Wafer alignment method using resolution measurement for product features

Abstract

The present invention provides a method for determining the position of a product feature on a substrate, comprising the steps of: obtaining a plurality of position measurements of one or more product features on the substrate, wherein the measurements are referenced with respect to a positioning system used to displace the substrate between the measurements or to a plane parallel to the surface of the substrate; and determining a distortion component of the substrate based on the position measurements.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] The present application claims priority to EP application No. 20174607.0 filed on May 14, 2020, EP application No. 20208071.9 filed on November 17, 2020, and EP application No. 63 / 180910 filed on April 28, 2021, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a method for determining corrections for a process, a semiconductor manufacturing process, a lithography device, a lithography cell, and an associated computer program product. Background Technology

[0004] A lithography device is a machine configured to apply a desired pattern to a substrate. A lithography device can be used, for example, in the manufacture of integrated circuits (ICs). A lithography device can project a pattern (also called a "design layout" or "design") from a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer).

[0005] To project a pattern onto a substrate, a lithography device may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Common wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. A lithography device using extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 to 20 nm, for example 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than a lithography device using electromagnetic radiation with a wavelength of, for example, 193 nm.

[0006] Low-k1 lithography can be used to process features with dimensions smaller than the traditional resolution limits of lithography devices. In this process, the resolution formula can be expressed as CD = k1 × λ / NA, where λ is the wavelength of the radiation employed, NA is the numerical aperture of the projection optics within the lithography device, CD is the critical dimension (typically the minimum printed feature size, but in this case, half-pitch), and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it becomes to reproduce on a substrate a pattern resembling the geometry and dimensions planned by the circuit designer to achieve specific electrical functionality and performance. To address this problem, complex fine-tuning steps may be applied to the lithography projection device and / or design layout. For example, this includes, but is not limited to, NA, customized illumination schemes, the use of phase-shift patterning devices, various optimizations of design layouts such as optical proximity correction (OPC, sometimes also called "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement techniques (RET)." Alternatively, a strict control loop to control the stability of the lithography device may be used to improve pattern reproduction at low k1.

[0007] International patent application WO 2015049087, the entire contents of which are incorporated herein by reference, discloses a method for obtaining diagnostic information related to an industrial process. In order to obtain object data representing positional deviations or other parameters measured at points spatially distributed across each wafer, alignment data or other measurements are performed at a stage during the execution of a lithography process. Overlays and alignment residuals reveal a pattern across the wafer, commonly known as a fingerprint.

[0008] In semiconductor manufacturing, fingerprints of critical dimension (CD) performance parameters can be corrected using a simple control loop. Typically, a feedback mechanism controls the average dose per wafer using a scanner (a type of lithography device) as an actuator. Similarly, in the case of overlay, which is an overlay performance parameter, fingerprints caused by the processing tool can be corrected by adjusting the scanner actuator.

[0009] Coarse Post-Development Inspection (ADI) measurements are used as input to a wide-area model used to control the scanner (typically a run-to-run method). Less frequently measured dense ADI measurements are used for exposure-specific modeling. Exposure-specific modeling is performed on fields with large residuals by modeling with higher spatial density using dense data. Corrections requiring such denser metrology sampling cannot be performed frequently without adversely impacting throughput.

[0010] Typically, the problem is that model parameters based on coarse ADI data do not accurately represent densely measured parameter values. This can result from crosstalk between model parameters and the uncaptured portions of the fingerprint. Furthermore, such models may have excessive dimensionality for these coarse data sets. This leads to the problem that uncaptured fingerprints are not fully captured by the field-specific model during run-to-run control. Another issue is the irregular spare-to-dense behavior of distributed sampling, where different wafers (and different lots) have different sampling rates to substantially obtain dense measurement results when overlaying many wafer layouts. Large residuals exist between the modeled coarse data and the densely measured parameter values. This results in poor fingerprint technology, leading to non-optimal correction per exposure.

[0011] In the case of alignment control, it is also a problem that only a small number (about 40) of alignment marks can be measured during exposure to avoid affecting throughput. High-order alignment control requires a denser alignment layout and affects throughput. As illustrated in FIG. 5, a solution to this problem is to measure denser alignment marks in an offline tool (Takehisa Yahiro et al., “Feed-forward alignment correction for advanced overlay process control using a standalone alignment station “Litho Booster””, Proc. SPIE 10585, Metrology, Inspection, and Process Control for Microlithography XXXII, incorporated herein by reference), and feed-forward this high-order correction during exposure, while lower-order corrections are still calculated during exposure.

[0012] For overlay control, dense overlay measurements are practically performed only once every few lots (known as high-order parameter updates) to update high-order corrections. The high-order parameters used to determine the scanner control recipe do not change between high-order parameter update measurements.

[0013] Conventional techniques for alignment are based on a position measurement system for dedicated alignment or overlay marks on a substrate, such as measuring the position relative to a reference of an alignment system (in a lithography device or in an independent alignment station).

[0014] However, because the available space on the production reticle for accommodating measurement marks is limited, the number of alignment marks and / or overlay marks (measurement marks) is typically limited. Consequently, if high-order distortion of the substrate dominates the alignment mark positions, for example, within-field behavior, the accuracy of (field-by-field) control operations using position measurements on the measurement marks is limited.

[0015] Additionally, the location of the measurement mark may be exposed to a source of variation that should not be the target of the field-specific control action mentioned above. The problem to be solved

[0016] The objective of the present invention is to overcome the problems associated with methods according to the prior art. means of solving the problem

[0017] In a first aspect of the present invention, a method for determining the position of a product feature on a substrate is provided, comprising the steps of: obtaining a plurality of position measurements of one or more product features on a substrate—the measurements being referenced with respect to a positioning system used to displace the substrate between the measurements or to a plane parallel to the surface of the substrate—and determining a distortion component of the substrate based on the position measurements. Brief explanation of the drawing

[0018] Embodiments of the present invention will be described only in the manner exemplified below with reference to the attached schematic drawings: - Fig. 1 illustrates a schematic overview of a lithography apparatus; - Fig. 2 illustrates a schematic overview of a lithography cell; - FIG. 3 illustrates a schematic representation of holistic lithography showing cooperation among three technologies important for optimizing semiconductor manufacturing; - FIG. 4 is a flowchart illustrating an alignment method according to one embodiment; - FIG. 5 is a flowchart illustrating a feed-forward overlay method according to one embodiment; and - FIG. 6 is a flowchart illustrating a feedback overlay method according to one embodiment. Specific details for implementing the invention

[0019] In this specification, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g., radiation having wavelengths of 365, 248, 193, 157, or 126 nm) and EUV (e.g., extreme ultraviolet radiation having wavelengths in the range of about 5-100 nm).

[0020] As used herein, the terms “reticle,” “mask,” or “patterning device” may be broadly interpreted to refer to a general patterning device that can be used to impart a patterned cross-section corresponding to a pattern to be formed within a target portion of a substrate to an incoming radiation beam. The term “optical valve” may also be used in this context. In addition to traditional masks (transmissive or reflective; binary, phase-shift, hybrid, etc.), other examples of such patterning devices include programmable mirror arrays and programmable (LCD) arrays.

[0021] Figure 1 schematically depicts a lithography apparatus (LA). A lithography device (LA) comprises an illumination system (also called an illuminator (IL)) configured to control a radiation beam (B) (e.g., UV radiation or DUV radiation or EUV radiation), a mask (e.g., mask table) (MT) connected to a first positioner (PM) configured to support a patterning device (e.g., mask) (MA) and to accurately position the patterning device (MA) according to specific parameters, a substrate support (e.g., wafer table) (WT) connected to a second positioner (PW) configured to hold a substrate (e.g., resist-coated wafer) (W) and to accurately position the substrate support according to specific parameters, and a projection system (e.g., refractive projection lens system) (PS) configured to project a pattern imparted to the radiation beam (B) by the patterning device (MA) onto a target portion (C) (e.g., including one or more dies) of the substrate (W).

