Method for controlling spectral waveforms, laser apparatus, exposure apparatus, and method for manufacturing electronic devices

Abstract

Even if the spectral waveform is constant, changes in the longitudinal chromatic aberration of the projection optical system alter the contrast at the focus position of the central wavelength component, which can result in variations in imaging performance depending on the exposure equipment. [Solution] A method for controlling the spectral waveform of laser light output from a laser device to an exposure device includes acquiring the longitudinal chromatic aberration of the exposure device, setting a target value for the evaluation value using the relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform, and controlling the spectral waveform using the target value.

Description

[Technical Field]

[0001] This disclosure relates to a method for controlling spectral waveforms, a laser apparatus, an exposure apparatus, and a method for manufacturing electronic devices. [Background technology]

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

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

[0004] [Patent Document 1] International Publication No. 2002 / 073670 [Patent Document 2] Summary of U.S. Patent Application Publication No. 2011 / 200922

[0005] A method for controlling a spectral waveform relating to one aspect of this disclosure is a method for controlling the spectral waveform of laser light output from a laser device to an exposure device, which includes acquiring the longitudinal chromatic aberration of the exposure device, setting a target value for the evaluation value using the relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform, and controlling the spectral waveform using the target value.

[0006] A laser device relating to one aspect of this disclosure is a laser device connectable to an exposure apparatus, comprising: a laser oscillator that outputs laser light; a spectral waveform adjuster that adjusts the spectral waveform of the laser light; and a processor configured to acquire the longitudinal chromatic aberration of the exposure apparatus, set a target value for the evaluation value using the relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform, and control the spectral waveform adjuster using the target value.

[0007] An exposure apparatus according to one aspect of the present disclosure is an exposure apparatus connectable to a laser apparatus, comprising: a projection optical system that forms an image on a wafer surface using laser light output from the laser apparatus; a sensor that measures contrast on the wafer surface; a stage that moves the sensor along the optical path axis of the laser light; and a processor configured to acquire the longitudinal chromatic aberration of the exposure apparatus using the stage and the sensor, set a target value for the evaluation value using the relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform of the laser light, and transmit the target value to the laser apparatus.

[0008] A method for manufacturing an electronic device according to one aspect of this disclosure includes acquiring the longitudinal chromatic aberration of an exposure apparatus, setting a target value for the evaluation value using the relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform of the laser light output from a laser device connected to the exposure apparatus, outputting the laser light generated by controlling the spectral waveform using the target value to the exposure apparatus, and exposing a photosensitive substrate with laser light within the exposure apparatus in order to manufacture an electronic device. [Brief explanation of the drawing]

[0009] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] FIG. 1 schematically shows the configuration of an exposure system in a comparative example. [Figure 2] FIG. 2 schematically shows the configuration of a laser device according to a comparative example. [Figure 3] FIG. 3 is a block diagram for explaining the functions of a spectrum measurement control processor in a comparative example. [Figure 4] FIG. 4 is a graph showing an example of an estimated spectrum waveform I(λ) of laser light. [Figure 5] FIG. 5 schematically shows the difference in focus by a projection optical system according to the spectrum of laser light. [Figure 6] FIG. 6 is a graph showing the distribution of the focus position of laser light in an exposure apparatus. [Figure 7] FIG. 7 schematically shows the difference in focus according to the longitudinal chromatic aberration K of a projection optical system. [Figure 8] FIG. 8 is a graph showing the relationship between the longitudinal chromatic aberration K and the contrast at the first position F1 when the spectrum waveform is constant. [Figure 9] FIG. 9 schematically shows the configuration of a laser device according to an embodiment of the present disclosure. [Figure 10] FIG. 10 shows an example of a reticle pattern used for measuring the longitudinal chromatic aberration K. [Figure 11] FIG. 11 schematically shows a part of an exposure apparatus according to an embodiment. [Figure 12] FIG. 12 shows the light intensity distribution measured by a sensor when the wafer surface moves to the position Za. [Figure 13] FIG. 13 shows the light intensity distribution measured by a sensor when the wafer surface moves to the position Zb. [Figure 14] FIG. 14 shows the light intensity distribution measured by a sensor when the wafer surface moves to the position Zc. [Figure 15] FIG. 15 is a graph showing an example of the result of measuring the contrast while moving a workpiece table in a direction parallel to the Z axis. [Figure 16]FIG. 16 is a graph showing the relationship between the position on the wafer surface and the contrast when two different wavelengths are used. [Figure 17] FIG. 17 is a graph showing yet another example of the spectral waveform of the laser light. [Figure 18] FIG. 18 is a graph showing yet another example of the spectral waveform of the laser light. [Figure 19] FIG. 19 shows a rectangular imaging pattern used for evaluating the imaging performance. [Figure 20] FIG. 20 is a graph showing the simulation result of the imaging performance in the exposure apparatus. [Figure 21] FIG. 21 is a graph showing the simulation result of the imaging performance in the exposure apparatus. [Figure 22] FIG. 22 is a flowchart showing the procedure for measuring the spectral evaluation value V in the embodiment. [Figure 23] FIG. 23 shows an imaging pattern used for comparing the usefulness of the spectral evaluation value V and the spectral line width E95. [Figure 24] FIG. 24 is a graph showing the relationship between the spectral line width E95 and ΔCD in the imaging pattern of FIG. 23. [Figure 25] FIG. 25 is a graph showing the relationship between the spectral evaluation value V and ΔCD in the imaging pattern of FIG. 23. [Figure 26] FIG. 26 shows another imaging pattern used for comparing the usefulness of the spectral evaluation value V and the spectral line width E95. [Figure 27] FIG. 27 is a graph showing the relationship between the spectral line width E95 and ΔCD in the imaging pattern of FIG. 26. [Figure 28] FIG. 28 is a graph showing the relationship between the spectral evaluation value V and ΔCD in the imaging pattern of FIG. 26. [Figure 29] FIG. 29 is a graph showing the relationship between the spectral evaluation value V of Equation 4 and ΔCD in the imaging pattern of FIG. 23. [Figure 30]Figure 30 is a graph showing the relationship between the spectral evaluation value V in Equation 4 and ΔCD in the imaging pattern of Figure 26. [Figure 31] Figure 31 is a graph showing the relationship between longitudinal chromatic aberration K and the focus distribution evaluation value DK when the spectral waveform is kept constant. [Figure 32] Figure 32 is a graph showing the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V set in the embodiment. [Figure 33] Figure 33 shows a table illustrating the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V set in the embodiment. [Figure 34] Figure 34 is a graph showing the relationship between vertical chromatic aberration K and contrast at the focus position when the spectral evaluation value V is set so that the focus distribution evaluation value DK is constant. [Figure 35] Figure 35 is a flowchart showing the procedure for generating a table in the embodiment. [Figure 36] Figure 36 is a flowchart showing the procedure for spectral control in the embodiment. [Figure 37] Figure 37 is a flowchart showing the process by which the laser device acquires the longitudinal chromatic aberration K. [Figure 38] Figure 38 is a flowchart showing the process by which the exposure apparatus acquires the longitudinal chromatic aberration K. [Figure 39] Figure 39 is a flowchart showing the process by which the laser device controls the spectrum using the target value Vt. [Figure 40] Figure 40 is a flowchart showing the process by which the exposure apparatus controls the spectrum using the target value Vt. Embodiment

[0010] <Contents> 1. Comparative Example 1.1 Configuration of the exposure apparatus 100 1.2 Operation of the exposure apparatus 100 1.3 Configuration of Laser Device 1 1.3.1 Laser Oscillator 20 1.3.2 Monitor Module 16 1.3.3 Various Processing Devices 1.4 Operation 1.4.1 Laser control processor 30 1.4.2 Laser Oscillator 20 1.4.3 Monitor Module 16 1.4.4 Wavelength Measurement Control Unit 50 1.4.5 Spectrum Measurement Control Processor 60 1.5 Challenges of the Comparative Example 2. Laser device 1a that controls the spectral waveform according to the longitudinal chromatic aberration K. 2.1 Configuration 2.2 Measurement of vertical chromatic aberration K 2.3 Measurement of spectral evaluation value V 2.4 Comparison of spectral evaluation value V and spectral linewidth E95 2.5 Variations of Spectral Evaluation Value V 2.6 Control of spectral evaluation value V according to vertical chromatic aberration K 2.7 Table Generation 2.8 Operation of Spectrum Control 2.8.1 Acquisition of longitudinal chromatic aberration K using laser device 1a 2.8.2 Acquisition of longitudinal chromatic aberration K using exposure device 100 2.8.3 Spectral control using target value Vt by laser device 1a 2.8.4 Spectral control using target value Vt by exposure apparatus 100 2.9 Effect 3. Others

[0011] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are examples of the disclosure and are not intended to limit the scope of this disclosure. Furthermore, not all configurations and operations described in each embodiment are necessarily essential to the configurations and operations of this disclosure. The same reference numerals are used for identical components, and redundant descriptions are omitted.

