Air gauge measurement system

Abstract

An air gauge includes at least one nozzle arranged to expel gas into a gap between the nozzle and a surface and also includes at least one tap for communicating a pressure in the gap to a pressure sensor, wherein the nozzle and the gap are displaced from one another to mitigate the effects of turbulence from the nozzle on the magnitude of the pressure communicated by the tap.

Description

AIR GAUGE MEASUREMENT SYSTEMCROSS-REFERENCE TO RELATED APPLICATION

[0001] The Application claims priority of US provisional application number 63 / 707,444 which was filed on 15 October, 2024, which is incorporated herein its entirety by reference.FIELD

[0002] The present disclosure relates to measurement devices, for example, devices for measuring variations in the heights (levelness) of a substrate surface in lithographic apparatuses and systems.BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0004] The height variation or levelness of the surface of the substrate is measured preliminary to projecting a pattern onto a layer of radiation sensitive material provided on the surface. The substrate height measurements are used to create a substrate height map which assists accurate projection of a pattern onto the substrate.

[0005] One device which can be used in obtaining height measurements is a level sensor based on a type of pressure measurement device referred to as an air gauge. Use of an air gauge has many potential benefits. An air gauge, for example, is capable of very high resolution. Also, in the context of lithographic apparatuses, an air gauge has no sensitivity to layers below the surface being measured. An air gauge can sense only the top surface of resist on a substrate, which is a superior reference surface for focus control in wafer lithography.

[0006] To increase the throughput, however, it will be necessary to reduce the amount of time the level sensor needs to measure the levelness of the wafer. One approach may be to implement an array of level sensors arranged to measure the height of multiple spots on the wafer simultaneously. Implementing an array of level sensors, however, is hindered by the fact that conventional level sensors are for the most part bulky, expensive, and difficult to miniaturize.

[0007] These challenges can be addressed to some extent by using multi-wafer microelectromechanical systems (MEMS) technology which makes it possible to miniaturize the individual air gauges and reduce their cost. MEMS technology can help to fabricate a large number of air gauges for parallel level sensing. There is still a challenge, however, in miniaturizing the pressuresensor while maintaining its accuracy. Also, to the extent the individual pressure gauges incorporate electronic devices, bonding of wafers can damage the electronic wiring which complicates the process of fabricating these devices and increases their cost.

[0008] Accordingly, it is desirable to improve the fabrication and operation of level sensors.SUMMARY

[0009] The following presents a summary of one or more embodiments in order to facilitate a basic understanding of the disclosed subject matter. This summary is not an extensive overview of all contemplated embodiments and is not intended to identify any elements as being key or critical nor set limits on the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments as a prelude to the more detailed description that is presented later.

[0010] According to an aspect of an embodiment there is disclosed an air gauge for measuring a levelness of a test surface, the air gauge comprising a nozzle body, a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap, a first gas inlet in fluid communication with the reference gap, a second gas inlet in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface, and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap. The differential pressure sensor is in fluid communication with the first gas inlet only indirectly through the reference gap and a reference pressure tap and in fluid communication with the second gas inlet only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlet or the second gas inlet.

[0011] The first gas inlet may be configured as a first channel through the nozzle body and the second gas inlet may be configured as a second channel through the nozzle body. The air gauge may further comprise a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.

[0012] The nozzle body may be comprised of a plurality of bonded wafers. The nozzle body may be constructed by selective laser etching of glass. The nozzle body may be constructed by 3D printing a polymer material.

[0013] The nozzle body may have a generally cylindrical configuration having a longitudinal axis. The nozzle body may have a cavity on the longitudinal axis, and the reference pressure tap may extend from the cavity to the reference gap along a first segment of the longitudinal axis, and the measurement pressure tap may extend from the cavity to the measurement gap along a second segment of the longitudinal axis.

[0014] The differential pressure sensor may be positioned within the cavity. The differential pressure sensor may be positioned outside of the cavity and arranged in fluid communication with an interior of the cavity through at least one channel.

[0015] The nozzle body may have a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, and the reference pressure tap may extend from the first cavity to the reference gap along a first segment of the longitudinal axis, and the measurement pressure tap may extend from the second cavity to the measurement gap along a second segment of the longitudinal axis.

[0016] The differential pressure sensor may be positioned outside of the nozzle body and in fluid communication with the first cavity and the second cavity. The first gas inlet may communicate with the reference gap through a first annular chamber coaxial with the longitudinal axis and the second gas inlet may communicate with the measurement gap through a second annular chamber coaxial with the longitudinal axis and axially displaced from the first annular chamber.

[0017] According to another aspect of an embodiment there is disclosed an air gauge for measuring a levelness of a test surface, the air gauge comprising a nozzle body, a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap, a plurality of first gas inlets in fluid communication with the reference gap, a plurality of second gas inlets in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface, and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap. The differential pressure sensor is in fluid communication with the plurality of first gas inlets only indirectly through the reference gap and a reference pressure tap and in fluid communication with the plurality of second gas inlets only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlets or the second gas inlets.

[0018] The plurality of first gas inlets may be configured as a plurality of first channels through the nozzle body and the plurality of second gas inlets may be configured as a plurality of second channels through the nozzle body.

[0019] The air gauge may further comprise a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.

[0020] The nozzle body may be comprised of a plurality of bonded wafers.

[0021] The nozzle body may have a generally cylindrical configuration having a longitudinal axis.The first gas inlets may be positioned symmetrically around the nozzle body at a first position along the longitudinal axis. The second gas inlets may be positioned symmetrically around the nozzle body at a second position along the longitudinal axis axially displaced from the first position.

[0022] The nozzle body may a cavity on the longitudinal axis, and the reference pressure tap may extend from the cavity to the reference gap along a first segment of the longitudinal axis, and the measurement pressure tap may extend from the cavity to the measurement gap along a second segment of the longitudinal axis.

[0023] The differential pressure sensor may be positioned within the cavity. The nozzle body may have a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, and the reference pressure tap may extend from the first cavity to the reference gap along a first segment of the longitudinal axis, and the measurement pressure tap may extend from the second cavity to the measurement gap along a second segment of the longitudinal axis.

[0024] The differential pressure sensor may be positioned outside of the nozzle body and in fluid communication with the first cavity and the second cavity.

