Method of making nanoridges in hard ceramic coatings

Abstract

A method of reducing adhesion of an object to a surface for use in a lithographic process includes receiving, at a control computer, instructions for a tool configured to modify the surface, and forming a modified surface having a trench and a ridge in a determined manner based on the instructions received at the control computer, the ridges reduce adhesion by reducing the contact surface area of the modification surface. Another device includes a modification surface including grooves and ridges that form a reduced contact surface area to reduce adhesion of an object to the modification surface, the ridges having elastic properties that result in an increase in the reduced contact surface area when a plurality of ridges are elastically deformed.

Description

[0001] This application is a divisional application of the Chinese patent application with international application number PCT / EP2019 / 078691, international application date October 22, 2019, national application number 201980071950.4, and invention name “Method for manufacturing nano-ridges in hard ceramic coatings”. Background Art

[0002] A lithographic projection apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In this case, a patterning device (e.g., a mask) may contain or provide a pattern corresponding to a single layer of the IC (a "design layout"), and the pattern may be transferred to a target portion (e.g., including one or more dies) on a substrate (e.g., a silicon wafer) that has been coated with a layer of radiation-sensitive material ("resist"), such as by irradiating the target portion with a pattern on the patterning device. Typically, a single substrate contains a plurality of adjacent target portions, and the pattern is transferred to these target portions one at a time by the lithographic projection apparatus. In one type of lithographic projection apparatus, the pattern on the entire patterning device is transferred to one target portion at a time; such an apparatus may also be referred to as a stepper. In an optional apparatus, a step-scanning apparatus may cause the projection beam to scan the patterning device in a given reference direction (the "scanning" direction) while synchronously moving the substrate parallel or antiparallel to the reference direction. Different portions of the pattern on the patterning device are gradually transferred to one target portion. Since typically a lithographic projection apparatus will have a reduction ratio M (e.g. 4), the speed F of the substrate movement will be 1 / M times the speed F at which the projection beam scans the patterning device. More information on lithographic apparatus can be found in, for example, US 6,046,792, which is incorporated herein by reference.

[0003] Before the pattern is transferred from the patterned device to the substrate, the substrate can undergo various processes such as priming, resist coating, and soft baking. After exposure, the substrate can undergo other processes ("post-exposure processes"), such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. This series of processes is used as the basis for making a single layer of a device (e.g., an IC). The substrate can then 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 entire process or a variation thereof is repeated for each layer. Ultimately, a device will be present in each target portion on the substrate. The devices are then separated from each other by techniques such as cutting or sawing, so that the individual devices are mounted on a carrier, connected to pins, etc.

[0004] Therefore, manufacturing devices such as semiconductor devices typically involves processing a substrate (e.g., a semiconductor wafer) using multiple manufacturing processes to form various features and multiple layers of the device. Such layers and features are typically manufactured and processed using, for example, deposition, lithography, etching, chemical mechanical polishing, and ion implantation. Multiple devices can be manufactured on multiple dies on a substrate and then separated into individual devices. This device manufacturing process can be considered a patterning process. The patterning process includes a patterning step, such as optical and / or nanoimprint lithography using a patterning device in a lithography apparatus to transfer the pattern on the patterning device to the substrate, and typically, but optionally, includes one or more related patterning processing steps, such as resist development by a developing device, baking the substrate using a baking tool, etching using the pattern using an etching device, etc.

[0005] As mentioned above, photolithography is a central step in the manufacture of devices such as ICs, where patterns formed on a substrate define the functional elements of a device such as a microprocessor, memory chip, etc. Similar photolithography techniques are also used in the formation of flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0006] As semiconductor manufacturing processes continue to advance, the size of functional elements continues to decrease, while the number of functional elements (e.g., transistors) per device has remained steadily increasing for decades, following a trend known as "Moore's Law." At the current state of the art, the layers of a device are manufactured using a lithography projection apparatus that projects a design layout onto a substrate using illumination from a deep ultraviolet illumination source, thereby creating individual functional elements with dimensions well below 100 nanometers, i.e., less than half the wavelength of radiation from the illumination source (e.g., a 193 nanometer illumination source).

[0007] According to the resolution formula CD = k1 × λ / NA, where λ is the wavelength of radiation used (e.g., 248nm or 193nm), NA is the numerical aperture of the projection optical system in the lithography projection apparatus, CD is the "critical dimension" - the minimum feature size usually printed, and k1 is the empirical resolution factor. The process of printing features with a size smaller than the classical resolution limit of the lithography projection apparatus can be called low k1 lithography. In general, the smaller the k1, the more difficult it is to reproduce a pattern similar to the shape and size planned by the designer on the substrate to achieve specific electrical functions and performance. In order to overcome these difficulties, complex fine-tuning steps are applied to the lithography projection apparatus, the design layout or the patterning device. These include, for example, but not limited to, optimization of NA and optical coherence settings, customized illumination schemes, the use of phase-shifted patterning equipment, optical proximity correction (OPC, sometimes also referred to as "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement technology" (RET). The term "projection optical system" used herein should be broadly interpreted to include various types of optical systems, such as refractive optical systems, reflective optical systems, aperture optical systems, and catadioptric optical systems. The term "projection optical system" may also include components operating according to any of these design types for collectively or individually directing, shaping or controlling a projection beam of radiation. The term "projection optical system" may include any optical component in a lithographic projection apparatus, regardless of where the optical component is located in the optical path of the lithographic projection apparatus. The projection optical system may include optical components for shaping, adjusting and / or projecting radiation from a source before the radiation passes through a patterning device, and / or optical components for shaping, adjusting and / or projecting radiation after the radiation passes through a patterning device. The projection optical system typically does not include a source and a patterning device. Summary of the invention

[0008] In one aspect, a method for reducing adhesion of an object used in a lithography process to a surface includes receiving instructions at a control computer for a tool configured to modify a surface, and forming a modified surface having grooves and ridges in a deterministic manner based on the instructions received at the control computer, wherein the ridges reduce adhesion by reducing a contact surface area of ​​the modified surface.

[0009] In some variations, the modified surface can be caused by plastic deformation of the surface due to the tool tip of the mobile tool so that there is substantially no material loss. The method can also include acquiring an image of the surface from an imaging device, registering the tool tip in the coordinate space of the surface based on the image, and controlling the tool to move the tool tip to a predefined coordinate in the coordinate space to create grooves and ridges. The control can have a horizontal resolution of 1 micron or less and a vertical resolution of 10 nanometers or less, and wherein the resolution of the force transmitted by the tool tip is 1 millinewton or less. The control can also include controlling the tool tip to form a modified surface with multiple parallel ridges, or controlling the tool tip to form a modified surface with a non-uniform ridge density corresponding to a non-uniform granulation (burl) load. When forming the modified surface, the surface can be between 15 and 40 degrees Celsius.

[0010] Furthermore, there may be a computer program product including a non-transitory computer-readable medium having recorded thereon instructions, the instructions implementing the above-mentioned method when executed by a computer.

[0011] In a related aspect, an apparatus for a photolithography process includes a modified surface, the modified surface including grooves and ridges that form a reduced contact surface area to reduce adhesion of an object to the modified surface, wherein at least 60% of the ridges have a height variation of less than 100 nanometers. The ridges may have a ridge height measured from an average height of the unmodified surface. At least 80% of the ridges may have a height variation of less than 100 nanometers, at least 60% of the ridges may have a height variation of less than 100 nanometers, or at least 80% of the ridges may have a height variation of less than 5 nanometers. The height variation may be measured on substantially all of the modified surface.

[0012] The device may have a plurality of granules, the granules comprising grooves and ridges on the corresponding granule surfaces. At least some of the plurality of granules may have a coating, wherein the grooves and ridges are formed in the coating. The grooves and ridges may be parallel, and may include a mountain top, wherein the grooves and ridges are formed on the mountain top. The grooves and ridges may be formed substantially perpendicular to the mountain top.

[0013] The modified surface may be on a knot extending from a substrate. The substrate may be a mask fixture, a wafer fixture, or a wafer stage. The knot may also include a coating, and the modified surface may be located on the coating. The coating may be a hard ceramic coating, and the surface may be a knot surface made of a plurality of knots.

[0014] The nodules may include a hilltop, and the grooves and ridges are formed at an oblique angle to the hilltop. The oblique angle may be about 90 degrees. The modified surface may include a groove and two ridges on either side of the groove. The groove may have a depth between 50 and 150 nanometers, or a depth of about 100 nanometers. The ridges have a height between 2 and 50 nanometers, or about 10 nanometers.

