JP2001276759A - Cleaning-fluid for glass substrate and method for cleaning glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning fluid for a glass substrate which shows an outstanding performance of removing polishing particles sticking to the surface of the glass substrate as well as a method for cleaning the glass substrate. SOLUTION: In the precision cleaning method for the glass substrate comprising five processes such as preliminary cleaning, primary chemical solution cleaning, secondary chemical solution cleaning, rinsing and drying, the glass substrate 12 is soaked in a cleaning tank 20 in the primary chemical solution cleaning process. The cleaning fluid 21 is composed of 50-200 mg/L hydrogen fluoride and 5 mg/L or more ozone in a dissolved state. The glass substrate is cleaned by ultrasonic wave using the cleaning fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning solution and a cleaning method for a glass substrate, and more particularly to a cleaning solution and a cleaning method for a glass substrate used for a magnetic disk, a liquid crystal glass or the like.

[0002]

2. Description of the Related Art For example, in the production of a glass substrate for a magnetic disk, first, the surface of a disk-processed glass substrate is polished with abrasive grains. At this time, cleaning is performed to remove the abrasive particles attached to the glass surface.However, if the cleaning is insufficient, the abrasive particles remain on the glass surface, making it impossible to perform a normal recording / reproducing operation as a magnetic disk or a magnetic head. Cause damage. In addition, the flying height of the magnetic head has been decreasing more and more in recent years, and there has been a demand for a cleaning method that removes fine particles and does not cause uneven etching during cleaning. As a method of cleaning this kind of glass substrate,
The present applicant has previously filed an application for Japanese Patent Application No. 10-319014. In this method, the abrasive particles are removed by etching the surface of the glass substrate using a cleaning liquid in which hydrofluoric acid and sulfuric acid are mixed.

[0003]

However, it has been found that cleaning with the above-mentioned cleaning solution is effective for removing abrasive particles, but fine etching unevenness occurs on the glass surface because the concentration of the cleaning solution is rather high. The object of the present invention is
A cleaning solution and a cleaning solution for a glass substrate, which can solve the problems of the prior art described above and can effectively remove abrasive particles adhered and remaining on the glass surface, and do not cause fine etching unevenness on the glass surface. It is to provide a method.

[0004]

In order to achieve the above-mentioned object, the glass substrate cleaning solution according to the present invention is 50 to 200 m.
g / L of hydrogen fluoride (hereinafter referred to as HF) and 5 mg
/ L or more ozone is dissolved.

Further, a method of cleaning a glass substrate according to the present invention is a method of cleaning a glass substrate by removing the polishing particles from the glass substrate having the polishing particles adhered to the glass surface, wherein the glass substrate is used in an amount of 50 to 200 mg. / L HF and 5
It is characterized by being immersed in a cleaning solution in which mg / L or more of ozone is dissolved and ultrasonically cleaned. Further, the present invention is characterized in that the glass substrate washed above is further immersed in an ammonium fluoride aqueous solution or an alkaline solution and subjected to ultrasonic cleaning.

[0006]

In the present invention, the chemical interaction between HF and ozone dissolved in the cleaning liquid and the physical action by ultrasonic waves work in synergy to remove abrasive particles attached to the glass surface efficiently. Further, since the concentration of HF dissolved in the cleaning liquid is low, the degree of etching is weak, and fine etching unevenness does not occur on the surface of the glass.

In the present invention, oxidizing hydroxyl radicals are generated by the ozone in the cleaning solution, and the hydroxyl radicals enhance the wettability of the glass surface and weaken the adhesion between the glass surface and the abrasive particles. Further, the glass surface is etched by the HF having a low concentration in the cleaning liquid, and the abrasive particles attached to the glass surface at this time are easily separated from the glass surface. While the improvement of the wettability of the glass surface by the ozone and the etching by the HF proceed almost at the same time, the physical action by the ultrasonic wave is added, and the abrasive particles are efficiently removed as described above.

