Measuring apparatus, measuring method and method of manufacturing device

Abstract

A measuring apparatus for measuring a substrate, the measuring apparatus comprising: an optical sensor configured to measure a surface of the substrate by emitting a light beam; a fluid supply device configured to supply a conditioning fluid, the conditioning fluid traversing the light beam and flowing in a slit between the measurement device and a surface of the substrate; wherein the optical sensor is configured to: perform a first measurement process when the measurement device is moved relative to the substrate at a first speed, and perform a second measurement process when the measurement device is moved relative to the substrate at a second speed higher than the first speed; and the fluid supply device is configured to supply the conditioning fluid at a first flow rate during the first measurement process and to supply the conditioning fluid at a second flow rate higher than the first flow rate during the second measurement process.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 23155897.4 filed on February 9, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a measuring device for measuring a substrate in a lithography apparatus, a measuring method, and a method for manufacturing a device. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a substrate (typically a target portion of the substrate). Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In this instance, a patterning device (alternatively referred to as a reticle or mask) is used to generate the circuit patterns to be formed on the individual layers of the IC. This pattern can be transferred to a target portion (e.g., comprising a portion of a die, a die, or multiple dies) located on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically achieved by imaging onto a layer of radiation-sensitive material (resist) disposed on the substrate. Typically, a single substrate will contain a network of adjacent target portions that are patterned sequentially. Known lithographic apparatus include so-called steppers, in which target portions are illuminated by exposing the entire pattern onto each target portion at once; and so-called scanners, in which target portions are illuminated by scanning a radiation beam across the pattern in a given direction (the "scanning" direction) while the substrate is simultaneously scanned parallel or antiparallel to that direction. Patterns can also be transferred from a patterning device to a substrate by printing the pattern onto the substrate.

[0005] Continuous advancements in semiconductor manufacturing processes have consistently reduced the size of circuit components, while the number of functional elements (e.g., transistors) per device has steadily increased for decades, following a trend commonly referred to as "Moore's Law." To keep pace with Moore's Law, the semiconductor industry is pursuing technologies capable of producing increasingly smaller features. To project patterns onto substrates, lithography equipment uses electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be patterned on the substrate. Typical wavelengths currently used are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Lithography equipment using extreme ultraviolet (EUV) radiation (having a wavelength in the 4 nm to 20 nm range, such as 6.7 nm or 13.5 nm) can be used to form smaller features on substrates than can be formed using lithography equipment using, for example, 193 nm radiation.

[0006] Given the increasing levels of precision required for device fabrication, obtaining accurate measurements of substrates has become increasingly important. These measurements include horizontal alignment (which can be achieved by detecting marks on the substrate's surface using alignment sensors) and leveling (which can be achieved by measuring the topography of the substrate's surface using level sensors). Typically, these sensors are optical. Once these measurements are taken, the lithography equipment can be calibrated accordingly to compensate for any misalignment and non-planarity of the substrate during fabrication.

[0007] In the context of required accuracy, it is known that poor control of the conditions of the fluid (e.g., air) located in the optical path of a sensor can reduce measurement accuracy. These conditions can include the fluid's composition, temperature, and so on. Therefore, attempts have been made to control the fluid conditions by supplying a conditioning fluid flow to the optical path. The conditioning fluid can be controlled to have known and stable conditions. This way, the optical path can be protected from interference from external fluids (e.g., the ambient fluid surrounding the measurement device).

[0008] However, known attempts to control fluid conditions cannot provide completely stable conditions. This limits the level of accuracy that sensors can achieve, as well as the speed at which they can measure across a substrate. This, in turn, restricts the smallest features that can be achieved with photolithography, increases scrap rates, and limits production speeds. Summary of the Invention

[0009] It is therefore an object of the present invention to increase the level of precision achievable with photolithographic techniques.

[0010] Therefore, another object of the present invention is to reduce the scrap rate when manufacturing devices using photolithographic techniques.

[0011] Therefore, it is also an object of the present invention to increase the production speed of photolithography.

[0012] According to one aspect of the present invention, a measurement device is provided for measuring a substrate in a lithographic apparatus, the measurement device comprising: an optical sensor configured to measure a surface of the substrate by emitting a light beam; a fluid supply device configured to supply a conditioning fluid, the conditioning fluid crossing the light beam and flowing in a slit between the measurement device and the surface of the substrate;

[0013] wherein the optical sensor is configured to: perform a first measurement process when the measuring device moves relative to the substrate at a first speed, and perform a second measurement process when the measuring device moves relative to the substrate at a second speed higher than the first speed;

[0014] The fluid supply device is configured to supply the regulating fluid at a first flow rate during the first measurement process, and to supply the regulating fluid at a second flow rate higher than the first flow rate during the second measurement process.

[0015] According to another aspect of the present invention, there is provided a method for measuring a substrate in a lithographic apparatus using a measurement device, the method comprising:

[0016] emitting a light beam toward a surface of the substrate; and

[0017] supplying a conditioning fluid that traverses the light beam and flows in a slit adjacent the surface of the substrate;

[0018] During a first measurement process, the substrate is moved at a first speed relative to the light beam and the conditioning fluid is supplied at a first flow rate; and

[0019] During a second measurement process, the substrate is moved relative to the light beam at a second speed higher than the first speed while the conditioning fluid is supplied at a second flow rate higher than the first flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0021] Figure 1 schematically illustrates a lithographic apparatus according to an embodiment of the present invention;

[0022] Figure 2 Schematically shows Figure 1 A cross section of the measuring device shown in ;

[0023] Figures 3a to 3d Various flow profiles of the conditioning fluid are schematically shown;

[0024] Figure 4 The control volume is schematically shown in a three-dimensional view;

[0025] Figure 5 The control volume is schematically shown in plan view;

[0026] Figure 6 schematically illustrates leveling detection of a substrate; and

[0027] Figure 7 The horizontal alignment of the substrate is schematically shown. DETAILED DESCRIPTION

[0028] In this document, the terms "radiation" and "beam" are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm or 126 nm) and EUV (extreme ultraviolet radiation, e.g., having a wavelength in the range of about 5 nm to 100 nm).

[0029] As used herein, the terms "reticle," "mask," or "patterning device" should be broadly interpreted as referring to a general patterning device that can be used to impart an incident radiation beam with a patterned cross-section that corresponds to the desired pattern produced in a target portion of the substrate. The term "light valve" may also be used in this context. In addition to classic masks (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0030] Figure 1 A lithographic apparatus according to an embodiment of the invention is schematically shown. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam PB (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., mask table) MT configured to support a patterning device (e.g., mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to certain parameters; a substrate support (e.g., substrate table) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam PB by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0031] In operation, the illumination system IL receives a radiation beam PB from a radiation source SO (e.g., via a beam delivery system BD). The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for directing, shaping, and / or controlling the radiation. The illuminator IL may be used to condition the radiation beam PB so as to have a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0032] The term "projection system" as used herein should be broadly interpreted as covering various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic, and / or electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used and / or other factors (e.g., use of immersion liquid or use of vacuum). Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system."

[0033] The lithographic apparatus may be of a type in which at least a portion of the substrate W is covered by a liquid having a relatively high refractive index (e.g. water) to fill the space between the projection system PS and the substrate W - this is also known as immersion lithography. Further information on immersion technology is given in US 6,952,253, which is incorporated herein by reference.

[0034] The lithographic apparatus may also be of a type having two or more substrate supports WT (also referred to as a "dual stage"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and / or preparatory steps for subsequent exposure of a substrate W may be performed on a substrate W located on one substrate support WT while another substrate W located on another substrate support WT is being used to expose a pattern on the other substrate W.

