Communications: electrical – Condition responsive indicating system – Specific condition
Utility Patent
2000-03-20
2001-01-02
Wu, Daniel J. (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S673000, C250S297000, C250S559290, C250S559400, C414S937000, C414S940000
Utility Patent
active
06169490
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a protective device. More particularly, the present invention relates to an installation with light-intercepting sensors for detecting any improperly placed wafer boat in the outlet port of a stocking unit so that accidental collision between wafer boats is prevented.
2. Description of the Related Art
Inside a semiconductor manufacturer plant, stocking units are normally used to store wafer boats. In general, each stocking unit has two inlet ports and two outlet ports. When a wafer boat needs to be stored inside the stocking unit, the wafer boat is placed inside one of the inlet ports. After a while, the wafer boat is transported into a storage area inside the stocking unit. On the other hand, when someone needs to retrieve a wafer boat inside the stocking unit, the bar code of a desired wafer boat is fed into the master controller of the stocking unit. Once the bar code for a particular wafer boat is fed, the stocking unit automatically transfers the desired wafer boat to one of the outlet ports so that the boat can be taken away by an operator.
FIG. 1
is a top view of a conventional stocking unit used in most semiconductor manufacturing plants. As shown in
FIG. 1
, a conventional stocking unit
10
includes an in-stock area
12
, an out-stock area
14
and a storage area
16
. The in-stock area
12
has two inlet ports
18
and
20
, located on the inner and outer flank of the in-stock area
12
, respectively. The inlet ports
18
and
20
are areas for placing wafer boats that need to be placed in the storage area
16
. The out-stock area
14
also has two outlet ports
22
and
24
, located on the inner and outer flank of the out-stock area
14
, respectively. The outlet ports
22
and
24
are temporary storage areas for wafer boats leaving the storage area
16
.
When a particular a wafer boat needs to be stored inside the stocking unit
10
, the wafer boat is put in the inlet port
18
at the outer flank of the in-stock area
12
. This wafer boat will be carried to the inlet port
20
at the inner flank of the in-stock area
12
and then moved on into the storage area
16
. In order to retrieve a wafer boat from the storage area
16
, a bar code of the desired wafer boat must be fed into a master controller (not shown, but coupled to the stocking unit
10
). The stocking unit
10
automatically pulls out the desired wafer boat from the storage area
16
and transfers the wafer boat to the outlet port
22
at the inner flank of the out-stock area
14
. Ultimately, the desired wafer boat is moved to the inlet port
24
at the outer flank of out-stock area
14
for the operator to take away.
FIG. 2
is a detailed top view of one of the inlet-ports
18
of the stocking unit shown in FIG.
1
. The inlet-port
20
, the outlet port
22
and the outlet port
24
all have the same structure as the inlet-port
18
. Here, inlet-port is used as an example, only.
As shown in
FIG. 2
, the inlet port
18
has four wafer boat supporters
26
a
,
26
b
,
26
c
and
26
d
for supporting a wafer boat
30
. The four wafer boat supporters
26
a
-
26
d
are separated from each other by a fixed distance and positioned at the corners of a square centered upon the inlet port area
18
. In addition, wafer boat sensors
28
a
and
28
b
are installed on the wafer boat supporters
26
a
and
26
c
for detecting the presence of the wafer boat
30
. When pressure from a wafer boat is transmitted to any one of the sensors
28
a
and
28
b
, the presence of a wafer boat is implied so that the stocking unit
10
is immediately informed.
However, due to human operational errors, it is possible for somebody to mistake the outlet port for a temporary storage area for wafer boats. Sometimes, due to the improper positioning of a wafer boat in the port areas, wafer boat sensors in the outlet port areas may not detect the presence of a wafer boat. This often leads to a collision between the wafer boat retrieved from the storage area and the misplaced wafer boat in the outlet port area. Problems caused by mishandling of the wafer boats can be illustrated with an example.
FIGS. 3A through 3D
are top views of a conventional stocking unit and illustrate how damages to wafer boats can arise from human mishandling.
In
FIG. 3A
, two wafer boats
41
and
42
are stationed at the outlet ports
22
and
24
of the stocking unit, respectively. Other wafer boats inside the storage area
16
(not shown) and waiting to go out are stuck when the two outlet ports
22
and
24
are still occupied. To take out other wafer boats, an operator must take out the wafer boat
41
in the outlet port
24
first. If anyone needs to retrieve a wafer boat such as wafer boat
43
inside the stocking unit
10
, both outlet ports
22
and
24
must be emptied.
In
FIG. 3B
, someone who wants wafer boat
43
takes out wafer boat
41
from the outlet port
24
and puts wafer boat
41
in the inlet port
18
. Meanwhile, wafer boat
42
moves out to outlet port
24
, and wafer boat
43
is now stationed in outlet port
22
. In other words, as soon as the wafer boat
42
moves to the outlet port
24
, the wafer boat
43
inside the storage area
16
is able to move into the outlet port
22
.
In
FIG. 3C
, the person who needs wafer boat
43
takes out wafer boat
42
and then waits until the wafer boat has moved to the outlet port
24
before taking the wafer boat
43
out.
In
FIG. 3D
, the person who has taken away the wafer boat
43
now puts the wafer boat
42
back in the outlet port
24
because the wafer boat
42
belongs to somebody else. However due to the improper placement of the wafer boat
42
, the wafer boat sensors
32
a
and
32
b
inside the outlet port
24
cannot detect the presence of any wafer boat. In the absence of a signal that implies the presence of a wafer boat in the outlet port
24
, another wafer boat that needs to get out from the stocking unit
10
is transferred directly to the outlet port
24
. Hence, the outgoing wafer boat may collide with the wafer boat
42
already inside the outlet port
24
possibly damage the wafer.
On the other hand, if the wafer boat
41
is improperly placed inside the inlet port
18
, sensors
28
a
and
28
b
in the inlet port
18
are unable to detect the presence of any wafer boat. However, no harm is done because the stocking unit
10
will not respond to any input request in the absence of any wafer boat in the inlet ports
18
and
20
.
SUMMARY OF THE INVENTION
The invention provides an installation for protecting the outlet port of a stocking unit. The system includes an outlet port, four wafer boat supporters, two wafer boat sensors, a first light-intercepting sensor and a second light-intercepting sensor. The four wafer boat supporters are used for supporting a wafer boat and the supporters are separated from each other by a fixed distance positioned at the corners of a square centered upon the outlet port. The two wafer boat sensors are installed on the respective wafer boat supporters at the opposite corners. The wafer boat sensors are used for detecting the pressure in the presence of a wafer boat. The first light-intercepting sensor is mounted on one side of the outlet port while the second light-intercepting sensor is mounted on the other side of the outlet port. When there is no wafer boat in the outlet port, the first light-intercepting sensor is capable of receiving light coming from the second light-intercepting sensor. Conversely, the second light-intercepting sensor is capable of receiving light coming from the first light-intercepting sensor. However, if a wafer boat is placed inside the outlet port, light is blocked by the wafer boat. According to the pressure on the wafer boat sensors and the light-intercepting conditions of the light-intercepting sensors, the stocking unit is able to determine if any wafer boat is present in the outlet port. Hence, the order whether to move any wafer boat from the storage area of the stocking unit or not can be decided more accurately.
Huang Jiawei
J. C. Patents
United Microelectronics Corp.
Wu Daniel J.
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