Electrostatic chuck configured to provide consistent clamping force

Abstract

Examples relating to an electrostatic chuck (ESC) for clamping a substrate in a manner that provides consistent radial clamping force across the surface of the substrate are disclosed. In one example, an ESC comprises a substrate-facing surface comprising a plurality of contact features. The contact features are configured to support the substrate. Contact area sizes of at least some contact features of the plurality of contact features vary based at least on locations of the contact features on the substrate-facing surface.

Description

Docket No. LRC24303PPCTELECTROSTATIC CHUCK CONFIGURED TO PROVIDE CONSISTENT CLAMPING FORCEBACKGROUND

[0001] An electrostatic chuck (ESC) can be used in a substrate processing tool to hold and immobilize a substrate, such as a silicon wafer, while performing processing such as etching, deposition, and lithography.SUMMARY

[0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0003] Examples are disclosed that relate to an electrostatic chuck (ESC) configured to help reduce damage to substrate backsides during clamping compared to other ESCs. In one example, an ESC comprises a substrate-facing surface comprising a plurality of contact features. The contact features are configured to support the substrate. Contact area sizes of at least some contact features of the plurality of contact features vary based at least on locations of the contact features on the substrate-facing surface.

[0004] In some such examples, the substrate-facing surface comprises a central region, an intermediate region, and an outer region. The intermediate region is radially interposed between the central region and the outer region. The contact area sizes of at least some contact features in the intermediate region are less than the contact area sizes of at least some contact features in the central region and at least some contact features in the outer region.

[0005] Alternatively or additionally, in some such examples, fill ratios of contact areas of the contact features relative to total surface areas in the central region, the intermediate region, and the outer region vary.Docket No. LRC24303PPCT

[0006] Alternatively or additionally, in some such examples, the fill ratios of the contact features in the central region, the intermediate region, and the outer region vary within a range of .01% - 100%.

[0007] Alternatively or additionally, in some such examples, the plurality of contact features are distributed across the substrate-facing surface in a spiral pattern.

[0008] Alternatively or additionally, in some such examples, the spiral pattern comprises a Vogel spiral pattern.

[0009] Alternatively or additionally, in some such examples, the spiral pattern comprises one or more of a logarithmic spiral pattern, a golden spiral pattern or a Fibonacci spiral pattern.

[0010] Alternatively or additionally, in some such examples, the contact area sizes of the plurality of contact features vary as a function of a clamping force profile that defines a threshold clamping force to clamp the substrate to the plurality of contact features.

[0011] In another example, a substrate processing tool comprises a processing chamber and an ESC positioned within the processing chamber. The ESC includes a substrate-facing surface and a plurality of contact features protruding from the substrate-facing surface. The plurality of contact features are configured to support a substrate. Contact area sizes of at least some contact features of the plurality of contact features vary based at least on locations of the contact features on the substrate-facing surface.

[0012] In some such examples, the substrate-facing surface comprises a central region, an intermediate region, and an outer region. The intermediate region is radially interposed between the central region and the outer region. The contact area sizes of at least some contact features in the intermediate region are less than the contact area sizes of at least some contact features in the central region and at least some contact features in the outer region.

[0013] Alternatively or additionally, in some such examples, fill ratios of contact areas of the contact features relative to total surface areas in the central region, the intermediate region, and the outer region vary.

[0014] Alternatively or additionally, in some such examples, the plurality of contact features are distributed across the substrate-facing surface in a spiral pattern.

[0015] Alternatively or additionally, in some such examples, the spiral pattern comprises a Vogel spiral pattern.Docket No. LRC24303PPCT

[0016] Alternatively or additionally, in some such examples, the spiral pattern comprises one or more of a logarithmic spiral pattern, a golden spiral pattern, or a Fibonacci spiral pattern.

[0017] Alternatively or additionally, in some such examples, the contact area sizes of the plurality of contact features varies as a function of a clamping force profile that defines a threshold clamping force to clamp the substrate to the plurality of contact features as a function of location (e.g., radial location) on an ESC.

[0018] In yet another example, an ESC for clamping a substrate comprises a substrate-facing surface comprising a plurality of contact features. The plurality of contact features are configured to support the substrate. The plurality of contact features are distributed across the substrate-facing surface in a spiral pattern.

[0019] In some such examples, the spiral pattern comprises one or more of a logarithmic spiral pattern, a Vogel spiral pattern, a golden spiral pattern, or a Fibonacci spiral pattern.

[0020] Alternatively or additionally, in some such examples, one or more of contact area sizes of contact features, contact area shapes of contact features, or fill ratios of contact features vary based at least on one or more of locations of the contact features on the substrate-facing surface or a coating applied to the substrate surface of the ESC

[0021] Alternatively or additionally, in some such examples, the substratefacing surface comprises a central region, an intermediate region, and an outer region. The intermediate region is radially interposed between the central region and the outer region on the substrate-facing surface. The contact area sizes of at least some contact features in the intermediate region are less than the contact area sizes of at least some contact features in the central region and at least some contact features in the outer region.

[0022] Alternatively or additionally, in some such examples, fill ratios of contact areas of the contact features relative to total surface areas in the central region, the intermediate region, and the outer region vary.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 schematically shows a functional block diagram of an example substrate processing tool including an electrostatic chuck (ESC).Docket No. LRC24303PPCT

[0024] FIG. 2 shows an example ESC including a plurality of contact features arranged in a Vogel spiral pattern.

