High cleanliness article transport system

#The invention relates to portable containers for allowing articles to be transported and processed while maintaining very high levels of cleanliness, particularly containers for holding reticles used in the integrated circuit and other microscopic device manufacturing industry.

#A reticle is an optically clear or reflective substrate covered on one side with an opaque or light attenuating film, in which a pattern is formed by photolithography or other similar processes. Often, it is made of quartz coated with chrome. The reticle carries an image of part of an electrical circuit, which image is used as a master for repeated projection onto a semiconductor wafer to make integrated circuits. During production of the reticle, the coated side is held uppermost and the reticle is supported on its uncoated side or is held by the beveled edges/corners during handling and processing. After the reticle has passed final inspection, a pellicle may be attached to the coated side to help protect the image area from particulate deposition and chemical contamination. The reticle then is placed into a shipping box that is sealed to protect it from contamination while in transit to the semiconductor factory where it will be used. Upon arrival at the point of use, the reticle is transferred into another box which is designed so that it can be opened automatically by the lithography tool that uses the reticle. The reticle is placed in this box with the coated side (and pellicle, if fitted) facing downwards, typically resting on support points that contact the coated underside of the reticle in the region outside the pellicle frame.

#The rigid structures that laterally define the reticle containment volume in the box cannot prevent the reticle from moving on the support points, as there must be clearance space between such boundary structures and the reticle to allow for dimensional and positional tolerances of the box parts and of the reticle itself, as well as the placement accuracy of the handling mechanism that moves the reticle into and out of the box. Current implementations of reticle boxes either restrict reticle movement when the box is closed by applying a downward force on the reticle to hold it against the support points or by moving a retaining mechanism against a vertical side of the reticle to hold it against a rigid vertical structure in the box. Examples of such mechanisms can be found in U.S. Pat. No. 4,815,912 and US Patent Application Publication No. 2002/0066692.

#A more complete understanding of the invention may be obtained by reference to the drawings, in which:

#FIG. 1 is an exploded perspective view of a conventional reticle standard mechanical interface (SMIF) pod as is currently used in semiconductor production facilities;

#FIG. 2 shows a cross-section in the direction of lines 2-2 of FIG. 1 of the conventional reticle SMIF pod of FIG. 1 in a closed position holding a reticle;

#The invention is described herein with reference to FIGS. 1-7. It should be understood that the structures and systems depicted in schematic form in FIGS. 1-7 are used to explain the invention and are not precise depictions of actual structures and systems in accordance with the invention. The preferred embodiments described herein are exemplary and are not intended to limit the scope of the invention, which is defined in the claims below. Embodiments in accordance with the invention are described herein mainly with reference to the handling of reticles in standard mechanical interface (SMIF) pods. It is understood, however, that the invention would be applicable to other kinds of containers and also would be useful for protecting a wide variety of articles, particularly in semiconductor manufacturing facilities. In this disclosure, when vertical and horizontal directions are mentioned, they refer to the corresponding directions in FIGS. 2 and 4-7.

#FIGS. 1-3 schematically illustrate reticle standard mechanical interface (SMIF) pods that currently are used in semiconductor production. The pod 300 is constructed in two separable parts, the top box section 302 and the base section 314, which are held together when the pod is closed, typically by a locking mechanism 328. An automation handle 306 preferably is integrally formed with top section 302. This handle allows automated systems to lift the pod robotically. The locking mechanism 328 comprises lock sections 326A affixed to the top, the locks having movable tenons 327 which engage mortises 326B on the base 314, the combined action of which compresses the compliant gasket 324 to form a gas tight seal between the two parts 314 and 302. It is normal for the sealing face 325 in the pod top, against which the gasket is compressed, to be disposed horizontally which allows for lateral movement of the base 314 within the opening 320 in the pod top 302. The reticle 304 is placed on the pod base by hand or by a robotic end effector and is supported on rigid supports 330, being laterally constrained between fixed vertical boundaries 332A and 332B. Reticle 304 is held against the rear vertical boundary 335 by a movable restraint mechanism 334 (FIG. 3) that pushes the reticle 304 rearward when the pod is closed. The reticle 304 is held in contact with the supports 330 in the closed pod by sprung stop mechanisms 334 that are fixed inside the pod top section 302. The force applied vertically downward on the reticle supports 330 by sprung stop mechanisms 334 increases the friction at the support points, as well as acting to resist lateral motion of the reticle 304 on the supports 330 and lateral motion of the pod door base within the opening in the pod top. This friction increases the likelihood of particle generation at the reticle support points.

#FIG. 4 schematically depicts a front cross-sectional view of an apparatus 90 in accordance with the present invention for raising a reticle off the supports that receive it when it is placed in a SMIF pod and compliantly restraining it at a safe distance from the supports when the pod is closed. When the pod is opened, again the reticle is lowered back onto the conventional supports allowing the reticle to be accessed by a conventional retrieval mechanism.