Electrostatic clamp

Abstract

The present disclosure relates to an electrostatic clamp for a lithographic apparatus, the electrostatic clamp comprising: a clamp body; a substantially planar electrode arrangement comprising a plurality of electrodes arranged into a plurality of segments and one or more connection layers configured to allow individual addressing of the plurality of electrodes; a plurality of burls protruding from the clamp body; and one or more demultiplexers in electrical communication with the one or more connection layers, wherein the one or more demultiplexers are configured to sequentially address a selection of the plurality of electrodes by a voltage source, thereby providing a voltage to the selected electrodes.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to European application 24167835.8, filed on 29 March 2024, and that European application is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to electrostatic clamps. Electrostatic clamps are suitable for use in photolithography equipment. The invention also relates to methods of using such electrostatic clamps, and photolithography equipment including such electrostatic clamps. Background Technology

[0004] A photolithography apparatus is a machine configured to apply a desired pattern onto a substrate. Photolithography apparatus can be used, for example, to manufacture integrated circuits (ICs). It can project a pattern from a patterning apparatus (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0005] To project a pattern onto a substrate, a photolithography apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Compared to photolithography apparatus that uses radiation with a wavelength of, for example, 193 nm, photolithography apparatus that uses extreme ultraviolet (EUV) radiation in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0006] Photolithography equipment may suffer from one or more optical aberrations (e.g., coma or astigmatism). Furthermore, the provided substrate may not be perfectly flat. Both optical aberrations and uneven substrates can lead to reduced pattern projection quality because they place the substrate's projection surface outside the focal plane.

[0007] It may be desirable to provide a device that eliminates or mitigates one or more problems associated with the prior art. Summary of the Invention

[0008] According to a first aspect, an electrostatic clamp for a photolithography apparatus is provided, the electrostatic clamp comprising: a clamp body; a plurality of protrusions projecting from the clamp body and defining a support surface for supporting an object on the electrostatic clamp using respective top surfaces of the plurality of protrusions; a generally planar electrode arrangement comprising at least two independently addressable electrodes disposed between an insulator and spaced apart by an insulating layer in a direction perpendicular to the plane of the electrode arrangement, wherein, when viewed in a direction perpendicular to the plane of the electrode arrangement, a first electrode of the at least two electrodes at most partially overlaps with a second electrode of the at least two electrodes, wherein the first electrode is closer to the support surface than the second electrode; wherein the at least two independently addressable electrodes are configured to generate an attractive electrostatic field for securing an object to the plurality of protrusions when a voltage is applied to the at least two independently addressable electrodes during use. Advantageously, providing electrodes spaced apart in a direction perpendicular to the plane of the electrode arrangement allows for providing a plurality of independently addressable electrodes adjacent to each other.

[0009] The object may be a substrate or a pattern forming apparatus.

[0010] In one embodiment, the electrostatic clamp may further include a voltage source configured to apply the voltage to the at least two independently addressable electrodes to generate an attractive electrostatic field for securing an object to the plurality of protrusions. The voltage source may be configured to apply a voltage difference in the range of 100V to 4000V, preferably in the range of 500V to 1500V, between any of the at least two independently addressable electrodes.

[0011] In one embodiment, the thickness of the insulating layer is 2 μm to 30 μm, preferably 4 μm to 15 μm.

[0012] In one embodiment, the spacing between any of the at least two independently addressable electrodes in the direction perpendicular to the plane of the electrode sheet is at least 2 μm. In another embodiment, the spacing between any of the at least two independently addressable electrodes in the direction perpendicular to the plane of the electrode sheet can be up to 30 μm.

[0013] In one embodiment, the at least two independently addressable electrodes are configured as a periodic array of elongated electrode plates. For example, the total number of independently addressable electrodes may be four.

[0014] In one embodiment, the at least two independently addressable electrodes are positioned such that no gap is left between the at least two electrodes when viewed in a direction perpendicular to the plane in which the electrodes are arranged; preferably, the overlap between adjacent edges of the at least two electrodes is between 0 and 200 μm when viewed in a direction perpendicular to the plane in which the electrodes are arranged. Advantageously, the absence of gaps between the electrodes maximizes the area or region of the electrodes, and thereby maximizes the clamping force.

[0015] In one embodiment, the at least two independently addressable electrodes are positioned so that they do not overlap when viewed in a direction perpendicular to the plane in which the electrodes are arranged; preferably, when viewed in a direction normal to the plane in which the electrodes are arranged, there is a gap between 0 and 100 μm between adjacent edges of the at least two electrodes.

[0016] In one embodiment, the at least two independently addressable electrodes are configured such that the length of the elongated electrode plate is aligned with the scanning direction of the photolithography apparatus.

[0017] In one embodiment, the at least two independently addressable electrode plates are configured such that the pitch of the at least two independently addressable electrode plates is in the range of 1 mm to 15 mm, preferably in the range of 2 mm to 10 mm. In another embodiment, the at least two independently addressable electrode plates are configured such that the pitch of the at least two independently addressable electrode plates approximately corresponds to an integer factor of the maximum field width of the photolithography apparatus.

[0018] In one embodiment, the generally planar electrode arrangement includes electrode plates covering a generally planar surface of the clamp body, preferably wherein the plurality of protrusions project from the clamp body through the electrode plates. In an alternative embodiment, the generally planar electrode arrangement may be positioned within the clamp body, meaning it is embedded within the clamp body.

[0019] In one embodiment, the insulating layer comprises benzocyclobutane (BCB). In another embodiment, the insulating layer may comprise glass.

[0020] According to a second aspect, a method is provided for using an electrostatic fixture according to the first aspect in a photolithography apparatus, wherein the method includes: placing an object onto the electrostatic fixture; and applying different voltages of the same polarity to the at least two electrodes. The different voltages induce deformation in the object.

