Lithographic apparatus, metrology system, adaptive phased array illumination and collector device and method thereof

Abstract

A system includes a radiation source, a phased array, and a detector. The phased array generates a beam of radiation and directs the beam toward a target structure on a substrate. The phased array includes a plurality of optical elements and a waveguide. The plurality of optical elements transmits a radiation wave. The plurality of waveguides direct radiation from the radiation source to the plurality of optical elements. A portion of each waveguide of the plurality of waveguides includes a material that adjusts a phase of the radiation waves such that the radiation waves accumulate to form a beam. The optical properties of the material in the waveguide are adjusted in a non-volatile and reversible manner while monitoring the beam formed by the optical phased array until a desired beam profile is obtained. The detector receives radiation scattered by a target and generates a measurement signal based on the received radiation.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to U.S. Application No. 63 / 435,187, filed on December 23, 2022, the entire content of which is incorporated herein by reference. Technical field

[0003] The present disclosure relates to a lithographic apparatus. For example, the present disclosure relates to an adaptive phased array or phase array illumination and collector device for lithographic apparatuses and systems. Background art

[0004] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, typically on a target portion of the substrate. For example, a lithographic apparatus can be used in the manufacture of integrated circuits (ICs). In such a case, a patterning device, alternatively referred to as a mask or a reticle, can be used to generate a circuit pattern to be formed on a single layer of the IC. The pattern can be transferred onto a target portion (e.g., including a portion of a die, one or more dies) on the substrate (e.g., a silicon wafer). Typically, the pattern is transferred by imaging the pattern onto a layer of radiation - sensitive material (resist) provided on the substrate. Usually, a single substrate will contain a grid of adjacent target portions that are successively patterned. Known lithographic apparatuses include so - called steppers and so - called scanners. In a stepper, each target portion is irradiated by exposing the entire pattern onto the target portion at once. In a scanner, each target portion is irradiated by synchronously scanning the target portion parallel or anti - parallel to a given direction (the "scanning" direction) while the radiation beam scans the pattern in this scanning direction. The pattern can also be transferred from the patterning device onto the substrate by imprinting the pattern onto the substrate.

[0005] During a lithographic operation, different processing steps may need to be sequentially formed on different layers of the substrate. Therefore, it may be necessary to position the substrate with high accuracy relative to a previously formed pattern on the substrate. Typically, alignment marks are placed on the substrate to be aligned and positioned relative to a second object. A lithographic apparatus can use an alignment device to detect the position of the alignment marks and use the alignment marks to align the substrate to ensure accurate exposure from the mask. The misalignment between alignment marks at two different layers is measured as an overlay error.

[0006] To monitor the lithography process, parameters of the patterned substrate are measured. The parameters can include, for example, overlay errors between consecutive layers formed in or on the patterned substrate, and critical line widths of the developed photosensitive resist. Such measurements can be performed on product substrates and / or on dedicated metrology targets. There are various techniques for measuring microstructures formed during the lithography process, including using scanning electron microscopes and various dedicated tools. A fast and non-invasive form of dedicated inspection tool is a scatterometer in which a radiation beam is directed onto a target on the surface of the substrate, and the properties of the scattered or reflected beam are measured. By comparing the properties of the beam before and after it is reflected or scattered by the substrate, the properties of the substrate can be determined. This can be done, for example, by comparing the reflected beam with data stored in a library of known measurement results for known 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 into a specific narrow angular range. In contrast, an angularly resolved scatterometer uses a monochromatic radiation beam and measures the intensity of the scattered radiation as a function of angle.

[0007] Such an optical scatterometer can be used to measure parameters such as the critical dimension of the developed photosensitive resist, or the overlay error (OV) between two layers formed in or on the patterned substrate. The properties of the substrate can be determined by comparing the properties of the illumination beam before and after it is reflected or scattered by the substrate.

[0008] An optical phased array can be used to generate an illumination beam in a metrology tool. An optical phased array can also be used to collect the reflected or scattered beam in a metrology tool. For example, the phase relationship between the optical elements of the optical phased array can be tuned to generate a desired radiation profile for the illumination beam or the scattered beam. The phase relationship between the optical elements can be determined by the phase accumulated by the propagation of light in the respective waveguides of the optical phased array towards each optical element. An optical phased array consisting of passive optical elements such as waveguides and antennas may not be tunable. The tunability of the emitted radiation profile can be achieved by including additional elements such as phase shifters in the optical phased array. Additionally, a tunable phase shifter can use a voltage signal, which can increase power consumption and result in heat dissipation in the optical phased array. SUMMARY OF THE INVENTION

[0009] Accordingly, it is desirable to improve the performance of optical phased arrays. For example, it is desirable to provide a tunable and non-volatile and / or reversible optical phased array as discussed in the embodiments described herein.

[0010] In some embodiments, a system includes a radiation source, a phased array, and a detector. The phased array generates a radiation beam and directs the beam towards a target structure on a substrate. The phased array includes a plurality of optical elements and a plurality of waveguides. The plurality of optical elements transmit radiation waves. The plurality of waveguides direct radiation from the radiation source to the plurality of optical elements. A portion of each of the plurality of waveguides includes a material that adjusts the phase of the radiation wave such that the radiation waves accumulate to form a beam. The detector receives radiation scattered by the target structure and generates a measurement signal based on the received radiation.

[0011] Those skilled in the relevant art will understand that in some embodiments, the optical phased array can also be used in reverse: for collecting, capturing, receiving, etc. beams rather than emitting them. In some embodiments, a system includes a radiation source, a phased array, and a detector. The radiation source irradiates a target structure on a substrate. The phased array collects radiation scattered from the target. The phased array includes a plurality of optical elements and a plurality of waveguides. The plurality of optical elements receive radiation waves. The plurality of waveguides direct radiation from the plurality of optical elements to the detector. A portion of each of the plurality of waveguides includes a material that adjusts the phase of the radiation wave such that the received scattered waves accumulate in the detector. The detector receives radiation scattered by the target structure from the optical phased array and generates a measurement signal based on the received radiation.

[0012] In some embodiments, a method includes depositing a material on a portion of each of a plurality of waveguides of a phased array. The phased array includes a plurality of optical elements that radiate radiation waves. The method also includes: modifying the state of the material to adjust the phase of the radiation wave such that the radiation waves accumulate to form a radiation beam; coupling a first beam to the phased array; monitoring the response of the phased array; and determining when a desired response is obtained based on the monitored response.

[0013] In some embodiments, an optical tool includes a first radiation source, a second radiation source, an optical system, a detector, and a controller. The first radiation source generates a first beam. The first radiation source is coupled to a phased array. The second radiation source generates a second beam. The optical system directs the second beam to a portion of the phased array. The portion of the phased array is coated with a material. The material changes the phase of the radiation wave emitted by the phased array such that the radiation waves accumulate to form a radiation beam. The detector receives the radiation beam generated by the phased array and generates a measurement signal based on the received radiation beam. The controller controls the characteristics of the second beam based on the measurement signal and a desired profile of the radiation beam.

[0014] The additional features of the present disclosure, as well as the structures and operations of various embodiments, are described in detail below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Based on the teachings contained in the present invention, additional embodiments will be apparent to those skilled in the relevant art. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated herein and constitute a part of this specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and enable those skilled in the relevant art to implement and use the embodiments described herein.

[0016] Figure 1A A schematic diagram showing a reflective lithography apparatus according to some embodiments.

[0017] Figure 1B A schematic diagram showing a transmissive lithography apparatus according to some embodiments.

[0018] Figure 2 A more detailed schematic diagram showing a reflective lithography apparatus according to some embodiments.

[0019] Figure 3 A schematic diagram showing a lithography cell according to some embodiments.

[0020] Figure 4A and Figure 4B A schematic diagram showing an inspection apparatus according to some embodiments.

[0021] Figure 5 A schematic diagram showing an optical phased array according to some embodiments.

[0022] Figure 6 A schematic diagram showing an optical system according to some embodiments.

[0023] Figure 7 A flowchart of a method for tuning an optical phased array according to some embodiments.