[0015] In a related aspect, an apparatus may include a modified surface including grooves and ridges that form a reduced contact surface area to reduce adhesion of an object to the modified surface, the ridges having elastic properties that cause the reduced contact surface area to increase when multiple ridges are elastically deformed.

[0016] In some variations, the modified surface may be formed by multiple plastic deformations of an unmodified surface. When no deforming force is applied to the plurality of ridges, the reduced contact surface area of ​​the plurality of ridges may be less than 5% of the total contact surface area. When a downward clamping pressure of at least 0.5 bar is applied to a portion of the object, the reduced contact surface area may increase to greater than 25% of the total surface area defined by the outermost ridges. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain aspects of the subject matter disclosed herein and, together with the description, help explain some principles associated with the disclosed embodiments.

[0018] Figure 1 A block diagram showing various subsystems of a lithographic projection apparatus according to an embodiment is shown.

[0019] Figure 2 An exemplary flow chart for simulating lithography in a lithographic projection apparatus according to an embodiment is shown.

[0020] Figure 3 is a simplified top view of a wafer placed on a grain surface of a wafer stage in accordance with an embodiment.

[0021] Figure 4 is a simplified side view of a coated nodule according to an embodiment.

[0022] Figure 5 A simplified side view of a nodule is shown with several exemplary ridges and grooves formed by a tool, according to an embodiment.

[0023] Figure 6 Exemplary images of grooves and ridges are shown, according to an embodiment.

[0024] Figure 7 A simplified top view of a nodule is shown with several exemplary ridges formed on the nodule surface, in accordance with an embodiment.

[0025] Fig. 8A is a simplified diagram showing the variation in ridge height according to an embodiment.

[0026] Figure 8B is a simplified diagram illustrating an uncompressed elastic ridge according to an embodiment.

[0027] Figure 8Cis a simplified diagram illustrating a compressive elastic ridge according to an embodiment.

[0028] Fig. 9 is a simplified top view of a nodule with several exemplary ridges formed across the top of a hill on the nodule surface, according to an embodiment.

[0029] Fig.10 is a process flow chart of controlling a tool to form grooves and ridges according to an embodiment.

[0030] Fig.11 is a block diagram of an example computer system in accordance with an embodiment.

[0031] Fig.12 is a schematic diagram of a lithographic projection apparatus according to an embodiment.

[0032] Fig.13 is a schematic diagram of another lithography projection apparatus according to an embodiment.

[0033] Fig.14 is a detailed view of a lithographic projection apparatus according to an embodiment.

[0034] Fig.15 is a detailed view of a source collector module of a lithographic projection apparatus according to an embodiment. DETAILED DESCRIPTION

[0035] Although specific reference may be made herein to the manufacture of ICs, it should be expressly understood that the description herein has many other possible applications. Those skilled in the art will appreciate that in the context of such alternative applications, any use of the terms "reticle," "wafer," or "die" herein should be considered interchangeable with the more general terms "mask," "substrate," and "target portion," respectively.

[0036] In this document, the terms "radiation" and "beam" are used to include all types of electromagnetic radiation, including UV radiation (e.g., having a wavelength of 365, 248, 193, 157 or 126 nanometers) and EUV (extreme ultraviolet radiation, e.g., having a wavelength in the range of about 5-100 nanometers).

[0037] The patterned device may include or may form one or more design layouts. The design layout may be generated using a computer aided design (CAD) program, a process generally referred to as electronic design automation (EDA). Most CAD programs follow a set of predetermined design rules in order to create a functional design layout / patterned device. These rules are set by process and design constraints. For example, the design rules define the spatial tolerances between devices (e.g., gates, capacitors, etc.) or interconnects to ensure that the devices or lines do not interact with each other in an undesirable manner. One or more design rule constraints may be referred to as "critical dimensions" (CDs). The device critical dimension may be defined as the minimum width of a line or hole or the minimum spacing between two lines or two holes. Therefore, CD determines the overall size and density of the designed device. Of course, one of the goals of device manufacturing is to faithfully reproduce the original design intent on a substrate (via a patterned device).

[0038] The term "mask" or "patterning device" as used herein may be broadly interpreted as referring to a general patterning device that can be used to impart a patterned cross-section to an incident radiation beam, corresponding to the pattern to be created in a target portion of the substrate; the term "light valve" may also be used in this context. In addition to classical masks (transmissive or reflective; binary, phase-shifting, hybrid, etc.), other examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0039] An example of a programmable mirror array may be a matrix-addressable surface having a viscoelastic control layer and a reflective surface. The basic principle behind such a device is that (for example) addressed areas of the reflective surface reflect incident radiation as diffracted radiation, while unaddressed areas reflect incident radiation as undiffracted radiation. Using appropriate filters, the undiffracted radiation can be filtered out of the reflected beam, leaving only the diffracted radiation; in this way, the beam is patterned according to the addressing pattern of the matrix-addressable surface. Appropriate electronic methods can be used to perform the required matrix addressing.

[0040] An example of a programmable LCD array is given in US Pat. No. 5,229,872, which is incorporated herein by reference.

[0041] Figure 1A block diagram of various subsystems of a lithographic projection apparatus 10A according to an embodiment is shown. The main components are: a radiation source 12A, which may be a deep ultraviolet excimer laser source or other type of source including an extreme ultraviolet (EUV) source (as described above, the lithographic projection apparatus itself need not have a radiation source); an illumination optical system, which, for example, defines a partial coherence (expressed in σ) and may include optical systems 14A, 16Aa and 16Ab that shape the radiation from the source 12A; a patterning device 18A; and a transmission optical system 16Ac that projects an image of the patterning device pattern onto a substrate plane 22A. An adjustable filter or aperture 20A at a pupil plane of the projection optical system may limit the range of beam angles incident on the substrate plane 22A, where the largest possible angle defines the numerical aperture NA of the projection optical system = n sin (Θ max ), where n is the refractive index of the medium between the substrate and the last element of the projection optical system, and θ max is the maximum angle of the beam that exits the projection optical system and can still impinge on the substrate plane 22A.

[0042] In a lithographic projection apparatus, a source provides illumination (i.e., radiation) to a patterning device, and a projection optical system directs and shapes the illumination onto a substrate via a patterning device. The projection optical system may include at least some of components 14A, 16Aa, 16Ab, and 16Ac. An aerial image (AI) is a radiation intensity distribution at the substrate level. A resist model may be used to calculate a resist image from an aerial image, an example of which may be found in U.S. Patent Application Publication No. US2009-0157630, the disclosure of which is incorporated herein by reference in its entirety. The resist model is only related to the properties of the resist layer (e.g., the effects of chemical processes occurring during exposure, post-exposure baking (PEB), and development). The optical properties of the lithographic projection apparatus (e.g., the properties of illumination, patterning equipment, and projection optical systems) indicate an aerial image and may be defined in an optical model. Since the patterning equipment used in the lithographic projection apparatus may be changed, it is desirable to separate the optical properties of the patterning equipment from the optical properties of the rest of the lithographic projection apparatus including at least a source and a projection optical system. Details of techniques and models for converting design layouts into various lithographic images (e.g., aerial images, resist images, etc.), applying OPC using these techniques and models, and evaluating performance (e.g., in terms of process window) are described in U.S. Patent Application Publication Nos. US2008-0301620, 2007-0050749, 2007-0031745, 2008-0309897, 2010-0162197, and 2010-0180251, the contents of each of which are incorporated herein by reference in their entirety.

[0043] One aspect of understanding the photolithography process is understanding the interaction of radiation and patterning devices. The electromagnetic field of the radiation after passing through the patterning device can be determined by the electromagnetic field of the radiation before the radiation reaches the patterning device and a function that characterizes the interaction. This function can be called the mask transmission function (which can be used to describe the interaction through the transmission patterning device and / or the reflection patterning device).

[0044] The mask projection function can have a variety of different forms. One form is binary. The binary mask transmission function has any one of two values ​​(e.g., zero and a positive constant) at any given position on the patterned device. The mask transmission function in binary form can be referred to as a binary mask. Another form is continuous. That is, the modulus of the transmittance (or reflectance) of the patterned device is a continuous function of the position on the patterned device. The phase of the transmittance (or reflectance) can also be a continuous function of the position on the patterned device. The mask transmission function in continuous form can be referred to as a continuous tone mask or a continuous transmission mask (CTM). For example, a CTM can be represented as a pixelated image, in which each pixel can be assigned a value between 0 and 1 (e.g., 0.1, 0.2, 0.3, etc.), rather than a binary value of 0 or 1. In an embodiment, the CTM can be a pixelated grayscale image, in which each pixel has a value (e.g., a normalized value in the range [-255, 255], in the range [0, 1] or [-1, 1] or other appropriate ranges).

