Determination of measurement error in etalons

Abstract

Accessing information related to the etalon, the etalon being associated with a calibration parameter having a pre-set default value, the etalon being configured to produce an interference pattern comprising a plurality of fringes from the received light beam, and the information related to the etalon comprising first spatial information related to a first fringe of the plurality of fringes and second spatial information related to a second fringe of the plurality of fringes. Determining a first wavelength value of the received light beam based on the spatial information related to the first fringe and an initial value of the calibration parameter. Determining a second wavelength value of the received light beam based on the spatial information related to the second fringe and the initial value of the calibration parameter. Comparing the first wavelength value and the second wavelength value to determine a measurement error value.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application No. 63 / 043,312, filed on June 24, 2020, entitled “DETERMINATION OF MEASUREMENT ERROR IN AN ETALON,” which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to the determination of measurement errors in etalons. Eetalons can be used in deep ultraviolet (DUV) optical systems. Background Technology

[0004] An etalon is an optical cavity made of two partially reflective optical surfaces. Eetalons produce interference patterns and can be used to measure or estimate the wavelength of light incident on them. Summary of the Invention

[0005] In one aspect, a method includes: accessing information associated with an etalon, the etalon being associated with calibration parameters having preset default values, the etalon being configured to generate an interference pattern comprising a plurality of fringes from a received beam, and the information associated with the etalon including first spatial information associated with a first fringe of the plurality of fringes and second spatial information associated with a second fringe of the plurality of fringes; determining a first wavelength value of the received beam based on the spatial information associated with the first fringe and initial values ​​of the calibration parameters; determining a second wavelength value of the received beam based on the spatial information associated with the second fringe and initial values ​​of the calibration parameters; and comparing the first wavelength value and the second wavelength value to determine a measurement error value.

[0006] The implementation may include one or more of the following features.

[0007] The method may further include determining whether to adjust a preset default value of the calibration parameters based on the measurement error value. The measurement error value may include the difference between a first wavelength value and a second wavelength value, and the preset default value may be adjusted to a value that makes the measurement error value less than a threshold. The preset default value may be adjusted to a value that makes the measurement error value zero.

[0008] Calibration parameters may include the focal length of the lens at the output of the etalon, and measurement errors may include the difference between the first wavelength value and the second wavelength value.

[0009] The first spatial information may include the diameter of the first stripe, and the second spatial information may include the diameter of the second stripe.

[0010] The method may further include guiding the beam to an etalon. A first fringe may be generated by a first portion of the beam, and a second fringe may be generated by a second portion of the beam. The beam may include multiple pulses, the first portion of the beam may include the first pulse of the multiple pulses, and the second portion of the beam may include the second pulse of the multiple pulses. The beam may include a continuous wave beam, the first portion of the beam may include a first sample of the beam, and the second portion of the beam may include a second sample of the beam. The method may further include: changing an initial value of a calibration parameter to an updated value of the calibration parameter; actuating an optical element to thereby change the wavelength of the received beam; determining a first wavelength value of the received beam based on spatial information associated with the first fringe and the updated value of the calibration parameter; determining a second wavelength value of the received beam based on spatial information associated with the second fringe and the updated value of the calibration parameter; and comparing the first wavelength value and the second wavelength value based on the updated value of the calibration parameter to determine a measurement error value. Before determining the second wavelength value, the optical element may be actuated to increase or decrease the wavelength. The first wavelength value and the second wavelength value may be determined more than once each time the optical element is actuated. The method may further include determining whether to adjust the preset default value of the calibration parameters by comparing an error measurement determined based on the initial value of the calibration parameters with an error measurement determined based on the updated value of the calibration parameters.

[0011] The initial values ​​for the calibration parameters can be preset default values.

[0012] The first and second stripes can be in the interference pattern simultaneously.

[0013] In another aspect, the method for calibrating an etalon includes: accessing information associated with the etalon, the etalon being associated with calibration parameters having preset default values, the etalon being configured to generate an interference pattern comprising multiple fringes from a received beam, and the information associated with the etalon including first spatial information associated with a first fringe of the multiple fringes and second spatial information associated with a second fringe of the multiple fringes; determining a measurement error value of the etalon based on the first spatial information, the second spatial information, and an initial value of the calibration parameters; and analyzing the measurement error value to determine whether to adjust the preset default values.

[0014] The implementation may include one or more of the following features.

[0015] The calibration parameters may include the focal length of the lens at the output of the etalon. The method may further include: determining a first wavelength value based on first spatial information; and determining a second wavelength value based on second spatial information. Measurement error may include the difference between the first wavelength value and the second wavelength value.

[0016] The calibration parameters may include multiple initial values. Determining the measurement error value may include simulating multiple measurement error values ​​for each of the multiple initial values. Each measurement error value may be based on one of the multiple initial values ​​of the calibration parameters, a first spatial information, a second spatial information, and the calibration parameters. Analyzing the measurement error value may include analyzing the simulated measurement error value.

[0017] In another aspect, an optical measurement device for a light source includes: an etalon including a focusing lens configured to focus light onto an image plane; an optical detector configured to detect an interference pattern generated by the etalon and generate information associated with the etalon; and a control system coupled to the optical detector. The etalon is associated with calibration parameters associated with the focusing lens, and the calibration parameters have preset default values. The information includes first spatial information for a first fringe and second spatial information for a second fringe. The control system is configured to: determine a measurement error value of the etalon based on the first spatial information, the second spatial information, and the initial values ​​of the calibration parameters from the detector; and analyze the measurement error value to determine whether to adjust the preset default values.

[0018] The implementation may include one or more of the following features.

[0019] The light source can include deep ultraviolet (DUV) light sources.

[0020] In another aspect, a light source includes: a light generating device; and an optical measuring device. The optical measuring device includes: an etalon including a focusing lens configured to focus light onto an image plane; an optical detector configured to detect an interference pattern generated by the etalon and generate information associated with the etalon; and a control system coupled to the optical detector. The etalon is associated with calibration parameters associated with the focusing lens, the calibration parameters having preset default values. The information includes first spatial information for a first fringe and second spatial information for a second fringe. The control system is configured to: determine a measurement error value of the etalon based on the first spatial information, the second spatial information, and the initial value of the calibration parameters from the detector; and analyze the measurement error value to determine whether to adjust the preset default values.

[0021] The implementation may include one or more of the following features.

[0022] The light generating device may include a deep ultraviolet (DUV) light source. The light generating device may include a master oscillator. The light generating device may further include a power amplifier. The light generating device may include multiple master oscillators.

[0023] The light source may further include optical elements configured to receive light from the light generating device and guide the light to the etalon. The optical elements may be dispersive optical elements.

[0024] Implementations of any of the above techniques may include systems, methods, processes, devices, or apparatuses. Details of one or more implementations are set forth in the accompanying drawings and the following description. Other features will be apparent from the specification, drawings, and claims. Attached Figure Description

[0025] Figure 1A This is a block diagram of an example system.

[0026] Figure 1B An example of an interference pattern is shown.

[0027] Figure 1C yes Figure 1A A block diagram of one aspect of the system.

[0028] Figure 2A This is a block diagram of an example optical measurement device.

[0029] Figure 2B and 2C Another example involving interference patterns.

[0030] Figure 3 and 4 This is a flowchart illustrating an example of a process for determining the measurement error of a datum.

[0031] Figure 5 An example diagram of the measurement error of a etalon is shown.

[0032] Figure 6 This is a flowchart illustrating an example of a process for determining the measurement error of a datum.

[0033] Figure 7 An example diagram of the measurement error of a etalon is shown.

[0034] Figure 8A An example of a deep ultraviolet (DUV) optical system that can be used with an optical measurement device is shown.

[0035] Figure 8B This is an example of a projection optics system.

[0036] Figure 9A This is a block diagram of an example of a spectrum adjustment device.

[0037] Figure 9B An example of a prism is shown.

