Deformation measurement of a clamped object with an integrated optics near-field sensor

Abstract

Deformation measurement of a clamped object (e.g., a reticle, water, etc.) with an integrated optics near-field sensor is described. The sensor is configured to sense interaction between an electromagnetic field of the sensor and the object. Sensor output is used to determine a gap distance to the object based on the interaction. Changes in the electromagnetic field caused by gap distance changes result in changes in the output from the sensor. With a plurality of sensors, several gap distances at a plurality of locations can be determined, which collectively indicate deformation of the object. The measured deformation can be used to adjust (e.g., in real-time or otherwise) semiconductor patterning and / or other manufacturing processes, for example.

Description

DEFORMATION MEASUREMENT OF A CLAMPED OBJECT WITH AN INTEGRATED OPTICS NEAR-FIELD SENSORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 570,923 which was filed on March 28, 2024 and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] This description relates generally to deformation measurement of a clamped object with an integrated optics near-field sensor.BACKGROUND

[0003] A lithography (e.g., projection) apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device (e.g., a mask) may contain or provide a pattern corresponding to an individual layer of the IC (“design layout”), and this pattern can be transferred onto a target portion (e.g. comprising one or more dies) on a substrate (e.g., silicon wafer) that has been coated with a layer of radiation-sensitive material (“resist”), by methods such as irradiating the target portion through the pattern on the patterning device. In general, a single substrate contains a plurality of adjacent target portions to which the pattern is transferred successively by the lithographic projection apparatus, one target portion at a time. In one type of lithographic projection apparatus, the pattern on the entire patterning device is transferred onto one target portion in one operation. Such an apparatus is commonly referred to as a stepper. In an alternative apparatus, commonly referred to as a step-and-scan apparatus, a projection beam scans over the patterning device in a given reference direction (the “scanning” direction) while synchronously moving the substrate parallel or anti-parallel to this reference direction. Different portions of the pattern on the patterning device are transferred to one target portion progressively. During pattern transfer, a reticle or a wafer may be clamped. Deformation of the clamped reticle or wafer may cause patterning or other semiconductor process defects.SUMMARY

[0004] Deformation and / or other measurement of a clamped object (e.g., a reticle, wafer, etc.) with an integrated optics near-field sensor is described. The sensor is configured to generate an output based on an interaction between an electromagnetic field of the sensor and the object. Sensor output is used to determine a gap distance to the object based on the interaction. Changes in the electromagnetic field caused by gap distance changes result in changes in the output from the sensor. With a plurality of sensors, several gap distances at a plurality of locations can be determined, which collectively indicate deformation of the object. The measured deformation can be used to adjust (e.g.,in real-time or otherwise) semiconductor patterning and / or other manufacturing processes, for example, and / or for other advantageous purposes.

[0005] According to an embodiment, a clamping system is provided. The system includes a base configured to removably hold an object (e.g., a reticle, a wafer, etc.); and a sensor coupled to the base. The sensor comprises integrated optical components configured to sense interaction between an electromagnetic field of the sensor and the object. For example, the sensor may be an integrated optics near-field sensor. The sensor is configured to generate an output conveying information related to a gap distance between the object and the base, based on the interaction.

[0006] In some embodiments, the system comprises a radiation source such as a laser configured to generate radiation configured to pass through the sensor. A wavelength and / or other characteristics of the radiation from the radiation source are configured to be tuned according to a resonant frequency of the sensor and / or other factors. An input edge coupler of the system may be configured to edge couple radiation from the radiation source to the sensor.

[0007] In some embodiments, the integrated optical components are configured such that changes in the electromagnetic field caused by gap distance changes between the object and the base cause changes in the radiation in a sensor. The changes in the radiation in the sensor result in changes in the output, which are indicative of the gap distance changes. The integrated optical components of a sensor may comprise one or more waveguides, resonators, mirrors, splitters, interferometers, and / or other components. These may form a micro ring resonator, a Mach-Zehnder interferometer, a coupled micro-ring resonator system, and / or other structures, for example. In some embodiments, a size of; a shape of; an orientation of; a separation from; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; a quality factor impacted by a shape, sidewall roughness, and / or material of; and / or other characteristics of one or more of the integrated optical components is configured to be adjusted to change a range and / or sensitivity of the sensor.

[0008] In some embodiments, the system comprises a radiation detector configured to receive the output from the sensor and generate an electrical signal useable for determining the gap distance. The radiation detector may comprise a photodetector, for example, and / or other detectors. An output edge coupler of the system may be configured to edge couple the output from the sensor to the radiation detector.

[0009] In some embodiments, the base comprises a clamp, the sensor is coupled to the clamp, and the clamp is configured to releasably clamp the object with the sensor coupled to the clamp. For example, the base and / or the clamp may comprise one or more electrodes configured to provide electrostatic force configured to removably hold or otherwise clamp the object. As another example, vacuum clamping (e.g., in deep ultraviolet (DUV) applications) may be used. The base may comprise a chuck coupled to the clamp and / or other components. The chuck is configured to hold the clamp, the sensor, and the object, and facilitate movement of the clamp, the sensor, and the object.

[0010] In some embodiments, there are burls extending from the clamp. The burls are configured to contact the object. The sensor is coupled to the clamp between the burls such that the burls contact the object but the sensor does not. For example, a thickness of the sensor may be 10 microns or less, and a width of the sensor may be 2 mm or less. This is configured to be smaller than a separation between the burls and thinner than a thickness of the burls.

[0011] In some embodiments, a plurality of additional sensors are coupled to the base (e.g., on the clamp, between the burls), with the plurality of additional sensors configured to generate a plurality of additional outputs conveying information related to gap distances between the object and the base at a plurality of locations across the base. The gap distances between the object and the base may collectively indicate deformation of the object, a shape of the object, and / or other information about the object.

[0012] In some embodiments, the clamping system is part of a lithography apparatus used in semiconductor manufacturing.

[0013] According to another embodiment, there is provided a clamping method. The method comprises one or more operations performed by the clamping system described above.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts.

[0015] Fig. 1 schematically depicts a lithography apparatus, according to an embodiment.

[0016] Fig. 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment.

[0017] Fig. 3 illustrates a portion of an extreme ultra violet (EUV) lithographic apparatus, according to an embodiment.

[0018] Fig. 4 illustrates an example of typical deformation that may be experienced by an object (e.g., a reticle) during patterning in a lithography apparatus, according to an embodiment.

[0019] Fig. 5 illustrates a clamping system, according to an embodiment.

[0020] Fig. 6 illustrates a more detailed view of a sensor that is coupled to (and may form part of) the clamping system, according to an embodiment.

[0021] Fig. 7 illustrates several more details related to a base, sensors, a clamp, and a chuck of the clamping system, according to an embodiment.

[0022] Fig. 8 illustrates clamp burls relative to an example sensor, according to an embodiment.

[0023] Fig. 9 illustrates data generated using a micro-ring resonator based sensor 504 in the presence of a reticle (e.g., an object), according to an embodiment.

[0024] Fig. 10 illustrates plots showing the change in the effective index (of a sensor) as a function of the gap between an object (e.g., a reticle in this example) and a sensor, according to an embodiment.

[0025] Fig. 11 illustrates a clamping method, according to an embodiment.

