Target supply system, extreme ultraviolet light generation device, and method for manufacturing electronic devices

Abstract

To suppress a reduction in gas pressure inside a melting tank, even if a surface temperature of a liquid target substance inside the melting tank is lowered.SOLUTION: A target supply system 261 includes: a load lock chamber C2 capable of storing a solid target substance 27a; a solid target supply pipe 42 connected to the load lock chamber C2; a pressure controller 62 for controlling a gas pressure supplied from outside; a gas pressure supply pipe connected to the pressure controller 62; a melting tank C3 which is connected to both the solid target supply pipe and the gas pressure supply pipe, melts the solid target substance 27a supplied through the solid target supply pipe from the load lock chamber C2, and generates the liquid target substance 27a; a nozzle 72 for discharging the liquid target substance 27 by the gas pressure supplied to the melting tank through the gas pressure supply pipe from the pressure controller 62; and a buffer tank 64 communicating with the melting tank and supplying the gas pressure, when the solid target substance is supplied to the melting tank.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a target supply system, an extreme ultraviolet light generating apparatus, and a method of manufacturing an electronic device.

Background Art

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in photolithography of semiconductor processes has been rapidly progressing. In the next generation, microfabrication of 10 nm or less will be required. For this reason, the development of an exposure apparatus that combines an EUV light generating apparatus that generates extreme ultraviolet (EUV) light with a wavelength of about 13 nm and a reduced projection reflection optics is expected.

[0003] As an EUV light generating apparatus, the development of an LPP (Laser Produced Plasma) type apparatus that uses plasma generated by irradiating a target material with pulsed laser light is progressing. [[ID=第十七]]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] A target supply system according to one aspect of the present disclosure comprises: a load lock chamber capable of containing a solid target material; a solid target supply pipe connected to the load lock chamber; a pressure regulator for adjusting the gas pressure supplied from the outside; a gas pressure supply pipe connected to the pressure regulator; a melting tank connected to both the solid target supply pipe and the gas pressure supply pipe, which melts the solid target material supplied from the load lock chamber via the solid target supply pipe to produce a liquid target material; a nozzle for discharging the liquid target material by gas pressure supplied from the pressure regulator to the melting tank via the gas pressure supply pipe; and a buffer tank that communicates with the melting tank and supplies gas pressure when supplying the solid target material to the melting tank.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: a laser device comprising: an

[0007] A method for manufacturing an electronic device according to one aspect of the present disclosure includes: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a laser device output from the target supply system and irradiating a target that has reached a predetermined region with pulsed laser light; an EUV focusing mirror for focusing extreme ultraviolet light emitted from a plasma generated in a predetermined region; an extreme ultraviolet light generation device comprising: an extreme ultraviolet light generation device comprising: a target supply system an EUV focusing mirror for focusing extreme ultraviolet light emitted from a plasma generated in a predetermined region; an extreme ultraviolet light generation device comprising: an extreme ultraviolet light generation device comprising: an extreme ultraviolet light generation device comprising: an extreme ultraviolet light generation device comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: a target supply system comprising: an EUV focusing mirror for irradiating a target that has reached a predetermined region with pulsed laser light; an extreme ultraviolet light generation device comprising: an extreme ultraviolet light generation device comprising: an extreme [Brief explanation of the drawing]

[0008] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] Figure 1 schematically shows the configuration of an exemplary LPP-type EUV light generation system. [Figure 2] Figure 2 schematically shows the configuration of the target supply system in the comparative example. [Figure 3] Figure 3 shows the operating procedure of the target supply system in the comparative example. [Figure 4] Figure 4 is a graph showing the change in gas pressure inside the molten tank when the solid target material is supplied from the load lock chamber to the molten tank. [Figure 5] Figure 5 is a graph showing the change in target velocity when the gas pressure change shown in Figure 4 occurs in the molten tank. [Figure 6]Figure 6 schematically shows the configuration of the target supply system according to the first embodiment. [Figure 7] Figure 7 shows the operation procedure of the target supply system according to the first embodiment. [Figure 8] Figure 8 is a graph illustrating the temperature change associated with heat transfer after a solid target material is supplied to the inside of the molten tank. [Figure 9] Figure 9 is a graph showing the temperature drop corresponding to the ratio ΔMsn / Msn. [Figure 10] Figure 10 shows a list of the gas pressure, volume, number of moles, and temperature inside the melting tank and buffer tank, respectively, before and after the temperature of the gas inside the melting tank drops. [Figure 11] Figure 11 is a graph showing the volume of the buffer tank according to the ratio ΔMsn / Msn. [Figure 12] Figure 12 schematically shows the configuration of the target supply system according to the second embodiment. [Figure 13] Figure 13 schematically shows the configuration of the target supply system according to the third embodiment. [Figure 14] Figure 14 schematically shows the configuration of the target supply system according to the fourth embodiment. [Figure 15] Figure 15 shows the configuration of the adjustment mechanism and the solid target supply valve, and their operation is shown in combination with Figure 16. [Figure 16] Figure 16 shows the configuration of the adjustment mechanism and the solid target supply valve, and their operation is shown in combination with Figure 15. [Figure 17] Figure 17 shows the operation procedure of the target supply system according to the fourth embodiment. [Figure 18] Figure 18 schematically shows the configuration of the pressure regulator used in each embodiment. [Figure 19] Figure 19 schematically shows the configuration of the exposure apparatus connected to the EUV light generation system. [Figure 20] Figure 20 schematically shows the configuration of the inspection device connected to the EUV light generation system. Embodiment

[0009] <Content> 1. Overall description of EUV light generation system 11 1.1 Configuration 1.2 Operation 2. Comparative example 2.1 Configuration 2.1.1 Reservoir tank C1 2.1.2 Load lock chamber C2 2.1.3 Melting tank C3 2.1.4 Various piping 2.2 Operation 2.3 Problems of the comparative example 3. Target supply system 261 in which buffer tank 64 is connected to gas pressure supply pipe L0 3.1 Configuration 3.2 Operation 3.3 Temperature drop ΔT of the gas inside melting tank C3 3.4 Gas pressure drop ΔP due to temperature drop ΔT 3.5 Function 4. Target supply system 262 in which melting tank C3 is removable 4.1 Configuration 4.2 Operation 4.3 Function 5. Variations in the arrangement of buffer tank 64 5.1 Configuration 5.2 Operation 5.3 Function 6. Target supply system 264 for detecting the liquid level of melting tank C3 6.1 Configuration 6.2 Operation 6.3 Function 7. Others 7.1 Pressure regulator 62 7.2 EUV light utilization device 6 7.3 Supplementary

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are examples of the disclosure and are not intended to limit the scope of this disclosure. Furthermore, not all configurations and operations described in each embodiment are necessarily essential to the configurations and operations of this disclosure. The same reference numerals are used for identical components, and redundant descriptions are omitted.

[0011] 1. Overall description of the EUV light generation system 11 1.1 Configuration Figure 1 schematically shows the configuration of an LPP-type EUV light generation system 11. The EUV light generator 1 is used together with a laser device 3. In this disclosure, the system including the EUV light generator 1 and the laser device 3 is referred to as the EUV light generation system 11. The EUV light generator 1 includes a chamber 2 and a target supply system 26. The chamber 2 is a sealable container. The target supply system 26 supplies a target 27 containing a target material into the chamber 2. The target material may include tin, terbium, gadolinium, lithium, xenon, or any combination of two or more of these.

[0012] The wall of chamber 2 is provided with a through-hole. This through-hole is covered by a window 21, through which pulsed laser light 32 output from the laser device 3 passes. Inside chamber 2, an EUV focusing mirror 23 with a spheroidal reflective surface is positioned. The EUV focusing mirror 23 has a first and a second focal point. A multilayer reflective film is formed on the surface of the EUV focusing mirror 23, in which molybdenum and silicon are alternately layered. The EUV focusing mirror 23 is positioned such that its first focal point is located in the plasma generation region 25 and its second focal point is located in the intermediate focal point 292. A through-hole 24 is provided in the center of the EUV focusing mirror 23, through which pulsed laser light 33 passes.

[0013] The EUV light generation apparatus 1 includes an EUV light generation processor 5, a target sensor 4, etc. The EUV light generation processor 5 is a processing unit that includes a memory 501 in which a control program is stored, and a CPU (central processing unit) 502 that executes the control program. The EUV light generation processor 5 is specially configured or programmed to perform various processes included in this disclosure. The target sensor 4 detects at least one of the presence, trajectory, position, and velocity of the target 27. The target sensor 4 may also have an imaging function.

