Semiconductor wafer loading and unloading apparatus

Abstract: A transport container for transporting a plurality of semiconductor wafers as stacked therein. The container includes a box-shaped container body having four peripheral walls, and an upper lid for closing and opening an upper opening of the container body. The front wall of the container body is pivotable between an open position and a closed position. The upper lid and front wall are opened when the semiconductor wafers are loaded into or unloaded from the transport container. An apparatus is provided for loading and unloading the semiconductor wafers into/from the transport container. The apparatus includes a cassette table for supporting a cassette for storing the semiconductor wafers in multiple stages at predetermined intervals, a container table for supporting the transport container openable and closable for storing the semiconductor wafers stacked alternately with protective sheets of guard paper, and a robot arm substantially opposed to each of the cassette table and the container table for transporting the semiconductor wafers between the cassette and the transport container.

Description: BACKGROUND OF THE INVENTION (1) Field of Invention This invention relates to apparatus for loading and unloading semiconductor wafers (hereinafter referred to simply as wafers also). More particularly, such apparatus are used to unload wafers from cassettes and load the wafers in a stacked state in transport containers, or to unload wafers from transport containers and load the wafers in the cassettes, when transporting the wafers in packages from a wafer manufacturing plant to a separate semiconductor device assembly plant. (2) Description of the Related Art The above containers are used in transporting the wafers in packages from a wafer manufacturing plant to a separate semiconductor device assembly plant. The apparatus noted above are operable to unload wafers from cassettes in which the wafers are arranged in multiple stages at predetermined intervals, and load the wafers in a stacked state in the transport containers, or to unload wafers from the transport containers and load the wafers in the cassettes. Conventionally, one apparatus is used exclusively to unload the wafers from the cassettes in which the wafers are arranged in multiple stages at predetermined intervals, and load the wafers in a stacked state in the transport containers, and another apparatus is used exclusively to unload wafers from the transport containers and load the wafers in the cassettes. The entire apparatus therefore tends to be large and costly. Each transport container used for the above purpose may be the type having a container body for storing a plurality of semiconductor wafers arranged in vertical posture at predetermined intervals, and an upper lid placed on the container body. Another type of transport container includes a cylindrical or box-shaped container body for storing a plurality of semiconductor wafers in a stacked state, and an upper lid placed on an upper end of the container body. The former type of container for storing semiconductor wafers arranged in vertical posture has the advantage of allowing the wafers to be loaded and unloaded relatively easily. However, since this container supports the wafers in positions adjacent edges thereof, the wafers to be stored therein are limited to those strong wafers having a thickness in the order of 350 to 800 µm before back grinding, for example. When this container is used in transporting wafers having a thickness in the order of 150 to 300 µm after back grinding, the wafers could easily be cracked by vibrations or the like occurring during transport. The latter transport container for storing semiconductor wafers in a stacked state supports the wafers at surfaces thereof. Thus, this type of container can transport even thin wafers without damage done thereto. However, when the wafers are loaded into or unloaded from the container body by using a suction arm or the like, the wafers must be moved in horizontal posture only through the upper opening of the container body. When the wafers are moved vertically for storage in the container body or for withdrawal therefrom, edges of the wafers could easily knock against inner walls or opening of the container body. Thin wafers in horizontal posture will easily be broken or chipped though a contact made in a vertical direction. Thus, a troublesome operation is required, such as moving wafers into and out of the container body at ultraslow speed or operating the suction arm or the like with high precision. In particular, the deeper the container is, the greater vertical amount the wafers must be moved, entailing a correspondingly greater possibility of contact, thereby to encounter the above inconvenience. Further, the conventional transport containers have no function to release static electricity from wafers or to preclude static electricity from being generated during transport. Such static electricity may ruin semiconductor elements in the wafers. US 5,061,144 discloses an apparatus for loading and unloading semiconductor wafers according to the preamble of claim 1. The known apparatus includes a wafer holding member for holding a semiconductor wafer, and driving mechanisms for conveying the wafer holding member to resist