Substrate alignment system

Abstract

A substrate alignment system, comprising: a fixed support; a plurality of detectors; a plurality of detector holders, each of the detector holders configured to hold an associated one of the detectors; a plurality of intermediate supports, each intermediate support operatively disposed between an associated one of the detector holders and the fixed support; a plurality of flexures, the fixed support and each intermediate support having at least one of the flexures therebetween, and each intermediate support and the associated one of the detector holders having at least one of the flexures therebetween; and a plurality of actuators, each of the actuators configured to effect relative positioning between the detectors by moving an associated one of the intermediate supports or the associated one of the detector holders, the relative positioning causing flexing of at least one of the flexures.

Description

SUBSTRATE ALIGNMENT SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 650,228 which was filed on May 21, 2024 and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] The description herein relates generally to a substrate alignment system.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. In these lithography apparatuses, a patterning device is held by a patterning device chuck with an optically contacted clamp.

[0004] In photolithography, measurement of the substrate is frequently performed to ensure the proper alignment of the pattern layer. There are many pattern layers that are exposed on top of one another in a particular target portion. These many pattern layers interact with each other to create a working chip. A substrate alignment system is used to confirm that the pattern is transferred to the substrate with the desired accuracy. The substrate alignment system detects the alignment of the pattern to confirm that the pattern layer is aligned to the previous pattern layer. Further, the substrate alignment system confirms that the resolution or sharpness of the pattern layer meets the required threshold. A substrate alignment system includes a detector that measures the substrate marks on the substrate from the pattern layer. Several prior art substrate alignment systems utilize only a single detector. Once measurement is complete for a particular substrate mark, the detector is moved to the next substrate mark for further measurement. A way to measure more alignment marks in a giventime-interval is to use several alignment detectors in parallel. Heretofore, existing parallel alignment detectors have had various problems requiring improvement. Further, clamping parallel alignment detectors to a fixed interface results in undesired settling effects and positioning errors on the submicrometer level.SUMMARY

[0005] Among other things, the present application utilizes a combination of supports, flexures and actuators to adjust the pitch between the detectors in an accurate way while diminishing settling effects and positioning errors. As a result, the substrate alignment system having multiple detectors is compatible for different substrate mark pitch widths. Consequently, different applications having different spacing between substrate marks can all use the same substrate alignment system.

[0006] According to an embodiment, there is provided a substrate alignment system. The substrate alignment system comprises a fixed support; a plurality of detectors; a plurality of detector holders, each of the detector holders configured to hold an associated one of the detectors; a plurality of intermediate supports, each intermediate support operatively disposed between an associated one of the detector holders and the fixed support; a plurality of flexures, the fixed support and each intermediate support having at least one of the flexures therebetween, and each intermediate support and the associated one of the detector holders having at least one of the flexures therebetween; and a plurality of actuators, each of the actuators configured to effect relative positioning between the detectors by moving an associated one of the intermediate supports or the associated one of the detector holders, the relative positioning causing flexing of at least one of the flexures.

[0007] In some embodiments, at least a pair of flexures is disposed between each intermediate support and the associated detector holder.

[0008] In some embodiments, a pair of flexures is disposed between each intermediate support and the fixed support.

[0009] In some embodiments, the alignment system is configured to measure alignment marks on a substrate, and wherein the actuators effect movement of the associated intermediate support in a direction at an angle dcp with the x-direction and / or the associated detector holder in an x-direction generally parallel to the substrate.

[0010] In some embodiments, the flexures are elongated members that extend longitudinally in a z- direction generally perpendicular to the substrate, and wherein each of the flexures are flat members that extend generally in a plane.

[0011] In some embodiments, the planes of the flexures between the detector holders and the intermediate supports are angled with respect to the planes of the flexures between the intermediate supports and the fixed support.

[0012] In some embodiments, each of the flexures provides more flexibility in a direction perpendicular to the plane in which it lies in comparison with being relatively stiff in a directionwithin the plane in which it lies.

[0013] In some embodiments, the plurality of detectors are generally aligned along an x-axis, with a pitch between them in the x-direction, and wherein the flexures are more flexible in the x-direction in comparison with a y-direction, which is perpendicular to the x-direction and the z-direction, wherein actuation of the actuators is configured to adjust the pitch between the detectors.

[0014] In some embodiments, the planes of the flexures between the intermediate supports and the fixed support are slightly rotated with respect to a z-axis such that the planes of the flexures are not exactly perpendicular to the x-direction and the planes of the flexures between the intermediate supports and the detector holder are slightly rotated with respect to the z-axis such that the planes of the flexures are not exactly perpendicular to the x-direction, such that the actuation of the actuators to move the detectors in the x-direction causes fine adjustment of the detectors in the y-direction.

[0015] In some embodiments, movement of the intermediate support is expressed as XI, movement of the detector holder is expressed as X2, and wherein when movement of XI = *X2, the movement of the detector holder will be linear in the x-direction.

[0016] In some embodiments, when movement of XI = *X2+5, the detector holder will alsomove in the y-direction based on the value of 5.

[0017] In some embodiments, dcp is the angle that the plane of the flexure between the fixed support and intermediate support forms with respect to the y-direction, such that movement XI of the intermediate support in the x-direction causes a relatively smaller movement Y1 of the intermediate support in the y-direction, as follows: Y1 = tan(7 / p) XI .

[0018] In some embodiments, the substrate alignment system is configured to measure alignment marks on a substrate, and wherein the actuators effect movement of the associated intermediate support at a small angle cp with the x-direction and / or the associated detector holder in the x-direction, generally parallel to the substrate.

[0019] In some embodiments, the flexures are elongated members that extend longitudinally in a direction at an angle with the z-direction and wherein each of the flexures are flat members that extend generally in a plane.

[0020] In some embodiments, the planes of the flexures between the detector holders and the intermediate supports are angled with respect to the planes of the flexures between the intermediate supports and the fixed support.

[0021] In some embodiments, each of the flexures provides more flexibility in a direction perpendicular to the plane in which it lies in comparison with being relatively stiff in a direction within the plane in which it lies.

[0022] In some embodiments, wherein the plurality of detectors are generally aligned along the x- axis, with a pitch between them in the x-direction, and wherein the flexures are more flexible in the x- direction in comparison with the y-direction, which is perpendicular to the x-direction and z-direction,wherein actuation of the actuators is configured to adjust the pitch between the detectors.

[0023] In some embodiments, the planes of the flexures between the intermediate supports and the fixed support are slightly rotated with respect to a y-axis such that the planes of the flexures are not exactly perpendicular to the x-direction and the planes of the flexures between the intermediate supports and the detector holder are slightly rotated with respect to the y-axis such that the planes of the flexures are not exactly perpendicular to the x-direction, such that the actuation of the actuators to move the detectors in the x-direction causes fine adjustment of the detectors in the z-direction.

[0024] In some embodiments, movement of the intermediate support is expressed as XI, movement of the detector holder is expressed as X2, and wherein when movement of XI = *X2, the movement of the detector holder will be linear in the x-direction.

