Flash discharge lamp and flash irradiation device

Abstract

To provide a flash discharge lamp that enhances an optical output during lighting and restrains discoloration of a trigger tube over a long period of time.SOLUTION: A flash discharge lamp includes an arc tube (11) that extends in a first direction and is transparent to light, a pair of electrodes (12p, 12n) arranged to face each other in the first direction inside the arc tube, and a trigger tube (13) arranged to be adjacent to the arc tube. The trigger tube includes a proximal conductor (14) that includes a core material made of a conductive material having a relatively high melting point and extending along the first direction, and a protective layer that is formed on the outer surface of the core material, made of at least one element belonging to platinum group elements, and has a relatively low melting point, the proximal conductor (14) being arranged to be adjacent to the arc tube, and a light-transmitting insertion tube (13a) that extends along the first direction, accommodates at least a part of the proximal conductor therein and is transparent to light.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a flash discharge lamp and a flash irradiation device. [Background technology]

[0002] Conventionally, flash irradiation devices have been used for heat treatment of semiconductor substrates and heat treatment in the manufacturing process of printable electronics, etc. In particular, in recent years, with the miniaturization of semiconductor processes, instantaneous heat treatment methods using flash irradiation devices have attracted attention as a method for activating implanted impurities while suppressing their diffusion due to long-term heating.

[0003] A flash discharge lamp (also called a "flash lamp") suitable for a heat treatment device for semiconductor wafers is controlled to emit high-power light momentarily for heating. To achieve such control, a flash discharge lamp is known that includes an electrode (conductor) for applying a trigger voltage to the outer wall surface of the light-emitting tube while a voltage is being applied between the discharge electrodes (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-071942 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, semiconductor manufacturing processes have made great strides toward higher density and finer resolution, and due to the constraints of substrate area, processes that construct circuits three-dimensionally on a substrate are being considered, and studies are also being conducted to reduce the thickness of each layer stacked. In such semiconductor manufacturing processes, it is required that the layers to be processed in the annealing process can be sufficiently heated, while layers that are not to be processed are not affected as much as possible. To achieve such processing, flash discharge lamps that can reduce the heat input depth in the annealing process are expected.

[0006] As a method for reducing the heat input depth when irradiating a flash of light for heat treatment, shortening the lighting time of the flash discharge lamp while maintaining the total amount of light energy irradiated to the workpiece in one lighting operation has been studied. As a result of this study, a flash discharge lamp that has a shorter lighting time and a higher light output in one lighting operation has been expected recently.

[0007] Therefore, the present inventors have conducted extensive research into a flash discharge lamp that has a shorter lighting time and a higher light output, and have found that the following problems arise.

[0008] In many flash discharge lamps, a conductor (hereinafter sometimes referred to as a "proximal conductor") that functions as a trigger electrode for starting lighting is arranged on the outer wall surface of the light-emitting tube or near the light-emitting tube, as in the invention described in the above Patent Document 1. In order to generate a discharge between a pair of electrodes, this proximal conductor applies a high-voltage pulse to ionize the light-emitting gas sealed in the light-emitting tube while a voltage required for lighting is applied between the pair of electrodes.

[0009] In addition, the proximity conductor may be partially evaporated by the heat generated when a flash occurs, which may cause contamination of the lamp house and workpiece, or may adhere to the outside of the arc tube and promote recrystallization of the quartz glass, which may lead to the lamp exploding. To deal with this phenomenon, a trigger tube in which the proximity conductor is housed in a dielectric container such as glass (hereinafter sometimes referred to as the "insertion tube") is sometimes used as a starting mechanism.

[0010] In view of the above-mentioned background, the inventors conducted experiments to shorten the lighting time using a flash discharge lamp equipped with a trigger tube, and noticed that blackening of the inner wall surface of the insertion tube, which in the past was occasionally observed after a certain amount of time had passed since the start of use, appeared relatively early.

[0011] The blackening that appears on the trigger tube absorbs some of the light emitted from the flash discharge lamp, which may result in a reduction in the light intensity on the irradiated surface of the semiconductor wafer and a decrease in the uniformity of the illuminance distribution.

