JP2011070823A - Discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To constitute an electrode with various solids assembled therein, having electrode characteristics uninfluenced by such a constitution. <P>SOLUTION: In this short arc type discharge lamp, a metal member 40 of high melting point is SPS-joined to a metal member 50 of high thermal conductivity, to constitute an anode 30. A junction face S is formed along a perpendicular to an electrode axis X, i.e. an anode cross-section radial direction, by joining the truncated cone shaped metal member 40 to the columnar metal member 50. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a discharge lamp used for an exposure apparatus or the like, and more particularly to an electrode structure of a high output discharge lamp such as a short arc type discharge lamp.

  In a short arc type discharge lamp, an object to be exposed such as a substrate is irradiated with high-intensity light. In order to increase the size of the object to be exposed and further improve the throughput, it is required to increase the output of the discharge lamp, and accordingly, the rated power consumption must be increased. When the power is increased, the conventional electrode structure affects the electron emission, heat emission, durability, and the like. Therefore, an electrode structure in which different metals such as crystals and types are combined is required.

  For example, when the rated power is increased, the current density at the cathode tip is large, so that the electrode wears up, and the bright spot of the arc discharge moves, resulting in an unstable discharge. In order to stabilize the arc discharge, an electrode structure is known in which the tip of the cathode is melted by a direct current discharge treatment device and the crystal structure of the tip is coarsened (see Patent Document 1).

  Further, when the rated power is increased, the amount of current flowing between the electrodes of the lamp increases and the electrode temperature rises. In particular, the anode tip becomes hot and the anode tip melts and evaporates over time. As a result, the luminous efficiency is reduced due to unstable arc discharge and adhesion of the metal inside the tube due to anode melting, and the lamp life is reduced due to electrode consumption.

  In order to prevent such electrode melting due to overheating, an electrode structure is known in which a metal material having a higher thermal conductivity and a lower melting point than that of a metal electrode body is enclosed in the interior space of the body (see Patent Document 2). There, a lid member is welded to a bottomed cylindrical metal member to form an electrode provided with a sealed space.

Japanese Patent Laid-Open No. 2002-110083 JP 2004-259644 A

  Even if the crystal structure and metal composition in the vicinity of the electrode surface are changed, the overall electrode characteristics such as thermal conductivity, conductivity, and durability cannot be greatly improved. In particular, in the case of a high-power discharge lamp, a great improvement in heat release characteristics cannot be expected. However, when an electrode is configured by combining the same type or different types of members, the bonding state between the members affects the durability, thermal conductivity, and the like.

  For example, when a metal member is joined by welding such as beam welding to form an electrode, the diameter of the metal crystal is enlarged along the joining surface, and the diameter is not uniform. Further, the change in the crystal diameter along the electrode axis direction becomes discontinuous, and a crystal boundary appears at the junction. For this reason, the electrode strength decreases at the joint portion.

  Also, if the crystal size is non-uniform and the crystal size along the electrode axis direction is discontinuous, the heat conduction characteristics along the electrode axis direction will be uniform over the entire joint surface. The heat transport inside the electrode does not work well. As a result, a local overheating state is generated inside the electrode, which accelerates electrode consumption.

  Therefore, it is required to configure the electrode by combining a plurality of members so as not to adversely affect the electrode characteristics.

  The discharge lamp of the present invention includes a discharge tube and a pair of electrodes disposed in the discharge tube, and is configured as, for example, a short arc type discharge lamp (particularly a high-power discharge lamp). At least one electrode of the discharge lamp is configured by an electrode obtained by solid-phase bonding a plurality of solid members, and at least one solid member is made of a metal member. Regarding the solid phase bonding method, it is preferable to apply diffusion bonding which is one of solid phase bonding methods using thermal diffusion, electric field diffusion, etc. In this case, by a discharge plasma sintering method (SPS sintering method) or the like. Solid members are joined together.

  In the present invention, the solid-state members prepared separately are solid-phase bonded, so that the structure of the metal crystal is excellent in terms of durability and thermal conductivity at the bonding surface. The diameter of the metal crystal is substantially uniform along the joint surface between the solid members, and the crystal structure along the direction perpendicular to the joint surface is inclined near the joint surface. That is, the crystal is stepwise and continuous in the vicinity of the joint surface, and there is no sudden crystal structure change.