[0025] In some embodiments, wherein with the flexures rotated over a small angle cp, by movement of corrections in the z-direction may be made for the plurality of detectors whenapplying a non-zero X1value.

[0026] In some embodiments, the fixed support comprises a single fixed frame.

[0027] In some embodiments, the fixed support comprises a plurality of fixed frames.

[0028] In some embodiments, the actuators comprise a solenoid, a piezoelectric actuator, a servo motor, a stepper motor, an electric motor, a pneumatic motor, a hydraulic motor, a linear actuator, or any combination thereof with or without an additional transmission.

[0029] In some embodiments, the flexures are wire electrical discharge machined metal members.

[0030] In some embodiments, the flexures are made from a flexible material.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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 will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:FIG. 1A is a schematic illustration of a reflective lithographic apparatus, according to an embodiment of the present disclosure.FIG. IB is a schematic illustration of a transmissive lithographic apparatus, according to an embodiment of the present disclosure.FIG. 1C is a more detailed schematic illustration of the reflective lithographic apparatus, according to an embodiment of the present disclosure.FIG. 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment.FIG. 3 is a block diagram of an example computer system, according to an embodiment.FIG. 4 is a schematic illustration of detector positioning in a substrate alignment system, according to an embodiment of the present disclosure.FIG. 5 is a schematic illustration of a substrate alignment system having a plurality of detectors, according to an embodiment of the present disclosure.FIG. 6 is a schematic illustration of one detector in a substrate alignment system, according to an embodiment of the present disclosure.FIG. 7 is a schematic illustration of one detector in a substrate alignment system along cross-section A-A of FIG. 5, according to an embodiment of the present disclosure.FIG. 8 is a schematic illustration of one detector in a substrate alignment system, according to another embodiment of the present disclosure.DETAILED DESCRIPTION

[0032] Although specific reference may be made in this text to the manufacture of integrated circuits (ICs), 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.”

[0033] 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, whence the individual devices can be mounted on a carrier, connected to pins, etc.

[0034] 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.

[0035] Lithography is a step in the manufacturing of devices 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.

[0036] As semiconductor manufacturing processes continue to advance, the dimensions of functional elements have continually been reduced while the number of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as “Moore’s law”. At the current state of technology, layers of devices are manufactured using lithographic projection apparatuses that project a design layout onto a substrate using illumination from a deep-ultraviolet illumination source or an extreme -ultraviolet source, creating individual functional elements having dimensions well below 100 nm, i.e. less than half the wavelength of the radiation from the illumination source (e.g., a 193 nm illumination source).

[0037] This process in which features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus are printed, is commonly known as low-kl lithography, according to the resolution formula CD = klxk / NA, where I is the wavelength of radiation employed (currently in most cases 248nm or 193nm), NA is the numerical aperture of projection optics in the lithographic projection apparatus, CD is the “critical dimension’ -generally the smallest feature size printed-and kl is an empirical resolution factor. In general, the smaller kl the more difficult it becomes to reproduce a pattern on the substrate that resembles the shape and dimensions planned by a designer in order to achieve particular electrical, optical or other functionality and performance. To overcome these difficulties, sophisticated fine-tuning steps are applied to the lithographic projection apparatus, the design layout, or the patterning device. These include, for example, but not limited to, optimization of NA and optical coherence settings, customized illumination schemes, use of phase shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as “optical and process correction”) in the design layout, overlay measurement, or other methods generally defined as “resolution enhancement techniques” (RET).

[0038] The term “projection optics” as used herein should be broadly interpreted as encompassing various types of optical systems, including refractive optics, reflective optics, apertures and catadioptric optics, for example. The term “projection optics” may also include components operatingaccording to any of these design types for directing, shaping, or controlling the projection beam of radiation, collectively or singularly. The term “projection optics” may include any optical component in the lithographic projection apparatus, no matter where the optical component is located on an optical path of the lithographic projection apparatus. Projection optics may include optical components for shaping, adjusting and / or projecting radiation from the source before the radiation passes the patterning device, and / or optical components for shaping, adjusting and / or projecting the radiation after the radiation passes the patterning device. The projection optics generally exclude the source and the patterning device.

[0039] FIGS. 1A and IB are schematic illustrations of a lithographic apparatus 100 and lithographic apparatus 100’, in or for which embodiments of the present disclosure may be implemented. Lithographic apparatus 100 and lithographic apparatus 100’ each include the following: an illumination system (illuminator) IL configured to condition a radiation beam B (for example, ultraviolet (UV), deep ultraviolet (DUV) or extreme ultraviolet (EUV) radiation); a support structure (for example, a mask table) MT configured to support a patterning device (for example, a mask, a reticle, or a dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA; and, a substrate table (for example, a wafer table) WT (e.g., WTa, WTb or both) configured to hold a substrate (for example, a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithographic apparatus 100 and 100’ also have a projection system PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion (for example, comprising one or more dies) C of the substrate W. In lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In lithographic apparatus 100’, the patterning device MA and the projection system PS are transmissive.

[0040] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B.

[0041] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA, the design of at least one of the lithographic apparatus 100 and 100’, and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT can be a frame or a table, for example, which can be fixed or movable, as required. By using sensors, the support structure MT can ensure that the patterning device MA is at a desired position, for example, with respect to the projection system PS.

[0042] The term “patterning device” MA should be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in the target portion C of the substrate W. The pattern imparted to the radiation beam B cancorrespond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0043] The patterning device MA may be transmissive (as in lithographic apparatus 100’ of FIG. IB) or reflective (as in lithographic apparatus 100 of FIG. 1 A). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, and programmable LCD panels. 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 so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B which is reflected by a matrix of small mirrors.

[0044] The term “projection system” PS can encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors, such as the use of an immersion liquid on the substrate W or the use of a vacuum. A vacuum environment can be used for EUV or electron beam radiation since other gases can absorb too much radiation or electrons. A vacuum environment can therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0045] Lithographic apparatus 100 and / or lithographic apparatus 100’ can be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such “multiple stage” machines, the additional substrate tables WT can be used in parallel, or preparatory steps can be carried out on one or more tables while one or more other substrate tables WT are being used for exposure. In some situations, the additional table may not be a substrate table WT. For example, alignment measurements using an alignment sensor AS and / or level (height, tilt, etc.) measurements using a level sensor LS may be made (in FIG. IB).

[0046] Referring to FIGS. 1 A and IB, the illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 100, 100’ can be separate physical entities, for example, when the source SO is an excimer laser. In such cases, the source SO is not considered to form part of the lithographic apparatus 100 or 100’, and the radiation beam B passes from the source SO to the illuminator IL with the aid of a beam delivery system BD (in FIG. IB) including, for example, suitable directing mirrors and / or a beam expander. In other cases, the source SO can be an integral part of the lithographic apparatus 100, 100’ — for example when the source SO is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD, if required, can be referred to as a radiation system.

[0047] 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 theintensity 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.

