Muffler and lithographic apparatus for thermal conditioning system

Abstract

A muffler configured to mutate sound waves in a thermal conditioning fluid in a thermal conditioning fluid conduit, and the muffler includes: an open inlet configured to be connected to the thermal conditioning fluid conduit for fluid communication with the thermal conditioning fluid in the thermal conditioning fluid conduit; a muffler housing, the muffler housing comprising an internal cavity connected to the open inlet; a compliant member dividing the interior cavity into a thermal conditioning fluid cavity and a substantially enclosed gas cavity, where the thermal conditioning fluid cavity is connected to the inlet; an inlet conduit configured to receive the thermal conditioning fluid; the muffler includes an inlet conduit, an outlet conduit, and a plurality of parallel conduits each forming a fluid passage, the plurality of parallel conduits being disposed in at least one of the inlet conduit and the outlet conduit.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to European application 23166311.3, filed on April 3, 2023, and incorporates the entire contents of this European application by reference. TECHNICAL FIELD

[0003] The present invention relates to a muffler, a thermal conditioning system comprising such a muffler, a lithographic apparatus comprising such a thermal conditioning system, and a method of thermally conditioning an object of a lithographic apparatus. BACKGROUND

[0004] A lithographic apparatus is a machine constructed to apply a desired pattern to a substrate. The lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). For example, the lithographic apparatus can project a pattern from a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate.

[0005] To project the pattern onto the substrate, the lithographic apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which can be formed on the substrate. A lithographic apparatus which uses extreme ultraviolet (EUV) radiation, having a wavelength within a range of 4-20 nm, for example 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a 193 nm wavelength.

[0006] An object of a lithographic apparatus can be provided with a thermal conditioning system comprising a fluid conduit for guiding a thermal conditioning fluid. The fluid conduit is configured to guide the thermal conditioning fluid to the object to be thermally conditioned, through the object and to evacuate the thermal conditioning fluid from the object. The object can for example be a projection system mirror of a projection system of a lithographic apparatus or can for example be a stage, such as a wafer stage of a lithographic apparatus. It has been observed that the thermal conditioning conduit can guide disturbances, such as vibrations, to the object. This can be undesirable because these disturbances can cause for example vibrations or other movements of the object. It has been suggested to provide the thermal conditioning conduit with a muffler which can provide compliance in order to dampen the disturbances. Movements of the object, such as a mirror or a substrate table of a lithographic apparatus, can cause inaccuracies in the imaging of a pattern on a substrate. Inaccuracies can translate into overlay errors which can adversely affect the accuracy of the lithographic apparatus. SUMMARY

[0007] It is desirable to provide a lithographic apparatus with a high overlay accuracy.

[0008] According to an aspect of the present invention, there is provided a muffler configured to dampen acoustic waves of a thermal conditioning fluid in a thermal conditioning fluid conduit, the muffler comprising:

[0009] an open inlet configured to be connected to the heat regulating fluid conduit for fluid communication with the heat regulating fluid in the heat regulating fluid conduit;

[0010] a muffler housing comprising an internal cavity connected to the open inlet;

[0011] a compliant member arranged in the internal cavity, wherein the compliant member divides the internal cavity into a heat regulating fluid cavity and a gas cavity, wherein the heat regulating fluid cavity is connected to the inlet and wherein the gas cavity forms a substantially closed space;

[0012] an inlet conduit configured to receive the heat regulating fluid, the inlet conduit being connected between the open inlet and an upstream portion of the heat regulating fluid conduit and being configured to supply the heat regulating fluid from the upstream portion of the heat regulating fluid conduit to the open inlet;

[0013] an outlet conduit configured to discharge the heat regulating fluid, the outlet conduit being connected between the open inlet and a downstream portion of the heat regulating fluid conduit and being configured to discharge the heat regulating fluid from the open inlet to the downstream portion of the heat regulating fluid conduit,

[0014] wherein the muffler further comprises a plurality of parallel conduits each forming a fluid passage, the plurality of parallel conduits being arranged in at least one of the inlet conduit and the outlet conduit.

[0015] According to an aspect of the present invention, there is provided a heat regulating system configured to heat regulate an object, wherein the heat regulating system comprises a heat regulating fluid conduit configured to be connected to the object and configured to provide a flow of the heat regulating fluid to the object; and at least two mufflers according to the present invention, wherein the at least two mufflers are arranged in series along the heat regulating fluid conduit.

[0016] According to an aspect of the present invention, there is provided a lithographic apparatus comprising an object and a heat regulating system according to the present invention for heat regulating the object.

