Land vehicles: bodies and tops – Bodies – Accessories
Reexamination Certificate
1999-08-03
2001-03-27
Bratlie, Steven A. (Department: 3652)
Land vehicles: bodies and tops
Bodies
Accessories
C414S941000, C901S046000, C294S907000
Reexamination Certificate
active
06206441
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for transferring wafers by a robot blade and more particularly, relates to an apparatus and a method for transferring wafers by a robot blade that is equipped with distance sensors mounted in the bottom surface of the blade such that the distance between the blade and an adjacent surface below is continuously monitored to avoid scratching the surface of a wafer positioned below or colliding with a wafer pedestal.
BACKGROUND OF THE INVENTION
In the fabrication processes for semiconductor devices, a semi-conducting wafer is normally processed through many different fabrication steps, i.e., sometimes as many as several hundred. These processing steps may include deposition processes, etching processes, ion implantation processes and a variety of other processes. The fabrication equipment utilized in these processes may include process chambers that are arranged in a cluster formation with a center loadlock chamber for delivering and withdrawing wafers to and from each process chamber.
One of the key components in a loadlock chamber is a wafer blade that is normally controlled by a robotic arm. The wafer blade is also known as a robot blade. The robot blade can be constructed of a thin piece of metal such that it holds a wafer securely for delivering it into process chambers through narrow slit valves provided in the sides of the process chambers that join the loadlock chamber.
In a typical loadlock chamber, a robot blade and a storage elevator are provided. The loadlock chamber provides a wafer handling center in a clustered processing machine by isolating the plurality of process chambers from the surrounding atmosphere through the use of slit valves between the loadlock chamber and the process chambers. A cassette indexer or a SMIF pod may provide the source of wafers for the robot blade in the loadlock chamber. The loadlock chamber is normally provided with a self-contained vacuum system that maintains the interior of the chamber particle free and at a slightly higher pressure than the process chambers during wafer transfers to and from the process chambers. The self-contained vacuum system further provides the loadlock chamber with atmospheric pressure during wafer transfers to and from a cassette indexer. In a normal arrangement, up to about four process chambers can be mounted on a loadlock chamber.
A typical robot blade
10
is shown in FIG.
1
. The robot blade
10
is constructed of a robot arm
12
, and a wafer holder
14
. The wafer holder
14
has a small thickness X such that it can go through narrow slit valves for delivering or withdrawing wafers to and from a process chamber or a cassette indexer. The robot arm
12
is constructed of a robot
18
and a mechanical arm
20
. The wafer holder
14
is constructed of a blade portion
22
, a pair of object sensors
24
,
26
mounted in a top surface of the blade and a printed circuit board
32
for controlling the sensors
24
,
26
.
FIG. 1A
shows a cross-sectional view of the wafer holder
14
holding a wafer
40
on top. In the configuration shown in
FIG. 1A
, a wafer
40
is carried on a top surface
16
of the blade
22
. The object sensors
24
,
26
are utilized to sense the presence of the wafer
40
which is properly positioned on the blade
22
.
In utilizing the robot blade
10
shown in
FIGS. 1 and 1A
, the blade is used in a robot transfer system for transferring wafers between a load/unload chamber and a process chamber, for instance, during a pick/place actuation from chamber electrode/cassette. A serious processing problem arises in utilizing the robot blade, i.e., the scratching of wafer surfaces by the backside of the blade during a transfer in or out of a wafer cassette. Moreover, when a transfer has been made to a process chamber, the backside of the robot blade may scratch the top surface of a wafer pedestal and causing serious damages. In the normal configuration of a commercial robot blade, there is no provision for detecting any possible scratching or colliding of the blade with either a wafer or with a wafer pedestal. This presents a serious problem in that wafer scratching is frequently not detected such that problem persists until a large number of wafers have been scratched resulting in a great loss in throughput.
It is therefore an object of the present invention to provide an apparatus for transferring wafers by using a robot blade that does not have the drawbacks or shortcomings of the conventional robot blades.
It is another object of the present invention to provide an apparatus for transferring wafers by a robot blade that does not present the danger of scratching wafers in a wafer cassette.
It is a further object of the present invention to provide an apparatus for transferring wafers by a robot blade that does not present the danger of scratching a wafer pedestal in a process chamber.
It is another further object of the present invention to provide an apparatus for transferring wafers by a robot blade that is equipped with a distance sensor mounted in a bottom surface of the blade.
It is still another object of the present invention to provide an apparatus for transferring wafers by a robot blade that is equipped with a distance sensor mounted in such a way that a top surface of the sensor is flush with the bottom surface of the blade.
It is yet another object of the present invention to provide an apparatus for transferring wafers by a robot blade that is equipped with a capacitance sensor mounted in a bottom surface of the blade.
It is still another further object of the present invention to provide a method for transferring wafers by a robot blade by mounting a distance sensor in a bottom surface of the blade such that a minimum distance with an adjacent surface below can be maintained.
It is yet another further object of the present invention to provide a method for transferring wafers by providing a robot blade that is equipped with a capacitance sensor in a bottom surface of the blade, measuring a distance between the blade and an adjacent surface below, and stopping the blade motion when the distance measured is less than a minimum distance.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus and a method for transferring wafers by a robot blade equipped with distance sensors in a bottom surface of the blade are provided.
In a preferred embodiment, a robot blade for transferring wafers can be provided which includes a blade member of generally elongated shape adapted for carrying a wafer on a top surface, the blade member has at least two extended leg portions, and a total length that is larger than a diameter of the wafer it carries, at least one recess provided in a bottom surface and juxtaposed to a tip of the at least two extended leg portions, and at least one distance sensor for sensing a distance between the bottom surface of the blade member and an adjacent surface below the bottom surface mounted in the at least one recess.
In the robot blade for transferring wafers, the distance sensor may be the capacitance type, or may be a sensor selected from a capacitance sensor, an ultrasonic sensor or an optical sensor. The robot blade may further include at least one object sensor positioned in the top surface of the blade for sensing the presence or absence of an object that is carried by the blade. The robot blade may further include a blade member of generally elongated shape equipped with two extended leg portions, the leg portions may each be provided with a capacitance sensor mounted in a recess in the bottom surface of the leg portions. The robot blade may be mounted on a robot arm.
The present invention is further directed to a method for transferring wafers that can be carried out by the operating steps of first providing a wafer blade mounted on a robot arm, the blade has at least two extended leg portions for holding a wafer thereon, providing at least one distance sensor in a bottom surface of the at least two extended leg portions such that a t
Doung Su-Yi
Lu Chuan-Yuan
Tseng Chi-Yun
Wen Ming-chien
Bratlie Steven A.
Taiwan Semiconductor Manufacturing Company , Ltd.
Tung & Associates
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