[0012] 1. Comparative Example Figure 1 schematically shows the configuration of the exposure system in the comparative example. The comparative example in this disclosure is a configuration that the applicant recognizes as being known only to the applicant, and is not a prior art example acknowledged by the applicant.

[0013] The exposure system includes a laser device 1 and an exposure device 100. The laser device 1 includes a laser control processor 30. The laser control processor 30 is a processing unit that includes a memory 132 in which a control program is stored and a CPU (central processing unit) 131 that executes the control program. The laser control processor 30 is specially configured or programmed to perform various processes included in this disclosure. The laser device 1 is configured to output laser light toward the exposure device 100.

[0014] 1.1 Configuration of the exposure apparatus 100 The exposure apparatus 100 includes an illumination optical system 101, a projection optical system 102, and an exposure control processor 110. The illumination optical system 101 illuminates the reticle pattern of a reticle (not shown) placed on the reticle stage RT with laser light incident from the laser device 1. The projection optical system 102 projects the laser light that has passed through the reticle at a reduced size onto a workpiece (not shown) placed on the workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a resist film, and is movable by the stage 103.

[0015] The exposure control processor 110 is a processing unit that includes a memory 112 in which a control program is stored and a CPU 111 that executes the control program. The exposure control processor 110 is specially configured or programmed to perform various processes included in this disclosure. The exposure control processor 110 controls the exposure apparatus 100 and transmits and receives various data and signals to and from the laser control processor 30.

[0016] 1.2 Operation of the exposure apparatus 100 The exposure control processor 110 transmits data for the target wavelength, data for the target pulse energy, and a trigger signal to the laser control processor 30. The laser control processor 30 controls the laser device 1 according to this data and signal. The exposure control processor 110 synchronizes the reticle stage RT and the workpiece table WT, moving them in opposite directions. This allows the workpiece to be exposed with laser light that reflects the reticle pattern. Through this exposure process, a reticle pattern is transferred to a semiconductor wafer. Subsequently, electronic devices can be manufactured through a series of subsequent processes.

[0017] 1.3 Configuration of Laser Device 1 Figure 2 schematically shows the configuration of a laser apparatus 1 according to a comparative example. The laser apparatus 1 includes a laser oscillator 20, a power supply 12, a monitor module 16, a laser control processor 30, a wavelength measurement control unit 50, and a spectrum measurement control processor 60. The laser apparatus 1 is connectable to an exposure apparatus 100.

[0018] 1.3.1 Laser Oscillator 20 The laser oscillator 20 includes a laser chamber 10, a discharge electrode 11a, a narrowband module 14, and a spectral waveform adjuster 15a. The narrowband module 14 and the spectral waveform adjuster 15a constitute the laser resonator. The laser chamber 10 is positioned in the optical path of the laser resonator. Windows 10a and 10b are provided at both ends of the laser chamber 10. A discharge electrode 11a and a pair of discharge electrodes (not shown) are arranged inside the laser chamber 10. The discharge electrode (not shown) is positioned to overlap with the discharge electrode 11a in the direction of the V-axis perpendicular to the plane of the paper. The laser chamber 10 is filled with a laser gas, which may include, for example, argon or krypton as a rare gas, fluorine as a halogen gas, and neon as a buffer gas.

[0019] The power supply 12 includes a switch 13 and is connected to the discharge electrode 11a and a charger (not shown).

[0020] The narrowbanding module 14 includes a plurality of prisms 14a and 14b and a grating 14c. The prism 14b is supported by a rotating stage 14e. The rotating stage 14e is configured to rotate the prism 14b around an axis parallel to the V-axis according to a drive signal output from the wavelength driver 51. By rotating the prism 14b, the selectable wavelength of the narrowbanding module 14 is changed.

[0021] The spectral waveform adjuster 15a includes a cylindrical plano-convex lens 15b, a cylindrical plano-concave lens 15c, and a linear stage 15d. The cylindrical plano-concave lens 15c is positioned between the laser chamber 10 and the cylindrical plano-convex lens 15b. The cylindrical plano-convex lens 15b and the cylindrical plano-concave lens 15c are arranged so that the convex surface of the plano-convex lens 15b and the concave surface of the plano-concave lens 15c face each other. The convex surface of the plano-convex lens 15b and the concave surface of the plano-concave lens 15c each have focal axes parallel to the V-axis. The flat surface opposite the convex surface of the plano-convex lens 15b is coated with a partial reflective film.

[0022] 1.3.2 Monitor Module 16 The monitor module 16 is positioned in the optical path of the laser light between the spectral waveform adjuster 15a and the exposure apparatus 100. The monitor module 16 includes beam splitters 16a, 16b, and 17a, an energy sensor 16c, a high-reflection mirror 17b, a wavelength detector 18, and a spectrometer 19.

[0023] The beam splitter 16a is located in the optical path of the laser light output from the spectral waveform adjuster 15a. The beam splitter 16a is configured to transmit a portion of the laser light output from the spectral waveform adjuster 15a towards the exposure apparatus 100 with high transmittance, while reflecting the other portion. The beam splitter 16b is located in the optical path of the laser light reflected by the beam splitter 16a. The energy sensor 16c is located in the optical path of the laser light reflected by the beam splitter 16b.

[0024] The beam splitter 17a is located in the optical path of the laser light that has passed through the beam splitter 16b. The high-reflectivity mirror 17b is located in the optical path of the laser light that has been reflected by the beam splitter 17a.

[0025] The wavelength detector 18 is positioned in the optical path of the laser light that has passed through the beam splitter 17a. The wavelength detector 18 includes a diffusion plate 18a, an etalon 18b, a focusing lens 18c, and a line sensor 18d.

[0026] The diffusion plate 18a is located in the optical path of the laser light that has passed through the beam splitter 17a. The diffusion plate 18a has numerous irregularities on its surface and is configured to transmit and diffuse the laser light. The etalon 18b is located in the optical path of the laser light that has passed through the diffusion plate 18a. The etalon 18b includes two partial reflection mirrors. The two partial reflection mirrors face each other with an air gap of a predetermined distance and are bonded together via a spacer.

[0027] The focusing lens 18c is located in the optical path of the laser light that has passed through the etalon 18b. The line sensor 18d is the optical path of the laser light that has passed through the focusing lens 18c and is located at the focal plane of the focusing lens 18c. The line sensor 18d is an optical distribution sensor that includes a number of photodetectors arranged in one dimension. Alternatively, instead of the line sensor 18d, an image sensor that includes a number of photodetectors arranged in two dimensions may be used as the optical distribution sensor. The line sensor 18d may include a processor (not shown).

[0028] The line sensor 18d receives interference fringes formed by the etalon 18b and the focusing lens 18c. The interference fringes are an interference pattern of laser light, having a concentric circular shape, and the square of the distance from the center of these concentric circles is proportional to the change in wavelength. A processor (not shown) may be configured to statistically process and output data reflecting the interference pattern.

[0029] The spectrometer 19 is positioned in the optical path of the laser light reflected by the high-reflectivity mirror 17b. The spectrometer 19 includes a diffusion plate 19a, an etalon 19b, a focusing lens 19c, and a line sensor 19d. The line sensor 19d may include a processor (not shown). These configurations are similar to those of the diffusion plate 18a, etalon 18b, focusing lens 18c, and line sensor 18d included in the wavelength detector 18, except that the etalon 19b has a smaller free spectral range than the etalon 18b, and the focusing lens 19c has a longer focal length than the focusing lens 18c.

[0030] 1.3.3 Various Processing Devices The spectral measurement control processor 60 is a processing unit that includes a memory 61 in which a control program is stored, a CPU 62 that executes the control program, and a counter 63. The spectral measurement control processor 60 is specially configured or programmed to perform various processes included in this disclosure.

[0031] Memory 61 also stores various data for calculating the spectral linewidth. This data includes the instrument function S(λ) of the spectrometer 19. Counter 63 counts the number of laser pulses by counting the number of times an electrical signal containing pulse energy data is received from the energy sensor 16c. Alternatively, counter 63 may count the number of laser pulses by counting the oscillation trigger signals output from the laser control processor 30.

[0032] The wavelength measurement control unit 50 is a processing unit that includes a memory (not shown) in which a control program is stored, a CPU (not shown) that executes the control program, and a counter (not shown). The counter included in the wavelength measurement control unit 50 also counts the number of laser pulses, similar to the counter 63.

[0033] In this disclosure, the laser control processor 30, the wavelength measurement control unit 50, and the spectrum measurement control processor 60 are described as separate components, but the laser control processor 30 may also function as the wavelength measurement control unit 50 and the spectrum measurement control processor 60.

[0034] 1.4 Operation 1.4.1 Laser control processor 30 The laser control processor 30 receives setting data for the target pulse energy and target wavelength of the laser light from the exposure control processor 110 included in the exposure apparatus 100. The laser control processor 30 receives a trigger signal from the exposure control processor 110.

