Inspection device, wedge-shaped system for reducing aberration and manufacturing method of wedge-shaped system

Abstract

A method of reducing optical aberrations in an optical system includes determining aberrations caused by the optical system. The determining includes transmitting a first radiation beam having a first wavelength through a wedge-shaped system of an optical system. The wedge system includes a radiation curable adhesive disposed between the first wedge and the second wedge. The determining further includes analyzing the first beam using a detector disposed downstream of the wedge system to determine an aberration. The method further includes curing the radiation curable adhesive based on the analysis of the first beam. The curing includes using a spatial light modulator to adjust an intensity distribution of a second radiation beam having a second wavelength different from the first wavelength based on an analysis of the first beam. The curing further includes directing the second beam to the radiation curing adhesive to induce a position dependent optical property at the radiation curing adhesive.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Application 63 / 535,149, filed on August 29, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure relates to measurement systems, such as optical sensors used in lithography systems and processes for inspection measurements. Background Technology

[0003] A photolithography apparatus is a machine that applies a desired pattern onto a substrate (typically onto a target portion of the substrate). For example, a photolithography apparatus can be used to fabricate integrated circuits (ICs). In this instance, a patterning apparatus (which may be a mask or stencil) can be used to generate circuit patterns to be formed on various layers of the IC. This pattern can be transferred onto a target portion (e.g., including a portion of a die, one or more dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (photoresist, or simply "resist") provided on the substrate. Typically, a single substrate will contain a network of adjacent target portions patterned sequentially. Known photolithography apparatuses include so-called steppers (where each target portion is irradiated by exposing the entire pattern onto the target portion at once) and so-called scanners (where each target portion is irradiated by scanning the pattern with a radiation beam in a given direction ("scanning" direction) while simultaneously scanning target portions parallel or antiparallel to that scanning direction). A pattern can also be transferred from a patterning apparatus to a substrate by imprinting the pattern onto the substrate.

[0004] During photolithography operations, different processing steps may require different layers to be formed sequentially on a substrate. Therefore, it may be necessary to position the substrate with high accuracy relative to the previously formed pattern. Typically, alignment marks are placed on the substrate to be aligned and positioned with reference to a second object. The photolithography apparatus can use alignment devices to detect the position of the alignment marks and use the alignment marks to align the substrate to ensure accurate exposure from the mask. Misalignment between alignment marks at two different layers is measured as overlay error.

[0005] To monitor the photolithography process, parameters of the patterned substrate are measured. These parameters may include, for example, overlay errors between successive layers formed in or on the patterned substrate and the critical linewidth of the developing photoresist. This measurement can be performed on product substrates and / or specialized measurement targets. Various techniques exist for measuring the microstructures formed in the photolithography process, including the use of scanning electron microscopy and various specialized tools. One rapid and non-invasive form of specialized inspection tool is a scatterometer, where a radiation beam is directed onto a target on the substrate surface, and the properties of the scattered or reflected beam are measured. By comparing the properties of the beam before and after reflection or scattering by the substrate, the properties of the substrate can be determined. For example, this can be done by comparing the reflected beam with data stored in a library of known measurements associated with known substrate properties. A spectroscopic scatterometer directs a broadband radiation beam onto the substrate and measures the spectrum (intensity as a function of wavelength) of the radiation scattered over a specific narrow angular range. In contrast, an angle-resolved scatterometer uses a monochromatic radiation beam and measures the intensity of the scattered radiation as a function of angle.

[0006] This type of optical scattering instrument can be used to measure parameters such as the critical size (CD) of the developing photoresist or the overlay error (OV) between two layers formed in or on a patterned substrate. The properties of the substrate can be determined by comparing the properties of the beam before and after it is irradiated by the substrate.

[0007] Optical aberrations have been one of the major challenges for metrology tools used in the fabrication of nanoscale devices. Due to size requirements, many options for handling aberrations are often accompanied by high costs and incompatibility. Summary of the Invention

[0008] Therefore, it is desirable to reduce aberrations in high-precision inspection tools. The features disclosed herein can be used to cost-effectively mitigate aberrations using optical components suited to small volume constraints.

[0009] In some aspects, an inspection apparatus includes a radiation source, a wedge system, optical devices, and a detector. The radiation source is configured to generate radiation. The wedge system includes a first wedge, a second wedge, and a radiation-curing adhesive disposed between the first and second wedges. The first wedge is configured to receive radiation. The second wedge is configured to output radiation. The radiation-curing adhesive includes region-dependent optical properties configured to adjust the radiation wavefront. The optical devices are configured to guide radiation toward a target to generate scattered radiation from the target. The detector is configured to receive the scattered radiation from the target and generate a measurement signal based on the scattered radiation and the adjustment of the wavefront.

[0010] In some aspects, the wedge system includes a first wedge, a second wedge, and a radiation-curing adhesive disposed between the first and second wedges. The first wedge is configured to receive radiation. The second wedge is configured to output radiation. The radiation-curing adhesive includes region-dependent optical properties configured to adjust the radiation wavefront.

[0011] In some aspects, a method for reducing optical aberrations in an optical system may include one or more of the following operations. The method may include determining aberrations caused by the optical system. Determining the aberrations may include transmitting a first radiation beam having a first wavelength through a wedge system of the optical system. The wedge system may include a first wedge and a second wedge, and a radiation-curing adhesive disposed between the first and second wedges. Determining the aberrations may further include analyzing the first beam using a detector disposed downstream of the wedge system to determine the aberrations. The method may further include curing the radiation-curing adhesive based on the analysis of the first beam. Curing the radiation-curing adhesive may include adjusting the intensity distribution of a second radiation beam having a second wavelength different from the first wavelength using a spatial light modulator based on the analysis of the first beam. Curing the radiation-curing adhesive may further include directing the second beam to the radiation-curing adhesive to induce position-dependent optical properties at the radiation-curing adhesive, thereby reducing the aberrations. The radiation-curing adhesive responds to the second wavelength.

[0012] Other features of various aspects of this disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the specific aspects described herein. Such aspects are presented herein for illustrative purposes only. Additional aspects will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0013] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, are further used to explain the principles of the disclosure and to enable those skilled in the art to make and use the aspects described herein.

[0014] Figure 1A A reflective lithography apparatus according to some aspects of this disclosure is shown.

[0015] Figure 1B A transmission lithography apparatus according to some aspects of this disclosure is shown.

[0016] Figure 2 Further details of a reflective lithography apparatus according to some aspects of this disclosure are shown.

[0017] Figure 3 The photolithography unit according to some aspects of this disclosure is shown.

[0018] Figure 4A , 4B Figures 5 and 6 show inspection devices according to some aspects of this disclosure.

[0019] Figure 6 A flowchart of a method for reducing optical aberrations in an optical system according to some aspects of this disclosure is shown.

[0020] The features of this disclosure will become more apparent when viewed in conjunction with the accompanying drawings, through the detailed description of the embodiments described below, wherein similar reference numerals consistently identify corresponding elements. In the drawings, similar reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, typically, the leftmost numeral(s) of the reference numeral(s) identifies the drawing in which the reference numeral(s) first appear. Unless otherwise indicated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. Detailed Implementation

[0021] The various aspects described herein, as well as the references to "an aspect," "one aspect," "exemplary aspect," "example aspect," etc., in the specification, may include a particular feature, structure, or characteristic, but each aspect may not necessarily include that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same aspect. Further, when a particular feature, structure, or characteristic is described in conjunction with an aspect, it is to be understood that, whether or not explicitly described, it is within the knowledge of those skilled in the art to achieve such a feature, structure, or characteristic in conjunction with other aspects.

[0022] Spatial terms (such as “below,” “under,” “lower,” “above,” “above,” “upper,” etc.) may be used herein for convenience of description to describe the relationship of an element or feature to another element or feature(s) illustrated in the accompanying drawings. In addition to the orientations depicted in the accompanying drawings, spatial relative terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein may be interpreted accordingly.

[0023] The terms “approximately”, “approximately”, etc., may be used herein to indicate a given number of values ​​that may vary based on a particular technique. Based on a particular technique, the terms “approximately”, “approximately”, etc., may indicate a given number of values ​​that vary within, for example, 10% to 30% of that value (e.g., ±10%, ±20%, or ±30% of the value).

