Device and method for generating extreme ultraviolet super-continuous light source with luminous efficiency at wave band of 10-20 nm

Abstract

The invention belongs to the field of laser plasmas, and discloses a device and a method for generating an extreme ultraviolet (EUV) super-continuum light source with luminous efficiency at a 10-20nm waveband, which can be used for quantity detection in advanced semiconductor manufacturing. The device comprises a vacuum pump set, a vacuum chamber, a target material, an EUV spectral measurement system, a laser, a half-wave plate and polarizer combination, a focusing lens and a beam expanding lens, the vacuum pump is used for pumping air to enable the vacuum chamber to keep a proper vacuum degree, and the target material is irradiated by laser to generate plasma to emit supercontinuum radiation of 10-20 nm. According to the invention, after spectral radiation energy and laser-EUV radiation conversion efficiency are quantified through an EUV spectral measurement system and a radiation calibration and energy calculation method, focusing spot sizes with optimal luminous efficiency under different laser wavelengths, laser pulse time and laser energy are obtained, and finally, the maximum luminous efficiency of different laser parameters in a 10-20nm wave band is realized.

Description

Technical Field

[0001] The invention belongs to the field of laser plasma, and relates to a device and method for generating an extreme ultraviolet (EUV) supercontinuum light source with high luminous efficiency in the 10-20nm band. Background Art

[0002] In the field of semiconductor manufacturing, extreme ultraviolet lithography (EUV) based on laser-produced plasma (LPP) technology has become a key technology for mass production at 7nm and below process nodes. As metal oxide semiconductor field effect transistors (MOSFETs) have reached the limit of planar arrays on silicon wafers, technologies such as 3D NAND flash memory and gate-all-around (GAA) devices have enabled the transformation of microchip manufacturing processes to 3D geometric structures due to their scalability and high performance. However, this complex three-dimensional structure has caused metrology challenges in the manufacturing process, requiring extremely high yields. The industry currently lacks a solution that can meet non-destructive requirements and is suitable for high-volume manufacturing (HVM).

[0003] The EUV supercontinuum light source with a wavelength range of 10-20nm has demonstrated its unique advantages and potential in solving the above problems in the research progress of scattering measurement, such as: the resolution of short wavelength is higher than that of visible light; the profile parameters can be separated from the scattered signal in this wavelength range; the broadband spectrum characteristics make it carry more information. Therefore, the EUV supercontinuum light source has shown great application prospects in key measurement and detection links of chip manufacturing, such as defect detection of EUV masks, EUV photoresist research, measurement of critical dimensions (CD) and overlay accuracy, and measurement of edge placement errors.

[0004] Therefore, in order to meet different detection needs, it is particularly important to develop an extreme ultraviolet supercontinuum light source with high luminous efficiency in the wavelength range of 10-20nm. Patent document CN105333953A discloses a tunable wide-band laser plasma extreme ultraviolet light source, which can produce extreme ultraviolet light with strong radiation in the 13.X nm and 6.X nm bands, and by controlling the laser power density acting on the target material, the radiation intensity of the two bands can be effectively controlled. However, the luminous efficiency of the alloy target in this band is much lower than that of the pure tin target. Moreover, the complexity of the laser plasma radiation process means that it is difficult to optimize the luminous efficiency without the support of EUV spectral measurement characterization technology by guiding the adjustment of laser parameters based solely on theoretical calculations. It is particularly critical that the focused spot size has a significant effect on the luminous efficiency of the extreme ultraviolet supercontinuum light source, and under different laser wavelengths, laser pulse times, and laser energy conditions, the focused spot size that achieves the best luminous efficiency is different. Summary of the invention

[0005] To address the deficiencies of the above-mentioned prior art, the present invention provides an extreme ultraviolet (EUV) supercontinuum light source generation device and method with high luminous efficiency in the 10-20nm band, which optimizes the radiation of LPP plasma in the 10-20 nanometer band to achieve extreme ultraviolet supercontinuum radiation with high luminous efficiency.

