System and method for transferring and aligning wafers

Abstract

There is provided a method and system for transferring wafers. Wafers in a FOUP are horizontally aligned by vibrating the FOUP before unloading the wafers from the FOUP. Thereafter, a mapping process may be accurately performed, and the wafers stably unloaded from the FOUP.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] Embodiments of the invention relate to an apparatus and a method for handling wafers during the fabrication of semiconductor devices. More particularly, embodiments of the invention relate to an apparatus and method for horizontally aligning wafers in a container.

[0003] This application claims priority to Korean Patent Application No. 2005-88856 filed Sep. 23, 2005, the subject matter of which is hereby incorporated by reference.

[0004] 2. Description of the Related Art

[0005] Semiconductor devices are fabricated by applying a complex sequence of processes to wafers that serve as a substrate for the devices. Fabrication processes are generally performed in a so-called "clean room" wherein an extreme degree of cleanliness is maintained. To avoid potential contamination and aid in the efficient handling of wafers, they are commonly stored and transferred in open type wafer containers within the clean room environment. However, it is very expensive to maintain a clean room at the required level of cleanliness. As a result, clean rooms tend to be relatively small in size, but are often surrounded by ancillary clean areas having a very high degree of cleanliness, but not nearly as clean as the clean room itself. Wafers are often stored in these ancillary clean areas in hermetically sealed wafer containers. Such containers are used to protect wafers from contamination by foreign substance (e.g., particles), as well as trace chemical contamination. The so-called Front Open Unified Pod (hereinafter, referred to as FOUP) is one example of a conventionally available hermetic wafer container.

[0006] The fabrication of contemporary semiconductor devices is characterized by increasing wafer diameters (e.g., a migration from 200 to 300 mm), and increased automation of the fabrication processes. Automation of fabrication processes, including the transfer of wafers to/from a clean room, is facilitated by wafer transfer systems. The Equipment Front End Module (hereinafter, referred to as EFEM) is one type of commonly used wafer transfer system. The EFEM is connected within a semiconductor fabrication facility so as to transfer wafers between one or more FOUPs and various work stations, including clean rooms, within the facility.

[0007] An exemplary load port for an EFEM is disclosed in U.S. Pat. No. 6,473,996. When a FOUP is placed on a station of the load port, a door of the FOUP is opened by a door opener. A determination is then made as to whether wafers are loaded into a plurality of slots within the FOUP. A mapping process is then performed to identify the number of the wafers loaded in the FOUP. If data about a particular wafer in a slot does not correspond to the mapping data, the transfer process is interrupted. On the other hand, if the mapping data corresponds, then the wafers are removed from the FOUP and transferred to the identified process facility. Once the wafers are completely processed, they are returned to the FOUP and the door of the FOUP is closed to again hermetically seal the FOUP from the external environment.

[0008] A FOUP may be transferred between work stations in a process facility (and between different process facilities) by automated devices, such as overhead transfer equipment or human workers. Wafers inserted in the slots of the FOUP often deviate from a true horizontal plane during transfer of the FOUP due to mechanical vibrations. In such cases, the deviating wafers can not be accurately detected by the sensor performing the mapping process. As a result, the mapping data is different from the predetermined data, generating facility errors and interrupting the process. Also, deviating wafers may not be stably loaded on a transferring arm. Unstably loaded wafers may fall from the transferring arm and be damaged.

SUMMARY OF THE INVENTION

[0009] Embodiments of the present invention provide an apparatus and a method for handling wafers which ensures that wafers are inserted into the slots of a container without deviation from a desired planar arrangement. This result reduces handling errors, process interruptions, and the potential for damage to the wafers.

[0010] In one embodiment, the invention provides; a method of transferring wafers from a container, the wafers being inserted into slots within the container, the method comprising; placing the container on a load port, aligning the wafers in the container, and thereafter unloading the wafers from the container, wherein aligning the wafers comprises shaking the container by applying an external mechanical force to cause the wafers to settle onto the slots.

[0011] In another embodiment, the invention provides a wafer transfer system adapted to transfer wafers from a container to a process facility, the wafers being received into slots within the container, the wafer transfer system comprising; a load port adapted to receive and support the container, a frame positioned between the load port and the process facility and comprising a transfer robot adapted to transfer the wafers from the container to the process facility, and an alignment unit adapted to settle the wafers into the slots in horizontal alignment by mechanically shaking the container supported by the load port.

