JPH08298253A - Cleaning method of substrate used for manufacturing pellicle film - Google Patents

Abstract

PURPOSE: To remove residues of fluororesin and a ground layer attached to the edge and rear of a substrate by a method wherein the substrate is dipped into a hot alkali water solution or a heated cleaning agent which contains a surfactant. CONSTITUTION: A substrate 4 is dipped into a hot alkali water solution 2 or a cleaning agent 2 which contains a surfactant in a heated tank 1. The hot alkali water solution 2 contains 1% or more by weight of strong alkaline chemical compound or is set higher than 13 in pH value. The cleaning agent 2 contains 1% or more by weight of the surfactant. Hot alkali water solution 2 or a heated cleaning agent 2 which contains the surfactant is circulated by a pump 7 and jetted out against the end face of the substrate 4. It is preferable that an ultrasonic cleaning operation is carried out while the substrate 4 is dipped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a substrate used for manufacturing a thin film of a protective device used for the purpose of preventing dust or the like from adhering to a mask or reticle (hereinafter referred to as "mask"). Regarding

[0002]

2. Description of the Related Art In the manufacture of semiconductor integrated circuits, the step of patterning a semiconductor wafer coated with a resist material by exposure is an important step that affects the yield of integrated circuits. In this step, if scratches or dust are present on the mask, which is the original pattern, the scratches or foreign substances are printed on the wafer together with the pattern, which may cause a short circuit or disconnection of the produced circuit. Therefore, protection and dust protection of the mask are extremely important issues for improving productivity. For this reason, it has been proposed and put into practical use to cover one or both surfaces of the mask with a transparent plastic thin film called a pellicle for the purpose of protecting the mask and preventing dust.

Conventionally, as the exposure light source used in the photolithography process, among the bright lines of a high pressure mercury lamp,
G-line, h-line and i-line are used, and as the pellicle film, film materials such as nitrocellulose, cellulose acetate and polyvinyl alcohol have been mainly used. However, in recent years, with the progress of technology in the semiconductor industry, the density and integration of integrated circuits have increased, and both the line width and the line spacing of a projected pattern on a wafer have become smaller. In response to this, the wavelength of exposure light has been shortened, and ultraviolet rays (wavelength of 250 nm or less) by excimer laser such as KrF have begun to be used.

Since the energy increases as the wavelength of light becomes shorter, the pellicle film used in these wavelength regions is required to have sufficient light resistance, whereas the conventional protective film has sufficient light resistance to deep ultraviolet rays. Was low, and sufficient durability was not obtained. As a material that meets such requirements,
Various pellicles made of a fluorine-containing resin have been proposed.

The film formation of the resin thin film is generally carried out by a spin coating method in which a resin solution is dropped on a substrate such as quartz glass or a silicon wafer which rotates at a high speed. After drying, the film is peeled from the substrate to obtain a film. . Film formation can be performed directly on the substrate, but in the case of a fluororesin, since it easily extends or deforms during peeling, it has a low affinity with the fluororesin and a resin that does not contain a fluorine atom is previously formed as a base layer. Is often formed on a substrate and used as a film-forming substrate.

On the substrate from which the fluorine-containing resin thin film has been peeled off, the residual resin remains on the edges and the back surface, and the underlayer remains on the front surface. When the substrate is reused, the resin remaining on the substrate is completely removed. Need to be removed. When the material for the thin film is cellulose resin or polyvinyl alcohol, the resin remaining on the substrate is first decomposed and removed with an acid such as sulfuric acid, and then ultrasonic cleaning or scrubbing is performed in pure water before IPA vaporization. If it was washed and dried, it could be reused sufficiently. However, in the case of fluorine-containing resin,
Since it was not decomposed by sulfuric acid, it was difficult to reuse the substrate once used.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an effective cleaning method for a substrate used for producing such a fluororesin thin film.

[0008]

Therefore, the present inventors have
In the method of cleaning a substrate used for producing a fluororesin thin film, by dipping it in a hot alkaline aqueous solution or a cleaning agent containing a heated surfactant, the remaining portion of the fluororesin attached to the substrate edge part or the back surface or It has been found that it is effective for removing and removing the underlayer.

