KR20230004240A - Short arc type discharging lamp - Google Patents

Abstract

To provide a long-life short arc type discharging lamp which has excellent heat dissipation properties and suppresses evaporation of electrode materials when the lamp is turned on. The short arc type discharging lamp comprises: a light emitting tube; and a pair of electrodes disposed opposite each other inside the light emitting tube. At least one electrode of the pair of electrodes has a cylindrical outer peripheral surface, and the outer peripheral surface has an uneven structure in which a plurality of circumferential grooves extending in the circumferential direction are arranged in an axial direction, and a first film containing ceramics formed on the uneven surface of the uneven structure, and satisfies the relationship of 1<=b/a<=4 when the groove depth of the circumferential groove is a (μm) and the distance from the groove bottom of the circumferential groove to the surface of the first film is b (μm).

Description

Short arc type discharge lamp {SHORT ARC TYPE DISCHARGING LAMP}

The present invention relates to a short arc type discharge lamp.

BACKGROUND OF THE INVENTION A short arc discharge lamp (hereinafter, simply referred to as a "lamp") is widely used as a light source for an exposure apparatus used in manufacturing processes of semiconductor elements or liquid crystal display elements. This short-arc type discharge lamp is configured such that an anode and a cathode are disposed facing each other in a light emitting tube, and a light emitting material such as mercury or xenon gas is sealed in the light emitting tube.

In such a short arc type discharge lamp, since the thermal load applied to the anode during lighting is high, evaporation of the electrode material occurs due to overheating of the anode, etc., and this evaporation product adheres to the inner wall of the light emitting tube, It is known to blacken. When the light emitting tube is blackened, the light transmittance of the light emitting tube is lowered.

In order to solve this problem, a technique for suppressing the temperature rise of the electrode by forming a heat radiation layer on the surface of the electrode is known, and in Patent Document 1, a heat radiation layer containing at least one metal oxide is formed on the outer surface of the anode. A lamp is disclosed.

Japanese Patent Laid-Open No. 2004-259639

In the lamp described in Patent Literature 1, in order to improve the adhesion strength of the heat dissipation layer, an uneven surface having an Rmax of 10 μm or more is formed on the surface of the anode, and the heat dissipation layer is formed on the surface. In addition, an example in which the surface layer of the heat dissipation layer is set to Rmax of 2 μm to 100 μm is disclosed.

In order to improve heat dissipation, it is preferable to make the surface of the heat dissipation layer a concavo-convex surface. However, even if irregularities are formed on the surface of the anode, depending on the thickness of the heat dissipation layer formed thereon, irregularities (concavities and convexities reflecting the concavo-convex shape of the surface of the anode) are not formed on the surface of the heat dissipation layer, and heat cannot be effectively dissipated. There are cases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a short arc type discharge lamp with excellent heat dissipation and suppressed evaporation of an electrode material when the lamp is turned on.

A short arc type discharge lamp according to the present invention includes a light emitting tube and a pair of electrodes disposed facing each other inside the light emitting tube,

At least one electrode of the pair of electrodes has a cylindrical outer peripheral surface,

The outer peripheral surface has a concavo-convex structure in which a plurality of circumferential grooves extending in the circumferential direction are arranged in an axial direction, and a first film containing ceramics formed on the concavo-convex surface of the concavo-convex structure,

When the groove depth of the circumferential groove is a (μm) and the distance from the groove bottom of the circumferential groove to the surface of the first film is b (μm), the relationship of the following formula (1) is satisfied will be.

1≤b/a≤4 (1)

According to this configuration, since irregularities reflecting the concavo-convex shape of the concavo-convex structure are formed on the surface of the first film, heat dissipation is improved by the concavo-convexity. As a result, since the short arc discharge lamp of the present invention is excellent in heat dissipation of the electrode, evaporation of the electrode material at the time of lighting the lamp is suppressed and the life is increased.

In the short arc discharge lamp of the present invention, the ceramics may contain at least one of metal oxides, metal carbides, metal borides, metal silicides, and metal nitrides.

Moreover, in the short arc type discharge lamp of this invention, the said ceramics may have a structure which has zirconium oxide as a main component.

