JPH11317442A - Method of storing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of packing a wafer, wherein a wafer case is filled with an inert gas while preventing the infiltration of dirt, and a wafer case used in the same method. SOLUTION: A wafer case 10 is placed within a vacuum container 30. Next, the vacuum container 30 is depressurized to have air exhausted from the container 30, and at the same time, a filter unit 15 exhausts the air from the case for depressurizing it. Thereafter, while nitrogen gas is put into the vacuum container 30 for filling the container 30 with the nitrogen gas, the case 10 too is filled with nitrogen gas through the filter unit 15. Thus, since the wafer case 10 is provided with the filter unit 15, this allows the case to be filled with nitrogen gas, while preventing the infiltration of dirt inside the vacuum container 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer storing method for storing a silicon wafer or the like in a wafer case, and more particularly to a wafer storing method for filling an inert gas into a wafer case while preventing intrusion of dust.

[0002]

2. Description of the Related Art A semiconductor wafer such as a silicon wafer manufactured in a wafer manufacturing factory is usually sealed with a gasket (packing material) in a clean room in order to prevent damage or contamination during transportation. Stored in a wafer case. The interior of this clean room is generally filled with air at a room temperature (around 20 ° C.) at a humidity of about 50%, which is obtained by filtering dirt and dust. By the way, no matter how high the clean room is, small amount of fine dust and dust are floating in this room at present.

[0003] Therefore, when the wafer case is sealed in the clean room, fine dusts in the clean room enter the case. In this garbage,
It often contains organic matter. Furthermore, especially when the outside air temperature is lowered during transportation, the moisture contained in the air in the clean room sealed in the wafer case causes dew condensation. Na, Z uniformly distributed in
Fine foreign matters such as n and Ca are attracted by the tension of water droplets and locally concentrated, which may cause abnormal growth of fine particles. Moreover, as a result, even if the condensation is eliminated, there is a problem that the foreign matter is left, and the mirror surface of the wafer is locally clouded, thereby deteriorating the quality of the silicon wafer.

As a conventional technique for solving these problems, there is known a wafer storing method in which an inert gas such as N ₂ gas is filled in a wafer case to prevent the condensation or the like. In this conventional method, first, in a vacuum vessel,
A wafer case in which a wafer is stored and sealed is placed. Then, the air in the wafer case is extracted from the gap between the lid and the container body by reducing the pressure in the vacuum container with a vacuum pump. Then, N _{2 is} placed in this vacuum vessel.
Supply inert gas such as gas. As a result, the inert gas is filled into the wafer case from the gap of the lid.

[0005]

However, in such a conventional wafer storage method, since the inside of the vacuum container is usually contaminated, when the inert gas is filled in the wafer case, the inside of the vacuum container is not filled. There is a risk that fine dust existing in the wafer case may also enter the wafer case. As a result, there is a problem that dirt adheres to the surface of the stored silicon wafer and the surface is contaminated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for storing a wafer in which a wafer case can be filled with an inert gas while preventing intrusion of dust and the like. Another object of the present invention is to provide a wafer storage method capable of holding a wafer surface in a clean state.

[0007]

According to the first aspect of the present invention, there is provided a process for preparing a wafer case in which gas can flow in and out only through a filter in a sealed state, and storing a semiconductor wafer in the wafer case. And sealing, and a step of arranging the wafer case containing the semiconductor wafer inside the sealed space, and depressurizing the sealed space in which the wafer case is arranged, thereby reducing the gas inside the wafer case. Discharging from the filter to the outside of the wafer case, and a step of depressurizing the inside of the wafer case, and after this depressurizing step, by supplying an inert gas into the sealed space, the inside of the wafer case is passed through the filter. Filling the wafer with an inert gas.

In the case of air transport of semiconductor wafers, the in-flight pressure when the aircraft flies at an altitude of several thousand to 10,000 m is 0.7 to 0.7.
Reaches 0.8 atm. Therefore, it is preferable that the degree of sealing of the wafer case is designed so that the gas flows in and out only through the filter under this condition.