[0026] Fig. 12 is a block diagram of an example computer system, according to an embodiment.DETAILED DESCRIPTION

[0027] In general, a mask or reticle (e.g., an object) may be a transparent block of material that is covered with a pattern defined by a different, opaque material. Various masks are fed into a lithographic apparatus and used to form layers of a semiconductor device on a substrate such as a wafer. The pattern defined on a given mask or reticle corresponds to features produced in one or more layers of the semiconductor device. Often, a plurality of masks or reticles are automatically fed into a lithographic apparatus during manufacturing and used to form corresponding layers of a semiconductor device. The same is true for wafers and / or other objects. A chuck and a clamp (e.g., an electrostatic reticle clamp) in the lithographic apparatus is used to secure a mask or reticle during processing. Similar chucks and clamps may be used to clamp a substrate such as a semiconductor wafer and / or other objects.

[0028] During semiconductor processing, a reticle increases in temperature because it absorbs radiation. This often causes reticle deformation, shape change, size change, and / or has other undesired effects. The deformation, shape change, and size change must be measured and accounted for to produce working integrated circuits (IC’s). Currently, measurements are performed using a limited number of measurement marks on the front of the reticle, or by encoders on a chuck. These measurements are used in conjunction with predictive models to correct or otherwise account for reticle deformation. Unfortunately, these measurements are only performed in a few locations on the reticle because of the limited number of measurement marks (which are not in areas with the reticle or semiconductor pattern), are not usually performed in real time (or near real time) during processing because of the reliance on predictive models, and / or have other disadvantages.

[0029] A new clamping system is described herein. As described above, deformation and / or other characteristics of a clamped object (e.g., a reticle, water, etc.) are measured with an integrated optics near-field sensor. The sensor is configured to generate an output based on an interaction between an electromagnetic field of the sensor and the object. Sensor output is used to determine a gap distance to the object based on the interaction. Changes in the electromagnetic field caused by gap distance changes result in changes in the output from the sensor. With a plurality of sensors, several gap distances at a plurality of locations can be determined, which collectively indicate deformation of the object. The measured deformation can be used to adjust (e.g., in real-time or otherwise) semiconductor patterning and / or other manufacturing processes, for example, and / or for other purposes. In addition, the sensors: are small enough to be placed in proximity to (e.g., between burlsof a clamp holding the object), and make measurements for, patterned areas of an object (e.g., the reticle or wafer); tens, hundreds, or even thousands of sensors may be used, which provides more finely detailed sampling information for many areas across an object; and / or each (integrated optics near-field) sensor can provide data with sub-nanometer accuracy. Other advantages are contemplated.

[0030] Although specific reference may be made in this text to the manufacture of integrated circuits, it should be understood that the description herein has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle”, “wafer” or “die” in this text should be considered as interchangeable with the more general terms “mask”, “substrate” and “target portion”, respectively. In addition, any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

[0031] As an introduction, prior to transferring a pattern from a patterning device such as a mask to a substrate, the substrate may undergo various procedures, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other procedures (“post-exposure procedures”), such as a post-exposure bake (PEB), development, a hard bake and measurement and / or other inspection of the transferred pattern. This array of procedures is used as a basis to make an individual layer of a device, e.g., an IC. The substrate may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, chemical mechanical polishing, etc., all intended to finish an individual layer of the device. If several layers are required in the device, then the whole procedure, or a variant thereof, is repeated for each layer. Eventually, a device will be present in each target portion on the substrate. These devices are then separated from one another by a technique such as dicing or sawing, after which the individual devices can be mounted on a carrier, connected to pins, etc.

[0032] Manufacturing devices, such as semiconductor devices, typically involves processing a substrate (e.g., a semiconductor wafer) using a number of fabrication processes to form various features and multiple layers of the devices. Such layers and features are typically manufactured and processed using, e.g., deposition, lithography, etch, chemical mechanical polishing, ion implantation, and / or other processes. Multiple devices may be fabricated on a plurality of dies on a substrate and then separated into individual devices. This device manufacturing process may be considered a patterning process. A patterning process involves a patterning step, such as optical and / or nanoimprint lithography using a patterning device in a lithographic apparatus, to transfer a pattern on the patterning device to a substrate and typically, but optionally, involves one or more related pattern processing steps, such as resist development by a development apparatus, baking of the substrate using a bake tool, etching using the pattern using an etch apparatus, etc. One or more metrology processes are typically involved in the patterning process.

[0033] Lithography is a step in the manufacturing of device such as ICs, where patterns formed on substrates define functional elements of the devices, such as microprocessors, memory chips, etc. Similar lithographic techniques are also used in the formation of flat panel displays, micro-electro mechanical systems (MEMS) and other devices.

[0034] Fig. 1 schematically depicts an embodiment of a lithographic apparatus LA that may include and / or associated with the present systems and / or methods. The apparatus comprises: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation, DUV radiation, or EUV radiation); a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters; a substrate table (e.g. a wafer table) WT (e.g., WTa, WTb or both) configured to hold a substrate (e.g. a resist-coated wafer) W and coupled to a second positioner PW configured to accurately position the substrate in accordance with certain parameters; and a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies and often referred to as fields) of the substrate W. The projection system is supported on a reference frame (RF). As depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

[0035] The illuminator IL receives a beam of radiation from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising for example suitable directing mirrors and / or a beam expander. In other cases, the source may be an integral part of the apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0036] The illuminator IL may alter the intensity distribution of the beam. The illuminator may be arranged to limit the radial extent of the radiation beam such that the intensity distribution is non-zero within an annular region in a pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in a pupil plane of the illuminator IL may be referred to as an illumination mode.

[0037] The illuminator IL may comprise adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. Generally, at least the outer and / or inner radial extent (commonly referred to as o-outer and o-inner, respectively) of the intensity distribution in a pupil plane of theilluminator can be adjusted. The illuminator IL may be operable to vary the angular distribution of the beam. For example, the illuminator may be operable to alter the number, and angular extent, of sectors in the pupil plane wherein the intensity distribution is non-zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different illumination modes may be achieved. For example, by limiting the radial and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution may have a multi-pole distribution such as, for example, a dipole, quadrupole or hexapole distribution. A desired illumination mode may be obtained, e.g., by inserting an optic which provides that illumination mode into the illuminator IL or using a spatial light modulator.

[0038] The illuminator IL may be operable to alter the polarization of the beam and may be operable to adjust the polarization using adjuster AD. In addition, the illuminator IL generally comprises various other components, such as an integrator IN and a condenser CO. The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation. Thus, the illuminator provides a conditioned beam of radiation B, having a desired uniformity and intensity distribution in its cross section.

[0039] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system.

[0040] The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a pattern in a target portion of the substrate. In an embodiment, a patterning device is any device that can be used to impart a radiation beam with a pattern in its crosssection to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in a target portion of the device, such as an integrated circuit.

[0041] A patterning device may be transmissive or reflective. Examples of patterning devices include reticles or masks, programmable mirror arrays, and programmable LCD panels. Reticles or masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in aradiation beam, which is reflected by the mirror matrix.

[0042] The projection system PS may comprise a plurality of optical (e.g., lens) elements and may further comprise an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase variations across the pupil plane throughout the field). To achieve this, the adjustment mechanism may be operable to manipulate one or more optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system wherein its optical axis extends in the z direction. The adjustment mechanism may be operable to do any combination of the following: displace one or more optical elements; tilt one or more optical elements; and / or deform one or more optical elements. Displacement of an optical element may be in any direction (x, y, z, or a combination thereof). Tilting of an optical element is typically out of a plane perpendicular to the optical axis, by rotating about an axis in the x and / or y directions although a rotation about the z axis may be used for a non-rotationally symmetric aspherical optical element. Deformation of an optical element may include a low frequency shape (e.g. astigmatic) and / or a high frequency shape (e.g. free form aspheres). Deformation of an optical element may be performed for example by using one or more actuators to exert force on one or more sides of the optical element and / or by using one or more heating elements to heat one or more selected regions of the optical element. In general, it may not be possible to adjust the projection system PS to correct for apodization (transmission variation across the pupil plane). The transmission map of a projection system PS may be used when designing a patterning device (e.g., mask) MA for the lithography apparatus LA. Using a computational lithography technique, the patterning device MA may be designed to at least partially correct for apodization.

