Source mask optimization based on system effects on lithographic apparatus

Abstract

A source mask optimization (SMO) is described. The SMO includes determining a source configuration (e.g., an illumination pupil) of a lithographic apparatus for a first feature in a first layer of a pattern based on a system effect on a component of the lithographic apparatus that causes a feature-dependent imaging performance change of a second feature in a second layer of the pattern. For example, the system effect on the lithographic apparatus component includes mirror warming. Mirror-heat-based SMO is performed for the illumination pupil of the first layer using a cost function for the performance of the second layer. For example, as a representative example, mirror-heat-based SMO may be performed to generate a metal layer illumination pupil that produces less mirror-heat effects on subsequent via layer exposures, and / or mirror-heat-based SMO may be performed to generate a via layer illumination pupil that is less sensitive to mirror heat caused by previous metal layer exposures.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority of European Application No. 22216705.8 filed on December 27, 2022, and incorporates the entire content of this European application herein by reference. Technical field

[0003] The present disclosure relates to source - mask optimization based on system effects on a lithographic apparatus. Background art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can, for example, project a pattern (also often referred to as a "design layout" or "design") present on 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 the pattern onto the substrate, the lithographic apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features that can be formed on the substrate. Typical wavelengths currently in use are 365 nm (i - line), 248 nm, 193 nm, and 13.5 nm. Compared to a lithographic apparatus using radiation having a wavelength of, for example, 193 nm, a lithographic apparatus using extreme ultraviolet (EUV) radiation having a wavelength in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0006] Low - k1 lithography can be used to process features smaller than the classical resolution limit of the lithographic apparatus. In such a process, the resolution formula can be expressed as CD = k1×X / NA, where X is the wavelength of the radiation employed, NA is the numerical aperture of the projection optics in the lithographic apparatus, CD is the "critical dimension" (usually the smallest feature size printed, but in this case the half - pitch), and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it becomes to reproduce on the substrate a pattern similar in shape and size to that planned by the circuit designer in order to achieve a specific electrical functionality and performance. To overcome these difficulties, complex fine - tuning steps can be applied to the lithographic projection apparatus and / or the design layout. These steps include, for example, but are not limited to, optimization of NA, custom illumination schemes, use of phase - shifting patterning devices, various optimizations of the design layout such as optical proximity correction (OPC, sometimes also referred to as "optical and process correction") in the design layout, source - mask optimization (SMO), or other methods generally defined as "resolution enhancement techniques" (RET). Summary of the invention

[0007] According to embodiments of the present disclosure, based on a prediction or evaluation of the performance of a second layer, source optimization based on system effects (e.g., mirror heating) is performed to obtain a source configuration (e.g., illumination pupil) for a first layer in a lithography process. In some embodiments, SMO based on mirror heating can be performed to generate a previous (first) (e.g., metal) layer illumination pupil, wherein the effect of mirror heating on the patterning of a subsequent (second) (e.g., via) layer is mitigated. In some embodiments, SMO based on mirror heating can be performed to generate a second (e.g., via) layer illumination pupil with reduced sensitivity to aberrations induced by mirror heating caused by exposure of a previous metal layer. It should be noted that the layers in such examples can be reversed such that the via layer is the first layer and the metal layer is the second layer, and / or the first layer and the second layer can both be metal layers or both be via layers, and / or the layers can be associated with different wafers in different production batches, and / or other configurations are possible. This is in contrast to existing mirror heating-aware source mask optimization methods that typically optimize the source and optionally an existing mask for a patterning layer based on the predicted performance of the same layer, where the predicted performance of the same layer lists only the mirror heating associated with that layer as an important factor.

[0008] According to an embodiment, a method for source optimization or source mask optimization for a lithography apparatus is provided. The lithography apparatus includes components configured to image a pattern onto a substrate. The method includes determining a source configuration for a first feature in a first layer of the pattern for the lithography apparatus based on a system effect on the lithography apparatus components that causes a feature-dependent change in imaging performance of a second feature in a second layer, wherein the second layer and the first layer can have the same pattern or different patterns. For example, the first layer is processed (e.g., exposed) on the lithography apparatus before the second layer. In some embodiments, the first layer will be processed immediately before the second layer. In some embodiments, the first layer will be processed before another layer and then the second layer. A model (e.g., a mirror heating model) can be used to simulate the system effect during the lithography process of the first layer. In some embodiments, determining the source configuration includes determining an illumination pupil and / or other operations.

[0009] In some embodiments, system effects on a lithographic apparatus component are caused by one or more previous exposures for one or more previous patterning operations. In some embodiments, system effects on a lithographic apparatus component are determined by simulation based on one or more previous exposures for one or more previous patterning operations. In some embodiments, system effects on a lithographic apparatus component are an input to source-mask optimization. In some embodiments, system effects on a lithographic apparatus component include component heating, component cooling, component drift, component variation for different substrate batches, illumination offset, mask-to-mask variation, overlay effects, aberration effects, attenuation, recalibration or resetting, and / or dose or pupil residuals.

[0010] In some embodiments, the lithographic apparatus component includes a mirror, a lens, and / or an entire optical system (e.g., which includes one or more mirrors, one or more lenses, and / or several other components), and system effects on the lithographic apparatus include mirror heating and / or lens heating.

[0011] In some embodiments, system effects on a lithographic apparatus component vary over time during an exposure and / or over multiple exposures.

[0012] In some embodiments, feature-dependent imaging performance changes include changes that vary based on the shape, location, size, material, layer, and / or function of features in a pattern layer.

[0013] In some embodiments, the method includes determining a source configuration based on system effects on a lithographic apparatus component that cause feature-dependent imaging performance changes in a first feature in a first layer of a pattern and a second feature in a second layer. Determining the source configuration for the first feature includes co-optimizing the source configuration for the first feature in the first layer of the pattern and the second feature in the second layer based on system effects on the lithographic apparatus component that are simulated or measured and that cause feature-dependent imaging performance changes in the first feature and the second feature.

[0014] In some embodiments, the method includes determining a second source configuration for a second feature in a second layer of a pattern based on a second feature sensitivity of a system effect, where the system effect is associated with the processing of a first feature in a first layer. The first layer is processed before the second layer. In some embodiments, the sensitivity corresponds to the sensitivity of imaging performance to a heating effect. In some embodiments, the sensitivity corresponds to the sensitivity of an aberration (Zernike or Tatian) of an important segmentation line metric, including EPE, CD, and PPE sensitivities. The sensitivity indicates the severity of the influence of the aberration wavefront on the metric. The source configuration for processing the second layer is determined based on the system effect caused by processing the first feature in the first layer on a lithography apparatus component. In some embodiments, the sensitivity is determined by simulating one or more previous exposures for one or more previous patterning operations. In some embodiments, a mirror heating model is used to predict the heating effect generated by processing the first layer, and the model output (e.g., the resulting wavefront or aberration) is used in a source optimization process to generate the source configuration for processing the second layer. In some embodiments, the source optimization process uses a cost function including an indication of the sensitivity of the second layer to the aberration caused by mirror heating.

[0015] In some embodiments, a first mask including a first portion of a pattern design layout may be used to generate the first feature, and a second mask including a second portion of the same or a different pattern design layout may be used to generate the second feature.

[0016] In some embodiments, determining the source configuration includes performing source mask optimization on the source configuration for the first feature in the first layer by a cost function indicating the imaging performance of the second feature in the second layer.

[0017] The two layers can belong to the same pattern or different patterns, the same design layout or different design layouts, and / or the same or different products (e.g., wafers). In some embodiments, the first layer is a metal layer and the second layer is a via layer. In some embodiments, when determining the source configuration for features (e.g., vias) in the second layer of a lithographic apparatus, the first (e.g., metal) layer is exposed before the second (e.g., via) layer, and the heating from the exposure of the first layer is taken into account. It should be noted that the layers in such examples can be reversed, such that the via layer is the first layer and the metal layer is the second layer, and / or the first layer and the second layer can both be metal layers or both be via layers, and / or the layers can be associated with different wafers in different production batches, and / or other configurations are possible. In some embodiments, the source configuration or the first layer is optimized such that the impact of system effects generated during the processing of the first layer on the imaging performance of one or more subsequent second layers has been reduced or eliminated. In some embodiments, the source configuration for a second layer in a subsequent process is determined such that the imaging performance has a reduced sensitivity to system effects caused by the previous processing of the first layer.