[0012] In view of the above problems, an object of the present invention is to provide a flash discharge lamp and a flash irradiation device that further increase the light output when lit and suppress discoloration of the trigger tube over a long period of time. [Means for solving the problem]

[0013] The flash discharge lamp of the present invention is an arc tube extending in a first direction and transparent to light; a pair of electrodes disposed opposite each other in the first direction inside the arc tube; a trigger tube disposed adjacent to the light emitting tube; The trigger tube is a proximal conductor disposed proximate to the arc tube, the proximal conductor having a core made of a conductive material extending along the first direction and having a relatively high melting point, and a protective layer formed on an outer surface of the core, the protective layer being made of at least one element belonging to the platinum group and having a relatively low melting point; The present invention is characterized in that it further comprises an insertion tube that is transparent to light and extends along the first direction and has at least a portion of the proximal conductor housed therein.

[0014] In the flash discharge lamp, The protective layer may be made of at least one element selected from the group consisting of rhodium (Rh), ruthenium (Ru), platinum (Pt), and iridium (Ir).

[0015] In this specification, the term "exhibiting transparency" is intended to mean that the transmittance for visible light is at least 80% or more. For a discolored arc tube, if a non-discolored part is checked and this part is transparent to light, it corresponds to a "light-transmitting arc tube."

[0016] In this specification, the term "close to" is used to mean that they are in contact with each other or that they are arranged at a distance smaller than the average thickness of the tube wall of the arc tube.

[0017] Furthermore, in this specification, the term "consisting of" is used to include not only cases where the target component consists only of a specified material, but also cases where the content of the specified material in the target component is 80% or more.

[0018] Furthermore, the platinum group elements are a general term for precious metal elements that belong to groups 8, 9, and 10 in the fifth and sixth periods of the periodic table, and specifically include rhodium (Rh), ruthenium (Ru), platinum (Pt), iridium (Ir), palladium (Pd), and osmium (Os).

[0019] The present inventors speculate as follows about the cause of discoloration of the insertion tube.

[0020] First, the materials that make up the arc tube and insertion tube must meet the following three requirements: (1) They must have a certain degree of optical transparency to the light (especially visible light) emitted from the arc tube so as not to reduce the efficiency of light irradiation on the workpiece, (2) They must have sufficient insulation to prevent electrical conduction between the trigger tube and the surrounding metal parts, etc., around which the trigger tube is placed, and (3) They must have a certain degree of heat resistance, taking into account the temperature rise that occurs when the light is turned on.

[0021] Materials that satisfy these requirements include, for example, ceramics such as glass (quartz, borosilicate) and translucent alumina, which are mainly composed of oxides, and sapphire. When the proximal conductor, which has absorbed a portion of the light emitted from the light emitting tube and is in a high temperature state, comes into contact with the insertion tube, the temperature of the inner surface of the insertion tube near the contact portion rises locally. Oxygen is liberated from the insulating material of the insertion tube, which is activated by this temperature rise. When oxygen exists as a gas around the proximal conductor that has become hot, the proximal conductor is likely to oxidize quickly. The inventors speculate that the first main factor of the above-mentioned discoloration of the insertion tube is that the oxide generated by the reaction between the proximal conductor and oxygen adheres to the inner wall surface of the insertion tube.

[0022] In addition, the molecular structure of the inner wall of the insertion tube where oxygen liberation occurs changes from the original SiO2 to SiO or Si, causing discoloration and opacity. The inventors have inferred through various analyses that this phenomenon is the second main factor that causes the inner wall of the insertion tube to blacken. They also infer that the discoloration thus generated gradually grows with an increase in the number of flashes, causing the trigger tube to discolor.

[0023] Furthermore, when the power input to the flash discharge lamp is increased to increase the light output, the operating temperature of the light emitting tube and the insertion tube tends to become higher as the power input increases.

[0024] In this way, shortening the lighting time and increasing the light output leads to an increase in the temperature of the adjacent conductor and the insertion tube when the light is turned on. From this perspective, the inventors surmise that shortening the lighting time and increasing the light output causes the temperatures of the adjacent conductor and the insertion tube to become higher than before, making it easier for the above-mentioned reaction to occur, which causes discoloration to appear earlier.

[0025] Therefore, after extensive research, the inventors came up with the idea of ​​suppressing oxidation of the core material by covering the outer surface of the core material, which is made of a material with a relatively high melting point that does not melt even at high temperatures, with a platinum group element that is resistant to oxidation.

