Systems and methods for stabilizing optical columns against displacement or rotation

Abstract

The present invention provides a system and method for stabilizing an optical column. A system may include: an optical column; a frame configured to support the optical column, the frame having a first coefficient of thermal expansion (CTE); and a subframe configured to be coupled to the optical column at at least two locations by a first anchor and a second anchor to stabilize the optical column and prevent displacement or rotation of the optical column caused by thermal expansion of the frame or the optical column, the subframe having a second CTE lower than the first CTE.

Description

Technical Field

[0001] The description herein generally pertains to maskless manufacturing and patterning processes. More specifically, the present invention includes systems and methods for stabilizing optical columns. Prior Technology

[0002] Lithography equipment can be used, for example, to manufacture integrated circuits (ICs). In this case, a patterning device (e.g., a mask) may contain or provide a pattern ("design layout") corresponding to individual layers of the IC, and this pattern can be transferred onto a target portion (e.g., containing one or more dies) on a substrate (e.g., a silicon wafer) coated with a layer of radiation-sensitive material ("resist") by means such as irradiating the target portion with a pattern on the patterning device. Generally, a single substrate contains a plurality of adjacent target portions, and the pattern is sequentially transferred to the plurality of adjacent target portions by the lithography equipment, one target portion at a time. In one type of lithography equipment, the entire pattern on the patterning device is transferred to a single target portion at once; this device may also be called a stepper. In an alternative device, a stepping scanning device allows a projection beam to scan the patterning device in a given reference direction ("scanning" direction) while simultaneously moving the substrate parallel or antiparallel to this reference direction. Different portions of the pattern on the patterning device are progressively transferred to a single target portion. Because, generally speaking, lithography devices will have a reduction ratio M (e.g., 4), the substrate moving speed F will be 1 / M time, at which point the projection beam scans the patterning device. Further information about lithography devices can be found, for example, in US 6,046,792, which is incorporated herein by reference.

[0003] Before a pattern is transferred from a patterning apparatus to a substrate, the substrate may undergo various processes, such as applying a primer, coating with resist, and soft baking. After exposure, the substrate may undergo other processes ("post-exposure processes"), such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. This array of processes forms the basis for manufacturing individual layers of a device (e.g., an IC). The substrate may then undergo various processes, such as etching, ion implantation (doping), metallization, oxidation, chemical mechanical polishing, etc., all intended to refine the individual layers of the device. If several layers are required in the device, the entire process or its variations are repeated for each layer. Ultimately, a device will exist in each target portion on the substrate. These devices are then separated from each other using techniques such as dicing or sawing, thereby allowing individual devices to be mounted on a carrier, connected to pins, etc.

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

[0005] As mentioned, lithography is a central step in the manufacturing of devices such as ICs, in which patterns are formed on a substrate to define functional elements such as microprocessors and memory chips. Similar lithography techniques are also used to form flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0006] As semiconductor manufacturing processes continue to advance, the size of functional components has been shrinking over the decades, while the number of functional components, such as transistors, per device has been steadily increasing, following a trend known as Moore's Law. In the current state of technology, lithography equipment is used to fabricate the layers of a device. This equipment projects a design layout onto a substrate using illumination from a deep ultraviolet light source, thereby producing individual functional components with dimensions well below 100 nm (i.e., less than half the wavelength of radiation from the illumination source, such as a 193 nm source).

[0007] According to the resolution formula CD = k1 × λ / NA, this process of printing features with dimensions smaller than the classical resolution limit of lithography equipment can be called low-k1 lithography, where λ is the wavelength of the radiation used (e.g., 248 nm or 193 nm), NA is the numerical aperture of the projection optics in the lithography equipment, CD is the "critical size" – typically, the smallest feature size printed – and k1 is the experimental resolution factor. Generally speaking, the smaller k1 is, the more difficult it becomes to reproduce patterns on a substrate that resemble the shape and size planned by the designer to achieve specific electrical functions and performance. To overcome these difficulties, complex fine-tuning steps are applied to lithography equipment, design layouts, or patterning devices. These include, but are not limited to, optimization of NA and optical coherence settings, customized illumination schemes, the use of phase-shift patterning devices, optical proximity correction (OPC, sometimes also called "optical and procedural correction") in the design layout, or other methods generally defined as "resolution enhancement techniques" (RET). As used herein, the term "projection optics" should be broadly interpreted to encompass various types of optical systems, including, for example, refractive optics, reflective optics, aperture and reflective-refractive optics. The term "projection optics" may also include components operating according to any of these design types for collectively or individually guiding, shaping, or controlling a projected radiation beam. The term "projection optics" may include any optical component in a lithography apparatus, regardless of its location within the optical path of the lithography apparatus. Projection optics may include optical components for shaping, adjusting, and / or projecting radiation from a source before it passes through a patterning device, and / or for shaping, adjusting, and / or projecting radiation after it has passed through the patterning device. Projection optics typically exclude both the source and the patterning device. Summary of the Invention

[0008] A system and method for stabilizing an optical column to prevent thermal effects are disclosed. In a first embodiment, a system includes an optical column and a frame configured to support the optical column, the frame having a first coefficient of thermal expansion (CTE). The system also includes a subframe configured to be coupled to the optical column at at least two locations by first and second anchors to stabilize the optical column and prevent displacement or rotation of the optical column caused by thermal expansion within the frame or the optical column. The subframe has a second CTE lower than the first CTE.

[0009] In some variations, the optical column may be suspended at its distal end below a transverse frame section of the frame, and a sub-frame may be coupled to the optical column at its proximal end. The sub-frame may be coupled to the optical column at approximately one level of the microlens array within the optical column. The frame may be primarily made of steel with a CTE of approximately 14 µm / m / K. The sub-frame may be primarily made of cordierite with a CTE of approximately 0.03 µm / m / K.

[0010] In other variations, the first and second anchors can be configured to couple to the subframe and optical column to stabilize the optical column and prevent in-plane displacement and rotation about a longitudinal axis passing through the optical column perpendicular to the plane. In-plane displacement may not exceed 10 micrometers, and rotation about a longitudinal axis passing through the optical column perpendicular to the plane may not exceed 10 microradians.

[0011] In other variations, there may be several optical pillars, several first anchors, and several second anchors. Each of the first and second anchors may be coupled to a corresponding optical pillar within the optical pillars.

[0012] In some variations, the first anchor can be configured to remain stable and prevent displacement of the optical post in at least two directions perpendicular to its axis. The first anchor may extend at least partially in a first direction and at least partially in a second direction. The first anchor may be substantially centered on one side of the optical post.

[0013] In other variations, the second anchor may be coupled to the optical post at a different location than the first anchor, thereby resisting rotation of the optical post about the longitudinal axis.

[0014] In other variations, the subframe may further include a third anchor, wherein the coupling system at at least two locations is performed by the first anchor and further by the third anchor. The first and third anchors may be coupled to the optical post at the same location. The third anchor may be configured to maintain stability to prevent displacement of the optical post in at least two directions perpendicular to the longitudinal axis of the optical post, wherein the third anchor extends at least partially opposite to the first of the two directions and at least partially in the second of the two directions. The first, second, and third anchors may all be on one side of the subframe.

[0015] In some variations, the subframe may include a first transverse subframe segment, to which a first anchor and a second anchor are coupled. The subframe may include a release mechanism that allows the first transverse subframe segment to be detached from a second transverse subframe segment of the subframe.

[0016] In other variations, the frame may include two vertical frame segments symmetrically located at opposite ends of the transverse frame segments to allow the optical column to be positioned therebetween, wherein a subframe is coupled to the two vertical frame segments, thereby centering the subframe within the frame.

[0017] In some variations, the subframe can be configured to couple to an external body to resist vertical displacement. The system may include a Z-actuator coupled to the optical column and configured to compensate for vertical displacement of the optical column.

[0018] In one related example, a method for stabilizing an optical column to prevent displacement or rotation includes supporting the optical column with a frame having a first coefficient of thermal expansion (CTE). The method also includes coupling the optical column to a subframe at at least two locations via a first anchor and a second anchor to stabilize the optical column and prevent displacement or rotation of the optical column caused by thermal expansion within the frame or the optical column, the subframe having a second CTE lower than the first CTE.

[0019] In some variations, the method may further include stabilizing the optical column using first and second anchors to prevent in-plane displacement and rotation about a longitudinal axis passing through the optical column perpendicular to the plane. The method may further include coupling a subframe to the optical column at approximately one level of the microlens array located within the optical column. The method may further include coupling a second anchor to the optical column at a location different from the first anchor, thereby resisting rotation of the optical column about its longitudinal axis. The method further includes coupling a third anchor to the subframe, wherein this coupling at at least two locations is performed by means of the first anchor and further by means of the third anchor. Simple Explanation of the Diagram

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate certain aspects of the subject matter disclosed herein and, together with the description, help to clarify some principles associated with the disclosed embodiments. In the drawings,

[0021] Figure 1 illustrates a block diagram of various subsystems of a lithography device according to one embodiment.

