Method and apparatus for determining control data for a lithographic apparatus

Abstract

A method for determining an input to a lens model for determining a set value for manipulation of a lens of a lithographic apparatus when addressing at least one of a plurality of fields of a substrate, the method comprising: receiving parameter data for at least one field, the parameter data relating to one or more parameters of the substrate within the at least one field, the one or more parameters being at least partially sensitive to manipulation of the lens as part of an exposure performed by the lithographic apparatus; receiving lens model data associated with the lens; and determining the input based on the parameter data and the lens model data.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 19210585.6 filed on November 21, 2019, EP application 19218161.8 filed on December 19, 2019, and EP application 20161954.1 filed on March 10, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a method and apparatus for determining control data for a lithographic apparatus. In particular, the present invention may relate to determining a request for input to a lens model to determine setpoints for manipulation of a lens of the lithographic apparatus. Background Art

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

[0005] To project a pattern onto a substrate, a lithographic apparatus uses electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. Typical wavelengths currently used are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Compared to lithographic apparatuses that use radiation with a wavelength of, for example, 193 nm, lithographic apparatuses that use extreme ultraviolet (EUV) radiation with a wavelength in the range of 4-20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on a substrate.

[0006] Low k1 lithography can be used to process features with dimensions smaller than the classical resolution limit of the lithographic apparatus. In such processes, the resolution formula can be expressed as CD = k1 × λ / NA, where λ is the wavelength of the radiation employed, NA is the numerical aperture of the projection optics in the lithographic apparatus, CD is the "critical dimension" (usually the minimum feature size printed, but in this case, half the pitch), and k1 is the empirical resolution factor. In general, the smaller k1 is, the more difficult it is to reproduce a pattern on the substrate that is similar in shape and size to that designed by the circuit designer in order to achieve 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 include, for example, but not limited to, optimization of the NA, customized illumination schemes, use of phase-shifted 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, or other methods generally defined as "resolution enhancement techniques" (RET). Alternatively, a tight control loop for controlling the stability of the lithographic apparatus can be used to improve the reproduction of patterns at low k1.

[0007] In order to monitor the quality and performance of the lithographic patterning process, inspections of the pattern exposed by the lithographic apparatus can be performed. These inspections may include several types of measurements performed by different types of metrology tools. The measurements can be used to monitor different parameters of the patterned substrate. The measurements can be used to identify one or more errors in the exposed pattern, and relevant corrections to the lithographic patterning process can be determined based on the identified errors. These corrections can be applied to the lithographic patterning process to improve future exposures performed by the lithographic apparatus. In order to determine how to update the lithographic patterning process, a model can be used to associate the identified errors and / or desired corrections with updates or adjustments to the lithographic process settings. In order to improve the output of the model and obtain better results, the data provided as input to the model can be optimized. Summary of the Invention

[0008] According to one aspect of the present invention, a method for determining control data for a lithographic apparatus is provided. The method includes receiving parameter data associated with a plurality of fields on a substrate. The parameter data is provided as an input to a cost function. The method also includes evaluating a cost function extending across the plurality of fields, wherein the cost function is based on control characteristics of the lithographic apparatus. The cost function provides an output including a correction configured to reduce residual variance in a performance parameter across the plurality of fields on the substrate. The method may further include determining control data based on the output.

[0009] Optionally, the control characteristics of the lithographic apparatus may include one or more boundary conditions for the correction.

[0010] Alternatively, the cost function may determine the control data to minimize the residual of the performance parameter across the multiple fields.

[0011] Optionally, the calibration may comprise an actuator control setting for at least one actuator of the lithographic apparatus.

[0012] Alternatively, the control data may include a routing sequence for exposure of the plurality of fields.

[0013] Optionally, the output may include a routing sequence for exposures of multiple fields.

[0014] Optionally, the method may further comprise determining a preparation time to be provided to the lithography for implementing the control data.Based at least in part on the preparation time, boundary conditions for the correction may be determined.

[0015] Optionally, determining the setup time may include determining a residual of a performance parameter of a first setup time for the one or more fields. Determining the setup time may also include determining a residual of a performance parameter of a second setup time for the one or more fields, wherein the second setup time is longer than the first setup time. One of the first setup time and the second setup time may be selected as the setup time provided to the lithographic apparatus. The selection may be based on a comparison of the residual for the first setup time and the residual for the second setup time with a threshold residual value.

[0016] Alternatively, the threshold residual value may represent an upper limit on the residual that results in a valid field.

[0017] According to another aspect of the present disclosure, there is provided an apparatus for determining control data of a lithographic apparatus, the apparatus comprising one or more processors configured to execute the method as described above.

[0018] In one aspect of the present invention, a method is provided for determining an input to a lens model to determine a set value for manipulation of a lens of a lithographic device when addressing at least one of a plurality of fields of a substrate, the method comprising: receiving parameter data for at least one field, the parameter data relating to one or more parameters of the substrate within the at least one field, the one or more parameters being at least partially sensitive to manipulation of the lens as part of an exposure performed by the lithographic device; receiving lens model data relating to the lens; and determining the input based on the parameter data and the lens model data.

[0019] Optionally, the at least one field may comprise a local field. The parameter data may comprise parameter data associated with a location within the local field. Determining the input may comprise optimizing the input to apply corrections to one or more parameters, wherein the corrections may be identified by the parameter data associated with a location within the local field.

[0020] Optionally, the optimization input may include: determining an initial setting value within the local field based on a first lens model, wherein the first lens model is based on lens model data; and evaluating the initial setting value to determine a setting value for a portion outside the local field across the entire field to determine a target setting value.

[0021] Optionally, the first lens model may be further configured to determine an input corresponding to a target setting value.

[0022] Alternatively, the first lens model may be a local field aware lens model configured not to optimize input for positions outside the local field.

[0023] Optionally, optimizing the input may include: determining a plurality of temporary inputs based on the parameter data; and selecting one of the plurality of temporary inputs based on the lens model data.

[0024] Optionally, determining one or more of the plurality of provisional inputs may include extrapolating parameter data outside the local field based on parameter data within the local field.

[0025] Optionally, selecting one of the plurality of provisional inputs may comprise selecting a provisional input that applies a correction to the parameter that is closest to a correction identified from the parameter data.

[0026] Alternatively, the correction may be a correction for errors identified in the parameter data.

[0027] Optionally, the lens model data may include a copy of the lens model.

[0028] Optionally, the lens model data may include dynamic data for the lens.

[0029] Alternatively, determining the input may include determining the input for the first field based on the input for the second field.

[0030] Alternatively, the first field may be a partial field and the second field may be a full field.

[0031] Optionally, the local field may be adjacent to the full field.

[0032] Optionally, the input may also be determined based on dynamic data for the lens and / or the importance of the local field and / or the full field.

[0033] Optionally, the importance of the global field may be greater than the importance of the local field.

[0034] Alternatively, the importance of the local field and / or the global field may be based on the number of structures to be patterned in the field and / or the size of at least a portion of the structures to be patterned in the field.

[0035] Optionally, determining the input may include optimizing the input to apply corrections to parameters across the field.

[0036] Optionally, the parameter data may include local field parameter data and full field parameter data. Optimizing the input may include: determining an input for the full field based on the full field parameter data; and determining an input for the local field based on the local field parameter data and using the input for the full field as a constraint.

[0037] Optionally, the parametric data may include measurement data.

[0038] Optionally, manipulation of the lens may include setting a position of one or more lens manipulators, wherein the lens manipulators may be configured to apply deformations to the lens.

[0039] Optionally, the one or more parameters may include one or more of overlay accuracy data, critical dimension data, leveling data, alignment data, or edge position error data.

[0040] Optionally, the parametric data may be associated with one or more of pattern offset, overlay accuracy, alignment aberration, or focus error.

[0041] Optionally, the method may further include: providing input to a lens model; and determining a set value for manipulation of the lens based on the lens model.

[0042] Optionally, the method may further include providing a setting value to the lens. The lithographic apparatus may be configured to perform lithographic exposure of the substrate using the provided lens setting value.

[0043] According to another aspect of the present disclosure, there is provided an apparatus for configuring input to a lens model to determine one or more settings of a lens of a lithographic apparatus, the apparatus comprising one or more processors configured to perform the method as described above.

[0044] According to another aspect of the present invention, there is provided a lithographic apparatus comprising the apparatus as described above.

[0045] According to another aspect of the present invention, there is provided a lithography cell comprising an apparatus as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0047] Figure 1 depicts a schematic overview of a lithographic apparatus;

[0048] Figure 2 A schematic overview of a lithography unit is depicted;

[0049] Figure 3 depicts a schematic representation of overall lithography showing the collaboration between three key technologies used to optimize semiconductor manufacturing;

[0050] Figure 4 A flowchart depicting steps in a method for determining control data for a lithographic apparatus; and

[0051] FIG5( a ) depicts the route order of an exposure sequence following a typical exposure bend, e.g., following adjacent field positions;

[0052] FIG5( b ) depicts the route order of the exposure sequence based on the determined correction values;

[0053] Figure 6 a flow chart depicting steps in a method for determining the makeready time available for a lithographic apparatus;

[0054] Figure 7 depicts a flow chart including steps in a method of determining input to a lens model;

[0055] Figure 8 (a) depicts a portion of a substrate including fringe fields;

[0056] Figure 8 (b) depicts a schematic representation of the extrapolated data;

[0057] Figure 9 depicts a schematic representation of steps in a method for determining settings for manipulating a lens;

[0058] Figure 10 depicts an example first lens model for determining input to the lens model;

[0059] Figure 11 Depicting an example first lens model for determining input to a lens model;

[0060] Figure 12 depicts a schematic representation of a portion of a substrate including a plurality of fields for which setpoints have been determined;

[0061] Figure 13 Depicted are schematic representations of steps in a method for determining inputs to a lens model. DETAILED DESCRIPTION

[0062] In this document, the terms "radiation" and "beam" are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and EUV (extreme ultraviolet radiation, e.g., having a wavelength in the range of about 5 nm-100 nm).

