NL2006220A - Lithographic apparatus and device manufacturing method. - Google Patents

Description

LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD

FIELD

[0001] The present invention relates to a lithographic apparatus and a method for manufacturing a device.

BACKGROUND

[0002] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. 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 an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning’-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0003] In order to transfer the pattern of a patterning device onto a target portion on a substrate, the lithographic apparatus can be provided with a measurement system such as an optical encoder measurement system or an interferometer measurement system. The former can e.g. include an irradiation system to direct an irradiation beam to a scale (e.g. a one- or two-dimensional grating) for measuring a position of the scale relative to the measurement system. As the performance requirement, together with a demand for an increased functionality, of lithographic apparatuses is ever increasing, volume or area conflicts may occur inside a lithographic apparatus. In addition, more detailed positional information may be required, e.g. on (in)-homogeneous expansion, shape information including distortion. Obtaining such information would require additional sensors or measurement systems with could increase the volume or area conflict.

SUMMARY

[0004] It is desirable to provide a lithographic apparatus with an improved measurement system.

[0005] According to an embodiment of the invention, there is provided a lithographic apparatus including: 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 apparatus is provided with an optical measurement system including: an irradiation source to provide an irradiation beam; optics to split the irradiation beam in a measurement beam and a reference beam and direct the measurement beam to a first scale, the optics further being arranged to direct at least one of multiple diffracted beams diffracted from the first scale upon irradiation by the measurement beam to a second scale; a first detector to receive at least two of multiple further diffracted beams diffracted from the second scale upon irradiation by the at least one of multiple diffracted beams to determine a first position quantity of the first scale with respect to the second scale; a second detector to receive the reference beam and at least one of the multiple further diffracted beams to determine a second position quantity of the first scale with respect to the second scale on the basis of the at least one of the multiple further diffracted beams and the reference beam.

[0006] According to an embodiment of the invention, there is provided a device manufactured according to the method including: determining a position of a pattern from a patterning device with respect to substrate by: - providing a first scale; - providing a second scale; - providing an irradiation beam; - splitting the irradiation beam in a measurement beam and a reference beam by means of optics and directing the measurement beam to a first scale, directing at least one of multiple diffracted beams diffracted from the first scale upon irradiation by the measurement beam to a second scale by means of the optics; - receiving at least two of multiple further diffracted beams diffracted from the second scale upon irradiation by the at least one of multiple diffracted beams by a first detector to determine a first position quantity of the first scale with respect to the second scale; - receiving the reference beam and at least one of the multiple further diffracted beams to determine a second position quantity of the first scale with respect to the second scale on the basis of the at least one of the multiple further diffracted beams and the reference beam by a second detector and - transferring a pattern from a patterning device onto a substrate.

[0007] In an embodiment, the first scale can e.g. be provided on the patterning device, the substrate, a stage or any other surface of interest of the lithographic apparatus.

[0008] The second scale can e.g. be mounted to a metrology frame, to the first or second detector or any other surface of interest.

[0009] The first and second scale may also be mounted on the same (monolithic) structure in order to determine or monitor any deformations of the structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0011] Figure 1 depicts a lithographic apparatus according to an embodiment of the invention;

[0012] Figure 2a depicts a top view of an optical measurement system as can be applied in a lithographic apparatus according to an embodiment of the invention;

[0013] Figure 2b shows a side view of the optical measurement system of figure 2a.

[0014] Figure 2c shows a further side view of the optical measurement system of figure 2a.

[0015] Figure 3 schematically depicts an optical measurement system as can be applied in a lithographic apparatus according to an embodiment of the invention.

[0016] Figures 4a-4f schematically depict various options for obtaining an out-of-plane interferometer measurement of a first scale with respect to a second scale that can be applied in an optical measurement system as applied in a lithographic apparatus according to an embodiment of the invention.

[0017] Figures 5a-5b schematically depict various options for obtaining an out-of-plane encoder based measurement of a first scale with respect to a second scale which can be applied in an optical measurement system as applied in a lithographic apparatus according to an embodiment of the invention.

[0018] Figures 6a-6i schematically depict further options for obtaining an out-of-plane encoder based measurement of a first scale with respect to a second scale which can be applied in an optical measurement system as applied in a lithographic apparatus according to an embodiment of the invention.

