JPH06312131A - Purification using dielectric barrier discharge lamp - Google Patents

Abstract

PURPOSE:To clean an object with a large area to be washed uniformly and rapidly to remove a contaminant of inorganic substance by arranging the object in an atmosphere of chlorine and irradiating the object with an ultraviolet light projected from a dielectric barrier discharge lamp having a radiative light within a wavelength range of specific value, by using a mixed gas of xenon and chlorine as an electric discharge gas. CONSTITUTION:A semiconductor wafer 8 as an object to be washed is arranged in an atmosphere of chlorine, and is irradiated using an ultraviolet light emitted from dielectric barrier discharge lamps 4a to 4e which have radiative light within a wavelength range of 300 to 320 expressed in units of nm, by using a mixed gas of xenon and chlorine as an electric discharge gas, to clean the semiconductor wafer 8. The dielectric barrier discharge lamps 4a to 4e are installed in close proximity to the semiconductor wafer 8 in a cleaning duct 3, and the semiconductor wafer 8 is supported by a supporting device 5. The supporting device 5 has an electric heater for changing the temperature of the semiconductor wafer 8, and a movement mechanism for adjusting a distance between the semiconductor wafer 8 and the dielectric barrier discharge lamps 4a to 4e.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called photo-cleaning method for cleaning and removing contaminants of several molecules to several tens of nanometers layer adhering to silicon wafers, glass, ceramics, plastics, etc. under UV irradiation. Regarding

[0002]

2. Description of the Related Art As a technique related to the present invention, there is, for example, Japanese Patent Laid-Open Publication No. 1-144560.
It describes a lamp using a dielectric barrier discharge (also known as ozonizer discharge or silent discharge. See the revised edition "Discharge Handbook" published by the Institute of Electrical Engineers of Japan, June 2001, Reprint 7th edition, page 263). It has been known for a long time that organic substances can be removed by irradiating ultraviolet rays in an ozone atmosphere, and a cleaning method using a low-pressure mercury lamp as an ultraviolet light source has been put into practical use. These conventional methods have problems that the inorganic substances cannot be removed, it is difficult to uniformly wash a large area, and the washing speed is not always sufficient.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning method capable of uniformly removing a contaminant consisting of an inorganic material on a large-area object at a high speed.

[0004]

The above object of the present invention is to place an object to be cleaned in a chlorine atmosphere, use a mixed gas of xenon and chlorine as a discharge gas, and use a wavelength range of 300 to 320 expressed in nm. It is achieved by irradiating the object to be cleaned with ultraviolet rays emitted from a dielectric barrier discharge lamp having a radiant light in the wavelength range of 1 to clean the object to be cleaned.

[0005]

[Function] A mixed gas of xenon and chlorine is used as the discharge gas, and the dielectric barrier discharge is performed by appropriately adjusting the discharge conditions such as gas pressure, discharge gap length, and discharge power density. Is formed, nm
Wavelength range 300 with maximum value at wavelength 308 expressed in units
A dielectric barrier discharge lamp is obtained which has radiated light from 1 to 320. When an object to be cleaned is irradiated with ultraviolet rays emitted from a dielectric barrier discharge lamp using a mixed gas of xenon and chlorine as a discharge gas in an atmosphere containing chlorine, ultraviolet rays near 308 nm dissociate chlorine molecules. To generate active chlorine atoms, and these active chlorine atoms react with the contaminants adhering to the object to be cleaned to form chlorides having a high vapor pressure, so that the contaminants can be removed and cleaning can be performed. It will be possible. The ultraviolet light of 308 is, in addition to the generation of chlorine atoms,
By directly acting on the contaminants, they activate or decompose the contaminants and accelerate the cleaning rate.

The dielectric barrier discharge lamp emits 30
A monochromatic ultraviolet ray having a narrow wavelength range near 8 nm cannot be generated by a conventional low pressure mercury discharge lamp. Further, since the dielectric barrier discharge lamp is characterized in that the temperature of the lamp can be lowered and the degree of freedom of the shape of the lamp is large, the dielectric barrier discharge lamp having an arbitrary shape is close to the object to be cleaned. It is possible to irradiate light with a characteristic spectral distribution, which cannot be obtained with a combination of conventional low pressure mercury discharge lamps and high pressure arc discharge lamps, evenly over a large area and with high efficiency. Will be possible. Therefore, it is possible to uniformly wash a large area with high efficiency and high speed using a small device. Also, as in the present invention, 308 nm
In the cleaning method using only the ultraviolet light in the vicinity, the energy of the ultraviolet light in the vicinity of 308 nm is smaller than that of the light emitted from the low-pressure mercury lamp which has been conventionally used, that is, 254 nm and 185 nm. There are few, and there is no distortion in the glass,
High-quality cleaning is possible.

