Cold start adjustment in light source

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 radiation; receiving a request from a photolithography exposure apparatus to enter a production mode, the production mode including the light source generating radiation and providing the radiation to the photolithography exposure apparatus; upon receiving the request to enter the production mode, initiating a cold start if idle parameters are exceeded, the cold start indicating that the efficiency of the light source is lower than the nominal efficiency required by the photolithography exposure apparatus to expose a substrate to radiation from the light source; and automatically adjusting the idle parameters based on a model of characteristics related to the cold start, the model being constructed from previous operating data of the light source.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to U.S. Application No. 63 / 434,237, filed December 21, 2022, entitled "COLD START CONDITIONING IN A LIGHT SOURCE," which is incorporated herein by reference in its entirety.

[0002] The disclosed subject matter relates to an apparatus for a light source, such as a deep ultraviolet light source. [Background technology]

[0003] Photolithography is a process by which semiconductor circuits are formed or designed on a substrate, such as a silicon wafer. An optical source generates deep ultraviolet (DUV) light or radiation that is used to expose photoresist on the wafer. DUV light can include wavelengths, for example, from about 100 nanometers (nm) to about 400 nm. Often, the optical 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 projection optics, which project the beam through a mask onto the photoresist. The photoresist and wafer are then etched and cleaned, and the photolithography process is then repeated as necessary. Summary of the Invention

[0004] In some general aspects, a method is implemented for controlling a light source, the method including: operating a light source in an idle mode in which the light source does not generate radiation; receiving a request from a photolithography exposure apparatus to enter a production mode, the production mode including the light source generating radiation and providing the radiation to the photolithography 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 photolithography exposure apparatus to expose a substrate to radiation from the light source; and automatically adjusting the idle parameter based on a model of characteristics related to the cold start, the model constructed from previous operating data of the light source.

[0005]

[0005] Implementations may include one or more of the following aspects. For example, the method may further include constructing a model of a characteristic associated with a cold start. The model of the characteristic associated with a cold start may be constructed by constructing a lookup table. The lookup table may be constructed by receiving input-output data pairs from the light source and detecting a pattern within the input-output data pairs, where such pattern signifies the completion of a single exposure job on a substrate. The lookup table may model a relationship between one or more aspects of the light source associated with an idle mode and a characteristic 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 a time from when the last pulse of radiation from the light source was generated to a time when the photolithography 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 a normalized number of pulses of radiation from the light source during a period of use extending from when the last pulse of radiation from the light source was generated to when the last pulse of radiation from the light source was generated immediately before the idle mode began. 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 may be a change in voltage supplied to electrodes in a gas discharge chamber of the light source. The idle parameter may be adjusted based on the constructed model by determining the last value of the normalized pulse number of radiation from the light source before entering an idle mode, selecting an idle time related to the determined last value of the normalized pulse number 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 may be based on a change in the voltage supplied to the electrodes that is closest to, but does not exceed, the change in the cold start voltage indicator.

[0006]

[0006] A model of the characteristics associated with cold start can be constructed by designing and training a radial basis function network.

[0007] 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 idle parameter may be adjusted based on the constructed model by selecting an idle time based on the constructed model and setting the idle parameter to be the selected idle time. The constructed 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.

[0008]

[0008] The cold start may be initiated by instructing the photolithography exposure apparatus that a cold start is occurring. The photolithography exposure apparatus being instructed that a cold start is occurring may cause the photolithography exposure apparatus to avoid using radiation to expose a substrate. The method may further include, after initiating the cold start, terminating the cold start after exceeding the cold start duration. Radiation from the light source may be provided to the photolithography exposure apparatus by exposing a substrate to radiation from the light source upon completion of the cold start, or immediately after entering a production mode if a cold start is not initiated.

[0009] In another general aspect, an apparatus for controlling a light source includes a prediction module configured to build a model of characteristics associated with a cold start of the light source from previous operating 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 radiation, where the generation mode includes the light source providing radiation to a photolithography exposure apparatus, to receive a request to enter the generation mode from the photolithography exposure apparatus, where upon receiving the request to enter the generation mode, the cold start indicates that the efficiency of the light source is lower than a nominal efficiency required by the photolithography exposure apparatus to expose a substrate to radiation from the light source, to initiate a cold start if an idle parameter is exceeded, and to automatically adjust the idle parameter based on the built model.

[0010] Implementations may include one or more of the following features: For example, radiation from a light source provided to a photolithography exposure apparatus may be used to expose a substrate to radiation from the light source upon completion of a cold start, or immediately after entering a production mode if a cold start is not initiated.

[0011] The prediction module may include a data collection module configured to receive data related to previous operational data of the light source, and a data analysis module configured to analyze the data from the data collection module to form information related to the previous operational data of the light source and provide the information to a memory. The data collection module may classify the received data into one of multiple types of data. The data analysis module may be 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 within the single data stream, each type pattern terminating upon completion of a single substrate job, and calculating, for each type pattern, one or more aspects of the light source associated with idle mode and characteristics indicative of a cold start. The radiation may be provided in pulses of light, and the data collection module may be configured to receive data for each pulse of light. The data analysis module may be configured to receive the classified data from the data collection module in clusters of pulses.

[0012]

[0012] The apparatus may further include a memory configured to store a constructed model of characteristics related to cold starts. The prediction module may be configured to provide the constructed model to be stored in the memory, and the controller may be configured to access the constructed model from the memory.

[0013] 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 constructed model by selecting the idle time based on the constructed model and setting the idle parameter to be the selected idle time. The constructed model may model a relationship between one or more aspects of the light source associated with an idle mode and a characteristic indicative of a cold start. [Brief explanation of the drawings]

[0014] [Figures 1A-1C]

[0014] FIG. 1 is a block diagram of a photolithography system including a light source, a controller, and a photolithography exposure apparatus at different times. [Figure 2]

[0015] FIG. 2 is a block diagram of one implementation of the photolithography system of FIGS. 1A-1C. [Figure 3]

[0016] FIG. 2 is a block diagram of one implementation of the photolithography system of FIGS. 1A-1C. [Figure 4]

[0017] FIG. 4 is a block diagram of one implementation of the control device of FIGS. 1A-1C, 2, or 3. [Figure 5]

[0018] 1A to 1C, 2, 3, or 4 to control a light source, including adjusting idle parameters associated with an idle mode based on a model of a cold start. [Figure 6]

[0019] 1A-1C, 2, 3, or 4 to build a model of a cold start. [Figure 7A]

[0020] 1 is a graph of the maximum amplitude of the voltage signal provided to the excitation mechanism of the light source as a function of time for previous operating data of the light source. [Figure 7B]

[0021] 7B is the graph of FIG. 7A showing how the controller detects patterns in previous operating data. [Figure 8]

[0022] 7C is a graph of the distribution of data pairs extracted from patterns in the previous operating data of FIGS. 7A and 7B, the graph being of normalized pulse count of radiation from the light source versus idle time between patterns. [Figure 9]

[0023] 7 is a graph of a lookup table constructed from data pairs extracted using the procedure of FIG. 6 that can be used as a model for cold start. [Figure 10]

