Electrostatic clamp

Abstract

An electrostatic clamp is disclosed. This electrostatic clamp is used to hold an object by electrostatic force. The clamp includes a first conductive element and a second conductive element disposed between the first conductive element and a plane in which the object is held. The second conductive element is spaced less than 100 micrometers from the first conductive element. A method for manufacturing an electrostatic clamp for holding an object by electrostatic force in a photolithography apparatus is also disclosed.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to US application 63 / 571,544, filed March 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to an electrostatic clamp, and more particularly to an electrostatic clamp for holding a substrate or mask in a photolithography apparatus. Background Technology

[0004] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. Lithography apparatus can be used, for example, to manufacture integrated circuits (ICs). A lithography apparatus can project a pattern (often referred to as a “design layout” or “design”) from a patterning apparatus (e.g., a mask) onto a radiation-sensitive material (resist) layer disposed on a substrate (e.g., a wafer).

[0005] As semiconductor manufacturing processes continue to advance, the size of circuit components has been shrinking, while the number of functional elements (such as transistors) in each device has been increasing over the decades, following a trend commonly known as "Moore's Law." To keep pace with Moore's Law, the semiconductor industry is pursuing technologies capable of creating increasingly smaller features. To project patterns onto a substrate, photolithography equipment can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features that can be patterned on the substrate. Typical wavelengths currently used are 365 nm (i-line), 248 nm (KrF), 193 nm (ArF), and 13.5 nm (EUV). Compared to photolithography equipment using, for example, radiation with a wavelength of 193 nm, photolithography equipment using extreme ultraviolet (EUV) radiation in the wavelength range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form even smaller features on the substrate.

[0006] At such short wavelengths, precise positioning of the patterning apparatus and / or substrate within the photolithography equipment is essential.

[0007] Such lithography equipment may be equipped with one or more clamps to hold the patterning apparatus and / or substrate onto an object support such as a mask stage or wafer stage. The clamps may be, for example, mechanical clamps, vacuum clamps, or electrostatic clamps. Because areas of EUV lithography equipment must operate under near-vacuum conditions, electrostatic clamps may be particularly suitable for operation at EUV wavelengths.

[0008] Electrostatic clamps are typically kept in a low-pressure, hydrogen-rich environment, which is generally non-conductive. As a result, residual charges may accumulate on the dielectric or ungrounded surfaces of the clamp, and these residual charges may, for example, be unevenly distributed across the surface.

[0009] In some exemplary electrostatic clamps of the prior art, the electric field caused by residual charge may be too high at the edge regions of the electrodes, which in some examples may cause charge to be injected from the electrode edges into the dielectric substrate or component in which the electrodes are formed. Such charge injection may be referred to in the art as “buried charge” or “buried barrier leakage.” Known techniques for releasing residual charge may be ineffective for such buried leakage.

[0010] Furthermore, during use in clamping operations, any defects in the dielectric substrate, such as those in layers immediately adjacent to the electrode edges, may pose an increased risk of electrical breakdown due to the effectively amplified field at the electrode edges. The potential future increase in the required clamping pressure and therefore the applied voltage could further increase the likelihood of such electrical breakdown.

[0011] Therefore, it is desirable to provide an electrostatic clamping method and / or device that is not affected by excessive leakage from the buried barrier.

[0012] The purpose of at least one embodiment of at least one aspect of the present invention is to eliminate or at least mitigate at least one of the aforementioned disadvantages of the prior art. Summary of the Invention

[0013] According to a first aspect of this disclosure, an electrostatic clamp is provided for holding an object by electrostatic force, the clamp comprising: a first conductive element; and a second conductive element disposed between the first conductive element and a plane in which the object is held, and the second conductive element being spaced from the first conductive element by less than 100 micrometers.

[0014] In existing electrostatic clamps that implement only a single conductive element, a relatively strong electric field may be emitted from a single radiating point at the edge of the conductive element, leading to excessive burial barrier leakage and / or creating a breakdown risk point. However, by advantageously implementing two conductive elements as described above, the two conductive elements can jointly act as a smaller point source for emitting the electric field. That is, by implementing two conductive elements relatively close together, the conductive elements can jointly emit a weaker electric field around the edge or end regions of the conductive element, due to the electric field emitted perpendicular to the surface of the conductive element.

[0015] Furthermore, since using two conductive elements may reduce the electric field strength and thus reduce leakage into the burial barrier, in use, the clamping voltage may be increased to exceed the clamping voltage of a single conductive element clamp before reaching the baseline equivalent electric field strength in the burial barrier. This can advantageously lead to an increase in clamping pressure.

[0016] The first conductive element and / or the second conductive element may each be formed as a layer of conductive material (e.g., metal). In use, the first conductive element and / or the second conductive element may each operate as an electrode.

