Integrated optics distance, leveling and tilt sensor

Abstract

The present system(s) and method(s) use an integrated photonic sensor to determine tilt angle present at the metrology region or mark. The integrated photonic sensor uses two pairs of grating couplers, each pair having an emitting grating coupler and a capturing grating coupler. The positions of the grating couplers may be fixed where a first capturing grating coupler will capture a peak captured light value of its paired emitting grating coupler when the angle of tilt at the region is a positive angle, and a second capturing grating coupler will capture a peak captured light value of its paired emitting grating coupler when the angle of tilt at the region is a negative angle. Using this fixed configuration and knowing the tilt angles at which peak coupling efficiencies would be captured, a ratio is computed using the two captured light values. A tilt angle is determined using this ratio.

Description

INTEGRATED OPTICS DISTANCE, LEVELING AND TILT SENSORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 658,991 which was filed on June 12, 2024 and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] This description relates to determining a degree of tilt for imaging a substrate with an integrated photonic sensor.BACKGROUND

[0003] A lithographic projection apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A patterning device (e.g., a mask) may include or provide a pattern corresponding to an individual layer of the IC (“design layout”), and this pattern can be transferred onto a target portion (e.g. comprising one or more dies) on a substrate (e.g., silicon wafer) that has been coated with a layer of radiation-sensitive material (“resist”), by methods such as irradiating the target portion through the pattern on the patterning device. In general, a single substrate includes a plurality of adjacent target portions to which the pattern is transferred successively by the lithographic projection apparatus, one target portion at a time. In one type of lithographic projection apparatus, the pattern on the entire patterning device is transferred onto one target portion in one operation. Such an apparatus is commonly referred to as a stepper. In an alternative apparatus, commonly referred to as a step-and-scan apparatus, a projection beam scans over the patterning device in a given reference direction (the “scanning” direction) while synchronously moving the substrate parallel or anti-parallel to this reference direction. Different portions of the pattern on the patterning device are transferred to one target portion progressively.

[0004] Prior to transferring the pattern from the patterning device to the substrate, the substrate may undergo various procedures, such as priming, resist coating, and a soft bake. After exposure, the substrate may be subjected to other procedures (“post-exposure procedures”), such as a post-exposure bake (PEB), development, a hard bake and measurement / inspection of the transferred pattern. This array of procedures is used as a basis to make an individual layer of a device, e.g., an IC. The substrate may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, deposition, chemo-mechanical polishing, etc., all intended to finish the individual layer of the device. If several layers are required in the device, then the whole procedure, or a variant thereof, is repeated for each layer. Eventually, a device will be present in each target portion on the substrate. These devices are then separated from one another by a technique such as dicing or sawing, such that the individualdevices can be mounted on a carrier, connected to pins, etc. This device manufacturing process may be considered a patterning process.

[0005] Lithography is a central step in the manufacturing of device such as ICs, where patterns formed on substrates define functional elements of the devices, such as microprocessors, memory chips, etc. Similar lithographic techniques are also used in the formation of flat panel displays, microelectromechanical systems (MEMS) and other devices.

[0006] As semiconductor manufacturing processes continue to advance, the dimensions of functional elements have continually been reduced while the number of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as “Moore’s law.” At the current state of technology, layers of devices are manufactured using lithographic projection apparatuses that project a design layout onto a substrate using illumination from a deep-ultraviolet illumination source, creating individual functional elements having dimensions well below 100 nm, i.e. less than half the wavelength of the radiation from the illumination source (e.g., a 193 nm illumination source).

[0007] This process in which features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus are printed, is commonly known as low-ki lithography, according to the resolution formula CD = kjxk / NA, where I is the wavelength of radiation employed (currently in most cases 248nm or 193nm), NA is the numerical aperture of projection optics in the lithographic projection apparatus, CD is the “critical dimension’ -generally the smallest feature size printed-and ki is an empirical resolution factor. In general, the smaller ki the more difficult it becomes to reproduce a pattern on the substrate that resembles the shape and dimensions planned by a designer in order to achieve particular electrical functionality and performance. To overcome these difficulties, sophisticated fine-tuning steps are applied to the lithographic projection apparatus, the design layout, or the patterning device. These include, for example, but are not limited to, optimization of NA and optical coherence settings, customized illumination schemes, use of phase shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as “optical and process correction”) in the design layout, or other methods generally defined as “resolution enhancement techniques” (RET).SUMMARY

[0008] The metrology system(s) and method(s) described below provide for a sensor to measure the tilt of a substrate on a surface, such as a wafer on a stage in the lithographic apparatus. The integrated photonic sensor is based on grating couplers. The integrated photonic sensor uses a combination of grating couplers to either illuminate (though illumination with grating couplers may be optional) and / or capture the reflected light from the surface / substrate, for determining its tilt and / or other purposes. The illuminator can be replaced by fiber, microlenses, or micromirrors. The capturing grating couplers canbe replaced by fiber, microlenses, micromirrors, or photodetectors. This approach can provide continuous tilt measurement. This approach is less expensive and uses less physical volume for components in an imaging system than current approaches. This approach also eliminates potential issues with aberration with existing optics designs.

[0009] The integrated photonic sensor is based on two pairs of grating couplers, each pair having an emitting grating coupler and a capturing grating coupler. The positions of the grating couplers may be fixed such that a first capturing grating coupler will capture a peak captured light value of its paired emitting grating coupler when the angle of tilt at the region is a positive angle, and a second capturing grating coupler will capture a peak captured light value of its paired emitting grating coupler when the angle of tilt at the region is a negative angle. Using this fixed configuration and knowing the tilt angles at which peak coupling efficiencies would be captured, a ratio can be computed using the two captured light value values. A tilt angle can be determined using this computed ratio. Note that the principles described herein may be used for applications beyond the metrology tilt sensor application described above.

[0010] In addition, the present disclosures introduce a composite or collection of sensors where some are configured to perform a focus / leveling measurement while others are configured to measure the tilt. The focus and tilt sensors may be interspersed on an array so that multiple regions of a substrate may be measured simultaneously. Using just a single array of these sensors may allow for more rapid and denser scanning of substrate measurements than current methods. The array of sensors may be made wide enough so that a single scan or fewer scans along or across just one axis is sufficient to provide measurements of the entire substrate. In contrast, existing solutions may require the scan to be performed in patches on the substrate, such that multiple scans are needed to comprehensively obtain measurements throughout the entire substrate.

[0011] According to an embodiment, a system for determining an angle of tilt of a substrate is presented. The system may include: a sensor; and a processor operatively coupled to the sensor; the sensor comprising a plurality of grating couplers. A first grating coupler of the plurality of grating couplers is configured to emit a first optical beam at a region on the substrate. A second grating coupler of the plurality of grating couplers is configured to measure a first captured light value after the first optical beam reflects off the region on the substrate. The captured light value may be a measure of captured light value, for example. A third grating coupler of the plurality of grating couplers is configured to emit a second optical beam at the region on the substrate. A fourth grating coupler of the plurality of grating couplers is configured to measure a second captured light value after the second optical beam reflects off the region on the substrate. The processor is configured to: compute a ratio using the first captured light value and the second captured light value; and compute the angle of tilt of the region on the substrate using the computed ratio.

[0012] In some embodiments, to compute the ratio, the processor is configured to compute a difference between the first and second captured light value values, compute a total captured power of the first and second captured light value values, and compare the computed difference to the total captured power.

[0013] In some embodiments, the second grating coupler is configured to capture the first captured light value at a maximum when the angle of tilt of the region is a positive angle.

[0014] In some embodiments, the fourth grating coupler is configured to capture the second captured light value at a maximum when the angle of tilt of the region is a negative angle.

[0015] In some embodiments, the first grating coupler is positioned diagonally opposite to the second grating coupler with respect to the region on the substrate; the third grating coupler is positioned laterally opposite to the first grating coupler with respect to the region on the substrate, and the fourth grating coupler is positioned laterally opposite to the second grating coupler with respect to the region on the substrate. This embodiment helps to avoid the overlap between the grating couples. If the grating couplers are placed in different layers, they can all be on the same axis.

[0016] In some embodiments, the first and second grating couplers are positioned in a predetermined manner such that the second grating coupler is configured to capture the first captured light value of the first optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a positive angle of tilt and a predetermined standard deviation.

[0017] In some embodiments, the third and fourth grating couplers are positioned in a predetermined manner such that the fourth grating coupler is configured to capture the second captured light value of the second optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a negative angle of tilt and a predetermined standard deviation.

[0018] In some embodiments, a system for determining an angle of tilt on a substrate and a measurement of focus on the substrate is presented. The system may include: a plurality of tilt sensors; a plurality of focus sensors; and at least one processor. Each of the tilt sensors comprises a plurality of grating couplers. A first grating coupler of the plurality of grating couplers is configured to emit a first optical beam at a region on the substrate. A second grating coupler of the plurality of grating couplers is configured to measure a first captured light value after the first optical beam reflects off the region on the substrate. A third grating coupler of the plurality of grating couplers is configured to emit a second optical beam at the region on the substrate. A fourth grating coupler of the plurality of grating couplers is configured to measure a second captured light value after the second optical beam reflects off the region on the substrate. The at least one processor is configured to: compute a ratio using the first captured light value and the second captured light value; and compute the angle of tilt of the region on the substrate using the computed ratio.

[0019] In some embodiments, the plurality of tilt sensors and the plurality of focus sensors are arranged in an array sufficiently wide such that the entire substrate can be measured for tilt angles and focus measurements using a single scan of the array.

[0020] In some embodiments, a method of determining an angle of tilt in a substrate is presented. The method may include: emitting, by a first grating coupler of a plurality of grating couplers, a first optical beam at a region on the substrate; capturing, by a second grating coupler of the plurality of grating couplers, a first captured light value after the first optical beam reflects off the region on the substrate; emitting, by a third grating coupler of the plurality of grating couplers, a second optical beam at the region on the substrate; capturing, by a fourth grating coupler of the plurality of grating couplers, a second captured light value after the second optical beam reflects off the region on the substrate; computing, by a processor, a ratio using the first captured light value and the second captured light value; and computing the angle of tilt of the region on the substrate using the computed ratio.

