Cold start adjustment in light sources

Abstract

A method for controlling a light source includes operating the light source in an idle mode in which the light source does not generate any radiation; receiving a request from the lithographic exposure apparatus to enter a production mode, the production mode comprising generating radiation by the light source and supplying radiation to the lithographic exposure apparatus; upon receiving a request to enter a production mode, if the idle parameter is exceeded, initiating a cold start indicating that the efficiency of the light source is lower than the nominal efficiency required by the lithographic exposure apparatus to expose the substrate to radiation from the light source; and automatically adjusting the idle parameters based on a model of characteristics associated with the cold start, the model being developed in accordance with previous operational data of the light source.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 434,237, filed on December 21, 2022, entitled “COLD START CONDITIONING IN A LIGHT SOURCE,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The disclosed subject matter relates to an apparatus for a light source, such as, for example, a deep ultraviolet light source. Background Art

[0004] Photolithography is a process for forming or designing semiconductor circuits on substrates such as silicon wafers. An optical source or light source generates deep ultraviolet (DUV) light or radiation for exposing the photoresist on the wafer. The DUV light can comprise, for example, a wavelength of about 100 nanometers (nm) to about 400nm. Typically, the light source is a laser source (e.g., an excimer laser), and the DUV light is a pulsed laser beam. The DUV light from the light source interacts with a projection optical system that projects a beam through a mask onto the photoresist. The photoresist and wafer are then etched and cleaned, and the photolithography process is then repeated as needed. Summary of the Invention

[0005] In some general aspects, a method for controlling a light source is performed. The method includes: operating the light source in an idle mode, in which the light source does not generate any radiation; receiving a request from a lithographic exposure apparatus to enter a production mode, the production mode including the light source generating radiation and supplying the radiation to the lithographic exposure apparatus; upon entering the production mode, initiating a cold start if an idle parameter is exceeded, the cold start indicating that the efficiency of the light source is lower than a nominal efficiency required by the lithographic exposure apparatus to expose a substrate to radiation from the light source; and automatically adjusting the idle parameter based on a model of characteristics associated with the cold start, the model being developed based on previous operating data of the light source.

[0006] Implementations may include one or more of the following aspects. For example, the method may further include developing a model of characteristics associated with a cold start. The model of characteristics associated with a cold start may be developed by developing a lookup table. The lookup table may be developed by receiving input-output data pairs from a light source and detecting patterns in the input-output data pairs that indicate the completion of a single exposure job at a substrate. The lookup table may model a relationship between one or more aspects of the light source associated with an idle mode and characteristics indicative of a cold start. The one or more aspects of the light source associated with an idle mode may include an idle time and a normalized number of pulses of radiation from the light source before entering the idle mode. The idle time may correspond to the time from the last pulse of radiation generated by the light source until the lithographic exposure apparatus requests another pulse of radiation from the light source, and the normalized number of pulses of radiation from the light source before entering the idle mode may correspond to the normalized number of pulses of radiation from the light source during a usage window that extends until the last pulse of radiation from the light source is generated just before the idle mode begins. The characteristic indicative of a cold start may be a change in the value of an excitation signal provided to the light source to generate radiation. The change in the value of the excitation signal can be a change in the voltage supplied to the electrodes within the gas discharge chamber of the light source. The idle parameter can be adjusted based on the developed model by determining a last value of a normalized number of pulses of radiation from the light source before entering the idle mode, selecting an idle time associated with the determined last value of the normalized number of pulses of radiation from the light source before entering the idle mode, and setting the idle parameter based on the selected idle time. The selected idle time can be based on a change in the voltage supplied to the electrodes that is closest to, but does not exceed, a change in the voltage indicator of a cold start.

[0007] A model of the characteristics associated with cold starts can be developed by designing and training a radial basis function network.

[0008] The idle parameter may be an idle time setting, and when the idle time exceeds the idle time setting, a cold start may be initiated. The idle parameter may be adjusted based on the developed model by selecting an idle time based on the developed model and setting the idle parameter to the selected idle time. The developed model may model a relationship between one or more aspects of the light source associated with an idle mode and characteristics indicative of a cold start.

[0009] A cold start may be initiated by indicating to the lithographic exposure apparatus that a cold start is occurring. Indicating to the lithographic exposure apparatus that a cold start is occurring may cause the lithographic exposure apparatus to avoid exposing the substrate with radiation. The method may further include, after initiating the cold start, terminating the cold start after a cold start period has expired. Radiation from the light source may be supplied to the lithographic exposure apparatus by exposing the substrate to radiation from the light source upon completion of the cold start or, if a cold start is not initiated, directly upon entering production mode.

[0010] In other general aspects, an apparatus for controlling a light source includes: a prediction module configured to develop a model of characteristics associated with a cold start of the light source based on previous operational data of the light source; and a controller in communication with the prediction module. The controller is configured to: operate the light source in an idle mode in which the light source does not generate any radiation; receive a request from a lithographic exposure apparatus to enter a production mode, the production mode comprising the light source providing radiation to the lithographic exposure apparatus; upon receiving the request to enter the production mode, initiate a cold start if an idle parameter is exceeded, the cold start indicating that the efficiency of the light source is below a nominal efficiency required by the lithographic exposure apparatus to expose a substrate to radiation from the light source; and automatically adjust the idle parameter based on the developed model.

[0011] Implementations may include one or more of the following features: For example, radiation from the light source provided to the lithographic exposure apparatus may be used to expose the substrate to radiation from the light source upon completion of a cold start, or directly upon entering production mode if a cold start is not initiated.

[0012] The prediction module may include: a data collection module configured to receive data related to previous operating data of the light source; and a data analysis module configured to analyze the data from the data collection module, form information related to the previous operating data of the light source, and provide the information to a memory. The data collection module may classify the received data into one of a plurality of types of data. The data analysis module may be configured to analyze the data from the data collection module by: combining the plurality of types of data into a single data stream; detecting type patterns in the single data stream, wherein each type pattern terminates when a single substrate job is completed; and for each type pattern, calculating one or more aspects of the light source associated with an idle mode and characteristics indicative of a cold start. The radiation may be provided in light pulses, and the data collection module may be configured to receive data for each light pulse. The data analysis module may be configured to receive the classified data from the data collection module in pulse clusters.

[0013] The apparatus may further include a memory configured to store the developed model of characteristics associated with cold starts. The prediction module may be configured to provide the developed model for storage in the memory, and the controller may be configured to access the developed model from the memory.

[0014] The idle parameter may be an idle time setting, and a cold start may be initiated when the idle time exceeds the idle time setting. The controller may be configured to adjust the idle parameter based on the developed model by selecting an idle time based on the developed model and setting the idle parameter to the selected idle time. The developed model may model a relationship between one or more aspects of the light source associated with an idle mode and characteristics indicative of a cold start. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A-Figure 1C is a block diagram of a lithography system including a light source, a control device, and a lithography exposure device at respective different times;

[0016] Figure 2 yes Figure 1A-Figure 1C A block diagram of the implementation of the lithography system;

[0017] Figure 3 yes Figure 1A-Figure 1C A block diagram of the implementation of the lithography system;

[0018] Figure 4 yes Figure 1A-Figure 1C 、 Figure 2 or Figure 3 A block diagram of an implementation of a control device;

[0019] Figure 5 is Figure 1A-Figure 1C 、 Figure 2 、 Figure 3 or Figure 4 a flowchart of a process for controlling a light source executed by a control device, comprising adjusting an idle parameter associated with an idle mode based on a cold start model;

[0020] Figure 6 is Figure 1A-Figure 1C 、 Figure 2 、 Figure 3 or Figure 4 A flow chart of a process performed by a control device for developing a cold start model;

[0021] Figure 7A is a graph showing a maximum amplitude of a voltage signal supplied to an actuation mechanism in the light source as a function of time for previous operating data of the light source;

[0022] Figure 7B yes Figure 7Aa diagram illustrating how a control device detects patterns in previous operation data;

[0023] Figure 8 It is from Figure 7A and Figure 7B a graph of distribution of data pairs extracted from patterns in previous operation data, the graph being a graph of normalized pulse counts of radiation from a light source versus idle time between patterns;