[0024] 1A to 1C, 2, 3, or 4 to adjust idle parameters based on a model of cold start constructed according to the procedure of FIG. 6. [Figure 11A]

[0025] 11 is a graph of a lookup table that may be used by a controller to adjust idle parameters using the flowchart of FIG. 10. [Figure 11B]

[0026] 11 is a graph of a lookup table that may be used by a controller to adjust idle parameters using the flowchart of FIG. 10. DETAILED DESCRIPTION OF THE INVENTION

[0015]

[0027] 1A-1C each show a block diagram of photolithography system 100 at a different time. Photolithography system 100 includes light source 105, controller 120, and photolithography exposure apparatus 170. Controller 120 communicates with light source 105 via data connection 125 and with photolithography exposure apparatus 170 via data connection 126 to control the operation of light source 105. FIG. 1A shows the operation of photolithography system 100 and light source 105 in production mode MA at time t equal to t1. FIG. 1B shows the operation of photolithography system 100 and light source 105 in idle mode MB at time t equal to t2. And FIG. 1C shows the operation of photolithography system 100 and light source 105 in production mode MA at time t equal to 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. Three time periods are shown for illustrative purposes only. Photolithography system 100 may operate for more than three time periods.

[0016]

[0028] In generation mode MA, light source 105 generates radiation 110 (e.g., a pulsed light beam) that is directed to photolithography exposure apparatus 170 (e.g., via one or more optical elements 115). Sometimes, as shown in FIG. 1A, photolithography exposure apparatus 170 uses this radiation 110 to expose substrate 171. Sometimes, as shown in FIG. 1C, photolithography exposure apparatus 170 does not use this radiation 110 to expose substrate 171 because light source 105 has notified photolithography exposure apparatus 170 (via data connection 126) that the radiation 110 is of poor quality. In this situation, light source 105 generates radiation 110, but the radiation 110 does not have the properties required by photolithography exposure apparatus 170 to expose substrate 171. For example, the situation shown in FIG. 1C may occur when light source 105 is operating in a cold start. During a cold start, the light source 105 is operating at a lower efficiency (e.g., energy efficiency) than the nominal efficiency required by the photolithography exposure tool 170 to expose the substrate 171. During a cold start, the photolithography exposure tool 170 is indicated by the light source 105 that the radiation 110 is of poor quality. The photolithography exposure tool 170 can then make appropriate adjustments so that the radiation 110 generated by the light source 105 during the cold start is not used to expose the substrate 171.

[0017]

[0029] In idle mode MB, the light source 105 does not generate radiation 110, and thus no radiation 110 is directed to the photolithography exposure tool 170 (e.g., via one or more optical elements 115). For example, during idle mode MB, there is a pause in the generation of radiation 110. In idle mode MB, the light source 105 may be de-energized or turned off, or may be powered on and not generating any radiation 110.

[0018]

[0030] Generally, the light source 105 generates radiation 110 under command from an excitation signal 111 during generation mode MA. The excitation signal 111 may be generated by the controller 120 (and transmitted over data connection 125), by another control system not shown in FIGS. 1A-1C, or by a separate device, such as a voltage or current source, controlled by the controller 120 or another control system. The excitation signal 111 is any type of signal sufficient to cause the light source 105 to generate radiation 110 (a pulsed light beam). For example, the excitation signal 111 may be a signal applied to an excitation mechanism within the light source 105 (e.g., electrodes 306A1 and 306A2 in FIG. 3 ). The radiation 110 may be a pulsed or continuous wave light beam, or the light beam may be a laser beam. The light source 105 may 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 bursts of pulses of the light beam during the generation mode MA. The bursts of pulses may include hundreds or thousands of pulses of light. The excitation signal 111 is applied to the light source 105 or components of the light source 105 when the light source is in the generation mode MA. On the other hand, the excitation signal 111 is not applied to the light source 105 (or to any components of the light source 105) during the idle mode MB.

[0019]

[0031] A cold start is initiated by the light source 105 after the light source 105 and photolithography system 100 have operated in idle mode MB for a certain duration. Specifically, a cold start is initiated when the light source 105 receives a request from the photolithography exposure tool 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 may occur when the light source 105 is “warming up.” The efficiency of the light source 105 falls below the nominal efficiency whenever the light source 105 and photolithography system 100 operate in idle mode MB for a duration that exceeds a minimum duration. Therefore, the light source 105 must warm up before its efficiency is suitable for production mode MA. For example, the minimum duration may be on the order of a few seconds, e.g., 1 second, 2 seconds, or even 10 seconds. In other examples, the minimum duration may be on the order of several minutes, such as 1 minute, 5 minutes, or 10 minutes. In yet another example, the minimum duration may be longer than 10 minutes. The amount of efficiency loss that occurs during idle mode MB may vary depending on the age of the light source 105 and the total time the light source 105 operates in idle mode MB (such time corresponds to idle time). To restore the light source 105 to its nominal efficiency from its inefficient operation during idle mode MB when the light source 105 is ready to enter the generation mode MA, the light source 105 may operate in a cold start to generate enough pulses of the light beam 110 to effectively warm up the light source 105. For example, during a cold start, the light source 105 may generate thousands (e.g., 10,000) of pulses of the light beam 110 before the efficiency of the light source 105 reaches its nominal efficiency. During a cold start, the value of the excitation signal 111 is increased to compensate for the loss in energy efficiency of the light beam 110. Once the energy efficiency is restored to a level above the nominal efficiency required to process the substrate 171, the value of the excitation signal 111 can be lowered or reduced.As will be described below, this difference in the value of excitation signal 111 from the beginning of cold start operation to the end of cold start is a characteristic that can be used by controller 120 to detect when a cold start is occurring.

[0020]

[0032] Operating the light source 105 with a cold start has advantages. Specifically, by operating the light source 105 with a cold start until its efficiency reaches its nominal efficiency, errors, unscheduled downtime, and expensive reprocessing or scrapping of substrates 171 can be reduced or avoided because the photolithography exposure tool 170 does not use poor quality radiation 110 to expose the substrate 171. A cold start allows the light source 105 to effectively "warm up" and prevents the photolithography exposure tool 170 from using substandard radiation 110 during this warm-up period.

[0021]

[0033] As described above, a cold start is initiated by light source 105 after light source 105 receives a request from photolithography exposure tool 170 to enter production mode MA and when light source 105 has been operating in idle mode MB for a duration (idle time) that exceeds idle parameter ITmin. Idle parameter ITmin is a parameter associated with light source 105. Idle parameter ITmin may correspond to the minimum duration described above. Light source 105 and photolithography system 100 may also operate in cold start for a cold start period CSPer.

[0022]

[0034] Instead of simply assigning a fixed value to the idle parameter ITmin (the parameter that controls the initiation of a cold start), controller 120 includes a component configured to automatically adjust the value of the idle parameter ITmin, thereby reducing the number of falsely initiated cold starts, initiating cold starts when necessary, and thus increasing the availability of light source 105 as desired for photolithography exposure apparatus 170. In particular, controller 120 can automatically adjust the value of idle parameter ITmin based on a model of one or more characteristics related to cold starts of light source 105. For example, as described above, one characteristic related to cold starts is the difference or change in the value of excitation signal 111 from the beginning of cold start operation to the end of cold start. Controller 120 can build the model from previous operating data of light source 105.

