Method for manufacturing a discharge lamp and an electrode for a discharge lamp

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

Technical Field

[0001] The present invention relates to a discharge lamp used in an exposure apparatus or the like, and more particularly to a short arc type discharge lamp and a method for manufacturing an electrode for a discharge lamp.

Background Art

[0002] In a large short arc type discharge lamp, in order to improve the production efficiency of semiconductor and liquid crystal manufacturing, the power is increasing. When the electrode structure becomes large with the increase in power, the weight of the electrode places a burden on the sealing portion, and there is a risk that the glass member may 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 the weight.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, by forming the concave portion (hole), the volume of the electrode decreases, the heat capacity of the electrode decreases, and tungsten constituting the electrode evaporates due to excessive temperature rise, resulting in blackening adhering to the inner wall of the arc tube, which may reduce the lifespan.

[0005] Therefore, an object of the present invention is to provide a discharge lamp and a method for manufacturing an electrode for a discharge lamp that are lightweight and can suppress the possibility of blackening.

Means for Solving the Problems

[0006] The present invention includes a discharge tube and a pair of electrodes disposed opposite to each other inside the discharge tube, wherein at least one of the electrodes has an internal space, Inside the internal space, a heat transfer body made of inorganic substances and / or organic substances other than metal, which has a lower density than the electrode material constituting the internal space, is provided. The heat transfer body has a boiling point lower than the boiling point of the electrode material constituting the internal space, and is a discharge lamp characterized by boiling when the discharge lamp is lit. The present invention relates to a discharge tube and a pair of electrodes arranged opposite to each other inside the discharge tube. At least one of the electrodes has an internal space. Inside the internal space, at least one of argon, krypton, and xenon, and a heat transfer body made of inorganic substances and / or organic substances other than metal are enclosed. The heat transfer body has a boiling point lower than the boiling point of the electrode material constituting the internal space, and is a discharge lamp characterized by boiling when the discharge lamp is lit. Further, the present invention forms a body member having a recess around the central axis and a lid member covering the recess of the body member, and in the recess of the body member, there is a heat transfer body made of inorganic substances and / or organic substances other than metal, and the boiling point is Recessed portion lower than the boiling point of the electrode material constituting it, and a heat transfer body that boils when the discharge lamp is lit is placed, It is a method for manufacturing an electrode for a discharge lamp, characterized by solid-phase bonding of the body member or an intermediate member joined to the body member and the lid member.

Advantages of the Invention

[0007] According to at least one embodiment, the electrode can be lightened, and blackening due to evaporation of the electrode material can be suppressed. Note that the effects described here are not necessarily limited, and may be any of the effects described in this specification or effects different from them.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a short arc type discharge lamp according to an embodiment. The short arc type discharge lamp 10 is a discharge lamp that can be used as a light source of an exposure apparatus for forming a pattern, and includes a discharge tube (light emitting tube) 11 made of transparent quartz glass. In the discharge tube 11, a cathode 20 and an anode 30 are arranged to face each other at a predetermined interval.

[0010] On both sides of the spherical discharge tube 11, sealing tubes 12a and 12b made of quartz glass are integrally provided with the discharge tube 11 so as to face each other, and both ends of the sealing tubes 12a and 12b are closed by caps 13a and 13b. Inside the sealing tubes 12a and 12b, conductive electrode support rods 14a and 14b for supporting the metallic cathode 20 and anode 30 are disposed, and are connected to conductive lead rods 16a and 16b via metal foils 15a and 15b such as metal rings (not shown) and molybdenum. The sealing tubes 12a and 12b are welded to a glass tube (not shown) provided inside the sealing tubes 12a and 12b, whereby a discharge space filled with mercury and a rare gas is sealed. The discharge lamp 10 is arranged along the vertical direction such that the anode 30 is on the upper side and the cathode 20 is on the lower side.

[0011] The lead rods 16a and 16b are connected to an external power supply unit, and a voltage is applied between the cathode 20 and the anode 30 via a metal member, a metal foil, and the electrode support rods 14a and 14b. When power is supplied to the discharge lamp 10, an arc discharge occurs between the electrodes, and a spectral line (ultraviolet light) by mercury is emitted.

[0012] Around the discharge lamp 10, a reflecting mirror (condensing mirror) (not shown) that is a rotational ellipsoid is arranged to form an illumination device. When the lamp is lit, the light emitted from the discharge lamp 10 is reflected by the reflecting mirror. The reflected light is condensed at the secondary focus and guided to the irradiation object through an illumination optical system (not shown) or the like. For example, when the illumination device is provided in an exposure device, the photosensitive surface of the substrate is irradiated with light.

[0013] FIG. 2 is an enlarged cross-sectional view of the anode 30 of the discharge lamp shown in FIG. 1. 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 both the cathode 20 and the anode 30. The anode 30 has a body member 31 and a lid member 32. An electrode support rod 14b is fitted to the lid member 32.

[0014] The body member 31 is, for example, a cylindrical member having one end surface closed and the other end surface open, that is, having a concave portion around the central axis. The 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 a metal such as tungsten or molybdenum or an alloy thereof. An internal space S sealed in the body member 31 is formed by closing the open end surface of the concave portion with the lid member 32.

