Photolithography system and method

Abstract

The present disclosure relates to photolithography systems and methods. A photolithography exposure system includes: a light source; a substrate stage; and a mask stage located between the light source and the substrate stage along a light path from the light source to the substrate stage. The photolithography exposure system also includes a reflector located along the light path. The reflector includes: a first layer having a first material and a first thickness; a second layer having the first material and a second thickness different from the first thickness; and a third layer located between the first and second layers and having a second material different from the first material.

Description

Technical Field

[0001] The present disclosure generally relates to photolithography systems and methods. Background Art

[0002] The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs, each with smaller and more complex circuits than the previous one. During the evolution of ICs, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (e.g., the smallest component (or line) that can be produced using a manufacturing process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and reducing associated costs. However, this scaling down also increases the complexity of processing and manufacturing ICs. Summary of the Invention

[0003] According to one embodiment of the present disclosure, a photolithography exposure system is provided, comprising: a light source; a substrate stage; a mask stage located between the light source and the substrate stage along a light path from the light source to the substrate stage; and a reflector, wherein along the light path, the reflector comprises: a first layer having a first material and a first thickness; a second layer having the first material and a second thickness different from the first thickness; and a third layer located between the first layer and the second layer and having a second material different from the first material.

[0004] According to another embodiment of the present disclosure, a lithography exposure system is provided, comprising: an optical path between a light source and a substrate table; a first reflector having a first incident angle along the optical path, the first reflector comprising: at least three first material layers having a first number of seed layer materials, a second number of layer thicknesses, and a first order of the first material layers; and a second reflector having a second incident angle along the optical path, the second incident angle being different from the first incident angle, the second reflector comprising: at least three second material layers having a third number of seed layer materials, a fourth number of layer thicknesses, and a second order of the second material layers, and satisfying at least one of the following conditions: the third number is different from the first number; the fourth number is different from the second number; or the second order is different from the first order.

[0005] According to another embodiment of the present disclosure, a method for manufacturing a reflector structure is provided, comprising: forming a plurality of intermediate reflective multilayer structure configurations by executing a reverse design algorithm; and forming a reflective multilayer based on a reflective multilayer structure configuration selected from the plurality of intermediate reflective multilayer structure configurations by: forming a first material layer having a first material and a first thickness; forming a second material layer on the first material layer, the second material layer having a second material and a second thickness that are respectively different from the first material and the first thickness; and forming a third material layer on the second material layer, the third material layer having the first material and a third thickness that is different from the first thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Various aspects of the present disclosure may be best understood from the following detailed description when read in conjunction with the accompanying drawings. It is noted that, in accordance with standard industry practice, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of discussion.

[0007] Figure 1A-1E is a view of a portion of a lithography scanner according to an embodiment of the present disclosure.

[0008] Figures 2A to 3D are diagrams of various embodiments of mirror structures for a lithography scanner according to various aspects of the present disclosure.

[0009] Figure 4-6B 2 is a diagram illustrating a method of manufacturing a reflective mirror structure according to various aspects of the present disclosure.

[0010] Figure 7 are views illustrating a method of manufacturing a semiconductor device according to various aspects of the present disclosure.

[0011] Figure 8-Figure 9 is a diagram illustrating a method of manufacturing a reflective mirror structure through a machine learning process according to various aspects of the present disclosure. DETAILED DESCRIPTION

[0012] The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are merely examples and are not intended to be limiting. For example, forming a first feature above or on a second feature in the description below may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features so that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and / or letters in various examples. This repetition is for the purpose of simplicity and clarity and does not, in itself, indicate a relationship between the various embodiments and / or configurations discussed.

[0013] Furthermore, spatially relative terms (e.g., "below," "beneath," "below," "above," "upper," etc.) may be used herein to facilitate describing the relationship of one element or feature illustrated in the figures relative to another element or feature. These spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly.

[0014] For ease of description, terms such as "approximately," "roughly," "substantially," and the like may be used herein. One of ordinary skill in the art will be able to understand and derive the meaning of these terms. For example, "approximately" may indicate a dimensional change of 20%, 10%, 5%, and the like, but other values ​​may be used where appropriate. Large features (e.g., the longest dimension of a semiconductor fin) may vary by less than 5%, while very small features (e.g., the thickness of an interface layer) may vary by as much as 50%, and both types of changes may be represented by the term "approximately." "Substantially" is generally stricter than "approximately," such that a change of 10%, 5%, or less may be appropriate, but is not limited to such. A "substantially planar" feature may have a deviation from a straight line within a range of 10% or less. A material having a "substantially constant concentration" may have a concentration variation along one or more dimensions within a range of 5% or less. Again, one of ordinary skill in the art will be able to understand and derive the appropriate meaning of these terms based on industry knowledge, current manufacturing techniques, and the like.

[0015] The present disclosure relates generally to lithographic apparatus for fabricating semiconductor devices, and more particularly to reflective multilayers of field facet mirrors, pupil facet mirrors, reticles / masks, projection mirrors, and the like. At advanced technology nodes, dimension scaling (reduction) becomes increasingly difficult. Lithographic techniques employ increasingly shorter exposure wavelengths, including deep ultraviolet (DUV; approximately 193-248 nm), extreme ultraviolet (EUV; approximately 10-100 nm, particularly 13.5 nm), and X-rays (approximately 0.01-10 nm), to ensure precise patterning at scaled-down dimensions.

[0016] A typical EUV scanner is a lithography device that includes about 10 reflectors, such as the various mirrors and masks listed above. The reflectivity of each reflector is typically less than about 70% (see, for example, Figure 1B ), for example, about 67%. Thus, the total reflectivity on a path including 10 reflectors may be less than about 2% (R 10 =0.67 10 ≈1.8%), which means that the EUV energy loss exceeds 98%. It is observed that some of this EUV energy loss due to reflectivity is the result of two effects. First, only two materials are used in the multilayer mirror structure, typically molybdenum and silicon. Second, only one or two thicknesses are used, resulting in a high level of periodicity in the alternating material layers (e.g., Si, Mo, Si, Mo) across the depth of the ML mirror structure.

[0017] In embodiments of the present disclosure, a significant increase in reflectivity in a reflective multilayer can be achieved by eliminating the two limitations described above. The number of materials can be increased to three (adding ruthenium), four (adding ruthenium and strontium), or more than four. Using a greater number of materials allows each layer to be arbitrarily ordered / placed relative to its adjacent layers. The thickness of the alternating layers can be non-periodic, so that each layer of the reflective multilayer can have an arbitrary thickness relative to the other layers of the reflective multilayer. With a large number of design levers (layer materials, thicknesses, ordering of layers) at play, the reflectivity of the reflective multilayer can be further enhanced by the intelligent use of algorithms (e.g., random "path finding" algorithms that search for local and / or global maxima of reflectivity, or various machine learning techniques based on big data and neural networks). In the accompanying drawings, the reflective multilayer is shown as planar for simplicity. In some embodiments, some or all of the reflective multilayers can be further curved, so that the curvature of the reflective multilayer can be a further consideration for increasing the reflectivity of a single reflector.

[0018] The present disclosure further describes a method for fabricating a semiconductor device using a reflector including an ML mirror structure having enhanced reflectivity during a photolithography operation. The method generally includes the following operations: depositing a mask layer over a substrate; patterning the mask layer using the ML mirror structure having enhanced reflectivity; and removing material of a layer below the mask layer exposed by an opening in the mask layer formed during the patterning operation.

[0019] Figure 1A 1 is a schematic diagram and simplified diagram of a lithography exposure system 10 according to some embodiments. In some embodiments, the lithography exposure system 10 is an extreme ultraviolet (EUV) lithography system designed to expose a resist layer using EUV radiation, and may also be referred to as an EUV system 10. According to some embodiments, the lithography exposure system 10 includes a light source 120, an illuminator 140, a mask stage 16, a projection optics module (or projection optics box (POB)) 30, and a substrate stage 24. Elements of the lithography exposure system 10 may be added or omitted, and the present disclosure should not be limited by the embodiments.

[0020] In certain embodiments, light source 120 is configured to generate optical radiation having a wavelength within a range between approximately 1 nm and approximately 100 nm. In one specific example, light source 120 generates EUV radiation having a wavelength centered around approximately 13.5 nm. Therefore, light source 120 is also referred to as an EUV radiation source. However, it should be understood that light source 120 is not limited to emitting EUV radiation. Light source 120 can be used to perform any high-intensity photon emission that excites the target fuel.

[0021] In various embodiments, the illuminator 140 includes various refractive optical components, such as a single lens or a lens system having multiple reflectors 100, such as a lens (zone plate) or reflective optical devices (for EUV lithography exposure systems), such as a single mirror or a mirror system having multiple mirrors, to direct light from the light source 120 onto the mask stage 16, and in particular, onto the mask 18 fixed to the mask stage 16. In the present embodiment, in which the light source 120 generates light in the EUV wavelength range, reflective optical devices are used. In some embodiments, the illuminator 140 includes at least three lenses.

[0022] The mask stage 16 is configured to hold the mask 18. In some embodiments, the mask stage 16 includes an electrostatic chuck (e-chuck) for holding the mask 18. This is because gas molecules absorb EUV radiation, and the lithography exposure system for EUV lithography patterning is maintained in a vacuum environment to avoid EUV intensity loss. In the present disclosure, the terms mask, photomask, and reticle are used interchangeably. In the present embodiment, the mask 18 is a reflective mask. An exemplary structure of the mask 18 includes a substrate having a suitable material, such as a low thermal expansion material (LTEM) or fused quartz. In various examples, the LTEM includes TiO2-doped SiO2 or other suitable materials with low thermal expansion. The mask 18 includes a reflective multilayer deposited on a substrate.

[0023] The projection optics module (or projection optics box (POB)) 30 is configured to image the pattern of the mask 18 onto the semiconductor wafer 22 (fixed on the substrate stage 24 of the lithography exposure system 10). In some embodiments, the POB 30 has refractive optics (e.g., for UV lithography exposure systems) or reflective optics (e.g., for EUV lithography exposure systems) in various embodiments. The POB 30 collects light emitted from the mask 18, which carries an image of the pattern defined on the mask. The illuminator 140 and the POB 30 are collectively referred to as the optical module of the lithography exposure system 10. In some embodiments, the POB 30 includes at least six reflective optics.