[0017] According to an aspect of the application, there is provided a method of thermally conditioning an object of a lithographic apparatus, comprising providing a flow of a thermally conditioning fluid to the object via a thermally conditioning fluid conduit, the method comprising damping disturbances in an interference frequency band in the thermally conditioning fluid by at least two dampers according to any of the application, the at least two dampers being arranged in series along the thermally conditioning fluid conduit. BRIEF DESCRIPTION OF DRAWINGS

[0018] Embodiments of the application will now be described, by way of example only, with reference to the accompanying schematic drawings in which:

[0019] - Figure 1 A lithographic system comprising a lithographic apparatus and a radiation source is depicted;

[0020] - Figure 2A And Figure 2B A highly schematic view of a part of a thermally conditioning system with dampers that can be employed herein is depicted;

[0021] - Figures 3A to 3C A frequency response diagram is depicted, based on which the influence of a damper will be explained;

[0022] - Figures 4A to 4C A highly schematic view of an embodiment of a damper is depicted;

[0023] - Figures 5A to 5C A view of an embodiment of a damper according to the application is depicted;

[0024] - Figure 6 A highly schematic view of an embodiment of a thermally conditioning system according to the application is depicted; and

[0025] - Figure 7 A frequency response diagram is depicted, based on which the influence of a damper in a thermally conditioning system will be explained. DETAILED DESCRIPTION

[0026] Figure 1 A lithographic system comprising a radiation source SO and a lithographic apparatus LA is shown. The radiation source SO is configured to generate and supply an EUV radiation beam B to the lithographic apparatus LA. The lithographic 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.

[0027] The illumination system IL is configured to condition the EUV radiation beam B before it is incident upon the patterning device MA. The illumination system IL can also include a facetted field mirror device 10 and a facetted pupil mirror device 11, collectively referred to as facetted mirror devices. The facetted field mirror device 10 and the facetted pupil mirror device 11 together provide for the desired cross-sectional shape and the desired intensity distribution of the EUV radiation beam B at the patterning device MA. Instead of the facetted field mirror device 10 and the facetted pupil mirror device 11, other refractive or reflective optical elements can be used.

[0028] After being so conditioned, the EUV radiation beam B is incident upon the patterning device MA. As a result of the interaction between the EUV radiation beam B and the patterning device MA, a patterned EUV radiation beam B’ is generated. The projection system PS is configured to project the patterned EUV radiation beam B’ onto the substrate W. For this purpose, the projection system PS can include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B’ onto the substrate W held by the substrate table WT. The projection system PS can apply a reduction factor to the patterned EUV radiation beam B’, and thus form an image of features having a size smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 can be applied. Although the projection system PS is illustrated as having only two mirrors 13, 14 in Figure 1 The projection system PS can include a different number of mirrors (e.g., six or eight mirrors).

[0029] The substrate W can include a previously formed pattern. In that case, the lithography apparatus LA aligns the image formed by the patterned EUV radiation beam B’ with the pattern previously formed on the substrate W.

[0030] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure substantially below atmospheric pressure, can be provided in the radiation source SO, in the illumination system IL, and / or in the projection system PS.

[0031] The radiation source SO can be a laser-produced plasma (LPP) source, a discharge-produced plasma (DPP) source, a free electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0032] Figure 2AA highly schematic diagram of a thermal regulation system comprising a fluid conduit FD connected to an object OBJ is depicted. The thermal regulation system is configured to thermally regulate an object. The fluid conduit, also referred to as thermal regulation fluid conduit, comprises a thermal regulation fluid supply conduit FSD for supplying thermal regulation fluid to the object OBJ, and a thermal regulation fluid discharge conduit FDD for discharging thermal regulation fluid from the object OBJ. The fluid conduit can form a fluid flow passage in or on the object, e.g. a fluid channel in the object or a fluid conduit on the object, e.g. at the backside of the object. The thermal regulation fluid can be formed by any suitable fluid, such as a liquid (e.g. water) or a gas. The thermal regulation system can be configured to heat the object, to cool the object, to thereby stabilize the object at a desired temperature or in a desired temperature range. The object can for example be a mirror of a projection system of a lithographic apparatus, or a stage such as a wafer stage of a lithographic apparatus. The thermal regulation fluid can be supplied by any suitable supply means, such as a pump, a pressurizing device, etc.

[0033] Figure 2B A schematic diagram of a portion of a fluid supply conduit of a thermal regulation system according to Figure 2A the present invention is depicted. According to an aspect of the present invention, the fluid supply conduit and the fluid discharge conduit are each provided with two sound dampers SL. A sound damper can be understood as an element having a low hydraulic stiffness compared to the hydraulic stiffness of the thermal regulation conduit. The hydraulic stiffness can be understood as the ratio of the pressure increment over the discharge volume increment of the fluid, K_hyd = dp / dV, wherein p is the absolute pressure and V is the gas volume.

