Laser device and method for manufacturing electronic device

Abstract

A laser device according to one aspect of the present disclosure comprises: an oscillator that outputs a pulsed laser; a rotating table that supports an optical element arranged on an optical path of the pulsed laser; a grating on which the pulsed laser is incident via the optical element; a first drive mechanism that drives the rotating table to change the incident angle of the laser to the grating; a second drive mechanism that drives the rotating table with a smaller driving amount than the first drive mechanism to change the incident angle of the laser to the grating; a wavelength monitor that measures the central wavelength of the pulsed laser; and a processor that periodically changes the target wavelength of the pulsed laser, outputs a drive command to the second drive mechanism based on the target wavelength and a measured value of the wavelength monitor to control the central wavelength to the target wavelength, the processor calculates a moving average of the drive command value of the second drive mechanism within an interval that is an integer multiple of the wavelength command period, returns the second drive mechanism to an initial position when the moving average exceeds a threshold value, and cancels the change in the incident angle caused by the return action by driving the first drive mechanism.

Description

Technical Field

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

[0002] In recent years, in semiconductor exposure devices, as semiconductor integrated circuits become smaller and more highly integrated, there is a demand for improved resolution. Therefore, the wavelength of light emitted from an exposure light source has been shortened. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs a laser with a wavelength of about 248nm and an ArF excimer laser device that outputs a laser with a wavelength of about 193nm are used.

[0003] The spectral line width of the natural oscillation light of the KrF excimer laser device and the ArF excimer laser device is relatively wide, about 350 to 400 pm. Therefore, when the projection lens is constructed using a material that allows ultraviolet light such as KrF and ArF lasers to pass through, chromatic aberration sometimes occurs. As a result, the resolution may be reduced. Therefore, it is necessary to narrow the spectral line width of the laser output from the gas laser device to a level where chromatic aberration can be ignored. Therefore, in order to narrow the spectral line width, a narrowing module (Line Narrowing Module: LNM) containing narrowing elements (etalon, grating, etc.) is sometimes provided in the laser resonator of the gas laser device. Hereinafter, a gas laser device with a narrowed spectral line width is referred to as a narrowed gas laser device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-23198 Summary of the invention

[0007] A laser device according to one aspect of the present disclosure comprises: an oscillator that outputs a pulsed laser; an optical element that is arranged on an optical path of the pulsed laser; a rotating table that supports the optical element; a grating that is arranged so that the pulsed laser is incident through the optical element and diffracted light of a wavelength corresponding to the incident angle of the pulsed laser is returned to the oscillator; a first driving mechanism that drives the rotating table to rotate the optical element, thereby changing the incident angle of the pulsed laser on the grating; a second driving mechanism that drives the rotating table with a smaller driving amount than the first driving mechanism to rotate the optical element, thereby changing the incident angle of the pulsed laser on the grating; and a wavelength monitor that measures the center wavelength of the pulsed laser. The invention relates to a processor that periodically changes the target wavelength of the pulsed laser, outputs a drive instruction to the second drive mechanism to change the incident angle according to the target wavelength and the measured value of the wavelength monitor, thereby controlling the center wavelength to the target wavelength, the processor calculates the moving average of the drive instruction value of the second drive mechanism within an interval that is an integer multiple of the wavelength instruction period, and returns the second drive mechanism to an initial position when the calculated moving average exceeds a threshold value, and offsets the change in the incident angle caused by returning the second drive mechanism to the initial position by driving the first drive mechanism, wherein the wavelength instruction period is a period for periodically changing the target wavelength.

[0008] Another aspect of the present disclosure is a method for manufacturing an electronic device, comprising the following steps: generating laser light by a laser device, outputting the laser light to an exposure device, exposing the laser light on a photosensitive substrate in the exposure device to manufacture the electronic device, wherein the laser device comprises: an oscillator that outputs pulsed laser light; an optical element that is arranged on an optical path of the pulsed laser light; a rotating table that supports the optical element; a grating that is arranged so that the pulsed laser light is incident through the optical element and diffracted light of a wavelength corresponding to the incident angle of the pulsed laser light is returned to the oscillator; a first driving mechanism that drives the rotating table to rotate the optical element, thereby changing the incident angle of the pulsed laser light on the grating; and a second driving mechanism that drives the rotating table with a smaller driving amount than the first driving mechanism to rotate the optical element, thereby Changing the incident angle of the pulsed laser incident on the grating; a wavelength monitor that measures the central wavelength of the pulsed laser; and a processor that periodically changes the target wavelength of the pulsed laser, outputs a drive instruction to the second drive mechanism based on the target wavelength and the measured value of the wavelength monitor to change the incident angle, thereby controlling the central wavelength to the target wavelength, the processor calculates the moving average of the drive instruction value of the second drive mechanism within an interval that is an integer multiple of the wavelength instruction period, and when the calculated moving average exceeds a threshold value, the second drive mechanism is returned to an initial position, and the change in the incident angle caused by returning the second drive mechanism to the initial position is offset by the drive of the first drive mechanism, and the wavelength instruction period is a period for periodically changing the target wavelength.

[0009] A laser device according to another aspect of the present disclosure comprises: an oscillator that outputs a pulsed laser; a first optical element that is arranged on an optical path of the pulsed laser; a first rotating table that supports the first optical element; a second optical element that is arranged on an optical path of the pulsed laser; a second rotating table that supports the second optical element; a grating that is arranged so that the pulsed laser is incident via the first optical element and the second optical element and diffracted light of a wavelength corresponding to the incident angle of the pulsed laser is returned to the oscillator; a first driving mechanism that drives the first rotating table to rotate the first optical element, thereby changing the incident angle of the pulsed laser on the grating; and a second driving mechanism that drives the second rotating table with a smaller driving amount than the first driving mechanism to rotate the second optical element, thereby changing the incident angle of the pulsed laser on the grating. An incident angle of a pulsed laser incident on a grating; a wavelength monitor that measures the central wavelength of the pulsed laser; and a processor that periodically changes a target wavelength of the pulsed laser, outputs a drive instruction to a second drive mechanism based on the target wavelength and the measured value of the wavelength monitor to change the incident angle, thereby controlling the central wavelength to the target wavelength, the processor calculates a moving average of the drive instruction value of the second drive mechanism within an interval that is an integer multiple of a wavelength instruction period, returns the second drive mechanism to an initial position when the calculated moving average exceeds a threshold value, and offsets the change in the incident angle caused by returning the second drive mechanism to the initial position by driving the first drive mechanism, wherein the wavelength instruction period is a period for periodically changing the target wavelength.

[0010] Another aspect of the present disclosure is a method for manufacturing an electronic device, comprising the following steps: generating a laser beam by a laser device, outputting the laser beam to an exposure device, and exposing the laser beam on a photosensitive substrate in the exposure device to manufacture the electronic device, wherein the laser device comprises: an oscillator that outputs a pulsed laser beam; a first optical element that is arranged on an optical path of the pulsed laser beam; a first rotating table that supports the first optical element; a second optical element that is arranged on an optical path of the pulsed laser beam; a second rotating table that supports the second optical element; a grating that is arranged so that the pulsed laser beam is incident through the first optical element and the second optical element, and diffracted light of a wavelength corresponding to the incident angle of the pulsed laser beam is returned to the oscillator; a first driving mechanism that drives the first rotating table to rotate the first optical element, thereby changing the incident angle of the pulsed laser beam on the grating; and a second driving mechanism that rotates the first rotating table at a wavelength greater than the incident angle of the first optical element. A first drive mechanism drives the second rotating table with a small driving amount to rotate the second optical element, thereby changing the incident angle of the pulsed laser incident on the grating; a wavelength monitor, which measures the central wavelength of the pulsed laser; and a processor, which periodically changes the target wavelength of the pulsed laser, outputs a driving instruction to the second drive mechanism according to the target wavelength and the measured value of the wavelength monitor to change the incident angle, thereby controlling the central wavelength to the target wavelength, the processor calculates the moving average of the driving instruction value of the second drive mechanism within an interval that is an integer multiple of the wavelength instruction period, returns the second drive mechanism to an initial position when the calculated moving average exceeds a threshold value, and offsets the change in the incident angle caused by returning the second drive mechanism to the initial position by driving the first drive mechanism, the wavelength instruction period being a period of periodically changing the target wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Hereinafter, several embodiments of the present disclosure will be described as simple examples with reference to the accompanying drawings.

[0012] Figure 1 An example of an exposure pattern of step and scan exposure on a wafer is shown.

[0013] Figure 2 The relationship between one scanning field on the wafer and the scanning beam is shown.

[0014] Figure 3 An example of an exposure area of ​​a scanning beam is shown.

[0015] Figure 4 is a graph showing an example of a burst pulse.

[0016] Figure 5 The structure of an excimer laser device according to a comparative example is schematically shown.

[0017] Figure 6 It is a plan cross-sectional view of the movable retainer.

[0018] Figure 7 This is a front view of the movable holder on the wavelength selective mirror side as seen from the grating side inside the narrowband cell.

[0019] Figure 8 An example of a burst pulse for switching two wavelengths is shown.

[0020] Fig. 9 Shown with Figure 8 An example of a piezoelectric command corresponding to the control of switching between two wavelengths is shown.