[0022] In operation, the illumination system (IL) receives a radiation beam from a radiation source (SO) through a beam delivery system (BD). The illumination system (IL) may include various types of optical components for directing, shaping, or controlling radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, and / or any combination thereof. The illuminator (IL) may be used to adjust the radiation beam (B) so that it has a desired spatial and angular intensity distribution in its cross-section on the plane of the patterning device (MA).

[0023] The term “projection system (PS)” as used herein shall be broadly interpreted to include various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic, and / or electrostatic optical systems, and / or any combination thereof, which are suitable for the exposure radiation being used or for other factors such as the use of immersion liquid or vacuum. Any use of the term “projection lens” in this specification may be considered to have the same meaning as the more general term “projection system (PS).”

[0024] The lithography device (LA) may be of the type in which a portion of the substrate (W), which is a rectangular area on the substrate typically called a "field" or "exposure field," is exposed by a radiation beam (B) that passes through a projection system (PS) while the substrate (W) moves horizontally relative to the radiation beam (B). While the substrate (W) is being exposed while moving, the patterning device (MA) also moves in a direction opposite to the direction of substrate movement relative to the illumination light. The field on the substrate (W) being exposed is exposed from one side of the field to the other side of the field along the direction of substrate movement by scanning the field with the radiation beam (B) while moving the substrate (W) relative to the radiation beam (B). The pattern within the patterning device (MA) is also scanned from one side of the pattern to the other side along the direction of patterning device movement by the illumination light due to the movement of the patterning device (MA) during exposure. The portion of the pattern applied to the radiation beam (B) changes while scanning the pattern with the illumination light. The field is exposed from one side of the field to the other while the portion of the pattern applied within the radiation beam (B) changes from the portion of the pattern on one side of the pattern to the portion of the pattern on the other side. The entire pattern within the patterning device (MA) is transferred to the field by scanning the scanning field and the pattern from one side to the other. The radiation beam (B) irradiated onto the field of the substrate (W) is called the "slit area" or "exposure slit area." Therefore, in this type of lithography device (LA), the slit area is scanned across each field of the substrate (W) to transfer the pattern.

[0025] During field scanning, the substrate (W) and the patterning device (MA) are moved by the second positioner (PW) and the first positioner (PM), respectively. This movement of the substrate (W) and the patterning device (MA) by the positioners is controlled in synchronization, so that when a slit area on the field is at any position within the field, a corresponding portion of the pattern to be transferred to that position within the field is imparted within the radiation beam (B). For example, the pattern within the patterning device (MA) is the same size as the field on the substrate (W), and the patterning device (MA) and the substrate (W) are controlled to move in opposite directions at the same speed. If the pattern within the patterning device (MA) is X times larger than the field size within the substrate (W), the movement of the patterning device (MA) is controlled to be X times faster than the movement of the substrate (W). If the motion control of the substrate (W) and the patterning device (MA) is not synchronized, the pattern to be transferred to the field is distorted by the deviation from the synchronized motion control. The pattern to be transferred to the field may also be distorted for other reasons, such as relative rotation between the substrate (W) and the patterning device (MA) during movement. For example, if the patterning device is scanned by illumination light that is slightly off the scanning direction, the part of the pattern to be applied within the radiation beam (B) is rotated. Then, the part of the pattern to be transferred to the corresponding position within the field is also rotated. The opposite holds true if the substrate (W) is scanned by a radiation beam (B) that is slightly off the scanning direction. Therefore, relative rotation between the patterning device (MA) and the substrate (W) during scanning of the field also affects the distortion of the pattern to be transferred to the field. Factors such as the relative speed between the substrate (W) and the patterning device (MA) during scanning, and the relative rotation between the substrate (W) and the patterning device (MA), affect the accuracy of pattern transfer. These scanning factors that affect pattern transfer accuracy are called scan profiles.

[0026] The lithography apparatus (LA) may be of a type in which at least a portion of the substrate can be covered by a liquid having a relatively high refractive index, such as water, to fill the space between the projection system (PS) and the substrate (W), and this is also called immersion lithography. More information regarding the immersion technique is provided in US6952253, which is incorporated herein by reference.

[0027] The lithography device (LA) may be of a type having two or more substrate supports (WT) (also called a "dual stage"). In such a "multi-stage" machine, the substrate supports (WT) may be used in parallel, and / or steps for preparing subsequent exposure of a substrate (W) may be located on one of the substrate supports (WT), while another substrate (W) on another substrate support (WT) is used to expose a pattern on the other substrate (W).

[0028] In addition to the substrate support (WT), the lithography device (LA) may include a measurement stage. The measurement stage is configured to hold a sensor and / or a cleaning device. The sensor may be configured to measure the properties of the projection system (PS) or the properties of the radiation beam (B). The measurement stage may hold multiple sensors. The cleaning device may be configured to clean a part of the lithography device, for example, a part of the projection system (PS) or a part of the system providing the immersion solution. The measurement stage may move under the projection system (PS) when the substrate support (WT) moves away from the projection system (PS).

[0029] During operation, a radiation beam (B) is incident on a patterning device, for example, a mask (MA) held on a support structure (MT), and is patterned by a pattern (design layout) on the patterning device (MA). As it crosses the patterning device (MA), the radiation beam (B) passes through a projection system (PS) that focuses the beam onto a target portion (C) of a substrate (W). With the help of a second positioner (PW) and a position measurement system (IF), the substrate support (WT) can be moved precisely to position, for example, different target portions (C) in the path of the radiation beam (B) at a focused and aligned position. Similarly, a first positioning device (PM) and possibly other position sensors (not clearly depicted in FIG. 1) can be used to accurately position the patterning device (MA) with respect to the path of the radiation beam (B). The patterning device (MA) and the substrate (W) can be aligned using mask alignment marks (M1, M2) and substrate alignment marks (P1, P2). Although the substrate alignment marks (P1, P2) occupy dedicated target portions as illustrated, they may also be located in the space between the target portions. When the substrate alignment marks (P1, P2) are located between the target portions (C), they are known as scribe lane alignment marks.

[0030] As illustrated in FIG. 2, a lithography device (LA) may form part of a lithography cell (LC), also referred to as a lithocell or (litho)cluster, and also includes a device for performing pre-exposure and post-exposure processes on a substrate (W). Typically, such a device includes a spin coater (SC) for depositing a resist layer, for example, to control the solvent in the resist layer or to control the temperature of the substrate (W), a developer (DE) for developing the exposed resist, a chill plate (CH), and a bake plate (BK). A substrate handler or robot (RO) picks up the substrate (W) from input / output ports (I / O1, I / O2), moves them between different process devices, and delivers the substrate (W) to a loading bay (LB) of the lithography device (LA). The device within the lithocell, also commonly referred to as a track, is typically under the control of a track control unit (TCU) that can be controlled by a supervisory control system (SCS), and the supervisory control system can also control a lithography device (LA) through a lithography control unit (LACU).

[0031] In order to ensure that a substrate exposed by a lithography device (LA) is exposed accurately and consistently, it may be desirable to inspect the substrate to measure properties of the patterned structure, such as overlay error between subsequent layers, line thickness, and critical dimension (CD). For this purpose, an inspection tool (not shown) may be included in a lithography cell (LC). If an error is detected, particularly if the inspection is performed before another substrate (W) of the same batch or lot is to be exposed or processed, adjustments may be made, for example, to the exposure of the subsequent substrate or to other process steps to be performed on the substrate (W).