[0021] In embodiments where the object is a substrate, the deformation induced in the substrate is configured to be aligned perpendicular to the scanning direction of the lithography apparatus.

[0022] In one embodiment, the voltage difference between any of the at least two independently addressable electrodes is in the range of 100V to 4000V, preferably in the range of 500V to 1500V.

[0023] According to a third aspect, a photolithography apparatus is provided, the photolithography apparatus comprising: an irradiation system configured to modulate a radiation beam; a support structure configured to support a patterning apparatus capable of patterning the radiation beam on a cross-section of the radiation beam to form a patterned radiation beam; a projection system configured to project the patterned radiation beam onto a substrate; and a substrate stage configured to hold the substrate, the substrate stage comprising: an electrostatic clamp according to a first aspect; and a voltage source configured to apply a voltage to the at least two independently addressable electrodes for the purpose of generating an attractive electrostatic field for securing an object to the plurality of protrusions.

[0024] The third aspect's device and the method according to the second aspect have effects similar to those of the electrostatic clamp of the first aspect. This means that various aspects and features of the invention set forth above or below can be combined with various other aspects and features of the invention, as will be readily apparent to those skilled in the art.

[0025] According to a fourth aspect, an electrostatic chuck for a photolithography apparatus is provided, the electrostatic chuck comprising: a chuck body; a generally planar electrode arrangement including a plurality of electrodes and one or more connection layers, the plurality of electrodes being arranged in multiple segments, the one or more connection layers being configured to allow individual addressing of the plurality of electrodes; a plurality of protrusions projecting from the chuck body; and one or more demultiplexers electrically connected to the one or more connection layers, wherein the one or more demultiplexers are configured to sequentially address selection of the plurality of electrodes by a voltage source, thereby providing a voltage to the selected electrode. Providing a plurality of electrodes arranged in multiple segments allows for a wide range of deformations to be applied to an object placed on the chuck. Furthermore, providing demultiplexers reduces the complexity of external connections. The plurality of protrusions define support surfaces for supporting an object on the electrostatic chuck using their respective top surfaces. The object may be a substrate or a patterning apparatus.

[0026] In one embodiment, the generally planar electrode arrangement includes electrode plates covering a generally planar surface of the clamp body, wherein the plurality of protrusions project from the clamp body through the electrode plates. In an alternative embodiment, the generally planar electrode arrangement may be positioned within the clamp body, meaning it is embedded within the clamp body.

[0027] In one embodiment, the length of the protuberance is in the range of 250 μm to 5000 μm.

[0028] In one embodiment, the one or more demultiplexers are configured to address electrodes during varying time periods, thereby changing the voltage of the electrodes.

[0029] In one embodiment, each demultiplexer is configured to electrically disconnect the electrode from the voltage source after the electrode has been addressed by the demultiplexer, and the electrode is configured to maintain the voltage applied by the voltage source.

[0030] In one embodiment, the electrostatic clamp includes a corresponding number of electrodes and protrusions.

[0031] In one embodiment, each electrode is arranged around a protrusion.

[0032] In one embodiment, each of the plurality of electrodes corresponds to a plurality of protuberances. In one embodiment, one electrode may correspond to 1 to 10 protuberances. In one embodiment, the clamp may have between 10 and 50 segments. A segment may have dozens, hundreds, or thousands of electrodes.

[0033] In one embodiment, each segment of the electrostatic clamp is electrically connected to a corresponding demultiplexer.

[0034] In one embodiment, the electrodes of a segment are configured to be energized to have the same polarity. The voltage difference between any of the at least two electrodes within a segment can be between 100V and 4000V, for example, up to 1000V.

[0035] In one embodiment, the electrode is hexagonal.

[0036] In one embodiment, the electrostatic clamp includes 100 to 50,000 electrodes, for example, 1,000 to 10,000 electrodes.

[0037] In one embodiment, the protuberance substantially comprises porous chromium nitride.

[0038] In one embodiment, the electrode is configured to provide actuation perpendicular to the electrode sheet, between 10 nm and 20 nm.

[0039] In a fifth aspect, a method of using an electrostatic clamp according to the fourth aspect is provided, wherein the method includes: placing an object onto the electrostatic clamp; using one or more demultiplexers configured to sequentially address selection of a plurality of electrodes from a voltage source, thereby providing a voltage to the selected electrode. The voltage induces deformation in the object.

[0040] The voltage difference between any of the two electrodes in a section can be between 100V and 4000V, for example, up to 1000V.

[0041] In a sixth aspect, a photolithography apparatus is provided, the photolithography apparatus comprising: an irradiation system configured to adjust a radiation beam; a support structure configured to support a pattern forming apparatus capable of patterning the radiation beam on a cross-section of the radiation beam to form a patterned radiation beam; a projection system configured to project the patterned radiation beam onto a substrate; and a substrate stage configured to hold the substrate, the substrate stage including an electrostatic clamp according to a fourth aspect.

[0042] In a seventh aspect, a photolithography apparatus is provided, the photolithography apparatus comprising: an irradiation system configured to adjust a radiation beam; a support structure configured to support a pattern forming apparatus capable of patterning the radiation beam on a cross-section of the radiation beam to form a patterned radiation beam; a projection system configured to project the patterned radiation beam onto a substrate; and a substrate stage configured to hold the substrate; the support structure for the pattern forming apparatus comprising an electrostatic clamp according to a fourth aspect.

[0043] The generally planar electrode arrangement described above may include electrode plates covering a generally planar surface of the fixture body, wherein a plurality of protrusions protrude from the fixture body through the electrode plates.

