Method of determining operational data, computer program and lithographic apparatus

Abstract

Disclosed herein is a computer system configured to perform a method of determining operational data for a control system of a lithographic apparatus, the method comprising: determining initial operational data for use in performing exposure processes on a substrate; repeatedly changing the initial operational data and determining one or more performance metrics of the changed operational data so as to determine changes to the initial operational data that improve the one or more performance metrics; and using operational data with an applied change so as to improve one or more of the performance metrics; wherein: the operational data includes the route of the substrate for performing the exposure processes and the movement of the substrate along the route; and the applied change to the operational data includes a change to the route and / or a change to the acceleration of the substrate along part of the route.

Description

METHOD OF DETERMINING OPERATIONAL DATA, COMPUTER PROGRAM ANDLITHOGRAPHIC APPARATUSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 24152597.1 which was filed on 18 January 2024 and of EP application 24173146.2 which was filed on 29 April 2024 and of EP 24178480.0 which was filed on 28 May 2024 and of EP application 24199612.3 which was filed on 10 September 2024 and which are incorporated herein in their entirety by reference.FIELD

[0002] The present invention relates to a method of determining operational data for controlling substrate movements during exposure processes. For a given detectivity performance, embodiments include using a model to determine changes to operational data so as to increase throughput. Embodiments also include using the model to determine changes to operational data so as to improve the detectivity performance.BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as “design layout” or “design”) of a patterning device (e.g., a mask) onto a layer of radiation- sensitive material (resist) provided on a substrate (e.g., a wafer). Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the "scanning" -direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as ‘Moore’s law’. To keep up with Moore’s law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm.

[0005] Further improvements in the resolution of smaller features may be achieved by providing an immersion liquid having a relatively high refractive index, such as water, on the substrate during exposure. The effect of the immersion liquid is to enable imaging of smaller features since theexposure radiation will have a shorter wavelength in the liquid than in gas. The effect of the immersion liquid may also be regarded as increasing the effective numerical aperture (NA) of the system and also increasing the depth of focus.

[0006] The immersion liquid may be confined to a localized area between the projection system of the lithographic apparatus and the substrate by a fluid handling structure.

[0007] There is a general need to improve lithographic processes.SUMMARY

[0008] In an immersion lithography process, defects in printed patterns can occur due to the presence of bubbles of gas in the immersion liquid and / or droplets of immersion liquid that are left on the surface of the substrate. Many approaches to minimising the creation of such bubbles and droplets and to ameliorate their effects have been proposed, for example: providing a CO2 environment adjacent the immersion liquid; special coatings on the substrate and substrate support; extracting gas and liquid from a gap between the edge of the substrate and the substrate support; and varying scanning routes and speeds. However, it has not so far been possible to completely eliminate the occurrence of bubbles and droplets and the defects that they cause.

[0009] In many cases, the rate of defects can be reduced (increasing yield) by slowing down scanning speeds or other recipe modifications that come at the cost of reducing the throughput of the lithographic process.

[0010] Embodiments provide techniques for increasing the achievable throughput given the rate of defects that can be tolerated. Embodiments also provide techniques for decreasing the rate of defects without substantially reducing throughput.

[0011] According to a first aspect of the present invention, there is provided a computer system configured to perform a method of determining operational data for a control system of a lithographic apparatus, the method comprising: determining initial operational data for use in performing exposure processes on a substrate; repeatedly changing the initial operational data and determining one or more performance metrics of the changed operational data so as to determine changes to the initial operational data that improve the one or more performance metrics; and using operational data with an applied change so as to improve one or more of the performance metrics; wherein: the operational data includes the route of the substrate for performing the exposure processes and the movement of the substrate along the route; the one or more performance metrics include the overall time required for the exposure processes, the detectivity rate of the exposure processes and / or the sustainability of the exposure processes; and the applied change to the operational data includes a change to the route and / or a change to the acceleration of the substrate along part of the route.

[0012] According to a second aspect of the present invention, there is provided a method of determining operational data for controlling a lithographic apparatus, the method comprising: determining initial operational data for use in performing exposure processes on a substrate;repeatedly changing the initial operational data and determining one or more performance metrics of the changed operational data so as to determine changes to the initial operational data that improve the one or more performance metrics; and using operational data with an applied change so as to improve one or more of the performance metrics; wherein: the operational data includes the route of the substrate for performing the exposure processes and the movement of the substrate along the route; the one or more performance metrics include the overall time required for the exposure processes, the defectivity rate of the exposure processes and / or the sustainability of the exposure processes; and the applied change to the operational data includes a change to the route and / or a change to the acceleration of the substrate along part of the route.

[0013] According to a third aspect of the present invention, there is provided a method to improve operational data that is a recipe for an exposure process, comprising: providing the recipe for exposing a substrate in the exposure process; based on the recipe, determining a first motion plan with a first duration taking the least exposure time in the exposure process, the first motion plan containing a plurality of movements along neighbouring regions over a first portion of the substrate; determining a set of locations on the substrate having a risk of defect in the exposure process according to the first motion plan; based on the set of locations, determining a second motion plan with a second duration to reduce the risk of defect in the exposure process, the second motion plan containing at least one movement along at least two spaced apart regions over a second portion of the substrate and the second duration longer than the first duration; calculating time difference between the first duration and the second duration; and based on the time difference, modifying the timing of the second motion plan of the exposure process to minimise the time difference such that the exposure process according to the second motion plan completes at substantially the same time as that according to the first motion plan.

[0014] According to a fourth aspect of the present invention, there is provided a method of manufacturing devices using an immersion lithographic apparatus, the method comprising performing exposure processes in dependence on operational data determined according to any of the second and third aspects.

[0015] According to a fifth aspect of the present invention, there is provided a computer program comprising computer interpretable code that, when executed by a control system of an immersion lithographic apparatus, causes the immersion lithographic apparatus to perform exposure processes in dependence on operational data determined according to any one of the second and third aspects.

[0016] According to a sixth aspect of the present invention, there is provided an immersion lithographic apparatus comprising: a liquid confinement structure; a positioner; a projection system for projecting a radiation beam onto a substrate held by the positioner; and a controller configured to control the positioner and the projection system to perform exposure processes in accordance with operational data determined according to any of the second and third aspects.

[0017] According to a seventh aspect of the present invention, there is provided a computer system configured to perform a method of determining operational data for a control system of a lithographic apparatus, the method comprising: obtaining, for each of a plurality of zones on the face of moveable structure that holds a substrate during a scanning process, risk level data for each of a plurality of performance metrics; and determining operational data for use when an exposure field of view is above each zone during the scanning process in dependence on the obtained risk level data; wherein the risk level data is dependent on the properties of a specific product being manufactured and / or user preference data.

[0018] According to an eighth aspect of the present invention, there is provided a method of determining operational data for controlling a lithographic apparatus, the method comprising: obtaining, for each of a plurality of zones on the face of moveable structure that holds a substrate during a scanning process, risk level data for each of a plurality of performance metrics; and determining operational data for use when an exposure field of view is above each zone during the scanning process in dependence on the obtained risk level data; wherein the risk level data is dependent on the properties of a specific product being manufactured and / or user preference data.

[0019] According to a ninth aspect of the present invention, there is provided a computer program comprising computer interpretable code that, when executed by a control system of an immersion lithographic apparatus, causes the immersion lithographic apparatus to perform exposure processes in dependence on operational data determined according to the eighth aspect.

[0020] According to a tenth aspect of the present invention, there is provided an immersion lithographic apparatus comprising: a liquid confinement structure; a positioner; a projection system for projecting a radiation beam onto a substrate held by the positioner; and a controller configured to control the positioner and the projection system to perform exposure processes in accordance with operational data determined according to the eighth aspect.

[0021] According to a eleventh aspect of the present invention, there is provided a computer system configured to perform a method of determining the position a substrate on a substrate support, the method comprising: obtaining properties of the substrate; obtaining properties of the substrate support; obtaining one or more performance measures of the substrate when loaded on the substrate support; and determining the position the substrate on the substrate support in dependence on the properties of the substrate, the properties of the substrate support, and the one or more performance measures.

[0022] According to a twelfth aspect of the present invention, there is provided a method of determining the position a substrate on a substrate support, the method comprising: obtaining properties of the substrate; obtaining properties of the substrate support; obtaining one or more performance measures of the substrate when loaded on the substrate support; and determining the position the substrate on the substrate support in dependence on the properties of the substrate, the properties of the substrate support, and the one or more performance measures.

[0023] Further embodiments, features and advantages of the present invention, as well as the structure and operation of the various embodiments, features and advantages of the present invention are described in detail below with reference to the accompanying drawings.DESCRIPTION OF THE DRAWINGS

[0024] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which corresponding reference symbols indicate corresponding parts, and in which:Figure 1 depicts a schematic overview of the lithographic apparatus;Figures 2 and 3 depict, in cross-section, two different versions of a fluid handling system for use in a lithographic projection apparatus;Figure 4 is a diagram illustrating an exemplary route for production exposure of a substrate;Figure 5 shows a method performed within a model according to an embodiment;Figure 6 schematically shows a substrate that is loaded on a substrate support;Figure 7 schematically shows, in plan view, the movement of a substrate positioner 900 relative to an exposure field of view during a scanning process;Figure 8 shows different zones on the face of the substrate positioner 900;Figure 9 shows actions performed when an exposure field of view is above different zones on the face of the substrate positioner 900; andFigure 10 schematically shows, in plan view, part of a fluid handling structure 1101 and part of a gap 1102 between a substrate W and a substrate support WT.

[0025] The features shown in the Figures are not necessarily to scale, and the size and / or arrangement depicted is not limiting. It will be understood that the Figures include optional features which may not be essential to the invention. Furthermore, not all of the features of the apparatus are depicted in each of the figures, and the Figures may only show some of the components relevant for describing a particular feature.DETAILED DESCRIPTION

[0026] In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g., with a wavelength of 365, 248, 193, 157 or 126 nm).

[0027] The term “reticle”, “mask” or “patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term “light valve” can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase- shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.

[0028] Figure 1 schematically depicts a lithographic apparatus. The lithographic apparatus includes an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., UV radiation or DUV radiation), a mask support (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA in accordance with certain parameters, a substrate support (e.g., a substrate table) WT constructed 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 WT in accordance with certain 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 patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0029] In operation, the illumination system IL receives the radiation beam B from a radiation source SO, e.g., 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 radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at a plane of the patterning device MA.

[0030] The term “projection system” used herein should be broadly interpreted as encompassing various types of projection system, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and / or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

[0031] The lithographic apparatus is of a type wherein at least a portion of the substrate W may be covered by an immersion liquid having a relatively high refractive index, e.g., water, so as to fill an immersion space 11 between the projection system PS and the substrate W - which is also referred to as immersion lithography. More information on immersion techniques is given in US 6,952,253, which is incorporated herein by reference.