[0022] Figure 2 illustrates an exemplary flowchart for simulating a lithography in a lithography projection device according to one embodiment.

[0023] Figure 3 illustrates an optical column supported by a frame and stabilized by a subframe according to one embodiment.

[0024] Figure 4 illustrates a bottom view of Figure 3 depicting an anchor member of a subframe according to one embodiment.

[0025] Figure 5 includes a perspective view illustrating the stability at the end of an optical column according to one embodiment.

[0026] Figure 6 illustrates an exemplary example of a subframe that maintains stability to prevent displacement and rotation that may occur in the disclosed system, according to one embodiment.

[0027] Figure 7 illustrates an example of finite element analysis performed according to an embodiment to simulate changes in the frame and optical pillars attributed to thermal effects.

[0028] Figure 8 illustrates a flowchart depicting an exemplary method for stabilizing an optical column according to one embodiment.

[0029] Figure 9 is a block diagram of an example computer system according to one embodiment.

[0030] Figure 10 is a schematic diagram of a lithography device according to one embodiment.

[0031] Figure 11 is a schematic diagram of another lithography device according to one embodiment.

[0032] Figure 12 is a detailed view of a lithography device according to one embodiment.

[0033] Figure 13 is a detailed view of the source collector module of a lithography device according to an embodiment. Implementation

[0034] While IC manufacturing may be specifically referenced herein, it should be clearly understood that the description herein has many other possible applications. For example, it can be used to manufacture integrated optical systems, guide and detection patterns for magnetic domain memory, liquid crystal display panels, flat panel displays, thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of these alternative applications, any use of the terms "mask," "wafer," or "die" herein should be considered interchangeable with the more general terms "mask," "substrate," and "target portion," respectively.

[0035] In this document, the terms “radiation” and “beam” are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., having wavelengths of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultraviolet radiation, e.g., having wavelengths in the range of about 5 to 100 nm).

[0036] Patterned devices can contain or form one or more design layouts. Design layouts can be generated using CAD (Computer-Aided Design) programs, often referred to as EDA (Electronic Design Automation). Most CAD programs follow a predetermined set of design rules to generate functional design layouts / patterned devices. These rules are set through processing and design constraints. For example, design rules define the space tolerances between devices (such as gates, capacitors, etc.) or interconnects to ensure that these devices or lines do not interact with each other in an undesirable manner. One or more of these design rule constraints can be called "critical dimensions" (CD). The critical dimension of a device can be defined as the minimum width of a line or hole, or the minimum space 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 (via the patterned device) on the substrate.

[0037] The terms "mask" or "patterning device" as used herein can be broadly interpreted as any general patterning device that imparts a patterned cross-section to an incident radiation beam, the patterned cross-section corresponding to a pattern to be generated in a target portion of a substrate. In this context, the term "light valve" may also be used. Besides classic masks (transmissive or reflective; binary, phase-shifting, hybrid, etc.), other examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0038] An example of a programmable mirror array could be a matrix-addressable surface with a viscoelastic control layer and a reflective surface. The underlying principle of this device is (for example): the addressed regions of the reflective surface reflect incident radiation as diffracted radiation, while the unaddressed regions reflect incident radiation as non-diffracted radiation. Using appropriate filters, the non-diffracted radiation can be filtered out from the reflected beam, leaving only the diffracted radiation; in this way, the beam becomes patterned according to the addressing pattern of the matrix-addressable surface. Suitable electronic methods can be used to perform the desired matrix addressing.

[0039] Examples of programmable LCD arrays are given in U.S. Patent No. 5,229,872, which is incorporated herein by reference.

[0040] Figure 1 illustrates a block diagram of various subsystems of a lithography projection apparatus 10A according to an embodiment. The main components are: a radiation source 12A, which may be a deep ultraviolet excimer laser source or other types of sources including extreme ultraviolet (EUV) sources (as discussed above, the lithography projection apparatus itself does not need to have a radiation source); illumination optics, which, for example, define partial coherence (represented as mean square deviation) and may include optics 14A, 16Aa, and 16Ab that shape the radiation from source 12A; a patterning device 18A; and a transmission optics 16Ac that projects an image of a pattern from the patterning device onto a substrate plane 22A. An adjustable filter or aperture 20A at the pupil plane of the projection optics can limit the range of beam angles that illuminate the substrate plane 22A. The maximum possible angle is defined as the numerical aperture NA of the projection optics = n sin(Θmax), where n is the refractive index of the medium between the substrate and the last element of the projection optics, and Θmax is the maximum angle of the beam emitted from the projection optics that can still illuminate the substrate plane 22A.

[0041] In a lithography apparatus, a source provides illumination (i.e., radiation) to a patterning device, and projection optics guide and shape the illumination onto a substrate via the patterning device. The projection optics may include at least some of components 14A, 16Aa, 16Ab, and 16Ac. The aerial image (AI) is the distribution of radiation intensity at the substrate layer. A resist image can be calculated from the aerial image using a resist model, an example of which can be found in U.S. Patent Application Publication No. 2009-0157630, the disclosure of which is hereby incorporated by reference in its entirety. The resist model relates only 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 lithography apparatus (e.g., the illumination properties of the patterning device and the projection optics) define the aerial image and can be defined in the optical model. Because the patterning device used in the lithography device can be modified, it is necessary to separate the optical properties of the patterning device from the optical properties of the rest of the lithography device, which includes at least the source and projection optics. Details of the techniques and models used to transform design layouts into various lithography images (e.g., aerial images, resist images, etc.), to apply OPC using such techniques and models, and to evaluate performance (e.g., based on program windows) are described in U.S. Patent Application Publications Nos. 2008-0301620, 2007-0050749, 2007-0031745, 2008-0309897, 2010-0162197, and 2010-0180251, the disclosures of which are hereby incorporated by reference in their entirety.

[0042] Understanding one aspect of lithography is understanding the interaction between radiation and the patterning device. The electromagnetic field of the radiation after it passes through the patterning device can be determined from the electromagnetic field of the radiation before it reaches the patterning device and a function that characterizes this interaction. This function can be called the masking transmission function (which can be used to describe the interaction between the transmission patterning device and / or the reflection patterning device).

[0043] Masking transmission functions can take various forms. One form is binary. A binary masking transmission function has either one of two values ​​(e.g., zero and a positive constant) at any given location on the patterning apparatus. A masking transmission function in binary form can be called a binary mask. Another form is continuous. That is, the modulus of the transmissivity (or reflectivity) of the patterning apparatus is a continuous function of the location on the patterning apparatus. The phase of the transmissivity (or reflectivity) can also be a continuous function of the location on the patterning apparatus. A masking transmission function in continuous form can be called a continuous tone mask or a continuous transmission mask (CTM). For example, a CTM can be represented as a pixelated image, where each pixel can be assigned a value between 0 and 1 (e.g., 0.1, 0.2, 0.3, etc.) instead of a binary value of 0 or 1. In one embodiment, the CTM may be a pixelated grayscale image, wherein each pixel has several values ​​(e.g., normalized values ​​in the range [-255, 255], in the range [0, 1], or [-1, 1], or other suitable ranges).

[0044] The thin masking approximation (also known as the Kirchhoff boundary condition) is widely used to simplify the determination of the interaction between radiation and a patterning device. The thin masking approximation assumes that the thickness of the structure on the patterning device is extremely small compared to the wavelength, and the width of the structure on the mask is extremely large compared to the wavelength. Therefore, the thin masking approximation assumes that the electromagnetic field behind the patterning device is the product of the incident electromagnetic field and the mask transmission function. However, as lithography processes use radiation with increasingly shorter wavelengths and the structure on the patterning device becomes increasingly smaller, the assumptions of the thin masking approximation can be decomposed. For example, due to the finite thickness of the structure (e.g., the edge between the top surface and the sidewalls), the interaction between radiation and the structure ("mask 3D effect" or "M3D") can become significant. Including this scattering in the mask transmission function allows the mask transmission function to better capture the interaction between radiation and the patterning device. The mask transmission function under the thin masking approximation can be called the thin mask transmission function. The masking transmission function that encompasses the M3D effect can be called the M3D masking transmission function.

[0045] According to one embodiment of the present invention, one or more images can be generated. These images include various types of signals that can be characterized by the pixel values ​​or intensity values ​​of each pixel. Depending on the relative values ​​of pixels within the image, the signal may be referred to as, for example, a weak signal or a strong signal, as will be understood by those skilled in the art. The terms "strong" and "weak" are relative terms based on the intensity values ​​of pixels within the image, and the specific values ​​of intensity may not limit the scope of the invention. In one embodiment, strong and weak signals can be identified based on selected threshold values. In one embodiment, the threshold value may be fixed (e.g., the midpoint between the highest and lowest intensities of pixels within the image). In one embodiment, a strong signal may refer to a signal having a value greater than or equal to the average signal value across the image, and a weak signal may refer to a signal having a value less than the average signal value. In one embodiment, the 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 the pixel with the highest intensity). Furthermore, each pixel within the image is considered a variable. According to this embodiment, derivatives or partial derivatives can be related to the determination of each pixel within the image, and the value of each pixel can be determined or modified based on an evaluation based on a cost function and / or a gradient-based calculation of the cost function. For example, a CTM image may include pixels, where each pixel is a variable that can take any real value.