[0026] Among metallic elements, platinum group elements are precious metal elements that have a relatively high melting point (1700°C or higher) and are highly resistant to oxidation and corrosion. For this reason, platinum group elements hardly melt even at the temperature at which the arc tube and insertion tube soften (for example, about 1000°C to 1700°C for quartz glass, depending on the composition and impurity concentration, etc.). To ensure that the core does not melt, a material with a relatively high melting point is used for the protective layer.

[0027] In other words, even if the lighting time of the flash discharge lamp having the above configuration is shortened and the light output is increased, the core material is protected from contact with oxygen desorbed from the insertion tube by the protective layer made of a platinum group element, so that the insertion tube is unlikely to discolor. Furthermore, the core material does not melt, at least within the temperature range in which the insertion tube can be used.

[0028] Here, the platinum group elements include the above-mentioned six elements, and rhodium (Rh), ruthenium (Ru), platinum (Pt), and iridium (Ir) are suitable as materials for forming the protective layer, as they have relatively high adhesion to other metals that are the core material. In addition, palladium (Pd) and osmium (Os) are particularly rare precious metal elements, so rhodium (Rh), ruthenium (Ru), platinum (Pt), and iridium (Ir) are suitable as materials for forming the protective layer, also in terms of manufacturing costs.

[0029] Furthermore, in the flash discharge lamp, The trigger tube may be hermetically sealed with the space through which the proximal conductor is inserted being substantially in a vacuum state or filled with an inert gas.

[0030] In this specification, the term "substantially a vacuum state" refers to a state in which the atmospheric pressure in a space is 1 Pa or less.

[0031] The provision of the insertion tube has the effect of facilitating discharge between the proximity conductor and the electrode in the arc tube, since the dielectric material constituting the insertion tube is placed in place of the air present in the space between the proximity conductor and the arc tube. In order to further enhance this effect, it is preferable that the space inside the trigger tube in which the proximity conductor is housed is vacuum or filled with an inert gas. Examples of the inert gas include xenon (Xe) gas, argon (Ar) gas, and nitrogen (N) gas.

[0032] In the flash discharge lamp, The protective layer may have a thickness of 100 μm or less.

[0033] The flashlight irradiation device of the present invention comprises: The present invention is characterized by comprising the above-mentioned flash discharge lamp.

[0034] The flashlight irradiation device of the present invention may be configured to include either a single flashlight discharge lamp or a plurality of flashlight discharge lamps. Effect of the Invention

[0035] According to the present invention, a flash discharge lamp is realized which has a higher light output when lit and which is prevented from discoloring for a long period of time. [Brief description of the drawings]

[0036] [Figure 1] 2 is a schematic cross-sectional view of an embodiment of a flashlight irradiation device as viewed in the Y direction. FIG. [Diagram 2]2 is a diagram illustrating only the flash discharge lamp of FIG. 1; [Diagram 3] 3 is an enlarged view of an area A1 in FIG. 2. [Figure 4] 1 is a diagram showing the configuration of a lighting circuit for a verification experiment. [Diagram 5] 13 is a schematic cross-sectional view of a flash discharge lamp according to another embodiment when viewed in the Y direction. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The flash discharge lamp of the present invention will be described below with reference to the drawings. Note that the following drawings are all schematic illustrations, and the numbers on the drawings do not necessarily correspond to the actual numbers.

[0038] Fig. 1 is a schematic cross-sectional view of one embodiment of a flash light irradiation device 1 when viewed in the Y direction, and Fig. 2 is a drawing illustrating only the flash light discharge lamp 10 of Fig. 1. As shown in Fig. 1 and Fig. 2, the flash light irradiation device 1 of this embodiment includes a flash light discharge lamp 10, a reflecting member 20, and a support base 30 on which a workpiece W1 is placed. Note that for convenience of illustration, only one flash light discharge lamp 10 is shown in Fig. 1, but the flash light irradiation device 1 may be equipped with a plurality of flash light discharge lamps 10.

[0039] 1, the direction along the tube axis of the arc tube 11 is defined as the X direction, the direction in which the flash discharge lamp 10 faces the workpiece W1 is defined as the Z direction, and the direction perpendicular to the X direction and the Z direction is defined as the Y direction. The X direction corresponds to the first direction.

[0040] As described above, in this specification, when expressing a direction, if there is a need to distinguish between positive and negative directions, the direction is described with a positive or negative sign, such as "+Z direction" and "-Z direction." When expressing a direction without distinguishing between positive and negative directions, the direction is simply described as "Z direction."

