JP7175144B2 - Wafer storage container and wafer storage method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wafer storage container and a storage method thereof that prevent abrasion powder (hereinafter also referred to as foreign particles) from adhering to wafers due to friction between the wafer and the wafer holder.

Conventionally, as a method of storing and transporting a plurality of semiconductor wafers (hereinafter referred to as wafers), one wafer is stored in a wafer case (housing), and a plate-shaped wafer retainer (spring) is placed on the wafer. In some cases, the wafer is placed and the wafer case is engaged with another wafer case or a lid body (cover) so that the wafer is sandwiched between the wafer holder and the wafer case. Moreover, a container is known in which a plurality of such wafer cases are stacked and then a lid is placed on the uppermost wafer case to store and transport a plurality of wafers (see Patent Document 1).

In the container, the leg portion of the wafer retainer contacts the peripheral edge of the wafer, and the wafer retainer and the wafer case sandwich the peripheral edge of the wafer. However, when the lid that presses the wafer holder or another wafer case is rotated in the opening/closing direction, the wafer holder rotates together with the lid or the upper wafer case, and the wafer holder is held in place. It may slide against the wafer. At this time, if the wafer retainer slides against the wafer, the wafer will be damaged, and friction between the wafer and the wafer retainer will generate abrasion powder (foreign particles) in the wafer case, contaminating the wafer surface and impairing performance. I was afraid.

In order to solve the above problem, the wafer retainer is made rotatable in the center of the lid or the upper wafer case with a support shaft so that the wafer can be held uniformly and rotates together with the relative rotation of the upper and lower wafer cases. There is known a wafer storage container capable of suppressing the occurrence of foreign particles due to the friction between the wafer and the wafer holder, and the performance deterioration of the wafer caused by this phenomenon (see Patent Document 2).

Japanese Patent Publication No. 48-28953 JP-A-2006-56573

According to studies by the present inventors, even in a container that prevents the wafer retainer from rotating integrally with the upper wafer case, the wafer retainer contacts the wafer when pressed by the upper wafer case. It has been found that the leg of the wafer retainer attached to the wafer may also rub against the wafer when it moves in the radial direction of the wafer, and foreign particles may be generated due to the friction between the wafer and the wafer retainer.

In addition, when the wafer is too small to be clamped by the wafer retainer at its periphery, the wafer retainer may be used in the opposite direction to clamp the wafer by bringing the center of the wafer retainer into contact with the center of the wafer. In this case, unlike the wafer storage container described in Patent Literature 2, the wafer retainer cannot be rotated to the center of the lid or the upper wafer case by the support shaft, so co-rotation of the wafer retainer can be suppressed. Instead, the central portion of the wafer retainer slides against the wafer, and friction between the wafer and the wafer retainer can generate foreign particles. In addition, when the lid or other wafer case is rotated in the opening/closing direction, the wafer or the wafer holder is displaced, so that the central portion of the wafer holder also slides against the wafer, causing friction between the wafer and the wafer holder. may generate foreign particles.

Since wafers are often put in and taken out of a wafer storage container many times during evaluation and transportation, foreign particles adhere to them many times. The foreign particles adhering to the wafer not only contaminate the surface of the wafer and lower the yield of the product, but also contaminate the film formation equipment, processing equipment and cleaning equipment in the subsequent steps. Therefore, a wafer storage container is desired in which adhesion of foreign particles to wafers is further suppressed.

Therefore, the problem to be solved by the present invention is to provide a wafer storage container and a wafer storage method capable of suppressing adhesion of foreign particles to wafers even when wafers are repeatedly taken in and out.

