Extreme ultraviolet light generation device and method for manufacturing electronic devices

Abstract

To provide an extreme ultraviolet light generation device.SOLUTION: An extreme ultraviolet light generation device comprises: a chamber including a plasma generation region 25; a target supply part for supplying a target to the plasma generation region; a laser light condensation mirror for condensing pulse laser light to the plasma generation region; and an EUV condensation mirror 23 having a reflection plane for reflecting the EUV light radiated from the plasma generation region. The EUV condensation mirror is arranged so that the reflection plane falls within an angle range where ion energy is less than an average value of a spatial distribution of the ion energy at a position separated by a prescribed distance, from the plasma generation region of ions diffusing from the plasma generation region.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to an extreme ultraviolet light generating apparatus and a method for manufacturing electronic devices. [Background technology]

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in semiconductor photolithography has been progressing rapidly. Next-generation models will require microfabrication of 10 nm or less. Therefore, the development of exposure systems combining EUV light generators that produce extreme ultraviolet (EUV) light with a wavelength of approximately 13 nm and reduced projection reflection optics is highly anticipated.

[0003] As for EUV light generation devices, development is progressing on LPP (Laser Produced Plasma) type devices that use plasma generated by irradiating a target material with pulsed laser light. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Summary of U.S. Patent Application Publication No. 2010 / 078579

[0005] An extreme ultraviolet light generation apparatus according to one aspect of the present disclosure comprises: a chamber including a plasma generation region; a target supply unit for supplying a target to the plasma generation region; a laser beam focusing mirror for focusing pulsed laser light onto the plasma generation region; and an EUV focusing mirror having a reflective surface for reflecting EUV light emitted from the plasma generation region, wherein the reflective surface is positioned within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region is less than the average value of the ion energy.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating extreme ultraviolet light with an extreme ultraviolet light generation apparatus comprising: a chamber including a plasma generation region; a target supply unit for supplying a target to the plasma generation region; a laser beam focusing mirror for focusing pulsed laser light onto the plasma generation region; and an EUV focusing mirror having a reflective surface for reflecting EUV light emitted from the plasma generation region, wherein the reflective surface of the EUV focusing mirror is positioned such that it falls within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region of ions diffusing from the plasma generation region is less than the average value of the ion energy; outputting the extreme ultraviolet light to an exposure apparatus; and exposing a photosensitive substrate to the extreme ultraviolet light in the exposure apparatus in order to manufacture an electronic device.

[0007] A method for manufacturing an electronic device according to one aspect of this disclosure includes irradiating a mask with extreme ultraviolet light generated by an extreme ultraviolet light generation device, which comprises: a chamber including a plasma generation region; a target supply unit for supplying a target to the plasma generation region; a laser beam focusing mirror for focusing pulsed laser light onto the plasma generation region; and an EUV focusing mirror having a reflective surface for reflecting EUV light emitted from the plasma generation region, wherein the reflective surface of the EUV focusing mirror is positioned such that the reflective surface falls within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region of ions diffusing from the plasma generation region is less than the average value of the ion energy; inspecting the mask for defects using the inspection results; selecting a mask using the inspection results; and exposing and transferring a pattern formed on the selected mask onto a photosensitive substrate. [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 the EUV light generation system for the comparative example. [Figure 2] Figure 2 shows the arrangement of the EUV focusing mirrors in the comparative example. [Figure 3]Figure 3 shows the arrangement of the EUV focusing mirror in the first embodiment. [Figure 4] Figure 4 is a graph showing the spatial distribution of ion energy when the pulse width of the pulsed laser light is 4 ns. [Figure 5] Figure 5 shows how the pre-pulsed laser light is irradiated onto the target. [Figure 6] Figure 6 shows how pulsed laser light is irradiated onto the secondary target. [Figure 7] Figure 7 shows how ions from the target material diffuse from a secondary target irradiated with pulsed laser light. [Figure 8] Figure 8 shows the arrangement of the EUV focusing mirror in the second embodiment. [Figure 9] Figure 9 shows the arrangement of the EUV focusing mirror in the third embodiment. [Figure 10] Figure 10 is a graph showing the spatial distribution of ion energy when the pulse width of the pulsed laser light is set to 20 ns. [Figure 11] Figure 11 shows how pre-pulsed laser light is irradiated onto the target. [Figure 12] Figure 12, along with Figures 13 and 14, shows the pulsed laser light irradiating the secondary target in a time series. [Figure 13] Figure 13 shows the pulsed laser light irradiating the secondary target in a time series, along with Figures 12 and 14. [Figure 14] Figure 14 shows the pulsed laser light irradiating the secondary target in a time series, along with Figures 12 and 13. [Figure 15] Figure 15 shows the arrangement of the EUV focusing mirror in the fourth embodiment. [Figure 16] Figure 16 shows a first example of an ion detector arranged to detect ion energy. [Figure 17] Figure 17 shows a second example of an ion detector arranged to detect ion energy. [Figure 18]FIG. 18 shows an example of detection results by an ion detector. [Figure 19] FIG. 19 schematically shows the configuration of an exposure apparatus connected to an EUV light generation system. [Figure 20] FIG. 20 schematically shows the configuration of an inspection apparatus connected to an EUV light generation system. Embodiment