[0008] The concentration of ozone in the cleaning solution must be 5 mg / L or more. When the amount is less than 5 mg / L, the wettability of the glass surface is insufficiently improved, and the action of detaching the abrasive particles from the glass surface is reduced. Further, as the concentration of ozone in the cleaning liquid is higher, the action of detaching the abrasive particles from the glass surface is improved. However, even if it exceeds 20 mg / L, the detachment action of the abrasive particles hardly improves.
Therefore, the concentration of ozone in the cleaning liquid is preferably 5 to 20 mg / L from the viewpoint of economy.

[0009] The concentration of HF in the cleaning solution is 50 to 200 mg.
/ L. If it is less than 50 mg / L, the etching by HF becomes insufficient, and the action of detaching the abrasive particles from the glass surface is reduced. Also, 200
If the amount exceeds mg / L, the etching with HF proceeds more than necessary, and fine etching unevenness occurs on the surface of the glass.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a preferred embodiment of a precision cleaning process of a glass substrate incorporating a cleaning method according to the present invention, which includes a pre-cleaning process, a primary chemical cleaning process, and a secondary chemical solution. It consists of five steps: a washing step, a rinsing step, and a drying step.

In the pre-cleaning step, the glass substrate 12 housed in the substrate cassette 14 is immersed in pure water 17 in a pre-cleaning tank 16 and subjected to ultrasonic cleaning by ultrasonic waves emitted from an ultrasonic generator 18. At the time of cleaning, the pure water 17 is continuously replenished from the lower part of the cleaning tank 16, and the pure water 17 is renewed by flowing over the replenished amount from the trough 19 at the upper part of the tank to maintain the cleanliness.

After the abrasive particles adhering to the surface of the glass substrate are roughly removed by the above-described pre-cleaning step, the polishing method according to the present invention is applied.
Move on to the next chemical cleaning step. In this step, the pre-cleaned glass substrate 12 is immersed in the cleaning liquid 21 in the primary chemical liquid cleaning tank 20 while being housed in the substrate cassette 14, and is ultrasonically cleaned by ultrasonic waves from the ultrasonic generator 22. The frequency of the ultrasonic wave generated from the ultrasonic generator 22 is 35 to 6
It is preferable to select in the range of 0 kHz. Cleaning liquid 21
Is 50 to 200 mg / L HF and 5 m
A solution in which g / L or more of ozone is dissolved is used. Cleaning liquid 2
For convenience, it is convenient to purchase and use a pre-mixed product. However, since the concentration of dissolved ozone tends to decrease with the passage of time, it is preferable to directly supply the dissolved ozone to the washing tank by using a compounding device. During cleaning, the cleaning liquid 21 is continuously replenished from the lower part of the cleaning tank 20, and the replenishment is allowed to flow from the trough 23 in the upper part of the tank to maintain the concentration and the cleanliness of the cleaning liquid 21. The trough 23
When the cleaning liquid 21 which has overflowed from the tank is returned to the primary chemical cleaning tank 20 again and the control means (not shown) controls the concentrations of HF and ozone to fall within a predetermined range, the amount of the cleaning liquid 21 used can be reduced. it can. Most of the abrasive particles adhered to the glass surface by the first chemical liquid washing step are separated from the glass surface. However, there is also a phenomenon in which the abrasive particles that have been peeled off once again adhere to the glass surface, and a considerable number of the abrasive particles remain and adhere to the glass substrate. For this reason, the next-stage secondary chemical cleaning step is performed.

In the secondary chemical cleaning step, the glass substrate 12 after the primary chemical cleaning is accommodated in the substrate cassette 14 and immersed in a cleaning liquid 25 in a secondary chemical cleaning tank 24. Ultrasonic cleaning with ultrasonic waves. As the cleaning liquid 25, a solution such as an aqueous solution of ammonium fluoride or aqueous ammonia is preferably used. That is, the pH of these cleaning solutions is neutral or alkaline, and the zeta potential of the surfaces of the immersed glass substrate and the abrasive particles is both negative. For this reason, the negatively charged glass substrate and the abrasive particles repel each other, so that re-adhesion hardly occurs. In particular, when an aqueous solution of ammonium fluoride having a concentration of about 0.5% is used as the cleaning liquid 25, a slight amount of etching action is exerted on the glass surface, and the action of removing abrasive particles remaining on the glass surface is further promoted. During cleaning, the cleaning liquid 25 is continuously replenished from the lower portion of the cleaning tank 24, and the replenishment is allowed to flow over the trough 28 in the upper part of the tank, thereby maintaining the concentration and cleanliness of the cleaning liquid 25.