[0048] The illuminator IL can include an adjuster AD (in FIG. IB) for adjusting the angular intensity distribution of the radiation 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 the illuminator can be adjusted. In addition, the illuminator IL can comprise various other components (in FIG. IB), such as an integrator IN and a condenser CN. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0049] Referring to FIG. 1A, the radiation beam B is incident on the patterning device (for example, mask) MA, which is held on the support structure (for example, mask table) MT, and is patterned by the patterning device MA. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (for example, mask) MA. After being reflected from the patterning device (for example, mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF2 (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor IF1 (for example, an interferometric device, linear encoder, or capacitive sensor) can be used to accurately position the patterning device (for example, mask) MA with respect to the path of the radiation beam B. Patterning device (for example, mask) MA and substrate W can be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2.

[0050] Referring to FIG. IB, the radiation beam B is incident on the patterning device (for example, mask MA), which is held on the support structure (for example, mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system PS is supported on a reference frame RF.

[0051] 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.

[0052] With the aid of the second positioner PW and position sensor IF2 (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). The position sensor IF2 measures the substrate table WT in three dimensions. In this example, the position sensor IF2 is an interferometric device. The z-direction interferometers are positioned tothe side of the substrate table WT. The interferometric mirrors have 45-degree angled surfaces attached to the left and the right side of the substrate table WT. The interferometric lasers are mounted such that the laser light is incident upon the interferometric mirrors. FIG. IB shows the relationship between the interferometric lasers and the mirrors of the position sensor IF2. Similarly, the first positioner PM and another position sensor IF1 (shown in FIG. 1A) can be used to accurately position the mask MA with respect to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during a scan). The position sensor IF1 measures the mask table MT in three dimensions. In this example, the position sensor IF1 is an interferometric device. The z- direction interferometers are positioned to the side of the mask table MT. The interferometric mirrors have 45-degree angled surfaces attached to the left and the right side of the mask table MT. The interferometric lasers are mounted such that the laser light is incident upon the interferometric mirrors.

[0053] In general, movement of the mask table MT can 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 can 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 mask table MT can be connected to a short-stroke actuator only or can be fixed. Mask MA and substrate W can be aligned using mask alignment marks Ml, M2, and substrate alignment marks Pl, P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they can be located in spaces between target portions (known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

[0054] The lithographic apparatus 100 and 100’ can be used in at least one of the following modes:

[0055] 1. In step mode, the support structure (for example, mask table) MT and the substrate tableWT are kept essentially stationary, while an entire pattern imparted to the radiation beam B 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.

[0056] 2. In scan mode, the support structure (for example, mask table) MT and the substrate tableWT are scanned synchronously while a pattern imparted to the radiation beam B 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 (for example, mask table) MT can be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0057] 3. In another mode, the support structure (for example, mask table) MT is kept substantially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO can be 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 ascan. This mode of operation can be readily applied to maskless lithography that utilizes a programmable patterning device, such as a programmable mirror array.

[0058] Combinations and / or variations on the described modes of use or entirely different modes of use can also be employed.

[0059] In some embodiments, lithographic apparatus 100 includes an extreme ultraviolet (EUV) source, which is configured to generate a beam of EUV radiation for EUV lithography. In general, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0060] FIG. 1C shows the lithographic apparatus 100 in more detail, including the source collector apparatus SO, the illumination system IL, and the projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 120 of the source collector apparatus SO. An EUV radiation emitting plasma 110 may be formed by a discharge produced plasma source. EUV radiation may be produced by a gas or vapor, for example Xe gas, Li vapor or Sn vapor in which the hot plasma 110 is created to emit radiation in the EUV range of the electromagnetic spectrum. The hot plasma 110 is created by, for example, an electrical discharge causing an at least partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor or any other suitable gas or vapor may be required for efficient generation of the radiation. In an embodiment, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0061] The radiation emitted by the hot plasma 110 is passed from a source chamber 111 into a collector chamber 112 via an optional gas barrier or contaminant trap 113 (in some cases also referred to as contaminant barrier or foil trap) which is positioned in or behind an opening in source chamber 111. The contaminant trap 113 may include a channel structure. Contamination trap 113 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap 113 further indicated herein at least includes a channel structure, as known in the art.

[0062] The collector chamber 112 may include a radiation collector CO which may be a so-called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 151 and a downstream radiation collector side 152. Radiation that traverses collector CO can be reflected off a grating spectral filter 140 to be focused at a virtual source point IFP. The virtual source point IFP is commonly referred to as the intermediate focus, and the source collector apparatus is arranged such that the intermediate focus IFP is located at or near an opening 119 in the enclosing structure 120. The virtual source point IFP is an image of the radiation emitting plasma 110. Grating spectral filter 140 is used in particular for suppressing infra-red (IR) radiation.

[0063] Subsequently the radiation traverses the illumination system IL, which may include a facetted field mirror device 122 and a facetted pupil mirror device 124 arranged to provide a desired angular distribution of the radiation beam 121, at the patterning device MA, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the radiation beam121 at the patterning device MA, held by the support structure MT, a patterned beam 126 is formed and the patterned beam 126 is imaged by the projection system PS via reflective elements 128, 130 onto a substrate W held by the wafer stage or substrate table WT.

[0064] More elements than shown may generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 140 may optionally be present, depending upon the type of lithographic apparatus. Further, there may be more mirrors present than those shown in the FIGS., for example there may be 1-6 additional reflective elements present in the projection system PS than shown in FIG. 1C.

[0065] Collector optic CO, as illustrated in FIG. 1C, is depicted as a nested collector with grazing incidence reflectors 153, 154 and 155, just as an example of a collector (or collector mirror). The grazing incidence reflectors 153, 154 and 155 are disposed axially symmetric around an optical axis O and a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[0066] As shown in FIG. 2, the lithographic apparatus 100 or 100’ (indicated as “LA” in Fig. 2) may form part of a lithographic cell LC, also sometimes referred to as 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.

[0067] In order 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 material property, 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 (FIGS. 1A-1C) 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 100 or 100’.

[0068] 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.

[0069] There are various techniques for making measurements of the structures formed in the patterning process, including the use of a scanning electron microscope, an image-based measurement tool and / or various specialized tools. As discussed above, a fast and non-invasive form of specialized metrology tool is one in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered (diffracted / reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. This may be termed diffraction-based metrology. One such application of this diffraction-based metrology is in the measurement of feature asymmetry within a target. This can be used as a measure of overlay, for example, but other applications are also known. For example, asymmetry can be measured by comparing opposite parts of the diffraction spectrum (for example, comparing the -1stand +lstorders in the diffraction spectrum of a periodic grating). Another application of diffraction-based metrology is in the measurement of feature width (CD) within a target.

[0070] 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)).

[0071] 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 targetportions of a substrate are faulty, further exposures may be performed only on those target portions which meet specifications.

[0072] 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.

[0073] 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).

