NL2013507A - An encoderhead system, a positioning system and a lithographic apparatus. - Google Patents

Description

AN ENCODERHEAD SYSTEM, A POSITIONING SYSTEM AND A LITHOGRAPHIC

APPARATUS

FIELD

[001] The invention relates to an encoderhead system arranged to cooperate with a surface of an encoder scale so as to provide a signal representative of a position of the encoderhead system relative to the encoder scale along a first axis, wherein the first axis is in a plane parallel to the surface. The invention relates to a stage positioning system comprising the encoderhead system. The invention relates to a lithographic apparatus comprising the stage positioning system.

BACKGROUND

[002] A lithographic apparatus is an apparatus that can be used in the manufacture of integrated circuits (ICs). In that instance, 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 by a radiation beam via a projection system onto a target portion on a substrate, such as a silicon wafer. Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material provided on the substrate. In general, a single substrate will contain an array of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time. Known lithographic apparatus also include so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction while synchronously scanning the substrate parallel or anti parallel to this direction.

[003] The substrate needs to be accurately positioned relative to the projection system to project the pattern of each layer of the IC correctly on the substrate. To position the substrate, the substrate is held be a substrate table. The substrate table is moveable relative to the projection system. The substrate table is provided with an actuator to move the substrate table. To measure the position of the substrate table, the substrate table may be provided with an encoder measurement system.

[004] The encoder measurement system comprises an encoderhead and an encoder scale. The encoderhead is arranged to project a measurement beam onto a surface of the encoder scale. The surface of the encoder scale has a grating pattern. The measurement beam is emitted from a grating on the encoderhead. The encoder scale diffracts the measurement beam and reflects diffracted measurement beam back to the encoderhead. Based on the diffracted measurement beam, the encoderhead is able to determine its position relative to the encoder scale.

[005] In a known lithographic apparatus, the encoderhead is mounted on the wafer table and the encoder scale is mounted on a reference frame holding the projection system. Such a known lithographic apparatus is described in yet unpublished PCT/EP2013/068930, hereby incorporated by reference. The lithographic apparatus may have multiple encoderheads close together to improve the accuracy of the encoder measurement system. In another type of known lithographic apparatus, the encoderhead is coupled to the reference frame holding the projection system and the encoder scale is connected to the substrate table. Such a known lithographic apparatus is described in WO 2013/100202 Al, hereby incorporated by reference.

SUMMARY

[006] The known lithographic apparatus may be improved. When the measurement beam travels between the encoderhead and the encoder scale, the measurement beam encounters disturbances, such as air pressure variations, air temperature variation and air composition variations. The disturbances negatively affect the measurement beam, causing the measurement beam to be less representative of the position of the encoder the scale relative to the encoderhead. When multiple encoderheads are put close together to improve the measurement accuracy of the encoder measurement system, the outside surfaces of the encoderheads are put against each other. However, because each encoderhead has a length of about 40mm in the measurement direction, and width of about 15 mm in a direction perpendicular to the measurement direction, there is a distance of about 15 to 40 mm between the gratings on each encoderhead that emit the measurement beam towards the encoder scale. This distance causes the disturbances for the measurement beam of each encoderhead to be uncorrelated. Because the disturbances are uncorrelated, the disturbances have a significant negative influence on the accuracy of the encoder measurement system.

[007] In an aspect of the invention, there is provided an encoderhead system that has an improved accuracy.

[008] In a first aspect of the invention, there is provided an encoderhead system arranged to cooperate with a surface of an encoder scale so as to provide a signal representative of a position of the encoderhead system relative to the encoder scale along a first axis, wherein the first axis is in a plane substantially parallel to the surface, the encoderhead system including: a first encoderhead; a second encoderhead; wherein the first encoderhead includes: a first direction element; a first grating; a second grating; a third grating; a fourth grating; a first reflective element; and a first sensor; wherein the first direction element is arranged to direct a first input beam toward the encoder scale, wherein the first grating is arranged to receive a first diffracted beam created by the encoder scale under control of the first input beam, wherein the first grating comprises a first area at which the first grating is arranged to receive the first diffracted beam, wherein the first grating is arranged to direct the first diffracted beam toward the first reflective element, wherein the reflective element is arranged to reflect the first diffracted beam toward the third grating, wherein the third grating is arranged to receive the first diffracted beam wherein the second grating is arranged to receive a second diffracted beam created by the encoder scale under control of the first input beam, wherein the second grating comprises a second area at which the second grating is arranged to receive the second diffracted beam, wherein the second grating is arranged to direct the second diffracted beam toward the reflective element, wherein the reflective element is arranged to reflect the second diffracted beam toward the fourth grating, wherein the fourth grating is arranged to receive the second diffracted beam, wherein the sensor is arranged to receive a first combined beam from the encoder scale, wherein the first combined beam is created by the encoder scale under control of the first diffracted beam directed to the encoder scale by the third grating and of the second diffracted beam directed to the encoder scale by the fourth grating, wherein the second encoderhead includes: a second direction element; a fifth grating; a sixth grating; a seventh grating; a eighth grating; a second reflective element; and a second sensor; wherein the second direction element is arranged to direct a second input beam toward the encoder scale, wherein the fifth grating is arranged to receive a third diffracted beam created by the encoder scale under control of the second input beam, wherein the fifth grating comprises a third area at which the fifth grating is arranged to receive the third diffracted beam, wherein the fifth grating is arranged to direct the third diffracted beam toward the second reflective element, wherein the second reflective element is arranged to reflect the third diffracted beam toward the seventh grating, wherein the seventh grating is arranged to receive the third diffracted beam, wherein the sixth grating is arranged to receive a fourth diffracted beam created by the encoder scale under control of the second input beam, wherein the sixth grating comprises a fourth area at which the sixth grating is arranged to receive the fourth diffracted beam, wherein the sixth grating is arranged to direct the fourth diffracted beam toward the reflective element, wherein the second reflective element is arranged to reflect the fourth diffracted beam toward the eighth grating, wherein the eighth grating is arranged to receive the fourth diffracted beam, wherein the second sensor is arranged to receive a second combined beam from the encoder scale, wherein the combined beam is created by the encoder scale under control of the third diffracted beam directed to the encoder scale by the seventh grating and of the fourth diffracted beam directed to the encoder scale by the eighth grating, wherein the first area and the second area are aligned along the first axis, wherein the third area and the fourth area arc aligned along the first axis, wherein a projection of the first area on a second axis and a projection of the third area on the second axis are substantially adjacent to each other, wherein the second axis is in the plane and is perpendicular to the first axis.

[009] According to the first aspect, the encoderhead system is able to create two combined beams. Each combined beam is representative of a position of the encoderhead relative to the encoder scale. Since the encoderheads are arranged such that the a projection of the first area on a second axis and a projection of the third area on the second axis are substantially adjacent to each other, the beams creating the two combined beams have passed through the air between the encoder scale and the encoderheads closely together. The distance between the beams may be only a few millimeters. As a result, both combined beams have encountered substantially the same disturbances. Because the disturbances are the same, the disturbances correlate to each other. As a result of this correlation, the accuracy of the signal representative of the position of the encoder scale relative to the encoderhead system is improved when the two signals from each of the encoderheads are combined.

[0010] In a first embodiment, there is provided an encoderhead system wherein a projection of the first area on the first axis and a projection of the third area on the first axis are at a first distance from each other.

[0011] In a second embodiment, there is provided an encoderhead system wherein at least one of the first grating, the second grating, the fifth grating and the sixth grating comprises a 2D grating.

[0012] According to the second embodiment, the 2D grating is able to diffract at least one of the diffracted beams into two directions. By diffracting the diffracted beam into two directions, the part of the diffracted beam before the 2D grating is in a different plane than the part of the diffracted beam after the 2D grating. Since the two parts of the diffracted beam are not in the same plane, a radiation source and a sensor can easily arranged relative to each other. The radiation source provides the input beam. The sensor is arranged to receive the combined beam. Γ00131 In a third embodiment, there is provided an encoderhead system including a monolithic component having a first surface on which the first grating, the second grating, the third grating, the fourth grating, the fifth grating, the sixth grating, the seventh grating and the eighth grating are arranged.

