Methods for manufacturing laser systems and electronic devices

Abstract

This invention provides a laser system that improves the uniformity of the light intensity distribution of a laser beam. [Solution] The laser system comprises a laser oscillator, a lens array including a first lens into which a first portion of the laser beam output from the laser oscillator is incident, a second lens into which a second portion of the laser beam different from the first portion and having a smaller spatial coherence length than the first portion is incident, and which has a smaller pitch than the first lens, and a condenser lens that superimposes the first and second portions that have passed through the lens array onto a common irradiation surface.

Description

Technical Field

[0001] The present disclosure relates to a laser system and a method for manufacturing an electronic device.

Background Art

[0002] In recent years, in semiconductor exposure apparatuses, with the miniaturization and high integration of semiconductor integrated circuits, an improvement in resolution has been demanded. For this reason, the shortening of the wavelength of light emitted from an exposure light source has been advanced. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs laser light with a wavelength of about 248 nm and an ArF excimer laser device that outputs laser light with a wavelength of about 193 nm are used.

[0003] The spectral linewidth of the spontaneous emission light of a KrF excimer laser device and an ArF excimer laser device is as wide as 350 to 400 pm. Therefore, when a projection lens is configured with a material that transmits ultraviolet rays such as KrF and ArF laser light, chromatic aberration may occur. As a result, the resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from the gas laser device to such an extent that chromatic aberration can be ignored. For this reason, in the laser resonator of the gas laser device, a narrowbanding module (Line Narrowing Module: LNM) including a narrowbanding element (such as an etalon or a grating) may be provided to narrow the spectral linewidth. A gas laser device whose spectral linewidth is narrowed is called a narrowbanded gas laser device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] A laser system according to one aspect of the present disclosure includes a laser oscillator, a lens array including a first lens into which a first portion of a laser beam output from the laser oscillator is incident, a second lens into which a second portion of the laser beam, different from the first portion and having a smaller spatial coherence length than the first portion, is incident, and having a smaller pitch than the first lens, and a condenser lens that superimposes the first and second portions that have passed through the lens array onto a common irradiation surface.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating a laser beam with a laser system comprising: a laser oscillator; a lens array including a first lens into which a first portion of a laser beam output from the laser oscillator is incident; a second lens into which a second portion of the laser beam, different from the first portion and having a smaller spatial coherence length than the first portion, is incident and having a smaller pitch than the first lens; and a condenser lens that superimposes the first and second portions that have passed through the lens array onto a common irradiation surface; outputting the laser beam to an exposure apparatus; and exposing the laser beam onto a photosensitive substrate in the exposure apparatus in order to manufacture an electronic device. [Brief explanation of the drawing]

[0007] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] Figure 1 shows the configuration of the laser system in the comparative example. [Figure 2] Figure 2 shows an example of the light intensity distribution in the beam cross-section of a laser beam incident on a homogenizer. [Figure 3] Figure 3 shows the configuration of the homogenizer in the comparative example. [Figure 4] Figure 4 shows the configuration of another homogenizer in the comparative example. [Figure 5] Figure 5 shows the spatial coherence length and lens pitch at various points in the beam cross-section of the laser beam. [Figure 6]Figure 6 shows an example of a method for measuring the spatial coherence length in different parts of a laser beam. [Figure 7] Figure 7 shows an example of the contrast measurement results for each pinhole spacing. [Figure 8] Figure 8 shows the configuration of the homogenizer in the first embodiment. [Figure 9] Figure 9 is a diagram illustrating the definition of pitch. [Figure 10] Figure 10 shows a first example of the lens pitch in the first embodiment. [Figure 11] Figure 11 shows a second example of the lens pitch in the first embodiment. [Figure 12] Figure 12 shows a third example of the lens pitch in the first embodiment. [Figure 13] Figure 13 shows the configuration of the homogenizer in a modified example of the first embodiment. [Figure 14] Figure 14 shows an example of lens pitch in a modified version of the first embodiment. [Figure 15] Figure 15 shows the two-dimensional light intensity distribution of the irradiated surface in the comparative example. [Figure 16] Figure 16 shows the light intensity distribution obtained by integrating the light intensity distribution shown in Figure 15 in the X direction for each Y coordinate. [Figure 17] Figure 17 shows the two-dimensional light intensity distribution of the irradiated surface in the first embodiment. [Figure 18] Figure 18 shows the light intensity distribution obtained by integrating the light intensity distribution shown in Figure 17 in the X direction for each Y coordinate. [Figure 19] Figure 19 shows the configuration of the homogenizer in the second embodiment. [Figure 20] Figure 20 shows the configuration of the homogenizer in a modified example of the second embodiment. [Figure 21] Figure 21 shows the configuration of the homogenizer in the third embodiment. [Figure 22] Figure 22 shows the configuration of the laser system in the fourth embodiment. [Figure 23]FIG. 23 shows the detailed configuration of the laser system. [Figure 24] FIG. 24 shows the configuration of the exposure system. Embodiment

[0008] <Content> 1. Comparative Example 1.1 Laser System 100a 1.2 Homogenizer 1a 2. Problems of the Comparative Example 3. Method for Measuring the Spatial Coherence Length Xc 4. Lens Array 10c with Different Pitch P According to the Spatial Coherence Length Xc 4.1 Overview 4.2 Definition of Pitch P 4.3 Pitch P of Lenses 11c to 17c 4.3.1 First Example 4.3.2 Second Example 4.3.3 Third Example 4.4 Focal Length of Lenses 11c to 17c 4.5 Lens Array 10d Including the Light-Shielding Portion M 4.6 Function 5. Lens Array 10e with the Principal Planes of Lenses 11e to 17e Shifted from Each Other 5.1 Principal Planes of Lenses 11e to 17e 5.2 Lens Array 10f Including the Light-Shielding Portion M 5.3 Function 6. Lens Array Including the First and Second Lenticular Lenses 10g and 20g 6.1 Configuration 6.2 Function 7. Homogenizer 1c with the Irradiation Surface 5 Located Inside the Laser Amplifier PO 7.1 Configuration 7.2 Operation 7.2.1 Operation of the Laser Oscillator MO 7.2.2 Operation of the Laser Amplifier PO 7.2.3 Operation of the Optical Pulse Stretcher 99 7.3 Function 8. Others 8.1 Manufacturing Method of Electronic Devices 8.2 Supplementary

[0009] 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.

[0010] 1. Comparative Example 1.1 Laser System 100a Figure 1 shows the configuration of laser system 100a in the comparative example. The comparative example in this disclosure is a configuration that the applicant recognizes as being known only to the applicant, and is not a known example acknowledged by the applicant.