The inventors of the present invention have made intensive studies to solve the above problems. As a result, foreign particles were observed at the point where the wafer holder and the wafer came into contact, and furthermore, it was found that the characteristics of the shape of the wafer holder were directly reflected in the wafer. The present inventors have found that adhesion of foreign particles to the wafer can be suppressed by using

That is, the first aspect of the present invention includes a first wafer case having a first cylindrical portion and a first end wall that closes one end of the first cylindrical portion, a second cylindrical portion and one end of the second cylindrical portion that is closed. a second wafer case having a second end wall to which the second cylindrical portion can be engaged with the first cylindrical portion; a wafer retainer disposed between the first and second end walls; Engaging/fixing means for fixing and unlocking the first and second cylindrical portions of the first and second wafer cases are provided, and between the first and second end walls, the wafer retainer and the A wafer storage container in which wafers are sandwiched between first end walls, wherein at least one cellulose-derived material selected from the group consisting of cellulose and lyocell is placed between the wafer retainer and the wafers . a non-woven fabric anti-fouling sheet containing the anti-fouling sheet , wherein the wafer retainer and the wafer are in contact with each other through the anti-fouling sheet .

A second aspect of the present invention provides a first wafer case having a first cylindrical portion and a first end wall that closes one end of the first cylindrical portion, a second cylindrical portion and one end of the second cylindrical portion that is closed. a second wafer case having a second end wall to which the second cylindrical portion can be engaged with the first cylindrical portion; a wafer retainer disposed between the first and second end walls; Engaging/fixing means for fixing and unlocking the first and second cylindrical portions of the first and second wafer cases are provided, and between the first and second end walls, the wafer retainer and the A method of storing wafers in a wafer storage container having first end walls sandwiching the wafers, wherein the wafer retainer and the wafers are made of at least one cellulose-derived material selected from the group consisting of cellulose and lyocell. It is a wafer storage method in which the wafers are brought into contact with each other through an antifouling sheet of nonwoven fabric containing .

The present invention is characterized in that the wafer storage container is provided with an antifouling sheet, and the wafer retainer and the wafer are brought into contact with each other through the antifouling sheet. As described above, the foreign particles adhering to the wafer are abrasion powder due to friction between the wafer holder and the wafer.

In the present invention, when the wafer is held between the wafer holder and the first end wall, the wafer holder and the wafer are in contact with each other through the antifouling sheet, so the wafer holder and the wafer do not come into direct contact with each other. do not have. Therefore, when the first cylindrical portion of the first wafer case and the second cylindrical portion of the second wafer case are fixed or released, the wafer retainer is pressed or released by the second wafer case, and the legs of the wafer retainer are released. To open and close a lid or another wafer case when the wafer retainer cannot hold the peripheral edge of the wafer because the wafer is small or the like even if the wafer moves in the radial direction, and the wafer retainer is used in the opposite direction. Even if the central portion of the wafer retainer slides against the wafer due to the deviation of the wafer or the wafer retainer when rotating in the direction, the generation of foreign particles due to the friction between the wafer and the wafer retainer can be suppressed. In addition, the fixing and releasing of the fixing and fixing between the first cylindrical portion of the first wafer case and the second cylindrical portion of the second wafer case are performed by relative rotation, and even if the wafer retainer rotates together with the second wafer case, the wafer retainer cannot be secured. The contact with the wafer through the antifouling sheet can suppress the generation of foreign particles generated when the wafer retainer slides against the wafer. Wafers free of foreign particles not only improve the yield in subsequent processes, but also prevent contamination of deposition equipment, processing equipment, and cleaning equipment. Furthermore, the appearance inspection process and cleaning for removing foreign particles can be omitted, and productivity is also improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which illustrates typically an example of the wafer storage container of this invention. It is a figure which illustrates typically an example of the shape of a wafer holder. FIG. 10 is an image of a wafer in which no rub marks due to foreign particles were observed with a Nomarski differential interference microscope; FIG. It is an image of a wafer in which friction marks due to foreign particles are observed by a Nomarski differential interference microscope.

Hereinafter, the wafer storage container of the present invention will be described in detail.