[0063] As used herein, the terms "reticle," "mask," or "patterning device" should be broadly interpreted to refer to a general patterning device that can be used to impart an incident radiation beam with a patterned cross-section corresponding to the pattern to be produced in a target portion of the substrate. The term "light valve" may also be used herein. In addition to classical masks (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0064] Figure 1 A lithographic apparatus LA is schematically depicted. The lithographic apparatus LA comprises an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation), a mask support (e.g., mask table) T configured to support a patterning device (e.g., mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to specific parameters, a substrate support (e.g., wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support according to specific parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0065] In operation, the illumination system IL receives a radiation beam from a radiation source SO, for example, via a beam delivery system BD. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for directing, shaping, and / or controlling the radiation. The illuminator IL may be used to condition the radiation beam B so that it has a desired spatial and angular intensity distribution in a cross-section at the plane of the patterning device MA.

[0066] The term "projection system" PS as used herein should be broadly interpreted as encompassing various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used, and / or to other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0067] 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) so as to fill the space between the projection system PS and the substrate W, which is also known as immersion lithography. More information on immersion technology is given in US 6,952,253, which is incorporated herein by reference.

[0068] The lithographic apparatus LA may also be of a type having two or more substrate supports WT (also referred to as a "dual stage"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and / or steps for preparing a substrate W for subsequent exposure may be performed on a substrate W on one of the plurality of substrate supports WT while another substrate W on another substrate support WT is being used to expose a pattern on the other substrate W.

[0069] In addition to the substrate support WT, the lithographic apparatus LA may further comprise a measurement stage. The measurement stage is arranged to hold sensors and / or cleaning equipment. The sensors may be arranged to measure characteristics of the projection system PS or characteristics of the radiation beam B. The measurement stage may hold a plurality of sensors. The cleaning equipment may be arranged to clean a portion of the lithographic apparatus, such as a portion of the projection system PS or a portion of a system for providing immersion liquid. The measurement stage may be moved beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0070] In operation, a radiation beam B is incident on a patterning device (e.g. a mask) MA held on a mask support T and is patterned by a pattern (design layout) present on the patterning device MA. After passing through the mask MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of the substrate W. With the aid 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 ( Figure 1The patterning device MA may be accurately positioned relative to the path of the radiation beam B using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 are shown occupying dedicated target portions, they may be located in spaces between target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are referred to as scribe line alignment marks.

[0071] like Figure 2 As shown, the lithography apparatus LA may form part of a lithography cell LC, which is sometimes also referred to as a lithography group or (lithography) cluster, which typically also includes equipment for performing pre-exposure and post-exposure processing on a substrate W. Conventionally, these equipment include: a spin coater SC for depositing a resist layer; a developer DE for developing the exposed resist; a chill plate CH and a bake plate BK, for example for regulating the temperature of the substrate W, for example for regulating the solvent in the resist layer. A substrate handler or robot RO picks up substrates W from input / output ports I / O1, I / O2, moves the substrates W between the different processing equipment, and transfers the substrates W to a loading station LB of the lithography apparatus LA. The components in the lithography cell, which are also generally referred to as tracks, are typically under the control of a track control unit TCU, which itself may be controlled by a supervisory control system SCS, which may also control the lithography apparatus LA, for example via a lithography control unit LACU.

[0072] In order to ensure that substrates W exposed by the lithographic apparatus LA are correctly and consistently exposed, it is desirable to inspect the substrates to measure characteristics of the patterned structures, such as overlay errors between successive layers, line thickness, critical dimensions (CD), etc. For this purpose, an inspection tool (not shown) may be included in the lithography cell LC. If errors are detected, adjustments may be made, for example, to the exposure of subsequent substrates or to other processing steps to be performed on the substrate W, particularly if the inspection is completed before other substrates W of the same batch or lot are yet to be exposed or processed.

[0073] The inspection apparatus, which may also be referred to as a metrology apparatus, is used to determine properties of a substrate W, in particular how properties vary from one substrate W to another, or how properties associated with different layers of the same substrate W vary from layer to layer. Alternatively, the inspection apparatus may be configured to identify defects on the substrate W and, for example, may be part of the lithography cell LC, or may be integrated into the lithography apparatus LA, or may even be a standalone device. The inspection apparatus may measure properties on a latent image (the image in the resist layer after exposure), or a semi-latent image (the image in the resist layer after a post-exposure bake step PEB), or a developed resist image (wherein exposed or unexposed portions of the resist have been removed), or even an etched image (after a pattern transfer step such as etching).

[0074] Typically, the patterning process in the lithographic apparatus LA is one of the most critical steps in the process, which requires high precision in the size and position of the structures on the substrate W. In order to ensure this high precision, three systems can be combined in a system such as Figure 3 . One of these systems is a lithography apparatus LA that is (virtually) connected to a metrology tool MT (a second system) and a computer system CL (a third system). The key to this "holistic" environment is to optimize the collaboration between these three systems to enhance the overall process window and provide a tight control loop to ensure that the patterning performed by the lithography apparatus LA remains within the process window. The process window defines the range of process parameters (e.g., dose, focus, overlay accuracy) within which a particular manufacturing process produces a defined result (e.g., a functional semiconductor device)—typically, within this range, variations in process parameters of the lithography process or patterning process are permitted.

[0075] The computer system CL can use (part of) the design layout to be patterned to predict which resolution enhancement technology to use and perform computational lithography simulations and calculations to determine which mask layout and lithographic equipment settings achieve the maximum total process window (in Figure 3 In general, the resolution enhancement techniques are arranged to match the patterning possibilities of the lithographic apparatus LA. The computer system CL may also be used to detect where within the process window the lithographic apparatus LA is currently operating (e.g. using input from the metrology tool MT) to predict where the resolution enhancement techniques may be due to, for example, suboptimal processing (e.g., in the process window). Figure 3 Whether there is a defect is determined by an arrow pointing to "0" in the second scale SC2).

[0076] The metrology tool MT may provide input to the computer system CL to enable accurate simulations and predictions, and may provide feedback to the lithographic apparatus LA to identify, for example, possible drift in the calibration state of the lithographic apparatus LA (e.g., Figure 3) depicted by multiple arrows in the third scale SC3.

[0077] Different types of metrology tools MT can be used with the lithographic apparatus LA to measure different aspects or characteristics of a pattern exposed on a substrate by lithography. The metrology tool MT can use radiation, such as electromagnetic radiation, to interrogate the pattern on the substrate. The metrology tool MT can include, for example, a scatterometer. Example characteristics that can be measured by the metrology tool TM to determine exposure quality include overlay accuracy OVL, alignment AL, and leveling data LVL.

[0078] The metrology tool MT can be used to inspect the quality and / or characteristics of a pattern exposed on a substrate. This inspection can be used to detect errors in the exposed pattern. The identified errors can be analyzed to determine updates to the settings of the lithographic apparatus to improve future exposures of the lithographic apparatus, for example by partially or completely removing the pattern errors from subsequent exposures of the same pattern. One element of the lithographic exposure that can be modified in response to the detection of a pattern error is the characteristics of the radiation beam used to expose the substrate. The lithographic apparatus LA can control settings of a radiation source, such as the power of the radiation, pulse duration, etc. The lithographic apparatus LA can control characteristics (e.g., speed, route, etc.) of a trajectory along which multiple fields are exposed on a wafer. The lithographic apparatus LA can include optical components for controlling and manipulating the radiation beam used for lithographic exposure. Methods and apparatus are described herein for determining updates to control settings related to one or more of the above-mentioned elements of the apparatus LA or any other characteristics that affect the patterning process performed by the lithographic apparatus LA. The control settings can be determined individually or in combination with each other.

[0079] A substrate exposed by a lithographic apparatus LA may include errors introduced by various elements controlling the exposure process. Parameter data for one or more parameters on one or more previously exposed substrates can be used to identify errors present in a patterned substrate. The identified errors can be residuals in parameters that represent the quality of the exposed pattern / performance of the patterning process. An analysis of the identified errors can be performed to determine how to address and compensate for the errors in subsequent exposures. A patterning profile (also known as an exposure profile) can be implemented by the lithographic apparatus to perform exposures. Corrections to the profile can be determined based on the errors identified in previous exposures to remove / reduce errors in future exposures. These corrections can be implemented in the form of changes / corrections to control the settings of one or more actuators within the lithographic apparatus. An actuator can be an element of the lithographic apparatus that controls an aspect of the exposure process (e.g., a radiation source, radiation control (e.g., via a lens), stage / substrate control, etc.). The methods and apparatus described herein are directed to improving the control of the lithographic apparatus LA to reduce errors in the exposed pattern. Specifically, the methods can be used to reduce residual errors in a pattern exposed by the lithographic apparatus LA.

[0080] The parameter data of the substrate may include measurement data. The measurement data may be measurement data of a lithographically patterned substrate. The measurement data may include data related to one or more parameters of the substrate and / or one or more parameters of a structure patterned on the substrate. This may be referred to as parameter data. Following the measurement data, other forms of parameter data may be provided for the substrate, such as simulation parameter data. Parameter data may be provided for each exposure field on the substrate. Based on the parameter data, one or more corrections to the pattern may be determined. The parameter data may be parameter data of previously exposed patterns on one or more substrates. The one or more previously exposed patterns may be the same as the pattern to be exposed. The parameter data may include measurement data and / or simulation data of the exposed pattern on the substrate. Parameter data may be provided for multiple locations on the substrate.

[0081] Based on the parameter data, errors in parameter values ​​present in the parameter data can be identified. This can be done, for example, by comparing the parameter data of the substrate with expected values ​​for these parameters. Errors in the parameter data can represent deviations of the substrate parameter values ​​from the expected values ​​for these parameters. In addition to the parameter values ​​themselves or as an alternative, the parameter data can also include data related to the errors in the parameter values. The identified errors can also be considered as instructions for corrections to be applied to the exposed pattern in order to remove the identified errors. Corrections to the pattern can be converted into corrections to the photolithographic patterning process used to expose the pattern. These corrections can be applied to the photolithographic patterning process so that future exposures of the same pattern as the pattern for which the parameter data was provided can be improved.

