Measuring device, measuring method, and device manufacturing method

Abstract

A measurement device for measuring a substrate includes an optical sensor configured to measure a surface of the substrate by emitting a light beam, and a fluid supply configured to supply a conditioning fluid that intersects the light beam and flows through a slit between the measurement device and the substrate surface. The optical sensor is configured to perform a first measurement process while the measurement device is moving relative to the substrate at a first speed, and to perform a second measurement process while the measurement device is moving relative to the substrate at a second speed that is faster than the first speed. The fluid supply 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 that is higher than the first flow rate during the second measurement process.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to European Patent Application No. 23155897.4, filed February 9, 2023, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a measuring device, a measuring method and a method for manufacturing a device for measuring substrates in a lithographic apparatus. [Background technology]

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that case, patterning devices, alternatively called masks or reticles, can be used to generate a circuit pattern that will be formed in an individual layer of the IC. This pattern can be transferred onto the target portion (e.g. comprising part of a die, one die or several dies) on the 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. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning a radiation beam in a given direction (the "scan" direction) while the substrate is scanned synchronously parallel or anti-parallel to the given direction (the "scan" direction). It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements are constantly shrinking, while the amount of functional elements, such as transistors, per device has been steadily increasing for decades, following a trend commonly referred to as "Moore's Law." To keep up with Moore's Law, the semiconductor industry is seeking technologies capable of producing increasingly smaller features. To project patterns onto a substrate, lithography systems can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Lithography systems using extreme ultraviolet (EUV) radiation, with wavelengths in the 4 nm to 20 nm range, e.g., 6.7 nm or 13.5 nm, can produce smaller features on a substrate than lithography systems using radiation with a wavelength of, e.g., 193 nm.

[0005]

[0005] In view of the increasingly stringent precision of device manufacturing, it is becoming increasingly important to perform precise measurements of the substrate. These measurements include horizontal alignment, which can be achieved by detecting markers on the substrate surface using an alignment sensor, and level sensing, which can be achieved by measuring the topography of the substrate surface using a level sensor. Typically, these sensors can be optical sensors. Once these measurements are performed, the lithography apparatus can be calibrated accordingly to compensate for misalignment and non-planarity of the substrate during manufacturing.

[0006]

[0006] It is known that in situations where precision is required, poor control of fluid (e.g., air) conditions in the optical path of a sensor can degrade measurement accuracy. These conditions can include fluid composition, temperature, etc. Attempts have been made to control the fluid conditions by supplying a flow of conditioning fluid to the optical path. The conditioning fluid can be controlled to have a known, stable condition. This allows the optical path to be free of perturbations from external fluids, such as the ambient fluid around the measurement device.

[0007] However, known attempts to control fluid conditions do not provide completely stable conditions, which limits the accuracy that sensors can achieve and the speed at which they can measure across a substrate, thereby limiting the smallest features that lithography can achieve, increasing waste rates and limiting production speeds. Summary of the Invention

[0008]

[0008] It is therefore an object of the present invention to increase the precision achievable by lithography.

[0009] Another object of the present invention is to reduce the waste rate in device manufacturing using lithography.

[0010] Yet another object of the present invention is to increase lithographic production speed.

[0011] According to an aspect of the present invention, there is provided a measurement device 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 beam of light; a fluid supply configured to supply a conditioning fluid that traverses the light beam and flows within a slit between the measurement device and the surface of the substrate; the optical sensor is configured to perform a first measurement process while the measurement device is moving relative to the substrate at a first speed, and to perform a second measurement process while the measurement device is moving relative to the substrate at a second speed that is faster than the first speed; The fluid supply is configured to supply the conditioning fluid at a first flow rate during a first measurement process and to supply the conditioning fluid at a second flow rate higher than the first flow rate during a second measurement process.

[0012] According to another aspect of the present invention, there is provided a method of measuring a substrate in a lithographic apparatus using a measurement device, the method comprising: projecting a light beam onto a surface of a substrate; providing a conditioning fluid flowing through a slit adjacent to a surface of the substrate and across the light beam; moving the substrate relative to the light beam at a first speed and supplying a conditioning fluid at a first flow rate during a first measurement process; During a second measurement process, moving the substrate relative to the light beam at a second speed faster than the first speed while supplying the conditioning fluid at a second flow rate higher than the first flow rate; Includes. [Brief explanation of the drawings]

[0013]

[0013] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0014] [Figure 1] 1 depicts a schematic representation of a lithographic apparatus according to one embodiment of the invention; [Figure 2] 2 shows a schematic cross section of the measuring device shown in FIG. 1; [Figures 3a-3d] 10A and 10B show schematic flow profiles of conditioning fluids. [Figure 4] The control volume is shown schematically in a three-dimensional view. [Figure 5] The control volume is shown in plan view. [Figure 6]10 illustrates a schematic representation of level sensing of a substrate. [Figure 7] 10 shows a schematic representation of the horizontal alignment of the substrate. DETAILED DESCRIPTION OF THE INVENTION

[0015]

[0014] In this document, the terms "radiation" and "beam" are used to encompass 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 to 100 nm).

[0016] The terms "reticle," "mask," or "patterning device," as used herein, may be broadly interpreted as referring to a general-purpose patterning device that can be used to impart a patterned cross-section to an incoming radiation beam, corresponding to the pattern to be created in a target portion of a substrate. The term "light valve" can also be used in this context. Besides the classic mask (transmissive or reflective mask, binary mask, phase-shifting mask, hybrid mask, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0017] 1 schematically depicts a lithographic apparatus according to an embodiment of the present invention, comprising: 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. 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. 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.

[0018]

[0017] In operation, the illumination system IL receives the radiation beam PB from the radiation source SO, for example via the 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 can be used to condition the radiation beam PB so that it has a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0019]

[0018] The term "projection system" PL as used herein should be interpreted broadly and can encompass various types of projection systems, including refractive optical systems, reflective optical systems, catadioptric optical systems, anamorphic optical systems, magnetic optical systems, electromagnetic optical systems, and / or electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used and / or other factors such as the use of an immersion liquid or a vacuum. Where the term "projection lens" is used herein, it can be considered as synonymous with the more general term "projection system".

[0020] The lithographic apparatus may also be of a type in which at least a part of the substrate W may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system PS and the substrate W. This is also known as immersion lithography. More information about immersion techniques is given in US 6,952,253, which is incorporated herein by reference.

[0021] The lithographic apparatus may also be of a type having two (also called "dual stage") or more substrate supports WT. In such a "multi-stage" machine, the substrate supports WT can be used in parallel and / or a substrate W placed on one substrate support WT can be used to expose a pattern thereon while a substrate W placed on another substrate support WT is undergoing preparation steps for a subsequent exposure.

[0022] In addition to the substrate support WT, the lithographic apparatus may include a measurement stage (not shown). The measurement stage is arranged to hold a sensor and / or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam PB. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example part of the projection system PS or part of the system for providing immersion liquid. When the substrate support WT is remote from the projection system PS, the measurement stage may be moved below the projection system PS.