[0017] The second conductive element can be separated from the first conductive element by less than 50 micrometers.

[0018] The second conductive element can be separated from the first conductive element by less than 20 micrometers.

[0019] Advantageously, by placing the first and second conductive elements so close together, the first and second conductive elements can operate together as a single electrode in use, but a relatively weak electric field is generated at the edge region compared to the scheme implemented by a single conductive element of an electrostatic clamp.

[0020] An electrostatic clamp may include a dielectric layer. The dielectric layer may extend between a first conductive element and a second conductive element.

[0021] The electrostatic clamp may include a first dielectric substrate and a second dielectric substrate. A first conductive element and a second conductive element may be disposed between the first dielectric substrate and the second dielectric substrate.

[0022] An electrostatic clamp may include a plurality of protrusions extending from a surface to define a plane in which the object is held. A first conductive element and a second conductive element may extend between the plurality of protrusions.

[0023] Each of the plurality of protrusions may extend through a corresponding hole in each of the first and second dielectric substrates.

[0024] There may be a gap between the outer surface of each protrusion and the corresponding opposing surface of each of the first and second dielectric substrates.

[0025] The outer surface of each protrusion and the corresponding opposing surface of each of the first and second dielectric substrates may include a conductive layer.

[0026] The first dielectric substrate and the second dielectric substrate may extend closer to each protrusion than the first conductive element and the second conductive element.

[0027] One of the first conductive element and the second conductive element may extend further toward each protrusion than the other of the first conductive element and the second conductive element.

[0028] The dielectric layer may include a polymer. Optionally, the polymer may include benzocyclobutene.

[0029] The first conductive element and / or the second conductive element may include a metal. Optionally, the metal may include chromium.

[0030] The first dielectric substrate and / or the second dielectric substrate may include glass. Optionally, the glass may include at least one of the following: borosilicate; fused silica; Corning® EAGLE XG® glass; ULE (ultra-low coefficient of thermal expansion) glass; and / or Schott BOROFLOAT®.

[0031] One of the first and second dielectric substrates can be fixed to the surface from which a plurality of protrusions extend by an adhesive.

[0032] The object can be a substrate used in photolithography projection technology, such as a wafer.

[0033] The object can be a photolithographic projection mask or a mask blank in at least one of the photolithographic projection devices.

[0034] The object may be a mask processing device and / or a mask manufacturing device.

[0035] According to a second aspect of this disclosure, a method of using an electrostatic clamp as described in the first aspect is provided, the method comprising: configuring the electrostatic clamp to hold an object by electrostatic force by biasing a first conductive element and a second conductive element to the same potential.

[0036] In the example, the same potential of the first conductive element and the second conductive element can be a first potential, which is different from the second potential at the surface of each of the plurality of protrusions.

[0037] According to a third aspect of this disclosure, a photolithography apparatus including an electrostatic clamp as described in the first aspect is provided.

[0038] According to a fourth aspect of this disclosure, a method for manufacturing an electrostatic clamp for holding an object by electrostatic force in a photolithography apparatus is provided, the method comprising the steps of: forming a first conductive element on a dielectric substrate; forming a second conductive element spaced less than 100 micrometers from the first conductive element; and disposing the dielectric substrate such that the second conductive element is disposed between the first conductive element and a plane in which the object is held.

[0039] The method may include the step of forming a dielectric layer. The dielectric layer may be formed such that it extends between a first conductive element and a second conductive element. The dielectric layer may be formed on one or both of the first conductive element and the second conductive element.

[0040] According to a fifth aspect of this disclosure, an electrostatic clamp is provided for holding an object by electrostatic force, the clamp including a conductive element formed on a dielectric substrate and extending between a plurality of protrusions defining a plane in which the object is held; wherein the edge portion of the conductive element includes curved and / or overhanging sections.

[0041] The foregoing description is intended to be exemplary and not restrictive. This disclosure includes one or more corresponding aspects, embodiments, or features, individually or in various combinations, whether specifically stated (including claimed) in such combination or individually. It should be understood that features defined above according to any aspect of this disclosure or below with respect to any particular embodiment of this disclosure may be used alone or in combination with any other defined features in any other aspect or embodiment, or form another aspect or embodiment of this disclosure. Attached Figure Description

[0042] Embodiments of the invention will now be described by way of example only with reference to the accompanying schematic diagrams, in which:

[0043] - Figure 1 This illustrates a lithography system including lithography equipment and a radiation source;

[0044] - Figure 2 An example depicting a cross-section of a portion of a prior art electrostatic clamp;

[0045] - Figure 3 Depicting as in Figure 2 Examples of electrode layers implemented in existing electrostatic clamps;