[0032] The lithographic apparatus may be of a type having two or more substrate supports WT (also named “dual stage”). In such a “multiple stage” machine, the substrate supports WT may be used in parallel, and / or steps in preparation of a subsequent exposure of the substrate W may be carried out on the substrate W located on one of the substrate support WT while another substrate W on the other substrate support WT is being used for exposing a pattern on the other substrate W.

[0033] In addition to the substrate support WT, the lithographic apparatus may comprise a measurement stage (not depicted in figures). The measurement stage is arranged to hold a sensor and / or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. Thecleaning device may be arranged to clean part of the lithographic apparatus, for example a part of the projection system PS or a part of a system that provides the immersion liquid. The measurement stage may move beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0034] In operation, the radiation beam B is incident on the patterning device, e.g., mask, MA which is held on the mask support MT, and is patterned by the pattern (design layout) present on patterning device MA. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and a position measurement system IF, the substrate support WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and possibly another position sensor (which is not explicitly depicted in Figure 1) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B. Patterning device MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2.Although the substrate alignment marks Pl, P2 as illustrated occupy dedicated target portions, they may be located in spaces between target portions. Substrate alignment marks Pl, P2 are known as scribe-lane alignment marks when these are located between the target portions C.

[0035] To clarify the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axis, i.e., an x-axis, a y-axis and a z-axis. Each of the three axis is orthogonal to the other two axis. A rotation around the x-axis is referred to as an Rx-rotation. A rotation around the y- axis is referred to as an Ry -rotation. A rotation around about the z-axis is referred to as an Rz- rotation. The x-axis and the y-axis define a horizontal plane, whereas the z-axis is in a vertical direction. The Cartesian coordinate system is not limiting the invention and is used for clarification only. Instead, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, such that the z-axis has a component along the horizontal plane.

[0036] Immersion techniques have been introduced into lithographic systems to enable improved resolution of smaller features. In an immersion lithographic apparatus, a liquid layer of immersion liquid having a relatively high refractive index is interposed in the immersion space 11 between a projection system PS of the apparatus (through which the patterned beam is projected towards the substrate W) and the substrate W. The immersion liquid covers at least the part of the substrate W under a final element of the projection system PS. Thus, at least the portion of the substrate W undergoing exposure is immersed in the immersion liquid.

[0037] In commercial immersion lithography, the immersion liquid is water. Typically the water is distilled water of high purity, such as Ultra-Pure Water (UPW) which is commonly used in semiconductor fabrication plants. In an immersion system, the UPW is often purified and it may undergo additional treatment steps before supply to the immersion space 11 as immersion liquid.Other liquids with a high refractive index can be used besides water as the immersion liquid, for example: a hydrocarbon, such as a fluorohydrocarbon; and / or an aqueous solution. Further, other fluids besides liquid have been envisaged for use in immersion lithography.

[0038] In this specification, reference will be made in the description to localized immersion in which the immersion liquid is confined, in use, to the immersion space 11 between the final element and a surface facing the final element. The facing surface is a surface of substrate W or a surface of the supporting stage (or substrate support WT) that is co-planar with the surface of the substrate W. (Please note that reference in the following text to surface of the substrate W also refers in addition or in the alternative to the surface of the substrate support WT, unless expressly stated otherwise; and vice versa). A fluid handling structure IH present between the projection system PS and the substrate support WT is used to confine the immersion liquid to the immersion space 11. The immersion space 11 filled by the immersion liquid is smaller in plan than the top surface of the substrate W and the immersion space 11 remains substantially stationary relative to the projection system PS while the substrate W and substrate support WT move underneath.

[0039] Other immersion systems have been envisaged such as an unconfined immersion system (a so-called ’All Wet’ immersion system) and a bath immersion system. In an unconfined immersion system, the immersion liquid covers more than the surface under the final element. The liquid outside the immersion space 11 is present as a thin liquid film. The liquid may cover the whole surface of the substrate W or even the substrate W and the substrate support WT co-planar with the substrate W. In a bath type system, the substrate W is fully immersed in a bath of immersion liquid.

[0040] The fluid handling structure IH is a structure which supplies the immersion liquid to the immersion space 11, removes the immersion liquid from the immersion space 11 and thereby confines the immersion liquid to the immersion space 11. It includes features which are a part of a fluid supply system. The arrangement disclosed in PCT patent application publication no. WO 99 / 49504 is an early fluid handling structure comprising pipes which either supply or recover the immersion liquid from the immersion space 11 and which operate depending on the relative motion of the stage beneath the projection system PS. In more recent designs, the fluid handling structure IH extends along at least a part of a boundary of the immersion space 11 between the final element of the projection system PS and the substrate support WT or substrate W, so as to in part define the immersion space 11.

[0041] The fluid handing structure IH may have a selection of different functions. Each function may be derived from a corresponding feature that enables the fluid handling structure IH to achieve that function. The fluid handling structure IH may be referred to by a number of different terms, each referring to a function, such as barrier member, seal member, fluid supply system, fluid removal system, liquid confinement structure, etc..

[0042] Immersion liquid may be used as the immersion fluid. In that case the fluid handling structure IH may be a liquid handling system. In reference to the aforementioned description,reference in this paragraph to a feature defined with respect to fluid may be understood to include a feature defined with respect to liquid.

[0043] A lithographic apparatus has a projection system PS. During exposure of a substrate W, the projection system PS projects a beam of patterned radiation onto the substrate W. To reach the substrate W, the path of the radiation beam B passes from the projection system PS through the immersion liquid confined by the fluid handling structure IH between the projection system PS and the substrate W. The projection system PS has a lens element, the last in the path of the beam, which is in contact with the immersion liquid. This lens element which is in contact with the immersion liquid may be referred to as ‘the last lens element’ or “the final element”. The final element is at least partly surrounded by the fluid handling structure IH. The fluid handling structure IH may confine the immersion liquid under the final element and above the facing surface.

[0044] As depicted in Figure 1, the lithographic apparatus comprises a controller or control system 500. The controller or control system 500 is configured to control the substrate support WT.

[0045] Figure 2 schematically depicts a localized liquid supply system or fluid handling system. The liquid supply system is provided with a fluid handling structure IH (or liquid confinement structure), which extends along at least a part of a boundary of the immersion space 11 between the final element of the projection system PS and the substrate support WT or substrate W. The fluid handling structure IH is substantially stationary relative to the projection system PS in the XY plane though there may be some relative movement in the Z direction (in the direction of the optical axis). In an example, a seal is formed between the fluid handling structure IH and the surface of the substrate W and may be a contactless seal such as a gas seal (such a system with a gas seal is disclosed in EP 1,420, 298) or liquid seal.

[0046] The fluid handling structure IH at least partly confines the immersion liquid in the immersion space 11 between the final element of the projection system PS and the substrate W. The immersion space 11 is at least partly formed by the fluid handling structure IH positioned below and surrounding the final element of the projection system PS. Immersion liquid is brought into the immersion space 11 below the projection system PS and within the fluid handling structure IH by one of liquid openings 13. The immersion liquid may be removed by another of liquid openings 13. The immersion liquid may be brought into the immersion space 11 through at least two liquid openings 13. Which of liquid openings 13 is used to supply the immersion liquid and optionally which is used to remove the immersion liquid may depend on the direction of motion of the substrate support WT.

[0047] The immersion liquid may be confined in the immersion space 11 by a contactless seal such as a gas seal 16 formed by a gas which, during use, is formed between the bottom of the fluid handling structure IH and the surface of the substrate W. The gas in the gas seal 16 is provided under pressure via inlet 15 to the gap between the fluid handling structure IH and substrate W. The gas is extracted via outlet 14. The overpressure on the gas inlet 15, vacuum level on the outlet 14 and geometry of the gap are arranged so that there is a high-velocity gas flow inwardly that confines theimmersion liquid. Such a system is disclosed in US 2004 / 0207824, which is hereby incorporated by reference in its entirety. In an example, the fluid handling structure IH does not have the gas seal 16.

[0048] Figure 3 is a side cross-sectional view that depicts a further liquid supply system or fluid handling system. The arrangement illustrated in Figure 3 and described below may be applied to the lithographic apparatus described above and illustrated in Figure 1. The liquid supply system is provided with a fluid handling structure IH (or a liquid confinement structure), which extends along at least a part of a boundary of the immersion space 11 between the final element of the projection system PS and the substrate support WT or substrate W.

[0049] The fluid handling structure IH at least partly confines the immersion liquid in the immersion space 11 between the final element of the projection system PS and the substrate W. The immersion space 11 is at least partly formed by the fluid handling structure IH positioned below and surrounding the final element of the projection system PS. In an example, the fluid handling structure IH comprises a main body member 53 and a porous member 33. The porous member 33 is plate shaped and has a plurality of holes (i.e., openings or pores). The porous member 33 may be a mesh plate wherein numerous small holes 84 are formed in a mesh. Such a system is disclosed in US 2010 / 0045949 Al, which is hereby incorporated by reference in its entirety.

[0050] The main body member 53 comprises supply ports 72, which are capable of supplying the immersion liquid to the immersion space 11, and a recovery port 73, which is capable of recovering the immersion liquid from the immersion space 11. The supply ports 72 are connected to a liquid supply apparatus 75 via passageways 74. The liquid supply apparatus 75 is capable of supplying the immersion liquid to the supply ports 72 through the corresponding passageway 74. The recovery port 73 is capable of recovering the immersion liquid from the immersion space 11. The recovery port 73 is connected to a liquid recovery apparatus 80 via a passageway 79. The liquid recovery apparatus 80 recovers the immersion liquid recovered via the recovery port 73 through the passageway 29. The porous member 33 is disposed in the recovery port 73. Performing the liquid supply operation using the supply ports 72 and the liquid recovery operation using the porous member 33 forms the immersion space 11 between the projection system PS and the fluid handling structure IH on one side and the substrate W on the other side.

[0051] Figure 4 depicts an exemplary route R40 followed by a substrate W for exposure of target portions C001 to Cl 07 on the substrate W. The route R40 shows the relative movement between the substrate W and the fluid handling structure IH. The relative movement may be provided by the substrate support WT moving the substrate W with the fluid handling structure IH remaining stationary. The substrate support WT may be referred to as a scanner. The route, that R40 is an example of, may be referred to as the scanner exposure route.

[0052] In Figure 4, the target portions are exposed in the numbered order. Target portions depicted with dense hatching, e.g., C104, are edge target portions that are exposed at a low speed. Target portions depicted with light hatching, e.g., C085, are edge target portions that are exposed at a lowspeed, but faster than the densely hatched target portions. Edge target portions are exposed but the exposure motion covers only the part of the target portion that overlaps the substrate W, not the full length of the edge target portion. Route R40 has been calculated by attempting to optimize for throughput and includes long diagonal motions R41, R42. Diagonal motions R41, R42 are transfer moves between the exposure of a target portion at the end of one row and the exposure of the target portion at the beginning of the next. Diagonal motion R41 comes after exposure of edge target portion C104 and repositions the substrate for exposure of edge target portion C105. Diagonal motion R42 comes after exposure of edge target portion C003 and repositions the substrate W for exposure of edge target portion C004.