[0023] In operation, the radiation beam PB is incident on the patterning device MA, e.g., a mask, which is held on the mask support MT, and is patterned by a pattern (design layout) present on the patterning device MA. After traversing the patterning device MA, the radiation beam PB passes through the projection system PS, which focuses the radiation beam PB onto a target portion C of the substrate W. The second positioner PW and position measurement system PMS can be used to accurately move the substrate support WT, for example, to position various target portions C at focused and aligned positions in the path of the radiation beam PB. Similarly, the first positioner PM, and possibly further position sensors (not explicitly shown in FIG. 1 ), can be used to accurately position the patterning device MA with respect 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. The substrate alignment marks P1, P2 may occupy dedicated target portions C, as shown, or may be located in spaces between the target portions C. When substrate alignment marks P1, P2 are located between target portions C, they are known as scribe-line alignment marks. Suitable techniques are described further in US 2009 / 195768 A, which is incorporated herein by reference.

[0024]

[0023] For clarity of the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes: x, y, and z. Each of the three axes is orthogonal to the other two. Rotation about the x-axis is referred to as Rx rotation. Rotation about the y-axis is referred to as Ry rotation. Rotation about the z-axis is referred to as Rz rotation. The x- and y-axes define a horizontal plane, and the z-axis is vertical. The Cartesian coordinate system does not limit the invention and is used for clarity only. For clarity of the invention, other coordinate systems, such as a cylindrical coordinate system, may be used. The Cartesian coordinate system may be oriented differently, for example, so that the z-axis has a component along the horizontal plane.

[0025] 1 , the substrate support WT is movable and moves the substrate W held by the substrate support WT from at least a substrate measurement position to a substrate processing position. In FIG. 1 , the substrate support position that holds the substrate W in the processing position, i.e., the substrate processing position, is designated WT(P). The substrate support position that holds the substrate W in the measurement position, i.e., the substrate measurement position, is designated WT(M). By way of example, the substrate measurement position WT(M) may be positioned away from the downstream end E of the projection system PS, and the substrate processing position WT(P) may be positioned near and / or opposite the downstream end E of the projection system PS.

[0026] When the substrate support WT holds the substrate W in a processing position, i.e., the 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 in the same position on the substrate support WT while the substrate support WT is moved from a respective substrate measurement zone, for example the substrate measurement position WT(M), to a respective substrate projection zone, for example the substrate processing position WT(P).

[0027] For example, the substrate measurement position WT(M) and the substrate processing position WT(P) may be located within the same internal part or chamber of the apparatus, such as a substrate zone WZ of the apparatus. By way of example, an intermediate frame part 3 of the apparatus (e.g., a metrology frame part) may substantially separate this internal substrate zone WZ from one or more other apparatus zones, 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, such as when the substrate measurement position WT(M) is located outside the apparatus.

[0028] As will be apparent to those skilled in the art, movement of the substrate support WT between the desired substrate measurement position WT(M) and the substrate processing position WT(P) can be performed by various means. For example, at least a portion of such movement can be provided using a second positioner PW, a substrate support conveyor, and / or one or more other transport mechanisms. In another embodiment, the substrate support WT is movable in a substantially single imaginary plane or level from the substrate measurement position WT(M) to the substrate processing position WT(P). As a non-limiting example, in FIG. 1 , the substrate support WT is movable in a substantially horizontal direction H or in the XY plane, allowing the substrate W to be moved in a substantially horizontal direction H or along the XY plane from the substrate measurement position WT(M) to the substrate processing position WT(P) or vice versa.

[0029] The position measurement system PMS may include any type of sensor suitable for determining the position of the substrate support WT. The position measurement system PMS may include 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 include a combined interferometer and encoder system. 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 metrology 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 a time derivative of the position, such as velocity or acceleration.

[0030] The position measurement system PMS may include an encoder system (not shown). Such an encoder system is known, for example, from US2007058173A1, which is incorporated herein by reference. The encoder system includes an encoder head, a grating, and a sensor. The encoder system is capable of receiving 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 original radiation beam. At least one of the primary radiation beam and the secondary radiation beam is generated by diffracting the original radiation beam by a grating. If both the primary radiation beam and the secondary radiation beam are generated by diffracting the original radiation beam by a grating, the primary radiation beam must have a different diffraction order from the secondary radiation beam. The different diffraction orders are, 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. This signal represents the position of the encoder head relative to the grating. One of the encoder head and the grating can be located on the substrate support WT. The other of the encoder head and the grating can be located on an intermediate frame part 3, such as a metrology frame or a base frame. For example, multiple encoder heads are located on the metrology frame and the grating is located on the upper surface of the substrate support WT. In another example, the grating is located on the lower surface of the substrate support WT and the encoder head is located below the substrate support WT.

[0031] The position measurement system PMS may include an interferometer system (not shown). Interferometer systems are known, for example, from US Pat. No. 6,020,964, which is incorporated herein by reference. The interferometer system may include a beam splitter, a mirror, a reference mirror, and a sensor. The radiation beam is split into a reference beam and a measurement beam by the beam splitter. 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. This signal represents the displacement of the mirror. In one embodiment, the mirror is connected to the substrate support WT. The reference mirror can be connected to a metrology frame. In one embodiment, the measurement beam and the reference beam are combined into the combined radiation beam by additional optical components rather than a beam splitter.

[0032] The lithographic apparatus comprises a measurement device including optical sensors 10, 11, 12 configured to or capable of measuring at least one aspect and / or property of the substrate W when the substrate support WT holds the substrate in a substrate measurement position WT(M). Such a measurement device is shown schematically in the figures and can be constructed in various ways. In alternative embodiments, the measurement device can be configured to measure or monitor the substrate W using one or more measurement beams. For example, in alternative embodiments, the optical sensors 10, 11, 12 can direct or emit one or more measurement light beams towards the surface of the substrate W. For example, the measurement device can then be configured to detect one or more portions of the one or more measurement light beams reflected from the substrate surface.

[0033]

[0032] In this specification, the term "light beam" should be interpreted broadly. A measurement (light) beam may be any suitable radiation beam that can be at least partially reflected by the surface of the substrate W to be measured. For example, the measurement beam may comprise a light beam of one or more radiation wavelengths in the visible range, and / or a light beam having one or more different radiation wavelengths.

[0034] For example, the measuring device can be configured to measure the position and / or orientation of the substrate W relative to the substrate support (or table) WT. Such a position and / or orientation of the substrate W can include a specific alignment or misalignment of the substrate W relative to the substrate support WT, one or more substrate positions measured in a direction parallel to the surface of the substrate, a specific tilt of the substrate W, a specific rotational substrate position, a level, thickness, and / or height position of the substrate measured perpendicular to the substrate surface, and / or other substrate positions and / or orientations. For example, the measuring device can 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. The measuring device can also be configured to detect the position of the substrate support WT when the substrate support WT holds the substrate W at the substrate measurement position WT(M). Furthermore, the measuring device can provide the measuring device with (predetermined) information about 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 can include control means capable of controlling the measuring device, and the measurement results can be used to calculate or estimate specific characteristics of the substrate W. Such control means are not shown, but it will be clear to one skilled in the art how such control means can be constructed.