[0024] According to the specific embodiments set forth below, when combined with the drawings, the features of the present disclosure will become more apparent, in which like reference numerals always identify corresponding elements. In the drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost digit of a reference numeral identifies the drawing in which the reference numeral first appears. Unless otherwise stated, the drawings provided throughout the present disclosure should not be construed as being to scale. DETAILED DESCRIPTION

[0025] This specification discloses one or more embodiments that incorporate features of the present disclosure. The disclosed embodiments are provided by way of example. The scope of the invention is not limited to the disclosed embodiments. The claimed features are defined by the claims appended hereto.

[0026] The described embodiments and phrases such as "one embodiment", "an embodiment", "example embodiment", etc. mentioned in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include the specific features, structures, or characteristics. Moreover, such phrases do not necessarily refer to the same embodiment. Additionally, when a specific feature, structure, or characteristic is described in connection with an embodiment, it should be understood that implementing such a feature, structure, or characteristic in combination with other embodiments, whether or not explicitly described, is within the knowledge of those skilled in the art.

[0027] For ease of description, spatial relative terms such as "below", "beneath", "lower", "above", "on", "higher", etc. may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. In addition to the directions depicted in the figures, the spatial relative terms are also intended to encompass different orientations of the device during use or operation. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0028] As used herein, the term "about" indicates a value related to a given quantity that may vary based on the specific technology. Based on the particular technology, the term "about" may indicate a value of the given quantity that varies within, for example, 10% to 30% above or below the value (e.g., ±10%, ±20%, or ±30% of the value).

[0029] Embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present disclosure may 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 may 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 may include: read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.). Additionally, herein, firmware, software, routines, and / or instructions may be described as performing certain actions. However, it should be understood that such descriptions are for convenience only, and these actions are actually generated by a computing device, a processor, a controller, or other devices that execute the firmware, software, routines, instructions, etc.

[0030] However, before describing such embodiments in more detail, it is instructive to present an example environment in which embodiments of the present disclosure may be implemented.

[0031] Exemplary lithography system

[0032] Figure 1A and Figure 1B are schematic illustrations of a lithographic apparatus 100 and a lithographic apparatus 100', respectively, in which embodiments of the present disclosure may be implemented. Each of the lithographic apparatus 100 and the lithographic apparatus 100' includes the following components: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask table) MT configured to support a patterning device (e.g., a mask, a reticle, or a dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA; and a substrate table (e.g., a wafer table) WT configured to hold a substrate (e.g., a wafer coated with a resist) W and connected to a second positioner PW configured to accurately position the substrate W. The lithographic apparatuses 100 and 100' also have a projection system PS configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion (e.g., including one or more dies) C of the substrate W. In the lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In the lithographic apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0033] The illumination system IL may include various types of optical components, such as refractive, reflective, reflektive, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for guiding, shaping, or controlling the radiation beam B.

[0034] The support structure MT holds the patterning device MA depending on the orientation of the patterning device MA relative to a reference system, the design of at least one of the lithographic apparatuses 100 and 100', and other conditions (such as whether the patterning device MA is held in a vacuum environment). The support structure MT may employ mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT may be, for example, a frame or a table that can be fixed or moved as needed. By using sensors, the support structure MT can ensure that the patterning device MA is, for example, located at a desired position relative to the projection system PS.

[0035] The term "patterning device" MA is broadly interpreted as referring to any device that can be used to impart a pattern to a radiation beam B in a cross-section of the radiation beam B, so as to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a particular functional layer of a device that is created in the target portion C to form an integrated circuit.

[0036] The terms "inspection device", "metrology system", etc. may be used herein to refer to, for example, a device or system that is used to measure properties of a structure (e.g., overlay error, critical dimension parameters), or that is used in a lithographic apparatus to inspect a wafer (e.g., an alignment device).

[0037] The patterning device MA may be of a transmissive type (as in Figure 1B lithographic apparatus 100’) or of a reflective type (as in Figure 1A lithographic apparatus 100). Examples of patterning devices MA include a mask / mask, a programmable mirror array, or a programmable LCD panel. Masks are well known in lithography and include mask types such as binary masks, alternating phase shift masks, or attenuated phase shift masks, 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 an incident radiation beam in a different direction. The tilted mirrors impart a pattern to the radiation beam B that is reflected by the matrix of small mirrors.

[0038] The term "projection system" PS as used herein includes any type of projection system, including refractive, reflective, refraction-reflective, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, as is suitable for the exposure radiation being used or for other factors such as the use of an immersion liquid or a vacuum on the substrate W. A vacuum environment may be used for EUV or electron beam radiation, since other gases may absorb too much radiation or electrons. Thus, a vacuum environment can be provided for the entire beam path by means of a vacuum wall and a vacuum pump.

[0039] Lithographic apparatus 100 and / or lithographic apparatus 100’ may be of a type having two (dual-platform) or more substrate tables WT (and / or two or more mask tables). In such a "multi-substrate table" machine, additional substrate tables WT can be used in parallel, or one or more other substrate tables WT can be used for exposure while preparatory steps are being performed on one or more of the tables. In some cases, the additional tables may not be substrate tables WT.

[0040] The lithographic apparatus may also be of the type in which at least a portion of the substrate is covered by a liquid having a relatively high refractive index, e.g. water, to fill the space between the projection system and the substrate. The immersion liquid may also be applied to other spaces in the lithographic apparatus, e.g. the space between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of a projection system. The term "immersion" as used herein does not mean that a structure such as a substrate must be immersed in a liquid, but "immersion" only means that the liquid is located between the projection system and the substrate during exposure.

[0041] Reference Figure 1A and Figure 1B , the illuminator IL receives a radiation beam from a radiation source SO. When the source SO is an excimer laser, the source SO and the lithographic apparatus 100, 100' may be separate physical entities. In this case, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam is passed from the source SO to the illuminator IL by means of a beam delivery system BD (in Figure 1B ) comprising, for example, suitable directing mirrors and / or beam expanders. In other cases, the source SO may be an integral part of the lithographic apparatus 100, 100' - for example, when the source SO is a mercury lamp. The source SO, the illuminator IL and, if required, the beam delivery system BD may together be referred to as the radiation system.

[0042] The illuminator IL may include an adjuster AD (in Figure 1B ) for adjusting the angular intensity distribution of the radiation beam. In general, at least the outer radial extent and / or the inner radial extent of the intensity distribution in the pupil plane of the illuminator may be adjusted (commonly referred to as σ - outer and σ - inner respectively). In addition, the illuminator IL may include various other components (in Figure 1B ), such as an integrator IN and a condenser CO. The illuminator IL may be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross - section.

[0043] Reference Figure 1A, the radiation beam B is incident on the patterning device (e.g., a mask) MA and is patterned by the patterning device MA, which is held on the support structure (e.g., a mask table) MT. In the lithographic apparatus 100, the radiation beam B is reflected from the patterning device (e.g., a mask) MA. After being reflected from the patterning device (e.g., a mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. By means of a second positioner PW and a position sensor IF2 (e.g., an interferometer device, a linear encoder, a 2D encoder or a capacitive sensor), the substrate table WT can be accurately moved (e.g., to position different target portions C in the path of the radiation beam B). Similarly, a first positioner PM and another position sensor IF1 can be used to accurately position the patterning device (e.g., a mask) MA relative to the path of the radiation beam B. The patterning device (e.g., a mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0044] Reference Figure 1B , the radiation beam B is incident on the patterning device (e.g., mask MA) and is patterned by the patterning device, which is held on the support structure (e.g., mask table MT). After traversing the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil PPU that is conjugate to the illumination system pupil IPU. A portion of the radiation originates from the intensity distribution at the illumination system pupil IPU, traverses the mask pattern without being affected by diffraction at the mask pattern, and produces an image of the intensity distribution at the illumination system pupil IPU.

[0045] The projection system PS projects an image of the marker pattern MP onto a photoresist layer coated on the substrate W, wherein the image is formed by diffracted beams generated from the marker pattern MP by radiation passing through the intensity distribution. For example, the mask pattern MP may include an array of lines and spaces. Diffraction of radiation different from the zero-order diffraction at the array generates deflected diffracted beams that have a direction change in a direction perpendicular to the lines. The non-diffracted beam (i.e., the so-called zero-order diffracted beam) traverses the pattern without any change in the propagation direction. The zero-order diffracted beam passes through the upper lens or upper lens group of the projection system PS (located upstream of the conjugate pupil PPU of the projection system PS) to reach the conjugate pupil PPU. A part of the intensity distribution in the conjugate pupil PPU plane 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. The aperture device PD is provided, for example, at or substantially in the plane including the conjugate pupil PPU of the projection system PS.