[0024] Figure 9 It can be used as a cold start model and use Figure 6 A diagram of a lookup table developed based on the extracted data pairs;

[0025] Figure 10 is Figure 1A-Figure 1C 、 Figure 2 、 Figure 3 or Figure 4 The control device performs the Figure 6 Flowchart of the process of adjusting idle parameters using a cold start model developed based on the process;

[0026] Figure 11A is a diagram of a lookup table that a control device can use to use Figure 10 Flowchart to adjust idle parameters; and

[0027] Figure 11B is a diagram of a lookup table that a control device can use to use Figure 10 to adjust the idle parameters. DETAILED DESCRIPTION

[0028] Figure 1A-Figure 1C Each of the figures is a block diagram of a lithography system 100 during a different time period, and the lithography system 100 includes a light source 105, a control device 120, and a lithography exposure device 170. The control device 120 communicates with the light source 105 via a data connection 125 and communicates with the lithography exposure device 170 via a data connection 126 to control the operation of the light source 105. Figure 1A shows the operation of the lithography system 100 and the light source 105 during the production mode MA at time t equal to t1; Figure 1B shows the operation of the lithography system 100 and the light source 105 during the idle mode MB at time t equal to t2; Figure 1COperation of the lithography system 100 and light source 105 during production mode MA is shown when time t equals t3. Time t1 occurs during a first time period, time t2 occurs during a second time period, and time t3 occurs during a third time period. The first time period occurs before the second time period, and the second time period occurs before the third time period. The three time periods are shown for illustrative purposes only. The lithography system 100 may operate in more than three time periods.

[0029] In production mode MA, light source 105 generates radiation 110 (such as a pulsed light beam) which is directed (e.g., through one or more optical elements 115) to lithographic exposure device 170. Sometimes, as Figure 1A As shown, a photolithography exposure apparatus 170 uses the radiation 110 to expose a substrate 171. Figure 1C As shown, because the light source 105 has informed the lithography exposure apparatus 170 (via the data connection 126) that the quality of the radiation 110 is poor, the lithography exposure apparatus 170 does not use the radiation 110 to expose the substrate 171. In this case, the light source 105 generates radiation 110, but the radiation 110 does not have the properties that the lithography exposure apparatus 170 needs to expose the substrate 171. For example, if the light source 105 is operating from a cold start, this may occur. Figure 1C 1. During a cold start, the light source 105 operates at an efficiency (such as energy efficiency) that is lower than the nominal efficiency required for the lithographic exposure apparatus 170 to expose the substrate 171. During a cold start, the light source 105 indicates to the lithographic exposure apparatus 170 that the radiation 110 is of poor quality. Therefore, the lithographic exposure apparatus 170 can be appropriately adjusted so that it does not use the radiation 110 generated by the light source 105 to expose the substrate 171 during the cold start.

[0030] In the idle mode MB, the light source 105 does not generate radiation 110, and thus no radiation 110 is directed (e.g., through one or more optical elements 115) to the lithographic exposure device 170. For example, during the idle mode MB, the generation of radiation 110 is suspended. In the idle mode MB, the light source 105 can be powered off or turned off, or powered on and not generating any radiation 110.

[0031] Typically, the light source 105 generates radiation 110 during the generation mode MA under the command of an excitation signal 111. The excitation signal 111 may be generated by the control device 120 (and may be transmitted via the data connection 125); Figure 1A-Figure 1CThe excitation signal 111 is generated by another control system not shown in the figure; or by a separate device, such as a voltage source or current source controlled by the control device 120 or other control system. The excitation signal 111 is any type of signal sufficient to cause the light source 105 to generate the radiation 110 (pulsed light beam). For example, the excitation signal 111 can be an excitation mechanism (such as, for example, Figure 3 6A1, 306A2). The radiation 110 can be a pulsed light beam or a continuous wave, and the light beam can be a laser beam. The light source 105 can be a deep ultraviolet (DUV) optical system that emits radiation 110 in the DUV wavelength range. In some implementations, the light source 105 emits pulses in a burst of pulses of the light beam during the production mode MA. The pulse burst can include hundreds or thousands of light pulses. When the light source is in the production mode MA, the excitation signal 111 is applied to the light source 105 or a component of the light source 105. On the other hand, during the idle mode MB, the excitation signal 111 is not applied to the light source 105 (or any component of the light source 105).

[0032] After the light source 105 and the lithography system 100 have been operating in idle mode MB for a certain duration, a cold start is initiated by the light source 105. Specifically, the cold start is initiated when the light source 105 receives a request from the lithography exposure apparatus 170 to enter production mode MA, but the light source 105 determines that the efficiency of the radiation 110 generated by the light source 105 is significantly lower than the nominal efficiency required to process the substrate 171. For example, a cold start can occur when the light source 105 is "warming up." As long as the light source 105 and the lithography system 100 operate in idle mode MB for a duration exceeding a minimum duration, the efficiency of the light source 105 will drop below the nominal efficiency. Therefore, the light source 105 needs to warm up before its efficiency is suitable for production mode MA. For example, the minimum duration can be on the order of a few seconds, such as one, two, five, or even ten seconds. In other examples, the minimum duration can be on the order of several minutes, such as one, two, five, or ten minutes. In still other examples, the minimum duration can be greater than ten minutes. The amount of efficiency loss that occurs during idle mode MB can vary depending on the age of light source 105 and the total time light source 105 operates in idle mode MB (such time corresponding to idle time). To restore light source 105 to nominal efficiency from the inefficient operation during idle mode MB when light source 105 is ready to enter production mode MA, light source 105 can be operated in a cold start to generate sufficient pulses of light beam 110 to effectively warm up light source 105. For example, during a cold start, light source 105 can generate thousands (e.g., 10,000) of pulses of light beam 110 before the efficiency of light source 105 reaches nominal efficiency. During the cold start, the value of excitation signal 111 is increased to compensate for the loss in energy efficiency of light beam 110. After the energy efficiency has recovered to a level equal to or greater than the nominal efficiency required for processing substrate 171, the value of excitation signal 111 can be decreased or reduced. As described below, this difference in the value of excitation signal 111 from the beginning of operation in the cold start to the end of the cold start is a characteristic that can be used by control device 120 to detect when a cold start has occurred.

[0033] It is beneficial to operate the light source 105 in a cold start. Specifically, by operating in a cold start until the efficiency of the light source 105 reaches the nominal efficiency, errors, unplanned downtime, and expensive rework or rejection of substrates 171 can be reduced or avoided because the lithography exposure apparatus 170 does not use poor quality radiation 110 to expose the substrates 171. The cold start allows the light source 105 to effectively "warm up" and prevents the lithography exposure apparatus 170 from using substandard radiation 110 during this warm-up period.

[0034] As described above, after the light source 105 receives a request to enter the production mode MA from the lithography exposure apparatus 170, and if the light source 105 has been operating in the idle mode MB for a duration (idle time) exceeding the idle parameter ITmin, a cold start is initiated by the light source 105. The idle parameter ITmin is a parameter associated with the light source 105. The idle parameter ITmin may correspond to the minimum duration described above. Furthermore, the light source 105 and the lithography system 100 may operate in the cold start mode for a cold start period CSPer.

[0035] Rather than simply assigning a fixed value to the idle parameter ITmin (a parameter that controls the initiation of a cold start), the control device 120 also includes a component configured to automatically adjust the value of the idle parameter ITmin to reduce the number of erroneously initiated cold starts and to initiate a cold start when necessary, thereby increasing the availability of the light source 105, as desired by the lithography exposure apparatus 170. In particular, the control device 120 can automatically adjust the value of the idle parameter ITmin based on a model of one or more characteristics associated with a cold start of the light source 105. For example, as described above, one characteristic associated with a cold start is the difference or change in the value of the excitation signal 111 from the start of the cold start operation to the end of the cold start. The control device 120 can develop this model based on previous operating data of the light source 105.

