Multi-pulse extreme ultraviolet super-continuous light source and generation method thereof

Abstract

The invention discloses a multi-pulse efficient extreme ultraviolet super-continuous light source and a generation method thereof. The multi-pulse efficient extreme ultraviolet super-continuous light source comprises a vacuum chamber, a collecting mirror group, a laser focusing lens, a beam expander, a polarization beam splitter, a half-wave plate, a tin target material and a plurality of lasers, a tin target material is bombarded by a plurality of laser pulses to generate tin plasma emitting extreme ultraviolet super-continuum radiation, and the extreme ultraviolet super-continuum radiation is collected by a collecting mirror group. The energy and laser spots of the two laser beams are optimized to adjust the electron temperature and electron density distribution of the plasma in a multi-dimensional manner, so that the optimal extreme ultraviolet super-continuum radiation emission condition is achieved. Compared with a monopulse mode, higher luminous efficiency from laser to extreme ultraviolet super-continuum radiation can be realized, and the power expansibility of the extreme ultraviolet super-continuum light source can be more effectively improved.

Description

Technical Field

[0001] The invention belongs to a plasma extreme ultraviolet supercontinuum light source system, in particular to an extreme ultraviolet wide-spectrum light source of a semiconductor advanced node quantity detection device and a generation method thereof. Background Art

[0002] At present, the advanced semiconductor process node has achieved mass production of the 7nm process node, and the higher node process technology has become mature. In the advanced process node manufacturing process, the microchip manufacturing process has shifted to a three-dimensional structure. The complex three-dimensional structure has brought difficulties in chip quantity detection. In order to maintain a high yield rate, a more advanced quantity detection solution needs to be introduced.

[0003] The scattered quantity detection technology based on extreme ultraviolet (EUV) supercontinuum radiation has advantages in 3D profile measurement and overlay (alignment stacking), showing its application potential in chip quantity detection. However, the current way of generating EUV supercontinuum radiation still faces many limitations, which affects its widespread application in the field of quantity detection. First of all, the synchrotron radiation light source is not only expensive due to its complex structure and large device, but also difficult to integrate into a desktop quantity detection system, which limits its convenient application in semiconductor production lines. Secondly, although the discharge plasma light source can provide EUV radiation, its large plasma area causes the light-emitting area to be too wide, which is not conducive to the efficient collection of radiation energy, thus affecting the accuracy and efficiency of quantity detection.

[0004] In contrast, laser plasma light sources are considered ideal EUV supercontinuum radiation sources due to their small plasma area, high conversion efficiency, and good power scalability. However, existing laser plasma technology mainly uses a single pulse method to generate EUV supercontinuum radiation. Although this method can achieve a high instantaneous luminous efficiency, in many mass detection applications, a higher average laser power is required to maintain continuous and stable EUV output. The manufacturing cost of high average power lasers is extremely high.

[0005] Therefore, the main challenge currently faced by the application of EUV supercontinuum radiation technology in the field of quantity detection is: how to improve the utilization rate of the average laser power without significantly increasing the cost, so as to reduce the dependence on high-cost lasers, thereby promoting the wider application of EUV supercontinuum radiation technology in the field of semiconductor quantity detection. Summary of the invention

[0006] The present invention provides a multi-pulse extreme ultraviolet supercontinuum light source and a generation method thereof, which can achieve a higher conversion efficiency than a single pulse by exciting plasma with a multi-pulse laser and more effectively improve the power scalability of the extreme ultraviolet supercontinuum light source.

[0007] The technical solution of the present invention:

[0008] The present invention provides a multi-pulse extreme ultraviolet supercontinuum light source, which is characterized by comprising:

[0009] The vacuum chamber is evacuated by a vacuum pump to maintain the internal vacuum degree at 10 -4 -10 -5 In the Pascal range;

[0010] A tin target material, mounted on a movable platform or a rotating table in the vacuum chamber, for generating plasma;

[0011] A laser focusing lens, used for focusing the laser pulse onto the tin target;

[0012] a collecting mirror assembly for collecting the extreme ultraviolet supercontinuum radiation emitted by the tin plasma;

[0013] At least two lasers, respectively emitting a main heating laser pulse and an auxiliary heating laser pulse, bombarding the tin target through the laser focusing lens to generate tin plasma and emit extreme ultraviolet supercontinuum radiation, wherein the wavelength range of the extreme ultraviolet supercontinuum radiation is 10-20nm;

[0014] The main heating laser pulse is used to heat the tin plasma to generate extreme ultraviolet supercontinuum radiation, and the auxiliary heating laser pulse is used to heat the boundary cold zone of the plasma generated by the main pulse laser.

[0015] Furthermore, it also includes:

[0016] A polarization beam splitter and a first half-wave plate combination for adjusting the laser energy of the main heating pulse;

[0017] A polarization beam splitter and a second half-wave plate are combined to adjust the laser energy of the auxiliary heating pulse;

[0018] Laser beam expander, used to change the laser spot shape and size of the auxiliary heating pulse.

