Star-coupled capillary discharge double-vacuum 13.5 nm light source collection device

Abstract

The invention discloses a star-linked capillary discharge double-vacuum 13.5 nm light source collection device, and relates to the technical field of extreme ultraviolet lithography light sources. The star-linked capillary discharge double-vacuum 13.5 nm light source collection device comprises a star-linked capillary and electrodes, the electrodes are arranged at the two ends of the capillary, the capillary is sleeved with a vacuum discharge chamber, a collection window is arranged on the vacuum discharge chamber, and an anode of the star-linked capillary discharges to a cathode at the same time. The common cathode is grounded, working gas in the capillary flows from the anode to the cathode, and the gas pressure is controllable. According to the invention, the output power of the extreme ultraviolet light is to be improved, and the discharge repetition frequency of 10Hz can meet the requirements of extreme ultraviolet lithography production; a pneumatic system is adopted for supplying air, so that discharge debris, light source impurities and the like are greatly reduced, and the purity of extreme ultraviolet light is improved; the light-emitting length of the star-linked capillary tube is prolonged, and the output of extreme ultraviolet light is facilitated; compared with a traditional capillary tube discharge device, the extreme ultraviolet light is emitted from the capillary tube and collected in the vacuum discharge chamber outside the capillary tube, the collection amount is greatly increased, and the power of the extreme ultraviolet light is also increased.

Description

Technical Field

[0001] The present invention relates to the technical field of extreme ultraviolet lithography light sources, and in particular, to a star-connected capillary discharge double-vacuum collection 13.5 nm light source device. Background Art

[0002] The extreme ultraviolet (EUV) light source with a wavelength of 13.5 nm can still provide sufficient depth of focus under the condition of meeting the minimum feature line width, and has been used in the industrial production below the 10 nm technology node of extreme ultraviolet lithography (EUVL). Extreme ultraviolet light sources usually come from synchrotron radiation sources, laser plasma light sources, gas discharge plasma light sources, and laser-assisted discharge plasma light sources. Synchrotron radiation sources are costly, have complex devices, are difficult to control, and have troublesome electron injection, making it difficult to be suitable for industrial production. Laser plasma light sources first convert electrical energy into light energy and then into the radiation energy of the plasma, reducing the energy conversion efficiency. Laser plasma light sources essentially utilize the transient luminescence of the plasma, and it is difficult to control the temperature and density of the plasma. These parameters affect the luminescence process of the plasma. In addition, laser parameters are also the main factors that need to be adjusted. Moreover, issues such as target material selection, target shape processing, vacuum control, target debris, and light source impurities cannot be avoided. Therefore, this light source is rarely directly used in EUVL industrial production.

[0003] The extreme ultraviolet light source is the origin of extreme ultraviolet lithography technology. Extreme ultraviolet lithography technology usually adopts a reflective exposure system. The molybdenum-silicon multilayer mirror has a reflectivity as high as 70% for 13.5 nm extreme ultraviolet light. Therefore, extreme ultraviolet lithography uses extreme ultraviolet light with a wavelength of 13.5 nm. In addition, extreme ultraviolet light with a wavelength of 13.5 nm can achieve a resolution below 10 nm while ensuring sufficient depth of focus.

[0004] Both laser plasmas and discharge plasmas can output extreme ultraviolet light at 13.5 nm. Currently, the light source used in extreme ultraviolet lithography machines mainly adopts a laser-assisted discharge plasma light source. The laser first ablates a tin target to form a laser plasma. This laser plasma contains free electrons, gaseous tin atoms, ions of various valence states, etc. If the vacuum degree of the target chamber is not enough, the laser plasma may also contain impurities such as tin oxide. Usually, the 13.5 nm extreme ultraviolet photons come from Sn5+. The laser plasma has a complex composition and it is very difficult to directly use it in EUVL production. Therefore, it is necessary to use the discharge method to pinch the laser plasma. On the one hand, convert electrical energy into plasma radiation energy, ionize tin atoms or low-valence ions into Sn5+, and on the other hand, compress the plasma to a specific temperature and density. The energy levels of tin atoms are already very rich, and the energy levels of Sn5+ are even richer. Even if the laser hits the tin target and all become Sn5+, if the temperature and density of the laser plasma do not meet the conditions for radiating 13.5 nm, photons of 13.5 nm will not be radiated. Thus, by controlling the discharge parameters, not only can the abundance of Sn5+ be increased, but also the plasma conditions for radiating 13.5 nm can be satisfied as much as possible. Even so, the optical power of the light source outputting 13.5 nm light per shot is still very low. The only way is to greatly increase the working repetition frequency, which is generally as high as several thousand hertz. High-repetition-frequency operation has extremely high requirements for the stability of the optical path system and the lithography stage. At the same time, heat dissipation is also an issue that cannot be ignored. Moreover, the impact of target debris, discharge debris, and light source impurities on the 13.5 nm optical power is an unavoidable problem.

