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    • 专利摘要:
    A lithographic apparatus comprises a support constructed to support a patterning device, a substrate table constructed to hold a substrate; and a projection system configured to project the patterned radiation beam onto a target portion of the substrate, The lithographic apparatus comprises a position control system 5 configured to drive the support and the substrate table and an imaging error correction system configured to correct an imaging error of the projecting. The imaging error correction system comprises a memory configured to store an imaging error correction map, and an imaging error correction processor being configured to derive an imaging error correction at the target portion from the imaging error correction map, assign a first part of the imaging error correction to the substrate table and a second part of the 10 imaging error correction to the support, and output to the position control system a substrate table correction signal on the basis of the first part of the imaging error correction and a support correction signal on the basis of the second part of the imaging error correction. Fig. 2 15
    公开号:NL2020279A
    申请号:NL2020279
    申请日:2018-01-16
    公开日:2018-08-24
    发明作者:Altini Valerio
    申请人:Asml Netherlands Bv；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION [001] The present invention relates to a lithographic apparatus comprising an imaging error correction system.
    BACKGROUND ART [002] 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 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 onto a target portion (e.g. comprising 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. 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, 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.
    [003] When projecting the pattern onto the substrate, a correction is applied to provide that the pattern or part thereof is projected onto the substrate at a low error. The correction may take account of various factors, such as a height of the substrate. The more layers are provided on the substrate, the higher a substrate height, which is to be corrected as it would otherwise result in an imaging onto the substrate out of the plane of focus. In present solutions, such overlay and focus corrections arc performed by correcting a position of the substrate table. Due to various causes, the correction may be position dependent. For example the height of the substrate may vary according to a height profile. As a result, the corrected position of the substrate table may vary in 6 degrees of freedom along a plane of the substrate table, in order to position the substrate table most close to a plane of focus of the projection system, thus to minimize overlay and focus errors. In order to provide a high throughput of the lithographic apparatus, the substrate table may move at a high speed. Hence, the corrections in 6 degrees of freedom are to be performed at a high speed.
    [004] Overlay and focus corrections which are actuated may put stress on a dynamic of the substrate table. A correction capability is related to substrate table dynamic limitations, to substrate table servo errors, to substrate table encoders errors and to the internal deformations of the substrate table. All of these limitations may introduce overlay and focus penalties when trying to actuate for high frequent overlay and focus variations. The Metrology models which define set-points for the substrate table may take into account the substrate table limitations and may fallback to a sub-optimal definition of the set-points in case the limits are exceeded.
    SUMMARY OF THE INVENTION [005] It is desirable to provide a lithographic apparatus that enables a low overlay error and a low focus error.
    [006] According to an aspect of the invention, there is provided a lithographic apparatus comprising: [007] a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;
    [008] a substrate table constructed to hold a substrate;
    [009] a projection system configured to project the patterned radiation beam onto a target portion of the substrate;
    [010] a position control system configured to drive the support and the substrate table during a projecting of the pattern of the patterning device onto the target portion of the substrate; and [011] an imaging error correction system configured to correct an imaging error of the projecting, [012] the imaging error correction system comprising a memory configured to store an imaging error correction map; and an imaging error correction processor being configured to
    - derive an imaging error correction at the target portion from the imaging error correction map;
    - assign a first part of the imaging error correction to the substrate table and a second part ol’ the imaging error correction to the support; and
    - output to the position control system a substrate table correction signal on the basis of the first part of the imaging error correction and a support correction signal on the basis of the second part of the imaging error correction;
    [013] wherein the position control system is configured to drive the substrate table using the substrate table correction signal and to drive the support using the support correction signal.
    BRIEF DESCRIPTION OF THE DRAWINGS [014] 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:
    Figure 1 depicts a lithographic apparatus in which embodiments of the invention may be provided;
    Figure 2 depicts a block schematic view of a part of a lithographic apparatus according to an embodiment of the invention;
    Figure 3 depicts a highly schematic top view of an illumination field on a substrate, and
    Figure 4A - 4G depict graphs of substrate table and support actuation, based on which an embodiment of the invention will be explained.
    DETAILED DESCRIPTION [015] Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus comprises an illumination system IL, a support structure MT, a substrate table WT and a projection system PS.
    [016] The illumination system IL is configured to condition a radiation beam B. The support structure MT (e.g. a mask table) is constructed to support a patterning device MA (e.g. a mask) and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters. The substrate table WT (e.g. a wafer table) is constructed to hold a substrate W (e.g. a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate in accordance with certain parameters. 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 (e.g. comprising one or more dies) of the substrate W.