[0011] The laser system 100a includes a laser oscillator MO and a homogenizer 1a. The laser oscillator MO is a discharge-excited gas laser device, such as an excimer laser device, and is configured to output a laser beam B. The configuration of the homogenizer 1a will be described later with reference to Figure 3. The laser beam B passes through the homogenizer 1a and is irradiated onto the irradiation surface 5. In a device that performs processing using the laser beam B, the irradiation surface 5 is the processing surface of the workpiece.

[0012] Figure 2 shows an example of the light intensity distribution in the beam cross-section of the laser beam B incident on the homogenizer 1a. The shape of the beam cross-section of the laser beam B is, for example, approximately rectangular, but it may have a non-uniform light intensity distribution due to the distribution of laser gas in the laser oscillator MO or the bias of the discharge that excites the laser gas. The homogenizer 1a emits the laser beam B in such a way that the light intensity distribution in the beam cross-section of the laser beam B on the irradiation surface 5 is made uniform.

[0013] 1.2 Homogenizer 1a Figure 3 shows the configuration of homogenizer 1a in a comparative example. Homogenizer 1a includes a lens array 10a and a condenser lens 30a. The lens array 10a includes lenses 11a to 14a arranged in the beam cross-section of the laser beam B. Each of the lenses 11a to 14a is, for example, a convex lens. In Figure 3, the leader lines with symbols corresponding to lenses 11a to 14a and the condenser lens 30a indicate the position of the principal surface of each of those lenses.

[0014] The laser beam B includes a portion B1 that enters lens 11a, a portion B2 that enters lens 12a, a portion B3 that enters lens 13a, and a portion B4 that enters lens 14a.

[0015] Each of the sections B1 to B4 changes its divergence angle as it passes through the lens array 10a. In Figure 3, each of the sections B1 to B4 is emitted with a negative divergence angle, then focuses, and enters the condenser lens 30a as a beam with a positive divergence angle. In Figure 3, the optical path axis and the outer edge of the optical path for each of the sections B1 to B4 are shown by dashed lines.

[0016] The condenser lens 30a superimposes portions B1 to B4, which have passed through the lens array 10a, onto a common illumination surface 5. Figure 3 shows how the optical path axes of portions B1 to B4 are superimposed onto the central portion of the illumination surface 5, the upper rays of portions B1 to B4 in Figure 3 are superimposed onto the upper portion of the illumination surface 5, and the lower rays of portions B1 to B4 in Figure 3 are superimposed onto the lower portion of the illumination surface 5. By superimposing each portion of the laser beam B in this way, the light intensity distribution is made uniform.

[0017] 2. Issues with the Comparative Example Figure 4 shows the configuration of another homogenizer 1b in a comparative example. Homogenizer 1b may be used instead of homogenizer 1a shown in Figure 1. Homogenizer 1b differs from homogenizer 1a in that the number of lenses 11b to 18b constituting the lens array 10b is greater than the number of lenses 11a to 14a constituting the lens array 10a. The pitch P of each lens 11b to 18b is smaller than that of lenses 11a to 14a. Note that in Figure 4, the dashed lines indicating the optical path axes of portions B1 to B8 that pass through lenses 11b to 18b, respectively, are omitted. In other respects, the lens array 10b, each lens 11b, 12b, etc., and the condenser lens 30b constituting homogenizer 1b are substantially the same as the corresponding configuration of homogenizer 1a.

[0018] Geometrically, the smaller the pitch P of each lens 11b to 18b, the more the laser beam B is divided into multiple parts and superimposed on the irradiation surface 5, thus increasing the effect of homogenizing the light intensity distribution. However, if the pitch P becomes smaller than the spatial coherence length Xc of the laser beam B, the diffracted light from each end of lenses 11b to 18b will be superimposed, causing interference fringes to be generated on the irradiation surface 5, which may result in insufficient homogenization of the light intensity distribution.

[0019] Figure 5 shows the spatial coherence length Xc and lens pitch P at different points in the beam cross-section of laser beam B. The horizontal axis of Figure 5 represents the position in the Y direction in Figure 4, and the vertical axis of Figure 5 represents the spatial coherence length Xc and pitch P. Since the pitch P corresponds to the width of the lens in the Y direction, each of the rectangles shown in Figure 5 is a square, and the length of one side of each square represents the pitch P of each lens. As shown in Figure 5, the spatial coherence length Xc may not be uniform in the beam cross-section of laser beam B. For example, the spatial coherence length Xc may be large in the central part of laser beam B and small in the peripheral part. In contrast, the pitch P of lenses 11b to 18b in the comparative example are equal to each other.

[0020] In this case, for lenses 12b and 17b, the pitch P is approximately equal to the spatial coherence length Xc, so a sufficient effect is obtained to improve the uniformity of the light intensity distribution, and the generation of interference fringes is also suppressed. However, for lenses 11b and 18b at the ends of the lens array 10b, the pitch P is greater than the spatial coherence length Xc, so even if the pitch P were to be made smaller, there would be room to improve the uniformity of the light intensity distribution, but this effect is not fully obtained. On the other hand, for lenses 13b to 16b near the center of the lens array 10b, the pitch P is smaller than the spatial coherence length Xc, so there is a possibility of interference fringes occurring.

[0021] Therefore, in the comparative example, even when the pitch P was adjusted, there were problems such as insufficient improvement in the uniformity of the light intensity distribution in a portion of the laser beam B, or interference fringes being generated in other portions.

[0022] The embodiments described below relate to improving the uniformity of the light intensity distribution and suppressing the generation of interference fringes by setting the pitch P of the multiple lenses included in the lens array to a pitch P corresponding to the spatial coherence length Xc, rather than making them equal to each other.

[0023] 3. Method for measuring spatial coherence length Xc Figure 6 shows an example of a method for measuring the spatial coherence length Xc in each portion of the laser beam B. In this example, the light diffracted by the double pinholes formed in the mask 61 is observed on a screen 62 sufficiently far from the mask 61, and the visibility of the interference fringes FR is measured as contrast V. As the pinhole spacing d is gradually increased from 0 in each portion of the laser beam B that differs in the Y direction, the contrast V of the interference fringes FR formed on the screen 62 decreases.

[0024] Figure 7 shows an example of the measurement results of contrast V for each pinhole spacing d. The pinhole spacing d at which the contrast V becomes less than or equal to the threshold Vth can be measured as the spatial coherence length Xc in that portion. The threshold Vth is set to a value such that, if it is below this value, the coherence is sufficiently low and it is judged to be greater than the measurement noise of contrast V, for example, a value between 3% and 5%. For example, the spatial coherence length Xc obtained from Figure 7 is approximately 1.3 mm.

[0025] In addition to measuring the spatial coherence length Xc in each portion of the laser beam B that is different in the Y direction, the spatial coherence length Xc may also be measured in each portion that is different in the X direction.