[0015] Here, a solid heat transfer body 33 is provided in the internal space S. 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 lid member 32 that constitute the internal space S, and is made of an inorganic substance and / or an organic substance other than a metal. The inorganic substance and / or the organic substance other than a metal is, for example, any one of oxides, carbides, salts, or a combination thereof, or is resin-based. Specifically, tungsten oxide, bismuth oxide, silicon oxide, calcium carbide, magnesium fluoride (MgF2), calcium fluoride (CaF2), fluororesin, silicone resin, etc. can be mentioned as the material of the heat transfer body 33. Hereinafter, in the present embodiment, a case where magnesium fluoride or calcium fluoride is used for the heat transfer body 33 will be described as an example.

[0016] When the electrode materials of the body member 31 and the lid member 32 are 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). The non-metallic magnesium fluoride and calcium fluoride have a lower density than the tungsten of the electrode material.

[0017] Therefore, the anode 30 enclosing the heat transfer body 33 made of non-metal can be made lighter compared to the anode in which the internal space S is occupied by metal. As shown in FIG. 1, since the discharge lamp has a cantilever structure, by reducing the weight of the electrodes, cracks in the sealing tube and breakage (fracture) of the electrode support rods can be prevented. Further, since the heat transfer body 33 is enclosed in the internal space S, the heat capacity is increased compared to a hollow electrode as in the conventional case, and the possibility of blackening can be reduced. Furthermore, since the heat transfer body 33 has a heat transfer function, heat can be transported to the support rod 14b side, contributing to a temperature drop at the tip of the electrode (anode 30).

[0018] Also, the boiling point of the heat transfer body 33 is lower than the boiling points of the electrode materials of the body member 31 and the lid member 32 constituting the internal space S, and it boils when the discharge lamp 10 is lit. When the electrode materials of the body member 31 and the lid member 32 are tungsten, the melting point is (about 3410 °C) and the boiling point is (about 5555 °C). The melting point of magnesium fluoride is (about 1263 °C) and the boiling point is (about 2260 °C). The melting point of calcium fluoride is (about 1418 °C) and the boiling point is (about 2533 °C). The melting point and boiling point of the heat transfer body 33 composed of these inorganic compounds are lower than those of the electrode materials. That is, the heat transfer body 33 has a lower boiling point than the electrode materials (tungsten or molybdenum) constituting the internal space S, and is a heat transfer body that boils at least when the discharge lamp is lit. When the heat transfer body vaporizes during lighting, the temperature of the electrode further decreases due to the heat of vaporization and boiling heat transfer.

[0019] When the discharge lamp is lit, the temperature at the tip of the anode 30 becomes extremely high (for example, 2000°C to 2500°C). When the heat transfer medium 33 is magnesium fluoride or calcium fluoride, as the temperature of the anode 30 rises after lighting, the heat transfer medium 33 changes from a solid to a liquid and further boils. The boiling point is the temperature at which the liquid changes to a gas. In the lit state, the heat transfer medium 33 exists in both liquid and gas states. The heat transfer medium 33 is a heat transfer medium 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 transitions within the internal space S. Therefore, by transporting the heat generated at the tip of the anode 30 to the side of the electrode support rod 14b of the anode 30 by three heat transfer methods: convection of the liquid, latent heat of vaporization, and boiling heat transfer, the temperature rise at the tip of the anode 30 can be suppressed, and the evaporation of tungsten in the anode 30 can be suppressed.

[0020] Figure 3 shows a modified example (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 its protruding height toward the lid member 32 side and is not configured by a sudden deformation such as a protrusion. By this convex curved surface 34, the stress generated during the phase change of the heat transfer medium 33 is relaxed. That is, by forming a gentle convex curved surface 34 on the bottom surface, the force attempting to locally deform the bottom surface can be relaxed, and stress concentration can be avoided. In particular, since the internal pressure of the internal space S increases when the heat transfer medium 33 boils, for the present invention that actively utilizes boiling heat transfer, the convex curved surface 34 that can avoid stress concentration is an advantageous configuration. Also preferably, the entire bottom surface has a curved surface, and it is good to make the vicinity of the center convex.

[0022] Since there is a space in the internal space S where the heat transfer body 33 does not exist, an inert gas (rare gas) is enclosed in this space. The rare gas is any one of argon, krypton, and xenon. These rare gases have different thermal conductivities. The relationship of the magnitudes of the thermal conductivities is (xenon < krypton < argon). Depending on the thermal conductivity of the rare gas, the amount of heat transferred from the rare gas to the electrode support rod 14b side changes, so the temperature in the internal space S also changes. For example, in the case of a rare gas with a high thermal conductivity, a large amount of heat is transferred to the electrode support rod 14b side, so the temperature in the internal space S can be suppressed. In a state where the temperature in the internal space S is low, a rare gas with a high thermal conductivity easily conducts heat from the heat transfer body 33. The heat transfer body from which heat has been taken away becomes less likely to boil accordingly. That is, the time until boiling becomes longer. Thus, when it is desired to shorten the time until the heat transfer body 33 boils, a rare gas with a low thermal conductivity is enclosed, and when it is desired to lengthen the time until boiling, a rare gas with a high thermal conductivity is enclosed. By changing the type of rare gas to be enclosed, the time until the heat transfer body 33 boils can be changed.