[0025] FIG. 3 shows another example ESC including a plurality of contact features arranged in a Fibonacci spiral pattern.

[0026] FIG. 4 shows an ESC including a plurality of contact features arranged in a hexagonal pattern to support a substrate.

[0027] FIG. 5 shows an example ESC including a plurality of contact features arranged in a spiral pattern to support a substrate.

[0028] FIG. 6 shows an example plot of radial clamping force on a substrate provided by the ESC shown in FIG. 4.

[0029] FIG. 7 shows an example plot of radial clamping force on a substrate provided by the ESCs shown in FIGS. 2 and 5.DETAILED DESCRIPTION

[0030] The term “electrostatic chuck” (“ESC”) generally represents a device used in a substrate processing tool to hold and immobilize a substrate using electrostatic forces.

[0031] The term “substrate” generally represents any object that can be processed in a substrate processing tool.

[0032] The term “substrate-facing surface” generally represents a surface of an ESC with contact features to support a substrate.

[0033] The term “contact feature” generally represents an ESC structure configured to physically contact a substrate when the substrate is supported by the ESC.

[0034] The term “contact area” generally represents an area in which contact occurs between a contact feature and a substrate.

[0035] The term “radial location” generally represents a distance of a contact feature from a center of the ESC.

[0036] The term “azimuthal location” generally represents a horizontal position of a contact feature measured in degrees clockwise from a reference point on the ESC3

[0037] The term “fill ratio” generally represents a ratio of contact areas of contact features on a surface of an ESC (or a region of the ESC) relative to a total surface area of the substrate-facing surface of the ESC (or of the region of the ESC).Docket No. LRC24303PPCT

[0038] The term “spiral pattern” generally represents a curved pattern that rotates around a center location while changing in radius.

[0039] The term “Vogel spiral pattern” generally represents a pattern formed by tangent disks of geometrically increasing radii placed in locations whose polar coordinates are mathematically derived. More particularly, a Vogel spiral pattern forms a mesh of spiral arms. A Vogel spiral pattern can be given by the following equations: ( 1) r = c(n)'1'2, and (2) 0 ==:n x 137.508°, where 0 is the angle, r is the radius or distance from the center, n is the index number of an arm, and c is a constant scaling factor.

[0040] The term “golden spiral pattern” generally represents another pattern formed by tangent disks of geometrically increasing radii placed in locations whose polar coordinates are mathematically derived. More particularly, a golden spiral pattern is a logarithmic spiral with a growth factor given by the golden ratio ((a+b) / a = a / b).

[0041] The term “Fibonacci spiral pattern” generally represents another pattern formed by tangent disks of geometrically increasing radii placed in locations whose polar coordinates are mathematically derived.

[0042] The term “clamping force profile” generally represents a threshold clamping force to clamp a substrate to contact features as a function of location (e.g., radial location) on the ESC.

[0043] The term “substrate processing tool” generally represents a machine including a processing chamber and other hardware configured to enable processing of substrates to be conducted in the processing chamber.

[0044] The term “processing chamber” generally represents an enclosure in which chemical and / or physical processes are performed on substrates. Example chemical and / or physical processes include deposition processes, etching processes, and lithographic processes.

[0045] As mentioned above, an electrostatic chuck (ESC) can be used in a substrate processing tool to hold and immobilize a substrate, such as a silicon wafer, during processing. An ESC includes one or more clamping electrodes arranged such that, when a voltage is applied to the clamping electrode(s), electrostatic forces are generated between the clamping electrode(s) and the substrate. These forces attract the substrate towards the surface of the ESC, effectively holding the substrate in place. After processing is complete, the voltage applied to the clamping electrode(s) can beDocket No. LRC24303PPCT turned off, causing the electrostatic forces to dissipate. This allows the substrate to be easily removed from the ESC.

[0046] ESCs typically include a plurality of substantially uniformly sized contact features arranged on the surface of the ESC in a pattern where spacing and / or distribution between the contact features does not vary across the surface of the ESC. Example patterns include grid patterns and hexagonal patterns.

[0047] Due to the plurality of contact features being uniformly sized and arranged in a fixed pattern across the surface of the ESC, the contact features of the ESC can provide inconsistent radial clamping force along some substrates, such as substrates with bowing. The inconsistent radial clamping force comprising both underclamping and over-clamping can cause defects on the backside of the substrate, such as scratches and burrs as will be discussed herein. The term “over-clamping” refers generally to a clamping force that exceeds a threshold clamping force to clamp a location of the substrate to an ESC. The term “under-clamping” refers generally to a clamping force that is less than the threshold clamping force. FIGS. 6 and 7, described below, show a threshold clamping force profile of an example substrate compared to actual radial clamping forces applied to the example substrate by different ESC configurations. Example bowing that can be experienced by substrates include concave / dish bowing, convex / dome bowing, center / saddle bowing, and / or edge bowing). Bowing of a substrate can occur, for example, in substrates with a relatively large number of layers deposited on the substrate, as the stress in the layers can be imparted to the substrate, thereby deforming the substrate. Examples include substrates on which three-dimensional (3D) memory structures are being fabricated, such as 3D NAND memory. 3D NAND memory fabrication involves depositing a relatively large number of alternating layers of silicon oxide / silicon nitride, or alternating layers of silicon oxide / polycrystalline silicon, on a substrate to form layers of memory structures. The relatively large number of alternating layers can cause stress that results in bowing of a substrate. In other examples, bowing can occur in other types of substrates undergoing other types of processing operations.