[0043] The lithographic apparatus may be of a type having two (dual stage) or more tables (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, a substrate table WTa and a table WTb below the projection system without a substrate that is dedicated to, for example, facilitating measurement, and / or cleaning, etc.). In such “multiple stage” machines, the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure. For example, alignment measurements using an alignment sensor AS and / or level (height, tilt, etc.) measurements using a level sensor LS may be made.

[0044] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by the illumination system IL. The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g., an interferometric device, linear encoder, 2-D encoder, or capacitive sensor), the substrate table WT can be moved accurately, e.g. to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is notexplicitly depicted in Fig. 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0045] The depicted apparatus may be used in a step mode and / or a scan mode. In step mode, the support structure MT and the substrate table WT are kept essentially stationary, while a pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. In scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure MT may be determined by the (de-) magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion. In another mode, the support structure MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed, and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above. Combinations and / or variations on the above-described modes of use or entirely different modes of use may also be employed.

[0046] A substrate may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure herein may be applied to such and other substrateprocessing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already includes multiple processed layers.

[0047] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g. having a wavelength of 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0048] Various patterns on or provided by a patterning device may have different process windows, i.e., a space of processing variables under which a pattern will be produced within specification. Examples of pattern specifications that relate to potential systematic defects include checks for necking, line pull back, line thinning, critical dimension (CD), edge placement, overlapping, resist top loss, resist undercut and / or bridging. The process window of the patterns on a patterning device or an area thereof may be obtained by merging (e.g., overlapping) process windows of each individual pattern. The boundary of the process window of a group of patterns comprises boundaries of process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the group of patterns. These patterns can be referred to as “hot spots” or “process window limiting patterns (PWLPs),” which are used interchangeably herein. When controlling a part of a patterning process, it is possible and economical to focus on the hot spots. When the hot spots are not defective, it is most likely that other patterns are not defective.

[0049] As shown in Fig. 2, the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to a lithocell or cluster, which also includes apparatuses to perform pre- and post-exposure processes on a substrate. Conventionally these include one or more spin coaters SC to deposit one or more resist layers, one or more developers to develop exposed resist, one or more chill plates CH and / or one or more bake plates BK. A substrate handler, or robot, RO picks up one or more substrates from input / output port I / Ol, I / O2, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus. These apparatuses, which are often collectively referred to as the track, are under the control of a track control unit TCU which is itself controlled by the supervisory control system SCS, which also controls the lithographic apparatus via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0050] In order to ensure that a substrate that is exposed by the lithographic apparatus is exposed correctly and consistently and / or in order to monitor a part of the patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., an optical lithography step), it is desirable to inspect a substrate or other object to measure or determine one or more properties such as alignment, overlay (which can be, for example, between structures in overlying layers or between structures in a same layer that have been provided separately to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, a materialproperty, etc. For example, contamination on reticle clamp membranes (e.g., as described herein) may adversely affect overlay because clamping a reticle over such contamination will distort the reticle. Accordingly, a manufacturing facility in which lithocell LC is located also typically includes a metrology system that measures some or all of the substrates W (Fig. 1) that have been processed in the lithocell or other objects in the lithocell. The metrology system may be part of the lithocell LC, for example it may be part of the lithographic apparatus LA (such as alignment sensor AS (Fig. 1)).

[0051] The one or more measured parameters may include, for example, alignment, overlay between successive layers formed in or on the patterned substrate, critical dimension (CD) (e.g., critical linewidth) of, for example, features formed in or on the patterned substrate, focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberrations of an optical lithography step, etc. This measurement may be performed on a target of the product substrate itself and / or on a dedicated metrology target provided on the substrate. The measurement can be performed after-development of a resist but before etching, after-etching, after deposition, and / or at other times.

[0052] Thus, in a device fabrication process (e.g., a patterning process, a lithography process, etc.), a substrate or other objects may be subjected to various types of measurement during or after the process. The measurement may determine whether a particular substrate is defective, may establish adjustments to the process and apparatuses used in the process (e.g., aligning two layers on the substrate or aligning the patterning device to the substrate), may measure the performance of the process and the apparatuses, or may be for other purposes. Examples of measurement include optical imaging (e.g., optical microscope), non-imaging optical measurement (e.g., measurement based on diffraction such as the ASML YieldStar metrology tool, the ASML SMASH metrology system), mechanical measurement (e.g., profiling using a stylus, atomic force microscopy (AFM)), and / or non- optical imaging (e.g., scanning electron microscopy (SEM)).

[0053] Metrology results may be provided directly or indirectly to the supervisory control system SCS. If an error is detected, an adjustment may be made to exposure of a subsequent substrate (especially if the inspection can be done soon and fast enough that one or more other substrates of the batch are still to be exposed) and / or to subsequent exposure of the exposed substrate. Also, an already exposed substrate may be stripped and reworked to improve yield, or discarded, thereby avoiding performing further processing on a substrate known to be faulty. In a case where only some target portions of a substrate are faulty, further exposures may be performed only on those target portions which meet specifications.

[0054] Within a metrology system, a metrology apparatus is used to determine one or more properties of the substrate, and in particular, how one or more properties of different substrates vary, or different layers of the same substrate vary from layer to layer. As noted above, the metrology apparatus may be integrated into the lithographic apparatus LA or the lithocell LC or may be a standalone device.

[0055] To enable the metrology, one or more targets can be provided on the substrate. In an embodiment, the target is specially designed and may comprise a periodic structure. In an embodiment, the target is a part of a device pattern, e.g., a periodic structure of the device pattern. In an embodiment, the device pattern is a periodic structure of a memory device (e.g., a Bipolar Transistor (BPT), a Bit Line Contact (BLC), etc. structure).

[0056] The present systems, and / or methods may be used as stand-alone tools and / or techniques, and / or or used in conjunction with semiconductor manufacturing processes, to enhance the accurate transfer of complex designs to physical wafers.

[0057] As described above, a clamping system may be used in a lithographic and / or metrology apparatus to clamp an object such as a patterning device (e.g., a reticle), a substrate such as a wafer, and / or other objects. Before clamping, the lithographic apparatus (for example) may move the object through typical movements and / or positions of a reticle to clamping position.

[0058] By way of a non-limiting example, Fig. 3 illustrates example portions of lithographic apparatus 300 (e.g., similar to an or the same as the lithographic apparatus shown in Fig. 1). Fig. 3 illustrates a portion of an extreme ultra violet (EUV) lithographic apparatus. Fig. 3 illustrates an example embodiment of an object 302 (e.g., in transit to and / or in proximity to a clamp 312 of lithographic apparatus 300) and various components of lithographic apparatus 300 including a tool handler and / or other components. Object 302 (e.g., a reticle in this example) is configured to be brought into apparatus 300 using a reticle pod. Object 302 is secured from the outside environment in an inner pod. Object 302 in the inner pod is placed on an EUV inner pod baseplate. Object 302 is moved from outside vacuum through the reticle handling system on to the turret of a tool handler of lithographic apparatus 300. In some embodiments, lithographic apparatus 300 can be configured for deep ultraviolet (DUV) lithography with one or more adjustments from what is shown in Fig. 3. This may utilize vacuum clamping, for example. The base may comprise a chuck coupled to the clamp and / or other components.