In the rinsing step, the secondary chemical cleaning tank 24
First, the substrate cassette 14 pulled up from the container is immersed in pure water 32 in the rinsing tank 26 for a predetermined time. The structure of the rinsing tank 26 is the same as that of the pre-cleaning tank 16 and the chemical liquid cleaning tanks 20 and 24. The rinsing tank 26 is ultrasonically cleaned by ultrasonic waves from an ultrasonic generator 29 to remove the cleaning liquid 25 adhered to the glass substrate 12. Wash off.

In the next drying step, the substrate cassette 14 pulled up from the rinsing tank 26 is placed in a drying box 33, and pure water adhering to the glass substrate 12 is removed by a known means. This drying process completes a series of precision cleaning. By sequentially performing each of the above steps, for example, with a tact time of 3 minutes, a glass substrate with almost no abrasive particles or cleaning liquid remaining on the surface can be obtained.

The cleaning liquid according to the present invention is useful not only as a cleaning liquid when immersing and cleaning a glass substrate, but also as a cleaning liquid when performing scrubbing cleaning using a brush or the like.

[0017]

EXPERIMENTAL EXAMPLE 1 A 2.5 inch soda glass substrate for a magnetic disk was polished with abrasive grains, and a glass substrate having abrasive particles adhered to its surface was used as a test material. The polishing conditions at this time were: cerium oxide having a particle size of 0.4 to 0.8 μm was used as polishing abrasive grains, and cerium oxide suspended in pure water at 10% by weight was used as a polishing liquid. Using this polishing liquid, a polishing pressure of 75 gf / cm ² and a table rotation speed of 4 were obtained by a polishing apparatus.
Polishing was performed at 0 rpm for 10 minutes. The polished glass substrate was subjected to ultrasonic cleaning using pure water at room temperature to obtain a test sample.

When the test sample is subjected to ultrasonic cleaning using a cleaning solution in which HF and ozone are dissolved,
The effect of concentration on removal characteristics was investigated. The experimental conditions were
The concentration of dissolved ozone in the washing solution was kept constant at 10 mg / L, and the HF concentration was changed within the range of 0 to 500 mg / L. The test sample is immersed in a cleaning solution having a temperature of 15 ° C.
Ultrasonic cleaning for minutes. The frequency of the ultrasonic wave at this time is 45k
Hz.

The removal performance was evaluated by observing the test sample after washing with a microscope of 200 times magnification and visually counting the number of particles having a particle size of about 0.3 μm or more that had not been removed and remained. Regarding the etching unevenness, the surface roughness of the test sample was measured with an atomic force microscope, and the surface average roughness (Ra) of each test sample was determined.

FIGS. 2 and 3 show the results of an experiment conducted under the above-described conditions. In FIG. 2, the horizontal axis represents HF in the cleaning solution.
The concentration and the vertical axis indicate the number of particles remaining per glass substrate. As is clear from FIG.
At 0 mg / L or more, the number of residual particles is 500 particles / substrate or less, indicating good cleaning performance. HF concentration is 50mg / L
If it is less than this, the removal performance will decrease.

In FIG. 3, the horizontal axis represents the HF concentration in the cleaning solution,
The vertical axis indicates the ratio between the surface average roughness of the test sample after cleaning and the surface average roughness before cleaning. As is clear from FIG.
When the HF concentration is 200 mg / L or less, the surface average roughness ratio is 1
That is, the smoother surface can be formed by washing. When the HF concentration exceeds 200 mg / L, the surface average roughness ratio becomes 1 or more, and it can be seen that the etching proceeds more than necessary and uneven etching occurs.