[0023]

[0035] 2, an implementation 200 of photolithography system 100 is shown that includes an implementation 205 of light source 105 and an implementation 220 of controller 120. Controller 220 includes memory 221, a prediction module 222 configured to access memory 221, a controller 223 configured to access memory 221 and communicate with prediction module 222, and an input / output interface 224. A data connection 225 enables communication between controller 220 and light source 205, and a data connection 226 enables communication between controller 220 and photolithography exposure apparatus 170.

[0024]

[0036] The prediction module 222 may include one or more processors, such as a general-purpose or special-purpose microprocessor, or any one or more processors of any type of digital computer. These processors execute instructions, access data stored in the memory 221, and may also write data to the memory 221. Similarly, the controller 223 may include one or more processors, such as a general-purpose or special-purpose microprocessor, or any one or more processors of any type of digital computer. These processors execute instructions, access data stored in the memory 221, and may also write 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 portions or components. The memory 221 may store data and information used in the operation of the controller 220. For example, the memory 221 stores information related to previous operating data of the light source 205.

[0025]

[0037] The input / output interface 224 enables the controller 220 to exchange data and signals with an operator, the light source 205, the photolithography 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 hardware and / or software subsystems of the light source 205 via a data connection 225. For example, the light source 205 may provide the controller 220 with information related to idle time and / or other information about the light source 205 through the input / output interface 224. In some implementations, the input / output interface 224 receives instructions or commands from the photolithography exposure apparatus 170 and / or from hardware and / or software subsystems of the photolithography exposure apparatus 170 via a data connection 226. The input / output interface 224 may include one or more of a visual display device, a keyboard, and a communication interface, such as a universal serial bus (USB) connection and / or any type of network interface, such as Ethernet. The input / output interface 224 may also allow communication without physical contact, for example through an IEEE 802.11, Bluetooth, or near field communication (NFC) connection.

[0026]

[0038] Each data connection 225, 226 may be a physical cable or other physical data conduit (such as a cable that supports the transmission of data according to IEEE 802.3), a wireless data connection (such as a data connection that provides data via IEEE 802.11 or Bluetooth), or a combination of wired and wireless data connections. Data provided over data connection 225 or 226 may be transmitted via any type of protocol or format.

[0027]

[0039] The light source 205 includes a pumping mechanism 206 and a gain medium 207. To generate radiation 110 (as in generation mode MA of FIG. 1A or 1C ), a pumping signal 111 is applied to the light source 205 to pump the pumping mechanism 206. The pumping mechanism 206 pumps the gain medium 207 in response to the pumping 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 may be a gas, a crystal, a glass, a semiconductor, or a liquid. The pumping mechanism 206 is any mechanism capable of pumping the gain medium 207. For example, the pumping mechanism 206 may be a plurality of electrodes that pump the gaseous gain medium 207. The pumping signal 111 may 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 source or a current source) to generate an electrical signal that is provided to the pumping mechanism 206. The excitation signal 111 may be a time-varying direct current (DC) or alternating current (AC) electrical signal, such as a sinusoidal voltage signal or a square wave voltage signal, or a combination of these signals. Properties of the excitation signal 111 that are important and adjustable 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 property related to the time-varying signal.

[0028]

[0040] 2, controller 220 is shown as separate from light source 205 and connected via data connection 225. However, in some implementations, controller 220 is implemented as part of light source 205, such that light source 205 and controller 220 are part of a single integrated package (e.g., enclosed within the same housing). In these implementations, data connection 225 may be a data path that enables communication between software modules, one of which implements aspects of controller 220 and other of which implement other functionality of light source 205. Controller 220 (and specifically, prediction module 222 and controller 223) may monitor characteristics of excitation signal 111.

[0029]

[0041] 3 , an implementation 305 of light source 105 or 205 is shown as part of a photolithography system 300. Photolithography system 300 includes an implementation 370 of photolithography exposure apparatus 170. Light source 305 generates radiation 310 that is provided to photolithography exposure apparatus 370 during a generation mode MA. Light source 305 may be, for example, an excimer light source that outputs a pulsed light (or laser) beam as radiation 310. As pulsed light beam 310 enters photolithography exposure apparatus 370, it is directed through projection optics 372 and projected onto substrate 371 to form one or more microelectronic features in photoresist on substrate 371.

[0030]

[0042] Photolithography system 300 includes a control system 319, which may include controller 120 / 220 and other components and modules.

[0031]

[0043] Light source 305 is a two-stage laser system that includes a master oscillator stage 308A that provides a seed light beam 309 to a power amplifier stage 308B. Master oscillator stage 308A and power amplifier stage 308B may be considered subsystems of light source 305, or may be considered systems that are part of light source 305. Power amplifier stage 308B receives seed light beam 309 from main oscillator stage 308A and amplifies the seed light beam 309 to generate a light beam 310 for use in a photolithography exposure tool 370. For example, main oscillator stage 308A may emit a pulsed seed light beam 309 having a pulse energy of approximately 1 millijoule (mJ) per pulse, and these pulses may be amplified by power amplifier stage 308B to approximately 10-20 mJ. Master oscillator stage 308A includes a gas discharge chamber 312A with two elongated electrodes 306A1 and 306A2, a gain medium 307A that is a gas mixture, and a blower for circulating the gas between electrodes 306A1 and 306A2 in discharge chamber 312A. A resonator is formed between an optical module 313A (e.g., a spectral feature selection module) on one side of discharge chamber 312A and an output coupler 314A on the second side of discharge chamber 312A. Spectral feature selection module 313A is configured to fine-tune the spectral output of seed light beam 309. Beam combining optics 318 are positioned to modify the size, shape, and / or direction of seed light beam 309 as needed for use by power amplifier stage 308B. Power amplifier stage 308B includes beam combining optics 316 that receive seed light beam 309 and direct it through gas discharge chamber 312B to beam folding optics 313B, which modify or change the direction of the seed light beam so that it is transmitted back into gas discharge chamber 312B. Gas discharge chamber 312B includes a pair of elongated electrodes 306B1 and 306B2, a gain medium 307B that is a gas mixture, and a blower for circulating the gas between electrodes 306B1,2 in discharge chamber 312B.

[0032]

[0044] The gas mixture used in the gas discharge chambers 312A and 312B can be any gas suitable for generating a light beam of the wavelength and bandwidth required for the application. In the case of an excimer light source, the gas mixture may contain a noble gas, such as argon or krypton, a halogen, such as fluorine or chlorine, and a small amount of xenon, excluding helium and / or neon, as a buffer gas. 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 with short (e.g., on the order of 1 nanosecond) current pulses in a high-voltage discharge by applying a voltage (excitation signal 311A, 311B) to the respective elongated electrodes 306A1, 306A2, 306B1, and 306B2.