<Wafer storage container>
The wafer storage container of the present invention includes a first wafer case having a first cylindrical portion and a first end wall that closes one end of the first cylindrical portion, a second cylindrical portion and one end of the second cylindrical portion that closes. a second wafer case having a second end wall and capable of engaging said second tubular container with said first tubular container; a wafer retainer disposed between said first and second end walls; Engaging/fixing means for fixing and unlocking the first and second cylindrical portions of the first and second wafer cases are provided, and the wafer retainer and the wafer retainer are provided between the first and second end walls. The wafer storage container is configured such that the wafers are sandwiched between the first end walls, and is characterized by further comprising an antifouling sheet between the wafer retainer and the first end walls.

In the present invention, a first wafer case having a first cylindrical portion and a first end wall that closes one end of the first cylindrical portion, and a second cylindrical portion and a second end wall that closes one end of the second cylindrical portion and wherein the second cylindrical portion can be engaged with the first cylindrical portion; a wafer retainer provided between the first and second end walls; Engaging/fixing means for fixing and unlocking the first and second cylindrical portions of the wafer case are provided, and between the first and second end walls, the wafer retainer and the first end wall Wafer storage containers that can be used as a wafer storage container that sandwiches wafers include a wafer storage and transport container described in Japanese Patent Publication No. 48-28953, and a wafer transfer container described in Japanese Patent Application Laid-Open No. 2006-56573. etc.

The wafer storage container of the present invention will be described below with reference to FIG.

<Wafer case>
In the wafer storage container of the present invention, the first wafer case (1) has a first cylindrical portion (6) and a first end wall (7) closing one end of the first cylindrical portion (6). The first cylindrical part (6) and the first end wall (7) constitute a storage part for storing the wafer (5) and function as a tray. The shape of the first end wall (7) may be such that only the periphery of the wafer (5) to be accommodated is in contact with it, and is preferably curved downward into a conical or concave shape. In the storage part for storing the wafer (5), the wafer (5) is stored, and a wafer retainer (3) and an antifouling sheet (4) are arranged.

The second wafer case (2) has a second tubular portion (8) and a second end wall (9) closing one end of the second tubular portion (8). The second cylindrical portion (8) of the second wafer case (2) is engaged with the first cylindrical portion (6) of said first wafer case (1) and the second end wall (9) closes the first wafer case (8). 1) Close the storage section. The second wafer case (2) may have a flat second end wall (9) and function as the lid of the wafer storage container of the present invention.

Further, the second wafer case (2) is provided with the first cylindrical portion (6) of the first wafer case (1) on the surface of the second end wall (9) opposite to the surface having the second cylindrical portion (8). The cylindrical portion and the second end wall (9) may constitute a storage portion for storing the wafer (5) in the same manner as the first wafer case (1). In this case, the second wafer case (2) functions as a lid for the first wafer case (1) and at the same time has a storage section for storing the wafer (5).

Furthermore, the first wafer case (1) is placed on the surface of the first end wall (7) opposite to the surface having the first tubular portion (6), and the second tubular portion (8) of the second wafer case (2) is , and the first wafer case (1) and the second wafer case (2) may have the same shape. By doing so, the first cylindrical portion (6) and the second cylindrical portion (8) of each wafer case can be engaged, and three or more wafer cases can be stacked and used. In this case, the first wafer case (1) corresponds to the second wafer case (2), the second wafer case (2) corresponds to the first wafer case (1), and the first wafer case (1) and the second wafer case (1) The case (2) serves as the first wafer case (1) and the second wafer case (2), respectively.

The shape of the first cylindrical portion (6) and the second cylindrical portion (8) of the first and second wafer cases (1, 2) may be a known shape such as a cylindrical shape or a rectangular shape. ). The size may be selected from the size, thickness, storage stability, and number of wafers (5) to be stored. The material may be any known material, preferably polypropylene, fluororesin, or polycarbonate, which can be used repeatedly by washing, more preferably conductive polypropylene treated with conductivity, or polycarbonate, which has high strength and is easy to stack.

When a plurality of wafers are housed in one wafer case, the shape of the wafer case includes a shape having a plurality of wafer housing portions in one wafer case. A plurality of wafer holders (3) may be installed according to the number of wafer storage units. In order to improve workability, the wafer retainer may be fixed to the portion of the wafer case that functions as the lid.

