Lithographic apparatus, temperature sensor, and fiber bragg grating sensor

Abstract

This invention provides a lithography apparatus comprising an illumination system, a projection system, a temperature-sensitive object, and a temperature sensor. The temperature sensor includes a detector and a waveguide device thermally coupled to the temperature-sensitive object and includes an input terminal, a downstream terminal, and a first scattering feature and a second scattering feature. The illumination system illuminates a pattern of a patterned device. The projection system projects an image of the pattern onto a substrate. Based on temperature, the first scattering feature reflects a first spectrum, allowing radiation not reflected by the first scattering feature to flow downwards. Based on temperature, the second scattering feature reflects a second spectrum different from the first spectrum, allowing radiation not reflected by the second scattering feature to flow downwards. The detector is positioned to receive radiation including the reflected first spectrum and the reflected second spectrum from the input terminal and generates a measurement signal based on the received radiation.

Description

[Technical Field]

[0001] This invention relates to lithography apparatus and methods. For example, projection optics that can be used to guide EUV radiation in a lithography process to manufacture semiconductor devices can be subjected to thermal management processes. [Previous Technology]

[0002] A lithography apparatus is a machine that coats a desired pattern onto a substrate, typically onto a target portion of the substrate. Lithography apparatuses can be used, for example, in the manufacture of integrated circuits (ICs). In this case, a patterning device (which is alternatively called a mask or magnifying mask) can be used to generate a circuit pattern to be formed on individual layers of the IC. This pattern can be transferred onto a target portion (e.g., a portion containing one or more dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically performed by imaging onto a radiation-sensitive material (resist) layer disposed on the substrate. Generally, a single substrate will contain a network of consecutively patterned adjacent target portions. Known lithography apparatuses include: a so-called stepper, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once; and a so-called scanner, in which each target portion is irradiated by scanning the pattern in a given direction ("scanning" direction) via a radiation beam while simultaneously scanning target portions parallel or antiparallel 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.

[0003] Lithography apparatuses typically include an illumination system that modulates radiation generated by a radiation source before it is incident on the patterned device. The patterned EUV beam can be used to create minute features on a substrate. Extreme ultraviolet light (sometimes also called soft X-rays) is generally defined as electromagnetic radiation having wavelengths in the range of about 5 to 100 nm. A specific wavelength of interest for photolithography appears at 13.5 nm.

[0004] Methods for generating EUV light include, but are not limited to, converting a source material into a plasma state having chemical elements with emission lines in the EUV range. Such elements may include, but are not limited to, xenon, lithium, and tin.

[0005] In one method commonly referred to as laser-generated plasma ("LPP"), the desired plasma can be generated by irradiating a source material, for example, in the form of droplets, streams, or lines, with a laser beam. In another method commonly referred to as discharge-generated plasma ("DPP"), the desired plasma can be generated by positioning a source material having suitable emission lines between a pair of electrodes and causing a discharge between the electrodes.

[0006] A technique for manufacturing ICs involves projecting a patterned EUV radiation beam onto a substrate. The projection optics may use a reflector. Because the EUV beam may not be perfectly uniform in terms of cross-sectional intensity, the optical energy absorbed by the reflector may be uneven, resulting in localized temperature differences and subsequent deformation of the reflector. The distorted wavefront of the reflected light can be caused by using a mirror with such temperature-induced deformation. This can increase error estimation, thereby reducing the marketability and competitive advantage of affected thermally sensitive components.

[0007] A method for addressing non-uniformity in a thermally sensitive object may involve using a targeted heating system and a temperature sensor. The temperature sensor can generate information about temperature non-uniformity in the thermally sensitive object, and the heating system can supply heating energy (e.g., laser) to relatively low-temperature regions of the thermally sensitive object based on the information provided by the temperature sensor. Although conventional temperature sensors (e.g., thermistors) can be used, such conventional temperatures may present various problems (e.g., difficulties in implementation, limited scalability, electrical noise, or the like). [Summary of the Invention]

[0008] Therefore, there is a need to improve temperature sensing technology to increase the accuracy of temperature correction methods and reduce the error tolerance for heat-sensitive objects, such as in the projection optics of lithography devices.

[0009] In some embodiments, a lithography apparatus includes an illumination system, a projection system, a temperature-sensitive object, and a temperature sensor. The illumination system is configured to illuminate a pattern of a patterned device. The projection system is configured to project an image of the pattern onto a substrate. The temperature sensor is thermally coupled to the temperature-sensitive object. The temperature sensor includes a waveguide device and a detector. The waveguide includes an input terminal, a downstream terminal opposite to the input terminal, and a first scattering feature and a second scattering feature. The first scattering feature is configured to reflect a first spectrum based on a temperature at the first scattering feature. Radiation not reflected by the first scattering feature is allowed to propagate downstream. The second scattering feature is configured to reflect a second spectrum based on a temperature at the second scattering feature. Radiation not reflected by the second scattering feature is allowed to propagate downstream. The detector is positioned to receive radiation from the input terminal including the reflected first spectrum and the reflected second spectrum, and generates a measurement signal based on the received radiation.

[0010] In some embodiments, a system includes a temperature-sensitive object, a temperature sensor, and a controller. The temperature sensor includes a waveguide device and a detector. The temperature sensor is thermally coupled to the temperature-sensitive object. The waveguide device includes an input terminal, a downstream terminal opposite to the input terminal, and a first scattering feature and a second scattering feature. The first scattering feature is configured to reflect a first spectrum based on a temperature at the first scattering feature. Radiation not reflected by the first scattering feature is allowed to propagate downstream. The second scattering feature is configured to reflect a second spectrum based on a temperature at the second scattering feature. Radiation not reflected by the second scattering feature is allowed to propagate downstream. The detector is positioned to receive radiation including the reflected first spectrum and the reflected second spectrum from the input terminal, and generates a measurement signal based on the received radiation. The controller is configured to receive the measurement signal and generate a control signal based on the measurement signal.

[0011] In some embodiments, a method includes placing a waveguide device having one or more scattering characteristics in thermal communication with a heating source. The method further includes propagating radiation via the waveguide device. The method further includes receiving radiation reflected by the one or more scattering characteristics at a detector, the reflected radiation including a reflected spectrum corresponding to the one or more scattering characteristics. The method further includes correlating the reflected spectrum with the temperature of the waveguide device. The method further includes adjusting the temperature of the heating source. The method further includes correlating the adjusted reflected spectrum corresponding to the one or more scattering characteristics with the adjusted temperature.

[0012] Other features of various embodiments of the invention are described in detail below with reference to the accompanying drawings. It should be noted that the invention is not limited to the specific embodiments described herein. These embodiments are presented herein for illustrative purposes only. Additional embodiments will become apparent to those skilled in the art based on the teachings contained herein.

Implementation Method

[0026] This specification discloses and includes one or more embodiments of the features of the present invention. The disclosed embodiments are provided as examples. The scope of the present invention is not limited to the disclosed embodiments. The claimed features are defined by the appended claims.

[0027] The described embodiments and references to "an embodiment," "an example embodiment," etc., in this specification may include specific features, structures, or characteristics, but each embodiment may not necessarily include such specific features, structures, or characteristics. Furthermore, these phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, it should be understood that, whether explicitly described or not, implementing this feature, structure, or characteristic in conjunction with other embodiments is within the understanding of those skilled in the art.

[0028] For ease of description, spatial relative terms such as "below," "under," "lower," "above," "on," "upper," and similar terms may be used herein to describe the relationship between one element or feature and another element or feature(s) illustrated in the figures. In addition to the orientations depicted in the figures, spatial relative terms are also intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptive terms used herein shall be interpreted accordingly.

[0029] The term “about” may be used herein to indicate a given quantity value that may vary based on a particular technique. Based on a particular technique, the term “about” may indicate a given quantity value that varies, for example, within 10% to 30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0030] Embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. Machine-readable media may include any means for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, machine-readable media may include read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.); and other media. Furthermore, firmware, software, conventions, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only, and such actions are actually caused by a computing device, processor, controller, or other device executing firmware, software, conventions, instructions, etc.

[0031] However, before describing these embodiments in more detail, it is presented as an instructional example environment in which embodiments of the invention may be implemented.

[0032] Example Microfilm System

[0033] FIG1 shows a schematic illustration of a lithography apparatus 100 in which an embodiment of the present invention may be implemented. The lithography apparatus 100 includes: an illumination system (illuminator) IL configured to modulate a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask stage) MT configured to support a patterning device (e.g., a mask, a magnifying mask, or a dynamic patterning device) MA and connected to a first positioner PM configured to precisely position the patterning device MA; and a substrate stage (e.g., a wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. The lithography apparatus 100 also has a projection system PS configured to project a pattern imparted by the patterning device MA to the radiation beam B onto a target portion (e.g., comprising one or more dies) C of the substrate W. In the lithography device 100, the patterning device MA and the projection system PS are reflective.

[0034] The illumination system IL may include various types of optical components for guiding, shaping, or controlling the radiated beam B, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components or any combination thereof. The illumination system IL may also include a sensor ES that provides measurements of, for example, energy per pulse, photon energy, intensity, average power, and one or more of the like. The illumination system IL may include a measurement sensor MS for measuring the movement of the radiated beam B, and a uniformity compensator UC that allows control of the uniformity of the illumination slits. The measurement sensor MS may also be located in other locations. For example, the measurement sensor MS may be on or near the substrate stage WT.

