156 is assigned to each of the performance metrics 1120k (each associated with an operational state 1030k). The failure priority 1156 for the PADropout performance metric 1120k is 1, meaning that the PADropout performance metric 1120k has the highest priority, and the failure priority 1156 for the MODropout performance metric 1120k is 2, meaning that the MODropout performance metric 1120k has the second highest priority, but lower than the priority of the PADropout performance metric 1120k. Thus, if both the fault status 1025 of the PADropout performance metric 1120k and the fault status 1025 of the MODropout performance metric 1120k are flagged during the current usage time, the control module 1015 can select the gas discharge chamber 804B (PA gas discharge chamber) and send an instruction 1031 to the blower 808B of the gas discharge chamber 804B because the PADropout performance metric 1120k (and operational status) has a higher priority (to remove any faults) and the fault type 1155 for the PADropout performance metric 1120i is a PA fault type (associated with the PA gas discharge chamber).

[0101]

[0120] As another example, referring to the exemplary table 1180 of FIG. 11, Dropouts (both PA and MO) have higher failure priorities 1156 (1 and 2, respectively) than H / VDivergence performance metric 1120i (which has a failure priority 1156 of 9).

[0102]

[0121] As described above, a fault condition 1025 identified by the fault monitoring module 1012 for an operating state 1030k is flagged if the performance metric 1020k associated with the monitored operating state 1030k is not within a threshold range for that performance metric 1020k, or is cleared if the performance metric 1020k associated with the monitored operating state 1030k is within a threshold range for that performance metric 1020k. The control module 1015 selects the gas discharge chamber 1004i only if the fault condition 1025 is flagged.

[0103]

[0122] As described above, control module 1015 is similar in at least some general aspects to control module 115. As such, control module 1015 may include an increment module 1014, a decrement module 1016, and optionally a baseline module 1018. Modules 1014, 1016, and 1018 may be configured with additional components or systems as detailed above and described with respect to modules 114, 116, and 118. As described above, increment module 1014 is configured to increase the operating speed of a particular blower 1008i, and decrement module 1016 is configured to decrease the operating speed of a particular blower 1008i. Baseline module 1018 is configured to adjust the baseline speed of a particular blower 1008i, as described above.

[0104]

[0123] As described above, for each monitored operating condition 1030k, the fault monitoring module 1012 identifies a fault condition 1025, a fault type 1055, and a fault priority 1056. This fault information is then received by the control module 1015, which responsively selects at least one gas discharge chamber 1004i and sends instructions 1031 to the corresponding blower 1008i. In accordance with the instructions 1031, the increment module 1014 and the decrement module 1016 can be configured to adjust the operating speed of the selected blower 1008i. Also in accordance with the instructions 1031, the baseline module 1018 can be configured to adjust the baseline speed of the selected blower 1008i. For example, if it is determined that the operating speed of the selected blower 1008i is below the baseline speed, the baseline module 1018 can be used to increase or decrease the operating speed of the blower 1008i.

[0105]

[0124] The baseline module 1018 can also be configured to adjust the baseline speed of one or more blowers 1008i based on other parameters, including the age or operating hours of the gas discharge chamber 1004i of a given blower 1008i. For example, the baseline speed of a blower 1008i of a gas discharge chamber 1004i that has been operating for a longer period of time can be increased by the baseline module 1018 more than the baseline speed of a blower 1008i of a gas discharge chamber 1004i that has been operating for a shorter period of time.

[0106]

[0125] Referring to FIG. 12, apparatus 1010 (which is an embodiment of apparatus 110, 810, or 910) performs procedure 1260 for controlling multiple blowers (such as blower 1008i), each blower disposed within a gas discharge chamber (such as gas discharge chamber 1004i) of light source 1000.

[0107]

[0126] Procedure 1260 includes monitoring 1261 one or more operational conditions 1030k of light source 1000. For example, as described above with reference to FIG. 10 , fault monitoring module 1012 monitors one or more operational conditions 1030k of light source 1000 every fixed period of use of light source 1000 (and light-generating device 1005). As described above, if a single operational condition 1030k is being monitored, k is 1, or if multiple operational conditions 1030i are being monitored, k is a set of integers from 1 to an integer greater than 1. For each monitored operational condition 1030k (1261), device 1010 (e.g., fault monitoring module 1012) identifies 1262 a fault condition 1025 and a fault type 1055. As described above, fault type 1055 relates to which blower 1008i of gas discharge chamber 1004i is affecting the monitored operational condition 1030k. In particular, the fault type 1055 may relate to the blower 1008i of the gas discharge chamber 1004i that has the greatest impact on the monitored operational condition 1030k. In some implementations, the apparatus 1010 (specifically, the fault monitoring module 1012) may also identify 1262 a fault priority 1056.

[0108]

[0127] Next, the apparatus 1010 (e.g., upon the control module 1015 receiving the fault condition 1025 and the fault type 1055 from the fault monitoring module 1012) selects (1264) at least one gas discharge chamber 1004i. As described above, the control module 1015 may select (1264) at least one gas discharge chamber 1004i based on the identified fault condition 1025 and the identified fault type 1055. For example, with reference to FIGS. 8 and 11 , if the only operating condition having a flagged fault condition 1025 corresponds to the PADropout performance metric 1120k, then the PA gas discharge chamber 804B may be selected in 1264 because the fault type for this performance metric 1120k is PA 1155 (FIG. 11).