[0014] According to the third embodiment, the first grating and the second grating can be made on the first surface and can be put closely together in the second direction. This minimizes the size of the encoderhead system.

[0015] In a fourth embodiment, there is provided an encoderhead system wherein the monolithic component has a second surface, wherein at least one of the first reflective element and the second reflective element are on the second surface.

[0016] According to the fourth embodiment, the first grating, the second grating and the reflective element are on the same monolithic component. As a result, the reflective element has a fixed position relative to the first grating and the second grating, so there is no need for any adjustment equipment to change the position of the reflective element relative to the first grating and/or second grating. Because of the absence of such adjustment equipment, the encoderhead system can be made smaller.

[0017] In a fifth embodiment there is provided an encoderhead system including an interferometer on the first surface.

[0018] According to the fifth embodiment, the interferometer measures a distance between two parts of the encoder system on the first surface. The interferometer measures the distance by providing an interferometer beam from one of the two parts to the other of the two parts via air surrounding the encoderhead system. Since the positions of the two parts are substantially fixed relative to each other, any change detected by the interferometer is substantially caused by disturbances of the air through which the interferometer beam travels. By determining the disturbances with the interferometer, the signal of the encoderhead system can be corrected for the disturbances and the accuracy of the encoderhead system is increased.

[0019] In a sixth embodiment, there is provided an encoderhead system including a third encoderhead, wherein the third encoderhead includes: a third direction element; a ninth grating; a tenth grating; an eleventh grating; a twelfth grating; and a third reflective clement; a third sensor; wherein the third direction element is arranged to direct a third input beam toward the encoder scale, wherein the ninth grating is arranged to receive a fifth diffracted beam created by the encoder scale under control of the third input beam, wherein the ninth grating comprises a fifth area at which the ninth grating is arranged to receive the fifth diffracted beam, wherein the ninth grating is arranged to direct the third diffracted beam toward the third reflective element, wherein the third reflective element is arranged to reflect the third diffracted beam toward the eleventh grating, wherein the eleventh grating is arranged to receive the third diffracted beam wherein the tenth grating is arranged to receive a sixth diffracted beam created by the encoder scale under control of the third input beam, wherein the tenth grating comprises a sixth area at which the tenth grating is arranged to receive the sixth diffracted beam, wherein the tenth grating is arranged to direct the sixth diffracted beam toward the third reflective element, wherein the third reflective element is arranged to reflect the sixth diffracted beam toward the twelfth grating, wherein the twelfth grating is arranged to receive the sixth diffracted beam, wherein the third sensor is arranged to receive a thirdcombined beam from the encoder scale, wherein the third combined beam is created by the encoder scale under control of the fifth diffracted beam directed to the encoder scale by the eleventh grating and of the sixth diffracted beam directed to the encoder scale by the twelfth grating, wherein the fifth area and the sixth area are aligned along the first axis, wherein the projection of the first area on a second axis and a projection of the fifth area on the second axis are substantially adjacent to each other..

[0020] According to the sixth embodiment, there are three encoderheads to determine a position in the first direction. Since the projections of the first area, the third area and the fifth area are substantially adjacent to each other on the second axis, a rotation around a third axis can be determined. The third axis is perpendicular to the first axis and the second axis. Since the encoderhead head is able to determine the rotation around the third axis, drift of the encoderhead system around the third axis can be determined.

[0021] In a seventh embodiment, there is provided an encoderhead system wherein the ninth grating, the tenth grating, the eleventh grating and the twelfth grating are arranged on the first surface.

[0022] In an eighth embodiment, there is provided an encoderhead system wherein the projection of the first area on the first axis and the projection of the fourth area on the first axis are at a second distance from each other.

[0023] In a ninth embodiment, there is provided an encoderhead system wherein the first area and the third area are aligned along a first line in the plane, wherein the first area and the fifth area are aligned along a second line in the plane, wherein an angle between the first line and the second line is substantially 90 degrees.

[0024] According to the ninth embodiment, the first area, the third area and the fifth area are aligned in a beneficial way for a calibration method known as “stitching”. During stitching, the encoderhead system is positioned at a first position relative to the encoder scale. All encoderheads of the encoderhead system give a signal representative of their positions relative to the encoder scale. Then the encoderhead system is positioned at a second position relative to the encoder scale. In the second position, the second encoderhead measures the same position that the first encoderhead measured at the first position. For every further position, the second encoderhead measures the same position that the first encoderhead measured at the previous position. Since the angle between the first line and the second line are substantially 90 degrees, stitching can be done fast and accurately along both the first axis and the second axis.

[0025] In a tenth embodiment, there is provided an encoderhead system wherein the first encoderhead includes a first splitter, a thirteenth grating, a fourteenth grating, a fifteenth grating, a sixteenth grating, a fourth reflective element and a fourth sensor; wherein the splitter is arranged to split the first input beam into a first beam and a second beam, wherein the first diffracted beam and the second diffracted beam are created by the encoder scale under control of the first beam, wherein the thirteenth grating is arranged to receive a seventh diffracted beam created by the encoder scale under control of the second beam, wherein the thirteenth grating comprises a seventh area at which the thirteenth grating is arranged to receive the seventh diffracted beam, wherein the thirteenth grating is arranged to direct the seventh diffracted beam toward the fourth reflective element, wherein the fourth reflective element is arranged to reflect the seventh diffracted beam toward the fifteenth grating, wherein the fifteenth grating is arranged to receive the seventh diffracted beam, wherein the fourteenth grating is arranged to receive an eighth diffracted beam created by the encoder scale under control of the second beam, wherein the fourteenth grating comprises an eighth area at which the fourteenth grating is arranged to receive the eighth diffracted beam, wherein the fourteenth grating is arranged to direct the eighth diffracted beam toward the fourth reflective element, wherein the fourth reflective element is arranged to reflect the eighth diffracted beam toward the sixteenth grating, wherein the sixteenth grating is arranged to receive the eight diffracted beam, wherein the fourth sensor is arranged to receive a fourth combined beam from the encoder scale, wherein the fourth combined beam is created by the encoder scale under control of the seventh diffracted beam directed to the encoder scale by the fifteenth grating and of the eighth diffracted beam directed to the encoder scale by the sixteenth grating, wherein the first area, the seventh area and the eighth area are aligned along the first axis.

[0026] According to the tenth embodiment, the first encoderhead is able to determine a position of the first encoderhead relative to the encoder scale along a third axis. The third axis is perpendicular to the first axis and to the second axis. The encoderhead is able to determine the position along the third axis, by performing calculations using a signal representative of the first combined beam and a signal representative of the fourth combined beam.

[0027] In an eleventh embodiment, there is provided an encoderhead system wherein the thirteenth grating, the fourteenth grating, the fifteenth grating and the sixteenth grating are arranged on the first surface.

[0028] In a twelfth embodiment, there is provided an encoderhead system wherein the second encoderhead includes a second splitter, a seventeenth grating, an eighteenth grating, a nineteenth grating, a twentieth grating, a fifth reflective element and a fifth sensor; wherein the second splitter is arranged to split the second input beam into a third beam and a fourth beam, wherein the third diffracted beam and the fourth diffracted beam are created by the encoder scale under control of the third beam, wherein the seventeenth grating is arranged to receive a ninth diffracted beam created by the encoder scale under control of the fourth beam, wherein the seventeenth grating comprises a ninth area at which the seventeenth grating is arranged to receive the ninth diffracted beam, wherein the seventeenth grating is arranged to direct the ninth diffracted beam toward the fifth reflective element, wherein the fifth reflective element is arranged to reflect the ninth diffracted beam toward the nineteenth grating, wherein the nineteenth grating is arranged to receive the ninth diffracted beam wherein the eighteenth grating is arranged to receive a tenth diffracted beam created by the encoder scale under control of the fourth beam, wherein the eighteenth grating comprises a tenth area at which the eighteenth grating is arranged to receive the tenth diffracted beam, wherein the seventeenth grating is arranged to direct the tenth diffracted beam toward the fifth reflective element, wherein the fifth reflective element is arranged to reflect the tenth diffracted beam toward the twentieth grating, wherein the twentieth grating is arranged to receive the tenth diffracted beam, wherein the fifth sensor is arranged to receive a fifth combined beam from the encoder scale, wherein the fifth combined beam is created by the encoder scale under control of the ninth diffracted beam directed to the encoder scale by the fifteenth grating and of the tenth diffracted beam directed to the encoder scale by the twentieth grating, wherein the third area, the ninth area and the tenth area are aligned along the first axis, wherein the projection of the first area on a second axis and a projection of the ninth area on the second axis are substantially adjacent to each other.

