Patent Application
20230107078
As consumer devices have gotten smaller and smaller in response to consumer demand, the individual components of these devices have necessarily decreased in size as well. Semiconductor devices, which make up a major component of devices such as mobile phones, computer tablets, and the like, have been pressured to become smaller and smaller, with a corresponding pressure on the individual devices (e.g., transistors, resistors, capacitors, etc.) within the semiconductor devices to also be reduced in size. The decrease in size of devices has been met with advancements in semiconductor manufacturing techniques such as lithography.
For example, the wavelength of radiation used for lithography has decreased from ultraviolet to deep ultraviolet (DUV) and, more recently to extreme ultraviolet (EUV). Further decreases in component size require further improvements in resolution of lithography which are achievable using extreme ultraviolet lithography (EUVL). EUVL employs radiation having a wavelength of about 1-100 nm.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
The advanced lithography process, method, and materials described in the current disclosure can be used in many applications, including fin-type field effect transistors (FinFETs). For example, the fins may be patterned to produce a relatively close spacing between features, for which the above disclosure is well suited. In addition, spacers used in forming fins of FinFETs can be processed according to the above disclosure.
Embodiments of the present disclosure generally relate to extreme ultraviolet (EUV) lithography systems and methods. More particularly, it is related to EUV lithography tools and methods of refilling a droplet generator (DG) and/or replacing (i.e., swapping) a droplet generator in the EUV lithography tool with another droplet generator. In an EUV lithography tool, a laser-produced plasma (LPP) generates extreme ultraviolet radiation which is used to image a photoresist coated substrate. In an EUV lithography tool, an excitation laser heats metal (e.g., tin, lithium, etc.) target droplets to ionize the droplets to plasma which emits the EUV radiation. For reproducible generation of EUV radiation, the target droplets arriving at the focal point (also referred to herein as the “zone of excitation”) have substantially the same size and arrive at the zone of excitation at the same time as an excitation pulse from the excitation laser arrives.
The EUV lithography system 100 also employs an illuminator 110. In some embodiments, the illuminator 110 includes various reflective optics, such as a single mirror or a mirror system having multiple mirrors, so as to direct the light EL from the radiation source 200 onto a mask 130 secured on a mask stage 120.
In some embodiments, the mask stage 120 includes an electrostatic chuck (e-chuck) used to secure the mask 130. In this context, the terms mask, photomask, and reticle are used interchangeably. In the present embodiment, the mask 130 is a reflective mask. One exemplary structure of the mask 130 includes a substrate with a low thermal expansion material (LTEM). For example, the LTEM may include TiO2 doped SiO2, or other suitable materials with low thermal expansion. The mask 130 includes a reflective multi-layer (ML) deposited on the substrate. The ML includes a plurality of film pairs, such as molybdenum-silicon (Mo/Si) film pairs (e.g., a layer of molybdenum above or below a layer of silicon in each film pair). Alternatively, the ML may include molybdenum-beryllium (Mo/Be) film pairs, or other suitable materials that are configurable to highly reflect the EUV light EL. The mask 130 may further include a capping layer, such as ruthenium (Ru), disposed on the ML for protection. The mask 130 further includes an absorption layer, such as a tantalum boron nitride (TaBN) layer, deposited over the ML. The absorption layer is patterned to define a layer of an integrated circuit (IC). The mask 130 may have other structures or configurations in various embodiments.
The EUV lithography system 100 also includes a projection optics module (or projection optics box (POB)) 140 for imaging the pattern of the mask 130 onto a semiconductor substrate W (e.g., wafer) secured on a substrate stage (e.g., wafer stage) 150 of the EUV lithography system 100. The POB 140 includes reflective optics in the present embodiment. The EUV light EL that is directed from the mask 130 and carries the image of the pattern defined on the mask 130 is collected by the POB 140. The illuminator 110 and the POB 140 may be collectively referred to as an optical module of the EUV lithography system 100. In the present embodiment, the semiconductor substrate W is a semiconductor wafer, such as a silicon wafer or other type of wafer to be patterned. The semiconductor substrate W is coated with a resist layer sensitive to the EUV light EL in the present embodiment. Various components including those described above are integrated together and are operable to perform EUV lithography exposing processes.