Further, ultrasonic waves are applied during the immersion. A hot alkaline aqueous solution or a detergent containing a heated surfactant is forcedly circulated and sprayed onto the immersed substrate. It was found that the effect is further enhanced by the method described above, and that the effect is further enhanced by performing showering after the immersion, and the present invention has been completed.

The cleaning substrate targeted by the present invention may be any substrate used in the step of producing a thin film made of a fluororesin, and the fluororesin may be of any kind. , Asahi Glass Co., Ltd. fluorine-containing resin (trade name "CYTOP"), DuPont USA fluorine-containing resin (trade name "Teflon AF1600") and the like.

Therefore, the present invention relates to a method for cleaning a substrate used for producing a fluorine-containing resin thin film, in which a hot alkaline aqueous solution heated to a temperature of 70 ° C. or higher, preferably 80 to 100 ° C., or a cleaning agent containing a surfactant is used. It is characterized by being immersed in the agent. The hot alkaline aqueous solution contains 1 wt% or more, preferably 2 to 5 wt% of a strong alkaline compound, or P
The one having H of 13 or more is used. If the amount of the strongly alkaline compound is 1 wt% or less or the pH is 13 or less, the effect is small,
On the other hand, if it is 10 wt% or more, when the substrate is glass or the like, there is a risk of damage.

As the concentration of the surfactant used in the detergent containing the surfactant, the undiluted solution may be used as it is or the diluted solution may be used. The dilution concentration depends on the kind of the surfactant, but is preferably about 1 to 80 wt%. Water is usually used as the diluent, but other organic solvents such as ethyl alcohol, isopropyl alcohol, toluene and hexane can also be used.

The longer the time for immersing the substrate is, of course, the greater the effect. However, in general, it is preferably 2 hours or less, preferably 1 hour or less, and in view of work efficiency, it is preferably 30 seconds or more and 5 minutes or less. Then, ultrasonic cleaning is preferably performed at the time of immersion. In another preferred method, a hot alkaline aqueous solution or a cleaning agent containing a heated surfactant is forcedly circulated and sprayed onto the substrate.

For example, as shown in FIG. 1, the method of spraying onto the substrate is to immerse the substrate 4 in the cleaning liquid 2 in the tank 1 in the same plane as the spray pipe 3 provided in the vertical direction in the vertical direction. The method of spraying the cleaning liquid from the spray pipe 3 on one end surface thereof, as shown in FIG. 2, the cleaning liquid is sprayed by the spray pipe 5 to the central portions of both surfaces of the substrate 4 which is vertically immersed in the cleaning liquid in the bath. As shown in FIG. 3, the substrate 4 is immersed vertically in the cleaning liquid 2 in the bath, and the cleaning liquid is applied to the lower end surface of the substrate 4 through the spray pipe 6 on the same plane as the substrate 4 below. There are spraying methods and the like. Among them, the method shown in FIG. 3 is preferable because of its excellent peeling effect.

Also in the method shown in FIG. 3, it is desirable that the cleaning liquid be uniformly sprayed along the substrate. FIG.
This shows an improved jig for this purpose. The box-shaped header 8 has two rows of outlets 9 formed on the upper surface, and the cleaning liquid sent into the header is maintained at a uniform pressure in the header. As a result, the air is blown out evenly through the air outlet 9 of the header 8. As shown in the figure, it is desirable to arrange the substrate vertically so that the cleaning liquid is uniformly sprayed on both sides of the substrate.

In a further preferred method, showering with water is carried out after immersion in a hot alkaline aqueous solution or a detergent containing a heated surfactant for a predetermined time. Examples of the strongly alkaline compound used in this method include NaOH,
Examples thereof include KOH and Ca (OH) ₂ . Further, the surfactant is preferably a non-phosphoric acid type which does not cause pollution of waste water. Examples of these include alkylbenzene sulfonate, alkylnaphthalene sulfonate,
Anionic surfactants containing higher alcohol sulfate ester salts, alkyl ether sulfates, etc., and nonionic surfactants containing polyoxyethylene alkyl ethers, polyoxy secondary alcohol ethers, polyoxyethylene alkylphenyl ethers, etc. It is also possible to use one of these surfactants or a mixture of two or more thereof. Further, as a cleaning agent containing a surfactant,
As a cleaning agent for glass or the like, a commercially available one may be used.