[0021] In some embodiments, computing the ratio comprises: computing a difference between the first and second captured light value values; computing a total captured power of the first and second captured light value values; and comparing the computed difference to the total captured power.

[0022] In some embodiments, a semiconductor device manufacturing method is described. The method may include: receiving a substrate with a photoresist layer; directing radiation from a radiation source to transfer a pattern from a reticle onto the photoresist layer; determining an angle of tilt in a region of the substrate, comprising: emitting, by a first grating coupler of a plurality of grating couplers, a first optical beam at a region on the substrate; capturing, by a second grating coupler of the plurality of grating couplers, a first captured light value after the first optical beam reflects off the region on the substrate; emitting, by a third grating coupler of the plurality of grating couplers, a second optical beam at the region on the substrate; capturing, by a fourth grating coupler of the plurality of grating couplers, a second captured light value after the second optical beam reflects off the region on the substrate; computing, by a processor, a ratio using the first captured light value and the second captured light value; and computing the angle of tilt of the region on the substrate using the computed ratio and removing a portion of the photoresist layer to form a pattern over the substrate.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above aspects and other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.FIG. 1 schematically depicts a lithography apparatus, according to an embodiment.FIG. 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment.FIG. 3 schematically depicts an example inspection system, according to an embodiment.FIG. 4 schematically depicts an example metrology technique, according to an embodiment.FIG. 5 illustrates the relationship between a radiation illumination spot of an inspection system and a metrology target, according to an embodiment.FIG. 6 illustrates a system configured for imaging a substrate, according to an embodiment. This may include determining an angle of tilt in one or more metrology targets, for example.FIG. 7 shows an illustration of the optical geometry that a tilt sensor of the present disclosure is designed to capture.FIG. 8 shows a plan view of the sensor apparatus over the substrate, according to some embodiments.FIG. 9 shows example graphs of how the captured light value of the grating couplers in the tilt sensor are a function of the tilt in the target substrate.FIG. 10 shows several graphs that provide sensitivity analysis to aid in the design of the tilt sensor and its placement relative to the region being examined on the target substrate.FIG. 11 shows example design parameters for the emitting and capturing grating couplers, according to some embodiments.FIG. 12 shows an example scanning process of the tilt sensor along a path.FIG. 13 shows how the scanning process of one sensor can be replicated along an apparatus to scan a much wider area within a single scan, according to some embodiments.FIG. 14 illustrates a method for imaging a substrate, according to some embodiments.FIG. 15 is a block diagram of an example computer system, according to some embodiments.DETAILED DESCRIPTION

[0024] In semiconductor device manufacturing, metrology operations typically include determining the position of a metrology mark (or marks) and / or other target in a layer of a semiconductor device structure. This position is typically determined by irradiating a metrology mark with radiation and comparing characteristics of different diffraction orders of radiation reflected from the metrology mark. Such techniques are used to measure overlay, alignment, and / or other parameters.

[0025] To address these issues, the present system(s) and method(s) use an integrated photonic sensor to determine any tilt angle present at the metrology region or mark. The integrated photonic sensor is based on grating couplers where, by changing a grating period and / or duty cycle, the amplitude and the phase of the grating coupler mode is engineered to have an optimum captured light value for a specific tilt angle (or initial / known tilt angle). A captured light value is determined between an emitting grating coupler (for example) and a receiving grating coupler based on emitted radiation, such as a photonic beam, with a certain amplitude and phase configured for a known position relative to (e.g.,a distance from) a substrate, and reflected radiation received from the substrate. A tilt angle is determined based on the captured light value and the known position. Note that the principles described herein may be used for applications beyond the metrology focus sensor application described above.

[0026] By way of a brief introduction, the description below relates to semiconductor device manufacturing and patterning processes. The following paragraphs also describe several components of systems and / or methods for semiconductor device metrology. These systems and methods may be used for measuring overlay, alignment, etc., in a semiconductor device manufacturing process, for example, or for other operations.

[0027] Although specific reference may be made in this text to the measurement of overlay, alignment, or other parameters, and the manufacture of integrated circuits (ICs) for semiconductor devices, it should be understood that the description herein has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle,” “wafer” or “die” in this text should be considered as interchangeable with the more general terms “mask,” “substrate” and “target portion,” respectively.

[0028] The term “projection optics” as used herein should be broadly interpreted as encompassing various types of optical systems, including refractive optics, reflective optics, apertures and catadioptric optics, for example. The term “projection optics” may also include components operating according to any of these design types for directing, shaping or controlling the projection beam of radiation, collectively or singularly. The term “projection optics” may include any optical component in the lithographic projection apparatus, no matter where the optical component is located on an optical path of the lithographic projection apparatus. Projection optics may include optical components for shaping, adjusting and / or projecting radiation from the source before the radiation passes the patterning device, and / or optical components for shaping, adjusting and / or projecting the radiation after the radiation passes the patterning device. The projection optics generally exclude the source and the patterning device.

[0029] FIG. 1 schematically depicts an embodiment of a lithographic apparatus LA. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation, DUV radiation, or EUV radiation); a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters; a substrate table (e.g. a wafer table) WT (e.g., WTa, WTb or both) configured to hold a substrate (e.g. a resist-coated wafer) W and coupled to a second positioner PW configured to accurately position the substrate in accordance with certain parameters; and a projection system (e.g. a refractive projection lens system) PS configuredto project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies and often referred to as fields) of the substrate W. The projection system is supported on a reference frame RF. As depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array or employing a reflective mask).

[0030] The illuminator IL receives a beam of radiation from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising for example suitable directing mirrors and / or a beam expander. In other cases, the source may be an integral part of the apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0031] The illuminator IL may alter the intensity distribution of the beam. The illuminator may be arranged to limit the radial extent of the radiation beam such that the intensity distribution is non-zero within an annular region in a pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in a pupil plane of the illuminator IL may be referred to as an illumination mode.

[0032] The illuminator IL may comprise adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. Generally, at least the outer and / or inner radial extent (commonly referred to as o-outer and o-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. The illuminator IL may be operable to vary the angular distribution of the beam. For example, the illuminator may be operable to alter the number, and angular extent, of sectors in the pupil plane wherein the intensity distribution is non-zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different illumination modes may be achieved. For example, by limiting the radial and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution may have a multi-pole distribution such as, for example, a dipole, quadrupole or hexapole distribution. A desired illumination mode may be obtained, e.g., by inserting an optic which provides that illumination mode into the illuminator IL or using a spatial light modulator.

[0033] The illuminator IL may be operable to alter the polarization of the beam and may be operable to adjust the polarization using adjuster AD. The polarization state of the radiation beam across a pupil plane of the illuminator IL may be referred to as a polarization mode. The use of different polarizationmodes may allow greater contrast to be achieved in the image formed on the substrate W. The radiation beam may be unpolarized. Alternatively, the illuminator may be arranged to linearly polarize the radiation beam. The polarization direction of the radiation beam may vary across a pupil plane of the illuminator IL. The polarization direction of radiation may be different in different regions in the pupil plane of the illuminator IL. The polarization state of the radiation may be chosen in dependence on the illumination mode. For multi-pole illumination modes, the polarization of each pole of the radiation beam may be generally perpendicular to the position vector of that pole in the pupil plane of the illuminator IL. For example, for a dipole illumination mode, the radiation may be linearly polarized in a direction that is substantially perpendicular to a line that bisects the two opposing sectors of the dipole. The radiation beam may be polarized in one of two different orthogonal directions, which may be referred to as X-polarized and Y-polarized states. For a quadrupole illumination mode, the radiation in the sector of each pole may be linearly polarized in a direction that is substantially perpendicular to a line that bisects that sector. This polarization mode may be referred to as XY polarization. Similarly, for a hexapole illumination mode the radiation in the sector of each pole may be linearly polarized in a direction that is substantially perpendicular to a line that bisects that sector. This polarization mode may be referred to as TE polarization.

[0034] In addition, the illuminator IL generally comprises various other components, such as an integrator IN and a condenser CO. The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation. Thus, the illuminator provides a conditioned beam of radiation B, having a desired uniformity and intensity distribution in its cross section.

[0035] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

[0036] The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a pattern in a target portion of the substrate. In an embodiment, a patterning device is any device that can be used to impart a radiation beam with a pattern in its crosssection to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of thesubstrate, for example if the pattern includes phase-shifting features or so-called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in a target portion of the device, such as an integrated circuit.

[0037] A patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, 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 incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam, which is reflected by the mirror matrix.

[0038] The term “projection system” should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system.”

[0039] The projection system PS may comprise a plurality of optical (e.g., lens) elements and may further comprise an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase variations across the pupil plane throughout the field). To achieve this, the adjustment mechanism may be operable to manipulate one or more optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system wherein its optical axis extends in the z direction. The adjustment mechanism may be operable to do any combination of the following: displace one or more optical elements; tilt one or more optical elements; and / or deform one or more optical elements. Displacement of an optical element may be in any direction (x, y, z, or a combination thereof). Tilting of an optical element is typically out of a plane perpendicular to the optical axis, by rotating about an axis in the x and / or y directions although a rotation about the z axis may be used for a non-rotationally symmetric aspherical optical element. Deformation of an optical element may include a low frequency shape (e.g. astigmatic) and / or a high frequency shape (e.g. free form aspheres). Deformation of an optical element may be performed for example by using one or more actuators to exert force on one or more sides of the optical element and / or by using one or more heating elements to heat one or more selected regions of the optical element. In general, it may not be possible to adjust the projection system PS to correct for apodization (transmission variation across the pupil plane). The transmission map of a projection system PS may be used when designing a patterning device (e.g., mask) MA for the lithography apparatus LA. Using a computational lithography technique, the patterning device MA may be designed to at least partiallycorrect for apodization.