[0053] It will be seen that this production route mostly consists of straight line motions in the scan (+ / -Y) or transverse (+ / -X) directions. This measure, together with the described speed variations for selected edge portions, may be effective to reduce defects due to immersion liquid loss (watermarks) or bubbles becoming entrained in the immersion liquid. Other measures and other routes can be devised, but there is always a compromise to be determined between defectivity rate (rate of defects) and throughput.

[0054] It is known for the movement speeds on the scanner exposure route to be determined by a model. The model may determine the movement speed along scanner exposure route in dependence on a determination of the risk of defects occurring. Accordingly, the model may attempt to determine the maximum usable movement speeds along the scanner exposure route for an expected defectivity rate.

[0055] Limitations of known models for determining the scanner exposure route include the model attempting to optimize the speed of movement only. Known models do not attempt to optimize exposure trajectory features such as the exposure order, the exposure direction, and including detours in a route. Known models also do not determine sophisticated movement controls such as control of acceleration, control of jerk (which is the rate of change of acceleration), and control of snap (which is the rate of change of jerk).

[0056] A further limitation of known techniques is the determination of the expected defectivity rate. Known techniques do not include all of the factors that may contribute to defects occurring, such as the properties of the resist and specific details of the substrate support WT and fluid handling structure IH.

[0057] Embodiments provide an improved model for determining the scanner exposure route, movement speeds on the scanner exposure route and / or the expected defectivity rate.

[0058] The model according to embodiments is able to determine improvements to the scanner exposure route in dependence on more features than known techniques. For example, the model may determine improvements in dependence on the exposure layout, resist type / process, substrate support WT properties and fluid handling structure IH properties. The model may iteratively determine improvements to the scanner exposure route.

[0059] Embodiments provide model-based predictive feedforward control. The model may be both physics based and also heuristics / user based. It may therefore be a combined physics and heuristics / user based model. Heuristics / user based inputs to the model include user defined parameters of the exposure process, such as the resist contact angle, exposure field layout, etc.. The inputs to the model may also include properties of the substrate support WT, the fluid handling structure IH, the movement and trajectory profiles of the substrate stage, and any other physical parameters that are relevant to the exposure process.

[0060] The output of the model is a determination of operational data that the model has attempted to optimise for throughput and / or detectivity rate by determining the scanner exposure route, e.g., the order of the exposure processes, scan directions, movement speeds, acceleration, jerk and / or snap.

[0061] The model may be used to pre-determine a scanner exposure route, and the properties of the scanner exposure route, prior to an exposure process being started. When used in this way, the model may be referred to as an off-scanner or off-line model. The model may also be used to determine changes to a scanner exposure route, and the properties of the scanner exposure route, during an exposure process. When used in this way, the model may be referred to as an on-scanner or inline model.

[0062] The model according to embodiments is described in more detail below.

[0063] The input data to the model may include physical data on one or more of the processes, fluid handling structure IH, substrate support WT and the substrate stage. Physical data on the processes may include one or more of the substrate W properties, the resist contact angle, leaching properties, and the resist type (such as negative tone development or positive tone development). Physical data on the fluid handling structure IH may include data on one or more of the properties of the fluid flows, the shape of the fluid handling structure IH and the fly height of the fluid handling structure IH. Physical data on the substrate support WT may include data on one or more of the fluid extraction system, ring structure of the substrate support WT radially outwards of the substrate W, properties of the fluid flows in the fluid extraction system, the shape and dimensions of the fluid extraction system, and the gap between the ring structure and the substrate W. Physical data on the substrate stage may include data on one or more of the routing, maximum usable snap, movement constraints (such as remaining over the substrate W throughout the exposure processes) and the movement required to setup the first exposure process.

[0064] The input data to the model may also include heuristics and / or user based data. This may include data from user observations, such as defects determined from previous use cases that may not be easily predictable defects. This may also include user data on advantageous techniques that have been determined from previous use cases. For example, it may include data on techniques that are particularly effective for a specific application. The input heuristics and / or user based data may also include user defined parameters of the exposure process, such as the resist contact angle, exposure field layout, the order of fields to be exposed (partially or completely), enforced scan directions (forexample, if it is known that a certain combination of parameters is disadvantageous, then a more advantageous parameter combination may be pre-determined), starting state etc..

[0065] The input data to the model may include any other data relevant to the performance of exposure processes and / or the movement of the substrate W. The input data to the model may be generated from within the parts of the lithographic apparatus that perform the scanning processes.

[0066] The model determines, in dependence on the received inputs, the expected defectivity rate at all of the exposure locations, and any other relevant locations, on the substrate W. The model determines operational data. The operational data may include the order in which areas on the substrate W are exposed, the scanner exposure route, scan directions and any other relevant properties for the movement of the substrate W and / or exposure processes. The model may attempt to determine the operational data so that the throughput of the exposure processes is maximised without the expected defectivity rate exceeding a predetermined threshold and / or that the operational data appears to be close to optimal.

[0067] The determined operational data by the model may be output from the model as a recipe, or sub-recipe, so that they may be executed.

[0068] The model may use an iterative process to determine the operational data. The model may make an initial determination of operational data that has an expected defectivity rate that meets the user defined specification. In an iterative process, the model may repeatedly change the initially determined operational data in an attempt to determine new operational data that improves a performance metric with the expected defectivity rate still meeting the user defined specification. The performance metric may be, for example, the throughput (i.e. the required time for all of the exposure processes). For example, the iterative process may attempt to determine new operational data that improves the throughput with the expected defectivity rate still meeting the user defined specification. The iterative process may alternatively attempt to determine new operational data that reduces the expected defectivity rate without substantially reducing the throughput.

[0069] Figure 5 shows a method performed within the model for iteratively improving the operational data according to an embodiment.

[0070] The model may comprise a first determination block 501, second determination block 502, third determination block 503 and fourth determination block 504. The model may receive data from a first input 601, second input 602, third input 603 and fourth input 604. The model may output data through a data output 701.

[0071] The first determination block 501 may receive, from the first input 601, an exposure recipe. The exposure recipe may be dependent on user requirements. The exposure recipe may define the exposure areas of a substrate W and the exposure conditions at each exposure area. The first determination block 501 may determine, in dependence on the exposure recipe, initial operational data. The initial operational data may define an exposure order, scan directions and movement speeds / accelerations / jerks / snaps. The first determination block 501 may attempt to determine theoperational data such that a performance metric, such as throughput, is maximised. The first determination block 501 may provide the determined initial operational data to the second determination block 502.

[0072] The second determination block 502 may receive, from the second input 602, heuristics / user based data. The heuristics / user based data may be the above-described heuristics / user based data. The second determination block 502 may receive, from the third input 603, physical data. The physical data may be the above-described physical data.

[0073] The second determination block 502 may determine the defectivity risk of the received operational data in dependence on the heuristics / user based data and the physical data. If the determined defectivity risk exceeds a predetermined threshold, that may be a user defined threshold, then this is a determination that the operational data is improvable (i.e. NOK). The operational data may be sent to the fourth determination block 504 so that changes to the operational data may be made. If the determined defectivity risk does not exceed a predetermined threshold, that may be a user defined threshold, then this is a determination that the operational data is usable (i.e. OK). The operational data may be output from the model through data output 701.

[0074] The fourth determination block 504 may receive operational data that has been determined as improvable by the second determination block 502. The fourth determination block 504 may also receive, from the fourth input 604, exposure routing change data. The exposure routing change data may comprise heuristics and other data, relevant to how the operational data may be changed.

[0075] In dependence on the received data, the fourth determination block 504 may determine conditions, such as restraints, on scan speeds, preparatory move speeds, preparatory areas, exposure order, scan directions, settling time constraints, and any other relevant aspects of the operational data. The fourth determination block 504 may output the determined conditions and operational data to the third determination block 503.

[0076] The third determination block 503 may determine and apply changes to the operational data in dependence on the determined conditions by the fourth determination block 504.

[0077] The third determination block 503 may output the changed operational data to the second determination block 502. The second determination block 502 may repeat the process of determining a defectivity risk with the received operational data from the third determination block 503. If the determined defectivity risk exceeds a predetermined threshold, that may be a user defined threshold, then this is a determination that the operational data is improvable (i.e. NOK). The determination that the operational data is improvable may alternatively, or additionally, be made on a detection that defects are forming in a persistent pattern on a substrate W and / or a detection based on the substrate W fingerprint. The operational data may be sent to the fourth determination block 504 so that changes to the operational data may be made. If the determined defectivity risk does not exceed a predetermined threshold, that may be a user defined threshold, then this is a determination that theoperational data is usable (i.e. OK). The operational data may be output from the model through data output 701.

[0078] The process of changing the operational data by transferring it from the second determination block 502, to the fourth determination block 504, to the third determination block 503 and then back to the second determination block 502 may be repeated in a loop at least until second determination block 502 determines that determined changes to the initial operational data are usable. Accordingly, the model may iteratively improve the operational data with each execution of the loop. The operational data that is determined as usable may be output through data output 701. The output operational data may be executed by the control system 500 of the substrate support WT and / or any of the other parts of the lithographic apparatus that are controlled to provide the relative movement between a substrate W and a fluid handling structure IH during exposure processes.

[0079] Embodiments include the model executing the loop for changing the operational data with operational data that has been determined to be usable. This may determine further improved operational data that may be output through data output 701.

[0080] The model of embodiments may be used to pre-determine operational data prior to an exposure process being started. When used in this way, the model may be referred to as an off- scanner or off-line model. The model may also be used to determine changes to operational data during an exposure process. When used in this way, the model may be referred to as an on-scanner or inline model.

[0081] Examples of changes to operational data that may be determined by the model according to embodiments are described below.

[0082] Embodiments include determining and applying changes to the operational data that reduce its expected defectivity rate without reducing the throughput. This allows faster speeds to be used without the determined defectivity risk exceeding the predetermined threshold.

[0083] For example, a defect that may occur is big bubble formation. A cause of big bubble formation is the fluid handling structure IH crosses over the notch of the substrate W where a large gap (that may be about 500pm) between an edge of the substrate W and an edge of the substrate support WT is present. The big bubble formation may be avoided, or reduced, by controlling the acceleration or jerk of the substrate W to be constant as the notch of the substrate across the gap. Changing the operational data to apply such control of the acceleration or jerk of the substrate W may reduce the expected defectivity rate without reducing throughput.

[0084] Defects may also increase due to long linear relative movements between the substrate W and the fluid handling structure IH. For example, with reference to Figure 4, a route may sequentially include the target portions C106, C100, C090, C079, C067, C054, C041, C029. C018, C008 and C002. This is a long linear route and the risk of defects occurring due to water loss is high. To reduce the defectivity risk, the model according to embodiments may determine and apply a change to the operational data so that the sequence of target portions does not include such long linear moves.For example, the model may determine that an alternative order in which target portions are exposed is C106, C100, C099, C107, C090, C079, C091, etc.. Such a change in route may reduce the expected defectivity rate. If the changed route reduces the throughput, then the model may determine other changes that may be made to the operational data for increasing the throughput for the specific type of lithographic apparatus. Embodiments may thereby determine changes to the operational data that reduce the defectivity rate without substantially decreasing the throughput. Embodiments may similarly be used to determine how to increase throughput without increasing the defectivity rate.

