WO2018210402A1

WO2018210402A1 - Method of measuring fluid properties and capacitive measurement device

Info

Publication number: WO2018210402A1
Application number: PCT/EP2017/061604
Authority: WO
Inventors: Max DIEZ; Neil Morrison
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2017-05-15
Filing date: 2017-05-15
Publication date: 2018-11-22
Anticipated expiration: 2019-11-15
Also published as: CN212060021U; TW201910760A

Abstract

Measurement device (100) adapted for measuring properties of a fluid (200) to be monitored, like a photo-resist for nano-imprint lithography. The measurement device (100) includes a flow capacitor device (101) having a fluid inlet and a fluid outlet, the flow capacitor device (101) being configured to allow the fluid (200) to be monitored to pass through the flow capacitor device from the fluid inlet to the fluid outlet; and an evaluation unit (300) electrically connected to the flow capacitor device (101), the evaluation unit (300) being adapted for determining a capacitance of the flow capacitor device (101) during fluid passage.

Description

METHOD OF MEASURING FLUID PROPERTIES AND CAPACITIVE

MEASUREMENT DEVICE

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the field of fluid parameter analysis, in particular embodiments of the present disclosure relate to concentration measurements of UV-curable lacquer such as photoresist / carrier solvent mixtures. Furthermore, embodiments of the present disclosure relate to a method of measuring properties of a fluid.

BACKGROUND

[0002] In microelectronics fabrication technology deposition of 3-D structures onto thin films or foils is widely used. A more recent technology for thin-film deposition is based on nano-imprint lithography, NIL. In this process, an UV or electron beam curable lacquer, e.g. a liquid photoresist mixed with carrier solvent is printed directly onto a film to be processed. Subsequently the UV or electron beam curable lacquer / solvent mixture is cured. Then, layers on the film can be etched at positions, where no UV or electron beam curable lacquer film is present. The nano-imprinting process is critical, because the thickness of the photoresist layer has to be adjusted within a very limited range. If the film thickness is too large, etching issues occur. If the film thickness is too low, failures and structuring issues during the lithography process arise.

[0003] The material which is printed onto the film to be processed includes a mixture of UV or electron beam curable lacquer such as e.g. photoresist, and carrier solvent. The mixture can contain premixed/predefined components or it can be prepared as "mixed-on-the-fly". Photoresist and carrier solvent in general exhibit different boiling points. Thereby, during the lithography process, the fluid mixing ratio between the photoresist material and the carrier solvent can change such that the above-mentioned appropriate film thickness cannot be maintained any longer. [0004] In order to monitor the mixing ratio of UV or electron beam curable lacquer (e.g. photoresist) and carrier solvent a dye and/or tracers could be used as additives. Such monitoring process, however, can have a deleterious influence on the properties of the fluid to be monitored, due to the possible contamination of photoresist-solvent mixtures.

[0005] Furthermore, IR spectroscopy is a well-known technique for measuring fluid composition. In this respect, Fourier transform infrared spectroscopy (FTIR) is a common technique for analyzing the chemical composition of the fluid. Due to the chemical similarity of the photoresist material and the carrier solvent material, however, this kind of spectroscopy measurement technique is a error-prone.

[0006] In view of the above, an improved fluid measurement system would be beneficial.

SUMMARY

[0007] In view of the above, the present disclosure provides the following.

[0008] According to an aspect, a measurement device adapted for measuring properties of a fluid to be monitored is provided. The measurement device includes a flow capacitor device having a fluid inlet and a fluid outlet, the flow capacitor device being configured to allow the fluid to be monitored to pass through the flow capacitor device from the fluid inlet to the fluid outlet; and an evaluation unit electrically connected to the flow capacitor device, the evaluation unit being adapted for determining a capacitance of the flow capacitor device during fluid passage.

[0009] According to another aspect, a method of measuring properties of a fluid to be monitored is provided. The method includes guiding the fluid to be monitored through a flow capacitor device; measuring a capacitance of the flow capacitor device; and evaluating a dielectric constant of the fluid to be monitored. According to yet another aspect, an imprint apparatus adapted for performing nano-imprint lithography is provided, the imprint apparatus including a measurement device adapted for measuring properties of a fluid to be monitored. According to yet another aspect, use of a measurement device adapted for measuring properties of a fluid to be monitored is provided.

[0010] Further embodiments, aspects, details and advantages are evident from the dependent claims, the description, and the drawings. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, can be had by reference to embodiments. The components in the figures are not necessarily true to scale, instead emphasis is placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts.