[0035] In addition to the substrate support WT, the lithographic apparatus can include a measurement stage (not shown). The measurement stage is arranged to hold sensors and / or cleaning equipment. The sensors can be arranged to measure properties of the projection system PS or properties of the radiation beam PB. The measurement stage can hold multiple sensors. The cleaning equipment can be arranged to clean part of the lithographic apparatus, such as part of the projection system PS or part of the system for providing immersion liquid. The measurement stage can be moved beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0036] In operation, a radiation beam PB is incident on a patterning device MA (e.g. a mask) which is held on a mask support MT and is patterned by a pattern (design layout) present on the patterning device MA. After having passed through the patterning device MA, the radiation beam PB passes through a projection system PS which focuses the radiation beam PB onto a target portion C of a substrate W. With the aid of a second positioner PW and a position measurement system PMS, the substrate support WT can be precisely moved, for example in order to position a different target portion C in the path of the radiation beam PB at a focused and aligned position. Similarly, a first positioner PM and possibly a further position sensor (not shown) are provided. Figure 1A further position sensor (not shown explicitly in FIG) can be used to precisely position the patterning device MA relative to the path of the radiation beam PB. The patterning device MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 are shown occupying dedicated target portions C, the substrate alignment marks P1, P2 can be located in the spaces between target portions C. When the substrate alignment marks P1, P2 are located between target portions C, they are referred to as scribe lane alignment marks. Suitable techniques are described in more detail in US 2009 / 195768 A, which is incorporated herein by reference.

[0037] To illustrate the present invention, a Cartesian coordinate system is used. A Cartesian coordinate system has three axes: the x-axis, the y-axis, and the z-axis. Each of the three axes is orthogonal to the other two axes. Rotation about the x-axis is called an Rx rotation. Rotation about the y-axis is called an Ry rotation. Rotation about the z-axis is called an Rz rotation. The x-axis and the y-axis define a horizontal plane, while the z-axis is in the vertical direction. The Cartesian coordinate system does not limit the present invention and is used for illustration only. Conversely, another coordinate system (e.g., a cylindrical coordinate system) can be used to illustrate the present invention. The orientation of the Cartesian coordinate system can be different, for example, so that the z-axis has a component along the horizontal plane.

[0038] In one embodiment, Figure 1 As shown, the substrate support WT is movable to transfer a substrate W held by the substrate support WT from at least a substrate measurement position to a substrate processing position. Figure 1 In the figure, a substrate support position for holding substrate W in a processing position, i.e., a substrate processing position, is denoted by WT(P). A substrate support position for holding substrate W in a measurement position, i.e., a substrate measurement position, is denoted by WT(M). As an example, substrate measurement position WT(M) may be positioned away from downstream end E of projection system PS, while substrate processing position WT(P) may be positioned close to and / or opposite to downstream end E of projection system PS.

[0039] When the substrate support WT holds the substrate W in a processing position (i.e., substrate processing position WT(P)), the substrate W can be illuminated by the projection system PS. In particular, when the substrate W is in the substrate measurement position WT(M), the substrate W cannot be exposed by the projection system PS. Preferably, the substrate W remains at the same position on the substrate support WT during movement of the substrate support WT from a corresponding substrate measurement area (e.g., substrate measurement position WT(M)) to a corresponding substrate projection area (e.g., substrate processing position WT(P)).

[0040] For example, the substrate measurement position WT(M) and the substrate processing position WT(P) may be located in the same internal region or chamber of the apparatus—for example, within a substrate zone WZ of the apparatus. For example, an intermediate frame member 3 (e.g., a metrology frame member) in the apparatus may substantially separate this internal substrate zone WZ from one or more other apparatus regions (such as the projection system zone PZ). Alternatively, the substrate measurement position WT(M) and the substrate processing position WT(P) may be located in different zones, for example, if the substrate measurement position WT(M) is located outside the apparatus.

[0041] The movement of the substrate support WT between the desired substrate measurement position WT(M) and the substrate processing position WT(P) may be achieved in a variety of ways, as will be clear to those skilled in the art. For example, at least part of the movement may be provided by means of a second positioner PW, a substrate support conveyor and / or one or more other transport mechanisms. In another embodiment, the substrate support WT is capable of being moved from the substrate measurement position WT(M) to the substrate processing position WT(P) substantially within a single virtual or horizontal plane. As a non-limiting example, in Figure 1 In the embodiment, the substrate support can be moved in a substantially horizontal direction H, or in the XY plane, to move the substrate W from the substrate measurement position WT(M) to the substrate processing position WT(P), or vice versa, in a substantially horizontal direction or along the XY plane.

[0042] The position measurement system PMS may comprise any type of sensor suitable for determining the position of the substrate support WT. The position measurement system PMS may comprise any type of sensor suitable for determining the position of the mask support MT. The sensor may be an optical sensor, such as an interferometer or an encoder. The position measurement system PMS may comprise a combined system of an interferometer and an encoder. The sensor may also be another type of sensor, such as a magnetic sensor, a capacitive sensor or an inductive sensor. The position measurement system PMS may determine the position relative to a reference, such as the projection system PS or an intermediate frame part 3, such as a measurement frame. The position measurement system PMS may determine the position of the substrate support WT and / or the mask support MT by measuring the position or by measuring the time derivative of the position, such as a velocity or an acceleration.

[0043] The position measurement system (PMS) may include an encoder system (not shown). Encoder systems are known, for example, from US2007058173A1, which is hereby incorporated by reference. The encoder system includes an encoder head, a grating, and a sensor. The encoder system can receive a primary radiation beam and a secondary radiation beam. Both the primary radiation beam and the secondary radiation beam originate from the same radiation beam, i.e., the primary radiation beam. At least one of the primary radiation beam and the secondary radiation beam is produced by diffracting the primary radiation beam using a grating. If both the primary radiation beam and the secondary radiation beam are produced by diffracting the primary radiation beam using a grating, the primary radiation beam needs to have different diffraction orders than the secondary radiation beam. Different diffraction orders include, for example, +1, -1, +2, and -2. The encoder system optically combines the primary radiation beam and the secondary radiation beam into a combined radiation beam. A sensor in the encoder head determines the phase or phase difference of the combined radiation beam. The sensor generates a signal based on the phase or phase difference. The signal represents the position of the encoder head relative to the grating. One of the encoder head and the optical grating can be arranged on the substrate support WT. The other of the encoder head and the optical grating can be arranged on an intermediate frame component 3, such as a metrology frame or a base frame. For example, multiple encoder heads are arranged on the metrology frame, while the optical grating is arranged on the top surface of the substrate support WT. In another example, the optical grating is arranged on the bottom surface of the substrate support WT, while the encoder head is arranged below the substrate support WT.

[0044] The position measurement system PMS may comprise an interferometer system (not shown). An interferometer system is known, for example, from US Pat. No. 6,020,964, which is hereby incorporated by reference herein. The interferometer system may comprise a beam splitter, a mirror, a reference mirror and a sensor. The radiation beam is split by the beam splitter into a reference beam and a measurement beam. The measurement beam propagates to the mirror and is reflected by the mirror back to the beam splitter. The reference beam propagates to the reference mirror and is reflected by the reference mirror back to the beam splitter. At the beam splitter, the measurement beam and the reference beam are combined into a combined radiation beam. The combined radiation beam is incident on a sensor. The sensor determines the phase or frequency of the combined radiation beam. The sensor generates a signal based on the phase or frequency. The signal represents the displacement of the mirror. In one embodiment, the mirror is connected to the substrate support WT. The reference mirror may be connected to the measurement frame. In one embodiment, the measurement beam and the reference beam are combined into the combined radiation beam by additional optical components (instead of the beam splitter).

[0045] The lithographic apparatus includes a measurement device comprising optical sensors 10, 11, 12. The optical sensors 10, 11, 12 are configured or capable of measuring at least one aspect and / or property of the substrate W while the substrate support WT holds the substrate W at a substrate measurement position WT(M). Such a measurement device, which has been schematically illustrated in the accompanying drawings, can be implemented in a variety of ways. In another embodiment, the measurement device can be configured to measure or monitor the substrate W using one or more measurement beams. For example, in another embodiment, the optical sensors 10, 11, 12 can direct or emit one or more measurement beams toward the surface of the substrate W. In this case, the measurement device can also be configured to detect one or more portions of the measurement beam(s) reflected by the surface of the substrate, for example.