The cleaning test substrate sample used in this example is as follows. A 1 wt% methyl isobutyl ketone solution of nitrocellulose (trade name "HIG-1") manufactured by Asahi Kasei Kogyo Co., Ltd. was dropped on a quartz glass substrate to form a nitrocellulose layer having a thickness of 0.1 µm by a spin coat method. did. This is used as a substrate for the production of a fluorine-containing resin thin film, and the product name "CT of Asahi Glass Co., Ltd.
-Solv. A fluorine-containing resin thin film of about 0.8 μm was similarly dropped by a spin coating method using a 7 wt% solution of a fluorine-containing resin (trade name “CYTOP]) (intrinsic viscosity = 0.34) manufactured by the same company using 160” as a solvent. Is formed and then dried, and the film on the surface is peeled off.

Example 1 A 3% NaOH aqueous solution was heated to 70 ° C. to immerse a cleaning test substrate sample. After 30 minutes, the film was pulled up and rinsed with water, and then the peeling condition of the film was checked. As a result, it was found that the remaining part of the fluorine-containing resin at the edge of the substrate and the underlayer on the surface were effectively removed.

Here, for the inspection of the peeling condition of the film, for the remaining portion of the fluorine-containing resin adhered to the edge portion and the back surface of the substrate, a mending tape (trade name "Scotch") manufactured by Sumitomo 3M Ltd. was used. It is performed by peeling off the fluorine-containing resin residue on the edge and the back surface and checking the amount attached to the tape.For the base layer on the substrate surface, apply a light to the substrate surface in the dark and see the reflected light. This was done by checking the removal state.

Example 2 A test was conducted in the same manner as in Example 1 except that the immersion time was shortened to 5 minutes. Example 3 Washing was performed in the same manner as in Example 2 except that a 3% NaOH aqueous solution was heated to 80 ° C. As a result, the degree of removal of the remaining portion of the fluorine-containing resin on the edge portion of the substrate and the underlying layer on the surface was greater than in Example 2.

Example 4 As shown in FIG. 1, a 1% NaOH aqueous solution was placed in a tank 1, heated to 70 ° C., circulated at a rate of 50 liters per minute by a pump 7, and immersed in the aqueous solution of the substrate 4. Sprayed on one end face. After 5 minutes, it was pulled up and rinsed with water, and then the peeling condition of the film was checked. As a result, the rest of the fluorine-containing resin at the edge of the substrate and most of the underlying layer on the surface were removed.

Example 5 Washing was performed under the same conditions as in Example 4 except that a 3% NaOH aqueous solution was used. As a result, the degree of removal of the remaining portion of the fluorine-containing resin at the edge portion of the substrate and the underlayer on the surface was greater than in Example 4. Example 6 Washing was performed under the same conditions as in Example 5 except that the temperature of the aqueous NaOH solution was 80 ° C. As a result, the degree of removal of the remaining portion of the fluorine-containing resin at the edge of the substrate and the underlayer on the surface was greater than in Example 5.

Example 7 After immersion, showering with water was carried out for 1 minute, except that
Washing was performed under the same conditions as in Example 6. As a result, the remaining portion of the fluorine-containing resin at the edge of the substrate and the underlying layer on the surface were almost completely removed. Example 8 The temperature of a 3% NaOH aqueous solution was set to 80 ° C., and the ultrasonic cleaning was performed using an ultrasonic cleaning device (trade name [UT-304F] manufactured by Sharp Corporation) without spraying the liquid. . As a result, the same effect as in Example 6 was found.

Example 9 A test was conducted under the same conditions as in Example 7 except that a detergent containing a surfactant (detergent manufactured by Shoko Tsusho Co., Ltd., trade name "Hikari Ace S") was used as the washing liquid. As a result, the same effect as in Example 7 was observed. Example 10 The substrate washed by the method of Example 6 was further immersed in sulfuric acid heated to 100 ° C. for 10 minutes, and then washed with water. Then, ultrasonic cleaning was performed in pure water for 10 minutes, and finally, cleaning and drying was performed with IPA vapor. When the washed substrate was observed by applying a light to the surface of the substrate in a dark place, no stain that could hinder its reuse was observed.

