KR102652346B1 - Efem - Google Patents

Abstract

It becomes easier to allow the inert gas to flow vertically in the transfer chamber, making it difficult for dust to fly up.
The EFEM includes a housing 2 that constitutes a transfer chamber inside, a support plate 37 for forming an FFU installation chamber 42 above the transport chamber within the housing 2, and an FFU installation chamber 42. It includes a supply pipe 47 for supplying nitrogen, and three fans arranged to cover each of the communication openings 37a formed in the support plate 37. The supply pipe 47 has three supply ports 47a distributed in the FFU installation chamber 42.

Description

EFEM{ＥＦＥＭ}

The present invention relates to an Equipment Front End Module (EFEM) capable of supplying an inert gas to a closed transfer chamber and replacing it with an inert gas atmosphere.

Patent Document 1 discloses a load port in which a FOUP (Front-Opening Unified Pod) in which a wafer (semiconductor substrate) is accommodated is loaded, and a transfer chamber in which the transfer of the wafer is performed, the load port being closed by connecting to an opening provided in the front wall. An EFEM is described that includes this housing and transfers wafers between a FOUP and a processing device that performs a predetermined process on the wafer.

Conventionally, the influence of oxygen and moisture in the transfer chamber on semiconductor circuits manufactured on wafers was small, but in recent years, with the further miniaturization of semiconductor circuits, their influence has become more apparent. Therefore, the EFEM described in Patent Document 1 is configured so that the inside of the transfer chamber is filled with nitrogen, which is an inert gas. Specifically, the EFEM includes a circulation passage composed of a return chamber and a gas return passage for circulating nitrogen inside the housing, a gas supply means for supplying nitrogen to the upper space of the gas return passage, and a gas return passage to the upper space of the gas return passage. It has a plurality of fans arranged to deliver inert gas to the transfer chamber, and gas discharge means for discharging nitrogen from the lower portion of the gas return path. Nitrogen is supplied and discharged appropriately according to changes in oxygen concentration, etc. within the circulation flow path. This makes it possible to maintain the inside of the transfer chamber in a nitrogen atmosphere.

Japanese Patent Publication No. 2015-146349

However, in the EFEM described in Patent Document 1, the gas supply means is connected to the upper space of the gas return path, and the inert gas is supplied from the connection point, that is, one supply port, so the fan in the upper space The pressure on the suction side changes for each fan, and the amount supplied from each fan to the transfer room changes. That is, when inert gas is supplied from one side of the arrangement direction of a plurality of fans, a sufficient amount of inert gas is supplied to one fan, but the amount of inert gas supplied to the other fan is less than that of one fan. That is, in the upper space, the pressure on the suction side of one fan is greater than that of the other fan, and fluctuations occur in the amount of inert gas supplied from each fan to the transfer chamber. As a result, the airflow of the inert gas in the transfer chamber is disturbed, causing the problem that dust easily flies up.

Therefore, the object of the present invention is to provide an EFEM that makes it easy to allow the inert gas to flow vertically in the transfer chamber and to make it difficult for dust to fly up.

The EFEM of the present invention includes a housing closed by connecting a load port to an opening provided in a partition and internally forming a transfer chamber for transporting a substrate, and a substrate transport device disposed within the transport chamber and transporting the substrate. and a partition member installed in the housing and forming an upper space above the transfer chamber, an inert gas supply means for supplying an inert gas to the upper space, and formed on the partition member, the transport chamber and A plurality of communication ports communicating the upper space, a plurality of blowers arranged to cover each of the communication ports and sending the inert gas of the upper space to the transfer chamber through the communication ports, and a plurality of blowers located at a lower part of the transfer chamber. It is installed and includes a gas suction port for sucking inert gas in the transfer chamber, a gas return path for returning the inert gas sucked from the gas suction port to the upper space, and a gas discharge means for discharging the gas in the transfer chamber. It is available. And, the inert gas supply means has a plurality of supply ports for supplying the inert gas, which are distributedly arranged in the upper space, and the plurality of supply ports drive the plurality of blowers when viewed from the upper and lower directions. It is disposed only on the side opposite to the gas return path.

According to this, it becomes possible to dispersely supply the inert gas supplied to the upper space from the inert gas supply means from a plurality of supply ports. For this reason, it becomes possible to supply the inert gas evenly throughout the upper space, and the variation in pressure on the suction side of the plurality of blowers in the upper space becomes small. Therefore, it becomes difficult for variations in the amount of inert gas supplied from each blower to the transfer chamber to occur. As a result, it becomes easier to allow the inert gas to flow vertically in the transfer chamber, and it becomes difficult for dust to fly up.

In the present invention, the supply port is configured to supply the inert gas toward the area where the distance to the supply port is closest in any of the partition walls and partition members of the housing for dividing the upper space and the external space. It is desirable to have As a result, the force of the inert gas supplied from the supply port is weakened in any of the partition members and partitions, and the inert gas flows along any of the partition members and partitions. For this reason, the airflow in the upper space flowing from the gas return path to the blower becomes less likely to be disturbed, and the variation in pressure on the suction side of the plurality of blowers in the upper space becomes smaller. Accordingly, fluctuations in the amount of inert gas supplied from each blower to the transfer chamber are further suppressed.

Furthermore, in the present invention, a plurality of the gas suction ports are provided in the lower part of the transfer chamber, and the gas return path includes a plurality of first flow paths extending upward from each of the plurality of gas suction ports, and the It is preferable to have a second flow path connected to a plurality of first flow paths and further include a discharge port for delivering the gas in the second flow path to the upper space. As a result, the gas from the transfer chamber first flows through the plurality of first flow paths to the second flow path and then flows into the upper space. By allowing the gas from the plurality of first flow paths to once flow into the second flow path in this way, it becomes possible to absorb fluctuations in the amount of gas flowing between the plurality of first flow paths. For this reason, the amount of gas delivered from the delivery port is more stable than when the gas is delivered directly from each first flow path to the upper space, and fluctuations in the amount of inert gas supplied from each blower to the transfer chamber are further suppressed.

Additionally, in the present invention, the second flow path extends along the arrangement direction of the plurality of first flow paths, and the discharge port is respectively arranged between two adjacent first flow paths in the arrangement direction. It is desirable to have As a result, the amount of gas delivered from the discharge port to the upper space becomes more stable, and fluctuations in the amount of inert gas supplied from each blower to the transfer chamber are further suppressed.

