Method for manufacturing laser devices and electronic devices

Abstract

The present invention provides a laser device that reduces beam coherence and suppresses energy loss. [Solution] The laser device 10A comprises an oscillator 12 that emits pulsed laser light, a random phase plate 14 arranged in the optical path of the pulsed laser light, and an optical pulse stretcher 100 arranged in the optical path of the pulsed laser light that has passed through the random phase plate, which extends the pulse time width of the pulsed laser light by transmitting a portion of the pulsed laser light and causing another portion to circulate at least once in a delay optical path, thereby outputting transmitted light and circulating light.

Description

[Technical Field]

[0001] This disclosure relates to a laser apparatus and a method for manufacturing an electronic device. [Background technology]

[0002] In recent years, semiconductor lithography equipment has been required to improve resolution as semiconductor integrated circuits become smaller and more integrated. Therefore, efforts are being made to shorten the wavelength of light emitted from lithography light sources. For example, gas laser equipment used for lithography includes KrF excimer laser equipment that outputs laser light with a wavelength of approximately 248 nm, and ArF excimer laser equipment that outputs laser light with a wavelength of approximately 193 nm.

[0003] The spectral linewidth of the spontaneously emitted light from KrF and ArF excimer laser systems is broad, ranging from 350 to 400 pm. Therefore, when a projection lens is constructed using a material that transmits ultraviolet light, such as KrF and ArF laser light, chromatic aberration may occur. As a result, resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from a gas laser system until chromatic aberration is negligible. For this reason, gas laser systems may be equipped with a Line Narrowing Module (LNM) containing narrowing elements (such as etalons or gratings) within the laser resonator to narrow the spectral linewidth. In the following, a gas laser system with a narrowed spectral linewidth will be referred to as a narrow-band gas laser system. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Summary of International Publication No. 2018 / 138819

[0005] A laser device according to one aspect of this disclosure includes an oscillator that emits pulsed laser light, a random phase plate arranged in the optical path of the pulsed laser light, and an optical pulse stretcher arranged in the optical path of the pulsed laser light that has passed through the random phase plate, which extends the pulse time width of the pulsed laser light by transmitting a portion of the pulsed laser light and causing another portion to circulate at least once in a delay optical path, thereby outputting transmitted light and circulating light.

[0006] A method for manufacturing an electronic device according to another disclosure includes generating laser light with a laser apparatus comprising: an oscillator that emits pulsed laser light; a random phase plate arranged in the optical path of the pulsed laser light; and an optical pulse stretcher arranged in the optical path of the pulsed laser light that has passed through the random phase plate, which transmits a portion of the pulsed laser light and causes another portion to circulate at least once in a delay optical path to output transmitted light and circulating light, thereby extending the pulse time width of the pulsed laser light; outputting the laser light to an exposure apparatus; and exposing a photosensitive substrate with the laser light 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 an example of a speckle image, which captures a pattern consisting of light and dark spots. [Figure 2] Figure 2 shows a histogram of the brightness and darkness of the speckle image shown in Figure 1. [Figure 3] Figure 3 schematically shows an example of the configuration of a laser device related to a comparative example. [Figure 4] Figure 4 is an explanatory diagram of a method for shifting the beam angle by changing the number of beam orbits within the OPS. [Figure 5] Figure 5 is an explanatory diagram of a method for shifting the beam position by changing the number of beam orbits within the OPS. [Figure 6] Figure 6 schematically shows an example of the configuration of a laser device according to Embodiment 1. [Figure 7]FIG. 7 is an explanatory diagram schematically showing an operation of shifting an optical path of the circumferential light by a configuration combining a random phase plate and an OPS. [Figure 8] FIG. 8 is a diagram schematically showing an example of a pixel pattern of the random phase plate. [Figure 9] FIG. 9 is a diagram showing a change in an electric field of a beam passing through the random phase plate. [Figure 10] FIG. 10 is a diagram showing a change in an electric field of a beam passing through the OPS. [Figure 11] FIG. 11 is a diagram showing a change in an electric field by a combination of the random phase plate and the OPS in Embodiment 1. [Figure 12] FIG. 12 is a diagram showing a change in an electric field of a beam when the OPS is arranged in the front (upstream side) and the random phase plate is arranged in the subsequent stage. [Figure 13] FIG. 13 shows a cross section of a beam emitted from the OPS. [Figure 14] FIG. 14 is a diagram showing a method of measuring a shift amount when the beam is shifted by the OPS. [Figure 15] FIG. 15 schematically shows an example of a configuration of an exposure apparatus. Embodiment