[0006] The technical solution of the present invention:

[0007] On the one hand, the present invention provides an extreme ultraviolet supercontinuum light source generating device with luminous efficiency in the 10-20nm band, which is characterized by comprising:

[0008] The vacuum chamber contains the target material and is maintained for 10 -3 -10 -5 Pascal's vacuum;

[0009] A laser is used to emit a driving laser, which is focused by a focusing mirror and then irradiated on a target material to generate plasma and radiate an EUV supercontinuum light source. The wavelength of the driving laser is in the range of 1 to 10 μm, and the output energy, pulse time and laser focus spot size of the laser are adjustable;

[0010] An EUV spectrum measurement system, connected to the vacuum chamber via a flange, for measuring the spectrum distribution and radiation energy of the EUV supercontinuum light source;

[0011] a collecting mirror, disposed in or near the vacuum chamber, for collecting EUV radiation generated by the plasma and directing it to a detection system;

[0012] a detection system for receiving and analyzing EUV radiation directed by the collecting mirror;

[0013] Wherein, the tin target material is in liquid or solid form, and the emission peak of the unresolvable transition peak (UTA) of the tin target material is near 13.5nm; the computer is used to measure, calibrate and calculate the energy of EUV radiation, so as to quantify and characterize the radiation energy of 10-20nm and the conversion efficiency of laser to 10-20nm supercontinuum radiation.

[0014] Furthermore, it also includes:

[0015] A half-wave plate and a polarizer combination, arranged between the laser and the focusing lens, is used to adjust the polarization state and intensity of the laser;

[0016] The beam expander is arranged between the focusing lens and the target material, and is used to expand the diameter of the laser beam to cover the surface of the target material.

[0017] The EUV spectrum measurement system comprises a first slit, a cylindrical mirror group, a plane mirror, a second slit, an EUV grating and a detector arranged in sequence along the optical path, wherein the detector and the second slit are respectively located at the front and rear focal lengths of the EUV grating

[0018] Preferably, the vacuum pump group consists of a dry pump and a molecular pump to provide the required vacuum degree.

[0019] Preferably, the target material is placed on a movable or rotating platform to facilitate adjustment of the position and angle of the target material.

[0020] Preferably, the surface of the collecting mirror is coated with Au or Ru to form a coating layer to improve the reflection efficiency of 10-20nm supercontinuum radiation.

[0021] Preferably, the use of tin droplet targets can modulate the shape and density of the targets by double pulses, while solid tin can make the light source system simple and compact.

[0022] Preferably, the laser type may be a solid laser, a gas laser, a fiber laser, etc., and the output energy, pulse time and laser focus spot size of the laser are adjustable.

[0023] On the other hand, the present invention also provides a method for using the above device to generate an extreme ultraviolet supercontinuum light source with luminous efficiency in the 10-20nm band, which is characterized in that it includes the following steps:

[0024] S1. Set the wavelength, energy, pulse time and focus spot size of the laser so that the laser irradiates the target through the focusing lens to generate plasma emitting 10-20nm EUV supercontinuum radiation;

[0025] S2. Collect and measure EUV supercontinuum radiation through the EUV spectrum measurement system, and calculate the spectrum distribution and radiation energy under the current parameters;

[0026] S3. Use the absorption edge of Si, Al, and Zr materials or the characteristic spectral lines of ion emission to calibrate the wavelength of the EUV spectrum measurement system, and use a standard light source to calibrate the efficiency of the EUV spectrum measurement system;

[0027] S4. Under the condition of fixed laser wavelength, laser pulse time and laser energy, change the laser focus spot size, observe and record EUV radiation energy;

[0028] S5. According to the recorded EUV radiation energy, determine the focus spot size for optimal luminous efficiency under different laser wavelengths, laser pulse times, and laser energies.

[0029] Further, the method further comprises the following steps:

[0030] S6. Apply the optimized parameters to actual production, and use the detection system to monitor and characterize the radiation energy and conversion efficiency of the EUV supercontinuum light source in real time.

[0031] Furthermore, the step S3. further includes:

[0032] S3.1 Based on wavelength calibration and efficiency calibration, the detector counts at different wavelengths and the actual photon count response curve entering the EUV spectrum measurement system are calculated;

[0033] S3.2 Calculate the total number of photons of different wavelengths in the EUV spectral system through the response curve and the detector count, and obtain the radiation energy at different wavelengths;

[0034] S3.3 Based on the solid angle of the EUV spectral system receiving EUV radiation, the radiation energy and conversion efficiency in the wavelength range of 10 to 20 nm at a solid angle of 2π for the plasma are calculated.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] Aiming at the demand for quantitative detection in advanced semiconductor manufacturing, the present invention adopts the mechanism of EUV supercontinuum radiation emitted by laser-generated plasma to achieve in-depth quantification and precise characterization of EUV radiation energy and laser-EUV radiation conversion efficiency:

[0037] 1. By integrating EUV spectrum measurement system, radiation calibration technology and energy calculation method, the present invention accurately quantifies the spectral radiation energy and laser-EUV radiation conversion efficiency, and then determines the focus spot size that achieves the best luminous efficiency under different laser parameters. Ultimately, the maximum luminous efficiency of different laser parameters is achieved.

