JPH049373B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ultraviolet cleaning device with excellent cleaning effects. Conventionally, ozone generated from ultraviolet lamps has been used to decompose and clean contaminants. For example, as a pre-treatment when applying a photoresist to a silicon wafer, organic contaminants in the atmosphere that have adhered to the silicon wafer can be decomposed by additional cleaning immediately before application, or they can adhere to the substrate during sputtering deposition using an electron beam. It has been found that additional cleaning can significantly improve the adhesion of coated or deposited films, as in the case of organic contaminants such as oil from vacuum pumps. By the way, when an ultraviolet lamp, such as a low-pressure mercury lamp, is turned on, ultraviolet rays of the mercury resonance line with a wavelength of 254 nm are mainly emitted to the outside, and ultraviolet rays of 185 nm and a small amount of other wavelengths are also emitted. The mechanism by which ozone is produced by these ultraviolet rays and its cleaning action are thought to be as follows. h〓 (185nm) + O ₂ (air) → O + O (1) O + O ₂ (air) → O ₃ (2) h〓 (254nm) + O ₃ → O ^* +O ₂ (3) O ^* +CmHnOl (organic contaminant) → CO, CO ₂ , H ₂ O (gasifies and scatters) (4) That is, ozone is generated by ultraviolet rays with a wavelength of 185 nm, and then this ozone is decomposed by ultraviolet rays with a wavelength of 254 nm, producing oxygen as a generating group. However, the oxygen of this generating group decomposes organic contaminants and scatters them in a gaseous state. Therefore, in order to carry out the reaction of equation (4) efficiently and at high speed, h〓 (185 nm) and h〓 of equations (1) and (3) are required.
It would be better if the intensities of (254nm) were in harmony with each other. In other words, when these intensities are respectively I ₁₈₅ and I ₂₅₄ , their ratio α=I ₁₈₅ /
I ₂₅₄ appears to be an important factor in the efficiency of UV cleaning. However, according to devices and research reports that have been put into practical use so far, the value of α is small and in a limited range, for example, the value is 0.03 ("Cleaning Design", Kindai Editorial Publishing, Autumn 1981 issue). and also
0.05 (1982 Japan Society of Applied Physics Report 28a-V-3)
However, it has been found that it is not necessarily the optimal value based on extensive research and research. Therefore, the present invention generates ozone with the light of an ultraviolet lamp, and uses the oxygen generated by the decomposition of this ozone to remove organic pollutants attached to the surface of objects and organic pollutants floating in gases with low power consumption. With the aim of providing an ultraviolet cleaning device that can be disassembled and cleaned extremely efficiently and at high speed, the present inventors have conducted intensive research by varying the value of α over an unprecedented wide range. The result, α
The present invention was completed by finding the optimal range of . The object to be cleaned with organic contaminants and the gas to be cleaned that contains organic contaminants coexist with oxygen gas, and the wavelength
An ultraviolet lamp emitting light at 185 nm and 254 nm is placed against organic contaminants and oxygen gas;
When the outputs of 185 nm and 254 nm light are I ₁₈₅ and I ₂₅₄ , respectively, this ratio α=I ₁₈₅ /I ₂₅₄ is set in the range of 0.08 to 0.3. The measurement of α = I ₁₈₅ / I ₂₅₄ is approximated by the ratio of the energy density on a plane parallel to the axis at a position more than 10 times the distance from the center of the lamp's light emitting part in the direction perpendicular to the axis. Ta. Since 185 nm ultraviolet light is absorbed by air, the measurement was performed in a vacuum or in a non-absorbing atmosphere. Embodiments of the present invention will be specifically described below with reference to the drawings. The drawing is a simplified horizontal view of the ultraviolet cleaning device of the present invention, and in FIG. 1, a belt conveyor 2 is stretched inside a box-shaped main body 1.
An ultraviolet lamp 4, which is a low-pressure mercury lamp, is installed on the conveyor 2 via a filter 3. The object to be cleaned 5 placed on the conveyor 2 from the entrance 1a advances while being irradiated and cleaned by the lamp 4, and when it finishes passing under the lamp 4, the cleaning is completed and it is taken out from the exit 1b. A suction fan 6 is provided below the main body 1 to exhaust cooling air, ozone, and further decomposed gaseous pollutants. Figure 2 shows an example used when the object to be cleaned is a gas coexisting with oxygen gas and contaminants are floating in it, and the object to be cleaned flows inside at a predetermined speed. A window hole 7a made of synthetic quartz is provided in the tube body 7, and a lamp 4 is mounted on the upper part of the window hole 7a.
is installed, and ultraviolet rays are irradiated into the tube body 7 through the window hole 7a. When the object to be cleaned finishes passing through the window hole 7a, the cleaning is completed. Next, I will explain the results of investigating the cleaning effect by varying α over a wide range.
is a 450W low-pressure mercury lamp with a tube diameter of 20 mm and an arc length of 100 cm, and the value of α was changed by controlling the coldest point temperature of the low-pressure mercury lamp and changing the transmittance of filter 3 for light with a wavelength of 185 nm. The object to be cleaned 5 is a quartz plate with a diameter of 10 mm, which is ultrasonically cleaned in ethyl alcohol for 30 minutes, further washed with 16 MΩcm pure water and dried, and dye (rhodamine B) as an organic contaminant is removed with ethyl alcohol. This was melted and applied on a quartz plate. This object to be cleaned 5 is the lamp 4.
The change in the transmittance of 633 nm light before and after irradiation was measured and used as a proxy for the cleaning effect. The measurement results are shown in Table 1. Here, the transmittance of each object to be cleaned 5 before irradiation is 96
%, 100% after irradiation is marked ◎, approximately 99%
Those with 98% are marked with △, those with about 97% are marked with ×.

[Table] As is clear from Table 1, the cleaning effect is excellent when α is in the range of 0.08 to 0.3, and especially from 0.1 to 0.3.
Almost complete cleaning was possible within the range of 0.2. On the other hand, when α is less than 0.08 or exceeds 0.3, the harmony between h〓(185) and h〓(254) is lost, and the cleaning effect decreases, resulting in poor efficiency. Therefore, by setting α of the light source system of the ultraviolet cleaning device of the present invention in the range of 0.08 to 0.3, which has not been attempted before, the ultraviolet cleaning device has excellent cleaning effects, consumes less power, and can process at high speed. can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing another embodiment. 1...Main body, 2...Belt conveyor, 3...
Filter, 4...Lamp, 5...Object to be cleaned.

Claims (1)

[Claims] 1 The object to be cleaned with organic contaminants and the gas to be cleaned containing organic contaminants coexist with oxygen gas, and the wavelength
An ultraviolet lamp emitting light at 185 nm and 254 nm is placed opposite the organic contaminant and oxygen gas;
When the output of 254nm light is I ₁₈₅ and I ₂₅₄ respectively,
An ultraviolet cleaning device characterized in that this ratio α=I ₁₈₅ /I ₂₅₄ is set in a range of 0.08 to 0.3.