WAFER STORAGE CONTAINER CLEANING APPARATUS, AND WAFER STORAGE CONTAINER CLEANING METHOD

A wafer container cleaner includes a cleaning bath capable of accommodating a housing jig that houses a wafer container including a container body and a cover, liquid-supply nozzles for supplying cleaning liquid or the like into the cleaning bath, and a liquid-discharge nozzle for discharging to-be-discharged fluid out of the cleaning bath. The container body has a depth wall at a side opposite a container opening. In an accommodating state where the container body mounted on the storage fixture with the container opening facing downward is accommodated in the cleaning bath, the liquid-supply nozzles are provided so that respective liquid-supply openings through which the cleaning liquid or the like is discharged face an inner side of the depth wall and the liquid-discharge nozzle is provided so that a discharge opening through which the to-be-discharged fluid is sucked in faces a center of the inner side of the depth wall.

TECHNICAL FIELD

The present invention relates to a wafer container cleaner for cleaning a wafer container including a container body for storing a plurality of wafers and a cover for closing a container opening of the container body and a cleaning method of the wafer container.

BACKGROUND ART

Typical cleaning methods of a wafer container are a shower method and an immersion method. The shower method uses cleaning liquid or cleaning water (e.g. pure water), which is directly sprayed onto a wafer container to clean the wafer container. In the immersion method, a wafer container is immersed in a first cleaning bath filled with cleaning liquid and then is immersed in a second cleaning bath filled with cleaning water to remove the cleaning liquid.

Patent Literature 1 discloses a cleaning method of a wafer container, which includes: a local cleaning step of locally cleaning a part of a container body of the wafer container in contact with a packing using a high-pressure jet or the like; and an overall cleaning step of cleaning the entirety of the wafer container by the shower method or the immersion method.

CITATION LIST

Patent Literature 1 JP 2020-72215 A

SUMMARY OF THE INVENTION

Problem(s) to be Solved by the Invention

As depicted inFIG.9, a container body11of a typical wafer container is provided with, for instance, a depth wall11A at a side opposite a container opening11B. At an inner side of the depth wall11A, a central cavity22is provided at the center of the depth wall11A and peripheral cavities21A and21B are provided around the central cavity22. Further, convex portions23A and23B are provided between the peripheral cavities21A and21B and the central cavity22.

When the container body11is immersed in the cleaning liquid or the like in the cleaning bath of the wafer container cleaner with the container opening11B facing downward, air is sometimes left at the peripheral cavities21A and21B and the central cavity22. In this case, the cleaning liquid or the like does not reach the peripheral cavities21A and21B and the central cavity22, failing to sufficiently clean the wafer container.

Further, a cover12of the wafer container is provided with a pair of latch mechanisms24(seeFIG.10A) for fixing and locking the cover12with the container body11and a front retainer25(seeFIG.10B) for pressing and fixing a wafer onto an inner side of the container body11. When the cover12is to be cleaned by the shower method or the immersion method, the cleaning liquid or the like sometimes does not reach minute parts and hollows of the latch mechanisms24, the front retainer25and the like, thereby failing to sufficiently clean the wafer container.

In addition, according to the immersion method, though the container body11is immersed in the cleaning water after immersing the container body11in the cleaning liquid, the cleaning liquid sometimes cannot be washed out by the cleaning water to be left in a form of residual cleaning liquid inside the container body11. The residual liquid sometimes deteriorates the container body11with age or causes appearance defects (e.g. stain caused by water scale).

The related art disclosed in Patent Literature 1, which is not constructed in consideration of the above problems, fails to solve the above problems.

Thus, a wafer container cleaner and a cleaning method of the wafer container capable of improving cleaning performance for the wafer container have been desired.

An object of the invention is to provide a wafer container cleaner and a cleaning method of the wafer container capable of improving cleaning performance for the wafer container.