[0033]

[0045] The one or more optical elements 315 are configured to redirect the light beam 310 to the photolithography exposure apparatus 170. The light source 305 may further include one or more metrology modules 317 that measure aspects of the light source 305, the seed light beam 309, and / or the light beam 310. For example, the metrology module 317 may include a light beam analysis module configured to measure various parameters of the light beam 310 (such as bandwidth, wavelength, energy, etc.). The light beam analysis module may be implemented within the set of optical elements 315. As another example, the metrology module 317 may include a line center analysis module that receives the seed light beam 309 from the output coupler 314A and measures or monitors the wavelength of the seed light beam 309. The line center analysis module may be positioned along a path between the output coupler 314A and the beam combining optics 316, or may be located at the output of the light source 305 or within the set of optical elements 315. As another example, metrology module 317 may include a metrology module that tracks one or more parameters related to previous operation of light source 305, which one or more parameters may be provided to control system 319 to constitute the above-mentioned "previous operating data," and controller 120 within control system 319 may then use this previous operating data to construct a model of light source 305. The model relates to one or more characteristics related to a cold start of light source 305.

[0034]

[0046] The light beam 310 is a pulsed light beam and may include one or more bursts of pulses that are temporally distinct from one another. Each burst may include one or more pulses of light. In some implementations, a burst may include hundreds of pulses, e.g., one burst may include 100-400 pulses of the light beam 310. When the gain medium 307A is pumped by applying a voltage 311A ​​to the electrodes 306A1 and 306A2, the gain medium 307A emits light. When the voltage 311A ​​is applied to the electrodes 306A1 and 306A2 in pulses, the light emitted from the gain medium 307A is also pulsed. The repetition rate of the pulsed light beams 309 and 310 may be determined by the rate at which the voltage 311A ​​is applied to the electrodes 306A1 and 306A2, with each application of the voltage 311A ​​producing a pulse of light. Pulses of light generated in gas discharge chamber 312A propagate through gain medium 307A and exit chamber 312A through output coupler 314A. Thus, a train of pulses is created by periodically repeating application of voltage 311A ​​to electrodes 306A1 and 306A2. The repetition rate of the pulses can range from approximately 500 Hertz (Hz) to 6000 Hz. In some implementations, the repetition rate can be greater than 6000 Hz, for example, tens of thousands of Hz, such as 12,000 Hz or more.

[0035]

[0047] Signals from control system 319 can also be used to control electrodes 306A1, 306A2, 306B1, and 306B2 in master oscillator stage 308A and power amplifier stage 308B, respectively. In this manner, control system 319 can control the pulse energy of each of master oscillator stage 308A and power amplifier stage 308B, and thus the energy of light beam 310. There may 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 properties of light beam 310, such as the bandwidth or coherence of light beam 310. Light beam 310 can have an average output power of tens of watts (W), for example, in a range from about 50 W to about 130 W.

[0036]

[0048] 4, an implementation 420 of controller 120 / 220 is shown for light source 105. Controller 420 includes memory 421 (an implementation of memory 221), a prediction module 422 (an implementation of prediction module 222), a controller 423 (an implementation of controller 223), and an input / output interface 424 (an implementation of input / output interface 224). Data from light source 105 travels over data connection 225 to prediction module 422 via input / output interface 424. Data from controller 423 may also travel over data connection 225 to light source 105 via input / output interface 424. Prediction module 422 includes a data collection module 427 and a data analysis module 428. The data collection module 427 and the data analysis module 428 may each have access to or include one or more processors of the prediction module 422 to execute instructions, access data, and write data to memory 421.

[0037]

[0049] The data collection module 427 is configured to receive data (previous operational data) from the light source 105 via the input / output interface 424. The data collection module 427 is further configured to classify the received data into one of a number of types of data. In this example, there are three data classifications, which are labeled D1, D2, and D3. However, in other implementations, there may be more than three or only two data classifications.

[0038]

[0050] Examples of data types are described below. As described above, in generation mode MA, light source 105 generates radiation 110, which may be in the form of a pulsed light beam. Data received from light source 105 may be provided for each pulse of light beam 110, and thus, this data is received as a stream of data at the rate at which the pulses of light beam 110 are generated. In some implementations, previous operational data received by data collection module 427 may include one or more properties related to excitation signal 111 (or 311A). For example, data collection module 427 may receive the time T at which each pulse of light beam 110 is generated. Time T may be determined by the time at which excitation signal 111 is provided to excitation mechanism 206 of light source 105. If excitation signal 111 is a time-varying signal, such as a sinusoidal voltage signal, data collection module 427 may receive the time T at which the voltage signal reaches its maximum value. Time T may have a range or width; that is, pulses may be generated over a 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 the frequency of the time-varying signal, the duty cycle of the time-varying signal, the number of pulses (or normalized number of pulses) of the excitation signal 111, and / or any other property related to the time-varying signal.

[0039]

[0051] Additionally, the photolithography exposure apparatus 170 may use pulses of the light beam 110 for different purposes. For example, often at the start of generation mode MA or immediately prior to the start of exposure of the substrate 171, the photolithography exposure apparatus 170 may use pulses of the light beam 110 to perform internal calibration, and data related to 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 photolithography exposure apparatus 170 may use some pulses of the light beam 110 for internal generation not related to calibration, and data related to such pulses is classified as D3 data. During this internal generation, pulses of the light beam 110 are not provided to the substrate 171. As another example, the photolithography exposure apparatus 170 may use some pulses of the light beam 110 for external generation, and data related to such pulses is classified as D2 data. During external generation, pulses of the light beam 110 are provided to the substrate 171.

[0040]

[0052] The data analysis module 428 is configured to analyze the classified data (D1, D2, D3) output from the data collection module 427. Based on the classified data (D1, D2, D3), the data analysis module 428 is configured to generate or construct information I related to previous operational data of the light source 105, which information I is provided to and stored in the memory 421. The data analysis module 428 will now be described in more detail. In some implementations, the data analysis module 428 includes a set of sub-modules 429, 430, and 431, each performing one or more specific tasks. The sub-module 429 may be referred to as a synthesis module, the sub-module 430 may be referred to as a pattern module, and the sub-module 431 may be referred to as an extraction module. Although the sub-modules 429, 430, and 431 are shown as separate boxes, functionality between the sub-modules 429, 430, and 431 may be shared or implemented by a single module, such as the data analysis module 428.

[0041]

[0053] Referring to FIG. 5, procedure 580 is performed by controller 120, 420 for controlling light source 105 (which may be light source 205 or 305). In describing procedure 580, reference will be made to FIGS. 1A-1C and 4. Procedure 580 is divided into sub-procedures 580A, 580B, and 580C, which are performed in parallel or in conjunction with one another. Procedure 580A includes operating light source 105 in an idle mode MB (581), in which light source 105 does not generate radiation 110. For example, in idle mode MB, excitation signal 111 is not provided to light source 105. As described above, in idle mode MB, light source 105 does not generate radiation 110, and thus, no radiation 110 is directed to photolithography exposure apparatus 170, as shown in FIG. 1B.

