FOUP

Abstract

To provide a FOUP suitable for transporting and storing a thin wafer.SOLUTION: A FOUP includes a cassette having an opening for loading and unloading a semiconductor substrate and an internal space for housing the semiconductor substrate, and a door provided in the opening so as to be openable and closable, the cassette includes wafer teeth on inner surfaces of both side walls, the wafer teeth are provided with supporting ridges that support the semiconductor substrate, a portion including at least the tip of the supporting ridge is inclined downward toward the inside, and the height of the tip is higher than the height of the portion where the outer edge of the semiconductor substrate housed in the predetermined position is located by 70 μm or more.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a FOUP, which is a semiconductor transport container for transporting, storing, etc., semiconductor substrates with a diameter of 300 mm, and in particular to a FOUP for thin wafers. [Background technology]

[0002] In the field of semiconductor technology, semiconductor transport containers with clean interiors are used to transport and store semiconductor substrates in a clean environment, and FOUPs (Front Opening Unified Pods) are used as containers for semiconductor substrates with a diameter of 300 mm (Non-Patent Document 1).

[0003] The FOUP has a cassette having an opening for loading and unloading semiconductor substrates and an internal space for accommodating the semiconductor substrates, and a door that is provided at the opening so as to be able to be opened and closed. The cassette has an internal space that is generally symmetrical when viewed from the opening, and has a pair of wafer teeth on the inner surfaces of both side walls. The wafer teeth have a number of support pieces, and support ridges are formed on the upper surfaces of the support pieces that extend inward. The semiconductor substrate is placed on the support ridges. The door is provided with a retainer on its inner surface for lightly pressing the semiconductor substrate toward the rear when the door is closed, so that the semiconductor substrate does not move.

[0004] The semiconductor substrate has an edge exclusion area (EDA) on its periphery that cannot be used in semiconductor manufacturing, and a fixed quality area (FQA) that is used in semiconductor manufacturing inside the edge exclusion area. According to SEMI standards, the thickness of a 300 mm diameter wafer is 775 μm. However, among 300 mm diameter wafers, there are thin wafers with a thickness of 200 μm or less in order to miniaturize semiconductor chips. Since thin wafers are as thin as 200 μm or less, even silicon wafers made of metal crystals, for example, become flexible and have a problem of poor handling. In order to improve the handling of thin wafers, TAIKO wafers have been proposed in which only the inner part of the wafer is ground to form a thin film part while leaving the outer periphery intact (Patent Documents 1 and 2, Non-Patent Document 2).

[0005] FIG. 9 shows a schematic diagram of a conventional FOUP containing multiple thin wafers W, which are TAIKO wafers, as viewed from the opening side, and an enlarged schematic diagram of the support piece portion. The cassette is provided on the inner surface of both side walls with a pair of left and right wafer teeth 11. Wafer teeth 11 are provided with a plurality of support pieces 12 arranged at regular intervals in the vertical direction, and support ridges 13 are formed on the upper surfaces of support pieces 12 and extend inward. The thin wafer W accommodated in the container has its thin film portion bent downward, but the portion supported by the supporting ridges 13 cannot bent. Therefore, the portion of the thin wafer W supported by the supporting ridges 13, particularly the portion in contact with the tip 13E of the supporting ridges, is more deformed than other portions, and the load is concentrated thereon. This portion where the load is concentrated, specifically the portion in contact with the tip 13E and its surrounding area, is prone to defects and cannot be used in semiconductor manufacturing, which may reduce the number of chips that can be obtained from one wafer, resulting in a lower yield.

[0006] 9, the wafer teeth 11 are provided with a plurality of support pieces 12 spaced about 10 to 20 mm apart above and below, but if the thin wafer W bends downward, the gap for inserting a transfer arm (about 6 mm thick) between the thin wafers W stored above and below becomes narrow, which may result in transfer failure. In order to provide a sufficient gap between the thin wafers W stored above and below, the thin wafers W are stored by spacing the support pieces 12 of the wafer teeth 11 one level apart, but this reduces the number of wafers that can be stored in one FOUP by half or more, reducing productivity and at least doubles the number of FOUPs required.

