Laser device and method for manufacturing electronic device

Abstract

The laser device comprises: a laser resonator; a cavity arranged on an optical path of the laser resonator; a pair of electrodes arranged in the cavity; a power supply for applying a voltage to the electrodes; a storage unit storing a voltage value for making the pulse energy of the pulse laser a predetermined value; and a control unit for setting an applied voltage value of the voltage applied to the electrodes, the control unit setting an applied voltage value for outputting a pulse having a pulse number greater than 1 and less than i, which indicates the order of the pulses, among a plurality of pulses included in the pulse laser output in one burst oscillation among a plurality of burst oscillations, based on a voltage command value and the voltage value stored in the storage unit, and setting an applied voltage value for outputting a pulse having a pulse number greater than i and less than j, based on the voltage command value and an offset value relative to the voltage command value, wherein i is an integer greater than 1 and j is an integer greater than i.

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, at 350 to 400 pm. Therefore, when a 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 the laser resonator of the gas laser device, there is sometimes a narrowing module (Line Narrowing Module: LNM) containing narrowing elements (etalon, grating, etc.) to narrow the spectral line width. Hereinafter, a gas laser device whose spectral line width is narrowed is referred to as a narrowed gas laser device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: U.S. Patent No. 6418155

[0007] Patent Document 2: U.S. Patent Application Publication No. 2018 / 309259 Summary of the invention

[0008] A laser device according to one aspect of the present disclosure performs multiple burst oscillations including a first burst oscillation and a second burst oscillation performed after the first burst oscillation in accordance with a voltage command value and a trigger signal input from an external device to output pulsed laser light, wherein the laser device comprises: a laser resonator; a cavity arranged on an optical path of the laser resonator; a pair of electrodes arranged in the cavity; a power supply for applying a voltage to the electrodes; a storage unit storing a voltage value for making the pulse energy of the pulsed laser light a predetermined value; and a control unit for setting an applied voltage value of the voltage applied to the electrodes, wherein the control unit sets an applied voltage value for outputting a pulse having a pulse number of 1 or more and less than i, which indicates the order of the pulses, among a plurality of pulses included in a burst oscillation of the multiple burst oscillations, based on the voltage command value and the voltage value stored in the storage unit, and sets an applied voltage value for outputting a pulse having a pulse number of i or more and less than j, based on the voltage command value and an offset value with respect to the voltage command value, wherein i is an integer greater than 1 and j is an integer greater than i.

[0009] A method for manufacturing an electronic device according to one aspect of the present disclosure includes the steps of generating pulsed laser light by a laser device, outputting the pulsed laser light to an exposure device, and exposing the pulsed laser light to a photosensitive substrate in the exposure device to manufacture the electronic device. A laser device performs multiple burst oscillations including a first burst oscillation and a second burst oscillation performed after the first burst oscillation according to a voltage command value and a trigger signal input from an external device to output pulsed laser light. The laser device comprises: a laser resonator; a cavity arranged on an optical path of the laser resonator; a pair of electrodes arranged in the cavity; a power supply for applying a voltage to the electrodes; a storage unit storing a voltage value for making the pulse energy of the pulsed laser light a predetermined value; and a control unit for setting an applied voltage value of the voltage applied to the electrodes. The control unit sets an applied voltage value for outputting a pulse having a pulse number greater than 1 and less than i, which indicates the order of the pulses, among a plurality of pulses included in the pulsed laser light outputted in one burst oscillation among the multiple burst oscillations, based on the voltage command value and the voltage value stored in the storage unit, and sets an applied voltage value for outputting a pulse having a pulse number greater than i and less than j, based on the voltage command value and an offset value relative to the voltage command value, wherein i is an integer greater than 1 and j is an integer greater than i. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Hereinafter, several embodiments of the present disclosure will be described as simple examples with reference to the accompanying drawings.

[0011] Figure 1 The structure of a laser device according to a comparative example is schematically shown.

[0012] Figure 21 is a pulse waveform diagram showing an example of a trigger signal Tr[n] output from the exposure device control unit to the switch via the laser control unit.

[0013] Figure 3 This is a graph showing the change in pulse energy E[n] when the voltage command value HVcmd[n] is set to a fixed value and burst oscillation is performed in the comparative example.

[0014] Figure 4 Graph showing changes in pulse energy E[n] when feedback control is performed on voltage command value HVcmd[n] in the comparative example.

[0015] Figure 5 The structure of the laser device according to the first embodiment is schematically shown.

[0016] Figure 6 The contents of the data table stored in the storage unit are conceptually shown.

[0017] Figure 7 It is a timing chart schematically showing the operation of the laser control unit.

[0018] Figure 8 This is a flowchart showing the processing of the laser control unit in the first embodiment.

[0019] Fig. 9 This is a flowchart showing the process of updating parameters in the first embodiment.

[0020] Fig.10 It is a graph showing the relationship between the applied voltage value HV[n] and the pulse energy E[n] acquired in order to calculate the parameters GainHV and Const.

[0021] Fig.11 This is a flowchart showing the process of setting the applied voltage value HV[n] in the first embodiment.

[0022] Fig.12 This is a graph for explaining the principle of calculating the target pulse energy Et based on the voltage command value HVcmd[1].

[0023] Fig.13 This is a flowchart showing control using the data table in the first embodiment.

[0024] Fig.14 This is a graph for explaining the principle of setting the applied voltage value HV[n] based on the target pulse energy Et and the voltage value HVtbl[p,n].

[0025] Fig.15 This is a flowchart showing control using the offset value Offset[n] in the first embodiment.

[0026] Fig.16 It is a graph showing the transition of the applied voltage value HV[n] in the first embodiment.

[0027] Fig.17 This is a flowchart showing the process of updating parameters in the second embodiment.

[0028] Fig.18 It is a graph showing the transition of the applied voltage value HV[n] acquired in order to calculate the total attenuation amount TD.

[0029] Fig.19 This is a flowchart showing control using the offset value Offset[n] in the second embodiment.

[0030] Fig. 20 This is a graph showing a first example of transition of the applied voltage value HV[n] in the second embodiment.

[0031] Fig.21 This is a graph showing a second example of the transition of the applied voltage value HV[n] in the second embodiment.

[0032] Fig. 22 This is a flowchart showing control using the offset value Offset[n] in the third embodiment.

[0033] Fig.23 This is a graph showing an example of transition of the applied voltage value HV[n] in the third embodiment.

[0034] Fig.24 This is a flowchart showing the process of setting the applied voltage value HV[n] in the fourth embodiment.

[0035] Fig.25 Graph showing the change of pulse energy E[n] when the applied voltage value HV[n] is set to a fixed value and burst oscillation is performed at different repetition frequencies F.

[0036] Fig.26 This is a flowchart showing control in the case where the pulse number n is greater than 1 and less than i in the control using the data table in the fourth embodiment.

[0037] Fig. 27 : is a graph showing the change of the applied voltage value HVa[n] when the applied voltage value HV[n] is corrected so that the pulse energy E[n] is maintained at a constant value.

[0038] Fig.28 This is a flowchart showing control using the offset value Offset[n] in the first example of the fifth embodiment.

[0039] Fig.29 3 is a graph for explaining the process of correcting the total attenuation amount TD and the attenuation timing j in the first example.

[0040] Fig.30 This is a flowchart showing control using the offset value Offset[n] in the second example of the fifth embodiment.

[0041] Fig.31 This is a graph for explaining the process of correcting the total attenuation amounts TDa, TDb and the attenuation timings g, h, j in the second example.

[0042] Fig.32 The structure of an exposure device connected to a laser device is schematically shown. DETAILED DESCRIPTION

[0043] content

[0044] 1. Laser device of comparative example

[0045] 1.1 Structure

[0046] 1.2 Action

[0047] 1.3 Issues of Comparative Example

[0048] 2. Laser device for adjusting applied voltage

[0049] 2.1 Structure

[0050] 2.2 Action

[0051] 2.2.1 Overview

[0052] 2.2.2 Measurement of pulse energy E[n]

[0053] 2.2.3 Main routine

[0054] 2.2.4 Parameter Update (S1)

[0055] 2.2.5 Setting of applied voltage value HV[n] (S2)

[0056] 2.2.5.1 Control of using data table (S27)

[0057] 2.2.5.2 Control using bias value (S29)

[0058] 2.3 Function

[0059] 3. Laser device that attenuates the bias value by a fixed amount each time

[0060] 3.1 Parameter Update (S1)

[0061] 3.2 Control using bias value (S29)

[0062] 3.3 Function

[0063] 4. Laser device that changes the attenuation of the bias value

[0064] 4.1 Control using bias value (S29)

[0065] 4.2 Function

[0066] 5. Laser device that corrects the applied voltage value according to the repetition frequency

[0067] 5.1 Setting of applied voltage value HV[n] (S2)

[0068] 5.2 Control of using data tables (S28c)

[0069] 5.3 Function

[0070] 6. Laser device that corrects the total attenuation and attenuation timing according to the repetition frequency

[0071] 6.1 Example 1

[0072] 6.2 Case 2

[0073] 6.3 Function

[0074] 7. Others

[0075] Below, the embodiments of the present disclosure are described in detail with reference to the accompanying drawings. The embodiments described below illustrate 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.