[0038] Figure 10 An example of a deep ultraviolet (DUV) optical system that can be used with optical measurement devices is shown. Detailed Implementation

[0039] Figure 1A This is a block diagram of System 100. Figure 1A In the diagram, dashed lines between elements represent the optical path along which light travels, and solid lines between elements represent the signal path along which information and / or data travels. System 100 includes a light generation module 110 that generates a light beam 116. The light beam 116 propagates along path 114 to device 180. Device 180 is any device that uses the light beam 116. Device 180 can be a photolithography device (such as...) Figure 8A and Figure 10 The scanner device 880) or power amplifier, such as ( Figure 10 The power amplifier 1012_2).

[0040] System 100 also includes a beam splitter 117 that guides a portion 116' of the beam 116 to the optical measurement device 160. The beam splitter 117 can be, for example, a beam splitter that guides a portion 116' to the optical measurement device 160 while allowing residual light in the beam 116 to continue propagating to the device 180. The optical measurement device 160 is used to measure the wavelength of the beam 116. The optical measurement device 160 includes an etalon 130, a detector 140, and a control system 150. The etalon 130 includes two parallel optical elements 133A and 133B spaced apart by a distance 136, and an output lens 134. See also... Figure 1C The output lens 134 has a focal length of 163 and focuses the incident light onto the image plane 137. The image plane 137 coincides with the active region 142 of the detector 140. Figure 1C It is a block diagram of the active region 142 and the image plane 137.

[0041] Also refer to Figure 1B The output of the etalon 130 is an interference pattern 139 focused on the image plane 137. Figure 1B Interference pattern 139 is shown in image plane 137. Figure 1B In the example, interference pattern 139 consists of multiple concentric rings formed at image plane 137. Figure 1B Two fringes, 139_1 and 139_2, are shown. Fringe 139_1 is a first-order fringe, and fringe 139_2 is a second-order fringe. First-order fringe 139_1 and second-order fringe 139_2 are two consecutive fringes. According to Equation 1, the wavelength of light in part 116' is related to the diameter of the fringes in the interference pattern 139:

[0042]

[0043] Where λ is the wavelength of light incident on the etalon 130 (part 116' in this example), ND is the optical path length between optical elements 133A and 133B (distance 136 in this example), m is the order of a particular fringe, d is the diameter of a particular fringe, and FD is the focal length of the output lens 134. The fringe order m is an integer and can be, for example, a relatively large number, such as an integer equal to or greater than 10,000.

[0044] Enobe 130 is used to measure the wavelength of light in section 116'. Enobe 130 is associated with measurement error, which can be absolute or wavelength-dependent at a particular wavelength. One source of wavelength-dependent measurement error can arise when a fixed detector (such as detector 140) in image plane 137 uses fringes of a different order compared to a previous wavelength determination to determine the wavelength value. In other words, when measuring the wavelength of the same light through fringes of different orders in the same interference pattern, the measurement based on the wavelength of first-order fringe 139_1 and / or second-order fringe 139_2 may be inaccurate. Specifically, this measurement error can cause the determined wavelength value to change artificially between two different measurements, even if the true wavelength of the incident light has not changed.

[0045] The etalon 130 is associated with at least one calibration parameter 131. The value of FD is the calibration parameter 131. The value of FD is determined when the etalon 130 is manufactured. However, the value of FD may drift or change during the lifespan of the etalon 130. For example, the value of FD may change due to alignment offset caused by thermal cycling (heating and / or cooling) that may occur during the use of the etalon 130. Alignment offset can manifest as a change in the FD value. Techniques for determining the FD value during the use and / or lifespan of the etalon 130 are discussed below. Details of an example implementation of the optical measuring device 160 are discussed before discussing the techniques associated with determining the value of calibration parameter 131.

[0046] Figure 2A This is a block diagram of the optical measuring device 260. The optical measuring device 260 is an extension of the optical measuring device 160. Figure 1AThe optical measurement device 260 includes an input lens 232, a etalon 230, an output lens 234 (or focusing lens 234), and a detector 240. A portion 116' is diffused and passes through an aperture 235 of the optical measurement device 260. The portion 116' can be intentionally diffused by an optical diffuser (not shown) placed at a plane 237 between the beam splitter 117 and the aperture 235. The aperture 235 is located at the focal plane of the input lens 232. The input lens 232 collimates the portion 116' before it enters the etalon 230. The output lens 234 has a focal length 263 and focuses light onto the image plane. The detector 240 is positioned such that its active region 242 coincides with the image plane.

[0047] exist Figure 2A In the example shown, the etalon 230 includes a pair of partially reflective optical elements 233A and 233B. Optical elements 233A and 233B are located between an input lens 232 and an output lens 234. Optical elements 233A and 233B have corresponding reflective surfaces 238A and 238B spaced apart by a distance 236. The distance 236 can be a relatively short distance (e.g., millimeters to centimeters). Optical elements 233A and 233B are wedge-shaped to prevent interference fringes from forming on the back surface (the surface opposite to surfaces 238A and 238B). The back surface may have an anti-reflective coating. Other implementations of the etalon 230 are also possible. For example, in other implementations, optical elements 233A and 233B are parallel plates and not wedge-shaped. In yet another example, the etalon 230 may consist of only a single plate with two parallel partially reflective surfaces.

[0048] Also refer to Figure 2B The etalon 230 interacts with part 116' and outputs an interference pattern 239. Figure 2B An interference pattern 239 in the image plane of lens 234 at a certain moment is shown. The interference pattern 239 comprises multiple fringes. Two of the multiple fringes (239_1 and 239_2) are in... Figure 2B As shown in the diagram. Interference pattern 239 includes a dark region created by destructive interference of portion 116' and a bright region produced by constructive interference of portion 116'. The regions of constructive interference are fringes 239_1 and 239_2. The dark region is shown in gray shading and lies between the bright regions. Fringe 239_1 and 239_2 are concentric rings in the image plane of the output lens 234. Each ring in the fringe group is a first-order (m) interference pattern, where m is an integer equal to or greater than 1. Fringe 239_1 is a first-order fringe, and fringe 239_2 is a second-order fringe.

[0049] Interference pattern 239 is sensed at active region 242 of detector 240. Detector 240 is any type of detector capable of sensing light in interference pattern 239. For example, active region 242 may be a linear photodiode array comprising multiple elements of the same size arranged at equal intervals along a single dimension in a package. Each element in the photodiode array is sensitive to the wavelength of portion 116'. As another example, detector 240 may be a two-dimensional sensor, such as a two-dimensional charge-coupled device (CCD) or a two-dimensional complementary metal-oxide-semiconductor (CMOS) sensor.

[0050] Detector 240 is connected to control system 250 via data link 254. Control system 250 includes electronic processing module 251, electronic memory 252, and I / O interface 253. Electronic processing module 251 includes one or more processors adapted to execute computer programs, such as general-purpose or special-purpose microprocessors, and any one or more processors of any type of digital computer. Typically, the electronic processor receives instructions and data from read-only memory, random access memory (RAM), or both read-only memory and RAM. Electronic processing module 251 may include any type of electronic processor. One or more electronic processors of electronic processing module 251 execute instructions and access data stored in electronic memory 252. One or more electronic processors are also capable of writing data to electronic memory 252.

[0051] Electronic memory 252 is any type of computer-readable or machine-readable medium. For example, electronic memory 252 may be volatile memory, such as RAM, or non-volatile memory. In some implementations, electronic memory 252 includes both non-volatile and volatile portions or components. Electronic memory 252 may store data and information used in the operation of control system 250. Electronic memory 252 may also store instructions (e.g., in the form of computer programs) that cause control system 250 to interact with optical measuring device 260. For example, instructions may be to cause electronic processing module 251 to implement... Figure 3 , 4 The electronic memory 252 also stores instructions for the processes discussed in section 6. The electronic memory 252 also stores information about the etalon 230, such as initial values ​​or preset values ​​for the predefined calibration parameter 231. These predefined or preset values ​​may be values ​​determined during factory calibration or values ​​determined using processes such as those discussed below (300, 400, or 600). The calibration parameter 231 may be, for example, the focal length of the lens 234. In another example, the electronic memory 252 may also store a range of indicated values ​​or specifications of values ​​related to the acceptable amount of measurement error for the etalon 230.