[0012] In another embodiment, the invention provides a wafer aligner adapted to horizontally align wafers inserted into slots of a container, the substrate aligner comprising; an alignment station, a shake plate disposed on the alignment station and adapted to receive the container, and a shake plate driver adapted to shake the shake plate to thereby cause settling of the wafers onto their respective slots.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a view illustrating an example of a wafer handling apparatus employing a wafer transfer system according to an embodiment of the invention;

[0014] FIG. 2 is a perspective view of the container in FIG. 1;

[0015] FIG. 3 is a perspective view of the load port in FIG. 1;

[0016] FIGS. 4A and 4B are respective views illustrating a case wherein a wafer deviates from a desired plane arrangement, and a case wherein wafers are properly aligned in a container;

[0017] FIG. 5 is a perspective view of a load port in which an aligner having a striker is installed;

[0018] FIG. 6 is a flowchart illustrating a method of transferring wafers in a wafer transfer system according to an embodiment of the invention;

[0019] FIGS. 7 to 10 are related views illustrating a process of separating the door from the body of the container of the apparatus shown in FIG. 1; and

[0020] FIG. 11 is a view illustrating another example of an aligner adapted to align wafers in a container.

DESCRIPTION OF EMBODIMENTS

[0021] Reference will now be made to several embodiments of the invention, examples of which are illustrated in the accompanying drawings. However, the present invention is not limited to only the illustrated embodiments. Rather, the embodiments are presented as teaching examples.

[0022] FIG. 1 is a view illustrating a wafer handling apparatus employing a wafer transfer system 30 according to an embodiment of the invention. Referring to FIG. 1, the wafer handling apparatus generally comprises a container 10, a wafer transfer system 30, and a process facility (or work station) 20.

[0023] Container 10 is adapted to receive semiconductor substrates in the form of wafers. A hermetic container may be used as container 10 to protect the wafers from particle and/or chemical contamination during transfer. In one particular embodiment of the invention a FOUP is used as the hermetic container.

[0024] FIG. 2 is a perspective view of FOUP 10. Referring to FIG. 2, FOUP 10 comprises a body 12 having an interior space accessible through a door 14. A plurality of slots 12a are formed parallel to one another in at least one inner wall of body 12, and are adapted to receive respective edge portions of an inserted wafer. Latch holes 14b and registration holes 14a are formed in door 14 of FOUP 10. A plate spring (not shown) may be installed in an inner side of the door 14 to press the wafers into FOUP 10 when door 14 is closed.

[0025] Process facility 20 may perform a chemical vapor deposition process, a dry etching process, a thermal treatment, a development process, or a cleaning process, etc. Although is not shown, a load lock chamber, a transfer chamber, and process chambers adapted to perform one or more of the aforementioned processes may be included in process facility 20.

[0026] Wafer transfer system 30 transfers the wafers between FOUP 10 and process facility 20. In the illustrated example, wafer transfer system 30 comprises a load port 100, a frame 200, a transfer robot 220, and an alignment unit 300. Frame 200 has a substantially rectangular shape. Of the sidewalls of frame 200, a transfer port 202a allowing transfer of the wafers W is formed on a rear wall 202 adjacent to process facility 20. An opening is formed in a front wall 204 which faces rear wall 202. An exhaust port 206 is provided at a lower portion of frame 200 to exhaust air.

[0027] A fan filter unit 240 is provided at an upper portion of frame 200 to help maintain cleanliness within frame 200. A fan 242 generates a streamline flow of air from the upper portion of frame 200 down towards the lower portions of frame 200. A filter 244 removes contamination particles from the air entering frame 200.

[0028] Transfer robot 220 is provided in frame 200 to transfer the wafers between FOUP 10 and process facility 20. One or more transfer robots 220 may be so provided.

[0029] A mapping unit 260 is also provided in wafer transfer system 30 to determine whether wafers are placed in slots 12a of FOUP 10. Mapping unit 260 may comprise a light emitting sensor and a light receiving sensor (both not shown), and may be associated with transfer robot 220 or a door holder 182. One conventionally understood mapping method applicable to the working example shown in FIG. 1 determines the presence or absence of wafers by selectively illuminating portions of container 10 with light and detecting a return optical signal.