[0045] The thin mask approximation, also known as the Kirchhoff boundary condition, is widely used to simplify the determination of the interaction of radiation with the patterned device. The thin mask approximation assumes that the thickness of the structure on the patterned device is small compared to the wavelength, and the width of the structure on the mask is large compared to the wavelength. Therefore, the thin mask approximation assumes that the electromagnetic field behind the patterned device is the product of the incident electromagnetic field and the mask transmission function. However, as lithography processes use radiation with shorter and shorter wavelengths and the structures on the patterned device become smaller and smaller, the assumptions of the thin mask approximation may break down. For example, due to finite thickness ("mask 3D effect" or "M3D"), the interaction of radiation with the structure (e.g., the edge between the top surface and the sidewall) may become significant. Including this scattering in the mask transmission function can enable the mask transmission function to better capture the interaction of radiation with the patterned device. The mask transmission function under the thin mask approximation can be referred to as a thin mask transmission function. The mask transmission function that includes M3D can be referred to as an M3D mask transmission function.

[0046] According to an embodiment of the present disclosure, one or more images may be generated. An image includes various types of signals, which may be characterized by a pixel value or an intensity value of each pixel. Depending on the relative values ​​of the pixels within the image, as will be understood by those of ordinary skill in the art, a signal may be referred to as, for example, a weak signal or a strong signal. The terms "strong" and "weak" are relative terms based on the intensity values ​​of the pixels within the image, and the specific value of the intensity may not limit the scope of the present disclosure. In an embodiment, a strong signal and a weak signal may be identified based on a selected threshold. In an embodiment, the threshold may be fixed (e.g., the midpoint of the highest intensity and the lowest intensity of the pixels within the image). In an embodiment, a strong signal may refer to a signal having a value greater than or equal to the average signal value of the entire image, and a weak signal may refer to a signal having a value less than the average signal value. In an embodiment, a relative intensity value may be based on a percentage. For example, a weak signal may be a signal having an intensity less than 50% of the highest intensity of a pixel within the image (e.g., a pixel corresponding to a target pattern may be considered to be a pixel having the highest intensity). In addition, each pixel within the image may be considered to be a variable. According to the present embodiment, a derivative or partial derivative may be determined for each pixel within the image, and the value of each pixel may be determined or modified based on an evaluation of a cost function and / or calculation of a gradient-based cost function. For example, a CTM image may include pixels, where each pixel is a variable that may take any real value.

[0047] Figure 2 An exemplary flow chart for simulating lithography in a lithography projection apparatus according to an embodiment is shown. A source model 31 represents the optical properties of a source (including radiation intensity distribution and / or phase distribution). A projection optical model 32 represents the optical properties of a projection optical system (including changes in radiation intensity distribution and / or phase distribution caused by the projection optical system). A design layout model 35 represents the optical properties of a design layout (including changes in radiation intensity distribution and / or phase distribution caused by a design layout 33), and a design layout represents the arrangement of features on or formed by a patterning device. An aerial image 36 can be simulated from the design layout model 35, the projection optical model 32, and the design layout model 35. A resist image 38 can be simulated from the aerial image 36 using a resist model 37. The simulation of lithography can, for example, predict the profile and CD in the resist image.

[0048] More specifically, it should be noted that the source model 31 can represent the optical properties of the source, including but not limited to numerical aperture settings, illumination sigma (σ) settings, and any specific illumination shapes (e.g., off-axis radiation sources such as annular, quadrupole, dipole, etc.). The projection optical model 32 can represent the optical properties of the projection optical system, including aberrations, distortions, one or more refractive indices, one or more physical dimensions, one or more physical dimensions, etc. The design layout model 35 can represent one or more physical properties of a physical patterning device, such as described in U.S. Patent No. 7,587,704, which is incorporated by reference in its entirety. The goal of the simulation is to accurately predict, for example, edge placement, aerial image intensity slope, and / or CD, which can then be compared to the expected design. The expected design is typically defined as a pre-OPC design layout that can be provided in a standardized digital file format such as GDSII or OASIS or other file formats.

[0049] From the design layout, one or more portions, referred to as "clips," may be identified. In an embodiment, a set of clips are extracted that represent complex patterns in the design layout (typically about 50 to 1000 clips, although any number of clips may be used). These patterns or clips represent small portions of the design (i.e., circuits, cells, or patterns), and more specifically, clips typically represent small portions that require special attention and / or verification. In other words, a clip may be a portion of the design layout, or may be similar or have similar behavior to a portion of the design layout, where one or more key features are identified through experience (including customer-provided clips), by trial and error, or by running full-chip simulations. A clip may contain one or more test patterns or gauge patterns.

[0050] An initial larger set of clips may be provided a priori by the customer based on one or more known key feature areas in the design layout that require specific image optimization. Alternatively, in another embodiment, an initial larger set of clips may be extracted from the entire design layout using some automatic (e.g., machine vision) or manual algorithm that identifies one or more key feature areas.

[0051] In a lithographic projection apparatus, as an example, the cost function can be expressed as

[0052]

[0053] where (z1, z2, …, z N ) are N design variables or their values. p (z1,z2,…,z N ) can be the design variables (z1, z2, …, z N ), for example, for the design variables (z1, z2, …, zN ) is the difference between the actual and expected values ​​of a characteristic for a set of values. p is with f p (z1,z2,…,z N ) is a weight constant associated with the feature. For example, a feature may be the position of an edge of a pattern measured at a given point on the edge. p (z1,z2,…,z N ) can have different weights w p For example, if a particular edge has a narrower range of allowed positions, then the value for f that represents the difference between the actual and expected positions of the edge is p (z1,z2,…,z N )’s weight w p Can be assigned higher values. p (z1,z2,…,zN ) It can also be a function of the interlayer characteristics, which are in turn design variables (z1, z2, ..., z N ). Of course, CF(z1, z2, …, z N ) is not limited to the form in equation 1. CF(z1, z2, ..., z N ) may be in any other suitable form.

[0054] The cost function may represent any one or more suitable characteristics of the lithographic projection apparatus, the lithographic process, or the substrate, such as focus, CD, image shift, image distortion, image rotation, random variation, throughput, local CD variation, process window, inter-layer characteristics, or a combination thereof. In one embodiment, the design variables (z1, z2, ..., z N ) includes one or more selected from dose, global bias of the patterning device and / or illumination shape. Since it is usually the resist image that indicates the pattern on the substrate, the cost function may include a function representing one or more characteristics of the resist image. For example, f p (z1,z2,…,z N ) can simply be the distance between a point in the resist image and the expected position of that point (i.e., the edge placement error EPE p (z1,z2,…,z N )). Design variables can include any adjustable parameters, such as adjustable parameters of the source, patterning device, projection optical system, dose, focus, etc.

[0055] The lithographic apparatus may include components collectively referred to as "wavefront manipulators", which may be used to adjust the shape of the wavefront and the intensity distribution and / or phase shift of the radiation beam. In an embodiment, the lithographic apparatus may adjust the wavefront and intensity distribution at any position along the optical path of the lithographic projection apparatus, such as before the patterning device, near the pupil plane, near the image plane, and / or near the focal plane. The wavefront manipulator may be used to correct or compensate for certain distortions of the wavefront and intensity distribution and / or phase shift caused by, for example, temperature changes in the source, patterning device, lithographic projection apparatus, thermal expansion of components of the lithographic projection apparatus, and the like. Adjusting the wavefront and intensity distribution and / or phase shift may change the value of the characteristic represented by the cost function. Such changes may be simulated from a model, or actually measured. The design variables may include parameters of the wavefront manipulator.

[0056] The design variables may have constraints, which can be expressed as (z1, z2, ..., z N )∈Z, where Z is a set of possible values ​​for the design variables. One possible constraint on the design variables may be imposed by the desired throughput of the lithographic projection apparatus. Without such a constraint imposed by the desired throughput (throughput), the optimization may produce a set of unrealistic values ​​for the design variables. For example, if dose is the design variable, without such a constraint, the optimization may produce dose values ​​that make the throughput economically impossible to achieve. However, the usefulness of a constraint should not be interpreted as a necessity. For example, throughput may be affected by the pupil fill ratio. For certain illumination designs, a low pupil fill ratio may discard radiation, resulting in lower throughput. The chemical properties of the resist may also affect throughput. Slower resists (e.g., resists that require a higher amount of radiation to be properly exposed) result in lower throughput.

[0057] As used herein, the term "patterning process" refers to a process that produces an etched substrate by applying a specific light pattern as part of a photolithography process.