[0052] I / O interface 253 is any type of interface that allows control system 250 to exchange data and signals with an operator, other devices, and / or an automated process running on another electronic device. For example, in embodiments where data or instructions stored on electronic memory 252 can be edited, this editing can be performed via I / O interface 253. I / O interface 253 may include one or more visual displays, a keyboard, and communication interfaces such as parallel ports, universal serial bus (USB) connections, and / or any type of network interface, such as, for example, Ethernet. I / O interface 253 may also allow contactless communication via, for example, IEEE 802.11, Bluetooth, or near field communication (NFC) connections.

[0053] The control system 250 is coupled to the various components of the equipment 260 via a data connection 254. The data connection 254 is any type of connection that allows the transmission of data, signals, and / or information. For example, the data connection 254 can be a physical cable or other physical data conduit (such as a cable supporting the transmission of data based on 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.

[0054] Figure 3 This is a flowchart of process 300. Process 300 is used to determine the measurement error value. Process 300 can be controlled by control system 250. Figure 2A ) to be executed. For example, process 300 can be executed by one or more electronic processors in processing module 251. Relative to measuring device 260 ( Figure 2A Let's discuss the process 300.

[0055] Information related to etalon 230 is accessed (310). This information can be accessed from electronic memory 252 or via I / O interface 253. The information related to etalon 230 includes first spatial information related to the first fringe and second spatial information related to the second fringe. The first and second fringe can be two different fringes formed simultaneously. For example, the first fringe can be fringe 239_1, and the second fringe can be fringe 239_2. As discussed above, fringe 239_1 and fringe 239_2 are two different fringes formed by a single light pulse or by the same sample of a continuous wave beam. Relative to Figure 4 The process 400 discussed is an example of this method. In other implementations, the first fringe is a fringe in the interference pattern formed at a first time moment, and the second fringe is a fringe in the interference pattern formed at a second time moment. For example, in these implementations, the first fringe may be a fringe formed by a first light pulse incident on the etalon 230, while the second fringe may be a fringe formed by a second light pulse incident on the etalon 230 after the first light pulse. Relative to Figure 6 The process discussed in section 600 is an example of this method. The first spatial information can be the diameter of the first fringe. The second spatial information can be the diameter of the second fringe.

[0056] The information associated with the standard 230 also includes the initial value of calibration parameter 231. The initial value of calibration parameter 231 may be a factory calibration value determined when the standard 230 is assembled. In some embodiments, the initial value of calibration parameter 231 is a value determined during a previous execution of process 300. The preset default value of calibration parameter 231 may be stored in and accessed from electronic memory 252.

[0057] A first wavelength value (320) is determined based on the spatial information associated with the first fringe and the initial value of calibration parameter 231. A second wavelength value (330) is determined based on the spatial information associated with the second fringe and the initial value of calibration parameter 231.

[0058] A first wavelength value and a second wavelength value are compared to determine a measurement error value (340). The measurement error value is a value representing the difference between the first wavelength value and the second wavelength value. For example, the measurement error value can be determined by subtracting the first wavelength value from the second wavelength value, and vice versa. Other implementations are also possible. For example, the measurement error value can be the ratio of the first wavelength value to the second wavelength value.

[0059] Figure 4 This is a flowchart of process 400. Process 400 is another example of a process for determining the measurement error value and the value of calibration parameter 231. Relative to interference pattern 239 ( Figure 2B and 2C Let's discuss process 400. Interference pattern 239 is the output of etalon 230 at a certain moment. Process 400 can be executed by control system 250.

[0060] The initial value of calibration parameter 231 is accessed (410). The value of calibration parameter 231 can be accessed from electronic memory 252 or provided to control system 250 via I / O interface 253. In this example, calibration parameter 231 is FD. The initial value of calibration parameter 231 can be a predefined and default value determined when ephemeris 230 is manufactured. The initial value of calibration parameter 231 can also be a value of the calibration parameter determined in a previous iteration of process 400.

[0061] The diameter (fringe diameter d1) of the first fringe 239_1 is determined. For example, and referring to... Figure 2B and Figure 2CThe stripe diameter d1 can be determined based on the data generated by detector 240. In this example, the stripe diameter d1 can be the count of pixels between two points on opposite sides of the first stripe 239_1 determined from the image data generated by detector 240. Other implementations are also possible, and the stripe diameters d1 and d2 can be determined in any way.

[0062] The first wavelength value (λ1) is determined based on the determined fringe diameter d1 and the initial value of the calibration value (420). For example, the first wavelength (λ1) can be determined using the initial value of parameter 231, the order (m) of the first fringe 239_1, the known value of ND, and the fringe diameter d1 in Equation 1. Similarly, the diameter (fringe diameter d2) of the second fringe 239_2 is determined. The second wavelength value (λ2) is determined based on the determined fringe diameter d2 and the initial value of the calibration value (430). The second wavelength value (λ2) can be determined using the initial value of parameter 231, the order (m) of the second fringe 239_2, the known value of ND, and the fringe diameter d2 in Equation 1. The first fringe 239_1 and the second fringe 239_2 have a continuous order. For example, if the order (m) of the first fringe 239_1 is 10,001, then the order (m) of the second fringe 239_2 is 10,002.

[0063] The measurement error (440) is determined by comparing the first wavelength value (λ1) and the second wavelength value (λ2). The measurement error can be determined by finding the difference between the first wavelength value (λ1) and the second wavelength value (λ2). In the absence of a measurement error, the first wavelength value and the second wavelength value are the same because the light used to create the first fringe 239_1 and the second fringe 239_2 is the same. Therefore, the difference between the first wavelength value (λ1) and the second wavelength value (λ2) is a characterization of the measurement error. This difference can be determined by subtracting the first wavelength value (λ1) from the second wavelength value (λ2), and vice versa. Furthermore, the measurement error can be the absolute value of the difference. Therefore, the measurement error can be positive, negative, or zero (in the absence of a measurement error).

[0064] The measurement error is compared to a specification to determine whether calibration parameter 231 (FD in this example) should be adjusted. The specification can be a range of values ​​including positive and negative values ​​or a single positive threshold. The measurement error is compared to the specification to determine whether the value of calibration parameter 231 should be adjusted (450). If the value of calibration parameter 231 is within the specification or less than the threshold, the value of calibration parameter 231 is accurate, and process 400 returns (410) to continue monitoring the measurement error. If the value of calibration parameter 231 is outside the specification, the value of calibration parameter 231 is adjusted (460). The value of calibration parameter 231 is adjusted until the first wavelength value (λ1) and the second wavelength value (λ2) are within the specification. For example, if the specification is zero, the value of calibration parameter 231 is adjusted until Equation 1 produces the same wavelength value for the first fringe 239_1 and the second fringe 239_2.

[0065] After the value of calibration parameter 231 has been adjusted, process 400 returns (410) to continue monitoring the measurement error of the etalon, or process 400 may terminate. The adjusted value of calibration parameter 231 may be stored in electronic memory 252 (470). In implementations that store the adjusted value of calibration parameter 231, the adjusted value of calibration parameter 231 may be used as the initial value of calibration parameter 231 in subsequent executions of process 400. In some implementations, the adjusted calibration parameter 231 is not stored and / or is not used in subsequent executions of process 400. In these implementations, the factory-determined value of calibration parameter 231 is always used as the initial value of calibration parameter 231.

[0066] Figure 5 This is a graph showing example data of measurement error based on the value of calibration parameter 231 (FD). Figure 5 In the example, the measurement error is the difference between the first wavelength value (λ1) determined in (420) and the second wavelength value (λ2) determined in (430). The factory-determined value of calibration parameter 231 is 18352 pixels. However, as Figure 5 As shown, using the factory-determined value of calibration parameter 231 results in a measurement error of approximately 2.5 femtometers (fm). The value of calibration parameter 231 is... Figure 5 The values ​​shown vary within a range, and the measurement error is determined at each value of calibration parameter 231. For example... Figure 5 As shown, when the value of calibration parameter 231 is 18353 pixels, the measurement error is zero. The value of calibration parameter 231 is adjusted to be equal to 18353 pixels, and the wavelength of portion 116' is measured using the interference pattern output by etalon 130 and Equation 1 (using the updated value of FD). By adjusting the value of calibration parameter 231, the measurement error is eliminated, making the wavelength value determined from the output of etalon 230 accurate.