[0032] An inspection device, which may also be called a measuring device, is used to determine the properties of a substrate (W), and specifically how properties of different substrates (W) or properties associated with different layers of the same substrate (W) change depending on the layer. Alternatively, the inspection device may be configured to identify defects on the substrate (W), and may be, for example, part of a lithocell (LC), or integrated into a lithography device (LA), or even a standalone device. The inspection device may measure the properties of a latent image (an image within the resist layer after exposure), a semi-latent image (an image within the resist layer after a baking step (PEB) after exposure), a developed resist image (where exposed or unexposed portions of the resist have been removed), or even an etched image (after a pattern transfer step such as etching).

[0033] Typically, the patterning process within the lithography device (LA) is one of the most critical steps in the process, requiring high dimensional and placement accuracy of the structure on the substrate (W). To ensure this high accuracy, three systems may be integrated in a so-called "holistic" control environment, as schematically illustrated in FIG. 3. One of these systems is the lithography device (LA) (virtually) connected to a metrology tool (MT) (second system) and a computer system (CL) (third system). An important aspect of this "holistic" environment is to optimize the cooperation between these three systems to improve the overall process window and provide a strict control loop to ensure that the patterning performed by the lithography device (LA) remains within the process window. The process window defines the range of process parameters (e.g., dose, focus, overlay) within which a specific manufacturing process provides a defined result (e.g., a functional semiconductor device)—typically, the process parameters of the lithography process or the patterning process can vary within it.

[0034] The computer system (CL) may use the design layout (or part thereof) to be patterned to predict the resolution enhancement technique to be used, and may perform computational lithography simulations and calculations to determine which mask layout and lithography device settings obtain the maximum overall process window of the patterning process (indicated by the double arrow at the first scale (SC1) in FIG. 3). Typically, the resolution enhancement technique is implemented to match the patternability of the lithography device (LA). The computer system (CL) may also be used to detect where the lithography device (LA) is currently operating within the process window (e.g., using input from a metrology tool (MT)) to predict, for example, whether defects may exist due to suboptimal processing (indicated by the arrow pointing to "0" at the second scale (SC2) in FIG. 3).

[0035] The measurement tool (MT) can provide input to the computer system (CL) that enables accurate simulation and prediction, and can provide feedback to the lithography device (LA) to identify drift (indicated by multiple arrows on the third scale (SC3) in FIG. 3) that may be in a calibration state of the lithography device (LA), for example.

[0036] Substrate alignment methodology is typically performed by measuring dedicated metrology marks on the substrate. To be detectable by an alignment sensor, these marks include mark features with a pitch of μm. The mark features can be further segmented so that the marks behave in a manner optically similar to the device structure (product feature).

[0037] However, more segmented marks respond differently to lens aberrations and process artifacts when compared to actual product features. Therefore, while the location of actual product features is a critical parameter for process correction in semiconductor manufacturing, the measured alignment mark location will not represent the actual location of the product features.

[0038] In one embodiment, alignment measurements are performed directly on a device structure, for example, on one or more product features, using high-resolution measurements, for example, a scanning electron microscope (SEM) or e-beam measurements. The e-beam measurement tool can capture an image containing individual product features and determine the individual locations of the product features by machine vision technology, for example, pattern recognition. In another example, the high-resolution measurement system is based on optically positioning the product features by using a high NA detection system and / or a detection system based on illumination of the product features at small wavelengths (XUV, EUV, DUV), or an atomic force microscope (AFM) or a scanning tunneling microscope (STM).

[0039] A resolution measurement (alignment) system acquires the position of a product feature relative to a reference point or reference grid on the substrate itself or a substrate holder (e.g., a wafer table (WT)). Typically, this is achieved by referencing the Field-of-View (FOV) of the resolution measurement system relative to the coordinate system of the substrate positioning system. The substrate positioning system may operate within a standalone alignment system that includes the resolution measurement system, or within a lithography device that includes the resolution measurement system. By referencing the FOV as described, the acquired position of the product feature can be used to reconstruct a distortion map of the substrate. The determined distortion map can subsequently be used to control a processing step, such as a lithography exposure step. Because position measurements can be performed on a large number of product features potentially contained within the (exposure) field or sub-field (e.g., a die area within the field), the distortion map can be determined accurately and on a very small spatial scale; For example, fetching high-order distortion components enables control within the high-order field or sub-field. Therefore, instead of relying on dense post-exposure data, such as an overlay measured by a scatterometer, a control component (a lens or stage actuator of a lithography device) for high-order control based on data directly acquired during the alignment step (e.g., data corresponding to the same substrate being controlled) may be pre-configured.

[0040] Up until now, it has been assumed that the FOV of the high-resolution measurement system is referenced to the substrate positioning system. This is desirable because, typically, to inspect product features, the position of the substrate must follow the desired portion of the substrate (containing the product features to be inspected) to be moved within the (fixed) FOV of the high-resolution measurement system. Therefore, translation of the substrate needs to be applied to the substrate during the measurement sequence. This typically requires accurate referencing of the FOV to the coordinate system of the translation (substrate positioning) system.

[0041] Alternatively, the FOV of the resolution measurement system is moved parallel to a desired sampling position on the substrate; for example, if the resolution measurement system is based on an e-beam, the inspection beam can be oriented to correspond to a desired sampling position on the wafer. In this case, the (variable) FOV position needs to be referenced with respect to the coordinate system of the substrate (plane).

[0042] Furthermore, position measurements based on product features typically represent the actual device structure placement (error) and are therefore more suitable for use in deriving substrate position and / or projection lens corrections configured to at least partially compensate for deviations from the nominal values ​​of the measured product feature positions.

[0043] In order to reference the FOV of the measurement alignment system to a substrate positioning system or a substrate (plane) coordinate system, a separate schematic substrate alignment step using a structure similar to a conventional target, e.g., a target mark, may be performed in addition to the measurement on the product feature using the resolution alignment system. The separate schematic substrate alignment step may be based on the measurement of the conventional alignment mark.

[0044] In one embodiment, the device may include multiple different types of product features where overlay is important. Alignment measurements can be performed independently for each feature type. Then, overall device performance can be optimized based on measurements of these product features.

[0045] The alignment measurement of the present invention can be performed in-line (e.g., by an alignment tool placed within the lithography device) or offline (e.g., by an alignment tool placed outside the lithography device). The advantage of the in-line measurement is that the alignment measurement is performed while the substrate is clamped on the substrate table of the lithography device, and the substrate is exposed by the lithography device while being held by the same substrate holder used during the alignment measurement. Therefore, the substrate deformation (distortion) measured during the in-line alignment measurement is expected to be (almost) identical to the actual deformation of the substrate during lithography exposure. The disadvantage of the in-line resolution alignment is that throughput may be affected and / or resist degradation may occur.

[0046] The advantage of offline resolution alignment measurement is that more alignment marks and product feature locations can be measured without reducing the throughput of the lithography exposure process, enabling higher-order alignment models and corrections. Another advantage of offline measurement is that the exposure resist does not degrade. The disadvantage of offline measurement is that the offline alignment measurement is performed on a substrate held by a substrate holder different from the substrate table of the lithography device that subsequently exposes the substrate. Therefore, additional care is required to correct the effects of substrate deformation caused by the clamping difference between the lithography device and the alignment measurement tool.

[0047] In order to account for differences between substrate deformations induced by clamping in the case of offline resolution alignment measurements, it is proposed that anchoring measurements be performed. Anchoring measurements may include the following:

[0048] 1) Coarse offline measurement of product features and / or alignment marks on a substrate using a high-resolution metrology tool placed outside the lithography device. The coarse offline measurement may be a subset of the dense offline measurement.

[0049] 2) Coarse inline measurements for identical product features and / or alignment marks on the substrate are performed using an alignment system within the lithography device.