[0012] The accompanying drawings relate to embodiments of the disclosure and are described in the following:

[0013] Figure 1 illustrates a measurement device including a flow capacitor device connected to an evaluation unit, according to an embodiment of the present disclosure;

[0014] Figure 2 illustrates a setup for determining inductive surface charge of a polarized fluid, according to another embodiment of the present disclosure;

[0015] Figure 3 is a cross sectional view of the flow capacitor device of the measurement device shown in Figure 1 , according to an embodiment of the present disclosure;

[0016] Figure 4 depicts a current measurement unit having an ampere meter and which can be adapted for measuring a current through the flow capacitor device shown in Figure 1 and in Figure 3; [0017] Figure 5 depicts a voltage measurement unit having a voltmeter and which can be adapted for measuring a voltage drop across the flow capacitor device shown in Figure 1 and in Figure 3;

[0018] Figure 6 illustrates a fluid mixture control device including the flow capacitor device with the electrically connected evaluation unit for controlling a fluid mixture provided by a refill line, according to yet another embodiment of the present disclosure;

[0019] Figure 7 is a flowchart for illustrating a method of measuring properties of a fluid to be monitored, according to an embodiment of the present disclosure;

[0020] Figure 8 illustrates a capacitance measurement bridge including the flow capacitor device and a reference capacitor, according to yet another embodiment of the present disclosure;

[0021] Figure 9 is a perspective view of a flow capacitor device according to yet another embodiment of the present disclosure; and

[0022] Figure 10 is a cross-sectional view of the flow capacitor device shown in Figure 9.

DETAILED DESCRIPTION

[0023] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which specific embodiments are shown by way of illustration. Because components of embodiments can be positioned in a number of different orientations, directional terminology can be used for purpose of illustration and is in no way limiting. It is to be understood that other embodiments can be utilized and structural or logical changes can be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. The embodiments being described use specific language, which should not be construed as limiting the scope of the appended claims. The drawings are not to scale and are for illustrative purposes only. For clarity, the same elements or manufacturing actions have been designated by the same references in the different drawings if not stated otherwise.

[0024] Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations.

[0025] As used herein, the term "flow capacitor device" should be understood as describing a capacitor the dielectric material of which can be represented by a fluid or by a fluid and gas mixture to be monitored. In other words, the fluid to be monitored can be allowed to pass through the capacitor from a fluid inlet of the flow capacitor device to a fluid outlet of the flow capacitor device during measurement operation such that the fluid can represent the dielectric material between the capacitor electrodes.

[0026] As used herein, the term "evaluation unit" should be understood as describing a unit which can be adapted for evaluation of electrical parameters of an electrical component, e.g. of a capacitor. After having measured electrical parameters, e.g. a capacitance of the capacitor can be determined. In order to be capable of performing such evaluations or determinations the evaluation unit can include a microprocessor and/or memory devices.

[0027] According to aspects, the present disclosure proposes a measurement device adapted for measuring properties of a fluid to be monitored. The measurement device includes a flow capacitor device having a fluid inlet and a fluid outlet, the flow capacitor device being configured to allow the fluid to be monitored to pass through the flow capacitor device from the fluid inlet to the fluid outlet; and an evaluation unit electrically connected to the flow capacitor device, the evaluation unit being adapted for determining a capacitance of the flow capacitor device during fluid passage. [0028] Moreover, according to yet other aspects, the present disclosure proposes a method of measuring properties of a fluid to be monitored. The method includes guiding the fluid to be monitored through a flow capacitor device; measuring a capacitance of the flow capacitor device during fluid passage; and evaluating a dielectric constant of the fluid to be monitored.

[0029] Figure 1 illustrates a measurement device 100 including a flow capacitor device 101 connected to an evaluation unit 300, according to an embodiment of the present disclosure. The flow capacitor device 101 has a fluid inlet 108 and a fluid outlet 109, both in fluid communication with a flow cavity 104. The flow cavity 104 is a space which extends between a first or outer electrode 102 and a second or inner electrode 103 of the flow capacitor device 101 . After inflow 201 of a fluid 200 to be monitored the fluid 200 acts as the dielectric medium of the flow capacitor device 101 .

[0030] According to an embodiment which can be combined with other embodiments described herein, the evaluation unit 300 can be provided for determining electrical parameters of an electrical component to be measured. Such kind of electrical component, e.g. can be the electrical portion of the flow capacitor device 101 . In other words, the evaluation unit 300 can be connected to the electrodes of the flow capacitor device 101 such that a determination of the capacitance of the flow capacitor device 101 can be provided. After having measured the capacitance of the flow capacitor device 101 further parameters such as a value of a dielectric constant of a medium between the electrodes of the flow capacitor device 101 can be determined. In order to be able of performing such evaluations or determinations the evaluation unit 300 can include a microprocessor and/or memory devices.

