Cleaning portions of lithographic apparatus

Abstract

Removal of contaminating particles from a jig of a lithographic apparatus is described. The used clamp has a burs top that is contaminated by contamination particles that need to be cleared prior to return to the service. Currently, in order to completely clean the top of the burs of such clamps, the hard and electrically conductive coating covering the top of the burs is peeled off and a fresh coating is applied. This entails disconnecting the clamp from the chuck, peeling off various coatings from non-burst regions of the clamp, and removing high voltage connections. Thereafter, the high voltage connection is reconstructed and the various coatings are re-applied, and then the jig is qualified. Finally, the clamp is reconnected to the chuck, and the manufacturing can be continued. A new cleaning method enables cleaning of the top of the burs without having to disconnect the clamp or remove the cap to perform a top refresh of the burs, which saves hours or weeks of downtime.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Application No. 63 / 423,927, filed Nov. 9, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present description generally relates to methods and systems for cleaning portions of a lithographic apparatus. Background Art

[0004] A lithographic (e.g., projection) apparatus can be used, for example, to manufacture integrated circuits (ICs). In such a case, a patterning device (e.g., a mask) can contain or provide a pattern corresponding to an individual layer (“design layout”) of the IC, and the pattern can be transferred to a target portion (e.g., including one or more dies) on a substrate (e.g., a silicon wafer) of a layer that has been coated with a radiation-sensitive material (“resist”) by methods such as irradiating the target portion through the pattern on the patterning device. Typically, a single substrate contains multiple adjacent target portions, and the pattern is transferred to these target portions sequentially by the lithographic projection apparatus, one target portion at a time. In one type of lithographic projection apparatus, the pattern over the entire patterning device is transferred to one target portion in a single operation. Such a device is commonly referred to as a stepper. In an alternative device (commonly referred to as a stepper-scanner), the projection beam scans the patterning device along a reference direction while synchronously moving the substrate parallel or antiparallel to a given reference direction (“scan direction”). Different portions of the pattern on the patterning device are transferred stepwise to one target portion. Summary of the Invention

[0005] Removing contaminant particles from the chuck of a lithographic apparatus is described. The top of the chuck protrusion is typically coated with a hard and conductive ceramic, such as TiN or CrN. Typically, a used chuck has protrusions or the top of the protrusions contaminated with contaminant particles that need to be removed before it can be returned to service. The contamination can bind very firmly to the coating on the top of the protrusion and cannot be removed by simple mechanical action. One way to clean the top of the protrusion completely is to strip the hard and conductive coating and apply a fresh such coating. This requires disconnecting the chuck from its chuck plate, removing various coatings from the non-protrusion area of the chuck, and removing the high-voltage connection. Thereafter, the high-voltage connection is re-established and a cover is added, various coatings are reapplied, and then the chuck is qualified. Finally, the chuck is reconnected to the chuck plate and manufacturing can continue.

[0006] Advantageously, the novel cleaning method(s) and system(s) described below can clean the top of the node without disconnecting the chuck from its fixture or removing the high-voltage connection to perform top node refresh, saving several hours of lithography tool downtime and / or having other advantages. Compared with existing methods, the method and system can better eliminate particle contamination from the fixture; require less cleaning time; do not require disconnecting the chuck or disassembling the lithography tool; prevent potential damage to the fixture due to improper operation of other cleaning devices; and have other advantages.

[0007] According to one embodiment, a method for cleaning an object support of a lithography apparatus is provided. The method includes applying a chemical cleaning agent to the surface of the object support to release contaminant particles from the surface. The method includes causing relative movement between a cleaning tool and the surface to remove contaminant particles from the surface. The method further includes applying an organic liquid to the surface to remove the chemical cleaning agent from the surface.

[0008] In some embodiments, the method further includes generating pre-cleaning image data of the surface, the pre-cleaning image data of the surface confirming the presence and / or one or more types of contaminant particles. The image data includes one or more images from a microscopic examination of the surface.

[0009] In some embodiments, the method further includes determining an initial flatness of the surface before cleaning to confirm the presence of contaminant particles and the need for removal. In some embodiments, the initial flatness is determined using high-voltage phase measuring interferometry.

[0010] In some embodiments, the method further includes determining a pre-cleaning contaminant particle distribution map for the surface. In some embodiments, the contaminant particle distribution map is determined using microscopic examination. In some embodiments, the contaminant particle distribution map is determined using white light interferometry.

[0011] In some embodiments, the method further includes determining whether to apply the chemical cleaning agent to the surface and / or where on the surface to apply the chemical cleaning agent, causing relative movement between the cleaning tool and the surface, and / or applying the organic liquid, based on the image data of the surface, the flatness of the surface, and / or the contaminant particle distribution on the surface.

[0012] In some embodiments, the method further includes performing post-cleaning uniform ion beam milling on the surface. In some embodiments, the contaminant particles have been completely removed or reduced in size to a small enough size such that uniform ion beam milling can then remove the contaminant particles.

[0013] In some embodiments, the method further includes determining a post - cleaning contamination particle distribution map for the surface and comparing the post - cleaning contamination particle distribution map with a pre - cleaning contamination particle distribution map for the surface to confirm that the method used for cleaning has successfully removed most or all of the contamination particles from the surface. In some embodiments, the post - cleaning contamination particle distribution map is determined using white - light interferometry.

[0014] In some embodiments, the method further includes determining the post - cleaning flatness of the surface and comparing the post - cleaning flatness with the pre - cleaning initial flatness of the surface to confirm that the method used for cleaning has successfully removed most or all of the contamination particles from the surface. In some embodiments, the post - cleaning flatness is determined using high - voltage phase - measuring interferometry.

[0015] In some embodiments, in response to the post - cleaning flatness breaching a flatness threshold, the method further includes performing ion - beam milling on the surface to bring the post - cleaning flatness within the flatness specification.

[0016] In some embodiments, the surface includes a top of a bump or a portion of the top of a bump.

[0017] In some embodiments, the chemical cleaning agent includes potassium hydroxide for tantalum contamination particles, a chromium etchant for chromium contamination particles, or a combination thereof.

[0018] In some embodiments, the cleaning tool is a glass puck. In some embodiments, the relative movement includes lateral movement, serpentine movement, circular movement, or a combination thereof.

[0019] In some embodiments, the object support is a chuck.

[0020] In some embodiments, cleaning includes planarizing and / or removing contamination particles.

[0021] In some embodiments, applying the chemical cleaning agent, causing the relative movement, and applying the organic liquid are performed when the chuck is coupled to the chuck of the lithography apparatus. In some embodiments, applying the chemical cleaning agent, causing the relative movement, and applying the organic liquid are performed when the chuck is disconnected from the chuck of the lithography apparatus. In some embodiments, the object support and the lithography apparatus are associated with semiconductor manufacturing.

[0022] According to another embodiment, there is provided a system for cleaning an object support of a lithography apparatus, including: a chemical cleaning agent configured to be applied to the surface of the object support to release contamination particles from the surface; a cleaning tool configured to be caused to move relative to the surface to remove contamination particles from the surface; and an organic liquid configured to be applied to the surface to remove the chemical cleaning agent from the surface.

[0023] According to another embodiment, a system for cleaning a mask holder of a lithographic apparatus is provided, comprising: a chemical cleaning agent configured to be applied to the surface of the mask holder to release contaminant particles from the surface; a cleaning tool configured to be caused to move relative to the surface to remove contaminant particles from the surface; and an organic liquid configured to be applied to the surface to remove the chemical cleaning agent from the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings incorporated in and forming a part of this specification illustrate one or more embodiments and, together with the description, illustrate such embodiments. Embodiments of the invention will now be described, by way of example only, with reference to the drawings, in which corresponding reference numerals indicate corresponding parts, and in which:

[0025] Figure 1 A lithographic apparatus is schematically depicted according to one embodiment.

[0026] Figure 2 An embodiment of a lithography cell or cluster is schematically depicted according to one embodiment.

[0027] Figure 3A A part of an extreme ultraviolet (EUV) lithographic apparatus is shown according to one embodiment.

[0028] Figure 3B A part of a deep ultraviolet (DUV) lithographic apparatus is shown according to one embodiment.

[0029] Figure 3C is according to one embodiment Figure 3B An enlarged view of a part of the lithographic apparatus shown.

[0030] Figure 4 An example of contaminant particles on a mask holder is shown according to one embodiment.

[0031] Figure 5 A method for cleaning a fixture of a lithographic apparatus is shown according to one embodiment.

[0032] Figure 6 A high-voltage phase measurement interferometric flatness measurement of a fixture surface is shown according to one embodiment.

[0033] Figure 7 A white light interferogram of the contaminant particle distribution across a bump surface is shown according to one embodiment.

[0034] Figure 8Shows a chemical cleaning agent applied to the surface of a reticle chuck (e.g., the top of one or more protrusions) according to an embodiment to release contaminant particles from the surface (too small to be visible in this figure).

[0035] Figure 9 Shows a second white light interferogram according to an embodiment, but for Figure 7 the post - cleaning contaminant particle distribution across the same protrusion surface and chuck shown in

[0036] Figure 10 Shows white light interferometer inspection data and scanning electron microscope inspection data for the cleaned surface (e.g., the top of the protrusion) of the chuck from the previous figure according to an embodiment.

[0037] Figure 11 Shows another white light interferogram of the contaminant particle distribution across the protrusion surface after ion beam milling (and after cleaning) according to an embodiment.

[0038] Figure 12 Shows relatively low - magnification and high - magnification images of the chuck surface (in this case, the top of the protrusion) at various stages of the cleaning method described in Figure 5 according to an embodiment.