[0014] Furthermore, the EUV light generator 1 includes a connecting section 29 that connects the inside of the chamber 2 with the inside of the EUV light utilization device 6. An example of the EUV light utilization device 6 will be described later with reference to Figures 19 and 20. Inside the connecting section 29, there is a wall 291 with an aperture formed therein. The wall 291 is positioned such that its aperture is located at the second focal point of the EUV focusing mirror 23.

[0015] Furthermore, the EUV light generation device 1 includes a laser light transmission device 34, a laser light focusing mirror 22, a target retrieval unit 28 for retrieving the target 27, and the like. The laser light transmission device 34 includes an optical element for defining the transmission state of the pulsed laser light 32, and an actuator for adjusting the position, orientation, etc., of this optical element.

[0016] 1.2 Operation Referring to Figure 1, the operation of the EUV light generation system 11 will be explained. The pulsed laser light 31 output from the laser device 3 passes through the laser light transmission device 34 and enters the chamber 2 as pulsed laser light 32, passing through the window 21. The pulsed laser light 32 travels along the laser light path inside the chamber 2, is reflected by the laser light focusing mirror 22, and is irradiated onto the target 27 as pulsed laser light 33.

[0017] The target supply system 26 outputs the target 27 toward the plasma generation region 25 inside the chamber 2. The target 27 is irradiated with pulsed laser light 33. The target 27, irradiated with pulsed laser light 33, becomes plasma, and synchrotron radiation 251 is emitted from the plasma. The EUV light contained in the synchrotron radiation 251 is reflected by the EUV focusing mirror 23 with a higher reflectivity than light in other wavelength ranges. The reflected light 252, which includes the EUV light reflected by the EUV focusing mirror 23, is focused at an intermediate focusing point 292 and output to the EUV light utilization device 6. Note that multiple pulses contained in the pulsed laser light 33 may be irradiated onto a single target 27.

[0018] The EUV photogeneration processor 5 controls the entire EUV photogeneration system 11. The EUV photogeneration processor 5 processes the detection results of the target sensor 4. Based on the detection results of the target sensor 4, the EUV photogeneration processor 5 controls the timing of the output of the target 27, the output direction of the target 27, etc. Furthermore, the EUV photogeneration processor 5 controls the oscillation timing of the laser device 3, the direction of propagation of the pulsed laser beam 32, the focusing position of the pulsed laser beam 33, etc. The various controls described above are merely examples, and other controls may be added as needed.

[0019] 2. Comparative Example 2.1 Configuration Figure 2 schematically shows the configuration of a target supply system 26 according to a comparative example. The comparative examples in this disclosure are forms that the applicant recognizes as being known only to the applicant, and are not known examples acknowledged by the applicant. As shown in Figure 2, the target supply system 26 according to the comparative example includes a reservoir tank C1, a load lock chamber C2, a melting tank C3, a target supply processor 60, solid target supply pipes 41 and 42, a measuring device 61, a pressure regulator 62, and an exhaust pump 63.

[0020] The target supply processor 60 is a processing unit that includes a memory 601 in which a control program is stored, and a CPU 602 that executes the control program. The target supply processor 60 corresponds to a processor in this disclosure. The target supply processor 60 is specially configured or programmed to perform various processes included in this disclosure.

[0021] 2.1.1 Reservoir Tank C1 The reservoir tank C1 is a container for holding a solid target material 27a, such as tin. The solid target material 27a may be, for example, spherical particles of approximately the same size. Alternatively, it may be particles of a shape other than spherical. The temperature inside the reservoir tank C1 is lower than the melting point of the target material. The gas pressure inside the reservoir tank C1 is approximately the same as atmospheric pressure.

[0022] The measuring device 61 is located at the lower end of the reservoir tank C1. The reservoir tank C1 is connected to the solid target supply pipe 41 via the measuring device 61, and the solid target supply pipe 41 is connected to the load lock chamber C2. A solid target supply valve VT1 is located in the solid target supply pipe 41.

[0023] Under normal circumstances, the measuring device 61 stops supplying the solid target material 27a to the solid target supply pipe 41. The weighing device 61 can weigh the solid target material 27a supplied from the reservoir tank C1 and pass it towards the load lock chamber C2. Weighing the solid target material 27a includes counting the number of particles of the solid target material 27a. The weighed solid target material 27a moves by gravity and passes through the solid target supply pipe 41 and the solid target supply valve VT1 to the load lock chamber C2. Once a predetermined amount of solid target material 27a has passed through, the weighing device 61 stops the passage of the solid target material 27a.

[0024] 2.1.2 Load Lock Chamber C2 The load lock chamber C2 is a container configured to accommodate the solid target material 27a supplied from the reservoir tank C1. The temperature inside the load lock chamber C2 is lower than the melting point of the target material. The load lock chamber C2 is connected to the common pipe L3 via the second pipe L2, and to the pressure regulator 62 via the common pipe L3. The pressure regulator 62 will be described later.

[0025] The load lock chamber C2 is connected to a solid target supply pipe 42, which is connected to a molten tank C3. A solid target supply valve VT2 is located in the solid target supply pipe 42. The solid target supply valve VT2 is normally closed to prevent gas from flowing from inside the molten tank C3 toward the load lock chamber C2. The solid target supply valve VT2 is temporarily opened to supply solid target material 27a from the load lock chamber C2 to the molten tank C3.

[0026] 2.1.3 Melting Tank C3 The molten tank C3 is a container that holds the target material supplied from the load lock chamber C2 via the solid target supply pipe 42. The molten tank C3 is connected to the solid target supply pipe 42 and, through a portion of the solid target supply pipe 42, to the first piping L1. The molten tank C3 is further connected to the common piping L3 via the first piping L1 and, through the common piping L3, to the pressure regulator 62. The pressure regulator 62 is connected to a gas cylinder G1 outside the target supply system 26. The gas cylinder G1 contains high-pressure noble gases such as argon gas and helium gas as pressurized gases. The pressure regulator 62 adjusts the gas pressure supplied from the gas cylinder G1 and supplies it to the molten tank C3. The target supply processor 60 controls the pressure regulator 62 so that the gas pressure inside the molten tank C3 is adjusted to a predetermined gas pressure. The predetermined gas pressure is lower than the gas pressure supplied from the gas cylinder G1 and higher than atmospheric pressure.

[0027] A heater 71 and a nozzle 72 are located in the molten tank C3. The heater 71 is connected to a power supply (not shown) and heats the inside of the molten tank C3 to a predetermined temperature higher than the melting point of the target material. The power supply is controlled based on the output of a temperature sensor (not shown) located in the molten tank C3, thereby controlling the temperature inside the molten tank C3. As a result, the solid target material 27a is melted in the molten tank C3 to produce a liquid target material.

[0028] The nozzle 72 is positioned at the lower end of the molten tank C3 in the direction of gravity. The tip of the nozzle 72 opens into the chamber 2 (see Figure 1). The liquid target material inside the molten tank C3 is discharged from the opening at the tip of the nozzle 72 due to the difference between the gas pressure supplied by the pressure regulator 62 and the gas pressure inside the chamber 2. When the nozzle 72 is vibrated by a piezoelectric element (not shown), the jet-like liquid target material discharged from the nozzle 72 separates into droplets, forming the target 27.

[0029] 2.1.4 Various types of piping The first pipe L1, the second pipe L2, and the common pipe L3 constitute the gas pressure supply pipe L0. The first pipe L1 is the pipe between the branch section SP and the connection section CP of the solid target supply pipe 42, the second pipe L2 is the pipe between the branch section SP and the load lock chamber C2, and the common pipe L3 is the pipe between the pressure regulator 62 and the branch section SP. The connection section CP is located between the solid target supply valve VT2 of the solid target supply pipe 42 and the molten tank C3. A first gas pressure supply valve V1 is located in the first pipe L1. The first pipe L1 supplies gas pressure from the branching section SP to the molten tank C3. A second gas pressure supply valve V2 is located in the second pipe L2. The second pipe L2 supplies gas pressure from the branching section SP to the load lock chamber C2.

[0030] Here, we have described the case where the first pipe L1 is connected to the molten tank C3 via a portion of the solid target supply pipe 42, but the first pipe L1 may be connected directly to the molten tank C3 without going through the solid target supply pipe 42.