[0007] Furthermore, when a thin wafer is placed in a FOUP and the door is closed, the retainer on the inside of the door gently presses the thin wafer towards the back, which can cause cracks in the thin wafer. If a crack occurs in a thin wafer, fragments fly off and contaminate the inside of the FOUP, rendering not only the cracked wafer but all the wafers stored there defective, resulting in a significant drop in yield. In addition, a FOUP with a crack cannot be used until cleaning and drying are completed, so it is necessary to have a spare FOUP on hand to avoid a drop in productivity. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2007-19461 A [Patent Document 2] JP 2007-35756 A [Non-patent literature]

[0009] [Non-Patent Document 1] SEMI Standard E47.1, “MECHANICAL SPECIFICATION FOR FOUPS USED TO TRANSPORT AND STORE 300mm WAFERS” [Non-Patent Document 2] TAIKO Process, [online], retrieved on December 2, 2020, DISCO Corporation, Internet<URL:https: / / www.disco.co.jp / jp / solution / library / grinder / taiko_process.html> Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a FOUP that is particularly suitable for transporting and storing thin wafers. [Means for solving the problem]

[0011] The means for solving the problems of the present invention are as follows. 1. A cassette having an opening for loading and unloading a semiconductor substrate and an internal space for accommodating the semiconductor substrate, and a door provided at the opening in an openable and closable manner; the cassette has wafer teeth on the inner surfaces of both side walls; The wafer teeth include support protrusions for supporting a semiconductor substrate, A FOUP characterized in that at least a portion including the tip of the support ridge is inclined downward toward the inside, and the height of the tip is 70 μm or more lower than the height of the portion where the outer edge of a semiconductor substrate accommodated in a specified position is located. 2. The wafer teeth on the inner surface of each side wall have at least two support ridges, The FOUP described in 1. is characterized in that, among the support ridges supporting one semiconductor substrate, the intra-teeth support distance, which is the distance between the two support ridges that are furthest apart in the direction in which the semiconductor substrate is loaded and unloaded, is 110 mm or more and 170 mm or less, and the opening support distance, which is the distance between the two support ridges that are closest to the opening, is 245 mm or more and 270 mm or less. 3. The door has a stopper on the inner surface to prevent the semiconductor substrate from moving, 3. The FOUP according to claim 1 or 2, wherein when the door is closed, there is a gap of 1500 μm or less between the stopper and the accommodated semiconductor substrates. 4. A cassette having an opening for loading and unloading a semiconductor substrate and an internal space for accommodating the semiconductor substrate, and a door provided at the opening in an openable and closable manner; the door has a stopper on an inner surface thereof for preventing movement of the semiconductor substrate; A FOUP characterized in that, when the door is closed, a gap of 1500 μm or less exists between the stopper and the semiconductor substrate accommodated therein. Effect of the Invention

[0012] A FOUP in which at least the tip portion of the supporting ridge has an inwardly sloping portion, and the height (h1) of the inner tip of this ridge is 70 μm or more lower than the height (h2) of the portion where the outer edge of the semiconductor substrate stored in a specified position is located (h2-h1≧70 μm), can prevent contact between the thin film portion of the stored thin wafer and the tip of the supporting ridge, thereby reducing the occurrence of defects in the flatness application area and maintaining a high yield. A FOUP with an intra-teeth support distance of 110 mm or more and 170 mm or less and an opening support distance of 245 mm or more and 270 mm or less has excellent productivity because it exhibits little deflection even when storing thin wafers, and a transport arm can be inserted between the stored thin wafers even when all stages of the wafer teeth are filled with thin wafers. In a FOUP that has a gap of 1,500 μm or less between the stopper and the contained semiconductor substrate when the door is closed, the contained semiconductor substrate is not pressed down, preventing the occurrence of cracks even when thin wafers are contained therein, thereby maintaining high yield and productivity. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic diagram of the FOUP according to the first embodiment in a closed state. [Diagram 2] FIG. 2 is a schematic diagram of the FOUP according to the first embodiment in an open state. [Diagram 3] FIG. 4 is a perspective cross-sectional view of the wafer teeth on the left side. [Figure 4]FIG. 2 is an enlarged schematic diagram of a thin wafer placed on the supporting ridges of the FOUP according to the first embodiment, as viewed from the horizontal direction. [Diagram 5] FIG. 2 is a schematic diagram of the FOUP according to the first embodiment, viewed from above when the FOUP accommodates a thin wafer in a predetermined accommodation position. [Figure 6] Schematic diagram of a stopper. [Figure 7] FIG. 2 is a schematic diagram of the FOUP according to the first embodiment, viewed from above in the vicinity of the stopper when the FOUP accommodates a thin wafer in a predetermined accommodation position. [Figure 8] FIG. 13 is a schematic diagram of a FOUP according to a second embodiment, viewed from above when the FOUP accommodates a thin wafer in a predetermined accommodation position. [Figure 9] A schematic cross-sectional view of a conventional FOUP housing multiple thin wafers, as viewed from the opening side, and an enlarged schematic view of the support piece portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention relates to a FOUP, and more particularly to a FOUP suitable for storing, transporting, etc., thin wafers having a thickness of 200 μm or less in a flatness applicable area. The FOUP of the present invention basically satisfies SEMI Standard E47.1 (Non-Patent Document 1).

