Object stage

Abstract

The invention relates to an objective table which can be used in a lithographic apparatus. The stage includes an electrostatic clamp including at least one electrode disposed between insulating layers. The stage also includes a second clamp including an array of electrically connected burls, the burls including a layer of resistive material at an object receiving surface of the burls.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to EP application 22216399.0, filed on Dec. 23, 2022, the entire content of which is incorporated herein by reference. Field of the Invention

[0003] The present invention relates to a stage for holding an object such as a lithography substrate. The stage may form part of a lithography apparatus or a lithography tool. Background Art

[0004] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. A lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus can, for example, project a pattern present on a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate.

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

[0006] The substrate patterned by the lithography apparatus is held on a substrate stage. The substrate stage includes a substrate chuck configured to firmly hold the substrate on the substrate stage while the substrate is being patterned and then allow the substrate to be removed from the substrate stage once patterning is complete. In an EUV system, the substrate chuck is an electric chuck (conventional vacuum chucks cannot be used because EUV lithography apparatuses use a vacuum environment). A problem associated with an electric substrate chuck is that it may be difficult to ensure that the substrate is held strongly enough to avoid slippage of the substrate during lithography patterning while avoiding excessive friction between the substrate stage and the substrate.

[0007] More specifically, when the substrate is loaded onto the substrate stage, with the clamp closed, the substrate should be able to be positioned on the substrate stage and release any stress. The substrate stage is provided with an array of protrusions, and the friction between the substrate and the protrusions should be low enough to allow the substrate to relax to a stress-free state. If the substrate does not relax to a stress-free state but remains stressed, this can correspond to deformation of the substrate. Such deformation may result in the formation of a poor-quality pattern on the substrate. Therefore, low friction is required when the substrate clamp is closed. When the substrate clamp is turned on, the substrate clamp pulls the substrate onto the protrusions, thereby generating friction between the protrusions and the substrate. This friction should be sufficient such that the local heating of the substrate that occurs during the exposure of the pattern on the substrate does not generate an expansion force large enough to overcome the friction. In other words, when the substrate is heated during the lithography exposure, the substrate does not slide on the protrusions.

[0008] It may be desirable to solve the above problems in a manner not disclosed or suggested by the prior art. Summary of the Invention

[0009] According to a first aspect of the present invention, there is provided a stage including an electrostatic chuck and a second chuck, the electrostatic chuck including at least one electrode disposed between insulating layers, and the second chuck including an array of electrically connected protrusions, the protrusions including a resistive material layer at the object receiving surface of the protrusions.

[0010] Advantageously, the electrostatic chuck provides an initial clamping force sufficient to prevent the object from sliding on the stage, and the second chuck provides an additional clamping force after the initial clamping force.

[0011] The second chuck can be a Johnsen-Rahbek type chuck.

[0012] The resistive material can be doped diamond.

[0013] The resistive material can be boron-doped diamond.

[0014] The resistive material layer can have a resistivity of at least 10 6 Ohm cm.

[0015] The resistive material layer can have a thickness of at least 100 nm.

[0016] The electrostatic chuck can be provided with an array of openings. The protrusions can be formed of a conductive material extending through the openings.

[0017] The protrusions can be integrally formed with a conductor, and wherein the electrostatic chuck is fixed to the conductor.

[0018] The conductor can be provided with an annular groove surrounding the protrusions.

[0019] The conductor may include a flat portion located between the nodules, and the flat portion receives an electrostatic chuck.

[0020] A conductive material may be disposed on top of the electrostatic chuck, and the conductive material extends over the nodules and electrically connects the nodules.

[0021] The electrostatic chuck may include two electrodes disposed between insulating layers, and the electrodes are electrically isolated from each other.

[0022] The Johnsen-Rahbek chuck may include two conductive portions, and the conductive portions are electrically insulated from each other.

[0023] According to a second aspect of the invention, there is provided a lithographic apparatus comprising an illumination system and a projection system, and further comprising a stage according to the first aspect of the invention.

[0024] The lithographic apparatus may be a dual-stage lithographic apparatus having two (or more) stages. Two (or more) object stages may be according to the first aspect of the invention.

[0025] According to a third aspect of the invention, there is provided a lithographic tool, wherein the lithographic tool further comprises a stage according to the first aspect of the invention.

