A kind of plasma extreme ultraviolet light source driven by synchrotron radiation high harmonic

Abstract

The application provides a kind of plasma extreme ultraviolet light source driven by high-order harmonic of synchrotron radiation, including target material from target material generator, and synchrotron radiation generating device aiming at target material, synchrotron radiation generating device is set to introduce and irradiate high-order harmonic synchrotron radiation main pulse to plasma, the plasma extreme ultraviolet light source further includes plasma generating device generating and emitting ionized target material beam to target material to obtain plasma, and the beam is high-power laser or high-energy synchrotron radiation pre-pulse.The plasma extreme ultraviolet light source of the application uses synchrotron radiation with high-order harmonic as driving light source and interacts with plasma, efficiently excites to generate high-power extreme ultraviolet light of certain wavelength, thereby effectively utilizes existing synchrotron radiation light source waste wave, realizes high-power output of extreme ultraviolet light.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithography, and particularly relates to a kind of plasma extreme ultraviolet light source driven by high harmonic of synchrotron radiation, which is suitable for being used as the light source of a lithography machine. BACKGROUND

[0002] With the development of semiconductor chip industry, the extreme ultraviolet lithography light source as a key factor of lithography technology is also developing. From the ultraviolet band high-voltage discharge mercury lamp g-line (436 nm) to i-line (365 nm), to the quasi-molecular laser KrF (248 nm) and ArF (193 nm) in deep ultraviolet band. The most advanced extreme ultraviolet lithography machine uses 13.5 nm (4% bandwidth) extreme ultraviolet light (EUV).

[0003] The current ways that can be used to generate EUV lithography light mainly include synchrotron radiation source, free electron laser (FEL), laser plasma (LPP), discharge plasma (DPP) and laser-assisted discharge plasma (LDP).

[0004] But the generation of X-ray laser is much more difficult than that of general laser, on the one hand, the X-ray laser pump source needs to have high enough pump power density, on the other hand, the quantum efficiency of X-ray laser generation is low. In order to meet the needs of the development of lithography, it is necessary to develop high-power EUV light source.

[0005] The existing LPP, DPP and LDP EUV light sources are all through high-energy beams to make the target temperature rise, so as to generate high-temperature, high-density plasma and emit EUV light. At present, all the three ways are developing, the light output angle of DPP and LDP is severely limited, which restricts the final output light power. Therefore, the mainstream EUV light source in the field of lithography at present is LPP light source. Such as the ASML company in the Netherlands and the Gigaphoton company in Japan, which are all developing LPP light source. Free electron laser has been rapidly developing since it was proposed by John M. J. Madey in 1971, but it has not been applied to lithography technology at present.

[0006] The application of synchrotron radiation source in the field of lithography at present is mainly some special line stations for research and development. Such as the X-ray interference lithography line station of Shanghai synchrotron radiation facility and Swiss synchrotron radiation facility, which is to expose photoresist by using the interference fringes of two or more coherent X-ray beams or EUV beams. By using the directionality of the undulator radiation, these line stations can obtain small enough light spot for photoresist detection. But for chip manufacturing, the total light power is still too low. It is worth noting that the high harmonic of the synchrotron radiation undulator source is not utilized, and is usually removed as a heat load.

[0007] In the case of a large magnetic deflection coefficient of a synchrotron undulator, the high harmonic wave has the characteristics of high power (more than 99% of the total output energy), high energy photon content, and small divergence angle. However, there is no technology of using the high harmonic wave of the synchrotron undulator as an extreme ultraviolet light source. In the existing EUV light source, the LPP light source uses a CO2 laser as a driving source, and the DPP and LDP light sources use a discharge plasma as a main driving source. In the prior art, the high harmonic wave in the synchrotron light source is not utilized, but only as a heat load to be processed.

[0008] Therefore, there is an urgent need for a new extreme ultraviolet lithography light source to utilize the above characteristics of the high harmonic wave of the synchrotron undulator to efficiently excite and generate high-power extreme ultraviolet light of a certain wavelength. SUMMARY

[0009] The purpose of the present application is to provide a plasma extreme ultraviolet light source to effectively utilize the high harmonic wave in the synchrotron and realize high-power extreme ultraviolet light output.

[0010] In order to achieve the above purpose, the present application provides a synchrotron high harmonic wave driven plasma extreme ultraviolet light source, characterized in that it comprises a target material from a target material generator and a synchrotron radiation generating device aligned with the target material, the synchrotron radiation generating device is arranged to introduce and irradiate a synchrotron main pulse with a high harmonic wave onto a plasma; the plasma extreme ultraviolet light source further comprises a plasma generating device arranged to generate and emit a beam to ionize the target material to the target material to obtain a plasma, the beam is a high-power laser or a high-energy synchrotron pre-pulse; wherein the high-power laser is generated by an auxiliary high-power laser module; the high-energy synchrotron pre-pulse is generated by the synchrotron radiation generating device.