[0030] Load port 100 contacts front wall 204 of frame 200 and supports FOUP 10 during the transfer process. FIG. 3 is a perspective view further illustrating load port 100 of FIG. 1.

[0031] Referring to FIGS. 1 and 3, load port 100 comprises a vertical frame 160, a station 120, a conveying plate 140, a plate driver 170, and a door opener 180. Vertical frame 160 is inserted into opening of front wall 204 of frame 200 so as to be connected with frame 200. A through hole 162 is formed in vertical frame 160 to facilitate the transfer of the wafers. In the illustrated example, through hole 162 has a substantially rectangular shape.

[0032] Station 120 is mounted on a side of vertical frame 160, and conveying plate 140 is coupled onto an upper surface of station 120. In the illustrated example, station 120 has a substantially flat upper surface, and a guide groove 122 is formed in a middle portion of the flat upper surface to act as a guide for a conveying plate 140 to linearly move towards vertical frame 160.

[0033] Conveying plate 140 has an upper plate 142 of substantially rectangular shape and a lower plate 144 extending downward from upper plate 142 and being inserted into guide groove 122. A plurality of kinematic fins 142a may be formed on conveying plate 140. In use, kinematic fins 142a are inserted into grooves (not shown) formed in a lower surface of FOUP 10, such that FOUP 10 is placed in a predetermined position on conveying plate 140.

[0034] Door opener 180 opens and closes door 14 of FOUP 10 once FOUP 10 has been placed on conveying plate 140. Door opener 180 includes door holder 182, an arm 184, and a holder driver (not shown). Door holder 182 is formed with a size and shape corresponding to through hole 162. Arm 184 is fixedly coupled to a rear surface of door holder 182. The holder driver is coupled to arm 184, as to facilitate movement of arm 184 up, down, right or left. The holder driver may be installed in station 120. Latch keys 182b adapted for insertion to latch holes 14b of door 14 (see, FIG. 2) and registration pins 182a adapted for insertion to registration holes 14a are installed on door holder 182.

[0035] As illustrated above, the wafers are inserted into slots 12a within FOUP 10. However, the wafers may be inserted in such a manner that deviations from a desired planar alignment (e.g., a horizontal planar alignment) occur. Alternatively, mechanical vibrations caused by auto-transfer system, such as an overhead transfer (not shown), may cause deviations in the alignment of the wafers within FOUP 10. Under these circumstances, mapping unit 260 may fail to properly detect the presence of deviating wafers within FOUP 10 during the mapping process.

[0036] Accordingly, alignment unit 300 is adapted to align the wafers within FOUP 10 in a desired planer alignment. In one embodiment, alignment unit 300 vibrates or shakes FOUP 10 to motivate any deviating wafers into a desired horizontal alignment. In one specific embodiment, alignment member 300 mechanically vibrates or strikes FOUP 10 to accomplish this result.

[0037] In one embodiment, FOUP 10 is vibrated linear reciprocation. In this exemplary approach, a controller 310 within alignment unit 300 controls movement of plate driver 170. Controller 310 controls the movement of plate driver 170 in such a manner that conveying plate 140, whereon FOUP 10 has been placed, is linearly reciprocated. For example, controller 310 controls the plate driver 170, such that conveying plate 140 reciprocates back and forth with guide groove 122. A reciprocating distance as well as the speed of reciprocation for conveying plate 140 may be defined such that the wafers in FOUP 10 are sufficiently vibrated to ensure a flat horizontal alignment within their respective slots 12a.

[0038] FIGS. 4A and 4B are comparative views illustrating one case wherein a wafer within a plurality of wafers W in not properly seated within its slot 12a, and another case following mechanical vibration of the wafers within FOUP 10. As illustrated in FIG. 4A, when FOUP 10 is initially placed on load port 100, one edge of a wafer W is properly placed within a slot 12a, but the other edge of the wafer is not. However, when FOUP 10 is vibrated, the unseated edge of the wafer properly settles onto slot 12a, thus properly aligning the wafer.