[0019] Figures 7a-7f schematically depict more options for obtaining an out-of-plane encoder based measurement of a first scale with respect to a second scale which can be applied in an optical measurement system as applied in a lithographic apparatus according to an embodiment of the invention

[0020] Figure 8a schematically depicts an embodiment for a tilt measurement in a first view.

[0021] Figure 8b schematically depicts the embodiment for a tilt measurement in a second view.

[0022] Figure 9a schematically depicts an embodiment for a double tilt measurement in a first view.

[0023] Figure 9b schematically depicts the embodiment for a double tilt measurement in a second view.

DETAILED DESCRIPTION

[0024] Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus includes an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or any other suitable radiation), a patterning device support or support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioning device PM configured to accurately position the patterning device in accordance with certain parameters. The apparatus also includes a substrate table (e.g. a wafer table) WT or "substrate support" constructed to hold a substrate (e.g. a resist-coated wafer) W and connected to a second positioning device PW configured to accurately position the substrate in accordance with certain parameters. The apparatus further includes 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. including one or more dies) of the substrate W.

[0025] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, to direct, shape, or control radiation.

[0026] The patterning device support holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The patterning device support can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The patterning device support may be a frame or a table, for example, which may be fixed or movable as required. The patterning device support may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

[0027] The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

[0028] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

[0029] The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid 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”.

[0030] As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

[0031] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables or "substrate supports" (and/or two or more mask tables or "mask supports"). In such “multiple stage” machines the additional tables or supports may be used in parallel, or preparatory steps may be carried out on one or more tables or supports while one or more other tables or supports are being used for exposure.

[0032] The lithographic apparatus may also 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 and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the patterning device (e.g. mask) and the projection system. Immersion techniques can be used to increase the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that a liquid is located between the projection system and the substrate during exposure.

[0033] Referring to Figure 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD including, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0034] The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

[0035] The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the patterning device support (e.g., mask table) MT, and is patterned by the patterning device. Having traversed the patterning device (e.g. mask) MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioning device PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the patterning device support (e.g. mask table) MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioning device PM. Similarly, movement of the substrate table WT or "substrate support" may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the patterning device support (e.g. mask table) MT may be connected to a short-stroke actuator only, or may be fixed.

Patterning device (e.g. mask) MA and substrate W may be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device (e.g. mask) MA, the patterning device alignment marks may be located between the dies.

[0036] The depicted apparatus could be used in at least one of the following modes: 1. In step mode, the patterning device support (e.g. mask table) MT or "mask support" and the substrate table WT or "substrate support" are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT or "substrate support" is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

2. In scan mode, the patterning device support (e.g. mask table) MT or "mask support" and the substrate table WT or "substrate support" are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT or "substrate support" relative to the patterning device support (e.g. mask table) MT or "mask support" may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion.

3. In another mode, the patterning device support (e.g. mask table) MT or "mask support" is kept essentially stationary holding a programmable patterning device, and the substrate table WT or "substrate support" is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or "substrate support" or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0037] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[0038] Figures 2a-2c schematically depict an embodiment of an optical measurement system as can be applied to determine a position quantity of e.g. the patterning device (e.g. mask) MA and/or the substrate W, the stage MT, WT, MM or WM, as shown in the lithographic apparatus of Figure 1. As such, the optical measurement system can facilitate an accurate projection of a pattern on the patterning device (e.g. mask) MA onto a target portion of the substrate W. Figures 2a-2c schematically depict the measurement system in three different views (a top view in an XY plane, see figure 2a, and two side views in an XZ, see figure 2c and YZ plane, see figure 2b).

[0039] The optical measurement system as shown includes an irradiation system having an irradiation source 101 providing an irradiation beam 3. The measurement system includes an optical system (e.g. optics) to split the irradiation beam 3 in a measurement beam 4 and a reference beam 6 (such optics can e.g. include a beam splitter 100) and direct the measurement beam 4 to a first scale 5. The optics are further arranged to direct at least two of multiple diffracted beams 9 diffracted from the first scale 5 upon irradiation by the measurement beam 4 to a second scale 11, whereupon the second scale provides in multiple further diffracted beams. In order to do so, the optics as shown in Figure 2a-2c include a plurality of mirrors 7. The mirrors 7 may, in an embodiment, be polarizing mirrors so as to change the polarization of the diffracted beams. The first and second scale 5,11 may be one- or two dimensional diffraction structures. Two dimensional structures such as cross gratings or chess board patterns may diffract the light in multiple directions, thus providing multiple diffracted beams. In the embodiment as shown in Figure 2a-2c, both the first and second scale 5,11 are considered to be two-dimensional gratings. The measurement system further includes a first detector arranged to detect at least two further diffracted beams that are diffracted from the second scale 11 upon irradiation by at least two diffracted beams from the first scale in order to determine a first position quantity of the first scale with respect to the second scale. In the arrangement as shown, the first position quantity can e.g. be a relative X- or Y-position of the first scale with respect to the second scale. As shown, the first detector include a detection sensor 132. The further diffracted beams are received by the detection sensor via mirror 129 which is part of the optics.