[0035] The laser control processor 30 transmits setting data for the applied voltage applied to the discharge electrode 11a to the power supply 12 based on the target pulse energy. The laser control processor 30 also transmits setting data for the target wavelength to the wavelength measurement control unit 50. Furthermore, the laser control processor 30 transmits an oscillation trigger signal based on the trigger signal to the switch 13 included in the power supply 12.

[0036] 1.4.2 Laser Oscillator 20 Switch 13 turns ON when it receives an oscillation trigger signal from the laser control processor 30. When switch 13 is ON, power supply 12 generates a pulsed high voltage from the electrical energy stored in a charger (not shown) and applies this high voltage to the discharge electrode 11a.

[0037] When a high voltage is applied to the discharge electrode 11a, a discharge occurs inside the laser chamber 10. The energy of this discharge excites the laser medium inside the laser chamber 10, causing it to transition to a higher energy level. When the excited laser medium subsequently transitions to a lower energy level, it emits light with a wavelength corresponding to the energy level difference.

[0038] Light generated inside the laser chamber 10 is emitted outside the laser chamber 10 through windows 10a and 10b. The light emitted from window 10a of the laser chamber 10 has its beam width expanded by prisms 14a and 14b and is then incident on the grating 14c. Light incident on the grating 14c from prisms 14a and 14b is reflected by multiple grooves in the grating 14c and diffracted in directions corresponding to the wavelength of the light.

[0039] The prisms 14a and 14b reduce the beam width of the diffracted light from the grating 14c and return that light to the laser chamber 10 through the window 10a. The spectral waveform adjuster 15a transmits and outputs a portion of the light emitted from the window 10b of the laser chamber 10, and reflects the other portion back into the inside of the laser chamber 10 through the window 10b.

[0040] In this way, the light emitted from the laser chamber 10 travels back and forth between the narrowband module 14 and the spectral waveform tuner 15a, and is amplified each time it passes through the discharge space inside the laser chamber 10. This light is narrowed each time it is folded back by the narrowband module 14. The laser-oscillating and narrowbanded light is then output as laser light from the spectral waveform tuner 15a.

[0041] The linear stage 15d included in the spectral waveform tuner 15a moves the cylindrical plano-concave lens 15c along the optical path between the laser chamber 10 and the cylindrical plano-convex lens 15b according to the drive signal output from the spectral driver 64. This changes the wavefront of the light traveling from the spectral waveform tuner 15a to the narrowband module 14. As a result of this change in wavefront, the spectral waveform and spectral linewidth of the laser light change.

[0042] 1.4.3 Monitor Module 16 The energy sensor 16c detects the pulse energy of the laser light and outputs the pulse energy data to the laser control processor 30, the wavelength measurement control unit 50, and the spectrum measurement control processor 60. The pulse energy data is used by the laser control processor 30 to feedback control the setting data of the applied voltage applied to the discharge electrode 11a. In addition, the electrical signal including the pulse energy data can be used by the wavelength measurement control unit 50 and the spectrum measurement control processor 60 to count the number of pulses, respectively.

[0043] The wavelength detector 18 generates interference fringe waveform data from the light intensity at each of the photodetectors included in the line sensor 18d. The wavelength detector 18 may also use the integrated waveform obtained by integrating the light intensity at each of the photodetectors as the interference fringe waveform data. The wavelength detector 18 may generate the integrated waveform multiple times and use the average waveform obtained by averaging the multiple integrated waveforms as the interference fringe waveform data. The wavelength detector 18 transmits interference fringe waveform data to the wavelength measurement control unit 50 in accordance with the data output trigger output from the wavelength measurement control unit 50.

[0044] The spectrometer 19 generates a raw waveform that reflects the amount of light in each of the photodetectors included in the line sensor 19d that receives the interference fringes. Alternatively, the spectrometer 19 generates an integrated waveform Oi by integrating the raw waveforms over Ni pulses. The spectrometer 19 generates the integrated waveform Oi Na times and generates an average waveform Oa by averaging the Na integrated waveforms Oi. The number of integration pulses Ni is, for example, 5 pulses or more and 8 pulses or less, and the number of averaging cycles Na is, for example, 5 times or more and 8 times or less.

[0045] The spectral measurement control processor 60 may count the number of integrated pulses Ni and the number of averaging cycles Na, and the spectrometer 19 may generate the integrated waveform Oi and the average waveform Oa according to the trigger signal output from the spectral measurement control processor 60. The memory 61 of the spectral measurement control processor 60 may store the setting data for the number of integrated pulses Ni and the number of averaging cycles Na.

[0046] The spectrometer 19 extracts a portion of the waveform corresponding to the free spectral range from the average waveform Oa. The extracted portion of the waveform shows the relationship between the distance from the center of the concentric circles that constitute the interference fringes and the light intensity. The spectrometer 19 obtains the measured spectral waveform O(λ) by performing a coordinate transformation on this waveform to show the relationship between wavelength and light intensity. This coordinate transformation of a portion of the average waveform Oa to show the relationship between wavelength and light intensity is also called mapping to spectral space. The measured spectral waveform O(λ) corresponds to the measured waveform in this disclosure.

[0047] The spectrometer 19 transmits the measured spectral waveform O(λ) to the spectral measurement control processor 60 in accordance with the data output trigger output from the spectral measurement control processor 60. The spectral measurement control processor 60 may perform one or all of the following processes instead of the spectrometer 19: the calculation of the integrated waveform Oi, the calculation of the average waveform Oa, and the acquisition of the measured spectral waveform O(λ) by mapping to the spectral space. The spectral measurement control processor 60 may also perform both the process of generating the average waveform Oa and the process of acquiring the measured spectral waveform O(λ) instead of the spectrometer 19.

[0048] 1.4.4 Wavelength Measurement Control Unit 50 The wavelength measurement control unit 50 receives target wavelength setting data from the laser control processor 30. The wavelength measurement control unit 50 also calculates the center wavelength of the laser beam using the interference fringe waveform data output from the wavelength detector 18. The wavelength measurement control unit 50 provides feedback control of the center wavelength of the laser beam by outputting a control signal to the wavelength driver 51 based on the target wavelength and the calculated center wavelength.

[0049] 1.4.5 Spectrum Measurement Control Processor 60 The spectral measurement control processor 60 receives the measured spectral waveform O(λ) from the spectrometer 19. Alternatively, the spectral measurement control processor 60 may receive the raw waveform from the spectrometer 19, integrate and average the raw waveform, map it to the spectral space, and obtain the measured spectral waveform O(λ). Alternatively, the spectral measurement control processor 60 may receive the integrated waveform Oi from the spectrometer 19, average the integrated waveform Oi, map it to the spectral space, and obtain the measured spectral waveform O(λ). Alternatively, the spectral measurement control processor 60 may receive the average waveform Oa from the spectrometer 19, map the average waveform Oa to the spectral space, and obtain the measured spectral waveform O(λ). The spectral measurement control processor 60 calculates the estimated spectral waveform I(λ) from the measured spectral waveform O(λ) as follows.

[0050] Figure 3 is a block diagram illustrating the functions of the spectral measurement control processor 60 in the comparative example. The spectrometer 19 has instrument-specific measurement characteristics, which are expressed as the instrument function S(λ) as a function of wavelength λ. Here, when laser light having an unknown spectral waveform T(λ) is incident on the spectrometer 19 having the instrument function S(λ) and measured, the measured spectral waveform O(λ) is expressed as the convolution integral of the unknown spectral waveform T(λ) and the instrument function S(λ), as shown in Equation 1 below.

number

[0051] The Fourier transform F(O(λ)) of the measured spectral waveform O(λ) is equal to the product of the Fourier transforms F(T(λ)) and F(S(λ)) of the two functions T(λ) and S(λ), respectively, as follows: F(O(λ)) = F(T(λ)) × F(S(λ)) This is called the convolution theorem.

[0052] The spectral measurement control processor 60 pre-measures the instrument function S(λ) of the spectrometer 19 and stores it in memory 61. To measure the instrument function S(λ), coherent light having a wavelength approximately the same as the central wavelength of the laser light output from the laser device 1, and having a narrow spectral linewidth that can be considered approximately a delta function, is incident on the spectrometer 19. The measured spectral waveform of the coherent light from the spectrometer 19 can be used as the instrument function S(λ).

[0053] The CPU 62 included in the spectral measurement control processor 60 performs an inverse convolution integral of the measured spectral waveform O(λ) of the laser light using the instrument function S(λ) of the spectrometer 19. Inverse convolution integral refers to the calculation process of estimating an unknown function that satisfies the convolution integral equation. The waveform obtained by the inverse convolution integral is called the estimated spectral waveform I(λ). The estimated spectral waveform I(λ) shows the relationship between the wavelength and light intensity of the estimated unknown spectral waveform T(λ). The estimated spectral waveform I(λ) is represented by the symbol * representing the inverse convolution integral. -1 It can be expressed as follows using . I(λ)=O(λ)* -1 S(λ)

[0054] The inverse convolution integral can theoretically be calculated as follows. First, the following equation can be derived from the convolution theorem. F(I(λ))=F(O(λ)) / F(S(λ)) By performing the inverse Fourier transform on both sides of this equation, the result of the inverse convolution integral can be obtained. That is, the notation for the inverse Fourier transform is F. -1 Therefore, the estimated spectral waveform I(λ) can be expressed as follows. I(λ)=F -1 (F(O(λ)) / F(S(λ)))

[0055] However, in actual numerical calculations, inverse convolution integrals using Fourier transforms and inverse Fourier transforms are susceptible to noise components in the measurement data. For this reason, it is desirable to calculate inverse convolution integrals using iterative methods that can suppress the influence of noise components, such as the Jacobi method and the Gauss-Seidel method.