[0074] In an embodiment, the target on a substrate may comprise one or more 1-D periodic structures (e.g., gratings), which are printed such that after development, the periodic structural features are formed of solid resist lines. In an embodiment, the target may comprise one or more 2-D periodic structures (e.g., gratings), which are printed such that after development, the one or more periodic structures are formed of solid resist pillars or vias in the resist. The bars, pillars, or vias may alternatively be etched into the substrate (e.g., into one or more layers on the substrate).

[0075] In an embodiment, one of the parameters of interest of a patterning process is overlay. Overlay can be measured using dark field scatterometry in which the zeroth order of diffraction (corresponding to a specular reflection) is blocked, and only higher orders processed. Diffractionbased overlay using dark-field detection of the diffraction orders enables overlay measurements on smaller targets. These targets can be smaller than the illumination spot and may be surrounded by device product structures on a substrate. In an embodiment, multiple targets can be measured in one radiation capture.

[0076] As lithography nodes keep shrinking, more and more complicated wafer designs may be implemented. Various tools and / or techniques may be used by designers to ensure complex designs are accurately transferred to physical wafers. These tools and techniques may include mask optimization, source mask optimization (SMO), OPC, design for control, and / or other tools and / or techniques. For example, a source mask optimization process is described in United States Patent No. 9,588,438 titled “Optimization Flows of Source, Mask and Projection Optics”, which is incorporated in its entirety by reference.

[0077] 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.

[0078] FIG. 3 is a block diagram that illustrates a computer system CS that can assist in implementing the methods, flows, or the system(s) disclosed herein. Computer system CS may beincluded in and / or electronically coupled to the lithography apparatus 100 or 100’ described above (FIGS. 1A-1C). Computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO1 (or multiple processors PRO1, PRO2, etc.) coupled with bus BS for processing information. Computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to bus BS for storing information and instructions to be executed by processor PRO1. Main memory MM also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor PRO1. Computer system CS further includes a read only memory ROM or other static storage device coupled to bus BS for storing static information and instructions for processor PRO1. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to bus BS for storing information and instructions.

[0079] Computer system CS may be coupled via bus BS to a display DS, such as a cathode ray tube (CRT) or flat panel or touch panel display for displaying information to a computer user. An input device ID, including alphanumeric and other keys, is coupled to bus BS for communicating information and command selections to processor PROl. Another type of user input device is cursor control CC, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor ROM and for controlling cursor movement on display DS. 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.

[0080] According to one embodiment, portions of one or more flows and / or methods described herein may be performed by computer system CS in response to processor PROl executing one or more sequences of one or more instructions contained in main memory MM. Such instructions may be read into main memory MM from another computer-readable medium, such as storage device SD. Execution of the sequences of instructions contained in main memory MM causes processor PROl to perform the flows and / or process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory MM. 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.

[0081] The term “computer-readable medium” or “machine readable medium” as used herein refers to any medium that participates in providing instructions to processor PROl 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 SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus BS. Transmission media can also take the form of acoustic or light waves, such as thosegenerated 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.

[0082] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor PRO1 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 such as the internet. A modem local to computer system CS can receive the data and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus BS can receive the data carried in the infrared signal and place the data on bus BS. Bus BS carries the data to main memory MM, from which processor PRO1 retrieves and executes the instructions. The instructions received by main memory MM may optionally be stored on storage device SD either before or after execution by processor PRO1.

[0083] Computer system CS may also include a communication interface CI coupled to bus BS. Communication interface CI provides a two-way data communication coupling to a network link NL that is connected to a local network LAN. For example, communication interface CI 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 CI 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 CI sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

[0084] Network link NL typically provides data communication through one or more networks to other data devices. For example, network link NL may provide a connection through local network LAN to a host computer HC or to data equipment operated by an Internet Service Provider ISP. Internet Service Provider ISP in turn provides data communication services through the worldwide packet data communication network, now commonly referred to as the “Internet” INT. Local network LAN and Internet INT both use electrical, electromagnetic, or optical signals that carry digital data streams. The signals through the various networks and the signals on network link NL and through communication interface CI, which carry the digital data to and from computer system CS, are exemplary forms of carrier waves transporting the information.

[0085] Computer system CS can send messages and receive data, including program code, through the network(s), network link NL, and communication interface CL In the Internet example, a server SV might transmit a requested code for an application program through Internet INT, Internet ServiceProvider ISP, local network LAN and communication interface CL One such downloaded application may provide all or part of a method described herein, for example. The received code may be executed by processor PRO1 as it is received, and / or stored in storage device SD, or other nonvolatile storage for later execution. In this manner, computer system CS may obtain application code in the form of a carrier wave.

[0086] As opposed to a single alignment sensor, such as the alignment sensor AS in FIG. IB, a plurality of generally aligned detectors (i.e., generally along a straight line) can be used to simultaneously measure multiple alignment marks. The plurality of detectors provide for generally parallel alignment measurement beams and allows for the simultaneous measurement of multiple alignment marks, which significantly speeds up the alignment process in comparison with a single detector. Alternatively, many more alignment points can be measured when a plurality of detectors are used. For example, if 100 points are measured using a single alignment sensor, then 700 points can be measured when using 7 sensors. However, one of the challenges of using a plurality of detectors is that all the individual detectors need to be accurately positioned with respect to the field pitch on a substrate.

[0087] FIG. 4 is a schematic illustration of detector positioning in a substrate alignment system, according to an embodiment of the present disclosure. As illustrated, radiation beams (e.g., infrared or visible light, for example) 105A, 105B, 105C, 105D, and 105E emanate from the plurality of detectors. The first detector produces the radiation beam 105A, the second detector adjacent to the first detector produces the radiation beam 105B, and so on. The plus signs in the radiation beams 105A, 105B, . . . , 105E signify the center of the beams. In order to achieve accurate measurement, the displacements between the detectors must be within certain limits. For example, in one embodiment, the displacement (positions) of the detectors in the x-direction, expressed as AX, can be accurately positioned within ±100nm of one another. The displacement in the y-direction, or AY, can be accurately positioned within ±100nm of one another. In other words, in the y-direction, the detectors should be positioned within ±100nm from a center line CL. Both x- and y-accuracy are intended to place all the detectors exactly above alignment marks in adjacent fields,

[0088] FIG. 5 is a schematic illustration of a substrate alignment system 10 having a plurality of detectors 4A, 4B, 4C, according to an embodiment of the present disclosure. The embodiment of the substrate alignment system 10 is for a xy-adjustment mechanism. The number of detectors corresponds to the number of substrate marks that can be measured at one time. For example, for 7 parallel detectors, 7 substrate marks can be simultaneously measured. For simplicity, in the embodiment illustrated in FIG. 5, three detectors are shown and described as a non-limiting example In one embodiment, the plurality of detectors are configured and positioned to have the same pitch as the substrate marks being measured, and the distance between the substrate alignment detectors can be varied accordingly. By applying flexures and actuators as described below, the spacing between the detectors can be changed. As a result, the substrate alignment system having multiple detectors iscompatible for measuring different alignments marks, having different mark pitch widths. Consequently, different applications requiring different spacing between substrate marks can all use the same substrate alignment system.

