JP3214154B2 - Cleaning method using dielectric barrier discharge lamp - Google Patents

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 from several molecules to several tens of nanometers attached to silicon wafers, glass, ceramics, plastics, etc. under ultraviolet irradiation. About.

[0002]

2. Description of the Related Art As a technique related to the present invention, there is, for example, Japanese Patent Application Laid-Open No. 1-144560.
It describes a lamp using a dielectric barrier discharge (also known as an ozonizer discharge or a silent discharge; see the revised edition of the “Discharge Handbook” published by the Institute of Electrical Engineers of Japan, reprinted 7th edition, June 1991, page 263). It has long been known that organic matter 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 to practical use. These conventional methods have problems such as the inability to remove inorganic substances, difficulty in uniformly cleaning a large area, and insufficient cleaning speed.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning method capable of uniformly and quickly removing a large-area object to be processed from inorganic contaminants.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to dispose an object to be cleaned in a chlorine atmosphere, use a mixed gas of xenon and chlorine as a discharge gas, and provide a wavelength range of 300 to 320 expressed in nm. This is achieved by irradiating the object to be cleaned with ultraviolet rays radiated from a dielectric barrier discharge lamp having radiation light in the wavelength range described above to clean the object to be cleaned.

[0005]

The excimer molecule of xenon and chlorine is obtained by using a mixed gas of xenon and chlorine as a discharge gas and performing a dielectric barrier discharge under appropriate discharge conditions such as gas pressure, discharge gap length, and discharge power density. Is formed and nm
Has a maximum value at a wavelength 308 expressed in units and has a wavelength range of 300
To 320 provide a dielectric barrier discharge lamp with radiation. When the object to be cleaned is irradiated with ultraviolet light emitted from a dielectric barrier discharge lamp using a mixed gas of xenon and chlorine as a discharge gas in an atmosphere containing chlorine, the ultraviolet light at about 308 nm dissociates chlorine molecules. To generate active chlorine atoms, and the active chlorine atoms react with the contaminants attached to the object to be cleaned to form chlorides having a high vapor pressure, so that the contaminants can be removed and the cleaning can be performed. Will be possible. The ultraviolet light of 308, in addition to the generation of chlorine atoms,
Activates or decomposes contaminants by acting directly on them, accelerating the cleaning rate.

The dielectric barrier discharge lamp radiates 30
Monochromatic ultraviolet light in a narrow wavelength range around 8 nm cannot be generated by a conventional low-pressure mercury discharge lamp. In addition, since the dielectric barrier discharge lamp has features such as lowering the temperature of the lamp and a large degree of freedom in the shape of the lamp, the dielectric barrier discharge lamp having an arbitrary shape close to the object to be cleaned. To irradiate a large area, uniformly, and efficiently with light with a characteristic spectral distribution that cannot be obtained with conventional low-pressure mercury discharge lamps or high-pressure arc discharge lamps alone. Becomes possible. Therefore, it is possible to clean a large area uniformly with high efficiency and high speed using a small apparatus. Further, as in the present invention, 308 nm
In the cleaning method using only ultraviolet light in the vicinity, ultraviolet light in the vicinity of 308 nm has lower energy than 254 nm and 185 nm, which are emission light of a conventionally used low-pressure mercury lamp. Less, and does not cause distortion in the glass,
High quality cleaning becomes possible.

By radiating ultraviolet rays in the above wavelength range, high efficiency and high quality cleaning can be achieved. The reason is that the ultraviolet light in the above wavelength range is obtained by using a mixed gas of xenon and chlorine as a main luminescent gas.
Although light can be emitted by excimer molecules of xenon and chlorine, use of these gases makes it possible to realize a state in which the emission gas is less deteriorated and the light extraction window is less deteriorated.

[0008]

FIG. 1 is 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 in proximity to the silicon wafer 8 to be cleaned. The silicon wafer 8 is supported by a support 5, and the support 5 includes a conventional means for changing the temperature of the object to be cleaned, such as an electric heater, and the object to be cleaned and the dielectric barrier discharge lamp. There is a moving mechanism for adjusting the distances between 4a, 4b, 4c, 4d, and 4e.

FIG. 2 is a schematic diagram of a coaxial cylindrical dielectric barrier discharge lamp used in the embodiment. 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 also serves as a dielectric barrier for a dielectric barrier 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 an ultraviolet reflector is provided on the inner diameter of the inner tube 14. A cooling fluid 19 flows inside the cylindrical metal electrode 16 to lower the temperature of the entire dielectric barrier discharge lamp. Discharge vessel 13
Is provided with a ring-shaped getter 18 at one end. The discharge space 20 is filled with a discharge gas for forming excimer molecules by a dielectric barrier discharge. The transparent electrode 17 made of a metal mesh provided on the surface of the dielectric 15 and the inner diameter of the inner tube 14 reflect ultraviolet light. Cylindrical metal electrode 16 also serving as plate
Is applied to the discharge space 2 by the AC power supply 26.
A so-called dielectric barrier discharge, also known as an ozonizer discharge or a silent discharge, occurs in the dielectric material 15 and the transparent electrode 1.
7, ultraviolet rays are emitted with high efficiency. Although not shown in the figure, the surface of the transparent electrode 17 is covered with an ultraviolet-permeable resin, glass, or the like, as required, to be electrically insulated.
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, a mixed gas of 200 Torr of xenon and chlorine is sealed as a main component of the luminescent gas of the dielectric barrier discharge lamps 4a, 4b, 4c, 4d, and 4e. 3 with value
It emits ultraviolet light in the wavelength range from 00 to 320 nm. The ultraviolet light decomposes 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 and 4e and the silicon wafer 8 to be cleaned is 3 mm. The gas 1 injected from the processing fluid supply port 2 is argon at 0.9 atm and chlorine gas at 0.1 atm in partial pressure.
In the preliminary space 6 in the inside, the ultraviolet light of short wavelength emitted from the dielectric barrier discharge lamp is decomposed into active chlorine atoms. A mixed gas of chlorine gas and active chlorine atoms is blown onto the object 8 to be cleaned. In addition to chlorine atoms generated by decomposition of chlorine molecules in the processing space 7 and chlorine atoms generated by decomposition of chlorine gas in the preliminary space 6, an oxide film layer on the surface of the silicon wafer formed by being exposed to the air. Are removed and washed at high speed. Further, since the 308 nm ultraviolet ray reaches the wafer 8 to be cleaned, the ultraviolet ray activates the silicon surface, and the active chlorine atoms receive electrons from the active silicon surface and become positive chlorine ions as negative chlorine ions. It is drawn into the charged silicon crystal lattice, and volatile chloride is generated. Therefore, the object to be cleaned can be cleaned at a higher speed.