[0076] 1. Laser device of comparative example

[0077] 1.1 Structure

[0078] Figure 1 The structure of the laser device 1 of the comparative example is schematically shown. The laser device 1 is used together with the exposure device 100 as an external device. The exposure device 100 includes an exposure device control unit 110 .

[0079] The laser device 1 includes a cavity 10, a charger 12, a pulse power module (PPM) 13, a narrowband module 14, an output coupling mirror 15, and a laser control unit 30. The narrowband module 14 and the output coupling mirror 15 constitute a laser resonator.

[0080] The cavity 10 is disposed on the optical path of the laser resonator. Windows 10a and 10b are provided in the cavity 10. An opening is formed in a part of the cavity 10, and the opening is blocked by an insulating member 29. A plurality of conductive members 29a are embedded in the insulating member 29.

[0081] The cavity 10 contains a pair of electrodes 11a and 11b and a cross-flow fan 21, and also contains laser gas as a laser medium. The laser medium is, for example, F2, ArF, KrF, XeCl or XeF. The electrode 11a is supported by an insulating component 29. The electrode 11a is electrically connected to the pulse power module 13 via a conductive component 29a. The electrode 11b is supported by a return plate 10c located inside the cavity 10. The electrode 11b is connected to the ground potential via the return plate 10c. There is a circuit for supplying laser gas between the cavity 10 and the return plate 10c. Figure 1 A gap (not shown) through which the depth side and the front side of the paper surface pass.

[0082] The rotating shaft of the cross flow fan 21 is connected to a motor 22 disposed outside the chamber 10 . The cross flow fan 21 is configured to circulate the laser gas inside the chamber 10 .

[0083] The charger 12 holds electric energy for supplying to the pulse power module 13. The pulse power module 13 includes a switch 13a. The charger 12 and the pulse power module 13 constitute the power supply in the present disclosure. The narrowband module 14 includes wavelength selection elements such as a prism 14a and a grating 14b. The output coupling mirror 15 is composed of a partial reflection mirror.

[0084] The laser control unit 30 is composed of a computer device including a CPU (central processing unit) 38 and a memory 39. The memory 39 stores programs and data required for information processing. The CPU 38 is configured to read various data according to the program stored in the memory 39 and perform information processing.

[0085] 1.2 Action

[0086] The exposure device control unit 110 sends a voltage command value HVcmd[n] and a trigger signal Tr[n] to the laser control unit 30. The laser control unit 30 sends a setting signal of the voltage command value HVcmd[n] to the charger 12, and sends a trigger signal Tr[n] to the switch 13a.

[0087] The switch 13a is turned on when receiving the trigger signal Tr[n] from the laser control unit 30. When the switch 13a is turned on, the pulse power module 13 generates a pulsed high voltage using the electric energy stored in the charger 12. The pulse power module 13 applies the high voltage to the electrodes 11a and 11b.

[0088] When a high voltage is applied to electrodes 11a and 11b, a discharge is generated between electrodes 11a and 11b. The energy of the discharge excites the laser gas in cavity 10 to transition to a higher energy level. Then, when the excited laser gas transitions to a lower energy level, light of a wavelength corresponding to the energy level difference is emitted.

[0089] The light generated in the cavity 10 is emitted to the outside of the cavity 10 through the windows 10a and 10b. The light emitted from the window 10a is enlarged in beam width by the prism 14a and is incident on the grating 14b. The light incident on the grating 14b from the prism 14a is reflected by the multiple grooves of the grating 14b and diffracted in the direction corresponding to the wavelength of the light. The grating 14b is configured in a Littrow configuration so that the incident angle of the light incident on the grating 14b from the prism 14a is consistent with the diffraction angle of the diffracted light of the desired wavelength. As a result, the light near the desired wavelength returns to the cavity 10 through the prism 14a.

[0090] The output coupling mirror 15 transmits a part of the light emitted from the window 10 b and outputs it, and reflects the other part and returns it to the cavity 10 .

[0091] In this way, the light emitted from the cavity 10 reciprocates between the narrowband module 14 and the output coupling mirror 15. The light is amplified each time it passes through the discharge space between the pair of electrodes 11a and 11b. In addition, the light is narrowbanded each time it returns to the narrowband module 14. The light that is narrowbanded by laser oscillation is output from the output coupling mirror 15 as a pulsed laser.

[0092] The pulsed laser output from the laser device 1 is incident on the exposure device 100. The exposure device 100 includes an energy monitor (not shown), and the exposure device control unit 110 obtains the measurement result of the pulse energy E[n] of the pulsed laser from the energy monitor. The exposure device control unit 110 sets the voltage command value HVcmd[n] through feedback control based on the measured pulse energy E[n] and the setting data of the target pulse energy Etcmd.

[0093] Figure 2 1 is a pulse waveform diagram showing an example of a trigger signal Tr[n] output from the exposure device control unit 110 to the switch 13 a via the laser control unit 30 . Figure 2 The horizontal axis shows time T, and the vertical axis shows signal intensity. The exposure device control unit 110 outputs a trigger signal Tr[n] at a repetition frequency F during a certain period. The laser device 1 performs laser oscillation based on the trigger signal Tr[n] output at the repetition frequency F, and outputting pulsed laser at the repetition frequency F is called "burst oscillation".

[0094] After the exposure device control unit 110 outputs the trigger signal Tr[n] at the repetition frequency F, the output of the trigger signal Tr[n] is suspended. Then, the exposure device control unit 110 outputs the trigger signal Tr[n] again at the repetition frequency F. The period during which the output of the trigger signal Tr[n] is suspended between the first burst oscillation and the next second burst oscillation is referred to as a "suspended period".

[0095] The period of burst oscillation corresponds to, for example, the period of exposure of one exposure area of ​​the semiconductor wafer in the exposure device 100. The rest period corresponds to, for example, the period of moving the imaging position of the mask pattern from one exposure area to another exposure area in the exposure device 100 or the period of replacing the semiconductor wafer.

[0096] The pulse laser output from the laser device 1 in one burst oscillation includes a plurality of pulses corresponding to the trigger pulse of the trigger signal Tr[n]. The pulse number representing the order of the pulses among the plurality of pulses output from the laser device 1 in one burst oscillation is set to n. The pulse number n is defined as increasing one by one in the order of 1, 2, 3, ... from the pulse at the beginning of the burst oscillation for each burst oscillation. In the present disclosure, [n] is added to the end of the number for signals outputted individually for each pulse and data measured individually for each pulse. In addition, when referring to a specific pulse among these signals and data, [1], [2], etc. are sometimes added to the end of the number.

[0097] 1.3 Issues of Comparative Example

[0098] Figure 3 This is a graph showing the change in pulse energy E[n] when the voltage command value HVcmd[n] is set to a fixed value and burst oscillation is performed in the comparative example. Figure 3 The horizontal axis shows the pulse number n. When pulse laser is output at a high repetition frequency in burst oscillation, the laser gain may decrease. The decrease in laser gain is Figure 3 In other words, even if the voltage command value HVcmd[n] is fixed, the pulse energy E[n] is sometimes high at the beginning of the burst oscillation, and then the pulse energy E[n] decreases. In addition, sometimes the pulse energy E[1] is significantly high when the pulse number n is 1, and then the pulse energy E[n] decreases sharply. Sometimes in the middle of the burst oscillation, the pulse energy E[n] temporarily stabilizes, and then the pulse energy E[n] further decreases.

[0099] In addition, depending on the length of the rest period from the end of the first burst oscillation to the start of the second burst oscillation, the laser gain may be restored. If the laser gain is restored, the pulse energy E[n] is restored. The changes in the laser gain and the pulse energy E[n] during the burst oscillation may depend on the characteristics of the laser device 1.

[0100] Figure 4 Graph showing changes in pulse energy E[n] when feedback control is performed on voltage command value HVcmd[n] in the comparative example. Figure 4 and Figure 3 In contrast, the vertical axis is extended to emphasize the change in pulse energy E[n].

[0101] The exposure device control unit 110 sets the voltage command value HVcmd[1] according to the setting data of the target pulse energy Etcmd in the first pulse (n=1) of the burst oscillation. When the first pulse (n=1) of the burst oscillation is output, the laser gain recovers depending on the length of the pause period, and the pulse energy E[1] may be significantly higher than the target pulse energy Etcmd.

[0102] Therefore, the exposure device control unit 110 sets the voltage command value HVcmd[2] for the next pulse (n=2) through feedback control based on the difference between the pulse energy E[1] and the target pulse energy Etcmd. Figure 3 As shown in FIG. 1 , when the next pulse (n=2) is output, the laser gain sometimes decreases significantly compared to when the first pulse (n=1) is output. Figure 4 As shown, the pulse energy E[2] of the next pulse (n=2) may be significantly lower than the target pulse energy Etcmd.

[0103] As described above, due to the feedback control of the exposure device control unit 110 , the pulse energy E[n] may become unstable, especially immediately after the burst oscillation starts, which may adversely affect the exposure performance.