[0026] 4. Lens array 10c with different pitches P depending on the spatial coherence length Xc. 4.1 Overview Figure 8 shows the configuration of homogenizer 1c in the first embodiment. Homogenizer 1c may be used instead of homogenizer 1a shown in Figure 1. Homogenizer 1c differs from homogenizers 1a and 1b in that the pitch P of the lenses 11c to 17c constituting the lens array 10c is not uniform.

[0027] 4.2 Definition of Pitch P Figure 9 is a diagram illustrating the definition of pitch P. In this disclosure, pitch P is defined as the distance between the medians between the centers of adjacent lenses. For example, suppose the lens array includes lenses 11 to 13. The distance between the median CL1 between the centers of adjacent lenses 11 and 12 and the median CL2 between the centers of adjacent lenses 12 and 13 is the pitch P2 of lens 12. That is, when half of the distance C1 between the centers of adjacent lenses 11 and 12 is L1, and half of the distance C2 between the centers of adjacent lenses 12 and 13 is L2, the sum of L1 and L2 is the pitch P2 of lens 12.

[0028] Regarding the pitch P of lenses 11 and 13 at the ends of the lens array, the pitch P is defined as twice the distance between the center of the lens and the median line between the centers of the adjacent lens. For example, the pitch P1 of lens 11 is twice the distance L1 between the center of lens 11 and the median line CL1 between the centers of lenses 11 and 12. The pitch P3 of lens 13 is twice the distance L2 between the center of lens 13 and the median line CL2 between the centers of lenses 13 and 12.

[0029] These pitches P1 to P3 do not necessarily coincide with the distance C1 between the centers of adjacent lenses 11 and 12, and the distance C2 between the centers of adjacent lenses 12 and 13. Furthermore, the pitches P1 to P3 are larger than or equal to the aperture sizes D1 to D3 of lenses 11 to 13. In Figure 8, the pitch P of lenses 11c to 17c is approximately equal to the aperture size of lenses 11c to 17c.

[0030] 4.3 Pitch P of lens 11c~17c Figures 10 to 12 show first to third examples of the pitch P of lenses 11c to 17c in the first embodiment. Similar to Figure 5, Figures 10 to 12 also show the spatial coherence length Xc in each portion of the beam cross-section of the laser beam B. Each of the rectangles shown in Figures 10 to 12 is a square, and the length of one side of each square represents the pitch P of each lens.

[0031] As shown in the first to third examples below, it is desirable to increase the pitch P of the lens into which the portion of the laser beam B with a large spatial coherence length Xc is incident, and to decrease the pitch P of the lens into which the portion with a small spatial coherence length Xc is incident. For example, the pitch P of lens 15c into which portion B5, which has a smaller spatial coherence length Xc than portion B4, is incident should be smaller than the pitch P of lens 14c into which portion B4 of the laser beam B is incident. Similarly, the pitch P of lens 16c into which portion B6, which has a smaller spatial coherence length Xc than portion B5, is incident should be smaller than the pitch P of lens 15c into which portion B5 is incident.

[0032] Here, we illustrate the case where the spatial coherence length Xc is large in the central part of the laser beam B and small in the peripheral part. For example, the distance between the portion B4 with a large spatial coherence length Xc and the center C of the beam cross-section of the laser beam B (see Figure 8) is shorter than the distance between the portion B5, which has a smaller spatial coherence length Xc than portion B4, and the center C of the beam cross-section. In this case, the pitch P of lens 15c, which is located further from the center of the lens array 10c, is made smaller than that of lens 14c, which is located at the center of the lens array 10c. However, this disclosure is not limited to this, and the spatial coherence length Xc may be small in the central part of the laser beam B and large in the peripheral part.

[0033] 4.3.1 Example 1 In the first example shown in Figure 10, the pitch P of each lens is the maximum value of the spatial coherence length Xc of the portion of the laser beam B that is incident on that lens. For example, the pitch P of lens 14c is the maximum value Xc4max of the spatial coherence length Xc of the portion B4 incident on lens 14c. The pitch P of lens 15c is the maximum value Xc5max of the spatial coherence length Xc of the portion B5 incident on lens 15c.

[0034] The pitch P of each lens may be greater than the maximum value of the spatial coherence length Xc of the portion of the laser beam B that enters that lens.

[0035] 4.3.2 Second Example In the second example shown in Figure 11, the pitch P of each lens is greater than the minimum value of the spatial coherence length Xc of the portion of the laser beam B incident on that lens. Furthermore, the pitch P of each lens is less than the maximum value of the spatial coherence length Xc of the portion of the laser beam B incident on that lens. For example, the pitch P of lens 14c is greater than the minimum value Xc4min of the spatial coherence length Xc of the portion B4 incident on lens 14c, and less than the maximum value Xc4max. The pitch P of lens 15c is greater than the minimum value Xc5min of the spatial coherence length Xc of the portion B5 incident on lens 15c, and less than the maximum value Xc5max. The pitch P of lens 16c is greater than the minimum value Xc6min of the spatial coherence length Xc of the portion B6 incident on lens 16c, and less than the maximum value Xc6max.

[0036] 4.3.3 Third Example In the third example shown in Figure 12, the pitch P of each lens is the average value of the spatial coherence length Xc of the portion of the laser beam B that is incident on that lens. For example, the pitch P of lens 14c is the average value Xc4avg of the spatial coherence length Xc of the portion B4 incident on lens 14c. The pitch P of lens 15c is the average value Xc5avg of the spatial coherence length Xc of the portion B5 incident on lens 15c. The pitch P of lens 16c is the average value Xc6avg of the spatial coherence length Xc of the portion B6 incident on lens 16c.

[0037] The pitch P of each lens may be greater than the average value of the spatial coherence length Xc of the portion of the laser beam B that enters that lens.

[0038] 4.4 Focal length of lens 11c~17c Referring again to Figure 8, the aperture size of lenses 11c to 17c decreases as the pitch P decreases. For example, the aperture size of lens 15c is smaller than that of lens 14c. The parameters and arrangement of lenses 11c to 17c are set as follows so that the size difference at the illumination surface 5 of portions B1 to B7 that have passed through lenses 11c to 17c is small, and preferably the sizes at the illumination surface 5 of portions B1 to B7 are equal to each other.

[0039] Lenses 11c to 17c have longer focal lengths as their aperture size decreases. In other words, among the portions B1 to B7 that pass through lenses 11c to 17c, the portion that passes through a lens with a smaller aperture size has a longer distance between the principal surface of lens 11c to 17c and the focusing position R1 to R7. For example, the second distance between the principal surface of lens 15c and the focusing position R5 of portion B5 that passes through lens 15c is longer than the first distance between the principal surface of lens 14c and the focusing position R4 of portion B4 that passes through lens 14c.

