JPH087836A - Discharge lamp for semiconductor exposure - Google Patents

Abstract

PURPOSE:To obtain a high quality of discharge lamp for semiconductor exposure by prescribing the content of the OH group in the quartz glass of a discharge lamp in a specified range in weight ppm, or prescribing the metallic impurity density in the quartz glass less than a specified value in weight ppm. CONSTITUTION:In a spherical luminous tube 1 made of a quartz glass, an anode 2, and a cathode 3 are provided placing a distance L. In the cathode 3, the tip of an inner lead 11 is made in a specific form, a tangsten wire 12 is wound at a little rear side from the tip, and a short arc type discharge lamp which is lighted by a DC power source is formed. And the outer surface of a chip 13 is covered by a heat insulating membrane 14, while the low temperature part of the luminus tube 1 at the rear side of an electrode is covered by a heat insulating membrane 15. In the luminous tube 1, specific Pa of Hg and Xe are sealed. In this case, the OH group including amount in the quartz glass is made 300 to 800 in weight ppm, or the metallic impurity density in the quartz glass is made less than 1 in weight ppm. As a result, a color center is hardly generated on the quartz glass, the absorption by a thermal oscillation is little, and a discharge lamp which can pick up the light with the wave length 240nm to 254nm efficiently for a long period can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a wavelength of 240 to 254n.
The present invention relates to a light source lamp for a semiconductor exposure apparatus that prints a circuit pattern by using ultraviolet rays of m.

[0002]

2. Description of the Related Art Recent advances in VLSI development are remarkable,
As the degree of integration increases, high resolution is required, and a lamp having a short wavelength of light required for exposure is required. In the prior art, when exposing a semiconductor device having an integration degree of 1 Mbits or less, the g-line (center wavelength 436 nm) of a mercury lamp is used, and for a semiconductor device having an integration degree of more than that, modified illumination is used. , I-line (center wavelength 365 nm), it has been possible to manufacture a semiconductor device of about 64 MDRAM. High resolution and high NA as a light source necessary for exposing semiconductor devices of 256 MDRAM or more
A KrF laser (248 nm) capable of achieving the above has been proposed, and various experiments have been conducted for practical use. However, since this light source is coherent light, it is becoming difficult to achieve high resolution due to the interference effect between the resist film thicknesses on the wafer, and since this light source is irradiated in a pulsed manner, the glass material used as a lens and There are still many problems to be solved, such as large power damage to the reflector and short life.

On the other hand, attempts have been made to utilize the light emission around a wavelength of 250 nm of a mercury lamp as a light source for manufacturing a highly integrated semiconductor device of 256 MDRAM. For example, J. Vac. Sei. Technol. B7 (6) 1989, PP1607-161
As can be seen from Fig. 2, a reflection optical system is adopted to eliminate the chromatic aberration of the glass material, and the exposure wavelength band can be widened, so that the interference effect due to the resist film thickness can be prevented. Further, it is known that the damage to the glass material can be avoided because the peak intensity of light is much smaller than that of the laser. By the way, in the mercury lamp used in the semiconductor exposure apparatus as described above, according to Japanese Patent Publication No. 62-2428, the radiation wavelength range from the mercury lamp is 200 to 250 nm.
Becomes stronger when the amount of mercury filled per unit volume of the arc tube is M (mg / cc) and the rare gas filling pressure is P 1 ≦ M
It is specified that ≦ 13, 0.1 × 10 ⁵ ≦ P ≦ 1 × 10 ⁶ . However, according to the above enclosure amount, it is not possible to obtain a sufficiently strong radiant intensity that can be industrially used,
Throughput decrease in the semiconductor exposure process, that is,
This has led to a decrease in productivity. Further, in order to obtain the intensity that can be industrially used, there is no other way but to greatly increase the lamp input. According to this method, the device becomes large in size, and the heat radiation from the lamp also increases, The current situation is that new problems that are difficult to solve, such as thermal damage to the device, are emerging.