In some embodiments, the target droplets TD are metal droplets, such as droplets of tin (Sn), lithium (Li), or an alloy of Sn and Li. In some embodiments, the target droplets TD each have a diameter in a range from about 10 microns (μm) to about 100 μm. For example, in an embodiment, the target droplets TD are tin droplets, having a diameter of about 10 μm to about 100 μm. In other embodiments, the target droplets TD are tin droplets having a diameter of about 25 μm to about 50 μm. In some embodiments, the target droplets TD are supplied through a nozzle 235 of the droplet generator 230 at a rate in a range from about 50 droplets per second (i.e., an ejection-frequency of about 50 Hz) to about 50,000 droplets per second (i.e., an ejection-frequency of about 50 kHz). In some embodiments, the target droplets TD are supplied at an ejection-frequency of about 100 Hz to about 25 kHz. In other embodiments, the target droplets TD are supplied at an ejection frequency of about 500 Hz to about 10 kHz. The target droplets TD are ejected through the nozzle 235 and into a zone of excitation ZE at a speed in a range of about 10 meters per second (m/s) to about 100 m/s in some embodiments. In some embodiments, the target droplets TD have a speed of about 10 m/s to about 75 m/s. In other embodiments, the target droplets TD have a speed of about 25 m/s to about 50 m/s.
In some embodiments, an excitation laser LB generated by the excitation laser source 220 is a pulse 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 a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser source with a wavelength in the infrared region of the electromagnetic spectrum. For example, the laser source 220 has a wavelength of 9.4 μm or 10.6 μm, in an embodiment.
In some embodiments, the excitation laser LB includes a pre-heat laser and a main laser. In such embodiments, the pre-heat laser pulse (interchangeably referred to herein as the “pre-pulse) is used to heat (or pre-heat) a given target droplet to create a low-density target plume with multiple smaller droplets, which is subsequently heated (or reheated) by a pulse from the main laser, generating increased emission of EUV light.
In some embodiments, the pre-heat laser pulses have a spot size about 100 μm or less, and the main laser pulses have a spot size in a range of about 150 μm to about 300 μm. In some embodiments, the pre-heat laser and the main laser pulses have a pulse-duration in the range from about 10 ns to about 50 ns, and a pulse-frequency in the range from about 1 kHz to about 100 kHz. In some embodiments, the pre-heat laser and the main laser have an average power in the range from about 1 kilowatt (kW) to about 50 kW. The pulse-frequency of the excitation laser LB is matched with the ejection-frequency of the target droplets TD in some embodiments.
The excitation laser LB is directed through a window OW in the collector 240 into the zone of excitation ZE. The window OW is made of a suitable material substantially transparent to the excitation laser LB. The generation of the pulse lasers is synchronized with the ejection of the target droplets TD through the nozzle 235. As the target droplets TD move through the excitation zone ZE, the pre-pulses heat the target droplets TD and transform them into low-density target plumes. A delay between the pre-pulse and the main pulse is controlled to allow the target plume to form and to expand to an optimal size and geometry. In some embodiments, the pre-pulse and the main pulse have the same pulse-duration and peak power. When the main pulse heats the target plume, a high-temperature plasma is generated. The plasma emits EUV radiation EL, which is collected by the collector mirror 240. The collector 240 further reflects and focuses the EUV radiation EL toward the illuminator 110 (as shown in
In some embodiments, the collector 240 is designed with a proper coating material and shape to function as a mirror for EUV collection, reflection, and focusing. In some embodiments, the collector 240 is designed to have an ellipsoidal geometry. In some embodiments, the coating material of the collector 240 is similar to the reflective multilayer of the EUV mask 130 (as shown in
In some embodiments, the high-temperature plasma may cool down and become vapors or small particles (collectively, debris) PD. The debris PD may deposit onto the surface of the collector 240, thereby causing contamination thereon. Over time, the reflectivity of the collector 240 degrades due to debris accumulation and other factors such as ion damages, oxidation, and blistering. Once the reflectivity is degraded to a certain degree, the collector 240 reaches the end of its usable lifetime and may need to be swapped out (i.e., replaced with a new collector).