Furthermore, in the present invention, it is preferable that the outlet is arranged at a position between the supply port and the blower in a cross direction that intersects the arrangement direction of the plurality of blowers. As a result, the airflow in the upper space flowing from the gas return path to the blower becomes less likely to be disturbed, and fluctuations in the amount of inert gas supplied from each blower to the return chamber are further suppressed.

In addition, from another point of view, the EFEM of the present invention includes a housing closed by connecting a load port to an opening provided in a partition and forming a transfer chamber therein for transporting a substrate, and installed within the housing, and a housing in the transfer chamber. A partition member for forming an upper space above, a plurality of communication ports formed in the partition member and communicating the transfer chamber and the upper space, and installed in the communication ports, and allowing gas in the upper space to enter the transfer chamber. A plurality of fan filter units for sending, a plurality of gas suction ports provided at the lower part of the transfer chamber and sucking in gas in the transfer chamber, and a gas return for returning the gas sucked from each of the gas suction ports to the upper space. It is equipped with a furnace. In addition, the gas return passage includes a plurality of first flow passages extending from each of the plurality of gas suction ports, and is connected to the plurality of first flow passages so that the gas flows in from the first flow passage, and the gas flows into the upper portion. It is provided with a second flow path for delivering to the space and an outlet for delivering the gas in the second flow path to the upper space, and the outlet is located below the upper ends of the plurality of fan filter units.

According to this, the gas from the transfer chamber first flows through the plurality of first flow paths to the second flow path and then flows into the upper space. By allowing the gas from the plurality of first flow paths to once flow into the second flow path in this way, it becomes possible to absorb the variation in the flow rate of the gas between the plurality of first flow paths. For this reason, the amount of gas delivered from the delivery port is more stable than when the gas is delivered directly from each first flow path to the upper space, and fluctuations in the amount of gas supplied from each blower to the transfer chamber are suppressed.

Additionally, in the present invention, the second flow path extends in a direction intersecting the extension direction of the first flow path, and the gas flowing through the gas return path flows from the first flow path through the second flow path. It is preferable that the direction of the airflow changes when the airflow flows, and also when it flows into the upper space from the second flow path. Thereby, in the second flow path, the flow of gas in the extending direction of the first flow path can be made gentle. Therefore, compared to the case where the gas flows into the upper space as is without changing the direction of the airflow from the first flow path to the upper space, it is possible to make it difficult to disturb the airflow in the upper space.

In addition, in the present invention, the substrate transfer device has a base portion whose position is fixed and a transfer portion disposed above the base portion to convey the substrate, and is disposed in the transfer chamber, wherein the transfer chamber includes: , an installation may be arranged below the transport area where the substrate is transported by the transport unit, and the gas suction port may be arranged at a position that does not overlap with either the base part or the installation when viewed from the vertical direction.

According to the EFEM of the present invention, it becomes possible to supply the inert gas evenly throughout the upper space, and the variation in pressure on the suction side of the plurality of blowers in the upper space is reduced. Therefore, it becomes difficult for variations in the amount of inert gas supplied from each blower to the transfer chamber to occur. As a result, it becomes easier to allow the inert gas to flow vertically in the transfer chamber, and it becomes difficult for dust to fly up.

1 is a plan view showing a schematic configuration of an EFEM and its surroundings according to an embodiment of the present invention.
FIG. 2 is a diagram showing the electrical configuration of the EFEM shown in FIG. 1.
FIG. 3 is a front view of the housing shown in FIG. 1 when viewed from the front.
FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. 3.
FIG. 5 is a cross-sectional view taken along line VV shown in FIG. 3.
FIG. 6 is a cross-sectional view taken along line VI-VI shown in FIG. 3.
Figure 7 is a side cross-sectional view of the load port showing a door closed state.
Figure 8 is a side cross-sectional view of the load port showing a state in which the door is open.

EFEM1 according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 8. In addition, for convenience of explanation, the direction shown in FIG. 1 is assumed to be the front-back, left-right direction. That is, in this embodiment, the direction in which the EFEM (Equipment Front End Module) 1 and the substrate processing device 6 are aligned is the front-back direction, with the EFEM (1) side at the front and the substrate processing device 6 at the front. The side is toward the rear. Additionally, the direction in which the plurality of load ports 4 are arranged orthogonal to the front-back direction is referred to as the left-right direction. Additionally, the direction perpendicular to both the front-back direction and the left-right direction is referred to as the up-down direction.

(Rough configuration of EFEM and its surroundings)

First, the schematic structure of the EFEM 1 and its surroundings will be explained using FIGS. 1 and 2. Fig. 1 is a plan view showing the schematic configuration of the EFEM 1 and its surroundings according to the present embodiment. FIG. 2 is a diagram showing the electrical configuration of EFEM 1. As shown in FIG. 1, EFEM 1 includes a housing 2, a transfer robot 3 (substrate transfer device), three load ports 4, and a control device 5. Behind the EFEM 1, a substrate processing device 6 is disposed to perform a predetermined process on the wafer W (substrate). The EFEM 1 moves the wafer between the FOUP (Front-Opening Unified Pod) 100 loaded in the load port 4 and the substrate processing device 6 by the transfer robot 3 disposed in the housing 2. (W) is given and received. The FOUP 100 is a container that can accommodate a plurality of wafers W arranged in the vertical direction, and an openable cover 101 is installed at the rear end (the end on the housing 2 side in the front-back direction). . The FOUP 100 is transported, for example, by a known OHT (overhead traveling unmanned guided vehicle: not shown). Between the OHT and the load port 4, FOUP 100 is exchanged.

The housing 2 is for connecting the three load ports 4 and the substrate processing device 6. Inside the housing 2, a transfer chamber 41 is formed which is substantially sealed against external space and is used to transfer the wafer W without exposing it to the outside air. When the EFEM (1) is operating, the transfer chamber (41) is filled with nitrogen. Additionally, in this embodiment, the transfer chamber 41 is filled with nitrogen, but any inert gas other than nitrogen (for example, argon, etc.) may be used. The housing 2 is configured so that nitrogen circulates in the internal space including the transfer chamber 41 (details will be described later). Additionally, an openable door 2a is provided at the rear end of the housing 2, and the transfer chamber 41 is connected to the substrate processing device 6 with the door 2a spaced apart.