[0067] Figure 6 This is a flowchart of process 600. Process 600 is another example of a process for determining the measurement error of a datum (such as datum 130 or datum 230). Process 600 is discussed in relation to datum 230 and control system 250.

[0068] The initial value of calibration parameter 231 is changed to an updated value (610). The initial value of calibration parameter 231 may be a factory calibration value, a value determined during previous operational use of the standard 230, a value generated by an automated process (such as a random process), or a value provided by the operator of control system 250. The initial value of calibration parameter 231 can be changed by adding a predetermined constant to the initial value of calibration parameter 231. In some embodiments, the initial value of calibration parameter 231 is changed by a specific amount indicated by the operator of control system 250 or by a pre-programmed recipe or formula.

[0069] The wavelength (620) of the light in portion 116' is changed. The wavelength of the light in portion 116' is changed by a known amount. For example, the wavelength of the light in portion 116' can be changed by actuating an optical element associated with light source 110 (such as... Figure 9A The known quantity is changed by prisms 922, 923, 924, or 925, such that the wavelength of the light leaving the optical element changes by a known quantity relative to the light incident on the optical element. Next, process 600 uses one or more instances of the interference pattern 239 output by etalon 230 to estimate the wavelength value of the light in section 116', where each of the two instances is output at a different time. For example, beam 116 (and section 116') can be a pulsed beam comprising light pulses, each pulse separated from adjacent pulses by a finite amount of time during which the light generation module 110 does not emit light. In this example, a first instance of the interference pattern 239 is generated by illuminating etalon 230 with a first pulse in section 116', and a second instance of the interference pattern 239 is generated by illuminating etalon 230 with a second pulse in section 116'.

[0070] The first wavelength value (λ1) is determined (630) using fringes from a first instance of interference pattern 239. The first wavelength value (λ1) is determined using Equation 1, where m is the fringe order, FD is the updated value of calibration parameter 231 determined in (610), and d is the fringe diameter. The first wavelength value (λ1) can be determined from more than one instance of interference pattern 239. For example, the first wavelength value (λ1) can be determined from 50 or more instances of interference pattern 239. The individual values ​​of the first wavelength value (λ1) can be averaged or filtered together to remove or reduce noise, and the averaged or filtered value can be used as the first wavelength value (λ1).

[0071] The wavelength of the light in section 116' is changed again (640). The wavelength of the light in section 116' can be changed by the same known quantity as in (620). The second wavelength value (λ2) is determined (650) using fringes from one or more instances of interference pattern 239. The second wavelength value (λ2) is determined in the same manner as discussed in (630) by using Equation 1, where m is the order of the fringe, FD is the updated value of calibration parameter 231 determined in (610), and d is the diameter of the fringe. The second wavelength value (λ2) can be determined based on more than one instance of interference pattern 239. For example, the second wavelength value (λ2) can be determined 10, 50, or 100 times and then averaged to mitigate the effects of noise and mechanical vibration.

[0072] The measurement error associated with the updated value of calibration parameter 231 is determined (660). The measurement error is the difference between the determined first wavelength value (λ1) and the determined second wavelength value (λ2), taking into account the nominal sensitivity (NS) of the system, which is the actual wavelength of the control section 116' (the actuation optics in this example). The nominal sensitivity is a constant value and can be determined by the manufacturer and stored in electronic memory 252. The nominal sensitivity is the amount of change in wavelength relative to a unit change in the optical element, which determines the wavelength of light incident on the etalon 230. For example, if the optical element is a prism coupled to a PZT actuator, the nominal sensitivity is the amount of wavelength change for each unit change in the prism position. The measurement error (ME) can be determined from Equation 2:

[0073] ME = (S-NS)(OA) Equation (2),

[0074] Where ME is the measurement error, S is the current sensitivity, NS is the nominal sensitivity, and OA is a measure of the actuation of the optical element in units of distance. OA can be determined by Equation 3:

[0075] Equation (3) is OA = P2 - P1.

[0076] Where P2 is the position of the optical element when light with the second wavelength is provided by the optical element, and P1 is the position of the optical element when light with the first wavelength is provided by the optical element. The current sensitivity (S) is calculated based on the variation in the measured wavelength and the position of the optical element, and can be determined from Equation 4:

[0077]

[0078] Where λ1 is the first wavelength value determined in (630), λ2 is the second wavelength value determined in (650), P2 is the position of the optical actuator when light with the second wavelength value (λ2) is provided to the etalon 230, and P1 is the position of the optical actuator when light with the first wavelength value (λ1) is provided to the etalon 230. Although the above examples related to Equations 2, 3, and 4 discuss the position of the optical element, other distance metrics related to the position of the optical element may also be used. For example, in embodiments where the relationship between the position of the actuator and the position of the optical element is known, the position of the actuator may be used as the position of the optical element.

[0079] The measurement error (ME) is stored in the electronic memory 252 or output via the I / O interface 253.

[0080] Process 600 can return to (610) to determine, using (610)-(660) as described above, different updated values ​​for calibration parameter 231 and measurement error (ME) for another wavelength of portion 116'. For example, the wavelength can be increased or decreased in (620) compared to previous iterations of (610)-(660). In some implementations, a counter is incremented (665) each time process 600 returns to (610) to track how many measurement errors have been determined.

[0081] After the measurement error has been determined for one or more values ​​of calibration parameter 231 or for more than a specified number of values ​​of calibration parameter 231, the determined calibration values ​​are analyzed (670). For example, the absolute value of the measurement error can be determined, and the minimum error measurement value can be found from the absolute value. The value of calibration parameter 231 associated with the minimum error measurement is determined.

[0082] For example, Figure 7 Two sets of measurement error values, in femtometers (fm), are shown based on the updated values ​​of calibration parameter 231, expressed as pixel values. Each measurement error value in the first set is indicated by a solid circle. Each measurement error value in the second set is indicated by a hollow circle. The first set of measurement error values ​​is determined by performing (610)–(660) on multiple different values ​​of calibration parameter 231. Each time the value of calibration parameter 231 is updated at (610) to a different value, an optical element (such as a prism) is actuated to increase the wavelength of light in portion 116', and the measurement error is determined at (660). The second set is shown as curve 754. The second set of measurement error values ​​is determined by performing (610)–(660) on multiple different values ​​of calibration parameter 231. Each time the value of calibration parameter 231 is updated at (610) to a different value, an optical element (such as a prism) is actuated to decrease the wavelength of light in portion 116'.

[0083] The first set of measurements was fitted with a linear relationship 753, and the second set of measurements was fitted with a linear relationship 754. The value of FD corresponding to the intersection of linear relationships 753 and 754 is the minimum measurement error. Figure 7 As shown, the slopes of relation 753 and 754 are opposite in magnitude, but their absolute values ​​can also differ. The difference in absolute values ​​may be caused by hysteresis in the actuator of the moving optical element. Figure 7 In the example, the actuator is a piezoelectric actuator that first compresses from its nominal size to actuate the prism to increase the wavelength (to generate a first set of measurement error values), and then expands back to its nominal size to decrease the wavelength (to generate a second set of measurement error values). The mechanical effects caused by compression and expansion result in a slightly different absolute value of the slope of relation 753 compared to the absolute value of the slope of relation 754.

[0084] exist Figure 7 In the example shown, the value of calibration parameter 231 corresponding to the minimum measurement error is approximately 18369. Conversely, the default value of calibration parameter 231 is approximately 18362 and is associated with higher measurement errors.

[0085] If using the default value results in a measurement error greater than the specification, adjust the preset default value (680) of calibration parameter 231. Figure 7 In the example, the default value of calibration parameter 231 caused a measurement error value exceeding the specification, and the value of calibration parameter 231 was adjusted to the value of calibration parameter 231 corresponding to the minimum value of the measurement error (690). Then process 600 ends.

