JPH08236492A - Optical cleaning method - Google Patents

Abstract

PURPOSE: To improve th cleaning efficiency of an optical cleaning method and, at the same time, to reduce the damage to an object to be cleaned by ultraviolet rays or heat by turning on and turning off ultraviolet lamps while the object is cleaned by repeatedly turning on and turning off the power source of the ultraviolet lamps. CONSTITUTION: About five dielectric barrier discharge lamps 4 which are composed of ultraviolet lamps are arranged closely to an object 8 to be cleaned in a cleaning duct 3 while the lamps 4 are connected in parallel with one power source 10 and the object 8 is supported by a supporting jig 5. The object 8 is cleaned by using such an irradiating device by turning on and turning off the lamps 4 while the object 8 is cleaned by repeatedly turning on and turning off the power source 10. When the lamps 4 are turned on, the object 8 is cleaned by the same action as that of the prior art optical cleaning. In addition, even when the lamps 4 are turned off, the object 8 is cleaned, because contaminants are decomposed as a result of a reaction between the contaminants and the active oxygen species remaining in the duct 3. Therefore, the object 8 can be cleaned with a cleaning efficiency which is higher than that obtained when the lamps 4 are continuously turned on. In addition, the object 8 is not damage by heat, because the temperatures of the lamps 4 do not rise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a so-called photo-cleaning method for cleaning and removing contaminants of several tens of molecular layers from several molecules adhering to glass, silicon semiconductor wafers, semiconductor photomasks, ceramics, plastics, etc. Photoresist removal.

[0002]

2. Description of the Related Art As a technique related to the present invention, for example, there is JP-A-1-144560.
It describes a lamp using a dielectric barrier discharge (also known as ozonizer discharge or silent discharge. See the revised edition of the "Discharge Handbook" published by the Institute of Electrical Engineers of Japan, June 2001, 7th edition, page 263). In this lamp, it is known that a dielectric barrier discharge lamp having a central wavelength at a wavelength of 172 nm, which is filled with xenon, has an ability to generate active oxygen species having a higher oxidizing power than a low pressure mercury lamp.

On the other hand, in recent years, as a method for removing organic pollutants on the surface of an object to be irradiated without contacting the object, removing unnecessary photoresist, and precision dry cleaning, "UV" utilizing the cooperative action of ultraviolet rays and ozone is used. / O ₃ treatment ”has been developed and put to practical use. Regarding the “UV / O ₃ ” processing, for example, the book “New Technology of Utilizing Ozone” (published by San Yu Shobo, November 20, 1986), Chapter 9 (pages 301 to 3)
(Page 13) describes the principle, equipment, cleaning effect, and application in detail. According to this, ozone emits vacuum ultraviolet light of 185 nm emitted from a low-pressure mercury lamp to air or air to which oxygen is added. Or, it is generated by irradiating oxygen gas. Then, a part of the ozone is decomposed by the light of far ultraviolet light 254 nm emitted from the same low-pressure mercury lamp, and the ozone and the ozone decomposition gas are brought into contact with the surface of the object to be treated to remove the organic contaminants on the surface. The surface is dry and precision cleaned by oxidizing it, converting it to a low molecular weight oxide such as carbon dioxide or water, and removing it.

The method described above is a method of continuously irradiating a low pressure mercury lamp (wavelengths 254 nm and 185 nm), but has the following drawbacks. (1) The cleaning efficiency is insufficient and the cleaning speed is insufficient. (2) It is difficult to control the amount of ultraviolet rays, and excessive ultraviolet rays to the object to be processed cause damage to the object to be irradiated. (3) Since a large amount of heat is generated, thermal damage to the irradiated object cannot be avoided. (4) Only continuous lighting is possible, and the lamp has to be turned on even when the object to be irradiated is not irradiated, resulting in high power consumption and frequent lamp replacement. (5) It is difficult to uniformly wash a large area because uneven cleaning occurs and a plurality of lamps cannot be turned on and off with one power source at a time.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is high cleaning efficiency.
It is an object of the present invention to provide an optical cleaning method which is less likely to be damaged by ultraviolet rays and heat, has a low lamp replacement frequency, and can precisely clean a large area.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is arranged such that an object to be irradiated is placed in an atmosphere containing oxygen, and the oxygen and the object to be irradiated are irradiated with ultraviolet rays from an ultraviolet lamp. In the UV / O ₃ cleaning method of irradiating with UV light, the UV lamp is turned on and off during cleaning by repeatedly inputting and shutting off an electric input to the UV lamp.

