WO2021155990A1

WO2021155990A1 - A stage system, stage system operating method, inspection tool, lithographic apparatus, calibration method and device manufacturing method

Info

Publication number: WO2021155990A1
Application number: PCT/EP2020/087474
Authority: WO
Inventors: Yang-Shan Huang; Raimond Visser
Original assignee: Asml Netherlands B.V.
Priority date: 2020-02-07
Filing date: 2020-12-21
Publication date: 2021-08-12
Also published as: CN115023654A

Abstract

A stage (ST) that is moveable relative to a reference (RE) including: a bearing (BE) to support and guide movement of the stage relative to the reference in a 2D plane; and an actuator system (ACT) to apply forces to the stage relative to the reference to move or position the stage relative to the reference in the 2D plane, wherein the actuator system includes at least one actuator device (CL) configured to have an engaged mode, in which the actuator device is engaged with the stage to allow the stage to move along with the actuator device, and a disengaged mode, in which the actuator device is disengaged from the stage allowing the stage and the actuator device to move independently.

Description

A STAGE SYSTEM, STAGE SYSTEM OPERATING METHOD, INSPECTION TOOL, LITHOGRAPHIC APPARATUS, CALIBRATION METHOD AND DEVICE MANUFACTURING METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 20156073.7 which was filed on February 7, 2020 and which is incorporated herein in its entirety by reference.

FIELD

[0002] The present invention relates to a stage system, an operating method for such a stage system, an inspection tool, a lithographic apparatus including such a stage system, a calibration method and a device manufacturing method using such a stage system.

BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as “design layout” or “design”) of a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer).

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as ‘Moore’ s law’ . To keep up with Moore’ s law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within a range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm.

[0005] Low-ki lithography may be used to process features with dimensions smaller than the classical resolution limit of a lithographic apparatus. In such process, the resolution formula may be expressed as CD = ^cl/NA, where l is the wavelength of radiation employed, NA is the numerical aperture of the projection optics in the lithographic apparatus, CD is the “critical dimension” (generally the smallest feature size printed, but in this case half-pitch) and ki is an empirical resolution factor. In general, the smaller ki the more difficult it becomes to reproduce the pattern on the substrate that resembles the shape and dimensions planned by a circuit designer in order to achieve particular electrical functionality and performance. To overcome these difficulties, sophisticated fine-tuning steps may be applied to the lithographic projection apparatus and/or design layout. These include, for example, but are not limited to, optimization of NA, customized illumination schemes, use of phase shifting patterning devices, various optimization of the design layout such as optical proximity correction (OPC, sometimes also referred to as “optical and process correction”) in the design layout, or other methods generally defined as “resolution enhancement techniques” (RET). Alternatively, tight control loops for controlling a stability of the lithographic apparatus may be used to improve reproduction of the pattern at low-ki.

[0006] Hence, in lithographic processes, it is desirable to make frequently measurements of the structures created, e.g., for process control and verification. Tools to make such measurement are typically called metrology tools or inspection tools. Different types of metrology tools for making such measurements are known, including scanning electron microscopes or various forms of scatterometer metrology tools. Scatterometers are versatile instruments which allow measurements of the parameters of a lithographic process by having a sensor in the pupil or a conjugate plane with the pupil of the objective of the scatterometer, measurements usually referred as pupil based measurements, or by having the sensor in the image plane or a plane conjugate with the image plane, in which case the measurements are usually referred as image or field based measurements. Such scatterometers and the associated measurement techniques are further described in patent applications US2010/0328655, US2011/102753A1, US2012/0044470A, US2011/0249244, US2011/0026032 or EP1,628,164A, incorporated herein by reference in their entirety. Aforementioned scatterometers may measure gratings using light from soft x-ray and visible to near-IR wavelength range.

[0007] In a first embodiment, the scatterometer is an angular resolved scatterometer. In such a scatterometer reconstruction methods may be applied to the measured signal to reconstruct or calculate properties of the grating. Such reconstruction may, for example, result from simulating interaction of scattered radiation with a mathematical model of the target structure and comparing the simulation results with those of a measurement. Parameters of the mathematical model are adjusted until the simulated interaction produces a diffraction pattern similar to that observed from the real target.

[0008] In a second embodiment, the scatterometer is a spectroscopic scatterometer. In such spectroscopic scatterometer, the radiation emitted by a radiation source is directed onto the target and the reflected or scattered radiation from the target is directed to a spectrometer detector, which measures a spectrum (i.e. a measurement of intensity as a function of wavelength) of the specular reflected radiation. From this data, the structure or profile of the target giving rise to the detected spectrum may be reconstructed, e.g. by Rigorous Coupled Wave Analysis and non-linear regression or by comparison with a library of simulated spectra.

