Lithographic apparatus thermal conditioning system and method

Abstract

A thermal conditioning system is configured to thermally condition a subject. The thermal conditioning system includes a fluid conduit configured to be connected to the subject and configured to provide a flow of thermal conditioning fluid to the subject. The fluid conduit includes a supply conduit configured to be connected to the subject and to supply the thermal conditioning fluid to the subject and a thermal conditioning fluid configured to be connected to and from the subject and a discharge conduit that discharges the thermal conditioning fluid. The supply conduit and / or the discharge conduit are each provided with at least two mufflers arranged in series along the supply conduit and along the discharge conduit, respectively.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to European Application No. 22213728.3, filed on Dec. 15, 2022, the entire content of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a thermal regulation system, a lithographic apparatus comprising such a thermal regulation system, and a method of thermally regulating an object of a lithographic apparatus. Background art

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

[0005] To project a pattern onto a substrate, a lithographic apparatus can use electromagnetic radiation. The wavelength of such radiation determines the minimum size of features that can be formed on the substrate. Compared to a lithographic apparatus that uses radiation having a wavelength of, for example, 193 nm, a lithographic apparatus that uses extreme ultraviolet (EUV) radiation having a wavelength in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0006] An object of the lithographic apparatus can be provided with a thermal regulation system including fluid conduits for guiding a thermal regulation fluid. The fluid conduits are configured to guide the thermal regulation fluid to an object to be thermally regulated, through the object, and to discharge the thermal regulation fluid from the object. The object can be, for example, a projection system mirror of the projection system of the lithographic apparatus or can be, for example, a platform such as a wafer stage of the lithographic apparatus. It has been observed that the thermal regulation conduits can conduct perturbations, such as vibrations, to the object. This can be undesirable because such perturbations can cause, for example, vibrations or other movements of the object. It has been proposed to provide the thermal regulation conduits with mufflers that can provide compliance to suppress the perturbations. Movements of the object (such as a mirror or a substrate stage of the lithographic apparatus) can cause inaccuracies in the imaging of the pattern on the substrate. The inaccuracies can translate into overlay errors that can adversely affect the accuracy of the lithographic apparatus. Summary of the invention

[0007] There is a desire to provide a lithographic apparatus having high overlay accuracy.

[0008] According to one aspect of the invention, there is provided a thermal regulation system configured to thermally regulate an object, wherein the thermal regulation system includes a fluid conduit configured to be connected to the object and configured to provide a flow of a thermally regulating fluid to the object, the fluid conduit including a supply conduit configured to be connected to the object and supply the thermally regulating fluid to the object and a discharge conduit configured to be connected to the object and discharge the thermally regulating fluid from the object, wherein at least one of the supply conduit and the discharge conduit is provided with at least two silencers arranged in series along the corresponding at least one of the supply conduit and the discharge conduit.

[0009] According to another aspect of the invention, there is provided a lithographic apparatus including an object and a thermal regulation system for thermally regulating the object according to the invention, wherein the object is one of a projection system mirror and a substrate table of the lithographic apparatus.

[0010] According to yet another aspect of the invention, there is provided a method of thermally regulating an object of a lithographic apparatus, including providing a flow of a thermally regulating fluid to the object via a fluid conduit, wherein the fluid conduit is connected to the object and wherein the fluid conduit includes a supply conduit connected to the object to supply the thermally regulating fluid to the object and a discharge conduit connected to the object to discharge the thermally regulating fluid from the object, wherein at least one of the supply conduit and the discharge conduit is provided with at least two silencers arranged in series along the corresponding at least one of the supply conduit and the discharge conduit.

[0011] According to still another aspect of the invention, there is provided a method of tuning silencers in a fluid conduit of a thermal regulation system configured to thermally regulate an object, the method including: defining a perturbation frequency band in which the transmission of perturbations from a perturbation entry point to the object is to be reduced, providing at least two silencers in the fluid supply conduit between the perturbation entry point and the object, providing at least two silencers in the fluid discharge conduit between the perturbation entry point and the object, and using the inertia of the thermally regulating fluid between the silencers such that the resonance of the mass of the thermally regulating fluid between the silencers is sized to be at a resonance frequency below the perturbation frequency band. Description of the Drawings

[0012] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0013] Figure 1 A lithographic system including a lithographic apparatus and a radiation source is depicted;

[0014] Figure 2A and Figure 2BA height schematic diagram depicting a part of the thermal regulation system according to an aspect of the present invention;

[0015] Figures 3A to 3C A frequency response diagram is depicted, and the effects of the present invention will be explained based on these diagrams;

[0016] Figures 4A to 4C A height schematic diagram depicting an embodiment of a muffler that can be used in the thermal regulation system according to the present invention;

[0017] Figure 5 A height schematic diagram depicting another embodiment of a muffler that can be used in the thermal regulation system according to the present invention;

[0018] Figure 6 A height schematic diagram depicting a membrane of a muffler that can be used in the thermal regulation system according to the present invention;

[0019] Figure 7 A height schematic diagram depicting yet another embodiment of a muffler that can be used in the thermal regulation system according to the present invention;

[0020] Figure 8 A height schematic diagram depicting yet another embodiment of a muffler that can be used in the thermal regulation system according to the present invention;

[0021] Figure 9 and Figure 10 A height schematic diagram depicting a negative compliance mechanism that can be used in a muffler;

[0022] Figure 11 A height schematic diagram depicting another embodiment of the thermal regulation system according to the present invention;

[0023] Figures 12A to 12C A detailed view depicting yet another other embodiment of the thermal regulation system according to the present invention;

[0024] Figures 13A to 13C A height schematic diagram depicting an additional embodiment of a muffler that can be used in the thermal regulation system according to the present invention;

[0025] Figure 14 A height schematic partial view depicting yet another additional embodiment of a muffler that can be used in the thermal regulation system according to the present invention;

[0026] Figure 15 A height schematic diagram depicting yet another additional embodiment of a muffler that can be used in the thermal regulation system according to the present invention. Detailed Description

[0027] Figure 1A lithography system is shown including a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography apparatus LA. The lithography apparatus LA includes 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.