[0040] The lithographic apparatus may be of a type having two (dual stage) or more tables (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, a substrate table WTa and a table WTb below the projection system without a substrate that is dedicated to, for example, facilitating measurement, and / or cleaning, etc.). In such “multiple stage” machines, the additional tables may be used in parallel, or preparatory steps may be conducted on one or more tables while one or more other tables are being used for exposure. For example, alignment measurements using an alignment sensor AS and / or level (height, tilt, etc.) measurements using a level sensor LS may be made.

[0041] The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the patterning device and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0042] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by the illumination system IL. The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder, 2-D encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in Fig. 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected to a shortstroke actuator only, or may be fixed. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations inwhich more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0043] The depicted apparatus may be used in at least one of the following modes. In step mode, the support structure MT and the substrate table WT are kept essentially stationary, while a pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. In scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure MT may be determined by the (de-) magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion. In another mode, the support structure MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed, and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0044] Combinations and / or variations on the above-described modes of use or entirely different modes of use may also be employed.

[0045] The substrate may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already includes multiple processed layers.

[0046] The terms “radiation” and “beam” used herein with respect to lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g. having a wavelength of 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0047] Various patterns on or provided by a patterning device may have different process windows.i.e., a space of processing variables under which a pattern will be produced within specification. Examples of pattern specifications that relate to potential systematic defects include checks for necking, line pull back, line thinning, CD, edge placement, overlapping, resist top loss, resist undercut and / or bridging. The process window of the patterns on a patterning device or an area thereof may be obtained by merging (e.g., overlapping) process windows of each individual pattern. The boundary of the process window of a group of patterns comprises boundaries of process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the group of patterns.

[0048] As shown in FIG. 2, the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to as a lithocell or cluster, which also includes apparatuses to perform pre- and post-exposure processes on a substrate. Conventionally these include one or more spin coaters SC to deposit one or more resist layers, one or more developers to develop exposed resist, one or more chill plates CH and / or one or more bake plates BK. A substrate handler, or robot, RO picks up one or more substrates from input / output port I / Ol, I / O2, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus. These apparatuses, which are often collectively referred to as the track, are under the control of a track control unit TCU which is itself controlled by the supervisory control system SCS, which also controls the lithographic apparatus via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0049] In order that a substrate that is exposed by the lithographic apparatus is exposed correctly and consistently and / or in order to monitor a part of the patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., an optical lithography step), it is desirable to inspect a substrate or other object to measure or determine one or more properties such as alignment, overlay (which can be, for example, between structures in overlying layers or between structures in a same layer that have been provided separately to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, a material property, etc. Accordingly, a manufacturing facility in which lithocell LC is located also typically includes a metrology system that measures some or all of the substrates W (FIG. 1) that have been processed in the lithocell or other objects in the lithocell. The metrology system may be part of the lithocell LC, for example it may be part of the lithographic apparatus LA (such as alignment sensor AS (FIG. 1)).

[0050] The one or more measured parameters may include, for example, alignment, overlay between successive layers formed in or on the patterned substrate, critical dimension (CD) (e.g., critical linewidth) of, for example, features formed in or on the patterned substrate, focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberrations of an optical lithography step, etc. This measurement is often performed on one or more dedicated metrology targets provided on the substrate. The measurement can be performed after-development of a resist butbefore etching, after-etching, after deposition, and / or at other times.

[0051] There are various techniques for making measurements of the structures formed in the patterning process, including the use of a scanning electron microscope, an image -based measurement tool and / or various specialized tools. A fast and non-invasive form of specialized metrology tool is one in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered (diffracted / reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Traditionally, this may be termed diffraction-based metrology. Applications of this diffraction-based metrology include the measurement of overlay, alignment, etc. For example, overlay and / or alignment can be measured by comparing parts of the diffraction spectrum (for example, comparing different diffraction orders in the diffraction spectrum of a periodic grating).

[0052] Thus, in a device fabrication process (e.g., a patterning process or a lithography process), a substrate or other objects may be subjected to various types of measurement during or after the process. The measurement may determine whether a particular substrate is defective, may establish adjustments to the process and apparatuses used in the process (e.g., aligning two layers on the substrate or aligning the patterning device to the substrate), may measure the performance of the process and the apparatuses, or may be for other purposes. Examples of measurement include optical imaging (e.g., optical microscope), non-imaging optical measurement (e.g., measurement based on diffraction such as the ASML YieldStar metrology tool, the ASML SMASH metrology system), mechanical measurement (e.g., profiling using a stylus, atomic force microscopy (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)).

[0053] Metrology results may be provided directly or indirectly to the supervisory control system SCS. If an error is detected, an adjustment may be made to exposure of a subsequent substrate (especially if the inspection can be done soon and fast enough that one or more other substrates of the batch are still to be exposed) and / or to subsequent exposure of the exposed substrate. Also, an already exposed substrate may be stripped and reworked to improve yield, or discarded, thereby avoiding performing further processing on a substrate known to be faulty. In a case where only some target portions of a substrate are faulty, further exposures may be performed only on those target portions which meet specifications. Other manufacturing process adjustments are contemplated.

[0054] A metrology system may be used to determine one or more properties of the substrate structure, and in particular, how one or more properties of different substrate structures vary, or different layers of the same substrate structure vary from layer to layer. The metrology system may be integrated into the lithographic apparatus LA or the lithocell LC, or may be a stand-alone device.

[0055] To enable the metrology, often one or more targets are specifically provided on the substrate. Typically, the target is specially designed and may comprise a periodic structure. For example, thetarget on a substrate may comprise one or more 1-D periodic structures (e.g., geometric features such as gratings), which are printed such that after development, the periodic structural features are formed of solid resist lines. As another example, the target may comprise one or more 2-D periodic structures (e.g., gratings), which are printed such that after development, the one or more periodic structures are formed of solid resist pillars or vias in the resist. The bars, pillars, or vias may alternatively be etched into the substrate (e.g., into one or more layers on the substrate).

[0056] FIG. 3 depicts an example metrology (inspection) system 10 that may be used to detect overlay, alignment, and / or perform other metrology operations. It comprises a radiation or illumination source 2 which projects or otherwise irradiates radiation onto a substrate W (e.g., which may typically include a metrology mark). The redirected radiation is passed to a sensor such as a spectrometer detector 4 and / or other sensors, which measures a spectrum (intensity as a function of wavelength) of the specular reflected and / or diffracted radiation, as shown, e.g., in the graph on the left of FIG. 4. The sensor may generate a metrology signal conveying metrology data indicative of properties of the reflected radiation. From this data, the structure or profile giving rise to the detected spectrum may be reconstructed by one or more processors PRO, a generalized example of which is shown in FIG. 4, or by other operations.

[0057] As in the lithographic apparatus LA in FIG. 1, one or more substrate tables (not shown in FIG. 4) may be provided to hold the substrate W during measurement operations. The one or more substrate tables may be similar or identical in form to the substrate table WT (WTa or WTb or both) of FIG. 1. In an example where inspection system 10 is integrated with the lithographic apparatus, they may even be the same substrate table. Coarse and fine positioners may be provided and configured to accurately position the substrate in relation to a measurement optical system. Various sensors and actuators are provided, for example, to acquire the position of a target portion of interest of a structure (e.g., a metrology mark), and to bring it into position under an objective lens. Typically, many measurements will be made on target portions of a structure at different locations across the substrate W. The substrate support can be moved in X and Y directions to acquire different targets, and in the Z direction to obtain a desired location of the target portion relative to the focus of the optical system. It is convenient to think and describe operations as if the objective lens is being brought to different locations relative to the substrate, when, for example, in practice the optical system may remain substantially stationary (typically in the X and Y directions, but perhaps also in the Z direction) and the substrate moves. Provided the relative position of the substrate and the optical system is correct, it does not matter in principle which one of those is moving, or if both are moving, or a combination of a part of the optical system is moving (e.g., in the Z and / or tilt direction) with the remainder of the optical system being stationary and the substrate is moving (e.g., in the X and Y directions, but also optionally in the Z and / or tilt direction).

[0058] For typical metrology measurements, a target 30 on substrate W may be a 1-D grating, which is printed such that after development, the bars are formed of solid resist lines (e.g., which may be covered by a deposition layer), and / or other materials. Or the target 30 may be a 2-D grating, which is printed such that after development, the grating is formed of solid resist pillars, and / or other features in the resist.

[0059] The bars, pillars, vias, and / or other features may be etched into or on the substrate (e.g., into one or more layers on the substrate), deposited on a substrate, covered by a deposition layer, and / or have other properties. Target (portion) 30 (e.g., of bars, pillars, vias, etc.) is sensitive to changes in processing in the patterning process (e.g., optical aberration in the lithographic projection apparatus such as in the projection system, focus change, dose change, etc.) such that process variation manifests in variation in target 30. Accordingly, the measured data from target 30 may be used to determine an adjustment for one or more of the manufacturing processes, and / or used as a basis for making the actual adjustment.

[0060] For example, the measured data from target 30 may indicate overlay for a layer of a semiconductor device. The measured data from target 30 may be used (e.g., by the one or more processors PRO and / or other processors) for determining one or more semiconductor device manufacturing process parameters based the overlay, and determining an adjustment for a semiconductor device manufacturing apparatus based on the one or more determined semiconductor device manufacturing process parameters. In some embodiments, this may comprise a stage position adjustment, for example, or this may include determining an adjustment for a mask design, a metrology target design, a semiconductor device design, an intensity of the radiation, an incident angle of the radiation, a wavelength of the radiation, a pupil size and / or shape, a resist material, and / or other process parameters.

