Contaminant analysis measurement system, lithographic apparatus, and method thereof

Abstract

An inspection system, lithographic apparatus, and inspection method are provided. An illumination inspection system includes an illumination system, a detection system, and a processing circuit. The illumination system generates a broadband beam and illuminates a surface of an object with an illumination broadband illumination beam. The illumination broadband beam has a continuous spectral range. The illumination detection system receives radiation scattered at the illumination surface and radiation scattered by structures near the illumination surface. The illumination detection system generates a detection signal based on an optical response to the illumination broadband illumination beam. The illumination processing circuit analyzes the illumination detection signal. The illumination processing circuit distinguishes between spurious signals and signals corresponding to defects on the illumination surface based on the illumination analysis. The illumination spurious signals are attenuated at least a portion of the illumination continuous spectral range.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 010,353, filed April 15, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to lithography systems, such as inspection systems for detecting contaminants on photomasks in lithography equipment. Background Technology

[0004] A lithography apparatus is a machine that applies a desired pattern onto a substrate (typically onto a target portion of the substrate). Lithography apparatuses can be used, for example, in the fabrication of integrated circuits (ICs). In this instance, a patterning apparatus (alternatively referred to as a mask or photomask) can be used to generate a circuit pattern to be formed on a single layer 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 radiation-sensitive material (resist) layer provided on the substrate. Typically, a single substrate will contain a network of adjacent target portions patterned sequentially. Known lithography 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.

[0005] During photolithography, different processing steps may require different layers to be formed sequentially on the substrate. For each pattern transfer process, the layer order is typically achieved by exchanging different masks according to the desired pattern for each layer.

[0006] Typical photolithography systems operate within sub-nanometer tolerances, involving patterns on a photomask and their transfer from the photomask to the wafer. Within the environment of a photolithography apparatus, highly dynamic processes occur, such as photomask switching, wafer switching, controlled gas flow, vacuum chamber wall venting, liquid distribution (e.g., photoresist coating), temperature variations, metal deposition, rapid movement of numerous actuated components, and structural wear. Over time, these dynamic processes introduce and accumulate contaminant particles within the photolithography apparatus. These contaminant particles on the photomask can introduce errors into the transferred pattern. Therefore, maintaining a contaminant-free photomask is desirable, enabling accurate pattern transfer onto the wafer with sub-nanometer accuracy while minimizing false positives. Summary of the Invention

[0007] Improved inspection techniques are needed to detect contaminants on critical optical components of lithography equipment.

[0008] In some embodiments, a system includes an irradiation system, a detection system, and processing circuitry. The irradiation system generates a broadband beam and irradiates the surface of an object with the broadband beam. The broadband beam has a continuous spectral range. The detection system receives radiation scattered at the surface and radiation scattered by structures near the surface. The detection system generates a detection signal based on the optical response to the broadband irradiation beam. The processing circuitry analyzes the detection signal. Based on the analysis, the processing circuitry distinguishes between spurious signals and signals corresponding to defects on the surface. Spurious signals are attenuated in at least a portion of the continuous spectral range.

[0009] In some embodiments, a method includes: irradiating a surface of an object with a broadband irradiation beam having a continuous spectral range; receiving scattered radiation at a detector, the scattered radiation including radiation scattered from the surface and radiation scattered by structures near the surface; generating a detection signal representing an optical response to the broadband irradiation beam based on the received scattered radiation; analyzing the detection signal; and distinguishing between spurious signals and signals corresponding to defects on the surface based on the analysis, wherein spurious signals are attenuated in at least a portion of the continuous spectral range.

[0010] In some embodiments, a photolithography apparatus includes an irradiation device, a projection system, and a measurement system. The measurement system includes an irradiation system, a detection system, and a processor. The irradiation system generates a broadband beam and irradiates the surface of an object with the broadband irradiation beam. The broadband beam has a continuous spectral range. The detection system receives radiation scattered at the surface and radiation scattered by structures near the surface. The detection system generates a detection signal based on the optical response to the broadband irradiation beam. The processing circuit analyzes the detection signal. The processing circuit distinguishes between spurious signals and signals corresponding to defects on the surface based on the analysis. Spurious signals are attenuated in at least a portion of the continuous spectral range.

[0011] Other features of this disclosure, as well as the structure and operation of the various embodiments, are described in detail below with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0012] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the disclosure and enable those skilled in the art to make and use the embodiments described herein.

[0013] Figure 1A A schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0014] Figure 1B A schematic diagram of a transmission lithography apparatus according to some embodiments is shown.

[0015] Figure 2 A more detailed schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0016] Figure 3 A schematic diagram of a photolithography unit according to some embodiments is shown.

[0017] Figure 4 A schematic diagram of a particle inspection system according to some embodiments is shown.

[0018] Figure 5 The signal reflected from the diffraction pattern is shown according to some embodiments.

[0019] Figure 6 The diagram illustrates signals reflected from particles and signals reflected from diffraction patterns according to some embodiments.

[0020] Figure 7A The spectral characteristics of the luminescence and detector are shown according to some embodiments.

[0021] Figure 7B The emission profile of a broadband light source and the spectral characteristics of a detector are shown according to some embodiments.

[0022] Figure 8 A particle inspection system according to some embodiments is shown.

[0023] Figure 9 A particle inspection system according to some embodiments is shown.

[0024] Figure 10A A particle inspection system with flat-top spectral sensitivity according to some embodiments is shown.

[0025] Figure 10B The spectral sensitivity of a particle inspection system according to some embodiments is shown.

[0026] Figure 11 A particle inspection system including multiple detectors is shown according to some embodiments.

[0027] Figure 12 A flowchart of an inspection method according to some embodiments is shown.

[0028] The features of this disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein the same reference numerals always identify corresponding elements. In the drawings, the same reference numerals generally indicate the same, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost numeral(s) of the reference numerals identify the drawing in which the reference numeral first appears. Unless otherwise indicated, the drawings provided in this disclosure should not be construed as being drawn to scale. Detailed Implementation

[0029] This specification discloses one or more embodiments of the features incorporated herein. The disclosed embodiments(s) are provided as examples. The scope of this disclosure is not limited to the disclosed embodiments(s). The claimed features are defined by the appended claims.

[0030] The described embodiments and references to "an embodiment," "embodiment," "example embodiment," etc., in the specification indicate that the described embodiments may include a particular feature, structure, or characteristic, but each embodiment may not necessarily include that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is to be understood that, whether explicitly described or not, it is within the knowledge of those skilled in the art to implement such a feature, structure, or characteristic in conjunction with other embodiments.

[0031] Spatial relative 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.