[0038] 2. The present invention successfully established a characterization model for laser-EUV radiation conversion efficiency, which not only revealed the influence of different laser parameters on EUV radiation efficiency, but also provided a scientific basis for optimizing laser parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic structural diagram of a device for generating an EUV supercontinuum light source with high luminous efficiency in the 10-20 nanometer band according to an embodiment of the present invention;

[0040] Figure 2 Schematic diagram of the optical path of the EUV spectrum measurement system of the present invention;

[0041] Figure 3 This is a schematic diagram of the 10-20nm supercontinuum radiation spectrum of the present invention;

[0042] In the figure: 1. vacuum pump group; 2. vacuum chamber; 3. target material; 4. EUV spectrum measurement system; 41 first slit, 42 cylindrical mirror group, 43 plane mirror, 44 second slit, 45 EUV grating, 46 detector; 5. laser; 6. half-wave plate and polarizer combination; 7. focusing lens; 8. collecting mirror; 9. detection system; 10. laser beam; 11. extreme ultraviolet beam; 12. beam expander; 13. data transmission line; 14. computer. DETAILED DESCRIPTION

[0043] In order to make the technical solutions in the embodiments of the present invention clear and complete, the present invention is described in detail below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0044] This embodiment provides a device and method for generating an EUV supercontinuum light source with high luminous efficiency in the 10-20 nanometer band, aiming to meet the high-precision measurement and detection requirements in advanced semiconductor manufacturing. Figure 1 , Figure 1 It is a structural schematic diagram of an EUV supercontinuum light source generating device with high luminous efficiency in the 10-20 nanometer band according to an embodiment of the present invention. As shown in the figure, an EUV supercontinuum light source generating device with high luminous efficiency in the 10-20 nanometer band includes a vacuum chamber 2, a target material 3, an EUV spectrum measurement system 4, a laser 5 and its supporting components, a collecting mirror 8 and a detection system 9.

[0045] Vacuum chamber 2: maintained at 10 by vacuum pump set 1 -5 Pascal vacuum to ensure efficient transmission and measurement of EUV radiation.

[0046] The target material 3 is placed in the vacuum chamber 3 and uses tin as the target material, which can be in the form of liquid or solid. The main unresolvable transition peak (UTA) emission peak of the tin target is located near 13.5 nanometers, which is suitable for generating EUV supercontinuum radiation in the 10-20 nanometer band. The liquid tin target can modulate its morphology and density by double pulse mode, while the solid tin target makes the light source system simpler and more compact.

[0047] The EUV spectrum measurement system 4 is connected to the vacuum chamber 2 through a flange and is used to measure and characterize the spectrum distribution and radiation energy of the EUV supercontinuum light source. Figure 2 As shown, it includes a first slit 41, a cylindrical mirror group 42, a plane mirror 43, a second slit 44, an EUV grating 45 and a detector 46 arranged in sequence along the optical path, wherein the distance between the cylindrical mirror group and the grating and the detector is related to the curvature radius of the cylindrical mirror, and the EUV grating, the detector and the second slit should be placed at the front and rear focal lengths of the grating.

[0048] The first slit 41 is used to limit the range of light passing through, and only allows light of a specific direction or a specific size to pass through, that is, the first slit ensures that the irradiation area of ​​the light emitted by the light source on the cylindrical group is smaller than the actual size of the cylindrical group;

[0049] The cylindrical mirror group 42 focuses or diverges the light to adjust the focal length and spot size of the light so that the spot size at the detector is smaller than the detector array surface;

[0050] A plane mirror 43 is used to reflect light to change the propagation direction of the light and ensure that the light is parallel to the horizontal plane;

[0051] The second slit 44 is used to adjust the amount of light entering the rear optical element and the spectral resolution of the system.