[0050] Clamping fingerprints corresponding to offline and inline measurements are compared and used to determine a delta fingerprint representing differences within substrate deformation caused by the use of different substrate holders. The delta fingerprint is then used to correct the offline-determined substrate distortion, allowing the corrected substrate deformation to better represent the substrate deformation occurring during lithography exposure. Additionally, a dense offline measurement is performed on the product features. The dense offline measurement can then be corrected using a coarse offline measurement.

[0051] Before initiating lithography exposure, corrected substrate deformation information and inline alignment measurements can be used to configure the lithography exposure step so that the substrate positioning system and projection lens of the lithography device optimally compensate for substrate distortion while exposing the substrate.

[0052] The preceding description relates to using tools such as SEM / e-beam metrology to perform alignment metrology (in addition to CD metrology). This will continue to expand and extend to other pattern placement metrology, such as overlays. These pattern placement metrology can be performed across the wafer at sub-nm levels.

[0053] The e-beam tool used may include one or more stages and a stage measurement system operable to determine the position of said / each stage with an accuracy well below 1 nm (e.g., less than 0.5 nm or less than 0.2 nm). The e-beam tool may also have a landing energy sufficiently high to be measurable through the stack and / or resist. This landing energy may be greater than 10 kEV or greater than 20 kEV; for example, in the range of 10 kEV to 50 kEV.

[0054] Regarding alignment, the metrology image (e.g., e-beam or SEM image) can be aligned to a reticle reference file or .gds file that describes the layout information or expected location of each reticle feature. Depending on the visibility range of the metrology tool, it may be possible to align 1,000 to 10,000 features to the reticle reference file. This can be expected to provide alignment results (reproducibility or measurement uncertainty) well below the 1 nm level (e.g., 0.1 nm).

[0055] The position of the measurement image on the wafer can also be measured at a level of less than a nanometer: in this way, the stage position can be determined with an accuracy level nearly equal to that of the scanner stage. For example, the measurement tool may be provided with an interferometric system for stage position measurement to provide sufficient reproducibility and relative accuracy of the stage position measurement.

[0056] If the stage position is known at a sub-nm level, it is possible to measure the positions of both the alignment mark on the wafer and (directly) any device quantum. This then enables the measurement of the relative position or offset of the device with respect to the alignment mark. Sufficiently high landing energy enables measurements at both the alignment mark and the bottom lattice quantum of any device of interest.

[0057] These e-beam metrology tools can be provided as standalone alignment metrology stations for measuring wafers prior to exposure. Because e-beam metrology is slower than optical metrology, the scanner may still include an optical alignment tool so that the e-beam tool measures only a subset or percentage of all wafers being exposed and the optical tool is used to measure all wafers.

[0058] In this way, it is possible to measure the aligned positions of the actual device (e.g., in-die positions) as densely as desired. In this manner, it is possible to capture scribe lane-die distortions (e.g., local etching effects, topology influences, in-die stress).

[0059] It is possible to perform wide-area wafer alignment using an optical scanner alignment sensor (e.g., a 6 or 10-parameter model or a higher-order model) and compare the results of this scanner alignment data with previously measured aligned positions on the same mark using an e-beam tool. In this way, it is possible to correct the difference in chucking (wafer load grid) between the standalone e-beam tool and the scanner.

[0060] 4 is a flowchart illustrating an alignment measurement method according to one embodiment.

[0061] In step 400, a first tool or an e-beam tool (e.g., a standalone e-beam alignment station) may be used to measure first tool target alignment data including the location of an alignment mark on the wafer. Assuming the e-beam tool has sufficient landing energy, the alignment mark may be a buried alignment mark; for example, the layer being aligned is measured regardless of its depth within the stack. Additionally, the wafer may be coated within a resist.

[0062] In step 410, an e-beam tool may be used to measure first tool device alignment data, which includes the position of the device structure within the same layer as the alignment mark measured in step 400. Unlike optical alignment measurements, the device structure does not need to have periodicity to be measured by the e-beam tool.

[0063] In step 420, the first tool target alignment data is referenced with respect to the reference grid, and in step 430, the first tool device alignment data is referenced with respect to the reference grid.

[0064] In step 440, both the referenced first tool target alignment data and the first tool device alignment data may be used to construct an alignment-to-device offset for some or all of the devices being measured. This offset may include the difference in device-specific measurement positions within the first tool device alignment data compared to the measured positions within the first tool target alignment data. To obtain an average of the actual in-die distortion, the device measurements may be averaged over multiple occurrences of each device for each die.

[0065] In step 450, the offset determined in step 440 can be integrated within a dense grid of alignment offsets for each alignment mark across, for example, one or more of the die, field, and wafer.

[0066] In step 460, a scanner alignment tool or an optical alignment tool (second metrology tool) is used to measure alignment marks on the wafer to acquire second tool target alignment data. The first tool target alignment data and the second tool target alignment data can be compared to determine the difference or delta grid between these two datasets. This delta grid is attributed to the difference that occurs because a different stage is used for measurement on a standalone alignment station than the one used for alignment within the scanner (i.e., chucking difference or delta wafer load grid).

[0067] In step 470, a dense alignment correction grid is determined from a dense grid of alignment offsets (e.g., per-device offsets) obtained in step 450 and corrected for the chucking difference determined in step 460.

[0068] A dense grid correction can be applied to the scanner as a feedforward correction (e.g., on an alignment grid). In this way, a dense alignment grid can be used to correct the alignment for all wafers for which alignment data is acquired using only an optical alignment tool (e.g., within the scanner). This can be a number of wafers, and only a few wafers are actually measured using an e-beam alignment tool. The e-beam alignment tool may be used periodically, for example, only for the first wafer of a lot. In this way, the optical alignment measurements performed on alignment marks within the scanner can be corrected to match (at least partially matched) what is performed directly on specific features by the e-beam tool.

[0069] The same basic principle can be applied to the correction of overlay measurements, which suffers from the same problem as alignment measurements, particularly that overlay measurements are typically performed on targets that need to have a periodic pattern of sufficiently large pitch to be optically measured. This means that targets do not necessarily represent the device structure truthfully, resulting in what is called the measurement-device offset (the difference between the measured overlay on the target and the actual overlay on the product structure). Target-based optical overlay measurements may include micro-diffraction-based overlay measurements (μDBO). In μDBO, the overlay is determined from the intensity difference of corresponding or complementary higher diffraction orders (e.g., +1 and -1 diffraction orders). These diffraction orders can be imaged within the image plane (e.g., a dark-field image where the zero order is blocked in front of the image plane), and the intensity is averaged across the region of interest (ROI) within each image of the diffraction order. It is also known that optical overlay metrology is performed directly on a product structure or a target simulating a product structure, which is commonly referred to as in-device metrology (IDM). IDM may be based on detecting an angle-resolved spectrum scattered from the device structure within the pupil plane. However, IDM requires a periodic structure, and therefore not all device structures can be measured in this manner. Another optical overlay metrology technique to which the concept disclosed herein is applicable is image-based overlay (IBO). IBO metrology may involve determining the relative offset between two or more layers on a sample based on the relative imaged positions of features of an overlay target within different layers of interest.This method may use dedicated targets such as box-in-box targets, where the overlay is determined from the position of a first box imaged within one layer and a second box imaged within another layer, and one box is smaller than the other and is located within it. There exist other IBO methods and target types to which the concepts of this specification are equally applicable.

[0070] FIG. 5 is a flowchart describing a method for performing overlay feedforward correction according to one embodiment. In step 500, the overlay fingerprint of the previous layer may be measured using an optical measurement tool (a second measurement tool) to measure wafer-specific overlay targets (e.g., after etching). Such measurements may be, for example, IBO, DBO, μDBO, or IDM target-based measurements to acquire second tool target overlay data. This may include high throughput measurements on all wafers that allow wafer-level feedforward correction to be determined for the corresponding wafer. Since this step may be performed for each wafer, this step may include sparse measurements (e.g., one or two targets per field).