[0036] See also Figure 2 , shows an implementation 200 of the lithography system 100, which includes an implementation 205 of the light source 105 and an implementation 220 of the control device 120. The control device 220 includes a memory 221, a prediction module 222 configured to access the memory 221, a controller 223 configured to access the memory 221 and communicate with the prediction module 222, and an input / output interface 224. A data connection 225 enables communication between the control device 220 and the light source 205, and a data connection 226 enables communication between the control device 220 and the lithography exposure apparatus 170.

[0037] The prediction module 222 includes one or more processors, such as general-purpose or special-purpose microprocessors, and any one or more processors of any type of digital computer. These processors execute instructions and access data stored on the memory 221, and are also capable of writing data to the memory 221. Similarly, the controller 223 includes one or more processors, such as general-purpose or special-purpose microprocessors, and any one or more processors of any type of digital computer. These processors execute instructions and access data stored on the memory 221, and are also capable of writing data to the memory 221. The memory 221 may include volatile memory (such as random access memory (RAM)) or non-volatile memory. In some implementations, the memory 221 includes both non-volatile and volatile parts or components. The memory 221 may store data and information used in the operation of the control device 220. For example, the memory 221 stores information related to previous operating data of the light source 205.

[0038] The input / output interface 224 allows the control device 220 to exchange data and signals with an operator, the light source 205, the lithographic exposure apparatus 170, and / or an automated process running on another electronic device. In some implementations, the input / output interface 224 receives data from the light source 205 and / or from the hardware and / or software subsystems of the light source 205 via a data connection 225. For example, the light source 205 can provide information related to idle time and / or other information about the light source 205 to the control device 220 via the input / output interface 224. In some implementations, the input / output interface 224 receives instructions or commands from the lithographic exposure apparatus 170 and / or from the hardware and / or software subsystems of the lithographic exposure apparatus 170 via a data connection 226. The input / output interface 224 can include one or more of a visual display, a keyboard, and a communication interface, such as, for example, a universal serial bus (USB) connection and / or any type of network interface, such as, for example, Ethernet. The input / output interface 224 may also allow for contactless communication through, for example, IEEE 802.11, Bluetooth, or Near Field Communication (NFC) connections.

[0039] Each data connection 225, 226 can be a physical cable or other physical data conduit (such as a cable supporting data transmission based on IEEE 802.3), a wireless data connection (such as a data connection providing data via IEEE 802.11 or Bluetooth), or a combination of wired and wireless data connections. The data provided via the data connection 225 or 226 can be sent using any type of protocol or format.

[0040] The light source 205 includes an excitation mechanism 206 and a gain medium 207. To generate radiation 110 (e.g. Figure 1A or Figure 1C During the generation mode MA, an excitation signal 111 is applied to the light source 205 and excites the excitation mechanism 206. The excitation mechanism 206 excites the gain medium 207 in response to the excitation signal 111. The gain medium 207 is any medium suitable for generating radiation 110 at the wavelength, energy, and bandwidth required for the application. For example, the gain medium 207 can be a gas, a crystal, a glass, a semiconductor, or a liquid. The excitation mechanism 206 is any mechanism capable of exciting the gain medium 207. For example, the excitation mechanism 206 can be a plurality of electrodes that excite the gaseous gain medium 207. The excitation signal 111 can be, for example, an electrical signal (such as a voltage signal or an RC voltage signal) or a command signal that causes an additional element (such as a voltage or current source) to generate an electrical signal that is provided to the excitation mechanism 206. The excitation signal 111 can be a time-varying direct current (DC) electrical signal or an alternating current (AC) electrical signal, such as a sinusoidal voltage signal or a square wave voltage signal, or a combination of these signals. Important and adjustable properties of the excitation signal 111 include the amplitude of the time-varying signal, the average amplitude of the time-varying signal, the minimum amplitude of the time-varying signal, the frequency of the time-varying signal, the duty cycle of the time-varying signal, and / or any other properties related to the time-varying signal.

[0041] exist Figure 2 In the example of FIG, the control device 220 is depicted as being separate from the light source 205 and connected via a data connection 225. However, in some implementations, the control device 220 is implemented as part of the light source 205, such that the light source 205 and the control device 220 are part of a single integrated package (such as, for example, enclosed within the same housing). In these implementations, the data connection 225 can be a data path that allows the software modules to communicate with one of the software modules that implement various aspects of the control device 220 and another of the software modules that implement other functions of the light source 205. The control device 220 (and in particular the prediction module 222 and the controller 223) can monitor characteristics of the excitation signal 111.

[0042] refer to Figure 3 , an implementation 305 of light source 105 or 205 is shown as part of a lithography system 300. The lithography system 300 includes an implementation 370 of the lithography exposure apparatus 170. The light source 305 generates radiation 310 that is provided to the lithography exposure apparatus 370 during production mode MA. The light source 305 can be, for example, an excimer light source that outputs a pulsed light (or laser) beam as radiation 310. When the pulsed light beam 310 enters the lithography exposure apparatus 370, it is directed through a projection optical system 372 and projected onto a substrate 371 to form one or more microelectronic features in a photoresist on the substrate 371.

[0043] The lithography system 300 includes a control system 319 , which may include the control device 120 / 220 and other components and modules.

[0044] Light source 305 is a two-stage laser system that includes a master oscillator stage 308A for providing a seed beam 309 to a power amplifier stage 308B. Master oscillator stage 308A and power amplifier stage 308B can be considered subsystems of light source 305 or a system that is part of light source 305. Power amplifier stage 308B receives seed beam 309 from master oscillator stage 308A and amplifies seed beam 309 to generate beam 310 for use in lithography exposure apparatus 370. For example, master oscillator stage 308A can emit pulsed seed beam 309 with a pulse energy of approximately 1 millijoule (mJ) per pulse, and these pulses can be amplified to approximately 10-20 mJ by power amplifier stage 308B. The master oscillator stage 308A includes a gas discharge chamber 312A having two elongated electrodes 306A1 and 306A2, a gain medium 307A as a gas mixture, and a fan for circulating the gas between the electrodes 306A1, 306A2 in the discharge chamber 312A. A resonator is formed between an optical module 313A (such as a spectral signature selection module) on one side of the discharge chamber 312A and an output coupler 314A on a second side of the discharge chamber 312A. The spectral signature selection module 313A is configured to finely tune the spectral output of the seed beam 309. The beam coupling optical system 318 is positioned to modify the size, shape, and / or direction of the seed beam 309 as needed for use by the power amplifier stage 308B. The power amplifier stage 308B includes a beam coupling optical system 316 that receives the seed beam 309 and directs the seed beam through the gas discharge chamber 312B and to a beam steering optical element 313B, which modifies or changes the direction of the seed beam so that it is sent back into the gas discharge chamber 312B. The gas discharge chamber 312B includes a pair of elongated electrodes 306B1 and 306B2, a gain medium 307B that is a gas mixture, and a fan for circulating the gas between the electrodes 306B1 and 306B2 in the discharge chamber 312B.

[0045] The gas mixture used in the gas discharge chambers 312A, 312B can be any gas suitable for generating a beam of light of the wavelength and bandwidth required for the application. For an excimer source, the gas mixture can include a rare gas (e.g., argon or krypton), a halogen (e.g., fluorine or chlorine), and a trace amount of xenon as a buffer gas in addition to helium and / or neon. Specific examples of gas mixtures include argon fluoride (ArF), which emits light at a wavelength of approximately 193 nm, krypton fluoride (KrF), which emits light at a wavelength of approximately 248 nm, or xenon chloride (XeCl), which emits light at a wavelength of approximately 351 nm. The excimer gain medium (gas mixture) is pumped in a high voltage discharge with short (e.g., nanosecond-order) current pulses by applying a voltage (excitation signal 311A, 311B) to the respective elongated electrodes 306A1, 306A2, 306B1, 306B2.

