JP2001151537A - Quartz article having sand-blasted surface and method for cleaning the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quartz article the surface of which is subjected to sand blasting and in which particles can be prevented from being generated from the sand-blasted surface. SOLUTION: In this quartz article which has a sand-blasted surface and is manufactured by cleaning the sand-blasted surface, the numbers of four kinds of particles, namely, particles having 0.2-0.3 μm (excluding 0.3 μm) particle size, particles having 0.3-0.5 μm (excluding 0.5 μm) particle size, particles having 0.5-1.0 μm (excluding 1.0 μm) and particles having >=1.0 μm particle size, all of which particles are generated from the sand-blasted surface of the quartz article by blowing clean air on the surface, are adjusted to <=30, <=60, <=60 and <=10 [per CF (cubic foot) of ambient air] respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz article used in a silicon wafer processing step and a method for cleaning the quartz article.

[0002]

2. Description of the Related Art Conventionally, a silicon wafer is subjected to CVD processing, etching, ashing, etc. in a silicon wafer processing step. In this processing step, a quartz article is used to place or hold the wafer. Used.

[0003] Since high heat of 1000 ° C or more is used in this processing step, stress is applied to the contact portion between the wafer and the quartz glass surface due to the difference in the thermal expansion coefficient between the quartz glass and the silicon wafer, and the wafer contacts the wafer contact portion. Traces occur.

In the case where a product generated in a silicon wafer processing step adheres to the surface of a glass article as a thin film, when the processing is completed and the glass article is cooled, the thin film and the glass may be mixed with each other. The glass article may be cracked or broken due to a difference in thermal expansion coefficient.

Further, when the glass article is cooled, the product having a weak adhesion peels off from the glass surface, but when the surface roughness of the glass surface is small, the adhesion of the product is large, Even when there is no cracking or breakage of the glass article, the thin film may peel off in the next silicon wafer processing step to generate particles.

In order to prevent the occurrence of the contact marks and reduce the contact area with the wafer, the surface of the quartz article is subjected to sandblasting to roughen the surface of the quartz article to form irregularities to form a grained surface. . In addition, by making it grainy,
When the silicon wafer is cooled after the completion of the processing, the stress applied to the grain surface of the glass takes various directions, so that the product adhering to the glass surface does not peel off during the cooling.

[0007]

However, this grained surface may be used to scrape off silica particles from the contact with the wafer, or to increase the surface of the article due to the grained surface. As a result of retaining particles on the eye surface, even after passing through the cleaning process of the quartz article, the particles may fly up during wafer processing and adhere to the pattern surface of the wafer to cause a pattern abnormality.

The size of generated particles is 0.2 μm.
Under the current situation where wiring patterns have become smaller than 0.1 μm or less, it is a major problem to prevent the generation of particles even with fine particles of 0.3 μm or less. Has become.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a quartz article having a grained surface, in which generation of particles is prevented, and a method for cleaning the quartz article.

[0010]

Means for Solving the Problems The first invention is an invention of an article, which is a quartz article having a grained surface and having a grained surface produced by cleaning the surface. ,
The number of particles per 1 cubic foot (CF) generated from the surface is 0.2 μm or more to 0.
30 or less less than 3 μm, 0.3 μm or more to 0.5 μm
The number is less than 60, less than or equal to 0.5 μm to less than 1.0 μm is less than 60, and more than 1.0 μm is less than or equal to 10.

Here, "CF" means "cubi".
Although it means "c feet", it is a matter of course that the unit is not limited to "CF" as long as the unit has substantially the same volume as this. Then, particles in the atmosphere, for example, suck in air of 0.1 CF and determine how many things are present in it.
The measurement can be performed by using the reflection of the laser light, and the measurement can be obtained by multiplying the measurement by ten. At that time, clean air filtered by a HEPA filter is blown onto the quartz article in a clean atmosphere having a cleanness of 1000 or less, and particles generated from the quartz article at that time are measured by a particle counter. Therefore, according to the first invention, the generation of particles can be extremely reduced as compared with the quartz article cleaned by the conventional technique.

