Method of monitoring performance, method of manufacturing device, computer program and lithographic apparatus

Abstract

A method of monitoring performance of an immersion lithography apparatus, the method comprising: moving a test substrate relative to a liquid confinement structure through a series of test route portions while projecting exposure radiation through an immersion liquid onto a photosensitive layer on the test substrate such that the photosensitive layer is exposed; wherein the series of test route parts comprise a first test route part and a second test route part; and the second test route part and the first test route part are symmetrical.

Description

Cross-reference to related applications

[0001] This application claims priority to EP application 23203252.4, filed on October 12, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to a method for monitoring the performance of a lithography apparatus, a method for manufacturing devices, a computer program, and a lithography apparatus. Background Technology

[0003] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. For example, a lithography apparatus can be used to manufacture integrated circuits (ICs). For instance, a lithography apparatus can project a pattern (often referred to as a “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 lithography apparatuses include: so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once; and so-called scanners, in which each target portion is irradiated by scanning the pattern with a radiation beam in a given direction (“scanning” direction) while simultaneously scanning the substrate parallel to or antiparallel to that direction.

[0004] As semiconductor manufacturing processes continue to advance, the size of circuit elements has been continuously shrinking, while the number of functional elements (such as transistors) in each device has been steadily increasing for decades, following a trend commonly known as 'Moore's Law'. To keep pace with Moore's Law, the semiconductor industry has been pursuing technologies that enable the creation of increasingly smaller features. To project patterns onto a substrate, photolithography devices use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features that can be patterned on the substrate. Typical wavelengths currently used are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm.

[0005] Further improvements in resolution for smaller features can be achieved by providing an immersion fluid (such as water) with a relatively high refractive index on the substrate during exposure. The effect of the immersion fluid is that it enables imaging of smaller features because the exposure radiation has a shorter wavelength in a fluid compared to in a gas. The effect of the immersion fluid can also be viewed as increasing the effective numerical aperture (NA) of the system and also increasing the depth of focus.

[0006] The immersion fluid can be confined by the fluid handling structure to a local area between the projection system of the photolithography device and the substrate. Summary of the Invention

[0007] In immersion lithography, defects can occur in the printed pattern due to bubbles in the immersion liquid and / or droplets remaining on the substrate surface. For example, many methods have been proposed to minimize the generation of these bubbles and droplets and mitigate their impact: providing a CO2 environment near the immersion liquid; special coatings on the substrate and substrate support; extracting gas and liquid from the gap between the substrate edge and the substrate support; and changing the scan path and speed. However, to date, it is not possible to completely eliminate the occurrence of bubbles and droplets and the defects they cause.

[0008] In many cases, defect rates can be reduced (yields increased) by lowering scan speeds or other formulation modifications that reduce throughput. Therefore, lithography machines can be configured with process parameters that balance throughput and yield to maximize the production of functional devices. To achieve this balance, the performance of the lithography apparatus must be monitored to avoid adverse effects on the output from variations in machine performance (often referred to as drift).

[0009] One method for monitoring performance is to expose test substrates between production substrate batches using stage movement, a subset of major production routes known to be particularly prone to defect generation. The test substrates are inspected to detect defects immediately, using only minimal process steps to develop the substrates and determine the defect rate. If the defect rate is low, it may be necessary to expose many test substrates to accurately determine the defect rate, which reduces the time available for exposing production substrates.

[0010] According to the present invention, a method for monitoring the performance of an immersion lithography apparatus is provided, the method comprising: The test substrate is moved relative to the liquid confinement structure through a series of test path sections, while exposure radiation is projected onto the photosensitive layer on the test substrate through the immersion liquid, thus exposing the photosensitive layer. The series of test routes includes a first test route section and a second test route section; and The second test route is symmetrical to the first test route.

[0011] According to the present invention, a method for manufacturing a device using an immersion lithography apparatus is provided, the method comprising, in sequence: The first batch of production substrates was exposed onto the device pattern using an immersion lithography apparatus; The method for monitoring the performance of the immersion lithography apparatus described above; and The second batch of production substrates was exposed onto the device pattern using an immersion lithography apparatus.

[0012] According to the present invention, a computer program including computer-interpretable code is provided, which, when executed by the control system of an immersion lithography apparatus, causes the immersion lithography apparatus to perform the above-described method.

[0013] According to the present invention, an immersion lithography apparatus is provided, comprising: Liquid confinement structure; Positioner; A projection system for projecting a radiation beam onto a substrate held by a positioner; and The controller is configured to control the positioner and projection system to: The test substrate is moved relative to the liquid-confined structure through a series of test path sections, while a radiation beam is projected through the immersion liquid onto the photosensitive layer on the test substrate, thus exposing the photosensitive layer. The series of test routes includes a first test route section and a second test route section; and The second test route is symmetrical to the first test route.

[0014] Other embodiments, features, and advantages of the present invention, as well as the structure, operation, features, and advantages of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0015] Embodiments of the invention will now be described by way of example only with reference to the accompanying schematic diagrams, wherein corresponding reference numerals indicate corresponding parts, and wherein: Figure 1 A schematic overview of the photolithography apparatus is provided; Figure 2 and Figure 3 Two different versions of the fluid handling system used for the photolithography projection device are depicted in cross-section; Figure 4 This is a diagram illustrating an exemplary route for production exposure of a substrate; Figure 5 This is a diagram illustrating a portion of the test route used in an embodiment of the present invention; Figure 6 It is a diagram illustrating the symmetry that can be used in embodiments of the present invention; and Figure 7 This is a flowchart of an embodiment of the present invention.

