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    • 专利摘要:
    The invention relates to a substrate support for supporting the substrate. The substrate support comprises the main body, a clamping device and the dither device. The main body comprises the support surface for supporting the substrate W. The clamping device is arranged to provide the clamping force to clamp the substrate Won the support surface. The dither device is configured to dither the clamping force. The dither device may be configured to dither the clamping force While the substrate W is being loaded onto the support surface.
    公开号:NL2018555A
    申请号:NL2018555
    申请日:2017-03-21
    公开日:2017-10-31
    发明作者:Onvlee Johannes；Franciscus Johannes De Groot Antonius；Ferdinand Vles David；Symens Wim
    申请人:Asml Netherlands Bv；
    IPC主号:
    专利说明:

    SUBSTRATE SUPPORT, LITHOGRAPHIC APPARATUS AND LOADING METHOD
    BACKGROUND
    Field of the Invention [01] The present invention relates to a substrate, support, a lithographic apparatus and & loading method. Description of the Related Art [02] 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 Saver of the IC. This pattern can be transferred onto a target portion (e.g. including pari of, one, or several dies) oh 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”~dsrection) while synchronously scanning the substrate parallel or ami-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.
    [83] in a known embodiment of a lithographic apparatus, a substrate is loaded on a support surface of a substrate support by a robot which holds the substrate at the bottom side of the substrate. To make loading of the substrate on a substantially horizontal support surface possible, three loading pins, also called e~ pins, are provided in the substrate table. The loading pins are movable between an extended position, in which the upper ends of the loading pins extend above the substrate table, and a retracted position, in which the upper ends of the loading pins are retracted in the substrate table.
    [94] During the loading of the substrate on the substrate table, the robot loads the substrate on the three loading pins in the extended position. Since the substrate will be received on the loading pins extending above the support surface, the robot can be withdrawn leaving the substrate on the loading pins.
    [95] Then, the loading pins can be moved to the retracted position to place the substrate on the support surface. The support surface is defined by upper ends of the multiple burls provided on, and extending from, a main body of the substrate table.
    [96] The shape of the substrate during the loading sequence is defined by, among other things, the gravity sag of the substrate when supported on the loading pins and the shape of the substrate itself, which may he warped, for example due to preceding processing steps. There is limited freedom to manipulate the fimd substrate shape, once it is loaded on the support surface.
    [07] As a result, duritsg the loads tig, different portions of the substrate will usually touch the burls of the support surface at different moments. In the time period between the substrate first touching one or mom burls and the substrate being completely supported by the burls, the shape of the substrate changes from an initial shape, caused by the substrate being supported by only three loading pins in gravity, to a final shape when supported by the multiple burls. Typically, during this time period, portions of the substrate, in particular its outer edge, should slide over the burls in order for the substrate to be arranged in an optimal flattened shape on the support surface.
    [08] Further, when the substrate is at least partially supported on the support surface, the substrate may be clamped on the support surface, for example by a vacuum clamp or an electrostatic damp. The vacuum force or electrostatic force will flatten a non-flat, warped substrate on the support surface and pull it down on the bur is. This pulling down of the substrate on the support surface also should result in sliding of the substrate over the burls of the support surface to enable the substrate to be substantially arranged in the optimal flattened shape on the support surface.
    [09] To facilitate sliding of the substrate over the burls, it would he beneficial to make the friction of the burls can be made as low possible. However, this would result in relatively easy sliding of the substrate over the substrate support during the projection of the patterned beams on dm substrate, in particular since the substrate support and the substrate supported thereon are subject to high accelerations aatd decelerations during the projection process. Therefore, it is undesirable that the friction of dse substrate support, in particular the burls is lowered to facilitate sliding of the substrate oxer the burls.
    [18] When loading of the substrate on the support surface, defined by the upper ends of the burls, does not result in sliding of the substrate over the burls, for example caused by a large friction between the substrate and the burls, there may be internal stresses/forces in the substrate when it is held by the support. These internal stresses are undesirable, since these internal stresses may ha ve an influence on the position and/or shape of the substrate during the projection a patterned beam on the substrate. Since ..this position and/or shape may be;different in different projections on the same substrate, the internal stresses may adversely affect the overlay performance of the lithographic apparatus.