[0025] The first gas inlets may communicate with the reference gap through a first annular chamber coaxial with the longitudinal axis and the second gas inlets may communicate with the measurement gap thorough a second annular chamber coaxial with the longitudinal axis and axially displaced from the first annular chamber.

[0026] According to another aspect of an embodiment there is disclosed a levelness measurement system for measuring a levelness of a test surface, the levelness measurement system comprising an array of air gauges, each of the air gauges comprising a nozzle body, a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap, a first gas inlet in fluid communication with the reference gap, a second gas inlet in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface, and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap. The differential pressure sensor may be in fluid communication with the first gas inlet only indirectly through the reference gap and a reference pressure tap and in fluid communication with the second gas inlet only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlet or the second gas inlet.

[0027] Each first gas inlet may be configured as a first channel through the nozzle body and the second gas inlet may be configured as a second channel through the nozzle body.

[0028] Each of the air gauges further may comprise a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.

[0029] The array of air gauges is comprised of a plurality of bonded wafers.

[0030] The array may be comprised of a periodic arrangement of the plurality of air gauges. The nozzle body for each air gauge may have a generally cylindrical configuration having a longitudinal axis. The nozzle body for each air gauge may have a cavity on the longitudinal axis, and the reference pressure tap may extend from the cavity to the reference gap along a first segment of the longitudinal axis, and the measurement pressure tap may extend from the cavity to the measurement gap along a second segment of the longitudinal axis.

[0031] The differential pressure sensor for each air gauge may be positioned within the cavity.

[0032] The nozzle body for each air gauge may have a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, and the reference pressuretap may extend from the first cavity to the reference gap along a first segment of the longitudinal axis, and the measurement pressure tap may extend from the second cavity to the measurement gap along a second segment of the longitudinal axis.

[0033] The differential pressure sensor for each air gauge may be positioned outside of the nozzle body and be in fluid communication with the first cavity and the second cavity.

[0034] The first gas inlet for each air gauge may communicate with the reference gap through a first annular chamber coaxial with the longitudinal axis and the second gas inlet may communicate with the measurement gap through a second annular chamber coaxial with the longitudinal axis and axially displaced from the first annular chamber.

[0035] According to another aspect of an embodiment there is disclosed a semiconductor measurement apparatus comprising at least three bonded wafers together comprising an annular gas inlet, the annular gas inlet being arranged around the circumference of a central pressure tap wherein the central pressure tap further comprises a reference pressure tap, a differential pressure sensor, and a measure pressure tap, and the annular gas inlet being further configured to supply gas to an annular nozzle, the annular nozzle being further configured to supply gas to a fixed reference area and to supply gas to a substrate to be measured.

[0036] The at least three bonded wafers further comprise an annular shroud through which gas from the reference area and gas from the substrate to be measured exit.

[0037] Further embodiments, features, and advantages of the subject matter of the present disclosure, as well as the structure and operation of the various embodiments are described in detail below with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the relevant art(s) to make and use embodiments described herein. The drawings are not to scale unless otherwise indicated or clear from context.

[0039] FIG. 1A is a schematic diagram of a lithographic apparatus, according to some aspects.

[0040] FIG. IB is a schematic diagram of a lithographic apparatus, according to some aspects.

[0041] FIG. 2 is a schematic diagram of a lithographic apparatus, according to some aspects.

[0042] FIG. 3 is a schematic diagram of a lithographic cell, according to some aspects.

[0043] FIG. 4 is a schematic diagram of a gas gauge measurement device, according to some aspects.

[0044] FIGS. 5A, 5B, and 5C, and 5D show arrangements of measurement device arrays, according to some aspects.

[0045] FIG. 6 is a partially schematic diagram of an air gauge according to some aspects.

[0046] FIG. 7A is a top view of an air gauge according to some aspects.

[0047] FIG. 7B is a cross-sectional side view of an air gauge according to some aspects.

[0048] FIG. 8 is a perspective view of a nozzle body for an air gauge according to some aspects.

[0049] FIG. 9 is a perspective view of a nozzle body for an air gauge according to some aspects.

[0050] FIGS. 10A-10C are perspective views of internal components of a nozzle body according to some aspects.

[0051] The features of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements.DETAILED DESCRIPTION

[0052] This specification discloses one or more embodiments that incorporate the features of the present disclosure. The disclosed embodiment(s) are provided as examples. The scope of the present disclosure is not limited to the disclosed embodiment(s). Claimed features are defined by the claims appended hereto.

[0053] The embodiment(s) described, and references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but not every embodiment may necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0054] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, can be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0055] The term “about” as used herein indicates the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the term “about” can indicate a value of a given quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0056] Embodiments of the disclosure can be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine -readable medium, which can be read and executed by one or more processors. Amachine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine -readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, and / or instructions can be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

[0057] Before describing such embodiments in more detail, however, it is instructive to present an example environment in which embodiments of the present disclosure can be implemented.

[0058] FIGS. 1A and IB are schematic illustrations of a lithographic apparatus 100 and lithographic apparatus 100’, respectively, in which aspects of the present disclosure can 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, deep ultra violet or extreme ultra violet 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 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.

[0059] The illumination system IL can include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B.

[0060] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA with respect to a reference frame, 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 can 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.

[0061] 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 can correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0062] The terms “inspection apparatus,” “metrology system,” or the like may be used herein to refer to, e.g., a device or system used for measuring a property of a structure (e.g., overlay error, critical dimension parameters) or used in a lithographic apparatus to inspect an alignment of a wafer (e.g., alignment apparatus).

[0063] The patterning device MA can be transmissive (as in lithographic apparatus 100’ of FIG. IB) or reflective (as in lithographic apparatus 100 of FIG. 1A). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, or attenuated phase shift, as well as various hybrid mask types. 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 to the radiation beam B, which is reflected by a matrix of small mirrors.

[0064] 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.

[0065] 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.

[0066] The lithographic apparatus can also be of a type wherein at least a portion of the substrate can be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the proj ection system and the substrate . An immersion liquid can also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0067] Referring to FIGS. 1A 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.

[0068] 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 “n-outer” and “n-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 CO. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0069] 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 IF 1 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 PI, P2.