[0005] In the prior art, when a ceramic capillary discharges, the following problems exist: 1. Electrode ablation generally occurs during capillary discharge, generating electrode debris; 2. Wall erosion usually accompanies capillary discharge, generating wall debris; 3. The working substance in the capillary may react with the debris in the plasma state, generating light source impurities. All debris and light source impurities may radiate stray light of other wavelengths or absorb 13.5 nm photons; 4. End-face collection is generally adopted for capillary discharge. The end surface area of the capillary where the plasma is pinched and emits light is very small. With a very low collection efficiency, the optical power of 13.5 nm is very low. To solve the above problems, a star-connected capillary discharge double-vacuum collection 13.5 nm light source device is proposed. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a star-connected capillary discharge double-vacuum collection 13.5 nm light source device, which solves the problems that in the current capillary discharge, the electrodes are generally ablated to generate electrode debris; the inner wall of the capillary is usually eroded to generate wall debris; the working substance in the capillary may react with the debris in the plasma state to generate light source impurities, and all the debris and light source impurities may radiate stray light of other wavelengths or absorb 13.5 nm photons; the capillary discharge generally adopts an end-face collection method, and the end surface area of the pinched plasma in the capillary for emitting light is very small, and the light power of 13.5 nm is very low under the condition of very low collection efficiency.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a star-connected capillary discharge double-vacuum collection 13.5 nm light source device, including a star-connected capillary, an anode and a common cathode. The anode is placed at the outer end of the star-connected capillary. A vacuum discharge sub-chamber and a vacuum discharge chamber are also sleeved outside the star-connected capillary. A collection window is also provided at the center of the left side of the vacuum discharge chamber. The inside of the star-connected capillary is also communicated with an external circulating gas supply system. The vacuum discharge chamber is composed of two sets of star-connected capillary discharge systems.

[0008] Preferably, the vacuum discharge sub-chamber is a cylindrical stainless steel shell, and the star-connected capillary and the vacuum discharge sub-chamber are in different vacuum environments.

[0009] Preferably, the anode and the common cathode are made of tungsten copper. The anode and the common cathode are respectively arranged at the outer end and the inner end of the star-connected capillary. The common cathode is connected to the ground through a wire.

[0010] Preferably, the outer end of the star-connected capillary is communicated with an air inlet, and the inner end of the star-connected capillary is communicated with an air outlet. The air inlet and the air outlet are connected to an external circulating gas supply system.

[0011] Preferably, the connection endpoints of the air inlet and the air outlet with the star-connected capillary are both located outside the vacuum discharge sub-chamber, and the star-connected capillary and the vacuum discharge sub-chamber are sealed and isolated by a seal.

[0012] Preferably, the collection window is opened at the center of the left side of the vacuum discharge chamber.

[0013] Preferably, the vacuum discharge sub-chamber and the vacuum discharge chamber are integrally formed, and the inside of the vacuum discharge sub-chamber and the vacuum discharge chamber is communicated. The inside of the vacuum discharge sub-chamber and the vacuum discharge chamber is in a vacuum state.

[0014] Preferably, the common cathode provided at the inner end of the star-connected capillary is conducive to the synchronous discharge of the star-connected capillary. The common cathode structure is electrically connected to the common cathode ground through a wire to ensure operation safety.

[0015] Compared with the prior art, the advantages of the present invention are as follows: The present invention greatly improves the output power of extreme ultraviolet light, and a discharge repetition frequency of 10 Hz can meet the requirements of extreme ultraviolet lithography production; the extreme ultraviolet light is generated inside the capillary and collected in the vacuum discharge chamber, and is not affected by discharge debris and light source impurities; the pneumatic system is used for gas supply, greatly reducing discharge debris and light source impurities and improving the purity of extreme ultraviolet light; the luminous length of the star-connected capillary is extended, which is conducive to the output of extreme ultraviolet light. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the working principle diagram of the present invention; Figure 2 is the structural schematic diagram of the present invention; Figure 3 is the structural schematic diagram from another perspective of the present invention.

[0017] The reference numerals in the drawings are: 1. Star-connected capillary; 2. Anode; 3. Common cathode; 4. Air inlet; 5. Exhaust port; 6. Common cathode ground; 7. Power supply; 8. Collection window; 9. Vacuum discharge sub-chamber; 10. Vacuum discharge chamber. DETAILED DESCRIPTION OF THE INVENTION

[0018] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations.