[0026] According to a fourth aspect of the invention, there is provided a stage comprising: a first chuck configured to hold an object using a first clamping mechanism; and a second chuck configured to hold an object using a second clamping mechanism.

[0027] Advantageously, two different clamping mechanisms may provide different clamping forces that may be applied at different times (e.g., one clamping force may be initially applied and a second clamping force may be provided subsequently such that two clamping forces are applied after a period of time).

[0028] According to a fifth aspect of the invention, there is provided a lithographic method performed using a dual-stage lithographic apparatus, the method comprising: placing a substrate on a substrate stage comprising an electrostatic chuck and a Johnsen-Rahbek chuck, supplying power to the electrostatic chuck and the Johnsen-Rahbek chuck, moving the substrate stage to a measurement system of the dual-stage lithographic apparatus, then measuring a characteristic of the substrate while charge accumulates on the Johnsen-Rahbek chuck, and moving the substrate stage to a projection system of the dual-stage lithographic apparatus and projecting a pattern onto the substrate using the projection system.

[0029] Advantageously, the electrostatic chuck provides an initial clamping force sufficient to prevent the substrate from sliding on the substrate table during substrate measurement, and after the initial clamping force, the Johnsen-Rahbek chuck provides an additional force. The additional force applied by the Johnsen-Rahbek chuck can inhibit the sliding of the substrate during the lithographic exposure.

[0030] Features of different aspects of the invention may be combined. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0032] Figure 1 A lithographic system including a lithographic apparatus and a substrate table according to an embodiment of the invention is schematically depicted;

[0033] Figure 2 A cross-section of a part of a substrate table according to an embodiment of the invention is schematically depicted;

[0034] Figure 3 Schematically depicted as viewed from above Figure 2 of the substrate table; and

[0035] Figure 4A and Figure 4B Schematically depict a cross-section of a substrate table and a substrate table as viewed from above according to alternative embodiments of the invention, respectively. DETAILED DESCRIPTION

[0036] Figure 1 A lithographic system including a radiation source SO and a lithographic 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 lithographic apparatus LA. The lithographic apparatus LA includes an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, a measurement system MS, and a substrate loading system SL. The lithographic system also includes two substrate tables WT1, WT2, which are configured to support a substrate W. Each of the substrate tables WT1, WT2 may be according to an embodiment of the invention. The support structure MT may be according to an embodiment of the invention. As further explained below, the substrate chuck may include an electrostatic chuck and a Johnsen-Rahbek chuck.

[0037] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. In addition, the illumination system IL may include a faceted field mirror device 10 and a faceted field pupil mirror device 11. The faceted field mirror device 10 and the faceted field pupil mirror device 11 together provide an EUV radiation beam B having a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may include other mirrors or devices in addition to or instead of the faceted field mirror device 10 and the faceted field pupil mirror device 11.

[0038] After being conditioned in this way, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B' is produced. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may include a plurality of mirrors 13, 14, which are configured to project the patterned EUV radiation beam B' onto a substrate W held by a substrate table WT2. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image having features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although in Figure 1 the projection system PS is shown as having only two mirrors 13, 14, the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0039] The substrate W may include a previously formed pattern. In this case, the lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0040] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure far below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL, and / or in the environment of the projection system PS (which may also include a measurement system MS).

[0041] For example, Figure 1The radiation source SO shown is of a type that can be referred to as a laser-produced plasma (LPP) source. A laser system 1, which can include, for example, a CO2 laser, is arranged to deposit energy into a fuel via a laser beam 2, such as tin (Sn) provided from, for example, a fuel emitter 3. Although tin is mentioned in the following description, any suitable fuel can be used. The fuel can be, for example, in liquid form and can be, for example, a metal or an alloy. The fuel emitter 3 can include a nozzle configured to direct tin, for example in the form of droplets, along a trajectory towards a plasma formation region 4. The laser beam 2 is incident on the tin at the plasma formation region 4. Depositing the laser energy into the tin creates a tin plasma 7 at the plasma formation region 4. During the de-excitation and recombination of the electrons and ions in the plasma, radiation including EUV radiation is emitted from the plasma 7.