The engaging and fixing means for enabling the first cylindrical portion (6) of the first wafer case (1) and the second cylindrical portion (8) of the second wafer case (2) to be fixed and unlocked are relative rotation, hinge , clips, and taping, among which the relative rotation method is preferable because it is easy to apply pressure uniformly and is excellent in airtightness.

As the first and second wafer cases (1, 2) of the wafer storage container of the present invention, known commercially available wafer trays, wafer tray covers, wafer transfer containers, wafer shippers, chip trays, etc. may be used. can be done.

Since the wafer storage container of the present invention clamps the peripheral edge of the wafer, the wafer may be stored with the front surface of the wafer facing upward or downward. After the wafers are stored in the wafer storage container, even if foreign substances adhering to the second wafer case (2) and the wafer retainer (3) fly during transportation, they are difficult to adhere to the front surface of the wafers, so that they are stored face down. is preferred.

<Wafer holder>
The wafer retainer (3) in the wafer storage container of the present invention consists of a leaf spring-like thin plate having a central portion and a plurality of legs (10) extending radially outwardly therefrom. Each tip of the leg (10) is curved to one side, and the central portion of the wafer retainer (3) as a whole touches the second end wall (9) of the second wafer case (2). so that the leg (10) presses the inner surface of the first end wall (7) of the first wafer case (1) (the surface of the wafer (5) when the wafer (5) is accommodated) with which the leg (10) contacts at its end. It has a substantially arcuate cross-sectional shape. In addition, when the wafer holder (3) cannot hold the peripheral edge of the wafer (5) because the wafer (5) is too small, the wafer holder (3) is used in the opposite direction to remove the wafer. The wafer can also be clamped by bringing the central part of the retainer (3) into contact with the center of the wafer (5). (7) pressing the inner surface (the surface of the wafer (5) when the wafer (5) is stored), the leg (10) at its end the second end wall (9) of the second wafer case (2); Press. The wafer retainer (3) has a diameter that allows the edge of the leg (10) to clamp the wafer (5) at the peripheral edge of the wafer (5), or the edge of the leg (10) is the second wafer case (2 ) or the first cylindrical portion (6) of the first wafer case (1). The direction of the leg portion (10) of the wafer holder (3) may be determined from the diameter and shape of the wafer.

When the second wafer case (2) is attached to the first wafer case (1), the edge or central portion of the leg (10) of the wafer retainer (3) holds the wafer (5) at its edge to the first edge. The wafer (5) is clamped and held by pressing against the peripheral edge of the wall (7).

The leg portion (10) of the wafer holder (3) is attached to the wafer (5) or the first end wall (7) of the first wafer case (1) or the second end wall (9) of the second wafer case (2). It suffices if the pressure is evenly distributed, and 4 or more are preferable, and 8 or more are more preferable. A typical wafer holder is shown in FIG. The material is the same as that of the first and second wafer cases, preferably polypropylene, polybutylene terephthalate, low-density polyethylene, or fluororesin, which can be repeatedly used by washing, and more preferably conductive polypropylene that has been treated to be conductive. If one wafer case has a plurality of storage units for storing wafers and one wafer case can store a plurality of wafers, it is possible to prepare a wafer retainer (3) for each wafer or hold a plurality of wafers. It is recommended to use a wafer holder that can hold the wafer.

As the wafer retainer (3) of the wafer storage container of the present invention, a well-known one commercially available as a wafer tray spring or the like can be used.