[0028] The illumination system IL is configured to condition the EUV radiation beam B before the EUV radiation beam B is incident on the patterning device MA. Additionally, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and the faceted pupil mirror device 11 together provide a desired cross-sectional shape and a desired intensity distribution to the EUV radiation beam B. In addition to or instead of the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may include other mirrors or devices.

[0029] After being conditioned in this way, the EUV radiation beam B interacts with the patterning device MA. Due to this interaction, 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 may 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 may apply a reduction factor to the patterned EUV radiation beam B’, thereby forming an image having features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is Figure 1 illustrated as having only two mirrors 13, 14 in the figure, the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0030] The substrate W may include a previously formed pattern. In such a 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.

[0031] A relative vacuum may be provided in the radiation source SO, in the illumination system IL, and / or in the projection system PS, i.e., a small amount of gas (e.g., hydrogen) at a pressure sufficiently lower than atmospheric pressure.

[0032] The radiation source SO may 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.

[0033] Figure 2ASchematic elevation depicting a thermal regulation system including a fluid conduit FD connected to an object OBJ. The thermal regulation system is configured to thermally regulate the object. The fluid conduit includes a thermal regulation fluid supply conduit FSD for supplying a thermal regulation fluid to the object OBJ and a thermal regulation fluid discharge conduit FDD for discharging the thermal regulation fluid from the object OBJ. The fluid conduit may form a fluid flow channel in or on the object, such as forming a fluid channel in the object or forming a fluid conduit on the object (e.g., at the rear side of the object). The thermal regulation fluid may be formed of any suitable fluid, such as a liquid (e.g., water) or a gas. The thermal regulation system may be configured to heat the object, cool the object, thereby stabilizing the object at a desired temperature or within a desired temperature range. The object may be, for example, a mirror such as a projection system of a lithographic apparatus, or a platform such as a wafer stage of a lithographic apparatus. The thermal regulation fluid may be supplied by any suitable supply member (such as a pump, a pressurizing member, etc.).

[0034] Figure 2B Schematic depicting a portion of a fluid supply conduit of a thermal regulation system according to Figure 2A According to one aspect of the present invention, at least one of the fluid supply conduit and the fluid discharge conduit is provided with two silencers SL. According to one aspect of the present invention, each of the fluid supply conduit and the fluid discharge conduit is provided with two silencers SL. The silencer 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 to the fluid discharge volume increment, Khyd = dp / dV, where p is the absolute pressure and V is the gas volume.

[0035] It has been observed that such silencers provide damping to suppress disturbances. Such silencers can provide, for example, a disturbance suppression of 10 to 30 times. However, the inventors have designed that a substantially higher disturbance suppression can be achieved with such silencers, which can be, for example, 10 to 30 times higher in magnitude compared to known suppression.

[0036] Return Figure 2B , as explained above, according to one aspect of the present invention, at least two silencers are provided in the supply conduit and / or at least two silencers are provided in the return conduit. The silencers SL1, SL2 are arranged in series along the supply conduit, the discharge conduit or both the supply conduit and the discharge conduit. Thus, along the supply conduit, one of the at least two silencers is upstream of the other of the at least two silencers. Similarly, along the discharge conduit, one of the at least two silencers is upstream of the other of the at least two silencers. The thermal regulation fluid between the silencers SL1, SL2 provides a thermal regulation fluid mass TCFM.

[0037] The inventors have designed a component of two mufflers in series and a thermoregulating fluid forming a thermoregulating fluid mass in a conduit between the mufflers that can provide a resonance behavior that results in a roll-off above the resonance frequency. By sizing the mufflers, their compliance, and the thermoregulating fluid mass between the mufflers, the resonance frequency can be determined to be below the disturbance band, thus enabling more effective suppression of disturbances in the disturbance band being transmitted via the fluid conduit to the object.

[0038] According to one aspect of the present invention, there is provided a method of tuning a muffler in a fluid conduit of a thermoregulating system configured to thermoregulate an object, the method comprising: defining a disturbance band in which transmission of disturbances from a disturbance entry point to the object is to be reduced, providing at least two mufflers in a fluid supply conduit between the disturbance entry point and the object, providing at least two mufflers in a fluid discharge conduit between the disturbance entry point and the object, and using the inertia of the mufflers and a thermoregulating fluid between the mufflers such that the resonance of the inertia of the thermoregulating fluid between the mufflers is sized to be at a resonance frequency below the disturbance band.

[0039] The use of multiple mufflers in series in the schematic of the present invention. These mufflers have the ability to be effective at higher frequencies (e.g., above 80 Hz). By using at least two mufflers in series, the gas volume of each muffler effectively creates a low stiffness in the water circuit by producing a low hydraulic stiffness (K_hyd = dp / dV). Subsequently, the hydraulic stiffness of the gas volume can be derived as K_hyd = γp / V (adiabatic case). In the above formula, γ (gamma) is the adiabatic index, 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 the resonance frequency. Below this frequency, there may be no additional benefit of multiple mufflers; at this frequency, there may be amplification; however, above this frequency, the mass between the mufflers can start to decouple and effectively obtain a -2 slope. 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 pressure or increasing the gas volume) or increasing the hydraulic mass of the duct between the mufflers M_(hyd duct) = ρL / A (increasing the length or reducing the duct cross-sectional area), this resonance frequency can be lowered, enabling higher reduction (especially related to the above 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, allowing an effective -4 slope or even higher to be achieved. Tuning the stiffness of the mufflers and the hydraulic mass of the duct between the mufflers allows for effectively avoiding resonance amplification and obtaining the final muffling efficiency. From a dynamic perspective, placing multiple mufflers in series with sufficient distance between them is the key technological breakthrough for currently introducing DCM.