[0059] As described above, object 302 (e.g. a reticle in this example) is heated in lithographic apparatus 300 due to radiation absorption and / or other factors during patterning (see Fig. 1 and the corresponding description). This may lead to object 302 (reticle) deformation, shape change, size change, and / or other undesirable effects.

[0060] For example, Fig. 4 illustrates an example of typical deformation that may be experienced by object 302 (e.g., a reticle). The deformation may be caused by heating in lithographic apparatus 300 (Fig. 3) and / or LA (Fig. 1) due to radiation absorption and / or other factors during patterning. Fig. 4 illustrates a top view 410 (of out of plane deformation), a bottom view 412 (of out of plane deformation), and a perspective view 414 of deformation in object 302. As shown by the different shades in views 410-414, deformation tends to increase near the edges of object 302, but can vary at least a small amount across most areas of object 302. In this example, there is deformation in a positive direction out of the page, and some deformation in a negative direction into the page).Deformation like the deformation shown in Fig. 4 can cause patterning errors, among other negative effects.

[0061] Fig. 5 illustrates a new electrostatic clamping system 500. In some embodiments, clamping system 500 is part of a lithography apparatus used in semiconductor manufacturing. Clamping system may be used to clamp reticles, wafers, and / or other objects. System 500 comprises a base 502 configured to removably hold an object (e.g., object 302 shown in Fig. 4, Fig. 3, etc., such as a reticle, a wafer, etc.) a sensor 504 coupled to base 502, and / or other components. Sensor 504 comprises integrated optical components 506 configured to sense interaction between an electromagnetic field of sensor 504 and the object. For example, sensor 504 may be an integrated optics near-field sensor. Sensor 504 is configured to generate an output conveying information related to a gap distance between the object and base 502, based on the interaction (e.g., as shown in Fig. 6 - 10 and described below) and / or other information. Changes in the electromagnetic field caused by gap distance changes result in changes in the output from sensor 504. With a plurality of sensors 504 (e.g., tens, hundreds, or even thousands, also as shown and described below), several gap distances at a plurality of locations can be determined, which collectively indicate deformation of the object. The measured deformation can be used to adjust (e.g., in real-time or otherwise) semiconductor patterning and / or other manufacturing processes, for example, and / or may be used for other advantageous purposes.

[0062] In some embodiments, system 500 comprises a radiation source 510 configured to generate radiation 512 configured to pass through sensor 504. Source 510 may comprise a laser, and / or other coherent radiation sources. A wavelength and / or other characteristics of radiation 512 from radiation source 510 are configured to be tuned according to a resonant frequency of sensor 504 and / or other factors. For example, if there is a fabrication error, the resonant frequency of sensor 504 may shift. Another approach is to adjust (e.g., trim) one or more of the integrated optical components to match with a wavelength of radiation 512 from radiation source 510. An input edge coupler 520 of system 500 may be configured to edge couple radiation 512 from radiation source 510 to sensor 504. As shown in Fig. 5, this may include conducting radiation 512 into and / or through a waveguide 522 and / or other structures between input edge coupler 520 and one or more portions of sensor 504. For example, radiation 512 is coupled to a second waveguide 523 in sensor 504 through waveguide 522. Waveguide 523 is in proximity to a ring resonator 525 (in this example). At the resonance of these integrated optical components 506, the transmission through waveguide 523 changes as the gap between sensor 504 and object 302 (see other figures) changes. The output 530 of waveguide 523 is coupled back to waveguide 522 and transferred to a radiation detector 540.

[0063] In some embodiments, integrated optical components 506 are configured such that changes in the electromagnetic field caused by gap distance changes between the object (e.g., an object 302 shown in Fig. 4, Fig. 3, etc., such as a reticle) and base 502 cause changes in the radiation in sensor 504. The changes in the radiation in sensor 504 result in changes in outputs 530 from sensor 504, which are indicative of the gap distance changes. Integrated optical components 506 of sensor 504may comprise one or more waveguides, resonators, mirrors, splitters, interferometers, and / or other components. These may form a micro ring resonator, a Mach-Zehnder interferometer, a coupled micro-ring resonator system, and / or other structures, for example. In some embodiments, a size of; a shape of; an orientation of; a separation from; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; a quality factor impacted by a shape, sidewall roughness, and / or material of; and / or other characteristics of one or more of the integrated optical components 506 is configured to be adjusted to change a range and / or sensitivity of sensor 504.

[0064] In some embodiments, system 500 comprises a radiation detector 540 configured to receive output 530 from sensor 504 and generate an electrical signal useable for determining the gap distance. Radiation detector 540 may comprise a photodetector, for example, and / or other detectors. An output edge coupler 542 of system 500 may be configured to edge couple output 530 from sensor 504 to radiation detector 540.

[0065] In some embodiments, base 502 comprises a clamp 550 (e.g., similar to and / or the same as reticle clamp 312 shown in Fig. 3 and described above) and / or other components. Sensor 504 is coupled to clamp 550, and clamp 550 is configured to releasably clamp the object with sensor 504 coupled to clamp 550. For example, base 502 and / or clamp 550 may comprise one or more mechanisms 560 for generating clamping force. An example mechanism may be one or more electrodes configured to provide electrostatic force configured to removably hold or otherwise clamp the object, vacuum components, and / or other components. Base 502 may comprise a chuck 552 coupled to clamp 550 and / or other components. Chuck 552 is configured to hold clamp 550, sensor 504, and the object, and facilitate movement of clamp 550, sensor 504, and the object, among other operations.

[0066] Though not shown in Fig. 5, in some embodiments, a plurality of additional sensors 504 are coupled to base 502 (e.g., on clamp 550), with the plurality of additional sensors 504 configured to generate a plurality of additional outputs 530 conveying information related to gap distances between the object (e.g., a reticle or a wafer as described above) and base 502 at a plurality of locations across base 502. The gap distances between the object and base 502 may collectively indicate deformation of the object, a shape of the object, a size of the object, and / or other information about the object.

[0067] Fig. 6 - 10 illustrate additional details related to one or more of the components and / or techniques described above with respect to Fig. 5.

[0068] For example, Fig. 6 illustrates a more detailed view 600 of sensor 504. Sensor 504 comprises integrated optical components 506 configured to sense interaction between an electromagnetic field 602 of sensor 504 and an object (e.g., object 302 shown in Fig. 4, Fig. 3, etc., such as a reticle, a wafer, etc.). Integrated optics based sensors such as sensor 504 can measure a change in a geometry with sub-nanometer accuracy due to a change in the near-field response (e.g., the interaction between the electromagnetic field 602 of sensor 504 and an object 302). Fig. 6 showsone possible example embodiment of integrated optical components 506, where an integrated optics micro-ring resonator 608 (similar to or the same as 525 in Fig. 5) is used in conjunction with a waveguide 609 (similar to or the same as 523 in Fig. 5). Resonator 608 works as a gap distance sensor. As shown in view 610 (a side view), resonator 608 may be supported by a base 616.

[0069] In some embodiments, integrated optical components 506 are configured such that changes in electromagnetic field 602 caused by gap distance changes between the object 302 (e.g., object 302 is also shown in Fig. 4, Fig. 3, etc., such as a reticle) and base 502 (Fig. 5) cause changes in the radiation in sensor 504. The changes in the radiation in sensor 504 result in changes in outputs 530 (Fig. 5) from sensor 504, which are indicative of the gap distance changes. In some embodiments, a size of; a shape of; an orientation of; a separation between; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; a quality factor impacted by a shape, sidewall roughness, and / or material of; and / or other characteristics of resonator 608 and / or waveguide 609 is configured to be adjusted to change a range and / or sensitivity of sensor 504. For example, a distance between resonator 608 and waveguide 609 may be adjusted, a diameter of resonator 608 may be changed, etc.