[0011] The plasma generating device is only an auxiliary high-power laser module, or the plasma generating device is only the synchrotron radiation generating device.

[0012] The target material generator is arranged to accurately drop the liquid target material at a required time interval and droplet size, and the target material is a tin droplet or a lithium fluoride liquid column.

[0013] The length of the synchrotron main pulse is on the order of 10 ps, and the power is 100 W to 2000 W.

[0014] The beam is a high-energy synchrotron pre-pulse, the length of the synchrotron pre-pulse is on the order of 100 nanoseconds, and the power is 100 W to 5000 W; the synchrotron radiation generating device is in a synchrotron mixed operation mode.

[0015] The beam is high-power laser generated by a CO2 laser or a solid-state laser, the synchronous radiation generating device and the auxiliary high-power laser module are connected with a synchronous time control system, and the synchronous time control system is also connected with a photoelectric detector or a target generator.

[0016] The target and the auxiliary high-power laser module and the synchronous radiation generating device are provided with an extreme ultraviolet beam collecting mirror, so that the generated extreme ultraviolet light is collected by the extreme ultraviolet beam collecting mirror and outputted outward, the extreme ultraviolet beam collecting mirror is provided with a through hole for the auxiliary high-power laser module and the synchronous radiation generating device to irradiate the target, and the extreme ultraviolet beam collecting mirror is a focusing curved mirror facing the target.

[0017] The synchronous radiation generating device and the target are provided with a synchronous radiation reflecting focusing mirror system, the synchronous radiation reflecting focusing mirror system is arranged to focus the synchronous radiation with high-order harmonics generated by the synchronous radiation generating device on the plasma, and the synchronous radiation reflecting focusing mirror system is composed of two oppositely arranged small curvature mirrors.

[0018] The synchronous radiation generating device is a synchronous radiation undulator or a wiggler.

[0019] The synchronous radiation generating device and the target are located at the central axis position of the beam line, and a blocker for blocking bremsstrahlung is arranged at the central axis position of the light speed line on the side of the target away from the synchronous radiation undulator, the target generator, the target and the extreme ultraviolet beam collecting mirror are located in the same vacuum system.

[0020] The plasma extreme ultraviolet light source of the application utilizes the characteristics of high power (more than 99% of the total output energy), high-energy photon content and small divergence angle of the high-order harmonics of the synchronous radiation, uses the synchronous radiation with high-order harmonics as a driving light source to act on the pre-ionized plasma, efficiently excites and generates high-power extreme ultraviolet light of a certain wavelength, and effectively utilizes the existing synchronous radiation light source waste wave to realize high-power output of extreme ultraviolet light. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a structure schematic diagram of a synchronous radiation high-order harmonic driven plasma extreme ultraviolet light source according to an embodiment of the application. DETAILED DESCRIPTION

[0022] The synchronous radiation high-order harmonic driven plasma extreme ultraviolet light source of the application is based on the following principles:

[0023] Theoretical calculation shows that the high harmonic of the synchrotron radiation, when acting on a specific plasma under certain conditions, will significantly generate the EUV lithography light of the required frequency after considering the basic process of the interaction between the plasma and the high harmonic. Therefore, the synchrotron radiation high harmonic driven plasma EUV light source of the present application utilizes the high harmonic (i.e. the surplus wave of the synchrotron radiation source) generated in the synchrotron radiation as a driving light source, and interacts with the plasma obtained by pre-ionization, and the de-excitation of the ions generates the EUV light of the required frequency, wherein the photon frequency of the synchrotron radiation harmonic should be much greater than the photon frequency of the output EUV light.

[0024] Figure 1 Fig. 1 is a structural schematic diagram of a synchrotron radiation high harmonic driven plasma EUV light source according to an embodiment of the present application, which is suitable for being used as an EUV lithography light source and can obtain a hundred-watt output power. As shown in Fig. 1, the synchrotron radiation high harmonic driven plasma EUV light source comprises a target 1 from a target generator 11, and a target ionization wave beam generating module auxiliary high-power laser module 2 and a synchrotron radiation generating device 3 aligned with the target 1. Figure 1

[0025] The target generator 11 is configured to accurately drop the liquid target at a required time interval and droplet size, as used in the LPP laser. The material of the target 1 is tin (Sn) or lithium fluoride (LiF). In the embodiment, the target 1 is a tin droplet falling from the target generator 11. In other embodiments, the target 1 can also be a lithium fluoride liquid column.