[0031] In the second piping L2, between the load lock chamber C2 and the second gas pressure supply valve V2, piping L5 for supplying purge gas and piping L8 for exhaust are connected. Piping L5 is connected to an external gas cylinder G2 of the target supply system 26. Gas cylinder G2 contains a rare gas such as argon or helium as a purge gas. The gas pressure in gas cylinder G2 may be lower than the gas pressure in gas cylinder G1, and may be even lower than the gas pressure adjusted by the pressure regulator 62. The gas pressure in gas cylinder G2 may be slightly higher than atmospheric pressure. Alternatively, a pressure regulator (not shown) may be placed in piping L5, and the gas pressure of the purge gas supplied from gas cylinder G2 may be adjusted to a pressure lower than the gas pressure adjusted by the pressure regulator 62 and higher than atmospheric pressure. A valve V5 is located in piping L5. Piping L8 branches into piping L6 and piping L7. Piping L6 is equipped with valve V6 and exhaust pump 63. Piping L7 is equipped with valve V7. Exhaust pump 63 is configured to forcibly exhaust the gas inside load lock chamber C2, thereby lowering the gas pressure inside load lock chamber C2 below atmospheric pressure.

[0032] 2.2 Operation Figure 3 shows the operation procedure of the target supply system 26 according to the comparative example. The solid target material 27a inside the reservoir tank C1 is supplied to the molten tank C3 via the load lock chamber C2 as follows.

[0033] In S11, the operation starts with the solid target supply valves VT1 and VT2, the first and second gas pressure supply valves V1 and V2, and valves V5 to V7 all closed. The heater 71 heats the inside of the molten tank C3 to a predetermined temperature higher than the melting point of the target material. In S12, the target supply processor 60 opens the first gas pressure supply valve V1. This supplies the gas pressure regulated by the pressure regulator 62 to the molten tank C3, adjusting the pressure inside the molten tank C3 to high pressure. At the same time, the target supply system 26 begins supplying the target 27, and consumption of the liquid target substance begins. In S14, the target supply processor 60 waits for a certain period of time to elapse and for the liquid target substance to be consumed, and then proceeds to the next step.

[0034] In S21, the target supply processor 60 opens the solid target supply valve VT1. In S22, the target supply processor 60 controls the weighing device 61 to weigh a predetermined amount of solid target material 27a. The weighing device 61 counts the solid target material 27a one particle at a time as it passes through, and stops the passage of solid target material 27a once the predetermined amount has passed through. As a result, the solid target material 27a is supplied to the load lock chamber C2. In S23, the target supply processor 60 closes the solid target supply valve VT1. Thus, the solid target supply valve VT1 is opened before the measuring instrument 61 passes through the solid target material 27a, and is closed once a predetermined amount of solid target material 27a has passed through the solid target supply valve VT1.

[0035] In S31, the target supply processor 60 starts the exhaust pump 63 and then opens valve V6. In S32, the target supply processor 60 closes valve V6 and then stops exhaust pump 63. The gas inside load lock chamber C2 is then exhausted to the outside. In S33, the target supply processor 60 opens valve V5, and then closes valve V5. This supplies purge gas from gas cylinder G2 into the load lock chamber C2. The processes in S31 to S33 may be performed only once, or they may be repeated multiple times to increase the purity of the purge gas inside the load lock chamber C2.

[0036] In S41, the target supply processor 60 closes the first gas pressure supply valve V1. This prevents a rapid fluctuation in the gas pressure inside the melting tank C3 when the second gas pressure supply valve V2 is opened in S42. When the first gas pressure supply valve V1 is closed, the gas pressure inside the molten tank C3 decreases slightly. This is because as the liquid target substance is discharged from the nozzle 72 and the volume of the liquid target substance inside the molten tank C3 decreases, the volume of gas inside the molten tank C3 increases. However, if the time between closing the first gas pressure supply valve V1 and opening it in S43 is short, large fluctuations in the gas pressure inside the molten tank C3 are suppressed.

[0037] In S42, the target supply processor 60 opens the second gas pressure supply valve V2. As a result, the gas pressure regulated by the pressure regulator 62 is supplied to the load lock chamber C2, and the inside of the load lock chamber C2 is adjusted to a high pressure. By adjusting the inside of the load lock chamber C2 to a high pressure, the rapid fluctuation of the gas pressure inside the molten tank C3 when the first gas pressure supply valve V1 is opened in S43 is suppressed.

[0038] In S43, the target supply processor 60 opens the first gas pressure supply valve V1. With the first and second gas pressure supply valves V1 and V2 open, the gas pressure inside the load lock chamber C2 and the gas pressure inside the melting tank C3 become approximately the same.

[0039] In S51, the target supply processor 60 opens the solid target supply valve VT2. At this time, all of the solid target material 27a inside the load lock chamber C2 is supplied to the molten tank C3. As a result of S43, the gas pressure inside the load lock chamber C2 and the gas pressure inside the molten tank C3 are approximately the same, so the gas pressure fluctuation inside the molten tank C3 when the solid target supply valve VT2 is opened is small. The solid target material 27a supplied to the molten tank C3 melts and mixes with the liquid target material that was already contained and molten in the molten tank C3. The heater 71 suppresses the decrease in temperature inside the molten tank C3. In S53, the target supply processor 60 closes the solid target supply valve VT2.

[0040] In S61, the target supply processor 60 closes the second gas pressure supply valve V2. This prevents a rapid fluctuation in the gas pressure inside the molten tank C3 when the valve V7 is opened in S62. In S62, the target supply processor 60 opens valve V7. This releases the gas inside the load lock chamber C2 to the outside of the target supply system 26, and the gas pressure inside the load lock chamber C2 becomes approximately equal to atmospheric pressure. In S63, the target supply processor 60 closes valve V7. In S64, the target supply processor 60 returns to processing in S14.

[0041] In the comparative example, the solid target material 27a contained inside the reservoir tank C1, which is at approximately atmospheric pressure, can be supplied into the high-pressure molten tank C3. Even if the liquid target material inside the molten tank C3 is consumed, the solid target material 27a can be replenished without replacing the molten tank C3, thus reducing the downtime of the EUV light generator 1.

[0042] 2.3 Challenges of the Comparative Example Figure 4 is a graph showing the change in gas pressure P inside the molten tank C3 when the solid target material 27a is supplied from the load lock chamber C2 to the molten tank C3. In S43, the gas pressure inside the load lock chamber C2 and the gas pressure inside the melting tank C3 are made to be approximately the same, so the gas pressure fluctuation inside the melting tank C3 when the solid target supply valve VT2 is opened in S51 is small. However, as the solid target material 27a supplied to the melting tank C3 melts, the surface temperature of the liquid target material inside the melting tank C3 may decrease. This temperature change may cause the gas pressure P inside the melting tank C3 to fluctuate. The gas pressure P is returned to the desired pressure by the control of the pressure regulator 62, but it may take some time for the gas pressure P to stabilize.

[0043] Figure 5 is a graph showing the change in velocity V of target 27 when the gas pressure P shown in Figure 4 occurs in the molten tank C3. Since the liquid target material is output from the nozzle 72 due to the pressure difference between the inside of the molten tank C3 and the inside of the chamber 2, the velocity V of target 27 also fluctuates in accordance with the fluctuations in the gas pressure P inside the molten tank C3. When the velocity V of target 27 fluctuates, the position of target 27 when the pulsed laser light 33 (see Figure 1) irradiates target 27 fluctuates, which can cause fluctuations in the amount and location of plasma generation. This can cause fluctuations in characteristics such as the pulse energy and intensity distribution of the EUV light, and may impair the stability of the quality of the EUV light.

[0044] In some embodiments described below, the configuration is such that even if the surface temperature of the liquid target substance inside the melting tank C3 decreases, the decrease in the gas pressure P inside the melting tank C3 is suppressed.

[0045] 3. Target supply system 261 with buffer tank 64 connected to gas pressure supply pipe L0. 3.1 Configuration Figure 6 schematically shows the configuration of the target supply system 261 according to the first embodiment. The target supply system 261 includes a buffer tank 64 in addition to the configuration of the comparative example. The composition of the gas inside the buffer tank 64 may be the same as the composition of the gas contained in the gas cylinder G1.

[0046] The buffer tank 64 is connected to the molten tank C3 via the gas pressure supply pipe L0. The gas pressure supply path from the buffer tank 64 to the molten tank C3 merges with the first pipe L1, specifically the gas pressure supply path from the first gas pressure supply valve V1 to the molten tank C3. A valve V4 is located in the piping connecting the buffer tank 64 to the first pipe L1.

[0047] The buffer tank 64 is connected to the molten tank C3 via the solid target supply pipe 42. The gas pressure supply path from the buffer tank 64 to the molten tank C3 merges with the solid target supply pipe 42 in the supply path of the solid target material 27a from the solid target supply valve VT2 to the molten tank C3. Therefore, even when the solid target supply valve VT2 is closed, i.e., when the solid target material 27a is not supplied from the load lock chamber C2 to the molten tank C3, gas pressure fluctuations inside the molten tank C3 are suppressed.

