Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/04—Electrodes; Screens; Shields
  • H01J61/06—Main electrodes
  • H01J61/073—Main electrodes for high-pressure discharge lamps
  • H01J61/0732—Main electrodes for high-pressure discharge lamps characterised by the construction of the electrode
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/04—Electrodes; Screens; Shields
  • H01J61/06—Main electrodes
  • H01J61/073—Main electrodes for high-pressure discharge lamps
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/04—Electrodes; Screens; Shields
  • H01J61/06—Main electrodes
  • H01J61/073—Main electrodes for high-pressure discharge lamps
  • H01J61/0735—Main electrodes for high-pressure discharge lamps characterised by the material of the electrode
  • H01J61/0737—Main electrodes for high-pressure discharge lamps characterised by the material of the electrode characterised by the electron emissive material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/84—Lamps with discharge constricted by high pressure
  • H01J61/86—Lamps with discharge constricted by high pressure with discharge additionally constricted by close spacing of electrodes, e.g. for optical projection

Definitions

• the invention relates to a short-arc high-pressure discharge lamp for direct current operation with a discharge vessel which has two diametrically opposed necks into which an anode and a cathode made of tungsten are melted gas-tight and which contains a filling of at least one noble gas and possibly mercury.
• Such lamps are used as mercury arc lamps, in particular for microlithography in the semiconductor industry, for the exposure of wafers and as xenon arc lamps for cinema and video projection.
• the mercury short-arc high-pressure discharge lamps used for the exposure process have to deliver a high light intensity in the ultraviolet wavelength range - in some cases limited to a few nanometers - with the light generation being limited to a small space.
• Such cathodes thus far preferably contain a doping of thorium oxide Th0 2 , which is reduced to thorium Th during lamp operation, occurs in this metallic form on the cathode surface and there leads to a reduction in the work function of the cathode.
• the lowering of the work function is accompanied by a reduction in the operating temperature of the cathode, which leads to a longer service life of the cathode, since less cathode material evaporates at lower temperatures.
• Th0 2 as a dopant is due to the fact that the evaporation of the dopant is relatively low and therefore leads to little disruptive precipitation in the lamp bulb (blackening, deposits).
• the excellent suitability of Th0 2 correlates with a high melting point of the oxide (3323 K) and metal (2028 K).
• the solution to the environmental problem is particularly urgent for lamps with high operating currents greater than 20 A, such as are used in microlithography or projection technology, since these lamps have a particularly high activity owing to the electrode size.
• the productivity of the imagesetter depends crucially on the amount of light that the lamp provides. Piston linings and electrode burn-back reduce the available useful light and lead to a loss of productivity of the very expensive systems due to increasing exposure times.
• This object is achieved in a short-arc high-pressure discharge lamp with the features of the preamble of claim 1 in that at least the material of the cathode tip contains, in addition to the tungsten, lanthanum oxide La 2 0 3 and at least one further oxide from the group Hf0 2 and Zr0 2 .
• the molar amount of Zr0 2 and Hf ⁇ 2 should advantageously be at least 2% of the molar amount of La 2 0 3 , but at the same time should not exceed the molar amount of La 2 0 3 , since the favorable influence on the luminous flux is always accompanied by an increased burn-back of the cathode , An excess of La 2 0 3 is guaranteed if the proportion by weight of Hf0 2 is not more than 0.65 times or the proportion by weight of Zr0 2 is not more than 0.38 times that of La 2 0 3 .
• the addition of the second oxide has a significant influence on the luminous flux and electrode burn-back during lamp operation.
• a mercury arc lamp with an output of 1.75 kW, a La 2 0 3 content of the cathode tip of 2.0% by weight and a further oxide showed the following properties in tests after 1500 hours of operation:
• cathodes made of thorium-free material have a larger arc base, especially when using mixed oxides.
• the optimal burn-back of such cathodes can be ensured if the plateau size of the cathode is adapted accordingly. If the size of the plateau was not adapted, the arch would either start at a plateau edge (in the case of a plateau that is too large) or would extend far beyond the edge of the plateau (plateau too small). In both cases, if the size of the plateau was not optimized, electrode damage and associated increased burn-back would be detectable. Since the plateau can be both flat and curved, the optimum plateau size can best be determined technically by specifying the current density in the cathode at a distance of 0.5 mm behind the cathode tip.
• FIG. 1 shows a mercury short-arc high-pressure discharge lamp according to the invention, in section
• FIG. 2 shows a detail of the cathode of the mercury short-arc high-pressure discharge lamp according to FIG. 1
• FIG. 3 shows a xenon short-arc high-pressure discharge lamp according to the invention, partly in section
• FIG. 4 shows the electrode arrangement of the xenon short-arc high-pressure discharge lamp according to FIG. 3, in an enlarged representation