    [017] 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 radiation.
    [018] The term ‘radiation beam” used herein encompass 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.
    [019] 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 structure 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, which 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.
    [020] 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 such 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 will correspond to a particular functional layer in a device being created in the target portion C, such as an integrated circuit.
    [021] The patterning device MA 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 B in different directions. The tilted mirrors impart a pattern in a radiation beam B which is reflected by the mirror matrix. [022] The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including retractive, 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.
    [023] 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).
    [024] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables WT (and/or two or more mask tables). In such “multiple stage” machines the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure. In addition to one or more substrate tables WT, the lithographic apparatus may have a measurement stage that is arranged to be at a position beneath the projection system PS when the substrate table WT is away from that position. Instead of supporting a substrate W, the measurement stage may be provided with sensors to measure properties of the lithographic apparatus. For example, the projection system may project an image on a sensor on the measurement stage to determine an image quality.
    [025] 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 and the substrate. 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.
    [026] Referring to figure 1, the illumination system IL receives a radiation beam B from a radiation source SO. The radiation source SO and the lithographic apparatus may be separate entities, for example when the radiation source SO is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam B is passed from the radiation 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 radiation source SO may be an integral part of the lithographic apparatus, for example when the radiation source SO is a mercury lamp. The radiation source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.
    [027] The illumination system IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam B. Generally, al 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 illumination system can be adjusted. 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. [028] The radiation beam B is incident on the patterning device MT, 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 beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may be realized with the aid of a long-stroke module and a short-stroke module, which form part of the first positioner PM. The long-stroke module may provide coarse positioning of the short-stroke module over a large range of movement. The short-stroke module may provide fine positioning of the support structure MT relative to the long-stroke module over a small range of movement. 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 positioner PW. The long-stroke module may provide coarse positioning of the short-stroke module over a large range of movement. The short-stroke module may provide fine positioning of the substrate table WT relative to the long-stroke module over a small range of movement. 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. Patterning device MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks Pl, P2 as illustrated occupy dedicated target portions, they may be located in spaces between target portions C (these are known as scribe-lane alignment marks). 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.
    [029] The depicted apparatus could be used in at least one of the following modes:
    [030] In a first mode, the so-called step mode, the support structure MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam B is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT 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.
    [031] hi a second mode, the so-called scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparled to the radiation beam B is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure MT 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.
    [032] In a third mode, the support structure MT is kept essentially stationary holding a programmable patterning device, 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, such as a programmable mirror array of a type as referred to above.
    [033] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.
    [034] Figure 2 depicts a block schematic view of a part of a lithographic apparatus. The lithographic apparatus comprises the support structure MT, also referred to as “support MT”, the projection system PS, and the substrate table WT. The support holds a patterning device MA, such as a reticle. The substrate table WT holds a substrate W, such as a wafer. A radiation beam B provided by a source of radiation (not shown) projects the pattern of the patterning device MA onto a target portion C of the substrate W. The lithographic apparatus comprises a position control system PCS that is connected to the support MT and the substrate table WT in order to drive the support MT and the substrate table WT during the projecting of the pattern onto the target portion C of the substrate. The position control system PCS provides that the support MT and the substrate table WT move synchronously: for example when the lithographic apparatus is of the scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e. a single dynamic exposure). [035] The lithographic apparatus further comprises an imaging error correction system ICS. The imaging error correction system ICS comprises a memory MEM in which an imaging error correction map ECM is stored. The imaging error correction map ECM represents an imaging error in the projecting of the pattern onto the substrate W, as is to be corrected. The imaging error may originate from any source of modelled and/or measured error, such as an error from inline feedback / feedforward models, and an error from external loops such as any overlay and/or focus applications. The imaging error may form a profile along a surface of the substrate W, hence the imaging error correction map may represent the imaging error along a horizontal plane, i.e. a plane substantially parallel to the surface of the substrate W held by the substrate table WT. The imaging error correction system further comprises an imaging error correction processor ECP. By the imaging error correction processor ECP, an imaging error correction, i.e. an imaging error correction value is determined in order to take account of the error correction. The imaging error correction, i.e. the imaging error correction value, is derived from the imaging error correction map ECM. The imaging error correction processor ECP is configured to assign a first part FP of the imaging error correction to the substrate table WT and to assign a second part SP of the imaging error correction to the support MT. The imaging error correction processor ECP accordingly outputs a substrate table correction signal WTC on the basis of the first part FP of the imaging error correction and outputs a support correction signal MTC of the basis of the second part SP of the imaging error correction. The position control system PCS receives both the substrate table correction signal WTC and the support correction signal MTC. The position control system PCS drives the substrate table WT using the substrate table correction signal and drives the support MT using the support correction signal MTC. The position control system PCS may further drive the substrate table WT and the support MT based on any other setpoint, such as a sequence of setpoints that define a scanning motion. The position control system PCS may combine the substrate table correction signal WTC with any other input, such as setpoints and/or feedback signals, to drive the substrate table WT and may combine the support correction signal MTC with any other input, such as setpoints and/or feedback signals, to drive the support MT. The combining of the substrate table correction signal WTC respectively the combining of the support correction signal MTC with any other input may be an adding of the substrate table correction signal WTC respectively the support correction signal MTC to any other input.