[0024] Enumerated adjectives (such as "first," "second," "third," etc.) can be used to distinguish similar elements, but do not establish order, hierarchy, number, or permanent numerical assignment (unless otherwise mentioned). For example, the terms "first target" and "second target" can be used in a manner similar to "i-th target" and "j-th target" to help distinguish between two targets without specifying a particular order, hierarchy, number, or immutable numerical correspondence.

[0025] Various aspects of this disclosure can be implemented in hardware, firmware, software, or any combination thereof. Various aspects of this disclosure can also be implemented as instructions stored on a machine-readable medium that can be read and executed by one or more processors. A machine-readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium can include read-only memory (ROM); random access memory (RAM); disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.) and others. Furthermore, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that this description is merely for convenience, and such actions are caused by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc. The term "machine-readable medium" may be used interchangeably with similar terms such as "computer program product," "computer-readable medium," "non-transitory computer-readable medium," etc. The term "non-transitory" may be used herein to characterize one or more forms of computer-readable medium other than transient propagation signals.

[0026] However, it is beneficial to present example environments in which various aspects of this disclosure can be implemented before describing these aspects in more detail.

[0027] Example lithography system

[0028] Figure 1A and 1BPhotolithography apparatus 100 and photolithography apparatus 100', which can implement various aspects of the present disclosure, are shown respectively. Photolithography apparatus 100 and photolithography apparatus 100' each include: an irradiation system (irradiator) IL configured to modulate a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., mask stage) MT configured to support a patterning apparatus (e.g., a mask, stencil, or dynamic patterning apparatus) MA and connected to a first positioner PM configured to accurately position the patterning apparatus MA; and a substrate stage (e.g., wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Photolithography apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted by the radiation beam B by the patterning apparatus MA onto a target portion (e.g., including one or more dies) C of the substrate W. In photolithography apparatus 100, the patterning apparatus MA and the projection system PS are reflective. In the photolithography apparatus 100', the pattern forming device MA and the projection system PS are transmissive.

[0029] The irradiation system IL may include various types of optical components, such as refractive, reflective, reflective-refractive, magnetic, electromagnetic, electrostatic or other types of optical components or any combination thereof, for guiding, shaping or controlling the radiation beam B.

[0030] The support structure MT holds the patterning apparatus MA in a manner dependent on the orientation of the patterning apparatus MA relative to a reference frame, the design of at least one of the lithography apparatuses 100 and 100', and other conditions such as whether the patterning apparatus MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning apparatus MA. The support structure MT can be a frame or a stage, and can be fixed or movable. For example, by using sensors, the support structure MT can ensure that the patterning apparatus MA is positioned relative to the projection system PS at a desired location.

[0031] The term "patterning apparatus" MA should be interpreted broadly to refer to any apparatus that can be used to impart a pattern to a radiation beam B in its cross-section, such as creating a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B can correspond to a specific functional layer in the apparatus created in the target portion C to form an integrated circuit.

[0032] The pattern forming device MA can be transmissive (e.g., in...) Figure 1B In the photolithography apparatus 100') or reflective (such as in Figure 1A(In the photolithography apparatus 100). Examples of pattern forming apparatus MA include photomasks, masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in photolithography and include mask types such as binary mask types, alternating phase-shift mask types, or attenuation phase-shift mask types, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect the incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B reflected by the array of small mirrors.

[0033] The term "projection system" PS can encompass any type of projection system, including refractive, reflective, reflective-refractive, magnetic, electromagnetic, and electrostatic optical systems or any combination thereof, as suitable for the exposure radiation used or for other factors such as immersion on a substrate W or the use of a vacuum. A vacuum environment can be used for EUV or electron beam radiation because other gases may absorb excessive radiation or electrons. Therefore, a vacuum environment can be provided throughout the beam path by means of vacuum walls and vacuum pumps.

[0034] The lithography apparatus 100 and / or lithography apparatus 100' can be of the type having two (dual-platform) or more substrate stages WT (and / or two or more mask stages). In such a "multi-platform" machine, the additional substrate stages WT can be used in parallel, or preparation steps can be performed on one or more stages while one or more other substrate stages WT are being used for exposure. In some cases, the additional stage may not be a substrate stage WT.

[0035] Photolithography apparatuses can also be of the type in which at least a portion of the substrate can be covered with a liquid (e.g., water) having a relatively high refractive index to fill the space between the projection system and the substrate. Immersion liquid can also be applied to other spaces within the photolithography apparatus, such as the space between the mask and the projection system. Immersion techniques are well known in the art to increase the numerical aperture of the projection system. The term “immersion” as used herein does not mean that the structure (such as the substrate) must be submerged in the liquid. For example, during exposure, the liquid can be positioned between the projection system and the substrate.

[0036] refer to Figure 1A and 1B The irradiator IL receives a radiation beam from the radiation source SO. The source SO and the lithography apparatus 100, 100' can be separate physical entities, for example, when the source SO is an excimer laser. In this case, the source SO is not considered part of forming the lithography apparatus 100 or 100', and is delivered by means of a beam delivery system BD (in [the context of the lithography apparatus 100 or 100') including, for example, suitable directional mirrors and / or beam expanders). Figure 1BIn the lithography apparatus 100, 100', the radiation beam B is delivered from the source SO to the irradiator IL. In other cases, the source SO may be an integral part of the lithography apparatus 100, 100', for example, when the source SO is a mercury lamp. The radiation system may include the source SO, the irradiator IL, and / or the beam delivery system BD.

[0037] The irradiator IL may include an adjuster AD (in) Figure 1B The irradiator (IL) is used to adjust the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial ranges of the intensity distribution in the pupil plane of the irradiator (generally referred to as "σ outer" and "σ inner," respectively) can be adjusted. Additionally, the irradiator IL may include various other components (in... Figure 1B (In the middle), such as integrator IN and convergent CO. Irradiator IL can be used to adjust the radiation beam B so as to have the desired uniformity and intensity distribution in its cross-section.

[0038] refer to Figure 1A A radiation beam B is incident on a patterning apparatus (e.g., a mask) MA and patterned by the patterning apparatus MA, which is held on a support structure (e.g., a mask stage) MT. In the lithography apparatus 100, the radiation beam B is reflected from the patterning apparatus (e.g., the mask) MA. After reflection from the patterning apparatus (e.g., the mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate stage WT can be accurately moved (e.g., to position different target portions C in the path of the radiation beam B) by means of a second positioner PW and a position sensor IF2 (e.g., an interferometer, a linear encoder, or a capacitive sensor). Similarly, a first positioner PM and another position sensor IF1 can be used to accurately position the patterning apparatus (e.g., the mask) MA relative to the path of the radiation beam B. The patterning apparatus (e.g., the mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0039] refer to Figure 1B A radiation beam B is incident on a patterning apparatus (e.g., a mask MA) and patterned by the patterning apparatus, which is held on a support structure (e.g., a mask stage MT). After traversing the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil conjugate PPU that is the same as the illumination system pupil IPU. Part of the radiation is emitted from the intensity distribution at the illumination system pupil IPU and traverses the mask pattern without being affected by diffraction at the mask pattern, creating an image of the intensity distribution at the illumination system pupil IPU.

[0040] The projection system PS projects an image of a mask pattern MP onto a photoresist layer coated on a substrate W, where the image is formed by diffracted beams generated from radiation from the mask pattern MP via an intensity distribution. For example, the mask pattern MP may comprise an array of lines and spaces. Radiation diffraction located at the array, distinct from zero-order diffraction, generates deflected diffracted beams whose direction changes perpendicular to the lines. Non-diffracted beams (i.e., the so-called zero-order diffracted beams) traverse the pattern without any change in propagation direction. The zero-order diffracted beam traverses the upper lens or upper lens group of the projection system PS, reaching the pupil conjugate PPU upstream of the projection system PS. The intensity distribution portion in the plane of the pupil conjugate PPU and associated with the zero-order diffracted beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. For example, an aperture device PD is disposed or substantially disposed in the plane comprising the pupil conjugate PPU of the projection system PS.

