Fluid volume determination in a lithographic system

Abstract

The present invention relates to a method for determining a first fluid volume (610; 710; 810) in a second fluid volume in a fluid-conducting element (630; 730; 830) of a lithography system (1), comprising: a) providing at least two pressure-fluctuation sensors for measuring the pressure at different points within the fluid-conducting element (630; 730; 830); b) measuring the pressure by means of each of the at least two pressure-fluctuation sensors; c) determining a pressure-to-pressure transfer function on the basis of the measured pressures; and d) determining the first fluid volume (610; 710; 810) on the basis of the pressure-to-pressure transfer function.

Description

[0001] Carl Zeiss SMT GmbH

[0002] 1

[0003] FLUID AMOUNT DETERMINATION IN A LITHOGRAPHIC SYSTEM

[0004] The present invention relates to a method and a device for determining a first fluid quantity in a second fluid quantity in a fluid-carrying element of a lithography system, as well as a corresponding lithography system.

[0005] The content of priority application DE 10 2024 211 897.4 is fully incorporated by reference.

[0006] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system, which includes an illumination system and a projection system. The image of a mask (reticule) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system. This transfers the mask structure onto the photosensitive coating of the substrate.

[0007] Driven by the pursuit of ever smaller structures in the production of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e., mirrors, instead of the previously used refracting optics, i.e., lenses.

[0008] Illuminating the reflective surface of a mirror with light (such as EUV light) can cause the mirror to heat up (e.g., EUV - Carl Zeiss SMT GmbH).

[0009] 2

[0010] Reflection of an EUV lithography projection lens (POB) can occur. This is also known as mirror heating. This can lead to a change in the optical properties of the mirror and thus undesirably affect the imaging properties of a mask structure onto a substrate. This, in turn, can ultimately contribute to an undesirable deterioration of the lithography process.

[0011] In some cases, the heating of a mirror can be counteracted by providing internal cooling. However, it should be noted that not only reflective optics can experience heating, but also refractive and diffractive optics, which may likewise require appropriate cooling to ensure temperature stabilization and / or to guarantee the desired acoustodynamic behavior of the system. Cooling of any of the aforementioned systems can be achieved, for example, by transporting a cooling fluid through dedicated cooling channels within the system. Other systems in which determining the fill state of a fluid-carrying system is important may also be subject to undesirable heating.

[0012] Since the operation of a POB (Power Over Bus) occasionally needs to be interrupted, e.g., for maintenance purposes, or possibly to replace subsystems, the channels used for cooling must be evacuated and refilled before recommissioning. This can result in air or gas bubbles remaining in the system. These remaining bubbles can lead to undesirable (hydro-)dynamic and acoustic effects.

[0013] A problem that often arises from this is that the presence, location, and size of the bubbles are frequently not predictable beforehand. Carl Zeiss SMT GmbH

[0014] 3

[0015] The presence of bubbles is measurable. Often, the presence of bubbles only becomes apparent through errors or a loss of performance during operation of the lithography system. This can require shutting down and refilling the system, which can be time-consuming and negatively impact system availability.

[0016] Furthermore, the presence of bubbles can lead to further defects, such as flow-acoustic vibrations, also known as water line acoustics (WLA). Externally imposed accelerations, for example, from the acceleration of a wafer stage, can be transmitted to a fluid-filled pipe attached to the frame structure of a base frame and associated with the lithography system. These fluctuations can then be transferred as pressure variations, which can propagate, for example, within a coolant and ultimately reach the proofing box (POB). This can continue as far as a mirror, where the changing pressures can generate forces. These resulting disturbances can lead to uncorrectable line-of-sight (LoS) defects, resulting in a performance loss of the lithography system.

[0017] Currently, no efficiently implementable processes are known that can satisfactorily detect existing bubbles, although the Mean Time To Repair (MTTR), possibly associated with the presence of bubbles, can be considered a major influencing factor on the downtime of a lithography system. The MTTR can be composed of various process times required to commission a lithography system.

[0018] This problem can be at least partially overcome by using silencers. These can be positioned in such a way that these pressure fluctuations in, for example, a coolant at or from a Carl Zeiss SMT GmbH

[0019] 4

[0020] Suppressing the cutoff frequency (e.g., the Helmholtz frequency). However, the currently used design concept for such silencers can lead to increased complexity during filling or emptying of the cooling channels.

[0021] Therefore, there is a need to improve the filling and handling of cooling channels filled with a cooling medium, such as those used in a lithography system.

[0022] The present invention therefore sets itself the objective technical task of enabling efficient and precise detection of a fill level in a cooling circuit.

[0023] According to a first aspect, a method for determining a first fluid quantity within a second fluid quantity in a fluid-carrying element of a lithography system is proposed. The method comprises the following steps:

[0024] a) Providing at least two pressure fluctuation sensors for pressure measurement at different locations within the fluid-carrying element; b) Detecting a pressure using each of the at least two pressure fluctuation sensors;

[0025] c) Determining a pressure-to-pressure transfer function based on the detected pressures; and

[0026] d) Determining the initial fluid quantity based on the pressure-to-pressure transfer function.

[0027] Since one or more parameters of the pressure-to-pressure transfer function (e.g., resonance behavior, resonance frequency, and / or amplitude) depend on the first fluid quantity in the second fluid quantity and / or the presence of the first fluid quantity in the second fluid quantity, the first fluid quantity can be determined based on the pressure-to-pressure transfer function. Carl Zeiss SMT GmbH

[0028] 5

[0029] The at least two pressure fluctuation sensors are, for example, positioned at different locations within the fluid-carrying element with respect to a longitudinal direction of extension of the fluid-carrying element, for pressure measurement. For example, the at least two pressure fluctuation sensors are provided at different locations along a longitudinal direction of extension of the fluid-carrying element, at least partially inside and / or at least partially outside the fluid-carrying element.

[0030] According to one embodiment, in step b) a time course of pressure is recorded using each of the at least two pressure fluctuation sensors.

[0031] According to another embodiment, the pressure-to-pressure transfer function is based on a ratio, in a fourier-transformed form, of a respective time course of the pressures detected by the at least two pressure fluctuation sensors.

[0032] For example, the pressure-to-pressure transfer function is based on a ratio of the time profiles recorded by the at least two pressure fluctuation sensors and a Fourier transformation of this ratio.

[0033] According to another embodiment, in step d):

[0034] a resonance frequency of the specific pressure-to-pressure transfer function is determined;

[0035] a deviation of the determined resonant frequency from a predetermined resonant frequency; and

[0036] the first fluid quantity is determined based on the specified deviation.

[0037] The resonance frequency of the pressure-to-pressure transfer function can shift depending on the initial fluid quantity (e.g., to a different frequency). Carl Zeiss SMT GmbH

[0038] 6

[0039] shifting the frequency (e.g., a resonance frequency) of a combination of the first and second fluid quantities changes depending on the presence of the first fluid quantity and / or on the quantity and / or volume of the first fluid quantity in the second fluid quantity. Thus, based on a deviation of the determined resonance frequency of the pressure-to-pressure transfer function of the combination of the first fluid quantity and the second fluid quantity from a predetermined resonance frequency, conclusions can be drawn about the first fluid quantity.

[0040] The resonance frequency of the specific pressure-to-pressure transfer function is, for example, a resonance peak and / or a maximum of the specific pressure-to-pressure transfer function.

[0041] The predetermined resonance frequency is, for example, a reference resonance frequency. The predetermined resonance frequency is, for example, a resonance frequency of the second fluid quantity alone, that is, without the presence of the first fluid quantity in the second fluid quantity.

[0042] According to a further embodiment, in step b) a pressure of a combination of the first fluid quantity and the second fluid quantity in the fluid-carrying element is detected by means of each of the at least two pressure fluctuation sensors.

[0043] According to another embodiment, the method has:

[0044] Varying the absolute pressure in the fluid-carrying element.

[0045] Varying the absolute pressure in the fluid-carrying element is, for example, varying the absolute pressure of a fluid (e.g., a combination of the first and second fluid quantities) within the fluid-carrying element. Carl Zeiss SMT GmbH

[0046] 7

[0047] By varying the absolute pressure of the combined first and second fluid volumes within the fluid-carrying element, a resonance frequency and / or a resonance peak of the pressure-to-pressure transfer function of the combined first and second fluid volumes can shift (e.g., towards a different frequency). Furthermore, the first fluid volume may exhibit a compressibility that differs from that of the second. Thus, based on the shift of the resonance frequency and / or the resonance peak of the pressure-to-pressure transfer function when varying the absolute pressure, the first fluid volume within the second fluid volume can be determined.

[0048] According to another embodiment, in step d):

[0049] a resonance frequency of the specific pressure-to-pressure transfer function is determined;

[0050] a compressibility and / or stiffness of a combination of the first fluid quantity and the second fluid quantity in the fluid-carrying element is determined based on the specified resonance frequency; and

[0051] the first fluid quantity is determined based on the specified compressibility and / or stiffness.