[0086] Figure 8A and Figure 10 Examples of deep ultraviolet (DUV) optical systems that can be used with optical measuring devices 160 or 260 are shown. In the example below, optical measuring device 260 is shown for use with a DUV optical system.

[0087] refer to Figure 8A and 8B The system 800 includes a light generation module 810, which provides an exposure beam (or output beam) 816 to a scanner device 880. The light generation module 810 and the scanner device 880 are implementations of the light generation module 110 and the device 180, respectively. Figure 1A ).

[0088] System 800 also includes a beam splitter 117, an optical measurement device 260, and a control system 250. The beam splitter 117 guides a portion of the exposure beam 816 to the optical measurement device 260, which is used to measure the wavelength of the exposure beam 816. The control system 250 is coupled to the optical measurement device 260. Figure 8A In the example, the control system 250 is also coupled to the light generation module 810 and various components associated with the light generation module 810.

[0089] The light generation module 810 includes an optical oscillator 812. The optical oscillator 812 generates an output beam 816. The optical oscillator 812 includes a discharge chamber 815 surrounding a cathode 813-a and an anode 813-b. The discharge chamber 815 also contains a gas gain medium 819. The potential difference between the cathode 813-a and the anode 813-b forms an electric field in the gas gain medium 819. The potential difference can be generated by applying a voltage to the cathode 813-a and / or the anode 813-b by controlling a voltage source 897. The electric field provides energy to the gain medium 819 sufficient to cause population inversion and enable the generation of light pulses via stimulated emission. The repeated creation of this potential difference forms a pulse train, which is emitted as the beam 816. The repetition rate of the pulse beam 816 is determined by the rate at which the voltage applied to the electrodes 813-a and 813-b is applied.

[0090] The gain medium 819 is pumped by applying voltage to electrodes 813-a and 813-b. The duration and repetition rate of the pulses in the pulse beam 816 are determined by the duration and repetition rate of the voltage applied to electrodes 813-a and 813-b. The repetition rate of the pulses can range, for example, between approximately 500 and 6,000 Hz. In some embodiments, the repetition rate can be greater than 6,000 Hz, and can be, for example, 12,000 Hz or greater. Each pulse emitted from the optical oscillator 812 can have a pulse energy of, for example, approximately 1 millijoule (mJ).

[0091] The gas gain medium 819 can be any gas suitable for generating a beam of light with the wavelength, energy, and bandwidth required for the application. The gas gain medium 819 can include more than one type of gas, and the various gases are referred to as gas components. For an excited excimer source, the gas gain medium 819 can contain rare gases such as, for example, argon or krypton; or halogens such as, for example, fluorine or chlorine. In implementations where halogens are the gain medium, the gain medium also includes trace amounts of xenon in addition to buffer gases such as helium.

[0092] The gas gain medium 819 can be a gain medium that emits light in the deep ultraviolet (DUV) range. DUV light can include wavelengths, for example, from about 100 nanometers (nm) to about 400 nm. Specific examples of the gas gain medium 819 include argon fluoride (ArF) emitting light at a wavelength of about 193 nm, krypton fluoride (KrF) emitting light at a wavelength of about 248 nm, or xenon chloride (XeCl) emitting light at a wavelength of about 351 nm.

[0093] A resonator is formed between a spectral adjustment device 895 on one side of the discharge chamber 815 and an output coupler 896 on the second side of the discharge chamber 815. The spectral adjustment device 895 may include diffractive optical components such as gratings and / or prisms, which fine-tune the spectral output of the discharge chamber 815. The diffractive optical components may be reflective or refractive. In some embodiments (such as...) Figure 9A As shown, the spectral adjustment device 895 includes multiple diffractive optical elements. For example, the spectral adjustment device 895 may include four prisms, some of which are configured to control the center wavelength of the beam 816, and others are configured to control the spectral bandwidth of the beam 816.

[0094] Also refer to Figure 9A A block diagram of a spectral adjustment device 995 is shown. The spectral adjustment device 995 can be used as a spectral adjustment device 895 in the light generation module 810.

[0095] The spectral adjustment device 995 includes a set of optical features or components 921, 922, 923, 924, 925 arranged to optically interact with the light beam 816. A control system 250 is connected to one or more actuation systems 921A, 922A, 923A, 924A, 925A, which are physically coupled to their respective optical components 921, 922, 923, 924, 925. The actuation systems 921A, 922A, 923A, 924A, 925A may include an axis (such as axis 926A) that causes components coupled to the axis to rotate about an axis parallel to the axis. The actuation systems 921A, 922A, 923A, 924A, and 925A also include electronic and mechanical devices such as motors and electronic interfaces for communicating with the control system 250 and for receiving electrical power.

[0096] Optical component 921 is a dispersive optical element, such as a grating or prism. Figure 9A In the example, optical component 921 is a reflective grating including a diffraction surface 902. Optical components 922, 923, 924, and 925 are refractive optical elements and may be, for example, prisms. Optical components 922, 923, 924, and 925 form a beam expander 901 having an optical magnification OM 965. The OM 965 of the beam 816 passing through the beam expander 901 is the ratio of the lateral width Wo of the beam 816 exiting the beam expander 901 to the lateral width Wi of the beam 816 entering the beam expander 901.

[0097] The surface 902 of the grating 921 is made of a material that reflects and diffracts the wavelength of the beam 816. Each of the prisms 922, 923, 924, and 925 is used to disperse and redirect the beam 816 as it passes through the prism body. Each of the prisms 922, 923, 924, and 925 is made of a material that transmits the wavelength in the beam 816. For example, if the beam 816 is in the DUV range, then the prisms 922, 923, 924, and 925 are made of a material that transmits light in the DUV range (such as, for example, calcium fluoride).

[0098] Prism 925 is furthest from grating 921, and prism 922 is closest to grating 921. Beam 816 enters the spectral adjustment device through aperture 955 and then passes through prisms 925, 924, 923, and 922 (in that order). With each passing of prisms 925, 924, 923, and 922, beam 816 is optically magnified and redirected (refracted at an angle) to the next optical component. After passing through prisms 925, 924, 923, and 922, beam 816 is reflected from surface 902. Then, beam 816 passes through prisms 922, 923, 924, and 925 (in that order). With each passing of prisms 922, 923, 924, and 925, beam 816 is optically compressed as it propagates toward aperture 955. After passing through prisms 922, 923, 924, and 925, beam 816 exits the spectral adjustment device 995 through aperture 955. After exiting the spectral adjustment device 995, beam 816 passes through chamber 815 and is reflected from output coupler 896 to return to chamber 815 and the spectral adjustment device 995.

[0099] The spectral characteristics of beam 816 can be adjusted by changing the relative orientation of optical components 921, 922, 923, 924 and / or 925. (Reference) Figure 9B The rotation of prism P (which can be any of prisms 922, 923, 924, or 925) about an axis perpendicular to the plane of the page changes the angle of incidence of the beam 816 onto the incident surface H(P) of the rotating prism P. Furthermore, the two local optical qualities of the beam 816 passing through the rotating prism P, namely the optical magnification OM(P) and the beam refraction angle δ(P), are functions of the angle of incidence of the beam 816 onto the incident surface H(P) of the rotating prism P. The optical magnification OM(P) of the beam 816 passing through prism P is the ratio of the lateral width Wo(P) of the beam 816A leaving prism P to the lateral width Wi(P) of the beam 816 entering prism P.

[0100] The change in the local optical magnification OM(P) of beam 816 at one or more prisms P within beam expander 901 causes an overall change in the optical magnification OM965 of beam 816 passing through beam expander 901. Additionally, the change in the local beam refraction angle δ(P) of beam 816A at the surface 902 of grating 921 causes an incident angle 962(P) of beam 816A. Figure 9A The overall change can be achieved by altering the incident angle 962 (where the beam 816 is incident on the surface 902 of the grating 921). Figure 9A The wavelength of beam 816 can be adjusted by changing the optical magnification 965 of beam 816. The spectral bandwidth of beam 816 can be adjusted by changing the optical magnification 965 of beam 816.