[0082] To determine patterning errors on an exposed substrate, parameter data can be provided to a cost function. Based on parameter data from previously exposed substrates, the cost function can be used to determine how to correct errors during the patterning process. Because the computational cost of determining corrections can be high, calculations and other analyses can be performed separately for each exposure field. The calculations and analyses applied can be the same for each field. This can reduce the overall computational cost for the entire substrate and the required computation time. However, using such a simplified approach of determining corrections for different fields separately can mean that the corrections determined are suboptimal. For example, because an actuator may be limited in the type / range of changes in control settings (e.g., speed, range, direction) that can be implemented between successive exposure fields, the corrections applied to the field to be exposed in the previous and subsequent fields can affect the corrections that can be achieved. Furthermore, in some cases, not all fields should be analyzed in the same manner. For example, edge fields may have different shapes from one another and from the internal fields on the substrate. Furthermore, some fields on the substrate may include patterned structures with higher or lower tolerances to exposure errors. The cost function described herein can address at least some of the issues and challenges described herein.

[0083] Generally disclosed herein is a method for Figure 4 A method for determining control data for a lithographic apparatus is described. In step 1100, the method receives parameter data associated with a plurality of fields on a substrate. The plurality of fields may, for example, be all fields on an exposed substrate layer. In step 1102, the parameter data for the plurality of fields is provided as input to a cost function. The cost function has knowledge of the lithographic apparatus. The cost function may be based on control characteristics of the lithographic apparatus. The cost function may extend across a plurality of fields, meaning that it may take into account a plurality of fields to perform analysis. In step 1104, the cost function and the input are evaluated to obtain an output. The output includes a correction. The correction may be a correction to a patterning profile to be exposed by the lithographic apparatus. Specifically, the correction may reduce the residual of a performance parameter across a plurality of fields on the substrate. In step 1106, control data may be determined based on the cost function output.

[0084] An advantage of the cost function described above is that corrections configured to reduce patterning errors can be determined for multiple fields, meaning that the effects of corrections from previous and subsequent fields on each other can be considered. This can increase the likelihood of corrections. For example, actuator range and speed limits can be determined for each field relative to the settings of the previously exposed field. This increases the total correction range available to the substrate.

[0085] An advantage of using a cost function based on knowledge of the control characteristics of the device may be that the cost function may correct for residual errors introduced by the control of the lithographic device. That is, there may be a difference between the design that needs to be produced by the patterning scheme and the design actually patterned by the lithographic device. This may be because the lithographic device, and in particular the actuators that implement the control settings within the lithographic device, may introduce errors in the exposure. By including knowledge of the device in the cost function, these actuator errors may be corrected. As an alternative and / or in addition to the relationship between the pattern design and the control settings for the device, the control characteristics may include: information about the current state of the lithographic device (e.g., lens heating feedforward, lens feedback, reticle heating, reticle alignment), information about the substrate (e.g., substrate temperature, substrate alignment), and information about external requests from devices that interact with the lithographic device (e.g., metrology tools, data analysis tools).

[0086] Control characteristics of the lithographic apparatus LA may include information about how the lithographic apparatus LA can implement an exposure profile (e.g., a pattern design). This information may be generally related to the lithographic apparatus, or may be related to one or more specific actuators forming part of the lithographic apparatus. The control characteristics may, for example, include information about limitations on control settings that may be implemented by actuators in the lithographic apparatus.

[0087] The control characteristic may include one or more boundary conditions for the correction. The boundary conditions may be based on knowledge of the limitations of one or more actuators implementing the control settings in the lithographic apparatus. The limitations on the actuator may include, for example, the movement speed of the actuator / actuator element, the movement range, the movement direction, crosstalk causing undesirable effects, etc. The limitation may be a short time result available between subsequent exposures relative to the speed of the actuator. By including knowledge of the limitations of the actuator in the cost function, they can be taken into account when determining the correction, for example by using them as boundary conditions. The advantage of this is that the effect of the limitations can be accounted for by the cost function over multiple fields.

[0088] The control data may be or may include control settings for one or more actuators of the lithographic apparatus LA, or may include other types of data from which control settings can be determined. Examples of control data include a routing sequence of multiple fields to be exposed across the substrate, settings for a lens manipulator, and power settings, pulse duration settings, or other radiation property settings for radiation provided by a radiation source.

[0089] Reducing pattern error can be viewed as improving the consistency of the actual parameter value with the expected value of that parameter in the pattern design. The degree of correspondence between the actual parameter value and the designed parameter value can be viewed as a measure of the performance of the patterning process. Consequently, such parameters can be referred to as performance parameters. Examples of performance parameters include overlay accuracy, alignment, leveling, critical dimension, focus, dose, etc.

[0090] The errors identified and reduced by the cost function can be residuals. Residuals can be understood as errors that cannot be described by the model. Residuals can be distinguished from control errors, which are errors that can be described by the control model used to determine the control settings, but cannot be actuated. After the control settings for the lithographic apparatus used to expose the pattern design have been determined, for example, by the control model, residuals may still exist. Consequently, residuals can be identified and corrected based on metrology data or other data associated with previously exposed substrates.

[0091] The cost function may have knowledge of the patterning process, thereby being able to analyze the received parameter data and identify one or more errors on the substrate. The cost function may also have knowledge of the lithographic apparatus, as described above, thereby being able to determine how to correct the identified errors on a previously exposed substrate, and how to implement these corrections. To this end, the cost function may determine one or more corrections to the patterning recipe. The cost function may provide an output indicative of the determined corrections. This may, for example, be in the form of corrections to the patterning recipe, control settings to be provided to the lithographic apparatus LA, or any other form of control data from which updated control settings for the lithographic apparatus LA can be determined.

[0092] In addition to knowledge about the patterning process and lithographic equipment, the cost function may also have (and may be based on) knowledge about the characteristics of the application and process used to determine the patterning profile and / or control settings based on the desired process design. This may be advantageous because it allows the cost function to account for and correct for errors introduced by this part of the patterning process.

[0093] A cost function can determine control data to minimize the error in the next exposure of a pattern performed by the lithographic apparatus across multiple fields. The error to be minimized can, for example, be the residual of a performance parameter across the multiple fields. There are many different ways to define error minimization. For example, the average error across each of the multiple fields can be minimized, thereby giving each field the same importance weight. In another example, different fields can be given different weights for determining error reduction across the multiple fields. This can be used to prioritize error reduction in multiple fields with smaller critical dimensions / stricter performance requirements. In some cases, the edge fields can be given less importance than the interior fields due to the smaller number of structures present in the edge fields and / or the higher likelihood of error at the edge of the substrate. This can result in the fields at the edge of the substrate being sacrificed as non-yielding fields. Alternatively, in cases where edge field error correction is considered possible, the fields at the edge of the substrate can be given more importance than the interior fields because the error tolerance in the interior fields can be slightly higher. The decision on whether to sacrifice the edge fields can apply not only to the edge fields, but also to the dies included in the edge fields. A field may comprise multiple dies, wherein separate dies may form part of separate product structures. One skilled in the art will appreciate that different ways of implementing error minimization fall within the scope of this disclosure, provided that minimization is performed on multiple fields on a substrate.

[0094] The output provided by the cost function includes a correction implemented in the form of a change in the control settings of the lithographic apparatus LA. The correction can be expressed in terms of performance parameters (e.g., desired changes in overlay accuracy, alignment, focal length, etc.). The correction can also be expressed in terms of control data associated with the lithographic apparatus. The control data can include control settings for the lithographic apparatus, that is, control settings that can be directly provided to one or more actuators of the lithographic apparatus. The control data can also include data that requires some additional processing to form the control settings to be provided to one or more actuators. Such processing can be performed by the lithographic apparatus itself or by a processing application external to the lithographic apparatus.

[0095] An advantage of determining corrections in the form of control settings for one or more actuators of a lithographic apparatus is that it allows the cost function to correct for errors introduced by the actuators. This error can be considered as a residual error of the one or more actuators. Specifically, if there are differences between the control settings corresponding to the pattern design and the control settings corresponding to the exposed pattern due to errors introduced by the actuators, the cost function can account for these differences.

[0096] In a specific example, the amount of change that an actuator can apply to a control setting may be limited between two consecutive exposures. Thus, the range of settings that can be implemented by the actuator for a particular field may depend on the settings that were applied to the actuator in the field of the previous exposure. In the case where the cost function determines the control setting for each field separately, the range over which the control setting can be implemented is unknown when no information from the previous field is used. The cost function can, for example, solve this problem by setting the same range (boundary conditions) for each field. However, this results in tighter restrictions than are necessary and may result in corrections that may not be available. In other words, even if the best determined correction is actually achievable by the actuator given the practical restrictions, the best determined correction may fall outside the tighter boundary conditions that are applied.

[0097] In order for the cost function to provide a corrected output taking into account the control settings of one or more actuators, knowledge about these actuators may be included in the control characteristics of the lithographic apparatus on which the cost function is based. This information may be used in the cost function in the form of a separate term to be minimized. An example cost function that does not take into account the actuator settings may be:

[0098]

[0099] Here, x1 can be a value determined by a cost function, x0 is the expected design value, and b1 is a boundary condition imposed by the lithography system. C1 and A1 can be similar matrices that link the pattern design to a model set by the matching scheme. This model can, for example, form part of the computer system CL described above. The error that can be determined using the example cost function described above can be considered a fitting error by the computer system CL. In general, C1 and A1 can only partially describe the actuation capability of the lithography apparatus LA. That is, C1 and A1 may not contain all information about the actuation capability of the lithography apparatus LA.

[0100] More detailed knowledge about the actuators (than used in the above cost function) may be implemented in the form of additional terms that may be used to estimate expected actuation errors produced by one or more actuators of the lithographic apparatus LA.