[0040] Effectiveness of achieving a higher frequency: The distance between the gas volume and the duct can limit the frequency at which an effective use of the gas volume can be obtained. This duct portion is referred to as the neck of the silencer and the associated resonance frequency can be referred to as 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. By increasing the stiffness of the silencer (increasing the pressure or reducing the gas volume) or reducing the hydraulic mass of the neck of the silencer (reducing the length or increasing the neck diameter), this resonance frequency can be increased such that the gas volume is effectively sensed for higher frequencies (especially associated with approximately 80 Hz). To eliminate the risk of gas dissolution over time, a compliant interface is added. The requirement for such an interface is that its stiffness is low enough such that the sum of the stiffness of the gas volume and the stiffness of the compliant interface can still meet the requirements. Additionally, the inertia of the bellows can be small enough such that the Helmholtz frequency can remain high enough. Finally, the structural resonance of the compliant interface can be high enough, at least higher than the Helmholtz frequency, such that it does not degrade the sound silencing performance.

[0041] Figure 3A and Figure 3B depicting an accompanying drawing, which depicts a graph of the relationship between the frequency on the vertical axis and the frequency on the horizontal axis of the transmission of perturbations via the duct to the object. As Figure 3A depicted therein, a single silencer in the supply duct FSD and the return duct (i.e., the fluid discharge duct FDD) provides a roll-off of 2 times per octave (i.e., 10 times per decade) above the roll-off frequency Froll. As Figure 3B depicted therein, two silencers in series in the supply duct and the return duct can provide a roll-off of 2 times per octave from the roll-off frequency Froll to the resonance frequency Fres, while providing a triple roll-off, i.e., 8 times per octave above the resonance frequency. The resonance frequency Fres can be determined by the resonance of the double silencer and the mass of the thermally regulated fluid in the duct between the two silencers.

[0042] Thus, according to the above, a single silencer combined with a non-reflective acoustic boundary condition (critically damped) can provide a -1 slope, i.e., 10 times per decade. Two silencers in series can provide a -3 slope, i.e., 1000 times per decade (-1 slope, i.e., 10 times per decade, can result from the combination of the silencer and the non-reflective acoustic boundary condition; -2 slope, i.e., 100 times per decade can result from the decoupled mass between the silencers).

[0043] In an embodiment, at least two mufflers and a thermoregulating fluid in a fluid conduit interconnected with the at least two mufflers form a resonator. The thermoregulating fluid in the conduit interconnected with the at least two mufflers, respectively, in the supply conduit and in the return conduit provides mass, while the mufflers provide compliance. The mass of the thermoregulating fluid between the mufflers and the compliance of the mufflers can exhibit resonance behavior, as Figure 3B shown by the resonance frequency Fres in

[0044] Figure 3C A frequency plot is depicted where the vertical axis depicts the transmission of perturbations via the conduit to the object, and the horizontal axis depicts frequency. As Figure 3C depicted in, for example, a single such muffler SL in the supply conduit and / or in the return conduit provides Helmholtz resonance at the Helmholtz resonance frequency inclination ω HR , where the inclination 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 ), where 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 Helmholtz resonance frequency inclination ω HR involves a roll-off at a -2 slope. As Figure 3C further depicted in, two mufflers in series (e.g., in the supply conduit and / or in the return conduit) can provide a resonance peak at the sloshing frequency, where the sloshing resonance frequency is equal to the square root of the quotient of [twice the hydraulic compliance of the muffler and the hydraulic mass in the conduit between the two mufflers], ω S = √ (2K Hyd / M Hyd ). Where ω S is the sloshing frequency, 2K Hyd is twice the hydraulic compliance of the muffler and M Hyd is the hydraulic mass in the conduit between the mufflers. Thus, the mufflers decouple the hydraulic mass in the middle of the decoupled mufflers (low stiffness elements), thereby achieving -40 dB / decade suppression in the pressure transmission on a force input (-2 slope) above the sloshing resonance frequency. Multiple muffler pairs ( ) allow benefiting from a large amount of decoupled mass, thereby producing For example, as Figure 3C depicted in, the pair provides two sloshing resonance frequencies ω S , and always provides a -4 slope. The sloshing resonance frequency ω S can be lower than the Helmholtz resonance frequency ω HR , because of the larger hydraulic mass of the fluid between the mufflers. The sloshing resonance frequency ω S can be sized to be lower than the perturbation frequency band of the perturbation to be suppressed, such that the propagation of the perturbation is significantly suppressed due to the -2 slope per muffler pair. Tuning the hydraulic mass in the middle of the muffler , the hydraulic mass of the pipe between the conduit and the muffler or the muffler compliance allows optimizing the suppression behavior. Sizing the hydraulic mass between the mufflers and the muffler compliance such that the sloshing frequency of the muffler pair is lower than the perturbation frequency band allows the -2 slope per muffler pair to be obtained in the perturbation frequency band, such that the perturbation in the perturbation frequency band can be suppressed by the -2 slope per muffler pair.

[0045] In an embodiment, the resonator is a series resonator. The series resonator can utilize the mass of the thermoregulating fluid between the two mufflers, and thus can use the mass present in the fluid conduit. Therefore, no additional mass is required, resulting in a very small increase in weight.

[0046] Figures 4A to 4C Schematically depicts three different embodiments of a muffler. Figure 4A The muffler SL depicted in is formed by an internal space that is partially filled with a gas that can avoid dissolving in the thermoregulating fluid. When pressurized by the thermoregulating fluid, the gas can form elasticity.