[0032] As used herein, the term "approximately" indicates the value of a given quantity that can vary based on a particular technique. Based on a particular technique, the term "approximately" can indicate the value of a given quantity that varies within, for example, 10% to 30% of that value (e.g., ±10%, ±20%, or ±30% of the value).

[0033] Embodiments of this disclosure can be implemented in hardware, firmware, software, or any combination thereof. Embodiments 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 means 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.). Further, 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 in fact caused by a computing device, processor, controller, or other means of executing firmware, software, routines, instructions, etc. The term "non-transient" may be used herein to characterize computer-readable media used for storing data, information, instructions, etc., with the sole exception of transient propagation signals.

[0034] However, it is beneficial to present an example environment in which the embodiments of this disclosure can be implemented before describing such embodiments in more detail.

[0035] Example lithography system

[0036] Figure 1A and 1B Schematic illustrations of lithography apparatus 100 and 100', respectively, to which embodiments of the present disclosure may be implemented, are shown. Lithography apparatus 100 and 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., a 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., a 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. Lithography 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., comprising one or more dies) C of the substrate W. In the lithography apparatus 100, the pattern forming apparatus MA and the projection system PS are reflective. In the lithography apparatus 100', the pattern forming apparatus MA and the projection system PS are transmissive.

[0037] 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.

[0038] 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, which may be fixed or movable as needed. 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.

[0039] 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.

[0040] The pattern forming apparatus MA can be transmissive (e.g., in...) Figure 1B In a lithography device 100') or a reflective type (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 two-state 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 to the radiation beam B reflected by the array of small mirrors.

[0041] 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 optical path by means of vacuum walls and vacuum pumps.

[0042] The lithography apparatus 100 and / or lithography apparatus 100' can be of the type having two (dual-stage) or more substrate stages WT (and / or two or more mask stages). In such a "multi-stage" machine, additional substrate stages WT can be used in parallel, or preparatory 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.

[0043] 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 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. As used herein, the term “immersion” does not mean that structures such as the substrate must be submerged in the liquid; rather, immersion simply means that the liquid is located between the projection system and the substrate during exposure.

[0044] Reference 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 handled by a beam delivery system BD (in [location missing]) including, for example, suitable directional mirrors and / or beam expanders. Figure 1B In the lithography system 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 integrated part of the lithography apparatus 100, 100', for example, when the source SO is a mercury lamp. The source SO, the irradiator IL, and (if necessary) the beam delivery system BD may be referred to as the radiation system.

[0045] The irradiator IL may include an adjuster AD (in) Figure 1B (In the middle), used to adjust the angular intensity profile of the radiation beam. Typically, at least the outer and / or inner radial ranges of the intensity profile 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 concentrator CO. Irradiator IL can be used to adjust the radiation beam B so as to have the desired uniformity and intensity profile in its cross-section.

[0046] Reference Figure 1AA 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.

[0047] Reference 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 passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto the 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 profile at the illumination system pupil IPU and passes through the mask pattern unaffected by diffraction at the mask pattern, creating an image of the intensity profile at the illumination system pupil IPU.

[0048] The projection system PS projects an image MP' of a mask pattern MP onto a photoresist layer coated on a substrate W, wherein the image MP' is formed by a diffracted beam generated from the marked pattern MP by radiation from an intensity profile. For example, the mask pattern MP may comprise an array of lines and spaces. Radiation diffraction located at the array and different from zero-order diffraction generates a deflected diffracted beam whose direction changes in a direction perpendicular to the lines. The non-diffracted beam (i.e., the so-called zero-order diffracted beam) passes through the pattern without any change in its propagation direction. The zero-order diffracted beam passes through the upper lens or upper lens group of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, and reaches the pupil conjugate PPU. The intensity profile portion in the plane of the pupil conjugate PPU and associated with the zero-order diffracted beam is an image of the intensity profile 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.

[0049] The projection system PS is arranged to capture not only the zeroth-order diffraction beam, but also the first-order or higher-order diffraction beams (not shown) by means of a lens or lens group L. In some embodiments, 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, the first-order diffraction beam interferes with the corresponding zeroth-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 depth of focus and tolerable exposure dose deviation). In some embodiments, astigmatism can be reduced by providing a radiating pole (not shown) in the opposite confinement of the illumination system pupil IPU. Further, in some embodiments, astigmatism can be reduced by blocking the zeroth-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.

[0050] With the aid of a second positioner PW and a position sensor IF (e.g., an interferometer, linear encoder, or 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).

[0051] 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 only to the 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 disposed on the mask MA, the mask alignment marks can be located between the dies.

[0052] The mask stage MT and patterning apparatus MA can be located within a vacuum chamber V, where an in-vacuum robot IVR can be used to move patterning apparatus such as masks into and out of the vacuum chamber. Alternatively, when the mask stage MT and patterning apparatus 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 need to be calibrated to smoothly transfer any payload (e.g., a mask) to a stationary motion base at the transfer station.

[0053] Photolithography equipment 100 and 100' can be used in at least one of the following modes:

[0054] 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 offset in the X and / or Y directions, allowing different target portions C to be exposed.

[0055] 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.

[0056] 3. In another mode, the support structure (e.g., mask stage) MT remains essentially 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 programmable mirror arrays.

[0057] Combinations and / or variations of the described usage patterns, or entirely different usage patterns, may also be adopted.

[0058] In some embodiments, the lithography apparatus can generate DUV and / or EUV radiation. For example, the lithography apparatus 100' can be configured to operate using a DUV source. In another example, 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.

[0059] Figure 2The 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 a very hot plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is created, for example, by a discharge that results in at least partially ionized plasma. To efficiently generate radiation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor may be required. In some embodiments, a plasma that excites tin (Sn) is provided to generate EUV radiation.

[0060] Radiation emitted by the thermal plasma 210 is transferred from the source chamber 211 to the collector chamber 212 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.

[0061] 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 passing through the collector CO may be reflected from a grating spectral filter 240 to be focused into a virtual source point IF. The virtual source point IF is generally referred to as the intermediate focus, and the source collector device is arranged such that the intermediate focus IF is located at or near an opening 219 in the enclosed structure 220. The virtual source point IF is an image of the radiative emission plasma 210. The grating spectral filter 240 is specifically used to suppress infrared (IR) radiation.

[0062] Subsequently, radiation passes through an illumination system IL, which may include a faceted field mirror assembly 222 and a faceted pupil mirror assembly 224, arranged to provide a desired angular distribution of the radiation beam 221 at the patterning apparatus MA and a desired uniformity of radiation intensity at the patterning apparatus MA. As the radiation beam 221 is reflected at the patterning apparatus MA held by the 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 held by a wafer stage or substrate stage WT.

[0063] More components than shown can typically be present in the illumination optics unit IL and the projection system PS. Depending on the type of lithography equipment, 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.

[0064] 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.

