JP3341927B2 - Method and apparatus for cleaning a solid surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning solid surfaces, and more particularly to a method and apparatus for cleaning contaminants such as particulate matter and organic substances adhered to solid surfaces. The cleaning method and apparatus of the present invention include semiconductors, liquid crystals, various facilities, devices, instruments, products, surfaces of semi-finished products in advanced fields such as medical treatment, for example, walls of a clean room, walls of a wafer or liquid crystal transfer device, It can be applied to clean the walls of storages, carrier boxes, sterilization boxes, wafers and liquid crystals.

[0002]

2. Description of the Related Art Conventionally, as a cleaning technique, there is a cleaning method using a liquid. The method of cleaning uses liquids, which limits the field of application, increases the size of the apparatus, requires a mechanism for removing adhered liquid after cleaning and a drying step, and has the problem of recontamination. Was. As a cleaning technique using no liquid, a method as shown in FIG. 5 has been conventionally known. However, the target particle diameter in recent advanced industries is generally several μm or less, and the contact method cannot be used without effect for particles of several tens μm or less. Further, the non-contact type vacuum system and air knife system are similarly ineffective for particles having a size of several tens μm or less. The ultrasonic air method is effective up to the smallest target particle diameter among the conventional methods, and is effective even when it is several μm or more.
There is no effect when the thickness is 1 μm or less.

On the other hand, the present inventor previously irradiates the wafer with at least one selected from ultraviolet rays, radiation, and laser in an electric field in cleaning the wafer to emit photoelectrons from the wafer to cause the wafer to adhere to the adhered particles and the vicinity of the wafer. Collect fine particles of
There has been proposed a method of removing (Japanese Patent Laid-Open No. 4-239,13).
No. 1). This method is effective depending on the type and particle size of the adhered particles. However, if the particle size is too small, the effect may not be sufficiently obtained depending on the type of the adhered particles, and thus there is a need for improvement.

[0004] All of these techniques have a problem that the target is a particulate matter (essentially an inorganic substance) and has no effect on the surface contamination of an organic substance (such as a hydrocarbon). On the other hand, the UV / O ₃ purification method is applied for removing organic contamination, but there is a problem that it is not effective for removing particles (essentially inorganic). By the way, the actual pollution is
Since it is often a mixture of particulate matter and organic matter, the appearance of a new method effective for these particulate matter and organic matter has been expected.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and is intended to be used in a particular field of the advanced industry, which is expected to increase rapidly in the future, especially for finely adhered particles of 1 μm or less.
An object of the present invention is to provide a method and an apparatus for cleaning a solid surface that can effectively remove not only inorganic substances but also contaminants in which inorganic substances and organic substances are combined.

[0006]

According to the present invention, there is provided a method for cleaning a solid surface, comprising the steps of:
UV to said solid surface, laser, small selected from radiation
According to the present invention, there is provided a method for cleaning a solid surface, which comprises transmitting ultrasonic waves under an electric field under at least one type of irradiation .

Further , the present invention relates to an apparatus for cleaning a solid surface , comprising: an electric field setting electrode and an ultrasonic oscillation source to be applied to the solid surface;
ー 、 irradiate at least one kind selected from radiation
Ru der that the cleaning system of the solid surface, characterized in that it comprises a WESTERN.

Next, each configuration of the present invention will be described in detail. The electrode may be any as long as an electric field can be formed between the cleaning surface and the electrode, and an electrode material (eg, a tungsten material) in a known charging device can be suitably used. The shape can be appropriately selected and used, such as a linear shape, a rod shape, a net shape, a lattice shape, and a plate shape. The intensity of the electric field between the electrode and the cleaning surface may be such that the emitted photoelectrons act on the contact point of the cleaning surface of the adhered fine particles against the adhesion of the fine particles, and usually 10 V / cm.
１００100 kV / cm. The type, shape, electric field forming method and electric field strength of the electrode
Preliminary tests can be appropriately performed and determined according to the required performance and the like.

An ultraviolet lamp emits photoelectrons from a cleaned surface by irradiating the cleaned surface with an electric field.
Well-known ultraviolet sources can be used. In addition, in order to simultaneously remove attached organic substances (such as hydrocarbons), ozone generation and / or active oxygen generation from the ozone are performed simultaneously. That is, with respect to photoelectron emission from the cleaning surface, an ultraviolet lamp having an energy (eV) wavelength larger than the work function (eV) of the material of the cleaning surface may be used, such as a mercury lamp or a deuterium lamp. Light sources can be used. In addition, any organic substances can be removed as long as they generate ozone and generate active oxygen from the ozone.