[0101]

[0102] Among them, C1 * , C1 and A t A similar matrix could be used to link the pattern design to the model for the lithographic equipment control. * Uses the same basis as C1, but can usually differ in the sampling locations. t * 、A tIt can represent the characteristics of the lithographic equipment (actuator). C t 、A t Can be used with C1 * 、C1 different basis. C t 、A t Can be used for lithography equipment LA. C1 * , C1 can be used to transmit information between the computer system CL and the lithographic apparatus LA. x1 can be a value corresponding to the control data determined by the cost function. t This can be the optimal actuator setting corresponding to x1. b1, b t may be boundary conditions associated with the computer system CL and the lithographic apparatus LA, respectively. Those skilled in the art will appreciate that the above are examples of cost functions and that other forms of cost functions may be used, which are used to reduce the error between the design pattern and the exposed pattern.

[0103] The above cost function can use a single cost reduction and / or minimization step for multiple fields on the substrate (e.g., all fields on the substrate). As mentioned above, determining corrections for multiple fields as part of the same calculation or part of a group of calculations may cause the cost function to have a high computational cost. This problem can be solved by using a large-scale optical solver as the cost function. The large-scale optimization solver can be, for example, a quadratic solver using sparse linear algebra. The matrices C1, A1, A s 、C1 * The model used to determine the control settings can be a sparse representation. The sparse nature of the cost function makes it possible and practical to obtain a solution within the timing constraints required to calculate the corrections for the substrate to be exposed. Due to the sparsity of the matrix, the Hessian of the optimization problem will be sparse, and the constraints on the corrections will also be sparse. This allows for relatively low computational cost for a given number of fields.

[0104] A cost function can determine control data for a lithographic apparatus LA, wherein the control data is associated with degrees of freedom for controlling the apparatus. In other words, the cost function can determine control values ​​for one or more parameters associated with a lithographic exposure. An example of a degree of freedom / parameter that a cost function can set is a set value for a lens manipulator, as described in more detail below.

[0105] Another degree of freedom available to the cost function will be described with respect to Figures 5(a) and 5(b), namely the route sequence, that is, the order in which the fields on the substrate are exposed. As described above, a lithographic exposure may include multiple exposure fields, wherein the device exposes these fields one by one. In a large number of manufacturing applications of lithographic equipment, reducing the total exposure time of the substrate is often a primary goal. The route sequence can be determined to expose as many fields as possible in a given time. For example, this can be achieved by limiting the amount of distance that the stage (wafer stage WT) on which the substrate is placed needs to travel during exposure of the substrate. The lithographic equipment can be a scanner, wherein the scanning direction sequence can be in a vertical direction (e.g., scanning up and down). Therefore, the movement of the substrate by the stage can be in a horizontal direction perpendicular to the scanning direction. The fields along the horizontal direction can be called rows. In applications where exposure time is a key consideration, the device can expose multiple adjacent fields sequentially. The route sequence can follow fields with adjacent positions across the substrate.

[0106] FIG5( a ) shows the route sequence following a typical exposure sequence. The exposure sequence can be an exposure warp. In an exposure warp, successive fields to be exposed can be adjacent on the same row. When a field on a row has been exposed, the sequence can move to the next row. The next row can be adjacent to the row just exposed, or it can be a row elsewhere on the substrate. The exposure fields are plotted on the x-axis according to the route sequence. A representation of the correction values ​​for the field is shown on the y-axis in arbitrary units. As can be seen in the figure, there is no clear relationship between the correction values ​​of adjacent fields (adjacent positions on the x-axis). This may result in the correction changes being determined being impossible to implement due to boundary conditions caused by the limitations imposed by the lithographic apparatus. As a result, the correction may differ from the preferred setting, taking into account the limitations of the actuator. In some cases, high-volume manufacturing may be too important for the route sequence to be a degree of freedom. However, in other cases, such as where the volume / speed of manufacturing is less critical, the route sequence can be provided as a degree of freedom.

[0107] FIG5( b) depicts a diagram showing a schematic representation in which the route order in which fields on a substrate are exposed has been organized based on the determined correction values. This means that adjacent fields on a substrate do not have to be exposed immediately following each other. Compared to a setting in which adjacent fields are exposed continuously, this route order can result in more time being required between successive exposures to give the wafer stage time to reposition the substrate. An advantage of this setting can be that the fields exposed in succession have small variations in the correction between them, which means that boundary conditions are less likely to interfere with the desired control settings to be applied. The small variations between the fields exposed in succession can fall within the limitations of the actuators of the lithographic apparatus LA. As a result, it can be better to determine the correction to be applied via a cost function. For example, in research and development use of the apparatus, or for patterning processes operating very close to the finest resolution limit of the lithographic apparatus LA, this approach, which prioritizes correction quality rather than manufacturing volume, may be preferred.

[0108] The route sequence of Figure 5(b) can be determined by a cost function to minimize the correction variation between successive exposures without taking into account the position of successive fields relative to each other. This is in contrast to Figure 5(a), where the relative positions of successive fields are taken into account regardless of the differences in the corrections to be applied. The cost function can determine a route sequence that strikes a balance between the differences in the corrections to be applied and the positions on the substrate. For example, fringe fields, that is, fields at the edge of the wafer, may generally require stronger corrections than interior fields. For example, the cost function can determine to expose all fringe fields together (large expected corrections), potentially ordering them so that similar corrections are exposed in succession. The interior fields (small expected corrections) can be exposed before or after the fringe fields.

[0109] After the route sequence, the amount of preparation time can be provided as a parameter / degree of freedom, that is, the amount of time the lithographic apparatus can use to implement corrections for the next exposure. Between two exposures of the lithographic apparatus, corrections to the exposure settings can be determined. The amount of time required to implement a particular correction can depend on the speed of the actuator that implements the correction. The amount of time required to implement a particular correction can also depend on the difference between the current setting value of the actuator and the setting value associated with the correction to be implemented. The correction can be determined, for example, by a cost function as described above. The amount of time spent implementing the correction can be known to the cost function and can be taken into account by the cost function in the form of boundary conditions applied to the correction to be determined. Corrections to multiple control data values ​​can be implemented to correct residuals during the exposure process. Examples of such control data values ​​can include, for example, wafer stage position, mask stage position, lens actuator setting value, radiation characteristics (wavelength, power, pulse duration), etc.

[0110] The amount of time a lithographic apparatus can use to perform corrections, also known as setup time, can be determined by the time between two exposures of the lithographic apparatus. In known embodiments, the available setup time can be kept as low as possible in order to maximize the number of exposures performed by the lithographic apparatus. This can be the case, for example, in high-volume manufacturing applications and uses of lithographic apparatus. When the time between exposures is kept low, the time available for performing corrections is also kept low. This can result in strict boundary conditions being applied to the cost function. This can mean that the quality of the determined corrections can be reduced due to limitations on the range of corrections that can be performed.

[0111] In some embodiments, setup time can be provided as a degree of freedom. Increasing the setup time between exposures can be used as a tool to mitigate the boundary conditions imposed by the cost function. The decision on how much to increase the setup time and how much to increase it can be based on finding a balance between improving the correction performance and reducing the manufacturing volume by increasing the time between exposures. The benefit of improved correction can depend on the specific design and patterning requirements of the pattern to be exposed. Therefore, the advantage of increased available setup time can be evaluated individually for each pattern design. The overall benefit of the substrate layer can also be evaluated.

[0112] Although the quality of the exposed pattern can be considered on a continuous scale, a discrete pass / fail judgment can also be made on the exposed pattern quality, for example as a corresponding percentage between the exposed pattern and the design pattern. That is, the quality of the exposed pattern in the tube core of the field can either result in a valid product or part of the product (OK) or an invalid product or part of the product (NOK). This can also be expressed in terms of OK / NOK residuals, that is, an error is still allowed for whether the field is valid (OK) or invalid (NOK). The boundary between the OK residual value and the NOK residual value can be called a residual threshold. The residual threshold can represent an upper limit on the residual that results in a valid exposure patterned on the field. The decision on whether to increase the available preparation time can be based on whether it will result in an increase in the proportion of fields exposed with OK residuals and / or the size of the increase from NOK field exposures to OK field exposures.

[0113] Therefore, it is recommended to provide an interface that determines the highest permissible residual error in the exposed pattern in order to still achieve a good residual error when exposing the field. This maximum permissible residual error can be the same for all fields on a substrate, or it can be determined individually for each field. Based on the maximum permissible residual error, it can be evaluated whether an increased setup time should be applied.

[0114] In example embodiments, a layer on a substrate may be divided into multiple regions, where each region represents a separate product unit, also referred to as a die, on that layer. In many cases, an exposure field may include multiple regions (die). However, in some applications, a single product may be spread across multiple exposure fields stitched together, in which case a region may span multiple exposure fields. The same regional division may exist across at least some layers on the substrate. A product may include multiple regions across each of the multiple layers on the final patterned substrate.

[0115] Based on the increase in the number of areas within a field with OK residuals, a decision can be made whether to increase the setup time for the exposure field. This evaluation, based on the evaluation of OK / NOK areas rather than the field itself, can result in setup time decisions that provide a higher yield of OK products (die). This can allow for more realistic setup time decisions based on an increase in effective final product yield. For example, if some areas within a field have lower residual thresholds than other fields, it may be important to set the setup time based on the OK residual threshold for these areas. For example, due to stringent patterning requirements, some areas may have lower error tolerances. This may result in a higher setup time required for the exposure field containing these areas in order to pass the OK threshold. Besides regions, OK / NOK residual evaluations can also be performed on multiple layers on a substrate. For example, an evaluation can be performed on each layer on a finished substrate, with the decision on whether to increase the setup time based on the increase in OK final products achieved on the final exposed substrate. Determining the setup time based on the number of products passing the OK residual threshold can also be considered an assessment of the yield of the patterning process.

[0116] The amount of areas where OK residuals are achieved can be considered a key performance indicator for the lithographic patterning process. As an alternative or in addition to evaluating multiple areas across a single layer, the final product yield can be used. As described above, the yield can be evaluated for separate layers on a substrate (i.e., multiple areas in a single layer), or for multiple layers forming a final product (multiple areas in different layers forming part of the same final product). The allowed preparation time can be adjusted individually for the exposure of one or more layers on a substrate in order to increase the die yield in the layer and / or the total product yield on that substrate.