[0085] In a preferred embodiment, the model is used to improve operational data that is a recipe for an exposure process. The model may receive a recipe for exposing a substrate W in the exposure process. Based on the recipe, the model may determine a first motion plan with a first duration taking the least exposure time in the exposure process. The first motion plan may contain a plurality of movements along neighbouring regions over a first portion of the substrate W. The model may then determine a set of locations on the substrate W having a risk of defect in the exposure process according to the first motion plan. Based on the determined set of locations having a risk of defect, the model may determine a second motion plan with a second duration to reduce the risk of defect in the exposure process. The second motion plan may contain at least one movement along at least two spaced apart regions over a second portion of the substrate and the second duration may be longer than the first duration. The model may calculate the time difference between the first duration and the second duration and determine how to modify the timing of the second motion plan of the exposure process so as to minimise the time difference. As a result of the determined modification to the second motion plan, the exposure process according to the second motion plan may complete at substantially the same time as that according to the first motion plan.

[0086] Embodiments also include using the model to determine other changes to the operational data and / or the model being used to improve other performance metrics than defectivity rate and throughput.

[0087] There is a general need to improve the sustainability of lithographic processes. Examples of how sustainability can be improved include reducing carbon dioxide use and reducing the power consumption.

[0088] In immersion lithography, carbon dioxide is supplied to a gas knife in the fluid handling structure IH. The use of a gas knife reduces immersion related defects. Carbon dioxide is chosen specifically because it dissolves in water quickly. The carbon dioxide is supplied to the fluid handling structure IH by a Mass Flow Controller (MFC). In known techniques, carbon dioxide is continuously supplied to the gas knife during both production and non-production states of the lithographic apparatus. The carbon dioxide consumption of the lithographic apparatus due to the gas knife alone may be about 10kg of carbon dioxide per hour.

[0089] The total electrical power consumption of a lithographic apparatus may be about 80kW, which, depending on how the electricity is generated, may result in the release of 40kg of carbon dioxide per hour into the atmosphere.

[0090] Embodiments include using the model to determine changes to the lithographic processes that improve sustainability. In particular, the model may be used to determine changes to operational data of processes so as to reduce the carbon dioxide consumption and / or reduce power the consumption of the lithographic apparatus. For example, carbon dioxide may only be used in the gas knife when the lithographic apparatus is in a production state and the use of carbon dioxide is required to meet the required defectivity rate. The supply of carbon dioxide to the fluid handling structure IH may be stopped whenever the lithographic apparatus is in a non-production state, i.e. when no lithographic processes are being performed. The supply of carbon dioxide to the fluid handling structure IH may also be stopped whenever the lithographic apparatus is in a transition state, i.e. when it is changing between a production and a non-production state, and vice-versa. If a supply of carbon dioxide to the fluid handling structure IH is required when the lithographic apparatus is in a transition state, embodiments include the model determining changes for reducing the times required for the transient states so as to reduce the overall carbon dioxide consumption.

[0091] The model may receive user defined instructions on the relative importance of throughput, defectivity rate, accuracy (i.e. overlay performance) and sustainability in the performed processes. The model may then determine the operational data so as to improve the performed processes given the user defined instructions as well as the specific circumstances, as defined by the exposure recipe, substrate W properties etc..

[0092] In a first example of the user defined instructions, the lowest achievable defectivity rate is required. The model may then attempt to determine the fastest achievable route and operating conditions that also provide the lowest achievable defectivity rate. This may involve slowing down the relative movement between the substrate W and fluid handling structure IH at specific locations and supplying only carbon dioxide to the gas knife.

[0093] In a second example of the user defined instructions, the defectivity rate does not need to be as low as achievable and improved sustainability of the processes is preferred. The model may determine that the gas supply to the gas knife may be extremely clean dry air (XCDA) instead of carbon dioxide. The model may then attempt to determine the achievable fastest route and operational conditions that also provide the specified defectivity rate.

[0094] In all situations, the model may determine that, when the lithographic apparatus is idle or performing actions such as conditioning moves that are not defectivity critical, the gas knife should be switched off to avoid unnecessary use of carbon dioxide. Conditioning moves are moves that are performed when the lithographic apparatus is in a non-production state to maintain an appropriate operating temperature. The model may also determine to take actions that reduce the overall powerconsumption of the lithographic apparatus without substantially reducing the performance of the lithographic processes.

[0095] Embodiments include the model determining the applied separation distance, i.e. fly height, between the fluid handling structure IH and the substrate W. The separation distance may be defined as the minimum distance between the fluid handling structure IH and the substrate W in a direction orthogonal to the plane in which the substrate W is moved. The separation distance is required to prevent the fluid handling structure IH and the substrate W from contacting each other.

[0096] The lithographic apparatus may be configured so that the separation distance may be changed by any amount at any time. The model may determine and apply variable separation distances as appropriate for maximizing performance given the user requirements and specific circumstances.

[0097] The performance of lithographic processes is dependent on the separation distance between the fluid handling structure IH and a substrate W. When a relatively large separation distance is used, the forces experienced by the substrate W are relatively low and this reduces the occurrence of any type of defect that such forces may cause. However, when a relatively large separation distance is used, the tolerable relative movement speed between the fluid handling structure IH and the substrate W is reduced. If the relative movement speed is too high for a particular separation distance, substantial water loss and / or water marks may occur. Water loss and / or water marks may cause defects due to imaging errors and thermal effects.

[0098] To increase throughput without substantially increasing the defectivity, the model may determine, for example, to use a relatively larger constant separation distance and slower relative movement speed during critical moves, such as for each scanning movement during an exposure process along scanning routes. However, during non-critical moves, such as preparatory movements for moving the substrate W to a position from which a new scanning movement may be started, a lower separation distance and faster relative movement speed may be used. The lower separation distance increases the forces experienced by the substrate W. However, this is may not substantially reduce the performance because critical moves are not being performed. The throughput may thereby be increased due to the faster usable relative movement speed of the substrate W and the fluid handling structure IH during each preparatory movement. For a given separation distance and use case, there is a maximum relative movement speed that may be used without a substantial drop in performance occurring. The maximum relative movement speed may vary between different use cases. Embodiments include determining the relationship between the maximum relative movement speed and the separation distance for each use case. The relationship may be stored, such as encoded in a look-up table. The look-up table may comprise data on usable fly heights and may be referenced in attempts to optimise performance.

[0099] Embodiments also include the model determining to set the separation distance so that substrates W with different thicknesses may be appropriately used without the risk of collisions substantially increasing.

[0100] The operational data determined by the model according to embodiments may therefore include the applied separation distance. Different separation distances may be used at different times. The separation distances may be determined in dependence on the heuristics / user based data and / or the physical data.

[0101] Embodiments also include the model determining the used position of the substrate W on the substrate support WT.

[0102] Figure 6 schematically shows a substrate 801 that is loaded on a substrate support 800. The substrate 801 may be the same as the earlier described substrate W. The substrate support 800 may be the same as the earlier described substrate support WT. The substrate support 800 comprises a ring 802a and a main body 802b. The ring 802a may have a circular shape or any other suitable shape such as square. The substrate 801 may have a conventional circular shape or any other suitable shape.

[0103] When the substrate 801 is loaded on the substrate support 800, the substrate 801 may be supported by the main body 802b and, in the plane of the substrate 801, surrounded by the ring 802a. There may be an annular gap 803a, 803b between the substrate 801 and the ring 802a. The gap 803a, 803b is required to avoid direct physical contact between the substrate 801 and the ring 802a. Any contact between the substrate 801 and the ring 802a may increase the defectivity by damaging and / or deforming the substrate 801.

[0104] When the fluid handling structure IH crosses over the gap 803a, 803b in a relative movement between the fluid handling structure IH and the substrate 801 and / or the substrate support 800, there may be an interaction between the fluid handling structure IH and the gap 803a, 803b. For example, there may be a fluid flow through the gap 803a, 803b and this may cause a performance reduction. It may be desirable for the gap 803a, 803b to be small so as to reduce the fluid flow through the gap 803a, 803b.

[0105] Conventionally, the substrate 801 is always positioned as centrally as achievable within the ring 802a. Assuming that there are no roundness errors of the circular substrate 801 and ring 802a, the size of the gap 803a, 803b is constant around the circumference of the centrally positioned substrate 801. At the diametrically opposite locations 803a and 803b, the gap 803a, 803b is therefore the same.

[0106] It has been realised that the central positioning of the substrate 801 within the ring 802a is not necessarily the preferred location of the substrate 801 within the ring 802a. The design of the products or devices that are being manufactured on the substrate 801 may result in the tolerable defectivity varying over different regions of the substrate 801. The regions of the substrate 801 in which the tolerable defectivity is low may not be located symmetrically on the substrate 801. That isto say, for example, the features manufactured near the gap 803a may have a lower defectivity than the features that are manufactured near the gap 803b.

[0107] Embodiments include the model determining an off-centre location of the substrate 801 within the ring 802a. The off-centre location of the substrate 801 intentionally causes a variation of the gap 803a, 803b around the circumference of the substrate 801. At locations where the size of the gap 803a is small, the fluid flow through the gap 803a is reduced and this may decrease the defectivity. At locations where the size of the gap 803b is large, the fluid flow through the gap 803b is increased and this may increase the defectivity.

[0108] For a number of different types of application (i.e. use case), the performances at noncentral locations of the substrate W may be calibrated and stored, such as encoded in a look-up table. The look-up table may comprise data on the usable positions of the substrate 801 on the substrate support 800 and may be referenced in attempts to optimise performance.

[0109] For example, for a specific type of application, the model may use the look-up table to determine that the overall performance may be improved by locating the substrate 801 off-centre so that the gap 803a is less than the gap 803b. This positioning of the substrate 801 may improve the overall performance. For example, although the defectivity of the features manufactured near the gap 803b may increase, this would be acceptable if the increased defectivity in this region was tolerable.

[0110] Embodiments also include the model determining an off-centre location of the substrate 801 within the ring 802a so as to improve the fluid flow properties. When the substrate 801 is centrally positioned within the ring 802a, it is possible that the fluid flow through the gap 803a, 803b is not uniform around the circumference of the substrate 801. The non-uniform fluid flow may be caused by the implementation of the fluid extraction system and / or other circumstances. The model according to embodiments may determine an off-centre location of the substrate 801 so that the fluid flow through the gap 803a, 803b is more uniform.

[0111] The model according to embodiments may therefore determine an off-centre location of the substrate 801 within the ring 802a as appropriate for maximizing performance given the user requirements and specific circumstances.

[0112] The operational data determined by the model according to embodiments may therefore include the position of the substrate 801 on the substrate support 802a, 802b. The position of the substrate 801 on the substrate support 800 may be determined in dependence on the heuristics / user based data and / or the physical data.

