Electrode structure for improving discharge stability and excimer laser

Abstract

The invention provides an electrode structure for improving discharge stability and an excimer laser, the electrode structure comprises a strip-shaped cathode and an anode which are arranged in a discharge cavity, and the cathode and / or the anode are / is provided with a plurality of cooling through holes; the cooling through holes penetrate through the two side faces of the cathode and / or the anode in the width direction and are integrally distributed in the flowing direction of the working gas in the discharge cavity, and part of the working gas flows from one side of the cathode and / or the anode to the other side of the cathode and / or the anode through the cooling through holes and is used for cooling the cathode and / or the anode. The surface temperature of the electrode can be effectively reduced, filamentous discharge development is inhibited, and the filamentous discharge is prevented from being evolved into arc discharge; and the problems of electrode damage, gas service life reduction and poor light beam quality caused by discharge instability are solved.

Description

Technical Field

[0001] The invention relates to the field of laser technology, and in particular to an electrode structure and an excimer laser for improving discharge stability. Background Art

[0002] In the field of high-end lithography, high-repetition-rate excimer lasers are the dominant light sources used in the field of semiconductor lithography due to their high repetition rate, narrow line width and high energy. For excimer lasers, the stability of high-repetition-rate discharge has a very important influence on the performance of the output laser spot index, the discharge cavity and the life of the working gas. Among them, hot spot discharge will appear on the cathode surface of the excimer laser under high-repetition-rate discharge conditions. The appearance of hot spot discharge will cause the uniform and stable glow discharge at the initial moment to evolve into an uneven and less stable filamentary discharge.

[0003] Current research generally believes that cathode hot spots caused by high current density in discharge plasma are the main reason for the conversion of discharge from glow discharge to filamentary discharge. When hot spot discharge occurs on the cathode surface, the electron density in the local area will increase rapidly, thereby initiating a filamentary discharge channel in which the cathode and anode are connected. Compared with the adjacent discharge area, the filamentary discharge channel has the characteristics of small channel impedance and large current density, which will further promote the increase of cathode temperature in the local area, and the hot spot discharge will be stronger, forming a positive feedback loop deterioration, and may lead to the transition of arc discharge. When the anode temperature of the discharge chamber is too high, the electrode loss rate will increase.

[0004] In view of the above problems, the present invention proposes a novel electrode design, which can effectively reduce the electrode temperature, thereby reducing the electrode temperature, inhibiting the development of filamentary discharge, and improving the stability of discharge. Summary of the invention

[0005] The object of the present invention is to provide an electrode structure and an excimer laser for improving discharge stability, so as to solve at least one of the above-mentioned technical problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides an electrode structure for improving discharge stability, comprising: a cathode and an anode in a long strip shape arranged in a discharge chamber, wherein the cathode and / or the anode are provided with a plurality of cooling through holes; The cooling through holes penetrate both sides of the cathode and / or anode in the width direction, and are arranged along the flow direction of the working gas in the discharge chamber as a whole. Part of the working gas flows from one side of the cathode and / or anode through the cooling through holes to the other side of the cathode and / or anode, so as to cool the cathode and / or anode.

[0007] Furthermore, it also includes an insulating ceramic plate for installing the cathode and / or anode, and the insulating ceramic plate is provided with through holes or through grooves running through both sides at the positions corresponding to the air inlet and / or air outlet of the cooling hole, which are used to guide and accelerate the working gas to flow into and out of the cooling hole.

[0008] Furthermore, the cooling through hole is a straight through hole or a spiral through hole.

[0009] Furthermore, the cathode and / or anode is composed of a base belt and a first auxiliary belt, and the first auxiliary belt is made of a material with thermal conductivity (or heat dissipation performance) worse than that of the base belt; in the length direction, two of the first auxiliary belts are symmetrically embedded on the mounting steps at both ends of the base belt, and in the height direction, the first auxiliary belt is arranged on the side away from the discharge end face of the electrode.

[0010] Furthermore, the cooling through hole is provided on the first auxiliary belt.

[0011] Generally, both ends of the electrode are severely corroded. The present invention can change the electrode material composition and internal structure by arranging the first auxiliary belt at both ends of the cathode and / or the anode, so as to achieve changes in the electron flux, ion flux and electron temperature on the electrode surface of the discharge area during the discharge process, thereby improving the non-uniformity of the discharge electric field, reducing the overall ablation difference of the electrode, and extending the service life of the electrode or the discharge chamber. At the same time, it can improve the stability of the laser dose output by the excimer laser light source and the stability of the light beam; and the cooling through holes running through both sides can improve the cooling performance of the first auxiliary belt.