[0048] The buffer tank 64 contains a gas at a lower temperature than the gas inside the molten tank C3 when the target substance is heated inside the molten tank C3 and the nozzle 72 discharges the liquid target substance. The gas temperature inside the buffer tank 64 can be room temperature. The buffer tank 64 contains gas that is at a pressure higher than atmospheric pressure but lower than the gas pressure supplied from the gas cylinder G1 to the pressure regulator 62. The gas pressure inside the buffer tank 64 is equivalent to the gas pressure regulated by the pressure regulator 62.

[0049] 3.2 Operation Figure 7 shows the operation procedure of the target supply system 261 according to the first embodiment. In S11a, the operation starts with the solid target supply valves VT1 and VT2, the first and second gas pressure supply valves V1 and V2, and valves V5 to V7 all closed, as well as valve V4.

[0050] In S12, after the first gas pressure supply valve V1 is opened, in S13a, the target supply processor 60 opens valve V4 when the gas pressure inside the molten tank C3 reaches the target pressure. This connects the buffer tank 64 to the molten tank C3. Therefore, the buffer tank 64 is also in communication with the molten tank C3 when the solid target material 27a is supplied to the molten tank C3 in S51. As a result, even if the gas temperature inside the molten tank C3 decreases due to the supply of the solid target material 27a to the molten tank C3, gas is quickly supplied from the buffer tank 64 to the molten tank C3, thus suppressing changes in the gas pressure inside the molten tank C3. Valve V4 may be kept open at all times, and valve V4 may be omitted. The operation in S14 to S64 is the same as in the comparative example.

[0051] 3.3 Temperature drop ΔT of the gas inside molten tank C3 The temperature drop ΔT of the gas inside molten tank C3 due to the supply of solid target material 27a can be calculated as follows. Here, we show a calculation example for a steady state as a first-order approximation. That is, ΔT is defined as the temperature drop when, after supplying solid target material 27a to molten tank C3, all of the solid target material 27a has melted and all of the liquid target material and gas inside molten tank C3 are at the same temperature. However, the specific heat of the gas is not considered.

[0052] Figure 8 is a graph illustrating the temperature change associated with heat transfer after the solid target material 27a is supplied to the inside of the molten tank C3. Before the supply of the solid target material 27a to the molten tank C3, the liquid target material present inside the molten tank C3 loses heat to the solid target material 27a, reaching a temperature of Tt to Tt-ΔT, as shown by the thick solid line in Figure 8. Meanwhile, the solid target material 27a supplied to the molten tank C3 receives heat from the liquid target material, as shown by the dashed line in Figure 8. It is heated from temperature Tr to its melting point Tm, and after melting, it reaches a temperature of Tt-ΔT.

[0053] The amount of heat Qout absorbed by the solid target material 27a from the liquid target material present inside the molten tank C3 before the solid target material 27a was supplied to the molten tank C3 is as follows: Qout = ΔT·Msn·Cm ···(a1) Here, Msn is the mass of the liquid target material that was present inside the molten tank C3 before the solid target material 27a was supplied to the molten tank C3. Cm is the specific heat of the liquid target substance. For example, the specific heat Cm of liquid tin, which is 0.243 J / g, is used.

[0054] The amount of heat Qin received by the solid target material 27a supplied into the molten tank C3 is the sum of the following heat quantities Qin1 to Qin3.

[0055] Qin1: The amount of heat absorbed by the solid target material 27a supplied to the molten tank C3 until it reaches its melting point Tm. Qin1=(Tm-Tr)·ΔMsn·Cs ···(a2) For example, the melting point Tm of tin, 505.13K, can be used as the target material. For example, a temperature Tr of room temperature 293.2K is used for the solid target material 27a before it is supplied into the molten tank C3. ΔMsn is the mass of the solid target material 27a supplied into the molten tank C3. Cs is the specific heat of the solid target material 27a supplied to the inside of the molten tank C3. For example, the specific heat of solid tin, which is 0.226 J / g, is used as the specific heat Cs.

[0056] Qin2: The amount of heat absorbed by the solid target material 27a supplied to the molten tank C3 from the time it reaches its melting point Tm until it melts. Qin² = Hm·ΔMsn ···(a3) Here, Hm is the heat of fusion of the target substance, and for example, the heat of fusion of solid tin, 59.6 J / g, is used as the heat of fusion Hm.

[0057] Qin3: The amount of heat absorbed by the solid target material 27a supplied to the molten tank C3 from the time it melts until it reaches a steady state. Qin3=(Tt-ΔT-Tm)·ΔMsn·Cm ···(a4) The temperature Tt of the liquid target substance before supplying the solid target substance 27a into the molten tank C3 is assumed to be, for example, 533.9K. By subtracting the temperature drop ΔT from the temperature Tt, the temperature of the liquid target substance when it reaches a steady state after supplying the solid target substance 27a into the molten tank C3 is obtained, and by further subtracting the melting point Tm, the temperature change from when the solid target substance 27a melts until it reaches a steady state is obtained.

[0058] According to the law of conservation of energy, Qout and Qin are equal, so equation (a5) is obtained from equations (a1) to (a4). ΔT·Msn·Cm=(Tm-Tr)·ΔMsn·Cs+Hm·ΔMsn+(Tt-ΔT-Tm)·ΔMsn·Cm ···(a5)

[0059] Rearranging equation (a5), the temperature drop ΔT can be calculated using the following equation (a6). ΔT=ΔMsn {(Tm-Tr) Cs+Hm+(Tt-Tm) Cm} / {(Msn+ΔMsn) Cm} (a6) Assuming that Msn is sufficiently larger than ΔMsn, the temperature drop ΔT can be approximated by the following equation (a7). ΔT≒{(Tm-Tr)·Cs / Cm+Hm / Cm+(Tt-Tm)}·ΔMsn / Msn ···(a7)

[0060] The constant {(Tm-Tr)·Cs / Cm+Hm / Cm+(Tt-Tm)} in equation (a7) is constant. Therefore, the temperature drop ΔT is approximately proportional to the ratio ΔMsn / Msn of the mass ΔMsn of the solid target material 27a supplied to the molten tank C3 to the mass Msn of the liquid target material that was present inside the molten tank C3 before the solid target material 27a was supplied to the molten tank C3.

[0061] Figure 9 is a graph showing the temperature drop ΔT as a function of the ratio ΔMsn / Msn. By replacing the parameters in equation (a6) with specific numerical values ​​and varying the ratio ΔMsn / Msn from 0% to 3.3%, the temperature drop ΔT is plotted, resulting in the graph shown in Figure 9. The approximate formula for this graph is as follows: ΔT = 4.7618 × (ΔMsn / Msn) × 100

[0062] 3.4 Gas pressure drop ΔP due to temperature drop ΔT The gas pressure drop ΔP inside molten tank C3 and buffer tank 64 due to the temperature drop ΔT inside molten tank C3 can be calculated as follows. Here, we show a calculation example for a steady state as a first-order approximation. That is, ΔP is the gas pressure drop when the gas pressure P inside molten tank C3 and buffer tank 64 are the same. However, even if the temperature inside molten tank C3 decreases, the gas temperature inside buffer tank 64 is assumed to remain unchanged and be the same as the temperature Tr of the solid target material 27a.

[0063] Figure 10 shows a list of the gas pressure, volume, number of moles, and temperature inside molten tank C3 and buffer tank 64, respectively, before and after the temperature of the gas inside molten tank C3 decreases.

[0064] The equation of state for the gas inside molten tank C3 before the temperature of the gas inside molten tank C3 decreases is as follows: Pt·Vbh=n1·R·Tt ···(b1) Here, Pt is the target gas pressure of the pressure regulator 62. Vbh is the volume of gas inside the molten tank C3. The volume of gas inside the molten tank C3, Vbh, is equivalent to the total volume of the molten tank C3 minus the volume of the liquid target substance inside the molten tank C3. n1 is the number of moles of gas inside molten tank C3 before the temperature of the gas inside molten tank C3 drops. R is the gas constant.

[0065] The equation of state for the gas inside the buffer tank 64 before the temperature of the gas inside the molten tank C3 drops is as follows: Pt·Vbr=n²·R·Tr ···(b²) Here, Vbr is the volume of the buffer tank 64. n2 is the number of moles of gas inside the buffer tank 64 before the temperature of the gas inside the molten tank C3 drops.