[0046] Figure 2 illustrates an exemplary flowchart for simulating a lithography projection apparatus according to one embodiment. Source model 31 represents the optical characteristics of the source (including radiation intensity distribution and / or phase distribution). Projection optics model 32 represents the optical characteristics of the projection optics (including changes in radiation intensity distribution and / or phase distribution caused by the projection optics). Design layout model 35 represents the optical characteristics of a design layout (including changes in radiation intensity distribution and / or phase distribution caused by design layout 33), which is a representation of a feature configuration on or formed by a patterning device. An aerial image 36 can be simulated from the design layout model 35, the projection optics 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 the lithography can, for example, predict the contours and CDs in the resist image.

[0047] More specifically, it should be noted that source model 31 may represent the optical characteristics of a source, including but not limited to numerical aperture settings, illumination mean square deviation (σ) settings, and any particular illumination shape (e.g., off-axis radiation sources, such as rings, quadrupoles, dipoles, etc.). Projection optics model 32 may represent the optical characteristics of a projection optics, including aberrations, distortion, one or more refractive indices, one or more entity sizes, one or more entity dimensions, etc. Design layout model 35 may represent one or more physical properties of a physical patterning device, such as those described, for example, in U.S. Patent No. 7,587,704, which is incorporated herein 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 with the intended design. The intended design is generally 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.

[0048] From this design layout, one or more portions referred to as "clips" can be identified. In one embodiment, a set of clips is extracted, representing complex patterns in the design layout (typically about 50 to 1000 clips, but any number of clips can be used). These patterns or clips represent small portions of the design (i.e., circuits, cells, or patterns), and more specifically, these clips typically represent small portions requiring specific attention and / or verification. In other words, a clip can be part of the design layout, or can be similar or have similar behavior to parts of the design layout, wherein one or more critical features are identified by experience (including clips provided by the customer), trial and error, or performing full-chip simulation. Clips may contain one or more test patterns or gauge patterns.

[0049] The initial large clip set can be provided a priori by the customer based on one or more known critical feature regions in the design layout that require specific image optimization. Alternatively, in another embodiment, the initial large clip set can be extracted from the entire design layout by using some automatic (such as machine vision) or manual algorithm that identifies the one or more critical feature regions.

[0050] In lithography devices, as an example, the cost function can be expressed as follows: (Equation 1)

[0051] in There are N design variables or their values. Can be a design variable Functions, such as design variables The difference between the actual value and the expected value of the property of the set of values. To and Associated weighting constants. For example, a characteristic could be the position of the edge of a pattern measured at a given point on the edge. Different Can have different weights For example, if a particular edge has a narrow permissible position range, then the term used to represent the difference between the actual and expected positions of the edge is... Weight A higher value can be given. It can also be a function of interlayer characteristics, which in turn are design variables. The function of. Of course, Not limited to the form in Equation 1. It may be in any other suitable form.

[0052] The cost function can represent any one or more suitable characteristics of the lithography device, lithography program, or substrate, such as focus, CD, image shift, image distortion, image rotation, randomness, output, local CD variation, program window, interlayer characteristics, or a combination thereof. In one embodiment, design variables... It includes one or more shapes selected from dosage, global bias of the patterning device, and / or illumination. Since resist images often define a pattern on a substrate, the cost function may include functions representing one or more characteristics of the resist image. For example, It can simply be the distance between the expected positions of one point and another point in the resist image (i.e., edge placement error). Design variables can include any adjustable parameters, such as those related to the source, patterning device, projection optics, dose, focus, etc.

[0053] Lithography apparatuses may include components collectively referred to as "wavefront manipulators" that can be used to adjust the shape of the wavefront and the intensity distribution and / or phase shift of the radiated beam. In one embodiment, the lithography apparatus can adjust the wavefront and intensity distribution at any location along the optical path of the lithography 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 can be used to correct or compensate for certain distortions in the wavefront and intensity distribution and / or phase shift caused by, for example, temperature variations in the source, patterning device, lithography projection apparatus, thermal expansion of components of the lithography projection apparatus, etc. Adjusting the wavefront and intensity distribution and / or phase shift can change the value of a characteristic represented by a cost function. These changes can be simulated from a model or actually measured. Design variables may include parameters of the wavefront manipulator.

[0054] Design variables can have constraints, which can be expressed as follows: ,in This represents the set of possible values ​​for design variables. A possible constraint on the design variables can be imposed by the desired output of the lithography equipment. Without this constraint imposed by the desired output, optimization can result in an impractical set of values ​​for the design variables. For example, if dose is a design variable, optimization without this constraint could yield dose values ​​that make the output economically impossible. However, the usefulness of a constraint should not be interpreted as its necessity. For example, output can be affected by the pupil fill ratio. For some lighting designs, a low pupil fill ratio can sacrifice radiation, resulting in lower output. Output can also be affected by the chemical reaction of the resist. Slower resists (e.g., those requiring proper exposure to higher amounts of radiation) result in lower output.

[0055] As used herein, the term "patterning process" refers to the process of creating a specified pattern on an etched substrate by applying light as part of a lithography process.

[0056] As used in this article, the term "target pattern" refers to an idealized pattern to be etched onto a substrate.

[0057] As used herein, the term "printed pattern" refers to a solid pattern etched onto a substrate based on a target pattern. Printed patterns may include, for example, grooves, channels, recesses, edges, or other two-dimensional and three-dimensional features generated by lithography.

[0058] As used herein, the term "program model" means a model that simulates one or more models of a patterning process. For example, a program model may include any combination of the following: an optical model (e.g., modeling a lens system / projection system used to deliver light in a lithography process and may include modeling the final optical image of light entering the photoresist), a resist model (e.g., modeling the physical effects of the resist, such as chemical effects attributable to light); an OPC model (e.g., used to create a target pattern and may include sub-resolution resist features (SRAF), etc.); an imaging device model (e.g., modeling the content that an imaging device can image from a printed pattern).

[0059] As used herein, the term "imaging apparatus" means any number of devices and associated computer hardware and software, or a combination thereof, that can be configured to produce an image of a target (such as a printed pattern or a portion thereof). Non-limiting examples of imaging apparatuses may include: scanning electron microscopes (SEM), X-ray machines, etc.

[0060] As used in this article, the term "calibration" means to modify (e.g., improve or adjust) and / or verify something, such as a program model.

[0061] Figure 3 illustrates an optical column supported by a frame and stabilized by a subframe according to one embodiment. Figure 4 illustrates a bottom view of Figure 3 depicting an anchor of the subframe according to one embodiment. For high-precision lithography processes, it may be necessary to stabilize components to prevent unacceptable displacement or rotation that could introduce errors into the lithography process. For example, temperature changes can cause expansion or contraction of one or more dimensions of various components in a so-called "optical column". An optical column may include components that can be substantially arranged along an axis to form a "column", such as microlens arrays, focusing optics, digital mirror devices, etc. The exemplary lithography apparatus 10A depicted in Figure 1 is an example of an optical column. However, it should be understood that any optical column may contain different components in which any component may be in different positions. Thermal expansion / contraction can therefore cause optical components in the optical column to shift or rotate, so that they are not in the desired position. The present invention therefore provides numerous embodiments for stabilizing components in an optical column.

[0062] For example, the position of an optical column can be stabilized relative to a machine reference (e.g., a metric frame or coordinate system). By stabilizing the position of the optical column in a "stress-free" manner, no (or very limited) stress is introduced into the optical column, meaning that the internal components of the column also remain in place. Some mounting devices described herein can constrain six degrees of freedom (3 translations, 3 rotations), so the system can be constrained but not over-constrained. Therefore, some embodiments described herein may utilize six pillars, one pillar for each degree of freedom. The stabilization of the components of the optical column can also be achieved by mechanically stabilizing specific components of the optical column with a minimum allowable translation / rotation (e.g., MLA). As described herein, this may include positioning subframes / anchors at the shortest possible mechanical distance from the specific component. Although the present invention primarily addresses displacement and rotation attributable to thermal effects, the embodiments described herein can also provide stabilization for similar displacement and rotation attributable to other causes (e.g., mechanical strain, vibration, airflow, etc.).