[0008] -Contents- 1. Explanation of Terms 1.1 Speckle 1.2 Random Phase Plate 2. Comparative Example 2.1 Configuration 2.2 Operation 2.3 Problems 3. Embodiment 1 3.1 Configuration 3.2 Operation 3.3 Regarding Changes in Electric Field by Random Phase Plate and OPS 3.3.1 Change in Electric Field by Random Phase Plate 3.3.2 Change in Electric Field by Combination of Random Phase Plate and OPS 3.3.3 Comparative Example 3.3.4 Differences in the Electric Field Changes Due to the Difference in the Positional Relationship between the Random Phase Plate and the OPS 3.4 Configuration in Which a Random Phase Plate is Arranged in the Delay Optical Path of the OPS 3.5 Location of the Random Phase Plate When Multiple OPSs are Provided 3.6 Effects 4. Method for Measuring the Shift Amount L by the OPS 5. Method for Manufacturing an Electronic Device 6. About the Processor 7. Others

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Also, not all of the configurations and operations described in each embodiment are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and duplicate explanations are omitted.

[0010] 1. Explanation of Terms 1.1 Speckle "Speckle" is the bright and dark spots that occur when laser light is scattered by a random medium. FIG. 1 is a diagram showing an example of a speckle image obtained by imaging a pattern composed of bright and dark spots. Also, FIG. 2 is a diagram showing the brightness histogram of the speckle image shown in FIG. 1.

[0011] Generally, the speckle contrast SC is used as a speckle evaluation index. Let σ be the standard deviation of the intensity of the speckle image and I micron (with a micron marked above I) be the average of the intensity of the speckle image. Then, the speckle contrast SC can be expressed by the following formula (1).

[0012]

Equation

[0013] 1.2 Random Phase Plate A "random phase plate" is composed of two types of phase-shift cells: pixels with a transmission phase shift of 0 and pixels with a transmission phase shift of π. The area ratio of pixels with a shift of 0 to pixels with a shift of π is, for example, 1:1. The shape of the pixels in a random phase plate is a regular polygon such as a square or a regular hexagon, but the shape of the pixels is not limited to regular polygons. The length of a pixel indicates the length of one side when the shape of the pixel is an equilateral triangle or a regular square, and the distance between opposite sides when the shape of the pixel is a regular hexagon.

[0014] 2. Comparative Example 2.1 Configuration Figure 3 schematically shows an example configuration of the laser apparatus 10 according to the comparative example. The comparative example in this disclosure is a form that the applicant recognizes as being known only to the applicant, and is not a prior art example acknowledged by the applicant.

[0015] The laser device 10 is an excimer laser device that includes an oscillator (MO) 12, a monitor module 16, a shutter 18, and a laser control processor 20. An optical pulse stretcher (OPS) 100, a monitor module 16, and a shutter 18 are arranged in this order on the optical path of the pulsed laser light output from the MO 12.

[0016] MO12 includes a chamber 120, a charger 122, a pulse power module (PPM) 124, a narrowband converter 126, and an output coupling mirror 128.

[0017] The narrowband expansion device 126 includes a prism beam expander (not shown) and a grating (not shown). The prism beam expander and the grating are arranged in a Littrow configuration such that the angle of incidence and the angle of diffraction coincide.

[0018] The output coupling mirror 128 is, for example, a reflective mirror with a reflectivity of 40-60%. The output coupling mirror 128 and the narrowband converter 126 constitute an optical resonator. The chamber 120 is positioned on the optical path of the optical resonator.

[0019] The chamber 120 includes a pair of electrodes 130a and 130b, an insulating member 132, a front window 134, and a rear window 136.

[0020] Chamber 120 is filled with a laser gas of ArF, KrF, XeCl, or XeF.