[0015] "First embodiment" A FOUP according to a first embodiment of the present invention is shown in Figures 1 and 2. Note that throughout this specification, the drawings are merely schematic diagrams for understanding the specific configurations, and do not accurately reflect the actual shapes. Therefore, some of the structures are exaggerated in order to facilitate understanding of the present invention.

[0016] The FOUP 100 of the first embodiment has a cassette 110 having an opening O for loading and unloading semiconductor substrates and an internal space S for accommodating the semiconductor substrates, and a door 120 provided at the opening O so as to be freely opened and closed. Cassette 110 has a pair of wafer teeth 111 on the inner surface of both side walls. The wafer teeth have 25 support pieces 112 arranged at regular intervals in the vertical direction. The number of support pieces can be, for example, 13, depending on the number of semiconductor substrates to be stored. In the FOUP of the present invention, the wafer teeth can be molded separately from the cassette so as to be detachably attached to the cassette, or can be molded integrally with the cassette. The door 120 has a stopper 121 on its inner surface for preventing the semiconductor substrate from moving.

[0017] FIG. 3 shows a perspective cross-sectional view of the left wafer tooth. Two support ridges 113 extending inward are formed at intervals of 140 mm in the loading / unloading direction (front-rear direction when viewed from the opening) on ​​the upper surface of the support piece 112. At least a portion including the tip of the support ridges 113 is inclined downward toward the inside.

[0018] FIG. 4 is a schematic cross-sectional view of a state in which a thin wafer W, which is a TAIKO wafer, is placed on the supporting ridges 113, as viewed from the horizontal direction. The support ridge 113 slopes inwardly and downwardly from the middle of the thick film portion (periphery excluded region) of the thin wafer W to the tip 113E, and the height (h1) of the tip 113E is lower by 70 μm or more than the height (h2) of the portion where the outer edge Wo of the semiconductor substrate accommodated in a predetermined position is located (h2-h1≧70 μm). Note that, although the upper and lower surfaces of the support piece 112 are horizontal in Fig. 4, for example, the upper surface of the support piece can be sloped inwardly and downward, and the upper surface of the support ridge can be parallel to the upper surface of the support piece. In the present invention, the support ridge may have at least a portion including the tip that is inclined downward toward the inside, and the entire portion located below the semiconductor substrate accommodated in a predetermined position may be inclined downward. The downwardly inclined portion of the support ridge does not have to be inclined upward toward the inside, and may have a horizontal portion. The downward inclination is not limited to a flat surface with a constant inclination, and may be a curved surface with a variable inclination, or may be a combination of two or more flat surfaces with different inclinations, or one or more flat surfaces and one or more curved surfaces.

