JP2705023B2 - Oxidation method of workpiece - 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 oxidizing an object to be treated, and more particularly to a method for oxidizing a surface of a metal or a semiconductor material, or a method for oxidizing and removing these objects by dry precision cleaning or the like. The latter method of oxidizing and removing
Specifically, there are a method of removing dirt of an organic compound attached to a surface of a metal or a glass plate, and a method of removing unnecessary photoresist on a silicon wafer in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In recent years, as a method for removing organic contaminants adhering to a surface of an object to be treated such as metal or glass without damaging the object, and a method for forming an oxide film layer on the surface, ultraviolet light and ultraviolet light have been used. Processing technology utilizing the cooperative action of ozone has been developed and has been put to practical use. This technology is described, for example, in the book “New Technology Using Ozone” (published by Sanchu Shobo, Showa 6
Chapter 9 (November 20, 2001) (Pages 301 to 313)
Page, hereafter referred to as Document A. ), Principles, equipment, cleaning effect,
The application is explained in detail. According to that, 185 nm which is a vacuum ultraviolet light emitted from a low-pressure mercury lamp
Is irradiated to air containing oxygen or oxygen gas to generate ozone. Then, part of the ozone is decomposed by 254 nm light, which is far ultraviolet light emitted from the same low-pressure mercury lamp, to generate an active oxidative decomposition product that is a decomposition gas of ozone. Is to be contacted. As for the cleaning of organic contaminants, the contact oxidizes the organic contaminants attached to the surface of the object to be converted into low-molecular oxides such as carbon dioxide and water, which are then converted to the surface of the object. By removing it from above, the surface of the object can be dry-precisely cleaned.

As another method, ozone is not generated by 185 nm light which is vacuum ultraviolet light.
The ozone produced by the ozone generator is led directly to the processing chamber, and the ozone is decomposed by irradiating ozone with 254 nm light, which is far ultraviolet light emitted from a low-pressure mercury lamp, and the ozone and active oxidative decomposed products are treated. In some cases, the material is brought into contact with the surface of an object to oxidize and remove organic contaminants on the surface.

[0004] In the technique described in the above document A, the ozone concentration becomes low when the ozone generator is not used.
The value of (d × p) determined by the value of the distance d (cm) through which the light of 85 nm passes and the value of the oxygen partial pressure p (atmospheric pressure) had to be equal to or more than a certain value. Specifically,
When the oxygen partial pressure p is 0.2 atm, the distance d needs to be 10 cm or more. Thus, in general, (d ×
It was a reality that the value of p) had to be greater than 2. For this reason, there is a drawback that the apparatus becomes large, and at the same time, high concentration ozone cannot be obtained.
The processing speed was slow in removing organic contaminants by oxidation.
In addition, when an ozone generator is used, it is an expensive device itself, which causes an economic problem and limits the conditions under which it can be used.

[0005] On the other hand, the technology of the synergistic action of ultraviolet light and ozone is described in, for example, the Materials of the Institute of Illumination Research (LS-90-8-1
3) (The Illuminating Engineering Institute of Japan, October 21, 1990,
Pages 36 to 41, hereinafter referred to as Document B. ), An apparatus for removing unnecessary photoresist on a silicon wafer called "optical asher" has been developed. In this document, as with the technique described in the document A, two methods, one using an ozone generator and the other using no ozone generator, are described. However, a photoresist having a normal thickness, for example, about 1 μm, is used. In order to quickly remove methane, a combination of a low-pressure mercury lamp and an ozone generator is eventually required. Therefore, drawbacks such as an increase in the cost of the apparatus itself, an increase in the cost of the processing steps, an increase in the installation floor area, and the like are pointed out.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and high concentration ozone can be obtained without using an ozone generator. The object of the present invention is to increase the speed of the oxidation treatment of the object by efficiently generating active oxidative decomposition products. Another object of the present invention is to provide a processing method that can reduce the size of the processing apparatus inexpensively.

[0007]

In order to achieve the above object, the following oxidation method is employed. (1) Vacuum ultraviolet light radiated from a dielectric barrier discharge lamp filled with xenon gas is irradiated to a fluid containing oxygen to generate ozone and an active oxidative decomposition product by a photochemical reaction. The decomposition product is brought into contact with the object to be processed, and the object to be processed is oxidized. (2) In addition, while performing the oxidation method described in (1) above, the object to be processed is directly irradiated with the vacuum ultraviolet light emitted from the dielectric barrier discharge lamp, and the object to be processed is oxidized by the cooperative action thereof. It is to let. (3) Further, after irradiating ozone and active oxidative decomposition products generated by the oxidation method described in (1) with far-ultraviolet light to further generate active oxidative decomposition products and increase the activity thereof, The object is oxidized by being brought into contact with the object. (4) A fluid containing oxygen is simultaneously irradiated with vacuum ultraviolet light radiated from a dielectric barrier discharge lamp filled with xenon gas and far ultraviolet light radiated from a far ultraviolet light source, and ozone and ozone are irradiated by a photochemical reaction. An active oxidative decomposition product is generated, and the ozone and the active oxidative decomposition product are brought into contact with the object to be oxidized to oxidize the object. (5) In the oxidation method according to the above (4), the irradiance of far ultraviolet light on the material surface of the object to be treated is I (mW / cm
² ) For a fluid containing oxygen present between the dielectric barrier discharge lamp and the object to be treated, the shortest transmission distance of vacuum ultraviolet light emitted from the lamp is d (cm), and the oxygen partial pressure is p. When (atmospheric pressure) is set, the value of (p × d) / (1 + I ^1/2 ) is specified to be smaller than 0.33.