[0035] In an embodiment, the measurement device may be provided with one or more optical sensors 12, for example alignment sensors, to measure the positions of substrate alignment markers P1, P2 that may be provided on the substrate W to detect the position of the substrate W in a particular plane (such as the XY plane in Figure 1). An embodiment of an alignment sensor is shown schematically in Figure 2. The alignment sensor may be configured to emit one or more alignment measurement beams 9 towards the surface of the substrate W held at the substrate measurement position WT(M) and to detect reflected portions of the alignment measurement beams 9.

[0036] A suitable optical (alignment or position) sensor 12 can use 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, such as that described in US 6,961,116. Various improvements and modifications of position sensors have been developed, for example as disclosed in US 2015261097 A1. The entire contents of these publications are incorporated herein by reference.

[0037] 7 is a schematic block diagram of an embodiment of a known alignment sensor AS, for example as described in US 6,961,116, which is incorporated herein by reference. A radiation source RSO provides a radiation beam RB of one or more wavelengths. The radiation beam RB is redirected by redirecting optics as an illumination spot SP onto a mark, such as a substrate alignment mark P1, P2, positioned on the substrate W. In this example, the redirecting optics includes a spot mirror SM and an objective lens OL. The illumination spot SP that illuminates the substrate alignment mark P1, P2 may have a diameter that is slightly smaller than the width of the substrate alignment mark P1, P2 itself.

[0038]

[0037] The radiation diffracted by the mark AM can be collimated (in this example via the objective lens OL) into an information-bearing beam IB. The term "diffraction" is intended to include zero-order diffraction (which may be referred to as reflection) from the mark. A self-referencing interferometer SRI, for example of the type disclosed in the above-mentioned US 6,961,116, can cause the information-bearing beam IB to interfere with itself after it has been received by the photodetector PD. If the radiation source RSO produces more than one wavelength, additional optics (not shown) may be included to provide separate beams. If desired, the photodetector PD may be a single element or may include multiple pixels. The photodetector PD may include a sensor array.

[0039]

[0038] Additionally, the redirecting optical system, which in this example includes a spot mirror SM, can function to block zero-order radiation reflected from the substrate alignment marks P1, P2, so that the information-carrying beam IB contains only higher-order diffracted radiation from the substrate alignment marks P1, P2 (this is not essential for the measurement, but improves the signal-to-noise ratio).

[0040]

[0039] The intensity signal SI is fed to a processing unit PU. The combination of optical processing in block SRI and computational processing in unit PU outputs values ​​of the X and Y position on the substrate W relative to a reference frame.

[0041] A single measurement of the type illustrated only determines the position of the substrate alignment marks P1, P2 within a certain range corresponding to one pitch of the substrate alignment marks P1, P2. Coarser measurement techniques are used in conjunction with this to identify which period of the sine wave contains the marked position. The same process can be repeated at coarse and / or fine levels with different wavelengths for increased accuracy and / or robust detection of the substrate alignment marks P1, P2, regardless of the material from which the substrate alignment marks P1, P2 are made and the material below and / or above which the substrate alignment marks P1, P2 are provided. Wavelengths can be optically multiplexed and demultiplexed for simultaneous processing and / or multiplexed by time or frequency division.

[0042] Alternatively or additionally, the measurement device may be provided with one or more optical sensors 10, 11, i.e., level sensors, configured to detect a particular leveling of the substrate W held at the substrate measurement position WT(M). In the embodiment of Fig. 2, the optical sensors 10, 11, i.e., level sensors, include a plurality of level measurement beam emitters configured to emit 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. As shown in Fig. 2, the one or more alignment measurement beams 9 and the one or more level measurement beams 8 may be directed by each optical sensor 10, 11, 12 towards substantially the same position m on the substrate surface. Alternatively, it is also possible to direct the various measurement beams 8, 9 towards different substrate portions. Furthermore, as shown in FIG. 2, the angle of incidence of the level measurement beam 8 described above can be significantly larger (close to 90 degrees, e.g., greater than 45 degrees, greater than 55 degrees, greater than 60 degrees, greater than 70 degrees, or up to about 80 degrees) than the angle of incidence of the alignment measurement beam 9 described above (the angle of incidence measured relative to the normal to the substrate surface).

[0043] More specifically, the level sensor may be arranged to measure the topography of the top surface of the substrate (or wafer) W. From these measurements, a map of the topography of the substrate W, also called a height map, may be generated, showing the height of the substrate W as a function of position on the substrate W. This height map may then be used to correct the position of the substrate W during pattern transfer on the substrate W, in order to provide an aerial image of the patterning device MA at the correct focus position on the substrate W. It will be understood that in this context, "height" refers generally to an out-of-plane dimension with respect to the substrate W (also called the Z-axis). Typically, a level or height sensor performs measurements at a fixed position (with respect to its own optical system) and height measurements are made at positions throughout the substrate W as a result of relative movement between the substrate W and the measurement device, including the level sensor.

[0044]

[0043] Figure 6 shows a schematic diagram of an example of a level or height sensor LS known in the art. Figure 6 only illustrates the principle of operation. In this example, the level sensor LS comprises an optical system including a projection unit LSP functioning as an optical sensor 10, e.g., a level measuring beam emitter, and a detection unit LSD functioning as an optical sensor 11, e.g., a level measuring beam detector. The projection unit LSP may include a radiation source LSO providing a radiation beam LSB provided by a projection grating PGR of the projection unit LSP. The radiation source LSO may be, for example, a broadband radiation source, such as a narrowband or supercontinuum light source, polarized or unpolarized, pulsed or continuous, e.g., a polarized or unpolarized laser beam. The radiation source LSO may include multiple radiation sources with different colors or wavelength ranges, e.g., multiple LEDs. The radiation source LSO of the level sensor LS is not limited to visible radiation but may additionally or alternatively include UV and / or IR radiation, as well as any wavelength range suitable for reflection from the surface of the substrate W.

[0045]

[0044] The projection grating PGR is a periodic grating including a periodic structure, which results in a radiation beam BE1 having a periodically varying intensity. The radiation beam BE1 having a periodically varying intensity is directed towards a measurement position m on the substrate W at an angle of incidence ANG relative to an axis normal to the incident substrate surface (Z-axis) between 0 and 90 degrees, typically between 70 and 80 degrees. At measurement position m, the patterned radiation beam BE1 is reflected from the substrate W (indicated by arrow BE2) and directed towards a detection unit LSD.

[0046] To determine the height level at the measurement position m, the level sensor LS further comprises a detection system including 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 may be identical to the projection grating PGR. The detector DET generates a detector output signal indicative of the received light, e.g. indicative of the intensity of the received light, like a photodetector, or a detector output signal representing the spatial distribution of the received intensity, like a camera. The detector DET may comprise any combination of one or more detector types.

[0047]

[0046] By means of triangulation techniques, the height level at the measurement position m can be determined. The detected height level is typically related to the signal intensity measured by the detector DET, which has a periodicity that depends, inter alia, on the design of the projection grating PGR and the (tilted) angle of incidence ANG.

