NL2006149A - Lithographic apparatus and method for correcting. - Google Patents

Description

LITHOGRAPHIC APPARATUS AND METHOD FOR CORRECTING

FIELD

[0001] The present invention relates to a lithographic apparatus and a method for correcting a position of a support structure of a lithographic apparatus.

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] Generally, a lithographic apparatus includes one or more supports to hold an object, e.g. the substrate or the patterning device. These supports, e.g. a substrate table configured to hold the substrate and a patterning device support configured to hold the patterning device, may be moveable in two orthogonal directions relative to a reference structure, e.g. in plane of the object and out of plane of the object, which usually corresponds to in and out of plane of a top surface of the support structure. A direction in plane of the object can also be referred to as a direction substantially perpendicular to the radiation beam imparted to the object, and a direction out of plane of the object can alternatively be referred to as parallel to the radiation beam.

[0004] To meet the further increasing demands in lithography, the support needs to be positioned with increasing accuracy relative to the radiation beam and/or reference structure. A lithographic apparatus therefore includes a positioning system with a position measurement system to measure a position of the support structure relative to the reference structure, an actuation system to move the support structure, and a control system providing drive signals to the actuation system in dependency of output signals from the position measurement system.

[0005] Positioning the support in the direction in plane of the object is desirable for overlay. Overlay is the accuracy within which layers are printed in relation to layers that have previously been formed, and is an important factor in the yield, i.e. the percentage of correctly manufactured devices.

[0006] Positioning the support in the direction out of plane of the object is important for focus of the pattern, for instance onto the substrate, and determines the amount of blur of the pattern on the substrate. It has been found that the focus characteristics of current lithographic apparatus may not be satisfactory to meet the future demands of lithographic apparatus.

SUMMARY

[0007] It is desirable to provide an improved lithographic apparatus, in particular a lithographic apparatus with improved focus characteristics.

[0008] According to an embodiment of the invention, there is provided a lithographic apparatus including a reference structure; a support to hold an object, the support being moveable in a first direction and a second direction relative to the reference structure, the first direction being at an angle, in an embodiment orthogonal, to the second direction; a position measurement system to provide a first measurement signal corresponding to a position of the support relative to the reference structure in the first direction and a second measurement signal corresponding to a position quantity of the support relative to the reference structure in the second direction; a data processor configured to correct the first measurement signal with a value which is dependent on movement of the support relative to the reference structure in the second direction in order to provide a first corrected measurement signal representative of the position of the support relative to the reference structure in the first direction, wherein the data processor is configured to derive movement of the support relative to the reference structure in the second direction from the second measurement signal.

[0009] According to another embodiment of the invention, there is provided a method for correcting a position of a support of a lithographic apparatus relative to a reference structure in a first direction, wherein the support is moveable relative to the reference structure in the first direction and in a second direction at an angle, in an embodiment orthogonal, to the first direction, the method including providing a first measurement signal corresponding to a position of the support relative to the reference structure in the first direction; providing a second measurement signal corresponding to a position quantity of the support relative to the reference structure in the second direction; deriving movement of the support in the second direction relative to the reference structure based on the second measurement signal; and correcting the first measurement signal with a value which is dependent on the movement of the support relative to the reference structure in the second direction, thereby providing a first corrected measurement signal representative for the position of the support in the first direction relative to the reference 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 2 depicts a part of the lithographic apparatus of Figure 1 in schematic block view according to an embodiment of the invention;

[0013] Figure 3 depicts a data processing device of the lithographic apparatus of Figure 1 in schematic block view according to an embodiment of the invention;

[0014] Figure 4 depicts a position measurement system suitable for a lithographic apparatus according to an embodiment of the invention;

[0015] Figure 5 depicts schematically a part of a position measurement system and a data processing device suitable for a lithographic apparatus according to an embodiment of the invention; and

[0016] Figure 6 depicts a support structure with a position measurement system according to another embodiment of the invention.