    SUMMARY
    [11] It is desirable to provide a substrate support which provides improved positioning of a substrate on a substrate support in order to reduce oyerlay ertors caused bysubstrate load grid defpmation. Further, it is desirable to provide a substrate support that enables loading and/or unloading of a substrate ou the support surface which results in less wear of the suppOEt surface and/or the substrate, [12] According to am embodiment of the invention, there is provided a substrate support for support! ttg a substrate, comprising: a body; a clamping device; and a dither device; wherein the body comprises a support surface for support#mg the substrate, wherein the clamping device is arranged to provide a damping force to clamp the substrate on the support surface, wherein the dither device is configured to dither the clamping force, [13] According to an embodiment of the invention, there is provided a lithographic apparatus comprising: the substrate support of one of the preceding clauses; an illumination system configured to conditio» a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam With a pattern in its cross-section to form a patterned radiation beam; and a projection system configured to project the patterned radiation beatn onto a target portion of the lliliir [14] According to an embodiment of the invention, there is provided a loading method, comprising: transferring a substrate from a handling device onto a support surface, providing a clamping force to clamp the substrate on the support surface, dithering the damping force while partly supporting the substrate with the handling device and partly supporting the substrate with die support surface,
    BRIEF DESCRIPTION OF THE DRAWINGS
    [15] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schermde drawings m which corresponding reference symbols indicate corresponding pasts, and in which:
    Figure I depicts schematically a lithographic apparatus comprising a substrate stage according to an embodiment of the invention
    Figure 2 shows a first embodiment of a substrate support according to an embodiment of the invention;
    Figure 3 shows a second embodiment of a substrate support according to an embodiment of the invention;
    Figure 4 shows a third embodiment of a substrate support according to an embodiment of the invention;
    Figure 5 shows a fourth embodiment of a substrate support according to an embodiment of the invention; and
    Figure 6 shows a fifth embodiment of a substrate support according to an embodiment of the invention.
    Figure 7 shows a sixth embodiment of a substrate support according to an embodiment of the invention.
    DETAILED DESCRIPTION
    [16] Figure I schematically depicts a lithographic tspparatus according to one embodiment of the invention. The apparatus includes an illuminadon system (illuminator) !L configured to-condition a radiation beam B (e.g. UV radiation or any other suitable radiation), a 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 fltfr patterning device in accordance with certain parameters. The apparatus also includes a substrate support, (e.g. a wafer fable) WT or "substrate table" 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.
    [27] The illumination system 1L. 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.
    [18] The mask support structure MT supports, i.e. bears the weight of, the patterning device MA. it holds the patterning device MA 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 mask support structure can use mechanical, vacuum, electrostatic or other damping techniques; to hold the patterning device. The mask support structure may be a frame or a table, for example, which may he fixed dr movable as required. Thé mask support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system PS. Any use of the terms “reticle'’ or “mask” herein may he considered synonymous with the more general term “patterning device.” [19] The term “patterning device" used herein shouid 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 W. It should be noted that the pattern imparted to the radiation beam may not exactly corresponds 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.
    [20] 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 she minor matrix.
    [21] The term “projection system" used herein shouid 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. Arty use of the term "projection lens” herein may be considered as synonymous with the more general term “projection .......system”.
    [22] 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.
    [23] 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).
    [24] 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. In addition to one or more substrate supports, the lithographic apparatus may have a measurement stage pro vided with at least one sensor to measure a property of the substrate support or a property of the radiation beam exiting the projection system. The measurement stage may be arranged not to hold a substrate, [25] The lithographic apparatus may also be of a type wherein at least a portion of the substrate W may be covered by n liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system PS and the substrate W, An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the patterning device MA and the projection system PS, Immersion techniques 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 substmte, must. be submerged in liquid, hut rather only means that a liquid is located between the projection system and the substrate during exposure, [26] Referring to figure 1, the illuminator ÏL 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 exeimer laser. In such cases, the radiation souace SO is not ciinsidered to foms pait oF the lithographic apparatus and the radiation beam is passed from the radiation source SO to the illuminator ÏL with the aid of a beam delivery system BD including, for example, suitable directing mirrors and/or a beam expander. In other eases 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 !L, together with the beam deli very system BD if required, may be referred to as a radiation system, f27] The illuminator it may include an adjuster AD configured to adjust the angular intensity distribution o the radiation beam, Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and cr-inner, respectively) of the intensity distribution in a pupil plane of the illuminator IL can be adjusted. In addition, the illuminator EL may include various other components, such as an integrator IN tmd 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.