[0042]

[0054] The light source 105 remains in idle mode MB until or unless a request to enter production mode MA is received (582). The light source 105 receives a request to enter production mode MA from the photolithography exposure tool 170 via the data connection 126. If a request to enter production mode MA is received in 582, the light source 105 begins production mode MA (583). For example, in production mode MA, an excitation signal 111 (which may be generated by the controller 120) is provided to the light source 105. As described above, in production mode MA, the light source 105 generates radiation 110 that is directed to the photolithography exposure tool 170, as shown in FIG. 1A or 1C. If a request to enter production mode MA is not received in 582, the light source 105 continues operating 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 photolithography exposure tool 170 via the data connection 126. If the request to end production mode MA is received at 584, the light source 105 ends production mode MA and operates in idle mode (581).

[0043]

[0055] Upon entering production mode MA at 583, procedure 580B is performed. In practice, upon receiving a request to enter production mode at 582, controller 120 immediately queries procedure 580B. Procedure 580B first queries (585) whether an idle parameter has been exceeded; if the idle parameter has not been exceeded at 585, production mode MA begins (583) and cold start is not initiated. On the other hand, if controller 120 determines (585) that the idle parameter has been exceeded, production mode MA begins (583), but cold start is initiated (586). As described above, the idle parameter ITmin is a parameter associated with light source 105. The idle parameter ITmin may correspond to an idle time setting, such as a minimum duration. Thus, cold start may be initiated when the idle time exceeds this idle time setting or the minimum duration ITmin. As described above, light source 105 receives (582) a request from photolithography exposure tool 170 to enter production mode MA, but initiates a cold start when light source 105 determines that its efficiency is lower than the nominal efficiency required by photolithography exposure tool 170 to expose substrate 171 to radiation 110. In this case, the properties of radiation 110 are not up to the standard required by photolithography exposure tool 170. In cold start (586), light source 105 generates radiation 110 and also notifies photolithography exposure tool 170 via data connection 126 about the sub-standard properties of radiation 110. Light source 105 may specifically indicate to photolithography exposure tool 170 that a cold start is occurring.

[0044]

[0056] Controller 120 further queries whether the cold start period CSPer has passed (587). If the cold start period CSPer has passed at 587, controller 120 terminates the cold start and notifies the photolithography exposure tool 170 that the properties of radiation 110 are within the standards required by photolithography exposure tool 170 to expose substrate 171 to radiation 110 (588).

[0045]

[0057] Procedure 580 includes subprocedure 580C, which is performed automatically and periodically during subprocedure 580A. For example, an instance of subprocedure 580C may be performed at a regular frequency, such as every second, every minute, or every 10 minutes. Subprocedure 580C includes automatically adjusting (589) idle parameters based on a model of characteristics related to cold start. For example, the idle parameters may be adjusted in 589 by selecting an idle time based on a model of characteristics related to cold start and setting the idle parameters to be the selected idle time.

[0046]

[0058] A model of the characteristics is built from previous operating data of the light source 105. The idle parameters control whether a cold start is initiated. By automatically adjusting the idle parameters, the controller 120 can better know when or if a cold start will occur after the photolithography exposure tool 170 sends a request for radiation 110 over the data connection 126. Thus, if the idle parameters are decreased at 589, the bar for initiating a cold start at 585 will be lowered, and the light source 105 will be more likely to notify the photolithography exposure tool 170 that a cold start is occurring (when the cold start is initiated) at 586, and the photolithography exposure tool 170 will refrain from using radiation 110 to expose the substrate 171 when production mode MA is initiated at 583. On the other hand, if the idle parameter is increased at 589, the bar for initiating a cold start at 585 will be higher, the light source 105 will be less likely to notify the photolithography exposure tool 170 that a cold start is occurring, and the photolithography exposure tool 170 will be able to expose the substrate 171 using radiation 110 shortly after the start of production mode MA at 583. By adjusting the value of the idle parameter at 589, the controller 120 will be less likely to initiate a cold start at 586 when one is not needed, and less likely to miss the initiation of a cold start 586 when one is actually needed.

[0047]

[0059] In some implementations, the model of cold start-related characteristics (589) can be in the form of a look-up table. In other implementations, the model of cold start-related characteristics (589) is in the form of a radial basis function network. In either case, the model of cold start-related characteristics (589) models the relationship between one or more aspects of the light source 105 associated with idle mode MB and characteristics indicative of a cold start. For example, the one or more aspects of the light source 105 associated with idle mode MB can include idle time and a normalized number (or duty cycle) of pulses of radiation 110 from the light source 105 before entering idle mode MB. The idle time corresponds to the time when the last pulse of radiation 110 from the light source 105 was generated (during the generation mode at 583) to the time when the photolithography exposure apparatus 170 requests another pulse of radiation 110 from the light source 105 at 582. The normalized number of pulses of radiation from light source 105 before entering idle mode MB at 581 corresponds to the normalized number of pulses of radiation 110 from light source 105 during a period of use (which may be given in hours or pulses) extending until the last pulse of radiation 110 from light source 105 is generated just before idle mode MB begins at 581. One characteristic indicative of a cold start is a change in the value of excitation signal 111 provided to light source 105 to generate radiation 110. For example, with reference to FIG. 3 , the change in the value of excitation signal 111 may be a change in voltage 311A ​​supplied to electrodes 306A1,2 in gas discharge chamber 312A of light source 305.

[0048]

[0060] 6, procedure 650 may be performed to build a model of characteristics related to cold start, and such model is used to adjust idle parameters at 589. Generally, controller 120 builds the model used at 589 based on historical data of light source 105 collected by controller 120. In discussing procedure 650, reference will also be made to FIG. 4 and FIGS. 7A and 7B.

[0049]

[0061] Procedure 650 includes receiving 651 data relating to previous operational data of light source 105. For example, with reference to Figure 4, data collection module 427 is configured to receive the previous operational data via data connection 225 and input / output interface 424. The previous operational data may be provided by metrology module 317 (Figure 3).

[0050]

[0062] Procedure 650 includes classifying (652) each received datum into one of multiple types of data. For example, referring to FIG. 4 and as described above, the data collection module 427 is configured to classify each datum 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. This single data stream D0 includes each datum as well as its associated classification as a function of the use of the light source 105 within the stream D0. In the example provided, each datum is given by the time T at which a pulse of the light beam 110 is generated (the time after which the excitation signal 111 is transmitted 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. Referring also to FIG. 7A, a period of the 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 as a function of time T for each pulse in light beam 110. The classification (D1, D2, or D3) of each data point in graph 740 is illustrated by a different pattern fill. The illustrated clusters correspond to sets of pulses in light beam 110; the longer the cluster, the more pulses in light beam 110 are in that set. For example, cluster 741 of pulses classified as D1 type has more pulses than cluster 742 of pulses classified as D3 type, which in turn has more pulses than cluster 743 of pulses classified as D2 type. By way of example, there may be tens of thousands of pulses in cluster 741, thousands of pulses in cluster 742, and hundreds of pulses in cluster 743.