[0061] FIG. 5 illustrates a plan view of a typical target (e.g., metrology mark) 30, and the extent of a typical radiation illumination spot S in the system of FIG. 4. Typically, to obtain a diffraction spectrum that is free of interference from surrounding structures, the target 30, in an embodiment, is a periodic structure (e.g., grating) larger than the width (e.g., diameter) of the illumination spot S. The width of spot S may be smaller than the width and length of the target. The target, in other words, is ‘underfilled’ by the illumination, and the diffraction signal is essentially free from any signals from product features and the like outside the target itself. The illumination arrangement may be configured to provide illumination of a uniform intensity across a back focal plane of an objective, for example. Alternatively, by, for example, including an aperture in the illumination path, illumination may be restricted to on axis or off axis directions.

[0062] FIG. 6 illustrates a system 600 configured for imaging a substrate, according to an embodiment. This may include determining a tilt angle at one or more regions or marks on one or moremetrology targets 30, for example. A target 30 may comprise one or more metrology marks, such as diffraction grating targets, formed in a substrate 602 such as a semiconductor wafer, collectively referred to as target 30, for example. Target 30 may comprise one or more structures in the patterned substrate capable of providing a diffraction signal. One or more targets 30 may be included in a layer of a substrate in a semiconductor device structure, for example. In some embodiments, the feature comprises a geometric feature such as a ID or 2D feature, and / or other geometric features. By way of several non-limiting examples, the feature may comprise a grating, a line, an edge, a fine -pitched series of lines and / or edges, and / or other features.

[0063] System 600 comprises a radiation sensor 604 configured to receive radiation from target 30 and generate a signal indicative of a field image position of the radiation. The radiation may be used to obtain images of the metrology targets 30, and / or for other uses. The radiation may comprise illumination such as light and / or other radiation. System 600 comprises an optical component 606 configured to receive the radiation reflected from target 30 and substrate 602 and direct the radiation toward sensor 604. System 600 includes a radiation emitter 625 configured to emit radiation having an emitted amplitude and phase configured for a known position relative to substrate 602; and a radiation receiver 635 configured to receive reflected radiation from substrate 602. The reflected radiation has a reflected amplitude and phase. System 600 has one or more processors PRO operatively connected with emitter 625 and receiver 635. The one or more processors PRO are configured to determine a captured light value between emitter 625 and receiver 635 based on the emitted radiation and the received reflected radiation; and determine a height for imaging substrate 602 based on the captured light value and the known position. Emitter 625 and receiver 635 may be coupled to other components of system 600 or they may form their own stand-alone structure. Emitter 625, receiver 635, the captured light value, the angle of incidence and the height are all discussed in detail below related to FIGS. 7- 15.

[0064] System 600 may be similar to and / or the same as system 10 shown in FIG. 3. In FIG. 6, additional detail is illustrated for system 600 compared to system 10. In some embodiments, system 600 may form a portion of system 10 described above with respect to FIG. 3. System 600 may be a subsystem of system 10, for example. In some embodiments, one or more components of system 600 may be similar to and / or the same as one or more components of system 10. In some embodiments, one or more components of system 600 may replace, be used with, and / or otherwise augment one or more components of system 10.

[0065] System 600 comprises radiation source 612; optical component 606; an overlay detection branch 660 with a sensor 604; a beam splitter 670; an alignment branch 680; various lenses, reflectors, and other optical components (with an example objective 690 labeled in FIG. 6); and / or other components. In some embodiments, the components of system 600 form a portion of an overlay and / oralignment sensor that is used in a semiconductor manufacturing process. Radiation source 612 is configured to generate radiation along a first optical path 621. In some embodiments, radiation from radiation source 612 and / or other radiation sources may be provided to emitter 625. The radiation may have a target wavelength and / or wavelength range, a target intensity, and / or other characteristics. The target wavelength and / or wavelength range, the target intensity, etc., may be entered and / or selected by a user, determined by the system (e.g., system 10 shown in Fig. 3) based on previous measurements, and / or determined in other ways. In some embodiments, the radiation comprises light and / or other radiation. In some embodiments, the light comprises visible light, infrared light, near infrared light, and / or other light. In some embodiments, the radiation may be any radiation appropriate for interferometry.

[0066] In some cases, as described above, system 600 includes a separate focus branch 650. A focus measurement 675 made by focus branch 650 requires detection apertures 677 and 679 along with corresponding sensors 681 and 683 before focus and another after focus. A zero-defocus position is defined when the two sensors detect the same radiation 685 intensity. Intensity is determined before and after a focus position conjugate to a substrate, and a normalized difference is determined to be the focus position. In FIG. 6, FS stands for Focus Signal (e.g., a representation of a (best) focus position) which has been determined for prior systems by the equation for FS shown in Fig. 6, S 1 and S2 are first and second intensities at the respective sensors, O stands for object which in this example can be a substrate (e.g., a wafer) plane, 01702’ represent a conjugate plane of O, and P is a pupil plane.

[0067] In other cases, the system 600 includes a different kind of focus sensor. Instead of using focus branch 650 and the principles of focus measurement described above, system 600 uses emitter 625 and receiver 635 to determine an imaging height (e.g., a focus position) as described below. This new architecture reduces costs and bulk compared to prior systems because the components of focus branch 650 are not required, and / or has other advantages. The emitter 625 and receiver 635 may include at least one focus sensor and also at least one tilt sensor, which will be described in more detail below. That is, the emitter 625 may include multiple sensors, where at least one is configured to measure focus and at least another is configured to measure tilt of the substrate.

[0068] To measure focus, emitter 625 may include a sensor that is configured to emit radiation having an emitted amplitude and phase configured for a known position relative to substrate 602. The known position may be a known or initial focus position for system 600, for example. In some embodiments, emitter 625 comprises an emitting grating, an emitter in free space, an optical fiber, and / or other emitters. Emitter 625 may comprise an emitting grating, for example. The emitting grating may be configured to emit the radiation having the emitted amplitude and phase by adjusting a grating period and / or duty cycle of the emitting grating.

[0069] Reflected radiation from substrate 602 (e.g., a different portion of reflected radiation than thatused for the overlay and / or alignment described above) is received with radiation receiver 635. The reflected radiation has a reflected amplitude and phase. In some embodiments, receiver 635 comprises a receiving grating and / or other receivers. In some embodiments, emitter 625 and receiver 635 comprise gratings formed in silicon-based substrates. In some embodiments, the silicon-based substrates comprise waveguides configured to guide incident radiation (e.g., from source 612) to emitter 625, and / or received radiation from receiver 635 (e.g., so that a corresponding signal can be processed by processor PRO).

[0070] A captured light value between emitter 625 and receiver 635 is determined based on the emitted radiation and the received reflected radiation. The captured light value of this focus sensor is determined with one or more processors operatively connected with the emitter and the receiver (e.g., one or more processors PRO). A height for imaging substrate 602 is determined based on the captured light value and the known (e.g., initial focus) position. The height may be a metrology focus position for system 600, for example. In some embodiments, the height is determined based on a linear relationship between the captured light value and a system objective defocus. A sensitivity of the height determination may be at least about lOOnm, 120nm, or 140nm, for example.

[0071] In some embodiments, one or more processors PRO are configured to automatically adjust a focus position of system 600 for imaging target 30 based on the determined height so that a subsequent image of target 30 and / or substrate 602 is in focus. This may include generating, with radiation source 612 and one or more lenses and / or other components of system 600, incident radiation and directing the radiation toward emitter 625 (e.g., via waveguides in a substrate as described above).

[0072] By changing the grating period and / or the duty cycle of emitter 625 and / or receiver 635 (FIG. 6), the amplitude and the phase of a grating coupler mode can be engineered. The captured light value (77) of a grating coupler is defined as:where Hm (incident field) and Pinare the magnetic field and the power distribution of an incident beam on the grating coupler, respectively, and EGC (grading mode) and Pae are the electric field and the power distribution of the grating coupler mode, respectively. To achieve an optimum coupling, the amplitude and the phase of the incident beam and the grating coupler mode should have the maximum overlap. For a Gaussian incident beam, the phase front is flat at the focus, but it has a parabolic shape with opposite signs before and after the focus. If the Gaussian beam has an inclined incidence on a surface, the lateral location of the beam and the traveling distance is changed when there is a defocus. In the present systems and methods, grating couplers are designed which have the optimum captured lightvalue for different defocuses. As defocus is changed, the captured light value (SI and S2) can have different functions for different grating couplers. In some embodiments, instead of designing two different grating couplers, the same grating couplers may be used but loaded with metasurfaces which have positive or negative power. In general, the descriptions of the focus sensor may be consistent with the published disclosure “Integrated Photonic Sensor,” published digitally 23 December 2022, which is incorporated herein by reference.

[0073] The lithographic apparatus LA and radiation source SO described herein can be used in a method for manufacturing a semiconductor device. A semiconductor device manufacturing method comprises receiving a substrate W with a photoresist layer. The method further comprises directing a radiation beam from radiation source SO to transfer a pattern from a mask onto the photoresist layer. This could be achieved by a patterning device which is configured to form a patterned radiation beam, imparting the patterned radiation beam onto the photoresist layer. The method for manufacturing a semiconductor device further comprises the step of removing a portion of the photoresist layer to form the pattern over the substrate W.

[0074] The substrate W may be made of silicon or other semiconductor materials. Alternatively or additionally, the substrate W may include other semiconductor materials such as germanium (Ge) or carbon (C). In some embodiments, the semiconductor substrate is made of a compound semiconductor such as III-V compound semiconductors, II- V compound semiconductors, and / or any suitable integration of Group IV materials. In some embodiments, the substrate W may be a silicon-on-insulator (SOI) or a germanium-on-insulator (GOI) substrate.

[0075] The semiconductor device made from the substrate W may have various device elements. Examples of semiconductor device elements that are formed over the substrate W include transistors (e.g., planar or non-planar metal oxide semiconductor field effect transistors (MOSFET), bipolar junction transistors (BJT), high-voltage transistors, high-frequency transistors, etc.), diodes, CMOS image sensors, passive devices, and / or other applicable elements. Various processes may be performed to form the semiconductor device elements, such as deposition, etching, implantation, epitaxial growth, polishing, thermal treatment, and / or other suitable processes. In some embodiments, the substrate W is coated with a photoresist layer sensitive to the EUV light.