[0018] In some embodiments, the source configuration is determined based on a lithographic simulation of imaging a first feature and an edge placement error cost function generated for the first feature, the edge placement error cost function including one or more terms for system effects on the lithographic apparatus components that cause a change in the imaging performance of a second feature in the second layer. The simulation based on the first feature can include, for example, using a mask pattern designed for the first layer during a source optimization or source mask optimization process. During the lithographic simulation, for example, the system effects can be modeled based on the first layer features by a mirror heating model. During source optimization (for processing the first layer), the source is adjusted based on a cost function that includes an indication of the predicted imaging performance of the second layer (e.g., one or more second layers as described herein). The cost function can also include an indication of the predicted imaging performance of the first layer.

[0019] In some embodiments, the lithographic apparatus components include an illumination source and projection optics configured to image a pattern onto a substrate. The method includes determining one or more adjustments to one or more of the source configuration, the pattern, the projection optics, or the illumination source based on system effects on the lithographic apparatus components that cause a feature-dependent change in the imaging performance, until a termination condition is met. In some embodiments, the termination condition includes the determination that the features patterned onto the substrate will substantially match the target design.

[0020] In some embodiments, performing source mask optimization includes modeling a lithographic process for imaging a pattern onto a substrate. In some embodiments, the model for modeling the process for imaging a pattern onto a substrate uses the determined source configuration.

[0021] In some embodiments, the method includes co-optimizing a mask with a source configuration for a first feature of a first layer of a pattern based on a system effect that changes an imaging performance of a second feature in a second layer that causes a pattern on a lithography tool component.

[0022] In some embodiments, there is provided a non-transitory computer-readable medium having instructions thereon that, when executed by a computer, cause the computer to perform one or more of the operations of the method described above.

[0023] In some embodiments, there is provided a system including one or more processors configured by machine-readable instructions to perform one or more of the operations of the method described above.

[0024] Other advantages of embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, which illustrate certain example embodiments by way of illustration and example. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments and, together with the description, explain these embodiments. Embodiments will now be described by way of example only with reference to the accompanying schematic drawings, in which corresponding reference signs indicate corresponding parts, and in which:

[0026] Figure 1 is a schematic view of a lithographic projection apparatus according to an embodiment.

[0027] Figure 2 depicts a schematic overview of a lithography cell according to an embodiment.

[0028] Figure 3 depicts a schematic representation of an overall lithography that represents the collaboration between three technologies for optimizing semiconductor manufacturing.

[0029] Figure 4 schematically illustrates the basic principle of source mask optimization according to an embodiment.

[0030] Figure 5 plots the wavefront aberration (in a given production lot) that changes over time due to mirror heating according to an embodiment.

[0031] Figure 6 illustrates an exemplary method for system effect-aware source mask optimization for a lithography apparatus according to an embodiment.

[0032] Figure 7A diagram is provided for determining a source configuration for a first feature in a first layer of a pattern of a lithographic apparatus based on a system effect on a lithographic apparatus component that causes a feature-dependent change in imaging performance related to a second feature in a second layer of the pattern.

[0033] Figure 8 A comparison is shown between source mask optimization based on existing system effects (e.g., mirror heating) and a new method of source mask optimization based on system effects (e.g., mirror heating) as described herein according to an embodiment.

[0034] Figure 9 The diagram for determining a source configuration for a first feature in a first layer of a pattern of a lithographic apparatus based on a system effect on a lithographic apparatus component that causes a feature-dependent change in imaging performance related to a second feature in a second layer of the pattern according to an embodiment is not limited to input from only one (second) layer.

[0035] Figure 10 A schematic diagram of an example computer system according to an embodiment that can be used for one or more of the operations described herein. DETAILED DESCRIPTION

[0036] Source optimization (SO) or SMO is described for a lithographic apparatus to reduce system effects in a lithographic process. SO includes determining a source configuration (e.g., determining an illumination pupil) for a first feature in a first layer of a pattern of the lithographic apparatus based on a system effect on the imaging performance of a second feature in a second layer that is processed later than the first layer. Although embodiments of the present disclosure are described in more detail with respect to mirror heating effects, the present disclosure can be used to address other system effects such as component heating, component cooling, component drift, component variations for different substrate batches, illumination offset, mask-to-mask changes, overlay effects, aberration effects, attenuation, recalibration or resetting, and / or dose or pupil residuals, etc. Layers of a pattern can refer to different layers with the same pattern for one product, a first layer for one product, and a second layer for a different product, etc. (e.g., not necessarily just the order of layers in a single stack).

[0037] The perception of mirror heating (as a potentially representative example of a system effect) in SMO typically considers only the mirror heating associated with the processed pattern layer, optimizes the source for the pattern layer based on the imaging performance of the layer, and in some cases optimizes the mask, where the mirror heating effect can be determined by simulation or by using empirical data. The result is often a source configuration (e.g., illumination pupil) with slightly lower nominal (imaging) contrast performance but better contrast performance under the mirror heating conditions for the layer. For example, this reduces the impact on imaging caused by the heat associated with the layer, and / or reduces the aberration sensitivity of the layer. However, sometimes the problems caused by mirror heating are not (or not only or not primarily) caused by the mirror heating associated with the current layer, but by the mirror heating from a previous exposure that affects another (or the next patterned) layer. For example, the mirror heating associated with the first exposure of a first (e.g., metal) layer may affect the exposure of a second patterned (e.g., via) layer.

[0038] Compared to previous methods, the present system and method are configured such that SMO based on system effects (e.g., mirror heating) is performed on the source configuration (e.g., illumination pupil) for the first layer using a cost function for the performance of a second (different) layer. As described below, the order of batch exposures on a lithography apparatus is related to the wafer imaging performance. Layer B may suffer from mirror heating caused by the patterning operation associated with layer A, where A is exposed before B; but layer B can be higher or lower in the stack, or part of a completely different product. As a specific example, SMO based on mirror heating can be performed to generate an illumination pupil for the metal layer that has a smaller mirror heating impact on the subsequent via layer exposure, and / or SMO based on mirror heating can be performed to generate an illumination pupil for the via layer that is less sensitive to the mirror heating caused by the previous metal layer exposure.

[0039] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings, which are provided as illustrative examples of the present disclosure to enable those skilled in the art to practice the present disclosure. The following figures and examples are not meant to limit the scope of the present disclosure to a single embodiment, but other embodiments are possible by means of the interchange of some or all of the described or illustrated elements. Where certain elements of the present disclosure can be implemented in part or in whole using known components, only those parts of such known components that are necessary to understand the present disclosure will be described, and detailed descriptions of other parts of such known components will be omitted so as not to obscure the present disclosure. Unless otherwise specified herein, as will be understood by those skilled in the art, embodiments described as implemented in software should not be limited thereto, but may include embodiments implemented in hardware or a combination of software and hardware, and vice versa. In this specification, embodiments showing a single component should not be considered limiting; rather, the present disclosure is intended to cover other embodiments including a plurality of identical components, and vice versa, unless expressly stated otherwise herein. Additionally, unless so expressly set forth, the applicant does not intend for any term in this specification or the claims to be construed in an uncommon or special sense. The present disclosure covers current and future known equivalents of known components referred to herein by way of illustration.

[0040] Although the manufacture of integrated circuits (ICs) may be specifically referenced herein, it should be understood that the description herein has many other applications. For example, it can be used in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal display (LCD) panels, thin film magnetic heads, and the like. Those skilled in the art should appreciate that in the context of such alternative applications, any use herein of the terms "reticle", "wafer", or "die" can be respectively interchanged with the more general terms "mask", "substrate", and "target".

[0041] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g., having wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and EUV (extreme ultraviolet radiation, e.g., having wavelengths in the range of about 5 nm to 100 nm).

[0042] A (e.g., semiconductor) pattern forming device may include or may form one or more design layouts. A CAD (Computer-Aided Design) process may be utilized to generate the design layout, which process is often referred to as EDA (Electronic Design Automation). Most CAD processes follow a set of predefined design rules in order to produce a functional design pattern / pattern forming device. These rules are set by processing and design constraints. For example, the design rules define the space tolerances between devices (such as gates, capacitors, etc.) or interconnect lines in order to ensure that the devices or lines do not interact with each other in an undesired manner. The design rules may include or specify particular parameters, limits on ranges of parameters, or other information. One or more of the design rule limitations or parameters may be referred to as “critical dimension” (CD). The critical dimension of a device may be defined as the minimum width of a line or hole or the minimum space between two lines or two holes, or other features. Thus, the CD determines the overall size and density of the designed device. One of the goals in device manufacturing is to faithfully reproduce the original design intent on a substrate (via the pattern forming device).