[0041] The projection system PS is arranged to capture (e.g., using a lens or lens group L) a zero-order diffraction beam, a first-order diffraction beam, and / or higher-order diffraction beams (not shown). In some aspects, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to utilize the resolution enhancement effect of dipole illumination. For example, a first-order diffraction beam interferes with a corresponding zero-order diffraction beam at the level of the wafer W to create an image of the line pattern MP with the highest possible resolution and process window (i.e., a combination of available depth of focus and tolerable exposure dose deviation). In some aspects, astigmatic aberration can be reduced by providing a radiating pole (not shown) in the opposite confinement of the illumination system pupil IPU. Further, in some aspects, astigmatic aberration can be reduced by blocking the zero-order beam in the projection system pupil conjugate PPU associated with the radiating pole in the opposite confinement. This is described in more detail in US 7,511,799 B2, published March 31, 2009, which is incorporated herein by reference in its entirety.

[0042] With the aid of a second positioner PW and a position sensor IFD (e.g., an interferometric device, a linear encoder, or a capacitive sensor), the substrate stage WT can be accurately moved (e.g., to position different target portions C within the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (not in...) Figure 1B (As shown in the figure) can be used to accurately position the mask MA relative to the path of the radiation beam B (e.g., after mechanical retrieval from the mask library, or during scanning).

[0043] Typically, movement of the mask stage MT can be achieved using a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of the first positioner PM. Similarly, movement of the substrate stage WT can be achieved using a long-stroke module and a short-stroke module forming part of the second positioner PW. In the case of a stepper (opposite to the scanner), the mask stage MT can be connected to a short-stroke actuator, or it can be fixed. The mask MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they can be located in the space between the target portions (called scribing alignment marks). Similarly, when more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

[0044] The mask stage MT and patterning equipment MA can be located within a vacuum chamber V, where an in-vacuum robot IVR can be used to move patterning equipment such as masks into and out of the vacuum chamber. Alternatively, when the mask stage MT and patterning equipment MA are outside the vacuum chamber, an out-of-vacuum robot can be used for various transport operations, similar to the in-vacuum robot IVR. Both the in-vacuum and out-of-vacuum robots can be calibrated to smoothly transfer any payload (e.g., a mask) to a stationary motion base at the transfer station.

[0045] Photolithography devices 100 and 100' can be used in at least one of the following modes:

[0046] 1. In step mode, while the entire pattern imparted by the radiation beam B is projected onto the target portion C in one go (i.e., a single static exposure), the support structure (e.g., mask stage) MT and the substrate stage WT remain substantially stationary. The substrate stage WT is then displaced in the X and / or Y directions, allowing different target portions C to be exposed.

[0047] 2. In scanning mode, as the pattern imparted to the radiation beam B is projected onto the target portion C (i.e., single dynamic exposure), the support structure (e.g., mask stage) MT and the substrate stage WT are scanned synchronously. The velocity and direction of the substrate stage WT relative to the support structure (e.g., mask stage) MT can be determined by the magnification (reduction) and image inversion characteristics of the projection system PS.

[0048] 3. In another mode, the support structure (e.g., mask stage) MT remains substantially stationary, thus holding the programmable patterning apparatus in place, and the substrate stage WT is moved or scanned as the pattern imparted by the radiation beam B is projected onto the target portion C. A pulsed radiation source SO can be employed, and the programmable patterning apparatus is updated as needed after each movement of the substrate stage WT or between consecutive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography, which utilizes programmable patterning apparatus such as a programmable mirror array.

[0049] Combinations and / or variations of the described usage patterns, or entirely different usage patterns, may also be adopted.

[0050] In some aspects, the lithography apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Typically, the EUV source is configured in a radiation system, and a corresponding irradiation system is configured to modulate the EUV radiation beam from the EUV source.

[0051] In some aspects, the lithography apparatus 100' includes an extreme ultraviolet (DUV) source configured to generate a DUV radiation beam for DUV lithography. Typically, the DUV source is configured in a radiation system, and a corresponding irradiation system is configured to modulate the DUV radiation beam from the DUV source.

[0052] Figure 2 The lithography apparatus 100 is shown in more detail, including a source-collector device SO, an irradiation system IL, and a projection system PS. The source-collector device SO is constructed and arranged such that a vacuum environment can be maintained within a closed structure 220 of the source-collector device SO. EUV radiation-emitting plasma 210 can be formed by a plasma source generated by a discharge. EUV radiation can be generated by a gas or vapor, such as xenon, lithium vapor, or tin vapor, wherein the EUV radiation-emitting plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The EUV radiation-emitting plasma 210 is created, for example, by a discharge that results in at least partially ionized plasma. For efficient radiation generation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor can be used. In some aspects, a plasma that excites tin (Sn) (e.g., via laser excitation) is provided to generate EUV radiation.

[0053] Radiation emitted by the EUV radiation-emitting plasma 210 enters the collector chamber 212 from the source chamber 211 via an optional gas barrier or contaminant trap 230 (also referred to in some cases as a contaminant barrier or fin trap) located in or behind an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further indicated herein includes at least a channel structure.

[0054] Collector chamber 212 may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation traversing the collector CO may be reflected from a grating spectral filter 240 to be focused in a virtual source point INTF. The virtual source point INTF is generally referred to as the intermediate focus, and the source collector arrangement is such that the intermediate focus INTF is located at or near an opening 219 in the enclosed structure 220. The virtual source point INTF is an image of the EUV radiation-emitting plasma 210. The grating spectral filter 240 is specifically used to suppress infrared (IR) radiation.

[0055] Subsequently, a radiation traversal illumination system IL, which may include a faceted field mirror device 222 and a faceted pupil mirror device 224, is arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA and a desired uniformity of radiation intensity at the patterning device MA. As the radiation beam 221 is reflected at the patterning device MA, held by a support structure MT, a patterned beam 226 is formed, and the patterned beam 226 is imaged by a projection system PS via reflective elements 228 and 229 onto a substrate W, which is held by a wafer platform or substrate stage WT.

[0056] More components than shown can typically be present in the illumination optical unit IL and the projection system PS. Depending on the type of photolithography apparatus, the grating spectral filter 240 may optionally be present. Furthermore, more than shown components may be present. Figure 2 More mirrors are shown, such as those with Figure 2 In contrast, the projection system PS may contain 1 to 6 additional reflective elements.

[0057] like Figure 2 The collector optics CO illustrated is depicted as a nested collector with grazing incidence reflectors 253, 254, and 255, as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are arranged axially symmetrically about the optical axis O, and preferably, this type of collector optics CO is used in combination with a plasma source generated by a discharge, commonly referred to as a DPP source.

[0058] Example lithography unit

[0059] Figure 3 A lithography unit 300, sometimes referred to as a lithography cell or cluster, is shown according to some aspects. A lithography apparatus 100 or 100' may form part of the lithography unit 300. The lithography unit 300 may also include one or more devices for performing pre-exposure and post-exposure processes on the substrate. Conventionally, these include a spin coater SC for depositing a resist layer, a developer DE for developing the post-exposure resist, a cooling plate CH, and a baking plate BK. A substrate handler or robot RO picks up substrates from input / output ports I / O1, I / O2, moves them between different process devices, and delivers them to the loader LB of the lithography apparatus 100 or 100'. These devices, generally collectively referred to as tracks, are controlled by a track control unit TCU, which in turn is controlled by a monitoring system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Therefore, different devices can be operated to maximize throughput and processing efficiency.

[0060] Example inspection device

[0061] To control the photolithography process and accurately place device features on the substrate, alignment marks are typically provided on the substrate, and the photolithography apparatus includes one or more inspection devices for accurately positioning the marks on the substrate. These alignment devices are essentially position measuring devices. Different types of marks and different types of alignment devices and / or systems are known from different times and from different manufacturers. One system widely used in current photolithography apparatuses is based on a self-reference interferometer described in U.S. Patent No. 6,961,116 (denBoef et al.). Typically, the marks are measured individually to obtain the X and Y positions. However, combined X and Y measurements can be performed using the technique described in U.S. Publication No. 2009 / 195768 A (Bijnen et al.). The entire contents of these disclosures are incorporated herein by reference.

[0062] Figure 4A A cross-sectional view of an inspection apparatus 400, which may be implemented as part of a photolithography apparatus 100 or 100', is shown according to some aspects. In some aspects, the inspection apparatus 400 may be configured to align a substrate (e.g., substrate W) relative to a patterning apparatus (e.g., patterning apparatus MA). The inspection apparatus 400 may also be configured to detect the position of alignment marks on the substrate and use the detected alignment mark positions to align the substrate relative to the patterning apparatus or other components of the photolithography apparatus 100 or 100'. Such alignment of the substrate can ensure accurate exposure of one or more patterns on the substrate.