[0040] In some embodiments, described in more detail below, one or more additional diffractions of the further diffracted beams (either on the first or second scale) can occur prior to the detection of the further diffracted beams by the first detector. Thus, the at least two of multiple further diffracted beams may undergo one or more yet further diffractions on the first and/or second scale before being received by the first detector.

[0041] The measurement system as shown in Figures 2a-2c further includes a second detector (including a detection sensor 132) to receive the reference beam 3 and at least one of the further diffracted beams. Based on this, the second detector can determine a second position quantity of the first scale with respect to the second scale. In the arrangement as shown, the second position quantity corresponds to a Z-position of the first scale 5 relative to the second scale 11, i.e. the distance between the first and second scale in a direction substantially perpendicular to a plane parallel to the first and second scale (i.e. the XY-plane). Thus, the measurement system as shown enables to provide a first in-plane position quantity (in plane with respect to a plane parallel to the scales) and a second out-of-plane position quantity (perpendicular to the scales). In the embodiment, the out-of-plane measurement is obtained from a comparison of the reference beam 6 and a beam diffracted on both scales and can thus also be described as an interferometer based measurement. The in-plane measurement on the other hand is an encoder based measurement based on the detected further diffracted beam arriving, via detection mirror 129 at detection sensor 132. In the arrangement as shown, the first detector includes two detection sensors, 132,133 receiving the further diffracted beams from mirrors 129 resp. 130 and whereby each detector can determine a different position quantity, due to the application of two-dimensional scales 5,11. This can more clearly be seen from the top view in Figure 2a-2c: as shown, the measurement beam 4, is directed in the Z-direction out of the plane of the top view in Figure 2a and is diffracted on a two dimensional grating (not shown) which is tilted 45 degrees with respect to the irradiation beam 3. The grating diffracts the beam in four primary diffracted beams 9 which are directed by the mirrors 7 to the second grating (not shown) which diffracts the beam for the second time in the direction of the detector mirror 129,130 which reflects the further diffracted beams 15 to detection sensors 132,133. The optics further include two quarter lambda plates 145 configured to provide a phase shift in a beam passing the plates.

[0042] In such an arrangement, both relative X- and Y-position of the first scale with respect to the second scale can be determined. As such, the measurement system as describes thus enables a 2D in-plane position measurement (based on an encoder measurement) combined with a 1D out-of-plane position measurement (based on an interferometer measurement) using a single irradiation beam 3.

[0043] In an embodiment, the mirrors 7 and optical components 129,130 and 100 can be mounted on a long stroke mover WM, MM of the lithographic apparatus as shown in Figure 1. The irradiation source 101 and the detection sensors 131,132 and 133 can be mounted elsewhere, e.g. on a balance mass (not shown) that is movable with respect to the long stroke mover WM, MM. Components 7, 129,130 and 100 could e.g. be placed on a metrology frame as well. The detection sensors 131,132 and 133 and components 7,129,130 and 100 can e.g. be placed at the same body, resulting in more conventional metrology architecture.

[0044] The irradiation source, optical components and sensors can be arranged in different manners: - the irradiation source and detectors, all optics, and the second scale can be arranged in one sensor housing (i.e. a common housing), resulting in a non-wireless set-up, - the irradiation source detectors, and all optics in can be arranged in one sensor housing resulting in a non-wireless set-up, - the illumination source and all optics can be arranged in one housing resulting in a partially wireless set-up, - the detectors and all optics can be mounted in one housing resulting in a partially wireless set-up, - the second scale, and all optics can be mounted in one housing resulting in a wireless set-up), - all optics can be mounted in one housing resulting in a wireless set-up.

[0045] In the latter two configurations, the irradiation source and detectors can be part of a single component or not.