[0046] - Figure 4 Describing the in Figure 2 Simulation of the electric field at the electrode layer;

[0047] - Figure 5 An example depicting the arrangement of conductive elements in an electrostatic clamp according to an embodiment of the present disclosure;

[0048] - Figure 6 Depicted in Figure 5 An example of the electric field strength in the region at the edge of the conductive element of an electrostatic clamp, as depicted in the image;

[0049] - Figure 7An example depicting the arrangement of conductive elements in an electrostatic clamp according to another embodiment of the present disclosure;

[0050] - Figure 8 Depicted in Figure 7 An example of the electric field strength in the region at the edge of the conductive element of an electrostatic clamp, as depicted in the image;

[0051] - Figure 9 An example depicting the arrangement of conductive elements in an electrostatic clamp according to another embodiment of the present disclosure; and

[0052] - Figure 10 A method for manufacturing an electrostatic clamp for holding an object in a photolithography apparatus by electrostatic force is described. Detailed Implementation

[0053] Figure 1 A lithography system including a radiation source SO and a lithography apparatus LA is shown. 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 support WT, also referred to as a substrate stage, configured to support a substrate W.

[0054] The irradiation system IL is configured to adjust the EUV radiation beam B before it is incident on the pattern forming apparatus MA. Therefore, the irradiation system IL may include a faceted field mirror assembly 10 and a faceted pupil mirror assembly 11. Together, the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11 provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The irradiation system IL may include other mirrors or devices besides or replacing the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11.

[0055] After such adjustment, the EUV radiation beam B interacts with the patterning apparatus MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. 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 a substrate support WT. The projection system PS may 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 equal to 4 or 8 may be applied. Although the projection system PS... Figure 1The projection system PS is shown as having only two mirrors 13 and 14, but the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0056] The substrate W may include a previously formed pattern. In this case, the photolithography equipment LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0057] A relative vacuum can be provided in the radiation source SO, the irradiation system IL, and / or the projection system PS, i.e., a small amount of gas (e.g., hydrogen) at a pressure far below atmospheric pressure.

[0058] 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.

[0059] The substrate support includes a clamp 100, also referred to as a chuck, configured to hold the substrate W against the substrate support WT. The clamp 100 can be held within a recess in the substrate support WT. The clamp 100 is an electrostatic clamp 100, and references are made to... Figures 5 to 9 It was described in more detail.

[0060] The body of the electrostatic clamp 100 generally corresponds to the substrate W in shape and size. At least on the upper surface of the clamp, such as the surface adjacent to the substrate W in use, the clamp has a protrusion referred to in the art as a tab. The tab extends from the upper surface of the clamp to define a plane in which the substrate W is held.

[0061] It will become clear that the term "on" is used for... Figure 1 In the context of an exemplary lithography apparatus LA, the electrostatic fixture 100 is shown in a particular orientation. It will be understood that the disclosed fixture can be configured in various orientations, and therefore the term "on" should be understood in the context of the particular described use.

[0062] Furthermore, it will be understood that, in the example, this electrostatic clamp 100 may be additionally or alternatively implemented on the support structure MT for clamping the pattern forming apparatus MA in the desired position.

[0063] Figure 2 An example depicting a portion of a cross-section of a prior art first electrostatic clamp 200 and a prior art second electrostatic clamp 250, and Figure 3 Depicting as in Figure 2 Examples of electrode layers implemented in existing electrostatic clamps 200 and 250.

[0064] What will become clear is that... Figure 2The accompanying figures are not scale drawings of the electrostatic clamp, but are intended to illustrate the provision of one or more conductive elements, such as electrodes, in the space between the protrusions, as described in more detail below.

[0065] An exemplary prior art first electrostatic clamp 200 includes a base 210. This base may be formed of silicon-infiltrated silicon carbide (SiSiC). The base 210 includes a plurality of protrusions 215, such as projections, extending from the base 210. The upper sides of the plurality of protrusions 215 define a plane 295 for supporting an object used in photolithography projection technology, such as a substrate of a wafer, or a photolithography projection mask or mask blank in at least one of a photolithography projection apparatus, a mask processing apparatus, and / or a mask manufacturing apparatus.

[0066] In the example, each of the plurality of protrusions 215 in the exemplary prior art first electrostatic clamp 200 comprises a substantially truncated conical shape. The diameter of the upper portion of each protrusion may, for example, range from 100 micrometers to 500 micrometers; the height of each protrusion, such as the distance from the base of each protrusion, may, for example, range from 300 micrometers to 2000 micrometers. It will be understood that such geometry and dimensions are provided for illustrative purposes only, and in other examples, the protrusions 215 may have the shape of a cuboid, cylinder, pyramid, cone, truncated pyramid and / or truncated cone, etc., and may have different dimensions.

