Extreme ultraviolet light generation system, method for controlling extreme ultraviolet light generation system, and method for manufacturing electronic device

Abstract

To solve the problem that energy stability of EUV light by an extreme ultraviolet (EUV) light generation system is poor.SOLUTION: A control method of an extreme ultraviolet light generation system including a target supply unit configured to supply a target, a laser device configured to irradiate the target with a laser beam, an EUV energy sensor configured to detect energy of extreme ultraviolet light generated by irradiating the target with the laser beam, a light adjuster configured to adjust the energy of the laser beam, and a processor configured to adjust the light adjuster by PID control based on an output of the EUV energy sensor, the control method comprising: A processor acquires a first indicator value for an output of the EUV energy sensor and a second indicator value different from the first indicator value, and determines a control gain in the PID control based on the first and second indicator values.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to an extreme ultraviolet light generation system, a control method for an extreme ultraviolet light generation system, and a method for manufacturing an electronic device. [Background technology]

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in optical lithography for semiconductor processes has progressed rapidly. In the next generation, fine processing of 10 nm or less will be required. For this reason, there is a demand for the development of semiconductor exposure equipment that combines a device for generating extreme ultraviolet (EUV) light with a wavelength of approximately 13 nm and a reduced projection reflective optical system.

[0003] As an EUV light generation device, development of an LPP (Laser Produced Plasma) type device that uses plasma generated by irradiating a target material with laser light is progressing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2020 / 0067259 [Patent Document 2] Summary of the specification of U.S. Patent Application Publication No. 2022 / 0110205

[0005] According to one aspect of the present disclosure, there is provided a control method for an extreme ultraviolet light generation system including: a target supply unit that supplies a target; a laser device that irradiates the target with laser light; an EUV energy sensor that detects the energy of extreme ultraviolet light generated by irradiating the target with the laser light; a light regulator that adjusts the energy of the laser light; and a processor that adjusts the light regulator by PID control based on an output of the EUV energy sensor, wherein the processor obtains a first index value for the output of the EUV energy sensor and a second index value different from the first index value, and determines a control gain in the PID control based on the first and second index values.

[0006] An extreme ultraviolet light generation system according to one aspect of the present disclosure includes a target supply unit that supplies a target, a laser device that irradiates laser light onto the target, an EUV energy sensor that detects the energy of extreme ultraviolet light generated by irradiating the target with the laser light, a light regulator that adjusts the energy of the laser light, and a processor that adjusts the light regulator by PID control based on an output of the EUV energy sensor, the processor acquiring a first index value for the output of the EUV energy sensor and a second index value different from the first index value, and determining a control gain in the PID control based on the first and second index values.

[0007] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating extreme ultraviolet light using an extreme ultraviolet light generation system including: a target supply unit that supplies a target; a laser device that irradiates laser light onto the target; an EUV energy sensor that detects energy of extreme ultraviolet light generated by irradiating the target with the laser light; a light regulator that adjusts the energy of the laser light; and a processor that adjusts the light regulator by PID control based on an output of the EUV energy sensor, the processor acquiring a first index value for the output of the EUV energy sensor and a second index value different from the first index value, and determining a control gain in the PID control based on the first and second index values; outputting the extreme ultraviolet light to an exposure apparatus; and exposing a photosensitive substrate in the exposure apparatus to the extreme ultraviolet light to manufacture an electronic device.

[0008] A method for manufacturing an electronic device according to one aspect of the present disclosure includes inspecting a mask for defects by irradiating the mask with extreme ultraviolet light generated by an extreme ultraviolet light generation system including: a target supply unit that supplies a target; a laser device that irradiates laser light onto the target; an EUV energy sensor that detects energy of extreme ultraviolet light generated by irradiating the target with the laser light; a light regulator that adjusts the energy of the laser light; and a processor that adjusts the light regulator by PID control based on an output of the EUV energy sensor, the processor obtaining a first index value for the output of the EUV energy sensor and a second index value different from the first index value, and determining a control gain in the PID control based on the first and second index values; selecting a mask using the inspection results; and exposing and transferring a pattern formed on the selected mask onto a photosensitive substrate. [Brief explanation of the drawings]

[0009] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] Figure 1 shows the configuration of an LPP-type EUV light generation system. [Figure 2]FIG. 2 shows the configuration of an EUV light generation system according to a comparative example. [Figure 3] FIG. 3 is a block chart of EUV light energy control in a comparative example. [Figure 4] FIG. 4 is a flowchart of a comparative example of determining a control gain in EUV light energy control. [Figure 5] FIG. 5 is a graph showing the relationship between the integral gain set in the comparative example and the deviation and variation in the energy of EUV light. [Figure 6] FIG. 6 is a flowchart of a control gain determination process in EUV light energy control according to the first embodiment. [Figure 7] FIG. 7 is a graph showing the relationship between the integral gain set in the first embodiment and the deviation and variation in the energy of EUV light. [Figure 8] FIG. 8 is a graph showing the relationship between the integral gain set in the second embodiment and the deviation and variation in the energy of EUV light. [Figure 9] FIG. 9 shows the configuration of an exposure tool connected to an EUV light generation system. [Figure 10] Figure 10 shows the configuration of the inspection device connected to the EUV light generation system. Embodiment