[0070] 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 has a pupil conjugate PPU to an illumination system pupil IPU. Portions of radiation emanate from the intensity distribution at the illumination system pupil IPU and traverse a mask pattern without being affected by diffraction at the mask pattern and create an image of the intensity distribution at the illumination system pupil IPU.

[0071] The projection system PS projects an image of the mask pattern MP, where the image is formed by diffracted beams produced from the mask pattern MP by radiation from the intensity distribution, onto a photoresist layer coated on the substrate W. For example, the mask pattern MP can include an array of lines and spaces. A diffraction of radiation at the array and different from zeroth order diffraction generates diverted diffracted beams with a change of direction in a direction perpendicular to the lines. Undiffracted beams (i.e., so-called zeroth order diffracted beams) traverse the pattern without any change in propagation direction. The zeroth order diffracted beams traverse an upper lens or upper lens group of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, to reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zeroth order diffracted beams is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IU. The aperture device PD, for example, is disposed at or substantially at a plane that includes the pupil conjugate PPU of the projection system PS.

[0072] The projection system PS is arranged to capture, by means of a lens or lens group U, not only the zeroth order diffracted beams, but also first-order or first- and higher-order diffracted beams (not shown). In some embodiments, dipole illumination for imaging line patterns extending in a direction perpendicular to a line can be used to utilize the resolution enhancement effect of dipole illumination. For example, first-order diffracted beams interfere with corresponding zeroth-order diffracted beams at the level of the wafer W to create an image of the line pattern MP at highest possible resolution and process window (i.e., usable depth of focus in combination with tolerable exposure dose deviations). In some embodiments, astigmatism aberration can be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. Further, in some embodiments, astigmatism aberration can be reduced by blocking the zeroth order beams in the pupil conjugate PPU of the projection system associated with radiation poles in opposite quadrants. This is described in more detail in U.S Patent No. 7,511,799 B2, issued March 31, 2009, and titled “Uithographic Projection Apparatus and a Device Manufacturing Method.”

[0073] All patent applications, patents, and printed publications cited herein are incorporated herein by reference in their entireties, except for any definitions, subject matter disclaimers or disavowals, and except to the extent that the incorporated material is inconsistent with the express disclosure herein, in which case the language in this disclosure controls.

[0074] With the aid of the second positioner PW and position sensor IFD (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 (not shown in FIG. IB) 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).

[0075] 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.

[0076] Mask table MT and patterning device MA can be in a vacuum chamber V, where an invacuum robot IVR can be used to move patterning devices such as a mask in and out of vacuum chamber. Alternatively, when mask table MT and patterning device MA are outside of the vacuum chamber, an out-of-vacuum robot can be used for various transportation operations, similar to the invacuum robot IVR. Both the in-vacuum and out-of-vacuum robots need to be calibrated for a smooth transfer of any payload (e.g., mask) to a fixed kinematic mount of a transfer station.

[0077] The lithographic apparatus 100 and 100’ can be used in at least one of the following modes:

[0078] 1. In step mode, the support structure (for example, mask table) MT and the substrate table WT 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.

[0079] 2. In scan mode, the support structure (for example, mask table) MT and the substrate table WT 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.

[0080] 3. In another mode, the support structure (for example, mask table) MT is kept substantially stationary while 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 a scan. This mode of operation can be readily applied to maskless lithography that utilizes a programmable patterning device, such as a programmable mirror array.

[0081] Combinations and / or variations on the described modes of use or entirely different modes of use can also be employed.

[0082] In a further embodiment, lithographic apparatus 100 includes an extreme ultraviolet (EUV) source, which is configured to generate a beam of EUV radiation for EUV lithography. In general, theEUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0083] FIG. 2 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 220 of the source collector apparatus SO. An EUV radiation emitting plasma 210 can be formed by a discharge produced plasma source. EUV radiation can be produced by a gas or vapor, for example Xe gas, Li vapor, or Sn vapor in which the very hot plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is created by, for example, an electrical discharge causing at least a partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor can be required for efficient generation of the radiation. In some aspects, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0084] The radiation emitted by the hot plasma 210 is passed from a source chamber 211 into a collector chamber 212 via an optional gas barrier or contaminant trap 230 (in some cases also referred to as contaminant barrier or foil trap), which is positioned in or behind an opening in source chamber 211. The contaminant trap 230 can include a channel structure. Contamination trap 230 can also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further indicated herein at least includes a channel structure.

[0085] The collector chamber 212 can include a radiation collector CO, which can be a so-called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation that traverses collector CO can be reflected off a grating spectral filter 240 to be focused in a virtual source point INTF. The virtual source point INTF is commonly referred to as the intermediate focus, and the source collector apparatus is arranged such that the intermediate focus INTF is located at or near an opening 219 in the enclosing structure 220. The virtual source point INTF is an image of the radiation emitting plasma 210. Grating spectral filter 240 is used in particular for suppressing infra-red (IR) radiation.

[0086] Subsequently the radiation traverses the illumination system IL, which can include a faceted field mirror device 222 and a faceted pupil mirror device 224 arranged to provide a desired angular distribution of the radiation beam 221, at the patterning device MA, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the beam of radiation 221 at the patterning device MA, held by the support structure MT, a patterned beam 226 is formed and the patterned beam 226 is imaged by the projection system PS via reflective elements 228, 229 onto a substrate W held by the wafer stage or substrate table WT.

[0087] More elements than shown can generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 240 can optionally be present, depending upon the type of lithographic apparatus. Further, there can be more mirrors present than those shown in the FIG. 2,for example there can be one to six additional reflective elements present in the projection system PS than shown in FIG. 2.

[0088] Collector optic CO, as illustrated in FIG. 2, is depicted as a nested collector with grazing incidence reflectors 253, 254, and 255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 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.

[0089] FIG. 3 shows a lithographic cell 300, also sometimes referred to as a lithocell or cluster, according to some aspects. Lithographic apparatus 100 or 100’ can form part of lithographic cell 300. Lithographic cell 300 can also include one or more apparatuses to perform pre -exposure and postexposure processes on a substrate. In some examples, these include spin coaters SC to deposit resist layers, developers DE to develop exposed resist, chill plates CH, and bake plates BK. A substrate handler, or robot, RO picks up substrates from input / output ports I / O 1, 1 / O2, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus 100 or 100’. These devices, which are often collectively referred to as the track, are under the control of a track control unit TCU, which is itself controlled by a 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.