[0012] The connection between the first auxiliary belt and the base belt is mainly metal metallurgical bonding or mechanical bonding. The electrode base belt can be made of electrode materials in the prior art and is in a long strip shape; for example, the electrode base belt is a strip made of brass alloy. The first auxiliary belt is made of a material with poorer thermal conductivity than the base belt, such as a metal-based ceramic composite material.

[0013] Furthermore, the length of the first auxiliary belt is 1 / 20 to 1 / 10 of the length of the cathode.

[0014] Furthermore, it also includes a second auxiliary belt, which is made of a material (such as pure copper) with better thermal conductivity (or heat dissipation performance) than the base belt; In the length direction, the second auxiliary belt is embedded in the middle of the base belt, and in the width direction of the base belt, the second auxiliary belt is arranged on a side away from (facing away from) the pre-ionization device in the discharge chamber.

[0015] Furthermore, the cooling through hole is provided on the second auxiliary belt.

[0016] Furthermore, the diameter of the cooling through hole is 1 mm-10 mm.

[0017] Furthermore, a plurality of rows of cooling through holes are arranged on the cathode, and a plurality of cooling through holes are arranged at intervals on each row.

[0018] Furthermore, the cooling through holes in two adjacent rows are arranged in a staggered manner.

[0019] Furthermore, the spacing between the cooling through holes is 2 mm-20 mm.

[0020] Preferably, the length of the second auxiliary tape is 1 / 10 to 3 / 4 of the length of the base tape.

[0021] Preferably, the width of the second auxiliary band is 1 / 4 to 1 / 2 of the width of the base band.

[0022] The second aspect of the present invention discloses an excimer laser using the electrode structure for improving discharge stability.

[0023] By adopting the above technical solution, the present invention has the following beneficial effects: The cathode structure provided by the present invention can effectively reduce the cathode surface temperature, inhibit the development of filamentary discharge, and prevent it from evolving into arc discharge; and the anode structure provided by the present invention can effectively reduce the anode surface temperature and reduce electrode loss; the electrode structure and excimer laser of the present invention can improve the problems of electrode damage, reduced gas life and poor beam quality caused by discharge instability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of the structure of the electrode structure provided in Example 1 of the present invention; Figure 2 for Figure 1 A view of the electrode structure shown; Figure 3 A schematic diagram of the structure of the electrode structure provided in Example 2 of the present invention; Figure 4 A schematic diagram of the structure of the electrode structure provided in Example 3 of the present invention; Figure 5 A schematic diagram of the structure of the electrode structure provided in Example 4 of the present invention; Figure 6 is a schematic structural diagram of the cathode in Example 5 of the present invention; Figure 7 for Figure 6 Middle DD section view; Figure 8 is a schematic structural diagram of the electrode structure in Example 6 of the present invention; Fig. 9 for Figure 8 Horizontal cross-section of the cathode.

[0026] Fig.10 Schematic diagram of the structure of the cathode in Example 7 of the present invention; Fig.11 Schematic diagram of the structure of a single-cavity laser in Example 8 of the present invention; Fig.12 Schematic diagram of the structure of a dual-cavity laser in Example 9 of the present invention; Reference numerals: 10-cathode; 11-cooling through hole; 11a-air inlet; 11b-air outlet; 12-base band; 13-first auxiliary band; 14-second auxiliary band; 20-anode; 30-pre-ionization device; 40-insulating ceramic plate; 41-via; 50-discharge cavity; 60-line width narrowing module, 70-output coupling mirror; 80-first optical path turning module; 900-second optical path turning module; 100-optical path inversion module. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] The present invention is further explained below in conjunction with specific implementation modes.

[0031] Example 1 like Figure 1 As shown, the present embodiment provides an electrode structure for improving discharge stability, including a discharge chamber, a long cathode 10, an anode 20 and a pre-ionization device 30 arranged in the discharge chamber, and a plurality of cooling holes 11 are arranged on the cathode 10.

[0032] The cooling through hole 11 passes through two side surfaces of the cathode 10 in the width direction and is arranged along the flow direction Y of the working gas in the discharge chamber as a whole. Part of the working gas flows from one side of the cathode 10 to the other side of the cathode 10 through the cooling through hole 11 to cool the cathode 10.