The transfer robot 3 is disposed in the transfer chamber 41 and transfers the wafer W. The transfer robot 3 includes a base unit 90 (see FIG. 3) whose position is fixed, and an arm mechanism 70 (transfer) disposed above the base unit 90 that holds and transfers the wafer W. (see FIG. 3) and a robot control unit 11 (see FIG. 2). The transfer robot 3 mainly performs the operation of taking out the wafer W from the FOUP 100 and handing it over to the substrate processing device 6, or receiving the wafer W processed by the substrate processing device 6 and carrying it to the FOUP. Perform the operation to return to (100).

The load port 4 is for loading the FOUP 100 (see FIG. 7). As shown in FIGS. 1 and 5, the plurality of load ports 4 are arranged in a left-right direction along the partition wall 33 on the front side of the housing 2. Each load port 4 closes three openings 33a1 (see Fig. 4) formed in the partition 33 of the housing 2 at the base 51 (see Fig. 7) at the rear end. As a result, the transfer chamber 41 within the housing 2 is configured as a substantially sealed space. Additionally, the load port 4 is configured to replace the atmosphere within the FOUP 100 with nitrogen. At the rear end of the load port 4, a door 4a, which is part of an opening and closing mechanism 54 described later, is installed. The door 4a is opened and closed by the door driving mechanism 55 (part of the opening and closing mechanism 54). The door 4a is configured to be able to unlock the cover 101 of the FOUP 100 and to maintain the cover 101. With the door 4a holding the unlocked cover 101, the door drive mechanism 55 opens the door 4a, thereby opening the cover 101. As a result, the wafer W in the FOUP 100 can be taken out by the transfer robot 3. Additionally, the wafer W can be stored in the FOUP 100 by the transfer robot 3.

As shown in FIG. 2, the control device 5 includes a robot control unit 11 of the transfer robot 3, a load port control unit 12 of the load port 4, and a control unit (as shown) of the substrate processing device 6. not connected) and communicates with these control units. In addition, the control device 5 is electrically connected to the oximeter 85, pressure gauge 86, hygrometer 87, etc. installed in the housing 2, and receives measurement results from these measuring devices, ) to obtain information about the atmosphere within. Additionally, the control device 5 is electrically connected to the supply valve 112 and the discharge valve 113 (described later), and appropriately adjusts the nitrogen atmosphere in the housing 2 by adjusting the opening degrees of these valves.

As shown in FIG. 1, the substrate processing apparatus 6 has, for example, a load lock chamber 6a and a processing chamber 6b. The load lock room 6a is a room for temporarily waiting the wafer W, which is connected to the transfer room 41 away from the door 2a of the housing 2. The processing chamber 6b is connected to the load lock chamber 6a apart from the door 6c. In the processing chamber 6b, a predetermined process is performed on the wafer W using a processing mechanism (not shown).

(Housing and its internal composition)

Next, the housing 2 and its internal structure will be explained using FIGS. 3 to 6. Figure 3 is a front view of the housing 2 when viewed from the front. FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. 3. FIG. 5 is a cross-sectional view taken along line V-V shown in FIG. 3. FIG. 6 is a cross-sectional view taken along line VI-VI shown in FIG. 3. In addition, in FIGS. 3 and 6, illustration of the partition wall is omitted. In Fig. 5, illustration of the transport robot 3 and the like is omitted, and the load port 4 is shown with a two-dot chain line.

The housing 2 as a whole has a substantially rectangular parallelepiped shape. As shown in FIGS. 3 to 5, the housing 2 has pillars 21 to 26, a connecting pipe 27, and partition walls 31 to 36. Partition walls 31 to 36 are installed on the pillars 21 to 26 extending in the vertical direction, and the internal space of the housing 2 (transfer room 41 and FFU installation room 42) is almost completely exposed to the external space. It is composed of airtight seals.

More specifically, as shown in FIG. 4, at the front end of the housing 2, the pillars 21 to 24 are arranged in order while being spaced apart from each other from the left direction to the right direction. That is, the four pillars 21 to 24 are arranged along the left and right directions. Additionally, as shown in FIG. 3, the pillars 21 to 24 are erected so as to follow the vertical direction. The pillars 21 and 24 are composed of first parts 21b and 24b arranged on the lower side and second parts 21c and 24c arranged on the upper side. The first portions 21b and 24b are installed standing on the partition wall 31, and their upper ends are connected to the connector 27. Additionally, the pillars 22 and 23 are also installed standing on the partition wall 31, and their upper ends are connected to the connecting pipe 27. These first portions 21b, 24b and pillars 22, 23 have approximately the same length in the vertical direction. The second parts 21c and 24c are on the connecting pipe 27 and are installed standing at a position overlapping the first parts 21b and 24b along the vertical direction. On both left and right sides of the rear end of the housing 2, two pillars 25 and 26 are arranged standing upright along the vertical direction. The connection pipe 27 extends in the left and right direction (the direction in which the four pillars 21 to 24 are arranged) and is connected to the four pillars 21 to 24.

As shown in FIG. 3, a partition wall 31 is arranged at the bottom of the housing 2, and a partition wall 32 is arranged at the ceiling part. As shown in Fig. 4, a partition wall 33 is arranged at the front end, a partition wall 34 is arranged at the rear end, a partition wall 35 is arranged at the left end, and a partition wall 36 is arranged at the right end. The partition 33 is formed with the three openings 33a1 described above. These three openings 33a1 are arranged between the four pillars 21 to 24 in the left and right directions, and are closed by the base 51 of the load port 4. At the right end of the housing 2, a loading portion 83 (see FIG. 3) is provided on which an aligner 84, which will be described later, is loaded. The aligner 84 and the loading portion 83 are also accommodated inside the housing 2 (see Fig. 4).

As shown in FIG. 5, a support plate 37 (compartment member) extending in the horizontal direction is disposed at the upper portion of the housing 2 and at the rear end side of the connector 27. Accordingly, the interior of the housing 2 is divided into the above-described transfer chamber 41 and the FFU installation chamber 42 formed above the transfer chamber 41. That is, the support plate 37 forms an FFU installation chamber 42 as an upper space above the transfer chamber 41 in the internal space of the housing 2.