As a material of the filter, various synthetic resins such as nitrocellulose, cellulose acetate, ethylene tetrafluoride resin (PTFE), and hydrophilic tetrafluoroethylene resin can be used. In addition, a known filter such as a membrane filter made of these materials can be used. The average pore size of the filter is not limited as long as it can filter out dust and the like floating in the atmosphere. The external dimensions of the filter are not limited as long as the filter can withstand the pressure difference between the inside and outside of the case. Further, the mounting position of the filter may be any part such as the container body and the lid. Moreover, you may assemble to both members. Further, the number of filters to be assembled is not limited. These matters also correspond to claim 2.

The object forming the closed space is not limited as long as it can accommodate a wafer case and can be sealed with high security. For example, a vacuum container, a glove box, a clean room where these are usually provided, and the like can be given. As an inert gas that can be replaced with the air inside the wafer case, for example, N 2
₂ gas, Ar gas and the like.

According to a second aspect of the present invention, the wafer case includes a container main body, a lid for sealing the container main body, and a filter attached to at least one outer wall of the container main body and the lid. Even when the external pressure of the wafer case is lower than its internal pressure by 0.05 to 0.2 atm, the wafer case maintains the hermeticity between the lid and the container body. 2. The wafer storage method according to claim 1, wherein gas can flow through the inside and outside of the case, and the filter can filter fine dust having a size of 0.05 μm or more by 99.9% or more. As the material of the container body and the lid, for example, polycarbonate (PC), polyethylene (PE), polypropylene (PP), polystyrene (P
S), various plastics such as polyetheretherketone (PEEK) and polybutylterephthalate (PBT), and metals such as hard aluminum and stainless steel. Usually, a gasket is interposed between the container body and the lid in order to enhance the sealing inside the case when the lid is closed. The reason why the sealing is maintained by the differential pressure is that the wafer case must be able to cope with the air transport of the semiconductor wafer. This filter has a performance capable of filtering 99.9% of dust or dust of 0.05 μm or more by a particle counter. This is because if the filter can filter dust having a particle size of less than 0.05 μm, the time required for the replacement of the inert gas becomes long.

According to a third aspect of the present invention, when the volume of the wafer case is set to V liter, the filter comprises:
3. The wafer storage method according to claim 2, wherein inflow and outflow of gas are allowed at a value of V / 1500 (mol / min) or more. The speed of gas filtration by the filter is V / 1500 (mol
If the pressure is less than (/ min), the time for eliminating the pressure difference between the inside and outside of the wafer case becomes too long, and the time for replacing the air inside the wafer case with the inert gas becomes long. The number of filters in this case is arbitrary, as described above. In the case of a plurality of filters, the above condition is satisfied as a whole.

According to a fourth aspect of the present invention, there is provided the wafer storing method according to the second or third aspect, wherein the filter is a membrane filter made of tetrafluoroethylene resin.

According to a fifth aspect of the present invention, there is provided the wafer storing method according to any one of the first to fourth aspects, wherein the inert gas is a nitrogen gas.

[0015]

According to the first to fifth aspects of the present invention, when purging the air in the wafer case with an inert gas, first, the wafer case in which the wafer is sealed is placed in the closed space. Next, the pressure in the closed space is reduced. As a result, at the same time as the internal air in the space is exhausted, the air in the case is extracted to the outside of the case via the filter, and the inside of the case is reduced in pressure. Thereafter, when an inert gas is supplied into the sealed space, the inside of the sealed space is filled with the inert gas. At the same time, the inside of the wafer case is filled with the inert gas through the filter. In this way, by attaching the filter to the wafer case, the case can be filled with the inert gas while preventing intrusion of dust floating in the sealed space. Thereafter, the wafer case is usually packed in, for example, an aluminum film bag or a laminate bag while being filled with the inert gas, and then shipped to a device factory or the like by various transportation means. In some cases, it is packed in a laminated bag in a closed space (gas injection, laminate packing, and heat sealing in a closed space).

In particular, according to the second aspect of the present invention, as a filter, 99.9% of dirt or dust of 0.05 μm or more is used.
If a material that can be filtered as described above is employed, when filling the case with an inert gas, it is possible to perform filtering with fairly fine dust in a closed space.

