Lithography system

Abstract

A lithography system includes a light source and at least one reflector. The light source comprises a liquid drop generator, a liquid storage device, a monitoring assembly and a collector. A reservoir is in fluid communication with the droplet generator. A monitoring assembly has at least two electrodes connected to the exterior of the reservoir. A collector is located below the droplet generator. The reflector is optically coupled with the collector.

Description

Technical Field

[0001] The present disclosure relates to a lithography system for semiconductor integrated circuits. Background Art

[0002] The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have resulted in generations of ICs, each with smaller and more complex circuits than the previous one. During IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased, while geometry size (i.e., the smallest component (or line) that can be produced using a manufacturing process) has decreased. This scaling process generally provides benefits by increasing production efficiency and reducing associated costs. However, this scaling also increases the complexity of processing and manufacturing ICs. Utility Model Content

[0003] According to some embodiments of the present invention, a lithography system includes a light source and at least one reflector. The light source includes a droplet generator, a reservoir, a monitoring assembly, and a collector. The reservoir is in fluid communication with the droplet generator. The monitoring assembly includes at least two electrodes connected to the exterior of the reservoir. The collector is located below the droplet generator. The reflector is optically coupled to the collector.

[0004] According to some embodiments of the present invention, a lithography system includes a light source and at least one reflector. The light source includes a droplet generator, at least one low-pressure reservoir, a high-pressure reservoir, a monitoring assembly, and a collector. The high-pressure reservoir is in fluid communication with the at least one low-pressure reservoir. The droplet generator is in fluid communication with the high-pressure reservoir. The monitoring assembly has at least two electrodes connected to the exterior of the high-pressure reservoir. A collector is located below the droplet generator. The reflector is optically coupled to the collector.

[0005] According to some embodiments of the present invention, a lithography system includes a light source and a lens system. The light source includes a droplet generator, a reservoir, a high-resolution capacitance measurement device, and a collector. The reservoir is in fluid communication with the droplet generator. The high-resolution capacitance measurement device has at least two electrodes connected to the exterior of the reservoir. The collector is located below the droplet generator. The lens system is optically coupled to the collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The various aspects of the present disclosure are best understood from the following detailed description in conjunction with the accompanying drawings. Note that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of discussion.

[0007] Figure 1A and Figure 1Bis a partial view of a lithography scanner according to an embodiment of the present disclosure;

[0008] Figures 2 to 7 are views of various embodiments of a tin supplier with a lithography scanner metrology system according to various aspects of the present disclosure;

[0009] Figure 8 and Figure 9 is a flow chart of a method for manufacturing a device according to various aspects of the present disclosure.

[0010]

Explanation of symbols

[0011] 10: System

[0012] 16: Curtain Station

[0013] 18: veil

[0014] 20: Supply System

[0015] 22:Semiconductor wafer

[0016] 24:Substrate table

[0017] 26: Mask layer

[0018] 30: Droplet Generator

[0019] 31: Liquid reservoir

[0020] 32: Nozzle assembly

[0021] 35: Droplet container

[0022] 40: Gas source

[0023] 41: Gas pipeline

[0024] 50:Laser generator

[0025] 51: Laser Pulse

[0026] 52:Lighting point

[0027] 55: Window

[0028] 60: Collector

[0029] 61: Optical axis

[0030] 65:Container wall

[0031] 66: Pump

[0032] 68: Pump

[0033] 70: Monitoring device

[0034] 71:Measuring tools

[0035] 73:Analyzer

[0036] 80: Target material / target fuel

[0037] 82: Droplets

[0038] 84:EUV light / EUV radiation

[0039] 88: Plasma

[0040] 90:Controller

[0041] 100: Lens system

[0042] 120: Light source

[0043] 140:Illuminator

[0044] 180:Projection optical module

[0045] 200: Monitoring components / measurement systems

[0046] 220: High-resolution capacitance measuring device / LCR meter / microcontroller

[0047] 222: Conductive thread

[0048] 224:Analog-to-digital converter

[0049] 226:Processor / Controller

[0050] 228: Siren

[0051] 230: Electrode

[0052] 231:Liquid reservoir

[0053] 232:Liquid reservoir

[0054] 233:Liquid reservoir

[0055] 250:Transmission pipeline

[0056] 270, 270A~270C: valve

[0057] 300, 500, 600, 700: sidewall

[0058] 330B: Electrode

[0059] 330L:Electrode

[0060] 330R:Electrode

[0061] 330T:Electrode

[0062] 330: Electrode

[0063] 332: Insulation layer

[0064] 333, 533, 633, 733: Liquid reservoir

[0065] 510, 610: bottom wall

[0066] 530H: horizontal electrode

[0067] 530V, 630V1~630V3: vertical electrode

[0068] 630C: Center electrode (area)

[0069] 630U, 732: base electrode

[0070] 630X: Extended electrode (area)

[0071] 734: Strip electrode

[0072] 800, 900: Craftsmanship

[0073] 810, 820, 825, 830, 840, 850, 910, 920, 930, 940: Operation

[0074] iv-iv: section line

[0075] X: X-axis direction

[0076] Y: Y-axis direction

[0077] Z: Z-axis direction DETAILED DESCRIPTION

[0078] The following disclosure provides many different embodiments or examples for implementing different features of the subject matter. Specific examples of components and arrangements are described below to simplify the disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the description below, forming a first feature above or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features so that the first and second features may not be in direct contact. In addition, the disclosure may repeat element symbols or letters in various examples. This repetition is for simplicity and clarity and does not, in itself, specify the relationship between the various embodiments or configurations discussed.

[0079] Furthermore, for ease of description, spatially relative terms, such as "below," "beneath," "beneath," "above," and "above," may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0080] Terms such as "about", "substantially", etc. may be used herein to facilitate description. Those skilled in the art will be able to understand and deduce the meaning of these terms.

[0081] The present disclosure relates generally to lithography equipment used to manufacture semiconductor devices, and more particularly to a tin supply apparatus and method that improves the continuous supply of liquid tin to a droplet generator of an extreme ultraviolet (EUV) lithography apparatus.

[0082] At advanced technology nodes, scaling down becomes increasingly challenging. Lithography techniques are employing shorter exposure wavelengths, including deep ultraviolet (DUV; approximately 193-248 nanometers, or "nm"), extreme ultraviolet (EUV; approximately 10-100 nm, particularly 13.5 nm), and X-rays (approximately 0.01-10 nm), to ensure precise patterning at these scaled-down dimensions. In an EUV scanner, EUV light is generated by a laser pulse striking a tin droplet. This light is then reflected onto the wafer by multiple mirrors and a reflective mask.

[0083] In the new generation of EUV light sources, the tin liquid can be refilled without stopping the lithography system. First, solid tin is inserted into a chamber, such as a low-pressure reservoir with a heater. The solid tin is then melted to form liquid tin, which is then transferred to another heated reservoir by applying a small pressure (e.g., 10 psi to 30 psi). This other heated reservoir is used for high-pressure operation. A communication tube is used to continuously drive the liquid tin from the high-pressure reservoir to a droplet generator, which forms microscale tin droplets and injects them into the source container.

