Microwave plasma EUV light source based on resonant cavity

Abstract

The invention discloses a microwave plasma EUV (Extreme Ultraviolet) light source based on a resonant cavity, which comprises a microwave and light emitting conformal system, a microwave feed-in system, a working medium supply system and a cavity cooling system, and a hollow grid conformal structure with a microwave sub-wavelength size is introduced into the inner surface of the resonant cavity, so that the EUV light can smoothly penetrate through the surface of the cavity and is guided out of the cavity under the condition that the distribution of a microwave field in the cavity is not influenced, and the problem of contradiction between microwave field closing and EUV light leading-out in a traditional resonant cavity is solved. In addition, efficient coupling of microwave energy in the cavity can be guaranteed, efficient extraction of EUV light beams can be achieved by reasonably designing the size and shape of the grids, common microwave leakage and energy loss in traditional design are avoided, and therefore the energy conversion efficiency of the whole light source is improved.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic technology, and in particular relates to a design of a microwave plasma EUV light source based on a resonant cavity. Background Art

[0002] Extreme Ultra Violet (EUV) light sources have important applications in semiconductor manufacturing, micro-nano processing, and high-resolution imaging. The wavelength of EUV light is usually 10 to 15 nanometers, which can achieve higher resolution than traditional deep ultraviolet (DUV) light sources. It is one of the key technologies for next-generation integrated circuit manufacturing and nano-scale precision processing. In order to meet the needs of modern lithography processes for higher precision and smaller feature sizes, the development of efficient and stable EUV light sources has become an important research direction in the current field of optoelectronic technology.

[0003] At present, the realization of EUV light source mainly relies on two technical routes: laser plasma (LPP) light source and discharge plasma (DPP) light source. LPP light source irradiates metal target (such as tin) through high-power laser to form high-temperature plasma, which radiates strong EUV light. This technology can provide higher EUV radiation efficiency, but its input laser power is the main bottleneck restricting the further improvement of output power of LPP light source. In addition, since the solid target used by LPP light source is easy to produce metal debris under laser bombardment, the optical system is contaminated, the service life of optical components is shortened, and the system maintenance cost is increased. DPP light source generates plasma in xenon gas, liquid tin, etc. through electrical discharge, thereby radiating EUV light. Compared with LPP light source, DPP light source has a simpler structure and avoids the pollution problem of solid target, but its radiation efficiency is low, and electrode erosion and arc instability during discharge limit the life and output power of the light source.

[0004] In order to solve the limitations of traditional LPP and DPP light sources in terms of stability and power output, EUV light sources based on microwave discharge plasma (i.e., microwave plasma light sources, MPP) have gradually become an emerging technical solution in recent years. Microwave discharge plasma excites gas media through high-frequency microwaves to produce high-temperature and high-density plasma, and radiates EUV light under appropriate conditions. Compared with traditional LPP and DPP light sources, MPP technology has the following important advantages: (1) Higher output power potential: Microwave discharge plasma technology can use high-power microwave sources to form stable high-density plasma and achieve EUV output power above kW level. This feature enables MPP light sources to meet the needs of next-generation advanced lithography technology for high-power EUV light sources, thereby significantly improving the production efficiency and manufacturing accuracy of lithography processes. (2) Reduce optical system contamination: MPP light sources use gases such as xenon as ionization materials and do not produce solid debris, thereby effectively avoiding the contamination of the optical system by solid target debris in LPP light sources, extending the service life of optical components, and reducing system maintenance costs. (3) The availability of microwave sources and high system integration: High-power microwave sources are relatively easy to obtain, and microwave discharge plasma light sources do not require complex laser optical path systems. They have a more compact structure and are easy to integrate and industrialize.

[0005] Although microwave discharge plasma technology has significant advantages in output power and stability, its application in EUV light sources still faces many technical challenges. For example, how to achieve efficient microwave energy coupling and stable maintenance of plasma in the resonant cavity structure; how to design an optical structure that can effectively guide EUV beams so that EUV light can be smoothly extracted from the cavity without affecting the distribution and resonance characteristics of the microwave field. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the existing microwave discharge light source based on the resonant cavity cannot effectively lead out EUV light, and proposes a microwave plasma EUV light source based on the resonant cavity.