According to the third aspect of the present invention, the rate of gas inflow and outflow through the filter is set to V / 1500 (mol /
Minutes), the replacement with the inert gas can be performed in a relatively short time. Further, a pressure difference between the inside and outside of the case in air transportation or the like can be released in a short time.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for storing a wafer according to an embodiment of the present invention and a wafer case used therein will be described. FIG. 1A is an explanatory view showing a step of discharging air inside the wafer case of the wafer storage method according to one embodiment of the present invention. FIG. 1B is an explanatory view showing a process of filling the wafer case with N ₂ gas. FIG. 2 is an overall perspective view of a wafer case according to one embodiment of the present invention.
FIG. 3 is a front view of a wafer case according to one embodiment of the present invention. FIG. 4 is a plan view of the same. FIG. 5 is an enlarged cross-sectional view taken along the line AA of FIG. 2 while the lid is closed. FIG. 6A is a partially enlarged cross-sectional view showing the structure of the joint between the container body and the lid. FIG. 6B is a schematic view for explaining the compression deformation of the gasket. FIG. 7 is an enlarged perspective view of the filter unit. FIG. 8 is an enlarged sectional view of the use state of the filter unit.

As shown in FIGS. 2 to 4, reference numeral 10 denotes a wafer case according to an embodiment of the present invention. This wafer case 10 is, for example, an 8-inch silicon wafer 11
A wafer cassette 100 in which a maximum of 25 sheets are inserted,
A rectangular box-shaped container main body 12 in which the wafer cassette 100 is stored, a lid 13 for closing an opening on the upper surface of the container main body 12, a container main body 12 and a lid 13
An annular rubber gasket 14 which is an example of a packing material interposed between outer walls of an opening peripheral portion of the opening 13 and a filter unit 15 mounted on an inner surface of a corner of an upper wall of the lid 13 and communicating between the inside and the outside of the case. It is a sealed case with an internal capacity of about 15000 cc. The lid 13 is formed in a rectangular shallow dish shape in which the upper side when the lid is closed is concave.

As the material of the container body 12 and the lid 13, transparent or translucent polypropylene (PP) and polycarbonate (PC) are used. The gasket 14 is made of an annular rubber having a rectangular cross section. It is interposed between the peripheral edges of the flange-shaped opening of the container body 12 and the lid 13 and serves as a packing material for ensuring the tightness of the wafer case 10. More specifically, as shown in FIGS. 6A and 6B, the gasket 14 has a head slightly projecting from a seal groove 30 having a rectangular cross section provided around the opening periphery of the container body 12. It is stored. In the gasket 14, a concave portion 34 is formed in the outer periphery (non-compressed portion) of the gasket 14 over the entire periphery. Therefore, a gap 35 is formed between the non-compressed surface of the gasket 14 and the wall of the seal groove 30.

The lid 13 is provided with a high airtightness through the gasket 14 at the opening of the container body 12 so as to withstand a pressure difference between the inside and outside of the case during air transportation of 0.2 atm. It is closed with the lid. Then, on the surface of the upper wall of the lid 13, the wafer 11 can be seen through the transparent upper wall.
Is displayed in accordance with the thickness position corresponding to the number. As shown in FIG. 8, a boss-shaped hole 13 projecting into the container in a tapered shape is formed at one corner of the upper wall of the lid 13.
a is formed. The hole 13a is provided with a ventilation hole communicating between the inside and outside of the case. The base 16a of the housing 16 of the filter unit 15 is fitted in the hole 13a.

On the other hand, as shown in FIG. 6, the lower surface of the seal groove 30 of the container body 12 and the upper surface of the seal groove 32 formed on the peripheral edge of the lid 13 respectively correspond to the upper and lower surfaces of the gasket 14. A pair of ribs 31 and 33 in contact with each other are provided around. Therefore, when the lid is closed, the upper and lower portions of the gasket 14 are crushed by the ribs 31 and 33 (see FIG. 6A). However, the gap 35 formed between the non-compressed surface of the gasket 14 and the side wall of the seal groove 30 serves as a relief for the gasket 14 that has been crushed and bulged (see FIG. 6B). As a result, the gasket 14 subjected to the compressive force is smoothly deformed without being hindered by the side wall of the seal groove 30. Therefore, the operation of closing the lid 13 is facilitated, and the reliability of the sealing function at the joint is improved. With such a closed structure, the lid 13 is closed at the opening of the container main body 12 with high airtightness that can withstand a pressure difference of 0.2 atm between the inside and outside of the case.