[0035] The support structure MT holds the patterned device MA in a manner dependent on the orientation of the patterned device MA relative to the reference frame, the design of the lithography apparatus 100, and other conditions (such as whether the patterned device MA is held in a vacuum environment). The support structure MT can hold the patterned device MA using mechanical, vacuum, electrostatic, or other clamping techniques. The support structure MT can be, for example, a frame or stage, which can be fixed or movable as needed. By using sensors, the support structure MT can ensure that the patterned device MA is, for example, in the desired position relative to the projection system PS.

[0036] The term "patterning device" MA should be broadly interpreted as any device that can be used to impart a pattern to the radiation beam B in the cross-section of the radiation beam B so as to generate a pattern in the target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in the device generated in the target portion C to form an integrated circuit.

[0037] The patterning device MA can be reflective. Examples of patterning devices MA include magnifying masks, masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase-shift, or attenuated phase-shift, as well as various hybrid mask types. Examples of programmable mirror arrays employ a matrix configuration of small mirrors, each of which can be individually tilted to reflect the incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam B reflected by the matrix of small mirrors.

[0038] The term "projection system" PS can encompass any type of projection system suitable for the exposure radiation used or for other factors such as the use of a wetting liquid on a substrate W or the use of a vacuum, including refractive, reflective, reflective-refractive, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof. A vacuum environment can be used for EUV or electron beam radiation because other gases can absorb excessive radiation or electrons. Therefore, a vacuum environment can be provided throughout the beam path by means of vacuum walls and vacuum pumps.

[0039] The lithography apparatus 100 may be of the type having two (dual-stage) or more substrate stages WT (and / or two or more mask stages). In such "multi-stage" machines, additional substrate stages WT can be used in parallel, or one or more stages can be used for preparatory steps while one or more other substrate stages WT are used for exposure. In some cases, the additional stages may not be substrate stages WT.

[0040] Lithography apparatuses may also fall into the following categories: at least a portion of the substrate may be covered by a liquid (e.g., water) having a relatively high refractive index to fill the space between the projection system and the substrate. The wetting liquid may also be applied to other spaces within the lithography apparatus, such as between the mask and the projection system. Immersion techniques are well known in this art for increasing the numerical aperture of the projection system. As used herein, the term "immersion" does not mean that a structure such as the substrate must be submerged in the liquid, but only that the liquid is located between the projection system and the substrate during exposure.

[0041] The illuminator IL receives a radiated beam from the radiation source SO. The source SO and the lithography device 100 may be separate physical entities, for example, when the source SO is an excimer laser. In such cases, the source SO is not considered part of the lithography device 100, and the radiated beam B is transmitted from the source SO to the illuminator IL by means of a beam delivery system BD (not shown) including, for example, suitable guide mirrors and / or beam expanders. In other cases, such as when the source SO is a mercury lamp, the source SO may be an integral part of the lithography device 100. The source SO and the illuminator IL, together with the beam delivery system BD (if necessary), may be referred to as a radiation system.

[0042] To avoid overcomplicating the diagram, the illuminator IL may include other components not shown. For example, the illuminator IL may include an adjuster for adjusting the angular intensity distribution of the radiated beam. Generally, at least the outer and / or inner radial ranges of the intensity distribution in the pupil plane of the illuminator (generally referred to as "σ outer" and "σ inner," respectively) can be adjusted. The illuminator IL may include a beam accumulator and / or a condenser (not shown). The illuminator IL can be used to adjust the radiated beam B to have a desired uniformity and intensity distribution in its cross-section. The desired uniformity of the radiated beam B can be maintained by using a uniformity compensator. The uniformity compensator includes a plurality of protrusions (e.g., fingers) that can be adjusted in the path of the radiated beam B to control the uniformity of the radiated beam B. A sensor can be used to monitor the uniformity of the radiated beam B.

[0043] A radiation beam B is incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a mask stage) MT, and is patterned by the patterning device MA. In the lithography apparatus 100, the radiation beam B is reflected from the patterning device (e.g., the mask) MA. After reflection from the patterning device (e.g., the mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate stage WT can be accurately moved (e.g., to position different target portions C in the path of the radiation beam B) by means of a second locator PW and a position sensor IF2 (e.g., an interferometric device, a linear encoder, or a capacitive sensor). Similarly, a first locator PM and another position sensor IF1 can be used to accurately position the patterning device (e.g., the mask) MA relative to the path of the radiation beam B. Mask alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device (e.g., the mask) MA with the substrate W.

[0044] The lithography device 100 can be used in at least one of the following modes:

[0045] 1. In step mode, when the entire pattern applied to the radiation beam B is projected onto the target portion C in one step, the support structure (e.g., mask stage) MT and the substrate stage WT remain substantially stationary (i.e., single static exposure). Then, the substrate stage WT is shifted in the X and / or Y directions so that different target portions C can be exposed.

[0046] 2. In scanning mode, when the pattern applied to the radiation beam B is projected onto the target portion C (i.e., single dynamic exposure), the support structure (e.g., mask stage) MT and the substrate stage WT are scanned simultaneously. The speed and direction of the substrate stage WT relative to the support structure (e.g., mask stage) MT can be determined by the magnification (reduction ratio) and image inversion characteristics of the projection system PS.

[0047] 3. In another mode, while the pattern applied to the radiation beam B is projected onto the target portion C, the support structure (e.g., a mask stage) MT remains substantially stationary, thereby holding the programmable patterning device, while the substrate stage WT moves or scans. A pulsed radiation source SO can be used, and the programmable patterning device is updated as needed after each movement of the substrate stage WT or between successive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography using programmable patterning devices (such as programmable mirror arrays).

[0048] Combinations and / or variations or completely different usage patterns described may also be adopted.

[0049] In another embodiment, the lithography apparatus 100 includes an EUV radiation source configured to generate an EUV radiation beam for EUV lithography. Generally, the EUV radiation source is configured to be in a radiation system, and a corresponding illumination system is configured to modulate the EUV radiation beam of the EUV source.

[0050] Figure 2A shows in more detail a lithography apparatus 100 (e.g., Figure 1) comprising a source collector device SO, an illumination system IL, and a projection system PS according to some embodiments. The source collector device SO is constructed and configured such that a vacuum environment can be maintained within the enclosure structure 220 of the source collector device SO. EUV radiation emitting plasma 210 may be formed by a discharge-generated plasma source. EUV radiation may be generated by a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor), wherein an extreme thermal plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The extreme thermal plasma 210 is generated, for example, by a discharge that causes at least a partially ionized plasma. For efficient radiation generation, Xe, Li, Sn vapor, or any other suitable gas or vapor with a partial pressure of, for example, 10 Pa may be required. In some embodiments, an excited tin (Sn) plasma (e.g., via laser excitation) is provided to generate EUV radiation.

[0051] Radiation emitted by the thermoplasm 210 is transferred from the source chamber 211 to the collector chamber 212 via an optional gas barrier or contaminant trap 230 (also referred to in some cases as a contaminant barrier or foil trap) positioned in or behind an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further indicated herein includes at least a channel structure.

[0052] Collector chamber 212 may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation traversing the collector CO may be reflected from the grating filter 240 to be focused into a virtual source point IF. The virtual source point IF is often referred to as the intermediate focus, and the source collector arrangement is configured such that the intermediate focus IF is located at or near the opening 219 in the enclosure structure 220. The virtual source point IF is an image of the radiative emission plasma 210. The grating filter 240 is specifically designed to suppress infrared (IR) radiation.

[0053] Subsequently, radiation traverses the illumination system IL, which may include a faceted field mirror device 222 and a faceted pupil mirror device 224, configured to provide the desired angular distribution of the radiation beam 221 at the patterned device MA, and to provide the desired uniformity of radiation intensity at the patterned device MA. After the radiation beam 221 is reflected at the patterned device MA held by the support structure MT, a patterned beam 226 is formed, and the patterned beam 226 is imaged onto the substrate W held by the wafer stage or substrate stage WT by the projection system PS via the reflective elements 228 and 229.

[0054] Additional elements beyond those shown may typically be present in the illumination optics unit IL and the projection system PS. Depending on the type of lithography device, a grating filter 240 may be present. Furthermore, more mirrors than those shown in FIG. 2A may be present; for example, one to six additional reflective elements may be present in the projection system PS in addition to those shown in FIG. 2A.

[0055] In some embodiments, the illumination optics unit IL may include a sensor ES that provides measurements of one or more of, such as pulse energy, photon energy, intensity, average power, and the like. The illumination optics unit IL may include a measurement sensor MS for measuring the movement of the radiated beam B, and a uniformity compensator UC that allows control of the uniformity of the illumination slit. The measurement sensor MS may also be located in other locations. For example, the measurement sensor MS may be on or near the substrate stage WT.

[0056] As shown in Figure 2A, the collector optics CO is depicted as a nested collector with grazing incidence reflectors 253, 254, and 255, serving only as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are arranged symmetrically around the optical axis O, and this type of collector optics CO is preferably used in combination with a discharge plasma source (often called a DPP source).