[0009] In a third embodiment, the scatterometer is a ellipsometric scatterometer. The ellipsometric scatterometer allows for determining parameters of a lithographic process by measuring scattered radiation for each polarization state. Such metrology apparatus emits polarized light (such as linear, circular, or elliptic) by using, for example, appropriate polarization filters in the illumination section of the metrology apparatus. A source suitable for the metrology apparatus may provide polarized radiation as well. Various embodiments of existing ellipsometric scatterometers are described in US patent applications 11/451,599, 11/708,678, 12/256,780, 12/486,449, 12/920,968, 12/922,587, 13/000,229, 13/033,135, 13/533,110 and 13/891,410 incorporated herein by reference in their entirety. [00010] In one embodiment of the scatterometer, the scatterometer is adapted to measure the overlay of two misaligned gratings or periodic structures by measuring asymmetry in the reflected spectrum and/or the detection configuration, the asymmetry being related to the extent of the overlay. The two (typically overlapping) grating structures may be applied in two different layers (not necessarily consecutive layers), and may be formed substantially at the same position on the wafer. The scatterometer may have a symmetrical detection configuration as described e.g. in co-owned patent application EP1,628,164A, such that any asymmetry is clearly distinguishable. This provides a straightforward way to measure misalignment in gratings. Further examples for measuring overlay error between the two layers containing periodic structures as target is measured through asymmetry of the periodic structures may be found in PCT patent application publication no. WO 2011/012624 or US patent application US 2016/0161863, incorporated herein by reference in its entirety.

[00011] Other parameters of interest may be focus and dose. Focus and dose may be determined simultaneously by scatterometry (or alternatively by scanning electron microscopy) as described in US patent application US2011/0249244, incorporated herein by reference in its entirety. A single structure may be used which has a unique combination of critical dimension and sidewall angle measurements for each point in a focus energy matrix (FEM - also referred to as Focus Exposure Matrix). If these unique combinations of critical dimension and sidewall angle are available, the focus and dose values may be uniquely determined from these measurements.

[00012] A metrology target may be an ensemble of composite gratings, formed by a lithographic process, mostly in resist, but also after etch process for example. Typically the pitch and line-width of the structures in the gratings strongly depend on the measurement optics (in particular the NA of the optics) to be able to capture diffraction orders coming from the metrology targets. As indicated earlier, the diffracted signal may be used to determine shifts between two layers (also referred to ‘overlay’) or may be used to reconstruct at least part of the original grating as produced by the lithographic process. This reconstruction may be used to provide guidance of the quality of the lithographic process and may be used to control at least part of the lithographic process. Targets may have smaller sub-segmentation which are configured to mimic dimensions of the functional part of the design layout in a target. Due to this sub-segmentation, the targets will behave more similar to the functional part of the design layout such that the overall process parameter measurements resembles the functional part of the design layout better. The targets may be measured in an underfilled mode or in an overfilled mode. In the underfilled mode, the measurement beam generates a spot that is smaller than the overall target. In the overfilled mode, the measurement beam generates a spot that is larger than the overall target. In such overfilled mode, it may also be possible to measure different targets simultaneously, thus determining different processing parameters at the same time.

[00013] Overall measurement quality of a lithographic parameter using a specific target is at least partially determined by the measurement recipe used to measure this lithographic parameter. The term “substrate measurement recipe” may include one or more parameters of the measurement itself, one or more parameters of the one or more patterns measured, or both. For example, if the measurement used in a substrate measurement recipe is a diffraction-based optical measurement, one or more of the parameters of the measurement may include the wavelength of the radiation, the polarization of the radiation, the incident angle of radiation relative to the substrate, the orientation of radiation relative to a pattern on the substrate, etc. One of the criteria to select a measurement recipe may, for example, be a sensitivity of one of the measurement parameters to processing variations. More examples are described in US patent application US2016/0161863 and published US patent application US 2016/0370717A1 incorporated herein by reference in its entirety.

[00014] As is known, the lithographic apparatus and/or metrology tools employ stage systems which may comprise a long-stroke module and a short-stroke module. The short-stroke module is typically arranged to move a mask support or a substrate table relative to the long-stroke module with a high-accuracy over a small range of movement. The long-stroke module is typically arranged to move the short-stroke module relative to a reference with a relatively low accuracy over a large range of movement.

[00015] An advantage of the combination of the long-stroke module and the short-stroke module is that such a stage system is able to move the mask support or substrate table relative to a reference with a high accuracy over a large range of movement.

[00016] However, a drawback of the combination of the long-stroke module and the short-stroke module is that the stage itself must carry more components on the moving world: motors to move the short stroke module, cooling water supply and electrical supply. Consequently, the combination of long-stroke module and short-stroke module requires a lot of volume and is expensive, especially with increasing acceleration demands.

SUMMARY

[00017] Considering the above, it is an object of the invention to provide an improved stage system, in particular a stage system which has a simpler architecture.

[00018] According to an embodiment of the invention, there is provided a stage system including: a stage that is moveable relative to a reference; a bearing to support and guide movement of the stage relative to the reference in a 2D plane; and an actuator system to apply forces to the stage relative to the reference to move or position the stage relative to the reference in the 2D plane, wherein the actuator system includes at least one actuator device configured to have an engaged mode, in which the actuator device is engaged with the stage to allow the stage to move along with the actuator device, and a disengaged mode, in which the actuator device is disengaged from the stage allowing the stage and the actuator device to move independently.

[00019] An advantage of the stage system according to the invention is that the actuator devices of the actuator system are not stacked upon each other, i.e. on top of each other, where only one actuator device is configured to operate on the stage while the other actuator device is configured to operate on the one actuator device and thus indirectly operates on the stage. The present arrangement allows the two actuator devices to operate both on the stage, simultaneously or in sequence. The use of an engaged and disengaged mode allows the actuator device to selectively operate on the stage. As a result of these features, the stage system has a simpler architecture resulting in lower costs while similar performance may be obtainable due to the now possible lower moving mass of the stage system.

[00020] In an embodiment, the bearing is a contactless or low-friction bearing, e.g. an air bearing. This minimizes the friction which friction may cause disturbances and position errors. It is preferred that the bearing causes no or minimal disturbances and causes no or minimal position errors.