[0009] <Content> 1. Comparative Example 1.1 Configuration 1.2 Operation 2. Problems of the Comparative Example 3. EUV Condensing Mirror 23 Arranged in an Angle Range of 90° to 180° 3.1 Arrangement of EUV Condensing Mirror 23 3.2 Spatial Distribution of Ion Energy 3.3 Cause of the Spatial Distribution of Ion Energy 3.4 Action 4. EUV Condensing Mirror 23 Arranged in an Angle Range of 125° to 180° 4.1 Arrangement of EUV Condensing Mirror 23 4.2 Spatial Distribution of Ion Energy 4.3 Action 5. EUV Condensing Mirror 23 Arranged in an Angle Range of 21° to 127° 5.1 Arrangement of EUV Condensing Mirror 23 5.2 Spatial Distribution of Ion Energy 5.3 Cause of the Spatial Distribution of Ion Energy 5.4 Action 6. EUV Condensing Mirror 23 Having Through-Hole 24 Surrounding an Angle Range of 21° 6.1 Arrangement of EUV Condensing Mirror 23 6.2 Action 7. Others 7.1 Measurement of Ion Energy 7.1.1 Arrangement of Ion Detector <00​​​​​​7.3 Supplement

[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. Comparative Example 1.1 Configuration Figure 1 schematically shows the configuration of an EUV light generation system 11 according to a comparative example. The EUV light generation device 1 is used together with the laser system 3. In this disclosure, the system including the EUV light generation device 1 and the laser system 3 is referred to as the EUV light generation system 11.

[0012] The laser system 3 includes a main pulsed laser device (MPL) that outputs pulsed laser light 31, as well as a pre-pulsed laser device (PPL) that outputs pre-pulsed laser light (not shown). The pulsed laser light 31 is also called the main pulsed laser light.

[0013] The EUV light generator 1 includes a chamber 2 and a target supply unit 26. The chamber 2 is a sealable container. The target supply unit 26 supplies a target 27 containing a target substance into the chamber 2. The target substance may include tin, terbium, gadolinium, lithium, xenon, or any combination of two or more of these.

[0014] 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 system 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. The direction from the first focus to the second focus is defined as the Z direction. The direction of movement of target 27 perpendicular to the Z direction is defined as the Y direction. The direction perpendicular to both the Y and Z directions is defined as the X direction.

[0015] The EUV light generator 1 includes a processor 5, a target sensor 4, etc. The 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 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.

[0016] 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.

[0017] 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 laser light and an actuator for adjusting the position, orientation, etc., of this optical element.

[0018] 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 system 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 through the chamber 2 along the laser light path, is reflected by the laser light focusing mirror 22, and is irradiated onto the target 27 as pulsed laser light 33. The pre-pulsed laser light shares an optical path with the pulsed laser light 32 by the laser light transmission device 34, is reflected by the laser light focusing mirror 22, and irradiates the target 27 before the pulsed laser light 33. Alternatively, the pre-pulsed laser light may irradiate the target 27 through a separate optical path from the pulsed laser light 33.

[0019] The wavelength of the pulsed laser light 33 and the pre-pulsed laser light is preferably 1.06 μm using a YAG (yttrium aluminum garnet) laser, but it may also be 355 nm using the third harmonic of a YAG laser, 532 nm using the second harmonic of a YAG laser, 1.3 μm using a YLF (yttrium lithium fluoride) laser, or 10.6 μm using a CO2 laser.

[0020] The fluence of the pre-pulsed laser light is 0.1 J / cm² at the irradiation position on target 27. 2 More than 100J / cm 2 The following conditions apply, with a pulse width of 1 ps to 100 ns. The fluence of the pulsed laser light 33 is 10 J / cm² at the irradiation position on the target 27. 2 More than 3000J / cm 2 The following conditions apply, with a pulse width of 1 ns or more and 100 ns or less.

[0021] The fluence of the pre-pulsed laser light is 1 J / cm². 2 More than 20J / cm 2 The following is more desirable: The fluence of the pulsed laser light 33 is 100 J / cm². 2 More than 2000J / cm 2 The following is more desirable: The pulse width of the pulsed laser light 33 is more preferably between 4 ns and 20 ns.

[0022] The target supply unit 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 the 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.

[0023] The processor 5 controls the entire EUV light generation system 11. The processor 5 processes the detection results from the target sensor 4. Based on the detection results from the target sensor 4, the processor 5 controls the timing of the output of the target 27, the output direction of the target 27, etc. Furthermore, the processor 5 controls the oscillation timing of the laser system 3, the direction of propagation of the pulsed laser light 32, the focusing position of the pulsed laser light 33, etc. The various controls described above are merely examples, and other controls may be added as needed.