[0043] As used herein, the term “mask” or “pattern forming device” may be broadly interpreted to mean a general semiconductor pattern forming device that can be used to impart a patterned cross-section to an incident radiation beam, the patterned cross-section corresponding to a pattern to be produced in a target portion of a substrate. In addition to classical masks (transmissive or reflective; binary, phase-shift, hybrid, etc.), examples of other such pattern forming devices include programmable mirror arrays and programmable LCD arrays.

[0044] As used herein, the term “patterning process” means the process of producing an etched substrate by applying a specified pattern of light as part of a lithography process. However, the “patterning process” may also include (e.g., plasma) etching, as many of the features described herein may provide benefits for forming the printed pattern using an etching (e.g., plasma) process.

[0045] As used herein, the term “pattern” means an idealized pattern that will be etched on a substrate (e.g., a wafer). The pattern may have two or three dimensions, be formed in a layer, and / or have other characteristics.

[0046] As used herein, “printed pattern” (or pattern on a substrate) means the physical pattern etched on a substrate based on a target pattern. For example, the printed pattern may include grooves, channels, recesses, edges, or other two- and three-dimensional features produced by a lithography process.

[0047] As used herein, the term “calibrate” means to modify (e.g., improve or adjust) or verify something, such as a model.

[0048] A patterning system may be a system that includes any or all of the components described herein and other components configured to perform any or all of the operations associated with these components. For example, a patterning system may include a lithographic projection apparatus, a scanner, a system configured to apply or remove a resist, an etching system, or other systems.

[0049] As an introduction, Figure 1 is a schematic diagram of a lithographic projection apparatus LA according to an embodiment. The lithographic projection apparatus LA includes: an illumination system (also referred to as an illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., a mask table) MT configured to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to certain parameters; a substrate support (e.g., a wafer table) WT configured to hold a substrate (e.g., a wafer coated with a resist) W and connected to a second positioner PW configured to accurately position the substrate support according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project the 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.

[0050] In operation, the illumination system IL receives the radiation beam from a radiation source SO via, for example, a beam delivery system BD. The illumination system IL may include various types of optical components for guiding, shaping, and / or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components or any combination thereof. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0051] The term "projection system" PS as used herein should be interpreted broadly to encompass various types of projection systems suitable for the exposure radiation used and / or other factors such as the use of an immersion liquid or the use of a vacuum, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic, and / or electrostatic optical systems or any combination thereof. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0052] The lithographic apparatus LA may be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index (e.g., water) to fill the space between the projection system PS and the substrate W - this is also referred to as immersion lithography.

[0053] The lithographic apparatus LA can also be of the type having two or more substrate supports WT (also referred to as "dual stage"). In such a "multi-stage" machine, the substrate supports WT can be used in parallel, and / or the steps of subsequent exposure of the substrate W on a substrate W located on one of the substrate supports WT can be carried out while another substrate W on another substrate support WT is used for exposing a pattern on another substrate W.

[0054] In addition to the substrate support WT, the lithographic apparatus LA can include a measurement stage. The measurement stage is arranged to hold sensors and / or cleaning devices. The sensors can be arranged to measure properties of the projection system PS and / or properties of the radiation beam B. The measurement stage can hold a plurality of sensors. The cleaning device can be arranged to clean a part of the lithographic apparatus, such as a part of the projection system PS or a part of the system providing the immersion liquid. The measurement stage can move under the projection system PS when the substrate support WT is away from the projection system PS.

[0055] In operation, the radiation beam B is incident on a patterning device MA (e.g., a mask) held on a mask support MT and is patterned by the pattern (design layout) presented on the patterning device MA. After having traversed the mask MA, the radiation beam B passes through a projection system PS that focuses the beam onto a target portion C of the substrate W. By means of a second positioner PW and a position measurement system IF, the substrate support WT can be accurately moved, for example, in order to position different target portions C in the path of the radiation beam B in a focused and aligned position. Similarly, a first positioner PM and possibly another position sensor (which is not explicitly depicted in Figure 1 ) can be used to accurately position the patterning device MA relative to the path of the radiation beam B. Mask alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device MA and the substrate W. Although the substrate alignment marks P1, P2 as illustrated occupy exclusive target portions, the substrate alignment marks can be located in the space between the target portions. When the substrate alignment marks P1, P2 are located between the target portions C, these substrate alignment marks are referred to as scribe alignment marks.

[0056] Figure 2 A schematic overview of a lithographic cell LC is depicted. As Figure 2 shown, a lithographic projection apparatus (shown in Figure 1 and illustrated in Figure 2 as the lithographic apparatus LA) can form part of a lithographic cell LC which is sometimes also referred to as a lithographic cell or (lithographic) cluster and which often also includes equipment for performing pre-exposure processes and post-exposure processes on the substrate W ( Figure 1). Conventionally, these devices include a spin coater SC configured to deposit a resist layer, a developer for developing the exposed resist, a chill plate CH for adjusting the temperature of the substrate W (e.g., for adjusting the solvent in the resist layer), and a bake plate BK. A substrate transfer device or robot RO picks up the substrate W from the input / output ports I / O1, I / O2, moves the substrate W between different process devices, and transfers the substrate W to the feed table LB of the lithography apparatus LA. Devices in the lithography unit, often collectively referred to as a coat / develop system, are typically under the control of a coat / develop system control unit TCU, which itself may be controlled by a management control system SCS, which may also control the lithography apparatus LA via, for example, a lithography control unit LACU.

[0057] To correctly and consistently expose the substrate W exposed by the lithography apparatus LA ( Figure 1 ), it is desirable to detect the substrate to measure properties of the patterned structures, such as feature edge placement, overlay error between subsequent layers, line thickness, critical dimension (CD), etc. For this purpose, an inspection tool (not shown) may be included in the lithography unit LC. If an error is detected, the exposure of subsequent substrates or other processing steps to be performed on the substrate W may be adjusted, especially if the inspection is performed before other substrates W in the same lot or batch are still to be exposed or processed.

[0058] An inspection device, which may also be referred to as a metrology device, is used to determine the properties of the substrate W and, in particular, how the properties of different substrates W vary or how the properties associated with different layers of the same substrate W vary from layer to layer. The inspection device is alternatively configured to identify defects on the substrate W and may, for example, be part of the lithography unit LC, or may be integrated into the lithography apparatus LA, or may even be a separate device. The inspection device may use the actual substrate (e.g., a charged particle - SEM - image of a wafer pattern) or an image of the actual substrate to measure properties of a latent image (an image in the resist layer after exposure), a semi - latent image (an image in the resist layer after a post - exposure bake step PEB), a developed resist image (where the exposed or unexposed portions of the resist have been removed), an etched image (after a pattern transfer step such as etching), or otherwise.

[0059] Figure 3 A schematic representation depicting overall lithography, which represents the collaboration between three technologies for optimizing semiconductor manufacturing. Generally, the patterning process in the lithography apparatus LA is one of the most critical steps in a process that requires high accuracy in the dimensioning and placement of structures on the substrate W ( Figure 1 ). To ensure this high accuracy, three systems (in this example) may be combined in a so - called "holistic" control environment, asFigure 3 as schematically depicted therein. One of these systems is a lithographic apparatus LA, which is (in fact) connected to a metrology device (e.g., metrology tool) MT (second system) and to a computer system CS (third system). The "overall" environment can be configured to optimize the collaboration between these three systems to enhance the overall process window and provide a tight control loop, thereby ensuring that the patterning performed by the lithographic apparatus LA remains within the process window. The process window defines a range of process parameters (e.g., dose, focus, overlay), within which a particular manufacturing process produces a defined result (e.g., a functional semiconductor device), and typically within the defined result, allows variations in the process parameters during the lithographic process or patterning process.

[0060] The computer system CS can use (a portion of) the design layout to be patterned to predict which resolution enhancement techniques are to be used, and perform computational lithography simulations and calculations to determine which mask layouts and lithographic apparatus settings achieve the maximum overall process window for the patterning process (depicted by the double arrows in Figure 3 ). Typically, the resolution enhancement techniques are arranged to match the patterning capabilities of the lithographic apparatus LA. The computer system CS can also be used to (e.g., using inputs from the metrology tool MT) detect where the lithographic apparatus LA is currently operating within the process window, to predict whether there are defects that can be attributed to, for example, sub-optimal processing (depicted by the arrow pointing to "0" in Figure 3 ).

