JP3335833B2 - Cleaning method and cleaning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method and a cleaning apparatus for removing deposits on the surface of an object to be cleaned such as a substrate in a liquid crystal substrate manufacturing process or a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In a process of manufacturing a liquid crystal substrate, a metal film such as indium (In) is sputtered on a substrate surface to form a metal film, and a resist layer is formed on the metal film. There is a step of forming an electrode by etching the resist layer to partially remove the metal film, and a step of forming an alignment film on the metal electrode.
In the case of a liquid crystal substrate using a TFT, a step of forming a metal film by sputtering or CVD for forming the TFT,
This includes a coating step of forming a resist layer, an etching step of removing a part of the metal film, and the like.

In the process of manufacturing such a liquid crystal substrate, particles in the air adhere to the surface of the substrate, and metals and organic substances adhere to the surface of the substrate in an etching process and a process of forming a resist layer. A film may also be formed. If such a contaminant is attached to the interface between the substrate and the electrode or between the electrode and the alignment film, the contact between the electrodes is deteriorated, and the resistance is increased and the wiring is poor. Therefore, the removal of such deposits is a very important process for manufacturing a high-performance device, and it is necessary to clean the substrate surface at each stage of the substrate manufacturing process and remove the deposits as much as possible. . In particular, in the step of forming a TFT, it is necessary to make the surface on which each metal layer is laminated a high-cleaning interface.

Conventionally, in order to remove deposits on the substrate surface,
The surface of the substrate was cleaned using chlorofluorocarbon gas, but chlorofluorocarbon gas has a strong detergency but adversely affects the natural environment.
Currently not used. Therefore, a cleaning method and a cleaning apparatus using pure water as shown in FIG. 5 have been studied. In the cleaning method and the cleaning apparatus, a step 1 is performed in which pure water (or water) containing a detergent is dropped on a surface of a liquid crystal substrate and the surface is cleaned with a brush. It has a dropping or spraying step 2 and a drying step 3 using an air knife or the like.

[0005]

In the cleaning method and cleaning apparatus shown in FIG. 5, in the step 1 of cleaning with a brush by dropping a detergent, it is effective to remove relatively large particles of 10 μm or more. There is a limit in removing fine particles. In addition, although organic substances can be removed to some extent, metal contaminants attached to the substrate surface cannot be removed, and the substrate surface is damaged by brushes, and electrodes formed on the substrate surface are easily damaged. There are drawbacks.

Next, in the conventional cleaning step 2 using pure water to which ultrasonic vibration is applied, a relatively low frequency vibration of about 40 kHz or 50 kHz is applied to the pure water. When ultrasonic vibration is applied to pure water, the vibration is reflected on the liquid surface of the pure water to form coarse and dense in the liquid and a cavity is generated in a dense portion (cavitation effect). Particles on the substrate surface are peeled off by the cavitation effect.

However, the size of the particles that can be removed by the cavitation effect is inversely proportional to the frequency of the ultrasonic vibration. Therefore, the particles that can be removed by pure water having a relatively low frequency of 40 kHz or 50 kHz are relatively large. It is impossible to remove fine particles of 2 μm or less. Further, in the cleaning by the cavitation effect using low-frequency ultrasonic vibration, organic substances can be removed to some extent, but it is difficult to remove metals attached to the substrate surface.

As described above, the combination of the cleaning step 1 and the cleaning step 2 shown in FIG. 5 has a drawback that it is difficult to remove the metal, and the removal of minute particles and organic substances is not perfect. Furthermore, the cleaning process using a brush has a fatal disadvantage that the substrate is easily damaged. Therefore, it is not preferable as a combination of the washing steps.

The present invention has been made to solve the above-mentioned conventional problems. By optimizing a combination of cleaning steps, both large and small particles can be removed, and there is an effect on the removal of organic substances and metals. It is another object of the present invention to provide a cleaning method and a cleaning apparatus that do not damage the substrate surface.

[0010]

The cleaning method of the present invention comprises:
The method includes both a step of cleaning the object to be cleaned by applying pure water to which a low frequency vibration of 00 kHz or less is applied, and a step of cleaning the object to be cleaned by applying pure water to which high frequency vibration of 1 MHz or more is applied. It is a feature.

In the above, it is preferable that ozone is mixed in pure water which gives high frequency vibration.

