Methods and systems for providing loopback diagnostics

Abstract

Methods and systems for validating one or more sensors, one or more circuit boards, one or more connectors, or the like in lithographic apparatuses and systems are provided. For example, a metrology system (600) includes a first circuit board (603) including a sensor (611) and a multiplexer (613) configured to receive a first analog signal (621) corresponding to a first digital signal (619)) and output a second analog signal (625). The metrology system (600) further includes a second circuit board (601) including a processor (605) configured to generate the first digital signal (619). The processor (605) is further configured to receive a second digital signal (631) corresponding to the second analog signal (625) output from the multiplexer (613). The processor (605) is further configured to determine whether a fault exists in one or more of the first circuit board (603), the second circuit board (601), or a connection between the first circuit board (603) and the second circuit board (601) based on the received second digital signal (631).

Description

METHODS AND SYSTEMS FOR PROVIDING LOOPBACK DIAGNOSTICSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 610,907, filed December 15, 2023, titled METHODS AND SYSTEMS FOR PROVIDING LOOPBACK DIAGNOSTICS, which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to loopback diagnostic methods and systems, for example, methods and systems for validating one or more sensors, one or more circuit boards, one or more connectors, one or more cables, or the like in lithographic apparatuses and systems.BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which can be a mask or a reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiationsensitive material (photoresist or simply “resist”) provided on the substrate . In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatuses include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning” - direction) while synchronously scanning the target portions parallel or anti-parallel to this scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] The lithographic apparatus can include a radiation source for generating the radiation beam that is used in the lithographic apparatus. The radiation source can include (or be coupled) to one or more metrology devices that can be used to measure one or more parameters of the radiation beam and / or the radiation source. One or more circuit boards, one or more connectors, one or more cables, or the like can be used between sensor(s) of the metrology device and a controller used for analyzing the data collected by the sensor(s). In various configurations of the radiation source, a data path between the sensor and the controller (which can include one or more circuit boards, one or more connectors, one or more cables, or the like) may not be not validated. Such a data path is a vulnerable path that can have faults and / or can be susceptible to noise. One or more of devices, connectors, cables, etc. can thus have complications or unreliability in data transmission.SUMMARY

[0005] Accordingly, methods and systems for validating one or more sensors, one or more circuit boards, one or more connectors, one or more cables, or the like in lithographic apparatuses and systems are provided.

[0006] In some aspects, a metrology system includes a first circuit board including a sensor configured to detect a radiation beam generated by a radiation source and a multiplexer configured to receive a first analog signal corresponding to a first digital signal and output a second analog signal. The metrology system further includes a second circuit board including a processor configured to generate the first digital signal where the first digital signal or the first analog signal is transmitted to the first circuit board. The processor is further configured to receive a second digital signal corresponding to the second analog signal output from the multiplexer of the first circuit board. The processor is further configured to determine whether a fault exists in one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board based on the received second digital signal.

[0007] In some aspects, a method includes generating, by a first circuit board of a metrology system, a first digital signal and converting, by the first circuit board, the first digital signal to a first analog signal. The method further includes transmitting, by the first circuit board, the first analog signal to a second circuit board of the metrology system and receiving, by the first circuit board, a second digital signal from the second circuit board, wherein the second digital signal corresponds to a second analog signal output from a multiplexer of the second circuit board. The method also includes determining, by the first circuit board, whether a fault exists in one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board based on the received second digital signal.

[0008] In some aspects, a non-transitory computer-readable storage medium, having stored thereon program instructions that, upon execution by at least one processor, cause the at least one processor to perform operations including generating, by a first circuit board of a metrology system, a first digital signal and converting, by the first circuit board, the first digital signal to a first analog signal. The operations further include transmitting, by the first circuit board, the first analog signal to a second circuit board of the metrology system and receiving, by the first circuit board, a second digital signal from the second circuit board, wherein the second digital signal corresponds to a second analog signal output from a multiplexer of the second circuit board. The operations further include determining, by the first circuit board, whether a fault exists in one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board based on the received second digital signal.

[0009] In some aspects, a metrology test circuit includes a signal generator configured to generate a first test signal, where the first test signal has a voltage range within an expected voltage output rangeof a first type of sensor. The metrology test circuit further includes a communications port configured to transmit the test signal to a first type of metrology module, where the first type of metrology module includes a sensor of the first type of sensor. The communications port is further configured to receive a first measurement signal from the first type of metrology module. The metrology test circuit further includes a processor configured to perform a first comparison between the first measurement signal and the first test signal. The processor is further configured to determine whether a fault exists in one or more of the metrology test circuit, the first type of metrology module, or a connection between the metrology test circuit and the first type of metrology module based on the first comparison.

[0010] Further features of various aspects of the present disclosure are described in detail below with reference to the accompanying drawings. It is noted that the present disclosure is not limited to the specific aspects described herein. Such aspects are presented herein for illustrative purposes only. Additional aspects will be apparent to those skilled in the relevant art(s) based on the teachings contained herein.BRIEF DESCRIPTION OF THE DRAWINGS / FIGURES

[0011] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable those skilled in the relevant art(s) to make and use aspects described herein.

[0012] FIG. 1 shows a lithographic apparatus, according to some aspects.

[0013] FIG. 2 shows a lithographic cell, according to some aspects.

[0014] FIGS. 3-5 show radiation sources, according to some aspects.

[0015] FIG. 6 shows an exemplary system for providing a loopback diagnostic, according to some aspects.

[0016] FIG. 7 shows an example method for a system (for example, a loopback diagnostic system) performing the loopback diagnostic, according to some aspects.

[0017] FIG. 8 shows an exemplary voltage ramp stepping pattern, according to some aspects.

[0018] FIG. 9 is an example computer system for implementing some aspects or portion(s) thereof.

[0019] The features of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to-scale drawings.DETAILED DESCRIPTION

[0020] The aspects described herein, and references in the specification to “one aspect,” “an aspect,” “an exemplary aspect,” “an example aspect,” etc., indicate that the aspects described can include a particular feature, structure, or characteristic, but every aspect may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same aspect. Further, when a particular feature, structure, or characteristic is described in connection with an aspect, it is understood that it is within the knowledge of those skilled in the art to effect such feature, structure, or characteristic in connection with other aspects whether or not explicitly described.

[0021] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, can be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein can likewise be interpreted accordingly.

[0022] The terms “about,” “approximately,” or the like can be used herein to indicate the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the terms “about,” “approximately,” or the like can indicate a value of a given quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0023] Enumerative adjectives (e.g., “first,” “second,” “third,” or the like) can be used to distinguishing like elements without establishing an order, hierarchy, quantity, or permanent numeric assignment (unless otherwise noted). For example, the terms “first target” and “second target” can be used in a manner analogous to “ithtarget” and “jthtarget” so as to facilitate the distinguishing of two targets without specifying a particular order, hierarchy, quantity, or immutable numeric correspondence.

[0024] Aspects of the present disclosure can be implemented in hardware, firmware, software, or any combination thereof. Aspects of the disclosure can also be implemented as instructions stored on a computer-readable medium, which can be read and executed by one or more processors. A machine- readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine -readable medium can include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines, and / or instructions can be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. The term “machine -readable medium” can be interchangeable with similar terms, forexample, “computer program product,” “computer-readable medium,” “non-transitory computer- readable medium,” or the like . The term “non-transitory” can be used herein to characterize one or more forms of computer readable media except for a transitory, propagating signal.

[0025] Before describing such aspects in more detail, however, it is instructive to present an example environment in which aspects of the present disclosure can be implemented.

