Lithographic apparatus thermal conditioning system and method

Abstract

A thermal conditioning system is configured to thermally condition an object. The thermal conditioning system comprises a fluid duct configured to be connected to the object and to provide a flow of thermal conditioning fluid to the object. The fluid duct comprises a supply duct configured to be connected to the object and to supply the thermal conditioning fluid to the object, and an exhaust duct 5 configured to be connected to the object and to exhaust the thermal conditioning fluid from the object. The supply duct and / or the exhaust duct are each provided with at least two silencers arranged in series along the supply duct and along the exhaust duct, respectively.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to European Application No. 22213728.3, filed December 15, 2022, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a thermal conditioning system, a lithographic apparatus comprising such a thermal conditioning system, and a method for thermal conditioning an object in a lithographic apparatus. [Background technology]

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can, for example, project a pattern in a patterning device (e.g. a mask) onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0004]

[0004] To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. To form smaller features on a substrate than lithographic apparatuses that use radiation having a wavelength of, for example, 193 nm, lithographic apparatuses that use extreme ultraviolet (EUV) radiation having a wavelength in the range of 4 nm to 20 nm, for example, 6.7 nm or 13.5 nm, may be used.

[0005] An object of a lithographic apparatus may be provided with a thermal conditioning system, which includes a fluid duct for guiding a thermal conditioning fluid. The fluid duct is configured to guide the thermal conditioning fluid to the object to be thermally conditioned and to expel the thermal conditioning fluid from the object through the object. The object may be, for example, a projection system mirror of a projection system of a lithographic apparatus, or a stage, such as a wafer table of the lithographic apparatus. It has been observed that the thermal conditioning duct may induce disturbances, such as vibrations, into the object. This may be undesirable because such disturbances may result in, for example, vibrations or other movements of the object. It has been proposed to provide the thermal conditioning duct with a silencer that can provide compliance to suppress the disturbances. Movement of an object, such as a mirror or substrate table of a lithographic apparatus, may result in inaccuracies in the imaging of a pattern on a substrate. The inaccuracies may be converted into overlay errors, which may adversely affect the accuracy of the lithographic apparatus. Summary of the Invention

[0006] It is desirable to provide a lithographic apparatus with high overlay accuracy.

[0007]

[0007] According to one aspect of the present invention, there is provided a thermal conditioning system configured to thermally condition an object, the thermal conditioning system comprising a fluid duct configured to be connected to the object and to provide a flow of thermal conditioning fluid to the object, the fluid duct comprising a supply duct configured to be connected to the object and to supply the thermal conditioning fluid to the object, and an exhaust duct configured to be connected to the object and to exhaust the thermal conditioning fluid from the object, at least one of the supply duct and the exhaust duct being provided with at least two silencers arranged in series along at least one of the supply duct and the exhaust duct.

[0008]

[0008] According to another aspect of the present invention, there is provided a lithographic apparatus comprising an object and a thermal conditioning system according to the present invention for thermally conditioning the object, the object being one of a projection system mirror and a substrate table of the lithographic apparatus.

[0009]

[0009] According to yet another aspect of the present invention, there is provided a method for thermally conditioning an object in a lithographic apparatus, comprising providing a flow of thermal conditioning fluid to the object through a fluid duct, the fluid duct being connected to the object, the fluid duct having a supply duct connected to the object to supply the thermal conditioning fluid to the object, and an exhaust duct connected to the object to exhaust the thermal conditioning fluid from the object, at least one of the supply duct and the exhaust duct being provided with at least two silencers arranged in series along at least one of the supply duct and the exhaust duct.

[0010]

[0010] According to yet another aspect of the present invention, there is provided a method for adjusting a silencer in a fluid duct of a thermal conditioning system configured to thermally condition an object, the method comprising: defining a disturbance frequency band in which transmission of disturbance from a disturbance generation point to the object should be reduced; providing at least two silencers between the disturbance generation point in the fluid supply duct and the object; providing at least two silencers between the disturbance generation point in the fluid discharge duct and the object; and specifying that the silencers are sized using the inertia of the thermal conditioning fluid between the silencers so that resonance of the mass of the thermal conditioning fluid between the silencers is at a resonant frequency below the disturbance frequency band. [Brief explanation of the drawings]

[0011]

[0011] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0012] [Figure 1] 1 depicts a lithography system comprising a lithographic apparatus and a radiation source. [Figure 2A-2B] 1 shows a highly schematic view of a portion of a thermal regulation system according to an aspect of the present invention; [Figure 3A-3C] A frequency response diagram is shown, and the effect of the present invention is explained based on this. [Figures 4A-4C] 1 shows a highly schematic view of an embodiment of a silencer that can be used in a thermal regulation system according to the present invention; [Figure 5] 1 shows a highly schematic view of another embodiment of a silencer that can be used in a heat regulation system according to the present invention; [Figure 6] 1 shows a highly schematic view of a silencer membrane that can be used in a thermal regulation system according to the invention; [Figure 7] 10 shows a highly schematic view of yet another embodiment of a silencer that may be used in a heat regulation system according to the present invention; [Figure 8] 1 shows a highly schematic view of yet another embodiment of a silencer that may be used in a heat regulation system according to the present invention; [Figure 9-10] 1 shows a highly schematic illustration of a negative compliance mechanism that may be used in a silencer. [Figure 11] 1 shows a highly schematic view of another embodiment of a thermal regulation system according to the present invention; [Figures 12A-12C] 1 shows a highly schematic view of yet another embodiment of a thermal regulation system according to the present invention; [Figures 13A-13C] 1 shows a highly schematic view of a further embodiment of a silencer that can be used in a heat regulation system according to the invention; [Figure 14] 10 shows a highly schematic partial view of yet another embodiment of a silencer that can be used in a heat regulation system according to the present invention; [Figure 15] 1 shows a highly schematic view of yet another embodiment of a silencer that may be used in a heat regulation system according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 shows a lithography system comprising a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate a beam of EUV radiation B and to provide the beam of EUV radiation B to the lithography apparatus LA. The lithography apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g. a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0014] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. To that end, the illumination system IL may comprise a facetted field mirror device 10 and a facetted pupil mirror device 11. The facetted field mirror device 10 and the facetted pupil mirror device 11 together give the EUV radiation beam B a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may comprise other mirrors or devices in addition to or instead of the facetted field mirror device 10 and the facetted pupil mirror device 11.

