US20090308784A1

US20090308784A1 - Wafer storage carrier

Info

Publication number: US20090308784A1
Application number: US12/478,046
Authority: US
Inventors: Katsuhiro Yoshino
Original assignee: Oki Semiconductor Co Ltd
Current assignee: Lapis Semiconductor Co Ltd
Priority date: 2008-06-13
Filing date: 2009-06-04
Publication date: 2009-12-17
Also published as: JP2009302287A; JP5118560B2

Abstract

It is an object of the invention to provide a wafer storage carrier that makes it possible to prevent wafers from being damaged or broken, regardless of the state of wafer warpage.

A top plate and two side wall plates secured to left and right edges of the top plate describe two rectangular open-ended sides. One of these rectangular open-ended sides is closed off by a rear wall plate. At least two support rods constituting a wafer support shelf are affixed to a central portion of the rear wall plate with respect to the transverse direction, extending toward the other rectangular open-ended side.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a wafer storage carrier for accommodating and transporting semiconductor wafers.
2. Description of the Related Art
Semiconductor wafers (hereinafter, simply referred to as “wafer(s)”) used as a material for semiconductor elements are obtained by thinly slicing ingots made of a substantially cylindrical silicon monocrystal to produce disk-shaped plates having a prescribed thickness. Wafers are typically manufactured at a thickness of approximately 0.5 to 1.0 mm in order to make them easier to handle during the semiconductor manufacturing steps, but thin wafers having a thickness of 150 μm or less are also produced to accommodate the dimensional and characteristic requirements of semiconductor devices.
Wafer storage carriers have conventionally been used to prevent contact between wafers when they are stored or moved between manufacturing steps used to manufacture semiconductor elements. A reason wafer storage carriers are used is to avoid any problems arising as a result of a wafer surface getting scratched when coming into contact with another wafer, the wafer breaking, the wafer surfaces electrostatically or otherwise sticking together, or other similar circumstances. Another reason is to allow a plurality of sliced wafers to be readily conveyed one at a time to the apparatuses used in a subsequent step.
Typical wafer storage carriers have a substantially cubic structure, with an opening present on one side and a space allowing the wafer to be accommodated inside the cube. For example, a wafer storage carrier 1 shown in FIG. 1( a) includes a top portion 2. The top portion 2 is connected to a left wall portion 3 and a right wall portion 4 that faces left wall portion 3. A bottom surface portion 5 is connected to the left wall portion 3 and the right wall portion 4 on a surface that faces the top portion 2. Furthermore, a rear surface wall portion 6 is provided to a region that closes off one of two rectangular opening-end sides formed by the top portion 2, the left wall portion 3, the right wall portion 4, and the bottom surface portion 5. In addition, a plurality of left and right protruding portions 7 are provided facing inward on the left wall portion 3 and the right wall portion 4, which are the sides disposed on the left and right with respect to the direction in which a wafer W is conveyed. The wafers W that are loaded into the interior of the wafer storage carrier are supported by the right and left protruding portions 7. Specifically, and as shown in FIG. 1( b), the wafer is supported by having an edge portion positioned in a pocket 8, which is a space between two vertically disposed protruding portions 7, whereby the wafer W is supported and accommodated within the wafer storage carrier 1.
In Patent Document 1, there is disclosed a wafer heat treatment apparatus for supporting both ends and the central portion of the wafer, thereby making it possible to prevent the wafer from warping during heat treatment.
[Patent Document 1] W02004/001835