[0048]

[0047] The projection unit LSP and / or the detection unit LSD may include further optical elements, such as lenses and / or mirrors (not shown), along the path of the patterned radiation beam between the projection grating PGR and the detection grating DGR.

[0049]

[0048] In one embodiment, the detection grid DGR may be omitted and the detector DET may be placed in the place where the detection grid DGR was located. Such a configuration provides a more direct detection of the image of the projection grid PGR.

[0050]

[0049] 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 to generate an array of measurement areas m or spots to cover a larger measurement range.

[0051] For example, US 7,265,364 and US 7,646,471, both of which are incorporated herein by reference, disclose various height sensors of this general type. US 2010233600 A1, which is incorporated herein by reference, discloses a height sensor that uses UV radiation rather than visible or infrared radiation. WO 2016102127 A1, which is incorporated herein by reference, describes a compact height sensor that uses a multi-element detector to detect and recognize the position of a grating image without the need for a detection grating.

[0052]

[0051] It is also possible to provide the measuring device with one or more other sensors, such as, for example, one or more planar encoders (not shown). Also, as will be clear to those skilled in the art, if the measuring device is configured to use one or more measuring fields, the measuring device may include one or more suitable field generators, such as, for example, one or more electromagnetic field generators if the measuring field is an electromagnetic field.

[0053] The measurement device may provide remote sensing means for detecting the position and / or orientation of the substrate W before it is illuminated by the projection system PS. In particular, the measurements 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 in a different manner. In another embodiment, the substrate W is not repositioned relative to the substrate support WT during the period spanning from measuring or detecting the position / or orientation of the substrate by the measurement device to projecting the radiation beam PB onto the substrate W by the projection system PS. In that case, the measurements of the measurement system are not used for (re)aligning the substrate W relative to the substrate support WT.

[0054] Alternatively, before projecting the patterned radiation beam PB onto the substrate W, the measurements of the measurement system are used to (re)align the substrate W relative to the substrate support WT.

[0055] The optical sensors 10, 11, 12 can perform several different measurement processes. Depending on the measurement process, the measurement device can move at different speeds v relative to the substrate W (note that speed v should be understood in a relative sense, i.e., depending on the frame of reference, either the substrate W or the measurement device can be considered to be "moving"). In particular, the measurement device moves at a first speed v1 relative to the substrate W during a first measurement process, and at a second speed v2 relative to the substrate W during a second measurement process.

[0056] It may be desirable to be able to perform different measurement processes at different speeds v, balancing measurement accuracy against the time required to complete the measurement process. That is, it is generally desirable to perform the measurement process at the fastest possible speed v, provided that adequate accuracy can be reliably achieved. For example, it may be possible to perform level sensing (e.g., measuring the topography of the surface of the substrate W) at a faster speed v than horizontal alignment (e.g., detecting substrate alignment markers P1, P2 on the surface of the substrate W).

[0057] However, it has been found that in situations where measurement accuracy is required, the flow of fluid (whether liquid or gas) through which the light beams 8, 9 pass can change the refractive index of the fluid to such an extent that measurement accuracy is substantially reduced. For example, if the measurement device is moving at a high speed v relative to the substrate W, significant backflow of fluid can occur from outside the slit S towards the vicinity of the position m where the light beams 8, 9 are incident on the surface of the substrate W. At such high speeds v, the fluid within the slit S and near the position m can also become turbulent. Such backflow and turbulence can be unpredictable and can reduce measurement accuracy by significantly changing the refractive index of the fluid.

[0058]

[0057] It may therefore be desirable 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 of ambient fluid reaching those paths. Therefore, a supply of conditioning fluid F is provided to the measurement device. 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 path of the measurement beams 8, 9 of the measurement device. An embodiment of such a conditioning system is shown schematically in Figures 1 and 2.

[0059] As shown in FIG. 2, the measurement device is configured to supply a conditioning fluid F such that the conditioning fluid F traverses the light beams 8, 9 and flows within a slit S between the measurement device and the surface of the substrate W. More specifically, the measurement device may include a space-filling and / or space-closing body 4 having a fluid flow control surface 14. The fluid flow control surface 14 extends facing the substrate measurement position WT(M) (see FIG. 2). The fluid flow control surface 14 may be positioned to provide or close the slit S with at least a substrate surface portion of a substrate W held at the substrate measurement position WT(M). This substrate surface portion faces away from the substrate support WT and, during use, receives the measurement beams 8, 9 of the measurement device. 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 extends facing the entire surface of the substrate W placed at the substrate measurement position WT(M), and may optionally extend facing at least a surface portion of the opposite substrate support WT. In this way, a relatively long and narrow slit S can be provided between the surface of the substrate W and the space-filling and / or space-enclosing body 4 .

[0060] Such fluid flow control surface 14 can be arranged and configured in various ways. For example, the fluid flow control surface 14 can be a substantially flat, substantially continuous, i.e., uninterrupted, surface, except for the opening 141, through which the conditioning fluid F from the space-filling / closure body 4 enters the slit S and through which the light beams 8, 9 pass between the optical sensors 10, 11, 12 and the surface of the substrate W. The fluid flow control surface 14 can be interrupted by other features as needed. While the fluid flow control surface 14 can be substantially flat, it need not be microscopically smooth and can have small surface features. For example, the fluid flow control surface 14 can be profiled, include small fluid-guiding grooves, and / or include specific undulations to guide the fluid along the fluid flow control surface 14 in a desired direction.

[0061] As described above, the measurement device performs a first measurement process while moving relative to the substrate W at a first speed v1, and performs a second measurement process while moving relative to the substrate W at a second speed v2 that is faster than the first speed v1. The first measurement process may be an alignment process that measures the positions of substrate alignment marks P1, P2 on the substrate W, which may be performed at a speed that is sufficiently slow so as to be considered quasi-static. The second measurement process may be a level sensing process that measures the topography of the surface of the substrate W, which may be performed at a high speed, for example up to about 3.0 m / s or 4.5 m / s.

[0062]

[0061] Therefore, a simple approach to providing a barrier to ambient fluid flow is to supply 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 determined primarily by the supply of conditioning fluid F, largely excluding perturbations from the ambient fluid. This allows for improved consistency and predictability of fluid conditions for different measurement processes, which can be calibrated accordingly.

[0063] However, as discovered by the present inventors, this simple approach has drawbacks. To maximize the rejection or counteract perturbations from the ambient fluid within the slit S, the conditioning fluid F can be supplied at an arbitrarily high flow rate, but such a high flow rate can generate turbulence within the space-filling / closure body 4. For example, as shown in FIG. 2 , the conditioning fluid F can be supplied through a fluid passage 40, which may have constrictions and / or bends that are prone to generating turbulence. Specifically, the fluid passage 40 can be provided with a sieve 26 to make the flow profile more uniform, but this can generate turbulence if the flow rate is too high. Certain measurement processes are particularly sensitive to such turbulence. For certain other measurement processes, this type of turbulence may be acceptable if the required measurement accuracy is achieved.