    [28] The radiation beam B is incident on the patterning device MA. which is held on the mask support structure MT, and is patterned by the patterning device MA, Having traversed the patterning device MA, the radiation beam B passes through tbe projection system PS, which focuses the beam onto a target portion C of the substrate W, With the aid of the second positioning device PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate support WT can he moved accurately, e.g, so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam S» e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the mask support structure MT may be realized with the aid of a long-stroke module (coarse positioning) arid a short-stroke module (fine positioning), which form part of the first positioning device PM. Similarly, movement of the substrate support WT 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 scantier) the mask 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 PK 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 MA, the mask alignment marks may be located between the dies.
    [29] The depicted apparatus could be used in at least one of the following modes: 1. In step snode, the mask support structure MT and the substrate support WT are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one iiine tie. a single static exposure). The substrate support 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 (units the size of the target portion C imaged in a single statie exposure, 2. In scan mode, the mask support structure MT and the substrate support WT or “substrate table” are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion € (i,e. a single dynamic exposure). The velocity and direction ofthe substrate support WT or ’’substrate table” relative to the mask support structure MT may be determined by the (de-)magnitlcation and image reversal characteristics of the projection system PS. In scats snode, the maximum size of the exposnre field limits the width (tit 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 mask support structure MT is kept essentiallystationary holding a programmable patterning device, and the substrate support WT or "substrate table" 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 devsee is updated.as.inquired after each movement of the substrate support WT or in between successive radiation pulses during & scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable .patterns ng device, such as a programmable mirror array of a type as referred to above.
    [30] Combinations and/or variations on the above described modes of use or entirely different modes of nse may also be employed. ...[31]... The lithographic apparatus comprises a substrate support WT. An upper part of the substrate support WT is shown in more detail in Figure 2 in cross-section.
    [32] The substrate support WT comprises a mas» body MB and a plurality of burls B extending front the: main body MS to a supporting height to define a support surface S. The support surface S is configured to support the substrate W on tbs substrate support WT. During manufacture of the substrate support WT, the burls B are machined and polished with high precision to «brain a fiat horizontal support surface S. The burls B limit the surface area of contact between the substrate support WT and the substrate W so as to prevent contamination on the substrate support WT or on the bottom of the substrate W to affect lire substrate W when the substrate W is supported on the support surface S, [33] Further, a vacuum space VS between the burls B is delimited by a sealing ring SR. This vacuum space VS may be used to create an underpressure to damp the substrate W ou the support surface S, in particular on the upper ends of the burls B, The vacuum space VS between the burls B and limited by the sealing ring SR is -hereto connected via vacuum conduite VC to a vacuum source VSO, [34] To load or unload the subt^rde''WWfil^'^'^b^rate support WT, the substrate support WT is provided with a set of loading pins LP configured to receive and support the substrate W, [35] It the example shown, the set of loading pins LP comprises three pins (only two shown) extending substantially vertically. Each loading pin LP is movable between a retracted position and an extended position, In the retracted position, an upper end of the loading pin LP is arranged below the support surface S. In the extended position, the upper end of the loading pin LP extends above the support surface S. In Figure 2 the loading pins LP are shown in the extended position and the substrate W is supported by the loading pins LP, The substrate W is for instance loaded on the loading pins LP by a. loading device, such as a loading robot;...... .
    [36] When loading the substrate W on the support surface S. the loading pins LF are lowered into the mans body MB of the substrate support WT so that the substrate W comes to rest on the burls B, The substrate W is usually not perfectly flat, For example, preceding process steps may result In the substrate W being warped. Furthermore, due to gravity, the. shape of the substrate W may be influenced when the substrate W is supported ou the loading pins LP.
    [37] As a result of the non-flatness of the substrate W, the substrate W will not be flat when the substrate W is lowered onto the support surface S and the substrate W may have to slide over the burls B in order to adapt a flattened shape on the support surface 3. In order to clamp the substrate W on the support surface S. the vacuum, clamp system will exert a. clamping force on the substrate W by creating an underpressure in the vacuum space VS. This damping may result in further flattening, and as a consequence sliding, of Use substrate W on the support surface S. The vacuum damp system may comprise the vacuum space VS, the sealing ring SR and the vacuum conduit VC.