[0015] After being conditioned in this way, the EUV radiation beam B interacts with the patterning device MA. This interaction results in a patterned EUV radiation beam B'. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may comprise a number of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by a substrate table WT. The projection system PS may apply a demagnification factor to the patterned EUV radiation beam B', thereby forming an image having smaller features than corresponding features on the patterning device MA. For example, a demagnification factor of 4 or 8 may be applied. Although the projection system PS is shown in Figure 1 as having only two mirrors 13, 14, the projection system PS may include a different number of mirrors (e.g. 6 or 8 mirrors).

[0016]

[0015] The substrate W may include a pre-formed pattern, in which case the lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pre-formed pattern on the substrate W.

[0017] A relative vacuum, ie a small amount of gas (eg hydrogen) at a pressure significantly below atmospheric pressure, may be provided in the source SO, in the illumination system IL and / or in the projection system PS.

[0018]

[0017] The source SO may be a laser-produced plasma (LPP) source, a discharge-produced plasma (DPP) source, a free-electron laser (FEL), or any other source capable of producing EUV radiation.

[0019] FIG. 2A shows a highly schematic diagram of a thermal conditioning system including a fluid duct FD connected to an object OBJ. The thermal conditioning system is configured to thermally condition the object. The fluid duct includes a thermal conditioning fluid supply duct FSD for supplying a thermal conditioning fluid to the object OBJ and a thermal conditioning fluid discharge duct FDD for discharging the thermal conditioning fluid from the object OBJ. The fluid duct may form a fluid flow path within or on the object, such as a fluid channel within the object or a fluid duct on the object, for example, on the rear side of the object. The thermal conditioning fluid may be formed by any suitable fluid, such as a liquid, e.g., water, or a gas. The thermal conditioning system may be configured to heat the object or to cool the object, thereby providing that the object is stabilized at a desired temperature or within a desired temperature range. The object may be, for example, a mirror of a projection system of a lithographic apparatus or a stage, such as a wafer table, of a lithographic apparatus. The thermal conditioning fluid may be supplied by any suitable supply means, such as a pump, a pressurizing means, or the like.

[0020]

[0019] Figure 2B shows a schematic diagram of a portion of the fluid supply duct of the thermal conditioning system shown in Figure 2A. According to one aspect of the invention, at least one of the fluid supply duct and the fluid exhaust duct is provided with two silencers SL. According to one aspect of the invention, the fluid supply duct and the fluid exhaust duct are each provided with two silencers SL. A silencer may be understood as an element having a low hydraulic stiffness compared to the hydraulic stiffness of the thermal conditioning duct. The hydraulic stiffness may be understood as the ratio of the pressure increment to the volume increment of the displaced fluid, K_hyd = dp / dV, where p is the absolute pressure and V is the volume of gas.

[0021] It has been observed that the silencer itself provides damping for suppressing disturbances. The silencer itself may provide, for example, 10 to 30 times the suppression of disturbances. However, the inventors have contemplated that by utilizing such a silencer, substantially higher suppression of disturbances may be achieved, which suppression may be orders of magnitude higher, for example, 10 to 30 times higher, compared to known suppression.

[0022] 2B , as described above, according to one aspect of the present invention, at least two silencers are provided in the supply duct and / or at least two silencers are provided in the return duct. The silencers SL1 and SL2 are arranged in series along the supply duct, along the exhaust duct, or along the supply duct and the exhaust duct. Thus, along the supply duct, one of the at least two silencers is upstream of the other of the at least two silencers. Similarly, along the exhaust duct, one of the at least two silencers is upstream of the other of the at least two silencers. The thermal conditioning fluid between the silencers SL1 and SL2 defines a thermal conditioning fluid mass TCFM.

[0023]

[0022] The inventors have devised that assembling two silencers in series in a duct, with the thermal conditioning fluid between the silencers forming a thermal conditioning fluid mass, can provide a resonant behavior that results in a roll-off above the resonant frequency. By sizing the silencers, their compliance, and the thermal conditioning fluid mass between the silencers, the resonant frequency can be determined to be below the disturbance frequency band, thereby more effectively suppressing disturbances in the disturbance frequency band from being transmitted through the fluid duct to the object.

[0024]

[0023] According to one aspect of the present invention, there is provided a method for adjusting a silencer in a fluid duct of a thermal conditioning system configured to thermally condition an object, the method comprising: defining a disturbance frequency band in which transmission of disturbance from a disturbance generation point to the object should be reduced; providing at least two silencers between the disturbance generation point in the fluid supply duct and the object; providing at least two silencers between the disturbance generation point in the fluid discharge duct and the object; and specifying that the inertia of the thermal conditioning fluid between the silencers is used to size the silencers so that the resonance of the inertia of the thermal conditioning fluid between the silencers is at a resonant frequency below the disturbance frequency band.

[0025]

[0024] The present invention outlines the use of multiple silencers in series, which has the ability to be effective up to higher frequencies (e.g., above 80 Hz). Using at least two silencers in series, the gas volume of each silencer effectively creates a low stiffness in the water circuit by generating a low hydraulic stiffness (K_hyd = dp / dV). The hydraulic stiffness of the gas volume can then be derived as K_hyd = γp / V (adiabatic condition). In the above equation, γ (gamma) is the adiabatic index, p is the absolute pressure, and V is the gas volume. By placing two silencers in series, the mass between the silencers can begin to resonate at a resonant frequency. Below this frequency, there will be no additional benefit from multiple silencers and there will be amplification at this frequency, but above this frequency, the mass between the silencers can begin to decouple, effectively resulting in a -2 slope. This is similar to a mechanical mass-spring isolation system. Thus, by placing multiple silencers in series, significantly higher levels of suppression can be achieved. Furthermore, by decreasing the silencer stiffness (reducing the pressure or increasing the gas volume) or increasing the hydraulic mass of the duct between the silencers, M_(hydraulic duct)=ρL / A (increasing the length or decreasing the duct cross-sectional area), this resonant frequency can be lowered, resulting in even higher levels of reduction (especially around the aforementioned frequencies, e.g., around 80 Hz). Placing more than two silencers in series can be applied to create multiple masses that begin to separate between the silencers, effectively reaching slopes of -4 or higher. By adjusting the silencer stiffness and the hydraulic mass of the duct between the silencers, it is possible to effectively avoid resonance amplification and achieve ultimate noise reduction performance. Placing multiple silencers in series with sufficient distance between them is currently a key technological breakthrough for the implementation of DCM from a dynamics perspective.