[0052] For example, the first fluid volume exhibits a compressibility that differs from that of the second fluid volume. Therefore, the compressibility of the combined volume of the first and second fluid volumes within the fluid-carrying element can depend on the first fluid volume. Thus, the first fluid volume can be determined based on its specific compressibility.

[0053] According to a further embodiment, the method can include filling the fluid-carrying element with the second quantity of fluid. Carl Zeiss SMT GmbH

[0054] 8

[0055] According to a further embodiment, the method can comprise performing a first flushing operation in the fluid-carrying element with the second fluid quantity for a first flushing time at a first flow velocity along a first flushing direction. Furthermore, the method can comprise detecting the first fluid quantity in the second fluid quantity and performing a second flushing operation in the fluid-carrying element with the second fluid quantity for the first flushing time at the first flow velocity along a second flushing direction, which is opposite to the first flushing direction. The method can also comprise re-detecting the first fluid quantity in the second fluid quantity and determining the first fluid quantity based on the detection and re-detecting. The detection and / or re-detecting of the first fluid quantity can be performed based on steps a) to d) described above.

[0056] According to a further aspect, a method for determining a first fluid quantity within a second fluid quantity in a fluid-carrying element of a lithography system is proposed. The method can include filling the fluid-carrying element with the second fluid quantity and performing a first flushing operation in the fluid-carrying element with the second fluid quantity for a first flushing time at a first flow velocity along a first flushing direction. Furthermore, the method can include measuring the first fluid quantity within the second fluid quantity and performing a second flushing operation in the fluid-carrying element with the second fluid quantity for a first flushing time at the first flow velocity along a second flushing direction, which is opposite to the first flushing direction.Furthermore, the method can include re-measuring the first fluid quantity within the second fluid quantity and determining the first fluid quantity based on the measurement and re-measurement. Carl Zeiss SMT GmbH.

[0057] 9

[0058] The initial fluid quantity can be measured and / or measured again, for example, based on steps a) to d) described above.

[0059] In some examples, the first fluid may be dissolved in the second fluid. In other examples, the first fluid may be contained within the second fluid without being mixed (e.g., in the sense of an emulsion).

[0060] The first fluid may be contained locally within the second fluid. In other cases, the first fluid may be distributed throughout the second fluid.

[0061] Filling can involve introducing the second quantity of fluid into the initially essentially empty fluid-carrying element (e.g., for commissioning a device in which the fluid-carrying element is implemented). In some examples, at least part of the first quantity of fluid may already be partially contained within the fluid-carrying element initially.

[0062] In this context, a flushing process can be understood as a process that involves the flow of at least a portion of the second fluid along the fluid-carrying element. Any quantities of the first fluid contained within the fluid-carrying element can be driven along a longitudinal direction of the fluid-carrying element by the flushing process, thereby changing the position of the first fluid.

[0063] The rinsing time can be, for example, less than 24 hours, preferably less than 12 hours, even more preferably less than 5 hours, even more preferably less than 1 hour, even more preferably less than 30 minutes, and most preferably less than 1 minute. Carl Zeiss SMT GmbH

[0064] 10

[0065] The rinsing process can be based on a laminar flow of the second fluid in the fluid-carrying element.

[0066] The first flow velocity can be less than 20 m / s, preferably less than 7 m / s and most preferably less than 3.5 m / s.

[0067] The second flow velocity can be changed relative to the first flow velocity by a factor of 2. Changing the second flow velocity relative to the first flow velocity can involve increasing the second flow velocity relative to the first flow velocity. Alternatively, changing the second flow velocity relative to the first flow velocity can involve decreasing the second flow velocity relative to the first flow velocity.

[0068] The filling process can be monitored using an input sensor. For example, the flow rate of the second fluid quantity can be monitored during filling.

[0069] The execution of the first rinsing process and the second rinsing process can each encompass the entire second fluid quantity or can each encompass only a part of the second fluid quantity.

[0070] The initial fluid quantity can be detected or re-detected using sensors, as described below.

[0071] A fluid associated with the first fluid quantity can be different from a fluid associated with the second fluid quantity. This means that the first fluid quantity can be chemically different from the second fluid quantity. Carl Zeiss SMT GmbH

[0072] 11

[0073] The first fluid quantity can contain only a single fluid. Alternatively, the first fluid quantity can contain a multitude (i.e., at least two) different fluids. The second fluid quantity can contain only a single fluid. Alternatively, the second fluid quantity can contain a multitude (i.e., at least two) different fluids. The first fluid can differ from the second fluid in its chemical composition. The fluid associated with the first fluid quantity can be enriched, among other things, by dissolution processes involving one or more components of the fluid associated with the second fluid quantity.

[0074] By performing the flushing in two opposite directions, it is possible to allow the first fluid volume to flow a first distance in the first flushing direction before subsequently flowing in the second flushing direction (ideally by the first distance). This allows for the determination and compensation of asymmetrical conditions in the fluid-carrying element (e.g., if the first fluid volume is advanced a distance during the first flushing process that differs from the distance during the second flushing process). This enables improved determination of the first fluid volume within the second fluid volume and largely suppresses any systematic errors that may be present.

[0075] In one embodiment (e.g., an embodiment of the method according to the first or the further aspect; this also applies to all further embodiments), the method can furthermore include a temporary interruption of the first rinsing process and a continuation of the first rinsing process with a second flow velocity, which differs from the first flow velocity. Carl Zeiss SMT GmbH

[0076] 12

[0077] The procedure may include a temporary interruption of the second flushing process and a continuation of the second flushing process at the second flow velocity.

[0078] The temporary interruption of the initial rinsing process can be for a period of less than one week, preferably less than one day, preferably less than 12 hours, and most preferably less than one hour. In some examples, the interruption can also be for a period of more than one week.

[0079] In addition to temporary interruption, a fluid-tight sealing of at least the fluid-carrying element can be carried out, for example to suppress fluid exchange (e.g. with an environment of the fluid-carrying element).

[0080] Changing the initial flow velocity to the second flow velocity can prevent turbulence of the first fluid and / or the second fluid volume. This can allow for a more accurate measurement of the first fluid volume or a more accurate re-measurement of the first fluid volume.

[0081] In a further embodiment, the method can also include filling the fluid-carrying element with a third quantity of fluid before filling the fluid-carrying element with the second quantity of fluid.

[0082] The third fluid quantity can be associated with a third fluid. This third fluid can be, for example, a water-glycol mixture, salt water, water with added microparticles, and / or another suitable fluid. In some examples, the fluid can also comprise a mixture of the previously mentioned components. Carl Zeiss SMT GmbH

[0083] 13

[0084] The fluid associated with the third fluid quantity may differ from the fluid associated with the first and / or second fluid quantities, e.g., with respect to its chemical and / or physical properties. In some examples, the fluid associated with the third fluid quantity may be the same as the fluid associated with the first or second fluid quantity.

[0085] Filling the fluid-carrying element with the third fluid can, for example, increase the holding time and detectability of the first fluid in the second fluid. This can be achieved, for example, by using microparticles or a salt to increase the outgassing tendency (of the fluid-carrying element and / or the system under consideration) and / or to slow the absorption of the first fluid.

[0086] This way, the detection of the initial fluid quantity can be improved.

[0087] In a further embodiment, the method can include performing a reference measurement of a fourth fluid quantity in the second fluid quantity during the filling of the fluid-carrying element, wherein the determination of the first fluid quantity further includes determining the first fluid quantity at least partially based on the reference measurement of the fourth fluid quantity.

[0088] The reference measurement can be performed using the input sensor or at least one additional input sensor. The input sensor can be different from the sensor used for acquisition and / or reacquisition (e.g., in terms of its type).

[0089] In some cases, filling the fluid-carrying element may involve at least a partial introduction of a first fluid (to which the first fluid quantity is associated) into a second fluid (to which the second fluid quantity is associated). By performing the reference measurement during filling, Carl Zeiss SMT GmbH

[0090] 14

[0091] It is possible to determine which fourth fluid quantity, which can be condensed into the first fluid quantity to be measured, was introduced into the fluid-carrying element by filling.

[0092] A fluid associated with the fourth fluid quantity can be the same as the fluid associated with the first fluid quantity.

[0093] Measuring the fourth fluid quantity can allow for improved inferences about the location, surface area, and / or volume of the second or fourth fluid quantity. In particular, this method can prevent and suppress inaccurate statements regarding the first fluid quantity, possibly caused by the filling process.

[0094] In a further embodiment, the method can include changing the temperature of the second fluid quantity from a first temperature to a second temperature before filling the fluid-carrying element.

[0095] The second temperature can be changed by less than ± 25°C, preferably by less than ± 10°C and most preferably by less than ± 5°C relative to the first temperature.

[0096] Changing the temperature can involve decreasing the temperature of the second fluid volume relative to the first. Alternatively, changing the temperature can involve increasing the temperature of the second fluid volume relative to the first.

[0097] In a further embodiment, the method can increase the pressure on the stationary or flowing fluid column of the first and second fluid quantities in a closed volume (e.g., by sealing off a relevant fluid-carrying element and compressing a first Carl Zeiss SMT GmbH contained therein).

