JPS61193358A - Light source - Google Patents

Abstract

PURPOSE:To obtain a light source of a long service life with little change in the luminous intensity and the spectrum with the passage of time, by plasma- radiating a sealed gas excited by laser beams in a bulb. CONSTITUTION:Laser beams from a laser radiator 1 are formed into an adequate beam form through optical system members 2 and 3, transmitted through the laser passage, and focused by a focusing optical member 4 to a focus point in a bulb 5. At the focus in the bulb, an electromagnetic field is generated which is strong enough to excite the sealed gas discharged, and a high temperature plasma of the sealed gas generated by a discharge radiates spectra including ultraviolet rays and infrared rays. Since this system has no electrode in the bulb, no change of luminous intensity or spectrum from the evaporation or spattering of the electrode is generated, and a long service life can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a light source device, and more particularly to a light source device suitable as an ultraviolet/deep ultraviolet light source that causes a sealed gas to emit plasma light by excitation with a laser beam.

[Prior art] Light source devices in semiconductor manufacturing equipment such as exposure equipment include
In addition to sufficient emission intensity in a desired wavelength range, there are various requirements such as long life and stable position of the emission center.

Conventionally, mercury vapor or rare gas (Xe) has been used as an ultraviolet or deep ultraviolet light source for photolithography.
This type generates an arc discharge between electrodes in a glass tube filled with gas (gas, etc.), and as the electrodes are exposed to the arc discharge, they become extremely high temperature and gradually evaporate, and the high speed generated by the arc It is unavoidable that the electrodes are worn out due to sputtering by particles, and the metal generated by these evaporation or sputtering adheres to the inner wall surface of the tube and changes the wavelength transmittance in the ultraviolet region, so the emission intensity decreases over time. and the spectrum gradually change, and at the same time, changes in the arc shape and the position of the emission center occur due to changes in the electrode shape.
Therefore, their lifespan is generally said to be limited to several hundred hours, and semiconductor manufacturing equipment has often been forced to stop in order to replace them. Furthermore, when replacing the tubes, the positions of the electrodes were slightly different for each tube, so it was necessary to fine-tune the position of the tubes each time the tubes were replaced.

[Objective and Summary of the Invention] The present invention solves the problems of the prior art as described above, and provides a light source device in which the emission intensity and spectrum change little over time, and the emission center position can be stably determined by an external optical system. A laser beam is focused from the outside on the gas sealed in a tube, and the excitation caused by the laser beam causes discharge destruction of the filled gas, and the filled gas is released at the focal position of the focused laser beam inside the tube. By generating high-temperature plasma, a light source with a stable emission intensity and emission center position with a spectral distribution according to the composition of the gas enclosed in the gas is obtained.

In the light source device of the present invention, since there are no electrodes inside the bulb, the emission intensity and spectrum do not change due to the effects of evaporation or sputtering, and a long life can be obtained. Since it is determined by the focal position of the laser beam, it can always be maintained stably and will not change even when the tube is replaced.

In the present invention, the sealed gas determines the emission spectrum distribution depending on its component composition. For example, for use in the ultraviolet to far ultraviolet region, a rare gas such as Xe, halogen gas, argon gas, mercury vapor, etc. may be sealed with a specific composition. obtain. In this case, the material of the tube itself is selected depending on the transmittance of the target wavelength range. For example, for ultraviolet or far ultraviolet light, calcium fluoride, lithium fluoride, magnesium fluoride, quartz glass, sapphire, etc. are used.

[Example] Examples of the present invention are as follows.

FIG. 1 is a configuration diagram showing an example of the basic configuration of a light source device according to the present invention, in which a laser oscillator 1 oscillates continuous or pulsed laser light with sufficient intensity to discharge excite the sealed gas. 2
and 3 are optical system members for transmitting laser light in a suitable shape that is easy to handle, and the transmitted laser light is focused at a focal position within tube 5 by condensing optical system member 4. The tube 5 is made of a material that transmits far ultraviolet rays and has a luminescent gas such as a rare gas such as Xe, argon gas, or mercury vapor sealed therein. Reference numeral 6 denotes a reflective optical system member for causing the laser beam that has passed through the tube 5 to enter the tube one more time, and is conjugate with the condensing optical system member 4.

The laser beam from the laser oscillator 1 is formed into an appropriate beam shape by the optical system member 2.3, transmitted along a required optical path, and condensed by the condensing optical system member 4 to a focal position within the tube 5. get together. At the focal point set approximately at the center of the tube 5, the strong energy of the laser beam generates a sufficiently strong electromagnetic field to excite the filled gas to discharge, and the high temperature plasma of the filled gas generated by the discharge generates ultraviolet light. Radiation is provided in a spectrum that includes deep ultraviolet radiation. In this case, the laser light that did not contribute to discharge excitation enters the reflective optical system component 6, is reflected there, and is focused again on the focal point within the bulb.

The light source device of the present invention is particularly suitable for semiconductor manufacturing equipment due to its emission intensity, spectrum, and stability of the emission center position. As a specific example of such an application, an example of application to an exposure apparatus is shown in FIG.

In Figure 2, the same symbols as in Figure 1 indicate the same thing,
Furthermore, 7 is an elliptical mirror for focusing and light, 8 is an illumination optical system device of an exposure apparatus, 9 is a mask, and 10 is a wafer. When the far ultraviolet rays emitted from the tube 5 are focused by the elliptical mirror 7 and projected onto the mask 9 by the illumination optical system device 8,
The circuit pattern of mask 9 is transferred to wafer 10 coated with photoresist. - [Effects of the Invention] As described above, according to the present invention, the sealed gas is excited with laser light within the tube to emit plasma light, so there is no need to provide electrodes within the tube. Therefore, the various problems of the conventional technology caused by the presence of electrodes can be solved all at once, and a long-life light source device with little change in emission intensity and spectrum over time can be obtained, and the emission center position can be changed regardless of the tube. Since it is determined by the focal position of the external condensing optical system, it is always stable and does not change even when the tube is replaced, making it easy to replace the tube, so you can prepare tubes with various filled gases. It also becomes easy to selectively obtain source light with various spectral distributions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of its application to semiconductor manufacturing equipment. 1: Laser oscillator, 2.3: Optical system components, 4: Focusing optical system components, 5: Tube, 6: Reflective optical system components.

Claims (1)

[Scope of Claims] 1. A gas-filled tube as a light emitting body, an excitation laser oscillation device, and an optical system device for condensing laser light from the laser oscillation device into the tube. 1. A light source device characterized in that the emitted laser light excites gas enclosed in a bulb to emit light. 2. The filled gas is a gas for ultraviolet or deep ultraviolet light emission such as rare gas, halogen gas, argon gas, mercury vapor,
Claim 1, characterized in that the bulb is made of a material that transmits light in the ultraviolet to deep ultraviolet region, such as calcium fluoride, lithium fluoride, magnesium fluoride, quartz glass, sapphire, etc. The light source device described in .