In-situ purge system for article containers

Details In-situ purge system for article containers In-situ purge system for article containers

2002-11-22

2004-08-10

Douglas, Steven O. (Department: 3751)

Fluent material handling, with receiver or receiver coacting mea

Combined

C141S066000, C414S217000, C156S345420

Reexamination Certificate

active

06772805

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to systems for purging particles and moisture from containers, and more particularly relates to a system suitable for purging moisture and potential wafer-contaminating particles from wafer cassette containers or pods used to transport semiconductor wafers in a semiconductor production facility.
BACKGROUND OF THE INVENTION
A standardized mechanical interface (SMIF) system is disclosed in U.S. Pat. Nos. 4,532,970 and 4,534,389. Such a SMIF system is designed to reduce particle fluxes onto semiconductor wafers and/or reticles in a semiconductor production facility. The SMIF system prevents or minimizes particle contamination of the wafers during transport and storage of the wafers by ensuring that gaseous media surrounding the wafers is essentially stationary relative to the wafers, and further, by preventing exposure of the wafers to particles from the ambient environment.
The SMIF concept is based on the use of a small volume of motion- and contamination-controlled, particle-free gas to provide a clean environment for semiconductor wafers and other articles. Further details of one such system are described in a paper entitled,“SMIF: A TECHNOLOGY FOR WAFER CASSETTE TRANSFER IN VLSI MANUFACTURING”, by Mihir Parikh and Ulrich Kaempf,
Solid State Technology
, July 1984, pp. 111-115.
SMIF systems are designed to prevent contamination by particles which range from below 0.02 &mgr;m to above 200 &mgr;m. Due to the small geometries of the components in modern semiconductor integrated circuits, particles falling within this size range can significantly adversely affect semiconductor processing. Current geometry sizes for semiconductor integrated circuits have reached less than half a micron, and those circuits are adversely affected by particles having a size as small as 0.01 &mgr;m. In the future, semiconductor integrated circuits will be marked by increasingly smaller geometry sizes, requiring protection from contamination by correspondingly smaller particles.
In a typical SMIF system, semiconductor wafers are stored and transported in wafer cassette containers, or pods, and are transferred from the pod to processing equipment typically in the following manner. First, the pod is placed at the interface port of a processing tool. Each pod includes a box and a box door designed to mate with doors on the interface ports of the processing equipment enclosures. Then, latches release the box door, and the box door and the interface port door are opened simultaneously such that particles which may have adhered to the external door surfaces are trapped or sandwiches between the box and interface port doors. A mechanical elevator lowers or translates the two doors, with the cassette riding on top, into the enclosure-covered space. The cassette is transferred by gravity or a manipulator and placed onto the cassette platform of the equipment. After processing, the reverse operation takes place.
Another conventional method for transferring semiconductor wafers from a pod to a processing tool is shown in
FIGS. 1-3
of the drawings, which illustrate side views of a SMIF arm cassette loading device
10
. The SMIF arm cassette loading device
10
includes a base
11
which is supported on a floor or other supporting surface (not illustrated) in a clean room, and a frame
12
is upward-standing from the base
11
. A pod support platform
14
is provided on the frame
12
. A SMIF arm
13
is mounted on the frame
12
for bidirectional vertical displacement thereon, and a guide arm
17
for the SMIF arm
13
typically extends upwardly from the frame
12
. Accordingly, a wafer pod
18
, characterized by a cover
19
which is fitted with a removable bottom pod door
20
and contains a wafer cassette
21
that holds multiple semiconductor wafers
22
, is initially placed on the pod support platform
14
, as illustrated in FIG.
1
. Next, a lifting mechanism (not illustrated) raises the SMIF arm
13
which, in turn, lifts the cover
19
from the removable pod door
20
in the bottom of the cover
19
as the cover
19
is detached from the pod door
20
. The pod door
20
remains on the pod support platform
14
and continues to support the cassette bottom plate
23
of the exposed wafer cassette
21
thereon, as illustrated in
FIG. 2. A
robotic arm
16
then transfers the wafer cassette
21
, still holding the semiconductor wafers
22
, to an indexer
27
, as illustrated in
FIG. 3
, which indexer
27
indexes the wafers
22
before loading them into the load lock
26
of a processing tool
25
. After they are processed in the processing tool
25
, the wafers
22
are transferred back from the indexer
27
to the pod support platform
14
, as illustrated in FIG.
2
. Finally, the SMIF arm
26
is lowered to lower the cover
19
of the wafer pod
18
onto the pod door
20
to again enclose the wafer cassette
21
and wafers
22
, as shown in FIG.
1
. The pod
18
is then transferred to another processing tool or a stocker either manually or by means of automatically-guided vehicles (AGVs) or overhead transport vehicles (OHTs) that travel on predetermined routes or tracks.
One of the problems associated with the foregoing type of SMIF arm cassette loading device
10
is that ambient air, moisture and some particulate impurities tend to become recaptured in the cover
19
of the pod
18
when the cover
19
is lowered back in place on the pod door
20
on the pod support platform
14
. Resulting exposure of the wafers
22
to humidity, atmospheric air and foreign particles in the pod
18
during subsequent transfer to the next processing tool tends to induce corrosion and contamination of the wafers
22
, as well as shorten wafer Q-time and adversely affect wafer yield performance.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a system which is capable of purging atmospheric air, moisture and particles from an article-carrying container in a manufacturing or other facility.
Another object of the present invention is to provide an in-situ purge system which is capable of purging contaminants, moisture and ambient air from a wafer cassette container or wafer pod to increase the product wafer Q-time and yield performance of semiconductor wafers.
Still another object of the present invention is to provide an in-situ purge system which is capable of restoring a desired gaseous environment for semiconductor wafers on a water cassette inside a wafer cassette container or pod.
Another object of the present invention is to provide a method for the purging of moisture, ambient air and potential wafer-contaminating particles from a semiconductor wafer pod interior and restoring a normal clean gaseous environment inside the pod to minimize yield contamination and corrosion of semiconductor wafers transferred in a semiconductor production facility.
In accordance with these and other objects and advantages, the present invention comprises an in-situ purge system for charging the interior of a semiconductor wafer pod with nitrogen gas after the pod is exposed to ambient moisture, air and particles in a clean room. A gas supply line extends into the pod interior from a gas source, and a gas exhaust line extends from the pod interior to remove moisture, particles and excess gas from the pod interior as the pod contains a wafer-filled cassette and rests typically on a SMIF arm before transfer to a processing tool or other destination in the facility. The removable bottom door of the pod and the bottom plate of the cassette are modified to receive the gas supply line and the gas exhaust line.


REFERENCES:
patent: 5217053 (1993-06-01), Foster et al.
patent: 6267123 (2001-07-01), Yoshikawa et al.
patent: 6315858 (2001-11-01), Shinozuka et al.

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