In addition, radiation and / or laser irradiation can be performed instead of the above-mentioned ultraviolet rays. Any of these may be used as long as they emit photoelectrons by irradiating the clean surface. Regarding photoelectron emission by radiation irradiation, the present inventor has already proposed it, so that it can be used appropriately (Japanese Patent Application Laid-Open No. Sho 62-24459).
Regarding laser irradiation, there is another proposal by the present inventors (Japanese Patent Application Laid-Open No. 61-186744). Laser irradiation is preferable depending on the application device because it has an action of peeling off attached fine particles by itself in addition to the action of emitting photoelectrons.

These irradiation sources can be used alone or in combination of two or more depending on the type, scale, required performance and the like of the apparatus. Any ultrasonic wave can be used as long as it causes the adhered fine particles, which have changed in shape to be easily peeled, to be peeled off from the adhered surface. The frequency is usually 1 kHz to 5,000 kHz, preferably 10 kHz to 300 kHz, and a well-known generating means can be appropriately used. Examples of the generating means include a piezoelectric vibrator, a polymer piezoelectric film, an electrostrictive vibrator, a rangpan-type vibrator, a magnetostrictive vibrator, an electrodynamic transducer, and a capacitor transducer. The frequency and generation means to be used should be determined by conducting appropriate preliminary tests according to the application field, the type and size of the attached fine particles, the type and shape of the attached surface, the wavelength and intensity of the electric field and irradiation ultraviolet light, the device scale, the shape, the required performance, etc. Can be.

[0012]

The mechanism of removing adhered fine particles according to the present invention is basically different from a plurality of functions (photoemission from the adhered surface,
The details are not known because it is considered to be a synergistic effect of the action of an electric field, an ultrasonic wave, and the like, but it is presumed that mainly the following mechanism is passed. That is, the adhered fine particles act on the van der Waals force acting on the adhesion of the fine particles to the contact point between the adhered fine particles and the surface by the action of the photoelectron emission from the cleaning surface and the action of the electric field. Therefore, the adhesion of the fine particles is weakened.

Further, the attached fine particles are aggregated by the action of an electric field, the apparent particle size increases, and the attached fine particles have a size that facilitates peeling. Here, since the energy of the ultrasonic wave acts on the microparticles and the vicinity thereof, the separation of the adhered microparticles is easily achieved. The separated fine particles float near the substrate surface. The suspended particulates are charged by the emitted photoelectrons and are cleaned by collecting the charged particulates on the electrodes, as already proposed in another invention of the present inventors. (E.g.,
Japanese Patent Publication No. 3-5859, Japanese Patent Laid-Open Publication No. Hei 4-171061, etc.)

Further, the irradiation of the cleaning surface with at least one of ultraviolet rays, laser, and radiation by applying an electric field is performed by setting an electric field so that the attached fine particles are aggregated and changed to a shape and a size that are easily peeled. Further, photoelectrons are emitted from the cleaned surface, thereby exerting a separating action on the attached fine particles on the surface, and further, the separated fine particles are charged by the photoelectrons, and the electrodes collect and remove the fine particles. is there. In other words, the cleaned surface is used as a photoelectron emitting material, and the accompanying action is effectively used.

[0015]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Embodiment 1 FIG. 1 is a schematic explanatory view of an apparatus for cleaning the surface of a liquid crystal substrate (ITO / glass). In FIG. 1, fine particles 2 and organic substances (hydrocarbons) 3 adhere to the surface of a substrate 1. The cleaning device mainly includes an electrode 4, an ultraviolet lamp 5,
An ultrasonic oscillator 6 is provided. When an electric field is formed between the substrate 1 and the electrode 4 and the substrate 1 is irradiated with ultraviolet light from the ultraviolet lamp 5, photoelectrons 7 are emitted from the substrate surface 8 by a photoelectric effect.