[0041] The reflecting member 20 has a reflecting surface 21 that reflects the light L1 emitted from the flash discharge lamp 10, and is disposed so as to reflect the light L1 emitted from the flash discharge lamp 10 and traveling toward the +Z side toward the -Z side, as shown in Fig. 1. Note that the size, shape, etc. of the reflecting member 20 shown in Fig. 1 and Fig. 2 are merely examples. The reflecting member 20 is, for example, an aluminum (Al) plate.

[0042] The support table 30 is a base having a plurality of pins 30a on which the workpiece W1 is placed. The configuration of the support table 30 for supporting the workpiece W1 shown in Fig. 1 and Fig. 2 is merely an example, and as long as the workpiece W1 can be stopped or fixed at a predetermined position, the support table 30 may be configured to support the workpiece W1 by hooking the outer edge of the workpiece W1. The distance between the flash discharge lamp 10 and the workpiece W1 in the Z direction is appropriately adjusted depending on the type of the workpiece W1, the processing step, etc., but is set to 30 mm in this embodiment.

[0043] The flash discharge lamp 10 includes an arc tube 11, a pair of electrodes (12p, 12n), a trigger tube 13, a proximal conductor 14, a first power supply line (15, 15), and a second power supply line 16.

[0044] The arc tube 11 is a quartz glass tube filled with a light emitting gas, has a straight tube shape extending in the X direction, and is transparent to light L1. The arc tube 11 includes a pair of electrodes (12p, 12n) spaced apart on the inside in the X direction. The arc tube 11 of this embodiment has a length of 550 mm in the X direction, an outer diameter of 25 mm, and an inner diameter of 20 mm when viewed in the X direction.

[0045] The pair of electrodes (12p, 12n) are arranged such that the distance between them in the X direction is 500 mm. Note that the shapes of the electrodes (12p, 12n) shown in Figs. 1 and 2 are merely examples, and the electrodes (12p, 12n) are not limited to these shapes. The electrodes (12p, 12n) are connected to a lighting circuit (not shown) via first power supply lines (15, 15).

[0046] 1 and 2, a trigger tube 13 having an insertion tube 13a housing a proximity conductor 14 extending in the X direction on the inside is provided on the outer wall surface on the +Z side of the light emitting tube 11. The trigger tube 13 may be provided on the -Z side of the light emitting tube 11, but is preferably provided on the +Z side of the light emitting tube 11 in consideration of the energy loss of light L1 emitted from the light emitting tube 11 and traveling directly toward the workpiece W1.

[0047] The insertion tube 13a of this embodiment has an outer diameter of 4 mm, an inner diameter of 2 mm, and a total length of 530 mm when viewed in the X direction. The proximal conductor 14 has an outer diameter of 1 mm when viewed in the X direction, and a total length of 520 mm. The insertion tube 13a accommodates the proximal conductor 14, one end of which is cut, in the inner space, and is shrink-sealed at a portion where a sealing molybdenum foil (not shown) to which the end is welded is disposed so that the space is substantially in a vacuum state.

[0048] The space inside the insertion tube 13a may be filled with an inert gas and hermetically sealed. Also, as long as the lighting operation can be performed without any problems, the space inside the insertion tube 13a does not need to be hermetically sealed.

[0049] The second feeder 16, which is connected to the proximal conductor 14 via a shrink seal portion, is connected to a trigger circuit (not shown).

[0050] The insertion tube 13a in this embodiment is made of quartz glass like the arc tube 11, and is welded to the arc tube 11. However, the arc tube 11 and the insertion tube 13a may be made of different materials, and may be spaced apart from each other as long as they are arranged close to each other. Note that both the arc tube 11 and the insertion tube 13a do not have to be made of quartz glass.

[0051] Fig. 3 is an enlarged view of region A1 in Fig. 2. As shown in Fig. 3, the proximal conductor 14 of this embodiment includes a core material 14a made of a conductive material and a protective layer 14b formed on the outer surface of the core material 14a. The core material 14a of the proximal conductor 14 of this embodiment is a wire made of tungsten (W).

[0052] In this embodiment, the protective layer 14b of the proximal conductor 14 is made of platinum (Pt) and has a thickness adjusted to be within a range of 0.03 μm to 3.5 μm. From the viewpoints of preventing the core material 14a from being oxidized and of preventing the proximal conductor 14 from being unnecessarily large, the thickness of the protective layer 14b is preferably 0.03 μm to 100 μm, and more preferably 0.05 μm to 50 μm.