[0039] Figure 13 Is a flowchart for a supplier to refurbish a contaminated chuck surface according to an embodiment (including the operations of the cleaning method described in Figure 5 )

[0040] Figure 14 Is a block diagram of an example computer system according to an embodiment. Detailed Description

[0041] Typically, a mask or reticle can be a block of transparent material that is covered with a pattern defined by different opaque materials. Alternatively, a mask or reticle can be a block of opaque material that is coated with, for example, a patterned mirror. Various masks are fed into a lithography apparatus and are used to form layers of a semiconductor device. The pattern defined on a given mask or reticle corresponds to features created in one or more layers of the semiconductor device. Typically, multiple masks or reticles are automatically fed into the lithography apparatus during manufacturing and are used to form corresponding layers of the semiconductor device. A fixture (e.g., an electrostatic reticle fixture) in the lithography apparatus is used to protect the mask or reticle during processing. The fixture can become contaminated with material particles (lateral dimensions of about 1 - 3 μm and height > 25 nm) transferred from the reticle, causing performance degradation over time and requiring periodic cleaning to restore performance. These contaminating particles can cause performance to degrade over time and, for example, provide nucleation sites for further contamination growth and / or cause other process issues.

[0042] Cleaning these fixtures may require stopping the lithography apparatus and the manufacturing process. Such cleaning can take hours or weeks to complete, may introduce other contaminants into the system, and / or have other drawbacks. Used fixtures typically have surfaces (such as the top of the tines) contaminated with contaminating particles that need to be removed before the fixture can be returned to service. The top of the fixture tines is typically coated with a hard and conductive ceramic such as TiN or CrN. The contamination can bond very firmly to the tine top coating and cannot be removed by simple mechanical action.

[0043] To fully clean the top of the tines of such a fixture, the hard and conductive coating covering the tine top is stripped and a fresh coating is applied. This requires disconnecting the fixture from the chuck, stripping various coatings from the non-tine areas of the fixture, stripping the hard and conductive coating, and removing the high-voltage connections. Thereafter, the high-voltage connections are re-established and a cover is added, various coatings (including the coating on the tine top) are reapplied, and then the fixture is qualified for resuming manufacturing use. Finally, the fixture is reconnected to the chuck and manufacturing can continue.

[0044] Disconnecting the chuck from the fixture poses an inherent risk of damaging the fixture and / or the chuck. Disconnection also affects the flatness of the fixture, such that flat-top operations for the entire cycle are required, which increases the time required for fixture cleaning. High-voltage connections are sealed by attaching other hardware (such as glass) using structural epoxy. The structural epoxy is strong enough that when removed, the underlying barrier is typically damaged. Severe barrier damage around the high-voltage connection can render the fixture unusable. Regarding stripping the hard and conductive coating, the structures created in the surface (such as glass) of the bump for assisting in clamping may not match the pattern in the hard and conductive coating. For example, when the original coating is stripped, it typically leaves an imprint of the initial coating pattern. When a fresh coating is applied, registration issues may occur, and the fresh coating may already have a non-optimal structure prior to construction. This can affect the roughness of the fixture and generally requires structural mapping, which further increases the cleaning cycle time.

[0045] In contrast, the present system and method provide a new cleaning technique that enables cleaning of the top of the bump and / or other surfaces without disconnecting the fixture or removing high-voltage connections to perform top bump refresh. Using the present cleaning method and system to clean the chuck of a lithographic apparatus can also save hours or weeks of downtime associated with prior inspection and cleaning methods, avoid damaging the fixture due to improper operation of manual cleaning devices, and / or have other advantages.

[0046] Although the present description may specifically refer to the manufacture of integrated circuits (ICs), it should be understood that the description herein also has many other possible applications. For example, it can be used in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal display panels, thin film magnetic heads, etc. Those skilled in the art should understand that in the context of these alternative applications, any use of the terms "reticle", "die", or "chip" herein should be considered as interchangeable with the more general terms "mask", "substrate", and "target portion", respectively. Additionally, any use of the term "reticle" or "mask" herein can be considered synonymous with the more general term "patterning device".

[0047] As an introduction, before transferring a pattern from a patterning device (such as a mask) to a substrate, the substrate may need to undergo various processes, such as priming, photoresist coating, and soft baking. After exposure, the substrate may need to undergo other processes (“post-exposure processes”), such as post-exposure bake (PEB), development, hard bake, and measurement and / or other inspections of the transferred pattern. This series of processes is used as the basis for manufacturing a single layer of a device (such as an IC). Subsequently, the substrate may undergo various processes, such as etching, ion implantation (doping), metallization, oxidation, chemical mechanical polishing, etc., all of which are aimed at completing a single layer of the device. If several layers are required in the device, the whole process or its variant is repeated for each layer. Eventually, the devices will appear in each target part on the substrate. Then, these devices are separated from each other by techniques such as cutting or sawing, so that individual devices can be mounted on carriers, connected to pins, etc.

[0048] Manufacturing devices (such as semiconductor devices) generally involve processing a substrate (such as a semiconductor wafer) using a variety of manufacturing processes to form various features and multiple layers of the device. These layers and features are typically fabricated and processed using, for example, deposition, lithography, etching, chemical mechanical polishing, ion implantation, and / or other processes. Multiple devices can be fabricated on multiple die on a substrate and then separated into individual devices. The device manufacturing process can be regarded as a patterning process. The patterning process involves patterning steps, such as optical and / or nanoimprint lithography using a patterning device in a lithographic apparatus to transfer the pattern on the patterning device to the substrate, and typically (but optionally) involves one or more related pattern processing steps, such as resist development by a developing device, baking the substrate using a baking tool, etching using a pattern by an etching device, etc. One or more metrology processes are typically involved in the patterning process.

[0049] Lithography is a step in manufacturing devices (such as ICs) where the pattern formed on the substrate defines the functional elements of the device, such as microprocessors, memory chips, etc. Similar lithography techniques are also used in the formation of flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0050] As semiconductor manufacturing processes continue to evolve, the size of functional elements has been continuously reduced, while the number of functional elements of a device (such as transistors) has increased steadily over the past few decades, following a trend commonly known as “Moore's Law”. In the current state of the technology, the layers of a device are fabricated using a lithographic projection apparatus that projects a design layout onto a substrate using illumination from a deep ultraviolet light source, creating individual functional elements with dimensions far below 100 nm (i.e., smaller than half the wavelength of the radiation from the light source (e.g., a 193 nm light source)).

[0051] The process in which features having dimensions smaller than the classical resolution limit of a lithographic projection apparatus are printed is generally referred to as low-k1 lithography. According to the resolution formula CD = k1 × λ / NA, where λ is the wavelength of the radiation used (currently most commonly 248 nm or 193 nm in most cases), NA is the numerical aperture of the projection optics in the lithographic projection apparatus, CD is the "critical dimension" - typically the smallest feature size printed - and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it is to reproduce on a substrate a pattern similar in shape and size to that planned by a designer to achieve a specific electrical function and performance. To overcome these difficulties, complex fine-tuning steps are applied to the lithographic projection apparatus, the design layout, or the patterning device. These include, but are not limited to, for example, optimization of NA and optical coherence settings, customized illumination schemes, use of phase-shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as "optical and process correction") in the design layout, overlay measurement, or other methods generally defined as "resolution enhancement techniques" (RET).

[0052] As used herein, the term "projection optics" should be understood broadly to encompass various types of optical elements, such as including refractive optical elements, reflective optical elements, apertures, and catadioptric optical elements. The term "projection optics" can also include components operating according to any of these design types for collectively or singly directing, shaping, or controlling the projection beam of radiation. The term "projection optics" can include any optical component in a lithographic projection apparatus, regardless of where the optical component is located on the optical path of the lithographic projection apparatus. The projection optics can include optical components for shaping, adjusting, and / or projecting the radiation from the source before the radiation passes through the patterning device, and / or for shaping, adjusting, and / or projecting the radiation after the radiation passes through the patterning device. The projection optics generally do not include the source and the patterning device.

[0053] Figure 1An embodiment of a lithographic apparatus LA that can be included in and / or associated with the present system and / or method is schematically depicted. The apparatus includes: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a support structure (e.g., a mask table) MT configured to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device according to certain parameters; a substrate table (e.g., a wafer table) WT (e.g., WTa, WTb, or both) configured to support a substrate (e.g., a wafer coated with resist) W and coupled to a second positioner PW configured to accurately position the substrate according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., including one or more dies and commonly referred to as a field) of the substrate W. The projection system is supported by a reference frame (RF). As shown, the apparatus is of the transmissive type (e.g., using a transmissive mask). Alternatively, the apparatus can also be of the reflective type (e.g., using a programmable mirror array of the type described above, or using a reflective mask).

[0054] The illuminator IL receives the radiation beam from a radiation source SO. For example, when the source is an excimer laser, the source and the lithographic apparatus can be separate entities. In such a case, the radiation source is not considered to form part of the lithographic apparatus, and the radiation beam is transferred from the radiation source SO to the illuminator IL by means of a beam delivery system BD, which, for example, includes suitable directing mirrors and / or beam expanders. In other cases, for example, when the source is a mercury lamp, the source can be an integral part of the apparatus. The source SO, the illuminator IL, and, if necessary, the beam delivery system BD together can be referred to as the radiation system.

[0055] The illuminator IL can vary the intensity distribution of the beam. The illuminator can be arranged to limit the radial extent of the radiation beam such that the intensity distribution is non-zero within an annular region in the pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL can be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in the pupil plane of the illuminator IL can be referred to as the illumination mode.

[0056] The illuminator IL may include a regulator AD configured to regulate the (angular / spatial) intensity distribution of the beam. Generally, at least the outer radial extent and / or the inner radial extent of the intensity distribution in the pupil plane of the illuminator (commonly referred to as σ - outer and σ - inner, respectively) can be adjusted. The illuminator IL may be operable to change the angular distribution of the beam. For example, the illuminator may be operable to change the number and angular extent of the sectors in the pupil plane where the intensity distribution is non - zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different illumination patterns can be achieved. For example, by restricting the radial and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution can have a multipole distribution, such as, for example, a dipole distribution, a quadrupole distribution, or a hexapole distribution. The desired illumination pattern can be obtained, for example, by inserting an optical element in the illuminator IL that provides that illumination pattern or by using a spatial light modulator.