[0098] 15

[0099] (Fluid quantity and a second fluid quantity contained therein). This can increase the solubility of the first fluid quantity in the second fluid quantity. This may, in turn, increase the dwell time of the first fluid quantity in the second fluid quantity and improve the detection accuracy of the first fluid quantity over time.

[0100] In this context, a holding time can be understood as a period of time during which a system of two or more fluids remains in a defined state to allow specific processes or changes to occur. The holding time allows the system to reach thermodynamic equilibrium, during which the concentrations of the dissolved substances can stabilize. The duration of the holding time will be determined by various factors, including temperature, pressure, and the initial concentration of the dissolved substances. These parameters influence the solubility, reaction rate, and the time required to reach equilibrium.

[0101] In a further embodiment, determining the first fluid quantity can include determining the position of at least a part of the first fluid quantity in the fluid-carrying element.

[0102] Determining the position of at least part of the initial fluid volume can be achieved by capturing the time course of a sensor signal, where the sensor is configured to detect an initial fluid volume. This can be a sensor type as described herein.

[0103] The position can be determined from a flushing time (e.g., the first and / or second flush) and a flushing rate (e.g., a first and / or second flush). The time span, measured from the start of the flushing process until the point at which the first fluid quantity is measured, multiplied by a corresponding value from Carl Zeiss SMT GmbH, can then be used to calculate the position.

[0104] 16

[0105] From the flow velocity, it can be deduced at which position within the fluid-carrying element at least part of the initial fluid quantity was present.

[0106] In this way, the functionality of the method described herein can be extended from simply determining the initial fluid quantity to determining its position or size. Based on the determined position of the initial fluid quantity, it can then be determined whether this quantity is critical for the operation of, for example, a cooling system, or whether it is non-critical and can therefore remain in the fluid-carrying element. If the position of the initial fluid quantity is considered critical, the fluid-carrying element can be refilled.

[0107] In some examples, the fluid-carrying component can be divided into at least two fluid-carrying components. These at least two fluid-carrying components can extend parallel to each other along a longitudinal direction. Each of the at least two fluid-carrying components can contain a sensor, which can be used to determine the initial fluid quantity.

[0108] In a further embodiment, the method can include initiating at least a local reduction of the first fluid quantity in the second fluid quantity at the specified position of the first fluid quantity.

[0109] In one example, the initial fluid quantity could be a gas mixture. In such a case, reducing the initial fluid quantity can be understood as venting the fluid-carrying element, with the venting ultimately leading (at least locally) to the reduction of the initial fluid quantity. Carl Zeiss SMT GmbH

[0110] 17

[0111] The reduction, at least locally, can be based on the specific position of the first fluid quantity.

[0112] In this way, it is possible not only to efficiently detect an initial fluid quantity, but also to reduce the initial fluid quantity to a desired target value.

[0113] In a further embodiment, the detection and / or re-detection of the first fluid quantity can further include the detection of a compressibility of the first fluid quantity and the second fluid quantity in the fluid-carrying element.

[0114] In some examples, the first fluid volume may have a compressibility that differs from that of the second fluid volume. This can lead to the compressibility of the combination of the first and second fluid volumes in the fluid-carrying element being dependent on the first fluid volume.

[0115] By measuring the compressibility of the first fluid quantity and the second fluid quantity, it is thus possible to efficiently measure the first fluid quantity within the second fluid quantity.

[0116] In a further embodiment, the detection and / or re-detection of the first fluid quantity can further comprise providing at least three pressure fluctuation sensors in the fluid-carrying element for detecting the speed of sound in the first and second fluid quantities, as well as detecting the speed of sound in the first and second fluid quantities using the at least three provided pressure fluctuation sensors. Carl Zeiss SMT GmbH

[0117] 18

[0118] In some examples, the first fluid volume may have a sound velocity that differs from the sound velocity of the second fluid volume. By measuring the sound velocity of a combination of the first fluid volume and the second fluid volume, it is possible to determine at which position within the second fluid volume at least a portion of the first fluid volume is present. This can, for example, involve determining a position at which at least a local change in the sound velocity occurs.

[0119] Determining the speed of sound can involve emitting a test sound wave from a test sound wave transmitter into a combination of the first fluid quantity and the second fluid quantity. The emitted test sound wave can be received by a test sound wave receiver located at a different location than the test sound wave transmitter. The test sound wave receiver can be positioned at a known distance from the test sound wave transmitter, or the signal path of the emitted sound waves can be known. Based on this, it is possible to determine the travel time of the test sound wave in the combination and thus the speed of sound.

[0120] Determining the speed of sound can, for example, involve passing the first and second fluid volumes past a pressure fluctuation sensor, thereby recording the temporal evolution of the sound speed. The pressure fluctuation sensor can be configured to detect pressure fluctuations in the passing combination of the first and second fluid volumes, which are caused by the sound waves.

[0121] In some examples, the measurement of the speed of sound can also be carried out with fewer than three pressure fluctuation sensors, as Carl Zeiss SMT GmbH

[0122] 19

[0123] e.g. with at least two pressure fluctuation sensors or with at least one pressure fluctuation sensor.

[0124] In this way, an initial fluid quantity can be determined efficiently.

[0125] In a further embodiment, the detection and / or re-detection of the first fluid quantity can further comprise the provision of at least two pressure fluctuation sensors, a variation of an absolute pressure in the fluid-carrying element, a detection of a pressure using each of the at least two pressure fluctuation sensors, and a determination of a pressure-to-pressure transfer function based on the detected pressures. Finally, the determination of the first fluid quantity can be based at least partially on the pressure-to-pressure transfer function.

[0126] Varying the absolute pressure in the fluid-carrying element can increase the static pressure within that element. This can lead to an increase in the effective stiffness of a combination of the first and second fluid volumes. For example, if a certain amount of the first fluid volume is contained within the second, and the first fluid volume is more compressible than the second, this can result in greater compression of the combination than in a case where the first fluid volume is not contained within the second, or where the first fluid volume is incompressible. The increase in the stiffness of the combination can manifest itself, for example, as a shift in a resonance within a pressure-to-pressure transfer function, as described herein. Carl Zeiss SMT GmbH

[0127] 20

[0128] The at least two pressure fluctuation sensors can be attached at different locations along a longitudinal extension direction of the fluid-carrying element.

[0129] A pressure-to-pressure transfer function can be understood as a function that results from a ratio of two pressure fluctuation measurements inside the fluid-carrying element at two different locations.

[0130] The first fluid sample can generate local differences in compressibility in the second fluid sample, which can then be recorded and used to draw conclusions about the first fluid sample.

[0131] This allows for efficient determination of the initial fluid quantity.

[0132] In a further embodiment, the detection and / or re-detection of the first fluid quantity can further comprise providing at least two partial pressure sensors at two different locations in the fluid-carrying element along a flushing direction of the first fluid quantity and the second fluid quantity, determining the first fluid quantity using the at least first partial pressure sensor and the second partial pressure sensor respectively, and deriving, based on determining whether there is a leak in the fluid-carrying element between the first partial pressure sensor and the second partial pressure sensor.

[0133] The leak can cause an increase in the initial fluid volume over time. This can occur, for example, if the pressure outside the fluid-carrying element is higher than the pressure inside the fluid-carrying element. Carl Zeiss SMT GmbH

[0134] 21

[0135] A leak can also include at least local outgassing, e.g., of an initial amount of fluid from the fluid-carrying element (or into the fluid-carrying element).

[0136] Determining whether there is a leak between the first partial pressure sensor and the second partial pressure sensor may involve determining whether a partial pressure measured by the second partial pressure sensor is greater than a partial pressure measured by the first partial pressure sensor.

[0137] In this way, it may be possible to identify a cause for an increase in the initial fluid quantity.

[0138] In a further embodiment, the detection and / or re-detection of the first fluid quantity can further include providing a partial pressure sensor and / or a gas saturation sensor and a degasser, as well as detecting a time profile of a partial pressure using the partial pressure sensor and / or a saturation of the first fluid quantity using the gas saturation sensor with the aid of the degasser, and determining the first fluid quantity based on the detected time profile.

[0139] Operation of the degasser can contribute to a reduction of the first fluid quantity in the fluid-carrying element in order to achieve a degassed state in which the first fluid quantity has been substantially removed from the second fluid quantity.

[0140] By recording the time course with and without a degasser, it is possible to determine the influence of the degasser on the initial fluid volume. This can allow conclusions to be drawn about the initial fluid volume originally contained in the fluid-carrying element. Carl Zeiss SMT GmbH

[0141] 22

[0142] According to a second aspect, a computer program is proposed. The computer program comprises instructions which, when executed by a computer, cause it to perform one or more steps of a procedure as described herein.

[0143] In some examples, a computer program product can be provided that may contain instructions which, when executed by a computer, cause the computer to perform the steps of the procedure described herein. A computer program product, such as a computer program tool, may be provided or delivered, for example, as a storage medium such as a memory card, USB flash drive, CD-ROM, DVD, or as a downloadable file from a server on a network. This may be done, for example, over a wireless communication network by transmitting a suitable file containing the computer program product or the computer program tool.