[0056] 1.5 Challenges of the Comparative Example Figure 4 is a graph showing an example of an estimated spectral waveform I(λ) of laser light. The horizontal axis in Figure 4 represents the wavelength deviation Δλ from the center wavelength. The estimated spectral waveform I(λ) is a waveform that shows the light intensity of each wavelength component included in the wavelength range of the estimated spectral waveform I(λ). The value obtained by integrating the estimated spectral waveform I(λ) over a certain wavelength range is called the spectral energy in that wavelength range. The total width of the portion that accounts for 95% of the total spectral energy of the entire wavelength range of the estimated spectral waveform I(λ) is called the spectral linewidth E95. In Figure 4, the estimated spectral waveform I(λ) of the first laser light with a spectral linewidth E95 of 0.3 pm is shown as a solid line, and the estimated spectral waveform I(λ) of the second laser light with a spectral linewidth E95 of 0.4 pm is shown as a dashed line. Because the angle of refraction at the lens surface differs depending on the wavelength of the laser light, the exposure performance of the exposure device 100 will differ if the spectral waveform is different.

[0057] Figure 5 schematically illustrates the difference in focus achieved by the projection optical system 102 according to the spectrum of the laser light. In Figure 5, the cases in which a first laser beam with a spectral linewidth E95 of 0.3 pm and a second laser beam with a spectral linewidth of 0.4 pm are incident on the projection optical system 102 are shown. The central wavelengths of the first and second laser beams are the same. When the first laser beam is incident on the projection optical system 102, the focus position of the central wavelength component, which is the peak wavelength, becomes a first position F1 at a predetermined distance from the projection optical system 102. The focus position of the wavelength component that is 0.1 pm longer than the central wavelength becomes a second position F2, which is even further away from the projection optical system 102 than the first position F1. The imaging performance of that wavelength component at the first position F1 is lower than the imaging performance of the central wavelength component.

[0058] When the second laser beam is incident on the projection optical system 102, the focus position of the central wavelength component and the focus position of the wavelength component 0.1 pm longer than the central wavelength are the same as the first and second positions F1 and F2, respectively. However, the second laser beam contains more wavelength components 0.1 pm longer than the central wavelength than the first laser beam. The higher the proportion of wavelength components different from the central wavelength, the lower the imaging performance at the first position F1.

[0059] Furthermore, the second laser beam also contains wavelength components that are 0.2 pm longer than the central wavelength. The focus position of the wavelength components that are 0.2 pm longer than the central wavelength is a third position F3, which is even further away from the projection optical system 102 than the second position F2. The larger the wavelength difference from the central wavelength, the lower the imaging performance of that wavelength component at the first position F1.

[0060] Therefore, even if the focus position of the central wavelength component is the same, the imaging performance may differ if the spectral linewidth E95 is different.

[0061] Figure 6 is a graph showing the distribution of laser beam focus positions in the exposure apparatus 100. The vertical axis represents the focus position along the Z-axis shown in Figure 1, and the horizontal axis represents the light intensity of the wavelength component focused at each focus position. The spectral linewidth E95 of the laser beam is 0.3 pm. The distribution of focus positions when the longitudinal chromatic aberration K of the projection optical system 102 of the exposure apparatus 100, i.e., the difference in focus position per 1 pm wavelength difference, is 250 nm / pm, is shown by a solid line, and the distribution of focus positions when the longitudinal chromatic aberration K of the projection optical system 102 is 500 nm / pm is shown by a dashed line.

[0062] Figure 7 schematically shows the difference in focus depending on the longitudinal chromatic aberration K of the projection optical system 102. Assuming that the focus position of the central wavelength component is constant at the first position F1 regardless of the longitudinal chromatic aberration K, the focus position of the wavelength component 0.1 pm longer than the central wavelength differs depending on the longitudinal chromatic aberration K. If the longitudinal chromatic aberration K is 250 nm / pm, the focus position of that wavelength component will be the second position F2, 25 nm away from the focus position of the central wavelength component, and if the longitudinal chromatic aberration K is 500 nm / pm, it will be the fourth position F4, 50 nm away from the focus position of the central wavelength component.

[0063] Thus, the focus position of wavelength components 0.1 pm longer than the central wavelength differs depending on the longitudinal chromatic aberration K. The further the focus position of that wavelength component is from the first position F1, the worse the imaging performance at the first position F1 for that wavelength component becomes. Therefore, even if the focus position of the central wavelength component is the same, the imaging performance may differ if the longitudinal chromatic aberration K is different.

[0064] Figure 8 is a graph showing the relationship between longitudinal chromatic aberration K and contrast at the first position F1, when the spectral waveform is kept constant. Figure 8 shows the case where a line-and-space reticle pattern with line and space widths of 100 nm each is used. The line-and-space reticle pattern will be described later with reference to Figure 10. Even if the spectral waveform is constant, a change in the longitudinal chromatic aberration K of the projection optical system 102 alters the contrast at the focus position of the central wavelength component, which can cause variations in imaging performance due to differences in the exposure device 100. Therefore, conventional spectral control using the spectral linewidth E95 as an indicator may not be able to adequately control imaging performance. Contrast will be discussed later.

[0065] In the embodiments described below, the desired exposure performance can be obtained by controlling the spectral waveform according to the longitudinal chromatic aberration K of the projection optical system 102.

[0066] 2. Laser device 1a that controls the spectral waveform according to the longitudinal chromatic aberration K. 2.1 Configuration Figure 9 schematically shows the configuration of a laser apparatus 1a according to an embodiment of this disclosure. In the laser apparatus 1a, the memory 61 included in the spectral measurement control processor 60 stores data 611 that stores the relationship between longitudinal chromatic aberration K and spectral evaluation value V. Data 611 will be described later.

[0067] 2.2 Measurement of vertical chromatic aberration K Figure 10 shows an example of a reticle pattern used to measure longitudinal chromatic aberration K. To measure the longitudinal chromatic aberration K of the projection optical system 102, a line-and-space reticle pattern with alternating transparent and opaque sections, as shown in Figure 10, is placed on the reticle stage RT (see Figure 1).

[0068] Figure 11 schematically shows a part of the exposure apparatus 100 according to the embodiment. A sensor 43 is placed on the workpiece table WT to measure the longitudinal chromatic aberration K. The sensor 43 may be a light distribution sensor containing a large number of light-receiving elements arranged in one dimension, similar to the line sensor 18d (see Figures 2 and 9), or it may be an image sensor containing a large number of light-receiving elements arranged in two dimensions.

[0069] The workpiece table WT is movable in a direction parallel to the Z-axis by the stage 103 (see Figure 1). By moving the workpiece table WT, the wafer surface can be moved to positions Za, Zb, and Zc shown in Figure 11.

[0070] Figures 12 to 14 show the light intensity distribution measured by the sensor 43 when the wafer surface moves to positions Za to Zc, respectively. In Figures 12 to 14, the horizontal axis represents the position in the Y-axis direction, and the vertical axis represents the light intensity I at each position. The light intensity distribution shown in Figures 12 to 14 shows alternating bright and dark areas, corresponding to the reticle pattern shown in Figure 10. The light intensity in the dark areas includes the minimum value of light intensity I, Imin. The maximum value of light intensity I in the bright areas surrounded by the dark areas at both ends is defined as Imax. The larger the difference between the maximum value Imax and the minimum value Imin, the greater the contrast can be evaluated. The contrast can be defined as the difference between the maximum value Imax and the minimum value Imin, or as the difference between the maximum value Imax and the minimum value Imin divided by the sum of the maximum value Imax and the minimum value Imin.

[0071] Figure 15 is a graph showing an example of the results of measuring contrast while moving the workpiece table WT in a direction parallel to the Z axis. Moving the workpiece table WT changes the position of the wafer surface, and the contrast changes accordingly. When the contrast is highest at position Zb on the wafer surface, position Zb becomes the focus position.

[0072] Figure 16 is a graph showing the relationship between wafer surface position and contrast when using two different wavelengths. Let Z1 be the first focus position when using the first wavelength λ1, and Z2 be the second focus position when using the second wavelength λ2, which is shorter than the first wavelength λ1. In this case, the longitudinal chromatic aberration K can be defined by the following equation. K = (Z1 - Z2) / (λ1 - λ2) In other words, the longitudinal chromatic aberration K is given by the ratio of the difference between the first and second focus positions Z1-Z2 to the difference between the first and second wavelengths λ1-λ2.