[0084] Because the reservoir is heated (e.g., up to 250 degrees Celsius or higher) and at high pressure (e.g., up to 15,000 psi), high-pressure reservoirs cannot measure how much liquid tin is present. While liquid level can be calculated and simulated based on the timed consumption of solid tin, these calculations are highly unreliable and can lead to false alarms that the tin supply system has run out of tin. This is due, at a minimum, to mechanical tolerances in the delivery pipes, tin leaks in valves, and voids formed within the system. As a result, the tin supply system may be shut down by activating interlocks, and in worse cases, the tin supply system and / or lithography system may be damaged. Physical probes and weight measurements for direct liquid level measurement are unacceptable because any invasive method would reduce the tin supply system's ability to withstand high pressures. Furthermore, because the target liquid is metallic, any invasive probe or sensor could become contaminated. Sensors may also not survive or maintain reliability under the high-temperature and high-pressure operating conditions within the high-pressure reservoir.

[0085] In embodiments of the present disclosure, a level measurement system or monitoring assembly is included on a high-pressure reservoir used in an EUV light source, providing non-invasive and accurate level measurement of liquid tin inside the high-pressure reservoir. In these embodiments, a non-invasive method measures the level of high-pressure metal liquid. By measuring the capacitance and frequency response through a high-frequency signal input within the reservoir, the time-varying level of the liquid tin can be measured. The electrodes used to perform the measurement are formed by a highly conductive layer wrapped in an insulating layer. To improve the measurement quality, several electrode placement embodiments are provided. The electrode settings can be parallel or orthogonal to obtain better resolution. The shape of the electrodes can be stripes, rings, or any special geometric shape. Since there is no invasive device for measurement, the reservoir can withstand high voltage loads. The measurement system provides accuracy and personnel safety during the measurement of liquid tin level, and can further be used for alarm, safety and diagnostic issuance.

[0086] Figure 1A FIG. 1 is a simplified schematic diagram of a lithographic exposure system 10 according to some embodiments. The lithographic exposure system 10 is described in detail to facilitate understanding of a metrology system for a liquid tin reservoir that supplies liquid tin to a droplet generator of the lithographic exposure system 10 .

[0087] In some embodiments, the lithography exposure system 10 is an extreme ultraviolet (EUV) lithography system designed to expose a photoresist layer using EUV radiation, and may also be referred to as an EUV system 10. The EUV system 10 may also be referred to as an EUV scanner or a lithography scanner. According to some embodiments, the lithography exposure system 10 includes a light source 120, an illuminator 140, a mask stage 16, a projection optics module (or projection optics box (POB)) 180, and a substrate stage 24. Elements of the lithography exposure system 10 may be added or omitted, and the present disclosure is not limited to these embodiments.

[0088] In certain embodiments, light source 120 is configured to generate optical radiation having a wavelength between approximately 1 nm and approximately 100 nm. In one specific example, light source 120 generates EUV radiation having a wavelength centered at approximately or substantially 13.5 nm. Therefore, light source 120 is also referred to as an EUV radiation source. However, it should be understood that light source 120 should not be limited to emitting EUV radiation. Light source 120 may be used to perform any high-intensity photon emission from an excited target fuel.

[0089] In various embodiments, the illuminator 140 includes various refractive optical elements, such as a single lens or a lens system 100 having multiple reflectors, for example, a lens (zone plate) or alternative reflective optical devices (for EUV lithography exposure systems), such as a single mirror or a mirror system having multiple mirrors, to direct light from the light source 120 onto the mask stage 16, and particularly onto the mask 18 fixed to the mask stage 16. In embodiments where the light source 120 generates light in the EUV wavelength range, reflective optical devices are used. In some embodiments, the illuminator 140 includes at least two lenses, at least three lenses, or more lenses.

[0090] The mask stage 16 is used to hold a mask 18. In some embodiments, the mask stage 16 includes an electrostatic chuck to hold the mask 18. An electrostatic chuck is beneficial because gas molecules absorb EUV radiation and can be operated in a lithography exposure system for EUV lithography patterning that is maintained in a vacuum environment to prevent loss of EUV intensity. In this disclosure, the terms mask, reticle, and hood are used interchangeably. In this embodiment, the mask 18 is a reflective mask. An example structure for the mask 18 includes a substrate comprising a suitable material, such as a low thermal expansion material (LTEM) or fused silica. In various embodiments, the LTEM comprises TiO2-doped SiO2 or other suitable materials with low thermal expansion. The mask 18 comprises a reflective multilayer deposited on the substrate. The mask stage 16 is operable to translate in two horizontal directions, such as the X-axis and the Y-axis, to expose different regions of the semiconductor wafer 22 to light having a pattern generated by the mask 18. The semiconductor wafer 22 may have a mask layer 26 , which may be a photoresist layer sensitive to light carrying the pattern of the mask 18 .

[0091] Projection optics module (or projection optics box (POB)) 180 is used to image the pattern on mask 18 onto semiconductor wafer 22 mounted on substrate stage 24 of lithography exposure system 10. In some embodiments, POB 180 may include refractive optics (such as used in UV lithography exposure systems) or alternatively reflective optics (such as used in EUV lithography exposure systems). Light directed from mask 18 and carrying an image of the pattern on the mask is collected by POB 180. Illuminator 140 and POB 180 may be collectively referred to as the optical module of lithography exposure system 10. In some embodiments, POB 180 includes at least six reflective optics.

[0092] In some embodiments, semiconductor wafer 22 may be made of silicon or other semiconductor materials. Alternatively or additionally, semiconductor wafer 22 may include other basic semiconductor materials, such as germanium (Ge). In some embodiments, semiconductor wafer 22 is made of compound semiconductors such as silicon carbide (SiC), gallium arsenide (GaAs), indium arsenide (InAs), or indium phosphide (InP). In some embodiments, semiconductor wafer 22 is made of alloy semiconductors such as silicon germanium (SiGe), silicon germanium carbide (SiGeC), gallium arsenic phosphide (GaAsP), or gallium indium phosphide (GaInP). In some other embodiments, semiconductor wafer 22 may be a silicon-on-insulator (SOI) or germanium-on-insulator (GOI) substrate.

[0093] Furthermore, semiconductor wafer 22 may include various device elements. Examples of device elements formed in semiconductor wafer 22 include transistors (e.g., metal oxide semiconductor field effect transistors (MOSFETs), complementary metal oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), high-voltage transistors, high-frequency transistors, p-channel and / or n-channel field-effect transistors (PFETs / NFETs), etc.), resistors, capacitors, diodes, and / or other suitable components. Various processes are performed to form the device elements, such as deposition, etching, implantation, lithography, annealing, and / or other suitable processes. In some embodiments, semiconductor wafer 22 is coated with a photoresist layer that is sensitive to EUV radiation. Various elements, including those described above, are integrated together and are operable to perform lithography processes.

[0094] The lithography exposure system 10 may further include other modules or be integrated (or coupled) with other modules, such as a cleaning module designed to provide hydrogen to the light source 120 and a tin supply system designed to provide liquid tin to the light source 120. The hydrogen helps reduce contamination in the light source 120. For further description of the light source 120, see Figure 1B supply.

[0095] exist Figure 1B In some embodiments, light source 120 is shown in a simplified diagram. In some embodiments, light source 120 utilizes a dual-pulse laser produced plasma (LPP) mechanism to generate plasma 88 and further generates EUV radiation from the plasma. Light source 120 includes a droplet generator 30, a droplet container 35, a laser generator 50, a laser produced plasma (LPP) collector 60, a monitoring device 70, and a controller 90. Some or all of the aforementioned components of light source 120 may be maintained under vacuum. It should be understood that components of light source 120 may be added or omitted and are not limited by the embodiments.