[0046] The projection system PS is arranged to capture not only the zero-order diffracted beam but also the first-order or first-order and higher-order diffracted 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 lines may be used to utilize the resolution enhancement effect of dipole illumination. For example, the first-order diffracted beam interferes with the corresponding zero-order diffracted beam at the level of the wafer W to produce an image of the line pattern MP with as high a resolution and process window (i.e., the available depth of focus combined with the admissible exposure dose deviation) as possible. In some embodiments, astigmatism can be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. Additionally, in some embodiments, astigmatism can be reduced by blocking the zero-order beam in the conjugate pupil PPU of the projection system that is associated with the radiation poles in the opposite quadrants. This is described in more detail in US 7,511,799 B2, issued on March 31, 2009, the entire content of which is incorporated herein by reference.

[0047] By means of a second locator PW and a position sensor IFD (e.g., an interferometer device, a linear encoder, a 2D encoder, or a capacitive sensor), the substrate table WT can be accurately moved (e.g., to position different target portions C in the path of the radiation beam B). Similarly, a first locator PM and another position sensor (not shown in Figure 1B can be used to accurately position the mask MA relative to the path of the radiation beam B (e.g., after mechanical retrieval from a mask library or during scanning).

[0048] Generally, the movement of the mask table MT can be achieved by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of the first positioner PM. Similarly, the movement of the substrate table WT can be achieved by using a long-stroke module and a short-stroke module forming part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected only to the short-stroke actuator or can be fixed. The mask MA and the substrate W can be aligned using mask alignment marks M1, M2, and substrate alignment marks P1, P2. Although the illustrated substrate alignment marks occupy dedicated target portions, they can be located in the space between multiple target portions (these are called scribe alignment marks). Similarly, in the case where more than one die is provided on the mask MA, the patterning device alignment marks can be located between these dies.

[0049] The mask table MT and the patterning device MA can be located in a vacuum chamber, where an in-vacuum robot IVR can be used to move the patterning device (such as a mask or a reticle) into and out of the vacuum chamber. Alternatively, when the mask table MT and the patterning device 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 transfer any payload (e.g., a mask) smoothly to a fixed kinematic mount at the transfer station.

[0050] The lithographic apparatuses 100 and 100 can be used in at least one of the following modes:

[0051] In the step mode, the support structure (e.g., the mask table) MT and the substrate table WT remain substantially stationary, while the entire pattern imparted to the radiation beam is projected onto the target portion C in one go (i.e., a single static exposure). Then, the substrate table WT is moved in the X and / or Y direction so that different target portions C can be exposed.

[0052] In the scan mode, the support structure (e.g., the mask table) MT and the substrate table WT are scanned synchronously while the pattern imparted to the radiation beam is projected onto the target portion C (i.e., a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure (e.g., the mask table) MT can be determined by the magnification (reduction ratio) and the image inversion characteristics of the projection system PS.

[0053] In another mode, while holding the support structure (e.g., a mask table) MT of the programmable patterning device substantially fixed and moving or scanning the substrate table WT, the pattern imparted to the radiation beam B is projected onto the target portion C. A pulsed radiation source SO can be employed, and the programmable patterning device is updated as needed after each movement of the substrate table WT or between successive radiation pulses during scanning. This operating mode can be readily applied to maskless lithography using a programmable patterning device such as a programmable mirror array.

[0054] Combinations and / or variations of the described usage modes or completely different usage modes can also be employed.

[0055] In a further embodiment, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Generally, the EUV source is arranged in a radiation system, and the corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0056] Figure 2 The lithographic apparatus 100 is shown in more detail, including the source collector apparatus SO, the illumination system IL, and the projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment is maintained within the enclosure structure 220 of the source collector apparatus SO. A plasma 210 emitting EUV radiation can be formed by a discharge-produced plasma source. The very hot plasma 210 in which EUV radiation is generated can be produced by a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor). For example, the very hot plasma 210 is produced by causing a discharge in at least a partially ionized plasma. To effectively generate radiation, it may be necessary, for example, for a partial pressure of 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor. In some embodiments, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0057] The radiation emitted by the hot plasma 210 is transferred from the source chamber 211 to the collector chamber 212 via an optional gas barrier or contaminant trap 230 located in or behind the opening in the source chamber 211 (which in some cases is also referred to as a contaminant barrier or flap trap). The contaminant trap 230 can include a channel structure. The contaminant trap 230 can also include a gas barrier, or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 as further indicated herein includes at least a channel structure.

[0058] The collector chamber 211 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 out to be focused at a virtual source point INTF. The virtual source point is commonly referred to as the intermediate focus INTF, and the source collector device is arranged such that the intermediate focus INTF is located at or near the opening 219 in the enclosure structure 220. The virtual source point INTF is an image of the radiation emitting plasma 210. The grating spectral filter 240 is particularly used to suppress infrared (IR) radiation.

[0059] Subsequently, the radiation traverses the illumination system IL, which may include a faceted field mirror device 222 and a faceted pupil mirror device 224, arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA, and a desired radiation intensity uniformity at the patterning device MA. When the radiation beam 221 is reflected at the patterning device MA, it is held by the support structure MT to form a patterned beam 226, and the patterned beam 226 is imaged by the projection system PS via reflection elements 228, 229 onto a substrate W held by a wafer table or a substrate table WT.

[0060] There may generally be more elements in the illumination optics unit IL and the projection system PS than the elements shown. The grating spectral filter 240 may optionally be present, depending on the type of lithographic apparatus. Additionally, there may be more mirrors than Figure 2 the mirrors shown in Figure 2 e.g., there may be one to six additional reflection elements in the projection system PS than

[0061] The collector optics CO (as illustrated in Figure 2 is depicted as a nested collector with grazing incidence reflectors 253, 254 and 255 only as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are axially symmetrically arranged around the optical axis O, and this type of collector optics CO is preferably used in combination with a discharge generated plasma source (often referred to as a DPP source).

[0062] Exemplary lithography cell

[0063] Figure 3Shows a lithography cell 300, sometimes also referred to as a lithography cell or cluster, according to some embodiments. The lithography apparatus 100 or 100' may form part of the lithography cell 300. The lithography cell 300 may also include one or more devices for performing pre-exposure processes and post-exposure processes on a substrate. In some examples, these include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chill plate CH, and a bake plate BK. A substrate transfer device or robot RO picks up substrates from input / output ports I / O1, I / O2, moves the substrates between different process devices, and transfers the substrates to the feed table LB of the lithography apparatus 100 or 100'. These devices are generally collectively referred to as a track or a coat and develop system and are under the control of a track or coat and develop system control unit TCU, which is itself controlled by a management control system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Thus, different devices can be operated to maximize throughput and processing efficiency.

[0064] Exemplary inspection device

[0065] To control the lithography process to accurately place device features on the substrate, alignment marks are typically provided on the substrate, and the lithography apparatus includes one or more inspection devices to accurately position the marks on the substrate. These alignment devices are effective position measurement devices. Different types of marks and different types of alignment devices and / or systems are known from different times and different manufacturers. One type of system widely used in current lithography apparatuses is based on a self-referencing interferometer as described in U.S. Patent No. 6,961,116 (den Boef et al.). Typically, the marks are measured separately to obtain an X position and a Y position. However, the combined X and Y measurements can be performed using the techniques described in U.S. Publication No. 2009 / 195768 A (Bijnen et al.). The entire contents of both of these publications are incorporated herein by reference.

[0066] Figure 4A Schematic cross-sectional view showing an inspection device 400 according to an embodiment. The metrology system 400 may be implemented as part of the lithography apparatus 100 or 100'. In some embodiments, the inspection device 400 may be configured to align a substrate (e.g., substrate W) relative to a patterning device (e.g., patterning device MA). The inspection device 400 may also be configured to detect the position of alignment marks on the substrate and align the substrate using the detected positions of the alignment marks relative to the patterning device or other components of the lithography apparatus 100 or 100'. Such alignment of the substrate can ensure accurate exposure of one or more patterns on the substrate.