coating mechanism and the like. SUMMARY OF THE INVENTION This invention has been made having regard to the state of the art noted above, and its object is to provide an apparatus for loading and unloading semiconductor wafers, which apparatus has a small overall construction and is low cost, with functional components arranged in a rational manner and for combined use. According to the present invention the objects are fulfilled by an apparatus as defined in claim 1. When the apparatus according to this invention is used for packing and transporting semiconductor wafers, the handling robot is operated to hold and unload the wafers, one at a time, from the cassette placed on the cassette table, and to move the wafers into the transport container in an open state and stack the wafers therein. The operation of the handling robot to supply the semiconductor wafers into the transport container is carried out alternately with an operation of a separately provided handling robot to supply guard paper. When a predetermined number of wafers has been loaded in the stacked state, the transport container is closed and transported out of the apparatus. When this apparatus is use for unloading semiconductor wafers transported in the transport container, the transport container is opened on the container table, and the handling robot is operated to hold and unload the wafers, one at a time, from the container and load the wafers into the cassette. The operation of the handling robot to load the semiconductor wafers into the cassette is carried out alternately with an operation of a separately provided handling robot to remove guard paper from the transport container. As noted above, the apparatus according to this invention may be used both for transferring semiconductor wafers from the cassette to the transport container and for transferring wafers from the transport container to the cassette. This construction realises a cost reduction compared with a case of providing separate apparatus dedicated to the two transfer operations. Besides, the entire apparatus may be formed compact by arranging the respective functional components as substantially opposed to the handling robot. The semiconductor wafer loading and unloading apparatus according to this invention further comprises an aligner for positionally adjusting the semiconductor wafers delivered thereto, and a guard paper transport mechanism for transporting the guard paper into and out of the transport container, wherein the handling robot is substantially opposed to each of the cassette tables, the container table and the aligner, the robot arm being swivelable, vertically movable, horizontally extendible and retractable, and rotatable to turn upside down, for transporting the semiconductor wafers among the cassette, the aligner and the transport container. When the apparatus having the above construction is used for packing and transporting semiconductor wafers, the handling robot is operated to unload the wafers by supporting the wafers at reverse surfaces thereof, one at a time, from the cassette placed on the cassette table. The handling robot first supplies each wafer to the aligner for adjusting the wafer to a predetermined position and posture. Thereafter, the handling robot picks up the wafer again. The handling robot is swiveled to a position opposed to the container table, and the robot arm is rotated to turn the wafer upside down. In this way, the handling robot successively moves the wafers into the transport container in an open state and stacks the wafers therein. The operation of the handling robot to supply the semiconductor wafers into the transport container is carried out alternately with an operation of the guard paper transport mechanism to supply guard paper. When a predetermined number of wafers have been loaded in the stacked state, the transport container is closed and transported out of the apparatus. When this apparatus is used for unloading semiconductor wafers transported in the transport container, the transport container is opened on the container table, and the handling robot is operated to unload the wafers by supporting the wafers at reverse surfaces thereof, one at a time, from the container. Subsequently, the guard paper transport mechanism is operated to remove guard paper from the transport container. These operations are repeated alternately. The wafers unloaded are turned over so that observe surfaces thereof face upward, and are successively supplied to the aligner. After the wafers are adjusted to a predetermined position and posture, the handling robot picks up the wafers again, and load them into the cassette. The use of the aligner noted above allows the wafer transfer operations to be carried out reliably. The handling robot is operable for extending the robot arm into the cassette placed on the cassette table storing the semiconductor wafers at the predetermined intervals, with patterned surfaces facing up to suck a reverse surface of each of the semiconductor wafers and remove each semiconductor wafer, and when loading the semiconductor wafers into the transport container, operable for rotating the robot arm suction-supporting the reverse surface of each semiconductor wafer to turn upside down each semiconductor wafer, and thereafter stacking each semiconductor wafer with the