JP2016080037A - Method of application of wafer storage container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of application of wafer storage container capable of restricting occurrence of stain-like particles at a wafer stored in a wafer storage container.SOLUTION: This invention relates to a method of application of a wafer storage container comprising a container main body storing wafers, a lid for opening or closing an opening part of the container main body and a sealing gasket removably arranged between a lid member for opening or closing an opening part of the container main body. After treatment of the removable gasket immersing the removable gasket in alcohol inclusion solution with alcohol concentration of 50 vol% or more than one hour, the opening part of the container main body storing the wafer is closed with the lid while the gasket is being placed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for using a wafer storage container, and more particularly to a method for using a container for aligning and storing silicon single crystal wafers.

  In recent years, miniaturization of devices has progressed, and further quality improvement of silicon wafers has become essential. In particular, particles (dust generation dust), which is one of quality items, are very important items for the above-mentioned miniaturization. In other words, in order to reduce particles, it is necessary to consider the adhesion from the inspection apparatus or the storage container in addition to the silicon wafer itself, and to aim at higher cleanliness.

  Here, as a container for storing a wafer, for example, a silicon single crystal wafer, FOSB (Front Opening Shipping Box) or FOUP (Front-Opening Unified Pod) is used as an automatic opening / closing container mainly composed of a silicon wafer having a diameter of 300 mm. (See Patent Document 1).

  In use, the wafer storage container having such a structure is washed with a special cleaning liquid made of ultrapure water, isopropyl alcohol, or the like, and after the surface dirt is removed, the precision substrate is stored and used for transportation or storage. (See Patent Document 2).

JP 2005-64378 A JP 2004-342844 A

  However, the present inventors have found that, in spite of performing the cleaning as described above, spot-like particles may be generated with respect to particles that are important items in the wafer stored in the storage container. It was. FIG. 5 is an example of an SEM image of a spot-like particle adhering to a silicon wafer, and has a shape as if splashed.

  The present invention has been made in view of the above-described problems, and provides a method for using a wafer storage container capable of suppressing the generation of spot-like particles on a wafer stored in the wafer storage container. With the goal.

  In order to achieve the above object, the present invention is provided with a container main body for storing a wafer, a lid for opening and closing an opening of the container main body, and a detachable arrangement between the lid and the container main body. A wafer storage container having a sealing gasket, wherein the removable gasket is subjected to a treatment of immersing in an alcohol-containing solution having an alcohol concentration of 50 vol% or more for 1 hour or more, Provided is a method for using a wafer storage container, wherein the opening of the container main body storing the wafer is closed by the lid while being interposed.

  When the present inventors diligently investigated the above-mentioned spot-like particles (shaped as if splashed on the wafer surface as the name suggests), it was caused by outgas from the gasket which is a member of the storage container. I understood. Therefore, for example, there has been a need for improvement so that spot-like particles can be easily suppressed without changing the gasket material.

  Then, as in the present invention, the container is removed with a gasket that has been subjected to a long-time treatment (hereinafter also simply referred to as gasket treatment) using a high-concentration alcohol-containing solution by removing the removable gasket. If the opening of the main body is closed, the outgas component in the gasket can be dissolved in the alcohol-containing solution by the gasket process, and the content in the gasket can be reduced in advance. The generation of particle-like particles can be suppressed.

  At this time, the alcohol can be ethyl alcohol.

  Ethyl alcohol has the advantage of being easy to handle because of its low toxicity and easy disposal.

  Further, the alcohol concentration can be set to 100 vol%.

  By using an alcohol-containing solution having a high alcohol concentration in this way, the content of the outgas component in the gasket can be further reduced by gasket processing.

  Further, the gasket may be made of a thermoplastic elastomer.

  A gasket using a thermoplastic elastomer is suitable for the present invention because the effect of suppressing spot-like particles can be obtained more remarkably.

  As described above, according to the present invention, it is possible to suppress the generation of spot-like particles caused by outgas from the gasket, which is generated on the stored wafer.

It is a flowchart which shows an example of the usage method of this invention. It is explanatory drawing which shows an example of a wafer storage container. It is a graph which shows the outgas amount of a gasket. It is a flowchart which shows an example of the conventional cleaning method of a gasket. It is an observation figure of a spot-like particle on a wafer surface.

Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
As a result of intensive studies on the spot-like particles detected from the wafer stored in the wafer storage container, the present inventors have found that the outgas from the gasket is the cause as described above.