[0007] The technical solution of the present invention is: a microwave plasma EUV light source based on a resonant cavity, comprising a microwave and light output conformal system, a microwave feeding system, a working fluid supply system and a cavity cooling system, wherein the microwave and light output conformal system comprises a spherical resonant cavity and a reflector, the spherical resonant cavity is arranged at the focus inside the concave surface of the reflector, the microwave feeding system comprises a microwave source and a waveguide, the microwave source is electrically connected to a power supply, and is used to generate microwave energy, and couple the microwave energy to the inside of the spherical resonant cavity through the waveguide, and the working fluid supply system and the cavity cooling system are both arranged on the inner wall of the spherical resonant cavity.

[0008] Furthermore, the surface of the spherical resonant cavity is a hollow grid conformal structure of microwave sub-wavelength size, and the hollow grid conformal structure includes a metal wall surface and vacuum hollows arranged at intervals on the metal wall surface.

[0009] Furthermore, the vacuum hollow shape is circular or any polygonal shape.

[0010] Furthermore, the vacuum hollow aperture is less than or equal to 1 / 10 of the microwave wavelength and greater than 10 times the EUV light wavelength.

[0011] Furthermore, the metal wall surface is made of a metal material with high electrical conductivity.

[0012] Furthermore, the geometric shape of the reflector is a parabolic concave surface or an ellipsoidal concave surface.

[0013] Furthermore, the material of the reflector is a coating material with high reflectivity.

[0014] Furthermore, the waveguide is a coaxial waveguide.

[0015] Furthermore, the working fluid supply system includes a working fluid layer arranged on the inner wall of the spherical resonant cavity, a working fluid delivery pipe connected to the working fluid layer, and a working fluid inlet opened on the working fluid layer, and the working fluid inlet is used to introduce inert gas into the interior of the spherical resonant cavity.

[0016] Furthermore, the cavity cooling system includes a cooling layer arranged on the inner wall of the spherical resonant cavity and parallel to the working medium layer, and the cooling layer is respectively connected to the coolant inlet pipe and the coolant outlet pipe.

[0017] The beneficial effects of the present invention are:

[0018] (1) Efficient extraction of EUV beams: The present invention achieves efficient extraction of EUV beams without affecting the microwave field distribution, thereby improving the energy efficiency of the overall light source by designing the resonant cavity surface as a microwave sub-wavelength-sized hollow grid conformal structure.

[0019] (2) Compact structure and high integration: The present invention integrates the resonant cavity and the EUV light extraction device into one through a conformal design of the resonant cavity hollow grid, effectively avoiding the microwave leakage and beam scattering problems caused by the separate design in the traditional structure, simplifying the overall light source structure, and reducing the manufacturing and maintenance costs of the system.

[0020] (3) Improved system output power and stability: The EUV light source in the present invention uses a group of multiple magnetron microwave sources as microwave generating elements, uses different microwave sources at different positions in the resonant cavity, and superimposes energy for multiple heating to increase the total power, achieving EUV light output power of more than kW level, and meeting the demand for high-power EUV light sources for the next generation of advanced lithography technology.

[0021] (4) Design and implementation of a new EUV light source: The present invention implements a new EUV light source with reliable functions and stable operation through the design of microwave and light output conformal system, microwave feeding system, working fluid supply system and cavity cooling system, which is expected to replace the existing conventional EUV light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Shown is a structural diagram of a microwave plasma EUV light source based on a resonant cavity provided in an embodiment of the present invention.

[0023] Figure 2 FIG. 1 is a schematic diagram of the spherical resonant cavity structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are only exemplary and are intended to explain the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0025] The present invention provides a microwave plasma EUV light source based on a resonant cavity, such as Figure 1 and Figure 2 As shown together, it includes a microwave and light output conformal system, a microwave feeding system, a working fluid supply system and a cavity cooling system.

[0026] Among them, the microwave and light output conformal system includes a spherical resonant cavity and a reflector. The spherical resonant cavity is arranged at the focus of the concave surface of the reflector. The microwave feeding system includes a microwave source and a waveguide. The microwave source is electrically connected to the power supply to generate microwave energy and couple the microwave energy to the inside of the spherical resonant cavity through the waveguide. The working fluid supply system and the cavity cooling system are both arranged on the inner wall of the spherical resonant cavity.