[0029] According to the twelfth embodiment, the second encoderhead is arranged to determine a position of the second encoderhead relative to the encoder scale along the third axis. Since the first area of the first encoderhead and the ninth area of the second encoderhead are adjacent when projected on the second axis, the first encoderhead and the second encoderhead together are able to determine a rotation at least partly along first axis.

[0030] In a thirteenth embodiment, there is provided an encoderhead system wherein the seventeenth grating, the eighteenth grating, the nineteenth grating and the twentieth grating are arranged on the first surface.

[0031] In a fourteenth embodiment, there is provided an encoderhead system wherein the third encoderhead includes a third splitter, a twenty-first grating, a twenty-second grating, a twenty-third grating, a twenty-fourth grating, a sixth reflective element and a sixth sensor; wherein the third splitter is arranged to split the third input beam into a fifth beam and a sixth beam, wherein the fifth diffracted beam and the sixth diffracted beam are created by the encoder scale under control of the fifth beam, wherein the twenty-first grating is arranged to receive a eleventh diffracted beam created by the encoder scale under control of the fifth beam, wherein the twenty-first grating comprises a eleventh area at which the twenty-first grating is arranged to receive the eleventh diffracted beam, wherein the twenty-first grating is arranged to direct the eleventh diffracted beam toward the sixth reflective element, wherein the sixth reflective element is arranged to reflect the eleventh diffracted beam toward the twenty-third grating, wherein the twenty-third grating is arranged to receive the eleventh diffracted beam, wherein the twenty-second grating is arranged to receive a twelfth diffracted beam created by the encoder scale under control of the sixth beam, wherein the twenty-second grating comprises a twelfth area at which the twenty-second grating is arranged to receive the twelfth diffracted beam, wherein the twenty-second grating is arranged to direct the twelfth diffracted beam toward the sixth reflective element, wherein the sixth reflective element is arranged to reflect the twelfth diffracted beam toward the twenty-fourth grating, wherein the twenty-fourth grating is arranged to receive the twelfth diffracted beam, wherein the sixth sensor is arranged to receive a sixth combined beam from the encoder scale, wherein the sixth combined beam is created by the encoder scale under control of the eleventh diffracted beam directed to the encoder scale by the twenty-third grating and of the twelfth diffracted beam directed to the encoder scale by the twenty-fourth grating, wherein the fifth area, the eleventh area and the twelfth area are aligned along the first axis, wherein the projection of the first area on a second axis and a projection of the eleventh area on the second axis are substantially adjacent to each other.

[0032] According to the fourtheenth embodiment, the third encoderhead is arranged to determine a position of the third encoderhead relative to the encoder scale along the third axis. Since the first area of the first encoderhead and the eleventh area of the third encoderhead are adjacent when projected on the second axis, the first encoderhead and the third encoderhead together are able to determine a rotation at least partly along second axis.

[0033] In a fifteenth embodiment, there is provided an encoderhead system wherein the twenty-first grating, the twenty-second grating, the twenty-third grating and the twenty-fourth grating are arranged on the first surface.

In a second aspect of the invention, there is provided a positioning system including an encoderhead system of one of the above embodiments; the encoder scale; a reference body; a moveable body being moveable relative to the reference body; wherein one of the encoderhead system and the encoder scale is connected to the moveable body, wherein the other of the encoderhead system and the encoder scale is connected to the reference body, wherein the encoderhead system is arranged to provide a signal representative of a position of the moveable body relative to the reference body in the first direction.

[0034] According to the second aspect of the invention, the positioning system is able to move the moveable body more accurately relative to the reference body.

[0035] In an sixteenth embodiment, there is provided a positioning system including a gas nozzle arranged to supply a flow of gas between the encoderhead system and the scale, wherein the gas nozzle at least partly surrounds the encoderhead system.

[0036] According to the sixteenth embodiment, the encoderhead system is significantly smaller than a combination of multiple known encoderheads. For known encoderheads, each encoderhead is surrounded by its own gas nozzle to achieve an acceptable flow of gas between the encoderhead system and the encoder scale. Because the encoderhead system according to the invention is smaller, a gas nozzle can be provided that surrounds the encoderhead system. So the gas nozzle at least partly surrounds the first encoderhead and the second encoderhead. Since the gas nozzle at least partly surrounds both encoderheads, any disturbances caused by the gas nozzle are substantially the same for both encoderheads. The disturbances are correlated as a result. Since the disturbances are correlated, the disturbances have less influence on the accuracy of the encoderhead system.

[0037] In a third aspect of the invention, there is provided a lithographic apparatus including the positioning system of one of the above embodiments, the lithographic apparatus including a projection system to project a pattern from a patterning device onto a substrate; a support structure to support the patterning device; a substrate table to hold the substrate; a metrology frame to support the projection system; wherein the substrate table comprises the moveable body, wherein the metrology frame comprises the reference body.

[0038] According to the third aspect, the substrate table can be moved more accurately relative to the metrology frame. As a result, the pattern is projected onto the substrate more accurately, resulting in high-quality device created on the substrate.

In a seventeenth embodiment, there is provided a lithographic apparatus including a further encoderhead, wherein the further encoderhead is arranged to cooperate with the encoder scale to provide a further signal representative of a position of the further encoderhead relative to the encoder scale along the first axis, wherein the further encoderhead is arranged on one of the moveable body and the reference body so as to provide the further signal when the encoderhead system is unable provide the signal.

[0039] According to the seventeenth embodiment, the lithographic apparatus is able to maintain a signal representative of the position of the substrate table relative to the metrology frame in case the encoderhead system is unable to provide that signal. The encoderhead system may be unable to provide the signal, when the encoderhead faces a distortion of the encoder scale. The distortion may be a gap between two parts of the encoder scale, a droplet of liquid such as immersion liquid, or a scratch. The further encoder may have a low accuracy. The further encoder may be sufficiently accurate to determine a period of the encoder scale, so the encoderhead system can start with determining the position in the correct period when the encoderhead system has passed the distortion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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: [0041] Figure 1 depicts a lithographic apparatus according to the invention; [0042] Figure 2A depicts a first encoderhead of the encoderhead system according to an embodiment of the invention in a front view; [0043] Figure 2B depicts the first encoderhead in a side view; [0044] Figure 2C depicts the first encoderhead in a top view; [0045] Figure 3A depicts a second encoderhead of the encoderhead system according to an embodiment of the invention in a front view; [0046] Figure 3B depicts the second encoderhead in a side view; [0047] Figure 3C depicts the second encoderhead in a top view; [0048] Figure 4 depicts the encoderhead system from a top view; [0049] Figure 5 depicts a further embodiment of the encoderhead system from a top view; [0050] Figure 6A depicts a third encoderhead of the encoderhead system according to an embodiment of the invention in a front view; Γ0051] Figure 6B depicts the third encoderhead in a side view; [0052] Figure 6C depicts the third encoderhead in a top view; [0053] Figure 7 depicts yet a further embodiment of the encoderhead system from a top view; [0054] Figures 8A, 8B and 8C depict the first encoderhead of the encoderhead system according to another embodiment from different views, and

[0055] Figure 9 depicts the encoderhead system according to yet another embodiment. DETAILED DESCRIPTION

[0056] Figure 1 schematically depicts a lithographic apparatus with the encoderhead according to an embodiment of the invention. The lithographic apparatus may comprise an illumination system IL, a support structure MT, a substrate table WT and a projection system PS.