[0089] In one embodiment, the detectors 4A, 4B, 4C are held (e.g., clamped, adhered by an adhesive, or otherwise secured) by detector holders 2A, 2B, 2C, respectively. The detector holders 2A, 2B, 2C are coupled to intermediate supports 1A, IB, 1C, respectively. Specifically, detector holder 2A is coupled to intermediate support 1A using a pair of spaced flexures E2A and E3A, detector holder 2B is coupled to intermediate support IB by a pair of spaced flexures E2B and E3B, and detector holder 2C is coupled to intermediate support 1C by a pair of spaced flexures and E2C and E3C. As illustrated, in one embodiment, the intermediate supports are disposed above the detector holders. Each of the intermediate supports 1A, IB, 1C are coupled to a fixed support 3. Specifically, intermediate support 1A is coupled to the fixed support 3 by a pair of spaced flexures El A and E4A, intermediate support IB is coupled to the fixed support 3 by a pair of spaced flexures E1B and E4B, and intermediate support 1C is coupled to fixed support by a pair of spaced flexures E1C and E4C. As shown, each of the flexures, when at rest (without stress being applied thereto) extends generally parallel to the other flexures in the z-direction (toward and away from the substrate). The flexures E1A-E4C are elongated members that extend longitudinally in the z-direction.

[0090] The fixed support 3 can be a frame or other structure that remains stationary and can function as a reference point or a plurality of reference points from which the positions of the detectors 4A, 4B, and 4C (or their holders) can be measured.

[0091] Beams of radiation 5 A, 5B, 5C are emitted from the detectors 4A, 4B, 4C, respectively, downward in a z-direction toward the substrate marks on the substrate W. The radiation is diffracted or reflected by the alignment marks on the substrate W, and reflected light that has been diffracted by the alignment marks is recaptured by the sensors (e.g., the scatterometers) of detectors 4A, 4B, 4C, respectively. As a result, the captured beams of light are measured by the detectors 4A, 4B, 4C to determine the locations and characteristics of the substrate mark. Though not shown in FIG. 5, each of the detectors 4A, 4B, 4C can be moved in the x-direction by an associated detector holder actuator 12A (shown in FIG. 6). Similarly, each of the intermediate supports 1A, IB, 1C can be moved in the x-direction by an associated intermediate support actuator 11A (shown in FIG. 6). Therefore, the detectors 4A, 4B, 4C can be moved relative to one another in the x-direction.

[0092] In one embodiment, the detector holders, flexures, and intermediate supports are all formed from the same material (such as a metal material, for example steel or aluminum). In one embodiment, these structures are shaped / formed by using a wire EDM process. In another embodiment, one or more of these components can be formed separately from the other components and then attached to one another by known attachment methods.

[0093] In one embodiment, the substrate alignment system 10 may be positioned away from the lithographic apparatus 100, 100’ at a separate location. In another embodiment, the substratealignment system 10 may be positioned within the lithographic apparatus 100, 100’. In this case, the substrate alignment system 10 may be positioned next to the projection system PS in lithographic apparatus 100, 100’ in FIGS. 1A-1C. In one embodiment, the substrate alignment system 10 may be positioned at and replace the alignment sensor AS of FIG. IB. The substrate alignment system 10 performs substrate alignment by measuring substrate marks. For example, the detectors 4A, 4B, 4C are capable of measuring substrate alignment marks Pl, P2 on the substrate W, shown in FIGS. 1A and IB. Although only two substrate alignment marks Pl, P2 are shown on the substrate W, more alignment marks can be provided and measured simultaneously using the multiple detectors described here. For example, as non-limiting embodiments, there can be anywhere between 3 to 15 or more detectors suitable for measuring the substrate alignment marks on the substrate W. In one example embodiment, the substrate alignment system 10A has seven parallel detectors generally aligned in the x-direction to cover half the width of a particular substrate W.

[0094] The plurality of detectors 4A, 4B, 4C are generally aligned along an x-axis with a pitch PAB, PBC between them in the x-direction, as seen in FIG. 5. As mentioned previously, each of the detectors 4A, 4B and 4C may be moved by associated actuators (described in more detail as item 12A in conjunction with FIG. 6). This is accomplished by the actuators moving the detector holders 2A, 2B and / or 2C, with each detector holder having one or more individual actuators associated therewith. In addition, the movement of the detectors 4A, 4B, and 4C is further facilitated by a plurality of actuators (described more in detail as item 11 A in FIG. 6) that move the intermediate supports 1 A, IB, and / or 1C. As a result, the pitch between the detectors can be adjusted as desired. Specifically, the actuators can be used to move the detector 4A relative to the detector 4B and / or 4C. Similarly, the detector 4B can be moved relative to detectors 4 A and / or 4C, and detector 4C may be moved by the associated actuators to position the detector 4C relative to the detectors 4A and / or 4B. As a result, each of the detectors 4A, 4B, 4C can be positioned in the x-direction relative to the other detectors. Therefore, the pitch between the detectors 4A, 4B, 4C may be adjusted to accommodate differing pitch widths of the alignment marks on various substrates W.

[0095] In one non-limiting example, the pitches PAB and PBC may each be between 10-100 mm. In one embodiment, the pitches PAB and PBC range from 22-26 mm. In one embodiment, the pitch PAB may be of a different width than the pitch PBC, and in another embodiment the pitch widths can be the same. If the substrate mark pitch width is variable, then the width of the pitches PAB and PBC can be different to adapt to the substrate mark pitch widths.

[0096] FIG. 6 is a schematic illustration of one detector 4A in the substrate alignment system 10, according to an embodiment of the present disclosure. The detector 4A will be described in detail below. It should be appreciated that the descriptions of the detector 4A will also apply to the other detectors 4B, 4C, etc.

[0097] A detector holder actuator 12A contacts one side of the detector holder 2 A and moves the detector holder 2A by a displacement X2 in the x-direction that is generally parallel to the substrateW. Similarly, an intermediate support actuator 11 A contacts the intermediate support 1 A and moves the intermediate support 1 A by a movement amount XI in the x-direction. These actuators 11 A and 12A operate together to control the position and any potential angle of the radiation 5 A being emitted from the detector 4A.

[0098] The actuators 11 A, 12A are shown in FIG. 6 to be attached to the intermediate support 1 A and the detector holder 2A, respectively. However, the actuators 11 A, 12A may be integrated into the body of the intermediate support 1A and the detector holder 2A, respectively. The actuators 11 A, 12A may comprise a solenoid, a piezoelectric actuator, a servo moto, a stepper motor, an electric motor, a pneumatic motor, a hydraulic motor, a linear actuator, a piezostepper, or any combination thereof with or without an additional transmission. In addition, more than one actuator may be provided to control the movement and position of the detector holder 2A, and more than one actuator may be provided to control the movement and position of the intermediate support 1 A to provide even more control of positioning.