    [38] The vacuum clamp system is art example of a clamping device arranged to provide the clamping force to damp the substrate W on the support surface S, The dither device DD is configured to dither the damping force, The damping force may comprise a vacuum force provided by the vacuum clamp system. The dither device DD may be arranged to dither the vacuum force, [39] To avoid internal stresses in the substrate W supported and clamped on the support surface S, and to improve overlay performance, it is desirable that the friction between the top ends of the burls B and the substrate W is low such that the substrate W oast easily slide over burls B when the substrate W is flattened during loading, and in particular damping of the substrate W on the support surface S.
    [4Ö] At the same time it is desirable that during the actual lithographic process, i.e. during projecting a patterned beam of radiation onto a target portion C of the substrate W. there is high friction between the top ends of the burls B and the substrate W to avoid that the substrate W shifts with respect to the support surface S during accelerations; and/or decelerations of the substrate support WT, [41] Thus, during loading a low friction between the burls B and the substrate W is desirable, while during the actual lithographic process a high friction between the burls B and the substrate W is desirable, [42] In the substrate support WT shown in Figure 2, the friction of the burls B is selected such that the friction obtained is sufficient to ensure that the substrate W is held m a fixed post non with respect to the substrate W during the actual lithographic process, in particular during accelerations and/or decelerations of the substrate support WT.
    [43] Further, a dither device DD is provided configured to vibrate the. substrate W during loading and/or unloading of the substrate W on the support surface S in order to reduce a friction between the support surface S and the substrate W. This reduced friction facilitates sliding of the substrate W over the burls B during this loading and/or unloading.
    [44] The dither device DD of the embodiment of Figure 2 is'configured'to apply pressure waves on the substrate W to vibrate the substrate W. These pressure waves are created by a speaker system SSY arranged in the vacuum conduits VC of the vacuum damping system, [45] The speaker system SSY is mounted in a chamber CH and connected to an amplifier AM that provides a signal to the speaker system SSY to emit pressure waves into the vacuum corsduits VC. The pressure waves will propagate to the vacuum space VS where the pressure waves will have a vibrating effect on the substrate W, At least some gas, such as aity is in die vacuum conduits VC to propagate the pressure waves.
    [46] This vibrating effect will reduce the friction between the burls B and the substrate W. As a result, the substrate W will more easily slide over the burls B and internal stresses in the substrate Yv are avoided or at least substantially reduced and the substrate W will more easily move to the desired flammed position, As a result, the overlay performance of the lithographic process east be improved, i.e. less substrate deformation during loading of the substrate W on the substrate support WT results in better overlay performance.
    [47 j Ii Is remarked that reducing the friction between the burls B and the substrate W has a further advantageous effect In that wear of the buris B and/or substrate W due to -he sliding of the substrate W over the buris B can be substantially reduced, [48] Further, it is remarked that since the vacuum conduits VC are used to create an underpressure in the vacuum space VS to exert a clamping force, l.e.. a vacuum force, on the substrate W, the lower pressure in the vacuum conduits VC and the vacuum space VS will negatively influence the propagation of the pressure waves. It may be desirable to provide an air injection system AIN that supplies air into the vacuum clamping system, in particular into the chamber CH in front of the speaker system SSY to 'improve the propagation of the pressure waves through the vacuum conduits VC end the vacuum space 111 [49] Further, the speaker system SSY is preferably arranged close to the vacuum space VS so that the pressure waves quickly reach the vacuum space VS. The speaker system SSY may comprise multiple speakers arranged at differentilocations to effectively vibrate the substrate W supported on the support surface S.
    [50] The pressure waves emitted by the speaker system SSY may have·'any suitable excitation frequency, for example between 1 kHz and I MHe.
    [51] The excitation frequency and an excitation amplitude of the pressure waves are selected to effectively reduce the friction between the buris B and the substrate W. It should te avoided that the substrate W is completely released bom the support surface W due to tire vibrations caused by the pressure waves. Also, the excitation frequency and excitation amplitude of the pressure waves should selected such that the substrate W, as a whole, is not substantially displaced over the support surface S to an undesirable position for the lithographic process.
    [52] Preferably, the excitation frequency and excitation amplitude of the pressure waves are selected jireh that she substrate W will remain in contact with all respective buris 8, but it may also he possible that the substrate W is temporarily icieased from a few of the burls B due to the vibrations.
