EUV light generation apparatus, electronic device manufacturing method, and inspection method

Abstract

To provide an EUV light generator having small temporal variation of energy.SOLUTION: An EUV light generator includes: a chamber; a pre-pulse laser 3P; a main pulse laser 3M emitting a main pulse laser beam; a combiner 409 for combining light paths of a pre-pulse laser beam and the main pulse laser beam; a condensing unit 22A for condensing the pre-pulse laser beam and the main pulse laser beam combined in the light paths to a target; a stage 84 for changing a position of the condensing unit; a first actuator for changing a direction of travel of the main pulse laser beam; an EUV light sensor for detecting EUV energy; a laser energy sensor 445 for detecting pulse energy of the main pulse laser beam; and an EUV light generation control part 5B for controlling the stage so as to reduce temporal variation of the EUV energy and controlling the first actuator so as to enlarge a ratio of EUV energy to the pulse energy.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an EUV light generation apparatus, an electronic device manufacturing method, and an inspection method. [Background technology]

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in optical lithography for semiconductor processes has progressed rapidly. In the next generation, fine processing of 10 nm or less will be required. For this reason, there is a demand for the development of semiconductor exposure equipment that combines a device for generating extreme ultraviolet (EUV) light with a wavelength of approximately 13 nm and a reduced projection reflective optical system.

[0003] As an EUV light generation device, development of a Laser Produced Plasma (LPP) type device that uses plasma generated by irradiating a target material with laser light is progressing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2014 / 0203194 [Patent Document 2] Summary of the specification of U.S. Patent Application Publication No. 2018 / 0343729

[0005] an EUV light generation apparatus according to one aspect of the present disclosure, the EUV light generation apparatus including: a pre-pulse laser that outputs pre-pulse laser beams to be irradiated onto a target supplied within a chamber; a main pulse laser that outputs main pulse laser beams to be irradiated onto the target irradiated with the pre-pulse laser beam; a combiner that combines the optical paths of the pre-pulse laser beam and the main pulse laser beam; a focusing unit that focuses the pre-pulse laser beam and the main pulse laser beam, the optical paths of which are combined, onto the target; a stage that changes the position of the focusing unit; a first actuator that is disposed upstream of the combiner and changes the direction of travel of the main pulse laser beam before the optical paths are combined; an EUV light sensor that detects EUV energy of the EUV light emitted from the target irradiated with the main pulse laser beam; a laser energy sensor that detects the pulse energy of the main pulse laser beam before it is irradiated onto the target; and an EUV light generation controller that controls the stage to reduce temporal variation in the EUV energy detected by the EUV light sensor, and controls the first actuator to increase a ratio of the EUV energy to the pulse energy detected by the laser energy sensor.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes a pre-pulse laser that outputs pre-pulse laser light to be irradiated onto a target supplied into a chamber, a main pulse laser that outputs main pulse laser light to be irradiated onto the target irradiated with the pre-pulse laser light, a combiner that combines the optical paths of the pre-pulse laser light and the main pulse laser light, a focusing unit that focuses the combined optical paths of the pre-pulse laser light and the main pulse laser light onto the target, a stage that changes the position of the focusing unit, a first actuator that is arranged upstream of the combiner and that changes the traveling direction of the main pulse laser light before the optical paths are combined, and a focusing unit that focuses the target irradiated with the main pulse laser light. an EUV light generation controller that controls the stage to reduce the temporal variation in the EUV energy detected by the EUV light sensor and the first actuator to increase the ratio of the EUV energy to the pulse energy detected by the laser energy sensor, and irradiates the target with the pulsed laser beam to generate EUV light, outputs the EUV light to an exposure apparatus, and exposes the EUV light onto a photosensitive substrate in the exposure apparatus to manufacture an electronic device.

[0007] An inspection method according to one aspect of the present disclosure includes a pre-pulse laser that outputs pre-pulse laser light to be irradiated onto a target supplied into a chamber, a main pulse laser that outputs main pulse laser light to be irradiated onto the target irradiated with the pre-pulse laser light, a combiner that combines optical paths of the pre-pulse laser light and the main pulse laser light, a focusing unit that focuses the pre-pulse laser light and the main pulse laser light, whose optical paths have been combined, onto the target, a stage that changes the position of the focusing unit, a first actuator that is disposed upstream of the combiner and that changes the traveling direction of the main pulse laser light before the optical paths are combined, and a laser beam that emits radiation from the target irradiated with the main pulse laser light. an EUV light generation controller that controls a stage to reduce the temporal variation in the EUV energy detected by the EUV light sensor and controls a first actuator to increase the ratio of the EUV energy to the pulse energy detected by the laser energy sensor, and irradiates a target with pulsed laser light to generate EUV light, outputs the EUV light to an inspection device as an inspection light source, and exposes a mask to the EUV light in the inspection device to inspect the mask. [Brief explanation of the drawings]

[0008] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a diagram illustrating the schematic configuration of an LPP type EUV light generation system. [Figure 2] FIG. 2 is a diagram schematically illustrating the configuration of an EUV light generation system including a target supply device according to a comparative example. [Figure 3] FIG. 3 is a diagram showing the arrangement of the EUV light sensor. [Figure 4] FIG. 4 is a block diagram showing EUV energy center of gravity control. [Figure 5]FIG. 5 is a diagram schematically illustrating the configuration of an EUV light generation apparatus according to the first embodiment of the present disclosure. [Figure 6] FIG. 6 is a block diagram showing control of the pulse energy of the main pulse laser beam. [Figure 7] FIG. 7 is a flowchart showing the laser irradiation position control according to the first embodiment. [Figure 8] FIG. 8 is a flowchart showing irradiation position adjustment according to the technique of the present disclosure. [Figure 9] FIG. 9 is a flowchart showing the details of the location search. [Figure 10] FIG. 10 is a diagram showing an example of obtaining the index. [Figure 11] FIG. 11 is a diagram showing an example of a small amount of movement in the direction of improvement. [Figure 12] FIG. 12 is a diagram illustrating an example of index acquisition by additional search according to the technique of the present disclosure. [Figure 13] FIG. 13 is a diagram showing an example of moving to an additional search position. [Figure 14] FIG. 14 is a diagram schematically illustrating the configuration of an EUV light generation system according to the second embodiment. [Figure 15] FIG. 15 is a diagram showing an example of the arrangement of the mist sensors. [Figure 16] FIG. 16 is a diagram showing an example of an image of a diffused target captured by a mist sensor. [Figure 17] FIG. 17 is a flowchart showing laser irradiation position control according to the second embodiment. [Figure 18] FIG. 18 is a flowchart showing irradiation position adjustment according to the technique of the present disclosure. [Figure 19] FIG. 19 is a flowchart showing the details of the location search. [Figure 20] FIG. 20 shows a flowchart of the irradiation position adjustment including the process of compensation by the light collecting unit. [Figure 21] FIG. 21 shows a schematic configuration of an exposure apparatus connected to an EUV light generation system. [Figure 22]FIG. 22 shows a schematic configuration of an inspection device connected to an EUV light generation device. Embodiment

[0009] <Contents> 1. Overview of the EUV light generation system 1.1 Configuration 1.2 Operation 2. EUV light generation system according to a comparative example 2.1 Configuration 2.2 Operation 2.3 Challenges 3. EUV Light Generation System of First Embodiment 3.1 Configuration 3.2 Operation 3.3 Actions and Effects 4. Second embodiment of EUV light generation system 4.1 Configuration 4.2 Operation 4.3 Actions and Effects 4.4 Variations 5.Other

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0011] 1. Overview of the EUV light generation system 1.1 Configuration FIG. 1 schematically illustrates the configuration of an LPP-type EUV light generation system 11. The EUV light generation system 1 is used together with at least one laser device 3. In the present application, a system including the EUV light generation system 11 and the laser device 3 is referred to as the EUV light generation system 11. As illustrated in FIG. 1 and described in detail below, the EUV light generation system 1 includes a chamber 2 and a target supply device 26. The chamber 2 is configured to be sealable. The target supply device 26 is attached, for example, so as to penetrate the wall of the chamber 2. The material of the target 27 output from the target supply device 26 includes tin. The material of the target 27 may also include a combination of tin with terbium, gadolinium, lithium, or xenon. The target 27 is droplet-shaped.

