JP7692778B2 - Discharge lamp and method of manufacturing electrode for discharge lamp - Google Patents

Description

The present invention relates to a discharge lamp used in exposure devices and the like, and in particular to a short arc type discharge lamp and a method for manufacturing electrodes for discharge lamps.

Large short-arc discharge lamps are becoming increasingly high-powered in order to improve the production efficiency of semiconductor and liquid crystal manufacturing. If the electrode structure becomes larger as the power increases, the weight of the electrode puts a strain on the sealing part, and there is a risk of the glass member being damaged. As a countermeasure, Patent Document 1 describes a hollow electrode that is lightweighted by forming a recess (hole) on the back of the electrode.

JP 2008-305782 A

However, forming a recess (hole) reduces the volume of the electrode, lowering the electrode's heat capacity, and excessive temperature rise can cause the tungsten that makes up the electrode to evaporate and adhere to the wall of the light-emitting tube, resulting in blackening and a shortened lifespan.

Therefore, the object of the present invention is to provide a discharge lamp and a method for manufacturing electrodes for a discharge lamp that are lightweight and have a reduced risk of blackening.

The present invention includes a discharge tube and
A pair of electrodes disposed opposite each other within the discharge tube,
At least one of the electrodes has an interior space;
A heat transfer body having a lower density than the electrode material constituting the internal space and made of an inorganic material and/or an organic material other than metal is provided in the internal space;
The boiling point of the heat conductor is lower than the boiling point of the electrode material constituting the internal space, and the discharge lamp is characterized in that it boils when the discharge lamp is turned on.
The present invention includes a discharge tube and
A pair of electrodes disposed opposite each other within the discharge tube,
At least one of the electrodes has an interior space;
At least one of argon, krypton, and xenon and a heat transfer body made of an inorganic material and/or an organic material other than metal are enclosed in the internal space,
The boiling point of the heat conductor is lower than the boiling point of the electrode material constituting the internal space, and the discharge lamp is characterized in that it boils when the discharge lamp is turned on.
The present invention also provides a method for producing a discharge lamp comprising the steps of: forming a body member having a recess around a central axis; and forming a cover member for covering the recess of the body member; and placing a heat transfer body in the recess of the body member, the heat transfer body being made of an inorganic material and/or an organic material other than metal, the heat transfer body having a boiling point lower than the boiling point of the electrode material constituting the recess , and boiling when the discharge lamp is turned on;
The method for manufacturing an electrode for a discharge lamp is characterized in that a body member or an intermediate member to be joined to the body member is solid-state joined to a lid member.

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

FIG. 1 is a diagram showing a schematic diagram of a short arc type 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 modified example of an embodiment of the present invention.

One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a short arc type discharge lamp according to one embodiment. The short arc type discharge lamp 10 is a discharge lamp that can be used as a light source for an exposure device that forms a pattern, and includes a discharge tube (light emitting tube) 11 made of transparent quartz glass. A cathode 20 and an anode 30 are arranged opposite each other with a predetermined distance between them in the discharge tube 11.

Quartz glass sealing tubes 12a and 12b are integrally provided on both sides of the bulb-shaped discharge tube 11 so as to face each other, and both ends of the sealing tubes 12a and 12b are sealed by bases 13a and 13b. Conductive electrode support rods 14a and 14b supporting metallic cathode 20 and anode 30 are provided inside the sealing tubes 12a and 12b, and are connected to conductive lead rods 16a and 16b via metal rings (not shown) and metal foils 15a and 15b such as molybdenum. The sealing tubes 12a and 12b are fused to glass tubes (not shown) provided inside 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 supply, and a voltage is applied between the cathode 20 and the anode 30 via the metal member, the 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 mercury emits bright lines (ultraviolet light).

The illumination device is configured by arranging a spheroidal reflecting mirror (light-collecting mirror) (not shown) around the discharge lamp 10. When the lamp is turned on, the light emitted from the discharge lamp 10 is reflected by the reflecting mirror. The reflected light is collected at a secondary focus and guided to an object to be illuminated via an illumination optical system (not shown). For example, if the illumination device is provided in an exposure device, the light is irradiated onto the photosensitive surface of a substrate.

Figure 2 is an enlarged cross-sectional view of the anode 30 of the discharge lamp shown in Figure 1. In the following explanation, an example in which the present invention is applied to the anode is 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 cover member 32. The electrode support rod 14b is fitted into the cover member 32.