[0024] In this embodiment, the semiconductor wafer 22 can be made of silicon or other semiconductor materials. Alternatively or additionally, the semiconductor wafer 22 can include other basic semiconductor materials such as germanium (Ge). In some embodiments, the semiconductor wafer 22 is made of compound semiconductors such as silicon carbide (SiC), gallium arsenide (GaAs), indium arsenide (InAs), or indium phosphide (InP). In some embodiments, the semiconductor wafer 22 is made of alloy semiconductors such as silicon germanium (SiGe), silicon germanium carbide (SiGeC), gallium arsenic phosphide (GaAsP), or gallium indium phosphide (GaInP). In some other embodiments, the semiconductor wafer 22 can be a silicon-on-insulator (SOI) or germanium-on-insulator (GOI) substrate.

[0025] In addition, the semiconductor wafer 22 can have various device elements. Examples of device elements formed in the semiconductor wafer 22 include transistors (e.g., metal oxide semiconductor field effect transistors (MOSFETs), complementary metal oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), high voltage transistors, high frequency transistors, P-channel and / or N-channel field effect transistors (PFETs / NFETs), etc.), diodes and / or other applicable elements. Various processes are performed to form the device elements, such as deposition, etching, implantation, photolithography, annealing and / or other suitable processes. In some embodiments, in the present embodiment, the semiconductor wafer 22 is coated with a resist layer that is sensitive to EUV radiation. Various components including those described above are integrated together and are operable to perform a photolithography process.

[0026] The photolithography exposure system 10 may further include other modules, or be integrated (or coupled) with other modules, such as a cleaning module designed to provide hydrogen gas to the light source 120. The hydrogen gas helps to reduce contamination in the light source 120.

[0027] Figure 1B is a partial view of a reflector 100 that may be included in the illuminator 140, the mask 18, and / or the POB 30. The reflector 100 is configured to reflect incident light 85 having an incident energy Ei and incident at an angle of incidence θ. Some of the incident energy Ei is absorbed by the reflector 100 and is reflected from the incident surface of the reflector 100 with a reflected energy Er via reflected light 86. In some embodiments, the reflectivity of the reflector 100 is at least 75%. In some embodiments, the reflectivity is at least 77%. The higher reflectivity of the reflector 100 improves the overall throughput of the EUV system 10. For example, with a reflectivity of 75% for each individual reflector 100, for an EUV system 10 including ten reflectors 100, the total reflectivity exceeds 5.5% (0.75 10 =5.6%), which is an improvement of more than three times compared to a reflector 100 having a reflectivity of 67%. For a reflectivity of 77%, an EUV system 10 including ten reflectors 100 exhibits a total reflectivity of more than 7% (0.77 10 =7.3%), which is approximately four times higher than the reflector 100 having a reflectivity of 67%.

[0028] The reflector 100 includes a reflective multilayer including first material layers 11A-11E collectively referred to as "first material layer 11" or "reflector layer 11" and second material layers 12A-12E collectively referred to as "second material layer 12" or "spacer layer 12". The first material layer 11 and the second material layer 12 may be further collectively referred to as "material layers 11, 12". Although Figure 1B, five of each of the first material layer 11 and the second material layer 12 are shown, but the reflector 100 may include more first material layers 11 and second material layers 12, for example, approximately 50 of each, but there may be fewer or more in various embodiments. In some embodiments, the first material layer 11 is or includes molybdenum, and the second material layer 12 is or includes silicon. The reflective multilayer includes a plurality of film pairs, such as molybdenum-silicon (Mo / Si) film pairs (for example, molybdenum layer 11B is above or below silicon layer 12B or 12A in each film pair). Alternatively, the reflective multilayer may include a molybdenum-beryllium (Mo / Be) film pair, or other suitable materials that can be configured to reflect EUV radiation. The reflector 100 may further include a cap layer (not specifically shown for simplicity) disposed on the reflective multilayer for protection, such as ruthenium (Ru). When the reflector 100 is a mask 18, the reflector 100 may further include an absorption layer, such as a tantalum boron nitride (TaBN) layer, deposited on the reflective multilayer. The absorber layer is patterned to correspond to a layer of an integrated circuit (IC).Alternatively, another reflective layer may be deposited over the reflective multilayer and patterned to correspond to a layer of the integrated circuit, thereby forming an EUV phase-shift mask.

[0029] Figure 1C is a detailed view of the reflection of light in the reflector 100 according to various embodiments. Figure 1B In order to simplify the illustration, a single arrow represents incident light 85, and a second single arrow represents reflected light 86. For a reflective multilayer having up to one hundred total layers, the reflection of light is a complex process including reflection and transmission at each material interface, such as Figure 1C For example, incident light 85 is partially reflected at an upper surface 111U of a first material layer 11A, which is the uppermost first material layer closest to a light source (e.g., reflector 100 or light source 120), to form first reflected light 86A of reflected light 86. Transmitted light 87A of incident light 85 traverses the first material layer 11A before reaching a lower surface 111L of the first material layer 11A, which substantially meets an upper surface 112U of a second material layer 12A immediately below the first material layer 11A.

[0030] At the interface between the first material layer 11A and the second material layer 12A, the transmitted light 87A is further reflected and transmitted to form internal reflected light 88A and transmitted light 87B, respectively. Figure 1CInternally reflected light 88B and 88C are further shown. Internally reflected light 88A-88C may be collectively referred to as internally reflected light 88. Internally reflected light 88B is reflected by first material layer 11B from transmitted light 87B incident on the interface between second material layer 12A and first material layer 11B. In some embodiments, composite light 89 is formed, which includes internally reflected light from internally reflected light 88C and transmitted light from internally reflected light 88B.

[0031] Transmitted light 86E is light that escapes from the reflector 100 when the composite light 89 is incident on the interface between the reflective multilayer and the cap layer or the external environment (e.g., a vacuum). Typically, the reflected light 86, including reflected lights 86A-86J, includes some combination of reflected light (e.g., first reflected light 86A), transmitted light (e.g., transmitted lights 86B, 86C, 86D), and composite light (e.g., composite lights 86E-86J).

[0032] Based on the above, a rigorous calculation can be performed on all transmissions and reflections throughout the reflective multilayer to calculate the reflectivity of the reflective multilayer. This calculation can be based on multiple parameters, including but not limited to the incident light wavelength, incident light intensity, incident angle, material properties of each layer (e.g., extinction coefficient and / or refractive index of each first multilayer 11 and second multilayer 12), thickness of each layer, and the order of the layers.

[0033] Figure 1D is a graph showing the material properties of various materials on the coordinate axes of refractive index n (horizontal axis) and extinction coefficient K (vertical axis). In some embodiments, based on the material of each layer, the reflectivity at the interface of the two materials can be approximated as the difference in refractive index. For example, for the interface of a first material with refractive index n1 and a second material with refractive index n2, the reflectivity at the interface can be approximated as |n1-n2|. In general, to maximize the reflectivity at each interface in a reflective multilayer, it can be observed that the difference between the refractive indices n1, n2 of adjacent layers should be large, and the extinction coefficient K of all materials should be low.

[0034] Thus, in some embodiments, it may be desirable to select an extinction coefficient K < 0.02 (e.g. Figure 1D In general, materials with an extinction coefficient K greater than 0.02 do not provide a significant benefit to the overall reflectivity of the reflective multilayer. Materials below the horizontal dashed line have an extinction coefficient K < 0.02 and include Ru, Tc, Mo, Nb, Ti, Zr, Y, Sc, etc. In addition, in order to achieve good reflection at the interface between each pair of two adjacent layers, it is preferred that the materials of the adjacent layers exhibit a significant separation between them along the horizontal axis. In some embodiments, the reflective multilayer includes layers of ruthenium, molybdenum, strontium and / or silicon, such as Figure 1D In some embodiments, the reflective multilayer may further include a layer of niobium or another suitable material.

[0035] Based on calculations of the reflectivity of reflective multilayers, high reflectivity can be achieved through a random inverse design approach that seeks increasingly higher reflectivity by combining layers of materials with arbitrary, non-periodic sequences of materials and thicknesses. These thicknesses can be lower limits based on constraints on practical fabrication of thin films of each material type. Thus, the lower limit for ruthenium can be different from that for molybdenum, which can be different from that for strontium and silicon. Figure 4-6B Various randomized reverse design procedures are shown in .

[0036] Figure 1E Shown Figure 1A 1. The partial optical path of the lithography exposure system 10 includes the mask stage 16, two reflectors 100A and 100B before the mask stage 16, and a reflector 100C after the mask stage 16. The reflectors 100A and 100B can be part of the illuminator 140, and the reflector 100C can be part of the projection optical module 30.

[0037] Figure 1E The partial optical path of FIG. 8 shows that after being reflected by reflectors 100A, 100B, mask stage 16 and reflector 100C, incident light 84 becomes reflected light 88. More specifically, the incident light 84 has an incident energy E i0 The incident light 84 is incident at an angle of incidence θ0 (relative to the normal of the reflector 100A (perpendicular to Figure 1E The incident light 84 is partially reflected and partially attenuated by the reflector 100A. r0 The reflected light 85 is the portion of the incident light 84 that is reflected by the reflector 100A. With respect to the reflector 100B, the reflected light 85 also has an energy equal to E r0 The incident energy E i1 The incident light 85 is incident on the reflector 100B at an incident angle θ1. The incident light 85 is reflected to form a reflected / incident light 86 having an energy E r1 / E i2 The incident light 86 is incident on the mask stage 16 at an incident angle θ2 and is reflected to form a mask having energy E r2 / E i3 The incident light 87 is incident on the reflector 100C at an incident angle θ3 and is reflected to form a light having energy E r3 / E i4 of reflected / incident light 88.

[0038] Although the reflective multilayers of each of the reflectors 100A-100C and the mask stage 16 may be identical, Figure 1E As shown (although not specifically labeled), generally the reflective multilayers of each of the reflectors 100A-100C and the mask stage 16 may have different designs. For example, the reflector 100B may have more, fewer, or the same number of layers 11-14 (first, second, third, and / or fourth layers 11-14; Figures 2A-2F ), and may have more, fewer, or the same number of layers 11-14 as reflector 100C. In some embodiments, reflector 100B has more, fewer, or the same number of layer types as reflector 100A, and has more, fewer, or the same number of layer types as reflector 100C. In some embodiments, some of reflectors 100A-100C and mask stages 16 have the same reflective multilayer design, while others have different designs. In this way, each of reflectors 100A-100C and mask stages 16 can be independently designed to achieve high reflectivity based on relative position and / or incident angles θ0-θ3 relative to the immediately preceding and / or immediately succeeding reflector or mask stage. In some embodiments, some of reflectors 100A-100C or mask stages 16 include non-periodic and non-alternating reflective multilayers. In some embodiments, some of reflectors 100A-100C or mask stages 16 include non-periodic and alternating reflective multilayers. In some embodiments, some of the reflectors 100A- 100C or mask stages 16 include periodic and alternating reflective multilayers.

