Lithography system preventive maintenance operation method

Abstract

This invention provides a preventive maintenance operation method for a lithography system, comprising the following steps: spraying metal droplets from the reservoir of a droplet generator toward an excitation area in front of a collector; emitting an excitation laser toward the excitation area, causing the metal droplets to be heated by the excitation laser to generate extreme ultraviolet (EUV) radiation; stopping the emission of the excitation laser; depressurizing the reservoir of the droplet generator; cooling the droplet generator to a temperature not lower than approximately 150°C; and backfilling the reservoir of the droplet generator with solid metal material at a temperature not lower than approximately 150°C.

Description

Technical Field

[0001] The embodiments disclosed herein generally relate to extreme ultraviolet (EUV) lithography methods. More specifically, this disclosure relates to preventative maintenance methods for lithography systems, including refilling the droplet generator and replacing the droplet generator in an EUV lithography tool with another droplet generator. Background Technology

[0002] Driven by consumer demand, consumer devices have become increasingly smaller, inevitably leading to a reduction in the size of their individual components. Semiconductor devices, the main components of devices such as mobile phones and tablets, have been forced to become smaller, and the individual elements within these devices (e.g., transistors, resistors, capacitors) have also been forced to shrink accordingly. This reduction in device size has been met with advancements in semiconductor manufacturing technologies such as lithography.

[0003] For example, the wavelengths of radiation used in lithography have decreased from ultraviolet to deep ultraviolet (DUV) and are closer to extreme ultraviolet (EUV). Further reductions in component size require further improvements in lithography resolution, which can be achieved using extreme ultraviolet lithography (EUVL). EUVL uses radiation with wavelengths of approximately 1-100 nm. Summary of the Invention

[0004] According to some embodiments of this disclosure, a method includes the following steps: spraying a metal droplet from a reservoir of a droplet generator toward an excitation region in front of a collector; emitting an excitation laser toward the excitation region such that the metal droplet is heated by the excitation laser to generate extreme ultraviolet (EUV) radiation; stopping the emission of the excitation laser; depressurizing the reservoir of the droplet generator; cooling the droplet generator to a temperature not lower than about 150°C; and backfilling the reservoir of the droplet generator with a solid metal material at a temperature not lower than about 150°C.

[0005] According to some embodiments of this disclosure, a method includes the following steps: turning on a laser source to generate an excitation laser; turning on a droplet generator to eject metal droplets from the droplet generator, wherein the trajectory of the metal droplets intersects the optical path of the excitation laser, such that the metal droplets are heated by the excitation laser to generate extreme ultraviolet (EUV) radiation; turning off the droplet generator; after turning off the droplet generator, cooling the droplet generator to a temperature not lower than 150°C; after cooling the droplet generator, turning on the droplet generator using a first robotic arm; after turning on the droplet generator, backfilling the droplet generator's reservoir with a solid metal material at a temperature not lower than 150°C; and after backfilling the droplet generator's reservoir, reheating the droplet generator.

[0006] According to some embodiments disclosed herein, a method includes the following steps: spraying a metal droplet from a reservoir of a droplet generator toward an excitation region in front of a collector; emitting an excitation laser toward the excitation region, such that the metal droplet is heated by the excitation laser to generate extreme ultraviolet (EUV) radiation; stopping the emission of the excitation laser; depressurizing the reservoir of the droplet generator; cooling the droplet generator to a temperature not lower than 150°C; backfilling the reservoir of the droplet generator with a solid metal material at a temperature not lower than 150°C; extracting oxygen and moisture from the reservoir of the droplet generator; and resuming the emission of the excitation laser after extracting the oxygen and moisture.

[0007] According to some embodiments of this disclosure, a method includes the following steps: ejecting metal droplets from a reservoir of a first droplet generator assembled to a container; emitting an excitation laser toward an excitation region via a laser source to generate extreme ultraviolet (EUV) radiation; shutting off the first droplet generator; cooling the first droplet generator to a temperature not lower than 150°C; removing the first droplet generator from the container at a temperature not lower than about 150°C; and assembling a second droplet generator onto the container.

[0008] According to some embodiments of this disclosure, a method includes the following steps: turning on a laser source to emit an excitation laser toward a container; turning on a first droplet generator to eject metal droplets from the droplet generator into the container, wherein the trajectory of the metal droplets intersects the optical path of the excitation laser, such that the metal droplets are heated by the excitation laser to generate extreme ultraviolet (EUV) radiation; turning off the first droplet generator; after turning off the first droplet generator, cooling the first droplet generator to a temperature not lower than 150°C; after cooling the first droplet generator, removing the droplet generator from the container using a first robotic arm; and after removing the first droplet generator from the container, assembling a second droplet generator onto the container.

[0009] According to some embodiments of this disclosure, a method includes the following steps: dropping a metal droplet into an excitation region in front of a collector in a container, which is sprayed from a first droplet generator; emitting an excitation laser toward the excitation region such that the metal droplet is heated by the excitation laser to generate extreme ultraviolet (EUV) radiation; stopping the emission of the excitation laser; depressurizing the reservoir of the first droplet generator; cooling the first droplet generator to a temperature not lower than 150°C; after cooling the first droplet generator, replacing the first droplet generator with a second droplet generator; and after replacing the first droplet generator with the second droplet generator, resuming the emission of the excitation laser.

[0010] A lithography system preventative maintenance device includes a droplet generator, a storage tank, a direct backfill system, a direct backfill controller, a first robotic arm, and a first robot controller. The droplet generator includes a reservoir and a nozzle in fluid communication with the reservoir. The direct backfill system is connected between the storage tank and the reservoir of the droplet generator. The direct backfill controller controls the direct backfill system to transport target material from the storage tank to the reservoir when the droplet generator ejects droplets of target material through the nozzle. The first robot controller controls the first robotic arm to open the storage tank in response to a temperature below the melting point of tin, rather than below approximately 150°C. Attached Figure Description

[0011] The features disclosed herein can be better understood when read in conjunction with the accompanying drawings, and with reference to the following detailed description. It should be noted that, in accordance with industry standard practice, the various features are not drawn to scale. In fact, the dimensions of each feature may be arbitrarily increased or decreased for clarity of explanation.

[0012] Figure 1 This is a schematic diagram of a lithography system according to some embodiments of the present disclosure;

[0013] Figure 2 This is a schematic diagram of an EUV radiation source according to some embodiments of this disclosure;

[0014] Figure 3 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0015] Figure 4 A schematic diagram of a robotic arm for backfilling a droplet generator assembly according to some embodiments of this disclosure;

[0016] Figure 5 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0017] Figure 6 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0018] Figure 7 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0019] Figure 8 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0020] Figure 9 Methods for preventive maintenance (PM) operations according to some embodiments of this disclosure;

[0021] Figure 10 Methods for operating PM according to some embodiments of this disclosure;

[0022] Figure 11 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0023] Figure 12 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0024] Figure 13 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0025] Figure 14 A schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure;

[0026] Figure 15 Methods for operating PM according to some embodiments of this disclosure;

[0027] Figure 16A and Figure 16B The following are experimental results based on some embodiments disclosed herein.

[0028] [Symbol Explanation]

[0029] 100 EUV Microfilm System

[0030] 110 illuminators

[0031] 120 shielding platform

[0032] 130 mask

[0033] 140 Projection optical module (or projection optical box)

[0034] 150 Substrate Stage (Wafer Stage)

[0035] 200 EUV radiation source (radiation source)

[0036] 210 Container

[0037] 212 Lid

[0038] 220 laser source

[0039] 222 Laser Controller

[0040] 230 Droplet Generator

[0041] 231 Savings Account

[0042] 231a sidewall

[0043] 231b Bottom wall

[0044] 232 Lid

[0045] 232I Gas Inlet

[0046] 232O Gas Outlet

[0047] 233 Holder

[0048] 234 Capillary

[0049] 234a First End

[0050] 234b Second End

[0051] 234c sidewall

[0052] 235 nozzle

[0053] 236a Heating element

[0054] 236b heating element

[0055] 237 Outer shell

[0056] 237a Internal Part

[0057] 237b External Part

[0058] 237O Entrance

[0059] 238 Piezoelectric Actuator

[0060] 240 collectors

[0061] 250 Droplet Collector

[0062] 260 Straight-line Backfill System

[0063] 262 Low-pressure vessels

[0064] 264 Backfill Pipeline

[0065] 266 High-pressure vessel

[0066] 268 Delivery Pipeline

[0067] 269 ​​Straight-line backfill controller

[0068] 270 First Buffer Gas Source

[0069] 272 Second Buffer Gas Source

[0070] 280 Exhaust System

[0071] 282 Exhaust Pipeline

[0072] 284 pump

[0073] 300 Temperature Control System

[0074] 310 Radiator

[0075] 320 fan

[0076] 330 Temperature Control Device

[0077] 332 slots

[0078] 332G Gas Tank

[0079] 332L liquid tank

[0080] 332S Solid Tank

[0081] 334 Heating / Cooling Element

[0082] 334G Heating / Cooling Element

[0083] 334L heating / cooling element

[0084] 334S heating / cooling element

[0085] 390 bracket

[0086] 400 Temperature Control Circuit

[0087] 510 sensor

[0088] 520 Sensors

[0089] 530 Sensors

[0090] 910 Robotic Arm (DG Open / Close Robotic Arm)

[0091] 911 base

[0092] 912 arms

[0093] 913 Forearm

[0094] 914 Wrist Component

[0095] 915 clamps

[0096] 916 Robot Controller

[0097] 920 Robotic Arm (Backfilling Robotic Arm)

[0098] 921 base

[0099] 922 arms

[0100] 923 Forearm

[0101] 924 Wrist Component

[0102] 925 clamps

[0103] 926 Robot Controller

[0104] A1-A8 axes

[0105] BT rod-shaped solid target material

[0106] CP thermal cap

[0107] DC pressure reducing device

[0108] DCL gas pipeline

[0109] EL EUV radiation

[0110] GA buffer gas

[0111] GIP gas inlet pipe

[0112] GOP gas output pipe

[0113] HE heating element

[0114] HU heating unit

[0115] IM thermal conductive wire

[0116] IP input tube

[0117] LB-excited laser

[0118] LIP liquid inlet tube

[0119] LOP liquid outlet tube

[0120] OM thermal conductive wire

[0121] OP output tube

[0122] OW Windows

[0123] PC pressurization device

[0124] PCL gas pipeline

[0125] PD fragments

[0126] S101-S109 Cubes

[0127] S201-S208 squares

[0128] S301-S309 Cubes

[0129] SL supply pipeline

[0130] ST storage tank

[0131] TD target droplet

[0132] TM target material

[0133] W Semiconductor substrate

[0134] ZE Excitation Region Detailed Implementation

[0135] The following disclosure provides numerous different embodiments or examples to achieve different features of each embodiment. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these examples are merely illustrative and not intended to be limiting. For example, the formation of a first feature above or on a second feature in the following description may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features may be formed between the first and second features such that the first and second features are not in direct contact. Additionally, element symbols and / or letters may be repeated in various examples of this disclosure. This repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0136] Furthermore, spatial relative terms, such as “below,” “under,” “lower,” “above,” “upper,” and the like, are used herein for ease of description to describe the relationship between one element or feature illustrated in the figures and another element(s) or feature(s). Apart from the directions depicted in the figures, spatial relative terms are intended to encompass different orientations of elements in use or operation. Devices may be oriented in different ways (rotated 90 degrees or in other directions), and the spatial relative descriptive terms used herein can therefore be interpreted in the same way.