The body member 31 is tubular, e.g., cylindrical, with one end face closed and the other end face open. In other words, it has a recess around the central axis. The lid member 32 is diffusion bonded to the open end face 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 of these. 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.

In this embodiment, 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 materials of the body member 31 and the cover member 32 that constitute the internal space S, and is made of inorganic and/or organic substances other than metals. The inorganic and/or organic substances other than metals are, for example, oxides, carbides, salts, or combinations of these, or resins. Specifically, tungsten oxide, bismuth oxide, silicon oxide, calcium carbide, magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), fluororesin, silicon resin, and the like are examples of materials for the heat transfer body 33. In the following, in this embodiment, a case where magnesium fluoride or calcium fluoride is used for the heat transfer body 33 will be described as an example.

When the electrode material of the body member 31 and the cover 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). The non-metallic magnesium fluoride and calcium fluoride have a lower density than the electrode material tungsten.

Therefore, the anode 30 in which the heat transfer body 33 made of a material other than metal is enclosed can be made lighter than an anode in which the internal space S is occupied by metal. As shown in FIG. 1, a discharge lamp has a cantilever structure, so by making the electrode lighter, it is possible to prevent cracks in the sealed tube and damage (breakage) of the electrode support rod. In addition, 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, it can transport heat to the support rod 14b side, contributing to a decrease in the temperature of the tip of the electrode (anode 30).

The boiling point of the heat transfer body 33 is lower than that of the electrode material of the body member 31 and the cover member 32 that 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 cover member 32 is tungsten, the melting point is (approximately 3410°C) and the boiling point is (approximately 5555°C). The melting point of magnesium fluoride is (approximately 1263°C) and the boiling point is (approximately 2260°C). The melting point of calcium fluoride is (approximately 1418°C) and the boiling point is (approximately 2533°C). The melting point and boiling point of the heat transfer body 33 made of these inorganic compounds are lower than those of the electrode material. In other words, the heat transfer body 33 is a heat transfer body that has a lower boiling point than the electrode material (tungsten or molybdenum) that constitutes the internal space S, and boils at least when the discharge lamp is lit. When the heat transfer material evaporates during operation, the temperature of the electrodes drops further due to the heat of vaporization and boiling heat transfer.

When the discharge lamp is turned on, the temperature of the tip of the anode 30 becomes very high (for example, 2000°C to 2500°C). If the heat conductor 33 is magnesium fluoride or calcium fluoride, the heat conductor 33 changes from a solid to a 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 lit state, the heat conductor 33 exists in both a liquid and a gas state. The heat conductor 33 is a heat conductor whose boiling point is higher than the minimum temperature of the internal space S and lower than the maximum temperature of the internal space S, and repeats phase transitions within the internal space S. Therefore, by using the three heat transfer methods of liquid convection, vaporization heat, and boiling heat transfer, the heat generated at the tip of the anode 30 can be transported to the electrode support rod 14b side of the anode 30, thereby suppressing the temperature rise at the tip of the anode 30 and suppressing the evaporation of tungsten from the anode 30.

FIG. 3 shows a modified example (anode 30A) of the anode 30 of the present invention. This anode 30A has a convex curved surface 34 in which 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 configured with a sudden deformation like a protrusion. This convex curved surface 34 relieves the stress generated during the phase change of the heat transfer body 33. That is, by forming a gentle convex curved surface 34 on the bottom surface, the force that locally deforms the bottom surface is relieved, and stress concentration can be prevented. In particular, since the internal pressure of the internal space S increases when the heat transfer body 33 boils, the convex curved surface 34 that can avoid stress concentration is an advantageous configuration for the present invention that actively utilizes boiling heat transfer. In addition, it is preferable that the entire bottom surface has a curved surface and the center is convex.

In the internal space S, there is a space where the heat transfer body 33 does not exist, so an inert gas (rare gas) is sealed in this space. The rare gas is either argon, krypton, or xenon. These rare gases have different thermal conductivities. The relationship between 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, if the rare gas has a high thermal conductivity, a lot of heat is transferred to the electrode support rod 14b side, so the temperature in the internal space S is suppressed. When the temperature in the internal space S is low, the rare gas with a high thermal conductivity easily transfers heat from the heat transfer body 33. The heat transfer body from which heat has been removed becomes less likely to boil. In other words, it takes longer to boil. In this way, if you want to shorten the time it takes for the heat transfer body 33 to boil, you can fill it with a rare gas that has a low thermal conductivity, and if you want to lengthen the time it takes for the heat transfer body 33 to boil, you can fill it with a rare gas that has a high thermal conductivity. Depending on the type of rare gas filled in, you can change the time it takes for the heat transfer body 33 to boil.