[0039] From a system perspective, considering the distance between reflectors, the incident angle, the curvature of the reflectors, etc., the individual reflectors 100A- 100C and / or the mask stage 16 can be designed to have high reflectivity, and the entire optical path can also be designed to have high reflectivity.

[0040] Figure 2A 、 Figure 2C and Figure 2E is a partial cross-sectional view of a reflective multilayer 20A, 20B, 20C according to various embodiments. Figure 2B 、 Figure 2D and Figure 2F 20A, 20B, 20C are enlarged views of the regions 200A, 200B, 200C of the reflective multilayers 20A, 20B, 20C, respectively. As described above, the design of the reflective multilayers 20A, 20B, 20C may depend on many factors. Thus, although Figure 2A-2F The drawings illustrate various features related to particular embodiments but should not be construed as limiting to any one specific design or configuration.

[0041] exist Figure 2A , a reflective multilayer 20A is shown, which includes two types of material layers 11, 12. In some embodiments, the first material layer 11 is a molybdenum layer, and the second material layer 12 is a silicon layer. The thickness of each material layer 11, 12 measured along the Z direction can be substantially constant along a horizontal plane, for example, along a plane as shown in FIG. Figure 2A , and further along the Y direction (not specifically labeled) that is orthogonal to both the X direction and the Z direction. Each material layer 11A-11I can have any thickness within the process limitations, and each material layer 12A-12I can have any thickness within the process limitations. In some embodiments, the thickness T of the first material layer 11 and the second material layer 12 is 11A -T 12I Each is at least about 5 angstroms, and the material layers 11, 12 are deposited by an ALD process. In some embodiments, the thickness T 11A -T 12I Below 5 angstroms, voids or other non-uniformities may occur, thereby reducing yield. In some embodiments, the thickness of the first material layer 11 is in the range of about 20 angstroms to about 40 angstroms. In some embodiments, the thickness of the second material layer 12 is in the range of about 30 angstroms to about 45 angstroms. Figure 3A A further description of the thickness and variations across the reflective multilayer 20A is provided.

[0042] like Figure 2A and Figure 2B As shown, in a reflective multilayer 20A configuration comprising only two types of material layers 11 and 12, the material layers 11 and 12 alternate along the Z direction. Thus, material layer 12C is below material layer 11C, material layer 11C is below material layer 12B, material layer 12B is below material layer 11B, and so on. With the exception of the top and bottom layers of the reflective multilayer 20A, each intermediate first material layer 11 directly contacts the second material layer 12 above it and the second material layer 12 below it. For example, first material layer 11B is in direct contact with both second material layer 12A and second material layer 12B. Similarly, second material layer 12B is in direct contact with first material layer 11B and first material layer 11C. Thus, the reflective multilayer 20A can be said to be alternating and periodic in terms of material.

[0043] exist Figure 2B Since only two types of material layers 11 and 12 are included, it can be said that the reflective multilayer 20A includes a plurality of layers with an arbitrary period P. A 、P B 、P C ,...,P I Each cycle (for example, cycle P B ) is the thickness of the two layers (for example, the thickness T of the first material layer 11B 11Band the thickness T of the second material layer 12B 12B ). Because the thickness T 11A -T 12I is arbitrary, so the period P A 、P B 、P C ,...,P I is arbitrary, and the period of each bilayer can be greater, less than, or equal to that of the overlying or underlying (adjacent) bilayer. Figure 2B As shown, the period P corresponding to the double layer including the first material layer 11B and the second material layer 12B B is smaller than the period P corresponding to the double layer including the first material layer 11C and the second material layer 12C. C In some embodiments, the period P A and period P C The reflective multilayer 20A is the same, but the first material layers 11A and 11C have different thicknesses, and the second material layers 12A and 12C have different thicknesses. The reflective multilayer 20A can be said to be non-alternating with respect to thickness. Typically, the reflective multilayer 20A has at least one bilayer whose period is different from the period of some or all of the remaining multilayers of the reflective multilayer 20A. Thus, the reflective multilayer 20A can also be said to be non-periodic with respect to thickness. In some embodiments, the degree of bilayer non-periodicity can be calculated as the deviation of the period of each bilayer around an average value. Figure 3D A more detailed description of the degree of bilayer aperiodicity is provided.

[0044] exist Figure 2C and Figure 2D In FIG. 1 , the reflective multilayer 20B is shown in a cross-sectional view, and the region 200B is shown in an enlarged view. The reflective multilayer 20B includes three different materials in the material layers 11, 12, and 13. Figure 2A and Figure 2B The first material layer 11 and the second material layer 12 are described in detail. In some embodiments, the third material layer 13 is a ruthenium layer. The thickness of the third material layer 13 measured along the Z direction can be substantially constant along the horizontal plane, for example, along the horizontal plane. Figure 2C , and further along the Y direction (not specifically marked) orthogonal to both the X direction and the Z direction. Each material layer 13A-13I can have any thickness within the process limitations. In some embodiments, the thickness T of the third material layer 13 is 13A -T 13I (not specifically labeled) are each at least about 5 angstroms, and the third material layer 13 is deposited by an ALD process. In some embodiments, the thickness T 13A -T 13IBelow 5 angstroms, voids or other non-uniformities may occur, thereby reducing yield. In some embodiments, in the reflective multilayer 20B, the thickness of the first material layer 11 is in the range of about 5 angstroms to about 35 angstroms. In some embodiments, the thickness of the second material layer 12 is in the range of about 25 angstroms to about 50 angstroms. In some embodiments, the thickness of the third material layer 13 is in the range of about 5 angstroms to about 50 angstroms. Figure 3B A further description of the thickness and variations across the reflective multilayer 20B is provided.

[0045] Further references Figure 2D As shown in region 200B, reflective multilayer 20B can be understood as being non-periodic and non-alternating in terms of thickness and material. As shown, third material layer 13A is in contact with first material layer 11A and second material layer 12A. In some embodiments, third material layer 13A is said to be between first material layer 11A and second material layer 12A. Turning to first material layer 11B and second material layer 12B, there is no third material layer between first material layer 11B and second material layer 12B. First material layer 11B contacts second material layer 12A and second material layer 12B. Thus, reflective multilayer 20B is non-alternating in terms of material. Similarly, reflective multilayer 20B is non-periodic in terms of material.

[0046] refer to Figure 1D The graph of molybdenum and ruthenium is relatively close to each other and is located on the lower left side of the graph. Figure 2D , between every two second material layers 12 (e.g., silicon), at least one of the first material layer 11 (e.g., molybdenum) or the third material layer 13 (e.g., ruthenium) may be located in the middle. For example, a single first material layer 11B is located between the second material layers 12A and 12B. A first material layer 11C and a third material layer 13B are located between the second material layers 12B and 12C. In some embodiments, although not in Figure 2D Specifically shown in FIG, but a single third material layer 13 can be located between two adjacent second material layers 12, so that the third material layer 13 contacts the second material layer 12 above and the second material layer 12 below. In this way, Figure 2D The reflective multilayer 20B can be considered as a stack of bilayers, each bilayer including a second material layer 12 (or "spacer layer 12") and at least one first or third material layer 11, 13 (or "reflective layer 11, 13"). Due to the change in the material of the reflector layer 11 and / or 13 of each bilayer, the reflective multilayer 20B is non-periodic in terms of material.

[0047] exist Figure 2E and Figure 2F, the reflective multilayer 20C is shown in cross-sectional view, and the region 200C is shown in an enlarged view. The reflective multilayer 20C includes four different materials in the material layers 11, 12, 13, and 14. Figures 2A-2D The first material layer 11, the second material layer 12, and the third material layer 13 are described in detail. In some embodiments, the fourth material layer 14 (also referred to as "spacer layer 14") is a strontium layer. The thickness of the fourth material layer 14 measured along the Z direction can be substantially constant along a horizontal plane, for example, along the horizontal plane. Figure 2E , and further along the Y direction (not specifically labeled) orthogonal to both the X direction and the Z direction. Each material layer 14A-14I can have any thickness within the process limitations. In some embodiments, the thickness T of the fourth material layer 14 is 14A -T 14I (not specifically labeled) are each at least about 5 angstroms, and the fourth material layer 14 is deposited by an ALD process. In some embodiments, the thickness T 14A -T 14I Below 5 angstroms, voids or other non-uniformities may occur, thereby reducing yield. In some embodiments, in the reflective multilayer 20C, the thickness of the first material layer 11 is in the range of about 5 angstroms to about 35 angstroms. In some embodiments, the thickness of the second material layer 12 is in the range of about 15 angstroms to about 50 angstroms. In some embodiments, the thickness of the third material layer 13 is in the range of about 5 angstroms to about 50 angstroms. In some embodiments, the thickness of the fourth material layer 14 is in the range of about 5 angstroms to about 40 angstroms. Figure 3C A further description of the thickness and variations across the reflective multilayer 20C is provided.

[0048] refer to Figure 1D The graph of silicon and strontium is relatively close to each other and is located on the lower right side of the graph. Figure 2F , the reflective multilayer 20C can be considered as a stack of bilayers, each bilayer comprising at least one second or fourth material layer 12, 14 (or "spacer layer 12, 14") and at least one first or third material layer 11, 13 (or "reflector layer 11, 13"). Figure 2G-2L An example of a dual layer 30A-30F according to various embodiments is shown in FIG. Figure 2F At least one of the first material layer 11 (e.g., molybdenum) or the third material layer 13 (e.g., ruthenium) may be between at least two spacer layers 12 and 14 (e.g., silicon or strontium). For example, a single third material layer 13A may be between spacer layers 12C and 14C and spacer layers 12D and 14D. Due to the material variations of each bilayer reflector layer 11 and / or 13 and spacer layers 12 and / or 14, the reflective multilayer 20C is non-periodic in terms of material.

[0049] Figures 3A-3D 300A-300C are diagrams illustrating designs of reflective multilayers 20A-20C, respectively, and in particular, graphs 300A-300C illustrating the relative thicknesses and order of the first, second, third, and / or fourth material layers 11-14 in the reflective multilayers 20A-20C, respectively. In some embodiments, the first material layer 11 is molybdenum, the second material layer 12 is silicon, the third material layer 13 is ruthenium, and the fourth material layer 14 is strontium. As previously described, the order and thickness of the material layers 11-14 are arbitrary and may depend on a variety of factors, including the wavelength of the incident light, the angle of incidence of the incident light, the distance from the previous reflector, the distance to the next reflector, and other appropriate factors. Thus, Figures 3A-3D Each configuration shown in represents a solution that may be globally or locally optimal for high reflectivity based on factors unique to the reflective multilayer 20A-20C, but may not be globally or locally optimal if even one of these factors is significantly changed (e.g., by more than about 1% in any direction).