Here, as the shape of the dielectric barrier discharge lamp, in particular, it is easy to use a double cylindrical type or a flat type, and all or a part of the vacuum ultraviolet light extraction portion is made of synthetic quartz glass or sapphire. It can be said that a material selected from alkali metal halides and alkaline earth metal halides is good.

Further, as a deep ultraviolet light source, a high-pressure mercury lamp, a low-pressure mercury lamp, a krypton-fluorine excimer lamp or a krypton-fluorine excimer laser can be used. It is more preferable that at least one of vacuum ultraviolet light and far ultraviolet light is irradiated.

In practice, the shortest distance of transmission of vacuum ultraviolet light radiated from the dielectric barrier discharge lamp to the fluid containing oxygen present between the lamp and the object to be processed is d (c
m), when the oxygen partial pressure is p (atmospheric pressure), in order to make the processing speed faster than the current method and further increase the economic effect, d ×
It is preferable to define p to be smaller than 0.6, and in the case of removing unnecessary photoresist, when oxidizing the object to be processed, the surface layer of the surface or the oxide of the substance is liberated from the surface as a gas. Or oxidize to remove.

[0011]

[Function] A dielectric barrier discharge lamp is filled with a discharge gas that forms excimer molecules in a discharge vessel, and a dielectric barrier discharge (also known as an ozonizer discharge or a silent discharge. New edition (discharge handbook) published by the Institute of Electrical Engineers of Japan in 2001. June Reprint 7
The excimer molecule is formed by printing (see page 263) and light emitted from the excimer molecule is extracted. Quartz glass etc. is used for the dielectric, and the occurrence of arc discharge is suppressed by interposing it in the discharge path.Also, since the discharge does not concentrate at a specific place, the density of generated ultraviolet light is almost uniform. it can. In addition, this dielectric barrier discharge lamp emits ultraviolet light having a short wavelength of 172 nm and selectively generates light of a single wavelength close to the line spectrum with high efficiency. It has various features not found in lamps. For a dielectric barrier discharge lamp, for example,
It is disclosed in JP-A-2-7353 and U.S. Pat. No. 4,837,484. In the present invention, a gas having xenon is used as the discharge gas sealed in the discharge vessel, and in particular, xenon gas or a gas containing xenon as a main component is used.

In the dielectric barrier discharge lamp, xenon atoms are excited to be in an excimer state (Xe ₂ *), and when the excimer state is again dissociated into xenon atoms, light having a wavelength of about 172 nm is generated. It can be seen that irradiating oxygen with this 172 nm light gives a higher concentration of ozone than irradiating oxygen with 185 nm light radiated from a conventional low-pressure mercury lamp. It was also found that active oxidative decomposition products can be obtained from ozone. Further, active oxidative decomposition products can be obtained from high-concentration ozone by light having a wavelength of 254 nm emitted from a high-pressure mercury lamp or a low-pressure mercury lamp provided separately from the dielectric barrier discharge lamp.

This principle can be described by a chemical reaction formula as follows. First, the reaction of generating ozone O ₃ from oxygen is O ₂ + hγ ₁ → O _3, and the active oxidative decomposition products O, O ^* from this ozone O ₃
Is O ₃ + hγ ₁ → O ^* + 2O O ₃ + hγ ₂ → O ^* + O ₂ . In each case, one reaction occurs with one photon. Hγ ₁ and hγ ₂ in this equation both mean light of a specific wavelength, and in this case, mean that oxygen or ozone absorbs light of a specific wavelength. The ozone O ₃ generation reaction occurs when oxygen O ₂ absorbs light in a vacuum ultraviolet region shorter than a wavelength of 200 nm. The degree of absorption is generally called an absorption coefficient, which continuously changes in accordance with a change in wavelength, and has a sharper change in the continuous change. This sudden change
This occurs remarkably in a region larger than the wavelength of 150 nm, and in particular, the absorption coefficient for the light of the wavelength of 172 nm is larger than that of the light of the wavelength of 185 nm by one digit or more. As a result, comparing the case of using a lamp that emits light with a wavelength of 185 nm and the case of using a lamp that emits light of a wavelength of 172 nm with the same emission light intensity as the lamp, it is found that the former uses the same amount of ozone to obtain the same amount of ozone. The latter requires a transmission distance of about 20 cm, while the latter requires a transmission distance of about 1 cm. In other words, even at the same radiation light intensity, the wavelength 172
The ozone concentration (ppm) on the surface of the object to be treated by the lamp that emits light of nm is about one order of magnitude higher than that of the lamp that emits ultraviolet light of 185 nm. On the other hand, the ozonolysis reaction for generating the active oxidative decomposition product is based on absorption of ozone O ₃ with respect to vacuum ultraviolet light or far ultraviolet light, and this ozone O ₃ absorption has a wavelength of 172 nm or 185 nm. Wavelength 250 compared to light
The light of nm is several times larger. Furthermore, even if it is an active oxidative decomposition product, it is considered that the activity of O ^* is larger than that of O. By irradiating the active oxidative decomposition product with far ultraviolet light, the decomposition product having a high activity is obtained. Therefore, it can be said that the activity can be increased as a whole.