[0039] The wafers W are aligned in FOUP 10 before door 14 is opened. This prevents the wafers W from falling out of FOUP 10 when it's vibrated. The wafers W may be aligned in FOUP 10, after latch keys 182b of door holder 182 are coupled to latch holes 14b of door 14 to unlock door 14, but before door 14 is separated from body 12 of FOUP 10.

[0040] In the aforementioned method, conveying plate 140 linearly reciprocates along guide groove 122 to vibrate FOUP 10. However, FOUP 10 may be vibrated using other methods. For example, conveying plate 140 may be reciprocated or vibrated in any reasonable direction using many different techniques.

[0041] Also, in the aforementioned exemplary method, conveying plate 140 is acted upon to vibrate FOUP 10. However, FOUP 10 may be vibrated by reciprocating door holder 182, up, down, right and/or left, or back and forth when FOUP 10 is coupled to door holder 182.

[0042] In another embodiment, an alignment unit 300 may include a striker 320 adapted to mechanically strike FOUP 10. FIG. 5 illustrates an example wherein striker 320 is installed on load port 100. Referring to FIG. 5, striker 320 includes a strike bar 322, a moving rod 324, and the strike bar driver (not shown). Strike bar 322 is adapted to strike FOUP 10 or conveying plate 140 to directly impart a settling impact to FOUP 10. Strike bar 322 may have a rod shape terminating in a spherical head. Strike bar 322 is horizontally disposed relative to conveying plate 140. Moving rod 324 is coupled to strike bar 322, and in the illustrated example includes a horizontal rod 324a horizontally disposed to penetrate through a hole 124 formed in a sidewall of station 120 and a vertical rod 324b vertically extending from an end of horizontal rod 324a. Strike bar 322 is coupled to an end of vertical rod 324b. Moving rod 3245 is mechanically coupled to the strike bar driver.

[0043] A method of transferring wafers using the aforementioned wafer transfer system 30 will now sequentially described with collective reference to FIGS. 6 to 10. FIG. 6 is a flowchart illustrating an exemplary method of transferring wafers according to an embodiment of the invention, and FIGS. 7 to 10 are related views sequentially illustrating a process of separating door 14 from body 12 of FOUP 10.

[0044] Door holder 182 is inserted into through hole 162, and FOUP 10 is placed on conveying plate 140 by an overhead transfer (FIG. 7, S10).

[0045] Conveying plate 140 then moves towards door holder 182. Registration pins 182a of door holder 182 are inserted into registration holes 14a of door 14, and latch keys 182b of door holder 182 are inserted into latch holes 14b of door 14. Latch keys 182b of door holder 182 rotate in latch holes 14b, and thus door holder 182 is coupled to door 14 (FIG. 8, S20).

[0046] Conveying plate 140 reciprocates along a guide groove 122, vibrating FOUP 10 (FIG. 9, S30).

[0047] Then, door holder 182 moves back and down under the control of the holder driver. Thus, door 14 of FOUP 10 is separated from body 12, thereby opening FOUP 10 (FIG. 10, S40).

[0048] In the aforementioned embodiment, FOUP 10 is vibrated after door 14 of FOUP 10 is coupled to door holder 182. However, on the other hand, FOUP 10 may be vibrated before door 14 of FOUP 10 is coupled to door holder 182.

[0049] Next, the presence or absence of wafers in slots 12a is detected by mapping unit 260. A process is performed wherein detected data is checked in relation to predetermined input data. Then, wafers are sequentially unloaded from FOUP 10 by transfer robot 220, and transferred to process facility 20. Once processed, a wafer is re-loaded back into FOUP 10.

[0050] Once all wafers have been processed, door holder 182 moves up and forward, and door 14 of FOUP 10 is again coupled to body 12. The latch keys rotate, and conveying plate 140 moves along guide groove 122 in a direction away from door holder 182. Selectively, after door 14 of FOUP 10 is coupled to body 12, conveying 140 may linearly reciprocate along guide groove 122, thereby settling and aligning the wafers W in FOUP 10.

[0051] In the aforementioned embodiment, the wafers are aligned in FOUP 10 before being transferred from FOUP 10 by wafer transfer system 30. However, in another embodiment of the invention, the wafers may be aligned using another approach. This approach relies on an aligner 400 to horizontally align wafers in a container 10. This approach will be briefly described with reference to FIG. 11.