[0024] 2. Issues with the Comparative Example Figure 2 shows the arrangement of the EUV focusing mirror 23 in the comparative example. The direction opposite to the direction of propagation of the pulsed laser beam 33 toward the plasma generation region 25 is defined as 0°. The angles relative to the 0° direction are shown as 15, 30, 45, ..., 180. The EUV focusing mirror 23 is positioned such that its through-hole 24 is located in the 0° direction. The first focal point of the reflective surface 23a is located in the plasma generation region 25, and the intermediate focal point 292 of the reflected light 252, which is the second focal point, is located in the 180° direction.

[0025] Figure 2 further shows a polar coordinate graph of the spatial distribution of ion energy in the comparative example, superimposed on the figure. The plasma generation region 25 is the origin, and the distance from the origin to the thick dashed lines in each direction corresponds to the ion energy height of the target material at a predetermined distance from the plasma generation region 25. The ion energy height is indicated by the numerical values ​​2, 4, 6, ..., 14 attached to the thin dashed concentric circles centered on the plasma generation region 25, and the unit is keV. The method of measuring ion energy will be described later with reference to Figures 16 to 18.

[0026] The spatial distribution of ion energy is approximately axially symmetric with respect to the optical path axis of the pulsed laser beam 33. Within this spatial distribution, the ion energy is higher in the angular range from 0° to 90° than in the angular range from 90° to 180°. In the comparative example, the reflective surface 23a of the EUV focusing mirror 23 is located in the angular range of 0° to 90° where the ion energy is high. The EUV focusing mirror 23 may be contaminated, degraded, or have its lifespan shortened by ions from the target material which have high ion energy.

[0027] 3. EUV focusing mirrors 23 positioned within an angular range of 90° to 180° 3.1 Arrangement of EUV focusing mirror 23 Figure 3 shows the arrangement of the EUV focusing mirror 23 in the first embodiment. In Figure 2, the pulsed laser beam 33 passes through the through-hole 24 of the EUV focusing mirror 23 and is focused into the plasma generation region 25, whereas in Figure 3, the pulsed laser beam 33 passes outside the EUV focusing mirror 23 and is focused into the plasma generation region 25. The outer edge of the reflective surface 23a as seen from the intermediate focusing point 292 is approximately circular. The spatial distribution of ion energy is the same as in Figure 2.

[0028] The EUV focusing mirror 23 is positioned such that the entire reflective surface 23a is located within an angular range where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is greater than 90° and less than or equal to 180°. In other words, it is desirable that all or part of the reflective surface 23a is not located within the angular range of 0° to 90°. Furthermore, it is desirable not to place the EUV focusing mirror 23 at a position 180° from which the pulsed laser light 33 that has passed through the plasma generation region 25 passes. The pulsed laser light 33 that has passed through the plasma generation region 25 passes outside the EUV focusing mirror 23 and is incident on a laser damper (not shown).

[0029] However, if the angular range in which the reflective surface 23a is located is too narrow, the amount of EUV light reaching the intermediate focal point 292 may be insufficient. It is desirable that the EUV focusing mirror 23 be positioned such that the reflective surface 23a extends from a position where the angle is 95° to a position where the angle is 150°. The EUV focusing mirror 23 may extend outside the angular range of 95° to 150°, as long as it is within an angular range greater than 90° and less than or equal to 180°.

[0030] 3.2 Spatial distribution of ion energy Figure 4 is a graph showing the spatial distribution of ion energy when the pulse width of the pulsed laser light 33 is 4 ns. In Figure 4, the open circles represent measurement results in several directions, and the thick dashed lines represent approximate straight lines derived from the measurement results. The spatial distribution of ion energy shown in Figures 2 and 3 corresponds to Figure 4 when rewritten as a polar coordinate graph.

[0031] In Figure 4, Eavg is defined as the average value of the ion energy of the target material measured for each of several angles between 0° and 180°. The target material is, for example, tin. In the angular range greater than 90° and less than or equal to 180°, the ion energy is less than the average value Eavg. By positioning the EUV focusing mirror 23 such that the reflective surface 23a falls within the angular range where the ion energy is less than the average value Eavg, contamination of the reflective surface 23a by ions from the target material can be suppressed. The pulse width of the pulsed laser light 33 is not limited to 4ns; similar results can be obtained if it is within the range of 3.6ns to 4.4ns.

[0032] 3.3 Causes of Spatial Distribution of Ion Energy Figure 5 shows how the pre-pulsed laser beam 33a is irradiated onto the target 27. The target 27 diffuses or expands due to the energy of the pre-pulsed laser beam 33a, becoming the secondary target 27a shown in Figure 6.

[0033] Figure 6 shows the pulsed laser beam 33 irradiating the secondary target 27a. The pulse width of the pulsed laser beam 33 is set to 4 ns.