[0034] It has been observed that such sound dampers provide attenuation to suppress disturbances. Such sound dampers can provide for a disturbance suppression of e.g. a factor 10 to 30. However, the inventors have realized that a significantly higher disturbance suppression can be reached using such sound dampers, which suppression can be a factor of e.g. 10 to 30 higher compared to known dampers.

[0035] Returning to Figure 2B As explained above, at least two sound dampers are provided in the supply conduit and at least two sound dampers are provided in the return conduit. The sound dampers SL1, SL2 are arranged in series along the supply conduit as well as along the discharge conduit. Thus, along the supply conduit, one of the at least two sound dampers is located upstream with respect to the other of the at least two sound dampers. Similarly, along the discharge conduit, one of the at least two sound dampers is located upstream with respect to the other of the at least two sound dampers. The thermal regulation fluid between the sound dampers SL1, SL2 provides a thermal regulation fluid mass TCFM.

[0036] It has been realized by the inventors that a combination of two mufflers in series with a thermal conditioning fluid forming a thermal conditioning fluid mass in the conduit between the mufflers can provide a resonance behavior resulting in a roll-off above the resonance frequency. By setting the size or dimensions of the mufflers, their compliance and the thermal conditioning fluid mass between the mufflers, the resonance frequency can be determined to be below the interference frequency band, thus enabling a more effective suppression of the interference in the interference frequency band from being transmitted to the object via the fluid conduit.

[0037] Multiple mufflers in series have the ability to be effective up to higher frequencies (e.g. above 80 Hz). Using at least two mufflers in series, the gas volume of each muffler effectively creates a low stiffness in the water loop by generating a low hydraulic stiffness (K_hyd = dp / dV). Subsequently, the hydraulic stiffness of the gas volume can be derived as K_hyd = γ p / V (adiabatic condition). In the above equation, γ (gamma) is the adiabatic exponent, p is the absolute pressure and V is the gas volume. By placing two mufflers in series, the mass between the mufflers can start to resonate at a resonance frequency. Below this frequency, there can be no additional benefit of multiple mufflers; at this frequency, there can be amplification; however, above this frequency, the mass between the mufflers can start to decouple and effectively obtain a slope of -2. This is similar to a mechanical mass spring isolation system. In this way, significantly higher suppression can be achieved by placing multiple mufflers in series. Additionally, by reducing the stiffness of the mufflers (reducing the pressure or increasing the gas volume) or increasing the hydraulic mass M_ (hyd duct) = p L / A of the conduit between the mufflers (increasing the length or reducing the conduit cross-sectional area), this resonance frequency can be lowered such that a higher reduction is achieved (especially in relation to the above-mentioned frequency, e.g. 80 Hz). Placing more than 2 mufflers in series can be applied to create multiple masses between the mufflers that start to decouple such that a slope of -4 or even higher can be effectively achieved. Tuning the stiffness of the mufflers and the hydraulic mass of the conduit between the mufflers allows to effectively avoid resonance amplification and achieve the final muffling performance. From a dynamics point of view, placing multiple mufflers in series with sufficient distance in between is a significant technical breakthrough that is currently introduced by the DCM.

[0038] Effectiveness at higher frequencies: The distance between the gas volume and the conduit limits the frequencies at which the gas volume can be effectively utilized. This conduit section is referred to as the neck of the muffler, and its associated resonant frequency can be called the Helmholtz frequency f_HR. Below this frequency, the gas volume is effectively sensed; at this frequency, 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 sensed. This resonant frequency can be increased by increasing the stiffness of the muffler (increasing pressure or decreasing the gas volume) or by decreasing the hydraulic mass of the muffler neck (decreasing length or increasing neck diameter), making it possible to effectively sense the gas volume at higher frequencies (especially those related to approximately 80 Hz). To eliminate the risk of gas dissolution over time, a compliant interface is added. This interface is required to have sufficiently low stiffness so that the sum of the gas volume stiffness and the stiffness of the compliant interface still meets the requirements. Additionally, the inertia of the bellows can be small enough so that the Helmholtz frequency can remain sufficiently high. Finally, the structural resonance of the compliant interface can be high enough, at least above the Helmholtz frequency, so that it does not degrade the sound wave silencing performance.