[0050] Typically, the reflective multilayer 20A-20C may include at least one region, for example, extending from a first depth to a second depth along the Z axis (see, for example, Figure 2E ). In each region, each of the material layers 11-14 can exhibit one or more of a variety of trends. For example, in a single region comprising approximately 10 layers (each layer being at least two of the material layers 11-14), the trends can include at least an amplitude slope trend and a variation trend. In some embodiments, the amplitude slope trend can be upward, downward, or lateral, wherein the average thickness of any one of the material layers 11-14 can increase approximately (e.g., slope>0.1 angstroms / layer), decrease (e.g., slope<-0.1 angstroms / layer), or remain approximately the same over the region (e.g., -0.1 angstroms / layer<slope<0.1 angstroms / layer). In some embodiments, the variation trend can be large or small, such that the variation in thickness around the average thickness in the region is high or low, respectively.

[0051] exist Figure 3A In the embodiment, the first line 311A ​​is formed from the first material layer 11A to the first material layer 11N (see Figure 2A ) shows the average thickness of the first material layer 11, and the first material layer 11N may be the first material layer 11 on the reflective multilayer 20A that is farthest from the incident light. The second line 312A is arranged from the second material layer 12A to the second material layer 12N (see Figure 2A) shows the average thickness of the second material layer 12, which may be the second material layer 12 on the reflective multilayer 20A that is farthest from the incident light. Upper strip lines 311A_U and 312A_U respectively show the upper thickness deviation from the average thickness shown by the first line 311A ​​and the second line 312A. In some embodiments, the upper thickness deviation is the maximum deviation, the first deviation, or another deviation therebetween. Lower strip lines 311A_L and 312A_L respectively show the lower thickness deviation from the average thickness shown by the first line 311A ​​and the second line 312A. In some embodiments, the lower thickness deviation is the maximum deviation, the first deviation, or another deviation therebetween.

[0052] In some embodiments, the first material layers 11 alternate with the second material layers 12, and each of the first material layers 11 and the second material layers 12 has any thickness. In some embodiments, the first material layers 11 are substantially thinner than the second material layers 12. For example, more than 90% of the second material layers 12 can be thicker than the thickest first material layer 11. In some embodiments, more than 90% of the second material layers 12 are thicker than the average thickness of the first material layers 11. In some embodiments, making the spacer layers 12 generally thicker than the reflector layer 11 provides better overall reflectivity of the reflector 100 including the reflective multilayer 20A.

[0053] like Figure 3A As further shown in FIG, the reflective multilayer 20A including only the first material layer 11 and the second material layer 12 may include at least two different regions 301A and 302A. Figure 3A In the illustrated embodiment, the first region 301A of the reflective multilayer 20A may include the first material layer 11 and the second material layer 12 on the left side of the separation line 350A. The second region 302A may include the material layers 11 and 12 on the right side of the separation line 350A. In the first region 301A on the left side of the separation line 350A, the amplitude slope of the material layer 11 may be slightly downward, and the thickness of the material layer 11 may have substantial variation. The amplitude slope of the material layer 12 may be slightly upward, and the thickness of the material layer 12 may have significant variation. In the second region 302A, the amplitude slope of the material layers 11 and 12 may be substantially horizontal (slightly downward or slightly upward), and the variation trend of the thickness of the material layers 11 and 12 may be low.

[0054] In some embodiments, the variation (or "coefficient of variation (CV)") can be quantified as the standard deviation divided by the mean. For illustrative purposes, the average thickness of the first material layer 11 in the first region 301A can be approximately 31 nm, and the standard deviation of the thickness of the first material layer 11 in the first region 301A can be approximately 2.3 nm, resulting in a variation of approximately 7.4% for the first material layer 11 in the first region 301A. In the second region 302A, the average thickness of the first material layer 11 can be approximately 27 nm, and the standard deviation can be approximately 0.2 nm, resulting in a variation of approximately 0.74% for the first material layer 11 in the second region 302A, or approximately one-tenth the variation in the first region 301A. For the second material layer 12, those in the first region 301A can have a variation of approximately 4.8%, and those in the second region 302A can have a variation of approximately 1.7%, or approximately one-third the variation in the first region 301A. In some embodiments, the thickness variation of the material layers 11 and 12 in the first region 301A is in a range of about 2% to about 20%, and the thickness variation of the material layers 11 and 12 in the second region 302A is in a range of about minimum process variation (e.g., 0.01%) to about 10%. A thickness variation of the material layers 11 and 12 less than about 2% may result in an insufficient increase in reflectivity.

[0055] Figure 3D Shown with Figure 3A 300A corresponds to a histogram 390A, which can further help describe the thickness variation across all layers in the reflective multilayer 20A. The histogram 390 of the reflective multilayer 20A includes multiple non-overlapping thickness ranges R1-R9. Each thickness range of the thickness ranges R1-R9 can be, for example, approximately 1 angstrom wide, without excluding other suitable widths greater than or less than approximately 1 angstrom. Line 350D shows the average thickness of the material layers 11 and 12. Lines 351D and 352D represent one standard deviation below and above the average thickness, respectively. As a non-limiting example, the average thickness represented by line 350D can be approximately 69.5 nm, and the standard deviation can be approximately 1.5 nm, corresponding to a thickness variation of approximately 2.2%.

[0056] exist Figure 3B , graph 300B depicts the Figure 2C-2DFIG20B is a diagram illustrating a first line 311B, a second line 312B, and a third line 313B corresponding to the average thickness of the first material layer 11, the second material layer 12, and the third material layer 13 of the reflective multilayer 20B. Upper strip lines 311B_U, 312B_U, and 313B_U respectively illustrate upper thickness deviations from the average thicknesses shown by the first line 311B, the second line 312B, and the third line 313B. In some embodiments, the upper thickness deviation is a maximum deviation, a first deviation, or another deviation therebetween. Lower strip lines 311B_L, 312B_L, and 313B_L respectively illustrate lower thickness deviations from the average thicknesses shown by the first line 311B, the second line 312B, and the third line 313B. In some embodiments, the lower thickness deviation is a maximum deviation, a first deviation, or another deviation therebetween.

[0057] In some embodiments, the first material layers 11 do not necessarily alternate with the second material layers 12 and / or the third material layers 13, and each of the first material layers 11, the second material layers 12, and the third material layers 13 have any thickness. In some embodiments, the first material layers 11 are substantially thinner than the second material layers 12. For example, greater than 90% of the second material layers 12 can be thicker than the thickest first material layer 11. In some embodiments, greater than 90% of the second material layers 12 are thicker than the average thickness of the first material layers 11. In some embodiments, the third material layers 13 are substantially thinner than the second material layers 12. For example, greater than 90% of the second material layers 12 can be thicker than the thickest third material layer 13 (this is the case in Figure 3B (not specifically shown in the figure). In some embodiments, more than 90% of the second material layers 12 are thicker than the average thickness of the third material layers 13. Figure 3B It will be appreciated that the reflector layers 11, 13 shown by lines 311B, 313B are not as thick as the spacer layer 12. However, a small portion (eg, <10%) of the reflector layers 11, 13 may have a thickness greater than the average thickness of the spacer layer 12.

[0058] Further references Figure 3B , depicts five distinct regions 301B-305B, which highlight certain characteristics of the composition of reflective multilayer 20B regarding the sequence and relative thicknesses of the first, second, and third material layers 11-13. In first region 301B, to the left of line 350B, only layers of third material layer 13 and second material layer 12 are included. Intermediate layers of first material layer 11 are absent in first region 301B. In some embodiments, first region 301B may include only layers of first material layer 11 and second material layer 12, without an intermediate layer of third material layer 13. Furthermore, the average thicknesses of second material layer 12 and third material layer 13 are approximately similar in first region 301B (e.g., within approximately 20% of each other).

[0059] In the second region 302B between lines 350B and 351B, the first material layer 11 is first present in the reflective multilayer 20B. In the second region 302B, the thickness of the third material layer 13 has a downward amplitude slope trend, and the thicknesses of the first material layer 11 and the second material layer 12 each have an overall upward amplitude slope trend.

[0060] In a third region 303B between lines 351B and 352B, a majority (e.g., >90%) of the reflector layers 11, 13 have a thickness that is substantially less than that of the spacer layer 12. In some embodiments, the average thickness of either reflector layer 11, 13 is at least about 20% thinner than the average thickness of the spacer layer 12. In some embodiments, the first material layer 11 is generally thicker than the third material layer 13 in the third region 303B, such that the average thickness of the first material layer 11 is at least about 10% greater than the average thickness of the third material layer 13.

[0061] In a fourth region 304B between lines 352B and 353B, the second material layer 12 and the third material layer 13 have generally lateral amplitude slope trends and low thickness variation. The first material layer 11 has high thickness variation and a lateral amplitude slope trend. The average thickness of the second material layer 12 is greater than the average thickness of the first material layer 11, which in turn is greater than the average thickness of the third material layer 13.

[0062] In the fifth region 305B to the right of line 353B, the first material layer, the second material layer, and the third material layers 11-13 all exhibit substantially transverse amplitude slope trends and low thickness variations. In some embodiments, the reflective multilayer 20B has the smallest thickness variation in the region farthest from the surface on which light is incident (e.g., the fifth region 305B).

[0063] exist Figure 3C , the graph 300C depicts the Figure 2E-2F11C, second line 312C, third line 313C, and fourth line 314C, corresponding to the average thickness of the first material layer 11, second material layer 12, third material layer 13, and fourth material layer 14 of the reflective multilayer 20C. Upper strip lines 311C_U, 312C_U, 313C_U, and 314C_U respectively indicate upper thickness deviations from the average thickness indicated by the first line 311C, the second line 312C, the third line 313C, and the fourth line 314C. In some embodiments, the upper thickness deviation is a maximum deviation, a first deviation, or another deviation therebetween. Lower strip lines 311C_L, 312C_L, 313C_L, and 314C_L respectively indicate lower thickness deviations from the average thickness indicated by the first line 311C, the second line 312C, the third line 313C, and the fourth line 314C. In some embodiments, the lower thickness deviation is the maximum deviation, the first deviation, or another deviation therebetween.