[0113] In order to utilise off-centre positioning of the substrate 801 within the ring 802a to improve overall performance, it is necessary for the effective size of the gap 803a, 803b to be known at all locations around the substrate 801 when the substrate 801 is loaded on the substrate support 800. Uncertainties in the determined effective size of the gap 803a, 803b may reduce the accuracy of operational parameters for improving the overall performance.

[0114] The actual size and variation of the gap 803a, 803b may be determined by using a camera to capture an image of the gap 803a, 803b. However, there is no existing camera for this in a lithographic apparatus and introducing a new camera for measuring the position of a substrate 801 on a substrate support 800 would increase costs. The incorporation of a new camera within the lithographic apparatus is also complicated and may compromise the performance of some of the other processes.

[0115] Embodiments include alternatively using a model to determine the effective size of the gap 803a, 803b around the substrate 801 on the substrate support 800. Advantageously, no new hardware may be required to determine the effective size of the gap 803a, 803b. Embodiments also include controlling processes in dependence on the determined effective size of the gap 803a, 803b. This may improve the performed processes and thereby increase yield and / or throughput.

[0116] Embodiments model the effective size of the gap 803a, 803b around the substrate 801 on the substrate support 800 in dependence on the properties of the substrate 801, the properties of the substrate support 800, and the performance of the substrate 801 and substrate support 800.

[0117] The properties of the substrate 801 may be measurable and / or known. The properties of the substrate 801 that are used by the model may include the thickness, shape, warpage and diameter of the substrate 801. The properties of the substrate 801 may at least partially be determined from measurements made when the substrate 801 is loaded on the substrate support 800. The properties of the substrate 801 may also include data that is known prior to the substrate 801 being loaded on the substrate support 800.

[0118] The properties of the substrate support 800 may be measurable and / or known. The properties of the substrate support 800 that are used by the model may include the shape of the substrate support 800, in particular the shape of the ring 802a. The model may also use measurements, or estimations, of the static and dynamic loading properties of the substrate support 800. The static loading properties are physical properties specific to each substrate support 800. The dynamic loading properties are the physical responses of the substrate 801 and substrate support 800 when the substrate 801 is loaded on the substrate support 800. The properties of the substrate support 800 may at least partially be determined from measurements made when the substrate 801 is loaded on the substrate support 800. The properties of the substrate support 800 may also include data that is known prior to the substrate 801 being loaded on the substrate support 800.

[0119] The performance of the substrate 801 and substrate support 800 may be measured when the substrate 801 is loaded on the substrate support 800. The performance measure that is used by the model may include, for example, a measurement of the properties of the fluid flow through the gap 803a, 803b. For example, the variation in the fluid flowrates through the gap 803a, 803b may be measured at different locations within the gap 803a, 803b in response to a pre-determined fluid flow. The fluid flowrate variation may then be used as a performance measure.

[0120] The properties of the fluid flow through the gap 803a, 803b are dependent on the properties of the substrate 801, the properties of the substrate support 800 and the effective gap 803a, 803b. A model may therefore determine the effective gap 803a, 803b by determining the gap 803a, 803b that provides the measured fluid flow properties given the determined properties of the substrate 801 and the determined properties of the substrate support 800.

[0121] Accordingly, embodiments provide a model that determines the size and variation of the effective gap 803a, 803b between the substrate 801 and the ring 802a. The determination of the effective gap 803a, 803b is a determination of the position the substrate 801 on the substrate support 800. Embodiments also include determining operational data, and / or corrections over time to operational data, in dependence on the determined effective gap 803a, 803b so as to improve performance. Embodiments may determine changes to be made over time to the effective gap 803a, 803b for improving performance. The required changes may be determined based on operational data and / or data on the product that is being manufactured. Further measurements of the fluid flow rate variation may be used to determine the actual changes to the effective gap 803a, 803b that are made.

[0122] Embodiments include using the model to determine the effective gap 803a, 803b for each individual substrate 801 when it is loaded on a substrate support 800, as well as determining operational data, and / or corrections over time to operational data, in dependence on each determined effective gap 803a, 803b.

[0123] Embodiments also include a model for dynamically determining the exposure strategy so as to attempt to optimise performance given the acceptable production risks under the specific circumstances. This includes dynamically determining operating conditions such as the scanner exposure route, movement speeds on the scanner exposure route, focus and other factors that influence the production rate, defectivity rate and sustainability.

[0124] Figure 7 schematically shows, in plan view, the movement of a substrate positioner 900 relative to an exposure field of view (FOV) during a scanning process of a single layer during the manufacture of a product. The substrate positioner 900 is a moveable structure that supports a substrate 905. The substrate positioner 900 may be configured to hold the earlier described substrate support WT supporting the substrate 905 as a separate component or be integral with the substrate support WT. The substrate 905 may be the same as the earlier described substrates W.

[0125] The substrate positioner 900 also comprises regions 901, 902, 903 and 904 that may be used for calibration and / or measurement purposes. For example, in order for a patterning device, i.e., reticle, alignment measurement to be made, the scanning process may move the substrate positioner 900 so that the exposure FOV is above one of the regions 901, 902, 903 and 904.

[0126] The route of the substrate positioner 900 relative to the exposure FOV comprises an initial path 906 of the scanning process. On the initial path 906, the substrate positioner 900 is moved relative to the exposure FOV so that the exposure FOV is above region 901, region 902 and part of the substrate 905. The route of the substrate positioner 900 relative to the exposure FOV alsocomprises a final path 907 of the scanning process. On the final path 907, the substrate positioner 900 is moved relative to the exposure FOV so that the substrate 905 is moved away from the exposure FOV. The route of the substrate positioner 900 relative to the exposure FOV during the main part of the scanning process, that occurs between the initial path 906 and the final path 907, is not shown in Figure 7.

[0127] As shown in Figure 8, different zones on the face of the substrate positioner 900 and substrate 905 may be identified. Figure 8 shows six zones that are identified as Zl, Z2, Z3, Z4, Z5 and Z6. It should be understood that there may be any number of zones and each zone may cover a different area of the substrate positioner 900 and substrate 905 from that shown in Figure 8. The combined areas of all of the zones may cover the entire face of the substrate positioner 900 and substrate 905. Each zone may partially overlap with one or more other zones.

[0128] The actions that may be performed when the exposure FOV is above each zone are shown in Figure 9. It should be noted that Figure 9 illustrates that different actions are performed in different zones over a period of time and that the time periods in Figure 9 are not shown to scale.

[0129] The upper row 1001 shows the different actions and the lower row 1002 shows the zone of the substrate positioner 900 and substrate 905 that the exposure FOV is above when each of the actions is performed.

[0130] Action 1003 may be an exchange operation that requires moving the substrate positioner 900 so that the exposure FOV is above parts of Zl and Z2.

[0131] Actions 1004, 1005 and 1006 may be measurements and / or calibrations, such as reticle alignment measurements, during which the exposure FOV is above Z2 of the substrate positioner 900 only.

[0132] Action 1007 may be a move to first exposure operation that requires moving the substrate positioner 900 so that the exposure FOV is above parts of Z2 and Z3.

[0133] Action 1008 may comprise the main part of the scanning process and require moving the substrate positioner 900 so that the exposure FOV is above parts of Z3, Z4 and Z5.

[0134] Action 1009 may be the end sequence of the scanning process and require moving the substrate positioner 900 so that the exposure FOV is above parts of Z4 and Z6.

[0135] Embodiments determine risk levels that are related to the processes performed in each of the zones during a scanning process. Each risk level may define the risk associated with the extent of an error occurring and / or a manufacturing defect occurring.

[0136] Table 1 shows a risk matrix that includes all of the risk levels that are related to the processes performed in each of the zones during a scanning process.TABLE 1

[0137] Each column in Table 1 is for a different performance metric. The performance metrics may include focus, overlay, the stability of the sensors, defectivity, machine material damage control(MMDC) and many other performance metrics. The rows in Table 1 correspond to the different zones, i.e. Z1 to Z6.

[0138] Each risk level is an entry wk nfor k = 1 to K, and n = 1 to N, where K is the total number of zones and N is the total number of performance metrics.

[0139] Each risk level wk nis defined in dependence on operating conditions, that may alternatively be referred to as operational data, that it is dependent on. Accordingly, wk n(v, t, a,j) is a risk level that is defined in dependence on: v = velocity t = time a = acceleration j =jerk

[0140] Each risk level wk nmay be defined in dependence on additional and / or alternative operating conditions to velocity, time, acceleration and jerk.

[0141] The individual risk levels in Table 1 provide an expected risk for a performance metric at a specific location given the operating conditions. An overall risk level, P (layer), for the layer being manufactured during a scanning process may be calculated as:

[0142] The overall risk level, P (lay er), should be less than or equal to a pre-determined overall risk level, which is DefinedValue(layer). The pre-determined overall risk level is an overall risk level that has been defined as acceptable by a user.

[0143] For each performance metric in each zone, the acceptable risks to the user may be determined in dependence on the properties of the specific product being manufactured and the user’ s preferences (i.e. user preference data). For example, given the properties of the specific product being manufactured, in Z2 the focus accuracy may be of low importance but in Z4 the focus accuracy may be of high importance. The acceptable risk level for focus in Z2 may therefore be high and the acceptable risk level for focus in Z4 may be low. The operating conditions (e.g. velocity, time, acceleration and jerk) may be determined differently for the operations in Z2 and Z4, with the operating conditions still determined so as to meet the acceptable levels in Z2 and Z4. The risk of focus errors occurring in Z2 may then relatively high and the risk of focus errors occurring in Z4 relatively low. The acceptable risk levels may also be dependent on user preferences. For example, the user may prefer to have a high productivity rate with an increased defectivity rate, or alternatively prefer to have a lower productivity rate with a reduced defectivity rate. The acceptable risk levels may be adjusted accordingly in dependence on this user preference.

[0144] The model according to embodiments may determine an acceptable pre-determined overall risk level and a performance metric for each zone given the properties of the specific product being manufactured and the user’s preferences. Default values may be used for any risk levels that cannot be determined from the properties of the specific product being manufactured and / or specified user’s preferences.

[0145] The model may then attempt to optimise all of the operating conditions, by tuning all of the operating conditions in all of the zones, so as to determine an exposure strategy that attempts to optimise performance whilst staying with all of the defined acceptable risk levels for each performance metric in each region. For example, the exposure strategy according to embodiments may provide an overall throughput, lower overall defectivity rate and / or improved sustainability than exposure strategies determined according to known techniques.

[0146] The present embodiment may differ from previous embodiments in that the model may not use an iterative process to determine an exposure strategy. An exposure strategy may be determined directly from the information / data on acceptable risk levels, and any other required data.

[0147] Embodiments also include the use of a model to mitigate the generation of, and defects caused by, bubble formation and / or water loss. The model may alternatively, or additionally, be used to determine how to decrease the overall time required for processes for a given bubble formation and / or water loss caused defectivity rate.