In other words, the method for oxidizing an object to be treated according to the present invention employs an innovative method of using a dielectric barrier discharge lamp which efficiently emits light having a wavelength of 172 nm, which is vacuum ultraviolet light. _{that 3} can generate a first feature, a further deep ultraviolet light wavelength 254n
m, the active oxidative decomposition product can be efficiently generated from the high concentration of ozone O ₃ ,
The second feature is to increase the activity. By using these features to oxidize the object to be processed, the processing speed can be greatly increased as compared with the conventional method.
Specifically, ozone O ₃ is generated by light having a wavelength of 185 nm, which is a conventional method, and the absorption of ozone O ₃ by light having a wavelength of 254 nm is used as compared with the conventional method.
According to the present invention, the concentration (ppm) of the active oxidative decomposition product can be increased by about one digit, and therefore, the oxidation treatment of the object can be accelerated. Here, the oxidation of the object is
Both the case where the surface of the object to be treated itself is oxidized and the case where the substance attached to the object to be treated is oxidized are included.

[0015]

FIG. 1 is an explanatory view of an example of a dielectric barrier discharge lamp (hereinafter also referred to as "lamp") used in the present invention. The discharge vessel 1 has a parallel plate shape made of synthetic quartz glass. Generally, the object to be processed is often a plate-shaped object, and therefore, this shape is convenient for batch processing the surface of the object to be processed. The dimensions and shapes are, for example, 10 cm in length x 10 cm in width in inner dimensions
Those having a height of 0.6 cm are applied. The mesh electrode 2 is composed of a Monel wire provided on the upper and lower portions of the discharge vessel 1.
The interior of the discharge vessel 1 is filled with xenon gas and a power supply 3
When power is supplied to the reticulated electrode 2 by means of, a dielectric barrier discharge with a plasma length of 0.6 cm, for example, is generated inside the discharge vessel 1 using quartz glass as a dielectric. The quartz glass also serves as a vacuum ultraviolet light extraction section, and emits light having a wavelength of 172 nm, which is vacuum ultraviolet light, from the discharge vessel 1 from an excimer state obtained by such discharge. Since the treatment for removing organic contaminants targeted by the present invention is generally performed in an oxygen atmosphere, the lamp is particularly preferably made of a material that transmits vacuum ultraviolet light well, such as a synthetic quartz glass plate 5 made of a mesh. Preferably, the electrode 2 is covered, and a space 4 formed between the discharge vessel 1 and the quartz glass plate 5 is filled with nitrogen gas. Inside the discharge vessel 1, as described above,
In addition to the case in which only xenon gas is sealed, a gas in which xenon gas is the main component and neon, argon, or the like is sealed is used. The amount of xenon gas charged is, for example, 30
0 Torr. Also, from the reticulated electrode 2, for example, 4V2
A voltage of 0 KHz is applied.

FIG. 2 shows an apparatus for cleaning the surface of an object to be processed using the dielectric barrier discharge lamp. Inside the processing chamber 7, there is a sample table 8, an object 9 to be processed placed thereon, and a dielectric barrier discharge lamp 100 (hereinafter, simply referred to as a lamp). The object 9 is, for example, a 1 cm × 1 cm glass slide. Further, the processing chamber 7 is provided with an inlet 10 and an outlet 11 for a gas containing oxygen.
For example, a nitrogen gas source 14 and an oxygen gas source 15 are connected via a mixing chamber 12 and a valve 13. In addition, a decomposition device for the discharged ozone can be attached to the outlet 11 as needed. The reason for mixing the nitrogen gas here is to adjust the cleaning efficiency by changing the partial pressure P of oxygen. When such a device irradiates the slide glass, which is the object to be processed 9, with light having a wavelength of 172 nm from the lamp 100, active oxidative decomposition products are generated according to the above-described principle, and the organic substances adhered to the slide glass are generated. Contaminants can be removed by oxidation. The amount of the active oxidative decomposition products generated and the cleaning effect on organic contaminants are determined by the distance d (cm) between the surface of the lamp 100 and the surface of the slide glass and the partial pressure p (atmospheric pressure) of oxygen in the processing chamber 7.
, The partial pressure p of oxygen in the mixing chamber 12 can be adjusted, and the sample stage 8 has a vertical movement mechanism (not shown). In this device, for example, the lamp is turned on with an electric input of 20 W and a light output on the lamp surface of 30 mW / cm ² .

Next, by using the apparatus shown in FIG. 2, the distance d (cm) between the surface of the lamp 100 and the surface of the slide glass will be described.
And an experimental example in which the cleaning rate of organic contaminants was examined by changing the oxygen partial pressure p (atmospheric pressure) in the processing chamber 7. In the experiment, the lamp 100 was turned on with the aforementioned electric input (W) and light output (mW / cm ² ). Also,
In this experiment, the washing time was defined as follows. Slide glass on isopropyl alcohol (hereinafter IPA)
That. ) Is subjected to ultrasonic cleaning for about 5 minutes to produce a filter having a contact angle with water of 20 degrees. Then, by performing the cleaning method according to the present invention on the slide glass, a time until the angle becomes 3 degrees was defined as a cleaning time T (second). Here, the contact angle with respect to water is, as shown in FIG. 12, an angle θ formed by a water drop on the slide glass, and this angle θ has a great relationship with the degree of cleaning of the slide glass surface.
This is described in detail on pages 308 to 313 of the aforementioned Reference A. According to the contact angle of 3 degrees set here, according to page 309 of the above-mentioned document, the thickness of the organic contaminant layer is less than 0.1 molecular layer, and several molecules are on the slide glass. However, it is presumed that the particles are slightly adhered, and it can be considered that they have been sufficiently washed. On the other hand, the setting angle of 20 degrees before the experiment means that the thickness of the organic contaminant layer is one or more molecules and the monomolecular layer is attached to the entire surface of the slide glass and spreads. is there.