  Even in the vicinity of the joint surface, the conductivity, thermal conductivity, and durability are stable, so heat conductivity, durability, etc. are locally reduced, there is no risk of sudden partial electrode consumption, and heat transfer An electrode structure having excellent characteristics can be obtained by selecting and bonding different or similar solid members so as to improve the properties, electron emission characteristics, durability, and the like.

  What is necessary is just to determine the combination of a solid member according to the objectives, such as a heat transport effect and durability, and what is necessary is just to determine an electrode shape according to the objective. For example, in a short arc type discharge lamp or the like, the electrode is constituted by a truncated cone-shaped electrode tip and a cylindrical electrode body, but the joint surface is a combination of solid members, the electrode tip according to the shape, Or it is located in the electrode body part.

  As a combination of solid members, it is also possible to join a solid member constituting a part of the electrode tip portion and the electrode body portion and a solid member constituting the remaining electrode body portion, and the electrode body portion and the electrode tip portion. The solid member constituting a part of the part and the solid member constituting the remaining electrode tip can be joined. Alternatively, the electrode tip portion and the electrode body portion may be formed of separate solid members and joined.

  Considering the enhancement of the heat transport effect along the electrode axis direction, solid members having different thermal conductivities are joined, and the electrode body on the electrode support rod side is constituted by the solid members having relatively high thermal conductivities. A high melting point solid member such as pure tungsten can be configured as the electrode portion. On the other hand, it is possible to form a free electrode shape by joining solid members, and it is also possible to form electrodes by joining solid members of the same type and the same characteristics.

  The number of solid members constituting the electrode is arbitrary, and is constituted by, for example, a first solid member having an electrode tip surface and a second solid member solid-phase bonded to the first solid member.

  When the entire electrode tip is formed of a single solid member, the first solid member can be formed by a truncated cone-shaped electrode tip and a columnar joint having the same diameter as the second solid member. . With such an electrode structure, it is possible to design the structure of the body part relatively freely, such as forming an internal space in the body part and forming a heat radiation fin in the circumferential direction.

  On the other hand, when only a part of the electrode tip portion is constituted by one solid member, the second solid member is constituted by the body portion and the frustoconical electrode joining portion joined to the first solid member. Such an electrode structure enables a design that changes only the characteristics of the electrode tip.

  Usually, the electrode shape is symmetric about the electrode axis, and heat and current move along the electrode axis. Therefore, it is desirable to dispose the solid member in the right place and in the appropriate material along the electrode axis, and the solid member is preferably solid-phase bonded so that the bonding surface is formed along the direction perpendicular to the electrode axis. On the other hand, for example, when the electrode is cut and formed after solid-phase bonding, the bonding surface is formed along the direction perpendicular to the electrode axis, so that the electrode stability during operation is excellent.

  For example, in a discharge lamp in which the anode is disposed vertically upward, when a solid member having high thermal conductivity is joined to an electrode tip such as tungsten, the distance in the electrode axis direction is equal from the electrode tip surface to the joint surface. Therefore, there is no variation in the heat transport along the electrode axis, the temperature distribution during lamp operation is a symmetric distribution around the electrode axis, and electrode wear due to local overheating does not occur.

  In consideration of preventing the electrode from overheating, it is desirable to increase the heat release effect together with the heat transport. If the contact surfaces of the solid members to be joined are not completely flat, gaps are partially generated along the joining surfaces. If heat is released from the gap while the lamp is lit, electrode overheating can be prevented. Therefore, it is preferable to solid-phase join solid members having contact surfaces that form gaps along the joining surfaces. In particular, a wedge may be formed near the electrode surface, and a gap may be provided to form a fin shape on the electrode surface.

  An electrode for a discharge lamp according to the present invention is an electrode disposed in a discharge tube of a discharge lamp, and includes a first solid member having an electrode tip surface and a second solid member that is solid-phase bonded to the first solid member. , At least one is a metal member, the crystal diameter of the metal member is substantially uniform along the joint surface between the first and second solid members, and the crystal structure along the perpendicular direction of the joint surface is near the joint surface It is characterized by being inclined.