[0148] In a known model for mitigating the generation of, and defects caused by, bubble formation and / or water loss, a prediction is made of the fields on a substrate W where defects due to bubble formation and water loss may occur. A predicted field is determined to be large if its area is greater than a threshold level and the predicted field is considered to be small if its area is less than a threshold level (that may be the same threshold level). When a predicted field is large, this is associated with an increased risk of a defect occurring. To reduce the expected extent of the predicted defects, the relative movement speed of the substrate W and the fluid handling structure IH may be reduced in each predicted large field. When a predicted field is small, this is associated with a lower risk of a defect occurring and so the relative movement speed of the substrate W and the fluid handling structure IH may be reduced by a lesser extent.

[0149] A limitation of the above model is that the size of the predicted fields on a substrate W where defects may occur are not necessarily related to actual risk level of a defect occurring. In particular, the model may determine a large field at risk of water loss and bubble formation but the actual risk level over the large field may be low. In this circumstance, slowing down the relative movement speed of the substrate W and the fluid handling structure IH in response to the determination of a large field at risk may unnecessarily reduce the speed of the performed processes. Similarly, the model may determine a small field at risk of water loss and bubble formation but the actual risk level over the small field may be high. In this circumstance, despite the determined field being small, it is necessary to slow down the relative movement speed of the substrate W and the fluid handling structure IH to prevent an increase of the defectivity rate.

[0150] The present embodiment improves on the above model by determining the risk associated with the predicted fields in which a defect may occur due to bubble formation and / or water loss.

[0151] Figure 10 schematically shows, in plan view, part of a fluid handling structure 1101 and part of a gap 1102 between a substrate W and a substrate support WT. The fluid handling structure 1101 may be the same as the earlier described fluid handling structures IH. The gap 1102 may correspond to gap 803a, 803b in Figure 6 and its overall shape may be annular.

[0152] As described earlier with reference to Figure 6, when a substrate W is loaded on a substrate support WT, a ring 802a of the substrate support WT surrounds the substrate W in the plane of the substrate W. There is an annular gap 803a, 803b between the substrate W and the ring 802a, i.e., the surrounding part of the substrate support WT. The gap 803a, 803b is required to avoid direct physicalcontact between the substrate W and the ring 802a. In Figure 10, the gap 1102 has been approximated to a linear gap 1102. The actual gap 1102 would have a slight curvature that decreases as the radius of the substrate W increases. An angle relative to part of the gap 1102 may be defined as an angle relative to the tangent of the curvature at the part of the gap 1102.

[0153] When the fluid handling structure 1101 crosses over the gap 1102 in a relative movement between the fluid handling structure 1101 and the substrate support WT, there may be an interaction between the fluid handling structure 1101 and the gap 1102. For example, there may be a fluid flow through the gap 1102 and this may be a main cause of water loss and bubble generation. There is an angle a between an edge 1104 of the fluid handling structure 1101 and the gap 1102. The is also an angle cp between the edge 1104 of the fluid handling structure 1101 and the movement direction 1103 of the fluid handling structure 1101 relative to the substrate support WT. The angles a and cp are dependent on the route of the substrate W / substrate support WT during the exposure processes and the orientations of the substrate W / substrate support WT along the route.

[0154] It is realised that the amount of water loss and / or bubble generation that occurs when the fluid handling structure 1101 crosses over the gap 1102 is dependent on the angles a and cp. When the angle a is small, then the fluid extraction holes in the fluid handling structure 1101 are more aligned with the gap 1102 when crossing the gap 1102. This decreases the stability of the meniscus and increases the risk of defects caused by water loss on the substrate W and bubble formation. The risk of defects may reduce as the angle a is increased and reach a minimum when the angle a is at about 45°. The risk of defects may remain substantially unchanged when a is greater than about 45°.

[0155] The duration of the gap 1102 crossing is dependent on the angle cp. For a given relative movement speed of the substrate W and the fluid handling structure IH, the risk of defects occurring may reduce as the duration of the gap 1102 crossing is reduced. The risk of defects caused by water loss on the substrate W and bubble formation is therefore also dependent on the angle cp.

[0156] The risk of defects caused by water loss on the substrate W and bubble formation is also dependent on dimensions of the gap 1102 where the fluid handling structure 1101 crosses the gap 1102. The dimensions of the gap 1102 include the width of the gap 1102 and the curvature of the gap 1102. The width of the gap 1102 where the fluid handling structure 1101 crosses the gap 1102 may be set by determining where to locate the substrate W on the substrate support WT. However, the curvature of the gap 1102 is a fixed operating parameter defined by the dimensions of the substrate W and the surrounding part of the substrate support WT.

[0157] By determining the risk of a defect occurring in dependence on the angles a and cp, more accurate determinations may be made of: whether it is necessary to slow down the relative movement speed of the substrate W and the fluid handling structure IH, the number of slowdowns that are required to contain each defect, and / or the extent of each slowdown that is required.

[0158] The present embodiment provides a model for attempting to optimise the route of a substrate W / substrate support WT and the angles a and cp that occur along the route. The model determines thedefect risk associated with each angle a and cp during a gap 1102 crossing along the route. The model may then attempt to determine an improved route, and / or orientations of the substrate W / substrate support WT along the improved route, so as to reduce the risk of defects occurring. The improved route may reduce the water loss and bubble related defects for a given throughput, or increase the throughput for a given defectivity rate. The model may determine the improvements to the route iteratively.

[0159] The model of the present embodiment may be a stand-alone model implemented in a computer system for controlling the operations in a lithographic apparatus.

[0160] Alternatively, the model of the present embodiment may be implemented with the abovedescribed model for predicting the fields on a substrate W where defects are expected to occur.

[0161] Alternatively, the model of the present embodiment may be implemented together with the above-described the models of embodiments for iteratively improving the determination of the scanner exposure route, movement speeds / accelerations on the scanner exposure route, and / or determining operational data for reducing the defectivity rate. In particular, the determined changes to the operational data include changes the angle a and / or the angle cp.

[0162] Embodiments also include determining the properties of an exposure process so as to reduce the extent of defects caused by edge water loss. In particular, the scanner exposure route and / or the movement speeds on the scanner exposure route may be determined in a way that attempts to minimise the extent of edge water loss.

[0163] As described earlier, in an immersion lithographic apparatus, there is an immersion space 11 that is filled with immersion liquid that is typically water. The immersion space 11 remains substantially stationary relative to the projection system PS while the substrate W and substrate support WT move underneath it. A fluid handling structure IH both supplies immersion liquid to the immersion space 11 and removes immersion liquid from the immersion space 11. The fluid handling structure IH thereby substantially confines the immersion liquid to the immersion space 11 with the immersion liquid having a meniscus between the fluid handling structure IH and substrate W.

[0164] Edge water loss is an effect that can cause loss of the immersion liquid from the immersion space 11. Edge water loss may occur at the edge of the substrate W. For example, film pulling may cause edge water loss. The movement of the substrate W relative to the fluid handling structure IH has a drag effect on the meniscus of the immersion liquid. The drag, which is experienced in particular at the trailing edge, i.e. receding edge, of the fluid handling structure IH in the relative movement, can cause droplets of immersion liquid on the surface of the substrate W. Such droplets, that are typically water droplets, may reduce yield. In particular, the droplets may cause water marks when the droplets are bulldozed. In addition, the droplets may cause big bubble formation, and consequent imaging defects, when there is a collision between the leading edge, i.e. advancing edge, of the fluid handling structure IH with the droplets.

[0165] As described earlier with reference to Figures 6 and 10, when a substrate W is loaded on a substrate support WT, a ring 802a of the substrate support WT surrounds the substrate W in the plane of the substrate W. There is an annular gap 803a, 803b, 1102 between the substrate W and the ring 802a, i.e., the surrounding part of the substrate support WT. The gap 803a, 803b, 1102 is required to avoid direct physical contact between the substrate W and the ring 802a. The locations at which the fluid handling structure IH crosses the gap 803a, 803b, 1102 may be associated with an increased risk of edge water loss occurring.

[0166] The known technique for reducing edge water loss effects is to reduce the movement speeds on one or more parts of the scanner exposure route. The speed reduction may be implemented through either manual control or automatic control. The automatic control may use layout information to predict the exposure route, determine the edge water loss that may occur along the exposure route, calculate the alignment of the fluid handling structure IH’ s trailing edge during the crossing of the gap 803a, 803b, 1102, determining a slower movement speed based on the alignment, and reducing the actual movement speed to the determined slower movement speed at the crossing of the gap 803a, 803b, 1102.

[0167] It has been found out that, in some circumstances, the known technique of reducing the movement speeds on one or more parts of the scanner exposure route may actually increase edge water loss effects. The overall detectivity rate and / or extent resulting from edge water loss may therefore increase. The increase in edge water loss effects may be caused by the change in movement speeds and / or trajectory / routing of the substrate support WT, and / or the exposure routing, reducing the control of the immersion liquid in the immersion space 11. The changed movement speeds may also increase the edge water loss effects due to the resulting changes in the exposure route, the length of the exposure route, the location of the gap 803a, 803b, 1102 crossing, and / or the movement direction after the gap 803a, 803b, 1102 crossing.

[0168] It has been found out that the scanner exposure routing, also referred to herein as exposure routing, may have a greater influence on the occurrence of edge water loss than the movement speed. A reduction in edge water loss effects may therefore be achieved through an improved determination of all of the properties of an exposure process, including the exposure routing.

[0169] Embodiments attempt to optimise the exposure routing determination so as to reduce edge water loss effects. The exposure routing determination according to embodiments is explained below.

[0170] In embodiments, a best case scenario exposure process may be determined for a specific product. The best case scenario exposure process provides a preferred edge water loss performance level for which the defect rate / extent due to edge water loss are acceptable given the user specifications. In the best case scenario exposure process, the edge water loss performance level is determined to be good and preferably close to optimum. For the best case scenario exposure process, contact line speed curves may be determined for the gap 803a, 803b, 1102 crossings for every edge water loss move of trailing edge of the fluid handling structure IH. The contact line speed curvesprovide the movement speeds of gap 803a, 803b, 1102 crossings that are expected to minimise the occurrence of edge water loss effects.

[0171] The contact line speed curves may be used to attempt to optimise the determination of the properties of exposure processes that are different from the best case scenario. Each exposure process may be determined so that it closely matches the contact line speeds of the best case scenario, so far as possible given the restrictions imposed by user and other requirements.

[0172] The below equation may be used to attempt to optimise an exposure routing:where:N = the total number of exposure fieldsF = an exposure field k = an edge water loss move C = a contact line speed curve J = is a function that is minimised to attempt to determine optimal properties of and exposure process

[0173] Embodiments include minimising the function J over the differences between the contact speed line curves (Q of the best case scenario (Cop() and a new case (Cnew) for every edge water loss move (k). The minimisation attempts to determine the best exposure field F properties. The input arguments for each exposure field F may include, for example, the preparatory-speed, the scan-speed, and other properties. The minimisation process may determine changes to the input arguments so as to attempt to determine the properties of each exposure field F for minimising the occurrence of edge water loss.