[0065] Exemplary photolithography unit

[0066] According to some embodiments, Figure 3 A lithography unit 300, sometimes also referred to as a lithography cell or cluster, is shown. 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. Typically, these include a spin coater SC for depositing a resist layer, a developer DE for developing the resist after exposure, 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 then delivers them to the loading rack 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.

[0067] Exemplary contaminant detection equipment

[0068] In some embodiments, a measurement system can be used to inspect an object to determine its cleanliness. Inspection techniques can be performed such that unwanted defects on a surface (e.g., the surface of a mask or substrate) are successfully detected while minimizing false detections (or false alarms). Inspection techniques may include optical inspection.

[0069] The terms “defect,” “flaw,” and “imperfection” are used in this document to refer to deviations or inconsistencies between the structure and specified tolerances. For example, a flat surface may have defects such as scratches, holes or grooves, foreign particles, or stains.

[0070] In the context of defects, the terms “foreign particle,” “contaminant particle,” “contaminant,” etc., may be used herein to refer to unexpected, atypical, undesirable, etc. (undesirable herein) particulate matter present in a region or on a surface not designed to tolerate the presence of undesirable particulate matter, or otherwise adversely affecting the operation of the device in which particulate matter is present. Some examples of foreign particles may include dust, stray photoresist, or other displaced material within the lithography apparatus. Examples of displaced materials may include steel, Au, Ag, Al, Cu, Pd, Pt, Ti, etc. Material displacement may be due to processes such as fabricating metal interconnects on a substrate and friction and impact on actuating structures. Contaminants may enter sensitive components (e.g., masks or substrates) in the lithography apparatus and increase the likelihood of errors occurring during the lithography process. Embodiments of this disclosure provide structures and functions for detecting defects on sensitive components of a lithography apparatus or process.

[0071] False alarms or misjudgments are detrimental to photolithography. For example, false alarm detection may unnecessarily prompt maintenance actions (such as mask replacement) or even suggest discarding perfectly compliant masks, thus slowing down production. Several solutions are being considered in the industry to improve the accuracy and precision of particle size measurements; however, such solutions (e.g., multi-directional illumination, multi-imaging techniques involving polarization) may not provide sufficient attenuation of the false alarm rate because the pattern printed on the mask is not known. Embodiments of this disclosure provide structures and functions for reducing instances or eliminating false alarms.

[0072] Figure 4 A schematic diagram of a particle inspection system 400 according to some embodiments is shown. In some embodiments, the particle inspection system 400 may be implemented in a photolithography apparatus. The particle inspection system 400 may include an irradiation system 402, a detection system 404, and a processor 406. The irradiation system 402 may include a radiation source 408. The irradiation system 402 may include one or more radiation adjustment elements 410 (e.g., any one of a polarizer, wavelength filter, focusing element, beam splitter, beam combiner, etc.).

[0073] The particle inspection system 400 may include a housing 412. The housing 412 may include one or more compartments. The housing 412 may include windows 414 and 416.

[0074] However, before describing embodiments of the particle inspection system 400 in more detail, it is beneficial to present examples of objects that can be inspected using the particle inspection system 400. In some embodiments, the object may be a mask 418. The mask 418 may include pattern features 420. Pattern features 420 may include, for example, product and alignment mark patterns to be transferred onto a substrate via a photolithography process. Foreign particles 422 on the surface 424 of the mask 418 may negatively affect photolithography because when foreign particles are trapped between the mask 418 and the mask stage, they may print through or otherwise distort the shape of the mask 418, or, when trapped between them, cause damage to the mask or mask stage surface, or transfer to the mask stage, thereby contaminating it and potentially contaminating or damaging other masks loaded on the same stage.

[0075] In some embodiments, radiation source 408 may generate a radiation beam 426 to illuminate mask 418. Radiation beam 426 may include a broadband beam spanning a continuous spectral range (e.g., a wide bandwidth). In other words, radiation source 408 may be a white light source. For example, the continuous spectral range may cover the visible spectrum, ultraviolet-visible spectrum, or ultraviolet-visible-infrared spectrum. One or more radiation adjustment elements 410 (e.g., wavelength filters) may be used to select the wavelength to be used to illuminate mask 418. Additionally or alternatively, radiation source 408 may include two or more broadband radiation sources to generate different portions of the broadband spectrum (e.g., a first radiation source from approximately 400 nm to approximately 900 nm in the visible spectrum and a second radiation source from approximately 225 nm to approximately 400 nm in the UV spectrum). Radiation source 408 includes broadband sources such as, for example, an incandescent light bulb, a natural source (e.g., sunlight), a light-emitting diode (LED) emitting a broadband spectrum, a tunable laser, a xenon lamp, or a supercontinuum laser.

[0076] In some embodiments, the detection system 404 may include a sensor element 428 and a focusing element 430 (e.g., an objective lens or lens system). In some embodiments, the detection system 404 may be a single-unit photodetector (no more, as it may not be able to resolve the image), in which case the sensor element 428 may be a photodiode. However, a single-unit photodetector may be necessary when size, ease of assembly, and / or cost efficiency are significant factors. In one example, a region of interest on surface 424 of mask 418 can be scanned. The detection system 404 may have a detection range from ultraviolet to near-infrared.

[0077] In some embodiments, the detection system 404 may be an image capture device or a multi-unit photodetector (e.g., a two-dimensional array of photodetectors). Sensor element 428 may include a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS). The detection system 404 may include multiple sensor elements or detectors to cover the continuous spectral range and / or extended field of view of the detection system 405. For example, the multiple sensor units may include GaN detectors and InGaAs detectors. The detection system 404 may have a spectral range that overlaps with the continuous spectral range.

[0078] In some embodiments, the detection system 404 may be a wavelength-sensitive detection system. The detection system 404 may include a spectrometer or a color camera. Inspection systems using wavelength-sensitive detection systems... Figure 8 It is shown and described in the text.

[0079] In some embodiments, the detection system 404 may be a wavelength-insensitive detection system. Inspection systems using wavelength-insensitive detection systems in... Figure 9 It is shown and described in the text.

[0080] In some embodiments, the detection system 404 may receive radiation scattered at surface 424 and radiation scattered by structures (e.g., pattern features 420) near the surface, represented by detected radiation 432. The detected radiation 432 scattered at surface 424 may include radiation scattered by particles 422 placed on surface 424. The detection system 404 may generate a detection signal based on the received radiation. The detection signal may include information about the received radiation, such as intensity, phase, etc.

[0081] Processor 406 can receive and analyze detection signals. Processor 406 can distinguish between spurious signals and signals corresponding to the presence of particles 422 on surface 424 based on the analysis and intensity profile of the radiation beam or irradiation beam. That is, particle inspection system 400 is able to distinguish between two types of detected radiation: (1) radiation associated with particles 422 (e.g., actual detection of foreign particles) and (2) radiation associated with structures other than particles 422 (e.g., false alarms caused by spurious signals from radiation scattered from pattern features 420).