Further, the cleaning apparatus of the present invention comprises a low-frequency cleaning chamber provided with a water supply section for supplying pure water to which low-frequency vibration of 100 kHz or less is applied to an object to be cleaned, and pure water to which high-frequency vibration of 1 MHz or more is applied. A high-frequency cleaning chamber provided with a water supply section for supplying to the object to be cleaned is arranged continuously, and the object to be cleaned can be moved between the two cleaning chambers.

[0013] In the above, it is preferable that an ozone mixing section is provided in a supply path of pure water to a water supply section of the high frequency cleaning chamber.

In the present invention, a cleaning chamber for performing cleaning with two types of cleaning water, pure water to which low-frequency vibration is applied and pure water to which high-frequency vibration is applied, is provided continuously. The object to be cleaned moves between the rooms, and two types of cleaning are performed continuously. However, a water supply unit for supplying the two types of cleaning water may be provided in one cleaning chamber, and the cleaning using the two types of cleaning water may be continuously performed in the same cleaning chamber.

In a low-frequency cleaning chamber, pure water having a frequency of 100 kHz or less, for example, 70 kHz, 50 kHz, or 40 kHz
Ultrasonic vibration of Hz is applied, and the pure water is dropped on the object to be cleaned such as a liquid crystal substrate, or jetted by a nozzle, or is dropped or jetted on a rotating object to be cleaned. When a low-frequency vibration of 100 kHz or less is applied to pure water, the vibration propagates in the liquid, is reflected at an interface between the liquid and air, and is formed in the liquid surface to have a density distribution based on the vibration wavelength. A cavity is formed in this dense portion (cavitation), and particles adhering to the object to be cleaned are peeled off and removed by the cavitation effect. However,
The size of particles that can be removed by the cavitation effect is inversely proportional to the frequency of vibration in pure water.
In the case of a cleaning liquid having a low frequency vibration of 00 kHz or less, 10
It is effective for removing relatively large particles of μm or more. However, removal of particles having a size of less than 10 μm slightly reduces the effect, and it is difficult to remove fine particles of 2 μm or less. Although removal of organic substances is possible, it is not very effective.

Next, in the high-frequency cleaning chamber, high-frequency ultrasonic vibration of 1 MHz or more is applied to the pure water, and the pure water is dropped or sprayed on the object to be cleaned such as a liquid crystal substrate or the rotating object to be cleaned. On the other hand, pure water is dropped or sprayed. High-frequency ultrasonic vibration of 1 MHz or more easily escapes into the air from the interface between the liquid and air when propagated in the liquid, and cannot exhibit a cavitation effect such as a low frequency. However, the vibration propagating in the pure water gives an excessive acceleration to the surface of the object to be cleaned, and this acceleration has an effect of removing contamination on the surface of the object to be cleaned.

The removal of contamination by high-frequency acceleration is effective for relatively small particles, has a high effect of removing particles having a size of 10 μm or less, and can sufficiently remove fine particles having a size of 2 μm or less. is there. However, there is no relatively large particle removing effect. This point is complemented by the cleaning to which the low frequency ultrasonic vibration is applied.

The cleaning using cleaning water to which high-frequency ultrasonic vibration is applied is also effective for cleaning organic substances. Organic substances can be effectively removed by the shock wave or acceleration of high frequency vibration.

Next, it is difficult to remove metallic contaminants adhering to the object to be cleaned by using pure water to which low-frequency ultrasonic vibration is applied, but cleaning using pure water to which high-frequency ultrasonic vibration is applied. Then, the attached metal can be removed by the acceleration of the high frequency vibration. Further, if ozone is mixed with pure water to which ultrasonic vibration is applied to prepare cleaning water having an oxidizing power, the metal is oxidized by the ozone and becomes a positive ion of the metal, and is easily dissolved in the pure water. Also, in cleaning using oxidizing pure water containing ozone, organic substances adhering to the object to be cleaned are oxidized by ozone, and CO ₂ and O ₂ are removed.
And the effect of removing organic substances is increased.

As described above, by using the cleaning with pure water to which the low frequency ultrasonic vibration is applied and the cleaning with the pure water to which high frequency ultrasonic vibration is applied, relatively large particles and 10 μm or less can be obtained. Alternatively, minute particles of 2 μm or less can be effectively removed. Furthermore, it is possible to remove organic substances and metal contaminants. In particular, by using cleaning water in which high-frequency ultrasonic vibration is applied to pure water mixed with ozone, organic substances and metal contaminants can be more effectively removed. .