[0061] The metrology device (tool) MT can provide inputs to the computer system CS for accurate simulation and prediction, and can provide feedback to the lithographic apparatus LA to identify possible drifts, for example, in the calibration state of the lithographic apparatus LA (depicted by the multiple arrows in Figure 3 ).

[0062] During the lithographic process, it is desirable to frequently measure the structures produced, for example, for process control and verification. Tools for performing such measurements include metrology devices (tools) MT. Different types of metrology tools MT for performing such measurements are known, including scanning electron microscopes (SEM) or various forms of scatterometer metrology tools MT.

[0063] In some embodiments, the metrology tool MT is or includes a spectroscopic scatterometer, an ellipsometric scatterometer, or other light-based tool. A spectroscopic scatterometer can be configured to direct radiation emitted by a radiation source onto a target feature of a substrate and direct reflected or scattered radiation from the target to a spectrometer detector that measures the spectrum of specularly reflected radiation (i.e., a measurement of intensity as a function of wavelength). From such data, the structure or profile of the target that produced the detected spectrum can be reconstructed, for example, by rigorous coupled wave analysis and non-linear regression or by comparison with a library of simulated spectra. An ellipsometric scatterometer allows determination of parameters of a lithography process by measuring scattered radiation for each polarization state. Such a metrology tool (MT) emits polarized light (such as linearly, circularly, or elliptically polarized light) by using, for example, a suitable polarization filter in the illumination section of the metrology apparatus. A source suitable for the metrology apparatus can also provide polarized radiation.

[0064] It is often desirable to be able to computationally determine how a patterning process will produce a desired pattern on a substrate. Accordingly, simulations can be provided to simulate one or more portions of the process. The computational determination and / or simulation can be performed on a computing device, such as Figure 3 the computing device CS shown Figure 8 (and again below

[0065] ). For example, the computational determination and / or simulation can be used to configure one or more features of a patterning device pattern (e.g., perform optical proximity effect correction), one or more features of the illumination (e.g., change one or more characteristics of the spatial / angular intensity distribution of the illumination, such as changing the illumination pupil shape), and / or one or more features of the projection optics (e.g., numerical aperture, etc.). Such configuration can generally be referred to as mask optimization, source optimization, and projection optimization, respectively. The optimizations can be performed independently or combined in different combinations. One example is source-mask optimization (SMO), which involves the configuration of one or more features of a patterning device pattern together with one or more features of the illumination. For example, the prior art source-mask optimization process is described in U.S. Patent No. 9,588,438, which is incorporated herein by reference in its entirety.

[0066] In some embodiments, an optimization process such as SMO of a system can be represented as a cost function. The optimization process can include finding a set of parameters (source configuration, design variables, process variables, etc.) of the system that minimize the cost function. The cost function can have any suitable form depending on the objective of the optimization. For example, the cost function can be the weighted root mean square (RMS) of the deviation of certain characteristics (evaluation points) of the system from their expected values (e.g., ideal values). The cost function can also be the maximum value of these deviations (i.e., the worst deviation). The term "evaluation point" should be interpreted broadly to include any characteristic of the system, design, or manufacturing method. Due to the applicability of the embodiments of the system, design, and / or method, the design and / or process variables of the system can be restricted to a finite range and / or be interdependent. In the case of SMO and lithographic projection equipment, the constraints are often associated with the physical nature and characteristics of the hardware (such as the adjustable range and / or manufacturability design rules of the patterning device). For example, the evaluation points can include physical points on the resist image on the substrate (e.g., associated with edge placement error and / or other critical performance indicators), as well as non-physical characteristics such as dose and focus.

[0067] In a lithographic projection apparatus, by way of example, the cost function CF can be expressed as:

[0068]

[0069] where are N design variables or their values, and can be a function of the design variable such as the difference between the actual value and the expected value of a characteristic for a set of values of the design variable . In some embodiments, is a weight constant associated with . For example, the characteristic can be the position of the edge of a pattern measured at a given point on the edge. Different can have different weights . For example, if a particular edge has a narrow range of allowable positions, the weight for representing the difference between the actual position and the expected position of the edge can be given a higher value. can also be a function of interlayer characteristics, which in turn are a function of the design variable . Of course, is not limited to the form in the above equation and can take any other suitable form.

[0070] The cost function may represent any one or more suitable characteristics of a lithographic projection apparatus, a lithographic process, or a substrate, such as source configuration, focus, edge placement error (EPE), CD, image shift, image distortion, image rotation, stochastic variations, throughput, local CD variations, process window, interlayer characteristics, or a combination thereof. In some embodiments, the cost function may include a function representing one or more characteristics of the resist image. For example, it may be the distance between a point in the resist image and the expected position of the point (i.e., edge placement error ). The parameters may include any adjustable parameters, such as adjustable parameters of the source, patterning device, projection optics, dose, focus, etc. The parameters may also have constraints, which may be expressed as where, is the set of possible values of the parameter. For example, one possible constraint may be a limitation on the source configuration and / or the patterning device pattern for SMO.

[0071] Figure 4 Schematically illustrates an exemplary process of SMO 400. SMO 400 may receive one or more inputs 402, such as process information (e.g., in the form of one or more electronic models), target design, initial processing conditions, flow information (e.g., SMO.xml file), and / or other inputs 402. The process window (PW) conditions 404 are also known. SMO 400 may provide several outputs, including an optimal source configuration 406, an optimal wavefront 408, an optimized mask 410, optimized design rules and / or targets 412, process window and process variation band analysis 414, and / or other outputs.

[0072] In some embodiments, SMO 400 may be performed based on the cost function CF, such as:

[0073]

[0074] (e.g., a more specific version of the cost function described above), where V gc is an input variable related to process window conditions (e.g., focus, dose, mask writing error, mirror heating Zernike, Tatian polynomials, etc.) that can be changed, V mask is an input variable related to the mask, V wavefront is an input variable related to the wavefront, and V designis an input variable related to the target design. In this example, the SMO cost function is optimized based on the Edge Placement Error (EPE). The cost function CF also includes penalty terms. The penalty terms can be used for boundary conditions such as the Normalized Image Logarithm Slope (NILS), penalty for excessive dose (production volume), penalty for deviation range from the initial pupil or initial target, penalty associated with the RMS of Zernike, etc. Figure 4 Illustrated is the EPE optimization at the evaluation point 420 across multiple process window conditions 422 (illustrating the shape of a given feature 424 relative to the target design 426 for the feature). Figure 4 Also illustrated is an example process window box 430 for three different example variables 432, 434, 436. It should be noted that while the cost function CF described above utilizes EPE, additional weights can be added for CD or PPE. For example, a custom cost function based on CD asymmetry can be applied and / or other cost functions can be used. Generally, the optimization can be based on any imaging Key Performance Indicator (KPI) that depends on the source and / or pupil being optimized during SMO.

[0075] It is advantageous to be able to use SMO to control or correct system effects that cause changes in imaging performance on lithography equipment components. For example, system effect-aware SMO can be used to correct wavefront drift caused by optical heating, such as mirror heating in semiconductor manufacturing processes. By correcting the wavefront drift in the lithography system, defects in one or more fabricated devices during the semiconductor manufacturing process can be significantly reduced, where the wavefront drift is caused by the heating of optical elements (e.g., mirrors, lenses, etc.) in the lithography system.

[0076] In a lithography system, mirror heating, lens heating, and / or other system change factors related to the production of patterned devices such as semiconductor devices can cause defects (e.g., edge placement error, overlay error, etc.). This requires fast and precise in-situ correction capabilities to achieve stable imaging performance in a production manufacturing environment. Mirror heating can cause wavefront drift, which is provided by the optical projection system when the wavefront provided by the optical projection system of the lithography system is different from the target wavefront or the calibrated or cold lithography equipment state.

[0077] By way of non-limiting example, Figure 5 plotted is the wavefront aberration (e.g., which can be represented by Zernike or Tatian polynomials) 501 caused by mirror heating as a function of time 503 (for a given production batch). In Figure 5 shown are wafers 1 to 8 (w1, w2…, w8) for a wafer production batch. Figure 5Plot the original 505 aberration drift that would occur without correction (e.g., the time-varying 503 Zernike 501 changes caused by mirror heating). In contrast, for each wafer, Figure 5 Also shown are the mirror heating residuals 507, the projection optics correction model residuals 509, the last field 511 for the mirror heating residuals 507 (which is equal to the worst mirror heating residual), and the correction 513 determined by or based on scanner lens model correction. The mirror heating SMO need not affect aberration control, but it may affect the induced original Zernike or the sensitivity to the residuals 507. The correction may be applied by, for example, the projection optics correction model and / or other simulation models.