[0090] As mentioned, the flatness or degree of levelness of a substrate can affect the accuracy of a projection of an image onto the substrate during a lithographic exposure. Measuring variations in height, and therefore flatness, of a substrate before carrying out a lithographic exposure can allow for focus errors to be determined and corrected.

[0091] In some aspects, a height measurement device incorporates one or more air gauges. Current methods of fabricating air gauge measurement devices for lithographic apparatuses utilize costly drilling and milling techniques. These techniques limit the size, complexity, and manufacturability of a measurement device.

[0092] In some aspects, microfluidic air gauge measurement devices can be fabricated using wafer fabrication techniques. For example, components of an air gauge (e.g., inlet, reference channel, measurement channel, etc.) can be etched into a plurality of substrates. In some embodiments the various components can be etched onto a single layer. Then, multiple substrates can be bonded to form a measurement device. This can result in a smaller device with improved bandwidth and sensitivity and easier integration into a lithography apparatus. Additionally, wafer fabrication techniques can allow for fabrication of multiple measurement devices in parallel with minimal cost increases.

[0093] FIG. 4 which shows an air gauge 400. A gas such as air is introduced into a plenum 410 which directs the gas to a reference chamber 405 and a measure chamber 408, respectively. The flow path from the plenum 410 to the reference chamber 405 may include a flow restriction 420 as shown and the flow path from the plenum 410 to the measure chamber 408 may include a flow restriction 430 asshown. The reference chamber 405 is in fluid communication with a reference nozzle 440 which expels gas into a gap of known width between the reference nozzle 440 and a reference surface 445. Similarly, the measure chamber 408 is in fluid communication with a measure nozzle 450 which expels gas into a gap between the measure nozzle 450 and the surface of a wafer W. A bridge sensor 460 measures the difference in pressure between the pressure PR in the reference chamber 405 and the pressure PM in the measure chamber 408. The bridge sensor 460 develops a signal S having a characteristic, e.g., voltage, based on the pressure difference between the measure nozzle and the reference nozzle due to the difference in the leveling of the reference nozzle and the measure nozzle. The signal S can be used to infer the local height of the surface of the wafer W with sub-nanometer accuracy.

[0094] The measurement bridge sensor 460 can measure the height of a surface by measuring and / or inferring a pressure or flow differential between the reference chamber 405 and the measure chamber 408. In some aspects, bridge sensor 460 can comprise a flexible membrane in fluid communication with both the reference chamber 405 and the measure chamber 408. The flexible membrane can be configured to have no deflection when there is no pressure differential between the measurement and reference chambers. A further discussion of pressure sensing technologies can be found in U.S. Patent Pub. 2019 / 0017816, titled “Height Measurement Apparatus” and published on January 17, 2019.

[0095] Measurement device 400 can be used to measure multiple regions of a surface of substrate W. For example, measurement nozzle 450 of measurement device 400 can be scanned across the surface of substrate W. Alternatively, substrate W can be scanned beneath measurement nozzle 450 of measurement device 400. In some aspects, the z-position of the measurement device 400 can be fixed at a predetermined value during measurements.

[0096] Measurement device 400 can be integrated into a lithography apparatus. For example, measurement device 400 can be positioned in a carrier in a lithography apparatus and used to measure the height of a surface of a wafer and / or a lithography stage.

[0097] The measurement device 400 can be fabricated using multiple substrates. In some aspects, a measurement device can be fabricated using two substrates. A measurement device can be fabricated from a single substrate (e.g., using 3D printing techniques, as would become apparent to persons skilled in the art).

[0098] More than one measurement device can be fabricated in the plurality of substrates. For example, channels for an array of measurement devices can be etched simultaneously. FIGS. 5 A, 5B, 5C, and 5D show bottom views of a measurement arrays 500A, 500B, 500C, and 500D respectively. The bottom view of measurement arrays 500A, 500B, 500C and 500D show relative positions of measurement nozzles 450.

[0099] In FIG. 5A, measurement nozzles 450 are arranged as a series of linear arrays, according to some aspects. The linear arrays can be aligned such that measurement nozzles of successive rows and columns align with each other. In the example shown in FIG. 5 A, array 500A can cover an entiresurface of a 300 mm wafer. For example, array 500 can have about 100 rows and about 100 columns. In other examples, array 500A can comprise a smaller number of rows and / or columns. In some aspects, array 500 A can be a single linear array (e.g., one row of measurement devices).

[0100] In the example shown in FIG. 5B, measurement nozzles 450 are arranged as a series of staggered linear arrays. In array 500B, successive rows of linear arrays can be staggered such that measurement nozzles of each row are not perpendicularly aligned with the row above. A series of staggered linear arrays can provide greater coverage (i.e., have more measurement devices spaced closer together) than the series of linear arrays shown in FIG. 5A. Array 500B can cover an entire surface of a 300 mm wafer. For example, array 500B can have about 100 rows. In other examples, array 500B can comprise a smaller number of rows. Array 500B can comprise two staggered rows which are scanned in a circular pattern.

[0101] In FIG. 5C, measurement nozzles 450 are arranged in two perpendicular linear arrays. Array 500C can be rotated such that the measurement nozzles can measure different portions of a substrate. The measurement array 500C need only be rotated 90 degrees to get full coverage of the substrate. The configuration of array 500C can balance fast substrate measurements with a simplified fabrication design.

[0102] FIG. 5D shows a circular array of measurement nozzles 450. In array 500D, measurement nozzles 450 are arranged in circular patterns that extend radially from the center of the array.

[0103] Similarly to arrays 500A and 500B, array 500D can cover an entire surface of a 300 mm wafer. Thus, the configurations of arrays 500A, 500B, and 500D can measure an entire surface of a lithography wafer simultaneously. As an alternative, any of the arrays 500A, 500B, and 500D can have a smaller lateral extent than the surface of the wafer and then be moved laterally, for example along a circular path, to scan the entire surface of the wafer.

[0104] Arrays 500A, 500B, 500C, and 500D can contain any conceivable number of measurement devices subject only to engineering constraints. In some aspects, the number of measurement devices contained in an array can be determined by the area the array is intended to measure and / or by spacing concerns in a lithography apparatus.