[0066] From equations (b1) and (b2), the total number of moles n, which is the sum of the number of moles n1 of gas inside the molten tank C3 and the number of moles n2 of gas inside the buffer tank 64, is given by the following equation (b3). n=Pt·Vbh / (R·Tt)+Pt·Vbr / (R·Tr) ···(b3)

[0067] The equation of state for the gas inside molten tank C3 after the temperature of the gas inside molten tank C3 has dropped is as follows: P·Vbh=n10·R·(Tt-ΔT) ···(b4) Here, n10 is the number of moles of gas inside molten tank C3 after the temperature of the gas inside molten tank C3 has decreased.

[0068] The equation of state for the gas inside the buffer tank 64 after the temperature of the gas inside the molten tank C3 has decreased is as follows: P·Vbr=n20·R·Tr ···(b5) n20 is the number of moles of gas inside the buffer tank 64 after the temperature of the gas inside the molten tank C3 has decreased.

[0069] From equations (b4) and (b5), the total number of moles n, which is the sum of the number of moles n10 of gas inside the molten tank C3 and the number of moles n20 of gas inside the buffer tank 64, is given by the following equation (b6). n=P·Vbh / {R·(Tt-ΔT)}+P·Vbr / (R·Tr) ···(b6) The total number of moles, n, remains the same before and after the temperature of the gas inside the molten tank C3 decreases.

[0070] From equations (b3) and (b6), the gas pressure P inside the molten tank C3 and buffer tank 64 after the temperature drop is given by equation (b7) below. P={Pt·Vbh / (R·Tt)+Pt·Vbr / (R·Tr)} / [Vbh / {R·(Tt-ΔT)}+Vbr / (R·Tr)] ···(b7)

[0071] The gas pressure drop ΔP due to the temperature drop ΔT can be obtained by subtracting the gas pressure P from equation (b7) from the target gas pressure Pt of the pressure regulator 62, as shown in equation (b8). ΔP=Pt-{Pt·Vbh / (R·Tt)+Pt·Vbr / (R·Tr)} / [Vbh / {R·(Tt-ΔT)}+Vbr / (R·Tr)] ···(b8)

[0072] Therefore, an allowable value for the gas pressure drop ΔP can be set, and the volume Vbr of the buffer tank 64 that keeps the gas pressure drop ΔP below the allowable value can be calculated. From equation (b8), the volume Vbr of the buffer tank 64 that keeps the gas pressure drop ΔP below the allowable value depends on the temperature drop ΔT inside the molten tank C3. From Figure 9, the temperature drop ΔT depends on the ratio ΔMsn / Msn, so the volume Vbr of the buffer tank 64 that keeps the gas pressure drop ΔP below the allowable value depends on the ratio ΔMsn / Msn.

[0073] Figure 11 is a graph showing the volume Vbr of the buffer tank 64 according to the ratio ΔMsn / Msn. The volume Vbr of the buffer tank 64 that keeps the gas pressure drop ΔP below the allowable value is given by the following formula. Vbr = 4.2084 × (ΔMsn / Msn) × 100

[0074] Here, if the preferred range for the ratio ΔMsn / Msn is 0.33% or more and 3.3% or less, then the volume Vbr of the buffer tank 64 is preferably 1.4 liters or more and 14 liters or less. Furthermore, it is preferable that the volume Vbr of the buffer tank 64 is larger than the volume of the melting tank C3. The reason for setting the preferred range for the ratio ΔMsn / Msn to 0.33% or more and 3.3% or less is as follows: If the ratio ΔMsn / Msn is less than 0.33%, the solid target material 27a needs to be supplied more frequently, which may shorten the lifespan of the solid target supply valve VT2. If the ratio ΔMsn / Msn is higher than 3.3%, the temperature drop ΔT of the liquid target material inside the melting tank C3 becomes larger, which may make the formation of droplets constituting the target 27 unstable.

[0075] 3.5 Effect (1) According to the first embodiment, the target supply system 261 includes a load lock chamber C2, a solid target supply pipe 42, a pressure regulator 62, a gas pressure supply pipe L0, a melting tank C3, a nozzle 72, and a buffer tank 64. The load lock chamber C2 is configured to accommodate a solid target material 27a. The solid target supply pipe 42 is connected to the load lock chamber C2. The pressure regulator 62 regulates the gas pressure supplied from the outside. The gas pressure supply pipe L0 is connected to the pressure regulator 62. The melting tank C3 is connected to both the solid target supply pipe 42 and the gas pressure supply pipe L0 and melts the solid target material 27a supplied from the load lock chamber C2 via the solid target supply pipe 42 to produce a liquid target material. The nozzle 72 discharges the liquid target material by the gas pressure supplied from the pressure regulator 62 to the melting tank C3 via the gas pressure supply pipe L0. The buffer tank 64 is in communication with the molten tank C3 and supplies gas pressure when supplying the solid target material 27a to the molten tank C3. According to this, even if the temperature of the gas inside the molten tank C3 decreases when the solid target material 27a is supplied to the molten tank C3, the gas inside the buffer tank 64, which is in communication with the molten tank C3, is quickly supplied to the molten tank C3. This can suppress fluctuations in the gas pressure inside the molten tank C3. By suppressing fluctuations in the gas pressure inside the molten tank C3, the velocity V of the target 27 can be stabilized.

[0076] (2) According to the first embodiment, the buffer tank 64 contains a gas at a lower temperature than the gas inside the melting tank C3 when the nozzle 72 discharges the liquid target substance. According to this, the buffer tank 64 does not need to be heated to the temperature of the molten tank C3, so energy consumption can be reduced.

[0077] (3) According to the first embodiment, the pressure regulator 62 supplies a gas pressure higher than atmospheric pressure to the melting tank C3. The buffer tank 64 also contains gas at a pressure higher than atmospheric pressure. According to this, since both the molten tank C3 and the buffer tank 64 contain gas at a pressure higher than atmospheric pressure, the gas pressure fluctuations inside the molten tank C3 can be suppressed by connecting them.

[0078] (4) According to the first embodiment, the pressure regulator 62 supplies gas to the melting tank C3 at a gas pressure lower than the gas pressure supplied to the pressure regulator 62 from the outside. The buffer tank 64 also contains gas at a pressure lower than the gas pressure supplied to the pressure regulator 62 from the outside. According to this, since both the molten tank C3 and the buffer tank 64 contain gas at a lower pressure than the gas pressure supplied to the pressure regulator 62 from the outside, the gas pressure fluctuations inside the molten tank C3 can be suppressed by connecting them.

[0079] (5) According to the first embodiment, the buffer tank 64 has a larger volume than the melting tank C3. According to this, gas pressure fluctuations in the molten tank C3 can be sufficiently suppressed.

[0080] (6) According to the first embodiment, the volume of the buffer tank 64 is in the range of 1.4 liters or more and 14 liters or less. According to this, the gas pressure fluctuations in molten tank C3 may be within an acceptable range.

[0081] (7) According to the first embodiment, the buffer tank 64 is in communication with the melting tank C3 via the gas pressure supply pipe L0. According to this, disconnecting the molten tank C3 from the pressure regulator 62 and disconnecting the molten tank C3 from the buffer tank 64 can be achieved by disconnecting the gas pressure supply pipe L0 midway. Therefore, the amount of work required to maintain the molten tank C3 can be reduced. In this disclosure, the buffer tank 64 is not limited to being connected to the molten tank C3 via the solid target supply pipe 42. For example, the buffer tank 64 may be connected to the molten tank C3 by connecting the gas pressure supply pipe L0 directly to the molten tank C3 without going through the solid target supply pipe 42.

[0082] (8) According to the first embodiment, the buffer tank 64 is in communication with the molten tank C3 via the solid target supply pipe 42. According to this, if the solid target supply pipe 42 is insulated, separate insulation treatment at the connection between the molten tank C3 and the buffer tank 64 may become unnecessary. Therefore, the configuration for insulation can be simplified. In this disclosure, the buffer tank 64 is not limited to being connected to the molten tank C3 via the gas pressure supply pipe L0. For example, the buffer tank 64 may be connected directly to the solid target supply pipe 42 without going through the gas pressure supply pipe L0, thereby enabling the buffer tank 64 to communicate with the molten tank C3. Furthermore, in this disclosure, the buffer tank 64 may be connected directly to the melting tank C3 without going through either the gas pressure supply pipe L0 or the solid target supply pipe 42.