[0073] 2.3 Measurement of spectral evaluation value V Figures 17 and 18 are graphs showing yet another example of the spectral waveform of laser light. In each of Figures 17 and 18, the horizontal axis represents the wavelength deviation Δλ from the center wavelength. The spectral linewidth E95 of spectral waveforms #1 to #3 shown in Figure 17 and spectral waveforms #4 to #6 shown in Figure 18 is all 0.3 pm, but these spectral waveforms #1 to #6 have different shapes. Spectral waveforms #1 to #3 have an asymmetric spectral distribution in which the peak wavelength is shifted to a longer wavelength than the center wavelength, and the difference between the center wavelength and the peak wavelength is different from one another. The center wavelength here is, for example, 1 / e of the peak intensity. 2 This represents the center of the wavelength range with the above light intensity. Spectral waveforms #4 to #6 are symmetrical, but spectral waveform #4 has a gentler curve near the peak compared to a Gaussian distribution spectral waveform (see Figure 4). Spectral waveforms #5 and #6 have spectral distributions in which the peak wavelength is separated into two, and the difference between the central wavelength and the peak wavelength is different for each other.

[0074] The imaging performance of the exposure apparatus 100 was evaluated as follows using spectral waveforms #1 to #6. Figure 19 shows the rectangular imaging pattern used to evaluate imaging performance. A mask was used that was designed so that a rectangular imaging pattern with a horizontal dimension of 38 nm and a vertical dimension of 76 nm was formed on the wafer surface by the projection optical system 102 when a Gaussian spectral waveform was used. The vertical chromatic aberration K of the projection optical system 102 was set to 250 nm / pm. The deviation ΔCD from the vertical dimension of 76 nm was determined by simulation when the exposure amount was adjusted so that the horizontal dimension of the imaging pattern on the wafer surface was 38 nm when spectral waveforms #1 to #6 were used.

[0075] Figures 20 and 21 are graphs showing the simulation results of the imaging performance in the exposure apparatus 100. Figure 20 shows the case using spectral waveforms #1 to #3 shown in Figure 17, and Figure 21 shows the case using spectral waveforms #4 to #6 shown in Figure 18. As shown in Figure 20, the larger the difference between the center wavelength and the peak wavelength, and the greater the asymmetry, the greater the dimensional error on the wafer surface can be. Also, as shown in Figure 21, even with a symmetrical spectral distribution, the larger the difference from a Gaussian distribution, the greater the dimensional error on the wafer surface can be.

[0076] Thus, even if the spectral linewidth E95 is the same, the imaging performance in the exposure apparatus 100 may differ, and simply adjusting the spectral linewidth E95 to the target value may not be sufficient to obtain the desired exposure performance. Therefore, we define the spectral evaluation value V, which takes into account the shape of the spectral waveform, as follows.

[0077] First, the centroid wavelength λc of the estimated spectral waveform I(λ) is defined by the following equation 2.

number

[0078] The spectral evaluation value V of the estimated spectral waveform I(λ) is defined by the following equation 3.

number

[0079] The numerator of Equation 3 is a function of the light intensity represented by the estimated spectral waveform I(λ) and the wavelength deviation from the centroid wavelength λc (λ-λc). 2 This value is obtained by integrating the product of with respect to the wavelength range of the estimated spectral waveform I(λ). The spectral evaluation value V corresponds to the evaluation value in this disclosure.

[0080] The denominator of Equation 3 is the product of the constant λs and the value obtained by integrating the light intensity represented by the estimated spectral waveform I(λ) with respect to the wavelength range of the estimated spectral waveform I(λ). The constant λs can be any of the following (1) to (4). (1)1 (2) Centroid wavelength λc (3) Spectral linewidth E95 of estimated spectral waveform I(λ) (4) Standard deviation of a Gaussian distribution spectral waveform having the same spectral linewidth E95 as the estimated spectral waveform I(λ)

[0081] As shown in (1) above, when the constant λs is set to 1, the spectral evaluation value V has dimensions of the square of the wavelength λ. However, as shown in (2) to (4) above, by dividing by the constant λs obtained from a function of the wavelength λ, the spectral evaluation value V can be made to have dimensions of the wavelength λ.

[0082] Figure 22 is a flowchart showing the procedure for measuring the spectral evaluation value V in the embodiment. The spectral measurement control processor 60 generates an integrated waveform Oi and an average waveform Oa from the interference pattern of the laser light as follows, and calculates an estimated spectral waveform I(λ) and a spectral evaluation value V.

[0083] In S331, the spectral measurement control processor 60 reads the number of integrated pulses Ni and the number of averaging cycles Na from the memory 61. In S332, the spectral measurement control processor 60 receives raw waveforms that reflect the amount of light in each of the photodetectors included in the line sensor 19d, and generates an integrated waveform Oi by integrating them over Ni pulses. In S333, the spectral measurement control processor 60 generates an integrated waveform Oi Na times and generates an average waveform Oa by averaging the Na integrated waveforms Oi. In S334, the spectral measurement control processor 60 generates the measured spectral waveform O(λ) by mapping the average waveform Oa to the spectral space.

[0084] In S335, the spectral measurement control processor 60 reads the instrument function S(λ) of the spectrometer 19 from the memory 61. In S336, the spectral measurement control processor 60 calculates the estimated spectral waveform I(λ) by deconvolving and integrating the measured spectral waveform O(λ) using the device function S(λ).

[0085] In S338, the spectral measurement control processor 60 calculates the centroid wavelength λc of the estimated spectral waveform I(λ) using Equation 2. In S339, the spectral measurement control processor 60 calculates the spectral evaluation value V of the estimated spectral waveform I(λ) using Equation 3. After S339, the spectral measurement control processor 60 terminates the processing of this flowchart.

[0086] 2.4 Comparison of spectral evaluation value V and spectral linewidth E95 Next, the usefulness of the spectral evaluation value V and the evaluation method using it will be explained in comparison with the spectral linewidth E95. As explained below, the spectral evaluation value V can be applied to the shape of various imaging patterns.

[0087] Figure 23 shows the imaging patterns used to compare the usefulness of the spectral evaluation value V and spectral linewidth E95. The imaging patterns shown in Figure 23 include two types of patterns: a DENCE pattern with multiple exposure areas clustered together, and an ISO pattern located away from other exposure areas. ΔCD is defined as the deviation of the ISO pattern from its reference dimension when the exposure amount is adjusted so that the dimensions of the DENCE pattern are 45 nm. The reference dimension of the ISO pattern is the dimension of the ISO pattern when the spectral linewidth E95 is 0.01 pm.

[0088] Figure 24 is a graph showing the relationship between the spectral linewidth E95 and ΔCD in the imaging pattern of Figure 23, and Figure 25 is a graph showing the relationship between the spectral evaluation value V and ΔCD in the imaging pattern of Figure 23. For each of Figures 24 and 25, simulations were performed using numerous variations, including the spectral waveforms exemplified in Figures 17 and 18, and ΔCD was plotted.

[0089] Figure 24 shows two distinct trends in the ratio of the change in ΔCD to the change in spectral linewidth E95. Therefore, even when spectral linewidth E95 is measured, it may not be possible to accurately determine the imaging performance on the wafer surface. In Figure 25, the relationship between the spectral evaluation value V and ΔCD is almost a straight line. Therefore, by measuring the spectral evaluation value V, the imaging performance on the wafer surface can be determined. By controlling the spectral evaluation value V to a certain target value, the desired imaging performance can be achieved.

[0090] Figure 26 shows another imaging pattern used to compare the usefulness of the spectral evaluation value V and spectral linewidth E95. The imaging pattern shown in Figure 26 includes two types of patterns: a LINE pattern that mimics wiring and a SPACE pattern that mimics the gaps between adjacent wirings. ΔCD is defined as the deviation of the SPACE pattern from the reference dimension when the exposure is adjusted so that the dimensions of the LINE pattern are 100 nm.

[0091] Figure 27 is a graph showing the relationship between the spectral linewidth E95 and ΔCD in the imaging pattern of Figure 26, and Figure 28 is a graph showing the relationship between the spectral evaluation value V and ΔCD in the imaging pattern of Figure 26. For each of Figures 27 and 28, simulations were performed using numerous variations, including the spectral waveforms exemplified in Figures 17 and 18, and ΔCD was plotted.

[0092] Figure 27 shows two distinct trends in the ratio of change in ΔCD to change in spectral linewidth E95. Therefore, even when spectral linewidth E95 is measured, it may not be possible to accurately determine the imaging performance on the wafer surface. In Figure 28, the relationship between the spectral evaluation value V and ΔCD is almost a straight line. Therefore, by measuring the spectral evaluation value V, the imaging performance on the wafer surface can be determined. By controlling the spectral evaluation value V to a certain target value, the desired imaging performance can be achieved.