Means for Solving the Problem(s)

A wafer container cleaner according to an aspect of the invention is configured to clean a wafer container including a container body configured to store a plurality of wafers and a cover configured to close a container opening of the container body, the wafer container being housed in a housing jig that allows fluid circulation therethrough, the wafer container cleaner including: a cleaning bath configured to accommodate the housing jig housing the wafer container; a plurality of liquid-supply nozzles configured to supply cleaning liquid or cleaning water into the cleaning bath; and a liquid-discharge nozzle configured to discharge to-be-discharged fluid out of the cleaning bath, in which the container body includes a depth wall at a side opposite the container opening, at least one of the plurality of liquid-supply nozzles includes a liquid-supply opening through which the cleaning liquid or the cleaning water is discharged, the liquid-supply opening facing an inner side of the depth wall in an accommodating state where the container body mounted on the housing jig with the container opening facing downward is accommodated in the cleaning bath, and the liquid-discharge nozzle includes a discharge opening through which the to-be-discharged fluid is sucked in, the discharge opening facing a center of the inner side of the depth wall in the accommodating state.

In the wafer container cleaner according to the above aspect of the invention, a supply flow rate for supplying the cleaning liquid or the cleaning water into the container body is set larger than a discharge flow rate for discharging the cleaning liquid or the cleaning water from an inside of the container body through the liquid-discharge nozzle.

The wafer container cleaner according to the above aspect of the invention further includes an immersion-takeout movement mechanism configured to move the housing jig to an immersed state for the housing jig to be immersed in the cleaning liquid or the cleaning water in the cleaning bath and to a pulled-up state for the housing jig to be pulled up out of the cleaning liquid or the cleaning water from the immersed state.

A method for cleaning a wafer container according to another aspect of the invention is for cleaning a wafer container including a container body configured to store a plurality of wafers and a cover configured to close a container opening of the container body, the wafer container being housed in a housing jig that allows fluid circulation therethrough, the container body including a depth wall at a side opposite the container opening, the method including: immersing the housing jig housing the wafer container with the container opening of the container body facing downward in the cleaning bath filled with cleaning liquid or cleaning water, in which in an immersed state of the wafer container, the cleaning liquid or the cleaning water is supplied toward an inner side of the depth wall and to-be-discharged fluid is discharged from a region near a center of the inner side of the depth wall.

In the method for cleaning the wafer container according to the above aspect of the invention, in the immersion step, a supply flow rate for supplying the cleaning liquid or the cleaning water into the container body is set larger than a discharge flow rate for discharging the cleaning liquid or the cleaning water out of the container body.

The method for cleaning the wafer container according to the above aspect of the invention further includes causing at least one reciprocating movement of the housing jig between an immersed state for the housing jig to be immersed in the cleaning liquid or the cleaning water in the cleaning bath and a pulled-up state for the housing jig to be pulled up out of the cleaning liquid or the cleaning water from the immersed state.

According to the above aspects of the invention, cleaning performance of the wafer container can be improved.

DESCRIPTION OF EMBODIMENT(S)

Structure of Wafer Container Cleaner1

As depicted inFIGS.1to3, a wafer container cleaner1is configured to clean a wafer container2including a container body11configured to store a plurality of wafers and a cover12configured to close a container opening11B of the container body11, the wafer container2being housed in a housing jig3that allows fluid circulation therethrough.

The wafer container cleaner1includes a cleaning bath31, a plurality of liquid-supply nozzles32(eight liquid-supply nozzles32A to32H in the present exemplary embodiment), a plurality of side liquid-supply nozzles33(two side liquid-supply nozzles33A and33B in the present exemplary embodiment), a liquid-discharge nozzle34, and an immersion-takeout movement mechanism35.

The cleaning bath31is sized to be capable of accommodating the housing jig3housing the wafer container2. The cleaning bath31, which is in a form of a substantially rectangular box, has a bath opening31A at an upper end thereof.

In an accommodating state where the container body11(a frame drawn by a dash-dotted line DL inFIG.2) mounted on the housing jig3with the container opening11B facing downward is accommodated in the cleaning bath31, each of the liquid-supply nozzles32A to32H is configured to discharge cleaning liquid or cleaning water (e.g. pure water) through respective liquid-supply openings32AA to32HA thereof toward the depth wall11A of the container body11(seeFIGS.1and6).

As depicted inFIG.2, the liquid-supply nozzles32A to32H, which are each connected in series by connector pipes36A to36D to define a C-shape, are connected with a liquid-supply pipe37through a connector pipe36E.