[0076] Referring to FIG. 7, shown is an illustration of the optical geometry that a tilt sensor of the present disclosure is designed to capture. As previously mentioned, the emitter 625 and receiver 635 may include at least one tilt sensor, while in other cases the emitter 625 and receiver 635 can also include at least one focus sensor. FIGS. 7-11 describe the tilt sensor, while FIGS. 12-14 describe how a tilt sensor and focus sensor may be combined in a single system like the combination of emitter 625 and receiver 635.

[0077] Still referring to FIG. 7, ideally, a substrate 722 should be completely level as it is placed ina lithography machine. However, even a small tilt of the wafer, on the order of microradians, as exaggerated by angle cp (720), can create inaccuracies in the imaging process. Persons of skill in the art understand that grating couplers can be designed in specific ways to capture or measure particular pieces of information, depending on what is needed. In this case, two pairs of grating couplers (GCs), with both pairs having an emitting GC and a capturing GC, can be designed in a particular way to obtain measurements that extract the degree of tilt of a substrate even to microradian accuracy. Ultimately, the tilt sensor of the present disclosure is designed to determine the tilt angle cp (720).

[0078] FIG. 7 shows the geometry of a substrate with a degree of tilt that the two pairs of GCs are designed to determine. A tilted substrate leads to a change in two values: 1) the change in the horizontal distance Ax (708) of captured light value, from an emitting GC (see e.g., 802) at initial emitting position E (702) to a capturing GC (see e.g., 808), between a completely level wafer and a tilt in the wafer; and 2) a change in the distance Az (716) from the nominal region of measurement O (718) to the location C of the incident field on the capturing GC when the substrate is completely level, compared to the distance from O (718) to the new location C’ of the incident field in the capturing GC when the substrate is tilted.

[0079] Still referring to FIG. 7, geometry principles dictate that Ax (708), the distance from C to C’, is governed by the following equation (708):Ax = (d(tan(0) — tan(9 — 2<p)) (1)Here, d (712) is the distance from O (718) to the closest region N (706) of the tilt sensor, which is to say, the normal distance N (706). 9 is the angle formed between the vectors EG and ON, which is the same angle formed by ON and the reflecting vector OC to the capturing GC. These values are all based on the substrate being completely level and can be viewed as representing the ideal state or the control. These measurements may also be fixed and known because the positions and angles of the emitting and capturing GCs are fixed. What is not known is the tilt angle cp (720). Therefore, when Ax is measured by obtaining the position C’ in the capturing GC that results from the tilt of the measured substrate, the tilt angle cp (720) can be solved for using the equation (1) (708) of Ax as shown above and referenced in FIG. 7, because all values in equation (1) (708) besides cp are known at that point. 2cp (714) also represents the angle formed between OC and OC’. Also for reference, the vector ON’ (704) is the normal vector of the tilted substrate.

[0080] Similarly, still referring to FIG. 7, geometry principles dictate that Az, which is the difference in length between OC and OC’, is governed by the following equation (716): .2.Again, since the emitting and capturing GCs are fixed in position and angle, the values of d, C, and 6 are known. What is not known is the tilt angle cp (720). Therefore, when Az is determined by obtaining the position C’ in the capturing GC that results from the tilt of the measured substrate, the tilt angle cp (720) can also be solved for using the equation (2) (716) of Az as shown above and referenced in FIG. 7, because all values in equation (2) (716) besides cp are known at that point. The two equations for Az and Ax can be corroborated to verify the correct value of cp. These geometries demonstrate the general concept of what the capturing grating couples are designed to determine.

[0081] Referring to FIG. 8, shown is a plan view of the sensor apparatus over the substrate, according to some embodiments. There are two pairs of grating couplers, both pairs having an emitting GC 802 and 804 and a capturing GC 808 and 806, respectively. The capturing GCs 808 and 806 are designed to determine a captured light value, which is a measurement of power emitted from their respective emitting GCs 802 and 804, respectively. The ratio of the coupling efficiencies captured by the two capturing GC2 808 and 806 is used to determine the tilt angle. The calculations are shown and described in FIG. 9. A first pair of emitting and capturing GC, say 802 and 808, is fixed in place and designed to capture maximum captured light value when there is a positive tilt +cp. The first pair of GCs are fixed, such that the positive tilt angle +cp which produces the maximum captured light value captured by the capturing GC 808, is known upon design. In addition, the Gaussian distribution of the captured light value that would be captured by the first capturing GC 808 is also predetermined by how the first pair of GCs are positioned and structured. A second pair of emitting and capturing GC, say 804 and 806, is fixed in place and designed to capture maximum captured light value when there is a negative tilt -cp. The second pair of GCs are fixed, such the negative tilt angle -cp which produces the maximum captured light value captured by the capturing GC 806, is known upon design. In addition, the Gaussian distribution of the captured light value that would be captured by the second capturing GC 806 is also predetermined by how the second pair of GCs are positioned and structured.

[0082] The emitting GC 1 802 is positioned diagonally opposite the capturing GC 1 808 with respect to the nominal region being measured, such as region 0718. The emitting GC 2 804 may be positioned laterally opposite the first emitting GC 1 802, relative to the nominal region of measurement. Similarly, the capturing GC 2 806 is positioned diagonally opposite the emitting GC 2 804 relative to the nominal region of measurement, which would also be positioned laterally opposite the first capturing GC 1 808 relative to the nominal region of measurement. Therefore, a collection of four grating couplers, in two emitting and capturing pairs and facing opposite directions, fixed to the same nominal region O (e.g., 718), are designed to capture the two values of captured light value whose ratio is used to determine a tilt of the substrate.

[0083] Referring to FIG. 9, shown are example graphs and equations that visually show how thecaptured light value of the grating couplers in the tilt sensor are a function of the tilt in the target substrate. These graphs visually illustrate how the two pairs of GCs are used to compute the tilt based on a computed ratio of the coupling efficiencies captured by the two capturing GCs 808 and 806. As previously mentioned, the positions of the four GCs (two pairs) are fixed such that one pair of GCs is designed to capture maximum captured light value when there is positive tilt +cp. The equation for computing the captured light value IJGCI of this first capturing GC1 is shown in equation 912: are the capturingefficiency, the mode of the capturing grating coupler, the incident field on the grating coupler, the total power of the incident beam, and the total power of the grating coupler mode, respectively. This equation 912 defines the curve 910. Equation 912 specifies that the captured light value of capturing GC1 (e.g., GC 808) is maximum when there is a positive tilt. Equation 912 also specifies how wide or narrow the Gaussian distribution of the curve 910 is, as the captured light value of the first capturing GC1 IJGCI is a function of the angle of incidence, or tilt, Am(z)- The equation for computing the captured light value T|GC2 of this second capturing GC2 is shown in equation 914: are the capturingefficiency of the second pair, the mode of the second capturing grating coupler, the incident field on the second grating coupler, the total power of the incident beam, and the total power of the second grating coupler mode, respectively. This equation 914 defines the curve 908. Equation 914 specifies that the captured light value of capturing GC2 (e.g., GC 806) is maximum when there is a negative tilt in the same magnitude as equation 912 but in the opposite direction. Equation 914 also specifies how wide or narrow the Gaussian distribution of the curve 908 is, as the captured light value of the first capturing GC2 JGC2 is a function of the angle of incidence, or tilt, A,n(z). Again, the exact degree of tilt angle is determined beforehand and integrated into the design of the two pairs of GCs of the tilt sensor.

[0084] Graph 902 shows the amplitude of the optical beam for both pairs of the grating couplers GC 1 (802 and 808) and GC 2 (804 and 806), as well as the amplitude of the input supplied to both. As shown, the amplitudes are essentially equal, illustrating that there is no loss in the amplitude as a function of the input. Graph 904 shows the two Gaussian distribution curves 910 and 908 that are defined by the equations 912 and 914, respectively. The curves 910 and 908 represent that captured light value captured by the capturing GC1 and GC2, respectively, as a function of the tilt angle. As previously mentioned, the captured light value of the capturing GC1 is designed to be at its maximum when there is positive tilt, as reflected by the curve 910. The captured light value of the capturing GC2 is designed to be at its maximum when there is negative tilt, as reflected by the curve 908. The angle of incidence or the tilt angle can then be computed when obtaining the two captured light value values rfGci and t]cc2 as captured by the two capturing GCs (808 and 806).

[0085] To compute the tilt angle, the coupling efficiencies rjcci and rjcc2 are first measured by the capturing GCs (808 and 806). A ratio between the two values may be computed, called the tilt signal, which is defined by the equation 916:, where IJGCI and TJGC2 are the captured coupling efficiencies of capturing GC1 and capturing GC2, respectively. The value of the tilt signal as a function of the tilt angle is reflected in the curve of graph 906. This curve is derived simply from the ratios of the coupling efficiencies, i.e., the computed tilt signal, of the two Gaussian distribution curves 908 and 910 of the two pairs of grating couplers, as a function of the tilt angle.

[0086] As an example, the substrate may have a particular tilt angle that results in the capturing GC1 and capturing GC2 recording coupling efficiencies consistent with the points formed at the intersections with dashed line 918. That is, the captured light value of GC1, according to curve 910, is measured at approximately 0.68 (the intersection of curve 910 with dashed line 918), and the captured light value of GC2, according to curve 908, is measured at approximately 0.18 (the intersection of curve 908 with dashed line 918). The tilt signal ratio of the two captured light value values can then be computed using equation 916. That is, the tilt signal = (0.68-0.18) / (0.68+0.18) = 0.5 / 0.86 = 0.581. Referring to the curve in graph 906 that corresponds to the values of the tilt signal as a function of the tilt angle, the tilt signal being 0.581 corresponds to the intersection of the line 920, which shows that obtaining a tilt signal of 0.581 means that the tilt angle is approximately 0.27 milliradians (the intersection of dashed line 920 with the x-axis). The lines 918 and 920 are consistent with one another, in that the tilt angle is the same in both graphs. In other words, using two pairs of grating couplers that have captured light value Gaussian distribution profiles consistent with curves 910 and 908, measuring captured light value values of 0.68 and 0.18 for the two capturing GC1 and GC2, respectively, means that the tilt angle is approximately 0.27 milliradians.