[0042] The EUV radiation from the plasma is collected and focused by a collector 5. The collector 5 includes, for example, a near-normal incidence radiation collector 5 (sometimes more generally referred to as a normal incidence radiation collector). The collector 5 can have a multilayer mirror structure arranged to reflect EUV radiation (for example, EUV radiation having a desired wavelength such as 13.5 nm). The collector 5 can have an elliptical structure with two foci. The first focus can be at the plasma formation region 4 and the second focus can be at an intermediate focus 6, as described below.

[0043] The laser system 1 can be spatially separated from the radiation source SO. In this case, the laser beam 2 can be transmitted from the laser system 1 to the radiation source SO by means of a beam delivery system (not shown) including, for example, suitable steering mirrors and / or beam expanders and / or other optical devices. The laser system 1, the radiation source SO, and the beam delivery system can be considered together as a radiation system.

[0044] The radiation reflected by the collector 5 forms an EUV radiation beam B. The EUV radiation beam B is focused at the intermediate focus 6 to form an image at the intermediate focus 6 of the plasma present at the plasma formation region 4. The image at the intermediate focus 6 acts as a virtual radiation source for an illumination system IL. The radiation source SO is arranged such that the intermediate focus 6 is located at or near an opening 8 in an enclosure 9 of the radiation source SO.

[0045] A measurement system MS of a lithographic apparatus is configured to perform measurements of properties of a substrate W held on a substrate table WT1. The measurement system MS includes an alignment system configured to measure the position of alignment marks on the substrate with reference to alignment marks on the substrate table WT1. The measurement system also includes a level sensor configured to measure the topology of the substrate W. These measured properties are used to ensure accuracy when a pattern is subsequently projected onto the substrate W.

[0046] The lithographic apparatus LA is a dual-stage lithographic apparatus. That is, the lithographic apparatus includes two substrate tables WT1, WT2, and is configured such that a substrate W held on one of the substrate tables WT1 is simultaneously measured by a measurement system MS, and a pattern is applied to a substrate W held on the other substrate table WT2. For simplicity of terminology, one of the substrate tables WT1 may be referred to as the first substrate table, and the other substrate table WT2 may be referred to as the second substrate table. The dual-stage lithographic apparatus advantageously provides a higher throughput (i.e., the exposure of substrates per hour) than a single-stage lithographic apparatus, which typically performs measurements simultaneously with the exposure of the substrate. Once the substrate W held on the first substrate table WT1 has been measured and the substrate W held on the second substrate table WT2 has been exposed, the substrate table WT1 supporting the measured substrate W is moved under the projection system PS. At the same time, the exposed substrate W supported by the second substrate table WT2 is moved to the substrate loading system SL.

[0047] The substrate loading system SL includes a substrate handler (not shown) which is configured to remove the patterned substrate W from the second substrate table WT2 and then load a new substrate to be patterned onto the second substrate table. Once the substrate has been loaded onto the second substrate table WT2, the measurement system MS is used to measure the alignment mark positions and the topology of the substrate. At the same time, the substrate W held on the first substrate table WT1 is exposed by the lithographic apparatus.

[0048] The above method is repeated a number of times in order to expose a number of substrates using the lithographic apparatus.

[0049] Each substrate table WT1, WT2 includes a substrate chuck according to an embodiment of the present invention. The substrate chuck is closed before removing the exposed substrate from the substrate table, thereby allowing the substrate handler of the substrate loading system to easily remove the substrate from the substrate table. Then the unexposed substrate is placed on the substrate table WT1 (or WT2), and subsequently the substrate chuck is closed.

[0050] Figure 2 A cross-sectional portion of a substrate in one of the substrate tables WT1 is schematically depicted. Figure 1 The other substrate table WT2 may have the same construction. The substrate table WT1 includes a base 20 having a flat lowest surface 22. A boss array 24 projects upward from the base 20 (only some are labeled to avoid excessive complexity Figure 2 ). Between the bosses 24, the base 20 has a flat upper surface 26 (only one flat area is labeled to avoid excessive complexity Figure 2 ). An annular groove 28 surrounds each boss 24, thereby providing separation between the boss and the flat upper surface region 26. This separation reduces the stiffness of the boss, making the boss more flexible. This in turn reduces the likelihood of the substrate thermally sliding on the boss (the boss can bend to accommodate some expansion of the substrate during substrate exposure).