[0034] Figure 7 shows how ions (IONs) of the target material diffuse from the secondary target 27a irradiated with pulsed laser light 33. In the first embodiment, the pulsed laser light 33 has a short pulse width of 4 ns and high light intensity, so it rapidly heats a portion of the secondary target 27a. As a result, a low-density region 27b containing high-energy particles is generated in a portion of the secondary target 27a. Ions (IONs) of the target material are emitted from region 27b. If the low-density region 27b is biased upstream of the pulsed laser light 33, i.e., towards the -Z side in Figure 7, then more ions (IONs) are emitted in the -Z direction. It is presumed that the spatial distribution of ion energy shown in Figures 2 to 4 occurs as described above.

[0035] 3.4 Effect (1) According to the first embodiment, the EUV light generation device 1 includes a chamber 2 including a plasma generation region 25, a target supply unit 26, a laser light condensing mirror 22, and an EUV condensing mirror 23. The target supply unit 26 supplies a target 27 to the plasma generation region 25. The laser light condensing mirror 22 condenses pulsed laser light 33 on the plasma generation region 25. The EUV condensing mirror 23 has a reflecting surface 23a that reflects EUV light radiated from the plasma generation region 25, and the reflecting surface 23a is arranged so as to be within an angular range that is less than the average value Eavg of the ion energy in the spatial distribution of the ion energy at a position at a predetermined distance from the plasma generation region 25 of ions diffusing from the plasma generation region 25. According to this, since the reflecting surface 23a is within a region where the ion energy is low, contamination of the reflecting surface 23a can be suppressed.

[0036] (2) According to the first embodiment, the EUV light generation device 1 further includes a prepulse laser device PPL that outputs prepulse laser light irradiated to the target 27, and a main pulse laser device MPL that outputs pulsed laser light 33 irradiated to the target 27 irradiated with the prepulse laser light. The laser light condensing mirror 22 condenses both the prepulse laser light and the pulsed laser light 33 on the plasma generation region 25. According to this, since the prepulse laser light and the pulsed laser light 33 are irradiated to the target 27 from the same direction, the axis of rotational symmetry of the shape of the secondary target 27a and the optical path axis of the pulsed laser light 33 coincide, and the diffusion direction of the ions can be stabilized. Further, by making the optical path axis of the prepulse laser light coincide with the optical path axis of the pulsed laser light 33 and sharing the optical system including the laser light condensing mirror 22 for irradiating these lights to the target 27, the pointing accuracy of these lights is improved, and the diffusion direction of the ions can be stabilized.

[0037] (3) According to the first embodiment, the fluence of the prepulse laser light is 0.1 J / cm 2 or more and 100 J / cm 2The following conditions apply, with a pulse width of 1 ps to 100 ns. The fluence of the pulsed laser light 33 is 10 J / cm². 2 More than 3000J / cm 2 The following conditions apply, with a pulse width of 1 ns or more and 100 ns or less. According to this, EUV light can be efficiently generated by irradiating the secondary target 27a, which has been diffused or expanded by pre-pulsed laser light to achieve a desirable density, with pulsed laser light 33.

[0038] (4) The fluence of the prepulsed laser light is 1 J / cm² 2 More than 20J / cm 2 The following is more preferable, and the pulse width is more preferable to be between 1 ps and 100 ns. The fluence of the pulsed laser light 33 is 100 J / cm 2 More than 2000J / cm 2 The following is more preferable, and the pulse width is more preferably between 4 ns and 20 ns. According to this, EUV light can be generated even more efficiently.

[0039] (5) In the first embodiment, the average value Eavg is the average of the ion energies measured for each of several angles between 0° and 180° with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25. According to this, the design of the EUV light generator 1 can be simplified by considering the spatial distribution of ion energy to be axially symmetric with respect to the optical path axis of the pulsed laser light 33.

[0040] (6) According to the first embodiment, the laser beam focusing mirror 22 is positioned so that the pulsed laser beam 33 passes outside the EUV focusing mirror 23 and is focused into the plasma generation region 25. According to this, there is no need to form through-holes 24 in the EUV focusing mirror 23 for the pulsed laser light 33 to pass through, thus improving focusing efficiency and allowing the EUV focusing mirror 23 to be miniaturized.

[0041] (7) According to the first embodiment, the target 27 contains tin, and the pulse width of the pulsed laser light 33 is in the range of 3.6 ns to 4.4 ns. The angular range in which the reflective surface 23a should be contained is the range in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is greater than 90° and 180° or less. According to this, the reflective surface 23a can be contained within a region with low ion energy, thereby suppressing contamination of the reflective surface 23a.

[0042] (8) According to the first embodiment, the EUV focusing mirror 23 is positioned such that its reflective surface 23a extends from a position where the angle with respect to the direction opposite to the propagation direction of the pulsed laser light 33 incident on the plasma generation region 25 is 95° to a position where the angle is 150°. According to this, high EUV focusing efficiency can be obtained by using a wide range of angles with low ion energy. In all other respects, the first embodiment is the same as the comparative example.

