Abstract:
A latch mechanism for latching a lid of a clean box having a box body opening at one surface and a lid for closing the opening includes a latch member pivotal about a shaft mounted on the box body, a latch engagement portion provided on the lid for engaging with the latch member in its predetermined pivotal position, and a biasing member for biasing the latch member toward the latch engagement portion. A guide surface is provided in a portion, facing outwardly, of the opening of the box body of the latch member. When the clean box is installed on a load port, the guide surface is brought into a pressing contact with the latch guide provided in the load port so that the latch member pivots to release the latch of the lid.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lid latch mechanism for a clean box for transferring and reserving various articles to be processed such as semiconductor wafers in a clean condition in a process for manufacturing semiconductors, electronic part related products, optical discs or the like. 
     2. Related Background Art 
     Recently, in a manufacturing process that requires a high level clean environment such as a semiconductor device manufacturing process, a method such as a mini-environment or a local clean space where an entire factory is not kept clean but only the ambient environment for products is kept under a clean condition has been adopted. In brief, only the interior of the respective processing apparatus is kept clean, which is used in the manufacturing process, and the transfer and reservation of the articles to be processed between the respective processing apparatus (clean apparatus) are performed by using containers (i.e., clean boxes) whose interior is kept clean. 
     The clean box is a substantially rectangular box body opened at one surface, and has a plate-like door (i.e., lid) for closing the opening. In the case where the article to be processed such as a semiconductor wafer received in the clean box is loaded into a processing apparatus, the loading operation is performed through an additional device called a load port, mounted on the processing apparatus. The load port is a device mounted on the processing apparatus for opening and closing the lid of the clean box while keeping the clean box and the interior of the processing apparatus under the clean condition and for making it possible to transfer the article to be processed such as a semiconductor wafer housed in the clean box into the interior of the processing apparatus. The load port is sometimes called an opener because it opens the lid of the clean box. 
     The clean boxes are categorized into two types in accordance with the types of the associated load ports, i.e., a bottom down type which is opened at the bottom surface, for taking out the housed article in the downward direction of the box and a side open type which is opened at a side surface of the clean box for taking out the housed article in the sideway. 
     An example of the bottom down type clean box is shown in FIGS. 1A and 1B. FIG. 1A is a side elevational cross-sectional view of the clean box and FIG. 1B is a plan view of the lid (door). 
     As shown in FIG. 1A, a clean box  100  is composed of a substantially square-shaped box body  101  opened at one side surface (a bottom surface in case of the bottom down type clean box shown in FIGS. 1A and 1B) and a lid  102  for closing the opening of the box body  101 . A shelf-like carrier  103  for holding the stacked semiconductor wafers to be received in the box at an equal interval is fixed above the lid  102  in the example shown in FIGS. 1A and 1B. A flange portion  101   a  expanded outwardly is provided around the bottom surface opening of the box body  101  into which the lid  102  is inserted/engaged. 
     An annular groove  110  for vacuum suction is formed in a circumferential edge portion of the surface (upper surface) facing the box body  101  of the lid  102  in the example shown in FIGS. 1A and 1B. O-rings used as elastic seal members are mounted along the inside and the outside of the annular groove  110  along the annular groove  110 , respectively. Under the condition that the lid  102  closes the opening of the clean box body  101  in FIG. 2, the suction space formed by the annular groove  110  and the flanged portion  101   a  of the box body  101 , i.e., a space of an interior of the annular groove  110  closed at its upper portion by the flanged portion  101   a  of the box body  101  is evacuated to thereby suck the lid  102  to the box body  101 . The evacuation is performed from the back side of the lid by a means (not shown) through a gas passage  112  provided in communication with the annular groove  110 . For instance, the vacuum suction method using such a suction groove is described in Japanese Patent Application Laid-Open No. 10-321696. 
     In such type clean box, there is provided a mechanical latch for preventing the falling off of the lid since there is a fear that the lid would be fallen off in the case where the vacuum suction is broken down due to leakage at the seal portion or the like. 
     Also, in a conventional clean box where the above-described vacuum suction groove is not provided, a seal member such as an O-ring is mounted so as to surround the opening of the box on the lid  102  or the box body flange portion  101   a.  Also in this case, although the latch mechanism for latching the lid to the box body is provided, the function of the latch mechanism is not only to prevent the lid from falling off but also to fix the lid to the body under the sealed condition by depressing the lid to the box body and deforming the seal member (O-ring) between the box body and the lid. 
     An example of the conventional lid latch mechanism to be used for both the clean box provided with the above-described vacuum suction annular groove and the clean box provided with no annular groove is shown in FIG.  2 . FIG. 2 is a bottom view of the lid of the clean box  100  shown in FIGS. 1A and 1B. 
