Control method for discharge-excited laser device, discharge-excited laser device, and method for manufacturing electronic device

Abstract

A control method for a discharge excitation type laser device according to the present invention provided with a power supply that controls pulse energy of a pulsed laser light, the method including: in a first period, outputting pulsed laser light that includes a plurality of pulses from a discharge excitation type laser device while periodically varying the wavelength; calculating correction data that corrects a voltage command value set by the power supply according to the variation in wavelength using first time series data of the pulse energy of the plurality of pulses; and in a second period, acquiring the voltage command value, correcting the acquired voltage command value using the correction data, and outputting pulsed laser light from the discharge excitation type laser device according to the corrected voltage command value.

Description

Technical Field

[0001] The present disclosure relates to a method for controlling a discharge-excited laser device, a discharge-excited laser device, and a method for manufacturing an electronic device.

Background Art

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

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] In one aspect of the present disclosure, a control method for a discharge-excited laser device including a power supply for controlling the pulse energy of a pulsed laser beam includes, in a first period, outputting a pulsed laser beam including a plurality of pulses from the discharge-excited laser device while periodically varying the wavelength, calculating correction data for correcting a voltage command value set for the power supply in accordance with the variation in wavelength using first time-series data of the pulse energy of the plurality of pulses, and in a second period, acquiring the voltage command value, correcting the acquired voltage command value using the correction data, and outputting a pulsed laser beam from the discharge-excited laser device in accordance with the corrected voltage command value.

[0006] In one aspect of the present disclosure, a discharge-excited laser device includes a power supply for controlling the pulse energy of a pulsed laser beam and a processor for controlling the power supply. The processor outputs a pulsed laser beam including a plurality of pulses from the discharge-excited laser device while periodically varying the wavelength in a first period, calculates correction data for correcting a voltage command value set for the power supply in accordance with the variation in wavelength using first time-series data of the pulse energy of the plurality of pulses, acquires the voltage command value in a second period, corrects the acquired voltage command value using the correction data, and outputs a pulsed laser beam from the discharge-excited laser device in accordance with the corrected voltage command value.

[0007] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating pulsed laser light by a discharge-excited laser device including a power source that controls the pulse energy of the pulsed laser light and a processor that controls the power source, outputting the pulsed laser light to an exposure device, and exposing the pulsed laser light onto a photosensitive substrate in the exposure device to manufacture the electronic device. The processor outputs pulsed laser light including a plurality of pulses from the discharge-excited laser device while periodically varying the wavelength in a first period, calculates correction data for correcting a voltage command value set in the power source in accordance with the variation of the wavelength using first time-series data of the pulse energy of the plurality of pulses, acquires the voltage command value in a second period, corrects the acquired voltage command value using the correction data, and outputs pulsed laser light from the discharge-excited laser device in accordance with the corrected voltage command value.

Brief Description of the Drawings

[0008] Some embodiments of the present disclosure will be described below by way of example only with reference to the accompanying drawings.

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[0009] <Content> 1. Comparative Example 1.1 Exposure System 1.1.1 Configuration 1.1.2 Operation 1.2 Laser Device 100 1.2.1 Configuration 1.2.2 Operation 1.3 Narrowbanding Module 14 1.3.1 Configuration 1.3.2 Operation 1.4 Step-and-Scan Exposure 1.5 Example of Periodic Wavelength Change 1.6 Output Control of Pulsed Laser Light 1.6.1 Control by Laser Control Processor 130 1.6.2 Laser Control by Exposure Control Processor 210 1.7 Problems of the Comparative Example 2. Laser Device for Calculating Correction Data Using Time-Series Data of Pulse Energy En[ ] 2.1 Configuration 2.2 Control Block Diagram 2.3 Output Control of Pulsed Laser Light 2.4 Update Timing of Voltage Correction Table 134 2.5 Update Process of Voltage Correction Table 134 2.6 Operation 3. Laser Device for Calculating Correction Data by Further Using Time-Series Data of Voltage Command Value HVc[] 3.1 Update Process of Voltage Correction Table 134 3.2 Operation 4. Laser Device for Calculating Correction Data by Performing Fourier Transform on Time-Series Data of Pulse Energy En[] 4.1 Update Process of Voltage Correction Table 134 4.2 Operation 5. Laser Device for Calculating Correction Data by Performing Fourier Transform on Time-Series Data of Voltage Command Value HVc[] 5.1 Update Process of Voltage Correction Table 134 5.2 Operation 6. Laser Device for Calculating Correction Data for Each Pulse Number j within Wavelength Fluctuation Period 6.1 Update Process of Voltage Correction Table 134 6.2 Operation 7. Laser Device for Setting Voltage Command Value HVc Based on Target Pulse Energy Et 7.1 Control by Laser Control Processor 130 7.2 Control by Exposure Control Processor 210 8. Others 8.1 Configuration of Monitor Module 17 8.2 Operation of Monitor Module 17 8.3 Supplementary Explanation

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

[0011] 1. Comparative Example 1.1 Exposure System FIG. 1 schematically shows the configuration of the exposure system in the comparative example. The comparative example of the present disclosure is a form that the applicant recognizes as being known only to the applicant and is not a known example recognized by the applicant. The exposure system includes a laser device 100 and an exposure device 200. In FIG. 1, the laser device 100 is shown in a simplified manner.

[0012] The laser device 100 includes a laser control processor 130. The laser control processor 130 is a processing device including a memory 132 in which a control program is stored and a CPU (central processing unit) 131 that executes the control program. The laser control processor 130 is specially configured or programmed to execute various processes included in the present disclosure. The laser control processor 130 corresponds to the processor in the present disclosure. The laser device 100 is configured to output pulsed laser light toward the exposure device 200.

[0013] 1.1.1 Configuration As shown in FIG. 1, the exposure device 200 includes an illumination optical system 201, a projection optical system 202, and an exposure control processor 210.

[0014] The illumination optical system 201 illuminates a reticle pattern (not shown) of a reticle disposed on the reticle stage RT with pulsed laser light incident from the laser device 100. The projection optical system 202 reduces and projects the pulsed laser light transmitted through the reticle and forms an image on a workpiece (not shown) disposed on the workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a resist film.

[0015] The exposure control processor 210 is a processing device including a memory 212 in which a control program is stored and a CPU 211 that executes the control program. The exposure control processor 210 is specially configured or programmed to execute various processes included in the present disclosure. The exposure control processor 210 overall controls the exposure device 200.

[0016] 1.1.2 Operation The exposure control processor 210 transmits various parameters including the target wavelengths λ1 and λ2 and the voltage command value HVc, and the trigger signal, to the laser control processor 130. The laser control processor 130 controls the laser device 100 according to these parameters and signals. The target wavelengths λ1 and λ2 are target values of wavelengths. The target wavelength λ1 corresponds to the first target wavelength in the present disclosure, and the target wavelength λ2 corresponds to the second target wavelength in the present disclosure. The target wavelength λ1 is set to be a wavelength larger than the target wavelength λ2.

[0017] The exposure control processor 210 synchronizes the reticle stage RT and the workpiece table WT and moves them in parallel in opposite directions to each other. As a result, the workpiece is exposed with pulsed laser light reflecting the reticle pattern. Through such an exposure process, the reticle pattern is transferred onto the semiconductor wafer. Thereafter, an electronic device can be manufactured through a plurality of processes.

[0018] 1.2 Laser Device 100 1.2.1 Configuration FIG. 2 schematically shows the configuration of the laser device 100 in the comparative example. In FIG. 2, illustrations of some elements included in the exposure device 200 are omitted.

[0019] The laser device 100 is a discharge-excited type laser device. In addition to the laser control processor 130, it includes a laser chamber 10, a charger 12, a pulse power module (PPM) 13, a narrowbanding module 14, an output coupling mirror 15, and a monitor module 17. The narrowbanding module 14 and the output coupling mirror 15 constitute an optical resonator.

[0020] The laser chamber 10 is arranged in the optical path of the optical resonator. Windows 10a and 10b are provided in the laser chamber 10. The laser chamber 10 includes discharge electrodes 11a and a discharge electrode (not shown) that pairs with it inside. The discharge electrode (not shown) is positioned so as to overlap with the discharge electrode 11a in the direction perpendicular to the plane of FIG. 2. The laser chamber 10 is filled with a laser gas containing, for example, argon gas or krypton gas as a rare gas, fluorine gas as a halogen gas, neon gas as a buffer gas, and the like.