[0057] The illumination system IL is configured to condition a radiation beam B. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B.

[0058] The illumination system IL receives the radiation beam B 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 SO is not considered to form part of the lithographic apparatus and the radiation beam B is passed from the source SO to the illumination system IL with the aid of a beam delivery system BD comprising, for example, suitable directing mirrors and/or a beam expander. In other cases the source SO may be an integral part of the lithographic apparatus, for example when the source SO is a mercury lamp. The source SO and the illumination system IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0059] The illumination system IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. In addition, the illumination system IL may comprise various other components, such as an integrator IN and a condenser CO. The illumination system IL may be used to condition the radiation beam B, to have a desired uniformity and intensity distribution in its cross section.

[0060] The term "radiation beam" used herein encompasses all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 355, 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.

[0061] The support structure MT is for supporting a patterning device MA. The support structure MT is connected to a first positioner PM configured to accurately position the patterning device MA in accordance with certain parameters.

[0062] The support structure MT supports, i.e. bears the weight of the patterning device MA.

The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device MA is held in a vacuum environment. The support stmeture MT can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The support structure MT may be a frame or a table, for example a mask table, and may be fixed or movable as required. The support structure MT may ensure that the patterning device MA is at a desired position, for example with respect to the projection system PS.

[0063] The term "patterning device" used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section so as to create a pattern in a target portion C of the substrate W. It should be noted that the pattern imparted to the radiation beam B may not exactly correspond to the desired pattern in the target portion C of the substrate W, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam B will correspond to a particular functional layer in a device being created in the target portion C, such as an integrated circuit.

[0064] The patterning device MA may be transmissive or reflective. Examples of a patterning device MA include masks, reticles, 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. As here depicted, the apparatus is of a transmissive type, which employs a transmissive mask.

[00651 The substrate table WT, e.g. a wafer table, is for holding a substrate W, e.g. a resist coated wafer. The substrate table WT is connected to a second positioner PW configured to accurately position the substrate W in accordance with certain parameters.

[0066] The projection system PS is configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C of the substrate W.

[0067] The term "projection system" used herein should be broadly interpreted as encompassing any type of projection system PS, 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.

[0068] The radiation beam B is incident on the patterning device MA, which is held on the support structure MT, and is patterned by the patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS which focuses the radiation beam B onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF, 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. The position sensor IF may comprise an interferometric device, linear encoder or capacitive sensor. Similarly, the first positioner PM and another position sensor (which is not depicted in Figure 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B. In general, movement of the support structure MT may be realized with the aid of a long-stroke module and a short-stroke module. The long-stroke module provides coarse positioning of the short-stroke module relative to the projection system PS over a long range.

The short-stroke module provides fine positioning of the patterning device MA relative to the long-stroke module over a small range. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioning system PW. In the case of a stepper (as opposed to a scanner) the support structure MT may be connected to a short-stroke actuator only, or may be fixed.

[0069] 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 C. Similarly, in situations in which more than one die is provided on the patterning device MA, the mask alignment marks Ml, M2 may be located between the dies.

[0070] The lithographic apparatus may be of a type having at least one substrate table WT and at least one support structures MT. In addition to the at least one substrate table WT, the lithographic apparatus may comprise a measurement table, which is arranged to perform measurements. The measurement table may not be arranged to hold a substrate.

[0071] The lithographic apparatus may also be of a type wherein at least a portion of the substrate W may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system PS and the substrate W. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the patterning device MA and the projection system PS. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term "immersion" as used herein does not mean that a structure, such as a substrate W, must be submerged in liquid, but rather only means that liquid is located between the projection system PS and the substrate W during exposure.

[0072] The depicted lithographic apparatus could be used in at least one of the following three modes: [0073] In the first mode, the so-called step mode, the support structure MT and the substrate table WT are kept essentially stationary, while an entire pattern impaired to the radiation beam is projected onto a target portion C at one time. The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed.

[0074] In the second mode, the so-called scan mode, the patterning device MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C. The velocity and direction of the substrate table WT relative to the patterning device MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0075] In the third mode, the patterning device MT is kept essentially stationary holding a programmable patterning device MA, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. 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 in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device MA, such as a programmable mirror array of a type as referred to above.

[0076] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[0077] A positioning system, such as the first positioner PM and the second positioner PW, may be provided with an encoderhead system to determine the position of a moveable body. The moveable body may be the substrate table WT or the support structure MT. The position may be determined based on a position, a velocity, an acceleration or any other lime derivative of position.

[0078] Figures 2A ,2B and 2C depict the encoderhead system 10 and the encoder scale 20 from different views according to an embodiment. The encoderhead system 10 comprises a first encoderhead 100. The first encoderhead 100 comprises a first directing element 102, a first grating 106 a, a second grating 106b, a third grating 106c, a fourth grating 106d and a reflective element 110.

[0079] The encoderhead 100 is provided with a first inputbeam 113 from a radiation source. The first inputbeam 113 is directed towards the encoder scale 20 via the directing element 102. At the encoder scale 20, the inputbeam 113 is diffracted by a pattern on a surface 22 of the encoder scale 20. A first diffracted beam 116a is created by the encoder scale 20 by diffracting the inputbeam 113. The first diffracted beam 116a is directed towards the encoderhead 100. The first diffracted beam 116a is incident on the first grating 106a. The area on which the first grating 106a receives the first diffracted beam 116a is referred to as the first area 107a.

[0080] At the first area 107a, the first diffracted beam 116a is diffracted and is directed towards the reflective element 110. The reflective element 110 reflects the first diffracted beam 116a towards the third grating 106c. Then the first diffracted beam 116a is subsequently diffracted by the third grating 106c, directed towards the encoder scale 20 and diffracted by the encoder scale 20.

[0081] At the encoder scale 20, the inputbeam 113 is diffracted by the pattern on a surface 22 and a second diffracted beam 116b is created. The second diffracted beam 116b is directed towards the encoderhead 100. The second diffracted beam 116b is incident on the second grating 106b. The area on which the second grating 106b receives the second diffracted beam 116b is referred to as the second area 107b.

[0082] At the second area 107b, the second diffracted beam 116b is diffracted and is directed towards the reflective element 110. The reflective element 110 reflects the second diffracted beam 116b towards the fourth grating 106d. Then the second diffracted beam 116b is subsequently diffracted by the fourth grating 106d, directed towards the encoder scale 20 and diffracted by the encoder scale 20.

[0083] The first diffracted beam 116a and the second diffracted beam 116b are combined by the encoder scale in a first combined beam 122a. The first combined beam 122a is directed toward a sensor 130a. A change in a position of the encoder scale 20 relative to the first encoderhead 100 causes the phase of the first combined beam 122a to change. The sensor 130a is arranged to determine the change in the phase of the first combined beam 122a. Under control of the change in the phase, the detector 130a is arranged to provide a signal representative of the position of the first encoderhead 100 relative to the encoder scale 20.

[0084] The gratings 106a, 106b, 106c and 106d may all be on a first surface (142).

[0085] The encoderhead system 10 as shown in Figure 2A may be a so-called ID encoderhead system. AID encoderhead system may be used to determine a position in only one degree of freedom. A known ID encoderhead system is described in WO 02/23131 Al, hereby incorporated by reference.

[0086] Figures 3A, 3B and 3C depict the encoderhead system 10 and the encoder scale 20 from different views. The encoderhead system 10 comprises a second encoderhead 200. The second encoderhead 200 comprises a second directing element 202, a fifth grating 206a, a sixth grating 206b, a seventh grating 206c, an eighth grating 206d, and a second reflective element 210.

[0087] The encoderhead 100 is provided with a second inputbeam 213 from the radiation source. The second inputbeam 213 is directed towards the encoder scale 20 via the second directing element 202. At the encoder scale 20, the second inputbeam 213 is diffracted by a pattern on a surface 22 of the encoder scale 20. A third diffracted beam 216a is created by the encoder scale 20 by diffracting the second inputbeam 213. The third diffracted beam 216a is directed towards the second encoderhead 200. The third diffracted beam 216a is incident on the fifth grating 206a. The area on which the fifth grating 206a receives the third diffracted beam 216a is referred to as the third area 207a.