[0040] It is desirable that the difference between the third distance between the main surface of lens 14c and the main surface of condenser lens 30c, and the fourth distance between the main surface of lens 15c and the main surface of condenser lens 30c, is smaller than the difference between the first distance between the main surface of lens 14c and the focusing position R4, and the second distance between the main surface of lens 15c and the focusing position R5. In Figure 8, the main surfaces of lenses 11c to 17c and the main surface of condenser lens 30c are equidistant.

[0041] Furthermore, among the sections B1 to B7, the distance between the focusing position R1 to R7 and the main surface of the condenser lens 30c is shorter for the section that passes through a lens with a smaller aperture size. For example, the sixth distance between the focusing position R5 and the main surface of the condenser lens 30c in section B5, which passes through lens 15c, is shorter than the fifth distance between the focusing position R4 and the main surface of the condenser lens 30c in section B4, which passes through lens 14c.

[0042] Lens 14c corresponds to the first lens in this disclosure, lens 15c corresponds to the second lens in this disclosure, and lens 16c corresponds to the third lens in this disclosure. Part B4 corresponds to the first part in this disclosure, part B5 corresponds to the second part in this disclosure, and part B6 corresponds to the third part in this disclosure. Focusing position R4 corresponds to the first focusing position in this disclosure, and focusing position R5 corresponds to the second focusing position in this disclosure.

[0043] 4.5 Lens array 10d including light-shielding section M Figure 13 shows the configuration of homogenizer 1d in a modified example of the first embodiment. Homogenizer 1d may be used instead of homogenizer 1a shown in Figure 1. Homogenizer 1d differs from homogenizer 1c in that light-shielding sections M are placed between adjacent lenses among the lenses 11d to 17d that constitute the lens array 10d. In this case, the aperture sizes of lenses 11d to 17d become smaller than their respective pitches P. For example, if the planar shape of each of lenses 11d to 17d is circular, it is not possible to fill the entire plane of the lens array 10d with lenses, so light-shielding sections M may be placed between the lenses.

[0044] Figure 13 shows an example where, similar to the homogenizer 1c, the aperture size of lenses 11d to 17d is reduced as the pitch P decreases, but the disclosure is not limited to this. The aperture sizes of lenses 11d to 17d may be made equal to each other by making the light-shielding portion M near the center of the lens array 10d larger than the light-shielding portion M near the periphery of the lens array 10d.

[0045] Figure 14 shows an example of the pitch P of lenses 11d to 17d in a modified example of the first embodiment. Except for the reference numerals of lenses 11d to 17d, Figure 14 is the same as Figure 10. Alternatively, the pitch P of lenses 11d to 17d may be determined in the same way as in Figure 11 or Figure 12 in a modified example of the first embodiment.

[0046] In other respects, homogenizer 1d is the same as homogenizer 1c.

[0047] 4.6 Effect (1) According to the first embodiment, the laser system 100a comprises a laser oscillator MO, a lens array 10c, and a condenser lens 30c. The lens array 10c includes a lens 14c into which a portion B4 of the laser beam B output from the laser oscillator MO is incident, and a lens 15c into which a portion B5 different from portion B4 of the laser beam B, having a spatial coherence length Xc smaller than that of portion B4, is incident, and which has a pitch P smaller than that of lens 14c. The condenser lens 30c superimposes portions B4 and B5 that have passed through the lens array 10c onto a common irradiation surface 5.

[0048] According to this, the pitch P of lens 15c, which is incident on portion B5 with a smaller spatial coherence length Xc, is smaller than that of lens 14c, which is incident on portion B4 with a larger spatial coherence length Xc. Therefore, when the pitch P of lenses 14c and 15c is set to the optimal value for portion B4, the effect of uniformizing the light intensity distribution for portion B5 is insufficient, and when the pitch P of lenses 14c and 15c is set to the optimal value for portion B5, interference fringes caused by portion B4 are generated. This makes it possible to improve the uniformity of the light intensity distribution of the laser beam B while suppressing the generation of interference fringes.

[0049] Figure 15 shows the two-dimensional light intensity distribution of the irradiation surface 5 in the comparative example, and Figure 16 shows the light intensity distribution obtained by integrating the light intensity distribution shown in Figure 15 in the X direction for each Y coordinate. Figure 17 shows the two-dimensional light intensity distribution of the irradiation surface 5 in the first embodiment, and Figure 18 shows the light intensity distribution obtained by integrating the light intensity distribution shown in Figure 17 in the X direction for each Y coordinate. In Figures 15 and 16, the pitch P is set too small, resulting in large variations in light intensity due to interference, whereas in Figures 17 and 18, interference is suppressed and the light intensity distribution is made uniform. Note that Figures 17 and 18 do not represent the limits of the light intensity distribution uniformity performance according to this disclosure.

[0050] (2) According to the first embodiment, the lens array 10c includes a lens 16c into which a portion B6 different from both portions B4 and B5 of the laser beam B is incident, and which has a spatial coherence length Xc smaller than that of portion B5, and which has a pitch P smaller than that of lens 15c. The condenser lens 30c superimposes portions B4 to B6 that have passed through the lens array 10c onto a common irradiation surface 5.

[0051] According to this, by setting the pitch P of not only lenses 14c and 15c but also lens 16c to correspond to the spatial coherence length Xc, it is possible to obtain the effect of improving the uniformity of the light intensity distribution and the effect of suppressing the generation of interference fringes over a wide area of ​​the beam cross-section.

[0052] (3) According to the first embodiment, the distance between portion B4 and the center C of the beam cross-section of laser beam B is shorter than the distance between portion B5 and the center C.

[0053] According to this, when the spatial coherence length Xc is greater in the central part of the beam cross-section than in the peripheral part, it is possible to obtain the effect of improving the uniformity of the light intensity distribution and the effect of suppressing the generation of interference fringes.

[0054] (4) According to the first embodiment, the pitch P of lens 14c is greater than or equal to the maximum value Xc4max of the spatial coherence length Xc of portion B4, and the pitch P of lens 15c is greater than or equal to the maximum value Xc5max of the spatial coherence length Xc of portion B5.

[0055] According to this, the pitch P being smaller than the spatial coherence length Xc of portions B4 and B5 incident on lenses 14c and 15c is suppressed, and the generation of interference fringes can be suppressed more reliably.

[0056] (5) According to the first embodiment, the pitch P of lens 14c is greater than the minimum value Xc4min of the spatial coherence length Xc of portion B4, and the pitch P of lens 15c is greater than the minimum value Xc5min of the spatial coherence length Xc of portion B5.

[0057] According to this, the pitch P is prevented from becoming significantly smaller than the spatial coherence length Xc of portions B4 and B5 incident on lenses 14c and 15c, thereby suppressing the generation of interference fringes.