[0087] Referring to FIG. 10, shown are several graphs that provide sensitivity analysis to aid in the design of the tilt sensor and its placement relative to the region being examined on the target substrate. Illustration 1002 shows a side view of one tilt sensor having an emitting GC 1 and a capturing GC 2 with two example emitting beams onto a target substrate. The two emitting beams provide examples of how the beams may be angled onto the target substrate, to show examples of different configurations. The graphs in FIG. 10 provide some illustrations of what can happen when different angles of beam emission are chosen. Graph 1004 shows how the mode of the emitting GC is usually bigger than the mode of the capturing GC. Graph 1006 shows example plots of the influence of the beam waist of the capturing GC (Wo) on the beam waist of the emitting GC. Graph 1008 shows the influence of the incident angle (0;n) on the beam waist at the emitting GC. Graph 1010 shows the influence of theworking distance (d) on the beam waist at the emitting GC.

[0088] Referring to FIG. 11, example design parameters for the emitting and capturing grating couplers are provided, according to some embodiments. Illustration 1102 shows a side view of the different layers of the emitting grating coupler in view of the target substrate that is being measured (the Si substrate). As shown, there is a SiOz cladding, along with a SiN waveguide made of a solid piece SiN and periodic pieces of SiN with different thicknesses. The SiN waveguide includes a gap, here shown to be 50 nm as merely one example. A SiOz box separates the SiN waveguide with the substrate. In illustration 1104, the emitting GC is 200 micrometers long as one example. Illustration 1106 shows a side view of the different layers of the capturing grating coupler in view of the target substrate that is being measured (the Si substrate). As shown, there is also a SiOz cladding, along with a SiN waveguide made of two sets of periodic pieces of SiN with different thicknesses. The SiN waveguide includes a gap, here shown to be 50 nm as merely one example. A SiOz box separates the SiN waveguide with the substrate. In illustration 1108, the capturing GC is 30 micrometers long as one example. Because the mode of the capturing GC is much smaller, as shown in FIG. 10, the capturing GC does not need to be as large. Because the emitting and capturing GCs have different sizes, it also means that the outcoupling coefficients of the gratings are different. This suggests that the designs of the emitting GC and the capturing GC should be different, which lends itself to the different designs of the waveguides as shown in illustrations 1102 and 1106.

[0089] Referring to FIG. 12, an example scanning process of the tilt sensor along a path is shown. The emitting grating couplers 802 and 804 are configured to transmit a beam onto the target region 1204 and be captured by the capturing GCs 808 and 806, respectively. When positioned on an apparatus, the tilt sensor can obtain multiple measurements along a path 1202 of a substrate in extremely quick succession. The stars in the illustration, like 1204, represent the different target regions measured by the tilt sensor. The substrate may be placed on a stage that moves the substrate while the apparatus containing the tilt sensor is stationary. In other cases, the reverse may be true, where the tilt sensor moves while the substrate is stationary. This can provide a sufficient plot of the contours of the target substrate that represent rough the tilt angle features on the substrate roughly along the path 1202. These measurements can be used to adjust for and counteract overlay when trying to image the substrate.

[0090] Referring to FIG. 13, expanding on the illustration in FIG. 12, the scanning process of one sensor can be replicated along an apparatus to scan a much wider area within a single scan, as shown in the illustration of FIG. 13 and according to some embodiments. Here, sets of tilt sensors, such as the collection of four sensor 1302, and so on, can be arranged in a configuration to allow for parallel sensing across a wide range. In this example, there are twenty four sensors, each trained on a region width-wise. The substrate or the apparatus containing the sensors may be moved vertically, such as in the direction of the arrows 1304, so that multiple regions along the vertical lines may be scanned each by a singlesensor such as what is shown in FIG. 12. As previously shown, the sensors can be made with very little space, so multiple sensors can be populated in a small area to allow for a comprehensive sets of scans in a two-dimensional area. This allows for a single scan, moving the sensors along just a single direction such as direction 1304, to take measurements in a wide area. In contrast, existing scanners may be capable of only taking measurements in patches of areas, requiring more movements of the sensors, both in terms of directions of the movements and amount of movement.

[0091] In some embodiments, the sensors shown in FIG. 12 may alternate between tilt sensors and focus sensors. An example of a focus sensor suitable to be placed in this kind of configuration is described in “Integrated Photonic Sensor,” published digitally 23 December 2022, which is incorporated by reference herein. Thus, within each set of 4 sensors, where there are six sets as shown in FIG. 12, two may be pairs of tilt sensors while the other two may be pairs of the focus sensors, according to some embodiments.

[0092] Referring to FIG. 13, an example of the apparatus 1302 that holds the multiple tilt and / or focus sensors is shown over an example wafer 1304. The configuration is consistent with the arrangement shown in FIG. 12. The apparatus 1302 may be configured to simply move down along the page, which is to say, across the wafer substrate 1304, in the direction 1306, and take periodic measurements such as with the frequency shown in FIG. 11. It can be seen therefore that the apparatus 1302 may be capable of capturing a comprehensive set of measurements for both tilt and / or focus with just a single scan down the direction 1306. The small form factor and quick precision enabled by the present disclosures allows for this more efficient method of taking measurements, saving time and energy cost as a result.

[0093] FIG. 14 illustrates a method 1400 for determining an angle of tilt on a region of a substrate. In some embodiments, method 1400 is performed as part of an overlay and / or alignment sensing operation in a semiconductor device manufacturing process, for example. In some embodiments, one or more operations of method 1400 may be implemented in or by system 600 illustrated in FIG. 6, system 10 illustrated in FIG. 3, a computer system (e.g., as illustrated in Fig. 15 and described below), and / or in or by other systems, for example. The method 1400 may be consistent with the descriptions of FIGS. 7-13. In some embodiments, method 1400 comprises at operation 1402, emitting first radiation such as a first optical beam, from a first grating coupler, such as GC 802, at a region on a substrate. The first grating coupler may be part of a sensor apparatus configured to measure a tilt angle at the region on the substrate. At operation 1404, a first captured light value of the reflection of the first optical beam from the region on the substrate may be captured by a second grating coupler, such as GC 808. The second grating coupler may also be part of the sensor apparatus. At operation 1406, the method may include emitting second radiation such as a second optical beam, from a third grating coupler, such as GC 804, at the region on the substrate. The third grating coupler may be part of the sensor apparatus.At operation 1408, a second captured light value of the reflection of the second optical beam from the region on the substrate may be captured by a fourth grating coupler, such as GC 806. The fourth grating coupler may also be part of the sensor apparatus. The positions of the first, second, third, and fourth grating couplers may be fixed such that the first captured light value may be captured at a maximum peak when there is a positive tilt angle at the region, while the second captured light value may be captured at a maximum peak when there is a negative tilt angle at the region. At operation 1410, the processor may compute a ratio using the first captured light value and the second captured light value. For example, the processor may be configured to compute the tilt signal value described in FIG. 9 at equation 916. At operation 1412, the processor may compute the angle of tilt of the region using the computed ratio.

[0094] The operations of method 1400 are intended to be illustrative. In some embodiments, method 1400 may be accomplished with one or more additional operations not described, and / or without one or more of the operations discussed. For example, in some embodiments, method 1400 may include an additional operation comprising determining an adjustment for a semiconductor device manufacturing process. In other cases, the method 1400 may include taking multiple measurements along the substrate as described in any of FIGS. 11-13. Additionally, the order in which the operations of method 1400 are illustrated in FIG. 14 and described herein is not intended to be limiting.

[0095] In some embodiments, one or more portions of method 1400 may be implemented in and / or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of method 1400 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and / or software to be specifically designed for execution of one or more of the operations of method 1400 (e.g., see discussion related to FIG. 15 below).

[0096] In some embodiments, method 1400 includes determining overlay and / or alignment. Overlay and / or alignment are determined based on reflected diffracted radiation from a diffraction grating target on the substrate, the tilt angle, the focus position, the shift, and / or other information.

[0097] In some embodiments, method 1400 includes illuminating (and / or otherwise irradiating) one or more targets (e.g., target 30 shown in FIG. 3) in a patterned substrate with radiation. The radiation comprises light and / or other radiation. The radiation may be generated by a radiation source (e.g., source 2 shown in FIG. 3). In some embodiments, the radiation may be directed by the radiation source onto multiple targets, a single target, sub-portions (e.g., something less than the whole) of a target, and / or onto a substrate in other ways. In some embodiments, the radiation may be directed by theradiation source onto the target in a time varying manner. For example, the radiation may be rastered over a target (e.g., by moving the target under the radiation) such that different portions of the target are irradiated at different times. As another example, characteristics of the radiation (e.g., wavelength, intensity, etc.) may be varied. This may create time varying data envelopes, or windows, for analysis. The data envelopes may facilitate analysis of individual sub-portions of a target, comparison of one portion of a target to another and / or to other targets (e.g., in other layers), and / or other analysis.

[0098] In some embodiments, method 1400 comprises detecting reflected radiation (with the radiation sensor described above) directly from one or more diffraction grating targets (e.g., not part of a focus determination and instead part of an overlay measurement). Detecting reflected radiation comprises detecting one or more angle shifts in reflected radiation from one or more geometric features of the target(s). The one or more angle shifts correspond to one or more dimensions of a target. For example, the angle of reflected radiation from one side of a target is different relative to the angle of reflected radiation from another side of the target.