Therefore, the present inventors paid attention to the gasket cleaning performed before actually storing the wafer in the storage container.
Conventionally, when a wafer storage container is purchased and used, it is common to use it after removing and cleaning the gasket once (to store the wafer). More specifically, the cleaning flow is, for example, as shown in FIG. 4, shower water washing with pure water, immersion in pure water containing a surfactant, shower water washing with pure water, spin drying, clean oven drying, etc. Done in the flow.
Thus, conventionally, cleaning of a gasket, which is a member of a wafer storage container, is basically only water cleaning using a surfactant. And after performing such washing | cleaning etc., the opening part of the container main body which accommodated the wafer was closed with the cover body through the gasket.

  However, the present inventors have found that, in the conventional usage method including the cleaning step as shown in FIG. 4, spot-like particles are generated on the surface of the stored wafer, and further, the generation source is a gasket. The present invention was completed by finding that the effect of suppressing spot-like particles can be obtained by immersing in high-concentration alcohol (for example, ethyl alcohol) that is expected to have a cleaning effect on the outgas components of the inside for 1 hour or more. .

Hereinafter, the usage method of the wafer storage container of this invention is explained in full detail.
First, the wafer storage container which is the object of use will be described with reference to FIG. The wafer storage container 1 includes a container body 2, a lid 3, and a gasket 4. The container body 2 has a hollow inside and can store one or more wafers W. The container body 2 is formed with an opening 5 for inserting the wafer W into the container. The opening 5 can be opened and closed by fitting or removing the lid 3 from the opening 5.

  Here, FIG. 2 is an example in which the gasket 4 is attached to the lid 3. When the opening 5 is closed with the lid 3, a seal can be formed by the gasket 4. In addition, unlike the case of FIG. 2, a gasket can also be attached with respect to a container main body instead of a cover body. In any case, this gasket is detachably disposed between the lid and the container body, and serves as a seal when the opening of the container body is closed by the lid. I just need it.

  Further, the gasket is formed by using, for example, various polyolefin-based or polyester-based thermoplastic elastomers, fluorine rubber, silicone rubber, or the like, but is not limited (see JP 2000-21966 A). ), When carrying out the method of use of the present invention, those composed of thermoplastic elastomers are particularly suitable. This is because if the gasket uses a thermoplastic elastomer, the effect of suppressing spot-like particles can be remarkably obtained.

  Next, a procedure for using the wafer storage container 1 as shown in FIG. 2 (a procedure for storing the wafer W) according to the present invention will be described. FIG. 1 is a flowchart showing an example of a procedure in the present invention. As can be seen from FIG. 1, the removed gasket is immersed in an alcohol-containing solution of 50 vol% or more (100 vol% or less) for 1 hour or more (gasket treatment), then washed with water (treatment with water washing), and then separately The wafer is accommodated (accommodated) by closing the opening of the container body containing the wafer to be stored and transported with the lid while the gasket is interposed between the cleaned container body and the lid.

Hereinafter, each procedure will be specifically described.
(Gasket processing)
First, the gasket attached to the lid or the container body at the time of purchase or the like is removed, and this is immersed in an alcohol-containing solution of 50 vol% or more for 1 hour or more. Thereby, the outgas component in the gasket that causes the spot-like particles can be dissolved into the alcohol-containing solution, and the content of the outgas component can be reduced. Since the content of the outgas component is reduced, it is possible to suppress the amount of outgas generated during subsequent wafer storage and suppress the generation of spot-like particles.

  The material of the gasket is not limited as described above, but particularly when it is made of a thermoplastic elastomer, the effect of suppressing spot-like particles can be remarkably obtained.

  Moreover, although the alcohol used for an alcohol containing solution is not specifically limited, For example, ethyl alcohol can be used. Similar effects can be obtained with other alcohols such as methyl alcohol, but ethyl alcohol has the advantage of being easy to handle because it is less toxic and can be easily discarded.

In the present invention, high-purity alcohol (for example, 99.5 wt% or more) is prepared, and an alcohol-containing solution in which the high-purity alcohol is 50 vol% or more is required.
When the concentration is less than 50 vol%, it is difficult to reduce the amount of outgas from the gasket, so that the effect of suppressing the generation of spot-like particles on the surface of the stored wafer is hardly obtained.
On the other hand, by setting the concentration to 50 vol% or higher as in the present invention, it is possible to dissolve the outgas component more effectively into the alcohol-containing solution and to greatly reduce the content of the outgas component. is there.
Furthermore, it is preferable that the concentration be higher than 50 vol%, particularly 100 vol%. In this way, it is possible to reduce the spot-like particles more reliably.