[0064] Since each of the material layers 11-14 can have any thickness and order in the reflective multilayer 20C, the graph 300C can be similar in many respects to one or both of the graphs 300A, 300B. Figure 3C 3. The region 301C of the reflective multilayer 20C is highlighted in FIG. 3, which may be an intermediate region. In some embodiments, the intermediate region 301C may include a minimal layer of at least one of the material layers 11-14. Figure 3C As shown, in some embodiments, the reflective multilayer 20C includes a middle region 301C having a sparse layer (represented by point 313I) of the third material layer 13 (which is a reflector layer). In some embodiments, this may be due to the intelligent recombination of adjacent reflector layers of different materials into a single reflector layer of a single material (see FIG. Figures 6A to 6B Further described), such as a first material layer 11, which can be a molybdenum layer. This further highlights the non-periodic nature of the reflective multilayer 20C, where some reflector / spacer bilayers can include all four material layers 11-14, while others can include only three material layers, such as material layers 11, 12, 14. In some embodiments, in at least one region of the reflective multilayer 20C, at least one material layer (e.g., material layer 13) can be present in a range from about 1% of the total layers in the region to about 15% of the total layers in the region. The presence of at least one of the material layers at a percentage within the range can improve manufacturing yield and cost while maintaining a high reflectivity of the reflector 100 including the reflective multilayer 20C. In some embodiments, the total number of layers in the region is in a range from about 20 layers to about 100 layers.

[0065] Figure 4-6Bare various views illustrating a process 40 for forming a reflective multilayer according to various embodiments. Figure 4 is a flowchart of process 40, Figure 5 Shown with Figure 4 The graph corresponding to operation 412, and Figure 6A-6B is shown with Figure 4 The process 40 may be performed by a computing system that may include a processor, such as a general-purpose central processing unit (CPU), a graphics processing unit (GPU), or an application-specific integrated circuit (ASIC), a random access memory (RAM), and at least one communication bus configured to provide bidirectional signal transmission between the processor and the RAM.

[0066] exist Figure 4 In the embodiment of the present invention, process 40 begins with operation 400, in which a reflective multilayer structure M is provided, which may also be referred to as an "initial reflective multilayer structure M". In some embodiments, the reflective multilayer structure M is provided by creating a data object that includes an array or list of data structures representing various material layers. In some embodiments, each data structure includes at least a position (e.g., an integer from 0 to 99), a material (e.g., molybdenum, silicon, etc.), and a thickness (e.g., 30 nm) of the material layer represented. In some embodiments, each data structure includes a depth (e.g., from 0.00 nm to 50,000.00 nm), which may be recorded instead of or in addition to the position.

[0067] In some embodiments, in operation 400, the reflective multilayer structure M is further provided by establishing design constraints (or rules) related to the location, depth, material, and thickness of the material layers. For example, a minimum and / or maximum thickness can be set for each material based on manufacturing capabilities, and / or a maximum total number of layers can be set, and / or material selection exclusions can be set based on the material of the immediately preceding specified material layer. Material selection exclusions can be established rules that reduce the pool of available materials for a layer during randomization. For example, if the material of the first material layer 11 is randomly selected for the first layer, the material selection exclusion can consider removing the material of the first material layer 11 for the immediately subsequent second layer, so that the material of the second layer can only be randomly selected from the materials corresponding to the second material layer, the third material layer, or the fourth material layer 12-14. In another example, the removal can be based on whether the first layer is a reflector layer 11, 13 or a spacer layer 12, 14, so that the second layer can only be a spacer layer 12, 14 or a reflector layer 11, 13, respectively.

[0068] In some embodiments, a reflective multilayer structure M is further provided by assigning a random value to at least one of the material or thickness of each position. For example, the material layer at position 0 can be randomly assigned molybdenum as the material and 22 nm as the thickness. Then, the material layer at position 1 can be randomly assigned silicon as the material and a fixed thickness of 40 nm can be assigned as the thickness. The material layer at position 2 can be randomly assigned molybdenum with a thickness of 25 nm. This assignment operation can continue until a fixed number of layers is reached, or a random number (e.g., 75) of layers between a minimum number (e.g., 60) and a maximum number (e.g., 100) is reached.

[0069] In some embodiments, a periodic alternating configuration can be assigned to the layers of the reflective multilayer structure M. For example, the configuration can include a fixed number of alternating layers of the first material layer, the second material layer, the third material layer, and the fourth material layer 11-14, each having the same thickness. Selecting such a configuration can significantly reduce the processing burden of operation 400.

[0070] In operation 410, at least one technique is employed to find an optimal intermediate reflective multilayer structure M' (or "intermediate reflective multilayer structure configuration M'"). Technique 412 may include an inverse design technique, such as a local maximum path finding algorithm, a global maximum path finding algorithm, and / or a machine learning algorithm. As described above, technique 412 may be constrained by manufacturability constraints 414, which may include at least a minimum thickness constraint and a layer count constraint. Manufacturing constraints 414 may inform other techniques, such as intra-layer reorganization and / or inter-layer reorganization, which will be referenced. Figure 6A-6B Describe more fully.

[0071] Figure 5 Shown with Figure 4 The local and global maximum path finding algorithms corresponding to operations 420, 430, 440, 450. Figure 5 , a graph with reflectivity on the vertical axis and candidates on the horizontal axis is shown. Each of the initial reflective multilayer structure M and the subsequent intermediate reflective multilayer structure M' is a candidate.

[0072] In some embodiments, the local maximum path finding algorithm may receive an initial reflective multilayer structure M or an intermediate reflective multilayer structure M', change at least one parameter (position, depth, material, thickness) of at least one material layer, and calculate the maximum path finding algorithm by referring to the initial reflective multilayer structure M or the intermediate reflective multilayer structure M'. Figure 1C The technique described is used to calculate the reflectivity R, which corresponds to Figure 4Operation 410. Each cycle of the change of the initial reflective multilayer structure M or the intermediate reflective multilayer structure M' and the corresponding calculation of the reflectivity R can be referred to as a path finding cycle. In some embodiments, a certain number of path finding cycles can be set, such as 1000 cycles, 10000 cycles, or another suitable number of path finding cycles, after which the path finding algorithm can be terminated, and the optimal reflective multilayer structure M* for all path finding cycles can be determined and saved for use in manufacturing the reflector 100. In some embodiments, the path finding algorithm is terminated after a certain number of path finding cycles in which no significant improvement is found, such as 100 cycles, 10 cycles, or another suitable number of cycles, which can correspond to Figure 4 4. The transition from operation 420 to operation 430 in FIG.

[0073] In some embodiments, the change can be applied to a single layer, thereby changing the material, position, depth or thickness of the layer. In some embodiments, the change can be applied to multiple layers. In some embodiments, the change is random. For example, the change can affect a random number of layers, and / or the material, position, depth and / or thickness of each layer. In some embodiments, the change can include swapping layers. For example, the first layer at position 0 and the second layer at position 50 can be swapped so that the changed first layer occupies position 50 and the second layer occupies position 0. In some embodiments, the change is subject to manufacturability constraints 414. In some embodiments, the change includes adding or removing layers. For example, the second layer at position 50 can be removed so that after the change, the third layer originally located at position 51 occupies position 50, and the total number of layers of the intermediate reflective multilayer structure M' is reduced by one layer.

[0074] Some changes increase reflectivity, while other changes decrease reflectivity, which can correspond to Figure 4 Operation 420. For example, Figure 5 As shown, one or more changes are performed on the initial reflective multilayer structure M, and the reflectivity is improved (corresponding to Figure 4 430), and it is found that the first local maximum 520 has a reflectivity R max_local(0) , which is greater than the initial reflectivity R0 of the initial reflective multilayer structure M. In some embodiments, many changes (or change / calculation cycles, e.g., >100 cycles) occur before a change is reached that causes the reflectivity of the intermediate reflective multilayer structure M' to decrease. The first local maximum 520 can correspond to the last optimal intermediate reflective multilayer structure M' before the subsequent degenerate change. Each intermediate reflective multilayer structure M' can be stored in RAM, including the parameters and calculated reflectivities of all layers.

[0075] Figure 5The global maximum pathfinding algorithm is further illustrated. After identifying a first local maximum 520, a plurality of pathfinding cycles may initially result in a decrease in reflectivity R, followed by a plurality of pathfinding cycles resulting in an increase in reflectivity R. After one or more pathfinding cycles of increasing reflectivity R, a second local maximum 521 may be identified as having a reflectivity R greater than that corresponding to the first local maximum 520. max_local(0) Reflectivity R max_local(1) Again, there may be multiple pathfinding cycles where the reflectivity R decreases, followed by identifying a pathfinding cycle with a reflectivity R max_global The corresponding global maximum 530 is a number of path finding cycles that culminates in a global maximum 530 that is greater than any other local maximum 520, 521 in the graph 500. The identification and recording / storage of the optimal reflective multilayer structure M* corresponding to the global maximum 530 may correspond to Figure 4 After identifying and recording / storing the optimal reflective multilayer structure M*, process 40 may terminate at operation 450.

[0076] In some embodiments, if multiple pathfinding cycles are passed in which the reflectivity R is not significantly improved by modifying the layers of the intermediate reflective multilayer structure M', it may be desirable to avoid local maxima, such as the first local maximum 520. To avoid local maxima, a strong modification can be applied, wherein a large number of layers are affected by the strong modification. For example, the strong modification can include simultaneously randomizing the position, material, and / or thickness of at least 10% of the layers of the intermediate reflective multilayer structure M'. Applying the strong modification may initially result in a significant decrease in reflectivity R, followed by a substantial increase in reflectivity R in subsequent pathfinding cycles.

[0077] In some embodiments, after operation 450 in which the optimal reflective multilayer structure M* is recorded / stored, a reflective multilayer, such as one of the reflective multilayers 20A-20C, is manufactured according to the design of the recorded / stored optimal reflective multilayer structure M*, corresponding to Figure 4 Operation 460. For example, the optimal reflective multilayer structure M* may be a digital file(s) containing information about the positions, materials and thicknesses of the material layers 11-14, e.g. Figure 3B Represented in graphical form.

[0078] In some embodiments, operation 460 includes depositing a first material layer having a first material and a first thickness, depositing a second material layer having a second material and a second thickness, and so on, until all material layers 11-12, 11-13, and 11-14 of the reflective multilayers 20A-20C, respectively, have been deposited. Further manufacturing operations may be performed on the completed reflective multilayers 20A-20C, such as adding a capping layer or encapsulating the reflective multilayers 20A-20C in, for example, a protective package.