In addition, in this specification, "main component" is used as a term meaning the component whose content rate is the largest on a mass basis.

According to these configurations, the first coating film can exhibit excellent radioactivity as a high radiation film.

In the short arc discharge lamp of the present invention, the one electrode has an electrode front portion whose outer diameter decreases toward the tip,

A structure may be formed in which a second film containing a metal having a higher melting point than the ceramics is formed on the surface of all of the electrodes.

Further, in the short arc discharge lamp of the present invention, the one electrode has all of the electrodes whose outer diameter decreases toward the tip,

A configuration may be used in which fine groove processing is applied to the surface of all of the electrodes.

According to these structures, the heat dissipation property of an electrode can be further improved.

1 is an explanatory diagram showing the configuration of a short arc type discharge lamp according to the present embodiment.
FIG. 2 is an enlarged view of a region II of the short arc type discharge lamp shown in FIG. 1 .
FIG. 3 is an enlarged sectional view of the III portion region shown in FIG. 2 .
Fig. 4 is an enlarged sectional view in the case where the thickness of the first film is thick.
Fig. 5 is a traced SEM image of the cross section of the anode.
Fig. 6 is a traced SEM image of the cross section of the anode.
7 is a front view of an anode according to another embodiment.
8 is a front view of an anode according to another embodiment.

An embodiment of the short arc type discharge lamp according to the present invention will be described with reference to the drawings. In addition, each drawing below is shown schematically, and the size ratio on a drawing does not always match the actual size ratio, and the size ratio does not always match between each drawing.

Below, it demonstrates with appropriate reference to the XYZ coordinate system. In addition, when expressing a direction in this specification, when distinguishing a positive/negative direction, a positive/negative sign is attached and described, such as "+X direction" and "-X direction". In the case of expressing a direction without distinguishing between positive and negative directions, it is simply described as "X direction". That is, in this specification, when it is simply described as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y-direction and the Z-direction.

1 is an explanatory diagram showing the configuration of a short arc type discharge lamp according to the present embodiment. A short arc discharge lamp 1 (hereinafter, referred to as “lamp 1”) includes a light emitting tube 2 and an anode 3 and a cathode 4 disposed opposite to each other inside the light emitting tube 2. provide The positive electrode 3 and the negative electrode 4 are supported by lead rods 5, respectively.

The lamp 1 of the present embodiment is a large-sized lamp used in an exposure apparatus used in a manufacturing process of a semiconductor element or a liquid crystal display element, and has a rated power of 2 kW to 35 kW, for example.

The light emitting tube 2 is formed by bulging the center of a glass tube. The light emitting tube 2 is a region of a glass tube whose inner diameter increases from both ends in the X direction toward the center. The outer shape of the light emitting tube 2 is a sphere or an elliptical sphere.

The light emitting tube 2 has a pair of sealed tube portions 21 extending continuously in opposite directions from both ends of the light emitting tube 2 in the X direction. The light-emitting tube 2 and the sealed tube portion 21 are integrally formed of, for example, quartz glass. The central axes of the pair of sealed pipe portions 21 overlap each other and are indicated by an axis X1 in FIG. 1 .

Inside the light-emitting tube 2, a light-emitting space S1 is formed. A light emitting material such as mercury is sealed in the light emitting space S1.

Inside the light emitting tube 2, an anode 3 and a cathode 4 are disposed facing each other in the X direction. In this embodiment, the short arc type discharge lamp is a discharge lamp in which the anode 3 and the cathode 4 are disposed opposite to each other at a distance of 40 mm or less (value at room temperature without thermal expansion). In this embodiment, the material of the anode 3 is tungsten, and the material of the cathode 4 is thorium tungsten.

The lead rod 5 is connected to the positive electrode 3 and the negative electrode 4 and extends in the X direction within the sealed tube portion 21 . The anode 3 and the cathode 4 are fixed to the tip of the lead bar 5. The central axis of the lead bar 5 may overlap with the axis X1. For the lead rod 5, a material containing a high melting point metal such as tungsten is used.

The clasp 8 covers the side away from the positive electrode 3 and the negative electrode 4 of the sealed tube portion 21 . The clasp 8 is electrically connected to the lead bar 5.

