JPH11191396A5 - - Google Patents

Description

[0002]
2. Description of the Related Art
Excimer lamps are a type of discharge lamp used as an ultraviolet light source for photochemical reactions. The ultraviolet light (hereinafter referred to as "excimer light") generated by an excimer lamp has wavelengths of 172 nm, 222 nm, 308 nm, etc., depending on the type of discharge gas filled in the excimer lamp. Of these wavelengths, excimer light with a wavelength of 172 nm is preferably used for precision cleaning of silicon wafers in semiconductor manufacturing processes, and excimer light with a wavelength of 222 nm is preferably used for decomposing chlorine-based organic compounds.

According to this invention, since the internal electrode is disposed inside the U-shaped internal tube, it is as if at least two internal electrodes were provided within the discharge vessel, and this increases the opportunities for high frequency discharge between the external electrode and the internal electrode, improving luminous efficiency. Furthermore, since a high frequency voltage, particularly a high frequency voltage of 1 to 20 MHz, is applied between the external and internal electrodes, thermal efficiency is good and luminous efficiency relative to input power is improved.

According to this invention, the excimer lamp has an internal electrode mounted inside a U-shaped internal tube, and is comprised of a high-frequency power supply that applies high-frequency voltage, which increases the chance of high-frequency discharge occurring between the internal electrode and the external electrode. Furthermore, because this high-frequency discharge occurs through the application of a controlled high-frequency voltage, it has good thermal efficiency and can improve the light-emitting efficiency relative to the input power.

At least one U-shaped inner tube 3 is disposed inside the discharge vessel 2. This inner tube 3 is usually a quartz tube, which is a dielectric tube, specifically a synthetic quartz glass tube. An inner electrode 5 is provided inside the inner tube 3. As can be seen from Figures 1 and 2, this is equivalent to a configuration in which at least two inner electrodes 5 are provided inside the discharge vessel 2, which has the desirable effect of increasing the opportunities for high-frequency discharge between the inner tube 3 and the outer electrode 4. This increased opportunity for high-frequency discharge is extremely effective in improving the luminous efficiency of excimer light.

In this way, the liquid metal 7 or mesh-like metal 8 is disposed in the U-shaped inner tube 3 as the inner electrode 5, so that the inner electrode 5 does not come into direct contact with the discharge gas 6. This has the desirable effect of generating a high-frequency discharge uniformly in each part of the inner tube 3.

As described above, the ability to reduce the diameter of the inner tube 3 with the liquid metal as the inner electrode 5 means that two or more U-shaped inner tubes 3 can be provided in the discharge vessel 2, as shown in Figures 4 and 5, which increases the opportunities for high-frequency discharge between the inner tube 3 and the outer electrode 4, and is extremely effective in improving the luminous efficiency of the excimer light.

Furthermore, because the liquid metal that forms the internal electrode 5 does not come into direct contact with the discharge gas 6, there is the desirable effect that high-frequency discharge occurs uniformly throughout each part of the U-shaped internal tube 3, compared to when the metal comes into direct contact with the discharge gas. Furthermore, as described above, it is preferable that the internal tubes 3a, 3b, 3c, and 3d are provided approximately at the center of the discharge vessel 2. By arranging the internal tubes 3a, 3b, 3c, and 3d so that they are each spaced the same distance from the inner peripheral surface of the discharge vessel 2, it is possible to make the emission of excimer light on each of the internal tubes 3a, 3b, 3c, and 3d approximately the same, which is preferable.

As can be seen from the cross-sectional structures shown in Figures 2 and 5, the excimer lamp 1 can be configured in a similar manner to one provided with at least two or more internal electrodes by using a U-shaped internal tube 3. This means that, compared to the cross-sectional structure of a conventional excimer lamp as shown in Figure 7, by adjusting the dimensions of the discharge vessel 2 and internal tube 3 and the number of internal tubes 3, it is possible to increase the opportunity for high-frequency discharge in each of the internal tubes 3a, 3b, 3c, and 3d, thereby further improving the luminous efficiency of excimer light.