[0104] 2. Laser device for adjusting applied voltage

[0105] 2.1 Structure

[0106] Figure 5 The configuration of the laser device 1 according to the first embodiment is schematically shown. In the first embodiment, the laser device 1 further includes an energy monitor 17 and a storage unit 31 .

[0107] The energy monitor 17 includes a beam splitter 17a, a condenser lens 17b, and a light sensor 17c. The beam splitter 17a is arranged on the optical path of the pulse laser output from the output coupling mirror 15. The beam splitter 17a is configured to transmit a part of the pulse laser output from the output coupling mirror 15 toward the exposure device 100 with a high transmittance and reflect the other part. The condenser lens 17b and the light sensor 17c are arranged on the optical path of the pulse laser reflected by the beam splitter 17a.

[0108] The storage unit 31 is a storage device that stores a data table of the voltage value HVtbl[p,n]. The storage unit 31 can read and write the data table through the laser control unit 30.

[0109] Figure 6 The content of the data table stored in the storage unit 31 is conceptually shown. In the following description, a category p defined according to the length of the idle period is used. The category p of the idle period is defined, for example, as follows.

[0110] p=1: The idle period is 20 ms or more and less than 50 ms

[0111] p=2: The idle period is 50 ms or more and less than 80 ms

[0112] p=3: The idle period is 80 ms or more and less than 100 ms

[0113] When the idle period is 100 ms or longer, the type p of the idle period may be 4 or longer.

[0114] When the period from one trigger pulse to the next trigger pulse is less than 20 ms, it is determined that the pulse is not in a pause period but is in burst oscillation.

[0115] The storage unit 31 stores a data table that associates a voltage value HVtbl[p,n] that makes the pulse energy E[n] a predetermined value Estd with a combination [p,n] of the category p and the pulse number n during the rest period. The predetermined value Estd is a pulse energy that serves as a reference for the process of setting the applied voltage value HV[n] in the present disclosure, and is, for example, 10 mJ. The data table includes a voltage value HVtbl[p,n] corresponding to the pulse number n immediately after the burst oscillation starts. For example, the data table includes a voltage value HVtbl[p,1] when the pulse number n is 1 and a voltage value HVtbl[p,2] when the pulse number n is 2.

[0116] Regarding other points, the structure of the first embodiment is the same as that of the comparative example.

[0117] 2.2 Action

[0118] 2.2.1 Overview

[0119] Figure 7 2 is a timing chart schematically showing the operation of the laser control unit 30. Figure 7 In FIG. 1 , it is assumed that time progresses from the top to the bottom. The timing of receiving the voltage command value HVcmd[n] and the trigger signal Tr[n] from the exposure device control unit 110 is also shown. The laser control unit 30 performs the following processing according to the value of the pulse number n. Figure 7 In the following description, numbers beginning with S indicate corresponding step numbers in the flowcharts described below.

[0120] (1) n = 1

[0121] The laser control unit 30 measures the length of the rest period during the rest period (S22). The laser control unit 30 determines the category p based on the length of the rest period.

[0122] The laser control unit 30 receives the voltage command value HVcmd[1] from the exposure device control unit 110. The laser control unit 30 calculates the target pulse energy Et based on the voltage command value HVcmd[1] (S25). Fig.11 This will be described later. Since the laser control unit 30 does not receive the target pulse energy Etcmd set by the exposure device control unit 110, the laser control unit 30 performs the following processing using the target pulse energy Et calculated from the voltage command value HVcmd[1].

[0123] The laser control unit 30 searches the data table based on the combination [p, 1] of the rest period type p and the pulse number n, and reads the voltage value HVtbl[p, 1] that makes the pulse energy E[n] become the specified value Estd. The laser control unit 30 sets the applied voltage value HV[1] based on the target pulse energy Et and the voltage value HVtbl[p, 1] (S271). The processing of S271 refers to Fig.13 This will be described later. The laser control unit 30 sends a setting signal of the applied voltage value HV[1] to the charger 12 .

[0124] That is, the laser control unit 30 does not directly set the voltage command value HVcmd[1] as the applied voltage value, but sets the applied voltage value HV[1] using the voltage value HVtbl[p,1] read from the data table.

[0125] After the applied voltage value HV[1] is set, the laser control unit 30 receives the trigger signal Tr[1] from the exposure device control unit 110 and sends the trigger signal Tr[1] to the switch 13a.

[0126] (2) n = 2

[0127] When the pulse number n is 2, the type p of the pause period has been determined and the target pulse energy Et has been calculated. The laser control unit 30 searches the data table based on the combination [p, 2] of the type p of the pause period and the pulse number n, and reads the voltage value HVtbl[p, 2] that makes the pulse energy E[n] equal to the specified value Estd. The laser control unit 30 sets the applied voltage value HV[2] based on the target pulse energy Et and the voltage value HVtbl[p, 2] (S271). The laser control unit 30 sends a setting signal for the applied voltage value HV[2] to the charger 12.

[0128] After the applied voltage value HV[2] is set, the laser control unit 30 receives the trigger signal Tr[2] from the exposure device control unit 110 and sends the trigger signal Tr[2] to the switch 13a.

[0129] After setting the applied voltage value HV[2], the laser control unit 30 calculates the difference Dif between the voltage command value HVcmd[2] received from the exposure device control unit 110 and the applied voltage value HV[2] (S279). Fig.13 This will be described later. Alternatively, one of the transmission and reception of the trigger signal Tr[2] and the calculation of the difference Dif may be performed first.

[0130] (3)n≥3

[0131] When the pulse number n is 3, the laser control unit 30 calculates the offset value Offset[3] based on the difference Dif (S292). The offset value Offset[3] is, for example, the same value as the difference Dif. The laser control unit 30 sets the applied voltage value HV[3] (S293) by adding the offset value Offset[3] to the voltage command value HVcmd[3] received from the exposure device control unit 110. The laser control unit 30 sends a setting signal for the applied voltage value HV[3] to the charger 12. For details about the processing of S292 and S293, refer to Fig.15 This will be described later.

[0132] The processing of the laser control unit 30 when the pulse number n is 4 is the same as the above processing when the pulse number n is 3. The laser control unit 30 calculates the offset value Offset[4] based on the difference Dif (S292), and sets the applied voltage value HV[4] by adding the offset value Offset[4] to the voltage command value HVcmd[4] (S293). The processing of the laser control unit 30 when the pulse number n is 5 or more is also the same as the above processing when the pulse number n is 3. That is, when the pulse number n is 3 or more, the laser control unit 30 sets the applied voltage value HV[n] based on the voltage command value HVcmd[n] and the offset value Offset[n].

[0133] 2.2.2 Measurement of pulse energy E[n]

[0134] Refer again Figure 5 When the condenser lens 17b included in the energy monitor 17 condenses the pulse laser reflected by the beam splitter 17a to the optical sensor 17c. The optical sensor 17c transmits an electrical signal corresponding to the pulse energy E[n] of the pulse laser condensed by the condenser lens 17b to the laser control unit 30.

[0135] The pulse energy E[n] measured by the energy monitor 17 is used to update the parameters GainHV and Const for calculating the target pulse energy Et. Fig. 9 The processing of S12 will be described later.

[0136] In addition, the pulse energy E[n] measured by the energy monitor 17 is used to update the data table. Fig.13 The processing of S277 is described later.

[0137] 2.2.3 Main routine

[0138] Figure 8 : is a flowchart showing the processing of the laser control unit 30 in the first embodiment. The laser control unit 30 repeatedly performs the following two processes.

[0139] Parameter update (S1)

[0140] Setting of applied voltage value HV[n] (S2)

[0141] Next, each process is described.

[0142] 2.2.4 Parameter Update (S1)

[0143] Fig. 9 This is a flowchart showing the process of updating parameters in the first embodiment. Fig. 9 The treatment shown is Figure 8 The S1 subroutine.

[0144] In S11, the laser control unit 30 determines whether to update the parameters GainHV and Const used to calculate the target pulse energy Et. When the trigger signal Tr[n] received from the exposure device control unit 110 indicates the oscillation mode of the calibration oscillation, the laser control unit 30 determines to update the parameters GainHV and Const. When the trigger signal Tr[n] received from the exposure device control unit 110 indicates the oscillation mode of semiconductor exposure, the laser control unit 30 determines not to update the parameters GainHV and Const. The calibration oscillation is a laser oscillation performed in order for the exposure device control unit 110 to obtain parameters for feedback control based on the target pulse energy Etcmd. For example, the calibration oscillation is performed every time a semiconductor wafer is replaced.

[0145] When the parameters GainHV and Const are updated ( S11 : Yes), the laser control unit 30 proceeds to S12 .

[0146] In S12, the laser control unit 30 calculates and updates the parameters GainHV and Const based on the relationship between the applied voltage value HV[n] during calibration oscillation and the measured pulse energy E[n]. The applied voltage value HV[n] during calibration oscillation is the same value as the voltage command value HVcmd[n] received from the exposure device control unit 110.