[0053] As the material for the protective layer 14b, any one of the platinum group elements or a material containing multiple platinum group elements can be adopted. From the viewpoints of adhesion to the core material 14a and manufacturing costs, however, rhodium (Rh), ruthenium (Ru), platinum (Pt), and iridium (Ir) are preferable, and rhodium (Rh), ruthenium (Ru), and platinum (Pt) are particularly preferable.

[0054] Here, the material of the core material 14a has a higher melting point than the material of the protective layer 14b. In this embodiment, the melting point of the material of the core material 14a, tungsten (W), is 3422°C, and the melting point of the material of the protective layer 14b, platinum (Pt), is 1768°C. As long as the above relationship is satisfied with respect to the melting points, the material of the core material 14a is not limited to tungsten (W), and for example, molybdenum (Mo), which has a melting point of 2623°C, may be used.

[0055] The proximal conductor 14 is produced, for example, by a method of preparing a core material 14a and forming a thin film of a platinum group element that serves as a protective layer 14b on the outer surface of the core material 14a by metal vapor deposition or plating, or by a method of immersing the core material 14a in a material made of a platinum group element that has a higher melting point than platinum group elements that is melted in a crucible.

[0056] Next, a verification experiment was conducted to compare the occurrence of discoloration in the trigger tube 13 between a flash discharge lamp 10 equipped with a proximity conductor 14 having a core material 14a and a protective layer 14b and a flash discharge lamp of a conventional configuration, and the details of the experiment will be described below.

[0057] Example 1 Example 1 is the flash discharge lamp 10 of the above-described embodiment.

[0058] Example 2 Example 2 is similar to Example 1, except that the protective layer 14b made of rhodium (Rh) is used instead of the protective layer 14b made of platinum (Pt).

[0059] Example 3 Example 3 is similar to Example 1, except that the protective layer 14b made of ruthenium (Ru) is used instead of the protective layer 14b made of platinum (Pt).

[0060] Comparative Example 1 Comparative Example 1 is a flash discharge lamp of a conventional configuration, and is similar in configuration to Example 1, except that it includes a proximal conductor 14 made of a single core material 14a without a protective layer 14b.

[0061] Comparative Example 2 Comparative Example 2 is similar to Comparative Example 1, except that it includes an arc tube 11 and an insertion tube 13a that have been vacuum heated at 900°C for three hours to reduce the moisture (H2O) content as much as possible within the arc tube 11 and the insertion tube 13a.

[0062] Comparative Example 3 Comparative Example 3 is similar to Comparative Example 1, except that the proximal conductor 14 is a core material 14a whose surface is polished with sodium hydroxide (NaOH).

[0063] (conditions) Fig. 4 is a diagram showing the configuration of a lighting circuit for a verification experiment. The lighting circuit for the verification experiment includes a lighting circuit C1 connected to the electrodes (12p, 12n) of the flash discharge lamp 10, a trigger circuit C2 connected to the proximal conductor 14, and a control unit 5 that controls the switching elements (4, 8) of each circuit (C1, C2). Although not shown in Fig. 4, a DC power supply is connected in parallel to each capacitor (2, 7).

[0064] At the start of operation, the control unit 5 keeps both of the switching elements (4, 8) in the OFF state. At this time, the capacitors (2, 7) are charged by the DC power supply.

[0065] After the capacitor (2, 7) is charged, the control unit 5 switches the switching element 4 from the OFF state to the ON state.

[0066] Thereafter, the control unit 5 switches the switching element 8 from an OFF state to an ON state, thereby discharging the charge stored in the capacitor 7. Due to the discharge of the charge stored in the capacitor 7, an electromotive force is generated on the winding side connected to the proximal conductor 14 of the transformer 6. Then, a trigger voltage is applied to the proximal conductor 14.

[0067] When a trigger voltage is applied to the proximal conductor 14, a discharge occurs within the light-emitting tube 11, a discharge occurs between the electrodes (12p, 12n), and a flash of light is generated by the discharge of the charge stored in the capacitor 2.

[0068] Then, the flash discharge lamp 10 stops emitting light, completing a series of lighting operations.