[0082] In the context of radiation detection, terms such as “false,” “pseudo,” “ghost,” and “parasite” can be used to describe signals associated with radiation that do not interact with foreign particles.

[0083] In some embodiments, the distinction performed by processor 406 may include determining the binary presence (e.g., presence or absence) of particle 422. In some embodiments, the distinction performed by processor 406 may include determining the confidence level (e.g., percentage probability) of the potential presence of particle 422. Processor 406 may present the detection results to a user of particle inspection system 400 (e.g., on a computer monitor). The detection results may include any of, for example, the presence, location and / or size of particle 422, captured images, spectral analysis, etc.

[0084] Although specific embodiments have been described in the context of detecting foreign particles (e.g., particle 422), the embodiments described herein are not limited to particulate contamination detection. In some embodiments, the particle inspection system described herein can generally detect defects such as scratches, holes or grooves, foreign particles, stains, etc. It is desirable to detect all types of defects that pose a risk of disrupting the photolithography process.

[0085] Figure 5 The signal reflected from the diffraction pattern is shown according to some embodiments.

[0086] One aspect is discussed here. An illumination beam 502 is incident at an angle β onto a photolithographic patterning apparatus 504 (e.g., a photomask). The photolithographic patterning apparatus 504 includes a first diffraction structure 510 and a second diffraction structure 516 spaced apart by a distance R. The illumination beam 502 is refracted at a first surface 506 of the photolithographic patterning apparatus 504 (e.g., the photomask). The refracted light 508 is redirected by the first diffraction structure 510 and travels along path 512 toward the first surface 506. The light is reflected at the interface glass-air towards the second diffraction structure 516. The reflected light follows path 514 and is redirected by the second diffraction structure 516 toward the first surface 506. The reflected light exits the photolithographic patterning apparatus 504 via path 520 and enters the field of view (FOV) 518 of the inspection system of the inspection system. The reflected light illustrates an exemplary generation of a ghost signal. However, other mechanisms, such as multiple reflections and diffractions in a plane or three-dimensional reflections / refractions, can also generate ghost signals.

[0087] Reflections in light patterns such as those along paths 508, 512, 514, and 520 can lead to false detections, where a detector with FOV 518 can determine the presence of particles, when they are not present, or the false detection of multiple particles.

[0088] In one aspect, in order to couple the illumination beam 502 into the detection system via paths (508, 512, 514, and 520), the light must pass through a series of two diffraction events and at least one reflection from the glass-air interface. Two diffraction structures separated by a distance R are printed on a photolithographic patterning apparatus (e.g., a photomask). The period between the diffraction structures (e.g., the period between diffraction structures 510 and 516) is configured for discrete illumination wavelengths and directions to ensure that the light follows paths 508, 512, 514, and 520. In other words, the reflections that lead to false alarms may be wavelength-dependent (wavelength-sensitive) and can be attenuated for other wavelengths. It should be noted that multiple diffraction orders may satisfy the coupling condition due to the cyclic nature of diffraction. However, the reflections caused by the first few diffraction orders are likely the most significant, as diffraction efficiency typically decreases with increasing order.

[0089] In one aspect, a similar mechanism is responsible for false alarms when inspecting the front side of the mask (in which case light propagates through the air gap between the mask pattern and the mask, rather than through the glass).

[0090] Figure 6 The diagram illustrates signals reflected from particles according to some embodiments, as well as signals reflected / scattered from a diffraction pattern in a particle inspection system 600. In some aspects, the irradiation system may have limited control over how the irradiation light penetrates the lithographic pattern forming apparatus and the surface pattern cavity.

[0091] For example, such as Figure 6 As illustrated, a photolithography pattern forming apparatus 602 receives an illumination beam 604 for inspection purposes to check for the presence of particles 606 on its surface. The photolithography pattern forming apparatus may include an illumination system 616, which includes a light source 614. The illumination system may generate the illumination beam 604. The particles 606 may be located on the glass side of the photolithography pattern forming apparatus 602, and a first diffraction pattern (structure) 608 and a second diffraction pattern 610 may be located on the front side of the photolithography pattern forming apparatus 602. In one aspect, light entering the photolithography pattern forming apparatus 602 also reaches the first diffraction pattern 608 on the front side of the photolithography pattern forming apparatus and is reflected back to a detection system 612. The detection system 611 may include a sensor element 618. The illumination beam 604 irradiates the diffraction pattern, and the diffracted light, after reflection from the back surface, is ultimately redirected to the detection system 612 and detected as having a contaminant (false alarm).

[0092] In some embodiments, the irradiation beam 604 may have Figure 7A The diagram shows the narrow band profile. Figure 7AThe emission profile 702 and detector spectral characteristic profile 704 according to some embodiments are shown. The emission profile 702 is used for having a wavelength λ. c A narrow-band light source. The luminous profile 702 is in λ... c Centered on. Figure 6 The detection system 612 may have a spectral characteristic profile 704. The detection system 611 may have a detection range from a first wavelength λ1 to a second wavelength λ2.

[0093] Refer to the return Figure 6 The signal from particle 602 can be described as follows:

[0094]

[0095] Among them, I particle The captured light intensity is determined by particle scattering, E(λ) is the spectral emission of the light source 614 or the illumination system, QE(λ) is the quantum efficiency of the imaging system 612, and G... d It is the gain of the detection system, and R p These are parameters characterizing the spectral and directional scattering / diffraction efficiency of 606 particles. False alarm signals (i.e., ghosting, stray light) can be described as follows:

[0096]

[0097] Among them, I ghost The captured light intensity is scattered by the grating, E(λ) is the spectral emission of the light source 614, QE(λ) is the quantum efficiency of the imaging system 612, and G... d It is the gain of the detection system, R g It is a parameter characterizing the spectral and directional scattering / diffraction efficiency of the reflection from the grating and the glass-air interface. In other examples, the illumination beam 604 can have a broadband profile, and the detection system can have narrowband detection. The signal from particle 602 and the false alarm signal can also be described by equations (1) and (2), respectively.

[0098] Based on available data, parameter R p The value can be estimated to be between approximately 10⁻⁵ and approximately 10⁻⁷. In one aspect, the efficiency of the two-dimensional diffraction grating is approximately 10⁻², therefore, considering the two diffraction events and one refraction at the glass-air interface, R… g It can be estimated to be approximately 10⁻⁶. Since the integral ranges of equations (1) and (2) are equal, the stray light generated by the mask pattern can, in the worst-case scenario (particle efficiency of 10⁻⁷), be an order of magnitude brighter than the light scattered / diffracted by the particles. To avoid stray light, the spectral range of the signal integral is chosen, such as when it is impossible to use... Figure 5 The presented mechanisms are coupled.