[0101] Therefore, the spectral characteristics of the beam 816 can be altered or adjusted by controlling the orientation of the grating 921 and / or one or more prisms 922, 923, 924, 925 via corresponding actuators 921A, 922A, 923A, 924A, 925A. The actuators 921A, 922A, 923A, 924A, 925A can be, for example, piezoelectric actuators that change shape in response to the application of voltage. Other implementations of the spectral adjustment device are also possible.

[0102] Refer again Figure 8A The spectral characteristics of beam 816 can be adjusted in other ways. For example, the spectral characteristics of beam 816, such as spectral bandwidth and center wavelength, can be adjusted by controlling the pressure and / or gas concentration of the gas gain medium in chamber 815. For implementations where the light generation module 810 is an excited excimer source, the spectral characteristics of beam 816 (e.g., spectral bandwidth or center wavelength) can be adjusted by controlling, for example, the pressure and / or concentration of fluorine, chlorine, argon, krypton, xenon, and / or helium in chamber 815.

[0103] The pressure and / or concentration of the gas gain medium 819 can be controlled by the gas supply system 890. The gas supply system 890 is fluidly coupled to the interior of the discharge chamber 815 via a fluid conduit 889. The fluid conduit 889 is any conduit capable of delivering gas or other fluids with minimal or no fluid loss. For example, the fluid conduit 889 may be a pipe made of or coated with a material that does not react with one or more fluids delivered in the fluid conduit 889. The gas supply system 890 includes a chamber 891 that contains and / or is configured to receive a supply of one or more gases used in the gain medium 819. The gas supply system 890 also includes devices (such as pumps, valves, and / or fluid switches) that enable the gas supply system 890 to remove gas from or inject gas into the discharge chamber 815. The gas supply system 890 is coupled to the control system 250.

[0104] The optical oscillator 812 also includes a spectral analysis device 898. The spectral analysis device 898 is a measurement system that can be used to measure or monitor the wavelength of the light beam 816. Figure 8A In the example shown, the spectral analysis device 898 receives light from the output coupler 896. In some implementations, the spectral analysis device 898 is part of the optical measurement device 260.

[0105] The light generation module 810 may include other components and systems. For example, the light generation module 810 may include a beam preparation system 899. The beam preparation system 899 may include a pulse broadener that temporally broadens each pulse interacting with the pulse broadener. The beam preparation system may also include other components capable of acting on light, such as reflective and / or refractive optical elements (e.g., lenses and mirrors) and / or filters. In the example shown, the beam preparation system 899 is located in the path of the exposure beam 816. However, the beam preparation system 899 may be placed at other locations within the system 800.

[0106] System 800 also includes a scanner device 880. The scanner device 880 exposes a wafer 882 with a shaped exposure beam 816A. The shaped exposure beam 816A is formed by passing the exposure beam 816 through a projection optics system 881. The scanner device 880 may be a liquid immersion system or a drying system. The scanner device 880 includes a projection optics system 881 and a sensor system or metering system 870, through which the exposure beam 816 passes before reaching the wafer 882. The wafer 882 is held or received on a wafer holder 883. The scanner device 880 may also include, for example, temperature control devices (such as air conditioning and / or heating devices) and / or power supplies for various electrical components.

[0107] The metering system 870 includes a sensor 871. The sensor 871 can be configured to measure characteristics of the shaped exposure beam 816A, such as bandwidth, energy, pulse duration, and / or wavelength. The sensor 871 can be, for example, a camera or other device capable of capturing an image of the shaped exposure beam 816A at the wafer 882, or an energy detector capable of capturing data describing the amount of optical energy at the wafer 882 in the x-y plane.

[0108] Also refer to Figure 8B The projection optical system 881 includes a slit 884, a mask 885, and a projection objective including a lens system 886. The lens system 886 includes one or more optical elements. An exposure beam 816 enters the scanner device 880 and illuminates the slit 884, and at least some of the output beams 816 pass through the slit 884 to form a shaped exposure beam 816A. Figure 8A and 8BIn the example, slit 884 is rectangular and shapes the exposure beam 816 into an elongated rectangular beam, which is the shaped exposure beam 816A. Mask 885 includes a pattern that determines which portions of the shaped beam are transmitted by mask 885 and which portions are blocked by mask 885. Microelectronic features are formed on wafer 882 by exposing a radiation-sensitive photoresist material layer on wafer 882 with exposure beam 816A. The design of the pattern on the mask is determined by the desired specific microelectronic circuit features.

[0109] Figure 8A The configuration shown is an example for a DUV system. Other implementations are also possible. For example, the light generation module 810 may include N instances of optical oscillators 812, where N is an integer greater than 1. In these implementations, each optical oscillator 812 is configured to emit its own beam to a beam combiner that forms an exposure beam 816.

[0110] Figure 10 Another example configuration of the DUV system is shown. Figure 10 This is a block diagram of a photolithography system 1000, including a light generation module 1010 that generates a pulsed light beam 1016, which is provided to a scanner device 880. The photolithography system 1000 also includes a beam splitter 117, an optical measurement device 260, and a control system 250. The control system 250 is coupled to various components of the optical measurement device 260, the light generation module 1010, and the scanner device 1080 to control various operations of the system 1000. Figure 10 In the example, beam splitter 117 directs a portion of the output beam 1016 to the optical measurement device 260. Other implementations are also possible. For example, beam splitter 117 could be positioned to interact with seed beam 1018.

[0111] The light generation module 1010 is a two-stage laser system including a master oscillator (MO) 1012_1 that provides a seed beam 1018 to a power amplifier (PA) 1012_2. PA 1012_2 receives the seed beam 1018 from MO 1012_1 and amplifies the seed beam 1018 to generate a beam 1016 for use in the scanner device 880. For example, in some implementations, MO 1012_1 can emit pulsed seed beams with a seed pulse energy of approximately 1 millijoules (mJ) per pulse, and these seed pulses can be amplified by PA 1012_2 to approximately 10 to 15 mJ; however, other energies can be used in other examples.

[0112] MO 1012_1 includes a discharge chamber 1015_1 with two elongated electrodes 1013a_1 and 1013b_1, a gain medium 1019_1 for a gas mixture, and a fan (not shown) for circulating the gas mixture between electrodes 1013a_1 and 1013b_1. A resonator is formed between a line narrowing module 1095 on one side of the discharge chamber 1015_1 and an output coupler 1096 on the second side of the discharge chamber 1015_1.

[0113] The discharge chamber 1015_1 includes a first chamber window 1063_1 and a second chamber window 1064_1. The first chamber window 1063_1 and the second chamber window 1064_1 are located on opposite sides of the discharge chamber 1015_1. The first chamber window 1063_1 and the second chamber window 1064_1 transmit light in the DUV range and allow DUV light to enter and exit the discharge chamber 1015_1.

[0114] The line narrowing module 1095 may include diffractive optics such as a grating to fine-tune the spectral output of the discharge chamber 1015_1. The light generation module 1010 also includes a line center analysis module 1068 and a beam coupling optics system 1069 that receive the output beam from the output coupler 1096. The line center analysis module 1068 is a measurement system that can be used to measure or monitor the wavelength of the seed beam 1018. The line center analysis module 1068 may be placed at other locations within the light generation module 1010, or it may be placed at the output of the light generation module 1010.

[0115] The gas mixture serving as the gain medium 1019_1 can be any gas suitable for generating a beam with the wavelength and bandwidth desired for the application. For the excited excimer source, the gas mixture can contain rare gases such as argon or krypton, halogens such as fluorine or chlorine, and trace amounts of xenon other than buffer gases such as helium. Specific examples of the gas mixture include argon fluoride (ArF) emitting light at a wavelength of about 193 nm, krypton fluoride (KrF) emitting light at a wavelength of about 248 nm, or xenon chloride (XeCl) emitting light at a wavelength of about 351 nm. Therefore, in this implementation, beams 1016 and 1018 encompass wavelengths in the DUV range. The excited excimer gain medium (gas mixture) is pumped with short (e.g., nanosecond) current pulses during high-voltage discharge by applying voltage to the elongated electrodes 1013a_1 and 1013b_1.