FIG. 3 shows the results of the experiment. The numerical values in the table indicate the cleaning time T (seconds). In the figure, p is the partial pressure of oxygen in the processing chamber 7, and the total pressure of the processing chamber 7 is 1
The p (atmospheric pressure) at (1-p) N ₂ + pO ₂ is shown as the atmospheric pressure. For comparison, a similar experiment was performed using a low-pressure mercury lamp with an electric input of 450 W instead of the dielectric barrier discharge lamp 100, and the optimum condition for this low-pressure mercury lamp was a partial pressure p of oxygen. 0.2 atm, distance d
Even when (cm) was 12 cm, the cleaning time T required about 200 seconds. Then, the partial pressure p of oxygen shown in FIG.
Is 0.1 to 0.6 and the distance d (cm) is 0.5 to 5.0, the cleaning time T takes 200 seconds or more.

Generally, it is less than 60 seconds that the cleaning time T is considered to have a significant economic effect. Accordingly, when the case where the cleaning time T is 60 seconds or less is defined as the allowable cleaning processing time, the results shown in FIG. 3 indicate that the value of (distance (d) × partial pressure of oxygen (p)) is 0.6 or less. It can be seen that the processing can be performed within the processing time. In this experiment,
Although nitrogen gas was used as a gas mixed with oxygen,
Even when a similar experiment was performed using an inert gas such as argon Ar or krypton Kr in place of the nitrogen gas, the value of the cleaning time T was consistent within the range of the experimental data.

FIG. 4 shows another example of an apparatus for cleaning the surface of an object to be treated using a dielectric barrier discharge lamp. In this apparatus, a far ultraviolet light source set 101 including a mirror and a low-pressure mercury lamp is arranged along four sides of the dielectric barrier discharge lamp 100 in addition to the dielectric barrier discharge lamp 100. Therefore, the slide glass 9
Gas flowing in the vicinity of the dielectric barrier discharge lamp 1
00 and the far-ultraviolet light from the far-ultraviolet light source set 101. Although not shown in the figure, the dielectric barrier discharge lamp is mounted on a mechanism that can move up and down so that the distance d between the dielectric barrier discharge lamp 100 and the slide glass 9 can be changed. Here, the vacuum ultraviolet light emitted from the dielectric barrier discharge lamp 100 refers to light having a wavelength of 1 nm to 200 nm, and the far ultraviolet light emitted from the far ultraviolet light source set 101 refers to light having a wavelength of 200 nm to 370 nm. Say.

Next, a slide glass washing experiment was performed using this apparatus in the same manner as described above. Experiments by changing the illuminance on the surface of the glass slide 9 with respect to light in the far ultraviolet is external light wavelength 254nm and ^{70mW / cm 2, 25mW / cm} 2, 8mW / cm 2, in each of the illumination, the distance d and the oxygen The washing time T (second) was measured by changing the partial pressure p. Note that the radiation intensity of vacuum ultraviolet light from the dielectric barrier discharge lamp 100 is
It was set to 30 mW / cm ² at the vacuum ultraviolet light extraction part, that is, at the lower surface of the lamp 100. put it here,
The illuminance of the 254 nm deep ultraviolet light is a value measured in advance with p = 0. Since the amount of light reaching the slide glass changes depending on the value of the oxygen partial pressure P, the illuminance is measured in such a state.

FIG. 5 shows the results of this experiment. From the results,
In order for the cleaning time T to be equal to or less than the allowable cleaning processing time of 60 seconds, the value of (d × p) / (1 + I ^1/2 ) is set to 0.1.
It is suggested that smaller is better. Here, I means the radiant intensity of the far ultraviolet light on the surface of the object to be processed or on the material surface on the surface and the light intensity of the far ultraviolet light when there is no light absorption between them. However, in this experiment, the dielectric barrier discharge lamp 100 was illuminated with an illuminance of 30 mW /
Although it is turned on at cm ² , the illuminance of vacuum ultraviolet light at 172 nm is actually 300 mW / cm ² even in the case of natural air cooling.
Can be raised up to When the lamp is turned on with such a high output, the present inventors have assumed that the value of (d × p) / (1 + I ^1/2 ) is smaller than 0.33. It has been found that even if the processing is performed, the processing can be sufficiently performed within the allowable time.