[0039] Figure 3A and Figure 3B A schematic diagram depicting the transmission of interference from the conduit to the object along the vertical axis, with frequencies relative to the horizontal axis. For example... Figure 3A As depicted, individual silencers in the supply catheter FSD and the return catheter FRD provide a roll-off of 2 times per octave (i.e., 10 times per decibel) above the roll-off frequency Froll. Figure 3B As described, two silencers connected in series in the supply conduit and the return conduit can provide a roll-off of twice the frequency per octave from the roll-off frequency Froll to the resonant frequency Fres, while also providing a roll-off of three times, i.e., eight times the frequency per octave above the resonant frequency. The resonant frequency Fres can be determined by the resonance of the mass body of the thermoregulating fluid in the conduit between the two silencers.

[0040] Therefore, as described above, a single muffler combined with a non-reflective acoustic boundary condition (critical damping) can provide a slope of -1, i.e., 10 times per decade. A series of dual mufflers can provide a slope of -3, i.e., 1000 times per decade (a slope of -1 (i.e., 10 times per decade) can originate from the combination of the muffler and the non-reflective acoustic boundary condition, while a slope of -2 (i.e., 100 times per decade) can originate from the decoupled mass between the mufflers).

[0041] In embodiments, at least two mufflers together with the thermal regulating fluid in the fluid conduit interconnecting the at least two mufflers form a resonator. The thermal regulating fluid in the conduit interconnecting the at least two mufflers respectively in the supply conduit, in the return conduit provides the mass and the mufflers provide the compliance. The mass of the thermal regulating fluid between the mufflers and the compliance of the mufflers can exhibit a resonance behavior, in Figure 3B the resonance frequency Fres. The resonance behavior implies a frequency behavior involving two poles, so that if it is above the resonance frequency, 4 (further) roll-off per octave is observed, i.e. 100 (further) per decade of octave. In combination with the roll-off of the mufflers combined with the non-reflecting sound wave boundary conditions, a total of 1000 per decade of octave is observed. The resonance frequency can be a resonance due to sloshing of the fluid in the conduit between the mufflers.

[0042] Figure 3C a schematic diagram is depicted in which the frequency disturbing the transmission of sound via the conduit to the subject is depicted on the vertical axis with respect to the frequency on the horizontal axis. As depicted in Figure 3C a single such muffler SL in e.g. the supply conduit and / or in the return conduit provides a Helmholtz resonance at a falling Helmholtz resonance frequency ω HR , which is the square root of the quotient of the hydraulic compliance of the muffler and the hydraulic mass in the muffler fluid conduit, ω HR =√(K Hyd / M Hyd ), wherein ω HR is the Helmholtz resonance frequency, K Hyd is the hydraulic compliance of the muffler, and M Hyd is the hydraulic mass in the muffler fluid conduit. The falling Helmholtz resonance frequency ω HR involves a roll-off with a slope of -2. As further depicted in Figure 3C two mufflers in series (e.g. in the supply conduit and / or in the return conduit) can provide a resonance peak at a sloshing frequency, which is equal to the square root of the quotient of [twice the hydraulic compliance of the mufflers and the hydraulic mass in the conduit between the two mufflers], ω S =√(2K Hyd / M Hyd ). wherein ω S is the sloshing frequency, 2K Hyd is twice the hydraulic compliance of the mufflers, and M Hydfor the hydraulic mass in the conduit between the silencers. The silencers thus decouple the hydraulic mass between the silencers (low stiffness elements) so as to achieve -40 decibels per decade of suppression in the pressure transmission on force inputs above the sloshing resonance frequency (slope of -2). Multiple silencer pairs (N) allow to benefit from a large number of decoupled masses, resulting in Nx-40 dB / dec. For example, as depicted in Figure 3C The double pair provides two sloshing resonance frequencies ω S , providing a slope of -4. The sloshing resonance frequency ω S may be lower than the Helmholtz resonance frequency ω HR , due to the large hydraulic mass involved in the fluid between the silencers. The sloshing resonance frequency ω S may be sized lower than the disturbance band in which the disturbance is to be suppressed, so that the propagation of the disturbance is significantly suppressed due to the slope of -2 per silencer pair. Tuning the hydraulic mass between the silencers (M_hyd), the hydraulic mass in the pipe between the conduit and the silencers (M_hyd) or the silencer compliance (K_hyd) allows to optimize the suppression behavior. Sizing the hydraulic mass between the silencers and the silencer compliance so that the sloshing frequency of the silencer pair is lower than the disturbance band can allow to obtain a slope of -2 per silencer pair in the disturbance band, so that it enables to suppress the disturbance in the disturbance band by the slope of -2 per silencer pair.

[0043] In an embodiment, the resonator is a series resonator. The series resonator is able to utilize the mass of the thermal conditioning fluid between two silencers, thus the mass present in the fluid conduit can be used. Therefore, no additional mass is needed, resulting in a very small increase in weight.