By emitting ultraviolet rays in the above wavelength range, high efficiency and high quality cleaning can be achieved. Because, the ultraviolet rays in the above wavelength range, by using a mixed gas of xenon and chlorine as the main light emitting gas,
This is because light can be emitted by the excimer molecules of xenon and chlorine, but by using these gases, it is possible to realize a state in which the emission gas is less deteriorated and the light extraction window is less deteriorated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic view of a semiconductor wafer cleaning method according to an embodiment of the present invention. Dielectric barrier discharge lamps 4a, 4b, 4c, 4d and 4e are provided in the cleaning duct 3 close to the silicon wafer 8 which is the object to be cleaned. The silicon wafer 8 is supported by a support 5, which is a conventional means for changing the temperature of the object to be cleaned, such as an electric heater, the object to be cleaned and the dielectric barrier discharge lamp. It has a moving mechanism for adjusting the distance between 4a, 4b, 4c, 4d and 4e.

A schematic view of the coaxial cylindrical dielectric barrier discharge lamp used in the embodiment is shown in FIG. The discharge vessel 13 is made of quartz glass and has an inner tube 14 and an outer tube 15 arranged coaxially to form a hollow cylinder. The outer tube 15 serves as a dielectric barrier for discharge and a light extraction window. An electrode 17 made of a metal net that transmits light is provided on the outer surface thereof. A cylindrical metal electrode 16 also serving as a reflection plate for ultraviolet rays is provided on the inner diameter portion of the inner tube 14. A cooling fluid 19 is flown inside the cylindrical metal electrode 16 to lower the temperature of the entire dielectric barrier discharge lamp. Discharge vessel 13
A ring-shaped getter 18 is provided at one end of the. The discharge space 20 is filled with a discharge gas that forms excimer molecules by a dielectric barrier discharge, and the transparent electrode 17 made of a metal mesh provided on the surface of the dielectric 15 and the inner tube 14 have an inner diameter that reflects ultraviolet rays. Cylindrical metal electrode 16 that doubles as a plate
When a voltage is applied to the discharge space 2 by the AC power supply 26,
A so-called dielectric barrier discharge, which is also called an ozonizer discharge or a silent discharge, is generated in 0, and the dielectric 15 and the transparent electrode 1
Ultraviolet rays are radiated with high efficiency through 7. Although not shown in the drawing, the surface of the transparent electrode 17 is covered with an ultraviolet-transparent resin, glass, or the like to be electrically insulated, if necessary.
Further, it is desirable that the outer electrode 17 that is in direct contact with the object to be cleaned or the processing fluid is used at the ground potential.

In the first embodiment, 200 Torr of a mixed gas of xenon and chlorine is enclosed as the main component of the light emitting gas of the dielectric barrier discharge lamps 4a, 4b, 4c, 4d, 4e, and the maximum is around 308 nm. Has a value of 3
It emits ultraviolet light in the wavelength range of 00 to 320 nm. The ultraviolet rays decompose chlorine molecules into active chlorine atoms with high efficiency to generate active chlorine atoms. The shortest distance between the dielectric barrier discharge lamps 4a, 4b, 4c, 4d, 4e and the silicon wafer 8 as the object to be cleaned is 3 mm. The gas 1 injected from the processing fluid supply port 2 is argon at a partial pressure of 0.9 atm and chlorine gas at a pressure of 0.1 atm, and the cleaning duct 3
In the preparatory space 6 therein, ultraviolet rays of short wavelength emitted from the dielectric barrier discharge lamp decompose into active chlorine atoms. A mixed gas of chlorine gas and active chlorine atoms is blown onto the object to be cleaned 8. An oxide film layer on the surface of the silicon wafer formed by being exposed to the atmosphere by chlorine atoms generated by decomposition of chlorine gas in the spare space 6 in addition to chlorine atoms generated by decomposition of chlorine molecules in the processing space 7. Is removed and washed at high speed. Further, since ultraviolet light of 308 nm reaches the wafer 8 to be cleaned, the silicon surface is activated by this ultraviolet light, and active chlorine atoms receive electrons from the active silicon surface to become negative chlorine ions and become positive. The volatile chloride is generated by being drawn into the charged silicon crystal lattice, and thus the object to be cleaned can be cleaned at a higher speed.

Since the cooling fluid 19 is flown inside the cylindrical metal electrode 16 to lower the temperature of the entire dielectric barrier discharge lamp, there is no need to worry about heating the object to be cleaned by the dielectric barrier discharge lamp. , The distance between the object to be cleaned and the dielectric barrier discharge lamp can be made sufficiently small,
Therefore, it is possible to irradiate ultraviolet rays with high efficiency, and it is possible to wash and remove the object to be washed at high speed. In addition, unlike the conventional low-pressure mercury lamp, the dielectric barrier discharge lamp does not change the light output characteristics such as radiation efficiency even if the length and the distance between the lamps are changed. The lamps can be arranged so that they can be irradiated, and therefore a large area of the object to be cleaned can be uniformly cleaned with high efficiency. Also, unlike the conventional low-pressure mercury lamp, the light output can be changed by changing the input power to the lamp without changing the spectral distribution, so the input power to the lamp and the dielectric barrier discharge lamp and the object to be cleaned can be changed. By adjusting the distance between the objects, it is possible to control the amount of ultraviolet rays applied to the object to be cleaned 8. By reducing the amount of ultraviolet rays applied to the object to be cleaned 8, damage to the object to be cleaned due to ultraviolet rays is reduced, and high quality cleaning can be performed. By increasing the amount of ultraviolet rays applied to the object to be cleaned 8, the deteriorated object to be cleaned can be cleaned at high speed. The cleaning method of the present invention is most suitable for removing metallic iron, aluminum, sodium, chromium, and oxides thereof.