Furthermore, the excimer lamp 1 of the present invention emits excimer light by applying a high-frequency voltage between the external electrode 4 and the internal electrode 5 to generate a high-frequency discharge . Applying a high-frequency voltage to the excimer lamp 1 increases the amount of excimer light emitted relative to the input power, thereby achieving sufficient light-emitting efficiency and reducing power consumption, which is also economically advantageous.

At this time, the high frequency voltage output from the high frequency power supply 11 (see FIG. 6) is preferably 0.1 to 10 KV , and more preferably 0.1 to 5 KV . If the high frequency voltage is less than 0.1 KV , sufficient discharge does not occur between the external electrode 4 and the internal electrode 5, and sufficient excimer light cannot be emitted. If the high frequency voltage exceeds 10 KV , the amount of light emitted becomes saturated, and sufficient light emission efficiency cannot be obtained relative to the input power, and power consumption increases, resulting in poor efficiency.

The power supply device 9 shown here basically comprises a high-frequency power supply 11, a matching controller 10, inductances L1 and L2, and variable capacitors C1 and C2. Power of typically about 100 V is applied to the power supply device 9 from an AC power supply 12. This power is frequency-converted by the high-frequency power supply 11 to a predetermined frequency within the range of 1 to 20 MHz, as described above, and then output from the high-frequency power supply 11. As described above, the high-frequency voltage at this time is preferably 0.1 to 10 kV , and more preferably 0.1 to 5 kV . The circuit within the power supply device 9 shown in FIG. 6 adjusts the variable capacitor C1 using the matching controller 10 to match the output impedance Z1 output from the high-frequency power supply 11 with the input impedance Z2 input to the excimer lamp 1, thereby controlling the excimer lamp 1 to emit excimer light most efficiently.

For example, to irradiate excimer light with an irradiance of 10 mW/ ^cm² from the outer peripheral surface of the discharge vessel 2, in the case of an excimer light-emitting device 20 using the excimer lamp 1 of the present invention shown in Figure 1, a high-frequency wave of 13.56 MHz and a power of 25 to 30 W are simply input to the excimer lamp 1. However, in the case of a conventional excimer lamp having a cross-sectional structure such as that shown in Figure 7, the high-frequency discharge is not achieved by applying a high-frequency voltage, but rather a voltage of 1 to 10 KV is typically applied to the excimer lamp at a frequency of 100 to 300 KHz. Therefore, to irradiate excimer light with an irradiance of 10 mW/cm², a power of approximately 50 W must be input to the excimer lamp, resulting in poor light-emitting efficiency, approximately half that of the present invention.

[0036]
[Effects of the Invention]
As described above, in the excimer lamp of the present invention, the internal electrode is disposed inside the U-shaped internal tube, which is equivalent to providing at least two internal electrodes within the discharge vessel, increasing the opportunities for high-frequency discharge between the external electrode and the internal electrode and improving luminous efficiency. Furthermore, a high-frequency voltage, particularly a high-frequency voltage of 1 to 20 MHz, is applied between the external and internal electrodes, resulting in good thermal efficiency and improved luminous efficiency relative to input power.

Furthermore, the excimer light emitting device of the present invention is composed of an excimer lamp that increases the chance of high-frequency discharge between the internal electrode and external electrode arranged inside the U-shaped internal tube, and a high-frequency power supply for applying a high-frequency voltage between the external electrode and internal electrode, so that the light emitting device has good thermal efficiency and excellent light emitting efficiency relative to the input power.

Claims (3)

The discharge vessel is made of a dielectric material having excellent light transmission properties, and at least one U-shaped inner tube is disposed inside the discharge vessel. An outer electrode is disposed outside the discharge vessel, an inner electrode is disposed inside the inner tube, and a discharge gas is filled in the discharge vessel.
An excimer lamp characterized in that excimers are generated by applying a high frequency voltage between the external electrode and the internal electrode. 2. The excimer lamp according to claim 1, wherein the high-frequency voltage is applied at a frequency of 1 to 20 MHz. an excimer lamp comprising a discharge vessel made of a dielectric material having excellent light transmission properties, at least one U-shaped inner tube disposed inside the discharge vessel, an outer electrode disposed outside the discharge vessel, an inner electrode disposed inside the inner tube, and a discharge gas filled in the discharge vessel;
and a high frequency power supply for applying a high frequency voltage between the external electrode and the internal electrode.