[0044] Figures 4A to 4C Three different embodiments of a silencer are schematically depicted. Figure 4A The silencer SL depicted in Fig. 1 is formed by an internal space which is partially filled by a gas which can avoid to be dissolved in the thermal conditioning fluid. When pressurized by the thermal conditioning fluid, elasticity can be formed by the gas.

[0045] Figure 4B The silencer SL depicted in Fig. 2 comprises a membrane MEM which divides the internal space of the silencer into a part which is filled by a gas and a part which is filled by the thermal conditioning fluid, for example. The elasticity of the membrane, possibly in combination with the pressurization of the gas, makes the thermal conditioning fluid interacting with the silencer elastic.

[0046] Figure 4CAn acoustic silencer SL is depicted comprising a diaphragm shaped as a bellows BEL, which diaphragm divides an interior space of the acoustic silencer into a portion filled by a gas and a portion filled by a thermal regulating fluid, for example. The elasticity of the diaphragm shaped as a bellows, possibly in combination with pressurization or depressurization of the gas, makes the thermal regulating fluid interacting with the acoustic silencer elastic.

[0047] Figure 5A A perspective view of an acoustic silencer according to an embodiment of the present application is depicted. The acoustic silencer comprises an acoustic silencer housing SHS having an interior cavity CAV. The acoustic silencer comprises an open inlet OIL connected to a thermal regulating fluid conduit FD. The thermal regulating fluid conduit is configured to direct thermal regulating fluid to and / or from an object to be thermally regulated. The open inlet puts the acoustic silencer in fluid communication with the thermal regulating fluid in the thermal regulating fluid conduit. The interior cavity is connected or communicates to the open inlet and is connected with the thermal regulating fluid conduit via the open inlet. The acoustic silencer further comprises a compliant member CMP arranged in the interior cavity, wherein the compliant member divides the interior cavity into a thermal regulating fluid cavity FCA and a gas cavity GCA. One surface of the compliant member faces the thermal regulating fluid cavity and the opposite surface of the compliant member faces the gas cavity. The thermal regulating fluid can thus flow from the thermal regulating fluid conduit to the thermal regulating fluid cavity of the acoustic silencer via the open inlet. When the compliant member divides the cavity into the thermal regulating fluid cavity connected to the open inlet and the gas cavity, the gas cavity forms a substantially closed space which can be filled with a gas. The compliant member is thus subjected to the thermal regulating fluid pressure at one surface of the compliant member facing the thermal regulating fluid cavity and to the gas pressure by the gas on the opposite surface of the compliant member facing the gas cavity.

[0048] The thermal regulating fluid conduit, also identified as fluid conduit, can be formed by any fluid conduit, such as a tube, a hose, a channel, a bore, or any combination thereof. For example, the thermal regulating fluid conduit can comprise a fluid flow passage in or on the object, e.g. a fluid channel in the object or a fluid conduit on the object, e.g. at a back side of the object. As another example, the fluid conduit can comprise a fluid flow passage in or on the object in combination with a fluid supply conduit for supplying thermal regulating fluid to the object and a fluid discharge conduit for discharging thermal regulating fluid from the object.

[0049] The silencer further comprises an inlet conduit ILD and an outlet conduit OLD. The inlet conduit ILD is connected between the upstream portion of the heat regulating fluid conduit and the open inlet to receive heat regulating fluid from the upstream portion of the heat regulating fluid conduit and to provide the received heat regulating fluid to the open inlet. The outlet conduit OLD is connected between the open inlet and the downstream portion of the heat regulating fluid conduit to discharge heat regulating fluid from the open inlet to the downstream portion of the heat regulating fluid conduit.

[0050] According to the invention, the silencer further comprises a plurality of parallel conduits PD arranged parallel to each other. The parallel conduits each form a fluid passage for guiding heat regulating fluid. The plurality of parallel conduits PD is arranged in at least one of the inlet conduit ILD and the outlet conduit OLD. The plurality of parallel conduits can thus be arranged in the inlet conduit ILD or arranged in the outlet conduit OLD. In another embodiment, the parallel conduits are arranged in both the inlet conduit ILD and the outlet conduit OLD. The parallel conduits extend in the same direction as the one in which the one of the inlet conduit and the outlet conduit extends, i.e. the parallel conduits extend in the direction of flow of heat regulating fluid in the one of the inlet conduit and the outlet conduit. For example, the parallel conduits are arranged in the inlet conduit and extend parallel to each other and parallel to the direction of the inlet conduit. As another example, the parallel conduits are arranged in the outlet conduit and extend parallel to each other and parallel to the direction of the outlet conduit. The parallel conduits effectively divide the one of the inlet conduit and the outlet conduit in which the parallel conduits are arranged into a plurality of parallel passages each conducting heat regulating fluid. The parallel conduits can thus be understood as dividing the one of the inlet conduit and the outlet conduit in which the parallel conduits are arranged into a plurality of parallel passages each conducting heat regulating fluid. Figure 5A In the example depicted in Fig. 6, the parallel conduits are provided in the outlet conduit OLD.