[0067] In some embodiments, inspection device 400 may include an illumination system 412, a beam splitter 414, an interferometer 426, a detector 428, a beam analyzer 430, and an overlap calculation processor 432. The illumination system 412 may be configured to provide an electromagnetic narrowband radiation beam 413 having one or more passbands. In an example, the one or more passbands may be within a spectrum of wavelengths between approximately 500 nm and approximately 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a spectrum of wavelengths between approximately 500 nm and approximately 900 nm. The illumination system 412 may also be configured to provide one or more passbands having a substantially constant center wavelength (CWL) value over a long period of time (e.g., over the useful life of the illumination system 412). As discussed above, in the current alignment system, this configuration of the illumination system 412 may help prevent the actual CWL value from deviating from the desired CWL value. And, thus, compared to the current alignment device, using a constant CWL value may improve the long-term stability and accuracy of the alignment system (e.g., metrology device 400).

[0068] In some embodiments, the beam splitter 414 may be configured to receive the radiation beam 413 and split the radiation beam 413 into at least two radiation sub-beams. For example, the radiation beam 413 may be split into radiation sub-beams 415 and 417, as Figure 4AAs shown in. The beam splitter 414 may also be configured to direct the radiation sub-beam 415 onto the substrate 420 placed on the platform 422. In one example, the platform 422 may be movable in the direction 424. The radiation sub-beam 415 may be configured to illuminate the alignment marks or targets 418 located on the substrate 420. The alignment marks or targets 418 may be coated with a radiation-sensitive film. In some embodiments, the alignment marks or targets 418 may have a one-hundred-eighty-degree (i.e., 180°) symmetry. That is, when the alignment marks or targets 418 are rotated 180° about an axis of symmetry perpendicular to the plane of the alignment marks or targets 418, the rotated alignment marks or targets 418 may be substantially the same as the non-rotated alignment marks or targets 418. The targets 418 on the substrate 420 may be (a) a resist layer grating including grating bars formed of solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlapping target structure, the overlapping target structure including a resist grating stacked or interleaved on the product layer grating. The grating bars may alternatively be etched into the substrate. Such patterns are sensitive to chromatic aberrations and illumination symmetry in the lithographic projection apparatus, particularly the projection system PL, and the presence of such aberrations will manifest themselves as variations in the printed gratings. An in-line method for measuring linewidth, pitch, and critical dimensions in device manufacturing utilizes a technique known as "scatterometry". Scatterometry methods are described in "Multiparameter Grating Metrology Using SPIE Scatterometry" by Raymond et al. (J. Vac. Sci. Tech. B, Vol. 15, No. 2, pp. 361 - 368 (1997)) and "Specular Spectroscopic Scatterometry in DUV Lithography" by Niu et al. (SPIE, Vol. 3677 (1999)), both of which are incorporated herein by reference in their entirety. In scatterometry, light is reflected by the periodic structures in the target, and the resulting reflected spectrum is detected at a given angle. The structure that produces the reflected spectrum is reconstructed, for example, using rigorous coupled-wave analysis (RCWA) or by comparison with a library of modes obtained from simulations. Thus, the scatterometry data of the printed grating is used to reconstruct the grating. Parameters of the grating, such as linewidth and line shape, may be input into the reconstruction process, which is performed by the processing unit PU based on knowledge of the printing step and / or other scatterometry processes.

[0069] In some embodiments, according to the embodiment, the beam splitter 414 may also be configured to receive the diffracted radiation beam 419 and split the diffracted radiation beam 419 into at least two radiation sub-beams. The radiation beam 419 may be split into radiation sub-beams 429 and 439, as Figure 4Aas shown in

[0070] Note that even though the beam splitter 414 is shown as directing the radiation sub - beam 415 towards the alignment mark or target 418 and the diffracted radiation sub - beam 429 towards the interferometer 426, the present disclosure is not limited thereto. Those skilled in the relevant art will understand that other optical arrangements can be used to obtain similar results of irradiating the alignment mark or target 418 on the substrate 420 and detecting an image of the alignment mark or target 418.

[0071] As Figure 4A illustrated, the interferometer 426 can be configured to receive the radiation sub - beam 417 and the diffracted radiation sub - beam 429 through the beam splitter 414. In an example embodiment, the diffracted radiation sub - beam 429 can be at least a part of the radiation sub - beam 415 that can be reflected from the alignment mark or target 418. In an example of this embodiment, the interferometer 426 includes any suitable set of optical elements, for example, can be configured as a prism combination that forms two images of the alignment mark or target 418 based on the received diffracted radiation sub - beam 429. It should be understood that it is not necessary to form a good - quality image, but the features of the alignment mark 418 should be resolved. The interferometer 426 can also be configured to rotate one of the two images by 180° relative to the other of the two images and recombine the rotated image and the non - rotated image interferometrically.

[0072] In some embodiments, the detector 428 can be configured to receive the recombined image via the interferometer signal 427 and detect the interference resulting from the recombined image when the alignment axis 421 of the inspection device 400 passes through the center of symmetry (not shown) of the alignment mark or target 418. This interference may be due to the alignment mark or target 418 being symmetric about 180°, and according to the example embodiment, the recombined images interfere 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 an optical beam perpendicular to the substrate 420 and passing through the center of the 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 the wafer - marking process variations.

[0073] In another embodiment, the detector 428 determines the position of the center of symmetry of the alignment mark or target 418 by performing one or more of the following measurements:

[0074] Measuring the position change for each wavelength (position offset between each color);

[0075] For changes in the measurement position at each order (position offset between each diffraction order); and

[0076] For changes in the measurement position for each polarization (position offset between each polarization).

[0077] For example, this data can be obtained using any type of alignment sensor, such as a SMASH (SMart Alignment Sensor Hybrid) sensor, as described in U.S. Patent No. 6,961,116, which employs a self-referencing interferometer with a single detector and four different wavelengths, and extracts the alignment signal using software, or ATHENA (Advanced Technology using Higher-Order Alignment Enhancement), as described in U.S. Patent No. 6,297,876, which directs each of the seven diffraction orders to a dedicated detector, and both patents are incorporated herein by reference in their entirety.

[0078] In some embodiments, 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 the beam wavelength, polarization, or beam profile. The beam analyzer 430 can also be configured to determine the position of the stage 422 and correlate the position of the stage 422 with the position of the symmetry center of the alignment mark or target 418. In this way, the position of the alignment mark or target 418 and thus the position of the substrate 420 can be accurately known with reference to the stage 422. 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 symmetry center of the alignment mark or target 418 is known with 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 embodiments, according to other embodiments, the beam analyzer 430 can be directly integrated into the inspection device 400 or connected via several types of optical fibers: polarization-maintaining single-mode fibers, multimode fibers, or imaging fibers.

[0079] In some embodiments, the beam analyzer 430 may also be configured to determine overlap 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 that already exists on the substrate 420. The reference layer may be generated by exposing a reference pattern on the substrate by the lithography apparatus 100 and / or 100'. The exposure layer may be an exposed resist layer adjacent to the reference layer. The exposure layer may be generated by exposing an exposure pattern on the substrate 420 by the lithography apparatus 100 or 100'. The exposure pattern on the substrate 420 may correspond to the movement of the substrate 420 due to the stage 422. In some embodiments, measuring the overlap data may also indicate an offset between the reference pattern and the exposure pattern. The measured overlap data may be used as calibration data to calibrate the exposure pattern exposed by the lithography apparatus 100 or 100' such that, after calibration, the offset between the exposure layer and the reference layer can be minimized.

[0080] In some embodiments, the beam analyzer 430 may also be configured to determine a model of the product stack profile of the substrate 420 and may be configured to measure the overlap, critical dimension, and focus of the target 418 in a single measurement. The product stack profile contains information about the stacked products, such as alignment marks, the target 418, or the substrate 420, and may include optical signature metrology caused by process variations, which is a function 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 ieldstarTM manufactured by ASML of Veldhoven, the Netherlands, as described in U.S. Patent No. 8,706,442, which is incorporated herein by reference in its entirety. The beam analyzer 430 may also be configured to process information related to specific properties of the exposure pattern in the layer. For example, the beam analyzer 430 may process: overlap parameters (indicating the positioning accuracy or precision of the layer relative to a previous layer on the substrate, or the positioning accuracy or precision of the first layer relative to a mark on the substrate), focus parameters, and / or critical dimension parameters of the image depicted in the layer (e.g., line width and its variations). Other parameters are image parameters related to the quality of the image of the depicted exposure pattern.