[0083] (9) According to the first embodiment, a solid target supply valve VT2 is located in the solid target supply pipe 42. In addition, the gas pressure supply path from the buffer tank 64 to the melting tank C3 merges with the solid target supply pipe 42 in the supply path of the solid target material 27a from the solid target supply valve VT2 to the melting tank C3. According to this, even when the solid target material 27a is not supplied and the solid target supply valve VT2 is closed, the buffer tank 64 and the molten tank C3 can be connected, and fluctuations in the gas pressure inside the molten tank C3 can be suppressed.

[0084] (10) According to the first embodiment, the gas pressure supply pipe L0 includes a branch section SP, a first pipe L1 that supplies gas pressure from the branch section SP to the melting tank C3, a second pipe L2 that supplies gas pressure from the branch section SP to the load lock chamber C2, and a common pipe L3 between the pressure regulator 62 and the branch section SP. In addition, first and second gas pressure supply valves V1 and V2 are arranged in the first and second pipes L1 and L2, respectively. The gas pressure supply path from the buffer tank 64 to the melting tank C3 merges with the first pipe L1 in the gas pressure supply path from the first gas pressure supply valve V1 of the first pipe L1 to the melting tank C3. According to this, even when the first gas pressure supply valve V1 is closed to adjust the pressure inside the load lock chamber C2 (see S41-S43 in Figure 7), the buffer tank 64 and the molten tank C3 are connected, and fluctuations in the gas pressure inside the molten tank C3 can be suppressed. In all other respects, the first embodiment is the same as the comparative example.

[0085] 4. Removable target supply system 262 for molten tank C3 4.1 Configuration Figure 12 schematically shows the configuration of the target supply system 262 according to the second embodiment. The target supply system 262 includes a third gas pressure supply valve V3 in addition to the configuration of the target supply system 261 according to the first embodiment.

[0086] Similar to the first embodiment, the gas pressure supply pipe L0 includes a first pipe L1, a second pipe L2, and a common pipe L3. A first gas pressure supply valve V1 is located in the first pipe L1, and a second gas pressure supply valve V2 is located in the second pipe L2. Furthermore, the gas pressure supply path from the buffer tank 64 to the melting tank C3 merges with the first pipe L1 in the gas pressure supply path from the first gas pressure supply valve V1 of the first pipe L1 to the melting tank C3. In the second embodiment, the third gas pressure supply valve V3 is located in the gas pressure supply path from the first piping L1, specifically the point where it merges with the gas pressure supply path from the buffer tank 64, towards the melting tank C3.

[0087] The target supply system 262 further includes first to third joints J1 to J3. The first joint J1 is located in the gas pressure supply path of the first piping L1, from the third gas pressure supply valve V3 to the melting tank C3. The first joint J1 allows for disconnection and connection of the first piping L1 at any point along its course. The second joint J2 is located in the gas pressure supply path of the second piping L2, from the second gas pressure supply valve V2 to the load lock chamber C2. The second joint J2 allows for disconnection and connection of the second piping L2 at any point along the line. The third joint J3 is located in the supply path of the solid target material 27a from the measuring instrument 61 to the solid target supply valve VT1 within the solid target supply pipe 41. The third joint J3 allows for disconnection and connection of the solid target supply pipe 41 at any point along its course.

[0088] 4.2 Operation By disconnecting the respective pipes using the first to third joints J1 to J3, the melting tank C3 and load lock chamber C2 can be removed together. At this time, the gas pressure inside the buffer tank 64 can be maintained by closing the third gas pressure supply valve V3. The specific procedure is as follows.

[0089] (a) Turn off the power to heater 71. (b) With the solid target supply valve VT1, the second and third gas pressure supply valves V2 and V3, and valves V5 and V6 closed, open the solid target supply valve VT2 and valve V7. This brings the inside of the load lock chamber C2 and the melting tank C3 to atmospheric pressure. (c) Loosen the first to third joints J1 to J3. (d) Remove the molten tank C3 and the load lock chamber C2 together.

[0090] 4.3 Effect (11) According to the second embodiment, the gas pressure supply path from the buffer tank 64 to the melting tank C3 merges with the gas pressure supply pipe L0. In addition, a third gas pressure supply valve V3 is located in the gas pressure supply path from the point where it merges with the gas pressure supply path from the buffer tank 64 to the melting tank C3. According to this, by closing the third gas pressure supply valve V3, the melting tank C3 can be removed while maintaining the gas pressure inside the buffer tank 64. Therefore, after installing the new melting tank C3, it may not be necessary to refill the buffer tank 64 with gas.

[0091] (12) According to the second embodiment, the gas pressure supply pipe L0 includes a branch section SP, a first pipe L1 that supplies gas pressure from the branch section SP to the melting tank C3, a second pipe L2 that supplies gas pressure from the branch section SP to the load lock chamber C2, and a common pipe L3 between the pressure regulator 62 and the branch section SP. In addition, first and second gas pressure supply valves V1 and V2 are arranged in the first and second pipes L1 and L2, respectively. The gas pressure supply path from the buffer tank 64 to the melting tank C3 merges with the first pipe L1 in the gas pressure supply path from the first gas pressure supply valve V1 in the first pipe L1 to the melting tank C3. A third gas pressure supply valve V3 is arranged in the gas pressure supply path from the point where it merges with the gas pressure supply path from the buffer tank 64 in the first pipe L1 to the melting tank C3. According to this, even when the first gas pressure supply valve V1 is closed to adjust the pressure inside the load lock chamber C2 (see S41-S43 in Figure 7), the buffer tank 64 and the molten tank C3 are connected, and fluctuations in the gas pressure inside the molten tank C3 can be suppressed. Furthermore, by keeping the third gas pressure supply valve V3 closed, the melting tank C3 can be removed while maintaining the gas pressure inside the buffer tank 64.

[0092] (13) According to the second embodiment, the target supply system 262 includes a measuring instrument 61 that measures and supplies solid target material 27a to the load lock chamber C2. A first joint J1 is located in the gas pressure supply path from the third gas pressure supply valve V3 of the first piping L1 to the melting tank C3. A second joint J2 is located in the gas pressure supply path from the second gas pressure supply valve V2 of the second piping L2 to the load lock chamber C2. A third joint J3 is located in the supply path of solid target material 27a from the measuring instrument 61 to the load lock chamber C2. According to this, the molten tank C3 and the load lock chamber C2 can be removed from the target supply system 262 as a single unit. In all other respects, the second embodiment is the same as the first embodiment.

[0093] 5. Variations in the placement of buffer tank 64 5.1 Configuration Figure 13 schematically shows the configuration of the target supply system 263 according to the third embodiment. The target supply system 263 differs from the target supply system 261 according to the first embodiment in the arrangement of the buffer tank 64.

[0094] Similar to the first embodiment, the gas pressure supply pipe L0 includes a first pipe L1, a second pipe L2, and a common pipe L3. A first gas pressure supply valve V1 is located in the first pipe L1, and a second gas pressure supply valve V2 is located in the second pipe L2.

[0095] In the third embodiment, the gas pressure supply path from the buffer tank 64 to the melting tank C3 merges with the gas pressure supply pipe L0 in any of the following (a) to (c). (a) Between the branch SP of the first piping L1 and the first gas pressure supply valve V1 (b) Between the branch SP of the second pipe L2 and the second gas pressure supply valve V2 (c) Common piping L3

[0096] The target supply system 263 further includes first to third joints J1 to J3. The first to third joints J1 to J3 are the same as those described in the second embodiment.

[0097] 5.2 Operation By disconnecting the respective pipes using the first to third joints J1 to J3, the melting tank C3 and the load lock chamber C2 can be removed together. At this time, the gas pressure inside the buffer tank 64 can be maintained by closing the first and second gas pressure supply valves V1 and V2.

[0098] 5.3 Effect (14) According to the third embodiment, the gas pressure supply pipe L0 includes a branch section SP, a first pipe L1 that supplies gas pressure from the branch section SP to the melting tank C3, a second pipe L2 that supplies gas pressure from the branch section SP to the load lock chamber C2, and a common pipe L3 between the pressure regulator 62 and the branch section SP. In addition, first and second gas pressure supply valves V1 and V2 are arranged in the first and second pipes L1 and L2, respectively. The gas pressure supply path from the buffer tank 64 to the melting tank C3 joins the gas pressure supply pipe L0 in one of the following ways. (a) Between the branch SP of the first piping L1 and the first gas pressure supply valve V1 (b) Between the branch SP of the second pipe L2 and the second gas pressure supply valve V2 (c) Common piping L3 According to this, the buffer tank 64 can be placed in a spacious area away from the molten tank C3. Furthermore, by closing the first and second gas pressure supply valves V1 and V2, the melting tank C3 can be removed while maintaining the gas pressure inside the buffer tank 64.