In the FFU installation room 42, three FFUs (fan filter units) 44, which will be described later, are disposed. At the central portion of the support plate 37 in the front-back direction and at a position opposite to the FFU 44 in the vertical direction, three communication openings 37a are formed to communicate with the transfer chamber 41 and the FFU installation chamber 42. there is. As shown in FIG. 6, these three communication ports 37a are arranged in a row along the left and right directions. Additionally, the three communication ports 37a are arranged between the four pillars 21 to 24 in the left and right directions. Additionally, the partition walls 33 to 36 of the housing 2 are divided into a lower wall for the transfer chamber 41 and an upper wall for the FFU installation chamber 42 (for example, the partition wall 33a at the front end in FIG. 5 , 33b) and the rear end bulkheads 34a, 34b). The rotation speed of each FFU 44 is determined in advance so that the airflow speed in the conveyance area 200, which will be described later, becomes a desired value. The airflow speed in the conveyance area 200 is less than 1 m/s, preferably 0.1 m/s to 0.7 m/s, more preferably 0.2 m/s to 0.6 m/s, and is the target value. Accordingly, the number of rotations of each FFU is determined.

Next, the internal structure of the housing 2 will be described. Specifically, the configuration for circulating nitrogen within the housing 2, its surrounding configuration, and equipment disposed in the transfer chamber 41 will be described.

The configuration for circulating nitrogen within the housing 2 and its surrounding configuration will be explained using FIGS. 3 to 6. As shown in FIG. 5, a circulation path 40 for circulating nitrogen is formed inside the housing 2. The circulation path 40 is comprised of a return chamber 41, an FFU installation chamber 42, and a return path 43 (gas return path). In the circulation path 40, clean nitrogen is sent downward from the FFU installation chamber 42 through each communication port 37a, reaches the lower end of the return chamber 41, and then rises through the return path 43. and returns to the FFU installation room 42 (see arrow in FIG. 5). Hereinafter, it will be described in detail.

In the FFU installation room 42, as shown in FIGS. 5 and 6, there are three FFUs 44 arranged on the support plate 37 and three chemical filters 45 arranged on the FFUs 44. It is installed. As shown in FIG. 5, each FFU 44 has a fan 44a (blower) and a filter 44b, and is arranged on the support plate 37 so as to cover the communication opening 37a. As indicated by the arrow in FIG. 6, the FFU 44 sucks nitrogen in the FFU installation chamber 42 from around the FFU 44 by the fan 44a and sends it downward, while removing particles contained in the nitrogen ( (not shown) is removed by the filter 44b. The chemical filter 45 is for removing, for example, active gas that has entered the circulation path 40 from the substrate processing device 6. Nitrogen purified by the FFU 44 and the chemical filter 45 is delivered from the FFU installation chamber 42 to the transfer chamber 41 through the communication port 37a formed in the support plate 37. The nitrogen delivered to the transfer chamber 41 forms a laminar flow and flows downward.

The return path 43 is formed in the pillars 21 to 24 (pillar 23 in FIG. 5) and the connecting pipe 27 disposed at the front end of the housing 2. The interior of the first portions (21b, 24b) of the pillars (21, 24), the pillars (22, 23), and the connecting pipe (27) are hollow, and spaces (21a to 24a, 27a) through which nitrogen can circulate to each other are provided. Each is formed (see Figure 4). As shown in FIG. 4, the first portions 21b and 24b of the pillars 21 and 24 have a width in the left and right directions larger than those of the pillars 22 and 23. That is, the planar size of the spaces 21a and 24a (the first flow path) (i.e., the opening area of the first portions 21b and 24b) is the space 22a and 23a (the opening area of the pillars 22 and 23). It is bigger than that. In addition, the spaces 21a to 24a (first flow passages) are formed to extend in the vertical direction, and all extend from the lower ends of the pillars 21 to 24 to the position of the connecting pipe 27.

The connector 27 is disposed at the front end of the housing 2. The space 27a (second flow path) of the connector 27 extends in the left and right directions. Additionally, as shown in FIGS. 5 and 6 , communication openings 27b to 27e are formed on the lower surface of the connecting pipe 27 to communicate the spaces 21a to 24a and the space 27a with each other. Additionally, as shown in FIG. 6 , three discharge ports 27f to 27h that open toward the FFU installation chamber 42 (i.e., upward) are formed on the upper surface of the connection pipe 27. These three discharge ports 27f to 27h are arranged between the four pillars 21 to 24 in the left and right directions, and have a rectangular planar shape that is long in the left and right directions. Additionally, three discharge ports 27f to 27h are arranged at the front end of the housing 2. In this way, the connection pipe 27 is configured to allow the nitrogen flowing in from the four spaces 21a to 24a to join and then send it to the FFU installation chamber 42 from the three outlets 27f to 27h. there is. When nitrogen flows from the spaces 21a to 24a to the space 27a, the direction of the airflow changes from upward to the left and right, and flows from the space 27a through the discharge ports 27f to 27h into the FFU installation chamber 42. ), the direction of the airflow changes from left and right to upward. The return path 43 is formed by these spaces 21a to 24a and 27a. Additionally, the three discharge ports 27f to 27h are arranged at positions overlapping with the FFU 44 along the front-back direction. That is, the discharge ports 27f to 27h and the FFU 44 adjacent to each other in the front and rear directions correspond to each other. In addition, the three discharge ports 27f to 27h are formed long in the left and right directions and have a relatively large opening area. For this reason, the flow of gas delivered to the FFU installation chamber 42 from each discharge port 27f to 27h becomes gentle, and the pressure fluctuation on the suction side (upper side) of the three FFUs 44 becomes small. Additionally, the gas delivered to the FFU installation chamber 42 from the delivery ports 27f to 27h flows upward through the partition wall 33 and the FFU 44, as shown in FIG. 5 .

The return path 43 will be described in more detail with reference to FIG. 5 . Also, although the pillar 23 is shown in Figure 5, the same applies to the first portions 21b, 24b of the other pillars 21, 24 and the pillar 22. At the lower end of the pillar 23, an introduction duct 28 is provided to facilitate the introduction of nitrogen in the transfer chamber 41 into the return path 43 (space 23a). The introduction duct 28 is similarly installed in the other pillars 21, 22, and 24. Additionally, since the pillars 21 and 24 are formed to be wider in the left and right directions than the pillars 23, the installed introduction duct 28 is also formed to be wider, but other than that, the structure is the same. An opening 28a is formed in the introduction duct 28, and nitrogen that has reached the lower end of the return chamber 41 can flow into the return path 43. That is, the opening 28a is a gas suction port for sucking nitrogen in the transfer chamber 41 into the return path 43. Additionally, the opening 28a is configured to face downward. For this reason, it becomes possible to smoothly inhale the gas reaching the partition wall 31 from above without disrupting the flow of gas from above. Furthermore, it becomes possible to allow the gas sucked in through the opening 28a to flow upward without changing the airflow direction.