[0064]

[0063] It may therefore be desirable to supply the conditioning fluid F in an adaptive manner. Specifically, the fluid supply is configured to supply the conditioning fluid F at a first flow rate Q1 during a first measurement process, and to supply the conditioning fluid F at a second flow rate Q2, which is higher than the first flow rate, during a second measurement process. Thus, during a second measurement process performed at a high speed v2, the conditioning fluid F is supplied at a high flow rate Q2, thereby substantially protecting the fluid conditions in the slit S from perturbations by the ambient fluid. During a first measurement process performed at a low speed v1, the conditioning fluid F is supplied at a lower flow rate Q1, thereby limiting or completely avoiding the occurrence of turbulence in the fluid passage 40.

[0065] As mentioned above, the optical sensor may include an optical sensor 12, e.g., an alignment sensor configured to detect markers on the surface of the substrate W for horizontal alignment. Furthermore, to obtain the required measurement accuracy, this horizontal alignment may need to be performed at a quasi-static speed v. As the inventors have found, this type of alignment may be particularly sensitive to turbulence generated in the fluid passage 40 (due to the quasi-static speed v, perturbations from the ambient fluid may be small). Therefore, the horizontal alignment may be performed as a first measurement process at a low speed v1 and a low flow rate Q1 of the conditioning fluid F.

[0066] As mentioned above, the optical sensors 10, 11 may include a level sensor configured to measure the topology of the surface of the substrate W. It may be desirable to perform this level sensing at a high speed v (e.g., up to 3.0-4.5 m / s) to save time. As the inventors have found, this type of level sensing is primarily sensitive to perturbations from the ambient fluid and may be less sensitive to turbulence generated within the fluid passage 40. Thus, level sensing may be performed as a second measurement process at a high speed v2 and a high flow rate Q2 of the conditioning fluid F.

[0067] 3a to 3d, the effect of the flow rate of the conditioning fluid F can be understood in more detail. FIG. 3a shows a situation in which the substrate W is stationary (or quasi-static) relative to the measurement device. A low flow rate of conditioning fluid F is used, resulting in a low flow velocity within the slit S. Applying the no-slip condition (whereby a viscous fluid at a solid boundary is treated as having negligible or zero velocity relative to the solid boundary), the flow velocity at the fluid quantity control surface 14 and at the surface of the substrate W is zero. FIG. 3b shows a situation in which the low flow rate is maintained, but the substrate W is moving at a speed v relative to the measurement device (to the right as shown). Using the frame of reference of the measurement device and applying the no-slip condition, the flow velocity at the fluid quantity control surface 14 is zero and the flow velocity at the surface of the substrate W is v. As can be seen, a backflow of the ambient fluid occurs to the left of the measurement position m. The backflow is somewhat reduced by the low flow rate of conditioning fluid F, but the overall flow profile is still in the reverse direction. This causes a large amount of ambient fluid to flow from outside the slit S into the vicinity of the measurement position m.

[0068] FIG. 3c shows a situation in which the substrate W is stationary (or quasi-static) relative to the measurement device. A high flow rate of conditioning fluid F is used, resulting in a high flow velocity within the slit S. Due to the no-slip condition, the flow velocity at the fluid flow control surface 14 and the surface of the substrate W is zero. FIG. 3d shows a situation in which the high flow rate is maintained, but the substrate W is moving at a speed v (to the right as shown) relative to the measurement device. Similar to the situation shown in FIG. 3b, using the frame of reference 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, unlike FIG. 3b, the backflow of the ambient fluid is effectively suppressed by the high flow rate of conditioning fluid F. Specifically, only a thin layer of backflow remains near the surface of the substrate W, with the majority of the fluid flow directed away from the measurement position m. Therefore, the amount of ambient fluid attracted toward the measurement position m is reduced. The main part of the fluid flow within the slit S consists of conditioning fluid F flowing outward, away from the measurement position m. Therefore, the fluid conditions (e.g., refractive index) near the measurement location m are stable and repeatable, and the optical sensors 10, 11, 12 can be calibrated accordingly to obtain reliable and precise measurements without sacrificing measurement speed.

[0069]

[0068] The composition of the conditioning fluid F can be substantially identical to that of the ambient fluid. This composition is desirable because even when using high flow rates of conditioning fluid F, there may still be a small amount of backflow of the ambient fluid. Therefore, closely matching the conditioning fluid F to the ambient fluid can further stabilize the fluid conditions (e.g., refractive index) near the measurement location m. Of course, in addition to composition matching, temperature matching can also be achieved.

[0070] The ambient fluid may generally be a gas or air that may be present in the substrate zone WZ of the apparatus described above. For example, such ambient fluid may include gas emanating from one or more gas showers 30. The gas showers 30 may be configured to direct gas to areas of the apparatus other than the area of ​​the substrate measurement position WT(M). As an example, such one or more gas showers 30 may be provided to condition one or more interferometer beams IFB of the interferometer system IF described above (see FIGS. 1 and 2).

[0071] As mentioned above, the conditioning fluid F can be provided by the conditioning system 50 of the lithographic apparatus. The conditioning fluid F can likewise be a gas or air. In particular, the conditioning fluid F can be a controlled gas or gas mixture, for example, preferably dry, ultra-clean air, or one or more inert gases.

[0072] The conditioning system can also be configured to provide a thermally conditioned conditioning fluid F, particularly if the system is configured to thermally condition the conditioning fluid F. By way of example, the conditioning system may 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. The conditioning system may also include one or more fluid lines 23, 24 (shown in FIG. 1 ) and fluid pumps for injecting the conditioning fluid F into a desired location and / or removing or extracting the conditioning fluid F from such a location. A portion of a fluid conditioning system, which may include the heating and / or cooling system, control system, temperature sensors, and pumps described above, is illustrated schematically by conditioning system 50 in FIG. 1 . It will be apparent to one skilled in the art how the various portions of conditioning system 50 may be configured and arranged.

[0073] The space-filling and / or space-enclosing body 4 can be constructed in a variety of ways and from a variety of materials. For example, the body 4 can be a substantially solid body, structure, plate, and / or element, or the body 4 can be an at least partially hollow body, structure, plate, and / or element. The space-filling and / or space-enclosing body 4 can also have a substantially liquid-tight or hermetic outer surface, except where specifically indicated. In one embodiment, the space-filling and / or space-enclosing body 4 is mounted to an intermediate frame portion 3 of the apparatus. This frame portion separates an interior zone, such as the substrate zone WZ, from another interior zone of the apparatus, such as the projection system zone PZ. For example, the space-filling and / or space-enclosing body 4 can be integrally connected to or secured to the intermediate frame portion 3 of the apparatus, or can be made integral with the intermediate frame portion 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 or other materials.