[0057] The illuminator IL may be operable to change the polarization of the beam and may be operable to adjust the polarization using the regulator AD. The polarization state of the radiation beam on the pupil plane of the illuminator IL may be referred to as the polarization pattern. Using different polarization patterns can allow for higher contrast in the image formed on the substrate W. The radiation beam may be unpolarized. Alternatively, the illuminator may be arranged to linearly polarize the radiation beam. The polarization direction of the radiation beam may vary across the pupil plane of the illuminator IL. The polarization direction of the radiation may be different in different regions of the pupil plane of the illuminator IL. The polarization state of the radiation may be selected depending on the illumination pattern. For a multipole illumination pattern, the polarization of each pole of the radiation beam may be substantially perpendicular to the position vector of that pole in the pupil plane of the illuminator IL. For example, for a dipole illumination pattern, the radiation may be linearly polarized in a direction substantially perpendicular to the line bisecting the two opposite sectors of the dipole. The radiation beam may be polarized in one of two different orthogonal directions, which may be referred to as the X - polarization state and the Y - polarization state. For a quadrupole illumination pattern, the radiation in each sector of each pole may be linearly polarized in a direction substantially perpendicular to the line bisecting that sector. This polarization pattern may be referred to as XY polarization. Similarly, for a hexapole illumination pattern, the radiation in each sector of each pole may be linearly polarized in a direction substantially perpendicular to the line bisecting that sector. This polarization pattern may be referred to as TE polarization.

[0058] In addition, the illuminator IL typically includes various other components, such as an integrator IN and a condenser CO. The illumination system may include various types of optical components, such as refractive optical components, reflective optical components, magnetic optical components, electromagnetic optical components, electrostatic optical components, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation. Thus, the illuminator provides a conditioned radiation beam B that has a desired uniformity and intensity distribution across its cross-section.

[0059] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether the patterning device is held in a vacuum environment. The support structure can hold the patterning device using mechanical clamping techniques, vacuum clamping techniques, electrostatic clamping techniques, or other clamping techniques. The support structure can be, for example, a frame or a table, which can be fixed or movable as required. The support structure can ensure that the patterning device is in a desired position relative to the projection system, for example.

[0060] The term "patterning device" as used herein should be broadly understood to mean any device that can be used to impart a pattern in a target portion of a substrate. In one embodiment, the patterning device is any device that can be used to impart a pattern to a radiation beam in a cross-section of the radiation beam to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so-called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer being created in the target portion of the device, such as an integrated circuit.

[0061] The patterning device can be transmissive or reflective. Examples of patterning devices include masks or reticles, programmable mirror arrays, and programmable LCD panels. Masks or reticles are well known in lithography and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array is a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in a different direction. The tilted mirrors impart a pattern in the radiation beam that is reflected by the mirror matrix.

[0062] The term "projection system" as used herein should be construed broadly to cover any type of projection system, including refractive optical systems, reflective optical systems, catadioptric optical systems, magnetic optical systems, electro-magnetic optical systems, and electro-static optical systems, or any combination thereof, depending on the exposure radiation used or other factors such as the use of an immersion liquid or the use of a vacuum. Any use herein of the term "projection lens" may be considered synonymous with the more general term "projection system".

[0063] The projection system PS has an optical transfer function, which may be non-uniform and which affects the pattern imaged on the substrate W. For non-polarized radiation, such effects can be well described by two scalar maps that describe the transmission (apodization) and relative phase (aberration) of the radiation leaving the projection system PS as a function of its position in the pupil plane. These scalar maps (which may be referred to as the transmission map and the relative phase map) can be represented as a linear combination of a complete set of basis functions. A convenient set is the Zernike polynomials, which form a set of orthogonal polynomials defined on the unit circle. The determination of each scalar map may involve determining the coefficients in such an expansion. Since the Zernike polynomials are orthogonal on the unit circle, the Zernike coefficients can be determined by successively calculating the inner product of the measured scalar map with each Zernike polynomial and dividing it by the square of the norm of that Zernike polynomial.

[0064] The transmission map and the relative phase map are field and system dependent. That is, in general, each projection system PS will have a different Zernike expansion for each field point (i.e., each spatial position in its image plane). The relative phase in the pupil plane of the projection system PS can be determined by projecting radiation from a point source, for example, in the object plane (i.e., the plane of the patterning device MA) of the projection system PS through the projection system PS and measuring the wavefront (i.e., the locus of points having the same phase) using a shearing interferometer. A shearing interferometer is a common-path interferometer and thus, advantageously, no secondary reference beam is required to measure the wavefront. The shearing interferometer may include a diffraction grating (e.g., a two-dimensional grid) located in the image plane of the projection system (i.e., the substrate table WTa or WTb) and a detector arranged to detect the interference pattern in a plane conjugate to the pupil plane of the projection system PS. The interference pattern is related to the derivative of the phase of the radiation with respect to the coordinates in the pupil plane in the shearing direction. The detector may include an array of sensing elements, such as, for example, a charge-coupled device (CCD).

[0065] The projection system PS of a lithographic apparatus may not produce visible fringes, and thus the accuracy of the determination of the wavefront can be enhanced using phase stepping techniques such as, for example, moving a diffraction grating. The stepping can be performed in the plane of the diffraction grating and in a direction perpendicular to the direction of measurement scanning. The stepping range can be one grating period, and at least three (evenly distributed) phase steps can be used. Thus, for example, three scan measurements can be performed in the y direction, each scan measurement being performed for a different position in the x direction. This stepping of the diffraction grating effectively converts the phase change into an intensity change, allowing the phase information to be determined. The grating can be stepped in a direction perpendicular to the diffraction grating (the z direction) to calibrate the detector.

[0066] The diffraction grating can be scanned sequentially in two perpendicular directions, which two perpendicular directions can coincide with the axes (x and y) of the coordinate system of the projection system PS, or can be at an angle to these axes, such as 45 degrees. The scanning can be performed within an integer number of grating periods (for example, one grating period). The scanning averages the phase change in one direction, allowing the phase change in the other direction to be reconstructed. This allows the wavefront to be determined as a function of two directions.

[0067] The transmission (apodization) of the projection system PS in its pupil plane can be determined by, for example, projecting radiation from a point source in the object plane of the projection system PS (i.e., the plane of the patterning device MA) through the projection system PS and measuring the intensity of the radiation in a plane conjugate to the pupil plane of the projection system PS using a detector. The same detector as is used to measure the wavefront to determine the aberration can be used.

[0068] The projection system PS may include a plurality of optical (e.g., lens) elements and may also include an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase variations in the pupil plane across the field). To achieve this, the adjustment mechanism may be operable to manipulate one or more of the optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system in which its optical axis extends along the z-direction. The adjustment mechanism may be operable to perform any combination of the following: displacing one or more of the optical elements; tilting one or more of the optical elements; and / or deforming one or more of the optical elements. The displacement of the optical element may be in any direction (x, y, z, or a combination thereof). The tilting of the optical element is typically by rotation about an axis in the x-direction and / or the y-direction out of a plane perpendicular to the optical axis, although rotation about the z-axis may be used for non-rotationally symmetric aspherical optical elements. The deformation of the optical element may include low-frequency shapes (e.g., astigmatism) and / or high-frequency shapes (e.g., freeform aspheres). The deformation of the optical element may be performed by, for example, applying forces on one or more sides of the optical element using one or more actuators and / or heating one or more selected regions of the optical element using one or more heating elements. Typically, it may not be possible to adjust the projection system PS to correct for apodization (transmission variations in the pupil plane). When designing the patterning device (e.g., mask) MA for a lithographic apparatus LA, the transmission map of the projection system PS may be used. Using computational lithography techniques, the patterning device MA may be designed to at least partially correct for apodization.

[0069] The lithographic apparatus may be of the type having two (dual-stage) or more stages (e.g., two or more substrate stages WTa, WTb, two or more patterning device stages, one substrate stage WTa and one stage WTb located below the projection system without a substrate dedicated for, e.g., facilitating measurement and / or cleaning, etc.). In such a “multi-stage” machine, the additional stages may be used in parallel, or preparation steps may be performed on one or more stages while one or more other stages are being used for exposure. For example, alignment measurements using an alignment sensor AS and / or leveling (height, tilt, etc.) measurements using a leveling sensor LS may be carried out.

[0070] The lithographic apparatus may also be of the type in which at least a portion of the substrate may be covered with a liquid having a relatively high refractive index (e.g., water) to fill the space between the projection system and the substrate. The immersion liquid may also be applied to other spaces in the lithographic apparatus, such as between the patterning device and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of the projection system. As used herein, the term “immersion” does not mean that a structure (such as a substrate) must be immersed in a liquid, but only that the liquid is located between the projection system and the substrate during exposure.

[0071] In the operation of a lithographic apparatus, a radiation beam is conditioned and provided by an illumination system IL. The radiation beam B is incident on a patterning device (e.g., a mask) MA which is held on a support structure (e.g., a mask table) MT. After passing through the patterning device MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of a substrate W. By means of a second positioning device PW and a position sensor IF (e.g., an interferometric device, a linear encoder, a 2-D (two-dimensional) encoder or a capacitive sensor), the substrate table WT can be moved precisely, e.g., to position different target portions C in the path of the radiation beam B. Similarly, a first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1 it) can be used to precisely position the patterning device MA relative to the path of the radiation beam B, e.g., after mechanical retrieval from a mask library or during a scan. In general, the movement of the support structure MT can be realized by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) which form part of the first positioning device PM. Similarly, the movement of the substrate table WT can also be realized using a long-stroke module and a short-stroke module which form part of the second positioning device PW. In the case of a stepper (as opposed to a scanner), the support structure MT can be connected only to a short-stroke actuator or can be fixed. The patterning device MA and the substrate W can be aligned using patterning device alignment marks M1, patterning device alignment marks M2 and substrate alignment marks P1, substrate alignment marks P2. Although the substrate alignment marks as shown in the figure occupy dedicated target portions, they can be located in the spaces between the target portions (these spaces are called scribe alignment marks). Similarly, in the case where more than one die is provided on the patterning device MA, the patterning device alignment marks can be located between the dies.