[0093] 2.5 Variations of Spectral Evaluation Value V In Equation 3, the square of the wavelength deviation λ-λc from the centroid wavelength λc is (λ-λc). 2 While the above is used, this disclosure is not limited thereto. The spectral evaluation value V may be calculated by the following equation 4.

number

[0094] Equation 4 differs from Equation 3 in that, instead of squaring the wavelength deviation λ-λc as in Equation 3, the absolute value of the wavelength deviation λ-λc is raised to the power of N. The exponent N is a positive number. Equation 4 when the value of the exponent N is 2 is equivalent to Equation 3 when λs is 1.

[0095] Figure 29 is a graph showing the relationship between the spectral evaluation value V from Equation 4 and ΔCD in the imaging pattern of Figure 23. Figure 30 is a graph showing the relationship between the spectral evaluation value V from Equation 4 and ΔCD in the imaging pattern of Figure 26. In Figures 29 and 30, the simulation results for the cases where the exponent N in Equation 4 is 1, 2, and 3 are shown along with their respective regression lines. A correlation is observed between the spectral evaluation value V and ΔCD in all cases where the exponent N is 1, 2, and 3. By measuring such a spectral evaluation value V, the imaging performance on the wafer surface can be determined.

[0096] The coefficient of determination indicating the goodness of fit of the regression line is highest when the value of the power exponent N is 2 in both FIGS. 29 and 30. The value of the power exponent N is preferably 1.9 or more and 2.1 or less.

[0097] 2.6 Control of the spectral evaluation value V according to the longitudinal chromatic aberration K FIG. 31 is a graph showing the relationship between the longitudinal chromatic aberration K and the focus distribution evaluation value D K when the spectral waveform is fixed without change. The focus distribution evaluation value D K is an evaluation value that enables evaluation of the imaging performance by taking into account the longitudinal chromatic aberration K in the spectral evaluation value V, and is calculated by the following Equation 5.

Equation

[0098] Equation 5 corresponds to replacing the wavelength λ in Equation 3 with the product Kλ of the longitudinal chromatic aberration K and the wavelength λ and setting the constant λs to 1. When the spectral waveform is fixed without change, the focus distribution evaluation value D K is approximately proportional to the square of the longitudinal chromatic aberration K. This indicates that the larger the focus distribution evaluation value D K , the larger the deviation ΔCD from the reference dimension can be.

[0099] In the embodiment, the spectral evaluation value V is controlled so that the focus distribution evaluation value D K becomes constant regardless of the longitudinal chromatic aberration K.

[0100] FIG. 32 is a graph showing the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V set in the embodiment. The relationship between the longitudinal chromatic aberration K and the spectral evaluation value V is such that the focus distribution evaluation value D KThe value is set to remain constant regardless of the longitudinal chromatic aberration K. As a result, the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V shown in Figure 32 is such that the spectral evaluation value V is approximately inversely proportional to the square of the longitudinal chromatic aberration K. The memory 61 included in the spectral measurement control processor 60 may store the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V as data 611 that stores the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V.

[0101] Figure 33 shows a table illustrating the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V set in the embodiment. The relationship between the longitudinal chromatic aberration K and the spectral evaluation value V is given by the focus distribution evaluation value D K The value is set to remain constant regardless of the longitudinal chromatic aberration K. The memory 61 included in the spectral measurement control processor 60 may store a table associating longitudinal chromatic aberration K with spectral evaluation value V as data 611 that stores the relationship between longitudinal chromatic aberration K and spectral evaluation value V.

[0102] Figure 34 shows the focus distribution evaluation value D. K This graph shows the relationship between vertical chromatic aberration K and contrast at the focus position when the spectral evaluation value V is set to be constant. The focus distribution evaluation value D is calculated using the relationship shown in Figure 32 or Figure 33. K Since the spectral evaluation value V is set so that it remains constant, the contrast at the focus position is almost constant regardless of the vertical chromatic aberration K. That is, the focus distribution evaluation value D K When the spectral evaluation value V is controlled to remain constant, the change in contrast in response to changes in vertical chromatic aberration K is smaller than when the spectral evaluation value V is fixed. Focus distribution evaluation value D K By setting the spectral evaluation value V to be constant, the exposure performance can be stabilized regardless of the differences between the exposure devices 100.

[0103] Equation 5 replaces the wavelength λ in Equation 3 with the product Kλ of the longitudinal chromatic aberration K and the wavelength λ, but the disclosure is not limited to this. In Equation 4, the wavelength λ may be replaced with the product Kλ. In that case, the focus distribution evaluation value D when the spectral waveform is fixed without changing is... K It is approximately proportional to the vertical chromatic aberration K raised to the power of N. Focus distribution evaluation value D K If the spectral evaluation value V is set so that it remains constant regardless of the longitudinal chromatic aberration K, then the spectral evaluation value V will be approximately inversely proportional to the Nth power of the longitudinal chromatic aberration K.

[0104] 2.7 Table Generation Figure 35 is a flowchart showing the procedure for generating a table in the embodiment. The spectral measurement control processor 60 generates a table showing the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V as follows.

[0105] In S201, the spectral measurement control processor 60 evaluates the focus distribution value D K This is calculated using Equation 5.

[0106] In S202, the spectral measurement control processor 60 evaluates the focus distribution value D K A spectral evaluation value V is calculated for multiple values ​​of the longitudinal chromatic aberration K such that the value of the spectral evaluation value V remains constant, and the spectral evaluation value V and the longitudinal chromatic aberration K are associated and stored in memory 61. After S202, the spectral measurement control processor 60 terminates the processing of this flowchart.

[0107] 2.8 Operation of Spectrum Control Figure 36 is a flowchart illustrating the spectral control procedure in an embodiment. The spectral control shown in Figure 36 may be performed by the exposure control processor 110, the laser control processor 30, or the spectral measurement control processor 60. The exposure control processor 110, the laser control processor 30, and the spectral measurement control processor 60 each correspond to processors in this disclosure. In the description of Figure 36, these processors are collectively referred to simply as "processors." The processor sets a target value Vt for the spectral evaluation value V using the longitudinal chromatic aberration K as follows, and controls the spectral waveform adjuster 15a.

[0108] In S1, the processor acquires the longitudinal chromatic aberration K of the projection optical system 102 of the exposure apparatus 100. Details of S1 will be explained with reference to Figures 37 and 38.

[0109] In S2, the processor refers to data 611 which stores the relationship between longitudinal chromatic aberration K and spectral evaluation value V, and sets a target value Vt for spectral evaluation value V based on longitudinal chromatic aberration K. The relational expression described with reference to Figure 32 may be used as data 611, or the table described with reference to Figures 33 and 35 may be used.

[0110] In S3, the processor performs spectral control using the target value Vt. Details of S3 will be explained with reference to Figures 39 and 40. After S3, the processor terminates the processing of this flowchart.

[0111] 2.8.1 Acquisition of longitudinal chromatic aberration K using laser device 1a Figure 37 is a flowchart showing the process by which the laser device 1a acquires the longitudinal chromatic aberration K. The process shown in Figure 37 corresponds to the first example of the subroutine S1 in Figure 36.

[0112] In S11a, the laser control processor 30 controls the laser oscillator 20 to output laser light having a first wavelength λ1 to the exposure apparatus 100. In S12a, the laser control processor 30 receives a first focus position Z1 measured by the exposure apparatus 100 using laser light having a first wavelength λ1 from the exposure apparatus 100.

[0113] In S13a, the laser control processor 30 controls the laser oscillator 20 to output laser light having a second wavelength λ2 that is shorter than the first wavelength λ1 to the exposure apparatus 100. In S14a, the laser control processor 30 receives from the exposure apparatus 100 a second focus position Z2 measured by the exposure apparatus 100 using laser light having a second wavelength λ2.

[0114] In S15a, the laser control processor 30 calculates the longitudinal chromatic aberration K based on the first and second wavelengths λ1 and λ2 and the first and second focus positions Z1 and Z2. After S15a, the laser control processor 30 terminates the processing in this flowchart and returns to the processing shown in Figure 36.

[0115] 2.8.2 Acquisition of longitudinal chromatic aberration K using exposure device 100 Figure 38 is a flowchart showing the process by which the exposure apparatus 100 acquires the longitudinal chromatic aberration K. The process shown in Figure 38 corresponds to the second example of the subroutine S1 in Figure 36.

[0116] In S11b, the exposure control processor 110 transmits a setting signal for the first wavelength λ1 to the laser device 1a. In S12b, the exposure control processor 110 measures the first focus position Z1 using laser light having a first wavelength λ1.

[0117] In S13b, the exposure control processor 110 transmits a setting signal for a second wavelength λ2, which is shorter than the first wavelength λ1, to the laser device 1a. In S14b, the exposure control processor 110 measures the second focus position Z2 using laser light having a second wavelength λ2.

[0118] In S15b, the exposure control processor 110 calculates the vertical chromatic aberration K based on the first and second wavelengths λ1 and λ2 and the first and second focus positions Z1 and Z2. After S15b, the exposure control processor 110 terminates the processing in this flowchart and returns to the processing shown in Figure 36.