[0109]

[0128] The apparatus 1010 (via the control module 1015) sends 1266 a command 1031 to the blower 1008i of the selected at least one gas discharge chamber 1004i, where the command 1031 is based on the identified fault condition 1025 and the identified fault type 1055. The command 1031 may result in an adjustment or change in the operating speed (or baseline speed) of the blower 1008i. The command 1031 for adjusting or changing the operating speed of the blower 1008i in response to the identified fault condition 1025 and the fault type 1055 is described in more detail below with reference to FIGS. 13 and 14 . After the command 1031 is sent in 1266, the procedure 1260 proceeds to the next usage time and returns to step 1261. In some implementations, the usage time is a constant value. In other implementations, the usage time is generally a constant value but can be adjusted or reset to a different value depending on one or more actions taken in step 1266.

[0110]

[0129] With reference to Figure 13, if the control module 1015 determines that none of the fault conditions 1025 (identified in step 1262) are flagged, an active mode or state is entered. In the active state, procedure 1314 is performed by the control module 1015. The active state may include aspects of the decrement state 514 of Figure 6A and the baseline state 518 of Figure 6C. On the other hand, with reference to Figure 14, if the control module 1015 determines that one or more of the fault conditions 1025 (identified in step 1262) are flagged, a risk mode or state is entered. In the risk state, procedure 1416 is performed by the control module 1015. The risk state may include aspects of the increment state 516 of Figure 6D. The active state procedure 1314 of Figure 13 will now be described, followed by the risk state procedure 1416 of Figure 14.

[0111]

[0130] 13, in active state procedure 1314, a blower 1008i of at least one discharge chamber 1004i is selected at 1264 (FIG. 12). The operating speed of the selected blower 1008i is determined, and accordingly, instructions 1031 are sent by control module 1015 to complete step 1266, as shown in FIG. 12. For example, a gas discharge chamber blower 1008i may be selected at 1364 based on the gas discharge chamber blower 1008i selected during the most recent, prior use time. Thus, referring to FIG. 8, if blower 808A in gas discharge chamber 804A was selected for further analysis at 1364 during the most recent, prior use time, then blower 808B in gas discharge chamber 804B may be selected at 1364 during the current use time. Thus, in this example, the analysis alternates between blowers 808A and 808B for each use time.

[0112]

[0131] The control module 1015 (e.g., via the decrement module 1014) determines 1333 whether the operating speed of the selected blower 1008i is greater than the baseline speed. If the operating speed of the selected blower 1008i is not greater than the baseline speed 1333 (meaning that the operating speed of the selected blower 1008i is equal to or less than the baseline speed of the selected blower 1008i), the control module 1015 sends 1349 a command 1031 ( FIG. 10 ) to increase the operating speed of the selected blower 1008i. A new setpoint for the blower speed may be calculated, for example, by adding the incremental speed step size to the current blower speed. For example, the incremental speed step size may be 5 rpm. The control module 1015 may also reset the usage time at this point, if appropriate. For example, the usage time may be set to 10 million pulses of the light beam 1002.

[0113]

[0132] If the operating speed of the selected blower 1008i is greater than the baseline speed (1333), the control module 1015 determines whether the proposed new blower speed is greater than the baseline speed (1334). The proposed new blower speed corresponds to the current operating speed of the selected blower 1008i minus the decrement speed step size. If the proposed new speed of the selected blower 1008i is not greater than the baseline speed (i.e., the proposed new blower speed is at or less than the baseline speed in 1334), the control module 1015 sends (1312) a command 1031 to maintain the operating speed of the selected blower 1008i. Essentially, this corresponds to the state machine 510 transitioning from the decrement state 514 to the monitor state 512 in FIG. 5.

[0114]

[0133] If the proposed new blower speed is greater than the baseline speed (1334), the control module 1015 sends a command 1031 to decrease or decrement the operating speed of the selected blower 1008i (1342). The control module 1015 may calculate the new operating speed of the selected blower 1008i by subtracting the decrement speed step from the current operating speed of the selected blower 1008i. The decrement speed step may be, for example, 5 rpm.

[0115]

[0134] The operating speed of the selected blower 1008i is decreased by the decrement speed increment (1342). Meanwhile, the operating speed of the selected blower 1008i is increased by the increment speed increment (1349). The increment speed increment may be larger than the decrement speed increment. For example, the increment speed increment may be 5 revolutions per minute (rpm), while the decrement speed increment may be 5 rpm. In some implementations, the increment speed increment may be any value up to 25 rpm, and the decrement speed increment may be smaller than this value. Thus, if the increment speed increment is 20 rpm, the decrement speed increment may be 5 or 10 rpm.

[0116]

[0135] In addition, the control module 1015 can also control the baseline speed of each blower 1008i in each gas discharge chamber 1004i in the light-generating device 1005. Control of the baseline speed of a particular blower 1008i can be based on the age of the gas discharge chamber 1004i in which the blower 1008i is housed, as described above with reference to Figures 4A-4C.