[0072] The apparatus depicted can be used in at least one of the following modes: 1. In the step mode, the support structure MT and the substrate table WT remain substantially stationary while the pattern imparted to the radiation beam is projected onto the target portion C in one go (i.e., single static exposure). Then, the substrate table WT is offset in the X direction and / or Y direction such that different target portions C can be exposed. In the step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. 2. In the scan mode, the support structure MT and the substrate table WT are scanned synchronously while the pattern imparted to the radiation beam is projected onto the target portion C (i.e., single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure MT can be determined by the (reduction) magnification and image inversion characteristics of the projection system PS. In the scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, while the length of the scanning movement determines the height (in the scanning direction) of the target portion. 3. In another mode, the support structure MT remains substantially stationary, supporting the programmable patterning device, and the substrate table WT is moved or scanned while the pattern imparted to the radiation beam is projected onto the target portion C. In this mode, a pulsed radiation source is typically employed, and the programmable patterning device is updated as needed after each movement of the substrate table WT or between consecutive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography techniques that utilize programmable patterning devices (such as programmable mirror arrays of the type described above). Combinations and / or variations of the above-described usage modes or completely different usage modes can also be employed.

[0073] The substrate can be processed before or after exposure, for example, in a track (a tool that typically applies a layer of resist to the substrate and develops the resist after exposure) or a metrology or inspection tool. Where applicable, the disclosure herein can be applied to such substrate processing tools as well as other substrate processing tools. Additionally, the substrate can be processed more than once, for example, to create a multi-layer IC, such that the term "substrate" as used herein can also refer to a substrate that already includes multiple processed layers.

[0074] The terms "radiation" and "beam" as used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g., having wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having wavelengths in the range of 5 - 20 nm), as well as particle beams, such as ion beams or electron beams.

[0075] The various patterns on or provided by a patterning device may have different process windows, i.e., the space of process variables within which the pattern will be produced within specifications. Examples of pattern specifications related to potential systematic defects include inspection necking, line pullback, line slimming, critical dimension (CD), edge placement, overlay, resist top loss, resist undercut, and / or bridging. The process window on or for a region of a patterning device can be obtained by combining (e.g., overlapping) the process windows of each individual pattern. The boundaries of the process window of a set of patterns include the boundaries of the process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the set of patterns. These patterns may be referred to as "hot spots" or "process window limiting patterns (PWLP)", which are used interchangeably herein. When controlling a part of the patterning process, it is possible and cost-effective to focus on the hot spots. When the hot spots are defect-free, it is likely that the other patterns are also defect-free.

[0076] As Figure 2 shown, a lithographic apparatus LA can form part of a lithographic cell LC (sometimes also referred to as a lithocell or cluster), which also includes means for performing pre-exposure and post-exposure processes on a substrate. Conventionally, these include one or more spin coaters SC for depositing one or more resist layers, one or more developers for developing the exposed resist, one or more chill plates CH, and / or one or more bake plates BK. A substrate handler or robot RO picks up one or more substrates from input / output ports I / O1, input / output ports I / O2, moves them between different process means, and delivers them to the load port LB of the lithographic apparatus. These means (which are generally collectively referred to as the track) are controlled by a track control unit TCU, which in turn is controlled by a monitoring system SCS, which also controls the lithographic apparatus via a lithography control unit LACU. Thus, the different means can be operated to maximize throughput and processing efficiency.

[0077] For a substrate to be exposed by a lithographic apparatus to be exposed correctly and consistently and / or for monitoring parts of a patterning process (e.g., a device manufacturing process) including at least one pattern transfer step (e.g., an optical lithography step), it is necessary to inspect the substrate or other objects to measure or determine one or more properties such as alignment, overlay (overlay can be, for example, between structures in an overlying layer or between structures that have been provided to the layer separately, e.g., by a double patterning process, in the same layer), line thickness, critical dimension (CD), focus offset, material properties, etc. For example, contamination on a mask clamping film (e.g., as described herein) can adversely affect overlay because clamping a mask on such contamination will deform the mask. Thus, a manufacturing facility in which a lithography cell LC is located typically also includes a metrology system that measures parts or all of a substrate W that has been processed in the lithography cell ( Figure 1 ) or other objects in the lithography cell. The metrology system can be part of the lithography cell LC, for example it can be part of a lithographic apparatus LA (such as an alignment sensor AS ( Figure 1 ).

[0078] One or more measured parameters can include, for example, alignment, overlay between consecutive layers formed in or on a patterned substrate, critical dimension (CD) (e.g., critical line width) of features formed in or on a patterned substrate, focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberration of an optical lithography step, etc. The measurement can be performed on targets on the product substrate itself and / or on dedicated metrology targets provided on the substrate. The measurement can be performed after development of the resist but before etching, after etching, after deposition, and / or at other times.

[0079] There are various techniques for making measurements of structures formed in a patterning process, including using a scanning electron microscope, image-based measurement tools, and / or various dedicated tools. As described above, one fast and non-invasive form of dedicated metrology tool is a dedicated metrology tool in which a radiation beam is directed onto a target on the surface of a substrate and properties of the scattered (diffracted / reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. This can be referred to as diffraction-based metrology. One such application of this diffraction-based metrology is in the measurement of feature asymmetry within a target. For example, this can be used as a measurement of overlay, but other applications are also known. For example, asymmetry can be measured by comparing relative parts of a diffraction spectrum (e.g., comparing the -1st and +1st orders in the diffraction spectrum of a periodic grating). Another application of diffraction-based metrology is in the measurement of feature width (CD) within a target.

[0080] Thus, in device manufacturing processes (e.g., patterning processes, lithography processes, etc.), substrates or other objects may be subject to various types of measurements during or after the process. The measurements can determine whether a particular substrate is defective, can be used to adjust the process and the devices used in the process (e.g., align two layers on a substrate or align a patterning device to a substrate), can measure the performance of the process and the devices, or can be used for other purposes. Examples of measurements include optical imaging (e.g., optical microscopy), non-imaging optical measurements (e.g., diffraction-based measurements such as the ASML YieldStar metrology tool, the ASML SMASH metrology system), mechanical measurements (e.g., profilometry using a stylus, atomic force microscopy (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)).

[0081] The metrology results can be provided directly or indirectly to the monitoring system SCS. If an error is detected, the adjustment can be made to the subsequent exposure of the substrate (especially if the inspection can be done immediately and fast enough such that one or more other substrates in the batch will still be exposed) and / or to the subsequent exposure of the already exposed substrate. Additionally, the already exposed substrate can be stripped and reworked to improve the yield, or discarded, thus avoiding further processing of known defective substrates. In the case where only some target portions of the substrate are defective, further exposure can be performed only on those target portions that meet the specifications.

[0082] Within the metrology system, metrology devices are used to determine one or more properties of the substrate, and in particular how one or more properties vary between different substrates, or how one or more properties of different layers of the same substrate vary between the layers. As described above, the metrology devices can be integrated into the lithography apparatus LA or the lithography cell LC, or can be stand-alone devices.

[0083] To enable metrology, one or more targets can be provided on the substrate. In one embodiment, the targets are specially designed and can include periodic structures. In one embodiment, the targets are part of the device pattern, e.g., the periodic structures of the device pattern. In one embodiment, the device pattern is the periodic structure of a memory device (e.g., structures such as bipolar transistors (BPT), bit line contacts (BLC), etc.).

[0084] In one embodiment, the targets on the substrate can include one or more 1-D (one-dimensional) periodic structures (e.g., gratings), which are printed such that after development, these periodic structure features are formed by solid resist lines. In one embodiment, the targets can include one or more 2-D periodic structures (e.g., gratings), which are printed such that after development, one or more periodic structures are formed by solid resist pillars or vias in the resist. These bars, pillars, or vias can alternatively be etched into the substrate (e.g., into one or more layers on the substrate).

[0085] In one embodiment, one of the parameters of interest in the patterning process is overlay. Overlay can be measured using dark-field scattering methods, where the zero-order diffraction (corresponding to specular reflection) is blocked and only higher-order diffractions are processed. Diffraction-based overlay using dark-field detection of diffraction orders enables overlay measurements on smaller targets. These targets can be smaller than the illumination spot and can be surrounded by device product structures on the substrate. In one embodiment, multiple targets can be measured in a single radiation capture.

[0086] As lithography nodes continue to shrink, increasingly complex wafer designs can be realized. Various tools and / or techniques can be used by designers to ensure that complex designs are accurately transferred to the physical wafer. These tools and techniques can include mask optimization, source mask optimization (SMO), OPC, design for control, and / or other tools and / or techniques. For example, a source mask optimization process is described in U.S. Patent No. 9,588,438 (entitled "Optimization Flows of Source, Mask and Projection Optics"), which is hereby incorporated by reference in its entirety.

[0087] The present system and / or method can be used as a stand-alone tool and / or technique, and / or in combination with semiconductor manufacturing processes, to enhance the accurate transfer of complex designs to the physical wafer.