DETAILED DESCRIPTION

[0017] 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 mask 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 support structure in the form of 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.

[0018] 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.

[0019] 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.”

[0020] 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.

[0021] 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.

[0022] 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”.

[0023] 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).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 a position measurement system including a position sensor FM to measure a position in a second direction and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor) to measure a position in a first direction, the substrate table WT can be moved accurately with respect to a reference structure RS, 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 patterning device (e.g. 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 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.

[0029] 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.

[0030] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[0031] Figure 2 depicts in schematic block view a part of the lithographic apparatus of Figurel. Shown is the substrate table WT configured to hold the substrate W. The substrate table WT is moveable relative to the reference structure RS in two directions via the second positioning device PW which moves the substrate table WT relative to a base BA. The reference structure RS may be low-frequency supported by the base BA. The two directions include a first direction in Z and a second direction in X.

[0032] Also shown in Figure 2 is the position measurement system including the position sensors FM and IF, which respectively measure a position of the substrate table relative to the reference structure in Z-direction and X-direction. An output, i.e. a first measurement signal, of position sensor FM is referred to as 01 and corresponds to the position of the substrate table WT in the Z-direction. An output, i.e. a second measurement signal, of position sensor IF is referred to as 02 and corresponds to the position of the substrate table WT in the X-direction.

[0033] The outputs 01,02 are provided to a data processing device or data processor DPD, which is configured to correct output 01 with a value which is dependent on movement of the substrate table in the second direction to provide a corrected first measurement signal representative for the position in the Z-direction. Movement of the substrate table is derived from the second output 02. In this embodiment, the second output corresponds to the position of the substrate table in the second direction relative to the reference structure, so that movement of the substrate table can for instance be derived from the second output by a derivative operation to obtain information about the velocity of the substrate table, or multiple derivative operations to obtain information about the acceleration or jerk of the substrate table. Flowever, the second output may also correspond to other position quantities such as the velocity, acceleration or jerk, so that the derivative operation on the second output is not necessary.

[0034] It has been found by the inventors that inconsistencies in output 01 show a correlation with movement of the substrate table in the X-direction. This effect is similar to the already known inconsistencies in output 02 due to movement in the X-direction itself which are caused for example by a delay in a signal path of the position sensor IF. Delays in the signal path in turn may be caused by the tolerances or differences in optical path when a optical sensor is used, and/or by the electronics operating the position sensor. Due to the delay, the position information is not obtained at the desired time instant, although the eventually obtained position information is later on coupled to the desired time instant for control purposes. Thus as a result of movement in the X-direction, the delay causes a position error in the X position. Normally, a more intense movement in the X-direction will result in a larger position error in the X-direction. It has been found that the movement in the X-direction may also cause movement dependent disturbances in the measurement of the position of the support structure in the Z-direction. Therefore, correcting the output corresponding to the Z-direction for movement in the X-direction will result in a signal that more accurately represents the position in Z-direction. Using this more accurate signal in positioning the substrate table in Z-direction will result in a more accurate positioning of the substrate table in Z-direction and as this direction is related to the focus of the radiation beam onto the substrate, the focus of the lithographic apparatus can be improved.

[0035] Figure 3 depicts in schematic block view the data processing device DPD of Figure 2. Input to the data processor are the outputs 01 and 02 carrying the first and second measurement signal which correspond to the position of the substrate table in respectively the Z-direction and the X-direction. As movement is usually expressed in terms of velocity, acceleration or jerk of the substrate table, the output 02 which corresponds to a position is converted into a movement signal representing the movement of the substrate table in X-direction. Conversion of the position to the movement signal is done in movement unit MU. In an embodiment, the movement unitwill perform a derivative action on the output 02. As an example, a first derivative of the position yields the velocity, a second derivative of the position yields the acceleration, and the third derivative of the position yields the jerk. The output of the movement unit MU is used as a basis for determining a movement dependent correction value CV. The determination of the value CV is done by correction unit CU. Correction unit CU contains information about the disturbances introduced in the output 01 as function of the movement in the X-direction. This information may be stored as a look-up table or as a mathematical function.