    [036] The position control system PCS may be any suitable position control system PCS, such as a suitable programmed data processing device (such as a microprocessor or plural microprocessors), provided with suitable program instructions. The position control system PCS may further include drivers, such as electric motor drivers, that are controlled by the data processing device and which in turn drive actuators, such as motors, of the substrate table WT and the support MT. Similarly, the imaging error correction processor ECP may be formed by any suitable data processing system.
    [037] It is also imaginable that the imaging error correction processor ECP and the position control system PCS each employ software routines that are executed on a same dataprocessing architecture, such as a same data processing device. The imaging error correction map ECM may comprise plural values, each expressing a desired correction in terms of 6 Degrees Of Freedom (DOF), i.e. x, y, z, rx, ry, rz. at different locations on the substrate. For example, the imaging error correction map ECM may be formed by a matrix of 6 DOF corrections, the matrix of 6 DOF corrections extending along a plane substantially parallel to a surface of the substrate W, i.e. in the example described with reference to figure 1, the horizontal xy plane. [038] According to an aspect of the invention, the desired correction of the projection onto the substrate is divided over the substrate table WT and the support MT. As a result, comparted to the prior art situation where the desired correction is actuated by positioning the substrate table WT, excitation of the substrate table WT in terms of velocity, acceleration, jerk and snap may be held at a lower level. As a result, stress on a dynamic of the substrate table WT may be reduced. Furthermore, the correction capability of the substrate table WT is related to substrate table dynamic limitations, such as to substrate table servo errors, to substrate table encoders errors and to the internal deformations of the substrate table WT. Given these limitations, an improved correction may be achieved. Also, there may be less need to fall back to a sub-optimal definition of the set-points in case the limits are exceeded. Thus, actuation performance may be improved by taking advantage of a full dynamics of both support MT and substrate table WT at the same time. The set-points will be generated requesting less frequency in terms of velocity, acceleration, jerk, and/or snap of the substrate table WT and addressing to the support MT the remainder in a form of velocity, acceleration, jerk, and/or snap. Errors in actuation are related to the frequency of the stages movement, so the two stages moving less high frequent with respect to only one moving higher frequent, generates a total of less servo errors, encoder errors and internal chuck deformations.
    [039] It will be understood that, when assigning the first part FP to the substrate table WT and the second part SP to the support MT, an optical imaging transfer function of the projection system PS will be taken into account. For example, in case the projection system PS provides for an optical reduction by a optical imaging reduction factor, the corrections of the substrate table WT and the support MT will take into account the transfer function, e.g. the optical reduction factor. Likewise as the imaging error correction may contain to 6 degrees of freedom, the first part FP and the second part SP may each contain 6 degrees of freedom.
    [040] The first part FP and the second part SP may, taken together and taking account of the optical transfer function of the projection system PS, provide for an amount of correction as determined by the imaging error correction as derived from the imaging error correction map ECM, [041] It will be understood that the position control system PCS drives the substrate table WT and the support MT, thereby setting any suitable positioning parameter, including but not limited to the position, the velocity, the acceleration, the jerk and/or the snap. Velocity, acceleration jerk and/or snap may be obtained from a sequence of subsequent first parts FP respectively subsequent second parts SP.
    [042] Each entry in the imaging error correction map ECM may express a deviation of a position of the target portion C on the substrate W relative to a reference position on the substrate W. The reference position may be understood as a desired position, i.e. a position where the pattern is projected onto the substrate W which zero or minimal overlay and/or focus error. As explained above, the substrate W comprises a main surface that defines a plane. In the lithographic apparatus as described with reference to Figure 1, the substrate table WT holds the substrate W horizontally, hence the plane being a horizontal plane. The deviation may be understood as a deviation in a direction in the plane (which may result in an overlay error) and/or in a direction perpendicular to the plane (which may result in a focus error).