[0023] For example, when it is desired to boil the heat transfer body 33 early from the initial lighting stage to suppress the temperature rise of the anodes 30 and 30A, a rare gas with a low thermal conductivity is enclosed. On the other hand, if a sudden increase in the internal pressure of the internal space S occurs due to the sudden boiling of the heat transfer body 33, there is a possibility of damaging the anodes 30 and 30A. Therefore, a rare gas with a high thermal conductivity is enclosed and adjusted to lengthen the time until boiling.

[0024] The manufacturing method of the anode 30 shown in FIG. 2 will be described. The joint surface is the polished opening-side end face of the body member 31 having a recess formed around the central axis made of tungsten or the like. Similarly, the lower end face of the disk-shaped lid member 32 made of tungsten or the like is polished to form a joint surface.

[0025] Next, a heat transfer body 33 made of an inorganic substance and / or an organic substance other than a metal is placed in the recess (internal space S) formed in the body member 31. Next, the lid member 32 is placed over the open end face of the body member 31 to close the opening. Then, the body member 31 and the lid member 32 are sandwiched between pressure electrodes via a block and energized and heated while applying a predetermined pressure. By this joining process, the body member 31 and the lid member 32 are solid-phase joined. Note that an intermediate member may be inserted between the body member 31 and the lid member 32. Next, each of the solid-phase joined body member 31 and lid member 32 is machined by cutting along a predetermined cutting line to obtain the final electrode shape. As a result, an anode 30 in which a heat transfer body 33 is enclosed in an internal space S, as shown in FIG. 2, is formed. Note that when an inert gas is introduced into the internal space S, it may be introduced in a gaseous state or in a state solidified by liquid nitrogen.

[0026] As described above, one embodiment of the present technology has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. For example, the present invention can be applied to a short arc type xenon lamp that does not contain mercury or a discharge lamp other than the short arc type. In the case of an organic heat transfer body, it can also be applied to a small discharge lamp to which power of 1 kW or less is input. Further, although it is preferable that the heat transfer body exists in both liquid and gaseous states when the discharge lamp is lit, this is not necessarily the case. That is, the temperature of the electrode can be lowered only by the heat transfer function due to the convection of the molten heat transfer body. In addition, the configurations, methods, steps, shapes, materials, numerical values, etc. described in the above embodiments are merely examples, and different configurations, methods, steps, shapes, materials, numerical values, etc. may be used as necessary.

Explanation of Reference Numerals

[0027] 10... Discharge lamp, 11... Discharge tube, 12a, 12b... Sealing tube, 13a, 13b... Base, 14a, 14b... Electrode support rod, 20... Cathode, 30... Anode, 31... Body member, 32... Lid member, 33... Heat transfer body, S... Internal space

Claims

1. A discharge tube, and a pair of electrodes disposed opposite to each other inside the discharge tube, wherein at least one of the electrodes has an internal space, and a heat transfer body made of an inorganic substance and / or an organic substance other than a metal, having a density lower than that of the electrode material constituting the internal space, is provided in the internal space, and the boiling point of the heat transfer body is lower than the boiling point of the electrode material constituting the internal space, and the heat transfer body boils when the discharge lamp is lit. A discharge lamp characterized by this.

2. The discharge lamp according to claim 1, wherein the heat transfer body exists in both gaseous and liquid states when the discharge lamp is lit.

3. The discharge lamp according to claim 1 or 2, wherein the heat transfer body is any one of oxides, carbides, salts, or a combination thereof.

4. The discharge lamp according to any one of claims 1 to 3, wherein the heat transfer body is magnesium fluoride or calcium fluoride.

5. The discharge lamp according to any one of claims 1 to 4, wherein the bottom surface of the internal space has a curved surface, and the vicinity of the center of the curved surface is convex.

6. The discharge lamp according to claim 5, wherein the entire bottom surface is formed into a curved surface, and the vicinity of the center of the curved surface is convex.

7. A discharge tube, and a pair of electrodes disposed opposite to each other inside the discharge tube, wherein at least one of the electrodes has an internal space, and at least one of argon, krypton, and xenon and a heat transfer body made of an inorganic substance and / or an organic substance other than a metal are enclosed in the internal space, and the boiling point of the heat transfer body is lower than the boiling point of the electrode material constituting the internal space, and the heat transfer body boils when the discharge lamp is lit. A discharge lamp characterized by this. Claim 8 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 in the recess of the body member, there is placed a heat transfer medium made of an inorganic substance and / or an organic substance other than metal, having a boiling point lower than the boiling point of the electrode material constituting the recess, and boiling when the discharge lamp is lit. A method for manufacturing an electrode for a discharge lamp, characterized in that the body member or an intermediate member joined to the body member is solid-phase bonded to the lid member.

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