JP2023046479A - Discharge lamp and method for manufacturing discharge lamp electrode - Google Patents

Abstract

To prevent breakage of a glass member by reducing the weight of an electrode, and to suppress blackening due to evaporation of the electrode.SOLUTION: A discharge lamp includes a discharge tube, and a pair of electrodes facing each other in the discharge tube, and at least one of the electrodes has an internal space, and the internal space is provided with a heat transfer body made of an inorganic substance and/or an organic substance other than metal and having a density lower than that of the electrode material forming the internal space.SELECTED DRAWING: Figure 2

Description

The present invention relates to a discharge lamp used in an exposure apparatus and the like, and more particularly to a short arc discharge lamp and a method of manufacturing an electrode for a discharge lamp.

Large short-arc discharge lamps are increasing in power in order to improve production efficiency in the manufacture of semiconductors and liquid crystals. If the electrode structure becomes large in accordance with the increase in power, the weight of the electrodes will put a burden on the sealing portion, and there is a risk that the glass member will be damaged. As a countermeasure, Patent Document 1 describes a hollow electrode in which a concave portion (hole) is formed on the back surface of the electrode to reduce its weight.

Japanese Patent Application Laid-Open No. 2008-305782

However, the formation of recesses (holes) reduces the volume of the electrodes and reduces the heat capacity of the electrodes. There was a possibility that quenching occurred and shortened the life.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a discharge lamp and a method for manufacturing a discharge lamp electrode which are lightweight and can suppress the possibility of blackening.

The present invention comprises a discharge tube,
A pair of electrodes arranged opposite to each other in the discharge tube,
at least one electrode has an interior space;
The discharge lamp is characterized in that the internal space is provided with a heat transfer body made of an inorganic material and/or an organic material other than a metal and having a density lower than that of an electrode material forming the internal space.
The present invention comprises a discharge tube,
A pair of electrodes arranged opposite to each other in the discharge tube,
at least one electrode has an interior space;
The discharge lamp is characterized in that at least one of argon, krypton and xenon and a heat transfer body made of an inorganic substance other than metal and/or an organic substance are enclosed in an internal space.
In addition, the present invention is formed by molding a body member having a recess formed around the central axis and a lid member covering the recess of the body member, and forming a heat transfer body made of an inorganic material other than metal and/or an organic material in the recess of the body member. and
A method of manufacturing an electrode for a discharge lamp, characterized in that a body member or an intermediate member to be joined to the body member, and a cover member are solid-phase-bonded.

According to at least one embodiment, the weight of the electrode can be reduced, and blackening due to evaporation of the electrode material can be suppressed. Note that the effects described herein are not necessarily limited, and may be any effect described herein or an effect different from them.

FIG. 1 is a diagram schematically showing a short arc discharge lamp to which the present invention can be applied. FIG. 2 is a cross-sectional view showing the configuration of an anode according to one embodiment of the present invention. FIG. 3 is a cross-sectional view showing a modification of one embodiment of the present invention.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a short arc discharge lamp that is one embodiment. A short-arc discharge lamp 10 is a discharge lamp that can be used as a light source of an exposure device for forming a pattern, and includes a discharge tube (arc tube) 11 made of transparent quartz glass. A cathode 20 and an anode 30 are arranged in the discharge tube 11 so as to face each other with a predetermined gap therebetween.

Quartz glass sealing tubes 12a and 12b are provided integrally with the discharge tube 11 so as to face each other on both sides of the tube-shaped discharge tube 11, and both ends of the sealing tubes 12a and 12b are connected to bases 13a. and 13b. Inside the sealing tubes 12a and 12b, conductive electrode support rods 14a and 14b are arranged to support a metal cathode 20 and an anode 30, and a metal ring (not shown) and a metal foil 15a such as molybdenum. , 15b to conductive lead bars 16a, 16b, respectively. The sealing tubes 12a and 12b are welded to a glass tube (not shown) provided in the sealing tubes 12a and 12b, thereby sealing the discharge space containing mercury and rare gas. . The discharge lamp 10 is arranged vertically so that the anode 30 is on the upper side and the cathode 20 is on the lower side.