[0116] PA 1012_2 includes a beam coupling optics system 1069 that receives a seed beam 1018 from MO 1012_1 and guides the seed beam 1018 through discharge chamber 1015_2 to a beam steering optics element 1092. The beam steering optics element 1092 modifies or changes the direction of the seed beam 1018 so that the seed beam 1018 is sent back to discharge chamber 1015_2. The beam steering optics element 1092 and the beam coupling optics system 1069 form a loop and a closed-loop optical path, wherein the input to the ring amplifier and the output of the ring amplifier intersect at the beam coupling optics system 1069.

[0117] The discharge chamber 1015_2 includes a pair of elongated electrodes 1013a_2 and 1013b_2, a gain medium 1019_2, and a fan (not shown) for circulating the gain medium 1019_2 between the electrodes 1013a_2 and 1013b_2. The gas mixture forming the gain medium 1019_2 can be the same as the gas mixture forming the gain medium 1019_1.

[0118] The discharge chamber 1015_2 includes a first chamber window 1063_2 and a second chamber window 1064_2. The first chamber window 1063_2 and the second chamber window 1064_2 are located on opposite sides of the discharge chamber 1015_2. The first chamber window 1063_2 and the second chamber window 1064_2 transmit light in the DUV range and allow DUV light to enter and exit the discharge chamber 1015_2.

[0119] When gain medium 1019_1 or 1019_2 is pumped by applying voltage to electrodes 1013a_1, 1013b_1 or 1013a_2, 1013b_2 respectively, gain medium 1019_1 and / or 1019_2 emits light. The beam 1016 is pulsed when voltage is applied to the electrodes at regular time intervals. Therefore, the repetition rate of the pulsed beam 1016 is determined by the rate at which voltage is applied to the electrodes. For various applications, the repetition rate of the pulse can be in the range of approximately 500 to 6,000 Hz. In some implementations, the repetition rate can be greater than 6,000 Hz, and can be, for example, 12,000 Hz or greater, but other repetition rates can be used in other implementations.

[0120] The output beam 1016 can be guided through the beam preparation system 1099 before reaching the scanner device 880. The beam preparation system 1099 may include a bandwidth analysis module that measures various parameters of the beam 1016, such as bandwidth or wavelength. The beam preparation system 1099 may also include a pulse broadener that temporally broadens each pulse of the output beam 1016. The beam preparation system 1099 may also include other components capable of acting on the beam 1016, such as, for example, reflective and / or refractive optical elements (such as, for example, lenses and mirrors), filters, and optical apertures (including automatic shutters).

[0121] The DUV light generation module 1010 also includes a gas management system 1090, which is in fluid communication with the interior 1078 of the DUV light generation module 1010.

[0122] Other aspects of the invention are set forth in the following numbered clauses.

[0123] 1. An optical measuring device for a light source, the optical measuring device comprising:

[0124] A datum, comprising a focusing lens configured to focus light onto an image plane, wherein the datum is associated with calibration parameters related to the focusing lens, and the calibration parameters have preset default values;

[0125] An optical detector configured to detect an interference pattern generated by the etalon and generate information associated with the etalon, the information including first spatial information for a first fringe and second spatial information for a second fringe; and

[0126] A control system, coupled to the optical detector, is configured to:

[0127] The measurement error value of the etalon is determined based on the first spatial information from the detector, the second spatial information, and the initial values ​​of the calibration parameters; and

[0128] Analyze the measurement error value to determine whether to adjust the preset default value.

[0129] 2. The optical measuring apparatus according to Clause 1, wherein the light source includes a deep ultraviolet (DUV) light source.

[0130] 3. A light source, comprising:

[0131] Light generating device; and

[0132] Optical measuring device, including:

[0133] A datum, comprising a focusing lens configured to focus light onto an image plane, the datum being associated with calibration parameters related to the focusing lens, the calibration parameters having preset default values;

[0134] An optical detector configured to detect an interference pattern generated by the etalon and generate information associated with the etalon, the information including first spatial information for a first fringe and second spatial information for a second fringe; and

[0135] A control system, coupled to the optical detector, is configured to:

[0136] The measurement error value of the etalon is determined based on the first spatial information, the second spatial information, and the initial values ​​of the calibration parameters; and

[0137] Analyze the measurement error value to determine whether to adjust the preset default value.

[0138] 4. The light source according to Clause 3, wherein the light generating device includes a deep ultraviolet (DUV) light source.

[0139] 5. The light source according to Clause 4, wherein the light generating device includes a master oscillator.

[0140] 6. The light source according to Clause 4, wherein the light generating device further includes a power amplifier.

[0141] 7. The light source according to Clause 4, wherein the light generating device comprises a plurality of master oscillators.

[0142] 8. The light source according to Clause 3 further includes an optical element configured to receive light from the light generating device and direct the light to the etalon.

[0143] 9. The light source according to Clause 8, wherein the optical element is a dispersive optical element.

[0144] 10. A method comprising:

[0145] Access information related to an etalon, wherein the etalon is associated with calibration parameters having preset default values, the etalon is configured to generate an interference pattern comprising multiple fringes from a received beam, and the information related to the etalon includes first spatial information related to a first fringe of the multiple fringes and second spatial information related to a second fringe of the multiple fringes;

[0146] The first wavelength value of the received beam is determined based on the spatial information associated with the first stripe and the initial value of the calibration parameter;

[0147] The second wavelength value of the received beam is determined based on the spatial information associated with the second fringe and the initial value of the calibration parameters; and

[0148] The first wavelength value and the second wavelength value are compared to determine the measurement error value.

[0149] 11. The method according to Clause 10 further includes determining whether to adjust the preset default value of the calibration parameter based on the measurement error value.

[0150] 12. The method according to Clause 11, wherein the measurement error value includes the difference between the first wavelength value and the second wavelength value, and a preset default value is adjusted such that the magnitude of the measurement error value is less than a threshold value.

[0151] 13. The method according to Clause 12, wherein the preset default value is adjusted to a value such that the measurement error value is zero.

[0152] 14. The method according to Clause 10, wherein the calibration parameter includes the focal length of the lens at the output of the etalon, and the measurement error includes the difference between the first wavelength value and the second wavelength value.

[0153] 15. The method according to Clause 10, wherein the first spatial information includes the diameter of the first stripe, and the second spatial information includes the diameter of the second stripe.

[0154] 16. The method according to Clause 10 further includes directing the light beam toward the etalon; and wherein the first fringe is generated by a first portion of the light beam, and the second fringe is generated by a second portion of the light beam.

[0155] 17. The method according to Clause 16, wherein the light beam comprises a plurality of pulses, and the first portion of the light beam comprises a first pulse of the plurality of pulses, and the second portion of the light beam comprises a second pulse of the plurality of pulses.

[0156] 18. The method according to Clause 16, wherein the beam comprises a continuous wave beam, and the first portion of the beam comprises a first sample of the beam, and the second portion of the beam comprises a second sample of the beam.

[0157] 19. The method described in Clause 16 further includes:

[0158] Change the initial value of the calibration parameter to the updated value of the calibration parameter;

[0159] Actuating optical elements to thereby change the wavelength of the received light beam;

[0160] The first wavelength value of the received beam is determined based on the spatial information associated with the first fringe and the updated value of the calibration parameter;

[0161] The second wavelength value of the received beam is determined based on the spatial information associated with the second fringe and the updated value of the calibration parameters; and

[0162] The first wavelength value and the second wavelength value are compared to determine the measurement error value based on the updated value of the calibration parameter.

[0163] 20. The method according to Clause 19, wherein the optical element is actuated to increase or decrease the wavelength before the second wavelength value is determined.

[0164] 21. The method according to Clause 19, wherein the first wavelength value and the second wavelength value are determined more than once each time the optical element is actuated.

[0165] 22. The method according to Clause 20 further includes determining whether to adjust the preset default value of the calibration parameter by comparing the error measurement determined based on the initial value of the calibration parameter with the error measurement determined based on the updated value of the calibration parameter.