[0021] The charger 12 holds electrical energy for supplying to the pulse power module 13. The pulse power module 13 includes a charging capacitor and a switch (not shown). The charger 12 is connected to the charging capacitor. The charging capacitor is connected to the discharge electrode 11a. The charger 12 and the pulse power module 13 constitute the power source in the present disclosure.

[0022] The narrowbanding module 14 includes prisms 41 to 43, a grating 53, and a mirror 63. Details of the narrowbanding module 14 will be described later. The output coupling mirror 15 is composed of a partial reflection mirror.

[0023] A beam splitter 16 that transmits a part of the pulsed laser light with a high transmittance and reflects the other part is disposed in the optical path of the pulsed laser light output from the output coupling mirror 15. A monitor module 17 is disposed in the optical path of the pulsed laser light reflected by the beam splitter 16. Details of the configuration of the monitor module 17 will be described later with reference to FIG. 26.

[0024] 1.2.2 Operation The laser control processor 130 acquires various parameters including the target wavelengths λ1 and λ2 and the voltage command value HVc from the exposure control processor 210. The laser control processor 130 transmits a control signal to the narrowbanding module 14 based on the target wavelengths λ1 and λ2. The laser control processor 130 sets the acquired voltage command value HVc to the charger 12.

[0025] The laser control processor 130 receives a trigger signal from the exposure control processor 210. The laser control processor 130 transmits an oscillation trigger signal based on the trigger signal to the pulse power module 13. The switch included in the pulse power module 13 becomes on when it receives the oscillation trigger signal from the laser control processor 130. When the switch of the pulse power module 13 becomes on, the pulse power module 13 generates a pulsed high voltage from the electrical energy charged in the charger 12 and applies this high voltage to the discharge electrode 11a.

[0026] When a high voltage is applied to the discharge electrode 11a, discharge occurs in the discharge space between the discharge electrode 11a and a discharge electrode (not shown). Due to the energy of this discharge, the laser gas in the laser chamber 10 is excited and transitions to a high energy level. When the excited laser gas then transitions to a low energy level, it emits light with a wavelength corresponding to the energy level difference.

[0027] The light generated in the laser chamber 10 exits the laser chamber 10 through the windows 10a and 10b. The light exiting from the window 10a enters the narrowbanding module 14. Light near the desired wavelength among the light entering the narrowbanding module 14 is folded back by the narrowbanding module 14 and returned to the laser chamber 10.

[0028] The output coupling mirror 15 transmits a part of the light exiting from the window 10b and outputs it as pulsed laser light, and reflects the other part and returns it to the laser chamber 10.

[0029] In this way, the light emitted from the laser chamber 10 reciprocates between the narrowbanding module 14 and the output coupling mirror 15. Each time this light passes through the discharge space in the laser chamber 10, it is amplified. Also, each time this light is reflected by the narrowbanding module 14, it is narrowed, and becomes light having a sharp wavelength distribution centered on a part of the range of the selected wavelength by the narrowbanding module 14. Thus, the laser-oscillated and narrowed light is output as pulsed laser light from the output coupling mirror 15. Unless otherwise specified, the wavelength of the pulsed laser light refers to the central wavelength.

[0030] The monitor module 17 measures the wavelength of the pulsed laser light and transmits the measured wavelength to the laser control processor 130. The laser control processor 130 controls the narrowbanding module 14 based on the measured wavelength.

[0031] The pulsed laser light transmitted through the beam splitter 16 is incident on the exposure apparatus 200. The energy monitor 220 included in the exposure apparatus 200 measures the pulse energy En of the pulsed laser light. Based on the pulse energy En and the target pulse energy Et, the exposure control processor 210 calculates a voltage command value HVc and transmits it to the laser control processor 130. The pulse energy En of the pulsed laser light is controlled by the voltage command value HVc.

[0032] 1.3 Narrowbanding Module 14 1.3.1 Configuration The prisms 41, 42, and 43 are arranged in this order in the optical path of the light beam emitted from the window 10a. The prisms 41 to 43 are arranged such that the surfaces of the prisms 41 to 43 where the light beam enters and exits are all parallel to the V axis, and are each supported by a holder (not shown). The prism 43 is rotatable about an axis parallel to the V axis by a rotation stage 143. Examples of the rotation stage 143 include a rotation stage with a large movable range equipped with a stepping motor.

[0033] Mirror 63 is disposed in the optical path of the light beam that has passed through prisms 41 to 43. Mirror 63 is arranged such that the surface reflecting the light beam is parallel to the V-axis, and is rotatable about an axis parallel to the V-axis by a rotary stage 163. As an example of the rotary stage 163, a highly responsive rotary stage equipped with a piezo element can be mentioned.

[0034] Alternatively, prism 42 can be made rotatable by a rotary stage 143, prism 43 can be made rotatable by a rotary stage 163, and mirror 63 may not need to be rotated.

[0035] Grating 53 is disposed in the optical path of the light beam reflected by mirror 63. The direction of the grooves of grating 53 is parallel to the V-axis. Grating 53 is supported by a holder (not shown).

[0036] 1.3.2 Operation The light beam emitted from window 10a has its traveling direction changed by each of prisms 41 to 43 within a plane parallel to the HZ plane, which is a plane perpendicular to the V-axis, and the beam width is expanded within a plane parallel to the HZ plane. The light beam that has passed through prisms 41 to 43 is reflected by mirror 63 and enters grating 53.

[0037] The light beam incident on grating 53 is reflected by a plurality of grooves of grating 53 and diffracted in a direction corresponding to the wavelength of the light. Grating 53 is arranged in a retroreflective configuration such that the angle of incidence of the light beam incident on grating 53 from mirror 63 coincides with the diffraction angle of the diffracted light of the desired wavelength.

[0038] Mirror 63 reflects the light returned from grating 53 toward prism 43. Prisms 41 to 43 reduce the beam width of the light reflected by mirror 63 within a plane parallel to the HZ plane and return the light back into the laser chamber 10 through window 10a.

[0039] The laser control processor 130 controls the rotation stages 143 and 163 via a driver (not shown). According to the rotation angles of the rotation stages 143 and 163, the incident angle of the light beam incident on the grating 53 changes, and the wavelength selected by the narrowbanding module 14 changes. The rotation stage 143 is mainly used for coarse adjustment, and the rotation stage 163 is mainly used for fine adjustment.

[0040] The laser control processor 130 controls the rotation stage 163 based on the target wavelengths λ1 and λ2 received from the exposure control processor 210 so that the attitude of the mirror 63 changes periodically for each of a plurality of pulses. Thereby, the wavelength of the pulsed laser light changes periodically for each of a plurality of pulses. In this way, the laser device 100 can perform two-wavelength oscillation or multi-wavelength oscillation.

[0041] The focal length in the exposure apparatus 200 depends on the wavelength of the pulsed laser light. Since the pulsed laser light that has undergone two-wavelength oscillation or multi-wavelength oscillation and is incident on the exposure apparatus 200 can be imaged at a plurality of different positions in the direction of the optical axis of the pulsed laser light, the depth of focus can be substantially increased. For example, even when exposing a resist film with a large film thickness, the imaging performance in the thickness direction of the resist film can be maintained.

[0042] 1.4 Step and Scan Exposure Figure 3 shows an example of a semiconductor wafer WF#1 exposed by an exposure system. The semiconductor wafer WF#1 is, for example, a plate of single-crystalline silicon having a substantially disk shape. A photosensitive resist film is applied to the semiconductor wafer WF#1, for example. The exposure of the semiconductor wafer WF#1 is performed for each section such as scan fields SF#1, SF#2, etc. Each of the scan fields SF#1, SF#2 corresponds to a region where the reticle pattern of one reticle is transferred. The semiconductor wafer WF#1 is moved so that the scan field SF#1 is irradiated with pulsed laser light to expose the scan field SF#1. Thereafter, the semiconductor wafer WF#1 is moved so that the scan field SF#2 is irradiated with pulsed laser light to expose the scan field SF#2. Thereafter, similarly, while moving the semiconductor wafer WF#1, exposure up to the last scan field SF#max is performed.

[0043] Figure 4 shows an example of a trigger signal transmitted from the exposure control processor 210 to the laser control processor 130. When exposing one scan field SF#1 or SF#2, pulsed laser light is continuously output at a predetermined repetition frequency. Continuously outputting pulsed laser light at a predetermined repetition frequency is called burst output. When moving from one scan field SF#1 to another scan field SF#2, the burst output of the pulsed laser light is paused. Therefore, in order to expose one semiconductor wafer WF#1, the burst output is repeated a plurality of times.