[0051]

[0063] Next, procedure 650 includes detecting 653 a type pattern in the single data stream D0. Each type pattern terminates upon completion of a single job on the substrate 171. For example, the pattern module 430 receives the single data stream D0 and detects 653 a type pattern in the single data stream D0. Referring also to FIG. 7B, graph 745 illustrates the period of the data stream D0 shown in FIG. 7A after a type pattern has been detected. The type patterns are indexed by the variable i, with the current pattern being the ith pattern, or P(i), the most recent pattern being the (i-1)th pattern, or P(i-1), and the next to most recent pattern being the (i-2)th pattern, or P(i-2). In one implementation, there are six type patterns that the pattern module 430 is looking for. 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], and P6: [D1 D1 D2]. The pattern module 430 detects three patterns during data stream D0 of graph 745: P(i-2) = P1, P(i-1) = P5, and P(i) = P2. Pattern P(i-2) ends at time Te(i-2), when the (i-2)th job on substrate 171 is completed. Pattern P(i-1) begins at time Tb(i-1) and ends at time Te(i-1), when the next, i.e., (i-1)th, job on substrate 171 is completed. Pattern P(i) begins at time Tb(i) and ends at time Te(i), when the i-th job on substrate 171 is completed. Therefore, controller 420 operates light source 105 in idle mode MB (581) during idle time IT12 and idle time IT01. After T(i), another idle mode is entered. Controller 420 operates light source 105 in production mode MA (583) when a pattern is detected. Other patterns not shown in graph 745 may exist at other times in data stream D0. Also, there may be clusters of data that cannot be classified into any pattern.A single data stream D0 may contain many more patterns than those shown in the time span of graphs 740 and 745. Graphs 740 and 745 are provided for illustrative purposes only.

[0052]

[0064] Although only six type patterns are described in the above implementation, it is possible that there are fewer or more than six type patterns, or that the patterns differ from the six type patterns described above (P1, P2, P3, P4, P5, P6).

[0053]

[0065] Once these patterns are detected at 653, procedure 650 includes calculating (654) for each type pattern information Ipo (FIG. 4) that can be used to form a model, which can be stored (655) in memory 421. For example, extraction module 431 (FIG. 4) can calculate (654) from data stream D0 one or more aspects of light source 105 associated with idle mode and characteristics indicative of a cold start. This is described in more detail again with reference to FIG. 7B.

[0054]

[0066] For the ith pattern [P(i)] detected in the data stream D0, the extraction module 431 may calculate a corresponding aspect of the light source 105 associated with idle mode and a characteristic indicative of a cold start. As described above, the aspect of the light source 105 associated with idle mode may be the idle time IT(i), and the characteristic indicative of a cold start may be a voltage change ΔV(i) (during a transient). These are described below. For P(i), the corresponding idle time IT(i) is calculated as follows: IT(i)=Tb(i)−Te(i−1). Thus, the idle time IT(i) calculated for P(i) approximates the value IT01 in graph 745. For P(i), the corresponding voltage change (during a transient) is calculated as follows: ΔV(i)=AVmax of the first D1 data of P(i)−Avmax of the D3 data of P(i). ΔV(i) is shown in graph 745. As mentioned above, the value of ΔV(i) is characteristic of 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 radiation 110 from the light source 105 before entering the idle mode MB. In this case, NNPul of the ith pattern P(i) is given by:

[0055]

number

[0056] where TOTpul(i) is the total number of pulses of radiation 110 generated in the ith pattern P(i), and the values ​​of Te(i) and Tb(i) are shown in graph 745. In other implementations, NNPul(i) may be normalized over a different time window (which is the value of the denominator in Equation 1), for example, Te(i)-Te(i-1). In such implementations, the value of NNPul for the first pattern in data stream D0 may not be calculated because Te(i-1) does not exist at that time. Thus, the ith pattern P(i) in data stream D0 results in the following data pairs (represented as two-dimensional feature vectors):

[0057]

number

[0058]

[0067] These data pairs form a model that is stored in memory 421, and the model is represented by a look-up 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.

[0059]

[0068] 8 shows an example of such a distribution of data pairs in a simulation based on data queried for an operating light source 105 over a three-month period. In FIG. 8, each circle is at a location addressed by a corresponding feature vector defined on the left side of Equation 2. The pattern fill of each circle represents the range of amplitudes 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 of greater than 30 volts (V), ΔV(i)R2 may correspond to a voltage change of greater than 25 V but less than or equal to 30 V, ΔV(i)R3 may correspond to a voltage change of greater than 20 V but less than or equal to 25 V, ΔV(i)R4 may correspond to a voltage change of greater than 15 V but less than or equal to 20 V, and ΔV(i)R5 may correspond to a voltage change of less than or equal to 15 V.

[0060]

[0069] The tuning data pair for the model is given in Equation 2. This particular data is chosen because there is a strong relationship between the idle time IT and normalized pulse count NNpul (defined in the above equations) on the one hand, and the voltage change ΔV (defined above) as an indicator of cold start on the other. Specifically, it can be expected that the likelihood of a cold start increases as the idle time IT increases and / or the normalized pulse count NNpul decreases. This expectation is supported by FIG. 8, where a larger voltage change ΔV is more likely with a longer idle time IT. Another advantage of working with the two-dimensional feature vector of Equation 2 instead of considering only the idle time IT is that the data points are more dispersed, and the tuned model (in this case, a lookup table of data output from Equation 2) can more effectively distinguish between various situations. Also, cold start may depend on other factors not mentioned here, such as the age of the gas discharge chamber. The model (lookup table) does not take this factor into account. Nevertheless, the data-based look-up table model of Equation 2 can adapt to the aging of the gas discharge chamber if it is periodically retrained and kept up to date.

[0061]

[0070] Once stored in memory 421, the lookup table LUT (i.e., model) can be tuned to improve or maximize the performance of the lookup table. An example of tuning will now be described with reference to FIG. 9. After generating a tuning pair in the form of Equation 2, the data is used to tune lookup table LUT-9. Initially, zeros are written into each cell of lookup table LUT-9. Each cell of lookup table LUT-9 addresses a particular range of the variable under consideration. For example, if the length of each row cell is equal to 10, then the third row cell corresponds to values ​​of normalized pulse count NNpul in the range [20, 30], and the first row cell corresponds to values ​​of normalized pulse count NNpul in the range [0, 10]. The number in each cell of lookup table LUT-9 indicates the average change in RC voltage (ΔVave) during the transient of the data point occurring in that cell. After generating a new data pair according to Equation 2, the value of the corresponding cell of the look-up table LUT-9 may be updated to a new value ΔVave(j+1), for example, according to the following equation:

[0062]

number

[0063] where j is the index of the version of ΔVave, and α is a constant in the range [0, 1]. 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 more recently observed data.

[0064]

[0071] Once the lookup table LUT is stored in memory 421, the prediction module 422 may tune the lookup table using the data pairs (Equation 2) extracted from the most recent past data stream D0. After this initial tuning, the prediction module 422 runs iteratively over time, with a fixed time interval between each iteration. At each iteration, the prediction module 422 updates the tuned lookup table LUT stored in memory 421 with new data pairs (Equation 2) that have occurred since the last update to the lookup table LUT.