[0070] As described above, changes in electromagnetic field 602 caused by gap distance changes between the object (e.g., an object 302 shown in Fig. 4, Fig. 3, etc., such as a reticle) and base 502 (Fig. 5) cause changes in sensor 504, and / or radiation in sensor 504 For example, differences in the proximity of an object (e.g., a reticle) to a sensor 504 (e.g., caused by deformation of the reticle) result in differences in the electromagnetic field 602. Electromagnetic field 602 variation causes changes in the resonant frequency of resonator 608 and waveguide 609. This in turn causes the transmission response near the resonant frequency in radiation passing through resonator 608 and waveguide 609 to change, which changes the output 530 (Fig. 5) from sensor 504. Due to the changes, the effective index of waveguide 609 changes, and as a result, the resonant frequency of resonator 608 is shifted. By measuring transmission near the resonance, the change in the gap between sensor 504 and an object 302 can be determined with sub-nanometer accuracy. Note that, as mentioned above, sensor 504 is not limited to a micro-ring resonator. On-chip Mach-Zehnder interferometers, coupled microrings, and / or other sensor structures may be used.

[0071] Fig. 7 illustrates several more details related to base 502, sensors 504, clamp 550, and chuck 552 of system 500. In this example, base 502 comprises clamp 550 (e.g., similar to and / or the same as reticle clamp 312 shown in Fig. 3 and described above), multiple sensors 504 are coupled to clamp 550, and clamp 550 is configured to releasably clamp object 302 (e.g., a reticle in this example) with sensor 504 coupled to clamp 550. Base 502 and / or clamp 550 may comprise one or more mechanisms 560 configured to provide clamping (e.g., electrostatic, vacuum, etc.) force configured to removably hold or otherwise clamp object 302. Base 502 may comprise a chuck 552 coupled to clamp 550 and / or other components. Chuck 552 is configured to hold clamp 550, sensors 504, and object 302, and facilitate movement of clamp 550, sensor 504, and the object, among other operations.Sensors 504 are coupled to base 502 (e.g., on clamp 550), with sensors 504 configured to generate a plurality of outputs 530 (Fig. 5) conveying information related to gap distances 700 between object 302 (e.g., a reticle) and base 502 and / or sensors 504 at multiple locations 702 across base 502. The gap distances 700 between object 302 and base 502 and / or sensors 504 may collectively indicate deformation of object 302, a shape of object 302, a size of object 302, and / or other information about object 302.

[0072] In some embodiments, there are burls 710 extending from clamp 550. Burls 710 are configured to contact object 302. Sensors 504 are coupled to clamp 550 between burls 710 such that burls 710 contact object 302 but sensors 504 do not. For example, a thickness of sensors 504 may be 10 microns or less, and a width of sensors 504 may be 2 mm or less. This is configured to be smaller than the separation between burls 710 and thinner than a thickness of burls 710, for example.

[0073] Contacting may include touching, nearly touching, and / or other contacting. In some embodiments, the contacting is controlled by one or more processors, via the reticle handler turret gripper, and / or using other components of a lithography apparatus (e.g., as described herein). For example, a charge may be propagated through an electrode such that an opposite polarity is induced in a side of a clamped object configured to contact burls 710.

[0074] In Fig. 7, the left image shows side views of sensors 504, and the right image shows a top view of an example sensor 504. Multiple sensors may be placed on clamp 550 inside the space between burls. As described above, radiation 512 may be coupled into sensors 504 through an edge coupler, and transmitted radiation may be out-coupled (e.g., into a fiber coupled) to detector 540. Note that there are several approaches for in-coupling and out-coupling to sensors 504. The transmission near the resonance is sensitive to gap distance 700 between the back of object 302 (e.g., a reticle) and a sensor 504. Hence, any deformation due to object 302 heating impacts the transmission significantly. Measuring the transmission facilitates determination of reticle deformation (and / or shape, size, and / or other changes) in the z direction (the vertical direction in this figure) with sub-nanometer accuracy.

[0075] Burls 710 and an example sensor 504 are illustrated in more detail in Fig. 8. Burls 710 extend from clamp 550. Burls 710 are configured to contact object 302 (e.g., a reticle). Sensor 504 is coupled to clamp 550 between burls 710 such that burls 710 contact object 302 but sensor 504 does not. A thickness 800 of sensors 504 may be 10 microns or less, and a width 802 of sensors 504 may be 2 mm or less. This is configured to be smaller than the separation 804 between burls 710 and thinner than a thickness 806 of burls 710, for example.

[0076] Fig. 9 and Fig. 10 show example data for clamping system 500 (Fig. 5). A silicon photonic sensor 504 platform was used with input radiation having a 1550 nm wavelength to generate the data shown in Fig. 9 and Fig. 10. Such a sensor 504 can be fabricated in standard CMOS compatible foundries. The data illustrated in Fig. 9 and Fig. 10 shows that determination of sub-nm deformation is achievable. Based on the data in Fig. 9 and Fig. 10, object (e.g., reticle or wafer) deformation due toheating (in this example) is on the order of + 5 nm, and increases with increasing lithography apparatus (e.g., see lithography apparatus LA shown in Fig. 1) source power. In some embodiments, the photonic integrated circuit of a sensor 504 can be coated by a silicon dioxide cladding to protect the waveguides (e.g., resonator 608 and / or waveguide 609 shown in Fig. 6, for example) and object (reticle) from defects and outgassing. Since the components of a sensor 504 are passive, and the radiation source and / or the detector(s) can be outside a lithography apparatus, sensor(s) 504 also do not add any heat to the overall system. Tunable radiation sources such as lasers can be used tune input radiation to a resonant frequency of sensors 504 if there is any drift in the temperature and / or other environmental factors due to object (reticle) heating.

[0077] Specifically, Fig. 9 illustrates data generated using a micro-ring resonator based sensor 504 (Fig. 5) in the presence of a reticle (e.g., an object). The sensor related structures in the images in Fig. 9 can be compared to the structure shown in view 610 of Fig. 6, for example. Image 900 shows the cross section and the refractive index of each material for each element of the structure. There is a vacuum / air gap between the integrated optical components 506 and object 302 (e.g., the reticle). Image 902 shows the electric field component of the waveguide mode. Image 904 shows the same data in log scale to make the interaction between the waveguide mode and reticle (object 302) more visible. In this example, integrated optical components 506 are made from silicon, with a 450 nm width, and a height of 170 nm, and input radiation having a wavelength at about 1550 nm.

[0078] Fig. 10 illustrates plots 1000 and 1002 showing the change in the effective index 1004 (of a sensor 504) as a function of the gap 1006 between an object (e.g., a reticle in this example) and a sensor. Plot 1000 shows how the effective index of a ring resonator (in this example) changes with the gap. If the effective index changes, the resonant frequency is shifted. Plot 1002 shows the effective index 1004 around a gap 1006 of 200 nm. In this region the change in the effective index is 5neff = 103nm1. This means that for a 1 nm change in the gap, the effective index changes 103. The resonant frequency of the cavity (formed by one or more optical components 506, as shown in Fig. 6, for example ) is Ires= neff L, where Iresis the resonant wavelength, and L is the cavity length. For a cavity length of 1 micron, a change in the wavelength of 5 7 res = 5neff L = 103x 103= 1 nm is expected for a 1 nm change in the gap, which shows the sensitivity of the approach described herein. If a larger gap is needed, the cavity length can be increased, as one possible example, to achieve the same level of sensitivity.