[0031] According to an embodiment which can be combined with other embodiments described herein, the flow capacitor device 101 can be selected from the group consisting of a parallel-plate capacitor, a cylindrical capacitor and any combination thereof. [0032] According to an embodiment which can be combined with other embodiments described herein, the flow capacitor device 101 can act as a sensor capable of monitoring fluid properties during fluid passage. Thereby, an in-line monitoring process can be established. For in-line fluid monitoring of the fluid 200 an outflow 202 of the fluid 200 through the fluid outlet 109 can be provided. In other words, the amount of inflow 201 can correspond to the amount of outflow 202.

[0033] According to an embodiment which can be combined with other embodiments described herein, the evaluation unit 300 is electrically connected to both the outer electrode 102 and the inner electrode 103. The evaluation unit 300 can be mainly provided for determining a capacitance of the flow capacitor device 101 . The measured capacitance of the flow capacitor device 101 can vary according to the properties of the fluid 200 to be monitored.

[0034] An operation principle of the evaluation unit 300 will be explained herein below with respect to Figure 4, Figure 5 and Figure 8.

[0035] After having measured the capacitance of the flow capacitor device 101 , e.g. by means of a capacitance meter, the dielectric constant of the fluid 200 to be monitored can be determined. According to an embodiment which can be combined with other embodiments described herein, a measured combined dielectric constant of the fluid 200 to be monitored can be compared to stored dielectric constants of predefined fluids. The measured combined dielectric constant denoted by reference "kappa" (^K) is defined herein below. Thereby, it is possible to compare the parameters of the fluid 200 to be monitored with preset recipes. In this way, e.g. a concentration of carrier solvent within an UV or electron beam curable lacquer or a photoresist solution can be determined.

[0036] In addition to that, or alternatively, a detection of bubbles within the fluid 200 to be monitored can be provided. The dielectric constant of air or air bubbles within the fluid 200 to be monitored exhibit a dielectric constant which is close to the dielectric constant of vacuum. Thereby, gaseous components and entrained within the fluid 200 to be monitored can easily be detected. It is likewise possible to detect traces of fluids inside the capacitor under emptied conditions. The dielectric constant of a fluid is significantly higher than the dielectric constant of vacuum and strongly influences the measured capacitance.

[0037] In extension to this, an alteration in quality of the fluid is identifiable. If the fluid begins to decompose or somehow changes its chemistry, a drift in dielectric properties is measurable.

[0038] According to an embodiment which can be combined with other embodiments described herein, a cyclic process can be obtained, wherein an in-line detection of properties/parameters of the fluid 200 to be monitored can be provided. This in-line process can be used for updating the photoresist PR / carrier solvent CS mixture. According to another embodiment which can be combined with embodiments described herein, concentration drift of the photoresist / carrier solvent mixture can be determined.

[0039] In the following, the measurement principle for in-line monitoring of a fluid 200 to be monitored will be described. At first, a fluid pipe 204 can be provided. Then the flow capacitor device 101 is connected in a fluid communication with the fluid pipe 204. After flowing the fluid 200 to be monitored through the fluid pipe 204 and through the flow capacitor device 101 , a possibly changing capacitance of the flow capacitor device 101 can be measured. From the measured capacitance of the flow capacitor device 101 , a dielectric constant of the fluid 200 to be monitored can be evaluated. The dielectric constant of the fluid 200 to be monitored directly influences the capacitance reading. The determination of the dielectric constant of the fluid 200 can be used for identifying the fluid 200 to be monitored.

[0040] According to an embodiment which can be combined with other embodiments described herein, the properties of a fluid which is "mixed on-the-fly" can be determined in an appropriate manner. In addition to that, or alternatively, any change of the ratio of the photoresist with respect to the carrier solvent which has occurred due to the different boiling points of the fluid components can be detected "on-the-fly". [0041] For applications in nano-imprinting lithography mentioned above the fluid 200 to be monitored can include a mixture of photoresist PR (dielectric constant ε_r ^") and carrier solvent CS (dielectric constant ε_r ^'), both having different dielectric constants. The PR/CS mixture is guided through the flow capacitor device 101 . According to an embodiment which can be combined with other embodiments disclosed herein, an alternating voltage AC applied at the electrodes 102, 103 of the flow capacitor device 101 charges the capacitor 101 . Then, an individual time can be measured, until the capacitor 101 discharges. The involved discharging time is related to the capacitance C of the capacitor 101 . For simplification, in the following a parallel-plate capacitor having a plate separation D and a plate area A is regarded. The capacitance C of this capacitor is given by the following equation:

[0042] Herein, ε₀ is the dielectric constant of vacuum and "kappa" (^K) is the combined dielectric constant of the mixed and consisting fluids. A general approximation for two different mixed liquids can be achieved by the following two equations:

wherein %vol(PR) and %vol(CS) denote the volume percentage of the photoresist PR and the carrier solvent CS, respectively.