[0144] According to a third aspect, a device for determining a first fluid quantity within a second fluid quantity in a fluid-carrying element of a lithography system is proposed. The device may include:

[0145] at least two pressure fluctuation sensors for detecting pressure within the fluid-carrying element;

[0146] Means for determining a pressure-to-pressure transfer function based on the pressures detected by at least two pressure fluctuation sensors; and

[0147] Means for determining the initial fluid quantity based on the determined pressure ■ to ■ pressure transfer function.

[0148] According to one embodiment, the device comprises means for filling the fluid-carrying element with the second quantity of fluid, means for executing Carl Zeiss SMT GmbH

[0149] 23

[0150] The device comprises a first flushing process in the fluid-carrying element with the second fluid quantity for a first flushing time at a first flow velocity along a first flushing direction; means for detecting the first fluid quantity in the second fluid quantity; and means for performing a second flushing process in the fluid-carrying element with the second fluid quantity for the first flushing time at the first flow velocity along a second flushing direction, which is opposite to the first flushing direction. Furthermore, the device may include means for re-detecting the first fluid quantity in the second fluid quantity and means for determining the first fluid quantity based on the detection and re-detecting.

[0151] According to a further aspect, a device for determining a first fluid quantity within a second fluid quantity in a fluid-carrying element of a lithography system is proposed. The device can comprise means for filling the fluid-carrying element with the second fluid quantity, means for performing a first rinsing process in the fluid-carrying element with the second fluid quantity for a first rinsing time at a first flow velocity along a first rinsing direction, means for detecting the first fluid quantity within the second fluid quantity, and means for performing a second rinsing process in the fluid-carrying element with the second fluid quantity for the first rinsing time at the first flow velocity along a second rinsing direction, which is opposite to the first rinsing direction.Furthermore, the device may include means for re-detecting the first fluid quantity in the second fluid quantity and means for determining the first fluid quantity based on the detection and re-detecting.

[0152] The means for filling, the means for carrying out the first rinsing process, the means for carrying out the second rinsing process may include a controllable inlet pressure control, with which a fluid rate (i.e. a quantity of a fluid flowing through the fluid-carrying element per unit of time) of Carl Zeiss SMT GmbH

[0153] 24

[0154] The filling process, or the first and / or second rinsing process, can be controlled. Additionally or alternatively, the system can also include a controllable pump with which the fluid rate can be controlled.

[0155] The fluid-carrying element can be located within an optical element (such as a mirror (e.g., an EUV mirror)), a lens, or a grating. Additionally or alternatively, the fluid-carrying element can also be used in a cooled frame or support structure, a cooled measuring machine, a cooled mask repair device, etc.

[0156] In one embodiment (e.g., an embodiment of the device according to the third or further aspect; this also applies to all further embodiments of the device), the means for detecting and / or the means for re-detecting the first fluid quantity may comprise a partial pressure sensor, a sonar device, a laser Doppler anemometry device, a pressure sensor, a high-speed camera, an acoustic Doppler velocity measurement device, an electrochemical sensor, a gas analyzer, and / or a fluorescence imaging device.

[0157] In a further embodiment, the device may comprise means for carrying out the method as described herein and / or means for executing the computer program as described herein.

[0158] The means for executing the procedure or the means for executing the computer program can be provided, as described herein, e.g. as a processor (e.g. as a CPU) and / or as an FPGA.

[0159] According to a fourth aspect, a system for determining a first fluid quantity in a second fluid quantity in a fluid-carrying element of a Carl Zeiss SMT GmbH

[0160] 25

[0161] A lithography system is proposed. The system may include the apparatus as described herein and the computer program as described herein.

[0162] According to a fifth aspect, a lithography system is proposed which may include a device as described herein.

[0163] One or more of the algorithms / computer programs described here can be implemented directly in hardware (e.g., by appropriate means), in a software module executed by a processor, or in a combination of both. A software module can reside in random-access memory (RAM), flash memory, read-only memory (ROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from and write information to the storage medium. Alternatively, the storage medium can be integrated into the processor. The processor and the storage medium can be housed in an application-specific integrated circuit (ASIC).Alternatively, the processor and storage medium can be housed as discrete components within any component of a mobile computing platform. The computer program can, for example, also be executed on a Field Programmable Gate Array (FPGA).

[0164] The first fluid, the second fluid, and / or the third fluid can each be provided as a liquid and / or a gas. In some examples, each of the fluids described herein can also be provided as a superposition of at least one liquid and at least one gas. Carl Zeiss SMT GmbH

[0165] 26

[0166] In some cases, the aspects and embodiments described herein can be integrated into an optical system. The optical system is preferably a projection optic of the projection exposure system. However, the optical system can also be an illumination system. The projection exposure system can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm. The optical system can, for example, also be used in a DUV lithography system.

[0167] The aspects presented herein are not limited to the applications explicitly discussed. They extend to all systems and subsystems in the field of EUV lithography where it is important to provide a fill state (e.g., determining a first fluid quantity within a second fluid quantity) of a fluid-carrying system for characterizing and / or monitoring the fill state of a fluid-carrying element. In particular, the aspects presented herein are applicable to DUV applications, EUV collectors, and EUV illumination devices. Furthermore, they can also be applied in the field of mask inspection (e.g., EUV mask inspection). Additionally, the aspects presented herein can be applied in any other test or characterization environment related to lithography.

[0168] The optical system can also be used, for example, in a DUV lithography system.

[0169] "One" in this context is not necessarily to be understood as restricting it to exactly one element. Rather, it can also refer to multiple elements, such as two, Carl Zeiss SMT GmbH

[0170] 27

[0171] Three or more are provided for. Likewise, every other counter used here should not be understood as implying a restriction to exactly the stated number of elements. Rather, numerical deviations above and below this number are possible unless otherwise specified.

[0172] The embodiments and features described for the system or devices apply accordingly to the proposed methods and vice versa.

[0173] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0174] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the embodiments of the invention described below. The invention will now be explained in more detail with reference to preferred embodiments and the accompanying figures.

[0175] Fig. 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography!

[0176] Fig. 2 shows the meridional section of the projection exposure system shown in Fig. 1, where one of the mirrors included therein has been provided with a fluid-carrying element!

[0177] Fig. 3 shows a diagram of a print-to-print transfer function! Carl Zeiss SMT GmbH

[0178] 28

[0179] Fig. 4 shows a cross-section through an exemplary device for detecting a first quantity of fluid in a second quantity of fluid;

[0180] Fig. 5 shows a cross-section through an exemplary device for detecting a first quantity of fluid in a second quantity of fluid;

[0181] Fig. 6 shows a cross-section through an exemplary device for detecting a first quantity of fluid in a second quantity of fluid;

[0182] Fig. 7 shows a cross-section through an exemplary device for detecting a first quantity of fluid in a second quantity of fluid;

[0183] Fig. 8 shows a cross-section through an exemplary device for detecting a first quantity of fluid in a second quantity of fluid;

[0184] Fig. 9 shows a flow diagram of a method for determining a first fluid quantity in a second fluid in a fluid-carrying element of a lithography system;

[0185] Fig. 10 shows a device for determining a first fluid quantity in a second fluid in a fluid-carrying element of a lithography system; and

[0186] Fig. 11 shows a system for determining a first fluid quantity in a second fluid in a fluid-carrying element of a lithography system.

[0187] In the figures, identical or functionally equivalent elements have been labelled with the same reference symbols unless otherwise indicated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale. Carl Zeiss SMT GmbH

[0188] 29

[0189] Fig. 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of the illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optic 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0190] A reticule 7 arranged in the object field 5 is exposed. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in a scanning direction, via a reticule displacement drive 9.

[0191] Figure 1 illustrates a Cartesian coordinate system with an x-direction x, a y-direction y, and a z-direction z. The x-direction x runs perpendicular to the plane of the drawing. The y-direction y runs horizontally, and the z-direction z runs vertically. In Figure 1, the scan direction runs along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

[0192] The projection exposure system 1 comprises a projection optic 10. The projection optic 10 serves to image the object field 5 onto an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0193] A structure on the reticulum 7 is imaged onto a light-sensitive layer of a wafer 13 located in the image plane 12 within the image field 11. The wafer 13 is held by a wafer holder 14. Carl Zeiss SMT GmbH

[0194] 30

[0195] Wafer holder 14 can be moved, in particular along the y-direction y, via a wafer transfer drive 15. The movement of the reticle 7 via the reticle transfer drive 9 and the wafer 13 via the wafer transfer drive 15 can be synchronized with each other.

[0196] Light source 3 is an EUV radiation source. Light source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation 16 has a wavelength in the range between 5 nm and 30 nm. Light source 3 can be a plasma source, for example, an LPP source (Laser Produced Plasma) or a DPP source (Gas Discharged Produced Plasma). It can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (FEL).

