Lithographic apparatus and method with thermal control system

Abstract

A device comprising a compartment, the compartment comprising a wafer platform configured to hold a semiconductor wafer on a fixture, wherein the wafer platform is configured to follow a route within the compartment during operational use, the device comprising: a first component having a first surface facing a first portion of the route; a second component having a second surface facing a second portion of the route; and a thermal control system operable to maintain a first temperature of the first surface and a second temperature of the second surface at a common set point value.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to European application 19156434.3 filed on February 11, 2019, and the entire contents of said European application are incorporated herein by reference. Technical Field

[0003] The invention relates to a photolithography device and a photolithography method. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a substrate (usually to a target portion of a substrate). A lithographic apparatus can be used, for example, in the manufacture of an integrated circuit (IC). In that case, a pattern forming device (which is alternatively referred to as a mask or reticle) can be used to produce a circuit pattern to be formed on a single layer of the IC. This pattern can be transferred to a target portion (e.g., a portion including a die, a die, or several dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is usually performed via imaging onto a layer of a radiation-sensitive material (resist) disposed on the substrate. Typically, a single substrate will contain a network of adjacent target portions that are continuously patterned. Photolithography is widely considered to be one of the key steps in the manufacture of ICs and other devices and / or structures.

[0005] In order to reduce the minimum printable size, imaging may be performed using radiation having a short wavelength. Thus, it has been proposed to use an EUV radiation source providing EUV radiation in the range of, for example, 13 nm to 14 nm. It has further been proposed that EUV radiation having a wavelength less than 10 nm (e.g. in the range of 5 nm to 10 nm, such as 6.7 nm or 6.8 nm) may be used. Such radiation is referred to as extreme ultraviolet (EUV) radiation or soft x-ray radiation.

[0006] Overlay error indicates the deviation between the actual location of the reticle pattern imaged onto the wafer and the expected location. There is a threshold for this error, beyond which the imaging result is unacceptable. The order of magnitude is nanometers (in EUV) and shrinks with each new generation of EUV scanners. The process involves placing the next patterned layer in a stack of tens of layers onto the previously patterned layer, which together will ultimately form an integrated electronic circuit. Lateral displacement of one layer relative to another may cause the layers to not be properly connected, making the circuit unacceptable for operational use.

[0007] International patent application publication WO2018 / 041599 is incorporated herein by reference. The publication discloses an EUV lithography apparatus having a projection system configured to project a radiation beam patterned by a mask onto an exposure area on a substrate held on a substrate stage via a slit. The substrate stage is an element at the substrate platform and is in physical contact with the substrate, and can be physically and functionally integrated with an electrostatic clamp that clamps the substrate to the substrate stage. The electrostatic clamp has a cooling system for carrying away the heat generated at the clamp. The lithography apparatus operates in a scanning mode, in which the mask and the substrate are scanned simultaneously during projection. The radiation beam used to project a pattern onto the substrate transfers a large amount of heat to the substrate, which causes local heating of the substrate. The local expansion of the substrate caused by the heating reduces the accuracy of the overlap of the projected pattern with the pattern already present on the substrate. In order to solve this problem, the lithography apparatus disclosed in WO2018 / 041599 includes a cooling device located between the projection system and the substrate. The cooling device provides local cooling of the substrate near the area where the patterned radiation beam is incident on the substrate via the slit. In some embodiments, a pre-exposure calibration operation may be performed to ensure that the amount of cooling provided to the substrate by the cooling device is within a desired range. As the calibration operation does not need to be performed at a high frequency, the calibration operation may also utilize measurements obtained from a substrate table cooling system in addition to or instead of measurements obtained from sensors near a cooling surface of the cooling device.

[0008] It is desirable not to remove more heat from the substrate than that added by the radiation beam. Therefore, WO2018 / 041599 discloses that in some embodiments a heat shield is provided to reduce cooling in an area adjacent to the exposure area. In an embodiment, the heat shield is provided with one or more channels to allow cooling and / or heating of the heat shield by flowing a temperature regulating fluid through the channels. The flow of the temperature regulating fluid through one or more channels can be configured to maintain the heat shield at an ambient temperature such as, for example, about 22°C.

[0009] However, there remains the problem of ensuring that the amount of cooling provided by the cooling device balances (i.e. compensates for) the amount of heating by the radiation beam. The substrate table is configured to follow a route within a compartment of the lithographic apparatus. The problem is that the surfaces facing the substrate held on the fixture may be at different temperature levels. This means that each surface causes a different unknown heat load to the substrate.

[0010] This unknown heat load may adversely affect the calibration operation and hence the heat extraction by the cooling device.The resulting uncompensated heating of the radiation beam may reduce the accuracy with which the projected pattern is overlaid on the pattern already present on the substrate, ie increase the overlay error.

[0011] Furthermore, in addition to the local expansion of the substrate caused by the heating of the radiation beam, unknown thermal loads may also directly cause unwanted local expansion of the substrate. This further increases the overlay error. Summary of the invention

[0012] It is desirable to accurately control the heat extraction of the cooling device to compensate for radiation beam heating. Furthermore, it is desirable to reduce overlay errors caused by unwanted expansion of the substrate.

[0013] According to a first aspect of the invention there is provided a lithographic apparatus configured to project a patterned radiation beam via projection optics onto a target portion of a semiconductor wafer on a chuck held at a wafer stage in a compartment, wherein the wafer stage is configured to follow a route within the compartment in operational use of the lithographic apparatus, and wherein the lithographic apparatus comprises:

[0014] - a first component having a first surface facing a first portion of the route;

[0015] - a second component having a second surface facing a second portion of the route;

[0016] - a thermal control system operable to maintain a first temperature of the first surface and a second temperature of the second surface at a common set point magnitude.