[0046] Here, the term "beam" should be understood broadly. The measurement beam can be a suitable radiation beam that is at least partially reflected by the surface of the substrate W to be measured. For example, the measurement beam can include a radiation beam having one or more wavelengths in the visible light range and / or a beam having one or more different radiation wavelengths.

[0047] For example, the measurement device may be configured to measure the position and / or orientation of a substrate W relative to a substrate support (or stage) WT. The position and / or orientation of the substrate W may include: a certain alignment or misalignment of the substrate W relative to the substrate support WT; one or more substrate positions measured parallel to the substrate surface; a certain tilt of the substrate W; a certain rotational position of the substrate W; the horizontality, thickness, and / or height of the substrate measured perpendicular to the substrate surface; and / or other substrate positions and / or orientations. For example, the measurement device may be configured to provide data that can be used to detect the position of the substrate W relative to the substrate support WT in six different degrees of freedom. Furthermore, the measurement device may be configured to detect the position of the substrate support WT when the substrate support WT supports the substrate W at a substrate measurement position WT(M). Furthermore, the measurement device may be provided with (predetermined) information regarding the precise position of the substrate support WT when the substrate support WT holds the substrate W at the substrate measurement position WT(M). The apparatus may include a control device that controls the measurement device and utilizes the measurement results to calculate or estimate certain aspects of the substrate W. Such controls are not shown; it will be clear to those skilled in the art how such controls may be configured.

[0048] In an embodiment, the measuring device may be provided with one or more optical sensors 12, for example, alignment sensors, for measuring the positions of substrate alignment marks P1, P2 that may be provided on the substrate W to detect whether the substrate W is aligned with a certain plane (for example, Figure 1 The position in the XY plane. Figure 2 An embodiment of an alignment sensor is schematically shown in FIG. The alignment sensor may be configured to emit one or more alignment measurement beams 9 towards a surface of a substrate W held in a substrate measurement position WT(M) and to detect reflected portions of the alignment measurement beams 9 .

[0049] A suitable optical (alignment or position) sensor 12 can utilize optical phenomena such as diffraction and interference to obtain position information from substrate alignment marks P1, P2 formed on the substrate W. An example of an alignment sensor used in current lithographic apparatus is based on a self-referencing interferometer as described in US Pat. No. 6,961,116. Various enhancements and modifications of this position sensor have been developed, such as disclosed in US Pat. No. 2015261097A1. The contents of all of these publications are hereby incorporated herein by reference.

[0050] In more detail, Figure 7 FIG. 1 is a schematic block diagram of an embodiment of a known alignment sensor AS, such as that described in US Pat. No. 6,961,116, incorporated by reference. A radiation source RSO provides a radiation beam RB of one or more wavelengths, which is directed via steering optics as an illumination spot SP onto a mark (e.g., substrate alignment marks P1, P2 located on a substrate W). In this example, the steering optics include a spot mirror SM and an objective lens OL. The diameter of the illumination spot SP illuminating the substrate alignment marks P1, P2 can be slightly smaller than the width of the substrate alignment marks P1, P2 themselves.

[0051] Radiation diffracted by the mark AM can be collimated (in this example by the objective lens OL) into an information-carrying beam IB. The term "diffraction" is intended to include zero-order diffraction from the mark (which may be referred to as reflection). For example, a self-referencing interferometer SRI of the type disclosed in the aforementioned US Pat. No. 6,961,116 can cause the information-carrying beam IB to interfere with itself, after which the information-carrying beam IB is received by a photodetector PD. In the case where the radiation source RSO generates more than one wavelength, additional optical elements (not shown) may be included to provide separate beams. The photodetector PD may be a single element, or, if desired, may include multiple pixels. The photodetector PD may include a sensor array.

[0052] The steering optical element comprising the spot reflector SM in this example may also be used to block zero-order radiation reflected from the substrate alignment marks P1, P2 so that the information-carrying beam IB comprises only higher-order diffracted radiation from the substrate alignment marks P1, P2 (this is not necessary for the measurement, but improves the signal-to-noise ratio).

[0053] The intensity signal SI is provided to the processing unit PU. By combining the optical processing in the module SRI with the computational processing in the unit PU, the values ​​of the X and Y position of the substrate W relative to the reference frame are output.

[0054] A single measurement of the type shown determines only the position of the substrate alignment marks P1, P2 within a certain range corresponding to one pitch of the substrate alignment marks P1, P2. A coarser measurement technique is used in conjunction with this to identify which period of the sine wave is the period of the sine wave that contains the marked position. The measurement process at a coarser and / or finer level can be repeated at different wavelengths to improve the accuracy and / or robustly detect the substrate alignment marks P1, P2, regardless of the material from which the substrate alignment marks P1, P2 are made and the material on which and / or below which the substrate alignment marks P1, P2 are provided. The wavelengths can be optically multiplexed and demultiplexed to be processed simultaneously, and / or the wavelengths can be multiplexed by time division multiplexing or frequency division multiplexing.

[0055] As an alternative or in addition, the measuring device may be provided with one or more optical sensors 10, 11, i.e. level sensors, for detecting a certain levelness of the substrate W held in the substrate measurement position WT(M). Figure 2 In an embodiment of the present invention, the optical sensor 10, 11, such as a level sensor, comprises a plurality of level measurement beam emitters for emitting a plurality of substantially parallel level measurement beams 8 and one or more level measurement beam detectors for detecting reflected portions of the level measurement beams 8. Figure 2 As shown, the alignment measurement beam(s) 9 and the leveling measurement beam(s) 8 can be directed towards substantially the same position m of the surface of the substrate via respective optical sensors 10, 11, 12. Alternatively, the various measurement beams 8, 9 can be directed towards different portions of the substrate. Figure 2 As shown, the incident angle of the horizontal measurement beam 8 can be significantly greater (close to 90°, for example, greater than 45°, greater than 55°, greater than 60° or greater than 70°, or up to about 80°) than the incident angle of the alignment measurement beam 9 (the incident angle is measured relative to a normal perpendicular to the surface of the substrate).

[0056] More specifically, the level sensor can be arranged to measure the topography of the top surface of a substrate (or wafer) W. From these measurements, a topography map of the substrate W, also known as a height map, can be generated that indicates the height of the substrate W as a function of position on the substrate W. This height map can then be used to calibrate the position of the substrate W during pattern transfer to the substrate W, so as to provide an aerial image of the patterning device MA at a properly focused position on the substrate W. It will be understood that "height" in this context refers to a dimension that is significantly out of the plane of the substrate W (also known as the Z-axis). Typically, the level or height sensor performs measurements at a fixed position (relative to its own optical system), and relative motion between the substrate W and a measurement device including the level sensor results in height measurements at positions across the substrate W.

[0057] Examples of level or height sensors LS in the prior art are as follows: Figure 6 Schematically, Figure 6 Only the operating principle is illustrated. In this example, the sensor LS includes an optical system comprising a projection unit LSP serving as an optical sensor 10, i.e., a level measurement beam emitter, and a detection unit LSD serving as an optical sensor 11, i.e., a level measurement beam detector. The projection unit LSP may include a radiation source LSO providing a radiation beam LSB, which is imparted by a projection grating PGR of the projection unit LSP. The radiation source LSO may be, for example, a narrowband or broadband radiation source such as a supercontinuum light source, or a polarized or unpolarized, pulsed or continuous radiation source, such as a polarized or unpolarized laser beam. The radiation source LSO may include multiple radiation sources of different colors or wavelength ranges, such as multiple LEDs. The radiation source LSO of the level sensor LS is not limited to visible radiation but may additionally or alternatively include ultraviolet (UV) and / or infrared (IR) radiation, as well as any wavelength range suitable for reflection from the surface of the substrate W.

[0058] The projection grating PGR is a periodic grating comprising a periodic structure that results in a radiation beam BE1 having a periodically varying intensity. The radiation beam BE1 having a periodically varying intensity is directed toward a measurement position m located on a substrate W at an angle of incidence ANG between 0 and 90 degrees, typically between 70 and 80 degrees, relative to an axis perpendicular to the surface of the substrate (the Z axis). At the measurement position m, the patterned radiation beam BE1 is reflected by the substrate W (indicated by arrow BE2) and directed toward a detection unit LSD.