[0026] Example Lithographic Systems

[0027] FIG. 1 shows a lithographic apparatus 100, in which aspects of the present disclosure can be implemented. Lithographic apparatus 100 can include one or more of the following: an illuminator IL to condition a radiation beam B (e.g., deep ultra violet (DUV) radiation); a support structure MT (e.g., a mask table) to support a patterning device MA (e.g., a mask, a reticle, or a dynamic patterning device); a first positioner PM to accurately position patterning device MA; a substrate table WT (e.g., a wafer table) to hold a substrate W (e.g., a resist-coated wafer); and a second positioner PW to accurately position substrate W. Lithographic apparatus 100 can also include a projection system PS to project patterned radiation onto a target portion C (e.g., comprising one or more dies) of substrate W. The pattern can be imparted to radiation beam B by patterning device MA. In lithographic apparatus 100, patterning device MA and projection system PS can be transmissive.

[0028] In some aspects, illuminator IL can include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B.

[0029] In some aspects, support structure MT can hold patterning device MA in a manner that depends on the orientation of patterning device MA with respect to a reference frame, a design of lithographic apparatus 100, and other conditions, such as whether or not patterning device MA is held in a vacuum environment. Support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. Support structure MT can be, for example, a frame or a table (e.g., can be fixed ormovable). By using one or more positioning sensors (e.g., alignment sensor), support structure MT can ensure that patterning device MA is at a desired position, for example, with respect to the projection system PS.

[0030] In some aspects, the term “patterning device” can refer to a device that can be used to create a pattern of radiation at a cross-section of radiation beam B, such as to create a pattern at target portion C of substrate W. The pattern imparted to radiation beam B can correspond to a particular functional layer in a device being created at target portion C to form an integrated circuit. Examples of patterning devices MA include, for example, reticles, masks, or programmable LCD panels. Masks types used in lithography can include binary, alternating phase shift, or attenuated phase shift, as well as various hybrid mask types.

[0031] In some aspects, the term “projection system” can refer to any type of projection system (e.g., refractive, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof) suitable for the exposure radiation being used. Features of projection systems can account foradditional factors, such as the use of an immersion liquid on the substrate W or the use of a vacuum. For example, a projection system can be designed for use in a controlled gas environment such that the beam path can be conditioned as desired.

[0032] In some aspects, lithographic apparatus 100 can be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such “multiple stage” machines, the additional substrate tables WT can be used in parallel, or preparatory steps can be carried out on one or more tables while one or more other substrate tables WT are being used for exposure. In some situations, the additional table may not be a substrate table.

[0033] In some aspects, lithographic apparatus 100 can also be of a type in which at least a portion of substrate W can be covered by a liquid having a relatively high refractive index, e.g., water, so as to fdl a space between projection system PS and substrate W. An immersion liquid can also be applied to other spaces in lithographic apparatus 100, for example, between patterning device MA and projection system PS. Immersion techniques can increase the numerical aperture (NA) of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid. For example, a liquid can be disposed between projection system PS and substrate W during exposure.

[0034] In some aspects, illuminator IL can receive a radiation beam from source SO (e.g., radiation source). Source SO and lithographic apparatus 100 can be separate physical entities. For example, source SO can be a detached excimer laser such as a krypton fluoride (KrF) laser or an argon fluoride laser (ArF). In such cases, source SO is not considered to be part of the lithographic apparatus 100 and radiation beam B passes from source SO to illuminator IL with the aid of a beam delivery system BD. Beam delivery system BD can include, for example, suitable directing mirrors and / or a beam expander.

[0035] In some aspects, source SO can be an integral part ofthe lithographic apparatus 100. A radiation system (or illumination system) can include source SO, illuminator IL, and / or beam delivery system BD.

[0036] In some aspects, illuminator IL can include an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as “n-outer” and “n-inner,” respectively) of the intensity distribution in a pupil plane of illuminator IL can be adjusted. In addition, illuminator IL can include various other components, such as an integrator IN and a condenser CO. Illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0037] In some aspects, radiation beam B can be incident on patterning device MA, which is held on support structure MT, and is patterned by patterning device MA. Having traversed patterning device MA, radiation beam B can pass through projection system PS, which focuses the beam onto a target portion C of substrate W. Projection System PS has a pupil conjugate PPU to an illumination system pupil IPU. Portions of radiation emanate from the intensity distribution at the illumination system pupilIPU and traverse a mask pattern without being affected by diffraction at the mask pattern and create an image of the intensity distribution at the illumination system pupil IPU.

[0038] In some aspects, projection system PS can project an image of a pattern MP of patterning device MA. The image can be formed by diffracted beams produced from the pattern MP by radiation from the intensity distribution. The image can be projected on a photoresist layer coated on the substrate W. For example, pattern MP can include an array of lines and spaces.

[0039] In some aspects, lithographic apparatuses can include a deep ultraviolet (DUV) source, which is configured to generate a beam of DUV radiation for DUV lithography. In general, the DUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the DUV radiation beam of the DUV source.

[0040] Example Uithographic Cell

[0041] FIG. 2 shows a lithographic cell 200, also sometimes referred to a lithocell or cluster, according to some aspects. Uithographic apparatus 100 can form part of lithographic cell 200. Uithographic cell 200 can also include one or more apparatuses to perform pre- and post-exposure processes on a substrate. Examples of such apparatuses can include spin coaters SC to deposit resist layers, developers DE to develop exposed resist, chill plates CH, and bake plates BK. A substrate handler, or robot, RO can pick up substrates from input / output ports I / Ol, I / O2, move them between the different process apparatuses and deliver the substrates to a loading bay LB of lithographic apparatus 100. The different apparatuses, which are often collectively referred to as the track, can be under the control of a track control unit TCU, which can itself be controlled by a supervisory control system SCS. Supervisory control system can also control lithographic apparatus 100 via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0042] Example Radiation Source

[0043] There are many applications of pulsed-discharge radiation sources. In some aspects, a pulsed- discharge laser can be used for lithographic processes, medical procedures, machining via laser ablation, laser imprinting, and more. A lithographic apparatus is one example in which a stable radiation source is desirable.

[0044] The radiation source can include (or be coupled) to one or more metrology devices that can be used to measure one or more parameters of the radiation beam and / or the radiation source. The metrology devices can measure different attributes of the radiation beam (e.g., a laser) such as, but not limited to, wavelength, bandwidth, energy, and the like. For example, the metrology devices can be positioned at different stages of the path of the radiation beam and can measure one or more of wavelength, bandwidth (e.g., full width at half maximum (FWHM) or 95% integral (E95)), energy, or the like radiation beam. The sensor(s) of the metrology device can be positioned on a circuit board that can be separate from the circuit board(s) that include a controller for analyzing the data collected by the sensor(s) of the metrology device.

[0045] One or more circuit boards, one or more connectors, one or more cables, or the like can be used between the sensor and the controller. In this example, the data path between the sensor and the controller (which can include one or more circuit boards, one or more connectors, one or more cables, or the like) is not validated. This data path is a vulnerable path that can have faults / errors and / or can be susceptible to noise. One or more of devices, connectors, cables, etc. involved in this data path can have problems that are not identified until they introduce errors in transmitted data or fail to transmit data.

[0046] FIG. 3 shows a radiation source 300, according to some aspects. In some aspects, radiation source 300 is a pulsed-discharge radiation source. A gas discharge laser is an example of a pulsed- discharge radiation source. Source SO of lithographic apparatus 100 (FIG. 1) can use radiation source 300. Radiation source 300 can include a gas chamber 302, a window 304, conduit system 306, and one or more electrodes 310 (also “electrical connection”). Conduit system 306 can include a network of valves, conduits, and contaminant filters (not shown).

[0047] In some aspects, gas chamber 302 can confine a gas 308. Gas 308 can include fluorine, neon, krypton, argon, and the like. Gas 308 can be rarified via a pressure control system (e.g., vacuum system) that controls a pressure within gas chamber 302. Conduit system 306 is connected to gas chamber 302. Conduit system 306 can allow management of gas 308 in gas chamber 302. For example, conduit system 306 can direct a flow (e.g., circulation) of gas 308 to a filter within conduit system 306 to purify gas 308. A voltage / current can be supplied to gas 308 (e.g., via one or more electrodes 310) to generate radiation 312. The voltage / current can be in the form of pulses with sufficient power to strike a plasma of gas 308. The plasma can generate radiation with a set of wavelengths that depend on energy states of the plasma. The type of gas 308 (e.g., a mixture of argon and fluorine with additional gasses, or a mixture of krypton and fluorine with additional gasses) can determine the wavelengths that are produced (e.g., DUV wavelengths). Window 304 can allow radiation 312 to exit gas chamber 302.