[0033] The cooling through hole 11 may be a straight through hole or a spiral through hole. The straight through hole allows the working gas to flow through quickly, while the spiral through hole is equivalent to increasing the length of each through hole, thereby increasing the gas heat dissipation efficiency.

[0034] like Figure 2 As shown, the cathode 10 is provided with multiple rows of cooling through holes 11, and each row is provided with multiple cooling through holes 11 at intervals. The cooling through holes 11 in two adjacent rows are preferably arranged in a staggered manner.

[0035] The spacing between the cooling holes 11 can be 2 mm to 20 mm. The diameter of the cooling holes 11 can be 1 mm to 10 mm.

[0036] The distance between the cooling holes 11 in the bottom row of the cathode 10 and the lower surface of the cathode 10 (ie, the discharge end surface of the cathode 10 ) is at least 5 mm to prevent the local structure introduced by the cooling holes 11 from inducing discharge conduction with the anode 20 .

[0037] The electrode structure provided by the present invention can enable the working airflow to flow freely from one side of the cathode to the other side through the cooling holes, so that the working airflow can take away the heat inside the electrode and can effectively reduce the surface temperature of the cathode 10, inhibit the development of filamentary discharge, and prevent it from evolving into arc discharge; improve the problems of electrode damage, reduced gas life and poor beam quality caused by discharge instability.

[0038] Example 2 This embodiment is basically the same as Embodiment 1, except that: Reference Figure 3 As shown, this embodiment also includes an insulating ceramic plate 40 for mounting the cathode 10, and the insulating ceramic plate 40 is provided with a through hole 41 (or a through groove with a lower end opening) penetrating both sides at a position corresponding to the air inlet of the cooling through hole 11, which is used to guide and accelerate the working gas to flow into the cooling through hole 11. The aperture of the through hole 41 is not less than the aperture of the cooling through hole 11. The through hole 41 can effectively improve the gas field environment near the air inlet of the cooling through hole 11, reduce eddy currents and turbulence, and promote more working gas to flow into the cooling through hole 11.

[0039] This embodiment enables more working gas to flow through the cooling through holes 11 in a smoother manner, and accelerates the flow of the working gas through the discharge region, thereby accelerating the cooling of the cathode 10 .

[0040] Example 3 This embodiment is basically the same as Embodiment 1, except that: like Figure 4 As shown, a plurality of cooling holes 11 are also provided on the anode 20 , and the size, arrangement, and distance from the upper surface of the cooling holes 11 are substantially the same as those of the cooling holes 11 on the cathode 10 , and will not be described in detail here.

[0041] The electrode structure provided by the present invention allows the working airflow to flow freely from one side of the anode to the other side through the cooling holes, so that the working airflow takes away the heat inside the electrode and can effectively reduce the surface temperature of the anode 20, thereby reducing the loss of the electrode during discharge.

[0042] Example 4 This embodiment is basically the same as Embodiment 4, except that: Reference Figure 5 As shown, this embodiment also includes an insulating ceramic plate 201 for mounting the anode 20, and the insulating ceramic plate 201 is provided with through holes 202 and open slots 203 that penetrate both sides at the positions corresponding to the air inlet and the air outlet of the cooling through hole 11, which are used to guide and accelerate the inflow and outflow of the working gas from the cooling through hole 11. The aperture of the through hole 202 and the slot width of the open slot 203 are not less than the aperture of the cooling through hole 11.

[0043] This embodiment enables more working gas to flow through the cooling through holes 11 in a smoother manner, and accelerates the flow of the working gas through the discharge region, thereby accelerating the cooling of the anode 20 .

[0044] Example 5 This embodiment is basically the same as Embodiment 1, except that: Reference Figure 6and 7 As shown, the cathode 10 in this embodiment is composed of a base belt 12 and a first auxiliary belt 13. The first auxiliary belt 13 is made of a material with poorer thermal conductivity (or heat dissipation performance) than the base belt 12. In the length direction, two first auxiliary belts 13 are symmetrically embedded on the mounting steps at both ends of the base belt 12. In the height direction, the first auxiliary belt 13 is arranged on the side away from the anode 20, that is, the side away from the discharge end face of the cathode 10. Cooling holes 11 are arranged on both the base belt 12 and the first auxiliary belt 13.