According to a second aspect of the present invention, in the first aspect of the invention, a dielectric barrier discharge lamp is used as the ultraviolet lamp.

According to a third aspect of the present invention, in any one of the first or second aspect of the invention, the turn-off time is 30
It is done in less than a second.

The invention of claim 4 of the present invention is the same as claims 1 and 2.
Alternatively, in the invention of any one of claims 3 to 6, the amount of ultraviolet rays per one cycle is adjusted by changing the ratio of the turn-off time and the turn-on time.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the ultraviolet ray irradiation amount at the end of cleaning is smaller than the ultraviolet ray irradiation amount at the start of cleaning.

The invention of claim 6 of the present invention is the invention of claim 2
In the invention of any one of claims 3 and 4 or claim 5, a plurality of the dielectric barrier discharge lamps are connected in parallel to one power source and used.

[0012]

According to the first aspect of the present invention, in the UV / O ₃ cleaning method of arranging an object to be irradiated in an atmosphere containing oxygen and irradiating the oxygen and the object with ultraviolet rays, electricity to an ultraviolet lamp is applied. The lamp is turned on and off during cleaning by repeatedly inputting and shutting off the input.
Cleaning is performed by the same action as conventional light cleaning. in addition,
Even when the light is turned off, the reaction and decomposition of the remaining active oxygen species and contaminants occur, and cleaning is performed. It is known that the lifetime of active oxygen species is 110 seconds for O ( ¹ D) and several minutes for O ₂ ^* ( ¹ Δg), and these active oxygen species react with pollutants even when turned off, Disassembled and washed. Therefore, if the blinking is repeated, the cleaning speed increases with the same electric input.

According to the second aspect of the present invention, since the dielectric barrier discharge lamp containing xenon or the mixed gas of argon and chlorine as the discharge gas is used as the ultraviolet lamp in the first aspect of the invention, the wavelength is 172 nm.
Alternatively, vacuum ultraviolet light having a wavelength of 175 nm emits light with high efficiency, and oxygen molecules O ₂ are emitted in the ultraviolet light having a wavelength of 175 nm or less.
⁽³ Σg ^-) is dissociated directly, O ⁽¹ D) having a strong oxidizing power with high efficiency in addition to ozone ^{_{O 3, O 2 * (1}} Δg)
Since the active oxygen species such as can be generated, the cleaning rate is further increased.

The present inventors have also found that even if the dielectric barrier discharge lamp is repeatedly turned on and off, the lamp life is not shortened. That is, even if the above blinking lighting is repeated, the dielectric barrier discharge lamp is used, so that a long-life lamp device can be obtained.

In the invention of claim 3 of the present invention, in either of the invention of claim 1 or claim 2, the extinguishing time is set to 30 seconds or less. Is sufficiently present, and a sufficient cleaning speed can be obtained even when the lamp is turned off. The present inventors have found that when compared with the total lighting time when the extinguishing time is within 30 seconds, the cleaning efficiency is higher than that of a continuously lighting low-pressure mercury lamp or a dielectric barrier discharge lamp. The above effects and actions were particularly remarkable when the extinguishing time was 0.1 seconds to 5 seconds.