[0074] In one embodiment, during use, the closest distance between the fluid flow control surface 14 of the body 4 and the substrate surface (see FIG. 2), i.e., the width R of the slit S between the fluid flow control surface 14 and the substrate surface, is less than about 10 mm. For example, the closest distance between the fluid flow control surface 14 and the substrate surface, i.e., the slit width R, may be in the range of about 1 to 5 mm or about 1 to 2 mm. For example, the slit width R may be about 2.5 mm. Alternatively, the closest distance, i.e., the slit width R, may be less than about 2.5 mm or less than about 1 mm. More generally, it may be desirable to minimize the slit width R if possible collisions between the measurement device and the substrate W are to be avoided. This is because a small slit width R can eliminate perturbations from the ambient fluid even when the flow rates Q1, Q2 of the conditioning fluid F are small. The slit S may have a constant width R over part or all of the fluid flow control surface 14. As noted above, the fluid flow control surface 14 may be substantially flat and may include small surface features.

[0075] 2, the space-filling and / or space-enclosing body 4 can house one or more of the above-mentioned optical sensors 10, 11, 12 and / or field generators of the measurement device. Additionally, for example, in this embodiment, the space-filling and / or space-enclosing body 4 can include one or more measurement beam passages 5 for transmitting at least one measurement beam 8 of the measurement device between the optical sensors 10, 11, 12 and the opening 141 in the fluid flow control surface 14 through at least a portion of the body 4. It will be clear to one skilled in the art how the measurement beam passages 5 can be configured to take into account each measurement beam 8.

[0076] The measurement beam path 5 can at least partially overlap with the fluid path 40. For example, as shown in Figure 2, the measurement beam path 5 of the optical sensor 10 can partially overlap with the fluid path 40 shown on the left. Similarly, the measurement beam path 5 of the optical sensor 11 can partially overlap with the fluid path 40 shown on the right.

[0077] In embodiments where several fluid passages 40 are provided, all of the fluid passages 40 may direct the conditioning fluid F to the opening 141 surrounding the measurement location m. Furthermore, each fluid passage 40 may be used to direct a portion of the total flow rate Q of the conditioning fluid F. For example, two fluid passages 40 are shown in FIG. 2, each of which has a flow rate Q A and Q B It is possible to guide a fluid flow of Q A and Q B These flow rates sum to a total flow rate Q. In embodiments, more than two fluid passages 40 may be provided, with each such fluid passage 40 conducting a portion of the total flow rate Q. Thus, references herein to a first flow rate Q1 and a second flow rate Q2 refer to the total flow rate through the opening 141 during each measurement process, regardless of the number of fluid passages 40 provided. As used herein, unless otherwise indicated, the flow rates Q, Q1, Q2, and Q A , and Q Bcan be either a volumetric flow rate (e.g., liters / minute measured at atmospheric pressure (1.01325 bar) and a temperature of 0° C.), or a mass flow rate (e.g., grams / minute).

[0078] In general, when several fluid passages 40 are provided, it may be desirable to direct unequal proportions of the total flow Q to different fluid passages 40. That is, in the example shown in FIG. A and Q B are different (summing to Q). This asymmetry can help prevent the formation of a stagnation point at the measurement location m. For example, Q A :Q B (or Q B :Q A ) can have a 30:70 split, a 35:65 split, a 40:60 split, or a 45:55 split.

[0079]

[0078] A sieve 26 can be provided at a location through which the conditioning fluid F passes before entering the overlapping portion of the measurement beam 8 / fluid passage 40. For example, the sieve 26 can be provided directly at the location where the conditioning fluid F enters the overlapping portion.

[0080] The sieve 26 may include a porous material, a suitable gas dispenser, a monofilament cloth or fabric, one or more sheets with gas openings, or a different fluid distributor. In one embodiment of the present invention, the sieve 26 may have a thickness of less than about 1 mm. For example, the thickness may be about 0.5 mm or less. The sheet may be a metal or alloy sheet, such as stainless steel. In this case, relatively small fluid passage holes can be manufactured with high precision using laser drilling. It is also possible to manufacture the fluid passages 40 using different techniques. The sieve 26 may also be made of plastic, among other materials. In addition to laser drilling, various manufacturing methods can be used to provide the passage holes in the sieve 26, such as etching the passage holes, manufacturing the passage holes by electrical discharge machining, and / or using various processes such as metal deposition on a mask. The sieve 26 may also be referred to as a "microsieve." The sieve 26 may include one or more layers of one or more materials. The sieve 26 can be or provide a wall or wall portion of the space-filling and / or space-enclosing body 4. The fluid passage holes of the sieve 26 can have various diameters or dimensions. The diameter or width of each passage hole can be, for example, less than about 0.2 mm. For example, the diameter or width can be less than about 0.1 mm. Good results are obtained when the diameter or width of each passage hole is about 0.08 mm and the conditioning fluid F is a gas or gas mixture.

[0081]

[0080] As described above with reference to Figures 3a to 3d, when the measurement device is moving relative to the substrate W, a certain flow rate of the adjustment fluid F may be required to adequately counteract perturbations from the surrounding fluid, especially during rapid movement.

[0082] For example, the second (i.e., higher) flow rate Q2 can be set so that the average fluid speed within the region of substantially constant slit width R is at least about 70% of the second (i.e., faster) speed v2, such as 80%, 90%, 100%, 110%, 120%, 130%, or 140%, or up to 150%. As used herein, "average fluid speed" can refer to the (scalar) speed of the fluid averaged over the volume of space occupied by the region of substantially constant slit width R. Mathematically, the average fluid speed can be expressed as follows:

[0083]

number

[0084] where G is the volume occupied by a region of substantially constant slit width R, and u is the local scalar fluid speed at different points within G.

[0085] In another example, the second (i.e., higher) flow rate Q2 may be set so that the average fluid speed within the region of substantially constant slit width R is at least about 2.2 m / s, for example 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 speed range may correspond to a second speed v2 at which the measurement device moves relative to the substrate W.

[0086]

[0083] Referring now to Figure 4 for another definition of the flow rate Q, the control volume CV is defined by intersecting a (virtual) cylinder with the slit S, as shown. If the fluid flow control surface 14 is flat and parallel to the surface of the substrate W, the control volume CV will have a cylindrical shape. In other cases, the upper surface of the control volume CV may follow the topography of the fluid flow control surface 14. The cylinder has a radius r, a rotation axis perpendicular to the surface of the substrate W, and passes through the measurement position m. The radius r may be any value as long as the cylindrical surface of the control volume CV is entirely contained within the region of a substantially constant slit width R. In the minimum case, the radius r may be such that the control volume CV just contains the opening 141. In the maximum case, the radius r may be such that the control volume CV does not exceed the range 142 of the region of the constant slit width R. As shown in Figure 5, the radius r may be any value between these extremes. The surface area of ​​the cylindrical surface is A(r), which, when the fluid flow control surface 14 is flat and parallel to the surface of the substrate W, is equal to 2πrR.

[0087] 4 and 5, a total flow rate Q of the conditioning fluid F enters the control volume CV through the opening 141. In the illustrated example, the total flow rate Q is divided into two portions, namely Q, that enter the two fluid passages 40 shown in FIG. A and Q B Therefore, the flow rate leaving the control volume CV through the cylindrical surface is equal to the total flow rate Q inside. Therefore, assuming a constant fluid density, the average flow rate leaving the cylindrical surface is Q / A(r), where Q is the volumetric flow rate. This average flow rate is greatest when the radius r is smallest.