[0137] The advanced lithography processes, methods, and materials described in this disclosure can be used in many applications, including fin-type field-effect transistors (FinFETs). For example, fins can be patterned to create relatively tight spacing between features to be well-suited to this disclosure. Furthermore, the spacers used in the fins forming FinFETs can be treated according to the following disclosure.

[0138] This disclosure generally relates to extreme ultraviolet (EUV) lithography systems and methods. Specifically, this disclosure relates to EUV lithography systems and droplet generators (DGs) and methods for replacing (i.e., swapping) a droplet generator in an EUV lithography system with another droplet generator. In an EUV lithography system, laser-produced plasma (LPP) generates extreme ultraviolet radiation for imaging photoresist-coated substrates. In an EUV lithography system, an excitation laser heats a metal (e.g., tin, lithium, etc.) target droplet to ionize the droplet into the plasma that emits EUV radiation. For regenerable EUV radiation, the target droplets arriving at the focal point (also referred to herein as the "excitation region") are substantially the same size and arrive at the excitation region simultaneously with the excitation pulse from the excitation laser.

[0139] Figure 1 This is a schematic diagram of an EUV lithography system 100 according to some embodiments of this disclosure. In some embodiments, the EUV lithography system 100 is designed to expose a resist layer using EUV radiation (or EUV light). The resist layer is a material sensitive to EUV radiation. The EUV lithography system 100 uses a radiation source 200 to generate EUV radiation EL, such as EUV radiation having wavelengths ranging from about 1 nm to about 100 nm. In some embodiments, the EUV radiation EL has wavelengths concentrated around about 13.5 nm. Therefore, the radiation source 200 is also referred to as an EUV radiation source 200. The EUV radiation source 200 may generate EUV radiation using a laser-produced plasma (LPP) mechanism, which will be described further later.

[0140] The EUV lithography system 100 also uses an illuminator 110. In some embodiments, the illuminator 110 includes various reflective optics, such as a single mirror or a mirror system with multiple mirrors, to direct light EL from the radiation source 200 onto a mask 130 fixed on a mask stage 120.

[0141] In some embodiments, the mask stage 120 includes an electrostatic chuck (e-chuck) for securing the mask 130. In this context, the terms mask, photomask, and main photomask are used interchangeably. In this embodiment, the mask 130 is a reflective mask. An exemplary structure of the mask 130 includes a substrate having a low thermal expansion material (LTEM). For example, the LTM may include TiO2-doped SiO2, or other suitable materials having a low coefficient of thermal expansion. The mask 130 includes a reflective multilayer (ML) deposited on the substrate. The ML includes multiple pairs of thin films, such as molybdenum-silicon (Mo / Si) thin film pairs (e.g., a molybdenum layer above or below a silicon layer in each pair). Alternatively, the ML may include molybdenum-beryllium (Mo / Be) thin film pairs, or other suitable materials configured to efficiently reflect EUV radiation (EL). Mask 130 may further include a capping layer, such as ruthenium (Ru), disposed on ML for a protective function. Mask 130 further includes an adsorption layer, such as a boron nitride tantalum (TaBN) layer, deposited over ML. The adsorption layer is patterned to define an integrated circuit (IC) layer. In different embodiments, mask 130 may have other structures or configurations.

[0142] The EUV lithography system 100 also includes a projection optics box (POB) 140 for imaging the pattern of the mask 130 onto a semiconductor substrate W (e.g., a wafer), which is fixed to a substrate stage (e.g., a wafer stage) 150 of the EUV lithography system 100. In this embodiment, the projection optics box 140 includes reflective optics. EUV radiation EL, guided from and carrying an image of the pattern defined on the mask 130, is focused by the projection optics box 140. The illuminator 110 and the projection optics box 140 can be collectively referred to as the optical components of the EUV lithography system 100. In this disclosure, the semiconductor substrate W is a semiconductor wafer, such as a silicon wafer or other type of wafer to be patterned. In this embodiment, the semiconductor substrate W is coated with a resist layer sensitive to EUV radiation EL. The various components including the above-described components are integrated together and operatively perform the EUV lithography exposure process.

[0143] Figure 2This is a schematic diagram of an EUV radiation source 200 according to some embodiments of the present disclosure. The EUV radiation source 200 uses a laser-generated plasma (LPP) mechanism to generate plasma and further generate EUV radiation from the plasma. The radiation source 200 includes a container 210, a laser source 220, a droplet generator 230, a collector 240, and a droplet trap 250.

[0144] In some embodiments, the target droplet TD is a metal droplet, such as tin (Sn), lithium (Li), and an alloy of Sn and Li. In some embodiments, each target droplet TD has a diameter ranging from about 10 micrometers (μm) to about 100 μm. For example, in one embodiment, the target droplet TD is a tin droplet with a diameter of about 10 μm to about 100 μm. In other embodiments, the target droplet TD is a tin droplet with a diameter of about 25 μm to about 50 μm. In some embodiments, the target droplet TD is supplied via nozzle 235 of droplet generator 230 at a rate ranging from about 50 droplets per second (i.e., a jetting frequency of about 50 Hz) to about 50,000 droplets per second (i.e., a jetting frequency of about 50 kHz). In some embodiments, the target droplet TD is supplied at a jetting frequency of about 100 Hz to about 25 kHz. In other embodiments, the target droplet TD is supplied at a jetting frequency of about 500 Hz to about 10 kHz. The target droplet TD is ejected via nozzle 235 and enters the excitation region ZE at a velocity ranging from about 10 meters per second (m / s) to about 100 m / s. In some embodiments, the target droplet TD has a velocity of about 10 m / s to about 75 m / s. In other embodiments, the target droplet TD has a velocity of about 25 m / s to about 50 m / s.

[0145] In some embodiments, the excitation laser LB generated by the excitation laser source 220 is a pulsed laser. The excitation laser LB is generated by the excitation laser source 220. In some embodiments, the laser source 220 includes a carbon dioxide (CO2) or neodymium-doped yttrium aluminum garnet (Nd:YAG) laser source having a wavelength in the infrared region of the electromagnetic spectrum. For example, in an embodiment, the laser source 220 has a wavelength of 9.4 μm or 10.6 μm.

[0146] In some embodiments, the excitation laser LB includes a preheating laser and a main laser. In this embodiment, a preheating laser pulse (which may be referred to herein as a “prepulse”) is used to heat (or preheat) a given target droplet to produce a low-density target jet with multiple smaller droplets, which is subsequently heated (or reheated) by a pulse from the main laser to generate enhanced emission of EUV radiation.

[0147] In some embodiments, the preheating laser pulse has a spot size of about 100 μm or less, and the main laser pulse has a spot size ranging from about 150 μm to about 300 μm. In some embodiments, the preheating laser and the main laser pulse have a pulse duration ranging from about 10 ns to about 50 ns, and a pulse frequency ranging from about 1 kHz to about 100 kHz. In some embodiments, the average power of the preheating laser and the main laser ranges from about 1 kilowatt (kW) to about 50 kW. In some embodiments, the pulse frequency of the excitation laser LB is matched with the ejection frequency of the target droplet TD.

[0148] The excitation laser LB is guided to the excitation region ZE via a window OW in collector 240. The window OW is made of a suitable material that is substantially transparent to the excitation laser LB. The generation of the pulsed laser is synchronized with the ejection of the target droplet TD via nozzle 235. As the target droplet TD moves through the excitation region ZE, the pre-pulse heats the target droplet and converts it into a low-density target jet. The delay between the pre-pulse and the main pulse is controlled to allow the target jet to form and expand to an optimal size and geometry. In one embodiment, the pre-pulse and the main pulse have the same pulse duration and peak power. When the main pulse heats the target jet, a high-temperature plasma is generated. The plasma emits EUV radiation EL collected by collector 240. For lithography processes, collector 240 further directs the EUV radiation EL toward illuminator 110 ( Figure 1 (Illustrated) Reflection and focusing. The droplet trap 250 is used to capture excess target droplets. For example, some target droplets may be intentionally missed by the laser pulse.

[0149] In some embodiments, collector 240 is designed with a suitable coating material and shape to act as a mirror for collecting, reflecting, and focusing EUV. In some embodiments, collector 240 is designed with an elliptical geometry. In some embodiments, the coating material of collector 240 is consistent with that of EUV shield 130 (e.g., Figure 1 The reflective multilayer (illustrated) is similar. In some instances, the coating material of collector 240 includes ML (such as one or more Mo / Si thin film pairs) and may further include a cover layer (such as Ru) coated on ML to substantially reflect EUV radiation. In some embodiments, collector 240 may further include a grating structure designed to effectively scatter the laser beam directed into collector 240. For example, a silicon nitride layer is coated on collector 240 and patterned to have a grating pattern.

[0150] In some embodiments, the high-temperature plasma can be cooled and transformed into vapor or small particles (collectively referred to as fragment PD). Fragment PD can deposit on the surface of collector 240, resulting in contamination thereon. Over time, the reflectivity of collector 240 degrades due to fragment accumulation and other factors such as ionic damage, oxidation, and foaming. Once the reflectivity degrades to a certain extent, collector 240 reaches the end of its usable life and may need to be replaced (i.e., replaced with a new collector).