[0043] Thereby, the UV or electron beam curable lacquer/solvent or the photoresist/solvent concentration can be determined by measuring the capacitance C of the flow capacitor device 101 . In addition to that, or alternatively, continuous monitoring and point analysis can be provided for determining further fluid properties such as, but not limited to, the boil-off rate, a consumption quantity and a refill interval. This kind of continuous monitoring allows for "on-the-fly" determination of fluid properties. [0044] According to an embodiment which can be combined with other embodiments described herein, acetone can be used as a carrier solvent CS contained in the PR/CS mixture; for acetone the following relation holds:

An acrylate based, UV curable lacquer has a characteristic dielectric constant of -2-6 at 25°

[0045] By determining the capacitance of the flow capacitor device 101 , the evaluation unit 300 is capable of evaluating the dielectric constant ^K of the fluid 200 to be monitored and thus the fluid properties. In particular, due to different dielectric constants of the photoresist PR (dielectric constant ε_r ^") and the carrier solvent CS (dielectric constant ε_r ^'), a mixing ratio of the two fluids can be determined. Thereby, the flow capacitor device 101 can act as a real-time sensor for "on-the-fly" measurements of the composition of fluids passing through the cavity 104 of the flow capacitor device 101 . The complete processed fluid can be monitored and characterized continuously inline a cyclic process by the flow capacitor

[0046] According to an embodiment which can be combined with other embodiments described herein, the dielectric constant ^K of the fluid 200 to be monitored is determined on the basis of the dielectric constants of at least one of the dielectric constant £_r ^"of the photoresist PR, the dielectric constant ε_r ^' of the carrier solvent CS; a process mixture ratio of UV or electron beam curable lacquer or photoresist and carrier solvent, a concentration of fluid constituents, a concentration drift of fluid constituents, an amount of air and air bubbles in the fluid, a quality or state of disintegration of the fluid, a measure of specific concentrations of multi-mixed fluids under predefined conditions, traces of process chemicals after cleaning, and any combination thereof.

[0047] Figure 2 illustrates a setup for determining inductive surface charge of a polarized fluid, according to another embodiment of the present disclosure. A reference numeral 203 denotes the electric field lines within a capacitor 101 ' immersed into a fluid 200 to be monitored. The electric field 203 can be provided by the unit 300^'.

[0048] As shown in Figure 2, a determination of the specific dielectric constants of fluids 200 can be performed according to the following relation

[0049] wherein U is the voltage drop across the capacitor, g is the acceleration of gravity, p is the fluid's density and d is the distance between the two electrodes

[0050] Thereby, a change of height Ah is a measure for the dielectric constant of the fluid 200 to be monitored. In a first approximation, the height h is proportional to the measured capacity, which is dependent on or proportional to the dielectric constant ε_r.

[0051] It is noted here, however, that the setup according to Figure 2 is only for explanation purposes. The determination of specific fluid properties, on the other hand, can be performed by using the setup shown in Figure 1 and in Figure 3.

[0052] Figure 3 is a cross sectional view of the flow capacitor device 101 of the measurement device 100 shown in Figure 1 , according to an embodiment of the present disclosure which can be combined with other embodiments described herein. As shown in Figure 3, the flow capacitor device 101 can be provided as a cylindrical capacitor having an outer electrode 102 and an inner electrode 103. Spacer elements 105 are arranged between the outer electrode 102 and the inner electrode 103, the spacer elements 105 being electrically insulating, chemically stable and providing the flow cavity 104 between the outer electrode 102 and the inner electrode 103. These Spacer elements 105 fix the inner electrode 102 in a centered position with a rigid distance from outer electrode 102. The evaluation unit 300 is electrically connected to both the outer electrode 102 and the inner electrode 103. A reference numeral 203 denotes electric field lines of an electric field provided between the outer electrode 102 and the inner electrode 103. Furthermore, the cylindrical flow capacitor device 101 can be described by the following relations:

wherein η is the outer radius 107 of the inner electrode 103 and r₂ is the inner radius 106 of the outer electrode 102. The final capacitance is given by the following relation:

wherein I is the length of the cylindrical capacitor; ^vtube is the diameter of the outer tube 102, and is the diameter of the inner core 103.

[0053] The fluid 200 to be monitored can pass through the cavity 104 of the cylindrical flow capacitor device 101 , wherein its capacitance is determined, inter alia, by the fluid properties, in particular by the dielectric constant of the fluid 200 to be monitored. [0054] According to an embodiment which can be combined with other embodiments described herein, the flow capacitor device 101 can be selected from the group consisting of a parallel-plate capacitor, a cylindrical capacitor and any combination thereof.