    [043] Figure 3 depicts a top view of a part of a substrate surface, namely a projection field PF in which the pattern of the patterning device MA is to be projected. Plural imaging error correction values are provided, each associated with a particular location of the surface of the substrate W in the projection field. The imaging error correction values form a 2 dimensional imaging error correction map ECM, extending along a surface of the substrate W. Accordingly, in an embodiment, the imaging error correction map ECM comprises a two dimensional correction matrix of correction values along the plane, i.e. the plane defined by the main surface of the substrate W. Each imaging error correction value may comprise a 3 dimensional error correction value comprising an x, y, and z correction value. Also, rotation correction values rx, ry, rz may be provided. The imaging error correction processor ECP may select from the matrix a most appropriate entry, i.e. an entry that is most closest to the intended projection location, or interpolate between neighboring entries in the matrix, so as to obtain a desired imaging error correction.
    [044] In some embodiments, such as when the lithographic apparatus operates in a scanning mode, a projection slit PSL may be formed on the target portion C of the substrate W. The projection slit PSL is schematically depicted in Figure 3, As the projection slit PSL moves in respect of the substrate W during a scanning movement, following portions of the pattern are irradiated, causing the pattern to be irradiated onto the substrate W as a sequence of consecutive (overlapping or non-overlapping) projection slits PSL. The projection slit PSL may extend over plural entries in the imaging error correction map ECM, i.e. plural entries in the matrix.
    [045] In an embodiment, the entries in the matrix that correspond to the projection slit PSL, i.e. the entries that represent location on the substrate W that are covered by the projection slit PSL, are averaged. The averaging may be a 6 degrees of freedom averaging. As a result, the imaging error correction processor ECP may provide that, when projecting the projection slit PSL onto the substrate W, a correction is provided that provides, in average, a most optimal projection at the respective part of the substrate. Hence, both the substrate table WT and the support MT are driven so as to accommodate the correction. The imaging error correction map ECM may likewise comprise different values as seen along a direction of scanning of the projection slit PSL on the substrate W, for example as a result of a height profile of the substrate W. As a result, the required correction may exhibit changes during the scanning movement. As a scanning speed may be high, the associated required corrections may change at a high speed: as the corrections are assigned in part to the substrate table WT and in part to the support MT, it will be understood that an excitation (velocity, acceleration, jerk and/or snap) may be kept lower compared to the situation where the correction would have been assigned to the substrate table WT.
    [046] In an embodiment, the imaging error correction processor ECP is further arranged to assign a third part TP of the imaging error correction to the projection system PS. Accordingly, the position control system PCS further drives the projection system PS. The imaging error correction processor ECP outputs a projection system correction signal to the position control system PCS on the basis of the third part TP of the imaging error correction. The projection system correction may be formed by a lens adjustment, the projection system correction signal may correspondingly represent a projection system lens adjustment to be provided to a lens actuator of the projection system PS.
    [047] The first part FP and the second part SP (and optionally the third part TP) may be assigned in any suitable way. For example, the first part FP and second part SP may be set at a ratio. For example in a scanning lithographic apparatus, the ratio may be set per field, thus allowing per field to balance the correction performed by the substrate table WT versus the correction performed by the support MT, thus allowing per field to keep excitation of both within limits. In a further embodiment, the ratio may be set per projection slit PSL, thus allowing adjustment of the ratio per projection slit PSL, so as to provide that the excitations of the substrate table WT and support MT are kept within predetermined limits, as the ratio may be adjusted at each projection slit PSL. For example, when the imaging error correction shows a slow rates of change (implying low velocity, acceleration, jerk and./or snap), a large part of may be assigned to the substrate table WT, while as rates of change increase, the correction may be assigned al an appropriate ration to the substrate table WT and the support MT, taking account of dynamics of the substrate table WT and the support MT.