• Figure 1 shows in section an inventive mercury short-arc high-pressure discharge lamp 1 with an output of 1.75 kW. It has a piston 2 made of quartz glass, which is elliptically shaped. This is followed by two ends 3 on two opposite sides, which are designed as piston necks 4 and each contain holding parts 8.
• the necks have a front conical part 4a, which contains a support roller 5 made of quartz glass as an essential component of the holding part, and a rear cylindrical part 4b, which forms the sealing seal.
• the front part 4a has an indentation 6 of 5 mm in length.
• the wall thickness of the piston 2 in this area is approximately 4 mm.
• the axial length of the support roller is 17 mm.
• a shaft 10 of a cathode 7 with an outer diameter of 6 mm is axially guided in the bore of the first support roller and extends into the discharge volume and carries an integral head part 25 there.
• the shaft 10 is extended backwards beyond the support roller 5 and ends on a plate 12, which is followed by the sealing seal in the form of a cylindrical quartz block 13.
• This is followed by a second plate 14, which holds an external power supply in the form of a molybdenum rod 15 in the middle.
• On the outer surface of the quartz block 13, four foils 16 made of molybdenum are guided along in a manner known per se and melted gas-tight on the wall of the piston neck.
• the anode 26, consisting of a separate head part 18 and shaft 19, is held in the bore of the second support roller 5.
• the cathode 7 and the holding part 8 is shown in detail.
• the cathode 7 is composed of a circular cylindrical shaft 10 of 36 mm in length and a head 25 of 20 mm in length, the head 25, like the shaft, having an outside diameter of 6 mm.
• the end of the head 25 facing the anode is designed as a tip 11 with a tip angle ⁇ of 60 ° and has a plateau-shaped end 27 with a diameter of 0.5 mm.
• the holding part consists of support rollers 5 and several foils in its bore.
• a film 24 is wrapped around the shaft several times (two to four layers).
• a pair of narrow foils 23, which face each other on the wound foil 24 gene, serves to fix the support roller. For this purpose, they protrude beyond the support roller on the discharge side and are bent outwards.
• the material of the tip 11 of the cathode 7 has a doping of 2.0% by weight of La 2 0 3 and 0.5% by weight of Zr0 2 .
• the mercury short-arc high-pressure discharge lamp according to the invention has a discharge vessel with a volume of 134 cm 3 , which is filled with 603 mg of mercury and xenon with a cold filling pressure of 800 mbar.
• the operating current of the lamp with an electrode spacing of 4.5 mm is 60 A.
• the current density J in the cathode at a distance of 0.5 mm from the plateau tip is 66 A / mm 2 when the lamp is in operation.
• FIG. 3 shows a short-arc high-pressure discharge lamp 28 according to the invention with a pure Xe filling.
• the lamp 28 with a power consumption of 3 kW consists of a rotationally symmetrical lamp bulb 29 made of quartz glass, at the two ends of which a lamp neck 30, 31 is also attached made of quartz glass.
• a lamp neck 30, 31 is also attached made of quartz glass.
• an electrode rod 32 of a cathode 33 is melted in a gas-tight manner, the inner end of which carries a cathode head 34.
• an electrode rod 35 of an anode 36 is also sealed in a gas-tight manner, on the inner end of which an anode head 37 is fastened.
• base systems 38, 39 are attached for mounting and for electrical contacting.
• the cathode head 34 is composed of a conical end section 34a facing the anode head 37 and an end section 34b facing the electrode rod 32 with a circular-cylindrical and frustoconical section, whereby between these two sections 34a, 34b, as Heat accumulation designated 34c also of smaller diameter is located.
• the tip of the conical support facing the anode head 37 end portion 34a of the cathode head 34 with a cone angle ⁇ of 40 ° is designed as a hemisphere with a radius R of 0.6 mm.
• the lamp current is 100 A and the resulting current density at the reference surface is 0.5 mm behind the cathode tip 88 A / mm 2 .
• the anode head 37 consists of a circular cylindrical middle section 37a with a diameter D of 22 mm and two frustoconical end sections 37b, 37c which face the cathode head 34 and the electrode rod 35.
• the frustoconical end section 37c facing the cathode head 34 has a plateau AP with a diameter of 6 mm. All sections of the two electrodes 33, 36 consist of tungsten.
• the conical end section 34a of the cathode head 34 has a dosage of 2.0% by weight of La 2 0 3 and 0.5% by weight of Hf0 2 .
• the two electrodes 33, 36 are mounted opposite each other in the axis of the lamp bulb 29 in such a way that when the lamp is hot, there is an electrode spacing or an arc length of 3.5 mm.

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• Discharge Lamp (AREA)
• Discharge Lamps And Accessories Thereof (AREA)

Applications Claiming Priority (3)

Publications (3)

Family

ID=27762648

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (27)

Family Cites Families (26)

• 2002
  • 2002-03-05 DE DE10209426A patent/DE10209426A1/de not_active Withdrawn
• 2003
  • 2003-03-03 TW TW092104423A patent/TWI288943B/zh not_active IP Right Cessation
  • 2003-03-05 EP EP03720140A patent/EP1481418B8/de not_active Expired - Lifetime
  • 2003-03-05 CN CNA038052253A patent/CN1639833A/zh active Pending
  • 2003-03-05 WO PCT/DE2003/000707 patent/WO2003075310A1/de active Application Filing
  • 2003-03-05 KR KR1020047013779A patent/KR100944818B1/ko active IP Right Grant
  • 2003-03-05 JP JP2003573671A patent/JP4741190B2/ja not_active Expired - Fee Related
  • 2003-03-05 US US10/506,528 patent/US7279839B2/en not_active Expired - Lifetime

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