[0048] Bowing of a substrate can cause inconsistent processing across a substrate surface. The radial clamping force of an ESC can be used to flatten a substrate with bowing for more consistent processing across the substrate. However, due to the inconsistent radial clamping force experienced by a bowed substrate when clamped by an ESC with a uniform pattern of contact features, different regions of the substrate canDocket No. LRC24303PPCT be under-clamped or over-clamped. In other examples, the inconsistent clamping force may vary azimuthally across the surface of the bowed substrate. In regions of the substrate that are under-clamped, the substrate may not be sufficiently flattened, thereby leading to inconsistent processing across the substrate surface. As one example, localized under-clamping of the substrate with the ESC can result in poor thermal conductivity between the substrate and the ESC, leading to uneven or insufficient cooling. This can cause temperature variations across the substrate that affect processing uniformity. Further, in processes such as etching, deposition, or lithography, under-clamping can result in uneven processing, causing variations in etch rates, deposition thickness, or other process parameters across the substrate. As another example, inadequate radial clamping force may allow the substrate to shift or move relative to the ESC during processing. This can lead to misalignment issues, defects, or even breakage of the substrate, especially in high-precision applications. As another example, the ESC relies on electrostatic forces to hold the substrate in place. Underclamping can reduce these forces, leading to the possibility of electrical discharge or arcing, which can cause damage the substrate and / or the ESC. As yet another example, under-clamping can lead to gaps between the substrate and the ESC where particles or contaminants can accumulate. These contaminants can interfere with process of the substrate and lead to defects in the substrate.

[0049] In regions of the substrate that are over-clamped, the magnitude of the electrostatic force can be high enough to exceed the local yield strength of the substrate material and thereby create defects, such as scratches and burrs, on the substrate backside.

[0050] Accordingly, to address these and other issues, examples are disclosed that relate to an electrostatic chuck (ESC) for clamping a substrate in a manner that can help to clamp bowed substrates with a more consistent radial clamping force experienced radially across a surface of a substrate compared to other electrostatic chucks. Briefly, an electrostatic chuck comprises a substrate-facing surface with a plurality of contact features protruding from the substrate-facing surface. The plurality of contact features are configured to support the substrate. In some examples, contact area sizes of at least some contact features can vary based at least on locations of the contact features on the substrate-facing surface. Alternatively or additionally, in some examples, the plurality of contact features are arranged in a spiral pattern on the substrate-facing surface.Docket No. LRC24303PPCT

[0051] As will be discussed in further detail herein, these features of the ESC provide more consistent radial clamping force across the surface of the substrate relative to ESCs that lack either or both of contact features having contact area sizes that vary based at least on locations of the contact features on the surface of the ESC and contact features arranged in a spiral pattern on the surface of the ESC. This can help to avoid localized under-clamping while maintaining suitably low, consistent (and potentially nominal) levels of over-clamping across the surface of bowed substrates. Further, by providing more consistent radial clamping force across the surface of the substrate compared to ESCs that lack contact features having contact area sizes that vary based at least on locations of the contact features on the surface of the ESC and / or contact features arranged in a spiral pattern on the surface of the ESC, lower clamping voltages can be used, as the radial clamping force is distributed more uniformly across the surface of the substrate. ESCs that lack contact features having contact area sizes that vary based at least on locations of the contact features on the surface of the ESC and / or contact features arranged in a spiral pattern on the surface of the ESC apply clamping force inconsistently radially across the surface of the substrate, and thus require higher clamping voltages in order to effectively apply clamping force in localized regions on the surface of the substrate where contact features of ESCs have less consistent contact with the substrate. By using lower clamping voltages, overall clamping force is reduced. The number and / or severity of backside defects created as a result of localized over-clamping of the substrate can be reduced with the ESC relative to ESCs that lack contact features having contact area sizes that vary based at least on locations of the contact features on the surface of the ESC and / or contact features arranged in a spiral pattern on the surface of the ESC, due to the lower clamping voltages. Further, in different examples, an arrangement of the contact features on an ESC can be tailored to fit specific types of substrates, such as substrates that demonstrate different types of bowing, so that the clamping force can be radially and / or azimuthally distributed across the surface of the substrate as desired in order to remain consistent across the surface of that particular substrate configuration. In some examples, contact features of an ESC can be configured to distribute the clamping force radially and / or azimuthally across the surface of a substrate to provide consistent clamping force with minimal or no localized under-clamping or over-clamping.

[0052] FIG. 1 schematically shows an example substrate processing tool 100 that is configured to perform processing on a substrate 102, such as a silicon wafer. TheDocket No. LRC24303PPCT substrate processing tool 100 is referred to herein as the tool 100. In various examples, the tool 100 can be an atomic layer deposition (ALD) tool, a chemical vapor deposition (CVD) tool, or an etching tool. In further examples, the tool can be any other suitable kind of substrate processing tool.