[0147] Fig.10 : is a graph showing the relationship between the applied voltage value HV[n] and the pulse energy E[n] obtained for calculating the parameters GainHV and Const. In S12, the pulse energy E[n] is measured for each of the multiple applied voltage values ​​HV[n] that are different from each other, and an approximate straight line is calculated based on the relationship between the applied voltage value HV[n] and the pulse energy E[n]. The approximate straight line is represented by the following formula.

[0148] E[n]=HV[n]×A+B

[0149] At this time, the value of A is set to the new value of the parameter GainHV, and the value of B is set to the new value of the parameter Const.

[0150] Refer again Fig. 9 If the parameters GainHV and Const are not updated in S11 (S11: No), or after S12, the laser control unit 30 ends. Fig. 9 The processing of the flowchart shown in the figure returns Figure 8 Processing shown.

[0151] 2.2.5 Setting of applied voltage value HV[n] (S2)

[0152] Fig.11This is a flowchart showing the process of setting the applied voltage value HV[n] in the first embodiment. Fig.11 The treatment shown is Figure 8 The S2 subroutine.

[0153] In S21, the laser control unit 30 determines whether it is in the rest period based on the signal from the exposure device control unit 110. When the laser control unit 30 determines that it is in the rest period (S21: Yes), the process proceeds to S22. When the laser control unit 30 determines that it is not in the rest period (S21: No), the process proceeds to S23.

[0154] In S22, the laser control unit 30 measures the length of the pause period. After S22, the laser control unit 30 returns to S21. The laser control unit 30 repeats the processes of S21 and S22 and measures the length of the pause period until it is determined that the pause period is not in progress.

[0155] In S23, the laser control unit 30 receives the voltage command value HVcmd[n] from the exposure device control unit 110. Next, in S24, the laser control unit 30 determines whether the pulse number n is 1. When the pulse number n is 1 (S24: Yes), the laser control unit 30 advances the process to S25. When the pulse number n is not 1 (S24: No), the laser control unit 30 advances the process to S26.

[0156] In S25 , the laser control unit 30 calculates the target pulse energy Et based on the voltage command value HVcmd[1].

[0157] Fig.12 This is a graph illustrating the principle of calculating the target pulse energy Et based on the voltage command value HVcmd[1]. Fig.10 As described above, from the measurement results during calibration oscillation, it is known that the applied voltage value HV[n] and the pulse energy E[n] have the following relationship.

[0158] E[n]=HV[n]×GainHV+Const

[0159] The laser control unit 30 and the exposure device control unit 110 each independently obtain data based on the same calibration oscillation. Therefore, it is estimated that there is no significant difference between the data obtained by the laser control unit 30 and the data obtained by the exposure device control unit 110. Therefore, it is estimated that the target pulse energy Et calculated by the following formula using the voltage command value HVcmd[1] is not significantly different from the target pulse energy Etcmd set by the exposure device control unit 110.

[0160] Et=HVcmd[1]×GainHV+Const

[0161] Refer again Fig.11 In S26, the laser control unit 30 determines whether the pulse number n is less than i. Here, i is an integer greater than 1, which corresponds to the pulse number n when the control using the offset value Offset[n] is started. For example, i is 3. When the pulse number n is less than i (S26: Yes), the laser control unit 30 causes the process to enter S27. When the pulse number n is 1 and the process of the above S25 is completed, the laser control unit 30 also causes the process to enter S27. When the pulse number n is greater than i (S26: No), the laser control unit 30 causes the process to enter S29.

[0162] In S27, the laser control unit 30 performs control using the data table. The control using the data table refers to Fig.13 This will be described later.

[0163] In S29, the laser control unit 30 performs control using the offset value Offset[n]. Fig.15 This will be described later.

[0164] After S27 or S29, the laser control unit 30 ends Fig.11 The processing of the flowchart shown in the figure returns Figure 8 Processing shown.

[0165] 2.2.5.1 Control of using data table (S27)

[0166] Fig.13 This is a flowchart showing control using the data table in the first embodiment. Fig.13 The treatment shown is Fig.11 The S27 subroutine.

[0167] In S271, the laser control unit 30 reads the voltage value HVtbl[p,n] from the data table according to the combination [p,n] of the type p of the pause period and the pulse number n. Then, the laser control unit 30 sets the applied voltage value HV[n] according to the target pulse energy Et and the voltage value HVtbl[p,n].

[0168] Fig.14 Graphs are provided to illustrate the principle of setting the applied voltage value HV[n] based on the target pulse energy Et and the voltage value HVtbl[p,n]. The voltage value HVtbl[p,n] read out from the combination [p,n] of the type p and the pulse number n during the rest period is the voltage value that makes the pulse energy E[n] the specified value Estd. Fig.10As described above, the relationship between the applied voltage value HV[n] and the pulse energy E[n] can be expressed by an approximate straight line with the parameter GainHV as the slope. Therefore, by using the following formula of the parameter GainHV, the voltage value HVtbl[p,n] corresponding to the specified value Estd can be converted into the applied voltage value HV[n] corresponding to the target pulse energy Et.

[0169] HV[n]=HVtbl[p,n]+(Et-Estd) / GainHV

[0170] Refer again Fig.13 In S274, the laser control unit 30 determines whether the trigger signal Tr[n] is received from the exposure device control unit 110. If the trigger signal Tr[n] is not received (S274: No), the laser control unit 30 waits until the trigger signal Tr[n] is received. If the trigger signal Tr[n] is received (S274: Yes), the laser control unit 30 advances the process to S275.

[0171] In S275 , the laser control unit 30 outputs the trigger signal Tr[n] to the pulse power module 13 . As a result, the laser device 1 outputs pulse laser light, and the energy monitor 17 measures the pulse energy E[n] of the pulse laser light.

[0172] In S276 , the laser control unit 30 receives the measurement data of the pulse energy E[n] from the energy monitor 17 .

[0173] In S277, the laser control unit 30 updates the voltage value HVtbl[p,n] in the data table according to the difference between the pulse energy E[n] and the target pulse energy Et. The voltage value HVtbl[p,n] in the data table is calculated by the following equation.

[0174] HVtbl[p,n]

[0175] =HV[n]+(Et-E[n])×GainCont / GainHV-(Et-Estd) / GainHV

[0176] Here, GainCont is a proportional gain greater than 0 and less than 2. (Et-E[n])×GainCont / GainHV corresponds to the operation amount based on proportional control. Further, (Et-Estd) / GainHV is subtracted to convert it into a voltage value HVtbl[p,n] that makes the pulse energy E[n] equal to the predetermined value Estd.

[0177] The proportional gain GainCont may also be a different value depending on the pulse number n. For example, when the proportional gain when the pulse number n is 1 is set to GainCont[1] and the proportional gain when the pulse number n is 2 is set to GainCont[2], the voltage value HVtbl[p,n] in the data table may also be calculated by the following formula.

[0178] HVtbl[p,1]

[0179] =HV[1]+(Et-E[1])×GainCont[1] / GainHV-(Et-Estd) / GainHV

[0180] HVtbl[p,2]

[0181] =HV[2]+(Et-E[2])×GainCont[2] / GainHV-(Et-Estd) / GainHV

[0182] The data table may be updated for combinations other than the specific combination [p,n] of the category p and the pulse number n during the rest period. For example, when the pulse energy E[1] is obtained when the pulse number n is 1, not only the voltage value HVtbl[p,1] but also the voltage value HVtbl[p,2] may be updated. When the data table is updated for combinations other than the specific combination [p,n], a smaller proportional gain GainCont may be used than when the data table is updated for the specific combination [p,n].

[0183] The data table may be updated after outputting a pulse with pulse number n=1 and before outputting a pulse with pulse number n=2. Thus, the applied voltage value HV[n] when pulse number n=2 can be set based on the measurement result of the pulse energy E[n] when pulse number n=1.

[0184] The data table can be updated not only during the burst oscillation but also after a part of the gas inside the chamber 10 is replaced or after the gas concentration is adjusted.

[0185] In S278, the laser control unit 30 determines whether the pulse number n is i-1. The pulse when the pulse number n is i-1 is the last pulse among the pulses controlled using the data table (S27). When the pulse number n is i-1 (S278: Yes), the laser control unit 30 advances the process to S279.

[0186] In S279 , the laser control unit 30 calculates the difference Dif between the applied voltage value HV[n] and the voltage command value HVcmd[n] using the following equation.

[0187] Dif=HV[n]-HVcmd[n]

[0188] The difference Dif is used Fig.15 The S292.

[0189] If the pulse number n is not i-1 in S278 (S278: No), or after S279, the laser control unit 30 ends. Fig.13 The processing of the flowchart shown in the figure returns Fig.11 Processing shown.

[0190] 2.2.5.2 Control using bias value (S29)

[0191] Fig.15 This is a flowchart showing control using the offset value Offset[n] in the first embodiment. Fig.15 The treatment shown is Fig.11 The S29 subroutine.

[0192] In S292 , the laser control unit 30 calculates the offset value Offset[n] using the following equation.