[0021] Fig.10 This is a timing chart showing an example of the operation of the laser device according to the first embodiment.

[0022] Fig.11 This is a flowchart showing a control example in the laser device according to the first embodiment.

[0023] Fig.12 It is shown that it is applied to Fig.11 This is a flowchart of an example of a subroutine of step S13.

[0024] Fig.13 It is shown that it is applied to Fig.11 This is a flowchart of an example of a subroutine of step S19.

[0025] Fig.14 is shown to be applied to Fig.11 This is a flowchart of an example of a subroutine of step S22.

[0026] Fig.15 This is a timing chart showing an example of the operation of the laser device according to the second embodiment.

[0027] Fig.16 This is a timing chart for hysteresis correction performed by the laser device according to the third embodiment.

[0028] Fig.17 This is a flowchart showing a control example of hysteresis correction performed by the laser device according to the third embodiment.

[0029] Fig.18 It is shown that it is applied to Fig.17 This is a flowchart of an example of a subroutine of step S34.

[0030] Fig.19 It is shown that it is applied to Fig.18 This is a flowchart of an example of a subroutine of step S319.

[0031] Fig. 20 It is shown that it is applied to Fig.17 This is a flowchart of an example of a subroutine of step S35.

[0032] Fig.21 It is shown that it is applied to Fig. 20 This is a flowchart of an example of a subroutine of step S359.

[0033] Fig. 22 This is a flowchart showing a control example of a series of operations including oscillation adjustment and main exposure in the laser device according to the third embodiment.

[0034] Fig.23 It is shown that it is applied to Fig. 22 This is a flowchart of an example of a subroutine of step S51.

[0035] Fig.24 It is shown that it is applied to Fig. 22 This is a flowchart of an example of a subroutine of step S52.

[0036] Fig.25 It is shown that it is applied to Fig. 22 This is a flowchart of an example of a subroutine of step S53.

[0037] Fig.26 The structure of the laser device according to the fourth embodiment is schematically shown.

[0038] Fig. 27 The structure of a narrowband unit used in the laser device of the fifth embodiment is schematically shown.

[0039] Fig.28 The structure of the exposure device is schematically shown. DETAILED DESCRIPTION

[0040] -Table of contents-

[0041] 1. Explanation of terms

[0042] 1.1N Clearance Explanation

[0043] 1.2 Description of burst pulse

[0044] 1.3 Other terms

[0045] 2. Overview of Excimer Laser Device of Comparative Example

[0046] 2.1 Structure

[0047] 2.2 Action

[0048] 2.3 Topics

[0049] 3. Implementation Method 1

[0050] 3.1 Structure

[0051] 3.2 Action

[0052] 3.3 Description of Flowchart Showing Control Example

[0053] 3.4 Effects

[0054] 4. Implementation Method 2

[0055] 4.1 Structure

[0056] 4.2 Action

[0057] 4.3 Effects

[0058] 5. Implementation Method 3

[0059] 5.1 Structure

[0060] 5.2 Action

[0061] 5.3 Control Example of Hysteresis Correction

[0062] 5.4 Example of a series of control actions including oscillation adjustment and main exposure adjustment

[0063] 5.5 Effect

[0064] 6. Implementation Method 4

[0065] 6.1 Structure

[0066] 6.2 Action

[0067] 6.3 Effects

[0068] 7. Implementation Method 5

[0069] 7.1 Structure

[0070] 7.2 Action

[0071] 7.3 Effects

[0072] 8. About the manufacturing method of electronic devices

[0073] 9. Others

[0074] Below, the embodiments of the present disclosure are described in detail with reference to the accompanying drawings. The embodiments described below show several examples of the present disclosure and do not limit the content of the present disclosure. In addition, the structures and actions described in each embodiment are not necessarily all necessary for the structures and actions of the present disclosure. In addition, the same reference numerals are marked on the same structural elements and repeated descriptions are omitted.

[0075] 1. Explanation of terms

[0076] 1.1N Clearance Explanation

[0077] Figure 1 An example of an exposure pattern of step and scan exposure on the wafer WF is shown. Figure 1The plurality of rectangular areas shown in the wafer WF are scanning fields SF. The scanning field SF is an exposure area of ​​one scanning exposure, and is also called a scanning area. Figure 1 As shown, the chip WF is divided into multiple exposure areas (scanning fields) of specified sizes, and each exposure area is scanned and exposed during the period between the start (wafer start) and end (wafer end) of chip exposure, thereby performing chip exposure.

[0078] That is, in wafer exposure, the following steps are repeatedly performed: the first predetermined exposure area of ​​the wafer WF is exposed by the first scanning exposure (scan #1), and then the second predetermined exposure area is exposed by the second scanning exposure (scan #2). In one scanning exposure, a plurality of pulsed lasers can be continuously output from the laser device. This scanning exposure is repeated in sequence, and after the scanning exposure of all exposure areas of the first wafer WF is completed, the oscillation is adjusted again, and then wafer exposure of the second wafer WF is performed.

[0079] according to Figure 1 The step-and-scan exposure is performed in the order of the dashed arrows shown until wafer start → scan #1 → scan #2 → ... → scan #126 → wafer end. The wafer WF is an example of a semiconductor substrate (photosensitive substrate) coated with a resist.

[0080] Figure 2 The relationship between one scanning field SF on the wafer WF and the scanning beam SB is shown. The scanning beam SB is a roughly rectangular beam irradiation area with a roughly uniform light intensity distribution used in the scanning exposure of the scanning field SF. The roughly rectangular and roughly uniform beam shaped by the illumination optical system is irradiated onto the mask, and in the short axis direction of the beam (here, the Y axis direction), the mask and the wafer WF are moved in different directions in the Y axis direction according to the reduction ratio of the projection optical system while being exposed. Thus, in each scanning field SF on the wafer WF, the mask pattern is scanned and exposed.

[0081] exist Figure 2 In the figure, the direction toward the negative side of the Y-axis direction in the longitudinal direction is the scanning direction, and the direction toward the positive side of the Y-axis direction is the chip moving direction (stage moving direction). Figure 2 The direction parallel to the paper surface and perpendicular to the Y-axis direction (X-axis direction) is called the scanning width direction. Regarding the size of the scanning field SF on the wafer WF, for example, the Y-axis direction is 33 mm and the X-axis direction is 26 mm.

[0082] Figure 3An example of the irradiation area of ​​the scanning beam SB is shown. When the length of the scanning beam SB in the X-axis direction is Bx and the width in the Y-axis direction is By, Bx corresponds to the size of the scanning field SF in the X-axis direction, and By is much smaller than the size of the scanning field SF in the Y-axis direction.

[0083] The scanning beam SB is an area irradiated by one pulse of the pulsed laser, and is referred to as an N-gap. The number of pulses irradiated to each location on the wafer WF by scanning exposure is referred to as the N-gap pulse number N. SL . N gap pulse number N SL It is expressed by the following formula.

[0084] N SL =(By / Vy)·f

[0085] Vy: The scanning speed of the wafer in the Y-axis direction

[0086] f: laser repetition frequency (Hz)

[0087] When exposing the same scan field SF with multiple wavelengths, it is necessary to set the number of N gap pulses N SL The wavelength is changed within N intervals as one cycle.

[0088] 1.2 Description of burst pulse

[0089] Figure 4 Graph showing an example of burst pulses. The horizontal axis represents the number of pulses, and the vertical axis represents the wavelength. When the wafer WF is exposed, after the scanning exposure of one scanning field SF is completed, the pulse generation is stopped, and the stage is driven to move to the next scanning field SF for scanning exposure. In this case, the pulse waveform is as follows: Figure 4 As shown in FIG. 1 , a series of pulses irradiated at regular intervals and rest periods are repeated alternately. This type of pulse is called a burst pulse.

[0090] Figure 4 An example of exposing the same scanning field SF with two wavelengths (wavelengths λ1 and λ2) is shown. Here, the number of N gap pulses N is shown. SL For example, 10 pulses are used as one cycle. The target wavelength of the first 5 pulses in the cycle T is λ1, and the target wavelength of the second 5 pulses is λ2. However, the number of N gap pulses in the cycle T is N. SL , the switching timing of the two wavelengths and the number of pulses required for the exposure of the scanning field SF are not limited to Figure 4 For example, N gap pulse number N SL It can also be 30 pulses.

[0091] 1.3 Other terms

[0092] "Piezoelectric element" is synonymous with piezoelectric element. Piezoelectric element is sometimes simply expressed as "piezoelectric".

[0093] The term "parallel" in this specification may include the concept of approximately parallel in a range that can be regarded as substantially parallel in a technical sense. In addition, the term "perpendicular" or "orthogonal" in this specification may include the concept of approximately perpendicular or approximately orthogonal in a range that can be regarded as substantially perpendicular or substantially orthogonal in a technical sense.

[0094] 2. Overview of Excimer Laser Device of Comparative Example

[0095] 2.1 Structure

[0096] Figure 5 The structure of the excimer laser device 11 of the comparative example is schematically shown. The comparative example disclosed in the present invention is a method that the applicant recognizes that only the applicant knows, and is not a known example acknowledged by the applicant himself. The excimer laser device 11 has a laser cavity 12 in which a laser gas as a laser medium is sealed. A front window 17 and a rear window 19 that allow a pulsed laser 21 to pass through are respectively arranged at both ends of the laser cavity 12 via a holder not shown in the figure.