[0151] Container 210 has a lid 212 for ventilation and collection of fragment PD. In some embodiments, lid 212 is made of a suitable solid material, such as stainless steel. Lid 212 is designed and positioned around collector 240. Lid 212 may include a plurality of blades evenly distributed around the conical lid 212. In some embodiments, radiation source 200 further includes a heating unit HU disposed around a portion of lid 212. The heating unit HU is used to maintain the temperature inside lid 212 above the melting point of fragment PD, so that fragment PD does not solidify on the inner surface of lid 212. When fragment PD vapor comes into contact with the blades, it can condense into a liquid and flow into the lower portion of lid 212. The lower portion of lid 212 may provide orifices (not shown) for draining the fragment liquid from lid 212.

[0152] In some embodiments, a buffer gas GA is supplied from a first buffer gas source 270 via an orifice in the collector 240, through which a pulsed laser is delivered to the molten tin droplet. In some embodiments, the buffer gas is H2, He, Ar, N2, or another inert gas. In some embodiments, H radicals generated by the ionization of the H2 buffer gas are used for cleaning purposes. The buffer gas GA may also be supplied via one or more second buffer gas sources 272 toward and / or around the edge of the collector 240. Furthermore, the container 210 further includes an exhaust system 280 to allow the buffer gas to exit the container 210.

[0153] Hydrogen gas has low absorption of EUV radiation. Upon reaching the coated surface of collector 240, the hydrogen gas reacts chemically with the droplet metal to form hydrides, such as metal hydrides. When tin (Sn) is used as the target droplet TD, tin hydride (SnH4) is formed, which is a gaseous byproduct of the EUV generation process. The gaseous SnH4 is then pumped out via exhaust system 280.

[0154] The buffer gas GA serves various protective functions, including effectively protecting collector 240 from particulate contamination. Other suitable gases may be used alternatively or additionally. The buffer gas GA may be introduced into collector 240 via one or more gas lines through an opening (or slit) near the output window OW. The exhaust system 280 includes one or more exhaust lines 282 and one or more pumps 284. The exhaust lines 282 are connected to the wall of container 210 for receiving exhaust gases. In some embodiments, the cover 212 is designed to have a conical shape, wherein its wide base engages with collector 240 and its narrow top portion faces illuminator 110. Figure 1 In other embodiments, an exhaust line 282 is connected at its top to a cover 212. Mounting the exhaust line 282 on top of the cover 212 facilitates the discharge of debris PD from the gap defined by the collector 240 and the cover 212. The space within container 210 is maintained in a vacuum environment because the atmosphere absorbs EUV radiation.

[0155] In this embodiment, the temperature control system 300 may be arranged near or connected to the droplet generator 230, wherein the temperature control system 300 is at least configured to cool the droplet generator 230. In some embodiments, the temperature control system 300 may be configured to cool and / or heat the droplet generator 230, which will be discussed in more detail below.

[0156] Figure 3 This is a schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure. The droplet generator assembly includes a droplet generator 230 and a temperature control system 300. The droplet generator 230 includes a reservoir 231, a cover 232, a capillary tube 234, heating elements 236a and 236b, and a housing 237. Components of the droplet generator 230 may be added or omitted in some embodiments.

[0157] A reservoir 231 is configured to hold target material TM. Reservoir 231 may include a sidewall 231a and a bottom surface 231b. The sidewall 231a may be made of steel (e.g., stainless steel) or other suitable thermally conductive material. The sidewall 231a surrounds the outer edge of the bottom wall 231b and extends away from the bottom surface 231b. A heating element 236b may surround reservoir 231 for heating the target material TM and maintaining the target material TM at a temperature above its melting point for droplet generation. For example, during EUV radiation irradiation using EUV radiation source 200 (regarding...). Figure 2The temperature of the tin target material TM can be maintained within an operational range of approximately 231°C to approximately 300°C, or up to 2602°C, such that the tin target material TM melts without vaporizing. A housing 237 surrounds the reservoir 231 and the heating element 236b. The housing 237 may be made of steel (e.g., stainless steel) or other suitable thermally conductive material. The housing 237 may have an inlet 237O that allows the target material TM to be backfilled into the reservoir 231. A cover 232 is attached to the upper end of the housing 237 to cover the inlet 237O, and the cover 232 is detachable from the housing 237. Thus, when the droplet generator 230 is being backfilled, the cover 232 can be detached from the housing 237 to open the inlet 237O, allowing new rod-shaped solid target material to be inserted into the droplet generator 230 via the inlet 237O.

[0158] In some embodiments, a gas inlet 232I and a gas outlet 232O are formed on a cover 232. The gas inlet 232I is connected to a gas line PCL for guiding pumping gas, such as argon, into the reservoir 231. For example, a pressurizing device PC is configured to supply gas into the reservoir 231 via the gas line PCL. The gas outlet 232O is connected to a depressurizing device DC (e.g., a pump) via another gas line DCL for pumping gas out of the reservoir 231. The pressure in the reservoir 231 can be controlled by controlling the airflow in the gas lines PCL and DCL connected to the gas inlet 232I and the gas outlet 232O. For example, when the pressurizing device PC is turned on and the depressurizing device DC is turned off, the pressure in the reservoir 231 is increased. Thus, the increased gas pressure can force the molten target material TM in the reservoir 231 out of the reservoir 231 into the capillary 234, and thus the molten target material TM can flow through the capillary 234 to form subsequent splitting into one or more target droplets TD (e.g., Figure 2 (Illustrated) A continuous flow of target droplets TD exits the nozzle 235 at the tail end of capillary 234.

[0159] Capillary 234 is in fluid communication with reservoir 231 and nozzle 235. More specifically, capillary 234 includes a first end 234a closest to reservoir 231, a second end 234b furthest from reservoir 231, and a sidewall 234c between the first end 234a and the second end 234b. Nozzle 235 is located at the second end 234b furthest from reservoir 231. Target droplets TD (such as...) are ejected from nozzle 235. Figure 2 (Illustrated) can be controlled by an actuator (such as a piezoelectric actuator 238 surrounding the capillary 234). In some embodiments, a heating element 236a surrounding the capillary 234 heats the target material TM and maintains the target material TM at a temperature above the melting point of the target material TM for generating droplets.

[0160] In some embodiments, the droplet generator 230 includes a retainer 233 surrounding a housing 237, and the housing 237 has an inner portion 237a and an outer portion 237b on opposite sides of the retainer 233. A temperature control system 300 is at least partially located above the outer portion 237b of the housing 237. When the droplet generator 230 is inserted into the container 210 of the EUV radiation source 200 (e.g....), Figure 2 (As shown in the diagram), the retainer 233 is pressed against the outer surface of the lid 212 of the container 210 in an airtight manner. For example, Figure 3 The dashed line indicates the outer edge of the lid 212 when the droplet generator 230 is inserted into the container 210. Specifically, when the droplet generator 230 is inserted into the container 210, part of the reservoir 231, the inner part 237a of the outer casing 237, and the capillary 234 are inside the container 210, while another part of the reservoir 231, the outer part 237b of the outer casing 237, the retainer 233, and the temperature control system 300 are outside the container 210.

[0161] For example, a preventive maintenance (PM) operation of the droplet generator 230 is performed once a week. In some embodiments, the PM operation includes at least the following steps: depressurizing the droplet generator 230, cooling the target material TM in the droplet generator 230 to room temperature (from about 25°C to about 40°C), turning on the droplet generator 230, backfilling the reservoir 231 of the droplet generator 230 with a rod-shaped solid target material TM (e.g., a solder bar), turning off the droplet generator 230, and reheating the target material TM to a temperature above the melting point of the target material TM (about 231°C for tin).

[0162] However, PM operation is time-consuming because it takes several hours to allow the droplet generator 230 to cool naturally to room temperature, and then to reheat the refilled droplet generator 230 from room temperature to a temperature higher than the melting point of the target material TM. This time-consuming PM operation therefore reduces the yield of EUV lithography processes.

[0163] Therefore, in some embodiments disclosed herein, when backfilling the droplet generator 230, the droplet generator 230 is cooled to a target temperature above room temperature. More specifically, the droplet generator 230 is cooled to a temperature below the melting point of the target material TM (e.g., tin) (approximately 231°C) rather than below approximately 150°C. In this way, cooling time and reheating time can be effectively reduced, which in turn improves the yield of the EUV lithography process. Furthermore, if the droplet generator 230 is cooled to a target temperature below 150°C, the nozzle 235 will suffer from exacerbated clogging problems. In addition, it has been observed that the liquid-to-solid phase transition of the target material TM in the droplet generator 230 begins when the temperature reaches approximately 231°C and ends after the temperature reaches approximately 218°C. Therefore, the lower the temperature at which the cooling operation ends, the safer the backfilling operation. It was observed that if the cooling operation ends at a target temperature above approximately 224°C, the target material TM may not fully solidify and therefore tends to flow out of the droplet generator 230 during the backfill operation, which in turn degrades the backfill operation. Therefore, the droplet generator 230 can be cooled to a target temperature of approximately 150°C to approximately 224°C. In some embodiments, the cooling operation ends at a target temperature of approximately 150°C to approximately 210°C. In some embodiments, the cooling operation ends at a target temperature of approximately 150°C to approximately 200°C. In some embodiments, the cooling operation ends at a target temperature of approximately 150°C to approximately 175°C.

[0164] Because the cooling operation ends at a target temperature of not less than 150°C, manually opening, refilling, and closing the droplet generator 230 could be dangerous. Therefore, in some embodiments, one or more robotic arms can be used to automatically open, refill, and / or close the droplet generator 230. Exemplary robotic arms 910 and 920 for automatically opening, refilling, and / or closing the droplet generator 230 are described below. Figure 4 As shown in the diagram, the DG open / close robotic arm 910 can be used to open and close the droplet generator 230, and the backfill robotic arm 920 can be used to backfill the droplet generator 230.

[0165] The DG open / close robotic arm 910 includes a rotatable base 911, a rotatable arm 912, a rotatable forearm 913, a rotatable wrist member 914, a gripper 915, and a robot controller 916. The rotation of the base 911, arm 912, forearm 913, and wrist member 914 is controlled by the robot controller 916, allowing the gripper 915 to move in three dimensions. Thus, in the operation of opening the droplet generator 230, the movable gripper 915 clamps the cover 232 and then removes the cover 232 from the housing 237 of the droplet generator 230. Conversely, in the operation of closing the droplet generator 230, the gripper 915 clamping the cover 232 can be returned to the droplet generator 230, and then the cover 232 is secured to the housing 237.