FIG. 2 is an enlarged view of a region II of the lamp 1 shown in FIG. 1 . On a part of the surface of the anode 3, a first film 6 made of ceramics is formed.

The anode 3 has a cylindrical body portion 3a centered on the axis X1, and an electrode front portion 3b whose outer diameter decreases toward the tip (toward the cathode 4). . The first film 6 is formed on the outer circumferential surface of the cylindrical shape of the body portion 3a.

As the material of the first film 6, melting point, vapor pressure, emissivity, coefficient of thermal expansion and the like become important. In order to lower the temperature of the anode 3, the first film 6 is preferably made of a material with high emissivity so as to increase the amount of heat dissipation.

The first film 6 contains ceramics. This ceramics contains at least one of a metal oxide, a metal carbide, a metal boride, a metal silicide, and a metal nitride. As the material of the first film 6, a material having a melting point of 2000°C or higher can be used as appropriate, and examples thereof include aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), zirconium carbide (ZrC), and zirconium boride. (ZrB ₂ ), tantalum silicide (TaSi ₂ ), and zirconium nitride (ZrN).

FIG. 3 is an enlarged sectional view of the III portion region shown in FIG. 2 . As shown in FIG. 3 , a concave-convex structure 30 is formed on the outer circumferential surface of the body portion 3a of the anode 3 . The concavo-convex structure 30 is formed by arranging a plurality of circumferential grooves 31 extending in the circumferential direction of the body portion 3a in an axial direction (X direction). Such circumferential grooves 31 can be formed by lathe processing, for example. In the case of forming the circumferential grooves 31 by lathe processing, a plurality of circumferential grooves 31 for one round may be arranged independently in the axial direction, or the plurality of circumferential grooves 31 are spiral. It may be continuous in shape and made into one spiral groove as a whole.

On the concave-convex surface of the concavo-convex structure 30, a first film 6 is formed. The surface 6a of the first film 6 has concavo-convex patterns reflecting the concavo-convex shape of the concavo-convex structure 30. By forming unevenness reflecting the uneven shape of the uneven structure 30 on the surface 6a of the first film 6, the heat dissipation property is improved by the unevenness.

The irregularities appearing on the surface 6a of the first coating film 6 can be formed by controlling the thickness of the first coating film 6 . Fig. 4 is an enlarged cross-sectional view in the case where the first film 6 thicker than Fig. 3 is formed. As shown in FIG. 4 , when the thickness of the first coating film 6 is large, no irregularities reflecting the concavo-convex shape of the concavo-convex structure 30 are formed on the surface 6a, or even if formed, the concavo-convex structures are small.

In order to form irregularities reflecting the concavo-convex shape of the concavo-convex structure 30 formed on the surface of the anode 3 on the surface 6a of the first coating film 6 through earnest research, the inventors have found that in the circumferential direction When the groove depth of the groove 31 is a (μm) and the distance from the groove bottom 311 of the circumferential groove 31 to the surface 6a of the first coating film 6 is b (μm), It was found that it was necessary to adjust the thickness of the first film 6 so as to satisfy the relationship of 1≤b/a≤4. The distance b can also be referred to as the thickness of the first film 6 at the groove bottom 311 of the circumferential groove 31 .

When b/a is less than 1, the thickness of the first coating film 6 is too thin, so that protruding portions of the concave-convex structure 30 may be exposed. On the other hand, when b/a is greater than 4, the thickness of the first film 6 is too thick, and the surface 6a of the first film 6 has irregularities reflecting the concavo-convex shape of the concavo-convex structure 30. It is not formed, or even if it is formed, the unevenness is small, and the effect of improving the heat dissipation property cannot be obtained very much.

The groove depth a of the circumferential groove 31 is preferably 10 μm to 100 μm, for example. When the groove depth a is smaller than 10 μm, it is difficult to form irregularities on the surface 6a of the first coating film 6. Further, when the groove depth a is larger than 100 μm, it is difficult to form the first coating film 6 in the circumferential groove 31 .

The unevenness of the surface 6a has a height difference of 5 μm or more, preferably 10 μm or more. When the height difference is smaller than 5 μm, it is difficult to obtain an effect of increasing heat dissipation.