At the upper part of the introduction duct 28, an enlarged portion 28b is formed that widens rearward as it goes downward. A fan 46 is disposed within the introduction duct 28 and below the enlarged portion 28b. The fan 46 is driven by a motor (not shown), sucks nitrogen that has reached the lower end of the transfer chamber 41 into the return passage 43 (space 23a in FIG. 5), and discharges the nitrogen upward. Return to the FFU installation room (42). Nitrogen returned to the FFU installation chamber 42 is sucked into the FFU 44 side from the upper surface of the chemical filter 45, is purified by these FFUs 44 and the chemical filter 45, and is returned to the communication port 37a. ) is sent to the return room 41. As described above, nitrogen can circulate within the circulation path 40.

In addition, as shown in FIG. 3, at the upper rear end of the FFU installation chamber 42 (i.e., the rear end of the housing 2), there is a device for supplying nitrogen into the FFU installation chamber 42 (circulation path 40). A supply pipe 47 is disposed. The supply pipe 47 is connected to an external pipe 48 connected to the nitrogen source 111. A supply valve 112 capable of changing the supply amount of nitrogen per unit time is installed in the middle portion of the external pipe 48. An inert gas supply means is constituted by these supply pipes 47, external pipes 48, supply valves 112, and supply sources 111. Additionally, if an inert gas supply line is installed in a factory, etc., the supply line and the supply pipe 47 may be connected. For this reason, the inert gas supply means may be comprised only of the supply pipe 47.

As shown in FIGS. 3 and 6, the supply pipe 47 extends along the left and right directions, and three supply ports 47a are formed. The three supply ports 47a are arranged to be spaced apart from each other along the left and right directions, and nitrogen is supplied into the FFU installation chamber 42 from the supply pipe 47. As shown in FIGS. 5 and 6, these three supply ports 47a are formed at the lower end of the supply pipe 47, and an area 37b ( That is, it is configured to supply nitrogen toward the area where the distance to the supply port 47a of the support plate 37 is closest. Additionally, the three supply ports 47a are arranged in the same positional relationship with the center of the FFU 44 in the left and right directions. Thereby, the three supply ports 47a are arranged in the front-back direction at a position between the discharge ports 27f to 27h with the fan 44a interposed therebetween.

When nitrogen is supplied to the FFU installation chamber 42 from the three supply ports 47a of the supply pipe 47, the three supply ports 47a are distributed and arranged within the FFU installation chamber 42, so the nitrogen is supplied evenly throughout the FFU installation room (42). For example, when nitrogen is supplied directly into the FFU installation chamber 42 from one supply port of the external pipe 48 connected to the right end of the housing 2, the right-side portion of the FFU installation chamber 42 The pressure rises. That is, the pressure on the suction side of the FFU 44 disposed on the rightmost side becomes greater than that of the other two FFUs 44. If a large change occurs in the pressure on the suction side of the FFU 44 in this way, the amount of nitrogen supplied from the three FFUs 44 to the transfer chamber 41 is likely to change. However, in the present embodiment, nitrogen is supplied from three supply ports 47a spaced apart from each other in the left and right directions, so the variation in pressure on the suction side of the three FFUs 44 becomes small. Accordingly, the supply amount of nitrogen from the three FFUs 44 to the transfer chamber 41 is stable, and the nitrogen delivered to the transfer chamber 41 forms a laminar flow and flows downward.

Additionally, as shown in FIG. 5, a discharge pipe 49 for discharging the gas in the circulation path 40 is connected to the lower end of the load port 4. Additionally, as will be described later, the load port 4 communicates with the storage chamber 60 in which the door drive mechanism 55 is accommodated through a slit 51b formed in the base 51 (see Fig. 7). And the discharge pipe 49 is connected to the receiving chamber 60. The discharge pipe 49 is connected to, for example, an exhaust port not shown, and a discharge valve 113 capable of changing the amount of gas discharged per unit time in the circulation path 40 is installed in the middle of it. These discharge pipes 49 and discharge valves 113 constitute a gas discharge means.

The supply valve 112 and discharge valve 113 are electrically connected to the control device 5 (see Figure 2). This makes it possible to appropriately supply and discharge nitrogen into the circulation path 40. For example, when starting up the EFEM (1) (including, for example, starting up after maintaining the EFEM (1), etc.), if the oxygen concentration in the circulation path (40) is rising, the source (111) ), nitrogen is supplied to the circulation path 40 through the external pipe 48 and the supply pipe 47, and gases (gases: nitrogen and oxygen, etc.) within the circulation path 40 and the receiving chamber 60 are supplied through the discharge pipe 49. Oxygen concentration can be lowered by discharging oxygen (including oxygen). That is, the inside of the circulation path 40 and the receiving chamber 60 can be replaced with a nitrogen atmosphere. In addition, when the EFEM (1) is in operation, even if the oxygen concentration in the circulation path (40) increases, a large amount of nitrogen is temporarily supplied to the circulation path (40) and oxygen is discharged along with nitrogen through the discharge pipe (49). It can lower oxygen concentration. For example, in the EFEM 1 of the type that circulates nitrogen, in order to suppress leakage of nitrogen from the circulation path 40 to the outside and reliably suppress the intrusion of atmospheric air into the circulation path 40 from the outside, the circulation path 40 (40) It is necessary to keep the internal pressure slightly higher than the external pressure. Specifically, it is within the range of 1 Pa (G) to 3000 Pa (G), preferably 3 Pa (G) to 500 Pa (G), and more preferably 5 Pa (G) to 100 Pa (G). For this reason, when the pressure in the circulation path 40 deviates from the predetermined range, the control device 5 changes the discharge flow rate of nitrogen by changing the opening degree of the discharge valve 113, so that the pressure reaches the predetermined target pressure. Adjust as much as possible. In this way, the supply flow rate of nitrogen is adjusted based on the oxygen concentration and the discharge flow rate of nitrogen is adjusted based on the pressure, thereby controlling the oxygen concentration and pressure. In this embodiment, the differential pressure is adjusted to be 10 Pa (G).

