JP2732454B2 - High pressure mercury lamp - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short arc type high pressure mercury lamp suitable for an exposure lamp used in a semiconductor device production process.

[Prior art and its problems] In a bulb surrounding a light emitting space, mercury and a rare gas whose vapor pressure becomes about 1 atm to 30 atm during lighting are sealed, and a pair of anode and cathode electrodes are close to each other. The so-called short-arc type high-pressure mercury lamp, which is disposed opposite to the main body, often uses tungsten containing several percent of thorium oxide, so-called thoriated tungsten (hereinafter referred to as ThW) as its cathode. In order to promote the vaporization of mercury remaining in the hermetically sealed portion below the bulb, the electrodes are positioned such that the anode, which becomes hot at the time of lighting, is located below and the cathode is located above.

Incidentally, since such high-pressure mercury lamps have been transferred as exposure lamps in the semiconductor device production process, "fluctuations" in the brightness of arcs have become a very serious problem. One of the reasons is that besides the fact that accurate exposure is required in the production process,
This is because lamps have recently been used for pulse lighting. (For example, U.S. Pat.
However, as long as ThW is used for the cathode, the operating temperature of the cathode must be set at 2000 ° C or higher, and in fact, 2600 ° C or higher. The brightness of the arc is 100% of the median value due to the influence of changes in the arc length and electrical characteristics.
, "Wobble" of ± 2 to 3% occurs.

Therefore, in order to reduce the "wander", an electron emission material (hereinafter, referred to as an emitter) of an alkaline earth metal system (hereinafter, referred to as a barium system) having an operating temperature lower than ThW and causing less burning at the tip of the cathode. I can guess that it would be better to use.)). However, as described above, when the cathode is lit with the cathode positioned above, the tip of the cathode is located at the position where the cathode is most strongly heated in the bulb. Discolors immediately. Therefore, we considered replacing the ThW with a barium system, and lighting the lamp with the anode up and the cathode down. However, if the lamp is lit in such a state, it operates as a cathode even if the temperature of the cathode is set significantly lower than that in the case of ThW, but the temperature of the hermetically sealed portion below the bulb also decreases, and mercury staying there Vaporization slows down. Therefore, the rise time of the light quantity at the beginning of lighting (the time until the light quantity reaches the design light quantity) is delayed, and it has been found that the pulse lighting is extremely inconvenient.

[Object of the invention]

The present invention has been made in view of such circumstances,
Its purpose is to fill a bulb surrounding the light emitting space with mercury and a rare gas whose vapor pressure becomes about 1 to 30 atm when lit, and a pair of anode and cathode electrodes in close proximity. In high-pressure mercury lamps arranged opposite to each other, (1) less fluctuation of the bright spot of the arc, (2) less discoloration of the bulb, (3) fast rise of the light quantity, especially used in the semiconductor device production process To provide a high-pressure mercury lamp suitable for an exposure lamp to be used.

[Means for achieving the purpose]

In order to achieve this object, in the high-pressure mercury lamp, the invention according to claim 1, wherein the cathode supports a sintered body of a high-melting metal powder containing an alkaline earth metal-based emitter at its tip. Then, rhodium or rhenium plating is applied to the peripheral surface of the body portion, and a protruding portion is formed at the center of the rear end surface, and the front end portion of the metal foil for airtight sealing is connected to the peripheral portion of the rear end surface of the cathode. The central part of the metal foil is tightly clamped between the inner surface of the branch pipe extending from the bulb and the outer surface of the side of the glass cup arranged in the branch pipe. And the other end of the metal foil is guided to the external electric conductor material, and the position of the cathode is defined by the bottom of the crow cup where the branch tube portion near the body of the cathode and the projection of the cathode abut, In the electrodes, the anode is positioned above the cathode Characterized in that it is lit used in posture.

In the invention described in the second aspect, an inclined portion is formed between the side portion and the bottom portion of the glass cup, and the opening angle of the inclined portion is set to 30 degrees.
It shall be specified between ゜ and 150 ゜.

[Action]

The operating temperature of barium emitters is 1200 ° C
Since the temperature is about 1300 ° C., the anode is turned on by a DC power supply in a position above the cathode to suppress the temperature rise of the cathode, and the design temperature of the cathode can be set remarkably lower than that in the case of ThW. Accordingly, the tip of the cathode is hardly burnt, the "fluctuation" of the arc brightness is small, barium is hardly scattered, and the bulb is not discolored.

