Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2001-07-20
2003-11-25
Wu, Daniel J. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S686100, C340S680000, C340S542000, C250S559290, C250S559370, C250S559330, C250S548000, C250S221000
Reexamination Certificate
active
06653944
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a pod for transporting a cassette of semiconductor wafers and more particularly, relates to a semiconductor wafer transport pod equipped with a cover latch indicator to ensure that a cover is latched onto a base before the pod is picked up by an operator.
BACKGROUND OF THE INVENTION
The high level of automation used in fabricating semiconductor devices relies on sophisticated handling and transport equipment for moving semiconductor wafers between various processing stations. Most handling and transport operations are conducted under automatic control using a programmed computer which issues control signals for operating the equipment with little or no intervention by an operator. In many systems, standard mechanical interface (SMIF) pods are used to transport batches of wafers that are stored in cassettes. These pods include a base upon which the cassettes rest, and a cover removably secured to the base and completely enclosing the cassette. The cover protectively surrounds the cassette, and thus the wafers, from the surrounding environment which may contain airborne, contamination particles. SMIF pods are most often used to transport cassettes from one clean room environment to another, where during the transport movement, the wafers, if not covered, are exposed to the contaminating environment.
After a pod has reached the vicinity of a processing station within a protected, clean room environment, it is necessary to remove the cover so that automated wafer transfer robots can gain access the individual wafers held in the cassette. The covers are held on the pods by various types of latching mechanisms which are automatically actuated to latch and unlatch the cover by means of actuating controls positioned at each processing station. Thus, when a pod reaches a processing station, control mechanisms engage the latch mechanism on the pod to unlatch the cover, following which either an operator or a robotic mechanism removes the cover to expose the cassette. Following processing of a batch of wafers in the cassette, the cover is reinstalled on the pod base, either manually or robotically, after which the control mechanism is actuated to latch the cover on the base before the pod leaves the processing station.
Referring first to
FIG. 1
, in accordance with the prior art, a pod includes a generally rectangular base
15
upon which there is supported a cassette
12
containing a plurality of vertically spaced, semiconductor wafers (not shown) disposed in stacked relationship to each other. The pod also includes a cover
10
disposed over and protectively enclosing the cassette
12
. The cover
10
is provided with a peripheral flange
17
which engages an edge of the base
15
, so that the cover
10
is carried on the base
15
. A tag
36
is secured to one face of the cover
10
and is used to identify the pod and/or its contents. The tag
36
may comprise a simple bar code device or, an electronic device that can be automatically read by an electronic reader.
The cassette
12
is held on the base
15
by means of an H Bar
18
. The H Bar
18
forms a part of the top side of the base, and cooperates to receive a locking member on the base of the cassette
12
, in a bayonet like manner.
The base
15
includes a pair of outwardly slidably latch plates
16
having outer fingers
26
which are received in indentations or other recesses (not shown) on the inside wall of the cover
10
in order to lock the cover
10
on the base
15
. The latch plates
16
are driven by a circular rotatable plate
24
having a pair of drive pins
28
on the outer periphery thereof. The drive pins
28
are received within elongated slots (not shown) respectively in the latch plates
16
. The circular plate
24
is in turn driven by a pair of latch pins
42
that are driven to rotate by other apparatus present at the processing station (not shown) where the pod is delivered in order to load or unload wafers therefrom. Rotation of the plate
24
causes the drive pins
28
to move the latch plate
16
outwardly so that the fingers
26
move into retainers or indentations in the cover
10
, thereby latching the latter in place. However, in the event of slight misalignment or tilting of the cover
10
relative to the base
15
, or where there is a failure of any of the mechanical driving components, the cover
10
may fail to be properly latched down onto the base assembly
15
but such latching failure is not readily detectable by an operator.
In spite of the fact that positive latch mechanisms are employed to lock the cover on the pod base, occasions arise when, for a variety of reasons, the latch fails to lock the cover on the pod base. This may occur, for example, when a foreign article becomes lodged between the cover and the base or where the cassette becomes tilted on the base, thus interfering with proper seating of the cover. In other cases, the control mechanism for actuating the latch may malfunction. In many cases, failure of the latch mechanism to lock the cover on the pod base goes undetected by process operators. As a result, it is possible that contaminants may pass between the pod base and cover when the pod leaves the clean room environment, thereby resulting in possible contamination of the wafers.
Accordingly, there is a clear need in the art for an improved pod construction which provides a positive indication of when the cover is properly locked down on the pod base. The present invention is directed toward satisfying this need in the art.
It is therefore an object of the present invention to provide a pod for transporting a cassette of semiconductor wafers that does not have the drawbacks or shortcomings of the conventional pods.
It is another object of the present invention to provide a pod for transporting a cassette of semiconductor wafers that is equipped with a cover latch indicator.
It is a further object of the present invention to provide a semiconductor wafer transport pod that is constructed by a base, a cover, a latch means, and an indicator means.
It is another further object of the present invention to provide a semiconductor wafer transport pod equipped with a latch means including four latch keys, a power source and a wiring means in-between the four latch keys.
It is still another object of the present invention to provide a semiconductor wafer transport pod that is equipped with an indicator means of a light emitting diode which is lit when all latch keys are latched onto the cover of the pod.
SUMMARY OF THE INVENTION
In accordance with the present invention, a pod for transporting a cassette of semiconductor wafers that is equipped with a cover latch indicator is provided.
In a preferred embodiment, a pod for transporting a cassette of semiconductor wafers is provided which includes a base for supporting the cassette thereon; a cover removably carried on the base for protectively covering the cassette; latch means carried on the base for latching the cover on the base, the latch means is actuatable from a latched position in which the cover is latched on the base to a released position allowing removal of the cover from the base; an indicator means coupled with the latch means for providing a visual indication of the condition of the latch means.
In the pod for transporting a cassette of semiconductor wafers, the latch means may further include at least four latch keys situated around the base, each has an electrically conductive path between two ends of the key; a power source sufficient to activate the indicator means; and wiring means in-between the at least four latch keys, the power source and the indicator means, such that only when all four latch keys are in a latched position, electrical current flows through the wiring means to activate the indicator means. The indicator means may be a light emitting diode, or an indicator lamp. The power source may be a DC power source carried on the base, or a 1.5 V DC battery situated on the base. The wiring means connects the at least four latch keys in s
Chiang Am-Ming
Huang Hsin-Chieh
Nguyen Tai T.
Wu Daniel J.
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