[0052] EUV grating 45, used to diffract or split incident light so as to analyze the wavelength, intensity and other characteristics of the light;

[0053] The detector 46 receives the light from the EUV grating 45 and converts it into an electrical signal, which is then transmitted to the computer 14 via the data transmission line 13 for data processing.

[0054] Laser 5 and its supporting components: The type of laser 5 can be solid laser, gas laser, fiber laser, etc., and its output energy, pulse time and laser focus spot size can be adjusted. The laser beam is regulated by the half-wave plate and polarizer combination 6, and then focused on the target material 3 through the focusing lens 7 and the beam expander to generate plasma and radiate EUV light.

[0055] Collecting mirror 8: used to collect and transmit the extreme ultraviolet light beam generated by the plasma into the detection system 9; a reflector or reflector group capable of achieving focusing, such as a toroidal mirror or a KB elliptical cylindrical mirror group, is used, and the surface coating layer is made of metals such as Au and Ru to improve the reflection efficiency of 10-20nm supercontinuum radiation.

[0056] Detection system 9: used to analyze the extreme ultraviolet light beam generated by the plasma.

[0057] A method for generating an extreme ultraviolet (EUV) supercontinuum light source with high luminous efficiency in the 10-20nm band comprises the following steps:

[0058] S1. Parameter setting and adjustment: Set the laser's wavelength, energy, pulse time, and focus spot size as required. Perform preliminary measurements of EUV radiation using the EUV spectrum measurement system to understand the spectrum distribution and radiation energy under the current parameters.

[0059] S2. Spectral measurement and calibration: Use the EUV spectral measurement system to calibrate the wavelength and efficiency of the EUV supercontinuum light source. The wavelength calibration determines the spectral coverage of the system, and the efficiency calibration completes the calculation of the detector counts and the actual number of photons entering the EUV spectral measurement system at different wavelengths. Among them, wavelength calibration is to calibrate the wavelength of the EUV spectral measurement system using the absorption edge or ion emission characteristic spectrum of materials such as Si, Al, and Zr; efficiency calibration is to calibrate the overall efficiency of the EUV spectral measurement system using a standard light source. The total number of photons of different wavelengths in the EUV spectral system is obtained through the response curve and the detector count, and the radiation energy at different wavelengths is calculated. According to the solid angle of the EUV spectral system receiving EUV radiation, the radiation energy and conversion efficiency in the wavelength range of 10-20nm under the plasma 2π solid angle are calculated, so that the radiation of the EUV supercontinuum light source with a wavelength of 10 to 20nm can be characterized and monitored.

[0060] S3. Focus spot size optimization: Under the condition of fixed laser wavelength, energy and pulse time, the change of EUV radiation energy is observed by changing the laser focus spot size. The radiation energy under different focus spot sizes is accurately measured by EUV spectrum measurement system, and the conversion efficiency is calculated. By comparing the conversion efficiency under different focus spot sizes, the focus spot size with the best luminous efficiency is determined.

[0061] S4. Parameter adjustment and iteration: According to the optimal focus spot size, adjust and optimize the wavelength, energy and pulse time parameters of the laser. Repeat the steps of spectrum measurement, calibration and focus spot size optimization until the best combination to achieve maximum luminous efficiency under different laser parameter configurations is found.

[0062] The optimized parameters mentioned above are applied in actual production, and the radiation energy and conversion efficiency of EUV supercontinuum light source are monitored and characterized in real time through the detection system. Figure 3 As shown, the verification results show that the present invention can achieve the maximum luminous efficiency in the 10-20 nanometer band under different laser parameter configurations, providing strong technical support for high-precision measurement and detection in the field of semiconductor manufacturing.