[0057] FIG. 2B shows a schematic diagram of a selected portion of a lithography apparatus 100 (e.g., FIG. 1) according to some embodiments, but with alternative collector optics in the source collector device SO. It should be understood that structures shown in FIG. 2A but not presented in FIG. 2B (for clarity of illustration) may still be included in the embodiments referring to FIG. 2B. Elements in FIG. 2B having the same element symbols as those in FIG. 2A have the same or substantially similar structures and functions as described with reference to FIG. 2A. In some embodiments, the lithography apparatus 100 can be used, for example, to expose a substrate W such as a resist-coated wafer with a patterned EUV beam. In FIG. 2B, the illumination system IL and projection system PS together represent an exposure device 256 (e.g., an integrated circuit lithography tool, such as a stepper, scanner, stepping and scanning system, direct writing system, device using contact and / or proximity masking, etc.) using EUV light from the source collector device SO. The lithography apparatus 100 may also include a collector optics 258 that reflects EUV light from the thermoplasm 210 along a path into the exposure device 256 to irradiate the substrate W. The collector optics 258 may include a near-normal incident collector mirror having a reflective surface in the form of an elongated sphere (i.e., an ellipse rotating about its major axis), the elongated sphere having a hierarchical multilayer coating, for example, having alternating layers of molybdenum and silicon, and in some cases having one or more high-temperature diffusion barrier layers, smoothing layers, masking layers, and / or etch stop layers.

[0058] Exemplary lithography unit

[0059] Figure 3 illustrates a lithography unit 300 according to some embodiments, which is sometimes also referred to as a lithography unit or cluster. A lithography apparatus 100 may form part of the lithography unit 300. The lithography unit 300 may also include one or more devices for performing pre-exposure and post-exposure processes on a substrate. Conventionally, these include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH, and a baking plate BK. A substrate handler or robot RO picks up a substrate from input / output ports I / O1, I / O2, moves the substrate between different process devices, and delivers the substrate to the loading rack LB of the lithography apparatus 100. These devices, often collectively referred to as a coating and developing system (track), are controlled by a coating and developing system control unit TCU, which is itself controlled by a supervisory control system SCS, which in turn controls the lithography apparatus via a lithography control unit LACU. Therefore, different devices can be operated to maximize throughput and processing efficiency.

[0060] Example Temperature Control System

[0061] There is a significant technological space where variations and / or non-uniformity in tool temperature can affect device performance and / or the implementation of temperature-sensitive processes. One example is found in EUV lithography apparatus. Reflectors receiving EUV radiation can develop non-uniform heating of their optical surfaces. Errors (e.g., deformation) caused by localized non-uniform temperatures on the optical surfaces can affect lithography accuracy, thereby reducing pattern transfer quality and device yield (e.g., discarding or otherwise scrapping non-compliant devices). Temperature sensors can be used to generate information about temperature non-uniformity in heat-sensitive objects. Temperature control systems can adjust local temperatures by supplying heat (e.g., using lasers) and / or removing heat (e.g., using cooling systems) based on information provided by the temperature sensors. Although conventional temperature sensors (e.g., thermistors) can be used, these can present various problems (e.g., structural limitations, limited scalability, electrical noise, or the like).

[0062] Figures 4A and 4B illustrate an object 400 and a temperature sensor array 402 according to some embodiments. In some embodiments, the object 400 may be, for example, an optical element that receives radiation (e.g., a faceted field mirror device 222, a faceted pupil mirror device 224, a reflective element 228 or 229 (Figure 2A or Figure 2B) or the like). The object 400 may include a body 404 and a surface 406. The surface 406 may be an optical surface (e.g., a reflective surface). Figure 4A illustrates a side view and the configuration of the temperature sensor array 402 associated with the side view. Figure 4B illustrates a perspective front view of the surface 406 and the configuration of the temperature sensor array 402 associated with the front view. Figures 4A and 4B illustrate alternative or combined configurations.

[0063] In some embodiments, the object 400 may be any object with problems related to temperature variation and / or non-uniformity (e.g., a mask stage MT, a wafer stage WT (FIG. 1), a support structure, a sensor frame, an actuation stage, a substrate with reflective and / or transmissive patterns for system metrology functions, or the like) regardless of whether the temperature variation and / or non-uniformity is caused by direct exposure to optical energy. For example, the object 400 may be a device disposed in a system unrelated to lithography. In some embodiments, other sources of temperature variation and / or non-uniformity may include heat dissipation of electronic devices, ambient airflow, or the like.

[0064] In some embodiments, object 400 is a temperature-sensitive object. In the context of devices and hardware, the term "temperature-sensitive" may be used herein to refer to a structure that is susceptible to performance variations due to temperature changes. For example, object 400 may exhibit temperature variations and / or inhomogeneities, thereby producing undesirable effects. For example, if object 400 is an optical element, temperature variations and / or inhomogeneities may cause the optical element to warp, thereby introducing optical aberrations when using the optical element. Therefore, object 400 may be referred to as a temperature-sensitive object and surface 406 may be referred to as a temperature-sensitive surface.

[0065] In some embodiments, the temperature sensor array 402 may include temperature sensor elements 402a to 402d. The temperature sensor array 402 may be thermally coupled to the object 400. For example, the temperature sensor array 402 may be in contact with the object 400, the temperature sensor array 402 may be embedded within the body 404 (as illustrated in FIG. 4A), the temperature sensor array 402 may be attached to the surface of the object 400, or the like. In embodiments where the surface 406 is an optical surface, it may be disadvantageous to mount the temperature sensor array 402 on the surface 406. Additionally, the body 404 may be a thick block, thereby making it difficult to measure the temperature of the surface 406 by attaching the temperature sensor array 402 to the back side of the object 400 (e.g., the side opposite to the surface 406). Therefore, the body 404 may include a recess through which the temperature sensor elements 402a to 402d may be inserted. In this manner, temperature sensing elements 402a to 402d can be positioned close to surface 406 through the back side of object 400. Any suitable technique (e.g., drilling, molding, or the like) can be used to fabricate the recesses in body 404. The proximity of temperature sensing elements 402a to 402d to surface 406 allows the temperature sensor array to sense the localized temperature of different areas of surface 406. The approximate sensing area is illustrated by the dashed loop in Figure 4B.

[0066] In some embodiments, four temperature sensing elements are disclosed as a non-limiting example (e.g., as shown in Figures 4A and 4B). It should be understood that the number of temperature sensing elements may differ from four, for example, to accommodate specific structural and sensing constraints. The temperature sensor array 402 may further include wiring 408a to 408d electrically coupled to the corresponding temperature sensing elements 402a to 402d. Each of the temperature sensing elements 402a to 402d may include a thermistor, such as a negative temperature coefficient (NTC) resistor. Wiring 408a to 408d may be coupled to an electrical monitoring device (e.g., an ammeter, multimeter, or the like) (not shown). The electrical monitoring device can sense localized temperature changes as surface 406 absorbs varying amounts of heat energy (e.g., self-radiating light beams).

[0067] In some embodiments, it is desirable to obtain a high-resolution temperature or thermal map of surface 406. However, the temperature data provided by four temperature sensing elements (point sensors) may be insufficient or too coarse to obtain a high-resolution temperature map. One technique to overcome this limitation is to implement a higher density of temperature sensing elements. A problem with this implementation is that the object 400 may not be able to support the large number of grooves used for the implementation of a high-density temperature sensor. For a typical thermistor, the grooves may have dimensions in the millimeter or tens of millimeter range (e.g., depth, diameter, or the like). A higher density of thermistors can cause a significant amount of mass to be removed from the body 404, thereby making the object 400 structurally unstable. In one instance, structural instability can exacerbate warping effects under temperature changes and / or inhomogeneities, rendering the object 400 unusable for its intended purpose. Furthermore, conventional temperature sensors such as thermistors can introduce a number of additional unwanted problems (e.g., unwanted heating via current flowing through the sensor, electrical noise on wirings 408a to 408d, or the like).

[0068] In order to address the limitations of some conventional temperature sensing elements discussed above, in some embodiments, a waveguide with scattering characteristics can be configured as a distributed temperature sensor.

[0069] Figures 5A and 5B illustrate an object 500 and a temperature sensor array 502 according to some embodiments. In some embodiments, the object 500 may include a body 504 and a surface 506. Unless otherwise indicated, the object 500, body 504, and surface 506 may have similar structures and act as elements with similar designations in Figure 4 (e.g., object 400, body 404, and surface 406), and therefore will not be described redundantly. Figure 5A illustrates a side view and the configuration of the temperature sensor 502 associated with the side view. Figure 5B illustrates a perspective front view of surface 506 and the configuration of the temperature sensor 502 associated with the front view. Figures 5A and 5B illustrate alternative or combined configurations (e.g., waveguides at different depths and / or side-by-side).

[0070] In some embodiments, the temperature sensor 502 may include a waveguide device 510. The waveguide device 510 may include a scattering feature 512 (e.g., a first scattering feature) and a scattering feature 514 (e.g., a second scattering feature). The term "waveguide device" or its equivalent may be used herein to refer to a device that can propagate radiation by confining radiation within a cavity and / or medium. An example of a waveguide device is an optical fiber. The optical fiber may be single-mode or multi-mode. Another example of a waveguide device is a microwave cavity. Yet another example of a waveguide device is a strip of light-transmitting material attached to a substrate (e.g., as seen in photonic circuits). The waveguide device 510 may further include one or more additional scattering features 516. Scattering features 512 and 514, together with one or more additional scattering features 516, may be arranged in series along the waveguide device 510. The temperature sensor 502 may further include an interrogator device 518. Interrogator device 518 may include a radiation source 520 and / or a detector 522. It should be understood that the radiation source 520 and the detector 522 do not necessarily need to be configured within a single interrogator (i.e., the radiation source 520 and the detector 522 can be configured independently of each other). Temperature sensor 502 may further include one or more additional waveguide devices 524 thermally coupled to object 500. Each of the one or more additional waveguide devices 524 may include a scattering feature 526 (e.g., as described with respect to scattering features 512, 514, and / or 516).