[0026] Effectiveness up to higher frequencies: The distance between the gas volume and the duct can limit the frequency up to which the gas volume can be effectively used. This duct section can be called the silencer neck, and the associated resonant frequency can be called the Helmholtz frequency f_HR. Below this frequency, the gas volume is effectively felt, at which additional suppression can be achieved (less effort is required to compress the gas volume), and above this frequency, the gas volume is no longer effectively felt. This resonant frequency can be raised by increasing the silencer stiffness (increasing the pressure or decreasing the gas volume) or decreasing the hydraulic mass of the silencer neck (decreasing the length or increasing the neck diameter), so that the gas volume is effectively felt for higher frequencies (especially around 80 Hz). To eliminate the risk of gas dissolution over time, a flexible interface is added. What is required of this interface is that its stiffness is low enough so that the sum of both the gas volume stiffness and the flexible interface stiffness can still meet the requirements. Additionally, the inertia of the bellows may be small enough so that the Helmholtz frequency can remain sufficiently high. Finally, the structural resonance of the flexible interface may be high enough, at least above the Helmholtz frequency, so as not to degrade the acoustic damping performance.

[0027] 3A and 3B show diagrams in which the transmission of disturbances to an object through a duct is plotted on the vertical axis versus frequency on the horizontal axis. As shown in FIG. 3A, a single silencer in the supply duct FSD and return duct, i.e., fluid discharge duct FDD, provides a roll-off of a factor of 2 per octave, or 10 per frequency decade, above the roll-off frequency Froll. As shown in FIG. 3B, two silencers in series in the supply duct and return duct may provide a roll-off of a factor of 2 per octave from the roll-off frequency Froll to the resonant frequency Fres, but a roll-off of 3 times, or 8 per octave, above the resonant frequency. The resonant frequency Fres may be determined by the resonance of the dual silencers with the mass of thermal conditioning fluid between the two silencers in the duct.

[0028] Thus, as can be seen from the above, a single silencer, in combination with a non-reflective acoustic boundary condition (critical damping), can provide a slope of -1, i.e., a factor of 10 per frequency decade. Dual silencers in series can provide a slope of -3, i.e., a factor of 1000 per frequency decade (a slope of -1, i.e., a factor of 10 per frequency decade, can be provided by a silencer in combination with a non-reflective acoustic boundary condition, and a slope of -2, i.e., a factor of 100 per frequency decade, can be provided by separated mass between the silencers).

[0029] In one embodiment, at least two mufflers form a resonator with a thermal conditioning fluid in a fluid duct interconnecting the at least two mufflers. The thermal conditioning fluid in the duct interconnecting the at least two mufflers in a supply or return duct defines mass, while the mufflers define compliance. The mass of the thermal conditioning fluid between the mufflers and the compliance of the mufflers can exhibit resonant behavior as shown by the resonant frequency Fres in FIG. 3B. The resonant behavior suggests that two poles are involved in the frequency behavior, such that above the resonant frequency, a (further) roll-off of a factor of 4 per octave, or a (further) factor of 100 per frequency decade, is observed. Combined with the roll of the mufflers in combination with the non-reflective acoustic boundary condition, a total of a factor of 1000 per frequency decade is observed. The resonant frequency can be a resonance due to fluid sloshing between the mufflers in the duct.

[0030] 3C shows a frequency diagram in which the transmission of disturbances through a duct to an object is plotted on the vertical axis versus frequency on the horizontal axis. As shown in FIG. 3C, a single silencer SL, for example in a supply duct and / or return duct, will itself exhibit a Helmholtz resonant frequency dip ω at the square root of the quotient of the silencer's hydraulic compliance and the hydraulic mass in the silencer fluid conduit. HR provides a Helmholtz resonance of ω HR =√(K Hyd / M Hyd ), where ω HR is the Helmholtz resonance frequency, and K Hyd is the hydraulic compliance of the silencer, and M Hyd is the hydraulic mass in the silencer fluid conduit. Helmholtz resonance frequency dip ω HR , with a roll-off with a slope of -2. As further shown in FIG. 3C, two silencers in series, for example in the supply and / or return duct, may define a resonant peak at the sloshing frequency, which is equal to the square root of the quotient of twice the hydraulic compliance of the silencer and the hydraulic mass between the two silencers in the duct, ω S =√(2K Hyd / MHyd ), where ω S is the sloshing frequency, and 2K Hyd is twice the hydraulic compliance of the silencer, and M Hyd is the hydraulic mass between the silencers in the duct. Thus, a pair of silencers separates the hydraulic mass between the silencers (low stiffness elements) to achieve a -40 dB / decade suppression of pressure transmission over a force input (slope of -2) above the sloshing resonance frequency. Multiple pairs of silencers (N) allow benefiting from more separated mass, resulting in N x -40 dB / decade. For example, as shown in Figure 3C, a double pair separates two sloshing resonance frequencies ω S The slope of -4 is defined as follows: sloshing resonance frequency ω S is the Helmholtz resonance frequency ω because a larger hydraulic mass of fluid between the silencers is involved. HR The sloshing resonance frequency ω S may be sized so that the disturbances are below the disturbance frequency band where they should be suppressed, resulting in a significant suppression of the disturbance propagation as a result of a slope of -2 per silencer pair. The suppression behavior can be optimized by adjusting the hydraulic mass between the silencers (M_hyd), the hydraulic mass in the conduit between the duct and the silencer (M_hyd), or the silencer compliance (K_hyd). Sizing the hydraulic mass between the silencers and the silencer compliance to stipulate that the sloshing frequency of the silencer pair is below the disturbance frequency band can make it possible to obtain a slope of -2 per silencer pair in the disturbance frequency band, making it possible to suppress disturbances in the disturbance frequency band with a slope of -2 per silencer pair.