[0067] Multiple protrusions 215 may be arranged, for example, at intervals of about one to several millimeters between adjacent protrusions, such that the total area of ​​all protrusions 215 extending from the upper surface of the base 210 is less than about 10% of the total surface area of ​​the upper surface.

[0068] As another example, the exemplary prior art second electrostatic clamp 250 includes a plurality of protrusions 265, wherein each protrusion is disposed in a recess 290.

[0069] In practical examples, there may be hundreds, thousands or tens of thousands of protrusions 215, 265 distributed on electrostatic clamps with diameters of 200 mm, 300 mm, or 450 mm or larger.

[0070] Provided in Figure 2 The electrode device 220, referred to as "E-sheet" in the figure, extends between a plurality of protrusions 215, 265. The electrode device 220 includes a layered structure having a first (lower) dielectric substrate 225, at least one conductive element 240, and a second (upper) dielectric substrate 235.

[0071] In use, at least one conductive element 240 can be connected to a voltage source (not shown) via a conductive path. At least one conductive element 240 can be formed, for example, from polysilicon, gold, chromium, or aluminum.

[0072] At least one conductive element 240 may be formed next to, for example, adjacent to, the dielectric layer 255. The dielectric layer 255 may, for example, comprise a polymer such as benzocyclobutene (BCB). In the example, the dielectric layer may be approximately 1 micrometer to 100 micrometers thick, for example, approximately 9 micrometers thick. The primary purpose of the dielectric layer may be for bonding the first dielectric substrate 225 and the second dielectric substrate 235.

[0073] Although not depicted in the figure, a portion of the dielectric layer 255 may extend between at least one conductive element 240 and the first dielectric substrate 225 and / or the second dielectric substrate 235.

[0074] In the example, the first dielectric substrate 225 and / or the second dielectric substrate 235 may be formed of glass, such as alkali metal ion-free glass, for example, borosilicate glass. The glass may include, for example, at least one of the following: borosilicate; fused silica; Corning® Eagle XG® glass; ULE (ultra-low coefficient of thermal expansion) glass; and / or Schott BOROFLOAT®. The first dielectric substrate 225 may be referred to as the "bottom glass." The second dielectric substrate 235 may be referred to as the "top glass."

[0075] The electrode assembly 220 has an opening 270 that extends along a portion of the electrode assembly 220 larger than the diameter of the protrusions 215 and 265, and the protrusions 215 and 265 extend through the opening 270. The electrode assembly 220 forms a gap between its inner edge at the opening 270 and the protrusions 215 and 265. For this purpose, the opening 270 has a diameter less than 200 micrometers, for example, from 30 to 100 micrometers, larger than the diameter of the protrusions 215 and 265. The opening 270 can be, for example, a circle with a diameter of 600 to 800 micrometers, or any other shape that substantially conforms to the shape of the protrusions 215 and 265.

[0076] The electrode assembly 220 can be connected to the base 210 by an adhesive 275. The adhesive 275 can be electrically insulating, such that preferably no leakage current occurs from the electrode assembly 220 to the base 210, or only a negligible small leakage current occurs.

[0077] The total thickness of the electrode assembly 220 can be selected such that a gap in the range of, for example, 1 micrometer to 50 micrometers is formed between the upper side of the second dielectric layer 235 and the support plane 295 defined by the protrusion. Figure 3 The middle part is referred to as the "vacuum gap".

[0078] As in Figure 3 As depicted more clearly in the diagram, the aforementioned spacing exists between the outer surface of each protrusion 215, 265 and the corresponding opposing surface of each of the first dielectric substrates 225 and the second dielectric substrate 235.

[0079] The outer surface of each protrusion 215, 265 and the corresponding opposing surface of each of the first dielectric substrate 225 and the second dielectric substrate 235 include a conductive layer. In use, when the electrostatic clamp is configured to hold an object by electrostatic force, the conductive layer can be coupled to a voltage source (or ground) at a different potential than at least one conductive element 240.

[0080] Figure 4 Describing the in Figure 2 The electric field at the electrode device 220 is simulated. It can be seen that the highest electric field strength is in the region at the edge of at least one conductive element 240.

[0081] It is in this region that, due to the amplified field strength near the edge of at least one conductive element 240, negative charges can be injected from the edge of at least one conductive element 240 into the dielectric layer 255. This injected negative charge may be referred to in the art as a “buried barrier leakage,” wherein the dielectric layer 255 may be considered a “buried barrier.”