[0099] Detecting the one or more angle shifts in the reflected radiation from the target comprises measuring local angle shifts that correspond to different portions of a target. For example, the reflected radiation from a specific area of a target may comprise a sinusoidal waveform having a certain phase and / or amplitude. The reflected radiation from a different area of the target (or a target in a different layer) may also comprise a sinusoidal waveform, but one with a different angle of incidence. Detected reflected radiation may also comprise measuring an angle difference in reflected radiation of different diffraction orders. Detecting the one or more local angle shifts may be performed using Hilbert transformations, for example, and / or other techniques. Interferometry techniques and / or other operations may be used to measure phase and / or amplitude differences in reflected radiation of different diffraction orders.

[0100] In some embodiments, method 1400 comprises generating a metrology signal based on the detected reflected radiation from diffraction grating target(s), as described above. The metrology signal is generated by a sensor (such as detector 4 in FIG. 3, a camera, and / or other sensors) based on radiation received by the sensor. The metrology signal comprises measurement information pertaining to the target(s) on a substrate. For example, the metrology signal may be an overlay and / or alignment signal comprising overlay and / or alignment measurement information, and / or other metrology signals. The measurement information (e.g., an overlay value, an alignment value, and / or other information) may be determined using principles of interferometry and / or other principles.

[0101] The metrology signal comprises an electronic signal that represents and / or otherwise corresponds to the radiation reflected from the target(s). The metrology signal may indicate a metrology value associated with a diffraction grating target, for example, and / or other information. Generating the metrology signal comprises sensing the reflected radiation and converting the sensed reflectedradiation into the electronic signal. In some embodiments, generating the metrology signal comprises sensing different portions of the reflected radiation from different areas and / or different geometries of the target, and / or multiple targets, and combining the different portions of the reflected radiation to form the metrology signal. This may include generating and / or analyzing one or more images of a target, using the radiation described herein. This sensing and converting may be performed by components similar to and / or the same as detector 4 and / or processors PRO shown in FIG. 3, and / or other components.

[0102] In some embodiments, method 1400 comprises determining an adjustment for a semiconductor device manufacturing process. For example, this may include automatically adjusting, with the one or more processors, a location of a stage of a metrology system holding the substrate based on a determined tilt position so that a subsequent image of the substrate is properly level. In some embodiments, method 1400 includes determining one or more semiconductor device manufacturing process parameters. The one or more semiconductor device manufacturing process parameters may be determined based on one or more detected tilt variations, an overlay and / or alignment value indicated by the metrology signal, and / or other similar systems, and / or other information. The one or more parameters may include a parameter of the radiation (the radiation used for metrology), an overlay value, an alignment value, a metrology inspection location on a layer of a semiconductor device structure, a radiation beam trajectory across a target, and / or other parameters. In some embodiments, process parameters can be interpreted broadly to include a stage position, a mask design, a metrology target design, a semiconductor device design, an intensity of the radiation (used for exposing resist, etc.), an incident angle of the radiation (used for exposing resist, etc.), a wavelength of the radiation (used for exposing resist, etc.), a pupil size and / or shape, a resist material, and / or other parameters.

[0103] In some embodiments, method 1400 includes determining a process adjustment based on the one or more determined semiconductor device manufacturing process parameters, adjusting a semiconductor device manufacturing apparatus based on the determined adjustment, and / or other operations. This may be performed by one or more processors such as PRO shown in FIG. 3, a processor described as part of the computer system illustrated in FIG. 15 and described below, and / or other processors. For example, if a determined metrology measurement is not within process tolerances, the out of tolerance measurement may be caused by one or more manufacturing processes whose process parameters have drifted and / or otherwise changed so that the process is no longer producing acceptable devices (e.g., measurements may breach a threshold for acceptability). One or more new or adjusted process parameters may be determined based on the measurement determination. The new or adjusted process parameters may be configured to cause a manufacturing process to again produce acceptable devices.

[0104] For example, a new or adjusted process parameter may cause a previously unacceptablemeasurement value to be adjusted back into an acceptable range. The new or adjusted process parameters may be compared to existing parameters for a given process. If there is a difference, that difference may be used to determine an adjustment for an apparatus that is used to produce the devices (e.g., parameter “x” should be increased / decreased / changed so that it matches the new or adjusted version of parameter “x” determined as part of method 1400), for example. In some embodiments, method 1400 may include electronically adjusting an apparatus (e.g., based on the determined process parameters). Electronically adjusting an apparatus may include sending an electronic signal, and / or other communications to the apparatus, for example, which causes a change in the apparatus. The electronic adjustment may include changing a setting on the apparatus, for example, and / or other adjustments.

[0105] FIG. 15 is a diagram of an example computer system CS that may be used for one or more of the operations described herein. Computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or multiple processors similar to and / or the same as processor PRO shown in Fig. 3) coupled with bus BS for processing information. Computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to bus BS for storing information and instructions to be executed by processor PRO. Main memory MM also may be used for storing temporary variables or other intermediate information during execution of instructions by processor PRO. Computer system CS further includes a read only memory (ROM) ROM or other static storage device coupled to bus BS for storing static information and instructions for processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to bus BS for storing information and instructions.

[0106] Computer system CS may be coupled via bus BS to a display DS, such as a flat panel or touch panel display or a cathode ray tube (CRT) for displaying information to a computer user. An input device ID, including alphanumeric and other keys, is coupled to bus BS for communicating information and command selections to processor PRO. Another type of user input device is cursor control CC, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor PRO and for controlling cursor movement on display DS. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

[0107] In some embodiments, all or some of one or more operations described herein may be performed by computer system CS in response to processor PRO executing one or more sequences of one or more instructions contained in main memory MM. Such instructions may be read into main memory MM from another computer-readable medium, such as storage device SD. Execution of the sequences of instructions included in main memory MM causes processor PRO to perform the processsteps (operations) described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory MM. In some embodiments, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, the description herein is not limited to any specific combination of hardware circuitry and software.

[0108] The term “computer-readable medium” or “machine -readable medium” as used herein refers to any medium that participates in providing instructions to processor PRO for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus BS. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non- transitory, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge. Non-transitory computer readable media can have instructions recorded thereon. The instructions, when executed by a computer, can implement any of the operations described herein. Transitory computer-readable media can include a carrier wave or other propagating electromagnetic signal, for example.

[0109] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor PRO for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system CS can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus BS can receive the data carried in the infrared signal and place the data on bus BS. Bus BS carries the data to main memory MM, from which processor PRO retrieves and executes the instructions. The instructions received by main memory MM may optionally be stored on storage device SD either before or after execution by processor PRO.

[0110] Computer system CS may also include a communication interface CI coupled to bus BS. Communication interface CI provides a two-way data communication coupling to a network link NDL that is connected to a local network LAN. For example, communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, communication interfaceCI may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, communication interface CI sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

[0111] Network link NDL typically provides data communication through one or more networks to other data devices. For example, network link NDL may provide a connection through local network LAN to a host computer HC. This can include data communication services provided through the worldwide packet data communication network, now commonly referred to as the “Internet” INT. Local network LAN (Internet) may use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network data link NDL and through communication interface CI, which carry the digital data to and from computer system CS, are exemplary forms of carrier waves transporting the information.

[0112] Computer system CS can send messages and receive data, including program code, through the network(s), network data link NDL, and communication interface CL In the Internet example, host computer HC might transmit a requested code for an application program through Internet INT, network data link NDL, local network LAN, and communication interface CL One such downloaded application may provide all or part of a method described herein, for example. The received code may be executed by processor PRO as it is received, and / or stored in storage device SD, or other non-volatile storage for later execution. In this manner, computer system CS may obtain application code in the form of a carrier wave.