[0097] Inside the laser cavity 12, a pair of discharge electrodes 14 and 15 are Figure 5 A high voltage is applied between discharge electrodes 14 and 15 from a high voltage power supply 23 to generate pulse discharge, thereby exciting the laser gas, thereby generating pulse laser light 21 at a frequency of, for example, several kHz to several tens of kHz.

[0098] The generated pulse laser 21 is emitted, for example, toward the rear of the laser cavity 12 ( Figure 5 The narrowband laser 21 is incident on the narrowband laser unit 30 that narrows the band of the pulse laser 21. The narrowband laser unit 30 is surrounded by a narrowband laser box 31, and has prisms 32, 32, a wavelength selective mirror 34, a grating 33, and the like as optical elements.

[0099] A purge gas supply port 35 is provided in the wall of the narrowing box 31 . A purge gas 45 with low reactivity, such as a clean and dry rare gas or high-purity nitrogen, is introduced into the narrowing box 31 through the purge gas supply port 35 .

[0100] The pulse laser light 21 incident on the narrowband unit 30 is expanded by prisms 32, 32, reflected by wavelength selective mirror 34, and incident on grating 33 as a narrowband optical element. In grating 33, only the incident angle The pulse laser light 21 having a predetermined central wavelength λc is reflected. That is, the grating 33 is configured in a Littrow arrangement so that the incident pulse laser light 21 has a wavelength that is at an angle to the incident light. The diffracted light of the corresponding central wavelength λc returns to the laser cavity 12 .

[0101] The wavelength selective mirror 34 is mounted in a horizontal plane ( Figure 5 The movable holder 36 is rotatable in a plane parallel to the paper surface. The movable holder 36 is rotated to rotate the wavelength selection mirror 34, thereby changing the incident angle of the pulse laser 21 incident on the grating 33. As a result, the central wavelength λc of the pulsed laser 21 diffracted by the grating 33 changes. Figure 5 In the figure, reference numeral 20 denotes a laser optical axis of a pulse laser 21.

[0102] The narrow-band pulsed laser 21 is amplified by the discharge between the discharge electrodes 14 and 15 during the process of reciprocating between the grating 33 in the narrow-band unit 30 and the front mirror 16 that partially reflects the pulsed laser 21. Then, part of it is transmitted through the front mirror 16 and is transmitted forward ( Figure 5 The emitted pulse laser 21 is emitted to the right side of the image and enters the exposure device 25. A part of the emitted pulse laser 21 is directed by the beam splitter 22 to Figure 5 The lower one is selected and its central wavelength λc is monitored by the wavelength monitor 37.

[0103] Next, the structure of the movable holder 36 will be described. Figure 6 It is a plan cross-sectional view of the movable holder 36 . Figure 7 This is a front view of the movable holder 36 on the wavelength selection mirror 34 side as viewed from the grating 33 side inside the narrowband box 31. Figure 6 and Figure 7 As shown, the movable holder 36 has a quadrilateral mirror holder 38 to which the wavelength selection mirror 34 is fixed. The mirror holder 38 is pulled toward the narrowing box 31 by the urging force of a tension spring and a leaf spring 49 (not shown).

[0104] Furthermore, the first corner 38A and the second corner 38B of the four corners of the mirror holder 38 are pressed from the narrowing box 31 by the manual micrometer 50 and the support member 39. The support member 39, for example, makes the screw 47 protrude from the narrowing box 31 by a predetermined length and fixes it with the nut 46. In addition, the manual micrometer 50 can freely change the protrusion amount from the narrowing box 31 manually.

[0105] As described later, a piezoelectric element unit 41 is mounted on the third corner 38C of the mirror holder 38. The front end 41B of the piezoelectric element unit 41 contacts the ball screw unit 43 by the force of the tension spring and the leaf spring 49 (not shown), and presses the stepping motor unit 40. The piezoelectric element unit 41 is a fine motion drive mechanism including a piezoelectric element. The stepping motor unit 40 is a coarse motion drive mechanism including a stepping motor.

[0106] In addition, if Figure 5 As shown, the stepper motor unit 40 and the piezoelectric element unit 41 are both electrically connected to the processor 29. The processor 29 functions as a laser controller that controls the excimer laser device 11 as a whole. The processor 29 of the present disclosure is a processing device including a storage device storing a control program and a CPU (Central Processing Unit) that executes the control program. The processor 29 is specially configured or programmed to execute various processes included in the present disclosure.

[0107] The stepper motor unit 40 moves the motor shaft 48 (see Figure 6 ) is rotated a predetermined amount. The rear end portion 43B of the ball screw unit 43, whose thread teeth are precisely machined, is attached to the front end portion 48A of the motor shaft 48 via the coupling 42. The ball screw unit 43 is rotated while smoothly moving in a straight line in the front-rear direction through the guide 51.

[0108] The front end 43A of the ball screw unit 43 is precisely machined in a plane perpendicular to its longitudinal direction, and the front end 41B of the piezoelectric element unit 41, which is precisely machined into a spherical surface, abuts against the plane. Therefore, when the ball screw unit 43 rotates and moves forward and backward, the piezoelectric element unit 41 does not rotate but moves forward and backward. The rear end 41A of the piezoelectric element unit 41 is fixed to the ultraviolet cover 44, and the ultraviolet cover 44 is fixed to the mirror holder 38.

[0109] Wiring 52 of piezoelectric element unit 41 passes through the inside of ultraviolet cover 44 and reaches the outside of narrowing box 31 through an introduction hole (not shown) and is connected to processor 29. Piezoelectric element unit 41 expands and contracts in the front-rear direction by a length corresponding to the magnitude of voltage V applied through wiring 52.

[0110] The position of about 1 / 2 of the full stroke of the piezoelectric element unit 41 is called the neutral position. The voltage V that causes the piezoelectric element unit 41 to extend to the neutral position is called the neutral voltage V0. The processor 29 always applies the neutral voltage V0 to the piezoelectric element unit 41. Thus, the piezoelectric element unit 41 is maintained at the neutral position as the initial position.

[0111] The processor 29 outputs a signal to the movable holder 36 to extend or retract the stepping motor unit 40 or the piezoelectric element unit 41, thereby pushing or pulling the third corner 38C of the mirror holder 38 through the ultraviolet cover 44. As a result, the wavelength selection mirror 34 rotates, and the incident angle is changed, and the central wavelength λc of the pulse laser 21 changes.

[0112] At this time, the processor 29 performs wavelength control based on the center wavelength λc monitored by the wavelength monitor 37 so that the difference between the center wavelength λc and the target wavelength λ0, that is, the wavelength deviation Δλ, is less than a prescribed allowable range. In the following description, the case where the wavelength is controlled so that the wavelength deviation Δλ is less than a prescribed allowable range is referred to as bringing the center wavelength λc close to the target wavelength λ0.

[0113] In addition, the processor 29 outputs a command to the high-voltage power supply 23, thereby also controlling the pulse output of the pulse laser 21. Furthermore, the processor 29 communicates with the exposure device 25, and the exposure device 25 performs laser oscillation according to the oscillation command signal. In addition, the processor 29 sometimes outputs an oscillation command signal according to its own judgment to perform laser oscillation.

[0114] 2.2 Action

[0115] It is known that when the resist film is irradiated with the pulse laser 21 by the exposure device 25, exposure is performed at multiple wavelengths to increase the focal depth. When the focal depth is increased, the imaging performance in the thickness direction of the resist film can be maintained even when a thick resist film is exposed.

[0116] As a means of performing exposure at multiple wavelengths, for example, periodically switching the wavelength of the pulsed laser light 21 generated by the excimer laser device 11 between two wavelengths, a long wavelength and a short wavelength (see Figure 4 ). An example of the operation when wavelength λ1 and wavelength λ2 are set as target wavelengths and these two wavelengths are periodically switched is as follows.

[0117] [Step 1] The processor 29 receives two target wavelengths λ1 and λ2 and a period T for controlling the wavelengths from the exposure device 25. The period T is represented by the number of pulses in one period. The number of pulses representing the period T may also be the number of pulses irradiated to the same portion of the resist film on the wafer WF, that is, the number of N interval pulses N. SL .

[0118] [Step 2] The processor 29 drives the piezoelectric element unit 41 or the stepping motor unit 40 to rotate the wavelength selective mirror 34 so that the incident angle of the pulsed laser 21 incident on the grating 33 becomes change.

[0119] [Step 3] A portion of the narrowband pulse laser light 21 is taken out by the beam splitter 22 , and the wavelength is measured by the wavelength monitor 37 .

[0120] [Step 4] When the measured wavelength (central wavelength λc) deviates from the target wavelength λ1, the processor 29 drives the piezoelectric element unit 41 with excellent high-speed response to adjust the posture of the wavelength selective mirror 34 so that the central wavelength λc approaches the target wavelength λ1. The feedback control of step 4 is performed for each pulse.

[0121] [Step 5] When the time to switch the wavelength comes, the processor 29 drives the piezoelectric element unit 41 so that the wavelength of the pulsed laser 21 becomes the target wavelength λ2, thereby rotating the wavelength selective mirror 34, and making the incident angle of the pulsed laser 21 incident on the grating 33 change.