[0193] Offset[n]=Dif

[0194] That is, in Fig.15 In the processing, the offset value Offset[n] is set to a fixed value regardless of the value of the pulse number n.

[0195] In S293 , the laser control unit 30 sets the applied voltage value HV[n] according to the voltage command value HVcmd[n] and the offset value Offset[n] using the following equation.

[0196] HV[n]=HVcmd[n]+Offset[n]

[0197] The pulse number n is in the range of not less than i and less than j. Here, j is an integer greater than i, for example, a number obtained by adding 1 to the number of pulses in one burst oscillation.

[0198] Fig.16 It is a graph showing the transition of the applied voltage value HV[n] in the first embodiment. Fig.16 The horizontal axis of shows the pulse number n. When the pulse number n is 1 and when the pulse number n is 2, the applied voltage value HV[n] is set by control (S27) using the data table. Fig.16 The voltage command value HVcmd[n] after the pulse number n is 2 is also shown. Fig.13In S279, the difference Dif between the applied voltage value HV[2] and the voltage command value HVcmd[2] when the pulse number n is 2 is calculated. Fig.16 In the example shown, the difference Dif is a negative number.

[0199] Through S292, the offset value Offset[n] is set to the same value as the difference Dif.

[0200] Then, the voltage command value HVcmd[n] is added with the offset value Offset[n] by S293, thereby setting the applied voltage value HV[n]. The voltage command value HVcmd[n] is feedback-controlled by the exposure device control unit 110 so that the pulse energy E[n] is maintained at a value near the target pulse energy Etcmd. Figure 3 As described above, due to the characteristics of the laser device 1 , when the laser gain decreases during burst oscillation, the voltage command value HVcmd[n] increases accordingly.

[0201] Compared to the period immediately after the burst with pulse number n being greater than 1 and less than i, the change in laser gain is gentler when pulse number n is greater than i and less than j. Therefore, when pulse number n is greater than i and less than j, the pulse energy E[n] can be maintained at a value close to the target pulse energy Etcmd by feedback control by the exposure device control unit 110.

[0202] Furthermore, by setting the applied voltage value HV[n] using the same offset value Offset[n] as the difference Dif, a sudden change in the applied voltage value HV[n] is suppressed, and thus a stable pulse energy E[n] can be obtained.

[0203] Refer again Fig.15 In S294, the laser control unit 30 determines whether the trigger signal Tr[n] is received from the exposure device control unit 110. If the trigger signal Tr[n] is not received (S294: No), the laser control unit 30 waits until the trigger signal Tr[n] is received. If the trigger signal Tr[n] is received (S294: Yes), the laser control unit 30 enters the process into S295.

[0204] In S295, the laser control unit 30 outputs the trigger signal Tr[n] to the pulse power module 13. As a result, the laser device 1 outputs pulse laser light.

[0205] After S295, the laser control unit 30 ends Fig.15 The processing of the flowchart shown in the figure returns Fig.11 Processing shown.

[0206] 2.3 Function

[0207] (1) According to the first embodiment, in the period immediately after the burst with pulse number n less than i starts, the applied voltage value HV[n] is set based on the voltage value HVtbl[p,n] read from the data table ( Fig.13 Thus, even if the voltage command value HVcmd[n] varies during the period immediately after the burst starts, the appropriate applied voltage value HV[n] can be set according to the characteristics of the laser device 1.

[0208] According to the first embodiment, during a period in which the pulse number n is equal to or greater than i, the applied voltage value HV[n] is set according to the offset value Offset[n] ( Fig.15 Thus, when the control (S27) using the data table is transferred to the control (S29) using the offset value Offset[n], a sudden change in the applied voltage value HV[n] is suppressed, and a stable pulse energy E[n] can be obtained.

[0209] (2) According to the first embodiment, the voltage value HVtbl[p,n] is stored in the data table in correspondence with the combination of the type p of the pause period and the pulse number n. Then, the corresponding voltage value HVtbl[p,n] is read from the data table. Fig.13 Thus, it is possible to set an appropriate applied voltage value HV[n] in detail according to the type p of the rest period and the pulse number n.

[0210] (3) According to the first embodiment, the target pulse energy Et ( Fig.11 Then, the applied voltage value HV[n] is calculated based on the target pulse energy Et and the voltage value HVtbl[p,n] read from the data table ( Fig.13 Thus, even if the target pulse energy Etcmd set by the exposure device control unit 110 is not received, a pulse energy E[n] close to the target pulse energy Etcmd can be obtained.

[0211] (4) According to the first embodiment, the parameters GainHV and Const(1) for calculating the target pulse energy Et from the voltage command value HVcmd[1] are calculated based on the measurement data during the calibration oscillation. Fig. 9 Thus, the laser control unit 30 can obtain the parameters under the same conditions as the conditions under which the exposure device control unit 110 obtains the parameters.

[0212] (5) According to the first embodiment, the data table is updated based on the difference between the measured value of the pulse energy E[n] and the target pulse energy Et ( Fig.13Thus, even if the characteristics of the laser device 1 vary, it is possible to set an appropriate applied voltage value HV[n].

[0213] (6) According to the first embodiment, the data table is updated after the pulse with pulse number n=1 is output and before the pulse with pulse number n=2 is output ( Fig.13 Thus, it is possible to set an appropriate applied voltage value HV[n] as quickly as possible to follow the change in the characteristics of the laser device 1.

[0214] (7) According to the first embodiment, the offset value Offset[n] is calculated based on the difference Dif between the voltage command value HVcmd[n] for outputting the pulse with pulse number n=i-1 and the applied voltage value HV[n] ( Fig.13 S279, Fig.15 Thus, when the control (S27) using the data table is transferred to the control (S29) using the offset value Offset[n], a large change in the pulse energy E[n] can be suppressed.

[0215] (8) According to the first embodiment, the offset value Offset[n] is set to a fixed value without changing during the sudden oscillation, so that the calculation process can be suppressed from being complicated.

[0216] 3. Laser device that attenuates the bias value by a fixed amount each time

[0217] use Figures 17 to 21 The second embodiment is described. The second embodiment differs from the first embodiment in that the offset value Offset[n] is not a fixed value and decays during the burst oscillation. In the second embodiment, the period when the pulse number n is greater than i and less than j is defined as the decay period, and the offset value Offset[n] decays during the decay period. Here, j is an integer greater than i. The structure of the laser device 1 of the second embodiment is similar to that of the reference Figure 5 The structure is the same as that of the first embodiment described above.

[0218] 3.1 Parameter Update (S1)

[0219] Fig.17 This is a flowchart showing the processing of updating parameters in the second embodiment. Figure 8 The main routine in the first embodiment described is the same. Fig.17 The treatment shown is Figure 8 The S1 subroutine.

[0220] Fig.17 The S11 and S12 are processed with Fig. 9 The corresponding processing is the same as in Fig.17In the case where the parameters GainHV and Const are not updated ( S11 : No), or after S12 , the laser control unit 30 advances the process to S13 a .

[0221] In S13a, the laser control unit 30 determines whether to update the total attenuation amount TD. When the trigger signal Tr[n] received from the exposure device control unit 110 indicates the oscillation mode of the calibration oscillation, the laser control unit 30 determines to update the total attenuation amount TD. When the trigger signal Tr[n] received from the exposure device control unit 110 indicates the oscillation mode of the semiconductor exposure, the laser control unit 30 determines not to update the total attenuation amount TD. Furthermore, the laser control unit 30 may also determine to update the total attenuation amount TD after replacing part of the gas inside the chamber 10 or adjusting the gas concentration.

[0222] When updating the total attenuation amount TD ( S13 a : Yes), the laser control unit 30 proceeds to S14 a .

[0223] In S14a, the laser control unit 30 measures the drift amount Drift(x) of the applied voltage value HV[n] during calibration oscillation. The laser control unit 30 calculates the total attenuation amount TD based on the measured drift amount Drift(x), and updates the total attenuation amount TD.

[0224] Fig.18 ] is a graph showing the change of the applied voltage value HV[n] obtained in order to calculate the total attenuation amount TD. Figure 3 As described above, due to the characteristics of the laser device 1, the laser gain may decrease during burst oscillation. During calibration oscillation, when the applied voltage value HV[n] is set so that the pulse energy E[n] is maintained at a fixed value, the applied voltage value HV[n] increases. Therefore, the laser control unit 30 measures the increase in the applied voltage value HV[n] during the period from when the pulse number n is i to when the burst oscillation ends as the drift amount Drift(x). The laser control unit 30 also calculates the total attenuation amount TD based on the drift amount Drift(x).

[0225] The total attenuation amount TD is calculated by the following formula.

[0226] TD=Sum(Drift(x-9:x)) / 10

[0227] Here, Sum(Drift(x-9:x)) is the total value of the measurement results of the drift amount Drift(x) for the past 10 times. The total attenuation amount TD is equivalent to the moving average value of the drift amount Drift(x) for the past 10 times.

[0228] If the total attenuation amount TD is not updated in S13a (S13a: No) or after S14a, the laser control unit 30 ends. Fig.17 The processing of the flowchart shown in the figure returns Figure 8 Processing shown.