[0019] Refer to Figures 1-3 As shown, a light source device for star-connected capillary discharge double-vacuum collection of 13.5 nm includes a star-connected capillary 1, an anode 2, and a common cathode 3. The anode 2 is placed at the outer end of the star-connected capillary 1. The star-connected capillary 1 is also sleeved with a vacuum discharge sub-chamber 9 and a vacuum discharge chamber 10 on the outside. A collection window 8 is also provided in the center on the left side of the vacuum discharge chamber 10. The inside of the star-connected capillary 1 is also communicated with an external circulating gas supply system. The vacuum discharge chamber 10 is composed of two sets of star-connected capillary 1 discharge systems. The inner diameter of the star-connected capillary 1 is 10 mm, the wall thickness is 1-2 mm, the length is 90 mm, the voltage during discharge is 15-25 kV, the peak discharge current reaches 20 kA, and the pulse width is 200 ns.

[0020] Specifically, the vacuum discharge sub-chamber 9 is a cylindrical stainless steel shell. The star-connected capillary 1 and the vacuum discharge sub-chamber 9 are in different vacuum environments. The vacuum degree of the vacuum discharge sub-chamber 9 is independently controlled to avoid the interference of capillary discharge on the main vacuum discharge chamber 10 and optimize the purity of the optical path.

[0021] Further, the anode 2 and the common cathode 3 are made of tungsten copper. The anode 2 and the common cathode 3 are respectively arranged at the outer end and the inner end of the star-connected capillary 1. The common cathode 3 is connected to the common cathode ground 6 through a wire. The melting point of tungsten (3422 °C) matches the high-temperature environment of 20 kA pulsed discharge, prolonging the electrode life. The copper component improves the current-carrying capacity, reduces the joule heat loss, and the high hardness of tungsten reduces the material loss under plasma bombardment.

[0022] Further, the outer end of the star-connected capillary 1 is connected to the air inlet 4, and the inner end of the star-connected capillary 1 is connected to the exhaust port 5. The air inlet 4 and the exhaust port 5 are connected to the external circulating gas supply system. The gas composition inside the capillary (such as the Xe / Ar mixing ratio) is adjusted through the circulating gas supply system to optimize the 13.5 nm laser conversion efficiency.

[0023] Preferably, the connection endpoints of the air inlet 4 and the exhaust port 5 with the star-connected capillary 1 are both located outside the vacuum discharge chamber 9, and the inlets and outlets are located outside the vacuum chamber, preventing oil stains or impurities from entering the discharge area. The star-connected capillary 1 and the vacuum discharge chamber 9 are sealed and isolated by a seal. The seal between the capillary and the chamber prevents gas leakage and maintains the vacuum degree of the discharge chamber.

[0024] Specifically, the collection window 8 is opened at the central position on the left side of the vacuum discharge chamber 10. The collection aperture of the collection window 8 is 150 mm to 200 mm. The large aperture setting can improve the light collection efficiency (the theoretical efficiency is proportional to the aperture area), support high-power applications, and the central setting can ensure that the 13.5 nm extreme ultraviolet light (EUV) is output symmetrically along the main optical axis, simplifying the design of the subsequent focusing system.

[0025] Further, the vacuum discharge chamber 9 and the vacuum discharge chamber 10 are integrally formed, and the inside of the vacuum discharge chamber 9 and the vacuum discharge chamber 10 is connected. The inside of both the vacuum discharge chamber 9 and the vacuum discharge chamber 10 is in a vacuum state.

[0026] Further, the common cathode 3 arranged at the inner end of the star-connected capillary 1 is beneficial to the synchronous discharge of the star-connected capillary 1. The common cathode structure 3 is electrically connected to the common cathode ground 6 through a wire to ensure operation safety.