[0063] The terms “detection device” and “measurement system” may be used in this document to refer to, for example, equipment used to measure the properties of a structure (e.g., overlay sensor, critical size sensor, etc.), or equipment or systems used in a lithography apparatus to check wafer alignment (e.g., alignment sensor).

[0064] In some aspects, the inspection apparatus 400 may include an illumination system 412, a beam splitter 414, an interferometer 426, a detector 428, a beam analyzer 430, and a processor 432. The illumination system 412 may be configured to provide a narrow-band electromagnetic radiation beam 413 having one or more passbands. In one example, the one or more passbands may be within a wavelength spectrum between about 500 nm and about 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a wavelength spectrum between about 500 nm and about 900 nm. The illumination system 412 may also be configured to provide one or more passbands with a substantially constant center wavelength (CWL) value over a long period of time (e.g., throughout the lifetime of the illumination system 412). In current alignment systems, this configuration of the illumination system 412 helps prevent shifts between the actual CWL value and the desired CWL value, as discussed above. And, therefore, using a constant CWL value can improve the long-term stability and accuracy of the alignment system (e.g., the inspection apparatus 400) compared to current alignment apparatuses.

[0065] In some aspects, beam splitter 414 can be configured to receive radiation beam 413 and split radiation beam 413 into at least two radiation sub-beams. For example, as Figure 4AAs shown, the radiation beam 413 can be split into radiation sub-beams 415 and 417. The beam splitter 414 can also be configured to guide the radiation sub-beam 415 onto a substrate 420 placed on a platform 422. In one example, the platform 422 is movable along direction 424. The radiation sub-beam 415 can be configured to illuminate an alignment mark or target 418 located on the substrate 420. The alignment mark or target 418 can be coated with a radiation-sensitive film. In some aspects, the alignment mark or target 418 can have 180° symmetry. That is, when the alignment mark or target 418 is rotated 180° about an axis of symmetry perpendicular to the plane of the alignment mark or target 418, the rotated alignment mark or target 418 can be substantially identical to the unrotated alignment mark or target 418. The target 418 on substrate 420 can be (a) a resist layer grating comprising gratings formed by solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure comprising resist gratings overlaid or interlaced on the product layer grating. Alternatively, the gratings can be etched into the substrate. This pattern is sensitive to chromatic aberration in the photolithography projection apparatus, particularly the projection system PL, and the presence of illumination symmetry and this aberration will be manifested in variations in the printed grating. One in-line method used in device fabrication to measure linewidth, pitch, and critical dimensions utilizes a technique called “scattering measurement.” Methods for scattering measurements are described in “Multiparameter Grating Metrology Using Optical Scatterometry” by Raymond et al., published in Volume 15, Issue 2, Series B, Vacuum Science and Technology, 1997, pp. 361-368, and in “Specular Spectroscopic Scatterometry in DUV Lithography” by Niu et al., published in SPIE, Volume 3677, 1999, both of which are incorporated herein by reference in their entirety. In scattering measurements, light is reflected by a periodic structure in a target, and the resulting reflection spectrum at a given angle is detected. The structure that produces the reflection spectrum is reconstructed, for example, using rigorous coupled-wave analysis (RCWA) or by comparison with a simulated pattern library. Therefore, scattering measurement data of printed gratings are used to reconstruct the grating. The parameters of the grating, such as linewidth and shape, can be input into the reconstruction process performed by the processing unit (PU) through knowledge of the printing steps and / or other scattering measurement processes.

[0066] In some aspects, according to one aspect, beam splitter 414 can also be configured to receive diffracted radiation beam 419 and split diffracted radiation beam 419 into at least two radiation sub-beams. For example... Figure 4AAs shown, the diffraction beam 419 can be split into diffraction sub-beams 429 and 439.

[0067] It should be noted that although beam splitter 414 is shown to guide radiant sub-beam 415 toward alignment mark or target 418 and diffracted radiant sub-beam 429 toward interferometer 426, this disclosure is not limited thereto. Other optical arrangements can be used to obtain similar results of illuminating alignment mark or target 418 on substrate 420 and detecting images of alignment mark or target 418.

[0068] like Figure 4A As illustrated, interferometer 426 can be configured to receive a radiating sub-beam 417 and a diffracted radiating sub-beam 429 via beam splitter 414. In an example aspect, the diffracted radiating sub-beam 429 may be at least a portion of a radiating sub-beam 415 that can be reflected from the alignment mark or target 418. In this example aspect, interferometer 426 includes any suitable set of optical elements, such as a combination of prisms, which can be configured to form two images of the alignment mark or target 418 based on the received diffracted radiating sub-beam 429. It should be understood that forming a high-quality image is not required. Resolving the characteristics of the alignment mark 418 may be sufficient. Interferometer 426 can also be configured to rotate one of the two images by 180° relative to the other image and interferometrically reconstruct the rotated and unrotated images.

[0069] In some aspects, when the alignment axis 421 of the inspection apparatus 400 passes through the center of symmetry (not shown) of the alignment mark or target 418, the detector 428 can be configured to receive the reconstructed image via interferometer signal 427 and detect interference as a result of the reconstructed image. According to an example aspect, this interference may be due to the alignment mark or target 418 being 180° symmetrical, and the reconstructed image interfering constructively or destructively. Based on the detected interference, the detector 428 can also be configured to determine the position of the center of symmetry of the alignment mark or target 418, and thus detect the position of the substrate 420. According to an example, the alignment axis 421 can be aligned with a beam perpendicular to the substrate 420 and passing through the center of an image rotation interferometer 426. The detector 428 can also be configured to estimate the position of the alignment mark or target 418 by implementing sensor characteristics and interacting with variations in the wafer marking process.

[0070] In another aspect, detector 428 determines the position of the center of symmetry of alignment mark or target 418 by performing one or more of the following measurements:

[0071] 1. Measure the positional changes at various wavelengths (positional shifts between colors);

[0072] 2. Measure the positional changes of various orders (positional shifts between diffraction orders);

[0073] 3. Measure the positional changes of various polarizations (positional shifts between polarizations); and

[0074] 4. Measure the intensity difference between opposite orders of diffraction order pairs (e.g., characterize and correct for asymmetry).

[0075] This data can be obtained using any type of alignment sensor, such as the SMASH (SMart alignment sensor hybrid) sensor, as described in U.S. Patent No. 6,961,116, which employs a self-reference interferometer with a single detector and four different wavelengths and extracts the alignment signal in software; or Athena (using advanced techniques to enhance higher-order alignment), as described in U.S. Patent No. 6,297,876, which directs each of the seven diffraction orders to a dedicated detector, both of which are incorporated herein by reference in their entirety.

[0076] In some aspects, the beam analyzer 430 can be configured to receive and determine the optical state of the diffracted radiation sub-beam 439. The optical state can be a measure of beam wavelength, polarization, or beam profile. The beam analyzer 430 can also be configured to determine the position of the platform 422 and correlate the position of the platform 422 with the position of the center of symmetry of the alignment mark or target 418. Therefore, the position of the alignment mark or target 418 can be accurately known by reference to the platform 422, thereby accurately knowing the position of the substrate 420. Alternatively, the beam analyzer 430 can be configured to determine the position of the inspection device 400 or any other reference element, such that the center of symmetry of the alignment mark or target 418 can be known by reference to the inspection device 400 or any other reference element. The beam analyzer 430 can be a point or imaging polarimeter with some form of band selectivity. In some aspects, and in others, the beam analyzer 430 can be directly integrated into the inspection device 400 or via several types of fiber connections: polarization-maintaining single-mode, multimode, or imaging.

[0077] In some aspects, the beam analyzer 430 may also be configured to determine overlay data between two patterns on the substrate 420. One of these patterns may be a reference pattern on a reference layer. The other pattern may be an exposure pattern on an exposure layer. The reference layer may be an etched layer already present on the substrate 420. The reference layer may be generated by exposing a reference pattern on the substrate using lithography apparatus 100 and / or 100'. The exposure layer may be a resist layer exposed adjacent to the reference layer. The exposure layer may be generated by exposing an exposure pattern on the substrate 420 using lithography apparatus 100 or 100'. The exposure pattern on the substrate 420 may correspond to movement of the platform 422 relative to the substrate 420. In some aspects, the measured overlay data may also indicate the offset between the reference pattern and the exposure pattern. The measured overlay data may be used as calibration data to calibrate the exposure pattern exposed by lithography apparatus 100 or 100' such that, after calibration, the offset between the exposure layer and the reference layer can be minimized.