[0058] (6) According to the first embodiment, the pitch P of lens 14c is smaller than the maximum value Xc4max of the spatial coherence length Xc of portion B4, and the pitch P of lens 15c is smaller than the maximum value Xc5max of the spatial coherence length Xc of portion B5.

[0059] According to this, the pitch P becoming significantly larger than the spatial coherence length Xc of portions B4 and B5 incident on lenses 14c and 15c can be suppressed, thereby improving the uniformity of the light intensity distribution.

[0060] (7) According to the first embodiment, the pitch P of lens 14c is greater than or equal to the average value Xc of the spatial coherence length Xc of portion B4, Xc4avg, and the pitch P of lens 15c is greater than or equal to the average value Xc of the spatial coherence length Xc of portion B5, Xc5avg.

[0061] According to this, the pitch P being smaller than the spatial coherence length Xc of portions B4 and B5 incident on lenses 14c and 15c can be suppressed, thereby suppressing the generation of interference fringes.

[0062] (8) According to the first embodiment, the aperture size of lens 15c is smaller than the aperture size of lens 14c.

[0063] According to this, by making the aperture size of lens 14c with a large pitch P larger than the aperture size of lens 15c with a small pitch P, it is possible to suppress the attenuation of the laser beam B's energy in the lens array 10c.

[0064] (9) According to the first embodiment, the second distance between the main surface of lens 15c and the focusing position R5 of portion B5 that has passed through lens 15c is longer than the first distance between the main surface of lens 14c and the focusing position R4 of portion B4 that has passed through lens 14c.

[0065] According to this, by increasing the second distance from the main surface of the lens 15c with a small aperture to the focusing position R5, the portion B5 that has passed through the lens 15c is focused closer to the condenser lens 30c, and the divergence angle of the portion B5 emitted from the condenser lens 30c can be increased. Therefore, even the portion B5 that has passed through the lens 15c with a small aperture can have its size on the illumination surface 5 increased, bringing it closer to the size of the portion B4 that has passed through the lens 14c with a large aperture, and the variation in the size of portions B4 and B5 on the illumination surface 5 can be reduced.

[0066] (10) According to the first embodiment, the difference between the third distance between the main surface of lens 14c and the main surface of condenser lens 30c, and the fourth distance between the main surface of lens 15c and the main surface of condenser lens 30c are smaller than the difference between the first and second distances.

[0067] According to this, by reducing the difference between the third and fourth distances, the main surfaces of lenses 14c and 15c can be positioned closer to each other. Therefore, the manufacturing of the lens array 10c can be facilitated.

[0068] (11) According to the first embodiment, the sixth distance between the focusing position R5 and the main surface of the condenser lens 30c is shorter than the fifth distance between the focusing position R4 and the main surface of the condenser lens 30c.

[0069] According to this, even for portion B5 that has passed through lens 15c with a small aperture size, the size at the illumination surface 5 can be increased, thereby reducing the size variation at the illumination surface 5 for portions B4 and B5.

[0070] In other respects, the first embodiment is the same as the comparative example.

[0071] 5. Lens array 10e with the main surfaces of lenses 11e to 17e offset from each other. 5.1 Main surface of lens 11e~17e Figure 19 shows the configuration of homogenizer 1e in the second embodiment. Homogenizer 1e may be used instead of homogenizer 1a shown in Figure 1. Homogenizer 1e differs from homogenizer 1c in that the principal surfaces of lenses 11e to 17e constituting the lens array 10e are at different positions. It is similar to homogenizer 1c in that the pitch P of lenses 11e to 17e is reduced as the spatial coherence length Xc decreases.

[0072] Lenses 11e to 17e have smaller aperture sizes as the pitch P decreases. Preferably, the parameters and arrangement of lenses 11e to 17e are set as follows so that the size difference and the difference in divergence angle of the portions B1 to B7 incident on the illumination surface 5 are equal and their divergence angles are equal.

[0073] Lenses 11e to 17e have shorter focal lengths as their aperture size decreases. In other words, among the portions B1 to B7 that pass through lenses 11e to 17e, the portion that passes through a lens with a smaller aperture size has a shorter distance between the principal surface of lens 11e to 17e and the focusing position R1 to R7. For example, the second distance between the principal surface of lens 15e and the focusing position R5 of portion B5 that passes through lens 15e is shorter than the first distance between the principal surface of lens 14e and the focusing position R4 of portion B4 that passes through lens 14e.

[0074] Furthermore, the smaller the aperture size of lenses 11e to 17e, the shorter the distance between the main surfaces of lenses 11e to 17e and the main surface of condenser lens 30e. For example, the fourth distance between the main surface of lens 15e and the main surface of condenser lens 30e is shorter than the third distance between the main surface of lens 14e and the main surface of condenser lens 30e.

[0075] It is desirable that the difference between the fifth distance between the condenser lens 30e and the main surface of the condenser lens 30e, and the sixth distance between the condenser lens 30e and the main surface of the condenser lens 30e, is smaller than the difference between the first distance between the main surface of lens 14e and the focusing position R4, and the second distance between the main surface of lens 15e and the focusing position R5. In Figure 19, the focusing positions R1 to R7 and the main surface of the condenser lens 30e are equidistant.

[0076] The condensing positions R1 to R7, which correspond to the rear focal points of lenses 11e to 17e, should preferably be located on the front focal plane F of the condenser lens 30e.

[0077] It is desirable that the difference in numerical aperture between lenses 11e to 17e be small. In Figure 19, the numerical apertures of lenses 11e to 17e are equal.

[0078] Lens 14e corresponds to the first lens in this disclosure, and lens 15e corresponds to the second lens in this disclosure.

[0079] 5.2 Lens array 10f including light-shielding section M Figure 20 shows the configuration of homogenizer 1f in a modified example of the second embodiment. Homogenizer 1f may be used instead of homogenizer 1a shown in Figure 1. Homogenizer 1f differs from homogenizer 1e in that light-shielding sections M are arranged between adjacent lenses among the lenses 11f to 17f that constitute the lens array 10f.

[0080] In Figure 20, an example is shown in which, similar to homogenizer 1e, the aperture size of lenses 11f to 17f is reduced as the spatial coherence length Xc decreases. However, the disclosure is not limited to this, and the aperture sizes of lenses 11f to 17f may be made equal to each other.

[0081] In other respects, homogenizer 1f is the same as homogenizer 1e.

[0082] 5.3 Effect (12) According to the second embodiment, the aperture size of lens 15e is smaller than the aperture size of lens 14e, and the fourth distance between the main surface of lens 15e and the main surface of condenser lens 30e is shorter than the third distance between the main surface of lens 14e and the main surface of condenser lens 30e.

