JPH07308567A - Washing method and washing device for vessel - Google Patents

Abstract

PURPOSE:To provide a UV rays/ozone washing method and a washing device capable of washing org. matter stuck on the inner surface of a vessel in a short time. CONSTITUTION:The inside of the vessel 2 is evacuated, and the inner surface 3 of the vessel 2 is irradiated with UV rays 12, and also an ozone-containing gas 19 for washing is allowed to flow, or ozone is generated from a clarified air 22 by the UV rays remove matter stuck on the inner surface 3 of the vessel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing or conveyance of semiconductors or glass substrates which requires a high degree of cleanliness.
The present invention relates to a cleaning method and a cleaning device for removing deposits such as organic substances attached to the inner surface of a vacuum container used for storage and the like.

[0002]

2. Description of the Related Art In a vacuum, since there is no air flow or there is very little air flow, fine particles adhering to the wall of a vacuum vessel or piping parts are peeled off, It is unlikely that particles on the floor will fly up. Therefore, it is possible to create a class 0 (zero) space with extremely high cleanliness in a vacuum. A semiconductor manufacturing process may be performed under a vacuum, and for example, a film may be formed on a semiconductor or a liquid crystal panel in a vacuum.
Further, an object to be processed such as a wafer or a glass substrate may be stored or transported in a vacuum.

Thus, in vacuum, class 0
While it is possible to create a (zero) space with high cleanliness, one of the problems at that time is the problem of contamination during processing or storage. Among the pollutions, the contamination at the molecular level is a particularly difficult problem to solve, and in recent years, particular attention has been paid to it. The formation of oxides due to oxygen (O ₂ ) even at molecular level contamination is reduced by the amount of oxygen concentration during storage and transportation in a vacuum because the oxygen concentration is low, and there is little problem. However, the problem of organic contamination remains. This organic matter contamination is caused by a reverse flow of oil vapor used in an exhaust pump for forming a vacuum state, or when contaminants adhering to a vacuum container, piping parts and the like are detached and become molecular. That is, it is caused by carbon-based (C-based) molecules adhering to an object to be stored such as a wafer or a glass substrate or an object being manufactured.

When a film is formed on a wafer, glass substrate, or the like in which organic substances are attached, the film is likely to be peeled off, which causes a reduction in product yield. For organic matter pollution caused by the reverse flow of oil vapor, a dry pump has been used recently, or by installing a substance such as zeolite that absorbs oil between the exhaust pump and the vacuum container, It is decreasing. However, there is still no effective solution for the contamination of organic substances adhering to the vacuum container, and it remains a big problem. This is because in order to remove organic substances adhering to the inner surface of a vacuum container or the like, it is necessary to wash and bake the inner surface, but it is impossible to completely remove the organic substances of molecular order adhering to the inner surface. Because it is very difficult.

As a method for cleaning the organic substances attached to the inner surface of the container, a cleaning method using chlorofluorocarbon has been conventionally used, but the cleaning method using chlorofluorocarbon has a problem in terms of pollution. Therefore, for cleaning various containers such as a vacuum container or mechanical parts, ultrasonic cleaning in a detergent solution such as an acid, alkali, or organic solvent and ultrapure water are used as an alternative to the cleaning method using Freon gas. Ultrasonic cleaning is widely used. However, in general, when the inner surface of a container such as a vacuum container after cleaning with a liquid is measured by the contact angle method, the contact angle is more than ten degrees, and it is difficult to completely remove the organic matter. Note that the contact angle method is a method in which ultrapure water is dropped on the surface of an object to be cleaned and the contact angle of water droplets is large when organic matter is present on the surface, and the small contact angle when there is no organic matter. This is the method of judgment.

Further, as a method for cleaning the organic substances attached to the inner surface of such a container, conventionally, ultraviolet / ozone (UV / O) has been used.
₃ ) Cleaning method is known. FIG. 8 illustrates the principle of this ultraviolet / ozone cleaning method. Oxygen in the air (O
Changed ₂₎ ozone (O _3), oxygen ozone (O ₃₎ in the ultraviolet wavelength of 254 nm (O ₂₎ with oxygen-generating group (O
^* ) To decompose. The oxygen generating group (O ^*) is decomposed organic matter _{(C m H n O l)} 4 adhered to the container surface 3, the organics is incinerated as water (H ₂ O) and carbon dioxide (CO ₂₎ .