<Anti-fouling sheet>
The antifouling sheet (4) in the wafer storage container of the present invention is a sheet provided between the wafer retainer (3) and the first end wall (7). By bringing the wafer retainer (3) and the wafer (5) into contact with each other through the antifouling sheet (4) when storing in the storage container, the wafer (5) is held by the wafer retainer (3) and the first end wall (7). 5) to clamp the wafer (5), the leg (10) or the central portion of the wafer holder (3) and the wafer (5) come into direct contact, causing the wafer (5) and the wafer holder ( 3) to suppress the generation of foreign particles due to friction with the wafer (5), thereby suppressing the foreign particles from adhering to the wafer (5) and contaminating the wafer (5). The material of the antifouling sheet (5) is preferably a non-woven fabric that is flexible and does not easily generate dust. Examples include cellulose, cotton, lyocell, rayon, polyethylene, polypropylene, polyester and nylon. Among them, polyethylene that is compatible with electro-static discharge (hereinafter also referred to as ESD compatible) and has reduced ion extraction and outgassing is more preferable. Further, polyester and a composite of polyester and nylon, which are easily made into long fibers with low dust generation, are also preferable. The size and shape may be such that the wafer retainer (3) and the wafer (5) can be brought into contact with each other through the antifouling sheet (4). , and similarly shaped sheets. Furthermore, if you want to minimize the contact between the wafer (5) and the antifouling sheet (4), in order to reduce the contact area between the antifouling sheet (4) and the wafer (5), only the part where the wafer holder contacts For protection, a ring-shaped sheet may be used when the wafer retainer contacts at its legs, and a small-diameter sheet may be used when it contacts at its center. The thickness may be a thin film material such as a film or a thick film material such as a cushion, and a thickness of 0.10 mm to 3.0 mm is more preferable.

The antifouling sheet (4) may be fixed to the leg (10) or central portion of the wafer holder (3) in order to improve workability. Furthermore, in order to reduce the contact area with the wafer (5), an antifouling sheet (4) large enough to cover the leg (10) of the wafer retainer (3) may be adhered to the leg (10). preferable.

<Wafer>
The wafers (5) to be stored in the wafer storage container of the present invention are not limited, and may be mirror-polished wafers of silicon, compound crystals, nitride crystals, oxide crystals, etc., or wafers subjected to grinding, slicing, outer peripheral processing, etc. Samples in process can be stored. Among them, it is suitable for research and development level wafers for which cleaning technology has not been established, and wafers that are thick and come into strong contact with the wafer holder. Wafers whose outer periphery is ground, rectangular wafers, and the like are also applicable. Furthermore, small pieces of chips and the like are also applicable. The diameter may be accommodated in the wafer container, preferably 5 mm to 320 mm, more preferably 20 mm to 52 mm.

<Wafer storage>
In the method for storing wafers of the present invention, when the wafers (5) are stored in the above-described wafer storage container, the wafer retainer (3) and the wafer (5) are separated so that the wafer (5) does not come into direct contact with the wafer retainer (3). ) are brought into contact with each other via the antifouling sheet (4).

That is, after the wafer (5) is stored in the storage portion for storing the wafer (5) constituted by the first cylindrical portion (6) and the first end wall (7) of the first wafer case (1), An antifouling sheet (4) is arranged on the upper surface of a wafer (5), and a wafer holder (3) is further arranged on the antifouling sheet (4) to separate the wafer holder (3) and the wafer (5). are brought into contact with each other through the antifouling sheet (4). Next, by engaging and fixing the first cylindrical portion (6) of the first wafer case (1) and the second cylindrical portion (8) of the second wafer case (2), the wafer retainer (3) and the The wafer (5) is stored in the wafer storage container of the present invention while being sandwiched between the first end wall (7) and the wafer (5).

Thus, when the wafer (5) is sandwiched between the wafer holder (3) and the first end wall (7), the wafer holder (3) and the wafer (5) are separated from each other with the antifouling sheet (4) interposed therebetween. Since they are in contact with each other, the wafer holder (3) and the wafer (5) do not come into direct contact with each other, and the wafer holder (3) is held down by the second wafer case (2), and the legs of the wafer holder (3) are supported. Even if the part (10) moves in the radial direction of the wafer (5), if the wafer holder is used in the opposite direction, the wafer or the wafer holder (3) will shift, causing the central part of the wafer holder to move against the wafer. The generation of foreign particles due to friction between the wafer (5) and the wafer retainer (3) is suppressed even if the wafer (5) slides against the wafer. In addition, the first cylindrical portion (6) of the first wafer case (1) and the second cylindrical portion (8) of the second wafer case (2) are fixed and released by relative rotation to hold the wafer holder (3). rotates together with the second wafer case (2), the wafer retainer (3) is in contact with the wafer (5) through the antifouling sheet (4), so that the wafer retainer (3) is kept in contact with the wafer (5). ) is suppressed.