The vessel 210 has a cover 212 for ventilation and for collecting debris PD. In some embodiments, the cover 212 is made of a suitable solid material, such as stainless steel. The cover 212 is designed and disposed around the collector 240. The cover 212 may include a plurality of vanes, which are evenly spaced around the cone-shaped cover 212. In some embodiments, the radiation source 200 further includes a heating unit HU disposed around part of the cover 212. The heating unit HU functions to maintain the temperature inside the cover 212 above a melting point of the debris PD so that the debris PD does not solidify on the inner surface of the cover 212. When the debris PD vapor comes in contact with the vanes, it may condense into a liquid form and flow into a lower section of the cover 212. The lower section of the cover 212 may provide holes (not shown) for draining the debris liquid out of the cover 212.
In some embodiments, a buffer gas GA is supplied from a first buffer gas supply 270 through the aperture in collector 240 by which the pulse laser is delivered to the tin droplets. In some embodiments, the buffer gas is H2, He, Ar, N2 or another inert gas. In certain embodiments, H radicals generated by ionization of the H2 buffer gas is used for cleaning purposes. The buffer gas GA can also be provided through one or more second buffer gas supplies 272 toward the collector 240 and/or around the edges of the collector 240. Further, the vessel 210 further includes an exhaust system 280 so that the buffer gas is exhausted outside the vessel 210.
Hydrogen gas has low absorption to the EUV radiation. Hydrogen gas reaching the coating surface of the collector 240 reacts chemically with a metal of the droplet forming a hydride, e.g., metal hydride. When tin (Sn) is used as the droplet TD, stannane (SnH4), which is a gaseous byproduct of the EUV generation process, is formed. The gaseous SnH4 is then pumped out through the exhaust system 280.
The buffer gas GA is provided for various protection functions, which include effectively protecting the collector 240 from the contaminations by tin particles. Other suitable gas may be alternatively or additionally used. The gas GA may be introduced into the collector 240 through openings (or gaps) near the output window OW through one or more gas pipelines. The exhaust system 280 includes one or more exhaust lines 282 and one or more pumps 284. The exhaust line 282 is connected to the wall of the vessel 210 for receiving the exhaust. In some embodiments, the cover 212 is designed to have a cone shape with its wide base integrated with the collector 240 and its narrow top section facing the illuminator 110 (
In the present embodiments, a temperature control system 300 may be arranged adjacent to or connected to the droplet generator 230, in which the temperature control system 300 is at least configured for cooling the droplet generator 230. In some embodiments, the temperature control system 300 may be configured for cooling and/or heating the droplet generator 230, which will be discussed in greater detail below.
The reservoir 231 is configured for holding the target material TM. The 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 thermal conductive material. The sidewall 231a surrounds the outer edge of the bottom wall 231b and extends away from the bottom surface 231b. The heating elements 236b may surround the reservoir 231 for heating the target material TM and keeping the target material TM at a temperature above a melting point of the target material TM for generating liquid droplets. For example, during irradiating EUV radiation EL using the EUV radiation source 200 (referring to
In some embodiments, a gas inlet 2321 and a gas outlet 2320 are formed on the cover 232. The gas inlet 2321 is connected to a gas line PCL for introducing pumping gas, such as argon, into the reservoir 231. For example, a pressurizing device PC is configured to supply gas into the reservoir 231 through the gas line PCL. The gas outlet 2320 is connected to a depressurizing device DC (e.g., a pump) though another gas line DCL for pumping out the gas from the reservoir 231. By controlling the gas flow in the gas lines PCL and DCL connected to the gas inlet 2321 and the gas outlet 2320, the pressure in the reservoir 231 can be controlled. For example, when the pressurizing device PC is turned on and the depressurizing device DC is turned off, the pressure in the reservoir 231 increases. As a result, the molten target material TM in the reservoir 231 can be forced out of the reservoir 231 into the capillary tube 234 by the increased gas pressure, and thus the molten target material TM can flow through the capillary tube 234 establishing a continuous stream which subsequently breaks into one or more target droplets TD (as shown in
The capillary tube 234 is fluidly communicated with the reservoir 231 and the nozzle 235. In greater detail, the capillary tube 234 includes a first end 234a closest to the reservoir 231, a second end 234b farthest from the reservoir 231, and a sidewall 234c between the first and second ends 234a and 234b. A nozzle 235 is at the second end 234b farthest from the reservoir 231. Ejecting the target droplets TD (as shown in
In some embodiments, the droplet generator 230 includes a holder 233 encircling the outer shell 237, and the outer shell 237 has an interior portion 237a and an exterior portion 237b on opposite sides of the holder 233. The temperature control system 300 is at least partially over the exterior portion 237b of the outer shell 237. When the droplet generator 230 is inserted into the vessel 210 of the radiation source 200 (as shown in FIG. 2), the holder 233 presses against an outer surface of the cover 212 of the vessel 210 in an airtight manner. For example, the dashed line in
A prevention maintenance (PM) operation for the droplet generator 230 is performed, for example, on a weekly basis. In some embodiments, the PM operation at least includes depressurizing the droplet generator 230, cooling down the target material TM in the droplet generator 230 to a room temperature (from about 25° C. to about 40° C.), opening the droplet generator 230, refilling the reservoir 231 of the droplet generator 230 with a bar-shaped solid target material TM (e.g., tin bar), closing 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).