[0051] The base 20 and the protruding node 24 can be integrally formed from the same material. The material used to form the base 20 and the protruding node 24 is an electrical conductor, and can be silicon carbide or some other conductive ceramic. The protruding node 24 is electrically connected via the base 20.

[0052] A resistive material layer 30 is disposed on the tip of each protruding node 24. The resistive material can be, for example, diamond doped with boron. Other dopants can be used. The dopant should increase the conductivity of the diamond (or other resistive material 30). The concentration of the dopant can be provided such that the resistivity of the diamond (or other resistive material) is between 10 13 Ohm cm and 10 6 Ohm cm. The dopant can be provided at a concentration such that the diamond (or other resistive material) has a resistivity of about 10 8 Ohm cm.

[0053] The base 20 of the substrate stage WT1 is connected to a current source (not shown). The current source is controlled by a controller (not shown), which is configured to connect and disconnect the current source to and from the base 20 (and can apply a desired voltage to the base). When a substrate is present on the substrate stage WT1, the current source can be connected to the base 20 such that current is supplied to the base (and a voltage is applied to the base). Since the base 20 is a conductor, charge can easily flow through the base. Due to the voltage difference between the substrate W and the base 20, some current will flow through the resistive layer 30 on each protruding node 24. As a result, charge may accumulate on the upper surface of each resistive layer 30. This charge will cause the Johnsen-Rahbek clamping effect, thereby clamping the substrate to the substrate stage WT1. Thus, the base 20, the protruding node 24, and the resistive layer 30 form a Johnsen-Rahbek clamp 32.

[0054] The substrate stage WT1 further includes an electrostatic chuck 40. The electrostatic chuck includes an electrode 41 sandwiched between two layers of dielectric 42. The electrode 41 and the dielectric 42 include an opening 44 through which the protruding node 24 protrudes. The dielectric can be, for example, glass, sapphire, or silicon dioxide. The electrode can be formed, for example, of chromium, aluminum, or any coated metal layer. The electrostatic chuck 40 can be fixed to the base 20 by an adhesive 46.

[0055] Thus, the substrate stage WT1 includes a Johnsen-Rahbek clamp 32 and an electrostatic chuck 40.

[0056] The substrate stage WT1 can include additional layers, such as a support layer (not shown).

[0057] Figure 3Schematically depicts the substrate table WT1 as viewed from above. It can be seen that the substrate table WT1 includes a base 20 and a first part 40a and a second part 40b of an electrostatic chuck. The first half 40a of the electrostatic chuck is generally semi-circular. An opening 44 through which the boss 24 passes can be seen. The opening and the boss are schematically shown, and in practice there may be more bosses than depicted, where the bosses (and openings) are significantly smaller than the schematically shown bosses. In one embodiment, the boss may have a diameter of approximately 200 microns at the upper end. The opening may have a diameter of approximately 600 microns. The bosses may be separated by approximately 1.5 mm. The substrate table WT1 may have a diameter of approximately 300 mm. These are merely exemplary dimensions, and other dimensions may be used.

[0058] A voltage source 50 is connected to the first half 40a of the electrostatic chuck 40 and is configured to apply a voltage to the first half of the electrostatic chuck. The second half 40b of the electrostatic chuck is also semi-circular and is adjacent to but not in electrical contact with the first half of the electrostatic chuck. A voltage source 52 is connected to the second half 40b of the electrostatic chuck and is configured to apply a voltage to the electrostatic chuck. The voltage sources 50, 52 may be configured to apply voltages of opposite polarities to the two halves 40a, 40b of the electrostatic chuck. This is desirable because it can avoid or reduce the general accumulation of static charge on the substrate supported by the substrate table WT1. A current source 54 is connected to the base 20. The current source 54 may be an amplifier that controls current and voltage. The voltage and current sources 50, 52, 54 may all be controlled by a controller CT. Although the power sources 50, 52, 54 and the controller CT are described as being separate from the substrate table WT1, in practice they may all be located within the substrate table.