[0012] At least one through-hole is provided in the wall of the chamber 2. A window 21 is provided in the through-hole. A pulsed laser beam 32 output from the laser device 3 passes through the window 21. An EUV collector mirror 23 having, for example, an ellipsoidal reflective surface is disposed inside the chamber 2. The EUV collector mirror 23 has first and second focal points. A multilayer reflective film, for example, in which molybdenum and silicon are alternately stacked, is formed on the surface of the EUV collector mirror 23. The EUV collector mirror 23 is disposed so that, for example, its first focal point is located in the plasma generation region 25 and its second focal point is located at the intermediate focus (IF) 292. A through-hole 24 is provided in the center of the EUV collector mirror 23. The pulsed laser beam 33 passes through the through-hole 24.

[0013] The EUV light generation system 1 includes an EUV light generation controller 5 and a target sensor 4. The target sensor 4 has an imaging function and is configured to detect the presence, trajectory, position, speed, etc. of a target 27.

[0014] The EUV light generation system 1 also includes a connection part 29 that connects the interior of the chamber 2 with the interior of the external device 6. A wall 291 having an aperture 293 formed therein is provided inside the connection part 29. The wall 291 is positioned so that the aperture 293 is located at the second focal position of the EUV collector mirror 23.

[0015] Furthermore, the EUV light generation system 1 includes a laser beam direction control unit 34, a laser beam focusing mirror 22, and a target recovery unit 28 for recovering the target 27. The laser beam direction control unit 34 includes an optical element for defining the direction of travel of the laser beam, and an actuator for adjusting the position, attitude, etc. of the optical element.

[0016] 1.2 Operation 1, pulsed laser light 31 output from laser device 3 passes through laser light direction control section 34, passes through window 21 as pulsed laser light 32, and enters chamber 2. Pulsed laser light 32 travels through chamber 2 along at least one laser light path, is reflected by laser beam focusing mirror 22, and is irradiated as pulsed laser light 33 onto at least one target 27.

[0017] The target supply device 26 outputs the target 27 toward the plasma generation region 25 inside the chamber 2. The target 27 is irradiated with at least one pulse of the pulsed laser beam 33. The target 27 irradiated with the pulsed laser beam 33 is converted into plasma, and the plasma emits radiation 251. The EUV collector mirror 23 reflects the EUV light contained in the radiation 251 with a higher reflectance than light in other wavelength ranges. Reflected light 252, which includes EUV light reflected by the EUV collector mirror 23, is collected at an intermediate focus 292 and output to the external device 6. Note that one target 27 may be irradiated with multiple pulses of the pulsed laser beam 33. Hereinafter, the reflected light 252 may also be referred to as EUV light 252.

[0018] The EUV light generation controller 5 oversees the overall control of the EUV light generation system 11. The EUV light generation controller 5 processes image data of the target 27 captured by the target sensor 4. The EUV light generation controller 5 also controls, for example, the timing at which the target 27 is output and the output direction of the target 27. The EUV light generation controller 5 also controls, for example, the oscillation timing of the laser device 3, the direction of travel of the pulsed laser beam 32, and the focusing position of the pulsed laser beam 33. The various controls described above are merely examples, and other controls may be added as necessary.

[0019] 2. EUV light generation system according to a comparative example 2.1 Configuration

[0020] FIG. 2 is a partial cross-sectional view showing the configuration of an EUV light generation system 1A according to a comparative example. FIG. 3 is a diagram showing the arrangement of EUV light sensors 70c to 70e. As shown in FIGS. 2 and 3, the output direction of the EUV light is defined as the Z direction. The direction opposite to the output direction of the target 27 is defined as the Y direction. The direction perpendicular to both the Z direction and the Y direction is defined as the X direction. FIG. 2 shows the EUV light generation system 1A as viewed in the X direction. FIG. 3 shows the EUV light generation system 1A as viewed in the -Z direction.

[0021] The EUV light generation system 1A includes an EUV light generation controller 5A, a chamber 2A, a target supply device 26, a laser device 3, a laser beam direction controller 34A, and EUV light sensors 70c to 70e.

[0022] Inside the chamber 2A, there are provided a collector unit 22A, an EUV collector mirror 23, a target collector 28, an EUV collector mirror holder 81, plates 82 and 83, and a stage 84. A target supply device 26 is attached to the chamber 2A. EUV optical sensors 70c to 70e are arranged inside the chamber 2A, as will be described later.

[0023] The target supply device 26 is disposed so as to pass through a through-hole formed in the wall of the chamber 2A. The target supply device 26 stores the material of the molten target 27 inside. The target supply device 26 has an opening located inside the chamber 2A. A vibration device (not shown) is disposed near the opening of the target supply device 26.

[0024] The target supply device 26 is equipped with an XZ stage (not shown). The EUV light generation controller 5A controls the XZ stage based on the output of the target sensor 4 (see FIG. 1). By controlling the XZ stage, the trajectory of the target 27 can be adjusted so that the target 27 passes through the plasma generation region 25.

[0025] The laser device 3 includes a pre-pulse laser 3P and a main pulse laser 3M. The pre-pulse laser 3P is configured to output a pre-pulse laser beam 31P. The main pulse laser 3M is configured to output a main pulse laser beam 31M. The pre-pulse laser 3P is configured, for example, as a YAG laser device or a laser device using Nd:YVO4. The main pulse laser 3M is configured, for example, as a CO2 laser device. The main pulse laser 3M may be configured, for example, as a YAG laser device or a laser device using Nd:YVO4.

[0026] The laser beam direction control unit 34A includes high-reflection mirrors 341, 342, 345, 346, 405, and 406, and a combiner 409. The high-reflection mirrors 341, 342, 345, 346, 405, and 406 and the combiner 409 are supported by holders 343, 344, 347, 348, 407, 408, and 410, respectively.

[0027] The high-reflection mirrors 341 and 342 are disposed on the optical path of the pre-pulse laser beam 31P.

[0028] The high-reflection mirrors 345 and 346 are disposed in the optical path of the main pulse laser beam 31M.

[0029] The high-reflection mirror 405 is disposed in the optical path of the main pulse laser beam 31M reflected by the high-reflection mirror 346 .

[0030] The combiner 409 is located in the optical path of the pre-pulse laser beam 31P reflected by the high-reflection mirror 342. The combiner 409 is also located in the optical path of the main pulse laser beam 31M reflected by the high-reflection mirror 405. The combiner 409 is configured to reflect the pre-pulse laser beam 31P with high reflectivity and to transmit the main pulse laser beam 31M with high transmittance. The combiner 409 is configured to make the optical path axes of the pre-pulse laser beam 31P and the main pulse laser beam 31M approximately coincident.

[0031] The high-reflection mirror 406 is disposed in the optical path of the pre-pulse laser beam 31P reflected by the combiner 409 and the main pulse laser beam 31M transmitted through the combiner 409. The high-reflection mirror 406 is configured to reflect the pre-pulse laser beam 31P and the main pulse laser beam 31M toward the inside of the chamber 2A. In the present disclosure, for convenience of explanation, the pre-pulse laser beam 31P and the main pulse laser beam 31M reflected by the high-reflection mirror 406 may be collectively referred to as the pulse laser beam 32.

[0032] The plate 82 is fixed to the chamber 2. The plate 82 supports a plate 83. The focusing unit 22A includes a laser beam focusing mirror 221 and a laser beam focusing mirror 222.

[0033] The stage 84 is capable of adjusting the position of the plate 83 relative to the plate 82. By adjusting the position of the plate 83, the positions of the laser beam focusing mirror 221 and the laser beam focusing mirror 222 are adjusted. The positions of the laser beam focusing mirror 221 and the laser beam focusing mirror 222 are adjusted so that the pulsed laser beam 33 reflected by these mirrors is focused in the plasma generation region 25. For ease of explanation, the pre-pulse laser beam 31P and the main pulse laser beam 31M reflected by the laser beam focusing mirror 221 and the laser beam focusing mirror 222 may be collectively referred to as pulsed laser beam 33.