[0059] To determine the height level at the measurement location m, the level sensor LS further includes a detection system comprising a detection grating DGR, a detector DET, and a processing unit (not shown) for processing an output signal of the detector DET. The detection grating DGR can be identical to the projection grating PGR. The detector DET generates a detector output signal indicative of received light, for example, the intensity of the received light (e.g., with a photodetector) or the spatial distribution of the received intensity (e.g., with a camera). The detector DET can include any combination of one or more detector types.

[0060] By means of triangulation techniques the height level at the measurement position m can be determined. The detected height level is generally related to the signal strength measured by the detector DET, which has a periodicity that depends, among other factors, on the design of the projection grating PGR and the (tilted) angle of incidence ANG.

[0061] The projection unit LSP and / or the detection unit LSD may further comprise other optical elements, such as lenses and / or mirrors, along the path of the patterned radiation beam between the projection grating PGR and the detection grating DGR (not shown).

[0062] In an embodiment, the detection grating DGR can be omitted and the detector DET can be placed at the location of the detection grating DGR. This configuration provides a more direct detection of the image of the projection grating PGR.

[0063] To effectively cover the surface of the substrate W, the level sensor LS may be configured to project an array of measurement beams BE1 onto the surface of the substrate W, thereby generating an array of measurement regions m or spots covering a larger measurement range.

[0064] Common types of height sensors are disclosed, for example, in US Pat. No. 7,265,364 and US Pat. No. 7,646,471, both of which are incorporated herein by reference. A height sensor that uses ultraviolet radiation instead of visible or infrared radiation is disclosed in US Pat. No. 2010,233,600 A1, which is incorporated herein by reference. In WO 2016,102,127 A1, incorporated herein by reference, a compact height sensor is described that uses a multi-element detector to detect and identify the position of a grating image without requiring a detection grating.

[0065] The measuring device may also be provided with one or more other sensors, such as one or more planar encoders (not shown). Furthermore, where the measuring device is configured to use one or more measuring fields, the measuring device may comprise one or more suitable field generators, such as one or more electromagnetic field generators where the measuring field is an electromagnetic field, as will be clear to a person skilled in the art.

[0066] The measurement device may provide a remote sensing device for detecting the position and / or orientation of the substrate W before the substrate W is irradiated by the projection system PS. In particular, the results of the measurement of the position and / or orientation of the substrate W relative to the substrate support WT may be used to focus and / or direct the patterned radiation beam PB onto a desired portion of the substrate W, to position the substrate support WT relative to the patterned radiation beam PB, or to be used in a different manner. In another embodiment, the substrate W is not repositioned relative to the substrate support WT during the time from when the measurement device measures or detects the position / orientation of the substrate to when the projection system PS has projected the radiation beam PB onto the substrate W. In this case, the measurement results of the present measurement system are not used to (re)align the substrate W relative to the substrate support WT in this way.

[0067] Alternatively, the measurements of the measurement system are used to (re)align the substrate W relative to the substrate support WT before the patterned radiation beam PB is projected onto the substrate W.

[0068] The optical sensors 10, 11, 12 are capable of performing a plurality of different measurement processes. Depending on the measurement process, the measurement device can be moved at different speeds v relative to the substrate W (note that the speed v is to be understood in a relative sense, i.e., the substrate W or the measurement device can be considered to be "moving" relative to the reference frame). Specifically, during a first measurement process, the measurement device is moved at a first speed v relative to the substrate W. and during the second measurement process, the measuring device moves relative to the substrate W at a second speed move.

[0069] Considering the balance between measurement accuracy and the time it takes to complete the measurement process, different measurement processes may desirably be performed at different speeds v. That is, generally speaking, if sufficient accuracy can be reliably achieved, it may be desirable to perform the measurement process at the highest possible speed v. For example, horizontal sensing (e.g., measuring the topography of the surface of the substrate W) may be performed at a higher speed v than horizontal alignment (e.g., detecting substrate alignment marks P1, P2 located on the surface of the substrate W).

[0070] However, given the required degree of measurement accuracy, it has been found that the flow of the fluid (whether liquid or gas) through which the beams 8 and 9 pass can produce significant variations in the fluid's refractive index, significantly reducing measurement accuracy. For example, when the measurement apparatus moves at a relatively high velocity v relative to the substrate W, there is a significant backflow of the fluid from outside the slit S toward the vicinity of position m on the surface of the substrate W where the beams 8 and 9 are incident. At such a high velocity v, the fluid flow within the slit S and near position m may even become turbulent. This backflow and turbulence can be unpredictable and may induce drastic variations in the fluid's refractive index, thereby reducing measurement accuracy.

[0071] Therefore, it may be necessary to provide passive means or barriers to prevent ambient fluid from reaching the paths of the measurement beams 8, 9, or to reduce the likelihood that ambient fluid can reach these paths. Therefore, the measurement device is provided with a supply of a conditioning fluid F. In an embodiment, the fluid supply may be provided by a conditioning system 50 of the lithographic apparatus. The conditioning fluid F may be used to condition at least part of the paths of the measurement beams 8, 9 of the measurement device. An embodiment of such a conditioning system is schematically depicted in FIG. Figure 1 and Figure 2 .

[0072] like Figure 2 As shown, the measuring device is configured to supply a conditioning fluid F such that the conditioning fluid F crosses the light beams 8, 9 and flows in a gap S between the measuring device and the surface of the substrate W. More specifically, the measuring device may comprise a space-filling and / or space-enclosing body 4 having a fluid flow control surface 14. The fluid flow control surface 14 extends opposite the substrate measurement position WT(M) (see FIG. Figure 2 ). The fluid flow control surface 14 may be arranged to provide or enclose a slit S together with at least a substrate surface portion of a substrate W held at the substrate measurement position WT(M), said substrate surface portion facing away from the substrate support WT and receiving the measurement beam 8, 9 of the measurement device during use. The fluid flow control surface 14 may extend substantially parallel to the substrate surface of the substrate W held at the substrate measurement position WT(M). The fluid flow control surface 14 may extend opposite to the entire surface of the substrate W located in the substrate measurement position WT(M) and optionally opposite to at least a surface portion of the opposing substrate support WT. In this way, a relatively long, narrow slit S may be provided between the surface of the substrate W and the space-filling and / or space-enclosing body 4.

[0073] Such a fluid flow control surface 14 can be arranged and configured in a variety of ways. For example, in addition to the openings 141, the fluid flow control surface 14 can be a substantially flat, substantially continuous or uninterrupted plane, through which the conditioning fluid F enters the slit S from the space-filling / space-enclosing body 4 and the light beams 8, 9 are transmitted between the optical sensors 10, 11, 12 and the surface of the substrate W through the openings 141. The fluid flow control surface 14 can also be interrupted by other features as needed. Although the fluid flow control surface 14 can be substantially flat, the fluid flow control surface 14 does not need to be smooth at the microscopic level and can have smaller surface features. For example, the fluid flow control surface 14 can be contoured, including smaller fluid guiding grooves and / or including a protrusion, for example to guide the fluid to flow in a desired direction along the fluid flow control surface 14.

[0074] As described above, the measuring device moves relative to the substrate W at a first speed When moving, the measuring device performs a first measurement process, and the measuring device moves at a second speed higher than the first speed relative to the substrate W. While moving, the measuring device performs a second measurement process. The first measurement process may be an alignment process, in which the positions of substrate alignment marks P1 and P2 located on the substrate W are measured. The measurement of the positions of substrate alignment marks P1 and P2 located on the substrate W may be performed at a speed low enough to be considered quasi-static. The second measurement process may be a horizontal sensing process, in which the topography of the surface of the substrate W is measured. The measurement of the topography of the surface of the substrate W may be performed at a higher speed, for example, up to approximately 3.0 m / s or 4.5 m / s.