[0078] In some aspects, the beam analyzer 430 can also be configured to model the product stack profile of the substrate 420 and can be configured to measure the overlay, critical dimensions, and focal point of the target 418 in a single measurement. The product stack profile contains information about the stacked product, such as alignment marks, target 418, or substrate 420, and may include optical signature measurements caused by variations in the marking process (which are functions of illumination variations). The product stack profile may also include product grating profiles, mark stack profiles, and mark asymmetry information. An example of the beam analyzer 430 is the Yieldstar manufactured by ASML in Feldhoven, Netherlands. TM As described in U.S. Patent No. 8,706,442, which is incorporated herein by reference in its entirety. Beam analyzer 430 may also be configured to process information relating to specific properties of the exposure pattern in the layer. For example, beam analyzer 430 may process overlay parameters (an indication of the positioning accuracy of the layer relative to a preceding layer on the substrate, or the positioning accuracy of the first layer relative to markings on the substrate), focal length parameters, and / or critical dimension parameters (e.g., linewidth and its variation) of the image depicted in the layer. Other parameters are image parameters relating to the quality of the image depicting the exposure pattern.

[0079] In some respects, a detector array (not shown) can be connected to the bundle analyzer 430, allowing for accurate stack profile detection as discussed below. For example, detector 428 can be a detector array. Several options are possible for the detector array: multimode fiber bundles, discrete pin detectors for each channel, or CCD or CMOS (linear) arrays. For stability reasons, using multimode fiber bundles allows for remote positioning of any dissipative element. Discrete pin detectors offer a large dynamic range, but each requires a separate preamplifier. Therefore, the number of elements is limited. CCD linear arrays offer many elements that can be read out at high speed, and these elements are particularly interesting if phase-stepped detection is used.

[0080] In some respects, the second beam analyzer 430' can be configured to receive and determine the optical state of the diffracted radiation sub-beam 429, such as Figure 4B As shown. Optical state can be a measure of beam wavelength, polarization, or beam profile. The second beam analyzer 430' can be the same as beam analyzer 430. Alternatively, the second beam analyzer 430' can be configured to perform one or more functions of beam analyzer 430, such as determining the position of platform 422 and relating the position of platform 422 to the position of the alignment mark or target 418's center of symmetry. Therefore, the position of the alignment mark or target 418 can be accurately known by reference to platform 422, thereby accurately knowing the position of substrate 420. The second beam analyzer 430' can also be configured to determine the position of inspection device 400 or any other reference element, such that the center of symmetry of alignment mark or target 418 can be known by reference to inspection device 400 or any other reference element. The second beam analyzer 430' can also be configured to determine overlay data between two patterns and a model of the product stack profile of substrate 420. The second beam analyzer 430' can also be configured to measure the overlay, critical dimensions, and focus of target 418 in a single measurement.

[0081] In some aspects, and in others, the second beam analyzer 430' may be directly integrated into the inspection apparatus 400, or connected via several types of optical fibers: polarization-maintaining single-mode, multimode, or imaging. Alternatively, the second beam analyzer 430' and the beam analyzer 430 may be combined to form a single analyzer (not shown) configured to receive and determine the optical state of the diffracted sub-beams 429 and 439.

[0082] In some aspects, processor 432 receives information from detector 428 and beam analyzer 430. For example, processor 432 may be an overlay calculation processor. This information may include a model of the product stack profile constructed by beam analyzer 430. Alternatively, processor 432 may use received information about product markings to construct a model of the product marking profile. In either case, processor 432 may use or combine the product marking profile model to construct a model of the stacked product and overlay marking profiles. The stack model is then used to determine the overlay offset and minimize the spectral influence on the overlay offset measurement. Processor 432 may create a basic correction algorithm based on the information received from detector 428 and beam analyzer 430, including but not limited to the optical state of the illumination beam, alignment signal, associated position estimation, and optical state in the pupil, image, and additional plane. The pupil plane is a plane in which the radial position of the radiation defines the angle of incidence and the angular position defines the azimuth of the radiation. Processor 432 may utilize the basic correction algorithm to characterize inspection apparatus 400 with reference to wafer markings and / or alignment marks 418.

[0083] In some aspects, processor 432 can also be configured to determine the sensor-estimated printed pattern position offset error relative to each mark based on information received from detector 428 and beam analyzer 430. This information includes, but is not limited to, product stack profile, overlay measurements, critical dimensions, and the focal point of each alignment mark or target 418 on substrate 420. Processor 432 can utilize a clustering algorithm to group the marks into similar constant offset error sets and create an alignment error offset correction table based on this information. The clustering algorithm can be based on overlay measurements, position estimates, and additional optical stacking process information associated with each offset error set. Overlay is calculated for many different marks, such as overlay targets with positive and negative deviations around the programmed overlay offset. The target with the smallest measured overlay is considered as a reference (because it is measured with optimal accuracy). The overlay error can be inferred from this measured small overlay and the known programmed overlay of its corresponding target. Table 1 illustrates how this can be performed. The smallest measured overlay in the example shown is -1 nm. However, this is related to a target with a programmed overlay of -30 nm. This process may have introduced an overlay error of 29 nm.

[0084] The minimum value can be considered a reference point, and relative to this, the offset between the measured overlay and the expected overlay due to the programmed overlay can be calculated. This offset determines the overlay error for each marker or a set of markers with a similar offset. Thus, in the example of Table 1, the minimum measured overlay is -1 nm, and at the target location, the programmed overlay is 30 nm. The difference between the expected and measured overlays at other targets is compared to this reference. Tables such as Table 1 can also be obtained from markers and targets 418 under different irradiation settings, allowing the determination and selection of the irradiation settings that result in the minimum overlay error and their corresponding calibration factors. After this, the processor 432 can group the markers into similar sets of overlay errors. The criteria for grouping the markers can be adjusted based on different process controls, such as different error tolerances for different processes.

[0085] In some respects, processor 432 can identify that all or most members of the group have similar offset errors and, based on its additional optical stacking measurements, apply individual offset corrections from the clustering algorithm to each mark. Processor 432 can determine the correction for each mark and feed the correction back to lithography apparatus 100 or 100' to correct for errors in overlay, for example, by feeding the correction back to inspection apparatus 400.

[0086] Example aberration correction of optical systems

[0087] Optical aberrations (such as wavefront error (WFE)) have consistently been one of the major challenges for metrology tools used in the photolithography fabrication of nanoscale devices. When it comes to sensors (such as inspection apparatus 400), achieving machine-to-machine (M2M) matching is difficult. Ideally, each sensor is fabricated identically. However, due to uncertainties in part and component manufacturing, each sensor's construction may differ slightly. In other words, the M2M performance of sensor designs can be matched, but within certain tolerances. Consider measuring the same target 418 using two separate constructions of inspection apparatus 400, which differ slightly due to manufacturing uncertainties. The two versions of inspection apparatus 400 will produce very similar measurement results, but some systematic variations exist due to minor differences in construction. M2M mismatch can be considered as performance exceeding specified tolerances (e.g., sensor performance).

[0088] In some respects, aberrations can lead to M2M mismatch. Various types of aberrations can occur throughout the optical path of the inspection system 400, including spherical aberrations (e.g., Zernike Z9 / Z16 associated with certain user-designed alignment marks), astigmatism (e.g., Zernike Z5 / Z6), coma (e.g., Zernike Z7 / 8), cloverleaf, and higher-order Zernike terms. The sensitivity of all these aberrations to OV measurements may vary depending on the design of the overlay target made by the user of the inspection apparatus. Options for aberration compensators are limited and often expensive.

[0089] In some embodiments, many optical components within the sensor contribute to overall sensor aberration (e.g., lenses, high numerical aperture (NA) objectives, etc.), and they are difficult to compensate for without using very expensive methods, such as deformable mirrors, to actively control the aberrations. Deformable mirrors are very expensive and bulky devices. To achieve this, in sensors like Yieldstar... TM Implementing deformable mirrors in sensors will significantly alter the optical arrangement to accommodate the shape and size of deformable mirrors within existing volume constraints. Some methods described in this paper can cost-effectively address aberrations within small volume constraints.