[0063] As depicted in Figure 3, one example of system 300 may include an optical column 310 and a frame 320 configured to support the optical column 310. In some embodiments, the optical column may have its various components suspended (e.g., suspended) above a substrate 330 that receives light from a lithography assembly. Also depicted in Figure 3, the substrate 330 may be supported by a stage 340 (which in some embodiments may also be a metroframe) that can be moved in up to three dimensions by means of an actuator 350. In this way, the substrate 330 can be moved below the optical column to facilitate the delivery of light to the substrate at the desired location to produce the desired printed pattern.

[0064] Compared to the "suspended" embodiment described above, other embodiments can be considered, in which the system is in a different orientation (e.g., horizontal). Therefore, although much of the invention herein is provided with reference to a particular coordinate system (e.g., X, Y, Z), this should not be specifically interpreted as the Z-direction being vertical, etc. Similarly, for illustrative purposes, in some cases a direction will be referred to as positive or negative (e.g., +X or -X), but such constructions are also for illustrative purposes only and therefore should not imply any particular orientation of the disclosed system beyond what is disclosed or what a person skilled in the art would understand based on the invention.

[0065] As shown in the example of Figure 3, the optical column can be suspended at its distal end 312 below the transverse frame section 322 of the frame. A subframe is also depicted coupling to the optical column at its proximal end 314. As used herein, the term "distal end" refers to the end of the optical column furthest from the substrate. Similarly, the term "proximal end" refers to the end of the optical column closest to the substrate. However, it should be understood that the term "end" does not mean the extreme of the optical column, but rather the general area surrounding each end. Thus, for example, each "end" may include up to the last 40% of the optical column, but in other embodiments may include up to the last 30%, 20%, or 10% of the optical column.

[0066] Based on general disclosures related to addressing technical problems involving thermal expansion other than the desired thermal expansion, these components are described with reference to their thermal properties. For example, in some embodiments, the frame may have a first coefficient of thermal expansion (CTE). The CTE may be material-dependent, and therefore, examples of materials are disclosed that can be used with various embodiments. For example, in one embodiment, the frame may be made primarily of steel with a CTE of about 14 µm / m / K. As used herein, the description of a component “made primarily of” a particular material means that at least most of the components are made of that particular material. However, this also discloses that it is possible for the frame to include components made of different materials. For example, a steel frame may have portions of iron, plastic, aluminum, etc., and therefore may have different CTEs. Therefore, although the invention is often presented in a simplified interpretation, in which a given component (e.g., a frame or subframe) is considered to be made of a material having a particular CTE, it should be understood that practical limitations may involve combinations of materials with different CTEs. Therefore, the present invention explicitly covers embodiments covered by a more general concept, namely, a frame having a specific (general) CTE and subframes having different (general) CTEs, as described herein.

[0067] Figure 4 is a simplified bottom view of a portion of the system illustrated in Figure 3. For example, in the bottom view of Figure 4, an instance of a microlens array 410 that may be contained in any or all of the optical columns 310 is depicted.

[0068] In some embodiments, stability may be improved by a subframe having a second CTE lower than that of the first CTE of the frame. For example, in some embodiments, the subframe may be made primarily of cordierite with a CTE of about 0.03 µm / m / K. In other embodiments, portions of any of the subframes and / or anchors disclosed herein may be made primarily of zerodur (CTE ~0.007 µm / m / K) or nickel steel (CTE ~1.2 µm / m / K). Examples of "primarily" may include embodiments in which at least 60%, 70%, 80%, 90%, 95%, or 100% of the subframe and / or anchors are made of low-CTE materials. While it is considered that constructing subframes and / or anchors "primarily" of a particular low-CTE material helps to achieve their mechanical benefits, it should be understood that other materials (including combinations of low-CTE materials) may be utilized in the construction of the subframes and / or anchors. Therefore, in some implementations, the construction can be alternatively based on the overall CTE. For example, in some implementations, the subframe, primarily composed of microcrystalline glass, can be configured to have an overall CTE of approximately 0.007 µm / m / K, thus allowing for components with either higher or lower CTEs. In this way, the present invention covers the configuration of subframes to provide stability against thermal effects through combinations of material properties and anchor types / locations. While the materials described above are more suitable for providing improved stability, these materials are considered examples and many other low-CTE materials can be used to provide the technical benefits disclosed herein.

[0069] As further explained herein, some implementations may take advantage of the fact that complete stabilization of the optical column may not be necessary for every possible rotation and / or displacement. Similarly, in some embodiments, there may be locations along the optical column that can be considered more important for stabilization. As shown in Figure 4, some implementations of the subframe may be coupled to the optical column at approximately one level above the microlens array located within the optical column. This can be particularly important considering that the microlens array may be the last optic before light is delivered to the substrate and is therefore considered a critical component for stabilization. In other implementations, the bottommost part (at the proximal end) or the center of the optical column (along the column axis) may be the location of the subframe.

[0070] Figure 4 also illustrates an example of a subframe 360 ​​including first anchors 420 and second anchors 430 used to stabilize several optical pillars 310. In the depicted example, there are six optical pillars on each of the three depicted columns. However, it should be understood that the number of optical pillars and their distribution in any number of columns are arbitrary, and the depicted embodiment is merely an example. Therefore, as depicted in the exemplary embodiment of Figure 4, the present invention allows for a number of optical pillars, and thus allows for a number of first anchors and second anchors, each of which is coupled to a corresponding optical pillar in the group of optical pillars.

[0071] In some embodiments, the subframe can be configured to allow removal in a manner that minimizes disturbance to the precisely positioned optical pillars. For example, the subframe may include a first transverse subframe segment 460 (e.g., an elongated portion extending in the X direction). First and second anchors may be coupled to the first transverse subframe segment, thus the anchors are preferably positioned on one side of the optical pillar. In FIG. 4, only one first transverse subframe segment 460 is labeled, but it is apparent from the figures that multiple such transverse subframe segments may exist, for example, one transverse subframe segment for each column of the optical pillar. To further facilitate the removal of the subframe, some embodiments may further include a release mechanism 470 that allows the first transverse subframe segment 460 to be removed from a second transverse subframe segment 480 of the subframe. Examples of the release mechanism may include pins, magnetic couplers, screws, etc. As shown in the example of FIG. 4, the second transverse subframe segment 480 may be perpendicular (e.g., in the Y direction) to the first transverse subframe segment 460.

[0072] In the embodiment of Figure 4, the subframe can be configured to be coupled to the optical column at at least two locations via a first anchor 420 and a second anchor 430. This configuration can thus stabilize the optical column to prevent displacement and / or rotation of the optical column caused by thermal expansion within the frame or the optical column. As used herein, the term "displacement" refers to linear motion (e.g., X, Y, or Z). As used herein, the term "rotation" refers to angular motion about an axis X, Y, or Z and can be expressed as (Rx, Ry, or Rz).

[0073] In some embodiments, the first and second anchors can be configured to couple to the subframe and the optical column to stabilize the optical column and prevent displacement in a plane (e.g., the XY plane, as indicated in FIG. 4) and / or rotation about a longitudinal axis (e.g., along the Z-axis, as indicated in FIG. 3) passing through the optical column perpendicular to the plane. In some embodiments, this stabilization allows the system to allow displacement in the plane of no more than 10 micrometers. In other embodiments, the system can be stabilized at significantly smaller displacements, such as (e.g.) less than 300 nm, less than 200 nm, less than 160 nm, less than 120 nm, etc. Similarly, some embodiments provide stabilization such that rotation about a longitudinal axis passing through the optical column perpendicular to the plane does not exceed 10 microradians. In other embodiments, the system can be stabilized at significantly smaller rotations, such as (e.g.) less than 1000 nrad (nanoradians), less than 750 nrad, less than 500 nrad, less than 200 nrad, etc.

[0074] While the present invention covers any of the degrees of freedom (e.g., X, Y, Z, Rx, Ry, Rz) of a stable optical column, in some embodiments, it may be advantageous to stabilize only the degrees of freedom most important for the accurate delivery of light by the optical column. This selective stabilization can therefore provide significant technical benefits while reducing the overall complexity of the system compared to embodiments that stabilize all degrees of freedom. For example, one disclosed combination of stabilized degrees of freedom may include X, Y, and Rz. Exemplary embodiments of anchoring to provide this stabilization are further described herein. However, other combinations of stabilized degrees of freedom may include, for example, (X, Y, Z, and Rz) or (Y and Rz).

[0075] The disclosed anchoring system can provide stability in several different degrees of freedom. For example, in some implementations, the first anchor 420 can be configured to maintain stability against displacement of the optical column in at least two directions perpendicular (e.g., X and Y) to the axis (e.g., Z) of the optical column. This stability can be achieved by the first anchor extending at least partially in a first direction (e.g., X) and at least partially in a second direction (e.g., Y). This design can be seen in the example in Figure 4, where the first anchor 420 is at an angle relative to both the X-axis and the Y-axis. Although the first anchor can be located anywhere relative to the optical column, in the example of Figure 4, the first anchor is approximately centered on one side of the optical column. As used herein, the term "approximately centered" means within 30% of the center of one side of the optical column (of the length of one side of the optical column). However, as is evident from Figure 4, the present invention covers the connection of the anchor to the optical column very close to the center of one side of the optical column (e.g., ± 5%). As used herein, an "anchor" can be any component capable of securing two things (e.g., securing an elongated transverse section of a subframe to an optical column, or securing a frame to an optical column). Examples of anchors may include bars, trusses, rods, crossbars, supports, etc.