    [53] The vacuum conduit VC is configured to convey a flow from the support surface S to the vacuum source VSO. The flow may be a flow of ambient air or any other type of gas that surrounds the support surface S. The dither device DO may be arranged to altera cross-section of the vacuum conduit VC. By altering the cross-section, the flow is disturbed. The disturbance of the flow causes a change in pressure in the vacuum conduit VC. As a result, the pressure in the vacuum space VS changes. The changed pressure in the vacuum space VS causes a change in the vacuum force. So by altering the cross-section, the dither device DD can dither the vacuum force. The dither device DD may comprise a valve connected to the vacuum conduit VC, The valve rosy have a piezo element to control a cross-section of the valve, [54] it is remarked ihar a position measurement system PMS may be provided to measure a position of the substrate W or. the support surface S, Such position measurement system PMS, which for example may be capable of determining the position of the substrate W with respect to the support surface S by reading markers on the substrate W, may be used ίο check that the substrate W, as a whole, is not substantially displaced over the support surface S to an undesirable position for the lithographic process.
    [55] To optimally use the friction reducing effect of vibration of the substrate W during loading of the substrate W on the support surface 5, the dither device DD may be configured to vibrate the substrate W during a period in which the vacuum damping system is configured to increase the damping force from zero to a maximum damping force. The dither device DD may also be effectively used in the period that the substrate W is placed on the support surface S by lowering of the loading pins LP to the retracted position. This period may, in practice; at least partially overlap with the period in which the damping force is increased from zero to the maximum damping force, [56] When a substrate W is unloaded from the substrate support WT, the dither device DD may also effectively he used to reduce friction between the substrate W and the burls B, For example, during a period in which the vacuum clamping system is configured to decrease the damping force from the maximum damping force to zero, the dither device DD may vibrate the substrate W to reduce the friction between the burls B and the substrate W. The dither device DD may also effectively be used when the substrate W is lifted by the loading pins LP from the support surface S. During unloading reducing the friction between the burls B and the substrate W may in particular be useful in order to reduce the wear of the burls B and/or the substrate W, [57] It is remarked that in alternative embodiments of the dither device DD having a speaker system, the speaker system may be arranged at any other suitable location, For example, the speaker system may be arranged above the substrate W such that the pressure waves are emitted onto the top side of the substrate in order to vibtate the substrate W, [58] The above described advantages of a reduced friction between a support surface S, in particular burls B and a substrate W by vibrating the support surface S and/or the substrate W may also be obtained by alternative embodiments of a dither device DD. Some, of these alternative embodiments will now be described.
    [59] Figure 3 shows a second embodiment of a dither device DD according to the invention. The dither device DD of this second embodiment is configured to vibrate die body of the substrate support WT, at kast partially, in order to obtain a friction.reducing effect on the friction between the burls B and the substrate W.
    [60] The dither device DD of the embodiment of Figure 3 comprises multiple piezo elements PE that are configured to exert a vibrating force on the main body MB of tiie substrate support WT in a direction substantially parallel to the support surface S, as indicated by double headed arrows in Figure 3, The results tig vibration of the main body MB will have the desired friction reducing effect, on the contacts between the burls B and the substrate W. The piezo elements PE ate drivers by the amplifier AM in a suitable excitation frequency arid with a suitable excitation amplitude to effectively reduce the friction between the burls B and the substrate W, [61] Figure 4 shows a third embodiment, in which, similar to the second embodiment of Figure 3, piezo elements PE arc used in order to at least partially vibrate the main body MB of the substrate support WT in order to vibrate the burls B iwith respect to the substrate W. l<aj The main difference with the embodiment of Figure 3 is that in the embodiment of Figure 4 the direction of excitation of the main body MB is in a direction substantially perpendicular to the support surface S as indicated by double headed arrows in Figure 4. Vibrations of the main body MB in a direction substantially perpendicular to the support surface S will also Stave a friction reducing effect on the contacts between the substrate W and the burls B.
    [63] The amplifier AM is provided to drive the piezo dements PE, in particular during loading and unloading of the substrate W, with a suitable excitation frequency and excitation amplitude to obtain the desired friction reducing effect between the substrate W and the burls B. (64] It is remarked that in the embodiments of Figure 3 and 4 any other type of actuator that is suitable o vjbrale the main body MB, at least partially, with a suitable frequency and amplitude may also he applied. In particular, actuators configured to move the substrate support WT with respect to a reference object may be used to vibrate!the main body MB at least partially to obtain a friction reducing effect. These actuators to move the substrate support WT may for instance be a long-stroke actuator of a long-stroke module or a short-stroke aeiuator of a short-stroke module, as described with resect to Figure 1, or any other actuator configured: to move the. substrate support.