[0046] One or more optical elements 315 are configured to redirect the light beam 310 to the lithographic exposure apparatus 170. The light source 305 may also include one or more measurement modules 317 that measure various aspects of the light source 305, the seed beam 309, and / or the light beam 310. For example, the measurement module 317 may include a beam analysis module that is configured to measure various parameters of the light beam 310 (such as bandwidth, wavelength, energy). The beam analysis module may be implemented within the set of optical elements 315. As another example, the measurement module 317 may include a line center analysis module that receives the seed beam 309 from the output coupler 314A and measures or monitors the wavelength of the seed beam 309. The line center analysis module may be located along the path between the output coupler 314A and the beam coupling optical system 316, or may be placed at the output of the light source 305 or within the set of optical elements 315. As another example, the metrology module 317 may include a metrology module that tracks one or more parameters related to previous operation of the light source 305, where such one or more parameters are provided to the control system 319 and constitute the aforementioned “previous operation data,” and the control device 120 within the control system 319 may then use the previous operation data to develop a model of the light source 305. The model relates to one or more characteristics associated with a cold start of the light source 305.

[0047] Light beam 310 is a pulsed light beam and may include one or more bursts of pulses separated in time. Each burst may include one or more light pulses. In some implementations, a burst may include hundreds of pulses; for example, a burst may include 100-400 pulses of light beam 310. When gain medium 307A is pumped by applying voltage 311A to electrodes 306A1 and 306A2, gain medium 307A emits light. Furthermore, when voltage 311A is applied to electrodes 306A1 and 306A2 in a pulsed manner, the light emitted from gain medium 307A is also pulsed. The repetition rate of pulsed light beams 309 and 310 may be determined by the rate at which voltage 311A is applied to electrodes 306A1 and 306A2, with each application of voltage 311A generating a light pulse. The light pulses generated within gas discharge chamber 312A propagate through gain medium 307A and exit chamber 312A through output coupler 314A. Thus, a pulse train is generated by periodically and repeatedly applying voltage 311A to electrodes 306A1, 306A2. The repetition rate of the pulses can be between about 500 Hertz (Hz) and 6000 Hz. In some implementations, the repetition rate is greater than 6000 Hz and can be, for example, tens of thousands of Hz, such as 12000 Hz or higher.

[0048] Signals from control system 319 can also be used to control electrodes 306A1, 306A2, 306B1, 306B2 within master oscillator stage 308A and power amplifier stage 308B, respectively. In this way, control system 319 can control the respective pulse energies of master oscillator stage 308A and power amplifier stage 308B, and thereby control the energy of light beam 310. There can be a delay between the signal provided to electrodes 306A1 / 2 and the signal provided between electrodes 306B1 / 2. The amount of delay can affect the properties of light beam 310, such as the bandwidth or coherence of light beam 310. Light beam 310 can have an average output power in the range of tens of watts (W), for example, from about 50 W to about 130 W.

[0049] refer to Figure 4, an implementation 420 of the control device 120 / 220 is shown relative to the light source 105. The control device 420 includes a memory 421 (which is an implementation of the memory 221), a prediction module 422 (which is an implementation of the prediction module 222), a controller 423 (which is an implementation of the controller 223), and an input / output interface 424 (which is an implementation of the input / output interface 224). Data from the light source 105 is transmitted to the prediction module 422 via the input / output interface 424 via the data connection 225. Data from the controller 423 can also be transmitted to the light source 105 via the input / output interface 424 via the data connection 225. The prediction module 422 includes a data collection module 427 and a data analysis module 428. Each of the data collection module 427 and the data analysis module 428 can access or include one or more processors of the prediction module 422 to execute instructions, access data, and write data to the memory 421.

[0050] The data collection module 427 is configured to receive data (previous operation data) from the light source 105 via the input / output interface 424. The data collection module 427 is also configured to classify the received data into one of a plurality of data types. In this example, there are three data categories, and these data categories are labeled D1, D2, and D3. However, in other implementations, there may be more than three or only two categories of data.

[0051] Next, examples of data types are discussed. As described above, in production mode MA, the light source 105 generates radiation 110, and the radiation 110 can be in the form of a pulsed light beam. Data received from the light source 105 can be provided for each pulse of the light beam 110, and thus the data is received as a data stream at the rate at which pulses of the light beam 110 are generated. In some implementations, the previous operational data received at the data collection module 427 can include one or more attributes associated with the excitation signal 111 (or 311A). For example, the data collection module 427 can receive the time T at which each pulse of the light beam 110 is generated. The time T can be determined by the time at which the excitation signal 111 is provided to the excitation mechanism 206 of the light source 105. If the excitation signal 111 is a time-varying signal, such as a sinusoidal voltage signal, the data collection module 427 can receive the time T at which the voltage signal reaches a maximum value. The time T can have a range or width, meaning that the pulses can be generated within a certain period of time. As another example, the data collection module 427 may receive a minimum amplitude AVmin of the excitation signal 111 (such as an average value of the minimum voltage in the sinusoidal voltage signal 111) and a maximum amplitude AVmax of the excitation signal 111 (such as an average value of the maximum voltage in the sinusoidal voltage signal 111). In other implementations, the data collection module 427 receives other properties of the excitation signal 111, such as, for example, a frequency of the time-varying signal, a duty cycle of the time-varying signal, a number of pulses (or a normalized number of pulses) of the excitation signal 111, and / or any other properties related to a time-varying signal.

[0052] Furthermore, the lithographic exposure apparatus 170 may use the pulses of the light beam 110 for different purposes. For example, typically, at the start of production mode MA or immediately before exposure of the substrate 171 begins, the lithographic exposure apparatus 170 may use pulses of the light beam 110 to perform internal calibration, and data associated with such pulses used in this manner is classified as D1 data. During internal calibration, pulses of the light beam 110 are not provided to the substrate 171. As another example, the lithographic exposure apparatus 170 may use some pulses of the light beam 110 for internal production unrelated to calibration, and data associated with such pulses is classified as D3 data. During this internal production, pulses of the light beam 110 are not provided to the substrate 171. As another example, the lithographic exposure apparatus 170 may use some pulses of the light beam 110 for external production, and data associated with such pulses is classified as D2 data. During external production, pulses of the light beam 110 are provided to the substrate 171.

[0053] The data analysis module 428 is configured to analyze the classified data (D1, D2, D3) output from the data collection module 427. The data analysis module 428 is configured to form or develop information Ipo related to previous operating data of the light source 105 based on the classified data (D1, D2, D3), and the information Ipo is provided to and stored in the memory 421. Details regarding the data analysis module 428 are discussed below. In some implementations, the data analysis module 428 includes a set of submodules 429, 430, and 431, each of which performs one or more specific tasks. Submodule 429 can be referred to as a combination module, submodule 430 can be referred to as a pattern module, and submodule 431 can be referred to as an extraction module. Although the submodules 429, 430, and 431 are shown as distinct blocks, the functionality between the submodules 429, 430, and 431 can be shared or performed by a single module, such as the data analysis module 428.

[0054] refer to Figure 5 , a process 580 for controlling the light source 105 (which may be the light source 205 or 305) performed by the control device 120, 420. In discussing the process 580, reference is made to Figure 1A-Figure 1C and Figure 4 . Process 580 is decomposed into sub-processes 580A, 580B, 580C that are executed in parallel or in conjunction with each other. Process 580A includes operating the light source 105 in an idle mode MB, in which the light source 105 does not generate any radiation 110 (581). For example, in the idle mode MB, the excitation signal 111 is not provided to the light source 105. As described above, in the idle mode MB, the light source 105 does not generate radiation 110, and therefore no radiation 110 is directed to the lithographic exposure device 170, as Figure 1B shown.

[0055] The light source 105 remains in the idle mode MB until or unless a request to enter the production mode MA is received (582). The light source 105 receives the request to enter the production mode MA from the lithographic exposure apparatus 170 via the data connection 126. If the request to enter the production mode is received at 582, the light source 105 begins the production mode MA (583). For example, in the production mode MA, the excitation signal 111 (which may be generated by the control device 120) is supplied to the light source 105. As described above, in the production mode MA, the light source 105 generates radiation 110, which is directed to the lithographic exposure apparatus 170, as Figure 1A or Figure 1CAs shown. If no request to enter production mode MA is received at 582, the light source 105 continues to operate in idle mode (581). The light source 105 remains in production mode MA until or unless a request to end production mode MA is received (584). The light source 105 receives a request to end production mode MA from the lithographic exposure device 170 via the data connection 126. If a request to end production mode is received at 584, the light source 105 ends production mode MA and operates in idle mode (581).