[0026] The auxiliary high-power laser module 2 is configured to generate and emit laser to the target 1 to ionize the target 1, so as to obtain a plasma. Thus, the surface of the target 1 is formed into a plasma by inputting a beam (generally laser) with energy to the target 1, i.e. a sufficient number of surface atoms of the target 1 (tin droplet or lithium fluoride liquid column) are ionized, and the number of these ions determines the number of photons output by the plasma EUV light source of the present application. In the present application, the number of ions in the plasma is of the same order of magnitude as the existing LPP.

[0027] In the embodiment, the laser emitted by the auxiliary high-power laser module 2 to ionize the target 1 is only high-power laser, but not high-energy synchrotron radiation pre-pulse.

[0028] ​In other embodiments, the beam ionizing the target 1 can be a high-power laser or a high-energy synchrotron radiation prepulse. Specifically, to obtain the beam ionizing the target 1, when the beam includes a high-power laser, an auxiliary high-power laser module 2 is required to generate the high-power laser (thus serving as a plasma generation device that generates and emits a beam ionizing the target to obtain plasma). When the beam includes a high-energy synchrotron radiation prepulse, the prepulse needs to be generated by a synchrotron radiation generation device 3 (thus serving as a plasma generation device that generates and emits a beam ionizing the target to obtain plasma).

[0029] In other words, the auxiliary high-power laser module 2 used in this embodiment is only one form of plasma generation device. In other embodiments, the auxiliary high-power laser module 2 can be replaced by another type of plasma generation device, namely, a synchrotron radiation generation device 3. The plasma generation device is essential for the synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source of this invention. It is configured to generate and emit a beam that ionizes the target material to obtain plasma. The plasma generation device can be only the auxiliary high-power laser module 2, or only the aforementioned synchrotron radiation generation device 3, such that the beam is a high-power laser or a high-energy synchrotron radiation prepulse, but both the auxiliary high-power laser module 2 and the synchrotron radiation generation device 3 cannot be used simultaneously.

[0030] The high-energy synchrotron radiation prepulse or high-power laser emitted by the plasma generating device, and the synchrotron radiation main pulse emitted by the synchrotron radiation generating device 3, are both used to ionize the target material 1; the synchrotron radiation main pulse also has the function of controlling the excited state of ions. The synchrotron radiation main pulse generated by the synchrotron radiation generating device 3 (including undulator and torsion device) bombards the target material 1 through the synchrotron radiation generating device 4.

[0031] The synchrotron radiation prepulse has a length on the order of 100 nanoseconds and a power adjustable from 100W to 5000W; the main pulse has a length on the order of 10 ps and a power adjustable from 100W to 2000W. Both power settings are adjustable, allowing for optimized power distribution. The synchrotron radiation prepulse is synchrotron radiation, containing fundamental photons (13.5nm) and higher harmonics (13.5nm / 2, / 3, / 4, ..., corresponding to photon energies of 92.5eV, 92.5eV*2, *3, *4, ...). Photon energies range from 92.5eV to above 5000eV, after which the higher-energy harmonics begin to decrease significantly. The synchrotron radiation prepulse is generated by the accelerated radiation of an electron beam within the accelerator; the temporal distribution and energy of the electron beam within the accelerator are controllable.

[0032] The aforementioned synchrotron radiation main pulse and pre-pulse are generated by specially configured electron beam clusters within the synchrotron radiation storage ring of the synchrotron radiation generating device 3. Conventional electron beam clusters can also exist within this storage ring to generate corresponding synchrotron radiation for other beamlines and experimental stations, enabling related spectroscopy, diffraction, and imaging experiments. In this experimental setup, they also generate corresponding synchrotron radiation, but with lower power density and minimal impact. This operational mode constitutes a synchrotron radiation hybrid operation mode, meaning that the synchrotron radiation generating device 3 operates in a synchrotron radiation hybrid operation mode.

[0033] The high-power laser obtained by the auxiliary high-power laser module 2, like the synchrotron radiation prepulse of the synchrotron radiation generating device 3, serves to ionize the target material 1 and generate plasma. The high-power laser can be generated by a CO2 laser or a solid-state laser.