[0099] (15) According to the third embodiment, the target supply system 263 includes a measuring instrument 61 that measures and supplies solid target material 27a to the load lock chamber C2. A first joint J1 is located in the gas pressure supply path from the first gas pressure supply valve V1 of the first piping L1 to the melting tank C3. A second joint J2 is located in the gas pressure supply path from the second gas pressure supply valve V2 of the second piping L2 to the load lock chamber C2. A third joint J3 is located in the supply path of solid target material 27a from the measuring instrument 61 to the load lock chamber C2. According to this, the molten tank C3 and the load lock chamber C2 can be removed from the target supply system 263 as a single unit. In all other respects, the third embodiment is the same as the first embodiment.

[0100] 6. Target supply system 264 for detecting the liquid level in molten tank C3 6.1 Configuration Figure 14 schematically shows the configuration of the target supply system 264 according to the fourth embodiment. The target supply system 264 includes a sensor 73. The sensor 73 detects the liquid level of the liquid target substance inside the molten tank C3. When the sensor 73 detects that the liquid level of the liquid target substance inside the molten tank C3 has fallen below a threshold, the solid target substance 27a is supplied.

[0101] The target supply system 264 further includes an adjustment mechanism 66 that prevents the solid target material 27a supplied to the load lock chamber C2 from reaching the solid target supply valve VT2.

[0102] Figures 15 and 16 show the configuration of the adjustment mechanism 66 and the solid target supply valve VT2, respectively, and their operation is shown in combination with Figures 15 and 16. The adjustment mechanism 66 includes a receiving plate 66a and an actuator 66b. The receiving plate 66a is located near the lower end of the load lock chamber C2. The actuator 66b is configured to switch the adjustment mechanism 66 between a first state shown in Figure 15 and a second state shown in Figure 16 by moving the receiving plate 66a.

[0103] In the first state, the receiving plate 66a is positioned to block the connection from the load lock chamber C2 to the solid target supply pipe 42. This prevents the solid target material 27a from moving toward the solid target supply valve VT2. In the second state, the receiving plate 66a is positioned away from the connection point between the load lock chamber C2 and the solid target supply pipe 42. This allows the solid target material 27a to move toward the solid target supply valve VT2. The adjustment mechanism 66 is normally in the first state, and is temporarily in the second state when moving the solid target material 27a toward the solid target supply valve VT2.

[0104] The solid target supply valve VT2 is composed of a ball valve including, for example, a ball portion V2a and a body portion V2b. By rotating the ball portion V2a inside the body portion V2b in the direction of arrow R, it is switched between the closed state shown in Figure 15 and the open state shown in Figure 16.

[0105] 6.2 Operation Figure 17 shows the operation procedure of the target supply system 264 according to the fourth embodiment. In S11b, the operation starts with the solid target supply valves VT1 and VT2, the first and second gas pressure supply valves V1 and V2, and valves V4 to V7 all closed, and the adjustment mechanism 66 set to the first state.

[0106] In S12, the first gas pressure supply valve V1 is opened, and in S13a, the valve V4 is opened. Then, in S14b, when the sensor 73 detects that the liquid level inside the melting tank C3 has fallen below a predetermined position, the target supply processor 60 proceeds to S21 and starts supplying the solid target material 27a.

[0107] In steps S21 to S43, the process is the same as in the first embodiment in that the solid target material 27a is weighed and supplied to the load lock chamber C2, and the pressure inside the load lock chamber C2 is adjusted. However, the target supply processor 60 controls the weighing device 61 to supply the load lock chamber C2 with solid target material 27a in an amount of 0.33% to 3.3% of the mass of the liquid target material inside the melting tank C3, based on the output of the sensor 73.

[0108] In S51, when the solid target supply valve VT2 is in the open state, the adjustment mechanism 66 is set to the first state (see Figure 15), so the solid target material 27a remains inside the load lock chamber C2.

[0109] In S52b, the target supply processor 60 sets the adjustment mechanism 66 to the second state (see Figure 16). As a result, the solid target material 27a is supplied from the load lock chamber C2 to the molten tank C3 via the solid target supply pipe 42 and the solid target supply valve VT2. Since the adjustment mechanism 66 is set to the second state after the solid target supply valve VT2 is opened, damage to the solid target supply valve VT2 is suppressed.

[0110] In S53, after the solid target supply valve VT2 is closed, in S54b, the target supply processor 60 sets the adjustment mechanism 66 to the first state. Therefore, even when the solid target material 27a is supplied to the load lock chamber C2 again after returning to S14b in S64b, the solid target material 27a remains inside the load lock chamber C2. Steps S61 to S63 are the same as in the comparative example.

[0111] 6.3 Effect (16) According to the fourth embodiment, the target supply system 264 includes a sensor 73 for detecting the liquid level of the liquid target material inside the melting tank C3, and a measuring instrument 61 for measuring and supplying solid target material 27a to the load lock chamber C2. The target supply system 264 also includes a target supply processor 60 that controls the measuring instrument 61 to supply solid target material 27a to the load lock chamber C2 based on the output of the sensor 73. According to this, the timing or amount of supply of the solid target material 27a can be appropriately controlled.

[0112] (17) According to the fourth embodiment, the target supply processor 60 controls the weighing instrument 61 to supply a solid target material 27a to the load lock chamber C2 in an amount of 0.33% to 3.3% of the mass of the liquid target material inside the melting tank C3, based on the output of the sensor 73. According to this, setting the concentration to 0.33% or higher can reduce the frequency of use of the solid target supply valve VT2 and suppress its deterioration. Setting the concentration to 3.3% or lower can suppress the temperature drop ΔT of the liquid target substance inside the melting tank C3 and stabilize the formation of droplets that constitute the target 27. In all other respects, the fourth embodiment is the same as the first embodiment.

[0113] 7. Other 7.1 Pressure Regulator 62 Figure 18 schematically shows the configuration of a pressure regulator 62 used in each embodiment. The pressure regulator 62 includes a pressure control processor 620, valves Va and Vb, and a pressure gauge P.

[0114] The pressure control processor 620 is a processing unit that includes a memory 621 in which a control program is stored, and a CPU 622 that executes the control program. The pressure control processor 620 is specially configured or programmed to perform various processes included in this disclosure.

[0115] Valves Va and Vb are located in the piping between gas cylinder G1 and an exhaust device (not shown), and a common pipe L3 is connected between valves Va and Vb. A pressure gauge P is located in the common pipe L3.

[0116] When both valves Va and Vb are opened, gas leaks from the gas cylinder G1 to the exhaust system. However, the gas pressure supplied to the common piping L3 changes depending on the relationship between the opening degrees of valve Va and valve Vb. The pressure control processor 620 controls valves Va and Vb based on the gas pressure detected by the pressure gauge P, thereby adjusting the gas pressure supplied to the common piping L3.

[0117] 7.2 EUV light utilization equipment 6 Figure 19 schematically shows the configuration of the exposure apparatus 6a connected to the EUV light generation system 11. In Figure 19, the exposure apparatus 6a, which is an EUV light utilization apparatus 6 (see Figure 1), includes a mask irradiation unit 608 and a workpiece irradiation unit 609. The mask irradiation unit 608 illuminates the mask pattern on the mask table MT via a reflective optical system using EUV light incident from the EUV light generation system 11. The workpiece irradiation unit 609 images the EUV light reflected by the mask table MT onto a workpiece (not shown) placed on the workpiece table WT via a reflective optical system. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure apparatus 6a exposes the workpiece to EUV light reflecting the mask pattern by synchronously moving the mask table MT and the workpiece table WT in parallel. By transferring a device pattern onto a semiconductor wafer through this exposure process, an electronic device can be manufactured.

[0118] Figure 20 schematically shows the configuration of the inspection device 6b connected to the EUV light generation system 11. In Figure 20, the inspection apparatus 6b, which is an EUV light utilization apparatus 6 (see Figure 1), includes an illumination optical system 603 and a detection optical system 606. The illumination optical system 603 reflects EUV light incident from the EUV light generation system 11 and irradiates the mask 605 placed on the mask stage 604. The mask 605 here includes mask blanks before a pattern is formed. The detection optical system 606 reflects the EUV light from the illuminated mask 605 and forms an image on the light-receiving surface of the detector 607. The detector 607, having received the EUV light, acquires an image of the mask 605. The detector 607 is, for example, a TDI (time delay integration) camera. Based on the image of the mask 605 acquired through the above process, defects in the mask 605 are inspected, and a mask suitable for the manufacture of an electronic device is selected using the inspection results. Then, the pattern formed on the selected mask can be exposed and transferred onto a photosensitive substrate using the exposure apparatus 6a to manufacture an electronic device.