[0079] Fig. 11 illustrates a clamping method 1100. Method 1100 facilitates deformation and / or other measurement of a clamped object (e.g., a reticle, water, etc.) with an integrated optics near-field sensor. The sensor is configured to sense interaction between an electromagnetic field of the sensor and the object. Sensor output is used to determine a gap distance to the object based on the interaction. Changes in the electromagnetic field caused by gap distance changes result in changes in the output from the sensor. With a plurality of sensors, several gap distances at a plurality of locations can be determined, which collectively indicate deformation of the object. The measureddeformation can be used to adjust (e.g., in real-time or otherwise) semiconductor patterning and / or other manufacturing processes, for example, and / or for other advantageous purposes.

[0080] Method 1100 may be performed with a clamping system and / or other components, as described herein (e.g., clamping system 500 shown in Fig. 5). The clamping system may be part of a lithography apparatus, a metrology apparatus, and / or other systems. For example, the clamping system may be part of a lithography apparatus used in semiconductor manufacturing. In some embodiments, one or more operations of method 1100 are controlled by one or more processors and / or a computing system, as described below (see Fig. 12). The operations of method 1100 presented below are intended to be illustrative. In some embodiments, method 1100 may be accomplished with one or more additional operations not described, and / or without one or more of the operations discussed. Additionally, the order in which the operations of method 1100 are illustrated in Fig. 11 and described below is not intended to be limiting.

[0081] In some embodiments, one or more operations of method 1100 may be implemented in and / or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information, as described with respect to Fig. 12 below). The one or more processing devices may include one or more devices executing some or all of the operations of method 1100 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and / or software to be specifically designed for execution of one or more of the operations of method 1100 (e.g., see discussion related to Fig. 12 below). For example, the one or more processing devices may run software configured to control energization of an electrode of the clamping system, control a radiation source, control a radiation detector, determine gap distances, determine deformation, and / or perform other operations in the clamping system.

[0082] At an operation 1102, a base removably holds an object. The object may be a patterning device such as a reticle, a wafer, etc.. In some embodiments, the base comprises a clamp, the sensor is coupled to the clamp, and the clamp is configured to releasably clamp the object with the sensor coupled to the clamp. For example, the base and / or the clamp may comprise one or more electrodes configured to provide electrostatic force configured to removably hold or otherwise clamp the object. The base may comprise a chuck coupled to the clamp and / or other components. The chuck is configured to hold the clamp, the sensor, and the object, and facilitate movement of the clamp, the sensor, and the object.

[0083] In some embodiments, there are burls extending from the clamp. The burls are configured to contact the object. The sensor is coupled to the clamp between the burls such that the burls contact the object but the sensor does not. For example, a thickness of the sensor may be 10 microns or less, and a width of the sensor may be 2 mm or less. This is configured to be smaller than a separationbetween the burls and thinner than a thickness of the burls. In some embodiments, operation 1102 is performed by a base that is similar to and / or the same as base 502 shown in Fig. 5 and described above.

[0084] At an operation 1104, an output is generated with the sensor (coupled to the base). The output conveys information related to a gap distance between the object and the base. The sensor comprises integrated optical components configured to sense interaction between an electromagnetic field of the sensor and the object. For example, the sensor may be an integrated optics near-field sensor. The sensor is configured to generate the output based on the interaction.

[0085] In some embodiments, operation 1104 comprises generating radiation with a radiation source. The radiation source may be a laser and / or other radiation sources configured to generate radiation configured to pass through the sensor. A wavelength and / or other characteristics of the radiation from the radiation source are configured to be tuned according to a resonant frequency of the sensor and / or other factors. As part of operation 1104, an input edge coupler may be configured to edge couple radiation from the radiation source to the sensor.

[0086] In some embodiments, the integrated optical components are configured such that changes in the electromagnetic field caused by gap distance changes between the object and the base cause changes in the radiation in a sensor. The changes in the radiation in the sensor result in changes in the output, which are indicative of the gap distance changes. The integrated optical components of a sensor may comprise one or more waveguides, resonators, mirrors, splitters, interferometers, and / or other components. These may form a micro ring resonator, a Mach-Zehnder interferometer, a coupled micro-ring resonator system, and / or other structures, for example. In some embodiments, a size of; a shape of; an orientation of; a separation from; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; a quality factor impacted by a shape, sidewall roughness, and / or material of; and / or other characteristics of one or more of the integrated optical components is configured to be adjusted to change a range and / or sensitivity of the sensor.

[0087] In some embodiments, operation 1104 comprises receiving, with a radiation detector, the output from the sensor, and generating an electrical signal useable for determining the gap distance. The radiation detector may comprise a photodetector, for example, and / or other detectors. As part of operation 1104, an output edge coupler may be configured to edge couple the output from the sensor to the radiation detector. In some embodiments, operation 1104 is performed by a radiation source, input edge coupler, sensor, output edge coupler, and / or detector that are similar to and / or the same as radiation source 510, input edge coupler 520, sensor 504, output edge coupler 542, and / or detector 540, respectively, shown in Fig. 5 and described above.

[0088] In some embodiments, a plurality of additional sensors are coupled to the base (e.g., on the clamp, between the burls), with the plurality of additional sensors configured to generate a plurality of additional outputs conveying information related to gap distances between the object and the base at aplurality of locations across the base. The gap distances between the object and the base may collectively indicate deformation of the object, a shape of the object, and / or other information about the object.

[0089] Fig. 12 is a block diagram that illustrates a computer system 1200 that can assist in implementing the methods, flows, or the system(s) disclosed herein. Computer system 1200 may be included in and / or electronically coupled to lithography apparatus LA described above (Fig. 1, Fig. 3, etc.), system 400 shown in Fig. 4 and described above, and / or other systems. Computer system 1200 includes a bus 1202 or other communication mechanism for communicating information, and a processor 1204 (or multiple processors 1204, 1205, etc.) coupled with bus 1202 for processing information. Computer system 1200 also includes a main memory 1206, such as a random access memory (RAM) or other dynamic storage device, coupled to bus 1202 for storing information and instructions to be executed by processor 1204. Main memory 1206 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 1204. Computer system 1200 further includes a read only memory (ROM) 1208 or other static storage device coupled to bus 1202 for storing static information and instructions for processor 1204. A storage device 1210, such as a magnetic disk or optical disk, is provided and coupled to bus 1202 for storing information and instructions.

[0090] Computer system 1200 may be coupled via bus 1202 to a display 1212, such as a flat panel or touch panel display for displaying information to a computer user. An input device 1214, including alphanumeric and other keys, is coupled to bus 1202 for communicating information and command selections to processor 1204. Another type of user input device is cursor control 1216, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor 1204 and for controlling cursor movement on display 1212. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

[0091] According to one embodiment, portions of one or more flows and / or methods described herein may be performed by computer system 1200 in response to processor 1204 executing one or more sequences of one or more instructions contained in main memory 1206. Such instructions may be read into main memory 1206 from another computer-readable medium, such as storage device 1210. Execution of the sequences of instructions contained in main memory 1206 causes processor 1204 to perform the flows and / or process steps described herein. One or more processors in a multiprocessing arrangement may also be employed to execute the sequences of instructions contained in main memory 1206. In an alternative embodiment, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, the description herein is not limited to any specific combination of hardware circuitry and software.

[0092] The term “computer-readable medium” or “machine readable medium” refers to anymedium that participates in providing instructions to processor 1204 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device 1210. Volatile media include dynamic memory, such as main memory 1206. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus 1202. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH- EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.