     The latch mechanism has a circular rotary cam plate  201  provided rotatably substantially at a center of the interior of the lid  102 . Two cam grooves  201   a  and  201   b  are formed in the rotary cam plate  201 . The latch mechanism also has slidable latch members  203  and  204 . The latch members  203  and  204  are slidable up and down under the guidance of guide members  206  and  207 . Cam pins  205  and  206  are implanted in the latch members  203  and  204 , respectively, and the cam pins  205  and  206  are engaged with the cam grooves  201   a  and  201   b  of the rotary cam plate  201 , respectively. 
     As shown in FIG. 2, the respective cam grooves  201   a  and  201   b  are formed into a shape such that a distance from the center of the rotary cam plate  201  is changed depending on the circumferential position thereof. The latch members  203  and  204  are moved up and down in FIG. 2 in response to the clockwise and counterclockwise rotation of the rotary cam plate  201  in accordance with the cam shape. Thus, in response to the rotational position of the rotary cam plate  201 , the respective tip end portions  203   a  and  204   a  may take positions retracted and projected with respect to the circumference of the lid  102 . 
     In the case where the lid is mounted on the clean box body  101 , when the rotary cam plate  201  is rotated in the counterclockwise direction of FIG. 2 so that the tip end portions  203   a  and  204   a  of the latch members are projected from the circumference of the lid  102 , the tip end portions are engaged with tabs or holes (not shown) formed in the clean box body  101  to thereby latch the lid  102  to the clean box body  101 . Inversely, when the rotary cam plate  201  is fully rotated clockwise, the latch members  203  and  204  are slid to the innermost position indicated by two-dot-and-dash lines in FIG.  2 . In this case, the tip end portions  203   a  and  204   a  of the latch members are retracted from the circumference of the lid to thereby release the engagement with the clean box body. 
     A latch drive portion  209  is provided at the center of the rotary cam plate  201  for rotatably driving the cam plate  201 . A pair of circumferential holes  201   c  are formed in the latch drive portion  209 . 
     A mechanism for opening/closing the above-described latch is provided in the load port for transferring the article to be processed within the clean box to the processing apparatus. A latch opening/closing mechanism having two pins that engage with the circumferential holes  201   c  of the above-described latch drive portion  209  of the latch mechanism is provided in the load port table on which the clean box  100  is laid on the load port. The pins are driven to rotate the latch drive portion  209  to thereby open/close the latch of the clean box lid  102 . 
     The above-described conventional lid latch mechanism has the following disadvantage. First of all, the mechanism is complicated and needs a large number of mechanical parts. Accordingly, the cost is increased, and on the other hand, the possibility of breakdown is increased so that the operation would frequently be discontinued. Also, when the latch mechanism is to be closed and opened, a mechanism for opening/closing using a power of a motor, an actuator or the like is required (the latch opening/closing mechanism provided in the load port in the above-described conventional example). Also, this requires the increased cost and increases the possibility of breakdown due to its complicated structure. 
     Accordingly, there is a high demand to latch the lid to the clean box with a simpler mechanism. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a lid latch mechanism for a clean box, which has a simple structure for solving the above-noted defects. According to the present invention, there is provided a lid latch mechanism for latching a lid of a clean box having a box body opening at one surface and the lid for closing the opening, comprising: a latch member that is mounted on the box body and pivotal about a single shaft; a latch engagement portion provided on the lid for engaging the latch member in its predetermined pivotal position; and a biasing member for biasing the latch member toward the latch engagement portion, wherein a guide surface is provided on a portion, facing the outside of the opening of the box body of the latch member, and when the clean box is set on a load port, the guide surface is brought into contact with and pressed by a latch guide provided on the load port so that the latch member pivots to thereby release the latch of the lid. 
     Also, according to the present invention, there is provided a lid latch system for a clean box in a clean transfer system composed of the clean box having a box body opening at one surface and a lid for closing the opening and a load port for opening the clean box and loading into a clean apparatus an article to be transferred within the clean box, comprising: a clean box latch mechanism including a latch member that is mounted on the box body and pivotal about a single shaft, a latch engagement portion provided on the lid for engaging the latch member kept in a predetermined pivotal position, and a biasing member for biasing the latch member toward the latch engagement portion; and a latch guide mechanism as a projection provided on the load port, wherein when the clean box is set on the load port, the latch member is brought into contact with and pressed by the latch guide mechanism so that the latch member pivots to release the latch of the lid. 
     In the lid latch mechanism for the clean box and the lid latch system according to the present invention, it is possible to use a structure in which upon dismounting the clean box from the load port, the pressure of the latch mechanism by the latch guide on the load port is released, and then the latch member is forced by the biasing member to pivot to thereby engage with the latch engagement portion of the lid so that the lid is automatically latched. 