[0056] After entering the production mode MA at 583, process 580B is executed. In fact, after receiving the request to enter the production mode at 582, the control device 120 immediately queries process 580B. Process 580B first asks whether the idle parameter is exceeded (585), and if the idle parameter is not exceeded at 585, the production mode MA starts 583 and does not initiate a cold start. On the other hand, if the control device 120 determines at 585 that the idle parameter is exceeded, the production mode MA starts 583, but initiates a cold start (586). As described above, the idle parameter ITmin is a parameter associated with the light source 105. The idle parameter ITmin can correspond to an idle time setting, such as a minimum duration. Therefore, when the idle time exceeds the idle time setting or the minimum duration ITmin, a cold start can be initiated. As described above, when the light source 105 receives a request to enter production mode MA (582) from the lithographic exposure apparatus 170, but the light source 105 determines that its efficiency is lower than the nominal efficiency required by the lithographic exposure apparatus 170 to expose the substrate 171 to radiation 110, the light source initiates a cold start. In this case, the properties of the radiation 110 do not meet the standards required by the lithographic exposure apparatus 170. In the cold start (586), the light source 105 generates radiation 110 and also notifies the lithographic exposure apparatus 170 of the substandard properties of the radiation 110 via the data connection 126. The light source 105 can specifically indicate to the lithographic exposure apparatus 170 that a cold start is occurring.

[0057] The control device 120 also inquires whether the cold start period CSPer has been exceeded (587). If the cold start period CSPer is exceeded at 587, the control device 120 ends the cold start and notifies the lithography exposure apparatus that the properties of the radiation 110 are within the standard required by the lithography exposure apparatus 170 to expose the substrate 171 to the radiation 110 (588).

[0058] Process 580 includes a subprocess 580C that is automatically and periodically executed during subprocess 580A. For example, instances of subprocess 580C can be executed at a constant frequency, such as every second, every minute, or every ten minutes. Subprocess 580C includes automatically adjusting an idle parameter based on a model of characteristics associated with cold starts (589). For example, at 589, the idle parameter can be adjusted by selecting an idle time based on a model of characteristics associated with cold starts and setting the idle parameter to the selected idle time.

[0059] The model of the characteristics is developed based on previous operating data of the light source 105. The idle parameter controls whether a cold start is to be initiated. By automatically adjusting the idle parameter, the control device 120 is better able to know when or whether a cold start will occur after the lithography exposure apparatus 170 sends a request for radiation 110 via the data connection 126. Therefore, if the idle parameter is reduced at 589, the barrier to initiating a cold start at 585 is lower, and the light source 105 will be more likely to notify the lithography exposure apparatus 170 at 586 (when a cold start is initiated) that a cold start is occurring, and when the production mode MA is activated at 583, the lithography exposure apparatus 170 will postpone exposing the substrate 171 with radiation 110. On the other hand, if the idle parameter is increased at 589, the barrier to initiating a cold start at 585 is higher, and the light source 105 will be less likely to notify the lithography exposure apparatus 170 that a cold start is occurring, and the lithography exposure apparatus 170 will be able to expose the substrate 171 using radiation 110 immediately after the production mode MA begins at 583. By adjusting the value of the idle parameter at 589, the control apparatus 120 is less likely to initiate a cold start at 586 when a cold start is not required, and less likely to miss the initiation of a cold start 586 when a cold start is actually required.

[0060] In some implementations, the model of characteristics associated with a cold start (589) can be in the form of a lookup table. In other implementations, the model of characteristics associated with a cold start (589) is in the form of a radial basis function network. In both cases, the model of characteristics associated with a cold start (589) models the relationship between one or more aspects of the light source 105 associated with the idle mode MB and characteristics indicative of a cold start. For example, the one or more aspects of the light source 105 associated with the idle mode can include an idle time and a normalized number of pulses (or duty cycle) of radiation 110 from the light source 105 before entering the idle mode MB. The idle time corresponds to the time from when the last pulse of radiation 110 from the light source 105 was generated (during the production mode at 583) until the time at 582 when the lithographic exposure device 170 requests another pulse of radiation 110 from the light source 105. The normalized number of pulses of radiation from the light source 105 before entering the idle mode MB at 581 corresponds to the normalized number of pulses of radiation 110 from the light source 105 during a usage window (which may be given in time or number of pulses) that extends until the last pulse of radiation 110 from the light source 105 is generated just before the idle mode MB begins at 581. One characteristic indicative of a cold start is a change in the value of the excitation signal 111 provided to the light source 105 to generate the radiation 110. For example, referring to Figure 3 The change in the value of the excitation signal 111 may be a change in the voltage 311A supplied to the electrodes 306A1 and 306A2 within the gas discharge chamber 312A of the light source 305 .

[0061] refer to Figure 6 , a process 650 may be performed for developing a model of characteristics associated with cold starts, such model being used to adjust idle parameters at 589. Typically, the control device 120 develops the model used at 589 based on past data of the light source 105 collected by the control device 120. In discussing the process 650, reference is made to Figure 4 as well as Figure 7A and Figure 7B .

[0062] Process 650 includes receiving data related to previous operating data of light source 105 (651). For example, referring to Figure 4 The data collection module 427 is configured to receive the previous operation data via the data connection 225 and the input / output interface 424. The previous operation data can be obtained by the measurement module 317 ( Figure 3 )supply.

[0063] Process 650 includes classifying each received data into one of a plurality of types of data (652). Figure 4, as described above, the data collection module 427 is configured to classify each data as D1, D2 or D3. In some implementations, the combining module 429 is configured to receive the classified data (D1, D2, D3) from the data collection module 427 and combine the multiple types of data into a single data stream D0. The single data stream D0 includes each data plus the category associated with the data in the stream D0, which is a function of the light source 105 used. In the example provided, each data is given by the time T at which the pulse of the light beam 110 is generated (the time after which the excitation signal 111 is sent to the light source 105) and the maximum amplitude AVmax of the excitation signal 111 (such as the average value of the maximum voltage in the sinusoidal voltage signal 111). Also refer to Figure 7A , a window of data stream D0 is shown in graph 740 . The data in graph 740 includes information about the maximum amplitude AVmax (y-axis) of voltage signal 111 for each pulse of light beam 110 as a function of time T. Each data category (D1, D2, or D3) in graph 740 is depicted by a different pattern fill. The depicted clusters correspond to sets of pulses of light beam 110, and the longer the cluster, the more pulses of light beam 110 in that set. For example, pulse cluster 741, which is classified as type D1, has more pulses than pulse cluster 742, which is classified as type D3, which in turn has more pulses than pulse cluster 743, which is classified as type D2. For example, cluster 741 may contain tens of thousands of pulses, cluster 742 may contain thousands of pulses, and cluster 743 may contain hundreds of pulses.

[0064] Next, the process 650 includes detecting a type pattern in a single data stream D0 (653). Each type pattern terminates when a single job at the substrate 171 is completed. For example, at 653, the pattern module 430 receives a single data stream D0 and detects a type pattern in the single data stream D0. Also refer to Figure 7B , after the type pattern is detected, Figure 7AThe window of data stream D0 is shown in Figure 745. The type pattern is indexed by the variable i, and the current pattern is the i-th pattern or P(i), the last most recent pattern is the (i-1)th pattern or P(i-1), and the second most recent pattern is the (i-2)th pattern or P(i-2). In one implementation, the pattern module 430 is searching for six type patterns. These six type patterns are: P1: [D1 D3 D1 D2]; P2: [D3 D1 D2]; P3: [D1 D2]; P4: [D1 D1 D3 D1 D2]; P5: [D3 D1 D1 D2]; P6: [D1 D1 D2]. The pattern module 430 detects three patterns in the window of data stream D0 in Figure 745: P(i-2) = P1; P(i-1) = P5; and P(i) = P2. When the (i-2)th job at the substrate 171 is completed, the pattern P(i-2) ends at time Te(i-2). When the next or (i-1)th job at the substrate 171 is completed, the pattern P(il) starts at time Tb(i-1) and ends at time Te(il). When the i-th job at the substrate 171 is completed, the pattern P(i) starts at time Tb(i) and ends at time Te(i). Therefore, the control device 420 operates the light source 105 (581) in idle mode MB during the idle time IT12 and the idle time IT01. Another idle mode is entered after T(i). During the time when the pattern is detected, the control device 420 operates the light source 105 (583) in production mode MA. Other patterns not shown in Figure 745 may exist in other windows of the data stream D0. In addition, there may be data clusters that cannot be classified as any pattern. A single data stream D0 may include more patterns than shown in the windows of Figures 740 and 745. Figures 740 and 745 are provided for illustration purposes only.