[0119] 7.3 Supplement The above description is intended to be illustrative, not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made to the embodiments of this disclosure without departing from the claims. It will also be apparent to those skilled in the art that the embodiments of this disclosure can be used in combination.

[0120] Terms used in this specification and throughout the claims should be interpreted as "non-limiting" unless otherwise specified. For example, the terms "include" or "contained" should be interpreted as "not limited to those described as included." The term "possess" should be interpreted as "not limited to those described as possessing." The indefinite article "one" should be interpreted as "at least one" or "one or more." The term "at least one of A, B, and C" should be interpreted as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." Furthermore, it should be interpreted as including combinations of these with anything other than "A," "B," and "C."

Claims

1. A load lock chamber capable of containing a solid target material, A solid target supply pipe connected to the load lock chamber, A pressure regulator that adjusts the gas pressure supplied from an external source, A gas pressure supply pipe connected to the pressure regulator, A melting tank connected to both the solid target supply pipe and the gas pressure supply pipe, which melts the solid target material supplied from the load lock chamber via the solid target supply pipe to produce a liquid target material, A nozzle that discharges the liquid target substance by the gas pressure supplied from the pressure regulator to the melting tank via the gas pressure supply pipe, A buffer tank that communicates with the molten tank and supplies gas pressure when supplying the solid target material to the molten tank, Equipped with, The gas pressure supply pipe includes a branch section, a first pipe supplying gas pressure from the branch section toward the melting tank, a second pipe supplying gas pressure from the branch section toward the load lock chamber, and a common pipe between the pressure regulator and the branch section. First and second gas pressure supply valves are arranged in the first and second pipes, respectively. A target supply system in which the gas pressure supply path from the buffer tank to the melting tank merges with the first piping in the gas pressure supply path from the first gas pressure supply valve to the melting tank among the first piping.

2. A target supply system according to claim 1, The buffer tank contains a gas at a lower temperature than the gas inside the melting tank when the nozzle discharges the liquid target substance. Target supply system.

3. A target supply system according to claim 1, The pressure regulator supplies a gas pressure higher than atmospheric pressure to the melting tank. The buffer tank contains gas at a pressure higher than atmospheric pressure. Target supply system.

4. A target supply system according to claim 1, The pressure regulator supplies the melting tank with a gas pressure lower than the gas pressure supplied to the pressure regulator from the outside. The buffer tank contains gas at a pressure lower than the gas pressure supplied to the pressure regulator from the outside. Target supply system.

5. A target supply system according to claim 1, The buffer tank has a larger volume than the melting tank. Target supply system.

6. A target supply system according to claim 1, The volume of the buffer tank is within the range of 1.4 liters to 14 liters. Target supply system.

7. A target supply system according to claim 1, The buffer tank is connected to the melting tank via the gas pressure supply pipe. Target supply system.

8. A target supply system according to claim 1, The buffer tank is in communication with the melting tank via the solid target supply pipe. Target supply system.

9. A target supply system according to claim 8, A solid target supply valve is provided in the solid target supply pipe. The gas pressure supply path from the buffer tank to the melting tank merges with the solid target supply pipe in the solid target material supply path from the solid target supply valve to the melting tank within the solid target supply pipe. Target supply system.

10. A target supply system according to claim 1, The buffer tank is in communication with the melting tank when the first gas pressure supply valve is closed. Target supply system.

11. A target supply system according to claim 1, The gas pressure supply path from the buffer tank to the melting tank merges with the gas pressure supply pipe, A third gas pressure supply valve is positioned in the gas pressure supply path from the point where the gas pressure supply path from the buffer tank merges with the gas pressure supply path of the aforementioned gas pressure supply pipe, toward the melting tank. Target supply system.

12. A target supply system according to claim 1, A third gas pressure supply valve is positioned in the gas pressure supply path from the first piping, specifically in the section where it merges with the gas pressure supply path from the buffer tank, towards the melting tank. Target supply system.

13. A target supply system according to claim 12, The system further comprises a measuring device for weighing the solid target material and supplying it to the load lock chamber. A first fitting is positioned in the gas pressure supply path of the first piping, from the third gas pressure supply valve to the melting tank. A second fitting is positioned in the gas pressure supply path of the second piping, from the second gas pressure supply valve to the load lock chamber. A third joint is positioned in the supply path of the solid target material from the measuring instrument to the load lock chamber. Target supply system.

14. A target supply system according to claim 1, A sensor for detecting the liquid level of the target substance inside the melting tank, A weighing device for weighing the solid target material and supplying it to the load lock chamber, A processor that controls the weighing instrument to supply the solid target material to the load lock chamber based on the output of the sensor, A target supply system further equipped with additional features.

15. A target supply system according to claim 14, The processor controls the weighing instrument to supply the load lock chamber with a mass of the solid target material in an amount of 0.33% or more and 3.3% or less of the liquid target material inside the melting tank, based on the output of the sensor. Target supply system.

16. The target supply system according to claim 1, A laser device that irradiates a target that has been output from the target supply system and reached a predetermined area with pulsed laser light, An EUV focusing mirror that focuses extreme ultraviolet light emitted from the plasma generated in the predetermined region, An extreme ultraviolet light generating device equipped with [a specific feature].

17. A method for manufacturing electronic devices, A load lock chamber capable of containing a solid target material, A solid target supply pipe connected to the load lock chamber, A pressure regulator that adjusts the gas pressure supplied from an external source, A gas pressure supply pipe connected to the pressure regulator, A melting tank connected to both the solid target supply pipe and the gas pressure supply pipe, which melts the solid target material supplied from the load lock chamber via the solid target supply pipe to produce a liquid target material, A nozzle that discharges the liquid target substance by the gas pressure supplied from the pressure regulator to the melting tank via the gas pressure supply pipe, A buffer tank that communicates with the molten tank and supplies gas pressure when supplying the solid target material to the molten tank, Equipped with, The gas pressure supply pipe includes a branch section, a first pipe supplying gas pressure from the branch section toward the melting tank, a second pipe supplying gas pressure from the branch section toward the load lock chamber, and a common pipe between the pressure regulator and the branch section. First and second gas pressure supply valves are arranged in the first and second pipes, respectively. The gas pressure supply path from the buffer tank to the melting tank includes a target supply system that joins the first piping in the gas pressure supply path from the first gas pressure supply valve in the first piping to the melting tank, A laser device that irradiates a target that has been output from the target supply system and reached a predetermined area with pulsed laser light, An EUV focusing mirror that focuses extreme ultraviolet light emitted from the plasma generated in the predetermined region, Extreme ultraviolet light is generated by an extreme ultraviolet light generation device equipped with the following: Extreme ultraviolet light is output to the exposure device, In order to manufacture electronic devices, extreme ultraviolet light is exposed onto a photosensitive substrate in the exposure apparatus. A method for manufacturing electronic devices, including the following.

18. A method for manufacturing electronic devices, A load lock chamber capable of containing a solid target material, A solid target supply pipe connected to the load lock chamber, A pressure regulator that adjusts the gas pressure supplied from an external source, A gas pressure supply pipe connected to the pressure regulator, A melting tank connected to both the solid target supply pipe and the gas pressure supply pipe, which melts the solid target material supplied from the load lock chamber via the solid target supply pipe to produce a liquid target material, A nozzle that discharges the liquid target substance by the gas pressure supplied from the pressure regulator to the melting tank via the gas pressure supply pipe, A buffer tank that communicates with the molten tank and supplies gas pressure when supplying the solid target material to the molten tank, Equipped with, The gas pressure supply pipe includes a branch section, a first pipe supplying gas pressure from the branch section toward the melting tank, a second pipe supplying gas pressure from the branch section toward the load lock chamber, and a common pipe between the pressure regulator and the branch section. First and second gas pressure supply valves are arranged in the first and second pipes, respectively. The gas pressure supply path from the buffer tank to the melting tank includes a target supply system that joins the first piping in the gas pressure supply path from the first gas pressure supply valve in the first piping to the melting tank, A laser device that irradiates a target that has been output from the target supply system and reached a predetermined area with pulsed laser light, An EUV focusing mirror that focuses extreme ultraviolet light emitted from the plasma generated in the predetermined region, Extreme ultraviolet light generated by an extreme ultraviolet light generator is irradiated onto the mask to inspect for defects in the mask. Using the results of the above inspection, select a mask. The pattern formed on the selected mask is then exposed and transferred onto a photosensitive substrate. A method for manufacturing electronic devices, including the following.

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