[0047] Figure 4B Depicts a muffler SL including a membrane MEM that divides the internal space of the muffler into, for example, a portion filled with a gas and a portion filled with a thermoregulating fluid. The elasticity of the membrane (possibly in combination with the pressurization of the gas) provides the elasticity of the thermoregulating fluid that interacts with the muffler.

[0048] Figure 4C Depicts a muffler SL including a membrane formed as a bellows BEL that divides the internal space of the muffler into, for example, a portion filled with a gas and a portion filled with a thermoregulating fluid. The elasticity of the membrane formed as a bellows (possibly in combination with the pressurization or depressurization of the gas) provides the elasticity of the thermoregulating fluid that interacts with the muffler.

[0049] Figure 5 Depicts additional embodiments of a muffler. As Figure 5As depicted, 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 conduit (i.e., the fluid propagation direction). Due to the symmetrical arrangement, the force distribution of the silencer can be symmetrical with respect to the fluid flow direction of the thermoregulating fluid, thereby at least reducing the net effective force on the fluid conduit. The silencer with the membrane arranged symmetrically with respect to the fluid flow direction can be used in any thermoregulating system, i.e., its application is not limited to a thermoregulating system including a fluid supply conduit with at least two silencers and a fluid discharge conduit with at least two silencers.

[0050] Figure 6 A detailed view depicting the membrane that can be used in the silencer described above. Figure 6 The membrane depicted has a corrugated shape COR. Due to the corrugated shape of the membrane, the stiffness of the membrane can be reduced. The membrane can be made of metal, for example, with the limitation that the membrane is durable and can withstand various operating conditions. However, using metal, the membrane may be relatively rigid. The corrugated shape can partially compensate for the stiffness, thus achieving an effective and more desirable compliance. The silencer with the membrane having a corrugated shape can be used in any thermoregulating system, i.e., its application is not limited to a thermoregulating system including a fluid supply conduit with at least two silencers and a fluid discharge conduit with at least two silencers.

[0051] As explained above, the resonance of at least two silencers in combination with the mass of the thermoregulating fluid in the conduit between the silencers can provide resonance peaks in the disturbance transmission via the conduit. Since the resonance peaks can emphasize the disturbances at or near the resonance frequency, it may be desirable to increase some damping to reduce the resonance peaks and the corresponding disturbance transmission via the conduit. Thus, in an embodiment, each silencer can include a damper connected to the membrane. As Figure 7 in the example depicted, where the silencer SL includes a membrane MEM that separates the thermoregulating fluid from the remaining space SPC in the silencer SL. The damper DMP is connected to the membrane to suppress the movement (e.g., vibration) of the membrane. The damper can be connected to a fixed part of the silencer, such as its housing or outer wall. The membrane can include, for example, a metal membrane having a corrugated shape such as a bellows shape. The silencer with the damping described above can be used in any thermoregulating system, i.e., its application is not limited to a thermoregulating system including a fluid supply conduit with at least two silencers and a fluid discharge conduit with at least two silencers. Generally, the damper is not limited to being fixed to the external world: in an embodiment, the damper utilizes the flexure of the membrane itself, such as a viscoelastic material applied to the membrane.

[0052] In an embodiment, as Figure 8Schematically depicted, each silencer includes a negative compliance mechanism connected to the membrane. The negative compliance mechanism can reduce the compliance of the membrane. The membrane can be made of, for example, metal, provided that the membrane is durable and can withstand various operating conditions. However, using metal, the membrane may be relatively rigid. Negative compliance can partially compensate for the stiffness, thus achieving an effective and more desirable compliance. Negative compliance can be implemented in various ways. For example, Figure 8 A bent leaf spring BLS attached at the leaf spring attachment point LAP is depicted. A travel protection mechanism SPM, such as a travel limiter, prevents damage to the membrane and the bent leaf spring due to excessive deflection.

[0053] The bent leaf spring can form an example of a double compression spring. Any other implementation of the double compression spring can be envisioned, such as Figure 9 Schematically depicted in. The double compression spring SPR is compressed in a direction substantially parallel to the membrane MEM, i.e., perpendicular to the deflection direction ED of the membrane.

[0054] As Figure 10 Depicted in, to tension the double compression spring, the negative compliance mechanism can include a tensioning member TSM, which in this example is configured to tension the double compression spring in a direction substantially parallel to the membrane. The tensioning force of the tensioning member can help further increase the negative compliance of the double compression spring.

[0055] Including the membrane with the negative compliance mechanism connected as referred to above Figures 8 to 10 The silencer described can be used in any thermal regulation system, i.e., its application is not limited to a thermal regulation system including a fluid supply conduit with at least two silencers and a fluid discharge conduit with at least two silencers. In another embodiment, Figures 8 to 10 The negative compliance mechanism disclosed in can be combined with the self-regulating silencer disclosed in EP0679832A1.

[0056] Reference will be made to Figure 11 To explain additional embodiments. As Figure 11 Depicted in, the top part, one of the silencers SL in the fluid supply conduit FSD, one of the silencers in the fluid discharge conduit FDD, and a fluid conduit interconnected with one of the silencers in the conduit and one of the silencers in the fluid discharge conduit form an additional resonator. The offset of the resonant movement of the additional resonator is depicted in Figure 11 In, the bottom part shows the pressure along the conduit between the two silencers. When the zero pressure point ZPP is reached in the middle of the silencer, the offset (i.e., pressure) caused by the resonant behavior is maximum at the individual silencer SL. To reduce the disturbance of the moving mass of the thermal regulation fluid to the object, the object can be arranged at the zero pressure point ZPP of the additional resonator.

[0057] In cases where the ducts between two mufflers and an object (e.g., a mirror) cannot have the same length, the mufflers (compliance and mass) can be tuned to the hydraulic mass of the ducts in order to obtain a zero-pressure point at the object. For non-equal gas volumes, the zero-pressure point where no sloshing is felt can be displaced towards the less rigid one of the mufflers (e.g., towards the muffler with the larger gas volume).