[0017] According to a second aspect of the present invention, there is provided a photolithography method, comprising:

[0018] - projecting a patterned radiation beam via projection optics onto a target portion of a semiconductor wafer held on a chuck at a wafer stage in a compartment of a lithographic apparatus, wherein the lithographic apparatus comprises:

[0019] - a first component having a first surface facing a first portion of the route within the compartment; and

[0020] - a second component having a second surface facing a second portion of the route within the compartment;

[0021] - transporting the wafer platform along the route within the compartment; and

[0022] - operating a thermal control system to maintain a first temperature of the first surface and a second temperature of the second surface at a common set point magnitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which corresponding reference numerals indicate corresponding parts, and in which:

[0024] Figure 1 schematically depicting a lithographic apparatus with reflective projection optics;

[0025] Figure 2 Is a chip platform compartment Figure 1 A more detailed view of the device;

[0026] Figure 3 schematically illustrates measurement and exposure processes in a dual stage lithography apparatus according to known practice and modified according to an embodiment of the present invention;

[0027] Figure 4 schematically depicts a bottom view of the interior of a wafer stage compartment of a lithography apparatus;

[0028] Figure 5 a cross-sectional view schematically depicting the contents of a wafer stage compartment of a lithographic apparatus;

[0029] Figure 6 schematically depicts a cross-sectional view of exposure of a wafer on a cooled chuck, wherein the cooling device is used to compensate for radiation beam heating;

[0030] Figure 7 schematically depicts a cross-sectional view of exposure of a wafer on a cooled chuck, wherein a cooling device is used to compensate for radiation beam heating, and wherein there is parasitic wafer and chuck heating;

[0031] Figure 8 schematically depicts an implementation of active thermal control using a thermal control system according to an embodiment of the present invention; and

[0032] Fig. 9 An implementation of radiant beam heating compensation using active thermal control of other components with a cooling shroud according to an embodiment of the invention is schematically depicted. DETAILED DESCRIPTION

[0033] Figure 1 A lithographic apparatus 100 is schematically depicted. The apparatus comprises:

[0034] - Source module SO;

[0035] - an illumination system (illuminator) IL configured for conditioning a radiation beam B (e.g. EUV radiation);

[0036] a support structure (e.g., mask platform) MT configured to support a patterning device (e.g., mask or reticle) MA and connected to a first positioning device PM configured to accurately position the patterning device;

[0037] a substrate stage (eg wafer stage) WT configured to hold a substrate (eg a resist-coated wafer) W and connected to a second positioning device PW configured to accurately position the substrate; and

[0038] - a projection system (eg a reflective projection system) PS configured for projecting the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (eg comprising one or more dies).

[0039] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, to direct, shape, or control the radiation.

[0040] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions such as, for example, whether the patterning device is held in a vacuum environment. The support structure may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device. The support structure may comprise a frame or table, for example, which may be fixed or movable as desired. The support structure may ensure that the patterning device is in a desired position (e.g. relative to the projection system).

[0041] The term "patterning device" should be broadly interpreted as referring to any device that can be used to impart a pattern to a radiation beam in its cross-section so as to produce a pattern in a target portion of a substrate. The pattern imparted to the radiation beam may correspond to a specific functional layer in a device (such as an integrated circuit) formed in the target portion.

[0042] The pattern forming device can be transmissive or reflective. Examples of pattern forming devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary mask types, alternating phase shift mask types, attenuated phase shift mask types, and various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be discretely tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

[0043] Similar to the illumination system, the projection system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, as appropriate for the exposure radiation used, or for other factors such as the use of a vacuum. It may be desirable to use a vacuum for EUV radiation, since other gases may absorb too much radiation. Therefore, a vacuum environment may be provided to the entire beam path by means of vacuum walls and a vacuum pump.

[0044] As depicted here, the device is of the reflective type (eg, using a reflective mask).

[0045] The lithographic apparatus may be of a type having two ("dual stage") or more substrate platforms (and / or two or more mask stages). In such a "multi-stage" machine, the additional stages may be used in parallel, or preparatory steps may be performed on one or more stages while one or more other stages are being used for exposure.

[0046] refer to Figure 1 , the illuminator IL receives a beam of extreme ultraviolet radiation from a source module SO. Methods for generating EUV light include, but are not necessarily limited to, converting a material having at least one element (e.g., xenon, lithium, or tin) into a plasma state using one or more emission lines in the EUV range. In one such method (often referred to as laser produced plasma "LPP"), the desired plasma can be generated by irradiating a fuel (such as a droplet, stream, or cluster of a material having the desired line emitting element) with a laser beam. The source module SO may be a laser ( Figure 1 The source module is a part of an EUV radiation system (not shown in the figure), the laser is used to provide a laser beam for exciting the fuel. The resulting plasma emits output radiation, such as EUV radiation, which is collected using a radiation collector disposed in the source module. For example, when a CO2 laser is used to provide the laser beam for fuel excitation, the laser and the source module can be separate entities.

[0047] In these cases, the laser is not considered to form part of the lithographic apparatus, and the radiation beam is delivered from the laser to the source module by means of a beam delivery system BD comprising, for example, suitable directing mirrors and / or a beam expander. In other cases, the source may be an integral part of the source module (for example, when the source is a discharge produced plasma EUV generator (often referred to as a DPP source)).

[0048] The illuminator IL may comprise an adjuster for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial extent (generally referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. Furthermore, the illuminator IL may comprise various other components, such as a faceted field mirror arrangement and a faceted pupil mirror arrangement. The illuminator may be used to adjust the radiation beam to have a desired uniformity and intensity distribution in its cross section.

[0049] The radiation beam B is incident on a patterning device (e.g. a mask) MA held on a support structure (e.g. a mask stage) MT and is patterned by the patterning device MA. After reflection from the patterning device (e.g. a 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 positioning device PW and a position sensor PS2 (e.g. an interferometer device, a linear encoder or a capacitor sensor), the substrate stage WT can be accurately moved, for example in order to position a different target portion C in the path of the radiation beam B. Similarly, the first positioning device PM and a further position sensor PS1 can be used to accurately position the patterning device (e.g. a mask) MA relative to the path of the radiation beam B. The patterning device (e.g. a mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0050] An EUV diaphragm (e.g., a pellicle PE) is provided to protect the pattern forming device from particle contamination within the system. Such a pellicle is provided at the location shown and / or at other locations. Another EUV diaphragm SPF can be provided as a spectral purity filter, which is operable to filter out unwanted radiation wavelengths (e.g., DUV). These unwanted wavelengths may affect the photoresist on the wafer W in an undesirable manner. The SPF can also optionally help prevent the projection optics within the projection system PS from being contaminated by particles released during outgassing (or alternatively, a pellicle can be provided in place of the SPF to perform such an operation). Any of these EUV diaphragms may include any of the EUV diaphragms disclosed herein.