[0122] [Step 6] A portion of the pulse laser light 21 generated by the operation of step 5 is taken out by the beam splitter 22 , and the wavelength is measured by the wavelength monitor 37 .

[0123] [Step 7] When the measured wavelength deviates from the target wavelength λ2, the processor 29 drives the piezoelectric element unit 41 to adjust the posture of the wavelength selective mirror 34 so that the central wavelength λc approaches the target wavelength λ2. The feedback control of step 7 is also performed for each pulse.

[0124] [Step 8] When the timing for wavelength switching comes, the processor 29 drives the piezoelectric element unit 41 to rotate the wavelength selective mirror 34 so as to achieve the target wavelength λ1, thereby changing the incident angle of the pulsed laser 21 incident on the grating 33 to change.

[0125] Next, repeat the above steps 3 to 8.

[0126] 2.3 Topics

[0127] The piezoelectric element used in the narrowband unit 30 is affected by temperature, so the output to the input varies (drifts) over time. Therefore, the piezoelectric command is corrected for each pulse through feedback control, but when the piezoelectric element reaches the operating limit, the angle of the wavelength selective mirror 34 may not be adjusted further.

[0128] Therefore, it is conceivable to drive the stepping motor after the piezoelectric command value reaches a predetermined threshold value to adjust the posture of the wavelength selective mirror 34 and return the piezoelectric element to the neutral position.

[0129] However, if Figure 8 and Fig. 9As shown, when the target wavelength is switched from λ1 to λ2, the piezoelectric command value exceeds the threshold and the operating limit, and may not operate.

[0130] Figure 8 This is an example of a burst pulse that switches between two wavelengths. The horizontal axis represents the number of pulses, and the vertical axis represents the wavelength. Figure 4 Likewise, an example is shown in which the target wavelength of the first half of the 5 pulses in the cycle T of 10 pulses is set to λ1, and the target wavelength of the second half of the 5 pulses is set to λ2. Fig. 9 Shown with Figure 8 An example of a piezoelectric command corresponding to the switching control of two wavelengths is shown. The horizontal axis represents the number of pulses, and the vertical axis represents the piezoelectric command value. Fig. 9 The horizontal axis uses the same scale to represent Figure 8 The horizontal axis has the same pulse number range. Figure 8 As shown, the target wavelength varies discontinuously with two wavelengths, λ1 and λ2, as shown in FIG. Fig. 9 As shown, the piezoelectric command also changes discontinuously.

[0131] exist Fig. 9 The piezoelectric command value changes in a downward tilted manner because it carries a drift component caused by the temperature of the piezoelectric element. The piezoelectric element is affected by temperature, and the output corresponding to the command drifts. The processor 29 performs feedback control based on the difference between the measured value of the center wavelength reflecting the driving of the piezoelectric element and the target wavelength, and applies correction to the command value of the piezoelectric element. Therefore, the piezoelectric command value is as follows: Fig. 9 It changes obliquely like that.

[0132] Fig. 9 The single-dot chain line in the figure indicates the threshold value for the drive control of the stepping motor, and the double-dot chain line indicates the action limit of the piezoelectric element. In addition, the threshold value specifies the lower limit, so Fig. 9 In the case of the piezoelectric element, the command value will not reach the threshold value before the piezoelectric command on the long wavelength side of the third cycle ends, and the piezoelectric element can operate normally. However, when the piezoelectric command is switched from the long wavelength to the short wavelength of the third cycle, the piezoelectric command is as follows: Fig. 9 The dotted line in the figure exceeds the piezoelectric working limit, so the piezoelectric element cannot operate.

[0133] 3. Implementation Method 1

[0134] 3.1 Structure

[0135] The structure of the laser device of embodiment 1 can be Figures 5 to 7 The structures of the excimer laser devices 11 shown are the same.

[0136] 3.2 Action

[0137] The laser device of the first embodiment differs from the comparative example in the operation including the control executed by the processor 29. Next, the operation of the laser device of the first embodiment will be described with respect to the differences from the comparative example.

[0138] Fig.10 This is a timing chart showing an example of the operation of the laser device according to Embodiment 1. The horizontal axis can be understood as time or the number of pulses. Fig.10 The upper section shows a waveform WLc of a wavelength instruction, the middle section shows a waveform PZc of a piezoelectric instruction given to the piezoelectric element, and the lower section shows a waveform SMc of a stepping motor instruction given to the stepping motor.

[0139] Regarding the wavelength command waveform WLc, the command for wavelength λ1 and the command for wavelength λ2 are switched within the period T. Fig.10 , the waveform WLc of the wavelength instruction is represented as a rectangular wave, but the actual wavelength instruction is a discrete curve diagram indicating the target wavelength for each pulse. That is, the processor 29 changes the wavelength instruction that makes a plurality of pulses that set the target wavelength to λ1 continuous and the wavelength instruction that makes a plurality of pulses that set the target wavelength to λ2 continuous in a rectangular wave shape. The wavelength λ1 is an example of the "first wavelength" in the present disclosure. The wavelength λ2 is an example of the "second wavelength" in the present disclosure. The period T of the wavelength instruction that is periodically changed is called the wavelength instruction period.

[0140] Regarding the waveform PZc of the piezoelectric command, the command value changes greatly according to the switching of the command of wavelength λ1 and wavelength λ2. The first threshold and the second threshold are set for the piezoelectric command. The first threshold is a threshold that specifies the lower limit. Fig.10 The second threshold is the threshold that specifies the upper limit. Fig.10 The middle part is indicated as "threshold value (+)". The "center" shown between the threshold value (-) and the threshold value (+) indicates the command value of the neutral position.

[0141] The processor 29 performs feedback control of the piezoelectric command for each pulse during the wavelength command period of the wavelength λ1 or the wavelength command period of the wavelength λ2 to correct the influence of the temperature of the piezoelectric element. The feedback control is a control for correcting the piezoelectric command based on the difference between the center wavelength and the target wavelength measured by the wavelength monitor 37.

[0142] In addition, the processor 29 calculates the moving average of the piezoelectric command value for the interval that is an integral multiple of the wavelength command period of the rectangular wave, and drives the stepping motor to correct the drift of the piezoelectric command when the piezoelectric command moving average value PZmav exceeds the threshold value. For example, the interval for calculating the moving average of the piezoelectric command value may be one period of the wavelength command period, that is, period T.

[0143] exist Fig.10 In the figure, the piezoelectric command moving average value PZmav is shown by a dotted curve graph. In addition, the white circles and black dots shown on the curve graph of the piezoelectric command moving average value PZmav represent the moving average value PZAv calculated according to each cycle T, the white circles represent that the threshold value is not exceeded, and the black dots represent that the threshold value is exceeded. In addition, "not exceeding the threshold value" here means a value within the allowable range specified by the first threshold value and the second threshold value. In addition, "exceeding the threshold value" means a value that deviates from the allowable range specified by the first threshold value and the second threshold value. At the time when the moving average value PZAv shown by the black dots in the figure is obtained, the instruction for driving the stepping motor is changed, and the piezoelectric instruction is also changed accordingly.

[0144] The calculation interval of the moving average is period T, so the initial moving average is calculated at the end of the first period of the wavelength instruction period. Then, the moving average is calculated according to the time series. Fig.10 In the case of , the threshold value is exceeded at the black dot, so the stepper motor is driven here to return the piezoelectric element to the initial position (neutral position). In this way, even when the wavelength is greatly changed to two wavelengths, a long wavelength (wavelength λ1) and a short wavelength (wavelength λ2), the drift component of the piezoelectric element can be corrected by driving the stepper motor.

[0145] In addition, Fig.10 , an example is shown in which the stepping motor is driven at an integer multiple of the wavelength command cycle, but the timing of driving the stepping motor to perform correction, i.e., the stepping motor (STM) correction execution timing, may not be an integer multiple of the wavelength command cycle.

[0146] The case where the stepper motor is driven and the drift of the piezoelectric instruction is corrected based on the comparison of the piezoelectric instruction moving average value PZmav with the first threshold value and the second threshold value is called "piezoelectric drift correction". In the piezoelectric drift correction performed by the laser device of embodiment 1, when the piezoelectric instruction moving average value PZmav calculated within the interval of an integer multiple of the wavelength instruction period exceeds the threshold value, the piezoelectric element is returned to the neutral position (initial position), and the stepper motor is driven to offset the incident angle to the grating 33 caused by the action of returning the piezoelectric element to the neutral position by driving the stepper motor. changes.

[0147] The processor 29 obtains the moving average of the piezoelectric command value within an interval of an integer multiple of the wavelength command period, thereby separating the change component of the piezoelectric command value for wavelength change and appropriately detecting the drift component of the piezoelectric element. Fig.10In the example, when the moving average value PZAv is lower than the threshold value (-), the stepping motor unit 40 is shortened from the initial length P0. The shortening amount at this time may be substantially the same as the piezoelectric drive amount shortened from the neutral voltage V0 of the piezoelectric element to the threshold value (-).