[0058] A thermal regulation system with the zero-pressure point arranged at the object can be used in any thermal regulation system where the muffler is included in the thermal regulation fluid supply duct and the muffler is included in the thermal regulation fluid discharge duct, i.e., its application can be not limited to thermal regulation systems including a fluid supply duct with at least two mufflers and a fluid discharge duct with at least two mufflers.

[0059] According to a further embodiment, a diameter change can be provided in the duct between the two mufflers in order to displace the location of the zero-pressure point to a desired location at the object. When the duct diameter decreases and thus the flow area decreases, the hydraulic mass can increase.

[0060] The zero-pressure point is preferably located at the center of the object (e.g., a mirror) in order to minimize the influence of the sloshing of the thermal regulation fluid on the object.

[0061] Damping of the movement of the thermal regulation fluid can be provided by a resistance channel in the fluid duct, which has a higher fluid flow resistance relative to the remaining part of the fluid duct. Thus, in an embodiment, the fluid duct includes a resistance channel configured to provide a higher fluid flow resistance relative to the remaining part of the fluid duct. The resistance channel can be arranged between the mufflers, which can be used to damp the resonance peak at the resonance frequency described above. Similarly, the resistance channel can be arranged between the perturbation entry point and at least one of the mufflers to reduce the propagation of the perturbation from the perturbation entry point to the remaining part in the thermal regulation fluid duct. Similarly, the resistance channel can be arranged between at least one of the mufflers and the object. The resistance channel can be implemented, for example, by a part of the thermal regulation fluid duct with a narrower cross-section. An example is depicted in Figure 12B wherein the narrow part RES of the fluid duct FD of the resistance is depicted.

[0062] As an alternative or supplement to being implemented by a narrower cross-section of the duct, the resistance channel can be implemented by a fluid duct including a porous medium. Thus, in an embodiment, the resistance channel of the fluid duct includes a porous medium. The porous medium can provide the damping mentioned above. The porous medium can be added in the middle of the mufflers in the fluid duct or in the fluid pipeline of the muffler between the fluid duct and the membrane.

[0063] The narrow cross-section can provide additional effects, namely, the perturbations caused by the turbulence of the heat-regulating fluid can be shifted to higher frequencies. Such higher frequencies can be above the frequency range of interest, i.e., above the perturbation frequency band in which the transmission of perturbations is suppressed by the resonance effect. Figure 12A Schematically depicts a part of a fluid conduit for a heat-regulating fluid, depicting the flow direction FLD and the turbulence TUR generated by the flow of the heat-regulating fluid in the fluid conduit. The narrower the cross-section of the fluid conduit, the higher the frequency of the turbulence TUR can be. In an embodiment, the resonator is configured to attenuate the perturbations in the perturbation frequency band, wherein the cross-section of the conduit is sized such that the turbulence frequency band of the heat-regulating fluid in the conduit is higher than the perturbation frequency band.

[0064] As Figure 12C depicted in, the connection between the resistance channel RES and the remaining part of the fluid conduit FD can exhibit a change in the cross-section of the fluid conduit, and such a change may cause turbulence and other effects at the transition from the narrow part to the remaining part of the fluid supply conduit. To reduce the turbulence and other effects that may occur at the transition, a diverging section DIV or a converging section of the conduit can be provided.

[0065] As an Figure 12C alternative to the converging or diverging section DIV depicted in, Figure 12B the silencer SL depicted in can be provided at the connection between the part with high resistance (e.g., the narrow cross-section) and the remaining part of the fluid conduit.

[0066] A heat-regulating system including a channel with a higher fluid flow resistance can be used in any heat-regulating system, i.e., its application is not limited to a heat-regulating system including a fluid supply conduit with at least two silencers and a fluid discharge conduit with at least two silencers.

[0067] In an embodiment, the membrane includes a porous membrane to thereby reduce the effective compliance of the silencer. For example, a metal membrane can provide a durable implementation but may be too rigid. For example, a porous membrane provided with a plurality of narrow channels can reduce the effective compliance of the membrane.

[0068] Figure 13A A highly schematic cross-sectional side view depicting a part of the silencer. The silencer includes a piston lid PLD and a rollable membrane RMEM. The piston lid includes a piston lid front facing the heat-regulating fluid and a piston lid back facing the gas volume VOL filled with gas. The rollable membrane is arranged between the edge EDG of the piston lid and the inner surface of the wall SHW of the silencer housing. The rollable membrane and the piston lid can be connected, for example, by vulcanization. The piston lid can be circular or have any other suitable shape, such as oval. The diameter DIA of the piston lid P can be smaller than the inner diameter DIA of the gas volume in the silencer housing H, i.e., the inner diameter of the wall of the housing of the silencer. The rollable membrane extends between the edge of the piston head and the (e.g., circular) wall of the gas volume. The rollable membrane can extend around the edge of the piston head to seal the gap between the edge of the piston head and the wall of the gas volume of the silencer. The piston head is movable in the piston head stroke direction of the piston head (i.e., parallel to the wall of the gas volume in the housing of the silencer, i.e., in Figure 13A in the upward and downward directions). The piston head stroke direction can extend in a direction perpendicular to the front face of the piston head. Thus, when the piston head moves in the stroke direction, the volume of the thermoregulating fluid changes, i.e., it increases when the piston head moves backward and decreases when the piston head moves forward (i.e., towards the thermoregulating fluid).

