Semiconductor device manufacturing: process – With measuring or testing
Reexamination Certificate
2002-04-25
2004-04-06
Coleman, W. David (Department: 2823)
Semiconductor device manufacturing: process
With measuring or testing
C414S217100, C029S025010
Reexamination Certificate
active
06716651
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a wafer cassette/loadport assembly used on a microelectronic fabrication equipment and a method of using and more particularly, relates to a wafer cassette/loadport assembly with a built-in self-identification function and a method for operating the assembly.
BACKGROUND OF THE INVENTION
The conveying of a semiconductor wafer is important in the manufacturing of integrated circuit chips due to the delicate nature of the wafer. In fabricating an IC product, a multiplicity of fabrication steps, i.e. as many as several hundred, is required to complete the fabrication process. A semiconductor wafer or IC chips must be transported between various process stations in order to perform various fabrication processes.
For instance, to complete the fabrication of an IC chip, various steps of deposition, cleaning, ion implantation, etching and passivation steps must be carried out before an IC chip is packaged for shipment. Each of these fabrication steps must be performed in a different process machine, i.e. a chemical vapor
7
deposition chamber, an ion implantation chamber, an etcher, etc. A partially processed semiconductor wafer must be conveyed between various work stations many times before the fabrication process is completed. The safe conveying and accurate tracking of such semiconductor wafers or work-in-process parts in a semiconductor fabrication facility is therefore an important aspect of the total fabrication process.
Conventionally, partially finished semiconductor wafers or WIP parts are conveyed in a fabrication plant by automatically guided vehicles or overhead transport vehicles that travel on predetermined routes or tracks. For the conveying of semiconductor wafers, the wafers are normally loaded into cassettes pods, such as SMIF (standard machine interface) or FOUP (front opening unified pod), and then picked up and placed in the automatic conveying vehicles. For identifying and locating the various semiconductor wafers or WIP parts being transported, the cassettes or pods are normally labeled with a tag positioned on the side of the cassette or pod. The tags can be read automatically by a tag reader that is mounted on the guard rails of the conveying vehicle.
In modern semiconductor fabrication facilities, especially for the 200 mm or 300 mm fabrication plants, automatic guided vehicles (AGV) and overhead hoist transport (OHT) are extensively used to automate the wafer transport process as much as possible. The AGV and OHT utilize the input/output ports of a stocker to load or unload wafer lots, i.e. normally stored in FOUFs.
FIG. 1
is a perspective view of an overhead hoist transport system
32
consisting of two vehicles
34
,
36
that travel on a track
38
. An input port
40
and an output port
42
are provided on a stocker
30
. As shown in
FIG. 1
, the overhead transport vehicle
36
stops at a position for unloading a FOUP
44
into the input port
40
. The second overhead transport vehicle
34
waits on track
38
for input from stocker
30
until the first overhead transport vehicle
36
moves out of the way.
Similarly, the OHT system is used to deliver a cassette pod such as a FOUP to a process machine. This is shown in
FIG. 2. A
cassette pod
10
of the FOUP type is positioned on a loadport
12
of a process machine
14
. The loadport
12
is equipped with a plurality of locating pins
16
for the proper positioning of the cassette pod
10
. A detailed perspective view of the FOUP
10
is shown in FIG.
3
. 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 with a plate member
52
for gripping by a transport arm (not shown) of the OHT system (not shown).
When a wafer cassette is loaded onto a loadport of a process machine, problems occur when the cassette is not correctly identified leading to serious cross-contamination problems for the wafers contained in the cassette. For instance, in the same intra-bay, there may be twenty or thirty process machines each used for depositing a different material layer, for instance, the chemical vapor deposition of silicon oxide, polysilicon, copper or cobalt. When a wafer cassette, such as a FOUP is positioned on the wrong process machine that is setup for the deposition of a different material, the resulting contamination on wafers can be detrimental and extremely difficult to correct.
It is therefore an object of the present invention to provide a wafer cassette/loadport assembly that does not have the drawbacks or shortcomings of the conventional wafer cassette/loadport assemblies.
It is another object of the present invention to provide a wafer cassette/loadport assembly that is equipped with a built-in self-identification system.
It is a further object of the present invention to provide a wafer cassette/loadport assembly that is capable of self-identifying the type of wafer cassette placed on the loadport of a process machine.
It is another further object of the present invention to provide a wafer cassette/loadport assembly that has built-in, self-identification system for feeding information on the wafer cassette into a process controller.
It is still another object of the present invention to provide a wafer cassette/loadport assembly that has a built-in, self-identification system by providing conductive pins on the loadport as locating pins.
It is yet another object of the present invention to provide a method for identifying a wafer cassette that is positioned on a loadport by utilizing a built-in, self-identification system.
It is still another further object of the present invention to provide a method for identifying a wafer cassette positioned on a loadport by feeding information on the wafer cassette into a process controller and comparing to data stored therein.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus and a method for identifying a wafer cassette by a built-in, self-identification system are provided.
In a preferred embodiment, a wafer cassette/loadport assembly that has a built-in, self-identification system is provided which includes a wafer cassette equipped with a bottom plate having at least two recessed holes in a bottom surface of the plate, at least one of the at least two recessed holes is provided with a spring-loaded, laterally positioned, electrically conductive plate adapted to engage one of at least two pins situated on a top surface of a loadport; a loadport equipped with at least two pins on a top surface in positions that are in mirror image to the two recessed holes in the wafer cassette when the wafer cassette is placed on top of the loadport, each of the at least two pins is provided with two electrically conductive tips that are spaced-apart and electrically insulated from each other, the two tips are adapted to conduct electricity therein between when pressed against and intimately contact the spring-loaded, electrically conductive plate in one of the at least two recessed holes upon engagement between the loadport and the wafer cassette thereby sending an electrical signal to a process controller identifying the wafer cassette.
The wafer cassette/loadport assembly that has built-in, self-identification system may further include a process controller for receiving the electrical signal from the loadport and comparing to pre-stored data in the process controller. A number of the at least two recessed holes on the wafer cassette equals a number of the at least two pins on top of the loadport. The at least two pins on a top surface of the loadport are locating pins. The two electrically conductive tips are formed of aluminum, stainless steel or copper. The two electrically conductive tips are each connected by a lead wire for se
Huang Yu-Chih
Lien Robin
Peng Jung Huang
Weng Martin
Coleman W. David
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
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