The lead rods 16a and 16b are connected to an external power source, and voltage is applied between the cathode 20 and the anode 30 via the metal member, metal foil and electrode support rods 14a and 14b. When electric power is supplied to the discharge lamp 10, an arc discharge is generated between the electrodes, and a bright line (ultraviolet light) of mercury is emitted.

Around the discharge lamp 10, a spheroidal reflecting mirror (condensing mirror) (not shown) is arranged to constitute a lighting device. When the lamp is lit, light emitted from the discharge lamp 10 is reflected by the reflecting mirror. The reflected light is condensed at the secondary focal point and guided to the object to be irradiated via an illumination optical system (not shown) or the like. For example, when an illumination device is provided in an exposure device, light is applied to the photosensitive surface of the substrate.

FIG. 2 is an enlarged cross-sectional view of the anode 30 of the discharge lamp shown in FIG. In the following description, an example in which the present invention is applied to the anode will be described, but the present invention can also be applied to the cathode 20 or the cathode 20 and the anode 30. The anode 30 has a body member 31 and a lid member 32 . The electrode support rod 14b is fitted to the cover member 32. As shown in FIG.

The body member 31 has a tubular shape, for example, a cylindrical shape, with one end face closed and the other end face open. That is, it has a concave portion around the central axis. A lid member 32 is diffusion-bonded to the open end surface of the body member 31 . The body member 31 and the lid member 32 are made of metals such as tungsten and molybdenum, or alloys thereof. A sealed internal space S is formed in the body member 31 by closing the open end face of the recess with the lid member 32 .

A solid heat transfer body 33 is provided for the internal space S here. The heat transfer body 33 has a volume of 30% to 80%, for example, about 70% of the internal space S. The heat transfer body 33 has a lower density than the electrode material of the body member 31 and the cover member 32 that constitute the internal space S, and is made of an inorganic substance and/or an organic substance other than metal. Inorganic substances other than metals and/or organic substances are, for example, oxides, carbides, salts, or combinations thereof, or resin systems. Specifically, tungsten oxide, bismuth oxide, silicon oxide, calcium carbide, magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), fluororesin, silicone resin, and the like can be used as materials for the heat conductor 33 . In this embodiment, a case where magnesium fluoride or calcium fluoride is used for the heat conductor 33 will be described below as an example.

When the electrode material of the body member 31 and the lid member 32 is tungsten, the density is (19.25 g/cm^3). The density of magnesium fluoride is (3.15 g/cm^3). The density of calcium fluoride is (3.18 g/cm^3). Non-metallic magnesium fluoride and calcium fluoride have a lower density than the electrode material tungsten.

Therefore, the anode 30 enclosing the heat transfer body 33 made of a material other than metal can be made lighter than an anode in which the internal space S is occupied by metal. Since the discharge lamp has a cantilever structure, as shown in FIG. 1, by reducing the weight of the electrodes, it is possible to prevent cracks in the sealing tube and breakage (breakage) of the electrode support rods. Moreover, since the heat transfer body 33 is enclosed in the internal space S, the heat capacity is increased compared to a conventional hollow electrode, and the possibility of blackening can be reduced. Furthermore, since the heat transfer body 33 has a heat transfer function, heat can be transferred to the support rod 14b side, which contributes to the temperature reduction of the tip portion of the electrode (anode 30).

Moreover, the boiling point of the heat transfer body 33 is lower than the boiling point of the electrode material of the body member 31 and the lid member 32 which constitute the internal space S, and boils when the discharge lamp 10 is lit. When the electrode material of the body member 31 and the lid member 32 is tungsten, the melting point is (approximately 3410° C.) and the boiling point is (approximately 5555° C.). Magnesium fluoride has a melting point of (approximately 1263° C.) and a boiling point of (approximately 2260° C.). Calcium fluoride has a melting point of (about 1418° C.) and a boiling point of (about 2533° C.). The melting point and boiling point of the heat conductor 33 made of these inorganic compounds are lower than those of the electrode material. That is, the heat conductor 33 has a boiling point lower than that of the electrode material (tungsten or molybdenum) forming the internal space S, and boils at least when the discharge lamp is lit. Vaporization of the heat transfer body during lighting further lowers the temperature of the electrode due to heat of vaporization and boiling heat transfer.