[0051] The depicted apparatus can be used in a variety of modes. In a scanning mode, the pattern imparted to the radiation beam is projected onto a target portion C while the pattern forming device support (e.g., mask platform) MT and the substrate platform WT are scanned synchronously (i.e., a single dynamic exposure). The speed and direction of the substrate platform WT relative to the pattern forming device support (e.g., mask platform) MT can be determined by the (reduced) magnification and image reversal characteristics of the projection system PS. In scanning mode, the maximum size of the exposure field limits the width of the target portion in a single dynamic exposure (in the non-scanning direction), while the length of the scanning movement determines the height of the target portion (in the scanning direction). As is well known in the art, other types of lithographic apparatus and operating modes are possible. For example, stepping modes are known. In so-called "maskless" lithography, a programmable pattern forming device is held stationary but with a changing pattern, and the substrate platform WT is moved or scanned.

[0052] Combinations and / or variations on the above-described modes of use or entirely different modes of use may also be used.

[0053] Figure 2 An embodiment of the lithographic apparatus is shown in more detail, comprising a radiation system 42, the illumination system IL and the projection system PS. Figure 2 The radiation system 42 shown in FIG. 4 is of the type that uses a laser to generate a plasma as a radiation source. EUV radiation can be generated by a very hot plasma generated from, for example, xenon (Xe), lithium (Li) or tin (Sn). In an embodiment, Sn is used to generate a plasma so as to emit radiation in the EUV range.

[0054] The radiation system 42 embodies Figure 1 The radiation system 42 includes a source chamber 47, which in this embodiment not only substantially encloses the EUV radiation source, but also encloses the collector 50, Figure 2 In the example of FIG. 5 , the collector 50 is a normal incidence collector, ie, a normal incidence collector, such as a multilayer mirror.

[0055] As part of the LPP radiation source, a laser system 61 is constructed and arranged to provide a laser beam 63, which is delivered by a beam delivery system 65 through an aperture 67 provided in the collector 50. In addition, the radiation system includes a target material 69, such as Sn or Xe, supplied by a target material supply 71. In this embodiment, the beam delivery system 65 is arranged to establish a beam path that is generally focused on a desired plasma formation location 73.

[0056] In operation, target material 69, which may also be referred to as fuel, is supplied in the form of droplets by the target material supply 71. A trap 72 is provided on the opposite side of the source chamber 47 to capture fuel that has not been turned into plasma for any reason. When such droplets of the target material 69 reach a plasma formation location 73, the laser beam 63 impinges upon the droplets and EUV radiation emitting plasma is formed inside the source chamber 47. In the case of a pulsed laser, this involves timing the pulses of laser radiation to coincide with the passage of the droplets through the location 73. These conditions produce a plasma having a plurality of 10 5 A highly ionized plasma with an electron temperature of 1000 K is formed. Energetic radiation produced during deexcitation and recombination of these ions includes the desired EUV emitted from the plasma at position 73. The plasma formation position 73 and the aperture 52 are located at the first and second focal points of the collector 50, respectively, and the EUV radiation is focused by the normal incidence collector mirror 50 onto an intermediate focus IF.

[0057] The radiation beam emitted from the source chamber 47 passes through the illumination system IL via reflectors 53, 54, as shown in Figure 2 5 is directed by the radiation beam 56 in FIG. The reflector directs the beam 56 via the pellicle PE onto a patterning device (e.g. a reticle or mask) positioned on a support (e.g. a reticle stage or mask stage) MT. A patterned beam 57 is formed which is imaged by the projection system PS via reflective elements 58, 59 onto a substrate carried by a wafer stage or substrate stage WT. The substrate W is held on the substrate stage WT by an electrostatic clamp CL. The substrate stage WT and its clamp CL are housed in a wafer stage compartment WSC.

[0058] The projection system PS has projection optics installed in a container (box) providing a specific low pressure environment. Such a container is called a projection optics box (POB). The POB and the wafer stage compartment WSC are separate environments. During exposure, the photoresist may outgas due to the radiation received from the POB. These gases should not reach the projection optics because they may contaminate the surface of the mirror (POB contains reflective optical components in EUV). Contamination can then interfere with imaging. Therefore, a dynamic gas lock DGL (not shown in the figure) is provided to reduce this contamination.

[0059] More elements than shown may typically be present in the illumination system IL and the projection system PS. For example, there may be one, two, three, four or even more reflective elements instead of the two reflective elements shown. Figure 2 Two elements 58 and 59 are shown.

[0060] As will be known to those skilled in the art, reference axes X, Y and Z may be defined for measuring and describing the geometry and behavior of the apparatus, its various components, and the radiation beams 55, 56, 57. At each component of the apparatus, local reference coordinate systems for the X, Y and Z axes may be defined. The Z axis is substantially coincident with the direction of the optical axis O at a given point in the system and is substantially perpendicular to the plane of the pattern forming device (mask) MA when describing a spatial relationship relative to the pattern forming device and to the plane of the substrate W when describing a spatial relationship relative to the substrate W. In the source module (apparatus) 42, the X axis is substantially coincident with the direction of the fuel flow (69, described below), while the Y axis is orthogonal to the direction pointing outward from the page, as indicated. On the other hand, near the support structure MT holding the mask MA, the local X axis is substantially transverse to the scanning direction aligned with the local Y axis. For convenience, in the schematic diagrams Figure 2 In such a region, the X-axis points outward from the page, again as labeled. These designations are conventional in the art and will be adopted herein for convenience. In principle, any reference coordinate system may be chosen to describe the device and its behavior.

[0061] In addition to producing the desired EUV radiation, the plasma may also produce radiation of other wavelengths, such as in the infrared, visible, UV (ultraviolet) and DUV (deep ultraviolet) ranges. IR (infrared) radiation from the laser beam 63 may also be present. Non-EUV wavelengths are not desired in the illumination system IL and projection system PS, and various measures may be deployed to block non-EUV radiation. Figure 2 Schematically depicted, for IR, DUV and / or other unwanted wavelengths, a spectral purity filter SPF may be applied upstream of the virtual source point IF. Figure 2 In the particular example shown, two spectral purity filters are depicted, one within the source chamber 47 and one at the output of the projection system PS.

[0062] Figure 3 The steps for exposing a target portion (e.g., a die) on a substrate W in a dual-stage lithography apparatus are illustrated. Two substrate stages (also referred to as wafer stages) are configured to follow the wafer stage compartment ( Figure 2 The substrate is then transported along the route indicated by steps 200, 202, 204, 210, 212, 214, 216, 218, 210 and 220.