[0065]

[0072] Referring to FIG. 10 , in some implementations, the controller 423 (or the prediction module 422) performs a procedure 1089 for adjusting idle parameters based on a cold start model (lookup table LUT). In describing procedure 1089, reference is made to FIGS. 11A and 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. The controller 423 then selects an idle time IT associated with the determined last value of the normalized pulse count NNpul(i) (1057). For example, referring to FIG. 11A , the controller 423 selects the idle time IT by using the lookup table LUT-11A to find the row of the lookup table LUT-11A that corresponds to the determined normalized pulse count NNpul(i) of 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 to the left of or in this column within the highlighted row are less than the desired voltage change threshold ΔVthreshold. In this particular example, the voltage change threshold ΔVthreshold is 20V. The controller 423 then sets (1058) the idle parameter ITmin(i) based on the idle time IT selected from the selected column of the lookup table LUT-11A. As described above, each cell of the lookup table LUT-11A addresses a particular range of the variable under consideration. For example, if the length of each column cell is equal to 10, then the 9th column cell (selected and set as the idle parameter ITmin(i)) corresponds to one of the values ​​of the idle time IT in the range [80, 90]. For example, the idle parameter ITmin(i) may be set as the maximum value in the range [80, 90], and thus may be 90 in this example.

[0066]

[0073] As another example, in lookup table LUT-11B (FIG. 11B), the controller 423 determines the last value of the normalized pulse count NNpul(i) at 1056, which is indicated by the highlighted row of LUT-11B. All cells in this highlighted row are equal to zero. In this case, the controller 423 may select the rightmost column of this row to determine the idle parameter ITmin(i) at 1057 and 1058. The rightmost column is the 12th column, and the idle time IT of that cell corresponds to the range [110, 120]. Thus, the controller 423 may set the idle parameter ITmin(i) as 120. In some implementations, if the last value of the normalized pulse count NNpul(i) determined in 1056 is greater than the range of normalized pulse counts addressed by the top row of the lookup table LUT-11A, the controller 423 may use that top row to determine the idle parameter ITmin(i) in 1057, 1058.

[0067]

[0074] 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 this last value of the pulse count NNpul(i) has previously led to a determination of the idle parameter ITmin(i) that resulted in a cold start, the controller 423 can attempt to avoid this situation in the future by assigning a smaller value to the idle parameter ITmin(i).

[0068]

[0075] As mentioned above, to take into account the age of the gas discharge chamber 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).

[0069]

[0076] As mentioned above, in another implementation, the model (589) of cold start-related characteristics is in the form of a radial basis function network. Similar to the lookup table described above, the prediction module 422 designs and trains the radial basis function network using the paired data in the data stream D0 from Equation 2. Once the radial basis function network is designed and trained by the prediction module 422, the controller 423 may use this trained radial basis function network to automatically update the idle parameters ITmin(i). To this end, the input-output relationship of the trained radial basis function network is:

[0070]

number

[0071] 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 means that the pattern sequence is complete and a new value of NNpul can be calculated from Equation 2. If the voltage change ΔV(i) in Equation 4 is equal to 20V and the final value of NNpul is substituted into Equation 4, then:

[0072]

number

[0073] Therefore, equation 5 can be solved to find the value of ITmin(i).

[0074]

[0077] As described above, one of the aspects of the light source 105 related to 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), one of the aspects of the light source 105 related to the idle mode MB that can be calculated in step 654 (FIG. 6) is the duty cycle DC of the data cluster immediately before the idle time IT. Data classified as D2 data (used for external generation) is obtained at the end of each pattern, and then the duty cycle DC of this D2 data is determined. Thus, in these implementations, the ith pattern P(i) in the data stream DO results in the following data pair (expressed as a two-dimensional feature vector as in Equation 2):

[0075]

number

[0076] The vertical axis of the lookup table LUT can then represent the value of the duty cycle DC.

[0077]

[0078] As described above, controller 120 includes a component configured to automatically adjust the value of idle parameter ITmin so that the number of falsely initiated cold starts is reduced and cold starts are initiated when necessary, thereby increasing the availability of light source 105 as desired for photolithography exposure apparatus 170. In other implementations, controller 120 may additionally or alternatively be configured to automatically adjust the value of another cold start-related parameter, cold start period CSPer. In particular, controller 120 may automatically adjust the value of cold start period CSPer based on a model of one or more characteristics related to cold start of light source 105. For example, as described above, one characteristic related to cold start is the difference or change in the value of excitation signal 111 from the beginning of cold start operation to the end of cold start. Controller 120 may build the model from previous operating data of light source 105 in a manner similar to that described above.

[0078]

[0079] The implementation may be further described using the following clauses. 1. A method for controlling a light source, comprising: operating the light source in an idle mode in which the light source does not generate radiation; receiving a request from a photolithography exposure tool to enter a production mode, the production mode including the light source generating radiation and providing the radiation to the photolithography exposure tool; 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 the nominal efficiency required by the photolithography exposure apparatus to expose a substrate to radiation from the light source; automatically adjusting the idle parameters based on a model of characteristics associated with a cold start, the model being constructed from previous operating data of the light source; A method for providing 2. The method of clause 1, further comprising constructing a model of characteristics associated with cold starts. 3. The method of clause 2, wherein constructing the model of the characteristics associated with the cold start comprises constructing a lookup table. 4. The method of clause 3, wherein constructing the lookup table comprises receiving input-output data pairs from the light source and detecting a pattern in the input-output data pairs, wherein such pattern signifies completion of a single exposure job on the substrate. 5. The method of clause 3, wherein the lookup table models a relationship between one or more aspects of the light source associated with idle mode and a characteristic indicative of a cold start. 6. The method of clause 4, wherein one or more aspects of the light source associated with the idle mode include an idle time and a normalized number of pulses of radiation from the light source before entering the idle mode. 7. The method of clause 6, wherein the idle time corresponds to the time the last pulse of radiation from the light source is generated to the time the photolithography 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 idle mode corresponds to the normalized number of pulses of radiation from the light source during a period of use extending to the time the last pulse of radiation from the light source is generated immediately before the idle mode begins. 8. The method of clause 6, 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 radiation. 9. The method of clause 8, wherein the change in value of the excitation signal is a change in voltage supplied to an electrode in a gas discharge chamber of the light source. 10. The method of clause 9, wherein adjusting the idle parameters based on the constructed model comprises: 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 parameters based on the selected idle time. 11. The method of clause 10, wherein the selected idle time is based on the change in voltage supplied to the electrodes that is closest to but does not exceed the change in the cold start voltage indicator. 12. The method of clause 2, wherein constructing a model of characteristics associated with cold start comprises designing and training a radial basis function network. 13. The method of clause 1, wherein the idle parameter is an idle time setting and the cold start is initiated when the idle time exceeds the idle time setting. 14. The method of clause 13, wherein adjusting the idle parameters based on the constructed model comprises selecting an idle time based on the constructed model, and setting the idle parameters to be the selected idle time. 15. The method of clause 14, wherein the constructed model models a relationship between one or more aspects of the light source related to idle mode and characteristics indicative of a cold start. 16. The method of clause 1, wherein initiating the cold start comprises indicating to the photolithography exposure tool that a cold start is occurring. 17. The method of clause 16, wherein indicating to the photolithography exposure apparatus that a cold start has occurred causes the photolithography exposure apparatus to avoid using radiation to expose a substrate. 18. The method of clause 1, further comprising, after initiating the cold start, terminating the cold start after exceeding the cold start duration. 19. The method of clause 1, wherein providing radiation from the light source to the photolithography exposure apparatus comprises exposing the substrate to radiation from the light source upon completion of a cold start, or immediately after entering production mode if a cold start is not initiated. 20. A device for controlling a light source, comprising: a prediction module configured to build a model of characteristics associated with cold starts of the light source from previous operating data of the light source; a controller in communication with the prediction module, to operate the light source in an idle mode in which the light source does not produce radiation, receiving a request to enter the production mode from the photolithography exposure tool, wherein the production mode includes the light source providing radiation to the photolithography exposure tool; Upon receiving a request to enter the production mode, to initiate a cold start if an idle parameter is exceeded where the cold start indicates that the efficiency of the light source is less than the nominal efficiency required by the photolithography exposure tool to expose a substrate to radiation from the light source; and Automatically adjust idle parameters based on the constructed model a configured controller; An apparatus comprising: 21. The method of clause 20, wherein providing radiation from the light source to the photolithography exposure apparatus comprises exposing the substrate to radiation from the light source upon completion of a cold start, or immediately after entering production mode if a cold start is not initiated. 22. The prediction module a data collection module configured to receive data relating to previous operational data of the light source; a data analysis module configured to analyze data from the data collection module to form information relating to previous operational data of the light source and provide the information to a memory; 20. The device of clause 20, comprising: 23. The apparatus of clause 22, wherein the data collection module classifies the received data into one of a plurality of types of data. 24. The apparatus of clause 23, wherein the data analysis module is configured to analyze the data from the data collection module by combining multiple types of data into a single data stream, detecting type patterns within the single data stream, each type pattern terminating upon completion of a single substrate job, and calculating, for each type pattern, one or more aspects of the light source associated with idle mode and characteristics indicative of a cold start. 25. The apparatus of clause 24, wherein the radiation is provided in pulses of light and the data acquisition module is configured to receive data for each pulse of light. 26. The apparatus of clause 25, wherein the data analysis module is configured to receive the categorized data in clusters of pulses from the data collection module. 27. Further comprising a memory configured to store a constructed model of characteristics related to cold start; 21. The apparatus of clause 20, wherein the prediction module is configured to provide the constructed model to be stored in a memory, and the controller is configured to access the constructed model from the memory. 28. An 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. 29. The apparatus of clause 28, wherein the controller is configured to adjust the idle parameters based on the constructed model by selecting an idle time based on the constructed model and setting the idle parameters to be the selected idle time. 30. The apparatus of clause 29, wherein the constructed model models the relationship between one or more aspects of the light source related to idle mode and characteristics indicative of a cold start.