    [048] In an embodiment, the memory comprised in the imaging error correction system ICS is configured to store a predefined maximum substrate table motion parameter expressing a maximum of at least one of velocity, acceleration, jerk and snap of the substrate table WT (e.g. in 6 degrees of freedom) and a predefined maximum support motion parameter expressing a maximum of at least one of velocity, acceleration, jerk and snap of the support MT (e.g. in 6 degrees of freedom), the imaging error correction processor ECP being configured to apportion the first part FP of the imaging error correction so as to drive the substrate table WT to remain below the predefined maximum substrate table motion parameter and to apportion the second part SP of the imaging error correction so as to drive the support MT to remain below the predefined maximum support motion parameter. When taking account of a predetermined limit of e.g. velocity, acceleration, jerk and/or snap, the imaging error correction processor ECP may derive a velocity, acceleration, jerk and/or snap for the substrate table WT from a sequence of first parts FP and may derive a velocity, acceleration, jerk and/or snap for the support MT from a sequence of second parts SP. In case an adjustment is to be performed, the ratio’s for one or more of the time instances of the sequence may be changed, so as to change the first part FP and second part SP at one or more time instances in the sequence so as to remain below the predefined maximum.
    [049] Alternatively, using the predefined maximum substrate table motion parameter, a part ofthe imaging error correction may be assigned to the substrate table WT to fit within the predefined maximum substrate table motion parameter, a remainder being assigned to the support MT.
    [050] Figure 4A - 4G depict an example of a scanning overlay dy-correction as may be applied in a scanning lithographic apparatus according to an embodiment of the invention, A possible effect of the invention will be illustrated based on Figures 4A - 4G. Although an overlay dy correction is show'n, it will be understood that a same principle allows to other corrections, such as an overlay dx correction or an overlay dz correction.
    [051] Figure 4A depicts an overlay dy correction, In each of the figures 4A - 4G, time (displacement) is depicted along a horizontal axis and an excitation, an amplitude respectively a correction, as applicable, is depicted along a vertical axis. Figure 4A depicts a required correction, i.e. depicts a sequence of imaging error corrections, i.e. imaging error correction values, as may apply to an y direction. The correction has three steep transitions, as may for example occur during the scanning movement. Figures 4B and 4C depict an example according to the prior art where the correction has been assigned entirely to the substrate table WT. Figures 4D, 4E, 4F and 4G depict an example according to the invention, where the correction is partly assigned to the substrate table WT and partly to the support.
    [052] The imaging error corrections are depicted in Figure 4A are represented by a set of imaging error correction values, each representing an imaging error correction at a given moment in time, and each represented in Figure 4A by a dot in the graph.
    [053] In Figure 4B, the substrate table correction signal WTC as calculated from the imaging error correction signal, is depicted in a form of a sequence of data points providing an overlay OL. A corresponding jerk J (i.e. a derivative of the acceleration) is depicted in figure 4C. As follows from Figures 4B and 4C, a substrate table setpoint/trajectory (in solid line) defined in order to nicely follow the corrections (the data points in the figures) is steep too and makes use of high values of jerk. Figure 4C further depicts horizontal dashed lines. The horizontal dashed lines define the range of the jerk of the substrate table WT, in which the jerk may provide for a reliable substrate table performance, e.g. in terms of substrate table servo errors, substrate table encoders and substrate table deformations. As follows from Figure 4C, the high values of jerk exceed the dashed lines, hence may be out of a safe working region of the substrate table WT.
    [054] Figures 4D - 4G illustrate an operation of an embodiment in accordance with the invention. Figures 4D and 4E depicts a driving of the support MT, while figures 4F and 4G depict a driving of the substrate table WT. In the present example, the correction set is divided between the support MT and the substrate table WT, whereby % is assigned to the support and G is assigned to the substrate table WT. Accordingly, Figure 4D depicts a support correction signal MTC, while Figure 4F depicts a substrate table correction signal WTC. Similarly, Figure 4 E depicts a jerk associated with a motion profile of the support MT according to the support correction signal MTC, while Figure 4G depicts a jerk associated with the motion profile of the substrate table WT according to the substrate table correction signal WTC. As follows from Figures 4D - 4G, the trajectories of the substrate table WT and the support MT follow the input correction points as depicted in Figure 4A. It will be understood that, due to the optical transfer function of the projection system (e.g. an optical reduction), an absolute value of the correction at the support MT may differ from a similar correction at the substrate table WT, e.g. by a factor determined by the optical reduction. Both for the support MT as well as for the substrate table WT, the requested jerks are at acceptable values. Comparing the jerk of the substrate table WT as depicted in Figure 4C to the jerk of the substrate table WT as depicted in Figure 4G, the jerk has been lowered in Figure 4G to approximately 0,25 times the jerk in Figure 4C to remain within a safe substrate table working region. Similarly, the overlay has lowered in Figure 4F to 0,25 OL. As follows from Figure 4E, the support MT shows relatively smooth transitions with a relatively low jerk at approx. 3 times the overlay OL of the substrate table WT of Figures 4B and 3 times the jerk J of the substrate table WT of Figure 4C (taking account of the optical transfer function of the projection system), which may result in an accurate and low-noise performance.