[0016] The features shown in the accompanying drawings are not necessarily drawn to scale, and the dimensions and / or arrangements depicted are not limiting. It is to be understood that the drawings include optional features that may not be essential to the invention. Furthermore, not all features of the device are depicted in every drawing, and these drawings may only show some parts relevant to describing a particular feature. Detailed Implementation

[0017] In this document, the terms “radiation” and “beam” are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., with wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm).

[0018] The terms “mask,” “mask,” or “patterning device” as used herein can be broadly interpreted to refer to any general patterning device that can be used to impart a patterned cross-section to an incoming radiation beam, corresponding to a pattern to be created in a target portion of a substrate. The term “optical valve” can also be used in this context. Examples of such patterning devices, in addition to classic masks (transmissive or reflective masks, binary masks, phase-shifting masks, hybrid masks, etc.), include programmable mirror arrays and programmable LCD arrays.

[0019] Figure 1 A lithography apparatus is schematically depicted. The lithography apparatus includes an irradiation system (also called an irradiator) IL configured to adjust a radiation beam B (e.g., UV radiation or DUV radiation), a mask support (e.g., a mask stage) MT configured to support a pattern forming device (e.g., a mask) MA and connected to a first positioner PM (configured to accurately position the pattern forming device MA according to certain parameters), a substrate support (e.g., a substrate stage) WT configured to hold a substrate (e.g., a wafer coated with resist) W and connected to a second positioner PW (configured to accurately position a substrate support WT according to certain parameters), and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted by the radiation beam B by the pattern forming device MA onto a target portion C (e.g., including one or more dies) of the substrate W.

[0020] In operation, the irradiation system IL receives a radiation beam B from a radiation source SO, for example, via a beam delivery system BD. The irradiation system IL may include various types of optical components for guiding, shaping, and / or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components or any combination thereof. The irradiator IL can be used to modulate the radiation beam B to achieve a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0021] The term “projection system” as used herein should be interpreted broadly to encompass all types of projection systems, including refractive, reflective, refracting-reflective, distorting, magnetic, electromagnetic, and / or electrostatic optical systems or any combination thereof, as appropriate, depending on the exposure radiation and / or other factors used, such as the use of immersion liquids or vacuum. Any use of the term “projection lens” in this document may be considered synonymous with the more general term “projection system.”

[0022] The photolithography apparatus belongs to the type in which at least a portion of the substrate W can be covered by an immersion liquid (e.g., water) having a relatively high refractive index to fill the immersion space 11 between the projection system PS and the substrate W; this is also known as immersion lithography. More information on immersion techniques is given in US 6,952,253, which is incorporated herein by reference.

[0023] Photolithography apparatus can be of the type having two or more substrate supports WT (also known as "dual stages"). In such "multi-stage" machines, substrate supports WT can be used in parallel, and / or the step of preparing a substrate W for subsequent exposure can be performed on a substrate W located on one of the substrate supports WT, while another substrate W on other substrate supports WT is used to expose patterns on the other substrate W.

[0024] In addition to the substrate support WT, the lithography apparatus may include a measurement stage (not depicted in the figures). The measurement stage is arranged to hold sensors and / or cleaning devices. The sensors may be arranged to measure the properties of the projection system PS or the properties of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning devices may be arranged to clean part of the lithography apparatus, such as part of the projection system PS or part of a system providing immersion liquid. The measurement stage may be movable below the projection system PS when the substrate support WT is away from the projection system PS.

[0025] In operation, a radiation beam B is incident on a pattern forming device (e.g., a mask) MA held on a mask support MT, and patterned by a pattern (design layout) present on the pattern forming device MA. Having traversed the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position measurement system IF, the substrate support WT can be accurately moved, for example, to position different target portions C in the path of the radiation beam B at a focused and aligned location. Similarly, a first positioner PM and possibly another position sensor (not in...) Figure 1 (As clearly depicted in the diagram) can be used to accurately position the patterning device MA relative to the path of the radiation beam B. The patterning device MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2, as illustrated, occupy dedicated target portions, they can be located in the space between the target portions. When the substrate alignment marks P1, P2 are located between the target portions C, these are referred to as scribing alignment marks.

[0026] To illustrate the invention, a Cartesian coordinate system is used. A Cartesian coordinate system has three axes: the x-axis, the y-axis, and the z-axis. Each of these three axes is orthogonal to the other two. A rotation about the x-axis is called an Rx rotation. A rotation about the y-axis is called an Ry rotation. A rotation about the z-axis is called an Rz rotation. The x-axis and y-axis define a horizontal plane, while the z-axis is in the vertical direction. The Cartesian coordinate system is not limiting of the invention but is used only for illustration. Conversely, another coordinate system (such as a cylindrical coordinate system) can be used to illustrate the invention. The orientation of the Cartesian coordinate system can be different, for example, such that the z-axis has a component along the horizontal plane.

[0027] Immersion lithography has been introduced into photolithography systems to achieve improved resolution for smaller features. In an immersion lithography apparatus, a liquid layer of immersion fluid with a relatively high refractive index is inserted into an immersion space 11 between the apparatus's projection system PS (through which a patterned beam is projected toward the substrate W) and the substrate W. The immersion fluid at least covers a portion of the substrate W beneath the final element of the projection system PS. Therefore, at least a portion of the substrate W undergoing exposure is immersed in the immersion fluid.

[0028] In commercial immersion lithography, the immersion liquid is water. Typically, this water is highly purified distilled water, such as ultrapure water (UPW), commonly used in semiconductor manufacturing plants. In immersion systems, UPW is often purified, and it can undergo additional processing steps before being supplied to the immersion space 11 as the immersion liquid. Besides water, other liquids with high refractive indices can also be used as immersion liquids, such as hydrocarbons (e.g., fluorinated hydrocarbons) and / or aqueous solutions. Furthermore, the use of fluids other than liquids in immersion lithography has been envisioned.