    [65| Furthermore, it is remarked that actuators, for example piezo actuators may be used to exert vibrating forces on the main body MB in both a direction parallel to the support surface S and a direction perpendicular to the support surface S may be used or any other suitable direction, or combination of directions, [66] Figure 5 shows a fourth embodiment of a dither device DD according to the invention, In dus embodiment, instead of a vacuum clamping system, an electrostatic damp ESC is provided to clamp the substrate W with an electrostatic clamping force oa the support surface S. It is remarked that in this embodiment, the sealing ringiSR is not. present, as no vacuum space VS has to be created for a vacuum !IIi|i|ll|dil!l!: [67] The electrostatic clamp ESC is driven by an electrostatic damping signal provided by the signal generator SGE, In order to obtain the friction reducing effect, the signal generator SGE is configured to, during loading and/or unloading of a substrate W on/from the substrate support WT, superimpose a varying vibration signa! on the normal electrostatic damping signal io apply a varying damping force on the substrate W, The dither device DD may comprise the signal generator SGE, so the dither device DD may be arranged to generate the varying vibration signal, The electrostatic clamp ESC provides the electrostatic force based on the varying vibration signal.
    [68} This varying clamping force not only damps the substrate W on the support surface S, but also creates a vibration of the substrate W with respect to the burls B on which the substrate W is clamped in order to obtain the desired friction reducing effect during loading and/or unloading of a substrate W.
    [69] Figure 6 shows a fifth embodiment of a dither device DD according to the invention. In the embodiment of Figure 6, the dither device DD comprises a speaker system SSY which is used to create pressure waves. The speaker system SSY is arranged to create pressure waves in cooling fluid that runs through a cooling system circuit CSC in the main body MB of the substrate support WT. In an embodiment, instead of a cooling system'circuit CSC, a thermal conditioning system is used. Tire thermal conditioning system may be arranged to condition a temperature of the substrate support WT by cooling, heating or both cooling and heating. The thermal conditioning system may have a circuit containing a fluid. The speaker system SSY may be arranged to create pressure waves in the fluid in the circuit, [70] The dither device DD comprises an amplifier AM to drive the speaker system SSY with a desired excitation frequency and excitation amplitude. The pressure waves are propagated in the cooling fluid and used to vibrate the main body MB such that at least the burls B are also vibrated as a result of these pressure waves. This vibration of the hurls B creates a friction reducing effect as described above, [71 ] In the embodiments described above, the loading pins LP are arranged on the main body MB. Alternatively, the main body MB is provided with throngh holes. The loading pins LP may extend through the through holes. The loading pins LP may be arranged on another body than the main body.
    [72] In an embodiment, the substrate support WT is for supporting the substrate W. The substrate support WT comprises the main body MB, a clamping device and the dither device DD. The main body MB comprises the support, surface S for supporting the substrate W. The clamping device is arranged to provide the clamping force to clamp the substrate W on the support surface S. The dither device DD is configured to dither the clamping force. The dither device DD may be configured to dither the damping force ’while the substrate W is being loaded onto the support surface S.
    [73] The damping device may comprise the vacuum damp system. The clamping force may comprise the vacuum force provided by the vacuum damp system. Tlte dither device DD is arranged to dither the vacuum fores. The vacuum clamp may comprise the vacuum conduit VC for conveying a flow from the support surface S to the vacuum source VSO. The dither device DD may be arranged to alter a cross» section of the vacuum conduit VC. The dither device DD may comprise a piezo element, [74] The clamping device may comprise the electrostatic clamp ESC. The clamping force may comprise the electrostatic force provided by the electrostatic damp ESC, The dither device DD may he arranged to dither the electrostatic force. The dither device DD may be arranged to generate a signal, such, as the varying Vibration signal. The electrostatic clamp ESC may provide the electrostatic force based on the signal.
    [75] The dither device DD may be configured to dither the clamping force during a period in which the damping force increases from zero to a maximum damping force. The dither device DD may lx: configured to dither the clamping force during a period in which the clamping force decreases front a maximum clamping force to zero. The support surface S may be formed by a plurality of burls arranged on the main body MB. The dither device DD may be configured to dither the damping force at an excitation frequency between J kHz and 1 MHz.
    [76] in an embodiment, there is provided a lithographic apparatus comprising the substrate support WT of one of the embodiments described above, the 111 urnintsi i on system !L, the support MT and the projection system PS, The illumination system ÏL is configured to condition the radiation beam. The support MT is constructed to support the patterning device MA, The patterning device MA is capable of imparting the radiation beam with a pattern in its eross^section to form a patterned radiation beam. The projection system PS is configured to project the patterned radiation beam onto a target portion C of the substrate W.
