Data processing: generic control systems or specific application – Generic control system – apparatus or process – Digital positioning
Reexamination Certificate
1998-03-04
2001-03-06
Grant, William (Department: 2121)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Digital positioning
C700S121000
Reexamination Certificate
active
06198976
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to methods and apparatuses for handling a moving object, such as a substrate, in a processing system. Specifically, the present invention relates to methods and apparatuses for determining the center of a substrate while the substrate is moving through a substrate handling environment of a vacuum processing system.
2. Background of the Related Art
Vacuum processing systems for processing 100 mm, 200 mm, 300 mm or other diameter substrates are generally known. Typically, such vacuum processing systems have a centralized transfer chamber mounted on a monolith platform. The transfer chamber is the center of activity for the movement of substrates being processed in the system. One or more process chambers mount on the transfer chamber at the position of slit valves through which substrates are passed by a substrate handler, or robot, pivotably mounted in the transfer chamber. Access to the transfer chamber from a clean ambient environment is typically through one or more load lock chambers attached at other slit valves. The transfer chamber substrate handler is mounted in the middle of the transfer chamber and can access each of the process chambers and load lock chambers to transfer a substrate therebetween. The load lock chambers may open to a very clean room, referred to as the white area, or to a substrate handling chamber, typically referred to as a mini-environment. The mini-environment transfers substrates in a very clean environment at atmospheric pressure from pods, or cassettes or carriers, seated on pod loaders to the load lock chambers.
The mini-environment has a substrate handler for transferring the substrates. The substrate handler in the mini-environment is typically different from that in the transfer chamber, since it is typically capable of translational and vertical movement as well as rotation and extension; whereas, the substrate handler in the transfer chamber is typically only capable of rotation and extension. Either type of substrate handler has an arm assembly for manipulating the substrates that it transfers. One prevalent type of arm assembly has multiple arms pivotably attached to each other at pivot joints in order to extend and retract a blade, or end effector, which supports the substrate. The position of the arms is typically determined from an encoder that detects the angle of the pivot joints. A controller, such as a microcomputer, receives signals from the encoder and calculates the position of the blade.
A typical processing system includes a substrate center-finding system locates the center of the substrate in order to adjust the location of the substrate, so the substrate is centered on each of the structures which support the substrate in the system to avoid damage to the substrate and to ensure proper processing of the substrate. The center-finding system typically includes a set of emitter/sensor pairs, such as infrared beam emitters and sensors, for detecting the edge of the substrate. The center-finding system is typically disposed in a part of the processing system through which the substrate is passed, such as the transfer chamber or the mini-environment, so that the sensors can detect the edge of the substrate at several locations as the substrate passes through the beams. These substrate center-finding systems that determine the location of the center of a substrate while the substrate is moving are called on-the-fly center-finding systems.
On-the-fly center-finding systems are quite often used to make corrections for substrate misalignment. They typically consist of banks of through-beam or reflective sensors, such as an infrared emitter/sensor pair, arranged in the chamber through which the substrates pass. A typical arrangement for the sensors may have three to nine sensors arranged in one to three sensor banks. A substrate handler passes a substrate through the sensor beams. When the substrate interferes with, or cuts, a beam, the associated sensor is triggered and sends a signal to the controller indicating the trigger. When the controller receives a trigger signal, the controller records the encoder position. Thus, as the substrate is passed through the bank of sensors, information on the substrate position is obtained by recording the substrate handler encoder position every time a sensor triggers by and computing the substrate center from the positions. The accuracy and repeatability of existing methods, however, is dependent on the accuracy of placement and alignment of the sensors, the need to move the robot along straight line or circular paths and a known, constant speed of the substrate. For example, some types of on-the-fly center-finding systems require the substrate to be moved in a straight line through the sensor beams, use two sensors that must be arranged in a line perpendicular to the straight line of the substrate movement, assume the radius of the substrate, and do not work for substrates having substrate flats. Another type of center-finding system requires the substrate to be moved in a circular arc and uses three sensors that must be arranged in a line perpendicular to a tangent of the arc. Some centering-finding systems also require the use of a calibration substrate to calibrate the system, so the performance of the system is also dependent on the characteristics of the calibration substrate.
FIG. 1
a
shows an example of a substrate center-finding system such as the one described in U.S. Pat. No. 4,819,167, which is assigned in common with the present application and is incorporated herein by reference. In this center-finding system, a substrate
14
, on a blade
16
, is passed through an array of sensors
10
-
12
in a straight-line path in the direction of arrow A to determine the x-y coordinates of points on the edge of the substrate
14
, with the x-axis being in the direction of the substrate path. The sensors
10
-
12
are required to be positioned in a straight line that is perpendicular to the path (arrow A) of the substrate
14
and blade
16
. A further requirement is that the blade
16
has a hole
18
, which must be aligned with the middle sensor
11
. The location of the blade
16
is calibrated by sending a calibration substrate through the center-finding system to find the center of the blade
16
. Other prior art center-finding systems may also require the substrate to be moved in a straight line as described in this example, or may require that the substrate be moved in a circular line.
The center-finding system shown in
FIG. 1
a
requires seven coordinate points, one for the blade position, and six for the substrate position. As the substrate
14
and blade
16
pass through the sensors
10
-
12
, the blade
16
triggers the middle sensor
11
when the hole
18
is detected at point X
1
, thus providing the blade position. For some substrate center-finding systems of this type, the hole
18
may be very difficult to align to the sensor
11
and, thus, hard to detect. As the substrate
14
continues to move, the substrate
14
triggers the middle sensor
11
at the leading edge of the substrate
14
, point X
3
. The substrate
14
triggers the outer sensors
10
,
12
to provide the next leading edge positions at points X
2
and X
4
. The substrate
14
next triggers the outer sensors
10
,
12
to provide the trailing edge positions at points X
5
and X
7
. Finally, the substrate
14
triggers the middle sensor
11
to provide the last trailing edge position at point X
6
.
This center-finding system determines the x-coordinates for the points X
2
-X
7
by recording the distance the blade
16
has traveled at each of these points from point X
1
. The point X
1
, the blade position, is defined as the origin of the coordinate system, and the x-coordinate for the six substrate points are calculated with reference to the blade position. The average x-coordinate for each pair of substrate points for each sensor is calculated. If the substrate is completely circular, then all three averages should
Ebbing Peter F.
Sundar Satish
Applied Materials Inc.
Cabrera Zolia
Grant William
Thomason Moser & Patterson
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