[0021] Electrode 130b is connected to the high-voltage output terminal of the PPM 124 via an insulating member 132. Electrode 130a is connected to ground.

[0022] Electrodes 130a and 130b are arranged to have a predetermined gap between them. Electrodes 130a and 130b are discharge electrodes, and the space between electrodes 130a and 130b becomes the discharge space (discharge region).

[0023] The front window 134 and the rear window 136 are positioned so that the laser light generated in the discharge space can pass through them.

[0024] The PPM124 includes a switch 125 and a charging capacitor (not shown). The switch 125 is connected to a signal line that transmits an ON signal for the switch 125 from the laser control processor 20. The charger 122 is connected to the charging capacitor of the PPM124. The charger 122 receives charging voltage data from the laser control processor 20 and charges the charging capacitor of the PPM124 with a high voltage.

[0025] The OPS100 includes a beam splitter BS and four concave mirrors 101, 102, 103, and 104. The beam splitter BS is positioned in the optical path of the pulsed laser light output from MO12. The beam splitter BS is coated with a film that reflects a portion of the incident pulsed laser light and transmits the other portion. The reflectivity of the beam splitter BS is preferably 40% to 70%, and more preferably about 60%.

[0026] The concave mirrors 101-104 constitute the delayed optical path of the pulsed laser light reflected from the first surface of the beam splitter BS. Each of the concave mirrors 101-104 is a concave mirror with approximately the same focal length f1.

[0027] The concave mirrors 101 and 102 are positioned so that the pulsed laser light reflected from the first surface of the beam splitter BS is reflected by the concave mirror 101 and incident on the concave mirror 102. The concave mirrors 103 and 104 are positioned so that the pulsed laser light reflected from the concave mirror 102 is reflected by the concave mirror 103 and incident on the concave mirror 104. The concave mirror 104 is positioned so that the pulsed laser light reflected from the concave mirror 104 is incident on the second surface of the beam splitter BS, which is opposite to the first surface.

[0028] The concave mirrors 101 and 102 are positioned so that the pulsed laser light reflected from the first surface of the beam splitter BS is inverted and imaged as the first image on the first surface of the beam splitter BS. The concave mirrors 103 and 104 are positioned so that the first image is returned to the beam splitter BS and inverted and imaged as the second image on the second surface of the beam splitter BS. In this case, the optical path length L1 of the delayed optical path of the OPS100 is L1 = 8 × f1. The optical path length L1 refers to the one-circle delayed optical path length of the delayed optical path of the OPS100.

[0029] The beam splitter BS is positioned so that pulsed laser light transmitted through the first surface of the beam splitter BS without being reflected is incident on the monitor module 16.

[0030] The monitor module 16 is positioned on the optical path of the pulsed laser light output from the OPS 100. The monitor module 16 includes a beam splitter 162 and an optical sensor 164.

[0031] The optical sensor 164 is connected to the laser control processor 20, and the detection data from the optical sensor 164 is transmitted to the laser control processor 20. The shutter 18 is positioned on the optical path of the pulsed laser light that has passed through the monitor module 16, and is configured to switch between outputting the pulsed laser light to the outside of the laser device 10 and blocking the light. The shutter 18 is connected to the laser control processor 20 via a signal line that transmits signals for opening and closing the shutter.

[0032] The pulsed laser light output from the laser device 10 is input to the exposure device 80.

[0033] The laser control processor 20 is connected to the exposure control processor 82. The signal lines between the laser control processor 20 and the exposure control processor 82 include a signal line for the light emission trigger signal Tr, a signal line for the target pulse energy data Et, and signal lines for the exchange of other signals.

[0034] An amplifier including a laser chamber (not shown) may be placed between MO12 and OPS100.

[0035] MO12 may include a solid-state laser such as a YAG laser instead of an excimer laser. In that case, MO12 may also include a semiconductor optical amplifier (SOA) that extracts pulsed light from continuous light.

[0036] 2.2 Operation When the laser control processor 20 receives the target pulse energy Et and the oscillation preparation signal from the exposure control processor 82, it outputs a signal to close the shutter 18 and closes the output port of the laser device 10.