[0055] According to an embodiment which can be combined with other embodiments described herein, properties of the fluid 200 to be monitored can be continuously monitored during fluid passage through the flow capacitor device 101 . Thereby, an in-line or real-time measurement process can be established.

[0056] According to an embodiment which can be combined with other embodiments described herein, the evaluation unit 300 can include a current measurement unit 307 adapted for measuring a current flow 304 through the flow capacitor device 101 . In particular, Figure 4 depicts a setup for measuring the current 304 through the flow capacitor device 101 . The evaluation unit 300, for example, can include a current measurement unit 307 having an ampere meter 302 and can be adapted for measuring the current 304 through the flow capacitor device 101 shown in Figure 1 and in Figure 3. A series resistor 303, R_A is connected in series to the ampere meter 302. A power source 301 can provide electric power. The power source 301 can be designed such that it provides a constant supply voltage.

[0057] According to yet another modification thereof, the evaluation unit 300 can include a voltage measurement unit 308 which can be adapted for measuring a voltage drop 306 across the flow capacitor device 101 . In particular, Figure 5 depicts a setup for measuring the voltage drop 306 across the flow capacitor device 101 . In the case shown in Figure 5, the evaluation unit 300 can include a voltage measurement unit 308 having a voltmeter 305 and can be adapted for measuring the voltage drop 306 across the flow capacitor device 101 shown in Figure 1 and in Figure 3. A power source 309 can provide electric power. The power source 309 can be designed such that it provides a constant supply current.

[0058] The setups of the evaluation unit 300 described herein above with respect to Figure 4 and Figure 5 can be adapted for measuring the electrical parameters of the flow capacitor device 101 , and thus for determining the dielectric constant of a fluid 200 to be monitored which can be present in the flow cavity 104 of the flow capacitor device 101 .

[0059] Figure 6 illustrates a fluid mixture control device 400 including the flow capacitor device 101 with the electrically connected evaluation unit 300 for controlling a fluid refill 205 mixture PR/CS provided via a refill line 401 , according to an embodiment which can be combined with other embodiments described herein. As shown in Figure 6, a process cycle 209 can be provided such that an imprint fluid mixture 206 provided for an lacquer reservoir 402 has a desired composition. The flow capacitor device 101 can be used for measuring the properties of the fluid 200 to be monitored which can be provided at the inflow 201 side of the flow capacitor device 101 , and which can exit the flow capacitor device 101 at the outflow 202 side of the flow capacitor device 101 .

[0060] According to an embodiment which can be combined with other embodiments described herein, the evaluation unit 300 connected to the flow capacitor device 101 can be provided as a microcontroller unit. The microcontroller unit can output data related to the fluid properties, in particular to the mixing ratio of photoresist PR and carrier solvent CS. Furthermore, the microcontroller unit can be adapted for evaluating data obtained from the flow capacitor device 101 . In addition to that, or alternatively, the microcontroller unit can be used for storing measurement data.

[0061] According to yet another embodiment which can be combined with embodiments described herein, the microcontroller unit included in the evaluation unit 300 can be used to compare stored dielectric constants of premixed fluids with dielectric constants of the fluid 200 which is monitored on-the-fly.

[0062] The fluid 200 to be monitored is fed from a supply chamber 406 to the inflow 201 side of the flow capacitor device 101 by applying a pressurized gas through a gas inlet 404 and via a flow controller 405 towards the supply chamber 406. According to yet another modification thereof, the flow controller 404 can be adapted for controlling a flow rate of the fluid 200 be monitored through the flow capacitor device 101 . [0063] According to an embodiment which can be combined with other embodiments described herein, a reflow 207 output from the imprint tray 402 can be reused. To this end, the reflow 207 is filtered in a filter 403 such that a filtered reflow 208 is obtained. The filtered reflow 208 is collected in the output chamber 407 and can be provided for the process cycle 209.

[0064] It is noted here, that the fluid mixture control device 400 shown in Figure 6 can be used as an in-line device for in-line monitoring of a fluid 200 to be monitored. Thereby, an UV or electron beam curable lacquer, a photoresist, a carrier solvent and/or a mixture of UV or electron beam curable lacquer and carrier solvent, a photoresist and carrier solvent, and any combination thereof can be monitored on- the-fly.

[0065] According to an embodiment which can be combined with other embodiments described herein, the measurement device 100 including the flow capacitor device 101 can be used in an imprint lithography process, e.g. in a Roll-2- Roll process (R2R). Herein, a film can be deposited and imprinted. The imprinted material can act as an etch mask for a subsequent etching. Alternatively, a resist film can be deposited and imprinted. The imprinted material, for example a resist material, can be a permanent part of the product and forms a deposited film. Imprint lithography can be used to pattern films into a desired or predetermined shape by imprinting a material layer with a stamp.