According to a second aspect of the present invention, there is provided a method for cleaning a quartz article, wherein the quartz article is cleaned in a 3 to 10% HF solution in an atmosphere having a cleanness of 1,000 or less in a method for cleaning a quartz article having a grained surface. Brush cleaning process in 3
After appropriately combining a brush cleaning step with a 10% nitric acid solution and a brush cleaning step in an organic solvent, an ultrasonic cleaning step is performed in pure water, followed by drying. And

[0013] In a second aspect of the present invention, there is provided a method for cleaning a quartz article having a grained surface, wherein the quartz article is subjected to a brush cleaning step using an HF solution and an nitric acid solution in an atmosphere having a cleanness of 1000 or less. The brush cleaning process in pure water is alternately performed, and the brush cleaning process in pure water and the brush cleaning process in an organic solvent are performed alternately. Thereafter, the ultrasonic cleaning process in pure water is performed. , Followed by drying.

In the brush cleaning step using the HF solution,
The grain on the quartz surface is cleaned using a brush to remove quartz particles. In the brush cleaning step with nitric acid, impurities other than quartz, that is, metal salts and the like, which are impurities contained in sandblast, are ionized and removed. In the brush cleaning step in the organic solvent, an organic solvent acetone, ethanol, or the like is used.
Removes hydrophilic organic impurities. These organic solvents may be used in a mixture of lipophilicity and hydrophilicity, or the lipophilic organic solvent washing step and the hydrophilic organic solvent washing step may be performed separately. The ultrasonic cleaning step in the pure water is desirably performed while supplying pure water of high purity while flowing pure water or ultrapure water.

[0015] In a second aspect of the present invention, in the method for cleaning a quartz article having a grained surface, the quartz article is subjected to a first step: 3 to 10% HF solution in an atmosphere having a cleanness of 1000 or less. Brush cleaning process, second process: rinse cleaning process with pure water, third process: brush cleaning process with 3 to 10% nitric acid, fourth process: rinse cleaning process with pure water, fifth process: ultrapure Ultrasonic cleaning process in water, 6th process: brush cleaning process in organic solvent, 7th process: brush cleaning process in ultrapure water, 8th process: ultrapure water It is desirable to be configured to dry after the ultrasonic cleaning step.

First step: In the brush cleaning step using a 3 to 10% HF solution, as described above, the grain of the quartz surface is cleaned using a brush to remove quartz particles. If the HF solution is too concentrated, the surface of the quartz article is etched, so that the brush cleaning process becomes difficult. Third step: In the brush cleaning step with 3 to 10% nitric acid,
As described above, impurities other than quartz, that is, metal salts and the like, which are impurities contained in sandblast, are ionized and removed. Step 6: In the brush cleaning step in an organic solvent, an organic solvent such as acetone or ethanol is used.
Removes hydrophilic organic impurities. In addition, as described above,
These organic solvents may be used in a mixture of lipophilicity and hydrophilicity, or the lipophilic organic solvent washing step and the hydrophilic organic solvent washing step may be performed separately. Second step and fourth step
The rinsing step with pure water in the step, the brush cleaning step in ultrapure water in the seventh step, and the ultrasonic cleaning step in ultrapure water in the fifth and eighth steps are performed using pure water or It is desirable to carry out while supplying ultrapure water and supplying pure water of high purity.

The present invention is also applicable to a method in which the roughness of the surface which has been grained in advance is measured, and a brush having a bristle portion smaller than the interval between the convex portions of the unevenness is prepared, and the brush is used for cleaning. It is an effective means. According to such a technical means, since the cleaning is performed with a brush having a bristle portion smaller than the interval between the convex portions of the unevenness of the surface roughness, impurities in the valley portion can be cleaned well. At this time, the shape of the brush tip may be not a needle shape, but may be a minus screwdriver shape or a knife shape.

The cleaning in the ultrapure water is preferably performed by brush cleaning for 5 minutes or more, and ultrasonic cleaning for 15 minutes or more in an overflow state. In the first, third and sixth steps, 3 minutes is preferable. Desirably, the brush cleaning described above is performed.

It is also an effective means of the present invention that the brush washing step in the organic solvent in the sixth step is performed alternately in the organic solvent acetone and in the ethanol. With such a technique, organic impurities can be effectively removed.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention thereto, but are merely illustrative examples unless otherwise specified. Not just.

FIG. 1 is a view showing one use form of the quartz article, FIG. 2 is a view showing a cleaning step in the first half of the quartz article, and FIG. 3 is a view showing a washing step in the latter half of the quartz article. FIG. 1 schematically shows a CVD apparatus, in which a quartz reaction tube 3 is formed in a concentrically arranged transparent cylindrical shape, and a wafer 2 is placed on a pedestal 5 via a quartz glass wafer mounting table 1. Is placed.