[0059] The Johnsen-Rahbek chuck 21 and the electrostatic chuck 40 are electrically insulated from each other. Specifically, the electrode 41 of the electrostatic chuck 40 does not contact the base 20 or the boss 24 (as Figure 2 shown). This allows the electrostatic chuck 40 and the Johnsen-Rahbek chuck 32 to operate independently of each other.

[0060] Now refer to Figures 1 - 3Describe the use according to an embodiment of the present invention. The substrate W is loaded onto the first substrate stage WT1. The electrostatic chuck 40 is turned on and the substrate is clamped to the first substrate stage WT1. The clamping force is instantaneously applied by the electrostatic chuck 40. The Johnsen-Rahbek chuck 32 is also turned on. However, unlike the electrostatic chuck 40, the Johnsen-Rahbek chuck 32 takes a long time to establish the clamping force applied to the substrate. In the case of the electrostatic chuck 40, when the voltage sources 50, 52 are connected to the electrodes 40a, 40b, the voltages applied to the first part 40a and the second part 40b are immediately and effectively applied, thereby clamping the substrate immediately. However, in the case of the Johnsen-Rahbek chuck 32, it takes a rather long time to allow the charge to flow through the base 20 and the resistive layer 30. It is the accumulation of charge on the uppermost surface of the resistive layer 30 that provides the Johnsen-Rahbek clamping effect.

[0061] However, the rather long time before the clamping force is applied by the Johnsen-Rahbek chuck is not a problem because the substrate W supported by the first substrate stage WT1 is not immediately exposed after the substrate is placed on the substrate stage. Instead, as further explained above, the characteristics of the substrate W are measured by the measurement system MS, and this measurement by the measurement system MS takes some time, typically a few seconds, and this provides sufficient time for the Johnsen-Rahbek clamping force to be fully established. In one example, the Johnsen-Rahbek force can be fully established in about 1 second. Thus, advantageously, the electrostatic chuck provides an initial clamping force that is sufficient to prevent the substrate W from sliding on the first substrate stage WT1 during substrate measurement.

[0062] Once the measurement of the substrate W on the first substrate stage WT1 is completed and the lithographic exposure of the substrate W on the second substrate stage WT2 is completed, the first substrate stage WT1 is moved under the projection system PS. At the same time, the second substrate stage WT2 is moved to the substrate loading system SL. The lithographic exposure of the substrate W on the first substrate stage WT1 begins. By starting the long exposure of the substrate W on the first substrate stage WT1, the Johnsen-Rahbek force is fully established by the Johnsen-Rahbek chuck 32. Thus, the heating of the substrate W during exposure does not cause expansion and sliding due to the clamping force applied by the Johnsen-Rahbek chuck 32, whereas if only the electrostatic clamping force is applied, the heating would cause expansion and sliding of the substrate over the protrusions.

[0063] Once the exposure of the substrate W is completed, the first substrate table WT1 returns from below the projection system PS to the substrate loading system SL. Once the exposure of the substrate has been completed, the Johnsen-Rahbek clamp 32 can be switched off (i.e., the current source 54, which can be an amplifier controlling current and voltage, can be set to 0 V), as a result of which the charge will migrate back through the resistive layer 30 and dissipate within the base 20.

[0064] When the substrate table WT1 has reached the substrate loading system SL, the electrostatic chuck 40 can be switched off (e.g., set to 0 V). Once the substrate table has reached the substrate loading system SL, the charge at the upper surface of the resistive layer 30 may have dissipated sufficiently such that the substrate W can be lifted from the substrate table WT1 by the substrate handler. That is, the substrate W is no longer clamped to the substrate table WT1.

[0065] During loading (and unloading) of the substrate onto the substrate table WT1, the voltage sources 50, 52 and the current source 54 can all be set to 0 V.

[0066] The above method can be used in combination with a substrate table according to any embodiment of the present invention.

[0067] It is particularly advantageous to use doped diamond as the resistive layer 30. This is because diamond has the material properties (which can be referred to as tribological) required for the substrate table WT1. In particular, diamond is extremely difficult to wear and thus is not worn by the substrate over time. This is advantageous because wear of the surface will generate particulate contamination, and particulate contamination is not desired in a lithographic apparatus.