[0037] When the laser control processor 20 turns on the switch 125 of the PPM 124 in synchronization with the light emission trigger signal Tr at a predetermined repetition frequency, a high voltage is applied between the electrodes 130a and 130b.

[0038] When dielectric breakdown occurs between electrodes 130a and 130b, a discharge occurs between the two electrodes, exciting the excimer laser gas. As a result, the optical resonator, which consists of the narrowband converter 126 and the output coupling mirror 128, oscillates, and the narrowband pulsed laser light is output from the output coupling mirror 128.

[0039] The pulsed laser light output from the output coupling mirror 128 is extended to a predetermined pulse duration by passing through the delay optical path multiple times by the OPS 100.

[0040] A portion of the pulsed laser light that passes through the OPS100 is reflected by the beam splitter 162 and incident on the optical sensor 164. The optical sensor 164 measures the pulse energy E of the incident pulsed laser light. The data showing the measurement result is transmitted from the optical sensor 164 to the laser control processor 20.

[0041] The laser control processor 20 sets the charging voltage of the charger 122 so that the difference ΔE between the target pulse energy Et and the measured pulse energy E approaches 0.

[0042] When the difference ΔE falls within the acceptable range, the laser control processor 20 sends an oscillation readiness signal to the exposure control processor 82 and opens the shutter 18. The laser control processor 20 turns on the switch 125 of the PPM 124 in synchronization with the light emission trigger signal Tr from the exposure control processor 82. As a result, pulsed laser light is output from the MO 12, pulsed by the OPS 100, and pulsed laser light with an energy close to the target pulse energy Et is output from the laser device 10.

[0043] Pulsed laser light output from the laser device 10 is incident on the exposure device 80, and the pulsed laser light is irradiated onto a resist such as a semiconductor wafer (not shown).

[0044] 2.3 Challenges To reduce speckle contrast, it is necessary to reduce both the temporal and spatial overlap of the pulses. To reduce spatial overlap, a method is known in which the angle or position of the pulsed laser beam is shifted by the number of passes through the delay path of the OPS100. Hereafter, the pulsed laser beam may be simply referred to as the "beam".

[0045] Figure 4 is an explanatory diagram of a method for shifting the beam angle by the number of times the beam passes through the OPS100. Figure 5 is an explanatory diagram of a method for shifting the beam position by the number of times the beam passes through the OPS100. In Figures 4 and 5, the beam that has passed through the OPS100 0 times and is output from the OPS100 is shown by a solid line, the beam that has passed through 1 time and is output is shown by a dashed line, and the beam that has passed through 2 times and is output is shown by a dashed line. By adjusting the arrangement of the concave mirrors 101 to 104, the beam angle can be changed according to the number of times it passes, as shown in Figure 4.

[0046] Furthermore, by adjusting the arrangement of the concave mirrors 101-104, the beam position can be changed depending on the number of rotations, as shown in Figure 5. Note that in Figures 4, 5, and subsequent drawings, the illustration of light after the third rotation is omitted for illustrative purposes.

[0047] To reduce speckle contrast, it is necessary to increase the amount of angle and positional shift, but in that case, energy loss occurs due to vignetting of the beam.

[0048] For example, to reduce speckle contrast, if the beam angle is shifted (Figure 4), it is necessary to shift it by about half the divergence of the original beam, and if the beam position is shifted (Figure 5), it is necessary to shift it by about half the beam size.

[0049] There is a need for laser devices that reduce speckle contrast, that is, reduce beam coherence, and suppress energy loss.

[0050] 3. Embodiment 1 3.1 Configuration Figure 6 schematically shows an example of the configuration of the laser device 10A according to Embodiment 1. The differences between the laser device 10A shown in Figure 6 and the configuration shown in Figure 3 will be explained. The laser device 10A includes a random phase plate 14 between the OPS 100 and the MO 12. Hereafter, the random phase plate will also be referred to as "RPP".

[0051] The random phase plate 14 can be added anywhere between the OPS100 and the MO12. For example, if there are other optical elements between the OPS100 and the MO12, the random phase plate 14 may be placed upstream or downstream of those optical elements.