[0046] The measurement system as described thus enables a 3D position measurement of a first scale with respect to a second scale. The measurement system can be applied in a lithographic apparatus as e.g. shown in Figure 1 to determine the position of a first part of the apparatus relative to a second part of the apparatus by providing the first scale 5 to the first part and providing the second scale 11 to the second part. The first scale 5 may e.g. be provided to a patterning device MA (see e.g. Figure 1) e.g. a mask and the second scale 11 may be provided to a metrology frame which is connected to the projection system PS. Movement of the patterning device table MT may be realized with the aid of a long-stroke module configured to coarsely move a long stroke mover MM and a short-stroke module configured to finely move the patterning device MA with respect to the long stroke mover MM, which modules and mover form part of the first positioning device PM (see Figure 1). The passive components of the optical measurement system may be provided to the first positioning device PM, more particularly the components may be provided to the long stroke mover MM. The benefit of this embodiment is that the patterning device MA may be too small to provide space for the first scale 5 over the full range of movement of the first positioning device PM if the optical encoder measurement system is provided to the projection system PS and the first scale 5 to the patterning device MA. By providing the optical measurement system to the long stroke mover MM and providing measuring scales on the patterning device MA and on a metrology frame, the scale on the patterning device may be relatively small.

[0047] As another example, the first scale 5 may be provided to substrate table WT (see Figure 1) and the second scale 11 may be provided to a metrology frame which is connected to the projection system PS. Movement of the substrate table WT or "substrate support" may be realized using a long-stroke module configured to coarsely move a long stroke substrate mover WM and a short-stroke module configured to finely move the substrate table WT with respect to the long stroke substrate mover WM, which modules and mover form part of the second positioner PW. A benefit is that the dynamic and thermal requirements for the long stroke substrate mover WM are less critical than for the projection system PS and or the substrate table WT, which makes it easier to build an optical encoder measurement system with the right dynamic and thermal requirements.

[0048] As yet another example, the second scale 11 may be part of the same components as the components 7,129,130,100,131,132 and 133 thus obtaining a more classical sensor architecture.

[0049] In the embodiment as shown in Figure 2a-2c, the out-of-plane position measurement is based on a 0th order diffraction of the measurement beam 4 on both the first and second scale 5,11, as indicated by the arrows in Figure 2a-2c. The out-of-plane position measurement may however, as illustrated in Figure 3, also be obtained from other diffraction orders. In Figure 3, an optical measurement system as can be applied in a lithographic apparatus according to an embodiment of the invention is shown. The arrangement as shown (only in YZ-view) includes, similar to the arrangement as shown in Figure 2a-2c, a first and second scale 5,11, an irradiation source 101 providing an irradiation beam 3, detectors 131,132 and 133 configured to receive a further diffracted beam from the irradiation beam and determining a 3D position measurement of the first scale with respect to the second scale. In the arrangement as shown in Figure 3, the out-of-plane measurement is obtained, contrary to the arrangement of Figure 2a-2c, from -1st and 1st order diffractions at the first and second scale. This can be understood as follows: an incident measurement beam onto the first scale diffracts into a 1st order beam which follows the path indicated by a, b, c, d and returns back to the detector 131 via the path indicated by e. f, g, h, i form a similar path for a -1st order diffraction which also returns via path e towards the detector 131. As such, the non-zero order diffraction may equally be applied to obtain an out-of-plane position measurement of the first scale 5 with respect to the second scale 11. When 2D scales are applied, the vice versa paths d, c, b, a, e and i, h, g, f, e for the -1st and the 1st diffraction orders resp. are used as well. It is worth noting that each of the arrangements (either the arrangement of Figure 2 employing the 0th order diffraction or the arrangement of Figure 3 employing the -1st and 1st order diffraction) has its own merits and requirements.

[0050] The use of the 0th order diffraction for the out-of-plane measurement may result in a higher reflected light intensity for the interferometer based measurement but may result in a lower light intensity for the encoder based measurement. In order to apply the 0th order diffraction, the first and second scale should be such that the 0th order is not cancelled.

[0051] When the -1st and 1st order diffractions are used for the out-of-plane measurement, a cancellation of the 0th order is preferred. Such an arrangement may result in a higher reflected light intensity for the encoder based measurement but may result in a lower light intensity for the interferometer based measurement.