FIG. 6 is an explanatory diagram showing a method of oxidizing and removing organic contaminants adhering to a metal surface among the oxidizing methods described in the first and second aspects. That is,
Ozone and active oxidative decomposed products are generated by 172 nm light, which is vacuum ultraviolet light emitted from a dielectric barrier discharge lamp, and the ozone and active oxidative decomposed products oxidize and remove organic contaminants adhering to the metal surface. In addition, a method of directly irradiating 172 nm light, which is vacuum ultraviolet light, to a metal surface to oxidize and remove organic contaminants by the cooperative action thereof will be described. First, the structure of the apparatus will be described. The dielectric barrier discharge lamp 102 is disposed in an aluminum mirror 16 having a surface coated with magnesium boride. An aluminum plate 17 to which contaminants are attached is arranged. The distance between the aluminum plate 17 and the lamp 102 is, for example,
10 cm. Here, as the lamp 102, the one shown in FIG. 1 can be used, but a double cylindrical lamp described later can also be used. The atmosphere in the mirror 16 is such that air flows from above the mirror 16 so as to cool the lamp 102 and the mirror 16 and the like toward the aluminum plate 17. The total pressure of the atmosphere is about 1 atm, and the oxygen partial pressure is, for example, about 0.25 atm. With such a configuration, the lamp 10 having xenon gas can be used.
2 emits light of 172 nm, which is vacuum ultraviolet light, efficiently. The light is irradiated to the oxygen gas in the incoming air to generate ozone by a photochemical reaction, and the ozone is also irradiated with the light of the vacuum ultraviolet light to cause active oxidative decomposition. Things are created. When the active oxidative decomposition product comes into contact with the aluminum plate 17, organic contaminants adhering to the aluminum plate 17 can be washed well. In this embodiment, oxygen gas can be efficiently delivered onto the aluminum plate 17 using the mirror 16 and the mirror 1
The aluminum plate 17 is directly irradiated with the reflected light by the lamp 6 and the direct light from the lamp 102 or the vicinity thereof is irradiated to cause a photochemical reaction, so that the cleaning effect can be made particularly high. As an example of the effect of this method, when the lamp 102 is turned on with an electric input of 20 W and the emitted vacuum ultraviolet light of 172 nm is irradiated on the aluminum plate 17 for 40 seconds, the contact angle of the aluminum plate with water becomes What was initially 40 degrees has been reduced to 10 degrees. If organic contaminants can be washed to this extent, even if the printing ink is adhered to the surface of the washed aluminum plate 17, it can have sufficient strength for practical use. When the distance d between the aluminum plate 17 and the lamp 102 is reduced to 0.3 cm, vacuum ultraviolet light 17
Irradiation of 2 nm light was able to obtain the same effect in about 13 seconds.

FIG. 7 shows an example of a double cylindrical dielectric barrier discharge lamp 102. The discharge vessel 18 has a hollow cylindrical shape in which an inner tube 23 and an outer tube 24 made of quartz glass are coaxial, and has a substantially bamboo ring shape. The outer tube 24 also serves as a dielectric and a light extraction portion of the dielectric barrier discharge lamp, and the outer surface of the inner tube 23 has an aluminum film electrode 1 also serving as a reflection film.
9 is provided, and a metal mesh electrode 20 for transmitting light is provided on the outer surface of the outer tube 24. The discharge space 21 is filled with discharge gas xenon. The reticulated electrode 2
The electrode 0 is provided with an electrode oxidation preventing coat 22, which is not shown, but may be provided also on the electrode 19.
Generally, when treating the surface of a roll-wound film, the double cylindrical dielectric barrier discharge lamp having such a shape is formed by moving the film in a direction perpendicular to the lamp tube axis. It is convenient to treat the surface continuously. Incidentally, an example of such a lamp, the total length of about 100mm of the discharge vessel 18, the outer diameter D ₁ of the inner tube 23 is 6 mm, the inner diameter D ₂ of the outer tube 24 is 8 mm, they are, for example, OH groups by weight And quartz glass containing 700 ppm or less.

FIG. 8 is an explanatory diagram showing a method of oxidizing and removing organic contaminants adhering to a metal surface among the oxidizing methods described in claim 3. That is, ozone and active oxidative decomposition products are generated by 172 nm light, which is vacuum ultraviolet light radiated from the dielectric barrier discharge lamp, and the ozone and active oxidative decomposition products are subjected to a wavelength 25 of far ultraviolet light.
Irradiation with light of 4 nm generates an active oxidative decomposition product and increases the activity to oxidize and remove organic contaminants on the metal surface. First, the configuration of the device will be described.
The reaction duct 25 has a generally flat shape, in which a double-cylindrical dielectric barrier discharge lamp 102 and a low-pressure mercury lamp 103 are arranged spaced apart with their tube axes parallel. The reaction duct 25 is configured such that the air flowing from the lamp 102 flows toward the lamp 103, and an aluminum plate 17 as an object to be cleaned is disposed downstream of the lamp 103. The aluminum plate 17 does not need to be directly irradiated with the radiated light from the lamps 102 and 103, but depending on its position,
It is also possible to receive far ultraviolet light from the low-pressure mercury lamp 103. The distance between the lamp 102 and the lamp 103 is, for example, 15 cm, and the inflow air is about 1 atm. Further, the lamp 102 is turned on at an electric input of 20 W, and the lamp 103 is turned on at an electric input of 450 W. In such a configuration, the air that has flowed into the reaction duct 25 receives light having a wavelength of 172 nm, which is vacuum ultraviolet light emitted from the lamp 102, on the upstream side in the duct.
Then, oxygen causes a photochemical reaction to generate ozone, and an active oxidative decomposition product is also generated from the ozone. These ozone and active oxidative decomposition products are blown toward the downstream side, and further receive the light having a wavelength of 254 nm, which is the far ultraviolet light emitted from the lamp 103, so that the activity is further enhanced. Then, by contacting the aluminum plate 17 disposed further downstream, organic contaminants attached to the surface can be oxidized and removed. As an example of the effect of this method, by treating for about 36 seconds, the aluminum plate 17 having a contact angle to water of 40 degrees at first can be reduced to 10 degrees. Then, according to the aluminum plate 17 after the cleaning treatment, even if a printing ink or the like is adhered to the surface thereof, it was possible to maintain sufficient strength for practical use.