[0229] 3.2 Control using bias value (S29)

[0230] Fig.19 : is a flowchart showing control using the offset value Offset[n] in the second embodiment. In the second embodiment, the process of setting the applied voltage value HV[n] is the same as the process of the first embodiment except that the process of setting the applied voltage value HV[n] is control using the offset value Offset[n]. Fig.19 The treatment shown is Fig.11 The S29 subroutine.

[0231] In S292a, the laser control unit 30 calculates the offset value Offset[n] which decays as the pulse number n increases, using the following equation.

[0232] Offset[n]=Dif-TD×(in) / (ji)

[0233] Here, ji, which is obtained by subtracting i from j, becomes a value corresponding to the length of the decay period. Just after the decay period begins, pulse number n is a value close to i, so TD×(in) / (ji) becomes a value close to 0. Therefore, the offset value Offset[n] becomes a value close to the difference Dif. Just before the decay period ends, pulse number n is a value close to j, so TD×(in) / (ji) becomes a value close to -TD. Therefore, the offset value Offset[n] becomes a value close to the sum of the difference Dif and the total attenuation amount TD. When the total attenuation amount TD is divided by ji, the attenuation amount per pulse is obtained.

[0234] Processing and reference after S293 Fig.15 The corresponding processing in the first embodiment described is the same.

[0235] Regarding other aspects, the operation of the second embodiment is the same as that of the first embodiment.

[0236] 3.3 Function

[0237] Fig. 20 : is a graph showing a first example of the transition of the applied voltage value HV[n] in the second embodiment. Fig.19The offset value Offset[n] calculated by S292a of FIG. 1 is attenuated by a fixed amount each time as the pulse number n increases, from a value close to Dif to a value close to Dif+TD. Thus, the offset value Offset[n] is attenuated to correspond to the reference value. Fig.18 Since the drift amount Drift(x) described above is compensated, the change in the voltage command value HVcmd[n] can be made gentler than the change in the laser gain during the burst oscillation. Thus, a stable pulse energy E[n] can be obtained.

[0238] Fig.21 This is a graph showing a second example of the transition of the applied voltage value HV[n] in the second embodiment. Fig.21 The offset value Offset[n] calculated in Fig. 20 The offset value Offset[n] calculated in is the same. Fig.21 and Fig. 20 The difference lies in the change of the laser gain of the laser device 1. Fig.21 In the period from pulse number i to pulse number j, the laser gain changes by approximately a fixed amount each time. Fig.21 As shown in the figure, the laser gain changes as Fig. 20 Compared with the case where the voltage command value HVcmd[n] changes as shown in FIG. 1 , the voltage command value HVcmd[n] in the second embodiment changes more gradually. As a result, a stable pulse energy E[n] can be obtained.

[0239] According to the second embodiment, the total attenuation amount TD(x) of the offset value Offset[n] is calculated based on the drift amount Drift(x) of the applied voltage value HV[n]. Fig.17 As a result, the offset value Offset[n] is attenuated to compensate for the drift amount Drift(x), so that the voltage command value HVcmd[n] can be changed smoothly.

[0240] According to the second embodiment, the total attenuation amount TD( Fig.17 Thus, each time the semiconductor wafer is replaced, the total attenuation amount TD is updated, and the applied voltage value HV[n] that matches the latest laser characteristics can be set.

[0241] 4. Laser device that changes the attenuation of the bias value

[0242] use Figure 22-23 The third embodiment is described below. The third embodiment is different from the second embodiment in that the attenuation amount of the offset value Offset[n] is not fixed but varies during the burst oscillation. Figure 5 The structure is the same as that of the first embodiment described above.

[0243] 4.1 Control using bias value (S29)

[0244] Fig. 22 : is a flowchart showing control using the offset value Offset[n] in the third embodiment. Except for the control using the offset value Offset[n], the processing of the laser control unit 30 in the third embodiment is the same as the processing of the second embodiment. Fig. 22 The treatment shown is Fig.11 The S29 subroutine.

[0245] In the third embodiment, a plurality of attenuation periods with different attenuation amounts are set. The plurality of attenuation periods include a first attenuation period and a second attenuation period.

[0246] (1) The pulse number n in the first decay period is set to the following range.

[0247] i≤n <g

[0248] Here, g is an integer greater than i and less than j.

[0249] (2) The pulse number n between the first decay period and the second decay period is set to the following range.

[0250] g≤n <h

[0251] Here, h is an integer greater than or equal to g and less than or equal to j.

[0252] (3) The pulse number n in the second decay period is set to the following range.

[0253] h≤n <j

[0254] The attenuation period is specified by the above-mentioned g, h and j. In the following description, g, h and j are referred to as attenuation timing. By detecting the timing when the applied voltage value changes in the calibration oscillation, the attenuation timing g, h and j can be set. In addition, when there is no period in which the attenuation amount becomes 0 between the first attenuation period and the second attenuation period, g is set to a value equal to h. When there is no second attenuation period, h is set to a value equal to j. When there is no period in which the attenuation amount becomes 0 and there is no second attenuation period after the first attenuation period, g and h are set to values ​​equal to j.

[0255] In S292b, the laser control unit 30 calculates the offset value Offset[n] which decays as the pulse number n increases, using the following equation.

[0256] (1) The first decay period (i≤n <g)

[0257] Offset[n]=Dif-TDa×(in) / (gi)

[0258] Here, TDa is the total attenuation during the first attenuation period. Fig.18 The total attenuation amount TDa is calculated based on the drift amount Drift(x) in a certain period of time in the same manner as described above. The attenuation amount Ra per pulse in the first attenuation period is obtained by dividing the total attenuation amount TDa by gi.

[0259] Ra=TDa / (gi)

[0260] (2) Between the first decay period and the second decay period (g≤n <h)

[0261] Offset[n]=Dif+TDa

[0262] The total attenuation amount during this period is 0, and the attenuation amount Rm per pulse is also 0.

[0263] (3) Second decay period (h≤n <j)

[0264] Offset[n]=Dif+TDa-TDb×(hn) / (jh)

[0265] Here, TDb is the total attenuation during the second attenuation period. Fig.18 The total attenuation amount TDb is calculated based on the drift amount Drift(x) in a certain period of time in the same manner as described above. The attenuation amount Rb per pulse in the second attenuation period is obtained by dividing the total attenuation amount TDb by jh.

[0266] Rb=TDb / (jh)

[0267] The magnitude relationship among the attenuation amounts Ra, Rm, and Rb is as follows.

[0268] Rm <Rb<Ra

[0269] Ra corresponds to the first value in the present disclosure, Rm corresponds to the second value in the present disclosure, and Rb corresponds to the third value in the present disclosure.

[0270] Processing and reference after S293 Fig.15 The corresponding processing in the first embodiment described is the same.

[0271] 4.2 Function

[0272] Fig.23 Graph showing an example of the transition of the applied voltage value HV[n] in the third embodiment. Fig. 22The offset value Offset[n] calculated by S292b decays at respective decay amounts during the first decay period (i ≤ n < g) and the second decay period (h ≤ n < j). In this way, the decay amount changes as the pulse number n increases. Thus, the offset value Offset[n] can be decayed corresponding to the change characteristics of the laser gain. Therefore, compared with the change in the laser gain during burst oscillation, the change in the voltage command value HVcmd[n] can be made smoother. Thus, stable pulse energy E[n] can be obtained.

[0273] 5. Laser device that corrects the applied voltage value according to the repetition frequency

[0274] Use Figure 24 to Figure 27 The fourth embodiment will be described. The difference between the fourth embodiment and the first to third embodiments is that in the control using the data table, the applied voltage value HV[n] is corrected according to the repetition frequency F of the pulsed laser. The structure of the laser device 1 of the fourth embodiment is the same as the structure of the first embodiment described with reference to Figure 5 Explanation.

[0275] 5.1 Setting of the applied voltage value HV[n] (S2)

[0276] Fig.24 is a flowchart showing the process of setting the applied voltage value HV[n] in the fourth embodiment. The main routine in the fourth embodiment is the same as the main routine in the first embodiment described with reference to Figure 8 Explanation. Fig.24 The process shown is Figure 8 The subroutine of S2. Fig.24 The difference between the process shown and the first to third embodiments is that the control using the data table includes two processes, S27 and S28c. In other aspects, it is the same as the process described with reference to Fig.11 Explanation.

[0277] When the pulse number n is 1 in S24, after S25, the applied voltage value HV[n] is set through S27. The process of S27 is the same as the corresponding process in Fig.11 Explanation.

[0278] When the pulse number n is greater than 1 and less than i, in S26, it is determined that the pulse number n is less than i (S26: Yes), and the process transfers to S28c. In S28c, the applied voltage value HV[n] is calculated, and the applied voltage value HV[n] is corrected according to the repetition frequency F. After S28c, the laser control unit 30 ends Fig.24 The process of the flowchart shown and returns to Figure 8 The process shown.