[0075] Therefore, a simplified solution to provide a barrier to the ambient fluid flow can be to supply the conditioning fluid F at a sufficiently high flow rate so that the fluid conditions (e.g., refractive index) in the path of the light beams 8, 9 are primarily determined by the supply of the conditioning fluid F, and disturbances from the ambient fluid can be largely excluded. This can improve the consistency and predictability of the fluid conditions across different measurement processes, which can be calibrated accordingly.

[0076] However, as the inventors have discovered, this simplified solution has drawbacks. Although the conditioning fluid F can be provided at an arbitrarily high flow rate to maximize the removal or cancellation of disturbances from the ambient fluid located in the slit S, such a higher flow rate can generate turbulence within the space-filling / surrounding body 4. For example, Figure 2As shown, conditioning fluid F can be supplied via fluid channel 40, which can be constricted and / or have bends that tend to generate turbulence. Specifically, a screen 26 can be positioned within fluid channel 40 to provide a more uniform flow profile, but this can also create turbulence if the flow rate is too high. Some measurement processes are particularly sensitive to such turbulence. In other measurement processes, such turbulence may be tolerable provided the desired measurement accuracy can still be achieved.

[0077] Therefore, it is desirable to supply the conditioning fluid F in an adaptive manner. Specifically, the fluid supply device is configured to supply the conditioning fluid F at a first flow rate during the first measurement process. The regulating fluid F is supplied and during the second measurement process is supplied at a second flow rate higher than the first flow rate. Supply conditioning fluid F. Thus, at higher speeds During the second measurement, a higher flow rate The conditioning fluid F is supplied so that the fluid conditions in the slit S can be largely isolated from the disturbances caused by the ambient fluid. During the first measurement performed under low flow The conditioning fluid F is supplied so that the generation of turbulence in the fluid channel 40 is limited or completely avoided.

[0078] As previously mentioned, the optical sensor may include an optical sensor 12, for example, an alignment sensor, which is configured to detect a mark located on the surface of the substrate W for horizontal alignment. In addition, it may be necessary to perform this horizontal alignment at a quasi-static speed v to obtain the necessary measurement accuracy. As discovered by the present inventors, this type of alignment is particularly sensitive to turbulence generated in the fluid channel 40 (due to the quasi-static speed v, the disturbance from the ambient fluid may be small). Therefore, it is possible to perform the horizontal alignment at a lower speed of the regulating fluid F. and lower flow The following performs a horizontal alignment as the first measurement process.

[0079] As previously mentioned, the optical sensors 10, 11 may include a level sensor for measuring the topography of the surface of the substrate W. This level sensing may desirably be performed at a relatively high speed v (e.g., up to 3.0 m / s to 4.5 m / s) to save time. As discovered by the present inventors, such level sensing may be primarily sensitive to disturbances from the ambient fluid and less sensitive to turbulence generated within the fluid channel 40. Thus, it may be possible to perform level sensing at relatively high speeds of the conditioning fluid F. and higher flow Level sensing is performed as the second measurement process.

[0080] See also Figures 3a to 3dThe effect of regulating the flow rate of fluid F can be understood in more detail. Figure 3a The following illustrates a scenario in which the substrate W is stationary (or quasi-stationary) relative to the measurement apparatus. A lower flow rate of the conditioning fluid F is employed, resulting in a lower flow velocity within the slit S. Applying the no-slip condition (whereby the viscous fluid at the solid boundary is considered to have negligible or zero velocity relative to the solid boundary), the flow velocity at the fluid flow control surface 14 and the flow velocity at the surface of the substrate W are zero. Figure 3b The diagram shows a scenario where a relatively low flow rate is maintained, but the substrate W is moving relative to the measurement device at a velocity v (to the right, as indicated by the arrow). With the measurement device as the reference frame, the no-slip condition applies, with the flow velocity at the fluid flow control surface 14 being zero and the flow velocity at the surface of the substrate W being v. As can be seen, a backflow of ambient fluid occurs to the left of the measurement position m. The lower flow rate of conditioning fluid F slightly reduces this backflow, but the overall flow profile remains in the backflow direction. This results in a significant amount of ambient fluid from outside the slit S entering the vicinity of the measurement position m.

[0081] Figure 3c A scenario is shown in which the substrate W is stationary (or quasi-stationary) relative to the measurement device. A higher flow rate of the conditioning fluid F is used, resulting in a higher flow velocity in the slit S. Due to the no-slip condition, the flow velocity at the surface of the fluid flow control surface 14 and the substrate W remains zero. Figure 3d A scenario is shown in which a higher flow rate is maintained but the substrate W is moved relative to the measuring device at a speed v (to the right as indicated by the arrow). Figure 3b As in the scenario shown in , using the reference frame of the measurement device and applying the no-slip condition, the flow velocity at the fluid flow control surface 14 is zero, and the flow velocity at the surface of the substrate W is v. However, Figure 3b In contrast, the higher flow rate of conditioning fluid F effectively suppresses backflow of ambient fluid. Specifically, backflow occurs only in a thin layer near the surface of the substrate W, while the majority of the fluid flow is directed away from the measurement location m. Consequently, the amount of ambient fluid drawn toward the measurement location m is reduced. In contrast, the majority of the fluid flow within the slit S consists of the conditioning fluid F, which flows outward away from the measurement location m. Consequently, fluid conditions (e.g., refractive index) near the measurement location m are stable and repeatable, and the optical sensors 10, 11, and 12 can be calibrated accordingly to obtain reliable and accurate measurement results without sacrificing measurement speed.

[0082] The composition of the conditioning fluid F can be substantially identical to that of the ambient fluid. This can be desirable because, even when a relatively high flow rate of the conditioning fluid F is applied, a small amount of backflow of the ambient fluid can still occur. Therefore, by closely matching the conditioning fluid F to the ambient fluid, the fluid conditions (e.g., refractive index) near the measurement location m can be further stabilized. Of course, in addition to matching the composition, the temperature can also be matched.

[0083] The ambient fluid may be a gas or air that may be normally present in the substrate zone WZ of the apparatus. For example, such an ambient fluid may include gas originating from one or more gas showers 30 that may be used to direct gas to some other area of ​​the apparatus than to the area of ​​the substrate measurement position WT(M). As an example, the one or more gas showers 30 may be provided for adjusting one or more interferometer beams IFB of the interferometer system IF (see Figure 1 and Figure 2 ).

[0084] As mentioned above, the conditioning fluid F can be provided by the conditioning system 50 of the lithographic apparatus. The conditioning fluid F can similarly be gas or air. Specifically, the conditioning fluid F can be a controlled gas or a mixed gas, such as preferably dry ultra-clean air, or one or more inert gases.

[0085] Furthermore, in particular when the conditioning system is configured to thermally condition the conditioning fluid F, the conditioning system can be configured to provide a thermally controlled conditioning fluid F. As an example, the conditioning system can include: a heating and / or cooling system (not shown) for heating and / or cooling the conditioning fluid F, one or more temperature sensors for measuring the temperature of the conditioning fluid F, and a control system for controlling the heating and / or cooling system to heat and / or cool the conditioning fluid F to a desired and / or predetermined stable conditioning temperature. Furthermore, the conditioning system can include one or more fluid lines 23, 24 (e.g., Figure 1 ) and a fluid pump for pumping the regulating fluid F to desired locations and / or removing or extracting the regulating fluid F from these locations. Figure 1 The conditioning system 50 in FIG. 1 schematically indicates a portion of a fluid conditioning system that may include the aforementioned heating and / or cooling system, control system, temperature sensor, and pump. It will be apparent to those skilled in the art how the different portions of the conditioning system 50 may be configured and arranged.

[0086] The space-filling and / or space-enclosing body 4 can be constructed in various ways and using various materials. For example, the body 4 can be a substantially solid body, structure, plate and / or element, or the body 4 can be a body, structure, plate and / or element that is at least partially hollow. In addition, unless otherwise specifically stated, the space-filling and / or space-enclosing body 4 can have a substantially fluid-tight or sealed outer surface. In an embodiment, the space-filling and / or space-enclosing body 4 is mounted on an intermediate frame component 3 of the device, which separates an internal area of ​​the device, such as the substrate area WZ, from another internal area of ​​the device, such as the projection system area PZ. For example, the space-filling and / or space-enclosing body 4 can be integrally connected to or fixed to the intermediate frame component 3 of the device, or made into one component with the intermediate frame component 3. The space-filling and / or space-enclosing body 4 can be made of one or more metals, plastics, alloys and / or combinations of these materials or other materials.