[0044] When the exposure of the first semiconductor wafer WF#1 is completed, the output of the pulsed laser light to the exposure apparatus 200 is stopped in order to replace the semiconductor wafer WF#1 on the workpiece table WT with the second semiconductor wafer WF#2. However, adjustment light emission for the purpose of parameter adjustment or the like may be performed with an optical shutter (not shown) closed.

[0045] 1.5 Examples of Periodic Wavelength Changes Figure 5 is a graph showing an example of a periodic variation in wavelength. In Figure 5, the horizontal axis represents time and the vertical axis represents wavelength. Let the number of pulses in one burst output for exposing one scan field SF#1 or SF#2 be Nmax. If the repetition frequency of the pulsed laser light is F, the required time for one burst output is Nmax / F.

[0046] In the example shown in FIG. 5, between the target wavelengths λ1 and λ2, the wavelength varies periodically every 4 pulses. The wavelengths of the first and fourth pulsed laser lights are set to the target wavelength λ1, and the wavelengths of the second and third pulsed laser lights are set to the target wavelength λ2. Thereafter, similarly, generating 2 pulses at the target wavelength λ1 and generating 2 pulses at the target wavelength λ2 are repeated. In this way, the laser device 100 outputs pulsed laser light including a plurality of pulses while periodically varying the wavelength.

[0047] 1.6 Output control of pulsed laser light 1.6.1 Control by laser control processor 130 FIG. 6 is a flowchart showing the process for outputting pulsed laser light executed by the laser control processor 130 in the comparative example. In the comparative example, as described below, pulsed laser light is output using the voltage command value HVc received from the exposure control processor 210 as it is.

[0048] In S11, the laser control processor 130 obtains the voltage command value HVc by receiving the voltage command value HVc from the exposure control processor 210 of the exposure device 200.

[0049] In S17, the laser control processor 130 sets the voltage command value HVc to the charger 12.

[0050] In S18, the laser control processor 130 determines whether or not it has received a trigger signal from the exposure control processor 210. If it has not received the trigger signal (S18: NO), the laser control processor 130 waits until it receives the trigger signal. If it has received the trigger signal (S18: YES), the laser control processor 130 proceeds to S19 for processing.

[0051] In S19, the laser control processor 130 outputs pulsed laser light from the laser device 100 by transmitting an oscillation trigger signal based on a trigger signal to the pulse power module 13. After S19, the laser control processor 130 returns the process to S11 and repeats the processes from S11 to S19 to repeat the output of the pulsed laser light.

[0052] 1.6.2 Laser Control by Exposure Control Processor 210 FIG. 7 is a flowchart showing the process of laser control executed by the exposure control processor 210 in the comparative example. The exposure control processor 210 determines a voltage command value HVc so that the pulse energy En of the pulsed laser light approaches the target pulse energy Et as follows.

[0053] In S90, the exposure control processor 210 transmits the voltage command value HVc to the laser control processor 130 of the laser device 100. If it is the first time to transmit the voltage command value HVc, the exposure control processor 210 transmits the voltage command value HVc calculated based on the target pulse energy Et. If it is the second time or later to transmit the voltage command value HVc, the exposure control processor 210 transmits the voltage command value HVc updated in S95.

[0054] In S91, the exposure control processor 210 transmits a trigger signal to the laser control processor 130. Thereby, the laser device 100 outputs pulsed laser light. In S92, the exposure control processor 210 detects the pulse energy En of the pulsed laser light output from the laser device 100 by the energy monitor 220.

[0055] In S93, the exposure control processor 210 calculates the difference ΔEn between the detected pulse energy En and the target pulse energy Et by the following formula. ΔEn = En - Et As the target pulse energy Et, a constant value is set for each burst output.

[0056] In S94, the exposure control processor 210 converts the difference ΔEn into the voltage correction amount ΔHV according to the following formula. ΔHV = ΔEn / HVepgain Here, HVepgain represents the ratio of the change in the pulse energy En to the change in the voltage command value HVc.

[0057] In S95, the exposure control processor 210 updates the voltage command value HVc according to the following formula. HVc = HVc - ΔHV For example, when the pulse energy En detected in S92 is smaller than the target pulse energy Et, the difference ΔEn and the correction amount ΔHV become negative in S93 and S94. In this case, in S95, the negative correction amount ΔHV is subtracted from the voltage command value HVc, and the pulse energy En of the next pulse becomes larger.

[0058] After S95, the exposure control processor 210 returns the process to S90, and by repeating the processes from S90 to S95, calculates the voltage command value HVc and causes the laser device 100 to output pulsed laser light.

[0059] 1.7 Problems of Comparative Examples FIG. 8 is a graph showing the change in the pulse energy En when pulsed laser light is output while switching the target wavelengths λ1 and λ2. The horizontal axis of FIG. 8 indicates the pulse number i in the burst output, and the vertical axis indicates the pulse energy En. The voltage command value HVc is set to a constant value. Even when the voltage command value HVc is a constant value, the pulse energy En may change. By controlling the voltage command value HVc based on the target pulse energy Et described with reference to FIG. 7, the change in the pulse energy En can be suppressed to some extent.

[0060] However, when the target wavelengths λ1 and λ2 are switched at high speed as described with reference to FIG. 5, the pulse energy En may vary in accordance with the switching of the target wavelengths λ1 and λ2 as shown in FIG. 8. As a factor for the variation of the pulse energy En in accordance with the switching of the target wavelengths λ1 and λ2, vibration of the optical components due to the high-speed driving of the mirror 63 can be considered. If the pulse energy En varies frequently, the pulse energy En may not be sufficiently stabilized depending on the control described with reference to FIG. 7.

[0061] Furthermore, the variation of the pulse energy En contains many frequency components corresponding to the reciprocal of the wavelength variation period. The reciprocal of the wavelength variation period corresponds to the switching frequency of the target wavelengths λ1 and λ2. For this reason, the integrated value of the pulse energy En of the pulsed laser light generated at the target wavelength λ1 and the integrated value of the pulse energy En of the pulsed laser light generated at the target wavelength λ2 may not match. In this case, the exposure performance may become non-uniform in the thickness direction of the resist film.

[0062] 2. Laser device that calculates correction data using time-series data of pulse energy En[ ] 2.1 Configuration FIG. 9 schematically shows the configuration of the laser device 100a in the first embodiment. In the first embodiment, the laser control processor 130 includes an energy analysis unit 133 and a voltage correction table 134.

[0063] The energy analysis unit 133 statistically processes the data of the pulse energy En received from the monitor module 17 and calculates correction data. The energy analysis unit 133 may include a control program for performing such statistical processing and calculation of correction data. Alternatively, the energy analysis unit 133 may include hardware for performing such statistical processing and calculation of correction data.

[0064] The voltage correction table 134 stores correction data for correcting the voltage command value HVc in accordance with fluctuations in the wavelength of the pulsed laser light. The voltage correction table 134 corresponds to the table in the present disclosure.

[0065] FIG. 10 is a graph showing the correction data included in the voltage correction table 134. The horizontal axis in FIG. 10 indicates the pulse number i in the burst output, and the vertical axis indicates the correction value HVtbl included in the correction data. The correction value HVtbl changes corresponding to the switching between the target wavelengths λ1 and λ2. The voltage correction table 134 may be a table that stores the correction value HVtbl for each pulse number i, or may be in the form of a function, matrix, or other form. Regarding other points, the configuration of the first embodiment is the same as that of the comparative example.

[0066] 2.2 Control Block Diagram FIG. 11 is a control block diagram of the pulse energy En in the first embodiment. The energy control block 210a corresponds to the process in which the exposure control processor 210 calculates the difference ΔEn in S93 of FIG. 7.

[0067] The voltage conversion block 210b corresponds to the process in which the exposure control processor 210 calculates the correction amount ΔHV in S94 of FIG. 7. The voltage command value HVc is corrected using this correction amount ΔHV.

[0068] The voltage correction block 130a corresponds to the process in which the laser control processor 130 corrects the voltage command value HVc received from the exposure control processor 210 to calculate the voltage set value HVact. This process will be described later with reference to FIG. 12.

[0069] The pulsed laser light output block 100b corresponds to the process in which the laser device 100a applies a high voltage to the discharge electrode 11a according to the voltage set value HVact to output pulsed laser light. The pulse energy En of the pulsed laser light is fed back to the above-described process by the exposure control processor 210.