[0071] In step 510, e-beam measurement is performed on the same overlay target (e.g., post-etching inspection (AEI) target) to obtain first tool target overlay data (effectively the difference in position measurements for each of the two component grids or components of the overlay target). This may be performed on a subset of wafers (e.g., one per lot). In a manner similar to the previous embodiment, the second tool target overlay data and the first tool target overlay data may be compared to determine the difference or delta grid between these two datasets, the delta grid being approximately due to the stage difference (chucking difference) between the tools used.

[0072] In step 520, an e-beam tool may be used to measure an overlay on a device structure to obtain first tool device overlay data (this may be irregular / periodic). In other words, this may involve measuring the position of the device structure relative to a substantially previous layer or a structure within it. This step may be performed on the same subset of the wafer as in step (510).

[0073] In step 530, a dense die-in overlay grid can be determined from the first tool target overlay data and the first tool device overlay data. This dense die-in overlay grid can describe the die-in distortion for the overlay target measurement (e.g., a dense grid describing the MTD offset).

[0074] In step 540, using the second tool target overlay data, the first tool target overlay data, and the first tool device overlay data, wafer-level feedforward correction may be determined for exposure within the scanner, and exposure may be performed on each of the wafers being measured to acquire the second tool target overlay data. This may include optimizing the edge placement error (EPE) or overlay based on a dense die-in-overlay grid. The correction may be based on a measurement offset (MTD offset) between the first tool device overlay data and the second tool target overlay data (e.g., dense die-in-overlay grid), which is corrected for the chucking difference. For example, the optimization may be a weighted optimization across a number of determined MTD offsets (e.g., offsets by device type and / or wafer area), based on the EPE criticality (process window) of various devices using the first target metrology data as input. This multi-feature overlay optimization can be compared to CD die optimization currently used for dose control.

[0075] It may be acknowledged that the embodiments of FIG. 4 and FIG. 5 can be combined so that feedforward exposure correction can be obtained based on both alignment data according to the embodiment of FIG. 4 and overlay data according to the embodiment of FIG. 5. For example, both alignment data and overlay data may be used to determine a dense control grid correction for exposure.

[0076] In another embodiment, overlay feedback control that supports e-beam measurement is also disclosed. FIG. 6 is a flowchart illustrating such an embodiment.

[0077] In step 600, the first overlay fingerprint may be measured after etching using an optical measurement tool for measuring wafer-specific overlay targets. This measurement may be, for example, an IDM target-based measurement to acquire second tool post-etching overlay data or a second tool AEI overlay fingerprint (e.g., an IDM overlay fingerprint). This step may be performed for all wafers.

[0078] In step 610, the second overlay fingerprint may be measured after development using an optical measurement tool for measuring wafer-specific overlay targets. This measurement may be, for example, an IBO, DBO, or μDBO target-based measurement to acquire the second tool post-development overlay data or the second tool ADI overlay fingerprint (e.g., an IBO or DBO overlay fingerprint). This step may be performed for all wafers.

[0079] In step 620, ADI e-beam metrology may be performed, for example, on a subset of wafers measured in step 610 to obtain first tool post-development overlay data. This first tool ADI overlay data may include metrology data from an ADI where an IBO or DBO target is measured, from an ADI where an IDM target is measured, and for a device structure ADI (e.g., at least a high-importance device).

[0080] In step 630, AEI e-beam metrology may be performed, for example, on a subset of wafers measured in step 600 to obtain overlay data after the first tool etching. This first tool AEI overlay data may include metrology data from the AEI measured for the IDM target and for the AEI of the device structure (e.g., at least for a high-importance device). Step (630) may replace or be added to step (620).

[0081] In step 640, the first and second tool ADI overlay data and / or the first and second tool AEI overlay data are used for the following (where applicable):

[0082] - Determination of device-specific ADI MTD offset(s) (e.g., device-DBO) from a comparison of the target measurement and the device measurement obtained in step 620 to obtain the DBO measurement grid;

[0083] - Determination of device-specific AEI MTD offset(s) (e.g., IDM) from a comparison of the target measurement and the device measurement obtained in step 630 to obtain the IDM measurement grid;

[0084] - Determination of a device-specific process offset (e.g., the difference between the device measurements of ADI performed in step 620 and AEI performed in step 630) to obtain a dense grid (also a grid within the die) per device.

[0085] In step 650, using all datasets determined in the previous embodiment, feedback correction is determined. This may be based on multi-feature overlay optimization comparable to the CD die optimization used for dose, and includes weights based on overlay margin / device (EPE criticality). This step may further include enabling control of the overlay on the actual device using device-specific process offset and device-specific MTD. As described above, the second tool overlay data may be used together with one or both of the first tool post-development overlay data and the first tool post-etching overlay data to determine correction for stage difference or chucking difference between the tools used.

[0086] It may be acknowledged that the embodiment of FIG. 6 can be combined with one or both of the embodiments of FIG. 4 and FIG. 5.

[0087] Images captured by an e-beam tool can, of course, still be used for CD / local CDU measurements. Then, CD measurement data describing the device CD (e.g., data for multiple devices) is provided, which can be used for feedback scanner (dose) correction for same-layer exposure of subsequent lots, or can be used in combination with registration error data to determine feedforward correction (e.g., for dose / overlay) for next-layer exposure of the wafers being measured.

[0088] Ultimately, the e-beam tool can be used in conjunction with the device structure to perform alignment measurements directly on the device structure (e.g., instead of or alongside an optical alignment sensor such as AS in FIG. 1). In this way, alignment can be achieved more densely on any structure without the need to accommodate more (or arbitrary) alignment marks. Since the alignment measurements are performed directly on the device structure, the problem of measurement for device offset (the problem of the target behaving differently from the device structure) is avoided.

[0089] Offline resolution alignment measurements allow for the measurement of more alignment marks and product feature locations, and create the possibility of using alignment models that are improved (e.g., of higher order) than are possible with current inline measurement strategies. The available measurement time is typically insufficient for inline measurement strategies to measure the volume of marks required to execute a more desirable modeling strategy. For example, the following alignment granularity is currently commonly used:

[0090] - Inter-field: Wide-area wafer placement and deformation. This is currently accomplished using linear models (e.g., 6-parameter models) or "higher-order" models (typically up to 5th order);

[0091] - Within field: To sort average field fingerprints;

[0092] - Zone alignment: An interpolation / extrapolation method that can be used to capture more local deformations.

[0093] A disadvantage of existing alignment granularity is that very high-order fingerprints, such as those caused by scanner exposure, cannot be adequately compensated. Consequently, these fingerprints require correction by other means, such as overlay control based on feedback control loops. By their nature, these feedback control loops are always "catching up" because fingerprints change over time and thus tend to experience delays in correction. Additionally, they tend to suffer from wafer-to-wafer variation and lot-to-lot noise.

[0094] Therefore, for the offline measurement embodiments disclosed herein, it is proposed to measure a much denser alignment layout (which may include product structures and / or dedicated targets) than currently used (e.g., for inline alignment measurement), thereby allowing for higher-order alignment modeling.

[0095] These proposals may include performing alignment on any of the subsequent granularity and alignment modeling strategies or a combination thereof (where applicable):

[0096] - Field-specific (exposure) modeling: If sufficient targets exist within each field, field-specific modeling can be performed;

[0097] - All fields can be modeled individually; or field-specific modeling can be performed only on a subset of fields. For example, a first subset of fields within a first substrate area (e.g., within an inner substrate area) can be modeled using a first strategy such as an averaged field fingerprint strategy, and a second subset of fields within a second substrate area (e.g., within an outer substrate area where larger fluctuations may be predicted) can be modeled using a second strategy such as the field-specific modeling strategy. Of course, the decision on where and how frequently field-specific modeling is performed may depend on the overlay behavior / requirements.