In view of the above circumstances, recently, research on a semiconductor exposure discharge lamp capable of efficiently extracting ultraviolet rays having a wavelength of 240 nm to 254 nm for emitting mercury molecules has progressed, and for example, the amount of mercury enclosed is 14 mg / cm ³ to 30 m.
g / cm ³ , xenon from 0.1 × 10 ⁵ Pa to 5 × 1
A discharge lamp regulated to 0 Pa (25 ° C. standard) has been proposed. However, it has been found that when the lamp is used for a long period of time, the arc tube is distorted and the ultraviolet ray transmittance is lowered faster than the g-line lamp or the i-line lamp.
It was also found that when the exposure wavelength used was a short wavelength, the radiant intensity of ultraviolet rays when the lamp was designed was different from the radiant intensity of ultraviolet rays when the lamp was on.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to suppress early generation of distortion of a light emitting tube and deterioration of ultraviolet transmittance in a discharge lamp for semiconductor exposure using mercury molecule light emission having a wavelength of 240 nm to 254 nm. Alternatively, it is possible to obtain the ultraviolet radiation intensity at the time of design even when the lamp is on, and to provide a good discharge lamp for semiconductor exposure.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to dispose a pair of electrodes close to each other in an arc tube made of quartz glass, and to enclose mercury and a rare gas as an enclosure to obtain a wavelength of 240 nm.
In a discharge lamp for semiconductor exposure, which is capable of efficiently extracting the emission of mercury molecules in the range from 1 to 254 nm, the OH group content of the quartz glass is 300 ppm by weight.
To 800 can be achieved.

Alternatively, a pair of electrodes are arranged close to each other in an arc tube made of quartz glass, and mercury and a rare gas are enclosed as an enclosure to efficiently emit light of mercury molecules in a wavelength range of 240 nm to 254 nm. In a discharge lamp for semiconductor exposure which can be taken out, it can be achieved by defining the amount of metal impurities in the quartz glass to be 1 or less in ppm by weight.

[0008]

In the prior art, arc tubes for g-line lamps and i-line lamps are made of quartz with a low OH group content, for example ppm
Therefore, "anhydrous quartz" of several tens ppm or less or several ppm or less is used. During use, the temperature of the arc tube is 10
This is because there is an advantage that the emission of oxygen, hydrogen, water, etc. from the arc tube is small even at about 00 ° C. However, such a quartz easily causes a color center due to ultraviolet rays, which easily causes distortion and lowers the ultraviolet transmittance. Therefore, quartz gas containing a large amount of OH groups was used to prevent color centers from occurring. If the weight ppm is 300 or more, there is an effect of suppressing the generation of color centers. However, although there is a problem of releasing water and the like, by installing a getter of tantalum or zirconium in the arc tube, other problems brought about by this can be solved, but it is still preferable that the content does not exceed 800 ppm.

On the other hand, with respect to metallic impurities, the transmittance of quartz glass is usually inspected at room temperature, and if the material has a predetermined transmittance, it is used even if it is contained by several ppm by weight ppm. It was However, as described above, the arc tube is heated to about 1000 ° C. during lamp operation, and the increase in vibration energy of atoms and molecules of the impurity metal cannot be ignored. For example, for quartz glass containing 25 ppm of the impurity metal, the wavelength of 248 nm If you check the transmittance,
20 at 800 to 1000 ° C based on the measured value at room temperature
It was found that the transmittance decreased as much as%. Therefore, in the present invention, this problem has been solved by reducing the metal impurities to 1% by weight or less.

From the above-mentioned action, it is apparent that even better results can be obtained by using quartz glass having an appropriately large number of OH groups and a small amount of impurity metals.

[0011]

1 is an explanatory view of an embodiment of a discharge lamp for semiconductor exposure of the present invention. In the figure, reference numeral 1 denotes a quartz glass arc tube having a spherical shape, a spindle shape, a rugby ball shape or the like, and an anode 2 and a cathode 3 are arranged close to each other. L is the distance between both electrodes. In the lamp used in the experiment, L = 3 mm. On both sides of the arc tube 1, hermetically sealed portions 4 and 5 are connected, and molybdenum metal foils 6 and 7 are embedded. Reference numerals 8 and 9 are external lead members connected to the foils 6 and 7, and reference numerals 10 and 11 are internal lead members connected to the foils 6 and 7. In this embodiment, the cathode 3 is formed by processing the tip of the inner lead member 11 into a predetermined shape and winding the tungsten wire 12 at a position slightly rearward from the tip. That is, it is a short arc type discharge lamp that is turned on by a DC power supply. Reference numeral 13 is the remaining portion of the exhaust pipe used when the lamp is manufactured, that is, a so-called chip, and has a heat insulating film 14 on the outer surface thereof. Reference numeral 15 is a heat insulating film provided in a low temperature portion of the arc tube surrounding the back of the electrode.