[0052] Referring to FIG. 11, aligner 400 is adapted to horizontally align the wafers in FOUP 10, and comprises an alignment station 420, a shake plate 440, a shake plate driver 460, and a controller 480. Shake plate 440 is installed on an upper surface of alignment station 420. Shake plate 440 is substantially flat and has an upper plate 442 whereon FOUP 10 is placed, and a lower plate 444 extending downward from upper plate 442. In the illustrated example, upper plate 442 has a substantially rectangular shape, and lower plate 444 protrudes downward from a middle portion of upper plate 442.

[0053] An inserting groove 446 is formed through alignment station 420, and lower plate 444 of shake plate 440 is inserted into inserting groove 446. Inserting groove 446 has a larger diameter than that of lower plate 444. Shake plate driver 460 is installed under lower plate 444 to vibrate lower plate 444 up and down, right and left, and/or a back and forth. When FOUP 10 is placed on shake plate 440, shake plate driver 460 is controlled by controller 480 to vibrate shake plate 440. In one embodiment, shake plate driver 460 may linearly reciprocate shake plate 440 to vibrate the shake plate 440.

[0054] According to these various embodiments of the present invention, wafer placed in a container, such as a FOUP, may be stably transferred because the wafers are all properly aligned within the container. As a result, a subsequently performed mapping process may accurately determine the presence and absence of wafers within the container.

[0055] While the invention has been described in the context of several embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made thereto. Thus, it is intended that the present invention covers all such modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A method of transferring wafers from a container, the wafers being inserted into slots within the container, the method comprising: placing the container on a load port; aligning the wafers in the container; and thereafter unloading the wafers from the container, wherein the aligning the wafers comprises shaking the container by applying an external mechanical force to cause the wafers to settle onto the slots.

2. The method of claim 1, wherein the shaking of the container comprises mechanically vibrating the container.

3. The method of claim 2, wherein the vibrating of the container comprises linearly reciprocating a conveying plate associated with the load port, and wherein placing the container on the load port comprises placing the container on the conveying plate.

4. The method of claim 3, further comprising opening a door provided in a body of the container, wherein the opening of the door comprises: inserting latch keys formed on a door holder of a door opener into latch holes formed on the door of the container before the aligning of the container; and separating the door from the body of the container after the aligning of the container.

5. The method of claim 1, further comprising, after the unloading of the wafers from the container: re-loading the wafer into the container; and thereafter, aligning the wafers in the container by vibrating the container.

6. The method of claim 1, wherein the shaking of the container comprises imparting a physical impact to the container.

7. A wafer transfer system adapted to transfer wafers from a container to a process facility, the wafers being received into slots within the container, the wafer transfer system comprising: a load port adapted to receive and support the container; a frame positioned between the load port and the process facility and comprising a transfer robot adapted to transfer the wafers from the container to the process facility; and an alignment unit adapted to settle the wafers into the slots in horizontal alignment by mechanically shaking the container supported by the load port.

8. The wafer transfer system of claim 7, wherein the load port comprises: a station; a conveying plate associated with the station and adapted to receive the container; and a conveying plate driver adapted to linearly reciprocate the conveying plate, wherein the alignment unit comprises a controller adapted to control operation of the conveying plate driver.

9. The wafer transfer system of claim 7, wherein the alignment unit comprises a striker adapted to mechanically strike an outer wall of the container supported by the load port.

10. A wafer aligner adapted to horizontally align wafers inserted into slots of a container, the substrate aligner comprising: an alignment station; a shake plate disposed on the alignment station and adapted to receive the container; and a shake plate driver adapted to shake the shake plate to thereby cause settling of the wafers onto their respective slots.

11. The wafer aligner of claim 10, wherein the shake plate driver is adapted to vibrate the shake plate.

12. The wafer aligner of claim 10, wherein the shake plate driver reciprocates the shake plate back and forth, right and left, or up and down.

13. The Wafer aligner of claim 10, wherein the container is a hermetic container.

14. The wafer aligner of claim 13, wherein the hermetic container comprises a Front Open Unified Pod (FOUP).