[0048] FIG. 4 shows a radiation source 400, according to some aspects. In some aspects, the view in FIG. 4 can represent a more detailed and / or different view of a portion of radiation source 300 (FIG. 3) (some omissions can be made for clarity of drawing). Structures and functions of commonly numbered elements in FIGS. 3 and 4 are described above (e.g., matching elements can have reference numbers that share the two right-most numeric digits). Such elements can include gas chamber 402, gas 408, and electrodes 410.

[0049] In some aspects, radiation source 400 can include gas chamber 402, one or more electrodes 410, and a gas circulator 414. Gas circulator 414 can be blower or an external pressure system that is connected to gas chamber 402 via ducting. Gas chamber 402 can confine a gas. The gas can include fluorine, neon, krypton, argon, or other similar species (for example, argon fluoride). To generate radiation 312 (FIG. 3), an electrical pulse can be supplied to gas 408 via electrodes 410, thereby igniting a plasma of gas 408 at plasma region 416 of gas chamber 402. The generated plasma can release radiation, thereby operating as a radiation source. The perspective in FIG. 4 can be considered as being 90 degrees with respect to the perspective of FIG. 3 (e.g., whereas radiation 312 is shown in FIG. 3traveling to the right of the page (can also be left of the page), radiation can travel in / out of the page in FIG. 4).

[0050] In some aspects, in the process of generating radiation, gas 408 and electrodes 410 can interact chemically. For example, a material of electrodes 410 (e.g., copper) can chemically interact with a chemical content of gas 408 (e.g., fluoride) to create a dust-like byproduct (e.g., metal -fluoride by product). The airborne byproduct can become a contaminant that absorbs radiation in subsequent radiation pulses. Therefore, a gas flow 418 (indicated by arrows) can be implemented in order to optimize the production of radiation by circulating the spent portion of gas 408 and contaminants out of the plasma-generation zone while supplying unspent gas for the next plasma ignition. Gas circulator 414 can generate gas flow 418. Additional details about blower functions are described in WO 2022 / 140074, published on June 30, 2022, which is incorporated by reference herein in its entirety.

[0051] FIG. 5 shows a radiation source 500, according to some aspects. In some aspects, the view in FIG. 5 can represent a more detailed and / or different view of a portion of radiation sources 300 and 400 (FIG. 3 and 4) (some omissions can be made for clarity of drawing). Structures and functions of commonly numbered elements in FIGS. 3-5 are described above (e.g., matching elements can have reference numbers that share the two right-most numeric digits). Such elements can include gas chamber 502, gas 508, radiation 512, and gas circulator 514.

[0052] In some aspects, radiation source 500 can include additional elements that allow intensity gains that subsequently lead to the production of radiation 512. For example, radiation source 500 can include an output coupler 520, a wavelength selector 522, and a controller 524. Wavelengths selector 522 can include a wavelength-dependent reflector 526. For example, wavelength-dependent reflector 526 can include a refractive element (e.g., a prism) and / or a diffractive element (e.g., a grating). In some aspects, the metrology system of this disclosure can be positioned at the output of gas chamber 502 (e.g., before or after output coupler 520) to measure the radiation (e.g., radiation 528). For single chamber lasers, the metrology system controller can have a stepper motor controller IC and PZT voltages (e.g., controller 524) that control the prism position (e.g., actuator 530) in wavelength selector 522.

[0053] In some aspects, an electrical pulse is applied to gas 508 to ignite a plasma and generate radiation 512 (e.g., as described in reference to FIG. 3). Molecules of gas 508 can have multiple energy levels capable of decaying with the release of photons (photon wavelengths correspond to the multiple energy levels). Subsequently, abeam of radiation 528 is output from radiation source 500. In the context of lithographic processes, beam of radiation 528 can be radiation beam B of FIG. 1. A narrow and stable wavelength is desirable for lithographic processes because wavelength instabilities can adversely impact the accuracy of patterns that get printed on a substrate. As a non-limiting example, beam of radiation 528 can have a DUV wavelength of approximately 193 nm, which can be used for a lithographic process. Therefore, it is desirable to select a narrowband wavelength from the plurality of wavelengths that are generated in the plasma of gas 508.

[0054] In some aspects, wavelength selector 522 can be used to perform wavelength selection. The wavelength selection process can rely on laser oscillation to further amplify the radiation at the desired wavelength in comparison to the unselected wavelengths (thus reducing the bandwidth of the resulting radiation 528). The process can begin by allowing radiation 512 to propagate toward wavelength selector 522. Wavelength-dependent reflector 526 can reflect a portion of radiation 512 (the portion that has the selected wavelength) along an optical path through a laser gain medium (not shown) while rejecting other portions of radiation 512 that have undesirable wavelengths (e.g., diverting unselected wavelengths toward a beam dump). Hence, the wavelength of radiation 512 can be narrowed to a narrowband having a peak central wavelength and a small full -width-half-maximum. Wavelength selector 522 can be referred to as a narrowing device, narrowing module, line narrowing module (LNM), or the like.

[0055] In some aspects, the “gain path” can be defined between wavelength-dependent reflector 526 and output coupler 520, with the plasma of gas 508 being the gain medium. Lasing can be achieved as radiation 512 (at the selected wavelength) bounces back and forth between wavelength-dependent reflector 526 and output coupler 520 (output coupler 520 can have a reflective property). Output coupler 520 can include a partial reflector that allows a fraction of the, now amplified, radiation 512 (at the selected wavelength) to be output as beam of radiation 528.

[0056] In some aspects, gas chamber 502 can be referred to as a master oscillator (MO) chamber since radiation 512 is generated at gas chamber 502 and oscillates back and forth through gas chamber 502 to achieve intensity gains.

[0057] In some aspects, adjusting the wavelength (e.g., selecting another wavelength) can be achieved by adjusting a position of wavelength-dependent reflector 526 (e.g., rotating a diffractive or refractive element). Diffractive and refractive elements have wavelength-dependent scattering directions. As the position of the diffractive (or refractive) element is changed, a different wavelength can be aligned along the gain path while other wavelengths are directed away from the gain path. The lasing process can then amplify radiation 512 for the adjusted wavelength.

[0058] In some aspects, wavelength selector 522 can also include an actuator 530. wavelengthdependent reflector 526 can be disposed on actuator 530. Controller 524 can be used in to perform the wavelength selection or adjustment by actuating wavelength-dependent reflector 526 via actuator 530. It is desirable for actuator 530 to be capable of high positional accuracy, as well as high frequency adjustments (e.g., greater than 1 kHz, 10 kHz, or the like). Controller 524 can send a control signal 532 (e.g., a command, instructions, voltage / current signal, or the like). Actuator 530 can move according to control signal 532.

[0059] In some aspects, radiation source 500 can include a detector 534 to interrogate a portion of radiation 512. Detector 534 can be disposed at wavelength selector 522. Detector 534 can be referred to as a line-center analysis module (LAM) for analyzing one or more performance criteria (e.g., wavelength) of the linear narrowing module (wavelength selector 522). In some aspects, detector 534can include the metrology system of this disclosure. In some aspects, detector 534 can be located at the output of chamber 502. In some aspects, detector 534 can be disposed at other suitable locations for receiving a portion of radiation 512 or a portion of beam of radiation 528 (e.g., a portion of the beam, deflected by a mirror or by a beam splitter). Detector 534 can generate a measurement signal 536 that is indicative of a property of beam of radiation 528 (e.g., wavelength, bandwidth, power, intensity, timing, pulse duration, or other properties, or combinations thereof. Measurement signal 536 can be received at controller 524, as well as at other processing systems. Measurement signal 536 can be used for reporting a real -team status of the wavelength of beam of radiation 528.