[0045] The length of the first auxiliary belt 13 is 1 / 20 to 1 / 10 of the length of the cathode 10. The connection between the first auxiliary belt 13 and the base belt 12 is mainly metal metallurgical bonding or mechanical bonding. The electrode base belt 12 can be made of electrode materials in the prior art and is in a long strip shape; for example, the electrode base belt 12 is a strip made of brass alloy. The first auxiliary belt 13 is made of a material with poor thermal conductivity than the base belt 12, such as a metal-based ceramic composite material.

[0046] The first auxiliary belt 13 may also be arranged at both ends of the anode 20, and the arrangement method is the same as that on the cathode 10. Alternatively, the first auxiliary belt 13 is also arranged at both ends of the cathode 10 and the anode 20, and the specific arrangement method is the same as above, which will not be repeated.

[0047] Generally, both ends of the cathode 10 and the anode 20 are severely corroded. The present invention can change the electrode material composition and internal structure by arranging the first auxiliary belt 13 at both ends of the cathode 10 and / or the anode 20, so as to achieve changes in the electron flux, ion flux and electron temperature of the electrode surface in the discharge area during the discharge process, thereby improving the non-uniformity of the discharge electric field, reducing the overall ablation difference of the electrode, and extending the service life of the electrode or the discharge chamber. At the same time, it can improve the stability of the laser dose output by the excimer laser light source and the stability of the light beam; and the cooling through holes 11 running through both sides can improve the cooling performance of the first auxiliary belt 13.

[0048] Example 6 This embodiment is basically the same as Embodiment 1-5, except that: Reference Figure 8 and 9 As shown, the present embodiment further includes a second auxiliary belt 14, which is made of a material (such as pure copper) having a better thermal conductivity (or heat dissipation performance) than the base belt 12; in the length direction, the second auxiliary belt 14 is embedded in the middle of the base belt 12, and in the width direction of the base belt 12, the second auxiliary belt 14 is arranged on a side away from (away from) the pre-ionization device 30 in the discharge chamber. The base belt 12 and the second auxiliary belt 14 are provided with cooling holes 11.

[0049] Preferably, the length of the second auxiliary tape 14 is 1 / 10 to 3 / 4 of the length of the base tape 12 , and the width of the second auxiliary tape 14 is 1 / 4 to 1 / 2 of the width of the base tape 12 .

[0050] The second auxiliary belt 14 can also be arranged at both ends of the anode 20, and the arrangement method is the same as that on the cathode 10. Or the second auxiliary belt 14 is also arranged at both ends of the cathode 10 and the anode 20, and the specific arrangement method is the same as above, which will not be repeated.

[0051] The present invention can further change the electrode material composition and internal structure by setting the second auxiliary belt 14, so as to realize the change of the electron flux, ion flux and electron temperature on the electrode surface of the discharge area during the discharge process, thereby improving the non-uniformity of the discharge electric field, reducing the overall ablation difference of the electrode, extending the service life of the electrode or the discharge chamber, and at the same time improving the stability of the laser dose output by the excimer laser light source and the stability of the light beam.

[0052] Example 7 This embodiment is basically the same as Embodiment 1-6, except that: Reference Fig.10 As shown, in this embodiment, the cooling through hole 11 on the cathode 10 is in the shape of a bull horn as a whole. The cooling through hole 11 is arc-shaped in the flow direction Y of the working gas, and the aperture gradually decreases.

[0053] The cooling through hole 11 includes an air inlet 11a arranged on the windward side of the cathode 10 and an air outlet 11b arranged on the leeward side of the cathode 10. Preferably, the aperture of the air inlet 11a is 1.5-3 times the aperture of the air outlet 11b.

[0054] The pre-ionization device 30 may be arranged on the windward side of the cathode 10. More preferably, the pre-ionization device 30 is arranged on the leeward side of the cathode 10.

[0055] More preferably, in the direction close to or away from the lower discharge end surface of the cathode 10, the air inlet 11a of the same cooling through hole 11 is arranged away from the lower discharge end surface of the cathode 10, while the air outlet 11b of the cooling through hole 11 is arranged close to the lower discharge end surface of the cathode 10 relative to its air inlet 11a.

[0056] The air inlet 11a of the cooling through hole 11 is arranged on the windward side of the cathode 10. The temperature of the working gas near the cathode 10 is relatively low, so the working gas with a relatively low temperature can be introduced into the cathode 10 to cool the cathode 10; while on the leeward side of the cathode 10, the temperature of the part close to the lower discharge end face is higher, and it is more necessary to cool down. A more beneficial effect is that the air inlet 11a of the cooling through hole 11 is arranged on the windward side of the cathode 10 and closer to the root of the cathode 10, which is conducive to eliminating or weakening the vortex phenomenon of the working gas at the root of the cathode 10, and introducing more chaotic airflow into the cooling through hole 11, thereby making the working gas flow between the cathode 10 and the anode 20 more stable.