[0096] The droplet generator 30 is used to generate a plurality of elongated droplets 82 of the target fuel 80 into an excitation region, where at least one laser pulse 51 from the laser generator 50 strikes the droplets 82. Figure 1B. In one embodiment, the target fuel 80 comprises tin (Sn). In one embodiment, the droplets 82 may be formed into an elliptical shape. In one embodiment, the droplets 82 are generated at a rate of approximately 50 kilohertz (kHz) and introduced into the excitation region of the light source 120 at a speed of approximately 70 meters per second (m / s). Other materials may also be used for the target fuel 80, such as a tin-containing liquid material, such as a eutectic alloy containing tin, lithium (Li), and xenon (Xe). The target fuel 80 in the droplet generator 30 may be in a liquid phase.

[0097] The laser generator 50 is configured to generate at least one laser pulse to convert the droplet 82 into plasma 88. In some embodiments, the laser generator 50 is configured to generate a laser pulse 51 to the illumination point 52 to convert the droplet 82 into plasma 88, which generates EUV radiation 84. The laser pulse 51 is directed through a window (or lens) 55 and irradiates the droplet 82 at the illumination point 52. The window 55 is formed in the segmented collector 60 and is made of a suitable material that is substantially transparent to the laser pulse 51. The droplet container 35 captures and collects unused droplets 82 and / or scattered material from the droplet 82 resulting from the laser pulse 51 striking the droplet 82.

[0098] The plasma emits EUV radiation 84 which is collected by the collector 60. The collector 60 further reflects and focuses the EUV radiation 84 for use in a lithography process performed by an exposure tool. In some embodiments, the collector 60 has an optical axis 61 that is parallel to the z-axis and perpendicular to the x-axis. The collector 60 may include a single portion, as shown, or at least two portions offset from each other in the z-axis direction. The collector 60 may further include a container wall 65 having a first pump 66 and a second pump 68 attached thereto. In some embodiments, the first pump 66 and the second pump 68 include a scrubber for removing particles and / or gases from the collector 60. The first pump 66 and the second pump 68 may be collectively referred to herein as "pumps 66, 68."

[0099] In an embodiment, the laser generator 50 is a carbon dioxide (CO2) laser source. In some embodiments, the laser generator 50 is used to generate a laser pulse 51 having a single wavelength. The laser pulse 51 is transmitted via an optical component for focusing and determining the angle of incidence of the laser pulse 51. In some embodiments, the laser pulse 51 has a spot size of approximately 200-300 μm, such as 225 μm. The laser pulse 51 is generated to have a certain drive power to meet a wafer production target, such as a yield of 125 wafers per hour (WPH). For example, the laser pulse 51 has a drive power of approximately 23 kW. In various embodiments, the drive power of the laser pulse 51 is at least 20 kW, such as 27 kW.

[0100] Monitoring device 70 is used to monitor one or more conditions in light source 120 to generate data for controlling configurable parameters of light source 120. In some embodiments, monitoring device 70 includes a metrology tool 71 and an analyzer 73. If metrology tool 71 is used to monitor the conditions of droplets 82 supplied by droplet generator 30, metrology tool 71 may include an image sensor, such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor. Metrology tool 71 generates a monitoring image including an image or video of droplets 82 and transmits the monitoring image to analyzer 73. If metrology tool 71 is used to detect the energy or intensity of EUV light 84 generated by droplets 82 in light source 120, metrology tool 71 may include a plurality of energy sensors. The energy sensors may be any suitable sensor capable of observing and measuring electromagnetic radiation energy in the ultraviolet region.

[0101] The analyzer 73 is configured to analyze the signals generated by the metrology tool 71 and output a detection signal to the controller 90 based on the analysis results. For example, the analyzer 73 includes an image analyzer. The analyzer 73 receives data associated with the image transmitted from the metrology tool 71 and performs image analysis processing on the image of the droplet 82 in the excitation region. The analyzer 73 then transmits the data related to the analysis to the controller 90. The analysis may include flow path error or position error.

[0102] In some embodiments, two or more metrology tools 71 are used to monitor different conditions of the light source 120. One metrology tool 71 is used to monitor the condition of the droplets 82 supplied by the droplet generator 30, and another metrology tool 71 is used to detect the energy or intensity of EUV light 84 generated by the droplets 82 in the light source 120. In some embodiments, the metrology tool 71 is a final focus module (FFM) and is positioned in the laser generator 50 to detect light reflected from the droplets 82.

[0103] The controller 90 is configured to control one or more components of the light source 120. In some embodiments, the controller 90 is configured to drive the droplet generator 30 to generate droplets 82. Furthermore, the controller 90 is configured to drive the laser generator 50 to emit laser pulses 51. The controller 90 can control the generation of the laser pulses 51 to be associated with the generation of the droplets 82, so that the laser pulses 51 sequentially strike each droplet 82.

[0104] In some embodiments, the droplet generator 30 includes a reservoir 31 and a nozzle assembly 32. The reservoir 31 is used to contain a target material 80. In some embodiments, a gas line 41 is connected to the reservoir 31 for pumping gas (such as argon) from a gas source 40 into the reservoir 31. By controlling the gas flow in the gas line 41, the pressure in the reservoir 31 can be manipulated. For example, when gas is continuously supplied to the reservoir 31 via the gas line 41, the pressure in the reservoir 31 increases. Therefore, the target material 80 in the reservoir 31 can be forced to leave the reservoir 31 in the form of droplets 82. The reservoir 31 receives the target material 80, such as liquid tin, from a target supply system, which may include one or more low-pressure reservoirs and one or more high-pressure reservoirs. See below Figures 2 to 7 The target supply system according to various embodiments is described in detail. The operation of the target supply system during the manufacture of an integrated circuit (IC) device is described with reference to Figure 8 and Figure 9 The flowchart depicted in FIG.

[0105] Figure 2 FIG2 is a simplified diagram of a supply system 20 for supplying target material to a droplet generator 30 of a light source 120 according to various embodiments. The supply system 20 may be referred to interchangeably herein as a target supply system, a tin supply system, or a liquid tin supply system. The supply system 20 is monitored by a metrology system or "monitoring assembly" 200 that provides non-invasive measurement of the target material level in one or more reservoirs.

[0106] The supply system 20 includes a first liquid reservoir 231 , a second liquid reservoir 232 , one or more third liquid reservoirs 233 , a delivery line 250 , and a valve 270 .

[0107] The first reservoir 231 may be a low-pressure reservoir and may be referred to as the low-pressure reservoir 231. The first reservoir 231 may receive solid tin and heat it to form liquid tin, which may be transferred to the second reservoir 232. In some embodiments, the low-pressure reservoir 231 includes one or more reservoir containers, a heater, a pressure controller, an insulating jacket or wall, an access port, and a pressure monitoring and / or control interface. The reservoir container may be a non-reactive container capable of holding the solid tin. The container may be made of a high-strength, non-corrosive material such as stainless steel or an alloy with similar properties. The container is advantageously designed to withstand the range of operating temperatures and pressures associated with storing solid tin in a stable phase. A pressure controller may be integrated into the reservoir container. The pressure controller can regulate the internal pressure of the container to maintain the pressure within a selected low-pressure range. The pressure controller may include a pressure sensor, a regulator, and / or a safety valve to facilitate maintaining the pressure at a level conducive to melting the solid tin to form liquid tin. The reservoir container may be surrounded by an insulating jacket or wall. The wall acts as a thermal barrier, preventing external temperature fluctuations from affecting the stability of the tin within the reservoir container. An access port with a securely sealable lid may be provided on the reservoir container to allow solid tin to be loaded into the reservoir container and selectively removed. The access port is operable to form an airtight seal to prevent leakage of gas or solid tin. An external interface may be included in the first reservoir 231 for an operator to monitor the internal pressure and adjust the pressure controller accordingly. The interface may include a pressure gauge, an electronic sensor, a control knob or button, etc.