[0034] The EUV collector mirror 23 is fixed to a plate 82 via an EUV collector mirror holder 81 .

[0035] The target sensor 4 is a sensor that detects a target 27 passing through a target detection region R. The target detection region R is a predetermined region within the chamber 2A, and is an region located at a predetermined position on the target trajectory between the target supply device 26 and the plasma generation region 25.

[0036] Each of the EUV light sensors 70c to 70e is disposed at a position that enables evaluation of the EUV energy center of gravity position, which will be described later. For example, as shown in FIG. 3, the EUV light sensors 70c to 70e are attached to the wall surface of the chamber 2A. The EUV light sensors 70c to 70e are each directed toward the plasma generation region 25. The EUV light sensors 70c and 70d are disposed at positions that are parallel to the XZ plane and that are mirror images of each other across an imaginary plane that passes through the plasma generation region 25. The EUV light sensors 70d and 70e are disposed at positions that are parallel to the YZ plane and that are mirror images of each other across an imaginary plane that passes through the plasma generation region 25.

[0037] The pulse energy center of gravity position of the EUV light 252 is one of the indicators that reflects the position on the target 27 at which the pulse laser light 33 is irradiated. Controlling the pulse energy center of gravity position of the EUV light 252 to a predetermined value means that the pulse laser light 33 is irradiated at a desired position on the target 27. Hereinafter, the pulse energy of the EUV light 252 may be referred to as EUV energy. The pulse energy center of gravity position of the EUV light 252 may be simply referred to as "EUV energy center of gravity position." Furthermore, the performance of the EUV light 252 may be simply referred to as "EUV performance."

[0038] 2.2 Operation The EUV light generation controller 5A outputs a control signal to the target supply device 26. The target material stored inside the target supply device 26 is maintained at a temperature equal to or higher than the melting point of the target material by a heater (not shown). The target material inside the target supply device 26 is pressurized by an inert gas supplied into the target supply device 26.

[0039] The target material pressurized by the inert gas is output as a jet through the opening. The vibration device vibrates at least the components of the target supply device 26 around the opening, causing the jet of target material to be separated into a plurality of droplets (DL). Each droplet constitutes a target 27. The target 27 moves in the −Y direction along a trajectory from the target supply device 26 to the plasma generation region 25. The target collection unit 28 collects the target 27 that has passed through the plasma generation region 25.

[0040] The target 27 output into the chamber 2A advances in the form of a droplet and passes through the target detection region R. The target 27 that has passed through the target detection region R is supplied to the plasma generation region 25.

[0041] The target sensor 4 detects the timing when the target 27 passes through the target detection region R. The EUV light generation controller 5A receives the passing timing signal sent from the target sensor 4. The EUV light generation controller 5A determines the timing when the target 27 passes through the target detection region R when the passing timing signal becomes lower than a predetermined threshold. In other words, the EUV light generation controller 5A identifies the timing when the target 27 passes through the target detection region R based on the detection result of the target sensor 4. The EUV light generation controller 5A generates a target detection signal indicating that the target 27 has passed through the target detection region R when the passing timing signal becomes lower than the predetermined threshold.

[0042] The EUV light generation controller 5A outputs a first trigger signal to the pre-pulse laser 3P, at a timing delayed by a predetermined delay time from the timing at which the target detection signal is generated. The pre-pulse laser 3P outputs the pre-pulse laser beam 31P in accordance with the first trigger signal. After outputting the first trigger signal, the EUV light generation controller 5A outputs a second trigger signal to the main pulse laser 3M. The main pulse laser 3M outputs the main pulse laser beam 31M in accordance with the second trigger signal. In this manner, the laser device 3 outputs the pre-pulse laser beam 31P and the main pulse laser beam 31M in this order. The pre-pulse laser beam 31P preferably has a pulse duration on the order of picoseconds. The picosecond duration means 1 ps or more and less than 1 ns. The pre-pulse laser beam 31P may also have a pulse duration of 1 ns or more and less than 1 μs.

[0043] The pre-pulse laser beam 31P and the main pulse laser beam 31M are incident on the laser beam direction control unit 34A. The pre-pulse laser beam 31P and the main pulse laser beam 31M pass through the laser beam direction control unit 34A and are guided to the focusing unit 22A as pulsed laser beam 32. The pulsed laser beam 32 is reflected by a laser beam focusing mirror 221 included in the focusing unit 22A. The pulsed laser beam 32 reflected by the laser beam focusing mirror 221 is reflected by a laser beam focusing mirror 222 and focused in the plasma generation region 25 as pulsed laser beam 33.

[0044] The stage 84 adjusts the position of the plate 83 relative to the plate 82 in response to a control signal output from the EUV light generation controller 5A. Adjusting the position of the plate 83 adjusts the positions of the laser beam focusing mirror 221 and the laser beam focusing mirror 222. The plate 83 and the stage 84 form a moving stage that moves the laser beam focusing mirror 221 and the laser beam focusing mirror 222. In the following description, the plate 83 and the stage 84 may be collectively referred to simply as the moving stage. Moving the laser beam focusing mirror 221 and the laser beam focusing mirror 222 simultaneously changes the optical path axes of the pre-pulse laser beam 31P and the main pulse laser beam 31M included in the pulsed laser beam 33. As described above, the focal point of the laser beam focusing mirror 222 and the focusing point of the pulsed laser beam 33 substantially coincide with each other. Therefore, the direction and distance of movement of the plate 83 by the stage 84 substantially coincide with the direction and distance of movement of the focusing point of the pulsed laser beam 33.

[0045] When one of the targets 27 reaches the plasma generation region 25, the target 27 is irradiated with the pre-pulse laser beam 31P. The target 27 irradiated with the pre-pulse laser beam 31P diffuses into a mist. When the target 27 diffuses to a desired size, the target 27 is irradiated with the main pulse laser beam 31M. The target 27 diffused into a mist by being irradiated with the pre-pulse laser beam 31P is also referred to as a diffused target 27.

[0046] The target 27 irradiated with the main pulse laser beam 31M is turned into plasma, and this plasma emits radiation 251. EUV light 252 contained in the radiation 251 is selectively reflected by the EUV collector mirror 23 and focused at an intermediate focus 292 at the connection part 29. The EUV light 252 focused at the intermediate focus 292 is output toward the external device 6.

[0047] If the optical path axis of the pulsed laser beam 33 focused in the plasma generation region 25 deviates from the center of the droplet-shaped target 27, problems such as a decrease in EUV energy occur. However, it may be difficult to directly measure the deviation between the optical path axis of the pulsed laser beam 33 and the center of the target 27. Therefore, the EUV light generation controller 5A controls the optical path axis of the pulsed laser beam 33 using the EUV energy center of gravity as an index, according to the following principle.

[0048] Fig. 4 is a block diagram showing EUV energy center of gravity control. In Fig. 4, PPL-DL means the target 27 irradiated with the pre-pulse laser beam 31P. MPL-DL means the target 27 irradiated with the main pulse laser beam 31M. The EUV center of gravity characteristics of the PPL-DL indicate the characteristics of the position at which the pre-pulse laser beam 31P is irradiated on the target 27 in the plasma generation region 25. The EUV center of gravity characteristics of the MPL-DL indicate the characteristics of the position at which the main pulse laser beam 31M is irradiated on the target 27 in the plasma generation region 25. The EUV light generation controller 5A includes a calculation unit 51 and a position adjustment unit 52. The calculation unit 51 calculates an adjustment amount by PID (Proportional-Integral-Differential) calculation.

[0049] The EUV energy centroid position is the centroid position of the EUV energy distribution, and is a spatial position identified from a plurality of measurement values obtained by measuring the EUV energy with the EUV optical sensors 70c to 70e.

[0050] The EUV energy center of gravity position is an index for evaluating whether the irradiation conditions of the pulsed laser beam 33 are conditions that satisfy the EUV light performance. Therefore, controlling the EUV energy center of gravity position to match the target center of gravity position means that the pulsed laser beam 33 is appropriately irradiated onto the target 27.