[0036] It is mentioned explicitly here that movement of the support in the second direction may also be obtained directly by a suitable sensor, so that in that case movement unit MU can be omitted.

[0037] The value CV is added to the output 01 to correct the disturbances and obtain a first corrected measurement signal FMS representing the position of the substrate table in the Z-direction. The first corrected measurement signal FMS can then be used in a control loop positioning the substrate table in the Z-direction.

[0038] An embodiment of the invention is especially suitable to be used in an embodiment of a lithographic apparatus with a position measurement system that uses encoder type sensors to measure a position in X and Z direction at the same time. Such an encoder type sensor is shown in Figure 4.

[0039] Figure 4 depicts an encoder type sensor including a sensor head SH and a grid plate GP, the encoder type sensor being configured to measure a position of the sensor head SH with respect to grid plate GP. In this example, an incremental encoder is applied, providing a periodic sensor head output signal when moving the sensor heads with respect to the grid plate. Position information may be obtained from periodicity and phase of corresponding sensor head output signals of the sensor head. In the embodiment shown, a sensor head assembly is depicted emitting two measurement beams MB1, MB2 towards the grid plate. Due to an interaction with the pattern on the grid plate (which may be one dimensional or two dimensional), beams are returned towards the sensor head at an angle, as schematically depicted in Figure 4, and detected by a suitable sensor element SE1 ,SE2 of the sensor head. Thus, the sensor heads provide for two measurements, namely at A and at B on the grid plate GP. Each of the measurements provides for a sensitivity in horizontal as well as in vertical direction. A sensitivity of the left one of the sensor elements SE1 is schematically indicated by vector ea, while a sensitivity of the right one of the sensor elements SE2 is schematically indicated by eb. In a present, practical implementation, an angle of ea and eb with respect to horizontal will be small, smaller than indicated in Figure 4. In fact, the angles of ea and eb with respect to the horizontal plane are exaggerated somewhat for illustrative purposes. A measurement of the horizontal position can now be obtained from an addition of ea and eb. A measurement of the vertical position can be obtained from a subtraction of ea and eb, as outlined in the below expressions.

wherein posX and posZ represent a respective horizontal and vertical encoder position information, and ki and fa are gain factors compensating for the fact that the vectors ea and eb are not exactly directed in the horizontal or vertical direction.

[0040] Figure 5 depicts a part of a position measurement system and a data processor DPD suitable for a lithographic apparatus according to an embodiment of the invention, in particular an embodiment wherein the position measurement system includes an encoder type sensor as in Figure 4.

[0041] The encoder type sensor of Figure 4 outputs two sensor signal OT, 02’, which represent respectively the vectors ea, eb of Figure 4. In a processing unit or processor PU, the two signals are combined to output two outputs 01,02, i.e. a first and a second measurement signal, representing the position of a support structure in respectively a first direction and a second direction.

[0042] The outputs 01,02 are provided to the data processor DPD. Due to for instance errors in the grid plate, the outputs 01 and 02 show inconsistencies which are dependent on the position of the support structure in a corresponding direction itself. Information about these inconsistencies as a function of position is stored in correction units CU3 and CU4. These correction units convert the position information into a correction value CV3, CV4 which is added to the respective signals to correct for the position dependent inconsistencies. After correction by correction units CU3 and CU4, the signals still show some inconsistencies due to movement in the second direction.