Next, since the position of the cathode is defined by the bottom of the crow cup where the branch tube portion adjacent to the periphery of the body of the cathode and the projection formed at the center of the rear end face of the cathode abut, the body of the cathode and The gap with the branch pipe and the gap in the branch pipe rearward from the rear end face of the cathode can be significantly reduced. Therefore,
Since a small amount of mercury escapes into these gaps and stays near the cathode, even if the lamp is turned on with the cathode down, the delay in the vaporization of mercury can be minimized, and the rise of the amount of light is fast. No problem occurs even if the pulse is lit.

〔Example〕

FIG. 1 is an explanatory view of a main part of a high-pressure mercury lamp designed as an exposure lamp used in a semiconductor device production process.

In FIG. 1, reference numeral 1 denotes a spindle-shaped valve made of quartz glass, and reference numeral 2 denotes a branch portion integrally extending from the valve 1.
A glass cup 3, also made of quartz glass, is arranged inside the branch pipe part 2, and for example, four strips are formed between the inner surface of the branch pipe part 2 and the outer surface of the side part 31 of the glass cup 3. The molybdenum metal foil 4 is held under pressure to form a hermetically sealed portion. The rear end of the metal foil 4 is electrically led to an external electric conductor (not shown). Although the inside of the glass cup 3 is not shown, the internal structure and the connection structure of the rear end of the metal foil 4 are shown in FIGS.
2-47052, actual opening 62-47053, actual opening 62-47055, actual opening
62-47056, Japanese Utility Model Application Laid-Open No. 62-47057, Japanese Utility Model Application Laid-Open No. 62-47059, and various other design structures disclosed in the patent documents can be adopted.

The cathode 5 carries a sintered body 6 obtained by mixing and sintering 30 parts by weight of barium oxide with 100 parts by weight of tungsten powder on a cone-shaped tip portion 51. A rhodium or rhenium plating layer 7 is formed on the peripheral surface of the body 52 of the cathode 5. Therefore, even when the branch pipe portion 2 is heated and softened during the manufacture of the lamp, and the “squeezing” operation is performed, no damage accident occurs due to fusion between the inner surface of the branch pipe portion 2 and the body portion 52.

At the center of the rear end surface of the cathode 5, a protruding portion 53 is formed, and slightly protrudes from the peripheral portion. For example, the tips 41 of the four band-shaped metal foils 4 are radially connected to the peripheral portion 54 at regular intervals by a brazing material such as platinum, but the connection strength is not always sufficient. Therefore, the disk-shaped metal plate 8 is fixed by the method described below, and the leading end 41 of the metal foil 4 is pressed and held. The metal plate 8 has a central hole 81 for receiving the projection 53.
The outer diameter is substantially equal to the outer diameter of the body 52 of the cathode 5. Then, as shown in FIG. 2, the metal plate 8 is put on the front end portion 41 of the metal foil 4 so as to be in contact with the peripheral portion 54, and the metal plate 8 in the vicinity of the protruding portion 53 or in the vicinity of the protruding portion 53 is removed. When the metal plate 8 is slightly deformed by the punch, the metal plate 8 and the protruding portion 53 are fixed, and the distal end portion 41 of the metal foil 4 is firmly pressed and held, and does not come off even if a small tensile stress is applied. In FIG. 2, the symbol P is a deformed portion. Alternatively, the metal plate 8 and the front end portion 41 and the peripheral portion 54 of the metal foil 4 may be integrally welded by an electron beam or a plasma arc.

When the distal end portion 41 of the metal foil 4 is fixed to the peripheral portion 54 of the cathode 5, the operation of “squeezing” the branch pipe portion 2 is performed with the protruding portion 53 in contact with the bottom surface 32 of the glass cup 3. by this,
The gap between the body part 52 of the cathode 5 and the inner surface of the branch pipe part 2 is
The gap becomes the minimum necessary in consideration of the increase in the outer diameter due to the thermal expansion of the cathode, and the position of the cathode 5 is defined by the inner surface of the branch tube portion 2 and the bottom surface 32 of the glass cup 3. When the lamp is turned on, the cathode 5 is positioned below as shown in FIG. 1, so that the above-described holding structure is sufficient.

Since the gap between the body 52 of the cathode 5 and the inner surface of the branch pipe 2 and the gap behind the cathode 5 are extremely small, there is little room for mercury to escape through these gaps. , The vaporization of mercury is promoted, and the rise time of the light amount is shortened even in the case of pulse lighting.