[0081] In some embodiments, a detector array (not shown) may be connected to the beam analyzer 430 and allow for the possibility of accurate overlay profile detection, as discussed below. For example, the detector 428 may be a detector array. There may be a variety of options for the detector array: a multimode fiber bundle, discrete pin detectors per channel, or a CCD or CMOS (linear) array. For stability reasons, using a multimode fiber bundle may allow any dissipative elements to be located remotely. Discrete pin detectors may provide a large dynamic range, but each requires a separate preamplifier. Thus, the number of elements is limited. CCD linear arrays provide many elements that can be read out at high speed and are of particular interest when using phase-stepping detection.

[0082] In some embodiments, a second beam analyzer 430' may be configured to receive and determine the optical state of the diffracted radiation sub-beam 429, as Figure 4B shown. The optical state may be a measure of the beam wavelength, polarization, or beam profile. The second beam analyzer 430' may be the same as the beam analyzer 430. Alternatively, the second beam analyzer 430' may be configured to perform at least all of the functions of the beam analyzer 430, such as determining the position of the stage 422 and correlating the position of the stage 422 with the position of the center of symmetry of the alignment mark or target 418. In this way, the position of the alignment mark or target 418 and thus the position of the substrate 420 can be accurately known with reference to the stage 422. The beam analyzer 430' may also 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 is known with reference to the inspection device 400 or any other reference element. The second beam analyzer 430' may also be configured to determine the overlap data between two patterns and a model of the product overlay profile of the substrate 420. The second beam analyzer 430' may also be configured to measure the overlap, critical dimension, and focus of the target 418 in a single measurement.

[0083] In some embodiments, the second beam analyzer 430' may be directly integrated into the inspection device 400, or according to other embodiments, it may be connected via several types of optical fibers: polarization-maintaining single-mode fibers, multimode fibers, or imaging fibers. Alternatively, the second beam analyzer 430' and the beam analyzer 430 may be combined to form a single analyzer (not shown) that is configured to receive and determine the optical states of the diffracted radiation sub-beams 429 and 439.

[0084] In some embodiments, the processor 432 receives information from the detector 428 and the beam analyzer 430. For example, the processor 432 can be an overlay calculation processor. The information can include a model of the product overlay profile constructed by the beam analyzer 430. Alternatively, the processor 432 can use the received information about the product markings to construct a model of the product marking profile. In either case, the processor 432 uses or combines the model of the product marking profile to construct a model of the stacked product and the overlapping marking profile. The overlay model is then used to determine the overlay offset and to minimize the effect of the spectrum on the overlay offset measurement. The processor 432 can generate a basic correction algorithm based on the information received from the detector 428 and the beam analyzer 430, including but not limited to the illumination beam, the optical state of the alignment signal, the associated position estimate, and the optical state in the pupil, image, and other planes. The pupil plane is the plane in which the radial position of the radiation defines the angle of incidence and the angular position defines the azimuthal angle of the radiation. The processor 432 can characterize the inspection device 400 using the basic correction algorithm with reference to the wafer markings and / or alignment marks 418.

[0085] In some embodiments, the processor 432 can also be configured to determine, for each marking, an offset error of the printed pattern position relative to the sensor estimate based on the information received from the detector 428 and the beam analyzer 430. The information includes but is not limited to the product overlay profile, the measurements of the overlay, critical dimension, and focus for each alignment mark or target 418 on the substrate 420. The processor 432 can use a clustering algorithm to group the markings into sets of similar constant offset errors and generate an alignment error offset correction table based on the information. The clustering algorithm can be based on the overlay measurements, position estimates, and additional optical overlay process information associated with each set of offset errors. The overlay is calculated for multiple different markings, such as overlay targets with positive and negative deviations around a programmed overlay offset. The target with the smallest measured overlay is used as a reference (since it is measured with the best accuracy, i.e., precision). Based on the measured small overlay and its corresponding target's suppressed programmed overlay, the overlay error can be derived. Table 1 illustrates how this operation is performed. In the example shown, the smallest measured overlay 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.

[0086]

[0087] The minimum value can be used as a reference point relative to which the offset between the measured overlap and the expected overlap due to programmed overlap can be calculated. This offset determines the overlap error for each mark or set of marks having a similar offset. Thus, in the example of Table 1, at a target location with a programmed overlap of 30 nm, the minimum measured overlap is -1 nm. The differences between the expected and measured overlaps at other targets are compared to this reference. Tables such as Table 1 can also be obtained for marks and targets 418 under different illumination settings, and the illumination setting and its corresponding calibration factor that result in the minimum overlap error can be determined and selected. Thereafter, the processor 432 can group the marks into sets of similar overlap errors. The criteria for mark grouping can be adjusted based on different process controls, such as different error tolerances for different processes.

[0088] In some embodiments, the processor 432 can confirm that all or most of the members of the grouping have similar offset errors and apply individual offset corrections from a clustering algorithm to each mark based on its additional optical overlay metrology. The processor 432 can determine the correction for each mark and feed the correction back, for example, to the lithography apparatus 100 or 100' via the inspection device 400 to correct the error in the overlap.

[0089] Example illumination source

[0090] An optical phased array (OPA) can be used as an illumination or collection (e.g., capture, receive, etc.) module in metrology tools such as alignment sensors, overlay sensors, and leveling sensors. The OPA can also be used in sensing applications such as Lidar systems. The OPA described herein includes phase change materials to tune the phase relationship between optical elements after fabricating the OPA without using volatile phase shifters.

[0091] Figure 5 A schematic diagram of an optical phased array 500 according to some embodiments is shown. In some aspects, the optical phased array 500 can be part of the illumination system 412. The optical phased array 500 and its components (e.g., waveguides, optical elements) can be part of a photonic integrated circuit (PIC). The optical phased array 500 can include optical elements 502 (e.g., antennas), waveguides 504, and a bus waveguide 510.

[0092] In some embodiments, waveguide 504 is configured to direct radiation from bus waveguide 510 to optical element 502. The radiation may be supplied by radiation source 506 and received at the input of the phased array. In some aspects, radiation source 506 may be coupled to bus waveguide 510. In some aspects, radiation source 506 may generate one or more wavelengths. One or more wavelengths in the visible spectrum (e.g., from about 400 nm to about 750 nm), the near- to short-wavelength infrared spectrum (e.g., from about 750 nm to about 2.5 µm), or the mid-wavelength infrared spectrum to the long-wavelength infrared spectrum (e.g., from about 2.5 µm to about 20 µm). Optical element 502 may be configured to radiate radiation waves (e.g., by coupling out radiation from waveguide 504). Optical element 502 may be referred to herein as a "transmitter", "emitting element", etc., with reference to its function of emitting radiation. Although Figure 5 a 4×4 circuit layout is shown, it will be understood that OPA 500 may include any number of waveguides 504 and optical elements 502.

[0093] In some embodiments, the phase of the radiation waves emitted by each optical element 502 is adjusted such that the radiation waves accumulate to form a radiation beam. Each optical element in optical elements 502 may have a phase relationship relative to the other optical elements 502. By tuning the phase relationship between the individual optical elements, a desired radiation profile of light may be formed at a distance from OPA 500. The phase relationship between the individual optical elements may be determined by the phase accumulated by the propagation of light in waveguide 504, which directs light from bus waveguide 510 towards each individual optical element 502. The accumulated phase is a function of the effective refractive index of the waveguide mode and the waveguide length.

[0094] In some embodiments, material 508 may be deposited on waveguide 504 and / or optical element 502. In some aspects, material 508 may be deposited on a plurality of individual waveguides (e.g., 504a, 504b, 504c, 504d) leading to each respective optical element (e.g., 502a, 502b, 502c, 502d). In some aspects, material 508 may cover a portion of each waveguide. In some aspects, OPA 500 may be completely covered by material 508. Material 508 may be a material whose refractive index monotonically increases or decreases in response to an external stimulus and / or a phase change material (PCM). The material or PCM may be a chalcogenide-based phase change material. In some aspects, the optical constants (e.g., refractive index) of the material may be tuned until a desired emission profile of the radiation beam is obtained (emitted) from OPA 500.

[0095] In some embodiments, the material 508 can be amorphous and crystalline. When in the amorphous or crystalline state, the material 508 can have different optical properties (e.g., refractive index). In some aspects, to transition from the crystalline state to the amorphous state, the material 508 is heated above the melting temperature and continuously rapidly cooled. To transition from the amorphous state to the crystalline state, the material 508 is heated above its glass transition temperature and continuously slowly cooled such that the atoms can reorient into the crystalline state.