[0117] like Figure 6The following method depicted can be used to determine whether additional preparation time is allowed. In a first step 1300, residuals are calculated using the currently available preparation time. In a second step 1302, residuals are calculated for the increased preparation time. In a third step 1304, it can be evaluated whether the residuals obtained for the increased preparation time result in an increase in the OK residuals for field, regional and / or product performance. The increase (or lack thereof) in the OK residuals for field, regional and / or product performance for the increased preparation time compared to the current preparation time can be evaluated to determine whether the increased preparation time should be used. In some embodiments, the preparation time can be set to the increased preparation time 1306. In other embodiments, further testing can be performed by determining 1308 a different increase in preparation time and repeating steps 1302 and 1304 for a different increase in that time.

[0118] In an example embodiment, the first increased setup time selected in step 1302 may be the maximum allowable setup time. An iterative process may be used to test several setup times 1308 that are lower than the maximum allowable setup time. The effects of different setup times on OK residual performance may be compared to select a preferred increased setup time. This iterative process may be performed, for example, by gradually reducing the available setup time from the maximum allowable duration. This further evaluation may be used to find a minimum (optimal) setup time for which an increase in OK field, area, and / or product yield is achieved. A maximum allowable setup time may be determined based on a delay in the exposure process that is considered acceptable for the application.

[0119] As described above, an increase in setup time can result in a correction for the improvement in exposure being determined. Increased setup time can also be associated with a performance loss in the form of a reduced exposure amount performed within a given time. In addition, the increased setup time results in an increase in the time interval between the exposures of successive layers on the substrate. This may have an impact on the performance parameters of the exposure, such as the overlay accuracy between these layers. When known in advance, the increased setup time between different substrates does not affect the overlay accuracy. However, if the increase in setup time is not expected, the lithographic apparatus may have to unexpectedly (e.g., the position of the stage and the lens settings) delay the operation of the subsequent exposure. This may affect the overlay performance of the lithographic apparatus. The specific impact of the increased setup time on the different performance parameters of the patterned substrate may not always be known in detail.

[0120] The method of determining the optimal setup time may itself take time, during which the exposure may be further delayed if the exposure is performed using the computer system CL and / or lithographic equipment used for the exposure itself. This delay can be avoided by providing a model associated with the computer system CL and / or lithographic equipment LA, which can be used to calculate the setup time before the actual exposure is performed. The model can be based on data / knowledge of the lithographic equipment LA. The model can include a copy of the cost function. The model can include a digital copy of the lithographic equipment functionality for simulating the lithographic equipment. This can enable the model to determine how a specific setup time will affect the amount of field, area and / or product exposed with a residual below the OK threshold. Knowledge of the optimal setup time provided to the patterning process can be provided to the cost function and implemented during the exposure of the substrate. The boundary conditions implemented by the cost function can be modified to allow the cost function to determine corrections based on appropriate timing.

[0121] In some embodiments, the same setup time can be provided for exposure of each field and / or layer on a substrate. This can provide a similar level of cost function performance, so that the quality of the determined correction can be similar for different layers on a substrate. In some embodiments, different setup times can be provided for different fields and / or layers on a substrate. The different setup times can reflect different correction requirements for reaching an OK residual threshold for different layers.

[0122] When the preparation time is determined based on substrate yield, the yield can be determined based on the amount of work product on the final substrate or the amount of work product on the exposure fields and / or regions on one or more substrate layers. The yield threshold (that is, the minimum acceptable yield achieved based on the preparation time setting) can be the same for each field, region, and / or layer on the substrate. In other cases, different yield thresholds can be assigned to different fields, regions, and / or layers on the substrate. For example, this can be used to prioritize multiple regions on the substrate that include patterns that are considered to be of higher importance.

[0123] In an example scenario, the setup time required to implement control settings between the exposure of the first field and the exposure of the second field may fit comfortably within the available setup time determined for those exposures. However, the time required to implement control settings between the exposure of the second field and the exposure of the third field may exceed the available setup time. As a result, the third field can be exposed using the NOK residual. By determining separate setup times for the separate fields, a portion of the setup time not required for the exposure of the second field can be allocated to the exposure of the third field. This can improve the overall performance of the exposure on the substrate without increasing the total setup time.

[0124] The present disclosure will now discuss examples of actuators that can determine control data. The control data can relate to a lens in a lithographic apparatus and can be configured to apply determined corrections to improve control performance of the lens in the lithographic apparatus. The control data can be used to determine set values ​​for a plurality of lens manipulators, which are configured to apply deformations to the lens in order to control the lens. The set values ​​for the plurality of lens manipulators can also be referred to as control settings for the lens. The control data can relate to one or more corrections for errors in the lithographic exposure of one or more fields on a substrate. As described above, these corrections can be based on a model that links the pattern design to the settings of the selection scheme. A lens model can be used to convert the control data into set values ​​for the lens. The lens model can provide information for determining specific control settings for the actuator, that is, information about the lens manipulator that controls the lens.

[0125] In the following paragraphs, the conversion from model settings to dedicated control settings for the actuator is performed by means of a lens model that is separate from the cost function for determining the correction. However, in alternative embodiments, the functionality of the lens model can be incorporated into the cost function for determining the correction for the exposed pattern.

[0126] In an example embodiment of determining control data for a lithographic apparatus, the identified errors and the associated corrections to be applied to the patterned substrate may relate to parameters affected by the manipulation of a lens that controls the radiation performing the lithographic patterning process. Examples of substrate parameters (also referred to as performance parameters) that may be affected by the manipulation of a lens include overlay accuracy OVL, critical dimension CD (line thickness), alignment AL, leveling LVL, and edge positioning error EPE. Problems identified in the parameters may be associated with, for example, pattern shifts in the pattern, overlay accuracy errors, alignment errors, and / or focal length errors, or leveling problems on the substrate. It will be understood that these examples are not exhaustive, and other parameters and / or causes of errors may be used and identified. The identified errors described herein may also be referred to as residuals.

[0127] An optical assembly for controlling and manipulating radiation used to expose a pattern onto a substrate can include a plurality of optical elements, such as lenses, mirrors, and the like. The optical elements can have tunable properties that provide control over how the optical elements interact with the radiation. The optical assembly can, for example, include a lens with a plurality of lens manipulators. A lens manipulator can be a small element present within a lens that is capable of applying small corrections to the properties of the lens (e.g., distortion of the field image formed by the lens). The lens manipulator can control how radiation passing through the lens is manipulated by the lens. Settings (also referred to as setpoints) applied to a lens manipulator can determine how the lens manipulator changes the properties of the lens. A lens manipulator can change the properties of a lens by changing its position within the lens. Changes in the properties of the lens (as a result of adjusting the position of one or more lens manipulators) can, in turn, adjust how radiation passing through the lens is controlled. The setpoints can determine the position of the lens manipulator to achieve a desired optical effect in the lens.

[0128] In order to interpret the identified errors / corrections or determined desired setting values ​​for a lens, a lens model can be used. The lens model can receive as input a request for a correction, which is a correction of one or more errors identified for a lithographic exposure of a substrate. The lens model can output setting values ​​to be applied to the lens and / or lens manipulator based on the received input. The substrate can be divided into multiple exposure fields, also referred to as fields. Multiple fields on a substrate can be exposed separately during a lithographic exposure, for example, one after another. Separate exposure settings can be applied to separate fields. The lens can be used, for example, to continuously expose different fields on a substrate. Therefore, it can be said that an exposure field has a previous field and a subsequent field, with the previous field and the subsequent field being the field exposed before and after the field, respectively. The previous field and the subsequent field can also be referred to as the previous field and the subsequent field in a series of field exposures. The previous field and the subsequent field in a series can be adjacent fields on the substrate.

[0129] The request may provide different set values ​​for different fields to be exposed, so that different corrections may be applied to different fields. The lens model may receive as input a request relating to error correction for a plurality of fields to be exposed sequentially. The request for each field may be based on parameter data for that field. For example, each field on the substrate may comprise one or more measurement targets, which may be measured by the metrology tool MT to determine the characteristics of the pattern exposed on that field. The measurement targets may be, for example, measurement targets for overlay accuracy. The measurement data may be based on measurements of features other than the measurement targets, for example based on measurements of product features. Alternatively or additionally, the parameter data may comprise simulation data for one or more fields.

[0130] A lens model can be used during operation of a lithographic apparatus LA. Parameter data associated with one or more previous exposures performed by the apparatus can be provided to the lens model to update set values ​​and apply corrections identified based on the previous exposures. To avoid delays in the lithographic exposure process, it may be desirable to limit the amount of computational time required by the model. Therefore, the lens model may have certain constraints applied to it to reduce its computational cost. This may also result in suboptimal performance of the lens model and / or make the lens model less flexible or adaptable. For example, the lens model may be designed to calculate settings for fields on a substrate without considering the set values ​​for previous and / or subsequent fields exposed using the lens. The lens model may also assume that all fields on a substrate have the same shape, such as a rectangle. As a result, the lens model may be designed to receive requests for fields having a rectangular or other predetermined shape and may be unable to handle inputs having different shapes. This may cause problems for fields at the edge of the substrate, which are typically non-rectangular due to the generally circular shape of the substrate.

[0131] To provide a lens model with a request for the substrate's fringe field, metrology data may be used for only a portion of the desired field shape. The portion of the substrate's fringe field occupied by the substrate may be referred to as the local field. Extrapolation of parameter data available for the portion of the desired field shape not filled by the substrate may be used to create a request to fit the field to the desired shape (e.g., a rectangular shape). The extrapolation may be, for example, a polynomial extrapolation, where the extrapolation is based on the metrology data as input.

[0132] Receiving as input a request for extrapolation of the fringe field, the lens model can determine the setpoints for the field to be applied by the lens to expose the substrate. Because the extrapolated portion of the field does not correspond to substrate exposure, it represents a virtual portion of the request. Therefore, since the virtual portion does not correspond to the field on the substrate, the quality of the correction applied to it by the setpoints is irrelevant. However, a lens model designed to be computationally faster can be designed to process each input field in the same manner. As a result, the lens model can treat each input as part of the same request.