     It is preferable that the latch mechanism be provided in each of two opposite sides of the opening of the box body. 
     In the lid latch mechanism for the clean box and the lid latch system according to the present invention, it is preferable to use a lid latch mechanism for such a type clean box that the clean box has an annular groove formed so as to surround the opening in at least one of the box body and the lid, so that a vacuum suction annular space is formed between the box body and the lid in a condition where the lid closes the opening of the box body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B are views showing a clean box having a vacuum suction annular groove. FIG. 1A is a side elevational cross-sectional view of the clean box and FIG. 1B is a plan view of a lid; 
     FIG. 2 is a view showing a conventional lid latch mechanism; 
     FIG. 3 is a side elevational cross-sectional view showing a clean box (bottom down type) having a lid latch mechanism according to an embodiment of the present invention; 
     FIG. 4 is a bottom view showing the clean box shown in FIG. 3; 
     FIG. 5 is a schematic view showing a state in which the clean box is set on a load port of a semiconductor device manufacturing apparatus; 
     FIGS. 6A and 6B are side elevational cross-sectional view showing the operation of the lid latch mechanism when the clean box is set on the load port; 
     FIG. 7 is an exploded perspective view illustrative of the detail of the structure of the lid latch mechanism; and 
     FIGS. 8A and 8B are views of a clean box (side open type) according to another embodiment of the present invention. FIG. 8A is a side elevational view (partially in cross-section), and FIG. 8B is a frontal view as viewed from the opening. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the accompanying drawings. 
     FIGS. 3 and 4 are views showing a clean box provided with a lid latch mechanism according to the present invention. FIG. 3 is a side elevational cross-sectional view showing the clean box and FIG. 4 is a bottom view showing the clean box body. A clean box  1  according to the embodiment shown in FIG. 3 is a clean box for transferring and keeping semiconductor wafers in a semiconductor device manufacturing process. This clean box  1  has a substantially square-shaped clean box body  3  opened at a bottom surface and a lid  5  for closing the lower opening of the clean box body  3  in the same manner as in the conventional clean box shown in FIGS. 1A and 1B. A periphery of the opening bottom surface of the clean box body  3  expands outwardly to form a flange. A carrier  7  for holding a plurality of semiconductor wafers substantially at an equal interval in parallel with each other is fixed to the top surface of the lid  5 . 
     An annular groove  11  is formed so as to surround the opening of the box body  3  in the periphery of the top surface of the lid  5 . The annular groove  11  cooperates with O-rings  13   a  and  13   b  provided in the inside and the outside thereof to form an annular suction space for vacuum suction between the lid  5  and the clean box body  3 . The function of the suction space is the same as that of the conventional clean box described in conjunction with FIGS. 1A and 1B and therefore the explanation thereof will be omitted. 
     A plurality of latch mechanisms  9  for latching the lid  5  are provided at the outermost peripheral portion of the flanged portion of the clean box body  3 . As is apparent from FIG. 4, the clean box according to this embodiment has, in total, four latch mechanisms  9  two of which are provided in each of the two opposite sides of the bottom surface opening of the clean box body  3 . The latch mechanisms will be described in detail later. 
     A load port that is a device for opening the clean box and loading semiconductor wafers within the clean box into the processing apparatus will now be described. FIG. 5 is a schematic view showing the semiconductor processing apparatus and the load port related thereto and the clean box set on the load port. 
     A load port  20  is mounted depending upon a semiconductor processing apparatus  30 . The clean box  1  that has been transferred by a transfer system such as an overhead transfer (OHT) is set on a load port table  21  on the top surface of the load port  20 . Clean box guides  22  for positioning the clean box  1  in place on the table are provided on the load port table  21 . The load port  20  has an elevator type lid opening/closing mechanism  23  for opening the lid  5  of the clean box  1  downwardly and retracting it into the load port  20 . By the lid opening/closing mechanism  23 , a wafer W on the carrier  7  retracted downwardly together with the lid  5  as shown in FIG. 5 is transferred by an arm  35   a  of a transfer robot  35  to a processing stage  33  of the processing apparatus  30  where the wafer is subjected to a necessary process. Thereafter the wafer is returned back to the carrier by the transfer robot. 
     A local clean space is formed by an interior space including the load port  20 , the wafer processing apparatus  30  and the clean box  1  under the condition shown in FIG.  5 . In order to keep the space clean, a fan suction device  31  having a filter is provided in the upper portion of the apparatus  30 . A downward gas flow is generated in the apparatus by the fan suction device  31  to thereby lower the dust within the apparatus to keep the space within the apparatus  30  clean. The downward flow is discharged from the bottom surface of the apparatus to the outside. 