[0108] The liquid tin produced by the first reservoir 231 can be transferred to the second reservoir 232 via one of the transfer lines 250. A small pressure, such as about 10 psi to 30 psi, can be applied to the first reservoir 231 to transfer the liquid tin to the second reservoir 232. The second reservoir 232 can be similar to the first reservoir 231 in most aspects, but with some minor differences related to the second reservoir 232 containing liquid tin rather than primarily solid tin. The second reservoir 232 can be used to store tin in a liquid phase and transfer the liquid tin to the third reservoir 233. The second reservoir 232 can include or be connected to one of the valves 270, such as Figure 2 For example, valve 270 can be mounted on second reservoir 232, integrally formed with second reservoir 232, or connected to second reservoir 232 via one of delivery lines 250. A small pressure (e.g., approximately 10 psi to 30 psi) can be applied to second reservoir 232 to deliver liquid tin to delivery line 250 for delivery to third reservoir 233.

[0109] The valve 270 can be any suitable valve for controlling the flow of liquid tin from the second liquid reservoir 232 into the delivery line 250. For example, the valve 270 can be a ball valve, a spherical valve, a gate valve, a butterfly valve, a plug valve, a diaphragm valve, a needle valve, etc.

[0110] The third reservoir 233 may be a high-pressure reservoir, which provides various benefits for supplying liquid tin to the droplet generator 30 and forming the tin droplets 82 used to generate EUV light 84. To achieve high EUV light output, a large number of tin droplets are generated and efficiently converted into plasma. The high-pressure reservoir facilitates the storage and rapid release of liquid tin droplets, enabling a continuous and intense EUV light production process. EUV light generation benefits from smaller tin droplets, which may help improve conversion efficiency. A high-pressure reservoir with a carefully designed nozzle or orifice facilitates the production of tin droplets within a selected size range, thereby improving the conversion process. The high-pressure release of the tin droplets can lead to better plasma formation during the laser-target interaction, resulting in more intense and stable EUV light emission, thereby improving the performance and reliability of the EUV light source. In pulsed mode, where the laser and droplet generation are synchronized, the high-pressure reservoir facilitates the precise timing of droplet delivery, aligning with the laser pulses and ensuring consistent and controlled EUV light emission.

[0111] The third reservoir 233 can be similar in many aspects to the low-pressure reservoirs 231 and 232, but with some differences to accommodate holding liquid tin at much higher pressures. For example, the high-pressure reservoir 233 is used to store material under high pressure, such as at a pressure above atmospheric pressure. The pressure within the high-pressure reservoir may be several times greater than the ambient pressure. Therefore, the high-pressure reservoir 233 is designed to withstand the forces exerted by the high internal pressure. For example, the high-pressure reservoir 233 can be constructed using durable materials that can safely withstand high pressures, such as high-strength alloys or thick-walled containers that help maintain the reservoir's structural integrity. The high-pressure reservoir 233 can incorporate more complex pressure control components to regulate the pressure within a safe operating range and prevent overpressure. Some examples of pressure control components may include pressure relief valves, pressure sensors and transmitters, proportional-integral-derivative (PID) controllers, pressure regulators, solenoid valves, flow control valves, computer control systems, emergency shutdown systems, and the like.

[0112] like Figure 2 As depicted, in some embodiments, the supply system 20 includes two high pressure reservoirs 233. Valves 270B, 270C may be located between valve 270A attached to the second reservoir 232 and the respective high pressure reservoirs 233, as shown. Figure 2In the depicted embodiment, valve 270B is in direct fluid communication with valve 270A via a delivery line 250, and valve 270C is in indirect fluid communication with valve 270A via valve 270B and an additional delivery line 250. Each valve 270B, 270C can be connected to a respective high-pressure reservoir 233 via another delivery line 250, as shown. Each valve 270B, 270C can be a two-way valve that allows fluid to flow into and out of the high-pressure reservoir 233.

[0113] The high-pressure reservoirs 233 are in fluid communication with the droplet generator 30 via another delivery line 250. Using the delivery line 250, liquid tin from the high-pressure reservoirs 233 can be continuously driven to the droplet generator 30 to form micro-scale droplets 82 and inject these micro-scale droplets 82 into the source container. Each high-pressure reservoir 233 can deliver liquid tin directly to the droplet generator 30 via a valve 270 and the delivery line 250. In some embodiments, one of the high-pressure reservoirs 233 delivers liquid tin to the droplet generator 30 indirectly via the other high-pressure reservoir 233, so that one high-pressure reservoir can serve as a reserve storage for the other high-pressure reservoir.

[0114] The high-pressure reservoir 233 is used to continuously drive liquid tin to the droplet generator 30. However, when the liquid tin level is too low or is incorrectly determined to be too low, the supply system may stop operating. For example, an interlock may be activated, and in worse cases, the supply system 20 and / or the lithography system 10 may be damaged. Therefore, the supply system 20 includes a monitoring assembly 200 that is non-invasive and provides high-precision measurement of the liquid tin level in the high-pressure reservoir 233. This can avoid the above-mentioned problems and help achieve continuous delivery of liquid tin to the droplet generator 30 without sudden stops, which may damage the supply system 20 and / or the lithography system 10.

[0115] Figure 2 A monitoring assembly 200 is depicted in operation to measure capacitance associated with the level of liquid tin in a reservoir 233. The monitoring assembly 200 has at least two electrodes 230 attached to the exterior of the reservoir 233 and includes one or more of a high-resolution capacitance measuring device 220 (e.g., an LCR meter 220 or a microcontroller 220), an analog-to-digital converter (ADC) 224, a processor or controller 226, and an alarm 228. The arrangement and structure of the electrodes 230 are described with reference to FIG. Figures 3A to 7 Describe in more detail.

[0116] The LCR meter 220 is operable to measure inductance, capacitance, and / or resistance at two or more input ports. In some embodiments, the LCR meter 220 is operable to measure capacitance via a frequency input. Each input port can be electrically connected to one of the electrodes 230 via a conductive line 222, such as a cable or wire. Thus, the LCR meter 220 is operable to measure capacitance at two or more electrodes 230 attached to one or more corresponding walls of one of the reservoirs 233. The LCR meter 220 can output an analog signal (e.g., an analog voltage) associated with the measured capacitance via an output port.

[0117] In some embodiments, the LCR meter 220 measures capacitance using a four-terminal pair measurement device. The measurement can be performed in parallel or in series. In some embodiments, the impedance of the LCR meter 220 used during parallel measurements can be approximately 10 kilo-ohms. In some embodiments, the impedance of the LCR meter 220 used during series measurements can be approximately 10 ohms. The LCR meter 220 can input a frequency-varying signal, such as a high-frequency signal, and respond at the frequency of the measurement electrode 230. The signal frequency can be approximately 1 kilohertz (kHz), 100 kHz, 1 MHz, etc.