FIG. 9 is an explanatory view showing a method of oxidizing and removing organic contaminants adhering to a metal surface among the oxidizing methods described in claims 4 and 5. That is, 1 is a vacuum ultraviolet light emitted from a dielectric barrier discharge lamp.
Ozone and active oxidative decomposition products are generated by the light of 72 nm, and the ozone and active oxidative decomposition products are brought into contact with the metal surface having organic contaminants. Light of 254 nm, which is far ultraviolet light emitted from a mercury lamp, is also applied to the metal surface. That is, the oxidation treatment is performed using two lamps, a dielectric barrier discharge lamp and a low-pressure mercury lamp, and at least one of the two is used to directly irradiate the metal surface. First, the configuration of the apparatus will be described. In the mirror 16, three double-cylindrical dielectric barrier discharge lamps 102 are arranged in substantially the same plane, and two low-pressure mercury lamps 103 are further constituted by the lamps 102. They are arranged in substantially the same plane in parallel with the plane. In this case, "parallel" means that the lamp axes are parallel to each other, and the lamps are arranged in a zigzag shape when viewed from the lamp axis direction. The mirror 16 can be the same as that described with reference to FIG. Further, the lamp 102 and the aluminum plate 17 which is an example of a metal are processed by being brought close to a distance of, for example, about 0.3 cm. On the surface of the aluminum plate 17, far ultraviolet light radiated from the lamp 103 is used. There are places where some 254 nm light is irradiated and places where it is not irradiated, and even 172 nm light, which is vacuum ultraviolet light emitted from the lamp 102, causes uneven illuminance on the aluminum plate 17. For this reason, the sample stage 8 on which the aluminum plate 17 is placed is, for example,
It can be moved with z. And the lamp 10
2. The arrangement of the lamp 103 and the selection of the amplitude of the lamp 103 adjust the way of receiving the far ultraviolet light while making the illuminance of the vacuum ultraviolet light uniform on the aluminum plate 17. With such a configuration, the aluminum plate 1 placed on the sample table 8
Reference numeral 7 denotes vacuum ultraviolet light emitted from the lamp 102.
By receiving light of 72 nm, oxygen contained in the air causes a photochemical reaction to generate ozone and active oxidative decomposition products. At the same time, by receiving the light of 254 nm, which is far ultraviolet light emitted from the lamp 103, the activity of the ozone and the active oxidative decomposition products is increased, and the organic contaminants on the aluminum plate 17 are oxidized and removed. it can. The effect of this method is that the lamps 102 each have an electrical input of 20 W and the lamps 103 each have an electrical input of 45 W.
When turned on at 0 W, the contact angle of the aluminum plate 17 with water could be reduced from 40 degrees to 10 degrees in about 6 seconds.

In the embodiment described above, the organic contaminants adhering to the surface of the aluminum plate are oxidized and removed. Next, an apparatus having substantially the same configuration as the apparatus shown in FIG. The so-called optical ashing for oxidizing and removing the photoresist applied to the substrate will be described. In this case, by equipping the sample stage 8 with a heating mechanism such as a heater or a pipe for flowing cooling water, the temperature of the semiconductor wafer can be heated to a predetermined temperature. An ashing process can be performed by irradiating the photoresist with radiation emitted from 103. For example, a semiconductor wafer is 200
When the semiconductor wafer coated with a photoresist (model OMR83, manufactured by Tokyo Ohka Kogyo Co., Ltd.) at a thickness of 1 μm was heated to ℃, the ashing could be performed at a speed of 15 nm per second.

Next, a method of forming a silicon oxide film on the surface of a semiconductor wafer using an apparatus substantially similar to the apparatus shown in FIG. 9 will be described. A silicon wafer as an object to be processed is placed on the sample table 8, and five dielectric barrier discharge lamps 102 and four low-pressure mercury lamps 103 are arranged in a zigzag as described above. When the temperature of the sample stage 8 is heated to, for example, 400 ° C. and reciprocated at 5 Hz, a dense silicon oxide film having a thickness of 10 nm can be formed on the silicon wafer. Could be achieved in time. The above-described apparatus for removing organic contaminants and unnecessary photoresist is not shown, but is provided with a mechanism for blowing off such exhaust, whereas the apparatus for removing an oxide film according to this embodiment is not shown. The apparatus differs in that a mechanism for stably holding and controlling the fluid existing between the lamp and the workpiece is provided. Such a mechanism is also omitted in FIG.

Generally, forming a thin oxide film on the surface of a silicon wafer is commonly performed in an insulating layer forming step in the manufacture of semiconductor devices. However, the conventional method is carried out by heating at a high temperature of, for example, about 850 ° C. to 1000 ° C., compared with a high-humidity electric furnace, whereas the method of forming an oxide film of the present invention has significantly lower humidity and lower humidity. A high-quality oxide film can be obtained at a temperature.