[0029] In this specification, reference will be made in the description to partial immersion, wherein the immersion fluid is confined in use to an immersion space 11 between the final component and the surface facing the final component. The facing surface is the surface of the substrate W or the surface of a support stage (or substrate support WT) coplanar with the surface of the substrate W. (Note that unless otherwise explicitly stated, references to the surface of the substrate W below also refer to a supplement to or alternative to the surface of the substrate support WT; and vice versa). A fluid handling structure IH existing between the projection system PS and the substrate support WT is used to confine the immersion fluid to the immersion space 11. The immersion space 11, filled with the immersion fluid, is smaller in the plane 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 the substrate support WT move below.

[0030] Other immersion systems have been envisioned, such as unconfined immersion systems (so-called 'fully wetted' immersion systems) and bath-type immersion systems. In an unconfined immersion system, the area covered by the immersion liquid is larger than the surface beneath the final component. The liquid outside the immersion space 11 exists as a thin liquid film. The liquid can cover the entire surface of the substrate W, or even the substrate W and the substrate support WT coplanar with the substrate W. In a bath-type system, the substrate W is completely immersed in a bath of immersion liquid.

[0031] A fluid handling structure IH is a structure that supplies immersion liquid into, removes immersion liquid from, and thereby confines immersion liquid within immersion space 11. It includes features that are part of a fluid supply system. The arrangement disclosed in PCT patent application publication number WO 99 / 49504 is an earlier fluid handling structure that includes conduits for supplying or recovering immersion liquid from immersion space 11 and operates depending on the relative movement of the stage below projection system PS. In more recent designs, the fluid handling structure extends along at least a portion of the boundary of immersion space 11 between the final element of projection system PS and substrate support WT or substrate W, thereby partially defining immersion space 11.

[0032] A fluid handling structure (IH) can have a selection of different functions. Each function can be derived from the corresponding feature that enables the fluid handling structure IH to perform that function. The fluid handling structure IH can be referred to by many different terms, each referring to a function, such as barrier components, sealing components, fluid supply systems, fluid removal systems, liquid confinement structures, etc.

[0033] Immersion liquid can be used as immersion fluid. In this case, the fluid handling structure IH can be a liquid handling system. Referring to the above description, references to features defined relative to the fluid in this paragraph can be understood to include features defined relative to the liquid.

[0034] The photolithography apparatus has a projection system PS. During exposure of the substrate W, the projection system PS projects a patterned radiation beam onto the substrate W. To reach the substrate W, the path of the radiation beam B extends from the projection system PS through an immersion liquid confined by a fluid handling structure IH between the projection system PS and the substrate W. The projection system PS has a lens element in contact with the immersion liquid, i.e., the last element in the beam path. This lens element in contact with the immersion liquid may be referred to as the 'last lens element' or 'final element'. The final element is at least partially surrounded by the fluid handling structure IH. The fluid handling structure IH confines the immersion liquid below the final element and above the facing surface.

[0035] like Figure 1The depicted photolithography apparatus includes a controller 500. The controller 500 is configured to control the substrate support WT.

[0036] Figure 2 A localized liquid supply system or fluid handling system is schematically depicted. The liquid supply system is provided with a fluid handling structure IH (or liquid confinement structure) extending along at least a portion of the 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, although some relative movement may exist in the Z direction (optical axis direction). In the example, a seal is formed between the fluid handling structure IH and the surface of the substrate W, and this seal can be a non-contact seal, such as a gas seal (such a system with a gas seal is disclosed in EP1,420,298) or a liquid seal.

[0037] The fluid handling structure IH at least partially confines the immersion liquid within an immersion space 11 between the final element of the projection system PS and the substrate W. This immersion space 11 is formed at least partially by the fluid handling structure IH, which is positioned below and surrounds the final element of the projection system PS. The immersion liquid enters the immersion space 11 below the projection system PS and within the fluid handling structure IH through one of the liquid openings 13. The immersion liquid can be removed through another liquid opening 13. The immersion liquid can enter the immersion space 11 through at least two liquid openings 13. Which liquid opening 13 is used to supply the immersion liquid and, optionally, which liquid opening 13 is used to remove the immersion liquid may depend on the direction of movement of the substrate support WT.

[0038] Immersed liquid can be confined to the immersion space 11 by a contactless seal, such as a gas seal 16 formed by gas, which is formed between the bottom of the fluid processing structure IH and the surface of the substrate W during use. Gas in the gas seal 16 is supplied under pressure to the gap between the fluid processing structure IH and the substrate W via inlet 15. The gas is extracted via outlet 14. The overpressure at gas inlet 15, the vacuum at outlet 14, and the geometry of the gap are arranged such that there is an inward high-speed gas flow, thereby confining the immersed liquid. Such a system is disclosed in US 2004 / 0207824, which is incorporated herein by reference in its entirety. In the example, the fluid processing structure IH does not have a gas seal 16.

[0039] Figure 3 It is a side cross-sectional view depicting yet another liquid supply system or fluid handling system. Figure 3 The arrangements illustrated and described below can be applied to the above description and Figure 1The illustrated photolithography apparatus has a liquid supply system provided with a fluid handling structure IH (or liquid confinement structure) that extends at least a portion of the boundary of the immersion space 11 between the final element of the projection system PS and the substrate support WT or substrate W.

