U.S. patent application number 14/089439 was filed with the patent office on 2016-08-18 for substrate handling system for aligning and orienting substrates during a transfer operation.
This patent application is currently assigned to Brooks Automation, Inc.. The applicant listed for this patent is Brooks Automation, Inc.. Invention is credited to Matthew W. Coady.
Application Number | 20160240418 14/089439 |
Document ID | / |
Family ID | 53182810 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160240418 |
Kind Code |
A9 |
Coady; Matthew W. |
August 18, 2016 |
SUBSTRATE HANDLING SYSTEM FOR ALIGNING AND ORIENTING SUBSTRATES
DURING A TRANSFER OPERATION
Abstract
A system for sensing, orienting, and transporting wafers in an
automated wafer handling process that reduces the generation of
particles and contamination so that the wafer yield is increased.
The system includes a robotic arm for moving a wafer from one
station to a destination station, and an end-effector connected to
an end of the robotic arm for receiving the wafer. The end-effector
includes a mechanism for gripping the wafer, a direct drive motor
for rotating the wafer gripping mechanism, and at least one sensor
for sensing the location and orientation of the wafer. A control
processor calculates the location of the center and the notch of
the wafer based on measurements by the sensor(s) and generates an
alignment signal for rotating the wafer gripping mechanism so that
the wafer is oriented at a predetermined position on the
end-effector while the robotic arm is moving to another
station.
Inventors: |
Coady; Matthew W.; (Hollis,
NH) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Brooks Automation, Inc. |
Chelmsford |
MA |
US |
|
|
Assignee: |
Brooks Automation, Inc.
Chelmsford
MA
|
Prior
Publication: |
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Document Identifier |
Publication Date |
|
US 20150147148 A1 |
May 28, 2015 |
|
|
Family ID: |
53182810 |
Appl. No.: |
14/089439 |
Filed: |
November 25, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
13230280 |
Sep 12, 2011 |
8590956 |
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14089439 |
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11045545 |
Jan 28, 2005 |
8016541 |
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13230280 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/68 20130101;
H01L 21/68707 20130101 |
International
Class: |
H01L 21/68 20060101
H01L021/68; H01L 21/687 20060101 H01L021/687 |
Claims
1. A substrate transport apparatus comprising: a movable transport
arm; and an end effector movably connected to the transport arm,
and being adapted for holding a substrate thereon, the end effector
has an integral aligner and comprises a base and a printed circuit
board (PCB), the PCB being dependent from the base and forms at
least part of a motive portion of the aligner.
2. The apparatus according to claim 1, wherein the end effector has
at least one sensor thereon to sense a predetermined characteristic
of the semiconductor substrate.
3. The apparatus according to claim 2, wherein the predetermined
characteristic is at least one of an edge of the semiconductor
substrate or a fiducial feature of the semiconductor substrate.
4. The apparatus according to claim 2, further comprising a
controller in communication with the at least one sensor and the
aligner, and wherein the controller is programmed to actuate the
aligner for positioning the semiconductor substrate held by the
aligner based on information from the at least one sensor.
5. The apparatus according to claim 4, wherein the controller is
configured to rotate the substrate with the aligner substantially
simultaneously with the transport arm moving the semiconductor
substrate from one station to another station.
6. The apparatus according to claim 1, wherein the end effector has
a support member supporting the aligner, said support member being
defined by the PCB, the aligner comprising a rotatable passive grip
chuck being rotatably mounted relative to the support member to
rotate relative to the support member, and wherein the axis of
movement is an axis of rotation of an aligner motor.
7. The apparatus according to claim 6, wherein the motor is a
brushless motor and is located on the support member of the end
effector supporting the rotatable passive grip chuck, the brushless
motor being located on the support member at a location under the
rotatable passive grip chuck.
8. The apparatus according to claim 7, further comprising a
positional resolver connected to the rotatable passive grip chuck
for providing position information of the rotatable passive grip
chuck to a controller operating the motor.
9. The apparatus according to claim 1, wherein the aligner
comprises a motor with a stator and a rotor, the stator being
integral to the PCB, and the rotor being integral to the rotatable
passive grip chuck.
10. A substrate processing apparatus comprising: at least one
substrate transport apparatus, the at least one substrate transport
apparatus including a movable transport arm, an end effector
movably connected to the transport arm, the end effector having an
integral aligner with a rotatable passive grip chuck including
fixed substrate edge grip supports adapted for passively holding a
semiconductor substrate when the semiconductor substrate is rotated
by the rotatable passive grip chuck, and a motor configured to
rotate the rotatable passive grip chuck of the aligner.
11. The apparatus according to claim 10, wherein the end effector
has at least one sensor thereon to sense at least one of an edge of
the semiconductor substrate and a fiducial feature of the
semiconductor substrate.
12. The apparatus according to claim 11, further comprising a
controller in communication with the at least one sensor and the
motor, and wherein the controller is programmed to actuate the
motor for positioning the semiconductor substrate held by the
rotatable passive grip chuck based on information from the at least
one sensor.
13. The apparatus according to claim 12, wherein the controller is
configured to rotate the rotatable passive grip chuck with the
motor substantially simultaneously with the transport arm moving
the semiconductor substrate from one station to another
station.
14. The apparatus according to claim 10, wherein the end effector
has a support member supporting the rotatable passive grip chuck,
the rotatable passive grip chuck being rotatably mounted relative
to the support member to rotate relative to the support member, and
wherein the axis of movement is an axis of rotation of the
motor.
15. The apparatus according to claim 10, wherein the motor is a
brushless motor and is located on a support member of the end
effector supporting the rotatable passive grip chuck, the brushless
motor being located on the support member at a location under the
rotatable passive grip chuck.