In the second embodiment of the present invention, the article 8 to be cleaned in the first embodiment is a glass plate for a liquid crystal display panel, and dielectric barrier discharge lamps 4a, 4b, 4c, 4 are provided.
The shortest distance between d and 4e and the glass plate to be cleaned is 2 m
It was set to m. Dust consisting of oxides of silicon, sodium, etc. adhering to the glass surface was efficiently removed and washed. When visible light is transmitted like the object to be cleaned of the present embodiment, minute contamination becomes a problem, and the effect of the present invention is more exerted. Therefore, it can be similarly applied to cleaning the sapphire plate.

A third embodiment of the present invention is shown in FIG. The structure of the dielectric barrier discharge lamp is similar to that of FIG. 2, but in this embodiment, the outer tube 15 is provided with a metal electrode 16 also serving as a reflection plate of ultraviolet rays, and the inner tube 14 is provided with an inner diameter portion thereof. An electrode 17 made of a metal net that transmits light is provided. When the plastics to be cleaned, which is a polyethylene bottle 22 in this example, is allowed to pass through the inside of the inner tube of the dielectric barrier discharge lamp together with chlorine gas, the active chlorine atoms generated by the ultraviolet rays and the direct irradiation of the ultraviolet rays cause The outer surface of the polyethylene bottle 22 is washed. Since the dielectric barrier discharge lamp has a hollow cylindrical shape, it is possible to efficiently irradiate a cylindrical bottle with ultraviolet rays, and it is possible to perform high-speed and highly efficient cleaning.

In the fourth embodiment of the present invention, the same dielectric barrier discharge lamp as in the third embodiment is used to clean a crystal piece for a crystal unit or a member made of ceramics. The entire surface of the member made of crystal pieces or ceramics can be cleaned almost uniformly, and in particular, metal deposits can be removed and cleaned.

The features of the embodiment of the present invention described above are summarized as follows in comparison with the conventional low pressure mercury lamp and the cleaning method using chlorine gas. (1) Since the irradiation device can have an arbitrary shape corresponding to the object to be cleaned, a compact and simple cleaning method can be obtained. (2) Since high-density active chlorine atoms can be generated, high-speed and highly efficient cleaning becomes possible. (3) Since the object to be cleaned can be irradiated with low-energy ultraviolet light, the object to be cleaned can be cleaned at high speed without damage. (4) Since heating of the object to be cleaned by the dielectric barrier discharge lamp is small, cleaning at a low temperature becomes possible. (5) A large-area object to be cleaned can be uniformly cleaned with high efficiency. (6) It is possible to control the amount of ultraviolet rays radiated to the object to be cleaned, and thus high-quality cleaning becomes possible.

[0016]

As described above, according to the present invention,
It is possible to provide a cleaning method capable of uniformly cleaning a large-area object to be cleaned at a high speed with a small-sized method.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an example of a dielectric barrier discharge lamp used in the present invention.

FIG. 3 is an explanatory diagram showing an outline of an embodiment of the present invention.

[Explanation of symbols]

1 Processing Fluid Air 2 Processing Fluid Supply Port 3 Cleaning Duct 4a, 4b, 4c, 4d, 4e Dielectric Barrier Discharge Lamp 5 Support 8 Semiconductor Wafer 14 Inner Tube 15 Outer Tube 16, 17 Electrode 19 Cooling Fluid 20 Discharge Space 21 AC power supply 22 Polyethylene bottle

Claims (5)

[Claims] 1. A dielectric material having an object to be cleaned placed in a chlorine atmosphere, a gas containing a mixed gas of xenon and chlorine as a discharge gas, and radiating light in a wavelength range of 300 to 320 expressed in nm. A cleaning method using a dielectric barrier discharge lamp, which comprises irradiating the object to be cleaned with ultraviolet rays emitted from a barrier discharge lamp to clean the object to be cleaned. 2. The cleaning method using a dielectric barrier discharge lamp according to claim 1, wherein the object to be cleaned is a semiconductor wafer. 3. The cleaning method using a dielectric barrier discharge lamp according to claim 1, wherein the object to be cleaned is glass. 4. The cleaning method using a dielectric barrier discharge lamp according to claim 1, wherein the object to be cleaned is plastics. 5. The cleaning method using a dielectric barrier discharge lamp according to claim 1, wherein the object to be cleaned is ceramics.