[0096] In some aspects, the material 508 can be a chalcogenide-free material or PCM that may not return to a previous state. For example, the refractive index associated with the material or PCM can increase or decrease monotonically. In such a case, a phase shift equal to the desired phase shift plus an integer multiple of 2π is used.

[0097] In some embodiments, the material 508 can be heated by irradiating it with a light beam. The light beam can be absorbed by the material 508. The absorption can cause a temperature increase in the material 508. In one aspect, by heating the material above the melting temperature and rapidly cooling it, its state can be changed from the crystalline state to the amorphous state, and by heating it above the glass transition temperature and slowly cooling it, the state of the material can be changed from the amorphous state to the crystalline state. In one aspect, this modification of the state of the material changes the optical constants of the material 508. In some aspects, a portion of the material 508 changes between the amorphous and crystalline states. The phase accumulated by the light propagating through the waveguide 504 is modified due to the difference in optical properties between the amorphous and crystalline states.

[0098] In some embodiments, the change in the optical constants of the material 508 is maintained even after the light beam or heat is removed. The material 508 retains its state after tuning and thus retains its optical properties. Thus, the phase change is non-volatile. The state and optical constants of the material can be reversed by irradiating the material 508 with another light beam having different irradiation characteristics.

[0099] In some embodiments, the optical properties of the material 508 can be changed by applying an electrical signal. The OPA 500 can include an electrical connection. The electrical signal can be tuned to change the optical properties of the material 508.

[0100] In some embodiments, the optical properties of the material 508 can be tuned by coupling an optical pulse to the OPA 500. In some aspects, additional waveguides can be implemented on the PIC. The additional waveguides can be used to direct the optical pulse to the material 508.

[0101] In some embodiments, a heating probe can be used to apply heat to material 508. The heating probe can be aligned with the portion of OPA 500 covered by material 508. The temperature and duration of the heating can be varied to change the state of material 508 (e.g., from amorphous to crystalline or from crystalline to amorphous).

[0102] As discussed above, the optical phased array 500 can be used as an illumination source of inspection device 400. The radiation beam from the OPA can be directed towards a target structure (e.g., target 418 of FIG. 4). The target structure can scatter (e.g., diffract) the radiation. The scattered radiation can be received at a detector (e.g., detector 428 of FIG. 4), and a measurement signal can be generated. The measurement signal can be used to determine the position of alignment marks on the target structure or the result of a lithography process (e.g., overlay error).

[0103] Those skilled in the art will appreciate that Lorentz reciprocity can be applied to the OPA. Thus, the OPA can be used to collect radiation. In some embodiments, the source and the detector are interchangeable: the source becomes the detector and the detector becomes the source. The optical phased array 500 can be used as a collection device of inspection device 400. The source emits radiation towards a target structure (e.g., target 418 of FIG. 4). The target structure can scatter (e.g., diffract) the radiation. The scattered radiation can be collected by the OPA. The detector receives the collected radiation from the OPA, and a measurement signal can be generated. The measurement signal can be used to determine the position of alignment marks on the target structure or the result of a lithography process (e.g., overlay error). This is shown and discussed below.

[0104] Figure 6 is a schematic diagram of an optical system 600 according to some embodiments. In some embodiments, the optical system 600 can be used to tune the emission profile of OPA 604. The optical system 600 can include a first radiation source 628, a second radiation source 608, a controller 626, and a detector 624.

[0105] In some embodiments, the second radiation source 608 can generate a light beam 632. The light beam 632 is focused on the material 606 of OPA 604. In some aspects, the light beam 632 can be directed towards OPA 604 via a reflective element 610 (e.g., a mirror). The light beam 632 can pass through optical elements 612, 614 (e.g., lenses) and be focused on a target portion of the material 606 using an optical system 618 (e.g., an objective lens). The light beam 632 can cause the state of the material 606 to be modified. When the state of the material 606 is modified using the light beam 632 (e.g., a light pulse) from the second radiation source 608, the far-field emission profile emitted from OPA 604 is monitored using the detector 624.

[0106] In some embodiments, the first radiation source 628 is coupled to the OPA 604. The OPA 604 may radiate radiation waves that accumulate to form a radiation beam 630. The radiation waves are collected by the optical system 618. The beam splitter 616 may direct a portion of the radiation beam 630 towards the detector 624. The radiation beam 630 may be focused on the detector 624 using optical elements 620, 622 (e.g., lenses).

[0107] In some embodiments, the detector 624 may be a pixelated detector. The controller 626 may identify a cost function based on the shape of the desired far-field emission profile and the profile received from the detector 624. In some aspects, the cost function may indicate the difference between the received profile and the desired far-field emission profile. A feedback loop between the controller 626 and the second radiation source 608 may be used to achieve the desired far-field emission profile from the OPA 604. The controller 626 may control one or more properties of the second radiation source 608. Additionally or alternatively, the controller 626 may control the reflective element 610. In some aspects, an algorithm may be used to determine one or more properties of the second radiation source 608 such that the cost function is reduced or minimized.

[0108] In some embodiments, other optical components in the illumination system may be controlled to modify the illumination profile. In one aspect, a spatial light modulator in the illumination system may be used to generate the illumination profile of the second radiation source 608 that illuminates the material or PCM.

[0109] In some embodiments, the cost function may represent the average of the differences between the two-dimensional (2D) intensity of the desired far-field distribution and the 2D intensity profile obtained from the detector 624.

[0110] In some embodiments, one or more properties may include the intensity of the beam 632, the wavelength of the beam 632, and / or the incident position of the beam 632 on the material 606. For example, the wavelength of the beam 632 may be tuned from a first wavelength to a second wavelength. The incident position of the beam 632 on the material 606 may be changed by controlling the reflective element 610. For example, the reflective element 610 may be rotated to change the angle of incidence of the beam 632 on the optical system 618. Additionally, the controller 626 may control the position of the platform 602 that holds the OPA 604. In some aspects, the second radiation source 608 may generate a pulsed beam. The controller 626 may control the pulse duration or repetition rate of the second radiation source 608. For example, the pulse duration may be increased / decreased to increase / decrease the heating of the material 606.

[0111] In some embodiments, the emission profile of each optical element (antenna) among a plurality of optical elements of the OPA 604 is measured (obtained), and a cost function is minimized. This process is repeated for each optical element of the OPA 604.

[0112] In some embodiments, the wavelength of the light beam 632 generated by the second radiation source 608 can be selected such that the light beam is absorbed by the material 606. Absorption of the light beam can cause heating of the material 606, which results in a phase change. The light beam 632 can have a short wavelength. In some aspects, the wavelength of the light beam 632 can be about 400 nm. In some embodiments, the wavelength of the light beam radiated from the first radiation source 628 can be different from the wavelength of the light beam 632. For example, the light beam 632 can have a wavelength in the visible spectrum, and the first radiation source 628 can have a wavelength in the infrared spectrum. In other examples, the light beam 632 can have a wavelength in the infrared spectrum, and the first radiation source 628 can have a wavelength in the visible spectrum. In some aspects, the light generated from the first radiation source 628 is not absorbed by the material 606.

[0113] In some embodiments, the optical system 600 can be used to rewrite the OPA. That is, the optical system 600 can be used to change the phase of the material 606 to obtain another desired emission profile from the OPA 604.

[0114] In some embodiments, the optical system 600 can be part of a metrology system such as the inspection device 400. For example, the optical system 600 can be part of an alignment sensor, an overlay sensor, a leveling sensor, etc.

[0115] In some embodiments, a plurality of irradiation beams can be directed to the OPA 604, such as a plurality of waveguides of the OPA 604 are irradiated simultaneously, such that the phase of the material 606 is changed simultaneously at two or more locations. Consequently, the phase of the radiation wave radiated by each optical element corresponding to the waveguide on which the material is deposited is also changed. In some aspects, the second radiation source 608 can generate a plurality of beams. Each beam of the plurality of beams can be focused on a corresponding portion of each of the plurality of waveguides of the OPA 604. For example, the first beam can be focused on Figure 5 the waveguide 504a, and the second beam can be focused on Figure 5 the waveguide 504b. The first beam can be focused on the material deposited on the waveguide 504a. In some aspects, the first beam and the second beam can be focused on different portions of the waveguide 504a.