At the time of closing the lid, a jig for manually (or automatically) pressing the lid 13 against the container body 12 is disposed between the upper portions of the side plates of the container body 12 shown in FIGS. And a pair of hook lever portions 40. Hereinafter, this will be described. As shown in FIGS. 2 and 5, the hook / lever portion 40 includes a hook member 41 and a lever member 42, both of which are plate members. An engagement hole 41a is formed in an upper portion of the hook member 41, and a cutout portion is formed at a lower portion of the hook member 41, where the connection shaft 42a of the lever member 42 is supported. The container body 1 is provided on both sides of the base of the lever member 42.
A pair of mounting shafts 42b supported between ribs protruding from the upper part of the second side plate protrude. In addition, an engagement projection 13d that joins with the engagement hole 41a at the time of closing the lid protrudes from the opening peripheral portion of the lid 13 at a position facing each of the engagement holes 41a.

Therefore, at the time of closing the lid, the lid 13 is placed on the opening of the container body 12, and then each of the engaging holes 41a is engaged with the corresponding engaging projection 13d. Next, the lever member 42 is rotated downward in a vertical plane about the mounting shaft 42b. As a result, the hook member 41 is pushed down while being rotated about the connecting shaft 42a in a vertical plane. Thereby, the lid 13 is firmly closed. At the time of opening the cover, an operation opposite to this operation is performed.

As shown in FIGS. 7 and 8, the filter unit 15 is a small unit having a length of about 2.5 cm in the axial direction. The filter unit 15 includes a housing 16 and a filter 17 housed therein. The housing 16 is a small tubular body having a generally frame shape made of polypropylene, and is formed of the cylindrical base 1.
A disc-shaped filtering portion 16b having a storage portion for the filter 17 and a cylindrical portion 16c having a slightly smaller diameter are sequentially connected to the distal end side of 6a. In addition, this front part 16c may be cut to make the length of the filter unit 15 in the axial direction shorter. The filter 17 has a diameter of 25 mm, an average pore diameter of 0.5 μm (in the case of gas, particles of about 0.05 μm can be filtered), an effective filtration area of 4.0 cm ² , and a pressure resistance (at 25 ° C.) of 5.3 kgf / cm ² ( 5.3 × 10 ⁴ P
a), a polytetrafluoroethylene resin (PTF) having a heat resistant temperature of 60 ° C.
E) -made membrane filter is employed.

Next, a wafer storing method using the wafer case 10 according to this embodiment will be described. 2 to 4
As shown in (1), the wafer case 10 is assembled after cleaning the case parts. Further, a filter unit 15 is attached to the lid 13. A large number of silicon wafers 11 are stored in the main container 12. Thereafter, the lid 13 is closed via the hook lever portion 40 with the gasket 14 interposed therebetween. Thereby, the inside silicon wafer 11 is sealed well.

Next, as shown in FIG. 1A, the sealed wafer case 10 is placed in a vacuum vessel 30 which is an example of a sealed space. Then, vacuum vessel 3
The inside of the vacuum vessel 30 is depressurized by the vacuum pump 31 provided. By doing so, the air inside the container 30 is discharged. Moreover, at the same time, the air in the case is drawn out of the case via the filter unit 15. As a result, the inside of the case is also decompressed. In addition,
The internal air discharged from the case 10 is filtered by a filter 17 incorporated in the filter unit 15. Then, as shown in FIG. 1B, an N ₂ gas which is an example of an inert gas is supplied into the vacuum vessel 30. Thereby, the N ₂ gas is filled in the vacuum vessel 30. At the same time, the N ₂ gas in the vacuum vessel 30 is sucked through the filter unit 15 also into the wafer case 10 under reduced pressure. Thus, the wafer case 10
Is filled with N ₂ gas.

At this time, since the filter 17 is capable of filtering 99.9% or more of dust and dust having a size of 0.05 μm or more, when the N ₂ gas is supplied into the case, the fine dust in the outside air is extremely small. And dust can be filtered. Further, the gas filtration speed of the filter 17 is set to V
Since the pressure is set to / 1500 (mol / min), the pressure inside and outside the case can be made equal through the filter unit 15 in a maximum of about 30 minutes. As a result, the operation time for filling the wafer case 10 with the N ₂ gas can be reduced. Thereafter, the wafer case 10 is double-wrapped by an inner bag made of nylon (trade name of polyamide fiber) or polyethylene and an outer bag 19 made of an aluminum film while the wafer case 10 is filled with N ₂ gas. ,
Shipped to device factories using various transportation means.