[0070] 2.3 Output control of pulsed laser light FIG. 12 is a flowchart showing the process for output of pulsed laser light executed by the laser control processor 130 in the first embodiment. In the first embodiment, the voltage command value HVc received from the exposure control processor 210 is corrected as follows to calculate the voltage set value HVact.

[0071] The process of S11 is the same as that described with reference to FIG. 6. In S16a, the laser control processor 130 determines the correction value HVtbl(i) read from the voltage correction table 134. (i) means corresponding to the i-th pulse in the burst output. For example, when correcting the voltage command value HVc of the first pulse in the burst output, the correction value is HVtbl(1). The laser control processor 130 corrects the voltage command value HVc using the read correction value HVtbl(i) by the following formula to calculate the voltage set value HVact. HVact = HVc + HVtbl(i) The voltage set value HVact corresponds to the corrected voltage command value in the present disclosure.

[0072] In S17a, the laser control processor 130 sets the voltage set value HVact to the charger 12. The processes of S18 and S19 are the same as those described with reference to FIG. 6.

[0073] As described above, by reading the correction value HVtbl(i) from the voltage correction table 134 and correcting the voltage command value HVc, the correction of the voltage command value HVc can be performed at high speed for each pulse, and the pulse energy En can be stabilized. In the first embodiment, the laser control by the exposure control processor 210 is the same as that described with reference to FIG. 7.

[0074] 2.4 Update timing of the voltage correction table 134 FIG. 13 is a flowchart showing an update process of a voltage correction table 134 executed by a laser control processor 130 in the first embodiment.

[0075] In S20, the laser control processor 130 determines whether the burst output is in a pause state. For example, when the output of the pulsed laser light has not been performed for 1 second or more, it is determined that the burst output is in a pause state. If the burst output is in a pause state (S20: YES), the laser control processor 130 proceeds to S30.

[0076] In S30, the laser control processor 130 updates the correction data included in the voltage correction table 134. The process of S30 is performed by the energy analysis unit 133. Details of S30 will be described later with reference to FIG. 14.

[0077] If the burst output is not in a pause state (S20: NO), or after S30, the laser control processor 130 returns the process to S20. By such a process, the laser control processor 130 updates the correction data during the pause period after the end of the first burst output and before the start of the next second burst output. The period during which the first burst output is performed is an example of the first period in the present disclosure, and the period during which the second burst output is performed is an example of the second period in the present disclosure.

[0078] 2.5 Update Process of Voltage Correction Table 134 FIG. 14 is a flowchart showing details of the update process of the voltage correction table 134 in the first embodiment. The process shown in FIG. 14 corresponds to a subroutine of S30 in FIG. 13. FIG. 15 is a graph conceptually showing the average values Enavg, Enλ1avg, and Enλ2avg calculated in FIG. 14, and the differences ΔEnλ1 and ΔEnλ2. The horizontal axis of FIG. 15 indicates the pulse number i in the burst output, and the vertical axis indicates the pulse energy En.

[0079] In S31a of FIG. 14, the laser control processor 130 acquires time-series data of a plurality of pulse energies En[ ] in burst output. Here, [ ] means an array, and if it is blank inside [ ], it means the entire array corresponding to one burst output. The time-series data of the pulse energy En[ ] corresponds to the first time-series data in the present disclosure. As shown in FIG. 15, the pulse energy En may vary according to the target wavelengths λ1 and λ2.

[0080] The laser control processor 130 calculates the average value Enavg of the pulse energy En[ ]. The average value Enavg corresponds to the third average value in the present disclosure and serves as a reference for calculating correction data.

[0081] In S32a, the laser control processor 130 calculates the average value Enλ1avg of the pulse energy En[λ1] at the target wavelength λ1 and the average value Enλ2avg of the pulse energy En[λ2] at the target wavelength λ2. The pulse energy En[λ1] means an array of the pulse energy En of the first wavelength pulse P[λ1] output according to the target wavelength λ1 among the pulse energies En[ ]. Similarly, the pulse energy En[λ2] means an array of the pulse energy En of the second wavelength pulse P[λ2] output according to the target wavelength λ2. The average value Enλ1avg corresponds to the first average value in the present disclosure, and the average value Enλ2avg corresponds to the second average value in the present disclosure.

[0082] In S33a, the laser control processor 130 calculates the difference ΔEnλ1 between the average value Enλ1avg and the average value Enavg and the difference ΔEnλ2 between the average value Enλ2avg and the average value Enavg by the following equations. ΔEnλ1 = Enλ1avg - Enavg ΔEnλ2 = Enλ2avg - Enavg

[0083] In S34a, the laser control processor 130 converts the differences ΔEnλ1 and ΔEnλ2 into voltage correction amounts ΔHVλ1 and ΔHVλ2, respectively, by the following equation. ΔHVλ1 = ΔEnλ1 / HVepgain ΔHVλ2 = ΔEnλ2 / HVepgain

[0084] In S38a, the laser control processor 130 calculates correction values HVtbl[λ1] and HVtbl[λ2] according to the following equations and updates the correction data included in the voltage correction table 134. HVtbl[λ1] = HVtbl[λ1] - ΔHVλ1 HVtbl[λ2] = HVtbl[λ2] - ΔHVλ2 In this way, the correction values HVtbl[λ1] and HVtbl[λ2] are calculated for each target wavelength. Here, the initial values of HVtbl[λ1] and HVtbl[λ2] may be preset by adjustment emission (see FIG. 4).

[0085] To prevent overcorrection, the correction values HVtbl[λ1] and HVtbl[λ2] may be calculated using the values obtained by multiplying the correction amounts ΔHVλ1 and ΔHVλ2 by coefficients greater than 0 and less than 1, respectively.

[0086] The calculated correction values HVtbl[λ1] all form an array of the same value. Similarly, the correction values HVtbl[λ2] all form an array of the same value. However, the present disclosure is not limited to this, and the correction values HVtbl[λ1] and HVtbl[λ2] may be changed respectively in one burst output. For example, the correction values HVtbl[λ1] and HVtbl[λ2] may be calculated using the values obtained by multiplying the correction amounts ΔHVλ1 and ΔHVλ2 by a function of time.

[0087] According to the process shown in FIG. 14, correction data including correction values HVtbl[λ1] and HVtbl[λ2] is calculated using the time-series data of the pulse energy En[] in the first burst output. The correction data is stored in the voltage correction table 134. In the second burst output following the first burst output, the voltage command value HVc is corrected using the correction data read from the voltage correction table 134 by the process of S16a in FIG. 12. The average value of the entire correction values HVtbl[λ1] and HVtbl[λ2] may be set to 0 so that the integrated value of the pulse energy En[] does not change even when the voltage command value HVc is corrected (see FIG. 10).

[0088] 2.6 Operation (1) According to the first embodiment, correction data for the voltage command value HVc is calculated using the time-series data of the pulse energy En[] of a plurality of pulses output while periodically varying the wavelength. According to this, the voltage command value HVc can be corrected so as to suppress the variation in the pulse energy En accompanying the variation in the wavelength.

[0089] (2) According to the first embodiment, the correction data is calculated after the end of the period in which the first burst output is performed and before the start of the period in which the second burst output following the first burst output is performed. According to this, the voltage command value HVc can be corrected using the latest data for each burst output.

[0090] (3) According to the first embodiment, the correction data is stored in the voltage correction table 134, and the voltage command value HVc is corrected using the correction data read from the voltage correction table 134. By using the voltage correction table 134, the correction of the voltage command value HVc can be performed at high speed.

[0091] (4) According to the first embodiment, the correction data is calculated based on the average value Enavg of the pulse energy En[]. According to this, even if the target pulse energy Et set in the exposure apparatus 200 is unknown, the voltage command value HVc can be appropriately corrected based on the average value Enavg.

[0092] (5) According to the first embodiment, the average value Enλ1avg of the pulse energy En[λ1] at the target wavelength λ1, the average value Enλ2avg of the pulse energy En[λ2] at the target wavelength λ2, and the average value Enavg of the pulse energy En[ ] are calculated. The correction data is calculated using the difference ΔEnλ1 between the average value Enλ1avg and the average value Enavg, and the difference ΔEnλ2 between the average value Enλ2avg and the average value Enavg. According to this, the integrated value of the pulse energy En[λ1] at the target wavelength λ1 and the integrated value of the pulse energy En[λ2] at the target wavelength λ2 can be made closer to each other. Thereby, the exposure performance can be made uniform in the thickness direction of the resist film.