[0027] In the embodiment of the present invention, the waveguide is a coaxial waveguide, and a group of multiple microwave sources are selected as microwave generating elements. The peak power of each pulse reaches MW, and the average power reaches kW. Different microwave sources are used at different positions in the resonant cavity, and the energy is superimposed for multiple heating to increase the total power without changing the instantaneous power. A coupler and a converter are also connected between the microwave source and the waveguide. The waveguide extends into the spherical resonant cavity through an antenna to couple the microwave energy to the inside of the spherical resonant cavity. The shape and size of the antenna should be optimized according to the microwave frequency and cavity size to maximize the microwave power coupling efficiency.

[0028] In the embodiment of the present invention, the geometric dimensions of the spherical resonant cavity are precisely designed so that it can match a microwave source of a specific frequency and form a stable standing wave distribution inside the cavity, thereby ensuring the formation of a stable plasma inside the cavity.

[0029] In the embodiment of the present invention, the surface of the spherical resonant cavity is a hollow grid conformal structure of microwave sub-wavelength size, which can not only act as a metal wall to form a resonant cavity, but also allow EUV light to pass through for collection. The hollow grid conformal structure includes a metal wall and vacuum hollows arranged at intervals on the metal wall, wherein the vacuum hollow parts serve as light outlets to transmit the generated EUV light. The shape of the vacuum hollow is circular or any polygon (triangle, square, rectangle, etc.), and the specific shape can be flexibly designed according to the curvature of the cavity surface and the directional requirements of light extraction to achieve the best EUV light transmission effect. Taking a circle as an example in the embodiment of the present invention, Figure 2 shown.

[0030] In the embodiment of the present invention, the wavelength difference between extreme ultraviolet light and microwaves is utilized. The wavelength of microwaves is longer, while the wavelength of extreme ultraviolet light is much shorter. Therefore, the mesh aperture of the hollow mesh conformal structure is less than or equal to 1 / 10 of the microwave wavelength and greater than 10 times the wavelength of EUV light, thereby having a shielding effect on microwaves and being able to effectively transmit the EUV light generated inside the cavity.

[0031] In the embodiment of the present invention, the metal wall surface is made of a metal material with high electrical conductivity (such as copper, silver or aluminum).

[0032] In the embodiment of the present invention, the geometric shape of the reflector is a parabolic concave surface or an ellipsoidal concave surface, and the spherical resonant cavity is arranged at the focus of the concave surface, such as Figure 1 As shown. The reflector is made of a coating material with high reflectivity (such as a multilayer dielectric film), and is used to achieve directional output and focusing of the EUV beam. The position and angle of the reflector can be precisely adjusted according to the extraction direction of the beam to ensure that the beam can be extracted to the outside with the best direction and intensity. Figure 1 As shown, the reflector is fixed by a bracket.

[0033] In the embodiment of the present invention, the EUV light extraction and the spherical resonant cavity are designed as an integral conformal structure, and microwave resonance and EUV light extraction are achieved through the design of a hollow grid. This conformal design can form a stable microwave standing wave field in the cavity, and at the same time, the EUV light is extracted through the hollow structure on the cavity surface.

[0034] In the embodiment of the present invention, Figure 2As shown, the working fluid supply system includes a working fluid layer arranged on the inner wall of the spherical resonant cavity, a working fluid delivery pipe connected to the working fluid layer, and a working fluid inlet opened on the working fluid layer, and the working fluid inlet is used to introduce an inert gas into the interior of the spherical resonant cavity. In an embodiment of the present invention, the inert gas uses high-purity xenon (Xe) as a discharge medium. The gas flow rate is adjusted by a precision flow control device to ensure that the optimal working fluid concentration is always maintained inside the cavity. The concentration of xenon is crucial to the formation of plasma and the radiation intensity of EUV light, so it needs to be precisely controlled according to specific application conditions.