Next, equipment and the like placed in the transfer room 41 will be explained using FIGS. 3 and 4. 3 and 4, within the transfer chamber 41, the above-described transfer robot 3, the control unit accommodation box 81, the measuring instrument accommodation box 82, and the aligner 84. is placed. The control unit housing box 81 is installed, for example, on the left side of the base part 90 (see FIG. 3) of the transfer robot 3, and the wafer W is moved by the arm mechanism 70 (see FIG. 3). It is arranged below the conveyance area 200 where conveyance is carried out. The robot control unit 11 and the load port control unit 12 described above are accommodated in the control unit storage box 81. The measuring instrument storage box 82 is installed, for example, to the right of the base part 90 and is arranged below the transfer area 200 of the arm mechanism 70. The measuring device storage box 82 can accommodate measuring devices such as the above-described oximeter 85, pressure gauge 86, and hygrometer 87 (see FIG. 2). The control unit accommodating box 81 and the measuring instrument accommodating box 82 correspond to the installation of the present invention. The introduction duct 28 (see FIG. 4) described above is disposed in front of the base portion 90, the control portion accommodating box 81, and the measuring device accommodating box 82. That is, the opening 28a is disposed at a position that does not overlap with any of the base portion 90, the control unit accommodating box 81, and the measuring device accommodating box 82 when viewed from the up and down direction (vertical direction) (Fig. 4, see Figure 5).

The aligner 84 is used to detect how much the holding position of the wafer W held by the arm mechanism 70 (see FIG. 3) of the transfer robot 3 deviates from the target holding position. For example, there is a risk that the wafer W may move slightly inside the FOUP 100 (see FIG. 1) transported by the above-described OHT (not shown). Therefore, the transfer robot 3 temporarily loads the unprocessed wafer W taken out from the FOUP 100 onto the aligner 84 . The aligner 84 measures how far the wafer W is held from the target holding position by the transfer robot 3 and transmits the measurement result to the robot control unit 11 . Based on the measurement results, the robot control unit 11 corrects the holding position by the arm mechanism 70, controls the arm mechanism 70 to maintain the wafer W at the target holding position, and the substrate processing device ( It is conveyed to the load lock chamber (6a) of 6). As a result, the wafer W can be processed normally by the substrate processing device 6.

(Configuration of load port)

Next, the configuration of the load port will be described below with reference to FIGS. 7 and 8. Figure 7 is a side cross-sectional view of the load port showing the door closed state. Figure 8 is a side cross-sectional view of the load port showing a state in which the door is open. 7 and 8 are depicted with the outer cover 4b (see FIG. 5) located below the loading table 53 removed.

As shown in FIG. 7, the load port 4 includes a plate-shaped base 51 erected along the vertical direction, and a horizontal base 52 formed to protrude forward from the central portion in the vertical direction of the base 51. ) has. A loading table 53 for loading the FOUP 100 is installed on the upper part of the horizontal base 52. The loading table 53 can be moved forward and backward by a loading table driving unit (not shown) in a state in which the FOUP 100 is loaded.

The base 51 constitutes a part of the partition wall 33 that isolates the transfer chamber 41 from external space. The base 51 has a substantially rectangular planar shape that is elongated in the vertical direction when viewed from the front. Additionally, the base 51 has a window portion 51a formed at a position that can face the stacked FOUP 100 in the front-back direction. In addition, the base 51 has a slit 51b extending in the vertical direction through which a support frame 56 described later can be moved at a position lower than the horizontal base 52 in the vertical direction. The slit 51b is formed only in the range in which the support frame 56 can move up and down while penetrating the base 51, and the opening width in the left and right directions is small. For this reason, it becomes difficult for particles in the storage chamber 60 to enter the transfer chamber 41 through the slit 51b.

The load port 4 has an opening and closing mechanism 54 that can open and close the cover 101 of the FOUP 100. The opening/closing mechanism 54 has a door 4a capable of closing the window portion 51a, and a door drive mechanism 55 for driving the door 4a. The door 4a is configured to close the window portion 51a. Additionally, the door 4a is configured to be able to unlock the cover 101 of the FOUP 100 and to maintain the cover 101. The door driving mechanism 55 includes a support frame 56 for supporting the door 4a, and a movable block 58 that supports the support frame 56 movably in the forward and backward directions through a slide support means 57. and a slide rail 59 that supports the movable block 58 so as to be movable in the vertical direction with respect to the base 51.

The support frame 56 supports the rear lower portion of the door 4a, extends downward, passes through the slit 51b provided in the base 51, and protrudes toward the front of the base 51. It is a plate-shaped member. And the slide support means 57, the movable block 58, and the slide rail 59 for supporting this support frame 56 are installed in front of the base 51. That is, the drive location for moving the door 4a is outside the housing 2, and is accommodated in the storage chamber 60 provided below the horizontal base 52. The storage chamber 60 is surrounded by a horizontal base 52 and a substantially box-shaped cover 61 and base 51 extending downward from the horizontal base 52, and is in an almost sealed state. .

The discharge pipe 49 described above is connected to the bottom wall 61a of the cover 61. That is, the receiving chamber 60 and the discharge pipe 49 are connected. In this embodiment, the receiving chamber 60 and the discharge pipe 49 are connected in any case of the three load ports 4. This makes it possible to discharge the gas in the circulation path 40 from the discharge pipe 49 through the receiving chamber 60. When discharging gas from the discharge pipe 49, it is possible to discharge particles present in the receiving chamber 60 along with the gas. Additionally, a fan 62 facing the discharge pipe 49 is installed within the storage chamber 60 and on the bottom wall 61a. By installing the fan 62 in the storage chamber 60 in this way, it becomes easy to discharge gas from the storage chamber 60 to the discharge pipe 49 while suppressing the flying of particles. For example, if a fan is installed to blow the gas in the transfer chamber 41 toward the receiving chamber 60, the airflow in the transfer chamber 41 is likely to be disturbed, causing particles in the transfer chamber 41 to fly out. However, in this embodiment, since the fan 62 is disposed within the storage chamber 60, it is possible to suppress particles within the transfer chamber 41 from flying up.