[0088] As described above, the present cleaning system is configured to be used for cleaning the chuck of a lithography apparatus. By way of non-limiting example, Figure 3A , Figure 3B and Figure 3C show an example part of a lithography apparatus 300 (e.g., similar or identical to the lithography apparatus shown in Figure 1 ). Figure 3A Shows a part of an extreme ultraviolet (EUV) lithography apparatus. Figure 3B Shows a part of a deep ultraviolet (DUV) lithography apparatus. Figure 3C is according to one embodimentFigure 3B An enlarged view of a part of the lithographic apparatus shown in

[0089] Figure 3A Exemplary lithographic apparatus components near the chuck 312 of the lithographic apparatus 300 are shown, including tool processors 306, 307, 308, and / or other components. The lithographic apparatus 300 may include an EUV in-pod (EIP) 305, a rapid exchange device (RED), and / or other components. In some embodiments, the lithographic apparatus 300 is capable of being configured for deep ultraviolet (DUV) lithography using one or more adjustments shown in Figure 3A One or more of those shown are configured for deep ultraviolet (DUV) lithography. Figure 3B An exemplary DUV apparatus (e.g., having the chuck 312 of the lithographic apparatus 300 in these figures) and the various components of the lithographic apparatus 300 are shown, including tool processors 306, 307, 308, a reticle chuck 310, (a) reticle fixture(s) 312, and / or other components.

[0090] In some embodiments, tool processors 306, 307, 308 include a reticle processor turntable gripper 306, a reticle processor robot gripper 307 (having associated components 308 for gripping the reticle during transfer), and / or other components. The reticle processor robot gripper 307 may, for example, remove the reticle from the pod 320 (e.g., after the user places the reticle in the pod 320). The reticle processor turntable gripper 306 may, for example, move the reticle from the reticle processor robot gripper 307 to (a) reticle fixture(s) 312. The lithographic apparatus 300 may include various other mechanical components 322 (translation mechanisms, lift mechanisms, rotation mechanisms, motors, power generation and transmission components, structural components, etc.), which are configured to facilitate the movement and control of the reticle 302 through the lithographic apparatus 300. For example, the lithographic apparatus 300 may include an EUV in-pod (EIP), and a rapid exchange device (RED), and / or other components.

[0091] The present system and method are configured to be used to clean (a) fixture(s) 312 (e.g., (a) reticle fixture(s)) of the lithographic apparatus 300. In other embodiments, the present system and method described herein can be configured to clean any object support of the lithographic apparatus. The object support can include any fixture (e.g., a vacuum fixture or an electrostatic fixture) or support structure in the lithographic apparatus, including but not limited to a reticle (also referred to as a mask) fixture, a wafer (also referred to as a substrate) fixture, and a wafer stage. Figure 3C Is an enlarged view of a part of the apparatus 300.

[0092] Figure 3Cshows a reticle 302, a reticle handler turret chuck 306, a reticle chuck 310, reticle clamp(s) 312, a mechanical assembly 322, a reticle handler robot chuck 307, and / or other components. As Figure 3C shown, the reticle handler turret chuck 306 is configured to move the reticle 302 from the reticle handler robot chuck 307 to the reticle clamp(s) 312. Moving the reticle 302 can include moving the reticle 302 toward or away from the clamp(s) 312 in horizontal, vertical, and / or other directions. The reticle handler turret chuck 306 and / or the reticle handler robot chuck 307 can include various motors, translators, rotary assemblies, clamps, clips, power supplies, power transfer components, vacuum mechanisms, and / or other components that facilitate movement of the reticle 302.

[0093] Contaminant particles (such as nodules) on the clamp contact surface typically accumulate and grow larger over time on the clamp surface, and thus need to be cleaned regularly. The contaminant particles typically range in lateral dimension from about 2 to 5 μm and have a height (or thickness from the surface of the nodule of the clamp) up to about 100 to 200 nm. As the number of particles increases and the size of the contaminant particles grows, performance degradation such as overlay drift and / or other problems may occur. For example, within a relatively short time period (e.g., 1 to 3 months), the overlay can drift up to about 1 nm, and thus frequent cleaning is required because such drift is intolerable for semiconductor production. Accordingly, there is a desire for devices, systems, and methods for cleaning relevant parts of a lithographic apparatus (e.g., the clamp reticle and / or the wafer contact area).

[0094] Figure 4 shows an example of contaminant particles 400 on the reticle contact area 402 (e.g., the clamp surface) of a reticle clamp 404. In this example, the reticle contact area 402 (the clamp surface) is the nodule surface. The nodule surface can be wavy and / or have other shapes such that only certain portions of the nodule contact the reticle. Figure 4 View 410 shows white light interferometer data that shows contaminated nodules (in a circular distribution) on the clamp. For example, for embodiments with a wavy surface, the contamination may occur at the peaks of the nodule surface. View 412 shows relatively low magnification (e.g., 20 times (20X)) images of four different nodules. View 414 shows a higher magnification (e.g., 100 times) image, with a clean nodule shown on the left side of view 414 and a contaminated nodule shown on the right side of view 414. It should be noted that each nodule has a ridge surface or top that forms the reticle contact area 402.

[0095] Figure 5Method 500 for cleaning a chuck of a lithographic apparatus is shown. The chuck can be a chuck (e.g., an electrostatic chuck as described above) and / or other chuck / object support surface. Cleaning can include planarizing and / or removing contaminant particles from the chuck, and / or other operations. In some embodiments, one or more operations of method 500 can be controlled by one or more processors and / or computing systems, as described below (see Figure 14 ). Operations of method 500 (e.g., applying a chemical cleaner, causing relative movement, applying an organic liquid, and other operations described below) can be performed with the chuck coupled to or disconnected from the chuck of the lithographic apparatus. The operations of method 500 introduced below are illustrative. In some embodiments, method 500 can be completed with one or more additional operations not described and / or without one or more of the operations discussed. Additionally, Figure 5 the order of the operations of method 500 shown and described below is not intended to be limiting.

[0096] In some embodiments, one or more operations of method 500 can be implemented and / or controlled in one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information, as described below with respect to Figure 14 . The one or more processing devices can include one or more devices that execute some or all of the operations of method 500 in response to electronically stored instructions on an electronic storage medium. The one or more processing devices can include one or more devices configured by hardware, firmware, and / or software that are specifically designed to perform one or more operations of method 500 (e.g., see the discussion below with respect to Figure 14 ). For example, one or more processing devices can run software that is configured to form a mosaic of images of one or more chuck surfaces, control the performance of an initial planarization measurement, facilitate determination of an initial particle distribution map, use ion beam scribing to control uniform hits, facilitate determination of a final particle distribution map and / or compare the final particle distribution map with the initial particle distribution map, control the performance of a final planarization measurement, and / or perform other operations.

[0097] At operation 501, pre-clean image data of the surface of a fixture that confirms the presence of contaminant particles, confirms one or more types of contaminant particles, and / or confirms other information is generated. In some embodiments, the types of particles include tantalum contaminant particles, chromium contaminant particles, and / or other types of contaminant particles. In some embodiments, the surface includes a top of a bump or a portion of the top of a bump. In some embodiments, the image data includes one or more images from a microscopy of the surface. Two or more of these images can be (electronically) coupled or stitched together to form a mosaic of an image showing the surface of the top of the bump (or a portion thereof). For example, a microscopy magnification of 10 to 100 times can be employed in this inspection. The mosaic of the images can be analyzed to confirm the presence of contaminant particles, the type of contaminant particles, and / or other information.

[0098] At operation 502, the pre-clean initial flatness of the surface is determined. The pre-clean flatness is determined to, for example, confirm the presence of contaminant particles and the need for removal. In some embodiments, a computer system (such as Figure 14 the computer system shown in and described below) is configured to determine the pre-clean initial flatness of the surface to confirm the presence of contaminant particles and the need for removal. In some embodiments, the initial flatness is determined using high voltage phase measuring interferometry and / or other methods. In some embodiments, the computer system forms part of a high voltage phase measuring interferometer.

[0099] By way of non-limiting example, Figure 6 shows high voltage phase measuring interferometry flatness measurement data 600 for a fixture surface. Figure 6 Also shown is corresponding flatness measurement data 602 for the fixture surface obtained before the fixture was removed from service. The arrows show how the unevenness caused by the contamination deforms the surface of the clamped reticle such that the image projected from the reticle onto the wafer is misaligned. As can be seen from the variable shading colors in each dataset, the flatness of the fixture surface varies non-uniformly across the fixture surface.

[0100] Returning to Figure 5 , at operation 503, a pre-clean contaminant particle distribution map for the surface is determined. In some embodiments, the pre-clean contaminant particle distribution map is determined using microscopy. In some embodiments, the contaminant particle distribution map is determined using white light interferometry.

[0101] By way of non-limiting example, Figure 7 shows a white light interferogram 700 of the distribution of contaminant particles 702 across a bump surface 704. Figure 7Each point in is a knuckle surface 704 on the fixture, and the shading scale 710 plots the number of particles by the knuckle surface (in this example, the particle distribution matches the overlapping features for the fixture).

[0102] Returning to Figure 5 , at operation 504, a chemical cleaner is applied to the surface of the reticle fixture (e.g., one or more knuckle tops) to release contaminant particles from the surface. In some embodiments, the chemical cleaner includes potassium hydroxide for tantalum contaminant particles, a chromium etchant for chromium contaminant particles, or a combination thereof. The chemicals required to remove other particles (such as can be identified by techniques such as scanning electron microscopy / energy dispersive spectroscopy) are well known to those skilled in the art. The potassium hydroxide can be, for example, a 50% potassium hydroxide solution and / or other solutions.

[0103] By way of non-limiting example, Figure 8 illustrates a chemical cleaner 800 that is applied to the surface 802 of a reticle fixture 804 (e.g., one or more knuckle tops) to release contaminant particles (too small to be visible in this figure) from the surface 802. In this example, the chemical cleaner is a potassium hydroxide solution. The potassium hydroxide solution is selected for cleaning because in this example the contaminant particles are tantalum contaminant particles (e.g., determined based on operations 501, 502, and / or 503 as described above). The chemical cleaner 800 can be used in combination with a cleaning tool 850 (e.g., a mechanical cleaning tool such as a glass bead) to remove contaminant particles from the surface 802, and / or in combination with an organic liquid 852 applied to the surface 802 (e.g., for rinsing the surface 802) and to remove the chemical cleaner 800 from the surface 802, as described below.