[0051] The EUV light generation controller 5A evaluates the X-axis coordinate component of the EUV energy center of gravity position using an evaluation value Cx obtained by the following equation 1. The EUV light generation controller 5A also evaluates the Y-axis coordinate component of the EUV energy center of gravity position using an evaluation value Cy obtained by the following equation 2. Cx[%]={(E3-E2) / (E2+E3)}×100 ···(1) Cy[%]={(E1-E2) / (E1+E2)}×100 ···(2)

[0052] E1 is the measurement value of EUV energy by the EUV light sensor 70c. E2 is the measurement value of EUV energy by the EUV light sensor 70d. E3 is the measurement value of EUV energy by the EUV light sensor 70e. Cx represents the uneven distribution of EUV energy in the X-axis direction. Cy represents the uneven distribution of EUV energy in the Y-axis direction.

[0053] The EUV light generation controller 5A is configured to be able to perform EUV energy center of gravity control. EUV energy center of gravity control refers to feedback control of the collector unit 22A so that the EUV energy center of gravity matches a target center of gravity position based on the measurement results of each of the EUV light sensors 70c-70e during generation of the EUV light 252. Specifically, the EUV light generation controller 5A has the function of performing the following processes as EUV energy center of gravity control.

[0054] The EUV light generation controller 5A sends a first gate signal to each of the EUV light sensors 70c-70e at a timing delayed by a predetermined delay time from the timing at which the target detection signal is generated. The first gate signal is a signal that triggers each of the EUV light sensors 70c-70e to measure EUV energy. Upon receiving the first gate signal, each of the EUV light sensors 70c-70e measures the EUV energy and sends the measurement values E1-E3 to the EUV light generation controller 5A.

[0055] The EUV light generation controller 5A evaluates the EUV energy center of gravity position using the above formulas 1 and 2. The EUV light generation controller 5A identifies the deviation between the current EUV energy center of gravity position and the target center of gravity position based on the evaluation values Cx and Cy. As the target center of gravity position for EUV energy center of gravity control, the EUV light generation controller 5A uses the measured value of the center of gravity of the pulse energy of the EUV light 252 when the irradiation position of the pulse laser beam 33 with respect to the target 27 is optimized.

[0056] The EUV light generation controller 5A drives the stage 84 so that the measured value of the EUV energy center of gravity coincides with the target center of gravity. Specifically, the calculator 51 performs PID calculations based on the difference between the measured value of the pulse energy center of gravity and the target center of gravity, to determine the amount of adjustment of the stage 84 and send it to the position adjuster 52. The position adjuster 52 drives the stage 84 in accordance with the determined amount of adjustment, thereby moving the focusing position of the pulse laser beam 33.

[0057] 2.3 Challenges As described above, the EUV light generation controller 5A controls the EUV energy characteristics based on the target center of gravity position. The position adjuster 52 controls the pulsed laser beam 32 that has passed through the combiner 409 by moving the stage 84 based on the adjustment amount calculated by the calculator 51, so that the measured value of the EUV energy center of gravity position coincides with the target center of gravity position.

[0058] However, optical elements included in the laser beam direction control unit 34A and the focusing unit 22A may be deformed by being heated by the energy of the pulsed laser beam, causing changes in the optical paths of the pre-pulse laser beam 31P and the main pulse laser beam 31M. In this case, the temporal variation in the irradiation position of the pre-pulse laser beam 31P differs from the temporal variation in the irradiation position of the main pulse laser beam 31M, which may result in different changes in the EUV center-of-gravity characteristics of the PPL-DL and the MPL-DL. That is, deviation of the optical path of either the pre-pulse laser beam 31P or the main pulse laser beam 31M from the optimal optical axis causes a deviation in the position where the pulsed laser beam 33 irradiates the target 27, resulting in a change in the EUV energy center-of-gravity value. Here, deviation from the optimal optical axis refers to deviation in the coaxial relationship between the pre-pulse laser beam 31P and the main pulse laser beam 31M.

[0059] The stage 84 is a movable stage that holds and changes the position of the focusing unit 22A that focuses both the pre-pulse laser beam 31P and the main pulse laser beam 31M. Therefore, even if the stage 84 is moved, if the coaxial relationship between the pre-pulse laser beam 31P and the main pulse laser beam 31M is shifted, it is not possible to correct the positions of the pre-pulse laser beam 31P and the main pulse laser beam 31M so that they are each optimally irradiated. As a result, the pulse laser beam 33 is irradiated at a position shifted from the center of the target 27, which makes the EUV energy unstable and increases the amount of unnecessary flying matter. The flying matter is also called debris.

[0060] Furthermore, errors may occur in the measurement of the EUV energy center of gravity position calculated by the EUV light sensors 70c to 70e. The EUV light generation controller 5A cannot detect deviations in the coaxial relationship between the pre-pulse laser beam 31P and the main pulse laser beam 31M, and therefore controls the irradiation position using measurement values that include many errors. As a result, the target 27 may continue to be inappropriately irradiated with the pulsed laser beam 33. Therefore, it is necessary to use an index other than the EUV energy center of gravity value in controlling the irradiation position of the pulsed laser beam 33 on the target 27.

[0061] Therefore, the present disclosure discloses control of the irradiation position of the pulsed laser beam 33 on the target 27 using as indicators CE (Conversion Efficiency), which is the ratio of EUV energy to the pulse energy of the main pulsed laser beam, and EUV energy 3σ, which represents the temporal variation in EUV energy, as described below.Furthermore, the present disclosure discloses an EUV light generation apparatus and an electronic device manufacturing method that can suppress deviation of the coaxial relationship between the pre-pulse laser beam 31P and the main pulsed laser beam 31M and improve the stability of the EUV energy even when the optical path of the pulsed laser beam 33 changes due to thermal deformation of an optical element.

[0062] 3. EUV Light Generation System of First Embodiment An EUV light generation system and an EUV light generation method according to a first embodiment will be described. Note that the same components as those described above are designated by the same reference numerals, and redundant descriptions will be omitted unless otherwise specified.

[0063] 3.1 Configuration 5 is a schematic diagram illustrating the configuration of an EUV light generation system 1B according to a first embodiment of the present disclosure. The EUV light generation system 1B according to the first embodiment includes an EUV light generation controller 5B and a laser beam direction controller 34B. The EUV light generation system 1B has a function of compensating for deviations in the irradiation positions of the pre-pulse laser beam 31P and the main pulse laser beam 31M when deviations occur in the irradiation positions due to the influence of heat or the like.

[0064] The EUV light generation controller 5B controls the pulse energy of the main pulse laser beam so that the EUV energy is constant during continuous operation of the EUV light generation system 1B. Hereinafter, the pulse energy of the main pulse laser beam may be referred to as the MPL energy.

[0065] 6 is a block diagram showing the control of the MPL energy. The EUV light generation controller 5B includes a calculator 51B and an MPL energy controller 53. The calculator 51B calculates the adjustment amount by PID (Proportional-Integral-Differential) calculation.

[0066] Specifically, the calculation unit 51B performs PID calculation based on the difference between the total or average of the EUV energy measurement values obtained by the EUV light sensors 70c to 70e and the target EUV energy value. The calculation unit 51B determines, through the PID calculation, an adjustment amount for the MPL energy to keep the EUV energy constant, and sends the amount to the MPL energy control unit 53. The MPL energy control unit 53 controls the MPL energy by driving the main pulse laser 3M based on the determined adjustment amount.

[0067] Therefore, the EUV light generation controller 5B keeps the EUV energy constant by controlling the MPL energy based on the difference between the measurement value by the EUV photosensors 70c-70e and the target EUV energy value. However, it is difficult to maintain the EUV energy constant by simply controlling the MPL energy. This is because the characteristics of the EUV energy change due to thermal deformation of optical elements in the light path. Therefore, in the present disclosure, the EUV light generation controller 5B performs laser irradiation position control B, which includes adjusting the position at which the pulsed laser beam 33 is irradiated onto the target 27, using the EUV energy 3σ and CE as indicators. Note that CE is the value obtained by dividing the EUV energy by the MPL energy. In other words, CE is an indicator representing the conversion efficiency of MPL energy to EUV energy.