[0057] The aperture of the air outlet 11b of the cooling through hole 11 is relatively fine, which is conducive to forcing the working gas flowing into the cooling through hole 11 to gradually accelerate, and the higher the flow speed, the greater the cooling efficiency. In addition, the air outlets 11b are arranged more densely in the area (relatively high temperature area) close to the lower end discharge end surface of the leeward side of the cathode 10, which is conducive to centralized cooling of the high temperature area on the leeward side.

[0058] Furthermore, the high-speed working gas ejected from the gas outlet 11b of the cooling through hole 11 can guide the working gas flowing between the cathode 10 and the anode 20, and can also reduce the eddy current or disordered turbulence on the leeward side.

[0059] Example 8 like Fig.11 As shown, the present invention also discloses an excimer laser, which has a line width narrowing module 60, a discharge chamber 50, and an output coupling mirror 70. The working electrodes in the discharge chamber include a cathode 10 and an anode 20. One of the cathode 10 and the cathode 20, or both, adopts the structure disclosed in the above embodiments 1-6.

[0060] Example 9 like Fig.12 As shown, the present invention also discloses another excimer laser, which has a line width narrowing module 60, two discharge chambers 50, a first optical path turning module 80, a second optical path turning module 90, and an optical path reversing module 100. The working electrode in the discharge chamber includes a cathode 10 and an anode 20. One of the cathode 10, the cathode 20, or both of them adopt the structure disclosed in the above embodiments 1-6.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrode structure for improving discharge stability, characterized in that: include: A long cathode (10) and an anode (20) are arranged in the discharge chamber, wherein the cathode (10) and / or the anode (20) are provided with a plurality of cooling through holes (11); The cooling through holes (11) penetrate both sides of the cathode (10) and / or the anode (20) in the width direction, and are arranged along the flow direction of the working gas in the discharge chamber as a whole; part of the working gas flows from one side of the cathode (10) and / or the anode (20) to the other side of the cathode (10) and / or the anode (20) through the cooling through holes (11), so as to cool the cathode (10) and / or the anode (20).

2. The electrode structure according to claim 1, characterized in that: It also includes an insulating ceramic plate (40) for mounting the cathode (10) and / or the anode (20), wherein the insulating ceramic plate (40) is provided with through holes (41) or through grooves that penetrate through both sides at positions corresponding to the air inlet and / or the air outlet of the cooling through hole (11), for guiding and accelerating the working gas to flow into and out of the cooling through hole (11).

3. The electrode structure according to claim 1, characterized in that: The cooling through hole (11) is a straight through hole or a spiral through hole.

4. The electrode structure according to claim 1, characterized in that: The cathode (10) and / or the anode (20) is composed of a base belt (12) and a first auxiliary belt (13), wherein the first auxiliary belt (13) is made of a material having a thermal conductivity lower than that of the base belt (12); in the length direction, two of the first auxiliary belts (13) are symmetrically embedded on mounting steps at both ends of the base belt (12), and in the height direction, the first auxiliary belt (13) is arranged on a side away from the discharge end face of the electrode.

5. The electrode structure according to claim 4, characterized in that: The first auxiliary belt (13) is provided with the cooling through hole (11).

6. The electrode structure according to claim 4, characterized in that: The length of the first auxiliary belt (13) is 1 / 20 to 1 / 10 of the length of the cathode (10) and / or the anode (20).

7. The electrode structure according to claim 4, characterized in that: It also includes a second auxiliary belt (14), the second auxiliary belt (14) being made of a material having a better thermal conductivity than the base belt (12); In the length direction, the second auxiliary belt (14) is embedded in the middle of the base belt (12), and in the width direction of the base belt (12), the second auxiliary belt (14) is arranged on a side away from the pre-ionization device (30) in the discharge chamber.

8. The electrode structure according to claim 7, characterized in that: The cooling through hole (11) is provided on the second auxiliary belt (14).

9. The electrode structure according to claim 1, characterized in that: The cooling through hole (11) on the cathode (10) is in the shape of a bull horn as a whole; the cooling through hole (11) is in an arc shape in the flow direction (Y) of the working gas, and the hole diameter gradually decreases.

10. An excimer laser using the electrode structure according to any one of claims 1 to 9.

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