[0088] At the third area 207a, the third diffracted beam 216a is diffracted and is directed towards the second reflective element 210. The second reflective element 210 reflects the third diffracted beam 216a towards the seventh grating 206c. Then the third diffracted beam 216a is subsequently diffracted by the seventh grating 206c, directed towards the encoder scale 20 and diffracted by the encoder scale 20.

[0089] At the encoder scale 20, the second inputbeam 213 is diffracted by the pattern on the surface 22 and a fourth diffracted beam 216b is created. The fourth diffracted beam 216b is directed towards the second encoderhead 200. The fourth diffracted beam 216b is incident on a sixth grating 206b. The area on which the sixth grating 206b receives the fourth diffracted beam 216b is referred to as the fourth area 207b.

[0090] At the fourth area 207b, the fourth diffracted beam 216b is diffracted and is directed towards the second reflective element 210. The second reflective element 210 reflects the fourth diffracted beam 216b towards the eighth grating 206d. Then the fourth diffracted beam 216b is subsequently diffracted by the eighth grating 206d, directed towards the encoder scale 20 and diffracted by the encoder scale 20.

[0091] The third diffracted beam 216a and the fourth diffracted beam 216b are combined by the encoder scale in a second combined beam 222a. The second combined beam 222a is directed toward a second sensor 230a. A change in a position of the encoder scale 20 relative to the second encoderhead 200 causes the phase of the second combined beam 1222a to change. The second sensor 230a is arranged to determine the change in the phase of the second combined beam 222a. Under control of the change in the phase, the second sensor 230a is arranged to provide a signal representative of the position of the second encoderhead 200 relative to the encoder scale 20.

[0092] The gratings 206a, 206b, 206c and 206d may all be on the first surface 142.

[0093] Figure 4 depicts the encoderhead system 10 comprising the first encoderhead 100 and the second encoderhead 200 according to an embodiment of the invention in a top view. The topview shows the first surface 142 of component 140. On the surface the grating 106, 106b, 106c, 106d, 206a, 206b, 206c and 206d are arranged.

[0094] The encoderhead system 10 is provided with a beamsplitter 40. The beamsplitter 40 is arranged to split an inputbeam 30 from a radiation source into the first inputbeam 113 and the second inputbeam 213.

[0095] The beam splitter 40 may be provided with a mirror that is transparent to about 50% of the intensity of the inputbeam 30 to create the second inputbeam 213. The remaining 50% of the intensity of the inputbeam 30 is used to create the first inputbeam 113. Using such a beam splitter 30 provides the about the same intensity for the first inputbeam 113 and the second input beam 213.

[0096] The first area 107a, the second area 107b, the third area 207a and the fourth area 207b arc shown. The first area 107a is the area on which the first grating 106a receives the first diffracted beam 116a. The second area 107b is the area on which the second grating 106b receives the second diffracted beam 116b. The third area 207a is the area on which the fifth grating 206a receives the third diffracted beam 216a. The fourth area 207b is the area on which the sixth grating 206b receives the fourth diffracted beam 216b.

[0097] The first grating 106a may be larger than the first area 107a. The second grating 106b may be larger than the second area 107b. The fifth grating 206a may be larger than the third area 207a. The sixth grating 206b may be larger than the fourth area 207b.

[0098] Figure 4 shows area 107c, area 107d, area 207c and area 207d. Area 107c is the part of the third grating 106c that receives the first diffracted beam 116a. Area 107b is the part of the fourth grating 106d that receives the second diffracted beam 116b. Area 207c is the part of the seventh grating 206c that receives the third diffracted beam 216a. Area 207d is the part of the eighth grating 206d that receives the fourth diffracted beam 216b.

[0099] The areas 107a and 107b are aligned along the x-axis. The areas 107c and 107d are aligned along the x-axis. The areas 207a and 207b are aligned along the x-axis. The areas 207c and 207d are aligned along the x-axis.

[00100] There is a distance along the x-axis between the area 107a and the area 207a. There is a distance along the x-axis between the area 107b and the area 207b.

[00101] A projection 130 of the area 107a on the y-axis and a projection 230 of the area 207a on the y-axis are shown on line A-A. The projections 130 and 230 are adjacent relative to each other. There may be no gap or a small gap between the projections 130 and 230. The gap may be significantly smaller than the distance along the x-axis between the first area 105 and the first receiving area 107. This distance may be about 10-20 mm, whereas the gap between the projections 130 and 230 may be less than 5 mm, or less than 4 mm, or less than 3 mm. The gap may be just large enough to provide just enough space for a projection 132 of the area 107c on the y-axis. Γ001021 At least one of the gratings 106a, 106b, 106c, 106d, 206a, 206b, 206c and 206d may comprise a 2D grating. The 2D grating may have a pattern of two types of lines. One type of lines may be aligned along the x-axis, whereas the other type of lines may be aligned along the y-axis. The 2D grating may have a checkerboard pattern.

[00103] Figure 5 shows an embodiment of the invention as described above, except for what is stated below. Figure 5 shows an interferometer 400 arranged on the first surface 142. The interferometer 400 comprises an optical component 402, a reference mirror 404 and a measurement mirror 406. The interferometer receives a beam of radiation similar to one of inputbeams 113 and 213. The optical component 402 receives the beam of radiation and splits the beam of radiation in a reference beam 410 and a measurement beam 406. The reference beam 410 is directed by the optical component 402 toward the reference mirror 404. The reference mirror 404 may be on the first surface 142, or may be inside the component 140. The measurement beam 408 is directed by the optical component 402 toward the measurement mirror 406. The measurement beam 408 is directed through the air surrounding the encoderhead system 10, so disturbances in the air affect the measurement beam 408.

[00104] The reference mirror 404 reflects the reference beam 410 back to the optical component 402. The measurement mirror 406 reflects the measurement beam 408 back to the optical component 402. At the optical component 402, the reflected reference beam 410 and the reflected measurement beam 408 are interfered, so the effect of the disturbances can be determined.

[00105] Figure 6A, 6B and 6C depict the encoderhead system 10 and the encoder scale 20 for different views. The encoderhead system 10 comprises a third encoderhead 300. The third encoderhead 300 comprises a third directing element 302, a grating 306a, a grating 306b, a grating 306c, a grating 306d and a third reflective element 310.

[00106] The third encoderhead 300 is provided with a third inputbeam 313 from the radiation source. The thrid inputbeam 313 is directed towards the encoder scale 20 via the third directing element 302. At the encoder scale 20, the third inputbeam 313 is diffracted by a pattern on a surface 22 of the encoder scale 20. A fifth diffracted beam 316a is created by the encoder scale 20 by diffracting the third inputbeam 313. The fifth diffracted beam 316a is directed towards the third encoderhead 300. The fifth diffracted beam 316a is incident on the grating 306a. The area on which the grating 306a receives the fifth diffracted beam 316a is referred to as the area 307a.

[00107] At the area 307a, the fifth diffracted beam 316a is diffracted and is directed towards the third reflective element 310. The reflective element 310 reflects the fifth diffracted beam 316a towards the grating 306c. Then the fifth diffracted beam 316a is subsequently diffracted by the grating 306c, directed towards the encoder scale 20 and diffracted by the encoder scale 20.

[00108] At the encoder scale 20, the third inputbeam 313 is diffracted by the pattern on the surface 22 and a sixth diffracted beam 316b is created. The sixth diffracted beam 316b is directed towards the third encoderhead 300. The sixth diffracted beam 316b is incident on the grating 306b. The area on which the grating 306b receives the sixth diffracted beam 1316b is referred to as area 307b.

[00109] At the area 307b, the sixth diffracted beam 316b is diffracted and is directed towards the third reflective element 1310. The third reflective element 310 reflects the sixth diffracted beam 316b towards the grating 106d. Then the sixth diffracted beam 316b is subsequently diffracted by the grating 306d, directed towards the encoder scale 20 and diffracted by the encoder scale 20.