[0071] In some embodiments, the temperature sensor 502 may be thermally coupled to the object 500. For example, the temperature sensor array 502 may be in contact with the object 500, the temperature sensor 502 may be embedded within a hollow path in the body 504 (as illustrated in FIG. 5A), the temperature sensor 502 may be attached to a surface of the object 500, or the like. Any suitable technique (e.g., drilling, molding, or the like) may be used to fabricate the hollow path in the body 504.

[0072] In some embodiments, the radiation source 520 is configured to generate input radiation comprising at least a first and a second different spectrum (e.g., at least a first and a second different wavelength). For clarity, briefly refer to FIG6, which shows an example diagram of the spectrum of the input radiation generated by the radiation source 520 according to some embodiments. The vertical axis of the figure represents the radiation intensity in arbitrary units (au) and the horizontal axis represents the wavelength in arbitrary units (au).

[0073] In some embodiments, the spectrum generated by radiation source 520 may be represented by broadband spectrum 628. Broadband spectrum 628 can be considered as an overlap of multiple sub-spectrums. Furthermore, radiation source 520 is not limited to simultaneously generating broadband spectrum 628. For example, radiation source 520 may be a tunable laser with selectable sub-spectrums. It should be understood that radiation source 520 configured to generate broadband spectrum 628 may refer to embodiments that simultaneously generate broadband spectrum 628 or embodiments that generate sub-spectrums at corresponding time intervals, such that the aggregation of radiation generated at time intervals corresponds to broadband spectrum 628. Within the overlap, there may be sub-spectrum 630 (e.g., a first spectrum) and sub-spectrum 632 (e.g., a second spectrum) different from sub-spectrum 630. It should be understood that other sub-spectrums (not shown) may exist in the form of overlapping with sub-spectrums 630 and 632 that contribute to broadband spectrum 628. Subspectroscopy can be viewed as a narrow band (e.g., a narrow wavelength range centered around the peak wavelength), an extremely narrow peak (e.g., a delta function class), or something similar.

[0074] Referring again to FIG. 5, in some embodiments, waveguide device 510 may include an input end 534 and a downstream end 536 (near and far ends relative to interrogator device 518, radiation source 520, and / or detector 522, respectively). One or more additional waveguides 524 may also include input ends and downstream ends, functioning as described herein with respect to input ends 534 and downstream ends 536. Input end 534 may be optically coupled to interrogator device 518, radiation source 520, and / or detector 522. Input end 534 may be configured to receive input radiation generated by radiation source 520. Temperature sensor 502 may further include a terminating device 538. Terminating device 538 may include detector 540 (e.g., additional detector) and / or radiation discarding device 542 (e.g., beam dump).

[0075] In some embodiments, radiation having a broadband spectrum 628 can propagate downstream via waveguide device 510 and interact with the scattering characteristics of waveguide device 510. For example, scattering characteristic 512 can be configured to reflect a sub-spectrum of broadband spectrum 628 based on the temperature at scattering characteristic 512 (FIG. 6). Radiation not reflected by scattering characteristic 512 is allowed to propagate downstream. The reflected sub-spectrum can be, for example, sub-spectrum 630 (FIG. 6).

[0076] It should be understood that, in some embodiments, the specific selection of the reflected sub-spectrum described in the present example is not limiting. In some embodiments, the reflective properties of the scattering feature may be selected based on design parameters of the scattering feature (e.g., material selection, grating spacing, linewidth, or the like). It should also be understood that the radiation propagating through the scattering feature 512 may comprise a spectrum involving broadband spectrum 628 minus sub-spectrum 630.

[0077] In some embodiments, radiation propagating through scattering feature 512 may travel further downstream via waveguide device 510 to interact, for example, with downstream structures (e.g., other scattering features and / or terminal devices 538). For example, scattering feature 514 may be configured to reflect a sub-spectrum of broadband spectrum 628 based on the temperature at scattering feature 514 (FIG. 6). Radiation not reflected by scattering feature 514 is allowed to propagate downstream. As a non-limiting example, the reflected sub-spectrum may be, for example, (non-limiting) sub-spectrum 632 (FIG. 6). It should be understood that radiation propagating through scattering feature 514 may comprise the spectrum received from scattering feature 512 minus the spectrum received from spectrum 632 (i.e., broadband spectrum 628 minus sub-spectrums 630 and 632). Radiation propagating through scattering feature 512 may propagate further downstream via waveguide device 510 to interact with downstream structures (e.g., other scattering features and / or terminal devices 538).

[0078] It should be understood that in some embodiments, one or more additional scattering features 516 may be configured to function similarly to scattering features 512 and 514 but with different sub-spectrums. For example, one or more additional scattering features 516 may be configured to reflect one or more corresponding additional sub-spectrums based on the temperature at the corresponding location of one or more scattering features 516, while allowing unreflected radiation to propagate downstream. The scattering features may be configured such that the reflected sub-spectrums are different from each other. In this way, it is possible to distinguish reflections and correlate each reflected sub-spectrum with its corresponding scattering feature.

[0079] In some embodiments, scattering features 512 and 514 and / or one or more additional scattering features 516 may each comprise a Bragg reflector. In some embodiments, waveguide device 510 may comprise an optical fiber. In this context, scattering features 512 and 514 and / or one or more additional scattering features 516 may each comprise a fiber Bragg grating.

[0080] Briefly referring to FIG7, a temperature sensor 702 is shown according to some embodiments. In some embodiments, the temperature sensor 702 may also represent a more detailed view of the temperature sensor 502 (FIGs 5A and 5B). Unless otherwise indicated, the elements of FIG7 having similar reference numerals to those of FIG5A and 5B (e.g., reference numerals sharing the two rightmost digits) may have similar structures and functions. For simplicity, similar structures and structures omitted from the views (for clarity) will not be described in detail.

[0081] In addition to the structure and function described for the reference temperature sensor 702 (Figures 5A and 5B), in some embodiments, the temperature sensor 702 may also include an optical element 750. The radiation source 720 may generate radiation comprising a broadband spectrum 628 (Figure 6). The optical element 750 may be configured to direct radiation from the radiation source 720 toward the input terminal 734 of the waveguide device 710. The radiation having the broadband spectrum 628 may be emitted into the waveguide device 710 via the input terminal 734. The scattering feature 712 of the waveguide device 710 may be configured to reflect a sub-spectrum of the broadband spectrum 628 (Figure 6) based on the temperature at the scattering feature 712. Radiation not reflected by the scattering feature 712 is allowed to propagate downstream. The reflected sub-spectrum may be, for example, sub-spectrum 630 (Figure 6). It should be understood that the scattering feature 714 may have similar functionality with reference to different sub-spectrums (e.g., sub-spectrum 632 (Figure 6)). It should also be understood that additional scattering features can be implemented for different sub-spectrums.

[0082] In some embodiments, the detector 722 is located at or near the input terminal 734. The optical element 750 may be further configured to direct reflected radiation to the detector 722. The reflected radiation may include radiation having sub-spectrums 630 and 632 (FIG. 6)—that is, radiation reflected by scattering features 712 and 714. The transmitted radiation may continue downstream to exit the waveguide device 710 via the downstream terminal 736.

[0083] Referring again to FIG. 5, in some embodiments, a detector 522 is positioned at input 534 to receive radiation comprising sub-spectrums reflected by scattering features 512, 514, 516 and / or 526 (e.g., reflections of sub-spectrums 630 and 632). Detector 522 may comprise a spectrometer, oscilloscope, spectrum analyzer, wavelength analysis device or the like. Since the reflected sub-spectrums can be directly measured, it is desirable to position detector 522 to receive the reflected sub-spectrums from input 534. Indirect measurement could involve positioning a detector to receive downstream radiation at downstream 536 and analyzing lost sub-spectrums that have been removed from the input radiation. However, the latter configuration can easily introduce uncertainties due to attenuation and faulty scattering features, and increase the processing time for analyzing the detected spectra. In the context of radiation “reflected” by scattering features in waveguide devices, the terms “reflection,” “reflected,” “backscattering,” or similar terms can be used to refer to radiation that initially propagates downstream and then propagates upstream after interacting with the scattering features.

[0084] In some embodiments, the detector 522 may be configured to generate a measurement signal based on received radiation comprising a sub-spectrum reflected by the scattering features. The measurement signal may include temperature information corresponding to the location near scattering features 512 and 514 and / or one or more additional scattering features 516. Since waveguide devices can be fabricated to be much smaller than thermistors, a large number of scattering features can be distributed close to surface 506. For example, an optical fiber with a fiber Bragg grating (i.e., scattering features) may be fabricated with a cross-sectional dimension (e.g., diameter) on the order of 100 micrometers. The size requirement of the waveguide device may be orders of magnitude smaller than that of thermistors.