Since the cooling fluid 19 flows 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 of 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 an object to be cleaned at high speed. Also, unlike the conventional low-pressure mercury lamp, the dielectric barrier discharge lamp does not change the light output characteristics such as the radiation efficiency even if the length and the distance between the lamps are changed. It is possible to arrange the lamp so that irradiation can be performed, and therefore, it is possible to efficiently and uniformly clean a large-area object to be cleaned. 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. By adjusting the distance between the objects, the amount of ultraviolet light applied to the object to be cleaned 8 can be controlled. By reducing the amount of ultraviolet light applied to the object 8 to be cleaned, damage to the object to be cleaned due to ultraviolet light is further reduced, and high-quality cleaning can be performed. By increasing the amount of ultraviolet rays irradiated to the object 8 to be cleaned, the deteriorated object that is difficult to wash can be washed at high speed. The cleaning method of the present invention is most suitable for removing metallic iron, aluminum, sodium, chromium, and oxides thereof.

In a second embodiment of the present invention, the object 8 to be cleaned in the first embodiment is a glass plate for a liquid crystal display panel, and the dielectric barrier discharge lamps 4a, 4b, 4c, 4 are used.
The shortest distance between d and 4e and the glass plate to be cleaned is 2 m
m. Dust consisting of oxides such as silicon and sodium adhered to the glass surface was efficiently removed and cleaned. In the case where visible light is transmitted as in the case of the object to be cleaned according to the present embodiment, minute stains become a problem, and the effect of the present invention is further exhibited. Therefore, the present invention can be similarly applied to cleaning of a sapphire plate and the like.

FIG. 3 shows a third embodiment of the present invention. The structure of the dielectric barrier discharge lamp is similar to that of FIG. 2, but in this embodiment, a metal electrode 16 also serving as an ultraviolet reflector is provided on the outer surface of the outer tube 15, and an inner tube of the inner tube 14 is provided on the inner surface. An electrode 17 made of a metal net that transmits light is provided. When plastics, which is the object to be cleaned, in this example, a polyethylene bottle 22 and chlorine gas pass through the inside of the inner tube of the dielectric barrier discharge lamp, 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 cleaned. Since the dielectric barrier discharge lamp has a hollow cylindrical shape, the cylindrical bottle can be efficiently irradiated with ultraviolet rays, and high-speed and high-efficiency cleaning becomes possible.

The fourth embodiment of the present invention uses the same dielectric barrier discharge lamp as the third embodiment, and cleans a quartz crystal blank or a member made of ceramics. The entire surface of a member made of a crystal piece or a ceramic can be almost uniformly cleaned, and in particular, metal adhered substances can be removed and cleaned.

The advantages of the above embodiment of the present invention are summarized below as compared with a conventional low-pressure mercury lamp and a cleaning method using chlorine gas. (1) Since the irradiation device can have an arbitrary shape corresponding to an object to be cleaned, a small and simple cleaning method can be obtained. (2) Since high-density active chlorine atoms can be generated, high-speed and high-efficiency cleaning becomes possible. (3) Since the object to be cleaned can be irradiated with low-energy ultraviolet rays, cleaning can be performed at high speed without damaging the object to be cleaned. (4) Since the object to be cleaned is hardly heated by the dielectric barrier discharge lamp, cleaning at a low temperature becomes possible. (5) A large-area object to be cleaned can be efficiently and uniformly cleaned. (6) The amount of ultraviolet light applied to the object to be cleaned can be controlled, so that high-quality cleaning can be performed.

[0016]

As described above, according to the present invention,
A cleaning method capable of cleaning a large-area object to be cleaned uniformly and at a high speed by a small-sized method can be provided.

[Brief description of the 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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-7623 (JP, A) JP-A-63-162873 (JP, A) JP-A-2-280831 (JP, A) JP-A-4- 229671 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 19/12 C03C 23/00 C04B 41/91 C08J 7/00 303 H01L 21/304 645

Claims (5)

(57) [Claims] 1. A dielectric 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 having emission light in a wavelength range of 300 to 320 expressed in nm. A cleaning method using a dielectric barrier discharge lamp, comprising irradiating the object to be cleaned with ultraviolet rays emitted from a barrier discharge lamp to clean the object to be cleaned. 2. A 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. A cleaning method using a dielectric barrier discharge lamp according to claim 1, wherein the object to be cleaned is a ceramic.