When the discharge lamp is lit, the temperature of the tip of the anode 30 becomes extremely high (for example, 2000° C. to 2500° C.). When the heat transfer body 33 is magnesium fluoride or calcium fluoride, the heat transfer body 33 changes from solid to liquid as the temperature of the anode 30 rises after lighting, and then boils. The boiling point is the temperature at which a liquid changes to a gas, and in the lighting state, the heat transfer body 33 exists in both liquid and gas states. The heat transfer body 33 is a heat transfer body whose boiling point is higher than the lowest temperature of the internal space S and lower than the highest temperature of the internal space S, and repeats phase transition within the internal space S. Therefore, the heat generated at the tip of the anode 30 is transported to the electrode support rod 14b side of the anode 30 by three heat transfer methods of liquid convection, heat of vaporization, and heat transfer by boiling. temperature rise can be suppressed, and evaporation of tungsten from the anode 30 can be suppressed.

FIG. 3 shows a modification (anode 30A) of the anode 30 of the present invention. This anode 30A has a convex curved surface 34 such that the vicinity of the center of the bottom surface of the internal space S is convex. The convex curved surface 34 gradually increases in height toward the lid member 32 side, and is not formed by sudden deformation like a projection. The convex curved surface 34 relieves the stress generated when the heat transfer body 33 undergoes a phase change. That is, by forming the gently convex curved surface 34 on the bottom surface, the force that tends to locally deform the bottom surface is relieved, and stress concentration can be prevented. In particular, when the heat transfer body 33 boils, the internal pressure in the internal space S increases, so the convex curved surface 34 that can avoid stress concentration is an advantageous configuration for the present invention that positively utilizes boiling heat transfer. .

Also, preferably, the entire bottom surface has a curved surface and the vicinity of the center is convex. More preferably, the tip surface of the electrode has a recess formed around the centerline connecting the pair of electrodes. This recess is formed so that the distances from the tip of the cathode 20 are equal. The curved surface of the recess may be formed as a surface of revolution. When electrons are sent from the cathode 20 by such recesses, the strength of the electric field can be made uniform or nearly uniform, so the wear of the anode 30 can be suppressed, and the heat transfer body can be prevented from leaking from the worn portion. be able to.

Since the internal space S has a space where the heat conductor 33 does not exist, this space is filled with an inert gas (rare gas). The noble gas is argon, krypton, or xenon. These noble gases have different thermal conductivities. The thermal conductivity has a relationship of (xenon<krypton<argon). Since the amount of heat transmitted from the rare gas to the electrode supporting rod 14b side changes according to the thermal conductivity of the rare gas, the temperature in the internal space S also changes. For example, if the rare gas has a high thermal conductivity, a large amount of heat is transmitted to the electrode supporting rod 14b side, so the temperature in the internal space S can be suppressed. When the temperature in the internal space S is low, the heat from the heat conductor 33 is easily transferred to the rare gas with high thermal conductivity. The heat transfer body that has lost heat becomes less likely to boil. That is, it takes longer to boil. In this way, when the time until the heat transfer body 33 boils is desired to be shortened, a rare gas with a low thermal conductivity is enclosed, and when the time until the heat transfer body 33 boils is desired to be lengthened, a rare gas with a high thermal conductivity is enclosed. . Depending on the type of rare gas to be enclosed, the time until the heat transfer body 33 boils can be changed.

For example, when it is desired to boil the heat transfer body 33 early from the initial stage of lighting to suppress the temperature rise of the anodes 30 and 30A, a rare gas having a low thermal conductivity is enclosed. On the other hand, when the internal pressure of the internal space S rises rapidly due to the sudden boiling of the heat transfer body 33, the anodes 30 and 30A may be damaged. Adjustments are made to lengthen the time.