[00021] In an embodiment, an actuator device of the actuator system includes a clamp to bring said stage into the engaged mode. Preferably, the clamp is an electromagnetic clamp, an electrostatic clamp, a vacuum clamp or a clamp utilizing Van der Waals forces. The advantage of these type of clamps is that clamping is the result of attractive forces between the actuator device and the stage which attractive forces can be easily and quickly activated and deactivated.

[00022] In an embodiment, an actuator device of the actuator system includes a portion of the bearing to support and guide movement of the stage relative to said actuator device when said actuator device is in disengaged mode. As a result thereof, the actuator device is able to support the stage in both the engaged and disengaged mode. Further, the bearing portion may aid in inadvertent engagement between actuator device and stage.

[00023] In an embodiment, at least one actuator device of the actuator system is non-translatable relative to the reference. Such an actuator device is in particular suitable to maintain the position of the stage relative to the reference, i.e. the stage is not allowed to translate relative to the reference. In an embodiment, the at least one actuator device of the actuator system is stationary arranged relative to the reference, so that the stage can be held stationary relative to the reference using said at least one actuator device.

[00024] In another embodiment, at least one actuator device of the actuator system is rotatable relative to the reference about a rotation axis perpendicular to the 2D plane. This makes rotation of the stage easier as a single actuator device can rotate and rotate the stage along. When said at least one actuator device is also non-translatable, the actuator device is in particular suitable to rotate the stage without translating the stage. The possibility to rotate may be important, e.g. for pre-alignment of the substrate to an alignment camera or allowing a stationary sensor by measuring markers in rotated orientation.

[00025] In an embodiment, at least one actuator device is configured to apply forces in at least two different directions to move or position the stage relative to the reference in the 2D plane. The at least two different directions may correspond to translation directions, but may also correspond to one translation direction and one rotational direction or two translation directions and one rotational direction. As is known, two orthogonal translation directions generally known as XY movability in a Cartesian coordinate system may be replaced by the equivalent radial and rotational movability in a polar coordinate system.

[00026] In an embodiment, the clamp is an electromagnetic clamp, and wherein the stage includes a ferromagnetic material to cooperate with the electromagnetic clamp. As a result thereof, the stage does not require active motor parts.

[00027] In an embodiment, the ferromagnetic material is deformable in a direction out of the 2D plane to come into frictional engagement with the electromagnetic clamp in the engaged mode. An advantage thereof may be that the stage portion configured to hold a specimen such as a mask or substrate may have the same position in the direction out of the 2D plane in the engaged and disengaged mode and that thus the difference between the engaged and disengaged mode is the degree of deformation of the ferromagnetic material.

[00028] It will be apparent for the skilled person that although the above deformation of a portion of the stage has been described in respect of the ferromagnetic material, this feature may apply to any layer or stage portion configured to engage with the clamp to allow an easy switching between engaged and disengaged mode.

[00029] In an embodiment, the actuator system is configured to engage with the stage from below in the engaged mode of the actuator devices. This keeps the space above the stage free for metrology instruments such as sensors like scattero meters.

[00030] In an embodiment, the clamp is configured to bring the stage into frictional engagement with the actuator device by overcoming a bearing force applied by the bearing portion of the actuator device, e.g. the air bearing portion at said actuator device. This allows for quickly switching between the engaged mode and disengaged mode while ensuring the support of the stage.

[00031] In an embodiment, said actuator device is configured to bring the stage into frictional engagement with the actuator device by reducing a bearing force applied by the air bearing portion at said actuator device. An advantage of this embodiment is that this requires less energy to switch between engaged and disengaged mode.

[00032] In an embodiment, the stage system further comprises a measurement system to measure a position of the stage relative to the reference in a 2D plane. [00033] In an embodiment, the stage system further comprises a control unit to control the actuator system in dependency of an output of the measurement system and a setpoint signal.

[00034] In an embodiment, the actuator system comprises at least two actuator devices.

[00035] According to another embodiment of the invention, there is provided a method for operating a stage system according to the invention, wherein the method comprises the following steps: i. bringing at least one actuator device in engaged mode to move or position the stage relative to the reference; and ii. bringing said at least one actuator device in disengaged mode to move or position the actuator device relative to the reference independent of the stage.

[00036] An advantage of the above method is that the provision of at least two actuator devices allows the stage to be moved in a so-called stepping mode when the total distance to move the stage is larger than a moving range of an actuator device. An example of the stepping mode will be given below by assuming for the example only that the actuator system includes a first actuator device and a second actuator device.

[00037] In a first step, the first actuator device is provided in the engaged mode and the second actuator device is provided in disengaged mode. In a second step, the first actuator device is operated to move the stage relative to the reference and the second actuator device in a first direction. In a third step, the second actuator device is brought in the engaged mode and the first actuator device is brought in the disengaged mode. In a fourth step, the first actuator device is moved in opposite direction of the first direction after which the cycle can start again at the first step thereby stepwise moving the stage in the first direction.

[00038] When the second actuator device is non-translatable in the first direction or even stationary, the stage is not translated in the first direction during the third step, but when the second actuator device is able to move as well in the first direction, the moving speed of the stage can be increased by moving the second actuator device in the first direction as well when the second actuator device is in engaged mode and moving the second actuator device in the opposite direction of the first direction wen the second actuator device is in disengaged mode.