The PM operation, however, is time-consuming because it takes several hours to naturally cool down the droplet generator 230 to the room temperature and to then reheat the refilled droplet generator 230 from the room temperature to the temperature above the melting point of the target material TM. The time-consuming PM operation would thus reduce throughput of the EUV lithography processes.
As a result, in some embodiments of the present disclosure, when the droplet generator 230 is to be refilled, the droplet generator 230 is cooled down to a target temperature above room temperature. In greater detail, the droplet generator 230 is cooled down to a target temperature lower than the melting point (about 231° C.) of the target material TM (e.g., tin) but not lower than about 150° C. In this way, the cooling time duration and the reheating time duration can be effectively reduced, which in turn will improve throughput of the EUV lithography processes. Further, if the droplet generator 230 is cooled down to a target temperature lower than 150° C., the nozzle 235 would suffer from aggravated clogging issues. Moreover, it is observed that the liquid-to-solid phase transition of the target material TM in the droplet generator 230 begins once the temperature reaches about 231° C. and terminates after the temperature reaches about 218° C. As a result, the lower the temperature of the cooling operation terminates, the safer the refilling operation is. It is observed that if cooling operation terminates at a target temperature is higher than about 224° C., the target material TM might not be entirely solidified and thus prone to flow out of the droplet generator 230 during the refilling operation, which in turn would degrade the refilling operation. Therefore, the droplet generator 230 may be cooled down to a target temperature from about 150° C. to about 224° C. In some embodiments, the cooling operation terminates at the target temperature from about 150° C. to about 210° C. In some embodiments, the cooling operation terminates at the target temperature from about 150° C. to about 200° C. In some embodiments, the cooling operation terminates at the target temperature from about 150° C. to about 175° C.
Because the cooling operation terminates at the target temperature not lower than 150° C., it may be dangerous for manually opening, refilling and closing the droplet generator 230. Therefore, in some embodiments, one or more robot arms may be employed to automatedly open, refill and/or close the droplet generator 230. Exemplary robot arms 910 and 920 for automatedly opening, refilling and/or closing the droplet generator 230 are shown in
The DG opening/closing robot 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. Rotations of the base 911, the arm 912, the forearm 913 and the wrist member 914 are controlled by the robot controller 916 in such a way that the gripper 915 can be moved in a three-dimensional manner. As a result, in an operation of opening the droplet generator 230, the gripper 915 can be moved to grip the cover 232 and then unfasten the cover 232 from the outer shell 237 of the droplet generator 230. On the other hand, in an operation of closing the droplet generator 230, the gripper 915 gripping the cover 232 can be moved back to the droplet generator 230 and then fasten the cover 232 to the outer shell 237.
Similar to the DG opening/closing robot arm 910, the refilling robot arm 920 includes a rotatable base 921, a rotatable arm 922, a rotatable forearm 923, a rotatable wrist member 924, a gripper 925 and a robot controller 926. Rotations of the base 921, the arm 922, the forearm 923 and the wrist member 924 are controlled by the robot controller 926 in such a way that the gripper 925 can be moved in a three-dimensional manner. As a result, the gripper 925 gripping a bar-shaped solid target material BT (e.g., tin bar) can be moved to the opened droplet generator 230 and insert the bar-shaped solid target material BT into the reservoir 231.