[0082] Conversely, under opposite polarities, charge can be extracted from the interface between dielectric layer 255 and the first dielectric substrate 225 and / or the second dielectric substrate 235, leaving a positive charge after the clamping voltage is removed. Above a certain threshold, this residual charge may generate interfering forces in the electrostatic clamp, potentially deforming the object held by the electrostatic clamp and even potentially causing the object to stick to the electrostatic clamp. Because the charge is effectively buried, known charge cleaning techniques may be relatively ineffective.

[0083] Furthermore, due to this charge, and due to the amplified field, particularly in the case of one or more defects in the dielectric layer 255 or the first dielectric substrate 225 and / or the second dielectric substrate 235 near the edge E of at least one conductive element 240 during manufacturing, the risk of electrical breakdown may increase near the edge E of at least one conductive element 240. A possible future increase in the required clamping pressure and voltage could further increase the likelihood of such electrical breakdown.

[0084] Figure 5 An example depicting the arrangement of conductive elements in an electrostatic clamp 500 according to an embodiment of the present disclosure is shown. The electrostatic clamp 500 may be... Figure 1 An embodiment of the electrostatic clamp 100.

[0085] Figure 5 The electrostatic clamp 500 includes an electrode assembly comprising a first (lower) dielectric substrate 525 and a second (upper) dielectric substrate 535, similar to... Figures 2 to 4 The exemplary electrostatic clamps 200, 250 include a first dielectric substrate 225 and a second dielectric substrate 235.

[0086] Similarly, Figure 5 The electrostatic clamp 500 also includes a protrusion 515 and a spacer between the protrusion 515 and the electrode device. That is, each of the plurality of protrusions 515 is connected to... Figure 2 The example extends in a similar manner through the corresponding holes in each of the first dielectric substrate 525 and the second dielectric substrate 535. Therefore, for the sake of brevity, the protrusion 515 and the first dielectric substrate 525 and the second dielectric substrate 535 are not described in further detail at this time. Similarly, the outer surface of each protrusion 515 and the corresponding opposing surface of each of the first dielectric substrate 525 and the second dielectric substrate 535 each include a conductive layer.

[0087] Despite Figure 5 Only a portion of a single protrusion 515 is depicted, but it will be understood that the electrostatic clamp 500 includes a plurality of protrusions 515 that extend from a surface, for example from a base, to define a plane 595 in which the object is held.

[0088] However, existing electrostatic clamps 200, 250 and Figure 5 A significant difference between the electrostatic clamps 500 is the implementation of an electrode layer comprising a first conductive element 540a (e.g., a first electrode) and a second conductive element 540b (e.g., a second electrode).

[0089] In this embodiment, the first conductive element 540a and the second conductive element 540b are separated by less than 100 micrometers.

[0090] In practice, in some embodiments, the first conductive element 540a and the second conductive element 540b may be separated by less than 50 micrometers, or even less than 20 micrometers. In the depicted example, the first conductive element 540a and the second conductive element 540b are separated by approximately 9 micrometers.

[0091] The second conductive element 540b is disposed between the first conductive element 540a and a plane 595 in which the object is held (e.g., the plane 595 defined by the upper surface of the protrusion 515). The first conductive element 540a and the second conductive element 540b extend between the plurality of protrusions 515.

[0092] By advantageously implementing the two conductive elements 540a and 540b as described above, these two conductive elements 540a and 540b can be used together as a ratio Figures 2 to 4 The example of a single conductive element 240 has fewer point sources for emitting electric fields. That is, since the electric field is emitted perpendicular to the surfaces of conductive elements 540a and 540b, two conductive elements 540a and 540b that are relatively close to each other can jointly emit a weaker electric field around the edge E or end regions of conductive elements 540a and 540b.

[0093] Furthermore, since the use of two conductive elements 540a and 540b reduces the electric field strength and thus the amount leaking into the burial barrier, the clamping voltage can be increased to exceed the clamping voltage of a single conductive element clamp 200 and 250 before reaching the baseline equivalent electric field strength in the burial barrier. This can advantageously result in an increase in clamping pressure.

[0094] In use, the electrostatic clamp 500 can be configured to hold an object by electrostatic force by biasing a first conductive element 540a and a second conductive element 540b to the same potential. The same potential of the first conductive element 540a and the second conductive element 540b can be a first potential that is different from a second potential (e.g., ground potential) at the surface of each of the plurality of protrusions 515.

[0095] Each of the first conductive element 540a and the second conductive element 540b can be formed as a layer of conductive material (e.g., polycrystalline silicon, gold, chromium, or aluminum).

[0096] For example, the dielectric layer 555 of the "buried barrier" extends between the first conductive element 540a and the second conductive element 540b. That is, the first conductive element 540a and the second conductive element 540b are disposed between the first dielectric substrate 525 and the second dielectric substrate 535.