[0093] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor 1204 for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a network. Computer system 1200 can receive the data. Bus 1202 carries the data to main memory 1206, from which processor 1204 retrieves and executes the instructions. The instructions received by main memory 1206 may optionally be stored on storage device 1210 either before or after execution by processor 1204.

[0094] Computer system 1200 may also include a communication interface 1218 coupled to bus 1202. Communication interface 1218 provides a two-way data communication coupling to a network link 1220 that is connected to a local network 1222. For example, communication interface 1218 may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, communication interface 1218 may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, communication interface 1218 sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

[0095] Network link 1220 typically provides data communication through one or more networks to other data devices. For example, network link 1220 may provide a connection through local network 1222 to a host computer 1224 or to data equipment operated by an Internet Service Provider (ISP) 1226. ISP 1226 in turn provides data communication services through the worldwide packet data communication network, now commonly referred to as the “Internet” 1228. Local network 1222 and Internet 1228 both use electrical, electromagnetic, or optical signals that carry digital data streams. The signals through the various networks and the signals on network link 1220 and through communication interface 1218, which carry the digital data to and from computer system 1200, are exemplary forms of carrier waves transporting the information.

[0096] Computer system 1200 can send messages and receive data, including program code, through the network(s), network link 1220, and communication interface 1218. In the Internet example, a server 1230 might transmit a requested code for an application program through Internet 1228, ISP 1226, local network 1222 and communication interface 1218. One such downloaded application may provide all or part of a method described herein, for example. The received code may be executed by processor 1204 as it is received, and / or stored in storage device 1210, or other nonvolatile storage for later execution. In this manner, computer system 1200 may obtain application code in the form of a carrier wave.

[0097] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses:1. A clamping system, comprising: a base configured to removably hold an object; and a sensor coupled to the base, the sensor comprising integrated optical components configured to sense interaction between an electromagnetic field of the sensor and the object, the sensor configured to generate an output conveying information related to a gap distance between the object and the base based on the interaction.2. The system of clause 1 , wherein the base comprises one or more electrodes configured to provide electrostatic force configured to removably hold the object.3. The system of any of the previous clauses, wherein the integrated optical components are configured such that changes in the electromagnetic field caused by gap distance changes between the object and the base cause changes in radiation in the sensor, the changes in radiation in the sensor resulting in changes in the output indicative of the gap distance changes.4. The system of any of the previous clauses, wherein the integrated optical components comprise one or more waveguides, resonators, mirrors, splitters, and / or interferometers.5. The system of any of the previous clauses, wherein the sensor is an integrated optics near-field sensor.6. The system of any of the previous clauses, wherein the integrated optics near-field sensor comprises a micro ring resonator, a Mach-Zehnder interferometer, or a coupled micro-ring resonator system.7. The system of any of the previous clauses, wherein a size of; a shape of; an orientation of; a separation from; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; and / or a quality factor impacted by a shape, sidewall roughness, and / or material of; one or more of the integrated optical components is configured to be adjusted to change a range and / or sensitivity of the sensor.8. The system of any of the previous clauses, further comprising a plurality of additional sensors coupled to the base, with the plurality of additional sensors configured to generate a plurality of additional outputs conveying information related to gap distances between the object and the base at a plurality of locations across the base.9. The system of any of the previous clauses, wherein the gap distances between the object and the base indicate deformation of the object.10. The system of any of the previous clauses, wherein the gap distances between the object and the base at the plurality of locations across the base indicate a shape of the object.11. The system of any of the previous clauses, wherein the base comprises a clamp, the sensor is coupled to the clamp, and the clamp is configured to releasably clamp the object with the sensor coupled to the clamp.12. The system of any of the previous clauses, wherein the base further comprises a chuck coupled to the clamp, the chuck configured to hold the clamp, the sensor, and the object, and facilitate movement of the clamp, the sensor, and the object.13. The system of any of the previous clauses, further comprising burls extending from the clamp and configured to contact the object, wherein the sensor is coupled to the clamp between the burls such that the burls contact the object but the sensor does not.14. The system of any of the previous clauses, wherein a thickness of the sensor is 10 microns or less, and a width of the sensor is 2 mm or less, smaller than a separation between the burls and thinner than a thickness of the burls.15. The system of any of the previous clauses, further comprising a radiation source configured to generate radiation configured to pass through the sensor.16. The system of any of the previous clauses, wherein the radiation source is a laser.17. The system of any of the previous clauses, wherein a wavelength of the radiation from the radiation source is configured to be tuned according to a resonant frequency of the sensor.18. The system of any of the previous clauses, further comprising an input edge coupler configured to edge couple radiation from the radiation source to the sensor.19. The system of any of the previous clauses, further comprising a radiation detector configured to receive the output from the sensor and generate an electrical signal useable for determining the gap distance.20. The system of any of the previous clauses, wherein the radiation detector comprises a photodetector.21. The system of any of the previous clauses, further comprising an output edge coupler configured to edge couple the output from the sensor to the radiation detector.22. The system of any of the previous clauses, wherein the object comprises a reticle or a wafer, and the clamping system is part of a lithography apparatus used in semiconductor manufacturing.23. A clamping method, comprising: removably holding an object with a base; and generating, with a sensor coupled to the base, an output conveying information related to a gap distance between the object and the base, the sensor comprising integrated optical components configured to sense interaction between an electromagnetic field of the sensor and the object, the sensor configured to generate the output based on the interaction.24. The method of clause 23, wherein the base comprises one or more electrodes configured to provide electrostatic force configured to removably hold the object.25. The method of any of the previous clauses, wherein the integrated optical components are configured such that changes in the electromagnetic field caused by gap distance changes between the object and the base cause changes in radiation in the sensor, the changes in radiation in the sensor resulting in changes in the output indicative of the gap distance changes.26. The method of any of the previous clauses, wherein the integrated optical components comprise one or more waveguides, resonators, mirrors, splitters, and / or interferometers.27. The method of any of the previous clauses, wherein the sensor is an integrated optics near-field sensor.28. The method of any of the previous clauses, wherein the integrated optics near-field sensor comprises a micro ring resonator, a Mach-Zehnder interferometer, or a coupled micro-ring resonator system.29. The method of any of the previous clauses, further comprising adjusting a size of; a shape of; an orientation of; a separation from; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; and / or a quality factor impacted by a shape, sidewall roughness, and / or material of; one or more of the integrated optical components to change a range and / or sensitivity of the sensor.30. The method of any of the previous clauses, further comprising generating, with a plurality of additional sensors coupled to the base, a plurality of additional outputs conveying information related to gap distances between the object and the base at a plurality of locations across the base.31. The method of any of the previous clauses, wherein the gap distances between the object and the base indicate deformation of the object.32. The method of any of the previous clauses, wherein the gap distances between the object and the base at the plurality of locations across the base indicate a shape of the object.33. The method of any of the previous clauses, wherein the base comprises a clamp, the sensor is coupled to the clamp, and the clamp is configured to releasably clamp the object with the sensor coupled to the clamp.34. The method of any of the previous clauses, wherein the base further comprises a chuck coupled to the clamp, the chuck configured to hold the clamp, the sensor, and the object, and facilitate movement of the clamp, the sensor, and the object.35. The method of any of the previous clauses, further comprising burls extending from the clamp and configured to contact the object, wherein the sensor is coupled to the clamp between the burls such that the burls contact the object but the sensor does not.36. The method of any of the previous clauses, wherein a thickness of the sensor is 10 microns or less, and a width of the sensor is 2 mm or less, smaller than a separation between the burls and thinner than a thickness of the burls.37. The method of any of the previous clauses, further comprising generating, with a radiation source, radiation configured to pass through the sensor.38. The method of any of the previous clauses, wherein the radiation source is a laser.39. The method of any of the previous clauses, wherein a wavelength of the radiation from the radiation source is configured to be tuned according to a resonant frequency of the sensor.40. The method of any of the previous clauses, further comprising edge coupling, with an input edge coupler, radiation from the radiation source to the sensor.41. The method of any of the previous clauses, further comprising receiving, with a radiation detector, the output from the sensor, and generating an electrical signal useable for determining the gap distance.42. The method of any of the previous clauses, wherein the radiation detector comprises a photodetector.43. The method of any of the previous clauses, further comprising edge coupling, with an output edge coupler, the output from the sensor to the radiation detector.44. The method of any of the previous clauses, wherein the object comprises a reticle or a wafer, and the base and sensor are part of a clamping system is part of a lithography apparatus used in semiconductor manufacturing.