[0085] Therefore, in some embodiments, the scattering features provide a scalable solution for temperature mapping. Compared to thermistors, scattering features can be compact and configured at extremely high density. Each scattering feature can be a pixel of the temperature map. In this way, the measurement signal can contain information of a high-resolution temperature map of surface 506—in contrast to the coarse four-point thermistor setup in Figures 4A and 4B. In some embodiments, the waveguide device 510 can be positioned curved to conform to the curvature of surface 506.

[0086] To obtain a high-resolution temperature map of surface 506, in some embodiments, waveguide device 510 and one or more additional waveguide devices 524 may be configured as shown in FIG5B. In this configuration, one or more additional waveguide devices 524 may be arranged substantially parallel to and spaced apart from waveguide device 510. The scattering feature 526 in each of the one or more additional waveguide devices 524 may be configured to reflect different spectra and transmit radiation not reflected by the counterpart of the scattering feature 526 based on the temperature at the counterpart of the scattering feature 526. Detector 522 may include additional measurement channels corresponding to one or more additional waveguides 524. In this way, it is possible to make each of waveguide device 510 and one or more additional waveguides 524 identical or similar by marking temperature information with corresponding channel identifiers, while maintaining positional discrimination (e.g., pixel discrimination).

[0087] In some embodiments, waveguide device 510 and one or more additional waveguide devices 524 may be configured as shown in FIG5A. In this configuration, one or more additional waveguide devices 524 may be disposed within the object 500 at one or more different depths. One or more depths may be measured relative to surface 506 (or relative to a flat plane of surface 506 in the case of a curved surface 506). In this way, temperature sensors can be densely distributed throughout the entire body.

[0088] In some embodiments, the controller 544 (or another controller or processor) may receive measurement signals from the detector 522 and generate a high-resolution, two-dimensional or three-dimensional temperature map of the object 500.

[0089] In some embodiments, waveguide devices 510 and / or 524 may be enclosed within the object 500, rather than attached to a surface or slotted into a groove in the object 500. This configuration may be because attaching the waveguide device 510 to a critical surface could impair the performance of that surface (e.g., attaching the waveguide device to a reflective surface would affect reflection performance). Another reason for this configuration may be that leaving open grooves for inserting the waveguide device 510 into the body 504 could cause structural stability problems in the object 500. The structural stability of the object 500 is improved by surrounding the entire sidewalls of the waveguide device 510 with the material of the body 504.

[0090] In some embodiments, the waveguide device 510 may be positioned adjacent to the temperature-sensitive surface 506 (e.g., an optical surface) such that scattering features 512 and 514 are thermally connected to different regions of the temperature-sensitive surface. In some embodiments, the waveguide device 510 of a certain length may be positioned in a direction perpendicular to the surface 506 (e.g., the temperature-sensitive surface). This configuration allows for the measurement of the temperature gradient in the object 500 in a direction away from (or toward) the surface 506.

[0091] In some embodiments, waveguide devices 510 and / or 524 may have bends (e.g., the optical fiber may bend to its maximum bending radius). In some embodiments, waveguide devices 510 and / or 524 may be bend-insensitive optical fibers. In some embodiments, waveguide devices 510 and / or 524 may be arranged in a helical pattern within object 500. In some embodiments, waveguide devices 510 and / or 524 may be arranged in a serpentine pattern within object 500. The reason for using these configurations is to densely distribute the sensing elements to allow for high spatial resolution of temperature measurements. The example configurations are not limiting, and it should be understood that other configurations and combinations thereof may be used.

[0092] In some embodiments, the configurations shown in Figures 5A and 5B can be combined. For example, the waveguide devices can be configured in a "mesh" pattern. The waveguide devices at a first depth can be configured as shown in Figure 5B. Then, at a second depth different from the first depth, the waveguide devices can be configured to operate perpendicular (or at an angle) to the direction of the waveguide devices at the first depth.

[0093] In some embodiments, the system employing temperature sensor 502 (e.g., a lithography system) may also include controller 544 and heating system 546. Heating system 546 may be part of a temperature control system that includes not only heating system 546 but also other systems (e.g., a cooling system). The heating system may be configured to heat at least a portion of object 500. For example, heating may be targeted at a specific area of ​​surface 506, in which temperature non-uniformity of object 500 is reduced to prevent warping of surface 506. Controller 544 may be configured to receive measurement signals from detector 522. Controller 544 may be further configured to generate control signals based on the measurement signals. Temperature control system may receive control signals from controller 544 and adjust the temperature of at least a portion of object 500 based on the received control signals. For example, the control signals may include instructions to cause heating system 546 to heat a specific area of ​​object 500, i.e., a feedback process. Although Figure 5A shows the heating system 546 away from (detached from) the object 500, it should be understood that in some embodiments, the heating system 546 may include a heating element (e.g., a heating electrode (not shown)) physically coupled to the object 500.

[0094] In some embodiments, the heating system 546 may include a detached heating source (as illustrated in FIG. 5A). The heating source may include, for example, a radiation source. The heating source may include a laser or a plurality of lasers. The laser may be configured to generate infrared radiation (IR). IR is a wavelength region that can be readily absorbed by an object as heat. The laser may be configured to direct the IR radiation to a specific area of ​​the object 500 based on a control signal received from the controller 544.

[0095] In some embodiments, the radiation source of the heating system 546 may be configured to provide input radiation to the waveguide device 510, instead of radiation provided by the radiation source 520 or other sources. For example, an optical fiber may be used to guide the radiation from the radiation source of the heating system 546 to the input terminal 534 of the waveguide device 510. The input terminal 534 may be configured to receive radiation from the radiation source of the heating system 546.

[0096] In some embodiments, the terminating device 538, the detector 540, and / or the radiation discarding device 542 may be located at the downstream end 536. The terminating device 538 may be configured to receive radiation that has not yet been reflected by the scattering characteristics of the waveguide device 510. To prevent back reflection due to improper termination of the waveguide device 510, the radiation discarding device 542 may be configured to discard radiation received from the downstream end 536. The discarding mechanism may be, for example, using energy dissipation through light-to-heat conversion.

[0097] In some embodiments, detector 540 may be configured to receive radiation transmitted through a periodic structure and generate a measurement signal. A controller may be configured to receive the measurement signal and generate diagnostic information based on the measurement signal. The controller may be, for example, controller 544 or another controller (e.g., a processor as part of another system). Detector 540 may include a spectrometer, oscilloscope, spectrum analyzer, wavelength analysis device, or the like. Diagnostic information may include, for example, the health status of the radiation source generating the input radiation (e.g., radiation source 520), the state of its scattering characteristics (e.g., operational, unstable, faulty), or the like. The controller may be used to further enhance the diagnostic information to compare the radiation input at input 534 with the radiation output at downstream 536.

[0098] In some embodiments, the object 500 may be a deformable optical element—such as a deformable mirror. In some embodiments, the control signal from the controller 544 may include instructions to actuate a portion of the deformable optical element. The deformable optical element may receive the control signal and adjust its shape based on the received control signal. In this way, warping of the deformable optical element due to temperature changes can be compensated for by properly shaping the deformable optical element.

[0099] Temperature is required to accurately calibrate the reflective behavior of the scattering feature. Temperature changes at the scattering feature can alter the measurability of the reflected sub-spectrum. Figure 8 shows an example of a reflected sub-spectrum according to some embodiments. Unless otherwise indicated, elements of Figure 8 with similar reference numerals to those of Figure 6 (e.g., reference numerals sharing the two rightmost digits) may have similar properties.

[0100] In some embodiments, the reflected sub-spectrum 830 may correspond to radiation reflected by scattering feature 512 (FIG. 5) at a given temperature. The region surrounding scattering feature 512 (FIG. 5) may experience temperature changes as previously described. A temperature change in scattering feature 512 (FIG. 5) may cause the reflected spectrum to become reflected sub-spectrum 830'. The change in the reflected sub-spectrum caused by the temperature change may include, for example, a center wavelength shift, an intensity change, a bandwidth change, or a combination thereof. For example, a temperature change at scattering feature 514 (FIG. 5) may correspond to a shift of reflected sub-spectrum 832 to reflected sub-spectrum 832' (having a shorter wavelength than reflected sub-spectrum 832). A shift of reflected sub-spectrum 848 to reflected sub-spectrum 848' may correspond to a temperature change at other scattering features.

[0101] In some embodiments described to date, scattering features 512, 514, 516, and / or 526 may comprise deliberately engineered scattering features (e.g., fiber Bragg gratings). However, in some embodiments, scattering features 512, 514, 516, and / or 526 may be non-engineering features arbitrarily formed during the fabrication of waveguide device 510. For example, defects or non-conforming items may be arbitrarily formed during the fabrication of uniform optical fiber. Arbitrarily formed defects or non-conforming items can scatter light, effectively serving as scattering features.

[0102] In some embodiments, the scattering behavior of arbitrarily formed scattering features may be difficult to quantify. However, detection methods can be implemented to compensate for the lack of predictable scattering behavior. For example, the input radiation emitted into waveguide device 510 may be a predefined pulse (e.g., with known timing, phase, and / or spectrum). Even if the exact location of the arbitrarily formed scattering feature is unknown, the arbitrarily formed scattering feature may backscatter radiation toward detector 540. The location of the scattering event in waveguide device 510 can then be determined based on the analysis of the flight time of the input radiation and the subsequent returned backscattered radiation. Since the location of the arbitrarily formed scattering feature can be universally present throughout waveguide device 510, temperature sensor 502 can effectively be a continuous temperature sensor rather than a discrete temperature sensor.

