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1 CLAMP ELECTRODE MODIFICATION FOR IMPROVED OVERLAY TECHNICAL FIELD [0001] The present disclosure relates to electrostatic wafer clamps and methods for forming 5 and modifying electrode structures included in electrostatic wafer clamps. BACKGROUND [0002] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for 10 example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is interchangeably referred to as a mask or a reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC being formed. This pattern can be transferred onto a target portion (e.g., including part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of 15 radiation-sensitive material (e.g., resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Traditional lithographic apparatuses include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation 20 beam in a given direction (the “scanning”-direction) while synchronously scanning the target portions parallel or anti-parallel (e.g., opposite) to this scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate. [0003] As semiconductor manufacturing processes continue to advance, the dimensions of 25 circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as Moore's law. To keep up with Moore's law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The 30 wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are: 365 nm (i-line), 248 nm, and 193 nm in deep ultra violet (DUV) radiation systems; and 13.5 nm in extreme ultraviolet (EUV) radiation systems. EUV radiation, for example, electromagnetic radiation having wavelengths of around 50 nanometers (nm) or less (also sometimes referred to as soft x-rays), and 2 including light at a wavelength of about 13.5 nm, can be used in or with a lithographic apparatus to produce extremely small features in or on substrates, for example, silicon wafers. A lithographic apparatus which uses EUV radiation having a wavelength within a range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, can be used to form smaller features on a 5 substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm. [0004] It can be desirable to dictate and maintain tribological properties (e.g., friction, hardness, wear, etc.) on a surface of a substrate table. In some instances, a wafer clamp may be disposed on the surface of the substrate table. The wafer clamp may be, for example, a 10 vacuum clamp for use in DUV radiation systems or an electrostatic clamp for use in EUV radiation systems. A substrate table, or a wafer clamp attached thereto, has a surface level tolerance that can be difficult to meet because of precision requirements of lithographic and metrology processes. Wafers (e.g., semiconductor substrates), being relatively thin (e.g., < 1.0 millimeter (mm) thick) compared to a width of its surface area (e.g., > 100.0 mm wide), 15 are particularly sensitive to unevenness of the substrate table. Additionally, ultra-smooth surfaces in contact may become stuck together, which may present a problem when a substrate must be disengaged from the substrate table. To reduce the smoothness of the surface that interfaces with the wafer, the surface of the substrate table or wafer clamp may include burls formed by patterning and etching of a substrate. However, the wafer may sag in 20 areas located between burls due to a combination of forces applied to the wafer by the burls, electrostatic clamping, backfill gas pressure, wafer stiffness, and gravity. SUMMARY [0005] The present disclosure describes various aspects of systems, apparatuses, and methods 25 for manufacturing an electrostatic clamp having a modified electrode layer for increasing wafer flatness and reducing overlay errors and inter-burl wafer sag. [0006] In some aspects, the present disclosure describes an apparatus (e.g., a wafer clamp). The apparatus can include a dielectric layer that includes a plurality of burls configured to support an object. The apparatus can further include an electrostatic layer that includes one or 30 more electrodes. The electrostatic layer can be configured to generate an electrostatic force to electrostatically clamp the object to the plurality of burls in response to an application of one or more voltages to the one or more electrodes. A first magnitude of the electrostatic force in a first region of the dielectric layer can be different than a second magnitude of the electrostatic force in a second region of the dielectric layer. 3 [0007] In some aspects, the electrostatic layer can include an electrostatic sheet that includes a plurality of apertures configured to receive the plurality of burls such that the plurality of burls line up with the plurality of apertures of the electrostatic sheet. [0008] In some aspects, the apparatus can further include another dielectric layer, a first glass 5 substrate that includes the dielectric layer, and a second glass substrate that includes the electrostatic layer and the another dielectric layer. In some aspects, the electrostatic layer can be disposed vertically between the dielectric layer and the another dielectric layer. [0009] In some aspects, the first region of the dielectric layer can be disposed horizontally adjacent to one or more of the plurality of burls. In some aspects, the second region of the 10 dielectric layer can be disposed horizontally between two or more of the plurality of burls but not horizontally adjacent to the two or more of the plurality of burls. [0010] In some aspects, the electrostatic force can include an electrostatic clamp pressure. In some aspects, a first magnitude of the electrostatic clamp pressure in the first region of the dielectric layer can be greater than a second magnitude of the electrostatic clamp pressure in 15 the second region of the dielectric layer. [0011] In some aspects, a first portion of the one or more electrodes of the electrostatic layer can be disposed in a first horizontal plane. In some aspects, a second portion of the one or more electrodes of the electrostatic layer can be disposed in a second horizontal plane different from the first horizontal plane. 20 [0012] In some aspects, a first thickness of the first region of the dielectric layer can be greater than a second thickness of the second region of the dielectric layer. [0013] In some aspects, the electrostatic layer can include an electrode disposed vertically adjacent to the first region of the dielectric layer. In some aspects, the electrostatic layer can include no electrode disposed vertically adjacent to the second region of the dielectric layer. 25 [0014] In some aspects, the present disclosure describes a method for manufacturing an apparatus (e.g., a wafer clamp). The method can include forming a dielectric layer that includes a plurality of burls for supporting an object. The method can further include forming an electrostatic layer that includes one or more electrodes. The method can further include generating, using the electrostatic layer, an electrostatic force to electrostatically clamp the 30 object to the plurality of burls in response to an application of one or more voltages to the one or more electrodes. A first magnitude of the electrostatic force in a first region of the dielectric layer can be different than a second magnitude of the electrostatic force in a second region of the dielectric layer. 4 [0015] In some aspects, the forming of the electrostatic layer can include forming an electrostatic sheet that includes a plurality of apertures that receive the plurality of burls such that the plurality of burls line up with the plurality of apertures. In some aspects, the method can further include mounting the electrostatic sheet to the dielectric layer. 5 [0016] In some aspects, the forming of the dielectric layer can include forming the plurality of burls on a first glass substrate. In some aspects, the forming of the electrostatic layer can ...