SUMMARY OF THE INVENTION

The structures of the heat treatment apparatus disclosed in the Patent Document 1 and the wafer storage carrier 1 shown in FIG. 1 (hereunder, both the heat treatment apparatus and the wafer storage carrier 1 are referred to as “storage carrier”) are such that the edge portions of the wafer W are supported by a support portion (protruding portion 7 in FIG. 1) provided to left and right portions.
In a case where the wafer W is to be inserted into the storage carrier, the wafer W is typically inserted with the central portion supported. However, the position of the central portion and end portions of the wafer W with respect to the vertical direction will differ if the weight and finished configuration at the time of processing cause the wafer W to be in a warped state. Therefore, even in a case that the central portion of the wafer W is inserted into the storage carrier, both end portions of the wafer W might come into contact with the support portions of the storage carrier. The wafer W can be scratched or broken as a result of such contact.
Another problem with the wafer storage carrier 1 shown in FIG. 1 is that if the adjacent wafers W are warped in opposite directions, the wafers will contact each other in the central portion of the wafer W. Yet another problem is presented in the case that a wafer W is to be removed, wherein if adjacent wafers are in contact with each other or are closer than in their normal state (i.e., a state where non-warped wafers are disposed next to each other), an arm or another component of the loading/unloading apparatus may contact and/or break wafers other than the wafer W that is to be removed.
With the foregoing aspects of view, it is an object of the present invention to provide a wafer storage carrier that makes it possible to prevent wafer damage or breakage, regardless of the state of wafer warping.
To solve the problems, there is provided a wafer storage carrier comprising: a flat top plate; side wall plates secured to left and right ends of the top plate and disposed opposite each other; a rear wall plate for closing off one of two rectangular open-ended sides described by the top plate and the side wall plates; and a wafer support shelf having at least two support rods that are affixed in a central portion of the rear wall plate along a transverse direction and that extend towards the other rectangular opening surface.
The plane in which the wafer is supported by the wafer support shelf may be parallel to the top plate. There may be a plurality of wafer support shelves.
The support rods are made of metal and are clad in a Teflon® tube. The support rods may have a circular shape in cross-section.
The side wall plates and the rear wall plate may be capable of being detached from the top plate.
The wafers can be prevented from being damaged or broken, regardless of how warped they are, because the at least two support rods constituting the wafer support shelf and extending toward one of the two rectangular open-ended sides described by the two side wall plates secured to the top plate and the left and right edges thereof are affixed in the transversely central portion of the rear wall plate for closing off the other rectangular open-ended side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