16. The apparatus according to claim 15, further comprising a
positional resolver connected to the rotatable passive grip chuck
for providing position information of the rotatable passive grip
chuck to a controller operating the motor.
17. The apparatus according to claim 10, wherein the motor
comprises a stator and a rotor, the stator being integral to a base
of the end effector, and the rotor being integral to the rotatable
passive grip chuck.
18. An end effector for a substrate transport apparatus, the end
effector comprising: a support member; and an aligner connected to
the support member, and having a rotatable passive grip chuck
disposed on the support member, the rotatable passive grip chuck
including fixed substrate edge grip supports adapted for passively
holding a semiconductor substrate when the semiconductor substrate
is rotated by the rotatable passive grip chuck; and wherein the
aligner has a motor disposed on the support member and configured
to rotate the rotatable passive grip chuck.
19. The end effector according to claim 18, wherein the motor is a
brushless motor and is configured to support the rotatable passive
grip chuck.
20. The apparatus according to claim 18, wherein the motor
comprises a stator and a rotor, the stator being integral to the
support member and the rotor being integral to the rotatable
passive grip chuck.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/230,280 filed on Sep. 12, 2011 (now U.S.
Pat. No. 8,590,956 issued on Nov. 26, 2013) which is a continuation
of U.S. patent application Ser. No. 11/045,545 filed on Jan. 28,
2005 (now U.S. Pat. No. 8,016,541 issued on Sep. 13, 2011) which is
a continuation of International Patent Application No. US03/28391,
filed Sep. 10, 2003, the disclosures of which are incorporated by
reference herein in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The exemplary embodiments of the present invention relate to
a substrate transport system and, more particularly, to a substrate
transport system capable of orienting and aligning a substrate "on
the fly".
[0004] 2. Brief Description of Earlier Related Developments
[0005] In semiconductor fabrication processes, wafers are
transferred between stations, such as storage, queuing, processing
and other work stations. In typical automated wafer handling
processes, a wafer is first picked up by a robotic arm for transfer
from one station to another station. Next, the wafer is placed on
an aligner for aligning and centering the wafer to a desired
position using a notch or flat located on the wafer's edge. Once
properly aligned, the wafer is then placed in the desired station
for processing. After the processing is completed at the desired
station, the wafer may then be picked up and placed again at
another station.
[0006] Each time that the wafer is picked up, placed, and aligned,
contact is made with either the edge or the back side of the wafer
and particles are generated. For instance, in a single wafer
process cycle, the wafer may be contacted as many as twelve times
when using a three-axis aligner or at least eight times when a
single axis aligner is used.
[0007] In addition, the alignment process requires a dedicated
aligning device and a separate step in the wafer process cycle. The
dedicated aligning device often creates a bottleneck that limits
the wafer throughput in the system and also introduces additional
handling that generates particles. Adding aligners to the system
may help to slightly increase this throughput problem but creates
an undesirable increase in the cost, complexity and generation of
particles to the wafer handling system. Accordingly, a system is
desired for enhancing the wafer handling process by reducing the
generation of particles and wafer damage so that the wafer yield is
increased. Also, it is desired to increase the wafer throughput by
performing the alignment process in parallel with moving the
wafer.
[0008] In order to effect alignment/reorienting of the wafer (or
any other flat panel substrate/workpiece) in parallel with moving
the wafer so called "on the fly" alignment, the handling systems
are generally provided with means or drives for performing such
alignment. In conventional handling system, the "on the fly"
alignment drives have generally been used by systems that do not
employ "edge gripping" for holding the substrate. These non-edge
gripping systems, however, are generally falling into disfavor with
users (for edge-gripping systems) because the non-edge gripping
systems contact the wafer surface with the associated potential for
contamination. In the case of edge gripping systems, attempts have
been made to provide an "on the fly" alignment drive. These
conventional attempts take the form of a servomotor mounted away
from the wafer and the chuck holding the wafer on the handling
system. This is known as "off axis" mounting. The servomotor is
connected to the chuck by a suitable transmission that imparts
motion from the servomotor to the chuck. In conventional systems,
locating the motor away from the substrate minimizes potential for
particulate contaminants generated during motor operation coming in
contact with the wafer surfaces. Nevertheless, by employing a
transmission to connect the motor to the chuck, such as cables,
conventional systems still have the potential for having particles
contaminate the surface of the wafers being handled. Further, the
transmission, by its very nature as a further drive element between
motor and chuck, increases the possibility for inaccuracy in
placement/aligning of the substrate. The transmission further
increases the weight and complexity of the end effector with a
detrimental impact to the control of the handling system. Further,
due to the very tight height constraints, the chuck, of the end
effector is inserted between stacked wafers in a pod/cassette with
a pitch of about 10.0 mm and a wafer thickness of about 0.77 mm,
the transmission design is complex. Correspondingly, the
transmission may be unreliable and time consuming to install.
[0009] The present invention as evident from the exemplary
embodiments overcomes the problems of conventional handling systems
as will be described in greater detail below.
SUMMARY OF THE EXEMPLARY EMBODIMENTS
[0010] The present invention is directed to a system for locating
and orienting substrates, such as semiconductor wafers, during the
pick up and transfer steps in an automated substrate handling
process. In a semiconductor fabrication process, the system is able
to reduce the generation of particles from and the contamination of
semiconductor wafers. As a result, the wafer yield and throughput
of the fabrication process are increased.
[0011] More particularly, the system includes a robotic arm for
moving a wafer from one station to another station. An end-effector
is connected to an end of the robotic arm for handling the wafer.