[0093] (6) According to the first embodiment, correction values HVtbl[λ1] and HVtbl[λ2] are calculated for each target wavelength set during the period when the first burst output is performed. According to this, correction data including the correction values HVtbl[λ1] and HVtbl[λ2] can be calculated at high speed. In other respects, the first embodiment is the same as the comparative example.

[0094] 3. Laser apparatus that further calculates correction data using the time-series data of the voltage command value HVc[ ] 3.1 Update process of the voltage correction table 134 FIG. 16 is a flowchart showing details of the update process of the voltage correction table 134 in the second embodiment. The process shown in FIG. 16 corresponds to the subroutine of S30 in FIG. 13. FIG. 17 is a graph conceptually showing the average values HVcavg, HVcλ1avg, and HVcλ2avg calculated in FIG. 16, and the differences ΔHVcλ1 and ΔHVcλ2. The horizontal axis of FIG. 17 indicates the pulse number i in the burst output, and the vertical axis indicates the voltage command value HVc. FIG. 18 is a graph conceptually showing the average values Enavg, Enλ1avg, and Enλ2avg calculated in FIG. 16, and the differences ΔEnλ1 and ΔEnλ2. The horizontal axis of FIG. 18 indicates the pulse number i in the burst output, and the vertical axis indicates the pulse energy En.

[0095] The processes from S31a to S34a in FIG. 16 are the same as those described with reference to FIG. 14. When the voltage command value HVc is controlled so that the pulse energy En approaches the target pulse energy Et as described with reference to FIG. 7, as shown in FIG. 17, the variation of the voltage command value HVc may include a frequency component corresponding to the reciprocal of the wavelength variation period. Due to such a variation of the voltage command value HVc, the variation of the pulse energy En is suppressed to some extent. However, simply canceling the measured variation of the pulse energy En by the processes from S31a to S34a may not be able to sufficiently cancel the variation of the pulse energy En. To further stabilize the pulse energy En, it is desirable to correct the variation of the voltage command value HVc as well.

[0096] In S35b, the laser control processor 130 acquires the time-series data of a plurality of voltage command values HVc[ ] in the burst output. The time-series data of the voltage command value HVc[ ] corresponds to the second time-series data in the present disclosure.

[0097] The laser control processor 130 calculates the average value HVcavg of the voltage command values HVc[ ]. The average value HVcavg corresponds to the sixth average value in the present disclosure and serves as a reference for calculating the correction data.

[0098] In S36b, the laser control processor 130 calculates the average value HVcλ1avg of the voltage command value HVc[λ1] at the target wavelength λ1 and the average value HVcλ2avg of the voltage command value HVc[λ2] at the target wavelength λ2. The voltage command value HVc[λ1] means an array of the voltage command value HVc when outputting the first wavelength pulse P[λ1] according to the target wavelength λ1 among the voltage command values HVc[ ]. Similarly, the voltage command value HVc[λ2] means an array of the voltage command value HVc when outputting the second wavelength pulse P[λ2] according to the target wavelength λ2. The average value HVcλ1avg corresponds to the fourth average value in the present disclosure, and the average value HVcλ2avg corresponds to the fifth average value in the present disclosure.

[0099] In S37b, the laser control processor 130 calculates the difference ΔHVcλ1 between the average value HVcλ1avg and the average value HVcavg and the difference ΔHVcλ2 between the average value HVcλ2avg and the average value HVcavg by the following equations. ΔHVcλ1 = HVcλ1avg - HVcavg ΔHVcλ2 = HVcλ2avg - HVcavg

[0100] In S38b, the laser control processor 130 calculates correction values HVtbl[λ1] and HVtbl[λ2] by the following equations and updates the correction data included in the voltage correction table 134. HVtbl[λ1] = HVtbl[λ1] - (ΔHVλ1 - ΔHVcλ1) HVtbl[λ2] = HVtbl[λ2] - (ΔHVλ2 - ΔHVcλ2)

[0101] In FIG. 17, it is assumed that when the voltage command value HVc is varied compared to the case where the voltage command value HVc is made constant at the average value HVcavg, when the target wavelength λ1 is set, the voltage command value HVc becomes lower by ΔHVcλ1, and when the target wavelength λ2 is set, the voltage command value HVc becomes higher by ΔHVcλ2. In this case, as shown in FIG. 18, when the voltage command value HVc is varied compared to the case where the voltage command value HVc is constant, when the target wavelength λ1 is set, the pulse energy En becomes smaller by ΔHVcλ1 × HVepgain. Therefore, not only the correction based on the difference ΔEnλ1 is performed by the processes from S31a to S34a, but also the correction is further performed using the time-series data of the voltage command value HVc[ ] by the processes from S35b to S38b, so that the pulse energy En can be further stabilized. Similarly, when the voltage command value HVc is varied compared to the case where the voltage command value HVc is constant, when the target wavelength λ2 is set, the pulse energy En becomes larger by ΔHVcλ2 × HVepgain. Therefore, not only the correction based on the difference ΔEnλ2 is performed, but also the correction is further performed using the time-series data of the voltage command value HVc[ ], so that the pulse energy En can be further stabilized.

[0102] To prevent overcorrection, the correction value HVtbl[λ1] may be calculated using a value obtained by multiplying the correction amounts ΔHVλ1 and ΔHVcλ1 by a coefficient greater than 0 and less than 1. Further, the correction value HVtbl[λ2] may be calculated using a value obtained by multiplying the correction amounts ΔHVλ2 and ΔHVcλ2 by a coefficient greater than 0 and less than 1.

[0103] 3.2 Operation (7) According to the second embodiment, correction data is calculated using the time-series data of a plurality of voltage command values HVc[ ] set during the period in which the first burst output is performed. According to this, the variation in the voltage command value HVc set by the exposure apparatus 200 is also corrected, and the correction can be performed more appropriately.

[0104] (8) According to the second embodiment, correction data is calculated based on the average value HVcavg of the voltage command value HVc[ ]. According to this, even if the target pulse energy Et set in the exposure apparatus 200 is unknown, appropriate correction can be performed based on the average value HVcavg.

[0105] (9) According to the second embodiment, the average value HVcλ1avg of the voltage command value HVc[λ1] when the target wavelength λ1 is set, the average value HVcλ2avg of the voltage command value HVc[λ2] when the target wavelength λ2 is set, and the average value HVcavg of the voltage command value HVc[ ] are calculated. The correction data is calculated using the difference ΔHVcλ1 between the average value HVcλ1avg and the average value HVcavg, and the difference ΔHVcλ2 between the average value HVcλ2avg and the average value HVcavg. According to this, the variation of the voltage command value HVc set by the exposure apparatus 200 is also corrected, and the integrated value of the pulse energy En[λ1] at the target wavelength λ1 and the integrated value of the pulse energy En[λ2] at the target wavelength λ2 can be made closer to each other. In other respects, the second embodiment is the same as the first embodiment.

[0106] 4. Laser apparatus that calculates correction data by performing Fourier transform on time-series data of pulse energy En[ ] 4.1 Update process of voltage correction table 134 FIG. 19 is a flowchart showing details of the update process of the voltage correction table 134 in the third embodiment. The process shown in FIG. 19 corresponds to the subroutine of S30 in FIG. 13. FIG. 20 is a graph of spectrum data FFTen[ ] obtained by performing Fourier transform on the time-series data of the pulse energy En[ ] in FIG. 19. The horizontal axis in FIG. 20 indicates frequency, and the vertical axis indicates spectral density.

[0107] In S31c of FIG. 19, the laser control processor 130 acquires the time-series data of the pulse energy En[ ] of a plurality of pulses in the burst output.

[0108] The laser control processor 130 performs a Fourier transform on the time-series data of the pulse energy En[ ] to calculate the spectral data FFTen[ ]. The Fourier transform process can be performed by a fast Fourier transform. As shown in FIG. 20, the spectral data FFTen[ ] obtained by performing a Fourier transform on the time-series data of the pulse energy En[ ] of the pulsed laser light output with the wavelength periodically fluctuating has a peak at a specific frequency. This frequency corresponds to the reciprocal of the wavelength fluctuation period.