[0083] According to this, by making the fourth distance between the main surface of lens 15e, which has a smaller aperture size, and the main surface of condenser lens 30e shorter than the third distance between the main surface of lens 14e and the main surface of condenser lens 30e, the difference in size and the difference in divergence angle of portions B4 and B5 incident on the irradiation surface 5 can be reduced. Therefore, even if the irradiation surface 5 is shifted parallel to the direction of propagation of the laser beam B, the decrease in the uniformity of the laser beam B is suppressed.

[0084] (13) According to the second embodiment, the second distance between the main surface of lens 15e and the focusing position R5 of portion B5 that has passed through lens 15e is shorter than the first distance between the main surface of lens 14e and the focusing position R4 of portion B4 that has passed through lens 14e. Furthermore, the difference between the fifth distance between the focusing position R4 and the main surface of condenser lens 30e and the sixth distance between the focusing position R5 and the main surface of condenser lens 30e is smaller than the difference between the first and second distances.

[0085] According to this, by reducing the difference in distance between the focusing positions R4 and R5 and the main surface of the condenser lens 30e, the difference in the divergence angle of portions B4 and B5 that have passed through the condenser lens 30e can be reduced. Furthermore, by making the second distance between the main surface of lens 15e, which has a smaller aperture size, and the focusing position R5 shorter than the first distance between the main surface of lens 14e and the focusing position R4, the difference in beam diameter of portions B4 and B5 that have passed through the condenser lens 30e can be reduced. Therefore, even if the irradiation surface 5 is shifted parallel to the direction of propagation of the laser beam B, the decrease in the uniformity of the laser beam B is suppressed.

[0086] (14) According to the second embodiment, the lenses 14e and 15e and the condenser lens 30e are arranged such that the condensing positions R4 and R5, which correspond to the rear focal points of the lenses 14e and 15e respectively, are located on the front focal plane F of the condenser lens 30e.

[0087] According to this, by positioning the rear focal points of lenses 14e and 15e on the front focal plane F of the condenser lens 30e, the portions B4 and B5 that have passed through the condenser lens 30e can be treated as nearly parallel light, and a high-quality laser beam B can be output to the irradiation surface 5.

[0088] (15) According to the second embodiment, the numerical apertures of lenses 14e and 15e are equal to each other.

[0089] According to this, by making the numerical aperture equal, the widths of the optical paths of portions B4 and B5 that have passed through the condenser lens 30e can be made equal, and a high-quality laser beam B can be output to the irradiation surface 5.

[0090] In other respects, the second embodiment is the same as the first embodiment.

[0091] 6. Lens arrays containing 10g and 20g of the first and second lenticular lenses. 6.1 Configuration Figure 21 shows the configuration of homogenizer 1g in a third embodiment. Homogenizer 1g may be used instead of homogenizer 1a shown in Figure 1. Homogenizer 1g differs from homogenizers 1c to 1f in that it includes first and second lenticular lenses 10g and 20g and condenser lenses 30g and 40g. The first and second lenticular lenses 10g and 20g constitute the lens array of this disclosure. A laser beam B that has passed through the first lenticular lens 10g is incident on the second lenticular lens 20g. The condenser lenses 30g and 40g superimpose the respective portions of the laser beam B that have passed through the first and second lenticular lenses 10g and 20g onto a common irradiation surface.

[0092] Each of the lenses 11g to 17g that make up the first lenticular lens 10g has a focal axis parallel to the other, and its focal axis is, for example, parallel to the X direction. Each of the lenses 21g to 27g that make up the second lenticular lens 20g has a focal axis parallel to the other, and its focal axis is not parallel to the focal axes of lenses 11g to 17g, but is, for example, parallel to the Y direction.

[0093] The 30g condenser lens includes a cylindrical lens with a focal axis parallel to the focal axis of lenses 11g to 17g. The 40g condenser lens includes a cylindrical lens with a focal axis parallel to the focal axis of lenses 21g to 27g.

[0094] Similar to homogenizers 1c to 1f, a smaller spatial coherence length Xc reduces the pitch P of lenses 11g to 17g and lenses 21g to 27g. For example, the spatial coherence length Xc of the portion of laser beam B incident on lens 15g is smaller than that of the portion incident on lens 14g, and the pitch P of lens 15g is smaller than that of lens 14g. The spatial coherence length Xc of the portion of laser beam B incident on lens 25g is smaller than that of the portion incident on lens 24g, and the pitch P of lens 25g is smaller than that of lens 24g.

[0095] Lens 14g corresponds to the first lens in this disclosure, and lens 15g corresponds to the second lens in this disclosure. The focal axis of lens 14g corresponds to the first focal axis in this disclosure, and the focal axis of lens 15g corresponds to the second focal axis in this disclosure. The focal axis of condenser lens 30g corresponds to the third focal axis in this disclosure.

[0096] Lens 24g corresponds to the fourth lens in this disclosure, and lens 25g corresponds to the fifth lens in this disclosure. The portion of the laser beam B that enters lens 24g corresponds to the fourth portion in this disclosure, and the portion that enters lens 25g corresponds to the fifth portion in this disclosure. The focal axis of lens 24g corresponds to the fourth focal axis in this disclosure, and the focal axis of lens 25g corresponds to the fifth focal axis in this disclosure.

[0097] 6.2 Effect (16) According to the third embodiment, lenses 14g and 15g constitute a first lenticular lens 10g included in the lens array, and each has a focal axis parallel to the other.

[0098] According to this, by using the first lenticular lens 10g, the gap between lenses 14g and 15g can be reduced.

[0099] (17) According to the third embodiment, the condenser lens 30g includes a cylindrical lens having a focal axis parallel to the focal axes of lenses 14g and 15g.

[0100] According to this, by using a condenser lens 30g having a focal axis corresponding to the focal axes of lenses 14g and 15g, the portions of the laser beam B that have passed through lenses 14g and 15g, respectively, can be superimposed on a common irradiation surface 5.

[0101] (18) According to the third embodiment, the lens array includes a second lenticular lens 20g into which the laser beam B that has passed through the first lenticular lens 10g is incident. The second lenticular lens 20g includes a lens 24g into which a portion of the laser beam B is incident, and a lens 25g into which a portion of the laser beam B different from the portion incident on lens 24g and having a smaller spatial coherence length Xc than the portion incident on lens 24g is incident, and which has a smaller pitch P than lens 24g. Lenses 24g and 25g each have focal axes parallel to each other and non-parallel to the focal axes of lenses 14g and 15g, and condenser lenses 30g and 40g superimpose the portions of the laser beam B that have been incident on lenses 24g and 25g and passed through the lens array onto a common irradiation surface 5.

[0102] According to this, by using a second lenticular lens 20g that is not parallel to the focal axis of the first lenticular lens 10g, it is possible to obtain the effect of improving the uniformity of the light intensity distribution in multiple directions and the effect of suppressing the generation of interference fringes.

[0103] In other respects, the third embodiment is the same as the first and second embodiments.