[0117]

[0136] 14, in risk condition procedure 1416, control module 1015 has already determined in 1262 that at least one fault condition 1025 is flagged. Next, control module 1015 executes procedure 1464 to select a gas discharge chamber 1004i. First, control module 1015 decodes the fault conditions (1443). Specifically, control module 1015 analyzes the fault conditions of each monitored operating condition to determine which one or more fault conditions are flagged (1443). Control module 1015 determines whether two or more fault conditions 1025 are flagged (1444). If control module 1015 determines that only a single fault condition 1025 is flagged (1444), it selects the single fault condition (1445B). If the control module 1015 determines 1444 that there are multiple flagged fault conditions 1025, it selects 1445A one fault condition 1025 for further action based on the identified fault priority 1056. For example, as described above, with reference to table 1180 of FIG. 11 , the control module 1015 may select 1445A a single fault condition 1025 for further action by selecting the fault condition 1025 associated with the performance metric 1120k having the highest priority 1156. In table 1180, a lower number in the priority 1156 column corresponds to a higher priority 1156. Thus, in table 1180, the PADropout performance metric 1120k has the highest priority 1156, and the H / VDivergence performance metric 1120k has the lowest priority 1156. The control module 1015 then selects (1446) a gas discharge chamber 1004i based on the fault type associated with the selected fault condition 1025. Once the gas discharge chamber 1004i is selected in 1446, the control module 1015 transmits (1466) a command 1031 to increase the operating speed of the blower 1008i in the selected gas discharge chamber 1004i.

[0118]

[0137] 11 , some faults (associated with some performance metrics 1120k) are affected by more than one gas discharge chamber 1004i. In this case, the control module 1015 may select a gas discharge chamber 1004i in step 1446 based on the fault type 1055 Common associated with the selected fault condition 1025 by taking other factors into account. For example, the control module 1015 may select a gas discharge chamber 1004i in the current usage time that is different from the gas discharge chamber 1004i selected in step 1446 in the immediately preceding usage time. Thus, if the speed of blower 808B of gas discharge chamber 804B was increased (e.g., by 25 rpm) in step 1466 (FIG. 14) during the most recent prior use period and a Common fault type 1055 was associated with the flagged fault condition 1025 during the current use period, then the speed of blower 808A of gas discharge chamber 804A can be increased (e.g., by 25 rpm) in step 1466 (FIG. 14). As another example, in other embodiments, if the speed of blower 808B of gas discharge chamber 804B was decreased (e.g., by 5 rpm) in step 1342 (FIG. 13) during the most recent prior use period and a Common fault type 1055 was associated with the flagged fault condition 1025 during the current use period, then the speed of blower 808A of gas discharge chamber 804A can be increased (e.g., by 25 rpm) in step 1466 (FIG. 14). Meanwhile, in yet another embodiment, the control module 1015 may select the same gas discharge chamber 1004i within the current usage time (FIG. 14) as the gas discharge chamber 1004i selected in 1342 (FIG. 13) if the flagged fault condition 1025 is associated with a Common fault type 1044.If the speed of the gas discharge chamber blower 808B was reduced (e.g., by 5 rpm) in step 1342 (FIG. 13) during the most recent previous use period, and a Common fault type 1055 is associated with the flagged fault condition 1025 during the current use period, the speed of the gas discharge chamber 804B blower 808B can be increased (e.g., by 25 rpm) in step 1466 (FIG. 14).

[0119]

[0138] In some embodiments, the control module 1015 enters a hold state 1411 after sending command 1031 to the blower 1008i of the selected gas discharge chamber 1004i. The hold state may correspond to a hold usage time, such as 10 million pulses of the light beam 1002. No action is taken by the control module 1015 during the hold state 1411. The purpose of the hold state 1411 is to avoid taking action during the next usage time in response to a transient condition (which may manifest as a fault flagged in step 1262 during the next usage time). The control module 1015 further determines 1436 whether any fault conditions 1025 are still flagged. If any one of the fault conditions 1025 is still flagged in 1436, the control module 1015 repeats the risk condition procedure 1416. If all of the fault conditions 1025 are clear (and none are flagged) in 1436, the control module 1015 may thereby exit the risk condition procedure 1416 and return to monitoring 1261 one or more operational conditions 1030k of the light source 1000. The control module 1015 may also reset the amount of usage time before exiting the risk condition procedure 1416. For example, the usage time may be reset to 100 million pulses of the light beam 1002.

[0120]

[0139] In short, because the fault condition 1025 is flagged during the risk state procedure 1416, none of the blowers 1008i should be decremented until the control module 1015 determines in 1436 that all faults are clear; only the blower 1008i in the gas discharge chamber 1004i associated with the fault type 1055 needs to be incremented in 1466; if multiple flagged fault conditions 1025 occur simultaneously, the control module 1015 addresses the fault type 1055 that is most detrimental to the performance of the light source 1000 by selecting the fault type 1055 with the highest priority 1056 in 1445A.

[0121]

[0140] 15, graph 1581 is shown alongside graph 1585. Graphs 1581 and 1585 correspond to a simulation showing how apparatus 1010 responds depending on the health of light source 1000 (as determined from monitored operating conditions 1030k). In this simulation, it is assumed that PA fault type 1055 has a higher fault priority 1056 than Common fault type 1055. In discussing graphs 1581 and 1585, reference will be made to apparatus 1010 of FIG. 10 and light source 800 of FIG. 8.

[0122]

[0141] In graph 1581, the speed set points of blowers 1008i are tracked against the usage of light source 800. The speed set point of blower 808A for gas discharge chamber 804A is shown as a solid line (indicated at 1582A), and the speed set point of blower 808B for gas discharge chamber 804B is shown as a double line (indicated at 1582B). Fault condition 1025 is shown as a dashed line. Usage can be expressed in terms of the number of pulses of light beam 1002 generated by light source 1000, which in this example is shown in millions of pulses of light beam 1002. Thus, a value of 5 on the horizontal axis of graph 1581 corresponds to 0 to 5 trillion pulses of light beam 1002.