[0058] As used herein, the term "imaging device" means any number or combination of devices and associated computer hardware and software described in this specification that can be configured to generate an image of a target (e.g., a printed pattern or portion thereof) or an image of any surface and feature. Non-limiting examples of imaging devices may include: scanning electron microscope (SEM), atomic force microscope (AFM), X-ray machine, optical microscope, etc.

[0059] Some photolithography processes include, for example, using a reticle (or mask) to provide a specific light pattern at the photoresist to create a pattern for etching onto the wafer. In order to fix the mask and wafer in place, a clamping device can be used. Since the surface involved is very flat, it is important for the manufacturing process, so the undesirable consequence may be that the reticle will adhere to the mask fixture, the wafer may adhere to the wafer fixture or wafer stage where the wafer is located, etc. This adhesion may cause damage to the wafer, reticle, fixture, etc. The adhesion mechanism may include forming van der Waals bonds between components along the contact surface. Therefore, the embodiment of the disclosed subject matter solves the problem of adhesion by, for example, reducing the total van der Waals force between objects by reducing the contact area between the components, so that adhesion is less likely to occur. The reduced contact area can be formed in a determined manner by controlled formation of ridges on the surface of interest (e.g., wafer table top, fixture, etc.).

[0060] Figure 3 A simplified top view of a wafer 310 resting on a graining surface 340 of a wafer stage 320 is shown in accordance with an embodiment.

[0061] Wafer stage 320 is shown with a plurality of nodules 330 that combine to form a nodule surface 340. An exemplary wafer 310 may be placed on nodule surface 340. Figure 4 As further shown, a nub, as used herein, may include any material feature extending from a substrate, such as a wafer stage 320, a wafer chuck, a mask chuck, etc. to support a wafer 310 or a reticle.

[0062] The nodules may provide some nominal separation (and reduction in contact surface area) between the wafer 310 and the wafer stage 320. For example, by supporting the wafer 310 on the nodule surface 340 (which may be composed of a plurality of nodules 330 with certain spacing between the nodules 330), the above-mentioned van der Waals forces may be reduced and vacuum, cavitation, etc. may be avoided.

[0063] The embodiments described herein generally refer to a wafer placed on a wafer stage. However, this description is not intended to be limiting. For example, rather than a wafer and a wafer stage, aspects of the present disclosure may also be applied to other components (e.g., grooves in contact with a mask holder), as well as wafers placed on grooves of any type, number, and geometry with associated groove surfaces.

[0064] Figure 4 A simplified side view of a nodule 330 with a coating 420 is shown in accordance with an embodiment.

[0065] Figure 4The side view shown shows a plurality of exemplary granulation knots 330 extending from substrate 410. In some embodiments, as shown in the figure, granulation knot 330 can include coating 420 arranged on at least top surface of granulation knot 330, and it can be hard ceramic coating.Coating 420 can include titanium nitride (TiN), chromium nitride (CrN), diamond-like carbon (DLC), tantalum (Ta), tantalum boride (TaB), tungsten (W), tungsten carbide (WC), boron nitride (BN) etc. for example.Such coating can be added to granulation knot 330 to protect the granulation knot structure below.As used herein, term " granulation knot surface 430 " can refer to the top surface of granulation knot 330 when there is no coating 420, or refer to the top surface of coating 420 when such coating 420 is present on granulation knot 330.

[0066] Figure 5 A simplified side view of a nodule 330 is shown with several exemplary ridges 520 and grooves 510 formed by a tool 530 in accordance with an embodiment. Figure 6 An exemplary image of grooves and ridges 520 is shown, in accordance with an embodiment.

[0067] Figure 5 An example result of a method for reducing adhesion of an object at a surface in a lithography process is shown. The method may include receiving instructions at a control computer 560 for a tool 530 configured to modify a surface, such as Figure 5 As shown. Figure 6 As shown, the modification may include forming a modified surface 550 having grooves 510 and ridges 520 in a determined manner based on instructions received at a control computer 560 .

[0068] In some embodiments, tool 530 can be initially placed on the surface with relatively small initial force (for example, about 1mN, 2mN, 4mN or 10mN etc.), so that tool tip is temporarily fixed in the appropriate position on the surface. The vertical force can then be increased to a specified value, to utilize tool 530 to form an initial depression. The vertical force can be, for example, about 10mN, 20mN, 40mN, 75mN, 100mN, 150mN, 200mN, 500mN, 1N etc. The vertical force of tool 530 can keep constant during the horizontal travel period performed during the scratch formation. The computer control of tool 530 can include monitoring the displacement of lateral and / or vertical force and tool 530 during the scraping process. The programming of the position of tool 530 and the force applied can be pre-programmed with respect to known granulation position. In this way, the process can be fully automated and controlled by a computer, to provide deterministic scratches on granulation surfaces (or any other required surface).

[0069] Back to Figure 5, ridges 520 can reduce adhesion by reducing the contact surface area of ​​the surface. As used herein, "contact surface area" refers to the effective surface area that contacts an object placed on the modified surface 550. For example, referring to Figure 5 In the example of FIG. 5 , without the ridges 520 and grooves 510 shown, the contact surface area would be the entire top surface of the nodule. After modifying the surface, the contact surface area would be only the top of the ridges 520. This example is provided for illustrative purposes and is not intended to limit or exclude other embodiments of reducing the contact surface area through embodiments of the present disclosure.

[0070] like Figure 5 and Figure 6 As shown, modified surface 550 may include a groove 510 and two ridges 520 on either side of groove 510. In some embodiments, groove 510 may have a depth between 5 and 150 nanometers, approximately 100 nanometers, etc. Ridge 520 may have a height between 2 and 50 nanometers, approximately 10 nanometers, etc. For example, measurements taken on modified surface 550 may be displayed as a two-dimensional image 610, which may also be displayed as a three-dimensional image 620, such as Figure 6 As shown. Figure 6 6, topography 630 and cross-sectional height 640 (taken along a line intersecting the trench shown in topography 630) show the uniformity of ridge height produced by one example of the disclosed process. As can be seen in the image, but only by way of example, the ridges shown are fairly symmetrical and have nearly identical heights of approximately 10 nanometers.

[0071] In many of the embodiments herein, the modified surface 550 described above is shown on a granule 330 (or any number of granules 330) extending from a substrate 410, or equivalently, on a coating 420 on a granule 330. Figure 5 As shown, in some embodiments, the granulation 330 can have a coating 420, and the modified surface 550 is located on the coating 420. In some embodiments, the substrate can be a mask fixture, a wafer fixture or a wafer stage, or any other surface of any object that can have the ridges described herein. In this way, the present disclosure contemplates that the modified surface can be any surface, without limitation to granulation, granulation surface, ceramic coating on granulation, etc. For example, the surface can be a mask fixture, a wafer fixture, a wafer stage, etc. with ridges 520 formed directly on the surface. In addition, the method described herein can allow "room temperature" modification of the surface (for example, no additional heating or cooling is required to the surface before modification). In some embodiments, when the modified surface 550 is formed, the surface can be between 15 and 40 degrees Celsius.

[0072] Figure 5Also shown is an exemplary method of forming ridges 520 in a modified surface 550, wherein plastic deformation of the surface is induced by moving the tool tip 540 of the tool 530. Although the embodiments of the grooves 510 and ridges 520 described herein are shown as being formed by the tool 530 being pressed down (e.g., in a generally vertical manner), the present disclosure contemplates that any equivalent force may be applied to deform the surface. For example, the tool tip 540 may optionally be pressed from the vertical at an oblique angle (e.g., approximately 5°, 10°, 15°, 30°, 45°, 60°, 75°, etc.). Although any type and size of tool tip 540 may be used, in some embodiments, the tool tip 540 may be a diamond cone tool tip of 5, 20, 50, or 100 micron radius. Similar hard ceramics, metals or coatings may be used as tool tip materials, examples include but are not limited to cubic boron nitride (BN), tungsten carbide (WC), titanium nitride (TiN), chromium nitride (CrN), tungsten (W), tantalum carbide (TaC), tantalum boride (TaB), diamond-like carbon coating (DLC) or various oxides such as Al2O3. Similarly, various tip geometries for making ridges may include but are not limited to spherical, conical, Berkovich or cube corner types. Depending on the desired tip geometry, any of these tip geometries may be used.

[0073] In some embodiments, the modified surface 550 may be produced by plastic deformation of the surface caused by moving the tool tip 540. As used herein, the term "plastic deformation" refers to modification of a surface such that there is substantially no loss of material. For example, plastic deformation is different from the type of surface modification caused by, for example, sanding, stone grinding, digging, etc., in which material is removed from the surface and lost or displaced elsewhere (in the form of particles, dust, grains, etc.).