[0079] Steering Figure 6A-Figure 6B In some embodiments, as part of operation 410, reorganization is performed on at least two layers (typically adjacent or nearby layers) in the intermediate reflective multilayer structure M'. Reorganization can achieve a number of benefits, including restoring the layer count budget when the intermediate reflective multilayer structure M' is equal to or close to a layer count constraint. In some embodiments, the layer count constraint is the maximum number of layers that can be included in the optimal reflective multilayer structure M* corresponding to the reflective multilayers 20A-20C. Reorganization can also improve manufacturing yield, for example, by combining at least one layer that is at the minimum thickness constraint with another layer to produce a single thicker layer, which can generally be more easily manufactured with high uniformity.

[0080] Figure 6AIntralayer recombination 600A according to various embodiments is illustrated. As shown, reflective multilayer 20C includes three periods P1, P2, and P3, each period comprising two layers. First period P1 includes third material layer 13A above first material layer 11A. Second period P2 includes fourth material layer 14A below first material layer 11A and above second material layer 12A. Third period P3 includes third material layer 13B below second material layer 12A and above first material layer 11B. Fourth material layer 14A and second material layer 12A of second period P2 are both spacer layers 12 and 14, but are made of different materials and have different thicknesses. The first thickness of fourth material layer 14A may be equal to or close to the minimum thickness constraint, while the second thickness of second material layer 12A is significantly greater than the first thickness. Thus, fourth material layer 14A can recombine with second material layer 12A to form a recombined second material layer 12A' having a thickness substantially equal to the sum of the first and second thicknesses. In some embodiments, intra-layer reorganization 600A includes removing a layer, such as fourth material layer 14A, and increasing the thickness of another layer, such as second material layer 12A. In some embodiments, intra-layer reorganization 600A includes changing the material of a layer, such as fourth material layer 14A, from strontium to silicon and merging this layer with another layer, such as second material layer 12A. Intra-layer reorganization 600A, which produces reorganized second material layer 12A', eliminates one manufacturing operation (one layer instead of two), removes a relatively difficult-to-manufacture layer, and thickens a relatively easy-to-manufacture layer, thereby making it easier to manufacture.

[0081] Figure 6B Interlayer recombination 600B according to various embodiments is illustrated. As shown, reflective multilayer 20C includes four periods P1, P2, P3, and P4, each period comprising one or two layers. First period P1 includes fourth material layer 14A above second material layer 12A. Second period P2 includes third material layer 13A below second material layer 12A. Third period P3 includes second material layer 12B below third material layer 13A. Fourth period P4 includes third material layer 13B below second material layer 12B and above first material layer 11A. Third material layer 13A and second material layer 12B may be at or near a minimum thickness constraint. Thus, from a manufacturing perspective, it may be desirable to recombine relatively thin second material layer 12B and third material layer 13A with relatively thicker second material layer 12A and third material layer 13B, respectively.

[0082] After interlayer recombination 600B, reflective multilayer 20C' includes two fewer periods: a first period P1' and a fourth period P4'. First period P1' may include original fourth material layer 14A and reconstructed second material layer 12A' having a thickness substantially equal to the sum of the thicknesses of second material layers 12A and 12B. Fourth period P4' may include original first material layer 11A and reconstructed third material layer 13B' having a thickness substantially equal to the sum of the thicknesses of third material layers 13A and 13B. In some embodiments, interlayer recombination 600B includes removing two layers, such as third material layer 13A and second material layer 12B, and increasing the thickness of two layers, such as second material layer 12A and third material layer 13B. In some embodiments, interlayer recombination 600B includes changing the positions of two layers, such as swapping the positions of third material layer 13A and second material layer 12B, and merging the swapped layers with two other layers, such as third material layer 13B and second material layer 12A, respectively. Interlayer reorganization 600B to produce reorganized second material layer 12A' and reorganized third material layer 13B' eliminates two manufacturing operations (two layers instead of four), removes two relatively difficult to manufacture layers, and thickens two relatively easy to manufacture layers, making them easier to manufacture.

[0083] In some embodiments, recombination 600A, 600B results in a small but measurable decrease in the reflectivity of reflective multilayers 20A-20C. Thus, recombination 600A, 600B can be maintained when the resulting decrease in reflectivity of reflective multilayers 20A-20C is less than approximately 0.01%. For a lithography exposure system 10 including at least ten reflectors 100, and assuming that each reflector 100 performs ten recombination operations, the decrease in reflectivity across the optical path is approximately 1%. In some embodiments, a recombination budget can be established such that the overall decrease in reflectivity across the reflectors 100 does not exceed a threshold, such as approximately 0.1%, such that the decrease in reflectivity across the optical path including the ten reflectors 100 does not exceed approximately 1%. In some embodiments, recombination is abandoned when the decrease due to recombination is greater than approximately 0.01%.

[0084] Figure 7 FIG. 7 is a flow chart of a process 70 for manufacturing a semiconductor device using a photolithography exposure system 10 including at least one reflective multilayer 20A-20C. In operation 700, a mask layer is deposited on a substrate. The mask layer may include a hard mask (e.g., SiN) and one or more photoresist layers, which may include an anti-reflective layer. A semiconductor device typically includes patterned layers of semiconductor, dielectric, and conductor materials on and in a substrate. Prior to patterning by, for example, an etching system, a mask layer may be deposited over the material layer. Deposition may include any suitable deposition process, such as CVD, PVD, spin coating, and the like.

[0085] After depositing the mask layer, in operation 710, an opening is formed in the mask layer by a photolithography exposure system 10 including at least one reflective multilayer 20A, 20B, 20C having at least three layers with substantially different thicknesses. Figure 2F-2L As described, the positions, depths, materials, and thicknesses of the first, second, third, and fourth material layers 11-14 can be non-periodic and non-alternating. The openings can be formed by exposing the mask layer to the pattern of the mask stage 16 and then removing the exposed or unexposed portions of the mask layer. After removing the exposed or unexposed portions, the remaining portion of the mask layer includes the openings.

[0086] After the openings are formed, the material exposed by the openings is removed in operation 720. This material may be the material of the hard mask exposed by the openings in the photoresist layer(s). This material may be the material of the semiconductor, dielectric, or conductor layer exposed by the openings in the photoresist layer(s). Process 70 may be repeated multiple times to pattern a single layer of a semiconductor device, and may also be repeated multiple times to pattern multiple layers.

[0087] Figure 8 is a block diagram of a system 3324 according to one embodiment, which may be used to perform Figure 4 The control system of process 40. The control system 3324 uses machine learning to adjust the parameters of the intermediate reflective multilayer structure M'.

[0088] In one embodiment, the control system 3324 includes an analytical model 3302 and a training module 3304. The training module 3304 utilizes a machine learning process to train the analytical model 3302. The machine learning process trains the analytical model 3302 to select parameters for operation 410 that will result in an intermediate reflective multilayer structure M' having selected properties (e.g., high reflectivity R). Although the training module 3304 is shown as separate from the analytical model 3302, in practice, the training module 3304 can be part of the analytical model 3302.

[0089] Control system 3324 includes or stores training data set 3306. Training data set 3306 includes historical reflector data 3308 and historical environmental condition data 3310. Historical reflector data 3308 includes data related to the intermediate reflective multi-layer structure M' generated by operation 410. Historical environmental condition data 3310 includes data related to the simulated environment in which the intermediate reflective multi-layer structure M' is to be operated. As will be described in more detail below, training module 3304 utilizes a machine learning process to train analytical model 3302 using historical reflector data 3308 and historical environmental condition data 3310.

[0090] In one embodiment, historical reflector data 3308 includes data related to the position, depth, material and / or thickness of the material layer. For example, tens of thousands of intermediate reflective multilayer structures M' can be generated (initialized or changed) over the course of several hours or days. Each intermediate reflective multilayer structure M' can include material layers with different thicknesses, materials, and positions and / or depths. After each generation, the reflectivity of the intermediate reflective multilayer structure M' is calculated. Historical reflector data 3308 includes, for example, parameters for each layer of each intermediate reflective multilayer structure M' generated by operation 410. Therefore, historical reflector data 3308 can include thickness, material, depth, and position data for a large number of intermediate reflective multilayer structures M' generated by operation 410.

[0091] In one embodiment, historical reflector data 3308 may also include data related to the reorganization of the material layers in operation 410. For example, the change process may include a large number of reorganizations, during which the various material layers of the intermediate reflective multilayer structure M' are merged and / or rearranged. Historical reflector data 3308 may include reflectivity data of the intermediate reflective multilayer structure M' after each pathfinding cycle or group of pathfinding cycles. Therefore, historical reflector data 3308 may include not only data related to the total reflectivity of the intermediate reflective multilayer structure M' after the pathfinding process is complete, but may also include data related to the reflectivity of the intermediate reflective multilayer structure M' at various stages of the pathfinding process.

[0092] In one embodiment, historical environmental condition data 3310 includes various environmental conditions or parameters associated with historical reflector data 3308 during operation of intermediate reflective multi-layer structure M'. Thus, for each intermediate reflective multi-layer structure M' having data in historical reflector data 3308, historical environmental condition data 3310 may include environmental conditions or parameters that existed during the calculation of reflectivity. For example, historical environmental condition data 3310 may include data related to the surrounding atmosphere, the angle of incidence of incident light, the wavelength of incident light, the position of intermediate reflective multi-layer structure M' in the optical path, and the like.

[0093] In one embodiment, the training set data 3306 links the historical reflector data 3308 with the historical environmental condition data 3310. In other words, the material layer thickness, material composition, layer depth, or location associated with the intermediate reflective multilayer structure M' in the historical reflector data 3308 is linked (e.g., by labeling) to the environmental condition data 3310 and the reflectivity data associated with the intermediate reflective multilayer structure M'. As will be explained in more detail below, the labeled training set data can be used in a machine learning process to train the analytical model 3302 to predict material layer conditions that will result in high reflectivity for the reflector 100.

[0094] In one embodiment, control system 3324 includes processing resources 3312, memory resources 3314, and communication resources 3316. Processing resources 3312 may include one or more controllers or processors. Processing resources 3312 are configured to execute software instructions, process data, make thin film etch control decisions, perform signal processing, read data from memory, write data to memory, and perform other processing operations. Processing resources 3312 may include physical processing resources 3312 and / or virtual processing resources 3312. Processing resources 3312 may include cloud-based processing resources, including processors and servers accessed via one or more cloud computing platforms.