EMBODIMENT 1

First, a wafer storage carrier 10 used as an embodiment of the present invention will be described in detail with reference to FIGS. 2( a), (b), (c), and FIG. 3. As shown in FIGS. 2( a), (b), (c), and FIG. 3, the wafer storage carrier 10 has a flat top plate 11. The top plate 11 is present in the X-Y plane, with the Z-axis direction being the direction perpendicular thereto. The left side wall plate 12 and the right side wall plate 13 are secured to either end of the top plate 11 with respect to the transverse direction; i.e., the X-axis direction, and are disposed opposite each other. The left side wall plate 12 and the right side wall plate 13 are secured to the top plate 11 with screws 14. Having the left side wall plate 12 and the right side wall plate 13 secured to the top plate 11 enables two rectangular open-end sides to be formed within the X-Z plane. Screws 15 are used to secure the rear wall plate 16 in a position that closes off one of the rectangular open-end sides (the surface located on the “+” side in direction Y as shown in FIG. 2( a)); i.e., on the ends of the left side wall plate 12 and the right side wall plate 13. The rectangular open-end side that is not closed off (which is located on the “−” side along direction Y as shown in FIG. 2( a)) is the opening surface where wafers are inserted or removed. Screws 19 are used to secure the left bottom plate 17 and right bottom plate 18 to edge portions that are different from the edge portions of the left side wall plate 12 and the right side wall plate 13 that are connected to the top plate 11. The left bottom plate 17 and the right bottom plate 18 are connected to the central portion by a linking rod 20. The linking rod 20 makes it possible to prevent displacement or warping occurring along the X-axis of the left side wall plate 12 and the right side wall plate 13. A wafer support area 21 is the space that is enclosed by the aforedescribed top plate 11, the left side wall plate 12, the right side wall plate 13, the rear wall plate 16, the left bottom plate 17, the right bottom plate 18, and the coupling rod 20. The top plate 11, the left side wall plate 12, the right side wall plate 13, the rear wall plate 16, the left bottom plate 17, and the right bottom plate 18 may be made of a carbon-free resin capable of preventing power from being interrupted.
A handle portion 22 for allowing the wafer storage carrier 10 to be readily carried is anchored to the top surface of top plate 11 (the surface opposite the support area 21). The handle portion 22 may, for example, be shaped substantially like the letter “U.”
A stopper 23 that extends along the Z-axis direction and has one end secured to the top plate 11 has another end secured to a prescribed location on the left bottom plate 17 and the right bottom plate 18. As shown in FIG. 2( a), the stoppers 23 are provided to position the wafers in the Y-axis direction when the wafers are accommodated, and are provided at locations where the wafers will neither contact the rear wall plate 16 once accommodated nor project from of the support area 21. The stopper 23 may be made of a non-metallic; e.g., plastic, material. The reason for this is that if the stopper 23 is made of a metallic material, the surface of the wafers might get contaminated by the metal because the stopper 23 comes into contact with the wafers.
A rectangular opening 24 that extends in the direction of the Z-axis is provided in the central portion of the rear wall plate 16 with respect to the direction of the X-axis. The rectangular opening 24 is provided so that a sensor or other device can be used to confirm therethrough whether or not a wafer is supported in the support area 21. A plurality of the support rods 25 that flank the opening 24 are affixed in the central portion of the rear wall plate 16 with respect to the transverse direction (i.e., the central portion in the direction of the X-axis). The support rods 25 extend from the rear wall plate 16 toward the side where the rectangular open-end sides are not closed off (the “−” side along direction Y). The support rods 25 are preferably made of metal and clad in a Teflon® tube. The reason for this is that since the support rods 25 contact the wafers, using unclad metal rods makes it likely that the wafer surfaces will get contaminated by the metal. In order to reduce the area of contact with the wafer, the cross-portion of the support rods 25 along the X-Z plane is preferably circular in shape. There now follows a description of the locations where the support rods 25 are to be embeddedly affixed in the rear wall plate 16.
A method for embeddedly affixing the support rods 25 into the rear wall plate will now be described in detail with reference to FIGS. 4( a) and (b).
As indicated in FIG. 4( a), through-holes 26 are formed in the locations on the rear wall plate 16 where the support rods 25 are affixed. The shape of the cross-section of the through hole 26 along the X-Z plane is substantially similar to that of the support rods 25, and is, for example, circular. In addition, the cross-section of the through-hole 26 along the Y-Z plane is a shape that has a predetermined step. Specifically, the through-hole 26 comprises a small opening 26 a that has a small diameter, and a large opening 26 b that has a large diameter. The diameter of the through-hole 26 is larger on the “+” side of the Y-axis (i.e., outside the wafer storage carrier 10), and smaller on the “−” side of the Y-axis (towards the support area 21). Saying that the through-hole is “large” or “small” merely indicates a relative difference; the diameter is not standardized in terms of an absolute value.
The diameter of a support portion 25 a of the support rods 25 is slightly smaller than the diameter of the small opening 26 a, and the diameter of the head portion 25 b of the support rods 25 is slightly smaller than the diameter of the large opening 26 b of the through-hole 26. By “slightly smaller” is meant that the diameters are small enough so that the support rods 25 can be insertably fitted into the through-holes 26, but there will be no instance of the support rods 25 being readily displaced in the direction of the Z-axis (e.g., slanting downward towards the “−” side in the direction of the Y-axis).
Accordingly, when the support rods 25 are insertably fitted into the through-holes 26 in the direction of arrow 3 a, a head portion 25 b of the support rods 25 will contact the step portion formed by the small opening 26 a and the large opening 26 b of the through-holes 26; therefore, the support rods 25 will be incapable of advancing any further towards the support area 21 than as shown in FIG. 4( b). A removable head cap (not shown) may also be insertably fitted so that the head portion 25 b will be covered in a state where the support rods 25 are fitted into the through-holes 26. The head cap makes it possible to prevent displacement of the support rods 25.