[0076] In some implementations, a second anchor 430 may be present, coupled to the optical column at a different location than the first anchor, thereby resisting rotation of the optical column about its longitudinal axis (e.g., the Z-axis). It is evident that the eccentric position of the second anchor 430 is opposite to any rotation (Rz) along the axis of the optical column. Alternatively, only one anchor (e.g., the first anchor 420) may provide a pivot point for the optical column at the location where the first anchor is coupled to the optical column. To prevent this, a second anchor 430 may be provided to resist rotation (because the second anchor 430 would have to be compressed or stretched to allow the rotation). Although the second anchor can be located anywhere along one side of the optical column, in some implementations (such as those shown in Figure 4), the second anchor may be located near the end of one side of the optical column. Such a location provides a mechanical advantage due to the longer lever arm that provides the opposing torque for the rotation of the optical column.

[0077] As shown in Figure 4, some embodiments of the subframe may include a third anchor 440. In this way, coupling at at least two locations can be performed by the first anchor and further by the third anchor. In the example of Figure 4, the first and third anchors may be coupled to the optical column at the same location (e.g., forming the depicted triangle or "V" shaped assembly). The third anchor may be configured to remain stable to prevent displacement of the optical column in at least two directions perpendicular to the longitudinal axis of the optical column. This can be achieved by certain embodiments in which the third anchor extends at least partially opposite to a first direction (e.g., -X) and at least partially in a second direction (e.g., +Y). Thus, the first and second anchors can be stabilized in the X'-Y' plane at the same offset angle as the XY plane. The offset angle between X'-Y' and XY is the same as the angle of the anchor relative to the XY plane. However, the result is the same, because the mathematical span of the X'-Y' plane is the same as that of XY. As depicted, the first, second, and third anchors may all be located on one side of the subframe. However, in other embodiments, any of the disclosed anchors may be located on either side of the subframe, wherein they perform substantially the same mechanical stabilization.

[0078] Figure 5 includes a perspective view illustrating the stability at the end of an optical column according to one embodiment. As depicted in the embodiment of Figure 5, the frame may include two vertical frame segments 510 symmetrically located at opposite ends of the transverse frame segment 520 to allow the optical column to be positioned therebetween. Furthermore, a sub-frame may be coupled to the two vertical frame segments, thereby centralizing the sub-frame within the frame. The inset view of Figure 5 depicts an example of a combination of stabilization methods positioned at the proximal and distal ends of the optical column.

[0079] In some embodiments, a stabilizer may be present at the distal end 312 of the optical column. For example, the top illustration of Figure 5 shows that an X stabilizer 530 and / or a Y stabilizer 540 may be present. These stabilizers may be similar to the anchors described herein and are therefore rods, struts, or other types of mechanical supports. Thus, the stabilizer is generally considered to be part of the frame, and most embodiments may have stabilizers made of a material similar to the frame (e.g., a low CTE material not used for subframes). Also as shown in the top illustration, other embodiments may include a Z stabilizer 550. Although the Z stabilizer may be similar to the X and / or Y stabilizers, in some embodiments, the Z stabilizer may also include a Z actuator coupled to the optical column and configured to compensate for vertical displacement of the optical column. The Z actuator may be a hydropneumatic actuator, screw, differential thread, piezoelectric actuator, stepper motor-based actuator, linear motor, voice coil actuator, thermal actuator, harmonic drive actuator, etc. For example, expansion and / or contraction in the Z direction can be compensated for by corresponding relative adjustments of the Z actuator, either through temperature monitoring or by measuring mechanical displacement. Additionally, in some embodiments, the X and / or Y stabilizers may also include X and / or Y actuators configured to operate similarly to the Z actuators to compensate for X and / or Y displacement.

[0080] The previously illustrated example, also depicted in the bottom illustration of Figure 5, illustrates the coupling of the optical column to the first anchor 420, second anchor 430, and third anchor 440 of the subframe 360. In some embodiments, the subframe 360 ​​may be configured to be coupled to an external body to resist vertical displacement. For example, the subframe may be connected to the lower portion of the frame, but alternatively, it may be connected to another body, such as the overall support of the room where the lithography system is located, nearby walls, floor, or ceiling, etc. While this provides additional mechanical stability, this coupling to the external body can help provide a radiator or thermal inertia for any heat reaching the subframe.

[0081] In some implementations, instead of a subframe primarily composed of a low-CTE material, the subframe may be constructed of a higher-CTE material similar to the frame. In these embodiments, temperature control can be used to maintain the mechanical dimensions of the subframe. For example, the system may include a direct cooling system to maintain the physical configuration of the anchor to prevent temperature changes. A direct cooling system should be understood as a system that provides coolant directly to the subframe. For example, the subframe may be at least partially hollow, and a liquid coolant such as water may be provided through the subframe to extract heat. In other embodiments, the system may include an indirect cooling system. Examples of an indirect cooling system may include cold air blown over the subframe, fins, or other physical attachments that increase the surface area of ​​the subframe to radiate heat.

[0082] Figure 6 illustrates an exaggerated example of a subframe maintaining stability according to an embodiment to prevent displacement and rotation that may occur in the disclosed system. Figure 7 illustrates an example of finite element analysis performed according to an embodiment to simulate changes in the frame and optical pillar due to thermal effects. The top portion of Figure 6 is an example of a system in a nominal configuration (i.e., without displacement and / or rotation). The bottom portion of Figure 6 is an example of heat 610 reaching the system, causing the frame 322 with a relatively high CTE to expand. As can be seen, this causes the depicted displacement (exaggerated for illustrative purposes) on the X-axis of the optical pillar 310. However, a low CTE subframe 360 ​​is seen constraining the X-axis displacement of the optical pillar near the bottom of the optical pillar (e.g., near the position of the microlens array). As previously described, further stabilization may include, for example, using a Z-actuator to compensate for changes in the length of the optical pillar and / or changes in the linear distance between the top of the optical pillar (attached to the expanded frame) and the desired position of the microlens array. The thermal effects on the revealed system have been thoroughly investigated using an example of finite element analysis depicted in Figure 7. Here, the thermal effects are again used to illustrate frame 320 and optical column 310. The simulated subframe 360 ​​is shown by the darker portion at the bottom of the diagram.

[0083] Figure 8 illustrates a flowchart depicting an exemplary method for stabilizing an optical column according to one embodiment. A method for stabilizing an optical column to prevent displacement or rotation may include: at 810, supporting the optical column with a frame having a first coefficient of thermal expansion (CTE). At 820, the method may also include coupling the optical column to a subframe at at least two locations by means of a first anchor and a second anchor to stabilize the optical column and prevent displacement or rotation of the optical column caused by thermal expansion within the frame or the optical column, the subframe having a second CTE lower than the first CTE.

[0084] In other implementations, the method may further include the following features in any combination: The method may include stabilizing the optical column using a first anchor and a second anchor to prevent in-plane displacement and rotation about a longitudinal axis passing through the optical column perpendicular to the plane. A subframe may be coupled to the optical column at approximately one level of the microlens array located within the optical column. A second anchor may be coupled to the optical column at a different location from the first anchor, thereby resisting rotation of the optical column about its longitudinal axis. A third anchor may be coupled to the subframe such that coupling at at least two locations can be performed by the first anchor and further by the third anchor.

[0085] Figure 9 is a block diagram of an example computer system CS according to an embodiment.

[0086] A computer system CS includes a bus BS or other communication mechanism for transmitting information and a processor PRO (or multiple processors) coupled to the bus BS for processing information. The computer system CS also includes main memory MM, such as random access memory (RAM) or other dynamic storage devices, coupled to the bus BS for storing 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 to be executed by the processor PRO. The computer system CS further includes read-only memory (ROM) or other static storage devices coupled to the bus BS for storing static information and instructions for 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.

[0087] The computer system CS can be coupled via bus BS to a display DS for displaying information to the computer user, such as a cathode ray tube (CRT), flat panel, or touch panel display. Input devices ID, including alphanumeric keys and other keys, are coupled to bus BS to transmit information and command selections to the processor PRO. Another type of user input device is a cursor controller CC, such as a mouse, trackball, or cursor direction keys, used to transmit directional information and command selections to the processor PRO and to control cursor movement on the display DS. This input device typically has two degrees of freedom in two axes (a first axis (e.g., x) and a second axis (e.g., y)), allowing the device to specify a position in a plane. Touch panel (screen) displays can also be used as input devices.