[0010] <Contents> 1. Overview of the EUV Light Generation System 11 1.1 Configuration 1.2 Operation 2. Comparative Example 2.1 Configuration 2.2 Operation 2.3 Issues with the comparative example 3. Energy of EUV light E EUV EUV light generation system 11a: determining the control gain considering the 3σ variation of 3.1 Configuration and operation 3.2 Variations 3.3 Effect 4. Energy of EUV light E EUVThe EUV light generation system 11a determines the control gain so that the deviation Ed of 4.1 Configuration and operation 4.2 Effect 5. Timing of control gain determination process 6.Other 6.1 Example of EUV light utilization equipment6 6.2 Processor 5 6.3 Supplementary Information

[0011] 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. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0012] 1. Overview of the EUV Light Generation System 11 1.1 Configuration FIG. 1 shows the configuration of an LPP-type EUV light generation system 11. The EUV light generation system 1 is used together with a laser device 3. In the present disclosure, a system including the EUV light generation system 1 and the laser device 3 is referred to as the EUV light generation system 11. The EUV light generation system 1 includes a chamber 2 and a target supply unit 26. The chamber 2 is a sealable container. The target supply unit 26 supplies a target 27 containing a target material into the chamber 2. The target material may include tin, terbium, gadolinium, lithium, xenon, or a combination of any two or more of these.

[0013] A through-hole is provided in the wall of the chamber 2. The through-hole is closed by a window 21, through which laser light 32 output from the laser device 3 passes. An EUV collector mirror 23 having a reflective surface with an ellipsoidal shape is disposed inside the chamber 2. The EUV collector mirror 23 has first and second focal points. A multilayer reflective film in which molybdenum and silicon are alternately stacked is formed on the surface of the EUV collector mirror 23. The EUV collector mirror 23 is disposed so that its first focal point is located in the plasma generation region 25 and its second focal point is located at an intermediate focal point 292. A through-hole 24 is provided in the center of the EUV collector mirror 23, through which laser light 33 passes.

[0014] The EUV light generation system 1 includes a processor 5, a target sensor 4, etc. The configuration of the processor 5 will be described later. The target sensor 4 detects at least one of the presence, trajectory, position, and speed of the target 27. The target sensor 4 may also have an imaging function.

[0015] The EUV light generation system 1 also includes a connection part 29 that connects the interior of the chamber 2 with the interior of the EUV light utilization system 6. The EUV light utilization system 6 may be an exposure system 6a shown in FIG. 9 or an inspection system 6b shown in FIG. 10. A wall 291 having an aperture formed therein is provided inside the connection part 29. The wall 291 is positioned so that the aperture is located at the second focal point of the EUV collector mirror 23.

[0016] Furthermore, the EUV light generation system 1 includes a laser beam transmission device 34, a laser beam focusing mirror 22, and a target recovery unit 28 for recovering the target 27. The laser beam transmission device 34 includes an optical element for defining the transmission state of the laser beam 32, and an actuator for adjusting the position, attitude, etc. of the optical element.

[0017] 1.2 Operation The operation of the EUV light generation system 11 will be described with reference to Figure 1. Pulsed laser light 31 output from the laser device 3 passes through a laser light transmission device 34, passes through a window 21 as laser light 32, and enters the chamber 2. The laser light 32 travels through the chamber 2 along the laser light path, is reflected by the laser light focusing mirror 22, and is irradiated onto the target 27 as laser light 33.

[0018] The target supply unit 26 outputs the target 27 toward the plasma generation region 25 inside the chamber 2. The target 27 is irradiated with laser light 33. The target 27 irradiated with the laser light 33 is converted into plasma, and the plasma emits radiation 251. The EUV light contained in the radiation 251 is reflected by the EUV collector mirror 23 with a higher reflectance than light in other wavelength ranges. The reflected light 252 containing EUV light reflected by the EUV collector mirror 23 is collected at an intermediate focus 292 and output to the EUV light utilization device 6.

[0019] A single target 27 may be irradiated with multiple pulses contained in the laser beam 33. In this case, for example, the laser device 3 includes a pre-pulse laser and a main pulse laser (not shown). The pre-pulse laser beam output from the pre-pulse laser has lower energy than the main pulse laser beam output from the main pulse laser. The target 27 is diffused by the irradiation with the pre-pulse laser beam. The diffused target 27 is turned into plasma by the irradiation with the main pulse laser beam.

[0020] The processor 5 controls the entire EUV light generation system 11. The processor 5 processes the detection results of the target sensor 4. Based on the detection results of the target sensor 4, the processor 5 controls the timing at which the target 27 is output, the output direction of the target 27, etc. Furthermore, the processor 5 controls the oscillation timing of the laser device 3, the traveling direction of the laser beam 32, the focusing position of the laser beam 33, etc. The various controls described above are merely examples, and other controls may be added as necessary.

[0021] 2. Comparative Example 2.1 Configuration 2 shows the configuration of an EUV light generation system 11a according to a comparative example. The comparative example in the present disclosure is a configuration that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges.