[0087] In one embodiment, during use, the closest spacing between the fluid flow control surface 14 of the body 4 and the surface of the substrate (see Figure 2 ), or the width R of the slit S between the fluid flow control surface 14 and the surface of the substrate, is less than about 10 mm. For example, the closest distance between the fluid flow control surface 14 and the surface of the substrate, or the slit width R, can be in the range of about 1 mm to 5 mm or about 1 mm to 2 mm. For example, the slit width R can be about 2.5 mm. Alternatively, the closest distance, or the slit width R, can be less than about 2.5 mm or less than about 1 mm. More generally, it is desirable to minimize the slit width R as long as potential collisions between the measurement device and the substrate W are avoided. This is because a smaller slit width R can allow disturbances from the ambient fluid to be eliminated with a smaller flow rate Q1, Q2 of the regulating fluid. The slit S can have a constant width R over part or all of the fluid flow control surface 14. As previously described, the fluid flow control surface 14 can be substantially flat and can include relatively small surface features.

[0088] like Figure 2 As shown, the space-filling and / or space-enclosing body 4 can accommodate one or more of the optical sensors 10, 11, 12 and / or the field generator of the measurement device. Furthermore, for example, in this embodiment, the space-filling and / or space-enclosing body 4 can include one or more measurement beam channels 5 for allowing at least one measurement beam 8 of the measurement device to pass through at least a portion of the body 4 between the optical sensors 10, 11, 12 and the opening 141 in the fluid flow control surface 14. It will be clear to those skilled in the art how the measurement beam channels 5 can be configured according to the corresponding measurement beam 8.

[0089] The measuring beam channel 5 can at least partially coexist with the fluid channel 40. For example, Figure 2 As shown, the measuring beam channel 5 of the optical sensor 10 can partially coexist with the fluid channel 40 shown on the left. Similarly, the measuring beam channel 5 of the optical sensor 11 can also partially coexist with the fluid channel 40 shown on the right.

[0090] In an embodiment where a plurality of fluid channels 40 are provided, the fluid channels 40 can guide all of the regulating fluid F to the opening 141 surrounding the measurement position m. In addition, each fluid channel 40 can be used to guide a portion of the total flow rate Q of the regulating fluid F. For example, Figure 2 The two fluid channels 40 shown can be respectively A and Q B Direct the fluid flow, where Q A With Q B The sum of the total flow rate Q is provided. In an embodiment, more than two fluid channels 40 may be provided, and each such fluid channel 40 may guide a portion of the total flow rate Q. Therefore, the first flow rate referred to herein is and the second flow Refers to the total flow rate through the opening 141 during the corresponding measurement process, regardless of the number of fluid channels 40 provided. Unless otherwise specified, the flow rate used herein is and It can be a volume flow rate (eg, in liters per minute, measured at standard atmospheric pressure (1.01325 bar) and a temperature of 0°C), or a mass flow rate (eg, in grams per minute).

[0091] In general, where multiple fluid channels 40 are provided, it may be desirable to have unequal portions of the total flow Q pass through different fluid channels 40. Figure 2 In the example shown, Q A With Q B can be different (and add up to Q). This asymmetry can help avoid the formation of a stagnation point at the measurement location m. Specifically, Q A :Q B (or Q B :Q A ) can follow a 30:70 split, a 35:65 split, a 40:60 split, or a 45:55 split.

[0092] The screen 26 may be arranged at a position such that the conditioning fluid F passes through it before entering the concurrent portion of the measurement beam 8 / fluid channel 40. For example, the screen 26 may be provided directly at the position where the conditioning fluid F enters the concurrent portion.

[0093] The screen 26 may comprise a porous material, a suitable gas disperser, a monofilament cloth or fabric, one or more sheets with ventilation openings, or various fluid distribution devices. In embodiments of the present invention, the thickness of the screen 26 may be less than approximately 1 mm. For example, the thickness of the screen 26 may be approximately 0.5 mm or less. The sheet may also be a metal sheet or alloy sheet, such as stainless steel. In this case, relatively small fluid channels can be manufactured with high precision using laser drilling. The fluid channels 40 may also be manufactured using various techniques. The screen 26 may also be made of plastic or one or more different materials. In addition to laser drilling, various manufacturing methods may be used to provide the channels in the screen 26, such as etching channels, creating channels by electro-discharge machining, and / or using various processes such as depositing metal on a mask. The screen 26 may also be referred to as a "microscreen." The screen 26 may comprise one or more layers of one or more materials. The screen 26 may be or provide space-filling and / or space-enclosing walls or wall portions of the body 4. The fluid channels in the screen 26 may have various diameters or sizes. For example, the diameter or width of each channel may be less than approximately 0.2 mm. For example, the diameter or width may be less than 0.1 mm. Good results are obtained when the diameter or width of each channel is about 0.08 mm and the conditioning fluid F is a gas or a gas mixture.

[0094] As previously mentioned, see Figures 3a to 3d As mentioned, when the measuring device moves relative to the substrate W, in particular during fast movement, a certain flow rate of the conditioning fluid F may be required to be sufficient to counteract disturbances from the ambient fluid.

[0095] For example, the second flow rate (ie, the higher flow rate) can be is set so that the average fluid velocity in the region having a substantially constant slit width R is at least the second velocity (ie, the higher velocity) The average fluid velocity may be about 70%, for example, 80%, 90%, 100%, 110%, 120%, 130% or 140%, or up to about 150%. As used herein, "average fluid velocity" may refer to the (scalar) velocity of the fluid averaged over the volume of space occupied by a region having a substantially constant slit width R. Mathematically, the average fluid velocity may be expressed as:

[0096] where G is the volume of space occupied by a region of substantially constant slit width R, and u is the local scalar fluid velocity at different points within G.

[0097] For another example, the second flow rate (ie, higher flow rate) may be The average fluid velocity in the region having a substantially constant slit width R is set to be at least about 2.2 m / s, such as 2.4 m / s, 2.6 m / s, 2.8 m / s, 3.0 m / s, 3.2 m / s, 3.5 m / s, or 4.0 m / s, or up to about 4.5 m / s. This velocity range may correspond to a second velocity of the measurement device relative to the substrate W. .

[0098] For another definition of flow Q, please refer to Figure 4 . As shown in the figure, the control volume CV is defined by intersecting a (imaginary) cylinder with the slit S. If the fluid flow control surface 14 is flat and parallel to the surface of the substrate W, the control volume CV has the shape of a cylinder. Otherwise, the top surface of the control volume CV can follow the morphology of the fluid flow control surface 14. The cylinder has a radius r and has a rotation axis that is perpendicular to the surface of the substrate W and passes through the measurement position m. The radius r can be of any value as long as the cylindrical surface of the control volume CV is completely enclosed in a region with a substantially constant slit width R. In the case where the radius r is minimum, the radius r can be large enough only for the control volume CV to enclose the opening 141. In the case where the radius r is maximum, the radius r can be such that the control volume CV does not extend beyond the range 142 of the region of constant slit width R. As Figure 5 As shown, the radius r can have a value somewhere between the above extreme values. The surface area of ​​the cylindrical surface is A(r), which is equal to 2πrR when the fluid flow control surface 14 is flat and parallel to the surface of the substrate W.

[0099] like Figure 4 and Figure 5 As shown, the total flow Q of the regulating fluid F enters the control volume CV through the opening 141. In the example shown, the total flow Q consists of two parts Q A and Q B Composition, two parts Q A and Q B pass Figure 2 , the two fluid channels 40 shown in FIG. Therefore, the flow rate out of the control volume CV through the cylindrical surface is equal to the total flow rate Q entering. Accordingly, assuming a constant fluid density, the average flow velocity out of the cylindrical surface is Q / A(r), where Q is the volume flow rate. This average flow velocity is at its maximum when the radius r is at its minimum.