[0066] The basic imprint lithography process, e.g. can include (i) providing a coated substrate, (ii) coating the coated substrate with a polymer layer, (iii) embossing the substrate-layer system using a nano-imprinting device such as a stamp, (iv) curing of the substrate-layer system, e.g. using UV light, (v) releasing the substrate-polymer system from the nano-imprinting device, and (vi) etching the substrate-polymer system. Thereby, a basic imprint lithography process can include a first process step of depositing a layer, e.g. by vacuum deposition of metals, dielectrics and/or semiconductors. Then, a second process step of imprinting, e.g. of multiple mask levels as a single 3-D structure can be provided. After the imprinting step, an etching step for completion of patterning with wet and or dry sub-processes can be provided.

[0067] Curing of the substrate-layer can be provided by a curing unit. The curing unit can be selected from the group consisting of a light emission unit and a heating unit configured for curing the layer while imprinting the stamp in the layer, wherein emission is generated. For example, the light emission unit can emit UV light, particularly in the wavelength range from 410 nm to 190 nm. According to another example the emission unit can emit IR light, particularly in the wavelength range from 9-1 1 micrometers (CO₂ laser). According to yet another example the emission unit can emit broadband light from the IR to the UV with emission particularly in the wavelength range from 3 micrometers to 250 nm. This emission may be filtered to select only a portion of the blackbody emission using optical filters.

[0068] Imprinting or embossing a stamp in the layer of the UV curable layer or photoresist to generate a patterned layer can include fully or partially patterning the layer. Herein, the stamp can be released from the patterned layer, wherein particularly a pressure of a gas evolved from the layer during curing into a hollow space of a feature of the stamp can assist releasing the stamp or may release the stamp from the patterned layer of the substrate, respectively.

[0069] Figure 7 is a flowchart for illustrating a method of measuring properties of a fluid 200 to be monitored, according to an embodiment of the present disclosure. The procedure starts at a step 601 .

[0070] At a step 602, a fluid pipe 204 can be provided. The fluid pipe 204 which has been illustrated herein above with respect to Figure 1 , can be adapted for passing a fluid 200 to be monitored to the flow capacitor device 101 . The flow capacitor device 101 can be provided in fluid connection with the fluid pipe 204 at a step 603.

[0071] Then, at a step 604, the fluid 200 to be monitored is flown through the fluid pipe 204 and through the flow capacitor device 101 . Thereby, the fluid 200 to be monitored acts as the dielectric material of the flow capacitor device 101 within its cavity 104 such that the capacitance C of the flow capacitor device 101 is a function of the dielectric constant of the fluid 200 to be monitored. According to an embodiment which can be combined with other embodiments described herein, the fluid 200 to be monitored can be comprised of a photoresist PR (dielectric constant £_r ^") and a carrier solvent CS (dielectric constant ε_r ^'), both having different dielectric constants.

[0072] Thereafter, at a step 605, the capacitance C of the flow capacitor device 101 is measured. This measurement can be performed by using the evaluation unit 300 described herein above. Furthermore, at a step 606, the evaluation unit 300 can evaluate the dielectric constant(s) of the components of the fluid 200 be monitored. At a step 607, the procedure is ended.

[0073] Figure 8 illustrates a capacitance measurement bridge 500 which can include the flow capacitor device 101 and a reference capacitor 505, according to yet another embodiment which can be combined with other embodiments described herein. The process of measuring the capacitance C of the flow capacitor device 101 can include using a measurement bridge which can include the reference capacitor 505 as a reference element.

[0074] As shown in Figure 8, the measurement bridge 500 according to an embodiment is designed as an alternating voltage bridge for capacitance measurement. The measurement bridge 500 is powered by a supply voltage 506. The bridge voltage 507 can be measured between the terminals a and b. Furthermore, the bridge can include a first bridge resistor 501 electrically connected in parallel to the flow capacitor device 101 , and a second bridge resistor electrically connected in parallel to the reference capacitor 505, respectively. The remaining two bridge resistors are denoted as a third bridge resistor 503 and a fourth bridge resistor 504 electrically connected in series to each other.

[0075] As shown in Figure 8, and according to an embodiment which can be combined with other embodiments described herein, the bridge elements 501 , 502, 503, 505, 101 , and 505 are connected in a Wien bridge configuration. The bridge supply voltage 506 can be provided as an alternating voltage. The detected bridge voltage 507 is thus a measure for a relation between a capacitance C_f|_OW of the flow capacitor device 101 and a capacitance C_ref_erence of the reference capacitor 505.