[0105] Measurement nozzles 450 in arrays 500A, 500B, 500C, and 500D can have any conceivable spacing subject only to engineering constraints. The spacing between measurement devices can be determined by the size of the measurement devices. The spacing between measurement devices may be uniform or may be nonuniform.

[0106] The spacing, size, and number of measurement nozzles 450 shown in arrays 500A, 500B, 500C, and 500D are for illustration purposes and are not necessarily drawn to scale. Furthermore, arrays 500A, 500B, 500C, and 500D are example configurations and are non -limiting. Other array configurations can be envisaged based on the devices and techniques described herein.

[0107] The systems described above include one or more air gauges. It should be noted that although these devices are often referred to as air gauges, the working gas used in them is not limitedto air. In general, the working gas can be any type of clean gas. Thus, air gauges are sometimes known as gas gauges. As used herein, the term “air gauge” will encompass any type of gauge using the principles described above including gauges denominated as air gauges and gauges denominated as gas gauges

[0108] Air gauges may be manufactured using standard milling and boring techniques. It is also possible to use a layered fabrication method for manufacturing air gauges. This permits miniaturization of the pneumatic volume of the air gauge, thus providing ample bandwidth for the air gauge to be utilized as a part of a level sensor for detecting variations in the height of the surface of a semiconductor wafer.

[0109] Manufacturing a suitable air gauge using a layered fabrication method does, however, pose some challenges. For example, it is desirable to reduce the number of wafer stacks to reduce the bonding steps. This tends to decrease the design distance between the pressure sensor and the nozzles that introduce gas into the reference and measurement gaps. This brings the gas turbulence from the nozzles closer to the pressure sensor. The turbulence interferes with measurement of the static (stagnation point) pressure within the reference and measurement gaps.

[0110] To address challenges such as this, according to an aspect of an embodiment an air gauge is configured to reduce flow interaction between the gas supply and pressure measurement locations. In some embodiments, the air gauge has a generally cylindrical configuration having a central axial pressure tap and a peripheral arrangement of nozzles that are supplied with gas. This peripheral arrangement of nozzles may or may not be at least partially surrounded with a segmented annular outlet referred to herein as a “return shroud.” In some embodiments, the gas introduced into the reference gap by the reference side annular nozzles exits the reference gap through the shroud. In some embodiments, the gas introduced into the measure gap by the measure side annular nozzle and gas introduced into the measure gap by the return shroud exit the measure gap at the same location, leading to common mode rejection that makes it possible to design an air gauge having lower noise.[oni] Thus, according to an aspect of an embodiment, separate channels are provided for the measurement side for (1) delivery of gas to the surface to be measured and (2) pressure measurement. Also, according to an aspect of an embodiment, separate channels are provided for the reference side for (1) delivery of gas to the reference surface and (2) reference pressure measurement. Delivery of gas to the surface to be measured and to the reference surface is provided by nozzles while pressure measurement is provided by respective pressure taps that are distinct and laterally displaced from the nozzles. This divorces tap functionality from nozzle functionality. This permits a more compact design and provides for more design flexibility. Displacing the nozzles from the tap positions also serves to isolate the taps from exposure to flow noise.

[0112] FIG. 6 depicts an example of an air gauge 600 according to an aspect of an embodiment. FIG. 6 is a cross section of the air gauge 600 which includes a supply annular nozzle assembly 610 that is generally cylindrical and generally axially symmetric. As shown in FIG. 6, the supply annular nozzleassembly 610 includes gas inlets 620, 625, 630, and 635. Gas inlets 620 and 630 introduce gas to the reference side of a gas supply channel 615. Gas inlets 625 and 635 introduce gas to the measure side of a gas supply channel 615. The gas supply channel 615 is in fluid communication with a measure nozzle 640 and a reference nozzle 650. The reference nozzle 650 directs the gas against a fixed reference surface 675 which is a known distance from the reference nozzle 650. The measure nozzle 640 directs the gas toward a substrate 665 which is spaced away from the measure nozzle 640 at a distance to be measured.

[0113] The reference pressure in the reference gap between the reference nozzle 650 and the fixed reference 675 is transmitted by a reference pressure tap 670 to one side of a differential pressure sensor 680. The measure pressure in the measure gap between the measure nozzle 640 and the substrate 665 is transmitted by a measure pressure tap 660 to the other side of the differential pressure sensor 680. The differential pressure sensor 680 develops a signal that is indicative of the difference in pressure between the reference pressure and the measure pressure. From the signal the distance between the measure nozzle 640 and the substrate 665 can be inferred.

[0114] The differential pressure sensor 680 may be of any known type of device capable of sensing a difference between two pressures including devices capable of making absolute pressure measurements. As an example, the differential pressure sensor 680 may be a diaphragm differential pressure sensorthat uses the deflection of a diaphragm to measure the pressure difference. For example, the diaphragm differential pressure sensor 680 may include a membrane mechanically coupled to a strain gauge. Other candidates include piezoresistive, piezoelectric, magnetic, capacitive, and fiberoptic sensors. The differential pressure sensor 680 may also be an integrated optoelectronic device which may include a resonator such as a ring resonator, photonic crystal resonator, whispering gallery mode resonator, and Fabry Perot resonator.

[0115] Gas in the reference gap can be allowed to escape directly through an exhaust outlet. Alternatively, as shown in the example of FIG. 6, the gas entering the reference gap may be returned to the measure gap by a return shroud 690 to be exhausted by a return shroud exhaust 642.

[0116] As mentioned, the supply annular nozzle assembly 610 is essentially cylindrical so that the gas supply channel 615 and the return shroud 690 are substantially annular. This is visible in FIG. 7A which is a top view of the supply annual nozzle assembly 605. FIG. 7A shows that the gas inlets of 620, 625, 630, and 635 enter the supply annular nozzle assembly 605 through two sets of diametrically opposed ports. Also shown as the reference tap 670 which in the example shown is at the axial center of the supply annular nozzle assembly 605, the reference nozzle 650, and the return shroud 695.

[0117] FIG. 7B is a cutaway perspective view of the supply annular nozzle assembly 605. Again, the gas inlets 620 and 630 are shown as supplying gas to a reference side of the gas supply channel 615 while gas inlets 625 and 635 are shown as supplying gas to a measure side of the gas supply channel 615. The gas supply channel 615 feeds gas both to the reference nozzle 650 and the measure nozzle 640. The reference pressure tap 670 relays the reference pressure to a differential pressure sensor 680.A measure pressure tap 660 relays the measure pressure to the other side of the differential pressure sensor 680. FIG. 7B also shows the return shroud exhaust 642.