[00110] The fifth diffracted beam 316a and the sixth diffracted beam 316b are combined by the encoder scale in a third combined beam 322a. The third combined beam 322a is directed toward a third sensor 330a. A change in a position of the encoder scale 20 relative to the third encoderhead 300 causes the phase of the third combined beam 322a to change. The third sensor 330a is arranged to determine the change in the phase of the third combined beam 322a. Under control of the change in the phase, the third sensor 330a is arranged to provide a signal representative of the position of the third encoderhead 300 relative to the encoder scale 20.

[00111] The gratings 306a, 306b, 306c and 306d may all be on a first surface (142).

[00112] Figure 7 shows the encoderhead system 10 according to an embodiment of the invention. The encoderhead system 10 comprises the first encoderhead 100, the second encoderhead 200 and the third encoderhead 300. The beamsplitter 40 is arranged to split the inputbeam 30 into the first inputbeam 113, the second input beam 213 and the third inputbeam 313.

[00113] As seen in Figure 7, the grating 106a and grating 206a are aligned on a line C. The line C is in the xy-plane. Grating 106a and grating 306a are aligned on a line B. The line B is in the xy-plane. The angle between the line B and the line C is larger than zero, for example 90 degrees. With a non-zero angle, the encoderhead system can be used for the calibration method called stitching along both the x-axis and the y-axis. In addition or alternatively, gratings 106b and 206b are aligned substantially parallel to line C. In addition or alternatively, gratings 106b and 306b are aligned substantially parallel to line B. The encoderheads 100, 200 and 300 are positioned relative to each other at an offset along the x-axis, so that the first encoderhead 100 measures an x-position at a different location along the x-axis on the encoder scale 20 than the second encoderhead 200 and the third encoderhead 300.

[00114] In an embodiment, the first encoderhead 100 comprises a 2D-encoderhead, as seen in Figures 8A, 8B and 8C. A 2D encoderhead may measure a position of the encoderhead relative to the encoder scale 20 along the x-axis and along the z-axis. A known 2D-encoderhead is known from US 7,573,581 B2, hereby incorporated by reference.

[00115] In Figure 8A, the first encoderhead 100 is provided with a splitter 104. The splitter 104 is to split the first inputbeam 113 into two beams, beam 114 and beam 118. The splitter 104 may be any type of suited splitter, for example a beam splitter or a grating.

[00116] Beam 114 is diffracted by the encoder scale 20 and creates the diffracted beams 116 and 116b, as described above. Beam 118 is diffracted by the encoder scale 20 and creates diffracted beams 120a and 120b. Diffracted beam 120a is directed from the encoder scale 20 onto a grating 108a. The diffracted beam 120a is then directed onto a reflective element 112 and reflected onto a grating 108c. Diffracted beam 120b is directed from the encoder scale 20 onto a grating 108b. The diffracted beam 120b is then directed onto a reflective element 112 and reflected onto a grating 108d. The diffracted beams 120a and 120b are then both directed onto the encoder scale 20. At the encoder scale 20, the diffracted beams 120a and 120b are combined in a combined beam 122b. A change in a position of the encoder scale 20 relative to the first encoderhead 100 causes the phase of the combined beam 122b to change. The sensor 130b is arranged to determine the change in the phase of the combined beam 122b. Under control of the change in the phase, the sensor 130b is arranged to provide a signal representative of the position of the first encoderhead 100 relative to the encoder scale 20.

[00117] Since the splitter 104 provides the beams 114 and 118 each at a different angle to the encoder scale 20, each of the combined beams 122a and 122b is sensitive to a movement of the encoder scale 20 along the x-axis and the z-axis. So the encoderhead 100 can determine a position of the encoder scale 20 along both the x-axis and the z-axis.

[001181 Similar to the embodiment of Figures 8A-C, each or both of the second encoderhead 200 and the third encoderhead 300 may comprise a 2D-encoderhead.

[00119] The embodiment of Figure 9 is similar to the embodiments described above, except for what is stated below. The embodiment of Figure 9 comprises a fourth encoderhead 500. The fourth encoderhead 500 is similar to the cncodcrhcads 100, 200, 300 of any of Figures 2, 3 or 6, except for the orientation of the fourth encoderhead 500. The fourth encoderhead 500 has gratings 506a, 506b, 506c and 506d. An inputbeam is diffracted into two diffracted beams by the encoder scale 20. The encoder scale 20 is provided with a 2D-grating. The first diffracted beam is diffracted by grating 506a and reflected to grating 506c. The second diffracted beam is diffracted by grating 506b and reflected to grating 506d. The first and second diffracted beams are then combined by the encoder scale and directed onto a sensor. Since the gratings 506a and 506b are aligned along the y-axis, the sensor is able to determine a position of the encoder scale 20 relative to the encoderhead 500 along the y-axis. Alternatively or in addition, the gratings 506c and 506d are aligned along the y-axis.

[00120] The combination of the first encoderhead 100, the second encoderhead 200, the third encoderhead 300 and the fourth encoderhead 500 allows the encoderhead system 10 to determine 6 degrees of freedom.

[00121] Any of the embodiments of the encoderhead system 10 above may be provided with a gas nozzle to supply a flow of gas between the encoderhead system 10 and the encoder scale 20. Since the encoderhead system 10 can be made smaller than a known combination of encoderheads, the gas nozzle may surround the encoderhead system 10 and provide a high-quality flow of conditioned gas flow between the encoderhead system 10 and the encoder scale 20. The high-quality flow improves the accuracy of the encoderhead system 10.

[00122] In the lithographic apparatus, the encoderhead system 10 can be used in addition to a known encoderhead, such as disclosed in US 7,573,581 Bl, hereby incorporated by reference.

The encoderhead may be able to determine a position of the encoderhead relative to the encoder scale 20 when the encoderhead system 10 faces a distortion of the encoder scale 20. When the encoderhead system 10 faces a distortion of the encoder scale 20, the encoderhead system 10 may not be able to receive one of the combined beams 122A, 122B, 222A or 322A. The distortion may be a scratch or another type of damage to the encoder scale 20. The distortion may be a gap between two portions of the encoder scale 20, or an absence of encoder scale 20 at a certain position. The distortion may be a droplet of liquid on the encoder scale 20. The liquid may be immersion liquid.

[00123] In an embodiment the gratings on the first surface 142 are adjacent to each other. In an embodiment, a grating is applied to the first surface 142, wherein the grating comprises more than one of the gratings 106a-d, 206a-d, 306a-d and/or 506a-d. In an embodiment, the reflective elements 110, 122, 210 may be combined in a single reflective element.

[00124] 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 W and develops the exposed resist), a metrology tool and/or an inspection tool. Further, the substrate W may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate W used herein may also refer to a substrate W that already contains multiple processed layers.

[00125] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described.