[0043] 4. EUV focusing mirrors 23 positioned within an angular range of 125° to 180° 4.1 Arrangement of EUV focusing mirror 23 Figure 8 shows the arrangement of the EUV focusing mirror 23 in the second embodiment. The outer edge of the reflective surface 23a, as viewed from the intermediate focusing point 292, is approximately circular. The spatial distribution of ion energy is the same as in Figures 2 and 3.

[0044] The EUV focusing mirror 23 is positioned such that the entire reflective surface 23a is located within an angular range where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is greater than 125° and less than or equal to 180°. In other words, it is desirable that all or part of the reflective surface 23a is not located within the angular range of 0° to 125°.

[0045] However, if the angular range in which the reflective surface 23a is located is too narrow, the amount of EUV light reaching the intermediate focal point 292 may be insufficient. It is desirable that the EUV focusing mirror 23 be positioned such that the reflective surface 23a extends from a position where the angle is 130° to a position where the angle is 165°. The EUV focusing mirror 23 may extend outside the angular range of 130° to 165°, as long as it is within an angular range greater than 125° and less than or equal to 180°.

[0046] 4.2 Spatial distribution of ion energy Referring again to Figure 4, in the angular range greater than 125° and less than or equal to 180°, the ion energy is less than 90% of the average value Eavg. By positioning the EUV focusing mirror 23 such that the reflective surface 23a falls within the angular range where the ion energy is less than 90% of the average value Eavg, contamination of the reflective surface 23a by ions from the target material can be further suppressed.

[0047] 4.3 Effect (9) According to the second embodiment, the EUV focusing mirror 23 is positioned such that the reflective surface 23a falls within an angular range that is less than 90% of the average value Eavg. According to this, by arranging the EUV focusing mirror 23 only in an angular range where the ion energy is lower than the angular range in the first embodiment, contamination of the reflective surface 23a can be further suppressed.

[0048] (10) According to the second embodiment, the target 27 contains tin, and the pulse width of the pulsed laser light 33 is in the range of 3.6 ns to 4.4 ns. The angular range in which the reflective surface 23a should be contained is the range in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is greater than 125° and 180° or less. According to this, the reflective surface 23a can be contained within a region with low ion energy, thereby suppressing contamination of the reflective surface 23a.

[0049] (11) According to the second embodiment, the EUV focusing mirror 23 is positioned such that its reflective surface 23a extends from a position where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is 130° to a position where the angle is 165°. According to this, high EUV focusing efficiency can be obtained by using a wide range of angles with low ion energy. In all other respects, the second embodiment is the same as the first embodiment.

[0050] 5. EUV focusing mirrors 23 positioned within an angular range of 5.21° to 127° 5.1 Arrangement of EUV focusing mirror 23 Figure 9 shows the arrangement of the EUV focusing mirror 23 in the third embodiment. In the third embodiment, the EUV focusing mirror 23 is tilted so that the reflected light 252 reflected by the EUV focusing mirror 23 does not pass through the plasma generation region 25. The outer edge of the reflective surface 23a as seen from the intermediate focusing point 292 is approximately circular. Figure 9 further shows a polar coordinate graph of the spatial distribution of ion energy in the third embodiment, superimposed on the figure. In this spatial distribution, the ion energy is higher in the angular ranges from 0° to 21° and from 127° to 180° than in the angular range from 21° to 127°.

[0051] The EUV focusing mirror 23 is positioned such that the entire reflective surface 23a is contained within an angular range greater than 21° and less than 127° with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25. In other words, it is desirable that all or part of the reflective surface 23a is not located within the angular range of 0° to 21° or 127° to 180°.

[0052] However, if the angular range in which the reflective surface 23a is located is too narrow, the amount of EUV light reaching the intermediate focal point 292 may be insufficient. It is desirable that the EUV focusing mirror 23 be positioned such that the reflective surface 23a extends from a position where the angle is 40° to a position where the angle is 80°, and it is even more desirable that the reflective surface 23a extends from a position where the angle is 35° to a position where the angle is 100°. The EUV focusing mirror 23 may extend outside the angular range of 35° to 100°, as long as it is within an angular range greater than 21° and less than 127°.

[0053] 5.2 Spatial distribution of ion energy Figure 10 is a graph showing the spatial distribution of ion energy when the pulse width of the pulsed laser light 33 is set to 20 ns. In Figure 10, the open circles represent measurement results in several directions, and the thick dashed lines represent approximation curves derived from the measurement results. The spatial distribution of ion energy shown in Figure 9 corresponds to Figure 10 when rewritten as a polar coordinate graph.

[0054] In Figure 10, Eavg is defined as the average value of the ion energy of the target material measured for each of several angles between 0° and 180°. The target material is, for example, tin. In the angular range greater than 21° and less than 127°, the ion energy is less than the average value Eavg. By positioning the EUV focusing mirror 23 so that the reflective surface 23a falls within the angular range where the ion energy is less than the average value Eavg, contamination of the reflective surface 23a by ions from the target material can be suppressed. The pulse width of the pulsed laser light 33 is not limited to 20 ns; similar results can be obtained if the pulse width is within the range of 18 ns to 22 ns.