[0279] Fig.25Graph showing the change of pulse energy E[n] when the applied voltage value HV[n] is set to a fixed value and burst oscillation is performed at different repetition frequencies F. Fig.25 Only the pulse energy E[n] immediately after the burst oscillation starts is shown. Sometimes, the higher the repetition frequency F, the easier it is for the laser gain of the laser device 1 to decrease. The pulse energy E[1] of the pulse with pulse number n=1 does not depend on the repetition frequency F, but the pulse energy E[n] of the pulse with pulse number n=2 or more may depend on the repetition frequency F. Therefore, when the pulse number n is greater than 1 and less than i, the applied voltage value HV[n] is corrected in S28c.

[0280] 5.2 Control of using data tables (S28c)

[0281] Fig.26 This is a flowchart showing control in the case where the pulse number n is greater than 1 and less than i in the control using the data table in the fourth embodiment. Fig.26 The treatment shown is Fig.24 The S28c subroutine.

[0282] Processing and reference of setting applied voltage value HV[n] in S271 Fig.13 The corresponding processing described is the same.

[0283] In S272c, the laser control unit 30 sets the applied voltage value HVa[n] corrected according to the repetition frequency F by the following equation.

[0284] HVa[n]=HV[n]×(1+coef×(F-Fstd) / Fstd)

[0285] Here, Fstd is a reference frequency, for example, 4 kHz. The voltage value HVtbl[p,n] in the data table stored in the storage unit 31 is set to a value that makes the pulse energy E[n] become a predetermined value Estd in the burst oscillation at the reference frequency Fstd. In addition, coef is a weighting coefficient multiplied by the value (F-Fstd) / Fstd obtained by dividing the difference between the repetition frequency F and the reference frequency Fstd by the reference frequency Fstd.

[0286] When the laser control unit 30 is notified of the repetition frequency F by the exposure device control unit 110, the above correction is performed using the repetition frequency F. When the repetition frequency F is not notified by the exposure device control unit 110, the repetition frequency F is calculated based on the time difference between the trigger signal Tr[1] and the trigger signal Tr[2], and the above correction is performed.

[0287] Fig. 27Graph showing the change of applied voltage value HVa[n] when applied voltage value HV[n] is corrected so that pulse energy E[n] is maintained at a fixed value. Fig. 27 Only the applied voltage value HVa[n] immediately after the burst oscillation starts is shown. When the repetition frequency F is 3 kHz, the laser gain of the laser device 1 is not easily reduced compared to when the repetition frequency F is 4 kHz. Therefore, when the repetition frequency F is 3 kHz, the applied voltage value HVa[n] is corrected so that the applied voltage value HVa[n] becomes lower when the pulse number n is 2 or more than when the repetition frequency F is 4 kHz. Thus, the pulse energy E[n] can be made close to the desired value.

[0288] Refer again Fig.26 , Processing and reference of S274~S276 Fig.13 The corresponding processing described is the same.

[0289] In S277c, the laser control unit 30 updates the voltage value HVtbl[p,n] in the data table according to the difference between the pulse energy E[n] and the target pulse energy Et. Considering the correction based on the repetition frequency F, the voltage value HVtbl[p,n] in the data table is calculated by the following equation.

[0290] HVtbl[p,n]

[0291] =(HVa[n]+(Et-E[n])×GainCont / GainHV) / (1+coef×(F-Fstd) / Fstd)-(Et-Estd) / GainHV

[0292] Processing and reference of S278~S279 Fig.13 The corresponding processing described is the same.

[0293] Regarding other aspects, the operation of the fourth embodiment is the same as that of the first to third embodiments.

[0294] 5.3 Function

[0295] According to the fourth embodiment, even if the voltage value HVtbl[p,n] in the data table is not stored separately according to the repetition frequency F, the appropriate applied voltage value HVa[n] can be set according to the repetition frequency F.

[0296] 6. Laser device that corrects the total attenuation and attenuation timing according to the repetition frequency

[0297] use Figure 28 to Figure 31The fifth embodiment is described. The fifth embodiment is different from the first to fourth embodiments in that, in the control using the offset value Offset[n], the total attenuation amount TD and the attenuation timing j of the offset value Offset[n] are corrected according to the repetition frequency F of the pulsed laser. Figure 5 The structure of the first embodiment described is the same as that of the first embodiment described above. Figure 8 The main routine of the first embodiment described above is the same as that of the first embodiment. However, in the fifth embodiment, a process of calculating the total attenuation amount TD is performed. The process of calculating the total attenuation amount TD is the same as that of Fig.17 The processing is the same, so the description is omitted.

[0298] 6.1 Example 1

[0299] Fig.28 1 is a flowchart showing control using offset value Offset[n] in the first example of the fifth embodiment. Except for control using offset value Offset[n], the process of setting applied voltage value HV[n] in the first example is the same as the processes of the first to fourth embodiments. Fig.28 The treatment shown is Fig.11 The S29 subroutine. Alternatively, Fig.28 The treatment shown is Fig.24 The S29 subroutine.

[0300] In S291d, the laser control unit 30 corrects the total attenuation amount TD and the attenuation timing j of the offset value Offset[n] by the following equation, and calculates the corrected total attenuation amount TDm and the attenuation timing jm.

[0301] TDm=TD×F / Fstd

[0302] jm=j×F / Fstd

[0303] The correction based on the repetition frequency F can also be accompanied by a weighting using a coefficient.

[0304] Fig.29 Graphs are provided to explain the process of correcting the total attenuation amount TD and the attenuation timing j in the first example. Fig.29 The change of laser gain in the burst oscillation can be related to Fig.21 The total attenuation TD and the attenuation timing j are set to match the change in laser gain when the repetition frequency F is 4 kHz. The attenuation timing j can be set by detecting the timing when the applied voltage value HV[n] changes in the calibration oscillation. The total attenuation TD can be calculated based on the drift (x) of the applied voltage value HV[n] in the calibration oscillation.

[0305] When the repetition frequency F is 3 kHz or 2 kHz, the corrected total attenuation amount TDm and attenuation timing jm are calculated according to the above equations.

[0306] TD1=TD×3 / 4

[0307] j1=j×3 / 4

[0308] TD2=TD×2 / 4

[0309] j2=j×2 / 4

[0310] TD1 and j1 are respectively the corrected total attenuation amount and attenuation timing when the repetition frequency F is 3 kHz. TD2 and j2 are respectively the corrected total attenuation amount and attenuation timing when the repetition frequency F is 2 kHz.

[0311] By performing the calculation as described above, it is possible to calculate an appropriate offset value Offset[n] corresponding to the characteristics of the laser device 1 .

[0312] Refer again Fig.28 , S292d and S293d are treated with Fig.19 The processing of S292a and S293 is the same. However, several variables are replaced along with the correction.

[0313] The treatment of S294 and S295 is respectively Fig.19 The processing of S294 and S295 is the same.

[0314] 6.2 Case 2

[0315] Fig.30 1 is a flowchart showing control using the offset value Offset[n] in the second example of the fifth embodiment. Except for the control using the offset value Offset[n], the process of setting the applied voltage value HV[n] in the second example is the same as the processes in the first to fourth embodiments. Fig.30 The treatment shown is Fig.11 The S29 subroutine. Alternatively, Fig.30 The treatment shown is Fig.24 The S29 subroutine.

[0316] In S291e, the laser control unit 30 corrects the total attenuation amounts TDa, TDb and attenuation timings g, h, j of the offset value Offset[n] using the following equations, and calculates the corrected total attenuation amounts TDam, TDbm and attenuation timings gm, hm, jm.

[0317] TDam=TDa×F / Fstd

[0318] TDbm=TDb×F / Fstd

[0319] gm=g×F / Fstd

[0320] hm=h×F / Fstd

[0321] jm=j×F / Fstd

[0322] The correction based on the repetition frequency F can also be accompanied by a weighting using a coefficient.

[0323] Fig.31 Graphs are provided to illustrate the processing of correcting the total attenuation amounts TDa, TDb and the attenuation timings g, h, and j in the second example. Fig.31 The change of laser gain in the burst oscillation can be related to Fig.23 The total attenuation TDa, TDb and the attenuation timing g, h, j are set to match the change in laser gain when the repetition frequency F is 4 kHz. The attenuation timing g, h, j can be set by detecting the timing when the applied voltage value HV[n] changes in the calibration oscillation. The total attenuation TDa, TDb can be calculated based on the drift (x) of the applied voltage value HV[n] in the calibration oscillation.

[0324] When the repetition frequency F is 3 kHz or 2 kHz, the corrected total attenuation amounts TDam, TDbm and attenuation timings gm, hm, jm are calculated according to the above equations.

[0325] TDa1=TDa×3 / 4

[0326] TDb1=TDb×3 / 4

[0327] g1=g×3 / 4

[0328] h1=h×3 / 4

[0329] j1=j×3 / 4

[0330] TDa2=TDa×2 / 4

[0331] TDb2=TDb×2 / 4

[0332] g2=g×2 / 4

[0333] h2=h×2 / 4

[0334] j2=j×2 / 4

[0335] TDa1 and TDb1 are the corrected total attenuation amounts when the repetition frequency F is 3 kHz. Furthermore, g1, h1, and j1 are the corrected attenuation timings when the repetition frequency F is 3 kHz.