  In the method for manufacturing an electrode for a discharge lamp according to the present invention, a first solid member having an electrode tip surface is formed, a second solid member to be joined to the first solid member is formed, and at least one of them is a metal member. The contact surfaces of the first solid member and the second solid member are solid-phase bonded to each other.

  According to the present invention, an electrode in which various solids are combined can be configured without affecting the electrode characteristics.

It is the top view which showed typically the short arc type discharge lamp which is 1st Embodiment. It is a schematic sectional drawing of an anode. It is the figure which showed the discharge plasma sintering apparatus. It is an anode sectional view of a discharge lamp in a 2nd embodiment. It is the figure which showed the electron micrograph which showed the joining surface state of the anode by SPS joining. It is the figure which showed the electron micrograph which showed the joining surface state of the anode by electron beam joining.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view schematically showing the short arc type discharge lamp according to the first embodiment.

  The short arc type discharge lamp 10 is a discharge lamp that can be used as a light source of an exposure apparatus (not shown) for pattern formation, and includes a transparent quartz glass discharge tube (light emitting tube) 12. A cathode 20 and an anode 30 are opposed to the discharge tube 12 with a predetermined interval.

  On both sides of the discharge tube 12, quartz glass sealing tubes 13A and 13B are provided integrally with the discharge tube 12 so as to face each other, and both ends of the sealing tubes 13A and 13B are formed by caps 19A and 19B. It is blocked. The discharge lamp 10 is arranged along the vertical direction so that the anode 30 is on the upper side and the cathode 20 is on the lower side. As will be described later, the anode 30 is composed of two metal members 40 and 50.

  Inside the sealing tubes 13A and 13B, conductive electrode support rods 17A and 17B for supporting the metallic cathode 20 and the anode 32 are disposed, and a metal ring (not shown), a metal foil 16A such as molybdenum, etc. , 16B to the conductive lead rods 15A, 15B, respectively. The sealing tubes 13A and 13B are welded to glass tubes (not shown) provided in the sealing tubes 13A and 13B, so that the discharge space S in which mercury and a rare gas are sealed is sealed. The

  The lead rods 15A and 15B are connected to an external power source (not shown), and are connected between the cathode 20 and the anode 30 via the lead rods 15A and 15B, the metal foils 16A and 16B, and the electrode support rods 17A and 17B. A voltage is applied to. When electric power is supplied to the discharge lamp 10, arc discharge occurs between the electrodes, and a bright line (ultraviolet light) due to mercury is emitted.

  FIG. 2 is a schematic cross-sectional view of the anode.

  The anode 30 has an electrode structure in which metal members 40 and 50 are joined. The metal member 40 has the same diameter as the truncated cone-shaped portion 40A including the electrode tip surface 40S and the columnar metal member 50, and is a metal member. 50 is formed by a columnar portion 40B joined to 50. The metal member 40 is made of a high melting point such as pure tungsten or an alloy containing tungsten as a main component. On the other hand, the columnar metal member 50 is a metal having a higher thermal conductivity than the metal member 40 (for example, pure tungsten, molybdenum, tantalum having a getter effect, aluminum nitride having a high thermal conductivity, carbon material, etc. that can be formed into a large shape). It is comprised with the metal containing.

  The metal members 40 and 50 are diffusion-bonded according to a discharge plasma sintering (SPS sintering) method. Therefore, a diffusion layer is formed in the vicinity of the bonding surface S formed along the direction perpendicular to the electrode axis X. The diameter of the metal crystal is substantially uniform along the bonding surface S. Further, the crystal structure is inclined along the electrode axis X. Due to the tilting, the crystal diameter changes continuously and stepwise along the electrode axis X.

  By forming such a diffusion layer sandwiching the joint surface S, there is no variation along the joint surface S in terms of heat conduction characteristics and conductivity. While heat is transported from the electrode front end surface 40S (1000 ° C. or higher) to the electrode support rod 17B, the temperature distribution inside the anode is symmetrical with respect to the electrode axis X, The transport is not affected by the joint surface S.

  Further, the contact surfaces of the metal members 40 and 50 are not completely flat surfaces, but wedge-shaped gaps (not shown) are formed along the peripheral edge of the bonding surface S, that is, near the surface of the anode 30. Therefore, heat is released from the anode 30 at the bonding surface 30.

  FIG. 3 is a view showing a discharge plasma sintering apparatus.