[0022] In an EUV light generation system 11a according to the comparative example, a laser device 3 includes a master oscillator MO, an amplifier PA, an optical modulator OM, a beam splitter BS, and a laser energy sensor LS. The amplifier PA is disposed in the optical path of the laser beam output from the master oscillator MO.

[0023] An optical modulator OM is disposed in the optical path of the laser light output from the amplifier PA. The optical modulator OM is an example of an optical adjuster in the present disclosure. The optical adjuster may be included in the laser device 3. The optical modulator OM includes an acousto-optic element (not shown), and the transmittance of the laser light is controlled by an applied voltage applied to the acousto-optic element. The optical modulator OM may include an electro-optic element or an attenuator instead of the acousto-optic element, and the transmittance of the laser light may be controlled by an applied voltage to the electro-optic element or the attenuator. In the present disclosure, the applied voltage applied to the acousto-optic element, electro-optic element, or attenuator is referred to as the applied voltage of the optical modulator OM.

[0024] As another example of the optical adjuster in the present disclosure, a mechanism (not shown) that changes the pumping intensity of the master oscillator MO or the amplification efficiency of the amplifier PA may be provided instead of the optical modulator OM. For example, when the master oscillator MO or the amplifier PA is a solid-state laser, such a mechanism may be a mechanism that adjusts the current supplied to a pumping lamp for pumping a laser crystal.

[0025] In Fig. 2, a beam splitter BS is disposed in the optical path of the laser light output from the optical modulator OM. The beam splitter BS transmits a part of the laser light as laser light 31 with high transmittance and reflects the other part. A laser energy sensor LS is disposed in the optical path of the laser light reflected by the beam splitter BS and detects the energy E of the laser light. L and outputs it to the processor 5.

[0026] The chamber 2 is provided with a target timing sensor 4a, an EUV energy sensor 7a, and a laser beam focusing optical system 22a. The target timing sensor 4a includes a light source, a transfer optical system, and an optical sensor, all of which are not shown. The light source illuminates the target 27 that has reached a detection region 35 between the target supply unit 26 and the plasma generation region 25. The transfer optical system forms a portion of the image of the target 27 illuminated by the light source on the optical sensor. The optical sensor detects a change in the amount of light as the target 27 passes through the detection region 35. The EUV energy sensor 7a is provided at a position where a portion of the EUV light generated in the plasma generation region 25 is incident.

[0027] The processor 5 includes a modulation signal generator MG and a timing signal generator TG.

[0028] A gas supply device (not shown) may be arranged to supply hydrogen gas into the chamber 2. The gas supply device generates a gas flow corresponding to the amount of hydrogen gas supplied inside the chamber 2. If the target material contains tin, the tin adhering to optical elements such as the EUV collector mirror 23 is etched by the hydrogen gas, which may extend the life of the optical elements.

[0029] 2.2 Operation The master oscillator MO performs laser oscillation and outputs pulsed laser light. The timing of the output of the laser light by the master oscillator MO is determined by a trigger timing signal S output from a timing signal generator TG to the master oscillator MO. TThe amplifier PA amplifies the laser light emitted from the master oscillator MO.

[0030] The optical modulator OM adjusts the energy of the laser light by transmitting the laser light with a transmittance according to the applied voltage. The applied voltage to the optical modulator OM is determined by the modulation signal output from the modulation signal generator MG to the optical modulator OM. The modulation signal is a feedback control signal FB, which will be described later. EUV The timing for changing the voltage applied to the optical modulator OM is determined by the modulation timing signal S output from the timing signal generator TG to the optical modulator OM. M is defined by

[0031] The laser beam transmission device 34 guides the laser beam 31 incident from the optical modulator OM to the laser beam focusing optical system 22a as laser beam 32. The laser beam focusing optical system 22a focuses the laser beam 32 incident from the laser beam transmission device 34 onto the plasma generation region 25 as laser beam 33.

[0032] The target supply unit 26 outputs droplet-shaped targets 27 toward the plasma generation region 25, thereby supplying the targets 27 to the plasma generation region 25. The target timing sensor 4a detects the timing at which the targets 27 reach the detection region 35, and outputs a target detection signal S D is output to the timing signal generation unit TG.

[0033] The timing signal generator TG receives the target detection signal S from the target timing sensor 4a. D Trigger timing signal S to master oscillator MO based on T and outputs the modulation timing signal S to the optical modulator OM. M Output.

[0034] The laser light 33 is irradiated onto the target 27 in the plasma generation region 25. The EUV energy sensor 7a measures the energy E per pulse of the EUV light generated by irradiating the target 27 with the laser light 33.EUV and outputs the detection result to the modulation signal generation unit MG.

[0035] The modulation signal generation unit MG receives the energy E of the EUV light from the EUV energy sensor 7a. EUV A feedback control signal FB for controlling the applied voltage of the optical modulator OM based on EUV For example, the energy of EUV light E EUV is lower than the target value, the transmittance of the laser light by the optical modulator OM may be increased by increasing the voltage applied to the optical modulator OM. Increasing the transmittance of the laser light increases the energy of the laser light 31 output from the laser device 3, so that the laser light 33 imparts higher energy to the target 27. As a result, the energy E of the EUV light EUV becomes higher and can approach the target value.