[0040] The fluid processing structure IH at least partially confines the immersion liquid to an immersion space 11 between the final element of the projection system PS and the substrate W. The immersion space 11 is formed at least partially by the fluid processing structure IH positioned below and surrounding the final element of the projection system PS. In an example, the fluid processing structure IH includes a 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 in which a plurality of small holes 84 are formed in the mesh. Such a system is disclosed in US 2010 / 0045949 A1, the entirety of which is incorporated herein by reference.

[0041] The main component 53 includes a supply port 72 for supplying immersion liquid to the immersion space 11 and a recovery port 73 for recovering immersion liquid from the immersion space 11. The supply port 72 is connected to a liquid supply device 75 via a passage 74. The liquid supply device 75 supplies immersion liquid to the supply port 72 via the corresponding passage 74. The recovery port 73 recovers immersion liquid from the immersion space 11. The recovery port 73 is connected to a liquid recovery device 80 via a passage 79. The liquid recovery device 80 recovers the immersion liquid recovered via the recovery port 73 via a passage 29. A porous component 33 is disposed in the recovery port 73. The immersion space 11 is formed between the projection system PS and the fluid processing structure IH on one side and the substrate W on the other side by performing liquid supply operations using the supply port 72 and liquid recovery operations using the porous component 33.

[0042] Figure 4An exemplary route R40 is depicted, followed by a substrate W, for exposing target portions C001 to C107 on the substrate W. The target portions are exposed sequentially by number. Target portions depicted with dense shading (e.g., C104) are edge target portions exposed at a low rate. Target portions depicted with light shading (e.g., C085) are edge target portions, which are exposed at a slower rate but faster than the target portions depicted with dense shading. Edge target portions are exposed, but the exposure motion only covers the portion of the target portion that overlaps with the substrate W, not the full length of the edge target portion. Route R40 is calculated by optimizing throughput and includes long diagonal movements R41, R42. Diagonal movements R41, R42 are transfer movements between the exposure of a target portion at the end of a row and the exposure of a target portion at the beginning of the next row. Diagonal movement R41 occurs after the exposure of edge target portion C104 and repositions the substrate to expose edge target portion C105. The diagonal motion R42 occurs after the edge target portion C003 is exposed, and the substrate W is repositioned to expose the edge target portion C004.

[0043] As will be seen, this production route primarily consists of linear motion in the scanning (+ / -Y) or lateral (+ / -X) directions. This measure, along with the speed variation of the selected edge sections described, effectively reduces defects caused by immersion liquid loss (watermarks) or air bubbles trapped in the immersion liquid. Other measures and routes can be designed, but there is always a trade-off to be determined between defect rate and throughput.

[0044] To achieve this compromise, the lithography machine needs to be aware of the defect rate, the impact of speed variations on the defect rate, and any changes in this relationship. Therefore, it is well known that device production in a lithography apparatus is typically interrupted between batches to perform tests to monitor the defect rate performance of the lithography apparatus. These tests may involve exposing multiple substrates while moving them through a test path, a selected section of the overall production route sensitive to defects related to immersion liquid loss. The substrate exposed for testing purposes is referred to herein as the test substrate, and it is generally the same as the substrate exposed for device fabrication, referred to as the production substrate. However, the test substrate may not have undergone the previous exposure and processing steps. The number of defects appearing in the test substrate is then measured to determine whether the lithography apparatus is performing within specifications. Any deviation from expected performance (drift) can be addressed through maintenance actions or adjustments to the formulation of subsequent batches.

[0045] However, if the expected number of defects is low, for example, only a few or fewer defects per substrate, it may be necessary to perform test exposures on many test substrates. In this case, the time required for test exposures increases, and the production availability of the lithography apparatus decreases. Therefore, it is desirable to minimize the requirements for test exposures to monitor the performance of the lithography machine.

[0046] Now refer to Figures 5 to 7 Embodiments of the present invention are described. Figure 5 The text describes multiple test route segments that can be employed in embodiments of the invention to minimize the number of test substrates required to monitor the performance of the lithography apparatus. Figure 6 The diagram illustrates symmetry that can be used in embodiments of the present invention. Figure 7 This is a flowchart of a method according to an embodiment of the present invention.

[0047] like Figure 5 The depicted test exposure route 100 includes several test route sections 101 to 106, defined by dashed lines or dotted chain outlines. Test route sections 101 to 106 are designed to be particularly sensitive to the generation of defects, such as those caused by bubbles, floating bubbles, and watermarks. Test route sections 101 to 106 can be selected from a route library.

[0048] The first test path portion 101 corresponds to a portion of the production path to be executed in the production of a device whose performance is to be monitored in the photolithography apparatus. Desiredly, the first test path portion 101 includes at least one scanning segment (a period during which the substrate moves along a straight line at a constant speed) and a reversal segment (a period during which the substrate moves around a curved path to reverse its direction of movement). The second test path portion 102 is symmetrical to the first test path portion 101. In this case, the second test path portion 102 is mirror-symmetrical to the first test path portion 101 about an axis passing through the center of the substrate W and parallel to the scanning direction (Y-axis) of the production exposure. The third test path portion 103 is symmetrical to the first test path portion 101. In this case, the third test path portion 103 is mirror-symmetrical to the first test path portion 101 about an axis passing through the center of the substrate W and perpendicular to the scanning direction (Y-axis) of the production exposure. The fourth test path portion 104 is symmetrical to the third test path portion 103. In this case, the fourth test path portion 104 is mirror-symmetrical to the third test path portion 103 about an axis passing through the center of the substrate W and parallel to the scanning direction (Y-axis) of the production exposure.