[0166] 23. The method according to Clause 10, wherein the initial value of the calibration parameter is the preset default value.

[0167] 24. The method according to Clause 10, wherein the first fringe and the second fringe are simultaneously in the interference pattern.

[0168] 25. A method for calibrating a standard etalon, the method comprising:

[0169] Access information related to an etalon, wherein the etalon is associated with calibration parameters having preset default values, the etalon is configured to generate an interference pattern comprising multiple fringes from a received beam, and the information related to the etalon includes first spatial information associated with a first fringe among the multiple fringes and second spatial information associated with a second fringe among the multiple fringes;

[0170] The measurement error value of the etalon is determined based on the first spatial information, the second spatial information, and the initial values ​​of the calibration parameters; and

[0171] Analyze the measurement error value to determine whether to adjust the preset default value.

[0172] 26. The method according to Clause 25, wherein the calibration parameter includes the focal length of the lens at the output of the etalon.

[0173] 27. The method described in accordance with Clause 26 further includes:

[0174] Determine the first wavelength value based on the first spatial information; and

[0175] The second wavelength value is determined based on the second spatial information, wherein the measurement error includes the difference between the first wavelength value and the second wavelength value.

[0176] 28. The method described in accordance with Clause 25, wherein

[0177] The calibration parameters include multiple initial values;

[0178] Determining the measurement error value includes simulating multiple measurement error values ​​for each of the plurality of initial values, each measurement error value being based on one of the plurality of initial values ​​of the first spatial information, the second spatial information, and the calibration parameter; and

[0179] Analyzing the measurement error values ​​includes analyzing the simulated measurement error values.

[0180] Other implementations are within the scope of the terms.

Claims

1. An optical measuring device for a light source, the optical measuring device comprising: A datum, comprising a focusing lens configured to focus light onto an image plane, wherein the datum is associated with calibration parameters related to the focusing lens, the calibration parameters including the focal length of the focusing lens, and the calibration parameters having preset default values; An optical detector configured to detect an interference pattern generated by the etalon and generate information associated with the etalon, the information including first spatial information for a first fringe and second spatial information for a second fringe, the first spatial information including the diameter of the first fringe and the second spatial information including the diameter of the second fringe; as well as A control system, coupled to the optical detector, is configured to: The measurement error value of the etalon is determined based on the first spatial information from the detector, the second spatial information, and the initial value of the calibration parameter; as well as Analyze the measurement error value to determine whether to adjust the preset default value.

2. The optical measuring device according to claim 1, wherein the light source comprises a deep ultraviolet light source.

3. A light source, comprising: Light generating device; as well as Optical measuring device, including: A datum, comprising a focusing lens configured to focus light onto an image plane, the datum being associated with calibration parameters related to the focusing lens, the calibration parameters including the focal length of the focusing lens, and the calibration parameters having preset default values; An optical detector configured to detect an interference pattern generated by the etalon and generate information associated with the etalon, the information including first spatial information for a first fringe and second spatial information for a second fringe, the first spatial information including the diameter of the first fringe and the second spatial information including the diameter of the second fringe; and A control system, coupled to the optical detector, is configured to: Based on the first spatial information, the second spatial information, and the initial values ​​of the calibration parameters, the measurement error value of the etalon is determined; and Analyze the measurement error value to determine whether to adjust the preset default value.

4. The light source according to claim 3, wherein the light generating device comprises a deep ultraviolet light source.

5. The light source according to claim 4, wherein the light generating device includes a master oscillator.

6. The light source according to claim 4, wherein the light generating device further comprises a power amplifier.

7. The light source according to claim 4, wherein the light generating device comprises a plurality of master oscillators.

8. The light source of claim 3, further comprising an optical element configured to receive light from the light generating device and direct the light to the etalon.

9. The light source according to claim 8, wherein the optical element is a dispersive optical element.

10. A method for determining a measurement error value, comprising: Access information related to an etalon, wherein the etalon is associated with calibration parameters having preset default values, the etalon is configured to generate an interference pattern comprising a plurality of fringes from a received beam, and the information associated with the etalon includes first spatial information associated with a first fringe among the plurality of fringes and second spatial information associated with a second fringe among the plurality of fringes, the calibration parameters including the focal length of a lens at the output of the etalon, the first spatial information including the diameter of the first fringe, and the second spatial information including the diameter of the second fringe; Based on the spatial information associated with the first stripe and the initial value of the calibration parameter, a first wavelength value of the received beam is determined; Based on the spatial information associated with the second fringe and the initial values ​​of the calibration parameters, the second wavelength value of the received beam is determined; as well as The first wavelength value and the second wavelength value are compared to determine the measurement error value.

11. The method of claim 10, further comprising determining whether to adjust the preset default value of the calibration parameter based on the measurement error value.

12. The method of claim 11, wherein the measurement error value includes the difference between the first wavelength value and the second wavelength value, and a preset default value is adjusted to make the magnitude of the measurement error value less than a threshold value.

13. The method of claim 12, wherein the preset default value is adjusted to a value that makes the measurement error value zero.

14. The method of claim 10, wherein the measurement error includes the difference between the first wavelength value and the second wavelength value.

15. The method of claim 10, further comprising guiding the light beam to the etalon; and wherein the first fringe is generated by a first portion of the light beam, and the second fringe is generated by a second portion of the light beam.

16. The method of claim 15, wherein the light beam comprises a plurality of pulses, and the first portion of the light beam comprises a first pulse of the plurality of pulses, and the second portion of the light beam comprises a second pulse of the plurality of pulses.

17. The method of claim 15, wherein the beam comprises a continuous wave beam, and the first portion of the beam comprises a first sample of the continuous wave beam, and the second portion of the beam comprises a second sample of the continuous wave beam.

18. The method of claim 15, further comprising: Change the initial value of the calibration parameter to the updated value of the calibration parameter; Actuating optical elements to thereby change the wavelength of the received light beam; The first wavelength value of the received beam is determined based on the spatial information associated with the first stripe and the updated value of the calibration parameter. The second wavelength value of the received beam is determined based on the spatial information associated with the second fringe and the updated value of the calibration parameter; as well as The first wavelength value and the second wavelength value are compared to determine the measurement error value based on the updated value of the calibration parameter.

19. The method of claim 18, wherein the optical element is actuated to increase or decrease the wavelength before determining the second wavelength value.

20. The method of claim 18, wherein the first wavelength value and the second wavelength value are determined more than once each time the optical element is actuated.

21. The method of claim 19, further comprising determining whether to adjust the preset default value of the calibration parameter by comparing a measurement error value determined based on the initial value of the calibration parameter and a measurement error value determined based on the updated value of the calibration parameter.

22. The method of claim 10, wherein the initial value of the calibration parameter is the preset default value.

23. The method of claim 10, wherein the first fringe and the second fringe are simultaneously located within the interference pattern.

24. A method for calibrating a standard etalon, the method comprising: Access information related to an etalon, wherein the etalon is associated with calibration parameters having preset default values, the etalon is configured to generate an interference pattern comprising a plurality of fringes from a received beam, and the information associated with the etalon includes first spatial information associated with a first fringe among the plurality of fringes and second spatial information associated with a second fringe among the plurality of fringes, the calibration parameters including the focal length of a lens at the output of the etalon, the first spatial information including the diameter of the first fringe, and the second spatial information including the diameter of the second fringe; The measurement error value of the etalon is determined based on the first spatial information, the second spatial information, and the initial values ​​of the calibration parameters. as well as Analyze the measurement error value to determine whether to adjust the preset default value.

25. The method of claim 24, further comprising: The first wavelength value is determined based on the first spatial information; as well as The second wavelength value is determined based on the second spatial information, wherein the measurement error includes the difference between the first wavelength value and the second wavelength value.

26. The method of claim 24, wherein The calibration parameters include multiple initial values; Determining the measurement error value includes simulating multiple measurement error values ​​for each of the plurality of initial values, each measurement error value being based on one of the plurality of initial values ​​of the first spatial information, the second spatial information, and the calibration parameter; and Analyzing the measurement error values ​​includes analyzing the simulated measurement error values.

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