The end-effector may include a mechanism for gripping the wafer, a
mechanism, such as a motor, for moving the wafer gripping
mechanism, and at least one sensory system for sensing the location
and orientation of the wafer. A control processor operatively
connected to the robotic arm and the end-effector calculates the
location of the center and a notch or flat of the wafer based on
data from the at least one sensory system. The control processor
generates a signal to move the wafer gripping mechanism so that the
wafer is centered on the end-effector when picked by the
end-effector and is oriented at a predetermined position on the
end-effector while the robotic arm is moving to another station.
After the wafer is picked up by the end-effector, the control
processor can refine the calculation of the center of the wafer and
adjust the wafer's orientation before being dropped off at the next
station.
[0012] Other aspects, features and advantages of the present
invention are disclosed in the detailed description of the
exemplary embodiments that follows.
DESCRIPTION OF THE DRAWINGS
[0013] The exemplary embodiments will be more fully understood by
reference to the following detailed description of the invention in
conjunction with the drawings, of which:
[0014] FIG. 1 illustrates a block diagram of a wafer handling
system according to an embodiment of the present invention;
[0015] FIG. 2 illustrates a robotic arm and an end-effector used in
a wafer handling system according to an embodiment of the present
invention;
[0016] FIG. 3 illustrates exemplary wafer positioning measurements
according to an embodiment of the present invention;
[0017] FIG. 4 illustrates an example of a voltage output curve from
a capacitive sensor that may be used for sensing wafer edges;
[0018] FIG. 5 illustrates a wafer notch measurement according to an
embodiment of the present invention;
[0019] FIG. 6 illustrates a sensor configuration on an end-effector
according to an embodiment of the present invention;
[0020] FIG. 7 illustrates a detailed view of an end-effector
according to an embodiment of the present invention;
[0021] FIG. 8 is a perspective view of an end-effector according to
another embodiment of the present invention;
[0022] FIG. 9 is a plan view of the end-effector in FIG. 8 and a
substrate S;
[0023] FIG. 9A is a cross-section view of the end-effector and
substrate S taken along view line A-A in FIG. 9;
[0024] FIG. 9B is an enlarged partial cross-section view of the end
effector and substrate S in FIG. 9B;
[0025] FIG. 10 is an exploded perspective view of the end effector
in FIG. 8;
[0026] FIG. 11 is another perspective view of the end effector in
FIG. 8 with the chuck of the end effector rotated to a different
position from that shown in FIG. 8; and
[0027] FIG. 12 is a plan view of a stator and rotor of a motor of
the end effector shown in FIG. 8.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0028] A substrate handling system according to the present
invention provides a robotic arm configured to handle substrates,
such as semiconductor wafers, reticles, etc. The system is
operative to sense the substrate and center the substrate with
respect to the robotic arm's end-effector prior to picking up the
substrate. The system is also operative to orient the substrate in
a desired orientation and to calculate the center of the wafer
during transfer of the substrate to a destination station. The
system is particularly useful in transferring semiconductor wafers
between stations in a semiconductor fabrication process. The system
reduces the amount of wafer handling necessary between stations so
that the generation of particles from and contamination of the
wafers decreases, increasing wafer yield. The system eliminates a
separate alignment step, thereby increasing wafer throughput.
[0029] Referring to FIG. 1, the system includes one or more robotic
arm assemblies 20 operatively communicative with a control
processor 10 by, for example, a bus, cable or wireless connection
12. Each of the robotic arm assemblies 20 includes an end-effector
40 operatively communicative with the control processor 10 by a
bus, cable or wireless connection 14, which will be described in
more detail below, and is associated with one or more stations 30,
32 and 34 for moving substrates, such as wafers, therebetween. The
end-effector 40 includes a substrate gripper or mechanism 42 and a
sensory system 44. The control processor 10 calculates the location
of the center and an alignment feature, such as a notch or flat of
the wafer, based on data from sensors on the end-effector and
generates centering, aligning, and orienting signals for the
end-effector based on these calculations. The control processor 10
computes and communicates to the robotic arm assemblies 20 the
actual substrate center position, and the arm assembly positions
the end-effector 40 centered relative to the substrate before
gripping the substrate.
[0030] After the end-effector 40 grips the centered wafer, the
control processor 10 generates additional signals for rotating the
wafer and processing the sensor signals in order to finally
re-compute the wafer center, find the notch or flat position and
rotate the notch or flat in a desired position. The orientation,
alignment and robotic arm trajectory correction are performed while
the robotic arm moves the wafer from one station to another
station. The control processor 10 may include distributed control
architecture for performing the orientation, alignment and
correction. The control processor 10 may also be mounted in close
proximity to the end-effector 40 for independently controlling the
alignment feature.
[0031] FIG. 2 schematically illustrates a typical robotic arm
assembly 100 for moving a semiconductor wafer 102 from one station
to another station in the semiconductor fabrication process. The
arm assembly 100 includes an arm 120 mounted on a support 110, such
as a central column that houses a lifting mechanism (not shown) to
raise and lower the arm vertically. The arm 120 includes an inner
arm 122, an outer arm 124, and the end-effector 130. The inner arm
122 is supported by the central column 110 at a rotatable
"shoulder" joint 126 to effect rotation about a vertical axis
through the central column 110. Similarly, the outer arm 124 is
mounted to the inner arm 122 at a rotatable "elbow" joint 128 for
rotation about a vertical axis, and the end-effector 130 is mounted
to the outer arm 124 at a rotatable "wrist" joint 132 for rotation
about a vertical axis. Rotation about the three rotatable joints
126, 128 and 132 allows the end-effector 130 to move to any
coordinate position in a horizontal plane, while translation of the
arm 120 on the central column provides vertical motion. It will be
appreciated that the present invention can be used with other
robotic arm configurations.