[0074] Figure 7 A simplified top view of a nodule is shown having a plurality of exemplary ridges 520 formed on the nodule surface, according to an embodiment.

[0075] In some embodiments described herein, the grooves and ridges 520 may be formed into a specific predefined pattern. Figure 7 As shown, the grooves and ridges 520 may be parallel. This is shown in the example of ridges 520 formed on the coating 420 of the nodules 330, but such parallel ridge formation may be implemented on any desired surface.

[0076] Fig. 8A is a simplified diagram showing the variation of ridge height according to an embodiment.

[0077] The methods described herein allow ridges to be formed with little variation in ridge height, thereby providing the benefit of reduced sticking while still providing a level surface. Fig. 8AA plurality of ridges 856 are shown, with most of the ridges having heights 853 that vary within a particular range 851. As shown in this example, ten ridges are formed on an unmodified surface 852. Six of the ridges have ridge heights within the range 851. Three ridges have heights below the range 851, and one ridge has a height above the range 851. Thus, in some embodiments, due to precise computer control of the ridge formation process, at least 60% of the ridges that are positioned and configured to contact an object placed on the knot will have a height variation of less than 100 nanometers. In other words, at least 60% of the ridges (which will contact an object placed thereon) will have heights that fall within 100 nanometers of each other, such as from a peak (top of the ridge) to a valley between knots (e.g., Fig. 8A The term "height variation" as used herein is the variation between the minimum and maximum ridge heights. As used herein, ridge height 853 refers to the ridge height that can be measured from the average height of the unmodified surface 852.

[0078] In some embodiments, ridge height can be measured on the whole modification surface of the granulation region, for example, measured on the bend of the granulation top that forms wafer stage, mask fixture, wafer fixture etc. In this way, in an embodiment, height variation can be measured on substantially all modification surfaces. As used herein, "substantially all modification surfaces" refers to the whole granulation top, but does not include unmodified regions, such as the region between granulation, the region near the granulation top edge that may not include granulation, the region that happens not to have granulation or other surface modifications etc. In other embodiments, ridge height (relative to unmodified surface 852) can be measured on a smaller region, such as corresponding to the working area of ​​the circle or granulation top of the wafer. This can include a circle of, for example, 200 to 500 microns of diameter, which can correspond to the size of some wafers generally.

[0079] The above numbers are examples only, and in some variations, the percentage of ridges having a height variation of less than 100 nanometers can be at least 70%, 75%, 80%, 85%, 90%, 95%, or 99%. In another variation, the percentage of ridges having a height variation of 100 nanometers can also be 100%. In addition, in another embodiment, for each of the above percentages, the height variation can be less than 75 nanometers, 50 nanometers, 25 nanometers, 10 nanometers, 5 nanometers, 2.5 nanometers, 1 nanometer, or 0.5 nanometers.

[0080] Measuring ridge height can be performed by imaging the surface of the granule. Images of the granule surface can be acquired, for example, by white light interferometry, atomic force microscopy, scanning probe microscopy, etc. These images can be used to measure ridge height, for example Figure 6 and Fig. 8A, and can therefore be used in later runs to improve the deterministic scraping process or as active feedback to reduce height variations.

[0081] Figure 8B is a simplified diagram showing an uncompressed elastic ridge, according to an embodiment.

[0082] Figure 8B A simplified example of a granule 330 having a plurality of (uncompressed) ridges 856 forming a modified surface prior to applying compression is shown. Specifically, Figure 8B A top view and an exemplary partial cross-sectional view of a granule 330 are shown, but an additional exemplary cross-sectional view of an object 850 placed on a ridge 856 is included. Ridge 857 is shown to illustrate an example of a ridge where the height of ridge 857 can vary outside a specific height range. However, as previously described, various embodiments of the present disclosure contemplate formed ridges having different percentages of less than a specific height variation.

[0083] An object 850 (e.g., a portion of a wafer) is shown on top of a ridge 856 and has a reduced contact surface area 858 due to contact with only a small portion of the ridge (e.g., the tip). Since ridges typically have a small contact surface area at the top of the ridge, embodiments of the present disclosure may include a modified surface where the reduced contact surface area of ​​the ridge is less than 5% of the total contact surface area. An example of a defined total contact surface area is the area 859 surrounded by the outermost ridge 856a (the area shown is slightly larger than actual size for illustrative purposes). In other words, at Figure 8B In FIG. 8 , the outermost ridge 856a on a particular knot can define an area 859 occupied by the ridge that would contact the object 850 when no downward clamping force is applied to the object 850 (given the allowed variation in ridge height). Figure 8B As shown in the example of , the contact surface area will be an area 859 that is significantly larger than the reduced contact surface area 858 at the contact point of the ridge. When no force is applied, the top 858 of the granulation of the contact object 850 will occupy a surface area less than 5% of the total surface area within the defined area. In other embodiments, the reduced contact surface area can be less than about 2% of the contact surface area.

[0084] As described herein, embodiments of the present subject matter allow for the creation of surfaces with reduced adhesion by effectively reducing the contact surface area between an object 850 (e.g., a wafer) and a surface (e.g., a grained surface of a wafer stage). In some embodiments, for example, where the grooves and ridges have been formed by plastic deformation of an unmodified surface by a tool, the ridges may be elastic and compressible. Figure 8BAs shown, an apparatus consistent with embodiments disclosed herein may include a modified surface including grooves 854 and ridges 856 that form a reduced contact surface area 858 to reduce adhesion of an object 850 to the modified surface. The modified surface includes a small portion of a single knot top having a plurality of ridges 856. The ridges may have elastic properties that may cause the reduced contact surface area to increase when the ridges are elastically deformed, such as by applying a downward force. For example, as an object compresses the ridges and more of the ridges come into contact with the object, particularly an object clamped thereon, the (reduced) contact surface area 858 may increase (see below with reference to Figure 8C 858 ). This increase in contact surface area can have the benefit of increasing friction between the object and the modified surface when needed (e.g., when the object is clamped onto the modified surface). Conversely, when pressure between the object and the modified surface is removed (e.g., the object is not clamped), the ridges can elastically return to their normal shape, which has a reduced contact surface area 858, so that the object is less likely to adhere to the modified surface.

[0085] Figure 8C is a simplified diagram illustrating a compressive elastic ridge according to an embodiment.

[0086] Figure 8C An example of how the ridges can be elastically deformed to result in an increase in contact surface area is shown. When an external force 870 (e.g., a clamping force on the object) is applied to the object, the elastic properties of the ridges can allow for reversible compression of the ridges, which has the effect of increasing the portion of the ridges that is in contact with the object. This can have the effect of increasing the "reduced contact surface area" (indicated by arrow 868) compared to when no external force is applied.

[0087] In one embodiment, when at least 0.5 bar of downward clamping pressure 870 is applied to a portion of the object, the reduced contact surface area will increase to greater than 25% of the total surface area defined by the outermost ridge 856a. In another embodiment, the surface area of ​​the ridge top that contacts the object is greater than 50% of the total surface area, and in another embodiment, the ridge top is greater than 75% of the contact surface area when 0.5 bar of downward clamping pressure 870 is applied to the object. In another embodiment, when 0.5 bar of clamping force is applied downward, the surface area on the ridge top that contacts the object will increase by at least 10 times. Thus, for example, after applying a force of 0.5 bar, an initial contact surface area of ​​2% within the defined area of ​​the outermost ridge will increase to at least 20% of the contact surface area. It should be noted that the 0.5 bar clamping force is merely exemplary and is used only as an exemplary test point for characterizing one aspect of the present disclosure. In the practice of actually clamping a wafer to a workbench, other clamping forces may of course be used. Furthermore, when using a 0.5 bar clamping force as a test case, this force can be considered as the total force exerted by the object on the ridge top (which includes any gravitational force between the ridge top and the object 850). Furthermore, when calculating the contact surface area at the above test points, this should be done linearly along the plane generally defined by the outermost ridge tops of the contacting object, and should not include the complex surface area within the grooves of the grain.

[0088] Fig. 9 is a simplified top view of a granule having a plurality of exemplary ridges 520 formed on mountain tops 910 on the granule surface according to an embodiment. Some embodiments may include granules 330 having a "mountaintop" structure, which may be a raised area on the granule surface. Fig. 9 The embodiment shown in FIG. 5 shows a grain knot 330 including a mountain top 910 with grooves and ridges 520 formed at an oblique angle across the mountain top 910. The oblique angle may be about 90 degrees or substantially perpendicular to the mountain top 910.

[0089] Fig.10 is a process flow chart of controlling a tool to form grooves and ridges according to an embodiment.