    [055] It will be understood that, although the example as explained above with reference to figures 4A - 4G relates to a correction in y direction only, the same concept of assigning a part of the error correction to the substrate table WT and the remainder of the error to the support MT, may be applied in any other direction (e.g. the x direction or the z direction) as well.
    [056] Assigning a part of the imaging error correction to the substrate table WT and a part of the imaging error correction to the support MT, may provide a further advantage. Given limitation of the substrate table
    WT and the support, as well as the limitations of the actuators, encoders, etc., associated with the substrate table WT and the support, higher frequency overlay and/or focus variations may be addressed using the same hardware.
    [057] 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 IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.
    [058] 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.
    [059] 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-read able 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.
    [060] 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 constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;
    a substrate table constructed to hold a substrate;
    a projection system configured to project the patterned radiation beam onto a target portion of the substrate; a position control system configured to drive the support and the substrate table during a projecting of the pattern of the patterning device onto the target portion of the substrate; and an imaging error correction system configured to correct an imaging error of the projecting, the imaging error correction system comprising a memory configured to store an imaging error correction map; and an imaging error correction processor being configured to
    - derive an imaging error correction at the target portion from the imaging error correction map;
    - assign a first part of the imaging error correction to the substrate table and a second pail of the imaging error correction to the support; and
    - output to the position control system a substrate table correction signal on the basis of the first part of the imaging error correction and a support correction signal on the basis of the second part of the imaging error correction;
    wherein the position control system is configured to drive the substrate table using the substrate table correction signal and to drive the support using the support correction signal.
    2. The lithographic apparatus according to clause 1, wherein the position control system is configured to drive the substrate table at a desired speed, a desired acceleration, a desired jerk and/or a desired snap using the substrate table correction signal.
    3. The lithographic apparatus according to clause 1 or 2, wherein the position control system is configured to drive the support at a desired speed, a desired acceleration, a desired jerk and/or a desired snap using the support correction signal.
    4. The lithographic apparatus according to one of the preceding clauses, wherein the imaging error correction map is based on a deviation of aposition of the target portion on the substrate relative to a reference position on the substrate.
    5. The lithographic apparatus according to clause 4, wherein the substrate comprises a main surface defining a plane, wherein the deviation is in a direction in the plane and/or in a direction perpendicular to the plane.
    6. The lithographic apparatus according to clause 5, wherein the imaging error correction map comprises a two dimensional correction matrix of correction values along the plane, each correction value comprising a 3 dimensional error correction value.
    7. The lithographic apparatus according to one of clauses 4-6, wherein during the projecting the patterned radiation beam forms a projection slit on the target portion, wherein the imaging error correction comprises an average of entries of the error correction map corresponding to the projection slit.
    8. The lithographic apparatus according to any of the preceding clauses, wherein the position control system further drives the projection system, and wherein the imaging error correction processor is further configured to attribute a third part of the imaging error correction to the projection system, and to output a projection system correction signal to the position control system on the basis of the third part of the imaging error correction.
    9. The lithographic apparatus according to any of the preceding clauses, wherein the imaging error processor is configured to set a ratio and to assign the first part and the second part at the set ratio
    10. The lithographic apparatus according to clause 9, wherein the ratio is set per field.
    11. The lithographic apparatus according to clause 9, wherein during the projecting the patterned radiation beam forms a projection slit on the target portion and wherein the ratio is set per projection slit.
    12. The lithographic apparatus according to any of the preceding clauses, wherein the memory comprised in the imaging error correction system is configured to store a predefined maximum substrate table motion parameter expressing a maximum of at least one of velocity, acceleration, jerk and snap of the substrate table and a predefined maximum support motion parameter expressing a maximum of at least one of velocity, acceleration, jerk and snap of the support, the imaging error correction processor being configured to apportion the first part of the imaging error correction so as to drive the substrate table to remain below the predefined maximum substrate table motion parameter and to apportion the second part of the imaging error correction so as to drive the support to remain below the predefined maximum support motion parameter.
    权利要求:
    Claims (3)
    [1]
    CONCLUSION
    A lithography device comprising: an exposure device adapted to provide a radiation beam; a carrier constructed for carrying one
    [2]
    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; 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
    [3]
    10 target area of the substrate in a focal plane of the projection device.
    1/5
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    EP17156683|2017-02-17|
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