A microwave plasma EUV light source based on a resonant cavity

Abstract

The present invention discloses 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. The microwave and light output conformal system uses a spherical resonant cavity as the core structure for microwave energy coupling and plasma generation, and by introducing a microwave sub-wavelength-sized hollow grid conformal structure on the inner surface of the resonant cavity, EUV light can be smoothly transmitted through the cavity surface and guided to the outside of the cavity without affecting the microwave field distribution inside the cavity, thereby resolving the contradiction between microwave field sealing and EUV light extraction in traditional resonant cavities. In addition, the present invention can not only ensure the efficient coupling of microwave energy in the cavity, but also achieve efficient extraction of EUV beams by rationally designing the size and shape of the grid, while avoiding the common microwave leakage and energy loss in traditional designs, thereby improving the energy conversion efficiency of the overall light source.

Description

Technical Field

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

[0002] Extreme ultraviolet (EUV) light sources have important applications in semiconductor manufacturing, micro-nanofabrication, and high-resolution imaging. With a wavelength typically between 10 and 15 nanometers, EUV light can achieve higher resolution than traditional deep ultraviolet (DUV) light sources, making it a key technology for next-generation integrated circuit manufacturing and nanoscale precision machining. To meet the demands of modern lithography for higher precision and smaller feature sizes, the development of efficient and stable EUV light sources has become a key research area in optoelectronics.

[0003] Currently, the realization of EUV light sources relies primarily on two technical routes: laser-produced plasma (LPP) and discharge-produced plasma (DPP). LPP sources use a high-power laser to irradiate a metal target (such as tin), forming a high-temperature plasma that radiates intense EUV light. This technology offers high EUV radiation efficiency, but the input laser power is the main bottleneck restricting further increases in the output power of LPP sources. Furthermore, the solid target used in LPP sources is prone to generating metal debris when bombarded by laser light, which contaminates the optical system, shortens the lifespan of optical components, and increases system maintenance costs. DPP sources use electrical discharge to generate plasma in xenon gas, liquid tin, or other media, radiating EUV light. Compared to LPP sources, DPP sources have a simpler structure and avoid the problem of solid target contamination. However, their radiation efficiency is lower, and electrode erosion and arc instability during the discharge process limit the lifespan and output power of the 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 the lithography process. (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 material 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 convenient for system integration and industrial applications.

[0005] Although microwave discharge plasma technology offers significant advantages in output power and stability, its application in EUV light sources still faces numerous technical challenges. For example, how to achieve efficient microwave energy coupling and stable plasma maintenance within the resonant cavity structure, and how to design an optical structure that can effectively guide the EUV beam so that it can be smoothly extracted from the cavity without affecting the distribution and resonant 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 introduce 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, including 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 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 a power supply and is used to generate microwave energy and couple the microwave energy to the interior 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.

[0008] Furthermore, the surface of the spherical resonant cavity is a hollow grid conformal structure of microwave subwavelength 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 a circle or any polygon.

[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 reflector is made of 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 by designing the resonant cavity surface into a microwave sub-wavelength-sized hollow grid conformal structure. This can achieve efficient extraction of EUV beams without affecting the microwave field distribution, thereby improving the energy utilization efficiency of the overall light source.

[0019] (2) Compact structure and high integration: The present invention integrates the resonant cavity and EUV light extraction device into one through the 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 above kW level, and meeting the demand of the next generation of advanced lithography technology for high-power EUV light sources.

[0021] (4) Design and implementation of a new EUV light source: The present invention realizes 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 by 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] The exemplary embodiments of the present invention will now 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 merely exemplary and are intended to illustrate 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 into the interior 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 this embodiment of the present invention, the waveguide is a coaxial waveguide, and a set of multiple microwave sources is used as the microwave generating element. Each pulse has a peak power of MW and an average power of kW. Different microwave sources are used at different locations within the resonant cavity, and the energy is superimposed for multiple heating, thereby increasing the total power while maintaining the instantaneous power. A coupler and converter are also connected between the microwave source and the waveguide. The waveguide extends into the spherical resonant cavity via an antenna, coupling the microwave energy into the 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 portion serves as a light outlet 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 directionality requirements of the light extraction to achieve the best EUV light transmission effect. In the embodiment of the present invention, taking a circle as an example, Figure 2 shown.

[0030] In an embodiment of the present invention, the wavelength difference between extreme ultraviolet light and microwaves is utilized. The microwave wavelength is longer, while the extreme ultraviolet light wavelength is much shorter. Therefore, the grid aperture of the hollow grid conformal structure is less than or equal to 1 / 10 of the microwave wavelength and greater than 10 times the EUV light wavelength, 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 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 high-reflectivity coating material (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. In the embodiment of the present invention, Figure 1 As shown, the reflector is fixed by a bracket.

[0033] In this embodiment of the present invention, the EUV light extraction and spherical resonant cavity are designed as a conformal structure. A hollow grid design enables microwave resonance and EUV beam extraction. This conformal design creates a stable microwave standing wave field within the cavity while simultaneously extracting EUV light 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 adopts high-purity xenon (Xe) as the 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 gas is crucial to the formation of plasma and the radiation intensity of EUV light, so it needs to be precisely controlled according to the 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. 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. The coolant flows in the cooling layer and after sufficient heat exchange with the inner surface of the resonant cavity, it flows out of the cooling layer through the coolant outlet pipe carrying a large amount of heat. The coolant inlet pipe and the coolant outlet pipe together constitute Figure 1 Coolant pipes in the.

[0036] In an embodiment of the present invention, when microwave power is coupled into the cavity through a waveguide, the 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, forming 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 on the outside of the spherical resonant cavity for focusing and directionally guiding the extracted EUV light, achieving 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 a continuous supply of energy, the working fluid supply system ensures a uniform supply of the discharge working fluid, and the cavity cooling system ensures the normal operation of the system without burning. By designing the spherical resonant cavity and EUV light extraction into a hollow grid conformal structure, the present invention can achieve 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 it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. A microwave plasma EUV light source based on a resonant cavity, characterized in that: The microwave and light output conformal system comprises 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 and is used to generate microwave energy and couple the microwave energy into the interior 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. The surface of the spherical resonant cavity is a hollow grid conformal structure of microwave subwavelength size, and the hollow grid conformal structure includes a metal wall surface and vacuum hollows arranged at intervals on the metal wall surface.

2. The cavity-based microwave plasma EUV light source according to claim 1, characterized in that: The vacuum hollow shape is circular or any polygonal.

3. The cavity-based microwave plasma EUV light source according to claim 1, characterized in that: 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.

4. The cavity-based microwave plasma EUV light source according to claim 1, characterized in that: The metal wall surface is made of a metal material with high electrical conductivity.

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

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

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

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

9. The microwave plasma EUV light source based on a resonant cavity according to claim 8, 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.

Images