[0090] The methods and computer-implemented processes for controlling a tool described herein may include, at 1010 , receiving instructions at a control computer for a tool configured to modify a surface.

[0091] At 1020, a modified surface having grooves and ridges is formed in a determined manner based on instructions received at a control computer, wherein the ridges reduce adhesion by reducing a contact surface area of ​​the modified surface.

[0092] As described herein, forming ridges and grooves can be accomplished by precise and predefined control of a tool or other device that creates grooves to a specified size and in a specified pattern. In an embodiment, a portion of such a method may include acquiring an image of a surface from an imaging device, registering a tool tip in a coordinate space of the surface based on the image, and controlling the tool to move the tool tip to predefined coordinates in the coordinate space to produce grooves and ridges. Such an embodiment may be similar to a computer-aided manufacturing (CAM) process, in which ridges are formed by movement of a tool tip over a surface, either automatically or through user-provided instructions.

[0093] The imaging device may include, for example, a camera, microscope, sensor, etc. In other embodiments, registration of the tool tip may be performed by mechanical means, such as stops or set points of the surface that allow movement of the surface relative to the tool tip to be modified.

[0094] In some embodiments, the tool tip can be controlled to have a horizontal resolution of 1 micron or less and a vertical resolution of 10 nanometers or less. Likewise, the resolution of the force transmitted by the tool tip can be 1 millinewton or less.

[0095] According to the instruction received on the control computer, the tool tip can be controlled to form a modified surface with parallel ridges. Another embodiment may include controlling the tool tip to form a modified surface with a ridge of a non-uniform density corresponding to a non-uniform granulation load. The term "granulation load" refers to the weight (or pressure) applied on a given granulation. For example, if the wafer is clamped around the edge, the granulation load at the wafer edge may be higher than at the center. In this case, in some positions, the ridge may need to be placed thicker or more densely to support the increased pressure.

[0096] Fig.11 is a block diagram of an example computer system CS according to an embodiment.

[0097] The computer system CS comprises a bus BS or other communication mechanism for communicating information, and a processor PRO (or multiple processors) coupled to the bus BS for processing information. The computer system CS also comprises a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to the bus BS to store information and instructions to be executed by the processor PRO. The main memory MM can also be used to store temporary variables or other intermediate information during the execution of instructions executed by the processor PRO. The computer system CS also comprises a read-only memory (ROM) ROM or other static storage device coupled to the bus BS for storing static information and instructions of the processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to the bus BS for storing information and instructions.

[0098] The computer system CS can be coupled to a display DS via a bus BS, such as a cathode ray tube (CRT) or a flat panel or touch panel display, for displaying information to a computer user. An input device ID including alphanumeric and other keys is coupled to the bus BS for transmitting information and command selections to the processor PRO. Another type of user input device is a cursor control CC, such as a mouse, trackball or cursor direction keys, for transmitting direction information and command selections to the processor PRO and for controlling cursor movement on the display DS. The input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), which allows the device to specify a position in a plane. A touch panel (screen) display can also be used as an input device.

[0099] According to one embodiment, the computer system CS can be executed in response to the processor PRO executing one or more sequences of one or more instructions contained in the main memory MM to perform the part of one or more methods described herein. Such instructions can be read from another computer readable medium (such as storage device SD) into the main memory MM. Execution of the instruction sequence contained in the main memory MM causes the processor PRO to perform the processing steps described herein. One or more processors in a multiprocessing device can also be used to execute the instruction sequence contained in the main memory MM. In an optional embodiment, a hard-wired circuit device can be used to replace a software instruction or to be combined with a software instruction. Therefore, the description herein is not limited to any specific combination of hardware circuit devices and software.

[0100] The term "computer-readable medium" used herein refers to any medium that participates in providing instructions to the processor PRO for execution. This medium can take a variety of forms, including but not limited to non-volatile media, volatile media and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage devices SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wires and optical fibers, including wires that constitute bus BS. Transmission media can also take the form of sound waves or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-temporary, such as floppy disks, floppy disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, paper tapes, any other physical media with hole patterns, RAMs, PROMs, EPROMs, FLASH-EPROMs, any other memory chips or boxes. Non-temporary computer-readable media can record instructions thereon. When executed by a computer, the instructions can implement any feature described herein. Temporary computer-readable media can include carrier waves or other propagation electromagnetic signals.

[0101] When one or more sequences of one or more instructions are transmitted to the processor PRO for execution, various forms of computer-readable media may be involved. For example, the instructions may initially be contained on a disk of a remote computer. The remote computer may load the instructions into its dynamic memory and send the instructions via a telephone line using a modem. The modem local to the computer system CS may receive data on the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to the bus BS may receive the data carried in the infrared signal and place the data on the bus BS. The bus BS transmits the data to the main memory MM, from which the processor PRO retrieves and executes the instructions. The instructions received by the main memory MM may optionally be stored on a storage device SD before or after the processor PRO executes them.

[0102] The computer system CS may also include a communication interface CI coupled to the bus BS. The communication interface CI provides a bidirectional data communication coupling to a network link NDL connected to a local network LAN. For example, the communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a telephone line of a corresponding type. As another example, the communication interface CI 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 CI sends and receives electrical, electromagnetic or optical signals carrying digital data streams representing various types of information.

[0103] The network link NDL usually provides data communication to other data devices through one or more networks. For example, the network link NDL can provide a connection to the host HC through a local network LAN. This can include data communication services provided by the global packet data communication network, now generally referred to as the "Internet" INT. Local area networks LAN (Internet) all use electrical, electromagnetic or optical signals to transmit digital data streams. The signals through the various networks and the signals on the network data link NDL and through the communication interface CI, which transmit digital data to and from the computer system CS, are example forms of carrier waves that transmit information.

[0104] The computer system CS can send messages and receive data, including program codes, through the network, the network data link NDL and the communication interface CI. In the Internet example, the host computer HC can send the request code of the application program through the Internet INT, the network data link NDL, the local network LAN and the communication interface CI. For example, such a download application program can provide all or part of the method described herein. The received code can be executed by the processor PRO when received, and / or stored in the memory device SD or other non-volatile memory for later execution. In this way, the computer system CS can obtain the application code in the form of a carrier wave.

[0105] Fig.12 is a schematic diagram of a lithography projection apparatus according to an embodiment.

[0106] The lithographic projection apparatus may comprise an illumination system IL, a first object table MT, a second object table WT and a projection system PS.

[0107] The illumination system IL may condition the radiation beam B. In this particular case, the illumination system further comprises a radiation source SO.

[0108] A first object table (eg, patterning device table) MT may be provided with a patterning device holder to hold a patterning device MA (eg, a reticle) and connected to a first positioner to accurately position the patterning device relative to the article PS.

[0109] A second object table (substrate table) WT may be provided with a substrate holder to hold a substrate W (eg, a resistor coated silicon wafer) and connected to a second positioner to accurately position the substrate relative to the item PS.

[0110] A projection system ("lens") PS (eg, a refractive, catadioptric, or catadioptric optical system) can image an illuminated portion of patterning device MA onto a target portion C of substrate W (eg, comprising one or more dies).

[0111] As shown herein, the apparatus can be transmissive (i.e., with a transmissive patterning device). However, in general, it can also be reflective, for example (with a reflective patterning device). The apparatus can employ patterning devices of a different kind than a classical mask; examples include a programmable mirror array or an LCD matrix.

[0112] A source SO (e.g. a mercury lamp or an excimer laser, an LPP (laser produced plasma) EUV source) generates a beam of radiation. This beam is fed into an illumination system (illuminator) IL directly or after a conditioning device such as a beam expander Ex. The illuminator IL may comprise an conditioning device AD ​​for setting the outer and / or inner radial extent (usually referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the beam. Furthermore, it typically comprises various other components, such as an integrator IN and a condenser CO. In this way, the beam B impinging on the patterning device MA has a desired uniformity and intensity distribution in its cross section.

[0113] In some embodiments, the source SO may be within the housing of the lithographic projection apparatus (e.g., this is typically the case when the source SO is a mercury lamp), but it may also be remote from the lithographic projection apparatus, the radiation beam it generates being guided into the apparatus (e.g., with the aid of suitable guide mirrors); the latter may be the case when the source SO is an excimer laser (e.g., based on KrF, ArF or F2 lasers).