[0118] The capacitance of electrode 230 may be proportional to the volume of liquid tin in reservoir 233. For example, the capacitance may increase as the volume of liquid tin increases, and may decrease as the volume of liquid tin decreases. In some embodiments, for liquid tin of approximately 0 cm to approximately 5 cm, the capacitance may range between two values ​​in picofarads (pF), such as between approximately 170 pF and approximately 171 pF or between approximately 157 pF and approximately 158 pF. These are merely examples, and other values ​​may be associated with the level of liquid tin in reservoir 233. These values ​​may vary depending on the size and position of electrode 230, the frequency used by LCR meter 220 to measure capacitance (e.g., 1 kHz, 100 kHz, 1 MHz, etc.), the structure and material composition of electrode 230, the structure and material composition of the walls of reservoir 233, etc.

[0119] In some embodiments, the change in capacitance value is related to the level (e.g., height) of liquid tin in reservoir 233. For example, the capacitance value may increase by approximately 0.1 pF for each additional centimeter of liquid tin in reservoir 233, such as approximately 0.04 pF / cm, 0.08 pF / cm, 0.1 pF / cm, 0.12 pF / cm, or other values. The change in capacitance value may vary based on the frequency used by LCR meter 220 to measure capacitance. For example, a lower frequency may be associated with a higher capacitance value change (e.g., 0.12 pF / cm for a 1 kHz measurement frequency), and a higher frequency may be associated with a lower capacitance value change (e.g., 0.08 pF / cm for a 1 MHz measurement frequency). The noise level associated with capacitance measurement may vary depending on the frequency used to measure capacitance. For example, a higher frequency may be associated with a lower noise level, and a lower frequency may be associated with a higher noise level. Thus, in some embodiments, the LCR meter 220 may measure capacitance within a frequency range of about 50 kHz to about 200 kHz, such as about 100 kHz or substantially 100 kHz.

[0120] ADC 224 can be any suitable analog-to-digital converter and can be operated to output a digital signal (e.g., a sequence of high and low voltages) associated with the analog voltage output by LCR meter 220. The digital signal is associated with the capacitance of electrode 230. In some embodiments, ADC 224 is included in LCR meter 220. For example, LCR meter 220 can be a digital meter that outputs a digital signal representing the capacitance of electrode 230.

[0121] The processor or controller 226 can be any suitable processor, microprocessor, controller, microcontroller, etc., and can be operable to execute one or more instructions based on the digital signal output by the ADC 224. For example, the processor 226 can store the digital signal as a stored value in a memory (e.g., a register), compare the stored value with a selected threshold value, and output a control signal when the stored value exceeds or falls below the threshold value. Because the value stored based on the digital signal is associated with the capacitance of the electrode 230, the digital signal is based on the analog signal measured by the LCR meter 220.

[0122] To detect a low level of liquid tin in reservoir 233, the threshold value may be a low value associated with a low capacitance, which is associated with a low level of liquid tin. When the stored value is less than the low value, processor 226 may execute instructions to generate a low tin level signal that may trigger an action. For example, alarm 228 may be in data or electrical communication with processor 226. When the low tin level signal is generated, alarm 228 may be triggered to emit an audible sound. Alarm 228 may be operable to generate an audible sound that alerts a human operator to the low tin level in reservoir 233. In some embodiments, the triggered action may be generating a visual notification or alarm on a display device of a user interface, such as a computer terminal operated by a human operator. In some embodiments, the triggered action may be continuously outputting an estimated tin level in reservoir 233 to the user interface. The estimated tin level may be a percentage, a volume value (e.g., liters remaining), etc. In some embodiments, the triggered action may be an automatic routine that performs one or more of refilling the first reservoir 231 with solid tin, placing the lithography system 10 in a soft-off mode, or other appropriate actions to protect the lithography system 10 and / or the supply system 20 from damage due to depletion of liquid tin.

[0123] Figure 3A and Figure 3B FIG. 3 is a diagrammatic perspective view of electrodes 330B, 330T, 330L, and 330R arranged on a reservoir 333 according to various embodiments. The electrodes 330B, 330T, 330L, and 330R may be collectively referred to as electrodes 330 and may be used interchangeably with reference to FIG. Figure 2 The electrode 230 described above is the same or similar. The reservoir 333 can be the same as that described in reference Figure 2 The reservoir 233 described is the same or similar, such as the high pressure reservoir 333 that operates to store liquid tin and provide the liquid tin to the droplet generator 30 . Figure 4 For the Figure 3A A diagrammatic cross-sectional view of electrode 330 is shown along section line iv-iv.

[0124] exist Figure 3A , the top electrode 330T is attached to the upper portion of the side wall 300 of the reservoir 333, and the bottom electrode 330B is attached to the bottom portion of the side wall 300. The top electrode 330T and the bottom electrode 330B do not overlap each other. For example, the top electrode 330T can be attached to a first side of the side wall 300, and the bottom electrode 330B can be attached to a second side of the side wall 300 opposite the first side (e.g., offset 180 degrees for a cylindrical reservoir 333). The top electrode 330T can be offset from the bottom electrode 330B along the vertical or height axis of the reservoir 333 (e.g., in the Z-axis direction) by approximately the height of the reservoir 333. It should be understood that the top electrode 330T and the bottom electrode 330B shown in FIG. Figure 3A, with the top or lid omitted from view. References to the "height" of reservoir 333 generally refer to the liquid tin storage portion of reservoir 333 and do not include the height of the top or lid. Similarly, the bottom of reservoir 333 may have a thickness that helps prevent reservoir 333 from bursting under high pressure. This thickness may also be omitted from the "height" of reservoir 333. That is, top electrode 330T and bottom electrode 330B may each partially or completely overlap the liquid tin storage portion of reservoir 333, which may facilitate obtaining a clear reading of the liquid tin level in reservoir 333.

[0125] exist Figure 3B , the right electrode 330R and the left electrode 330L can be attached to opposite sides of the sidewall 300. The right electrode 330R and the left electrode 330L can overlap each other along the Z axis without being offset from each other along the Z axis. The overlap can be partial or complete. The right electrode 330R and the left electrode 330L can be offset from each other by a certain distance along the circumference of the sidewall 300 as shown (for example, in the XY plane). The distance can be, for example, about one-quarter of the circumference of the sidewall 300. In some embodiments, the distance is between about 1 / 8 of the circumference and about 1 / 3 of the circumference. A closer distance can correspond to a larger electrode, while a farther distance can correspond to better isolation between the two electrodes.

[0126] exist Figure 4 In the embodiment of the present invention, each electrode 330 (or electrode 230) may include a conductive layer 336 surrounded by an insulating layer 332. The conductive layer 336 may be or include a highly conductive material such as copper, tin, silver, gold, aluminum, tantalum, zinc, nickel, alloys, and / or multiple layers or combinations thereof. The thickness of the conductive layer 336 may range from approximately 20 microns to approximately 1000 microns. In some embodiments, the conductive layer 336 is a copper foil having a thickness of approximately 50 microns. The insulating layer 332 may be a dielectric material capable of electrically insulating the conductive layer 336 from the reservoir 333. For example, the insulating layer 332 may be or include a polymer (e.g., polytetrafluoroethylene, polyethylene, polypropylene, polyurethane, etc.), silicone rubber, glass, ceramic, or a combination thereof. Materials with a low coefficient of thermal expansion, such as borosilicate glass, aluminum oxide, or steatite ceramic, may be advantageous in reducing variations in the distance between the conductive layer and the liquid tin in the reservoir 333, which may improve the uniformity of the capacitance readings of the LCR meter 220. The insulating layer 332 is attached to the side wall 300 of the reservoir 333. The insulating layer 332 may be attached to the side wall 300 via a separate adhesive layer (omitted from the drawing), or the surface of the insulating layer 332 facing the side wall 300 may be the adhesive itself.