[0034] In this embodiment, a synchrotron radiation reflecting and focusing mirror system 4 is provided between the synchrotron radiation generating device 3 and the target material 1. This system is configured to focus the synchrotron radiation with higher harmonics generated by the synchrotron radiation generating device 3 onto the plasma. Taking the Shanghai Synchrotron Radiation Facility's soft X-ray interferometry (XIL) beamline as an example, the synchrotron radiation reflecting and focusing mirror system mainly consists of two small-curvature mirrors arranged opposite each other. These two small-curvature mirrors are symmetrically arranged with respect to the output optical axis of the synchrotron radiation generating device 3, so that the synchrotron radiation emitted from the undulator is focused onto the plasma on the output optical axis. The curvature of the small-curvature mirrors should be around 100 meters, and the grazing incident angle should be 5-10 degrees.

[0035] The synchrotron radiation generating device 3 is configured to introduce and irradiate the plasma with a synchrotron radiation main pulse carrying higher harmonics. This main pulse is used to regulate the excitation state of the plasma, allowing more ions to be further ionized to predetermined high-valence ions. Through other excitation and de-excitation processes, these ions reach the desired valence and excited states, thus producing extreme ultraviolet (EUV) light. The ion types are essentially the same before and after the main pulse; the main pulse optimizes the abundance of each ion and their excited state distribution.

[0036] In this embodiment, the synchrotron radiation generating device 3 is preferably a synchrotron radiation undulator. This synchrotron radiation undulator is used to introduce a synchrotron radiation main pulse with higher harmonics. It is directly connected to the front end of the synchrotron radiation device to extract broadband synchrotron radiation light (i.e., synchrotron radiation with higher harmonics) with a power density of 5000 keV. To obtain higher output power, the undulator gap should be adjusted to a smaller value, within the limits of available technology, to increase the high-frequency extension of the higher harmonics. In other embodiments, the synchrotron radiation generating device 3 can employ other technologies (such as a oscillator) to extract a synchrotron radiation main pulse with higher harmonics. In this embodiment, since the wavelength of the output extreme ultraviolet light is 13.5 nm, the synchrotron radiation main pulse with higher harmonics includes a fundamental photon (wavelength 13.5 nm) and corresponding higher harmonics (13.5 nm / 2, 13.5 nm / 3, 13.5 nm / 4, ..., corresponding to photon energies of 92.5 eV, 92.5 eV×2, 92.5 eV×3, 92.5 eV×4, ...). The photon energy ranges from 92.5 eV to above 5000 eV, and then the higher-energy harmonics begin to decrease significantly.

[0037] It should be noted that the synchrotron radiation main pulse includes not only the higher harmonics of synchrotron radiation, but also the fundamental wave with the same frequency as the output extreme ultraviolet light, as well as a trace amount of bent iron radiation. Similar to the extreme ultraviolet light output of plasma, the fundamental wave of synchrotron radiation with the same frequency can be used directly; the trace amount of bent iron radiation does not need to be removed. Therefore, the synchrotron radiation main pulse does not need to be filtered out and can directly irradiate the plasma on the surface of the target material 1.

[0038] Furthermore, an extreme ultraviolet (EUV) beam collecting mirror 5 is provided between the target material 1, the auxiliary high-power laser module 2, and the synchrotron radiation generating device 3, thereby collecting the generated EUV light through the EUV beam collecting mirror 5 and outputting it outward. The EUV beam collecting mirror 5 has a through hole for the auxiliary high-power laser module 2 and the synchrotron radiation generating device 3 to irradiate the target material 1. In this embodiment, the EUV beam collecting mirror 5 is a curved mirror facing the target material 1 for focusing. Taking the XIL beamline as an example, the curvature of the curved mirror should be around 10 meters. The target material 1 is positioned at the central axis of the EUV beam collecting mirror 5, so that 13.5 nm EUV light is finally extracted at the central focal point (i.e., the IF point) of the EUV beam collecting mirror 5 for use.

[0039] Both the synchrotron radiation generating device 3 and the target material 1 are located at the central axis of the beam line. A blocker 6 is positioned at the central axis of the beam line on the side of the target material 1 away from the synchrotron radiation undulator, used to block bremsstrahlung radiation. The material of the blocker 6 facing the target material 1 is a high-melting-point substance such as tungsten to block sputtered particles; the material of the blocker 6 facing away from the target material 1 is lead to block bremsstrahlung radiation. The cross-sectional area of ​​the blocker 6 in the extreme ultraviolet light beam direction is on the order of square centimeters.

[0040] The target generator 11, the target 1, and the extreme ultraviolet beam collecting mirror 5 are located in the same vacuum system (not shown). The vacuum system can be a combination of a mechanical pump and a molecular pump to achieve a vacuum level of 10. -6 Torr and above.