[00039] According to a further embodiment of the invention, there is provided a method for operating a stage system according to the invention, wherein the method comprises the following steps: i. bringing at least one actuator device in engaged mode to move the stage relative to the reference in a direction with a predetermined velocity; ii. when moving the stage in said direction with said predetermined velocity, bringing all actuator devices of the actuation system in disengaged mode for a predetermined amount of time; and iii. after said predetermined amount of time bringing at least one actuator device in engaged mode.

[00040] An advantage of this method is that this potentially provides a faster way of moving the stage over a distance larger than a moving range of an actuator device. By releasing the stage while moving, the stage shall keep on moving with substantially constant velocity. Once the desired end position is reached, an actuator device shall catch the stage using the engaged mode. For this method, it is preferred that the bearing is low-friction or even substantially frictionless.

[00041] In an embodiment, prior to step 3, the at least one actuator device is actuated to match the predetermined velocity of the stage in said direction. This has the advantage that bringing said at least one actuator device in engaged mode is carried out easily due to the same velocities after which forces can be applied in a controllable manner to the stage.

[00042] According to yet another embodiment of the invention, there is provided an inspection tool, alternatively referred to as metrology tool, including a sensor arrangement and a stage system according to the invention, wherein the sensor arrangement is configured to inspect a specimen supported on the stage.

[00043] In an embodiment, the specimen is a substrate, e.g. a wafer, and the stage includes a wafer clamp to hold the wafer during inspection.

[00044] According to a further embodiment of the invention, there is provided a lithographic apparatus including a stage system according to the invention and/or an inspection tool according to the invention.

[00045] In an embodiment, the lithographic apparatus further comprises: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; and a projection system configured to project the patterned radiation beam onto a target portion of the substrate, wherein the specimen is a substrate.

[00046] According to another embodiment of the invention, there is provided a calibration method to calibrate a lithographic apparatus according to the invention, comprising the step of adjusting parameters of the lithographic apparatus based on an output of the inspection tool.

[00047] According to yet another embodiment of the invention, there is provided a device manufacturing method wherein use is made of a lithographic apparatus according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS [00048] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

Figure 1 depicts a schematic overview of a lithographic apparatus;

Figure 2 schematically depicts a schematic overview of a lithographic cell;

Figure 3 schematically depicts a schematic representation of holistic lithography, representing a cooperation between three key technologies to optimize semiconductor manufacturing;

Figure 4 schematically depicts a stage system according to the invention Figure 5 schematically depicts a clamp of an actuator device of the stage system of Fig. 4 in two modes; and

Figure 6a-f schematically depicts six steps of an operating method of the stage system of Fig.

4.

DETAIFED DESCRIPTION

[00049] In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultra-violet radiation, e.g. having a wavelength in the range of about 5-100 nm).

[00050] The term “reticle”, “mask” or “patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term “light valve” can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable FCD array.

[00051] Figure 1 schematically depicts a lithographic apparatus FA. The lithographic apparatus FA includes an illumination system (also referred to as illuminator) IF configured to condition a radiation beam B (e.g., UV radiation, DUV radiation or EUV radiation), a mask support (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA in accordance with certain parameters, a substrate support (e.g., a wafer table) WT constructed to hold a substrate (e.g., a resist coated wafer)

W and connected to a second positioner PW configured to accurately position the substrate support in accordance with certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[00052] In operation, the illumination system IF receives a radiation beam from a radiation source SO, e.g. via a beam delivery system BD. The illumination system IF 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 radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross section at a plane of the patterning device MA.

[00053] The term “projection system” PS used herein should be broadly interpreted as encompassing various types of projection system, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and/or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system” PS.

[00054] The lithographic apparatus LA may be of a type wherein at least a portion of the substrate 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 - which is also referred to as immersion lithography. More information on immersion techniques is given in US6952253, which is incorporated herein by reference.

[00055] The lithographic apparatus LA may also be of a type having two or more substrate supports WT (also named “dual stage”). In such “multiple stage” machine, the substrate supports WT may be used in parallel, and/or steps in preparation of a subsequent exposure of the substrate W may be carried out on the substrate W located on one of the substrate support WT while another substrate W on the other substrate support WT is being used for exposing a pattern on the other substrate W. [00056] In addition to the substrate support WT, the lithographic apparatus LA may comprise a measurement stage. 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 B. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example a part of the projection system PS or a part of a system that provides the immersion liquid. The measurement stage may move beneath the projection system PS when the substrate support WT is away from the projection system PS.

[00057] In operation, the radiation beam B is incident on the patterning device, e.g. mask, MA which is held on the mask support MT, and is patterned by the pattern (design layout) present on patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and a position measurement system IF, the substrate support WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and possibly another position sensor (which is not explicitly depicted in Figure 1) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B. Patterning device MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2. Although the substrate alignment marks PI, P2 as illustrated occupy dedicated target portions, they may be located in spaces between target portions. Substrate alignment marks PI, P2 are known as scribe-lane alignment marks when these are located between the target portions C.

[00058] To clarify the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes, i.e., an x-axis, a y-axis and a z-axis. Each of the three axis is orthogonal to the other two axes. A rotation around the x-axis is referred to as an Rx-rotation. A rotation around the y- axis is referred to as an Ry -rotation. A rotation around about the z-axis is referred to as an Rz-rotation. The x-axis and the y-axis define a horizontal plane, whereas the z-axis is in a vertical direction. The Cartesian coordinate system is not limiting the invention and is used for clarification only. Instead, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, such that the z-axis has a component along the horizontal plane.