[0098] - Average sub-field modeling: This can be performed, for example, when little variation is observed across the sub-field.

[0099] - Sub-field modeling where some or all sub-fields are modeled separately.

[0100] - This can be very costly in terms of measurement effort and therefore can only be performed when there is large variation across sub-fields, and possibly only for a small subset of fields on the wafer (e.g., at extreme edges);

[0101] - Die-by-die: Essentially a special case of sub-field-by-die modeling, but has much higher granularity than a sub-field containing multiple dies.

[0102] - Modeling of a distortion fingerprint over an area (e.g., so-called slit area) associated with the extension of a radiation beam (B) across a substrate, e.g., a slit fingerprint:

[0103] Slit fingerprints are often characterized to a large extent by the contribution of projection optics (e.g., lenses) to the distortion fingerprint of the lithography device. Lens contributions (lens fingerprints) typically contain high-order components and therefore require dense distortion (alignment) measurements when they need to be determined. The product alignment method described above allows slit fingerprints to be determined because it relies solely on the presence of product features without the need to provide many alignment marks in a small area on the reticle corresponding to the slit area. Slit fingerprints may further include reticle errors.

[0104] - The slit fingerprint represents the distortion component of the substrate across the exposure slit area, for example, distortion indicated with respect to the distance from the center of the exposure slit area in the non-scanning direction. The distortion with respect to the distance from the center of the slit in the non-scanning direction can be calculated by averaging measurements of product features at the same distance from the center of the slit in the non-scanning direction.

[0105] Then, a high-order slit fingerprint can be identified using measurements of product features on the substrate. Then, for example, the lens fingerprint of the lithography device used to expose a previous layer of the substrate can be identified. Then, the identified lens fingerprint can be used to control a projection lens to compensate for the lens fingerprint in a subsequent layer and / or subsequent substrate to be exposed using the lithography device.

[0106] - Modeling of distorted fingerprints within a field parallel to the scanning direction, e.g., scan profile fingerprints:

[0107] - The scan profile fingerprint is a distortion of the transferred pattern within the field parallel to the scanning direction, attributed to the scan profile of the lithography device used for exposure. The scan profile is often characterized by a large range of contributions from relative velocity variations between the positioning device of the patterning device and the positioning device of the substrate during scanning. Additionally, the scan profile is characterized by contributions from relative rotational variations between the positioning device of the patterning device and the positioning device of the substrate during scanning. The scan profile fingerprint also contains high-order components and therefore requires dense distortion (alignment) measurements when it needs to be determined. The product alignment method described above allows the scan profile fingerprint to be determined because it relies solely on the presence of product features without the need to provide many alignment marks within the pattern on the reticle.

[0108] - The scan profile represents the distortion component of the substrate in the scanning direction on the field, for example, the distortion plotted with respect to the scanning direction position within the field coordinates. Scan profile distortion can be calculated by averaging measurements at the same field coordinate position in the scanning direction.

[0109] - The aforementioned method of product alignment is advantageous for determining scan profile fingerprints, for reasons such as slit fingerprints, in that the dense measurements required to determine high-order distortion can be performed using product features without introducing many alignment marks.

[0110] - Scan profile fingerprinting can be performed on an average field, such as an average scan-up field or a scan-down field. Scan profiles can also be performed on a single field (per exposure field).

[0111] Then, a high-order scan profile fingerprint can be identified using measurements of product features on the substrate. Then, distortion of the transferred pattern on the substrate caused by the scan profile, such as relative speed variations and / or relative rotation variations between the positioning device of the substrate stage and the positioning device of the patterning device, can be identified. Then, the identified scan profile fingerprint can be used to calibrate and / or control the positioning device of the substrate and the patterning device to compensate for the scan profile fingerprint in the subsequent layer and / or subsequent substrate to be exposed using the lithography device.

[0112] These strategies and granularities may also be combined with existing alignment strategies / granularities if desired (and applicable). In all the foregoing, the term sub-field may refer to dies, a single die, or even partial dies or any subset of sub-fields including partial dies.

[0113] In addition to or instead of the strategies described above, modeling may be performed per product feature. For example, to optimize edge placement (e.g., the placement of individual features), it is important to know the locations of different (e.g., critical) product features. Critical features may require special care when placed (e.g., they have a narrow process window). Feature-specific measurement and modeling allow for the optimization of edge placement. For example, different weights may be used for different features depending on their importance (e.g., depending on the location of the feature within the layout and / or the type of the feature).

[0114] Potentially, if the field-specific alignment fingerprint is stable within a specific group or set (e.g., across a lot, across a chuck, or across different groups of wafers), high granularity alignment (e.g., sub-field metrology) may be performed on only one wafer (e.g., the first wafer) or another subset per group. Then, the results of this alignment may be used for other wafers within the group (at least partially). In this way, these subsequent wafers require only coarse measurements, which can now be supplemented by the dense modeling performed on a single wafer. In this embodiment, only the densely measured wafers in the group are taken offline, while the remaining coarsely measured wafers can be measured inline. These latter wafers may be measured more coarsely than the current strategy (or at least provide a higher-order alignment strategy), improving overall throughput.

[0115] Another option for offline measurement is to perform distributed sampling across wafers. This will allow for higher-order modeling by group of lots / chucks / wafers, while performing lower-order modeling on a wafer-by-wafer basis. This is not possible in-line because all measurement data is required before modeling can be performed. Distributed sampling can include further variance across subsets of fields within a wafer (alternatively or additionally); for example, field-by-field modeling can be performed only on a subset of fields. This latter form of distributed sampling also becomes possible with in-line aligned measurements.

[0116] While offline alignment measurements on the device provide an advantage regarding scanner availability, this is not a requirement of the present invention. Any of offline or inline measurements, or measurements on the mark or on the device, may be possible.

[0117] Additional embodiments may be described using the following sections.

[0118] 1. A method for determining the distortion component of a substrate,

[0119] A step of obtaining multiple position measurements of one or more product features on a substrate—the measurements are referenced with respect to a positioning system used to displace the substrate or a plane parallel to the surface of the substrate—; and

[0120] A method for determining a distortion component, comprising the step of determining the distortion component of the substrate based on the plurality of position measurements.

[0121] 2. In Section 1,

[0122] A method for determining a distortion component, wherein the distortion component is associated with in-plane distortion of the substrate and / or the location of a product feature on the substrate.

[0123] 3. In Section 2,

[0124] The above method is,

[0125] A step of obtaining a measurement of one or more alignment marks on the substrate; and

[0126] A method for determining a distortion component, further comprising the step of determining the location of the product feature based on the measurement of the product feature and / or an image of the product feature, and the measurement of one or more alignment marks.

[0127] 4. In any one of Sections 1 through 3,

[0128] A method for determining a distortion component, wherein at least a portion of the measurement of the product feature and / or the image of the product feature is performed inline using an alignment tool placed within a lithography device.

[0129] 5. In any one of Sections 1 through 4,

[0130] A method for determining distortion components, wherein at least a portion of the measurement of the product features and / or images of the product features are performed offline using an alignment tool placed outside the lithography device or connected to the lithography device.

[0131] 6. In any one of Sections 3 through 5,

[0132] A method for determining a distortion component, wherein at least some of the measurements of the product features and / or images of the product features are performed offline, and at least some of the measurements of one or more alignment marks are performed inline.