In the illustrated example, an inclined portion 33 is provided between the bottom portion 32 and the side portion 31 of the glass cup 3. When the opening angle θ of the inclined portion 33 is 0 °, that is, when there is no inclined portion 33, even if the metal foil 4 is pulled backward, the stress is received by the metal plate 8 and It hardly communicates until 41. Therefore, in the sense that the metal foil 4 is fixed to the cathode 5, it is most preferable that there is no inclined portion 33. However, as is well known, it is very difficult to manufacture a lamp without the inclined portion 33. . Therefore, empirically, the opening angle θ
However, it is preferable to provide the inclined portion 33 having an angle of 30 ° to 150 °. When the opening angle θ is in this range, the lamp can be easily manufactured, and the metal foil 4 and the cathode 5 have sufficient strength for fixing.

 Next, an example of a lamp design will be described.

The body 52 of the cathode 5 has diameters and lengths of 11 mm and 40 mm, and the height of the protrusion 53 is 0.55 mm. And the tip 51
The cone shape is designed so that the operating temperature is about 1200 ° C. to 1300 ° C. Metal foil 4 has a thickness of 0.04 mm and a width of 10
4 mm, and the thickness of the metal plate 8 is 0.5 mm. Such a lamp is pulse-lit by a DC power supply by a method of superimposing pulses. In other words, low-level lighting with power consumption of 1 to 1.5KW and power consumption of 2KW (current about 40A, voltage about 50V)
And high level lighting are alternately turned on at one second intervals. Then, when the "sway" of the bright spot of the arc was measured, it was within a range of ± 0.5% when the median value was 100%, and it was confirmed that the "sway" was significantly reduced as compared with the conventional case. The lamp life is determined by comparing the intensity of the radiation wavelength used for exposure to the initial value.
The time to maintain 70% is set, but the target life of this lamp is 600 hours, and the data of "wander" in the lighting test is the value at 600 hours. In addition, as a well-known method of collecting the data, the light emitted from the bright spot of the arc was taken out from the slit and the change in the intensity was measured.

〔The invention's effect〕

The high-pressure mercury lamp of the present invention has a cathode emitter of ThW
Since the lamp is used for lighting by replacing the barium system with the cathode positioned below, the "blur" of the bright spot of the arc is small, and the discoloration of the bulb is also small. Since the gap around and behind the cathode body is extremely small, the escape of mercury to the rear is small, and the initial characteristics at the time of lighting and the lamp characteristics at the time of pulse lighting are good, and are used in the semiconductor device production process. It is possible to provide a high-pressure mercury lamp which is very preferable as an exposure lamp.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention, and FIG. DESCRIPTION OF SYMBOLS 1 ... Valve, 2 ... Branch pipe part, 3 ... Glass cup 4 ... Metal foil, 5 ... Cathode, 51 ... Tip part 52 ... Body part, 53 ... Projection part, 54 ... Perimeter Part 6: sintered body, 7: plating layer, 8: metal plate

Claims (2)

(57) [Claims] 1. A bulb surrounding a light emitting space is filled with mercury and a rare gas whose vapor pressure is about 1 atm to 30 atm at the time of lighting, and a pair of anode and cathode electrodes are arranged close to and opposed to each other. In the high-pressure mercury lamp described above, the cathode carries a sintered body of a high-melting metal powder containing an emitter of an alkaline earth metal system at the tip thereof, and a rhodium or rhenium plating is applied to the body peripheral surface. Then, a protruding portion is formed at the center of the end face, and the tip of the metal foil for hermetic sealing is connected to the periphery of the rear end face of the cathode, and is held and fixed by a metal plate from above, The central part of the foil is tightly clamped between the inner surface of the branch extending from the bulb and the outer surface of the side of the glass cup arranged in the branch, and the other end of the metal foil is externally held. Guided to the electric conductor material, the position of the cathode Is defined by a branch pipe portion that is close to the periphery of the body of the cathode and the bottom surface of the crow cup where the protruding portion of the cathode abuts, and the electrode is used for lighting with the anode positioned above the cathode. A high-pressure mercury lamp characterized in that: 2. The glass cup has an inclined portion between a side portion and a bottom portion, and an opening angle of the inclined portion is 30 ° to 15 °.
2. The high-pressure mercury lamp according to claim 1, wherein the angle is defined as 0 °.