[0166] Similar to the DG open / close robotic arm 910, the backfilling robotic arm 920 includes a rotatable base 921, a rotatable arm 922, a rotatable forearm 923, a rotatable wrist component 924, a gripper 925, and a robot controller 926. The rotation of the base 921, arm 922, forearm 923, and wrist component 924 is controlled by the robot controller 926, thereby allowing the gripper 925 to move in three dimensions. Thus, the gripper 925, which clamps a rod-shaped solid target material BT (e.g., a solder bar), can move to the open droplet generator 230 and insert the rod-shaped solid target material BT into the reservoir 231.

[0167] In some embodiments, robot controllers 916 and 926 are programmed to sequentially turn on, backfill, and turn off the droplet generator 230. For example, the droplet generator 230 is first turned on using a DG-activated turn-on robot arm 910, then the droplet generator 230 is backfilled using a backfill robot arm 920, and finally the droplet generator 230 is turned off using a DG-activated turn-off robot arm 910. In some embodiments, the robot arm 910 is controlled independently. In other words, the robot arm 910 is not controlled by the robot controller 926, and the backfill robot arm 920 is not controlled by the robot controller 916.

[0168] In some embodiments, robot controller 916 and robot controller 926 may include a processor, a central processing unit (CPU), a multiprocessor, a distributed processing system, an application-specific integrated circuit (ASIC), etc. In some embodiments, robot controller 916 and robot controller 926 are the same processor. In some other embodiments, robot controller 916 and robot controller 926 are located in different individual processors.

[0169] Figure 4 The diagram illustrates an example rotation of the DG opening / closing robotic arm 910. A base 911 is rotatable about axis A1. Arm 912 is connected to base 911 via a rotary joint or pivot joint so that arm 912 can rotate about axis A2, which is perpendicular to axis A1. Forearm 913 is connected to arm 912 via a rotary joint or pivot joint so that forearm 913 can rotate about axis A3, which is parallel to axis A1. Wrist member 914 is connected to arm 913 via a rotary joint or pivot joint so that wrist member 914 can rotate about axis A4, which is perpendicular to axes A1 to A3. Gripper 915 is connected to the end of wrist member 914 furthest from forearm 913 so that gripper 915 can move in three dimensions using rotational movements performed by base 911, arm 912, forearm 913, and wrist member 914.

[0170] Similarly, Figure 4The illustration shows an example rotation of a backfilling robotic arm 920. A base 921 is rotatable about an axis A5 parallel to axis A1. An arm 922 is connected to the base 921 via a rotary joint or pivot joint so that the arm 922 is rotatable about an axis A6 perpendicular to axis A5. A forearm 923 is connected to the arm 922 via a rotary joint or pivot joint so that the forearm 923 is rotatable about an axis A7 parallel to axis A5. A wrist member 924 is connected to the forearm 923 via a rotary joint or pivot joint so that the wrist member 924 is rotatable about an axis A8 perpendicular to axes A5 to A7. A gripper 925 is connected to the end of the wrist member 924 furthest from the forearm 923 so that the gripper 925 can move in three dimensions using rotational movements performed by the base 921, arm 922, forearm 923, and wrist member 924.

[0171] In some embodiments, clamps 915 and 925 are made of a material having a melting point higher than that of the target material TM (e.g., tin) (approximately 231°C) so that the opening / refilling / closing operation of the droplet generator 230 can be performed using clamps 915 and 925 as the target material TM begins to solidify in the droplet generator 230. For example, clamps 915 and 925 may be made of stainless steel or other suitable materials that can remain in a solid phase at temperatures higher than the melting point of the target material TM. In some embodiments, the opening / refilling / closing operation of the droplet generator 230 is performed in a low-oxygen and low-humidity environment because the nozzle 235 of the droplet generator 230 can be damaged by oxygen and moisture during the opening / refilling / closing operation. For example, the opening / refilling / closing operation of the droplet generator 230 may be performed in a vacuum environment (e.g., an oxygen-free and moisture-free environment). More specifically, before performing the open / backfill / close operation, the atmosphere surrounding the droplet generator 230 can be evacuated by a vacuum pump (not shown). In this way, oxygen and moisture are drawn out of the atmosphere surrounding the droplet generator 230 by the vacuum pump, which in turn protects the nozzle 235 from damage caused by oxygen and moisture, thus extending the life of the droplet generator 230.

[0172] although Figure 4 The embodiments depicted use robotic arms 910 and 920 to automatically open, refill, and close the droplet generator 230. However, in other embodiments, the droplet generator 230 may be manually opened, refilled, and closed by one or more experienced users (e.g., technicians and / or engineers). In such embodiments, experienced users may use one or more thermal isolation tools to manually open, refill, and close the droplet generator 230.

[0173] The steps of the coolant droplet generator 230 can be executed using the temperature control system 300, such as... Figure 3Illustration. In some embodiments disclosed herein, a temperature control system 300 is disposed near the reservoir 231 for cooling the droplet generator 230. The temperature control system 300 may include passive heat dissipation devices (e.g., a heat sink 310) and active heat dissipation devices (e.g., a fan 320). The heat sink 310 is capable of absorbing and dissipating heat from the reservoir 231 through its fins. For example, the heat sink 310 may be mounted on an outer portion 237b of the housing 237. In some embodiments, the heat sink 310 is in contact with the outer portion 237b of the housing 237. The fan 320 may be fixed relative to the droplet generator 230. For example, the temperature control system 300 may include a process fan 320 and connect the fan 320 to a bracket 390 of the housing 237. The fan 320 is disposed near the fins of the heat sink 310 for generating airflow to accelerate heat dissipation. In some embodiments, the airflow may be in a direction perpendicular to the outer portion 237b of the housing 237. In some embodiments, the airflow may be in a direction inclined with respect to the outer portion 237b of the housing 237. The exemplary fan 320 may be a single fan, multiple fans (e.g., dual fans, triple fans, or quad fans), an industrial fan, a high-power fan, or a turbo fan. In some embodiments, the droplet generator 230 may optionally include a temperature control circuitry or controller 400 electrically connected to the heating elements 236a and 236b and the fan 320 for controlling the temperature of the droplet generator 230 (e.g., for controlling cooling and / or reheating operations of the droplet generator 230). In some other embodiments, passive heat dissipation devices (e.g., radiator 310) may be omitted. In some other embodiments, active heat dissipation devices (e.g., fan 320) may be omitted.

[0174] By configuring the temperature control system 300, the cooling process of the target material TM can be accelerated, and thus the PM operation can be completed in less time. For example, the PM operation performed using the temperature control system 300 takes approximately 2 to 3 hours, which is less than the time required for a PM operation without the temperature control system 300. Furthermore, due to the shortened PM time, contaminants or particles falling into the container 210 and / or collector 240 as a result of the PM operation can be effectively reduced. Additionally, due to the shortened PM time, undesirable oxidation of the target material TM by oxygen-containing gases (e.g., O2, H2O) during the PM operation can also be reduced.

[0175] In some embodiments, the droplet generator 230 may further include a sensor 510 located near the reservoir 231. For example, the sensor 510 is located between the outer portion 237b of the housing 237 and the sidewall 231a of the reservoir 231. In some embodiments, the droplet generator 230 may further include a sensor 520 located near the tube 234. Sensors 510 and 520 can detect conditions of the droplet generator 230, such as pressure conditions, temperature conditions, etc. A temperature controller 400 is electrically connected to sensors 510 and 520. In this way, the detected conditions can be fed forward to the temperature controller 400, and thus the temperature controller 400 can start or stop the cooling step of the droplet generator 230 based on the detected conditions. Similarly, the temperature controller 400 can start or stop the heating step of the droplet generator 230 based on the detected conditions. In some embodiments, the temperature controller 400 may include a processor, a central processing unit (CPU), a multiprocessor, a distributed processing system, an application-specific integrated circuit (ASIC), etc.

[0176] In some embodiments, the droplet generator 230 may optionally include a charging circuit CC configured to flush ions into the droplet generator 230. The charging circuit CC may include an electrode CE located on the bottom wall 231b of the reservoir 231. The electrode CE is grounded or connected to a power source. However, it should be understood that many variations and modifications can be made to the embodiments disclosed herein. In some other embodiments, the electrodes are omitted, and the bottom wall 231b and / or side wall 231a of the reservoir 231 are made of a conductive material and electrically grounded or connected to a power source.

[0177] Figure 5 This is a schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure. This embodiment is similar to... Figure 3 In addition to the embodiments, Figure 5 The illustrated temperature control system 300 includes a liquid inlet pipe (LIP), a liquid outlet pipe (LOP), and an active temperature control device 330 in fluid communication with the liquid inlet pipe (LIP) and the liquid outlet pipe (LOP). The temperature control device 330 includes a liquid heating / cooling element 334L and a liquid tank 332L, wherein a temperature control circuit 400 is electrically coupled to the heating / cooling element 334L and the liquid tank 332L for controlling the liquid flow rate. The liquid inlet pipe (LIP) and the liquid outlet pipe (LOP) may be connected to the radiator 310 or the external portion 237b of the housing 237. The liquid inlet pipe (LIP) and the liquid outlet pipe (LOP) may surround the radiator 310. For example, the liquid inlet pipe (LIP) and the liquid outlet pipe (LOP) may be between the fins of the radiator 310. In some embodiments, the liquid inlet pipe (LIP) and the liquid outlet pipe (LOP) may be spirally arranged around the radiator 310. The heating / cooling element 334L can draw heat from the liquid, thereby cooling the liquid. In some embodiments, a fan device (regarding...) Figure 3 This can optionally be used to accelerate heat dissipation. In some embodiments, the active temperature control device 330 may further include a pump in fluid communication with the liquid inlet pipe LIP and the liquid outlet pipe LOP for controlling the liquid flow. In some other embodiments, the radiator 310 may be omitted.

[0178] During PM operation of the cooling droplet generator 230, liquid stored in the liquid tank 332L is introduced near the reservoir 231 via the liquid inlet pipe LIP, absorbing heat from the reservoir 231. The liquid is then introduced into the heating / cooling element 334L. The heating / cooling element 334L removes heat from the liquid and sends it back to the liquid tank 332L. The liquid can be water, a polar liquid, fluorine, a low-viscosity oil, other organic liquids, molten salts, molten metals, or other suitable thermally conductive liquids. For example, suitable thermally conductive liquids include a carrier liquid (e.g., water) dispersed with suitable thermally conductive nanoparticles, such as copper monoxide, alumina, titanium dioxide, carbon nanotubes, quartz, copper, silver rods, or other metals.