[0090] Figure 5 An inspection device 500 is shown according to some aspects. In some embodiments, the inspection device 500 may be an inspection device 400 with additional features. Figure 4A and 4B Another version of ). Therefore, it should be understood that, unless otherwise mentioned, the above refers to Figure 4A and 4B The description also applies to the inspection device 500. As an example, Figure 5 One or more marking elements in have the same Figure 4A and 4B The components illustrated in the figure are matched by reference numerals (e.g., reference numerals sharing two rightmost numbers), such as radiation beam 513, beam splitter 514, a portion 515 of radiation beam 513 (e.g., a first portion), and substrate 520.

[0091] In some aspects, the inspection apparatus 500 may include beam guiding devices (e.g., beam splitters 514, 540, and 542), an optical objective 544, a wedge system 546, a spatial light modulator (SLM) 548, and a detector 550 (e.g., a first detector). The inspection apparatus 500 may also include a detector 552 (e.g., a second detector). The wedge system 546 may include a wedge 554 (e.g., a first wedge), a wedge 556 (e.g., a second wedge), and a radiation-cured adhesive 558 disposed between them. Although the SLM 548 is illustrated as a reflective type (e.g., a digital micromirror), the SLM 548 may include any spatial light modulator (e.g., a liquid crystal) capable of adjusting the spatial distribution of illumination intensity.

[0092] In some respects, beam splitter 514 can split radiation beam 513 into portions 515 and 541 (e.g., a first portion and a second portion). While the term "beam splitter" indicates a beam-splitting function, it is important to understand that beam splitters also have other functions (e.g., guiding / redirecting radiation beams, combining radiation beams, etc.). For example, beam splitter 542 can guide / redirect radiation beam 513 via reflection. In another example, beam splitter 540 can combine the optical paths of radiation beam 513 and radiation beam 570'.

[0093] In some aspects, the radiation beam 513 (e.g., from the irradiation system 412) Figure 4A and 4B The generated beam initially has a wavefront 560. Wavefront 560 can be a wavefront of coherent or partially coherent illumination (e.g., spatially coherent but temporally incoherent, or vice versa). It is desirable that when the radiation beam 513 (or a portion thereof 515) strikes the target, its wavefront 562 is uniform (e.g., aberrant). The target can be a diffractive target, sensitive to inconsistent wavefronts, which, in turn, can lead to a wider error tolerance when the inspection device 500 is used for optical measurements. Each piece of optical hardware can introduce its own unique aberrations (e.g., any combination of Zernike's aforementioned components). This can be applied to the radiation beam source 513, beam splitters 514, 540 and / or 542, optical objectives 544, and wedge system 546. Additional wavefronts 564, 566, and 568 are noted at different parts of the optical path of the radiation beam 513, each wavefront varying slightly based on its preceding optical elements. Optical elements used for the redirection of the radiation beam 570' (such as beam splitter 540) can be removed after wavefront optimization, or they can be retained as part of the sensor product.

[0094] In some aspects, the radiation beam 513 (or a portion thereof 515) may be directed toward the substrate 520 (e.g., via a beam splitter 514). The substrate 520 may scatter the received radiation into scattered radiation 543.

[0095] In some respects, the wedge system 546 can be used to slightly offset or redirect the optical path of the radiation beam (e.g., to reduce ghosting signals that interfere with measurements and reduce measurement accuracy). Ghosting signals may be generated by unwanted reflections at one or more optical components. The wedge system 546 can also be used to reduce aberrations. To achieve this, a radiation-cured adhesive 558 is utilized.

[0096] In some aspects, radiation-curable adhesive 558 can be cured in a manner with region-dependent optical properties, such as refractive index or dispersion that varies based on location. Radiation-curable adhesive 558 can be cured using a radiation beam 570'. The radiation beam 570 can be incident on an SLM 548. The SLM 548 can control the intensity distribution of the radiation beam 570 to generate the radiation beam 570'. Depending on the radiation dose, local areas of the radiation-curable adhesive 558 can be cured at different amounts. When curing the radiation-curable adhesive 558, detectors 550 and / or 552 can be used to quantify wavefront aberrations. The measurements can be used as a feedback loop to adjust the intensity distribution of the radiation beam 570', thereby adjusting the local exposure dose at the radiation-curable adhesive 558, and thus adjusting the local optical properties of the radiation-curable adhesive 558.

[0097] In some respects, although Figure 5 The target is not shown in the diagram, but it should be understood that the inspection device 500 can measure the target (e.g., 418). Figure 4A and 4B One reason is... Figure 5 The setup in the image characterizes and reduces aberrations by incidenting a radiation beam 513 (or a portion thereof 515) onto the substrate 520. Once aberration processing is complete, the inspection device 500 can be used to measure the target, as described above. Figure 4A and 4B Described.

[0098] Figure 6 A flowchart of a method 600 for reducing optical aberrations in an optical system, based on several aspects, is shown. (Refer to...) Figure 5 One or more structures are introduced to describe some aspects of method 600.

[0099] In some aspects, during operation 602, aberrations caused by the optical system (e.g., inspection device 500) are determined. Operation 602 may include operations 604 and 606.

[0100] In some aspects, during operation 604, a radiation beam 513 having a first wavelength (e.g., a first radiation beam) is transmitted through a wedge system 546 of the optical system. At this stage, the radiation-cured adhesive 558 may be in a partially cured or uncured state. The radiation-cured adhesive 558 may be insensitive to or unresponsive to the first wavelength (e.g., radiation having the first wavelength will not cure the radiation-cured adhesive 558). One reason for this is that the radiation beam 513 may have a specific effect on the target (e.g., target 418). Figure 4A and 4B The wavelength will be used consistently during the actual measurement operation. Problems may arise if the optical properties of the wedge system 546 change during measurement or within repeated measurements. The first wavelength may include wavelengths from 400 nm to 900 nm (e.g., non-curing ultraviolet, visible range, and infrared). The non-curing ultraviolet may differ from the curing ultraviolet used for the radiation beam 570 / 570'.

[0101] In some aspects, during operation 606, a first beam is analyzed using a detector (e.g., 550, 552, or both) positioned downstream of the wedge system 546 to determine aberrations. It should be understood that analyzing the first beam may include analyzing radiation beam 513 (or a portion thereof 541) at detector 550, analyzing radiation beam 513 (or a portion thereof 515) at detector 552, or both. Analysis of radiation beam 513 (or a portion thereof 515) at detector 552 can be achieved by receiving scattered radiation 543 at detector 552. Scattered radiation 543 carries information about radiation beam 513 (or a portion thereof 515). Scattered radiation 543 can be generated by reflection at substrate 520 because there is no target in the optical path during this operation. Furthermore, scattered radiation 543 carries information about aberrations caused by optical objective 544. For high NA optical objective 544 (e.g., NA approximately 0.5 or greater), collective aberrations are expected to be primarily caused by optical objective 544. The technical effect of passing the radiation beam 513 (or a portion thereof 515) through the optical objective lens 544 for measurement is to characterize the element that contributes the most to aberrations.

[0102] In some aspects, the inspection system 500 can be considered to include two branches: an illumination branch and a detection branch. The illumination branch can cover those elements responsible for delivering radiation to the substrate 520 (or to the target during measurement). That is, the illumination branch can cover elements upstream of the substrate 520. For example, Figure 5A wedge system 546 disposed in the irradiation branch is shown. The detection branch may encompass detector(s) and those elements responsible for collecting scattered radiation and guiding it from substrate 520 (or from the target during measurement) to detector(s). That is, the detection branch may include elements downstream of substrate 520. For example, wedge system 546 may be removed from the irradiation branch and replaced by a wedge system 572 having the same construction at the detection branch (or the wedge system may be implemented in both the irradiation and detection branches).

[0103] In some embodiments, the radiation beam 513 (or a portion thereof 541) analyzed by detector 550 effectively measures the aberrations introduced by the illumination branch. This is because the radiation received at detector 550 bypasses the detection branch elements (e.g., bypasses the substrate 520 and optical objective 544). In addition to the analysis via detector 550, or alternatively, the radiation beam 513 (or a portion thereof 515) analyzed by detector 552 measures the aberrations introduced by both the illumination and detection branches. This is because detector 552 is positioned downstream of the wedge system 546, optical objective 544, and substrate 520. By comparing the analysis via detector 550 and the analysis via detector 552, the aberrations introduced by the detection branch can be inferred. The aberrations can be characterized using a wavefront-sensitive camera. Detectors 550 and 552 can be, for example, Shack-Hartmann wavefront sensors.