[0044] The devices of the sixth and seventh aspects, as well as the method according to the fifth aspect, have effects similar to those of the electrostatic clamp of the fourth aspect. This means that various aspects and features of the invention set forth above or below can be combined with various other aspects and features of the invention, as will be readily apparent to those skilled in the art. Attached Figure Description

[0045] Embodiments of the invention will now be described by way of example only, with reference to the accompanying schematic drawings, in which:

[0046] - Figure 1 A lithography system, including lithography equipment and a radiation source, is described;

[0047] - Figure 2 A top view of a fixture according to an embodiment of the present disclosure is schematically illustrated;

[0048] - Figure 3 The diagram illustrates the following: Figure 2 The selected profile of the fixture in the embodiment;

[0049] - Figure 4A schematically illustrated Figure 2 and Figure 3 A top view of the cut-off portion of the electrode sheet in the embodiment;

[0050] - Figure 4B The diagram shows Figure 4A The selected cross-section of the cut portion of the electrode sheet;

[0051] - Figure 5 The illustration shows the use of the basis Figures 2 to 4B The method of clamping in the embodiment of the example.

[0052] - Figure 6 The illustration shows the following based on Figures 2 to 5 A cross-section of the fixture in operation according to an embodiment;

[0053] - Figure 7 A top view of a fixture according to an alternative embodiment of the present disclosure is schematically illustrated;

[0054] - Figure 8A The diagram illustrates the following: Figure 7 A top view of the electrodes of the fixture in an embodiment;

[0055] - Figure 8B The diagram illustrates the following: Figure 7 and Figure 8A The selected profile of the fixture in the embodiment;

[0056] - Figure 9A The diagram shows Figures 7 to 8B The layer of the electrode sheet in the embodiment;

[0057] - Figure 9B The diagram shows Figure 9A The other layer of the section of the electrode sheet shown;

[0058] - Figure 9C The diagram shows Figure 9A and Figure 9B The other layer of the section of the electrode sheet shown; and

[0059] - Figure 10 The illustration shows the use of the basis Figures 7 to 9C The method of clamping in the embodiment of the example. Detailed Implementation

[0060] Figure 1 The lithography system shown includes a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography apparatus LA. The lithography apparatus LA includes an irradiation system IL, a support structure MT configured to support a pattern forming apparatus MA (e.g., a mask), a projection system PS, and a substrate stage assembly WT configured to support a substrate W.

[0061] The substrate stage assembly WT includes a clamp 15 and a base 16. The clamp 15 secures the substrate W to the substrate stage assembly WT. The base 16 connects the substrate stage assembly WT to means for controlling the position and speed of the substrate stage assembly. The base 16 may also include measuring devices, such as an interferometer.

[0062] The irradiation system IL is configured to modulate the EUV radiation beam B before it is incident on the patterning apparatus MA. Furthermore, the irradiation system IL may include a faceted field mirror assembly 10 and a faceted pupil mirror assembly 11. The faceted field mirror assembly 10 and the faceted pupil mirror assembly 11 together provide the EUV radiation beam B with the desired cross-sectional shape and the desired intensity distribution. In addition to, or in place of, the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11, the irradiation system IL may include other mirrors or devices.

[0063] After such adjustment, the EUV radiation beam B interacts with the patterning apparatus MA. This interaction produces a patterned EUV radiation beam B'. A projection system PS is configured to project the patterned EUV radiation beam B' onto a substrate W. For this purpose, the projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate stage WT. The projection system PS can apply a reduction factor to the patterned EUV radiation beam B' to form an image with features smaller than the corresponding features on the patterning apparatus MA. For example, a reduction factor of 4 or 8 can be applied. Although... Figure 1 The projection system PS shown has only two mirrors 13 and 14, but the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0064] The support structure MT and the substrate stage assembly WT can be Figure 1The substrate W (and substrate stage assembly WT) can move in the scanning direction, designated as the y-direction. This allows for the exposure of a larger area of ​​the pattern forming apparatus MA in a single dynamic scan exposure. The area exposed in a single dynamic scan exposure can be referred to as the exposure area. Between scan exposures, the substrate W (and substrate stage assembly WT) can move in the x-direction to allow for the exposure of multiple exposure areas.

[0065] The substrate W may include a previously formed pattern. In this case, the photolithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0066] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure much lower than atmospheric pressure, can be provided in the radiation source SO, the irradiation system IL, and / or the projection system PS.

[0067] The radiation source SO can be a laser-generated plasma (LPP) source, a discharge-generated plasma (DPP) source, a free-electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0068] In the following description, where multiple instances of the same component exist, only selected instances are labeled in the accompanying drawings for clarity. Furthermore, identical components will be represented by the same reference numerals. Additionally, references to the accompanying drawings are also included. Figure 1 The embodiments of this disclosure are described using a consistent axis throughout the text.

[0069] Now for reference Figures 2 to 6 A description of an example type of electrostatic clamp (see clamp 15) is provided. Throughout the specification, embodiments of the invention are detailed by means of a description of an electrostatic clamp for holding an object as a substrate. This description similarly applies to embodiments of the invention relating to an electrostatic clamp for holding a pattern forming apparatus.

[0070] Figure 2 A schematic top view of a fixture 20 is illustrated. The fixture 20 includes a fixture body 22 and a generally planar electrode arrangement in the form of electrode plates 23, each electrode plate 23 comprising a first half 24 and a second half 26. The first half 24 and the second half 26 of the electrode plate 23 are configured to carry charge in order to generate a charge for fixing a substrate (e.g., a substrate). Figure 1 The substrate (W) and similar objects attract electrostatic fields. The first half 24 and the second half 26 are configured to carry charges with opposite polarities.