    [77] The lithographic apparatus tray comprise a handing device. The handling device is arranged for loading the substrate W onto the support surface S and/or arranged for unloading the substrate W from the support surface S. Toe dither device DD is arranged to dither the clamping force while the substrate W is partly supported by the handling device and partly supported by the support surface S. The handling device may comprise the loading pins UP. The handling device may comprise the loading device, c,g,, the loading robot. The handling device may handle the substrate W by contacting the bottom side of die substrate W or the top side of the substrate W, For example, the handling device comprises a Bernoulli! gripper to support the substrate W from the top side of the substrate W, The Bernoulli gripper may provide a vacuum force to damp the substrate W onto the handling device. The Bernoulli! gripper may provide a gas film between the handling device and the substrate W to prevent physical contact between the handling device and the substrate W.
    [78] In an embodiment there is provided a loading method, comprising the steps of: i) transferring the substrate W from the handling device onto the support surface 5; ii) providing the damping force to clamp the substrate W on the support surfaces; lit) dithering the clamping force while partly supporting the substrate VV with the handling device and partly supporting the substrate W with the support surface S. The loading method may further comprise dithering the damping force while the clamping force increases from zero to a maximum clamping force.
    [79] A further embodiment is shown in Figure 7. Figure 7 shows a part of a cross-section of the main body MB. The main body MB comprises a first part PI, a second part P2 and a third part P3. The burls 8 are arranged on the top surface of the third part P3. The first part PI and the second part P2 are connected to each other via contact surface CSU. A piezolayer PZL Is arranged between the second part P2 and the third part P3. A bottom surface BSU of the piezolayer PZL is connected to the second part P2. A top surface TSU of the piezolayer PZL is connected to the third part P3.
    [80] The piezolayer PZL has piezo electric materia! that deforms when an electrical charge is applied to the piezo electric material. The piezolayer PZL may be arranged to deform along the z-axis when the electrical charge is applied. For example, the thickness of the piezolayer PZL may be altered by applying different, electrical charges. The piezolayer· PZL may be arranged to deform along x-axis, in this case, the piezolayer PZL forms a shear-piezo, In which the iopsurfaeeTSU moves relative to the bottom surface BSU along the x-direction. The piezolayer PZL may form a shear-piezo in which the iopsurfaeeTSU moves relative to the bottom surface BSU along a direction in the xy-plane.
    [81] When an electrical charge is applied to the piezolayer PZL. the topsurface TSU is moved relative to the bottom surface BSU, As a result, the third part P3 is moved relative to the second part P2. A movement of the third part P3 causes the hurls B to move.
    [82] An electrical charge may be applied that varies overtime to cause the burls B to vibrate. For example, the electrical charge may be applied as a sine-shaped function over time . The electrical charge may be applied as a series of step-functions in which the electrical charge varies over a plurality of values. The piezolayer PZL may move the burls B at a high frequency, for example with a frequency of 500 Hz - 5000 Hz, The amplitude of the movement snay be small, for example irvthe range of 10 nm -100 am. The movement may be referred to as dither. Tire piezolayer PZL may be considered a dither device DD. The dither may be along the z-direction, along the xy-plane or in a combination thereof. 1*31 When a substrate W is being loaded on the burls B, the piezolayer PZL may dither the burls B. When the substrate W contacts the burls B, the dither causes the friction between the substrate W and the burls B to reduced compared to a friction without dither, As a result, the substrate W may slide more easily over the burls B and the substrate W may be loaded with less internal stress. Dither may be applied after loading the substrate W onto the burls B, when the substrate W is fully supported by the burls 8, Dither may be applied during unload of the substrate W from the burls B. The dither may reduce the friction between the substrate :W and the burls B during unload which may help to reduce wear of the burls B.
    [84] The piezolayer PZL may be actuated by Use electrical charge to cause the burls B to vibrate as a standing wave. As the burls B vibrate as a standing wave, internal stress of the substrate W may be removed or reduced. Alternatively, the piezolayer PZL. may be actuated by the electrical charge to cause the burls B to vibrate as a travelling wave, [HSj The piezolayer PZL may fens', art integrated part of the main body MB. The piezolayer PZL may be ""connected to the second part PZ and the third past P3 via bonding or via deposition or a combination thereof. Bonding may take place in a Ore process. The burls B may be created and polished after the ptezolayer PZL is connected to the second part P2 and the third part Pi to acquire a desired flatness of the burls B.