[0063] The vacuum pre-aligner VPA is part of the wafer handling apparatus. The pre-aligner is a robot that places the substrate W' into the correct orientation (in the local XY plane) so that when it is transferred to the substrate stage at step 200 it has the correct orientation and is ready for measurement operations MEA.

[0064] The steps performed at the measurement station MEA are within the left dashed box, while the right dashed box shows the steps performed at the exposure station EXP. Sometimes, one of the substrate platforms WTa, WTb will be located at the exposure station, while the other substrate platform is located at the measurement station, as described above. At step 200, a new substrate W' is loaded from the vacuum pre-aligner VPA by a mechanism not shown in the figure. The two substrates (the substrate at the measurement station and the other substrate at the exposure station) are processed in parallel in order to increase the throughput of the lithography apparatus.

[0065] Reference is initially made to a newly loaded substrate W', which may be a previously unprocessed substrate and which is prepared with a new resist for exposure for the first time in the apparatus. However, typically, the lithographic process described will be only one step in a series of exposure and processing steps, so that the substrate W' has passed through this apparatus and / or other lithographic apparatus several times and may also undergo subsequent processes. With particular regard to the problem of improving overlay performance, the task is to ensure that the new pattern is applied exactly in the correct position on a substrate that has been subjected to one or more cycles of patterning and processing. These processing steps gradually introduce deformations in the substrate, which must be measured and corrected to achieve satisfactory overlay performance.

[0066] Previous and / or subsequent patterning steps (as just mentioned) may be performed in other lithographic equipment, and may even be performed in different types of lithographic equipment. For example, some layers in the device manufacturing process that are very demanding in terms of parameters such as resolution and overlay may be performed in more advanced lithographic tools than other layers that are less demanding. Thus, some layers may be exposed in immersion lithographic tools, while other layers are exposed in "dry" tools or in vacuum tools. Some layers may be exposed in tools operating at DUV wavelengths, while other layers are exposed using EUV wavelength radiation.

[0067] At 202, alignment measurements using substrate marks P1 (depicted as four crosses) and an image sensor (not shown) are used to measure and record the alignment of the substrate relative to substrate platform WTa / WTb. In addition, alignment sensor AS is used to measure several alignment marks across the substrate W'. In one embodiment, these measurements are used to establish a "wafer grid" that very accurately maps the distribution of the marks across the substrate, including any deformations from the nominal rectangular grid.

[0068] At step 204, a level sensor LS is also used to measure a wafer height (Z) map relative to the XY position. Typically, the height map is used only to achieve accurate focus of the exposed pattern. Primarily, the height map is used only to achieve accurate focus of the exposed pattern. The height map may additionally be used for other purposes.

[0069] When the substrate W' is loaded, configuration data 206 are received, which define the exposure to be performed and also define the properties of the wafer and the pattern previously generated on the wafer and the pattern to be generated on the wafer. The measurements of the wafer position, wafer grid and height map performed at 202, 204 are added to these configuration data, so that the complete set of configuration data and measurement data 208 can be transferred to the exposure station EXP. The measurement results of the alignment data include, for example, the X position and Y position of the alignment target formed in a fixed or nominally fixed relationship with the product pattern as the product of the lithography process. These alignment data obtained just before exposure are used to generate an alignment model, which has parameters that fit the model to the data. These parameters and the alignment model will be used during the exposure operation to correct the position of the pattern applied in the current lithography step. The model in use interpolates position deviations between the measured positions. Conventional alignment models may include four, five or six parameters, which together define the translation, rotation and scaling of the "ideal" grid at different sizes. Advanced models using more parameters are well known.

[0070] At 210, wafers W' and W are exchanged so that the measured substrate W' becomes substrate W and enters the exposure station EXP. Figure 1In the example apparatus of , this exchange is performed by exchanging substrate stages WTa and WTb within the apparatus so that substrates W, W' remain accurately clamped and positioned on those supports to preserve the relative alignment between the substrate stages and the substrates themselves. Therefore, once the stages have been exchanged, in order to utilize the measurement information 202, 204 for the substrate W (formerly W') in the control of the exposure step, all that is necessary is to determine the relative position between the projection system PS and the substrate stage WTb (formerly WTa). At step 212, mask alignment is performed using mask alignment marks (not shown in the figure). In steps 214, 216, 218, scanning movements and radiation are applied to consecutive target locations across the entire substrate W so as to complete the exposure of multiple patterns.

[0071] By using the alignment data and height map obtained at the measurement station during the performance of the exposure step, the patterns are accurately aligned relative to the desired locations, and in particular, relative to features previously placed on the same substrate. The exposed substrate, now marked as W", is unloaded from the apparatus at step 220 to ultimately undergo etching or other processes according to the exposed patterns.

[0072] Those skilled in the art will appreciate that the above description is a simplified overview of the many very detailed steps involved in one example of a real manufacturing situation. For example, there will often be separate stages of coarse and fine measurements using the same or different markings, rather than measuring alignment in a single pass. The coarse and / or fine alignment measurement steps may be performed before or after the height measurement, or interleaved.

[0073] Embodiments may include a scanner with a cooling hood or cooling device. The scanner has components whose surfaces are occasionally in the line of sight of the wafer. The components are all thermally conditioned so that they adopt the same temperature.

[0074] The lithographic scanner has cooling means for extracting heat from the wafer, the heat being generated by absorption of imaging radiation by the wafer.

[0075] The cooling power of the cooling device needs to be controlled very accurately and the required cooling power depends on many parameters.

[0076] The values ​​of these parameters may vary depending on the scenario and are considered in the wafer heating feed-forward (WHFF) model described below.

[0077] The mismatch between the extracted and generated heat causes thermally induced deformation of the wafer which results in overlay errors: undesired lateral displacement of locations of the imaged pattern relative to the desired locations.

[0078] The cooling device needs to be calibrated relative to the imaging radiation received at the wafer.An example of a calibration mechanism used involves monitoring the difference between the temperature of the cooling water of the electrostatic chuck at the inlet of the chuck and the temperature of the cooling water at the outlet of the chuck.

[0079] The temperature difference indicates the heat absorbed (or released) by the cooling water during its passage through the wafer chuck. Ideally, the temperature difference of the cooling water between the inlet and outlet represents the mismatch between the heat extracted by the cooling device and the heat generated in the wafer by the radiation received from the imaging radiation beam.