[0078] During wafer production, more than 90% of the energy entering the lithographic apparatus is absorbed by the optical system and does not reach the wafer. Due to the inherent physical properties of the lithographic apparatus mirrors (and / or lenses), the absorbed power heats the mirrors (and / or lenses), causing a non-uniform temperature distribution on the mirrors and causing mirror deformation. In turn, the mirror deformation causes the aberrations (e.g., wavefront and / or other) described above. The aberrations depend on time, power and dose, illumination mode, mask transmission and diffraction, lithographic apparatus details, application, and / or other factors. System effect (e.g., mirror heating) aware SMO mitigates these adverse conditions. To minimize the negative impact of mirror heating and / or other system effects on lithographic performance, system effect aware SMO provides a method to optimize the source in a dedicated way such that it is less sensitive to mirror heating and / or other system effects, and provides a system tool for evaluating the impact of mirror heating and / or other system effects.

[0079] As described above, several variables in the cost function are changed during the optimization process in SMO. In the case of system effect or mirror heating aware SMO, the mirror heating distribution that changes over time can also be used to change the Zernike or Tatian. Simulated mirror heating data is typically used as the mirror heating aware SMO input (but measured mirror heating data, simulation models based on calibrated mirror heating data, and / or other information can be used). SMO typically includes iteratively shifting pixels in the pupil to find the pupil with the maximum contrast. Aberrations, illumination errors, and stage errors are assumed to be zero. In the case of system effect or mirror heating aware SMO, cases with less than the maximum (imaging) contrast are tolerated, but mirror heating and / or other system effects (which cause aberrations, illumination errors, and stage errors) are considered, which enhances the overall accuracy and / or contrast of the patterning process.

[0080] Figure 6FIG. illustrates an exemplary computer-implemented method 600 for system-effect-aware SMO for a lithographic apparatus. The SMO of the method 600 includes determining (operation 602) a source configuration (e.g., determining an illumination pupil) for a first feature in a first layer of a pattern of the lithographic apparatus based on the effect of system effects on the feature-dependent imaging performance of a second feature in a second layer. (For example, system effects on lithographic apparatus components include mirror heating and / or other system effects.) In some embodiments, the method 600 is configured such that a cost function for the imaging performance of the second layer (e.g., EPE or other imaging characteristics of the second feature) is used to perform system-effect (e.g., mirror heating)-aware SMO for the source configuration (e.g., illumination pupil) of the first layer. The cost function may represent any one or more suitable characteristics of the lithographic projection apparatus, the lithographic process, or the substrate, such as source configuration, focus, edge placement error (EPE), CD, image shift, image distortion, image rotation, stochastic variation, throughput, local CD variation, process window, interlayer characteristics, or a combination thereof. The layers of the pattern may refer to different layers of the same pattern for one product, the first layer for one product and the second layer for a different product, etc. (e.g., not necessarily just the order of the layers in a single stack). The method 600 includes mask co-optimization with the source configuration for the first feature in the first layer of the pattern based on system effects on the lithographic apparatus components that cause a feature-dependent change in the imaging performance associated with the second feature in the second layer of the pattern. The method 600 further includes determining (operation 604) one or more adjustments for one or more of the source configuration, the pattern, the projection optics, the illumination source, and / or other variables based on system-effect-aware SMO and / or other operations.

[0081] The operations of method 600 are intended to be illustrative. In some embodiments, one or more additional operations not described may be employed and / or the method 600 may be implemented without one or more of the operations discussed. Additionally, the order in which the operations of the method 600 are illustrated and described herein is not intended to be restrictive. Figure 6 is illustrated and described herein.

[0082] In some embodiments, one or more portions of method 600 may be implemented in one or more processing devices (e.g., digital processors, analog processors, digital circuits designed to process information, analog circuits designed to process information, state machines, and / or other mechanisms for electronically processing information), and / or one or more portions of method 600 may be controlled by the one or more processing devices. The one or more processing devices may include one or more devices that perform some or all of the operations of method 600 in response to instructions electronically stored on an electronic storage medium. The one or more processing devices may include one or more devices (e.g., see the discussion related to Figure 8 below) that are specifically designed for the execution of one or more of the operations of method 600 through hardware, firmware, and / or software configuration.

[0083] At operation 602, the source configuration of the lithographic apparatus is determined. For example, determining the source configuration may include determining the characteristics (e.g., shape, size, location, etc.) of the illumination pupil. The source configuration is determined for a first feature in a first layer of the pattern (e.g., the first layer illumination pupil used in the simulation). The source configuration is determined based on the impact of system effects on the lithographic apparatus components on the predicted imaging performance of a second feature in a second layer. The system effects on the lithographic apparatus components are caused by one or more previous patterning operations performed on the processing of the first layer (e.g., exposure and / or other operations), and / or may have other causes. The system effects on the lithographic apparatus components may be determined by simulation based on the one or more previous patterning operations, for example, by applying a mirror heating model associated with the processing of the first layer. In some embodiments, the system effects may be measured in-situ on the scanner or generated based on empirical data. The system effects on the lithographic apparatus components may be input to SMO (e.g., as described above). The system effects on the lithographic apparatus components may include one or more of the lithographic apparatus components (e.g., mirrors and / or lenses) heating up, component cooling, component drift, component variations associated with different substrate batches, illumination offset, mask-to-mask changes, overlay effects, aberration effects, attenuation, dose or pupil residuals, and / or other system effects. The model may be configured to simulate these effects as generated during processing.

[0084] In some embodiments, a first mask including a first portion of the pattern design layout is used to generate a first feature, and a second mask including a second portion of the pattern design layout is used to generate a second feature.

[0085] Determining a source configuration includes performing source mask optimization on a source configuration for a first feature in a first layer using a cost function indicative of imaging performance of a second feature in a second layer. Performing source mask optimization can include modeling a lithography process for imaging a pattern onto a substrate. For example, the source configuration can be determined based on a lithography simulation of the processing of the first feature, and the source configuration can be optimized by using a cost function that includes terms dependent on feature-specific imaging performance of a second feature in a second layer of the pattern (e.g., as an example - the cost function can be based on different and / or additional critical features).

[0086] In some embodiments, operation 602 includes determining a source configuration based on both an imaging performance change associated with a first feature in a first layer of a pattern and an imaging performance change associated with a second feature in a second layer. For example, the cost function includes terms indicative of the imaging performance of the first and second features. Thus, the source configuration for the first feature is determined by means of a common optimization of the source configurations for the first feature in the first layer and the second feature in the second layer of the pattern.

[0087] In some embodiments, a lithography apparatus component includes a mirror and / or a lens, and system effects on the lithography apparatus include the mirror heating up and / or the lens heating up (e.g., as described above). System effects such as the mirror heating up and / or the lens heating up on a lithography apparatus component vary over time during an exposure. Feature-dependent imaging performance can be affected by system effects, and the effect depends on the shape, location, size, material, layer, and / or function of the feature in a layer of the pattern. For example, the mirror heating up and / or the lens heating up that vary over time during an exposure can cause changes in features in a layer of the pattern that vary based on the feature shape, location, size, material, layer, and / or function of the feature.

[0088] In some embodiments, alternatively or additionally, operation 602 includes determining a second source configuration for a second feature in a second layer of the pattern, where the second layer will be processed later than the first layer. The second source configuration can be determined based on the sensitivity of the second feature to system effects associated with processing the first layer. In some embodiments, a mirror heating model is applied to predict the heating effect from the processing of the first layer. The model output can be incorporated in a source optimization process for the second layer, where the source optimization can use a cost function indicative of the aberration sensitivity (caused by the heating effect) of the second feature. In some embodiments, the cost function in the source optimization process includes the EPE of the second feature and the (normalized) image log slope (ILS or NILS). The simulation can be determined based on one or more previous patterning operations (e.g., exposures) and / or other information for one or more other layers of the pattern (or different patterns on different products). In these embodiments, the source configuration for the first layer can be determined in any way. For example, the source configuration for the first layer can be based on system effects on the lithographic apparatus components that cause only feature-dependent imaging performance changes associated with the first feature in the first layer.