[0022]

[Experimental Example 2] The effect of ozone concentration on removal characteristics during cleaning using a cleaning solution containing HF and ozone dissolved therein was examined. The HF concentration in the washing solution was kept constant at 100 mg / L,
The ozone concentration was changed within the range of 0 to 40 mg / L.
All other experimental conditions, including the test sample, were performed under the same conditions as in Experimental Example 1.

FIG. 4 shows the results of an experiment conducted under the conditions described above. In FIG. 4, the horizontal axis is the ozone concentration in the cleaning liquid,
The vertical axis indicates the number of particles remaining per glass substrate. As is clear from FIG.
/ L or more, the number of residual particles is 500 particles / substrate or less,
Shows good cleaning performance. If the ozone concentration is less than 5 mg / L, the performance of removing particles is reduced. Further, even if the ozone concentration is 20 mg / L or more, the cleaning performance is not improved.

[0024]

[Experimental Example 3] Tests 1 to 8 in which the same test sample as that used in Experimental Example 1 was subjected to primary cleaning with the cleaning liquid shown in Table 1 and then to secondary cleaning were performed. The cleaning time in each test was 3 minutes for each cleaning, and the frequency of the ultrasonic wave at this time was 45 kHz. Of Tests 1 to 8, Tests 1 to 4 are tests according to the present invention, and Tests 5 to 8 are tests according to methods other than the present invention.

[0025]

[Table 1]

With respect to each of the test samples 1 to 8 described above, the number of particles having a particle size of about 0.3 μm or more remaining without being removed in the same manner as in Experimental Example 1 was visually counted. Regarding the etching unevenness, the maximum height (Rmax) of the test sample was measured by a surface roughness meter. Table 2 shows the number of residual particles (N) and the maximum height (Rmax) of the test sample after each washing in each test.

[0027]

[Table 2]

As is clear from Table 2, the number of residual particles (N) of the test samples 1 to 4 according to the present invention is 30 or less in each case, and the abrasive particles are effectively removed from the glass substrate. We were able to. In addition, the maximum height (Rma
x) was 10 nm or less, and no etching unevenness was observed. On the other hand, the results after the secondary cleaning in Tests 5 to 8 according to the method other than the present invention show that at least one of the removal effect of the abrasive particles or the maximum height (Rmax) shows a worse value than the method according to the present invention. Was.

[0029]

[Experimental Example 4] The same experiments as the above-described experiments using an aluminosilicate substrate or a ceramic glass substrate instead of a soda glass substrate as a raw material of a test sample were performed in a spot manner. As a result, the same results as those in the above experiments were obtained.

[0030]

According to the glass substrate cleaning solution and the cleaning method of the present invention, the abrasive particles can be effectively removed from the glass substrate having the abrasive particles adhered to the glass surface, and the etching unevenness also occurs. Nothing.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cleaning step for carrying out the present invention.

FIG. 2 is a first graph showing experimental results of Experimental Example 1.

FIG. 3 is a second graph showing experimental results of Experimental Example 1.

FIG. 4 is a graph showing experimental results of Experimental Example 2.

[Explanation of symbols]

 12 Glass substrate 14 Substrate cassette 20 Primary chemical cleaning tank 21 Cleaning liquid 22 Ultrasonic generator 24 Secondary chemical cleaning tank 25 Cleaning liquid 27 Ultrasonic generator

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Claims (3)

[Claims] (1) 50 to 200 mg / L of hydrogen fluoride and 5 m
g / L or more ozone dissolved in a glass substrate cleaning solution. 2. A method for cleaning a glass substrate, comprising removing the abrasive particles from a glass substrate having abrasive particles adhered to the glass surface, wherein the glass substrate is immersed in the cleaning liquid according to claim 1 for ultrasonic cleaning. A method of cleaning a glass substrate. 3. A method for cleaning a glass substrate, comprising washing and removing the abrasive particles from a glass substrate having abrasive particles adhered to the glass surface, wherein the glass substrate is immersed in the cleaning liquid according to claim 1 for ultrasonic cleaning. Cleaning the glass substrate by immersing the glass substrate in an aqueous solution of ammonium fluoride or an alkaline solution and performing ultrasonic cleaning.