Material or article handling – Apparatus for moving material between zones having different...
Reexamination Certificate
1999-04-12
2001-08-14
Werner, Frank E. (Department: 3652)
Material or article handling
Apparatus for moving material between zones having different...
C118S719000, C414S217100, C414S939000, C414S684300
Reexamination Certificate
active
06273664
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a coupling system for confined transfer of a flat object from a confinement box towards a processing unit for the object.
Said system may be used in particular for the transfer of silicon wafers placed individually in confinement boxes under controlled atmosphere, towards reactors such as chemical vapour deposition reactors or etching reactors, or plasma activated deposition reactors for example.
By confined box under controlled atmosphere is meant a box whose inner medium has a determined composition, cleanliness, purity and/or pressure.
START OF THE PRIOR ART
The transfer of flat objects, in particular of silicon wafers, is generally conducted in a clean room directly from a stepped basket containing the flat objects towards the processing unit.
The costs and technical difficulties connected with fitting out clean rooms of large volume that come under a high cleanliness category, have however led to the use of confined receptacles of small size able to contain the objects for which a clean environment is required.
These confined receptacles, described in detail below, also have the advantage of being able to maintain a pure atmosphere around the objects. By pure atmosphere is meant an atmosphere which does not contain any chemical contaminant products. It may, for example, be a nitrogen N
2
or rare gas atmosphere, such as argon for example.
Hereinafter a distinction is made between a pure atmosphere such as defined here, and a clean atmosphere which is characterized by a reduced number of particle contaminate elements (≦0.3 mm) per volume unit.
A first type of confined receptacle is designated by the acronym SMIF (Standardized Mechanical Interface). It is a box with a bell-shaped lid resting on a base tray. Sealed adjustment is provided between the lid and the base tray. These boxes also contain a basket in which semiconductor wafers are stacked.
These confined receptacles are used to move the wafers from their place of manufacture towards a processing unit, or from a processing unit towards a further processing unit, while keeping them in a confined atmosphere, that is clean and pure, such as defined above.
A detailed description of SMIF interfaces can be found in documents (
1
) and (
2
) whose references are given at the end of this disclosure.
To transfer the wafers from SMIF interfaces towards a processing unit, a transfer airlock equipped with an unloading robot is provided at the head of the processing unit. Such airlock, in which a clean and possibly pure atmosphere must be maintained, is indispensable in order to avoid contamination of the flat objects when they are removed from the confined receptacle. The transfer airlock is also called “mini-environment”, “enclosure”, or “canopy”. The basket and wafer unit it contains is removed from the confined receptacle inside the airlock, and the wafers are subsequently removed one by one from the basket and placed in the processing unit.
SMIF interfaces have a certain number of disadvantages however. Among the latter, mention may be made of the fact that they cannot prevent mutual pollution of the silicon wafers stored inside. Also, on account of their fixed capacity, approximately 25 wafers, these interfaces are not adapted to flexible use for just-in-time production.
Given these problems, other confinement receptacles have been designed in the form of individual boxes. Such boxes are described in documents (
1
) and (
2
) but also in document (
3
) whose reference is also given at the end of this disclosure. These boxes have a side opening for inserting and removing the wafers. They are closed in sealed manner by a pivoting door. To transfer the semiconductor wafers towards a processing unit, the individual boxes, like the SMIF interfaces, are placed in an airlock positioned in front of an in/out opening of the processing unit. The in/out opening of the processing unit is also closed by a door. An example of individual box and an opening system for its door is also described in document (
4
) whose reference is given at the end of this disclosure.
When an individual confinement box is in position, inside the airlock, in front of the opening of the processing unit, the doors of the box and processing unit may be opened to transfer the wafer.
The airlock, positioned at the entrance to the processing units, is a complex set of equipment in which a clean atmosphere must be maintained.
Also, the transfer airlock must be fitted with a transfer robot to withdraw the flat objects to be processed from their confinement box. Said equipment is shown in the figures of document (
2
) for example.
Additional difficulties arise when the wafers or flat objects must be maintained in a pure or inert atmosphere, for example a nitrogen atmosphere. These difficulties are, for example, connected with the need to frequently drain the airlock whose inside volume is generally fairly considerable, on account of the presence of the transfer robot in particular. An example of flat object transfer in a clean atmosphere is described in document (
5
) whose reference is also given at the end of this disclosure.
Also, the confinement receptacles and the airlocks of the processing units do not generally enable transfer of the wafers in a vacuum.
Therefore, one purpose of the present invention is to make available a coupling system for the confined transfer of a flat object from a confinement box towards a processing unit, which does not have the restrictions and disadvantages described above.
A further purpose of the invention is to propose said system with which it is possible to achieve transfer without causing a break in the clean atmosphere surrounding the objects.
Another purpose is also to set forth a system allowing transfer in a pure atmosphere.
Another purpose is to propose a system allowing the vacuum transfer of flat objects.
A further purpose of the invention is to propose a system which does not require its own transfer robot, but with which it is possible to make direct use of a robot already fitted to the processing unit in order to remove the flat objects from the confinement boxes.
A further purpose is to propose a simple system, less costly than the airlock systems, which requires little space.
Another purpose, finally, is to propose a system without an airlock, which remains compatible with the direct transfer of flat objects from a tiered basket such as described at the start of this disclosure.
DESCRIPTION OF THE DISCLOSURE
In order to reach the above-mentioned purposes, the object of the invention is more precisely a coupling system for the confined transfer of a flat object from a confinement box having a first side opening for the transfer of the flat object, and a first shutter, towards a unit for processing the flat object having at least a second opening for the transfer of the flat object.
In accordance with the invention, the system comprises:
means for the sealed coupling of the confinement box opening with the opening of the processing unit, these means having a second shutter, and
means of releasing the first and second shutters, after coupling the confinement box opening with the opening of the processing unit.
The transfer of the flat object from the confinement box towards the processing unit takes places via the sealed coupling means and is conducted by a mechanism for moving the flat object. Said mechanism exists on processing units in the form of a robot handling flat objects.
With the coupling means and the means for releasing the first and second openings, after coupling, it is possible to place in contact the inner spaces of the confinement box and the processing unit.
The coupling is impervious to the surrounding medium. The cleanliness and purity of the atmosphere in the box and inside the processing unit are therefore preserved.
Therefore, the system can operate in an environment other than that of a clean room without the need for a transfer airlock. Moreover, as indicated above, since no transfer airlock is required, it is possible to make direct use of th
Anderson Kill & Olick P.C.
Commissariat A l'Energie Atomique
Werner Frank E.
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