[0099] In one aspect, the irradiation beam 604 is a broadband irradiation beam with a continuous spectral range, such as... Figure 7B As shown.

[0100] Figure 7B Broadband light sources (e.g.) according to some embodiments are shown. Figure 4 The luminous profile 710 of the illumination system 402). Figure 6 The detection system 612 has a spectral characteristic profile 708. The detection system 611 may have a detection range from a first wavelength λ1 to a second wavelength λ2. The emission profile 710 or spectrum includes at least the wavelength range from the first wavelength λ1 to the second wavelength λ2.

[0101] Refer to the return Figure 6 The strength of the signal from particle 602 can be described as follows:

[0102]

[0103] Intensity is driven by the integration range, i.e., the spectral range of the light source and the spectral sensitivity of the detector. The intensity of stray light or ghosting is described by the following...

[0104]

[0105] Where λ c is the wavelength corresponding to the optimized wavelength, and ∧ is a parameter associated with the mutual spacing between the first diffraction pattern 608 and the second diffraction pattern 610. The intensity of the stray light signal is driven by the diffraction grating profile and the mutual spacing between the first diffraction pattern 408 and the second diffraction pattern 610. Therefore, the brightness of the diffraction grating profile can be determined by the efficiency R of the diffraction structure. g Driven. Intensity can be in the form of λ. c Defined within the narrowband wavelength range ±δ∧ centered on the sphere.

[0106] Figure 8 A particle inspection system 800 according to some embodiments is shown.

[0107] In some aspects, the particle inspection system 800 includes an illumination system 802 and a detection system 804. The illumination system 802 may include a radiation source 806. In some embodiments, the radiation source 806 may generate a broadband radiation beam 808 to illuminate a mask (object) 810. The mask 810 may include particles 816 and a diffraction pattern 822. The detection system 804 includes a wavelength-sensitive detector 824 (or sensing element). The detection system 804 determines the intensity profile of the scattered radiation as a function of wavelength. The scattered radiation includes scattered radiation from the particles 816 and stray light signals 818 (ghost signals).

[0108] Figure 812 shows the intensity profile of the stray light signal 818 (e.g., the signal generated due to the diffraction pattern 820). Figure 814 shows the intensity profile of the particle signal (i.e., due to the light scattered from the particle 816).

[0109] The signal generated by the light scattered from the particles 816 on surface 826 has an intensity profile corresponding to the intensity profile of the radiation source 806. The stray light 818 redirected by the diffraction pattern 822 has a discrete quantized spectral content, as shown in 812.

[0110] In some aspects, the particle inspection system 800 also includes a processor 820. The processor 820 of the particle inspection system 800 can receive an intensity profile of scattered radiation from the detection system 804. The processor 820 can compare the intensity profile of the scattered radiation with the intensity profile of a broadband illumination beam 808 generated by the illumination system 802. In one example, the processor 820 can normalize both the intensity profile of the scattered radiation and the intensity profile of the broadband illumination beam 808. The processor 820 can then compare the shape of the normalized intensity profile of the scattered radiation with the normalized intensity profile of the broadband illumination beam 808. In response to determining that the shape of the normalized intensity profile of the scattered radiation matches the normalized intensity profile of the broadband illumination beam, the processor 820 can determine that the detected radiation is generated by particles 816. In response to determining that the shape of the normalized distribution of the scattered radiation does not match the normalized intensity profile of the broadband illumination beam, the processor 820 determines that the scattered radiation is a false alarm. The signal is then discarded. In some embodiments, the processor 820 may determine the confidence level of the potential presence of particle 816 based on a comparison (e.g., based on a matching score) between the normalized intensity profile of the broadband illumination beam 808 and the normalized intensity profile of the scattered radiation.

[0111] Figure 9 A particle inspection system 900 according to some embodiments is illustrated. The particle inspection system 900 includes an illumination system 902 and a detection system 904. The illumination system 902 may include a radiation source 906. In some embodiments, the radiation source 906 may generate a broadband radiation beam 908 (i.e., a broadband illumination beam) to illuminate a mask (or object) 910. The mask 910 may include particles 916 and a diffraction pattern 922. The detection system 904 includes a wavelength-insensitive detector 924 (or a monochromatic detector). Scattered radiation includes scattered radiation from the particles 916 and stray light signals 918.

[0112] Figure 912 shows the intensity profile of the ghost signal 912. Figure 914 shows the intensity profile of the particle signal. As shown in Figure 914, the intensity of the signal from particle 916 increases linearly with the increase of the spectral integration range. In other words, the intensity of the signal corresponding to the scattering from particle 916 on surface 926 of mask 910 is proportional to the bandwidth of the continuous spectral range of radiation beam 908.

[0113] The particle inspection system also includes a processor 920. The processor 920 receives the intensity of the scattered radiation from the detection system 904.

[0114] In one aspect, the illumination system 902 can perform time-based filtering on a broadband illumination beam, or sequentially scan the wavelengths of the illumination system 902 across a continuous spectral range. In other words, the radiation beam 908 (illumination beam) can be tuned to a specific narrowband wavelength (a subrange of the continuous spectral range). In some embodiments, one or more spectral filters can be used to select one or more wavelengths of the radiation source. For example, filter 928 can be included in the illumination system 902 to filter the broadband radiation beam 908. Thus, a series of images can be acquired over different ranges of spectral integration. The signal generated by the particles 916 can be continuously detected during tuning. Conversely, the signal from the diffraction pattern 922 may not be continuously detected during tuning due to the wavelength dependence of the signal described previously herein. In one example, images can be continuously acquired, and the images are analyzed over time to identify changes in the image and signal. In another example, the signal is integrated over the scan time. The intensities at different regions are then compared to distinguish between particle regions and artifact regions (artifact signals). Due to integration over a wide spectral range, the particle signal steadily increases and continues to rise, while the stray light signal (i.e., the artifact signal) only increases in discrete frequency bands. In other words, the intensity ratio of particles to artifacts is increased. The image of particle 916 is qualitatively improved.

[0115] Filter 928 may include two or more narrowband filters. For example, the illumination system includes one or more wavelength-selective filters. In one aspect, filter 918 may be a tunable filter having a wavelength tuning range corresponding to the spectral range of detection system 904. In one aspect, multiple tunable filters, each with a different wavelength tuning range, are used. Processor 920 controls one or more tunable bandpass filters arranged to filter the broadband radiation beam 908.

[0116] The tunable filter can be a liquid crystal tunable filter, an acousto-optic tunable filter, or the like, as understood by one of ordinary skill in the art.