[0031]

[0030] In one embodiment, the resonator is a series resonator. The series resonator makes it possible to utilize the mass of the thermal conditioning fluid between the two silencers, and therefore the mass present in the fluid duct. As a result, no additional mass is required, and as a result, very little weight is added.

[0032] 4A to 4C show three different embodiments of the silencer. The silencer SL shown in Fig. 4A is formed by an inner space partially filled with a gas, which is not easily dissolved in the thermal conditioning fluid, and which can form elastic properties when pressurized by the thermal conditioning fluid.

[0033] 4B shows a silencer SL with a membrane MEM that divides the interior space of the silencer into a portion filled with, for example, gas and a portion filled with a thermal conditioning fluid, the elasticity of the membrane possibly combined with the pressurization of the gas defining the elasticity of the thermal conditioning fluid interacting with the silencer.

[0034] 4C shows a silencer SL with a membrane shaped as a bellows BEL that divides the silencer's interior space into, for example, a gas-filled portion and a thermal conditioning fluid-filled portion. The elasticity of the bellows-shaped membrane, possibly combined with the gas pressure or pressure reduction, determines the elasticity of the thermal conditioning fluid interacting with the silencer.

[0035]

[0034] Figure 5 shows a further embodiment of the silencer. As shown in Figure 5, the silencer includes a membrane shaped as a bellows in this example. The membrane is arranged symmetrically with respect to the fluid flow direction of the fluid duct, i.e., the fluid propagation direction. This symmetric arrangement allows the force distribution by the silencer to be symmetric with respect to the fluid flow direction of the thermal conditioning fluid, thereby at least reducing the net effective force acting on the fluid duct. A silencer with a membrane arranged symmetrically with respect to the fluid flow direction can be used in any thermal conditioning system. That is, its application may not be limited to a thermal conditioning system including a fluid supply duct with at least two silencers and a fluid discharge duct with at least two silencers.

[0036]

[0035] Figure 6 shows a detailed view of a membrane that can be used in the silencer described above. The membrane shown in Figure 6 has a corrugated shape COR. The corrugated shape of the membrane can reduce the stiffness of the membrane. If the membrane is strong and can withstand various operating conditions, the membrane may be manufactured from, for example, metal. However, using metal can make the membrane relatively stiff. The corrugated shape can partially compensate for the stiffness and thus achieve an effective, more desirable compliance. A silencer with a corrugated membrane can be used in any thermal conditioning system. That is, its application may not be limited to a thermal conditioning system including a fluid supply duct with at least two silencers and a fluid discharge duct with at least two silencers.

[0037] As explained above, resonance of at least two silencers combined with the mass of thermal conditioning fluid between the silencers in the duct can define a resonant peak in the disturbance transmission through the duct. Because the resonant peak can accentuate disturbances at or near the resonant frequency, it may be desirable to apply some damping to reduce the resonant peak and the corresponding disturbance transmission through the duct. Thus, in one embodiment, each silencer can include a damper connected to a membrane. An example is shown in FIG. 7, where the silencer SL includes a membrane MEM that separates the thermal conditioning fluid from the remaining space SPC within the silencer SL. A damper DMP is connected to the membrane to damp movement, e.g., vibration, of the membrane. The damper may be connected to a fixed portion of the silencer, for example, to its housing or outer wall. The membrane may include, for example, a metal membrane having a bellows-like corrugated shape. The above-described damping silencers can be used in any thermal conditioning system. That is, its application may not be limited to a thermal conditioning system having a fluid supply duct with at least two silencers and a fluid exhaust duct with at least two silencers. In general, the damper is not limited to being anchored to the outside world. In one embodiment, the damper utilizes the deflection of the membrane itself, for example, a viscoelastic material applied to the membrane.

[0038]

[0037] In one embodiment, as shown schematically in Figure 8, each silencer includes a negative compliance mechanism connected to the membrane. The negative compliance mechanism can reduce the compliance of the membrane. The membrane may be made of, for example, metal, provided that the membrane is robust and can withstand various operating conditions. However, using metal can make the membrane relatively stiff. The negative compliance partially compensates for the stiffness, and thus an effective, more desirable compliance can be achieved. The negative compliance can be implemented in various ways. For example, Figure 8 shows a buckled leaf spring BLS attached to a leaf spring attachment point LAP. A stroke protection mechanism SPM, such as a stroke limiter, prevents the membrane and buckled leaf spring from being damaged due to excessive excursion.

[0039]

[0038] A buckled leaf spring may form an example of a double compression spring. Any other embodiment of a double compression spring may be envisaged, such as that shown diagrammatically in Figure 9. The double compression spring SPR is compressed in a direction substantially parallel to the membrane MEM, i.e. perpendicular to the excursion direction ED of the membrane.

[0040] 10, to tension the dual compression spring, the negative compliance mechanism may include a tensioning member TSM configured to tension the dual compression spring, in this example in a direction substantially parallel to the membrane. The tensioning force of the tensioning member may help to further increase the negative compliance of the dual compression spring.

[0041]

[0040] A muffler comprising a membrane connected to a negative compliance mechanism as described above with reference to Figures 8 to 10 can be used in any thermal conditioning system. That is, its application may not be limited to a thermal conditioning system comprising a fluid supply duct having at least two mufflers and a fluid exhaust duct having at least two mufflers. In yet another embodiment, a negative compliance mechanism as disclosed in Figures 8 to 10 may be combined with a self-adjusting muffler as disclosed in EP 0 679 832 A1.