The wafer mounting table 1 is used in the above-mentioned CVD apparatus, and usually uses high heat of 1000 ° C. or more. Therefore, the wafer mounting table 1 made of quartz glass has a different thermal expansion coefficient from that of a silicon wafer. In order to prevent stress from being applied to the contact portion between the wafer 2 and the quartz glass surface and causing contact marks at the wafer contact portion, the wafer 2 is mounted by a sandblasting process (not shown) when the shape processing is completed by the NC machine tool 6. Necessary parts are grained.

It is desirable that the sandblast particles are harder than quartz glass and do not become a polluting source. However, none of these powder particles have no organic impurities, and contaminants must be tolerated. A subsequent washing step is essential.

The graining is performed by grinding, sand blasting, or the like. When the sand blasting is performed using SiO ₂ powder, the finely pulverized SiO ₂ powder is placed in the unevenness. Remains. For this purpose, it is necessary to forcibly scrape the fine powder with a brush. Further, during graining, impurities other than pure SiO ₂ may be mixed. Must be dissolved and removed from irregularities on the glass surface with a brush.

Next, a cleaning method will be described with reference to FIGS. First, the roughness of the grain portion 1a of the wafer mounting table 1 is measured by a roughness measuring device. The roughness measuring device measures the concave and convex pattern, measures the interval between the convex portions, and prepares a brush having a bristle portion dimension not larger than the interval between the convex portions. At this time, the shape of the brush tip may be not a needle shape, but may be a minus screwdriver shape or a knife shape.

After the grained wafer mounting table 1 is suctioned by a vacuum cleaner, the wafer mounting table 1 is moved to a clean room having a cleanliness of 1000 or less.
F) Fill the container 9 with the aqueous solution, put the wafer mounting table 1 in the aqueous solution, and wash it with the brush 8 for 3 minutes. In this step, small pieces of quartz adhering to the convex portions of the grain portion of the wafer mounting table 1 are scraped off, and the small quartz particles that have been caught in the valleys, which are the concave portions, are also scraped off, and these small pieces are removed. The attached organic impurities are also eliminated.

In the second step, rinsing with pure water is performed. In the third step, brush cleaning with an aqueous solution of 5% nitric acid is performed for 3 minutes. Here, impurities other than quartz, that is, metal salts and the like, which are impurities contained in sandblast, are ionized and removed.

In the fourth step, rinsing with pure water is performed. In the fifth step, ultrasonic cleaning is performed for 15 minutes while overflowing the ultrapure water in the ultrapure water to remove impurities attached to the surface of the wafer mounting table 1. Next, a cleaning step using an organic solvent is started. In a sixth step, brush cleaning in an organic solvent is performed.

In the sixth step, brush cleaning for 3 minutes is performed in a sixth step (1) using an organic solvent acetone,
Excluding lipophilic organic impurities, brush cleaning is performed for 3 minutes in a sixth step (2) using an organic solvent ethanol,
Removes hydrophilic organic impurities.

In the seventh step, brush cleaning is performed for 5 minutes while overflowing ultrapure water in ultrapure water. 8th
In the process, ultrasonic cleaning is performed for 15 minutes while overflowing the ultrapure water in the ultrapure water to remove impurities attached to the surface of the wafer mounting table 1. And it dries in a drying process.

[0031]

EXAMPLE The present example in which the above-described cleaning process was performed, and after a graining process, suction was performed by a vacuum cleaner, and then, in a clean room having a cleanness of 1000 or less, (first comparative example): 4.5% aqueous HF solution. Rinse with pure water after 3 minutes impregnation. (Second comparative example): After washing in an ultrasonic washing tank for 15 minutes, the sample was impregnated with a 4.5% HF aqueous solution for 10 minutes, and then rinsed with pure water. Was performed, and the number of particles attached to the object was measured by size, and the results in Table 1 were obtained. The particles were measured by blowing clean air filtered by a HEPA filter onto a quartz article in a clean atmosphere having a cleanness of 1000 or less, and measuring particles generated from the quartz article at that time by a particle counter. At that time, a clean air of 0.1 CF (cubic feet) was sucked in, and the size and the amount of the air were measured using the reflection of the laser light, and multiplied by ten. I asked.

[0032]

[Table 1]

From the results shown in Table 1, in Comparative Examples 1 and 2, the impregnation time with a 4.5% HF aqueous solution must be longer than 10 minutes. However, if it is performed for a long time, the graining of the quartz is etched and the roughness changes, and the desired roughness cannot be obtained. On the other hand, in this example, the number of particles was
The number of total particles is reduced to 1/25,
The number of particles less than 3 μm can be reduced to 1/18.