Next, another embodiment of a method of forming an oxide film on a silicon wafer will be described with reference to FIG. The discharge vessel 1 of the dielectric barrier discharge lamp is made of quartz glass and is of a flat type having a discharge space 21 therein. The discharge vessel 21 is filled with xenon gas to generate 172 nm light, which is vacuum ultraviolet light. Although the electrode 2 is provided outside the discharge vessel 21 but the emitted light is extracted only in one direction, the aluminum film 6 also serving as a mirror is formed on one electrode, and the other is a mesh electrode, so that it is efficient. Synchrotron radiation can be extracted. Further, since the present apparatus is used in an oxygen atmosphere, the quartz glass is provided with an antioxidant coat 22. The sample stage 28 is made of quartz glass, and the silicon wafer 26 is
And a heater 27 for heating is incorporated therein. As an example of such a dielectric barrier discharge lamp, the discharge vessel 1 is made of quartz glass having a thickness of 1 mm and has an inner size of 20 cm × 20 cm × 0.6 cm. In such an apparatus, the distance d (cm) between the lamp 1 and the silicon wafer 26 in the atmosphere is set to 0.2, and the intensity of light having a wavelength of 172 nm emitted from the lamp is about 100 mW / cm ² at the lamp surface. The lighting of the lamp is controlled by the power supply 3 so that In this case, the electric input of the lamp is, for example, 40
0W. Then, by changing the control temperature of the heater 27,
A test for forming a dense silicon oxide film having a thickness of 10 nm on the silicon wafer 26 was performed. The control temperature of the heater 27 can be raised to a maximum of 600 ° C.

The result is that when the silicon wafer 26 is maintained at about 450 ° C. by the heater 27, a silicon oxide having a thickness of 10 nm can be formed in about 1.5 hours. Can make the same silicon oxide in about 40 minutes. This indicates that a sufficient silicon oxide insulating film can be obtained at a significantly lower temperature than the conventional method using high-temperature oxidation.

Here, the dielectric barrier discharge lamp filled with xenon gas will be described in more detail.
Since the dielectric barrier discharge lamp emits vacuum ultraviolet light having a wavelength shorter than 200 nm, the discharge vessel must be made of a dielectric that transmits light in the relevant wavelength range. In some cases, the light extraction portion may be in all directions of the lamp, or may be in one specific direction. Therefore, it is sufficient that at least the light extraction portion has a structure that transmits light in the wavelength range, and the material of the extraction portion is not limited to synthetic quartz glass, but includes sapphire, alkali metal halide, and the like. A single crystal of an alkaline earth metal halide may be used. Then, a portion of the discharge vessel from which the ultraviolet light is not extracted may be provided with a reflective coat or an electrode serving also as a reflective coat.

Similarly, a wavelength of 200 nm to a wavelength of 300 n
The far-ultraviolet light source that emits m-ultraviolet light is not limited to the low-pressure mercury lamp described above, but may be a high-pressure mercury lamp that emits light in these wavelength ranges, a wavelength of 240 nm to 255 nm.
And a krypton-fluorine excimer laser emitting krypton.

FIG. 11 shows a lamp device including a dielectric barrier discharge lamp. This lamp device incorporates a double cylindrical dielectric barrier discharge lamp 33a, 33b, 33c having a structure similar to that of the dielectric barrier discharge lamp shown in FIG. 7 instead of the parallel plate type discharge vessel 1 in FIG. Then, instead of being covered with the synthetic quartz glass plate 5 in FIG. 1, a flat container 34 having a light extraction window 31 made of synthetic quartz glass is provided in a metal container 30 also serving as a light reflecting plate. Double cylindrical dielectric barrier discharge lamp 3
3a, 33b, 33c have, for example, an outer diameter of 26.6 m.
m, the discharge gap length is 5 mm, and the total length is 300 mm. The discharge gas is xenon of about 40 kPa. When a dielectric barrier discharge was performed in this lamp device,
Vacuum ultraviolet light centered at a wavelength of 172 nm was emitted with high efficiency. Further, by flowing a few liters of nitrogen gas per minute to the space 4, the electrodes 20a, 20b, 20c
In addition to the above, the absorption of vacuum ultraviolet light in the space 4 is eliminated, so that a substantially flat light source device was obtained. In this embodiment, since a large number of expensive synthetic quartz glass plates are not used, there is an advantage that a flat light source device can be obtained at low cost.

In the method for oxidizing an object to be treated according to the present invention, the surface of the metal is oxidized by alumite treatment of aluminum, surface oxidation treatment as a pre-treatment for printing on stainless steel, and further, vapor deposition on a glass plate. It can also be used for an oxidation treatment for improving the transparency of the metal oxide.

As a method for cleaning the surface of glass,
It can be used for precision cleaning for pre-processing of distributing electrodes and wiring to the glass of the liquid crystal display panel. The technique of the present invention is also useful for improving the thermocompression bonding strength of gold.

[0037]

According to the method for oxidizing an object to be treated according to the present invention, a dielectric barrier discharge lamp that emits vacuum ultraviolet light, which is light having a wavelength of 172 nm, is used. Since ozone and active oxidative decomposition products can be generated, the speed of oxidizing the object to be treated is significantly increased. In addition, by irradiating ozone and active oxidative decomposition products with far ultraviolet light, which is light having a wavelength of 254 nm, active oxidative decomposition products can be generated more efficiently and their activity can be increased. Therefore, as a result, the object can be oxidized quickly and the processing apparatus can be designed to be small. Further, since no ozone generator is used, an inexpensive processing method can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a planar dielectric barrier discharge lamp used in the present invention.

FIG. 2 is an explanatory view of a method of cleaning the surface of a slide glass.

FIG. 3 is a table of data of surface cleaning results.

FIG. 4 is an explanatory view of another surface cleaning method of the slide glass.

FIG. 5 is a table of data of other surface cleaning results.

FIG. 6 is an explanatory view of an embodiment of a method for oxidizing and removing organic contaminants on a metal surface.

FIG. 7 is an explanatory diagram of an example of a double cylindrical dielectric barrier discharge lamp used in the present invention.