[0095] In one embodiment, memory resources 3314 may include one or more computer-readable memories. Memory resources 3314 are configured to store software instructions associated with the functionality of the control system and its components, including, but not limited to, analytical model 3302. Memory resources 3314 may store data associated with the functionality of control system 3324 and its components. This data may include training set data 3306, current process condition data, and any other data associated with the operation of control system 3324 or any of its components. Memory resources 3314 may include physical memory resources and / or virtual memory resources. Memory resources 3314 may include cloud-based memory resources accessed via one or more cloud computing platforms.

[0096] In one embodiment, the communication resources 3316 may include wired and wireless communication resources that can facilitate communication via one or more networks (e.g., a wired network, a wireless network, the Internet, or an intranet). The communication resources 3316 may enable components of the control system 3324 to communicate with each other.

[0097] Figure 9 is a diagram showing a method according to an embodiment Figure 8 33. A block diagram of the operational and training aspects of the analytical model 3302 is provided. As previously described, the training set data 3306 includes data related to a plurality of previously generated intermediate reflective multilayer structures M'. Each previously generated intermediate reflective multilayer structure M' was generated under specific environmental conditions and resulted in a specific reflectivity. The material layer position, depth, material, and thickness parameters of each previously generated intermediate reflective multilayer structure M' are formatted into a corresponding reflector condition matrix 3352. The reflector condition matrix 3352 includes a plurality of data vectors 3354. Each data vector 3354 corresponds to a specific layer and includes at least four data scalars 3354A-3354D, which may include a position scalar 3354A, a depth scalar 3354B, a material scalar 3354C, and a thickness scalar 3354D.

[0098] Figure 9 The example shows a single reflector condition matrix 3352 that will be passed to the analysis model 3302 during the training process. Figure 9 In the example shown in FIG, reflector condition matrix 3352 includes nine data vectors 3354, each corresponding to a single material layer of intermediate reflective multilayer structure M'. Each data scalar 3354A-3354D is represented by a numerical value in the corresponding data vector 3354. For condition types that do not naturally have a numerical representation, such as material 3354C, a number can be assigned to each possible material.

[0099] The analysis model 3302 includes a plurality of neural layers 3356a-e. Each neural layer includes a plurality of nodes 3358. Each node 3358 may also be referred to as a neuron. Each node 3358 from the first neural layer 3356a receives a data value for each data field from the reflector condition matrix 3352. Thus, in Figure 9 In the example of FIG, each node 3358 from the first neural layer 3356a receives 36 data values ​​because the reflector condition matrix 3352 has 36 data scalars (9*4=36). Each neuron 3358 includes Figure 9 3352. Each node 3358 of the first neural layer 3356a generates a scalar value by applying the internal mathematical function F(x) to the data value of the data field 3354 from the reflector condition matrix 3352. More details about the internal mathematical function F(x) are provided below.

[0100] Each node 3358 of the second neural layer 3356b receives a scalar value generated by each node 3358 of the first neural layer 3356a. Figure 9 In the example shown in FIG, each node of the second neural layer 3356b receives four scalar values ​​because there are four nodes 3358 in the first neural layer 3356a. Each node 3358 of the second neural layer 3356b generates a scalar value by applying a corresponding internal mathematical function F(x) to the scalar value from the first neural layer 3356a.

[0101] Each node 3358 of the third neural layer 3356c receives a scalar value generated by each node 3358 of the second neural layer 3356b. Figure 9 In the example shown in FIG, each node of the third neural layer 3356 c receives five scalar values ​​because there are five nodes 3358 in the second neural layer 3356 b. Each node 3358 of the third neural layer 3356 c generates a scalar value by applying a corresponding internal mathematical function F(x) to the scalar value of the node 3358 from the second neural layer 3356 b.

[0102] Each node 3358 of the neural layer 3356 d receives a scalar value generated by each node 3358 of the previous neural layer (not shown). Each node 3358 of the neural layer 3356 d generates a scalar value by applying a corresponding internal mathematical function F(x) to the scalar value from the node 3358 of the previous neural layer (not shown).

[0103] The final neural layer includes only a single node 3358. The final neural layer receives the scalar values ​​generated by each node 3358 of the previous neural layer 3356d. The node 3358 of the final neural layer 3356e generates a data value 3368 by applying a mathematical function F(x) to the scalar value received from the node 3358 of the neural layer 3356d.

[0104] exist Figure 9 In the example of , data value 3368 corresponds to the predicted reflectivity of the intermediate reflective multilayer structure M' generated by the reflector data (corresponding to the value included in the reflector condition matrix 3352). In other embodiments, the final neural layer 3356e can generate multiple data values, each corresponding to a specific reflective multilayer characteristic, such as the reflectivity or other characteristic of the reflective multilayer. The final neural layer 3356e will include a corresponding node 3358 for each output data value to be generated. In one example, in the case of predicted reflectivity, the engineer can provide constraints that specify that the predicted reflectivity 3368 must fall within a selected range, such as greater than 70%. The analytical model 3302 will adjust the internal function F(x) to ensure that the data value 3368 corresponding to the predicted reflectivity will fall within the specified range.

[0105] During the machine learning process, the analytical model compares the predicted reflectivity in data value 3368 with the actual reflectivity, or strictly calculated reflectivity, of the intermediate reflective multilayer structure M' indicated by data value 3370. As previously described, for each set of historical environmental condition data, the training set data 3306 includes historical reflector data indicating the characteristics of the intermediate reflective multilayer structure M' resulting from the historical generation process (e.g., operation 410). Therefore, data field 3370 includes the actual reflectivity of the intermediate reflective multilayer structure M' resulting from the generation process, as reflected in the reflector condition matrix 3352. The analytical model 3302 compares the predicted reflectivity from data value 3368 with the actual reflectivity from data value 3370. The analytical model 3302 generates an error value 3372, which indicates the error, or difference, between the predicted reflectivity from data value 3368 and the actual reflectivity from data value 3370. The error value 3372 is used to train the analytical model 3302.

[0106] The training of the analytical model 3302 can be more fully understood by discussing the internal mathematical function F(x). Although all nodes 3358 are labeled with an internal mathematical function F(x), the mathematical function F(x) for each node is unique. In one example, each internal mathematical function has the following form:

[0107] F(x)=x1*w1+x2*w2+…xn*w1+b.

[0108] In the above equation, each value x1-xn corresponds to a data value received from a node 3358 in a previous neural layer, or in the case of the first neural layer 3356a, each value x1-xn corresponds to a corresponding data value from the data field 3354 of the reflector condition matrix 3352. Therefore, n for a given node is equal to the number of nodes in the previous neural layer. The value w1-wn is a scalar weight value associated with the corresponding node from the previous layer. The analytical model 3302 selects the value of the weight value w1-wn. The constant b is a scalar bias value and may also be multiplied by the weight value. The value generated by the node 3358 is based on the weight value w1-wn. Therefore, each node 3358 has n weight values ​​w1-wn. Although not shown above, each function F(x) may also include an activation function. The sum listed in the above equation is multiplied by the activation function. Examples of activation functions may include a rectified linear unit (ReLU) function, a sigmoid function, a hyperbolic tension function, or other types of activation functions.

[0109] After calculating error value 3372, analytical model 3302 adjusts weights w1-wn for each node 3358 of each neural layer 3356a-3356e. After analytical model 3302 adjusts weights w1-wn, analytical model 3302 again provides reflector condition matrix 3352 to input neural layer 3356a. Because the weights are different for each node 3358 of analytical model 3302, predicted reflectivity 3368 will be different from the previous iteration. Analytical model 3302 again generates error value 3372 by comparing actual reflectivity 3370 with predicted reflectivity 3368.

[0110] Analytical model 3302 again adjusts the weight values ​​w1-wn associated with each node 3358. Analytical model 3302 again processes reflector condition matrix 3352 and generates predicted reflectivity 3368 and associated error values ​​3372. The training process includes iteratively adjusting the weight values ​​w1-wn until error values ​​3372 are minimized.

[0111] Figure 9A single reflector condition matrix 3352 is shown being passed to the analytical model 3302. In practice, the training process involves passing a large number of reflector condition matrices 3352 through the analytical model 3302, generating a predicted reflectivity 3368 for each reflector condition matrix 3352, and generating an associated error value 3372 for each predicted reflectivity. The training process may also include generating an aggregated error value indicating the average error of all predicted reflectivities for a batch of reflector condition matrices 3352. After processing each batch of reflector condition matrices 3352, the analytical model 3302 adjusts the weighting values ​​w1-wn. The training process continues until the average error for all reflector condition matrices 3352 is less than a selected threshold tolerance. When the average error is less than the selected threshold tolerance, training of the analytical model 3302 is complete, and the analytical model is trained to accurately predict the reflectivity of the intermediate reflective multilayer structure M' based on environmental conditions. The analytical model 3302 can then be used to predict reflectivity and select reflector conditions that will result in the desired reflectivity. During use of the trained model 3302, an environmental condition vector or matrix representing the current environmental conditions for the current intermediate reflective multilayer structure M' and having a format similar to the reflector condition matrix 3352 is provided to the trained analytical model 3302. The trained analytical model 3302 can then predict the reflectivity of the intermediate reflective multilayer structure M' that will result from these environmental conditions.

[0112] Already about Figure 9 A specific example of a neural network-based analysis model 3302 is described. However, other types of neural network-based analysis models or types of analysis models other than neural networks may be utilized without departing from the scope of this disclosure. Furthermore, a neural network may have a different number of neural layers with a different number of nodes without departing from the scope of this disclosure.

[0113] Embodiments may provide advantages. Reflective multilayers 20A-20C have enhanced reflectivity due to various techniques, such as non-periodicity in layer ordering, free-form variable layer thicknesses, inverse random design, and / or additional layer materials. By combining these techniques, a lithography exposure system including ten reflective multilayers 20A-20C can achieve an increase in reflectivity of at least 15% for configurations using two materials and at least 50% for configurations using four or more materials. This increase in reflectivity enables higher wafer throughput per hour in EUV lithography, thereby enabling more cost-effective high-volume semiconductor electronic device manufacturing.

[0114] According to at least one embodiment, a photolithography exposure system includes: a light source; a substrate stage; and a mask stage located between the light source and the substrate stage along an optical path from the light source to the substrate stage. The photolithography exposure system also includes a reflector located along the optical path. The reflector includes: a first layer having a first material and a first thickness; a second layer having the first material and a second thickness different from the first thickness; and a third layer located between the first and second layers and having a second material different from the first material.