[0148] The wavelength selective mirror 34 is an example of an “optical element” in the present disclosure. The movable holder 36 that rotates the mirror holder 38 is an example of a “rotating stage” in the present disclosure. The stepping motor unit 40 including a stepping motor is an example of an incident angle of incidence on the grating 33. The mechanism for performing the coarse motion drive is an example of the "first drive mechanism" in the present disclosure. The piezoelectric element unit 41 including the piezoelectric element drives the mirror holder 38 with a smaller driving amount than the stepping motor to make the incident angle of the incident light on the grating 33 The mechanism for performing micro-motion driving is an example of the “second driving mechanism” in the present disclosure. The piezoelectric command is an example of the “driving command” in the present disclosure, and the piezoelectric command value is an example of the “driving command value” in the present disclosure. The laser cavity 12 is an example of the “oscillator” in the present disclosure.

[0149] 3.3 Description of Flowchart Showing Control Example

[0150] Fig.11 : is a flowchart showing a control example in the laser device according to Embodiment 1. In step S11, the processor 29 sets a threshold value of the piezoelectric command value. The threshold value includes Fig.10 The first threshold and the second threshold described in .

[0151] Next, in step S12, the processor 29 receives the N gap pulse number N from the exposure device 25. SL and wavelength amplitude information.

[0152] Next, in step S13, the processor 29 calculates the wavelength instruction value for one cycle T. The wavelength instruction for one cycle T is not limited to Fig.10 The rectangular wave shown as an example in FIG. 1 may also be a triangular wave, a sine wave, or the like.

[0153] Next, in step S14 , the processor 29 initializes the value of the pulse number n to n=1.

[0154] Next, in step S15 , the processor 29 drives the piezoelectric element using the voltage calculation value V1 of the pulse number n=1 as the piezoelectric command value.

[0155] Next, in step S16 , processor 29 detects a burst signal instructed from exposure device 25 .

[0156] Next, in step S17 , the processor 29 applies a high voltage to the discharge electrodes 14 and 15 of the laser cavity 12 to cause discharge to occur, thereby performing laser oscillation.

[0157] Next, in step S18 , the processor 29 performs wavelength measurement via the wavelength monitor 37 .

[0158] Next, in step S19 , the processor 29 calculates the piezoelectric command value when the wavelength is changed.

[0159] Next, in step S20 , the processor 29 calculates a piezoelectric command value based on the deviation between the measured wavelength and the target wavelength measured in step S18 .

[0160] Next, in step S21 , the processor 29 drives the piezoelectric element according to the piezoelectric command value calculated in step S20 .

[0161] Next, in step S22 , the processor 29 performs piezoelectric drift correction.

[0162] Next, in step S23, processor 29 determines whether the burst signal is OFF. If the burst signal instructed by exposure device 25 is ON and the determination result of step S23 is a "No" determination, processor 29 returns to step S17.

[0163] On the other hand, if the result of the determination in step S23 is "yes", the processor 29 ends the Fig.11 Flowchart of the process.

[0164] Fig.12 It is shown that it is applied to Fig.11 Flowchart of an example of a subroutine of step S13. In step S131, the processor 29 initializes the pulse number n to n=1.

[0165] Next, in step S132, the processor 29 calculates and stores the wavelength instruction value of the pulse number n.

[0166] Next, in step S133 , the processor 29 increments the pulse number n and updates the pulse number so that the value of n+1 is newly set as the value of the pulse number n.

[0167] Next, in step S134, the processor 29 determines whether the pulse number n exceeds the number of pulses in one period T, that is, the number of N gap pulses N. SL That is, the processor 29 determines whether n>N SL .

[0168] If the result of the determination in step S134 is "No", the processor 29 returns to step S132. On the other hand, if the result of the determination in step S134 is "Yes", the processor 29 ends the process. Fig.12 Flowchart of Fig.11 The main process.

[0169] Fig.13 It is shown that it is applied to Fig.11 Flowchart of an example of a subroutine of step S19 of FIG. 1. In step S191, the processor 29 increments the pulse number n and updates the pulse number so that the value of n+1 is newly set as the value of the pulse number n.

[0170] Next, in step S192 , processor 29 determines whether pulse number n exceeds the number of pulses in one cycle T.

[0171] If the result of determination in step S192 is a "No" determination, processor 29 proceeds to step S194. In step S194, processor 29 sets voltage calculation value Vn of pulse number n as the piezoelectric command value.

[0172] On the other hand, if the result of determination in step S192 is "yes", processor 29 proceeds to step S193. In step S193, processor 29 initializes pulse number n to n = 1. After step S193, processor 29 proceeds to step S194.

[0173] After step S194, processor 29 ends Fig.13 Flowchart of Fig.11 The main process.

[0174] Fig.14 It is shown that it is applied to Fig.11 Flowchart of an example of a subroutine of step S22. In step S221, the processor 29 calculates a moving average of the piezoelectric command value. The calculation interval of the moving average can be an integer multiple of the wavelength command period, which is set to period T here.

[0175] Next, in step S222, the processor 29 determines whether it is the STM calibration execution timing. The STM calibration execution timing may be every cycle, every pulse, or any preset timing.

[0176] If the result of the determination in step S222 is "No", the processor 29 ends the Fig.14 Flowchart of Fig.11 The main process.

[0177] On the other hand, if the result of the determination in step S222 is "yes", the processor 29 proceeds to step S223. In step S223, the processor 29 determines whether the moving average value of the piezoelectric command value is above the threshold value (-) and below the threshold value (+). When the moving average value of the piezoelectric command value obtained in step S221 is lower than the threshold value (-) or higher than the threshold value (+), the processor 29 determines that the moving average value exceeds the threshold value.

[0178] If the result of the determination in step S223 is "yes", the processor 29 ends the Fig.14 Flowchart of Fig.11 The main process.

[0179] On the other hand, if the result of the determination in step S223 is "No", the processor 29 proceeds to step S224. In step S224, the processor 29 drives the stepping motor. After step S224, the processor 29 ends Fig.14 Flowchart of Fig.11 The main process.

[0180] 3.4 Effects

[0181] According to the laser device of embodiment 1, when the wavelength instruction is periodically changed with a rectangular wave, the moving average of the piezoelectric instruction value is calculated within an interval of an integer multiple of the wavelength instruction period, thereby correctly detecting and correcting the drift of the piezoelectric instruction caused by temperature changes, etc.

[0182] Furthermore, the piezoelectric drift correction performed in the first embodiment enables the piezoelectric element to always operate at a neutral position, so that even when the wavelength command is periodically changed, hysteresis correction of the piezoelectric element becomes easy. Hysteresis correction will be described in the third embodiment described later.

[0183] 4. Implementation Method 2

[0184] 4.1 Structure

[0185] The structure of the laser device of the second embodiment can be Figures 5 to 7 The structures of the excimer laser devices 11 shown are the same.

[0186] 4.2 Action

[0187] The laser device of the second embodiment is different from the first embodiment in the operation including the control executed by the processor 29. Next, the operation of the laser device of the second embodiment is described with respect to the differences from the first embodiment.

[0188] Fig.15This is a timing chart showing an example of the operation of the laser device according to the second embodiment. Fig.15 The upper section shows a waveform WLc2 of a wavelength instruction, the middle section shows a waveform PZc2 of a piezoelectric instruction given to the piezoelectric element, and the lower section shows a waveform SMc2 of a stepping motor instruction given to the stepping motor.

[0189] The waveform WLc2 of the wavelength command is a triangular wave, and within the period T, the wavelength command changes for each pulse. Fig.15 The waveform WLc2 shown is drawn as a straight line, but is actually a waveform in which the discrete command value for each pulse changes slightly in a step-like manner (steps for each pulse).

[0190] The waveform PZc2 of the piezoelectric command changes in a triangular wave shape in conjunction with the triangular wave wavelength command. Fig.10 same.

[0191] The processor 29 calculates the moving average of the piezoelectric command value for the interval that is an integer multiple of the wavelength command period (period T) of the triangular wave, and drives the stepping motor to correct the drift of the piezoelectric command when the moving average value PZmav of the piezoelectric command exceeds the threshold. Fig.15 In FIG. 1 , the piezoelectric command moving average value PZmav is shown by a dashed line graph.

[0192] exist Fig.15 At the timing indicated by the black dot in , the drive command for the stepping motor is changed, and the piezoelectric command is also changed accordingly. Fig.15 In the embodiment 1, an example is shown in which the stepping motor is driven at an integer multiple of the period T. However, the timing of driving the stepping motor to perform correction may not be an integer multiple of the period T, which is the same as the first embodiment. The control flowchart in the second embodiment may also be the same as the first embodiment. Figure 11 to Figure 14 same.

[0193] exist Fig.15 In FIG. 1 , an example of changing the wavelength command in a triangular wave shape is shown, but the waveform of the wavelength command that is periodically changed is not limited to a triangular wave, and may be a sine wave or the like. The "sine wave" here is the same as the example of the triangular wave, and is a waveform of discrete changes for each pulse. The wavelength command may also be changed in a sine wave shape for each pulse.

[0194] 4.3 Effects

[0195] As described in Implementation 2, when the wavelength instruction is changed periodically by a triangular wave, a sine wave, etc., the moving average of the piezoelectric instruction value is calculated within an interval of an integer multiple of the period, thereby correctly detecting and correcting the drift of the piezoelectric instruction caused by temperature changes, etc.

[0196] 5. Implementation Method 3

[0197] 5.1 Structure

[0198] The structure of the laser device of embodiment 3 can be Figures 5 to 7 The structures of the excimer laser devices 11 shown are the same.