[0113] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses. In the following, further features, characteristics, and exemplary technical solutions of the present disclosure will be described in terms of clauses that may be optionally claimed in any combination:1. A system for determining an angle of tilt of a substrate, the system comprising: a sensor; and a processor operatively coupled to the sensor; the sensor comprising a plurality of grating couplers; wherein: a first grating coupler of the plurality of grating couplers is configured to emit a first optical beam at a region on the substrate; a second grating coupler of the plurality of grating couplers is configured to measure a first captured light value after the first optical beam reflects off the region on the substrate; a third grating coupler of the plurality of grating couplers is configured to emit a second optical beam at the region on the substrate; a fourth grating coupler of the plurality of grating couplers is configured to measure a second captured light value after the second optical beam reflects off the region on the substrate; and the processor is configured to: compute a ratio using the first captured light value and the second captured light value; and compute the angle of tilt of the region on the substrate using the computed ratio.2. The system of clause 1, wherein to compute the ratio, the processor is configured to compute a difference between the first and second captured light value values, compute a total captured power of the first and second captured light value values, and compare the computed difference to the total captured power.3. The system of any of the previous clauses, wherein the second grating coupler is configured to capture the first captured light value at a maximum when the angle of tilt of the region is a positive angle.4. The system of any of the previous clauses, wherein the fourth grating coupler is configured to capture the second captured light value at a maximum when the angle of tilt of the region is a negative angle.5. The system of any of the previous clauses, wherein: the first grating coupler is positioned diagonally opposite to the second grating coupler with respect to the region on the substrate; the third grating coupler is positioned laterally opposite to the first grating coupler with respect to the region on the substrate, and the fourth grating coupler is positioned laterally opposite to the second grating coupler with respect to the region on the substrate.6. The system of any of the previous clauses, wherein the first and second grating couplers are positioned in a predetermined manner such that the second grating coupler is configured to capture the first captured light value of the first optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a positive angle of tilt and a predetermined standard deviation.7. The system of any of the previous clauses, wherein the third and fourth grating couplers are positioned in a predetermined manner such that the fourth grating coupler is configured to capture the second captured light value of the second optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a negative angle of tilt and a predetermined standard deviation.8. A system for determining an angle of tilt on a substrate and a measurement of focus on the substrate, the system comprising: a plurality of tilt sensors; a plurality of focus sensors; and at least one processor; each of the tilt sensors comprising a plurality of grating couplers; wherein: a first grating coupler of the plurality of grating couplers is configured to emit a first optical beam at a region on the substrate; a second grating coupler of the plurality of grating couplers is configured to measure a first captured light value after the first optical beam reflects off the region on the substrate; a third grating coupler of the plurality of grating couplers is configured to emit a second optical beam at the region on the substrate; a fourth grating coupler of the plurality of grating couplers is configured to measure a second captured light value after the second optical beam reflects off the region on the substrate; and the at least one processor is configured to: compute a ratio using the first captured light value and the second captured light value; and compute the angle of tilt of the region on the substrate using the computed ratio.9. The system of any of the previous clauses, wherein the plurality of tilt sensors and the plurality of focus sensors are arranged in an array sufficiently wide such that the entire substrate can be measured for tilt angles and focus measurements using a single scan of the array.10. The system of any of the previous clauses, wherein to compute the ratio, the at least one processor is configured to compute a difference between the first and second captured light value values, compute a total captured power of the first and second captured light value values, and compare the computed difference to the total captured power.11. The system of any of the previous clauses, wherein the second grating coupler is configured to capture the first captured light value at a maximum when the angle of tilt of the region is a positive angle.12. The system of any of the previous clauses, wherein the fourth grating coupler is configured to capture the second captured light value at a maximum when the angle of tilt of the region is a negative angle.13. The system of any of the previous clauses, wherein: the first grating coupler is positioned diagonally opposite to the second grating coupler with respect to the region on the substrate; the third grating coupler is positioned laterally opposite to the first grating coupler with respect to the region on the substrate, and the fourth grating coupler is positioned laterally opposite to the second grating coupler with respect to the region on the substrate.14. The system of any of the previous clauses, wherein the first and second grating couplers are positioned in a predetermined manner such that the second grating coupler is configured to capture the first captured light value of the first optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a positive angle of tilt and a predetermined standard deviation.15. The system of any of the previous clauses, wherein the third and fourth grating couplers are positioned in a predetermined manner such that the fourth grating coupler is configured to capture the second captured light value of the second optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a negative angle of tilt and a predetermined standard deviation.16. A method of determining an angle of tilt in a substrate, the method comprising: emitting, by a first grating coupler of a plurality of grating couplers, a first optical beam at a region on the substrate; capturing, by a second grating coupler of the plurality of grating couplers, a first captured light value after the first optical beam reflects off the region on the substrate; emitting, by a third grating coupler of the plurality of grating couplers, a second optical beam at the region on the substrate; capturing, by a fourth grating coupler of the plurality of grating couplers, a second captured light value after the second optical beam reflects off the region on the substrate; computing, by a processor, a ratio usingthe first captured light value and the second captured light value; and computing the angle of tilt of the region on the substrate using the computed ratio.17. The method of any of the previous clauses, wherein computing the ratio comprises: computing a difference between the first and second captured light value values; computing a total captured power of the first and second captured light value values; and comparing the computed difference to the total captured power.18. The method of any of the previous clauses, wherein the second grating coupler is configured to capture the first captured light value at a maximum when the angle of tilt of the region is a positive angle.19. The method of any of the previous clauses, wherein the fourth grating coupler is configured to capture the second captured light value at a maximum when the angle of tilt of the region is a negative angle.20. The method of any of the previous clauses, wherein: the first grating coupler is positioned diagonally opposite to the second grating coupler with respect to the region on the substrate; the third grating coupler is positioned laterally opposite to the first grating coupler with respect to the region on the substrate, and the fourth grating coupler is positioned laterally opposite to the second grating coupler with respect to the region on the substrate.21. The method of any of the previous clauses, wherein the first and second grating couplers are positioned in a predetermined manner such that the second grating coupler is configured to capture the first captured light value of the first optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a positive angle of tilt and a predetermined standard deviation.22. The method of any of the previous clauses, wherein the third and fourth grating couplers are positioned in a predetermined manner such that the fourth grating coupler is configured to capture the second captured light value of the second optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a negative angle of tilt and a predetermined standard deviation.23. A semiconductor device manufacturing method, the method comprising: receiving a substrate with a photoresist layer; directing radiation from a radiation source to transfer a pattern from a reticle onto the photoresist layer; determining an angle of tilt in a region of the substrate, comprising: emitting, by a first grating coupler of a plurality of grating couplers, a first optical beam at a region on the substrate; capturing, by a second grating coupler of the plurality of grating couplers, a first captured light value after the first optical beam reflects off the region on the substrate; emitting, by a third grating coupler of the plurality of grating couplers, a second optical beam at the region on the substrate; capturing, by a fourth grating coupler of the plurality of grating couplers, a second captured light value after thesecond optical beam reflects off the region on the substrate; computing, by a processor, a ratio using the first captured light value and the second captured light value; and computing the angle of tilt of the region on the substrate using the computed ratio and removing a portion of the photoresist layer to form a pattern over the substrate.

[0114] Concepts disclosed herein may be associated with any generic imaging system for imaging sub wavelength features, and may be especially useful with emerging imaging technologies capable of producing increasingly shorter wavelengths. Emerging technologies already in use include EUV (extreme ultra violet), DUV lithography that is capable of producing a 193nm wavelength with the use of an ArF laser, and even a 157nm wavelength with the use of a Fluorine laser. Moreover, EUV lithography is capable of producing wavelengths within a range of 20-5nm by using a synchrotron or by hitting a material (either solid or a plasma) with high energy electrons in order to produce photons within this range.

[0115] While the concepts disclosed herein may be used for imaging on a substrate such as a silicon wafer, it shall be understood that the disclosed concepts may be used with any type of lithographic imaging systems, e.g., those used for imaging on substrates other than silicon wafers. In addition, the combination and sub-combinations of disclosed elements may comprise separate embodiments.

[0116] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. A system for determining an angle of tilt of a substrate, the system comprising: a sensor; and a processor operatively coupled to the sensor; the sensor comprising a plurality of grating couplers; wherein: a first grating coupler of the plurality of grating couplers is configured to emit a first optical beam at a region on the substrate; a second grating coupler of the plurality of grating couplers is configured to measure a first captured light value after the first optical beam reflects off the region on the substrate; a third grating coupler of the plurality of grating couplers is configured to emit a second optical beam at the region on the substrate; a fourth grating coupler of the plurality of grating couplers is configured to measure a second captured light value after the second optical beam reflects off the region on the substrate; and the processor is configured to: compute a ratio using the first captured light value and the second captured light value; and compute the angle of tilt of the region on the substrate using the computed ratio.

2. The system of claim 1 , wherein to compute the ratio, the processor is configured to compute a difference between the first and second captured light value values, compute a total captured power of the first and second captured light value values, and compare the computed difference to the total captured power.

3. The system of claim 1, wherein the second grating coupler is configured to capture the first captured light value at a maximum when the angle of tilt of the region is a positive angle.

4. The system of claim 1 , wherein the fourth grating coupler is configured to capture the second captured light value at a maximum when the angle of tilt of the region is a negative angle.

5. The system of claim 1, wherein: the first grating coupler is positioned diagonally opposite to the second grating coupler with respect to the region on the substrate;the third grating coupler is positioned laterally opposite to the first grating coupler with respect to the region on the substrate, and the fourth grating coupler is positioned laterally opposite to the second grating coupler with respect to the region on the substrate.

6. The system of claim 1 , wherein the first and second grating couplers are positioned in a predetermined manner such that the second grating coupler is configured to capture the first captured light value of the first optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a positive angle of tilt and a predetermined standard deviation.

7. The system of claim 1, wherein the third and fourth grating couplers are positioned in a predetermined manner such that the fourth grating coupler is configured to capture the second captured light value of the second optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a negative angle of tilt and a predetermined standard deviation.

8. A system for determining an angle of tilt on a substrate and a measurement of focus on the substrate, the system comprising: a plurality of tilt sensors; a plurality of focus sensors; and at least one processor; each of the tilt sensors comprising a plurality of grating couplers; wherein: a first grating coupler of the plurality of grating couplers is configured to emit a first optical beam at a region on the substrate; a second grating coupler of the plurality of grating couplers is configured to measure a first captured light value after the first optical beam reflects off the region on the substrate; a third grating coupler of the plurality of grating couplers is configured to emit a second optical beam at the region on the substrate; a fourth grating coupler of the plurality of grating couplers is configured to measure a second captured light value after the second optical beam reflects off the region on the substrate; and the at least one processor is configured to: compute a ratio using the first captured light value and the second captured light value; andcompute the angle of tilt of the region on the substrate using the computed ratio.

9. The system of claim 8, wherein the plurality of tilt sensors and the plurality of focus sensors are arranged in an array sufficiently wide such that the entire substrate can be measured for tilt angles and focus measurements using a single scan of the array.

10. The system of claim 8, wherein to compute the ratio, the at least one processor is configured to compute a difference between the first and second captured light value values, compute a total captured power of the first and second captured light value values, and compare the computed difference to the total captured power.

11. The system of claim 8, wherein the second grating coupler is configured to capture the first captured light value at a maximum when the angle of tilt of the region is a positive angle.

12. The system of claim 8, wherein the fourth grating coupler is configured to capture the second captured light value at a maximum when the angle of tilt of the region is a negative angle.

13. The system of claim 8, wherein: the first grating coupler is positioned diagonally opposite to the second grating coupler with respect to the region on the substrate; the third grating coupler is positioned laterally opposite to the first grating coupler with respect to the region on the substrate, and the fourth grating coupler is positioned laterally opposite to the second grating coupler with respect to the region on the substrate.

14. The system of claim 8, wherein the first and second grating couplers are positioned in a predetermined manner such that the second grating coupler is configured to capture the first captured light value of the first optical beam with according to a predetermined Gaussian distribution having a predetermined peak at a positive angle of tilt and a predetermined standard deviation.

15. The system of claim 8, wherein the third and fourth grating couplers are positioned in a predetermined manner such that the fourth grating coupler is configured to capture the second captured light value of the second optical beam with according to a predetermined Gaussiandistribution having a predetermined peak at a negative angle of tilt and a predetermined standard deviation.

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