[0104] In some aspects, in operation 608, radiation-cured adhesive 558 is cured based on analysis of the first beam. Operation 608 may include operations 610 and 612.

[0105] In some aspects, where aberrations are quantified based on the analysis of the first beam, the method can continue to spatially customize the curing dose. In operation 610, using an SLM 548, the intensity distribution of the radiation beam 570' (e.g., a second radiation beam) is adjusted based on the analysis of the first beam. The radiation beam 570' that generates the radiation beam 570 can be generated by a source that generates the second wavelength. The radiation-curing adhesive 558 can be sensitive to or responsive to the second wavelength (e.g., an ultraviolet wavelength less than 400 nm) while remaining unresponsive to the first wavelength. Based on the customization of the intensity distribution of the radiation beam 570', different regions of the radiation-curing adhesive 558 can be selectively cured, thereby causing localized position-dependent optical properties. For example, one region can have a specified refractive index, while another region can have a different specified refractive index. The resulting position-dependent optical properties can reduce aberrations in the inspection device 500. Aberration reduction can be determined in subsequent measurements.

[0106] In some aspects, in operation 614, the effectiveness of curing in reducing aberrations can be determined by measurement using detectors (e.g., 550, 552, or both). Operation 614 can be performed as described with reference to operation 606 and its sub-operations. After curing, radiation beam 513 can be transmitted through wedge system 546. Since radiation beam 513 is reused, the reuse of radiation beam 513 can be referred to as a “third radiation beam having a first wavelength” (e.g., to distinguish it from the previous first and second beams). In other words, in operation 614, radiation beam 513 is reapplied to wedge system 546. The transmitted third beam (e.g., radiation beam 513 or a portion thereof 515) can then be analyzed via detectors to determine aberration changes caused by spatially customized curing. Determining effectiveness may include determining whether the degree of aberration meets a prescribed threshold (e.g., reduced to or exceeding a threshold).

[0107] In some aspects, if the aberration reduction is found to be unsatisfactory, curing can be repeated. In operation 616, the radiation-cured adhesive 558 is further cured based on the determination of effectiveness. Operation 616 can be performed as described with reference to operation 608 and its sub-operations. After determining effectiveness using SLM 548, the intensity distribution of the radiation beam 570' can be adjusted based on the determination of effectiveness. Since the radiation beam 570' is reused, the reuse of the radiation beam 570' can be referred to as a "fourth radiation beam with a second wavelength" (e.g., to distinguish it from the previous first, second, and third beams). In other words, in operation 616, the radiation beam 570' is reapplied to the wedge system 546. The fourth beam can then be directed to the radiation-cured adhesive to adjust the position-related optical properties at the radiation-cured adhesive. Terms such as "first wavelength" and "second wavelength" can be interpreted as bands (e.g., narrowbands). For example, terms such as "wavelength" can include peak or center wavelength and wavelength range centered on the peak wavelength.

[0108] In some aspects, the determination of effectiveness and further curing can be repeated until the aberrations are reduced to meet a specified threshold. For example, method 600 may include determining the effectiveness of further curing of operation 616 via measurements using a detector. If the aberrations are unsatisfactory, additional curing can be spatially tailored to further adjust the position-related optical properties.

[0109] In some aspects of implementing wedge system 572 (whether alone or in addition to wedge system 546), it is to be understood that SLM 548 can be positioned toward wedge system 572 to guide beam 570', or an additional SLM can be used. The operations described above with reference to wedge system 546 can also be performed relative to wedge system 572.

[0110] Figure 6The method steps can be performed in any imaginable order, and it is not necessary to perform all the steps. Furthermore, the above... Figure 6 The method steps described herein are merely examples and not limiting. For example, in some aspects, wedge systems 546 and / or 572 may be assembled. The assembly operation may include placing a radiation-cured adhesive 558 on the facet of either of the wedges 554 and 556, and then joining the wedges 554 and 556 together. The assembly of the wedges 554 and 556 with the radiation-cured adhesive 558 may be performed such that the radiation-cured adhesive 558 has a substantially constant thickness (e.g., approximately 50 µm or less, approximately 30 µm or less, approximately 20 µm or less, approximately 10 µm or less, etc.). All the functions described herein form the basis for additional or alternative operations.

[0111] The embodiments may be further described using the following terms: 1. A method for reducing optical aberrations in an optical system, the method comprising: Determine the aberrations caused by the optical system, including: A wedge system for transmitting a first radiation beam having a first wavelength through an optical system, the wedge system comprising a first wedge and a second wedge, and a radiation-cured adhesive disposed between the first wedge and the second wedge; and The first beam is analyzed using a detector positioned downstream of the wedge system to determine aberrations; and Analysis based on the first beam is used to cure radiation-cured adhesives, including: Using a spatial light modulator, the intensity distribution of a second radiation beam is adjusted based on the analysis of the first beam, wherein the second beam has a second wavelength different from the first wavelength; and A second beam is directed to the radiation-cured adhesive to induce position-dependent optical properties at the radiation-cured adhesive, thereby reducing aberrations, wherein the radiation-cured adhesive is responsive to the second wavelength. 2. The method according to Clause 1 also includes: The effectiveness of curing in reducing aberrations is determined by measurements using a detector, including: To allow a third radiation beam with a first wavelength to pass through the wedge-shaped system; and The transmission of the third beam is analyzed via a detector to determine the changes in aberrations. 3. The method according to Clause 2, wherein the determination of validity includes determining whether the degree of aberration meets the threshold. 4. The method according to Clause 2 also includes: Further curing of radiation-cured adhesives based on efficacy determination includes: Using a spatial light modulator, the intensity distribution of a fourth radiation beam, having a second wavelength, is adjusted based on a determination of effectiveness; and The fourth beam is directed to the radiation-cured adhesive to adjust the position-related optical properties at the radiation-cured adhesive site. 5. The method according to Clause 4 also includes: The effectiveness of further curing is determined by measurements using a detector. 6. The method according to Clause 1 also includes: The optical objective lens that guides the first beam or a portion of the first beam through the optical system; and The first beam or a portion of the first beam is reflected at the substrate. 7. The method according to Clause 6, wherein the analysis of the first bundle used to determine the aberrations includes determining the contribution of an optical objective with a numerical aperture of approximately 0.5 or greater to the aberrations. 8. The method according to Clause 6, wherein the analysis of the first beam includes analyzing the first beam or a portion thereof using a detector positioned downstream of the wedge system, the optical objective, and the substrate. 9. According to the method of Clause 6, wherein: The detector is the first detector; This is Part One; The second portion of the first beam is sent to the second detector along a path excluding the optical objective and substrate; and The analysis of the first beam also includes using a second detector to analyze a second portion of the first beam. 10. The method according to Clause 6, wherein the wedge system is positioned downstream of the optical objective and the substrate. 11. According to the method of Clause 6, wherein: The wedge system is the first wedge system located upstream of the substrate; The optical system includes a second wedge system comprising a radiation-cured adhesive disposed between two wedges downstream of the substrate; and The first beam transmission through the wedge system includes passing the first beam through a first wedge system and a second wedge system. 12. The method according to Clause 1 further includes assembling the first wedge and the second wedge such that the thickness of the radiation-cured adhesive is substantially constant. 13. The method according to Clause 12, wherein the thickness is approximately 50 micrometers or less. 14. According to the method of Clause 1, wherein: Radiation-cured adhesives react to ultraviolet wavelengths; and The second wavelength falls within the wavelength range that includes the ultraviolet range. 15. The method according to Clause 1, wherein the first wavelength is within a wavelength range that includes both the infrared and visible ranges. 16. An inspection device, comprising: The radiation source is configured to generate radiation; Wedge system, including: The first wedge is configured to receive radiation; The second wedge is configured to output radiation; and A radiation-curing adhesive disposed between a first wedge and a second wedge, wherein the radiation-curing adhesive includes region-related optical properties configured to adjust the radiation wavefront; Optical equipment is configured to guide radiation toward a target in order to generate scattered radiation from the target; The detector is configured to receive scattered radiation from the target and generate a measurement signal based on adjustments to the scattered radiation and the wavefront. 17. The inspection apparatus according to Clause 16 further includes an optical objective disposed downstream of the optical device, wherein the numerical aperture of the optical objective is approximately 0.5 or greater. 18. The thickness of the radiation-cured adhesive is substantially constant according to the inspection apparatus of Clause 16. 19. The inspection device according to Clause 16, wherein: The wedge system is installed at the irradiation branch of the inspection device; The wedge system is installed at the detection branch of the inspection device; or A wedge system is positioned at the irradiation branch, and another wedge system is positioned at the detection branch, the latter including a radiation-cured adhesive between the two wedges. 20. A wedge-shaped system, comprising: The first wedge is configured to receive radiation; A second wedge is configured to output radiation; and a radiation-curing adhesive is disposed between the first and second wedges, wherein the radiation-curing adhesive includes region-dependent optical properties configured to adjust the radiation wavefront.