[0199] 5.2 Action

[0200] The laser device of the third embodiment differs from the first embodiment in the operation including the control performed by the processor 29. The operation of the laser device of the third embodiment will be described below with respect to the difference from the first embodiment. The laser device of the third embodiment performs the hysteresis correction shown below in addition to the operation of the first embodiment.

[0201] Fig.16 This is a timing chart for hysteresis correction performed by the laser device according to the third embodiment. Fig.16 The upper part shows the waveform WLc3 of the wavelength instruction, the middle part shows the waveform PZc3 of the piezoelectric instruction given to the piezoelectric element, and the lower part shows an example of the measurement result of the wavelength error EWL, which represents the difference between the wavelength instruction and the center wavelength measured by the wavelength monitor 37.

[0202] The processor 29 measures in advance the error between the piezoelectric command value immediately after the wavelength is changed and the piezoelectric command value immediately before the wavelength is changed next time when the wavelength command is periodically changed with a rectangular wave, and calculates the correction value of the piezoelectric command. Then, when the wavelength command is changed with the same driving mode, the piezoelectric command is corrected using the correction value to control the wavelength.

[0203] Will be in Fig.16 The wavelength instruction interval of wavelength λ1 changed at the timing indicated by number [1] is referred to as the first instruction interval, and the wavelength instruction interval of wavelength λ2 changed at the timing indicated by number [2] is referred to as the second instruction interval. Similarly, the wavelength instruction intervals changed at the timings indicated by numbers [3] to [9] are referred to as the third instruction interval to the ninth instruction interval.

[0204] The error between the piezoelectric command value immediately after the wavelength change of the first command interval in which the wavelength command is changed at the timing of the wavelength change indicated by number [1] and the piezoelectric command value immediately before the wavelength change indicated by number [2] is equivalent to the difference between the piezoelectric command value immediately after the start of the first command interval and the piezoelectric command value immediately before the end of the first command interval. The processor 29 measures the error of the piezoelectric command value in the first command interval, obtains a correction value to be applied to the first command interval after the next time the piezoelectric command is changed in the same driving mode based on the measured error, and applies the correction value to correct the piezoelectric command in the first command interval after the next time.

[0205] Similarly, the error between the piezoelectric command value just after the start of the kth command interval in which the wavelength command is changed at the timing of the wavelength change shown by the number [k] and the piezoelectric command value just before the end is measured, and based on the measured error, a correction value applied to the kth command interval after the next time the wavelength command is changed with the same driving mode is calculated, and the correction value is applied to correct the piezoelectric command in the kth command interval after the next time.

[0206] The driving mode at the timing indicated by number [1] is a mode in which the command value at the neutral position is changed to the command value corresponding to the wavelength λ1. The driving mode at the timing indicated by number [2] is a mode in which the command value corresponding to the wavelength λ1 is changed to the command value corresponding to the wavelength λ2. The driving modes at the timings of numbers [4], [6], and [8] are the same as the driving mode of number [2]. The same correction value can also be applied to the second command interval, the fourth command interval, the sixth command interval, and the eighth command interval.

[0207] The driving mode at the timing indicated by numbers [3], [5], and [7] is a mode in which the command value corresponding to wavelength λ2 is changed to the command value corresponding to wavelength λ1. The same correction value can also be applied to the third command interval, the fifth command interval, and the seventh command interval. The driving mode at the timing indicated by number [9] is a mode in which the command value corresponding to wavelength λ2 is changed to the command value of the neutral position.

[0208] Furthermore, the correction value may be calculated using the piezoelectric coefficient instead of the piezoelectric command error, based on the wavelength error immediately after the wavelength is changed. Fig.16 The bottom section of FIG. 1 shows examples of wavelength errors measured in each of the first command section to the ninth command section.

[0209] The processor 29 may also be configured according to Fig.16The processor 29 may store the measured value of the center wavelength corresponding to the target wavelength of the p-th pulse in the first burst pulse BP1, and correct the piezoelectric instruction for the p-th pulse in the subsequent second burst pulse BP2 according to the difference between the stored target wavelength of the p-th pulse and the measured value. p is an integer greater than 1, indicating the pulse number in the burst pulse.

[0210] The first burst pulse BP1 may be a setup oscillation before performing exposure (main exposure) of the wafer WF, and the second burst pulse BP2 may be a main exposure oscillation.

[0211] exist Fig.16 In the example described above, a correction value is obtained based on an error measured in a previous section of the same driving pattern and used for correction in the next corresponding section. However, the same correction value after averaging may be used for the same driving pattern.

[0212] For example, correction values ​​may be obtained from a plurality of intervals corresponding to the same driving mode in advance, and the correction values ​​may be averaged. Alternatively, after the correction value calculation is completed, the correction value average processing may be always performed and the correction value may be updated, and the wavelength may be repeatedly changed.

[0213] 5.3 Control Example of Hysteresis Correction

[0214] Fig.17 is a flowchart showing a control example of hysteresis correction performed by the laser device of the third embodiment. Steps S31, S32 and S33 may also be Fig.11 The corresponding steps of steps S11, S12 and S13 are the same.

[0215] After step S33 , in step S34 , the processor 29 performs processing for storing the relationship between the piezoelectric command value and the correction value when the wavelength is changed.

[0216] Next, in step S35 , the processor 29 uses the stored correction value to correct the hysteresis of the piezoelectric element when the wavelength is changed.

[0217] After step S35, the processor 29 ends Fig.17 Flowchart of the process.

[0218] Fig.18 It is shown that it is applied to Fig.17 This is a flowchart of an example of a subroutine of step S34. Fig.18 Steps S314, S315, S316, S317 and S318 may also be Fig.11The corresponding steps of steps S14, S15, S16, S17 and S18 are the same.

[0219] After step S318, in step S319, the processor 29 calculates the piezoelectric command value when the wavelength is changed and records the hysteresis correction value of the piezoelectric element.

[0220] Steps S320, S321, S322 and S323 after step S319 may also be performed with Fig.11 The corresponding steps of steps S20, S21, S22 and S23 are the same. If the determination result of step S323 is "no", the processor 29 returns to step S317. On the other hand, if the determination result of step S323 is "yes", the processor 29 ends. Fig.18 Flowchart of Fig.17 The main process.

[0221] Fig.19 It is shown that it is applied to Fig.18 Flowchart of an example of a subroutine of step S319. In step S341, the processor 29 calculates the correction value Vcn of the pulse number n based on the difference between the piezoelectric command value at the previous wavelength change and the current piezoelectric command value.

[0222] Next, in step S342, the processor 29 stores the pulse number n and its correction value Vcn in association with each other.

[0223] Next, in step S343, the processor 29 determines whether the pulse number n is greater than the number of N gap pulses N representing one cycle T. SL , that is, whether n>N SL If the result of the determination in step S343 is a "yes" determination, the processor 29 proceeds to step S346.

[0224] In step S346, processor 29 initializes pulse number n and sets it to n = 1. After step S346, processor 29 proceeds to step S347.

[0225] On the other hand, when the determination result of step S345 is a "No" determination, the processor 29 proceeds to step S347.

[0226] In step S347, the processor 29 sets the voltage calculation value Vn of pulse number n as the piezoelectric command value. After step S347, the processor 29 ends Fig.19 Flowchart of Fig.18 Flowchart of the process.

[0227] Fig. 20 It is shown that it is applied to Fig.17This is a flowchart of an example of a subroutine of step S35. Fig. 20 Steps S354, S355, S356, S357 and S358 may also be Fig.11 The corresponding steps of steps S14, S15, S16, S17 and S18 are the same.

[0228] After step S358, in step S359, the processor 29 performs hysteresis correction of the piezoelectric element and calculation of the piezoelectric command value when the wavelength is changed.

[0229] Steps S360, S361, S362 and S363 after step S359 may also be performed with Fig.11 The corresponding steps of steps S20, S21, S22 and S23 are the same. If the determination result of step S363 is "no", the processor 29 returns to step S357. On the other hand, if the determination result of step S363 is "yes", the processor 29 ends. Fig. 20 Flowchart of Fig.17 The main process.

[0230] Fig.21 It is shown that it is applied to Fig. 20 Flowchart of an example of a subroutine of step S359 of FIG. 1. In step S391, the processor 29 increments the pulse number n and updates the pulse number so that the value of n+1 is newly set as the value of the pulse number n.

[0231] Next, in step S392 , the processor 29 determines whether the pulse number n exceeds the number of pulses in one cycle T.

[0232] When the result of determination in step S392 is "NO", processor 29 proceeds to step S394. In step S394, processor 29 sets correction value Vcn of pulse number n as the piezoelectric command value.

[0233] On the other hand, if the result of determination in step S392 is "Yes", processor 29 proceeds to step S393. In step S393, processor 29 initializes pulse number n to n = 1. After step S393, processor 29 proceeds to step S394.

[0234] After step S394, processor 29 ends Fig.21 Flowchart of Fig. 20 Flowchart of the process.

[0235] 5.4 Example of a series of control actions including oscillation adjustment and main exposure adjustment

[0236] Fig. 22This is a flowchart showing a control example of a series of operations including oscillation adjustment and main exposure in the laser device according to the third embodiment.