[0068] By the amount of dopant provided in the diamond, the resistivity of the doped diamond resistive layer 30 can be selected as desired. As mentioned above, the dopant can be boron. Using a dopant to obtain the desired resistance advantageously has no significant effect on the tribology of the diamond (the tribology is determined by the diamond). This is because the percentage of dopant is very small compared to the percentage of carbon atoms. The tribology is determined by the crystal structure of the diamond and the dopant has no significant effect on this.

[0069] It is desirable to have a resistance that is high enough to avoid a high leakage current through the resistive layer 30. This is because a high leakage current may undesirably cause significant heating of the substrate and / or may damage the substrate (e.g., if the substrate has a conductive bottom surface). Conversely, since the Johnsen-Rahbek clamping force is caused by charge accumulation at the upper surface of the resistive layer 30, it may be desirable for the resistance of the resistive layer not to be so high that it takes too long for current to accumulate at the upper surface of the resistive layer and provide the clamping force.

[0070] The doped resistive layer 30 can for example have 10 13 Ohm cm and 10 6The resistivity between Ohm cm. The doped resistive layer 30 can, for example, have about 10 8 Ohm cm resistivity.

[0071] FIG. 4 schematically depicts a substrate stage WT1 including a substrate chuck according to an alternative embodiment of the present invention. Figure 4A A cross-section of a partial substrate chuck is schematically depicted, Figure 4B and a substrate chuck is schematically depicted as viewed from above. The substrate chuck includes a ceramic layer, such as SiSiC 60. A dielectric layer 62 is provided on top of the ceramic layer 60. The dielectric can, for example, be glass or any other insulator. Electrodes 64 are located on top of the dielectric layer 62. Another dielectric layer 66, which can also be glass or any other insulator, is provided on top of the electrodes 64. The dielectric layer 66 includes protrusions 68 provided in an array (as in the embodiment shown in Figure 2 and Figure 3 ). In Figure 4B , two electrodes 64a, b are marked and separated by a dashed line, but the electrodes are below another dielectric layer 66 and thus not visible.

[0072] A conductive material 70 (e.g., CrN) is deposited on another dielectric layer 66 (which can be referred to as the upper dielectric layer 66) in a grid-like arrangement. The conductive material 70 extends between the protrusions 68 and over the tops of the protrusions. Thus, the protrusions are electrically connected by the conductive material 70. The conductive material can, for example, have a thickness between 100 nm and 10 microns. A resistive layer 72 is provided on top of the conductive material 70 on each protrusion 68. The resistive layer 72 can be formed of, for example, diamond doped with, for example, boron. The resistive layer 72 can, for example, have a thickness between 100 nm and 10 microns.

[0073] The concentration of the dopant can be selected to provide a resistive layer 72 having a desired resistance. The resistive layer 72 can, for example, have 10 13 Ohm cm and 10 6 Ohm cm resistivity between. The resistive layer 72 can, for example, have approximately 10 8 Ohm cm resistivity.

[0074] In one embodiment, the substrate chuck can include an additional layer below the ceramic layer 60. For example, the structure shown in FIG. 4 can be fabricated twice, with one structure flipped and then bonded to the other. The lowest resistance material providing Johnsen-Rahbek clamping can be omitted from the lowest structure. The bottommost conductive material can be retained.

[0075] The substrate stage WT1 can include additional layers, such as a support layer (not shown).

[0076] Two voltage sources 84, 86 are connected to the first electrode 64a and the second electrode 64b. A current source 88 is connected to the conductive material 70. The current source 88 can be an amplifier that controls current and voltage. A controller CT controls the operation of the voltage and current sources 84, 86, 88. These can be located within the substrate stage WT1.

[0077] The first electrode 64a and the second electrode 64b form an electrostatic chuck. The conductive material 70 and the resistive layer 72 form a Johnsen-Rahbek chuck. Thus, the substrate stage WT1 includes a Johnsen-Rahbek chuck and an electrostatic chuck.

[0078] Figure 3 The base of the Johnsen-Rahbek chuck has been described and depicted in [reference] as a single entity to which a single current is applied. Similarly, in FIG. 4, the conductive materials 70 are interconnected to form a single conductor to which a single current is applied. However, in other embodiments, the Johnsen-Rahbek chuck can be provided as two or more electrically isolated entities.