[0065] Although only six types of patterns are described in the above implementation, there may be less than six types of patterns or more than six types of patterns, or these patterns may be different from the above six types of patterns (P1, P2, P3, P4, P5, P6).

[0066] After detecting these patterns at 653, process 650 includes calculating information Ipo ( Figure 4 )(654), and the model can be stored in the memory 421 (655). For example, the extraction module 431 ( Figure 4 ) may calculate one or more aspects of the light source 105 associated with the idle mode and characteristics indicative of a cold start at 654 based on the data stream D0. This will again be referred to Figure 7B Discuss in more detail.

[0067] For the i-th pattern [P(i)] detected in the data stream D0, the extraction module 431 can calculate the corresponding aspect of the light source 105 associated with the idle mode and the characteristic indicating a cold start. As described above, the aspect of the light source 105 associated with the idle mode can be the idle time IT(i), and the characteristic indicating a cold start can be the voltage change AV(i) (during the transient period). These will be discussed below. For P(i), the corresponding idle time IT(i) is calculated as follows: IT(i) = Tb(i) - Te(i-1). Therefore, the idle time IT(i) calculated for P(i) approximates the value of IT01 in Figure 745. For P(i), the corresponding voltage change during the transient period is calculated as follows: ΔV(i) = AVmax of the first D1 data in P(i) - AVmax of the D3 data in P(i). ΔV(i) is shown in Figure 745. As described above, the value of ΔV(i) is a characteristic indicating a cold start. Another aspect of the light source 105 associated with the idle mode MB that can be calculated is the normalized number of pulses or normalized pulse count (NNpul) of the radiation 110 of the light source 105 before entering the idle mode MB. In this case, the NNpul of the i-th pattern P(i) can be given by the following equation:

[0068]

[0069] where TOTpul(i) is the total number of pulses of radiation 110 generated in the i-th pattern P(i), and the value of Te(i) and the value of Tb(i) are shown in FIG745. In other implementations, NNpul(i) can be normalized over different time frames (i.e., the value of the denominator in Equation 1), such as, for example, Te(i) - Te(il). In such an implementation, it may be impossible to calculate the value of NNpul for the first pattern in the data stream D0 because Te(il) does not exist at that time. Therefore, the i-th pattern P(i) in the data stream D0 results in the following data pair (represented as a two-dimensional feature vector):

[0070]

[0071] These data pairs form a model stored in the memory 421 and the model is represented by a lookup table LUT. The total number of data pairs given by equation 2 is equal to the total number of patterns detected in one single data stream D0.

[0072] Figure 8 An example of the distribution of such data pairs in a simulation based on query data for operating light sources 105 over a three month period is shown. Figure 8, each circle is located at a location addressed by a corresponding eigenvector defined on the left side of Equation 2. The pattern fill of each circle represents the amplitude range of the corresponding voltage change ΔV(i) on the right side of Equation 2. For example, ΔV(i)R1 may correspond to a voltage change greater than 30 volts (V); ΔV(i)R2 may correspond to a voltage change greater than 25 V and less than or equal to 30 V; ΔV(i)R3 may correspond to a voltage change greater than 20 V and less than or equal to 25 V; ΔV(i)R4 may correspond to a voltage change greater than 15 V and less than or equal to 20 V; and ΔV(i)R5 may correspond to a voltage change less than or equal to 15 V.

[0073] The paired tuning data for the model is given in Equation 2. This particular data was chosen because there is a strong relationship between the idle time IT and the normalized pulse count NNpul (as defined in the above equations) on the one hand, and the voltage change ΔV (as defined above) as an indicator of a cold start on the other hand. Specifically, it can be expected that as the idle time IT increases and / or the normalized pulse count NNpul decreases, the chance of a cold start occurring increases. This expectation is in the Figure 8 This is demonstrated in , where larger voltage variations ΔV are more likely to occur at longer idle times IT. Another advantage of using the two-dimensional eigenvectors of Equation 2 rather than considering only the idle time IT is that the data points are more dispersed, and the tuned model (in this case, the data lookup table output from Equation 2) can more effectively distinguish between different situations. Furthermore, cold starts can depend on other factors not discussed here, such as the age of the gas discharge chamber. The model (lookup table) does not account for this factor. However, if regularly retrained and kept updated, the lookup table model derived from the data in Equation 2 can adapt to the age of the gas discharge chamber.

[0074] After the lookup table LUT (or model) is stored in the memory 421, it can be tuned to improve or maximize the performance of the lookup table. Figure 9An example of tuning is discussed. After generating a tuning pair in the form of Equation 2, the data is used to tune the lookup table LUT-9. Initially, each cell of the lookup table LUT-9 is filled with zeros. Each cell in the lookup table LUT-9 addresses a specific range of the variable under consideration. For example, if the length of each row cell is equal to 10, the third row cell corresponds to the value of the normalized pulse count NNpul in the range [20, 30], and the first row cell corresponds to the value of the normalized pulse count NNpul in the range [0, 10]. The number in each cell in the lookup table LUT-9 indicates the average value of the change in the RC voltage during the transient (ΔVave) for the data point occurring in that cell. After generating a new data pair according to Equation 2, the value of the corresponding cell in the lookup table LUT-9 can be updated to the new value ΔVave(j+l) according to the following formula, such as, for example:

[0075] ΔVave(j+1)=αΔVave(j)+(1-α)ΔVave(j-1), Equation 3

[0076] where j indexes the version of ΔVave and α is a constant in the range [0,1].

[0077] Note that past data (such as the value of ΔVave) stored in the lookup table LUT- 9 may be multiplied by a forgetting factor (weighting factor) before being combined with the most recently observed data.

[0078] After the lookup table LUT is stored in the memory 421, the prediction module 422 can use the data pairs (Equation 2) extracted from the most recent past data stream D0 to tune the lookup table. After this initial tuning, the prediction module 422 runs iteratively with a constant time period between each iteration. In each iteration, the prediction module 422 updates the tuned lookup table LUT stored in the memory 421 with the new data pairs (Equation 2) generated since the last update of the lookup table LUT.

[0079] refer to Figure 10 In some implementations, the controller 423 (or the prediction module 422) performs a process 1089 for adjusting idle parameters based on a cold start model (lookup table LUT). Figure 11A and Figure 11B First, the controller 423 calculates or determines the last value of the normalized pulse count NNpul(i) from the light source 105 before entering the idle mode MB (1056). The normalized pulse count NNpul(i) can be calculated according to Equation 1. Then, the controller 423 selects the idle time IT associated with the determined last value of the normalized pulse count NNpul(i) (1057). For example, referring to Figure 11A, the controller 423 uses the lookup table LUT-11A to select the idle time IT by looking up the row in the lookup table LUT-11A corresponding to the normalized pulse count NNpul(i) determined at 1056. The determined normalized pulse count NNpul(i) is highlighted in the lookup table LUT-11A. The controller 423 determines the rightmost column (the highlighted column in the lookup table LUT-11A) so that all numbers in the highlighted row, to the left of the column, or on the column are less than the desired voltage change threshold ΔVthreshold. In this particular example, the voltage change threshold ΔVthreshold is 20V. Next, the controller 423 sets the idle parameter ITmin(i) (1058) based on the idle time IT selected from the selected column of the lookup table LUT-11A. As described above, each cell in the lookup table LUT-11A addresses a specific range of the variable under consideration. For example, if the length of each column cell is equal to 10, the ninth column cell (selected and set to the idle parameter ITmin(i)) corresponds to a value of the idle time IT in the range [80, 90]. For example, the idle parameter ITmin(i) can be set to the maximum value in the range [80, 90], and thus it can be 90 in this example.