Subsequently, the opening and closing operations of the cover 101 and the door 4a of the FOUP 100 will be described below. First, as shown in FIG. 7, the FOUP 100 loaded on the loading table 53 in a state spaced apart from the base 51 is moved backward and the cover 101 is placed on the FOUP 100. Bring the door (4a) into contact. At this time, the door 4a of the opening/closing mechanism 54 unlocks the cover 101 of the FOUP 100, and the cover 101 is held.

Next, as shown in FIG. 8, the support frame 56 is moved backward. Thereby, the door 4a and the cover 101 move rearward. By doing this, the cover 101 of the FOUP 100 is opened and the door 4a is opened, and the transfer chamber 41 of the housing 2 and the FOUP 100 are communicated.

Next, as shown in FIG. 8, the support frame 56 is moved downward. Thereby, the door 4a and the cover 101 move downward. By doing this, the FOUP 100 is largely opened as a discharge inlet, and it becomes possible to move the wafer W between the FOUP 100 and the EFEM 1. Additionally, when closing the cover 101 and the door 4a, the opposite operation to that described above may be performed. Additionally, the serial operation of the load port 4 is controlled by the load port control unit 12.

As explained above, according to the EFEM 1 of the present embodiment, the three supply ports 47a are distributed and arranged within the FFU installation chamber 42, so that the supply is distributed evenly throughout the FFU installation chamber 42. It becomes possible to supply nitrogen. For this reason, the variation in pressure on the suction side of the fans 44a (blower) of the three FFUs 44 in the FFU installation room 42 becomes small. Therefore, the amount of nitrogen supplied from each fan 44a to the transfer chamber 41 is stabilized, and it becomes easy to allow nitrogen to flow vertically in the transfer chamber 41 (nitrogen forms a laminar flow), preventing dust from flying up. It gets difficult.

In addition, the discharge pipe 49 is connected to the receiving chamber 60 of each load port 4, and the gas is discharged to the outside of the circulation path 40 through the plurality of discharge pipes 49 and the plurality of receiving chambers 60. ) is done through. For this reason, compared to the case where only one discharge pipe 49 is installed, all of the gas flowing downward within the transfer chamber 41 can be discharged. As a result, the influence of nitrogen on the laminar flow formed in the transfer chamber 41 is reduced. Additionally, the laminar flow formed by nitrogen in the transfer chamber 41 may be formed at least in the transfer area 200 of the wafer W and above it.

In addition, in the transfer chamber 41, a control unit accommodating box 81 and a measuring instrument accommodating box 82 (installation) are disposed below the transfer area 200, and the opening 28a is the base when viewed from the vertical direction. It may be installed in a position that does not overlap with either the part 90 or the installation.

In addition, through an experiment of laminar flow visualization, the inventor of the present application found three locations above the transfer robot 3, above the control unit accommodating box 81, and above the measuring device accommodating box 82 (point 201 in FIG. 3, 202, 203), the air flow velocity was measured and the formation state of laminar flow was confirmed. In this embodiment, the rotation speed of each FFU was determined in advance so that the airflow speed in the conveyance area was 0.3 m/s. As a result, it was confirmed that backflow of gas into the transfer area 200 did not occur due to the gas colliding with the transfer robot 3 or the like. In addition, even if the supply amount of nitrogen from the supply source 111 (see FIG. 3) or the rotation speed of the fan 46 (see FIG. 5) are changed, the difference in gas flow rate between the three locations described above is less than 30%. Confirmed. In other words, it was confirmed that even if an installation was installed in the transfer area 200, a stable laminar flow was formed at least in the transfer area 200 and above.

Additionally, the supply port 47a is configured to supply nitrogen toward the area 37b of the support plate 37 that is the closest to the supply port 47a. As a result, the nitrogen supplied from the supply port 47a first flows along the support plate 37 with its force weakened in the region 37b of the support plate 37. For this reason, the airflow in the FFU installation chamber 42 flowing from the discharge ports 27f to 27h to the FFU 44 becomes difficult to be disturbed, and the pressure on the suction side of the FFU 44 in the FFU installation chamber 42 is reduced. Fluctuations become smaller. Accordingly, fluctuations in the amount of nitrogen supplied from the fan 44a of each FFU 44 to the transfer chamber 41 are further suppressed.

As a modification, the supply port 47a may be configured to supply nitrogen toward the partition 32 at the ceiling of the housing 2 or the partition 34 at the rear end. In this case as well, the momentum of the nitrogen supplied from the supply port 47a is weakened and flows, and the fluctuation in the amount of nitrogen supplied from the fan 44a of each FFU 44 to the transfer chamber 41 is further suppressed. do.

The return path 43 has a space 27a (second flow path) connected to four spaces 21a to 24a (first flow path), and has a discharge port ( Since 27f to 27h) are formed, the gas from the transfer chamber 41 first flows into the space 27a through the four spaces 21a to 24a and then flows into the FFU installation chamber 42. More specifically, as shown in FIG. 6, the gas from the space 21a is directed to the outlet 27f through the space 27a, and the gas from the space 22a is directed to the left and right sides through the space 27a. Directed toward the delivery ports 27f and 27g, the gas from the space 23a is directed toward the left and right discharge ports 27g and 27h through the space 27a, and the gas from the space 24a is directed through the space 27a. It flows toward the outlet (27h). By allowing the gas from the four spaces 21a to 24a to once flow into the space 27a in this way, it becomes possible to absorb the variation in the amount of gas flowing between the four spaces 21a to 24a. In this embodiment, the opening areas of the spaces 21a and 24a are larger than those of the spaces 22a and 23a, and the amount of gas flowing through the spaces 21a and 24a increases, but each space ( The gases from 21a to 24a) are combined and are delivered to the FFU installation chamber 42 from each outlet 27f to 27h. For this reason, the amount of gas delivered from the delivery ports 27f to 27h is more stable than when the gas is delivered directly to the FFU installation room 42 from each space 21a to 24a, and the suction of each fan 44a is more stable. Fluctuations in pressure on the side are also suppressed, and fluctuations in the amount of nitrogen supplied from each fan 44a to the transfer chamber 41 are further suppressed.

Since each outlet 27f to 27h is disposed between two adjacent spaces 21a to 24a in the left and right directions, there is a change in the amount of gas flowing from the two adjacent spaces 21a to 24a. Even if this occurs, the amount of gas delivered from the delivery ports 27f to 27h becomes more stable. For this reason, fluctuations in the amount of nitrogen supplied from the fan 44a to the transfer chamber 41 are further suppressed.