[0052] The concave mirrors 101, 102, 103, and 104 are positioned such that the optical path at emission is shifted depending on the number of rotations of the OPS 100. The positions of the concave mirrors 101, 102, 103, and 104 include cases where the optical path at emission is shifted due to the number of rotations, even if they are not intentionally positioned in that way. The concave mirrors 101, 102, 103, and 104 are examples of the “multiple mirrors” in this disclosure.

[0053] The other components are the same as those of the laser device 10 shown in Figure 3.

[0054] 3.2 Operation In the laser device 10A, a random phase plate 14 is placed upstream of the OPS 100, and the OPS 100 shifts the optical path of the circulating light according to the number of rotations.

[0055] Figure 7 is a schematic diagram illustrating the operation of shifting the optical path of the circulating light by combining the random phase plate 14 and the OPS100.

[0056] The pulsed laser light output from MO12 passes through the random phase plate 14. The beam after passing through the random phase plate 14 is incident on the OPS100. Inside the OPS100, the beam is split by the beam splitter BS. One beam passes through the beam splitter BS and exits the OPS100. The other beam, part of it circulates inside the OPS100 and is then reflected by the beam splitter BS and exits the OPS100, and the remaining part passes through the beam splitter BS and circulates inside the OPS100 once more. Hereinafter, the circulating light repeats the above operation.

[0057] The beam of the circulating light that has circulated through the delay optical path of the OPS100 at least once has a shifted optical path when exiting the OPS100 compared to the beam of the transmitted light that passes through the beam splitter BS without circulation. It is desirable that the shift of each optical path between the transmitted light and the circulating light is a parallel movement. The shift amount L of the optical path during parallel movement is preferably not less than the pixel size of the random phase plate 14.

[0058] FIG. 8 is a diagram schematically showing an example of the pixel pattern of the random phase plate 14. FIG. 8 shows an example of the random phase plate 14 in which square pixels are two-dimensionally arranged. The pixel size D of the random phase plate 14 may be defined as the length of one side of the square pixel. The pixel size D is preferably set to satisfy the following formula (2) in order to suppress an increase in beam divergence and further reduce beam spreading downstream of the random phase plate 14.

[0059] 0.5a ≦ D Formula (2) In formula (2), a is the size of the coherence region. In the case of a typical excimer laser device, a is not less than 0.1 mm and not more than 0.5 mm.

[0060] The pixel size D is not less than 0.5a, and in the case of an excimer laser device, the pixel size D is preferably not less than 0.05 mm. Note that it is more desirable that the pixel size D satisfies 0.5a < D.

[0061] As shown in Figure 7, it is desirable that the shift amount L during the parallel shift of the optical path of the circulating light output from OPS100 is greater than or equal to the pixel size D of the random phase plate 14, as this allows for more efficient reduction of speckle.

[0062] Furthermore, it is desirable that the shift amount L is less than twice the pixel size D, because this prevents the beam size from becoming too large and reduces losses due to vignetting of the beam downstream. In other words, it is desirable that the shift amount L satisfies the following equation (3).

[0063] D≦L≦2D Equation (3) The shift amount L is an example of "shift amount" in this disclosure. D ≤ L is an example of "shift amount is greater than or equal to the pixel size" in this disclosure. L ≤ 2D is an example of "shift amount is less than or equal to twice the pixel size" in this disclosure.

[0064] 3.3 Changes in the electric field due to random phase plates and OPS 3.3.1 Changes in the electric field due to random phase plates Figure 9 shows the change in the electric field of the beam as it passes through the random phase plate 14.

[0065] E(r,t) is a complex function representing the electric field. r=(x,y) represents the position on the beam, and t represents time. θ(r) is a function representing the phase distribution of the random phase plate 14, with values ​​of 0 or π distributed randomly.

[0066] When the beam passes through the random phase plate 14, the phase portion of the electric field changes, and the electric field of the beam is E as shown on the left side of Figure 9. in From there, E shown on the right out It changes like this.

[0067] 3.3.2 Changes in the electric field due to OPS Figure 10 shows the change in the electric field of the beam passing through OPS100. E0, E1, and E2 shown on the right side of Figure 10 represent the electric fields of 0-circulation, 1-circulation, and 2-circulation light, respectively.