In the present embodiment, the lipophilic organic solvent washing step and the hydrophilic organic solvent washing step are performed separately, but these organic solvents are used by mixing lipophilic and hydrophilic properties. Is also good.

In this embodiment, the quartz glass article is described as a wafer mounting table in a CVD apparatus. However, the present invention is not limited to this. A holding table that holds one end of the wafer and stands the wafer is provided. Needless to say, it may be a quartz article in which a wafer is placed inside and a blast treatment is performed on an inner surface of a container forming a processing atmosphere.

[0036]

As described above, the quartz article of the present invention can significantly reduce the generation of particles as compared with the quartz article cleaned by the prior art. The method for cleaning a quartz article according to the present invention includes brush cleaning with an aqueous solution of hydrogen fluoride (HF) and an aqueous solution of nitric acid, brush cleaning in an organic solvent, and pure water in pure water. Is combined with the ultrasonic cleaning while overflowing, so that it is possible to provide a cleaning method for removing impurities and reducing generation of particles.

[Brief description of the drawings]

FIG. 1 is a view showing one use form of a quartz article.

FIG. 2 is a view showing a first half cleaning step of a quartz article.

FIG. 3 is a view showing a cleaning process in the latter half of the quartz article.

[Explanation of symbols]

 Reference Signs List 1 wafer mounting table (quartz article) 1a grained surface 2 wafer 3 quartz reaction tube

Continued on the front page F term (reference) 4G014 AH08 AH23 4G059 AA04 AC30 5F004 AA15 AA16 BB20 BB29 5F045 BB14 EB11

Claims (8)

[Claims] 1. A quartz article having a grained surface and having a grained surface produced by cleaning the surface, wherein the number of particles per 1 CF (cubic foot) generated from the surface is determined. 30 or less from 0.2 μm to less than 0.3 μm, 60 or less from 0.3 μm to less than 0.5 μm, 60 or less from 0.5 μm to less than 1.0 μm, and 10 from 1.0 μm or more The following is a quartz article whose surface is grained. 2. A method for cleaning a quartz article having a grained surface, wherein the quartz article is brushed in a 3-10% HF solution in an atmosphere having a cleanness of 1000 or less;
The method is characterized in that after appropriately performing the brush cleaning step in a 30% nitric acid solution and the brush cleaning step in an organic solvent, an ultrasonic cleaning step in pure water is performed, followed by drying. Method for cleaning quartz articles whose surface is grained. 3. A method for cleaning a quartz article having a grained surface, wherein the quartz article is brush-cleaned with an HF solution and brushed with a nitric acid solution in an atmosphere having a cleanness of 1000 or less. The brush cleaning process in pure water and the brush cleaning process in an organic solvent are performed alternately.After that, the ultrasonic cleaning process in pure water is performed, and then drying. A method for cleaning a quartz article having a grained surface. 4. A method for cleaning a quartz article having a grained surface, comprising: cleaning the quartz article in an atmosphere having a cleanliness of 1000 or less; a first step: a brush cleaning step using a 3 to 10% HF solution; 2nd step: rinse cleaning step with pure water, 3rd step: brush cleaning step with 3 to 10% nitric acid, 4th step: rinse cleaning step with pure water, 5th step: ultra-pure water 6th step: brush cleaning step in organic solvent, 7th step: brush cleaning step in ultrapure water, 8th step: ultrasonic cleaning step in ultrapure water A method for cleaning a quartz article having a grained surface, wherein the quartz article is dried later. 5. The method according to claim 1, further comprising measuring a roughness of the surface which has been grained in advance, preparing a brush having a bristle portion smaller than an interval between protrusions of the unevenness, and cleaning the brush with the brush. The method for cleaning a quartz article having a grained surface according to claim 2, 3, or 4. 6. The surface according to claim 4, wherein the cleaning in the ultrapure water is a brush cleaning for 5 minutes or more and an ultrasonic cleaning for 15 minutes or more in an overflow state. Method of cleaning quartz articles. 7. The method according to claim 4, wherein the first, third, and sixth steps include brush cleaning for 3 minutes or more. 8. The quartz article having a grained surface according to claim 4, wherein the brush cleaning step in the organic solvent in the sixth step is performed alternately in an organic solvent acetone and in an ethanol solvent. Cleaning method.