[0104] Returning to Figure 5 , in some embodiments, operation 504 includes causing relative movement between the cleaning tool and the surface to remove contaminant particles from the surface. In some embodiments, the cleaning tool can be configured to move relative to the surface, the surface can be configured to move relative to the cleaning tool, or the cleaning tool and the surface can be configured to move relative to each other. In some embodiments, the cleaning tool is a glass bead or other similar cleaning tool. The cleaning tool can be any cleaning tool that is flat enough and not chemically reactive with the cleaning chemicals. The relative movement can include lateral movement, serpentine movement, circular movement, or a combination thereof. In some embodiments, the relative movement can be by a human operator, a mechanical actuator (e.g., as described below in Figure 14caused by a computer system such as the computer system shown and described herein and / or other devices. The relative motion is configured to remove contaminant particles from the chuck. For example, the range of the relative motion can be from at least about a few tenths of a micrometer (μm) to at least about 4 millimeters (mm). As another example, in the non-scanning direction of the lithographic apparatus, the range of the relative motion can be from at least about a few tenths of a micrometer (μm) to at least about 4 millimeters (mm), and in the scanning direction of the lithographic apparatus, the range of the relative motion can be up to at least about 2 mm. (However, if desired, for example, if the relative motion is caused by a human operator, these motions can be significantly larger).

[0105] In some embodiments, operation 504 includes receiving an input of and / or selecting a control command from a user via a user interface. The control command includes instructions for moving a cleaning tool based on an area of interest of the chuck of the lithographic apparatus (e.g., a surface such as the top of a bump), and / or other control commands.

[0106] In some embodiments, operation 504 includes determining whether to apply a chemical cleaning agent to the surface and / or where on the surface to apply the chemical cleaning agent, causing relative motion between the cleaning tool and the surface, applying an organic liquid (operation 505 described below), and / or performing other operations. One or more of these determinations can be made based on, for example, image data of the surface (see operation 501), flatness of the surface (see operation 502), distribution of contaminant particles on the surface (see operation 503), and / or other information. A computer system (such as Figure 14 the computer system shown herein and described below) can be configured to determine whether to apply a chemical cleaning agent to the surface and / or where on the surface to apply the chemical cleaning agent, where to cause relative motion between the cleaning tool and the surface, and / or where to apply the organic liquid based on image data of the surface, flatness of the surface, distribution of contaminant particles on the surface, and / or other information.

[0107] At operation 505, an organic liquid is applied to the surface. The organic liquid is applied to the surface and removes the chemical cleaning agent from the surface. In some embodiments, the organic liquid is alcohol (such as isopropyl alcohol) and / or other organic liquids. The organic liquid can be dried (e.g., using a drying tool such as a lint-free cloth, towel, hair dryer, etc.). In some embodiments, the organic liquid (such as isopropyl alcohol) can be configured to evaporate or otherwise dry relatively quickly to enhance operation 505.

[0108] At operation 506, post-cleaning uniform ion beam milling is performed on the surface. In some embodiments, contaminant particles have been completely removed from the surface or reduced in size to a small enough size such that uniform ion beam milling can then remove the contaminant particles.

[0109] In some embodiments, at operation 506, a post-clean contamination particle distribution map for the surface is determined. The post-clean contamination particle distribution map can be compared with the pre-clean contamination particle distribution map for the surface to confirm that method 500 for cleaning the surface has successfully removed most or all of the contamination particles from the surface. In some embodiments, the post-clean contamination particle distribution map is determined using white light interferometry and / or other detection techniques. In some embodiments, a computer system (such as Figure 14 the computer system shown and described below) can be configured to determine the post-clean contamination particle distribution map for the surface and compare the post-clean contamination particle distribution map with the pre-clean contamination particle distribution map for the surface to confirm that the method for cleaning has successfully removed most or all of the contamination particles from the surface.

[0110] At operation 507, the post-clean flatness of the surface is determined and the post-clean flatness is compared with the pre-clean initial flatness of the surface to confirm that the method for cleaning has successfully removed most or all of the contamination particles from the surface. The post-clean flatness can be determined, for example, using high voltage phase measuring interferometry. In response to the post-clean flatness breaching a flatness threshold (e.g., not being flat enough yet), method 500 and / or operation 507 also includes performing additional ion beam milling on the surface to bring the post-clean flatness within the flatness specification. In some embodiments, a computer system (such as Figure 14 the computer system shown and described below) can be configured to determine the post-clean flatness of the surface and compare the post-clean flatness with the pre-clean initial flatness of the surface to confirm that the method for cleaning has successfully removed most or all of the contamination particles from the surface.

[0111] By way of several more non-limiting examples, Figures 9 to 13 various examples of the above features are shown. Figure 9 A second white light interferogram 900 is shown, but shows the post-clean contamination particle 902 distribution on the same nodular surface 704 and fixture as shown in Figure 7 . Each point in Figure 9 again represents a nodular surface 704 on the fixture, and the shading scale 710 indicates the number of particles per nodular surface. As shown in Figure 9 , after cleaning with potassium hydroxide (see Figure 8 ), the contamination particle 902 distribution has changed relative to the contamination particle 702 distribution. It can be observed that the particles from the center of the fixture have been removed or have moved away from the center of the fixture towards the edge.

[0112] Figure 10Shows white light interferometry inspection data 1000 for a cleaned surface (e.g., the top of the bump) of the fixture from the previous figure, as well as scanning electron microscopy data 1002, scanning electron microscopy data 1004, and scanning electron microscopy data 1006. In some embodiments, other data such as energy dispersive X-ray spectroscopy data for the cleaned surface can be used. All of this data indicates that contaminant particles (e.g., tantalum oxide in this example) on the fixture surface have been removed by cleaning. For example, no contaminant particles are visible in the white light interferometry inspection data 1000 (e.g., an image of the top of the bump). The similarity and / or low contrast of the backscattered electron measurements in the scanning electron microscopy data 1002, scanning electron microscopy data 1004, and scanning electron microscopy data 1006 indicate a uniform top surface composition of the bump (no tantalum oxide contaminant particles). Similarly, energy dispersive X-ray spectroscopy data can be obtained to determine if there is a uniform top surface composition of the bump.

[0113] Figure 11 Shows another white light interferogram 1100 of the contaminant particle distribution across the bump surface after ion beam milling (and after cleaning) according to one embodiment. This other white light interferogram 1100 shows Figure 7 and Figure 9 the same bump surface 704 and the contaminant particle 1102 distribution on the fixture after cleaning and ion beam milling as shown. The ion beam milling can be performed, for example, by an ion beam milling system 1150. Figure 11 Each point in shows again a bump surface 704 on the fixture, and the shading scale 1110 indicates the number of particles per bump surface. As Figure 11 shown, after cleaning with potassium hydroxide (see Figure 8 ) and performing ion beam milling, the contaminant particle 1102 distribution has changed relative to the contaminant particle 702 and / or 902 distribution. It can be seen that the fixture is relatively clean with no particles 1102.

[0114] Figure 12 Shows Figure 5 relatively low magnification images 1200 and high magnification images 1202 of the fixture surface (the top of the bump in this example) at various stages of the cleaning method (e.g., method 500 as shown in Figure 5 ). These images can be obtained using a pre-clean imager 1250 and / or a post-clean imager 1250 (such as a microscope, white light interferometer, and / or other imager) (e.g., in the case where the imager 1250 is both the pre-clean imager 1250 and the post-clean imager 1250). Figure 12Shows the 1204 received fixture surface 1205, the 1206 surface 1205 after being cleaned by potassium hydroxide and a cleaning tool (e.g., Figure 5 as shown in and after operation 504 described above), the 1208 surface 1205 after being cleaned by an organic liquid (e.g., Figure 5 after operation 505 shown in), and the white light interferogram of the 1210 surface 1205 after being cleaned by ion beam milling. Figure 12 Shows how the contamination particles 1220 present on the 1204 received fixture surface 1205 are removed by these cleaning operations. For example, there are no particles 1220 after cleaning with potassium hydroxide and a cleaning tool 1206.

[0115] Figure 13 Is a flowchart 1300 of process 1302 for a supplier to refurbish a contaminated fixture surface (including the operations of the above-described cleaning method 500). Note that the process 1300 can also be performed or alternatively performed by the fixture owner and / or some other provider. The process 1300 begins when the fixture is returned 1304 to the supplier. A typical fixture can be returned 1304, for example, after approximately 1000 mask loading operations (e.g., as described above with respect to Figure 3A , Figure 3B and Figure 3C ). A determination 1306 is made as to whether the contaminated and / or damaged (e.g., nodule damage) fixture surface is repairable. If not repairable (''No'' at decision block 1307), the fixture is disconnected 1308 from the chuck, and the fixture is stripped and recoated 1310, which can take up to 15 weeks to complete. If repairable (''Yes'' at decision block 1307), a determination 1312 is made as to whether the fixture has been contaminated (e.g., contaminated with particles as described above). If not contaminated (''No'' at decision block 1313), the fixture remains in contact 1314 with the chuck, and low-usage repairs, cleaning, and / or other operations can be performed 1316 on the fixture and / or the fixture surface.

[0116] If the fixture is contaminated (Yes at decision block 1313), then a determination 1318 is made as to whether there is a sufficient amount (e.g., a thickness greater than about 150 nm) of a nodular top coating on the fixture surface. If so (Yes at decision block 1319), then a determination 1320 is made as to whether repair and / or cleaning 1350 can be performed without disconnecting the fixture from the chuck. If it can (Yes at decision block 1321), then the fixture remains in contact with the chuck 1322 and operations of the above-described method 500 (e.g., at least chemical cleaner and cleaning tool operation 504, and / or ion beam milling operation 506) are performed on the fixture surface. If repair and / or cleaning 1350 cannot be performed with the fixture in contact with the chuck (No at decision block 1321), then a determination 1324 is made as to whether repair and / or cleaning 1350 can be performed with the fixture disconnected from the chuck. If so (Yes at decision block 1325), then the fixture is disconnected from the chuck 1326, operations of the above-described method 500 (e.g., at least chemical cleaner and cleaning tool operation 504) are performed on the fixture surface, the fixture is re-contacted with the chuck 1328, and ion beam milling operation 507 is performed on the fixture surface.