[0116] In some aspects, each beam of the plurality of beams can be controlled independently of the other beams. In some aspects, optical elements can be used to obtain a plurality of beams from the light beam 632.

[0117] In some embodiments, the material 606 can be antimony(III) selenide (Sb2Se3) or antimony sulfide (Sb2S3). In some embodiments, a waveguide section having a length of about 22 μm is covered with Sb2Se3 so as to have a 2π phase change range. In one aspect, once a desired illumination profile is set in the OPA, due to the optical properties set in a non-volatile manner using the phase change material in the OPA, it does not consume power in the phase shifter during its normal operation as an illuminator. In addition, due to the flexibility of rewriting various emission profiles (e.g., using the optical system 600), fabrication errors can be corrected. Thus, the emission profile of the OPA can be measured after fabrication, and errors in fabrication can be corrected by changing the state of the phase change material before using the OPA as an illumination source in a metrology device.

[0118] Generally, it can be desirable to select a material or PCM so as to have minimal absorption while introducing a large phase change to light propagating through a waveguide coated with the material or PCM. It can be noted that many materials, such as phase change materials, have changes in both the real and imaginary parts of their refractive index between the amorphous and crystalline states and will absorb a portion of the light. Our method will also be applicable to such materials or phase change materials. Depending on the combination of the material or phase change material selection and the wavelength of the first radiation source, thus the phase or both the amplitude and phase of light propagating in a waveguide section coated with the material or phase change material can be tuned in a non-volatile and reversible manner, regardless of potentially introducing additional absorption into the system.

[0119] Figure 7 Method steps (e.g., using one or more processors) for performing a method 700 that includes the functions described herein are shown in accordance with some embodiments. Figure 7 The method 700 can be performed in any conceivable order and does not require all steps to be performed. In addition, the Figure 7 method steps described above only reflect examples of these steps and are not restrictive.

[0120] In some embodiments, the method 700 illustrates a method for adjusting a phased array illumination device.

[0121] In some embodiments, in step 702, a material is deposited on a portion of each of a plurality of waveguides of a phased array. In one aspect, the phased array includes a plurality of optical elements configured to radiate radiation waves.

[0122] In some embodiments, in step 704, the state of the material is modified to adjust the phase of the radiation wave such that the radiation waves accumulate to form a radiation beam.

[0123] In some embodiments, in step 706, a first beam is coupled to the phased array.

[0124] In some embodiments, in step 708, the response of the phased array is monitored.

[0125] In some embodiments, in step 710, it is determined whether the difference between the response and the desired response is greater than a threshold amount. If so, the operation returns to step 704. If not, the operation proceeds to step 712.

[0126] In some embodiments, in step 712, based on the monitored response, it is determined that the desired response has been obtained.

[0127] These embodiments may be further described using the following aspects:

[0128] 1. A system, comprising:

[0129] A radiation source;

[0130] A phased array configured to generate a radiation beam and direct the beam towards a target structure on a substrate, the phased array comprising:

[0131] A plurality of optical elements configured to transmit radiation waves, and

[0132] A plurality of waveguides configured to direct radiation from the radiation source to the plurality of optical elements, wherein a portion of each of the plurality of waveguides comprises a material configured to adjust the phase of the radiation wave such that the radiation waves accumulate to form the beam; and

[0133] A detector configured to receive radiation scattered by the target structure and generate a measurement signal based on the received radiation.

[0134] 2. The system according to aspect 1 or 21, wherein the phased array comprises a photonic integrated circuit, and the optical elements are formed on the photonic integrated circuit.

[0135] 3. The system according to aspect 1 or 21, wherein the material is a phase change material whose refractive index can be modified in a non-volatile and reversible manner in response to an external stimulus, or a material whose refractive index increases or decreases monotonically in response to an external stimulus.

[0136] 4. The system according to aspect 3, wherein the phase change material is a chalcogenide.

[0137] 5. The system according to aspect 1 or 21, wherein the material comprises a first portion in an amorphous state and a second portion in a crystalline state.

[0138] 6. The system according to aspect 1 or 21, wherein the radiation source is configured to generate one or more wavelengths, and the one or more wavelengths are in the visible spectrum or the infrared spectrum.

[0139] 7. The system according to aspect 1 or 21, wherein the radiation source is a first radiation source, the detector is a first detector, and the radiation beam is a first radiation beam, and the system further comprises:

[0140] a second radiation source configured to generate a second radiation beam, wherein the second radiation beam is focused on the portion of each of the plurality of waveguides;

[0141] a second detector configured to receive a portion of the first radiation beam; and

[0142] a controller configured to tune the characteristics of the second radiation source based on a difference between a profile of the received portion of the radiation beam and a desired profile of the radiation beam.

[0143] 8. The system according to aspect 7, wherein the second radiation source is configured to generate a plurality of beams, and each of the plurality of beams is focused on a respective portion of each of the plurality of waveguides.

[0144] 9. A method comprising:

[0145] depositing a material on a portion of each of a plurality of waveguides of a phased array, wherein the phased array includes a plurality of optical elements configured to radiate radiation waves;

[0146] modifying a state of the material to adjust a phase of the radiation waves such that the radiation waves accumulate to form a radiation beam;

[0147] coupling a first beam to the phased array;

[0148] monitoring a response of the phased array; and

[0149] determining when a desired response is obtained based on the monitored response.

[0150] 10. The method according to aspect 9 or 22, wherein the modifying further comprises:

[0151] directing a second beam to the portion of each of the plurality of waveguides to modify the state of the material.

[0152] 11. The method according to aspect 10, wherein the determining further comprises:

[0153] Determine a cost function indicative of a deviation between the desired response and the monitored response; and

[0154] Tune the intensity, pulse duration, irradiation position, or wavelength of the second beam based on the cost function.

[0155] 12. The method according to aspect 11, wherein:

[0156] The response is a two-dimensional intensity profile of the radiation beam; and

[0157] The cost function is an average of the differences between the two-dimensional intensity profile of the monitored response and the desired response.

[0158] 13. The method according to aspect 11, further comprising:

[0159] Determine the cost function associated with each of the plurality of optical elements.

[0160] 14. The method according to aspect 9 or 22, wherein:

[0161] The material is a phase change material; and

[0162] The modification further includes switching between an amorphous state and a crystalline state.

[0163] 15. The method according to aspect 9 or 22, wherein the modification further includes:

[0164] Direct a plurality of beams to respective portions of each of the plurality of waveguides.

[0165] 16. An optical tool, comprising:

[0166] A first radiation source configured to generate a first beam, wherein the first radiation source is coupled to a phased array;

[0167] A second radiation source configured to generate a second beam;

[0168] An optical system configured to direct the second beam to a portion of the phased array, wherein the portion of the phased array is coated with a material, and the material is configured to adjust the phase of the radiation wave emitted by the phased array such that the radiation waves accumulate to form a radiation beam;

[0169] A detector configured to receive the radiation beam generated by the phased array and generate a measurement signal based on the received radiation beam; and

[0170] a controller configured to control the characteristics of the second beam based on the measurement signal and a desired profile of the radiation beam.

[0171] 17. The optical tool according to aspect 16 or 23, wherein the first beam has a wavelength in the visible range or in the infrared range.

[0172] 18. The optical tool according to aspect 16 or 23, wherein the material is a phase change material and the phase change material switches between an amorphous state and a crystalline state based on the second beam.

[0173] 19. The optical tool according to aspect 16 or 23, wherein the characteristics of the second beam include the intensity, pulse duration, irradiation position, or wavelength of the second beam.

[0174] 20. The optical tool according to aspect 16 or 23, wherein:

[0175] the second beam has a wavelength such that the beam is absorbed by the material, and

[0176] the absorption changes the optical constants of the material such that the change in the optical constants is maintained after the second beam is turned off.

[0177] 21. A system, comprising:

[0178] a radiation source configured to irradiate the target structure;

[0179] a phased array configured to collect scattered radiation from a target structure on a substrate, the phased array comprising:

[0180] a plurality of optical elements configured to receive radiation waves, and

[0181] a plurality of waveguides configured to guide radiation from the plurality of optical elements to the detector, wherein a portion of each of the plurality of waveguides includes a material configured to adjust the phase of the radiation wave such that the radiation waves accumulate at the detector; and

[0182] a detector configured to receive radiation from the phased array to generate a measurement signal based on the received radiation.