[0119] 2.8.3 Spectral control using target value Vt by laser device 1a Figure 39 is a flowchart showing the process by which the laser device 1a controls the spectrum using the target value Vt. The process shown in Figure 39 corresponds to the first example of the subroutine S3 in Figure 36.

[0120] In S32, the laser control processor 30 outputs an oscillation trigger signal. When the oscillation trigger signal is output, laser light is output from the laser oscillator 20.

[0121] In S33, the laser control processor 30 measures the spectral evaluation value V using the laser light output from the laser oscillator 20. The processing in S33 is performed by the spectral measurement control processor 60 in the procedure described with reference to Figure 22.

[0122] In S34, the laser control processor 30 compares the spectral evaluation value V with the target value Vt and determines whether the spectral evaluation value V is within the acceptable range. For example, it determines whether the absolute value of the difference between the spectral evaluation value V and the target value Vt is smaller than the allowable error Ve. The target value Vt used here is the target value Vt set by the laser control processor 30, the spectral measurement control processor 60, or the exposure control processor 110 in S2 of Figure 36.

[0123] If the spectral evaluation value V is not within the acceptable range in S34 (S34: NO), the laser control processor 30 proceeds to S35. In S35, the laser control processor 30 transmits the determination result from S34 to the spectrum measurement control processor 60. The spectrum measurement control processor 60 controls the spectrum waveform adjuster 15a by driving the spectrum driver 64. For example, if the spectrum evaluation value V is greater than the target value Vt, the spectrum waveform adjuster 60 controls the spectrum waveform adjuster 15a to reduce the spectral linewidth, and if the spectrum evaluation value V is less than the target value Vt, it controls the spectrum waveform adjuster 15a to increase the spectral linewidth. After S35, the laser control processor 30 returns processing to S32.

[0124] If the spectral evaluation value V is within the acceptable range in S34 (S34: YES), the laser control processor 30 terminates the processing of this flowchart. After that, the laser device 1a continues to output laser light with the settings of the spectral waveform adjuster 15a fixed. Alternatively, the laser control processor 30 may return to processing in S32 and repeatedly measure and determine the spectral evaluation value V while continuing to output laser light.

[0125] 2.8.4 Spectral control using target value Vt by exposure apparatus 100 Figure 40 is a flowchart showing the process by which the exposure apparatus 100 controls the spectrum using the target value Vt. The process shown in Figure 40 corresponds to the second example of the subroutine S3 in Figure 36.

[0126] In S36, the exposure control processor 110 transmits the target value Vt of the spectral evaluation value V to the laser device 1a. Upon receiving the target value Vt, the laser device 1a performs spectral control using the target value Vt. The operation of the laser device 1a in this case may be the same as in Figure 39. After S36, the exposure control processor 110 terminates the processing in this flowchart and returns to the processing shown in Figure 36.

[0127] 2.9 Effect (1) According to embodiments of the present disclosure, a method for controlling the spectral waveform of laser light output from laser device 1a to exposure device 100 includes acquiring the longitudinal chromatic aberration K of exposure device 100, setting a target value Vt of the spectral evaluation value V using the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V, and controlling the spectral waveform using the target value Vt. According to this method, the vertical chromatic aberration K is acquired and the target value Vt of the spectral evaluation value V is set, so that appropriate spectral control is performed according to the differences in the exposure device 100, and the required exposure performance can be obtained.

[0128] (2) According to the embodiment, obtaining the longitudinal chromatic aberration K includes the laser device 1a outputting laser light having a first wavelength λ1 to the exposure device 100, and the laser device 1a receiving a first focus position Z1 at the first wavelength λ1 from the exposure device 100. It also includes the laser device 1a outputting laser light having a second wavelength λ2 different from the first wavelength λ1 to the exposure device 100, and the laser device 1a receiving a second focus position Z2 at the second wavelength λ2 from the exposure device 100. It also includes calculating the longitudinal chromatic aberration K using the first and second wavelengths λ1 and λ2 and the first and second focus positions Z1 and Z2. According to this, the vertical chromatic aberration K of the exposure device 100 can be accurately calculated by the laser device 1a acquiring the focus positions of two wavelengths.

[0129] (3) According to the embodiment, obtaining the longitudinal chromatic aberration K includes the exposure apparatus 100 transmitting a setting signal to the laser apparatus 1a to set a first wavelength λ1, and the exposure apparatus 100 measuring a first focus position Z1 based on the first wavelength λ1. It also includes the exposure apparatus 100 transmitting a setting signal to the laser apparatus 1a to set a second wavelength λ2 different from the first wavelength λ1, and the exposure apparatus 100 measuring a second focus position Z2 based on the second wavelength λ2. It also includes calculating the longitudinal chromatic aberration K using the first and second wavelengths λ1 and λ2 and the first and second focus positions Z1 and Z2. According to this, the vertical chromatic aberration K of the exposure device 100 can be accurately calculated by measuring the focus positions of two wavelengths.

[0130] (4) According to the embodiment, obtaining the longitudinal chromatic aberration K includes calculating the longitudinal chromatic aberration K using a first wavelength λ1, a first focus position Z1 in the exposure apparatus 100 when laser light having the first wavelength λ1 is incident on the exposure apparatus 100, a second wavelength λ2 different from the first wavelength λ1, and a second focus position Z2 in the exposure apparatus 100 when laser light having the second wavelength λ2 is incident on the exposure apparatus 100. According to this, the vertical chromatic aberration K of the exposure apparatus 100 can be accurately calculated by using two wavelength focus positions.

[0131] (5) According to the embodiment, obtaining the longitudinal chromatic aberration K includes obtaining the ratio of the difference between the first and second focus positions Z1 and Z2 to the difference between the first and second wavelengths λ1 and λ2. According to this method, the vertical chromatic aberration K can be obtained through a simple calculation.

[0132] (6) According to the embodiment, the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V is determined such that the change in contrast in response to the change in longitudinal chromatic aberration K is smaller than the change in contrast when the spectral evaluation value V is fixed. According to this, even with exposure devices 100 having different vertical chromatic aberration K, stable exposure performance can be obtained by controlling the spectral evaluation value V.

[0133] (7) According to the embodiment, the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V is determined such that the spectral evaluation value V is inversely proportional to the power of the longitudinal chromatic aberration K such that the exponent N is 1 or greater. According to this, the spectral evaluation value V can be set to an appropriate value depending on the vertical chromatic aberration K.

[0134] (8) According to the embodiment, the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V is determined such that the spectral evaluation value V is inversely proportional to the square of the longitudinal chromatic aberration K. According to this, the spectral evaluation value V can be set to a more appropriate value depending on the vertical chromatic aberration K.

[0135] (9) According to the embodiment, the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V is stored in a table that associates the longitudinal chromatic aberration K with the spectral evaluation value V. According to this, an appropriate spectral evaluation value V can be set by searching a table based on the longitudinal chromatic aberration K.

[0136] (10) According to the embodiment, the method for controlling the spectral waveform further includes obtaining a measured spectral waveform O(λ) from the interference pattern of the laser light output from the laser device 1a, and calculating a spectral evaluation value V using the measured spectral waveform O(λ). The spectral waveform is also controlled using the spectral evaluation value V and the target value Vt. According to this method, the spectral waveform is controlled so that the spectral evaluation value V obtained from the interference pattern approaches the target value Vt, thereby allowing the spectral evaluation value V to be controlled to an appropriate value.

[0137] (11) According to the embodiment, an estimated spectral waveform I(λ) showing the relationship between wavelength λ and light intensity is calculated using the measured spectral waveform O(λ), the centroid wavelength λc included in the wavelength range of the estimated spectral waveform I(λ) is calculated, and the product I(λ)(λ-λc) of the wavelength deviation from the centroid wavelength λc and the light intensity is calculated. 2 The spectral evaluation value V is calculated using the integral value obtained by integrating over the wavelength range. According to this method, an appropriate spectral evaluation value V can be calculated even for laser light with a spectral waveform different from that of a Gaussian distribution. Furthermore, the control of the spectral waveform can be applied to the shape of various imaging patterns.

[0138] (12) According to one embodiment, the laser device 1a connectable to the exposure apparatus 100 includes a laser oscillator 20 that outputs laser light, a spectral waveform adjuster 15a that adjusts the spectral waveform of the laser light, and a laser control processor 30. The laser control processor 30 acquires the longitudinal chromatic aberration K of the exposure apparatus 100, sets a target value Vt of the spectral evaluation value V using the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V, and controls the spectral waveform adjuster 15a using the target value Vt. According to this method, the vertical chromatic aberration K is acquired and the target value Vt of the spectral evaluation value V is set, so appropriate spectral control can be performed according to the differences in the exposure apparatus 100.