[0097] Similar to Figures 2 to 4 For example, dielectric layer 555 may comprise a polymer such as benzocyclobutene (BCB). In this example, dielectric layer 555 may be in a region approximately 9 micrometers thick. The primary purpose of dielectric layer 555 may be for bonding the first dielectric substrate 525 and the second dielectric substrate 535.

[0098] Although not depicted in the figure, a portion of the dielectric layer 555 may extend between the first conductive element 235 and the first dielectric substrate 225 and / or the second dielectric substrate 235.

[0099] Figure 6 Depicting Figure 5An example of the electric field strength in the region at the edge of the conductive element of an electrostatic clamp, as depicted in the figure. Figure 6 The graphs in the diagrams provide implementations of a single conductive element 240 of the electrostatic clamps 200, 250 (e.g., Figures 2 to 4 ) and the two conductive elements 540a, 540b of the electrostatic clamp 500 in the embodiment (e.g., Figure 5 A direct comparison between the embodiments.

[0100] It can be seen that for the same clamping pressure at the wafer level at a distance of up to approximately 1 micrometer from the second conductive element 540b, the electric field at the edge of the second conductive element 540b is approximately 1.36 times lower than the nominal design. Furthermore, this is still improved to a distance of approximately 10 micrometers.

[0101] Advantageously, this means relative to Figure 2 The electrostatic clamps 200 and 250 are for Figure 5 The novel electrostatic clamp 500 embodiment allows the voltage to be increased by a factor of approximately 1.36 before reaching the baseline equivalent electric field strength within the buried barrier. Assuming all other factors remain constant, this would be equivalent to increasing the pressure by approximately 1.85 times.

[0102] exist Figure 5 As can be seen in the embodiments, the first dielectric substrate 525 and the second dielectric substrate 535 extend closer to each protrusion 515 than the first conductive element 540a and the second conductive element 540b. In this exemplary embodiment, the first conductive element 540a and the second conductive element 540b are aligned such that the first conductive element 540a and the second conductive element 540b extend the same distance from each other in the direction toward the protrusion 515.

[0103] In comparison, Figure 7 Another example depicting the arrangement of conductive elements 740a, 740b in an electrostatic clamp 700 according to an embodiment of the present disclosure. The electrostatic clamp 700 may be... Figure 1 An embodiment of the electrostatic clamp 100.

[0104] In this example, the first conductive element 740a extends further than the second conductive element 740b in the direction toward the protrusion 715.

[0105] Advantageously, for the same clamping pressure (compared to the same first conductive element 540a and second conductive element 540b embodiments described above), a slightly improved reduction in the edge electric field can be achieved by slightly (e.g., about 1.39 times) increasing the area of ​​the first (bottom) conductive element 740a, equivalent to about 1.94 times the pressure increase. This is in Figure 8 As shown in the figure, Figure 8 Depicting by Figure 7Examples of electric field strength in the region of the edge E of the conductive elements 740a and 740b of the described electrostatic clamp 700 are shown. The insets in the graph depict the top and bottom electric field strengths (denoted as "top 900µm" and "bottom 900µm") when the distance from the second (top) conductive element 740b to the protrusion 715 is less than the distance from the first (bottom) conductive element 740a to the protrusion 715. The line depicting the top and bottom electric field strengths (denoted as "898.6µm") illustrates the case where the distance from the bottom conductive element 740a to the protrusion 715 is 1.4µm smaller than the distance from the top conductive element 740b to the protrusion 715, thus providing precisely (optimized) equal electric field strengths at the edges of the top and bottom conductive elements 740a and 740b.

[0106] Figure 9 An example of the arrangement of conductive elements in an electrostatic clamp 900 according to another embodiment of the present disclosure is depicted. The electrostatic clamp 900 may be... Figure 1 An embodiment of the electrostatic clamp 100.

[0107] Figure 9 The electrostatic clamp 900 includes an electrode assembly comprising a first (lower) dielectric substrate 925 and a second (upper) dielectric substrate 935, similar to... Figures 2 to 4 The exemplary electrostatic clamps 200, 250 include a first dielectric substrate 225 and a second dielectric substrate 235.

[0108] Similarly, Figure 9 The electrostatic clamp 900 also includes protrusions (not shown) and a spacer between the protrusions and the electrode device. Therefore, for the sake of brevity, the protrusions and the first dielectric substrate 925 and the second dielectric substrate 935 are not described in further detail at this time. Similarly, each of the outer surfaces of each protrusion and each of the corresponding opposing surfaces of each of the first dielectric substrate 925 and the second dielectric substrate 935 includes a conductive layer.