[0109] In S32c, the laser control processor 130 extracts the selected frequency component FFTen[freq] from the spectral data FFTen[ ]. Here, the frequency component FFTen[freq] corresponding to the reciprocal of the wavelength fluctuation period is selected. In the example shown in FIG. 20, the frequency component of 1000 Hz is selected. Alternatively, a frequency band including the peak of the spectral data FFTen[ ] and the surrounding frequencies may be selected. Alternatively, when the spectral data FFTen[ ] includes a plurality of peaks, a plurality of frequency components corresponding to those peaks may be selected.

[0110] In S33c, the laser control processor 130 calculates the energy data Enfft[ ] of the selected frequency by performing an inverse Fourier transform on the frequency component FFTen[freq]. The energy data Enfft[ ] includes the energy amplitude for each pulse. The inverse Fourier transform process can be performed by a fast inverse Fourier transform.

[0111] In S34c, the laser control processor 130 converts the energy data Enfft[ ] into the voltage correction amount HVfft[ ] by the following formula. HVfft[ ] = Enfft[ ] / HVepgain

[0112] In S38c, the laser control processor 130 calculates the correction value HVtbl[ ] by the following formula and updates the correction data included in the voltage correction table 134. HVtbl[] = HVtbl[] - HVfft[] In this way, the correction value HVtbl[] is calculated for each individual pulse in the burst output. Here, the initial value of the correction value HVtbl[] may be preset by adjustment emission (see Fig. 4).

[0113] To prevent overcorrection, the correction value HVtbl[] may be calculated using a value obtained by multiplying the correction amount HVfft[] by a coefficient greater than 0 and less than 1.

[0114] 4.2 Function (10) According to the third embodiment, correction data is calculated by extracting selected frequency components from the time-series data of the pulse energies En[] of a plurality of pulses output during the period when the first burst output is performed. According to this, fluctuations in the selected frequency components of the pulse energy En can be reduced, and the pulse energy En can be stabilized.

[0115] (11) According to the third embodiment, the selected frequency component is a frequency component corresponding to the reciprocal of the wavelength fluctuation period when the pulsed laser light is output during the period when the first burst output is performed. According to this, fluctuations in the frequency components corresponding to the switching frequencies of the target wavelengths λ1 and λ2 can be reduced, and the pulse energy En can be stabilized.

[0116] (12) According to the third embodiment, the time-series data of the pulse energy En[] is Fourier-transformed to calculate the spectrum data FFTen[]. The selected frequency component FFTen[freq] among the spectrum data FFTen[] is inverse Fourier-transformed to calculate the energy data Enfft[]. The correction data is calculated using this energy data Enfft[]. According to this, correction data corresponding to the phase shift between the switching of the target wavelengths λ1 and λ2 and the fluctuation of the pulse energy En is calculated, so that the pulse energy En can be more stabilized.

[0117] (13) According to the third embodiment, a correction value HVtbl[] is calculated for each individual pulse output during the period when the first burst output is performed. According to this, an appropriate correction value HVtbl[] can be calculated for each pulse. In other respects, the third embodiment is the same as the first embodiment.

[0118] 5. Laser device that calculates correction data by performing Fourier transform on time-series data of voltage command value HVc[] 5.1 Update process of voltage correction table 134 FIG. 21 is a flowchart showing the details of the update process of the voltage correction table 134 in the fourth embodiment. The process shown in FIG. 21 corresponds to the subroutine of S30 in FIG. 13.

[0119] The processes from S31c to S34c in FIG. 21 are the same as those described with reference to FIG. 19. When the voltage command value HVc is controlled so that the pulse energy En approaches the target pulse energy Et as described with reference to FIG. 7, as shown in FIG. 17, the variation of the voltage command value HVc may include a frequency component corresponding to the reciprocal of the wavelength variation period. As described in the second embodiment, in order to further stabilize the pulse energy En, it is desirable to correct the variation of the voltage command value HVc as well.

[0120] In S35d, the laser control processor 130 acquires the time-series data of a plurality of voltage command values HVc[] in the burst output.

[0121] The laser control processor 130 performs Fourier transform on the time-series data of the voltage command value HVc[] to calculate spectrum data FFThvc[]. The Fourier transform process can be performed by fast Fourier transform.

[0122] In S36d, the laser control processor 130 extracts the selected frequency component FFThvc[freq] from the spectral data FFThvc[]. The frequency of the frequency component FFThvc[freq] may be the same as the frequency of the frequency component FFTen[freq] selected in S32c.

[0123] In S37d, the laser control processor 130 calculates the voltage data HVcfft[] of the selected frequency by performing an inverse Fourier transform on the frequency component FFThvc[freq]. The voltage data HVcfft[] includes the voltage amplitude for each pulse. The inverse Fourier transform process can be performed by a fast inverse Fourier transform.

[0124] In S38d, the laser control processor 130 calculates the correction value HVtbl[] according to the following formula and updates the correction data included in the voltage correction table 134. HVtbl[] = HVtbl[] - (HVfft[] - HVcfft[])

[0125] To prevent overcorrection, the correction value HVtbl[] may be calculated using values obtained by multiplying the correction amounts HVfft[] and HVcfft[] by a coefficient greater than 0 and less than 1.

[0126] 5.2 Operation (14) According to the fourth embodiment, correction data is calculated by extracting a selected frequency component from the time-series data of a plurality of voltage command values HVc[] set during the period in which the first burst output is performed. By using the time-series data of the voltage command value HVc[], the variation in the voltage command value HVc set by the exposure apparatus 200 can also be corrected, and the correction can be performed more appropriately.

[0127] (15) According to the fourth embodiment, the time-series data of the voltage command value HVc[ ] is Fourier-transformed to calculate the spectrum data FFThvc[ ]. The selected frequency component FFThvc[freq] among the spectrum data FFThvc[ ] is inverse Fourier-transformed to calculate the voltage data HVcfft[ ]. Correction data is calculated using this voltage data HVcfft[ ]. According to this, correction data corresponding to the phase shift between the switching of the target wavelengths λ1 and λ2 and the fluctuation of the voltage command value HVc can be calculated, so that the pulse energy En can be more stabilized. Regarding other points, the fourth embodiment is the same as the third embodiment.

[0128] 6. Laser device that calculates correction data for each pulse number j within the wavelength fluctuation period 6.1 Update process of the voltage correction table 134 FIG. 22 is a flowchart showing the details of the update process of the voltage correction table 134 in the fifth embodiment. The process shown in FIG. 22 corresponds to the subroutine of S30 in FIG. 13. FIG. 23 is a graph showing the wavelength that changes periodically. The horizontal axis of FIG. 23 indicates the pulse number i in the burst output, and the vertical axis indicates the wavelength. The pulse number j within the wavelength fluctuation period indicates which pulse within the wavelength fluctuation period it is. For example, when the number of pulses in one cycle is 4 pulses, j is an integer from 1 to 4.

[0129] The process of S31a in FIG. 22 is the same as that described with reference to FIG. 14. However, the average value Enavg of the pulse energy En[ ] corresponds to the ninth average value in the present disclosure.

[0130] In S32e, the laser control processor 130 calculates the average value En#javg of the pulse energy En[#j] for each pulse number j within the wavelength fluctuation period. The pulse energy En[#j] means an array of the pulse energy En of the pulse number j among the pulse energies En[ ]. The pulse of the pulse number j corresponds to, for example, the pulse with the pulse number i being 1, 5, 9,... in the burst output if the value of j is 1, and corresponds to the pulse with the pulse number i being 2, 6, 10,... in the burst output if the value of j is 2. The average value En#javg is represented as En#1avg if the value of j is 1, and is represented as En#2avg if the value of j is 2. The average value En#1avg corresponds to the seventh average value in the present disclosure. The average value En#2avg corresponds to the eighth average value in the present disclosure. The number of the average values En#javg coincides with the maximum value of j.

[0131] In S33e, the laser control processor 130 calculates the difference ΔEn#j between the average value En#javg and the average value Enavg according to the following formula, respectively. ΔEn#j = En#javg - Enavg The difference ΔEn#j is represented as ΔEn#1 if the value of j is 1, and is represented as ΔEn#2 if the value of j is 2.

[0132] In S34e, the laser control processor 130 converts the difference ΔEn#j into a voltage correction amount ΔHV#j according to the following formula, respectively. ΔHV#j = ΔEn#j / HVepgain

[0133] Similar to the first embodiment, the correction value HVtbl[#j] may be calculated using the correction amount ΔHV#j. However, when the voltage command value HVc is controlled so that the pulse energy En approaches the target pulse energy Et as described with reference to FIG. 7, as shown in FIG. 17, the fluctuation of the voltage command value HVc may include a frequency component corresponding to the reciprocal of the wavelength fluctuation period. As described in the second embodiment, in order to stabilize the pulse energy En more, it is desirable to correct the fluctuation of the voltage command value HVc as well.