In some embodiments, the robot controllers 916 and 926 are programmed to opening, refilling and closing the droplet generator 230 in sequence. For example, the droplet generator 230 is opened using the DG opening/closing robot arm 910 at first, and then refilled using the refilling robot arm 920, followed by closing the droplet generator 230 using the DG opening/closing robot 910. In some embodiments, the robot arms 910 are independently controlled. In other words, the robot arm 910 is free from control by the robot controller 926, and the robot arm 920 is free from control by the robot controller 916.
In some embodiments, the robot controllers 916 and 926 may include processors, central processing units (CPU), multi-processors, distributed processing systems, application specific integrated circuits (ASIC), or the like. In some embodiments, the robot controllers 916 and 926 are in a same processor. In some other embodiments, the robot controllers 916 and 926 are in different individual processors, respectively.
Example rotation of the DG opening/closing robot arm 910 is illustrated in
Also illustrated in
In some embodiments, the grippers 915 and 925 are made of a material having a melting point higher than the melting point (about 231° C.) of the target material TM (e.g., tin), so that opening/refilling/closing operations of the droplet generator 230 can be performed using the grippers 915 and 925 as long as the target material TM in the droplet generator 230 starts solidifying. For example, the grippers 915 and 925 can be made of stainless steel or other suitable materials that can remain in a solid-phase at the temperature higher than the melting point of the target material TM. In some embodiments, the opening/refilling/closing operations of the droplet generator 230 are performed in a low oxygen and low moisture environment, because the nozzle 235 of the droplet generator 230 may be damaged by oxygen and moisture during the opening/refilling/closing operations. For example, the opening/refilling/closing operations of the droplet generator 230 may be performed in a vacuum environment (i.e., oxygen-free and moisture-free environment). In greater detail, the atmosphere around the droplet generator 230 may be vacuumed by a vacuum pump (not shown) before performing opening/refilling/closing operations. In this way, oxygen and moisture can be drawn away from the atmosphere around the droplet generator 230 by the vacuum pump, which in turn will protect the nozzle 235 from the damages caused by the oxygen and moisture, thus extending lifetime of droplet generator 230.
Although the embodiments depicted in
Cooling down the droplet generator 230 can be performed using the temperature control system 300, as illustrated in
Through the configuration of the temperature control system 300, the cooling operation of the target material TM can be accelerated, and thus the PM operation can take less time duration. For example, the PM operation performed with the temperature control system 300 takes about 2 hours to about 3 hours less than a PM operation performed without the temperature control system 300. Moreover, due to the shortened PM time duration, contaminations or particles falling in the vessel 210 and/or on the collector 240 caused by the PM operation can be effectively reduced. Furthermore, due to the shortened PM time duration, unwanted oxidation of the target material TM caused by oxygen-containing gases (e.g., O2, H2O) during the PM operation can be reduced as well.
In some embodiments, the droplet generator 230 may further include sensors 510 located adjacent to the reservoir 231. For example, the sensors 510 are between the exterior portion 237b of the outer shell 237 and the sidewall 231a of the reservoir 231. In some embodiments, the droplet generator 230 may further include sensors 520 near the tube 234. The sensors 510 and 520 may detect a condition of the droplet generator 230, such as a pressure condition, a temperature condition, or the like. The temperature controller 400 is electrically connected with the sensors 510, 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 cooling down the droplet generator 230 based on the detected conditions. Similarly, the temperature controller 400 can start or stop heating 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 multi-processor, a distributed processing system, an application specific integrated circuit (ASIC), or the like.
In some embodiments, the droplet generator 230 may optionally include a charging circuit CC configured for charging ions into the droplet generator 230. The charging circuit CC may include an electrode CE positioned at the bottom wall 231b of the reservoir 231. The electrode CE is connected to ground or connected to a power supply. However, it is appreciated that many variations and modifications can be made to embodiments of the disclosure. In some other embodiments, the electrode is omitted, and the bottom wall 231b and/or the sidewall 231a of the reservoir 231 are made of electrically conductive materials and are electrically connected to ground or connected to the power supply.
During the cooling down the droplet generator 230 in the PM operation, a liquid stored in the liquid tank 332L is introduced to adjacent the reservoir 231 though the liquid input pipe LIP, and absorbs the heat of the reservoir 231. Then, the liquid is directed to the heating/cooling element 334L. The heating/cooling element 334L remove the heat of the liquid, and send the liquid to the liquid tank 332L. The liquid may be water, polar liquids, fluorinates, low viscosity oils, other organic liquids, molten salts, molten metals, or other suitable thermally conductive liquid. For example, suitable thermally conductive liquid includes a carrier liquid (e.g., water) dispersed with suitable thermally conductive nanoparticles, such as copper oxide, alumina, titanium dioxide, carbon nanotubes, silica, copper, silver rods, or other metals.