[0099] In one embodiment, the detector 4A and the detector holder 2A are connected such that there is no relative movement and no degrees of freedom between the two elements. As a result, the detector holder actuator 12A moves together both the detector holder 2A and the detector 4A. In one embodiment, one flexure E2A is positioned on one side (in the -x-direction) of the detector 4A, while another flexure E3A is positioned on the other side (in the +x-direction) of the detector 4A. Similarly, one flexure El A is positioned on one side (in the -x-direction) of the detector 4A, while another flexure E4A is positioned on the other side (in the +x-direction) of the detector 4A. However, the embodiment is not limited to this. Both flexures E2A and E3A between the detector holder 2A and the intermediate support 1A may be on the same side of the detector 4A. Both flexures E2A and E3A may be on the -x-direction side of the detector 4A, or alternatively, both flexures E2A and E3A may be on the +x-direction side of the detector 4A. Both flexures El A and E4A between the intermediate support 1A and the fixed support 3 A may similarly be on the same side of the detector 4A as well. Further, though a pair of flexures E2A and E3A are disclosed for coupling between the detector holder 2A and the intermediate support 1A and a pair of flexures El A and E4A are disclosed for coupling between the intermediate support 1A and the fixed support 3, the invention is not limited to this. There may just be one flexure for coupling between the two components. As a result, it is possible to have just one flexure, such as E2A, positioned between the intermediate support and the detector holder 2A. It is also possible to have just one flexure, such as El A, positioned between the intermediate support 1A and the fixed support 3. On the other hand, it is also possible to have three or more flexures between the detector holder 2A and the intermediate support 1A or between the intermediate support 1A and the fixed support 3.

[0100] As mentioned previously, the detector holder 2A is coupled to the intermediate support 1 A by a pair of spaced flexures E2A and E3A. In other words, the flexures E2A and E3A are positioned between the detector holder 2A and the intermediate support 1A. In a similar manner, theintermediate support 1A is coupled to the fixed support 3 by flexures E1A and E4A. In other words, the flexures El A and E4A are positioned between the intermediate support 1 A and the fixed support 3.

[0101] As mentioned previously, the fixed support 3 comprises a fixed reference. The fixed support 3 may comprise a single fixed frame or a plurality of fixed frames. FIG. 6 shows a plurality of fixed supports 3, which may be connected to the same fixed frame or a plurality of fixed frames.

[0102] The flexures E1A-E4A will be described next. The flexures E1A-E4A are elongated and generally parallel to one another in the z-direction while at rest (not stressed). In one embodiment these flexures are identical elastic elements. The flexures E1A-E4A are shaped as flat elongate sheets or straps that may be made of a metal or other material and may be shaped by electrical discharge machined (EDM) wire as one option. The flexures can be made from various metals, such as titanium, steel, and / or aluminum or another material and are stiff in the plane in which they lie. In one embodiment, the flexures El A-E4A are formed by electrical discharge machined wire techniques (as a non-limiting example).

[0103] In one embodiment, the flexures E1A-E4A may be of uniform thickness along its length. In another embodiment, each flexure may be thicker in the middle at thinner than at the top and bottom where it meets the intermediate support 1A and the detector holder 2A, respectively. Making the flexures thinner in certain locations functions to concentrate the areas of flexure more in the thinner areas in comparison to the thicker areas. Thus, having flexures that are thinner at the ends will tend to keep the central portions more straight in comparison with the more flexible end portions, In one embodiment, the thickness of the flexures E1A-E4A may range between 0.2-1.5mm.

[0104] As shown in FIG. 7, each of the flexures are shown in cross section, illustrating the planes in which they lie, which are angled with respect to the X direction and the Y direction. Otherwise stated, the flexures are slightly rotated about the z-axis. Given its flat configuration, the flexures are relatively stiff in the plane in which they lie, and exhibits maximum flexibility in a direction perpendicular to that plane. As a result of the manner in which their planes are angled relative to the x and y directions, each of the flexures E1A-E4A provides more flexibility in the x-direction than the y- direction, as will be appreciated more fully from descriptions below. As will also be appreciated from below, while the actuators operate to exert movement to the detector holder 2A and the intermediate support 1A in the x-direction to control pitch between the detectors, the angle of the flexure plane enables the actuators to also control a position of the detector in the y-direction (although movement will be a lot less in the y-direction).

[0105] FIG. 7 illustrates that in one embodiment, the planes of the flexures E2A and E3A between the detector holder 2 A and the intermediate support 1A are parallel to one another and are angled with respect to the planes of the flexures El A and E4A between the intermediate support 1A and the fixed support 3. The planes of flexures El A and E4A are parallel to one another as well, as can also be appreciated from FIG. 7. In one embodiment, when no external forces are acting on the system, theflexures E1A and E4A have a slight rotation Rz = dcp as shown in FIG. 7, and the flexures E2A and E3A are preferably but not necessarily made with a slight rotation of the same magnitude in the opposite direction Rz = -dcp, also shown in FIG. 7. The angle dcp is the angle that the plane of the flexures E1A and E4A forms with respect to the y-direction as shown in FIG. 7. Similarly, the angle - dcp is the angle that the plane of the flexures E2A and E3A forms with respect to the y-direction. The flexures El A and E4A are rotated by magnitude dcp in a positive direction, while the flexures E2A and E3A are rotated by the same magnitude dcp but in a negative direction. For example, the angle dcp may be in the range of 1- lOOmrad. In a non-limiting embodiment, the angle dcp may be between 20 to 40 mrad, and in one embodiment, it is approximately 30mrad (e.g., approximately 1.7°).

[0106] As the flexures E1A and E4A are not perpendicular to the x-axis, a movement XI in the x- direction of the intermediate support 1 also yields a small movement Y1 in the y-direction, as seen in the vector diagram in FIG. 7. The displacement vectors show that for a displacement XI in the x- direction, a resulting displacement Y1 in the y-direction is created due to the angle dcp. A yi trigonometric equation can be used to solve for Y1 : tan dcp = — . As a result, Y1 = yi tan(d<p) * XI. Small-angle approximation can simplify the equation to a linear formula: dcp = — .As a result, Y1 is determined to be Y1 = dcp* A.