[0127] Figure 5 533 is a diagrammatic perspective view of another reservoir 533 having vertical electrodes 530V and horizontal electrodes 530H on the side wall 500 and bottom wall 510, respectively. The reservoir 533 can be used in most cases in the same manner as the reference Figures 2 to 3B The horizontal electrodes 530H and the vertical electrodes 530V may be collectively referred to as electrodes 530 and may be used interchangeably with the reference electrodes 530 in most cases. Figures 2 to 4 The electrodes 230, 330 described are the same or similar.

[0128] The horizontal electrode 530H can be attached to the bottom wall 510 of the reservoir 533, can overlap the center or diameter of the bottom wall 510, and can extend from one edge of the bottom wall 510 to the other edge of the bottom wall 510. In some embodiments, the horizontal electrode 530H is offset from the center or diameter of the bottom wall 510. For example, the horizontal electrode 530H can be located between the vertical electrode 530V and the center of the bottom wall 510, or the center of the bottom wall 510 can be located between the horizontal electrode 530H and the vertical electrode 530V. In some embodiments, the horizontal electrode 530H extends past at least one edge of the bottom wall 510, such as Figure 5 In some embodiments, the horizontal electrode 530H has one or both ends terminated at the short edge of the bottom wall 510 .

[0129] The electrodes 530 may be substantially flat along their lengths. The horizontal electrodes 530H may be flat along their lengths and widths. The vertical electrodes 530V may have a curvature along their widths that is substantially conformal to the curvature of the sidewalls 500. Figure 3A and Figure 3B Compared to the arrangement of electrodes 330 described, as Figure 5 The "orthogonal" arrangement of electrodes shown can have a capacitance change resolution that is as much as 2.5 times better. That is, when vertical electrodes 530V and horizontal electrodes 530H are arranged orthogonally to each other instead of diagonally to each other ( Figure 3A ) or relative to each other ( Figure 3B ) electrodes 330, the capacitance change per centimeter of liquid tin level in the reservoir can be about 2.5 times. For example, electrodes 330 that are diagonally opposite each other can be associated with a capacitance change of about 0.04 pF / cm, while orthogonal electrodes 530 can be associated with a capacitance change of about 0.1 pF / cm. Another advantage associated with perpendicular electrodes 530V is sensitivity to changes in the liquid tin level along the entire height of the reservoir 533.

[0130] Figure 6 FIG. 6 is a diagrammatic perspective view of another reservoir 633 having a plurality of vertical electrodes 630V1, 630V2, 630V3 and a base electrode 630U having a core electrode or central electrode region 630C and an extended electrode or extended electrode region 630X on the sidewall 600 and bottom wall 610, respectively. The reservoir 633 can be similar to the reference 633 in most cases. Figures 2 to 5The vertical electrodes 630V1, 630V2, 630V3 and the base electrode 630U may be collectively referred to as electrodes 630 and may be used interchangeably with the reference electrodes 630 in most cases. Figures 2 to 5 The electrodes 230, 330, 530 described are the same or similar.

[0131] exist Figure 6 In the embodiment, the electrode 630 includes three vertical electrodes 630V1, 630V2, and 630V3, which can facilitate amplification of the measured capacitance. The vertical electrodes 630V1, 630V2, and 630V3 can be evenly distributed around the circumference of the liquid reservoir 633 (e.g., offset by 120 degrees from each other), as shown, or can be irregularly distributed around the circumference of the liquid reservoir 633. The vertical electrodes 630V1, 630V2, and 630V3 can each have the same width, or can have different widths in the circumferential direction of the liquid reservoir 633.

[0132] The base electrode 630U can be attached to the bottom wall 610 of the reservoir 633 and can include a core or central electrode region 630C and an extended electrode region 630X. The base electrode 630U can be a continuous, unitary body. That is, the extended electrode region 630X can extend continuously from the central electrode region 630C rather than being a separate component attached thereto. The central electrode 630C can have a center aligned with the center of the bottom wall 610. The diameter of the central electrode 630C can be approximately half the diameter of the bottom wall 610. In some embodiments, the diameter of the central electrode 630C ranges from approximately 1 / 10 to approximately 3 / 4 the diameter of the bottom wall 610. The extended electrode 630X can extend from the central electrode 630C to the outer edge of the bottom wall 610. In some embodiments, the extended electrode 630X extends to a liquid level between approximately 2 / 3 and approximately the entire diameter of the bottom wall 610. The extended electrodes 630X may be arranged equidistantly between adjacent pairs of vertical electrodes 630V1, 630V2, and 630V3. For example, one of the extended electrodes 630X may be arranged between vertical electrode 630V1 and vertical electrode 630V2. One of the extended electrodes 630X may be equidistant from the vertical electrodes 630V1 and 630V2, or may be closer to one of the vertical electrodes 630V1 and 630V2 than the other.

[0133] Figure 7 FIG. 7 is another diagrammatic perspective view of another reservoir 733 having a strip electrode 734 and a base electrode 732. The reservoir 733 can be used in most cases in conjunction with the reference Figures 2 to 6 The reservoirs 233, 333, 533, 633 described above are the same or similar. The strip electrodes 734 and the base electrodes 732 can be used in most cases in conjunction with the reference Figures 2 to 6 The electrodes 230, 330, 530, 630 described are the same or similar.

[0134] exist Figure 7 In the embodiment, base electrode 732 is attached to the bottom wall of reservoir 733 and may have a circular or other suitable shape. Base electrode 732 may have a center aligned with the center of the bottom wall of reservoir 733. The diameter of the base electrode may range from about 1 / 4 to about the entire diameter of the bottom wall of reservoir 733. In some embodiments, base electrode 732 is offset from the center of the bottom wall.

[0135] The ribbon electrode 734 can be useful for accurate liquid level sensing within a selected liquid level range. The ribbon electrode 734 is attached to and extends completely around the circumference of the sidewall 700. In some embodiments, the ribbon electrode 734 may not extend completely around the circumference, but may extend substantially around the circumference, such as extending around more than 80% of the circumference. In some embodiments, the ribbon electrode 734 is located in the lower half of the reservoir 733, which can be useful for obtaining an accurate measurement of the liquid level when the liquid level is low or the liquid tin is nearly depleted (e.g., the reservoir 733 is nearly empty). For example, the ribbon electrode 734 can be located at a liquid level between approximately the bottom of the reservoir 733 and approximately halfway up the height of the reservoir 733.

[0136] It should be understood that in other embodiments, reference Figures 2 to 7 The various electrodes of the various embodiments described may be combined or replaced. For example, the base electrode 732 may be Figure 5 The horizontal electrode 530H or Figure 6 In another example, Figure 7 The reservoir 733 may have one or more strip electrodes 734 attached thereto, and the one or more strip electrodes 734 may be arranged offset from each other along the height of the reservoir 733 (eg, in the Z-axis direction).