[0133] 7. In Section 6,

[0134] A method for determining distortion components, wherein offline measurement and inline measurement are combined by coupling the deformation grid of an alignment tool used for offline measurement and inline measurement.

[0135] 8. In Section 1 or Section 2,

[0136] A method for determining a distortion component, wherein the plurality of position measurements include first tool measurement data measured using a first measuring tool, or first tool measurement data measured using the first measuring tool and second tool measurement data measured using a second measuring tool.

[0137] 9. In Section 8,

[0138] A method for determining a distortion component, wherein the first measurement tool is a scanning electron microscope tool and / or the second measurement tool is an optical measurement tool.

[0139] 10. In Section 9,

[0140] A method for determining a distortion component, wherein the scanning electron microscope measures at least one of a plurality of position measurements of one or more product features and / or targets on the substrate below the top layer of the substrate.

[0141] 11. In Section 10,

[0142] A method for determining a distortion component, wherein at least one of a plurality of position measurements is for one or more product features and targets on the same layer.

[0143] 12. In any one of Sections 9 through 11,

[0144] A method for determining distortion components in which the electron beam of a scanning electron microscope has a landing energy greater than 10 keV.

[0145] 13. In any one of Sections 9 through 12,

[0146] A method for determining distortion components, wherein the electron beam of the above scanning electron microscope has a landing energy of less than 50 keV.

[0147] 14. In any one of Sections 8 through 13,

[0148] A method for determining a distortion component, wherein the first tool measurement data comprises first tool target measurement data measured on a target and first tool device measurement data measured on a device structure.

[0149] 15. In Section 14,

[0150] The above method is,

[0151] The method includes the step of determining one or more measurement-device offsets for one or more device structures related to the first tool device measurement data from the first tool target measurement data and the first tool device measurement data, and

[0152] A method for determining a distortion component, wherein the above one or more measurement-device offsets include a comparison of a device-specific measurement value in the first tool device measurement data with respect to a corresponding measurement value in the first tool target measurement data.

[0153] 16. In Section 15,

[0154] The above method is,

[0155] A method for determining a distortion component, comprising the step of combining one or more measurement-device offsets within a dense grid of measurement offsets for each target.

[0156] 17. In Section 15 or 16,

[0157] The above method is,

[0158] A method for determining a distortion component, comprising the step of applying a dense grid of the measurement offset and / or one or more measurement-device offsets to a reference grid of an exposure device as a feedforward correction.

[0159] 18. In Section 15 or 16,

[0160] The above method is,

[0161] A method for determining a distortion component, comprising the step of applying a dense grid of the measurement offset and / or one or more measurement-device offsets to a reference grid of an exposure device as a feedback correction.

[0162] 19. In Section 17 or 18,

[0163] The above method is,

[0164] A step of determining stage correction and / or exposure correction from a comparison of the first tool target measurement data and the second tool target measurement data; and

[0165] A method for determining a distortion component, comprising the step of applying stage correction and / or exposure correction as the feedforward correction or feedback correction.

[0166] 20. In any one of Sections 14 through 19,

[0167] The above first tool target measurement data includes first tool target alignment data measured on an alignment mark, and

[0168] A method for determining a distortion component, wherein the first tool device measurement data includes first tool device alignment data measured on a device structure.

[0169] 21. In Section 20,

[0170] A method for determining a distortion component, wherein the second tool measurement data includes second tool target data measured on the alignment mark.

[0171] 22. In Section 20 or 21,

[0172] The above second measurement tool is a method for determining a distortion component, comprising an optical alignment sensor.

[0173] 23. In any one of Sections 14 through 19,

[0174] The above first tool target measurement data includes first tool target overlay data measured on an overlay target, and

[0175] A method for determining a distortion component, wherein the first tool device measurement data includes first tool device overlay data measured on a device structure.

[0176] 24. In Section 23,

[0177] The first tool target overlay data comprises one or both of the first tool post-etching target overlay data obtained after the etching step is performed on the target and the first tool post-development target overlay data obtained before the etching step is performed on the target.

[0178] A method for determining a distortion component, wherein the first tool device measurement data comprises one or both of the first tool etching-post-device overlay data obtained after the etching step is performed on the device structure and the first tool developing-post-device overlay data obtained before the etching step is performed on the device structure.

[0179] 25. In Section 24,

[0180] The above method is,

[0181] A method for determining a distortion component, comprising an additional step of determining an offset between the device overlay data after the first tool etching and the device overlay data after the first tool development.

[0182] 26. In any one of Sections 23 through 25,

[0183] A method for determining a distortion component, wherein the second tool measurement data includes second tool target data measured on the overlay target.

[0184] 27. In any one of Sections 23 through 26,

[0185] A method for determining a distortion component, wherein the second measurement tool includes an optical scattering measurement tool.

[0186] 28. In any one of Sections 1 through 27,

[0187] The above method is,

[0188] A method for determining a distortion component, further comprising the step of modeling the distortion component of the substrate for at least one exposure field or sub-field on the substrate according to a first field or sub-field model.

[0189] 29. In Section 28,

[0190] A method for determining a distortion component, wherein the step of modeling according to the first field or sub-field model is performed on a first average field or sub-field among a first subset of fields or sub-fields on the substrate.

[0191] 30. In Section 29,

[0192] A first subset of the above fields or sub-fields is within a first substrate region of the substrate, and

[0193] A method for determining a distortion component, wherein a second field or sub-field within a second substrate region of the above substrate is modeled according to a second field or sub-field model.

[0194] 31. In Section 30,

[0195] The first region above is an internal region of the substrate, and

[0196] A method for determining a distortion component, wherein the second zone above is an outer zone of the substrate.

[0197] 32. In any one of Sections 28 through 31,

[0198] A method for determining a distortion component, wherein the first field model or sub-field model comprises a die model or sub-die model that models one or more dies or sub-dies on the substrate.

[0199] 33. In any one of Sections 28 through 32,

[0200] The modeling of the first field or sub-field is performed on a first subset of a group of substrates, and

[0201] A distortion component determination method in which the result of modeling the first field or sub-field is used for a second subset of the group of substrates.

[0202] 34. In any one of Sections 28 through 33,

[0203] The above method is,

[0204] A method for determining a distortion component, further comprising the step of modeling locations among one or more locations of different product features.

[0205] 35. In Section 34,

[0206] A method for determining a distortion component, wherein different product features include product features of different types and / or product features located at different positions within the field of the substrate.

[0207] 36. In any one of Sections 1 through 35,

[0208] The above method is,

[0209] A method for determining a distortion component, further comprising modeling an exposure slit of a lithography device used to manufacture a previous layer of the substrate according to a distortion component of the substrate and / or a slit fingerprint model for at least one exposure field or sub-field on the substrate.

[0210] 37. In Section 36,

[0211] A method for determining distortion components, wherein the above slit fingerprint model includes a lens fingerprint model.

[0212] 38. In Section 36 or 37,

[0213] A method for determining a distortion component, wherein modeling according to the above slit fingerprint model is performed on a second average field of a second subset of fields or sub-fields of the substrate.

[0214] 39. In any one of Sections 1 through 38,

[0215] The above method is,

[0216] A method for determining a distortion component, further comprising the step of modeling a distortion component of the substrate for at least one exposure field or sub-field on the substrate according to a scan profile fingerprint model.

[0217] 40. In Section 39,

[0218] A method for determining a distortion component, wherein modeling according to the above scan profile fingerprint model is performed on a third average field of a third subset of fields or sub-fields of the substrate.

[0219] 41. In Section 40,

[0220] A method for determining a distortion component, wherein a third subset of the above fields or sub-fields includes a scan-up field or a scan-down field.

[0221] 42. In Section 39,

[0222] A method for determining distortion components, wherein modeling according to the above scan profile fingerprint model is performed for each exposure field.