[0036] 3 is a block diagram of EUV light energy control in a comparative example. The processor 5 as a controller calculates the energy E of EUV light input to an adder. EUV The optical modulator OM as an operating unit changes the energy of the laser beam 31 in response to the control signal. The emission characteristics of the EUV light output from the EUV light generation system 11a as a controlled object change in response to the energy E of the EUV light. EUV is measured and fed back to the adder.

[0037] The algorithm used by the processor 5 to calculate the control signal is, for example, a speed-type PID algorithm, and the following formula can be used:

number

[0038] where M is the manipulated variable and E is the energy of the EUV light E EUVwhere KP is the proportional gain, KI is the integral gain, KD is the differential gain, and τ is the time constant. The subscripts i, n, and n-1 of the manipulated variable M and the difference E indicate the values ​​for the ith, nth, and n-1th pulses of EUV light, respectively.

[0039] 4 is a flowchart of a comparative example of determining a control gain in EUV light energy control. The process shown in FIG. 4 is executed in a state where exposure or inspection is not being performed in the EUV light utilization apparatus 6.

[0040] In S1, processor 5 performs initial settings for EUV light generation to determine the control gain. EUV light generation for determining the control gain is desirably performed under conditions that minimize the impact of heating of chamber 2 on the emission characteristics of EUV light; for example, the on-time ratio of EUV light is set to 25% or less. In order to ensure sufficient data, the number of pulses in one burst oscillation is set to 1,000 to 20,000 pulses, and the number of bursts is set to three or more. Furthermore, processor 5 enables the energy control of EUV light, which was described with reference to FIG. 3.

[0041] In S2a, the processor 5 starts an index value acquisition loop. The index value acquisition loop is a loop from S2a to S2g, and is executed until acquisition of index values ​​at a plurality of predetermined gain levels is completed.

[0042] In S2b, processor 5 sets the control gain to one of a plurality of gain levels. The gain level may be determined for any one of proportional gain KP, integral gain KI, and derivative gain KD, or may be determined for each of two or three of them. For example, if a plurality of gain levels are determined for each of proportional gain KP and integral gain KI, the processes from S2b to S2e are performed for each combination of the gain level determined for proportional gain KP and the gain level determined for integral gain KI.

[0043] In S2d, the processor 5 performs test irradiation of EUV light by controlling the target supply unit 26 and the laser device 3 under the conditions set in S1. In S2e, the processor 5 calculates the energy E of EUV light based on the output of the EUV energy sensor 7a. EUV The deviation Ed is an example of a first index value in the present disclosure. The deviation Ed is calculated based on the energy E of the EUV light. EUV Alternatively, the deviation Ed may be calculated by dividing the EUV light energy E EUV Alternatively, the average value may be obtained by dividing the difference between the target value and the target value by the target value.

[0044] When the index value acquisition for all gain levels is completed, in S2g, the processor 5 ends the index value acquisition loop.

[0045] In S3, the processor 5 detects the energy E of the EUV light. EUV The processor 5 determines a control gain in PID control based on the deviation Ed of the input signal. For example, the processor 5 determines the control gain to a value that minimizes the deviation Ed. After S3, the processor 5 ends the processing of this flowchart.

[0046] 2.3 Issues with the comparative example FIG. 5 shows the relationship between the integral gain KI set in the comparative example and the energy E of the EUV light. EUV 10 is a graph showing the relationship between the deviation Ed and the variation 3σ of the EUV light energy E. The integral gain KI is determined to be the value KIopt at which the deviation Ed is at its minimum value Edmin, and PID control is performed. EUV The difference between the target value of can be minimized.

[0047] However, when PID control is performed using the integral gain KI value KIopt determined based on the deviation Ed, the EUV light energy E EUV In this case, even if the deviation Ed is at its minimum, the EUV light energy E EUV The stability of

[0048] 3. Energy of EUV light E EUV EUV light generation system 11a: determining the control gain considering the 3σ variation of 3.1 Configuration and operation 6 is a flowchart showing the control gain determination process for EUV light energy control according to the first embodiment. The configuration of the first embodiment is the same as that of the comparative example. In the first embodiment, steps S2c, S2f, and S3c are performed instead of steps S2b, S2e, and S3 in FIG. 4, respectively.

[0049] In S2c, for example, the processor 5 sets the integral gain KI to one of multiple gain levels. The gain level of the integral gain KI may be set to, for example, 2%, 4%, 10%, 20%, 40%, 60%, 80%, 100%, 150%, or 200%, or an initial value, an increase rate, and a final value may be set. Alternatively, an initial value, an increase value, and a number of increases may be specified. By repeating the index value acquisition loop including S2c, the integral gain KI is sequentially set to multiple values, and an index value is acquired for each value of the integral gain KI. In determining the integral gain KI, the proportional gain KP and the derivative gain KD may not be set to multiple gain levels, and the proportional gain KP and the derivative gain KD may be fixed. Alternatively, the proportional gain KP or the derivative gain KD may be changed as needed to suppress hunting or improve transient responsiveness. If the proportional gain KP or the derivative gain KD is changed, the index value acquisition may be redone for each value of the integral gain KI.