[0055] 5.3 Causes of Spatial Distribution of Ion Energy Figure 11 shows the prepulsed laser beam 33a irradiating the target 27. Figure 11 is the same as Figure 5.

[0056] Figures 12 to 14 show the time series of pulsed laser light 33 irradiating the secondary target 27a. The pulse width of the pulsed laser light 33 is set to 20 ns. In the third embodiment, the pulsed laser beam 33 has a long pulse width of 20 ns, resulting in lower light intensity than when the pulse width is shortened to 4 ns at the same fluence, thus slowly heating the secondary target 27a. As a result, as shown in Figure 14, a low-density region 27b containing high-energy particles is generated so as to penetrate the secondary target 27a. Ions (IONs) of the target material are emitted from region 27b. When the low-density region 27b penetrates from the upstream to the downstream side of the pulsed laser beam 33, IONs are emitted in both the +Z and -Z directions. It is presumed that the spatial distribution of ion energy shown in Figures 9 and 10 occurs as described above.

[0057] 5.4 Effect (12) According to the third embodiment, the target 27 contains tin, and the pulse width of the pulsed laser light 33 is in the range of 18 ns to 22 ns. The angular range in which the reflective surface 23a should be contained is the range in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is greater than 21° and less than 127°. According to this, the reflective surface 23a can be contained within a region with low ion energy, thereby suppressing contamination of the reflective surface 23a.

[0058] (13) According to the third embodiment, the EUV focusing mirror 23 is positioned such that its reflective surface 23a extends from a position where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is 40° to a position where the angle is 80°. According to this, high EUV focusing efficiency can be obtained by using a wide range of angles with low ion energy.

[0059] (14) According to the third embodiment, the EUV focusing mirror 23 is positioned such that its reflective surface 23a extends from a position where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is 35° to a position where the angle is 100°. According to this, by using a wider range of angles with lower ion energy, high EUV focusing efficiency can be obtained. In all other respects, the third embodiment is the same as the first embodiment.

[0060] EUV focusing mirror 23 having through holes 24 surrounding an angular range of 6.21° 6.1 Arrangement of EUV focusing mirror 23 Figure 15 shows the arrangement of the EUV focusing mirror 23 in the fourth embodiment. The outer edge of the reflective surface 23a as seen from the intermediate focusing point 292 is approximately circular. The spatial distribution of ion energy is the same as in Figures 9 and 10.

[0061] The EUV focusing mirror 23 in the fourth embodiment is similar to the comparative example in that its through-hole 24 is positioned in the 0° direction. The through-hole 24 is larger than that in the comparative example, and the outer edge of the through-hole 24 is positioned at a location where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is greater than 21°. As a result, the entire reflective surface 23a of the EUV focusing mirror 23 is contained within an angular range greater than 21° and less than 127° with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25.

[0062] However, if the angular range in which the reflective surface 23a is located is too narrow, the amount of EUV light reaching the intermediate focal point 292 may be insufficient. It is desirable that the EUV focusing mirror 23 be positioned such that the reflective surface 23a extends from a position where the angle is 25° to a position where the angle is 80°. The EUV focusing mirror 23 may extend outside the angular range of 25° to 80°, as long as it is within an angular range greater than 21° and less than 127°.

[0063] 6.2 Effect (15) According to the fourth embodiment, the EUV focusing mirror 23 has a through hole 24 through which the pulsed laser light 33 passes, and the outer edge of the through hole 24 is positioned at a location where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is greater than 21°. According to this, by making the through-hole 24 through which the pulsed laser light 33 passes larger, contamination of the reflective surface 23a near the through-hole 24 can be suppressed.

[0064] (16) According to the fourth embodiment, the EUV focusing mirror 23 is positioned such that its reflective surface 23a extends from a position where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light 33 incident on the plasma generation region 25 is 25° to a position where the angle is 80°. According to this, high EUV focusing efficiency can be obtained by using a wide range of angles with low ion energy. In all other respects, the fourth embodiment is the same as the third embodiment.

[0065] 7. Other 7.1 Measurement of Ion Energy 7.1.1 Arrangement of ion detectors Figure 16 shows a first example of an ion detector arranged to detect ion energy. To detect ion energy, an ion detector FC, such as a Faraday cup, is supported on a stage ST so that it can move at a predetermined distance from the plasma generation region 25 inside the chamber 2. The predetermined distance is, for example, 125 mm. The stage ST moves the ion detector FC along a movement path in a plane parallel to the YZ plane containing the plasma generation region 25, where the distance from the plasma generation region 25 is constant. When measuring ion energy, it is not necessary to place the EUV focusing mirror 23 inside the chamber 2. In this case, the spatial distribution of ion energy is almost axially symmetric with respect to the optical path axis of the pulsed laser beam 33, so by detecting the ion energy while moving the ion detector FC in a plane parallel to the YZ plane, the ion energy in each direction can be measured.