According to a fourth aspect of the present invention, in the invention according to any one of the first, second and third aspects, the ultraviolet ray amount per one cycle is changed by changing the ratio of the turn-off time and the turn-on time. Since it is adjustable, the amount of UV irradiation can be changed according to the type of object to be cleaned, and the amount of UV irradiation can be changed during the cleaning process.
Easy cleaning with low damage and no excess or deficiency of ultraviolet rays. Furthermore, it also contributes to the reduction of damage due to heat.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the ultraviolet irradiation amount at the end of cleaning is smaller than the ultraviolet irradiation amount at the start of cleaning. As a result, the cleaning progresses and the contaminants are removed, and the ultraviolet ray amount at the time when the irradiated object is exposed is reduced, the ultraviolet ray amount to the irradiated object is controlled, and the damage to the irradiated object is reduced, Optimum cleaning without excess or deficiency can be performed with low damage.

According to a sixth aspect of the present invention, in the photocleaning method according to any one of the second, third, fourth and fifth aspects, one power source includes a plurality of dielectric barrier discharge lamps. Since the lights are turned on in parallel, this lamp can be turned on and off by inputting and shutting off one power supply, irradiation of a large area can be performed, and the power supply device is inexpensive.

The method of dimming by blinking has been applied to plasma displays, liquid crystal backlights and the like, and is well known. However, the present invention is based on the finding that cleaning is performed even while the lamp is off, and in particular, the light cleaning method by flashing lighting of the dielectric barrier discharge lamp according to claims 2 to 5 is as follows. It is based on discovery. That is, (1) by using a dielectric barrier discharge lamp filled with xenon or a mixed gas of argon and chlorine, vacuum ultraviolet rays having a central wavelength of 172 nm or 175 nm are emitted. These vacuum ultraviolet rays have 18 times the absorption coefficient of oxygen molecules in the air when the central wavelength is 172 nm with xenon enclosed, compared with ultraviolet rays with a wavelength of 185 nm emitted by a low-pressure mercury lamp, and a mixed gas of argon and chlorine is enclosed. 12 when the center wavelength is 175 nm
It is twice as large and the density of active oxygen species is extremely high in an extremely narrow range near the lamp. Therefore, when the irradiation target is arranged in the vicinity of the lamp, the frequency of collision of the active oxygen species with the contaminants on the irradiation target is extremely high, and the active oxygen species easily diffuses onto the irradiation target during the extinguishing, As a result, the efficiency of reaction, decomposition and washing becomes extremely high. (2) Flashing does not shorten the lamp life. (3) The shape of the emission spectrum does not change depending on the blinking ratio. (4) A large number of lamps can be uniformly lit in parallel with one power source. (5) Since the vacuum ultraviolet ray can be emitted with high efficiency, thermal damage to the object to be irradiated is extremely small. By applying the above items (1) to (5), which could not be realized by the conventional discharge lamp, to the optical cleaning method, a completely new high-performance optical cleaning becomes possible.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic view of a light cleaning method according to a first embodiment of the present invention. Five dielectric barrier discharge lamps 4 were connected in parallel to one power supply 10. Five dielectric barrier discharge lamps 4 are provided in the cleaning duct 3 close to the object to be cleaned 8. The article to be cleaned 8 is supported by a support 5, which is a conventional means for changing the temperature of the article 8 to be cleaned, such as an electric heater, the article to be cleaned and a dielectric barrier discharge lamp. 4 has a moving mechanism for adjusting the distance between the two.