[0103] In some embodiments, the sub-spectrum corresponding to a plurality of backscattering events may depend on the temperature at the corresponding location of the waveguide device 510. Any suitable wavelength / frequency analysis method can be used to analyze the backscattering sub-spectrum. As a non-limiting example, optical time-domain reflectometry (OTDR) or optical frequency-domain reflectometry (OFDR) can be used to analyze the measurement signal generated by the detector 540.

[0104] Figure 9 illustrates the steps of a method for calibrating the temperature response of a scattering feature according to some embodiments. The calibration process may involve relating different states of the reflection spectrum to the corresponding temperatures of the scattering features. At step 902, a waveguide device having one or more scattering features is positioned in thermal communication with a heating source (e.g., in an oven). At step 904, radiation propagates through the waveguide device. At step 906, radiation reflected by one or more scattering features is received at a detector. At step 908, the reflected spectrum is correlated with the temperature of the waveguide device (i.e., the temperature of the scattering feature). At step 910, the temperature is adjusted by adjusting the heating source. At step 912, the adjusted reflection spectrum corresponding to one or more scattering features is correlated with the adjusted temperature of the waveguide device. The process is repeated at multiple temperatures. In this way, the temperature response of each scattering feature can be quantified. In some embodiments, the temperature response of each scattering feature can be programmed into a controller 544 (Figure 5). Furthermore, the calibration method steps in Figure 9 can be applied to both specially engineered designs and arbitrarily formed scattering characteristics.

[0105] In some embodiments, the method steps of FIG9 can be performed in any conceivable order and it is not necessary to perform all the steps. Furthermore, the method steps of FIG9 described above merely reflect examples of the steps and are not limiting. That is, other method steps and functions are conceivable based on the embodiments described in this invention.

[0106] Regarding some embodiments described earlier, it is understood that the heating system 546 may be part of a temperature control system that includes not only the heating system 546 but also other systems (e.g., a cooling system). FIG10 illustrates a temperature control system 1052 according to some embodiments. In some embodiments, the temperature control system may be implemented in embodiments having temperature-sensitive objects (e.g., in FIG5A, FIG5B, and FIG7). Unless otherwise indicated, the elements of FIG10 having similar reference numerals to those of FIG5A, FIG5B, and FIG7 (e.g., reference numerals sharing two rightmost digits) may have similar structures and functions. For simplicity, similar structures and structures omitted from the drawings (for clarity) will not be described in detail.

[0107] In some embodiments, the temperature control system 1052 may include a heating system 1046 and / or a cooling system 1058, both of which can be configured to adjust the temperature of at least a portion of the object 1000. Adjusting the temperature at a specific location on the object 1000 reduces temperature non-uniformity and subsequently reduces adverse effects (e.g., surface warping). The object 1000 may be a temperature-sensitive object. The object 1000 may include a body 1004 and a surface 1006 (e.g., a temperature-sensitive surface).

[0108] In some embodiments, the heating system 1046 may include a radiation source 1054 and an optical system 1056. The radiation source 1054 may generate radiation 1057 for radiating at least a portion of the object 1000. The optical system 1056 may direct the radiation 1057 toward the object 1000. The optical system 1056 may include any number and combination of optical elements—such as mirrors, digital micromirrors, lenses, prisms, or the like (not shown). It should be understood that the optical system 1056 may be used to direct the radiation 1057 to radiate a large area of ​​the surface 1006 (as shown in FIG. 10) or a specific portion of the surface 1006 based on feedback data provided by a temperature sensor (e.g., temperature sensor 502).

[0109] In some embodiments where radiation 1057 is used to activate a temperature sensor, optical system 1056 may be used to guide at least a portion of radiation 1057 as input radiation toward the input of a waveguide device (e.g., input 534 of waveguide device 510 (FIG. 5)). The input radiation may include a plurality of sub-spectrums as described with reference to FIG. 6 and FIG. 8.

[0110] In some embodiments, the object 1000 may further include one or more fluid channels 1060. The one or more fluid channels 1060 may be disposed at a depth below the surface 1006 (e.g., at a depth measured relative to the surface 1006). Although FIG10 illustrates a flat plane of the flat surface 1006 and the one or more fluid channels 1060, it should be understood that the plane of the one or more fluid channels 1060 may be curved. For example, if the surface 1006 is bowl-shaped, the one or more fluid channels 1060 may be curved to conform to the shape of the surface 1006 to provide uniform cooling.

[0111] In some embodiments, one or more fluid channels 1060 may be fluidly coupled to the cooling system 1058. One or more fluid channels 1060 may be used to allow cooling fluid from the cooling system 1058 to flow. Although the heating system 1046 may inject heat into the object 1000 to reduce temperature non-uniformity, the cooling fluid flowing through the fluid channels 1060 may remove heat from the object 1000 to allow for more thermal management options (e.g., preventing overheating, stabilizing the temperature, achieving steady state, removing heat from specific areas, or the like).

[0112] Figures 11A and 11B illustrate an object 1100 maintained by a cooling system and a temperature sensor according to some embodiments. Unless otherwise indicated, the element of Figure 11, having similar reference numerals to those of the elements in Figures 5A, 5B, 7, and 10 (e.g., reference numerals sharing the two rightmost digits), may have similar structures and functions. For simplicity, similar structures and structures omitted from the view (for clarity) will not be described in detail. Figure 11A illustrates a side view and the configuration of one or more waveguide devices 1110 associated with the side view. Figure 11B illustrates a perspective front view of surface 1106 and the configuration of one or more waveguide devices 1110 associated with the front view. Figures 5A and 5B illustrate alternative or combinatorial configurations (e.g., waveguides at different depths and / or side-by-side).

[0113] In some embodiments, the temperature sensor includes one or more waveguide devices 1110, which may have the structure and function described with respect to Figures 5A, 5B, and 6 through 10. The object 1100 may include one or more fluid channels 1160. Figure 11A illustrates different possible (and combinable) arrangements of one or more waveguide devices 1110 within the object 1100. In some embodiments, one or more waveguide devices 1110 may be disposed in a hollow path within the object 1100 at a depth between the surface 1106 and the depth of one or more fluid channels 1160. The length of one or more waveguide devices 1110 may be parallel to or perpendicular to one or more fluid channels 1160 (as shown in Figure 11B) or oriented perpendicular to one or more fluid channels 1160 (not shown). This configuration allows for high-resolution temperature mapping of the surface 1106 and implementation for cooling one or more fluid channels 1160 of the object 1100. Cooling fluid from cooling system 1058 (Figure 10) can flow through one or more fluid channels 1160.

[0114] In some embodiments, one or more waveguide devices 1110 may be disposed in at least one of one or more fluid channels 1160. This configuration allows for temperature measurement of the cooling fluid flowing in one or more fluid channels 1160.

[0115] In some embodiments, the length of one or more waveguide devices 1110 may be oriented perpendicular to the surface 1106 (not shown). This configuration allows for temperature measurement of the temperature gradient between the surface 1106 and one or more fluid channels 1160. This can be particularly useful for determining whether an object 1100 has reached a stable temperature (e.g., steady state) or whether the temperature is still fluctuating. Lithography apparatuses that use this method to manage the temperature of critical optical components can determine the allowable downtime between exposures of high-intensity radiation used in the lithography process, thereby maximizing manufacturing yield. Temperature control using heating system 1046 (FIG. 10) and / or cooling system 1058 (FIG. 10) can be performed simultaneously with, rather than alternately with, the exposure operations in the lithography apparatus.

[0116] In some embodiments, different configurations of one or more waveguide devices 1110 may be combined with each other and / or with the configurations described with respect to waveguide device 510 (FIG. 5) (e.g., see spiral pattern, serpentine pattern, different depths or the like).

[0117] Referring again to FIG5, in some embodiments, the time resolution of the temperature sensor 502 may be about 10 seconds or less, 5 seconds or less, 1 second or less, or 0.1 seconds or less. In some embodiments, the spatial resolution of the temperature sensor 502 may be about 100 mm or less, 50 mm or less, 25 mm or less, 10 mm or less, 5 mm or less, or 1 mm or less. In some embodiments, the accuracy of the temperature measurement performed by the temperature sensor 502 may be in the range of about 1 degree Celsius or less, 0.5 degrees Celsius or less, or 0.1 degrees Celsius or less.