[00059] As shown in Figure 2 the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to as a lithocell or (litho)cluster, which often also includes apparatus to perform pre- and post-exposure processes on a substrate W. Conventionally these include spin coaters SC to deposit resist layers, developers DE to develop exposed resist, chill plates CH and bake plates BK, e.g. for conditioning the temperature of substrates W e.g. for conditioning solvents in the resist layers. A substrate handler, or robot, RO picks up substrates W from input/output ports I/Ol, 1/02, moves them between the different process apparatus and delivers the substrates W to the loading bay LB of the lithographic apparatus LA. The devices in the lithocell, which are often also collectively referred to as the track, are typically under the control of a track control unit TCU that in itself may be controlled by a supervisory control system SCS, which may also control the lithographic apparatus LA, e.g. via lithography control unit LACU.

[00060] In order for the substrates W exposed by the lithographic apparatus LA to be exposed correctly and consistently, it is desirable to inspect substrates to measure properties of patterned structures, such as overlay errors between subsequent layers, line thicknesses, critical dimensions (CD), etc. For this purpose, inspection tools (not shown) may be included in the lithocell LC. If errors are detected, adjustments, for example, may be made to exposures of subsequent substrates or to other processing steps that are to be performed on the substrates W, especially if the inspection is done before other substrates W of the same batch or lot are still to be exposed or processed.

[00061] An inspection apparatus, which may also be referred to as a metrology apparatus, is used to determine properties of the substrates W, and in particular, how properties of different substrates W vary or how properties associated with different layers of the same substrate W vary from layer to layer. The inspection apparatus may alternatively be constructed to identify defects on the substrate W and may, for example, be part of the lithocell LC, or may be integrated into the lithographic apparatus LA, or may even be a stand-alone device. The inspection apparatus may measure the properties on a latent image (image in a resist layer after the exposure), or on a semi-latent image (image in a resist layer after a post-exposure bake step PEB), or on a developed resist image (in which the exposed or unexposed parts of the resist have been removed), or even on an etched image (after a pattern transfer step such as etching).

[00062] Typically the patterning process in a lithographic apparatus LA is one of the most critical steps in the processing which requires high accuracy of dimensioning and placement of structures on the substrate W. To ensure this high accuracy, three systems may be combined in a so called “holistic” control environment as schematically depicted in Fig. 3. One of these systems is the lithographic apparatus LA which is (virtually) connected to a metrology tool MT (a second system) and to a computer system CL (a third system). The key of such a “holistic” environment is to optimize the cooperation between these three systems to enhance the overall process window and to provide tight control loops to ensure that the patterning performed by the lithographic apparatus LA stays within a process window. The process window defines a range of process parameters (e.g. dose, focus, overlay) within which a specific manufacturing process yields a defined result (e.g. a functional semiconductor device) - typically within which the process parameters in the lithographic process or patterning process are allowed to vary.

[00063] The computer system CL may use (part of) the design layout to be patterned to predict which resolution enhancement techniques to use and to perform computational lithography simulations and calculations to determine which mask layout and lithographic apparatus settings achieve the largest overall process window of the patterning process (depicted in Fig. 3 by the double arrow in the first scale SCI). Typically, the resolution enhancement techniques are arranged to match the patterning possibilities of the lithographic apparatus LA. The computer system CL may also be used to detect where within the process window the lithographic apparatus LA is currently operating (e.g. using input from the metrology tool MT) to predict whether defects may be present due to e.g. sub-optimal processing (depicted in Fig. 3 by the arrow pointing “0” in the second scale SC2).

[00064] The metrology tool MT may provide input to the computer system CL to enable accurate simulations and predictions, and may provide feedback to the lithographic apparatus LA to identify possible drifts, e.g. in a calibration status of the lithographic apparatus LA (depicted in Fig. 3 by the multiple arrows in the third scale SC3).

[00065] As mentioned above by reference to the Figs. 1-3, the lithographic apparatus, the metrology tool and/or lithocell typically include a plurality of stage systems used to position a specimen, substrate, mask or sensor arrangement relative to a reference or other component. Examples thereof are the mask support MT and first positioner PM, the substrate support WT and the second positioner PW, the measurement stage arranged to hold a sensor and or a cleaning device, and the stage used in the inspection tool MT where a substrate W is positioned relative to e.g. a scanning electron microscope or some kind of scatterometer.

[00066] Any of these stage systems may be a stage system according to the invention as will be explained below in more detail by reference to the Figs. 4, 5 and 6a to 6f. [00067] Fig. 4 depicts schematically a cross-sectional view of a stage system including a stage ST that is moveable relative to reference RE. The reference RE in this embodiment may be a metrology frame carrying a sensor arrangement SA such as a scatterometer, configured to inspect a specimen SP, e.g. a substrate W, supported on the stage ST. In another embodiment, the reference RE is a frame supporting the projection system PS configured to project a patterned radiation beam onto a target portion of the substrate W supported by the stage ST. In yet another embodiment, the reference RE may be a frame supporting the illumination system configured to condition a radiation beam, wherein the stage ST supports a patterning device MA configured to impart the radiation beam with a pattern in its cross-section to form a patterned radiation beam.

[00068] The stage system includes a measurement system MS, e.g. comprising an interferometer, to measure a position of the stage ST relative to the reference RE. Although the below description will describe the stage system from a one-dimensional perspective, i.e. a perspective in plane of the drawing, it is explicitly noted here that the same applies to a direction out of plane of the drawing, so that the stage ST is moveable relative to the reference in a 2D plane. The measurement system MS is thus also configured to measure the position of the stage ST in said 2D plane.