[0060] In some aspects, radiation source 500 can also include one or more additional amplification chambers 540. Amplification chambers 540 can provide additional amplification of beam of radiation 528. Amplification chambers 540 can also be referred to as power amplifier (PA) chambers.

[0061] Additional details about wavelength-selection are described in U.S. Patent No. 8,254,420, issued on August 28, 2012, which is incorporated by reference herein in its entirety.

[0062] Example Methods and Systems for Providing a Loopback Diagnostic

[0063] FIG. 6 illustrates an exemplary system 600 for providing a loopback diagnostic, according to some aspects. Loopback diagnostic system 600 can be a metrology system. Additionally, or alternatively, loopback diagnostic system 600 can be part of a metrology system. Loopback diagnostic system 600 can be used with one or more of source SO of FIG. 1, radiation source 300 of FIG. 3, radiation source 400 of FIG. 4, and / or radiation source 500 of FIG. 5. Additionally, or alternatively, loopback diagnostic system 600 can be used with other radiation sources that can be used with other systems. For example, loopback diagnostic system 600 can be use with metrology systems used for measuring one or more parameters associated with lithography apparatuses (e.g., lithography apparatus 100 of FIG. 1.) According to some aspects, loopback diagnostic system 600 can be, can include, or can be part of controller 524 of FIG. 5.

[0064] According to some aspects, loopback diagnostic system 600 can include controller circuit board 601 and sensor circuit board 603. Controller circuit board 601 can include processor 605, digital -to- analog converter (DAC) 607, and deserializer 609. Illustrated systems are provided as exemplary parts of controller circuit board 601, and controller circuit board 601 can include other circuit(s) and subsystem(s). Also, although controller circuit board 601 is illustrated with separate components, the aspects of this disclosure can include any combination of these, less, or more components. Also, controller circuit board 601 of the aspects of this disclosure can include any number of processors, DACs, deserializers, and other circuit(s) and subsystem(s). According to some aspects, processor 605 can include one or more processor, an Field Programmable Gate Arrays (FPGA), a system on chip (SoC), an application-specific integrated circuit (ASIC), or the like.

[0065] Sensor circuit board 603 can include sensor 611, multiplexer 613, analog -to-digital converter (ADC) 615, and serializer 617. Illustrated systems are provided as exemplary parts of sensor circuit board 603, and sensor circuit board 603 can include other circuit(s) and subsystem(s). Also, althoughsensor circuit board 603 is illustrated with separate components, the aspects of this disclosure can include any combination of these, less, or more components. Also, sensor circuit board 603 of the aspects of this disclosure can include any number of sensors, multiplexers, ADCs, serializers, and other circuit(s) and subsystem(s).

[0066] Sensor circuit board 603 can be part of metrology system(s) used to measure one or more parameters of a radiation beam and / or a radiation source. As mentioned above, sensor 611 of sensor circuit board 603 can detect the radiation beam (e.g., a laser). Sensor 611 can output analog signal 623 (e.g., an analog voltage signal) where the processor 605 can measure different attributes of the radiation beam (e.g., a laser) such as, but not limited to, wavelength, bandwidth, energy, and the like based on analog signal 623. For example, sensor 611 of sensor circuit board 603 can be positioned at different stages of the path of the radiation beam and can measure one or more of wavelength, bandwidth (e.g., FWHM or E95)), energy, or the like radiation beam.

[0067] According to some aspects, the radiation beam generated by the radiation source (e.g., one or more of source SO of FIG. 1, radiation source 300, radiation source 400, or radiation source 500) can pass through one or more lenses, which project a pattern (e.g., a fringe pattern) onto sensor 611. In various implementations, sensor 611 can generate an analog video signal (e.g., analog signal 623) that has a time -dependent voltage indicative of intensity information for a number of pixels from a light- sensitive detector (e.g., 256 pixels, 512 pixels, 1024 pixels, 2048 pixels, or the like). The analog voltage (e.g., analog signal 623) can be converted to digital voltage (e.g., digital signal 627 using ADC 615). The digital voltage can be shifted serially (e.g., to digital signal 629 using serializer 617) and can be sent to controller circuit board 601 for analysis. Sensor 611 can be configured to output a video signal based on the sensed radiation beam. The output video signal can include peak voltage(s) representing areas of high (or highest) light intensity in the sensed radiation beam. The output video signal can be used (e.g., by processor 605) to determine one or more parameters associated with the radiation beam (and / or the radiation source).

[0068] Controller circuit board 601 and sensor circuit board 603 can be separate from each other and can be coupled to each other using cables (e.g., flexible cables), interface boards, connectors (e.g., blindmate connectors), harnesses, or the like. Processor 605 of controller circuit board 601 can be configured to receive and analyze data collected by sensor 611 of sensor circuit board 603. Additionally, or alternatively, and as discussed in more detail below, processor 605 of controller circuit board 601 can determine faults / errors and / or noise on one or more of controller circuit board 601, sensor circuit board 603, a connection between controller circuit board 601 and sensor circuit board 603, or the associated components of controller circuit board 601 and / or sensor circuit board 603. Additionally, or alternatively, and as discussed in more detail below, processor 605 of controller circuit board 601 can determine the latency of the serializer 617 and / or deserializer 609.

[0069] According to some aspects, processor 605 is configured to generate digital signal 619. Digital signal 619 is output from processor 605 and is input to DAC 607. According to some aspects, processor605 generates digital signal 619 for the loopback diagnostic processes discussed herein. Processor 605 can be configured to generate digital signal 619 specific for the particular loopback diagnostic process that processor 605 uses. In some aspects, processor 605 can generate and use different digital signals 619 for different loopback diagnostics. Additionally, or alternatively, processor 605 can generate and use the same digital signal 619 for different loopback diagnostics. In some aspects, processor 605 can include and / or be coupled to a Field Programmable Gate Arrays (FPGA) (not shown), where the FPGA is configured to generate digital signal 619, receive digital signal 631, and send digital signal 631 to processor 605 for analysis.

[0070] According to some aspects, digital signal 619 can include a voltage ramp stepping pattern. For example, the voltage ramp stepping pattern can include a plurality of voltage steps from a first voltage value to a second voltage value with a step value and back to the first voltage value. According to some aspects, the first voltage value can be minimum voltage value that a sensor (e.g., sensor 611) can provide and the second voltage value can be the maximum voltage value that the sensor (e.g., sensor 611) can provide.

[0071] In a non-limiting example, the voltage ramp stepping pattern can include the plurality of voltage steps from 0.3 v to 4.2 v and back down to 0.3 v. Each voltage step can represent one of 1024 pixels of video data. The voltage ramp stepping pattern can be a triangle pattern. An example of the voltage ramp stepping pattern is shown as pattern 800 in FIG. 8. As illustrated in FIG. 8, pattern 800 of digital signal 619 shows counts (on Y axis) for each pixel number (on X axis) of the video data. Counts can represent digitized voltage. In a non-limiting example, for a 16-bit ADC with a 0 to 4.036 V range, each count is 4.036 / (2A16) = 61.6pV. Successful conversion and return of a bandwidth-limited signal with this pattern can ensure that a driver and / or ADC 615 would properly covert any signal from any sensor 611 that generates voltage signals with a corresponding voltage range and bandwidth. It can solve problem(s) of testing the full range of possible sensor output signals. .

[0072] According to some aspects, the 1024 pixels of pattern 800 can be generated using a predetermined clock. In a non-limiting example, the predetermined clock can be 10 MHz. However, the aspects of this disclosure are not limited to this example. By using the predetermined clock, the triangle waveform of pattern 800 can also be used to validate that the timing is correct in terms of clock latency. Also, the 1024 pixels are provided as a non -limiting example and other number of pixels can be used.