[0050] In S2f, the processor 5 calculates the energy E of the EUV light based on the output of the EUV energy sensor 7a. EUV deviation Ed and the energy of EUV light E EUV The variation 3σ is an example of a second index value in the present disclosure. The variation 3σ is obtained by EUV It may be the standard deviation of the EUV light, or the variance value, which is the square of the standard deviation, or it may be a value obtained by multiplying either of these by a positive number, for example, 3. A small value of the variation 3σ indicates that the energy E of the EUV light is small.EUV This indicates that the stability of the

[0051] In S3c, processor 5 detects the energy of EUV light E EUV The processor 5 determines a control gain in the PID control based on both the deviation Ed and the variation 3σ. For example, the processor 5 determines the control gain so that the deviation Ed falls within a first allowable range and the variation 3σ falls within a second allowable range.

[0052] FIG. 7 shows the relationship between the integral gain KI set in the first embodiment and the energy E of the EUV light EUV 6 is a graph showing the relationship between the deviation Ed and the variation 3σ. The first allowable range of the deviation Ed is a range from 0 to a threshold Edth, and the second allowable range of the variation 3σ is a range from 0 to a threshold 3σth. The range of the integral gain KI in which the deviation Ed falls within the first allowable range is defined as Edok, and the range of the integral gain KI in which the variation 3σ falls within the second allowable range is defined as 3σok. By determining the integral gain KI to a value included in both the range Edok and the range 3σok, the deviation Ed falls within the first allowable range and the variation 3σ falls within the second allowable range, as described in S3c of FIG. 6. The integral gain KI determined in this manner is smaller than the value KIopt of the integral gain KI (see FIG. 5) at which the deviation Ed reaches its minimum value Edmin.

[0053] In the first embodiment, the integral gain KI is determined to a value that maximizes the difference between the variation 3σ and the threshold value 3σth in the region included in both the range Edok and the range 3σok. In the example shown in FIG. 7, the integral gain KI is determined to a value KIopt1 that maximizes the difference between the variation 3σ and the threshold value 3σth. In the present disclosure, maximum and minimum do not mean strict maximum and minimum values, and an error of 10%, preferably 5%, is allowed. In addition, the energy E of the EUV light is used instead of the variation 3σ. EUVAlternatively, a value indicating the stability of the variation 3σ may be used. The stability may be the reciprocal of the variation 3σ. When the magnitude relationship between the value of the variation 3σ and the value indicating the stability is reversed, that is, when the value indicating the stability increases as the value of the variation 3σ decreases, the integral gain KI is determined so that the stability is maximized.

[0054] 3.2 Variations In Figs. 6 and 7, the energy E of EUV light EUV In the above description, the variation 3σ of the energy of the EUV light is used as the second index value, but the present disclosure is not limited to this. EUV When the difference between the target value and the feedback control signal FB EUV The voltage applied to the optical modulator OM is adjusted by the EUV Instead of the variation 3σ of the energy of the EUV light, the variation of the voltage applied to the optical modulator OM may be used as the second index value. EUV The fluctuation of the laser light energy E L to the energy of EUV light E EUV Therefore, the energy of EUV light, E EUV Instead of the variation 3σ, the variation in conversion efficiency may be used as the second index value. The conversion efficiency may be calculated by the processor 5 based on the output of the laser energy sensor LS and the output of the EUV energy sensor 7a.

[0055] 3.3 Effect According to the first embodiment, the EUV light generation system 11a includes a target supply unit 26, a laser device 3, an EUV energy sensor 7a, an optical modulator OM, and a processor 5. The target supply unit 26 supplies a target 27. The laser device 3 irradiates the target 27 with laser light 33. The EUV energy sensor 7a measures the energy E of EUV light generated by irradiating the target 27 with the laser light 33. EUVThe optical modulator OM detects the EUV energy of the laser beam 33. The processor 5 adjusts the optical modulator OM by PID control based on the output of the EUV energy sensor 7a. The control method of the EUV light generation system 11a includes the processor 5 acquiring a first index value for the output of the EUV energy sensor 7a and a second index value different from the first index value, and determining a control gain in the PID control based on the first and second index values.

[0056] According to this, the control gain is determined based on two index values, so that the EUV light generation system 11a can be operated appropriately.

[0057] According to the first embodiment, the control gains are determined so that the first index value is within the first allowable range and the second index value is within the second allowable range.

[0058] According to this, even if it is not possible to set both the first and second index values ​​to their optimum values, the EUV light generation system 11a can be operated appropriately by setting them within their respective allowable ranges.

[0059] According to the first embodiment, the control gain is determined so as to maximize the difference between the second index value and the threshold value that defines the second acceptable range.

[0060] According to this, by selecting a control gain that makes the second index value an optimal value among the control gains that make the first and second index values ​​fall within their respective allowable ranges, the EUV light generation system 11a can be operated appropriately.