In some embodiments, the heating/cooling element 334L is a cooling system, such as a liquid nitride system, a liquid hafnium system, a cryogenics system, or a water cooling system. In some other embodiments, the heating/cooling element 334L is a heating and cooling system, in which the heating/cooling element 334L may heat or cool the liquid. For example, during reheating the droplet generator 230 in the PM operation, the temperature control system 300 may heat the droplet generator 230 by the heating/cooling element 334L. In some other embodiments, the active temperature control device 330 may include a cooling liquid gun ejecting a cooling liquid to the heat sink 310 directly, in which the cooling liquid may absorb the heat of the heat sink 310 and evaporate. For example, the cooling liquid may be water. The cooling liquid gun may be physically separated from the heat sink 310 and the droplet generator 230. In some other embodiments, a pipe (e.g., the pipe LIP) may connect the cooling liquid gun to the heat sink 310, such that the cooling liquid is ejected from the cooling liquid gun to reach the heat sink 310 through the pipe LIP. Other details of the present embodiments are similar to those aforementioned, and not repeated herein.
The heating/cooling element 334G may be a gas thermal exchanger with a compressor, a refrigerant based system (e.g., refrigerator) with a compressor, or the like. For example, by compressing the coolant from a gas state into a liquid state, heat is released from the coolant; by letting the coolant expands from the liquid state into the gas state, the coolant can soak up heat. In some embodiments, the heating/cooling element 334G may be a heating and cooling system, which may conduct a rapid thermal process to reheat the droplet generator 230 after refilling the droplet generator 230. For example, the heating/cooling element 334G may heat the gas coming from the gas output pipe GOP, and the heated gas is sent to the heat sink 310 through the gas input pipe GIP. In some embodiments where a rapid thermal process is conducted, the gas may be water vapor. Other details of the present embodiments are similar to those aforementioned, and not repeated herein. In some other embodiments, the active temperature control device 330 may include a cooling gas gun ejecting cooling gas to the heat sink 310 directly. For example, the cooling gas may be nitrogen. The cooling gas gun may be physically separated from the heat sink 310 and the droplet generator 230. In some other embodiments, a pipe (e.g., the pipe GIP) may connect the cooling gas gun to the heat sink 310, such that the cooling gas is ejected from the cooling gas gun to reach the heat sink 310 through the pipe GIP.
In some embodiments, the wires OM and IM are made of solid conductive material (e.g., aforementioned Cu, A1, or Cu-A1 Alloy). During cooling down the droplet generator 230 in the PM operation, the thermal conductive wires OM and IM absorb the heat of the reservoir 231 and transfer the heat to the solid heating/cooling element 334S. The solid heating/cooling element 334S absorbs and removes the heat of the thermal conductive wire IM, such that the thermal conductive wire IM is capable of continuing absorbing the heat of the reservoir 231. In some embodiments, the passive dissipation device (e.g., the heat sink 310) is thermally coupled to the thermal conductive wire IM and thermal conductive wire OM for drawing heat from the thermal conductive wire IM and thermal conductive wire OM to the ambient, thereby cooling the droplet generator 230. In some other embodiments, the wires OM and IM are composited. For example, the wires OM and IM has a hollow tube surrounding by solid conductive walls, and the hollow tube may accommodate liquid or gas for heat transmission. The composited wires OM and IM may be connected to the solid heating/cooling element 334S and the solid tank 332S, respectively. In some embodiments, the fan device (referring to
In some embodiments, the temperature control system 300 may conduct a rapid thermal process to heat the droplet generator 230. For example, the thermal conductive wire IM/OM can be connected to a heating wire, heating rod, heating piece, or the like. In some embodiments, the solid heating/cooling element 334S may act as a heating and cooling element. Other details of the present embodiments are similar to those aforementioned, and not repeated herein.