[0068] As shown in Figure 10, an electric field E is applied to OPS100. in When incident, the electric field E after passing through OPS100 out As shown on the right side of Figure 10, this is the superposition of the electric fields of each orbiting light.

[0069] In Figure 10, it is assumed that each time the beam orbits OPS100, the beam's optical path shifts by Δr and time is delayed by Δt.

[0070] a0, a1, and a2 are coefficients corresponding to the change in beam intensity with each OPS rotation, and are determined by the reflectivity of the beam splitter BS within OPS100 and the propagation loss within OPS100. Since OPS100 is a relay optical system, it is assumed that the electric field function remains unchanged even when the beam rotates, except for the shift in position r and time t on the beam.

[0071] 3.3.2 Changes in the electric field due to the combination of random phase plates and OPS Figure 11 shows the change in the electric field due to the combination of the random phase plate 14 and the OPS100 in Embodiment 1.

[0072] In Figure 11, E in This represents the electric field incident on the random phase plate 14, and E a This represents the electric field after the beam has passed through the random phase plate 14.

[0073] If the beam passes through the OPS100 after passing through the random phase plate 14, the electric field E of the beam output from the OPS100 out The following applies:

[0074] E out =E0+E1+E2+··· = a0E(r,t)expiθ(r) +a1E(r+Δr,t+Δt)expiθ(r+Δr) +a2E(r+2Δr,t+2Δt)expiθ(r+2Δr) +··· In the above equation, the position r of the phase part is shifted by Δr for each cycle. This is equivalent to the position of the random phase plate 14 changing for each OPS cycle.

[0075] 3.3.3 Comparative Example For comparison, the change in the electric field in a form where the positional relationship between the random phase plate 14 and the OPS 100 is reversed will be described.

[0076] FIG. 12 is a diagram showing the change in the electric field of the beam when the OPS 100 is arranged in the front (upstream side) and the random phase plate 14 is arranged in the subsequent stage.

[0077] In FIG. 12, E 0a , E 1a , E 2a represent the electric fields of the respective cycle lights after passing through the OPS 100. When the beam passes through the random phase plate 14 after passing through the OPS 100, the electric field E out of the beam output from the random phase plate 14 is as follows.

[0078] E out = E0 + E1 + E2 + ··· = a0E(r, t) expiθ(r) + a1E(r + Δr, t + Δt) expiθ(r) + a2E(r + 2Δr, t + 2Δt) expiθ(r) + ··· In the above equation, since the random phase plate 14 is stationary, the position r of the phase part is constant regardless of the cycle.

[0079] 3.3.4 Difference in the Change of the Electric Field Due to the Difference in the Positional Relationship between the Random Phase Plate and the OPS As is clear from comparing the configuration of Embodiment 1 described in FIG. 11 with the comparative example described in FIG. 12, the positions r of the phase parts of the finally output electric fields E out are different.

[0080] When the random phase plate 14 is located in front of the OPS 100 (Figure 11), the position r of the phase portion changes with each OPS cycle as follows: r → r + Δr → r + 2Δr → ... This has the same effect as the position of the random phase plate 14 changing with each OPS cycle.

[0081] In other words, as in the configuration of Embodiment 1 (Figure 11), if the beam's optical path is shifted using the OPS 100 positioned behind the random phase plate 14, the same effect as if the random phase plate 14 were moved can be obtained even if the random phase plate 14 is stationary.

[0082] Therefore, compared to simply using OPS100 alone for beam shifting (Figure 5), the configuration of Embodiment 1 (Figure 11) results in a greater reduction in coherence, thus increasing the effect of reducing speckle contrast.

[0083] Figure 13 shows the cross-sectional LC of the beam emitted from the OPS100. The beam emitted from the OPS100 includes transmitted light (0-cycle light) and cycle light. In the case of the laser device 10A according to Embodiment 1, the beam at position A shown in Figure 13 passes through different positions on the random phase plate 14 depending on the number of cycles, so as explained above, coherence can be efficiently reduced.