[0066] Figure 17 shows a second example of ion detectors arranged to detect ion energy. In this second example, multiple ion detectors FC1 to FC10 are arranged inside the chamber 2. Ion detectors FC1 to FC10 are arranged at multiple positions corresponding to the movement path of ion detector FC by the stage ST shown in Figure 16. By detecting ion energy with each of the ion detectors FC1 to FC10, the ion energy in each direction can be measured.

[0067] 7.1.2 Method for calculating ion energy Figure 18 shows an example of detection results from an ion detector. The detected ion energy and 1 cm⁻¹ detected at one location inside chamber 2. 2 The number of detected ions per unit area is plotted on a log-log graph as shown in Figure 18, and an approximate curve is obtained by curve fitting. From this approximate curve, the ion energy corresponding to the case where the number of ions per unit area is 1 can be calculated as the maximum ion energy. This maximum ion energy is taken as the ion energy in each embodiment.

[0068] 7.1.3 Effect (17) In each embodiment, the ion energy is the maximum ion energy at a predetermined distance from the plasma generation region 25. Since the maximum ion energy greatly affects the susceptibility to contamination, by positioning the reflective surface 23a within a region with low maximum ion energy, contamination of the reflective surface 23a can be suppressed.

[0069] (18) The maximum ion energy is calculated by curve fitting from the relationship between the detected ion energy and the number of detected ions detected at a predetermined distance from the plasma generation region 25, as the ion energy corresponding to the case where there is one ion per unit area. According to this method, the estimated maximum ion energy can be calculated with high accuracy.

[0070] 7.2 Example of EUV light utilization device 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.

[0071] 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.

[0072] 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.

[0073] Terms used throughout this specification and the claims should be interpreted as "non-limiting" unless otherwise specified. For example, terms such as "includes," "have," "equip," and "possess" should be interpreted as "not excluding the existence of components other than those described." Also, the modifier "one" should be interpreted as "at least one" or "one or more." Furthermore, 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 of these with anything other than "A," "B," and "C."

Claims

1. A chamber including a plasma generation region, A target supply unit that supplies a target to the plasma generation region, A laser beam focusing mirror that focuses pulsed laser light onto the plasma generation region, An EUV focusing mirror having a reflective surface that reflects EUV light emitted from the plasma generation region, wherein the reflective surface is positioned such that it falls within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region is less than the average value of the ion energy, Equipped with, The aforementioned target contains tin, The pulse width of the pulsed laser beam is in the range of 3.6 ns or more and 4.4 ns or less. The aforementioned angular range is a range in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region is greater than 90° and less than or equal to 180°, in an extreme ultraviolet light generation device.

2. An extreme ultraviolet light generating apparatus according to claim 1, A prepulse laser device that outputs prepulse laser light to be irradiated onto the target, A main pulse laser device that outputs pulsed laser light to be irradiated onto the target irradiated with the pre-pulsed laser light, Furthermore, The laser beam focusing mirror focuses both the pre-pulse laser beam and the pulsed laser beam onto the plasma generation region. Extreme ultraviolet light generator.

3. An extreme ultraviolet light generating apparatus according to claim 2, The fluence of the prepulsed laser light is 0.1 J / cm². ２ More than 100J / cm ２ The following: The pulse width of the prepulsed laser light is 1 ps or more and 100 ns or less. The fluence of the pulsed laser light is 10 J / cm². ２ More than 3000J / cm ２ The following: The pulse width of the pulsed laser light is 1 ns or more and 100 ns or less. Extreme ultraviolet light generator.

4. An extreme ultraviolet light generating apparatus according to claim 2, The fluence of the prepulsed laser light is 1 J / cm². ２ More than 20J / cm ２ The following: The pulse width of the prepulsed laser light is 1 ps or more and 100 ns or less. The fluence of the pulsed laser light is 100 J / cm². ２ More than 2000J / cm ２ The following: The pulse width of the pulsed laser light is 4 ns or more and 20 ns or less. Extreme ultraviolet light generator.

5. An extreme ultraviolet light generating apparatus according to claim 1, The average value is the average of the ion energies measured for each of a plurality of angles between 0° and 180° in the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region. Extreme ultraviolet light generator.

6. An extreme ultraviolet light generating apparatus according to claim 1, The laser beam focusing mirror is positioned such that the pulsed laser beam passes outside the EUV focusing mirror and is focused into the plasma generation region. Extreme ultraviolet light generator.

7. An extreme ultraviolet light generating apparatus according to claim 1, The EUV focusing mirror is positioned such that its reflective surface extends from a position where the angle with respect to the direction opposite to the propagation direction of the pulsed laser light incident on the plasma generation region is 95° to a position where the angle is 150°. Extreme ultraviolet light generator.