In the case of such ultraviolet / ozone cleaning, in order to increase the cleaning speed, that is, the ashing speed, it is necessary to increase the intensity of ultraviolet rays, increase the ozone concentration, and activate the reaction part where organic matter is ashed. Therefore, the point is to raise the temperature of the substrate to be cleaned. For this reason, in the conventional ultraviolet / ozone cleaning, an ultraviolet lamp having a high irradiation intensity and an ozonizer having the best performance to increase the ozone concentration were used in order to increase the cleaning speed. Further, the temperature of the inner surface of the container, which is the object to be cleaned, is set to be as high as possible to activate the reaction portion, and ultraviolet / ozone cleaning is performed.

[0008]

As is well known, ultraviolet rays are easily absorbed by oxygen (O ₂ ) in the atmosphere,
The irradiation intensity of ultraviolet rays is significantly reduced in the atmosphere. Therefore, in the conventional ultraviolet / ozone cleaning device used at normal pressure,
During the period from the UV lamp to the contaminated organic substances adhering to the surface of the object to be cleaned, the ultraviolet rays are absorbed by oxygen and the irradiation intensity is remarkably reduced. As a result, the cleaning rate by ozone ashing reaction is low. I had no choice.

For this reason, in order to wash the wafer, for example, the distance between the wafer and the ultraviolet lamp is made extremely small, about millimeter (mm), in order to obtain sufficient irradiation intensity of ultraviolet rays. In the case of cleaning a thin plate-like body whose thickness is almost the same regardless of the product such as a wafer, even if the distance between the object to be cleaned and the ultraviolet lamp is shortened, there is no problem in the operation associated with cleaning. However, when cleaning the inner surface of the vacuum container or the like, it is necessary to bring the ultraviolet lamp close to the inner surface of the container for scanning, but this requires a lot of time. Although it is theoretically possible to adopt such a cleaning method even if it takes time, if the UV lamp can be inserted into the inner surface of the container to be cleaned, the shape of the container to be cleaned In the case of a complicated shape that is not suitable for scanning an ultraviolet lamp, such cleaning of the inner surface of the container is impossible.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to clean organic substances adhering to the inner surface of a vacuum container or the like at a higher speed and even on the inner surface of a complicated shape. It is an object of the present invention to provide an ultraviolet / ozone cleaning method and a cleaning device capable of cleaning.

[0011]

In order to achieve the above object, the cleaning method of the present invention comprises evacuating the inside of a container, irradiating the inside surface of the container with ultraviolet rays, and flowing a cleaning gas containing ozone. Alternatively, clean air is caused to flow, and ozone is generated from the clean air by the ultraviolet rays to remove deposits adhering to the inner surface of the container.

Further, the cleaning apparatus of the present invention comprises a container which can be evacuated to vacuum, an ultraviolet ray generator which is arranged in the container and irradiates the inner surface of the container with ultraviolet rays, and a cleaning apparatus which contains oxygen or ozone in the container. And a gas supply source for supplying clean air.

[0013]

[Operation] The inside of the container is evacuated, the inside surface of the container is irradiated with ultraviolet rays in a vacuum atmosphere, and a cleaning gas containing ozone is flown or ozone is generated from clean air. It is possible to irradiate the object to be cleaned without receiving it. Therefore, oxygen, which is a generating group, is effectively formed from ozone, and it becomes possible to ash organic substances and the like at a high speed.

Irradiation of ultraviolet rays to the inner surface of the container
It is possible to perform the separation from the ultraviolet lamp to the inner surface of the container. Therefore, even if the inner surface of the container has irregularities having a complicated shape, it is possible to remove adhering substances such as organic substances from the inner surface of the container or the like in a short time as long as the irradiation of ultraviolet rays is possible.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings 1 to 7.

FIG. 1 shows the structure of a cleaning apparatus according to the first embodiment of the present invention. The vacuum space 1 is a space partitioned by the vacuum container 2, and the container inner surface 3 that is the cleaning target is the entire inner surface in contact with the space 1 of the vacuum container 2. The vacuum space 1 is connected to a needle valve 6, a valve 7, and a vacuum pump 8 via an exhaust hole 5. Therefore, by adjusting the needle valve 6, the exhaust amount by the vacuum pump 8 can be adjusted.