[0032] The end-effector 130 includes a wafer gripping mechanism
134, such as a vacuum wafer chuck, for gripping the wafer 102. It
is appreciated that edge grippers and other known wafer handling
mechanisms may also be used. A motor 136 or other suitable
mechanism is provided for rotating the wafer gripping mechanism 134
when orientation is required. One or more sensors 138 are mounted
at fixed and known locations on the end-effector 130 to sense the
location and notch orientation of the wafer 102 with respect to the
end-effector 130, described further below. Data collected by the
sensors 138 is communicated to the control processor 10, which
calculates the center of the wafer 102 and the location of its
notch or flat before the wafer 102 is gripped by the wafer gripping
mechanism 134. With the location data from the sensors 138, the
known center of the end-effector 130 is positioned underneath the
calculated center of the wafer 102, the end-effector 130 is raised
until the wafer gripping mechanism 134 contacts the underside of
the wafer 102, and the wafer gripping mechanism 134 is actuated to
grip the wafer 102. Once the wafer 102 is gripped, the robotic arm
assembly 100 moves the wafer 102 towards the next station. At the
same time, the end-effector 130 aligns the wafer 102 by rotating
the wafer gripping mechanism 134 to place-the notch or flat of the
wafer 102 in its desired orientation prior to releasing the wafer
102 at the next station.
[0033] The control processor 10 is able to calculate the location
of the wafer's center W.sub.c based on the sensor data. See FIG. 3.
The diameter of the wafer 102 is known. Commonly in semiconductor
fabrication, the wafers have a diameter of 300 mm. As noted above,
the locations of the sensors 138 are fixed with respect to the
end-effector 130 and are thus known by the control processor 10.
Thus, the center of the wafer 102 can be determined by sensing at
least two edge locations of the wafer 102, from which a chord
length can be calculated. Note that, if the sensors 138 are located
near the leading edge of the end-effector 130, that is, the edge of
the end-effector 130 that first moves underneath the wafer 102, the
control processor 10 can be instructed that the center of the wafer
102 is in front of the leading edge. Thus, two edge data points are
sufficient to enable the calculation of the location of the center
of the wafer 102 of known diameter. The control processor 10 is
then able to move the end-effector 130 to a desired alignment with
respect to the wafer 102, for example, with the wafer center
W.sub.c over a center E.sub.c or other desired point of the
end-effector 130.
[0034] Preferably, at least two sensors are placed at known
locations on the end-effector to sense at least two wafer edge
locations. It will be appreciated, however, that a single sensor
on-the end-effector can be used if the sensor is suitably moved to
sense two or more separate edge locations on a wafer. It will also
be appreciated that a greater number of sensors can be used to
provide a greater number of data points. If more than two data
points are used, an average of the calculated center points can be
determined.
[0035] The sensors 138 can be of any suitable type, such as
capacitive, optical, acoustic, or ultrasonic sensors. As an
example, if a capacitive sensor is used, the capacitance increases
as the sensor moves underneath a wafer. For each sensor, a voltage
output, which is proportional to impedance, is generated to select
an appropriate edge point, indicated, as an example, by a vertical
dashed line on FIG. 4. The actual edge point selected for use in
the subsequent calculations is determined by a set of real time
measurements and voltage/distance curves. The data processing
algorithm can use look-up tables, statistical inference, or
artificial intelligence, as would be known by one of skill in the
art.
[0036] The detected capacitance is also dependent on the distance
from the sensors to the bottom surface of the wafer. This distance
can vary if the wafer is, for example, warped or tilted within the
storage container. Thus, a sensor to detect this distance is
preferably provided. This sensor is located to pass underneath the
wafer in advance of the edge-detecting sensor. In this manner, the
distance to the wafer can be provided, which enables a better
determination of the edge to be made. For example, a calibration
curve or look-up table can be provided for the appropriate distance
from the wafer. Also, if the wafer is warped or tilted, the wafer
may not be gripped correctly. Typically, if the wafer is not
gripped correctly, the wafer gripping device ungrips and regrips or
it aborts the grip and reports an error. Thus, the distance sensors
can be used to determine if warping or a tilted wafer is present
and to improve the robustness of the system.
[0037] Once the end-effector 130 is in alignment with the wafer
102, the end-effector 130 is raised vertically until it contacts
the wafer 102. The wafer gripping mechanism 134 is engaged to grip
the wafer 102. For example, if the wafer gripping mechanism 134 is
a vacuum chuck, the chuck is actuated to draw the underside of the
wafer 102 to the chuck. The robotic arm assembly 100 then begins
the transfer of the wafer 102 to the next station. During this
transfer, the wafer gripping mechanism 134 may be rotated until the
notch or flat of the wafer 102 is detected by one of the sensors
138 located on the end-effector 130 for purposes of detecting the
notch. Once the notch is detected, the wafer gripping mechanism 134
is rotated until the notch is located in the desired orientation
for placement at the destination station.
[0038] The notch may be detected in any suitable manner. For
example, using a capacitive sensor, the capacitance decreases when
the notch overlays the sensor, which may appear as a spike in a
voltage/distance curve. As shown in FIG. 5, when the notch 104 is
positioned over one of the capacitive sensors 138, the value
measured by the sensor decreases, and when the notch 104 is not
positioned over any of the sensors 138, the value measured by the
sensor increases. In this example, a small sized sensor is
preferred to increase the resolution of capacitive variance and
enhance the accuracy in detecting the notch. Based on iterations of
these calculations and comparisons, the position of the notch 104
on the wafer 102 may be determined. Once the notch 104 is detected,
the wafer 102 may be oriented in the desired position. The control
processor 10 may also make further adjustments to the orientation
of the wafer 102 during the placing step when the end-effector 130
approaches the destination station. For example, knowing the
location of the center of the wafer 102 with respect to the
end-effector 130, the control processor 10 can move the
end-effector 130 as necessary to deposit the wafer 102 in a desired
position at the destination station.