[0042] A further embodiment will be described with reference to FIG. 11. As shown in the upper part of FIG. 11, one of the silencers SL of the fluid supply duct FSD, one of the silencers of the fluid exhaust duct FDD, and a fluid duct interconnecting one of the silencers of the duct and one of the silencers of the fluid exhaust duct form a further resonator. The lower part of FIG. 11 shows the excursion of the resonant movement through this further resonator, showing the pressure along the duct between the two silencers. The excursion (i.e., pressure) due to the resonant behavior is greatest at each silencer SL, but reaches a zero-pressure point ZPP between the silencers. To reduce the disturbance caused by the moving mass of the thermal conditioning fluid relative to the object, the object can be placed at the zero-pressure point ZPP of the further resonator.

[0043]

[0042] If it would be impossible to make the lengths of the ducts between the two mufflers and the object, e.g. a mirror, equal, the mufflers (compliance and mass) can be adjusted to the hydraulic mass of the ducting in order to obtain a point of zero pressure at the object. If the gas volumes are unequal, the point of zero pressure where no sloshing is felt can be displaced towards the less stiff one of the mufflers, e.g. towards the muffler with the larger gas volume.

[0044]

[0043] A thermal conditioning system in which the zero pressure point is located on the object can be used in any thermal conditioning system having a silencer provided in a thermal conditioning fluid supply duct and a silencer provided in a thermal conditioning fluid discharge duct, i.e., its application may not be limited to a thermal conditioning system having a fluid supply duct with at least two silencers and a fluid discharge duct with at least two silencers.

[0045] According to a further embodiment, a variation in diameter may be provided in the duct between the two silencers in order to displace the location of the zero pressure point to a desired location on the object. As the duct diameter, and therefore the flow area, decreases, the hydraulic mass may increase.

[0046]

[0045] The zero pressure point is preferably located at the center of the object, eg a mirror, to minimize the effect of sloshing of the thermal conditioning fluid on the object.

[0047]

[0046] The damping of the movement of the thermal conditioning fluid can be provided by a resistive passage in the fluid duct that has a higher fluid flow resistance relative to the rest of the fluid duct. Thus, in one embodiment, the fluid duct includes a resistive passage configured to provide a higher fluid flow resistance than the rest of the fluid duct. The resistive passage may be located between the silencers, which can help damp the resonant peaks at the above-mentioned resonant frequencies. Similarly, the resistive passage may be located between the disturbance initiation point and at least one of the silencers to reduce the propagation of the disturbance from the disturbance initiation point to the rest of the thermal conditioning fluid duct. Similarly, the resistive passage may be located between at least one of the silencers and the object. The resistive passage may be implemented, for example, by a portion of the thermal conditioning fluid duct having a narrower cross-section. An example is shown in FIG. 12B, which shows a resistive, narrow portion RES of the fluid duct FD.

[0048]

[0047] Alternatively or additionally to being implemented by a duct with a narrower cross section, the resistance passage may be implemented by a fluid duct comprising a porous medium. Thus, in one embodiment, the resistance passage of the fluid duct comprises a porous medium. The porous medium may provide the above-mentioned damping. The porous medium may be added between the silencers of the fluid duct or in the fluid conduit of the silencer between the fluid duct and the membrane.

[0049]

[0048] A narrow cross-section can provide an additional benefit: disturbances caused by turbulent flow of the thermal conditioning fluid can be shifted to higher frequencies. This higher frequency can be above the frequency range of interest, i.e., above the disturbance frequency band where disturbance transmission is suppressed by resonance effects. FIG. 12A schematically illustrates a portion of a fluid duct for a thermal conditioning fluid, showing the flow direction FLD and turbulence TUR resulting from the flow of the thermal conditioning fluid within the fluid duct. The narrower the cross-section of the fluid duct, the higher the frequency of the turbulence TUR can be. In one embodiment, the resonator is configured to attenuate disturbances in the disturbance frequency band, and the cross-section of the duct is sized to define that the turbulence frequency band of the thermal conditioning fluid within the duct exceeds the disturbance frequency band.

[0050] 12C, the connection between the resistance passage RES and the remainder of the fluid duct FD may present a change in the cross section of the fluid duct, which may result in turbulence and other effects at the transition in cross section from the narrow section to the remainder of the fluid supply duct. To reduce turbulence and other effects that may occur at the transition, a diverging or converging section of the duct may be provided.

[0051]

[0050] As an alternative to the converging or diverging section DIV shown in Figure 12C, a silencer SL as shown in Figure 12B may be provided at the connection between the part with high resistance (e.g. narrow cross section) and the rest of the fluid duct.

[0052] A thermal conditioning system with a passageway having a higher fluid flow resistance can be used in any thermal conditioning system, i.e., its application may not be limited to thermal conditioning systems with a fluid supply duct having at least two silencers and a fluid exhaust duct having at least two silencers.

[0053]

[0052] In one embodiment, the membrane comprises a porous membrane, thereby reducing the effective compliance of the silencer. For example, a metal membrane may provide a durable mounting, but may be too rigid. The porous membrane may comprise, for example, a plurality of narrow passages, which allows the effective compliance of the membrane to be reduced.

[0054] 13A shows a highly schematic cross-sectional side view of a portion of a silencer. The silencer comprises a piston lid PLD and a rollable membrane RMEM. The piston lid comprises a piston lid front surface facing the thermal conditioning fluid and a piston lid rear surface facing the gas volume VOL filled with gas. The rollable membrane is arranged between the piston lid edge EDG and the inner surface of the silencer housing wall SHW. The rollable membrane and the piston lid may be joined, for example, by vulcanization. The piston lid may be circular or have any other suitable shape, such as oval. The piston lid diameter DIA P is the inner diameter of the silencer housing gas volume DIA H, i.e., smaller than the inner diameter of the wall of the silencer housing. The rollable membrane extends between the edge of the piston lid and the (e.g., circular) wall of the gas volume. The rollable membrane may extend around the edge of the piston lid to seal the gap between the edge of the piston lid and the wall of the silencer gas volume. The piston lid is movable in a piston lid stroke direction of the piston lid, i.e., parallel to the wall of the silencer housing gas volume, i.e., up and down in FIG. 13A . The piston lid stroke direction may extend perpendicular to the front face of the piston lid. Thus, as the piston lid moves in the stroke direction, the volume of the thermal conditioning fluid changes, i.e., increases when the piston lid moves rearward and decreases as the piston lid moves forward, i.e., toward the thermal conditioning fluid.