[0118] FIG. 8 is a perspective view of the supply annular nozzle assembly 605. Visible in FIG. 8 are the gas inlet 620 and the gas inlet 625. Also visible in FIG. 8 are the lower ends of the measure pressure tap 660 at a central portion of the bottom of the supply annular nozzle assembly 605, the measure nozzle 640 which is radially displaced from the measure pressure tap 660, and a return shroud 695 positioned circumferentially around the bottom portion of the supply annular nozzle assembly 605.

[0119] The embodiments described above include a differential pressure sensor positioned inside the nozzle assembly. For some implementations it may be desirable to communicate the reference pressure and measure pressure to a position outside of the nozzle assembly to be measured there. Such an embodiment is shown in FIG. 9 and in FIGS. 10A - 10C.

[0120] FIG. 9 shows an architecture that allows for the pressure measurement to be made outside of the stack of layers making up the internal structure of the nozzle assembly. FIG. 9 is a perspective view of such a supply annular nozzle assembly 700 which includes a measure pressure tap 710 at its base. A reference tap 757 which would not be visible in FIG. 9 is shown in phantom. The embodiment of FIG. 9 also includes a measure pressure port 730 and a reference pressure port 720 which are in fluid communication with a measure gap and a reference gap, respectively, located within the supply annular nozzle assembly 700 as is described in more detail below. Gas lines 725 and 727 relay the reference pressure and the measure pressure, respectively, to a differential pressure sensor 705 positioned externally to the supply annular nozzle assembly 700.

[0121] The components within the supply annular nozzle assembly 700 can be made up of a stack of elements in a layered construction as shown in FIGS. 10A-10C. The element on the reference side of the stack, nozzle assembly reference side element 750, is shown in FIG. 10A. The nozzle assembly reference side element 750 includes structure defining a reference pressure duct 725 which communicates pressure from a pressure reference pressure tap 750 to the reference pressure port 720 of FIG. 9. The arrangement of FIG. 10A also includes a circular array of reference nozzles 755 that supply gas to the reference gap and segmented circumferential apertures 780 making up a portion of a return shroud 780.

[0122] The stack inside the supply annular nozzle assembly 700 also includes a nozzle assembly intermediate element 760, as shown in FIG. 10B. The nozzle assembly intermediate element 760 includes a gas supply 767 in fluid communication with a gas inlet 765. The gas supply 767 is configured as an annular gap that aligns with the reference nozzles 755 of the nozzle assembly reference side element 750 to direct gas from the gas inlet 765 to the reference nozzle 755. A lower portion of gas supply 767 is in fluid communication with measure nozzles as will be described below. The nozzle intermediate element 760 also includes segmented apertures making up an additional portion of the return shroud 780.

[0123] FIG. 10C shows a nozzle assembly measure side element 770 configured to be positioned at the measure side of the stack internal to the supply annular nozzle assembly 700. The nozzle assembly measure side element 770 includes structure defining a measure pressure duct 785 which communicates pressure from a measure reference pressure tap 710 to the measure pressure port 720 of FIG. 9. The arrangement of FIG. 10A also includes an array of measure nozzles 775 that supply gas to the reference gap and segmented circumferential apertures 780 making up a portion of the return shroud 780.

[0124] For all embodiments, the features of the nozzle assemblies and sensors may be formed in one substrate or in two or more bonded substrates, according to some aspects. Features in this context can include channels and / or through holes. The one or more substrates can be comprised of silicon, glass, copper foil laminates (e.g., precursors to PCB boards), plastics, polymers, or the like. In some aspects, features may be formed via etching. Etching can create nanometer and / or micrometer scale features on the one or more substrates. Each substrate in the one or more substrates can have different etched features, which when combined, can create a series of channels that form a measurement device. Substrates can be etched on multiple sides (e.g., top and bottom sides). Portions of a substrate can be coated and / or patterned before etching begins to guide the etching process.

[0125] In some aspects, other techniques, such as 3D printing, can be used to form features in the one or more substrates. For example, a 3D printer can print a plurality of substrates with features (e.g., channels and through holes) that, when combined, can create a series of channels that form a measurement device. A 3D printer can also print a single substrate comprising a series of channels that form a measurement device. In this case, a pressure sensor can be added to the substrate after the substrate is printed. A 3D printed substrate can comprise materials such as polymer materials, plastic compounds, resins, metals, or the like.

[0126] In some aspects, the one or more measurement devices can be configured to measure the height of a substrate, for example, by measuring differential pressure between a measurement nozzle and a reference nozzle. The one or more measurement devices can create a height map of a substrate by measuring the height at different areas of the substrate. The one or more measurement devices can measure multiple areas of a substrate simultaneously. The one or more measurement devices can be scanned across the surface of the substrate, or the substrate can be scanned beneath the one or more measurement devices.

[0127] The one or more measurement devices can be configured to form an array of measurement devices. The array of measurement devices can be linear array, a staggered array, a circular array, or the like. The array of measurement devices can take any of the forms described in reference to FIGS. 5 A, 5B. 5C, and 5D. The configuration of the array can be determined by the etching and bonding steps. For example, the spacing, positioning, and number of etched regions in the plurality of substrates can determine the number and configuration of measurement devices in the array of measurement devices.