[0049] It should be understood that the symmetry between the first test route portion 101 and the fourth test route portion 104 can be described in other ways. For example, the fourth test route portion 104 can be described as mirror-symmetric with respect to the second test route portion 102 about an axis passing through the center of the substrate W and perpendicular to the scan direction (Y-axis) of the production exposure. Moreover, the fourth test route portion 104 can be described as having 180° rotational symmetry with respect to the first test route portion 101 about an axis passing through the center of the substrate W and perpendicular to it (Z-axis).

[0050] The symmetry between the first test line section 101 to the fourth test line section 104 means that the probability of defects occurring between each test line section and its corresponding section in the production line can be expected to be substantially the same. Therefore, a test exposure route including four test line sections 101 to 104 will have approximately four times the probability of defects occurring compared to a test route with only one test line instance. This means that fewer test substrates can be used to determine the performance of the lithography apparatus compared to the case where only one test line section is included in the test exposure route. Alternatively, the performance of the lithography apparatus can be determined more accurately and / or more precisely compared to the case where only one test line section is included in the test exposure route.

[0051] Ideally, the symmetry between test route sections 101 to 104 corresponds to the symmetry present in the relevant sections of the liquid confinement structure. For example, if the features of the liquid confinement structure defining the immersion space 11 (e.g., gas seal 16) have a shape with mirror symmetry on the X and Y axes, then ideally, there should be a corresponding mirror symmetry between the different test route sections. If the features of the liquid confinement structure defining the immersion space 11 have rotational symmetry, then ideally, there should be a corresponding rotational symmetry between the different test route sections. For example, gas seal 16 may have a rhomboid or a rhomboid shape with rounded corners. Having symmetry between the test route sections corresponding to the symmetry of the liquid confinement structure ensures that the additional test route sections have the same probability of generating defects as the corresponding sections of the production route.

[0052] Figure 5 A first additional test line portion 105 and a second additional test line portion 106 are also depicted. One of the additional test line portions 105 and 106 corresponds to another portion of the production line where defects are easily generated. The first additional test line portion 105 and the second additional test line portion 106 have the aforementioned symmetry. The first additional test line portion 105 and the second additional test line portion 106 do not need to be symmetrical or even similar in shape to the test line portions 101 to 104. In addition to the aforementioned test line portions 101 to 104, using the additional test line portions 105 and 106, the performance of the lithography apparatus with respect to multiple production line portions can be measured using the same test substrate, but this is limited by the space on the test substrate.

[0053] When measuring the performance of a lithography apparatus relative to multiple parts of the production line, contrary to intuition, it is desirable to have more copies of the production line sections that are less likely to produce defects, so that the overall number of defects measured is more similar.

[0054] Desiredly, at least one test path section 101 to 106 includes an edge crossing during which at least a portion of the immersion space 11 containing the immersion liquid intersects with the edge of the test substrate. It is well known that edge crossings have a high probability of generating defects.

[0055] It should be noted that defects associated with route sections with a high probability of defect generation (such as route sections including edge intersections) are not necessarily located in or near the area of ​​substrate W scanned by that route section. This is because bubbles introduced into the immersion liquid at the edge intersection may take unpredictable time to drift into the path of the radiation beam B, resulting in imaging defects. Similarly, when the immersion liquid remains on substrate W, it may be pushed by subsequent movement of substrate W and remain at a point some distance from its origin. Therefore, apart from the aforementioned test route sections, it is expected that the entire test route will substantially cover the entire substrate W in a manner similar to the production route.

[0056] In some cases, the exposure path can be defined by specifying the die (or field) to be scanned, as well as the scanning sequence and orientation. The lithography apparatus is programmed to combine field scanning with standard rotation movement. Test paths can be specified in the same way. Additional parameters, such as scan speed, can also be specified. In some cases, the parameters of the test path (such as scan speed) may differ from those applied during production. In particular, parameter values ​​chosen for the test path may include, for example, increasing the probability of defects, such as increasing the scan speed. In this case, it may be desirable to calibrate the probability of defects generated in the test path relative to the probability of defects generated in the production path so that the test process accurately measures the defect rate of the production path. In other cases, periodically performing the test process may be sufficient to detect any changes in the results. Even if the exact nature and magnitude of the performance changes of the lithography apparatus are not yet known, such changes in the test results can effectively indicate performance changes in the lithography apparatus, thus prompting further investigation.

[0057] Although the invention has been described above as being used to monitor the performance of a lithography apparatus over time, it will also be understood that the invention can be used to compare the performance of different lithography apparatuses to achieve machine-to-machine matching.

[0058] As mentioned above, the test substrate is exposed to radiation beam B as it moves along the test path. Defects to be detected in this method can cause localized variations in the dose delivered to the photosensitive layer, for example, because air bubbles in the immersion liquid may act as lenses. Therefore, defects can be detected by developing and inspecting the exposed photoresist. In some cases, defects may be detectable as latent images before the photoresist is developed. In this test method, the photoresist need not be exposed to the pattern. However, to avoid the need to modify the patterning device, it may be convenient to expose the test substrate to the pattern used for producing the substrate. Alternatively, a pattern that is particularly sensitive to defects can be used to make defect detection easier.

[0059] Figure 6 This is a perspective view used to understand the different symmetries that may be employed in embodiments of the invention. As can be seen, test path portion 110 may reflect about axes A1 and A2 and / or rotate about axis A3. In this example, test path portion 113 is the test path portion reflected in axis A1; test path portion 111 is the test path portion 110 reflected in axis A2, and test path portion 112 is the test path portion 110 rotated about axis A3. These axes A1 to A3 are illustrated as mutually orthogonal and centered on the center of the substrate W. However, it will be understood that strict orthogonality is not required. Axes A1 to A3 also do not need to pass through the center of the substrate W. As understood, the test path portions used in the invention may exhibit combinations of symmetries, such as multiple mirror symmetries or mirror symmetries and rotational symmetries, and thus translational symmetries. Figure 6 In the diagram, test route sections 110 to 114 are depicted as simple L-shapes, making it easy to identify the symmetry, but this does not necessarily represent the actual shape of the test route sections.