The connector pipe36A is connected to each of lower ends of the liquid-supply nozzles32A to32C and the connector pipe36B. The connector pipe36B is connected to each of lower ends of the liquid-supply nozzles32A,32D, and32F and the connector pipes36C and36E. The connector pipe36C is connected to each of lower ends of the liquid-supply nozzles32F to32H and the connector pipe36D. The connector pipe36D is connected to each of lower ends of the liquid-supply nozzles32E and32H.

As depicted inFIG.1, an upper end37A of the liquid-supply pipe37penetrates through a bath bottom31B of the cleaning bath31to be connected with the connector pipe36E in the cleaning bath31. A lower end37B of the liquid-supply pipe37is connected to a liquid-supply pump (not depicted).

In the accommodating state where the container body11mounted on the housing jig3with the container opening11B facing downward is accommodated in the cleaning bath31, the liquid-discharge nozzle34penetrates through the bath bottom31B so that a discharge opening34A, through which to-be-discharged fluid is sucked in, is located close to the center of the inner side of the depth wall11A (seeFIGS.1and6). A lower end34B of the liquid-discharge nozzle34is connected to a liquid-discharge pump (not depicted). It should be noted that the height of the liquid-discharge nozzle34is substantially equal to the height of each of the liquid-supply nozzles32A to32H in the present exemplary embodiment.

A distance between the depth wall11A of the container body11and the liquid-supply openings32AA to32HA in the accommodating state is, though being different depending on the type of the container body11and the shape of the depth wall11A, preferably 50 mm or less, for instance. With the above distance being 50 mm or less, the cleaning liquid reaches every part of the depth wall11A to allow the interior of the container body11to be sufficiently cleaned. A fluid introduction unit (e.g. projection(s)), which is optionally provided at an end of the liquid-discharge nozzle34, is optionally in contact with the depth wall11A. In this arrangement, the to-be-discharged fluid and air can be vigorously sucked through a space, which is created between the depth wall11A and the discharge opening34A.

Side liquid-supply nozzles33A and33B are provided substantially at the center of an inner side of respective side walls31C and31D (right and left facing walls inFIG.2) of the cleaning bath31. In the same manner as the liquid-supply nozzles32A to32H, the side liquid-supply nozzles33A and33B are connected to a liquid-supply pump (not depicted). The side liquid-supply nozzles33A and33B are configured to discharge cleaning liquid or pure water toward the center of the cleaning bath31to clean an outer wall of the container body11and/or one side of the cover12.

Next, the housing jig3for housing the container body11and the cover12will be described with reference toFIG.4. InFIG.4, the housing jig3is depicted in broken lines and the latch mechanisms24and the front retainer25depicted inFIG.10Aare not depicted on the cover12. It should be noted thatFIGS.1,5, and6are depicted in a similar fashion.

The housing jig3is sized to be capable of housing the container body11and the cover12. The housing jig3, which is constructed by, for instance, assembling resin-made pipes into a rectangular parallelepiped whose sides are defined by coarse grids, allows fluid circulation therethrough. The components of the sides of the housing jig3constructed in a form of a rectangular parallelepiped are capable of being assembled and disassembled by loosening/fastening screws, nuts, and any other appropriate fasteners (not depicted) or by attaching/detaching joints (not depicted) for connecting the pipes. A lower opening3A is formed at a lower end of the housing jig3. The lower opening3A and the container opening11B are rectangles that are similar to each other, where the periphery of the lower opening3A is supported by the periphery of the container opening11B to house the container body11in the housing jig3.

As depicted inFIGS.1,5, and6, the immersion-takeout movement mechanism35is configured to move the housing jig3housing the container body11and the cover12to an immersed state for the housing jig3to be immersed in the cleaning liquid or the cleaning water in the cleaning bath31and to a pulled-up state for the housing jig3to be pulled up out of the cleaning liquid or the cleaning water from the immersed state. The immersion-takeout movement mechanism35is depicted as a pair of bent components inFIGS.1,5, and6. However, the actual immersion-takeout movement mechanism35is provided by a robot that is provided with a holder for holding an upper side of the housing jig3and is configured to move the housing jig3to the immersed state and the pulled-up state and to transfer the housing jig3to other location(s).