When the photoelectrons 7 are emitted from the substrate surface 8,
Due to the action of the emitted photoelectrons and the electric field, a force opposing the adhesive force acts on the attached fine particles on the substrate surface 8, and the attached fine particles aggregate to change into a shape and size that are easily peeled. here,
When ultrasonic waves are oscillated from the ultrasonic oscillator 6 toward the substrate surface 8, the attached fine particles 2 are separated from the substrate surface 8 (away from the surface) and become floating fine particles 9. Next, the floating fine particles 9 are charged by the photoelectrons 7 emitted to the substrate surface to become charged fine particles 10. The charged fine particles 10 are collected by the electrode 4 by the action of an electric field, and the separated fine particles are collected and removed.

On the other hand, the organic substances 3 adhering to the substrate surface 8 are converted into ozone (O ₃ ) generated by ultraviolet rays from the ultraviolet lamp 5.
And / or decomposed into CO ₂ and H ₂ O by active oxygen (O ^* ) generated from the ozone. FIG. 2 shows a schematic diagram of the decomposition and removal of the organic substance 3. In this way, the attached fine particles 2 and organic substances 3 on the substrate surface are removed and the surface is cleaned.
The electrode 4 is made of a lattice-like Cu—Zn material and has a thickness of 1000 V / cm.
It is. As the ultraviolet lamp 5, 184 nm and 254 nm
A low-pressure mercury lamp that emits at the same wavelength is used. Also,
The ultrasonic oscillator 6 has a spherical shell-shaped concave oscillator,
kHz is used.

The adhered contaminants on the surface may be in the form of adhered particulate matter bound to organic matter (hydrocarbon) or surrounded. In such a case, with the configuration of this example, all contaminants can be removed by a single apparatus for all contaminants, which is practically effective. In particular, the particulate matter is charged by the photoelectrons at the same time as the exfoliation and is collected by the electrode, so that the problem of contamination (recontamination) to the surroundings is eliminated, and the practical effect is increased.

Embodiment 2 FIG. 3 is an explanatory view showing surface cleaning of a liquid crystal substrate (ITO / glass) to which fine particles (particulate matter) 2 are adhered. The cleaning device mainly includes an electrode 4 and an ultrasonic oscillator 6. When an electric field is formed between the substrate 1 and the electric field 4, a force against the adhesive force acts on the attached fine particles 2 due to the action of the electric field, and the attached fine particles aggregate and grow, and change to a shape and a size that are easily peeled. Here, when ultrasonic waves are oscillated from the ultrasonic oscillator 6 toward the substrate surface 8, the attached fine particles are separated from the substrate surface 8 and removed from the surface. The fine particles 9 removed and removed from the surface can be removed by using a well-known appropriate fine particle collecting means, for example, a filter, a collecting electrode, or charging / collecting by photoelectrons (not shown).

Next, each configuration will be described. The material and the shape of the electrode 4 are the same as in the first embodiment. In this example, the intensity of the electric field is stronger than that of Example 1 because it has no photoelectron emission action, and is usually 1 to 100 kV / cm. The field of application, the type and size of the attached fine particles, the type and shape of the attached surface, Preliminary tests can be appropriately performed and determined depending on the scale of the apparatus, required performance, and the like. In this example, it is 5 kV / cm. The ultrasonic oscillator 6 is the same as that of the first embodiment.

Embodiment 3 FIG. 4 is another explanatory view showing the surface cleaning of the liquid crystal glass substrate 1 to which fine particles (particulate matter) 2 are adhered. The cleaning device mainly includes the electrodes 4a and 4b, the ultrasonic oscillator 6
It is composed of The substrate 1 is sandwiched, and the electrodes 4a, 4b
When an electric field is formed between the electrodes, the charge of the electrode 4a moves to the surface of the glass substrate 1, and electrons are emitted from the surface of the glass substrate 1. As a result, a force opposite to the adhesive force acts on the attached fine particles 2, and the attached fine particles aggregate and grow, and change to a shape and a size that are easily peeled. Here, when ultrasonic waves are oscillated from the ultrasonic oscillator 6 toward the substrate surface 8, the attached fine particles are separated from the substrate surface and removed from the surface.