[0089] By way of non-limiting example, the first layer can be a metal layer and the second layer can be a via layer of the pattern. In this example, the metal layer can be exposed before the via layer, and the heating from the exposure of the metal layer can be considered when determining the via source configuration for the via layer in the lithographic apparatus. The source configuration for the metal layer (e.g., illumination pupil shape, size, location, etc.) is determined such that the feature-dependent imaging performance changes associated with the vias in the via layer caused by system effects (e.g., mirror heating and / or lens heating) on the lithographic apparatus components are reduced or eliminated compared to the changes in the case where the source configuration is determined based only on the features of the metal layer or the via layer. In some embodiments, the source configuration for the via layer is determined such that the source configuration is less sensitive to system effects on the lithographic apparatus components that cause feature-dependent imaging performance changes associated with the features in the metal layer compared to the sensitivity in the case where the source configuration is determined based only on the features of the metal layer or the via layer.

[0090] Figure 7Provided is an actual illustration of a source configuration of a first feature in a first layer of a pattern for a lithographic apparatus, based on a system effect on a lithographic apparatus component that causes a feature-dependent change in imaging performance related to a second feature in a second layer of the pattern. In this example, the source configuration is the illumination pupil shape, size, and position. The first feature is a metal feature in a first metal layer. The system effect on the lithographic apparatus component includes and / or is caused by a mirror heating up. The second feature is a via hole in a second via hole layer of the pattern in this example. As described above, the layers of the pattern can refer to different layers of the same pattern for one product, the first layer for one product and the second layer for a different product, etc. (e.g., not necessarily just the layer sequence in a single stack).

[0091] Figure 7 Illustrated is a metal layer illumination pupil 700 of a pre-SMO 702, adjusted to minimize metal layer mirror heating 704, adjusted to minimize metal layer sensitivity to mirror heating 706, and a compromise illumination pupil 708. Figure 7 Also illustrated is a via hole layer pupil 710. It should be noted that the layers in such an example can be reversed such that the via hole layer is the first layer and the metal layer is the second layer, the first layer and the second layer can both be metal layers or both be via hole layers, and / or other configurations are possible. Figure 7 The top row 720 shows the metal layer illumination pupil 700 optimized for (1) metal layer heating and (2) metal layer sensitivity to mirror heating (advancing from the pre-SMO 702 shape and position to the shape and position adjusted to minimize metal layer mirror heating 704, to the adjusted shape and position configured to minimize metal layer sensitivity to mirror heating 706, and finally to the compromise illumination pupil 708). The top row 720 illustrates a typical mirror heating-aware SMO (e.g., an SMO that takes into account the mirror heating effect of the current metal layer of the pattern).

[0092] The middle row 730 and the bottom row 740 illustrate at Figure 6Embodiments of the method 600 shown and described herein. The middle row 730 illustrates a metal layer illumination pupil 700 (e.g., a source configuration for a first feature in a first layer of a pattern of a lithographic apparatus) that is optimized for (1) heating of a metal layer mirror and (2) sensitivity of a via layer to heating of the metal layer mirror (e.g., a system effect on a lithographic apparatus component that causes a feature-dependent change in imaging performance related to a second feature in a second layer of a pattern). As shown in the middle row 730, the metal layer illumination pupil 700 is configured with a feature shape, size, and position that generally accommodates or avoids the feature shape, size, and position of the via layer pupil 710 (e.g., so as not to cause unnecessary heating). Thus, when determining the source configuration for vias in a via layer of a lithographic apparatus, heating resulting from patterning of the metal layer is taken into account. The source configuration for the metal layer (e.g., illumination pupil shape, size, position, etc.) is determined such that feature-dependent changes in imaging performance related to vias in the via layer caused by system effects (e.g., mirror and / or lens heating) on a lithographic apparatus component are reduced or eliminated.

[0093] In the bottom row 740, the metal layer illumination pupil 700 is optimized for heating of the metal layer mirror, and the via layer illumination pupil 710 is optimized for sensitivity of the via layer to heating of the metal layer mirror. In this way, the source configuration for the via layer is configured to be less sensitive to system effects on a lithographic apparatus component that cause feature-dependent changes in imaging performance related to features in the metal layer, compared to the sensitivity in the case where the source configuration is determined based solely on features of the metal layer or the via layer.

[0094] Figure 8 Illustration of a comparison of an existing system effect (e.g., mirror heating)-based SMO 800 with new system effect (e.g., mirror heating)-based SMO methods 802 and 804 (e.g., both including different example embodiments of the method 600) described herein. In the SMO 800, the metal layer illumination pupil 810 causes 811 heating of the metal layer mirror 812. (It is noted that the metal illumination pupil and the metal layer are used only as examples.) A cost function based on EPE, NILS, and / or other key performance indicators is minimized 814 to optimize the metal layer illumination pupil 810 for the effect 816 of heating of the metal layer mirror and for the sensitivity of the metal layer to heating of the metal layer mirror 818.

[0095] In SMO 802, the cost function is changed (e.g., adding a cost for another (e.g., via) layer). Illuminating the metal layer pupil 810 again causes 811 the metal layer mirror to heat up 812. The cost function is again based on EPE, NILS, and / or other key performance indicators and is minimized 814 to optimize the metal layer pupil 810 with respect to the effect 816 of the metal layer mirror heating up and with respect to the metal layer sensitivity 818 to the metal layer mirror heating up. However, in SMO 802, the cost function is also minimized 820 to co-optimize the metal layer pupil 810 with respect to the effect 816 of the metal layer mirror heating up on the via layer and / or with respect to the via layer sensitivity 818 to the metal layer mirror heating up associated with the metal layer (e.g., for the via layer, using EPE, NILS, etc.). Both SMO 800 and SMO 802 (1) produce less heating (e.g., less localized), and (2) are configured such that any resulting heating is less problematic (e.g., having less overlap with diffraction orders - as Figure 7 shown in).

[0096] In SMO 804, the metal layer pupil 810 and the metal layer mirror heating up 812 (e.g., caused by it 811) are considered known or fixed. The cost function based on EPE, NILS, and / or other key performance indicators is minimized 820 to optimize the via layer pupil 850 with respect to the effect 852 of the metal layer mirror heating up and / or with respect to the via layer sensitivity 854 to the metal layer mirror heating up. The effect of the metal layer mirror heating up is equivalent here to the sensitivity of the via (since the metal is fixed and not affected here). In other words, the SMO input based on mirror heating (e.g., SMO 804) is changed (e.g., optimized for the via layer pupil 850 instead of for the metal layer pupil 810). SMO804 is configured such that a given heating is less problematic (e.g., having less overlap with diffraction orders).

[0097] Figure 9 Illustrating how the operations described above are not limited to inputs from only one layer. The SMOs described herein can be based on system effects caused by illumination pupils 900 for any number of additional layers 902 on the lithographic apparatus components (using the metal layer pupil as an example of a source configuration used in Figure 9 ), via layer illumination pupils, any amount of heating associated with the source configuration, and / or changed lens setting residuals (e.g., as used in Figure 9One example used therein is mirror heating, scanner cold lens aberration drift, etc.). In SMO 802 and SMO 804, for example, there may be additional mirror heating inputs. In some embodiments, for example, mirror heating Zernike polynomials are simulated based on the pupil and diffraction pupil (which uses the weighted sum of diffraction orders throughout the reticle features). Both can change after each iteration of the SMO. For the first use case ( Figure 9 at the center in), the cost function is a combination of metal and via-related variables. For the second use case ( Figure 9 on the right), the mirror heating model is run once because the metal illumination pupil design is already fixed.

[0098] Return to Figure 6 , the lithographic apparatus includes an illumination source, projection optics, and / or other components configured to image a pattern onto a substrate (as described above with respect to Figure 1 ). In some embodiments, performing source mask optimization (e.g., performing method 600) includes modeling the lithographic process for imaging a pattern onto a substrate. The model for modeling the process for imaging a pattern onto a substrate uses the determined source configuration (e.g., from operation 602) and / or other information.

[0099] In operation 604, one or more adjustments to one or more of the source configuration, pattern, projection optics, illumination source, and / or other components of the lithographic apparatus are determined. The one or more adjustments are determined based on modeled system effects of the lithographic apparatus components that cause feature-dependent imaging performance changes and / or other information. For example, adjustments are performed until a termination condition is met. The termination condition may include the determination that the features (model simulations of) patterned onto the substrate will approximately match the target design and / or other termination conditions. In other words, the system effect-aware SMO of method 600 (by optimizing the cost function as described above) is performed until the model simulation determination that the features patterned onto the substrate will approximately match the target design.