[0080] However, the cooling water of the wafer holder is exposed to parasitic heat loads in addition to the heat load from the exposure radiation. Examples of components in the scanner that represent parasitic heat loads are components that have a surface facing the wafer stage on their way through the wafer stage compartment. As a result, the parasitic heat loads interfere with the control of the heat extraction performed by the cooling device.

[0081] Figure 4 An example of a bottom view of the interior of a wafer stage compartment of a lithographic apparatus is schematically depicted. This is the view as it would be seen from the viewpoint of the wafer. The wafer transport device WH is located at the left side. Figure 3 The vacuum pre-aligner VPA shown in is a component of the wafer transport device. The measurement station MEA has a wafer platform heat shield with two components WS-HS-A and WS-HS-B, the wafer platform heat shield. The exposure station EXP has a wafer platform heat shield with two components WS-HS-C and WS-HS-D. In addition, at the exposure station EXP, the cooling hood heat shield component CH-HS is shown in close proximity to the projection optics box hatch component POB-H. The exposure is performed via the gap between the cooling hood heat shield CH-HS and the projection optics box hatch POB-H. These components face different parts of the route followed by the wafer platform, as shown in reference Figure 3 as described.

[0082] The metrology frame MF is shown by cross-hatched elements. The metrology frame is a trusted subsystem used as a reference for metrology components, such as components that accurately measure the position of the wafer stage and measure the topography of the wafer. The metrology frame is a very rigid construction in mechanical properties that is kept at a stable and precise temperature in order to minimize inaccuracies in the measurement results due to heat-induced deformations of the metrology frame.

[0083] Figure 5A cross-sectional view of the contents of a wafer stage compartment of a lithographic apparatus is schematically depicted. The metrology frame MF is again shown cross-hatched. The wafer transport apparatus has a component WH above the wafer W. The wafer transport apparatus also has a component in the form of a vacuum pre-aligner VPA below the wafer. Across the measurement station MEA and exposure station EXP, the wafer stage heat shield components WS-HS-A and WS-HS-B are shown above a wafer W supported by a clamp CL. In the exposure station EXP, the cooling hood heat shield component CH-HS and the projection optics box orifice component POB-H are shown above another wafer W, which is supported by its respective clamp CL. In the absence of operation of the embodiments described below, the surfaces of components WH, WS-HS-A / B / C / D, CH-HS and POB-H may have different temperatures, resulting in a number of parasitic heat loads to the wafer. The parasitic heat loads interfere with the control of heat extraction by the cooling apparatus, to which reference will now be made. Figure 6 and Figure 7 Describe it.

[0084] Figure 6 Schematically depicts a cross-sectional view of the exposure of a wafer on a cooled chuck, wherein the cooling device is used to compensate for the radiation beam heating. A cooling hood CH and its heat shield CH-HS (such as the cooling element and heat shield as disclosed in WO2018 / 041599) are provided to reduce the local cooling power P CH Provided to the wafer W. The purpose of cooling is to balance the local cooling power P CH With the radiation beam heating power P EUV .

[0085] The cooling hood CH is used to remove heat from the wafer W to prevent slipping and reduce the original overlap effect. In order to transfer heat from the wafer to the cooling hood, hydrogen gas for transferring heat is provided between cooling hood fingers (which are the parts of the cooling hood closest to the wafer in the downward direction) and the wafer W via the cooling hood, for example.

[0086] The required cooling power of the cooling hood CH is determined by the following equation:

[0087] P CH =h(p,T,z,TAC)*A*ΔT CH-wafer

[0088] where h is the heat transfer coefficient (depending on pressure, temperature, flight altitude and TAC), A is the surface area, and ΔT CH-waferis the temperature difference between the cooling hood and the wafer. The flying height is the distance between the (stationary) cooling hood and the wafer on the (moving) wafer platform WT. TAC is the thermal adaptation coefficient of the two surfaces and is a physical quantity that characterizes the behavior of gas or vapor particles when they collide with a solid or liquid bulk surface. The value of the adaptation coefficient depends on the surface properties and state and on the composition and pressure of the gas mixture in the environment, and on other parameters.

[0089] The power that needs to be extracted from the wafer is different for each product layer and should ideally be perfectly balanced with the EUV power and fed into the wafer heating feed forward model (WHFF model). The WHFF model enables prediction of the temperature difference to be neutralized by activating the cooling hood heater or chiller ( Fig. 9 928 in ). The model can also predict the original overlap effect ( Fig. 9 934), the original overlap effect can be obtained by POB ( Fig. 9 Optical system correction of 918).

[0090] Inputs to the WHFF model may include:

[0091] EUV power;

[0092] Reticle reflection curve;

[0093] The effective IR power in the wafer / fixture;

[0094] Cooling hood power P CH ;

[0095] Scanning speed

[0096] Fixture cooling water flow rate; and

[0097] DGL load curve.

[0098] Any mismatch in power between the model and reality may contribute to the overlay error.

[0099] To reduce overlay errors due to power mismatch, the cooling shroud power is calibrated relative to the EUV power. This calibration is performed by power measurements within the fixture. Since the system may drift, the balance is continuously monitored.

[0100] By comparing the measured temperature difference ΔT above the fixture with the modeled values ​​of the WHFF model, any imbalance can be corrected at least when it is caused by the cooling shroud and not by unknown parasitic heat loads.

[0101] The clamp CL is thermally controlled using cooling water CW. By monitoring the temperature T of the cooling waterout -T in (ΔT between the incoming cooling water and the outgoing cooling water), it can be determined how much heat P is extracted with respect to the cooling hood CH CH information.

[0102] When the flow rate is known and stable, the temperature difference ΔT above the clamp CL is calculated for the cooling hood power P CH In an ideal case, there is no parasitic heat load to the wafer and the measured power in the fixture is a balance between EUV and cooling hood. Different parasitic heat loads act on the wafer / fixture and these parasitic heat loads will interfere with the power measurement and these parasitic heat loads are now referenced to Figure 7 To describe it.

[0103] Figure 7 A cross-sectional view of exposure of a wafer on a cooled chuck is schematically depicted, wherein the cooling device is used to compensate for radiation beam heating, and wherein there is parasitic wafer and chuck heating.