At block S101, the laser source and the droplet generator are turned off. For example, as illustrated in
At block S102, the droplet generator is depressurized. For example, as illustrated in
At block S103, the droplet generator is cooled down to a target temperature not lower than 150° C. For example, the droplet generator 230 can be cooled down using the temperature control system 300 as illustrated in
At block S104, the droplet generator is opened. For example, as illustrated in
At block S105, the droplet generator is refilled. For example, as illustrated in
At block S106, the droplet generator is closed. For example, as illustrated in
At block S107, the droplet generator is reheated. For example, the droplet generator 230 can be reheated from the temperature not lower than 150° C. using the heating elements 236a, 236b, and/or the temperature control system 300 as illustrated in
In some embodiments, the temperature controller 400 is programmed to control the heating elements 236a, 236b, and/or the temperature control system 300 to terminate the reheating operation at the target temperature higher than a melting point (about 231° C.) of the bar-shaped target material BT (e.g., tin). In some embodiments, the termination of the reheating operation relies upon the detected temperature from the sensors 510 and 520 in the droplet generator 230. In particular, the reheating operation terminates in response to that the detected temperature from the sensors 510 and 520 reaches a range from about 231° C. to about 300° C., or up to about 2602° C., such that the tin material melts and does not vaporize.
At block S108, the droplet generator is pressurized. For example, as illustrated in
At block S109, the laser source is turned on. For example, as illustrated in
At block S201, the laser source and the droplet generator are turned off. For example, as illustrated in
At block S202, the droplet generator is depressurized. For example, as illustrated in
At block S203, the droplet generator is cooled down to a target temperature not lower than 150° C. For example, the droplet generator 230 can be cooled down using the temperature control system 300 as illustrated in
At block S204, the droplet generator is dismantled from the vessel. For example, as illustrated in
At block S205, another droplet generator filled with the target material is assembled to the vessel. For example, as illustrated in
At block S206, the replacement droplet generator is heated. For example, the replacement droplet generator 230 can be heated using the heating elements 236a, 236b and/or the temperature control system 300 as illustrated in
At block S207, the droplet generator is pressurized. For example, as illustrated in
At block S208, the laser source is turned on. For example, as illustrated in
The storage tank ST is configured to contain the target material TM. The target material TM in the storage tank ST is supplied to the droplet generator 230 via the in-line refill system 260. The in-line refill system 260 may include a low-pressure vessel 262, a refill line 264, a high-pressure vessel 266, and a transfer line 268. The low-pressure vessel 262 is coupled to the storage tank ST through a supply line SL. The refill line 264 connects the low-pressure vessel 262 to the high-pressure vessel 266 which has a higher gas pressure than the low-pressure vessel 262. The transfer line 268 connects the high-pressure vessel 266 to the droplet generator 230. The in-line refill system 260 may further include pumps and valves (not shown) connected to the vessels 262 and 266 of the in-line refill system 260 to control the pressures in the vessels 262 and 266, thereby controlling the flow of molten target material TM. When the in-line refill system 260 performs an in-line refilling operation, the target material TM in the storage tank ST is heated using, for example, one or more heating elements HE in the storage tank ST, to a temperature above the melting point of the target material TM, followed by pumping the molten target material TM to the low-pressure vessel 262 through the supply line SL and then to the high-pressure vessel 266 through the refill line 264. Thereafter, a pressure in the high-pressure vessel 266 can be controlled for directing 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 by continuously supplying gas into the vessel 266 through the gas inlet by pump(s) and blocking the gas outlet, the pressure in the vessel 266 increases to higher than the pressure in the reservoir 231. In this way, the molten target material TM in the vessel 266 can be forced out of the vessel 266 and into the reservoir 231 through the transfer line 268.
During the EUV lithography process, the pressurizing device PC pressurizes the molten target material TM from the reservoir 231 into the tube 234 for eject droplets of the target material TM. Moreover, an in-line refill controller 269 is programmed to trigger the in-line refilling operation during the EUV lithography process (i.e., during ejecting droplets of the target material TM). In other words, the molten target material TM in the storage tank ST is delivered to the reservoir 231 by using the in-line refill system 260 when the droplet generator 230 ejects droplets of the target material TM. As a result, the droplet generator 230 can be refilled in an in-line manner without stopping ejecting droplets. In some embodiments, the in-line refill controller 269 may include a processor, a central processing unit (CPU), a multi-processor, a distributed processing system, an application specific integrated circuit (ASIC), or the like.