[0060] The flowchart of an embodiment of the present invention is as follows Figure 7 As described. In step S1, the first batch of production substrates is exposed using the production route. In step S2, one or more test substrates are exposed using a test route that includes the aforementioned test route portion. In step S3, the test substrates are analyzed to determine metrics of the lithography apparatus performance. As mentioned above, the analysis of the test substrates may involve the development of photoresist or the detection of latent images in the photoresist. The analysis of the test substrates can be as simple as counting defects, or it may involve a more detailed analysis of the nature and location of the defects. Based on the analysis of the test substrates, in step S4, it is determined whether the performance of the lithography apparatus has changed (drifted).

[0061] If the performance of the lithography apparatus has been significantly altered, remedial measures can be taken as described in step S5. These remedial measures may involve some or all of the following: maintenance of the immersion lithography apparatus; adjustments to the operating parameters of the immersion lithography apparatus; and adjustments to the parameters of the production route. For example, if a test substrate reveals an increased defect rate due to watermarking, the liquid confinement structure can be examined to check for defects in the gas seal 16, such as blocked outlets. Alternatively or additionally, the flow rate or pressure of the gas seal 16 can be increased. Further, alternatively or additionally, the speed at which the substrate W moves during a portion of the production route can be reduced.

[0062] Subsequently, in step S6, the modified formulation may be used to expose additional batch production substrates. It will be understood that the analysis of the test substrates may take some time, especially in the case of photoresist development; therefore, the subsequent exposure of the production substrates in step S6 can be performed in parallel with the analysis of the test substrates in step S3.

[0063] Using multiple test path sections with different orientations can provide additional information about the location and cause of any variations in the performance of the lithography apparatus. For example, if in a symmetrical test path section, an increase in watermark associated with movement in the positive Y direction but not with movement in the negative Y direction, this could indicate a problem at the tail of the gas seal 16 when the substrate W moves in the positive Y direction.

[0064] The method of the present invention can be encoded in a computer program containing instructions to perform the invention, such as autonomously or according to instructions from a lithography machine. The computer program can be provided as an upgrade (e.g., a software upgrade) to an existing lithography apparatus. The computer program can be incorporated into the lithography apparatus during its manufacture.

[0065] The present invention can provide a photolithography apparatus. This photolithography apparatus may have any / all other features or components described above. For example, the photolithography apparatus may optionally include at least one or more of a source SO, an irradiation system IL, a projection system PS, a substrate support WT, etc.

[0066] Specifically, the lithography apparatus may include a projection system PS configured to project a radiation beam B toward a surface region of the substrate W. The lithography apparatus may also include a substrate support WT as described in any of the embodiments and variations above.

[0067] While specific applications of photolithography apparatus in IC manufacturing are discussed in this article, it should be understood that the photolithography apparatus described herein can have other applications. Possible other applications include the fabrication of integrated optical systems, guiding and detecting patterns in magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc.

[0068] Where the context permits, embodiments of the invention may be implemented using 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 means 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, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.); and others. Further, firmware, software, routines, and instructions may be described herein as performing certain actions. However, it should be understood that this description is merely for convenience, and such actions are in fact produced by a computing device, processor, controller, or other device executing firmware, software, routines, instructions, etc., and doing so enables actuators or other devices to interact with the physical world.

[0069] Although embodiments of the invention may be specifically referred to herein in the context of a lithography apparatus, embodiments of the invention may be used in other apparatuses. Embodiments of the invention may form part of a mask inspection apparatus, a measurement apparatus, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses may generally be referred to as lithography tools.