[0080] As another example, in the lookup table LUT-11B ( Figure 11B ), the controller 423 determines the last value of the normalized pulse count NNpul(i) at 1056, and this is shown by the highlighted row in LUT-11B. All cells in the highlighted row are equal to zero. In this case, the controller 423 can select the rightmost column in the row at 1057, 1058 to determine the idle parameter ITmin(i). The rightmost column is the twelfth column, and the idle time IT in the cell corresponds to the range [110, 120]. Therefore, the controller 423 can set the idle parameter ITmin(i) to 120. In some implementations, if the last value of the normalized pulse count NNpul(i) determined at 1056 is greater than the range of normalized pulse counts addressed by the top row of the lookup table LUT-11A, the controller 423 can use the top row at 1057, 1058 to determine the idle parameter ITmin(i).

[0081] In some implementations, the controller 423 determines the last value of the normalized pulse count NNpul(i) at 1056 and looks at the data stored in the stored lookup table LUT, and if the last value of the pulse count NNpul(i) previously resulted in determining an idle parameter ITmin(i) that previously resulted in a cold start, the controller 423 may attempt to avoid this situation in the future by assigning a smaller value to the idle parameter ITmin(i).

[0082] As described above, to account for the age of the gas discharge cell 312A and give more weight to recent data, the average change in voltage ΔVave stored in the LUT may be multiplied by a forgetting factor and then updated based on newly observed voltage changes ΔV(i).

[0083] As described above, in other implementations, the model (589) of the characteristics associated with cold starts is in the form of a radial basis function network. Similar to the above-mentioned lookup table, the prediction module 422 uses the paired data in the data stream D0 from Equation 2 to design and train the radial basis function network. After the radial basis function network is designed and trained by the prediction module 422, the controller 423 can use the trained radial basis function network to automatically update the idle parameter ITmin(i). To this end, the input and output relationship of the trained radial basis function network is as follows:

[0084] ΔV(i)=f(IT(i), NNpul(i-1)), Equation 4

[0085] Where f is the mathematical function of the trained radial basis function network. Whenever the prediction module 422 detects a new D2 data point in a single data stream, this indicates that the pattern sequence is complete and the new value of NNpul can be calculated according to Equation 2. If the voltage change ΔV(i) in Equation 4 is equal to 20V and the last value of NNpul is substituted into Equation 4, then:

[0086] 20 = f(ITmin(i), NNpul(i-1)). Equation 5

[0087] Therefore, Equation 5 can be solved to find the value of ITmin(i).

[0088] As described above, one aspect of the light source 105 associated with the idle mode MB that can be calculated is the normalized number of pulses or normalized pulse count (NNpul) of the radiation 110 from the light source 105 before entering the idle mode MB. In other implementations, instead of the normalized pulse count (NNpul), a normalized pulse count (NNpul) can be calculated at step 654 ( Figure 6 One aspect of the light source 105 associated with the idle mode MB, calculated at , is the duty cycle DC of the data cluster immediately preceding the idle time IT. Because data classified as D2 data (which is used for external production) is found at the end of each pattern, the duty cycle DC is determined for this D2 data. Therefore, in these implementations, the i-th pattern P(i) in the data stream D0 results in the following data pair (represented as a two-dimensional feature vector, as shown in Equation 2):

[0089]

[0090] And the vertical axis of the lookup table LUT may be the value of the duty cycle DC.

[0091] As described above, the control device 120 includes a component configured to automatically adjust the value of the idle parameter ITmin, thereby reducing the number of erroneously initiated cold starts and initiating a cold start when necessary, thereby increasing the availability of the light source 105, as desired by the lithographic exposure apparatus 170. In other implementations, the control device 120 may additionally or alternatively be configured to automatically adjust the value of the cold start period CSPer, which is another parameter associated with cold starts. In particular, the control device 120 may automatically adjust the value of the cold start period CSPer based on a model of one or more characteristics associated with cold starts of the light source 105. For example, as described above, one characteristic associated with cold starts is the difference or change in the value of the excitation signal 111 from the start of operation to the end of the cold start. The control device 120 may develop this model based on previous operational data of the light source 105 in a manner similar to that described above.

[0092] The implementation can be further described using the following terms.

[0093] 1. A method for controlling a light source, the method comprising:

[0094] operating the light source in an idle mode, wherein the light source does not generate any radiation;

[0095] receiving a request from a lithographic exposure apparatus to enter a production mode, the production mode comprising the light source generating radiation and supplying the radiation to the lithographic exposure apparatus;

[0096] upon entering production mode, initiating a cold start if an idle parameter is exceeded, the cold start indicating that the efficiency of the light source is below a nominal efficiency required by the lithographic exposure apparatus to expose a substrate to radiation from the light source; and

[0097] The idle parameters are automatically adjusted based on a model of characteristics associated with cold starts, the model being developed from previous operating data of the light source.

[0098] 2. The method of clause 1, further comprising developing the model of the characteristics associated with cold starts.

[0099] 3. The method of clause 2, wherein developing the model of the characteristics associated with cold starts comprises developing a lookup table.

[0100] 4. The method of clause 3, wherein developing the lookup table comprises receiving input-output data pairs from the light source and detecting patterns in the input-output data pairs that represent completion of a single exposure job at the substrate.

[0101] 5. The method of clause 3, wherein the lookup table models a relationship between one or more aspects of the light source associated with an idle mode and the characteristic indicative of a cold start.

[0102] 6. The method of clause 4, wherein the one or more aspects of the light source associated with the idle mode include an idle time and a normalized number of pulses of the radiation from the light source before entering idle mode.

[0103] 7. A method according to clause 6, wherein the idle time corresponds to the time from when the last pulse of radiation from the light source is generated until the time when the lithography exposure device requests another pulse of radiation from the light source, and the normalized number of pulses of the radiation from the light source before entering the idle mode corresponds to the normalized number of pulses of radiation from the light source during a usage window, the usage window extending until the last pulse of radiation from the light source is generated just before the idle mode starts.

[0104] 8. The method of clause 6, wherein the characteristic indicative of a cold start is a change in a value of an excitation signal provided to the light source to generate the radiation.

[0105] 9. The method of clause 8, wherein the change in the value of the excitation signal is a change in a voltage supplied to an electrode within a gas discharge cell of the light source.

[0106] 10. A method according to clause 9, wherein adjusting the idle parameter based on the developed model includes: determining a last value of a normalized number of pulses of radiation from the light source before entering the idle mode, selecting an idle time associated with the determined last value of the normalized number of pulses of radiation from the light source before entering the idle mode, and setting the idle parameter based on the selected idle time.

[0107] 11. The method of clause 10, wherein the selected idle time is based on a change in voltage supplied to the electrode that is closest to, but does not exceed, a change in voltage indicator of a cold start.

[0108] 12. The method of clause 2, wherein developing the model of the characteristics associated with cold starts comprises designing and training a radial basis function network.

[0109] 13. The method of clause 1, wherein the idle parameter is an idle time setting, and a cold start is initiated when the idle time exceeds the idle time setting.

[0110] 14. The method of clause 13, wherein adjusting the idle parameter based on the developed model comprises selecting an idle time based on the developed model, and setting the idle parameter to the selected idle time.

[0111] 15. The method of clause 14, wherein the developed model models a relationship between one or more aspects of the light source associated with an idle mode and the characteristic indicative of a cold start.

[0112] 16. The method of clause 1, wherein initiating a cold start comprises indicating to the lithographic exposure apparatus that a cold start is occurring.

[0113] 17. The method of clause 16, wherein indicating to the lithographic exposure apparatus that a cold start is occurring causes the lithographic exposure apparatus to refrain from exposing the substrate using the radiation.

[0114] 18. The method of clause 1, further comprising, after initiating the cold start, ending the cold start after a cold start period is exceeded.

[0115] 19. The method of clause 1, wherein supplying radiation from the light source to the lithographic exposure apparatus comprises exposing a substrate to radiation from the light source upon completion of a cold start or directly upon entering production mode if a cold start is not initiated.