[0223] 43. In any one of Sections 28 through 42,

[0224] A method for determining distortion components, wherein at least a portion of the measurement of the product features and / or images of the product features are performed offline using an alignment tool placed outside the lithography device or connected to the lithography device.

[0225] 44. In any one of Sections 1 through 43,

[0226] A method for determining distortion components in which at least some of the multiple position measurements are distributed across multiple substrates.

[0227] 45. In any one of Sections 2 through 44,

[0228] The above method is,

[0229] A method for determining a distortion component, further comprising the step of determining edge placement control of a product feature based on the position of the product feature.

[0230] 46. ​​In Section 45,

[0231] The above method is,

[0232] A method for determining a distortion component, further comprising the step of setting weights for product features based on the criticality of the product features.

[0233] 47. A method of exposing a substrate using a lithography apparatus,

[0234] A step of determining the location of a product feature on a substrate according to any one of Sections 2 through 44; and

[0235] A substrate exposure method comprising the step of at least partially exposing the substrate based on a determined location of the above-mentioned product features.

[0236] 48. In any one of Sections 2 through 47,

[0237] A substrate exposure method in which the step of measuring the product features or acquiring an image of the product features is performed using an electron beam device.

[0238] 49. An exposure apparatus including an electron beam device,

[0239] The above exposure device is configured to perform a method according to any one of Sections 1 to 48.

[0240] 50. An exposure system comprising an exposure device and an electron beam device for exposing a substrate,

[0241] An exposure system configured to perform a method according to any one of Sections 1 through 48 using the electron beam device.

[0242] While the use of lithography devices in the field of manufacturing ICs may be specifically mentioned in this specification, it should be understood that the lithography devices described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memory, flat panel displays, Liquid Crystal Displays (LCDs), thin film magnetic heads, etc.

[0243] Although embodiments of the invention have been specifically referenced in this specification in the context of inspection or measuring devices, embodiments of the invention may be used in other devices. Lithography. Embodiments of the invention may be part of a mask inspection device, a lithography device, or any device that measures or processes an object such as a wafer (or other substrate) or a mask (or other patterning device). Additionally, it should be noted that the terms measuring device or measuring system may encompass or be substituted for inspection device or inspection system. A measuring or inspection device may be used to detect defects on or within a substrate and / or defects in structures on the substrate as disclosed in this specification. In such embodiments, characteristics of structures on the substrate may relate, for example, to defects within the structures, the absence of specific parts of the structures, or the presence of unwanted structures on the substrate.

[0244] Although "measurement device / tool / system" or "inspection device / tool / system" are specifically referenced, these terms may refer to tools, devices, or systems of the same or similar types. For example, an inspection or measurement device comprising one embodiment of the present invention may be used to determine the characteristics of a physical system, such as a structure on a substrate or on a wafer. For example, an inspection or measurement device comprising one embodiment of the present invention may be used to detect defects in a substrate or defects in a structure on a substrate or on a wafer. In such embodiments, the characteristics of the physical structure may relate to defects within the structure, the absence of specific parts of the structure, or the presence of unwanted structures on the substrate or on the wafer.

[0245] Although specific references have been made above regarding the use of embodiments of the present invention in the context of optical lithography, it will be acknowledged that, where the context permits, the present invention is not limited to optical lithography and may be used in other applications, e.g., imprint lithography.

[0246] Although the aforementioned target or target structure (more generally, a structure on a substrate) is a metrology target structure specifically designed and formed for the purpose of measurement, in other embodiments, the attribute of interest may be measured in one or more structures that are functional parts of a device formed on a substrate. Many devices have a standard lattice-like structure. The terms structure, target lattice, and target structure as used herein do not require that such structure be specifically provided for the measurement being performed. For multi-sensitivity target embodiments, different product features may include many regions having varying sensitivities (such as varying pitch). Furthermore, the pitch P of the metrology target may be close to the resolution limit of the scatterer's optical system but much larger than the dimensions of a typical product feature manufactured by a lithography process within the target portion (C). In practice, the lines and / or spaces of the overlay lattice within the target structure may be manufactured to include smaller structures with dimensions similar to the product feature.

[0247] Although specific embodiments of the present invention have been described above, it will be understood that the invention may be practiced differently from that described. The above description is provided for illustrative purposes only and not for limiting purposes. Accordingly, it will be apparent to those skilled in the art that modifications to the invention as described may be made without departing from the scope of the claims set forth below.

Claims

Claim 1 A method for determining a distortion component of a substrate, comprising the step of obtaining a plurality of position measurements of one or more product features on or within the surface of a substrate and one or more alignment marks of the substrate, wherein the plurality of position measurements include first tool measurement data measured using a first measuring tool and second tool measurement data measured using a second measuring tool, and wherein the measurement of the one or more product features is referenced with respect to a positioning system used to displace the substrate or a plane parallel to the surface of the substrate; and the step of determining a distortion component of the substrate based on the plurality of position measurements. Claim 2 A method for determining a distortion component according to claim 1, wherein the distortion component is associated with one or both of the position of a product feature on the substrate and the in-plane distortion of the substrate. Claim 3 A method for determining a distortion component according to claim 2, further comprising the step of determining the location of the product feature based on the measurement of one or both of the product feature and the image of the product feature, and the measurement of one or more alignment marks. Claim 4 A method for determining a distortion component according to claim 3, wherein at least part of the measurement of one or both of the product feature and the image of the product feature is performed offline, and at least part of the measurement of one or more alignment marks is performed inline. Claim 5 A method for determining distortion components according to claim 4, wherein offline measurement and inline measurement are combined by coupling the deformation grid of an alignment tool used for offline measurement and inline measurement. Claim 6 delete Claim 7 A method for determining a distortion component according to claim 1, wherein (i) the first measuring tool is a scanning electron microscope tool and (ii) the second measuring tool is an optical measuring tool, or both. Claim 8 A method for determining a distortion component according to claim 7, wherein the first measuring tool is a scanning electron microscope tool, and the scanning electron microscope tool measures at least one of a plurality of position measurements of one or both of one or more product features and targets on the substrate below the top layer of the substrate. Claim 9 A method for determining a distortion component according to claim 1, wherein the first tool measurement data comprises first tool target measurement data measured on a target and first tool device measurement data measured on a device structure. Claim 10 A method for determining a distortion component according to claim 9, wherein the method comprises the step of determining one or more metrology-to-device offsets for one or more device structures related to the first tool device metrology data from the first tool target metrology data and the first tool device metrology data, and wherein the one or more metrology-to-device offsets comprise a comparison of a device-specific measurement value in the first tool device metrology data with a corresponding measurement value in the first tool target metrology data. Claim 11 A method for determining a distortion component according to claim 10, wherein the method comprises the step of combining one or more measurement-device offsets within a dense grid of measurement offsets for each target. Claim 12 A method for determining a distortion component according to claim 10, comprising the step of applying one or more measurement-device offsets to a reference grid of an exposure device as a feedforward correction or a feedback correction. Claim 13 A method for determining a distortion component according to claim 9, wherein the first tool target measurement data includes first tool target alignment data measured on an alignment mark, and the first tool device measurement data includes first tool device alignment data measured on a device structure. Claim 14 A method for determining a distortion component according to claim 9, wherein the first tool target measurement data includes first tool target overlay data measured on an overlay target, and the first tool device measurement data includes first tool device overlay data measured on a device structure. Claim 15 A method for determining a distortion component according to claim 1, further comprising one or both of modeling a distortion component of a substrate for at least one exposure field or sub-field on the substrate according to a first field, sub-field model or scan profile fingerprint model, and modeling an exposure slit of a lithography device used to manufacture a previous layer of the substrate according to a slit fingerprint model.

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