[0069] The rollable membrane can have an annular shape, for example, when the edge of the piston head is annular, or an elliptical shape when the edge of the piston head is elliptical. The inner edge of the rollable membrane is fastened to the edge of the piston head and the outer edge of the rollable membrane is fastened to the wall of the housing of the silencer. The inner and outer edges can likewise have an annular or elliptical shape. The compliant portion of the rollable membrane extends between the inner edge and the outer edge of the membrane and can likewise have an annular or elliptical shape. The compliant portion of the rollable membrane can bend between the inner edge and the outer edge of the membrane to have a convex surface and a concave surface. The concave surface can face the thermoregulating fluid. The convex surface can face the gas in the gas volume. Thus, the fluid pressure of the thermoregulating fluid on the concave surface of the rollable membrane maintains its bent shape. When the piston head moves in the piston stroke direction, the rollable membrane curls to move. As Figure 13A shown, when the piston head moves upward in the figure to the upper piston head position UPO (i.e., increasing the available volume of the thermoregulating fluid), the rollable membrane curls, whereby the portion supporting the edge of the piston head bends into a curve, while the bent portion of the rollable membrane straightens to support the inner wall of the volume. When the piston head moves downward in the figure to the lower piston head position LPO (i.e., reducing the available volume of the thermoregulating fluid), the rollable membrane curls, whereby the portion supporting the edge of the wall bends into a curve, while the bent portion of the rollable membrane straightens to support the edge of the piston head. Thus, the edge of the piston head and the inner wall of the volume form parallel extending (e.g., annular or elliptical) surfaces such that a portion of the rollable membrane is supported. Since the pressure of the thermoregulating fluid is higher than the pressure of the gas in the gas volume, the rollable membrane is pushed by the thermoregulating fluid to rest against the parallel extending annular or elliptical surface and bends to form a concave surface facing the thermoregulating fluid. It can be noted that Figure 13AThe curvature of the rollable membrane depicted means that the pressure of the heat regulating fluid is greater than the pressure of the gas in the gas volume VOL. Attributable to this pressure difference, the compliant portion of the rollable membrane can bend between the inner and outer edges of the membrane to have the convex and concave surfaces shown; the concave surface faces the heat regulating fluid and the convex surface faces the gas in the gas volume VOL. In an alternative arrangement, the pressure of the heat regulating fluid can be lower than the pressure of the gas in the gas volume VOL. In such an arrangement, the rollable membrane can bend in such a way that the convex surface faces the heat regulating fluid and the concave surface faces the gas in the gas volume VOL.

[0070] The rollable membrane can provide low stiffness or zero stiffness such that the piston head can move in the piston head stroke direction. Compared with other embodiments of the muffler described in this document, the combination of the movable piston head and the rollable membrane can provide a larger stroke because the stroke may be independent of the stress in the material. Since the piston head that forms most of the surface of the muffler in contact with the heat regulating fluid can be a rigid, solid material (such as metal) that is impermeable or nearly impermeable to the heat regulating fluid, steam penetration into the gas volume and the accompanying accumulation of steam of the heat regulating fluid in the gas volume can be reduced. The stiffness of the piston head can be high, thereby reducing parasitic resonance modes.

[0071] Figure 13B Depicting according to Figure 13A of the muffler's additional cross-sectional side view. Similar to Figure 13A the cross-sectional view in Figure 13B depicts the piston head PLD and the rollable membrane RMEM. The muffler also includes a muffler housing SH that forms a gas volume VOL to accommodate the gas. The muffler is in fluid communication with the heat regulating fluid in a heat regulating fluid conduit (such as a heat regulating fluid supply conduit FSD or a heat regulating fluid discharge conduit FDD). More particularly, the piston head and the rollable membrane form a partition that separates the gas volume from the heat regulating fluid flowing in the heat regulating fluid conduit. The muffler can be immediately connected to the heat regulating fluid conduit, that is, the flow of the heat regulating fluid in the heat regulating fluid conduit immediately passes through the piston head, as depicted in, for example, Figure 13B Alternatively, the muffler housing can also form a heat regulating fluid volume, whereby the piston head and the rollable membrane are arranged between the gas volume and the heat regulating fluid volume. In the latter case, the heat regulating fluid in the heat regulating fluid volume is in fluid communication with the heat regulating fluid in the heat regulating fluid conduit via a branch of the heat regulating fluid conduit, for example.

[0072] Figure 13BFurther depict a spring SPR configured to interact with the piston cap of the silencer. The stiffness of the spring can determine the stiffness of the silencer, since the stiffness of the spring can exceed the stiffness of the rollable membrane, thereby enabling the stiffness and stroke of the piston cap to be determined by selecting an appropriate spring. The spring can exert a force F on the piston cap in the direction towards the heat-regulating fluid in the heat-regulating fluid conduit comp , and thus can tend to push the heat-regulating fluid away. On the other hand, the pressure of the heat-regulating fluid in the heat-regulating fluid conduit can exceed the gas pressure of the gas in the gas volume, and thus can exert a thrust on the piston cap (represented by F stat ) and a thrust on the rollable membrane (represented by F roll ) to push the piston cap into the gas volume, i.e., in the direction opposite to the force exerted by the spring. In the equilibrium position, the force exerted by the spring and the force exerted by the pressure of the heat-regulating fluid applied to the piston cap and the rollable membrane are substantially opposite and have the same magnitude in the absolute sense. Determining the compliance of the spring can enable the determination of the resonance behavior of the silencer (e.g., the Helmholtz frequency) and the pressure range of the pressure of the heat-regulating fluid. The ability to withstand the constant pressure exerted by the pressure difference between the heat-regulating fluid on one side of the piston cap and the gas in the gas volume VOL and the force exerted by the spring on the other side enables the rollable membrane to roll up due to the pressure difference across the membrane. The spring can also constrain the movement of the piston cap in other directions (e.g., perpendicular to the piston movement direction). Generally, radial translation, flipping, and tilting of the piston cap can be prevented. It should be noted that, as an alternative to or in addition to the spring, a foam body with a specific stiffness can also be applied.