Next, each configuration will be described. Electrode 4
a is as described in the first and second embodiments. Electrode 4b
Any material may be used as long as it can form an electric field by sandwiching an object to be processed (a glass substrate in this example) in a pair with the electrode 4a, a well-known electrode material can be appropriately used, and a conductive material such as a metal is preferably used. Can be used. The electrode material 4b of this example is made of Cu-
Zn. The electric field strength is 1-100 kV / cm,
It depends on the material and shape of the electrode materials 4a and 4b, the type and size of the object to be treated, the material and surface condition (the ease with which the electric charge of the electrode 4b moves to the surface of the object to be treated by setting the electric field), etc. Preliminary tests can be determined. In this example, it is 10 kV / cm. The ultrasonic oscillator 6 is the same as in the first embodiment.

Example 4 In Example 1, an ITO / glass substrate (5 cm × 5 cm) was used.
Then, after applying the following fine particles, application to an electrode, ultraviolet irradiation, and ultrasonic oscillation were performed to examine the effect of removing the fine particles attached to the surface. Further, the substrate was exposed to air in a class 10,000 clean room overnight, the substrate was treated in the same manner, and the change in the contact angle of the surface was examined.

Electrode: Reticulated Cu-Zn material Ultraviolet (UV) lamp; Low-pressure mercury lamp (184 nm, 254 nm) 10 W Electric field between substrate and electrode; 1,000 V / cm Ultrasonic oscillator; Standard particles (PSL), 1.0 μm (average particle size) 0.506 μm (〃) Measurement of attached fine particles; actual measurement with a microscope Measurement of contact angle; droplet method (contact angle meter) The results are shown in Table 1.

[0025]

[Table 1] When only the electric field was used, the attached fine particles aggregated, and the apparent number of fine particles was reduced.

[0026]

According to the present invention, the following effects can be obtained. (1) In cleaning the surface, by transmitting ultrasonic waves to the surface under an electric field, the force of the electric field acts against the adhered fine particles, and the adhered fine particles aggregate and separate. Easy to shape
Changed in size. Since ultrasonic waves act on the fine particles,
The detachment of the attached fine particles from the surface was facilitated. As a result, removal of fine adhered particles of 1 μm or less could be easily achieved.

(2) In (1), ultraviolet light is applied to the cleaning surface.
By simultaneously irradiating at least one type of laser or radiation, photoelectrons are emitted from the surface to be cleaned, and the photoelectrons act as a force opposing the adhesive force of the attached fine particles. It became.

When an organic substance (eg, a hydrocarbon) is mixed (complexed) with the attached fine particles, an appropriate ultraviolet light source is selected (eg, a low-pressure lamp having 184 nm and 254 nm) so that ozone generated by ultraviolet irradiation and Since the attached organic matter is decomposed by the active oxygen, the attached inorganic matter and the organic matter can be removed at the same time, and the practicality has been improved. Since the separated fine particles are charged by the emitted photoelectrons, the charged fine particles are collected by the electrode. As a result, there is no contamination (secondary contamination) of the periphery due to the peeling fine particles, and a compact cleaning device capable of cleaning the surface and collecting and removing the peeling fine particles is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an apparatus of the present invention for cleaning the surface of a liquid crystal substrate.

FIG. 2 is an explanatory diagram showing a decomposition mechanism of an organic substance according to the present invention.

FIG. 3 is a schematic explanatory view of another apparatus of the present invention for cleaning the surface of a liquid crystal substrate.

FIG. 4 is a schematic explanatory view of another apparatus of the present invention for cleaning the surface of a liquid crystal substrate.

FIG. 5 is an explanatory diagram of a particle removal limit of a cleaning technique that does not use a liquid.

[Explanation of Signs] 1: substrate, 2: adhered fine particles, 3: adhered organic matter, 4, 4
a, 4b: electrodes, 5: ultraviolet lamp, 6: ultrasonic oscillator, 7: photoelectron, 8: substrate surface, 9: suspended particulates, 1
0: charged fine particles, 11: collected fine particles

Continuation of the front page (56) References JP-A-4-239131 (JP, A) JP-A-63-78530 (JP, A) JP-A-4-225513 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) B08B 7/00 H01L 21/304

Claims (2)

(57) [Claims] 1. A method for cleaning a solid surface, comprising:
Ultraviolet to a solid surface, few selected laser, the radiation
A method for cleaning a solid surface, comprising transmitting ultrasonic waves under an electric field under at least one kind of irradiation . 2. An apparatus for cleaning a solid surface, comprising: an electric field setting electrode and an ultrasonic oscillation source to be applied to the solid surface;
An irradiation source for irradiating at least one selected member .