[0053] The tool 100 comprises a processing chamber 104, and an ESC 106 and a showerhead 110, each positioned within the processing chamber 104. The ESC 106 is configured to support the substrate 102 within the processing chamber 104.

[0054] The ESC 106 comprises a substrate heater 107 configured to heat the substrate to temperatures suitable for different processing operations. In other examples, a heater can be omitted, or can be located elsewhere within the processing chamber 104. In some examples, the substrate heater 107 is configured to heat the substrate and / or processing environments to a temperature of 50 °C to 800 °C. In other examples, a temperature outside this range can be used.

[0055] The ESC 106 is configured to support and clamp the substrate 102 during processing. The ESC includes one or more clamping electrode(s) (not shown in in FIG. 1). The ESC 106 further includes a substrate-facing surface 112. A plurality of contact features 114 are formed on the substrate-facing surface 112 of the ESC 106 and are configured to support the substrate 102. The dimensions of contact features 114 are exaggerated for clarity. The contact features 114 are sized and shaped to contact and support the substrate 102. In one example, each of the contact features 114 may be circular with a flat surface that forms a contact area with the substrate 102. In other examples, the contact features 114 can assume any other shape that is suitable to support the substrate 102. The plurality of contact features 114 have structural features that promote more consistent radial clamping force (and / or azimuthal clamping force) across the surface of the substrate 102, as described in more detail below.

[0056] The showerhead 110 is configured to introduce processing gas(es) into the processing chamber 104. In other examples, a tool can comprise a nozzle or other apparatus for introducing processing gas(es) into the processing chamber 104, as opposed to or in addition to a showerhead. The showerhead 110 is connected to flow control hardware 116. The flow control hardware 116 connects the processing gas source(s) 120 to the processing chamber 104. The processing gas source(s) 120 can provide different types of processing gases in different examples, including film precursors, reactants, etchants, inhibitors, inert gases, etc.Docket No. LRC24303PPCT

[0057] The flow control hardware 116 can include any suitable components. Examples include mass flow controllers, valves, and conduits. For example, the flow control hardware 116 can comprise one or more valves controllable to place a selected gas source or selected gas sources in fluid connection with the showerhead 110. The flow control hardware 116 also can comprise one or more mass flow controllers or other controllers for controlling a mass flow rate of gas.

[0058] The tool 100 further comprises an exhaust system 122. The exhaust system 122 is configured to exhaust gases and / or process byproducts from the processing chamber 104. The exhaust system 122 can comprise any suitable hardware, including one or more low vacuum pumps and one or more high vacuum pumps. Together, the flow control hardware 116 and exhaust system 122 can be operated to control and achieve a selected pressure in processing chamber 104 during substrate processing. Further, the exhaust system 122 can be operated to purge the processing chamber 104.

[0059] The tool 100 further comprises a radiofrequency (RF) power source 124 that is electrically connected to the showerhead 110. The RF power source 124 is configured to form a plasma in the processing chamber 104 using a gas mixture. The tool 100 further comprises a matching network 126 for impedance matching of the RF power source 124. The RF power source 124 can be configured to provide radio frequency energy of any suitable frequency and power. Examples frequencies include 400 kHz, 13.56 MHz, 27 MHz, 60 MHz, and 90 MHz. In some examples, the RF power source 124 is configured to operate at a plurality of different frequencies and / or powers. For example, the RF power source 124 can output a low-frequency RF energy component and a high-frequency RF energy component to from a plasma in the processing chamber 104. Examples of frequencies for the low-frequency RF energy component can include frequencies of 3 MHz and below. In other examples, a tool may omit an RF power source and matching network, or more than one RF power source and matching network may be used.

[0060] The tool 100 further comprises a controller 128 configured to control operation of the tool 100. The controller 128 is operatively coupled to the ESC 106, the substrate heater 107, the flow control hardware 118, the exhaust system 122, and the RF power source 124. The controller 128 is configured to control various functions of the tool 100 to perform processing, such as deposition and / or etching.Docket No. LRC24303PPCT

[0061] In some implementations, the controller 128 is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processing equipment, including a substrate processing tool or tools (e.g. tool 100), chamber or chambers, a platform or platforms for processing, and / or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller 128, depending on the processing requirements and / or the type of system, may be programmed to control any of the processes disclosed herein, including substrate clamping, as well as the delivery of processing gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, RF generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and / or load locks connected to or interfaced with a specific system.

[0062] Broadly speaking, the controller 128 may be defined as electronics having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system.

[0063] The controller, in some implementations, may be a part of or coupled to a computer that is integrated with, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to followDocket No. LRC24303PPCT a current processing, or to start a new process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and / or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus as described above, the controller 128 may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

[0064] Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and / or manufacturing of semiconductor wafers.

[0065] As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and / or load ports in a semiconductor manufacturing factory.

[0066] As discussed above, the plurality of contact features 114 of the ESC 106 have structural features that promote consistent radial clamping force (and / or azimuthal clamping force) across the surface of the substrate 102. The structural features can helpDocket No. LRC24303PPCT to reduce burrs, scratches, and other defects from being formed on the backside of the substrate 102 when the ESC 106 clamps the substrate 102 during processing performed by the tool 100. This is at least in part due to the structural features of the contact areas allowing the use of relatively lower clamping voltages than ESCs that lack contact areas with such structural features.