[0079] In embodiments in which the Johnsen-Rahbek chuck includes a conductive base, two or more electrically insulating portions of the base can be structurally connected to form a rigid support for the substrate. The arrangement of the parts of the Johnsen-Rahbek chuck can be, for example, two semi-circles, in a manner corresponding to Figure 3 that of the electrostatic chuck shown. Other configurations of the two parts of the Johnsen-Rahbek chuck can be provided.

[0080] In embodiments in which the Johnsen-Rahbek chuck includes connected conductive material lines, a gap can be provided between the conductive materials along the centerline of the chuck. For example, a gap can be provided at the Figure 4B dashed line shown. Other configurations of the two or more parts of the Johnsen-Rahbek chuck can be provided.

[0081] Preferably, when the Johnsen-Rahbek chuck is provided in two parts, the number of protrusions in each half of the Johnsen-Rahbek chuck is the same.

[0082] The Johnsen-Rahbek chuck and the electrostatic chuck can have different arrangements. For example, the spacing between the two halves of the electrostatic chuck can extend in the Y direction, while the spacing between the two halves of the Johnsen-Rahbek chuck can extend in the X direction (Cartesian coordinates are included in the drawings for ease of description and understanding). In an embodiment in which the Johnsen-Rahbek chuck is provided in two parts, these parts can be provided with opposite polarities to minimize charge accumulation over time. In such a case, it may be desirable to provide resistive layers 30, 72 having sufficient resistance to avoid substantial current flow between the oppositely charged parts of the Johnsen-Rahbek chuck (i.e., via the substrate).

[0083] In one embodiment, the resistivity of the resistive layers 30, 72 can be at least 10 6 Ohm cm. The resistivity of the resistive layers 30, 72 can be as high as 10 13 Ohm cm. The resistivity of the resistive layers 30, 72 can be, for example, approximately 10 8 Ohm cm.

[0084] In one embodiment, the voltage source can be disconnected from the Johnsen-Rahbek chuck before the exposure of the substrate W is completed. This can be done if there is not enough time after the exposure of the substrate has been completed to allow the Johnsen-Rahbek force to be sufficiently reduced such that the substrate can be removed from the substrate stage.

[0085] In a conventional dual-stage lithography apparatus, once the substrate stage reaches the substrate loading system, the substrate can be removed from the substrate stages WT1, WT2, and once the substrate has been removed, a new substrate for exposure can be immediately placed on the substrate stage. In this conventional method, the characteristics of the newly loaded substrate can be measured before the exposure of the substrate is completed. As a result, there may be a pause during which the measured substrate is no longer being measured but is simply waiting until the exposure of the exposed substrate has been completed so that the measured substrate can then be moved under the projection system PS of the lithography apparatus. If the time taken to measure the substrate is significantly shorter than the time taken to expose the substrate such that there will be a pause of the measured substrate before it can be exposed, then alternatively the pause can be applied at the time point when the substrate stage reaches the substrate loading system SL for unloading. That is, the available time not used during the substrate measurement can be used to allow further release of the Johnsen-Rahbek chuck before the substrate is removed from the substrate stage. The pause can be, for example, 1 second or less.

[0086] Embodiments of the present invention can provide a clamping force caused by the Johnsen-Rahbek effect at the nodes and can also provide electrostatic clamping at the regions between the nodes. Thus, the clamping force can be applied to substantially the entire substrate held on the substrate tables WT1, WT2.

[0087] Although embodiments of the present invention have been described in connection with substrates and substrate tables, in other embodiments, the present invention can be used to clamp a mask MA (or other patterning device) to a support structure MT of a lithographic apparatus (see Figure 1 ), or to clamp some other object. Generally, embodiments of the present invention can be used to clamp an object. The tables of embodiments of the present invention can be referred to as carriers.

[0088] A voltage of about 3 kV (or higher) can be applied to the conductor(s) of the electrostatic chuck. A voltage of less than 250 V can be applied to the Johnsen-Rahbek chuck. The voltage applied to the Johnsen-Rahbek chuck can be less than 10 V, for example as low as 3 V.

[0089] Embodiments of the present invention generally relate to a combination of an electrostatic chuck and a chuck having an array of electrically connected nodes, the nodes including a resistive material layer at the object receiving surface of the nodes.