    [86] The piezolayer PZL is provided with electrodes to apply the electrical charge to the piezo electric material. The layout of the electrodes depends on the desired deformation of the piezolayer PZL. A pattern of the electrodes may be made using a lithographic process, Further, the piezolayer PZL may be applied as a continuous layer. Alternative, the piezolayer PZL may be applied as a layer with a plurality of portions. For example, the portions are arranged as concentric rings or as wedges. The portions may each be provided with a dedicated electrical charge, or the portions may be provided with a common electrical charge. The piezolayer PZL may have openings, for example to provide space for the loading pins LP.
    [87] In Figure 7, the piezolayer PZL is provided between the second part P2 and the third part P3, Alternatively, the piezolayer PZL is provide at the contact surface CSU, between the first part Pi and the second pari P2. Ahernativeley, the piezolayer PZL is provided in or below the first part PI, In an embodiment, multiple piezolayers PZL are provided.
    [88] 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, sudvasthe 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, auv use. of the terms “wafer’ or “die” hernia may be considered as synonymous with Use 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 die exposed tests!), 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 titan once, for example in order to create a multi-layer T€, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers, [89] 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, 5s not limited id optical lithography, ir, imprint lithography a topography io a patterning device defines the patters 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.
    [90] While- specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described.
    The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the ari 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 substrate support for supporting a substrate, comprising: |:::|ody| a clumping device: and a dither device; wherein the body comprises a support surface for supporting the substrate, wherein the clamping device Is arranged to provide a clamping force to damp the substrate on the support surface, wherein the dither device is configured to dither the damping fores. 2, The substrate support of clause 1, wherein the dither device is configured to dither the clamping force while the substrate is being loaded onto the support surface. 3, The substrate support of clause 1 or 2, wherein the damping device comprises a vacuum damp system, wherein the damping force comprises a vacuum force provided by the vacuum damp system, wherein the dither device is arranged to dither the vacuum force. 4, The substrate· support of clause 3, wherein the vacuum clamp comprises a vacuum conduit for conveying a flow front the support surface to a vacuum source, wherein the dither device is arranged to alter a cross-section of the vacuum conduit. 5, The substrate support of clause 4, wherein the dither' device comprises a piezo element 6, The substrate support of clause 1 or 2, wherein the clamping device comprises an electrostatic clamp, wherein the damping force comprises an electrostatic clamping force provided by the electrostatic clamp, wherein the dither device is arranged to dither the electrostatic damping force. 7, The substrate support of clause 6, wherein the dither device is arranged to generate a signal, wherein the electrostatic clamp provides the electrostatic damping force based on the signal. 8, The substrate support of one of the preceding clauses, wherein the dither device is configured to dither the clamping force during a period in which the clamping force increases from zero to a maximum clamping force, 9, The substrate support of one of the preceding clauses, wherein the dither device is configured to dither the damping force during a period in which the clamping force decreases from a maximum damping force to zero. 10, The substrate support of one of the preceding clauses, wherein the support surface is formed by a plurality of burls arranged on tire body. 11, The'Substrate support of one of the preceding clauses, wherein the.dither device is configured to dither the clamping force at an excitation frequency between I kHz and 1 MHz. 12, A lithographic apparatus comprising: the substrate support of one of the preceding clauses; an illumination system configured to condition a radiation beam; a support constructed io 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; and a projection system configured to project the patterned radiation beam onto a larger portion of the substrate, 13, The lithographic apparatus of clause 12, comprising a handing device, wherein the handling device is arranged for loading the substrate onto the support surface and/or arranged for unloading the substrate from the support surface, wherein the dither device is arranged to dither the damping force while the substrate is partly supported by the handling device and partly supported by the support surface. 14. A loading method, comprising; transferring a substrate from a handling device onto a support surface, providing a clamping force to damp the substrate on the support surface, dithering the damping force while partly supporting the substrate with the handling device and partly supporting the substrate with the support surface, 15, The loading method of clause 14, comprising: - dithering the damping force while the clamping force increases from aero to a maximum damping force.
    权利要求:
    Claims (1)
    [1]
    A lithography device comprising: an illumination 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.
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    法律状态:
    优先权:
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    EP16166176|2016-04-20|
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