[0071] Although not in order to be clear Figure 2 As shown, however, the clamp 20 also includes a plurality of protrusions 28, and optionally includes a voltage source 30, as shown in Figure 3 The best one to see.

[0072] Figure 3 The illustration shows a selected cross-section of the clamp 20 in the region of the first half 24. A plurality of protrusions 28 protrude from the clamp body 22. Each of the protrusions 28 defines a support surface S for supporting a substrate on the electrostatic clamp using its respective top surface. The protrusions 28 protrude through corresponding holes 25 in the electrode sheet 23 to allow contact with the substrate. The first half 24 of the electrode sheet covers or overlaps the clamp body 22.

[0073] The first half 24 of the electrode sheet includes at least two independently addressable electrodes, which will refer to Figure 4A and Figure 4B To describe in detail. Two independently addressable electrodes are configured to carry charge when a voltage is applied. Voltage source 30 is electrically connected to the first half 24 via link 32. Voltage source 30 is configured to apply a voltage to the two independently addressable electrodes for the purpose of generating an attractive electrostatic field for securing an object, such as a substrate, to a plurality of protrusions.

[0074] Figure 4A The diagram schematically illustrates a cut-off portion 40 of the first half 24 of the electrode sheet from a top view, showing the arrangement of two independently addressable electrodes. The first independently addressable electrode is configured as a first periodic array of elongated first electrode plates 42. The second independently addressable electrode is configured as a second periodic array of elongated second electrode plates 44. The first and second electrode plates 44 are interposed alternately to each other.

[0075] Figure 4B The diagram shows Figure 4A The first half 24 is a truncated portion 40, with a cross-section XX in the xz plane. A first electrode plate 42 and a second electrode plate 44 are disposed between an upper insulator 46 and a lower insulator 47. The first electrode plate 42 and the second electrode plate 44 are separated by an insulating layer 48 in a direction perpendicular to or orthogonal to the plane of the electrode plates (i.e., the z-direction, perpendicular to or orthogonal to the xy plane). The insulating layer serves to physically and electrically isolate the first electrode plate 42 from the second electrode plate 44, and by extension, to physically and electrically isolate the first independently addressable electrode from the second independently addressable electrode.

[0076] In this example, the first electrode formed by electrode plate 42 is closer to the support surface than the second electrode formed by electrode plate 44 in this example, and the first electrode at most partially overlaps the second electrode when viewed in a direction perpendicular to or orthogonal to the plane of the electrode arrangement. At least in the example shown, the first electrode plate 42 and the second electrode plate 44 (and by extension, two independently addressable electrodes) are positioned so that no visible gap or overlap is left between the electrodes when viewed in a direction perpendicular to or orthogonal to the plane of the electrode sheet. In some other embodiments, there may be overlap between the first electrode plate 42 and the second electrode plate 44 in the xy plane. Alternatively, the first electrode plate 42 and the second electrode plate 44 may be spaced up to 100 μm apart in a direction parallel to the plane of the electrode sheet (i.e., in the xy plane). The first electrode plate 42 and the second electrode plate 44 may be spaced at least 10 μm, 30 μm, or 50 μm apart in a direction parallel to the plane of the electrode sheet (i.e., in the xy plane). The additional spacing on the z-axis, the small spacing between the first electrode plate 42 and the second electrode plate 44 in a direction parallel to the plane of the electrode sheet, can provide further isolation between the first electrode plate and the second electrode plate, thereby reducing the risk of electrical breakdown between the first electrode plate and the second electrode plate.

[0077] The thickness of the insulating layer 48 can be between 2 μm and 30 μm, preferably between 4 μm and 15 μm. The z-axis spacing between the first electrode plate and the second electrode plate can be up to 30 μm. The insulating layer 48 can substantially comprise benzo-cyclo-butane (BCB) or glass.

[0078] Although physically separated, the electrode plates of each independently addressable electrode are electrically connected to each other.

[0079] In use, the first independently addressable electrode and the second independently addressable electrode are subjected to a first voltage and a second voltage of the same polarity, respectively. In the example, the voltage difference between the two independently addressable electrodes can be between 100V and 5000V, or between 500V and 4000V.

[0080] Although it has been referenced Figure 4A and Figure 4B The structure of the first half 24 of the electrode sheet is described in detail, but it should be understood that the structure of the second half 26 of the electrode sheet 23 can be substantially the same.

[0081] Figure 5 This is a schematic representation of method 60 using electrostatic clamp 20.

[0082] In step S1, the substrate W is placed on the electrostatic clamp 20.

[0083] In step S2, different voltages of the same polarity are applied to two independently addressable electrodes in the first half 24 and the second half 26 of the electrode arrangement (formed as electrode sheet 23 in this example). The different voltages modulate the attractive forces exerted on the various portions of the substrate, thereby inducing deformation, which will be described in further detail below.

[0084] Preferably, the electrostatic fixture is oriented such that the deformed wave vector(s) are aligned perpendicularly to the scanning direction of the lithography apparatus. Alternatively, the electrostatic fixture is oriented such that the resulting height variation is primarily along a direction perpendicular to the scanning direction of the lithography apparatus.

[0085] Figure 6 The substrate W, mounted on a clamp 20 and supported on a protrusion 28, is schematically illustrated along section XX. A first electrode plate 42 and a second electrode plate 44 are held at a first voltage and a second voltage, thereby generating a field whose intensity varies periodically along the x-axis. Due to the elongated shape of the first electrode plate 42 and the second electrode plate 44, the field is substantially constant along the y-axis. An attractive force or clamping force applied to a portion of the substrate is related to the local field strength. The periodically varying local field strength along the x-axis induces corresponding periodic deformations in the substrate W. Figure 6 In this model, the peak-to-peak amplitude of the deformation is indicated by Δ. The value of Δ is affected by a variety of factors, including voltage, substrate W, and the stiffness of the protrusion 28. In some embodiments, Δ can have a sensitivity of 1 nm / 100 V.