For example, if it is desired to boil the heat transfer body 33 early on in the lighting process to suppress the temperature rise of the anodes 30 and 30A, a rare gas with low thermal conductivity is enclosed. On the other hand, if a sudden boiling of the heat transfer body 33 causes a sudden increase in the internal pressure of the internal space S, there is a possibility that the anodes 30 and 30A may be damaged, so a rare gas with high thermal conductivity is enclosed and adjustments are made to lengthen the time until boiling.

The manufacturing method of the anode 30 shown in Figure 2 will be described. The open end surface of the body member 31, which is made of tungsten or the like and has a recess formed around its central axis, is polished to form a joining surface. Similarly, the lower end surface of the disk-shaped cover member 32, which is made of tungsten or the like, is polished to form a joining surface.

Next, a heat transfer body 33 made of an inorganic material and/or an organic material other than metal is placed in the recess (internal space S) formed in the body member 31 .
Next, the lid member 32 is placed on the open end face of the body member 31 to close the opening. Then, the top and bottom of the body member 31 and the lid member 32 are sandwiched between pressure electrodes via a block, and heated by applying an electric current while applying a predetermined pressure. This joining process results in a solid-state joining of the body member 31 and the lid member 32. An intermediate member may be inserted between the body member 31 and the lid member 32.
Next, the solid-phase-joined body member 31 and cover member 32 are each cut along a predetermined cutting line to form a final electrode shape. As a result, an anode 30 is formed in which a heat transfer body 33 is sealed in an internal space S, as shown in Fig. 2. When an inert gas is introduced into the internal space S, the inert gas may be introduced in a gaseous state or in a state solidified with liquid nitrogen.

Although one embodiment of the present technology has been specifically described above, the present invention is not limited to the above-mentioned 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, and a discharge lamp other than the short-arc type. In the case of an organic heat transfer material, the present invention can also be applied to a small discharge lamp to which a power of 1 kW or less is input. In addition, it is preferable that the heat transfer material exists in both a liquid and a gas state when the discharge lamp is turned on, but this is not necessarily the case. In other words, the temperature of the electrode can be reduced only by the heat transfer function due to convection of the molten heat transfer material. In addition, the configurations, methods, processes, shapes, materials, and values given in the above-mentioned embodiment are merely examples, and different configurations, methods, processes, shapes, materials, and values may be used as necessary.

10: discharge lamp, 11: discharge tube, 12a, 12b: sealed tube,
13a, 13b... metal caps, 14a, 14b... electrode support rods, 20... cathode,
30: anode; 31: body member; 32: cover member; 33: heat transfer body;
S...Internal space

Claims (8)

A discharge tube;
A pair of electrodes disposed opposite each other within the discharge tube,
At least one of the electrodes has an interior space;
A heat transfer body having a lower density than the electrode material constituting the internal space and made of an inorganic material and/or an organic material other than metal is provided in the internal space ;
A discharge lamp characterized in that 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 turned on . 2. The discharge lamp according to claim 1 , wherein the heat conductor exists in both a gaseous and liquid state when the discharge lamp is turned on. 3. The discharge lamp according to claim 1 , wherein the heat conductor is any one of an oxide, a carbide, and a salt, or a combination of these. 4. The discharge lamp according to claim 1 , wherein the heat conductor is made of magnesium fluoride or calcium fluoride. 5. The discharge lamp according to claim 1 , wherein the bottom surface of the internal space has a curved surface, and a central portion of the curved surface is convex. 6. The discharge lamp according to claim 5 , wherein the entire bottom surface is curved, and the central portion of the curved surface is convex. A discharge tube;
A pair of electrodes disposed opposite each other within the discharge tube,
At least one of the electrodes has an interior space;
The internal space is filled with at least one of argon, krypton, and xenon, and a heat transfer body made of an inorganic material and/or an organic material other than metal ,
A discharge lamp characterized in that 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 turned on . a body member having a recess formed around a central axis and a cover member for covering the recess of the body member, and a heat transfer body made of an inorganic material and/or an organic material 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 turned on, is placed in the recess of the body member;
A method of manufacturing an electrode for a discharge lamp, comprising solid-state bonding the body member or an intermediate member to be bonded to the body member and the lid member.

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