[0061] According to the first embodiment, the first index value is the deviation Ed of the output of the EUV energy sensor 7a.

[0062] According to this, the energy of EUV light, E EUV The deviation Ed can be set within an allowable range, and the EUV light generation system 11a can be operated appropriately.

[0063] According to the first embodiment, the second index value is the variation 3σ of the output of the EUV energy sensor 7a.

[0064] According to this, the energy of EUV light, E EUV By setting the control gain so that the variation 3σ of the EUV light generation system 11a is an optimal value, the EUV light generation system 11a can be operated appropriately.

[0065] According to the first embodiment, the optical modulator OM is disposed in the optical path of the laser beam, and the processor 5 is configured to control the applied voltage of the optical modulator OM based on the output of the EUV energy sensor 7 a. The second index value is the variation in the applied voltage.

[0066] According to this, the energy of EUV light, E EUV The EUV light energy E EUV This can prevent the variation 3σ from falling outside the allowable range.

[0067] According to the first embodiment, the EUV light generation system 11a further includes a laser energy sensor LS arranged in the optical path of the laser light. The processor 5 calculates the energy E of the laser light based on the output of the laser energy sensor LS and the output of the EUV energy sensor 7a. L to the energy of EUV light E EUV The second index value is the variation in conversion efficiency.

[0068] According to this, the energy of the laser light E L EUV light energy E EUV By using the variation in conversion efficiency, which is the ratio of EUV light energy E EUV This can prevent the variation 3σ from falling outside the allowable range.

[0069] According to the first embodiment, the control gain includes the integral gain KI, and the processor 5 sequentially sets the integral gain KI to a plurality of values ​​and obtains the first and second index values ​​for each value of the integral gain KI.

[0070] According to this, by sequentially setting the integral gain KI and performing test irradiation, an appropriate value for the integral gain KI can be found, and the first and second index values ​​can be brought closer to their respective target values.

[0071] According to the first embodiment, the control gains include a proportional gain KP, an integral gain KI, and a derivative gain KD, and the processor 5 fixes the proportional gain KP and the derivative gain KD, sequentially sets the integral gain KI to a plurality of values, and obtains first and second index values ​​for each value of the integral gain KI.

[0072] According to this, gain adjustment can be performed efficiently by fixing the proportional gain KP and the derivative gain KD.

[0073] According to the first embodiment, the first index value is the deviation Ed of the output of the EUV energy sensor 7a, and the processor 5 determines the integral gain KI to be a value smaller than the value KIopt of the integral gain KI at which the deviation Ed is minimum.

[0074] The integral gain KI is the energy of the EUV light E EUV When the deviation Ed of KIopt is determined to be the minimum, high gain is obtained, and the energy E of the EUV light EUV However, by making the integral gain KI smaller than the value KIopt, the variation 3σ can be suppressed.

[0075] In other respects, the first embodiment is similar to the comparative example.

[0076] 4. Energy of EUV light E EUV The EUV light generation system 11a determines the control gain so that the deviation Ed of 4.1 Configuration and operation FIG. 8 shows the relationship between the integral gain KI set in the second embodiment and the energy E of the EUV light. EUV 8 is a graph showing the relationship between the deviation Ed and the variation 3σ. The configuration of the second embodiment is the same as that of the comparative example and the first embodiment, and the flowchart for determining the control gain is the same as that of the first embodiment. The integral gain KI in the second embodiment is determined to a value that maximizes the difference between the deviation Ed and the threshold value Edth in the region included in both the range Edok and the range 3σok. In the example shown in FIG. 8, the deviation Ed monotonically decreases in the region included in both the range Edok and the range 3σok, so by determining the integral gain KI to the maximum value KIopt2 in that region, the difference between the deviation Ed and the threshold value Edth becomes maximum.

[0077] In Figure 8, the energy of EUV light E EUV The deviation Ed of EUV light energy E EUV In the above description, the variation 3σ of the energy of the EUV light is used as the second index value, but the present disclosure is not limited to this. EUV Instead of the variation 3σ, the variation in the applied voltage of the optical modulator OM may be used as the second index value, or the variation in the conversion efficiency may be used as the second index value. Also, a value indicating stability may be used instead of the variation.

[0078] 4.2 Effect According to the second embodiment, the control gain is determined so as to maximize the difference between the first index value and the threshold value that defines the first allowable range.

[0079] According to this, by selecting a control gain that makes the first index value an optimal value among the control gains that make the first and second index values ​​fall within their respective allowable ranges, the EUV light generation system 11a can be operated appropriately.

[0080] According to the second embodiment, the first index value is the deviation Ed of the output of the EUV energy sensor 7a.

[0081] According to this, the energy of EUV light, EEUV By setting the control gain so that the deviation Ed becomes an optimal value, the EUV light generation system 11a can be operated appropriately.

[0082] According to the second embodiment, the second index value is the variation 3σ of the output of the EUV energy sensor 7a.

[0083] According to this, the energy of EUV light, E EUV The variation 3σ can be kept within an allowable range, and the EUV light generation system 11a can be operated appropriately.