Example 11 A substrate washed under the same conditions as in Example 6 except that a detergent containing a surfactant (detergent manufactured by Shoko Tsusho Co., Ltd., trade name "Hikari Ace S") was used as the washing liquid was used. In the same manner as in No. 9, it was further immersed in sulfuric acid heated to 100 ° C. for 10 minutes, and then washed with water. Then, ultrasonic cleaning was performed in pure water for 10 minutes, and finally, cleaning and drying was performed with IPA vapor. When the washed substrate was observed by applying a light to the surface of the substrate in a dark place, no stain that could hinder its reuse was observed.

Comparative Example 1 Washing was performed under the same conditions as in Example 7 except that hot water of 80 ° C. was used and the immersion time was 30 minutes. As a result, the remaining portion of the fluorine-containing resin at the edge of the substrate and the underlying layer on the surface were hardly removed. Comparative Example 2 The substrate sample for cleaning test was immersed in sulfuric acid for 10 minutes and then washed with water. Further, ultrasonic cleaning was performed in pure water for 10 minutes, and finally, cleaning and drying were performed with IPA vapor. When the substrate after cleaning was examined, the fluorine-containing resin adhering to the edge portion and the back surface was hardly removed, and
Many streaky spots were observed.

The above results are shown in Table 1.

[0028]

[Table 1]

[0029]

The present invention is constructed as described above and has the following effects. If the substrate used for producing the fluorine-containing resin thin film is immersed in a hot alkaline aqueous solution at 70 ° C. or higher or a detergent containing a heated surfactant, the remaining portion of the fluorine-containing resin adhered to the edge portion or the back surface of the substrate It is effective for peeling and removing the underlayer.

Further, if the ultrasonic cleaning or the cleaning agent is forcedly circulated and sprayed on the substrate during the immersion, the effect is further enhanced. Further, when the cleaning agent is sprayed, if a jig having a header having a large number of outlets is used, the liquid is sprayed uniformly onto the substrate, and the effect is further enhanced. Further, the effect of peeling and removing can be further improved by performing showering with water after the immersion in the hot alkaline aqueous solution or the detergent containing the heated surfactant.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a method of spraying onto a substrate.

FIG. 2 is a schematic view showing another method of spraying onto a substrate.

FIG. 3 is a schematic view showing still another spraying method on the substrate.

4 is a schematic view of a jig used in the method shown in FIG.

[Explanation of symbols]

 1 ・ ・ Tank 2 ・ ・ Cleaning liquid 3, 5, 6 ・ ・ Spraying pipe

Claims (9)

[Claims] 1. A method for cleaning a substrate used for producing a thin film of a pellicle made of a fluorine-containing resin, characterized in that the substrate is immersed in a hot alkaline aqueous solution or a heated detergent-containing cleaning agent. Cleaning method. 2. The cleaning method according to claim 1, wherein ultrasonic cleaning is performed during the immersion. 3. A method of cleaning a substrate used for producing a thin film of a pellicle made of a fluorine-containing resin, wherein the substrate is immersed in a hot alkaline aqueous solution or a cleaning agent containing a heated surfactant, and the hot alkaline aqueous solution or heating is performed. A cleaning method, which comprises spraying a cleaning agent containing the surface-active agent onto a substrate. 4. The cleaning method according to claim 1, wherein the alkaline aqueous solution contains 1 wt% or more of a strongly alkaline compound or PH is 13 or more. 5. The cleaning agent containing a surfactant contains the surfactant in an amount of 1 wt% or more.
The described cleaning method. 6. The cleaning method according to claim 3, wherein the temperature of the cleaning solution containing the alkaline aqueous solution or the surface active agent which is soaked and sprayed is 70 ° C. or higher. 7. The cleaning method according to claim 6, wherein the spraying is performed from below on the lower end surface of the substrate immersed in the vertical direction. 8. The cleaning method according to claim 7, wherein the spraying is carried out uniformly on the entire surface of the substrate by using a jig having an outlet on the upper surface of the header. 9. The cleaning method according to claim 1, wherein showering with water is performed after the immersion.