[0117] In one aspect, processor 920 analyzes changes in the optical response of detection system 904 in response to a filter. For example, processor 920 can compare the intensity of detected radiation at various wavelengths. In response to determining that the intensity of the detected radiation changes in response to the filter (e.g., weakens or decreases when the wavelength is changed), processor 920 can determine that the detected radiation originates from stray light or artifact signals. Processor 920 can discard signals associated with stray light. In response to determining that the intensity of the detected radiation remains substantially constant in response to the filter, processor 920 can determine that the detected radiation originates from light scattered / diffracted by particle 916.

[0118] In one aspect, the radiation source 906 includes a tunable light source or one or more light sources that can be triggered sequentially. When the light source is tunable or during the sequential triggering of one or more light sources, changes in the optical response of the detection system 904 are analyzed as previously described herein. The tunable light source or one or more light sources may be used in conjunction with a tunable filter or without a tunable filter.

[0119] In some embodiments, processor 920 can analyze the detected signal. The analysis may include frequency analysis. Processor 920 can determine the nature of the detected radiation, such as, for example, the modulation frequencies present in the detected radiation and the amplitude and / or phase corresponding to each modulation frequency.

[0120] Figure 10A A particle inspection system 1000 according to some embodiments is shown. The particle inspection system 1000 includes an illumination system 1002 and a detection system 1004. The illumination system 1002 may include a radiation source 1006. In some embodiments, the radiation source 1006 may generate a broadband radiation beam 1008 to illuminate an object 1010. The illumination system 1002 may include one or more radiation adjustment elements 1012 (e.g., any one of a polarizer, wavelength filter, focusing element, beam splitter, beam combiner, etc.). Light emitted by the radiation source 1006 at different wavelengths may have different intensities (e.g., light emitted at different wavelengths). Figure 7B (Distribution 710). Furthermore, the quantum efficiency of the detection system 1004 can vary with wavelength. For example, the detection system 1004 can have a lower quantum efficiency for wavelengths close to the detection range limit (e.g., at the first wavelength λ1, and at the second wavelength λ2).

[0121] In one embodiment, the effective light sensitivity of the particle inspection system 1000 is wavelength-independent. In other words, the particle inspection system 1000 has flat-top spectral sensitivity. The spectral sensitivity 1018 of the particle inspection system 1000 is as follows: Figure 10BAs shown. Therefore, regardless of the operating wavelength of the particle inspection system 1000, the particle inspection system can have substantially equal sensitivity. Thus, the intensity of the scattered signal detected from particles on the surface of object 1010 is constant across the continuous spectral range. The intensity of the artifact signal at a specific wavelength is comparable to the intensity of the scattered signal detected from the particles at that specific wavelength. Therefore, the artifact signal appears darker compared to the overall intensity of the scattered signal detected from the particles.

[0122] In one aspect, the illumination system 1002 may include a spectral filter 1014 configured to match the emission spectrum of the radiation source 1006 with the quantum efficiency of the detection system 1004. The spectral filter 1014 may be a custom-designed absorptive filter / gain filter.

[0123] Alternatively or additionally, a spectral filter can be inserted into the detection path 1016.

[0124] The spectral sensitivity of a particle inspection system is driven by the application's ability to detect the system's minimum acceptable quantum efficiency (QE). Furthermore, spectral sensitivity decreases with increasing spectral range.

[0125] Figure 11 A particle inspection system 1100 according to some embodiments is shown.

[0126] In one aspect, the particle inspection system 1100 includes an irradiation system 1102 and a detection system 1104. The irradiation system 1102 may include a radiation source 1106. In some embodiments, the radiation source 1106 may generate a radiation beam 1108 to irradiate an object 1110. The detection system 1104 directs scattered radiation 1124 to a plurality of detectors. Each of the plurality of detectors is sensitive to a different wavelength (or a different subrange of wavelength).

[0127] For example, detection system 1104 may include a first detector 1114, a second detector 1116, and a third detector 1118. The first detector 1114, the second detector 1116, and the third detector 1118 may have different detection ranges. The first detector 1114 may be sensitive to light in a first wavelength range and insensitive to radiation in a second and third wavelength range associated with the second detector 1116 and the third detector 1118. Detection system 1104 may include radiation redirection elements 1120, 1122, configured to redirect a portion of scattered radiation 1124 to each of the first detector 1114, the second detector 1116, and the third detector 1118.

[0128] Figure 12A flowchart of an inspection method 1200 according to some embodiments is shown. It should be understood that the operations shown in method 1200 are not exhaustive, and other operations may be performed before, after, or between any of the illustrated operations. In various embodiments of this disclosure, the operations of method 1200 may be performed in a different order and / or using means different from those described as exemplary.

[0129] Operation 1202 includes irradiating the surface of an object with a broadband irradiation beam having a continuous spectral range (e.g., a radiation beam 426 generated by radiation source 408). For example, the surface of the object may be a photolithographic pattern forming apparatus or... Figure 4 The back side of the mask 418.

[0130] Operation 1204 includes receiving scattered radiation at a detector. Scattered radiation includes radiation scattered from the surface and radiation scattered by structures near the surface. This can be achieved by receiving radiation from a photolithographic patterning apparatus or... Figure 4 The scattered light is obtained by observing the particles or contaminants found on the back side of the mask 418.

[0131] Operation 1206 includes based on a detection system (e.g.) Figure 4 The scattered radiation received at the detection system 404) is used to generate a detection signal representing the optical response to the broadband illumination signal.

[0132] Operation 1208 includes using processing circuitry (e.g.) Figure 4 The processor 406 of the particle inspection system 400 analyzes the detection signal.

[0133] Operation 1210 includes analyzing and distinguishing between spurious signals and defects (e.g., on the surface of the photolithographic pattern forming apparatus) based on analysis. Figure 4 The signal of particle 422). The spurious signal is attenuated in at least a portion of the continuous spectral range previously described herein.

[0134] In some embodiments, modifications to the broadband illumination beam may be performed to produce a uniform spectral response across a continuous spectral range. For example, Figure 10A The filter 1014 can be used to obtain Figure 10B The uniform spectral response shown is 1018.

[0135] In some embodiments, there may be a determination operation that takes the intensity profile of the scattered radiation as a function of wavelength. For example, a wavelength-sensitive detector may be used.

[0136] In some embodiments, there may be a distinguishing operation that includes comparing the intensity profile of scattered radiation across a continuous spectral range with the intensity profile of a broadband irradiation beam.

[0137] In some embodiments, filtering of a broadband illumination beam over a continuous spectral range may be present when the detector is a wavelength-insensitive detector. For example, Figure 9 The filter 920 can be used to tune the wavelength of the broadband radiation beam 908 across a continuous spectral range of the radiation source 906 or to sequentially scan the wavelength of the radiation beam 908. Furthermore, analytical operations can be provided to detect changes in the optical response in response to the filter.