[0116] 20. A device for controlling a light source, the device comprising:

[0117] a prediction module configured to develop a model of characteristics associated with a cold start of the light source based on previous operational data of the light source; and

[0118] A controller, in communication with the prediction module, configured to:

[0119] operating the light source in an idle mode, wherein the light source does not generate any radiation;

[0120] receiving a request from a lithographic exposure apparatus to enter a production mode, the production mode comprising the light source providing radiation to the lithographic exposure apparatus;

[0121] upon receiving a request to enter production mode, initiating a cold start if an idle parameter is exceeded, the cold start indicating that the efficiency of the light source is below a nominal efficiency required by the lithographic exposure apparatus to expose a substrate to radiation from the light source; and

[0122] The idle parameters are automatically adjusted based on the developed model.

[0123] 21. The apparatus of clause 20, wherein providing radiation from the light source to the lithographic exposure apparatus comprises exposing a substrate to radiation from the light source upon completion of a cold start or directly upon entering production mode if a cold start is not initiated.

[0124] 22. The apparatus of clause 20, wherein the prediction module comprises:

[0125] a data collection module configured to receive data related to the previous operating data of the light source; and

[0126] A data analysis module is configured to analyze the data from the data collection module, form information related to the previous operation data of the light source, and provide the information to a memory.

[0127] 23. The apparatus of clause 22, wherein the data collection module classifies the received data into one of a plurality of types of data.

[0128] 24. An apparatus according to claim 23, wherein the data analysis module is configured to analyze the data from the data collection module by: combining the multiple types of data into a single data stream; detecting type patterns in the single data stream, wherein each type pattern terminates when a single substrate job is completed; and for each type pattern, calculating one or more aspects of the light source associated with the idle mode and the characteristics indicating a cold start.

[0129] 25. The apparatus of clause 24, wherein the radiation is provided in light pulses, and the data collection module is configured to receive the data for each light pulse.

[0130] 26. The apparatus of clause 25, wherein the data analysis module is configured to receive the classified data from the data collection module in bursts.

[0131] 27. The apparatus of clause 20, further comprising a memory configured to store the developed model of the characteristics associated with the cold start,

[0132] The prediction module is configured to provide the developed model for storage in a memory, and the controller is configured to access the developed model from the memory.

[0133] 28. The apparatus of clause 20, wherein the idle parameter is an idle time setting, and a cold start is initiated when the idle time exceeds the idle time setting.

[0134] 29. The apparatus of clause 28, wherein the controller is configured to adjust the idle parameter based on the developed model by selecting an idle time based on the developed model and setting the idle parameter to the selected idle time.

[0135] 30. The apparatus of clause 29, wherein the developed model models a relationship between one or more aspects of the light source associated with an idle mode and the characteristic indicative of a cold start.

[0136] The implementations described above and other implementations are within the scope of the following claims.

Claims

1. A method for controlling a light source, the method comprising: operating the light source in an idle mode, wherein the light source does not generate any radiation; receiving a request from a lithographic exposure apparatus to enter a production mode, the production mode comprising the light source generating radiation and supplying the radiation to the lithographic exposure apparatus; upon entering production mode, initiating a cold start if an idle parameter is exceeded, the cold start indicating that the efficiency of the light source is below a nominal efficiency required by the lithographic exposure apparatus to expose the substrate to radiation from the light source; as well as The idle parameters are automatically adjusted based on a model of characteristics associated with cold starts, the model being developed from previous operating data of the light source. 2 . The method of claim 1 , further comprising developing the model of the characteristics associated with cold starts, wherein developing the model of the characteristics associated with cold starts comprises developing a lookup table.

3. The method of claim 2, wherein developing the lookup table comprises: Input-output data pairs are received from the light source, and patterns in the input-output data pairs are detected, the patterns representing completion of a single exposure job at the substrate.

4. The method of claim 2 , wherein the lookup table models a relationship between one or more aspects of the light source associated with an idle mode and the characteristic indicative of a cold start, and wherein the one or more aspects of the light source associated with the idle mode comprise: The idle time and the normalized number of pulses of said radiation from said light source before entering idle mode.

5. A method according to claim 4, wherein the idle time corresponds to the time from when a last pulse of radiation from the light source is generated until the time when the lithographic exposure device requests another pulse of radiation from the light source, and the normalized number of pulses of the radiation from the light source before entering the idle mode corresponds to the normalized number of pulses of radiation from the light source during a usage window, the usage window extending until the last pulse of radiation from the light source is generated just before the idle mode begins.

6. A method according to claim 4, wherein the characteristic indicative of a cold start is a change in the value of an excitation signal provided to the light source to generate the radiation, and wherein the change in the value of the excitation signal is a change in the voltage supplied to an electrode within a gas discharge chamber of the light source.

7. The method of claim 1, further comprising developing the model of the characteristics associated with cold starts, wherein developing the model of the characteristics associated with cold starts comprises designing and training a radial basis function network. 8 . The method of claim 1 , wherein the idle parameter is an idle time setting, and a cold start is initiated when the idle time exceeds the idle time setting.

9. The method of claim 8, wherein adjusting the idle parameter based on the developed model comprises selecting an idle time based on the developed model and setting the idle parameter to the selected idle time.

10. The method of claim 1, wherein initiating a cold start comprises indicating to the lithographic exposure apparatus that a cold start is occurring, and wherein indicating to the lithographic exposure apparatus that a cold start is occurring causes the lithographic exposure apparatus to refrain from exposing the substrate using the radiation. The method of claim 1 , further comprising, after initiating the cold start, ending the cold start after a cold start period is exceeded.

12. The method of claim 1 , wherein supplying radiation from the light source to the lithographic exposure apparatus comprises: Upon completion of the cold start, or directly upon entering production mode if a cold start was not initiated, the substrate is exposed to radiation from the light source.

13. A device for controlling a light source, the device comprising: a prediction module configured to develop a model of characteristics associated with a cold start of the light source based on previous operational data of the light source; as well as a controller in communication with the prediction module, the controller being configured to: operating the light source in an idle mode, wherein the light source does not generate any radiation; receiving a request from a lithographic exposure apparatus to enter a production mode, the production mode comprising the light source providing radiation to the lithographic exposure apparatus; upon receiving a request to enter production mode, initiating a cold start if an idle parameter is exceeded, the cold start indicating that an efficiency of the light source is below a nominal efficiency required by the lithographic exposure apparatus to expose a substrate to radiation from the light source; as well as The idle parameters are automatically adjusted based on the developed model.

14. The apparatus of claim 13 , wherein providing radiation from the light source to the lithographic exposure apparatus comprises: Upon completion of the cold start, or directly upon entering production mode if a cold start was not initiated, the substrate is exposed to radiation from the light source.

15. The apparatus according to claim 13, wherein the prediction module comprises: a data collection module configured to receive data related to the previous operating data of the light source; as well as A data analysis module is configured to analyze the data from the data collection module, form information related to the previous operation data of the light source, and provide the information to a memory.

16. An apparatus according to claim 15, wherein the data collection module classifies the received data into one type of data among multiple types of data, wherein the data analysis module is configured to analyze the data from the data collection module by: combining the multiple types of data into a single data stream; detecting type patterns in the single data stream, wherein each type pattern terminates when a single substrate job is completed; and for each type pattern, calculating one or more aspects of the light source associated with the idle mode and the characteristics indicating a cold start.

17. The apparatus of claim 16, wherein the radiation is provided in pulses of light, and the data collection module is configured to receive the data for each pulse of light, and wherein the data analysis module is configured to receive the classified data from the data collection module in clusters of pulses.

18. The apparatus of claim 13, further comprising a memory configured to store the developed model of the characteristics associated with the cold start, The prediction module is configured to provide the developed model for storage in a memory, and the controller is configured to access the developed model from the memory.

19. The apparatus of claim 13, wherein the idle parameter is an idle time setting, and a cold start is initiated when the idle time exceeds the idle time setting.

20. The apparatus of claim 19, wherein the controller is configured to adjust the idle parameter based on the developed model by selecting an idle time based on the developed model and setting the idle parameter to the selected idle time.

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