The vacuum gauge 11 is for monitoring the degree of vacuum in the vacuum space 1. An ultraviolet lamp 12 is provided in the vacuum space 1. The ultraviolet lamp 12 irradiates the entire inner surface 3 of the container, which is an object to be cleaned. The leak hole 16 is connected to the N ₂ gas supply source 19 through a valve 17 and a filter 18 by piping to supply clean N ₂ gas as a leak gas into the vacuum space 1. Further, the hole 20 is opened to the atmosphere through the valve 21 and the filter 22, supplies clean air into the vacuum space 1, and the clean air forms ozone by ultraviolet rays. The cleanliness of the clean air introduced through the holes 20 is limited by the filter 22 to 0.1 .mu.m or less than class 10. Further, an ozonizer 13 for supplying ozone gas is provided in the vacuum container 2. Ozonizer 13 is a valve 1
4 is connected to the introduction hole 15 of the vacuum container 2 through the filter 22 and supplies ozone into the vacuum space 1. The O-ring 10 vacuum-seals the vacuum container 2 and the flange 9. When the ultraviolet lamp 12 is attached or detached, the vacuum space 1 is returned to atmospheric pressure by leak gas, and the vacuum container 2 is opened from the flange 9. In this embodiment, N ₂ gas is used as the leak gas, but clean air may be used as a matter of course.

In the ultraviolet / ozone cleaning apparatus of this embodiment, a low pressure ultraviolet mercury lamp is used as a source for irradiating the inner surface of the container with ultraviolet light. This UV lamp 1
Reference numeral 2 is a mercury lamp made of synthetic quartz that generates an electromagnetic wave of 184.9 nm. Further, as the ultraviolet lamp 12, various types such as a high pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, a deuterium lamp, an excimer laser can be used, and depending on the kind of contaminants adhered to the object to be cleaned, etc. It is appropriately selected and used. It should be noted that a general low-pressure mercury lamp coated with quartz glass is optimally used for removing the organic film in view of cost / performance.

A Convectron vacuum gauge is used as the vacuum gauge 11, and a roots pump is used as the vacuum pump 8. As the vacuum pump, an oil rotary pump, a roots pump, a diaphragm pump or the like can be used. However, since the oil rotary pump has a reverse flow of oil, it is preferable to use the roots pump or the diaphragm pump for exhausting. Further, at the time of vacuum exhaust, it is preferable to reduce the exhaust speed by the needle valve 6 so as to prevent generation of aerosol due to adiabatic expansion.

The required degree of vacuum in the vacuum space 1 is 20 to 200 Torr for the seal between the vacuum container 2 and the flange 9.
The O-ring seal 10 as shown in FIG. 1 is sufficient because it is a low vacuum region, but the O-ring seal is not limited to the O-ring seal, and the vacuum space 1 can be maintained at an appropriate vacuum degree. Any seal will do. Further, when the object to be cleaned is attached or detached, the vacuum container 2 is not fixed to the flange 9 by bolting or the like. For example, a sealing handle used for a door of a square desiccator or a corner chuck with a cock. Clips are enough.

With such a device structure, the ultraviolet lamp 12
Is loaded into the vacuum container 2, and the vacuum space 1 is evacuated. Then, in the cleaning apparatus of this embodiment, the ultraviolet lamp 1
Ultraviolet rays are generated from 2 to irradiate the inner surface 3 of the container, and at the same time, the valve 21 is opened from the introduction hole 20 to introduce the clean air filtered by the filter 20 into the vacuum space 1. The clean air in the vacuum space 1 is ozonized by ultraviolet rays, and oxygen (O ^* ) as a generating group is generated by the reaction between ozone and ultraviolet rays to ash organic substances attached to the inner surface of the container. As described above, the organic matter reacts with oxygen (O ^* ) as a generating group to become water (H ₂ O) and carbon dioxide (CO ₂ ) and is removed from the inner surface 3 of the container.

Further, the valve 21 is closed to shut off the introduction of clean air, and the valve 14 is opened to introduce ozone (O ₃ ) gas from the ozonizer 13 into the vacuum space 1 through the introduction hole 15. Ozone (O ₃ ) gas is decomposed into oxygen (O ₂ ) and oxygen (O _* ) which is a generating group by ultraviolet rays, and oxygen (O ₃ ) which is a generating group is decomposed.
_* ) Ashes the organic matter attached to the inner surface 3 of the container. or,
Instead of the ozonizer 13, an oxygen gas (O ₂ ) supply source may be provided to generate ozone (O ₃ ) by ultraviolet rays. Compared with forming ozone (O ₃ ) from clean air, a higher concentration of ozone (O ₃ ) is supplied, so that the cleaning speed can be made faster.