In a state where the support rods 25 are insertably fitted into the through-holes 26, the size of the head portion 25 b may be adjusted so that the rear wall plate 16 and the head portion 25 b will be coplanar. It is also possible to provide a prescribed groove to a part of the surface of the support rods 25 and the surface of the through-holes 26, and screw the support rods 25 into the through-holes 26.
There shall now be provided a detailed description of how the wafers are loaded, removed, and supported, with reference being made to FIG. 5.
As shown in FIG. 5, two support rods 25 are linearly provided in the direction of the X-axis so as to flank the opening 24 (i.e., so as to be situated next to one another with the opening 24 therebetween) on the rear wall plate 16. The two support rods 25 linearly affixed in the direction of the X-axis are symmetrically positioned with respect to each other to the left and right, with the axis of symmetry passing through the center of the rear wall plate 16 in the direction of the X-axis. The two support rods 25 that are linearly affixed in the direction of the X-axis are affixed at a substantially identical height in the direction of the Y-axis. As a pair, the two support rods 25 that are linearly affixed in the direction of the X-axis form a support shelf 41, which is shown by the dashed line. By “form a support shelf 41” is meant that since the two support rods 25 that are arranged in parallel to the direction of the X-axis support the wafers in parallel to the X-axis, the two support rods 25 function as a support shelf 41 that extends in the direction of the X-axis. Since the two support rods 25 that form the support shelf 41 are arranged in a line along the X-axis, the wafer support plane of the support shelf 41 is parallel to the top plate 11.
Twelve support rods 25 are linearly affixed on the rear wall plate 16 at a predetermined spacing in the direction of the Z-axis. Specifically, the twelve support rods 25 are affixed in a line in the direction of the Z-axis; i.e., the twelve support shelves 41 are formed by the support rods 25 in the support area 21. The number of support rods 25 is not limited to the number indicated in FIG. 5. Since the quantity will also change depending on the warping of the wafer and the dimensions of the wafer storage carrier 10, the number of support shelves 41 to be formed will also change.
Since the support rods 25 flank the opening 24 and are affixed in the central portion of the rear wall plate 16 with respect to the transverse direction, the edges of wafers to be loaded will not come into contact with the members constituting the support area 21, even in a case that the wafer warps upwards (the “+” side of the Z-axis) or downwards (the “−” side of the Z-axis). Accordingly, no consideration needs to be given to the position of the wafer edge in the direction of the Z-axis when the wafer is to be loaded, and it is possible to readily position and install the wafer based on the position of the central portion of each wafer in the Z-axis direction.
As shown in FIG. 5, wafers W1 through W5 are accommodated in the wafer storage carrier 10. The wafers W1, W2, and W4 warp to the upper side (the “+” direction of the Z-axis), the wafer W3 warps to the lower side (the “−” direction of the Z-axis), and the wafer W5 is not warped.
The gap between the ends of the differently warped wafer W2 and wafer W3 (i.e., the distance between the wafers W2 and W3) is small, but the gap in the central portion of the wafer is approximately the same or slightly larger. The gap in the central portion of the wafer is equivalent or greater than the pitch of the support rods 25; therefore, the arm of the wafer loading/unloading apparatus or other components do not contact adjacent wafers during the wafer unloading step. Accordingly, wafer warpage need not be a concern in the wafer removal process. Furthermore, since contact with the wafer edge is prevented, the width of the pitch of the support rods 25 may be set from approximately 4.76 to 9.52 mm, depending on the state of wafer warpage. For example, the through-holes 26 may be provided at a spacing of 2.38 mm or less along the Z-axis direction of the rear wall plate 16, and the position where the support rods 25 are to be insertably fitted may be determined according to the state of wafer warpage.
The gap between the edges of the wafer W3 and the wafer W4, which have different warp directions, is large, but in the central portion of the wafer the gap is approximately the same or slightly narrower than the pitch of the support rods 25. However, since the wafers are supported by the support rods 25 in the central portion, the degree to which warping causes the wafer to be displaced in the direction of the Z-axis in the central portion is extremely small, and no problems are presented in terms of the arm or other components of the wafer loading/unloading apparatus making contact with an adjacent wafer during the wafer removal step. Accordingly, wafer warpage need not be a concern during the wafer removal step, even when the wafers are supported as described above.
The central portion described above is preferably a position that is close to the center of the rear wall plate 16 in the direction of the X-axis, but includes conventional positions other than for supporting the wafer edges. Specifically, the support rods 25 may be affixed in a position of the rear wall plate 16 closer to the edge than the center in the direction of the X-axis.
Since the wafer storage carrier is secured using a plurality of screws, individual members can be removed, and broken ones individually replaced. Moreover, the fact that each member is removable means that individual members can be cleaned one at a time.
As mentioned above, according to the wafer storage carrier 10 of the present embodiment, wafer damage or breakage can be prevented, regardless of how warped the wafers are, because the at least two support rods 25 constituting the wafer support shelf 41 and extending toward one of the two rectangular open-ended sides described by the left side wall plate 12 and the right side wall plate 13 secured to the top plate 11 and the left and right edges of top plate 11 are affixed in the transversely central portion of the rear wall plate 16 for closing off the other rectangular open-ended side.