[0021]

FIG. 1 is a block diagram showing the structure of a cleaning apparatus according to the present invention, and FIG. 2 is a side view showing an example of the structure of a cleaning section (cleaning chamber) using cleaning water to which low-frequency vibration is applied. FIGS. 3 and 4 are side views showing a cleaning unit (cleaning chamber) using cleaning water to which high-frequency vibration is applied, for each configuration example. FIG.
As shown in (1), in the cleaning device of the present invention, the introduction section (introduction chamber)
A, low frequency applied water cleaning section (cleaning room) B, high frequency applied O ₃
A water washing unit (washing room) C, a drying unit (drying room) D, and a lead-out unit (lead-out room) E are provided continuously.

A communication port 11 is formed in the partition wall 10 separating the above-mentioned parts (each chamber), and the above-mentioned respective parts (each chambers) A to E communicate with each other. The transfer member holding the article W to be washed moves continuously from the introduction section A to the outlet section E, or the transfer member reciprocates between adjacent chambers, thereby introducing the article W to be washed such as a liquid crystal substrate. It is sequentially transferred from the section A to the derivation section E.

FIG. 2 shows an example of the structure of the low frequency applied water cleaning section (cleaning chamber) B. In the cleaning section B, the cleaning target W moves from the right side to the left side along the transport path L, and the cleaning liquid is supplied from the upper water supply unit 12 and the lower water supply unit 13 to the moving cleaning target W. . In the example of FIG.
The water supply units 12 and 13 are injection nozzles, and the cleaning water is injected from the water supply units 12 and 13 onto both the upper and lower surfaces of the article W to be cleaned. The pure water supply unit 14 is equipped with a membrane treatment device such as an ultrafiltration membrane or a reverse osmosis membrane device, an ion exchange device, an ultraviolet irradiation device, and the like, and includes fine particles of tap water, a colloidal substance, an organic substance, a metal, and a shadow. Ions, liquid oxygen and the like are removed to an extremely low concentration.

The water supply units 12 and 13 are provided at their bases with ultrasonic vibration oscillating units 12a and 13a. The oscillating units 12a and 13a emit a relatively low-frequency vibration of 70 kHz.
The low-frequency vibration is applied to the pure water supplied to 2a and 13a, and the cleaning target W
Injected to. In pure water to which low-frequency ultrasonic vibration is applied, relatively large particles on the surface of the object to be cleaned are removed by the cavitation effect, and organic substances are also removed to some extent.

FIG. 3 shows an example of the structure of a high-frequency applied O ₃ water cleaning section (cleaning chamber) C. In this cleaning section C,
The cleaning object W moves along the transport path L from the right side to the left side in the drawing, and cleaning water is sprayed and supplied from the upper water supply unit 15 and the lower water supply unit 16 to the upper and lower surfaces of the moving cleaning object W. Can be A supply path from the pure water supply section 14 to each of the water supply sections 15 and 16 is provided with a path branched by valves 18a and 18b, and an ozone (O ₃ ) mixing section 17 is provided in this path. By switching between the valves 18a and 18b, pure water supplied from the pure water supply unit 14 passes through the ozone mixing unit 17, and ozone is mixed. Ozone is mixed as required by switching the valves 18a and 18b, and pure water mixed with ozone and pure water not mixed with ozone can be selected and used.

The upper water supply section 15 and the lower water supply section 16 have:
A relatively high frequency ultrasonic oscillator of 5 MHz is provided integrally. Ultrasonic vibration of a relatively high frequency of 1.5 MHz is applied to the pure water supplied from the pure water supply unit 14 from the oscillation unit. When pure water to which ultrasonic vibration of 1.5 MHZ is applied is supplied to the object to be cleaned W from the water supply units 15 and 16, relatively small particles are generated from the surface of the object to be cleaned W by the acceleration and impact of the ultrasonic vibration. Is removed, for example, fine particles of 2 μm or less are also removed. In addition, organic substances on the surface of the cleaning object W can be removed.