[0055]

[0054] The rollable membrane may have, for example, an annular shape when the edge of the piston lid is circular, or an elliptical shape when the edge of the piston lid is elliptical. The inner edge of the rollable membrane is fixed to the edge of the piston lid, and the outer edge of the rollable membrane is fixed to the wall of the silencer housing. The inner and outer edges may also have an annular or elliptical shape. A flexible portion of the rollable membrane extends between the inner and outer edges of the membrane and may also have an annular or elliptical shape. The flexible portion of the rollable membrane may be curved between the inner and outer edges of the membrane to have a convex surface and a concave surface. The concave surface may face the thermal conditioning fluid. The convex surface may face the gas in the gas volume. Thus, the fluid pressure of the thermal conditioning fluid against the concave surface of the rollable membrane maintains its curved shape. When the piston lid moves in the piston stroke direction, the rollable membrane curls up and moves. 13A , as the piston lid moves upward to a piston lid upper position UPO, i.e., increasing the volume available for the thermal conditioning fluid, the rollable membrane curls, causing the portion that supports against the piston lid edge to bend, while the bent portion of the rollable membrane straightens to support against the interior wall of the volume. As the piston lid moves downward to a piston lid lower position LPO, i.e., decreasing the volume available for the thermal conditioning fluid, the rollable membrane curls, causing the portion that supports against the wall edge to bend, while the bent portion of the rollable membrane straightens to support against the piston lid edge. In this way, the edge of the piston lid and the interior wall of the volume form parallel extensions, such as annular or elliptical surfaces, allowing a portion of the rollable membrane to be supported. Because the pressure of the thermal conditioning fluid is greater than the pressure of the gas in the gas volume, the rollable membrane is pushed by the thermal conditioning fluid to abut against the parallel extending annular or elliptical surfaces and curve to form a concave surface facing the thermal conditioning fluid. It can be noted that the curvature of the rollable membrane as shown in Figure 13A suggests that the pressure of the thermal conditioning fluid is greater than the pressure of the gas in the gas volume VOL. Due to such a pressure difference, the flexible portion of the rollable membrane can curve between the inner and outer edges of the membrane to have convex and concave surfaces as shown.The concave surface faces the thermal conditioning fluid and the convex surface faces the gas in the gas volume VOL. In an alternative configuration, the pressure of the thermal conditioning fluid may be lower than the pressure of the gas in the gas volume VOL. In such a configuration, the rollable membrane may be curved so that the convex surface faces the thermal conditioning fluid and the concave surface faces the gas in the gas volume VOL.

[0056]

[0055] The rollable membrane may provide low or zero stiffness to allow movement of the piston lid in the direction of the piston stroke. Compared to other embodiments of the silencer described herein, the combination of a movable piston lid and a rollable membrane may provide a large stroke because the stroke may be independent of material stress. The piston lid, which forms the majority of the silencer surface in contact with the thermal conditioning fluid, may be a hard, solid material such as a metal that is impermeable or virtually impermeable to the thermal conditioning fluid, thereby reducing vapor (e.g., thermal conditioning fluid) penetration into the gas volume and the resulting accumulation of thermal conditioning fluid vapor within the gas volume. The piston lid may be highly stiff, thereby reducing parasitic resonant modes.

[0057] FIG. 13B shows a further cross-sectional side view of the silencer shown in FIG. 13A. The cross-sectional view of FIG. 13B, like FIG. 13A, shows the piston lid PLD and the rollable membrane RMEM. The silencer further comprises a silencer housing SH that forms a gas volume VOL for holding gas. The silencer is in fluid communication with a thermal conditioning fluid duct, such as a thermal conditioning fluid supply duct FSD or a thermal conditioning fluid exhaust duct FDD. More specifically, the piston lid and the rollable membrane form a separator that separates the gas volume from the thermal conditioning fluid flowing in the thermal conditioning fluid duct. The silencer may be directly connected to the thermal conditioning fluid duct, for example, as shown in FIG. 13B, in that the flow of thermal conditioning fluid in the thermal conditioning fluid duct passes in close proximity along the piston lid. Alternatively, the silencer housing may further form the thermal conditioning fluid volume, whereby the piston lid and the rollable membrane are disposed between the gas volume and the thermal conditioning fluid volume. In the latter case, the thermal conditioning fluid in the thermal conditioning fluid volume is in fluid communication with the thermal conditioning fluid in the thermal conditioning fluid duct, for example, via a branch of the thermal conditioning fluid duct.

[0058] 13B further shows a spring SPR configured to interact with the silencer piston lid. The stiffness of this spring may determine the stiffness of the silencer because it exceeds the stiffness of the rollable membrane, thereby allowing the stiffness and stroke of the piston lid to be determined by selecting an appropriate spring. The spring exerts a force F on the piston lid in a direction toward the thermal conditioning fluid in the thermal conditioning fluid duct. comp may be applied, which may tend to push the thermal conditioning fluid away. On the other hand, the pressure of the thermal conditioning fluid in the thermal conditioning fluid duct may exceed the gas pressure of the gas in the gas volume, thus increasing F stat As symbolized by F, the piston lid is pressed. rollThe rollable membrane, symbolized by , can push the piston lid into the gas volume, i.e., in the opposite direction compared to the spring force. In the equilibrium position, the spring force on the piston lid and the thermal conditioning fluid pressure force on the rollable membrane are substantially opposite and have the same magnitude in absolute terms. Determining the compliance of the spring can enable the determination of the resonant behavior of the silencer (e.g., Helmholtz frequency) and the pressure range of the thermal conditioning fluid pressure. The ability to withstand a constant pressure due to the pressure difference between the thermal conditioning fluid on one side of the piston lid and the gas in the gas volume VOL on the other side and the spring force allows the rollable membrane to curl due to the pressure difference on the membrane. The spring can also restrict movement of the piston lid in other directions, such as perpendicular to the direction of piston movement. Generally, radial translation, tipping, and tilting of the piston lid can be prevented. Note that a foam with a certain degree of stiffness can be applied instead of or in addition to the spring.