patterned surface facing down in the transport container, whereby the semiconductor wafers are stacked with the sheets of guard paper inserted in between. Preferably, the semiconductor wafer loading and unloading apparatus according to this invention further comprises an identification data reader for picking up images of surfaces of the semiconductor wafers positionally adjusted by the aligner to read identification data from the surfaces of the semiconductor wafers. By reading the identification data along with the wafers per se, the wafers may be stored in different transport containers or different cassettes as classified according to type. BRIEF DESCRIPTION OF THE DRAWINGS For the purpose of illustrating the invention, there are shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. Fig. 1 is an overall plan view of an apparatus for loading and unloading semiconductor wafers according to this invention; Fig. 2 is an overall front view of the apparatus according to this invention. Fig. 3 is an overall side view of the apparatus according to this invention. Fig. 4 is a perspective view showing an outward appearance of a transport container. DETAILED DESCRIPTION OF THE PREFERRED EMOBIMENTS Preferred embodiments of this invention will be described in detail hereinafter with reference to the drawings. <Apparatus for Loading and Unloading Semiconductor Wafers> Fig. 1 is an overall plan view of an apparatus embodying this invention. Fig. 2 is an overall side view thereof. The semiconductor wafer loading and unloading apparatus in this embodiment includes an apparatus base frame 1 having a handling robot 2 mounted in a substantially central position thereon. The robot 2 is surrounded by an aligner 3, two cassette tables 4, a transport container table 5 and a guard paper transport mechanism 6, all arranged on the base frame 1. The entire apparatus is built compact by arranging these mechanisms in an opposed relationship to the handling robot 2. The respective components will be described hereinafter. The handling robot 2 includes a suction head 2a secured to a robot arm 2b which is swivelable, vertically movable, horizontally extendible and retractable, and rotatable to turn upside down. By swiveling movement the robot arm 2b may be directed to a selected one of the aligner 3, cassette tables 4 and container table 5. By vertical and horizontal movement, the robot arm 2b may be set to a desired height and extended to and retracted from the aligner 3, cassette table 4 or container table 5. By rotation of the robot arm 2b, the suction surface of suction head 2a may be turned upward or downward. The aligner 3 includes a photoelectric sensor 3a or the like (Fig. 3) for picking up an image of an orientation flat of wafer W delivered thereto, thereby to detect a position and orientation of wafer W. The aligner 3 then adjusts the wafer W to a predetermined position and orientation as necessary. A CCD camera 7 is disposed above the aligner 3 for reading identification data affixed to the surface of wafer W by etching or other means. Each cassette table 4 is constructed to support a cassette C for storing a plurality of wafers W arranged, with obverse surfaces turned upward, at fixed vertical intervals determined by grooves and notches. The cassette C is fixed to the cassette table 4 to have a wafer inlet/outlet opening directed toward a swivel axis of the handling robot 2. The container table 5 supports a transport container A as shown in Fig. 4. The transport container A includes a box-shaped container body 21 having four peripheral walls, and an upper lid 22 for closing an upper opening of the container body 21. The front wall 21b of the container body 21 is pivotable to open and close. The transport container A will be described in greater detail hereinafter. The guard paper transport mechanism 6 includes a plurality of suction pads 8 supported to be vertically movable along an upstanding frame 9 which is in turn movable fore and aft along a fore-and-aft frame 10. This transport mechanism 6 transports guard paper P suction-supported by the suction pads 8 to supply guard paper P to the transport container A from above, or sucks to the suction pads 8 and collects sheets of guard paper P stacked alternately with wafers W in the cassette C. The semiconductor wafer loading and unloading apparatus in this embodiment has the above construction, and is used in transferring wafers W from cassette C to transport container A and from transport container A to cassette C. [Wafer Transfer from Cassette C to Transport Container A] (1) For this process, a cassette C or cassettes C storing wafers W arranged in multiple stages with patterned surfaces turned upward is/are placed on one or both of the cassette tables 4. The cassette C or cassettes C is/are fixed to the facing direction described hereinbefore. The upper lid 22 and front wall 21b of the transport container A on the container table 5 are opened. (2) First, the robot arm 2b is extended into the cassette C or one of the cassettes C. The robot arm 2b removes a wafer W with the reverse surface thereof suction-supported by the suction head 2a turned upward. Next, the robot arm 2b supplies the wafer W, with the obverse surface (patterned surface) facing up, onto a horizontally movable turntable of the aligner 3. While rotating the wafer