[0088] 3b and 3d, the reverse flow velocity is at most v, which is the speed at which the substrate W moves relative to the measurement device. To adequately cancel the reverse flow, the average flow velocity Q / A(r) exiting through the cylindrical surface can be set to be equal to v. In other words, Q can be set so that the dimensionless parameter Q / (A(r)*v) is about 1. For example, Q / (A(r)*v) can be set to at least about 0.7, such as about 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or 1.4, or at most about 1.5. If r is at a minimum (i.e., the control volume CV is just large enough to include the opening 141), then Q / (A(r)*v) can be set to these values.

[0089] As mentioned above, the second measurement process is performed at a faster speed v2 than the first measurement process and requires a second flow rate Q2 of the conditioning fluid F that is higher than the first measurement process. Therefore, the second flow rate Q2 can be set according to v2 using the above approach.

[0090] Alternatively, Q2 may be set according to a desired range of average flow velocities Q2 / A(r) exiting through the cylindrical surface. For example, Q2 may be set such that Q2 / A(r) is 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 at which the measurement device moves relative to the substrate W.

[0091] After the substrate measurement process, the substrate W may be transferred to a substrate processing position WT(P) where a patterned radiation beam PB patterned by the patterning device MA may be projected onto the substrate W. Herein, the detection results of at least one feature, characteristic, position and / or orientation of the substrate W may be used to accurately project the patterned radiation beam PB onto the substrate W.

[0092] In yet another embodiment, the detection of at least one feature, characteristic, position and / or orientation of the substrate W may be used to align the substrate W relative to the projection system PS for projecting the patterned radiation beam PB onto the substrate W. Furthermore, in another embodiment, the detection or measurement of the position and / or orientation of the substrate W may be used to align the substrate W relative to the aforementioned mask support MT configured to support the patterning device MA, or relative to the patterning device MA.

[0093] In this way, the measurement errors of the measurement system can be reduced and the device can be fabricated with high precision. As mentioned above, in another embodiment, there is no need to reposition the substrate W relative to the substrate support WT during the period spanning from measuring or detecting the position / orientation of the substrate by the measurement system to projecting the radiation beam PB onto the substrate W by the projection system PS.

[0094] While the above disclosure refers to providing conditioning fluid F in the slit S between the fluid flow control surface 14 and the surface of the substrate W, the present invention may alternatively or additionally be applied elsewhere. For example, as described above, an encoder (not shown) may be used to implement a position measurement system PMS for determining the position of the substrate support WT during the first and second measurement processes described above, in which, for example, optical sensors 10, 11, and 12 measure the surface of the substrate W. Accordingly, the encoder head may also be moved at first and second speeds v1 and v2 relative to the encoder grid. As with the measurement device, the trade-off between eliminating perturbations from the ambient fluid and avoiding the generation of turbulence in the internal passages may also apply to the encoder. Therefore, to control the flow conditions in the space between the encoder head and the grid, different flow rates of conditioning fluid may be supplied to the encoder head corresponding to the processes being performed at the first and second speeds v1 and v2. That is, for slow or quasi-static movements, a lower flow rate of conditioning fluid may be supplied. Conversely, for rapid movements, a higher flow rate of conditioning fluid may be supplied.

[0095]

[0092] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be appreciated that the lithographic apparatus described herein may have other applications, including 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, etc.

[0096] Although particular reference is made herein to embodiments of the invention in the context of lithography apparatus, embodiments of the invention may also be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus may be generally referred to as lithography tools. Such lithography tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0097]

[0094] Although the above makes specific reference to the use of embodiments of the present invention in the context of optical lithography, it will be appreciated that the present invention is not limited to optical lithography and may be used in other applications, such as imprint lithography, where the context permits.

[0098] Where the context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Also, embodiments of the present invention may be implemented as instructions stored on a machine-readable medium, which may 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, a machine-readable medium may include read-only memory (ROM), random-access memory (RAM), magnetic storage media, optical storage media, flash memory devices, electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines, and instructions may be described herein as performing certain actions. However, it will be recognized that such descriptions are merely for convenience and that such actions actually result from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., which, when executed, cause actuators or other devices to interact with the physical world.

[0099]

[0096] Aspects of the present invention are described in the following numbered clauses: 1. A measurement device for measuring a substrate (W) in a lithographic apparatus, comprising: an optical sensor (10, 11, 12) configured to measure the surface of the substrate (W) by emitting a light beam (8, 9); a fluid supply configured to supply a conditioning fluid (F) that flows in a slit (S) that intersects the light beam and between the measurement device and the surface of the substrate, the optical sensor is configured to perform a first measurement process while the measurement device is moving relative to the substrate at a first speed (v1) and to perform a second measurement process while the measurement device is moving relative to the substrate at a second speed (v2) that is faster than the first speed; A measurement device, wherein the fluid supply is configured to supply the conditioning fluid at a first flow rate (Q1) during a first measurement process, and to supply the conditioning fluid at a second flow rate (Q2) higher than the first flow rate during a second measurement process. 2. The measurement device of clause 1, wherein the optical sensor (12) includes an alignment sensor configured to detect a marker on the surface of the substrate. 3. The measurement device of clause 2, wherein the alignment sensor is configured to emit a light beam substantially perpendicular to the surface of the substrate. 4. A measuring device according to any one of clauses 1 to 3, wherein the optical sensor (10, 11) comprises a level sensor configured to measure the topography of the surface of the substrate. 5. A measuring device according to clause 4, wherein the level sensor is configured to emit a light beam at an angle of incidence greater than 45 degrees from the normal to the surface of the substrate, preferably at an angle of incidence between 70 and 80 degrees. 6. A measurement device according to any one of clauses 1 to 5, comprising a plurality of optical sensors configured to emit each optical beam towards substantially the same position (m) on the surface of the substrate. 7. A measuring device according to any one of clauses 1 to 6, wherein the conditioning fluid is a gas. 8. A measuring device according to clause 7, wherein the conditioning fluid comprises a gas or air, preferably ultra-clean dry air or one or more inert gases. 9. A measuring device as described in clause 8, wherein the fluid supply is configured to supply air as the conditioning fluid having substantially the same composition as ambient air. 10. A measuring device according to any one of clauses 1 to 9, wherein the slit between the measuring device and the surface of the substrate comprises a region of substantially constant slit width (R). 11. The measurement device of clause 10, wherein the second flow rate (Q2) is set so that the average fluid speed in the region of substantially constant slit width is about 70% to 150% of the second speed (v2). 12. A measuring device according to clause 10 or 11, wherein the second flow rate is set so that the average fluid speed in the region of substantially constant slit width is between 2.2 m / s and 4.5 m / s. 13. The second flow rate is set in the following range: 0.7≦Q2 / (A(r)*v2)≦1.5 where Q2 is the second flow rate, which is the volumetric flow rate, v2 is the second speed, 11. The measurement device of clause 10, wherein A(r) is the area of ​​the cylindrical surface of a portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is a value such that the area A(r) is entirely contained within a region of substantially constant slit width. 14. Q2 / A(r) is between 2.2 m / s and 4.5 m / s. where Q2 is the second flow rate, which is the volumetric flow rate, 11. The measurement device of clause 10, wherein A(r) is the area of ​​the cylindrical surface of a portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is a value such that the area A(r) is entirely contained within a region of substantially constant slit width. 15. A lithographic apparatus comprising a measurement device according to any one of clauses 1 to 14. 16. A method of measuring a substrate in a lithographic apparatus using a measurement device, comprising: emitting a light beam (8, 9) onto the surface of a substrate (W); providing a conditioning fluid (F) flowing through a slit (S) adjacent to the surface of the substrate and across the light beam; During a first measurement process, moving the substrate relative to the light beam at a first speed (v1) and supplying a conditioning fluid at a first flow rate (Q1); During a second measurement process, moving the substrate relative to the light beam at a second speed (v2) faster than the first speed while supplying the conditioning fluid at a second flow rate (Q2) higher than the first flow rate; A method comprising: 17. The method of clause 16, wherein the first measurement process includes measuring the position of an alignment marker on the substrate. 18. The method of clause 16 or 17, wherein the second measurement process comprises measuring the topography of the surface of the substrate. 19. The method of 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). 20. The method of any one of clauses 16 to 19, wherein the conditioning fluid is a gas. 21. The method of clause 20, wherein the conditioning fluid comprises air, preferably ultra-clean dry air or one or more inert gases. 22. The method of clause 21, wherein the conditioning fluid has substantially the same composition as ambient air. 23. The method of clauses 18 to 22, wherein the slit comprises a region of substantially constant slit width (R). 24. The method of clause 22, wherein the second flow rate (Q2) is set so that the average fluid speed in the region of substantially constant slit width is about 70% to 150% of the second speed (v2). 25. The method of clause 23, wherein the second flow rate is set so that the average fluid speed in the region of substantially constant slit width is between 2.2 m / s and 4.5 m / s. 26. The second flow rate is set in the following range: 0.7≦Q2 / (A(r)*v2)≦1.5 where Q2 is the second flow rate, which is the volumetric flow rate, v2 is the second speed, 24. The method of claim 23, wherein A(r) is the area of ​​the cylindrical surface of a portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is such that the area A(r) is entirely contained within a region of substantially constant slit width. 27. Q2 / A(r) is between 2.2 m / s and 4.5 m / s. where Q2 is the second flow rate, which is the volumetric flow rate, 24. The method of claim 23, wherein A(r) is the area of ​​the cylindrical surface of a portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is such that the area A(r) is entirely contained within a region of substantially constant slit width. 28. A method for measuring a device, including a method as set out in any of clauses 16 to 27.