[0019] Furthermore, the shape and size of the laser spot of the main heating pulse are changed by adjusting the focal length and defocus distance of the laser focusing lens.

[0020] Furthermore, the collecting mirror group includes a tire mirror and a plane mirror, the tire mirror is used to collect and focus the extreme ultraviolet supercontinuum radiation emitted by the plasma, and the plane mirror is used to adjust the angle of the emitted light.

[0021] The present invention also provides a method for generating a multi-pulse extreme ultraviolet supercontinuum light source, which is characterized in that it comprises the following steps:

[0022] ① Use at least two lasers to emit main heating pulses and auxiliary heating pulses respectively;

[0023] ② The main heating pulse is focused onto the tin target through a laser focusing lens to generate tin plasma and emit extreme ultraviolet supercontinuum radiation;

[0024] ③ When the main heating pulse reaches the maximum luminous efficiency, the auxiliary heating pulse is used to heat the boundary cold zone of the plasma generated by the main heating pulse;

[0025] ④ Collect and focus the extreme ultraviolet supercontinuum radiation emitted by the tin plasma through the collecting mirror group;

[0026] Among them, by adjusting the laser energy and laser spot size of the main heating pulse and the auxiliary heating pulse, the electron temperature and density distribution of the plasma are adjusted in multiple dimensions to improve the luminous efficiency and power scalability.

[0027] The main heating pulse is used to mainly heat the tin plasma and generate EUV supercontinuum radiation. The spot and energy of the main heating laser pulse are precisely controlled by the defocusing of the laser focusing lens, the polarization beam splitter and the half-wave plate combination to achieve maximum luminous efficiency. After the main heating pulse reaches the optimal setting, the auxiliary heating pulse is added to change its spot and energy through the beam expander, polarization beam splitter and half-wave plate combination to effectively heat the plasma boundary cold zone generated by the main pulse laser, further improving the luminous efficiency and power scalability.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) By introducing dual laser pulses to bombard the tin target to generate plasma and optimizing parameters such as laser energy and spot size, the demand for average laser power of the extreme ultraviolet supercontinuum light source is reduced.

[0030] 2) By controlling the laser energy and spot size of the two laser pulses (the main heating pulse and the auxiliary heating pulse), the electron temperature and density distribution of the plasma can be adjusted in multiple dimensions, achieving a higher conversion efficiency than a single-pulse extreme ultraviolet supercontinuum light source and increasing the power scalability of the extreme ultraviolet supercontinuum light source.

[0031] 3) The introduction of auxiliary heating pulses effectively heats the cold zone at the plasma boundary generated by the main pulse laser, which not only reduces energy loss, but also promotes uniform heating of the plasma, further improving the intensity and stability of EUV radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of a multi-pulse extreme ultraviolet supercontinuum light source according to an embodiment of the present invention

[0033] Markings in the figure: 1. Vacuum chamber; 2. Tin target; 3. Plane mirror; 4. Tire mirror; 5. EUV supercontinuum beam; 6. Laser beam; 7. Laser focusing lens; 8. First laser reflection mirror; 9. Polarization beam splitter; 10. Second laser reflection mirror; 11. Laser beam expander; 12. Main heating laser; 13. Auxiliary heating laser; 14. First half-wave plate; 15. Second half-wave plate. DETAILED DESCRIPTION

[0034] 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.

[0035] See also Figure 1 , Figure 1 It is a schematic diagram of the structure of a multi-pulse extreme ultraviolet supercontinuum light source of an embodiment of the present invention. As shown in the figure, the multi-pulse extreme ultraviolet supercontinuum light source includes a vacuum chamber 1, a tin target 2, a plane reflector 3, a tire mirror 4, an extreme ultraviolet supercontinuum beam 5, a laser beam 6, a laser focusing lens 7, a first laser reflector 8, a polarization beam splitter 9, a second laser reflector 10, a laser beam expander 11, a main heating laser 12, an auxiliary heating laser 13, a main heating laser half-wave plate 14 and an auxiliary heating laser half-wave plate 15.

[0036] The vacuum chamber 1 is evacuated by a vacuum pump group to maintain a relatively high vacuum of about 10-5 Pascal to reduce air scattering and absorption and improve the collection efficiency of EUV radiation.

[0037] The tin target 2 is mounted on a translation stage or a rotation stage and is installed in the vacuum chamber 1 .

[0038] Collecting mirror group: It consists of tire mirror 4 and plane mirror 3. The tire mirror 4 is responsible for collecting and focusing EUV supercontinuum radiation emitted by plasma, and the plane mirror 3 is used to adjust the angle of incident light. The surface of the mirror group (tire mirror 4 and plane mirror 3) adopts metal coating layers such as Au and Ru to improve reflectivity and durability.

[0039] Laser focusing lens 7: used to focus the laser pulse onto the tin target 2 to generate plasma.

[0040] Tin target: installed on a movable platform or rotating table to facilitate switching of target surfaces and extend service life.

[0041] Laser: including a main heating laser 12 and an auxiliary heating laser 13, which emit a main heating pulse and an auxiliary heating pulse respectively.