[0043] Movement in the second direction is derived from a second corrected signal SMS by movement unit MU, for instance by taking a derivative of the signal. An output of the movement unit MU is provided to correction units CU, CU2 which convert the movement information into a respective movement dependent correction value CV, CV2. The correction value CV is added to the output 01 and together with the addition of correction value CV4 forms a first corrected measurement signal FMS representing the position of the support structure in the first direction. The correction value CV2 is also added to the output 02 and together with the addition of correction value CV3 forms the second corrected measurement signal SMS which in turn forms the basis for determining the movement in the second direction. It is mentioned here that the correction for movement in the second direction of the position in the second direction is configured as a feedback loop. However, a feedforward loop is also envisaged.

[0044] Figure 6 depicts a substrate table WT and three encoder type sensors of which only the respective sensor heads SH1, SH2, and SH3 are shown. Each sensor head is similar to the encoder type sensor of Figure 4 and able to measure the position of the substrate table WT in two orthogonal directions. Sensor head SH1 outputs a signal X1 and a signal Z1 respectively corresponding to the X-direction and the Z-direction. Sensor head SH2 outputs a signal Y2 and a signal Z2 respectively corresponding to the Y-direction and the Z-direction. Sensor head SH3 outputs a signal X3 and a signal Z3 respectively corresponding to the X-direction and the Z-direction. To get six degree of freedom (DOF) position information about the substrate table WT, the signals may be used as follows: - position of the substrate table in X-direction is derived from signal X1 or signal X3; - position of the substrate table in Y-direction is derived from signal Y2; - position of the substrate table in Z-direction is derived from signal Z1, Z2, or Z3; - tilting of the substrate table about the X-direction, referred to as RX, is derived from the difference between signals Z2 and Z3; - tilting of the substrate table about the Y-direction, referred to as RY, is derived from the difference between signals Z1 and Z2; and - tilting of the substrate table about the Z-direction, referred to as RZ, is derived from the difference between signals X1 and X3.

[0045] It is possible that each encoder type sensor has inconsistencies in the Z-direction originating from movement in a horizontal direction (X-direction, Y-direction, or both). The Z1, Z2, and Z3 signals may thus each be corrected for movement in the corresponding X- or Y-direction. However, alternatively, a correction may also be applied directly to the six DOF position information derived from the signals.

[0046] It is also possible that the horizontal signals are disturbed by movement in the Z-direction, so that these signals may also be corrected for movement in the Z-direction. In most lithographic apparatus, the Z-direction is related to focus, so that the Z-position needs to be constant. In that case, movement in the Z-direction is small and corrections in the horizontal signals for movement in the Z-direction may not be necessary.

[0047] The value, i.e. correction value, used to correct a measurement signal corresponding to a position of a support structure may be obtained by the following actions: a) moving the support in a second direction relative to a reference structure along a path while measuring a position of the support in a first direction relative to the reference structure, the movement being performed at constant velocity; b) moving the support direction in the second direction relative to the reference structure along the path in an opposite direction with the same velocity as in step a) while measuring the position of the support in the first direction relative to the reference structure; c) determining inconsistencies between a measurement result of step a) and a measurement result of step b); and d) deriving the value from the inconsistencies for the velocity.

[0048] As the difference between the movement of step a) and step b) is the direction in which is moved, position dependent errors will cancel when comparing the two measurements results corresponding to the movements. The difference in measurement results is then determined by the movement and by comparing the measurement results, a velocity dependent error can be obtained, which forms the basis for the value to correct the position measurement signal. The abovementioned steps can be repeated for other velocities as well to obtain more information about the velocity dependent errors/inconsistencies and the velocity dependent value may be extrapolated and/or interpolated to also obtain velocity dependent values for non-measured velocities.

[0049] Similarly, an acceleration dependent value or jerk dependent value can be obtained, especially after the velocity dependent value is obtained, as the velocity dependent value can be used to distinguish between different causes of the disturbances.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.