[0104] Figure 7 include Figure 6 All elements of the cooling hood CH are removed, but parasitic heat loads are added. The hydrogen used to transport heat from the wafer W to the cooling hood CH can be dispersed in the compartment and also transport heat from the surface facing the wafer W and the chuck CL. This causes a heat load. For example, Figure 4 and Figure 5 The wafer stage heat shield components WS-HS-C and WS-HS-D shown in FIG. 1 have a structure that can transfer power P through the wafer. WS-HS provided to the surface of the fixture. In addition, for example, Figure 4 and Figure 5 The POB orifice component POB-H shown in FIG. 1 has a power source that can transfer power P through the wafer. POB-H provided to the surface of the fixture. In addition, Figure 4 and Figure 5 The measurement frame MF and the sensor attached thereto shown in FIG. 1 have the ability to transmit the power P via the chip. MF provided to the surface of the clamp. This may be the case if the clamp CL is thermally controlled at a temperature set point different from the temperature set point of the metrology frame MF.

[0105] As the wafer platform WT advances on its route through the wafer platform compartment, the wafer platform WT passes other components having surfaces facing respective portions of the route. These surfaces may cause parasitic heat loads. For example, the wafer transport device WH may transfer power P WHSimilarly, when the wafer is oriented and thermally conditioned on a vacuum pre-aligner VPA, the surface of the vacuum pre-aligner can transfer the power P to the fixture via the transfer of the wafer from the VPA. VPA (not shown in the figure) is provided to the clamp.

[0106] The parasitic heat load is summed via the wafer and fixture as the parasitic power P PAR , and compare it with the heating power P by the radiation beam EUV and the cooling hood power P CH The unbalanced fixture cooling power P CL Add. The power P caused by the heat load PAR and P CL is integrated into a cooling water CW temperature difference T out -T in This makes it impossible to use the cooling water CW temperature difference T out -T in to distinguish the actual source of the imbalance. The second problem with parasitic heat loads is that they will directly heat the wafer during exposure, which causes thermal expansion and additional overlay errors.

[0107] Embodiments of the present invention create a mini-environment in the wafer stage compartment to eliminate the parasitic heat load. This in turn enables online (in operational use) calibration and accurate control of the cooling shroud power.

[0108] The parasitic heat load can be eliminated by providing the same (or very close to the same) stable temperature to the surface facing the wafer from time to time.

[0109] These surfaces include a wafer chuck at the wafer stage, and a heat shield in a wafer stage compartment of the lithographic apparatus about which the wafer stage moves.

[0110] Preferably, the temperature of each of these surfaces is actively controlled to maintain a temperature set point despite the surfaces themselves receiving varying thermal loads in operational use of the lithographic apparatus.

[0111] To allow online cooling hood calibration, the parasitic heat load is removed from the equation. This is accomplished by a wafer stage compartment thermal mini-environment. Basically, this means that most or all wafer facing surfaces (including the fixture and wafer handling device) are actively controlled to the same temperature level. This is called active thermal control.

[0112] As discussed above, in the absence of active thermal control, Figure 4All surfaces shown facing the wafer platform may be at different temperature levels. This means that each surface causes a different unknown heat load to the wafer (via hydrogen conduction or radiation). This has an adverse impact on both online calibration and direct overlay effects.

[0113] In an initial state, all surfaces facing the wafer may have different temperature offsets.

[0114] In the isothermal state, all surfaces are calibrated to the same temperature relative to each other, but this temperature may differ from the measurement frame. There is a significant surface area that is still offset ( Figure 4 ), which still results in a parasitic heat load to the wafer / chuck.

[0115] In the best thermal match state, by lowering the set point of the wafer-facing surface to the set point of the metrology frame (22° C.), there is no longer a temperature difference between any of the surfaces. At this point, all parasitic heat loads from the wafer-facing surface are minimized.

[0116] To ensure that the temperature of each wafer-facing surface remains stable under the varying loads applied during exposure, active thermal control is used. This means that each module gets a separate control loop with, for example, a cooling water heater or chiller to maintain the set point, similar to the clamp. This approach is repeated for all wafer-facing surfaces. To enable active control of all surfaces to the same set point, for example exactly 22°C, the cooling water can be pre-cooled by approximately 100 mK below 22°C. To cool the cooling water, there are, for example, several options:

[0117] Separate Peltier elements per branch;

[0118] A single Peltier element pre-cools all branches;

[0119] Individual cabinets at reduced set points; and

[0120] A single cabinet with multiple outputs, each at a different temperature.

[0121] Figure 8 An implementation of active thermal control utilizing a thermal control system according to an embodiment of the present invention is schematically depicted.

[0122] The cabinet CAB pumps cooling water via the manifold MAN in a circuit through the various components in the wafer stage compartment. The components are the vacuum pre-aligner VPA, the electrostatic chuck CL, the mirror block MB, the wafer stage heat shield WS-HS (denoted Figure 4WS-HS-A / B / C / D in the vacuum VAC, each with independent thermal control), cooling hood heat shield CH-HS and POB orifice POB-H. A separate active thermal control unit ACTU is placed outside the vacuum VAC and holds all heaters H to control the cooling water set point for each branch separately. There are several additional temperature sensors required for control (each of which is depicted by a circle enclosing a cross). The sensors are used to measure the cooling water temperature difference ΔT across the corresponding heater H. H The sensor on the component is used to control the incoming cooling water temperature by measuring the cooling water temperature difference ΔT across the corresponding component. C to suppress the dynamic heat load in the system. Alternatively (not shown in the figure), the sensor can be located in the return branch of the module. Valve V is under the control of the ATCU to set the flow rate for calibration.

[0123] The top components VPA, CL, MB are independently controlled thermally. The top elements are operable to maintain temperature at a common set point magnitude (22°C in this example), but the top components are decoupled from the ATCU in how the water temperature is controlled. Because the top components also use water to actively control the wafer temperature, the feedback loop must be faster in this example than the ATCU controller can provide (which has multiple heaters mounted on the multiple components). Together, the ATCU and independent temperature controllers form a thermal control system.

[0124] Fig. 9 An implementation of radiant beam heating compensation using active thermal control of other elements using a cooling shroud according to an embodiment of the invention is schematically depicted.

[0125] The lithographic apparatus is configured to project a patterned radiation beam via projection optics 918 onto a substrate held in a compartment ( Figure 2 The wafer stage is configured to follow the route within the compartment (as shown in reference to FIG. 1 ) during operational use of the lithographic apparatus. Figure 3 A vacuum is maintained in the compartment, which is critical for use with EUV lithography, with an opening between the wafer stage compartment and the POB. The vacuum also has the effect of removing unwanted hydrogen used with the cooling device to reduce parasitic heat transfer from other components in the compartment to the wafer and fixture.