[0073] Although a voltage ramp stepping pattern is discussed as one example of digital signal 619, the aspects of this disclosure are not limited to this example and other pattems / signals can be used for digital signal 619.

[0074] According to some aspects, digital signal 619 generated by processor 605 for the loopback diagnostic can be a specific signal generated for a specific controller circuit board 601 and / or a specific sensor circuit board 603. In other words, processor 605 can generate digital signal 619 based on one or more parameters / requirements of controller circuit board 601 and / or sensor circuit board 603.

[0075] According to some aspects, digital signal 619 can be a signal including a low voltage (e.g., about minimum voltage provided by sensor 611) for each pixel (of, for example, 1024 pixels associated with the data generated by sensor 611). According to some aspects, digital signal 619 can be a signal including a high voltage (e.g., about maximum voltage provided by sensor 611) for each pixel (of, for example, 1024 pixels associated with the data generated by sensor 611).

[0076] According to some aspects, DAC 607 receives digital signal 619 and generates analog signal 620. Analog signal 620 is sent to sensor circuit board 603. According to some aspects, analog signal 621 is input to multiplexer 613. According to some aspects, analog signal 621 is the same (or substantially the same) as analog signal 620. Alternatively, and depending on any fault / error and / or noise on the connection between controller circuit board 601 and sensor circuit board 603, analog signal 621 can be different from analog signal 620. In these aspects, analog signal 621 can be analog signal 620 that is distorted by the fault / error and / or noise. Multiplexer 613 can be configured to receive two inputs and select which one would be output from multiplexer 613. For example, if the loopback diagnostic process is in progress, multiplexer 613 can be configured to receive analog signal 621 and output analog signal 625 based on analog signal 621 (e.g., analog signal 625 would be the same (or substantially the same) as analog signal 621). If the loopback diagnostic process is not in progress and sensor circuit board 603 is to output sensor data from sensor 611, multiplexer 613 can be configured to receive analog signal 623 (e.g., sensor data) from sensor 611 and output analog signal 625 based on analog signal 623 (e.g., analog signal 625 would be the same (or substantially the same) as analog signal 623).

[0077] According to some aspects, processor 605 can control the operations of multiplexer 613 to perform the loopback diagnostic processes or to send sensor data. Additionally, or alternatively, another controller (e.g., on sensor circuit board 603) can be used to control the operations of multiplexer 613. Additionally, or alternatively, the operations of multiplexer 613 can be manually controlled by a user.

[0078] The analog signal 625 is input to ADC 615. Output of ADC 615 is digital signal 627 converted from analog signal 625. Digital signal 627 is input to serializer 617. Serializer 617 and deserializer 609 can include functional blocks configured to convert parallel data into serial data. Serializer 617 and deserializer 609 can be used to speed up data communication between controller circuit board 601 and sensor circuit board 603 without having to increase a number of pins on these boards.

[0079] Serializer 617 is configured to receive digital signal 6 1 and can convert parallel data of digital signal 627 to serial data of digital signal 629. Digital signal 629 is sent over to controller circuit board 601. Controller circuit board 601 and sensor circuit board 603 can be separate from each other and can be coupled to each other using cables (e.g., flexible cables), interface boards, connectors (e.g., blindmate connectors), harnesses, or the like (not shown). Deserializer 609 receives digital signal 630 and converts the serial data of digital signal 630 to parallel data of digital signal 631. According to some aspects, digital signal 630 is the same (or substantially the same) as digital signal 629. Alternatively, and depending on any fault / error and / or noise on the connection between controller circuit board 601and sensor circuit board 603, digital signal 630 can be different from digital signal 629. In these aspects, digital signal 630 can be digital signal 629 that is distorted by the fault / error and / or noise.

[0080] Digital signal 631 is input to processor 605 for further analysis to determine whether any faults / errors and / or noise exists in one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 based at least on digital signal 631.

[0081] Analog signal 625, digital signals 627, 629, 630, and 631 travel the same path as an analog signal that is generated by sensor 611 (e.g., analog signal 623). Therefore, by generating and using digital signal 619 and controlling multiplexer 613, processor 605 can be able to test one or more of controller circuit board 601, sensor circuit board 603, a connection between controller circuit board 601 and sensor circuit board 603, or the associated components of controller circuit board 601 and / or sensor circuit board 603.

[0082] According to some aspects, to determine whether any faults / errors and / or noise exists, processor 605 is configured to compare digital signal 631 with digital signal 619. For example, processor 605 can store digital signal 619 (and / or a copy of digital signal 619) in a memory (not shown) . After receiving digital signal 631, processor 605 can compare digital signal 631 with digital signal 619 to determine whether any faults / errors and / or noise exists. For example, processor 605 may ascertain whether or not digital signal 631 is an exact reproduction of digital signal 619. As another example, processor 605 may ascertain whether digital signal 631 is an acceptably accurate reproduction of digital signal 619 (e.g., within tolerances, such as within tolerances due to noise expected in the transmission of analog signal 620 into analog signal 621). In a non-limiting example where digital signal 619 is the voltage ramp stepping pattern (e.g., pattern 800 of FIG. 8), processor 605 can compare a voltage of digital signal 619 for a given pixel number to corresponding voltage of digital signal 631 of the same pixel number.

[0083] If a difference between the two voltages meets a first condition, processor 605 can determine that no faults / errors and / or noise exists in one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 based at least on digital signal 631. If the difference between the two voltages meets a second condition, processor 605 can determine that faults / errors and / or noise exists in one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 based at least on digital signal 631. The first and second conditions can be based on the same threshold or based on different thresholds. For example, if a difference between the two voltages are less than a threshold, processor 605 can determine that no faults / errors and / or noise exists in one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 based at least on digital signal 631. If the difference between the two voltages are equal to or greater than that threshold, processor 605 can determine that faults / errors and / or noise exists in one or more of controller circuit board 601, sensorcircuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 based at least on digital signal 631.

[0084] According to some aspects, to determine whether any faults / errors and / or noise exists, processor 605 is configured to output digital signal 631 on, for example, a display device (not shown). A user of loopback diagnostic system 600 (and / or lithographic apparatus 100) can visually observe digital signal 631 on the display device to determine whether any faults / errors and / or noise exists on one or more of controller circuit board 601, sensor circuit board 603, a connection between controller circuit board 601 and sensor circuit board 603, or the associated components of controller circuit board 601 and / or sensor circuit board 603. In a non-limiting example, the triangle ramp pattern of pattern 800 can be used for digital signal 619 so that the user can observe whether any missing block of data (e.g., missing data for one or more pixels), any signal clipping, and / or any noise exists in digital signal 631 .

[0085] According to some aspects, processor 605 can generate and output (e.g., transmit) a static DC voltage as digital signal 619 to evaluate signal noise on digital signal 631. For example, as discussed above, processor 605 can compare the voltage level(s) of digital signal 619 with the corresponding voltage level(s) of received digital signal 631 to determine whether any faults / errors and / or noise exists on one or more of controller circuit board 601, sensor circuit board 603, a connection between controller circuit board 601 and sensor circuit board 603, or the associated components of controller circuit board 601 and / or sensor circuit board 603. Digital signal 619 can include a static DC voltage.

[0086] In various implementations, controller circuit board 601 is deployed in a laser system. In various implementations, controller circuit board 601 is deployed in a diagnostic tool adapted to be connected to a laser system. In various implementations, sensor circuit board 603 is deployed in a laser system. In various implementations, sensor circuit board 603 is deployed in spectroscopy module within a laser system, such as a linecenter analysis module, a bandwidth analysis module, or a combined linecenter and bandwidth analysis module.