[0128] Although specific reference can be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein mayhave other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCDs, thin-fdm magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein can be considered as specific examples of the more general terms “substrate” or “target portion,” respectively. The substrate referred to herein can be processed, before or after exposure, in for example a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) and / or a metrology unit. Where applicable, the disclosure herein can be applied to such and other substrate processing tools. Further, the substrate can be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0129] Although specific reference may have been made above to the use of embodiments of the present disclosure in the context of optical lithography, it will be appreciated that the present disclosure can be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device can be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0130] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present disclosure is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0131] The terms “radiation,” “beam of radiation,” or the like as used herein may encompass all types of electromagnetic radiation, for example, ultraviolet (UV) radiation (for example, having a wavelength X of 365, 248, 193, 157 or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (for example, having a wavelength in the range of 5-20 nm such as, for example, 13.5 nm), or hard X-ray working at less than 5 nm, as well as matter beams, such as ion beams or electron beams. The terms “light,” “illumination,” or the like may refer to non-matter radiation (e.g., photons, UV, X-ray, or the like). Generally, radiation having wavelengths between about 400 to about 700 nm is considered visible radiation; radiation having wavelengths between about 780-3000 nm (or larger) is considered IR radiation. UV refers to radiation with wavelengths of approximately 100-400 nm. Within lithography, the term “UV” also applies to the wavelengths that can be produced by a mercury discharge lamp: G- line 436 nm; H-line 405 nm; and / or, I-line 365 nm. Vacuum UV, or VUV (i.e., UV absorbed by gas), refers to radiation having a wavelength of approximately 100-200 nm. Deep UV (DUV) generally refers to radiation having wavelengths ranging from 126 nm to 428 nm, and in some embodiments, an excimer laser can generate DUV radiation used within a lithographic apparatus. It should be appreciated that radiation having a wavelength in the range of, for example, 5-20 nm relates to radiation with a certain wavelength band, of which at least part is in the range of 5-20 nm.

[0132] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all example embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0133] The present disclosure has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0134] While specific embodiments of the disclosure have been described above, it will be appreciated that embodiments of the present disclosure may be practiced otherwise than as described. The descriptions are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the disclosure as described without departing from the scope of the claims set out below.

[0135] The foregoing description of the specific embodiments will so fully reveal the general nature of the present disclosure that others can, by applying knowledge within the skill of the art, readily modify and / or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0136] The breadth and scope of the protected subject matter should not be limited by any of the above-described example embodiments, but should be defined only in accordance with the following claims and their equivalents. Aspects of the invention are set out in the clauses below.1. An air gauge for measuring a levelness of a test surface, the air gauge comprising: a nozzle body; a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap; a first gas inlet in fluid communication with the reference gap; a second gas inlet in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface; and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap; the differential pressure sensor being in fluid communication with the first gas inlet only indirectly through the reference gap and a reference pressure tap and in fluid communication with the second gas inlet only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlet or the second gas inlet.2. The air gauge of clause 1, wherein the first gas inlet is configured as a first channel through the nozzle body and the second gas inlet is configured as a second channel through the nozzle body.3. The air gauge of clause 1, further comprising a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.4. The air gauge of clause 1, wherein the nozzle body is comprised of a plurality of bonded wafers.5. The air gauge of clause 1, wherein the nozzle body is constructed by selective laser etching of glass.6. The air gauge of clause 1, wherein the nozzle body is constructed by 3D printing a polymer material.7. The air gauge of clause 1, wherein the nozzle body has a generally cylindrical configuration having a longitudinal axis.8. The air gauge of clause 7, wherein the nozzle body has a cavity on the longitudinal axis, wherein the reference pressure tap extends from the cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the cavity to the measurement gap along a second segment of the longitudinal axis.9. The air gauge of clause 8, wherein the differential pressure sensor is positioned within the cavity.10. The air gauge of clause 8, wherein the differential pressure sensor is positioned outside of the cavity and arranged in fluid communication with an interior of the cavity through at least one channel.11. The air gauge of clause 7, wherein the nozzle body has a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, wherein the reference pressure tap extends from the first cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the second cavity to the measurement gap along a second segment of the longitudinal axis.12. The air gauge of clause 11, wherein the differential pressure sensor is positioned outside of the nozzle body and in fluid communication with the first cavity and the second cavity.13. The air gauge of clause 7, wherein the first gas inlet communicates with the reference gap through a first annular chamber coaxial with the longitudinal axis and wherein the second gas inlet communicates with the measurement gap through a second annular chamber coaxial with the longitudinal axis and axially displaced from the first annular chamber.14. An air gauge for measuring a levelness of a test surface, the air gauge comprising: a nozzle body; a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap;a plurality of first gas inlets in fluid communication with the reference gap; a plurality of second gas inlets in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface; and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap; the differential pressure sensor being in fluid communication with the plurality of first gas inlets only indirectly through the reference gap and a reference pressure tap and in fluid communication with the plurality of second gas inlets only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlets or the second gas inlets.15. The air gauge of clause 14, wherein the plurality of first gas inlets is configured as a plurality of first channels through the nozzle body and the plurality of second gas inlets is configured as a plurality of second channels through the nozzle body.16. The air gauge of clause 14, further comprising a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.17. The air gauge of clause 14, wherein the nozzle body is comprised of a plurality of bonded wafers.18. The air gauge of clause 14, wherein the nozzle body has a generally cylindrical configuration having a longitudinal axis.19. The air gauge of clause 18, wherein the first gas inlets are positioned symmetrically around the nozzle body at a first position along the longitudinal axis.20. The air gauge of clause 19, wherein the second gas inlets are positioned symmetrically around the nozzle body at a second position along the longitudinal axis axially displaced from the first position.21. The air gauge of clause 19, wherein the nozzle body has a cavity on the longitudinal axis, wherein the reference pressure tap extends from the cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the cavity to the measurement gap along a second segment of the longitudinal axis.22. The air gauge of clause 21, wherein the differential pressure sensor is positioned within the cavity.23. The air gauge of clause 18, wherein the nozzle body has a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, wherein the reference pressure tap extends from the first cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the second cavity to the measurement gap along a second segment of the longitudinal axis.24. The air gauge of clause 23, wherein the differential pressure sensor is positioned outside of the nozzle body and in fluid communication with the first cavity and the second cavity.25. The air gauge of clause 18, wherein the first gas inlets communicate with the reference gap through a first annular chamber coaxial with the longitudinal axis and wherein the second gas inlets communicate with the measurement gap thorough a second annular chamber coaxial with the longitudinal axis and axially displaced from the first annular chamber.26. A levelness measurement system for measuring a levelness of a test surface, the levelness measurement system comprising: an array of air gauges, each of the air gauges comprising: a nozzle body; a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap; a first gas inlet in fluid communication with the reference gap; a second gas inlet in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface; and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap, the differential pressure sensor being in fluid communication with the first gas inlet only indirectly through the reference gap and a reference pressure tap and in fluid communication with the second gas inlet only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlet or the second gas inlet.27. The levelness measurement system of clause 26, wherein for each air gauge the first gas inlet is configured as a first channel through the nozzle body and the second gas inlet is configured as a second channel through the nozzle body.28. The levelness measurement system of clause 26, wherein each of the air gauges further comprises a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.29. The levelness measurement system of clause 26, wherein the array of air gauges is comprised of a plurality of bonded wafers.30. The levelness measurement system of clause 26, wherein the array is comprised of a periodic arrangement of the plurality of air gauges.31. The levelness measurement system of clause 26, wherein for each air gauge the nozzle body has a generally cylindrical configuration having a longitudinal axis.32. The levelness measurement system of clause 31, wherein for each air gauge the nozzle body has a cavity on the longitudinal axis, wherein the reference pressure tap extends from the cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the cavity to the measurement gap along a second segment of the longitudinal axis.33. The levelness measurement system of clause 32, wherein for each air gauge the differential pressure sensor is positioned within the cavity.34. The levelness measurement system of clause 31, wherein for each air gauge the nozzle body has a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, wherein the reference pressure tap extends from the first cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the second cavity to the measurement gap along a second segment of the longitudinal axis.35. The levelness measurement system of clause 34, wherein for each air gauge the differential pressure sensor is positioned outside of the nozzle body and in fluid communication with the first cavity and the second cavity.36. The levelness measurement system of clause 31, wherein for each air gauge the first gas inlet communicates with the reference gap through a first annular chamber coaxial with the longitudinal axis and wherein the second gas inlet communicates with the measurement gap through a second annular chamber coaxial with the longitudinal axis and axially displaced from the first annular chamber.37. A semiconductor measurement apparatus comprising: at least three bonded wafers together comprising an annular gas inlet; the annular gas inlet being arranged around the circumference of a central pressure tap wherein the central pressure tap further comprises a reference pressure tap, a differential pressure sensor, and a measure pressure tap; and the annular gas inlet being further configured to supply gas to an annular nozzle, the annular nozzle being further configured to supply gas to a fixed reference area and to supply gas to a substrate to be measured.38. The semiconductor measurement apparatus of clause 37, wherein the at least three bonded wafers further comprise an annular shroud through which gas from the reference area and gas from the substrate to be measured exit.