Cleaning Method of Wafer Container

Next, a cleaning method of the wafer container2with a use of the wafer container cleaner1constructed as described above will be described below with reference toFIGS.1,5, and6.

Initially, using the immersion-takeout movement mechanism35, the housing jig3, which houses the container body11and the cover12with the container opening11B facing downward, is immersed in the cleaning bath31filled with the cleaning liquid as depicted inFIG.1(immersion step).

Subsequently, the liquid-supply pump (not depicted) is driven to supply the cleaning liquid to the liquid-supply nozzles32A to32H through the liquid-supply pipe37and the connector pipes36A to36E to discharge the cleaning liquid through the liquid-supply openings32AA to32HA, and, simultaneously, to supply the cleaning liquid to the side liquid-supply nozzles33A and33B to discharge the cleaning liquid toward the center of the cleaning bath31, so that the cleaning liquid overflows from the bath opening31A of the cleaning bath31. Further, the liquid-discharge pump (not depicted) is driven to suck in the to-be-discharged fluid through the discharge opening34A of the liquid-discharge nozzle34to discharge the to-be-discharged fluid out of the cleaning bath31.

By driving the liquid-supply pump and the liquid-discharge pump as described above, flows of the cleaning liquid and the to-be-discharged fluid are caused as depicted by arrows inFIG.1.

As the immersion-takeout movement mechanism35immerses the housing jig3into the cleaning liquid toward the bath bottom31B of the cleaning bath31, the air in the container body11, which is sucked in through the liquid-discharge nozzle34together with the to-be-discharged fluid, is gradually discharged from the inside of the container body11.

It should be noted that, when the housing jig3eventually reaches the bath bottom31B, the air possibly remains in the peripheral cavities21A and21B and the central cavity22of the container body11.

However, in the accommodating state depicted inFIG.1, the liquid-supply openings32AA to32HA of the liquid-supply nozzles32A to32H are provided to be close to the inner side of the depth wall11A of the container body11and the discharge opening34A of the liquid-discharge nozzle34is provided to be close to the center of the inner side of the depth wall11A. In this state, the cleaning liquid is supplied toward the inner side of the depth wall11A and the to-be-discharged fluid is discharged from a region near the center of the inner side of the depth wall11A.

The above-described arrangement and operation allow the air remaining in the peripheral cavities21A and21B and the central cavity22to be displaced and concentrated at the region near the center of the inner side of the depth wall11A. The remaining air is thus discharged through the discharge opening34A together with the to-be-discharged fluid out of the container body11. Accordingly, the cleaning liquid can reach the peripheral cavities21A and21B and the central cavity22, so that the interior of the container body11can be sufficiently cleaned. In the exemplary embodiment, the plurality of liquid-supply nozzles32A to32H are located to surround the liquid-discharge nozzle34. Accordingly, air that is likely to be left at the depth wall11A of the container body11can be efficiently discharged.

The outer wall of the container body11and the cover12are cleaned by the cleaning liquid discharged through the side liquid-supply nozzles33A and33B toward the center of the cleaning bath31. At this time, since the housing jig3is configured to allow fluid circulation therethrough, the cleaning liquid, whose power is hardly reduced by the housing jig3, reaches the outer wall of the container body11and the cover12, so that the outer wall of the container body11and the cover12can be sufficiently cleaned.

In the immersion step, a supply flow rate for supplying the cleaning liquid into the container body11is set larger than a discharge flow rate for discharging the cleaning liquid out of the container body11. The cleaning liquid thus overflows from the container opening11B as depicted inFIG.1after the cleaning liquid reaches all parts of the container body11. Accordingly, circulation efficiency of the cleaning liquid in the container body11is improved as compared with an instance for discharging the cleaning liquid only through the liquid-discharge nozzle34, thereby further improving the cleanability of the wafer container2.