[0073] Figure 13C A cross-sectional view depicting another embodiment of the silencer, in which the spring SPR interacts with the piston cap PLD via a transmission mechanism TM. The transmission mechanism can increase the transmission ratio for the spring. In this example, the transmission mechanism forms a lever having an arm connected to the piston cap and an arm connected to the spring. The arm connected to the spring may be shorter compared to the arm connected to the piston cap. In this example, the arm connected to the spring and the arm connected to the piston cap provide a ratio of 1:i, where i > 1. As in the example depicted in Figure 13B , the transmission mechanism may be capable of using a tension spring instead of a compression spring. The tension of the tension spring can increase the frequency of the transverse vibration mode of the spring. In addition, the transmission mechanism can utilize a more rigid spring. Thus, 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 less rigid spring without a transmission mechanism.

[0074] Figure 14Depicts a portion of an additional embodiment of a silencer, wherein the spring SPR comprises a folded leaf spring connected to the perimeter of the piston lid PLD (e.g., equidistantly around the edge of the piston lid), such as three folded leaf springs. The folded leaf spring may be capable of reducing parasitic vibrations because the movement of the piston lid in directions other than the piston movement direction perpendicular to the piston surface facing the heat regulating liquid can be restricted. Figure 14 Each of the folded leaf springs depicted in Figure 14 comprises a first leaf spring portion FLP extending in the piston movement direction and a second leaf spring portion SLP extending at least partially perpendicular to the movement direction. The compliance of the second leaf spring portion can provide, for example, the compliance that enables the piston lid to move in the piston movement direction.

[0075] Figure 15 Depicts an additional embodiment of a heat regulating system comprising a plurality of silencers (in this example, 3 silencers SL1, SL2, SL3). The heat regulating system further comprises a gas supply system GSS configured to supply gas at an operating pressure and a gas conduit GSD connecting the gas supply system to the gas volume of the said or each silencer (i.e., the gas volume restricted by the piston lid and the rollable membrane). The gas supply system may be capable of connecting the gas volume of the silencer to the system pressure provided by the gas supply system. The system pressure can eliminate most of the pressure difference across the barrier between the gas in the gas volume and the heat regulating fluid. This can reduce the force provided by the spring (such as the spring described with reference to Figure 13B and Figure 13C . For a high-pressure system, the pressurization of the gas supply system may be of particular concern: the force required by the spring can be minimized, and thus the total energy of the return spring can be minimized. An additional advantage can be that the potential risk of penetration of the heat regulating fluid and its accumulation inside the gas volume can be avoided, for example, by the condensed heat regulating fluid in the gas supply system.

[0076] In an embodiment, the rollable membrane may comprise a radial fiber network configured to reinforce the rollable membrane. The radial fiber network can enable the rollable membrane to cope with high-pressure situations. In addition, the elastomer relaxation effect can be reduced and the risk of rupture of the rollable membrane can be reduced.

[0077] The heat regulating system described above can be used on a lithographic apparatus. Thus, a lithographic apparatus can be provided comprising an object and the heat regulating system described above for thermally regulating the object. The object can be a projection system mirror of the lithographic apparatus, such as Figure 1 depicted in Figure 1 and described with reference to Figure 1 the mirror devices 10, 11. In another embodiment, the object can be a substrate table WT of the lithographic apparatus, such as Figure 1 depicted in Figure 1 and described with reference to Figure 1The substrate table WT or the substrate platform of a lithographic apparatus as described. In a further embodiment, the object can be a support configured to support a patterning device, such as a mask table or a mask platform of a lithographic apparatus. In yet a further embodiment, the object can be a force frame or a sensor frame of a lithographic apparatus.

[0078] In an embodiment, a silencer can be connected to a structure of a lithographic apparatus, such as a force frame or a base frame. Thus, a resonator formed by the mass of the thermal regulation fluid between the double silencer and the silencer can reduce the transmission of perturbations from one of the structures of the lithographic apparatus towards the other via a fluid conduit. For example, in the case of thermal regulation of a projection system mirror, the fluid conduit passes through an intermediate frame (such as a force frame or a sensor frame of a 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 can be provided at at least one of the intermediate frame, the base frame, and the interface ring.

[0079] Aspects of the present invention can be formulated as a method of thermally regulating an object of a lithographic apparatus, including providing a flow of thermal regulation fluid to the object via a fluid conduit, wherein the fluid conduit is connected to the object and wherein the fluid conduit includes a supply conduit connected to the object to supply the thermal regulation fluid to the object and a discharge conduit connected to the object to discharge the thermal regulation fluid from the object, wherein the supply conduit and the discharge conduit are each provided with at least two silencers arranged in series along the supply conduit and along the discharge conduit respectively. Using the method according to the present invention, the same or similar advantages and effects as those obtained using a thermal regulation system according to an aspect of the present invention can be achieved. Similarly, the same or similar embodiments can be provided so as to achieve the same or similar effects as those described with reference to a thermal regulation system according to an aspect of the present invention.

[0080] Although the use of a lithographic apparatus in IC manufacturing may be specifically referred to herein, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include manufacturing integrated optical systems, guiding and detecting patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0081] Although embodiments of the present invention may be specifically referred to herein in the context of a lithographic apparatus, embodiments of the present invention can be used in other devices. Embodiments of the present invention can form part of a mask inspection device, a metrology device, or any device for measuring or processing an object such as a wafer (or other substrate) or a mask (or other patterning device). These devices can generally be referred to as lithographic tools. Such lithographic tools can use a vacuum situation or an ambient (non-vacuum) situation.

[0082] While the foregoing may have specifically referred to the use of embodiments of the present invention in the context of optical lithography, it should be understood that the present invention is not limited to optical lithography and can be used in other applications (e.g., imprint lithography) where the context permits.