[0086] In use, the scanning direction of the lithography apparatus is parallel to the y-axis: actuation of the substrate W along the z-axis during scanning exposure can mitigate flatness defects and / or aberrations along the y-axis. The lithography apparatus has limited actuation capability along the x-axis, which is perpendicular to the scanning direction. Some lithography apparatuses cannot easily correct higher-order (e.g., 3rd or higher order) optical aberrations or flatness defects perpendicular to the scanning direction (i.e., along the x-axis). The fixture 20 can mitigate these problems by inducing controlled corrective deformation of the substrate along a direction perpendicular to the scanning direction.

[0087] The widths of the first electrode plate 42 and the second electrode plate 44 are related to the exposure area width or field width of the photolithography apparatus. The width of the electrode plate can be an integer factor of the maximum field width, and the dimensions of the electrode plate are set to induce correction distortion. In some embodiments, the widths of the first electrode plate and the second electrode plate can be integer factors of the standard field width. In some embodiments, the widths of the first electrode plate 42 and the second electrode plate 44 can be between 1 mm and 15 mm, for example, between 2 mm and 10 mm, such as approximately 3 mm.

[0088] In correcting deformation, such as Figure 6The displacement of the substrate surface illustrated can be used to bring the substrate surface into the focal plane of the projection system and can also facilitate overlap correction (in-plane correction), including in embodiments of the invention where the object is a pattern forming apparatus. Although the term "focal plane" can be used to describe the focus of a projection system, in practice, the focus of a projection system may be non-planar due to aberrations of the projection system. Therefore, the term "focal plane" can be interpreted to encompass distorted focal points (i.e., non-planar). Embodiments of the invention can cause the substrate surface to be displaced to provide an exposure area having a non-planar shape corresponding to the focus of the projection system. In an alternative example, the exposure area of ​​a substrate having, for example, a concave surface portion can be corrected by deforming a concave surface portion into a flat surface portion. Typically, a displacement of the exposure area of ​​the substrate can be applied, bringing the substrate closer to the focus of the projection system.

[0089] In an alternative embodiment, the fixture 20 may also be oriented such that the long axes of the first and second electrode plates are perpendicular to the scanning direction. This allows for the correction of projection system aberrations in the scanning direction. Typically, projection system aberrations in the scanning direction can be corrected by raising and lowering the substrate stage during scanning exposure. However, in some lithography apparatuses, some aberrations in the scanning direction cannot be corrected by vertical movement of the substrate stage. Embodiments of the present invention can correct these aberrations.

[0090] The spacing between the first independently addressable electrode and the second independently addressable electrode in a direction perpendicular to or orthogonal to the plane of the electrode sheet can be compensated by voltage. In one example, where a substantially uniform field may be desired, the first electrode can be subjected to a lower voltage than the second electrode to compensate for the greater proximity of the first electrode plate 42 to the substrate than the proximity of the second electrode plate 44 to the substrate.

[0091] Narrower electrode plates allow for higher spatial frequency-induced deformation. This higher spatial frequency deformation can be used to mitigate the effects of higher-order aberrations.

[0092] refer to Figures 2 to 6 The described electrostatic clamp 20 has two electrodes arranged in an alternating array on each electrode plate. In other embodiments, each electrode plate may have three, four, five, or more electrodes. In other embodiments, one or more of the lower second electrode plates 44 may extend partially below the first electrode plate 42 when viewed along a plane perpendicular or orthogonal to the electrode arrangement, thereby creating an overlap between two adjacent electrode plates. In one example, the overlap may be between 0 and 200 micrometers.

[0093] Although the first half 24 and the second half 26 of the electrode plate 23 cover the fixture body 22 (in) Figure 3(The best view is in the center), but other arrangements are also possible. For example, the electrode arrangement of the fixture can be part of the fixture body or integrated within the fixture body.

[0094] Now for reference Figures 7 to 10 Descriptions are provided for alternative types of electrostatic clamps used as substrates or patterning apparatuses.

[0095] Figure 7 A schematic top view of the fixture 70 is illustrated. The fixture 70 includes a generally planar electrode arrangement, in this example formed as a generally planar electrode sheet 72, which includes a plurality of electrodes arranged in multiple segments 76. The electrode sheet 72 is divided into a first half 72a and a second half 72b.

[0096] Figure 8A A single electrode 74 and a corresponding protrusion 78 of the clamp 70 are shown. The electrode section 76 includes multiple electrodes 74. Figure 8B The illustration shows the path of clamp 70. Figure 8A The cross-section YY shows one of the electrodes 74 in situ within the electrode sheet 72. The electrode sheet 72 covers the fixture body 71. In another example, the electrode arrangement may be part of the fixture body or integrated within it. The electrode sheet 72 includes a dielectric body 82, which itself may include multiple insulating dielectric layers. The electrode sheet 72 also includes multiple electrodes 74, a first connection layer 84, and a second connection layer 86. The electrodes 74, the first connection layer 84, and the second connection layer 86 are spaced apart from each other in a direction perpendicular to or orthogonal to the plane of the electrode sheet by the multiple insulating / dielectric layers. The electrodes 74, the first connection layer 84, and the second connection layer 86 are housed within the dielectric body 82. The electrodes 74, the first connection layer 84, and the second connection layer 86 are electrically connected via a bridging connector 88.

[0097] Despite Figure 8B Not shown, but electrode 72 may also include one or more grounded shielding layers. In one example, a grounded shielding layer may be provided between the plurality of electrodes 74 and the first connection layer 84.