W on the turntable, the photoelectric sensor 3a or the like is operated to pick up images of peripheral edges of the wafer W, thereby to detect a position and orientation of wafer W. The aligner 3 then corrects the position and orientation. After the positional adjustment of wafer W, the suction head 2a sucks the wafer W facing up. Then, the robot arm 2b is swiveled to a position opposed to the front of the transport container A. During the swiveling movement, the robot arm 2b is rotated to turn the wafer W upside down. (3) Next, the robot arm 2b is advanced with the suction head 2a supporting the wafer W upside down. After inserting the wafer W through the open front of the transport container A to a predetermined position therein, the robot arm 2b lowers and releases the wafer W in the container A. (4) After loading the wafer W into the transport container A, the robot arm 2b is retracted to fetch a next wafer. Meanwhile, the guard paper transport mechanism 6 is operated to place a sheet of guard paper P on the wafer W deposited face down in the container A. (5) The above operation is repeated to stack wafers W and sheets of guard paper P alternately. When a predetermined number of wafers W have been deposited in the stacked state, the front wall 21a and upper lid 22b of the transport container A are closed. The transport container A is removed from the container table 5, and a new transport container A is set to the table 5. [Wafer Transfer from Transport Container A to Cassette C] (1) For this process, empty cassettes C are fixed to both cassette tables 4, and a transport container A storing wafers W is placed on the container table 5. The upper lid 22 and front wall 21b of the transport container A are opened. (2) First, the robot arm 2b is extended into the transport container A and withdraws therefrom an uppermost wafer W with the reverse surface (facing up) thereof sucked to the suction head 2a turned downward. Then, the suction head 2a is turned over to supply the wafer, with the obverse surface facing up, onto the turntable of the aligner 3. (3) The CCD camera 7 is operated to pick up an image of wafer W positionally adjusted by the aligner 3, thereby to read identification data affixed to the wafer surface. (4) Next, the robot arm 2b sucks the reverse surface of the wafer W having the patterned surface facing up. Based on the identification data read, the robot arm 2b is directed to a predetermined one of the cassettes C. Then, the robot arm 2b is extended to deposit the wafer W at an address designated in advance or at an upper or lower end position in that cassette C. The robot arm 2b is thereafter retracted to fetch a next wafer. (5) Meanwhile, the guard paper transport mechanism 6 is operated to pick up and collect an uppermost sheet of guard paper P from the transport container A. (6) The above operation is repeated to take wafers W and sheets of guard paper P alternately out of the transport container A. The wafers W taken out are stored in cassettes C as classified according to type. The above embodiment may be modified as follows: (1) The above apparatus includes two cassette tables 4 and one container table 5. However, the numbers of cassette tables and container tables may be varied as desired. (2) Where there is no need to align orientation flats of wafers, the aligner 3 may simply be what is known as a centering mechanism only for centering the wafers. (3) Bar codes may be employed as the identification data affixed to wafer surfaces. In this case, the CCD camera 7 is replaced by a bar code reader.

Claims: An apparatus for loading and unloading a plurality of semiconductor wafers into/from a transport container (A) for transporting the semiconductor wafers as stacked therein, said apparatus comprising: a cassette table (4) for supporting a cassette (C) for storing said semiconductor wafers in a vertical stack spaced apart by predetermined intervals; a container table (5) for supporting said transport container (A) openable and closable for storing said semiconductor wafers stacked alternately with protective sheets of guard paper; an aligner (3) for positionally adjusting said semiconductor wafers delivered thereto; and a handling robot (2) substantially opposed to each of said cassette table, said aligner, and said container table and including a swivelable suction robot arm (2b) for transporting said semiconductor wafers among said cassette (C) and said aligner (3) and said transport container (A); characterized in that the apparatus further comprises a guard paper transport mechanism (6) for transporting said guard paper into and out of said transport container (A), and in that said robot arm is vertically movable, horizontally extendible and retractable, and rotatable to turn upside down. For transporting said semiconductor wafers to and from said transport container (A). The apparatus as defined in claim 1, further comprising identification data reading means for picking up images of surfaces of said semiconductor wafers positionally adjusted by said aligner to read identification data from said surfaces of said semiconductor wafers.

Inventors: AMETANI MINORU, MIYAMOTO SABURO, AMETANI, MINORU, MIYAMOTO, SABURO
Applicants: NITTO DENKO CORP, NITTO DENKO CORPORATION
Application year: 1996
Main classification: H01L21
IPC codes: B65G49, H01L21