[0068] The stability of the EUV energy can be improved by using the EUV energy 3σ, which indicates the temporal variation of the EUV energy, as an index. The EUV energy 3σ is calculated, for example, by the following formula 3: EUV energy 3σ [%] = (3σ / μ) × 100 (3)

[0069] Here, σ is the standard deviation of the EUV energy for multiple pulses contained in a unit time. μ is the average value of the EUV energy for multiple pulses contained in a unit time. The EUV energy used to calculate the EUV energy 3σ is, for example, the sum or average of the EUV energy measurements by the EUV optical sensors 70c to 70e. The unit time is several seconds, for example, about 1 to 5 seconds. Here, instead of the EUV energy 3σ, for example, n times σ may be used as an index for the stability of the EUV energy.

[0070] As described above, CE is one indicator of the performance of an EUV light generation system. However, in conventional EUV light generation systems that are required to stably output a specified EUV energy at all times, CE has not been used as an indicator for controlling the EUV energy. This is because feedback control using CE as an indicator would not guarantee stable EUV energy. In other words, when the EUV energy decreases, control is performed to maintain a constant CE by reducing the MPL energy, and control to maintain a constant EUV energy may not be performed.

[0071] The laser beam direction control unit 34B includes a laser energy sensor 445, a first actuator M1, and a beam splitter 345B.

[0072] The first actuator M1 is attached to a holder 348. The first actuator M1 is arranged to control the optical path axis of the main pulse laser beam 31M by changing the attitude of the high-reflection mirror 346. The first actuator M1 according to the technique of the present disclosure is not limited to the above arrangement. The first actuator M1 may be an actuator that can control the angle of any of the high-reflection mirrors of the main pulse laser beam 31M from the main pulse laser 3M to the combiner 409. The first actuator M1 is connected to the EUV light generation controller 5B.

[0073] The beam splitter 345B is disposed in the optical path of the main pulse laser beam 31M output from the main pulse laser 3M. The beam splitter 345B is supported by a holder 347. That is, the beam splitter 345B is provided in place of the high-reflection mirror 345 in the EUV light generation system 1A. The beam splitter 345B is configured to reflect the main pulse laser beam 31M with high reflectance. Furthermore, the beam splitter 345B is configured to transmit a portion of the main pulse laser beam 31M toward the laser energy sensor 445.

[0074] The laser energy sensor 445 is an example of a laser energy sensor according to the technology of the present disclosure. The laser energy sensor 445 is disposed in the optical path of the main pulse laser beam 31M that passes through the beam splitter 345B. The laser energy sensor 445 detects the main pulse laser beam 31M that has passed through the beam splitter 345B and outputs the detection result to the EUV light generation controller 5B. The laser energy sensor 445 is not limited to the above-described arrangement and configuration. The laser energy sensor 445 may be disposed so as to measure the transmitted light by replacing any high-reflection mirror in the optical path of the main pulse laser beam 31M from the main pulse laser 3M to the combiner 409 with a beam splitter.

[0075] 3.2 Operation Next, the operation of the EUV light generation apparatus 1B according to the first embodiment will be described. Specifically, the laser irradiation position control B executed by the EUV light generation controller 5B according to this embodiment will be described.

[0076] 7 to 9 are flowcharts showing the processing procedure of laser irradiation position control B in the first embodiment. FIG. 7 is a flowchart showing laser irradiation position control B according to the first embodiment. In laser irradiation position control B, in loop 1, a focusing unit position adjustment step S110 and a main pulse laser irradiation position adjustment step S120 are alternately and repeatedly executed, and when a predetermined termination condition is satisfied, the control exits loop 1 and terminates. The predetermined termination condition for loop 1 may be, for example, detection of a transition to a state involving the stop of EUV light generation, such as detection of an EUV light output stop command input from the external device 6.

[0077] In the beam collecting unit position adjustment step S110, the position of the beam collecting unit 22A is adjusted using the EUV energy 3σ as an index. In the main pulse laser irradiation position adjustment step S120, the irradiation position of the main pulse laser beam 31M is adjusted using CE as an index. A common algorithm may be used for adjusting the position of the beam collecting unit 22A and adjusting the irradiation position of the main pulse laser beam 31M. Note that different parameters are used for the index, search width Δ, and tolerance of position deviation.

[0078] 8 is a flowchart showing an outline of the irradiation position adjustment B. The irradiation position adjustment B may be used as a common algorithm for adjusting the position of the focusing unit 22A and adjusting the irradiation position of the main pulse laser beam 31M. In the irradiation position adjustment B, loop 2 is performed in the order of X-axis → Y-axis → X-axis or Y-axis → X-axis → Y-axis (step S201). In loop 2, the position search operation is continued for the X-axis or Y-axis of the pulse laser beam 33 until the position deviation becomes less than the allowable value.

[0079] For example, when irradiation position adjustment B is performed in the order of X-axis → Y-axis → X-axis, if the position deviation of the two optimal X-positions is within the tolerance, loop 2 is exited. On the other hand, if the deviation of the second optimal X-position from the first optimal X-position during the two X-axis searches exceeds the tolerance, it is determined that further position searches are necessary, and irradiation position search B continues in step S220. Here, the tolerance is a preset value. The tolerance refers to an index below which no significant improvement can be expected even if further searches are performed. For example, if the deviation of the optimal X-position after the second search from the optimal X-position after the first search is within the tolerance, it is determined that no significant improvement can be expected even if further searches are performed, and loop 2 is exited.

[0080] In step S220, the irradiation position is shifted by a search width Δ in the positive and negative directions relative to the current position, and the direction of performance improvement is determined from data on three points including the current position. Here, in this embodiment, the negative direction is positioned on the opposite side of the current position from the positive direction, but the three points including the current position according to the technology of the present disclosure are not limited to this. The three points including the current position may be any point consisting of the current position, a first point different from the current position, and a second point different from the current position and the first point. The data on the three points also includes EUV energy 3σ and CE. For the focusing unit 22A, position search is performed in the direction in which the EUV energy 3σ decreases. For the main pulse laser beam 31M, position search is performed in the direction in which the CE increases. The search width Δ is determined by the sensitivity of CE to the laser spot position. In this embodiment, the search width Δ is approximately 0.5 to 5 μm. The search width Δ may be different values in the X and Y directions. In particular, when the spot intensity distribution is elliptical, it is preferable to set the search width Δ to different values in the X and Y directions.

[0081] 9 is a flowchart showing the details of position search B in step S220 in Fig. 8. First, in step S221, the EUV light generation control unit 5B reads the current irradiation position and sets a search axis. Furthermore, it reads a predetermined threshold, a search width Δ, a minute amount dΔ, and the number of additional searches N. The predetermined threshold, the search width Δ, the minute amount dΔ, and the number of additional searches N may initially be set to constant values and stored in a storage unit.

[0082] Next, processing is performed in Loop 3. In Loop 3, indices at the positions of the three points are obtained, and if the absolute value of the gradient is equal to or less than the threshold, it is determined that the condition for position search is met and the process exits Loop 3. If not, processing continues in Loop 3 until the condition for position search is met. Hereinafter, in this embodiment, the gradient of the indices at the positions of the three points may be simply referred to as the gradient.

[0083] Specifically, in step S223, the irradiation position is shifted by ±Δ from the current position, and index values are acquired at three positions including the current position. Fig. 10 shows an example of how the index is acquired. For example, when position search B is performed on the X axis, as shown in Fig. 10, indexes are acquired at position P3, which is a shift of the irradiation position from the current position P1 by +Δ, and at position P2, which is a shift of the irradiation position from the current position P1 by -Δ. Here, EUV energy 3σ or CE is acquired as the index. As a general rule, when searching for the position of the focusing unit 22A, EUV energy 3σ is acquired, and when searching for the position of the main pulse laser beam 31M, CE is acquired.

[0084] In step S224, the gradient of the index at the three points including the current position is calculated based on the index values acquired at the three points. For example, a linear approximation line is calculated based on the index values acquired at P1, P2, and P3, and the slope of the calculated linear approximation line is set as the gradient.