[0098] The electrode sheet 72 can be spaced apart from the fixture body 71, or attached to the fixture body 71 by an adhesive layer.

[0099] Electrode 74, first interconnect layer 84, second interconnect layer 86, and bridging connector 88, which are essentially planar made of chromium, can be formed using photolithography. For example, dielectric body 82 can be made of fused silica, titania-silicate glass (e.g., ultra-low expansion glass including Corning® ULE®), or borosilicate glass (e.g., Corning® EAGLE XG® glass, or Schott BOROFLOAT®).

[0100] In one example, the protrusion 78 may be made of silicon carbide, or preferably, the protrusion 78 may be made of porous chromium nitride.

[0101] Figure 9A The illustration shows a segment 76 of an electrode sheet 72 viewed in a direction perpendicular to or orthogonal to the plane of the electrode sheet, exposing electrodes 74. Each segment includes a plurality of electrodes 74. The electrodes 74 have a planar hexagonal geometry. Each electrode 74 is disposed around a protrusion 78. The plurality of protrusions 78 protrude from a clamp body 71 through the electrode sheet 72. The plurality of protrusions 78 are arranged in a hexagonal lattice pattern. The hexagonal electrodes 74 are hexagonally tiled. The electrodes 74 are physically and electrically isolated from each other by a dielectric material. In some embodiments, the width of the gap (in the xy plane) between each electrode 74 and its adjacent electrode may be at least 10 μm, 30 μm, or 50 μm. In other embodiments, the width of the gap between each electrode 74 and its adjacent electrode may be up to 100 μm.

[0102] In some embodiments, each segment 76 may include approximately 1000 individual electrodes 74. Only a small number of electrodes as shown in the figures are illustrated to clearly explain the invention. Alternatively or additionally, some embodiments of the clamp 70 may include a total of at least 10,000 individual electrodes 74. Alternatively or additionally, the electrodes 74 may have a width of approximately 1.5 mm.

[0103] Figure 9B The illustration shows section 76 as viewed in a direction perpendicular to or orthogonal to the plane of the electrode sheet, exposing the first connecting layer 84 beneath the electrode 74.

[0104] Figure 9C The illustration shows segment 76 as viewed in a direction perpendicular to or orthogonal to the plane of the electrode sheet, exposing a second connection layer 86 beneath the first connection layer 84. The second connection layer 86 is electrically connected to the demultiplexer 92.

[0105] The first connection layer 84 and the second connection layer 86 are configured to be connected to provide a separate connection to each output channel of the demultiplexer 92, thereby allowing individual addressing of the plurality of electrodes 74. In some embodiments, each segment 76 may be connected to a corresponding demultiplexer 92; in other embodiments, multiple segments 76 may be connected to a single demultiplexer 92.

[0106] The demultiplexer 92 is configured to sequentially address a voltage source to select a plurality of electrodes 74, thereby supplying voltage to the selected electrodes. The voltage source is connected via a high-voltage connector 96 and the addressing of the electrodes 74 is controlled via a low-voltage connector 94. To address all electrodes 74, the selection of electrodes can be configured to cover all electrodes 74 of one or more corresponding segments 76.

[0107] The operation and principle of demultiplexers are well known in the art. For example, demultiplexer 92 can be configured to electrically disconnect electrode 74 from a voltage source after electrode 74 has been addressed by demultiplexer 92, and the electrode can maintain the voltage applied by the voltage source. After disconnection, the electrode may experience a low leakage current and thus discharge slowly, thereby substantially maintaining the voltage of the electrode for an extended period of time. The voltage of each electrode can be substantially maintained by periodically addressing each electrode 74 at an appropriate frequency. In some embodiments, the RC time constant of the electrode can be approximately 0.24 s. The period between addressing each electrode can be set to approximately 1% of the RC time constant (e.g., up to 5% of the RC time constant). In this example, electrode 74 can be addressed at a frequency of approximately 400 Hz.

[0108] The demultiplexer 92 can be configured to address the electrode 74 during varying time periods, thereby changing the voltage of the electrode 74.

[0109] Using a demultiplexer allows multiple electrodes to be addressed with a smaller number of connectors, thus minimizing the complexity of any external wiring harness.

[0110] In use, electrode 74 can be addressed to induce a desired charge distribution on electrode sheet 72. The first half 72a and the second half 72b of electrode sheet 72 are configured to be in opposite polarities in order to maintain overall neutrality.

[0111] The varying charge distribution across multiple electrodes 74 and electrode plates 72 generates a field of varying intensity on the clamp 70. The attractive force or clamping force applied to a portion of the substrate is related to the local field intensity. This varying local field intensity can induce stress on any substrate placed on the clamp 70 (e.g., Figure 1The deformation of the substrate (W). The deformation of the substrate placed on the fixture 70 is facilitated by the flexibility or compliance of the protrusion 78, which can be compressed to different degrees depending on the applied load (this also applies to other embodiments).

[0112] Due to the hexagonal lattice arrangement of the electrodes 74 and the number of electrodes 74, the fixture 70 has relative isotropy and fine maximum spatial resolution, and can influence deformation patterns over a wide range.

[0113] Thermally induced stress at the exposure area of ​​the substrate means that the clamping force at the exposure area may be higher than the clamping force at the rest of the substrate. As a result, at least some of the electrodes 74 below the exposure area may be addressed more frequently than electrodes not below the exposure area. Electrodes 74 below regions of the substrate exposed to higher EUV doses can be addressed at a higher frequency. Electrodes 74 below the exposure area of ​​the substrate can be addressed immediately before and / or during exposure. During exposure, the exposure area can be selectively and specifically deformed as described above.