[0051] Figure 5B A cross-sectional view of the parallel conduits is depicted, wherein the cross-section intersects one of the inlet conduits ILD in which the parallel conduits PD are arranged. The conduits extend parallel to each other.

[0052] Figure 5C Another view of a portion of the silencer is depicted, depicting the open inlet OIL, the inlet conduit ILD and the outlet conduit OLD provided with a plurality of parallel conduits PD.

[0053] It has been thought by the inventors that the parallel conduits in the one of the inlet and outlet conduits can facilitate damping of one or more resonances of the heat regulating fluid in the fluid conduit. It has been found that the parallel conduits provide an additional frictional damping, which has been found to facilitate damping at the resonance frequency Fres. The frictional damping can be understood as a frictional effect of moving fluid particles to the walls of the fluid passage in the one of the inlet and outlet conduits.

[0054] In an embodiment, the plurality of parallel conduits comprises at least 2 conduits. The damping due to the parallel conduits can increase with (i) increasing channel length; (ii) decreasing channel diameter; (iii) decreasing porosity, wherein porosity can be defined as the number of channels times the ratio of the cross-sectional area of each channel to the cross-sectional area of the conduit.

[0055] The thermal regulation system can comprise a supply conduit supplying the thermal regulation fluid to the object and a discharge conduit discharging the thermal regulation fluid from the object. Both the supply conduit and the discharge conduit can form a propagation path along which the disturbance can reach the object to be thermally regulated. In order to provide damping in the supply conduit and in the discharge conduit at a frequency higher than the sloshing resonance frequency, both the supply conduit and the discharge conduit can be provided with a damper comprising a gas channel to attenuate the sloshing resonance peak. According to an embodiment of the present application, the thermal regulation fluid conduit thus comprises a supply conduit configured to be connected to the object and to supply the thermal regulation fluid to the object and a discharge conduit configured to be connected to the object and to discharge the thermal regulation fluid from the object, wherein the supply conduit and the discharge conduit are each provided with at least two dampers arranged in series along the supply conduit and along the discharge conduit, respectively. The at least two dampers can form a resonator with the thermal regulation fluid in the fluid conduit, i.e. the thermal regulation fluid conduit, interconnecting the at least two dampers.

[0056] Since the sloshing resonance provides a steep slope in the frequency response diagram above the sloshing resonance frequency, the double damper forming a resonator can provide high damping above the sloshing resonance frequency. According to an embodiment, the resonator is configured to attenuate the disturbance in a disturbance frequency band, wherein the resonance frequency of the resonator is lower than the disturbance frequency band. The resonator can be a series resonator.

[0057] As explained with reference to Figure 2A and Figure 2B The two dampers can be arranged in series in the supply conduit of the thermal regulation fluid conduit and in the discharge conduit of the thermal regulation fluid conduit. The two dampers in series provide a sloshing resonance mode providing a resonance at a resonance frequency Fresand an additional slope of -2 above the resonance frequency. In accordance with an embodiment of the present application, the resonance frequency Fresof the resonator is lower than the disturbance frequency band. Figure 2A and Figure 2BIn the present example, the slope below the resonance frequency is a slope of -1, and the slope providing above the resonance frequency is a slope of -3. While the slope of -3 provides enhanced attenuation of the disturbance (e.g., vibration) in the frequency range above the resonance frequency, the resonance peak at the resonance frequency can be high, such that the vibration is transmitted relatively high at the resonance frequency. The resonance can be attributed to the resonant mass of the thermal conditioning fluid in the thermal conditioning conduit between the two mufflers and the compliance of the mufflers. The compliance of the mufflers can be determined by the stiffness of the gas in the gas cavity (possibly in combination with the stiffness of the compliance member). The resonance peak can cause transmission of the disturbance at the resonance frequency to the object to be thermally conditioned.