[0076] According to an embodiment which can be combined with other embodiments described herein, a balanced bridge can be provided, wherein the reference capacitor 505 is adjusted such that the bridge voltage, for a specific capacitance C_f|_OW of the flow capacitor device 101 , equals zero: U_ab = 0. In this case a simple evaluation of the capacitance C_f|_OW of the flow capacitor device 101 , and thus the dielectric constant of the fluid 200 to be monitored, can be obtained if the remaining elements, i.e. the resistances of the bridge resistors 501 , 502, 503, and 504 are known.

[0077] According to yet another modification thereof, the bridge voltage 507 can be measured. In this case, the bridge voltage 507 can be different from zero: U_ab≠ 0. A continuous monitoring of the bridge voltage 507 is appropriate if, during an in-line process, changes of the dielectric constant of the fluid 200 to be monitored, and thus the composition of the photoresist/carrier solvent mixture should be monitored. In particular, according to yet another modification thereof, the properties of the fluid 200 to be monitored can be continuously monitored during fluid passage through the flow capacitor device 101 by monitoring the bridge voltage being different from zero:

[0078] According to an embodiment which can be combined with other embodiments described herein, the reference capacitor 505 which is electrically connected to the evaluation unit 300, can include a dielectric reference medium. According to yet another embodiment which can be combined with other embodiments described herein, the reference capacitor 505 can include a fluid passage adapted for passing a reference fluid provided as the dielectric reference medium through the reference capacitor 505.

[0079] The process of measuring the properties of a fluid 200 to be monitored which passes through the flow capacitor device 101 can be as follows: (i) providing the fluid pipe 204; (ii) providing the flow capacitor device 101 in fluid connection with the fluid pipe 204; (iii) providing the reference capacitor 505; (iv) flowing the fluid 200 to be monitored through the fluid pipe 204 and through the flow capacitor device 101 ; (v) flowing a reference fluid through the reference capacitor 505; (vi) measuring a bridge voltage 507 of the measurement bridge 500; and (vii) evaluating the dielectric constant of the fluid 200 to be monitored on the basis of the measured bridge voltage 507.

[0080] According to an embodiment which can be combined with other embodiments described herein, the process of measuring the properties of a fluid 200 to be monitored can include providing the reference capacitor 505, flowing a reference fluid through the reference capacitor 505, measuring a capacitance of the reference capacitor 505, and evaluating the dielectric constant of the fluid 200 to be monitored on the basis of the measured capacitances of both the flow capacitor device 101 and the reference capacitor 505.

[0081] According to an embodiment which can be combined with other embodiments described herein, the dielectric constant ^K of a mixed or combined fluid 200 to be monitored is determined on the basis of the dielectric constants of at least one of the dielectric constant ε_r ^"οf the photoresist PR, the dielectric constant ε_r ^' of the carrier solvent CS; a process mixture ratio of UV or electron beam curable lacquer or photoresist and carrier solvent, a concentration of fluid constituents, a concentration drift of fluid constituents, an amount of air and air bubbles in the fluid, a quality or state of disintegration of the fluid, a measure of specific concentrations of multi-mixed fluids under predefined conditions, traces of process chemicals after cleaning, and any combination thereof.

[0082] In order to operate the measurement bridge 500, an alternating supply voltage 506 provided by a supply voltage source U₀ of the measurement bridge 500 can be tuned in a frequency range from about 100 Hz to about 1000 kHz, in particular from about 100 Hz to about 10 kHz.

[0083] Figure 9 is a perspective view of a flow capacitor device 101 according to yet another embodiment which can be combined with embodiments described herein. As shown in Figure 9 an inner or core electrode 103 having a diameter 1 1 1 and an outer or tube electrode 102 having a diameter 1 10 are provided. As has been described herein above, a smaller spacing between the first or outer electrode 102 and the second or inner electrode 103 results in an increased capacitance of the cylindrical capacitor. According to a modification thereof, the cylindrical capacitor can be designed such that a capacitance value is in the Nanofarad (nF) range. As shown in Figure 9, the flow capacitor device 101 includes the spacer elements 105 in order to provide a defined space between the core or inner electrode 103 and the tube or outer electrode 102.

[0084] According to an embodiment which can be combined with other embodiments described herein, at least one of the diameter 1 1 1 of the core electrode 103 and the diameter 1 10 of the tube electrode 100 to can be adjusted such that a capacitance C of the flow capacitor device 101 can be adapted to a specific measurement situation.

[0085] According to an embodiment which can be combined with other embodiments described herein, the outer diameter 1 1 1 of the tube or first or outer electrode 102 is in a range from 6 mm to 10 mm, and preferably amounts to approximately 8 mm.