8. An extreme ultraviolet light generating apparatus according to claim 1, The EUV focusing mirror is positioned such that its reflective surface falls within an angular range that is less than 90% of the average value. Extreme ultraviolet light generator.

9. A chamber including a plasma generation region, A target supply unit that supplies a target to the plasma generation region, A laser beam focusing mirror that focuses pulsed laser light onto the plasma generation region, An EUV focusing mirror having a reflective surface that reflects EUV light emitted from the plasma generation region, wherein the reflective surface is positioned such that it falls within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region is less than the average value of the ion energy, Equipped with, The aforementioned target contains tin, The pulse width of the pulsed laser beam is in the range of 3.6 ns or more and 4.4 ns or less. The aforementioned angular range is the range in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region is greater than 125° and less than or equal to 180°. Extreme ultraviolet light generator.

10. An extreme ultraviolet light generating device according to claim 9, The EUV focusing mirror is positioned such that its reflective surface extends from a position where the angle with respect to the direction opposite to the propagation direction of the pulsed laser light incident on the plasma generation region is 130° to a position where the angle is 165°. Extreme ultraviolet light generator.

11. A chamber including a plasma generation region, A target supply unit that supplies a target to the plasma generation region, A laser beam focusing mirror that focuses pulsed laser light onto the plasma generation region, An EUV focusing mirror having a reflective surface that reflects EUV light emitted from the plasma generation region, wherein the reflective surface is positioned such that it falls within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region is less than the average value of the ion energy, Equipped with, The aforementioned target contains tin, The pulse width of the pulsed laser light is in the range of 18 ns or more and 22 ns or less. The aforementioned angular range is the range in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region is greater than 21° and less than 127°. Extreme ultraviolet light generator.

12. An extreme ultraviolet light generating apparatus according to claim 11, The EUV focusing mirror is positioned such that its reflective surface extends from a position where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region is 40° to a position where the angle is 80°. Extreme ultraviolet light generator.

13. An extreme ultraviolet light generating apparatus according to claim 11, The EUV focusing mirror is positioned such that its reflective surface extends from a position where the angle with respect to the direction opposite to the propagation direction of the pulsed laser light incident on the plasma generation region is 35° to a position where the angle is 100°. Extreme ultraviolet light generator.

14. An extreme ultraviolet light generating apparatus according to claim 11, The aforementioned EUV focusing mirror is Having a through hole through which the pulsed laser light passes, The outer edge of the through-hole is positioned at a location where the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region is greater than 21°. Extreme ultraviolet light generator.

15. An extreme ultraviolet light generating apparatus according to claim 11, The aforementioned EUV focusing mirror is Having a through hole through which the pulsed laser light passes, The reflective surface is positioned such that it extends from a position where the angle with respect to the direction opposite to the propagation direction of the pulsed laser light incident on the plasma generation region is 25° to a position where the angle is 80°. Extreme ultraviolet light generator.

16. An extreme ultraviolet light generating apparatus according to any one of claims 1, 9, and 11, The ion energy is the maximum ion energy at the predetermined distance. Extreme ultraviolet light generator.

17. An extreme ultraviolet light generating apparatus according to claim 16, The aforementioned maximum ion energy is the energy calculated by curve fitting from the relationship between the detected ion energy and the number of detected ions at the predetermined distance, as the ion energy corresponding to the case where there is one ion per unit area. Extreme ultraviolet light generator.

18. A method for manufacturing electronic devices, A chamber including a plasma generation region, A target supply unit that supplies a target to the plasma generation region, A laser beam focusing mirror that focuses pulsed laser light onto the plasma generation region, An EUV focusing mirror having a reflective surface that reflects EUV light emitted from the plasma generation region, wherein the reflective surface is positioned such that it falls within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region is less than the average value of the ion energy, Equipped with, The aforementioned target contains tin, The pulse width of the pulsed laser light is in the range of 18 ns or more and 22 ns or less. The aforementioned angular range is the range in which extreme ultraviolet light is generated by an extreme ultraviolet light generation device in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region is greater than 21° and less than 127°. The aforementioned extreme ultraviolet light is output to the exposure device, In order to manufacture an electronic device, the photosensitive substrate is exposed to the extreme ultraviolet light in the exposure apparatus. A method for manufacturing electronic devices, including the following.

19. A method for manufacturing electronic devices, A chamber including a plasma generation region, A target supply unit that supplies a target to the plasma generation region, A laser beam focusing mirror that focuses pulsed laser light onto the plasma generation region, An EUV focusing mirror having a reflective surface that reflects EUV light emitted from the plasma generation region, wherein the reflective surface is positioned such that it falls within an angular range where the spatial distribution of ion energy at a predetermined distance from the plasma generation region is less than the average value of the ion energy, Equipped with, The aforementioned target contains tin, The pulse width of the pulsed laser light is in the range of 18 ns or more and 22 ns or less. The aforementioned angular range is the range in which the angle with respect to the direction opposite to the direction of propagation of the pulsed laser light incident on the plasma generation region is greater than 21° and less than 127°. 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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