[0088] According to one embodiment, portions of one or more methods described herein can be executed by a computer system CS responding to a processor PRO executing one or more sequences of one or more instructions contained in main memory MM. These instructions can be read from another computer-readable medium (such as a storage device SD) into main memory MM. Execution of the instruction sequence contained in main memory MM causes processor PRO to execute the program steps described herein. One or more processors arranged in a multiprocessor configuration can also be used to execute the instruction sequence contained in main memory MM. In alternative embodiments, hard-wired circuitry can be used instead of or in combination with software instructions. Therefore, the description herein is not limited to any particular combination of hardware circuitry and software.

[0089] As used herein, the term "computer-readable media" means any media that participates in providing instructions to a processor (PRO) for execution. This media can take many forms, including (but not limited to) non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical discs or magnetic disks, such as storage devices (SD cards). Volatile media include dynamic memory, such as main memory (MM). Transmission media include coaxial cables, copper wires, and fiber optic components, including conductors containing buses (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-transitory, such as floppy disks, flexible magnetic 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 a perforated pattern, RAM, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or cartridges. Non-transitory computer-readable media may have instructions recorded thereon. When executed by a computer, the instructions may perform any of the features described herein. Temporary computer-readable media may include a carrier wave or other means of propagating electromagnetic signals.

[0090] The execution of one or more instructions (or sequences thereof) can involve various forms of computer-readable media. For example, initially, these instructions can be carried on a disk of a remote computer. The remote computer can load the instructions into its dynamic memory and transmit them via a modem over a telephone line. The modem at the computer system CS can receive data over the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to bus BS can receive the data carried in the infrared signal and place the data on bus BS. Bus BS carries the data to main memory MM, from which processor PRO fetches and executes the instructions. The instructions received from main memory MM can be stored on storage device SD, either before or after execution by processor PRO, depending on the circumstances.

[0091] The computer system CS may also include a communication interface CI coupled to a bus BS. The communication interface CI provides bidirectional data communication coupling to a network link NDL connected to a local area network (LAN). For example, the communication interface CI may be an integrated Services Digital Network (ISDN) card or modem to provide data communication connectivity with a corresponding type of telephone line. As another example, the communication interface CI may be a local area network (LAN) card to provide data communication connectivity with a compatible LAN. Wireless links may also be implemented. In any such implementation, the communication interface CI transmits and receives electrical, electromagnetic, or optical signals carrying digital data streams representing various types of information.

[0092] Network Data Links (NDLs) typically provide data communication with other data devices via one or more networks. For example, a Network Data Link (NDL) can provide a connection to a host computer (HC) via a Local Area Network (LAN). This may include providing data communication services via a global packet data communication network (now commonly referred to as the "Internet"). Local Area Networks (LANs) use electrical, electromagnetic, or optical signals carrying digital data streams. Signals through various networks and signals on the Network Data Link (NDL) via the Communication Interface (CI) are exemplary carrier forms for transmitting information, carrying digital data to and from the computer system (CS).

[0093] A computer system (CS) can send and receive messages (including code) via a network, network data link (NDL), and communication interface (CI). In an Internet example, a host computer (HC) can transmit requested code for an application via Internet (INT), network data link (NDL), local area network (LAN), and communication interface (CI). For example, a downloaded application may provide all or part of the methods described herein. The received code may be executed by the processor (PRO) upon receipt and / or stored in a storage device (SD) or other non-volatile storage for later execution. In this way, the computer system (CS) obtains application code in carrier form.

[0094] Figure 10 is a schematic diagram of a lithography device according to one embodiment.

[0095] The lithography equipment may include a lighting system IL, a first stage MT, a second stage WT, and a projection system PS.

[0096] The lighting system IL can adjust the radiated beam B. In this specific case, the lighting system also includes a radiation source SO.

[0097] The first object stage (e.g., patterning device stage) MT may have a patterning device holder for holding the patterning device MA (e.g., a magnifying mask) and be connected to a first locator for accurately positioning the patterning device relative to the item PS.

[0098] The second object stage (substrate stage) WT may have a substrate holder for holding the substrate W (e.g., a resist-coated silicon wafer) and be connected to a second locator for accurately positioning the substrate relative to the item PS.

[0099] A projection system ("lens") PS (e.g., a refractive, reflective, or reflective-refracting optical system) can image the irradiated portion of a patterning device MA onto a target portion C (e.g., containing one or more grains) of a substrate W.

[0100] As described herein, the device can be of the transmissive type (i.e., having transmissive patterning devices). However, generally speaking, it can also be of the reflective type, for example (having reflective patterning devices). The device can employ a different type of patterning device than a classic mask; examples include programmable mirror arrays or LCD matrices.

[0101] A source SO (e.g., a mercury lamp or excimer laser, LPP (laser-generated plasma) EUV source) generates a radiating beam. For example, this beam is fed directly or after passing through an adjustment device such as a beam expander Ex into an illumination system (illuminator) IL. The illuminator IL may include an adjustment device AD ​​for setting the outer radial range and / or inner radial range (typically referred to as σ_outer and σ_inner, respectively) of the intensity distribution in the beam. Additionally, it will typically include various other components, such as a beam accumulator IN and a condenser CO. In this way, the beam B incident on the patterning device MA has the desired uniformity and intensity distribution in its cross-section.

[0102] In some embodiments, the source SO may be inside the housing of the lithography device (as is often the case when the source SO is, for example, a mercury lamp), but it may also be located away from the lithography device, with the radiation beam generated by the source SO being guided into the device (e.g., by means of a suitable guiding mirror); the latter case may be when the source SO is an excimer laser (e.g., a laser based on KrF, ArF or F2).

[0103] The beam PB then intercepts the patterning device MA held on the patterning device stage MT. Having traversed the patterning device MA, the beam B can pass through the lens PL, which focuses the beam B onto the target portion C of the substrate W. With the aid of a second positioning device (and an interferometric measurement device IF), the substrate stage WT can be accurately moved, for example, to position different target portions C in the path of the beam PB. Similarly, the first positioning device can be used to accurately position the patterning device MA relative to the path of the beam B, for example, after mechanically retrieving the patterning device MA from the patterning device library or during scanning. Generally, the movement of the stages MT and WT can be achieved by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning). However, in the case of a stepper (relative to a stepping scanning tool), the patterning device stage MT may be connected only to the short-stroke actuator, or it may be fixed.

[0104] The drawn tool can be used in two different modes – step mode and scan mode. In step mode, the patterning stage MT is kept essentially stationary, and the entire patterning image is projected (i.e., a single "flash") onto the target portion C. The substrate stage WT is shifted in the x and / or y directions so that different target portions C can be illuminated by the beam PB.

[0105] In scanning mode, the same principle applies, except that the given target portion C is not exposed in a single "flash". Alternatively, the patterning stage MT can move at a speed v in a given direction (the so-called "scanning direction", e.g., the y-direction) so that the projected beam B scans the patterning image; simultaneously, the substrate stage WT moves simultaneously in the same or opposite directions 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 compromising resolution.

[0106] Figure 11 is a schematic diagram of another lithography device (LPA) according to one embodiment.

[0107] The LPA may include a source collector module SO, an illumination system (illuminator) IL configured to adjust the radiated beam B (e.g., EUV radiation), a support structure MT, a substrate stage WT, and a projection system PS.

[0108] A support structure (e.g., a patterning device stage) MT may be constructed to support a patterning device (e.g., a mask or a magnifying mask) MA and connected to a first positioner PM configured to accurately position the patterning device.

[0109] A substrate stage (e.g., a wafer stage) WT may be constructed to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate.

[0110] The projection system (e.g., a reflective projection system) PS can be configured to project a pattern applied to the radiation beam B by the patterning device MA onto a target portion C (e.g., containing one or more grains) of the substrate W.

[0111] As described herein, LPA can be of the reflective type (e.g., using a reflective patterning device). It should be noted that because most materials are absorptive in the EUV wavelength range, the patterning device can have a multilayer reflector comprising, for example, multiple stacks of molybdenum and silicon. In one example, the multilayer reflector has 40 pairs of molybdenum and silicon layers, each layer being a quarter wavelength thick. X-ray lithography can be used to produce even smaller wavelengths. Because most materials are absorptive at both EUV and X-ray wavelengths, the features defined by the patterned absorbing material segments on the topography of the patterning device (e.g., a TaN absorber on top of a multilayer reflector) will be printed (positive resist) or unprinted (negative resist).

[0112] The illuminator IL can receive an extreme ultraviolet (EUV) radiation beam from the source collector module SO. Methods for generating EUV radiation include, but are not limited to, converting a material having at least one element (e.g., xenon, lithium, or tin) into a plasma state using one or more emission spectra within the EUV range. In one such method (often referred to as laser-generated plasma (“LPP”), plasma can be generated by irradiating fuel (such as droplets, streams, or clusters of material having an emitting element) with a laser beam. The source collector module SO may be part of an EUV radiation system including a laser used to provide the laser beam for exciting the fuel. The resulting plasma emits output radiation (e.g., EUV radiation), which is collected using a radiation collector disposed within the source collector module. For example, when a CO2 laser is used to provide the laser beam for fuel excitation, the source and source collector modules may be separate entities.