[0117] Figure 14 FIG. is a block diagram of a computer system 1400 that can assist in implementing the methods, processes, or systems disclosed herein. The computer system 1400 may be included in and / or electrically coupled to the above-described lithographic apparatus LA ( Figure 1 , Figure 3A etc.). The computer system 1400 includes a bus 1402 or other communication mechanism for conveying information, and a processor 1404 (or multiple processors 1404, processor 1405, etc.) coupled to the bus 1402 for processing information. The computer system 1400 also includes a main memory 1406 coupled to the bus 1402, such as a random access memory (RAM) or other dynamic storage device, for storing information and instructions to be executed by the processor 1404. The main memory 1406 may also be used to store temporary variables or other intermediate information during execution of instructions to be executed by the processor 1404. The computer system 1400 also includes a read only memory (ROM) 1408 or other static storage device coupled to the bus 1402 for storing static information and instructions for the processor 1404. A storage device 1410 (such as a magnetic disk or optical disk) is provided and coupled to the bus 1402 for storing information and instructions.

[0118] The computer system 1400 can be coupled to a display 1412, such as a cathode ray tube (CRT) or a flat panel or touch panel display, via a bus 1402 for displaying information to a computer user. Input devices 1414 (including alphanumeric keys and other keys) are coupled to the bus 1402 for transmitting information and command selections to the processor 1404. Another type of user input device is a cursor control 1416, such as a mouse, trackball, or cursor direction keys, for transmitting direction information and command selections to the processor 1404 and for controlling the movement of a cursor on the display 1412. This input device typically has two degrees of freedom in two axes (i.e., a first axis (e.g., the x-axis) and a second axis (e.g., the y-axis)), which allows the device to specify a position in a plane. A touch panel (screen) display can also be used as an input device.

[0119] According to one embodiment, portions of one or more of the processes and / or methods described herein can be performed by the computer system 1400 in response to execution of one or more sequences of one or more instructions contained in the main memory 1406 by the processor 1404. Such instructions can be read into the main memory 1406 from another computer-readable medium, such as the storage device 1410. Execution of the sequences of instructions contained in the main memory 1406 causes the processor 1404 to perform the processes and / or processing steps described herein. One or more processors in a multiprocessing arrangement can also be employed to execute the sequences of instructions contained in the main memory 1406. In an alternative embodiment, hardwired circuitry can be used in place of or in combination with software instructions. Accordingly, the description herein is not limited to any specific combination of hardware circuitry and software.

[0120] As used herein, the term "computer-readable medium" or "machine-readable medium" refers to any medium that participates in providing instructions to the processor 1404 for execution. Such a medium can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as the storage device 1410. Volatile media includes dynamic memory, such as the main memory 1406. Transmission media includes coaxial cables, copper wire, and fiber optics, including the lines that comprise the bus 1402. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, floppy disks, flexible disks, hard disks, magnetic tape, any other magnetic medium, CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described below, or any other medium that can be read by a computer.

[0121] Computer-readable media of various forms may be involved in carrying one or more sequences of one or more instructions to the processor 1404 for execution. For example, these instructions may initially be carried on a magnetic disk of a remote computer. The remote computer may load the instructions into its dynamic memory and send the instructions over a network such as the Internet. A modem local to the computer system 1400 may receive the data and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to the bus 1402 may receive the data carried in the infrared signal and place the data on the bus 1402. The bus 1402 carries the data to the main memory 1406, and the processor 1404 fetches and executes the instructions from the main memory 1406. The instructions received by the main memory 1406 may optionally be stored on the storage device 1410 before or after being executed by the processor 1404.

[0122] The computer system 1400 may also include a communication interface 1418 coupled to the bus 1402. The communication interface 1418 provides a two-way data communication coupling to a network link 1420 connected to a local network 1422. For example, the communication interface 1418 may be an Integrated Services Digital Network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, the communication interface 1418 may be a Local Area Network (LAN) card to provide a data communication connection to a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface 1418 sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

[0123] The network link 1420 typically provides data communication to other data devices through one or more networks. For example, the network link 1420 may provide a connection through the local network 1422 to a main computer 1424 or to a data device operated by an Internet Service Provider (ISP) 1426. The ISP 1426 in turn provides data communication services through the global packet data communication network (now commonly referred to as the “Internet” 1428). Both the local network 1422 and the Internet 1428 use electrical, electromagnetic, or optical signals that carry digital data streams. Signals through various networks and signals on the network link 1420 and through the communication interface 1418, which carry digital data to or from the computer system 1400, are exemplary forms of carriers that convey information.

[0124] The computer system 1400 is capable of sending messages and receiving data (including program code) via one or more networks, network links 1420, and communication interface 1418. In an Internet example, server 1430 may send request code for an application via Internet 1428, ISP 1426, local network 1422, and communication interface 1418. For example, such a download application may provide all or part of the methods described herein. The received code may be executed by processor 1404 upon receipt thereof, and / or stored in storage device 1410 or other non-volatile memory for later execution. In this manner, the computer system 1400 may obtain application code in the form of a carrier wave.

[0125] Various embodiments of the present system and method are disclosed in the following numbered list of clauses:

[0126] 1. A method for cleaning an object support of a lithographic apparatus, comprising: applying a chemical cleaning agent to a surface of the object support to release contaminant particles from the surface; causing relative movement between a cleaning tool and the surface to remove the contaminant particles from the surface; and applying an organic liquid to the surface to remove the chemical cleaning agent from the surface.

[0127] 2. The method according to any one of the preceding clauses, further comprising: generating pre-cleaning image data of the surface, the pre-cleaning image data of the surface confirming the presence and / or one or more types of the contaminant particles.

[0128] 3. The method according to any one of the preceding clauses, wherein the image data comprises one or more images from a microscopy of the surface.

[0129] 4. The method according to any one of the preceding clauses, further comprising: determining an initial flatness of the surface before cleaning to confirm the presence of the contaminant particles and the need for removal.

[0130] 5. The method according to any one of the preceding clauses, wherein the initial flatness is determined using high voltage phase measuring interferometry.

[0131] 6. The method according to any one of the preceding clauses, further comprising: determining a pre-cleaning contaminant particle distribution map for the surface.

[0132] 7. The method according to any one of the preceding clauses, wherein the contaminant particle distribution map is determined using microscopy.

[0133] 8. The method according to any one of the preceding clauses, wherein the contaminant particle distribution map is determined using white light interferometry.

[0134] 9. The method according to any one of the preceding clauses further comprises: determining whether to apply the chemical cleaning agent on the surface and / or where to apply the chemical cleaning agent on the surface, causing the relative movement between the cleaning tool and the surface, and / or applying the organic liquid, based on the image data of the surface, the flatness of the surface, and / or the distribution of contaminant particles on the surface.

[0135] 10. The method according to any one of the preceding clauses further comprises: performing uniform ion beam grinding on the surface after cleaning.

[0136] 11. The method according to any one of the preceding clauses, wherein the contaminant particles have been completely removed or reduced in size to a small enough size such that the uniform ion beam grinding can then remove the contaminant particles.

[0137] 12. The method according to any one of the preceding clauses further comprises: determining a post - cleaning contaminant particle distribution map for the surface and comparing the post - cleaning contaminant particle distribution map with a pre - cleaning contaminant particle distribution map for the surface to confirm that the method used for cleaning has successfully removed most or all of the contaminant particles from the surface.

[0138] 13. The method according to any one of the preceding clauses, wherein the post - cleaning contaminant particle distribution map is determined using white light interferometry.

[0139] 14. The method according to any one of the preceding clauses further comprises: determining the post - cleaning flatness of the surface and comparing the post - cleaning flatness with the initial pre - cleaning flatness of the surface to confirm that the method used for cleaning has successfully removed most or all of the contaminant particles from the surface.

[0140] 15. The method according to any one of the preceding clauses, wherein the post - cleaning flatness is determined using high - voltage phase - measuring interferometry.

[0141] 16. The method according to any one of the preceding clauses, wherein in response to the post - cleaning flatness breaking through a flatness threshold, the method further comprises: performing ion beam grinding on the surface to bring the post - cleaning flatness within the flatness specification.

[0142] 17. The method according to any one of the preceding clauses, wherein the surface comprises a top of a nodule or a part of the top of a nodule.

[0143] 18. The method according to any one of the preceding clauses, wherein the chemical cleaning agent comprises potassium hydroxide for tantalum contamination particles, a chromium etchant for chromium contamination particles, or a combination thereof.

[0144] 19. The method according to any one of the preceding clauses, wherein the cleaning tool is a glass disk.

[0145] 20. The method according to any one of the preceding clauses, wherein the relative movement comprises lateral movement, serpentine movement, circular movement, or a combination thereof.

[0146] 21. The method according to any one of the preceding clauses, wherein the object support is a fixture.

[0147] 22. The method according to any one of the preceding clauses, wherein the cleaning comprises planarizing and / or removing the contamination particles.

[0148] 23. The method according to any one of the preceding clauses, wherein the application of the chemical cleaning agent, the causing of the relative movement, and the application of the organic liquid are performed with the fixture coupled to the chuck of the lithographic apparatus.

[0149] 24. The method according to any one of the preceding clauses, wherein the application of the chemical cleaning agent, the causing of the relative movement, and the application of the organic liquid are performed with the fixture disconnected from the chuck of the lithographic apparatus.

[0150] 25. The method according to any one of the preceding clauses, wherein the object support and the lithographic apparatus are associated with semiconductor manufacturing.

[0151] 26. A system for cleaning an object support of a lithographic apparatus, comprising: a chemical cleaning agent configured to be applied to a surface of the object support to release contamination particles from the surface; a cleaning tool configured to move relative to the surface to remove the contamination particles from the surface; and an organic liquid configured to be applied to the surface to remove the chemical cleaning agent from the surface.