[00069] The stage system ST further includes a frame FR, a bearing BE to support and guide movement of the stage relative to the reference RE and thus also the frame FR, an actuator system AS configured to move or position the stage ST relative to the reference RE in the 2D plane, and a substrate load and unload system LUS configured to load and unload a substrate W on the stage ST via the holes H in the stage ST.

[00070] Although the frame FR and reference RE are not connected in Fig. 4, thereby allowing to isolate the reference RE and the sensor arrangement SA from disturbances introduced into the frame FR, it is also envisaged that the frame FR and reference RE are interconnected, thereby allowing to use a simpler measurement system MS as for instance under certain conditions less degrees of freedom need to be measured to know the position of the stage ST in the 2D plane.

[00071] The load and unload system LUS comprises pins PI that can be moved up and down. When the stage ST is positioned over the load and unload system LUS, such that the holes H are right above the pins PI, the pins can be moved upwards through the holes to lift a substrate W from the stage ST. The substrate W can then be caught by e.g. a robot and moved to another processing station. Another (or the same) substrate W can then be (re)positioned on the pins PI and subsequently loaded onto the stage ST by lowering the pins PI to below the stage ST. The stage is then free to move in the 2D plane for further processing the substrate W.

[00072] The bearing BE is in this embodiment an air bearing providing a layer of air between the stage ST and the frame FR thereby providing a contactless bearing with relatively low friction.

[00073] The actuator system AS includes at least one actuator devices AD although one or more additional actuator devices may be present. Actuator device AD may be provided in different types, including but not limited to a moveable type in which the actuator device AD may be moveable in one direction only, e.g. a translational direction or a rotational direction (in which case the actuator device is non-translatable), to move or position the stage ST in the 2D plane, or in which the actuator device AD may be moveable in two directions, e.g. two translational direction or a translational direction and a rotational direction, or in which the actuator device AD may be moveable in three directions, namely two translational directions and a rotational direction. The rotational direction is then about a rotation axis perpendicular to the 2D plane. Additional movability outside of the 2D plane is also envisaged, e.g. a translation perpendicular to the 2D plane or a rotation about a rotation axis parallel to the 2D plane. An actuator device AD may further be of the stationary type.

[00074] The actuator device AD shown in Fig. 4 is moveable in at least one translational direction in plane of the drawing parallel to the stage ST. To this end, an actuator ACT, e.g. a Lorentz actuator, is provided to move the actuator device AD.

[00075] At an upper end of the actuator device AD, a clamp CL is provided. In this embodiment, the clamp CL is an electromagnetic clamp configured to cooperate with a ferromagnetic layer FL on the stage ST. The clamp CL is configured to selectively engage with or disengage from the stage ST so that the actuator device AD has an engaged mode in which the actuator device AD is engaged with the stage ST to allow the stage ST to move along with the actuator device AD, and a disengaged mode in which the actuator device AD is disengaged from the stage ST allowing the stage ST and the actuator device AD to move independently or phrase differently allowing the stage ST to move independent from the actuator device AD.

[00076] To explain the working principle of the clamp CL, reference is made to Fig. 5 in which the clamp CL and the ferromagnetic layer FL are depicted only. The clamp CL and the ferromagnetic layer FL have been depicted twice, wherein the left figure depicts the disengaged mode and the right figure depicts the engaged mode.

[00077] The clamp CL in this embodiment comprises a yoke YO, a coil CO and a bearing portion BP. The bearing portion BP is part of the air bearing BE (as shown in Figure 4) and provides a layer of air in between the bearing portion BP and the ferromagnetic layer FL as indicated by the arrows in the left figure. Due to the air bearing portion, a gap GA is present in between the clamp CL and the stage ST (not shown) at the location of the clamp CL. In the left figure, i.e. the disengaged mode, the coil CO is not energized and thus the clamp is not active. The stage ST (as shown in Figure 4) is then able to move relative to the actuator device AD (as shown in Figure 4), in which case the stage ST may be stationary and the actuator device AD moves, the actuator device AD is stationary and the stage ST moves, or both the actuator device AD and the stage ST move. During movement, but also when the stage ST does not move relative to the actuator device AD, the bearing portion BP supports the stage relative to the clamp CL.

[00078] When the coil CO is energized, the clamp CL and the ferromagnetic layer FL are attracted to each other thereby resulting in frictional engagement between the clamp CL and the ferromagnetic layer FL and allowing a magnetic flux through the yoke YO and the ferromagnetic layer FL as indicated by the double arrows. When bringing the actuator device AD in the engaged mode, the bearing portion BP may reduce a bearing force applied by the bearing portion BP in the disengaged mode, so that a relatively small attractive force will bring the clamp and ferromagnetic layer in frictional engagement. However, it is also possible that operation of the bearing portion is maintained and the coil CO is energized to overcome the bearing force applied by the bearing portion, which may allow faster switching between engaged and disengaged mode while always ensuring support by the bearing portion.

[00079] In the engage mode, there is no gap GA present anymore compared to the disengaged mode, which means that either the clamp CL has moved towards the ferromagnetic layer FL, or the ferromagnetic layer FL has moved towards the clamp CL, e.g. by deforming in a direction out of the 2D plane, or both the clamp CL and the ferromagnetic layer FL have moved to each other.