[0090] In a more general sense, embodiments of the present invention relate to a carrier including two chucks using different clamping mechanisms. The first clamping mechanism can be electrostatic, while the second clamping mechanism is a Johnsen-Rahbek type chuck. Alternatively, the first clamping mechanism can be vacuum, while the second clamping mechanism is electrostatic. Other combinations of clamping mechanisms can be used.

[0091] Although in this document specific reference may be made to the use of a lithographic apparatus in IC manufacturing, it should be understood that the lithographic apparatus described herein can have other applications. Possible other applications include the manufacture of integrated optical systems, the guiding and detecting of patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0092] Although embodiments of the present invention have been specifically referred to in the context of a lithographic apparatus in this document, embodiments of the present invention can be used in other devices. Embodiments of the present invention can form part of a mask inspection device, a metrology device or any device for measuring or processing an object such as a wafer (or other substrate) or a mask (or other patterning device). These devices are commonly referred to as lithographic tools. Such lithographic tools can use vacuum conditions or ambient (non-vacuum) conditions. A substrate chuck according to an embodiment of the present invention can form part of a lithographic tool.

[0093] Although specific embodiments of the present invention have been described above, it should be understood that the present invention can be implemented in a manner different from that described. The above description is intended to illustrate rather than limit. Therefore, it will be apparent to those skilled in the art that the described present invention can be modified without departing from the scope of the following claims.

[0094] Example

[0095] 1. A lithography method performed using a dual-stage lithography apparatus, the method comprising:

[0096] a. placing a substrate on a substrate stage including an electrostatic chuck and a Johnsen-Rahbek chuck;

[0097] b. supplying power to the electrostatic chuck and the Johnsen-Rahbek chuck;

[0098] c. moving the substrate stage to a measurement system of the dual-stage lithography apparatus, and then measuring characteristics of the substrate while charge accumulates on the Johnsen-Rahbek chuck; and

[0099] d. moving the substrate stage to a projection system of the dual-stage lithography apparatus, and using the projection system to project a pattern onto the substrate.

Claims

1. A stage, comprising: An electrostatic chuck, including at least one electrode disposed between insulating layers; And A second chuck, including an array of projections electrically connected, wherein the projections include a resistive material layer at an object receiving surface of the projections.

2. The stage according to claim 1, wherein the second chuck is a Johnsen-Rahbek type chuck.

3. The stage according to claim 1 or 2, wherein the resistive material is doped diamond.

4. The stage according to claim 3, wherein the resistive material is boron-doped diamond.

5. The stage according to any one of the preceding claims, wherein the resistive material layer has a resistivity of at least 10 6 Ohm cm, and / or wherein the resistive material layer has a thickness of at least 100 nm.

6. The stage according to any one of the preceding claims, wherein the electrostatic chuck is provided with an array of openings, and wherein the projections are formed of a conductive material and extend through the openings.

7. The stage according to claim 6, wherein the projections are integrally formed with a conductor, and wherein the electrostatic chuck is fixed to the conductor.

8. The stage according to claim 7, wherein the conductor is provided with an annular groove around the projections.

9. The stage according to any one of claims 7 to 8, wherein the conductor includes a flat portion located between the projections, and the flat portion receives the electrostatic chuck.

10. The stage according to any one of claims 1 to 5, wherein a conductive material is disposed on top of the electrostatic chuck, and the conductive material extends over the projections and electrically connects the projections.

11. The stage according to any one of the preceding claims, wherein the electrostatic chuck includes two electrodes disposed between insulating layers, the electrodes being electrically isolated from each other, and / or wherein the Johnsen-Rahbek chuck includes two conductive portions, the conductive portions being electrically isolated from each other.

12. A lithographic apparatus, including an illumination system and a projection system, and further including a stage according to any one of the preceding claims.

13. The lithographic apparatus according to claim 12, wherein the lithographic apparatus is a dual-stage lithographic apparatus, and wherein two stages are provided, and the two stages are according to any one of the preceding claims.

14. A semiconductor manufacturing tool, wherein the tool further includes a stage according to any one of claims 1 to 11.

15. A stage, including a first chuck and a second chuck, the first chuck being configured to clamp an object using a first clamping mechanism, and the second chuck being configured to clamp an object using a second clamping mechanism.

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