[0100] In some embodiments, operation 604 includes determining adjustments to the semiconductor device manufacturing process. In some embodiments, operation 604 includes determining one or more semiconductor device manufacturing process parameters. The one or more semiconductor device manufacturing process parameters may be determined based on, for example, the expected printed pattern characteristics and / or other information. In some embodiments, the process parameters may be broadly interpreted to include platform position, mask design, metrology target design, semiconductor device design, intensity of radiation (for exposing resist, etc.), incident angle of radiation (for exposing resist, etc.), wavelength of radiation (for exposing resist, etc.), pupil storage and / or shape, resist material, and / or other parameters.

[0101] In some embodiments, operation 604 includes determining a process adjustment based on one or more determined semiconductor device manufacturing process parameters and adjusting a semiconductor device manufacturing apparatus and / or other operations based on the determined adjustment. For example, if a determined measurement result is outside of a process tolerance, the out-of-tolerance measurement result can be caused by one or more manufacturing processes whose process parameters have drifted and / or otherwise changed such that the process no longer produces acceptable devices (e.g., the measurement result may breach an acceptable threshold). One or more new or adjusted process parameters can be determined based on the determination of the measurement result. The new or adjusted process parameters can be configured such that the manufacturing process again produces acceptable devices.

[0102] For example, the new or adjusted process parameters can cause a previously unacceptable measurement value to be adjusted back into an acceptable range. The new or adjusted process parameters can be compared to existing parameters for a given process. For example, if there is a difference, the difference can be used to determine an adjustment to the apparatus used to produce the device (e.g., parameter “x” should be increased / decreased / changed such that it matches the new or adjusted version of parameter “x” determined as part of method 600). In some embodiments, method 600 can include electrically adjusting the apparatus (e.g., based on the determined process parameters). Electrically adjusting the apparatus can include sending an electronic signal and / or other communication to the apparatus, such as which causes a change to the apparatus. Electrical adjustment can include, for example, changing a setting on the apparatus and / or other adjustment.

[0103] Figure 10 is a schematic diagram of an exemplary computer system CS that can be used for one or more of the operations described herein (which may be similar or identical to the CS shown in Figure 3 ). Computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or processors) coupled to bus BS for processing information. Computer system CS also includes a main memory MM coupled to bus BS for storing information and instructions to be executed by processor PRO, such as random access memory (RAM) or other dynamic memory. Main memory MM can also be used to store 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.

[0104] A computer system CS can be coupled by a bus BS to a display DS for displaying information to a computer user, such as a cathode ray tube (CRT) or a flat panel or touch panel display. An input device ID including alphanumeric and other keys is coupled to the bus BS for communicating information and command selections to a processor PRO. Another type of user input device is a cursor control CC for communicating direction information and command selections to the processor PRO and for controlling the movement of a cursor on the display DS, such as a mouse, trackball, or cursor direction keys. Such input devices typically have two degrees of freedom in two axes (a first axis (e.g., x) and a second axis (e.g., y)), allowing the device to specify a position in a plane. A touch panel (screen) display can also be used as an input device.

[0105] In some embodiments, one or more operations described herein can be performed by a computer system CS in response to one or more sequences of instructions included in a main memory MM being executed by a processor PRO. These instructions can be read into the main memory MM from another computer-readable medium, such as a storage device SD. Execution of the instruction sequences included in the main memory MM causes the processor PRO to perform the process steps (operations) described herein. One or more processors in a multiprocessing arrangement can also be used to execute the instruction sequences included in the main memory MM. In some embodiments, hardwired circuitry can 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.

[0106] The term "computer-readable medium" or "machine-readable medium" as used herein refers to any medium that participates in providing instructions to a processor PRO for execution. Such a medium can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as storage device SD. Volatile media includes volatile memory, such as main memory MM. Transmission media includes coaxial cables, copper wire, and fiber optics, including the wires that comprise the bus BS. Transmission media can also take the form of acoustic or light waves, such as acoustic or light waves generated during radio frequency (RF) and infrared (IR) data communications. A computer-readable medium can be non-transitory, such as a floppy disk, flexible disk, hard disk, magnetic tape, any other magnetic medium, CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, RAM, PROM, and EPROM, FLASH-EPROM, any other memory chip or cartridge. The non-transitory computer-readable medium can have (machine-readable) instructions recorded thereon. The instructions, when executed by a computer, can implement any of the operations described herein. For example, a transitory computer-readable medium can include a carrier wave or other propagating electromagnetic signal.

[0107] Various forms of computer-readable media may be involved in loading one or more sequences of one or more machine-readable instructions into the processor PRO for execution. For example, the instructions may initially be loaded onto a magnetic disk of a remote computer. The remote computer may load the instructions into its volatile memory and send the instructions via a telephone line using a modem. A modem local to the computer system CS may receive the data on the telephone line and use an infrared transmitter to convert the data into an infrared signal. An infrared detector coupled to the bus BS may receive the data carried in the infrared signal and place the data on the bus BS. The bus BS carries the data to the main memory MM, from which the processor PRO retrieves and executes the instructions. The instructions received by the main memory MM may optionally be stored on the storage device SD before or after being executed by the processor PRO.

[0108] The computer system CS may also include a communication interface CI coupled to the bus BS. The communication interface CI provides a two-way data communication coupling with a network link NDL that is connected to a local area network LAN. For example, the communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection with a corresponding type of telephone line. As another example, the communication interface CI may be a local area network (LAN) card that provides a data communication connection with a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface CI sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

[0109] The network link NDL typically provides data communication to other data devices via one or more networks. For example, the network link NDL may be provided by a local area network LAN to connect to a host computer HC. This may include data communication services provided via a global packet data communication network (now commonly referred to as the "Internet" INT). The local area network LAN (Internet) may use electrical, electromagnetic, or optical signals that carry digital data streams. Signals via various networks and signals on the network data link NDL and via the communication interface CI are exemplary forms of carrier waves that convey information, which load digital data into the computer system CS and carry digital data from the computer system.

[0110] A computer system CS can send messages and receive data (including program code) via a network, a network data link NDL, and a communication interface CI. In an Internet example, a host computer HC can transmit requested program code for an application program via the Internet INT, a network data link NDL, a local area network LAN, and a communication interface CI. For example, one such downloaded application program can provide all or part of the methods described herein. The received code can be executed by a processor PRO when it is received, or stored in a storage device SD or other non-volatile memory for later execution. In this way, the computer system CS can obtain application code in the form of a carrier wave.

[0111] The concepts disclosed herein can be used with any imaging, etching, polishing, inspection, etc. systems for sub-wavelength features and can be useful for emerging imaging technologies capable of generating increasingly shorter wavelengths. Emerging technologies include EUV (extreme ultraviolet), DUV lithography capable of generating a 193 nm wavelength through the use of an ArF laser and even a 157 nm wavelength through the use of a fluorine laser. Additionally, EUV lithography can generate wavelengths in the range of 20 nm to 50 nm by using a synchrotron or by shooting high-energy electrons at a material (solid or plasma) to generate photons in this range.

[0112] Embodiments of the present disclosure can also be described in terms of:

[0113] 1. A method for source mask optimization of a lithographic apparatus, the lithographic apparatus including components configured to image a pattern onto a substrate, the method comprising:

[0114] Determining a source configuration of the lithographic apparatus for processing a first feature in a first layer based on system effects associated with processing a second feature in a second layer on a lithographic apparatus component, wherein the first layer and the second layer are different layers.

[0115] 2. The method according to aspect 1, wherein the system effects on the lithographic apparatus component are determined by simulation.

[0116] 3. The method according to aspects 1 to 2, further comprising performing source mask optimization based on the system effects.

[0117] 4. The method according to any one of aspects 1 to 3, wherein the system effects on the lithographic apparatus component include component heating, component cooling, component drift, component variations for different substrate batches, illumination offset, mask-to-mask changes, overlay effects, aberration effects, attenuation, recalibration or resetting, and / or dose or pupil residuals.

[0118] 5. The method according to any one of aspects 1 to 4, wherein the lithographic apparatus component comprises a mirror and / or a lens, and the system effect on the lithographic apparatus comprises the mirror getting hot and / or the lens getting hot.