[0123]

[0142] In graph 1585, conditions of apparatus 1010 are plotted along the vertical axis, and each plotted condition is classified as either event 1586A relating to blower 808A of gas discharge chamber 804A or event 1586B relating to blower 808B of gas discharge chamber 804B.

[0124]

[0143] Between 0 and 5 units of usage, the fault status 1025 is zero (0), meaning no faults are flagged. Between 5 and 9 units of usage, the fault status 1025 is 2, meaning two faults are flagged, and the fault types 1055 of both of these flagged faults are PA fault types 1155. Between 9 and 15 units of usage, the fault status 1025 is 28, meaning 28 faults are flagged, and the fault types 1055 of both of these flagged faults include a mix of PA fault types 1155 and Common fault types 1155. Between 16 and 24 units of usage, the fault status 1025 is 26, meaning only the fault types 1055 of the flagged faults are Common fault types 1155.

[0125]

[0144] At the start of the simulation, between 0 and 5 units of usage, there are no flagged faults because fault status 1025 is zero (0). During this time, device 1010 operates in an active state in which device 1010 executes procedure 1260 and procedure 1314. Control module 1015 alternates between the two gas discharge chambers each time procedure 1260 is executed. Initially, gas discharge chamber 804A is selected in step 1264, and the operating speed of blower 808A is decremented in step 1342 (as indicated by the decline in line 1582A of graph 1581 and the "MO decrement" state of graph 1585). Thereafter, gas discharge chamber 804B is selected in step 1264 (after the use time has elapsed), and the operating speed of blower 808B is decremented in step 1342 (as shown by the decline in line 1582B of graph 1581 and the "PA decrement" status of graph 1585). Next, gas discharge chamber 804A is again selected in step 1264 (after the use time has elapsed), and the operating speed of blower 808A is decremented in step 1342 (as shown by the decline in line 1582A of graph 1581 and the "MO decrement" status of graph 1585).

[0126]

[0145] Between 5 and 15 units of usage, there is a flagged fault. The value of fault condition 1025 is approximately 28 in graph 1581, and as described above, control module 1015 decodes the value and determines (at step 1443) which one or more fault conditions are flagged. Control module 1015 determines that the flagged fault conditions include those with PA fault type 1155 (from 5 to 9 units of usage) and those with Common fault type 1155 (from 9 to 15 units of usage). Thus, device 1010 operates in a risk state in which device 1010 executes procedure 1260 and procedure 1416. As described above, in this simulation, it is assumed that PA fault type 1155 has a higher fault priority 1056 than Common fault type 1155. Therefore, throughout this usage window (5-15 units of usage), control module 1015 selects gas discharge chamber 804B in step 1446 and sends command 1031 to increase the operating speed of blower 808B for each usage time. This is indicated by the step in double line 1582B in graph 1581 and also by the "PA increment fault" condition in graph 1585.

[0127]

[0146] Between 16 and 24 units of usage, the fault condition 1025 is 26 (as shown in graph 1581), and the only fault type 1055 of these flagged faults is Common fault type 1155. Therefore, the device 1010 operates in a risk state where the device 1010 executes procedure 1260 and procedure 1416. Because the only fault type is Common fault type 1155, the control module 1010 alternates in step 1446 to select gas discharge chamber 804A and transmits command 1031 to increase the operating speed of blower 808A for the next hour of use. This is indicated by the step in single line 1582A of graph 1581 and also by the "MO increment fault" condition in graph 1585. In general, the control module 1010 alternates between increasing the operating speed of blower 808A and blower 808B for each hour of use. After blower 808A is increased in operating speed at usage unit 18, control module 1010 resets the usage time to a larger value incremented by 22. Thus, the next action occurs at usage unit 22, in which control module 1010 sends command 1031 to increase the operating speed of blower 808B, as indicated by the step in double line 1582B of graph 1581 and by "PA increment fault" on graph 1585.

[0128]