[00126] 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. An encoderhead system (10) arranged to cooperate with a surface (22) of an encoder scale (20) so as to provide a signal representative of a position of the encoderhead system (10) relative to the encoder scale (20) along a first axis (X), wherein the first axis (X) is in a plane substantially parallel to the surface (22), the encoderhead system (10) comprising: a first encoderhead (100); a second encoderhead (200); wherein the first encoderhead (100) comprises: a first direction element (102); a first grating (106a); a second grating (106b); a third grating (106c); a fourth grating (106d); a first reflective element (110); and a first sensor (130a); wherein the first direction element (102) is arranged to direct a first input beam (113) toward the encoder scale (20), wherein the first grating (106a) is arranged to receive a first diffracted beam (116a) created by the encoder scale (20) under control of the first input beam (113), wherein the first grating (106a) comprises a first area (107a) at which the first grating (106a) is arranged to receive the first diffracted beam (116a), wherein the first grating (106a) is arranged to direct the first diffracted beam (116a) toward the first reflective element (110), wherein the reflective element (110) is arranged to reflect the first diffracted beam (116a) toward the third grating (106c), wherein the third grating (106c) is arranged to receive the first diffracted beam (116a) wherein the second grating (106b) is arranged to receive a second diffracted beam (116b) created by the encoder scale (20) under control of the first input beam (113), wherein the second grating (106b) comprises a second area (107b) at which the second grating (107b) is arranged to receive the second diffracted beam (116b), wherein the second grating (108a) is arranged to direct the second diffracted beam (116b) toward the reflective element (110), wherein the reflective element (110) is arranged to reflect the second diffracted beam (lib) toward the fourth grating (106d), wherein the fourth grating (106d) is arranged to receive the second diffracted beam (116b), wherein the sensor (130a) is arranged to receive a first combined beam (122a) from the encoder scale (20), wherein the first combined beam (122a) is created by the encoder scale (20) under control of the first diffracted beam (116a) directed to the encoder scale (20) by the third grating (106c) and of the second diffracted beam (116b) directed to the encoder scale (20) by the fourth grating (106d), wherein the second encoderhead (200) comprises: a second direction element (202); a fifth grating (206a); a sixth grating (206b); a seventh grating (206c); a eighth grating (206d); a second reflective element (210); and a second sensor (230a); wherein the second direction element (202) is arranged to direct a second input beam (213) toward the encoder scale (20), wherein the fifth grating (206a) is arranged to receive a third diffracted beam (216a) created by the encoder scale (20) under control of the second input beam (213), wherein the fifth grating (206a) comprises a third area (207a) at which the fifth grating (206a) is arranged to receive the third diffracted beam (216a), wherein the fifth grating (206a) is arranged to direct the third diffracted beam (216a) toward the second reflective element (210), wherein the second reflective element (210) is arranged to reflect the third diffracted beam (216a) toward the seventh grating (206c), wherein the seventh grating (206c) is arranged to receive the third diffracted beam (216a), wherein the sixth grating (206b) is arranged to receive a fourth diffracted beam (216b) created by the encoder scale (20) under control of the second input beam (213), wherein the sixth grating (206b) comprises a fourth area (207b) at which the sixth grating (206b) is arranged to receive the fourth diffracted beam (216b), wherein the sixth grating (206b) is arranged to direct the fourth diffracted beam (216b) toward the reflective element (210), wherein the second reflective element (210) is arranged to reflect the fourth diffracted beam (216b) toward the eighth grating (206d), wherein the eighth grating (206d) is arranged to receive the fourth diffracted beam (216b), wherein the second sensor (230a) is arranged to receive a second combined beam (222a) from the encoder scale (20), wherein the combined beam (222a) is created by the encoder scale (20) under control of the third diffracted beam (216a) directed to the encoder scale (20) by the seventh grating (206c) and of the fourth diffracted beam (218b) directed to the encoder scale (20) by the eighth grating (206d), wherein the first area (107a) and the second area (107b) are aligned along the first axis (X), wherein the third area (207a) and the fourth area (207b) are aligned along the first axis (X), wherein a projection (130) of the first area (107a) on a second axis (Y) and a projection (230) of the third area (207a) on the second axis (Y) are substantially adjacent to each other, wherein the second axis (Y) is in the plane and is perpendicular to the first axis (X). 2. The encoderhead system (10) of clause 1, wherein a projection of the first area (107a) on the first axis (X) and a projection of the third area (207a) on the first axis (X) are at a first distance from each other. 3. The encoderhead system (10) of one of the preceding clauses, wherein at least one of the first grating (106a), the second grating (106b), the fifth grating (206a) and the sixth grating (206b) comprises a 2D grating. 4. The encoderhead system (10) of one of the preceding clauses, comprising a monolithic component (140) having a first surface (142) on which the first grating (106a), the second grating (106b), the third grating (106c), the fourth grating (106d), the fifth grating (206a), the sixth grating (206b), the seventh grating (206c) and the eighth grating (206d) are arranged. 5. The encoderhead system (10) of clause 4, wherein the monolithic component (140) has a second surface (144), wherein at least one of the first reflective element (110) and the second reflective element (210) are on the second surface (144). 6. The encoderhead system of clause 4 or 5, comprising an interferometer (400) on the first surface (142). 7. The encoderhead system (10) of one of the preceding clauses, comprising a third encoderhead, wherein the third encoderhead comprises: a third direction element (302); a ninth grating (306a); a tenth grating (306b); an eleventh grating (306c); a twelfth grating (306d); and a third reflective element (310); a third sensor (330a); wherein the third direction element (302) is arranged to direct a third input beam (313) toward the encoder scale (20), wherein the ninth grating (306a) is arranged to receive a fifth diffracted beam (316a) created by the encoder scale (20) under control of the third input beam (313), wherein the ninth grating (306a) comprises a fifth area (307a) at which the ninth grating (306a) is arranged to receive the fifth diffracted beam (316a), wherein the ninth grating (306a) is arranged to direct the third diffracted beam (316a) toward the third reflective element (310), wherein the third reflective element (310) is arranged to reflect the third diffracted beam (316a) toward the eleventh grating (306c), wherein the eleventh grating (306c) is arranged to receive the third diffracted beam (316a) wherein the tenth grating (306b) is arranged to receive a sixth diffracted beam (316b) created by the encoder scale (20) under control of the third input beam (313), wherein the tenth grating (306b) comprises a sixth area (307b) at which the tenth grating (307b) is arranged to receive the sixth diffracted beam (316b), wherein the tenth grating (306b) is arranged to direct the sixth diffracted beam (316b) toward the third reflective element (310), wherein the third reflective clement (310) is arranged to reflect the sixth diffracted beam (316b) toward the twelfth grating (306d), wherein the twelfth grating (306d) is arranged to receive the sixth diffracted beam (316b), wherein the third sensor (330a) is arranged to receive a thirdcombined beam (322a) from the encoder scale (20), wherein the third combined beam (322a) is created by the encoder scale (20) under control of the fifth diffracted beam (316a) directed to the encoder scale (20) by the eleventh grating (306c) and of the sixth diffracted beam (316b) directed to the encoder scale (20) by the twelfth grating (306d), wherein the fifth area (307a) and the sixth area (307b) are aligned along the first axis (X), wherein the projection (130) of the first area (107a) on a second axis (Y) and a projection of the fifth area (307a) on the second axis (Y) are substantially adjacent to each other. 8. The encoderhead system (10) of clause 7, wherein the ninth grating (306a), the tenth grating (306b), the eleventh grating (306c) and the twelfth grating (306d) are arranged on the first surface (142). 9. The encoderhead system (10) of clause 7 or 8, wherein the projection of the first area (107a) on the first axis (X) and the projection of the fourth area (307a) on the first axis (X) are at a second distance from each other. 10. The encoderhead system (10) of clause 9, wherein the first area (107a) and the third area (207a) are aligned along a first line (B) in the plane, wherein the first area (107a) and the fifth area (307a) are aligned along a second line (C) in the plane, wherein an angle between the first line (B) and the second line (C) is substantially 90 degrees. 