     Referring now to FIGS. 6A and 6B, the latch mechanism for the clean box and the related mechanism on the side of the load port will be described. FIGS. 6A and 6B are cross-sectional views showing the latch mechanism portion of the clean box and the related load port upper portion together. The latch mechanism is mainly composed of a latch member  40  mounted pivotally around a shaft  41 , a coiled spring  43  for pivoting the latch member in the right direction in the drawings, i.e., in the counterclockwise direction, and a stop  42  for limiting the pivotal motion of the latch member. The coiled spring  43  is mounted around a cylindrical projection  40   c  provided on the latch member  40 . 
     FIG. 6A shows a state just before the clean box has been lowered onto the load port. In this state, the lid  5  closes the opening of the clean box. Also, a hook portion  40   a  of the latch member  40  engages with a shoulder portion (i.e., stepped portion)  5   a  of a recess formed in the lid to latch the lid. Under this condition, the latch member  40  is biased in the counterclockwise around the shaft  41  by the coiled spring  43  and is kept in abutment with the stop  42  in the status shown in the drawing. Thereafter the clean box  1  is lowered while being guided by the clean box guides  22  and is positioned and laid at a predetermined position on the load port table  21 . When the clean box is guided by the clean box guides  22  to take a correct position, the latch member  40  of the latch mechanism  9  is in alignment with the projected latch guide  45  provided on the load port table  21 . 
     As is apparent from FIG. 6A, the bottom surface of the latch member  40  has a portion  40   b  that forms a slant surface. When the clean box  1  is to be loaded on the load port table  21  and the clean box is lowered while being guided by the clean box guides  22 , the latch guide  45  on the load port table  21  is brought into abutment with the slant portion  40   b  of the latch member  40 . Thus, the slant portion  40   b  is subjected to the force in the left side of FIG. 6A so that the latch member  40  pivots clockwise about the shaft  41  to disengage the hook portion  40   a  of the latch member  40  from the shoulder portion  5   a  of the lid  5 . Namely, when the clean box is seated on the load port, the state shown in FIG. 6B is taken. In this case, since the latch of the lid by the latch mechanism  9  is released, if the vacuum suction between the lid  5  and the clean box body  3  is released by a mechanism (not shown), the lid may be opened. 
     The latch mechanism  9  will now be described in more detail with reference to FIG. 7 which is an exploded perspective view showing one latch mechanism. The clean box according to this embodiment has four latch mechanisms  9  in total but each latch mechanism is the same in structure. The shaft  41  of the latch member  40  is placed on a groove  50   a  of a bearing member  50  and the bearing member  50  is mounted by bonding or screw fastening to a bearing bases  52  fixed to the inner surface of the flanged portion of the clean box body  3  to thereby form the latch mechanism. In this case, the coiled spring  43  is mounted around the projection  40   c  of the latch member  40  to work between a back plate  50   b  of the bearing member  50  and the latch member  40 . As has been apparent from the foregoing description, the latch mechanism according to the present invention may be very simply manufactured with a small number of mechanical parts. 
     Although the above-described clean box is of a type in which the bottom surface is opened and the article may be taken out from the bottom surface, the present invention is not limited to this specific structure but may be applied to a side open type clean box in which the side surface is opened in a sideway. This type clean box is shown in FIGS. 8A and 8B. FIG. 8A is a side elevational cross-sectional view showing a state in which the clean box is closed by the lid. FIG. 8B is a frontal view of the clean box body as viewed from the opening. Although the opening direction is different from that of the foregoing embodiment, the latch mechanism itself is the same in structure as the clean box in which the bottom surface is opened as shown in FIGS. 3 through 7. The same reference numerals are used to indicate the like parts and components and further explanation therefor will be omitted. Incidentally, although not shown, the clean box shown in FIGS. 8A and 8B also has an annular groove for vacuum suction for surrounding the opening. 
     Although the above-described clean box according to the embodiment has the four latch mechanisms  9 , the number of the latch mechanism is not limited thereto. Actually, if at least one latch mechanism is provided on each of the two opposed sides of the opening of the clean box body, it is possible to prevent the falling-off of the lid. 
     Also, in the above-described embodiments, the latch member  40  is engaged with the stepped portion  5   a  formed as a recess in a part of the lid, but the present invention is not limited thereto. For instance, it is possible to mount the portion that engages with the latch member  40  as a discrete member on the lid. 
     Since the lid latch mechanism for the above-described clean box is very simple in structure, the manufacture thereof is easy and there is almost no breakdown. 
     Also, with respect to the opening/closing of the latch, it is unnecessary to provide a complicated latch opening/closing mechanism on the side of the load port. It is sufficient to provide a simple projection such as a latch guide  45 . By employing this structure and laying the clean box on the load port, it is possible to automatically release the latch and to effect the latch when the clean box is raised.