[0197] The illumination radiation 16 emanating from the light source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 17 can be illuminated with the illumination radiation 16 at grazing incidence (GI), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector 17 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0198] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 Carl Zeiss SMT GmbH

[0199] 31

[0200] can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

[0201] The illumination optics 4 comprise a deflecting mirror 19 and, downstream in the beam path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with a beam-shaping effect in addition to its deflecting function. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first faceted mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field faceted mirror. The first faceted mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Only a few of these first facets 21 are shown as examples in Fig. 1.

[0202] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular edge contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets.

[0203] As is known, for example, from DE 102008009600 A1, the first facets 21 themselves can each be composed of a multitude of individual mirrors, in particular a multitude of micromirrors. The first facet mirror 20 can, in particular, be designed as a microelectromechanical system (MEMS system). For details, please refer to DE 102008009600 A1. Carl Zeiss SMT GmbH

[0204] 32

[0205] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

[0206] In the beam path of the illumination optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. If the second faceted mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil faceted mirror. The second faceted mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first faceted mirror 20 and the second faceted mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1614 008 B1, and US 6,573,978.

[0207] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0208] The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal edges, or alternatively, facets composed of micromirrors. Reference is also made to DE 102008009600 Al in this regard.

[0209] The second facets 23 can have planar or alternatively convex or concave curved reflective surfaces.

[0210] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (English: Fly's Eye Integrator). Carl Zeiss SMT GmbH

[0211] 33

[0212] It can be advantageous not to arrange the second faceted mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second faceted mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 102017220586 A1.

[0213] With the aid of the second faceted mirror 22, the individual first facets 21 are imaged into the object field 5. The second faceted mirror 22 is the last beam-shaping or indeed the last mirror for the illumination radiation 16 in the beam path before the object field 5.

[0214] In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to the imaging of the first facets 21 into the object field 5. The transmission optic can have exactly one mirror, or alternatively two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optic can in particular comprise one or two mirrors for normal incidence (Ni mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors).

[0215] In the embodiment shown in Fig. 1, the lighting optics 4 has exactly three mirrors after the collector 17, namely the deflecting mirror 19, the first faceted mirror 20 and the second faceted mirror 22.

[0216] In a further embodiment of the illumination optics 4, the deflecting mirror 19 can also be omitted, so that the illumination optics 4 after the collector 17 can then have exactly two mirrors, namely the first faceted mirror 20 and the second faceted mirror 22. Carl Zeiss SMT GmbH

[0217] 34

[0218] The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optic into the object plane 6 is regularly only an approximate imaging.

[0219] The projection optics 10 comprise a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0220] In the example shown in Fig. 1, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The projection optics 10 is a double-obscured optic. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0221] The reflective surfaces of the mirrors Mi can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflective surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0222] The projection optics 10 have a large object-image offset in the y-direction y between a y-coordinate of the center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction Carl Zeiss SMT GmbH

[0223] 35

[0224] The direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0225] The projection optics 10 can be anamorphic. In particular, they have different image scales βx, βy in the x and y directions. The two image scales βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive image scale β indicates an image without image inversion. A negative sign for the image scale β indicates an image with image inversion.

[0226] The projection optics 10 thus lead to a reduction in the x-direction x, that is, in the direction perpendicular to the scan direction, in a ratio of 4:1.

[0227] The projection optics 10 lead to a reduction of 8:1 in the y-direction y, that is, in the scan direction.

[0228] Other magnification ratios are also possible. Magnification ratios with the same sign and absolute value in the x and y directions (x, y), for example with absolute values ​​of 0.125 or 0.25, are also possible.

[0229] The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or, depending on the design of the projection optics 10, different. Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US 2018 / 0074303 A.

[0230] Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel for illuminating the object field 5. This can result in illumination according to Köhler's principle. The far field is illuminated using the first facets 21. Carl Zeiss SMT GmbH

[0231] 36

[0232] The object is divided into a multitude of object fields 5. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to them.

[0233] The first facets 21 are each superimposed on an associated second facet 23 to illuminate the object field 5 on the reticulum 7. The illumination of the object field 5 is particularly homogeneous. It preferably exhibits a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0234] The illumination of the entrance pupil of the projection optics 10 can be geometrically defined by the arrangement of the second facets 23. By selecting the illumination channels, in particular the subset of the second facets 23 that carry light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0235] Another preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

[0236] Further aspects and details of the illumination of the object field 5 and, in particular, the entrance pupil of the projection optics 10 are described below.

[0237] The projection optic 10 can, in particular, have a homocentric entrance pupil. This may be accessible. It may also be inaccessible. Carl Zeiss SMT GmbH

[0238] 37

[0239] The entrance pupil of the projection optics 10 cannot regularly be illuminated exactly by the second faceted mirror 22. When the projection optics 10 image the center of the second faceted mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found where the pairwise determined separation of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0240] The projection optics 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second faceted mirror 22 and the reticle 7. This optical element can then be used to account for the different positions of the tangential and sagittal entrance pupils.

[0241] In the arrangement of the components of the illumination optics 4 shown in Fig. 1, the second faceted mirror 22 is arranged in a plane conjugate to the entrance pupil of the projection optics 10. The first faceted mirror 20 is arranged tilted relative to the object plane 6. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the deflecting mirror 19. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the second faceted mirror 22.

[0242] Fig. 2 shows the projection exposure system 1 from Fig. 1, wherein at least the mirror M6 is provided with a fluid-carrying element F. The fluid-carrying element F can be provided as a cooling channel configured to guide a cooling fluid through the mirror M6 and thereby transfer heat energy (e.g., from a mirror heating system to the mirror). Carl Zeiss SMT GmbH

[0243] 38

[0244] (M6 was entered) to remove and thus cool the mirror M6 to a predetermined temperature value.

[0245] For this purpose, a reservoir 24 can be provided which contains at least a second quantity of fluid and which can be introduced, at least partially, as at least a second quantity of fluid into a feeder 25. The feeder 25 is fluidly connected to the fluid-carrying element F, so that the second quantity of fluid can also be introduced into the fluid-carrying element F.

[0246] The second amount of fluid can absorb heat energy stored in mirror M6 and thus heat up.

[0247] The second quantity of fluid can be discharged from the mirror M6 via outlet 26 and fed into a collection reservoir 27.

[0248] In addition to the second fluid quantity, the fluid-carrying element F and / or the inlet 25 and / or the outlet 26 can also contain at least a first fluid quantity. The first fluid quantity may already be initially contained in the aforementioned components or may be introduced at least partially by filling them with the second fluid quantity. In the latter case, the first fluid quantity is at least partially already contained in the second fluid quantity (e.g., in reservoir 24 (e.g., in dissolved form)).

[0249] The first fluid quantity can include, for example, O2, N2, CO2 and Ar, contaminants (e.g., algae or similar), sediments, suspended particles or a combination thereof.

[0250] The second fluid quantity can comprise water, ultrapure water, distilled water, a cooling oil (mineral oil, silicone, hydrocarbon, perfluoropolyether oil), air, or a combination thereof. In some cases, the second Carl Zeiss SMT GmbH

[0251] 39

[0252] The first fluid quantity must be suitable for cleanroom use. The second fluid quantity can be formulated in such a way that it does not cause contamination in the lithography system.

[0253] Fig. 3 shows a diagram 300 in which a pressure-to-pressure transfer function (P2P) is plotted against a frequency. The pressure-to-pressure transfer function was measured within the fluid-carrying element (e.g., the fluid-carrying element F or within another suitable fluid-carrying element). The fluid-carrying element may have been filled with a second fluid quantity and may additionally contain a first fluid quantity. The first fluid quantity may be considered undesirable in the second fluid quantity and may, for example, be air, i.e., represent an undesired gas mixture.

[0254] The pressure-to-pressure transfer function describes the ratio of two pressure measurements taken at different locations within the fluid-carrying element. For the pressure measurement in question, the absolute pressure in the fluid-carrying element may have been increased. The signal, initially recorded as a time series, was subsequently Fourier-transformed to derive frequency information from the recorded time series.

[0255] By varying the absolute pressure within the fluid-carrying element, a shift in the resonance peaks of the combination of the first fluid quantity and the second fluid quantity can be achieved.

[0256] By detecting this shift in the resonance frequency of the combination of the first and second fluid volumes, it is possible to conclude that the combination is compressible. Carl Zeiss SMT GmbH

[0257] 40

[0258] Since the compressibility can in turn depend on the amount of the first fluid (or its general presence), it is possible to deduce the actually predominant amount of the first fluid contained in the second fluid in this way.

[0259] If the first fluid quantity is provided as a gas, for example, it can refer to a totality of gas bubbles in the second fluid quantity. The individual gas bubbles can be dissolved and / or undissolved in the second fluid quantity and exhibit individual movement. The presence of the gas bubbles can lead to a shift in the resonance peaks of the combination of the first and second fluid quantities.