[0084] On the other hand, in the comparative example shown in Figure 12, the beam at point A passes through the same position on the subsequent random phase plate 14 regardless of the number of passes, so the coherence reduction effect is smaller compared to Figure 11.

[0085] To reduce the coherence of laser light, it is necessary to integrate beams that are uncorrelated or have little correlation. Shifting the position of the random phase plate 14 by a pixel size D effectively eliminates the correlation. In practice, because the number of pixels on the random phase plate 14 is finite, the correlation will not be completely zero, but for practical purposes, it can be considered close to zero.

[0086] Therefore, the amount of shift of the random phase plate 14 required to reduce coherence is equal to the pixel size D of the random phase plate 14.

[0087] 3.4 Configuration of placing random phase plates within the delay optical path of the OPS Another way to reduce coherence is to place the random phase plate 14 within the optical path of the OPS100. However, in this case, the beam passes through the random phase plate 14 each time it makes a circuit, increasing beam divergence and making it difficult to suppress vignetting. Therefore, it is preferable to place the random phase plate 14 in the optical path between the oscillator and the OPS100 rather than placing it within the optical path of the OPS100.

[0088] 3.5 Placement of random phase plates when multiple OPS are provided The laser device 10A is equipped with one OPS 100 downstream of the random phase plate 14, but it is also possible to have multiple OPS downstream of the random phase plate 14. For example, the laser device 10A may be configured to have not only OPS 100 as the first OPS, but also a second OPS (not shown) downstream of OPS 100. Furthermore, the laser device 10A may be configured to have a third OPS (not shown) further downstream of the second OPS.

[0089] In the case of a laser device equipped with multiple OPSs, it is desirable to place a random phase plate 14 in the optical path between the first OPS and the oscillator. Doing so will similarly reduce coherence in the subsequent OPSs.

[0090] 3.6 Action and Effects According to the laser device 10A, energy loss due to beam vignetting is suppressed and beam coherence is efficiently reduced, thereby efficiently reducing speckle contrast.

[0091] 4. Method for measuring the optical path shift amount L using OPS Figure 14 shows a method for measuring the amount of optical path shift L for each rotation when beam shifting is performed with OPS100. The amount of shift L can be measured by the following procedure.

[0092] [Procedure 1] First, as shown in the upper part of Figure 14, measure the beam profile BP_all of the beam emitted from OPS100. The beam profile BP_all is the beam profile obtained by integrating the beam profiles of the light from each of the 0-cycle, 1-cycle, 2-cycle, ... cycles. Note that the beam profiles BP_all and BP_0 are measured immediately after the beam splitter BS using a beam profiler or the like.

[0093] [Procedure 2] Next, the beam profile BP_0 is measured in OPS100 with the circular optical path shielded. By shielding the circular optical path, a beam profile BP_0 consisting only of zero circular light is obtained (see the middle section of Figure 14).

[0094] [Step 3] Calculate the difference BP_diff between beam profile BP_all and beam profile BP_0 (see the lower part of Figure 14).

[0095] [Step 4] The beam profile shift amount L is obtained by comparing the beam profile BP_0 with the difference BP_diff.

[0096] 5. Methods for manufacturing electronic devices Figure 15 schematically shows an example configuration of the exposure apparatus 80. In Figure 15, the exposure apparatus 80 includes an illumination optical system 804 and a projection optical system 806. The illumination optical system 804 illuminates the reticle pattern of a reticle (not shown) placed on the reticle stage RT with laser light incident from the laser device 10A. The projection optical system 806 reduces and projects the laser light that has passed through the reticle onto a workpiece (not shown) placed on the workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure apparatus 80 exposes the workpiece to laser light reflecting 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, a semiconductor device can be manufactured by going through several processes.

[0097] 6. About the processor Processors such as the laser control processor 20 and the exposure control processor 82 may be physically configured in hardware form to perform the various processes included in this disclosure. For example, the processor may be a computer including a memory storing control programs that define the various processes, and a processing unit that executes the control programs. The control programs may be stored in a single memory, or they may be divided and stored in multiple physically separate memories, and the various processes may be defined by the control program as a collection of these memories. The processing unit may be a general-purpose processing unit such as a CPU, or a purpose-specific processing unit such as a GPU.