EMBODIMENT 2

In Embodiment 1, two rows of support rods 25 are formed on the rear wall plate 16 flanking the opening 24 along the Z-axis; however, the support rods 25 may also be embeddedly affixed so as to form two or more rows of support rods 25 on each of the left and right sides of the opening 24. A wafer storage carrier of such description will be described in detail below with reference to FIGS. 6 and 7. Components that are the same as those in Embodiment 1 are indicated by the same symbols used in Embodiment 1 without the attendant description.
As shown in FIG. 6, pairs of support rods 25 are linearly provided in the rear wall plate 16 along the side of the X-axis and the “+” side of the X-axis, respectively, with the opening 24 in the center. The two support rods 25 linearly provided in the direction of the X-axis are symmetrically positioned with respect to each other to the left and right, with the axis of symmetry passing through the center of the rear wall plate 16 in the direction of the X-axis. The four support rods 25 linearly affixed along the X-axis are affixed at a substantially identical height in the direction of the Y-axis. As a set, the four support rods 25 linearly affixed along the X-axis form a support shelf 51, which is indicated by the dashed line. Since the support shelf 51 is formed merely by changing the number of rods used in Embodiment 1 from two to four, the description of how the support shelf 51 is formed is not given. As in Embodiment 1, the supporting plane of the support shelf 51 is parallel to the top plate 11.
Twelve support rods 25 are linearly provided at a predetermined spacing in the direction of the Z-axis, as in Embodiment 1; therefore, four rows of support rods 25 are formed in the direction of the Z-axis.
The wafer storage carrier 50 of Embodiment 2 has a larger number of support rods 25 in the X-axis, giving it an advantage over the wafer storage carrier 10 of Embodiment 1 in that the wafer can be more stably held.
As shown in FIG. 7, it is possible to remove only those of the support rods 25 linearly affixed in the direction of the X-axis that are close to the opening 24. Specifically, the position in which the support rods 25 are linearly affixed along the direction of the X-axis may be selectively changed depending on wafer warpage. In FIG. 7, four of the through-holes 26 are provided along the direction of the X-axis, but increasing the number of through-holes 26 disposed along the X-axis gives increased flexibility in terms of the positions in which the wafer can be supported.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is (a) a front view of a conventional wafer storage carrier, and (b) a magnified view of a portion of (a) that is enclosed by the dashed-dotted line 1 b;

FIG. 2 is (a) a top view of the wafer storage carrier according to Embodiment 1 of the present invention, (b) a front view of the wafer storage carrier according to Embodiment 1 of the present invention, and (c) a right side view of the wafer storage carrier according to Embodiment 1 of the present invention;

FIG. 3 is a perspective view of the wafer storage carrier according to Embodiment 1 of the present invention;

FIG. 4 is (a) a cross-sectional view of the wafer storage carrier according to Embodiment 1 of the present invention before the affixed portion of the support rods has been affixed, and (b) a cross-sectional view of the wafer storage carrier according to Embodiment 1 of the present invention after the affixed portion of the support rods has been affixed;

FIG. 5 is a front view of the wafer storage carrier according to Embodiment 1 of the present invention;

FIG. 6 is a front view of the wafer storage carrier according to Embodiment 2 of the present invention; and

FIG. 7 is a front view of the wafer storage carrier according to Embodiment 2 of the present invention.

This application is based on Japanese Patent Application No. 2008-155128 which is hereby incorporated by reference.

Description of Reference Numerals

10 Wafer storage carrier
11 Top plate
12 Left side wall plate
13 Right side wall plat
16 Rear wall plate
17 Left bottom plate
18 Right bottom plate
20 Linking rod
21 Support area
22 Handle portion
23 Stopper
24 Opening
25 Support rod
26 Through-hole
W1-W5 Wafer

Claims

1. A wafer storage carrier comprising:

a flat top plate;

side wall plates secured to left and right ends of said top plate so as to face one another;

a rear wall plate for closing off one of two rectangular open-ended sides formed by said top plate and said side wall plate; and

a wafer support shelf having at least two support rods that are embeddedly affixed in a central portion of the said rear wall plate along a transverse direction and that extend towards another one of said rectangular open-ended sides.

2. The wafer storage carrier of claim 1, wherein a wafer support surface of said wafer support shelf is parallel to said top plate.

3. The wafer storage carrier of claim 1, wherein a plurality of wafer support shelves are present.

4. The wafer storage carrier of claim 1, wherein the support rods are made of metal and are clad in a Teflon® tube.

5. The wafer storage carrier of claim 3, wherein said support rods are circular in cross-section.

6. The wafer storage carrier of claim 1, wherein said side wall plate and said rear wall plate are capable of being detached from said top plate.