[0112] The technical significance of the features disclosed herein lies in the ability to use optical components that are well-suited to small volume constraints and to reduce aberrations in optical systems cost-effectively, such as optical sensors used with photolithography processes (e.g., wedge systems can be much smaller and more cost-effective than deformable mirrors).

[0113] In this document, the terms “radiation,” “beam,” “light,” “irradiation,” etc., may be used to refer to one or more types of electromagnetic radiation, such as ultraviolet (UV) radiation (e.g., wavelengths λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (e.g., wavelengths in the range of 5 to 100 nm, such as, for example, 13.5 nm), or hard X-rays operating at less than 5 nm, and particle beams (such as ion beams or electron beams). Generally, radiation with wavelengths between about 400 and about 700 nm is considered visible radiation; radiation with wavelengths between about 780 and 3000 nm (or greater) is considered IR radiation. UV refers to radiation with wavelengths approximately 100 to 400 nm. In photolithography, the term “UV” also applies to wavelengths that can be produced by a mercury discharge lamp: G line 436 nm; H line 405 nm; and / or I line 365 nm. Vacuum UV or VUV (i.e., UV absorbed by a gas) refers to radiation with wavelengths approximately 100 to 200 nm. Deep UV (DUV) generally refers to radiation with wavelengths ranging from 126 nm to 428 nm, and in some respects, excimer lasers can generate DUV radiation for use within photolithography apparatuses. It should be understood that radiation with wavelengths in, for example, the range of 5 to 20 nm involves radiation with a specific band of wavelengths, at least a portion of which is within the 5 to 20 nm range.

[0114] Although some aspects of this disclosure are described in the context of a lithography apparatus in IC manufacturing, it should be understood that the lithography apparatus described herein can be used for other applications, such as the fabrication of integrated optical systems, the guiding and detection of patterns in magnetic domain memory, flat panel displays, LCDs, thin-film magnetic heads, etc. Those skilled in the art will appreciate that, in the context of such alternative applications, any use of the terms "wafer" or "die" herein can be considered as specific examples of the more general terms "substrate" or "target portion," respectively. The substrate can be processed before or after exposure in, for example, a track cell (a tool typically used to apply a resist layer to the substrate and develop the exposed resist) and / or a measurement cell. Where applicable, the aspects disclosed herein can be applied to such and other substrate processing tools. Furthermore, the substrate can be processed more than once, for example to create a multilayer IC, such that the term "substrate" as used herein can also refer to a substrate that already contains multiple processed layers.

[0115] Furthermore, although some aspects of this disclosure are described in the context of optical lithography, it should be understood that these aspects are not limited to optical lithography. For example, in imprint lithography, the morphology in a patterning apparatus defines a pattern created on a substrate. The morphology of the patterning apparatus can be pressed into a resist layer supplied to the substrate, whereby the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist has cured, the patterning apparatus is removed from the resist, thereby leaving a pattern therein.

[0116] It should be understood that the wording or terminology used herein is for descriptive and not limiting purposes, and that the terminology or terminology used herein is to be interpreted by those skilled in the art in light of the teachings herein.

[0117] The present disclosure has been described above using functional building blocks that illustrate the implementation of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks are arbitrarily defined herein. Alternating boundaries can be defined as long as the specified functions and their relationships are properly performed. The foregoing description of specific aspects will fully demonstrate the generality of the present disclosure, and others can readily modify and / or adapt various applications of such specific aspects by applying knowledge in the art without excessive experimentation and without departing from the general concepts of the present disclosure. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended to be within the meaning and scope equivalent to the disclosed aspects.

[0118] It should be understood that the Detailed Description section, rather than the Summary and Abstract section, is intended to be used to interpret the claims. The Summary and Abstract section may state one or more, but not all, aspects of this disclosure as conceived by the inventors, and is therefore not intended to limit this disclosure and the appended claims in any way. The breadth and scope of the protected subject matter should not be limited by any of the foregoing aspects, but should be defined solely by the following claims and their equivalents.

Claims

1. A method for reducing optical aberrations in an optical system, the method comprising: Determining the aberrations caused by the optical system includes: A wedge system for transmitting a first radiation beam having a first wavelength through the optical system, the wedge system comprising a first wedge and a second wedge, and a radiation-cured adhesive disposed between the first wedge and the second wedge; and The first beam is analyzed using a detector positioned downstream of the wedge system to determine the aberrations; and Based on the analysis of the first beam, curing the radiation-cured adhesive includes: Using a spatial light modulator, the intensity distribution of a second radiation beam is adjusted based on analysis of the first beam, wherein the second beam has a second wavelength different from the first wavelength; and The second beam is directed to the radiation-cured adhesive to induce position-dependent optical properties at the radiation-cured adhesive, thereby reducing the aberration, wherein the radiation-cured adhesive is responsive to the second wavelength.

2. The method according to claim 1, further comprising: Determining the effectiveness of curing in reducing the aberrations through measurements using the detector includes: A third radiation beam having the first wavelength is transmitted through the wedge system; and The changes in the aberrations are determined by analyzing the transmitted third beam via the detector.

3. The method of claim 2, wherein determining the effectiveness includes determining whether the degree of the aberration meets a threshold.

4. The method according to claim 2, further comprising: Based on the determination of the aforementioned effectiveness, the radiation-cured adhesive is further cured, including: Using the spatial light modulator, the intensity distribution of a fourth radiation beam, having the second wavelength, is adjusted based on a determination of the effectiveness; and The fourth beam is directed to the radiation-cured adhesive to adjust the position-related optical properties at the radiation-cured adhesive.

5. The method according to claim 4, further comprising: The effectiveness of the further curing is determined by measurement using the detector.

6. The method according to claim 1, further comprising: Guide the first beam or a portion of the first beam through the optical objective lens of the optical system; as well as The first beam or a portion thereof is reflected at the substrate.

7. The method of claim 6, wherein the analysis of the first beam for determining the aberration comprises: Determine the contribution of the optical objective with a numerical aperture of approximately 0.5 or greater to the aberration.

8. The method of claim 6, wherein the analysis of the first beam comprises: The detector disposed downstream of the wedge system, the optical objective, and the substrate is used to analyze the first beam or a portion thereof.

9. The method according to claim 6, wherein: The detector is the first detector; The aforementioned part is the first part; A second portion of the first beam is sent to the second detector along a path excluding the optical objective and the substrate; as well as The analysis of the first beam also includes using the second detector to analyze the second portion of the first beam.

10. The method of claim 6, wherein the wedge system is disposed downstream of the optical objective and the substrate.

11. The method according to claim 6, wherein: The wedge system is a first wedge system disposed upstream of the substrate; The optical system includes a second wedge system, the second wedge system including a radiation-cured adhesive disposed between two wedges arranged downstream of the substrate; and Transmitting the first beam through the wedge system includes transmitting the first beam through both the first wedge system and the second wedge system.

12. The method of claim 1, further comprising assembling the first wedge and the second wedge such that the thickness of the radiation-cured adhesive is substantially constant.

13. The method of claim 12, wherein the thickness is about 50 micrometers or less.

14. The method of claim 1, wherein: The radiation-curing adhesive is responsive to ultraviolet wavelengths; and The second wavelength is within a wavelength range that includes the ultraviolet range.

15. The method of claim 1, wherein the first wavelength is within a wavelength range including the infrared range and the visible range.

Images