[0059] FIG. 13C shows a cross-sectional view of a further embodiment of a silencer in which the spring SPR interacts with the piston lid PLD through a transmission mechanism TM. The transmission mechanism can add a transmission ratio to the spring. In this example, the transmission mechanism forms a lever with an arm connected to the piston lid and an arm connected to the spring. The arm connected to the spring may be short compared to the arm connected to the piston lid. In this example, the arm connected to the spring and the arm connected to the piston lid provide a ratio of 1:i, where i>1. As in the example shown in FIG. 13B, the transmission mechanism can make it possible to utilize a tension spring instead of a compression spring. The tension of the tension spring can increase the frequency of the lateral vibration mode of the spring. The transmission mechanism can also make it possible to utilize a stiffer spring. As a result, the internal mode of the spring can be shifted to a higher frequency, while achieving the same or similar compliance as would be achieved with a lower stiffness spring without the transmission mechanism.

[0060]

[0059] Figure 14 shows a portion of a further embodiment of a silencer, in which the spring SPR comprises three folded leaf springs, such as three folded leaf springs, connected to the outer periphery of the piston lid PLD, for example, equidistantly around the edge of the piston lid. The folded leaf springs may reduce parasitic vibrations in that movement of the piston lid in directions other than the direction of piston movement perpendicular to the piston face facing the thermal regulating liquid may be limited. The folded leaf springs shown in Figure 14 each comprise a first leaf spring portion FLP extending in the direction of piston lid movement and a second leaf spring portion SLP extending at least partially perpendicular to the direction of movement. The compliance of the second leaf spring portion may provide compliance that allows the piston lid to move in the direction of piston movement, for example.

[0061] FIG. 15 shows a further embodiment of a thermal conditioning system comprising multiple silencers, in this example three silencers SL1, SL2, and SL3. The thermal conditioning system further comprises a gas supply system GSS configured to supply gas at an operating pressure and a gas duct GSD connected between the gas supply system and the gas volume of the or each silencer, i.e., the gas volume limited by the piston lid and the rollable membrane. The gas supply system may allow the gas volume of the silencer to be connected to the system pressure provided by the gas supply system. The system pressure may largely offset the pressure difference across the barrier between the gas in the gas volume and the thermal conditioning fluid. This may reduce the force that must be provided by a spring, such as the spring described with reference to FIGS. 13B and 13C. Pressurization by the gas supply system may be particularly interesting for high-pressure systems. Because the force required from the spring may be minimized, the total energy of the backing spring may be minimized. An additional advantage would be that potential risks of permeation and accumulation of thermal conditioning fluid inside the gas volume, for example by condensed thermal conditioning fluid in the gas supply system, may be avoided. In one embodiment, the rollable membrane can include a web of radial fibers configured to reinforce the rollable membrane. The web of radial fibers can enable the rollable membrane to handle high pressure conditions and can reduce elastomeric relaxation effects and the risk of breakage of the rollable membrane.

[0062] The thermal conditioning system described above can be used in a lithographic apparatus. Thus, a lithographic apparatus can be provided, comprising an object and a thermal conditioning system as described above for thermally conditioning the object. The object can be a mirror of a projection system of a lithographic apparatus, such as the mirror devices 10 and 11 shown in and described with reference to FIG. 1 . In another embodiment, the object can be a substrate table WT of a lithographic apparatus, such as the substrate table WT shown in and described with reference to FIG. 1 , or a substrate stage of a lithographic apparatus. In yet another embodiment, the object can be a support configured to support a patterning device, such as a mask table or a mask stage of a lithographic apparatus. In yet another embodiment, the object can be a force frame or a sensor frame of a lithographic apparatus.

[0063] In one embodiment, the silencer may be connected to a structure of the lithographic apparatus, such as a force frame or a base frame. Thus, the resonator formed by the double silencer and the mass of thermal conditioning fluid between the silencers may reduce the transmission of disturbances from one of the structures of the lithographic apparatus through the fluid duct to another of the structures of the lithographic apparatus. For example, in the case of thermal conditioning of a projection system mirror, the fluid duct passes through an intermediate frame, such as a force frame or a sensor frame of the lithographic apparatus, a base frame of the lithographic apparatus, and an interface ring of the lithographic apparatus connected to a metrology frame of the lithographic apparatus. The silencer may be provided on at least one of the intermediate frame, the base frame, and the interface ring.

[0064]

[0063] One aspect of the present invention can be described as a method for thermally conditioning an object in a lithographic apparatus, comprising providing a flow of thermal conditioning fluid to the object via a fluid duct, the fluid duct being connected to the object, the fluid duct having a supply duct connected to the object for supplying the thermal conditioning fluid to the object and an exhaust duct connected to the object for exhausting the thermal conditioning fluid from the object, the supply duct and the exhaust duct each being provided with at least two silencers arranged in series along the supply duct or along the exhaust duct. Using the method according to the present invention, the same or similar advantages and effects can be achieved as using a thermal conditioning system according to an aspect of the present invention. Similarly, the same or similar embodiments can be provided that achieve the same or similar effects as those described with reference to a thermal conditioning system according to an aspect of the present invention.

[0065] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it will be appreciated that the lithographic apparatus described herein may have other applications, including the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0066] Although particular reference is made herein to embodiments of the invention in the context of lithography apparatus, embodiments of the invention may also be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus are sometimes referred to generically as lithography tools. Such lithography tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0067]

[0066] Although particular reference has been made above to the use of embodiments of the present invention in the context of optical lithography, it will be appreciated that the present invention is not limited to optical lithography and may be used in other applications, such as imprint lithography, where the context permits.

[0068]

[0067] While specific embodiments of the invention have been described above, it will be understood that the invention may be practiced otherwise than as described. The foregoing description is intended to be illustrative and not limiting. Thus, it will be apparent to those skilled in the art that modifications of the invention as described may be made without departing from the scope of the following claims.