[0067] FIG. 2 shows an example ESC 200 including a plurality of contact features 202 having characteristics that promote consistent radial clamping force (and / or azimuthal clamping force) across a surface of a substrate. ESC 200 is an example of the ESC 106 of in FIG. 1. The plurality of contact features 202 are formed on, and part of, a substrate-facing surface 204. The plurality of contact features 202 are configured to support a substrate above surrounding regions of the substrate-facing surface 204. In some examples, the shape, location, and / or pattern of the contact features 202 may be configured to keep a predefined gap between the substrate and the substrate facing surface 204 of the ESC 200. In other examples, the gap between the substrate and the substrate facing surface 204 of the ESC 200 can vary across the surface of the substrate depending at least on the shape of the substrate (e.g., as can be the case with a substrate having a saddle shape). In the illustrated example, the contact features 202 are circular in shape. In other examples, the contact features can have a different shape, such as a prism and / or a truncated pyramid. Further in other examples, one or more contact features can have a different shape from one or more other contact features. The shape of the contact features here refers to an in-plane, cross-sectional shape of the contact features parallel to the substrate facing surface of the ESC.

[0068] The contact features 202 have contact area sizes that vary based at least on locations of the contact features 202 on the substrate-facing surface 204. The contact area of a contact feature 200 defines an area of a surface of the contact feature that contacts the substrate when the substrate is clamped to the ESC 200. In some examples, the contact area sizes of the contact features 202 on the substrate-facing surface 204 can vary based at least upon radial locations measured from a center point of the on the substrate-facing surface 204 of the ESC 200. In other examples, the contact area sizes of the contact features 202 on the substrate-facing surface 204 can vary based at least upon azimuthal locations measured in degrees from a reference point on the substratefacing surface 204 of the ESC 200. In yet other examples, the contact area sizes can vary based upon any other variance in location of the contact features 202.Docket No. LRC24303PPCT

[0069] In some implementations, the contact area sizes of the contact features 202 vary as a function of a clamping force profile for the substrate that defines a threshold clamping force to clamp a substrate to the contact features 202 (e.g., a minimum force to clamp any portion of a substrate to the ESC). In some examples, the clamping force profile can vary radially and / or azimuthally across the surface of the substrate. The clamping force profile for a substrate depends on various characteristics of the substrate including, but not limited to, a material of the substrate, a shape of the substrate, and bowing or other deformities present in the substrate. Accordingly, clamping force profiles for different substrates differ based at least on the characteristics of the different substrates. As more specific examples, substrates with dish-shaped bowing, dome-shaped bowing, and saddle-shaped bowing can have different clamping force profiles from a flat substrate and from one another that provide consistent radial clamping force across the particular surfaces of the particular types of substrates.

[0070] In the illustrated example, the contact area sizes of contact features 202 vary from region to region across the substrate-facing surface 204 of the ESC 200. In some examples, the contact area sizes of contact features 202 vary radially across the surface of the ESC. In other examples, the contact area sizes of contact features vary azimuthally across the surface of the ESC. In the illustrated example, the substratefacing surface 204 of the ESC 200 comprises a central region 206, an intermediate region 208, and an outer region 210. The intermediate region 208 is radially interposed between the central region 206 and the outer region 210. The contact area sizes of at least some contact features 202 in the intermediate region 208 are less than the contact area sizes of at least some contact features in the central region 206 and at least some contact features in the outer region 210.

[0071] Note that the illustrated central region 206, the intermediate region 208, and the outer region 210 are one example. In other examples, the central, intermediate, and outer regions can have different radial dimensions. In some examples, the radial dimensions of the different regions are assigned based at least on characteristics of the substrate (e.g., the shape of the substrate, the material of the substrate).

[0072] In the illustrated example, the variance in contact areas sizes of the contact features 202 in the central region 206, intermediate region 208 and outer region 210 is based at least on the clamping force profile for the substrate that the ESC 200 is configured to clamp. In the illustrated example, the clamping force profile correspondsDocket No. LRC24303PPCT to a substrate having a dish type bow, caused by a stack of layers formed on the front surface of the substrate (e.g., a substrate used to form memory can have a dish type bow). In other examples, contact areas sizes of contact features in different regions vary differently according to a different clamping force profile for a substrate having a different type of bow (e.g. dome-shaped or saddle-shaped).

[0073] In some examples, fill ratios of the contact features 202 vary from region to region radially across the substrate-facing surface 204 of the ESC 200. A fill ratio is a ratio of contact areas of contact features 202 relative to a total surface area of the substrate-facing surface 204. The fill ratio can be defined in terms of the total substratefacing surface 204 or in terms of individual regions (e.g. central region 206, intermediate region 208 and outer region 210) on the substrate-facing surface 204. In the illustrated example, the fill ratio in the intermediate region 208 is less than the fill ratio in the central region 206 and the fill ratio in the outer region 210.