[0109] However, existing electrostatic clamps 200, 250 and Figure 9 A significant difference between the electrostatic clamps 900 is the implementation of an electrode layer including a conductive element 940, wherein the edge portion of the conductive element 940 includes a curved section 995 and / or a hanging section. Such curved sections 995 and / or hanging sections can be formed, for example, by photolithography, by etching processes (such as angular etching or selective etching), and / or selective deposition.

[0110] Furthermore, in this embodiment, the thickness of the conductive element 940 can be substantially greater than the thickness of each conductive element 540a, 540b, 740a, 740b in the above embodiments. In one example, the conductive element 940 can be approximately 9 to 10 micrometers thick, for example, substantially extending all or at least 90% of the distance between the first dielectric substrate 925 and the second dielectric substrate 935.

[0111] Because of the curved edge portion, the conductive element 940 can function less like a sharp edge than any of the conductive elements described above. Advantageously, this can also have the effect of reducing the electric field strength in the region of the curved edge.

[0112] Figure 10 Methods for manufacturing electrostatic clamps 500, 700 for holding objects in a photolithography apparatus by electrostatic force, according to embodiments of the present disclosure, are described.

[0113] The method includes step 1010 of forming a first conductive 540a element on a first substrate 525. The first substrate 525 may include a dielectric substrate. The first substrate 525 may include, for example, at least one of the following: borosilicate; fused silica; Corning® Eagle XG® glass; ULE (ultra-low coefficient of thermal expansion) glass; and / or Schott BOROFLOAT®. The first conductive 540a element can be formed by known deposition or photolithography methods. The first conductive 540a may be, for example, a... Figure 5 The first conductive part 540a in the embodiment.

[0114] The method includes step 1020 of forming a second conductive element 540b spaced less than 100 micrometers from the first conductive element 540a. The second conductive element 540b may, for example, be... Figure 5 The second conductive element 540b in the embodiment.

[0115] In some embodiments, step 1020 may include forming a dielectric layer 555 over the first conductive element 540a, and subsequently forming a second conductive element 540b over the dielectric layer 555, and then disposing a second substrate 535 over the second conductive element 540b.

[0116] In other embodiments, step 1020 may include forming a second conductive element 540b on the second substrate 535, and forming a dielectric layer 555 over one or both of the first and second conductive elements before disposing the second substrate 535 over the first substrate 525.

[0117] The method includes step 1030 of setting a first substrate 525 such that a second conductive element 540b is disposed between the first conductive element 540a and a plane in which an object is held. That is, the first substrate 525 can be adhered to a surface of a base from which protrusions extend, wherein the protrusions define a plane in which the object is held, as referenced above. Figures 5 to 9 The example described.

[0118] While specific applications of lithography equipment in IC manufacturing are discussed in this article, it should be understood that the lithography equipment described herein can have other applications. Possible other applications include the fabrication of integrated optical systems, patterning for guiding and detecting magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and more.

[0119] Although embodiments of the invention are specifically referred to herein in the context of lithography equipment, these embodiments 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 can be collectively referred to as lithography tools. Such lithography tools can use vacuum conditions or ambient (non-vacuum) conditions.

[0120] Although specific reference has been made above to embodiments of the invention used in the context of optical lithography, it will 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.

[0121] While specific embodiments of the invention have been described above, it will 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.

[0122] Figure Labels

[0123] LA lithography equipment

[0124] MA pattern forming device

[0125] MT support structure

[0126] SO radiation source

[0127] W substrate

[0128] WT substrate support

[0129] PS projection system

[0130] IL illumination system

[0131] B radiation beam

[0132] B' radiation beam

[0133] 10 Facet field mirror device

[0134] 11 Facet pupil mirror device

[0135] 13 Mirror

[0136] 14 Mirror

[0137] 100 Chuck

[0138] 200 Electrostatic chuck

[0139] 210 Base portion

[0140] 215 Protrusion

[0141] 220 Electrode device

[0142] 225 First dielectric substrate

[0143] 235 Second dielectric substrate

[0144] 240 Conductive element

[0145] 250 Electrostatic chuck

[0146] 255 Dielectric layer

[0147] 265 Protrusion

[0148] 270 Opening

[0149] 275 Adhesive

[0150] 290 Recess

[0151] 295 Plane surface

[0152] 500 Electrostatic chuck

[0153] 515 Protrusion

[0154] 525 First dielectric substrate

[0155] 535 Second dielectric substrate

[0156] 540a First conductive element

[0157] 540b Second conductive element

[0158] 555 Dielectric layer

[0159] 595 Plane surface

[0160] 700 Electrostatic Clamp

[0161] 715 Node

[0162] 740a First Conductive Element

[0163] 740b Second Conductive Element

[0164] 900 Electrostatic Clamp

[0165] 925 First Dielectric Substrate

[0166] 935 Second Dielectric Substrate

[0167] 940 Conductive Components

[0168] 995 Curved Section

[0169] 1010 First Step

[0170] 1020 Second Step

[0171] 1030 Third step.