[0179] In some embodiments, the heating / cooling element 334L is a cooling system, such as a liquid nitride system, a liquid hafnium system, a cryogenic system, or a water-cooled system. In some other embodiments, the heating / cooling element 334L is a heating and cooling system, wherein the heating / cooling element 334L can heat / cool a liquid. For example, during reheating of the droplet generator 230 in PM operation, the temperature control system 300 can heat the droplet generator 230 via the heating / cooling element 334L. In some other embodiments, the active temperature control device 330 may include a coolant gun that sprays coolant directly onto the radiator 310, wherein the coolant can absorb heat from the radiator 310 and evaporate. For example, the coolant may be water. The coolant gun may be physically separate from the radiator 310 and the droplet generator 230. In some other embodiments, a pipe (e.g., a pipe LIP) may connect the coolant gun to the radiator 310, such that coolant is sprayed from the coolant gun to the radiator 310 via the liquid inlet pipe LIP. Other details of this disclosure are similar to those described above and are not repeated here.

[0180] Figure 6 This is a schematic diagram of a droplet generator according to some embodiments of the present disclosure. This embodiment is similar to... Figure 5 In addition to the embodiments, Figure 6The illustrated temperature control system 300 includes a gas inlet pipe GIP, a gas outlet pipe GOP, and an active temperature control device 330 including a gas heating / cooling element 334G and a gas tank 332G. The active temperature control device 330 is in fluid communication with the gas inlet pipe GIP and the gas outlet pipe GOP. A temperature control circuit 400 is electrically coupled to the heating / cooling element 334G and the gas tank 332G for controlling the gas flow rate. The gas inlet pipe GIP and the gas outlet pipe GOP may contact the heat sink 310 or the outer portion 237b of the housing 237. The gas inlet pipe GIP and the gas outlet pipe GOP may surround the heat sink 310. For example, the gas inlet pipe GIP and the gas outlet pipe GOP may be between the fins of the heat sink 310. In some embodiments, the gas inlet pipe GIP and the gas outlet pipe GOP may be spirally arranged around the heat sink 310. During PM operation, while cooling the droplet generator 230, gas stored in the gas tank 332G is introduced into the gas reservoir 231 via the gas inlet pipe GIP, absorbing heat from the gas reservoir 231. The gas is then directed to the heating / cooling element 334G via the gas outlet pipe GOP. The heating / cooling element 334G removes the heat from the gas and sends it back to the gas tank 332G. The gas can be an extremely clean, dry gas (XCDA). In some embodiments, the gas can be Ar, CO, CO2, H, He, N2, Ne, O2, or other suitable gases. In some embodiments, a fan device (regarding...) Figure 3 It can optionally be used to accelerate heat dissipation. In some other embodiments, the heat sink 310 may be omitted.

[0181] The heating / cooling element 334G may be a gas heat exchanger with a compressor, a refrigerant-based system with a compressor (e.g., a cold storage), or the like. For example, heat is released from the refrigerant by compressing it from a gaseous state to a liquid state; the refrigerant can absorb heat by expanding it from a liquid state to a gaseous state. In some embodiments, the heating / cooling element 334G may be a heating and cooling system that can perform a rapid thermal process to reheat the droplet generator 230 after backfilling it. For example, the heating / cooling element 334G may heat gas from the gas output pipe GOP and send the heated gas to the radiator 310 via the gas input pipe GIP. In some embodiments where a rapid thermal process is performed, the gas may be water vapor. Other details disclosed herein are similar to those described above and will not be repeated here. In some other embodiments, the active temperature control device 330 may include a cooling gas gun that injects cooling gas directly into the radiator 310. For example, the cooling gas may be nitrogen. The cooling gas gun can be physically separated from the radiator 310 and the droplet generator 230. In some other embodiments, the gas inlet pipe can connect the cooling gas gun to the radiator 310, so that cooling gas is injected from the cooling gas gun through the gas inlet pipe GIP to reach the radiator 310.

[0182] Figure 7 This is a schematic diagram of a droplet generator according to some embodiments of the present disclosure. This embodiment is similar to... Figure 5 In addition to the embodiments, Figure 7 The illustrated temperature control system 300 includes thermally conductive wires IM and OM, and an active temperature control device 330 including solid heating / cooling elements 334S and solid tanks 332S. The thermally conductive wires IM and OM may contact the heat sink 310 or the outer portion 237b of the housing 237. The thermally conductive wires IM and OM may wrap around the heat sink 310. For example, the thermally conductive wires IM and OM may be between the fins of the heat sink 310. In some embodiments, the thermally conductive wires IM and OM may be spirally wound around the heat sink 310. The thermally conductive wires IM and OM are connected to the solid heating / cooling elements 334S and solid tanks 332S. The thermally conductive wires IM and OM may be made of aluminum, alumina, copper, manganese, marble, or a combination thereof. The solid heating / cooling element 334S may be a thermoelectric cooling module, such as a thermoelectric cooling chip and a thermoelectric cooler. In some other embodiments, the solid heating / cooling element 334S may be a thermoelectric cooler and heater, a heat exchanger with a compressor, a refrigerant-based system, etc. A temperature control circuit 400 is electrically coupled to the solid heating / cooling element 334S and the solid bath 332S to control the heat flow and the rate of heating and cooling.

[0183] In some embodiments, the thermally conductive wires OM and IM are made of a solid conductive material (e.g., Cu, Al, or a Cu-Al alloy as described above). During PM operation, while cooling the droplet generator 230, the thermally conductive wires OM and IM absorb heat from the reservoir 231 and transfer the heat to the solid heating / cooling element 334S. The solid heating / cooling element 334S absorbs and removes heat from the thermally conductive wire IM, allowing the thermally conductive wire IM to continue absorbing heat from the reservoir 231. In some embodiments, a passive heat dissipation device (e.g., a heat sink 310) is thermally coupled to the thermally conductive wires IM and OM to draw heat from the thermally conductive wires IM and OM into the environment, thereby cooling the droplet generator 230. In some other embodiments, the thermally conductive wires OM and IM are synthetic. For example, the thermally conductive wires OM and IM have a hollow tube surrounded by a solid conductive wall, and the hollow tube is adjustable for liquid or gas to be used for heat transfer. Heat-conducting wires OM and IM can be connected to the solid heating / cooling element 334S and the solid tank 332S, respectively. In some embodiments, the fan assembly (regarding...) Figure 3 It can optionally be used to accelerate heat dissipation. In some other embodiments, the heat sink 310 may be omitted.

[0184] In some embodiments, the temperature control system 300 can perform a rapid thermal process to heat the droplet generator 230. For example, thermally conductive wires IM / OM can be connected to heating wires, heating rods, heating plates, etc. In some embodiments, a solid heating / cooling element 334S can serve as both a heating and cooling element. Other details disclosed herein are similar to those described above and will not be repeated here.

[0185] Figure 8 This is a schematic diagram of a droplet generator according to some embodiments of the present disclosure. This embodiment is similar to... Figures 5 to 7 In this embodiment, in addition to the input tube IP and output tube OP being inserted between the accumulator 231 and the external portion 237b of the housing 237, such as Figure 8 The diagram illustrates this. In some embodiments, the input pipe IP and output pipe OP are surrounded by a heat-conducting cover CP, allowing heat from the reservoir 231 to be transferred to the input pipe IP via the heat-conducting cover CP. The input pipe IP / output pipe OP can be in the form of the liquid input pipe LIP / output pipe LOP, gas input pipe GIP / gas output pipe GOP, or heat-conducting wires IM / OM, as described above. The input pipe IP and output pipe OP are respectively connected to the tank 332 (e.g., liquid tank 332L, gas tank 332G, or solid tank 332S) and the heating / cooling element 334 (e.g., heating / cooling element 334L, heating / cooling element 334G, or heating / cooling element 334S). Other details of this disclosure are similar to those described above and will not be repeated here.

[0186] Figure 9 The illustrations depict methods of PM operation according to some embodiments of this disclosure. The descriptions are merely illustrative and are not intended to limit the scope of the descriptions specifically set forth in the claims. It should be understood that the methods can be adapted by… Figure 9 Additional steps are provided before, during, and after the illustrated steps, and some steps described below may be replaced or removed in additional embodiments of the method. The order of operations / processes may be interchanged.

[0187] In block S101, turn off the laser source and droplet generator. For example, as... Figure 2 The diagram shows that the laser source 220 is turned off by the laser controller 222, and the droplet generator 230 is shut down by turning off the pressurizing device PC, thus stopping the pressurization of the droplet generator 230. Figure 3 The illustration shows how this stops the emission of the excitation laser and the ejection of the metal droplets, thus halting the EUV lithography process. In some embodiments, the shutdown of the droplet generator 230 is synchronized with the shutdown of the laser source 220. In some other embodiments, the laser source 220 is shut down after the droplet generator 230 is shut down to prevent the excited target droplets TD from falling onto the collector 240.

[0188] At block S102, depressurize the droplet generator. For example, as... Figure 3 As shown in the diagram, the pressure of the droplet generator 230 can be reduced by turning on the pressure reducing device DC and turning off the pressure increasing device PC.

[0189] At block S103, the droplet generator is cooled to a target temperature not lower than 150°C. For example, a temperature control system 300 can be used to cool the droplet generator 230, such as... Figure 3 , Figure 5 , Figure 6 , Figure 7 or Figure 8 The diagram illustrates the process. In some embodiments, the temperature control circuit 400 is programmed to control the temperature control system 300 to trigger a cooling operation after the decompression operation of trigger block S102. In some embodiments, the temperature control circuit 400 is programmed to control the temperature control system 300 to terminate the cooling operation at a target temperature not lower than 150°C. In some embodiments, the termination of the cooling operation depends on the temperature detected by sensors 510 and 520 in the droplet generator 230. Specifically, the cooling operation terminates in response to the temperature detected by sensors 510 and 520 reaching the range of approximately 150°C to approximately 224°C.