[0183] 22. A method, comprising:

[0184] depositing a material on a portion of each of a plurality of waveguides of a phased array, wherein the phased array includes a plurality of optical elements configured to collect radiation waves;

[0185] Modify the state of the material to adjust the phase of the radiation wave such that the radiation beams accumulate to form a radiation wave;

[0186] Couple a first beam to the phased array;

[0187] Monitor the response of the phased array; and

[0188] Determine when a desired response is obtained based on the monitored response.

[0189] 23. An optical tool, comprising:

[0190] A first radiation source configured to generate a first beam, wherein the first radiation source is coupled to a phased array;

[0191] A second radiation source configured to generate a second beam;

[0192] An optical system configured to direct the second beam to a portion of the phased array, wherein the portion of the phased array is coated with a material, and the material is configured to adjust the phase of the radiation wave collected by the phased array such that the radiation waves accumulate;

[0193] A detector configured to receive the accumulated radiation wave from the phased array and generate a measurement signal based on the received radiation wave; and

[0194] A controller configured to control the characteristics of the second beam based on the measurement signal.

[0195] Although the lithographic apparatus is specifically mentioned herein for use in the manufacture of integrated circuits, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, the guiding and detecting of patterns in magnetic domain memories, liquid crystal displays (LCDs), thin film magnetic heads, etc. Those skilled in the art will understand that in the context of such alternative applications, any terms "wafer" or "die" used herein may be considered as specific examples of the more general terms "substrate" or "target portion" respectively. The substrate mentioned herein may be processed before or after exposure, for example in a track unit or a coat develop system unit (a tool typically applying a resist layer to the substrate and developing the exposed resist) and / or a metrology unit. Where applicable, the disclosures herein may be applied to such and other substrate processing tools. Additionally, the substrate may be processed more than once, for example to produce a multi-layer IC, such that the term substrate as used herein may also refer to a substrate that already contains multiple processed layers.

[0196] Although embodiments of the present disclosure have been specifically referenced above in the context of optical lithography, it will be understood that the present 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 topography in the patterning device defines the pattern created on the substrate. The topography of the patterning device can be imprinted into a resist layer supplied to the substrate, whereupon the resist is cured by application of electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist, leaving a pattern therein.

[0197] It should be understood that the wording or terminology herein is for descriptive and not restrictive purposes, such that the terms or wording in the present disclosure will be interpreted by those skilled in the relevant art in accordance with the teachings herein.

[0198] In addition, the terms "radiation", "radiation beam", or the like as used herein encompass all types of electromagnetic radiation, which includes ultraviolet (UV) radiation (e.g., having a wavelength λ of 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV or soft X-ray) radiation (e.g., having a wavelength in the range of 5 nm to 20 nm, such as, for example, a wavelength of 13.5 nm), or hard X-rays operating at less than 5 nm, as well as beams of matter (such as ion beams or electron beams). The terms "light", "exposure", etc. can refer to non-material radiation (e.g., photons, UV, X-rays, etc.). Generally, radiation having a wavelength between approximately 400 nm and approximately 700 nm is considered visible light radiation; radiation having a wavelength between approximately 780 nm and 3000 nm (or greater) is considered IR radiation. UV refers to radiation having a wavelength of approximately 100 nm to 400 nm. In lithography, the term "UV" also applies to wavelengths that can be generated 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 gas) refers to radiation having a wavelength of approximately 100 nm to 200 nm. Deep UV (DUV) generally refers to radiation having a wavelength range from 126 nm to 428 nm, and in embodiments, excimer lasers can generate DUV radiation for use within a lithographic apparatus. It should be understood that radiation having a wavelength in the range of, for example, 5 nm to 20 nm refers to radiation having at least partially a wavelength band within the range of 5 nm to 20 nm.

[0199] It will be understood that the Detailed Description section, rather than the Summary of the Invention section and the Abstract of the Specification section, is intended to explain the claims. As contemplated by the inventor, the Summary of the Invention section and the Abstract of the Specification section may set forth one or more, but not all, exemplary embodiments of the disclosure, and are therefore not intended to limit the disclosure and the appended claims in any way.

[0200] The present disclosure has been described above by means of functional building blocks that illustrate the embodiments and their interrelationships that specify the functions. For convenience of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are appropriately performed.

[0201] Although specific embodiments of the present disclosure have been described above, it should be understood that the embodiments of the present disclosure may be practiced in ways other than those described. These descriptions are intended to be exemplary rather than restrictive. Thus, those skilled in the art will appreciate that the disclosed content can be modified without departing from the scope of the claims set forth below.

[0202] The foregoing description of the specific embodiments will so fully disclose the general nature of the present disclosure that others can, without departing from the general concept of the present disclosure and without undue experimentation, readily modify and / or adapt various applications of these specific embodiments by applying knowledge within the scope of the art. Therefore, such adaptations and modifications are intended to fall within the meaning and scope of the equivalents of the disclosed embodiments based on the teachings and guidance presented herein.

[0203] The breadth and scope of the subject matter protected should not be limited by any of the exemplary embodiments described above, but should be defined only by the appended claims and their equivalents.

Claims

1. A system, comprising: A radiation source; A phased array configured to generate a radiation beam and direct the beam towards a target structure on a substrate, the phased array comprising: A plurality of optical elements configured to transmit radiation waves, and A plurality of waveguides configured to direct radiation from the radiation source to the plurality of optical elements, wherein a portion of each waveguide of the plurality of waveguides comprises a material configured to adjust the phase of the radiation wave such that the radiation waves accumulate to form the beam; And A detector configured to receive radiation scattered by the target structure and generate a measurement signal based on the received radiation.

2. The system according to claim 1, wherein, The phased array comprises a photonic integrated circuit, and the optical elements are formed on the photonic integrated circuit.

3. The system according to claim 1, wherein, The material is a phase change material whose refractive index can be modified in a non-volatile and reversible manner in response to an external stimulus, or a material whose refractive index monotonically increases or decreases in response to an external stimulus.

4. The system according to claim 3, wherein The phase change material is a chalcogenide.

5. The system according to claim 1, wherein The material comprises a first portion in an amorphous state and a second portion in a crystalline state.

6. The system according to claim 1, wherein The radiation source is configured to generate one or more wavelengths, and the one or more wavelengths are in the visible spectrum or the infrared spectrum.

7. The system according to claim 1, wherein The radiation source is a first radiation source, the detector is a first detector, and the radiation beam is a first radiation beam, and the system further comprises: A second radiation source configured to generate a second radiation beam, wherein the second radiation beam is focused on the portion of each waveguide of the plurality of waveguides; A second detector configured to receive a portion of the first radiation beam; and A controller configured to tune the characteristics of the second radiation source based on a difference between a profile of the received portion of the radiation beam and a desired profile of the radiation beam.

8. The system according to claim 7, wherein, The second radiation source is configured to generate a plurality of beams, and each beam of the plurality of beams is focused on a corresponding portion of each waveguide of the plurality of waveguides.

9. A method, comprising: Depositing a material on a portion of each waveguide of a plurality of waveguides of a phased array, wherein the phased array comprises a plurality of optical elements configured to radiate radiation waves; Modifying a state of the material to adjust a phase of the radiation wave such that the radiation waves accumulate to form a radiation beam; Coupling a first beam to the phased array; Monitoring a response of the phased array; And Determining when a desired response is obtained based on the monitored response.

10. The method according to claim 9, wherein the modifying further comprises: Directing a second beam to the portion of each waveguide of the plurality of waveguides to modify the state of the material.

11. The method according to claim 10, wherein, The determining further comprises: Determining a cost function indicative of a deviation between the desired response and the monitored response; and Tuning an intensity, a pulse duration, an illumination position, or a wavelength of the second beam based on the cost function.

12. The method according to claim 11, wherein: The response is a two-dimensional intensity profile of the radiation beam; and The cost function is the average of the differences between the two-dimensional intensity profile of the monitored response and the desired response.

13. The method according to claim 11, further comprising: Determining the cost function associated with each of the plurality of optical elements.

14. The method according to claim 9, wherein: The material is a phase change material; and The modification further includes switching between an amorphous state and a crystalline state.

15. The method according to claim 9, wherein the modification further includes: Directing a plurality of beams to respective portions of each of the plurality of waveguides.

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