[0074] Such variance in fill ratios between the central region 206, intermediate region 208 and outer region 210 is based at least on the clamping force profile for the substrate that the ESC 200 is configured to clamp. In the illustrated example, the clamping force profile corresponds to a substrate having a concave / dish type bow, such as a substrate on which a stack of layers is formed (e.g., a substrate used to form memory). In other examples, fill ratios in the central region 206, intermediate region 208 and outer region 210 vary differently according to a different clamping force profile for a substrate having different characteristics (e.g., having a different type of bow other than convex / dome type bow).

[0075] The fill ratio of the ESC may be set to any suitable value to promote consistent radial clamping force (and / or azimuthal clamping force) across the surface of the substrate being clamped by the ESC. Furthermore, the fill ratios within the individual regions on the substrate-facing surface of the ESC may vary within any suitable range of values to promote consistent localized clamping force within the different regions. In one example, the fill ratios may vary between regions within a range of .01% - 100%.

[0076] More generally, one or more of contact area sizes of contact features, contact area shapes of contact features, or fill ratios of contact features can vary based at least on locations of the contact features. Further, an ESC can include one or more coatings that are positioned between the substrate-facing surface of the ESC and a substrate being processed. Such coating(s) can be used to tailor an impedance of theDocket No. LRC24303PPCTESC, to protect the ESC from processing chemistries, and / or to perform other functions. Some coatings can be permanent, while other coatings can be applied before processing runs and removed in chamber cleaning processes. The coating(s) may include various materials, such as oxides, nitrides, metals, carbon-based materials, etc. Thus, in some examples, one or more of contact area sizes of contact features, contact area shapes of contact features, or fill ratios of contact features can be varied based upon a coating applied to (including a coating not yet applied but intended to be applied to) the substrate-facing surface of the ESC.

[0077] In some examples, the plurality of contact features may be distributed across the substrate-facing surface of the ESC in a spiral pattern. The use of a spiral pattern of contact features can help to promote more consistent radial clamping force (and / or azimuthal clamping force) across the surface of the substrate being clamped by the ESC than the radial clamping force of an ESC having a uniform contact area pattern. The spiral pattern of contact features causes radial distances between contact features to vary across the substrate-facing surface of the ESC in a manner that increases localized contact between the substrate and the plurality of contact features relative to an ESC in which contact features are evenly distributed (e.g., in a grid or hexagon pattern). In some examples, the spiral pattern is tuned to provide consistent radial clamping force for a particular type of substrate that may have a particular type of bowing.

[0078] In the illustrated example, the plurality of contact features 202 are distributed across the substrate-facing surface 204 in a Vogel spiral pattern that promotes localized contact and consistent radial clamping force between the contact features 202 and the substrate.

[0079] In other examples, the plurality of contact features may be distributed across the substrate-facing surface of the ESC according to a different spiral pattern. FIG. 3 shows another example ESC 300 including a plurality of contact features 302 arranged in a Fibonacci spiral pattern on a substrate-facing surface 304 of the ESC 300. For example, the ESC 300 may correspond to the ESC 106 shown in FIG. 1. In this example, each contact feature of the plurality of contact features 302 have the same contact area size. Even without the contact area sizes of the contact features 302 varying by location, the arrangement of the contact features 302 in the Fibonacci spiral pattern still can improve localized contact between the contact features 302 and a substrateDocket No. LRC24303PPCT being clamped to the ESC 300 relative to an ESC in which contact features are evenly distributed.

[0080] In other examples, contact area sizes of the contact features 302 arranged in the Fibonacci spiral pattern can vary based at least on locations of the contact features 302 on the surface 304 of the substrate-facing surface 306 of the ESC 300. For example, the contact area sizes of the contact features 302 can vary in a manner similar to the contact features 202 of the ESC 200 shown in FIG. 2. In other examples, the contact area sizes of the contact features 302 can vary in a different manner.

[0081] The plurality of contact features can be distributed across the substratefacing surface of the ESC according to any suitable spiral pattern. In still other examples, the plurality of contact features may be distributed in a golden spiral pattern or a logarithmic spiral pattern, among other types of spiral patterns.

[0082] FIGS. 4-5 show a comparison of localized contact between contact features of an ESC with evenly, and non-spirally, distributed contact features and a substrate (FIG. 4), and localized contact between contact features of an ESC according to the disclosed examples and a substrate (FIG. 5).

[0083] More particularly, FIG. 4 shows a portion of an ESC 400 including a plurality of contact features 402 arranged in a hexagonal pattern. In the hexagonal pattern, spacing between the contact features 402 does not vary across the surface of the ESC, such that each contact feature is spaced apart from each neighboring contact feature by the same distance. Additionally, the plurality of contact features 402 each have the same sized contact area. An arc 404 represents a portion of an edge (or other location) of a substrate contacting the contact features. Here, the arc 404 contacts with four contact features 402-1, 402-2, 402-3, 402-4 unevenly along the length of the arc 404. Such inconsistent localized contact between the contact features 402 and the arc 404 can result in inconsistent radial clamping force provided by the ESC 400. This example of uneven contact between the contact features 402-1, 402-2, 402-3, 402-4 and the arc 404 can be extrapolated to other positions across the surface of the ESC 400, such that the same or similar uneven contact occurs across the surface of the ESC 400. The uneven contact provided by the ESC 400 causes regions of localized underclamping and over-clamping of a substrate clamped by the ESC 400 as shown in FIG. 6 and described below.