[0100] like Figure 3b and 3d As shown in , the return flow velocity is at most v, where v is the velocity of the substrate W relative to the measuring device. In order to fully counteract the return flow, the average flow velocity flowing out through the cylindrical surface is can be set to be comparable to v. In other words, Q can be set so that the dimensionless parameter Q / (A(r)×v) is approximately 1. For example, Q / (A(r)×v) can be at least approximately 0.7, for example, approximately 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or 1.4, or up to approximately 1.5. In the case where r is at its minimum value (i.e., the control volume CV is just large enough to surround the opening 141), Q / (A(r)×v) can be set to these values.

[0101] As mentioned above, the second measurement process is performed at a higher speed than the first measurement process. The second flow rate of the regulating fluid F is higher than that of the first measurement process. Accordingly, the second flow rate can be set according to v2 using the above method. .

[0102] Alternatively, the average flow velocity out of the cylindrical surface can be calculated based on Setting the expected range For example, you can Set so that At least 2.2 m / s, such as 2.4 m / s, 2.6 m / s, 2.8 m / s, 3.0 m / s, 3.2 m / s, 3.5 m / s or 4.5 m / s, or up to about 4.5 m / s. This speed range may correspond to a second speed v2 of the measurement device relative to the substrate W.

[0103] After the substrate measurement process, the substrate W may be transferred to a substrate processing position WT(P), and a patterned radiation beam PB patterned by the patterning device MA may be projected onto the substrate W. Here, the results of the detection of at least one aspect, property, position and / or orientation of the substrate W may be used to accurately project the patterned radiation beam PB onto the substrate W.

[0104] Furthermore, in another embodiment, the results of the detection of at least one aspect, property, position and / or orientation of the substrate W may be used for aligning the substrate W relative to the projection system PS for projecting the patterned radiation beam PB onto the substrate W. Furthermore, in yet another embodiment, the results of the detection or measurement of the position and / or orientation of the substrate W may be used for aligning the substrate W relative to said mask support MT configured to support the patterning device MA, or relative to the patterning device MA.

[0105] In this way, measurement errors of the measurement system can be reduced and devices can be manufactured with higher precision. As previously mentioned, in another embodiment, the substrate W does not have to be repositioned relative to the substrate support WT during the time from the measurement device measuring or detecting the position / orientation of the substrate to the projection system PS having projected the radiation beam PB onto the substrate W.

[0106] Although the above disclosure relates to providing a conditioning fluid F in a slit S between a fluid flow control surface 14 and the surface of a substrate W, the present invention may alternatively or additionally be applied to other scenarios. For example, as previously described, an encoder (not shown) may be used to implement a position measurement system PMS for determining the position of a substrate support WT, such as in the first and second measurement processes described above, in which the optical sensors 10, 11, 12 measure the surface of the substrate W. Thus, the encoder head may also be moved relative to the encoder's grating at a first speed. and second speed Movement. Similar to the measuring device, the trade-off between excluding disturbances from the ambient fluid and avoiding the generation of turbulence in the internal channel can also be applied to the encoder. Accordingly, the encoder head can also be provided with a position corresponding to the first speed and second speed The process is performed under different flow rates of the regulating fluid to control the flow conditions in the space between the encoder head and the grating. In other words, for slow or quasi-static motion, a low flow rate of the regulating fluid can be provided. Conversely, for fast motion, a high flow rate of the regulating fluid can be provided.

[0107] Although specific reference may be made herein to the use of lithographic apparatus in the manufacture of integrated circuits, it should be understood that the lithographic apparatus described herein may also have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0108] While specific reference may be made herein to embodiments of the present invention in the context of lithographic equipment, embodiments of the present invention may also be applied to other equipment. Embodiments of the present invention may form part of mask inspection equipment, metrology equipment, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These equipment may be collectively referred to as lithographic tools. Such lithographic tools may operate under vacuum or ambient (non-vacuum) conditions.

[0109] Although specific reference may have been made above to the application of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention is not limited to the field of optical lithography and may be used in other applications such as imprint lithography, where the context permits.

[0110] Where context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium, which can be read and executed by one or more processors. A machine-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, machine-readable media may include read-only memory (ROM); random-access memory (RAM); magnetic storage media; optical storage media; flash memory devices; and electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.). Furthermore, firmware, software, routines, and instructions may be described herein as performing specific actions. However, it should be understood that such descriptions are merely for convenience and that such actions are actually performed by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., and that, during execution, they may cause actuators or other devices to interact with the physical world.

[0111] Various aspects of the invention are set out in the following numbered aspects:

[0112] 1. A measurement apparatus for measuring a substrate (W) in a lithographic apparatus, the measurement apparatus comprising:

[0113] an optical sensor (10, 11, 12) configured to measure a surface of a substrate (W) by emitting a light beam (8, 9);

[0114] a fluid supply device configured to supply a conditioning fluid (F) that traverses the light beam and flows in a slit (S) between the measurement device and the surface of the substrate;

[0115] The optical sensor is configured to: when the measuring device is at a first speed ( ) is moved relative to the substrate, and the measuring device is moved at a second speed ( ) performing a second measurement process while moving relative to the substrate;

[0116] The fluid supply device is configured to: during the first measurement process, supply the fluid at a first flow rate ( ) supplies the regulating fluid, and during the second measurement process supplies the regulating fluid at a second flow rate ( )Supply regulating fluid.

[0117] 2. The measuring device according to clause 1, wherein the optical sensor (12) comprises an alignment sensor configured to detect a mark located on the surface of the substrate.

[0118] 3. The measurement apparatus according to clause 2, wherein the alignment sensor is configured to emit a light beam that is substantially perpendicular to the surface of the substrate.

[0119] 4. The measuring device according to any one of the preceding aspects, wherein the optical sensor (10, 11) comprises a level sensor configured to measure the topography of the surface of the substrate.

[0120] 5. The measurement apparatus according to clause 4, wherein the level sensor is configured to emit a light beam at an angle of incidence greater than 45°, desirably between 70° and 80°, relative to a normal to the surface of the substrate.

[0121] 6. The measurement device according to any of the preceding aspects, comprising a plurality of optical sensors configured to emit respective light beams to substantially the same position (m) on the surface of the substrate.

[0122] 7. The measuring device according to any of the preceding aspects, wherein the conditioning fluid is a gas.

[0123] 8. The measurement device according to aspect 7, wherein the conditioning fluid comprises gas or air, ideally ultra-clean dry air or one or more inert gases.

[0124] 9. The measuring device according to aspect 8, wherein the fluid supply device is configured to supply air having a composition substantially the same as that of ambient air as the conditioning fluid.

[0125] 10. The measurement device according to any of the preceding aspects, wherein a slit between the measurement device and the surface of the substrate comprises a region having a substantially constant slit width R.

[0126] 11. The measuring device according to aspect 10, wherein the second flow rate ( ) is set so that the average fluid velocity in the region having a substantially constant slit width is approximately 70% to 150% of the second velocity (v2).

[0127] 12. The measuring device according to aspect 10 or 11, wherein the second flow rate is set so that the average fluid velocity in the region having the substantially constant slit width is between 2.2 m / s and 4.5 m / s.

[0128] 13. The measuring device according to aspect 10, wherein the second flow rate is set to the following range:

[0129] ,

[0130] Wherein, Q2 is the second flow rate, which is a volume flow rate;

[0131] v2 is the second speed;

[0132] A(r) is the area of ​​the cylindrical surface of the portion where an imaginary cylinder (CV) of radius r intersects the slit, wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W), and r has a value such that the area A(r) is completely enclosed within the region having the substantially constant slit width.

[0133] 14. The measuring device according to aspect 10, wherein: Between 2.2 m / s and 4.5 m / s, where is a second flow rate, wherein the second flow rate is a volume flow rate;

[0134] A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) of radius r that intersects the slit, wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W), and r has a value such that the area A(r) is completely enclosed within the region of substantially constant slit width.

[0135] 15. A lithographic apparatus comprising the measurement device according to any one of the preceding aspects.