Since the filter unit 15 containing the filter 17 is attached to the wafer case 10 as described above, it is possible to prevent the dust and the like floating in the vacuum vessel 30 from entering the case while keeping the N inside the case. _Two gases can be filled. By substituting the air in the wafer case 10 with the N ₂ gas, the adhesion of fine dust containing organic matter to the wafer is eliminated. Further, since the filter unit 15 having the filter 17 is simply assembled to the lid 13, the above-described effects can be obtained at a relatively low cost.

[0030]

According to the first to fifth aspects of the present invention,
When the air inside the wafer case is replaced with an inert gas, the replacement is performed through a filter, so that the inert gas can be filled in the wafer case while preventing intrusion of dust floating in the sealed space. . Further, since the inside of the wafer case is filled with the inert gas, surface contamination of the semiconductor wafer can be reliably prevented. The cleanliness of the semiconductor wafer can be maintained for a long time. Further, it is possible to prevent the quality of the semiconductor wafer from deteriorating.

In particular, according to the second aspect of the present invention, as a filter, 99.9 μm or more of dirt and dust is 99.9.
% Or more, so that when the inert gas is filled in the case, it is possible to filter fine particles in a closed space.

According to the third aspect of the present invention, when the volume of the wafer case is V as the filter, V /
The pressure difference between the inside and outside of the case can be released in a relatively short time because a gas whose flow rate is 1500 (mol / min) or more is used. As a result, the work time for filling the wafer case with the inert gas can be reduced.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing a step of discharging air inside a wafer case in a wafer storage method according to an embodiment of the present invention. (B) is an explanatory view showing a step of filling a wafer case with N ₂ gas according to one embodiment of the present invention.

FIG. 2 is an overall perspective view of a wafer case according to one embodiment of the present invention.

FIG. 3 is a front view of a wafer case according to one embodiment of the present invention.

FIG. 4 is a plan view of a wafer case according to one embodiment of the present invention.

FIG. 5 is an enlarged sectional view taken along the line AA of FIG. 2 while the lid is closed.

FIG. 6A is a partially enlarged cross-sectional view showing a structure of a joining portion between a container body and a lid. (B) is a schematic diagram for explaining compression deformation of the gasket.

FIG. 7 is an enlarged perspective view of a filter unit of a wafer case according to one embodiment of the present invention.

FIG. 8 is an enlarged sectional view of a use state of the filter unit of the wafer case according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 wafer case, 12 container body, 13 lid, 15 filter unit, 16 housing, 17 filter, 30 sealed space (vacuum container).

Claims (5)

[Claims] 1. A step of preparing a wafer case in which gas can flow in and out only through a filter in a sealed state, a step of storing and sealing a semiconductor wafer in the wafer case, and a step of storing the semiconductor wafer. A step of arranging the wafer case inside the sealed space, and by depressurizing the enclosed space in which the wafer case is arranged, exhausting the gas inside the wafer case from the filter to the outside of the wafer case, A step of depressurizing the inside of the case; and a step of supplying an inert gas into the closed space after the depressurizing step, thereby filling the inside of the wafer case with the inert gas through the filter. Method. 2. The wafer case includes a container body, a lid for sealing the container body, and a filter attached to at least one of the outer walls of the container body and the lid. 0.05 to internal pressure
In a wafer case in which the sealing property between the lid and the container body is maintained even when the pressure is lower by 0.2 atm, the gas inside and outside the wafer case can be circulated only through this filter, 2. The method according to claim 1, wherein the filter is capable of filtering 99.9% or more of fine dust having a size of 0.05 μm or more. 3. 3. When the volume of the wafer case is V liter, the filter is V / 1500 (mol /
3. The wafer storage method according to claim 2, wherein the gas is allowed to flow in and out at a value not less than (minute). 4. The filter according to claim 2, wherein the filter is a membrane filter made of tetrafluoroethylene resin.
3. The wafer storage method according to 1. 5. The wafer storage method according to claim 1, wherein the inert gas is a nitrogen gas.