Claims

CLAIMS1. An air gauge for measuring a levelness of a test surface, the air gauge comprising: a nozzle body; a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap; a first gas inlet in fluid communication with the reference gap; a second gas inlet in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface; and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap; the differential pressure sensor being in fluid communication with the first gas inlet only indirectly through the reference gap and a reference pressure tap and in fluid communication with the second gas inlet only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlet or the second gas inlet.

2. The air gauge of claim 1, wherein the first gas inlet is configured as a first channel through the nozzle body and the second gas inlet is configured as a second channel through the nozzle body.

3. The air gauge of claim 1, further comprising a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.

4. The air gauge of claim 1, wherein the nozzle body is comprised of a plurality of bonded wafers.

5. The air gauge of claim 1, wherein the nozzle body has a generally cylindrical configuration having a longitudinal axis.

6. The air gauge of claim 5, wherein the nozzle body has a cavity on the longitudinal axis, wherein the reference pressure tap extends from the cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the cavity to the measurement gap along a second segment of the longitudinal axis, wherein the differential pressure sensor is positioned within the cavity, and wherein the differential pressure sensor is positioned outside of the cavity and arranged in fluid communication with an interior of the cavity through at least one channel.

7. The air gauge of claim 5, wherein the nozzle body has a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, wherein the reference pressure tap extends from the first cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the second cavity to the measurement gap along a second segment of the longitudinal axis, and wherein the differential pressure sensor is positioned outside of the nozzle body and in fluid communication with the first cavity and the second cavity.

8. A levelness measurement system for measuring a levelness of a test surface, the levelness measurement system comprising: an array of air gauges, each of the air gauges comprising: a nozzle body; a fixed reference surface mechanically coupled to the nozzle body and having a portion spaced away from the nozzle body by a predetermined distance to define a reference gap; a first gas inlet in fluid communication with the reference gap; a second gas inlet in fluid communication with a measurement outlet adapted to be positioned across a measurement gap from the test surface; and a differential pressure sensor adapted to sense a pressure differential between the reference gap and the measurement gap, the differential pressure sensor being in fluid communication with the first gas inlet only indirectly through the reference gap and a reference pressure tap and in fluid communication with the second gas inlet only indirectly through the measurement gap and a measure pressure tap such that the differential pressure sensor is not directly exposed to the first gas inlet or the second gas inlet.

9. The levelness measurement system of claim 8, wherein for each air gauge the first gas inlet is configured as a first channel through the nozzle body and the second gas inlet is configured as a second channel through the nozzle body.

10. The levelness measurement system of claim 8, wherein each of the air gauges further comprises a return shroud channel communicating from the reference gap to the measurement gap through the nozzle body.

11. The levelness measurement system of claim 8, wherein the array of air gauges is comprised of a plurality of bonded wafers.

12. The levelness measurement system of claim 8, wherein for each air gauge the nozzle body has a generally cylindrical configuration having a longitudinal axis.

13. The levelness measurement system of claim 12, wherein for each air gauge the nozzle body has a cavity on the longitudinal axis, wherein the reference pressure tap extends from the cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the cavity to the measurement gap along a second segment of the longitudinal axis, and wherein for each air gauge the differential pressure sensor is positioned within the cavity.

14. The levelness measurement system of claim 12, wherein for each air gauge the nozzle body has a first cavity on the longitudinal axis and a second cavity on the longitudinal axis axially displaced from the first cavity, wherein the reference pressure tap extends from the first cavity to the reference gap along a first segment of the longitudinal axis, wherein the measurement pressure tap extends from the second cavity to the measurement gap along a second segment of the longitudinal axis, and wherein for each air gauge the differential pressure sensor is positioned outside of the nozzle body and in fluid communication with the first cavity and the second cavity.

15. A semiconductor measurement apparatus comprising : at least three bonded wafers together comprising an annular gas inlet; the annular gas inlet being arranged around the circumference of a central pressure tap wherein the central pressure tap further comprises a reference pressure tap, a differential pressure sensor, and a measure pressure tap; and the annular gas inlet being further configured to supply gas to an annular nozzle, the annular nozzle being further configured to supply gas to a fixed reference area and to supply gas to a substrate to be measured.

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