[00080] Fig. 6 depicts different steps in an operating method according to an embodiment of the invention, which may be referred to as a stepping mode. Use is made of a stationary actuator device SAD including a clamp CL, e.g. the clamp CL of Fig. 5, and a moveable actuator device MAD including a clamp, e.g. the clamp CL of Fig. 5.

[00081] In a first step, shown in Fig. 6a, the actuator device SAD is in engaged mode and the actuator device MAD is in disengaged mode, thereby holding the stage ST relative to the frame FR (and thus reference).

[00082] In a second step, shown in Fig. 6b, the actuator device MAD is also brought into engaged mode after which the actuator device SAD can be brought into the disengaged mode in a third step shown in Fig. 6c.

[00083] In a fourth step, shown in Fig. 6d, the actuator device MAD is moved over a certain distance as indicated by the arrow thereby moving the stage ST relative to the frame FR (and thus the reference).

[00084] In a fifth step, shown in Fig. 6e, the actuator device SAD is brought into the engaged mode while the actuator device MAD is brought into the disengaged mode, so that the actuator device MAD can be moved back in opposite direction in a sixth step as shown in Fig. 6f and indicated by the arrow to allow the sequence to start again at the first step.

[00085] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may 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, etc.

[00086] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may 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 an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non-vacuum) conditions.

[00087] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention, where the context allows, is not limited to optical lithography and may be used in other applications, for example imprint lithography.

[00088] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also 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, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.

[00089] 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 descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below. Other aspects of the invention are set-out as in the following numbered clauses.

1. A stage system including: a stage that is moveable relative to a reference; a bearing to support and guide movement of the stage relative to the reference in a 2D plane; and an actuator system to apply forces to the stage relative to the reference to move or position the stage relative to the reference in the 2D plane, wherein the actuator system includes at least one actuator device configured to have an engaged mode, in which the actuator device is engaged with the stage to allow the stage to move along with the actuator device, and a disengaged mode, in which the actuator device is disengaged from the stage allowing the stage to move independent from the actuator device.

2. A stage system according to clause 1, wherein the bearing is a contactless or low-friction bearing. 3. A stage system according to clause 1 or 2, wherein an actuator device of the actuator system includes a clamp to bring said actuator device into the engaged mode.

4. A stage system according to clause 3, wherein the clamp is an electromagnetic clamp, an electrostatic clamp, a vacuum clamp or a clamp utilizing Van der Waals forces.

5. A stage system according to any of clauses 1-4, wherein an actuator device of the actuator system includes a portion of the bearing to support and guide movement of the stage relative to said actuator device when said actuator device is in disengaged mode.

6. A stage system according to any of clauses 1-5, wherein at least one actuator device of the actuator system is non-translatable relative to the reference.

7. A stage system according to any of clauses 1-6, wherein at least one actuator device of the actuator system is rotatable relative to the reference about a rotation axis perpendicular to the 2D plane.

8. A stage system according to any of clauses 1-6, wherein at least one actuator device of the actuator system is stationary arranged relative to the reference.

9. A stage system according to any of clauses 1-5, wherein at least one actuator device is configured to apply forces in at least two different directions to move or position the stage relative to the reference in the 2D plane.

10. A stage system according to clause 2, wherein the bearing is an air bearing.

11. A stage system according to clause 3, wherein the clamp is an electromagnetic clamp, and wherein the stage includes a ferromagnetic material to cooperate with the electromagnetic clamp.

12. A stage system according to clause 11, wherein the ferromagnetic material is deformable in a direction out of the 2D plane to come into frictional engagement with the electromagnetic clamp in the engaged mode.

13. A stage system according to any of the clauses 1-12, wherein the actuator system is configured to engage with the stage from below in the engaged mode of the actuator devices.

14. A stage system according to clauses 3, 5 and 10, wherein the clamp is configured to bring the stage into frictional engagement with the actuator device by overcoming a bearing force applied by the air bearing portion at said actuator device.

15. A stage system according to clauses 3, 5 and 10, wherein said actuator device is configured to bring the stage into frictional engagement with the actuator device by reducing a bearing force applied by the air bearing portion at said actuator device.

16. A stage system according to any of the clauses 1-15, further comprising a measurement system to measure a position of the stage relative to the reference in a 2D plane.

17. A stage system according to clause 16, further comprising a control unit to control the actuator system in dependency of an output of the measurement system and a setpoint signal. A stage system according to any of the clauses 1-17, wherein the actuator system comprises at least two actuator devices. A method for operating a stage system according to clause 1, wherein the method comprises the following steps: i. bringing at least one actuator device in engaged mode to move or position the stage relative to the reference; and ii. bringing said at least one actuator device in disengaged mode to move or position the actuator device relative to the reference independent of the stage. A method for operating a stage system according to clause 1, wherein the method comprises the following steps: i. bringing at least one actuator device in engaged mode to move the stage relative to the reference in a direction with a predetermined velocity; ii. when moving the stage in said direction with said predetermined velocity, bringing all actuator devices of the actuation system in disengaged mode for a predetermined amount of time; and iii. after said predetermined amount of time bringing at least one actuator device in engaged mode. An inspection tool including a sensor arrangement and a stage system according to any of clauses 1-18, wherein the sensor arrangement is configured to inspect a specimen supported on the stage. An inspection tool according to clause 21, wherein the specimen is a wafer and the stage includes a wafer clamp to hold the wafer during inspection. A lithographic apparatus comprising a stage system according to any of clauses 1-18. A lithographic apparatus comprising an inspection tool according to clause 21 or 22. A lithographic apparatus according to clause 24, further comprising: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; and a projection system configured to project the patterned radiation beam onto a target portion of the substrate, wherein the specimen is a substrate. A calibration method to calibrate a lithographic apparatus according to clause 24 or 25, comprising the step of adjusting parameters of the lithographic apparatus based on an output of the inspection tool. A device manufacturing method wherein use is made of a lithographic apparatus according to any of clauses 23-25. A stage system including: a stage that is moveable relative to a reference; - a bearing to support and guide movement of the stage relative to the reference in a 2D plane; and an actuator system to apply forces to the stage relative to the reference to move or position the stage relative to the reference in the 2D plane, wherein the actuator system includes at least one actuator device configured to have an engaged mode, in which the actuator device is engaged with the stage to allow the stage to move along with the actuator device, and a disengaged mode, in which the actuator device is disengaged from the stage allowing the stage to move independent from the actuator device.