[0098] Furthermore, the processor may be programmed in software form to perform the various processes included in this disclosure. For example, the processor may have functions for performing the various processes implemented in a dedicated device such as an ASIC or a programmable device such as an FPGA.

[0099] The various processes included in this disclosure may be performed by one computer, one dedicated device, or one programmable device, or by the cooperation of multiple computers, multiple dedicated devices, or multiple programmable devices located physically separately. The various processes may be performed by at least two combinations of one or more computers, one or more dedicated devices, and one or more programmable devices.

[0100] The laser control processor 20 and exposure control processor 82 shown in Figures 3 and 6 may perform calculations by the processor and memory after the signals have been digitized by an analog electrical signal processing circuit or an AD converter in order to carry out the processes described in each embodiment.

[0101] Furthermore, the processing may be divided into multiple processing units using different processing functions than those described above, or it may be consolidated into a single processing unit. For example, the laser control processor 20 and the exposure control processor 82 may be consolidated into a single processing unit. These options are selected appropriately depending on the processing speed and accuracy.

[0102] 7. Other The above description is intended to be illustrative and 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.

[0103] Terms used in this specification and throughout 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. An oscillator that emits pulsed laser light, A random phase plate arranged in the optical path of the pulsed laser light, An optical pulse stretcher is placed in the optical path of the pulsed laser light that has passed through the random phase plate, and extends the pulse time width of the pulsed laser light by transmitting a portion of the pulsed laser light and causing another portion to circulate at least once in a delayed optical path, thereby outputting transmitted light and circulating light. A laser device equipped with the following features.

2. A laser apparatus according to claim 1, The optical paths of the transmitted light and the circulating light output from the optical pulse stretcher are misaligned. Laser device.

3. A laser apparatus according to claim 2, The shift in the optical paths of the transmitted light and the circulating light is a parallel shift. Laser device.

4. A laser apparatus according to claim 2, The aforementioned optical pulse stretcher is The delay optical path comprises a plurality of mirrors, The plurality of mirrors are arranged such that the delayed optical path and the optical path at the time of emission of each orbital light when the number of orbits is two or more are offset. Laser device.

5. A laser apparatus according to claim 2, The amount of deviation in the optical path that occurs each time the circulating light travels around the delayed optical path is greater than or equal to the pixel size of the random phase plate. Laser device.

6. A laser apparatus according to claim 5, The amount of displacement is less than or equal to twice the pixel size. Laser device.

7. A laser apparatus according to claim 1, When the size of the coherence region of the pulsed laser light emitted from the oscillator is a, The pixel size of the random phase plate is 0.5a or larger. Laser device.

8. A laser apparatus according to claim 1, The pixel size of the random phase plate is 0.05 mm or larger. Laser device.

9. A laser apparatus according to claim 1, The aforementioned optical pulse stretcher is Including a beam splitter and a concave mirror, Laser device.

10. A laser apparatus according to claim 9, The delayed optical path is composed of a plurality of the concave mirrors. Laser device.

11. A laser apparatus according to claim 1, The oscillator includes an excimer laser device, Laser device.

12. A laser apparatus according to claim 1, A second optical pulse stretcher is provided downstream of the first optical pulse stretcher, which is the optical pulse stretcher. Laser device.

13. A laser apparatus according to claim 12, A third optical pulse stretcher is provided downstream of the second optical pulse stretcher. Laser device.

14. A laser apparatus according to claim 1, The aforementioned random phase plate is stationary. Laser device.

15. A method for manufacturing electronic devices, An oscillator that emits pulsed laser light, A random phase plate arranged in the optical path of the pulsed laser light, An optical pulse stretcher is placed in the optical path of the pulsed laser light that has passed through the random phase plate, and extends the pulse time width of the pulsed laser light by transmitting a portion of the pulsed laser light and causing another portion to circulate at least once in a delayed optical path, thereby outputting transmitted light and circulating light. A laser device equipped with the following generates laser light: The laser light is output to the exposure apparatus, To manufacture an electronic device, the laser light is exposed onto a photosensitive substrate within the exposure apparatus. A method for manufacturing electronic devices, including

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