[0114] The light beam PB may then intercept the patterning device MA, which is held on the patterning device table MT. After passing the patterning device MA, the light beam B may pass through a lens PL, which focuses the light beam B onto a target portion C of the substrate W. With the aid of the second positioning device (and the interferometric measurement device IF), the substrate table WT may be precisely moved, for example, in order to position different target portions C in the path of the light beam PB. Similarly, the first positioning device may be used to precisely position the patterning device MA relative to the path of the light beam B, for example, after mechanical retrieval of the patterning device MA from a patterning device library, or during scanning. Typically, movement of the object tables MT, WT may be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning). However, in the case of a stepper (as opposed to a step-scan tool), the patterning device table MT may be connected only to a short-stroke actuator, or may be fixed.

[0115] The tool described can be used in two different modes: a step mode and a scan mode. In the step mode, the patterning device table MT remains substantially stationary and the entire patterning device image is projected at once (i.e., a single "flash") onto a target portion C. The substrate table WT can be shifted in the x and / or y direction so that a different target portion C can be illuminated by the beam PB.

[0116] In scan mode, essentially the same situation applies, except that a given target portion C is not exposed in a single "flash". Instead, the patterning device table MT moves in a given direction (the so-called "scanning direction", e.g. the y-direction) at a speed v, so that the projection beam B is scanned over the patterning device image; at the same time, the substrate table WT moves simultaneously in the same or opposite direction at a speed V=Mv, where M is the magnification of the lens PL (typically M=1 / 4 or 1 / 5). In this way, a relatively large target portion C can be exposed without having to compromise on resolution.

[0117] Fig.13 is a schematic diagram of another lithographic projection apparatus (LPA) according to an embodiment.

[0118] The LPA may comprise a source collector module SO, an illumination system (illuminator) IL configured to condition a radiation beam B (eg EUV radiation), a support structure MT, a substrate table WT and a projection system PS.

[0119] The support structure (e.g., patterning device stage) MT may be configured to support a patterning device (e.g., mask or reticle) MA and connected to a first positioner PM configured to accurately position the patterning device;

[0120] A substrate table (eg, wafer stage) WT may be configured to hold a substrate (eg, a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate.

[0121] The projection system (eg, a reflective projection system) PS may be configured to project a pattern imparted to the radiation beam B by patterning the device MA onto a target portion C of the substrate W (eg, comprising one or more dies).

[0122] As described herein, the LPA can be reflective (e.g., using a reflective patterning device). It is noted that because most materials are absorptive in the EUV wavelength range, the patterning device can have a multilayer reflector that includes, for example, multiple stacks of molybdenum and silicon. In one example, the multilayer reflector has 40 layers of molybdenum and silicon pairs, each layer being a quarter wavelength thick. Even smaller wavelengths can be produced using X-ray lithography. Since most materials are absorptive at EUV and X-ray wavelengths, a thin sheet of patterned absorbing material on the topography of the patterning device (e.g., a TaN absorber on top of a multilayer reflector) defines where features will be printed (positive resist) or not (negative resist).

[0123] The illuminator IL can receive an extreme ultraviolet radiation beam from a source collector module SO. Methods of generating EUV radiation include, but are not limited to, converting a material into a plasma state having at least one element, such as xenon, lithium, or tin, having one or more emission lines in the EUV range. In one such method, which is generally referred to as laser produced plasma ("LPP"), the plasma can be generated by irradiating a fuel such as a droplet, stream, or cluster of a material having a line emitting element with a laser beam. The source collector module SO can therefore be part of an EUV radiation system that includes a laser for providing a laser beam to excite the fuel. The generated plasma emits output radiation, such as EUV radiation, which is collected using a radiation collector disposed in the source collector module. The laser and the source collector module can be separate entities, such as when a CO2 laser is used to provide a laser beam for fuel excitation.

[0124] In this case, the laser may not be considered to form part of the lithographic apparatus, and the radiation beam may be delivered from the laser to the source collector module by means of a beam delivery system including, for example, suitable directing mirrors and / or a beam expander. In other cases, the source may be an integral part of the source collector module, for example when the source is a discharge produced plasma EUV generator, often referred to as a DPP source.

[0125] The illuminator IL may include an adjuster for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial extent of the intensity distribution in a pupil plane of the illuminator (typically referred to as σ outer and σ inner, respectively) may be adjusted. Furthermore, the illuminator IL may include various other components, such as a facet field and pupil mirror devices. The illuminator may be used to adjust the radiation beam to have a desired uniformity and intensity distribution in its cross section.

[0126] A radiation beam B may be incident on a patterning device (e.g., a mask) MA, which is held on a support structure (e.g., a patterning device table) MT, and patterned by the patterning device. After reflection from the patterning device (e.g., a mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor PS2 (e.g., an interferometer, a linear encoder, or a capacitive sensor), the substrate table WT may be precisely moved, for example, in order to position different target portions C in the path of the radiation beam B. Similarly, a first positioner PM and a further position sensor PS1 may be used to precisely position the patterning device (e.g., a mask) MA relative to the path of the radiation beam B. The patterning device (e.g., mask) MA and the substrate W may be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2.

[0127] The described apparatus LPA can be used in at least one of the following modes: a stepping mode, a scanning mode and a stationary mode.

[0128] In step mode, the support structure (e.g. patterning device table) MT and the substrate table WT are kept substantially stationary while an entire pattern imparted to the radiation beam is projected once onto a target portion C (i.e. a single static exposure). The substrate table WT is then moved in the X and / or Y direction so that a different target portion C can be exposed.

[0129] In scan mode, the support structure (e.g. patterning device table) MT and the substrate table WT are scanned synchronously (i.e. single dynamic exposure) as a pattern imparted to the radiation beam is projected onto a target portion C. The speed and direction of the substrate table WT relative to the support structure (e.g. patterning device table) MT may be determined by the (de)magnification and image reversal characteristics of the projection system PS.

[0130] In stationary mode, the support structure (e.g., patterning device table) MT remains substantially stationary to hold the programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, a pulsed radiation source is typically employed, and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography utilizing a programmable patterning device (e.g., a programmable mirror array).

[0131] Fig.14 is a detailed view of a lithographic projection apparatus according to an embodiment.

[0132] As shown, the LPA may include a source collector module SO, an illumination system IL, and a projection system PS. The source collector module SO is constructed and arranged so that a vacuum environment can be maintained in the closed structure ES of the source collector module SO. The EUV radiation emitting the thermal plasma HP may be formed by a plasma source generated by a discharge. The EUV radiation may be generated by a gas or vapor, such as Xe gas, Li vapor, or Sn vapor, wherein the thermal plasma HP is generated to emit radiation in the EUV range of the electromagnetic spectrum. The thermal plasma HP is generated by, for example, causing a discharge of at least partially ionized plasma. In order to effectively generate radiation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor may be required. In an embodiment, an excited tin (Sn) plasma is provided to generate EUV radiation.

[0133] The radiation emitted by the hot plasma HP enters the collector chamber CC from the source chamber SC via an optional gas barrier or contaminant trap CT (also referred to as a contaminant barrier or foil trap in some cases), which is located within or behind an opening of the source chamber SC. The contaminant trap CT may include a channel structure. The contaminant trap CT may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier CT further indicated herein includes at least a channel structure known in the art.

[0134] The collector chamber CC may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side US and a downstream radiation collector side DS. Radiation passing through the radiation collector CO may be reflected by a grating spectral filter SF and thereby focused in a virtual source point IF along the optical axis indicated by the dotted line "O". The virtual source point IF may be referred to as an intermediate focus, and the source collector module may be arranged such that the intermediate focus IF is located at or near an opening OP in the enclosed structure ES. The virtual source point IF is an image of the radiation emitting plasma HP.

[0135] The radiation then passes through an illumination system IL which may include a facet field mirror device FM and a facet pupil mirror device pm arranged to provide a desired angular distribution of the radiation beam B at the patterning device MA, and a desired uniformity of the amplitude of the radiation at the patterning device MA. When the radiation beam B is reflected at the patterning device MA held by the support structure MT, a patterned beam PB is formed and the patterned beam PB is imaged by the projection system PS via the reflective element RE onto a substrate W held by a substrate table WT.

[0136] In general, more elements than shown may be present in the illumination optics unit IL and the projection system PS. Depending on the type of lithographic apparatus, a grating spectral filter SF may optionally be present. Furthermore, there may be more mirrors than shown in the figures, for example, 1-6 additional reflective elements may be present in the projection system PS.

[0137] The collector optical system CO may be a nested collector with a grazing incidence reflector GR, as an example of a collector (or collector mirror). The grazing incidence reflector GR is arranged axisymmetrically around the optical axis O, and this type of collector optical system CO may be used in combination with a discharge produced plasma source (commonly referred to as a DPP source).

[0138] Fig.15 is a detailed view of a source collector module SO of a lithographic projection apparatus LPA according to an embodiment.