[0085] In step S225, the absolute value of the gradient calculated in step S224 is compared with a threshold value. If the absolute value of the gradient is equal to or less than the threshold value, the condition for terminating loop 3 is satisfied, and the process moves by a minute amount dΔ in the improvement direction, and then loop 3 is terminated. FIG. 11 shows an example of moving by a minute amount dΔ in the improvement direction. In step S226, as shown in FIG. 11, the process moves by the minute amount dΔ in the improvement direction, and then loop 3 is terminated. Here, dΔ<Δ. Also, in step S226, instead of moving in the improvement direction, direct movement to the improved position may be performed. Here, the improved direction or improved position refers to a direction or position where the EUV energy 3σ is reduced in the case of position search using the focusing unit 22A, and refers to a direction or position where the CE is increased in the case of position search using the main pulse laser beam 31M.

[0086] On the other hand, in step S225, the absolute value of the gradient calculated in step S224 is compared with the threshold value, and if the absolute value of the gradient is greater than the threshold value, the process proceeds to step S225A.

[0087] In step S225A, up to N additional searches are performed until the condition in step S225 is satisfied. In this embodiment, the additional searches are performed only in the improvement direction determined in step S225, but the additional searches according to the technology disclosed herein are not limited to this, and additional searches may be performed in directions other than the improvement direction. FIG. 12 shows an example of index acquisition by additional searches. For example, as shown in FIG. 12, when one additional search is performed, the search position is position P4, which is moved by the search width Δ from position P2. After up to N additional searches have been performed, proceed to step S226.

[0088] Fig. 13 shows an example of movement to an additional search position. In step S226, the position is moved by the search width Δ to additional search position P4 as shown in Fig. 13, and then the process returns to step S223, where the position search process is performed again so that the end condition of loop 3 is satisfied.

[0089] That is, in loop 3, position search is performed until the absolute value of the gradient becomes equal to or less than the threshold value. Then, after performing a maximum of N additional searches, if the conditions for loop 3 are satisfied and loop 3 is exited, the process proceeds to step S227.

[0090] In step S227, the axis improved by the additional search is recorded. The recorded axis is overwritten as the search axis read in S221 and is the first axis searched in the next position search. On the other hand, for positions that do not require additional search and satisfy the conditions of loop 3, the processing of step S227 is not performed and position search B is terminated.

[0091] As described above, the EUV light generation controller 5B performs position search B by controlling the stage 84 and the first actuator M1 based on the gradients of the index at the three points.

[0092] Other operations of the EUV light generation system 1B of the first embodiment may be similar to those of the EUV light generation system 1A of the comparative example.

[0093] 3.3 Actions and Effects As described above, the EUV light generation apparatus 1B of this embodiment includes the pre-pulse laser 3P that outputs the pre-pulse laser beam 31P to be irradiated onto the target 27 supplied into the chamber 2, the main pulse laser 3M that outputs the main pulse laser beam 31M to be irradiated onto the target 27 irradiated with the pre-pulse laser beam 31P, the combiner 409 that combines the optical paths of the pre-pulse laser beam 31P and the main pulse laser beam 31M, the focusing unit 22A that focuses the pre-pulse laser beam 31P and the main pulse laser beam 31M whose optical paths have been combined onto the target 27, the stage 84 that changes the position of the focusing unit 22A, and the main pulse laser 3M that is disposed upstream of the combiner 409 and outputs the main pulse laser beam 31M before the optical paths are combined. the EUV light generation controller 5B controls the stage 84 to reduce an EUV energy 3σ representing the temporal variation of the EUV energy detected by the EUV light sensors 70c to 70e, and to increase CE representing the ratio of the EUV energy to the pulse energy detected by the laser energy sensor 445.

[0094] The EUV light generation controller 5B controls the irradiation position of the main pulse laser beam 31M using CE, which has not been used conventionally, as an index. Furthermore, the EUV light generation controller 5B controls the irradiation position of the pulse laser beam 33 by adjusting the position of the focusing unit 22A using EUV energy 3σ as an index. As a result, it is possible to suppress deviation of the coaxial relationship between the pre-pulse laser beam 31P and the main pulse laser beam 31M, which would be caused by thermal deformation of optical elements.

[0095] Furthermore, the stability of the EUV energy is improved because the irradiation positions of the pre-pulse laser beam 31P and the main pulse laser beam 31M on the target 27 are always maintained in an optimal state. Furthermore, by operating under conditions that increase the CE, the generation of debris is reduced, and the life of the EUV collector mirror 23 is improved.

[0096] 4. Second embodiment of EUV light generation system Next, an EUV light generation system and an EUV light generation method according to a second embodiment will be described. Note that the same components as those described above are denoted by the same reference numerals, and redundant descriptions will be omitted unless otherwise specified.

[0097] 4.1 Configuration 14 is a schematic diagram illustrating the configuration of an EUV light generation system 1C according to the second embodiment. As shown in FIG. 14, the EUV light generation system 1C according to the second embodiment further includes a mist sensor 43 and a second actuator M2. The other configuration of the EUV light generation system 1C is similar to that of the EUV light generation system 1B according to the first embodiment.

[0098] The pre-pulse laser beam 31P focused on the plasma generation region 25 irradiates the target 27 supplied to the plasma generation region 25 at a first irradiation timing. When the target 27 is irradiated with the pre-pulse laser beam 31P, the target 27 is destroyed and transformed into a mist-like target 27 in which fine particles such as microdroplets and clusters are diffused in a mist-like form.

[0099] The mist sensor 43 is provided on a wall of the chamber 2A so as to face the plasma generation region 25. The mist sensor 43 captures an image of the diffused target 27 and transmits the image to the EUV light generation controller 5C. The operation of the mist sensor 43 is controlled by the EUV light generation controller 5C.

[0100] The mist sensor 43 is configured, for example, with a CCD (Charge-Coupled Device) image sensor, and captures an image of the target 27 illuminated by a lighting fixture (not shown) or a shadowgraph of the target 27. Note that multiple mist sensors 43 may be provided. FIG. 15 shows an example of the arrangement of the mist sensors 43. For example, as shown in FIG. 15, two mist sensors 43 may be arranged so that their observation axes form an angle of 90 degrees with each other.

[0101] Fig. 16 shows an example of an image of the diffused target 27 captured by the mist sensor 43. The EUV light generation controller 5C controls the mist sensor 43 to capture an image at a timing after the pre-pulse laser beam 31P is output, thereby acquiring the image shown in Fig. 16 as an example.

[0102] The EUV light generation controller 5C obtains a characteristic value of the diffused target 27 based on the image captured by the mist sensor 43. The characteristic value is a value related to the difference between the irradiated position of the target 27 with the pre-pulse laser beam 31P and the center of gravity of the target 27. The characteristic value includes at least one of the tilt, size, and position of the diffused target 27. The tilt of the diffused target 27 increases as the irradiated position of the pre-pulse laser beam 31P deviates from the center of gravity of the target 27. Furthermore, the amount of diffusion decreases as the irradiated position of the pre-pulse laser beam 31P deviates from the center of gravity of the target 27, and therefore the size of the diffused target 27 decreases. Furthermore, the amount of change in the position of the diffused target 27 decreases as the irradiated position of the pre-pulse laser beam 31P deviates from the center of gravity of the target 27.

[0103] For example, as shown in Fig. 16, when the shape of the diffused target 27 is elliptical, the inclination of the diffused target 27 is determined by the angle θ formed between an axis including the minor axis of the ellipse and the irradiation axis of the pre-pulse laser beam 31P. The size of the diffused target 27 is determined based on the major axis and minor axis of the ellipse. The position of the diffused target 27 is determined from the coordinates of the center of gravity of the ellipse.

[0104] The second actuator M2 is attached to the holder 344. The second actuator M2 is arranged to control the optical path axis of the pre-pulse laser beam 31P by changing the attitude of the high-reflection mirror 342. The arrangement of the second actuator M2 is not limited to the above. The second actuator M2 may be an actuator that can control the angle of any of the high-reflection mirrors of the pre-pulse laser beam 31P from the pre-pulse laser 3P to the combiner 409. The second actuator M2 is connected to the EUV light generation controller 5C.