A method for manufacturing the anode 30 shown in FIG. 2 will be described. A body member 31 made of tungsten or the like having a concave portion formed around a central axis has a polished joint surface on the opening side end face. Similarly, the lower end surface of a disk-shaped lid member 32 made of tungsten or the like is polished to form a joint surface.

Next, a heat transfer body 33 made of an inorganic material other than metal and/or an organic material is placed in the concave portion (internal space S) formed in the body member 31 .
Next, the lid member 32 is placed on the open end surface of the body member 31 to close the opening. Then, the body member 31 and the lid member 32 are sandwiched between the upper and lower portions of the body member 31 and the lid member 32 via the block, and are electrically heated while a predetermined pressure is applied. Through this bonding process, the body member 31 and the lid member 32 are solid phase bonded. An intermediate member may be inserted between the body member 31 and the lid member 32 .
Next, the body member 31 and the cover member 32 that are solid-phase bonded are cut along predetermined cutting lines to obtain the final electrode shape. As a result, the anode 30 in which the heat conductor 33 is enclosed in the internal space S is formed as shown in FIG. When the inert gas is introduced into the internal space S, it may be introduced in a gaseous state, or may be introduced in a state solidified with liquid nitrogen.

An embodiment of the present technology has been specifically described above, but the present invention is not limited to the above-described embodiment, and various modifications are possible based on the technical idea of the present invention. . For example, the present invention can be applied to a short arc type xenon lamp containing no mercury and a discharge lamp other than the short arc type. In the case of an organic heat transfer body, it can be applied to a small discharge lamp to which power of 1 kW or less is supplied. Also, the heat transfer medium preferably exists in both a liquid and a gaseous state when the discharge lamp is on, although this need not be the case. That is, the temperature of the electrode can be lowered only by the heat transfer function of the convection of the melted heat transfer material. In addition, the configurations, methods, processes, shapes, materials, numerical values, etc., given in the above-described embodiments are merely examples, and if necessary, different configurations, methods, processes, shapes, materials, numerical values, etc. may be used. good too.

10... discharge lamp, 11... discharge tube, 12a, 12b... sealing tube,
13a, 13b... caps, 14a, 14b... electrode supporting rods, 20... cathodes,
30... Anode, 31... Body member, 32... Lid member, 33... Heat conductor,
S...Internal space

Claims (10)

a discharge tube;
A pair of electrodes arranged oppositely in the discharge tube,
at least one electrode has an interior space;
A discharge lamp, wherein the internal space is provided with a heat transfer body made of an inorganic material and/or an organic material other than a metal and having a density lower than that of an electrode material forming the internal space. 2. The discharge lamp according to claim 1, wherein said heat conductor has a boiling point lower than that of an electrode material forming said internal space, and boils when said discharge lamp is lit. 3. A discharge lamp as claimed in claim 1 or 2, characterized in that the heat conductor exists in both gaseous and liquid states when the discharge lamp is lit. 4. The discharge lamp according to any one of claims 1 to 3, wherein said heat conductor is oxide, carbide, salt, or a combination thereof. 5. The discharge lamp according to claim 1, wherein said heat conductor is magnesium fluoride or calcium fluoride. 6. The discharge lamp according to any one of claims 1 to 5, wherein the bottom surface of the inner space has a curved surface, and the vicinity of the center of the curved surface is convex. 7. The discharge lamp according to claim 6, wherein the bottom surface is entirely curved, and the center of the curved surface is convex. 8. The discharge lamp according to any one of claims 1 to 7, wherein the tip surface of said at least one electrode has a surface of rotation formed around a centerline connecting said pair of electrodes. a discharge tube;
A pair of electrodes arranged oppositely in the discharge tube,
at least one electrode has an interior space;
A discharge lamp, wherein at least one of argon, krypton, and xenon and a heat transfer body made of an inorganic substance other than metal and/or an organic substance are enclosed in the internal space. A body member having a recess formed around a central axis and a lid member covering the recess of the body member are molded, and a heat transfer body made of an inorganic material other than metal and/or an organic material is placed in the recess of the body member,
A method of manufacturing an electrode for a discharge lamp, wherein the body member or an intermediate member to be bonded to the body member, and the lid member are solid-phase bonded.

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