[0084] Note that the arc 404 is just one example of a portion of the surface of the substrate that is supported by the contact features 402 of the ESC 400. OtherDocket No. LRC24303PPCT portions of the surface of the substrate may contact the contact features 402 of the ESC 400 in the same or similar manner as the arc 404 such that there would be inconsistent localized contact between those portions of the surface of the substrate and the contact features 402 of the ESC 400. In examples where the substrate is bowed (e.g., dome, dish, or saddle type bowing), the contact between the surface of the substrate and the contact features 402 of the ESC 400 may be even more inconsistent due to the surface of the substrate being non-parallel with the ESC 400 as a result of the bowing.

[0085] FIG. 5 shows a portion of an ESC 500 including a plurality of contact features 502 arranged in a spiral pattern. In the spiral pattern, spacing between the contact features 502 varies across the surface of the ESC 500. For example, the ESC 500 shown in FIG. 5 may correspond to the ESC 200 shown in FIG. 2. Additionally, the contact area sizes of the plurality of contact features 502 vary based at least on locations of the contact features on the surface of the ESC 500. An arc 504 representing an edge (or other portion) of a substrate contacts double the number of contact features relative to the ESC 400 shown in FIG. 5. In particular, contact features 502-1, 502-2, 502-3, 502-4, 502-5, 502-6 contact the arc 504. This example of contact between the contact features 502-1, 502-2, 502-3, 502-4, 502-5, 502-6 and the arc 504 can be extrapolated to other positions across the surface of the ESC 500. Such increased (or more consistent) localized contact between the contact features 502 and the arc 504 result in more consistent radial clamping force provided by the ESC 500 relative to the ESC 400 shown in FIG. 4.

[0086] Note that the arc 504 is just one example of a portion of the surface of the substrate that is supported by the contact features 502 of the ESC 500. Other portions of the surface of the substrate may contact the contact features 502 of the ESC 500 in the same or similar manner as the arc 504 such that the localized contact between those portions of the surface of the substrate and the contact features 502 of the ESC 500 would be more consistent than that of the substrate 400 shown in FIG. 4.

[0087] FIGS. 6-7 show a comparison of radial clamping force provided by the ESC 400 shown in FIG. 4 and by the ESCs 200 and 500 shown in FIG. 2 and 5.

[0088] More particularly, FIG. 6 shows a graph 600 including a plot 602 of a clamping force profile for a substrate with dish-shaped bowing as compared to a plot 604 of actual radial clamping force applied by the ESC 400 shown in FIG. 4 to the substrate with dish-shaped bowing. The graph 600 plots force vs radius with X = 0 on the X-axis corresponding to a center of the substrate and moving radially outwardDocket No. LRC24303PPCT across the substrate as X increases along the X-axis until the end of the plots 602, 604 corresponding to an edge of the substrate. The clamping force profile for the substrate defines the above-mentioned threshold clamping force to clamp the substrate to an ESC. For example, the threshold clamping force represented by the plot 602 can be an ideal clamping force for the substrate with a dish-shaped bow to be clamped to an ESC. As shown in the graph 600, the radial clamping force provided by the ESC 400 (plot 604) varies radially relative to the clamping force profile for the substrate (plot 602). Such inconsistent radial clamping force applied by the ESC 400 (shown in FIG. 4) creates regions of the substrate that are either under-clamped or over-clamped as indicated by the difference between the “ideal” plot 602 and the “actual” plot 604. In particular, a first under-clamping region 606-1 is located approximate to the center of the substrate and a second under-clamping region 606-2 is located radially near the edge of the substrate. These regions of the substrate that are under-clamped can lead to inconsistent processing of the substrate that can result in poor thermal conductivity between the substrate and the ESC, variations in etch rates, deposition thickness, and / or other process parameters of processes performed on the substrate, shifting or moving of the substrate relative to the ESC during processing, possibility of electrical discharge or arcing, forming of gaps between the substrate and the ESC where particles or contaminants can accumulate, and various other issues.

[0089] Further, a first over-clamping region 608-1 is located radially between the first and second under clamping regions 606-1, 606-2 and a second over-clamping region 608-2 is located radially at the edge of the substrate. These regions of the substrate that are over-clamped relatively strongly to avoid other areas being underclamped can pose a larger risk of defects (e.g., scratches, burrs) in the backside of the substrate compared to the use of over-clamping less strongly.