[0042] The main heating laser is emitted by the laser 12 and enters the polarization beam splitter 9 through the laser beam expander 11 and the reflector 10. The auxiliary heating laser is emitted by the laser 13 and enters the polarization beam splitter 9. The two laser beams are collected by the polarization beam splitter 9, reflected by the reflector 8, and focused by the focusing lens 7, and then bombarded onto the tin target 2. After the laser beam 6 interacts with the tin target 2, a plasma is generated to emit extreme ultraviolet supercontinuum radiation. Finally, the extreme ultraviolet supercontinuum radiation is collected and transmitted by the tire mirror 4 and the plane mirror 3.

[0043] The spot shape and size of the main heating pulse laser can be changed by replacing different focal length laser focusing lenses 7 and the defocus distance of the focusing lens 7. The laser spot shape and size of the auxiliary heating laser can be changed by changing the laser beam expander 11. The energy of the two laser beams is changed by combining a polarization beam splitter and a laser half-wave plate. By changing the focusing lens 7 and the polarization beam splitter 9 in combination with the main heating laser half-wave plate 14, the laser spot and laser energy of the main heating beam emitted by the main heating laser 12 are respectively changed to achieve maximum luminous efficiency. Under the optimal setting of the main heating beam emitted by the main heating laser 12, the laser emitted by the auxiliary heating laser is used to further heat the plasma. Further, the laser spot and energy output by the auxiliary heating laser are respectively changed by combining the laser beam expander 11 and the polarization beam splitter 9 with the auxiliary heating laser half-wave plate 15, and the cold zone at the plasma boundary is heated more effectively. In this way, a higher luminous efficiency than a single pulse can be achieved, and at the same time, the power scalability of the extreme ultraviolet supercontinuum light source is improved.

[0044] After the main heating pulse reaches the optimal setting, an auxiliary heating pulse (multiple beams are possible) is added. Through the combination of a beam expander, a polarization beam splitter and a half-wave plate, its spot and energy are changed to effectively heat the cold zone at the plasma boundary generated by the main pulse laser, further improving the luminous efficiency and power scalability.

Claims

1. A multi-pulse extreme ultraviolet supercontinuum light source, characterized in that: include: The vacuum chamber is evacuated by a vacuum pump to maintain the internal vacuum degree at 10 -4 -10 -5 In the Pascal range; A tin target material, mounted on a movable platform or a rotating table in the vacuum chamber, for generating plasma; A laser focusing lens, used for focusing the laser pulse onto the tin target; a collecting mirror assembly for collecting the extreme ultraviolet supercontinuum radiation emitted by the tin plasma; At least two lasers, respectively emitting a main heating laser pulse and an auxiliary heating laser pulse, bombarding the tin target through the laser focusing lens to generate tin plasma and emit extreme ultraviolet supercontinuum radiation, wherein the wavelength range of the extreme ultraviolet supercontinuum radiation is 10-20nm; The main heating laser pulse is used to heat the tin plasma to generate extreme ultraviolet supercontinuum radiation, and the auxiliary heating laser pulse is used to heat the boundary cold zone of the plasma generated by the main pulse laser.

2. The multi-pulse extreme ultraviolet supercontinuum light source according to claim 1, characterized in that: Also includes: A polarization beam splitter and a first half-wave plate combination for adjusting the laser energy of the main heating pulse; A polarization beam splitter and a second half-wave plate are combined to adjust the laser energy of the auxiliary heating pulse; Laser beam expander, used to change the laser spot shape and size of the auxiliary heating pulse.

3. The multi-pulse extreme ultraviolet supercontinuum light source according to claim 1, characterized in that: The shape and size of the laser spot of the main heating pulse are changed by adjusting the focal length and defocus distance of the laser focusing lens.

4. The multi-pulse extreme ultraviolet supercontinuum light source according to any one of claims 1 to 3, characterized in that: The collecting mirror group includes a tire mirror and a plane mirror. The tire mirror is used to collect and focus the extreme ultraviolet supercontinuum radiation emitted by the plasma, and the plane mirror is used to adjust the angle of the emitted light.

5. The multi-pulse extreme ultraviolet supercontinuum light source according to any one of claims 1 to 3, characterized in that: The auxiliary heating laser pulses are multiple beams.

6. A method for generating a multi-pulse extreme ultraviolet supercontinuum light source, characterized in that: The following steps are involved: ① Use at least two lasers to emit main heating pulses and auxiliary heating pulses respectively; ② The main heating pulse is focused onto the tin target through a laser focusing lens to generate tin plasma and emit extreme ultraviolet supercontinuum radiation; ③ When the main heating pulse reaches the maximum luminous efficiency, the auxiliary heating pulse is used to heat the boundary cold zone of the plasma generated by the main heating pulse; ④ Collect and focus the extreme ultraviolet supercontinuum radiation emitted by the tin plasma through the collecting mirror group; Among them, by adjusting the laser energy and laser spot size of the main heating pulse and the auxiliary heating pulse, the electron temperature and density distribution of the plasma are adjusted in multiple dimensions to improve the luminous efficiency and power scalability.

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