[0174] Each contact line speed curve may depend on the exposure field F, causing a specific gap 803a, 803b, 1102 crossing, and the exposure fields F,_; and ,+; that are respectively before and after the gap 803a, 803b, 1102 crossing. This is set out in the below equation:Ck = CkFi-1,Fi,Fi+1')

[0175] Embodiments provide a method of determining the properties of an exposure process. The method comprises obtaining a first set of contact line speed curves for a first exposure process that provides a preferred edge water loss performance. Each contact line speed curve in the first set of contact line speed curves defines a movement speed at which a fluid handling structure IH , or just the trailing edge of a fluid handling structure IH, may cross a gap between a substrate W and a substrate support WT with an edge water loss performance being achieved.

[0176] Embodiments comprise determining, for a second exposure process that is different from the first exposure process, a second set of contact speed line curves. Each contact line speed curve in the second set of contact line speed curves defines a movement speed at which a fluid handling structure IH, or a trailing edge of a fluid handling structure IH, crosses a gap 803a, 803b, 1102 between a substrate W and a substrate support WT.

[0177] Embodiments then determine the properties of the second exposure process so as to minimise the overall difference between the first and second set of contact speed line curves.

[0178] Embodiments also include using a model to determine the properties of an exposure process for reducing the extent of defects caused by edge water loss.

[0179] Accordingly, embodiments allow the improved determination of an exposure process, in particular the scanner exposure route and the movement speeds on the scanner exposure route, for reducing the extent of defects caused by edge water loss.

[0180] Embodiments include a number of modifications and variations to the above described techniques.

[0181] For example, embodiments have been described with reference to a model. Embodiments include the use of other tools than a model to perform the described processes for improving operational data. The model according to embodiments may be executed by a computer system. The computer system may be the same as, or separate from the controller or control system 500 of the lithographic apparatus.

[0182] The method of embodiments may be encoded in a computer program that contains instructions to perform embodiments, e.g., autonomously or at the instruction of the lithographer. The computer program may be provided as an upgrade, e.g., a software upgrade, for existing lithographic apparatus. The computer program may be incorporated in the lithographic apparatus at the time of manufacture thereof.

[0183] In embodiments, the second determination block 502 may determine the defectivity risk of the received operational data in dependence on the heuristics / user based data and the physical data. Embodiments also include the second determination block 502 being used to improve other performance metrics, such as reducing dynamic interaction (e.g. between the substrate support WT and the fluid handling structure IH) and to improve imaging / focus.

[0184] Embodiments may provide a lithographic apparatus. The lithographic apparatus may have any / all of the other features or components of the lithographic apparatus as described above. For example, the lithographic apparatus may optionally comprise at least one or more of a source SO, an illumination system IL, a projection system PS, a substrate support WT, etc..

[0185] Specifically, the lithographic apparatus may comprise the projection system PS configured to project the radiation beam B towards the region of the surface of a substrate W. The lithographic apparatus may further comprise the substrate support WT as described in any of the above embodiments and variations.

[0186] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, 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, liquidcrystal displays (LCDs), thin film magnetic heads, etc..

[0187] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented by instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.

[0188] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus.

[0189] Embodiments of the present invention are further described in the following numbered clauses:1. A computer system configured to perform a method of determining operational data for a control system of a lithographic apparatus, the method comprising: determining initial operational data for use in performing exposure processes on a substrate; repeatedly changing the initial operational data and determining one or more performance metrics of the changed operational data so as to determine changes to the initial operational data that improve the one or more performance metrics; and using operational data with an applied change so as to improve one or more of the performance metrics; wherein: the operational data includes the route of the substrate for performing the exposure processes and the movement of the substrate along the route; the one or more performance metrics include the overall time required for the exposure processes, the defectivity rate of the exposure processes and / or the sustainability of the exposure processes; and the applied change to the operational data includes a change to the route and / or a change to the acceleration of the substrate along part of the route.2. The computer system according to clause 1, further comprising receiving data related to the exposure processes; and determining the initial operational data in dependence on the received data.3. The computer system according to clause 2, wherein the received data related to the exposure processes includes physical data and heuristics / user based data.4. The computer system according to clause 3, wherein the physical data includes physical data on one or more of the performed processes for the exposure processes, a fluid handling structure, a substrate support and a substrate stage; wherein: the physical data on the performed processes includes one or more of the substrate properties, the resist contact angle, leaching properties and the resist type; the physical data on the fluid handling structure includes data on one or more of the properties of the fluid flows, the shape of the fluid handling structure and the usable fly heights of the fluid handling structure; the physical data on the substrate support includes data on one or more of the fluid extraction system, a ring structure of the substrate support radially outwards of the substrate, properties of the fluid flows in the fluid extraction system, the shape and dimensions of the fluid extraction system, the tolerable gap size between the ring structure and the substrate, and the usable positions of the substrate on the substrate support; and the physical data on the substrate stage includes data on one or more of the routing, maximum usable snap, movement constraints and the movement required to set-up the first exposure process.5. The computer system according to clause 3 or 4, wherein the heuristics / user based data includes data from user observations in previous use cases and user defined parameters of the exposure processes.6. The computer system according to any preceding clause, wherein the method is performed by a model.7. The computer system according to clause 6, wherein the model iteratively changes the operational data so as to determine improvements to one or more performance metrics of the operational data.8. The computer system according to any preceding clause, wherein the applied change to the operational data includes reducing the length of one or more linear movements along the route.9. The computer system according to any preceding clause, wherein the applied change to the operational data includes one or more of: using a different gas in gas knife of the lithographic apparatus; reducing the power consumption of the lithographic apparatus; changing the fly height of the fluid handling structure; changing the determination of where to position a substrate on the substrate support; changing the angle between an edge of the fluid handling structure and a gap between the substrate and a surrounding part of the substrate support; and changing the orientation of the fluid handling structure relative to the movement direction of the fluid handling structure.10. The computer system according to any preceding clause, wherein the applied change to the operational data includes arranging for the acceleration, or rate of change of acceleration, or rate of change of the rate of change of acceleration, to be substantially constant as a fluid handling structure crosses over a notch of the substrate.11. The computer system according to any preceding clause, wherein the method determines the operational data before starting the exposure processes that will use the operational data.12. The computer system according to any preceding clause, wherein the method determines changes to operational data whilst the exposure processes are being performed in dependence on the operational data.13. The computer system according to any preceding clause, wherein the lithographic apparatus is an immersion lithographic apparatus.14. A method of determining operational data for controlling a lithographic apparatus, the method comprising: determining initial operational data for use in performing exposure processes on a substrate; repeatedly changing the initial operational data and determining one or more performance metrics of the changed operational data so as to determine changes to the initial operational data that improve the one or more performance metrics; and using operational data with an applied change so as to improve one or more of the performance metrics; wherein: the operational data includes the route of the substrate for performing the exposure processes and the movement of the substrate along the route; the one or more performance metrics include the overall time required for the exposure processes, the defectivity rate of the exposure processes and / or the sustainability of the exposure processes; and the applied change to the operational data includes a change to the route and / or a change to the acceleration of the substrate along part of the route.15. The method according to clause 14, further comprising receiving data related to the exposure processes; and determining the initial operational data in dependence on the received data.16. The method according to clause 15, wherein the received data related to exposure processes includes physical data and heuristics / user based data.17. The method according to clause 16, wherein the physical data includes physical data on one or more of the performed processes for the exposure processes, a fluid handling structure, a substrate support and a substrate stage; wherein: the physical data on the performed processes includes one or more of the substrate properties, the resist contact angle, leaching properties and the resist type; the physical data on the fluid handling structure includes data on one or more of the properties of the fluid flows, the shape of the fluid handling structure and the usable fly heights of the fluid handling structure; the physical data on the substrate support includes data on one or more of the fluid extraction system, a ring structure of the substrate support radially outwards of the substrate, properties of the fluid flows in the fluid extraction system, the shape and dimensions of the fluid extraction system, the tolerable gap size between the ring structure and the substrate, and the usable positions of the substrate on the substrate support; and the physical data on the substrate stage includes data on one or more of the routing, maximum usable snap, movement constraints and the movement required to set-up the first exposure process.18. The method according to clause 15 or 16, wherein the heuristics / user based data includes data from user observations in previous use cases and user defined parameters of the exposure processes.19. The method according to any of clauses 14 to 18, wherein the method is performed by a model.20. The method according to clause 19, wherein the model iteratively changes the operational data so as to determine improvements to one or more performance metrics of the operational data.21. The method according to any of clauses 14 to 20, wherein the applied change to the operational data includes reducing the length of one or more linear movements along the route.22. The method according to any of clauses 14 to 21, wherein the applied change to the operational data includes one or more of: using a different gas in gas knife of the lithographic apparatus; reducing the power consumption of the lithographic apparatus; changing the fly height of the fluid handling structure; changing the determination of where to position a substrate on the substrate support; changing the angle between an edge of the fluid handling structure and a gap between the substrate and a surrounding part of the substrate support; and changing the orientation of the fluid handling structure relative to the movement direction of the fluid handling structure.23. The method according to any of clauses 14 to 22, wherein the applied change to the operational data includes arranging for the acceleration, or rate of change of acceleration, or rate of change of the rate of change of acceleration, to be substantially constant a fluid handling structure crosses over a notch of the substrate.24. The method according to any of clauses 14 to 23, wherein the method determines the operational data before starting the exposure processes that will use the operational data.25. The method according to any of clauses 14 to 24, wherein the method determines changes to operational data whilst exposure processes are being performed in dependence on the operational data.26. The method according to any of clauses 14 to 25, wherein the lithographic apparatus is an immersion lithographic apparatus.27. A method to improve operational data that is a recipe for an exposure process, comprising: providing the recipe for exposing a substrate in the exposure process; based on the recipe, determining a first motion plan with a first duration taking the least exposure time in the exposure process, the first motion plan containing a plurality of movements along neighbouring regions over a first portion of the substrate; determining a set of locations on the substrate having a risk of defect in the exposure process according to the first motion plan; based on the set of locations, determining a second motion plan with a second duration to reduce the risk of defect in the exposure process, the second motion plan containing at least one movement along at least two spaced apart regions over a second portion of the substrate and the second duration longer than the first duration; calculating time difference between the first duration and the second duration; and based on the time difference, modifying the timing of the second motion plan of the exposure process to minimise the time difference such that the exposure process according to the second motion plan completes at substantially the same time as that according to the first motion plan.28. A method of manufacturing devices using an immersion lithographic apparatus, the method comprising performing exposure processes in dependence on operational data determined according to any of clauses 14 to 27.29. A computer program comprising computer interpretable code that, when executed by a control system of an immersion lithographic apparatus, causes the immersion lithographic apparatus to perform exposure processes in dependence on operational data determined according to any one of clauses 14 to 27.30. An immersion lithographic apparatus comprising: a liquid confinement structure; a positioner; a projection system for projecting a radiation beam onto a substrate held by the positioner; and a controller configured to control the positioner and the projection system to perform exposure processes in accordance with operational data determined according to any of clauses 14 to 27.31. A computer system configured to perform a method of determining operational data for a control system of a lithographic apparatus, the method comprising: obtaining, for each of a plurality of zones on the face of moveable structure that holds a substrate during a scanning process, risk level data for each of a plurality of performance metrics; and determining operational data for use when an exposure field of view is above each zone during the scanning process in dependence on the obtained risk level data; wherein the risk level data is dependent on the properties of a specific product being manufactured and / or user preference data.32. A method of determining operational data for controlling a lithographic apparatus, the method comprising: obtaining, for each of a plurality of zones on the face of moveable structure that holds a substrate during a scanning process, risk level data for each of a plurality of performance metrics; and determining operational data for use when an exposure field of view is above each zone during the scanning process in dependence on the obtained risk level data; wherein the risk level data is dependent on the properties of a specific product being manufactured and / or user preference data.33. A computer program comprising computer interpretable code that, when executed by a control system of an immersion lithographic apparatus, causes the immersion lithographic apparatus to perform exposure processes in dependence on operational data determined according to clause 32.34. An immersion lithographic apparatus comprising: a liquid confinement structure; a positioner; a projection system for projecting a radiation beam onto a substrate held by the positioner; and a controller configured to control the positioner and the projection system to perform exposure processes in accordance with operational data determined according to clause 32.35. A method of determining the properties of an exposure process, the method comprising: obtaining a first set of contact line speed curves for a first exposure process that provides a preferred edge water loss performance, wherein each contact line speed curve in the first set of contact line speed curves defines a movement speed at which a trailing edge of a fluid handling structure may cross a gap between a substrate and a substrate support with a preferred edge water loss performance being achieved; determining, for a second exposure process that is different from the first exposureprocess, a second set of contact speed line curves, wherein each contact line speed curve in the second set of contact line speed curves defines a movement speed at which a trailing edge of a fluid handling structure crosses a gap between a substrate and a substrate support; and determining the properties of the second exposure process so as to minimise the overall difference between the first and second set of contact speed line curves.36. A computer program comprising computer interpretable code that, when executed by a control system of an immersion lithographic apparatus, causes the immersion lithographic apparatus to perform exposure processes determined according to the method of clause 35.37. An immersion lithographic apparatus comprising: a liquid confinement structure; a positioner; a projection system for projecting a radiation beam onto a substrate held by the positioner; and a controller configured to control the positioner and the projection system to perform exposure processes determined according to the method of clause 35.38. A computer system configured to perform a method of determining the position a substrate on a substrate support, the method comprising: obtaining properties of the substrate; obtaining properties of the substrate support; obtaining one or more performance measures of the substrate when loaded on the substrate support; and determining the position the substrate on the substrate support in dependence on the properties of the substrate, the properties of the substrate support, and the one or more performance measures.39. The computer system according to clause 38, wherein the properties of the substrate, the properties of the substrate support, and the one or more performance measures are measured and / or known data.40. The computer system according to clause 38 or 39, further comprising using a model to determine the position the substrate on the substrate support in dependence on the properties of the substrate, the properties of the substrate support, and the one or more performance measures.41. The computer system according to any of clauses 38 to 40, wherein the determination of the position of the substrate on the substrate support comprises a determination of the size and variation of the effective gap between the substrate and a ring of the substrate support.42. A method of determining the position a substrate on a substrate support, the method comprising: obtaining properties of the substrate; obtaining properties of the substrate support; obtaining one or more performance measures of the substrate when loaded on the substrate support; anddetermining the position the substrate on the substrate support in dependence on the properties of the substrate, the properties of the substrate support, and the one or more performance measures.43. The method according to clause 42, wherein the properties of the substrate, the properties of the substrate support, and the one or more performance measures are measured and / or known data.44. The method according to clause 42 or 43, further comprising using a model to determine the position the substrate on the substrate support in dependence on the properties of the substrate, the properties of the substrate support, and the one or more performance measures.45. The method according to any of clauses 42 to 44, wherein the determination of the position of the substrate on the substrate support comprises a determination of the size and variation of the effective gap between the substrate and a ring of the substrate support.