[0138] In some embodiments, there may be a guided operation of scattered radiation to a plurality of single-wavelength detectors, each of which is sensitive to a wavelength different from the others. The detection signals from each of the single-wavelength detectors can be analyzed to distinguish between spurious signals and signals corresponding to defects. For example, signals detected by two or more single-wavelength detectors may correspond to signals from defects.

[0139] In some embodiments, the measurement system described herein can be implemented within a larger system, such as a lithography apparatus.

[0140] The embodiments can also be described using the following terms:

[0141] 1. An inspection system, comprising:

[0142] The irradiation system is configured to generate a broadband irradiation beam with a continuous spectral range and to irradiate the surface of an object with the broadband irradiation beam.

[0143] The detection system is configured to receive radiation scattered at the surface and radiation scattered by structures near the surface, and to generate a detection signal based on the optical response to a broadband illumination beam; and the processing circuit is configured to...

[0144] Analyze the detection signal, and

[0145] Analysis is used to distinguish between spurious signals and signals corresponding to defects on the surface, wherein the spurious signals are attenuated in at least a portion of the continuous spectral range.

[0146] 2. The inspection system according to item 1 also includes:

[0147] Optical devices are configured to modify the broadband illumination beam to produce a uniform response of the detection system across the continuous spectral range of the illumination system.

[0148] 3. The inspection system according to clause 1, wherein the detection system is a wavelength-sensitive detection system and is further configured to determine the intensity profile of the scattered radiation as a function of wavelength.

[0149] 4. The inspection system according to clause 3, wherein the distinction includes comparing the intensity profile of scattered radiation across a continuous spectral range with the intensity profile of a broadband irradiation beam.

[0150] 5. The inspection system according to clause 4, wherein the intensity profile of the signal corresponding to a defect on the surface corresponds to the intensity profile of the broadband irradiation beam.

[0151] 6. The inspection system according to clause 1, wherein the detection system is a wavelength-insensitive detection system.

[0152] 7. According to the inspection system in clause 6, wherein

[0153] The illumination system is also configured to perform time-based filtering of the broadband illumination beam across a continuous spectral range; and

[0154] The analysis includes an analysis of the changes in the optical response to the filter.

[0155] 8. The inspection system according to clause 7, wherein the irradiation system includes one or more wavelength selective filters.

[0156] 9. The inspection system according to clause 7, wherein the irradiation system further includes a tunable filter.

[0157] 10. The inspection system according to clause 6, wherein the intensity of the signal corresponding to a defect on the surface is proportional to the bandwidth of the continuous spectral range.

[0158] 11. The inspection system according to clause 1, wherein the detection system is further configured to direct scattered radiation to a plurality of single-wavelength detectors, each of the plurality of single-wavelength detectors being sensitive to a wavelength different from the other single-wavelength detectors.

[0159] 12. The inspection system according to clause 1, wherein the continuous spectral range of the irradiation system corresponds to the spectral range of the detection system.

[0160] 13. An inspection method, comprising:

[0161] Irradiate the surface of an object with a broadband irradiation beam having a continuous spectral range;

[0162] The scattered radiation is received at the detector, which includes radiation scattered from the surface and radiation scattered by structures near the surface;

[0163] Based on the received scattered radiation, a detection signal representing the optical response to the broadband illumination signal is generated.

[0164] Analyze and detect signals; and

[0165] Analysis is used to distinguish between spurious signals and signals corresponding to defects on the surface, wherein the spurious signals are attenuated in at least a portion of the continuous spectral range.

[0166] 14. The inspection method according to clause 13 also includes:

[0167] Modify the broadband illumination beam to produce a uniform response across a continuous spectral range.

[0168] 15. The inspection method according to clause 13, wherein the detector is a wavelength-sensitive detector, and the method further includes determining the intensity profile of the scattered radiation as a function of wavelength.

[0169] 16. The inspection system according to clause 15, wherein the distinction includes comparing the intensity profile of scattered radiation across a continuous spectral range with the intensity profile of a broadband irradiation beam.

[0170] 17. The inspection method according to clause 13, wherein the detector is a wavelength-insensitive detector.

[0171] 18. The inspection method according to clause 17 also includes:

[0172] Time-based filtering of broadband illumination beams across a continuous spectral range; and

[0173] The optical response changes in response to the filtering analysis.

[0174] 19. The inspection method according to clause 11 also includes:

[0175] The scattered radiation is directed to multiple single-wavelength detectors, each of which is sensitive to a different wavelength than the other detectors.

[0176] 20. A photolithography apparatus, comprising:

[0177] An irradiation device configured to irradiate the pattern of a pattern forming apparatus;

[0178] A projection system is configured to project an image of a pattern onto a substrate; and

[0179] Measurement system, the measurement system including

[0180] The irradiation system is configured to generate a broadband irradiation beam with a continuous spectral range, and to irradiate the surface of the object with the broadband irradiation beam.

[0181] The detection system is configured to receive radiation scattered at the surface and radiation scattered by structures near the surface, and to generate a detection signal based on the optical response to a broadband illumination beam.

[0182] The processing circuit is configured as follows:

[0183] Analyze the detection signal, and

[0184] Analysis is used to distinguish between spurious signals and signals corresponding to defects on the surface, wherein the spurious signals are attenuated in at least a portion of the continuous spectral range.

[0185] 21. An inspection system, comprising:

[0186] An irradiation system is configured to generate an irradiation beam and irradiate the surface of an object with the irradiation beam having a wavelength that scans the spectrum across a continuous spectral range;

[0187] The detection system is configured to receive radiation scattered at a surface and radiation scattered by structures near the surface, and to generate a detection signal based on the received scattered radiation; and

[0188] The processing circuit is configured as follows:

[0189] Analyze the time values ​​of the intensity of the detected signal across a continuous spectral range, and

[0190] Analysis is used to distinguish between spurious signals and signals corresponding to defects on the surface, wherein the spurious signals are attenuated in at least a portion of the continuous spectral range.

[0191] While specific references may be made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein can have other applications, such as the fabrication of integrated optical systems, the guidance and inspection of patterns for magnetic domain memories, 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 synonymous with the more general terms “substrate” or “target portion,” respectively. The substrate referred to herein may be processed before or after exposure, for example in a track cell (a tool typically used to apply a resist layer to the substrate and develop the exposed resist), a measurement cell, and / or an inspection tool. Where applicable, this disclosure may be applied to such and other substrate processing tools. Furthermore, the substrate may be processed more than once, for example to create a multilayer IC, such that the term “substrate” as used herein may also refer to a substrate that already contains multiple processed layers.