[0105] The EUV light generation controller 5C controls the second actuator M2 based on the obtained characteristic values such as the tilt, size, and position of the diffused target 27. The EUV light generation controller 5C controls the second actuator M2 to change the position and direction of the pre-pulse laser beam 31P.

[0106] 4.2 Operation Next, the operation of the EUV light generation system 1C according to the second embodiment will be described. Specifically, the laser irradiation position control C executed by the EUV light generation controller 5C according to this embodiment will be described.

[0107] 17 to 19 are flowcharts showing the procedure for adjusting the optical path axis in the second embodiment. Fig. 17 is a flowchart showing laser irradiation position control C according to the second embodiment.

[0108] Compared to the laser irradiation position control B of the first embodiment, the laser irradiation position control C of the second embodiment further includes step S140 of diagnosing EUV performance and step S141 of adjusting the pre-pulse laser irradiation position. That is, in the laser irradiation position control C, steps S110, S120, S140, and S141 are alternately and repeatedly executed, and when a predetermined termination condition is satisfied, the control exits from loop 1C and terminates. The predetermined termination condition for loop 1C may be, for example, detection of a transition to a state involving the stop of EUV light generation, such as detection of an EUV light output stop command input from the external device 6.

[0109] In step S140, the EUV energy 3σ and CE are diagnosed as EUV performance. If the EUV performance is within a predetermined range, loop 1C is repeated. On the other hand, if the EUV performance is outside the predetermined range, the process proceeds to step S141.

[0110] In step S141, the EUV light generation controller 5C controls the second actuator M2 using the characteristic value of the diffused target 27 as an index. By controlling the second actuator M2, the EUV light generation controller 5C changes the position and direction of the pre-pulse laser beam 31P. This makes it possible to constantly maintain the irradiation position of the pre-pulse laser beam 31P on the target 27 in an optimal state.

[0111] 18 is a flowchart showing irradiation position adjustment C according to the technique of the present disclosure. The irradiation position adjustment C according to the second embodiment is the same as that of the first embodiment, except that in loop 2C, position search step S220C is executed instead of position search step S220 of the first embodiment.

[0112] 19 is a flowchart showing details of position search C. Position search C is similar to position search B according to the first embodiment except that, in loop 3C, step S223 of the first embodiment is replaced by step S223C.

[0113] Step S223C is similar to the processing of step S223 except that the characteristic value of the diffused target 27 is acquired as an index. That is, in position adjustment C, the EUV light generation controller 5C controls the second actuator M2 based on the acquired characteristic value of the diffused target 27 to search for the irradiation position of the pre-pulse laser beam 31P.

[0114] 4.3 Actions and Effects As described above, the EUV light generation apparatus 1C of this embodiment includes the pre-pulse laser 3P that outputs the pre-pulse laser beam 31P to be irradiated onto the target 27 supplied into the chamber 2, the main pulse laser 3M that outputs the main pulse laser beam 31M to be irradiated onto the target 27 irradiated with the pre-pulse laser beam 31P, the combiner 409 that combines the optical paths of the pre-pulse laser beam 31P and the main pulse laser beam 31M, the focusing unit 22A that focuses the combined optical paths of the pre-pulse laser beam 31P and the main pulse laser beam 31M onto the target 27, the stage 84 that moves the position of the focusing unit 22A, the first actuator M1 that is disposed upstream of the combiner 409 and that changes the traveling direction of the main pulse laser beam 31M before the optical paths are combined, the second actuator M2 that adjusts the irradiation position of the pre-pulse laser beam 31P, and the main pulse laser 3M that outputs the main pulse laser beam 31M to be irradiated onto the target 27 after the pre-pulse laser beam 31P has been irradiated. The system includes EUV light sensors 70c to 70e that detect EUV energy emitted from a target 27 irradiated with a laser beam 31M, a laser energy sensor 445 that detects the pulse energy of the main pulse laser beam 31M before it is irradiated onto the target 27, a mist sensor 43 that acquires characteristic values of the diffused target 27, and an EUV light generation control unit 5C that controls a stage 84 to reduce an EUV energy 3σ that indicates the temporal variation of the EUV energy detected by the EUV light sensors 70c to 70e, controls a first actuator M1 to increase CE, which is the ratio of the EUV energy to the pulse energy detected by the laser energy sensor 445, and controls a second actuator M2 to maintain an optimal irradiation position of the pre-pulse laser beam 31P relative to the target 27 based on the characteristic values of the diffused target 27.

[0115] In addition to the effects and advantages of the EUV light generation apparatus 1B according to the first embodiment, the EUV light generation apparatus 1C according to the second embodiment can constantly maintain the irradiation position of the pre-pulse laser beam 31P on the target 27 in an optimal state. As a result, even if the coaxial relationship between the pre-pulse laser beam 31P and the main pulse laser beam 31M changes due to thermal deformation of optical elements, the irradiation positions of the pre-pulse laser beam 31P and the main pulse laser beam 31M can be maintained in an optimal state.

[0116] 4.4 Variations Various modifications are possible to the EUV light generation apparatus in the second embodiment. For example, in the laser irradiation position control C, if the high-reflection mirror 346 and the high-reflection mirror 342 have a common offset, the offset can be compensated for by the focusing unit 22A.

[0117] 20 shows a flowchart of irradiation position adjustment D including a process of compensation by light collecting unit 22A. The irradiation position adjustment D is the same as irradiation position adjustment C except that it includes step S240.

[0118] In step S240, the focusing unit 22A is adjusted to correspond to the common offset between the high-reflection mirror 346 and the high-reflection mirror 342. The amount of adjustment due to the offset is calculated using an encoder value in the case of the focusing unit 22A. In the case of the main pulse laser beam 31M and the pre-pulse laser beam 31P, it is calculated using a control target of a pointing sensor or encoder values of the actuators M1 and M2. The control target of the pointing sensor may be a parameter related to the amount of angular displacement of the optical path axis of each of the pre-pulse laser beam 31P and the main pulse laser beam 31M, detected by a pointing sensor (not shown).

[0119] For example, when the adjustment amount of the irradiation position of the pre-pulse laser beam 31P is +15 μm in the X direction and the adjustment amount of the irradiation position of the main pulse laser beam 31M is +20 μm in the X direction, the focusing unit 22A is moved +15 μm in the X direction. At this time, the irradiation positions of the main pulse laser beam 31M and the pre-pulse laser beam 31P are offset by −15 μm in the X direction in synchronization with the operation of the focusing unit 22A.

[0120] It is known that the laser spot intensity distribution changes depending on the incident positions of the main pulse laser beam 31M and the pre-pulse laser beam 31P on the focusing unit 22A. Therefore, offset compensation can minimize changes in the incident positions of the main pulse laser beam 31M and the pre-pulse laser beam 31P on the focusing unit 22A. This suppresses changes in the laser spot intensity distribution, contributing to lowering the EUV energy 3σ and maintaining a high CE. Furthermore, it is possible to ensure a control range for the adjustment amount of the irradiation position of the pre-pulse laser beam 31P and the irradiation position of the main pulse laser beam 31M.

[0121] 5.Other FIG. 21 shows a schematic configuration of an exposure apparatus 6A connected to the EUV light generation system 1B. In FIG. 21, the exposure apparatus 6A, which serves as the external apparatus 6, includes a mask irradiation unit 68 and a workpiece irradiation unit 69. The mask irradiation unit 68 uses EUV light incident from the EUV light generation system 1B to illuminate a mask pattern on a mask table MT via a reflection optical system. The workpiece irradiation unit 69 focuses the EUV light reflected by the mask table MT onto a workpiece (not shown) placed on a workpiece table WT via a reflection 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 translating the mask table MT and the workpiece table WT. Electronic devices can be manufactured by transferring a device pattern onto a semiconductor wafer using the exposure process described above.