[0027] Working principle: Before the experiment, the device is connected to the power supply 7. At this time, the anode 2 is placed at the outer end of the star-connected capillary 1 made of glass, and the common cathode 3 is placed at the inner end. The common cathode is grounded 6, and the anode 2 discharges to the common cathode 3, generating high-temperature and high-density plasma inside the star-connected capillary 1. The working gas is xenon, provided by the circulating gas supply system. The gas enters the capillary from the air inlet 4. After the discharge is completed, the tail gas is discharged from the exhaust port 5, and the new working gas re-enters the star-connected capillary 1 to start the next discharge. As Figure 2As shown, the star-connected capillary 1 is placed inside the cylindrical stainless-steel vacuum discharge sub-chamber 9. There is an isolation seal between the star-connected capillary 1 and the vacuum discharge sub-chamber 9. The entire light source consists of two sets of star-connected capillary 1 discharge systems, with a total of 6 capillaries emitting light. A collection window 8 is opened in the center on the left side of the stainless-steel vacuum discharge chamber 10. The stainless-steel vacuum discharge sub-chamber 9 and the stainless-steel vacuum discharge chamber 10 are integrally formed and internally connected, and are pumped to a high vacuum. The extreme ultraviolet light emitted from the star-connected capillary 1 is not affected by discharge debris, light source impurities, etc. inside the stainless-steel vacuum discharge sub-chamber 9 and the stainless-steel vacuum discharge chamber 10. In this way, the luminous plasma is located inside the star-connected capillary 1, and the collection area of the extreme ultraviolet light is located inside the stainless-steel vacuum discharge chamber 10. Separating the luminous area and the collection area is beneficial to improving the output power of the extreme ultraviolet light. The star-connected capillary 1 made of glass has very good stability, with very few debris on the tube wall. The anode 2 and the common cathode 3 adopt tungsten-copper electrodes, and the electrode ablation amount is also not much. The total debris is significantly lower than that of the ceramic capillary discharge. Thus, the light source impurities generated are greatly reduced. In addition, the star-connected capillary discharge double-vacuum collection 13.5nm light source device uses circulating gas supply. Even if a small amount of debris or light source impurities are generated, after the discharge ends, they are discharged from the star-connected capillary 1 along with the exhaust gas, and new working gas enters the star-connected capillary 1 for re-discharge. This not only helps to improve the output power of the extreme ultraviolet light, but also maintains the purity of the light source. The mechanical and circuit connections involved in the present invention are common means adopted by those skilled in the art and can obtain technical inspiration through a limited number of experiments, which belong to common general knowledge.

[0028] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A star - linked capillary discharge double - vacuum collection 13.5nm light source device, characterized in that: It includes a star-connected capillary (1), an anode (2), and a common cathode (3). The anode (2) is placed at the outer end of the star-connected capillary (1). A vacuum discharge sub-chamber (9) and a vacuum discharge chamber (10) are also sleeved outside the star-connected capillary (1). A collection window (8) is also provided at the center on the left side of the vacuum discharge chamber (10). The inside of the star-connected capillary (1) is also connected to an external circulating gas supply system. The vacuum discharge chamber (10) is composed of two sets of star-connected capillary discharge systems.

2. The light source device for collecting 13.5 nm by star-connected capillary discharge double vacuum according to claim 1, characterized in that: The vacuum discharge sub-chamber (9) is a cylindrical stainless steel shell, and the star-connected capillary (1) and the vacuum discharge sub-chamber (9) are in different vacuum environments.

3. A 13.5nm light source device for star - linked capillary discharge double - vacuum collection according to claim 2, characterized in that: The anode (2) and the common cathode (3) are made of tungsten copper. The anode (2) and the common cathode (3) are respectively arranged at the outer end and the inner end of the star-connected capillary (1). The common cathode (3) is connected to the common cathode ground (6) through a wire.

4. A 13.5nm light source device for star - linked capillary discharge double - vacuum collection according to claim 3, characterized in that: The outer end of the star-connected capillary (1) is connected to an air inlet (4), and the inner end of the star-connected capillary (1) is connected to an air outlet (5). The air inlet (4) and the air outlet (5) are connected to an external circulating gas supply system.

5. A 13.5nm light source device with a star-connected capillary discharge double vacuum collection according to claim 4, characterized in that: The connection endpoints of the air inlet (4) and the air outlet (5) with the star-connected capillary (1) are both located outside the vacuum discharge sub-chamber (9), and the star-connected capillary (1) and the vacuum discharge sub-chamber (9) are sealed and isolated by a seal.

6. A 13.5nm light source device for star-connected capillary discharge double vacuum collection according to claim 5, characterized in that: The collection window (8) is opened at the central position on the left side of the vacuum discharge chamber (10).

7. A 13.5nm light source device for star - linked capillary discharge double - vacuum collection according to claim 6, characterized in that: The vacuum discharge sub-chamber (9) and the vacuum discharge chamber (10) are integrally formed, and the inside of the vacuum discharge sub-chamber (9) and the vacuum discharge chamber (10) is connected. The inside of the vacuum discharge sub-chamber (9) and the vacuum discharge chamber (10) are both in a vacuum state.

8. A 13.5nm light source device for star - linked capillary discharge double - vacuum collection according to claim 6, characterized in that: The common cathode (3) arranged at the inner end of the star-connected capillary (1) is beneficial to the synchronous discharge of the star-connected capillary (1). The common cathode structure (3) is electrically connected to the common cathode ground (6) through a wire to ensure operation safety.

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