FIG. 2 is a schematic explanatory view of a dielectric barrier discharge lamp used in the present invention. In FIG. 2, the discharge vessel 13 is made of synthetic quartz having a total length of 250 mm, and an inner tube 14 having an outer diameter of 14 mm and a wall thickness of 1 mm and an outer tube 15 having an inner diameter of 24 mm and a wall thickness of 1 mm are coaxially arranged to form a hollow cylindrical discharge space 20. It is a structure. The outer tube 15 also serves as a dielectric barrier for dielectric barrier discharge and a light extraction window member, and is provided with a mesh electrode 17. On the inner surface of the inner tube 14, an aluminum thin film electrode 16 which also serves as a light reflecting plate and an electrode for dielectric barrier discharge is provided. The discharge space 20 of the discharge container was filled with 250 torr of xenon gas as a discharge gas. A getter 18 is provided in the getter chamber. If necessary, a cooling fluid such as cooling nitrogen gas can flow into the inner space 19 of the lamp. Here, the power source 21 turned on the dielectric barrier discharge lamp at 50 W per input. As a result, the wavelength 172
Ultraviolet rays having a maximum emission value in nm were efficiently emitted.

Using such an irradiation device, the electric input per lamp of the above lamp was set to 50 W, and the cleaning speed with respect to the total irradiation time of ultraviolet rays when the blinking interval was changed was examined. In the evaluation, quartz glass was pretreated with ultrasonic cleaning in isopropyl alcohol for 5 minutes, naturally dried, and left in the atmosphere for a few days. Also,
The total irradiation time was the total lighting time, and the cleaning rate was evaluated by measuring the contact angle of pure water with a contact angle meter. It is said that the thicker the surface organic contamination layer is, the larger the contact angle is, and the contact angle is 3 degrees and the contact angle is about 0.1 molecular layer or less. Further, the contact angle of the quartz glass not irradiated with ultraviolet rays this time was 56 degrees.

For comparison, one 450 W input power source was used to continuously light one high-efficiency type low-pressure mercury lamp, and similar cleaning was performed to obtain data. At this time, the temperature of the glass surface of the object to be cleaned was heated by heat radiation from the lamp, and the surface temperature became 48 ° C.

The results are shown in FIG. FIG. 3 is an explanatory diagram of data in which the cleaning rate with respect to the total irradiation time is evaluated by the contact angle of water. From this result, when comparing the total irradiation time, comparing the time required from the non-irradiated contact angle to the contact angle of 3 degrees, which is considered to have completed the cleaning, the low pressure mercury lamp continuously lit for 240 seconds. Of the dielectric barrier discharge lamp of the present invention for 120 seconds, and for the dielectric barrier discharge lamp of the present invention of blinking lighting for 47 seconds when the ratio of the lighting time and the extinction time is 1: 3, and 77 seconds when 1: 1. It can be seen that cleaning can be performed with significantly higher cleaning efficiency than that of a low-pressure mercury lamp or a dielectric barrier discharge lamp that is lit.

In the case of the dielectric barrier discharge lamp, no temperature rise was observed on the surface of the quartz glass, and the object to be cleaned was not damaged by heating.

In the second embodiment of the present invention, the structure of the cleaning device is the same as that of the first embodiment, the object to be cleaned is changed to a semiconductor silicon wafer, and the unit time in the latter half 1/3 step of the optical cleaning step is changed. The ultraviolet irradiation amount per unit is reduced to about 50% of the irradiation amount in the first half 2/3 step. As a result, there was almost no damage. Generally, semiconductor silicon wafers are said to be greatly damaged by ultraviolet rays of short wavelength. However, the present invention has realized a photo-cleaning method with almost no damage by ultraviolet rays.

An explanatory view of the ultraviolet lamp device used in the third embodiment of the present invention is shown in FIG. The ultraviolet lamp device comprises a conventional low pressure mercury lamp 40, electrode devices 42a and 42b for electrically heating the electrodes 41a and 41b, and a main power supply 43 for supplying lamp power to the low pressure mercury lamp. When the lighting and extinction of the low-pressure mercury lamp 40 are repeated, the electrodes 41a and 41b are preheated by the power sources 42a and 42b for electric heating before the lamp voltage is supplied from the main power source 43. By such means, the electrodes 41a, 42b at the start of discharge of the lamp
It is possible to obtain a low-pressure mercury lamp device which is less worn out and whose life is not shortened even if blinking is repeated.