  In addition, as a component other than alcohol in the alcohol-containing solution, for example, water (ultra pure water) can be used.

The immersion time may be 1 hour or longer. If the time is less than 1 hour, the effect of reducing spot-like particles is thin, and there is no difference from water washing as in the conventional method. On the other hand, the outgas component can be removed from the gasket as it is soaked for a long time, but it can be appropriately determined from the efficiency in consideration of the magnitude and time of the effect. For example, it can be immersed for 4 hours, 8 hours, or even 24 hours. Although it can be soaked for a longer time than 24 hours, the working efficiency is remarkably lowered if the time is too long, so that it is preferably 50 hours or less, more preferably 24 hours or less.
As an immersion method, for example, an alcohol-containing solution may be placed in a quartz tank and a gasket may be immersed therein.

(Processing such as washing with water)
After the gasket treatment as described above is performed, the gasket is washed with water. This cleaning procedure is not particularly limited, and for example, the conventional cleaning method of FIG. 4 as described above can be performed. That is, shower water washing with pure water, immersion in pure water containing a surfactant, shower water washing with pure water, spin drying, and clean oven drying are performed in this order.

  In addition, other container bodies and lids are separately cleaned. The cleaning method is not particularly limited, and the gasket may be the same as the above-described water cleaning method, or cleaning may be performed using isopropyl alcohol or the like. For example, cleaning similar to the conventional method can be performed.

(Storing)
After the parts of the storage container are cleaned and dried in this manner, the wafers to be stored are aligned in the container body. And the opening part of a container main body is closed by a cover body through the gasket after the said process attached to the cover body or the container main body. By the above procedure, the wafer is accommodated in the wafer storage container and stored and transported.

  In the conventional method of use, spot-like particles have been generated on the wafer housed inside the container due to the outgas from the gasket. However, according to the present invention, the outgas component in the gasket is previously removed by gasket processing. Therefore, it is possible to effectively suppress the generation of spot-like particles due to the occurrence. Therefore, it is possible to provide a wafer with a very high cleanliness considering the contamination from the wafer storage container.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Examples 1 and 2, Comparative Examples 1 and 2)
Alcohol-containing solutions (about 23 ° C.) with different alcohol concentrations (vol%) were prepared in a quartz tank using 99.5 wt% ethyl alcohol (100 vol% (Example 1), 50 vol% (Example 2). ), 20 vol% (Comparative Example 1)).
Then, a polycarbonate wafer storage container for storing a silicon single crystal wafer having a diameter of 300 mm is prepared, the gasket (material: thermoplastic elastomer) is removed, and each is immersed in an alcohol-containing solution for the same time (24 hours). did.

The gasket treatment was performed as described above, and after the gasket taken out from the quartz tank was air-dried, the treatment such as washing with water in FIG. 1 was performed. And it attached to the wafer storage container, the 300-mm-diameter silicon single crystal wafer was accommodated in the container main body, and it closed with the cover body.
Then, the adhesion state of the particle to a wafer was evaluated.
Moreover, apart from Examples 1 and 2 and Comparative Example 1, without using a gasket treatment of immersing in an alcohol-containing solution, only water washing or the like (treatment of the flow of FIG. 4) as in the conventional method was used. The same evaluation was performed for the case (Comparative Example 2).

  In addition, the evaluation method of the adhesion state of the particles uses a simple device that oscillates the storage container after storing the silicon single crystal wafers one by one, and 5 minutes in the horizontal direction, 5 minutes in the vertical direction, and 10 cm in width. And rocked. After rocking, the number of particles of 37 nm or more on the silicon single crystal wafer was measured using a particle counter (SP3 manufactured by KLA Tencor), and the shape was observed with an SEM to discriminate spot-like particles. The results are shown in Table 1.

As shown in Table 1, first, in the case of immersion in alcohol (Examples 1 and 2 and Comparative Example 1), compared to the case without immersion in alcohol (Comparative Example 2), spot-like particles The occurrence rate (number of spot-like particles / total number of particles) was small.
Furthermore, it can be seen that a higher ethyl alcohol concentration is more effective. However, immersion in ethyl alcohol having a concentration of 20 vol% (Comparative Example 1) is not significantly different from Comparative Example 2 without immersion, and has almost no effect.
Therefore, in order to substantially suppress the generation of spot-like particles, it is necessary to use a high-concentration alcohol-containing solution of 50 vol% or more as in Examples 1 and 2.