[0190] In block S104, activate the droplet generator. For example, as shown... Figure 4 The illustration shows that the cap 232 of the droplet generator 230 can be removed from the housing 237 by using a DG to open / close the robotic arm 910 at a target temperature not lower than 150°C. In some embodiments, a programmed robot controller 916 controls a clamp 915 to remove the cap 232 from the housing 237 after the operation of the termination block S103. For example, the droplet generator opening operation depends on the temperature detected by sensors 510 and 520 in the droplet generator 230. Specifically, in response to the temperature detected by sensors 510 and 520 reaching the range of about 150°C to about 224°C, the clamp 915 is triggered to remove the cap 232 from the housing 237. In some other embodiments, the droplet generator 230 is manually opened by an experienced user using thermally insulated tools.

[0191] In block S105, the droplet generator is backfilled. For example, as... Figure 4The illustration shows that the open droplet generator 230 can be backfilled by inserting rod-shaped solid target material BT into the reservoir 231 of the open droplet generator 230 using a DG backfilling robotic arm 920 at a temperature not lower than approximately 150°C. In some embodiments, a programmed robot controller 926 triggers a clamp 925 to insert the rod-shaped solid target material BT into the reservoir 231 after the cover 232 has been removed from the housing 237. In some other embodiments, the droplet generator 230 is backfilled manually by an experienced user using thermally insulating tools.

[0192] In block S106, turn off the droplet generator. For example, as... Figure 4 The illustration shows that the cover 232 can be assembled to the housing 237 using a DG open / close robotic arm 910 at a target temperature of not less than 150°C, thereby shutting down the droplet generator 230. In some embodiments, a programmed robot controller 916 triggers a clamp 915 to assemble the cover 232 to the housing 237 after refilling the droplet generator 230. In some other embodiments, the droplet generator 230 is manually shut down by an experienced user using thermal isolation tools. In some embodiments, after refilling the droplet generator 230 and before shutting it down, the reservoir 231 in the droplet generator 230 can be evacuated using a vacuum pump (not shown). In this way, oxygen and moisture can be drawn out of the reservoir 231, thus extending the life of the droplet generator 230.

[0193] In block S107, the droplet generator is reheated. For example, the droplet generator 230 can be reheated from a temperature not lower than 150°C using heating elements 236a, 236b, and / or temperature control system 300. Figure 3 , Figure 5 , Figure 6 , Figure 7 or Figure 8 Illustration. In some embodiments, the programmed temperature control circuit 400 controls the heating element 236a, heating element 236b, and / or the temperature control system 300 to trigger a reheating operation after the droplet generator 230 is turned off. In some embodiments, before reheating the droplet generator 230, the droplet generator 230 may optionally be manually or automatically checked to ensure that there is no leakage in the turned-off droplet generator 230.

[0194] In some embodiments, the programmed temperature control circuit 400 controls the heating elements 236a, 236b, and / or the temperature control system 300 to terminate the reheating operation at a temperature above the melting point of the rod-shaped target material BT (e.g., tin) (approximately 231°C). In some embodiments, the termination of the reheating operation depends on the temperature detected by sensors 510 and 520 in the droplet generator 230. Specifically, the reheating operation terminates in response to the detected temperature from sensors 510 and 520 reaching a range from approximately 231°C to approximately 300°C, or up to approximately 2602°C, such that the tin material melts without vaporizing.

[0195] In block S108, pressurize the droplet generator. For example, as... Figure 3 As shown in the diagram, the reservoir 231 of the droplet generator 230 can be pressurized by simultaneously turning on the pressurizing device PC and turning off the depressurizing device DC. In this way, the droplet generator 230 can spray molten target droplets TD toward the excitation region ZE.

[0196] In block S109, turn off the laser source. For example, as follows: Figure 2 The diagram illustrates that the laser source 220 is activated via laser controller 222 to resume the emission of the excitation laser LB. In this manner, the laser source 220 can direct the excitation laser LB toward the excitation region ZE, thereby heating the target droplet TD and generating EUV radiation EL. This restores the EUV lithography process. In some embodiments, before activating the laser source 220, the droplet generator 230 may optionally be manually or automatically checked to ensure that the droplet generator 230 is properly ejecting the target droplet TD. In some embodiments, before activating the laser source, the container 210 may be evacuated using a vacuum pump (not shown). In this manner, oxygen and moisture can be extracted from the container 210, thus extending the lifespan of the droplet generator 230 disposed on the sidewall of the container 210.

[0197] Figure 10 A method for operating a PM according to some embodiments of this disclosure includes a droplet generator replacement operation (also known as a droplet generator exchange operation). The description is merely illustrative and is not intended to limit the scope of the claims specifically described thereafter. It should be understood that the PM can be operated by… Figure 10 Additional steps are provided before, during, and after the illustrated steps, and some steps described below may be replaced or removed in additional embodiments of the method. The order of operations / processes may be interchanged.

[0198] In block S201, turn off the laser source and droplet generator. For example, as... Figure 2 The diagram shows that the laser source 220 is turned off by the laser controller 222, and the droplet generator 230 is shut down by turning off the pressurizing device PC, thus stopping the pressurization of the droplet generator 230. Figure 3 The illustration shows that other details of block S201 are similar to those described in block S101, and therefore will not be repeated for the sake of simplicity.

[0199] At block S202, depressurize the droplet generator. For example, as... Figure 3 As shown in the diagram, the pressure of the droplet generator 230 can be reduced by turning on the pressure reducing device DC and turning off the pressure increasing device PC.

[0200] At block S203, the droplet generator is cooled to a target temperature not lower than 150°C. For example, a temperature control system 300 can be used to cool the droplet generator 230, such as... Figure 3 , Figure 5 , Figure 6 , Figure 7 or Figure 8 The illustration shows that other details of block S203 are similar to those described in block S103, and therefore will not be repeated for the sake of simplicity.

[0201] In block S204, remove the droplet generator from the container. For example, as... Figure 2 The illustration shows the removal of the droplet generator 230 from the lid 212 of the container 210 at a temperature not lower than 150°C. In some embodiments, the droplet generator 230 can be removed from the container 210 using a robotic arm 910 or robotic arm 920, such as... Figure 4 The illustration shows that in some embodiments, a programmed robot controller controls clamp 915 or clamp 925 to remove the droplet generator 230 from the container 210 after the cooling operation of the termination block S203. For example, the droplet generator opening operation depends on the temperature detected by sensors 510 and 520 in the droplet generator 230. Specifically, clamp 915 or clamp 925 is triggered to remove the droplet generator 230 from the container 210 in response to the detected temperature of sensors 510 and 520 reaching a range of about 150°C to about 224°C. In some other embodiments, the droplet generator 230 is manually removed from the container 210 by an experienced user using thermally insulating tools. In some embodiments, the removal operation is performed in a low-oxygen and low-humidity environment to extend the life of the droplet generator. For example, the removal operation is performed in a vacuum environment. More specifically, before removing the droplet generator 230 from the container 210, the atmosphere surrounding the droplet generator 230 can be evacuated using a vacuum pump (not shown). In this way, oxygen and moisture can be drawn out of the atmosphere surrounding the droplet generator 230 using the vacuum pump.

[0202] In block S205, another droplet generator filled with target material is assembled into the container. For example, as... Figure 2As shown in the diagram, after the droplet generator 230 is removed from the container 210, a next droplet generator 230 filled with target material TM (which may be interchangeably referred to as a displacement droplet generator) is assembled into the container 210 using, for example, a robotic arm 910 or a robotic arm 920. Figure 4 Illustration. In some other embodiments, the displacement droplet generator 230 is manually assembled to the container 210 by an experienced user using thermally insulating tools. In some embodiments, the assembly operation is performed in a low-oxygen and low-humidity environment to extend the life of the displacement droplet generator. For example, the replacement operation is performed in a vacuum environment. In some embodiments, after the displacement droplet generator 230 is assembled to the container 210, the reservoir 231 in the displacement droplet generator 230 can be evacuated using a vacuum pump (not shown). In this way, oxygen and moisture can be drawn out from the reservoir 231, thereby extending the life of the displacement droplet generator 230.

[0203] In block S206, the displacement droplet generator is heated. For example, the displacement droplet generator 230 can be reheated using heating elements 236a, 236b, and / or temperature control system 300, such as... Figure 3 , Figure 5 , Figure 6 , Figure 7 or Figure 8 The illustration shows that other details of block S206 are similar to those described in block S107, and therefore will not be repeated for the sake of simplicity.

[0204] In block S207, pressurize the droplet generator. For example, as... Figure 3 As shown in the diagram, the displacement droplet generator 230 can be pressurized by simultaneously turning on the pressurizing device PC and turning off the depressurizing device DC. In this way, the droplet generator 230 can spray molten target droplets TD toward the excitation region ZE.

[0205] In block S208, turn on the laser source. For example, as shown... Figure 2 The diagram shows that the laser source 220 is turned on via the laser controller 222. In this way, the laser source 220 can emit an excitation laser toward the excitation region ZE, thereby heating the target droplet TD and generating EUV radiation EL. This restores the EUV lithography process. In some embodiments, the container 210 can be evacuated by a vacuum pump (not shown) before turning on the laser source. In this way, oxygen and moisture can be drawn out of the container 210, thus extending the lifespan of the droplet generator 230 disposed on the sidewall of the container 210.

[0206] Figure 11 This is a schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure. The droplet generator assembly of this embodiment is similar to... Figure 3The droplet generator assembly in this embodiment may further include an in-line backfill system 260 and a storage tank ST.

[0207] A storage tank ST is configured to contain target material TM. The target material TM in the storage tank ST is supplied to a droplet generator 230 via a direct backfill system 260. The direct backfill system 260 may include a low-pressure vessel 262, a backfill pipe 264, a high-pressure vessel 266, and a delivery line 268. The low-pressure vessel 262 is coupled to the storage tank ST via a supply line SL. The backfill pipe 264 connects the low-pressure vessel 262 to the high-pressure vessel 266, which has a higher pressure than the low-pressure vessel 262. The delivery line 268 connects the high-pressure vessel 266 to the droplet generator 230. The direct backfill system 260 may further include a pump and valve (not shown) connected to the low-pressure vessel 262 and the high-pressure vessel 266 of the direct backfill system 260 to control the pressure of the low-pressure vessel 262 and the high-pressure vessel 266, thereby controlling the flow rate of the molten target material TM. When the direct backfill system 260 performs a direct backfill operation, the target material TM in the storage tank ST is heated to a temperature above the melting point of the target material TM using one or more heating elements HE in the storage tank ST, for example. The molten target material TM is then pumped to the low-pressure vessel 262 via the supply line SL, and subsequently pumped to the high-pressure vessel 266 via the backfill line 264. The pressure in the high-pressure vessel 266 can then be controlled to guide the molten target material TM from the high-pressure vessel 266 into the reservoir 231 of the droplet generator 230. For example, the high-pressure vessel 266 may include a gas inlet and a gas outlet, and gas is continuously supplied to the high-pressure vessel 266 via the gas inlet by a pump, and by closing the gas outlet, the pressure in the high-pressure vessel 266 is increased to a level higher than the pressure in the reservoir 231. In this way, the molten target material TM in the high-pressure vessel 266 can be pumped out of the high-pressure vessel 266 and enter the reservoir 231 via the delivery line 268.