[0039] The system may also include a teach process for improving
the true location of the stations when the system is initially
configured and whenever a system component is changed, such as an
aligner, POD door or stage, for instance. In the teach process, the
sensors 138 are first moved under or over a datum plate or a
locating feature (there may be multiple locating features)
positioned at known coordinates within the system. The data from
the sensors 138 are used to provide feedback on whether the robotic
arm assembly 100, is level and its absolute position in the global
coordinate system. The robotic arm assembly 100 is adjusted if the
data suggests that it is not level.
[0040] Next, the robotic arm assembly 100 moves to each work
station 30, 32, and 34. As the leading edge of the substrate is
detected, the center of the substrate is calculated. This
information is used as the new station location. Additionally,
information is provided on whether the station is level by
measuring the apparent distance from the substrate as the sensors
move under or over the substrate. With this information, a user may
manually adjust and level the station. These steps are repeated for
all of the work stations. This information may be also used to
measure system changes and to predict failures. This teach process
may be performed to improve the true locations of a full
end-aligner or end-effectors with sensors.
[0041] FIG. 6 illustrates an embodiment of the present invention in
which six sensors 150, 152, 154, 160, 162 and 164 are placed at
predetermined locations around the periphery of an end-effector
base 170. In this embodiment, three rectangular sensors 150, 152
and 154 are used for sensing the edge of the wafer 102 and three
circular sensors 160, 162 and 164 are used for sensing the notch
and the distance of the wafer 102 from the end-effector base 170.
The sensors 150, 152, 154, 160, 162 and 164 may be capacitive,
acoustic, optical, reflective or other types of known sensors. This
configuration of sensors allows the robotic arm to pick up the
wafer and to grip the wafer without having the wafer slip along the
surface of the wafer gripping mechanism or during placement in the
station. The motion of the end-effector base 170 as it passes under
the wafer 102 is used to detect the presence of the front and rear
positions of the wafer 102. These measurements in combination with
the geometry of the wafer (the diameter of the wafer) are used to
determine the wafer's center and to adjust the pickup position in
conjunction with geometric distance calculation algorithms. These
measurements may also be used for controlling edge grippers to
eliminate sliding or in cases where orientation of the notch is not
required.
[0042] Although six sensors are used in the embodiment of FIG. 6,
additional sensors and types of sensors may be used to increase the
accuracy for calculating the center and compensating for errors
such as a warped wafer, notches passing under the sensors and
differences in substrate sizes. Generally, a straight motion by the
end-effector under the wafer is used for pick up. However, other
non-linear motions may be used to gather additional data points
based on the number of sensors, and the size and-shape of the
substrate in conjunction with the motion. Such alternative motions
may reduce the number of necessary sensors to as little as one
sensor.
[0043] The end-effector, with its edge gripping mechanism, motor
and sensors, must be sufficiently thin to fit between wafers stored
in a stack. Typically, the distance between wafers in a stack is 10
mm of pitch and 0.77 mm of wafer thickness. FIG. 7 illustrates an
embodiment of an end-effector 200 according to the present
invention suitable for use with a stack of wafers with a small
distance between the wafers. The end-effector 200 includes an
end-effector base 202 that is connected to the robotic arm (not
shown in this figure) at a connecting portion 204 thereof. The
end-effector base 202 includes a first circular ledge 208 for
receiving a motor stator 210 therein. The inner race 228 of the
motor, such as a contact bearing, is seated on the end-effector
base 202, that circularly extends up and around from the middle of
the end-effector base 202. A motor rotor 214 and an encoder disk
216 are first disposed on the back surface of a wafer chuck 222.
Then, the wafer chuck 222 with the motor rotor 214 and the encoder
disk 216 together fit on the outer race of the contact bearing 212.
After this fit, a gap between the encoder read head 218 and the
encoder disk 216 is realized. Typically, the resulting gap is
approximately 1 to 2 mm. An opening 224 at the center of the
end-effector base 202 is connected to a vacuum channel (not shown).
A ring seal 226 is disposed between the opening 224 of the
end-effector base 202 and the bottom surface of the wafer chuck 222
for applying a vacuum across the top surface of the wafer chuck 222
to grip the wafers.
[0044] The end-effector base 202 further includes openings 230,
232, 234 and 236 for receiving sensors 240, 242, 244 and 246 that
are positioned around the outer peripheral portion of the
end-effector base 202. The openings 230, 232, 234 and 236 may be
circular, rectangular, elliptical or other shapes and are dependent
upon the designs of the sensors 240, 2.42, 244 and 246 that are
being used for the sensing application. The sensors 240, 242, 244
and 246 may be capacitive, acoustical, optical, reflective or other
known types of sensors for sensing applications such as determining
the presence, absence and height of the wafer above the base, for
example. To maximize the detection resolution, a plurality of
sensors are positioned around the base and the surface area of each
individual sensor is made as small as possible while still being
large enough to detect edges and surfaces. Also, rectangular shaped
sensors are preferred to detect wafer edges and circular shaped
sensors to detect the distance of the wafer from the sensor in
addition to edges and the notch of the wafer. However, it should be
realized that different sensor shapes and sizes may be used
depending upon the desired sensing application and resolution.