[0134] The process of S35b is the same as that described with reference to FIG. 16. However, the average value HVcavg of the voltage command value HVc[] corresponds to the 12th average value in the present disclosure.

[0135] In S36e, the laser control processor 130 calculates the average value HVc#javg of the voltage command value HVc[#j] for each pulse number j within the wavelength fluctuation period. The voltage command value HVc[#j] means an array of the voltage command value HVc of the pulse with the pulse number j among the voltage command values HVc[]. The average value HVc#javg is represented as HVc#1avg if the value of j is 1, and represented as HVc#2avg if the value of j is 2. The average value HVc#1avg corresponds to the 10th average value in the present disclosure, and the average value HVc#2avg corresponds to the 11th average value in the present disclosure. The number of the average values HVc#javg coincides with the maximum value of j.

[0136] In S37e, the laser control processor 130 calculates the difference ΔHVc#j between the average value HVc#javg and the average value HVcavg according to the following formula respectively. ΔHVc#j = HVc#javg - HVcavg The difference ΔHVc#j is represented as ΔHVc#1 if the value of j is 1, and represented as ΔHVc#2 if the value of j is 2.

[0137] In S38e, the laser control processor 130 calculates the correction value HVtbl[#j] according to the following formula, and updates the correction data included in the voltage correction table 134. HVtbl[#j] = HVtbl[#j] - (ΔHV#j - ΔHVc#j) In this way, the correction value HVtbl[#j] is calculated for each pulse number j within the wavelength fluctuation period. Here, the initial value of HVtbl[#j] may be preset by adjustment emission (see FIG. 4).

[0138] In order to prevent overcorrection, the correction value HVtbl[#j] may be calculated using values obtained by multiplying the correction amounts ΔHV#j and ΔHVc#j by a coefficient greater than 0 and less than 1.

[0139] The calculated correction value HVtbl[#j] forms an array of the same values for the same pulse number j. However, the present disclosure is not limited thereto, and the correction values HVtbl[#j] may be changed respectively in one burst output. For example, the correction value HVtbl[#j] may be calculated using values obtained by multiplying the correction amounts ΔHV#j and ΔHVc#j by a function of time.

[0140] 6.2 Operation (16) According to the fifth embodiment, the average value En#1avg of the pulse energy En[#1] of the pulse with the pulse number j being 1 within the wavelength fluctuation period, the average value En#2avg of the pulse energy En[#2] of the pulse with the pulse number j being 2, and the average value Enavg of the pulse energy En[ ] are calculated. The correction data is calculated using the difference ΔEn#1 between the average value En#1avg and the average value Enavg, and the difference ΔEn#2 between the average value En#2avg and the average value Enavg. According to this, correction data corresponding to the phase shift between the switching of the target wavelengths λ1 and λ2 and the fluctuation of the pulse energy En is calculated, so that the pulse energy En can be more stabilized.

[0141] (17) According to the fifth embodiment, the correction value HVtbl[#j] is calculated for each pulse number j within the wavelength fluctuation period when the pulsed laser light is output during the period in which the first burst output is performed. According to this, the correction data including the correction value HVtbl[#j] can be calculated at high speed.

[0142] (18) According to the fifth embodiment, the average value HVc#1avg of the voltage command value HVc[#1] when the pulse number j within the wavelength fluctuation period is 1, the average value HVc#2avg of the voltage command value HVc[#2] when the pulse number j is 2, and the average value HVcavg of the voltage command value HVc[ ] are calculated. The correction data is calculated using the difference ΔHVc#1 between the average value HVc#1avg and the average value HVcavg, and the difference ΔHVc#2 between the average value HVc#2avg and the average value HVcavg. According to this, correction data corresponding to the phase shift between the switching of the target wavelengths λ1 and λ2 and the fluctuation of the voltage command value HVc is calculated, so that the pulse energy En can be more stabilized. In other respects, the fifth embodiment is the same as the second embodiment.

[0143] 7. Laser device for setting the voltage command value HVc based on the target pulse energy Et 7.1 Control by the laser control processor 130 FIG. 24 is a flowchart showing the process for outputting pulsed laser light executed by the laser control processor 130 in the sixth embodiment. In the sixth embodiment, based on the target pulse energy Et received from the exposure control processor 210 as follows, the laser control processor 130 calculates the voltage command value HVc to obtain the voltage command value HVc. The configuration of the sixth embodiment may be the same as that of the first embodiment. However, the monitor module 17 measures not only the wavelength of the pulsed laser light but also the pulse energy En.

[0144] In S10f, the laser control processor 130 receives the target pulse energy Et from the exposure control processor 210. The target pulse energy Et does not have to be received for each pulse, and may be received, for example, for each burst output. In S12f, the laser control processor 130 detects the pulse energy En of the pulsed laser light by the monitor module 17.

[0145] In S13f, the laser control processor 130 calculates the difference ΔEn between the detected pulse energy En and the target pulse energy Et by the following equation. ΔEn = En - Et

[0146] In S14f, the laser control processor 130 converts the difference ΔEn into a voltage correction amount ΔHV by the following equation. ΔHV = ΔEn / HVepgain

[0147] In S15f, the laser control processor 130 updates the voltage command value HVc by the following equation. HVc = HVc - ΔHV For example, when the pulse energy En detected in S12f is smaller than the target pulse energy Et, the difference ΔEn and the correction amount ΔHV become negative numbers in S13f and S14f. In this case, in S15f, since the absolute value of the voltage command value HVc, which is a positive number, increases, the pulse energy En of the next pulse increases.

[0148] The processing from S16a to S19 is the same as that described with reference to FIG. 12. After S19, the laser control processor 130 returns the processing to S12f.

[0149] 7.2 Control by the exposure control processor 210 FIG. 25 is a flowchart showing the laser control processing executed by the exposure control processor 210 in the sixth embodiment. The exposure control processor 210 does not determine the voltage command value HVc.

[0150] In S80f, the exposure control processor 210 transmits the target pulse energy Et to the laser control processor 130 of the laser device 100a. The target pulse energy Et does not have to be transmitted for each pulse. For example, it may be transmitted for each burst output.

[0151] The process of S91 is the same as that described with reference to FIG. 7. By repeating the process of S91, the exposure control processor 210 causes the laser device 100a to output pulsed laser light. In other respects, the sixth embodiment is the same as any one of the first to fifth embodiments.

[0152] 8. Others 8.1 Configuration of Monitor Module 17 FIG. 26 schematically shows the configuration of the monitor module 17 used in the comparative example and the first to sixth embodiments. The monitor module 17 includes a beam splitter 17a, an energy sensor 17b, and an etalon spectrometer 18. The beam splitter 17a is located in the optical path of the pulsed laser light reflected by the beam splitter 16. The energy sensor 17b is located in the optical path of the pulsed laser light reflected by the beam splitter 17a.

[0153] The etalon spectrometer 18 is arranged in the optical path of the pulsed laser light transmitted through the beam splitter 17a. The etalon spectrometer 18 includes a diffusion plate 18a, an etalon 18b, a condenser lens 18c, and a line sensor 18d.

[0154] The diffusion plate 18a is located in the optical path of the pulsed laser light transmitted through the beam splitter 17a. The diffusion plate 18a has a large number of irregularities on its surface and is configured to transmit and diffuse the pulsed laser light. The etalon 18b is located in the optical path of the pulsed laser light transmitted through the diffusion plate 18a. The etalon 18b includes two partial reflection mirrors. The two partial reflection mirrors face each other with an air gap of a predetermined distance and are bonded together via a spacer.

[0155] The condenser lens 18c is located in the optical path of the pulsed laser light transmitted through the etalon 18b. The line sensor 18d is located on the optical path of the pulsed laser light transmitted through the condenser lens 18c and at the focal plane of the condenser lens 18c. The line sensor 18d receives the interference fringes formed by the etalon 18b and the condenser lens 18c. The interference fringes are an interference pattern of the pulsed laser light, have a concentric shape, and the square of the distance from the center of the concentric circles is proportional to the change in wavelength.