[0115] According to at least one embodiment, a photolithography exposure system includes: an optical path between a light source and a substrate stage; and a first reflector having a first angle of incidence along the optical path. The first reflector includes at least three first material layers. The first material layers have a first number of seed layer materials, a second number of layer thicknesses, and a first order of first material layers. The photolithography exposure system also includes a second reflector having a second angle of incidence along the optical path, the second angle of incidence being different from the first angle of incidence. The second reflector includes at least three second material layers. The second material layers have a third number of seed layer materials, a fourth number of layer thicknesses, and a second order of second material layers. At least one of the following conditions is satisfied: the third number is different from the first number; the fourth number is different from the second number; or the second order is different from the first order.

[0116] According to at least one embodiment, a method includes: forming a plurality of intermediate reflective multilayer structure configurations by executing a reverse design algorithm; and forming a reflective multilayer structure based on a reflective multilayer structure configuration selected from the plurality of intermediate reflective multilayer structure configurations. The reflective multilayer structure is formed by: forming a first material layer having a first material and a first thickness; forming a second material layer on the first material layer, the second material layer having a second material and a second thickness, respectively different from the first material and the first thickness; and forming a third material layer on the second material layer, the third material layer having the first material and a third thickness, different from the first thickness.

[0117] The features of several embodiments are summarized above so that those skilled in the art can better understand the various aspects of the present disclosure. It should be appreciated by those skilled in the art that they can easily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or advantages as the embodiments introduced herein. It should also be appreciated by those skilled in the art that these equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they can make various changes, substitutions, and modifications herein without departing from the spirit and scope of the present disclosure.

[0118] Example 1 is a photolithography exposure system, comprising: a light source; a substrate stage; a mask stage between the light source and the substrate stage along an optical path from the light source to the substrate stage; and a reflector, along the optical path, the reflector comprising: a first layer having a first material and a first thickness; a second layer having the first material and a second thickness different from the first thickness; and a third layer located between the first layer and the second layer and having a second material different from the first material.

[0119] Example 2 is the photolithography exposure system of Example 1, wherein the reflector further comprises: a fourth layer having a third material different from the first material and the second material.

[0120] Example 3 is the photolithography exposure system of Example 2, wherein the reflector further comprises: a fifth layer having a fourth material different from the first material, the second material, and the third material.

[0121] Example 4 is the photolithography exposure system of Example 3, wherein the first material, the second material, the third material, and the fourth material are each different materials having an extinction coefficient less than about 0.02.

[0122] Example 5 is the photolithography exposure system of Example 3, wherein the first material, the second material, the third material, and the fourth material are each a different one of silicon, molybdenum, strontium, beryllium, or ruthenium.

[0123] Example 6 is the photolithography exposure system of Example 2, wherein: the reflector further includes a sixth layer having the first material; and the fourth layer is located between the second layer and the sixth layer.

[0124] Example 7 is the lithography exposure system of Example 1, further comprising: an illuminator comprising at least two first reflectors and located between the light source and the mask stage along the optical path; and a projection optical box comprising at least two second reflectors and located between the mask stage and the substrate stage along the optical path; wherein the reflector is one of the at least two first reflectors or one of the at least two second reflectors; wherein the light source is an extreme ultraviolet (EUV) light source.

[0125] Example 8 is a lithography exposure system, comprising: an optical path between a light source and a substrate table; a first reflector having a first incident angle along the optical path, the first reflector comprising: at least three first material layers having a first number of seed layer materials, a second number of layer thicknesses, and a first order of the first material layers; and a second reflector having a second incident angle along the optical path, the second incident angle being different from the first incident angle, the second reflector comprising: at least three second material layers having a third number of seed layer materials, a fourth number of layer thicknesses, and a second order of the second material layers, and satisfying at least one of the following conditions: the third number is different from the first number; the fourth number is different from the second number; or the second order is different from the first order.

[0126] Example 9 is the photolithography exposure system of Example 8, wherein the first number is at least four and the third number is less than four.

[0127] Example 10 is the photolithography exposure system described in Example 8, wherein the first reflector includes: a first region extending from a first depth to a second depth of the first reflector; and a second region extending from a third depth to a fourth depth of the first reflector, the second region not overlapping with the first region along the depth of the first reflector, and the second region having a configuration of the first material layer different from that of the first region.

[0128] Example 11 is the photolithography exposure system of Example 10, wherein a thickness variation of the first material layer in the first region is greater than a thickness variation of the first material layer in the second region.

[0129] Example 12 is the photolithography exposure system of Example 10, wherein the first number in the first region differs from the first number in the second region by at least 1.

[0130] Example 13 is the photolithography exposure system described in Example 10, wherein the first material layer in the first region includes: a third material layer including a first material; and a fourth material layer including a second material different from the first material; wherein the third material layer has a thickness variation different from that of the fourth material layer.

[0131] Example 14 is a method for manufacturing a reflector structure, comprising: forming a plurality of intermediate reflective multilayer structure configurations by executing a reverse design algorithm; and forming a reflective multilayer based on a reflective multilayer structure configuration selected from the plurality of intermediate reflective multilayer structure configurations by: forming a first material layer having a first material and a first thickness; forming a second material layer on the first material layer, the second material layer having a second material and a second thickness respectively different from the first material and the first thickness; and forming a third material layer on the second material layer, the third material layer having the first material and a third thickness different from the first thickness.

[0132] Example 15 is the method of Example 14, wherein forming the plurality of intermediate reflection multilayer structure configurations includes forming a second intermediate reflection multilayer structure configuration by changing at least one parameter of at least one layer of the first intermediate reflection multilayer structure configuration.

[0133] Example 16 is the method of Example 15, wherein changing the at least one parameter comprises changing a position of the at least one layer.

[0134] Example 17 is the method of Example 15, wherein changing the at least one parameter comprises changing a material of the at least one layer.

[0135] Example 18 is the method of Example 15, wherein changing the at least one parameter includes changing a thickness of the at least one layer.

[0136] Example 19 is the method described in Example 14, wherein forming the plurality of intermediate reflection multilayer structure configurations includes recombining a first layer and a second layer of a first intermediate reflection multilayer structure configuration in the plurality of intermediate reflection multilayer structure configurations.

[0137] Example 20 is the method described in Example 19, wherein: the first layer has a first reflector material; the second layer has a second reflector material and is adjacent to the first layer; and the reorganization includes: changing the second layer from the second reflector material to the first reflector material.

Claims

1. A photolithography exposure system comprising: light source; substrate stage; a mask stage between the light source and the substrate stage along an optical path from the light source to the substrate stage; as well as A reflector, along the optical path, comprising: a plurality of first material layers, wherein the first material layers include molybdenum; a plurality of second material layers, wherein the second material layers include silicon; a plurality of third material layers, wherein the third material layers include ruthenium; a plurality of fourth material layers, wherein the fourth material layers include strontium; The positions, materials and thicknesses of the first material layer, the second material layer, the third material layer and the fourth material layer are non-periodic and non-alternating.

2. The photolithography exposure system according to claim 1, wherein: The first material layer, the second material layer, the third material layer, and the fourth material layer each have an extinction coefficient less than 0.

02.

3. The photolithography exposure system according to claim 1 , further comprising: an illuminator including at least two first reflectors and located between the light source and the mask stage along the optical path; as well as a projection optics box comprising at least two second reflectors and positioned between the mask stage and the substrate stage along the optical path; wherein the reflector is one of the at least two first reflectors or one of the at least two second reflectors; Wherein, the light source is an extreme ultraviolet (EUV) light source.

4. A photolithography exposure system comprising: an optical path between the light source and the substrate table; A first reflector has a first incident angle along the optical path, the first reflector comprising: a plurality of first material layers, wherein the first material layers include molybdenum; a plurality of second material layers, wherein the second material layers include silicon; a plurality of third material layers, wherein the third material layers include ruthenium; a plurality of fourth material layers, wherein the fourth material layers include strontium; wherein the positions, materials, and thicknesses of the first material layer, the second material layer, the third material layer, and the fourth material layer are non-periodic and non-alternating, and wherein each of the plurality of first material layers, the plurality of second material layers, the plurality of third material layers, and the plurality of fourth material layers has an extinction coefficient less than 0.02; and A second reflector has a second incident angle along the optical path, the second incident angle being different from the first incident angle, the second reflector comprising: a plurality of first material layers, wherein the first material layers include molybdenum; a plurality of second material layers, wherein the second material layers include silicon; a plurality of third material layers, wherein the third material layers include ruthenium; The positions, materials and thicknesses of the first material layer, the second material layer and the third material layer are non-periodic and non-alternating.

5. The photolithography exposure system according to claim 4, wherein: The first reflector comprises: a first region extending from a first depth to a second depth of the first reflector; and A second region extends from the third depth to a fourth depth of the first reflector, the second region not overlapping with the first region along the depth of the first reflector, and the second region having a different layer configuration than the first region.

6. The photolithography exposure system according to claim 5, wherein: The thickness variation of the layer in the first region is greater than the thickness variation of the layer in the second region.

7. The photolithography exposure system according to claim 5, wherein: The number of different material layers in the first region differs from the number of different material layers in the second region by at least one.

8. A method for manufacturing a reflector structure, comprising: forming a plurality of intermediate reflective multilayer structure configurations by executing an inverse design algorithm; as well as forming a reflective multilayer based on a reflective multilayer structural configuration selected from the plurality of intermediate reflective multilayer structural configurations, wherein the reflective multilayer comprises: a plurality of first material layers, wherein the first material layers include molybdenum; a plurality of second material layers, wherein the second material layers include silicon; a plurality of third material layers, wherein the third material layers include ruthenium; a plurality of fourth material layers, wherein the fourth material layers include strontium; The positions, materials and thicknesses of the first material layer, the second material layer, the third material layer and the fourth material layer are non-periodic and non-alternating.

9. The method according to claim 8, wherein Forming the plurality of intermediate reflective multilayer structures comprises: A second intermediate reflective multilayer structural configuration is formed by changing at least one parameter of at least one layer of the first intermediate reflective multilayer structural configuration.

10. The method according to claim 9, wherein: Changing the at least one parameter includes changing a position of the at least one layer.

11. The method according to claim 9, wherein: Changing the at least one parameter includes changing the material of the at least one layer.

12. The method according to claim 9, wherein Changing the at least one parameter includes changing a thickness of the at least one layer.

13. The method according to claim 8, wherein Forming the plurality of intermediate reflective multilayer structures comprises: The first layer and the second layer of a first intermediate reflective multilayer structure configuration of the plurality of intermediate reflective multilayer structure configurations are recombined.

14. The method according to claim 13, wherein: The first layer comprises a first reflector material; The second layer has a second reflector material and is immediately adjacent to the first layer; and The recombining includes changing the second layer from the second reflector material to the first reflector material.

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