[0208] During the EUV lithography process, the pressurizing device PC pressurizes molten target material TM from reservoir 231 into capillary 234 for ejecting droplets of target material TM. Furthermore, a programmable straight-flow backfill controller 269 triggers a straight-flow backfill operation during the EUV lithography process (i.e., during the ejection of droplets of target material TM). In other words, when droplet generator 230 ejects droplets of target material TM, molten target material TM in reservoir ST is conveyed to reservoir 231 using straight-flow backfill system 260. Thus, droplet generator 230 can backfill in a straight-flow manner without stopping droplet ejection. In some embodiments, straight-flow backfill controller 269 may include a processor, central processing unit (CPU), multiprocessor, distributed processing system, application-specific integrated circuit (ASIC), etc.

[0209] As described above, the temperature control system 300 may include a heat sink 310 and a fan 320. A temperature control circuit 400 is connected to the fan 320 and controls its operation. The temperature control system 300 (e.g., including the heat sink 310 and / or fan 320) may be located above the external portion 237b of the housing 237, the delivery line 268, a portion of the sidewall of the high-pressure vessel 266, and / or a portion of the sidewall of the low-pressure vessel 262. In short, the temperature control system 300 can be used to control the temperature of the direct discharge backfill system 260. Other details of this disclosure are similar to those described above and will not be repeated for the sake of brevity.

[0210] Figure 12 This is a schematic diagram of a droplet generator according to some embodiments of the present disclosure. This embodiment is similar to... Figure 11 In addition to the embodiments, Figure 12 The illustrated temperature control system 300 may include a liquid inlet pipe (LIP) and a liquid outlet pipe (LOP), and a temperature control device 330 in fluid communication with the liquid inlet pipe (LIP) and the liquid outlet pipe (LOP). The temperature control device 330 includes a water tank 332L and a liquid heating / cooling element 334L, such as... Figure 5 The temperature control system 300 (e.g., radiator 310 and liquid inlet pipe LIP and liquid outlet pipe LOP) may be located above or near the external portion 237b of housing 237, delivery line 268, a portion of the sidewall of high-pressure vessel 266, and / or a portion of the sidewall of low-pressure vessel 262. For example, radiator 310 and liquid inlet pipe LIP and liquid outlet pipe LOP may be connected to or in contact with the external portion 237b of housing 237, delivery line 268, a portion of the sidewall of high-pressure vessel 266, and / or a portion of the sidewall of low-pressure vessel 262. Other details of this disclosure are similar to those described above and will not be repeated for the sake of brevity.

[0211] Figure 13 This is a schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure. This embodiment is similar to... Figure 11 In addition to the embodiments, Figure 13 The temperature control system 300 includes a gas inlet pipe GIP and a gas outlet pipe GOP, and a temperature control device 330 in fluid communication with the gas inlet pipe GIP and the gas outlet pipe GOP. The temperature control device 330 includes a gas tank 332G and a gas heating / cooling element 334G, as per [reference needed]. Figure 6The temperature control system 300 (e.g., radiator 310 and gas inlet pipe GP) may be located above or near the external portion 237b of housing 237, delivery line 268, a portion of the sidewall of high-pressure vessel 266, and / or a portion of the sidewall of low-pressure vessel 262. For example, radiator 310 and gas inlet pipe GIP and gas outlet pipe GOP may be connected to or in contact with the external portion 237b of housing 237, delivery line 268, a portion of the sidewall of high-pressure vessel 266, and / or a portion of the sidewall of low-pressure vessel 262. Other details of this disclosure are similar to those described above and will not be repeated for the sake of brevity.

[0212] Figure 14 This is a schematic diagram of a droplet generator assembly according to some embodiments of the present disclosure. This embodiment is similar to... Figure 11 In some embodiments, the temperature control system 300 may include thermally conductive wires IM and OM, and a temperature control device 330 connected to the thermally conductive wires IM and OM. The temperature control device 330 includes a solid bath 332S and a solid heating / cooling element 334S, such as... Figure 7 The temperature control system 300 (e.g., radiator 310 and thermally conductive wires IM and OM) may be above or near the external portion 237b of housing 237, delivery line 268, a portion of the sidewall of high-pressure vessel 266, and / or a portion of the sidewall of low-pressure vessel 262. For example, radiator 310 and thermally conductive wires IM and OM may be connected to or in contact with the external portion 237b of housing 237, delivery line 268, a portion of the sidewall of high-pressure vessel 266, and / or a portion of the sidewall of low-pressure vessel 262. Other details of this disclosure are similar to those described above and will not be repeated for the sake of brevity.

[0213] Figure 15 This describes a method of PM operation according to some embodiments of this disclosure. The description is merely illustrative and is not intended to limit the scope of the claims specifically described thereafter. It should be understood that methods can be derived from... Figure 15 Additional steps are provided before, during, and after the illustrated steps, and some steps described below may be replaced or removed in additional embodiments of the method. The order of operations / processes may be interchanged.

[0214] In block S301, when the droplet generator sprays target droplets, a straight-flow backfill system is used to backfill the droplet generator online. For example, as... Figures 11 to 14 The diagram illustrates that, during the pressurization of the molten target material TM in the reservoir 231 by the pressurizing device PC to the point where droplets of the target material TM are ejected via the nozzle 235, the straight discharge backfill system 260 conveys the molten target material TM (e.g., molten tin) from the storage tank ST to the reservoir 231.

[0215] In block S302, shut down the droplet generator and the direct discharge backfill system. For example, as... Figure 2 The diagram shows that the laser source 220 is shut down via the laser controller 222. Additionally, as shown... Figure 11 The diagram shows that pressurizing the droplet generator 230 is stopped by turning off the pressurizing device PC, thus shutting down the droplet generator 230, and the straight backfill system 260 is shut down by the straight backfill controller 269.

[0216] At block S303, the storage tank of the direct backfill system is cooled to a target temperature of not less than 150°C. For example, the storage tank ST of the direct backfill system 260 can be cooled using a temperature control system 300, such as... Figure 11 , Figure 12 , Figure 13 or Figure 14 Illustration.

[0217] In block S304, open the storage tank of the straight-flow backfill system. For example, at a temperature not lower than 150°C, by using, for example... Figure 4 The robotic arm 910 shown in the illustration opens automatically. Figure 11 , Figure 12 , Figure 13 or Figure 14 The diagram shows a storage tank ST. In some embodiments, the robot controller 916 of the programmed robotic arm 910 controls the gripper 915 to open the storage tank ST after the operation of the termination block S303. For example, the storage tank opening operation depends on the temperature detected by the temperature sensor 530 in the storage tank ST. Specifically, in response to the temperature detected by the sensor 530 reaching the range of about 150°C to about 224°C, the gripper 915 is triggered to open the storage tank ST. In some other embodiments, the storage tank ST is opened manually by an experienced human user using thermally insulated tools.

[0218] In block S305, the storage tank of the backfill system is backfilled. For example, as... Figures 11 to 14 The diagram shows that after opening the storage tank ST, at a temperature not lower than approximately 150°C, using, for example... Figure 4 The illustrated robotic arm 920 automatically backfills the storage tank ST with solid target material TM. In some other embodiments, the storage tank ST is manually backfilled by an experienced human user using thermally insulating tools.

[0219] In block S306, shut down the storage slot of the straight backfill system. For example, as... Figures 11 to 14 The diagram illustrates that after the solid target material TM is placed into the storage tank ST at block S305, it is then subjected to a temperature not lower than 150°C, using methods such as... Figure 4The illustrated robotic arm 910 automatically closes the storage tank ST. In some other embodiments, the storage tank ST is manually backfilled by an experienced human user using thermal isolation tools.

[0220] In block S307, the storage tank is reheated. For example, by using one or more heating elements HE and / or temperature control system 300 in the storage tank ST, the storage tank ST can be reheated from a temperature not lower than 150°C to a temperature higher than the melting point of the target material TM, to melt the solid target material, such as... Figure 11 , Figure 12 , Figure 13 or Figure 14 Illustration.

[0221] In block S308, a straight-flow backfill system is used to backfill the droplet generator. For example, as... Figures 11 to 14 The diagram shows that the molten target material TM can be transported from the storage tank ST to the reservoir 231 of the droplet generator 230 using the straight backfill system 260.

[0222] In block S309, turn on the laser source. For example, as shown... Figure 2 The diagram shows that the laser source 220 is turned on by the laser controller 222. In this way, the laser source 220 can emit an excitation laser toward the excitation region ZE, thereby heating the target droplet TD and generating EUV radiation EL. In this way, the EUV lithography process is resumed.

[0223] Figure 16A Experimental results of a natural cooling droplet generator according to some embodiments of this disclosure. Figure 16B For the use of a fan according to some embodiments of this disclosure (e.g., Figure 3 Experimental results for the cooling droplet generator (fan 320) are presented. At time I0, the droplet generator assembly ejects droplets at a temperature TA higher than the melting point of the target material (e.g., tin). When time I is turned off, the droplet generator stops ejecting target droplets, heating elements 236a and 236b are turned off, and the temperature of the droplet generator's storage tank begins to decrease. The high backfill temperature TFH is the high temperature (e.g., from about 150°C to about 224°C) for performing the backfill process. The low backfill temperature TFL is the low temperature (e.g., 25°C) for performing another backfill process.

[0224] exist Figure 16A In the diagram, it takes time ΔIH1 to naturally lower the temperature of the droplet generator's reservoir from temperature TA to the high backfill temperature TFH, and time ΔIL1 to naturally lower the temperature of the droplet generator's reservoir from temperature TA to the low backfill temperature TFL. Clearly, time ΔIH1 is shorter than time ΔIL1, so that PM operation can be effectively shortened when backfilling is performed at a temperature not lower than 150°C, even if PM operation uses natural cooling.