[0156] The line sensor 18d is a light distribution sensor including a large number of light receiving elements arranged in a one-dimensional manner. Alternatively, instead of the line sensor 18d, an image sensor including a large number of light receiving elements arranged in a two-dimensional manner may be used as the light distribution sensor. Each of the light receiving elements is referred to as a channel. The light intensity distribution of the interference fringes can be obtained from the light intensity detected in each channel.

[0157] 8.2 Operation of the monitoring module 17 The energy sensor 17b detects the pulse energy En of the pulsed laser light and outputs data of the pulse energy En to the laser control processor 130. The data of the pulse energy En may be used by the laser control processor 130 for feedback control of the voltage command value HVc in the sixth embodiment. Also, the timing when the data of the pulse energy En is received can be used as a reference for the timing when the laser control processor 130 outputs a data output trigger to the etalon spectrometer 18.

[0158] The etalon spectrometer 18 generates a measurement waveform from the interference pattern of the pulsed laser light detected by the line sensor 18d. The etalon spectrometer 18 transmits the measurement waveform to the laser control processor 130 according to the data output trigger output from the laser control processor 130. The measurement waveform, also called a fringe waveform, shows the relationship between the distance from the center of the concentric circles constituting the interference fringes and the light intensity.

[0159] The laser control processor 130 calculates the center wavelength of the pulsed laser light as the measurement wavelength using the measurement waveform output from the etalon spectrometer 18. Alternatively, a controller (not shown) included in the etalon spectrometer 18 calculates the measurement wavelength and transmits it to the laser control processor 130. The laser control processor 130 performs feedback control of the center wavelength of the pulsed laser light by outputting a control signal to drivers (not shown) of the rotation stages 143 and 163 based on the target wavelengths λ1 and λ2 and the measurement wavelength.

[0160] 8.3 Supplementary The above description is intended as an illustration only and not a limitation. Thus, it will be apparent to those skilled in the art that modifications can be made to the embodiments of the present disclosure without departing from the scope of the claims. It will also be apparent to those skilled in the art that the embodiments of the present disclosure can be used in combination.

[0161] The terms used throughout this specification and the claims should be construed as "non-limiting" terms unless otherwise specified. For example, terms such as "comprising," "having," "including," and "containing" should be construed as not excluding the presence of components other than those described. Also, the modifier "one" should be construed to mean "at least one" or "one or more." Also, the term "at least one of A, B, and C" should be construed as "A," "B," "C," "A + B," "A + C," "B + C," or "A + B + C." Furthermore, it should be construed to include combinations with things other than "A," "B," and "C."

Claims

1. A control method for a discharge-excited laser device provided with a power supply for controlling the pulse energy of a pulsed laser beam, comprising: In a first period, outputting a pulsed laser beam including a plurality of pulses from the discharge-excited laser device while periodically varying the wavelength; Calculating correction data for correcting a voltage command value set in the power supply in accordance with the variation of the wavelength, using first time-series data of the pulse energies of the plurality of pulses; In a second period, acquiring the voltage command value, correcting the acquired voltage command value using the correction data, and outputting a pulsed laser beam from the discharge-excited laser device in accordance with the corrected voltage command value. A control method comprising the above steps.

2. The control method according to claim 1, wherein: The first period corresponds to a period in which a first burst output is performed, the second period corresponds to a period in which a second burst output following the first burst output is performed, and The correction data is calculated after the end of the first period and before the start of the second period. A control method.

3. The control method according to claim 1, wherein: The correction data is stored in a table, and The voltage command value is corrected using the correction data read from the table. A control method.

4. The control method according to claim 1, wherein: The correction data is calculated based on an average value of the pulse energies of the plurality of pulses. A control method.

5. The control method according to claim 1, wherein: Among the plurality of pulses, a first average value of the pulse energies of first wavelength pulses output in accordance with a first target wavelength; A second average value of the pulse energies of second wavelength pulses output in accordance with a second target wavelength among the plurality of pulses; A third average value of the pulse energies of the plurality of pulses; are calculated, and The correction data is calculated using a difference between the first average value and the third average value and a difference between the second average value and the third average value. A control method.

6. The control method according to claim 1, wherein: Correction values included in the correction data are calculated for each target wavelength set in the first period. A control method.

7. The control method according to claim 1, wherein: The correction data is further calculated using second time-series data of a plurality of the voltage command values set in the first period. A control method.

8. The control method according to claim 7, wherein: Calculating the correction data based on the average value of the plurality of voltage command values Control method

9. The control method according to claim 1, wherein Among the plurality of voltage command values set in the first period, the fourth average value of the voltage command values when the first target wavelength is set, and Among the plurality of voltage command values, the fifth average value of the voltage command values when the second target wavelength is set, and The sixth average value of the plurality of voltage command values, and Calculating the correction data by further using the difference between the fourth average value and the sixth average value and the difference between the fifth average value and the sixth average value Control method

10. The control method according to claim 1, wherein Extracting a selected frequency component from the first time-series data to calculate the correction data Control method

11. The control method according to claim 10, wherein The selected frequency component corresponds to a frequency component that is the reciprocal of the wavelength fluctuation period when the pulsed laser light is output in the first period Control method

12. The control method according to claim 1, wherein Performing Fourier transform on the first time-series data to calculate spectrum data, and calculating the correction data using the data obtained by performing inverse Fourier transform on the selected frequency component among the spectrum data Control method

13. The control method according to claim 1, wherein Calculating a correction value included in the correction data for each individual pulse output in the first period Control method

14. The control method according to claim 1, wherein Extracting a selected frequency component from the second time-series data of the plurality of voltage command values set in the first period to calculate the correction data Control method

15. The control method according to claim 1, wherein Performing Fourier transform on the second time-series data of the plurality of voltage command values set in the first period to calculate spectrum data, and further calculating the correction data using the data obtained by performing inverse Fourier transform on the selected frequency component among the spectrum data Control method

16. The control method according to claim 1, wherein Among the plurality of pulses, the seventh average value of the pulse energies of the pulses whose pulse numbers within the wavelength fluctuation period are the first value, and Among the plurality of pulses, the eighth average value of the pulse energies of the pulses whose pulse numbers are the second value The ninth average value of the pulse energies of the plurality of pulses, and calculate, and calculate the correction data using the difference between the seventh average value and the ninth average value and the difference between the eighth average value and the ninth average value. Control method.

17. The control method according to claim 1, calculating a correction value included in the correction data for each pulse number within a wavelength fluctuation period when outputting pulsed laser light in the first period. Control method.

18. The control method according to claim 1, among the plurality of voltage command values set in the first period, the tenth average value of the voltage command values set in a pulse whose pulse number within a wavelength fluctuation period is a first value, and among the plurality of voltage command values, the eleventh average value of the voltage command values set in a pulse whose pulse number is a second value, and the twelfth average value of the plurality of voltage command values, calculate, and further calculate the correction data using the difference between the tenth average value and the twelfth average value and the difference between the eleventh average value and the twelfth average value. Control method.

19. A power supply for controlling the pulse energy of pulsed laser light, and a processor for controlling the power supply, in a first period, output pulsed laser light including a plurality of pulses from a discharge-excitation type laser device while periodically varying the wavelength between a first wavelength and a second wavelength, calculate correction data for correcting a voltage command value set in the power supply according to the variation of the wavelength using first time-series data of the pulse energies of the plurality of pulses, in a second period, acquire the voltage command value from an exposure device, correct the acquired voltage command value using the correction data, and output pulsed laser light from the discharge-excitation type laser device according to the corrected voltage command values corresponding to the first wavelength and the second wavelength respectively. The processor, and A discharge-excitation type laser device comprising.

20. A method for manufacturing an electronic device, a power supply for controlling the pulse energy of pulsed laser light, and a processor for controlling the power supply, in a first period, output pulsed laser light including a plurality of pulses from a discharge-excitation type laser device while periodically varying the wavelength, calculate correction data for correcting a voltage command value set in the power supply according to the variation of the wavelength using first time-series data of the pulse energies of the plurality of pulses, during a second period, acquiring the voltage command value, correcting the acquired voltage command value using the correction data, and causing the discharge excitation laser device to output a pulsed laser beam in accordance with the corrected voltage command value; the processor; A pulsed laser beam is generated by the discharge excitation laser device comprising: A pulsed laser beam is output to an exposure device. In order to manufacture an electronic device, a photosensitive substrate is exposed to pulsed laser light in the exposure apparatus. A method for manufacturing an electronic device, comprising:

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