Claims

1. A stage system including: a stage that is moveable relative to a reference; a bearing to support and guide movement of the stage relative to the reference in a 2D plane; and an actuator system to apply forces to the stage relative to the reference to move or position the stage relative to the reference in the 2D plane, wherein the actuator system includes at least one actuator device configured to have an engaged mode, in which the actuator device is engaged with the stage to allow the stage to move along with the actuator device, and a disengaged mode, in which the actuator device is disengaged from the stage allowing the stage and the actuator device to move independently.

2. A stage system according to claim 1, wherein the bearing is a contactless or low-friction bearing.

3. A stage system according to claim 1 or 2, wherein an actuator device of the actuator system includes a clamp to bring said actuator device into the engaged mode.

4. A stage system according to claim 3, wherein the clamp is an electromagnetic clamp, an electrostatic clamp, a vacuum clamp or a clamp utilizing Van der Waals forces.

5. A stage system according to any of claims 1-4, wherein an actuator device of the actuator system includes a portion of the bearing to support and guide movement of the stage relative to said actuator device when said actuator device is in disengaged mode.

6. A stage system according to any of claims 1-5, wherein at least one actuator device of the actuator system is non-translatable relative to the reference.

7. A stage system according to any of claims 1-6, wherein at least one actuator device of the actuator system is rotatable relative to the reference about a rotation axis perpendicular to the 2D plane.

8. A stage system according to any of claims 1-6, wherein at least one actuator device of the actuator system is stationary arranged relative to the reference.

9. A stage system according to any of claims 1-5, wherein at least one actuator device is configured to apply forces in at least two different directions to move or position the stage relative to the reference in the 2D plane.

10. A stage system according to claim 2, wherein the bearing is an air bearing.

11. A stage system according to claim 3, wherein the clamp is an electromagnetic clamp, and wherein the stage includes a ferromagnetic material to cooperate with the electromagnetic clamp.

12. A stage system according to claim 11, wherein the ferromagnetic material is deformable in a direction out of the 2D plane to come into frictional engagement with the electromagnetic clamp in the engaged mode.

13. A stage system according to any of the claims 1-12, wherein the actuator system is configured to engage with the stage from below in the engaged mode of the actuator devices.

14. A stage system according to claims 3, 5 and 10, wherein the clamp is configured to bring the stage into frictional engagement with the actuator device by overcoming a bearing force applied by the air bearing portion at said actuator device.

15. A stage system according to claims 3, 5 and 10, wherein said actuator device is configured to bring the stage into frictional engagement with the actuator device by reducing a bearing force applied by the air bearing portion at said actuator device.

16. A stage system according to any of the claims 1-15, further comprising a measurement system to measure a position of the stage relative to the reference in a 2D plane.

17. A stage system according to claim 16, further comprising a control unit to control the actuator system in dependency of an output of the measurement system and a setpoint signal.

18. A stage system according to any of the claims 1-17, wherein the actuator system comprises at least two actuator devices.

19. A method for operating a stage system according to claim 1, wherein the method comprises the following steps: i. bringing at least one actuator device in engaged mode to move or position the stage relative to the reference; and ii. bringing said at least one actuator device in disengaged mode to move or position the actuator device relative to the reference independent of the stage.

20. A method for operating a stage system according to claim 1, wherein the method comprises the following steps: i. bringing at least one actuator device in engaged mode to move the stage relative to the reference in a direction with a predetermined velocity; ii. when moving the stage in said direction with said predetermined velocity, bringing all actuator devices of the actuation system in disengaged mode for a predetermined amount of time; and iii. after said predetermined amount of time bringing at least one actuator device in engaged mode.

21. An inspection tool including a sensor arrangement and a stage system according to any of claims 1-18, wherein the sensor arrangement is configured to inspect a specimen supported on the stage.

22. An inspection tool according to claim 21, wherein the specimen is a wafer and the stage includes a wafer clamp to hold the wafer during inspection.

23. A lithographic apparatus comprising a stage system according to any of claims 1-18.

24. A lithographic apparatus comprising an inspection tool according to claim 21 or 22.

25. A lithographic apparatus according to claim 24, further comprising: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; and a projection system configured to project the patterned radiation beam onto a target portion of the substrate, wherein the specimen is a substrate.

26. A calibration method to calibrate a lithographic apparatus according to claim 24 or 25, comprising the step of adjusting parameters of the lithographic apparatus based on an output of the inspection tool.

27. A device manufacturing method wherein use is made of a lithographic apparatus according to any of claims 23-25.