[0225] exist Figure 16B In the case of a temperature control system (e.g., fan and radiator), it takes time ΔIH2 to lower the accumulator temperature from temperature TA to the high backfill temperature TFH, and time ΔIL2 to lower the accumulator temperature from temperature TA to the low backfill temperature TFL. Clearly, time ΔIH2 is shorter than time ΔIL2, so that PM operation, including effective cooling, can be effectively shortened when backfilling is performed at a temperature not lower than 150°C.

[0226] In addition, Figure 16B The time ΔIH2 shown in the figure is related to Figure 15 The comparison of time ΔIH1 shown in the figure clearly shows that with a temperature control system (e.g., fan and heatsink), the cooling operation can take less time, which will in turn effectively shorten the PM operation.

[0227] Based on the foregoing discussion, it is evident that this disclosure offers advantages. However, it should be understood that not all advantages need to be discussed herein, and not all embodiments require particular advantages; other embodiments may provide additional advantages. One advantage is that the cooling and reheating operations in PM operation require less processing time, resulting in increased yield. Another advantage is that contaminants or particles in the UV container or collector can be effectively reduced due to the shortened PM duration. Yet another advantage is that, due to the shortened PM time, the generation of oxygen-containing gases (e.g., O2, H2O) from the undesirable oxidation of the target material during PM operation can be reduced.

[0228] According to some embodiments disclosed herein, the method includes the following steps: spraying a metal droplet from a reservoir of a droplet generator toward an excitation region in front of a collector; emitting an excitation laser toward the excitation region, such that the metal droplet is heated by the excitation laser to generate extreme ultraviolet (EUV) radiation; stopping the emission of the excitation laser; depressurizing the reservoir of the droplet generator; cooling the droplet generator to a temperature not lower than about 150°C; and backfilling the reservoir of the droplet generator with a solid metal material at a temperature not lower than about 150°C.

[0229] In the above embodiments, the step of refilling the reservoir of the droplet generator is performed automatically. In the above embodiments, the step of refilling the reservoir of the droplet generator is performed in a vacuum environment.

[0230] In the above embodiments, the method further includes opening the droplet generator at a temperature not lower than about 150°C before refilling the reservoir of the droplet generator, wherein a first robotic arm is used to open the droplet generator, and a second robotic arm, different from the first robotic arm, is used to perform the step of refilling the reservoir of the droplet generator.

[0231] In the above embodiments, the method further includes shutting down the droplet generator at a temperature not lower than about 150°C after backfilling the reservoir of the droplet generator, and reheating the reservoir of the droplet generator at a temperature not lower than about 150°C after shutting down the droplet generator. The droplet generator is shut down using a first robotic arm, and the step of backfilling the reservoir of the droplet generator is performed using a second robotic arm different from the first robotic arm.

[0232] In the above embodiments, the method further includes drawing oxygen and moisture out of the reservoir of the droplet generator; and resuming the emission of the excitation laser after drawing out the oxygen and moisture.

[0233] According to some embodiments of this disclosure, the method includes the following steps: spraying metal droplets from a reservoir of a first droplet generator assembled to a container; emitting an excitation laser onto the metal droplets to generate extreme ultraviolet (EUV) radiation; turning off the first droplet generator; cooling the first droplet generator to a temperature not lower than about 150°C; removing the first droplet generator from the container at a temperature not lower than about 150°C; and assembling a second droplet generator to the container.

[0234] In the above embodiments, the method further includes depressurizing the reservoir of the first droplet generator before cooling the first droplet generator.

[0235] In the above embodiments, the method further includes heating the second droplet generator after assembling it into the container.

[0236] In the above embodiments, the steps of removing the first droplet generator from the container and assembling the second droplet generator into the container are performed automatically.

[0237] In the above embodiments, the method further includes drawing oxygen and moisture out of the container; and resuming the emission of the excitation laser after drawing out the oxygen and moisture.

[0238] According to some embodiments of this disclosure, the apparatus includes a droplet generator, a storage tank, a direct backfill system, a direct backfill controller, a first robotic arm, and a first robot controller. The droplet generator includes a reservoir and a nozzle in fluid communication with the reservoir. The direct backfill system is connected between the storage tank and the reservoir of the droplet generator. The direct backfill controller controls the direct backfill system to transport target material from the storage tank to the reservoir when the droplet generator ejects droplets of target material through the nozzle. The first robot controller controls the first robotic arm to open the storage tank in response to a temperature below the melting point of tin, rather than below approximately 150°C.

[0239] In the above embodiment, the first robotic arm has a clamp made of a material having a melting point higher than that of tin.

[0240] In the above embodiment, the device further includes: a second robotic arm, not controlled by the first robot controller; and a second robot controller that, after the first robot controller controls the first robotic arm to open the storage tank, controls the second robotic arm to refill the storage tank. The second robotic arm has a clamp made of a material having a melting point higher than that of tin.

[0241] The foregoing summary outlines features or examples of several embodiments to enable those skilled in the art to better understand the nature of this disclosure. Those skilled in the art should understand that this disclosure can be readily used as the basis for designing or modifying other processes and structures to achieve the same purposes and / or benefits as the embodiments or examples described herein. Those skilled in the art should also recognize that such equivalent structures do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure.

Claims

1. A lithography system preventive maintenance operation method, characterized by, Includes the following steps: A metal droplet is sprayed from a reservoir of a droplet generator toward an excitation region in front of a collector; An excitation laser is emitted toward the excitation region, causing the metal droplet to be heated by the excitation laser to generate extreme ultraviolet radiation; Stop the emission of the laser that is stimulating it; Reduce the pressure in the reservoir of the droplet generator; The droplet generator was cooled to a temperature not lower than 150°C; and The reservoir of the droplet generator is backfilled with a solid metal material at a temperature not lower than 150°C, and the backfilling of the reservoir of the droplet generator is performed in a vacuum environment.

2. The lithography system preventive maintenance operation method of claim 1, wherein, The refilling of the reservoir of the droplet generator is performed automatically.

3. The lithography system preventive maintenance operation method of claim 1, wherein, Before backfilling the reservoir of the droplet generator, the droplet generator shall be turned on at a temperature not lower than 150°C.

4. The preventive maintenance operation method for a lithography system as described in claim 3, characterized in that, The droplet generator is opened using a first robotic arm.

5. The preventive maintenance operation method for a lithography system as described in claim 4, characterized in that, The reservoir of the droplet generator is refilled using a second robotic arm, which is different from the first robotic arm.

6. The preventive maintenance operation method for a lithography system as described in claim 1, characterized in that, include: After backfilling the reservoir of the droplet generator, the droplet generator is shut off at a temperature not lower than 150°C.

7. The preventive maintenance operation method for a lithography system as described in claim 6, characterized in that, The droplet generator is shut down using a first robotic arm.

8. The preventive maintenance operation method for a lithography system as described in claim 7, characterized in that, The reservoir of the droplet generator is refilled using a second robotic arm, which is different from the first robotic arm.

9. The preventive maintenance operation method for a lithography system as described in claim 6, characterized in that, include: After the droplet generator is turned off, the reservoir of the droplet generator is reheated at a temperature not lower than 150°C.

10. The preventive maintenance operation method for a lithography system as described in claim 1, characterized in that, include: Oxygen and moisture are drawn from the reservoir of the droplet generator; and After the oxygen and moisture are drawn out, the emission of the excitation laser is restored.

11. A preventive maintenance operation method for a lithography system, characterized in that, Includes the following steps: Turn on a laser source to generate an excitation laser; Turn on a droplet generator to eject a metal droplet from the droplet generator, wherein the trajectory of the metal droplet intersects the optical path of the excitation laser, so that the metal droplet is heated by the excitation laser to generate extreme ultraviolet radiation; Turn off the droplet generator; After shutting down the droplet generator, cool the droplet generator to a temperature not lower than 150°C. After the droplet generator is cooled, a first robotic arm is used to open the droplet generator; After the droplet generator is turned on, a reservoir of the droplet generator is backfilled with a solid metal material at a temperature not lower than 150°C, and the backfilling of the reservoir is performed in a vacuum environment; and After backfilling the reservoir of the droplet generator, the droplet generator is then heated.

12. The preventive maintenance operation method for a lithography system as described in claim 11, characterized in that, The reservoir of the droplet generator is refilled using a second robotic arm, which is different from the first robotic arm.

13. The preventive maintenance operation method for a lithography system as described in claim 11, characterized in that, Also includes: After shutting down the droplet generator, the laser source is turned off; as well as After reheating the droplet generator, the laser source is turned on again.

14. A preventive maintenance operation method for a lithography system, characterized in that, Includes the following steps: A metal droplet is sprayed from a reservoir of a droplet generator toward an excitation region in front of a collector; An excitation laser is emitted toward the excitation region, causing the metal droplet to be heated by the excitation laser to generate extreme ultraviolet radiation; Stop the emission of the laser that is stimulating it; Reduce the pressure in the reservoir of the droplet generator; Cool the droplet generator to a temperature not lower than 150°C; The reservoir of the droplet generator is backfilled with a solid metal material at a temperature not lower than 150°C, and the backfilling of the reservoir of the droplet generator is performed in a vacuum environment. Oxygen and moisture are drawn from the reservoir of the droplet generator; and After the oxygen and moisture are drawn out, the emission of the excitation laser is restored.

15. The preventive maintenance operation method for a lithography system as described in claim 14, characterized in that, include: Before refilling the reservoir of the droplet generator, a first robotic arm is used to open the droplet generator.

16. The preventive maintenance operation method for a lithography system as described in claim 15, characterized in that, include: The reservoir of the droplet generator is refilled using a second robotic arm, which is different from the first robotic arm.

17. The preventive maintenance operation method for a lithography system as described in claim 14, characterized in that, Also includes: After the reservoir of the droplet generator is backfilled, a first robotic arm is used to open the droplet generator.

18. The preventive maintenance operation method for a lithography system as described in claim 17, characterized in that, The reservoir of the droplet generator is refilled using a second robotic arm, which is different from the first robotic arm.

19. The preventive maintenance operation method for a lithography system as described in claim 14, characterized in that, The extraction of oxygen and moisture from the reservoir of the droplet generator is performed after the reservoir of the droplet generator is refilled.

20. The preventive maintenance operation method for a lithography system as described in claim 14, characterized in that, Also includes: After the oxygen and moisture are extracted, and before the emission of the excitation laser is restored, the droplet generator is heated again.

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