[0126] The lithographic apparatus has a first component, such as a cooling device heat shield component ( Figures 4 to 7The cooling device heat shield has a first surface 908 facing the first portion of the route. The cooling device heat shield is arranged to shield at least a portion of the cooling device from the wafer platform.

[0127] The lithographic apparatus has a second component, such as a wafer platform heat shield component ( Figure 4 and Figure 5 WS-HS-A / B / C / D), the wafer platform heat shield component has a second surface 912 facing the second portion of the route.

[0128] The thermal control systems 902, 906 are operable to maintain the first temperature of the first surface 908 and the second temperature of the second surface 912 at a common set point magnitude 900, in this example 22° C. This has the effect of reducing parasitic heat loads and variations in parasitic heat loads, which improves the cooling calibration of the cooling device, thereby reducing overlay errors.

[0129] If there is a temperature offset between the set point of the fixture and the common set point of the first surface and the second surface, the parasitic heat load will be constant and can be modeled or accounted for by calibration. However, the thermal control system 904 is operable to maintain the third temperature of the fixture 910 at a common set point magnitude 900. This has the beneficial effect of causing the parasitic heat load to tend toward zero, because all or most of the surfaces facing the wafer (including the fixture below the wafer and the component surface above the wafer) are thermally controlled using the common set point magnitude. Common set point magnitude means that the set points are the same, or within the range of thermal control tolerances of the surfaces. Preferably, the instances of the common set point used to control each component or surface are the same. Alternatively, the instances of the common set point may preferably differ by less than 0.05°C, or more preferably by less than 0.005°C. Thus, the instances of the common set point should be close enough that the parasitic heat load is reduced to significantly less than the fixture cooling power, preferably less than 5% of the fixture cooling power, and more preferably less than 1% of the fixture cooling power.

[0130] Additionally or alternatively, other heat shielding components (such as those described in reference Figure 4 and Figure 5 POB orifice as described) or the measurement frame (as referenced Figure 4 and Figure 5 The surfaces of the MF) described may be maintained at the common set point magnitude 900. These surfaces have the effect of reducing parasitic heat loads and variations in parasitic heat loads.

[0131] Cooling device 914( Figure 6 and Figure 7CH) is positioned in the projection optics ( Figure 2 The cooling device 914 is located below the PS in the target portion and is configured to extract heat generated by absorption of the radiation from the target portion. The cooling device has the effect of reducing the overlap error, as described above. The heat extraction P of the cooling device 914 shielded by its thermal shield 908 CH is controlled based on the measurement of fixture cooling 920 (ΔT 922). This is useful because direct measurements of chiller power, such as measuring the coolant liquid of the chiller, do not accurately reflect local cooling on the wafer. Once the common set point is achieved at the surface facing the wafer platform path, the measurement of fixture cooling provides a simple measure of the imbalance between the chiller power and the radiant beam heating power. In this example, the measurement of fixture cooling includes the cooling water CW temperature gradient (T out -T in ,like Figure 7 Such measurement has the advantage of being relatively simple.

[0132] The lithographic apparatus is operable to use a cooling device based heat extraction P CH The WHFF model 930 is used to control the projection system 918 to adjust 938 the patterned radiation beam to compensate for substrate deformation. The WHFF model 930 and its input data 924 are described above with reference to Figure 6 934, which are used to adjust 938 the patterned radiation beam. Adjusting the patterned radiation beam has the effect of reducing overlay errors. The integrity of the adjustment is maintained by controlling the temperature to a common set point at the surface facing the wafer platform path.

[0133] The lithographic apparatus further includes a wafer pre-aligner ( Figure 5 The thermal control system is operable to maintain the fourth temperature of the wafer pre-aligner at the common set point value 900. This is not shown in FIG. Fig. 9 , but is substantially the same as the control 906 of the wafer handler heat shield surface 912. Controlling the temperature of the pre-aligner in this manner has the effect of reducing the parasitic heat load on the wafer and fixture.

[0134] Embodiments remove substantially all parasitic heat loads from the wafer-facing surface toward the clamp. Embodiments also reduce direct heat load effects of the wafer-facing surface that contribute to thermal expansion of the wafer, thereby further reducing overlay error.

[0135] The terms "radiation" and "beam" as used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength of or about 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having a wavelength in the range of 5 nm to 20 nm), as well as particle beams, such as ion beams or electron beams.

[0136] The term "lens", where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components.

[0137] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0138] Aspect 1. A lithography device, which is configured to project a patterned radiation beam via a projection optical device onto a target portion of a semiconductor wafer on a fixture at a wafer platform held in a compartment, wherein the wafer platform is configured to follow a route within the compartment during operational use of the lithography device, and wherein the lithography device comprises: - a first component, the first component having a first surface facing a first portion of the route; - a second component, the second component having a second surface facing a second portion of the route; - a thermal control system, the thermal control system being operable to maintain a first temperature of the first surface and a second temperature of the second surface at a common set point value.

[0139] Aspect 2. A lithographic apparatus according to aspect 1, wherein the thermal control system is operable to maintain a third temperature of the chuck at the common set point magnitude.

[0140] Aspect 3. The lithography device according to Aspect 1 or Aspect 2 further includes a cooling device, which is positioned below the projection optical device and is configured to extract heat generated by absorption of the radiation from the target portion, wherein the heat extraction of the cooling device is controlled based on the measurement results of the cooling of the fixture.

[0141] Aspect 4. The lithographic apparatus according to aspect 3, wherein the measurement results of the cooling of the clamp include measurement results of cooling water temperature gradient and mass flow rate.

[0142] Aspect 5. A lithographic apparatus according to aspect 3 or aspect 4, wherein the lithographic apparatus is operable to control the projection system using a model based on the heat extraction of the cooling device to adjust the patterned radiation beam to compensate for substrate deformation.

[0143] Aspect 6. The lithography device according to any of the preceding aspects further includes a wafer pre-aligner, which is capable of operating to orient and thermally adjust the wafer before the wafer is transferred to the fixture, and wherein the thermal control system is capable of operating to maintain the fourth temperature of the wafer pre-aligner at the common set point value.

[0144] Aspect 7. A lithographic apparatus according to any preceding aspect, wherein in operational use of the lithographic apparatus, a vacuum is maintained in the compartment.

[0145] Aspect 8. The lithographic apparatus according to any preceding aspect, wherein the component comprises a device cooling device heat shield arranged to shield at least a portion of the cooling device from the wafer platform.