[0118] The embodiments may be further described using the following terms: 1. A lithography apparatus comprising: an illumination system configured to illuminate a pattern of a patterned device; a projection system configured to project an image of the pattern onto a substrate; a temperature-sensitive object; and a temperature sensor thermally coupled to the temperature-sensitive object, wherein the temperature sensor comprises: a waveguide device comprising: an input terminal configured to receive input radiation; and a downstream terminal opposite to the input terminal; A first scattering feature configured to reflect a first spectrum based on a temperature at the location of the first scattering feature, wherein radiation not reflected by the first scattering feature is allowed to propagate downstream; and a second scattering feature configured to reflect a second spectrum based on a temperature at the location of the second scattering feature, wherein radiation not reflected by the second scattering feature is allowed to propagate downstream; and a detector configured to receive radiation comprising the reflected first spectrum and the reflected second spectrum from the input terminal, and configured to generate a measurement signal based on the received radiation. 2. The lithography apparatus of claim 1, wherein: the first scattering feature is further configured such that the reflected first spectrum changes based on a temperature at the location of the first scattering feature; and the second scattering feature is further configured such that the reflected second spectrum changes based on a temperature at the location of the second scattering feature. 3. The lithography apparatus of claim 1, wherein: the temperature sensor further comprises a radiation source configured to generate the input radiation; and the input radiation comprises the first spectrum and the second spectrum. 4. The lithography apparatus of item 1, wherein the waveguide device is enclosed within the temperature-sensitive object, and one length of the waveguide device is disposed along a direction perpendicular to a temperature-sensitive surface of the temperature-sensitive object. 5. The lithography apparatus of item 1, wherein the temperature-sensitive object is an optical element or a support structure in the lithography apparatus. 6. The lithography apparatus of item 5, wherein the waveguide device is enclosed within the optical element and disposed close to an optical surface of the optical element, such that the first scattering feature and the second scattering feature are thermally connected to different regions of the optical surface. 7. The lithography apparatus of item 5, further comprising a controller configured to receive the measurement signal and generate a control signal based on the measurement signal, wherein the optical element includes a deformable mirror configured to receive the control signal and adjust its shape based on the received control signal. 8. The lithography apparatus of item 1, wherein the first scattering feature and the second scattering feature are each a Bragg reflector. 9. The lithography apparatus of item 1, wherein the waveguide device is an optical fiber and the first scattering feature and the second scattering feature are each a fiber Bragg grating. 10. The lithography apparatus of item 1, wherein the waveguide device is configured in a spiral pattern. 11. The lithography apparatus of item 1, wherein the waveguide device is configured in a serpentine pattern.12. The lithography apparatus of clause 1, wherein: the temperature sensor further includes one or more additional waveguide devices thermally coupled to the temperature-sensitive object; each of the one or more additional waveguide devices includes scattering features configured to reflect a corresponding spectrum based on the temperature at the counterpart of the scattering features; allowing radiation not reflected by the counterpart of the scattering features to propagate downstream; and the one or more additional waveguide devices are arranged parallel to and spaced apart from the waveguide device. 13. The lithography apparatus of clause 1, wherein: the temperature sensor further includes one or more additional waveguide devices thermally coupled to the temperature-sensitive object; each of the one or more additional waveguide devices includes scattering features configured to reflect a corresponding spectrum based on the temperature at the counterpart of the scattering features; allowing radiation not reflected by the counterpart of the scattering features to propagate downstream; and the one or more additional waveguide devices are disposed at corresponding depths, the depths being measured relative to a temperature-sensitive surface of the temperature-sensitive object, but different from the depth of the waveguide device. 14. The lithography apparatus of clause 1, further including a controller configured to receive the measurement signal and generate a two-dimensional or three-dimensional map of the temperature of the temperature-sensitive object based on the received measurement signal. 15. The lithography apparatus of claim 1, further comprising: a controller configured to receive the measurement signal and generate a control signal based on the measurement signal; and a temperature control system configured to receive the control signal and adjust the temperature of at least a portion of the temperature-sensitive object based on the received control signal. 16. The lithography apparatus of claim 15, wherein the temperature control system includes a heating system configured to heat at least the portion of the temperature-sensitive object based on the control signal to reduce temperature non-uniformity of the temperature-sensitive object. 17. The lithography apparatus of claim 15, wherein: the heating system includes a radiation source configured to generate radiation radiating at least the portion of the temperature-sensitive object; an optical system configured to guide a portion of the radiation from the radiation source to the input terminal of the waveguide device as the input radiation; and the portion of the radiation from the radiation source includes the first spectrum and the second spectrum. 18. The lithography apparatus of clause 15, wherein: the temperature control system includes a cooling system configured to adjust the temperature of at least one portion of the temperature-sensitive object based on the control signal; and the temperature-sensitive object includes one or more fluid channels configured to allow the flow of a cooling fluid from the cooling system. 19. The lithography apparatus of clause 18, wherein the cooling system is configured to adjust the temperature of at least one portion of the temperature-sensitive object based on the control signal.20. The lithography apparatus of claim 18, wherein: the one or more fluid channels are disposed at a depth measured relative to a temperature-sensitive surface of the temperature-sensitive object; and the waveguide device is disposed in a hollow path of the temperature-sensitive object at a depth between the temperature-sensitive surface and the depth of the one or more fluid channels. 21. The lithography apparatus of claim 18, wherein the waveguide device is disposed in at least one of the one or more fluid channels. 22. The lithography apparatus of claim 1, wherein the temperature sensor further includes an additional detector disposed at the downstream end of the waveguide device, the additional detector being configured to receive radiation propagating through the first scattering feature and the second scattering feature and to generate another measurement signal. 23. The lithography apparatus of claim 22, further including a controller configured to receive the other measurement signal and, based on the other measurement signal, generate diagnostic information about the temperature sensor. 24. The lithography apparatus of clause 1, wherein the temperature sensor is further included at the downstream end of the waveguide device in a radiation rejection device configured to reject radiation transmitted through the waveguide device. 25. A system comprising: a temperature-sensitive object; a temperature sensor thermally coupled to the temperature-sensitive object, wherein the temperature sensor includes: a waveguide device including: an input terminal configured to receive input radiation; a downstream terminal opposite to the input terminal; a first scattering feature configured to reflect a first spectrum based on a temperature at the first scattering feature, wherein radiation not reflected by the first scattering feature is allowed to propagate downstream; a second scattering feature configured to reflect a second spectrum based on a temperature at the second scattering feature, wherein radiation not reflected by the second scattering feature is allowed to propagate downstream; a detector disposed to receive radiation comprising the reflected first spectrum and the reflected second spectrum from the input terminal, and to generate a measurement signal based on the received radiation; and a controller configured to receive the measurement signal and to generate a control signal based on the measurement signal. 26. The system of claim 25, further comprising a temperature control system configured to receive a control signal and adjust the temperature of at least a portion of the temperature-sensitive object based on the received control signal. 27. The system of claim 25, wherein: the first scattering feature is further configured such that the reflected first spectrum changes based on a temperature change at the location of the first scattering feature; and the second scattering feature is further configured such that the reflected second spectrum changes based on a temperature change at the location of the second scattering feature. 28. The system of claim 25, wherein: the temperature sensor further comprises a radiation source configured to generate the input radiation; and the input radiation comprises the first spectrum and the second spectrum.29. The system of claim 25, wherein the waveguide device is an optical fiber and the first scattering feature and the second scattering feature are fiber Bragg gratings. 30. The system of claim 25, wherein the temperature sensor further includes an additional detector disposed at the downstream end of the waveguide device, configured to receive radiation propagated through the first scattering feature and the second scattering feature and generate another measurement signal. 31. The system of claim 30, wherein the controller is further configured to generate diagnostic information about the temperature sensor based on the other measurement signal. 32. The system of claim 25, wherein the system is a lithography device. 33. The system of claim 25, wherein: the temperature sensor further includes one or more additional waveguide devices thermally coupled to the temperature-sensitive object; each of the one or more additional waveguide devices includes a scattering feature configured to reflect a corresponding spectrum based on the temperature at the counterpart of the scattering feature; allowing radiation not reflected by the counterpart of the scattering feature to propagate downstream; and the one or more additional waveguide devices are arranged parallel to and spaced apart from the waveguide device. 34. The lithography apparatus of claim 25, wherein the controller is further configured to generate a two-dimensional or three-dimensional map of the temperature of the temperature-sensitive object based on the received measurement signal. 35. The system of claim 25, wherein the waveguide device is disposed in a hollow path within the temperature-sensitive object and close to the temperature-sensitive surface of the temperature-sensitive object, such that the first scattering feature and the second scattering feature are thermally connected to different regions of the temperature-sensitive surface. 36. The system of clause 25, wherein the detector is further configured to determine the location of one of the first scattering features in the temperature-sensitive object based on a time-of-flight of radiation received at the detector containing the first spectrum. 37. A method comprising: placing a waveguide device having one or more scattering features in thermal communication with a heating source; propagating radiation via the waveguide device; receiving radiation reflected by the one or more scattering features at a detector, the radiation including a reflected spectrum corresponding to the one or more scattering features; correlating the reflected spectrum with the temperature of the waveguide device; adjusting the temperature of the heating source; and correlating the adjusted reflected spectrum corresponding to the one or more scattering features with the adjusted temperature.

[0119] Although EUV lithography devices were described earlier, it should be understood that in some embodiments, any lithography device (e.g., deep ultraviolet type) and other non-lithography systems in unrelated technical spaces may implement the temperature measurement and control schemes described in the embodiments herein.

[0120] While reference may be specifically made herein to the use of lithography devices in IC manufacturing, it should be understood that the lithography devices described herein may have other applications, such as manufacturing integrated optical systems, guiding and detecting patterns for magnetic domain memory, flat panel displays, LCDs, thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of these alternative applications, any use of the terms "wafer" or "die" herein may be considered synonymous with the more general terms "substrate" or "target portion," respectively. The substrates mentioned herein may be processed before or after exposure in, for example, a coating and developing system unit (typically a tool for coating a resist layer onto a substrate and developing the exposed resist), a measurement unit, and / or a detection unit. Where applicable, the disclosure herein may be applied to these and other substrate processing tools. Furthermore, the substrate may be processed more than once, for example to produce a multilayer IC, such that the term "substrate" as used herein may also refer to a substrate that already contains multiple processed layers.