[0114] Within a segment 76 of electrode sheet 72, the voltage difference between any of the at least two electrodes within the segment can be as high as, for example, 1000V, to ensure that the breakdown field of the dielectric between electrodes 74 is not exceeded. Typically, the voltage difference between any of the at least two electrodes in each half of electrode sheets 72a, 72b can also be as high as, for example, 1000V. In some embodiments, electrode 74 can be configured to provide actuation perpendicular to or orthogonal to electrode sheet 72, between 10nm and 20nm.

[0115] Figure 10 This is a schematic representation of method 100 using fixture 70.

[0116] In step S1, the substrate is placed onto the electrostatic clamp 70.

[0117] At step S2, demultiplexer 92 is used to sequentially address the selection of multiple electrodes 74 by voltage sources, thereby providing voltage to the selected electrodes.

[0118] Voltage patterns at multiple electrodes 74 induce deformation patterns in the substrate.

[0119] The deformation pattern can be selected to compensate for substrate flatness defects and a wide variety of higher-order aberrations.

[0120] Furthermore, by applying high voltage only to the area of ​​the clamp currently exposed to EUV exposure (where thermally induced slippage can be a significant issue), operation can be performed at a lower average clamp voltage. A lower average clamp voltage reduces the risk of electrostatic discharge.

[0121] Although reference Figures 7 to 10 The described clamp 70 includes a corresponding number of electrodes and protrusions, but in other embodiments, the clamp may be configured such that each of the plurality of electrodes corresponds to a plurality of protrusions.

[0122] In other embodiments, the electrodes can have any number of shapes, not just hexagonal ones. In particular, when the protrusions are not arranged in a hexagonal lattice (e.g., a square lattice), electrodes of different shapes (e.g., square electrodes) can be used.

[0123] While specific references are made to the use of lithography equipment in IC manufacturing in this article, it should be understood that the lithography equipment described herein can have other applications. Other possible applications include manufacturing integrated optical systems, guiding and detecting patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc.

[0124] Although embodiments of the invention may be specifically referred to herein in the context of lithography equipment, embodiments of the invention can be used in other equipment. Embodiments of the invention can form part of mask inspection equipment, metrology equipment, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning apparatus). These devices are generally referred to as lithography tools. Such lithography tools can use vacuum conditions or ambient (non-vacuum) conditions.

[0125] Although the use of embodiments of the invention may have been specifically referenced above in the context of optical lithography, it should be understood that, where the context permits, the invention is not limited to optical lithography and can be used in other applications such as imprint lithography.

[0126] Where circumstances permit, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented by instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable magnetic storage medium may include: read-only memory (ROM); random access memory (RAM); magnetic storage medium; optical storage medium; flash storage device; electrical, optical, acoustic, or other forms of propagating signals (e.g., carrier waves, infrared signals, digital signals, etc.), etc. Furthermore, firmware, software, routines, and instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only, and these actions are actually generated by a computing device, processor, controller, or other means of executing firmware, software, routines, instructions, etc., and doing so enables actuators or other means to interact with the physical world.

[0127] Although specific embodiments of the invention have been described above, it should be understood that the invention can be practiced in ways other than those described. The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made to the described invention without departing from the scope of the claims set forth below.

[0128] Various aspects of this disclosure are described in the following numbered clauses:

[0129] 1. An electrostatic clamp for a photolithography equipment, comprising:

[0130] Fixture body;

[0131] Multiple protrusions protrude from the clamp body and define a support surface for supporting an object on the electrostatic clamp using the respective top surface of each of the multiple protrusions;

[0132] A generally planar electrode arrangement comprising at least two independently addressable electrodes disposed between an insulator and spaced apart by an insulating layer in a direction perpendicular to the plane of the electrode arrangement, wherein, when viewed in a direction perpendicular to the plane of the electrode arrangement, a first electrode of the at least two electrodes at most partially overlaps with a second electrode of the at least two electrodes, wherein the first electrode is closer to the support surface than the second electrode;

[0133] The at least two independently addressable electrodes are configured to generate an attractive electrostatic field for securing an object to the plurality of protrusions when a voltage is applied to the at least two independently addressable electrodes during use.

[0134] 2. The electrostatic clamp according to the preceding item, wherein the thickness of the insulating layer is 10 μm to 30 μm, preferably 4 μm to 15 μm.

[0135] 3. The electrostatic clamp according to any of the preceding clauses, wherein the structure of the at least two independently addressable electrodes is configured as a periodic array of elongated electrode plates.

[0136] 4. The electrostatic clamp according to any of the preceding clauses, wherein the at least two independently addressable electrodes are positioned such that no gap is left between the at least two electrodes when viewed in a direction perpendicular to the plane in which the electrodes are arranged; preferably wherein, when viewed in a direction perpendicular to the plane in which the electrodes are arranged, the overlap between adjacent edges of the at least two electrodes is between 0 and 200 μm.

[0137] 5. The electrostatic clamp according to any of the preceding clauses, wherein the at least two independently addressable electrodes are positioned so as not to overlap when viewed in a direction perpendicular to the plane in which the electrodes are arranged; preferably wherein, when viewed in a direction perpendicular to the plane in which the electrodes are arranged, there is a gap between 0 and 100 μm between adjacent edges of the at least two electrodes.

[0138] 6. The electrostatic fixture according to item 5, wherein the structure of the at least two independently addressable electrodes is configured such that the elongated electrode plate is configured to be aligned with the scanning direction of the photolithography apparatus.

[0139] 7. The electrostatic clamp according to clause 5 or 6, wherein the structure of the at least two independently addressable electrode plates is configured such that the pitch of the at least two independently addressable electrode plates is in the range of 1 mm to 15 mm, preferably in the range of 2 mm to 10 mm.