  In the spark plasma sintering method, pulsed electric energy is directly applied to the particle gaps of the green compact or compact, and the high temperature energy of the discharge plasma generated instantaneously by the spark discharge phenomenon is applied to thermal diffusion, electric field diffusion, etc. It is a sintering method.

  3 includes a vacuum chamber 110, and a metal having the shape shown in FIG. 2 between an upper punch 120A, a lower punch 120B, and a graphite die 140 provided in the vacuum chamber 110. The members 40 and 50 are installed with their contact surfaces in contact with each other. The metal members 40 and 50 are previously formed by metal processing such as cutting.

  The upper punch 120A and the lower punch 120B made of graphite are connected to the upper punch electrode 130A and the lower punch electrode 130B, respectively. After the inside of the apparatus is evacuated, a voltage is applied between the upper punch 120A and the lower punch 120B by the pulse power source 180.

  Along with energization, a pressure mechanism (not shown) applies pressure between the upper punch 120A and the lower punch 120B. After the temperature is instantaneously raised to a predetermined sintering temperature by the discharge plasma by energization, the pressure is applied for a certain period of time. Thereby, an anode having the shape shown in FIG. 2 is obtained.

  As described above, according to the present embodiment, the anode 30 of the short arc type discharge lamp 10 is configured by SPS joining the high melting point metal member 40 and the metal member 50 having high thermal conductivity. By joining the frustoconical metal member 40 and the columnar metal member 50, the joint surface S is along the direction perpendicular to the electrode axis X, that is, the anode cross-sectional radial direction.

  While the lamp is lit, the vicinity of the electrode tip surface 40S becomes very hot, but the heat of the tip is effectively transported to the electrode support rod side by the metal member 50. Thereby, electrode consumption due to electrode overheating can be prevented. Further, the thermal conductivity, conductivity, and the like are generally the same at the bonding surface S perpendicular to the electrode axis X, and there is no variation. Therefore, heat transport along the electrode axis occurs throughout the anode, and there is no risk of local overheating inside the electrode.

  FIG. 4 is a cross-sectional view of the anode of the discharge lamp in the second embodiment.

  The anode 60 is an electrode formed by joining the metal member 70 and the metal member 80. The metal member 70 includes a columnar portion 72 and a truncated cone portion 74 having a recess 74S. The metal member 80 having the electrode tip surface 80 </ b> S is molded so as to fit into the metal member 70. On the bonding surface S by SPS bonding, the metal crystal is substantially uniform along the radial direction of the bonding surface and is inclined along the direction of the electrode axis X.

  The electrode may be manufactured by a diffusion bonding method other than the SPS sintering method. For example, the electrode can be manufactured by a diffusion bonding method such as hot pressing (HP) or hot isostatic pressing (HIP) that sinters while pressing. Furthermore, solid phase bonding methods (friction welding method, ultrasonic bonding method, etc.) other than the diffusion bonding method can be applied, and the crystal structure can be inclined by such a method. The cathode may also have an electrode structure in which a plurality of metal members are solid-phase bonded.

  The metal constituting the electrode is not limited to the filling metal, and the concave metal and the metal to be the lid may be joined so as to provide a sealed space inside. In this case, the joining surface is formed on the electrode support bar side away from the electrode tip side. Instead of solid-phase joining the metal that has been cut and formed, it may be cut and formed after solid-phase joining the metal. In this case, the cutting operation can be performed stably because the joining surface is along the direction perpendicular to the electrode axis. . On the other hand, in consideration of electrode characteristics other than heat transport, the joining surface may be formed along a direction other than the direction perpendicular to the electrode axis. Furthermore, the gap formed along the joint surface can be wedge-shaped to form the electrode surface in a fin shape, thereby further enhancing the heat radiation effect. On the other hand, it is also possible to configure so that no gap is provided on the joint surface.

  The number of metals composing the electrode is arbitrary, and the electrode may be composed of three or more metals. Further, the same kind of metal may be solid-phase bonded. Furthermore, solid bonding may be performed using one as a metal member and the other as a non-metallic member (such as tungsten and ceramics), and at least one of the members to be bonded may be a metal. Even in such a combination of members, the metal crystal diameter along the joint surface is substantially constant, and the crystal structure is inclined along the electrode axis direction.