[0336] TDa2 and TDb2 are the corrected total attenuation amounts when the repetition frequency F is 2 kHz. In addition, g2, h2, and j2 are the corrected attenuation timings when the repetition frequency F is 2 kHz.

[0337] By performing the calculation as described above, it is possible to calculate an appropriate offset value Offset[n] corresponding to the characteristics of the laser device 1 .

[0338] Refer again Fig.30 , S292e and S293e are processed respectively with Fig. 22 The processing of S292b and S293 is the same. However, several variables are replaced along with the correction.

[0339] The treatment of S294 and S295 is respectively Fig. 22 The processing of S294 and S295 is the same.

[0340] Regarding other aspects, the operation of the fifth embodiment is the same as that of the first to fourth embodiments.

[0341] 6.3 Function

[0342] According to the fifth embodiment, even if the total attenuation amount TD and the attenuation timing j are not stored separately according to the repetition frequency F, the appropriate applied voltage value HVa[n] can be set according to the repetition frequency F.

[0343] 7. Others

[0344] Fig.32 The structure of the exposure device 100 connected to the laser device 1 is schematically shown. The laser device 1 generates pulsed laser light and outputs it to the exposure device 100 .

[0345] exist Fig.32In the embodiment, the exposure device 100 includes an illumination optical system 40 and a projection optical system 41. The illumination optical system 40 illuminates the mask pattern of the mask (not shown) arranged on the mask stage RT by pulse laser light incident from the laser device 1. The projection optical system 41 performs reduced projection of the pulse laser light after passing through the mask so that it is imaged on the workpiece (not shown) arranged on the workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure device 100 causes the mask stage RT and the workpiece stage WT to move synchronously and parallelly, thereby exposing the pulse laser light reflecting the mask pattern on the workpiece. After the mask pattern is transferred to the semiconductor wafer through the above exposure process, a plurality of processes are performed, thereby making it possible to manufacture semiconductor devices.

[0346] 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.

[0347] 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 "not excluding the existence of structural elements other than the recorded structural elements". 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 that outputs pulsed laser light by performing a plurality of burst oscillations including a first burst oscillation and a second burst oscillation performed after the first burst oscillation in accordance with a voltage command value and a trigger signal input from an external device, wherein: The laser device has: Laser resonator; a cavity, which is arranged on an optical path of the laser resonator; a pair of electrodes disposed in the cavity; a power source that applies a voltage to the electrodes; a storage unit storing a voltage value that causes the pulse energy of the pulse laser to reach a predetermined value; as well as a control unit that sets an applied voltage value of a voltage applied to the electrode, the control unit setting the applied voltage value for outputting a pulse having a pulse number greater than or equal to 1 and less than i, which indicates the order of pulses, among a plurality of pulses included in the pulsed laser output in one burst oscillation among the plurality of burst oscillations, based on the voltage command value and the voltage value stored in the storage unit, and setting the applied voltage value for outputting a pulse having a pulse number greater than or equal to i and less than j, based on the voltage command value and an offset value relative to the voltage command value, wherein i is an integer greater than 1 and j is an integer greater than i, The voltage command value is a command value of a voltage applied to the electrode. The storage unit stores a data table that associates a voltage value that causes the pulse energy of the pulse laser to reach the specified value with a length of a pause period from when the first burst oscillation ends to when the second burst oscillation starts and a combination of the pulse number. The control unit sets the applied voltage value for outputting the pulse having a pulse number greater than or equal to 1 and less than i, based on the voltage value read from the data table based on the length of the pause period and the pulse number, The control unit calculates the offset value based on a difference between the voltage command value for outputting the pulse with the pulse number i-1 and the applied voltage value for outputting the pulse with the pulse number i-1.

2. The laser device according to claim 1, wherein: The control unit calculates the target pulse energy according to the voltage command value, The control unit sets the applied voltage value for outputting the pulse having the pulse number being greater than or equal to 1 and less than i, based on the target pulse energy and the voltage value stored in the storage unit.

3. The laser device according to claim 2, wherein: The control unit calculates a parameter for calculating the target pulse energy from the voltage command value based on measurement data during calibration oscillation.

4. The laser device according to claim 2, wherein: The laser device further includes an energy monitor, which measures the pulse energy of the pulse laser. The control unit performs a process of updating the voltage value stored in the storage unit according to the difference between the pulse energy of the pulse laser and the target pulse energy.

5. The laser device according to claim 4, wherein: The control unit performs the process after outputting the pulse with the pulse number 1 and before outputting the pulse with the pulse number 2.

6. The laser device according to claim 1, wherein: The control unit sets the bias value for outputting the pulse having the pulse number being greater than or equal to i and less than j to a fixed value.

7. The laser device according to claim 1, wherein: The control unit sets the bias value for outputting pulses having pulse numbers greater than or equal to i and less than j to a value that decreases as the pulse number increases.

8. The laser device according to claim 1, wherein: The control unit sets the bias value for outputting pulses having pulse numbers greater than or equal to i and less than j to a value that is attenuated by a fixed amount each time as the pulse number increases.

9. The laser device according to claim 1, wherein: The control unit calculates a total attenuation amount of the bias value according to a drift amount of the applied voltage value, The offset value is calculated based on the total attenuation amount so that the offset value decays as the pulse number increases.

10. The laser device according to claim 9, wherein: The control unit calculates the total attenuation amount based on the drift amount during calibration oscillation.

11. The laser device according to claim 1, wherein: The control unit sets the bias value for outputting pulses having pulse numbers greater than or equal to i and less than j to a value obtained by changing an attenuation amount as the pulse number increases.

12. The laser device according to claim 1, wherein: The control unit sets the attenuation amount of the bias value used to output the pulse with a pulse number greater than i and less than g to a first value, and sets the attenuation amount of the bias value used to output the pulse with a pulse number greater than g and less than h to a second value smaller than the first value, and calculates the bias value, wherein g is an integer greater than i and less than j, and h is an integer greater than g and less than j.

13. The laser device according to claim 12, wherein: The control unit calculates the bias value by setting the attenuation amount of the bias value for outputting the pulse having the pulse number being greater than or equal to h and less than j to a third value that is smaller than the first value and greater than the second value.

14. The laser device according to claim 1, wherein: The control unit sets the applied voltage value corrected according to the repetition frequency of the pulse laser so as to output a pulse having a pulse number greater than 1 and less than i.

15. The laser device according to claim 14, wherein: The control unit sets the applied voltage value corrected so that the applied voltage value becomes lower as the repetition frequency of the pulsed laser light becomes smaller.

16. The laser device according to claim 1, wherein: The control unit calculates a total attenuation amount of the bias value according to a drift amount of the applied voltage value, The control unit corrects the total attenuation amount according to the repetition frequency of the pulsed laser. The control unit calculates the offset value based on the corrected total attenuation amount so that the offset value decays as the pulse number increases.

17. The laser device according to claim 1, wherein: The control unit sets the attenuation timing according to the change of the applied voltage value, The control unit corrects the attenuation timing according to the repetition frequency of the pulsed laser. The control unit calculates the offset value based on the corrected decay timing so that the offset value decays as the pulse number increases.

18. A method for manufacturing an electronic device, comprising the following steps: Generate pulsed laser light through a laser device, outputting the pulse laser to an exposure device, exposing the pulsed laser on a photosensitive substrate in the exposure device to manufacture an electronic device, The laser device performs a plurality of burst oscillations including a first burst oscillation and a second burst oscillation performed after the first burst oscillation in accordance with a voltage command value and a trigger signal input from an external device, thereby outputting a pulsed laser. The laser device has: Laser resonator; a cavity, which is arranged on an optical path of the laser resonator; a pair of electrodes disposed in the cavity; a power source that applies a voltage to the electrodes; a storage unit storing a voltage value that causes the pulse energy of the pulse laser to reach a predetermined value; as well as a control unit that sets an applied voltage value of a voltage applied to the electrode, the control unit setting the applied voltage value for outputting a pulse having a pulse number greater than or equal to 1 and less than i, which indicates the order of pulses, among a plurality of pulses included in the pulsed laser output in one burst oscillation among the plurality of burst oscillations, based on the voltage command value and the voltage value stored in the storage unit, and setting the applied voltage value for outputting a pulse having a pulse number greater than or equal to i and less than j, based on the voltage command value and an offset value relative to the voltage command value, wherein i is an integer greater than 1 and j is an integer greater than i, The voltage command value is a command value of a voltage applied to the electrode. The storage unit stores a data table that associates a voltage value that causes the pulse energy of the pulse laser to reach the specified value with a length of a pause period from when the first burst oscillation ends to when the second burst oscillation starts and a combination of the pulse number. The control unit sets the applied voltage value for outputting the pulse having a pulse number greater than or equal to 1 and less than i, based on the voltage value read from the data table based on the length of the pause period and the pulse number, The control unit calculates the offset value based on a difference between the voltage command value for outputting the pulse with the pulse number i-1 and the applied voltage value for outputting the pulse with the pulse number i-1.

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