[0140] 8. The electrostatic clamp according to any of the preceding clauses further includes a voltage source configured to apply the voltage to the at least two independently addressable electrodes for the purpose of generating an attractive electrostatic field for securing an object to the plurality of protrusions, wherein the voltage source is configured to apply a voltage difference in the range of 100V to 4000V, preferably in the range of 500V to 1500V, between any of the at least two independently addressable electrodes.

[0141] 9. The electrostatic clamp according to any of the preceding clauses, wherein the generally planar electrode arrangement includes electrode plates covering a generally planar surface of the clamp body, and wherein the plurality of protrusions protrude from the clamp body through the electrode plates.

[0142] 10. The electrostatic clamp according to the preceding paragraph, wherein the insulating layer comprises benzocyclobutane (BCB).

[0143] 11. A method for using an electrostatic fixture according to any one of the preceding clauses in a photolithography apparatus,

[0144] The method includes:

[0145] Place the object onto the electrostatic clamp;

[0146] Apply different voltages of the same polarity to the at least two electrodes;

[0147] The different voltages induce deformation in the object.

[0148] 12. The method according to clause 11, wherein the object is a substrate, and wherein the deformation induced in the substrate is configured to be aligned perpendicular to the scanning direction of the lithography apparatus.

[0149] 13. A photolithography apparatus, comprising:

[0150] An irradiation system configured to modulate a radiation beam;

[0151] A support structure configured to support a pattern forming apparatus capable of patterning the radiation beam on its cross-section to form a patterned radiation beam;

[0152] A projection system configured to project the patterned radiation beam onto a substrate; and

[0153] Substrate stage, the substrate stage being configured to hold the substrate, the substrate stage comprising:

[0154] The electrostatic clamp according to any one of the preceding items 1 to 10.

Claims

1. An electrostatic clamp for a photolithography equipment, comprising: Fixture body; A generally planar electrode arrangement, comprising: Multiple electrodes, said multiple electrodes being arranged in multiple segments; and One or more interconnect layers, the one or more interconnect layers being configured to allow individual addressing of the plurality of electrodes; Multiple protrusions protruding from the clamp body; and One or more demultiplexers, wherein the one or more demultiplexers are electrically connected to the one or more interconnect layers. The one or more demultiplexers are configured to sequentially address the selection of voltage sources to the plurality of electrodes, thereby providing voltage to the selected electrodes.

2. The electrostatic clamp according to claim 1, wherein, The generally planar electrode arrangement includes electrode plates covering the generally planar surface of the clamp body, wherein the plurality of protrusions protrude from the clamp body through the electrode plates.

3. The electrostatic clamp according to any one of the preceding claims, wherein, The one or more demultiplexers are configured to address electrodes during varying time periods, thereby changing the voltage of the electrodes.

4. The electrostatic clamp according to any one of the preceding claims, wherein, Each demultiplexer is configured to electrically disconnect the electrode from the voltage source after the electrode has been addressed by the demultiplexer, and the electrode is configured to maintain the voltage applied by the voltage source.

5. The electrostatic clamp according to any one of the preceding claims, wherein, The electrostatic clamp includes a corresponding number of electrodes and protrusions, or each of the plurality of electrodes corresponds to a plurality of protrusions.

6. The electrostatic clamp according to any one of the preceding claims, wherein, Each electrode is positioned around the protrusion.

7. The electrostatic clamp according to any one of the preceding claims, wherein, Each section of the electrostatic clamp is electrically connected to the corresponding demultiplexer.

8. The electrostatic clamp according to any one of the preceding claims, wherein, The electrodes in a section are configured to be energized to have the same polarity.

9. The electrostatic clamp according to any one of the preceding claims, wherein, The electrode is hexagonal.

10. The electrostatic clamp according to any one of the preceding claims, wherein, The electrostatic clamp includes 100 to 50,000 electrodes, preferably 1,000 to 10,000 electrodes.

11. The electrostatic clamp according to any one of the preceding claims, wherein, The protuberances are essentially composed of porous chromium nitride.

12. The electrostatic clamp according to any one of the preceding claims, wherein, The electrode is configured to provide actuation between 10 nm and 20 nm perpendicular to the electrode sheet.

13. A method of using an electrostatic clamp according to any one of the preceding claims, wherein, The method includes: Place the object onto the electrostatic clamp; Using the one or more demultiplexers, the one or more demultiplexers are configured to sequentially address the selection of voltage sources to the plurality of electrodes, thereby providing voltage to the selected electrodes.

14. A photolithography apparatus, comprising: An irradiation system configured to modulate a radiation beam; A support structure configured to support a pattern forming device, the pattern forming device being capable of patterning the radiation beam on its cross-section to form a patterned radiation beam; A projection system configured to project the patterned radiation beam onto a substrate; and A substrate stage configured to hold the substrate; The support structure and / or the substrate stage include an electrostatic clamp according to any one of claims 1 to 12.

15. An electrostatic clamp for a photolithography apparatus, comprising: Fixture body; Multiple protrusions protrude from the clamp body and define a support surface for supporting an object on the electrostatic clamp using the respective top surface of each of the multiple protrusions; A generally planar electrode arrangement comprising at least two independently addressable electrodes disposed between an insulator and spaced apart by an insulating layer in a direction perpendicular to the plane of the electrode arrangement, wherein, when viewed in a direction perpendicular to the plane of the electrode arrangement, a first electrode of the at least two electrodes at most partially overlaps with a second electrode of the at least two electrodes, wherein the first electrode is closer to the support surface than the second electrode; The at least two independently addressable electrodes are configured to generate an attractive electrostatic field for securing an object to the plurality of protrusions when a voltage is applied to the at least two independently addressable electrodes during use.

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