It is preferable that the thickness of the 1st membrane|film|coat 6 is 10 micrometers or more, for example. When the thickness of the film 6 is thin, sufficient emissivity cannot be obtained. In addition, in order to appropriately form unevenness on the surface 6a, the thickness of the first film 6 is preferably 100 μm or less, and more preferably 30 μm or less.

Formation of the first film 6 is performed by, for example, mixing particles of a material constituting the film 6 (for example, particles of zirconium oxide with a particle size of 10 μm or less) in a solvent (for example, nitrocellulose and acetic acid). butyl solvent), applied with a brush to the outer circumferential surface of the body portion 3a of the positive electrode 3, dried at 150°C for 30 minutes, and then subjected to heat treatment at 1900°C for 120 minutes in a vacuum atmosphere. all.

5 and 6 are diagrams obtained by tracing SEM images of the cross section of the anode 3. For the SEM image of the cross-section of the anode 3, first, an incision is made in the anode 3 with a grinder (blade), the anode 3 is broken starting from the location where the incision is made, and the fractured surface is displayed as a scanning electron microscope. It can be obtained by observing with a microscope (SEM). The thickness of the first film 6 can be measured by measurement software attached to the SEM.

5, the groove depth a of the circumferential groove 31 is 30 μm, and the distance b from the groove bottom 311 of the circumferential groove 31 to the surface 6a of the first coating film 6 is 50 μm. , that is, when b/a is about 1.66, the SEM image is traced. 6, the groove depth a of the circumferential groove 31 is 30 μm, and the distance b from the groove bottom 311 of the circumferential groove 31 to the surface 6a of the first coating film 6 is 150 μm. , that is, when b/a is 5, the SEM image is traced. In the example shown in FIG. 5 , irregularities reflecting the concavo-convex shape of the concavo-convex structure 30 are formed on the surface 6a of the first coating film 6 . On the other hand, in the example shown in FIG. 6 , almost no irregularities reflecting the concave-convex shape of the concavo-convex structure 30 are formed on the surface 6a of the first coating film 6 .

All electrodes 3b of the anode 3 may have a shape in which the outer diameter decreases toward the tip, and may not have a truncated cone shape in which the outer diameter decreases at a constant rate toward the tip, as shown in FIG. 2 . . For example, as shown in FIG. 7 , the outer circumferential surface of the front end 3b of the electrode may be configured to have a curved cross-sectional shape in which the ratio of the outer diameter decreasing toward the tip changes.

As shown in Fig. 8, a second film 7 containing a metal having a higher melting point than ceramics may be formed on the surface of the front electrode 3b. Since the 2nd film|membrane 7 containing metal with a higher melting point than ceramics has higher heat resistance than ceramics, there is no fear of peeling at the time of lamp lighting. By forming this second film 7, heat dissipation can be further improved.

A metal having a higher melting point than ceramics is, for example, tungsten. The formation of the second film 7 is performed, for example, by dispersing tungsten particles in a solvent, applying this to the outer circumferential surface of the electrode front end 3b of the anode 3 with a brush, and sintering.

Further, instead of forming the second film 7 on the surface of the front electrode 3b, fine groove processing may be applied. By performing fine groove processing, the heat dissipation property can be further improved. Fine groove processing can be performed with a laser processing machine. The fine grooves are formed with, for example, a depth of 650 μm and a pitch of 195 μm.

As mentioned above, although the embodiment of this invention was demonstrated based on drawing, it should be thought that a specific structure is not limited to these embodiment. The scope of the present invention is shown by not only the description of the embodiment described above but also the scope of the claims, and includes all modifications within the scope and meaning equivalent to the scope of the claims.

It is possible to employ the structure employed in each of the above embodiments to other arbitrary embodiments. The specific structure of each part is not limited only to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. In addition, you may arbitrarily select one or more configurations, methods, etc. according to various examples of modifications described below, and employ the configurations, methods, or the like according to the above-described embodiments.

In the above embodiment, the first coating 6 is formed only on the outer circumferential surface of the anode 3, but the first coating 6 may also be formed on the outer circumferential surface of the cathode 4, and the outer circumferential surface of the anode 3 It is also possible to form the first film 6 only on the outer circumferential surface of the cathode 4 without forming the first film 6 thereon.