[0087] In various implementations, controller circuit board 601 is configured to communicate with a plurality of types of sensor circuit boards (e.g., sensor circuit boards configured for used in various types of lasers, and / or sensor circuit boards configured for use in various models of a type of laser). In various implementations, controller circuit board 601 is configured so that analog signal 620 has voltage values representative of the output of a light sensor deployed in a spectroscopy module in a laser. In various implementations, controller circuit board 601 is configured so that analog signal 620 has voltage values representative of the output of a photodiode, a photodiode array, a photomultiplier tube, or a charge-coupled device. In various implementations, controller circuit board 601 is configured so that analog signal 620 has voltage values representative of the output of an amplifier circuit coupled to a photodiode, a photodiode array, a photomultiplier tube, or a charge-coupled device.

[0088] In various implementations, processor 605 and DAC 607 are configured to generate a plurality of types of analog signal 620 corresponding to a plurality of types of sensor 611. In various implementations, processor 605 is configured to ascertain a sensor type of sensor 611 and to generateanalog signal 620 to represent a range of voltage outputs of the ascertained sensor type. In various implementations, processor 605 is configured to ascertain a board type of circuit board 603 and to generate analog signal 620 to represent a range of voltage outputs of a sensor deployed on the ascertained board type.

[0089] Although some examples are provided, the aspects of this disclosure are not limited to these examples and other methods can be used for comparing digital signal 631 with digital signal 619 to determine whether any faults / errors and / or noise exists. Also, other digital signals for digital signal 619 can be used for determining whether any faults / errors and / or noise exists on one or more of controller circuit board 601 , sensor circuit board 603, a connection between controller circuit board 601 and sensor circuit board 603, or the associated components of controller circuit board 601 and / or sensor circuit board 603.

[0090] According to some aspects, determining whether faults / errors and / or noise exists can include making a determination whether a determined error is because of sensor 611 or is because one or more of controller circuit board 601 , sensor circuit board 603 , or a connection between controller circuit board 601 and sensor circuit board 603. For example, if sensor 611 is used to measure parameters of a radiation beam but instead one or more errors are measured, the loopback diagnostic processes of this disclosure can be used to determine whether the measured error(s) is because of sensor 611 or is because of one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603. In other word, by removing the output of sensor 611 (e.g., analog signal 623) using multiplexer 613 and running the loopback diagnostic, it can be determined if sensor 611 is the source of the measured error(s) or one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603.

[0091] Additionally, or alternatively, by using specific patterns for digital signal 619 as the source of loopback diagnostic process, processor 605 can be configured to determine one or more components of one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 that can be the source of faults / errors. Additionally, or alternatively, by using specific patterns for digital signal 619 as the source of loopback diagnostic process, processor 605 can be configured to determine one or more components of one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 that can be the source of noise measured on digital signal 631.

[0092] Additionally, or alternatively, when processor 605 determines faults / errors and / or noises associated with one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603, processor 605 can initiate one or more additional diagnostic processes to determine which components of one or more of controller circuit board 601, sensor circuit board 603, or a connection between controller circuit board 601 and sensor circuit board 603 may be the source of faults / errors and / or noises. As one example, a BIST(Built-in-Self Test) process can be use to rule out issues with the connections from serializer 617 to deserializer 609.

[0093] According to some aspects, processor 605 can also be configured to determine (e.g., calculate) a latency (e.g., a number of clock cycles) for serializing, transmitting, and / or deserializing digital signal 629 / 630 from input 633 of serializer 617 to output 635 of deserializer 609. Input 633 of serializer 617 and output 635 of deserializer 609 are schematically shown in FIG. 6. According to some aspects, the latency (e.g., the first number of clock cycles) for serializing, transmitting, and / or deserializing digital signal 629 / 630 from input 633 of serializer 617 to output 635 of deserializer 609 is not a fixed value and processor 605 is configured to determine (e.g., calculate) this latency.

[0094] Processor 605 can use the same loopback diagnostic process discussed above to determine the latency. For example, processor 605 can determine (e.g., calculate) the loopback time (e.g., the number of clock cycles) needed for the round trip of digital signal 619 going through controller circuit board 601 and sensor circuit board 603 and received as digital signal 631 at processor 605. For example, processor 605 can determine (e.g., calculate) the loopback time (e.g., the number of clock cycles) between a transmission time instance when digital signal 619 is output (e.g., transmitted) from processor 605 to a reception time instance when digital signal 631 is received at processor 605.

[0095] By knowing the latencies of DAC 607, multiplexer 613, and ADC 615, processor 605 can determine (e.g., calculate) the latency (e.g., the number of clock cycles) for serializing, transmitting, and / or deserializing digital signal 629 / 630 from input 633 of serializer 617 to output 635 of deserializer 609. In some examples, the values of the latencies of DAC 607, multiplexer 613, and ADC 615 can be stored in a memory (not shown) accessible by processor 605. Processor 605 can subtract the latencies of DAC 607, multiplexer 613, and ADC 615 from the determined loopback time to determine (e.g., calculate) the transmission latency between controller circuit board 601 and sensor circuit board 603. Processor 605 can determine the latency as half of the determined transmission latency between controller circuit board 601 and sensor circuit board 603. Additionally, or alternatively, processor 605 can determine the latency as the determined transmission latency between controller circuit board 601 and sensor circuit board 603.

[0096] According to some aspects, serializer 617 and deserializer 609 can be optional. In these aspects, digital signal 629 can be sent from sensor circuit board 603 to controller circuit board 601 in parallel data paths.

[0097] According to some aspects, both DAC 607 and ADC 615 can be located on one of sensor circuit board 603 or controller circuit board 601. For example, DAC 607 and ADC 615 can be located on controller circuit board 601. In this example, analog signal 620 is output from controller circuit board 601 to sensor circuit board 603 and analog signal 625 is output from sensor circuit board 603 to controller circuit board 601. Analog signal 625 then can be converted to digital signal 631 on controller circuit board 601.

[0098] Additionally, or alternatively, DAC 607 and ADC 615 can be located on sensor circuit board 603. In this example, digital signal 619 is output from controller circuit board 601 to sensor circuit board 603 and digital signal 627 (or digital signal 629) is output from sensor circuit board 603 to controller circuit board 601. Digital signal 619 then can be converted to analog signal 621 on sensor circuit board 603.

[0099] According to some aspects, DAC 607 can be located on sensor circuit board 603 and ADC 615 can be located on controller circuit board 601. In other words, different combinations of DAC 607, deserializer 609, ADC 615, and / or serializer 617 on sensor circuit board 603 or controller circuit board 601 can be used.

[0100] FIG. 7 illustrates an example method 700 for a system (for example, a loopback diagnostic system 600) performing the loopback diagnostic, according to some aspects. As a convenience and not a limitation, FIG. 7 may be described with regard to elements of FIGS. 1-6. Method 700 can represent the operation of a system (for example, a loopback diagnostic system 600 of FIG. 6) implementing mechanisms for performing the loopback diagnostic. Method 700 can also be performed by computer system 900 of FIG. 9. But method 700 is not limited to the specific aspects depicted in those figures and other systems may be used to perform the method as will be understood by those skilled in the art. It is to be appreciated that not all operations may be needed, and the operations may not be performed in the same order as shown in FIG. 7. The method steps of FIG. 7 can be performed in any conceivable order and it is not required that all steps be performed. Moreover, the method steps of FIG. 7 described above merely reflect an example of steps and are not limiting.

[0101] At 702, a first digital signal is generated. For example, a first circuit board (e.g., controller circuit board 601 of FIG. 6) of a metrology system (e.g., loopback diagnostic system 600 of FIG. 6) generates the first digital signal (e.g., digital signal 619). As discussed in detail above, the first digital signal can include different patterns, such as but not limited to, pattern 800 of FIG. 8. For example, generating the first digital signal can include generating a voltage ramp stepping pattern as the first digital signal. The voltage ramp stepping pattern can include a plurality of voltage steps from a first voltage value to a second voltage value with a step value and back to the first voltage value. Each voltage step of the plurality of voltage steps can represent one pixel of video data captured by a sensor (e.g., sensor 611 of FIG. 6).

[0102] At 704, the first digital signal is converted to a first analog signal. For example, the first circuit board (e.g., controller circuit board 601 of FIG. 6), using DAC 607 converts the first digital signal (e.g., digital signal 619) to the first analog signal (e.g., analog signal 620).