[0104] 7. Homogenizer 1c with irradiation surface 5 located inside laser amplifier PO 7.1 Configuration Figure 22 shows the configuration of the laser system 100h in the fourth embodiment. The laser system 100h includes a laser oscillator MO, a homogenizer 1c, a laser amplifier PO, and an optical element 9. Homogenizers 1d to 1g may be used instead of homogenizer 1c. The laser beam B that has passed through homogenizer 1c is incident on the laser amplifier PO, amplified, passes through the optical element 9, and is output from the laser system 100h.

[0105] Figure 23 shows the detailed configuration of the laser system 100h. The laser oscillator MO includes a laser chamber 70, a narrowband module 74, and an output coupling mirror 75.

[0106] The laser chamber 70 is positioned in the optical path of a laser resonator, which is composed of a narrowband module 74 and an output coupling mirror 75. The laser chamber 70 is provided with two windows 701 and 702. The laser chamber 70 houses discharge electrodes 711 and 712. The discharge electrodes 711 and 712 are connected to a pulse power supply (not shown). The laser chamber 70 houses the laser gas as the laser medium. The laser gas includes, for example, argon gas, fluorine gas, and neon gas. Alternatively, the laser gas includes, for example, krypton gas, fluorine gas, and neon gas.

[0107] The narrowband module 74 includes wavelength-selective elements such as a prism 741 and a grating 742. The output coupling mirror 75 is composed of a partial reflection mirror.

[0108] In the optical path of the laser beam B output from the output coupling mirror 75, the high-reflection mirror 761, homogenizer 1c, and high-reflection mirror 762 are arranged in this order.

[0109] The laser amplifier PO includes a laser chamber 80, a rear mirror 84, and an output coupling mirror 85. The laser chamber 80, the output coupling mirror 85, and the windows 801 and 802 associated with the laser chamber 80, and the discharge electrodes 811 and 812 are the same as the corresponding components in the laser oscillator MO.

[0110] The rear mirror 84 is positioned in the optical path of the laser beam B reflected by the high-reflection mirror 762. The rear mirror 84 is composed of a partial-reflection mirror. The rear mirror 84 and the output coupling mirror 85 constitute a laser resonator.

[0111] The optical element 9 includes, for example, a beam steering unit 96 and an optical pulse stretcher 99. The beam steering unit 96 includes high-reflection mirrors 961 and 962.

[0112] The optical pulse stretcher 99 is positioned in the optical path of the laser beam B after it has passed through the beam steering unit 96. The optical pulse stretcher 99 includes a beam splitter 995 and first to fourth concave mirrors 991 to 994.

[0113] 7.2 Operation 7.2.1 Operation of the laser oscillator MO In the laser oscillator MO, a pulse power supply (not shown) generates a pulsed high voltage, which is applied between the discharge electrodes 711 and 712. When a high voltage is applied between the discharge electrodes 711 and 712, a discharge occurs between them. The energy of this discharge excites the laser gas in the laser chamber 70, causing it to shift to a higher energy level. When the excited laser gas subsequently shifts to a lower energy level, it emits light with a wavelength corresponding to the energy level difference.

[0114] Light generated within the laser chamber 70 is emitted outside the laser chamber 70 through windows 701 and 702. Light emitted from window 701 has its beam width expanded by prism 741 and is incident on grating 742. Light incident on grating 742 from prism 741 is reflected by multiple grooves in grating 742 and diffracted in directions corresponding to the wavelength of light. Grating 742 is arranged in a Littrow configuration such that the angle of incidence of light incident on grating 742 from prism 741 matches the diffraction angle of diffracted light of the desired wavelength. As a result, light near the desired wavelength is returned to the laser chamber 70 via prism 741.

[0115] The output coupling mirror 75 transmits a portion of the light emitted from the window 702 and outputs it, while reflecting the other portion back to the laser chamber 70.

[0116] In this way, the light emitted from the laser chamber 70 travels back and forth between the narrowband module 74 and the output coupling mirror 75. This light is amplified each time it passes through the discharge space between the discharge electrodes 711 and 712. Furthermore, this light is narrowed each time it is folded back by the narrowband module 74. The resulting laser-oscillating and narrowbanded light is then output from the output coupling mirror 75 as laser beam B.

[0117] 7.2.2 Operation of the laser amplifier PO The laser beam B emitted from the output coupling mirror 75 is incident on the homogenizer 1c via the high-reflection mirror 761. The irradiation surface 5 onto which the laser beam B emitted from the homogenizer 1c is incident is a virtual surface located inside the laser amplifier PO. It is desirable that the irradiation surface 5 be located between the discharge electrodes 811 and 812. The laser beam B emitted from the homogenizer 1c is incident on the laser chamber 80 via the high-reflection mirror 762 and the rear mirror 84.

[0118] As the laser beam B enters the laser chamber 80, a pulse power supply (not shown) in the laser amplifier PO generates a pulsed high voltage, which is then applied between the discharge electrodes 811 and 812.

[0119] When a high voltage is applied between the discharge electrodes 811 and 812, a discharge occurs between them. The energy of this discharge amplifies the laser beam B that is incident on the laser chamber 80.

[0120] The light amplified within the laser chamber 80 travels back and forth between the rear mirror 84 and the output coupling mirror 85. This light is amplified each time it passes through the discharge space between the discharge electrodes 811 and 812. The thus amplified laser beam B is output from the output coupling mirror 85.

[0121] 7.2.3 Operation of the Optical Pulse Stretcher 99 The laser beam B output from the output coupling mirror 85 is incident on the beam splitter 995 of the optical pulse stretcher 99 in the rightward direction in Figure 23 via the beam steering unit 96. The beam splitter 995 transmits a portion of the laser beam B incident on the rightward direction in Figure 23 as beam Ba and reflects the other portion downward in Figure 23. The reflected laser beam B is sequentially reflected by the first to fourth concave mirrors 991 to 994 and incident on the beam splitter 995 in the downward direction in Figure 23.

[0122] The beam cross-section of the laser beam B incident from the beam steering unit 96 is imaged at a 1:1 size on the beam splitter 995 by the first to fourth concave mirrors 991 to 994. The beam splitter 995 reflects a portion of the laser beam B incident downwards in Figure 23 from the fourth concave mirror 994 to the right in Figure 23 and emits it as beam Bb.

[0123] A time difference exists between beams Ba and Bb, corresponding to the optical path length of the delayed optical path formed by the first to fourth concave mirrors 991 to 994. By spatially overlapping beams Ba and Bb, a laser beam B with an extended pulse width can be emitted.

[0124] 7.3 Effect (19) According to the fourth embodiment, the laser system 100h includes a laser amplifier PO into which the laser beam B that has passed through the condenser lens 30c is incident, and the irradiation surface 5 is a virtual surface located inside the laser amplifier PO.