[0100]

[0097] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The foregoing description is intended to be illustrative and not limiting. Accordingly, those skilled in the art will recognize that modifications may be made to the invention as described without departing from the scope of the claims set forth below.

Claims

1. 1. A measurement device for measuring a substrate (W) in a lithographic apparatus, comprising: an optical sensor (10, 11, 12) configured to measure the surface of said substrate (W) by emitting a light beam (8, 9); a fluid supply 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, The optical sensor detects whether the measuring device is at a first speed (v １ ), and performing a first measurement process while the measuring device is moving relative to the substrate at a second speed (v ２ ) configured to perform a second measurement process while moving relative to the substrate; The fluid supply is configured to provide a first flow rate (Q １ ), and during the second measurement process, supply the conditioning fluid at a second flow rate (Q ２ ) the measuring device configured to supply the conditioning fluid.

2. 2. The measuring device of claim 1, wherein the optical sensor (12) includes an alignment sensor configured to detect a marker on the surface of the substrate, and preferably the alignment sensor is configured to emit the light beam substantially perpendicular to the surface of the substrate.

3. 3. The measuring device of 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 each light beam towards substantially the same position (m) on the surface of the substrate, and / or the adjusting fluid is a gas.

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

5. The slit between the measurement device and the surface of the substrate includes a region of substantially constant slit width (R), and preferably the second flow rate (Q ２ ) means that the average fluid speed in the region of the substantially constant slit width is greater than the second speed (v ２ 5. The measuring device of claim 1, wherein the second flow rate is set to be about 70% to 150% of the average fluid speed in the region of substantially constant slit width, and / or the second flow rate is set to be about 2.2 m / s to 4.5 m / s.

6. the second flow rate is set to the following range, 0.7≦Q ２ / (A(r)*v ２ )≦1.5 Here, Q ２ is the second flow rate, which is a volumetric flow rate, v ２ is the second speed, A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is such that the area A(r) is entirely contained within the region of the substantially constant slit width, or Q ２ / A(r) is 2.2 m / s to 4.5 m / s, Here, Q ２ is the second flow rate, which is a volumetric flow rate, 6. The measurement device of claim 5, wherein A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is a value such that the area A(r) is entirely contained within a region of the substantially constant slit width.

7. A lithographic apparatus comprising a measurement device according to any one of claims 1 to 6.

8. 1. A method for measuring a substrate in a lithographic apparatus using a measurement device, comprising: emitting a light beam (8, 9) onto the surface of said substrate (W); providing a conditioning fluid (F) flowing through a slit (S) intersecting the light beam and adjacent to the surface of the substrate; During a first measurement process, the substrate is moved relative to the light beam at a first speed (v １ ) and a first flow rate (Q １ ) supplying said conditioning fluid; During a second measurement process, a second flow rate (Q ２ ), while supplying the conditioning fluid at a second speed (v ２ ) to move it, A method comprising:

9. the first measurement process includes measuring the position of an alignment marker on the substrate; and / or the second measurement process comprises 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 method of claim 8 , wherein the conditioning fluid is a gas.

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

11. 11. The method of claim 9 or 10, wherein the slit comprises a region of substantially constant slit width (R).

12. The second flow rate (Q ２ ) means that the average fluid speed in the region of the substantially constant slit width is greater than the second speed (v ２ ) is set to be about 70% to 150% of 12. The method of claim 11, wherein the second flow rate is set so that the average fluid speed in the region of substantially constant slit width is between 2.2 m / s and 4.5 m / s.

13. the second flow rate is set to the following range, 0.7≦Q ２ / (A(r)*v ２ )≦1.5 Here, Q ２ is the second flow rate, which is a volumetric flow rate, v ２ is the second speed, 12. The method of claim 11, wherein A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is a value such that the area A(r) is entirely contained within a region of the substantially constant slit width.

14. Q ２ / A(r) is 2.2 m / s to 4.5 m / s, Here, Q ２ is the second flow rate, which is a volumetric flow rate, 12. The method of claim 11, wherein A(r) is the area of ​​the cylindrical surface of the portion of an imaginary cylinder (CV) of radius r that intersects the slit, the axis of rotation of the imaginary cylinder being perpendicular to the surface of the substrate and passing through the position (m) where the light beam is incident on the substrate (W), and r is a value such that the area A(r) is entirely contained within a region of the substantially constant slit width.

15. A method for measuring a device, comprising the method of any of claims 8 to 14.

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