Wafer transport pod with linear door opening mechanism

Details Wafer transport pod with linear door opening mechanism Wafer transport pod with linear door opening mechanism

2002-02-07

2004-06-29

Kramer, Dean J. (Department: 3652)

Material or article handling

Apparatus for moving material between zones having different...

C414S940000, C206S710000

Reexamination Certificate

active

06755602

ABSTRACT:

FIELD OF THE INVENTION
The present invention broadly relates to semiconductor wafer processing equipment, and deals more particularly with an improved pod employed to protectively enclose and transfer a cassette containing a plurality of semiconductor wafers.
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. In more recent development, FOUP's (front open unified pod) are used for storing and transporting 12″ wafers.
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 (for SMIF) or on the back (for FOUP) before the pod leaves the processing station.
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 insures that the cover is properly locked onto the pod. The present invention is directed toward satisfying this need in the art.
FIG. 1
illustrates a cassette pod such as a FOUP that is installed on a process machine. The cassette pod
10
is positioned on a loadport
12
of the process machine
14
. The loadport
12
is normally equipped with a plurality of locating pins
16
for the proper positioning of the cassette pod
10
.
A detailed perspective view of the cassette pod, i.e. the FOUP
10
, is shown in FIG.
4
A. The FOUP
10
is constructed by a body portion
18
and a cover portion
28
. The body portion
18
is provided with a cavity
46
equipped with a multiplicity of partitions
48
for the positioning of 25 wafers of the 300 mm size. The body portion
18
is further provided with sloped handles
50
on both sides of the body for ease of transporting. On top of the body portion
18
is provided a plate member
52
for gripping by a transport arm (not shown) of an overhead hoist transport system. It should be noted that, for simplicity reasons, the latching mechanism for opening and closing the FOUP door, or the cover portion
28
, is not shown in FIG.
2
.
In the conventional cover member, or door
28
of the FOUP
10
, the door opening/closing mechanism is shown in
FIG. 3
in a plane view. Locking tabs
20
a
,
20
b
,
22
a
and
22
b
are provided at the top and at the bottom of the cover member
28
. Circular drive plates
24
a
and
24
b
are connected to the locking tabs
20
a
-
22
b
by mechanical linkage
26
a
and
26
b
and operated by latch holes
28
a
and
28
b
. A pair of latch keys (not shown) that are part of the door opener mechanism of the loadport (not shown) are inserted into the latch holes
28
a
and
28
b
and turned by a DC motor to lock or unlock the cover member
28
to the loadport opening. As shown in
FIG. 3
, when the drive plates
24
a
and
24
b
are turned in a clockwise direction, the locking tabs
20
a
,
20
b
,
22
a
and
22
b
are withdrawn into the frame of the cover member
28
and therefore, unlocking the cover member
28
from the body member
18
of the cassette pod
10
(shown in FIG.
2
). Conversely, when the drive plates
24
a
and
24
b
are turned by the DC motor in a counter-clockwise direction, the locking tabs
20
a
,
20
b
,
22
a
and
22
b
are extended out of the frame of the cover member
28
to engage receptacles (not shown) in the body member
18
and thus, locking the cover member
28
to the body member
18
of the cassette pod
10
.
Problems occur when operating the conventional door opening/closing mechanism shown in
FIG. 3
installed on a FOUP. For instance, the latch keys (not shown) that are turned by the DC motor sometimes are misaligned with the latch holes
28
a
and
28
b
and thus, the door opening or closing operation cannot be carried out. Secondly, the torque of the DC motor cannot always be precisely controlled such that the angle of turning, i.e. such as a 90° angle cannot be precisely controlled. A door opening or closing mechanism can not be completely executed when the angle of rotation is not exactly 90°. For instance, during a door locking operation, if the latch holes
28
a
and
28
b
are not turned to a perfect horizontal position in order to lock the cover member
28
to the body member
18
and when the FOUP
10
is later positioned on another process equipment, a similar set of door opening latch keys could not be inserted into the latch holes
28
a
and
28
b
and thus, the member
28
cannot be opened or unlocked from the body member
18
.
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 does not require a rotary-type door opening/closing mechanism.
It is a further object of the present invention to provide a pod for transporting a cassette of semiconductor wafers that utilizes a linear-type door opening/closing mechanism.
It is another further object of the present invention to provide a pod for transporting a cassette of semiconductor wafers by providing the cover member of the pod with locking tabs, drive plate and latch holes for engagement by latch keys provided on a door opening plate of a loadport.
SUMMARY OF THE INVENTION
In accordance with the present invention, a wafer transport pod that is equipped with a linear door opening mechanism is provided.
In a preferred embodiment, a pod for transporting a cassette of semiconductor wafers is provided which includes a body member constructed of a top wall, a bottom wall, a front wall and two sidewalls forming a back opening for loading or unl

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