[0058] It has been realized by the inventors that the resonance peak at the resonance frequency Fres can be reduced by a parallel passage in one of the inlet conduit and the outlet conduit. In an embodiment, the parallel conduit is provided in the inlet conduit of a downstream muffler of the mufflers. In another embodiment, the parallel conduit is provided in the outlet conduit of an upstream muffler of the mufflers. In yet another embodiment, the parallel conduit is provided in the inlet conduit of a downstream muffler of the mufflers and in the outlet conduit of an upstream muffler of the mufflers. It has been found that the parallel conduit provides additional frictional damping, which has been found to promote damping at the resonance frequency Fres. It has been realized by the inventors that the resonance of the thermal conditioning fluid involves one or more sectors of the thermal conditioning fluid where the periodic pressure change at the resonance frequency is highest, and one sector of the plurality of sectors of the thermal conditioning fluid where the periodic velocity change at the resonance frequency is highest. It has been further realized by the inventors that, in the case of a sloshing resonance or acoustic wave mode (standing wave), the one sector of the plurality of sectors of the thermal conditioning fluid where the periodic velocity change at the resonance frequency is highest is in the fluid mass body located between the mufflers, in the sector closest to the mufflers, i.e., in the inlet conduit of a downstream muffler of the mufflers and in the outlet conduit of an upstream muffler of the mufflers. It has been realized by the inventors that by specifically placing the parallel passage at the sector of the thermal conditioning fluid where the periodic velocity change at the resonance frequency is highest, an effective damping of the resonance can be provided. In addition to the damping of the sloshing mode, the acoustic wave mode (i.e., standing wave) can also be damped or attenuated.

[0059] Figure 6 A highly schematic view of a thermal conditioning fluid conduit with two mufflers in series is depicted. In the flow direction of the thermal conditioning fluid, visible are Figure 6The two silencers in series comprise an upstream silencer SLU and a downstream silencer SLD. The silencers SLU, SLD provide a sloshing resonance mode providing a resonance at a resonance frequency. In addition, a sound wave mode in the form of a standing wave is also formed between the two silencers. The upstream silencer comprises an inlet duct ILD and an outlet duct OLD. Similarly, the downstream silencer comprises an inlet duct ILD and an outlet duct OLD. A parallel duct PD is comprised in the ILD inlet duct of the downstream silencer SLD among the silencers and in the outlet duct OLD of the upstream silencer SLU among the silencers. Figure 7 A frequency diagram is depicted showing the frequency f at the horizontal axis and the transmission rate Tr of the vibrations along the vertical axis via the thermal regulation fluid in the thermal regulation fluid duct. Figure 7 A frequency diagram is depicted showing the frequency f at the horizontal axis and the transmission rate Tr of the vibrations along the vertical axis via the thermal regulation fluid in the thermal regulation fluid duct. Figure 2A and Figure 2B and Figure 6 and Figure 7 The resonance peak Fres represents the resonance at the sloshing frequency as shown in Fig. 6. The silencers thus form a series resonator. Adding damping exhibits a reduction of the resonance peak: adding damping in the thermal regulation fluid duct between the two silencers (i.e. in at least one of the inlet duct of the downstream silencer and the outlet duct of the upstream silencer) exhibits to provide damping reducing the resonance peak to Fres-d, while adding additional damping in the gas cavity by means of the gas passage exhibits to further reduce the resonance peak to Fres-d2.

[0060] The damping in one of the inlet duct and the outlet duct exhibits to provide multiple effects: on the one hand, the peak at the resonance frequency is reduced, on the other hand, the resonance frequency itself is also reduced to a certain extent. The reduction of the resonance frequency facilitates silencing above the resonance frequency, since the transition from a slope of -1 below the resonance frequency (-1SL) to a steeper slope of -3 above the resonance frequency (-3SL) starts at the lower resonance frequency Fres-d2, thus providing additional damping in the disturbance frequency band DFB above this frequency.

[0061] The at least two mufflers thus form (in series) a resonator with the thermal regulation fluid in the fluid conduit interconnecting the at least two mufflers, the resonator having a resonance frequency. The resonator is configured to attenuate disturbances in a disturbance frequency band above the resonance frequency. Thus, the resonance frequency of the resonator is lower than the disturbance frequency band. The plurality of parallel conduits form a resistive damper that reduces the resonance peak of the sloshing resonance mode of the series resonator and the acoustic wave mode formed between the series resonators.

[0062] The thermal regulation system described above can be included in a lithographic apparatus. The object to be thermally regulated by the thermal regulation system can be one of a projection system mirror of a projection system of the lithographic apparatus, a substrate table, a support for supporting a patterning device, a force frame and a sensor frame.

[0063] The invention can also be expressed as a method of thermally regulating an object of a lithographic apparatus, comprising providing a flow of a thermal regulation fluid to the object via a thermal regulation fluid conduit, the method comprising Figure 5A and Figure 5B damping or dampening disturbances in a disturbance frequency band in the thermal regulation fluid by at least two mufflers as described above with reference to

[0064] Although specific reference can be made in this text to the use of the lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein can have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc.

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

[0066] Although specific reference can be made in this text to the use of the lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein can have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc.