[0019] In the thin wafer W supported by the supporting ridges 113, the thick film portion on the periphery does not bend, and only the thin film portion bends downward. In the FOUP 100 of the first embodiment, the height (h1) of the tip 113E of the supporting ridges 113 is lower than the height (h2) of the portion where the semiconductor substrate outer edge Wo is located by 70 μm or more (h2-h1≧70 μm), thereby preventing contact between the supporting ridges 113 and the thin film portion of the thin wafer W, thereby reducing the occurrence of defects in the flatness application region located near the tip 113E of the supporting ridges 113. Furthermore, if the portion just outside the flatness application region comes into contact with the supporting ridges 113, a load will be applied, even if not as much as in direct contact, so it is preferable that the portion within 1 mm of the flatness application region does not come into contact with the tip 113E of the supporting ridges, and it is more preferable that the portion within 2 mm does not come into contact. The difference (h2-h1 (h2>h1)) between the height (h1) of the tip 113E of the support ridge 113 and the height (h2) of the portion where the outer edge Wo of the semiconductor substrate is located is preferably 80 μm or more, and more preferably 100 μm or more. Moreover, this difference (h2-h1) is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less.

[0020] Here, the FOUP is used for transporting, storing, etc., semiconductor substrates with a diameter of 300 mm, and is designed so that the semiconductor substrates are stored at a fixed position so that they do not move inside. FIG. 5 is a schematic diagram showing a top view of the FOUP 100 according to the first embodiment when the FOUP 100 accommodates a thin wafer W in a predetermined accommodation position.

[0021] The thin wafer W is placed on the support pieces 112 of the pair of left and right wafer teeth 111, and is therefore supported by the support ridges 113 at four points in total, two on each side. In the FOUP 100 of the first embodiment, among the supporting ridges 113 supporting one thin wafer W, the intra-teeth support distance d1, which is the distance between the two supporting ridges furthest from each other in the direction of loading / unloading the thin wafer W, is 140 mm, and the opening support distance d2, which is the distance between the two supporting ridges closest to the opening, is 251 mm. The starting points of these distances are the contact points of the supporting ridges 113 with the outer periphery of the thin wafer (semiconductor substrate). In the FOUP of the present invention, it is preferable that the support distance d1 within the teeth is 110 mm or more and 170 mm or less, and the support distance d2 at the opening is 245 mm or more and 270 mm or less. By setting the support distance d1 within the teeth and the support distance d2 at the opening within this range, the semiconductor substrate can be supported in a well-balanced manner while preventing the support piece 112 from interfering with the loading and unloading of the semiconductor substrate, and the amount of deflection when a thin wafer is accommodated can be reduced. In addition, among the support ridges formed on the support piece, the two support ridges furthest apart in the loading and unloading direction of the thin wafer W are preferably formed in positions that are line-symmetrical with respect to the center line in the left-right direction of the semiconductor substrate. By forming them in this way, the four support ridges support the semiconductor substrate in positions that are line-symmetrical with respect to the center line in the left-right direction of the semiconductor substrate, and therefore the semiconductor substrate can be supported in a well-balanced manner, and the amount of deflection when a thin wafer is accommodated can be reduced. Furthermore, in the FOUP of the present invention, by setting the intra-tooth support distance d1 and the opening support distance d2 within this range, it becomes easy to insert a transport arm between thin wafers placed on adjacent support pieces above and below, even if the vertical spacing between the multiple support pieces 112 on the wafer teeth 111 is 10 mm or less.

[0022] In the FOUP of the present invention, the intra-tooth support distance d1 is preferably 115 mm or more, more preferably 120 mm or more, and is preferably 165 mm or less, more preferably 160 mm or less, and even more preferably 155 mm or less. The opening support distance d2 is preferably 250 mm or more, and more preferably 265 mm or less.

[0023] In the FOUP 100 according to the first embodiment of the present invention, the door 120 is provided on its inner surface with a stopper 121 for preventing the movement of the semiconductor substrate. FIG. 6 shows a schematic diagram of the stopper 121, and FIG. 7 shows a schematic diagram of the vicinity of the stopper 121 seen from above when the thin wafer W is accommodated in a predetermined accommodation position of the FOUP 100. Stopper 121 includes a main body 122 fixed to the inner surface of the door, and two blades 123 connected to the left and right of the main body via elastic parts 124 . In the FOUP 100 of the first embodiment, when the door 120 is closed, the thin wafer W accommodated in a predetermined position and the stopper 121 are closest in distance to their blade portions 123, with a gap of 100 μm. In the FOUP 100 of the first embodiment, the stopper 121 does not come into contact with the thin wafer W accommodated in a predetermined position, and the thin wafer W is not pressed toward the back side when the door 120 is closed, so that cracking of the thin wafer W can be prevented.