[0079]

[0080] These and other implementations are within the scope of the following claims.

Claims

1. 1. A method for controlling a light source, comprising: operating the light source in an idle mode in which the light source does not generate radiation; receiving a request from a photolithography exposure tool to enter a production mode, the production mode including the light source generating radiation and providing the radiation to the photolithography exposure tool; Upon entering a 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 the nominal efficiency required by the photolithography exposure apparatus to expose a substrate to radiation from the light source; automatically adjusting the idle parameters based on a model of characteristics associated with a cold start, the model being constructed from previous operating data of the light source; and A method for providing

2. The method of claim 1 , further comprising: constructing a model of the cold start-related characteristics, wherein constructing the model of the cold start-related characteristics comprises constructing a lookup table.

3. 3. The method of claim 2, wherein constructing the lookup table comprises receiving input-output data pairs from the light source and detecting a pattern in the input-output data pairs, such a pattern signifying the completion of a single exposure job on the substrate.

4. 3. 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 characteristics indicative of a cold start, the one or more aspects of the light source associated with the idle mode including idle time and a normalized number of pulses of the radiation from the light source before entering an idle mode.

5. 5. The method of claim 4, wherein the idle time corresponds to a time from when a last pulse of radiation from the light source is generated to a time when the photolithography 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 an idle mode corresponds to a normalized number of pulses of radiation from the light source during a period of use extending until the last pulse of radiation from the light source is generated immediately before an idle mode begins.

6. 5. The method of claim 4, wherein the characteristic indicative of a cold start is a change in value of an excitation signal provided to the light source to generate the radiation, the change in value of the excitation signal being a change in voltage supplied to electrodes in a gas discharge chamber of the light source.

7. 10. The method of claim 1, further comprising: constructing a model of characteristics associated with the cold start; wherein constructing the model of characteristics associated with the cold start comprises designing and training a radial basis function network.

8. 2. 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. 9. The method of claim 8, wherein adjusting the idle parameter based on the constructed model comprises: selecting an idle time based on the constructed model; and setting the idle parameter to be the selected idle time.

10. 10. The method of claim 1, wherein initiating a cold start comprises instructing the photolithography exposure apparatus that a cold start is occurring, and wherein instructing the photolithography exposure apparatus that a cold start is occurring causes the photolithography exposure apparatus to avoid using the radiation to expose the substrate.

11. The method of claim 1 , further comprising terminating the cold start after a cold start duration has elapsed since initiating the cold start.

12. 10. The method of claim 1, wherein providing radiation from the light source to the photolithography exposure apparatus comprises exposing the substrate to radiation from the light source upon completion of a cold start, or immediately after entering a production mode if a cold start is not initiated.

13. 1. An apparatus for controlling a light source, comprising: a prediction module configured to build a model of characteristics associated with cold starts of the light source from previous operating data of the light source; a controller in communication with the prediction module, operating the light source in an idle mode in which the light source does not generate radiation; receiving a request from a photolithography exposure apparatus to enter a production mode, the production mode comprising the light source providing radiation to the photolithography exposure apparatus; upon receiving a request to enter the production mode, to initiate a cold start if an idle parameter is exceeded where a cold start indicates that the efficiency of the light source is less than the nominal efficiency required by the photolithography exposure apparatus to expose a substrate to radiation from the light source; and and automatically adjusting the idle parameters based on the constructed model. a configured controller; An apparatus comprising:

14. 14. The apparatus of claim 13, wherein providing radiation from the light source to the photolithography exposure apparatus comprises exposing the substrate to radiation from the light source upon completion of a cold start, or immediately after entering a production mode if a cold start is not initiated.

15. The prediction module: a data collection module configured to receive data relating to the previous operational data of the light source; a data analysis module configured to analyze the data from the data collection module to form information related to the previous operational data of the light source and provide the information to a memory; 14. The apparatus of claim 13, comprising:

16. 16. The apparatus of claim 15, wherein the data collection module classifies the received data into one of a plurality of types of data, and the data analysis module is 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 within the single data stream, each type pattern terminating upon completion of a single substrate job, and calculating, for each type pattern, one or more aspects of the light source associated with idle mode and characteristics indicative of a cold start.

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

18. a memory configured to store the constructed model of characteristics associated with the cold start; 14. The apparatus of claim 13, wherein the prediction module is configured to provide the constructed model as stored in a memory, and the controller is configured to access the constructed model from memory.

19. 14. 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. 20. The apparatus of claim 19, wherein the controller is configured to adjust the idle parameter based on the constructed model by selecting an idle time based on the constructed model and setting the idle parameter to be the selected idle time.

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