[0052] With respect to the out-of-plane position measurement as described in Figures 2a-2c and 3, it will be understood by the skilled person that various other options exist for obtaining such an out-of-plane, interferometer based, measurement. Figures 4a-6i schematically depict various ways of obtaining a position measurement of a first reflective surface (such as a first scale) relative to a second reflective surface (such as a second scale). As can be seen, the option as depicted in Figure 4b, substantially corresponds to the out-of-plane measurement as applied in Figure 2a-2c apart from the use of a reflective surface 300 to redirect a reference beam instead of a corner cube 150 as applied in Figure 2a-2c.

[0053] With respect to the in-plane position measurement as described in Figures 2 and 3 (i.e. the encoder based position measurement of the first scale relative to the second, it will be understood by the skilled person that various options exist for obtaining such a measurement. In Figure 7a-7e, four configurations are shown for determining a relative position of a first scale 5 with respect to a second scale using an incoming radiation beam 3 which is diffracted on the first and second scale. As shown, an incoming radiation beam (e.g. perpendicular to the plane of the figure) is reflected by a mirror 7 onto the first scale and diffracted towards the second scale 11. Near the second scale, use is made from a rooftop prism to reflect a further diffracted beam (i.e. reflected at the second scale) again towards the second scale whereupon a yet further diffraction occurs. Subsequently, the diffracted beam leaving the second scale is diffracted again on the first scale before being received, via the mirror 7, by a detector (not shown). Taking into account the volume available for the measurement system, the various options as shown provide alternative positions for the mirror 7, the scales and the rooftop prism. The various arrangements as shown in Figure 7a can e.g. be combined with an out-of-plane interferometer measurement as e.g. shown in Figures 2a-2c, 3 or 4a-6i. As an example, Figure 7b schematically depicts a measurement set-up as shown in the upper left corner of Figure 7a combined with an out-of-plane measurement as shown in Figure 2a-2c. Corresponding reference symbols of Figures 2a-2c and 7b indicate corresponding parts. The rooftop prisms as depicted in Figure 7a are represented by a pair or mirrors 7 in Figure 7b and have the same functionality.

[0054] The out-of-plane position measurement, based on 0th order diffraction, may be used for tilt metrology of one of the two scales as well. In this case, the reference bundle is redirected to the scale of interest, without encountering the other scale. Figure 8a shows a first view of an embodiment to measure the tilt of the target scale. Figure 8b shows a second view of the embodiment of figure 8a. Figures 9a and 9b show an embodiment for a double tilt measurement, measuring both Rx and Ry. Alternatively, only one single tilt is measured.

[0055] With respect to the applied optical elements in the various embodiments of the optical measurement system of the lithographic apparatus according to the invention, it is worth mentioning that various options exist: - In case an optical element is used to bend a beam, the element can e.g. be a mirror, a lens, any type of prism (e.g. a penta-prism) or diffractive optics can be applied.

- In case an optical element is used to obtain a parallel return path for a beam (e.g. the reference beam of the irradiation beam of the irradiation source), such an element can e.g. be a rooftop prism, a corner cube, a cats eye or a plan plate (optionally in combination with a scale).

With respect to the scales 5,11 as applied, it is worth mentioning that an equal grating pitch for both scales 5 and 11 is not mandatory, moreover, a double pitch distance may be preferred.

[0056] The optical measurement system as described above can provide, when applied in a lithographic apparatus according to an embodiment of the invention, one or more of the following benefits: - As the measurement system enables a 3 DOF (degrees of freedom) position measurement from a single target point (the incoming and diffracted beams can arrive and depart on the first scale from a single point) may result in a lower area or volume requirements (e.g. when the first scale is applied on a mask MA).

- Compared to conventional 2DOF encoder measurement systems, additional positional information can be obtained using the measurement system as described. This additional information allows for information on (in-)homogeneous expansion (X and/or Y magnification) and shape identification (distortion), as well as an improved non-rigid body control (by means of over-sensing in light-weight structures).

- An improved dynamics may be obtained, due to reduced mass of the measurement system compared to more conventional systems having multiple sensor housings and beam delivery components.

- An improved thermal performance can be obtained, since 3D solutions are more laser power efficient compared to the use of multiple 1D or 2D sensors; the diffractive orders are used more efficiently and additional orders used, in particular the 0th order. As a result, a lower laser power requirement can be obtained improving human safety and conditioning/dissipation of the apparatus.