[0113] In such cases, the laser lithography apparatus may not be considered part of the laser, and the radiated beam may be transmitted from the laser to the source collector module via a beam delivery system comprising, for example, suitable guide mirrors and / or beam expanders. In other cases, for example, when the source is a discharge-generating plasma EUV generator (often referred to as a DPP source), the source may be an integral part of the source collector module.

[0114] An illuminator IL may include an adjuster for adjusting the angular intensity distribution of the radiated beam. Generally, this adjuster can adjust at least the outer and / or inner radial ranges (typically referred to as σ_outer and σ_inner, respectively) of the intensity distribution in the pupil plane of the illuminator. Additionally, the illuminator IL may include various other components, such as faceted field mirror devices and faceted pupil mirror devices. The illuminator can be used to adjust the radiated beam to achieve the desired uniformity and intensity distribution across its cross-section.

[0115] A radiating beam B may be incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a patterning device stage) MT, and patterned by the patterning device. After reflection from the patterning device (e.g., the mask) MA, the radiating beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The substrate stage WT can be accurately moved, for example, to position different target portions C in the path of the radiating beam B, by means of a second locator PW and a position sensor PS2 (e.g., an interferometric measuring device, a linear encoder, or a capacitive sensor). Similarly, a first locator PM and another position sensor PS1 can be used to accurately position the patterning device (e.g., the mask) MA relative to the path of the radiating beam B. Patterning device alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device (e.g., the mask) MA and the substrate W.

[0116] The described device LPA can be used in at least one of the following modes: step mode, scan mode, and stationary mode.

[0117] In step mode, when the entire pattern applied to the radiation beam is projected onto the target portion C in one go, the support structure (e.g., patterning stage) MT and the substrate stage WT are kept substantially stationary (i.e., single static exposure). Then, the substrate stage WT is shifted in the X and / or Y directions to expose different target portions C.

[0118] In scanning mode, while projecting the pattern applied to the radiating beam onto the target portion C, the support structure (e.g., patterning stage) MT and the substrate stage WT are scanned simultaneously (i.e., single dynamic exposure). The speed and direction of the substrate stage WT relative to the support structure (e.g., patterning stage) MT can be determined by the magnification (reduction ratio) and image inversion characteristics of the projection system PS.

[0119] In static mode, as the pattern to be applied to the radiation beam is projected onto the target portion C, the support structure (e.g., the patterning stage) MT is kept substantially stationary, thereby holding the programmable patterning device, while the substrate stage WT is moved or scanned. In this mode, a pulsed radiation source is typically used, and the programmable patterning device is updated as needed after each movement of the substrate stage WT or between successive radiation pulses during a scan. This operating mode can be readily applied to maskless lithography using programmable patterning devices (such as programmable mirror arrays).

[0120] Figure 12 is a detailed view of a lithography device according to one embodiment.

[0121] 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 configured to maintain a vacuum environment within its enclosure structure ES. An EUV radiation-emitting thermoplasm HP can be formed by generating a plasma source through discharge. EUV radiation can be generated by a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor), wherein the thermoplasm HP is established to emit radiation in the EUV range of the electromagnetic spectrum. For example, the thermoplasm HP is established by a discharge that generates at least partially ionized plasma. For efficient radiation generation, Xe, Li, Sn vapor, or any other suitable gas or vapor with a partial pressure of, for example, 10 Pa may be required. In one embodiment, an excited tin (Sn) plasma is provided to generate EUV radiation.

[0122] Radiation emitted by the thermoplasm (HP) is transmitted from the source chamber (SC) to the collector chamber (CC) via a gas barrier or contaminant trap (CT, in some cases also referred to as a contaminant barrier or foil trap) positioned in or behind an opening in 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. As known in the art, the contaminant trap or contaminant barrier CT further indicated herein includes at least a channel structure.

[0123] 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 traversing the radiation collector CO may be reflected from a grating spectral filter SF to be focused along the optical axis indicated by the dotted line 'O' onto a virtual source point IF. The virtual source point IF may be referred to as the intermediate focus, and the source collector module is configured such that the intermediate focus IF is located at or near the opening OP in the enclosure structure ES. The virtual source point IF is an image of the radiative emission plasma HP.

[0124] Subsequently, radiation traverses the illumination system IL, which may include a faceted field mirror device FM and a faceted pupil mirror device PM, configured to provide the desired angular distribution of the radiated beam B at the patterning device MA and the desired uniformity of the radiation amplitude at the patterning device MA. After the radiated 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 onto the substrate W held by the substrate stage WT via the projection system PS and the reflective element RE.

[0125] Additional components beyond those shown may typically be present in the illumination optics unit IL and the projection system PS. Depending on the type of lithography equipment, a grating spectral filter SF may be present. Furthermore, more mirrors than are shown in the diagram may be present; for example, one to six additional reflective elements may be present in the projection system PS.

[0126] The collector optics CO can be a nested collector with a grazing incidence reflector GR, serving only as an example of a collector (or collector mirror). The grazing incidence reflector GR is positioned symmetrical about the optical axis O, and this type of collector optics CO can be used in combination with a discharge plasma source commonly referred to as a DPP source.

[0127] Figure 13 is a detailed view of the source collector module SO of a lithography device LPA according to an embodiment.

[0128] The source-collector module SO can be part of an LPA radiation system. A laser LA can be configured to store laser energy in a fuel such as xenon (Xe), tin (Sn), or lithium (Li), thereby generating a highly ionized plasma HP with an electron temperature of tens of eV. The high-energy radiation generated during the de-excitation and recombination of this plasma is emitted from the plasma, collected by a near-orthogonal incident collector optics CO, and focused onto an opening OP in the enclosed structure ES.

[0129] The concepts revealed in this paper can be simulated or mathematically modeled for any general imaging system used to image sub-wavelength features, and are particularly applicable to emerging imaging technologies capable of generating increasingly shorter wavelengths. Emerging technologies already in use include EUV (Extreme Ultraviolet) and DUV lithography, which can generate wavelengths of 193 nm using ArF lasers and even 157 nm using fluorine lasers. Furthermore, EUV lithography can generate wavelengths in the 20 to 50 nm range by using synchrotrons or by bombarding materials (solids or plasmas) with high-energy electrons, thereby generating photons within this range.

[0130] Although the concepts disclosed herein can be used for imaging on substrates such as silicon wafers, it should be understood that the disclosed concepts can be used with any type of lithography system, for example, for imaging on substrates other than silicon wafers.

[0131] The combinations and sub-combinations of elements disclosed herein constitute various embodiments and are provided merely as examples. Furthermore, the above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made as described without departing from the scope of the claims set forth below.