[0035] In the embodiment of the present invention, Figure 2 As shown, the cavity cooling system includes a cooling layer arranged on the inner wall of the spherical resonant cavity and parallel to the working medium layer, and the cooling layer is connected to the coolant inlet pipe and the coolant outlet pipe respectively. The coolant is input into the cooling layer through the coolant inlet pipe, and the coolant flows in the cooling layer. After sufficient heat exchange with the inner surface of the resonant cavity, the coolant carries a large amount of heat and flows out of the cooling layer through the coolant outlet pipe. The coolant inlet pipe and the coolant outlet pipe together constitute Figure 1 Coolant pipes in.

[0036] In an embodiment of the present invention, when microwave power is coupled to the interior of the cavity through a waveguide, a microwave electric field forms a standing wave in the cavity. Under the action of the standing wave field, the xenon gas is excited and ionized to form a high-density plasma. The plasma formation region is usually located at the point where the electric field intensity of the spherical resonant cavity is maximum, thereby ensuring the stability of the plasma. By adjusting the microwave input power and the gas pressure inside the cavity, the density and electron temperature of the plasma can be controlled, thereby optimizing the radiation efficiency of the EUV light. At the same time, a reflector assembly is provided outside the spherical resonant cavity for focusing and directional guiding the extracted EUV light, realizing parallel output of the light beam or focusing it to a specific point, thereby optimizing the output direction and intensity of the EUV light according to application requirements. The microwave feeding system ensures the continuous supply of energy, the working fluid supply system ensures the uniform supply of the discharge working fluid, and the cavity cooling system ensures the normal operation of the system without being burned. By designing the spherical resonant cavity and EUV light extraction into a hollow grid conformal structure, the present invention can realize microwave coupling, plasma generation, and EUV beam extraction and shaping in a single device, providing a new technical path and theoretical basis for the development of future efficient and compact EUV light sources.

[0037] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A microwave plasma EUV light source based on a resonant cavity, characterized in that: The invention comprises a microwave and light output conformal system, a microwave feeding system, a working fluid supply system and a cavity cooling system. The microwave and light output conformal system comprises a spherical resonant cavity and a reflector. The spherical resonant cavity is arranged at the focus of the concave surface of the reflector. The microwave feeding system comprises a microwave source and a waveguide. The microwave source is electrically connected to a power supply to generate microwave energy and couple the microwave energy to the inside of the spherical resonant cavity through the waveguide. The working fluid supply system and the cavity cooling system are both arranged on the inner wall of the spherical resonant cavity.

2. The microwave plasma EUV light source based on the resonant cavity according to claim 1, characterized in that: The surface of the spherical resonant cavity is a hollow grid conformal structure of microwave sub-wavelength size, and the hollow grid conformal structure includes a metal wall surface and vacuum hollows arranged at intervals on the metal wall surface.

3. The microwave plasma EUV light source based on the resonant cavity according to claim 2, characterized in that: The vacuum hollow shape is circular or any polygonal shape.

4. The microwave plasma EUV light source based on a resonant cavity according to claim 2, characterized in that: The vacuum hollow aperture is less than or equal to 1 / 10 of the microwave wavelength and greater than 10 times of the EUV light wavelength.

5. The microwave plasma EUV light source based on a resonant cavity according to claim 2, characterized in that: The metal wall surface is made of a metal material with high electrical conductivity.

6. The microwave plasma EUV light source based on a resonant cavity according to claim 1, characterized in that: The geometric shape of the reflector is a parabolic concave surface or an ellipsoidal concave surface.

7. The microwave plasma EUV light source based on a resonant cavity according to claim 1, characterized in that: The reflector is made of a coating material with high reflectivity.

8. The microwave plasma EUV light source based on a resonant cavity according to claim 1, characterized in that: The waveguide is a coaxial waveguide.

9. The microwave plasma EUV light source based on a resonant cavity according to claim 1, characterized in that: The working fluid supply system comprises a working fluid layer arranged on the inner wall of the spherical resonant cavity, a working fluid delivery pipe connected to the working fluid layer, and a working fluid inlet opened on the working fluid layer, wherein the working fluid inlet is used to introduce an inert gas into the cavity of the spherical resonant cavity.

10. The microwave plasma EUV light source based on a resonant cavity according to claim 9, characterized in that: The cavity cooling system comprises a cooling layer which is arranged on the inner wall of the spherical resonant cavity and is parallel to the working medium layer. The cooling layer is respectively connected to a coolant inlet pipe and a coolant outlet pipe.

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