[0139] (13) According to the embodiment, the laser control processor 30 controls the laser oscillator 20 to output laser light having a first wavelength λ1 to the exposure apparatus 100, and receives a first focus position Z1 at the first wavelength λ1 from the exposure apparatus 100. The laser control processor 30 also controls the laser oscillator 20 to output laser light having a second wavelength λ2 different from the first wavelength λ1 to the exposure apparatus 100, and receives a second focus position Z2 at the second wavelength λ2 from the exposure apparatus 100. The laser control processor 30 also calculates the longitudinal chromatic aberration K using the first and second wavelengths λ1 and λ2 and the first and second focus positions Z1 and Z2. According to this, the vertical chromatic aberration K of the exposure device 100 can be accurately calculated by the laser device 1a acquiring the focus positions of two wavelengths.

[0140] (14) According to one embodiment, the exposure apparatus 100, which can be connected to the laser apparatus 1a, comprises a projection optical system 102, a sensor 43, a stage 103, and an exposure control processor 110. The projection optical system 102 forms an image on the wafer surface using laser light output from the laser apparatus 1a. The sensor 43 measures the contrast on the wafer surface. The stage 103 moves the sensor 43 along the optical path axis of the laser light. The exposure control processor 110 uses the stage 103 and the sensor 43 to acquire the longitudinal chromatic aberration K of the exposure apparatus 100, sets a target value Vt of the spectral evaluation value V using the relationship between the longitudinal chromatic aberration K and the spectral evaluation value V of the laser light, and transmits the target value Vt to the laser apparatus 1a. According to this method, the vertical chromatic aberration K is acquired and the target value Vt of the spectral evaluation value V is set, so appropriate spectral control can be performed according to the differences in the exposure apparatus 100.

[0141] (15) According to the embodiment, the exposure control processor 110 transmits a setting signal to the laser device 1a to set a first wavelength λ1 and measures a first focus position Z1 based on the first wavelength λ1. It also transmits a setting signal to the laser device 1a to set a second wavelength λ2 different from the first wavelength λ1 and measures a second focus position Z2 based on the second wavelength λ2. Furthermore, it calculates the longitudinal chromatic aberration K using the first and second wavelengths λ1 and λ2 and the first and second focus positions Z1 and Z2. According to this, the vertical chromatic aberration K of the exposure device 100 can be accurately calculated by measuring the focus positions of two wavelengths.

[0142] 3. Others The above description is intended to be illustrative, not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made to the embodiments of this disclosure without departing from the claims. It will also be apparent to those skilled in the art that the embodiments of this disclosure can be used in combination.

[0143] Terms used throughout this specification and the claims should be interpreted as "non-limiting" unless otherwise specified. For example, terms such as "includes," "have," "equip," and "possess" should be interpreted as "not excluding the existence of components other than those described." Also, the modifier "one" should be interpreted as "at least one" or "one or more." Furthermore, the term "at least one of A, B, and C" should be interpreted as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." In addition, it should be interpreted as including combinations of these with anything other than "A," "B," and "C."

Claims

1. A method for controlling the spectral waveform of laser light output from a laser device to an exposure device, The longitudinal chromatic aberration of the exposure apparatus is obtained, The relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform is such that the change in contrast corresponding to the change in the longitudinal chromatic aberration is smaller than the change in contrast when the evaluation value is fixed, and the target value of the evaluation value is set using this relationship. The spectral waveform is controlled using the aforementioned target value. A control method that includes the following.

2. A control method according to claim 1, Obtaining the aforementioned longitudinal chromatic aberration means The laser device outputs laser light having a first wavelength to the exposure device. The laser device receives a first focus position with the first wavelength from the exposure device. The laser device outputs laser light having a second wavelength different from the first wavelength to the exposure device. The laser device receives the second focus position at the second wavelength from the exposure device. The longitudinal chromatic aberration is calculated using the first and second wavelengths and the first and second focus positions. A control method that includes the following.

3. A control method according to claim 1, Obtaining the aforementioned longitudinal chromatic aberration means The exposure apparatus transmits a setting signal to the laser apparatus to set a first wavelength. The exposure apparatus measures the first focus position according to the first wavelength, The exposure apparatus transmits a setting signal to the laser apparatus to set a second wavelength different from the first wavelength. The exposure apparatus measures the second focus position according to the second wavelength, The longitudinal chromatic aberration is calculated using the first and second wavelengths and the first and second focus positions. A control method that includes the following.

4. A control method according to claim 1, The longitudinal chromatic aberration is obtained by calculating the longitudinal chromatic aberration using a first wavelength, a first focus position in the exposure apparatus when laser light having the first wavelength is incident on the exposure apparatus, a second wavelength different from the first wavelength, and a second focus position in the exposure apparatus when laser light having the second wavelength is incident on the exposure apparatus. A control method that includes the following.

5. A control method according to claim 4, A control method for obtaining the longitudinal chromatic aberration, comprising obtaining the ratio of the difference between the first and second focus positions to the difference between the first and second wavelengths.

6. A control method according to claim 1, The aforementioned relationship is defined such that the evaluation value is inversely proportional to the power of the vertical chromatic aberration, with the exponent being 1 or greater. Control method.

7. A control method according to claim 1, The aforementioned relationship is defined such that the evaluation value is inversely proportional to the square of the vertical chromatic aberration. Control method.

8. A control method according to claim 1, The aforementioned relationship is stored in a table that associates the longitudinal chromatic aberration with the evaluation value. Control method.

9. A control method according to claim 1, A measurement waveform is obtained from the interference pattern of the laser light output from the aforementioned laser device. The evaluation value is calculated using the measured waveform. This further includes, The spectral waveform is controlled using the evaluation value and the target value. Control method.

10. A control method according to claim 9, Using the measured waveform, the spectral waveform showing the relationship between wavelength and light intensity is calculated. The representative wavelength included in the wavelength range of the spectral waveform is calculated, The evaluation value is calculated using the integral value obtained by integrating the product of the wavelength deviation function from the representative wavelength and the light intensity with respect to the wavelength range. Control method.

11. A laser device that can be connected to an exposure apparatus, A laser oscillator that emits laser light, A spectral waveform adjuster that adjusts the spectral waveform of laser light, It is a processor, The longitudinal chromatic aberration of the exposure apparatus is obtained, A processor configured to set a target value for the evaluation value using the relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform, wherein the relationship is defined such that the change in contrast corresponding to the change in the longitudinal chromatic aberration is smaller than the change in contrast when the evaluation value is fixed, and to control the spectral waveform adjuster using the target value, A laser device equipped with the following features.

12. A laser apparatus according to claim 11, The aforementioned processor, The laser oscillator is controlled to output laser light having a first wavelength to the exposure apparatus. The exposure apparatus receives the first focus position according to the first wavelength, The laser oscillator is controlled to output laser light having a second wavelength different from the first wavelength to the exposure apparatus. The exposure apparatus receives the second focus position according to the second wavelength, A laser apparatus for calculating the longitudinal chromatic aberration using the first and second wavelengths and the first and second focus positions.

13. A laser apparatus according to claim 11, The aforementioned relationship is defined such that the evaluation value is inversely proportional to the power of the vertical chromatic aberration, with the exponent being 1 or greater. Laser device.

14. An exposure apparatus that can be connected to a laser device, A projection optical system that forms an image on a wafer surface using laser light output from the laser device, A sensor for measuring the contrast on the wafer surface, A stage for moving the aforementioned sensor along the optical path axis of the laser beam, It is a processor, Using the stage and the sensor, the longitudinal chromatic aberration of the exposure apparatus is acquired. The relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform of the laser light is defined such that the change in contrast corresponding to the change in the longitudinal chromatic aberration is smaller than the change in contrast when the evaluation value is fixed, and the target value of the evaluation value is set using this relationship. The processor is configured to transmit the target value to the laser device, An exposure apparatus equipped with the following features.

15. An exposure apparatus according to claim 14, The aforementioned processor, A setting signal for setting the first wavelength is transmitted to the laser device. The first focus position is measured according to the first wavelength, A setting signal is transmitted to the laser device to set a second wavelength different from the first wavelength. The second focus position is measured according to the second wavelength, An exposure apparatus for calculating the longitudinal chromatic aberration using the first and second wavelengths and the first and second focus positions.

16. An exposure apparatus according to claim 14, The aforementioned relationship is defined such that the evaluation value is inversely proportional to the power of the vertical chromatic aberration, with the exponent being 1 or greater. Exposure apparatus.

17. A method for manufacturing electronic devices, By obtaining the longitudinal chromatic aberration of the exposure device, The relationship between the longitudinal chromatic aberration and the evaluation value of the spectral waveform of the laser light output from the laser device connected to the exposure apparatus is defined such that the change in contrast corresponding to the change in the longitudinal chromatic aberration is smaller than the change in contrast when the evaluation value is fixed, and the target value of the evaluation value is set using this relationship. The laser light generated by controlling the spectral waveform using the target value is output to the exposure apparatus. To manufacture the aforementioned electronic device, a laser beam is exposed onto a photosensitive substrate in the exposure apparatus. A method for manufacturing electronic devices, including the following.

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