[0147] The following clauses can be used to further describe the embodiments. 1. A control device for a light source including a plurality of gas discharge chambers with a blower disposed within each gas discharge chamber, comprising: a fault monitoring module configured to monitor one or more operational conditions of the light source and, for each monitored operational condition, identify a fault condition and a fault type relating to which blower of the gas discharge chamber is affecting the monitored operational condition; a control module configured to receive the identified fault condition and the identified fault type from the fault monitoring module, select at least one gas discharge chamber, and send a command to a blower in the selected at least one gas discharge chamber, the command being based on the identified fault condition and the identified fault type; a control device including: 2. The control device described in clause 1, wherein the fault monitoring module is configured to identify, for each monitored operating condition, a priority for the monitored operating condition, and the control module is configured to select at least one gas discharge chamber based on the identified priority. 3. The control device described in clause 1, wherein the fault monitoring module is configured to monitor one or more operating conditions of the light source every certain period of use of the light source, and the control module is configured to select at least one gas discharge chamber based on the gas discharge chamber selected by the control module during the most recent preceding period of use. 4. The control device of clause 1, wherein the plurality of gas discharge chambers includes a main oscillator gas discharge chamber and a power amplifier gas discharge chamber optically in series with the main oscillator gas discharge chamber, and the fault type is selected from a set of possible fault types including a power amplifier fault type, a main oscillator fault type, and a common fault type. 5. The control device of clause 1, wherein each of the one or more operating states is defined by a performance metric related to the light source or the light beam generated by the light source. 6. One or more performance metrics may be a wavelength histogram associated with the light beam; the energy dose error associated with the light beam; the energy error associated with the light beam; the bandwidth error associated with the light beam; the operating point of the master oscillator gas discharge chamber; the operating point of the power amplifier gas discharge chamber; the spectral feature accuracy associated with the light beam; and 6. The control device of clause 5, including an actuator operating point for the light source. 7. The control device of clause 1, wherein a fault condition identified for a monitored operating condition is flagged if a performance metric associated with the monitored operating condition is not within a threshold range for that performance metric, or is cleared if a performance metric associated with the monitored operating condition is within a threshold range for that performance metric. 8. The control device described in clause 1, wherein the fault monitoring module is configured to identify an overall fault condition based on the identified fault condition of each monitored operating condition, and the control module configured to select at least one gas discharge chamber and send instructions to a blower in the selected at least one gas discharge chamber includes a control module that decodes the overall fault condition to analyze the identified fault condition of each monitored operating condition. 9. The control device of clause 1, wherein the control module configured to select at least one gas discharge chamber and send commands to a blower in the selected at least one gas discharge chamber includes a control module configured to operate in an active mode if all of the identified fault conditions are clear and to operate in a risk mode if any one of the identified fault conditions is flagged. 10. The control device described in clause 9, wherein in an active mode, the control module is configured to send a command to reduce the operating speed of the blower in at least one selected gas discharge chamber by a decrement speed step size, and in a risk mode, the control module is configured to send a command to increase the operating speed of the blower in at least one selected gas discharge chamber by an incremental speed step size that is greater than the decrement speed step size. 11. The control device of clause 10, wherein the incremental speed step size is 40 revolutions per minute (rpm) or less, and the decrement speed step size is about 1 / 2, 1 / 3, 1 / 4, or 1 / 5 of the incremental speed step size. 12. In active mode, the control module: selecting one of the gas discharge chambers; If the reduced operating speed is above the baseline speed, transmitting a command to reduce the operating speed of a blower located within the selected gas discharge chamber to the reduced operating speed. 10. The control device according to clause 9, configured to: 13. The control device of clause 12, wherein the control module is further configured to transmit a command to increase the operating speed of the blower disposed within the selected gas discharge chamber if the current operating speed of the blower disposed within the selected gas discharge chamber is less than the baseline speed, and to transmit a command to maintain the operating speed of the blower disposed within the selected gas discharge chamber if the current operating speed of the blower disposed within the selected gas discharge chamber is the baseline speed. 14. The control device of clause 12, further comprising a baseline module configured to control a baseline speed of each blower in each gas discharge chamber, wherein control of a particular blower baseline speed is related to the age of the gas discharge chamber in which the blower is housed. 15. The fault monitoring module is further configured to identify a fault priority for each monitored operating condition; In Risk mode, the control module: analyzing each monitored operating condition for fault conditions to determine which one or more fault conditions are flagged; if multiple fault conditions are flagged, selecting one of the flagged fault conditions based on the identified fault priority, and if a single fault condition is flagged, selecting the single flagged fault condition; selecting a gas discharge chamber based on a fault type associated with the selected fault condition; Transmitting a command to increase the operating speed of the blower of the selected gas discharge chamber 10. The control device according to clause 9, configured to: 16. The control device of clause 15, wherein the fault type is associated with a single gas discharge chamber or associated with multiple gas discharge chambers, and in risk mode, the control module configured to select a gas discharge chamber based on the fault type associated with the selected fault situation includes either selecting a single gas discharge chamber associated with the fault type or selecting a gas discharge chamber from multiple gas discharge chambers associated with the fault type. 17. In risk mode, the operating speed of the blower of the selected gas discharge chamber is increased, and then the control module: Enters the hold state, After the hold state ends, receiving, for each monitored operating condition, the following identified fault conditions and fault types from the fault monitoring module; analyzing each monitored operating condition for fault conditions to determine which one or more fault conditions are flagged; If any of one or more fault conditions are flagged, i.e., if multiple fault conditions are flagged, selecting one of the flagged fault conditions based on the identified fault priority, and if a single fault condition is flagged, selecting the single flagged fault condition; selecting a gas discharge chamber based on a fault type associated with the selected fault condition; sending a command to increase the operating speed of the blower of the selected gas discharge chamber; If none of the one or more fault conditions have been flagged, enter risk mode and wait for the next identified fault condition and fault type from the fault monitoring module. 