  Next, examples of the present invention will be described. Here, the bonded surface state of the electrode formed by SPS bonding is compared with the bonded surface state formed by electron beam welding.

  FIG. 5A is a view showing an electron micrograph showing a state of a bonded surface of an anode by SPS bonding. FIG. 5B is a view showing an electron micrograph showing the state of the bonded surface of the anode by electron beam bonding.

  An electrode by SPS bonding is an electrode in which two metal members (body and tip) having different shapes and tungsten (WVMW W 15-40 ppmK) are bonded, and the frustoconical shape and circle shown in the first embodiment. It is composed of two columnar metals.

  Similarly, an electrode formed by electron beam bonding is composed of two metals. As an apparatus for performing SPS bonding, an SPS sintering apparatus manufactured by SPS Shintex Co., Ltd. was used, and bonding was performed under conditions of a sintering temperature of 1500 to 1700 ° C. and a vacuum atmosphere. On the other hand, an electron beam welding apparatus manufactured by NEC Control System Co., Ltd. was used for electron beam bonding.

  FIG. 5A shows a photograph of the bonding surface near the anode surface taken at the micro-order level, and the crystal structure of the electrode near the bonding surface is clarified. A joining surface is formed along the left-right direction of the paper surface, and a gap is formed in a wedge shape near the electrode surface along the joining surface. As shown in FIG. 5A, the diameter of the metal crystal along the bonding surface is substantially uniform, and the crystal structure is continuous along the electrode axis and is inclined.

  FIG. 5B also shows an enlarged photograph of the bonding surface near the anode surface. In FIG. 5B, it is clear that the metal particle diameter along the joining surface is non-uniform (see the vicinity of the electrode surface). Further, the crystal structure along the electrode axis direction (up and down direction in the drawing) also changes suddenly and intermittently and is not inclined.

  Thus, in the electrode formed by SPS sintering, the crystal structure is stabilized at the joint surface. As a result, the electrode strength and heat dissipation during lighting exhibit superior performance compared to conventional electrodes.

10 discharge lamp 12 discharge tube 30 anode 40 metal member (solid member, first solid member)
50 Metal member (solid member, second solid member)
S joint surface

Claims (9)

A discharge tube;
A pair of electrodes disposed in the discharge tube,
At least one of the electrodes is an electrode formed by solid-phase bonding a plurality of solid members,
At least one of the plurality of solid members is a metal member,
The crystal diameter of the metal member is substantially uniform along the joint surface between the members;
The discharge lamp according to claim 1, wherein a crystal structure along a direction perpendicular to a joint surface of the metal member is inclined near the joint surface.   The discharge lamp according to claim 1, wherein the joint surface is a surface along a direction perpendicular to the electrode axis.   The discharge lamp according to claim 1, wherein a gap is formed along the joint surface.   The discharge lamp according to any one of claims 1 to 3, wherein the plurality of solid members include solid members having different thermal conductivities.   The discharge lamp according to any one of claims 1 to 4, wherein the plurality of solid members are diffusion-bonded. The plurality of solid members include a first solid member having an electrode tip surface, and a second solid member that is solid-phase bonded to the first solid member,
2. The discharge lamp according to claim 1, wherein the first solid member has a frustoconical electrode tip and a columnar joint having the same diameter as that of the second solid member. The plurality of solid members includes a first solid member having an electrode tip surface, and a second solid member that is solid-phase bonded to the first solid member,
2. The discharge lamp according to claim 1, wherein the second solid member includes a body portion and a frustoconical electrode joint portion that joins the first solid member. An electrode arranged in a discharge tube of a discharge lamp,
A first solid member having an electrode tip surface;
A second solid member for solid phase bonding with the first solid member,
At least one of the first and second solid members is a metal member,
The crystal diameter of the metal member is substantially uniform along the joint surface between the first and second solid members;
An electrode for a discharge lamp, characterized in that a crystal structure along a direction perpendicular to a joint surface of the metal member is inclined near the joint surface. Forming a first solid member having an electrode tip surface;
Forming a second solid member to be joined to the first solid member;
A method for producing an electrode for a discharge lamp, wherein the contact surfaces of the first solid member and the second solid member, at least one of which is a metal member, are solid-phase bonded to each other.