[0070] Embodiments of the present invention are further described in the following numbered clauses: 1. A method for monitoring the performance of an immersion lithography apparatus, the method comprising: The test substrate is moved relative to the liquid confinement structure through a series of test path sections, while exposure radiation is projected onto the photosensitive layer on the test substrate through the immersion liquid, thereby exposing the photosensitive layer. The series of test routes includes a first test route and a second test route; and The second test route section is symmetrical to the first test route section. 2. The method according to Clause 1, wherein the first test route portion and the second test route portion have symmetry, the symmetry being selected from the group consisting of: mirror symmetry, rotational symmetry, and translational symmetry. 3. The method according to Clause 2, wherein the symmetry corresponds to the symmetry of the liquid confinement structure. 4. The method according to clauses 1, 2 or 3, wherein the first test path portion and the second test path portion are mirror-symmetric about a line of symmetry passing through the center of the substrate. 5. The method according to Clause 4, wherein the test path portion further comprises a third test path portion and a fourth test path portion, wherein the third test path portion and the fourth test path portion are respectively symmetrical about another line of symmetry to the first test path portion and the second test path portion, the other line of symmetry passing through the center of the substrate and desirably perpendicular to the line of symmetry passing through the center of the substrate. 6. The method according to Clause 1, 2 or 3, wherein the first test path portion and the second test path portion are rotationally symmetrical about the center of the substrate and perpendicular to the substrate. 7. The method according to any one of the foregoing clauses, wherein the series of test routes includes a first additional test route portion and a second additional test route portion; and The second additional test route section is symmetrical to the first additional test route section, but asymmetrical to either the first test route section or the second test route section. 8. The method according to any one of the preceding clauses, wherein at least one test path portion comprises at least one scanning segment and at least one turning segment, during said at least one scanning segment the test substrate moves relative to said liquid confinement structure along a substantially straight line at a substantially constant speed, and during said at least one turning segment the test substrate moves along a curved path such that the direction of movement of said test substrate changes by 90 degrees relative to the curve. 9. The method according to any one of the preceding clauses, wherein at least one test route portion includes an edge crossing, during which at least a portion of the immersion space containing the immersion liquid intersects with an edge of the test substrate. 10. The method according to any one of the preceding clauses further includes analyzing the photosensitive layer after the exposure during the test route portion to determine performance parameters of the immersion lithography apparatus, such as bubble defect rate and / or watermark rate. 11. The method according to Clause 9, wherein analyzing the photosensitive layer includes developing the photosensitive layer. 12. The method according to Clause 10, wherein analyzing the photosensitive layer includes detecting a latent image in the photosensitive layer. 13. A method for manufacturing a device using an immersion lithography apparatus, the method comprising, in sequence: The first batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus; Perform the method for monitoring the performance of the immersion lithography apparatus according to any one of the foregoing clauses; and The second batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus. 14. The method according to Clause 13, wherein the production substrate moves along the production path relative to the liquid confinement structure of the immersion lithography apparatus during exposure to the device pattern; and At least one test route section corresponds to a portion of the production route. 15. The method according to Clause 14, wherein, for at least a portion of the test route section, the speed at which the test substrate moves is faster than the speed at which the production substrate moves during the corresponding portion of the production route. 16. The method according to any one of clauses 13 to 15, further comprising a remedial action step based on the result of the monitoring step prior to the exposure of the second production substrate, wherein the remedial action is selected from the group consisting of: Maintenance procedures for the immersion lithography apparatus; Adjustment of the operating parameters of the immersion lithography apparatus; and Adjustment of the parameters of the production route. 17. A computer program comprising computer-interpretable code, which, when executed by a control system of an immersion lithography apparatus, causes the immersion lithography apparatus to perform the method according to any one of the preceding clauses. 18. An immersion lithography apparatus, comprising: Liquid confinement structure; Positioner; A projection system for projecting a radiation beam onto a substrate held by the positioner; and The controller is configured to control the locator and the projection system to: The test substrate is moved relative to the liquid-confined structure through a series of test path sections, while the radiation beam is projected through the immersion liquid onto the photosensitive layer on the test substrate, thereby exposing the photosensitive layer. The series of test routes includes a first test route and a second test route; and The second test route section is symmetrical to the first test route section. 19. The immersion lithography apparatus according to Clause 18, wherein the first test path portion and the second test path portion have symmetry selected from the group consisting of: mirror symmetry, rotational symmetry, and translational symmetry. 20. The immersion lithography apparatus according to Clause 19, wherein the symmetry corresponds to the symmetry of the liquid-confined structure. 21. An immersion lithography apparatus according to clauses 18, 19 or 20, wherein the first test path portion and the second test path portion are mirror-symmetric about a line of symmetry passing through the center of the substrate. 22. The immersion lithography apparatus according to Clause 21, wherein the test path portion further comprises a third test path portion and a fourth test path portion, wherein the third test path portion and the fourth test path portion are respectively symmetrical about another line of symmetry to the first test path portion and the second test path portion, the other line of symmetry passing through the center of the substrate and desirably perpendicular to the line of symmetry passing through the center of the substrate. 23. An immersion lithography apparatus according to clauses 18, 19 or 20, wherein the first test path portion and the second test path portion are rotationally symmetrical about an axis passing through the center of the substrate and perpendicular to the substrate. 24. The immersion lithography apparatus according to any one of clauses 18 to 23, wherein the series of test path portions includes a first additional test path portion and a second additional test path portion; and The second additional test route section is symmetrical to the first additional test route section, but asymmetrical to either the first test route section or the second test route section. 25. An immersion lithography apparatus according to any one of clauses 18 to 24, wherein at least one test path portion comprises at least one scanning section and at least one turning section, during said at least one scanning section the test substrate moves relative to said liquid confinement structure along a substantially linear path at a substantially constant speed, and during said at least one turning section the test substrate moves along a curved path such that the direction of movement of the test substrate changes by 90 degrees relative to the scanning section. 26. An immersion lithography apparatus according to any one of clauses 18 to 25, wherein at least one test path portion includes an edge crossing, during which at least a portion of the immersion space containing the immersion liquid intersects with an edge of the test substrate. 27. The immersion lithography apparatus according to any one of clauses 18 to 26, wherein the controller is further configured to control the positioner and the projection system to: Before performing the step of moving the test substrate, the first batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus; then The second batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus. 28. The immersion lithography apparatus according to Clause 27, wherein the controller is further configured to control the positioner and the projection system to move the production substrate along the production path relative to the liquid confinement structure of the immersion lithography apparatus during exposure to the device pattern; and At least one test route section corresponds to a portion of the production route.

[0071] 29. The immersion lithography apparatus according to Clause 28, wherein the controller is further configured to control the positioner and the projection system to move the test substrate at a speed faster than the speed at which the production substrate moves during the corresponding portion of the production route, for at least a portion of the test route.

[0072] Although specific references may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be understood that the invention is not limited to optical lithography where the context permits.

[0073] While specific embodiments of the invention have been described above, it will be understood that the invention can be practiced in other ways than those described. The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

Claims

1. A method for monitoring the performance of an immersion lithography apparatus, the method comprising: The test substrate is moved relative to the liquid confinement structure through a series of test path sections, while exposure radiation is projected onto the photosensitive layer on the test substrate through the immersion liquid, thereby exposing the photosensitive layer. The series of test routes includes a first test route and a second test route; and The second test route section is symmetrical to the first test route section.