[0045] In the embodiment of FIG. 7, three circular sensors 240, 242
and 244 and one rectangular sensor 246 are positioned around the
periphery of the end-effector base 202. Two of the circular sensors
240 and 242 are positioned towards the front the end-effector base
202 (typically the portion that first reaches the wafer) for first
sensing wafer edges. The other circular sensor 244 and the
rectangular sensor 246 are positioned near the periphery of the
end-effector base 202 that connects to the robotic arm.
Measurements from the rectangular sensor 246 and the two front
sensors 240 and 242 are sent to the control processor and are used
to center the wafer on the wafer chuck 222. Measurements from the
three circular sensors 240, 242 and 244 are also used to align the
planes of the wafer chuck 222 and the underside of the wafer. Once
the wafer is centered and aligned, the vacuum is applied to the
wafer chuck 222 and the wafer is gripped.
[0046] The robotic arm then moves the wafer to another station.
While the robotic arm is moving, one of the three circular
sensors-.240, 242 and 244 is used to detect the notch. The three
circular sensors 240, 242 and 244 are positioned so that the edge
of the wafer passes substantially through the middle of each
sensor. Once one of the sensors detects that the notch is directly
over it, the control processor may then generate orienting signals
to the end-effector 200 so that the notch is positioned at the
desired orientations. This orientation is typically completed
during the time that it takes for the wafer to reach the
destination station.
[0047] The present system centers the wafer on the wafer gripping
mechanism and positions the notch or flat in the desired
orientation while moving the wafer from one station to a
destination station without the need for a separate aligning or
centering device. Because impacts between the wafer and the
end-effector or the wafer and a cassette or stand generate
particles that may damage the wafer, the present invention
desirably minimizes picking up and placing of the wafers during the
handling process. By eliminating an aligning device, at least one
pick up and placing step is eliminated in the processing for each
wafer. As a result, the wafer throughput is greatly improved since
the alignment is done in parallel with the motion of the robotic
arm, which reduces both processing time and equipment costs. For
instance, if a cassette of 25 wafers is processed, a considerable
amount of time can be saved in addition to improving the
reliability of the system while drastically reducing particle
generation to improve wafer yield.
[0048] Referring now to FIG. 8 there is shown a perspective view of
an end effector 300 in accordance with another exemplary embodiment
of the present invention. End effector 300 is generally similar to
the other end effectors 130, 200 described before and shown in
FIGS. 2, 6 and 7. As with the other end effectors, end effector 300
can be mounted (at a joint similar to wrist joint 132) to the arm
assembly 100 (See FIG. 2) in a substantially similar manner as end
effectors 130, 200. Referring also to FIG. 10, which shows an
exploded perspective view, the end effector 300 generally comprises
a base 302, a chuck 322, and a motor 309. The base 302 is generally
configured to allow the end effector to be mounted for example to
the wrist joint 132 of the transfer arm 100 (see FIG. 2) as
described above. The chuck 322 is movably supported from the base
302. The chuck 322 has structures for holding a substrate S (see
for example FIG. 9) by edge gripping the substrate. As noted
before, substrate S (similar to substrate 102 in FIG. 2) may be any
suitable type of flat panel, such as a semiconductor wafer, a
reticle, a flat panel display, and is shown as having a
substantially circular outline for example purposes only. The motor
309 is also supported by the base 302 and is connected to the chuck
to move the chuck 322 relative to the base. The motor 309 is
located under the chuck and has an axis of motion R extending
substantially through the center C of the substrate S when the
substrate is held by the chuck 322. The motor 309 is a brushless
motor integral to the base and chuck, and is controlled by
controller 10 (see FIG. 1). The end effector 300 also includes a
positional resolver 316 that is communicably connected to the
controller 10. Sensors in the end effector, similar to the sensors
in end effector 200, locate a fiducial on the substrate S from
which the controller 10 finds the current orientation of the
substrate and determines the desired orientation. The motor 309,
under command from the controller 10, moves the chuck 322 until the
desired orientation is achieved.
[0049] In greater detail now, and with reference also to FIGS. 9,
9A-9B which respectively show a plan view, a cross-sectional view
through view line A-A, and an enlarged partial cross-sectional view
of the end effector 300 and substrate S, the base 302 of the end
effector generally comprises a rear section 302R (shown in phantom
in FIG. 8), and a front section 302F. The rear section 302R has
fixtures and attachments (not shown) possibly similar to base
sections 130, 202 for mounting the base 302, and hence the end
effector 300 to the arm. The front section 302F of the base 302
extends from the rear section 302R. The front section 302F in this
embodiment forms the front 307 (i.e. the portion inserted to
pick/place substrate S) of the end effector 300 (see FIG. 9). The
front section 302F of the end effector may be a one-piece member
(i.e. of unitary construction). In this embodiment, the front
section 302F of the base is a printed circuit board (PCB). As seen
in FIG. 9B, the PCB is self supporting and forms the structure of
the front section 302F of the base. As can be realized from FIGS. 9
and 9A, the PCB forming the front section supports the chuck 322 of
the end effector, and the substrate S held by the chuck. In
alternate embodiments, the front and rear sections of the base may
be included in a one-piece member PCB. In that case, a portion of
the PCB itself may provide the attachments for mounting the end
effector to the transport arm. In other alternate embodiments, the
front section of the base may be an assembly that includes a PCB
section supporting the chuck.