[0237] In step S51 , the processor 29 performs adjustment oscillation at the center wavelength.

[0238] Next, in step S52 , the processor 29 performs adjustment oscillation for checking the hysteresis of the piezoelectric element.

[0239] Next, in step S53 , the processor 29 performs main exposure oscillation.

[0240] Next, in step S54, the processor 29 determines whether to end the main exposure. If the determination result of step S54 is "No", the processor 29 returns to step S53. On the other hand, if the determination result of step S54 is "Yes", the processor 29 ends the main exposure. Fig. 22 Flowchart of the process.

[0241] Fig.23 It is shown that it is applied to Fig. 22 This is a flowchart of an example of a subroutine of step S51.

[0242] In step S511 , processor 29 receives data of the central wavelength from exposure device 25 .

[0243] Next, in step S512, the processor 29 performs laser oscillation.

[0244] Then, in step S513 , the processor 29 drives the stepping motor to thereby perform coarse adjustment of the wavelength.

[0245] Next, in step S514, the processor 29 determines whether the wavelength deviation between the measured wavelength and the designated center wavelength is within a threshold value. The threshold value here is a determination reference value that specifies the permissible range of the wavelength deviation. If the determination result of step S514 is "no", the processor 29 returns to step S512 and drives the stepping motor in step S513 to adjust the output wavelength.

[0246] If the result of determination in step S514 is "yes", the processor 29 proceeds to step S515. In step S515, the processor 29 performs laser oscillation.

[0247] Next, in step S516, the processor 29 drives the piezoelectric element to thereby perform fine control of the wavelength.

[0248] Next, in step S517, the processor 29 determines whether the wavelength performance satisfies the requested standard. If the determination result of step S517 is "No", the processor 29 returns to step S515. On the other hand, if the determination result of step S517 is "Yes", the processor 29 ends the process. Fig.23 Flowchart of Fig. 22 The main process.

[0249] Fig.24 It is shown that it is applied to Fig. 22 This is a flowchart of an example of a subroutine of step S52.

[0250] In step S521 , processor 29 sets a threshold value of the piezoelectric command value.

[0251] Next, in step S522, the processor 29 receives the N gap pulse number N from the exposure device 25. SL and wavelength amplitude information.

[0252] Next, in step S523, the processor 29 calculates the wavelength instruction value for one cycle. The subroutine applied to step S523 may also be the same as Fig.12 The flowchart is the same as

[0253] Next, in step S524, the processor 29 performs processing to store the relationship between the piezoelectric command value and the correction value when the wavelength is changed. The subroutine applied to step S524 may also be the same as Fig.18 The flowchart is the same as

[0254] After step S524, the processor 29 ends Fig.24 Flowchart of Fig. 22 The main process.

[0255] Fig.25 It is shown that it is applied to Fig. 22 This is a flowchart of an example of a subroutine of step S53.

[0256] In step S532, the processor 29 receives the N gap pulse number N from the exposure device 25. SL and wavelength amplitude information.

[0257] Next, in step S533, the processor 29 calculates the wavelength instruction value for one cycle. The subroutine applied to step S533 may also be the same as Fig.12 The flowchart is the same as

[0258] Next, in step S534, the processor 29 performs a process of correcting the hysteresis of the piezoelectric element when the wavelength is changed using the stored correction value. The subroutine applied to step S534 may also be used in conjunction with Fig. 20 The flowchart is the same as

[0259] After step S534, processor 29 ends Fig.25 Flowchart of Fig. 22 The main process.

[0260] 5.5 Effect

[0261] According to Embodiment 3, when the wavelength instruction is periodically changed, the wavelength error caused by the hysteresis of the piezoelectric element can also be corrected. In addition, when the correction value used in the hysteresis correction is obtained, the averaging process is repeatedly performed, thereby, when the hysteresis characteristics of the piezoelectric element change over time, it is also possible to appropriately correct it.

[0262] 6. Implementation Method 4

[0263] 6.1 Structure

[0264] Fig.26 The structure of the laser device 110 according to the fourth embodiment is schematically shown. Fig.26 The structure shown is Figure 5 The laser device 110 is an ArF excimer laser device, which replaces Figure 5 The narrowing unit 30 shown in the figure has a narrowing unit 30D. The narrowing unit 30D includes a first prism 32A, a second prism 32B, a third prism 32C, a fourth prism 32D, and a grating 33.

[0265] The third prism 32C has a wavelength control mechanism based on the coarse motion drive of the stepping motor unit 40 and a wavelength control mechanism based on the fine motion drive of the piezoelectric element unit 41. That is, the difference is that in the first to third embodiments, the wavelength is controlled by driving the wavelength selective mirror 34, whereas in the fourth embodiment, the wavelength is controlled by driving the third prism 32C. The third prism 32C is fixed to the rotating table 73, and the rotating table 73 is rotated by driving at least one of the stepping motor unit 40 and the piezoelectric element unit 41, so that the third prism 32C rotates. The third prism 32C rotates, thereby changing the incident angle of the pulse laser incident on the grating 33.

[0266] 6.2 Action

[0267] In the fourth embodiment, the third prism 32C is driven in place of the wavelength selective mirror 34 described in the first embodiment. Other operations may be the same as those in the first to third embodiments.

[0268] 6.3 Effects

[0269] The laser device 110 of the fourth embodiment can achieve the same effects as those of the first to third embodiments.

[0270] 7. Implementation Method 5

[0271] 7.1 Structure

[0272] Fig. 27 The structure of the bandwidth narrowing unit 30E used in the laser device 111 according to the fifth embodiment is schematically shown. Fig. 27 The structure not shown in FIG can also be used with Fig.26 Same. About Fig. 27 The structure shown is Fig.26 The differences are explained. Fig.26 In the embodiment, the stepping motor unit 40 and the piezoelectric element unit 41 are configured to drive the third prism 32C to rotate together. However, the optical element that is coarsely moved by the stepping motor unit and the optical element that is finely moved by the piezoelectric element unit may be different.

[0273] The laser device 111 of the fifth embodiment replaces Fig.26 The narrowbanding unit 30D shown in the figure has a narrowbanding unit 30E. The narrowbanding unit 30E replaces Fig.26 The fourth prism 32D includes a reflecting mirror 34E, and a rotating table 74 supporting the reflecting mirror 34E is driven by the piezoelectric element unit 41E.

[0274] exist Fig. 27 , an example of a structure in which the third prism 32C is roughly moved by the stepping motor unit 40E and the reflector 34E is finely moved by the piezoelectric element unit 41E is shown. Fig. 27 The piezoelectric element unit 41E and the stepping motor unit 40E shown in the figure make the third prism 32C perform fine movement by the piezoelectric element unit 41E, and make the reflector 34E perform coarse movement by the stepping motor unit 40E. When comparing the reflector 34E and the third prism 32C, even if they are rotated by the same angle, the reflector 34E can greatly change the path of the pulse laser. Therefore, the optical element driven by the piezoelectric element is preferably set to a reflector with excellent response performance.

[0275] 7.2 Action

[0276] In the fifth embodiment, the piezoelectric element unit 41E is used to finely move the reflection mirror 34E, and the stepping motor unit 40E is used to coarsely move the third prism 32C. Other operations may be the same as those of the first to fourth embodiments.

[0277] The third prism 32C is an example of the “first optical element” in the present disclosure, and the rotating table 73 is an example of the “first rotating table” in the present disclosure. The reflector 34E is an example of the “second optical element” in the present disclosure, and the rotating table 74 is an example of the “second rotating table” in the present disclosure. The stepping motor unit 40E is an example of the “first driving mechanism” in the present disclosure, and the piezoelectric element unit 41E is an example of the “second driving mechanism” in the present disclosure.

[0278] 7.3 Effects

[0279] The laser device 111 of the fifth embodiment can achieve the same effects as those of the first to fourth embodiments.

[0280] 8. About the manufacturing method of electronic devices

[0281] Fig.28 The structure example of the exposure device 25 is schematically shown. The exposure device 25 includes an illumination optical system 250 and a projection optical system 251. The illumination optical system 250 illuminates the mask pattern of the mask (not shown) arranged on the mask stage RT by the laser light incident from the laser system 11A. The projection optical system 251 performs reduced projection of the laser light transmitted through the mask so as to form an image on the workpiece (not shown) arranged on the workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a photoresist.

[0282] The exposure device 25 moves the mask stage RT and the work stage WT synchronously and in parallel, thereby exposing the workpiece to the laser reflecting the mask pattern. After the mask pattern is transferred to the semiconductor wafer through the above exposure process, a semiconductor device can be manufactured through multiple processes. The semiconductor device is an example of an "electronic device" in the present disclosure.

[0283] The laser system 11A may include the laser device described in the first, second, or third embodiment, or may include the laser device 110 or 111 described in the fourth or fifth embodiment.

[0284] 9. Others

[0285] The above description is not limiting but simply illustrative. Therefore, those skilled in the art will appreciate that changes can be made to the embodiments of the present disclosure without departing from the claims. In addition, those skilled in the art will appreciate that the embodiments of the present disclosure can be used in combination.