In the method for storing wafers of the present invention, the wafers are stored by sandwiching the wafers. Preferably, after the wafers are stored in the wafer storage container, even if foreign matter that has adhered to the second wafer case (2) or the wafer holder (3) flies during transportation, it will not easily adhere to the front side surface of the wafer, and will face downward. It is preferable to store in

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. The foreign particles on the wafer surface were evaluated by observation with a Nomarski differential interference microscope and micro-Raman spectrum analysis. The evaluation method is shown below.

<Nomarski differential interference contrast microscopy>
The wafer was observed in a bright field at a magnification of 100 to 500 using a Nomarski differential interference microscope (LV150 manufactured by Nikon Corporation).

<Analysis of composition of foreign particles by micro-Raman spectrum>
For the analysis of the composition of foreign particles by micro-Raman spectrum, an NRD-7100 micro-Raman spectrometer manufactured by JASCO Corporation was used. A laser with a wavelength of 531.98 nm was used as an excitation laser, and a slit with a width of 10 μm×length of 1000 μm and a grating of 600 lines/mm were used. The excitation laser output was set to 10.8 mW, and a 100-fold objective lens was used to focus the measurement spot to a diameter of about 1 μm. The exposure time at this time was set to 5 seconds, and integration was performed three times. The wave number of the measured Raman spectrum was calibrated by the Raman shift at the wave number of 521.448 cm ⁻¹ of the silicon substrate measured under the same conditions. Similarly, the wafer holder used was also measured to see if the spectra matched.

Example 1
(Wafer storage container and storage method)
The first wafer case and the second wafer case are a wafer tray for φ25.4 mm (manufactured by Florowair Entegris, model number: H22-10-0615-01), a wafer tray cover (manufactured by Florowair Entegris, model number: H22). -101-0615-02) was used. The material is polypropylene, and the first end wall of the first wafer case has a concavely curved shape. As wafers, aluminum nitride single crystal wafers with a diameter of 23 mm and a thickness of 601 μm were used, and the wafers were housed with the front surface facing the first end wall side of the first wafer case (stored downward). A nonwoven fabric (Crecia Technowipe (manufactured by Nippon Paper Crecia Co., Ltd.), model number: C100-S) was used as an antifouling sheet on the upper side of the wafer. The material is lyocell, which is a mesh-type nonwoven fabric with a thickness of about 0.15 mm. A circle with a diameter of about 24 mm was cut out, and one sheet was installed. A wafer tray spring (manufactured by Florowair Entegris, Model No.: H22-102-0815) with a diameter of 25.4 mm was used as the wafer holder, with the legs thereof contacting the wafer. It is made of polypropylene and has 8 legs. A second wafer case was placed on the wafer retainer and fixed to the first wafer case by a relative rotation method.

(Fixing and releasing the wafer storage container)
The first wafer case and the second wafer case were fixed carefully so that the wafer holder would not rotate. Furthermore, the fixation of the first wafer case and the second wafer case was released, and the wafer holder, antifouling sheet, and aluminum nitride single crystal wafer were taken out.

(Confirmation of foreign particles)
The operations of storage, fixing, release of fixation, and removal were repeated a total of 5 times. After that, the presence or absence of foreign particles on the wafer was observed with a Nomarski differential interference microscope. No rub marks due to foreign particles were observed on the wafer. An image observed by a Nomarski differential interference microscope is shown in FIG.