[0050] As can be realized from FIGS. 9 and 9B, the PCB forming the
front section 302F (the front section will be referred to
hereinafter as the PCB section of the base) is sized so that the
stack height of the end effector 300 can be admitted between
substrates having a 10.0 mm pitch. Accordingly, the board material
of the PCB may have high stiffness to minimize undesired
deflections of the base. The board material may be for example
Alumina ceramic, carbon fiber composite, or any other suitable
ceramic, composite, or plastic material having suitable insulating
and mechanical properties to form the board of the PCB. As seen in
FIG. 10, the stator 310 of motor 309 is formed in the PCB section
302F. In this embodiment, motor 309 is a rotary motor, though in
alternate embodiments the end effector may incorporate a linear or
planar motor in a manner substantially similar to that described
below. As seen in FIG. 10, the stator 310 may have a generally
circular configuration. The stator 310 may be formed integrally
with the PCB section, by cladding the PCB during PCB fabrication as
desired to define the windings of the stator. Any suitable cladding
process may be used such as a lithographic process forming a
desired number of layers on the PCB to generate the windings. The
windings may be formed of any suitable conductive material such as
copper, or tungsten. FIG. 12 shows a plan view of the stator
windings 310A-310C formed integral to the PCB. The configuration of
the windings 310A-310C shown in FIG. 12 is exemplary, and the
windings may be formed to have any suitable configuration. The
windings 310A-310C are disposed in the PCB to generate a magnetic
field oriented axially across the stator. In alternate embodiments,
the windings of the stator may be configured to generate a magnetic
field having any other desired orientation. The stator windings are
arranged in three phases 310A-310C as shown in FIG. 12, though in
alternate embodiments the stator windings may have any suitable
number of phases. In this embodiment, the stator is shown as having
(for example purposes) nine winding coils (three for each phase)
though any suitable size and number of winding coils may be used.
The PCB section 302F may further have formed therein suitable
conductive traces connecting the windings to a suitable power
source (not shown) and to the controller 10 (see FIG. 1). The
controller 10 controls the commutation of the stator windings
310A-310C as will be described further below to effect operation of
the motor 309.
[0051] As seen best in FIGS. 9A-9B, and 12, the PCB section 302F
has a recess 308 formed therein. The recess 308 in the PCB section
302F has a generally circular shape, and is substantially
concentric with the integral stator 310 formed in the PCB section.
The recess 308 provides support and coupling for the chuck 322 to
the base 302 of the end effector. The recess 308 may have a deeper,
substantially annular outer portion 306, and a more shallow inner
portion 307. The outer portion 306 forms a radial seating surface
306R and a horizontal seating surface 306H. The radial surface 306R
may be sized to form a close or press fit with the outer face of
the very low profile bearing 312 used for rotatably coupling the
chuck 322 to the base of the end effector. As noted before, the
concentric configuration of the recess 308, and hence of radial
surface 306R, with the stator results in the bearing 312 being
concentric with stator 310 when the bearing is placed in recess
306. The horizontal seating surface 306H supports the bearings 312
when placed in the recess as shown in FIG. 9B. As can be realized,
bearing 312 is capable of supporting both axial and radial loads.
Suitable examples of ultra-thin bearings for use with this
exemplary embodiment are available from Dynaroll Corp. (for example
Dynaroll Application No. B4-72T12). In alternate embodiments, any
other suitable bearing may be used to rotatably couple the chuck
and base. In still other alternate embodiments, the chuck may be
rotatably coupled to the base by any other suitable means such as
for example magnetic coupling.
[0052] Still referring to FIG. 9B, the raised inner portion 307
(compared to outer channel 308) has a pocket 307P in this
embodiment for mounting sensor 317 for the positional resolver 316
of the end effector. The PCB section 302F may include suitable
conductive traces (not shown) formed integrally into the PCB for
connecting the sensor 317 to the controller 10. Otherwise,
conductors 317C may be connected to the sensor 317 and extend over
a surface of the PCB section to connect the sensor to controller 10
as shown for example in FIG. 10 The PCB section 302F may include
any other desired number of recesses or pockets (not shown) similar
to openings 230, 232, 234, 236 in FIG. 7 for receiving sensors
similar to sensors 240, 242, 244, and 246 that are positioned
around the peripheral portion of the end-effector base for sensing
the position and orientation of the substrate.
[0053] Referring now to FIGS. 9, 9A-9B and 10, the chuck 322 may
include a structure member 324, as well as the motor rotor 314 and
a portion of the positional resolver 316, connected together as a
one-piece assembly as will be described further below. The chuck
structure member 324 may be a one-piece member or may be an
assembly as desired to reduce weight of the end effector as well as
weight on the PCB section 312F. The chuck structure member 324 may
be made from stiff light weight materials such as composites. The
structure member 324 may be substantially flat as shown or may have
any other suitable configuration. The upper surface 324U has a
suitable substrate support structure 326. The support structure 326
is configured to effect edge-gripping of the substrate S. In this
embodiment, as may be realized from the description herein, the
chuck structure member 324 is configured as a passive grip chuck
and the support structure 326 comprises pads 326P (four are shown
for example purposes) raised from the upper surface 324U. The pads
326P are arranged to contact the perimeter edge of the substrate
and passively grip the substrate (see FIG. 9). When the substrate
is picked with the end effector, the substrate is seated on the
pads 326P and a gap is formed as shown in FIG. 9B between the
substrate S and upper surface 324U of the chuck. In alternate
embodiments, one or more pads may be provided that are movable
(such as by pneumatic or electro-magnetic means) to engage the edge
of the substrate and grip the substrate between the pads. In this
embodiment, the PCB section 302F may be provided with a vacuum
source (not shown) similar to vacuum port 224 and seal ring 226
(see FIG. 7) for securing the substrate S to the chuck.