[0137] Figure 8 and Figure 9 Flowcharts of processes 800, 900 according to various embodiments. In some embodiments, process 800 for forming a device includes a number of operations (810, 820, 830, 840, and 850). In some embodiments, process 900 for monitoring the level of liquid tin includes a number of operations (910, 920, 930, and 940). Processes 800, 900 will be further described according to one or more embodiments. It should be noted that the operations of processes 800, 900 may be rearranged or otherwise modified within the scope of various aspects. It should be further noted that additional processes may be provided before, during, and after processes 800, 900, and some other processes may be only briefly described herein. In some embodiments, processes 800, 900 are Figures 1A to 7 The lithography exposure system 10, the supply system 20 and the measurement system 200 described in the embodiment are executed. Figures 1A to 7The structural elements described in illustrative embodiments are described, but processes 800 and 900 may be performed by a lithography exposure system, a supply system, and a metrology system having one or more structural elements that are different from the structural elements of the lithography system 10, the supply system 20, and the metrology system 200.

[0138] In operation 810, tin is supplied from a low-pressure reservoir (e.g., reservoir 232) to a high-pressure reservoir (e.g., reservoir 233). The tin may be liquid tin formed from solid tin melted in another low-pressure reservoir (e.g., reservoir 231) that is upstream of the low-pressure reservoir that supplies the high-pressure reservoir. Tin may be supplied to the high-pressure reservoir, as described with reference to FIG. Figure 2 As stated.

[0139] In operation 820, liquid tin is supplied from the high-pressure reservoir to the droplet generator (e.g., droplet generator 30). Operations 810 and 820 can be performed simultaneously. For example, when the supply of liquid tin from the high-pressure reservoir to the droplet generator depletes the liquid tin in the high-pressure reservoir, the low-pressure reservoir can supply additional liquid tin to the high-pressure reservoir to maintain a substantially constant level of liquid tin in the high-pressure reservoir.

[0140] During the supply of liquid tin from the high pressure reservoir to the droplet generator in operation 820, the level of the liquid tin in the high pressure reservoir is monitored in operation 825. The level of the liquid tin is monitored with reference to Figure 2 That is, the capacitance associated with the liquid level can be electrically connected to the electrodes (such as reference Figures 3A to 7 The monitoring of operation 825 can be performed by Figure 2 The processor 226 receives the digital signal from the ADC 224 or alternatively receives the digital signal from the LCR meter 220. Operation 825 may be a process including multiple operations. Figure 9 Process 900 is depicted as one embodiment of operation 825 .

[0141] In operation 830, tin droplets (e.g., Figure 1B Tin droplets 82) are generated by a droplet generator, which can be similar to the reference Figure 1A and Figure 1B Described droplet generator.

[0142] In operation 840, light is generated from the tin droplets. Figure 1A and Figure 1B The generation of EUV light from tin droplets is described in detail.

[0143] In operation 850, light generated from the tin droplets is used to form a pattern on the semiconductor wafer. For example, the radiation is reflected from the collector 60 and directed toward the mask layer 26. The radiation is reflected along the optical path between the collector 60 and the mask layer 26, which may be on the semiconductor wafer 22, such as Figure 1A As described. In some embodiments, radiation is reflected according to a pattern, such as that present on mask 18, which may be a reflective mask. The radiation may be EUV light having a wavelength centered around approximately 13.5 nm. The radiation having the pattern may expose a photosensitive layer, such as a photoresist, on the surface of the wafer, causing the pattern to be transferred to the photosensitive layer. An opening may then be formed in mask layer 26 by removing the patterned areas of mask layer 26 exposed to the radiation. In some embodiments, the opening may be formed by removing areas of mask layer 26 not exposed to the radiation. One or more layers of material beneath mask layer 26 are then removed to form a second opening. The removed material is located in the areas of the layer exposed by the opening in mask layer 26. In some embodiments, the layer is a dielectric layer, a semiconductor layer, or another layer. Features are then formed in the second opening in the layer. For example, source / drain regions may be epitaxially grown in the second opening. In another example, metal traces may be deposited in the second opening. In yet another example, a gate structure comprising a high-k dielectric layer and a metal layer is formed in the second opening.

[0144] Figure 9 is a flow chart of process 900, which is Figure 8 The process 900 may be performed to monitor the level of liquid tin in the reservoir.

[0145] Process 900 begins at operation 910, where capacitance is measured by an electrode attached to a reservoir containing liquid tin. Operation 910 may be referred to as Figure 2 The measurement may include inputting a high frequency analog signal to the electrode 230 and measuring the frequency response by the LCR meter 220. The operation of the LCR meter 220 is described with reference to Figure 2 Detailed description.

[0146] In operation 920, the digitized capacitance measurement associated with the frequency response is output to, for example, a processor or controller (e.g., processor 226). The digitized capacitance measurement may be referenced to Figure 2 The analog signal output by the LCR meter 220 can be converted to a digital signal by the ADC 224 to generate a digital capacitance measurement. In some embodiments, when the LCR meter 220 is a digital meter capable of directly outputting a digital signal rather than an analog signal, the LCR meter 220 outputs a digital signal.

[0147] In operation 930, it is determined whether the capacitance C of the electrode is less than the low liquid level threshold C lowThis determination can be made by referring to Figure 2 For example, the processor 226 may store the capacitance value in a temporary register of the memory based on the digital signal, and then compare the capacitance value with the low liquid level threshold C low Based on the comparison result, the processor 226 can determine whether the capacitance value exceeds or is less than the low liquid level threshold C low When the capacitance exceeds the low level threshold C low When the liquid level of the liquid tin in the reservoir is higher than the low level for which notification should be issued, the process 900 continues with operations 910 and 920 to measure the capacitance of the electrode. low When the processor 226 can take reference Figure 2 Any of the actions described above, such as generating a notification that the liquid tin level is low in operation 940, may be performed. In some embodiments, instead of or in addition to generating a notification in operation 940, the processor 226 may output a continuous measurement of the liquid tin level in the reservoir by outputting the capacitance value to a monitoring system, such as a supervisory control and data acquisition (SCADA) system, a manufacturing execution system (MES), etc. For example, the continuous measurement may be a percentage, a volume of liquid tin, or other suitable measurement that can be displayed on a user interface of a user terminal.

[0148] Embodiments may provide advantages. A measurement system 200 includes electrodes attached to a high-pressure reservoir, allowing for non-invasive and accurate measurement of the liquid tin level in the high-pressure reservoir. Improved liquid tin level measurement reduces sudden stops in the liquid tin flow, thereby protecting the lithography system 10 and the supply system 20 and reducing downtime for repair and restart of the lithography system 10 and / or the supply system 20.