[0084] In other respects, the second embodiment is similar to the first embodiment.

[0085] 5. Timing of control gain determination process The control gain determination process shown in FIG. 6 can be performed at any one of the following times (a) to (d).

[0086] (a) After replacing the laser device 3, for example, after replacing the main pulse laser, and before performing exposure or inspection in the EUV light utilization device 6

[0087] Even if the characteristics of the laser light 31 change due to individual differences in the laser device 3 when the laser device 3 is replaced, the EUV light generation system 11a can be operated appropriately by re-determining the control gain according to the present disclosure.

[0088] (b) After changing the light intensity at the position where the target 27 is irradiated with the laser light 33, and before performing exposure or inspection in the EUV light utilization device 6.

[0089] Even if the light intensity of the laser beam 33 changes, the EUV light generation system 11a can be operated appropriately by re-determining the control gain according to the present disclosure.

[0090] (c) After changing the setting value of the size of the target 27 and before performing exposure or inspection in the EUV light utilization device 6

[0091] Even if the optimum values ​​for the speed of the target 27 and the intensity of the laser light 33 change due to a change in the set value for the size of the target 27, the EUV light generation system 11a can be operated appropriately by re-determining the control gain in accordance with the present disclosure.

[0092] (d) After changing the gas flow around the target 27 and before performing exposure or inspection in the EUV light utilization device 6

[0093] Even if the trajectory of the target 27 changes due to a change in the gas flow, the EUV light generation system 11a can be operated appropriately by re-determining the control gain according to the present disclosure.

[0094] 6.Other 6.1 Example of EUV light utilization equipment6 FIG. 9 shows the configuration of an exposure tool 6a connected to the EUV light generation system 11a. The exposure tool 6a, which serves as the EUV light utilization tool 6 (see FIG. 1), includes a mask irradiation unit 608 and a workpiece irradiation unit 609. The mask irradiation unit 608 illuminates a mask pattern on a mask table MT via a reflection optical system with EUV light incident from the EUV light generation system 11a. The workpiece irradiation unit 609 forms an image of the EUV light reflected by the mask table MT onto a workpiece (not shown) placed on a workpiece table WT via a reflection optical system. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure tool 6a exposes the workpiece to EUV light reflecting the mask pattern by synchronously translating the mask table MT and the workpiece table WT. Electronic devices can be manufactured by transferring a device pattern onto a semiconductor wafer using the exposure process described above.

[0095] FIG. 10 shows the configuration of an inspection apparatus 6b connected to the EUV light generation system 11a. The inspection apparatus 6b, which serves as the EUV light utilization apparatus 6 (see FIG. 1), includes an illumination optical system 603 and a detection optical system 606. The illumination optical system 603 reflects EUV light incident from the EUV light generation system 11a and irradiates a mask 605 placed on a mask stage 604. The mask 605 here refers to a mask blank before a pattern is formed. The detection optical system 606 reflects the EUV light from the illuminated mask 605 and forms an image on the light-receiving surface of a detector 607. The detector 607 receives the EUV light and acquires an image of the mask 605. The detector 607 is, for example, a TDI (time delay integration) camera. The image of the mask 605 acquired through the above process is used to inspect the mask 605 for defects, and the inspection results are used to select a mask suitable for manufacturing electronic devices. The pattern formed on the selected mask is then exposed and transferred onto a photosensitive substrate using the exposure apparatus 6a, thereby manufacturing electronic devices.

[0096] 6.2 Processor 5 The processor 5 may be physically configured in the form of hardware to execute various processes included in the present disclosure. For example, the processor 5 may be a computer including a memory storing a control program that defines the various processes and a processing device that executes the control program. The control program may be stored in a single memory, or may be stored separately in multiple physically separate memories, with the various processes defined by the control program as a collection of these memories. The processing device may be a general-purpose processing device such as a CPU, or a processing device for a specific purpose such as a GPU.

[0097] The processor 5 may be programmed in the form of software to execute various processes included in the present disclosure. For example, the processor 5 may be implemented in a dedicated device such as an ASIC or a programmable device such as an FPGA, in which the functions for executing various processes are implemented.

[0098] The various processes included in the present disclosure may be performed by a single computer, a single dedicated device, or a single programmable device, or may be performed by cooperation of multiple physically separate computers, multiple dedicated devices, or multiple programmable devices. The various processes may be performed by a combination of at least two of one or more computers, one or more dedicated devices, and one or more programmable devices.

[0099] 6.3 Supplementary Information The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments can be used in combination.

[0100] Terms used throughout this specification and claims should be construed as "open ended" unless expressly stated otherwise. For example, words such as "comprise," "have," "comprise," and "equip" should be construed as meaning "without excluding the presence of elements other than those listed." In addition, the modifier "a" should be construed as meaning "at least one" or "one or more." In addition, 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," and should also be construed as including combinations other than "A," "B," and "C."