[0090] FIG. 7 shows a graph 700 including the plot 602 of the clamping force profile for the substrate with dish-shaped bowing as compared to a plot 702 of actual radial clamping force applied by the ESCs 200 and 500 shown in FIGS. 2 and 5 to the substrate with dish-shaped bowing. The ESC 200 will be referred to hereinbelow as providing consistent radial clamping force to the substrate with dish-shaped bowing as shown by the plot 702. It will be understood that the ESC 500 is configured to provide the same or similar consistent radial clamping force to the substrate with the dishshaped bowing and the concepts described herein are correspondingly applicable to the ESC 500. The radial clamping force provided by the ESC 200 (plot 702) is consistentDocket No. LRC24303PPCT relative to the clamping force profile for the substrate (plot 602) across the radius of the substrate. Such consistent radial clamping force applied by the ESC 200 creates no under-clamping regions, in this example. Further, the consistent radial clamping force applied by the ESC 200 shown in FIG. 2 creates a nominal over-clamping region 704, in this example, with no regions having as strong of over-clamping as region 608-1 and 608-2 of FIG. 6, for example. The radial clamping force applied by the ESC 200 can be adjusted to substantially match the clamping force profile for the substrate by adjusting a voltage applied to the ESC 200 in order to reduce or eliminate the over-clamping region 704. This adjustment is made possible by the consistent radial clamping force applied by the arrangement of the clamping features on ESC 200 across the substrate in accordance with the clamping force profile of the substrate. In addition, the spiral pattern of the contact features on the ESC 200 provide such consistent radial clamping force across the surface of the substrate that the number and / or severity of backside defects and other issues created as a result of clamping the substrate with the ESC 200 shown in FIG. 2 can be reduced relative to the localized under-clamping and overclamping caused by the ESC 400 shown in FIG. 4 that lacks contact features having contact area sizes that vary based at least on locations of the contact features on the surface of the ESC (as shown in FIG. 2) and / or contact features arranged in a spiral pattern on the surface of the ESC (as shown in FIG. 3).

[0091] It will be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific examples or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and / or described may be performed in the sequence illustrated and / or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed.

[0092] The subject matter of the present disclosure includes all novel and non- obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

Docket No. LRC24303PPCTCLAIMS:

1. An electrostatic chuck, comprising: a substrate-facing surface comprising a plurality of contact features configured to support a substrate, wherein contact area sizes of at least some contact features of the plurality of contact features vary based at least on locations of the contact features on the substrate-facing surface.

2. The electrostatic chuck of claim 1, wherein the substrate-facing surface comprises a first region, a second region, and a third region, wherein the contact area sizes of at least some contact features in the first region are less than the contact area sizes of at least some contact features in the second region and at least some contact features in the third region.

3. The electrostatic chuck of claim 2, wherein fill ratios of contact areas of the contact features relative to total surface areas in the first region, the second region, and the third region vary.

4. The electrostatic chuck of claim 3, wherein the fill ratios of the contact features in the first region, the second region, and the third region vary within a range of .01% - 100%.

5. The electrostatic chuck of claim 1, wherein the plurality of contact features are distributed across the substrate-facing surface in a spiral pattern.

6. The electrostatic chuck of claim 5, wherein the spiral pattern comprises a Vogel spiral pattern.

7. The electrostatic chuck of claim 5, wherein the spiral pattern comprises one or more of a logarithmic spiral pattern, a golden spiral pattern, or a Fibonacci spiral pattern.

8. The electrostatic chuck of claim 1, wherein the contact area sizes of the plurality of contact features vary as a function of a clamping force profile that defines a threshold clamping force to clamp the substrate to the plurality of contact features.Docket No. LRC24303PPCT9. A substrate processing tool, comprising: a processing chamber; and an electrostatic chuck positioned within the processing chamber, the electrostatic chuck including a substrate-facing surface comprising a plurality of contact features configured to support a substrate, wherein contact area sizes of at least some contact features of the plurality of contact features vary based at least on locations of the contact features on the substrate-facing surface.

10. The tool of claim 9, wherein the substrate-facing surface comprises a first region, a second region, and a third region, and wherein the contact area sizes of at least some contact features in the first region are less than the contact area sizes of at least some contact features in the second region and at least some contact features in the third region.

11. The tool of claim 10, wherein fill ratios of contact areas of the contact features relative to total surface areas in the first region, the second region, and the third region vary.

12. The tool of claim 9, wherein the plurality of contact features are distributed across the substrate-facing surface in a spiral pattern.

13. The tool of claim 12, wherein the spiral pattern comprises a Vogel spiral pattern.

14. The tool of claim 12, wherein the spiral pattern comprises one or more of a logarithmic spiral pattern, a golden spiral pattern or a Fibonacci spiral pattern.

15. The tool of claim 9, wherein the contact area sizes of the plurality of contact features vary as a function of a clamping force profile that defines a threshold clamping force to clamp the substrate of a given shape and magnitude to the plurality of contact features.Docket No. LRC24303PPCT16. An electrostatic chuck for clamping a substrate, the electrostatic chuck comprising: a substrate-facing surface comprising a plurality of contact features protruding from the substrate-facing surface and configured to support the substrate, wherein the plurality of contact features are distributed across the substrate-facing surface in a spiral pattern.

17. The electrostatic chuck of claim 16, wherein the spiral pattern comprises one or more of a Vogel spiral pattern, a logarithmic spiral pattern, a golden spiral pattern, or a Fibonacci spiral pattern.

18. The electrostatic chuck of claim 16, wherein one or more of contact area sizes of contact features, contact area shapes of contact features, or fill ratios of contact features, vary based at least on one or more of locations of the contact features on the substrate-facing surface, or a coating applied to the substrate facing surface of the ESC.

19. The electrostatic chuck of claim 18, wherein the substrate-facing surface comprises a first region, a second region, and a third region, and wherein the contact area sizes of at least some contact features in the first region are less than the contact area sizes of at least some contact features in the second region and at least some contact features in the third region.

20. The electrostatic chuck of claim 18, wherein fill ratios of contact areas of the contact features relative to total surface areas in the first region, the second region, and the third region vary.

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