Claims

1. An electrostatic clamp (500, 700) for holding an object by electrostatic force, said clamp comprising: First conductive element (540a, 740a); as well as A second conductive element (540b, 740b) is disposed between the first conductive element and the plane (595) in which the object is held, and the second conductive element is separated from the first conductive element by less than 100 micrometers.

2. The electrostatic clamp (500, 700) as described in claim 1, wherein, The second conductive element (540b, 740b) is separated from the first conductive element (540a, 740a) by less than 50 micrometers.

3. The electrostatic clamp (500, 700) as described in claim 1 or 2, wherein, The second conductive element (540b, 740b) is separated from the first conductive element (540a, 740a) by less than 20 micrometers.

4. The electrostatic clamp (500, 700) according to any of the preceding claims, comprising a dielectric layer (555) extending between the first conductive element (540a, 740a) and the second conductive element (540b, 740b).

5. The electrostatic clamp (500, 700) according to any of the preceding claims, comprising a first dielectric substrate (525) and a second dielectric substrate (535), wherein, The first conductive element and the second conductive element (540a, 540b, 740a, 740b) are disposed between the first dielectric substrate and the second dielectric substrate.

6. The electrostatic clamp (500, 700) according to any of the preceding claims, comprising a plurality of protrusions (515, 715) extending from a surface to define the plane in which the object is held, wherein, The first conductive element and the second conductive element (540a, 540b, 740a, 740b) extend between the plurality of protrusions.

7. The electrostatic clamp (500, 700) as described in claim 6 when dependent on claim 5, wherein: Each of the plurality of protrusions (515, 715) extends through a corresponding hole in each of the first and second dielectric substrates. There is a gap between the outer surface of each protrusion and the corresponding opposing surface of each of the first and second dielectric substrates (525, 535); and The outer surface of each protrusion and the corresponding opposing surface of each of the first and second dielectric substrates include a conductive layer.

8. The electrostatic clamp (500, 700) as described in claim 6 or 7, wherein, The first dielectric substrate and the second dielectric substrate (525, 535) extend closer to each protrusion than the first conductive element and the second conductive element (540a, 540b, 740a, 740b).

9. The electrostatic clamp (500, 700) as described in any one of claims 6 to 8, wherein, One of the first and second conductive elements (740a) extends further toward each protrusion than the other conductive element (740b).

10. The electrostatic clamp (500, 700) as described in any one of claims 4 to 9, wherein, At least one of the following: The dielectric layer (555) comprises a polymer, and optionally the polymer comprises benzocyclobutene; The first conductive element and / or the second conductive element (540a, 540b, 740a, 740b) comprises a metal, and optionally, the metal comprises chromium; The first dielectric substrate and / or the second dielectric substrate (525, 535) comprise glass, and optionally, the glass comprises borosilicate.

11. The electrostatic clamp (500, 700) as described in any one of claims 6 to 10, wherein, One of the first dielectric substrate and the second dielectric substrate (525, 535) is fixed to the surface from which the plurality of protrusions (515) extend by an adhesive.

12. The electrostatic clamp (500, 700) according to any of the preceding claims, wherein, The object is at least one of the following: The substrate (W) used in photolithography projection technology; and A photolithographic projection mask or mask blank in at least one of a photolithographic projection apparatus, a mask processing apparatus, and / or a mask manufacturing apparatus.

13. A method of using the electrostatic clamp (500, 700) as described in claim 12, the method comprising: The electrostatic clamp is configured to hold the object by electrostatic force by biasing the first conductive element and the second conductive element (540a, 540b, 740a, 740b) to the same potential.

14. A photolithography apparatus comprising an electrostatic clamp (500, 700) according to any one of claims 1 to 13.

15. A method for manufacturing an electrostatic clamp (500, 700) for holding an object by electrostatic force in a photolithography apparatus, the method comprising the steps of: A first conductive element (540a, 540a) is formed on a dielectric substrate. Forming a second conductive element (540b, 740b) separated from the first conductive element by less than 100 micrometers; and The dielectric substrate is configured such that the second conductive element is disposed between the first conductive element and the plane (595) in which the object is held.

16. An electrostatic clamp (900) for holding an object by electrostatic force, the clamp comprising: A conductive element (940) is formed on a dielectric substrate (925) and extends between a plurality of protrusions that define a plane in which the object is held. The edge portion of the conductive element includes curved and / or overhanging sections (995).

Images