[0041] Both the synchrotron radiation generating device 3 and the auxiliary high-power laser module 2 are connected to a synchronization time control system 7, which is also connected to a photodetector (not shown) or a target generator 11. The synchronization time control system 7 can coordinate the operating times of the synchrotron radiation generating device 3, the auxiliary high-power laser module 2, and the photodetector or target generator 11, enabling them to operate in sync.

[0042] Specifically, the synchronization time control system 7 is configured as follows: after the photodetector detects the falling target 1 or the target generator 11 generates the falling target 1, after a preset first delay, the synchrotron radiation prepulse and / or the high-power laser emitted by the auxiliary high-power laser module 2 are driven to bombard the target 1, ionizing its surface into plasma. Subsequently, after a preset second delay, the synchrotron radiation main pulse is driven to bombard the plasma through the synchrotron radiation generating device 3, so as to further ionize it into set high-valence ions, and through other excitation and de-excitation processes, it reaches the required ion valence state and excited state, and efficiently emits EUV light.

[0043] Therefore, the synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source of the present invention utilizes high-energy synchrotron radiation prepulses and / or high-power lasers incident on a target material such as a tin target, to precisely bombard it and ionize it to generate suitable plasma such as tin plasma (Sn). 7+ ~Sn 12+ Then, using a grazing incidence mirror system, the synchrotron radiation master pulse with high-order harmonics is aligned with the ionized target to introduce the master pulse into the plasma, where it interacts with the plasma to further ionize it, and reaches the set excited state through a series of processes; then, 13.5nm EUV light is generated through a de-excitation process.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. All simple and equivalent changes and modifications made in accordance with the claims and description of this application fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source, characterized in that, It includes a target material from a target material generator and a synchrotron radiation generating device aligned with the target material, the synchrotron radiation generating device being configured to introduce and irradiate the plasma with a synchrotron radiation master pulse carrying high-order harmonics. The plasma extreme ultraviolet light source further includes a plasma generating device configured to generate and emit a beam that ionizes the target material to obtain plasma. The beam is a high-power laser or a high-energy synchrotron radiation prepulse. The high-power laser is generated by an auxiliary high-power laser module. The high-energy synchrotron radiation prepulse is generated by a synchrotron radiation generating device. The higher harmonics in the synchrotron radiation main pulse serve as a driving light source, interacting with the plasma to de-excite ions and generate extreme ultraviolet light of the required frequency. The length of the synchrotron radiation main pulse is on the order of 10 ps, ​​and the power is 100W~2000W.

2. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 1, characterized in that, The plasma generating device is merely an auxiliary high-power laser module, or the plasma generating device is merely the aforementioned synchrotron radiation generating device.

3. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 1, characterized in that, The target generator is configured to precisely drop liquid target material at required time intervals and droplet sizes, wherein the target material is tin droplets or lithium fluoride liquid columns.

4. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 1, characterized in that, The beam is a high-energy synchrotron radiation prepulse, the length of which is on the order of 100 nanoseconds and the power is 100W~5000W; the synchrotron radiation generating device is in a synchrotron radiation hybrid operation mode.

5. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 1, characterized in that, The beam is a high-power laser, which is generated by a CO2 laser or a solid-state laser. The synchrotron radiation generating device and the auxiliary high-power laser module are both connected to a synchronization time control system, which is also connected to a photodetector or a target generator.

6. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 5, characterized in that, An extreme ultraviolet (EUV) beam collecting mirror is provided between the target material and the auxiliary high-power laser module and synchrotron radiation generating device, so that the generated EUV light is collected by the EUV beam collecting mirror and output outward. The EUV beam collecting mirror is provided with a through hole for the auxiliary high-power laser module and synchrotron radiation generating device to irradiate the target material, and the EUV beam collecting mirror is a curved mirror facing the target material for focusing.

7. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 1, characterized in that, A synchrotron radiation reflecting and focusing mirror system is provided between the synchrotron radiation generating device and the target material. The synchrotron radiation reflecting and focusing mirror system is configured to focus the synchrotron radiation with high-order harmonics generated by the synchrotron radiation generating device onto the plasma. The synchrotron radiation reflecting and focusing mirror system consists of two small-curvature reflectors arranged opposite each other.

8. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 1, characterized in that, The synchrotron radiation generating device is a synchrotron radiation oscillator or a torsion oscillator.

9. The synchrotron radiation high-harmonic driven plasma extreme ultraviolet light source according to claim 6, characterized in that, The synchrotron radiation generating device and the target are both located at the central axis of the beam line, and a blocker is provided on the side of the target away from the synchrotron radiation undulator at the central axis of the beam line to block bremsstrahlung radiation; the target generator, the target, and the extreme ultraviolet beam collecting mirror are located in the same vacuum system.

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