[Example]

Hereinafter, embodiments and the like specifically illustrating the configuration and effects of the present invention will be described.

A plurality of anodes 3 were prepared in which the groove depth a of the circumferential groove 31 and the thickness b of the first film 6 were changed as shown in Table 1. The circumferential groove 31 was formed by lathe processing. The groove depth of the circumferential groove 31 can be adjusted by changing the processing conditions for lathe processing. In addition, formation of the 1st membrane|film|coat 6 was performed as follows. Zirconium oxide particles having a particle size of 10 µm or less were added to a solvent composed of nitrocellulose and butyl acetate, mixed well, and then applied to the outer circumferential surface of the anode 3 with a brush. Then, after drying at 150°C for 30 minutes, heat treatment was performed at 1900°C for 120 minutes in a vacuum atmosphere. The thickness of the first film 6 can be adjusted by changing the viscosity of the solvent in which the zirconium oxide particles are dispersed.

The luminance retention rate when the lamp equipped with the anode 3 prepared by changing the specifications was lit at a rated 2 kW (voltage: 25 V, current: 80 A) for 500 hours was evaluated. Table 1 shows the evaluation results.

In addition, the illuminance retention rate is determined by first measuring the illuminance at the start of lighting with a photodetector sensitive to a wavelength of 365 nm, then measuring the illuminance after continuous lighting for 500 hours at rated power, and calculating the ratio with the initial illuminance. Saved.

In addition, specifications common to each lamp tested are as follows.

[light tube]

Material: Quartz Glass, Overall Length: 70mm

Maximum diameter: φ55mm

Enclosure: Mercury 2.5mg/cc

Distance between electrodes: 5mm

[anode]

Material: Tungsten

Length: 30mm

Diameter of main body: φ20mm

[cathode]

Material: Thorium Tungsten

Length: 20mm

Diameter of main body: φ6mm

As shown in Table 1, when b/a was 0.8 and 5, the illuminance retention rate after lighting for 500 hours was less than 80% regardless of the value of a. On the other hand, when b/a was 1 to 4, the illuminance retention rate exceeded 80% regardless of the value of a.

When b/a is in the range of 1 to 4, the positive electrode 3 has high heat dissipation, and since the evaporation amount of the electrode material is reduced, a high illuminance retention rate is realized. Moreover, in the range where b/a is 1-2, the effect is greater (90% or more).

1: short arc type discharge lamp (lamp) 2: luminous tube
3: anode 3a: body part
3b: front electrode 4: cathode
6: first film 6a: surface of the first film
7: second film 30: uneven structure
31: circumferential groove 311: groove bottom of the circumferential groove
a: groove depth of the circumferential groove
b: Distance from the groove bottom of the circumferential groove to the surface of the first film

Claims (5)

A light emitting tube and a pair of electrodes disposed facing each other inside the light emitting tube,
At least one electrode of the pair of electrodes has a cylindrical outer peripheral surface,
The outer peripheral surface has a concavo-convex structure in which a plurality of circumferential grooves extending in the circumferential direction are arranged in an axial direction, and a first film containing ceramics formed on the concavo-convex surface of the concavo-convex structure,
When the groove depth of the circumferential groove is a (μm) and the distance from the groove bottom of the circumferential groove to the surface of the first film is b (μm), the relationship of the following formula (1) is satisfied , short-arc discharge lamps.
1≤b/a≤4 (1) The method of claim 1,
The ceramics include at least one of metal oxides, metal carbides, metal borides, metal silicides, and metal nitrides. The method of claim 1,
The short arc type discharge lamp in which the said ceramics has zirconium oxide as a main component. The method of claim 1,
The one electrode has an electrode front portion whose outer diameter decreases toward the tip,
The short arc type discharge lamp, wherein a second film containing a metal having a higher melting point than the ceramics is formed on the surface of all of the electrodes. The method of claim 1,
The one electrode has all electrodes whose outer diameter decreases toward the tip,
A short arc type discharge lamp in which fine groove processing is applied to the surface of all of the electrodes.

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