Claims

1. 1. A thermal regulation system configured to thermally regulate an object, comprising: a fluid duct configured to be connected to the object and configured to provide a flow of thermal conditioning fluid to the object; the fluid duct comprises a supply duct configured to be connected to the object and to supply the thermal conditioning fluid to the object, and a discharge duct configured to be connected to the object and to discharge the thermal conditioning fluid from the object; A thermal conditioning system, wherein at least one of the supply duct and the exhaust duct is provided with at least two silencers arranged in series along said at least one respective one of the supply duct and the exhaust duct.

2. The thermal regulating system of claim 1 , wherein the at least two silencers form a resonator with the thermal regulating fluid in the fluid duct interconnecting the at least two silencers.

3. the resonator is configured to attenuate disturbances in a disturbance frequency band; The thermal regulation system of claim 2 , wherein the resonator has a resonant frequency below the disturbance frequency band.

4. The thermal regulation system of claim 2 or 3, wherein the resonator is a series resonator.

5. each silencer comprising a membrane configured to interact with the thermal regulating fluid; the membrane exhibits compliance; the membrane is a bellows; A thermal regulation system according to any one of claims 1 to 4, wherein the membranes are preferably arranged symmetrically with respect to the fluid flow direction of the fluid duct.

6. each silencer comprising a membrane configured to interact with the thermal regulating fluid; the membrane exhibits compliance; The thermal regulation system of claim 1 , wherein the membrane has a corrugated shape.

7. each silencer comprising a membrane configured to interact with the thermal regulating fluid; the membrane exhibits compliance; The thermal regulation system of claim 1 , wherein each silencer comprises a damper connected to the membrane.

8. each silencer comprising a membrane configured to interact with the thermal regulating fluid; the membrane exhibits compliance; The thermal regulation system of claim 1 , wherein each silencer comprises a negative compliance mechanism connected to the membrane.

9. The thermal regulating system of claim 8 , wherein the negative compliance mechanism comprises a dual compression spring.

10. The thermal regulation system of claim 8 or 9, wherein the negative compliance mechanism comprises a tension member connected to the membrane.

11. Each silencer is a piston lid configured to interact with the thermal regulating fluid and movable in a piston stroke direction; a rollable membrane connected to the piston lid and configured to roll up when the piston lid moves in the piston stroke direction; The thermal regulation system of claim 1 , comprising:

12. The thermal regulating system of claim 11 , wherein the rollable membrane forms a concave membrane surface facing the thermal regulating fluid.

13. The thermal regulation system of claim 11 or 12, wherein the silencer comprises a spring configured to interact with the piston lid.

14. The thermal regulating system of claim 13 , wherein the stiffness of the spring exceeds the stiffness of the rollable membrane.

15. 15. The thermal regulation system of claim 13 or 14, wherein the spring is configured to limit movement of the piston lid in a direction perpendicular to the piston stroke direction.

16. 16. The thermal regulation system of claim 13, comprising a transmission mechanism configured to provide a transmission ratio between the movement of the piston lid and the extension or compression of the spring.

17. The thermal regulation system of claim 13 , wherein the spring comprises at least one of a tension spring and a compression spring.

18. 18. The thermal regulation system of claim 13, wherein the spring comprises at least three folded leaf springs connected to an outer periphery of the piston lid.

19. 19. The thermal regulating system of claim 11, further comprising: a gas supply system configured to supply gas at an operating pressure; and a gas duct connected between the gas supply system and a volume of the silencer limited by the piston lid and the rollable membrane.

20. 20. The thermal regulation system of any one of claims 11 to 19, wherein the rollable membrane comprises a web of radial fibers configured to reinforce the rollable membrane.

21. one of the silencers of the supply duct, one of the silencers of the exhaust duct, and the fluid duct interconnecting the one of the silencers of the supply duct and the one of the silencers of the fluid exhaust duct form a further resonator; 21. The thermal regulation system of claim 1, wherein the object is positioned at a zero pressure point of the further resonator.

22. 22. The thermal regulating system of claim 1, wherein the fluid duct comprises a resistance passage configured to provide a higher resistance to fluid flow than the remainder of the fluid duct.

23. 23. The thermal regulation system of claim 22, wherein the resistance path is disposed between the silencers, or between a disturbance generation point and at least one of the silencers, or between at least one of the silencers and the object.

24. 24. The thermal regulating system of claim 22 or 23, wherein the connection between the resistance passage and the remainder of the fluid duct is a diverging or converging section of the duct.

25. 25. The thermal regulation system of claim 22, wherein the resistance passage of the fluid duct comprises a porous medium.

26. the resonator is configured to attenuate disturbances in a disturbance frequency band; 26. The thermal regulating system of claim 1, wherein the cross-section of the duct is sized to define a turbulence frequency band of the thermal regulating fluid within the duct that exceeds the disturbance frequency band.

27. 27. The thermal regulation system of claim 1, wherein the membrane comprises a porous membrane.

28. 28. A lithographic apparatus comprising an object and a thermal conditioning system according to any one of claims 1 to 27 for thermally conditioning the object, comprising: The lithographic apparatus, wherein the object is one of a projection system mirror, a substrate table, a support for supporting a patterning device, a force frame, and a sensor frame of the lithographic apparatus.

29. the object is the projection system mirror; the fluid duct passes through an intermediate frame, such as a force frame or a sensor frame, of the lithographic apparatus, a base frame of the lithographic apparatus, and an interface ring of the lithographic apparatus connected to a metrology frame of the lithographic apparatus; 29. The lithographic apparatus of claim 28, wherein the silencer is provided on at least one of the intermediate frame, the base frame, and the interface ring.

30. 1. A method for thermally conditioning an object in a lithographic apparatus, comprising: providing a flow of thermal conditioning fluid to the object through a fluid duct; the fluid duct is connected to the object; the fluid duct comprises a supply duct connected to the object to supply the thermal conditioning fluid to the object, and a discharge duct connected to the object to discharge the thermal conditioning fluid from the object; At least one of the supply duct and the exhaust duct is provided with at least two silencers arranged in series along the respective at least one of the supply duct and the exhaust duct.

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