[0103] At 706, the first analog signal is transmitted (e.g., output) to a second circuit board of the metrology system. For example, the first circuit board (e.g., controller circuit board 601 of FIG. 6) transmits (e.g., outputs) the first analog signal (e.g., analog signal 620) to the second circuit board (e.g. sensor circuit board 603 of loopback diagnostic system 600 of FIG. 6). According to some aspects, controller circuit board 601 outputs the first analog signal to sensor circuit board 603 over one or moreof cables (e.g., flexible cables), interface boards, connectors (e.g., blind-mate connectors), or the like (not shown).

[0104] At 708, a second digital signal is received from the second circuit board, where the second digital signal corresponds to a second analog signal output from a multiplexer of the second circuit board. For example, the first circuit board (e.g., controller circuit board 601) can receive the second digital signal (e.g., digital signal 630 and / or digital signal 631) from the second circuit board (e.g., sensor circuit board 603). The second digital signal (e.g., digital signal 630 and / or digital signal 631) corresponds to a second analog signal (e.g., analog signal 625) from the multiplexer (e.g., multiplexer 613) of the second circuit board (e.g., sensor circuit board 603 of FIG. 6).

[0105] At 710, it is determined whether a fault / error and / or noise exists in one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board based on the received second digital signal. For example, the first circuit board (e.g., using processor 605) can determine whether the fault / error and / or noise exists.

[0106] According to some aspects, determining whether the fault exists can include comparing the second digital signal with the first digital signal to determine one or more differences between the second digital signal with the first digital signal. The determining whether the fault exists can further include comparing the one or more differences with a threshold and determining that the fault exists if the one or more differences exceed the threshold.

[0107] According to some aspects, method 700 can further include controlling (e.g., using processor 605 and the first circuit board) the multiplexer (of the second circuit board) to change an input of the multiplexer from an output of the sensor (e.g., sensor 611 of the second circuit board) to an output of the first control board.

[0108] According to some aspects, the second circuit board (e.g., sensor circuit board 603 of FIG. 6) can include an analog-to-digital converter (e.g., ADC 615) configured to receive the first analog signal from the multiplexer and output a third digital signal (e.g., digital signal 627). The second circuit board (e.g., sensor circuit board 603 of FIG. 6) can further include a serializer (e.g., serializer 617) coupled to the analog-to-digital converter and configured to receive the third digital signal (e.g., digital signal 627) from the analog-to-digital converter and output a fourth digital signal (e.g., digital signal 629) to the first circuit board. The first circuit board (e.g., controller circuit board 601 of FIG. 6) can further include a deserializer (e.g., deserializer 609) configured to receive the fourth digital signal (e.g., digital signal 629 / 630) and output the second digital signal (e.g., digital signal 631) to the processor. Method 700 can further include determining a number of clock cycles from a first time instance when the third digital signal (e.g., digital signal 627) was received by the serializer to a second time instance when the second digital signal (e.g., digital signal 631) was output by the deserializer.

[0109] For example, method 700 can further include determining a second number of clock cycles from a third time instance when the first digital signal (e.g., digital signal 619) was generated to a fourth time instance when the second digital signal (e.g., digital signal 631) was received at the processor.Method 700 can further include determining the number of clock cycles based on the second number of clock cycles and one or more delay values. The one or more delay values can include one or more of latencies of DAC 607, multiplexer 613, and / or ADC 615.

[0110] According to some aspects, after determining the fault, the loopback diagnostic system can determine one or more components of one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board that was associated with the fault (error, and / or noise). The loopback diagnostic system can indicate (e.g., display) the determined component(s) (e.g., on a display device) such that the determine component(s) can be replaced and / or repaired. The repaired loopback diagnostic system (and / or the repaired sensor circuit board) can be used for measuring one or more parameters of a radiation beam of a radiation source. The measure one or more parameters can be used for, for example, calibration and / or quality control of the radiation source. As discussed above, the radiation source can used with (or as part of) a lithographic apparatus, a metrology apparatus, or other systems.[oni] Various aspects can be implemented, for example, using one or more computer systems, such as computer system 900 shown in FIG. 9. Computer system 900 can be any computer capable of performing the functions described herein such as, but not limited to, system 600. Computer system 900 includes one or more processors (also called central processing units, or CPUs), such as a processor 904. Processor 904 is connected to a communication infrastructure 906 (e.g., a bus). Computer system 900 also includes user input / output device(s) 903, such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure 906 through user input / output interface(s) 902. Computer system 900 also includes a main or primary memory 908, such as random access memory (RAM). Main memory 908 can include one or more levels of cache. Main memory 908 has stored therein control logic (e.g., computer software) and / or data.

[0112] Computer system 900 can also include one or more secondary storage devices or memory 910. Secondary memory 910 can include, for example, a hard disk drive 912 and / or a removable storage device or drive 914. Removable storage drive 914 can be a floppy disk drive, a magnetic tape drive, a compact disk drive, an optical storage device, tape backup device, and / or any other storage device / drive.

[0113] Removable storage drive 914 can interact with a removable storage unit 918. Removable storage unit 918 includes a computer usable or readable storage device having stored thereon computer software (control logic) and / or data. Removable storage unit 918 can be a floppy disk, magnetic tape, compact disk, DVD, optical storage disk, and / any other computer data storage device. Removable storage drive 914 reads from and / or writes to removable storage unit 918 in a well-known manner.

[0114] According to some aspects, secondary memory 910 can include other means, instrumentalities or other approaches for allowing computer programs and / or other instructions and / or data to be accessed by computer system 900. Such means, instrumentalities or other approaches may include, for example, a removable storage unit 922 and an interface 920. Examples of the removable storage unit 922 and the interface 920 can include a program cartridge and cartridge interface (such as that found in video gamedevices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and / or any other removable storage unit and associated interface.

[0115] Computer system 900 can further include a communication or network interface 924. Communication interface 924 enables computer system 900 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referenced by reference number 928). For example, communication interface 924 can allow computer system 900 to communicate with remote devices 928 over communications path 926, which may be wired and / or wireless, and which may include any combination of LANs, WANs, the Internet, etc. Control logic and / or data may be transmitted to and from computer system 900 via communication path 926.

[0116] The operations in the preceding aspects can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the preceding aspects may be performed in hardware, in software or both. In some aspects, a tangible, non-transitory apparatus or article of manufacture includes a tangible, non-transitory computer useable or readable medium having control logic (software) stored thereon is also referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system 900, main memory 908, secondary memory 910 and removable storage units 918 and 922, as well as tangible articles of manufacture embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as computer system 900), causes such data processing devices to operate as described herein.

[0117] Based on the teachings contained in this disclosure, it will be apparent to persons skilled in the relevant art(s) how to make and use aspects of the disclosure using data processing devices, computer systems and / or computer architectures other than that shown in FIG. 9. In particular, aspects may operate with software, hardware, and / or operating system implementations other than those described herein.

[0118] The terms “radiation,” “beam,” “light,” “illumination,” or the like can be used herein to refer to one or more types of electromagnetic radiation, for example, ultraviolet (UV) radiation (for example, having a wavelength X of 365, 248, 193, 157 or 126 nm). Generally, radiation having wavelengths between about 400 to about 700 nm is considered visible radiation; radiation having wavelengths between about 780-3000 nm (or larger) is considered IR radiation. UV refers to radiation with wavelengths of approximately 100-400 nm. Within lithography, the term “UV” also applies to the wavelengths that can be produced by a mercury discharge lamp: G-line 436 nm; H-line 405 nm; and / or, I-line 365 nm. Vacuum UV, or VUV (i.e., UV absorbed by gas), refers to radiation having a wavelength of approximately 100-200 nm. Deep UV (DUV) generally refers to radiation having wavelengths ranging from 126 nm to 428 nm, and in some aspects, an excimer laser can generate DUV radiation used within a lithographic apparatus. It should be appreciated that radiation having a wavelength in therange of, for example, 180-200 nm relates to radiation with a certain wavelength band, of which at least part is in the range of 180-200 nm.