Additionally, each of the discharge ports 27f to 27h is arranged in the front-back direction at a position between the supply ports 47a with the fan 44a interposed therebetween. As a result, the airflow in the FFU installation chamber 42 flowing from the return path 43 to the fan 44a becomes less likely to be disturbed, and fluctuations in the amount of nitrogen supplied from each fan 44a to the return chamber 41 are further suppressed. do.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes are possible as long as they are described in the claims. In the above-described embodiment, the three supply ports 47a formed in the supply pipe 47 are distributed and arranged in the FFU installation chamber 42, but the supply pipe 47 is provided with two or four or more supply ports 47a. In the provisional FFU installation room 42, they may be arranged dispersedly. Additionally, instead of the supply pipe 47, a porous pipe (for example, an air stone, etc.) may be disposed in the FFU installation chamber 42. In this case as well, a plurality of supply ports of the porous tubes are distributed and arranged in the FFU installation chamber 42, and the same effect as the above-described embodiment can be obtained.

Additionally, the plurality of supply ports 47a may be arranged anywhere in the FFU installation room 42. That is, it may be disposed on the front end side of the housing 2. Additionally, the opening 28a as a gas suction port may be disposed above the lower part of the transfer chamber 41. In addition, the return path 43 is composed only of the spaces 21a to 24a as the first flow path, and gas may be delivered directly to the FFU installation chamber 42 from each space 21a to 24a. In this case, the space as the first flow path may be 1 to 3 or 5 or more. Additionally, when the return path 43 has the space 27a as the second flow path, the space as the first flow path may be 2, 3, or 5 or more.

Additionally, each outlet 27f to 27h does not need to be arranged between two adjacent spaces 21a to 24a in the left and right directions. Two or four or more fans 44a (FFU 44) may be installed. In this case, the communication port 37a may also be formed on the support plate 37 to correspond to the fan 44a.

In addition, instead of the discharge ports 27f to 27h, for example, a punching metal (not shown) with a large number of holes may be installed on the entire upper surface of the connection pipe 27 to change the gas flow.

In addition, although the spaces 21a to 24a and 27a formed inside the pillars 21 to 24 and the connecting pipe 27 are assumed to be the return path 43, the space is not limited to this. That is, the return path 43 may be formed by another member.

1:EFEM
2: Housing
3: Transfer robot (substrate transfer device)
4: load port
21a to 24a: space (first flow path)
27a: space (second euro)
27f to 27h: outlet
28a: Opening (gas suction port)
33: Bulkhead
33a1: opening
37: support plate
37a: Yeontong-gu
37b: area
41: Return room
42: FFU installation room (upper space)
43: Return path (gas return path)
44a: Fan (blower)
47: Supply pipe (inert gas supply means)
47a: supply port
49: Discharge pipe (means for gas discharge)
W: wafer (substrate)

Claims (8)

a housing closed by connecting a load port to an opening provided in the partition, and forming a transfer chamber therein for transporting a substrate;
a substrate transfer device disposed in the transfer chamber and transporting the substrate;
a partition member installed in the housing and forming an upper space above the transfer chamber;
an inert gas supply means for supplying an inert gas to the upper space;
a plurality of communication ports formed in the partition member and communicating the transfer chamber and the upper space;
a plurality of blowers arranged to cover each of the communication openings and sending the inert gas in the upper space to the transfer chamber through the communication openings;
a gas suction port installed at a lower part of the transfer chamber and sucking in an inert gas in the transfer chamber;
a gas return passage for returning the inert gas sucked from the gas suction port to the upper space;
Equipped with gas discharge means for discharging gas in the transfer chamber,
The inert gas supply means has a plurality of supply ports for supplying the inert gas, which are distributedly arranged in the upper space,
EFEM, characterized in that the plurality of supply ports are disposed only on a side opposite to the gas return path with the plurality of blowers interposed therebetween when viewed from an upward and downward direction. The method of claim 1, wherein the supply port is configured to supply the inert gas toward an area in which the distance to the supply port is closest in any of the partition walls and partition members of the housing for dividing the upper space and the external space. EFEM, characterized by being The method according to claim 1 or 2, wherein a plurality of gas suction ports are provided at a lower part of the transfer chamber,
The gas return path has a plurality of first flow passages extending upward from each of the plurality of gas suction ports, and a second flow passage connected to the plurality of first flow passages,
EFEM, characterized in that it further has an outlet for delivering the gas in the second flow path to the upper space. The method of claim 3, wherein the second flow path extends along an arrangement direction of the plurality of first flow paths,
EFEM, characterized in that the discharge ports are respectively arranged between the two adjacent first flow paths in the arrangement direction. The EFEM according to claim 3, wherein the outlet is arranged at a position between the supply port and the blower in a direction intersecting the arrangement direction of the plurality of blowers. a housing closed by connecting a load port to an opening provided in the partition, and forming a transfer chamber therein for transporting a substrate;
a partition member installed in the housing and forming an upper space above the transfer chamber;
a plurality of communication ports formed in the partition member and communicating the transfer chamber and the upper space;
a plurality of fan filter units installed in the communication port and configured to send gas in the upper space to the transfer chamber;
a plurality of gas suction ports installed at a lower part of the transfer chamber and sucking gas in the transfer chamber;
and a gas return path for returning gas sucked from each of the gas suction ports to the upper space,
In the gas return path,
A plurality of first flow paths extending from each of the plurality of gas suction ports,
a second flow path connected to the plurality of first flow paths to allow the gas to flow in from the first flow path and discharge the gas to the upper space;
Provided with an outlet for delivering the gas in the second flow path to the upper space,
EFEM, wherein the outlet is located lower than the upper ends of the plurality of fan filter units. The method of claim 6, wherein the second flow path extends in a direction intersecting the extension direction of the first flow path,
The direction of the air flow of the gas flowing through the gas return path changes when it passes from the first flow path through the second flow path, and the direction of the air flow also changes when it flows into the upper space from the second flow path. EFEM characterized by being. The method according to claim 6 or 7, further comprising: a substrate transfer device disposed in the transfer chamber, the substrate transfer device having a base unit whose position is fixed, and a transfer unit disposed above the base unit to transfer the substrate;
In the transfer chamber, an installation is disposed below the transfer area where the substrate is transferred by the transfer unit,
EFEM, wherein the gas suction port is disposed at a position that does not overlap with either the base portion or the fixture when viewed from the vertical direction.

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