[0107] As the flexures E2A and E3A have a small built-in rotation Rz = -dcp, the detector holder 2A will also move in the y-direction during actuation in the x-direction of the actuators 11 A and 12A. Assuming the detector holder 2A makes twice the x-stroke compared to the intermediate support 1A (meaning the detector holder actuator 12A moves the detector holder 2 A twice the distance in the x- direction compared to the intermediate support actuator 11A moving the intermediate support 1A), the following equation can be applied: X2 = 2*X1 (or XI = *X2). For example, a displacement of XI= 3mm would result in a displacement of X2 = 6mm. A displacement Y2 in the y-direction of the detector holder 2 during actuation can be determined by the following:Y2 = Y movement of intermediate support 1+ Y relative movement with respect to intermediate support 1 = Yl - dcp * (X2 - XI)= dcp * XI - dcp * (2 * XI - XI)= 0

[0108] As a result, when X2 = 2*X1, then Y2 = 0. In other words, when the detector holder actuator 12A displaces the detector holder 2A at exactly twice the distance in the x-direction as compared to the intermediate support actuator 11A displacing the intermediate support 1A, the detector holder 2A does not move in the y-direction, and the detector holder 2A moves in a straight line along the x-direction. Consequently, the detector 4A will have a linear movement in the x-direction.If, however, the detector holder actuator 12A does not move at exactly double the x-distance compared to the intermediate support actuator 11 A, then the detector holder 2A will also move slightly in the y-direction. Using a displacement constant of the intermediate support actuator 11 A as 5, the following equation can be applied: XI = X2 + 8. For example, 8 can be in the range of0.01-0.2mm. In an embodiment, the constant 8 is equal to 0.1mm. Substituting into Y2 yields:

[0109] Simplifying the equation yields Y2 = 2*8*d(p. Tilting the flexures E1A-E4A with Rz = +d( / ) and Rz = -dcp creates an x-y manipulator. By adjusting the two degrees of freedom X2 and 8 in XI = X2 + 8 results in the equations X2 = X2 and Y2 = 2*8*d<p. It is noted that this is the linearized formula for small d<p. Moving the intermediate support 1A in the x-direction therefore causes fine adjustment of the detector holder 2A in the y-direction.

[0110] Further, the substrate alignment system is not limited to the embodiment described above. Other configurations are also possible. For example, the substrate alignment system could also be used rotated 90° about the x-axis. The substrate alignment system could also be rotated in other various amount about the axes.

[0111] In some cases, only the x-position and the z-position of the detectors needs sub-micron accuracy. The y-positioning of the detectors is then not so critical and therefore does not need adjustment. FIG. 8 is a schematic illustration of one detector 4Z in a substrate alignment system 10Z, according to another embodiment of the present disclosure. The embodiment for the substrate alignment system 10Z is for an xz-adjustment mechanism. This embodiment adjusts the x- and z- positions of the detector 4Z. A plurality of detectors 4Z may be positioned in an array in the substrate alignment system 10Z, similar to that shown in FIG. 5. Using such an array allows for adjusting the individual detectors 4Z with respect to each other at sub-micrometer precision in both the x-direction and the z-direction.

[0112] As the initial z-accuracy of the detector 4Z directly after assembly is on the order of ±5 um, a fine adjustment in the z-direction is needed after assembly. The height of the detector 4Z may be manipulated on a sub-micrometer level by making X1= A small variation X1createsa 1Z movement on the sub-micrometer level that is needed to reach the required z-accuracy for the detector 4Z.

[0113] In the case where <p = 0, the flexures are in the z-direction. As a result, the fine adjustment 4Z yields, with f> being a constant depending on the shape of flexures E1Z-E4Z and L0 being the distance between an intermediate support 1Z and a detector holder 2Z:For X2= 0, the solution yields AZ = 0 regardless of X2.

[0114] This means, however, that for X2= 0, the initial manufacturing tolerances of AZ being on the order of ±5 um cannot be corrected for to reach 100 nm accuracy.

[0115] As shown in FIG. 8, by rotating the flexures E1Z-E4Z a small angle <p. a z-adjustment may be made possible for X = 0. The AZ adjustment is shown as — Z for the intermediate support 1Z and — Z2for the detector holder 2Z, both of which are in the -z-direction. FIG. 8 shows that, in the initial stress-free situation, the flexures E1Z and E4Z are slightly rotated over an angle +<p. On the other hand, the flexures E2Z and E3Z are slightly rotated over an angle — <p.

[0116] When the detector 4Z now moves over — q < X < q, where q is a displacement of the detector 4Z in the x-direction, z-corrections may be made over the whole stroke by applying a value AX10 in the formula X1= X2+ AX as long as tan (<p) As a result, the small angle <pallows for z-adjustment for both X2#= 0 as well as X2= 0.

[0117] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses:1. A substrate alignment system, comprising: a fixed support; a plurality of detectors; a plurality of detector holders, each of the detector holders configured to hold an associated one of the detectors; a plurality of intermediate supports, each intermediate support operatively disposed between an associated one of the detector holders and the fixed support; a plurality of flexures, the fixed support and each intermediate support having at least one of the flexures therebetween, and each intermediate support and the associated one of the detector holders having at least one of the flexures therebetween; and a plurality of actuators, each of the actuators configured to effect relative positioning between the detectors by moving an associated one of the intermediate supports or the associated one of the detector holders, the relative positioning causing flexing of at least one of the flexures.2. The substrate alignment system of any of the previous clauses, wherein at least a pair of flexures is disposed between each intermediate support and the associated detector holder.3. The substrate alignment system of any of the previous clauses, wherein a pair of flexures is disposed between each intermediate support and the fixed support.4. The substrate alignment system of any of the previous clauses, wherein the alignment system is configured to measure alignment marks on a substrate, and wherein the actuators effect movement of the associated intermediate support in a direction at an angle dcp with the x-direction and / or the associated detector holder in an x-direction generally parallel to the substrate.5. The substrate alignment system of any of the previous clauses, wherein the flexures are elongated members that extend longitudinally in a z-direction generally perpendicular to the substrate, and wherein each of the flexures are flat members that extend generally in a plane.6. The substrate alignment system of any of the previous clauses, wherein the planes of the flexures between the detector holders and the intermediate supports are angled with respect to the planes of the flexures between the intermediate supports and the fixed support.7. The substrate alignment system of any of the previous clauses, wherein each of the flexures provides more flexibility in a direction perpendicular to the plane in which it lies in comparison with being relatively stiff in a direction within the plane in which it lies.8. The substrate alignment system of any of the previous clauses, wherein the plurality of detectors are generally aligned along an x-axis, with a pitch between them in the x-direction, and wherein the flexures are more flexible in the x-direction in comparison with a y-direction, which is perpendicular to the x-direction and the z-direction, wherein actuation of the actuators is configured to adjust the pitch between the detectors.9. The substrate alignment system of any of the previous clauses, wherein the planes of the flexures between the intermediate supports and the fixed support are slightly rotated with respect to a z-axis such that the planes of the flexures are not exactly perpendicular to the x-direction and the planes of the flexures between the intermediate supports and the detector holder are slightly rotated with respect to the z-axis such that the planes of the flexures are not exactly perpendicular to the x-direction, such that the actuation of the actuators to move the detectors in the x-direction causes fine adjustment of the detectors in the y-direction.10. The substrate alignment system of any of the previous clauses, wherein movement of the intermediate support is expressed as XI, movement of the detector holder is expressed as X2, and wherein when movement of XI = - 2 *X2, the movement of the detector holder will be linear in the x- direction.11. The substrate alignment system of any of the previous clauses, wherein when movement of XI =- *X2+5, the detector holder will also move in the y-direction based on the value of 5.12. The substrate alignment system of any of the previous clauses, wherein dcp is the angle that the plane of the flexure between the fixed support and intermediate support forms with respect to the y- direction, such that movement XI of the intermediate support in the x-direction causes a relatively smaller movement Y1 of the intermediate support in the y-direction, as follows: Y1 = tan(7 / p) XI .13. The substrate alignment system of any of the previous clauses, wherein the substrate alignment system is configured to measure alignment marks on a substrate, and wherein the actuators effect movement of the associated intermediate support at a small angle cp with the x-direction and / or the associated detector holder in the x-direction, generally parallel to the substrate.14. The substrate alignment system of any of the previous clauses, wherein the flexures are elongated members that extend longitudinally in a direction at an angle with the z-direction and wherein each of the flexures are flat members that extend generally in a plane.15. The substrate alignment system of any of the previous clauses, wherein the planes of the flexures between the detector holders and the intermediate supports are angled with respect to the planes of the flexures between the intermediate supports and the fixed support.16. The substrate alignment system of any of the previous clauses, wherein each of the flexures provides more flexibility in a direction perpendicular to the plane in which it lies in comparison with being relatively stiff in a direction within the plane in which it lies.17. The substrate alignment system of any of the previous clauses, wherein the plurality of detectors are generally aligned along the x-axis, with a pitch between them in the x-direction, and wherein the flexures are more flexible in the x-direction in comparison with the y-direction, which is perpendicular to the x-direction and z-direction, wherein actuation of the actuators is configured to adjust the pitch between the detectors.18. The substrate alignment system of any of the previous clauses, wherein the planes of the flexures between the intermediate supports and the fixed support are slightly rotated with respect to a y-axis such that the planes of the flexures are not exactly perpendicular to the x-direction and the planes of the flexures between the intermediate supports and the detector holder are slightly rotated with respect to the y-axis such that the planes of the flexures are not exactly perpendicular to the x-direction, such that the actuation of the actuators to move the detectors in the x-direction causes fine adjustment of the detectors in the z-direction.19. The substrate alignment system of any of the previous clauses, wherein movement of the intermediate support is expressed as XI, movement of the detector holder is expressed as X2, and wherein when movement of XI = - 2 *X2, the movement of the detector holder will be linear in the x- direction.20. The substrate alignment system of any of the previous clauses, wherein with the flexures rotated over a small angle cp, by movement of corrections in the z-direction may be madefor the plurality of detectors when applying a non-zero X1value.21. The substrate alignment system of any of the previous clauses, wherein the fixed support comprises a single fixed frame.22. The substrate alignment system of any of the previous clauses, wherein the fixed support comprises a plurality of fixed frames.23. The substrate alignment system of any of the previous clauses, wherein the actuators comprise a solenoid, a piezoelectric actuator, a servo motor, a stepper motor, an electric motor, a pneumatic motor, a hydraulic motor, a linear actuator, or any combination thereof with or without an additional transmission.24. The substrate alignment system of any of the previous clauses, wherein the flexures are wire electrical discharge machined metal members.25. The substrate alignment system of any of the previous clauses, wherein the flexures are made from a flexible material.