  With respect to the spot-like particles, Examples 1 and 2 in which the present invention was carried out had a smaller number of occurrences than that of Comparative Examples 1 and 2, and the occurrence rate was 1/4 or less, which could be extremely reduced. Among them, in Example 2 in the case of 100 vol%, the occurrence rate was 0%, and an excellent result could be obtained.

(Example 3-10, Comparative example 3-9)
Prepare alcohols with the same alcohol concentration (100 vol%, 50 vol%, 20 vol%) as in Example 1, Example 2 and Comparative Example 1, and change the immersion time (30 minutes, 1, 4, 8, 24 hours) 5 conditions) Gasket processing etc. were performed. Using the gasket, a silicon single crystal wafer was stored in a wafer storage container, and the occurrence rate of spot-like particles was evaluated in the same manner as in Example 1 to compare the effect of suppressing spot-like particles. The results are shown in Table 2.

  As shown in Table 2, it can be seen that in order to substantially suppress the generation of spot-like particles, it is necessary to immerse for 1 hour or longer in the gasket treatment. Even if an alcohol concentration of 100 vol% is used, if the immersion time is less than 1 hour, there is almost no suppression effect, and the effectiveness is low with respect to the conventional method.

(Examples 11-13, Comparative Example 10)
A gasket subjected to treatment (gasket treatment, washing with water, etc.) in the same manner as in Example 1 was prepared (gasket A1). Moreover, the gasket which performed water washing etc. similarly to the comparative example 2 was prepared (gasket B). Furthermore, a gasket was prepared that was processed under the same conditions as in Example 1 except that the immersion time was 8 hours (gasket A2). Moreover, the gasket which processed on the conditions same as Example 1 except having changed alcohol into methyl alcohol was prepared (gasket A3).
And about these gaskets, the amount of outgas was compared by GCMS method (Gas Chromatography and Mass Spectroscopy).

The GCMS method is a direct connection between a gas chromatograph and a mass spectrometer. Using this device, a gasket fragmented in units of several grams is heat-treated under vaporization heating conditions (20 minutes at 150 ° C.), and the amount of gas generated ( Outgas amount) was evaluated. The results are shown in FIG.
The vertical axis in FIG. 3 indicates a relative value normalized based on the outgas amount of the gasket B.

From the result of FIG. 3, when compared with the presence or absence of immersion in alcohol, gasket A1-A3 which was immersed in an alcohol-containing solution as in the present invention compared to gasket B which was not immersed in an alcohol-containing solution. The amount of outgas is decreasing.
Moreover, even when methyl alcohol is used for the alcohol-containing solution, the amount of outgas can be reduced, and it is estimated that the generation of spot-like particles can be suppressed. However, the amount of outgas was smaller when ethyl alcohol was used. That is, it is estimated that ethyl alcohol has a higher effect of reducing the outgas amount and suppressing the generation of spot-like particles. In addition, the outgas amount can be further reduced when immersed for a long time.

  Then, using these gaskets A1-A3 (Examples 11-13) and gaskets B (Comparative Example 10), a wafer is stored in a wafer storage container, and the rate of occurrence of spot-like particles is determined in the same manner as in Example 1. Evaluation was made and the suppression effect of spot-like particles was compared.

  As a result, the occurrence rate of spot-like particles became gasket A1, gasket A2, gasket A3, and gasket B in ascending order. It is the same as the order of decreasing outgas amount in FIG. 3, and it can be seen that the outgas from the gasket correlates with the occurrence rate of the spot-like particles. That is, it can be confirmed that the spot-like particles are caused by the outgas from the gasket.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  DESCRIPTION OF SYMBOLS 1 ... Wafer storage container, 2 ... Container main body, 3 ... Cover body, 4 ... Gasket, 5 ... Opening part, W ... Wafer.

Claims (4)

A wafer storage container comprising: a container main body for storing a wafer; a lid for opening and closing an opening of the container main body; and a sealing gasket detachably disposed between the lid and the container main body. How to use,
After the treatment of immersing the removable gasket in an alcohol-containing solution having an alcohol concentration of 50 vol% or more for 1 hour or more, the container body containing the wafer is held by the lid while the gasket is interposed. A method of using a wafer storage container, wherein the opening is closed.   The method for using a wafer storage container according to claim 1, wherein the alcohol is ethyl alcohol.   The method for using a wafer storage container according to claim 1 or 2, wherein the alcohol concentration is 100 vol%.   The method for using a wafer storage container according to any one of claims 1 to 3, wherein the gasket is made of a thermoplastic elastomer.

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