[0024] When a FOUP containing a thin wafer (semiconductor substrate) is transported, the semiconductor substrate may move unexpectedly in the FOUP. Even if the moving semiconductor substrate collides with the blade of the stopper, the impact can be absorbed by the elastic portion, so that the semiconductor substrate, especially the thin wafer, can be prevented from cracking. In order to prevent the semiconductor substrate from moving forcefully, it is preferable that the gap between the stopper and the semiconductor substrate is narrow. Specifically, in the FOUP of the present invention, the gap between the stopper and the semiconductor substrate contained in a predetermined position may be 1500 μm or less. It is preferable that the gap is 1200 μm or less, more preferably 800 μm or less, even more preferably 400 μm or less, and even more preferably 100 μm or less. There is no particular limit to the lower limit of this gap, but if the gap is too small, the stopper 121 and the semiconductor substrate W may come into contact due to manufacturing tolerances, etc., so it is preferable that the gap is 0.1 μm or more, and more preferably 1 μm or more.

[0025] When a TAIKO wafer was stored in the FOUP 100 of the first embodiment and the door 120 was closed, the tip of the support ridge 113 did not come into contact with the flatness application area of ​​the TAIKO wafer. In addition, when the door 120 was closed, the stopper 121 did not come into contact with the TAIKO wafer, and it was possible to prevent the TAIKO wafer from cracking. When the stored TAIKO wafer was observed from the horizontal direction and the amount of downward deflection of the center of the wafer was measured, the amount of deflection was 1.77 mm. It was confirmed that even if multiple support pieces 112 were provided at a pitch of 10 mm above and below, there was a gap of 8.2 mm or more between the stored TAIKO wafers, and this would not cause any obstacles when inserting the transfer arm.

[0026] "Second embodiment" The FOUP of the second embodiment is the same as the FOUP 100 of the first embodiment, except that the intra-tooth support distance d1 is 120 mm and the opening support distance d2 is 260 mm. FIG. 8 is a schematic diagram showing a FOUP 200 according to the second embodiment, viewed from above when the FOUP 200 accommodates a thin wafer W in a predetermined accommodation position. When the TAIKO wafers housed in FOUP200 were observed horizontally and the amount of downward deflection at the center of the wafer was measured, the amount of deflection was 1.85 mm. It was confirmed that even with multiple support pieces provided at a 10 mm pitch above and below, there was a gap of 8.1 mm or more between the housed TAIKO wafers, which would not cause any obstacles when inserting the transfer arm. [Explanation of symbols]

[0027] 100 FOUP according to the first embodiment 110 Cassette O opening S interior space 111 Wafer Teeth 112 Support piece 113 Support protrusion 113E Tip of supporting ridge 120 Doors 121 Stopper 122 Main body 123 Wing 124 Elastic part 200 Second embodiment of FOUP W Thin wafer

Claims

1. a cassette having an opening for loading and unloading a semiconductor substrate and an internal space for accommodating the semiconductor substrate; and a door provided at the opening in an openable and closable manner; the cassette has wafer teeth on the inner surfaces of both side walls; The wafer teeth each include at least two support ridges for supporting a semiconductor substrate, At least a portion including a tip of the support protrusion is inclined downward toward the inside, and the height of the tip is 70 μm or more lower than the height of a portion where an outer edge of a semiconductor substrate accommodated in a predetermined position is located; A FOUP characterized in that, among the support ridges supporting one semiconductor substrate, an intra-teeth support distance, which is the distance between the two support ridges that are furthest apart in the direction in which the semiconductor substrate is loaded / unloaded, is 110 mm or more and 170 mm or less, and an opening support distance, which is the distance between the two support ridges that are closest to the opening, is 245 mm or more and 270 mm or less.

2. the door has a stopper on an inner surface thereof for preventing movement of the semiconductor substrate; 2. The FOUP according to claim 1, wherein when the door is closed, there is a gap of 1500 μm or less between the stopper and the semiconductor substrate accommodated therein.

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