[0122] FIG. 22 shows a schematic configuration of an inspection system 6B connected to the EUV light generation system 1B. In FIG. 22, the inspection system 6B, which serves as the external device 6, includes an illumination optical system 63 and a detection optical system 66. The EUV light generation system 1B outputs EUV light to the inspection system 6B as an inspection light source. The illumination optical system 63 reflects the EUV light incident from the EUV light generation system 1B and irradiates a mask 65 placed on a mask stage 64. The mask 65 here includes a mask blank before a pattern is formed. The detection optical system 66 reflects the EUV light from the illuminated mask 65 and forms an image on the light-receiving surface of a detector 67. The detector 67 receives the EUV light and acquires an image of the mask 65. The detector 67 is, for example, a time delay integration (TDI) camera. The image of the mask 65 acquired through the above process is used to inspect the mask 65 for defects, and the inspection results are used to select a mask suitable for manufacturing electronic devices. Then, the pattern formed on the selected mask is exposed and transferred onto a photosensitive substrate using the exposure apparatus 6A, thereby manufacturing an electronic device.

[0123] In the inspection apparatus 6B, the above-mentioned EUV collector mirror 23 may be of a grazing incidence type. In addition, in Figures 21 and 22, an EUV light generation system 1C may be used instead of the EUV light generation system 1B.

[0124] The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to those skilled in the art that modifications may be made to the embodiments of the present disclosure without departing from the scope of the appended claims.

[0125] Terms used throughout this specification and the appended claims should be interpreted as "open ended" terms. For example, the terms "include" or "including" should be interpreted as "not limited to what is stated as including." The term "having" should be interpreted as "not limited to what is stated as having." Additionally, the modifier "a" used in this specification and the appended claims should be interpreted as "at least one" or "one or more." Additionally, 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," and should also be interpreted as including combinations other than "A," "B," and "C."

Claims

1. a pre-pulse laser that outputs pre-pulse laser light to be irradiated onto a target supplied into the chamber; a main pulse laser that outputs a main pulse laser beam to be irradiated onto the target that has been irradiated with the pre-pulse laser beam; a combiner that combines the optical paths of the pre-pulse laser beam and the main pulse laser beam; a focusing unit that focuses the pre-pulse laser beam and the main pulse laser beam, the optical paths of which are combined, onto the target; a stage for changing the position of the light collecting unit; a first actuator disposed upstream of the combiner and configured to change the propagation direction of the main pulse laser beam before the optical paths are combined; an EUV light sensor that detects EUV energy of EUV light emitted from the target irradiated with the main pulse laser light; a laser energy sensor that detects pulse energy of the main pulse laser beam before the target is irradiated with the main pulse laser beam; a mist sensor for acquiring a characteristic value of a diffused target that is a target irradiated with the pre-pulse laser beam; a second actuator that adjusts the irradiation position of the pre-pulse laser beam; controlling the stage so that the temporal variation of the EUV energy detected by the EUV light sensor is reduced; controlling the first actuator so that a ratio of the EUV energy to the pulse energy detected by the laser energy sensor increases; an EUV light generation controller that diagnoses performance related to EUV energy after controlling the first actuator, and controls the second actuator based on the characteristic value if the performance related to EUV energy is outside a predetermined range; An EUV light generation apparatus comprising:

2. An EUV light generation device according to claim 1, The performance regarding the EUV energy is the temporal variation of the EUV energy and the ratio of the EUV energy to the pulse energy.

3. 2. The EUV light generation system according to claim 1, the EUV light generation controller alternately controls the stage and the first actuator.

4. 2. The EUV light generation system according to claim 1, the EUV light generation controller, changing the irradiation position to a current position, a first point different from the current position, and a second point different from the current position and the first point, and acquiring the temporal variation and the ratio of the EUV energy as indexes at each of three positions including the current position, the first point, and the second point; the EUV light generation controller calculates gradients of the index at the positions of the three points; The EUV light generation apparatus controls the stage and the first actuator based on the gradient.

5. 5. The EUV light generation system according to claim 4, The second point is located on the opposite side of the current position from the first point.

6. 2. The EUV light generation system according to claim 1, The EUV light generation controller controls the pulse energy of the main pulse laser beam so that the EUV energy is constant.

7. The EUV light generation apparatus according to claim 6, the EUV light sensor includes a plurality of EUV light sensors; the EUV light generation controller determines an adjustment amount for the energy of the main pulse laser beam by PID calculation based on the difference between a sum or average of EUV energy measurement values obtained by the plurality of EUV light sensors and a target EUV energy value.

8. The EUV light generation system according to claim 1, The characteristic values include at least one of an inclination, a size, and a position of the diffuse target.

9. The EUV light generation apparatus according to claim 1, a first actuator for adjusting the position of the main pulse laser beam and a second actuator for adjusting the irradiation position of the pre-pulse laser beam have a common offset; The EUV light generation controller changes the position of the collector unit in accordance with the offset.

10. The EUV light generation system according to claim 1, an EUV light generation system, wherein the temporal variation of the EUV energy is an integer multiple of a standard deviation of the EUV energy for a plurality of pulses per unit time; 11. The EUV light generation apparatus according to claim 10, the temporal variation of the EUV energy is three times the standard deviation of the EUV energy; The unit time is 1 second or more and 5 seconds or less.

12. A method for manufacturing an electronic device, comprising: a pre-pulse laser that outputs pre-pulse laser light to be irradiated onto a target supplied into the chamber; a main pulse laser that outputs a main pulse laser beam to be irradiated onto the target irradiated with the pre-pulse laser beam; a combiner that combines the optical paths of the pre-pulse laser beam and the main pulse laser beam; a focusing unit that focuses the pre-pulse laser beam and the main pulse laser beam, the optical paths of which are combined, onto the target; a stage for changing the position of the light collecting unit; a first actuator disposed upstream of the combiner and configured to change the traveling direction of the main pulse laser beam before the optical paths are combined; an EUV light sensor that detects EUV energy of EUV light emitted from a target irradiated with the main pulse laser light; a laser energy sensor that detects pulse energy of the main pulse laser beam before the target is irradiated with the main pulse laser beam; a mist sensor for acquiring a characteristic value of a diffused target that is a target irradiated with the pre-pulse laser beam; a second actuator that adjusts the irradiation position of the pre-pulse laser beam; an EUV light generation controller that controls the stage to reduce temporal variation in the EUV energy detected by the EUV light sensor, controls the first actuator to increase a ratio of the EUV energy to the pulse energy detected by the laser energy sensor, diagnoses performance related to EUV energy after controlling the first actuator, and controls the second actuator based on the characteristic value if the performance related to EUV energy is outside a predetermined range; In an EUV light generation system comprising: Irradiating the target with pulsed laser light to generate EUV light; A method for manufacturing an electronic device, comprising: outputting the EUV light to an exposure apparatus; and exposing a photosensitive substrate to the EUV light in the exposure apparatus to manufacture an electronic device.

13. 1. A testing method comprising: a pre-pulse laser that outputs pre-pulse laser light to be irradiated onto a target supplied into the chamber; a main pulse laser that outputs a main pulse laser beam to be irradiated onto the target irradiated with the pre-pulse laser beam; a combiner that combines the optical paths of the pre-pulse laser beam and the main pulse laser beam; a focusing unit that focuses the pre-pulse laser beam and the main pulse laser beam, the optical paths of which are combined, onto the target; a stage for changing the position of the light collecting unit; a first actuator disposed upstream of the combiner and configured to change the traveling direction of the main pulse laser beam before the optical paths are combined; an EUV light sensor that detects EUV energy of EUV light emitted from a target irradiated with the main pulse laser light; a laser energy sensor that detects pulse energy of the main pulse laser beam before the target is irradiated with the main pulse laser beam; a mist sensor for acquiring a characteristic value of a diffused target that is a target irradiated with the pre-pulse laser beam; a second actuator that adjusts the irradiation position of the pre-pulse laser beam; an EUV light generation controller that controls the stage to reduce temporal variation in the EUV energy detected by the EUV light sensor, controls the first actuator to increase a ratio of the EUV energy to the pulse energy detected by the laser energy sensor, diagnoses performance related to EUV energy after controlling the first actuator, and controls the second actuator based on the characteristic value if the performance related to EUV energy is outside a predetermined range; In an EUV light generation system comprising: Irradiating the target with pulsed laser light to generate EUV light; an inspection method including: outputting the EUV light to an inspection device as an inspection light source; and exposing a mask to the EUV light in the inspection device to inspect the mask.

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