FIG. 2 illustrates the dependency of the cleaning rate on the shape of the container. (A) shows a container with a small shape, and (B) shows a container with a large shape. The distance from the ultraviolet lamp 12 to the inner surface 3 of the container, which is the irradiation surface, is L ₁ in the small container (A) and L ₂ in the large container (B), and L ₂ > L ₁ Relationship. As described above, in the vacuum atmosphere, the ultraviolet light emitted from the ultraviolet lamp 12 is hardly attenuated, so that a similar cleaning effect can be obtained regardless of the distance L to the irradiation surface. Therefore, even if the irradiation distance from the ultraviolet lamp to the inner surface of the container to be irradiated becomes long, the shape becomes large, or the shape of the inner surface becomes complicated, the shape of the ultraviolet lamp is changed or the ultraviolet lamp is newly installed. It is not necessary to irradiate the inside of the vacuum container 2, and the entire surface of the inner surface 3 of the container can be cleaned by an ultraviolet lamp arranged in the approximate center of the vacuum container 2.

FIG. 3 shows an ultraviolet / ozone cleaning apparatus for machine parts according to a second embodiment of the present invention. The configuration of the ultraviolet / ozone cleaning apparatus of this embodiment is the same as the ultraviolet / ozone cleaning apparatus shown in FIG.
The ozone cleaning device has the same configuration as that of the ozone cleaning device, and the same components are designated by the same reference numerals and the duplicate description thereof will be omitted. The present cleaning apparatus is intended for parts that require an extremely high degree of cleanliness, such as semiconductor wafers or glass substrates, as the object to be cleaned is not the inner surface of the vacuum container 2. Therefore, the object to be cleaned 24 is placed on the pedestal 25 in the vacuum container 2, irradiated with the ultraviolet lamp 12 in the vacuum space 1, and the organic matter attached to its surface by the clean air or the ozone gas supplied from the ozonizer 13. Is ashed. The pedestal 25 on which the object to be cleaned 24 is placed is rotatable and can be moved vertically. When the object 24 to be cleaned is placed on the pedestal 25, the inside of the container 2 is evacuated and ozone (O ₃ ) by air or an ozonizer is introduced to adjust the vacuum to a desired level, and the ultraviolet lamp switch is turned on. Put UV /
Carry out ozone cleaning. At this time, if the pedestal 25 is rotated, the ultraviolet light is uniformly applied to the cleaning target 24. When the shape of the object to be cleaned 24 is complicated and the portion to which the ultraviolet light is not irradiated is on the side surface or the back surface, the ultraviolet light may be guided from the light source portion by the graph fiber to be irradiated. Further, if the distance between the object to be cleaned 24 and the ultraviolet lamp 12 is adjusted by moving the pedestal 25 up and down, the illuminance is further increased and the cleaning effect can be enhanced.

FIG. 4 is an explanatory view of an apparatus manufactured as a trial for confirming the effect of ultraviolet / ozone cleaning under vacuum.
The configuration of the ultraviolet / ozone cleaning device is the same as that of the device shown in FIG. 1, but a semiconductor wafer contaminated with organic substances is used as the cleaning target 24. In this prototype device, three 6 W low-pressure ultraviolet mercury lamps are used as the ultraviolet lamp 12 for irradiating the object to be cleaned 24 with ultraviolet light, and these lamps are synthesized so that electromagnetic waves of 184.9 nm can be irradiated to the outside. Made of quartz. As the ozone generation source, clean air supplied from the filter 22 through the valve 21 is used, and the cleanliness of the introduced clean air is 0.1 μm and is class 10 or less. The vacuum degree in the vacuum chamber 1 is adjusted by operating the roots pump 8 with a displacement of 3000 l / min to evacuate the cleaning space 1 in the container 2 and adjusting the opening of the needle valve 6 and the clean air supply valve 21. Are in control. For the leak, clean N gas supplied from the N ₂ gas supply source 19 through the filter 18 and the valve 17 is used.
_Two gases are used.

FIGS. 5 to 7 are graphs of experimental data showing the cleaning effect of the cleaning device. In the graph shown in FIG. 5, the horizontal axis represents the ultraviolet irradiation time (min), and the vertical axis represents the contact angle (°) of the wafer surface after the cleaning. In the figure, the ● mark in FIG. 5 and the □ mark in FIG. 6 indicate 630 Torr where the vacuum degree is relatively low, and the ○ mark in FIG. 5 and the ● mark in FIG. 6 indicate data at 45 Torr where the vacuum degree is relatively high. The contact angle of the surface of the wafer to be cleaned before the ultraviolet / ozone cleaning was about 35 °, which indicated the presence of the organic film. In the above apparatus, the distance between the ultraviolet lamp 12 and the inner surface 3 of the container, which is the object to be cleaned, is 6
It is set to 3 mm. As shown in the figure, it can be seen that the contact angle decreases with the elapse of the ultraviolet irradiation time, that is, the organic film is removed. As is clear from the graph of FIG. 5, the higher the degree of vacuum, the smaller the contact angle in a short time. The contact angle of the wafer becomes 1.5 to 2.0 when the cleaning is sufficiently performed and the organic film is completely removed.