[0149] According to at least one embodiment, a method includes the following steps: forming a mask layer on a semiconductor wafer; forming tin droplets, including the following steps: supplying tin from a low-pressure tank to a high-pressure tank; monitoring the tin level in the high-pressure tank via at least two electrodes attached to the high-pressure tank; supplying tin from the high-pressure tank to a droplet generator in response to the tin level exceeding a threshold; and forming tin droplets using the tin supplied from the high-pressure tank via the droplet generator; generating light from the tin droplets; and patterning the mask layer using the light. In some embodiments of the present disclosure, monitoring the tin level includes measuring a capacitance value via an ammeter coupled to the at least two electrodes. In some embodiments of the present disclosure, measuring the capacitance value includes applying an alternating current signal to the at least two electrodes, wherein the frequency of the alternating current signal is in the range of 1 kHz to 1 MHz. In some embodiments of the present disclosure, the step of monitoring the tin liquid level includes applying a signal to the at least two electrodes, the at least two electrodes including: a first electrode attached to a side wall of the high-pressure liquid reservoir at a first vertical level; and a second electrode attached to the side wall at a second vertical level offset from the first vertical level. In some embodiments of the present disclosure, the first electrode and the second electrode are located on opposite sides of the high-pressure liquid reservoir along a horizontal direction. In some embodiments of the present disclosure, the step of monitoring the tin liquid level includes applying a signal to the at least two electrodes, the at least two electrodes including: a first electrode extending vertically along a side wall of the high-pressure liquid reservoir; and a second electrode extending horizontally along a base of the high-pressure liquid reservoir. In some embodiments of the present disclosure, the step of monitoring the tin liquid level includes applying a signal to the at least two electrodes, the at least two electrodes including: a first electrode attached to a base of the high-pressure liquid reservoir; and at least two second electrodes extending vertically along a side wall of the high-pressure liquid reservoir. In some embodiments of the present disclosure, the first electrode includes an inner portion and at least two extensions extending outward from the inner portion, and the at least two second electrodes are located in a plurality of gaps between the at least two extensions. In some embodiments of the present disclosure, the step of monitoring the tin liquid level includes applying a signal to the at least two electrodes, the at least two electrodes including: a first electrode attached to a base of the high-pressure liquid reservoir; and a second electrode completely surrounding a sidewall of the high-pressure liquid reservoir.

[0150] According to at least one embodiment, a method includes the steps of forming tin droplets, including the steps of: monitoring a tin level in a reservoir via at least two electrodes attached to the reservoir; supplying tin to a droplet generator in the reservoir in response to the tin level exceeding a threshold; forming tin droplets using the tin supplied from the reservoir via the droplet generator; and generating extreme ultraviolet (EUV) light from the tin droplets. In some embodiments of the present disclosure, monitoring the tin level includes: measuring a capacitance via an LCR meter connected to the at least two electrodes; generating a digital capacitance via an analog-to-digital converter connected to the LCR meter; determining the tin level via a processor connected to the analog-to-digital converter; and generating a notification in response to the tin level falling below the threshold. In some embodiments of the present disclosure, generating the notification includes generating an alarm. In some embodiments of the present disclosure, generating the notification includes outputting real-time data associated with the tin level. In some embodiments of the present disclosure, the method further includes controlling the supply of tin to the reservoir based on the real-time data.

[0151] In accordance with at least one embodiment, a system includes a light source comprising a droplet generator; a reservoir in fluid communication with the droplet generator; a monitoring assembly operable to measure capacitance associated with a tin level in the reservoir, the monitoring assembly having at least two electrodes attached to an exterior of the reservoir; a collector operable to form a light beam based on tin droplets formed by the droplet generator; and at least one reflector operable to direct the light beam onto a wafer table.

[0152] According to at least one embodiment, a lithography system includes a light source and at least one reflector. The light source includes a droplet generator, a reservoir, a monitoring assembly, and a collector. The reservoir is in fluid communication with the droplet generator. The monitoring assembly has at least two electrodes connected to the exterior of the reservoir. The collector is located below the droplet generator. The reflector is optically coupled to the collector. In some embodiments of the present disclosure, the at least two electrodes include: a first electrode attached to a sidewall of the reservoir; and a second electrode attached to a base of the reservoir. In some embodiments of the present disclosure, the first electrode completely surrounds the sidewall. In some embodiments of the present disclosure, the at least two electrodes include: a first electrode extending vertically along a sidewall of the reservoir; and a second electrode extending horizontally along a base of the reservoir. In some embodiments of the present disclosure, the at least two electrodes include: a first electrode attached to the sidewall of the reservoir at a first vertical level; and a second electrode attached to the sidewall at a second vertical level offset from the first vertical level. In some embodiments of the present disclosure, the first electrode and the second electrode are located on opposite sides of the liquid reservoir along a horizontal direction.

[0153] According to at least one embodiment, a lithography system includes a light source and at least one reflector. The light source includes a droplet generator, at least one low-pressure reservoir, a high-pressure reservoir, a monitoring assembly, and a collector. The high-pressure reservoir is in fluid communication with the at least one low-pressure reservoir. The droplet generator is in fluid communication with the high-pressure reservoir. The monitoring assembly has at least two electrodes connected to the outside of the high-pressure reservoir. The collector is located below the droplet generator. The reflector is optically coupled to the collector. In some embodiments of the present disclosure, the at least two electrodes include: at least one first electrode attached to a side wall of the high-pressure reservoir; and a second electrode attached to a base of the high-pressure reservoir. In some embodiments of the present disclosure, the at least one first electrode includes three vertical electrodes.

[0154] According to at least one embodiment, a lithography system includes a light source and a lens system. The light source includes a droplet generator, a reservoir, a high-resolution capacitance measurement device, and a collector. The reservoir is in fluid communication with the droplet generator. The high-resolution capacitance measurement device has at least two electrodes connected to the exterior of the reservoir. The collector is located below the droplet generator. The lens system is optically coupled to the collector.

[0155] The features of several embodiments are summarized above so that those skilled in the art can better understand the various aspects of the present disclosure. Those skilled in the art will understand that they can easily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or achieve the same advantages as the embodiments described herein. Those skilled in the art will also recognize that these equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and modifications may be made to these equivalent constructions without departing from the spirit and scope of the present disclosure.

Claims

1. A lithography system, characterized in that: Include: A light source comprising: a droplet generator; a liquid reservoir in fluid communication with the droplet generator; a monitoring assembly having at least two electrodes connected to the exterior of the reservoir; and a collector located below the droplet generator; and At least one reflector is optically coupled to the collector.

2. The system according to claim 1, wherein The at least two electrodes include: a first electrode attached to a side wall of the reservoir; and A second electrode is attached to a base of the reservoir.

3. The system according to claim 2, wherein: The first electrode completely surrounds the sidewall.

4. The system according to claim 1, wherein: The at least two electrodes include: a first electrode extending vertically along a side wall of the reservoir; and A second electrode extends horizontally along a base of the liquid reservoir.

5. The system according to claim 1, wherein: The at least two electrodes include: a first electrode attached to a side wall of the reservoir at a first vertical level; and A second electrode is attached to the sidewall at a second vertical level offset from the first vertical level.

6. The system according to claim 5, wherein: The first electrode and the second electrode are located at two opposite sides of the liquid reservoir along a horizontal direction.

7. A lithography system, characterized in that: Include: A light source comprising: at least one low-pressure liquid reservoir; a high-pressure fluid reservoir in fluid communication with the at least one low-pressure fluid reservoir; a droplet generator in fluid communication with the high-pressure liquid reservoir; a monitoring assembly having at least two electrodes connected to the exterior of the high-pressure fluid reservoir; and a collector located below the droplet generator; and At least one reflector is optically coupled to the collector.

8. The system according to claim 7, wherein: The at least two electrodes include: at least one first electrode attached to a side wall of the high-pressure liquid reservoir; and A second electrode is attached to a base of the high pressure liquid reservoir.

9. The system according to claim 8, wherein The at least one first electrode includes three vertical electrodes.

10. A lithography system, characterized in that: Include: A light source comprising: a droplet generator; a liquid reservoir in fluid communication with the droplet generator; a high-resolution capacitance measuring device having at least two electrodes connected to the exterior of the reservoir; and a collector located below the droplet generator; and A lens system is optically coupled to the collector.

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