When the low-pressure mercury lamp 40 is turned on and off,
In some cases, mercury adhered to the tube wall of the central part of the lamp and the ultraviolet rays were absorbed by the mercury, resulting in a decrease in the ultraviolet ray output. As a result of trial and error, the present inventors hold the temperature of the tube wall at the central portion of the lamp at 100 ° C. or higher, preferably 150 ° C. or higher when the low-pressure mercury lamp 40 blinks and lights. Have found that the above-mentioned mercury adhesion phenomenon disappears.

The light cleaning apparatus is the same as the light cleaning apparatus in the first embodiment except that the dielectric barrier discharge lamp and its power source are replaced with the low pressure mercury lamp and its power source shown in FIG.
After the object to be cleaned was installed in the cleaning device, the low pressure mercury lamp 40 was turned on. The main power supply 43 and the power supplies 42a and 42b for energization heating are high-frequency power supplies of 40 kHz,
During the light cleaning step, the electrodes 41a and 41b are constantly energized and heated, and the electrodes 41a and 41b are lit by repeating the lighting time of 50 ms and the extinction time of 50 ms, and the tube wall load during lighting of the low-pressure mercury lamp 40 is about 0. The temperature of the tube wall during lighting was turned on at 100 ° C. or higher by setting it to 0.2 W / cm ² . As a result, a sufficient cleaning speed can be obtained, and since the low-pressure mercury lamp is turned off while the object to be irradiated is installed in the light cleaning device, the worker may be exposed to harmful ultraviolet rays. There was also the advantage of being less.

[0030]

As described above, according to the present invention,
By performing blinking lighting, it is possible to provide a light cleaning method which has a high cleaning speed, less damage by ultraviolet rays and heat, less frequent lamp replacement, and a large area can be cleaned.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an example of a dielectric barrier discharge lamp used in the present invention.

FIG. 3 is an explanatory diagram of data of the contact angle of water with respect to the total irradiation time in the example of the present invention.

FIG. 4 is an explanatory diagram of another embodiment of the present invention.

[Explanation of symbols]

 1 Processing Fluid Air 2 Processing Fluid Supply Port 3 Cleaning Duct 4 Dielectric Barrier Discharge Lamp 5 Support Tool 8 Irradiation Object 10 Power Supply 14 Inner Tube 15 Outer Tube 16, 17 Electrode 19 Cooling Fluid 20 Discharge Space 21 AC Power Supply 40 Low-pressure mercury lamp 41a, 41b Electrode 42a, 42b Power supply for electrification heating 43 Main power supply

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location H01L 21/302 H01L 21/302 Z (72) Inventor Hiroshi Sugawara 1194 Sasato, Bessho-cho, Himeji-shi, Hyogo Address Ushio Electric Co., Ltd. (72) Inventor Tateman Hiramoto 1194 Sato, Bessho-cho, Himeji City, Hyogo Prefecture Ushio Electric Co., Ltd

Claims (6)

[Claims] 1. A UV / O ₃ cleaning method in which an object to be irradiated is placed in an atmosphere containing oxygen and the oxygen and the object to be irradiated are irradiated with ultraviolet rays from an ultraviolet lamp. The optical cleaning method characterized in that the ultraviolet lamp is turned on and off during cleaning by repeating the above procedure. 2. The photocleaning method according to claim 1, wherein a dielectric barrier discharge lamp is used as the ultraviolet lamp. 3. The photocleaning method according to claim 1, wherein the turn-off time is 30 seconds or less. 4. The photocleaning method according to claim 1, wherein the amount of ultraviolet rays per cycle can be adjusted by changing the ratio of the turn-off time and the turn-on time. 5. The ultraviolet irradiation amount at the end of cleaning is smaller than the ultraviolet irradiation amount at the start of cleaning.
The optical cleaning method described in. 6. A plurality of dielectric barrier discharge lamps are connected in parallel to one power source.
The photocleaning method according to claim 3, 4, or 5.