[0055] 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: a support configured to hold an object, the support being moveable in a first direction and a second direction relative to a reference structure; a position measurement system configured to provide a first measurement signal corresponding to a position of the support relative to the reference structure in the first direction and a second measurement signal corresponding to a position quantity of the support relative to the reference structure in the second direction; a data processor configured to correct the first measurement signal with a value which is dependent on movement of the support relative to the reference structure in the second direction in order to provide a first corrected measurement signal representative of the position of the support relative to the reference structure in the first direction, wherein the data processor is further configured to derive movement of the support relative to the reference structure in the second direction from the second measurement signal.

2. The lithographic apparatus of clause 1, wherein the position quantity of the support relative to the reference structure in the second direction corresponds to a position of the support relative to the reference structure in the second direction.

3. The lithographic apparatus of clause 1, wherein the position quantity of the support relative to the reference structure in the second direction corresponds to a velocity of the support relative to the reference structure in the second direction.

4. A lithographic apparatus according to clause 2, wherein the data processor is configured to correct the second measurement signal with a value which is dependent on the position of the support relative to the reference structure in the second direction to provide a second corrected measurement signal representative of the position of the support relative to the reference structure in the second direction, and wherein the data processor is configured to derive the movement of the support relative to the reference structure in the second direction from the second corrected measurement signal.

5. The lithographic apparatus of clause 1, wherein the position measurement system comprises a sensor with two sensor elements, and a processor, each sensor element having a sensitivity in both the first and the second direction, and the processor being configured to combine outputs of both sensor elements to provide respectively the first measurement signal and the second measurement signal.

6. The lithographic apparatus of clause 5, wherein the sensor comprises a grating and a sensor head arranged to cooperate with the grating, the sensor elements being arranged in the sensor head.

7. The lithographic apparatus of clause 1, wherein the first direction is out of plane of the object and the second direction is in plane of the object.

8. The lithographic apparatus of clause 1, comprising: a patterning device support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate support 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 support is the substrate support.

9. The lithographic apparatus of clause 1, comprising: a patterning device support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate support 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 support is the patterning device support.

10. The lithographic apparatus of clause 1, wherein movement of the support in the second direction is defined as one of the following position quantities of the support in the second direction relative to the reference structure: velocity, acceleration, jerk.

11. A method for correcting a position of a support of a lithographic apparatus relative to a reference structure in a first direction, wherein the support is moveable relative to the reference structure in the first direction and in a second direction, the method comprising: providing a first measurement signal corresponding to a position of the support relative to the reference structure in the first direction; providing a second measurement signal corresponding to a position quantity of the support relative to the reference structure in the second direction; deriving movement of the support in the second direction relative to the reference structure based on the second measurement signal; and correcting the first measurement signal with a value which is dependent on the movement of the support relative to the reference structure in the second direction so as to provide a first corrected measurement signal representative of the position of the support in the first direction relative to the reference structure.

12. The method of clause 11, wherein the position quantity of the second measurement signal corresponds to a position of the support in the second direction relative to the reference structure.

13. The method of clause 11, wherein the position quantity of the second measurement signal corresponds to a velocity of the support in the second direction relative to the reference structure.

14. The method of clause 11, wherein the movement of the support is defined as one of the following position quantities of the support structure in the second direction relative to the reference structure: velocity, acceleration, jerk.

15. The method of clause 11, wherein the first direction is out of plane of the object and the second direction is in plane of the object.

16. The method of clause 11, wherein the value is obtained by: a) moving the support in the second direction relative to the reference structure along a path while measuring the position of the support in the first direction relative to the reference structure, the movement being performed at constant velocity; b) moving the support in the second direction relative to the reference structure along the path in an opposite direction with the same velocity as in a) while measuring the position of the support in the first direction relative to the reference structure; c) determining an inconsistency between a measurement result of a) and a measurement result of b); and d) deriving the value from the inconsistency for the velocity.

17. The method of clause 16, wherein a) to d) are performed subsequently for different velocities.

18. The method of clause 16 or 17, wherein the value is extrapolated and/or interpolated to obtain the value also for non-measured velocities.

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.