2. The method of claim 1, wherein the first test route portion and the second test route portion have symmetry, the symmetry being selected from the group consisting of: mirror symmetry, rotational symmetry, and translational symmetry, wherein preferably the symmetry corresponds to the symmetry of the liquid confinement structure.

3. The method of claim 1 or 2, wherein the first test path portion and the second test path portion are mirror-symmetric about a line of symmetry passing through the center of the substrate, and preferably wherein the test path portion further comprises a third test path portion and a fourth test path portion, wherein the third test path portion and the fourth test path portion are respectively symmetric about another line of symmetry passing through the center of the substrate and preferably perpendicular to the line of symmetry passing through the center of the substrate.

4. The method of claim 1 or 2, wherein the first test path portion and the second test path portion are rotationally symmetrical about an axis passing through the center of the substrate and perpendicular to the substrate.

5. The method according to any one of the preceding claims, wherein the series of test routes includes a first additional test route portion and a second additional test route portion; and The second additional test path portion is symmetrical to the first additional test path portion but asymmetrical to either the first or second test path portion, and / or at least one of the test path portions includes at least one scanning segment and at least one turning segment, during which the test substrate moves relative to the liquid confinement structure at a substantially constant speed along a substantially straight line, during which the test substrate moves along a curved path such that the direction of movement of the test substrate changes by 90 degrees, and / or at least one of the test path portions includes an edge intersection, during which at least a portion of the immersion space containing the immersion liquid intersects with the edge of the test substrate.

6. The method according to any one of the preceding claims further comprises analyzing the photosensitive layer after the exposure during the test route portion to determine performance parameters of the immersion lithography apparatus, such as bubble defect rate and / or watermark rate.

7. The method of claim 6, wherein analyzing the photosensitive layer comprises developing the photosensitive layer, or wherein analyzing the photosensitive layer comprises detecting a latent image in the photosensitive layer.

8. A method for manufacturing a device using an immersion lithography apparatus, the method comprising, in sequence: The first batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus; Perform the method for monitoring the performance of the immersion lithography apparatus according to any one of the preceding claims; as well as The second batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus.

9. The method of claim 8, wherein the production substrate moves along the production path relative to the liquid confinement structure of the immersion lithography apparatus during exposure to the device pattern; and At least one test route portion corresponds to a portion of the production route, whereby, For at least a portion of the test route, the test substrate moves faster than the production substrate during the corresponding portion of the production route, and / or includes a remedial action step based on the result of the monitoring step prior to the exposure of the second production substrate, wherein the remedial action is selected from the group consisting of: Maintenance procedures for the immersion lithography apparatus; Adjustment of the operating parameters of the immersion lithography apparatus; and Adjustment of the parameters of the production route.

10. A computer program comprising computer-interpretable code, which, when executed by a control system of an immersion lithography apparatus, causes the immersion lithography apparatus to perform the method according to any one of the preceding claims.

11. An immersion lithography apparatus, comprising: Liquid confinement structure; Positioner; A projection system for projecting a radiation beam onto a substrate held by the positioner; as well as The controller is configured to control the locator and the projection system to: The test substrate is moved relative to the liquid-confined structure through a series of test path sections, while the radiation beam is projected through the immersion liquid onto the photosensitive layer on the test substrate, thereby exposing the photosensitive layer. The series of test routes includes a first test route and a second test route; and The second test route section is symmetrical to the first test route section.

12. The immersion lithography apparatus of claim 11, wherein the first test path portion and the second test path portion have symmetry selected from the group consisting of: mirror symmetry, rotational symmetry, and translational symmetry, wherein preferably, wherein the symmetry corresponds to the symmetry of the liquid confinement structure, and / or wherein the first test path portion and the second test path portion are mirror symmetric about a line of symmetry passing through the center of the substrate, wherein preferably, the test path portion further comprises a third test path portion and a fourth test path portion, wherein the third test path portion and the fourth test path portion are respectively symmetric about another line of symmetry passing through the center of the substrate and preferably perpendicular to the line of symmetry passing through the center of the substrate.

13. The immersion lithography apparatus of claim 12, wherein the first test path portion and the second test path portion are rotationally symmetrical about an axis passing through the center of the substrate and perpendicular to the substrate.

14. The immersion lithography apparatus according to any one of claims 11 to 13, wherein the series of test path portions includes a first additional test path portion and a second additional test path portion; and The second additional test path portion is symmetrical to the first additional test path portion but asymmetrical to either the first or second test path portion, and / or at least one test path portion includes at least one scanning segment and at least one turning segment, during which the test substrate moves relative to the liquid confinement structure at a substantially constant speed along a substantially linear path, and during the at least one turning segment the test substrate moves along a curved path such that the direction of movement of the test substrate changes by 90 degrees relative to the curve, and / or at least one test path portion includes an edge intersection, during which at least a portion of the immersion space containing the immersion liquid intersects with the edge of the test substrate, and / or wherein the controller is further configured to control the positioner and the projection system to: Before performing the step of moving the test substrate, the first batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus; then The second batch of production substrates is exposed onto the device pattern using the immersion lithography apparatus.

15. The immersion lithography apparatus of claim 14, wherein the controller is further configured to control the positioner and the projection system to move the production substrate along the production path relative to the liquid confinement structure of the immersion lithography apparatus during exposure to the device pattern; and At least one test route section corresponds to a portion of the production route, and preferably the controller is also configured to control the positioner and the projection system to move the test substrate at a speed faster than the speed at which the production substrate moves during the corresponding portion of the production route, targeting at least a portion of the test route section.

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