[0133] The lens model may not be able to distinguish between the virtual part of the request and the part of the request that represents the local field. The lens model will treat the virtual part and the local field part of the request as the same. The lens model will give equal values ​​to the local field part and the virtual part of the request. The set value may not fully conform to the correction contained in the request. The lens model can try to find the best fit to the entire request, thereby fitting to both the local field and the virtual part of the request. However, fitting to the virtual part of the request does not provide any real benefit to the quality of the correction applied by the set value. Fitting to the extrapolated field may even result in a set value that results in an exposure with worse error than before the correction was applied. The methods and apparatus described herein are intended to provide improved requests to the lens model to determine the set value for the lens.

[0134] Figure 7 A flow chart is depicted including steps in a method for determining input to a lens model. The input can be determined as a request provided to the lens model. The lens model can determine setpoints for manipulating a lens of a lithographic apparatus for at least one of a plurality of fields of a substrate. The methods described herein can be performed by one or more processors executing a sequence of instructions stored in a storage medium. The processors can be provided separately from the lithographic apparatus LA and / or the metrology tool MT.

[0135] In step 400, parameter data for at least one field on a substrate is received. The parameter data relates to one or more parameters of the substrate within the at least one field. The one or more parameters may be at least partially sensitive to manipulation of the lens as part of an exposure performed by the lithographic apparatus. In step 402, the method receives lens model data associated with the lens. The lens model data may include a copy of the lens model and / or may include other data characterizing the lens model. In step 404, the method determines a request based on the received parameter data and the lens model data. Once determined, the request may be provided as input to the lens model. The lens model may then determine set values ​​based on the received request. The lens model may determine set values ​​for each field. The set values ​​may be applied to the lithographic apparatus LA for lithographic exposure to pattern a structure on the substrate. The structure to be patterned may have the same intended design as the structure for which the parameter data was received.

[0136] like Figure 7An advantage of the described method may be that the input may be determined taking into account details of the lens model. The input may be determined at least in part by a cost function, wherein the lens model may form part of the control characteristic on which the cost function is based. The request to be input may be determined offline, that is, separately from the lithographic apparatus and the lens model. An advantage of determining the input offline, for example using one or more offline calculations, may be that more computing time is available, thereby allowing the use of more time-consuming (e.g., complex) calculations to be used to determine the input. This may improve the quality of the final input. The request may, for example, be determined to optimize the set value based on features of the lens model. The lens model data may, for example, be used to determine an extrapolation that results in the determination of the set value providing a good fit of the local field to the extrapolation. The lens model data may alternatively or additionally be used to take into account the set values ​​of one or more previous and / or subsequent fields exposed before and / or after the field. The manner in which the request may be optimized based on a combination of metrology data and lens model data will be explained in more detail below.

[0137] The parameter data may include one or both of metrology data and simulation data. Parameter data may be obtained for one or more previously lithographically patterned substrates. The parameter data may include data identifying errors in parameters of structures patterned within at least one field using the lithographic apparatus. The parameter data may, for example, include a fingerprint of one or more parameters, wherein the fingerprint may include data associated with one or more of pattern offset, overlay error, alignment error, and / or focus error.

[0138] The at least one field may comprise a local field. Figure 8 As depicted, the local fields may be fringe fields on the substrate. Figure 8 (a) shows a portion of a substrate 100, indicating multiple fields. These fields can all be of the same size. The image depicts a fringe field 102, where the fringe field is only partially filled by the substrate 100. An interior field 104 is also shown, where the substrate 100 covers the entire field. In the fringe field, parameter data can be provided at positions 106 covered by the substrate. No parameter data is available for positions 108 in the portion of the field not covered by the substrate 100. However, the lens model may expect requests to provide input for these points. An extrapolation can be determined to provide values ​​for positions 108 in the portion of the fringe field 102 not covered by the substrate 100. Figure 8(b) shows a schematic diagram of extrapolated data based on parameter data. The extrapolated data can be used to create a request 112, which can be referred to as an extrapolation request 112. Each extrapolation request 112 can be in a desired format to be input into the lens model. Each extrapolation request includes parameter data 116 that can be used for a local field covered by the substrate. The request 112 also describes a plurality of different possible extrapolations 118a, 118b for locations not covered by the substrate 100. The extrapolations 118a, 118b can be based on the parameter data 116. The parameter data 116 can include parameter data related to the location within the local field, such as measurement data. The determination request can include an optimization request to apply corrections to one or more parameters. The correction can be identified by the parameter data related to the location within the local field. The correction can be a correction for an error identified in the parameter data. This can, for example, involve determining which of the plurality of possible extrapolations 118a, 118b provides the best set value fit to perform the correction at the location 106 of the local field.

[0139] The step of optimizing the request may be performed using a first lens model based on the lens model data. The first lens model may include a cost function as described above. Figure 9 A schematic representation of steps in a method for determining setpoints 120 for manipulating a lens and entities performing these steps is depicted. A metrology tool MT and / or a simulation tool 600 may provide parameter data 116 related to one or more parameters of a substrate. The parameter data may be provided to a first lens model 602. The first lens model 602 may be determined based on the lens model data. The first lens model data may also be determined based on knowledge of the lithographic apparatus LA. The first lens model 602 may determine setpoints. The first lens model 602 may optimize the setpoints within a local field. To optimize the setpoints within the local field, the first lens model 602 may determine initial setpoints based on the parameter data 116. The initial setpoints may be determined for the portion of the field covered by the local field. The first lens model 602 may then evaluate the initial setpoints and determine a setpoint across the entire field. The setpoint for the entire field may include the initial setpoint for the local field. The first lens model 602 may also determine a request 112 corresponding to the determined setpoints. Because extrapolation is applied to obtain the requested extrapolated data 118, the request 112 may also be referred to as an extrapolation request. Due to the optimization steps applied by the first lens model 602 to determine the request, the request 112 may also be referred to as an optimization request or an optimization extrapolation request. The request 112 may be provided as input to a lens model 604 of the lithographic apparatus LA. The lens model may determine settings 120 for manipulating the lens. The determined settings 120 may be provided and implemented to the lens of the lithographic apparatus LA. Figure 9A comparison of corrections obtained by applying setpoints 120 and requests 112 is shown. The quality of request 112 can affect the extent to which the corrections applied by setpoints 120 resolve errors identified by parameter data 116. The quality of the fit of setpoints 120 to the request can also affect the extent to which the corrections applied by setpoints 120 resolve errors identified by parameter data 116.

[0140] The first lens model 602 can be based on lens model data. The first lens model can combine the lens model data with the parameter data 116 to determine the extrapolation request 112. The first lens model 602 can include a copy of the lens model. The first lens model can alternatively or additionally use knowledge of the structure and / or function of the lens model provided by the lens model data to determine or estimate the impact of the lens model on the request. The first lens model 602 can be applied offline, that is, separately from the operation of the lithography apparatus LA and the manipulation of the lens. For example, the first lens model can be used to determine the request before starting a lithography exposure. This can provide the first lens model 602 with additional computation time to determine the set values ​​compared to the case where the lens model 604 receives and processes inputs during the lithography exposure. This allows the first lens model 602 to be more computationally complex than the lens model 604.

[0141] Figure 10 An example first lens model 702 that can be based on a brute-force approach is depicted. The first lens model 702 can determine a plurality of extrapolation requests 710 based on parameter data 116 for a local field 102. The extrapolation can cover portions of the field outside the local field. The plurality of extrapolation requests 710 can be referred to as temporary inputs or temporary requests. The lens model data can include a copy 720 of the lens model. Each of the determined temporary requests 710 can be provided as an input to the copy 720 of the lens model. The copy 720 of the lens model can determine a setting value for each of the extrapolation requests 710. The first lens model 702 can then determine a preferred setting value from the plurality of determined setting values. Determining the preferred setting value can, for example, include determining a setting value that most accurately implements a correction in the local field covered by the substrate 100. A temporary request can be selected that applies a correction that is closest to the correction identified in the parameter data 116. The temporary request that provides the preferred setting value can be selected as an optimization request 730. The optimization request 730 can be provided to a lens model of the lithographic apparatus LA. Determining the preferred setting values ​​may also take into account the impact of the setting value associated with each temporary request on subsequent fields to be exposed.

[0142] Figure 11A second example implementation of the steps performed by a first lens model 802 is depicted. The first lens model can include a local field aware lens model 820 for determining set values ​​based on a fringe field. The local field aware model 820 can be based on a lens model. The local field aware lens model 820 can not need to consider optimizing portions of the field outside of the substrate. The local field aware model 820 can receive an input having a local field shape 810, e.g., having less parameter data 116. The local field aware model 820 can determine set values ​​830 for the lens based on the local field input 810 without extrapolating the data to the remainder of the field. An advantage of this approach is that the determined set values ​​830 can be optimized for the local field.

[0143] The determined set value 830 can be based on parameter data 116 rather than on extrapolated data. The set value 830 is not fitted as an extrapolated value in a virtual portion of the field. The first lens model 802 can further evaluate 840 the optical impact of the requested set value value on the full field outside the local field, the requested set value value being the result of optimizing the request for the local field covering the substrate. The set value for the full field can be used to determine a corresponding request in an appropriate format to be input to the lens model. This can involve evaluating the impact of the set value 830 on the full field and using the resulting impact as a request for input to the lens model. The first lens model 802 can determine this as an extrapolated request 850, which, when input to the lens model, outputs a set value that matches the optimized set value 830 determined by the local field-aware model 820. In some cases, the extrapolated request 850 can result in an output that matches the optimized set value 830. In other cases, the extrapolated request 850 can result in an output that is very similar to the optimized set value 830. The determined extrapolation request 850 may be provided as input to a lens model of the lithographic apparatus LA. The local field aware lens model 820 may use information about the exposure path of the field on the substrate. This information may be provided as part of the lens model data.