[0286] Unless explicitly stated otherwise, the terms used in this specification and claims as a whole should be interpreted as "non-limiting" terms. For example, terms such as "including", "having", "having", and "having" should be interpreted as "excluding the existence of structural elements other than the structural elements to be recorded". In addition, the modifier "one" should be interpreted as meaning "at least one" or "one or more". In addition, terms such as "at least one of A, B, and C" should be interpreted as "A", "B", "C", "A+B", "A+C", "B+C", or "A+B+C". Furthermore, it should be interpreted as also including combinations of them and parts other than "A", "B", and "C".

Claims

1. A laser device, comprising: an oscillator, which outputs a pulsed laser; An optical element, which is arranged on the optical path of the pulse laser; a rotating stage supporting the optical element; a grating configured to return diffracted light having a wavelength corresponding to an incident angle of the pulsed laser light to the oscillator when the pulsed laser light is incident through the optical element; a first driving mechanism that drives the rotating stage to rotate the optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; a second driving mechanism that drives the rotating table with a smaller driving amount than the first driving mechanism to rotate the optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; A wavelength monitor that measures the central wavelength of the pulsed laser; as well as a processor that periodically changes the target wavelength of the pulsed laser, and outputs a drive instruction to the second drive mechanism to change the incident angle according to the target wavelength and the measured value of the wavelength monitor, thereby controlling the center wavelength to the target wavelength, The processor calculates a moving average of the drive instruction values ​​of the second drive mechanism within an interval that is an integer multiple of a wavelength instruction cycle, and when the calculated moving average exceeds a threshold value, returns the second drive mechanism to an initial position, and offsets the change in the incident angle caused by returning the second drive mechanism to the initial position by driving the first drive mechanism. The wavelength instruction cycle is a cycle for periodically changing the target wavelength.

2. The laser device according to claim 1, wherein: The first driving mechanism includes a stepping motor, The second driving mechanism includes a piezoelectric element.

3. The laser device according to claim 1, wherein: The period for calculating the moving average is one cycle of the wavelength instruction cycle.

4. The laser device according to claim 1, wherein: The wavelength command period is the number of pulses irradiated to the same portion when the pulse laser is irradiated by scanning exposure.

5. The laser device according to claim 1, wherein: The processor changes, in a rectangular wave shape, a wavelength command for continuously providing a plurality of pulses for setting the target wavelength to a first wavelength and a wavelength command for continuously providing a plurality of pulses for setting the target wavelength to a second wavelength.

6. The laser device according to claim 1, wherein: The processor changes the target wavelength in a triangular wave or a sine wave for each pulse.

7. The laser device according to claim 1, wherein: The thresholds include a first threshold that specifies a lower limit and a second threshold that specifies an upper limit, When the moving average is lower than the first threshold value or when the moving average is higher than the second threshold value, the processor determines that the moving average exceeds the threshold value.

8. The laser device according to claim 1, wherein: The initial position is a position at 1 / 2 of the full stroke of the second driving mechanism.

9. The laser device according to claim 1, wherein: The processor calculates a correction value of the drive command of the second drive mechanism based on a difference between the drive command value of the second drive mechanism at each time point immediately after the wavelength is changed and immediately before the next wavelength change. When the wavelength is changed in the same driving mode as the driving mode of the wavelength change in which the correction value is calculated, the drive command of the second drive mechanism is corrected using the correction value.

10. The laser device according to claim 1, wherein: When p is an integer greater than or equal to 1, the processor stores the measured value corresponding to the target wavelength of the p-th pulse in the first burst pulse, The processor corrects a drive instruction of the second drive mechanism for the p-th pulse in a subsequent second burst pulse based on the stored relationship between the target wavelength of the p-th pulse and the measured value.

11. A method for manufacturing an electronic device, comprising the following steps: The laser is generated by a laser device, outputting the laser to an exposure device, exposing the laser on a photosensitive substrate in the exposure device to manufacture an electronic device, The laser device has: an oscillator, which outputs a pulsed laser; An optical element, which is arranged on the optical path of the pulse laser; a rotating stage supporting the optical element; a grating configured to return diffracted light having a wavelength corresponding to an incident angle of the pulsed laser light to the oscillator when the pulsed laser light is incident through the optical element; a first driving mechanism that drives the rotating stage to rotate the optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; a second driving mechanism that drives the rotating table with a smaller driving amount than the first driving mechanism to rotate the optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; A wavelength monitor that measures the central wavelength of the pulsed laser; as well as a processor that periodically changes the target wavelength of the pulsed laser, and outputs a drive instruction to the second drive mechanism to change the incident angle according to the target wavelength and the measured value of the wavelength monitor, thereby controlling the center wavelength to the target wavelength, The processor calculates a moving average of the drive instruction values ​​of the second drive mechanism within an interval that is an integer multiple of a wavelength instruction cycle, and when the calculated moving average exceeds a threshold value, returns the second drive mechanism to an initial position, and offsets the change in the incident angle caused by returning the second drive mechanism to the initial position by driving the first drive mechanism. The wavelength instruction cycle is a cycle for periodically changing the target wavelength.

12. A laser device, comprising: an oscillator, which outputs a pulsed laser; a first optical element disposed on an optical path of the pulsed laser; a first rotating stage supporting the first optical element; a second optical element disposed on an optical path of the pulsed laser; a second rotating stage supporting the second optical element; a grating configured to allow the pulse laser to be incident via the first optical element and the second optical element and to return diffracted light of a wavelength corresponding to an incident angle of the pulse laser to the oscillator; a first driving mechanism that drives the first rotating stage to rotate the first optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; a second driving mechanism that drives the second rotating table with a smaller driving amount than the first driving mechanism to rotate the second optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; A wavelength monitor that measures the central wavelength of the pulsed laser; as well as a processor that periodically changes the target wavelength of the pulsed laser, and outputs a drive instruction to the second drive mechanism to change the incident angle according to the target wavelength and the measured value of the wavelength monitor, thereby controlling the center wavelength to the target wavelength, The processor calculates a moving average of the drive instruction values ​​of the second drive mechanism within an interval that is an integer multiple of a wavelength instruction cycle, and when the calculated moving average exceeds a threshold value, returns the second drive mechanism to an initial position, and offsets the change in the incident angle caused by returning the second drive mechanism to the initial position by driving the first drive mechanism. The wavelength instruction cycle is a cycle for periodically changing the target wavelength.

13. The laser device according to claim 12, wherein: One of the first optical element and the second optical element is a reflecting mirror, and the other is a prism.

14. The laser device according to claim 12, wherein: The first driving mechanism includes a stepping motor, The second driving mechanism includes a piezoelectric element.

15. The laser device according to claim 12, wherein: The period for calculating the moving average is one cycle of the wavelength instruction cycle.

16. The laser device according to claim 12, wherein: The processor changes, in a rectangular wave shape, a wavelength command for continuously providing a plurality of pulses for setting the target wavelength to a first wavelength and a wavelength command for continuously providing a plurality of pulses for setting the target wavelength to a second wavelength.

17. The laser device according to claim 12, wherein: The processor changes the target wavelength in a triangular wave or a sine wave for each pulse.

18. The laser device according to claim 12, wherein: The processor calculates a correction value of the drive command of the second drive mechanism based on a difference between the drive command value of the second drive mechanism at each time point immediately after the wavelength is changed and immediately before the next wavelength change. When the wavelength is changed in the same driving mode as the driving mode of the wavelength change in which the correction value is calculated, the drive command of the second drive mechanism is corrected using the correction value.

19. The laser device according to claim 12, wherein: When p is an integer greater than or equal to 1, the processor stores the measured value corresponding to the target wavelength of the p-th pulse in the first burst pulse, The processor corrects a drive instruction of the second drive mechanism for the p-th pulse in a subsequent second burst pulse based on the stored relationship between the target wavelength of the p-th pulse and the measured value.

20. A method for manufacturing an electronic device, comprising the following steps: The laser is generated by a laser device, outputting the laser to an exposure device, exposing the laser on a photosensitive substrate in the exposure device to manufacture an electronic device, The laser device has: an oscillator, which outputs a pulsed laser; a first optical element disposed on an optical path of the pulsed laser; a first rotating stage supporting the first optical element; a second optical element disposed on an optical path of the pulsed laser; a second rotating stage supporting the second optical element; a grating configured to allow the pulse laser to be incident via the first optical element and the second optical element, and to return diffracted light of a wavelength corresponding to an incident angle of the pulse laser to the oscillator; a first driving mechanism that drives the first rotating stage to rotate the first optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; a second driving mechanism that drives the second rotating table with a smaller driving amount than the first driving mechanism to rotate the second optical element, thereby changing an incident angle of the pulsed laser beam incident on the grating; A wavelength monitor that measures the central wavelength of the pulsed laser; as well as a processor that periodically changes the target wavelength of the pulsed laser, and outputs a drive instruction to the second drive mechanism to change the incident angle according to the target wavelength and the measured value of the wavelength monitor, thereby controlling the center wavelength to the target wavelength, The processor calculates a moving average of the drive instruction values ​​of the second drive mechanism within an interval that is an integer multiple of a wavelength instruction cycle, and when the calculated moving average exceeds a threshold value, returns the second drive mechanism to an initial position, and offsets the change in the incident angle caused by returning the second drive mechanism to the initial position by driving the first drive mechanism. The wavelength instruction cycle is a cycle for periodically changing the target wavelength.

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