[0069] In this verification experiment, the above-mentioned lighting operation was repeated 20,000 times, and visual inspection was performed to see whether discoloration occurred in the arc tube 11 and the trigger tube 13.

[0070] (result) In Comparative Examples 1 to 3, discoloration was confirmed in the arc tube 11 after the lighting operation was repeated 20,000 times. In contrast, in Examples 1 to 3, no discoloration was confirmed in the trigger tube 13 even after the lighting operation was repeated 20,000 times.

[0071] For Examples 1 to 3, similar verification experiments were performed with the protective layer 14b having four different thicknesses of 0.05 μm, 1.26 μm, 1.80 μm, and 56.2 μm, but no discoloration of the trigger tube 13 was observed in any of the four thicknesses.

[0072] As described above, even if the lighting time of the flash discharge lamp 10 having the above configuration is shortened and the light output is increased, the core material 14a is protected by the protective layer 14b from contacting the oxygen desorbed from the insertion tube 13a, so that the insertion tube 13a is unlikely to discolor. Therefore, the flash discharge lamp 10 in this embodiment has a long life and high reliability.

[0073] [Another embodiment] Another embodiment will be described below. <1> Fig. 5 is a schematic cross-sectional view of a flash discharge lamp 10 of another embodiment when viewed in the Y direction. As shown in Fig. 5, the flash discharge lamp 10 may be equipped with adjacent conductors (14p, 14n) separated in the X direction. The adjacent conductors (14p, 14n) in this embodiment are arranged corresponding to a pair of electrodes (12p, 12n), but are controlled to be connected to the same node in the lighting circuit and have the same potential.

[0074] With the above configuration, since the proximal conductors (14p, 14n) are not arranged on the central side in the X direction, which is the main light emitting region of the arc tube 11, discoloration is less likely to occur around this region of the trigger tube 13.

[0075] Furthermore, in the flashlight irradiation device 1 equipped with the reflecting member 20 as shown in FIG. 1, the light L1 that is reflected by the reflecting member 20 and travels toward the workpiece W1 is not blocked by the proximate conductors (14p, 14n).

[0076] Therefore, according to the above configuration, the life of the flash discharge lamp 10 is extended and the blocking of the light L1 by the adjacent conductors (14p, 14n) is suppressed. Furthermore, even if discoloration occurs, the fluctuation of the illuminance of the light L1 irradiated to the workpiece W1 can be suppressed. In other words, the flash discharge lamp 10 having the above configuration has improved light output and higher reliability.

[0077] <2> The configurations of the flashlight irradiation device 1 and the flashlight discharge lamp 10 described above are merely examples, and the present invention is not limited to the configurations shown in the drawings. [Explanation of symbols]

[0078] 1 : Flash irradiation device 2: Capacitor 4: Switching element 5: Control section 6: Trance 7: Capacitor 8: Switching element 10: Flash discharge lamp 11: Arc tube 12n,12p: Electrode 13: Trigger tube 13a: Insertion tube 14, 14p, 14n: adjacent conductors 15: First feeder line 16: Second feeder line 20: Reflective material 21 : Reflective surface C1: Lighting circuit C2: Trigger circuit L1: light W1: Work W1a: Main surface

Claims

1. an arc tube extending in a first direction and transparent to light; a pair of electrodes disposed opposite each other in the first direction inside the arc tube; a trigger tube disposed adjacent to the light emitting tube; The trigger tube comprises: a proximal conductor disposed proximate to the arc tube, the proximal conductor having a core made of a conductive material extending along the first direction and having a relatively high melting point, and a protective layer formed on an outer surface of the core, the protective layer being made of at least one element belonging to the platinum group and having a relatively low melting point; a light-transmitting insertion tube extending along the first direction and housing at least a portion of the proximal conductor therein, the insertion tube being transparent to light.

2. 2. The flash discharge lamp according to claim 1, wherein the protective layer is made of at least one element selected from the group consisting of rhodium (Rh), ruthenium (Ru), platinum (Pt), and iridium (Ir).

3. 2. The flash discharge lamp according to claim 1, wherein the trigger tube is hermetically sealed with a space through which the proximal conductor is inserted being substantially in a vacuum state or filled with an inert gas.

4. 2. The flash discharge lamp according to claim 1, wherein the protective layer has a thickness of 100 [mu]m or less.

5. A flashlight irradiation device comprising the flashlight discharge lamp according to any one of claims 1 to 4.

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