[0136] 16. A method for measuring a substrate in a lithographic apparatus using a measurement device, comprising:

[0137] emitting a light beam (8, 9) toward the surface of the substrate (W); and

[0138] supplying a conditioning fluid (F) that traverses the light beam and flows in a slit (S) adjacent the surface of the substrate;

[0139] During the first measurement process at a first speed ( ) moves the substrate relative to the beam and at a first flow rate ( ) supplying a regulating fluid;

[0140] During the second measurement process, the substrate is moved relative to the light beam at a second speed (v2) higher than the first speed, while the substrate is moved relative to the light beam at a second flow rate (v3) higher than the first flow rate. )Supply regulating fluid.

[0141] 17. The method of clause 16, wherein the first measurement process comprises measuring a position of an alignment mark located on the substrate.

[0142] 18. The method of clause 16 or 17, wherein the second measurement process comprises measuring the topography of the surface of the substrate.

[0143] 19. The method according to any one of clauses 16 to 18, wherein the first measurement process and the second measurement process measure the substrate at substantially the same position (m).

[0144] 20. The method of any one of aspects 16 to 19, wherein the conditioning fluid is a gas.

[0145] 21. The method of aspect 20, wherein the conditioning fluid comprises air, ideally ultra-clean dry air, or one or more inert gases.

[0146] 22. The method of aspect 21, wherein the conditioning fluid has substantially the same composition as ambient air.

[0147] 23. The method of any one of clauses 18 to 22, wherein the slit comprises a region (R) having a substantially constant slit width.

[0148] 24. The method according to aspect 22, wherein the second flow rate ( ) is set so that the average fluid velocity in the region having a substantially constant slit width is approximately the second velocity ( ) of 70% to 150%.

[0149] 25. The method of clause 23, wherein the second flow rate is set such that the average fluid velocity in the region of substantially constant slot width is between 2.2 m / s and 4.5 m / s.

[0150] 26. The method according to aspect 23, wherein the second flow rate is set to the following range:

[0151] ;

[0152] in, is a second flow rate, wherein the second flow rate is a volume flow rate;

[0153] is the second speed;

[0154] A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) of radius r that intersects the slit, wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W), and r has a value such that the area A(r) is completely enclosed within a region having a substantially constant slit width.

[0155] 27. The method according to aspect 23, wherein: Between 2.2 m / s and 4.5 m / s,

[0156] in, is a second flow rate, wherein the second flow rate is a volume flow rate;

[0157] A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) of radius r that intersects the slit, wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W), and r has a value such that the area A(r) is completely enclosed within a region having a substantially constant slit width.

[0158] 28. A method of manufacturing a device comprising the method according to any one of clauses 16 to 27.

[0159] Although specific embodiments of the present invention have been described above, it will be appreciated that the present invention may be implemented in ways other than those described. The foregoing description is intended to be illustrative and not restrictive. Accordingly, those skilled in the art will appreciate that modifications may be made to the described invention without departing from the scope of the claims described below.

Claims

1. A measurement apparatus for measuring a substrate (W) in a lithographic apparatus, the measurement apparatus comprising: an optical sensor (10, 11, 12) configured to measure the surface of the substrate (W) by emitting a light beam (8, 9); and a fluid supply device configured to supply a conditioning fluid (F) that crosses the light beam and flows in a slit (S) between the measurement device and the surface of the substrate; Wherein, the optical sensor is configured to: when the measuring device is at a first speed ( ) is moved relative to the substrate, and the measuring device is moved at a second speed ( ) performing a second measurement process while moving relative to the substrate; The fluid supply device is configured to: supply the fluid at a first flow rate ( ) supplies the conditioning fluid, and during the second measurement process at a second flow rate ( ) supplies the regulating fluid.

2. The measuring device according to claim 1, wherein The optical sensor (12) comprises an alignment sensor configured to detect a mark located on the surface of the substrate, desirably wherein the alignment sensor is configured to emit a light beam substantially perpendicular to the surface of the substrate.

3. The measuring device according to claim 1 , wherein The optical sensor (10, 11) comprises a level sensor configured to measure the topography of the surface of the substrate, and / or comprises a plurality of optical sensors configured to emit respective light beams toward substantially the same position (m) on the surface of the substrate, and / or wherein the conditioning fluid is a gas.

4. The measuring device according to claim 3, wherein The level sensor is configured to emit a light beam at an incident angle greater than 45° relative to the normal to the surface of the substrate, the incident angle preferably being between 70° and 80°, and / or, wherein the conditioning fluid comprises gas or air, preferably ultra-clean dry air or one or more inert gases, preferably wherein the fluid supply device is configured to supply air having a composition substantially the same as that of ambient air as the conditioning fluid.

5. The measuring device according to any one of the preceding claims, wherein The slit between the measurement device and the surface of the substrate comprises a region (R) having a substantially constant slit width, desirably wherein the second flow rate ( ) is set so that the average fluid velocity in the region having a substantially constant slit width is approximately the second velocity ( ), and / or wherein the second flow rate is set so that the average fluid velocity in the region having a substantially constant slit width is between 2.2 m / s and 4.5 m / s.

6. The measuring device according to claim 5, wherein The second flow rate is set to the following range: ,in: is a second flow rate, wherein the second flow rate is a volume flow rate; is the second speed; A(r) is the area of ​​the portion of the cylindrical surface of an imaginary cylinder (CV) having a radius r that intersects the slit, wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W); and r has a value such that the area A(r) is completely enclosed within the region of substantially constant slit width, or in, Between 2.2 m / s and 4.5 m / s, where: is a second flow rate, wherein the second flow rate is a volume flow rate; A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) having a radius r that intersects the slit, wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W), and r has a value such that the area A(r) is completely enclosed within the region having the substantially constant slit width.

7. A lithographic apparatus comprising a measurement device as claimed in any preceding claim.

8. A method for measuring a substrate in a lithographic apparatus using a measurement device, the method comprising: emitting a light beam (8, 9) toward a surface of a substrate (W); as well as supplying a conditioning fluid (F) that traverses the light beam and flows in a slit (S) adjacent the surface of the substrate; During the first measurement process, at a first speed ( ) moves the substrate relative to the beam and at a first flow rate ( ) supplying the regulating fluid; During the second measurement process, the first speed is higher than the second speed ( ) while moving the substrate relative to the light beam at a second flow rate higher than the first flow rate ( ) supplies the regulating fluid.

9. The method of claim 8, wherein: The first measurement process includes measuring the position of an alignment mark located on the substrate, and / or the second measurement process includes measuring the topography of the surface of the substrate, and / or the first measurement process and the second measurement process measure the substrate at substantially the same position (m), and / or the regulating fluid is a gas.

10. The method of claim 9, wherein: The conditioning fluid comprises air, desirably ultra-clean dry air or one or more inert gases, desirably wherein the conditioning fluid has substantially the same composition as ambient air.

11. The method according to claim 9 or 10, wherein: The slit includes a region (R) having a substantially constant slit width.

12. The method of claim 11, wherein: The second flow rate ( ) is set so that the average fluid velocity in the region having the substantially constant slit width is approximately the second velocity ( ), or wherein the second flow rate is set so that the average fluid velocity in the region having a substantially constant slit width is between 2.2 m / s and 4.5 m / s.

13. The method of claim 11, wherein: The second flow rate is set to the following range: , in: is a second flow rate, wherein the second flow rate is a volume flow rate; is the second speed; A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) having a radius r that intersects the slit; wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W); and r has a value such that the area A(r) is completely enclosed within the region having the substantially constant slit width.

14. The method of claim 11, wherein: Between 2.2 m / s and 4.5 m / s, where: is a second flow rate, wherein the second flow rate is a volume flow rate; A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) having a radius r that intersects the slit, wherein the axis of rotation of the imaginary cylinder is perpendicular to the surface of the substrate and passes through the position (m) at which the light beam is incident on the substrate (W), and r has a value such that the area A(r) is completely enclosed within the region having the substantially constant slit width.

15. A method of manufacturing a device comprising the method according to any one of claims 8 to 14.

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