[0260] From this, it can be concluded that the resonance behavior of the second fluid volume (assumed to be in the absence of the first fluid volume in the second fluid volume) differs from the resonance behavior that results when a certain amount of the first fluid volume is contained in the second fluid volume. In the absence of the first fluid volume in the second fluid volume, a frequency f can develop. ideal set.

[0261] In this context, Fig. 3 shows the resonance behavior (i.e., a first resonance and higher harmonics derivable from it) for different first fluid quantities (indicated by V2' in arbitrary units (au) normalized to the value 1).

[0262] The presence of the first fluid quantity in the second fluid quantity can lead to damping and / or attenuation of the dynamic behavior. A degree of damping and / or attenuation can be associated with an increase in the first fluid quantity. Therefore, it is possible that a resonance frequency associated with the resonance behavior may shift towards lower frequencies with an increase in the first fluid quantity (or, in the case of Carl Zeiss SMT GmbH, this can occur).

[0263] 41

[0264] A decrease in the initial fluid quantity can lead to an increase in the resonance frequency t). Additionally, an increase in the initial fluid quantity can lead to a decrease in the amplitude of the pressure-to-pressure transfer function shown in Fig. 3 (or conversely, a decrease in the initial fluid quantity can lead to an increase in the amplitude).

[0265] In this way, it is possible to infer the possible presence of the first fluid in the second fluid by detecting the resonance behavior of the second fluid quantity.

[0266] Fig. 4 shows a cross-section through an exemplary device 400 for detecting a first fluid quantity in a second fluid quantity.

[0267] To capture the first fluid quantity within the second fluid quantity, the combination of the first fluid quantity and the second fluid quantity can be placed in a housing 410 provided for this purpose within the device 400. The combination 420 of the first fluid quantity (with volume V1) and the second fluid quantity (with volume V2) can, in an initial state, occupy a total volume V.

[0268] The device 400 can further comprise a punch 430. The punch 430 can be configured to move along a first direction L by at least a distance Ax. The movement of the punch 430 can be achieved, for example, by applying a pressure differential Ap. The pressure differential Ap can be applied such that the pressure in an external environment of the device 400 is chosen to be greater than the pressure inside the housing 410 of the device 400.

[0269] Applying the pressure difference Δp can also affect the total volume V by moving the piston 430 by the distance Δx, and Carl Zeiss SMT GmbH

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[0271] This can be compressed, e.g. to a compressed total volume V' (not shown in Fig. 4). This can ultimately also increase the pressure inside the enclosure 410.

[0272] By controlling the increase in pressure inside the device 400 and recording the associated change in volume, it can be concluded that the combination 420 is compressible.

[0273] In one embodiment, it is also possible to perform a controlled change in the total volume V and, based on this, to deduce the pressure change Δp. In such a scenario, it is also possible to move the piston 430, with a given constant cross-sectional area and at a constant speed, by the distance Δx. Since the relationship between the change in total volume and the resulting change in total volume V depends on the compressibility, a conclusion can be drawn in this way about the compressibility of the combination of the first fluid quantity and the second fluid quantity.

[0274] The compressibility of the first fluid volume may differ from that of the second fluid volume in some cases. Consequently, the compressibility of combination 420 can vary depending on the first and second fluid volumes.

[0275] Determining the compressibility of the combination 420 can therefore enable the determination of the first fluid quantity within the second fluid quantity.

[0276] The device 400 can be connected to the fluid-carrying element (e.g., the fluid-carrying element F as described with reference to Fig. 2) in fluid connection Carl Zeiss SMT GmbH

[0277] 43

[0278] stand. In this way, it is possible to detect an initial amount of fluid in the fluid-carrying element.

[0279] Fig. 5 shows a cross-section through an exemplary device 500 for detecting a first fluid quantity within a second fluid quantity. The first fluid quantity can be associated with a partial pressure PI in the interior 510 of a fluid-carrying element 520. The second fluid quantity can be associated with a partial pressure P2 in the interior 510 of the fluid-carrying element 520.

[0280] The exemplary device 500 can include a partial pressure sensor 530. The partial pressure sensor 530 can be configured to detect a partial pressure PI or P2 inside 510 of the fluid-carrying element 520. It can be provided that one partial pressure sensor 530, assigned to each fluid to be detected, is available.

[0281] A partial pressure sensor is a device for detecting the partial pressure of a specific fluid (e.g., a gas in a gas mixture or a liquid). The sensor typically consists of a selectively permeable membrane that allows the fluid to pass through and a measuring element that detects the fluid's concentration. The measuring element can be based on various principles, such as potentiometric or amperometric sensing methods. The sensor converts the fluid's partial pressure into an electrical signal that is proportional to the fluid concentration (e.g., the fluid volume). Partial pressure sensors enable precise and continuous monitoring of specific gas components in complex mixtures, which can be crucial for many analytical and regulatory applications.

[0282] Fig. 6 shows a cross-section through an exemplary device 600 for detecting a first fluid quantity within a second fluid quantity. Carl Zeiss SMT GmbH

[0283] 44

[0284] The first fluid quantity 610, together with a second fluid quantity, can be introduced into the interior 620 of a fluid-carrying element 630. A transmitter 640, which can be, for example, a sound source (e.g., an ultrasound source or a sonar source), can be provided inside the fluid-carrying element 630. The transmitter can, for example, be configured to introduce sound waves 650 into the interior 620 of the fluid-carrying element 630.

[0285] If the sound waves 650 thus generated encounter at least a portion of the first fluid quantity 610 in the second fluid quantity, the sound waves can be reflected back to a receiver 640 (e.g., a sound receiver or a transmitter-receiver, such as a sound-transmitting receiver). The receiver 640 can detect the reflected sound waves 650 and, from a difference between information about how the sound waves 650 were emitted and how they were received, calculate information about the position and size of the first fluid quantity 610.

[0286] Sound sources, such as transmitter 640, which are used to detect the first fluid quantity 610 in the second fluid quantity, can emit sound waves with frequencies between 10 kHz and 1 MHz. Higher (sound) frequencies can offer better resolution and thus detect smaller quantities of the first fluid quantity, but usually have a shorter range. Lower (sound) frequencies can have a greater range, but lower resolution and sensitivity.

[0287] Fig. 7 shows a cross-section through an exemplary device 700 for detecting a first fluid quantity 710 (e.g., an air bubble) in a second fluid quantity. The first fluid quantity 710 can be contained together with the second fluid quantity in an interior 720 of a fluid-carrying element 730. Carl Zeiss SMT GmbH

[0288] 45

[0289] Outside the fluid-carrying element 730, a laser source 740 can be provided. The laser source 740 can be configured to emit a laser beam 750, which can penetrate the interior 720 and potentially strike a portion of the first fluid volume 710. Through interaction of the laser beam 750 with the first fluid volume 710, a property (e.g., a wavelength or frequency) of the laser beam 750 can be influenced.

[0290] Detecting the first fluid volume using the 750 laser beam can be based on laser Doppler anemometry (LDA). LDA is a technique that uses laser light to measure the velocity of fluid particles, including bubbles, in a liquid. In the context of detecting a first fluid volume within a second fluid volume, LDA can be used to determine the velocity of, for example, bubbles (as part of the first fluid volume) as they move through the second fluid volume.

[0291] To detect a potential bubble velocity using LDA, the laser beam 750 is directed into the second fluid volume, where it interacts with at least a portion of the first fluid volume 710. While at least a portion of the first fluid volume 710 moves through the second fluid volume, at least a portion of the first fluid volume 710 (e.g., an air bubble) can scatter the laser beam 750, which can lead to a change in the frequency of the scattered light. This frequency change is called the Doppler shift and is directly proportional to the velocity of the portion of the first fluid volume 710.

[0292] By measuring the Doppler shift of the scattered laser beam 750, an LDA system can calculate the velocity of the first fluid quantity 710 in the second fluid quantity. Based on this information, the size and concentration of the portion of the first fluid quantity 710 can be estimated. Carl Zeiss SMT GmbH

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[0294] Monitor changes (e.g. an increase or decrease in the first fluid quantity 710) of the portion of the first fluid quantity 710 over time.

[0295] One advantage of LDA over other methods for measuring a first fluid quantity 710 in a second fluid quantity is that it can provide detailed information about the velocity and behavior of individual parts of the first fluid quantity 710, such as the velocity of individual bubbles.

[0296] Fig. 8 shows a cross-section through an exemplary device 800 for detecting a first fluid quantity 810 (e.g., an air bubble) in a second fluid quantity. The first fluid quantity 810 can be contained together with the second fluid quantity in an interior 820 of a fluid-carrying element 830.

[0297] A camera 840 (e.g., a high-speed camera) can be provided on an outer surface of the fluid-carrying element 830. The camera 840 can be provided in such a way that it can detect the movement of at least a portion of the first fluid quantity 810 within the second fluid quantity.

[0298] Camera 840 can, for example, capture a sequence of images (e.g., several hundred or several thousand images per second) of the first fluid quantity 810, thereby enabling an analysis of the size and behavior (e.g., velocity, drift direction, etc.) of a portion of the first fluid quantity. Camera 840 can be focused on a specific, desired area of ​​the second fluid quantity, so that the presence of at least a portion of the first fluid quantity within that area can be detected.

