Gas separation – Combined or convertible
Reexamination Certificate
2002-03-12
2003-04-01
Smith, Duane S. (Department: 1724)
Gas separation
Combined or convertible
C055S385200, C055S434000, C055SDIG001
Reexamination Certificate
active
06540803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to systems and methods of preventing contamination of a contaminant-free media volume and more particularly relates to a fluid media particle isolator between a contaminant-free media volume and a contaminated particle generating media volume.
2. Background Information
There is a requirement in some industries and applications to maintain a containment-free environment. This requirement means that there must be an isolation and separation of contaminated media from containment-free media. The processing of wafers to manufacture semiconductors is a good example of this requirement. Particles that might contaminate the wafers from which semiconductors are built must be kept isolated.
The wafers from which semiconductors are built are stored in large contaminant-free enclosures known as storage and transfer systems. The wafers stored in contaminant-free containers or moved in and out of the storage area by machinery known as a transfer system. The transfer systems use linear and rotary activators to transfer the wafers to and from the storage area. These actuators necessarily generate particles that can contaminate the wafers. The contamination of the wafers from these particles is a major cause of device failure and rejection during the manufacturing process.
Accordingly there are many techniques employed to isolate the media around the wafers from the media where the particles are generated by the machinery. One technique scavenges the area around the machinery where particles are generated with a vacuum.
This technique does somewhat reduce the migration of particles from the area of contaminated media to the containment-free media area. However a disadvantage and limitation of this vacuum technique is that a flexible mechanical separation is needed between the containment-free (clean zone) media area containing the wafers and the contaminated area of mechanical equipment which generates particles. The flexible mechanical separation is usually a sealing band made of flexible plastic or metal. The sealing band must be flexible to allow a mechanical actuator to transmit work such as moving wafers to and from storage. An identified problem of using the flexible mechanical band to create a differential pressure for the vacuum to be effective and help mechanically isolate contaminating particles from the wafers is the mechanical band produces contaminating particles when the mechanical actuator passes through the band.
The current state of the art for media isolation to prevent contamination includes the use of a physical barrier between the contaminant-free media volume and an adjacent media volume that may contain contaminates. These barriers either involve movable mechanical parts or encounter movable mechanical parts. When moving mechanical parts make contact or rub against one another they invariably produce particles that can contaminate a contaminant-free media volume. One example of such a system is disclosed and described in U.S. Pat. No. 5,615,988 of Weisler et al issued Apr. 1, 1977. This patent discloses a wafer transfer system having moving transfer system to transfer wafers from carriers in a storage area. A door in a wall separates the storage area from the transfer area. The door is opened to provide access to wafers in a storage carrier. The transfer system moves through the door to retrieve wafers. All these moving parts are going to cause a release of particles, known generally as “wear”, that can contaminate the wafers.
In the case of the mechanical seals described above, they are flexible to allow a transfer mechanism to move from one media volume to another to retrieve wafers. These parts rub together and produce contamination. Attempts to prevent the contamination involve creating a differential pressure by increasing pressure or applying a vacuum to one media volume. The combination of the mechanical seal with the differential pressure in most common applications creates a bias and establishes an unidirectional flow from one media volume to an adjacent media volume. Generally this is away from the contaminant-free media volume and toward the contaminated particle generating media volume. While these methods help they are not entirely effective to prevent a back flow of contaminating particles from entering the contaminant-free media volume particularly when the mechanical seal makes contact with the transfer mechanism.
It is thus one object of the invention to produce a fluid media isolator that differs from current state of the art devices by having no contacting, sliding, or rubbing parts when a transfer system actuator arm moves.
Another object of the present invention is to have a fluid media isolator that transfers clean media from the particle free (clean zone) wafer process area toward the particle generating contaminated (dirty zone).
Yet another object of the present invention is to provide a fluid media isolator that mechanically isolates a contaminant-free zone and a contaminate generating zone with a barrier comprises of tortuous media zone.
Still another object of the present invention is to provide a fluid media isolator on both sides of a transfer system actuator arm for forward or reverse travel with a linear actuator.
In yet another object of the present invention the fluid media isolator is mounted on both sides of an actuator arm for clockwise and counter-clockwise movement for a radial actuator.
Yet another object of the invention is to provide a device for isolating one volume of media from an adjacent volume of media that have a common connection between them.
Another object of the invention is to provide a device that can transfer media from one volume to another volume in a unidirectional manner while biasing back flow from one volume to another.
Still another object of the invention is to provide a fluid media isolator that can transfer and mix one media volume with another and pump in one direction.
Still another object of the invention is to provide a fluid media isolator comprised of a tortuous path separating a contaminant-free media volume from a contaminant generating volume and a fluid transfer device intersecting the tortuous path mounted for movement with the transfer system.
Another object of the present invention is to provide a fluid transfer device comprised of a plurality of vessels or cells that transfer fluid media from one vessel to another that is mounted in a tortuous path for movement with the transfer system actuator. The fluid transfer device pumps unidirectionally with each movement of the transfer device to establish unidirectional flow with substantially no backstream preventing any particles generated by a drive system for contaminating the containment-free media volume.
BRIEF DESCRIPTION OF THE INVENTION
The purpose of the present invention is to provide a system and method of isolating contaminant-free media volume from a particle generating and contaminated media volume.
The system and method of the invention separates and transfers volumes of media of one mechanically separated zone to another media volume. The media volumes are separated by a pair of adjacent walls having a tortuous or serpentine path formed between them. The tortuous path is formed by alternating interleaving partitions or fins on the inside surfaces of the walls. The alternating partitions extend the full length of the wall forming a media volume in the tortuous path between the walls. The walls separate the contaminant-free media volume or zone from the contaminated volume and has an entrance at one end communicating with the contaminant-free media volume and an exit to the contaminated media volume at the opposite end. Thus the space in the wall forms a continuous tortuous path between the two media zones.
A pump is formed by a series of vessels or cells coaxially integrated in the tortuous path between the walls. The series of vessels or cells are mounted on the wafer transfer actuator arm for reciprocating linear travel within the tortuous or serpentine p
Intrabay Automation, Inc.
O'Reilly David
Smith Duane S.
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