[0192] While the use of embodiments of this disclosure may have been specifically referenced above in the context of optical lithography, it is to be understood that this disclosure can be used in other applications, such as imprint lithography, and is not limited to optical lithography where the context permits. In imprint lithography, the morphology in the 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.

[0193] It should be understood that the wording or terminology used herein is for descriptive purposes and not for limitation, and that the wording or terminology of this disclosure is to be interpreted by those skilled in the art in light of the teachings herein.

[0194] As used herein, the term "substrate" describes the material to which the material layer is added. In some embodiments, the substrate itself may be patterned, and the material added on top of it may also be patterned, or may remain unpatterned.

[0195] While specific references may be made herein to the use of devices and / or systems according to this disclosure in the manufacture of ICs, it should be clearly understood that such devices and / or systems have many other possible applications. For example, they can be used in the manufacture of integrated optical systems, the guidance and detection of patterns for magnetic domain memories, LCD panels, thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms “mask,” “wafer,” or “die” herein should be considered to be replaced by the more general terms “mask,” “substrate,” and “target portion,” respectively.

[0196] Although specific embodiments of this disclosure have been described above, it is to be understood that this disclosure may be practiced in ways other than those described. This description is not intended to limit this disclosure.

[0197] It should be understood that the Detailed Description section, rather than the Summary and Abstract section, is intended to be used for interpreting the terms. The Summary and Abstract section may state one or more, but not all, exemplary embodiments of this disclosure as conceived by the inventors, and is therefore not intended to limit the disclosure and the appended terms in any way.

[0198] The present disclosure has been described above using functional building blocks that illustrate implementations 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.

[0199] The foregoing description of the specific embodiments will fully demonstrate the generality of this disclosure. By applying knowledge in the art, others can readily modify and / or adapt such specific embodiments to various applications without excessive experimentation or departing from the general concepts of this disclosure. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended to be within the meaning and scope of equivalence to the disclosed embodiments.

[0200] The breadth and scope of the protected subject matter should not be limited by any of the exemplary embodiments described above, but should be defined only by the following claims and their equivalents.

Claims

1. An inspection system, comprising: An irradiation system is configured to generate a broadband irradiation beam with a continuous spectral range and to irradiate the surface of an object with the broadband irradiation beam. The detection system is configured to receive radiation scattered at the surface and radiation scattered by structures near the surface, and to generate a detection signal based on the optical response to the broadband illumination beam. as well as The processing circuit is configured as follows: Analyze the spectral characteristics of the detected signal within the continuous spectral range, and Based on the analysis, a distinction is made between pseudo-signals corresponding to one or more internal reflections from the structure and defect signals corresponding to defects on the surface. The pseudo signal is attenuated in at least a portion of the continuous spectral range relative to other portions of the continuous spectral range.

2. The inspection system according to claim 1 further includes: Optical devices are configured to modify the broadband illumination beam to produce a uniform response of the detection system across the continuous spectral range of the illumination system.

3. The inspection system of claim 1, wherein the detection system is a wavelength-sensitive detection system and is further configured to determine the intensity profile of the scattered radiation as a function of wavelength.

4. The inspection system of claim 3, wherein the differentiation comprises comparing the intensity profile of the scattered radiation across the continuous spectral range with the intensity profile of the broadband irradiation beam.

5. The inspection system of claim 4, wherein the intensity profile of the defect signal corresponds to the intensity profile of the broadband irradiation beam.

6. The inspection system according to claim 1, wherein the detection system is a wavelength-insensitive detection system.

7. The inspection system according to claim 6, wherein The irradiation system is also configured to temporally filter the broadband irradiation beam across the continuous spectral range; and The analysis includes an analysis of the changes in the optical response in response to the filter light.

8. The inspection system of claim 7, wherein the irradiation system comprises one or more wavelength selective filters.

9. The inspection system of claim 7, wherein the irradiation system further comprises a tunable filter.

10. The inspection system of claim 6, wherein the intensity of the defect signal is proportional to the bandwidth of the continuous spectral range.

11. The inspection system of claim 1, wherein the detection system is further configured to direct the scattered radiation to a plurality of single-wavelength detectors, each of the plurality of single-wavelength detectors being sensitive to a wavelength different from the other single-wavelength detectors.

12. The inspection system of claim 1, wherein the continuous spectral range of the irradiation system corresponds to the spectral range of the detection system.

13. An inspection method, comprising: Irradiate the surface of an object with a broadband irradiation beam having a continuous spectral range; Scattered radiation is received at the detector, including radiation scattered from the surface and radiation scattered by structures near the surface; Based on the received scattered radiation, a detection signal representing the optical response to the broadband illumination beam is generated; Analyze the spectral characteristics of the detected signal within the continuous spectral range; as well as Based on the analysis, a pseudo signal corresponding to one or more internal reflections from the structure and a defect signal corresponding to a defect on the surface are distinguished, wherein the pseudo signal of at least a portion of the continuous spectral range is attenuated relative to other portions of the continuous spectral range.

14. The inspection method according to claim 13, further comprising: The broadband illumination beam is modified to produce a uniform response across the continuous spectral range.

15. The inspection method according to claim 13, wherein the detector is a wavelength-sensitive detector, and The method further includes determining the intensity profile of the scattered radiation as a function of wavelength.

16. The inspection method of claim 15, wherein the distinction comprises comparing the intensity profile of the scattered radiation across the continuous spectral range with the intensity profile of the broadband irradiation beam.

17. The inspection method according to claim 13, wherein the detector is a wavelength-insensitive detector.

18. The inspection method according to claim 17, further comprising: The broadband illumination beam is time-filtered across the continuous spectral range; as well as The changes in the optical response are analyzed in response to the filtering.

19. The inspection method according to claim 13, further comprising: The scattered radiation is directed to a plurality of single-wavelength detectors, each of which is sensitive to a different wavelength than the others.

20. A photolithography apparatus, comprising: An irradiation device configured to irradiate the pattern of a pattern forming apparatus; A projection system is configured to project an image of the pattern onto a substrate; as well as Measurement system, the measurement system comprising: The irradiation system is configured to generate a broadband irradiation beam with a continuous spectral range, and to irradiate the surface of the pattern forming apparatus with the broadband irradiation beam. A detection system is configured to receive radiation scattered at the surface and radiation scattered by structures near the surface, and to generate a detection signal based on the optical response to the broadband illumination beam. The processing circuit is configured as follows: Analyze the spectral characteristics of the detected signal within the continuous spectral range, and Based on the analysis, a pseudo signal corresponding to one or more internal reflections from the structure and a defect signal corresponding to a defect on the surface are distinguished, wherein the pseudo signal of at least a portion of the continuous spectral range is attenuated relative to other portions of the continuous spectral range.

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