In the lamp having the above structure, 20 mg / cm ³ of mercury and 0.5 × 10 ⁵ Pa of xenon were enclosed in the arc tube. All amounts are based on 25 ° C. This lamp is lit with a DC constant power source at about 2000W. The voltage is about 29V and the current is about 70A.

FIG. 2 shows a lamp having the above-mentioned structure and electrical rating, in which lamps having different OH group concentrations of the quartz glass material of the arc tube are manufactured, and the peak wavelength of 248 nm is in the range of 240 nm or 254 nm. It is explanatory drawing of the data which carried out comparative investigation of the irradiance of light. The data value is a measured value 100 hours after the lighting. In the figure, the irradiance is displayed as other values with the value of 1 in the case of a lamp having an OH group concentration of quartz glass of 700 ppm by weight. As shown in the judgment column, silica glass having an OH group of 300 ppm by weight or more is good, but if it is too large, other defects become remarkable.

FIG. 3 is an explanatory view of data obtained as a result of making a lamp using quartz glass with different amounts of metal impurities and performing the same test as in the case of OH group. In the figure, silica glass with an OH group concentration of 300 ppm by weight is used, and the irradiance is from 240 nm to 254 n.
The initial lighting value of the light in the range of m, the lamp (ri) value is 1
Displayed other as. When this lamp is lit as described above, the maximum temperature exceeds 1000 ° C. on the inner surface of the arc tube, and if the concentration of metal impurities is high, its effect appears. As can be understood from the data, 1 wt ppm or less is preferable.

[0015]

As can be understood from the above description of the invention and the embodiments, according to the present invention, when the exposure wavelength is shorter than that of the g-line or i-line in the production process of the highly integrated semiconductor device. , On the quartz glass of the arc tube that constitutes the discharge lamp,
By using a material that is less likely to generate a color center and one that is less absorbed by thermal vibration due to less metal impurities, a wavelength of 240n having a peak at a wavelength of 248nm.
It is possible to provide a semiconductor exposure discharge lamp that can efficiently extract light in the range of m to 254 nm for a long time.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of a semiconductor exposure discharge lamp of the present invention.

FIG. 2 is an explanatory diagram of data on an OH group.

FIG. 3 is an explanatory diagram of data on metal impurities.

[Explanation of symbols]

 1 Arc Tube 2 Anode 3 Cathode 4,5 Sealing Part 6,7 Molybdenum Metal Foil 8,9 External Lead Member 10,11 Internal Lead Member 12 Tungsten Wire 13 Chip 14,15 Heat Insulating Film

Claims (3)

[Claims] 1. A pair of electrodes are arranged in close proximity in an arc tube made of quartz glass, and mercury and a rare gas are enclosed as an enclosure to efficiently emit light of mercury molecules in a wavelength range of 240 nm to 254 nm. In a discharge lamp for semiconductor exposure, which can be taken out, the quartz glass has an OH group content of 30 ppm by weight.
Discharge lamp for semiconductor exposure, characterized in that it is 0 to 800. 2. A pair of electrodes are arranged close to each other in an arc tube made of quartz glass, and mercury and a rare gas are enclosed as an enclosure to efficiently emit light of mercury molecules in a wavelength range of 240 nm to 254 nm. A discharge lamp for semiconductor exposure, wherein the amount of metallic impurities in the quartz glass is 1 or less in ppm by weight. 3. A pair of electrodes are arranged close to each other in an arc tube made of quartz glass, and mercury and a rare gas are enclosed as an enclosure to efficiently emit light of mercury molecules in a wavelength range of 240 nm to 254 nm. In a discharge lamp for semiconductor exposure, which can be taken out, the quartz glass has an OH group content of 3 ppm by weight.
Discharge lamp for semiconductor exposure, characterized in that it is from 00 to 800 and the content of metal impurities is 1 or less in ppm by weight.