[0146] Aspect 9. The lithographic apparatus according to any preceding aspect, wherein the component comprises a heat shield. Aspect 10. The lithographic apparatus according to any preceding aspect, wherein the component comprises a metrology frame.

[0147] Aspect 11. A lithography method, comprising: - projecting a patterned radiation beam via a projection optical device onto a target portion of a semiconductor wafer on a fixture at a wafer platform held in a compartment of a lithography device, wherein the lithography device comprises: - a first component, the first component having a first surface facing a first portion of a route within the compartment; and - a second component, the second component having a second surface facing a second portion of the route within the compartment; - transporting the wafer platform along the route within the compartment; and - operating a thermal control system to maintain a first temperature of the first surface and a second temperature of the second surface at a common set point value.

[0148] Aspect 12. The photolithography method according to aspect 11, further comprising: operating the thermal control system to maintain the third temperature of the clamp at the common set point value.

[0149] Aspect 13. The lithography method according to Aspect 11 or Aspect 12 further includes: operating a cooling device positioned below the projection optical device to extract heat generated from the target portion via absorption of the radiation, wherein the heat extraction of the cooling device is controlled based on a measurement result of cooling of the fixture.

[0150] Aspect 14. The photolithography method according to aspect 13, wherein the measurement results of the cooling of the chuck include measurement results of cooling water temperature gradient and mass flow rate.

[0151] Clause 15. The lithography method according to clause 13 or clause 14, comprising: using a model based on the heat extraction of the cooling device to control the projection system to adjust the patterned radiation beam to compensate for substrate deformation.

[0152] Aspect 16. The lithography method according to any one of Aspects 11 to 15 further includes: using a wafer pre-aligner to orient and thermally adjust the wafer before the wafer is transferred to the fixture, and operating the thermal control system to maintain the fourth temperature of the wafer pre-aligner at the common set point value.

[0153] Aspect 17. The photolithography method according to any one of aspects 11 to 16, further comprising: maintaining a vacuum in the compartment.

[0154] Aspect 18. The lithography method according to any one of aspects 11 to 17, wherein the component comprises a device cooling device heat shield arranged to shield at least a portion of the cooling device from the wafer platform.

[0155] Aspect 19. The photolithography method according to any one of aspects 11 to 18, wherein the component comprises a heat shield.

[0156] Aspect 20. The lithography method according to any one of aspects 11 to 19, wherein the component comprises a metrology frame.

Claims

1. An active thermal control apparatus, the apparatus comprising a compartment, the compartment comprising a wafer platform configured to hold a semiconductor wafer on a fixture, wherein the wafer platform is configured to follow a path within the compartment in operational use, the apparatus comprising: - a first component having a first surface facing a first portion of the route; - a second component having a second surface facing a second portion of the route; a thermal control system operable to maintain a first temperature of the first surface and a second temperature of the second surface at a common set point magnitude, and a cooling device positioned below the projection optics through which a patterned beam of radiation is projected onto a target portion of the semiconductor wafer, the cooling device being configured to extract heat generated by absorption of the radiation from the target portion, wherein the heat extraction of the cooling device is controlled based on measurements of the cooling of the fixture. 2 . The active thermal control device of claim 1 , wherein the thermal control system is operable to maintain the third temperature of the fixture at the common set point magnitude. 3 . The active thermal control device of claim 1 , wherein the measurements of cooling of the fixture include measurements of cooling water temperature gradient and mass flow rate.

4. The active thermal management device of claim 1, wherein at least one of the first component and the second component comprises a device cooling device heat shield arranged to shield at least a portion of the cooling device from the wafer platform. 5 . The active thermal control device of claim 1 , wherein at least one of the first component and the second component comprises a thermal shield. 6 . The active thermal control device of claim 1 , wherein at least one of the first component and the second component comprises a metrology frame.

7. A lithography apparatus comprising the active thermal control device according to claim 1.

8. The lithographic apparatus of claim 7, wherein the lithographic apparatus is operable to control the projection optics using a model based on the heat extraction of the cooling device to adjust the patterned radiation beam to compensate for substrate deformation.

9. The lithographic apparatus according to any one of claims 7 to 8, further comprising a wafer pre-aligner operable to orient and thermally condition the wafer before the wafer is transferred to the fixture, and wherein the thermal control system is operable to maintain the fourth temperature of the wafer pre-aligner at the common set point value.

10. The lithographic apparatus of claim 7, wherein in operational use of the lithographic apparatus, a vacuum is maintained in the compartment.

11. A lithography method using active thermal control, comprising: - projecting a patterned beam of radiation via projection optics onto a target portion of a semiconductor wafer held on a chuck at a wafer stage in a compartment of a lithographic apparatus, wherein the lithographic apparatus comprises: - a first component having a first surface facing a first portion of the route within the compartment; and - a second component having a second surface facing a second portion of the route within the compartment; - transporting the wafer platform along the route within the compartment; - operating a thermal control system to maintain a first temperature of the first surface and a second temperature of the second surface at a common set point magnitude, and - operating a cooling device positioned below the projection optics to extract heat from the target portion generated via absorption of the radiation, wherein the heat extraction of the cooling device is controlled based on measurements of cooling of the fixture.

12. The photolithography method according to claim 11, further comprising: The thermal control system is operated to maintain a third temperature of the fixture at the common set point magnitude.

13. The photolithography method according to claim 11, wherein the measurement results of the cooling of the chuck include measurement results of the temperature gradient and mass flow rate of cooling water.

14. The photolithography method according to claim 11 or claim 13, comprising: The projection optics are controlled using a model based on the heat extraction of the cooling device to adjust the patterned radiation beam to compensate for substrate deformation.

15. The photolithography method according to claim 11, further comprising: A wafer pre-aligner is used to orient and thermally condition the wafer prior to transfer of the wafer to the fixture, and the thermal control system is operated to maintain a fourth temperature of the wafer pre-aligner at the common set point magnitude.

16. The photolithography method according to claim 11, further comprising: A vacuum was maintained in the compartment.

17. The lithography method of claim 11, wherein at least one of the first component and the second component comprises a device cooling device heat shield arranged to shield at least a portion of the cooling device from the wafer platform.

18. The photolithography method of claim 11, wherein at least one of the first component and the second component comprises a heat shield.

19. The lithography method of claim 11, wherein at least one of the first component and the second component comprises a metrology frame.

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