FIG. 8 is an explanatory view of another embodiment of the method of oxidizing and removing organic contaminants on a metal surface.

FIG. 9 is an explanatory view of another embodiment of the method of oxidizing and removing organic contaminants on a metal surface.

FIG. 10 is an explanatory diagram of a low-temperature oxidation method for a silicon wafer.

FIG. 11 is an explanatory diagram of a light source device using a double cylindrical dielectric barrier discharge lamp.

FIG. 12 is a diagram showing a state of a water droplet on a slide glass.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge container 2 Reticulated electrode 3 Power supply 7 Processing chamber 8 Sample stand 9 Slide glass 10 Oxidizing fluid inlet 11 Oxidizing fluid outlet 12 Mixing chamber 13 Valve 16 Mirror 17 Aluminum plate 18 Discharge container 19 Electrode 20 Electrode 21 Discharge space 22 Oxidation Prevention coat 25 Reaction vessel 100 Dielectric barrier discharge lamp 101 Deep ultraviolet light source set 102 Dielectric barrier discharge lamp 103 Low pressure mercury lamp

Continuation of the front page (72) Inventor Shinichi Iso 1194 Sado Bessho-cho, Himeji-shi, Hyogo Ushio Electric Co., Ltd. Examiner Hitoshi Maeda (56) References JP-A-2-97402 (JP, A) JP-A Heihei 1-228590 (JP, A) JP-A-4-182303 (JP, A)

Claims (11)

(57) [Claims] A fluid containing oxygen is irradiated with vacuum ultraviolet light radiated from a dielectric barrier discharge lamp filled with xenon gas to generate ozone and active oxidative decomposition products by a photochemical reaction. A method for oxidizing an object to be treated, wherein the oxidized decomposition product is brought into contact with the object to be oxidized. 2. A liquid containing oxygen is irradiated with vacuum ultraviolet light radiated from a dielectric barrier discharge lamp filled with xenon gas to generate ozone and an active oxidative decomposition product by a photochemical reaction. The object to be treated, wherein the object to be oxidized is oxidized by contacting the oxidized decomposition product with the object to be treated, and the object to be treated is also irradiated with the vacuum ultraviolet light so that the object to be treated is oxidized by their cooperative action. How to oxidize the material. 3. A fluid containing oxygen is irradiated with vacuum ultraviolet light radiated from a dielectric barrier discharge lamp filled with xenon gas to generate ozone and an active oxidative decomposed product by a photochemical reaction. Irradiating the oxidative decomposition product with far-ultraviolet light to increase the activity, and contacting the ozone and the active oxidative decomposition product with the increased activity with the processing object to oxidize the same; Oxidation method. 4. A photochemical reaction in which oxygen-containing fluid is simultaneously irradiated with vacuum ultraviolet light emitted from a dielectric barrier discharge lamp in which xenon gas is sealed and far ultraviolet light emitted from a far ultraviolet light source. Ozone and an active oxidative decomposition product are generated by the method, and the ozone and the active oxidative decomposition product are brought into contact with the processing object to oxidize the same. 5. The method according to claim 3, wherein the object is irradiated with at least one of vacuum ultraviolet light and far ultraviolet light when the object is oxidized. A method for oxidizing an object to be treated. 6. The method according to claim 3, wherein the deep ultraviolet light source is a high-pressure mercury lamp, a low-pressure mercury lamp, a krypton-fluorine excimer lamp, or a krypton-fluorine excimer laser. The method for oxidizing an object to be described. 7. An oxygen-containing fluid is present between a dielectric barrier discharge lamp and an object to be processed, and the shortest distance of vacuum ultraviolet light radiated from the lamp to the fluid is defined as d (c).
3. The method for oxidizing an object to be treated according to claim 2, wherein d × p is defined to be smaller than 0.6 when the oxygen partial pressure of the fluid is p (atmospheric pressure). . 8. The method according to claim 1, wherein when oxidizing the object, the surface layer of the object or the oxide of the object is oxidized so as to be removed from the object as a gas. The method for oxidizing an object to be processed according to any one of claims 1 to 7. 9. The method for oxidizing an object to be treated according to claim 1, wherein the shape of the dielectric barrier discharge lamp is a double cylindrical type or a planar type. 10. The vacuum ultraviolet light extraction portion of the dielectric barrier discharge lamp is made of a material selected from synthetic quartz glass, sapphire, alkali metal halide, or alkaline earth metal halide. The method for oxidizing an object to be processed according to claim 9. 11. A fluid containing oxygen is irradiated with vacuum ultraviolet light radiated from a dielectric barrier discharge lamp filled with xenon gas and far ultraviolet light radiated from a far ultraviolet light source, and is subjected to a photochemical reaction. Ozone and an active oxidative decomposition product are generated, and the ozone and the active oxidative decomposition product are brought into contact with the object to be processed, and the ultraviolet light is also applied to the object to be processed. When oxidizing the object, the irradiance of the far ultraviolet light when there is no light absorption between the object and the far ultraviolet light source on the surface of the object to be treated is defined as I (mW / cm ² ). For a fluid containing oxygen existing between the objects to be treated, the shortest transmission distance of vacuum ultraviolet light emitted from the lamp is d (cm), and the oxygen partial pressure is p.
A method for oxidizing an object to be processed, wherein the value of (p × d) / (1 + I ^1/2 ) is defined to be smaller than 0.33 when (atmospheric pressure) is set.