[0067] Embodiments of the present application can be implemented in hardware, firmware, software, or any combination thereof, depending on the circumstances. Embodiments of the present application can also be implemented as instructions stored on a machine-readable medium, which can be read and executed by one or more processors. A machine-readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium can include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions can be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from the operation of computers, processors, controllers, or other devices under their control, and that the resulting actions can cause actuators or other devices to interact with the physical world.

[0068] While specific embodiments of the application have been described above, it will be appreciated that the application can be practiced otherwise than as described. The description is intended to be illustrative, not restrictive. It will be apparent to those skilled in the art that modifications can be made to the described embodiments without departing from the scope of the claims set out below.

Claims

1. A silencer configured to silence sound waves in a heat-regulating fluid within a heat-regulating fluid conduit, the silencer comprising: An open inlet is configured to connect to the thermoregulating fluid conduit for fluid communication with the thermoregulating fluid in the thermoregulating fluid conduit; A muffler housing, the muffler housing including an internal cavity connected to the open inlet; A compliant member is arranged in the internal cavity, wherein the compliant member divides the internal cavity into a thermoregulating fluid cavity and a gas cavity, wherein the thermoregulating fluid cavity is connected to the inlet and wherein the gas cavity forms a substantially enclosed space; An inlet conduit configured to receive the thermoregulating fluid, the inlet conduit being connected between the open inlet and an upstream portion of the thermoregulating fluid conduit, and the inlet conduit being configured to supply the thermoregulating fluid from the upstream portion of the thermoregulating fluid conduit to the open inlet; An outlet conduit, configured to discharge the heat-regulating fluid, is connected between the open inlet and a downstream portion of the heat-regulating fluid conduit, and is configured to discharge the heat-regulating fluid from the open inlet to the downstream portion of the heat-regulating fluid conduit. The silencer further includes a plurality of parallel conduits, each forming a fluid channel, wherein the plurality of parallel conduits are arranged in at least one of the inlet conduit and the outlet conduit.

2. The silencer according to claim 1, wherein, The parallel conduit is arranged in the inlet conduit.

3. The silencer according to claim 1 or 2, wherein, The parallel conduit is arranged in the outlet conduit.

4. The muffler according to any one of the preceding claims, wherein, The plurality of parallel catheters includes at least two catheters.

5. A thermal conditioning system configured to thermally condition an object, wherein, The thermal conditioning system includes: a thermal conditioning fluid conduit configured to be connected to the object and configured to provide a flow of the thermal conditioning fluid to the object; and at least two silencers, the at least two silencers being silencers according to any one of the preceding claims, wherein the at least two silencers are arranged in series along the thermal conditioning fluid conduit.

6. The thermal control system according to claim 5, wherein, The plurality of conduits are disposed in at least one of the outlet conduit of the upstream silencer and the inlet conduit of the downstream silencer in the silencer.

7. The thermal control system according to claim 6, wherein, The thermoregulating fluid conduit includes: a supply conduit configured to be connected to the object and supply the thermoregulating fluid to the object; and a discharge conduit configured to be connected to the object and discharge the thermoregulating fluid from the object, wherein the supply conduit and the discharge conduit are each provided with the at least two silencers arranged in series along the supply conduit and the discharge conduit, respectively.

8. The thermal control system according to claim 7, wherein, The at least two mufflers together with the thermoregulating fluid in the fluid conduit that interconnects the at least two mufflers form a resonator.

9. The thermal control system according to claim 8, wherein, The resonator is configured to attenuate interference in the interference band, wherein the resonant frequency of the resonator is lower than that of the interference band.

10. The thermal control system according to claim 8 or 9, wherein, The resonator is a series resonator.

11. The thermal control system according to claim 10, wherein, The plurality of parallel conduits form a resistive damper, which is configured to provide damping for the swaying resonance modes of the series resonator.

12. The thermal control system according to claim 10 or 11, wherein, The plurality of parallel conduits form a resistive damper, which is configured to provide damping for the acoustic resonance modes of the series resonator.

13. A photolithography apparatus, comprising an object and a thermal conditioning system for thermally conditioning the object according to any one of claims 5 to 12.

14. The photolithography apparatus according to claim 13, wherein, The object is one of the following: the projection system reflector of the lithography equipment, the substrate stage, the support for the pattern forming apparatus, the force frame, and the sensor frame.

15. A method for thermally conditioning an object of a photolithography apparatus, comprising providing a flow of thermal conditioning fluid to the object via a thermal conditioning fluid conduit, the method comprising silencing interference in the thermal conditioning fluid in an interference frequency band by means of at least two silencers, said at least two silencers being silencers according to any one of claims 1 to 4, said at least two silencers being arranged in series along the thermal conditioning fluid conduit.

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