[0086] In Figure 10 a cross sectional view of the flow capacitor device 101 shown in Figure 9 is depicted. As shown in Figure 10, the core or inner electrode 103 is separated from the tube or outer electrode 102 by the spacer elements 105. In Figure 10 only a portion of the first or outer electrode 102 is shown. According to an embodiment which can be combined with other embodiments described herein, the core or inner electrode 103 can be designed such that it can be replaced without changing the tube or outer electrode 102. According to yet another modification or alternative thereof, the fluid 200 to be monitored can engulf the electrodes, i.e. the measurement area, completely or at least almost completely.

[0087] According to yet another modification, and outer diameter 1 10 of the core or second or inner electrode 103 can be adjusted such that a capacitance C of the flow capacitor device 101 can reach mid-Nanofarad (mid-nF) range such that an analysis of and an adaption to individual fluids 200 to be monitored can be provided. [0088] According to an embodiment which can be combined with other embodiments described herein, the setup of the flow capacitor device 101 shown in Figure 9 and Figure 10 can be easily disassembled such that cleaning of the entire device 101 can be facilitated.

[0089] While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention can be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1 . A measurement device adapted for measuring properties of a fluid to be monitored, the measurement device comprising: a flow capacitor device having a fluid inlet and a fluid outlet, the flow capacitor device being configured to allow the fluid to be monitored to pass through the flow capacitor device from the fluid inlet to the fluid outlet; and an evaluation unit electrically connected to the flow capacitor device, the evaluation unit being adapted for determining a capacitance of the flow capacitor device during fluid passage.

2. The measurement device according to claim 1 , further comprising a reference capacitor electrically connected to the evaluation unit, wherein the reference capacitor comprises a dielectric reference medium.

3. The measurement device according to claim 1 or 2, wherein the flow capacitor device is selected from the group consisting of a parallel-plate capacitor, a cylindrical capacitor and any combination thereof.

4. The measurement device according to any one of the preceding claims, wherein the evaluation unit comprises a capacitance measurement bridge, wherein the capacitance measurement bridge is preferably a Wien measurement bridge comprising both the flow capacitor device and the reference capacitor.

5. The measurement device according to any one of the claims 2 to 4, wherein the reference capacitor comprises a fluid passage adapted for passing a reference fluid provided as a dielectric reference medium through the reference capacitor.

6. The measurement device according to any one of the preceding claims, wherein the evaluation unit comprises a current measurement unit adapted for measuring a current through the flow capacitor device.

7. The measurement device according to any one of the preceding claims, wherein the evaluation unit comprises a voltage measurement unit adapted for measuring a voltage drop across the flow capacitor device.

8. The measurement device according to any one of the preceding claims, further comprising a flow controller adapted for controlling a flow rate of the fluid to be monitored through the flow capacitor device.

9. A method of measuring properties of a fluid to be monitored, the method comprising: guiding the fluid to be monitored through a flow capacitor device; measuring a capacitance of the flow capacitor device; and evaluating a dielectric constant of the fluid to be monitored.

10. The method according to claim 9, wherein the properties of the fluid are continuously monitored during fluid passage through the flow capacitor device.

1 1 .The method according to claim 9 or 10, further comprising: providing a reference capacitor; flowing a reference fluid through the reference capacitor; measuring a capacitance of the reference capacitor; and evaluating the dielectric constant of the fluid to be monitored on the basis of the measured capacitances of both the flow capacitor device and the reference capacitor.

12. The method according to any one of the claims 9 to 1 1 , wherein the dielectric constant of the fluid to be monitored is determined on the basis of the dielectric constants of at least one of the dielectric constant of an UV or electron beam curable lacquer, the dielectric constant of a photoresist, the dielectric constant of a carrier solvent; a process mixture ratio of UV or electron beam curable lacquer or photoresist and carrier solvent, a concentration of fluid constituents, a concentration drift of fluid constituents, an amount of air and air bubbles in the fluid, a quality or state of disintegration of the fluid, a measure of specific concentrations of multi-mixed fluids under predefined conditions, traces of process chemicals after cleaning, and any combination thereof.

13. The method according to any one of the claims 9 to 12, further comprising measuring the capacitance of the flow capacitor device using a measurement bridge which comprises the reference capacitor as a reference element, wherein a frequency of a supply voltage of the measurement bridge is preferably tuned in a frequency range from about 100 Hz to about 1000 kHz, in particular from about 100 Hz to about 10 kHz.

14. An imprint apparatus adapted for performing nano-imprint lithography, the imprint apparatus comprising a measurement device adapted for measuring properties of a fluid to be monitored according to any one of the claims 1 to 8.

15. Use of a measurement device adapted for measuring properties of a fluid to be monitored according to any one of the claims 1 to 8 in nano-imprint lithography.