[0132] Other embodiments are disclosed in the subsequent list of numbered entries: 1. A system comprising: an optical column; a frame configured to support the optical column, the frame having a first coefficient of thermal expansion (CTE); and a subframe configured to be coupled to the optical column at at least two locations by a first anchor and a second anchor to stabilize the optical column and prevent displacement or rotation of the optical column caused by thermal expansion of the frame or the optical column, the subframe having a second CTE lower than the first CTE. 2. The system of any of the preceding clauses, wherein the optical column is suspended at a distal end of the optical column below a transverse frame section of the frame, and the subframe is coupled to the optical column at a proximal end of the optical column. 3. The system as described in any of the preceding clauses, wherein the subframe is coupled to the optical column at approximately one level of one of the microlens arrays located in the optical column. 4. The system as described in any of the preceding clauses, wherein the frame is primarily made of steel with a CTE of approximately 14 µm / m / K. 5. The system as described in any of the preceding clauses, wherein the subframe is primarily made of cordierite with a CTE of approximately 0.03 µm / m / K. 6. A system as described in any of the preceding clauses, wherein the first anchor and the second anchor are configured to be coupled to the subframe and the optical column to stabilize the optical column and prevent displacement in a plane and rotation about a longitudinal axis passing through the optical column perpendicular to the plane. 7. A system as described in any of the preceding clauses, wherein the displacement in a plane does not exceed 10 micrometers and the rotation about a longitudinal axis passing through the optical column perpendicular to the plane does not exceed 10 microradians. 8. The system as described in any of the preceding clauses further comprises: a plurality of optical pillars; and a plurality of first anchors and a plurality of second anchors, each of the plurality of first anchors and the plurality of second anchors being coupled to a corresponding optical pillar among the plurality of optical pillars. 9. A system as described in any of the preceding clauses, wherein the first anchor is configured to remain stable to prevent displacement of the optical post in at least two directions perpendicular to one of the axes of the optical post. 10. The system of any of the preceding clauses, wherein the first anchor extends at least partially in one of the two directions in a first direction and at least partially in one of the two directions in a second direction. 11. The system as described in any of the preceding clauses, wherein the first anchor is substantially centered on one side of the optical post. 12. A system as described in any of the preceding clauses, wherein the second anchor is coupled to the optical post at a location different from that of the first anchor, thereby resisting the rotation of the optical post about a longitudinal axis. 13. The system of any of the preceding clauses, wherein the subframe further includes a third anchor, wherein the coupling system at the at least two locations is performed by the first anchor and further by the third anchor. 14. The system of any of the preceding clauses, wherein the first anchor and the third anchor are coupled to the optical column at the same location. 15. A system as described in any of the preceding clauses, wherein the third anchor is configured to remain stable to prevent displacement of the optical post in at least two directions perpendicular to one of the longitudinal axes of the optical post, wherein the third anchor extends at least partially opposite to one of the first directions and at least partially in one of the second directions. 16. The system as described in any of the preceding clauses, wherein the first anchor, the second anchor, and the third anchor are all on one side of the subframe. 17. The system as described in any of the preceding clauses, wherein the subframe further comprises a first transverse subframe segment, the first anchor and the second anchor being coupled to the first transverse subframe segment. 18. The system of any of the preceding items further includes a release mechanism that allows disassembly of one of the first transverse subframe segments from one of the second transverse subframe segments of the subframe. 19. The system of any of the preceding clauses, the frame further comprising two vertical frame segments symmetrically located at opposite ends of a transverse frame segment to allow the optical column to be positioned therebetween, wherein the subframe is coupled to the two vertical frame segments, thereby centered within the frame. 20. A system as described in any of the preceding clauses, wherein the subframe is configured to be coupled to an external body to resist a vertical displacement. 21. The system of any of the preceding clauses further includes a Z-actuator coupled to the optical column and configured to compensate for a vertical displacement of one of the optical columns. 22. A system as described in any of the preceding clauses, wherein the system is configured to manufacture a flat panel display. 23. A method for stabilizing an optical column to prevent displacement or rotation, the method comprising: supporting the optical column with a frame having a first coefficient of thermal expansion (CTE); and coupling the optical column to a subframe at at least two locations by a first anchor and a second anchor to stabilize the optical column to prevent displacement or rotation of the optical column caused by thermal expansion of the frame or the optical column, the subframe having a second CTE lower than the first CTE. 24. The method of any of the preceding method clauses, further comprising using the first anchor and the second anchor to stabilize the optical column to prevent displacement in a plane and rotation about a longitudinal axis passing through the optical column perpendicular to the plane. 25. The method of any of the preceding method clauses, the method further comprising coupling the subframe to the optical column at approximately one level of one of the microlens arrays located in the optical column. 26. The method of any of the preceding method clauses, the method further comprising coupling the second anchor to the optical post at a location different from the first anchor, thereby resisting the rotation of the optical post about a longitudinal axis. 27. The method of any of the preceding method clauses, the method further comprising coupling a third anchor to the subframe, wherein the coupling at the at least two locations is performed by means of the first anchor and further by means of the third anchor.

[0133] 10A: Microfilm projection equipment 12A: Radiation source 14A: Optical components 16Aa: Optical components 16Ab: Optical components 16Ac: Transmission optical components 18A: Patterning device 20A: Aperture 22A: Substrate Plane 31: Source Model 32: Projection Optical Component Model 35: Design Layout Model 36: Aerial Footage 37: Corrosion Resist Model 38: Resist Image 300: System 310: Optical column 312: Remote 314: Proximal 320: Frame 322: Horizontal Frame Section 330:Substrate 340: Stage 350: Actuator 360: Subframe 410: Microlens array 420: First anchoring element 430: Second anchoring element 440: Third anchoring element 460: First horizontal subframe section 470: Release Mechanism 480: Second transverse subframe section 510: Vertical section of the frame 520: Horizontal Frame Section 530:X stabilizer 540:Y stabilizer 550:Z Stabilizer 610: Calories 810: Steps 820: Steps AD: Adjustment device B: Radiation beam BS: Busbar C: Target Section CC: Vernier Control Unit / Collector Chamber CI: Communication Interface CO: Concentrator / Collector Optical Components CS: Computer System CT: Contaminant Trap DS: Downstream radiation collector side / display ES: Enclosure Structure FM: Faceted Field Mirror Device GR: Grazing incidence reflector HC: Main Computer HP: Thermoelectric Plasma / Ionized Plasma ID: Input device IF: Interferometric measurement equipment / virtual source IL: Illumination Optical Components / Illumination System IN: Optical Accumulator INT: Internet LA: Laser LAN: Local Area Network LPA: Lithography Equipment M1: Patterning device alignment mark M2: Patterned device alignment mark MA: Patterning device MM: Main Memory MT: First object stage / support structure NDL: Network Data Link O: Dashed line / optical axis OP: Open P1: Substrate alignment mark P2: Substrate alignment mark PB: Patterned beam PM: First Positioner / Faceted Pupil Mirror Device PRO: Processor PS: Projection system PS1: Position Sensor PS2: Position Sensor PW: Second Positioner ROM: Read-only memory SC: Source Chamber SD: Storage device SF: Grating spectral filter SO: Radiation Source / Collector Module US: Upstream radiation collector side W: substrate WT: Second object stage / substrate stage X: Direction Y: direction Z: Direction

Claims

1. A system for stabilizing an optical column, comprising: the optical column; a frame configured to support the optical column, the frame having a first coefficient of thermal expansion (CTE), wherein the optical column is suspended at a distal end of the optical column below a lateral frame section of the frame; and a subframe configured to be coupled to the optical column at at least two locations by a first anchor and a second anchor to stabilize the optical column and prevent displacement or rotation of the optical column caused by thermal expansion of the frame or the optical column, the subframe having a second CTE lower than the first CTE.

2. The system of claim 1, wherein the subframe is coupled to the optical column at a proximal end of one of the optical columns.

3. The system of claim 1, wherein the subframe is coupled to the optical column at approximately one level of one of the microlens arrays located in the optical column.

4. The system of claim 1, wherein the first anchor and the second anchor are configured to be coupled to the subframe and the optical column to stabilize the optical column and prevent displacement in a plane and rotation about a longitudinal axis passing through the optical column perpendicular to the plane.

5. The system of claim 1, further comprising: a plurality of optical pillars; and a plurality of first anchors and a plurality of second anchors, each of the plurality of first anchors and the plurality of second anchors being coupled to a corresponding optical pillar of the plurality of optical pillars.

6. The system of claim 1, wherein the first anchor is configured to remain stable to prevent displacement of the optical post in at least two directions perpendicular to one of the axes of the optical post.

7. The system of claim 1, wherein the second anchor is coupled to the optical post at a location different from that of the first anchor, thereby resisting the rotation of the optical post about a longitudinal axis.

8. The system of claim 1, wherein the subframe further includes a third anchor, wherein the coupling at the at least two locations is performed by the first anchor and further by the third anchor.

9. The system of claim 8, wherein the third anchor is configured to remain stable to prevent displacement of the optical post in at least two directions perpendicular to one of the longitudinal axes of the optical post, wherein the third anchor extends at least partially opposite to one of the first directions and at least partially in one of the second directions.

10. The system of claim 1, wherein the subframe further includes a first transverse subframe segment, the first anchor and the second anchor being coupled to the first transverse subframe segment.

11. The system of claim 1, wherein the frame further comprises two vertical frame segments symmetrically located at opposite ends of a transverse frame segment to allow the optical column to be positioned therebetween, wherein the subframe is coupled to the two vertical frame segments such that the subframe is centered within the frame.

12. The system of request item 1, wherein the subframe is configured to be coupled to an external body to resist a vertical displacement.

13. The system of claim 1, further comprising a Z-actuator coupled to the optical post and configured to compensate for a vertical displacement of one of the optical posts.

14. The system of request item 1, wherein the system is configured to manufacture a flat panel display.

15. A method for stabilizing an optical column to prevent displacement or rotation, the method comprising: supporting an optical column with a frame having a first coefficient of thermal expansion (CTE), wherein the optical column is suspended at a distal end of the optical column below a transverse frame section of the frame; and coupling the optical column to a subframe at at least two locations by a first anchor and a second anchor to stabilize the optical column to prevent displacement or rotation of the optical column caused by thermal expansion in the frame or the optical column, the subframe having a second CTE lower than the first CTE.

16. The method of claim 15, further comprising using the first anchor and the second anchor to stabilize the optical column to prevent displacement in a plane and rotation about a longitudinal axis passing through the optical column perpendicular to the plane.

17. The method of claim 15, further comprising coupling the subframe to the optical column at approximately one level of one of the microlens arrays located in the optical column.

18. The method of claim 15, further comprising coupling the second anchor to the optical post at a location different from the first anchor, thereby resisting the rotation of the optical post about a longitudinal axis.

19. The method of claim 15, further comprising coupling a third anchor to the subframe, wherein the coupling at the at least two locations is performed by means of the first anchor and further by means of the third anchor.

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