As described above, the temperature control system 300 may include a heat sink 310 and a fan 320. The controller 400 is connected to the fan 320 for controlling the operation of the fan 320. The temperature control system 300 (e.g., including the heat sink 310 and/or the fan 320) may be over the exterior portion 237b of the outer shell 237, the transfer line 268, a portion of a sidewall of the high-pressure vessel 266, and/or a portion of a sidewall of the low-pressure vessel 262. That is, the temperature control system 300 may be used to control a temperature of the refill system 260. Other details of the present embodiments are similar to those described above, and not repeated for the sake of brevity.
At block S302, the laser source, the droplet generator and the in-line refill system are turned off. For example, as illustrated in
At block S303, the storage tank of the in-line refill system is cooled down to a target temperature not lower than 150° C. For example, the storage tank ST of the in-line refill system 260 can be cooled down using the temperature control system 300, as illustrated in
At block S304, the storage tank of the in-line refill system is opened. For example, the storage tank ST as illustrated in
At block S305, the storage tank of the in-line refill system is refilled. For example, as illustrated in
At block S306, the storage tank of the in-line refill system is closed. For example, as illustrated in
At block S307, the storage tank is reheated. For example, the storage tank ST can be reheated from the 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 TM by using, for example, the one or more heating elements HE in the storage tank ST and/or the temperature control system 300, as illustrated in
At block S308, the droplet generator is refilled using the in-line refilled system. For example, as illustrated in
At block S309, the laser source is turned on. For example, as illustrated in
In
In
Moreover, comparing the time duration ΔIH2 as shown in
Based on the above discussions, it can be seen that the present disclosure offers advantages. It is understood, however, that other embodiments may offer additional advantages, and not all advantages are necessarily disclosed herein, and that no particular advantage is required for all embodiments. One advantage is that cooling and reheating operations in the PM operation take less process time, such that the yield rate is increased. Another advantage is that the contamination or particles in the EUV vessel or on the collector can be effectively reduced due to the shortened PM time duration. Still another advantage is that, due to the shortened PM time, unwanted oxidation of the target material caused oxygen-containing gases (e.g., O2, H2O) during the PM operation can be reduced.
According to some embodiments of the present disclosure, a method includes ejecting a metal droplet from a reservoir of a droplet generator toward a zone of excitation in front of a collector, emitting an excitation laser toward the zone of excitation, such that the metal droplet is heated by the excitation laser to generate extreme ultraviolet (EUV) radiation, halting the emission of the excitation laser, depressurizing the reservoir of the droplet generator, cooling down the droplet generator to a temperature not lower than about 150° C., and refilling the reservoir of the droplet generator with a solid metal material at the temperature not lower than about 150° C.
According to some embodiments of the present disclosure, a method includes ejecting a metal droplet from a reservoir of a first droplet generator assembled to a vessel, emitting an excitation laser to the metal droplet to generate extreme ultraviolet (EUV) radiation, turning off the first droplet generator, cooling down the first droplet generator to a temperature not lower than about 150° C., dismantling the first droplet generator from the vessel at the temperature at the temperature not lower than about 150° C., and assembling a second droplet generator to the vessel.
According to some embodiments of the present disclosure, an apparatus includes a droplet generator, a storage tank, an in-line refill system, an in-line refill controller, a first robot arm and a first robot controller. The droplet generator includes a reservoir and a nozzle fluidly communicated with the reservoir. The in-line refill system is connected between the storage tank and the reservoir of the droplet generator. The in-line refill controller controls the in-line refill system to deliver a target material from the storage tank to the reservoir when the droplet generator ejects a droplet of the target material through the nozzle. The first robot controller controls the first robot arm to open the storage tank in response to a temperature of the storage tank being lower than a melting point of tin but not lower than about 150° C.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
This application is a continuation application of U.S. patent application Ser. No. 17/338,441, filed Jun. 3, 2021, now U.S. Pat. No. 11,528,798, issued Dec. 13, 2022, which is a divisional application of U.S. patent application Ser. No. 16/548,731, filed Aug. 22, 2019, now U.S. Pat. No. 11,032,897, issued Jun. 8, 2021, all of which are herein incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16548731 | Aug 2019 | US |
| Child | 17338441 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17338441 | Jun 2021 | US |
| Child | 18064156 | US |