Subsequently, the immersion-takeout movement mechanism35causes at least one reciprocating movement of the housing jig3housing the container body11and the cover12between the pulled-up state (seeFIG.5) (i.e. a state where the housing jig3is pulled up out of the cleaning liquid from the immersed state where the housing jig3is immersed in the cleaning liquid in the cleaning bath31depicted inFIG.1) and the immersed state (seeFIG.6) (i.e. a state where the housing jig3is immersed in the cleaning liquid in the cleaning bath31) (immersion-pull-up movement step). In the immersion-pull-up movement step, the number of the reciprocating movements is preferably in a range from 1 to 5, more preferably approximately 3. The cleaning effect is small without the reciprocating movement. In contrast, work efficiency is lowered with 6 or more reciprocating movements.

The cleaning liquid, whose flow on the surface of the cover12is caused by the immersion-pull-up movement step, can reach minute parts and hollows of the latch mechanisms24, front retainer25, and the like depicted inFIG.10A, so that sufficient cleaning can be performed. In addition, remaining contamination (e.g. particles) on the container body11and the cover12can be reduced. Accordingly, the cleanability of the wafer container2can be improved.

A movement speed of the housing jig3between the pulled-up state and the immersed state is preferably determined so that the work efficiency can be improved without causing residual liquid on the container body11and the cover12.

After cleaning the wafer container2with the use of the cleaning liquid as described above, the immersion-takeout movement mechanism35moves the housing jig3housing the wafer container2to the wafer container cleaner1provided with the cleaning bath31filled with cleaning water (e.g. pure water), where the immersion step and the immersion-pull-up movement step are performed.

When the wafer container2is cleaned with the use of the cleaning water, the cleaning liquid can be more efficiently washed out than a typical arrangement, by supplying the cleaning water to the peripheral cavities21A and21B, discharging the liquid from a region near the central cavity22, overflowing the cleaning water from the container opening11B, and improving the cleaning effect by the immersion-pull-up movement step as described above in the operation using the cleaning liquid. Consequently, the cleaning liquid is more unlikely to remain on the container body11and the cover12. Accordingly, deterioration with age and appearance defects are unlikely to be caused on the container body11and the cover12.

Modifications

It should be noted that the specific arrangement of the invention, which is not limited by the exemplary embodiments of the invention described in detail with reference to the attached drawings, encompasses improvements, design modifications and the like as long as such improvements, modifications and the like are compatible with an object of the invention.

For instance, the liquid-supply nozzles32A to32H and the liquid-discharge nozzle34, which are fixed in the exemplary embodiment, are not necessarily configured as described in the exemplary embodiment. Specifically, the liquid-supply nozzle(s)32and the liquid-discharge nozzle34are optionally configured to be exchangeable with corresponding components of different lengths or capable of slightly moving up and down depending on the shape of the container body11. In this case, by arranging the liquid-supply nozzles32A to32H and the liquid-discharge nozzle34so that the height of the liquid-discharge nozzle34is equal to or different from the height of each or one or more of the liquid-supply nozzles32A to32H or the heights thereof are adjustable depending on the shape of the depth wall of the container body11, the liquid-supply nozzles32A to32H and the liquid-discharge nozzle34can be adapted to a plurality of types of wafer containers2with different shapes (e.g. without the peripheral cavities21A and21B and/or the central cavity22on the depth wall11A).

A fluid introduction unit (e.g. projection(s)) is optionally provided at an end of each of the liquid-supply nozzles32A to32H. The distance between the liquid-supply openings32AA to32HA and the depth wall11A in the accommodating state can be defined by the height of the fluid introduction unit to be in contact with the depth wall11A. The distance between the depth wall11A of the container body11and the liquid-discharge opening34A in the accommodating state is, though being different depending on the type of the container body11and/or the shape of the depth wall11A, for instance, preferably 50 mm or less. With the above distance being 50 mm or less, the to-be-discharged fluid and air can be sufficiently sucked in from various parts of the depth wall11A.

Alternatively, as illustrated inFIG.7A, a metal or resin-made in-liquid ejection nozzle41is optionally attached to an end of each of the liquid-supply nozzles32A to32H. The in-liquid ejection nozzle41, from which fluid is ejected in the liquid, sucks in the cleaning liquid or cleaning water near the in-liquid ejection nozzle using the negative pressure caused by the ejected fluid, thereby ejecting the cleaning liquid or cleaning water at a flow rate three to four times larger than the supply flow rate of the liquid-supply pump. With the in-liquid ejection nozzle41, the circulation efficiency of the cleaning liquid or cleaning water is improvable.