[0144] Multiple setpoints for lens manipulation can be determined for multiple fields. A different setpoint can be determined for each field on the substrate. Fields can be exposed sequentially by the lithographic apparatus. Successive fields can be exposed in rapid succession, which limits the time available for adjusting setpoints between exposures. Furthermore, the dynamics of lens manipulation may be limited. For example, the speed and range of movement of the lens manipulator across the lens may be limited. As a result, large changes between consecutive setpoints may not be possible. Information about the dynamics of the lens can be provided as part of the lens model data. This information is also referred to as dynamic data. The cost function can use this dynamic data to set boundary conditions. These boundary conditions can represent limitations on the types of corrections that can be applied by the lens. If the variation between two or more adjacent setpoints is large, the accuracy of the setpoints applied by the lens can be reduced. This, in turn, can reduce the accuracy of the corrections applied by lens manipulation, which can adversely affect the quality of the resulting pattern. To address this challenge, a request determined for one field can take into account requests determined for one or more adjacent fields.

[0145] Figure 12 A schematic diagram of a portion of a substrate 100 is depicted. The portion includes a plurality of fringe fields 102 and an internal field 104. The arrows indicate the order in which the fields are programmed to be exposed by the lithographic apparatus LA (alphabetical order from a to f). For each field, a set value is determined. The determined set value is Figure 12 If the set values ​​for different fields are determined independently of each other, they can vary greatly. Figure 12 As shown, the set point determined for the fringe field 102 is very different from the set point determined for the interior field 104. A system for steering a lens may not be able to apply such strong variations to a continuous field.

[0146] In order to resolve the potential problem of successive set values ​​being incompatible with each other, the set values ​​for a first field may be based on the set values ​​for one or more second fields. The one or more second fields may be adjacent fields. Adjacent fields may be fields that are programmed to be exposed before and / or after a field. Adjacent fields may be fields that are adjacent to each other. The lens model data may include data that allows the set values ​​of adjacent fields to be taken into account. The lens model data may, for example, include dynamic data for the lens. The dynamic data may include information about the speed and range of changes in manipulation that may be applied. This may, for example, include the speed at which a lens manipulator may move. The dynamic data of the lens may be used to determine whether multiple set values ​​for multiple fields may be successfully applied to the lens. If one or more changes between consecutive set values ​​are not suitable for implementation by the lens, one or more of the set values ​​may be adjusted. In Figure 12 In , the adjusted setpoints are depicted as dashed lines. For example, in Figure 12In FIG. 1 , the setpoints of the fringe fields 102 (fields c and d) can be adjusted to have smaller variations than the preceding field b and the following field e. The inner fields b and e can also be adjusted to accommodate the larger setpoint variations at the fringe fields c and d.

[0147] Figure 13 A schematic representation of steps in a method for determining inputs to a lens model is depicted, wherein set values ​​for a field can be determined based on set values ​​for one or more other fields. A first lens model 1002 can be provided to determine inputs to a lens model 1004. The first lens model can use a first module 1020 to determine set values ​​1030 for one or more interior fields 104. The lens model can use at least a portion of its available lens model data to determine the set values ​​1030 for the one or more interior fields 104. The lens model can then provide the determined set values ​​1030 to a second module 1040. The second module can use at least a portion of the lens model data and the determined set values ​​1030 for the one or more interior fields to determine set values ​​for one or more fringe fields 102. Based on the lens model data and the set values ​​for the interior fields 104, the second module can determine set values ​​for the fringe fields 102 that may be applied to the lens. The set values ​​1050 for the interior fields 104 and the fringe fields can be provided to the lens model 1004 for application during lithography of the lithographic apparatus LA.

[0148] The first lens model 1002 can be provided with information regarding the importance of the fields relative to one another. For example, a local field can have a lower importance than a full field. This may be because the full field has more available area and can therefore contain more patterned product features. The importance can be assigned based on the design of the pattern to be exposed on the substrate 100. The importance can, for example, correspond to the number of structures to be patterned in the field. The importance can also or alternatively correspond to the size of at least a portion of the structure to be patterned in the field. For example, due to more stringent patterning requirements for exposing structures with smaller critical dimensions, structures with smaller critical dimensions can be assigned greater importance.

[0149] The field can be divided into several fields, where different fields can have different importance assigned to them. The first lens model can use relative importance to determine the set values ​​in the fields. For example, the first field in the field can be assigned a higher importance relative to the second field in the field. For example, a region in the field of the design including structures with smaller dimensions can be assigned a higher importance than a region including structures with larger dimensions. The first lens model 1002 can prioritize the set values ​​of the first field over the second field.

[0150] The importance of fields and / or regions within a field on a substrate relative to each other can be provided to the first lens model 1002 as part of the parameter data 116. The first lens model can use the information about the relative importance of the fields to determine set values. The first lens model 1002 can, for example, determine initial set values ​​for a plurality of fields. The first lens model 1002 can then use the lens model data to determine whether changes between successive fields can be applied to the lens. If lens manipulation cannot reliably apply the initially determined changes, the first lens model can use this information to determine one or more adjustments to the initial set values. The adjustments can take into account the relative importance of the fields and / or regions within the fields.

[0151] In an example embodiment, a first lens model can be used to determine, in a first step, a plurality of set values ​​for a plurality of fields. In another step, using the plurality of set values ​​and dynamic data associated with lens model manipulation, the first lens model can determine whether manipulation of the lens can apply a change between successive set values. The first lens model can then determine one or more adjustments to the set values ​​to provide updated set values. The updated set values ​​can be provided as input to the lens model.

[0152] As described herein, the first lens model can be used to optimize inputs to be provided to the lens model for manipulating the lens. The functionality of the first lens models 602, 702, 802, 1002 described herein can be combined. For example, the first lens model can use extrapolation for a local field to determine inputs covering the entire field, and can also use adjacent fields to determine and / or adjust set values ​​for the field. The exemplary method described herein may include: determining inputs to the lens model for one or more of the entire fields based on parameter data for the entire field. The method can then determine inputs to the lens model or one or more local fields, for example using the extrapolation method described above. In order to determine the inputs for the local fields, the inputs for the entire field can be used as constraints.

[0153] The parameter data may relate to errors in the pattern exposed on the substrate. The parameter data may include information directly indicative of the errors. Alternatively or additionally, the errors may be determined based on the metrology data. This may be achieved, for example, by comparing the metrology data with expected values ​​for the patterned structure without errors.

[0154] One or more parameters may include overlay accuracy OVL. The method may provide parameter data for a plurality of parameters, including, for example, overlay accuracy OVL, alignment AL, leveling data LVL, edge position error data EPE, data related to focal length, and the like. The parameter data may include measurement data. The measurement data may be obtained by different measurement tools MT. The measurement data may be obtained for a structure patterned by the same lithography apparatus LA as the lithography apparatus for which the lens model request is determined. The parameter data may alternatively or additionally include simulation data related to a pattern exposed on a substrate. The simulation data may be based on measurement data. The parameter data may relate to previous iterations of lithographic exposure of the same pattern as the pattern for which the lens model request is determined. This may allow the exposure process to be updated based on data related to one or more previous iterations of the same exposure process. The parameter data may be associated with one or more of pattern offset, overlay accuracy error, alignment aberration, and / or focal length error.

[0155] The lens model data may include information about the lens model. The lens model data may include a copy of the lens model. The lens model data may include dynamic data about the lens. The dynamic data about the lens model may include information about how the performance of the lens changes based on adjustments to settings for the lens. This information may include information about, for example, the speed at which the settings can be adjusted or the exposure time.

[0156] Additional embodiments are disclosed in the following list of numbered clauses:

[0157] 1. A method for determining control data of a lithographic apparatus, the method comprising:

[0158] receiving parametric data associated with a plurality of fields of a substrate;

[0159] providing parameter data as input to the cost function;

[0160] evaluating a cost function extending across the plurality of fields, wherein the cost function is based on control characteristics of the lithographic apparatus, the cost function providing an output comprising a correction configured to reduce a residual of a performance parameter across the plurality of fields of the substrate;

[0161] Based on the output, control data is determined.

[0162] 2. The method of clause 1, wherein the control characteristics of the lithographic apparatus include one or more boundary conditions for the correction.

[0163] 3. A method according to any of the preceding clauses, wherein the cost function determines the control data to minimize the residual of the performance parameter across the plurality of fields.

[0164] 4. The method of any of the preceding clauses, wherein the correction comprises an actuator control setting for at least one actuator of the lithographic apparatus.

[0165] 5. A method according to any of the preceding clauses, wherein the control data comprises a routing sequence for exposure of the plurality of fields.

[0166] 6. The method of clause 5, wherein the output comprises a route sequence of exposures for a plurality of fields.

[0167] 7. A method according to any preceding clause, when dependent on clause 2, further comprising determining a preparation time to be provided to the lithographic apparatus for implementing the control data, wherein the boundary conditions are determined at least in part based on the preparation time.

[0168] 8. The method of clause 7, wherein determining the preparation time comprises

[0169] determining a residual of a performance parameter of a first preparation time for one or more fields;

[0170] determining a residual of a performance parameter for a second preparation time for the one or more fields, wherein the second preparation time is longer than the first preparation time;

[0171] Based on a comparison of the residual for the first setup time and the residual for the second setup time with a threshold residual value, one of the first setup time and the second setup time is selected as the setup time to be provided to the lithographic apparatus.

[0172] 9. The method of clause 8, wherein the threshold residual value represents an upper limit on the residual that results in a valid field.

[0173] 10. A method for determining input to a lens model to determine setpoints for manipulation of a lens of a lithographic apparatus when addressing at least one of a plurality of fields of a substrate, the method comprising:

[0174] receiving parameter data for at least one field, the parameter data relating to one or more parameters of the substrate within the at least one field, the one or more parameters being sensitive, at least in part, to manipulation of a lens as part of an exposure performed by the lithographic apparatus;

[0175] receiving lens model data associated with the lens;

[0176] Inputs are determined based on the parameter data and the lens model data.