[0152] 27. The system according to any one of the preceding clauses, further comprising a pre-clean imager configured to generate image data of the surface, the image data confirming the presence and / or one or more types of the contamination particles.

[0153] 28. The system according to any one of the preceding clauses, wherein the image data comprises one or more images from a microscopy examination of the surface.

[0154] 29. The system according to any one of the preceding clauses further includes a computer system configured to determine the initial flatness of the surface before cleaning to confirm the presence of the contaminant particles and the need for removal.

[0155] 30. The system according to any one of the preceding clauses, wherein the initial flatness is determined using high voltage phase measuring interferometry, and the computer system forms part of a high voltage phase measuring interferometer.

[0156] 31. The system according to any one of the preceding clauses further includes a microscope configured to determine a pre - cleaning contaminant particle distribution map for the surface.

[0157] 32. The system according to any one of the preceding clauses, wherein the contaminant particle distribution map is determined using microscopy.

[0158] 33. The system according to any one of the preceding clauses, wherein the contaminant particle distribution map is determined using white light interferometry and a white light interferometer.

[0159] 34. The system according to any one of the preceding clauses further includes a computer system configured to determine whether to apply the chemical cleaning agent to the surface and / or where to apply the chemical cleaning agent on the surface, where to cause the relative movement between the cleaning tool and the surface, and / or where to apply the organic liquid based on the image data of the surface, the flatness of the surface, and / or the distribution of contaminant particles on the surface.

[0160] 35. The system according to any one of the preceding clauses further includes an ion beam milling system configured to perform post - cleaning uniform ion beam milling on the surface.

[0161] 36. The system according to any one of the preceding clauses, wherein the contaminant particles have been completely removed or reduced in size to a small enough size such that the uniform ion beam milling can then remove the contaminant particles.

[0162] 37. The system according to any one of the preceding clauses further includes a computer system configured to determine a post - cleaning contaminant particle distribution map for the surface and compare the post - cleaning contaminant particle distribution map with the pre - cleaning contaminant particle distribution map for the surface to confirm that the method used for cleaning has successfully removed most or all of the contaminant particles from the surface.

[0163] 38. The system according to any one of the preceding clauses, wherein the post-clean contamination particle distribution map is determined using white light interferometry.

[0164] 39. The system according to any one of the preceding clauses, further comprising a computer system configured to determine the post-clean flatness of the surface and compare the post-clean flatness with the initial pre-clean flatness of the surface to confirm that the method used for cleaning has successfully removed most or all of the contamination particles from the surface.

[0165] 40. The system according to any one of the preceding clauses, wherein the post-clean flatness is determined using high voltage phase measuring interferometry.

[0166] 41. The system according to any one of the preceding clauses, wherein in response to the post-clean flatness breaking through a flatness threshold, ion beam milling is performed on the surface to bring the post-clean flatness within the flatness specification.

[0167] 42. The system according to any one of the preceding clauses, wherein the surface includes a top of a bump or a portion of the top of a bump.

[0168] 43. The system according to any one of the preceding clauses, wherein the chemical cleaning agent includes potassium hydroxide for tantalum contamination particles, a chromium etchant for chromium contamination particles, or a combination thereof.

[0169] 44. The system according to any one of the preceding clauses, wherein the cleaning tool is a glass disk.

[0170] 45. The system according to any one of the preceding clauses, wherein the relative movement includes lateral movement, serpentine movement, circular movement, or a combination thereof.

[0171] 46. The system according to any one of the preceding clauses, wherein the object support is a clamp.

[0172] 47. The system according to any one of the preceding clauses, wherein the cleaning includes flattening and / or removing the contamination particles.

[0173] 48. The system according to any one of the preceding clauses, wherein the application of the chemical cleaning agent, causing the relative movement, and the application of the organic liquid are performed with the clamp coupled to the chuck of the lithography apparatus.

[0174] 49. The system according to any one of the preceding clauses, wherein the application of the chemical cleaning agent, causing the relative movement, and the application of the organic liquid are performed with the clamp disconnected from the chuck of the lithography apparatus.

[0175] 50. A system according to any one of the preceding clauses, wherein the object support and the lithographic apparatus are associated with semiconductor manufacturing.

[0176] 51. A system for cleaning a mask holder of a lithographic apparatus, comprising: a chemical cleaning agent configured to be applied to a surface of the mask holder to release contaminant particles from the surface; a cleaning tool configured to move relative to the surface to remove the contaminant particles from the surface; and an organic liquid configured to be applied to the surface to remove the chemical cleaning agent from the surface.

[0177] The concepts disclosed herein can be associated with any general imaging system for imaging sub-wavelength features and can be particularly useful for emerging imaging technologies capable of generating increasingly shorter wavelengths. Emerging technologies already in use include EUV (extreme ultraviolet), DUV lithography, which can use an ArF laser to produce a 193 nm wavelength and even a fluorine laser to produce a 157 nm wavelength. Additionally, EUV lithography technology can generate wavelengths in the range of 20 to 5 nm by using a synchrotron or by bombarding a material (solid or plasma) with high-energy electrons in order to generate photons in that range.

[0178] While the concepts disclosed herein can be used to fabricate wafers on a substrate such as a silicon wafer, it should be understood that the concepts disclosed herein can be used in conjunction with any type of manufacturing system (e.g., a manufacturing system used to fabricate on a substrate other than a silicon wafer). Additionally, combinations and sub-combinations of the disclosed elements can include separate embodiments. For example, the cleaning system and / or method, and the associated lithographic apparatus can include separate embodiments, and / or these features can be used together in the same embodiment.

[0179] The foregoing description is intended to be illustrative and not restrictive. Accordingly, those skilled in the art will appreciate that modifications can be made as described without departing from the scope of the recited claims.

Claims

1. A method for cleaning an object support of a lithographic apparatus, comprising: applying a chemical cleaning agent to the surface of the object support to release contaminant particles from the surface; causing relative movement between a cleaning tool and the surface to remove the contaminant particles from the surface; and applying an organic liquid to the surface to remove the chemical cleaning agent from the surface.

2. The method according to claim 1, wherein applying the chemical cleaning agent, causing the relative movement, and applying the organic liquid are performed with the fixture coupled to the chuck of the lithographic apparatus or with the fixture disconnected from the chuck of the lithographic apparatus.

3. A system for cleaning an object support of a lithographic apparatus, comprising: a chemical cleaning agent configured to be applied to the surface of the object support to release contaminant particles from the surface; a cleaning tool configured to move relative to the surface to remove the contaminant particles from the surface; and an organic liquid configured to be applied to the surface to remove the chemical cleaning agent from the surface.

4. The system according to claim 3, further comprising a pre-clean imager configured to generate image data of the surface, the image data of the surface confirming the presence and / or one or more types of the contaminant particles, wherein the image data includes one or more images from microscopy of the surface.

5. The system according to claim 3, further comprising a computer system configured to determine an initial flatness of the surface before cleaning to confirm the presence of the contaminant particles and the need for removal, wherein the initial flatness is determined using a high voltage phase measuring interferometer and the computer system forms part of the high voltage phase measuring interferometer.

6. The system according to claim 3, further comprising a microscope configured to determine a pre-clean contaminant particle distribution map for the surface, wherein the contaminant particle distribution map is determined using microscopy.

7. The system according to claim 6, wherein the contaminant particle distribution map is further determined using white light interferometry and a white light interferometer.

8. The system according to claim 3, further comprising a computer system configured to determine, based on the image data of the surface, the flatness of the surface, and / or the contaminant particle distribution on the surface: whether to apply the chemical cleaning agent to the surface and / or where on the surface to apply the chemical cleaning agent; where to cause the relative movement between the cleaning tool and the surface; and / or where to apply the organic liquid.

9. The system according to claim 3 further includes an ion beam milling system configured to perform post-cleaning uniform ion beam milling on the surface, wherein the contaminant particles have been completely removed or reduced in size to a small enough size such that the uniform ion beam milling can then remove the contaminant particles.

10. The system according to claim 3 further includes a computer system configured to determine a post-cleaning contaminant particle distribution map for the surface and compare the post-cleaning contaminant particle distribution map with a pre-cleaning contaminant particle distribution map for the surface to confirm that most or all of the contaminant particles have been successfully removed from the surface, wherein the post-cleaning contaminant particle distribution map is determined using white light interferometry.

11. The system according to claim 3 further includes a computer system configured to determine the post-cleaning flatness of the surface and compare the post-cleaning flatness with the pre-cleaning initial flatness of the surface to confirm that most or all of the contaminant particles have been successfully removed from the surface, wherein the post-cleaning flatness is determined using high voltage phase measuring interferometry.

12. The system according to claim 11, wherein, in response to the post-cleaning flatness breaching a flatness threshold, ion beam milling is performed on the surface to bring the post-cleaning flatness within the flatness specification.

13. The system according to claim 3, wherein: the surface includes a top of a protrusion or a portion of the top of a protrusion; the chemical cleaning agent includes potassium hydroxide for tantalum contaminant particles, a chromium etchant for chromium contaminant particles, or a combination thereof; the cleaning tool is a glass disk; the relative movement includes lateral movement, serpentine movement, circular movement, or a combination thereof; the object support is a fixture; the cleaning includes planarizing and / or removing the contaminant particles; and the object support and the lithography apparatus are associated with semiconductor manufacturing.

14. The system according to claim 3, wherein the object support and the lithography apparatus are associated with semiconductor manufacturing.

15. A system for cleaning a mask holder of a lithography apparatus, comprising: a chemical cleaning agent configured to be applied to a surface of the mask holder to release contaminant particles from the surface; a cleaning tool configured to move relative to the surface to remove the contaminant particles from the surface; and an organic liquid configured to be applied to the surface to remove the chemical cleaning agent from the surface.

Images