Method and apparatus for detecting cross-slotted objects

#The present invention pertains to the detection of cross-slotted objects, and, more particularly, to a method and apparatus for displacing cross-slotted objects and detecting the displaced cross-slotted objects.

#The present invention was developed to improve the manufacture of semiconductors. The semiconductors are formed from "wafers" that are substantially planar-shaped fragile objects. These wafers are retained in slotted trays during the semiconductor manufacturing process. Because the wafers are constructed of thin, brittle, and expensive material, they must be carefully handled and stored.

#One method for storing such objects is to place them in a tray having a plurality of slots that are sized and shaped to receive the planar-shaped objects. The slots are evenly separated by spaces to permit a robotic arm to insert the objects in the tray and remove them therefrom. The tray has a first opening sized and shaped to permit the objects to be inserted into and removed from the slots in the tray. One recurring problem is the misplacement of the objects in the tray such that one side of the object is received in one slot and the other side of the object is received in an unmatching slot, resulting in a "cross-slotted" condition. In this condition, the object is disposed across one or more spaces separating the slots.

#The foregoing features and other advantages of the present invention will be more readily appreciated as the same become better understood from the following detailed description when taken in conjunction with the accompanying drawings, wherein:

#FIGS. 1A-C are top, side, and front plan views, respectively, of a wafer cassette tray;

#FIG. 2 is an isometric projection of the apparatus formed in accordance with the present invention wherein the cradle is shown in a fully tilted back or vertical position;

#The apparatus 10 for displacing and detecting cross-slottedobjects 12 will be described in conjunction with FIGS. 2-8. The apparatus 10 comprises a cradle 14 rotatable mounted on a frame 16. The cradle 14 is sized and shaped to support a tray 18 of objects 12 during a manufacturing process.

#The tray 18 is known in the art, and will be described briefly herein in connection with FIGS. 1A-1C. The tray 18 includes a pair of sidewalls 20 and 22 with rearward projecting legs 21 and 23 that are held in spaced parallel relationship by a top wall 24 and bottom wall 26. A handle 28 projects from the top wall 24. As shown in the top view in FIG. 1C, the sidewalls 20 and 22 define a large first opening 30 in the front of the tray 18 and a smaller second opening 32 at the back of the tray. The sidewalls 22 and 24 includes slots 34 for holding substantially planar-shaped objects 12 (as shown in FIG. 2). Each pair of slots 34 in the sidewalls 22 and 24 are separated by a space 36 formed between the slots 34.

#The first opening 30 is sized and shaped to permit objects 12 to be inserted into the slots 34 and removed therefrom. The second opening 32 is positioned opposite the first opening 30 to permit access to the slots 34 and spaces 36 from the rear of the tray 18. However, the second opening 32 is narrower than the first opening 30 so that the objects 12 are retained in the slots 34 and are not allowed to exit the back of the tray 18.