16. The control device according to clause 15, configured to: 18. The fault monitoring module is configured to monitor one or more operating conditions of the light source every certain usage time of the light source; 2. The control device of claim 1, wherein the period of time during which the light source is in use is measured as the number of pulses of the light beam generated by the light source. 19. The control device of clause 18, wherein the certain period of use includes a first certain period of use and a second certain period of use that is greater than the first certain period of use, and wherein the fault monitoring module is configured to operate using the second certain period of use after both identifying a flagged fault condition using the first certain period of use and identifying the absence of the flagged fault condition within a subsequent period of use. 20. A method of controlling a plurality of blowers, each blower being disposed within a gas discharge chamber of a light source, the method comprising: monitoring one or more operational conditions of the light source for each period of time the light source is in use; for each monitored operating condition, identifying a fault condition and a fault type relating to which blower of the gas discharge chamber is affecting the monitored operating condition; selecting at least one gas discharge chamber; sending a command to a blower in the at least one selected gas discharge chamber, the command being based on the identified fault condition and the identified fault type; A method comprising: 21. For each operating condition monitored, further including identifying a priority for the monitored operating condition; 21. The method of clause 20, wherein selecting the at least one gas discharge chamber includes selecting the at least one gas discharge chamber based on the identified priority. 22. The method of clause 20, wherein selecting at least one gas discharge chamber includes selecting at least one gas discharge chamber based on a gas discharge chamber selected during a most recent preceding period of use. 23. The method of clause 20, wherein a fault condition identified for a monitored operating condition is flagged if a performance metric associated with the monitored operating condition is not within a performance metric threshold range, or is cleared if a performance metric associated with the monitored operating condition is within a performance metric threshold range. 24. Further comprising identifying an overall fault condition based on the identified fault condition of each monitored operating condition; 21. The method of claim 20, wherein selecting at least one gas discharge chamber and transmitting instructions to a blower in the selected at least one gas discharge chamber includes decoding an overall fault condition to analyze the identified fault condition for each monitored operating condition. 25. The method of clause 20, wherein selecting at least one gas discharge chamber and sending instructions to a blower in the selected at least one gas discharge chamber includes operating in an active mode if all of the identified fault conditions are clear and operating in a risk mode if any one of the identified fault conditions is flagged. 26. The method of clause 25, wherein in the active mode, sending a command to the blower includes sending a command to decrease the operating speed of the blower in at least one selected gas discharge chamber by a decrement speed increment, and wherein in the risk mode, sending a command to the blower includes sending a command to increase the operating speed of the blower in at least one selected gas discharge chamber by an incremental speed increment that is greater than the decrement speed increment. 27. In active mode, selecting the at least one gas discharge chamber includes selecting one of the gas discharge chambers; 26. The method of clause 25, wherein sending a command to the blower includes sending a command to reduce an operating speed of a blower disposed in the selected gas discharge chamber to a reduced operating speed if the reduced operating speed is above the baseline speed. 28. The method of clause 27, wherein sending the command to the blower further includes sending a command to increase the operating speed of the blower disposed in the selected gas discharge chamber if the current operating speed of the blower disposed in the selected gas discharge chamber is equal to or less than the baseline speed, and wherein sending the command to the blower further includes sending a command to maintain the operating speed of the blower disposed in the selected gas discharge chamber if the current operating speed of the blower disposed in the selected gas discharge chamber is within a threshold of the baseline speed. 29. The method of clause 27, further comprising controlling a baseline speed of each blower in each gas discharge chamber, wherein controlling a particular blower baseline speed is related to the age of the gas discharge chamber in which the blower is housed. 30. Further comprising identifying a fault priority for each monitored operating condition; Operating in risk mode means: analyzing each monitored operating condition for fault conditions to determine which one or more fault conditions are flagged; selecting one of the flagged fault conditions based on the identified fault priority if multiple fault conditions are flagged, and selecting the single flagged fault condition if a single fault condition is flagged; selecting a gas discharge chamber based on a fault type associated with the selected fault condition; sending a command to increase the operating speed of the blower of the selected gas discharge chamber; 26. The method of claim 25, comprising: 31. The method of clause 30, wherein the fault type is associated with a single gas discharge chamber or associated with multiple gas discharge chambers, and operating in risk mode includes selecting a gas discharge chamber based on the fault type associated with the selected fault condition, including either selecting a single gas discharge chamber associated with the fault type or selecting a gas discharge chamber from multiple gas discharge chambers associated with the fault type. 32. Operating in risk mode involves increasing the operating speed of the blower of the selected gas discharge chamber, and then Entering a holding state, After the hold state ends, analyzing the identified subsequent fault conditions for each monitored operating condition to determine which one or more fault conditions are flagged; If any of one or more fault conditions are flagged, i.e., if multiple fault conditions are flagged, selecting one of the flagged fault conditions based on the identified fault priority, and if a single fault condition is flagged, selecting the single flagged fault condition; selecting a gas discharge chamber based on a fault type associated with the selected fault condition; sending a command to increase the operating speed of a blower of a selected gas discharge chamber; If none of the one or more fault conditions have been flagged, exit risk mode and wait for the next fault condition and fault type identified. 31. The method of clause 30, comprising: 33. A control device for a light source including a first gas discharge chamber and a second gas discharge chamber in optical series with the first gas discharge chamber, comprising: a fault monitoring module configured to periodically monitor one or more operational states of the light source and, for each monitored operational state, identify a fault condition; a control module configured to send a first command to a first blower in a first gas discharge chamber and a second command to a second blower in a second gas discharge chamber, the first command and the second command relating to speeds of the first blower and the second blower, respectively, and the first command and the second command are based on an identified fault condition; a control device including:

[0129]

[0148] These and other implementations are within the scope of the following claims.

Claims

1. 1. A control device for a light source including a plurality of gas discharge chambers with a blower disposed within each gas discharge chamber, comprising: a fault monitoring module configured to monitor one or more operational conditions of the light source and, for each monitored operational condition, identify a fault condition and a fault type relating to which blower of the gas discharge chamber is affecting the monitored operational condition; a control module configured to receive the identified fault condition and the identified fault type from the fault monitoring module, select at least one gas discharge chamber, and send instructions to the blower in the selected at least one gas discharge chamber, the instructions being based on the identified fault condition and the identified fault type; and a control device including:

2. the fault monitoring module is configured to, for each monitored operating condition, identify a priority for the monitored operating condition; The control device of claim 1 , wherein the control module is configured to select the at least one gas discharge chamber based on the identified priority.

3. 2. The control device of claim 1, wherein the fault monitoring module is configured to monitor the one or more operational conditions of the light source every fixed period of use of the light source, and the control module is configured to select at least one gas discharge chamber based on the gas discharge chamber selected by the control module during an immediately preceding period of use.

4. 2. The control device of claim 1, wherein the plurality of gas discharge chambers includes a master oscillator gas discharge chamber and a power amplifier gas discharge chamber in optical series with the master oscillator gas discharge chamber, and the fault type is selected from a set of possible fault types including a power amplifier fault type, a master oscillator fault type, and a common fault type.

5. The controller of claim 1 , wherein each of the one or more operating states is defined by a performance metric related to the light source or a light beam produced by the light source.

6. The one or more performance metrics: a wavelength histogram associated with said light beam; an energy dose error associated with said light beam; an energy error associated with said light beam; a bandwidth error associated with said light beam; the operating point of the master oscillator gas discharge chamber; the operating point of the power amplifier gas discharge chamber; a spectral feature accuracy associated with the light beam; and The control device of claim 5 including an actuator operating point for the light source.

7. The fault condition identified for the monitored operating condition is: a flag is raised if a performance metric associated with the monitored operating condition is not within a threshold range for that performance metric; or The control system of claim 1 , wherein the performance metric associated with the monitored operating condition is clear if it is within the threshold range for that performance metric.

8. 2. The control device of claim 1, wherein the fault monitoring module is configured to identify an overall fault condition based on the identified fault condition of each monitored operating condition, and the control module configured to select at least one gas discharge chamber and send the command to the blower in the selected at least one gas discharge chamber includes the control module decoding the overall fault condition to analyze the identified fault condition of each monitored operating condition.

9. 2. The control device of claim 1, wherein the control module configured to select at least one gas discharge chamber and send the command to the blower in the selected at least one gas discharge chamber comprises the control module configured to operate in an active mode if all of the identified fault conditions are clear and to operate in a risk mode if any one of the identified fault conditions is flagged.

10. 10. The control device of claim 9, wherein in an active mode, the control module is configured to transmit a command to decrease the operating speed of the blower in the selected at least one gas discharge chamber by a decrement speed increment, and in a risk mode, the control module is configured to transmit a command to increase the operating speed of the blower in the selected at least one gas discharge chamber by an incremental speed increment that is greater than the decrement speed increment.

11. 11. The control device of claim 10, wherein the incremental speed step size is 40 revolutions per minute (rpm) or less, and the decrement speed step size is approximately 1 / 2, 1 / 3, 1 / 4, or 1 / 5 of the incremental speed step size.

12. In an active mode, the control module: selecting one of the gas discharge chambers; If the reduced operating speed is above a baseline speed, then transmitting a command to reduce the operating speed of the blower located within the selected gas discharge chamber to the reduced operating speed. The control device according to claim 9 , configured to:

13. 13. The control device of claim 12, wherein the control module is further configured to: transmit a command to increase the operating speed of the blower disposed in the selected gas discharge chamber if the current operating speed of the blower disposed in the selected gas discharge chamber is less than the baseline speed; and transmit a command to maintain the operating speed of the blower disposed in the selected gas discharge chamber if the current operating speed of the blower disposed in the selected gas discharge chamber is the baseline speed.

14. 13. The control device of claim 12, further comprising a baseline module configured to control the baseline speed of each blower in each gas discharge chamber, wherein the control of a particular blower baseline speed is related to the age of the gas discharge chamber in which the blower is housed.

15. the fault monitoring module is further configured to identify a fault priority for each monitored operating condition; In risk mode, the control module: analyzing the fault conditions for each monitored operating state to determine which one or more fault conditions are flagged; if multiple fault conditions are flagged, selecting one of the flagged fault conditions based on the identified fault priority, and if a single fault condition is flagged, selecting the single flagged fault condition; selecting a gas discharge chamber based on the fault type associated with the selected fault condition; transmit a command to increase the operating speed of the blower of the selected gas discharge chamber The control device according to claim 9 , configured to:

16. the fault type is associated with a single gas discharge chamber or is associated with multiple gas discharge chambers; 16. The control device of claim 15, wherein in a risk mode, the control module configured to select the gas discharge chamber based on the fault type associated with the selected fault condition includes either selecting the single gas discharge chamber associated with the fault type or selecting a gas discharge chamber from the plurality of gas discharge chambers associated with the fault type.

17. In risk mode, after the operating speed of the blower of the selected gas discharge chamber is increased, the control module: Enters the hold state, After the holding state is completed, receiving the identified next fault condition and fault type from the fault monitoring module for each monitored operating condition; analyzing the fault conditions for each monitored operating state to determine which one or more fault conditions are flagged; If any of said one or more fault conditions is flagged, i.e. if multiple fault conditions are flagged, selecting one of the flagged fault conditions based on the identified fault priority, and if a single fault condition is flagged, selecting the single flagged fault condition; selecting a gas discharge chamber based on the fault type associated with the selected fault condition; sending a command to increase the operating speed of the blower of the selected gas discharge chamber; If none of the one or more fault conditions are flagged, exit risk mode and wait for the next identified fault condition and fault type from the fault monitoring module. The control device according to claim 15 , configured to:

18. 2. The control device of claim 1, wherein the fault monitoring module is configured to monitor the one or more operational states of the light source every certain period of time the light source is in use, the certain period of time being measured as a number of pulses of a light beam generated by the light source.