[0098] The concepts disclosed herein may be associated with any generic imaging system for imaging sub wavelength features, and may be especially useful with emerging imaging technologies capable of producing increasingly shorter wavelengths. Emerging technologies already in use include EUV (extreme ultra violet) lithography, deep ultra violet (DUV) lithography that is capable of producing a 193nm wavelength with the use of an ArF laser, and even a 157nm wavelength with the use of a Fluorine laser. Moreover, EUV lithography is capable of producing wavelengths within a range of 20-5nm by using a synchrotron or by hitting a material (either solid or a plasma) with high energy electrons in order to produce photons within this range.

[0099] While the concepts disclosed herein may be used for wafer manufacturing on a substrate such as a silicon wafer, it shall be understood that the disclosed concepts may be used with any type of manufacturing system, e.g., those used for manufacturing on substrates other than silicon wafers. In addition, the combination and sub-combinations of disclosed elements may comprise separate embodiments. For example, a reticle clamp alone, the membrane, and / or the associated lithography apparatus may comprise separate embodiments, and / or these features may be used together in the same embodiment.

[0100] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. A clamping system, comprising: a base configured to removably hold an object; and a sensor coupled to the base, the sensor comprising integrated optical components configured to sense interaction between an electromagnetic field of the sensor and the object, the sensor configured to generate an output conveying information related to a gap distance between the object and the base based on the interaction.

2. The system of claim 1, wherein: the base comprises one or more electrodes configured to provide electrostatic force configured to removably hold the object; the integrated optical components are configured such that changes in the electromagnetic field caused by gap distance changes between the object and the base cause changes in radiation in the sensor, the changes in radiation in the sensor resulting in changes in the output indicative of the gap distance changes; the integrated optical components comprise one or more waveguides, resonators, mirrors, splitters, and / or interferometers; the sensor is an integrated optics near-field sensor; and the integrated optics near-field sensor comprises a micro ring resonator, a Mach-Zehnder interferometer, or a coupled micro-ring resonator system.

3. The system of claim 1, wherein a size of; a shape of; an orientation of; a separation from; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; and / or a quality factor impacted by a shape, sidewall roughness, and / or material of; one or more of the integrated optical components is configured to be adjusted to change a range and / or sensitivity of the sensor.

4. The system of claim 1 , further comprising a plurality of additional sensors coupled to the base, with the plurality of additional sensors configured to generate a plurality of additional outputs conveying information related to gap distances between the object and the base at a plurality of locations across the base, wherein: the gap distances between the object and the base indicate deformation of the object.; and the gap distances between the object and the base at the plurality of locations across the base indicate a shape of the object.

5. The system of claim 1, wherein:the base comprises a clamp, the sensor is coupled to the clamp, and the clamp is configured to releasably clamp the object with the sensor coupled to the clamp; the base further comprises a chuck coupled to the clamp, the chuck configured to hold the clamp, the sensor, and the object, and facilitate movement of the clamp, the sensor, and the object; the system further comprises burls extending from the clamp and configured to contact the object, wherein the sensor is coupled to the clamp between the burls such that the burls contact the object but the sensor does not; and a thickness of the sensor is 10 microns or less, and a width of the sensor is 2 mm or less, smaller than a separation between the burls and thinner than a thickness of the burls.

6. The system of claim 1 , further comprising a radiation source configured to generate radiation configured to pass through the sensor, wherein: the radiation source is a laser; and a wavelength of the radiation from the radiation source is configured to be tuned according to a resonant frequency of the sensor;7. The system of claim 1, further comprising: an input edge coupler configured to edge couple radiation from the radiation source to the sensor; a radiation detector configured to receive the output from the sensor and generate an electrical signal useable for determining the gap distance, wherein the radiation detector comprises a photodetector; and an output edge coupler configured to edge couple the output from the sensor to the radiation detector.

8. The system of claim 1, wherein the object comprises a reticle or a wafer, and the clamping system is part of a lithography apparatus used in semiconductor manufacturing.

9. A clamping method, comprising: removably holding an object with a base; and generating, with a sensor coupled to the base, an output conveying information related to a gap distance between the object and the base, the sensor comprising integrated optical components configured to sense interaction between an electromagnetic field of the sensor and the object, the sensor configured to generate the output based on the interaction.

10. The method of claim 9, wherein:the base comprises one or more electrodes configured to provide electrostatic force configured to removably hold the object; the integrated optical components are configured such that changes in the electromagnetic field caused by gap distance changes between the object and the base cause changes in radiation in the sensor, the changes in radiation in the sensor resulting in changes in the output indicative of the gap distance changes. the integrated optical components comprise one or more waveguides, resonators, mirrors, splitters, and / or interferometers; the sensor is an integrated optics near-field sensor; and the integrated optics near-field sensor comprises a micro ring resonator, a Mach-Zehnder interferometer, or a coupled micro-ring resonator system.

11. The method of claim 9, further comprising: adjusting a size of; a shape of; an orientation of; a separation from; a material of; a coating on; an ambient temperature around; an ambient pressure around; a wavelength of radiation in; and / or a quality factor impacted by a shape, sidewall roughness, and / or material of; one or more of the integrated optical components to change a range and / or sensitivity of the sensor; comprising generating, with a plurality of additional sensors coupled to the base, a plurality of additional outputs conveying information related to gap distances between the object and the base at a plurality of locations across the base, wherein: the gap distances between the object and the base indicate deformation of the object; and the gap distances between the object and the base at the plurality of locations across the base indicate a shape of the object.

12. The method of claim 9, wherein: the base comprises a clamp, the sensor is coupled to the clamp, and the clamp is configured to releasably clamp the object with the sensor coupled to the clamp; the base further comprises a chuck coupled to the clamp, the chuck configured to hold the clamp, the sensor, and the object, and facilitate movement of the clamp, the sensor, and the object; burls extend from the clamp and are configured to contact the object, wherein the sensor is coupled to the clamp between the burls such that the burls contact the object but the sensor does not; and a thickness of the sensor is 10 microns or less, and a width of the sensor is 2 mm or less, smaller than a separation between the burls and thinner than a thickness of the burls.

13. The method of claim 9, further comprising:generating, with a radiation source, radiation configured to pass through the sensor, wherein the radiation source is a laser and a wavelength of the radiation from the radiation source is configured to be tuned according to a resonant frequency of the sensor; and edge coupling, with an input edge coupler, radiation from the radiation source to the sensor;14. The method of claim 9, further comprising: receiving, with a radiation detector, the output from the sensor, and generating an electrical signal useable for determining the gap distance, wherein the radiation detector comprises a photodetector; and edge coupling, with an output edge coupler, the output from the sensor to the radiation detector.

15. The method of claim 9, wherein the object comprises a reticle or a wafer, and the base and sensor are part of a clamping system is part of a lithography apparatus used in semiconductor manufacturing.

Images