[0299] If part of the initial fluid quantity 810 is present as a bubble (e.g., an air bubble), the quantity, size, and dynamics of the bubbles can be determined from the captured sequence of images. Carl Zeiss SMT GmbH

[0300] 47

[0301] Using image analysis techniques, the movement of individual bubbles can be tracked over time, and their size and concentration can be estimated based on their appearance in the images. One advantage of using high-speed cameras to capture and characterize bubbles is that they can provide detailed information about the behavior of individual bubbles, such as their shape, movement, and interactions with other bubbles.

[0302] In some examples, acoustic Doppler velocimetry (ADV) can be used to detect the first fluid volume. This method uses sound waves to detect the velocity of at least a portion of the first fluid volume within the second fluid volume.

[0303] Advanced Doppler Velocity (ADV) is a technique in which sound waves are used to measure the velocity of at least a portion of a first fluid volume (e.g., liquid particles, including bubbles) within a second fluid volume (e.g., a liquid such as water (or another suitable liquid, as described herein)). In conjunction with determining the bubble content in a combination of the first and second fluid volumes, ADV can be used to measure the velocity of bubbles as they rise, for example, through the water. To measure bubble velocity using ADV, a sound wave can be coupled into the combination of the first and second fluid volumes. As the bubbles move through the water, they scatter the sound wave, resulting in a change in the frequency of the scattered wave. This frequency change is called the Doppler shift and is directly proportional to the velocity of the bubbles.

[0304] By measuring the Doppler shift of the scattered sound wave, an ADV system can calculate the velocity of the bubbles in the water. (Based on Carl Zeiss SMT GmbH)

[0305] 48

[0306] This information allows the size and concentration of the bubbles to be estimated and changes in the bubble content to be monitored over time.

[0307] One advantage of ADV over other methods for measuring bubbles in water is that it can provide detailed information about the speed and behavior of individual bubbles. ADV can also measure the speed of the surrounding water, which can provide additional information about the flow dynamics of the water column.

[0308] Additionally or alternatively, it may also be possible to determine the initial fluid volume by taking a sample of at least a portion of it (e.g., using a water sampler or other sampling device). The sample can then be transferred to a container and sealed to prevent gas exchange with the surrounding atmosphere.

[0309] A small amount of the sample can then be taken from the container using a fluid-tight syringe. The syringe can then be inserted into the inlet of the gas analyzer, which measures the concentration of the gas of interest in the sample.

[0310] A gas analyzer can use various technologies to measure gas concentration, including infrared spectroscopy, mass spectrometry, or electrochemical sensors.

[0311] Alternatively, the initial fluid quantity can also be determined using gas chromatography (GC). This analytical technique allows the concentration of fluids, including bubbles, in liquids (e.g., water) to be measured. Carl Zeiss SMT GmbH

[0312] 49

[0313] In gas chromatography (GC), the gas sample is passed through a column containing a stationary phase, which separates the different gas components based on their chemical interactions with the stationary phase. The separated gases are then detected by a detector that generates a signal proportional to the concentration of the individual gas components.

[0314] The output signal of the GC system can then be used to estimate the concentration of various gases in the water sample, including gases present in bubbles. By comparing the concentrations of the different gases, the size and concentration of the bubbles in the water column can be estimated. One advantage of GC is that it allows for very accurate and precise measurements of gas concentrations.

[0315] In some examples, a fluorescence imaging method can be used to detect the first fluid volume. This method uses fluorescent dyes to visualize the behavior of at least a portion of the first fluid volume (e.g., bubbles) in the second fluid volume (e.g., water). Fluorescence imaging is a method that uses fluorescent dyes to visualize the behavior of the first fluid volume in the second fluid volume. Fluorescence imaging can be used to estimate the size, concentration, and behavior of at least a portion of the first fluid volume in the second fluid volume.

[0316] If at least part of the first fluid sample consists of bubbles (e.g., air bubbles), a fluorescent dye can be added to the second fluid sample to measure the bubble content using fluorescence imaging. The dye is selected based on its ability to bind to, for example, the gas phase of bubbles, allowing them to be visualized with a fluorescence microscope or other imaging system. Carl Zeiss SMT GmbH

[0317] 50

[0318] As the bubbles rise through the water, they are illuminated by a light source, causing the fluorescent dye to emit light at a specific wavelength. This emitted light can be detected with a fluorescence detector, which creates an image of the bubbles in the water column.

[0319] By analyzing images generated by a fluorescence imaging system, the size, concentration, and behavior of bubbles in the water column can be estimated. Using image analysis techniques, the movement of individual bubbles can be tracked over time, and their size and concentration can be estimated based on their appearance in the images.

[0320] In some examples, it may be possible to detect the initial fluid volume using a pressure sensor. If at least part of the initial fluid volume is present as bubbles (e.g., air bubbles), the sensor can be placed either directly or with a probe in the water column. As bubbles rise through the water, they cause pressure fluctuations in the surrounding water. These pressure fluctuations can be detected by the pressure sensor, which converts them into an electrical signal that can then be evaluated.

[0321] The size and frequency of pressure fluctuations allow us to estimate the size and concentration of bubbles in the water column. Larger bubbles and higher bubble concentrations cause greater pressure fluctuations than smaller bubbles or lower concentrations.

[0322] However, pressure sensors may not be as accurate or precise as other methods, such as dissolved gas sensors or sonar, and they are more susceptible to interference from other sources of pressure fluctuations in the water. These sensors measure the pressure changes caused by bubbles in the water. Carl Zeiss SMT GmbH

[0323] 51

[0324] Fig. 9 shows a flow diagram of a method 900 for determining a first fluid quantity in a second fluid quantity in a fluid-carrying element of a lithography system.

[0325] In step 910, the fluid-carrying element is filled with the second quantity of fluid.

[0326] In step 920, a first flushing process is carried out in the fluid-carrying element with the second amount of fluid for a first flushing time with a first flow velocity along a first flushing direction.

[0327] In step 930, the first fluid quantity is measured in the second fluid quantity.

[0328] In step 940, a second flushing process is carried out in the fluid-carrying element with the second amount of fluid for the first flushing time at the first flow velocity along a second flushing direction, which is opposite to the first flushing direction.

[0329] In step 950, the first fluid quantity is measured again in the second fluid quantity.

[0330] In step 960, the first fluid quantity is determined based on the initial measurement and subsequent measurement.

[0331] Fig. 10 shows a device 1000 for determining a first fluid quantity in a second fluid quantity in a fluid-carrying element of a lithography system. The device 1000 comprises a filling means 1010, a discharge means 1020, a detection means 1030, and a discharge means. Carl Zeiss SMT GmbH

[0332] 52

[0333] 1040, a means for re-measuring 1050 and a means for determining 1060.

[0334] The filling device 1010 is configured to fill the fluid-carrying element with the second quantity of fluid.

[0335] The means of execution 1020 is configured to perform a first flushing operation in the fluid-carrying element with the second fluid quantity for a first flushing time with a first flow velocity along a first flushing direction.

[0336] The means for detection 1030 is configured to detect the first fluid quantity in the second fluid quantity.

[0337] The means for execution 1040 is configured to execute a second flushing process in the fluid-carrying element with the second fluid quantity for the first flushing time at the first flow velocity along a second flushing direction which is opposite to the first flushing direction.

[0338] The re-capture device 1050 is configured to capture the first fluid quantity within the second fluid quantity.

[0339] The means of determination 1060 is configured to determine the initial fluid quantity based on the acquisition and reacquisition.

[0340] Fig. 11 shows a system 1100 for determining a first fluid quantity in a second fluid quantity in a fluid-carrying element of a lithography system. The system 1100 can comprise a device 1110 and a computer program 1120. Carl Zeiss SMT GmbH

[0341] 53

[0342] The device 1110 can be implemented as described herein.

[0343] The computer program 1120 can be implemented as described herein.

[0344] The sensors described herein can each be arranged inside or outside a fluid-carrying element. In some examples, it may also be possible to provide a corresponding sensor as a module that can be removed from the fluid-carrying element.