19. 20. The control device of claim 18, wherein the certain period of use includes a first certain period of use and a second certain period of use that is greater than the first certain period of use, and wherein the fault monitoring module is configured to operate using the second certain period of use after both identifying a flagged fault condition using the first certain period of use and identifying the absence of the flagged fault condition within a next period of use.

20. 1. A method of controlling a plurality of blowers, each blower being disposed within a gas discharge chamber of a light source, the method comprising: monitoring one or more operational conditions of the light source for each period of time the light source is in use; for each monitored operating condition, identifying a fault condition and a fault type relating to which blower of the gas discharge chamber is affecting said monitored operating condition; selecting at least one gas discharge chamber; transmitting a command to the blower in the selected at least one gas discharge chamber, the command being based on the identified fault condition and the identified fault type; A method comprising:

21. for each monitored operating condition, further comprising identifying a priority for the monitored operating condition; 21. The method of claim 20, wherein selecting the at least one gas discharge chamber comprises selecting the at least one gas discharge chamber based on the identified priority.

22. 21. The method of claim 20, wherein selecting the at least one gas discharge chamber comprises selecting the at least one gas discharge chamber based on the gas discharge chamber selected during a most recent preceding period of use.

23. The fault condition identified for the monitored operating condition is: a flag is raised if a performance metric associated with the monitored operating condition is not within a threshold range for the performance metric; or 21. The method of claim 20, wherein the performance metric associated with the monitored operating condition is clear if it is within the threshold range for the performance metric.

24. determining an overall fault condition based on the determined fault conditions for each monitored operating condition; 21. The method of claim 20, wherein selecting at least one gas discharge chamber and transmitting the command to the blower in the selected at least one gas discharge chamber includes decoding the overall fault condition to analyze the identified fault condition for each monitored operating condition.

25. 21. The method of claim 20, wherein selecting at least one gas discharge chamber and sending the command to the blower in the selected at least one gas discharge chamber comprises operating in an active mode if all of the identified fault conditions are clear and operating in a risk mode if any one of the identified fault conditions is flagged.

26. 26. The method of claim 25, wherein in the active mode, sending the command to the blower includes sending a command to decrease the operating speed of the blower in the selected at least one gas discharge chamber by a decrement speed increment, and in the risk mode, sending the command to the blower includes sending a command to increase the operating speed of the blower in the selected at least one gas discharge chamber by an incremental speed increment that is greater than the decrement speed increment.

27. In the active mode, selecting at least one gas discharge chamber includes selecting one of the gas discharge chambers; 26. The method of claim 25, wherein sending the command to the blower comprises sending a command to reduce the operating speed of the blower disposed in the selected gas discharge chamber to the reduced operating speed if the reduced operating speed is above a baseline speed.

28. 28. The method of claim 27, wherein sending the command to the blower further comprises sending a command to increase the operating speed of the blower located in the selected gas discharge chamber if a current operating speed of the blower located in the selected gas discharge chamber is equal to or less than the baseline speed, and sending the command to the blower further comprises sending a command to maintain the operating speed of the blower located in the selected gas discharge chamber if the current operating speed of the blower located in the selected gas discharge chamber is within a threshold of the baseline speed.

29. 28. The method of claim 27, further comprising controlling the baseline speed of each blower in each gas discharge chamber, wherein the control of a particular blower baseline speed is related to the age of the gas discharge chamber in which the blower is housed.

30. further comprising identifying a fault priority for each monitored operating condition; said operating in risk mode comprising: analyzing the fault conditions for each monitored operating condition to determine which one or more fault conditions are flagged; selecting one of the flagged fault conditions based on the identified fault priority if multiple fault conditions are flagged, and selecting the single flagged fault condition if a single fault condition is flagged; selecting a gas discharge chamber based on the fault type associated with the selected fault condition; sending a command to increase the operating speed of the blower of the selected gas discharge chamber; 26. The method of claim 25, comprising:

31. the fault type is associated with a single gas discharge chamber or is associated with multiple gas discharge chambers; 31. The method of claim 30, wherein operating in the risk mode includes selecting the gas discharge chamber based on the fault type associated with the selected fault condition, including either selecting the single gas discharge chamber associated with the fault type or selecting a gas discharge chamber from the plurality of gas discharge chambers associated with the fault type.

32. Operating in the risk mode includes increasing the operating speed of the blower of the selected gas discharge chamber after the operating speed of the blower of the selected gas discharge chamber is increased. entering a holding state; After the holding state is completed, analyzing the identified subsequent fault conditions for each monitored operating condition to determine which one or more fault conditions are flagged; If any of one or more fault conditions are flagged, i.e. selecting one of the flagged fault conditions based on the identified fault priority if multiple fault conditions are flagged, and selecting the single flagged fault condition if a single fault condition is flagged; selecting a gas discharge chamber based on the fault type associated with the selected fault condition; sending a command to increase the operating speed of the blower of the selected gas discharge chamber; if none of the one or more fault conditions are flagged, exiting risk mode and waiting for the next fault condition and fault type identified.

31. The method of claim 30, comprising:

33. 1. A control device for a light source including a first gas discharge chamber and a second gas discharge chamber in optical series with the first gas discharge chamber, comprising: a fault monitoring module configured to periodically monitor one or more operational states of the light source and, for each monitored operational state, identify a fault condition; a control module configured to send a first command to a first blower in the first gas discharge chamber and a second command to a second blower in the second gas discharge chamber, the first command and the second command relating to speeds of the first blower and the second blower, respectively, and the first command and the second command are based on the identified fault condition; a control device including:

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