[0125] According to this, by injecting a laser beam B with improved uniformity of light intensity distribution and suppressed interference fringe generation into the laser amplifier PO, the uniformity of the light intensity distribution of the laser beam B amplified by the laser amplifier PO can be improved. Furthermore, the localized high energy of the laser beam B injected into the subsequent optical element 9 can be suppressed, thereby improving the lifespan of the optical element 9.

[0126] 8. Other 8.1 Method for manufacturing electronic devices Figure 24 shows the configuration of the exposure system. The exposure system includes a laser system 100h and an exposure apparatus 200. Instead of laser system 100h, laser system 100a may be used in which homogenizer 1a is replaced with one of homogenizers 1c to 1g. Laser system 100h is configured to output a laser beam B toward the exposure apparatus 200.

[0127] The exposure apparatus 200 includes an illumination optical system 201 and a projection optical system 202. The illumination optical system 201 illuminates the reticle pattern of a reticle (not shown) placed on a reticle stage RT with a laser beam B incident from a laser system 100h. The projection optical system 202 reduces and projects the laser beam B that has passed through the reticle onto a workpiece (not shown) placed on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0128] The exposure apparatus 200 exposes the workpiece with a laser beam B that reflects the reticle pattern by synchronously moving the reticle stage RT and the workpiece table WT in parallel. After transferring the reticle pattern to the semiconductor wafer through the exposure process described above, an electronic device can be manufactured by going through several processes.

[0129] 8.2 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.

[0130] 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." In addition, it should be interpreted as including combinations of these with anything other than "A," "B," and "C."

Claims

1. A laser oscillator, A lens array, A first lens into which a first portion of the laser beam output from the laser oscillator is incident, A second portion of the laser beam, which is different from the first portion and has a smaller spatial coherence length than the first portion, is incident on a second lens having a smaller pitch than the first lens. The lens array includes, A condenser lens that superimposes the first and second portions that have passed through the lens array onto a common illumination surface, A laser system equipped with [the following features].

2. A laser system according to claim 1, The lens array further includes a third lens into which a third portion of the laser beam, distinct from both the first and second portions and having a smaller spatial coherence length than the second portion, is incident, and which has a smaller pitch than the second lens. The condenser lens superimposes the first to third portions that have passed through the lens array onto the common illumination surface. Laser system.

3. A laser system according to claim 1, The distance between the first portion and the center of the beam cross-section of the laser beam is shorter than the distance between the second portion and the center. Laser system.

4. A laser system according to claim 1, The pitch of the first lens is greater than or equal to the maximum value of the spatial coherence length of the first portion. The pitch of the second lens is greater than or equal to the maximum value of the spatial coherence length of the second portion. Laser system.

5. A laser system according to claim 1, The pitch of the first lens is greater than the minimum value of the spatial coherence length of the first portion. The pitch of the second lens is greater than the minimum value of the spatial coherence length of the second portion. Laser system.

6. A laser system according to claim 5, The pitch of the first lens is smaller than the maximum value of the spatial coherence length of the first portion. The pitch of the second lens is smaller than the maximum value of the spatial coherence length of the second portion. Laser system.

7. A laser system according to claim 1, The pitch of the first lens is greater than or equal to the average value of the spatial coherence length of the first portion. The pitch of the second lens is greater than or equal to the average value of the spatial coherence length of the second portion. Laser system.

8. A laser system according to claim 1, The aperture size of the second lens is smaller than the aperture size of the first lens. Laser system.

9. A laser system according to claim 8, The second distance between the main surface of the second lens and the second focusing position of the second portion that has passed through the second lens is longer than the first distance between the main surface of the first lens and the first focusing position of the first portion that has passed through the first lens. Laser system.

10. A laser system according to claim 9, The difference between the main surface of the first lens and the main surface of the condenser lens, and the difference between the main surface of the second lens and the main surface of the condenser lens, is smaller than the difference between the first and second distances. Laser system.

11. A laser system according to claim 9, The sixth distance between the second focusing position and the main surface of the condenser lens is shorter than the fifth distance between the first focusing position and the main surface of the condenser lens. Laser system.

12. A laser system according to claim 1, The aperture size of the second lens is smaller than the aperture size of the first lens. The fourth distance between the main surface of the second lens and the main surface of the condenser lens is shorter than the third distance between the main surface of the first lens and the main surface of the condenser lens. Laser system.

13. A laser system according to claim 1, The second distance between the main surface of the second lens and the second focusing position of the second portion that has passed through the second lens is shorter than the first distance between the main surface of the first lens and the first focusing position of the first portion that has passed through the first lens. The difference between the fifth distance between the first focusing position and the main surface of the condenser lens and the sixth distance between the second focusing position and the main surface of the condenser lens is smaller than the difference between the first and second distances. Laser system.

14. A laser system according to claim 1, The first and second lenses and the condenser lens are arranged such that the rear focal points of each of the first and second lenses are located on the front focal plane of the condenser lens. Laser system.

15. A laser system according to claim 14, The numerical apertures of the first and second lenses are equal to each other. Laser system.

16. A laser system according to claim 1, The first and second lenses constitute a first lenticular lens included in the lens array, and each has a first and second focal axis parallel to each other. Laser system.

17. A laser system according to claim 16, The condenser lens includes a cylindrical lens having a third focal axis parallel to the first and second focal axes. Laser system.

18. A laser system according to claim 16, The lens array further includes a second lenticular lens into which the laser beam that has passed through the first lenticular lens is incident, and the second lenticular lens is A fourth lens into which the fourth portion of the laser beam is incident, A fifth portion of the laser beam, which is different from the fourth portion and has a smaller spatial coherence length than the fourth portion, is incident on a fifth lens having a smaller pitch than the fourth lens. Includes, The fourth and fifth lenses each have fourth and fifth focal axes that are parallel to each other and non-parallel to the first and second focal axes. The condenser lens superimposes the fourth and fifth portions that have passed through the lens array onto the common illumination surface. Laser system.

19. A laser system according to claim 1, The laser beam that has passed through the condenser lens is incident on a laser amplifier. Furthermore, The irradiation surface is a virtual surface located inside the laser amplifier. Laser system.

20. A method for manufacturing electronic devices, A laser oscillator, A lens array, A first lens into which a first portion of the laser beam output from the laser oscillator is incident, A second portion of the laser beam, which is different from the first portion and has a smaller spatial coherence length than the first portion, is incident on a second lens having a smaller pitch than the first lens. The lens array includes, A condenser lens that superimposes the first and second portions that have passed through the lens array onto a common illumination surface, The laser beam is generated by a laser system comprising the following: The laser beam is output to the exposure apparatus, To manufacture the aforementioned electronic device, the laser beam is exposed onto a photosensitive substrate within the exposure apparatus. A method for manufacturing electronic devices, including the following.

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