[0119] 6. The method according to any one of aspects 1 to 5, wherein the system effect on the lithographic apparatus component varies over time during exposure.

[0120] 7. The method according to any one of aspects 1 to 6, wherein the system effect on the lithographic apparatus component causes a feature-dependent change in the imaging performance of the second feature in the second layer.

[0121] 8. The method according to aspect 7, wherein the feature-dependent change in the imaging performance comprises a change that varies based on the shape, location, size, material, layer, and / or function of the feature in the layer.

[0122] 9. The method according to any one of aspects 1 to 8, wherein the system effect on the lithographic apparatus component is caused by a first patterning operation related to the first layer, wherein the first patterning operation is performed before a second patterning operation related to the second layer.

[0123] 10. The method according to aspect 9, wherein the system effect is simulated or measured based on the first patterning operation.

[0124] 11. The method according to aspect 9, wherein determining the source configuration for processing the first layer comprises a source optimization process, wherein the source optimization process comprises simulating the lithography process associated with the first layer, and wherein the source optimization process comprises optimizing the source configuration based on the feature-dependent imaging performance of the second feature in the second layer.

[0125] 12. The method according to aspect 11, wherein the source configuration is optimized by using a cost function indicating the imaging performance of the second feature in the second layer.

[0126] 13. The method according to aspect 11, wherein the source configuration is further optimized based on the feature-dependent imaging performance of the first feature in the first layer.

[0127] 14. The method according to any one of aspects 1 to 8, wherein the system effect on the lithographic apparatus component is caused by a second patterning operation related to the second layer, wherein the second patterning operation is performed before a first patterning operation related to the first layer.

[0128] 15. The method according to aspect 14, wherein the system effect is simulated or measured based on the second patterning operation related to the second layer.

[0129] 16. The method according to aspect 15, wherein determining the source configuration for processing the first layer includes a source optimization process, wherein the source optimization process includes simulation of a lithography process associated with the first layer, and wherein the source optimization process includes optimizing the source configuration based on the imaging sensitivity of system effects associated with a second patterning operation with respect to the first feature of the first layer.

[0130] 17. The method according to aspect 16, wherein the source configuration for processing the first layer is determined based on the imaging sensitivity of system effects associated with a second patterning operation with respect to the first feature of the first layer.

[0131] 18. The method according to aspect 14, wherein the imaging sensitivity corresponds to the aberration sensitivity induced by system effects.

[0132] 19. The method according to aspect 14, wherein optimizing the source configuration includes using a cost function indicative of the aberration sensitivity of the first feature of the first layer, wherein the sensitivity corresponds to the aberration sensitivity of edge placement error (EPE), critical dimension (CD), and pattern placement error (PPE).

[0133] 20. The method according to aspect 14, wherein determining the source configuration includes an optimization process using a cost function including an indication of the sensitivity of the second layer to aberrations induced by mirror heating.

[0134] 21. The method according to aspect 20, wherein the source is optimized to reduce the aberration sensitivity induced by mirror heating.

[0135] 22. The method according to any one of aspects 1 to 21, wherein determining the source configuration includes determining the illumination pupil.

[0136] 23. The method according to any one of aspects 1 to 22, wherein the first layer is a metal layer and the second layer is a via layer, or the first layer is a via layer and the second layer is a metal layer, or both the first and second layers are metal or both are via layers; and wherein the layers are associated with the same wafer or with different wafers in different production batches.

[0137] 24. The method according to any one of aspects 1 to 23, wherein the first layer and the second layer are of different layer types.

[0138] 25. The method according to any one of aspects 1 to 24, wherein the lithography equipment components include an illumination source and projection optics configured to image a pattern onto a substrate; wherein the method further includes determining one or more adjustments for one or more of the source configuration, pattern, projection optics, or illumination source based on system effects on the lithography equipment components, and wherein the adjustments are performed on the lithography equipment during production.

[0139] 26. The method according to any one of aspects 1 to 25, wherein performing source mask optimization includes modeling a lithography process for imaging a pattern onto a substrate.

[0140] 27. A non - transitory computer - readable medium having instructions thereon, the instructions, when executed by a computer, implement the method according to any one of aspects 1 to 26.

[0141] 28. A system, comprising one or more processors configured by machine - readable instructions to execute the method according to any one of aspects 1 to 26.

[0142] While the concepts disclosed herein can be used in manufacturing with substrates such as silicon wafers, it should be understood that the disclosed concepts can be used with any type of manufacturing system (e.g., a manufacturing system for manufacturing on substrates other than silicon wafers).

[0143] In addition, combinations and sub - combinations of the disclosed elements can include separate embodiments. For example, one or more of the operations described above can be included in separate embodiments, or they can be included together in the same embodiment.

[0144] The foregoing description is intended to be illustrative, not restrictive. Accordingly, those skilled in the art will appreciate that modifications can be made as described without departing from the scope of the claims set forth below.

Claims

1. A method for source mask optimization for a lithographic apparatus, the lithographic apparatus comprising components configured to image a pattern onto a substrate, the method comprising: Determining a source configuration of the lithographic apparatus for processing a first feature in a first layer based on system effects associated with processing a second feature in a second layer on a lithographic apparatus component, wherein the first layer and the second layer are different layers.

2. The method according to claim 1, further comprising determining said systematic effects on components of the lithographic apparatus by simulation or measurement, and further comprising performing source mask optimization based on said systematic effects, wherein, Determining the source configuration includes determining an illumination pupil, wherein the system effects on the lithographic apparatus component include component heating, component cooling, component drift, component variations for different substrate batches, illumination offset, mask-to-mask changes, overlay effects, aberration effects, attenuation, recalibration or resetting, and / or dose or pupil residuals.

3. The method according to claim 1, wherein, The lithographic apparatus component includes a mirror and / or a lens, and the system effects on the lithographic apparatus include mirror heating and / or lens heating.

4. The method according to claim 1, wherein, The system effects on the lithographic apparatus component are caused by a first patterning operation associated with the first layer, wherein the first patterning operation is performed before a second patterning operation associated with the second layer.

5. The method according to claim 4, wherein Determining the source configuration for processing the first layer includes a source optimization process, wherein the source optimization process includes simulation of a lithographic process associated with the first layer, and wherein the source optimization process includes iteratively optimizing the source configuration based on feature-dependent imaging performance of the second feature in the second layer.

6. The method according to claim 5, wherein, Optimizing the source configuration is performed by using a cost function indicative of the imaging performance of the second feature in the second layer.

7. The method according to claim 6, wherein, The source configuration is further optimized based on feature-dependent imaging performance of the first feature in the first layer.

8. The method according to claim 1, wherein The system effects on the lithographic apparatus component are caused by a second patterning operation associated with the second layer, wherein the second patterning operation is performed before a first patterning operation associated with the first layer, and wherein the system effects are simulated or measured based on the second patterning operation associated with the second layer.

9. The method according to claim 8, wherein Determining the source configuration for processing the first layer includes a source optimization process, wherein the source optimization process includes simulation of a lithographic process associated with the first layer, and wherein the source optimization process includes optimizing the source configuration based on the imaging sensitivity of the system effects associated with the second patterning operation to the first feature of the first layer.

10. The method according to claim 9, wherein, Determining the source configuration for processing the first layer includes: iteratively optimizing the source configuration based on the imaging sensitivity of the system effects associated with the second patterning operation to the first feature of the first layer.

11. The method according to claim 10, wherein, The imaging sensitivity corresponds to the aberration sensitivity induced by the system effects.

12. The method according to claim 11, wherein, Optimizing the source configuration includes using a cost function indicative of the aberration sensitivity of the first feature of the first layer, wherein the sensitivity corresponds to the aberration sensitivity of edge placement error (EPE), critical dimension (CD), and pattern placement error (PPE).

13. The method according to claim 1, wherein, The first layer is a metal layer and the second layer is a via layer, or the first layer is a via layer and the second layer is a metal layer, or both the first layer and the second layer are metal layers or both are via layers; and wherein the layers are associated with the same wafer or with different wafers in different production batches.

14. The method according to claim 1, wherein, The first layer and the second layer are of different layer types.

15. The method according to claim 14, wherein The lithographic apparatus component includes an illumination source and projection optics configured to image the pattern onto the substrate; wherein the method further includes determining one or more adjustments to one or more of the source configuration, the pattern, the projection optics, or the illumination source based on the system effects on the lithographic apparatus component, and wherein the adjustment is performed on the lithographic apparatus during production.

Images