(reproduction confirmation test)
In order to confirm foreign particles under the above conditions, 4 sets of similar wafer containers, wafer holders, antifouling sheets, and wafers were prepared, and a reproduction confirmation test was conducted 4 times. As a result, no friction marks due to foreign particles were observed in three of the four times. The probability of generating friction marks due to foreign particles was 25%. It is considered that the friction marks caused by the foreign particles were generated because the nonwoven fabric used was of the mesh type and had thin portions.

Example 2
A reproducibility confirmation test was conducted in which foreign particles were confirmed four times in the same manner as in Example 1, except that the number of antifouling sheets was changed to two. As a result, no friction marks due to foreign particles were observed in 4 out of 4 times.

Example 3
The nonwoven fabric used as the antifouling sheet in Example 1 was changed to BEMCOT (R) lint-free (manufactured by Ozu Sangyo Co., Ltd., model number: 7-662-01). The material is cellulose and the thickness is about 0.05 mm. A circle with a diameter of about 24 mm was cut out, and one sheet was installed. Except for this, a reproduction confirmation test was carried out in the same manner as in Example 1, in which foreign particles were confirmed five times. As a result, no friction marks due to foreign particles were observed in 5 out of 5 times.

Reference example 1
The nonwoven fabric used as the antifouling sheet in Example 1 was changed to a horizontal wafer shipper insert of 150 mm (manufactured by Florowair Entegris, model number: HWS150-5TY500-INS). A reproducibility confirmation test was conducted in which foreign particles were confirmed five times in the same manner as in Example 1, except that the nonwoven fabric was a single-layer nonwoven fabric for ESD and the material was not polyethylene. As a result, no friction marks due to foreign particles were observed in 5 out of 5 times.

Comparative example 1
A reproducibility confirmation test was conducted in which foreign particles were confirmed four times in the same manner as in Example 1, except that the antifouling sheet was not used. As a result, friction marks due to foreign particles were observed four out of four times at the outer peripheral portion of the wafer and the portion where the wafer holder was in contact. As a result of micro-Raman spectroscopy analysis of foreign particles adhering to the wafer, components of the wafer holder were detected. FIG. 4 shows an image observed by a Nomarski differential interference microscope.

1 First wafer case 2 Second wafer case 3 Wafer retainer 4 Antifouling sheet 5 Wafer 6 First cylindrical portion 7 First end wall 8 Second cylindrical portion 9 Second end wall 10 Leg portion of wafer retainer

Claims (2)

a first wafer case having a first cylindrical portion and a first end wall closing one end of the first cylindrical portion;
a second wafer case having a second tubular portion and a second end wall closing one end of the second tubular portion, the second tubular portion being engageable with the first tubular portion;
a wafer retainer disposed between the first and second end walls;
Engaging and fixing means for fixing and unlocking the first and second cylindrical portions of the first and second wafer cases are provided,
A wafer storage container in which a wafer is sandwiched between the wafer retainer and the first end wall between the first and second end walls,
Further, an antifouling sheet made of non-woven fabric containing at least one cellulose-derived material selected from the group consisting of cellulose and lyocell is provided between the wafer holder and the wafer, and the wafer holder and the wafer are separated from each other by the antifouling sheet. A wafer storage container characterized by being in contact with each other through a dirty sheet . a first wafer case having a first cylindrical portion and a first end wall closing one end of the first cylindrical portion;
a second wafer case having a second tubular portion and a second end wall closing one end of the second tubular portion, the second tubular portion being engageable with the first tubular portion;
a wafer retainer disposed between the first and second end walls;
Engaging and fixing means for fixing and unlocking the first and second cylindrical portions of the first and second wafer cases are provided,
A method of storing wafers in a wafer storage container in which the wafers are held between the first and second end walls by the wafer retainer and the first end wall, the method comprising:
A method of storing wafers, wherein the wafer retainer and the wafers are brought into contact with each other through an antifouling sheet of non-woven fabric containing at least one cellulose-derived material selected from the group consisting of cellulose and lyocell .

Images