11. The encoderhead system (10) of one of the preceding clauses, wherein the first encoderhead (100) comprises a first splitter (104), a thirteenth grating (108a), a fourteenth grating (108b), a fifteenth grating (108c), a sixteenth grating (108d), a fourth reflective element (112) and a fourth sensor (130b); wherein the splitter (104) is arranged to split the first input beam (113) into a first beam (114) and a second beam (118), wherein the first diffracted beam (116a) and the second diffracted beam (116b) are created by the encoder scale (20) under control of the first beam (114), wherein the thirteenth grating (108a) is arranged to receive a seventh diffracted beam (120a) created by the encoder scale (20) under control of the second beam (118), wherein the thirteenth grating (108 a) comprises a seventh area (109a) at which the thirteenth grating (108a) is arranged to receive the seventh diffracted beam (120a), wherein the thirteenth grating (108 a) is arranged to direct the seventh diffracted beam (120a) toward the fourth reflective element (112), wherein the fourth reflective element (112) is arranged to reflect the seventh diffracted beam (120a) toward the fifteenth grating (108c), wherein the fifteenth grating (108c) is arranged to receive the seventh diffracted beam (120a) wherein the fourteenth grating (108b) is arranged to receive an eighth diffracted beam (120b) created by the encoder scale (20) under control of the second beam (118), wherein the fourteenth grating (108b) comprises an eighth area (109b) at which the fourteenth grating (108b) is arranged to receive the eighth diffracted beam (120b), wherein the fourteenth grating (108 a) is arranged to direct the eighth diffracted beam (120b) toward the fourth reflective element (112), wherein the fourth reflective element (112) is arranged to reflect the eighth diffracted beam (120b) toward the sixteenth grating (108d), wherein the sixteenth grating (108d) is arranged to receive the eight diffracted beam (120b), wherein the fourth sensor (130b) is arranged to receive a fourth combined beam (122b) from the encoder scale (20), wherein the fourth combined beam (122b) is created by the encoder scale (20) under control of the seventh diffracted beam (120a) directed to the encoder scale (20) by the fifteenth grating (108c) and of the eighth diffracted beam (120b) directed to the encoder scale (20) by the sixteenth grating (108d), wherein the first area (107a), the seventh area (109a) and the eighth area (109b) are aligned along the first axis (X). 12. The cncodcrhcad system (10) of clause 11, wherein the thirteenth grating (108a), the fourteenth grating (108b), the fifteenth grating (108c) and the sixteenth grating (106d) are arranged on the first surface (142). 13. The encoderhead system (10) of one of the preceding clauses, wherein the second encoderhead (200) comprises a second splitter (204), a seventeenth grating (208a), an eighteenth grating (208b), a nineteenth grating (208c), a twentieth grating (208d), a fifth reflective element (212) and a fifth sensor (230b); wherein the second splitter (204) is arranged to split the second input beam (213) into a third beam (214) and a fourth beam (218), wherein the third diffracted beam (216a) and the fourth diffracted beam (216b) are created by the encoder scale (20) under control of the third beam (214), wherein the seventeenth grating (208a) is arranged to receive a ninth diffracted beam (220a) created by the encoder scale (20) under control of the fourth beam (218), wherein the seventeenth grating (208a) comprises a ninth area (209a) at which the seventeenth grating (208a) is arranged to receive the ninth diffracted beam (220a), wherein the seventeenth grating (208a) is arranged to direct the ninth diffracted beam (220a) toward the fifth reflective element (212), wherein the fifth reflective element (212) is arranged to reflect the ninth diffracted beam (220a) toward the nineteenth grating (208c), wherein the nineteenth grating (208c) is arranged to receive the ninth diffracted beam (220a) wherein the eighteenth grating (208b) is arranged to receive a tenth diffracted beam (220b) created by the encoder scale (20) under control of the fourth beam (218), wherein the eighteenth grating (208b) comprises a tenth area (209b) at which the eighteenth grating (208b) is arranged to receive the tenth diffracted beam (220b), wherein the seventeenth grating (208a) is arranged to direct the tenth diffracted beam (220b) toward the fifth reflective element (212), wherein the fifth reflective element (212) is arranged to reflect the tenth diffracted beam (220b) toward the twentieth grating (208d), wherein the twentieth grating (208d) is arranged to receive the tenth diffracted beam (220b), wherein the fifth sensor (230b) is arranged to receive a fifth combined beam (222b) from the encoder scale (20), wherein the fifth combined beam (222b) is created by the encoder scale (20) under control of the ninth diffracted beam (220a) directed to the encoder scale (20) by the fifteenth grating (208c) and of the tenth diffracted beam (220b) directed to the encoder scale (20) by the twentieth grating (208d), wherein the third area (207a), the ninth area (209a) and the tenth area (209b) are aligned along the first axis (X), wherein the projection (130) of the first area (107a) on a second axis (Y) and a projection of the ninth area (209a) on the second axis (Y) are substantially adjacent to each other. 14. The encoderhead system (10) of clause 13, wherein the seventeenth grating (208a), the eighteenth grating (208b), the nineteenth grating (208c) and the twentieth grating (208d) are arranged on the first surface (142). 15. The encoderhead system (10) of one of the preceding clauses, wherein the third encoderhead (300) comprises a third splitter (304), a twenty-first grating (308a), a twenty-second grating (308b), a twenty-third grating (308c), a twenty-fourth grating (308d), a sixth reflective element (312) and a sixth sensor (330b); wherein the third splitter (304) is arranged to split the third input beam (313) into a fifth beam (314) and a sixth beam (318), wherein the fifth diffracted beam (316a) and the sixth diffracted beam (316b) are created by the encoder scale (20) under control of the fifth beam (314), wherein the twenty-first grating (308a) is arranged to receive a eleventh diffracted beam (320a) created by the encoder scale (20) under control of the fifth beam (318), wherein the twenty-first grating (308a) comprises a eleventh area (309a) at which the twenty-first grating (308a) is arranged to receive the eleventh diffracted beam (320a), wherein the twenty-first grating (308a) is arranged to direct the eleventh diffracted beam (320a) toward the sixth reflective element (312), wherein the sixth reflective element (312) is arranged to reflect the eleventh diffracted beam (320a) toward the twenty-third grating (308c), wherein the twenty-third grating (308c) is arranged to receive the eleventh diffracted beam (320a), wherein the twenty-second grating (308b) is arranged to receive a twelfth diffracted beam (320b) created by the encoder scale (20) under control of the sixth beam (318), wherein the twenty-second grating (308b) comprises a twelfth area (309b) at which the twenty-second grating (308b) is arranged to receive the twelfth diffracted beam (320b), wherein the twenty-second grating (308b) is arranged to direct the twelfth diffracted beam (320b) toward the sixth reflective element (312), wherein the sixth reflective element (312) is arranged to reflect the twelfth diffracted beam (320b) toward the twenty-fourth grating (308d), wherein the twenty-fourth grating (308d) is arranged to receive the twelfth diffracted beam (320b), wherein the sixth sensor (330b) is arranged to receive a sixth combined beam (322b) from the encoder scale (20), wherein the sixth combined beam (322b) is created by the encoder scale (20) under control of the eleventh diffracted beam (320a) directed to the encoder scale (20) by the twenty-third grating (308c) and of the twelfth diffracted beam (320b) directed to the encoder scale (20) by the twenty-fourth grating (308d), wherein the fifth area (307a), the eleventh area (309a) and the twelfth area (309b) are aligned along the first axis (X), wherein the projection (130) of the first area (107a) on a second axis (Y) and a projection of the eleventh area (309a) on the second axis (Y) are substantially adjacent to each other. 16. The encoderhead system (10) of clause 15, wherein the twenty-first grating (308a), the twenty-second grating (308b), the twenty-third grating (308c) and the twenty-fourth grating (308d) are arranged on the first surface (142). 17. A positioning system comprising: the encoderhead system (10) of one of clauses 1-16; the encoder scale (20); a reference body; a moveable body that is moveable relative to the reference body; wherein one of the encoderhead system (10) and the encoder scale (20) is connected to the moveable body, wherein the other one of the encoderhead system (10) and the encoder scale (20) is connected to the reference body, wherein the encoderhead system (10) is arranged to provide a signal representative of a position of the moveable body relative to the reference body in the first direction. 18. The positioning system of clause 17, comprising a gas nozzle arranged to supply a flow of gas between the encoderhead system (10) and the scale, wherein the gas nozzle at least partly surrounds the encoderhead system (10). 19. A lithographic apparatus comprising the positioning system of clause 17 or 18, the lithographic apparatus comprising a projection system to project a pattern from a patterning device onto a substrate; a support structure to support the patterning device; a substrate table to hold the substrate; a metrology frame to support the projection system; wherein the substrate table comprises the moveable body, wherein the metrology frame comprises the reference body. 20. The lithographic apparatus of clause 19, comprising a further encoderhead, wherein the further encoderhead is arranged to cooperate with the encoder scale (20) to provide a further signal representative of a position of the further encoderhead relative to the encoder scale (20) along the first axis (X), wherein the further encoderhead is arranged on one of the moveable body and the reference body so as to provide the further signal when the encoderhead system (10) is unable provide the signal.

Claims (1)

A lithography device comprising: an exposure device adapted to provide a radiation beam; a carrier configured to support a patterning device, which patterning device is capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam; 5 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.