When pure water from the pure water supply unit 14 is supplied through the ozone mixing unit 17, ozone is mixed with the pure water to generate oxidizing cleaning water, and the cleaning water is further supplied to the water supply unit 15. And 16 provide high frequency vibrations.
When the cleaning water mixed with ozone is used, the organic matter on the surface of the cleaning target W can be decomposed and removed effectively, and the metal can be oxidized and removed effectively. When the cleaning object W introduced from the introduction section A is cleaned by passing through the low frequency application water cleaning section B and the high frequency application ozone (O ₃ ) water cleaning section C, large particles on the surface of the cleaning object W are generated. All types of contaminants, fine particles, organics and metals can be removed. The object to be cleaned W after cleaning is sent to the drying section D, dried by a drying means such as an air knife, and led out from the lead-out section E.

FIG. 4 shows another example of the structure of the high frequency applied O ₃ water cleaning section C. In the apparatus shown in FIG. 4, a rotary table 21 is provided in a cleaning chamber, and an object to be cleaned W is set on the rotary table 21 and rotated. A moving nozzle 22 is provided as a water supply unit.
An oscillating unit 22a that emits high-frequency ultrasonic vibration of MHz is provided. Then, pure water is supplied to the moving nozzle 22 from the pure water supply unit 14 or pure water mixed with ozone by the ozone mixing unit 17 is supplied to the moving nozzle 22. The moving nozzle 22 is moved left and right by the moving mechanism 23, and the cleaning water is sprayed on the cleaning object W rotated by the rotary table 21.

The cleaning water is obtained by applying high-frequency ultrasonic vibration to pure water and further mixing ozone. The cleaning water removes fine particles, organic substances, and metals. Further, in the apparatus shown in FIG. 4, the cleaning object W is rotated and the cleaning water is jetted, so that high-frequency ultrasonic vibration acts uniformly on the cleaning object W. Further, after the cleaning water is injected, the object to be cleaned W can be rotated at a high speed to drain the water. In the above configuration example, ozone is mixed with pure water provided to the cleaning section C for applying high-frequency ultrasonic vibration, but ozone is mixed with pure water in the cleaning section B to which low-frequency ultrasonic waves are applied. May be done.

[0030]

As described above, in the present invention, the object to be cleaned is washed with two kinds of cleaning water, pure water to which low frequency vibration is applied and pure water to which high frequency vibration is applied. And various kinds of pollutants such as large and small particles and organic matter can be removed.

Further, by using pure water mixed with ozone, organic substances and metals can be effectively removed.

Further, since no brush is used, various contaminants can be effectively removed without damaging the object to be cleaned.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing a cleaning apparatus of the present invention;

FIG. 2 is a side view showing a configuration of a low-frequency application water cleaning unit;

FIG. 3 is a side view showing a configuration of a high-frequency application ozone water cleaning unit,

FIG. 4 is a side view showing a configuration of a high-frequency application ozone water cleaning unit having another configuration;

FIG. 5 is a block diagram illustrating a conventional liquid crystal substrate cleaning step.

[Explanation of symbols]

 A Introducing section B Low frequency applied water cleaning section C High frequency applied ozone water cleaning section D Drying section E Outgoing section W Object to be cleaned 12, 13 Water supply section 14 Pure water supply section 15, 16 Water supply section 17 Ozone mixing section 18a, 18b Valve 21 Rotary table 22 Moving nozzle

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuyuki Harada 2-1-14 Fuchu-cho, Fuchu-shi, Tokyo Pretec, Inc. (56) References JP-A-61-101283 (JP, A) JP-A-9 -24348 (JP, A) JP-A-9-75874 (JP, A) JP-A-9-6018 (JP, A) JP-A-2-214581 (JP, A) (58) Fields investigated (Int. . ^7, DB name) B08B 3/12

Claims (4)

(57) [Claims] 1. A process for cleaning an object to be cleaned by applying pure water to which low-frequency vibration of 100 kHz or less is applied, and a step of cleaning the object to be cleaned by applying pure water to which high-frequency vibration of 1 MHz or more is applied. A cleaning method comprising: 2. The cleaning method according to claim 1, wherein ozone is mixed in the pure water giving high-frequency vibration. 3. A low-frequency cleaning chamber provided with a water supply unit for supplying pure water to the object to be cleaned to which low-frequency vibration of 100 kHz or less is applied, and a water supply for supplying pure water to the object to be cleaned with high-frequency vibration of 1 MHz or more. A high-frequency cleaning chamber provided with a cleaning unit, wherein the cleaning object is movable between the two cleaning chambers. 4. The cleaning apparatus according to claim 3, wherein an ozone mixing section is provided in a path for supplying pure water to a water supply section of the high-frequency cleaning chamber.