- Cost and system complexity (alignment) of 3D sensor is expected to be lower than the use of multiple 1D or 2D sensor systems.

[0057] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as 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. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer 1C, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0058] 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 may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0059] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365,248,193,157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0060] The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[0061] 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 clauses set out below. Other aspects of the invention are set out as in the following numbered clauses: 1. A lithographic apparatus 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; a projection system configured to project the patterned radiation beam onto a target portion of the substrate, and an optical measurement system comprising an irradiation source configured to provide an irradiation beam; an optical system configured to split the irradiation beam into a measurement beam and a reference beam and direct the measurement beam to a first scale, the optical system further being arranged to direct at least two of multiple diffracted beams diffracted by the first scale upon irradiation by the measurement beam to a second scale; a first detector configured to receive at least two of multiple further diffracted beams diffracted by the second scale upon irradiation by the at least two of multiple diffracted beams to determine a first position quantity of the first scale with respect to the second scale; a second detector configured to receive the reference beam and at least one of the multiple further diffracted beams to determine a second position quantity of the first scale with respect to the second scale on the basis of the at least one of the multiple further diffracted beams and the reference beam.

2. The apparatus according to clause 1 wherein the optical system comprises a beam splitter configured to split the irradiation beam into the measurement beam and the reference beam.

3. The apparatus according to clause 1 or 2, wherein the optical system comprises a mirror, diffractive, refractive or polarizing optics.

4. The apparatus according to any preceding clause, wherein the first, or the second scale, or both the first and the second scale, are moveable with respect to the optical measurement system.

5. The apparatus according to any preceding clause, wherein the first scale is provided to the patterning device and the second scale is provided to a metrology frame.

6. The apparatus according to any of the clauses 1 to 4, wherein the first scale is provided to the substrate table and the second scale is provided to a metrology frame.

7. The apparatus according to any of the clauses 1 to 4, wherein the irradiation source, the first and second detector and the optics are mounted to a common housing.

8. The apparatus according to any of the clauses 1 to 4, wherein the irradiation source, the first and second detector, the optical system and the second scale are mounted to a common housing.

9. The apparatus according to any of the clauses 1 to 4, wherein the irradiation source and the optical system are mounted to a common housing.

10. The apparatus according to any preceding clause, wherein the first and second scales are two-dimensional gratings extending in an XY-plane.

11. The apparatus according to clause 10, wherein the first position quantity is a relative X or Y position of the first scale with respect to the second scale.

12. The apparatus according to clause 10 or 11, wherein the second position quantity is a distance between the first scale and the second scale in a Z-direction, substantially perpendicular to the XY-plane.

13. The apparatus according to any of the clauses 10 to 12, wherein the first detector comprises a first detector sensor configured to determine a relative X position of the first scale with respect to the second scale and a second detection sensor configured to determine a relative Y-position of the first scale with respect to the second scale.

14. The apparatus according to any preceding clause, wherein the second position quantity is determined from a 0th order diffraction and further beam.

15. The apparatus according to any of the clauses 1 to 13, wherein the second position quantity is determined from -1st and 1st order diffraction and further diffraction beams.

16. The apparatus according to any preceding clause, wherein the at least two of multiple further diffracted beams undergo one or more yet further diffractions on the first and/or second scale before being received by the first detector.

17. The apparatus according to any preceding clause, wherein the first and/or second scale comprise reflective optics.

18. The apparatus according to any of the clauses 1 to 16, wherein the first and/or second scale comprise refractive optics.

19. A device manufacturing method comprising: determining a position of a pattern from a patterning device with respect to substrate, the determining including splitting an irradiation beam into a measurement beam and a reference beam using an optical system and directing the measurement beam to a first scale, directing at least one of multiple diffracted beams diffracted by the first scale upon irradiation by the measurement beam to a second scale using the optical system; receiving at least one of multiple further diffracted beams diffracted by the second scale upon irradiation by the at least one of multiple diffracted beams by a first detector to determine a first position quantity of the first scale with respect to the second scale; receiving the reference beam and at least one of the multiple further diffracted beams to determine a second position quantity of the first scale with respect to the second scale on the basis of the at least one of the multiple further diffracted beams and the reference beam by a second detector; and transferring a pattern from a patterning device onto a substrate.

Claims (1)

A lithography device comprising: an exposure device adapted to provide a radiation beam; a carrier constructed to support a patterning device, the patterning device being capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam; a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.