[0118] The concepts disclosed herein may be associated with any generic imaging system for imaging sub wavelength or 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), 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 a high power laser in order to produce photons within this range.

[0119] 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, the cleaning system and / or method, and the associated lithography apparatus may comprise separate embodiments, and / or these features may be used together in the same embodiment.

[0120] 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 substrate alignment system comprising: a fixed support; a plurality of detectors; a plurality of detector holders, each of the detector holders configured to hold an associated one of the detectors; a plurality of intermediate supports, each intermediate support operatively disposed between an associated one of the detector holders and the fixed support; a plurality of flexures, the fixed support and each intermediate support having at least one of the flexures therebetween, and each intermediate support and the associated one of the detector holders having at least one of the flexures therebetween; and a plurality of actuators, each of the actuators configured to effect relative positioning between the detectors by moving an associated one of the intermediate supports or the associated one of the detector holders, the relative positioning causing flexing of at least one of the flexures.

2. The substrate alignment system of claim 1 , wherein at least a pair of flexures is disposed between each intermediate support and the associated detector holder.

3. The substrate alignment system of any of the preceding claims, wherein a pair of flexures is disposed between each intermediate support and the fixed support.

4. The substrate alignment system of any of the preceding claims, wherein the alignment system is configured to measure alignment marks on a substrate, and wherein the actuators effect movement of the associated intermediate support in a direction at an angle dcp with the x-direction and / or the associated detector holder in an x-direction generally parallel to the substrate.

5. The substrate alignment system of claim 4, wherein the flexures are elongated members that extend longitudinally in a z-direction generally perpendicular to the substrate, and wherein each of the flexures are flat members that extend generally in a plane.

6. The substrate alignment system of claim 5, wherein the planes of the flexures between the detector holders and the intermediate supports are angled with respect to the planes of the flexures between the intermediate supports and the fixed support.

7. The substrate alignment system of claim 6, wherein each of the flexures provides more flexibility in a direction perpendicular to the plane in which it lies in comparison with being relatively stiff in a direction within the plane in which it lies.

8. The substrate alignment system of claim 7, wherein the plurality of detectors are generally aligned along an x-axis, with a pitch between them in the x-direction, and wherein the flexures are more flexible in the x-direction in comparison with a y-direction, which is perpendicular to the x- direction and the z-direction, wherein actuation of the actuators is configured to adjust the pitch between the detectors.

9. The substrate alignment system of claim 8, wherein the planes of the flexures between the intermediate supports and the fixed support are slightly rotated with respect to a z-axis such that the planes of the flexures are not exactly perpendicular to the x-direction and the planes of the flexures between the intermediate supports and the detector holder are slightly rotated with respect to the z- axis such that the planes of the flexures are not exactly perpendicular to the x-direction, such that the actuation of the actuators to move the detectors in the x-direction causes fine adjustment of the detectors in the y-direction.

10. The substrate alignment system of claim 9, wherein movement of the intermediate support is expressed as XI, movement of the detector holder is expressed as X2, and wherein when movement of XI = - 2 *X2, the movement of the detector holder will be linear in the x-direction.

11. The substrate alignment system of claim 10, wherein when movement of XI = *X2+5, thedetector holder will also move in the y-direction based on the value of 5.

12. The substrate alignment system of claim 10, wherein dcp is the angle that the plane of the flexure between the fixed support and intermediate support forms with respect to the y-direction, such that movement XI of the intermediate support in the x-direction causes a relatively smaller movement Y1 of the intermediate support in the y-direction, as follows: Y1 = tan(c >)*Xl .

13. The substrate alignment system of claim 1, wherein the substrate alignment system is configured to measure alignment marks on a substrate, and wherein the actuators effect movement of the associated intermediate support at a small angle cp with the x-direction and / or the associated detector holder in the x-direction, generally parallel to the substrate14. The substrate alignment system of claim 13, wherein the flexures are elongated members that extend longitudinally in a direction at an angle with the z-direction and wherein each of the flexures are flat members that extend generally in a plane.

15. The substrate alignment system of claim 14, wherein the planes of the flexures between the detector holders and the intermediate supports are angled with respect to the planes of the flexures between the intermediate supports and the fixed support.

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