[0345] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. Carl Zeiss SMT GmbH

[0346] 54 REFERENCE SIGN LIST

[0347] 1 Projection exposure system 2 Lighting system

[0348] 3 light source

[0349] 4 Lighting optics

[0350] 5 object field

[0351] 6 Object level

[0352] 7 reticles

[0353] 8 label holders

[0354] 9 Reticle displacement drive 10 Projection optics

[0355] 11 Image field

[0356] 12 Image plane

[0357] 13 wafers

[0358] 14 wafer holders

[0359] 15 Wafer transfer drive 16 Illumination radiation

[0360] 17 Collector

[0361] 18 Intermediate focus plane

[0362] 19 deflecting mirrors

[0363] 20 first faceted mirror

[0364] 21 first facet

[0365] 22 second faceted mirror

[0366] 23 second facet

[0367] 24 Reservoir

[0368] 25 Feed

[0369] 26 Drain

[0370] 27 Collection reservoir

[0371] 300 Diagram Carl Zeiss SMT GmbH

[0372] 55

[0373] 400 Device for detecting a first fluid quantity in a second fluid quantity

[0374] 410 Enclosure

[0375] 420 combination

[0376] 430 stamps

[0377] 500 Device for detecting a first fluid quantity in a second fluid quantity

[0378] 510 Interior of a fluid-carrying element

[0379] 520 fluid-carrying element

[0380] 530 Partial pressure sensor

[0381] 600 Device for detecting a first fluid quantity in a second fluid quantity

[0382] 610 first fluid quantity

[0383] 620 Interior of a fluid-carrying element

[0384] 630 fluid-carrying element

[0385] 640 channels

[0386] 650 receivers

[0387] 700 Device for detecting a first fluid quantity in a second fluid quantity

[0388] 710 first fluid quantity

[0389] 720 Interior of a fluid-carrying element

[0390] 730 fluid-carrying element

[0391] 740 laser source

[0392] 750 laser beam

[0393] 800 Device for detecting a first fluid quantity in a second fluid quantity

[0394] 810 first fluid quantity

[0395] 820 Interior of a fluid-carrying element

[0396] 830 fluid-carrying element

[0397] 840 Camera Carl Zeiss SMT GmbH

[0398] 56,900 procedures

[0399] 910 steps

[0400] 920 steps

[0401] 930 steps

[0402] 940 steps

[0403] 950 steps

[0404] 960 steps

[0405] 1000 devices

[0406] 1010 filling agents

[0407] 1020 means of execution

[0408] 1030 means of recording

[0409] 1040 means of execution

[0410] 1050 resources for re-recording 1060 resources for determining

[0411] 1100 System

[0412] 1110 Device

[0413] 1120 Computer program

[0414] F fluid-carrying element

[0415] L first direction

[0416] ml mirror

[0417] M2 mirrors

[0418] M3 mirror

[0419] M4 mirrors

[0420] M5 mirror

[0421] M6 mirrors

[0422] PI partial pressure

[0423] P2 partial pressure

[0424] V 1 Volume

[0425] V2 volume Carl Zeiss SMT GmbH

[0426] 57

[0427] Δp pressure difference Δx distance

Claims

Carl Zeiss SMT GmbH 58 PATENT CLAIMS 1. Method for determining a first fluid quantity (610; 710; 810) in a second fluid quantity in a fluid-carrying element (630; 730; 830) of a lithography system (1), comprising: a) Providing at least two pressure fluctuation sensors for pressure measurement at different locations within the fluid-carrying element (630; 730; 830); b) Detection of pressure using each of the at least two pressure fluctuation sensors; c) Determining a pressure-to-pressure transfer function based on the detected pressures; and d) Determining the first fluid quantity (610; 710; 810) based on the pressure ■ to ■ pressure transfer function.

2. Method according to claim 1, wherein in step b) a time course of a pressure is recorded by means of each of the at least two pressure fluctuation sensors.

3. Method according to claim 1 or 2, wherein the pressure-to-pressure transfer function is based on a ratio, in a fourier-transformed form, of a respective time course of the pressures detected by the at least two pressure fluctuation sensors.

4. Method according to one of claims 1 to 3, wherein in step d): a resonance frequency of the specific pressure-to-pressure transfer function is determined; a deviation of the determined resonant frequency from a predetermined resonant frequency (f ideal ) is determined; and Carl Zeiss SMT GmbH 59 the first fluid quantity (610; 710; 810) is determined based on the determined deviation.

5. Method according to one of claims 1 to 4, wherein in step b) a pressure of a combination (420) of the first fluid quantity (610; 710; 810) and the second fluid quantity in the fluid-carrying element (630; 730; 830) is detected by means of each of the at least two pressure fluctuation sensors.

6. Method according to any one of claims 1 to 5, comprising: Varying the absolute pressure in the fluid-carrying element (630; 730; 830).

7. Method according to any one of claims 1 to 6, wherein in step d): a resonance frequency of the specific pressure-to-pressure transfer function is determined; a compressibility and / or stiffness of a combination (420) of the first fluid quantity (610; 710; 810) and the second fluid quantity in the fluid-carrying element (630; 730; 830) is determined based on the determined resonance frequency; and the first fluid quantity (610; 710; 810) is determined based on the specified compressibility and / or stiffness.

8. Method according to any one of claims 1 to 7, comprising before step b): Filling (910) the fluid-carrying element (630; 730; 830) with the second quantity of fluid.

9. Method according to claim 8, comprising: Performing (920) a first flushing process in the fluid-carrying element (630; 730; 830) with the second quantity of fluid for a first flushing time with a first flow velocity along a first flushing direction; Carl Zeiss SMT GmbH 60 Detection (930) of the first fluid quantity (610; 710; 810) in the second fluid quantity; Performing (940) a second flushing process in the fluid-carrying element (630; 730; 830) with the second amount of fluid for the first flushing time at the first flow velocity along a second flushing direction which is opposite to the first flushing direction; Re-collection (950) of the first fluid quantity (610; 710; 810) in the second fluid quantity; and Determining (960) the first fluid quantity (610; 710; 810) based on the acquisition and reacquisition, where the detection and / or re-detection of the first fluid quantity (610; 710; 810) is performed based on steps a) to d).

10. The method of claim 9, further comprising: Temporarily interrupting the first rinsing process; Continuing the first flushing process with a second flow velocity that differs from the first flow velocity; Temporarily interrupting the second rinsing cycle; and Continue the second flushing process with the second flow rate.

11. Method according to any one of claims 8 to 10, further comprising: Filling the fluid-carrying element (630; 730; 830) with a third quantity of fluid before filling the fluid-carrying element (630; 730; 830) with the second quantity of fluid.

12. Method according to any one of claims 8 to 11, further comprising: Performing a reference measurement of a fourth fluid quantity in the second fluid quantity during the filling of the fluid-carrying element (630; 730; 830), wherein the determination of the first fluid quantity (610; 710; 810) further constitutes a Carl Zeiss SMT GmbH 61 Determining the first fluid quantity (610; 710; 810) is included, at least partially, based on the reference measurement of the fourth fluid quantity.

13. Method according to any one of claims 8 to 12, further comprising: Changing the temperature of the second fluid quantity from a first temperature to a second temperature before filling the fluid-carrying element (630; 730; 830).

14. Method according to any one of claims 1 to 13, wherein determining the first fluid quantity further comprises: Determining the position of at least part of the first fluid quantity (610; 710; 810) in the fluid-carrying element (630; 730; 830).

15. The method of claim 14, further comprising: Initiating at least a local reduction of the first fluid quantity (610; 710; 810) in the second fluid quantity at the specified position of the first fluid quantity (610; 710; 810).

16. Method according to any one of claims 1 to 15, wherein determining, sensing and / or re-sensing the first fluid quantity (610; 710; 810) further comprises: Determining the compressibility of the first fluid quantity (610; 710; 810) and the second fluid quantity in the fluid-carrying element (630; 730; 830).

17. Method according to any one of claims 1 to 16, wherein determining, sensing and / or re-sensing the first fluid quantity (610; 710; 810) further comprises: Determining the speed of sound in the first fluid quantity (610; 710; 810) and the second fluid quantity using at least two provided pressure fluctuation sensors. Carl Zeiss SMT GmbH 62 18. Method according to any one of claims 1 to 17, wherein determining, sensing and / or re-sensing the first fluid quantity (610; 710; 810) further comprises: Providing at least two partial pressure sensors (530) at two different locations in the fluid-carrying element (630; 730; 830) along a flushing direction of the first fluid quantity (610; 710; 810) and the second fluid quantity; Determining the first fluid quantity (610; 710; 810) using at least the first partial pressure sensor (530) and the second partial pressure sensor (530); and Derive, based on determining whether there is a leak in the fluid-carrying element (630; 730; 830) between the first partial pressure sensor (530) and the second partial pressure sensor (530).

19. Method according to any one of claims 1 to 18, wherein determining, sensing and / or re-sensing the first fluid quantity (610; 710; 810) further comprises: Providing a partial pressure sensor (530) and / or a gas saturation sensor; Detecting the temporal profile of a partial pressure (530) using the partial pressure sensor and / or the saturation of the first fluid quantity (610; 710; 810) using the gas saturation sensor; and Determine, based on the recorded time course, the first fluid quantity (610; 710; 810).

20. Device (1000) for determining a first fluid quantity (610; 710; 810) in a second fluid quantity in a fluid-carrying element (630; 730; 830) of a lithography system (1), comprising: at least two pressure fluctuation sensors for detecting pressure within the fluid-carrying element (630; 730; 830); Carl Zeiss SMT GmbH 63 Means for determining a pressure-to-pressure transfer function based on the pressures detected by at least two pressure fluctuation sensors; and Means for determining the first fluid quantity (610; 710; 810) based on the determined pressure-to-pressure transfer function.

21. Lithography system (1) comprising a device according to claim 20.

Images