[0190] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention, where the context allows, is not limited to optical lithography.

[0191] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. A computer system configured to perform a method of determining operational data for a control system of a lithographic apparatus, the method comprising: determining initial operational data for use in performing exposure processes on a substrate; repeatedly changing the initial operational data and determining one or more performance metrics of the changed operational data so as to determine changes to the initial operational data that improve the one or more performance metrics; and using operational data with an applied change so as to improve one or more of the performance metrics; wherein: the operational data includes the route of the substrate for performing the exposure processes and the movement of the substrate along the route; the one or more performance metrics include the overall time required for the exposure processes, the defectivity rate of the exposure processes and / or the sustainability of the exposure processes; and the applied change to the operational data includes a change to the route and / or a change to the acceleration of the substrate along part of the route.

2. The computer system according to claim 1, further comprising receiving data related to the exposure processes; and determining the initial operational data in dependence on the received data, desirably wherein the received data related to the exposure processes includes physical data and heuristics / user based data.

3. The computer system according to claim 2, wherein the physical data includes physical data on one or more of the performed processes for the exposure processes, a fluid handling structure, a substrate support and a substrate stage; wherein: the physical data on the performed processes includes one or more of the substrate properties, the resist contact angle, leaching properties and the resist type; the physical data on the fluid handling structure includes data on one or more of the properties of the fluid flows, the shape of the fluid handling structure and the usable fly heights of the fluid handling structure; the physical data on the substrate support includes data on one or more of the fluid extraction system, a ring structure of the substrate support radially outwards of the substrate, properties of the fluid flows in the fluid extraction system, the shape and dimensions of the fluid extraction system, thetolerable gap size between the ring structure and the substrate, and the usable positions of the substrate on the substrate support; and the physical data on the substrate stage includes data on one or more of the routing, maximum usable snap, movement constraints and the movement required to set-up the first exposure process, and / or wherein the heuristics / user based data includes data from user observations in previous use cases and user defined parameters of the exposure processes.

4. The computer system according to any preceding claim, wherein the method is performed by a model, desirably wherein the model iteratively changes the operational data so as to determine improvements to one or more performance metrics of the operational data.

5. The computer system according to any preceding claim, wherein the applied change to the operational data includes reducing the length of one or more linear movements along the route, and / or wherein the applied change to the operational data includes one or more of: using a different gas in gas knife of the lithographic apparatus; reducing the power consumption of the lithographic apparatus; changing the fly height of the fluid handling structure; changing the determination of where to position a substrate on the substrate support; changing the angle between an edge of the fluid handling structure and a gap between the substrate and a surrounding part of the substrate support; and changing the orientation of the fluid handling structure relative to the movement direction of the fluid handling structure.

6. The computer system according to any preceding claim, wherein the applied change to the operational data includes arranging for the acceleration, or rate of change of acceleration, or rate of change of the rate of change of acceleration, to be substantially constant as a fluid handling structure crosses over a notch of the substrate, and / or wherein the method determines the operational data before starting the exposure processes that will use the operational data, and / or wherein the method determines changes to operational data whilst the exposure processes are being performed in dependence on the operational data, and / or wherein the lithographic apparatus is an immersion lithographic apparatus.

7. A method of determining operational data for controlling a lithographic apparatus, the method comprising: determining initial operational data for use in performing exposure processes on a substrate;repeatedly changing the initial operational data and determining one or more performance metrics of the changed operational data so as to determine changes to the initial operational data that improve the one or more performance metrics; and using operational data with an applied change so as to improve one or more of the performance metrics; wherein: the operational data includes the route of the substrate for performing the exposure processes and the movement of the substrate along the route; the one or more performance metrics include the overall time required for the exposure processes, the defectivity rate of the exposure processes and / or the sustainability of the exposure processes; and the applied change to the operational data includes a change to the route and / or a change to the acceleration of the substrate along part of the route.

8. The method according to claim 7, further comprising receiving data related to the exposure processes; and determining the initial operational data in dependence on the received data, desirably wherein the received data related to exposure processes includes physical data and heuristics / user based data.

9. The method according to claim 8, wherein the physical data includes physical data on one or more of the performed processes for the exposure processes, a fluid handling structure, a substrate support and a substrate stage; wherein: the physical data on the performed processes includes one or more of the substrate properties, the resist contact angle, leaching properties and the resist type; the physical data on the fluid handling structure includes data on one or more of the properties of the fluid flows, the shape of the fluid handling structure and the usable fly heights of the fluid handling structure; the physical data on the substrate support includes data on one or more of the fluid extraction system, a ring structure of the substrate support radially outwards of the substrate, properties of the fluid flows in the fluid extraction system, the shape and dimensions of the fluid extraction system, the tolerable gap size between the ring structure and the substrate, and the usable positions of the substrate on the substrate support; and the physical data on the substrate stage includes data on one or more of the routing, maximum usable snap, movement constraints and the movement required to set-up the first exposure process, and / orwherein the heuristics / user based data includes data from user observations in previous use cases and user defined parameters of the exposure processes.

10. The method according to any of claims 7-9, wherein the method is performed by a model, desirably wherein the model iteratively changes the operational data so as to determine improvements to one or more performance metrics of the operational data.

11. The method according to any of claims 7-10, wherein the applied change to the operational data includes reducing the length of one or more linear movements along the route, and / or wherein the applied change to the operational data includes one or more of: using a different gas in gas knife of the lithographic apparatus; reducing the power consumption of the lithographic apparatus; changing the fly height of the fluid handling structure; changing the determination of where to position a substrate on the substrate support; changing the angle between an edge of the fluid handling structure and a gap between the substrate and a surrounding part of the substrate support; and changing the orientation of the fluid handling structure relative to the movement direction of the fluid handling structure.

12. The method according to any of claims 7-11, wherein the applied change to the operational data includes arranging for the acceleration, or rate of change of acceleration, or rate of change of the rate of change of acceleration, to be substantially constant a fluid handling structure crosses over a notch of the substrate, and / or wherein the method determines the operational data before starting the exposure processes that will use the operational data, and / or wherein the method determines changes to operational data whilst exposure processes are being performed in dependence on the operational data, and / or wherein the lithographic apparatus is an immersion lithographic apparatus.

13. A method of manufacturing devices using an immersion lithographic apparatus, the method comprising performing exposure processes in dependence on operational data determined according to any of claims 7-12.

14. A computer program comprising computer interpretable code that, when executed by a control system of an immersion lithographic apparatus, causes the immersion lithographic apparatus to perform exposure processes in dependence on operational data determined according to any of claims 7-12.

15. An immersion lithographic apparatus comprising:a liquid confinement structure; a positioner; a projection system for projecting a radiation beam onto a substrate held by the positioner; and a controller configured to control the positioner and the projection system to perform exposure processes in accordance with operational data determined according to any of claims 7-12.

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