Claims

1. a target supply unit that supplies a target; a laser device that irradiates the target with laser light; an EUV energy sensor that detects energy of extreme ultraviolet light generated by irradiating the target with the laser light; an optical regulator for adjusting the energy of the laser light; a processor that adjusts the light adjuster by PID control based on the output of the EUV energy sensor; A method for controlling an extreme ultraviolet light generating system comprising: the processor: obtaining a first index value for an output of the EUV energy sensor and a second index value different from the first index value; determining a control gain in the PID control based on the first and second index values; Control method.

2. 2. The control method according to claim 1, the control gain is determined so that the first index value falls within a first allowable range and the second index value falls within a second allowable range. Control method.

3. 3. The control method according to claim 2, the control gain is determined so as to maximize a difference between the second index value and a threshold value that defines the second allowable range. Control method.

4. 4. The control method according to claim 3, the first index value is a deviation of the output of the EUV energy sensor; Control method.

5. 5. The control method according to claim 4, the second index value is a variation in the output of the EUV energy sensor; Control method.

6. 5. The control method according to claim 4, the optical adjuster is an optical modulator disposed in an optical path of the laser light, the processor is configured to control an applied voltage to the optical modulator based on an output of the EUV energy sensor; the second index value is a variation in the applied voltage; Control method.

7. 5. The control method according to claim 4, the extreme ultraviolet light generation system further includes a laser energy sensor disposed in an optical path of the laser light; the processor is configured to calculate a conversion efficiency from energy of the laser light to energy of the extreme ultraviolet light based on an output of the laser energy sensor and an output of the EUV energy sensor; the second index value is a variation in the conversion efficiency; Control method.

8. 3. The control method according to claim 2, the control gain is determined so as to maximize a difference between the first index value and a threshold value that defines the first allowable range. Control method.

9. 9. The control method according to claim 8, the first index value is a deviation of the output of the EUV energy sensor; Control method.

10. 10. The control method according to claim 9, the second index value is a variation in the output of the EUV energy sensor; Control method.

11. 2. The control method according to claim 1, the control gain includes an integral gain, and the processor sequentially sets the integral gain to a plurality of values ​​and obtains the first and second index values ​​for each value of the integral gain; Control method.

12. 2. The control method according to claim 1, the control gain includes a proportional gain, an integral gain, and a derivative gain, and the processor fixes the proportional gain and the derivative gain, sequentially sets the integral gain to a plurality of values, and obtains the first and second index values ​​for each value of the integral gain. Control method.

13. 2. The control method according to claim 1, the first index value is a deviation of the output of the EUV energy sensor, and the processor determines the control gain to be a value smaller than a control gain at which the deviation is minimum. Control method.

14. 2. The control method according to claim 1, the processor acquires the first and second index values ​​after the laser device is replaced and determines the control gain. Control method.

15. 2. The control method according to claim 1, the processor acquires the first and second index values ​​after changing the light intensity of the laser light at the position where the target is irradiated, and determines the control gain. Control method.

16. 2. The control method according to claim 1, the processor acquires the first and second index values ​​after changing the set value of the target size, and determines the control gain. Control method.

17. 2. The control method according to claim 1, the processor obtains the first and second index values ​​after changing the gas flow around the target and determines the control gain. Control method.

18. a target supply unit that supplies a target; a laser device that irradiates the target with laser light; an EUV energy sensor that detects energy of extreme ultraviolet light generated by irradiating the target with the laser light; an optical regulator for adjusting the energy of the laser light; a processor that adjusts the light adjuster by PID control based on an output of the EUV energy sensor, obtaining a first index value for an output of the EUV energy sensor and a second index value different from the first index value; the processor determining a control gain in the PID control based on the first and second index values; An extreme ultraviolet light generation system comprising:

19. A method for manufacturing an electronic device, comprising: a target supply unit that supplies a target; a laser device that irradiates the target with laser light; an EUV energy sensor that detects energy of extreme ultraviolet light generated by irradiating the target with the laser light; an optical regulator for adjusting the energy of the laser light; a processor that adjusts the light adjuster by PID control based on an output of the EUV energy sensor, obtaining a first index value for an output of the EUV energy sensor and a second index value different from the first index value; the processor determining a control gain in the PID control based on the first and second index values; generating the extreme ultraviolet light by an extreme ultraviolet light generating system comprising: outputting the extreme ultraviolet light to an exposure device; exposing a photosensitive substrate to the extreme ultraviolet light in the exposure apparatus to manufacture an electronic device; A method for manufacturing an electronic device, comprising:

20. A method for manufacturing an electronic device, comprising: a target supply unit that supplies a target; a laser device that irradiates the target with laser light; an EUV energy sensor that detects energy of extreme ultraviolet light generated by irradiating the target with the laser light; an optical regulator for adjusting the energy of the laser light; a processor that adjusts the light adjuster by PID control based on an output of the EUV energy sensor, obtaining a first index value for an output of the EUV energy sensor and a second index value different from the first index value; the processor determining a control gain in the PID control based on the first and second index values; and inspecting a mask for defects by irradiating the mask with the extreme ultraviolet light generated by the extreme ultraviolet light generating system, selecting a mask using the results of said testing; The pattern formed on the selected mask is transferred onto a photosensitive substrate by exposure. A method for manufacturing an electronic device, comprising:

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