As illustrated inFIG.7B, a cylindrical float42, which has fluid introduction units42A (e.g. projection(s)), is optionally loosely fitted to an end of the liquid-discharge nozzle34. The float42, which rises by buoyant force in the cleaning liquid or cleaning water to bring the fluid introduction units42A into contact with the depth wall11A, creates a space between the depth wall11A and the discharge opening34A to allow the to-be-discharged fluid and air to be vigorously sucked in. The float42, which is not necessarily provided, can improve the circulation efficiency of the cleaning liquid or the cleaning water once provided. In addition, the float42allows the to-be-discharged fluid to be constantly sucked in from a region near the depth wall11A irrespective of an immersion depth of the wafer container2.

The eight liquid-supply nozzles32A to32H, the two side liquid-supply nozzles33A and33B, and the single liquid-discharge nozzle34are exemplarily arranged as depicted inFIG.2in the exemplary embodiment. However, the number and location of the liquid-supply nozzle(s)32, the side liquid-supply nozzle(s)33, and the liquid-discharge nozzle(s)34are not limited to those of the exemplary embodiment. For instance, in place of or in addition to the side liquid-supply nozzles33A and33B, a side liquid-supply nozzle33is optionally provided substantially at the center of an inner side of each of the side walls31E and31F (vertically facing with each other inFIG.2) of the cleaning bath31.

The supply flow rate for supplying the cleaning liquid or cleaning water into the container body11, which is exemplarily set larger than the discharge flow rate for discharging the cleaning liquid or cleaning water out of the container body11through the liquid-discharge nozzle34in the exemplary embodiment, is not necessarily larger than the discharge flow rate. However, the supply flow rate larger than the discharge flow rate can achieve the above-described advantages.

Further, the housing jig3, which is constructed by assembling resin-made pipes into a rectangular parallelepiped whose sides are defined by coarse grids in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. The housing jig3is optionally in any form (e.g. assembling wire materials into a rectangular parallelepiped whose sides are defined by coarse grids) capable of housing the wafer container2and allowing the fluid circulation therethrough.

The immersion-takeout movement mechanism35, which is configured to perform the transfer step for transferring the housing jig3to another location in addition to the immersion step and the immersion-pull-up movement step in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. For instance, the immersion-takeout movement mechanism35is optionally dedicated to perform the immersion step and the immersion-pull-up movement step, where the transfer step of the housing jig3is performed by some other component(s).

Examples

Next, Examples of the invention will be described below. It should be noted that the scope of the invention is by no means limited to these Examples.

In Example 1, the immersion step was solely performed with the use of the wafer container cleaner1according to the exemplary embodiment. In Example 2, the immersion step and the immersion-pull-up movement step were performed with the use of the wafer container cleaner1. In contrast, a shower method was employed in Comparative 1. Subsequently, after the cleaned container body11was filled with pure water, an average number of particles having a particle diameter of 0.1 μm or more that were present per 0.1 ml pure water was measured in all of Examples 1 and 2 and Comparative 1.

The used wafer container was FOSB (Front Opening Shipping Box) manufactured by Miraial Co., Ltd. used for transporting and shipping wafers in all of Examples 1 and 2 and Comparative 1. The particles in the liquid were measured with a use of a particle sensor KS-40A manufactured by RION Co., Ltd.

Table 1 andFIG.8show examples of results of measuring, after filling the container body cleaned according to Examples 1 and 2 and Comparative 1 with pure water, the average number of particles having a particle diameter of 0.1 μm or more that were present in the 0.1 ml pure water.

Evaluation

In Comparative 1 using the shower method, the average number of the particles having a particle diameter of 0.1 μm or more was 1.08, which shows low cleaning performance. In contrast, according to Example 1 using the immersion method, the average number of the particles was 0.72, which shows improved cleaning performance as compared with Comparative 1. In Example 2, the average number of the particles was reduced to 0.61, which shows significantly improved cleaning performance.

EXPLANATION OF CODES