[0121] Although reference has been specifically made to the use of embodiments of the invention within the context of optical lithography, it should be understood that the invention can be used in other applications (e.g., imprint lithography) and is not limited to optical lithography where the context permits. In imprint lithography, the morphology of a patterned device defines a pattern formed on a substrate. The morphology of the patterned device can be pressed into a resist layer supplied to the substrate, where the resist is cured by applying electromagnetic radiation, heating, pressure, or a combination thereof. After the resist has cured, the patterned device is removed from the resist, thereby leaving a pattern therein.

[0122] It should be understood that the wording or terminology used herein is for descriptive purposes rather than limiting purposes, and that the terminology or terminology of this invention shall be interpreted by those skilled in the art in accordance with the teachings herein.

[0123] As used herein, the terms “radiation,” “beam,” “light,” “illumination,” or similar terms may encompass all types of electromagnetic radiation, such as ultraviolet (UV) radiation (e.g., having wavelengths λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (e.g., having wavelengths in the range of 5 to 100 nm, such as (e.g.) 13.5 nm), or hard X-rays operating at less than 5 nm, and particle beams, such as ion beams or electron beams. Generally, radiation having wavelengths between about 400 and about 700 nm is considered visible radiation; radiation having wavelengths between about 780 and 3000 nm (or greater) is considered IR radiation. UV refers to radiation having wavelengths between about 100 and 400 nm. In lithography, the term “UV” also applies to 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 a gas) refers to radiation with a wavelength of approximately 100 to 200 nm. Deep UV (DUV) generally refers to radiation with a wavelength in the range of 126 nm to 428 nm, and in some embodiments, excimer lasers can produce DUV radiation used within lithography apparatuses. It should be understood that radiation with a wavelength in, for example, the range of 5 to 20 nm refers to radiation having a wavelength band, at least a portion of which is in the range of 5 to 20 nm.

[0124] As used herein, the term "substrate" describes a material on which a material layer is added. In some embodiments, the substrate itself may be patterned, and the material added on top of the substrate may also be patterned, or may remain unpatterned.

[0125] Although reference may be specifically made herein to the use of the apparatus and / or system according to the invention in IC manufacturing, it should be clearly understood that such apparatus and / or system has many other possible applications. For example, it can be used in the manufacture of integrated optical systems, guiding and detection patterns for magnetic domain memory, LCD panels, thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms "mask," "wafer," or "die" herein should be considered as being replaced by the more general terms "mask," "substrate," and "target portion," respectively.

[0126] Although specific embodiments of the invention have been described above, it should be understood that the invention may be practiced in other ways different from those described. The description is not intended to limit the invention.

[0127] It should be understood that the Description of Embodiments section, rather than the Summary and Invention section, is intended to interpret the scope of the patent application. The Summary and Invention section may set forth one or more, but not all, exemplary embodiments of the invention as contemplated by the inventors, and therefore is not intended to limit the invention or the scope of the appended patent application in any way.

[0128] The present invention has been described above by means of function building blocks that illustrate implementations of specific functions and their relationships. For ease of description, the boundaries of these function building blocks have been arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are properly performed.

[0129] The foregoing description of specific embodiments will thus fully disclose the general nature of the invention, enabling others to easily modify and / or adapt these specific embodiments for various applications without departing from the general concept of the invention, by means of knowledge within the skill scope of applying this art, without engaging in improper experimentation. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended to be within the meaning and scope of equivalents of the disclosed embodiments.

[0130] The breadth and scope of the protected subject matter shall not be limited by any of the above exemplary embodiments, but shall be defined only according to the following claims and their equivalents. [Simplified Explanation of the Diagram]

[0013] The invention is illustrated in the accompanying drawings, which are incorporated herein and form part of this specification, and together with the description, are used to explain the principles of the invention and to enable those skilled in the art to perform and use the embodiments described herein.

[0014] Figure 1 illustrates a reflective lithography device according to some embodiments.

[0015] Figures 2A and 2B illustrate a reflective lithography device according to some embodiments.

[0016] Figure 3 illustrates a lithography unit according to some embodiments.

[0017] Figures 4A and 4B illustrate temperature sensor arrays according to some embodiments.

[0018] Figures 5A and 5B illustrate temperature sensor arrays according to some embodiments.

[0019] Figure 6 illustrates an example of the spectrum of radiation generated by a radiation source according to some embodiments.

[0020] Figure 7 illustrates a temperature sensor array according to some embodiments.

[0021] Figure 8 shows a graph of the reflector spectrum according to some embodiments.

[0022] Figure 9 illustrates the steps of a method for calibrating the temperature response of scattering characteristics according to some embodiments.

[0023] Figure 10 shows a temperature control system according to some embodiments.

[0024] Figures 11A and 11B show objects maintained by a cooling system and a temperature sensor according to some embodiments.

[0025] The features of the present invention will become more apparent from the following detailed description set forth in conjunction with the accompanying drawings, in which the same reference numerals are used throughout to identify corresponding elements. In the drawings, the same reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Furthermore, generally speaking, the leftmost digit of the reference numeral first appears in the drawing. Unless otherwise indicated, the drawings provided throughout the present invention should not be construed as tolerable drawings.

Claims

1. A lithography apparatus comprising: an illumination system configured to illuminate a pattern of a patterned device; a projection system configured to project an image of the pattern onto a substrate; a temperature-sensitive object; and a temperature sensor thermally coupled to the temperature-sensitive object, wherein the temperature sensor comprises: a waveguide device comprising: an input terminal configured to receive input radiation; a downstream terminal opposite to the input terminal; a first scattering feature configured to reflect a first spectrum based on a temperature at the first scattering feature, wherein radiation not reflected by the first scattering feature is allowed to propagate downstream; and a second scattering feature configured to reflect a second spectrum based on a temperature at the second scattering feature, wherein radiation not reflected by the second scattering feature is allowed to propagate downstream; A detector is positioned to receive radiation from the input terminal, including a first spectrum and a second spectrum of reflected radiation, and is configured to generate a measurement signal based on the received radiation; and a controller is configured to receive the measurement signal and generate a control signal based on the measurement signal, wherein the temperature-sensitive object includes a deformable mirror, which is configured to receive the control signal and adjust its shape based on the received control signal.

2. The lithography apparatus as described in claim 1, wherein: The first scattering feature is further configured such that the reflected first spectrum changes based on a temperature change at the first scattering feature; and the second scattering feature is further configured such that the reflected second spectrum changes based on a temperature change at the second scattering feature.

3. The lithography apparatus as described in claim 1, wherein: The temperature sensor further includes one radiation source configured to generate the input radiation; and the input radiation includes the first spectrum and the second spectrum.

4. The lithography apparatus of claim 1, wherein the waveguide device is enclosed within the temperature-sensitive object, and one of the lengths of the waveguide device is arranged in a direction perpendicular to one of the temperature-sensitive surfaces of the temperature-sensitive object.

5. The lithography apparatus of claim 1, wherein the waveguide device is enclosed in the deformable mirror and positioned close to one of the optical surfaces of the deformable mirror, such that the first scattering feature and the second scattering feature are thermally connected to different regions of the optical surface.

6. The lithography apparatus of claim 1, wherein the first scattering feature and the second scattering feature are each a Bragg reflector.

7. The lithography apparatus of claim 1, wherein the waveguide device is an optical fiber and the first scattering feature and the second scattering feature are each a fiber Bragg grating.

8. The lithography apparatus of claim 1, wherein the waveguide device is configured in a spiral pattern.

9. The lithography apparatus of claim 1, wherein the waveguide device is configured in a serpentine pattern.

10. The lithography apparatus as claimed in claim 1, wherein: The temperature sensor further includes one or more additional waveguide devices thermally coupled to the temperature-sensitive object; each of the one or more additional waveguide devices includes scattering features configured to reflect a corresponding spectrum based on the temperature at the counterpart of the scattering features; allowing radiation not reflected by the counterpart of the scattering features to propagate downstream; and the one or more additional waveguide devices are arranged parallel to and spaced apart from the waveguide device.

11. The lithography apparatus of claim 10, wherein the temperature-sensitive object is an optical element or a support structure in the lithography apparatus.

12. The lithography apparatus as claimed in claim 1, wherein: The temperature sensor further includes one or more additional waveguide devices thermally coupled to the temperature-sensitive object; each of the one or more additional waveguide devices includes scattering features configured to reflect a corresponding spectrum based on the temperature at the counterpart of the scattering features; allowing radiation not reflected by the counterpart of the scattering features to propagate downstream; and the one or more additional waveguide devices are disposed at corresponding depths, which are measured relative to a temperature-sensitive surface of the temperature-sensitive object, but are different from the depth of one of the waveguide devices.

13. The lithography apparatus of claim 12, wherein the temperature-sensitive object is an optical element or a support structure in the lithography apparatus.

14. The lithography apparatus of claim 1, wherein the controller is further configured to generate a two-dimensional or three-dimensional mapping of the temperature of the temperature-sensitive object based on the measurement signal.

15. The lithography apparatus of claim 14, wherein the temperature-sensitive object is an optical element or a support structure in the lithography apparatus.

16. The lithography apparatus of claim 1, further comprising: a temperature control system configured to receive the control signal and adjust the temperature of at least a portion of the temperature-sensitive object based on the received control signal.

17. The lithography apparatus of claim 16, wherein the temperature-sensitive object is an optical element or a support structure in the lithography apparatus.

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