[0139] The source collector module can thus be part of an LPA radiation system. The laser LA can be arranged to deposit laser energy into a fuel, such as xenon (Xe), tin (Sn) or lithium (Li), producing a highly ionized plasma HP with an electron temperature of tens of eV. The high-energy radiation produced during the de-excitation and recombination of these ions is emitted from the plasma, collected by the near normal incidence collector optics CO, and focused onto an opening OP in the enclosed structure ES.

[0140] The embodiments may be further described using the following terms:

[0141] 1. A method for reducing adhesion of an object to a surface for use in a photolithography process, the method comprising:

[0142] receiving, at a control computer, instructions for a tool configured to modify a surface; and

[0143] A modified surface having grooves and ridges is formed in a determined manner based on instructions received at a control computer, wherein the ridges reduce adhesion by reducing the contact surface area of ​​the modified surface.

[0144] 2. A method according to claim 1, wherein modifying the surface is caused by moving the tool tip of the tool causing plastic deformation of the surface such that there is substantially no loss of material.

[0145] 3. The method according to item 1, further comprising:

[0146] acquiring an image of the surface from an imaging device;

[0147] registering the tool tip in a coordinate space of the surface based on the image; and

[0148] The tool is controlled to move the tool tip to predefined coordinates in the coordinate space to create grooves and ridges.

[0149] 4. A method according to claim 3, wherein the control has a horizontal resolution of 1 micron or less and a vertical resolution of 10 nanometers or less, and wherein the resolution of the force transmitted by the tool tip is 1 millinewton or less.

[0150] 5. The method of claim 3, wherein the controlling further comprises controlling the tool tip to form a modified surface having a plurality of parallel ridges.

[0151] 6. The method of clause 3, wherein the controlling further comprises controlling the tool tip to form a modified surface having a non-uniform density of ridges corresponding to a non-uniform nodule loading.

[0152] 7. A method according to clause 1, wherein when forming the modified surface, the surface is between 15 and 40 degrees Celsius.

[0153] 8. A computer program product, comprising a non-transitory computer-readable medium having instructions recorded thereon, the instructions implementing any one of the methods described above when executed by a computer.

[0154] 9. An apparatus for photolithography, the apparatus comprising:

[0155] A modified surface comprising a plurality of grooves and ridges forming a reduced contact surface area to reduce adhesion of an object to the modified surface, wherein at least 60% of the plurality of ridges have a height variation of less than 100 nanometers.

[0156] 10. An apparatus as described in claim 9, wherein the plurality of ridges have a ridge height measured from an average height of the unmodified surface.

[0157] 11. A device according to item 9, wherein at least 80% of the plurality of ridges have a height variation of less than 100 nanometers.

[0158] 12. A device according to item 11, wherein at least 60% of the plurality of ridges have a height variation of less than 10 nanometers.

[0159] 13. A device according to item 9, wherein at least 80% of the plurality of ridges have a height variation of less than 5 nanometers.

[0160] 14. Apparatus according to clause 9, wherein the height variation is measured over substantially all of the modified surface.

[0161] 15. The device according to item 9 further comprises a plurality of granule knots, the granule knots comprising a plurality of grooves and ridges on the surfaces of the corresponding plurality of granule knots.

[0162] 16. The apparatus of clause 9, wherein at least some of the plurality of nodules have a coating, wherein a plurality of grooves and ridges are formed in the coating.

[0163] 17. A device according to item 9, wherein the plurality of grooves and ridges are parallel.

[0164] 18. The apparatus of claim 9, further comprising a plurality of mountain tops, wherein a plurality of grooves and ridges are formed across the mountain tops.

[0165] 19. An apparatus according to item 18, wherein the plurality of grooves and ridges are formed substantially perpendicular to the mountain top.

[0166] 20. A device according to item 9, wherein the modified surface is located on a granular junction extending from the substrate.

[0167] 21. The apparatus of item 20, wherein the substrate is a mask holder, a wafer holder or a wafer stage.

[0168] 22. The device of claim 20, wherein the nodule further comprises a coating and the modified surface is located on the coating.

[0169] 23. A device according to item 22, wherein the coating is a hard ceramic coating.

[0170] 24. The device according to item 9, wherein the surface is a knotted surface made of a plurality of knots.

[0171] 25. The apparatus of claim 20, wherein the nodules include mountain tops, and the grooves and ridges are formed at an oblique angle to the mountain tops.

[0172] 26. An apparatus according to item 25, wherein the bevel angle is approximately 90 degrees.

[0173] 27. A device according to item 9, wherein the modified surface includes a groove and two ridges located on either side of the groove.

[0174] 28. A device according to item 9, wherein the depth of the groove is between 50 and 150 nanometers.

[0175] 29. A device according to item 9, wherein the depth of the groove is about 100 nanometers.

[0176] 30. A device according to item 9, wherein the height of the ridges is between 2 and 50 nanometers.

[0177] 31. A device according to item 9, wherein the height of the ridges is about 10 nanometers.

[0178] 32. An apparatus comprising:

[0179] A modified surface includes a plurality of grooves and ridges that form a reduced contact surface area to reduce adhesion of an object to the modified surface, the plurality of ridges having elastic properties that cause the reduced contact surface area to increase when the plurality of ridges are elastically deformed.

[0180] 33. A device according to item 32, wherein the modified surface is formed by multiple plastic deformations of the unmodified surface.

[0181] 34. A device according to item 32, wherein, when no deforming force is applied to the plurality of ridges, the reduced contact surface area of ​​the plurality of ridges is less than 5% of the total contact surface area.

[0182] 35. Apparatus according to claim 32, wherein when a downward clamping pressure of at least 0.5 bar is applied to a portion of the object, the reduced contact surface area increases to greater than 25% of the total surface area defined by the outermost ridges.

[0183] The concepts disclosed herein can simulate or mathematically model any general imaging system for imaging sub-wavelength features and are particularly useful for emerging imaging technologies that can produce shorter and shorter wavelengths. Emerging technologies already in use include EUV (extreme ultraviolet), DUV lithography, which can produce 193nm wavelengths using ArF lasers, and even 157nm wavelengths using fluorine lasers. In addition, EUV lithography can produce wavelengths in the range of 20-50nm by using a synchrotron or by bombarding materials (solid or plasma) with high-energy electrons to produce photons in this range.

[0184] Although the concepts disclosed herein may be used for imaging on substrates such as silicon wafers, it should be understood that the disclosed concepts may be used with any type of lithography imaging system, such as a lithography imaging system for imaging on substrates other than silicon wafers.

[0185] The above description is intended to be illustrative, rather than restrictive. Therefore, it will be apparent to those skilled in the art that modifications as described can be made without departing from the scope of the claims.

Claims

1. A device comprising: A modified surface comprising a plurality of grooves and a plurality of ridges, wherein the plurality of grooves and the plurality of ridges form a reduced contact surface area to reduce adhesion of an object to the modified surface, wherein the plurality of ridges have elastic properties, and when the plurality of ridges are elastically deformed, the elastic properties cause the reduced contact surface area to increase.

2. The device of claim 1, wherein the modified surface is formed by a plurality of plastic deformations of an unmodified surface.

3. The device of claim 1, wherein the reduced contact surface area of ​​the plurality of ridges is less than 5% of a total contact surface area when no deforming force is applied to the plurality of ridges.

4. The apparatus of claim 1, wherein when a downward clamping pressure of at least 0.5 bar is applied to the portion of the object, the reduced contact surface area will increase to greater than 25% of the total surface area defined by the outermost ridges.

5. The apparatus of claim 1, wherein the plurality of ridges have a ridge height measured from an average height of the unmodified surface.

6. The device of claim 1, wherein at least 60% of the ridges in the plurality of ridges have a height variation of less than 100 nanometers.

7. The apparatus of claim 6, wherein said height variation is measured over substantially all of said modified surface.

8. The device of claim 1, wherein at least 80% of the ridges in the plurality of ridges have a height variation of less than 100 nanometers.

9. The device of claim 1, wherein at least 60% of the ridges in the plurality of ridges have a height variation of less than 10 nanometers.

10. The device of claim 1, wherein at least 80% of the ridges in the plurality of ridges have a height variation of less than 5 nanometers.

11. The device of claim 1, wherein at least some of the plurality of ridges are formed on a granular coating.

12. The device of claim 1, wherein the plurality of grooves and the plurality of ridges are parallel.

13. The apparatus of claim 1, further comprising a plurality of mountain tops, wherein the plurality of grooves and the plurality of ridges are formed across the mountain tops.

14. An apparatus according to item 13, wherein the plurality of grooves and the plurality of ridges are formed substantially perpendicular to the mountain top.

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