[0083] While specific embodiments of the present invention have been described above, it should be understood that the present invention can be practiced in other ways different from the described manner. The foregoing description is intended to be illustrative, not restrictive. Thus, those skilled in the art will appreciate that the described present invention can be modified without departing from the scope of the claims set forth below.

Claims

1. A thermal regulation system configured to thermally regulate an object, wherein, The thermal regulation system includes a fluid conduit configured to be connected to the subject and configured to provide a flow of a thermal regulation fluid to the subject. The fluid conduit includes a supply conduit configured to be connected to the subject and supply the thermal regulation fluid to the subject, and a discharge conduit configured to be connected to the subject and discharge the thermal regulation fluid from the subject. At least one of the supply conduit and the discharge conduit is provided with at least two mufflers arranged in series along the respective at least one of the supply conduit and the discharge conduit.

2. The thermal regulation system according to claim 1, wherein, The at least two mufflers and the thermal regulation fluid in the fluid conduit interconnecting the at least two mufflers form a resonator.

3. The thermal regulation system according to claim 2, wherein, The resonator is configured to attenuate perturbations in a perturbation frequency band, wherein the resonance frequency of the resonator is lower than the perturbation frequency band.

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

5. The thermal regulation system according to any one of the preceding claims, wherein, Each muffler includes a membrane configured to interact with the thermal regulation fluid, the membrane exhibiting compliance, wherein the membrane is a bellows, and wherein preferably the membrane is arranged symmetrically with respect to the fluid flow direction of the fluid conduit.

6. The thermal regulation system according to any one of the preceding claims, wherein, Each muffler includes a membrane configured to interact with the thermal regulation fluid, the membrane exhibiting compliance and wherein the membrane has a corrugated shape.

7. The thermal regulation system according to any one of the preceding claims, wherein, Each muffler includes a membrane configured to interact with the thermal regulation fluid, the membrane exhibiting compliance and wherein each muffler includes a damper connected to the membrane.

8. The thermal regulation system according to any one of the preceding claims, wherein, Each muffler includes a membrane configured to interact with the thermal regulation fluid, the membrane exhibiting compliance and wherein each muffler includes a negative compliance mechanism connected to the membrane.

9. The thermal regulation system according to claim 8, wherein, The negative compliance mechanism includes a double compression spring.

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

11. The thermal regulation system according to any one of the preceding claims, wherein, Each muffler includes: a piston head configured to interact with the thermal regulation fluid, the piston head being movable in a piston stroke direction; and a rollable membrane connected to the piston head and configured to roll when the piston head moves in the piston stroke direction.

12. The thermal regulation system according to claim 11, wherein, The rollable membrane forms a recessed membrane surface facing the thermal regulation fluid.

13. The thermal regulation system according to claim 11 or 12, wherein, The muffler includes a spring configured to interact with the piston head.

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

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

16. The thermal regulation system according to any one of claims 13 to 15, including a transmission mechanism configured to provide a transmission ratio between the movement of the piston head and the extension or compression of the spring.

17. The thermal regulation system according to any one of claims 13 to 16, wherein, The spring includes at least one of a tension spring and a compression spring.

18. The thermal regulation system according to any one of claims 13 to 17, wherein, The spring includes at least three folded leaf springs connected to the periphery of the piston head.

19. The thermal regulation system according to any one of claims 11 to 18 further comprises: A gas supply system configured to supply gas at an operating pressure; and a gas conduit connected between the gas supply system and the space in the muffler limited by the piston head and the rollable membrane.

20. The thermal regulation system according to any one of claims 11 to 19, wherein, The rollable membrane includes a radial fiber network configured to reinforce the rollable membrane.

21. The thermal regulation system according to any one of the preceding claims, wherein, One of the silencers in the supply duct, one of the silencers in the discharge duct, and the fluid duct interconnecting the one silencer in the supply duct and the one silencer in the discharge duct form additional resonators, wherein the object is arranged at a zero-pressure point of the additional resonators.

22. The thermal regulation system according to any one of the preceding claims, wherein, The fluid duct includes a resistance channel configured to provide a higher fluid flow resistance relative to the remainder of the fluid duct.

23. The thermal regulation system according to claim 22, wherein, The resistance channel is arranged between the silencers, or between the perturbation entry point and at least one of the silencers, or between at least one of the silencers and the object.

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

25. The thermal regulation system according to any one of claims 22 to 24, wherein, The resistance channel of the fluid duct includes a porous medium.

26. The thermal regulation system according to any one of the preceding claims, wherein, The resonator is configured to attenuate perturbations in the perturbation frequency band and wherein the cross-section of the duct is sized such that the turbulence frequency band of the thermoregulating fluid in the duct is higher than the perturbation frequency band.

27. The thermal regulation system according to any one of the preceding claims, wherein, The membrane includes a porous membrane.

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

29. A lithographic apparatus according to claim 28, wherein, The object is the projection system mirror, and wherein the fluid duct passes through an intermediate frame of the lithographic apparatus, a base frame of the lithographic apparatus, and an interface ring connecting the lithographic apparatus to a metrology frame of the lithographic apparatus, the intermediate frame being, for example, a force frame or a sensor frame, wherein the silencer is provided at at least one of the intermediate frame, the base frame, and the interface ring.

30. A method for thermally conditioning an object of a lithographic apparatus, comprising providing a flow of a thermally conditioning fluid to the object via a fluid conduit, wherein, The fluid duct is connected to the object and wherein the fluid duct includes a supply duct connected to the object to supply the thermoregulating fluid to the object, and a discharge duct connected to the object to discharge the thermoregulating fluid from the object, wherein at least one of the supply duct and the discharge duct is provided with at least two silencers arranged in series along the respective at least one of the supply duct and the discharge duct.

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