In the graph shown in FIG. 6, the horizontal axis indicates the irradiation distance (m
m), and the vertical axis shows the contact angle (°) on the wafer surface after the cleaning. The irradiation time of the ultraviolet lamp is 10 minutes. As shown in Fig. 6, the higher the degree of vacuum is
It is clear that the irradiation distance of ozone cleaning can be increased. That is, if the contact angle is 1.5 ° to 45 Torr at which the organic matter is completely removed from the surface of the object to be cleaned, 63 mm is 1
Irradiation for 0 minutes is sufficient, but the degree of vacuum is relatively low 6
At 30 Torr, the contact angle becomes 1.5 ° or more at a distance of 50 mm or more after irradiation for 10 minutes, and cleaning is not sufficiently performed.

FIG. 7 is a graph in which the horizontal axis represents the degree of vacuum (Torr) and the vertical axis represents the contact angle (°). The degree of vacuum when the irradiation time is constant (3 minutes) and the irradiation distance is constant (63 mm). The relationship of contact angles is shown. It has been shown that the higher the degree of vacuum is, the better it is, and a good cleaning effect is obtained in the state of the degree of vacuum between 20 and 200 Torr.

In the above embodiments, the cleaning of the vacuum container has been described as an example, but the object to be cleaned is not limited to the vacuum container, and various process treatments under normal pressure, or transportation and storage of wafers, etc. Of course, it can be applied to the container used for. Also, for ultraviolet rays, 184.9
The electromagnetic wave is not limited to ultraviolet rays having a wavelength of mm and 254 mm, and any electromagnetic wave that can generate an ozonizing action and oxygen as a generating group from ozone can be used. As described above, various modified embodiments are possible without departing from the spirit of the present invention.

[0030]

As described above, according to the present invention, it is possible to clean the inner surface of a vacuum container or the like in a short cleaning time by using the ultraviolet / ozone cleaning method in a vacuum atmosphere, and it is complicated. It can also be applied to the inner surface of a container having a shape.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an ultraviolet / ozone cleaning device in a vacuum atmosphere according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of the dependence of the shape of the container.

FIG. 3 is an explanatory diagram of an ultraviolet / ozone cleaning device in a vacuum atmosphere according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of an ultraviolet / ozone cleaning device that was prototyped for confirmation experiments.

FIG. 5 is a graph showing a cleaning effect by an ultraviolet / ozone cleaning method in a vacuum atmosphere.

FIG. 6 is a graph showing a cleaning effect by an ultraviolet / ozone cleaning method in a vacuum atmosphere.

FIG. 7 is a graph showing a cleaning effect by an ultraviolet / ozone cleaning method in a vacuum atmosphere.

FIG. 8 is an explanatory diagram showing the principle of an ultraviolet / ozone cleaning method.

[Explanation of symbols]

 1 vacuum space 2 vacuum container 3 object to be cleaned 8 vacuum pump 19 ozonizer 22 filter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B08B 9/08 (72) Inventor Takeshi Yoshioka 4-2-1 Honfujisawa, Fujisawa-shi, Kanagawa Company EBARA Research Institute

Claims (4)

[Claims] 1. The container is evacuated to irradiate the inside surface of the container with ultraviolet rays, and a cleaning gas containing ozone is caused to flow, or clean air is caused to flow to generate ozone from the clean air to generate ozone from the container. A method for cleaning a container, which comprises removing deposits adhering to the inner surface. 2. The cleaning method according to claim 1, wherein the irradiation of ultraviolet rays on the inner surface of the container is performed at a distance from the ultraviolet ray generator to the inner surface of the container. 3. A container that can be evacuated to vacuum, an ultraviolet ray generator that is disposed in the container and irradiates the inner surface of the container with ultraviolet rays, and a cleaning gas containing oxygen or ozone in the container.
Or a gas supply source that supplies clean air. 4. The container cleaning device according to claim 3, wherein the ultraviolet ray generator is fixed to a flange that is detachable from the container.