[0054] As noted before, the chuck 322 holds the motor rotor 314 as
well as a portion of the positional resolver. As shown in FIG. 9B,
the lower surface of the chuck support member 324 has a number of
pockets or recesses 328, 330, 332 formed therein. The recesses are
also indicated by dashed lines in FIG. 9. Recess 328 is sized to
receive the permanent magnets 314A, 314B forming the motor rotor
314. Referring again to FIG. 12, the rotor 314 in this embodiment
may be formed from a set of permanent magnets 314A, 314B arranged
with alternating polarity as shown. The magnets may have any
suitable shape (and are shown as having a circular shape for
example purposes only). As can be understood from FIGS. 9B and 12,
the recesses 328 receiving magnets 314A, 314B are shaped to conform
to the magnets. The magnets may be mounted or bonded in the
recesses with any suitable potting compound, adhesive, or any other
suitable means. In alternate embodiments, the rotor magnets may be
attached to the lower surface of the chuck without nesting in
pockets or recesses. As seen in FIG. 12, the rotor magnets 314A,
314B are arranged to operably cooperate with the stator windings
310A-310C in the PCB section 302F when the chuck is mounted on the
base. Further, the magnets are so arranged that the axis of
rotation R of the motor 309 extends substantially through the
center C of the substrate S when seated on support structure 326 of
the chuck (see FIG. 8).
[0055] As noted before, in this embodiment the chuck 322 is
positionally coupled to the base by bearing 312. Recess 332 in the
lower surface of the chuck (see FIG. 9B) is sized to conformally
receive the bearing 312. Correspondingly, recess 332 may have an
annular shape, forming an inner radial bearing surface 332R and a
horizontal seating surface 332H. As seen in FIG. 9B, when received
in recess 332, the bearing 312 bears with the inner face against
radial surface 332R and is seated on the upper face on seating
surface 332H. Thus, bearing 312 provides the positional alignment
between the motor rotor 314 in the chuck 322 and the motor stator
310 integral to the PCB section of the base 302 of the end
effector. As seen best in FIG. 9B, bearing 312 maintains a
clearance gap between chuck 322 and PCB section 302F when the two
are coupled. In the embodiment shown in FIG. 9B, the recess 330 of
the chuck receives the positional encoder 315 of the positional
resolver 316 (see also FIG. 8). As can be realized, motor 309 in
this embodiment is rotary, and hence the positional resolver may be
a rotary resolver using an encoder ring. In embodiments where the
motor is linear or planar, a linear or planar resolver may be used.
The resolver 316 may be any suitable type of resolver, such as an
optical resolver or electromagnetic resolver. In the case of an
optical resolver, the sensor 317 in the base, may be any suitable
optical sensor (e.g. Photo cell, CCD, laser). The encoder ring 315
may have any suitable optically readable indicia. In the case of an
electromagnetic resolver, the sensor may be a capacitive sensor,
and the encoder may have magnetic indicia/features so that the
output from the capacitive sensor provides indications of the
position/orientation of the chuck relative to the base. In other
alternate embodiments, the sensor of the resolver may be integrated
into the windings of the stator so that positional resolution of
the rotor may be provided to the controller by stator feedback. The
controller 10 uses the information from the rotary resolver for
commutating the windings of the motor 309 to effect motion of the
chuck 322, and hence the substrate S on the chuck, relative to the
base.
[0056] Motor 309 may be controlled by controller 10 to orient the
substrate S "on the fly" in a manner substantially similar to that
described before with reference to the embodiment shown in FIG. 7.
For example, after picking a substrate S, the controller may
operate motor 309 to rotate the chuck in a desired direction (e.g.
clockwise or counter-clockwise about axis R) until the fiducial
(notch, see FIG. 5) on the substrate is detected by a sensor
(similar to sensors 240, 242, 244 in FIG. 7). The controller may
use information from the sensor to generate orienting signals for
motor 309. This causes the end effector to rotate about axis R (see
FIG. 8) until the substrate S is in a desired position relative to
the end effector. In this position, however, the chuck 322 of the
end effector may be out of true with the sides of the end effector
base 302. The chuck 322 is shown in this out of true position in
FIG. 11. The base may be provided with suitable elevatable supports
350, if desired to allow resetting the chuck 322 while maintaining
the substrate orientation. Thus, the end effector is configured to
re-orient the chuck 322 relative to the base of the end effector
independent of an orientation of the substrate held on the end
effector. The elevatable supports may be of any suitable type,
including for example, piezo-electric, pneumatically actuated or
any others. In FIG. 11, four elevatable supports 350 are shown for
example purposes only. The supports 350 are located on the base 302
of the end effector to contact the perimeter edge of the substrate
S. As can be seen in FIG. 11, the supports may be raised or
elevated from the upper surface of the base 302 (in the direction
indicated by arrow Z in FIG. 11) to lift the substrate from support
structure 326 of the chuck. The substrate is seated on raised
supports 350 while the chuck is reset using motor 309 to a true
position (see FIG. 8). The supports 350 may then be lowered to
place the substrate S again on the chuck supports 326. The
orientation of the substrate S is thus maintained while the chuck
position is reset.
[0057] The end effector 300 in accordance with this exemplary
embodiment provides numerous advantages over conventional systems.
Incorporating, by way of example, the motor stator windings into
the end effector base, which is a PCB of unitary construction,
reduces overall weight of the end effector as well as minimizing
profile height. In addition, the base is provided with higher
stiffness by avoiding large cutouts in the base structure for
inserting the motor. Further advantages, for example further
reduction in end effector profile, are achieved by placement of the
rotor in the chuck. The "on-axis" position of the motor eliminates
use of a transmission thereby further eliminating weight,
complexity, and cost compared to conventional systems.
[0058] It will be apparent to those skilled in the art that other
modifications to and variations of the above-described techniques
are possible without departing from the inventive concepts
disclosed herein. Accordingly, the invention should be viewed as
limited solely by the scope and spirit of the appended claims.
* * * * *