Claims

1. An extreme ultraviolet supercontinuum light source generating device with luminous efficiency in the 10-20nm band, characterized in that: include: The vacuum chamber contains the target material and is maintained for 10 -3 -10 -5 Pascal's vacuum; A laser is used to emit a driving laser, which is focused by a focusing mirror and then irradiated on a target material to generate plasma and radiate an EUV supercontinuum light source. The wavelength of the driving laser is in the range of 1 to 10 μm, and the output energy, pulse time and laser focus spot size of the laser are adjustable; An EUV spectrum measurement system, connected to the vacuum chamber, for measuring the spectrum distribution and radiation energy of the EUV supercontinuum light source and transmitting them to a computer; a collecting mirror, disposed in or near the vacuum chamber, for collecting EUV radiation generated by the plasma and directing it to a detection system; a detection system for receiving and analyzing EUV radiation introduced by the collection mirror; Wherein, the tin target material is in the form of liquid or solid, and the emission peak of the unresolvable transition peak (UTA) of the tin target material is near 13.5nm; the computer is used to measure and calibrate EUV radiation, and the energy calculation method is used to quantify and characterize the EUV radiation energy, and the conversion efficiency of laser and EUV supercontinuum radiation, so as to determine the focused spot size that achieves the best luminous efficiency under different laser parameter configurations, and achieve the maximum luminous efficiency of different laser parameters.

2. The device for generating an extreme ultraviolet supercontinuum light source with luminous efficiency in the 10-20nm band according to claim 1, characterized in that: Also includes: A half-wave plate and a polarizer combination, arranged between the laser and the focusing lens, is used to adjust the polarization state and intensity of the laser; The beam expander is arranged between the focusing lens and the target material, and is used to expand the diameter of the laser beam to cover the surface of the target material.

3. The device for generating an extreme ultraviolet supercontinuum light source with luminous efficiency in the 10-20nm band according to claim 1, characterized in that: The vacuum pump group consists of a dry pump and a molecular pump to provide the required vacuum degree.

4. The device for generating an extreme ultraviolet supercontinuum light source with luminous efficiency in the 10-20nm band according to claim 1, characterized in that: The target material is placed on a movable or rotating platform to facilitate adjustment of the position and angle of the target material.

5. The device for generating an extreme ultraviolet supercontinuum light source with luminous efficiency in the 10-20nm band according to claim 1, characterized in that: The surface of the collecting mirror is coated with Au or Ru to form a coating layer to improve the reflection efficiency of 10-20nm supercontinuum radiation.

6. The device for generating an extreme ultraviolet supercontinuum light source with luminous efficiency in the 10-20 nm band according to any one of claims 1-5, characterized in that: The EUV spectrum measurement system comprises a first slit, a cylindrical mirror group, a plane mirror, a second slit, an EUV grating and a detector which are sequentially arranged along the optical path, wherein the detector and the second slit are respectively located at the front and rear focal lengths of the EUV grating.

7. A method for generating an extreme ultraviolet supercontinuum light source with luminous efficiency in the 10-20nm band using the device described in any one of claims 1-6, characterized in that: The steps include: S1. According to the quantity detection requirements in semiconductor manufacturing, the wavelength, energy, pulse time and focus spot size of the laser are set so that the laser is irradiated on the target through the focusing lens to generate plasma emitting 10-20nm EUV supercontinuum radiation; S2. Collect and measure EUV radiation using an EUV spectrum measurement system to obtain the spectrum distribution and radiation energy of the EUV supercontinuum light source under current parameters; S3. Use the absorption edge of Si, Al, and Zr materials or the characteristic spectral lines of ion emission to calibrate the wavelength of the EUV spectrum measurement system, and use a standard light source to calibrate the efficiency of the EUV spectrum measurement system; S4. Under the condition of fixed laser wavelength, laser pulse time and laser energy, change the laser focus spot size, observe and record EUV radiation energy; S5. According to the recorded EUV radiation energy, determine the focus spot size for optimal luminous efficiency under different laser wavelengths, laser pulse times, and laser energies.

8. The method according to claim 7, characterized in that The following steps are also included: S6. Apply the optimized parameters to actual production, and use the detection system to monitor and characterize the radiation energy and conversion efficiency of the EUV supercontinuum light source in real time.

9. The method according to any one of claims 7 or 8, characterized in that: The step S3. further includes: S3.1 Based on the wavelength calibration and efficiency calibration results, the detector counts at different wavelengths and the actual photon count response curves entering the EUV spectrum measurement system are calculated; S3.2 Calculate the total number of photons of different wavelengths in the EUV spectral system through the response curve and the detector count, and obtain the radiation energy at different wavelengths; S3.3 Based on the solid angle of the EUV spectral system receiving EUV radiation, the radiation energy and conversion efficiency in the wavelength range of 10 to 20 nm at a solid angle of 2π for the plasma are calculated.

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