[0177] 11. The method of clause 10, wherein the at least one field comprises a local field and the parameter data comprises parameter data relating to a location within the local field;

[0178] And wherein determining the input comprises optimizing the input to apply a correction to one or more parameters, wherein the correction is identified by the parameter data associated with a location within the local field.

[0179] 12. The method of claim 11, wherein optimizing the input comprises:

[0180] determining an initial setting value within the local field based on a first lens model, wherein the first lens model is based on the lens model data; and

[0181] The initial set point is evaluated to determine a set point across the portion of the full field outside of the local field to determine a target set point.

[0182] 13. The method of clause 12, wherein the first lens model is further configured to determine an input corresponding to a target setpoint.

[0183] 14. A method according to any of clauses 12 or 13, wherein the first lens model is a local field aware lens model configured not to optimize input for positions outside the local field.

[0184] 15. The method of any one of clauses 11 to 14, wherein optimizing the input comprises:

[0185] determining a plurality of temporary inputs based on the parameter data; and

[0186] Based on the lens model data, one of the plurality of temporary inputs is selected.

[0187] 16. The method of clause 15, wherein determining one or more provisional inputs of the plurality of provisional inputs comprises extrapolating parameter data outside the local field based on parameter data inside the local field.

[0188] 17. A method according to clause 15 or 16, wherein selecting one of the plurality of provisional inputs comprises applying a provisional input that is a correction to the parameter that is closest to the correction identified from the parameter data.

[0189] 18. The method of clause 17, wherein the correction is to errors identified in the parameter data.

[0190] 19. A method according to any of clauses 10-18, wherein the lens model data comprises a copy of the lens model.

[0191] 20. A method according to any of clauses 10-19, wherein the lens model data comprises dynamic data for the lens.

[0192] 21. A method as recited in any of clauses 10-20, wherein determining the input comprises determining the input for the first field based on the input for the second field.

[0193] 22. The method of clause 21, wherein the first field is a partial field and the second field is a full field.

[0194] 23. The method of clause 22, wherein the local field is adjacent to the full field.

[0195] 24. A method according to any of clauses 21 to 23, wherein the input is further determined based on dynamic data for the lens and / or the importance of the local field and / or the full field.

[0196] 25. The method of clause 24, wherein the importance of the global field is greater than the importance of the local field.

[0197] 26. The method according to clause 20 or 21, wherein the importance of the local field and / or the overall field is based on the number of structures to be patterned in the field and / or the size of at least a part of the structures to be patterned in the field.

[0198] 27. A method according to any of clauses 22 to 26, wherein determining the input comprises optimizing the input to apply corrections to parameters across the field.

[0199] 28. A method according to clause 27, wherein the parameter data comprises local field parameter data and global field parameter data, and wherein the optimization input comprises:

[0200] Determining input for the entire field based on the entire field parameter data; and

[0201] Based on the local field parameter data, inputs for the local field are determined and inputs for the full field are used as constraints.

[0202] 29. A method according to any of clauses 10-28, wherein the parametric data comprises metrological data.

[0203] 30. The method of any of clauses 10-29, wherein the manipulation of the lens comprises setting a position of one or more lens manipulators, wherein the lens manipulators are configured to apply a deformation to the lens.

[0204] 31. The method of any of clauses 10-30, wherein the one or more parameters include one or more of overlay accuracy data, critical dimension data, leveling data, alignment data, or edge position error data.

[0205] 32. The method of clause 31, wherein the parametric data is associated with one or more of pattern offset, overlay accuracy, alignment aberration, or focus error.

[0206] 33. The method according to any one of clauses 10-32, further comprising:

[0207] providing input to a lens model; and

[0208] Based on the lens model, set values ​​for manipulation of the lens are determined.

[0209] 34. The method according to clause 33, further comprising:

[0210] Provides setpoints to the lens,

[0211] The lithographic apparatus is configured to perform lithographic exposure of the substrate using the provided lens setting values.

[0212] 35. An apparatus for determining control data for a lithographic apparatus, the apparatus comprising one or more processors configured to perform the method according to any of clauses 1-9.

[0213] 36. An apparatus for configuring an input to a lens model to determine one or more settings for a lens of a lithographic apparatus, the apparatus comprising one or more processors configured to perform a method according to any one of clauses 10 to 34.

[0214] 37. A lithographic apparatus comprising an apparatus according to clause 35 or 36.

[0215] 38. A lithocell comprising an apparatus according to clause 37.

[0216] 39. A computer program product comprising computer readable instructions configured to perform the method according to any of clauses 1 to 34 when run on a suitable computer system.

[0217] Although specific reference may be made herein to the use of lithographic apparatus in IC manufacturing, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0218] Although specific reference may be made herein to embodiments in the context of lithographic apparatus, embodiments may be used in other apparatus. Embodiments may form part of mask inspection equipment, metrology equipment, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses may generally be referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0219] Although specific reference may be made herein to embodiments in the context of inspection or metrology equipment, embodiments may be used in other equipment. Embodiments may form part of mask inspection equipment, lithographic equipment, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). The term "metrology equipment" (or "inspection equipment") may also refer to an inspection equipment or an inspection system (or metrology equipment or metrology system). For example, an inspection apparatus including an embodiment may be used to detect defects in a substrate or defects in a structure on a substrate. In such embodiments, the characteristic of interest of a structure on a substrate may relate to a defect in the structure, the absence of a particular portion of the structure, or the presence of an unwanted structure on the substrate.

[0220] Although specific reference has been made above to the use of the embodiments in the context of optical lithography, it will be appreciated that the invention is not limited to optical lithography and may be used in other applications, such as imprint lithography, where the context permits.

[0221] While the targets or target structures described above (more generally, structures on the substrate) are metrology target structures that are specifically designed and formed for measurement purposes, in other embodiments, the characteristic of interest may be measured on one or more structures that are functional components of a device formed on the substrate. Many devices have a regular grating-like structure. The terms structure, target grating, and target structure as used herein do not require that the structure be provided specifically for the measurement being made. Furthermore, the pitch of the metrology target may be close to the resolution limit of the optical system of the scatterometer, or may be smaller, but may be much larger than the size of typical non-target structures, which are optionally product structures made by a photolithographic process in the target portion C. In practice, the lines and / or spaces of the overlaid grating within the target structure may be made to include smaller structures of similar size to the non-target structures.

[0222] Although specific embodiments have been described above, it will be appreciated that the present invention may be implemented in other ways than those described. The foregoing description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

[0223] Although specific reference is made to a "metrology device / tool / system" or an "inspection device / tool / system," these terms may refer to the same or similar types of tools, devices, or systems. For example, an inspection or metrology device including embodiments of the present invention may be used to determine characteristics of a structure on a substrate or on a wafer. For example, an inspection device or metrology device including embodiments of the present invention may be used to detect defects in a substrate or defects in a structure on a substrate or on a wafer. In such embodiments, the characteristic of interest of a structure on a substrate may relate to a defect in the structure, the absence of a particular portion of the structure, or the presence of an unwanted structure on the substrate or on the wafer.

[0224] Although specific reference is made to SXR and EUV electromagnetic radiation, it will be appreciated that the present invention may be practiced with all electromagnetic radiation, including radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays, where the context permits. As an alternative to optical metrology methods, the use of X-rays, optionally hard X-rays, for example radiation having a wavelength in the range of between 0.01 nm and 10 nm, or alternatively between 0.01 nm and 0.2 nm, or alternatively between 0.1 nm and 0.2 nm, is also contemplated for metrology measurements.

Claims

1. A method for determining inputs to a lens model for determining setpoints for manipulation of a lens of a lithographic apparatus when addressing at least one of a plurality of fields of a substrate, the method comprising: receiving parameter data for the at least one field, the parameter data relating to one or more parameters of the substrate within the at least one field, the one or more parameters being at least partially sensitive to manipulation of the lens as part of an exposure performed by the lithographic apparatus; receiving lens model data associated with the lens; The input is determined based on the parameter data and the lens model data.

2. The method of claim 1 , wherein the at least one field comprises a local field, and the parametric data comprises parametric data relating to a location within the local field; and wherein determining the input comprises: The input is optimized to apply corrections to the one or more parameters, wherein the corrections are identified by the parameter data associated with the location within the local field.

3. The method of claim 2, wherein optimizing the input comprises: determining an initial setting value within the local field based on a first lens model, wherein the first lens model is based on the lens model data; as well as The initial set point is evaluated to determine a set point across the full field for a portion outside of the local field to determine a target set point. The method of claim 3 , wherein the first lens model is further configured to determine an input corresponding to the target setting value.

5. The method of claim 3, wherein the first lens model is a local field-aware lens model configured to not optimize the input for positions outside the local field.

6. The method of claim 2, wherein optimizing the input comprises: determining a plurality of temporary inputs based on the parameter data; as well as Based on the lens model data, one of the plurality of temporary inputs is selected.

7. The method of claim 6, wherein determining one or more of the plurality of provisional inputs comprises: Parameter data outside the local field is extrapolated based on the parameter data within the local field.

8. The method of claim 6, wherein selecting one of the plurality of temporary inputs comprises selecting a temporary input that applies a correction to the parameter that is closest to a correction identified from the parameter data.

9. The method of claim 8, wherein the correction is a correction of an error identified in the parameter data.

10. The method of claim 1 , wherein determining the input comprises: An input for a first field is determined based on an input for a second field, wherein the first field is a partial field and the second field is a full field.

11. The method of claim 10, wherein determining the input comprises: The input is optimized to apply corrections to parameters in the full field.

12. The method of claim 1, wherein the one or more parameters include one or more of overlay accuracy data, critical dimension data, leveling data, alignment data, or edge position error data.

13. An apparatus for configuring input to a lens model to determine one or more settings for a lens of a lithographic apparatus, the apparatus comprising one or more processors configured to perform the method of claim 1.

14. A lithographic apparatus comprising the apparatus according to claim 13.

15. A computer program product comprising computer readable instructions configured to perform the method according to claim 1 when executed on a suitable computer system.

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