[0119] Although some aspects of the present disclosure are described in the context of lithographic apparatuses in the manufacture of ICs, it should be understood that lithographic apparatuses described herein can be used in other applications, for example, in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCDs, thin-fdm magnetic heads, etc. Those skilled in the art will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein can be considered as specific examples of the more general terms “substrate” or “target portion”, respectively. A substrate can be processed before or after exposure in, for example, a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) and / or a metrology unit. Where applicable, aspects disclosed herein can be applied to such and other substrate processing tools. Furthermore, a substrate can be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein can also refer to a substrate that already contains multiple processed layers.

[0120] Furthermore, although some aspects of the present disclosure are described in the context of optical lithography, it should be understood that aspects of the present disclosure are not limited to optical lithography. For example, in imprint lithography, a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device can be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0121] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0122] The present disclosure has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. The foregoing description of specific aspects will so fully reveal the general nature of the present disclosure that others can, by applying knowledge within the skill of the art, readily modify and / or adapt for various applications such specific aspects, without undue experimentation and without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed aspects, based on the teaching and guidance presented herein.

[0123] It is to be understood that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections can set forth one or more, but not necessarily all, aspects of the present disclosure as contemplated by the inventor(s),and thus, are not intended to limit the present disclosure and the appended claims in any way. The breadth and scope of the protected subject matter should not be limited by any of the above -described aspects, but should be defined in accordance with the following claims and their equivalents.

Claims

CLAIMS1. A metrology system, comprising: a first circuit board comprising: a sensor configured to detect a radiation beam generated by a radiation source; and a multiplexer configured to receive a first analog signal corresponding to a first digital signal and output a second analog signal; and a second circuit board comprising: a processor configured to generate the first digital signal, wherein the first digital signal or the first analog signal is transmitted to the first circuit board; wherein the processor is further configured to receive a second digital signal corresponding to the second analog signal output from the multiplexer of the first circuit board, and wherein the processor is further configured to determine whether a fault exists in one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board based on the received second digital signal.

2. The metrology system of claim 1, wherein the first circuit board further comprises: an analog-to-digital converter configured to receive the second analog signal from the multiplexer and output a third digital signal; and a serializer coupled to the analog-to-digital converter configured to receive the third digital signal from the analog-to-digital converter and output a fourth digital signal to the second circuit board.

3. The metrology system of claim 3, wherein the second circuit board further comprises: a digital-to-analog converter configured to convert the first digital signal to the first analog signal, wherein the first analog signal is sent to the first circuit board; and a deserializer configured to receive the fourth digital signal and output the second digital signal to the processor.

4. The metrology system of claim 1, wherein the processor is further configured to control the multiplexer to change an input of the multiplexer from an output of the sensor to an output of the second control board.

5. The metrology system of claim 1, wherein the connection between the first circuit board and the second circuit board comprises one or more of an interface board or a cable connecting the first circuit board and the second circuit board.

6. The metrology system of claim 1, wherein the processor is configured to generate a voltage ramp stepping pattern as the first digital signal.

7. The metrology system of claim 6, wherein the voltage ramp stepping pattern comprises a plurality of voltage steps from a first voltage value to a second voltage value with a step value and back to the first voltage value.

8. The metrology system of claim 7, wherein each voltage step of the plurality of voltage steps represents one pixel of video data captured by the sensor.

9. The metrology system of claim 1, wherein to determine whether the fault exists, the processor is configured to compare the second digital signal with the first digital signal to determine one or more differences between the second digital signal with the first digital signal.

10. The metrology system of claim 9. wherein to determine whether the fault exists, the processor is configured to: compare the one or more differences with a threshold; and determine that the fault exists if the one or more differences exceed the threshold.

11. The metrology system of claim 1, wherein: the first circuit board further comprises: an analog-to-digital converter configured to receive the second analog signal from the multiplexer and output a third digital signal; and a serializer coupled to the analog-to-digital converter configured to receive the third digital signal from the analog-to-digital converter and output a fourth digital signal to the second circuit board, the second circuit board further comprises a deserializer configured to receive the fourth digital signal and output the second digital signal to the processor, and the processor is further configured to determine a number of clock cycles from a first time instance when the third digital signal was received by the serializer to a second time instance when the second digital signal was output by the deserializer.

12. The metrology system of claim 11, wherein the processor is further configured to determine a second number of clock cycles from a third time instance when the first digital signal was generated to a fourth time instance when the second digital signal was received at the processor.

13. The metrology system of claim 12, wherein the processor is further configured to determine the number of clock cycles based on the second number of clock cycles and one or more delay values.

14. A method, comprising: generating, by a first circuit board of a metrology system, a first digital signal; converting, by the first circuit board, the first digital signal to a first analog signal; transmitting, by the first circuit board, the first analog signal to a second circuit board of the metrology system; receiving, by the first circuit board, a second digital signal from the second circuit board, wherein the second digital signal corresponds to a second analog signal output from a multiplexer of the second circuit board; and determining, by the first circuit board, whether a fault exists in one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board based on the received second digital signal.

15. The method of claim 14, wherein determining whether the fault exists further comprises comparing the second digital signal with the first digital signal to determine one or more differences between the second digital signal with the first digital signal.

16. The method of claim 15, wherein determining whether the fault exists comprises: comparing the one or more differences with a threshold; and determining that the fault exists if the one or more differences exceed the threshold.

17. The method of claim 14, further comprising: determining a number of clock cycles from a first time instance when a third digital signal was received by a serializer of the second circuit board to a second time instance when the second digital signal was output by a deserializer of the first circuit board.

18. The method of claim 17, further comprising: determining a second number of clock cycles from a third time instance when the first digital signal was generated to a fourth time instance when the second digital signal was received at the first circuit board.

19. The method of claim 18, wherein determining the number of clock cycles is based on the second number of clock cycles and one or more delay values.

20. A non-transitory computer-readable storage medium, having stored thereon program instructions that, upon execution by at least one processor, cause the at least one processor to perform operations comprising: generating, by a first circuit board of a metrology system, a first digital signal; converting, by the first circuit board, the first digital signal to a first analog signal; transmitting, by the first circuit board, the first analog signal to a second circuit board of the metrology system; receiving, by the first circuit board, a second digital signal from the second circuit board, wherein the second digital signal corresponds to a second analog signal output from a multiplexer of the second circuit board; and determining, by the first circuit board, whether a fault exists in one or more of the first circuit board, the second circuit board, or a connection between the first circuit board and the second circuit board based on the received second digital signal.

21. A metrology test circuit, comprising: a signal generator configured to generate a first test signal, wherein the first test signal has a voltage range within an expected voltage output range of a first type of sensor; a communications port configured to transmit the test signal to a first type of metrology module, wherein the first type of metrology module includes a sensor of the first type of sensor; wherein the communications port is further configured to receive a first measurement signal from the first type of metrology module; and a processor configured to perform a first comparison between the first measurement signal and the first test signal; wherein the processor is further configured to determine whether a fault exists in one or more of the metrology test circuit, the first type of metrology module, or a connection between the metrology test circuit and the first type of metrology module based on the first comparison.

22. The metrology test circuit of claim 21, wherein: the signal generator is further configured to generate a second test signal, wherein the second test signal has a voltage range within an expected voltage output range of a second type of sensor, the communications port is further configured to transmit the test signal to a second type of metrology module, wherein the second type of metrology module includes a sensor of the second type of sensor, the communications port is further configured to receive a second measurement signal from the second type of metrology module, the processor is further configured to perform a second comparison between the second measurement signal and the second test signal, andthe processor is further configured to determine whether a fault exists in one or more of the metrology test circuit, the second type of metrology module, or a connection between the metrology test circuit and the second type of metrology module based on the second comparison.

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