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SEMI E32-0997 © SEMI 1994 , 1997 39 6. The AGV (as prim ar y transfer partn er) begins t he transfer. 7. The AGV performs th e transfer. Notice that no HOCommand messages are needed s i nce this is a passive tr ansfer . …

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SEMI E32-0997 © SEMI 1994, 1997 38
and continue to retry at intervals. Note that a disconnect
may be normal in some cases where the link is only
made when the transfer partners are in close proximity.
2. TRLink's Not Matched
If two transfer partners are attempting different
handoffs using the same physical resources (locations,
mechanisms, etc.), the host should be informed via an
event. The partners shall continue to await an
appropriate HOReady message—allowing the host to
“fix” one or the other of the partners. If an equipment
has no current transfer and it receives a HOReady
message, it should hold that message until a transfer job
is defined for it.
3. HOCommand Not Accepted
If the secondary transfer partner cannot accept a micro
command from the primary partner, it should use the
HOCommand Response message to inform the primary
partner that the command was rejected. The primary
partner may affect some recovery or inform the host
that the transfer has failed.
4. HOCommand Failed in Execution
If the secondary transfer partner fails in the execution
of an HOCommand, it should notify the primary partner
of the problem. The primary partner may affect some
recovery or inform the host that the transfer has failed.
5. Transfer Not Confirmed
If the secondary transfer partner sends a negative
HOVerify Response message saying that the transfer
object has not been properly transferred, the primary
partner should not attempt recovery, but inform the host
that the transfer has failed.
6. Timeout Awaiting Partner Readiness (HOReady)
Timeout Awaiting Micro Command Completion
(HOCommand Response)
Timeout Awaiting Transfer Verify Response
(HOVerify Response)
In some cases, action may be required if a transfer
partner has been awaiting communication from its
partner. The equipment should monitor timeout periods
for each of the three cases. The factory user may need
to customize the timeout periods for his/her factory.
When a timeout occurs, the equipment should notify the
host (via a TRJobEvent message) that the situation has
occurred, reset the timer, and continue to await the
partner. The host is responsible for taking any further
action which is required (e.g., Stop or Pause command).
A1-4 Practical Applications — This section provides
examples of practical applications of the material
movement services as presented in this document. Four
examples are provided below. Within these are
presented some major variations expected in a factory
situation. These are not exhaustive in scope, but the
expectation is that reviewing these examples will help
the reader understand how to apply these concepts to a
real application. These examples are also not intended
to represent a cohesive implementation strategy, but
rather some alternatives that might be considered.
AGVs are used in the examples below because they are
familiar to most readers, not because they are favored
over other transfer agents. To simplify the explanation,
the examples below deal only with movement of
cassettes.
A1-4.1 Passive Transfer — In this example, a transfer
is to be performed between an AGV with robot arm and
a piece of processing equipment. A cassette is to be
picked up by the AGV for later delivery to another
piece of equipment. The equipment has a cassette
indexer and a port door, but no other port-related
mechanism that would either aid or hinder transfer. The
chosen transfer mechanism provides for the equipment
to act as a passive transfer partner with no micro level
communications required. This is called a passive
transfer. The primary transfer partner is the AGV.
The setup for the equipment is to check to make sure
that the correct material is in the specified port, drive
the cassette elevator to the home position (if not already
there), and open the port door. Note that the first two
setup activities could have been designed to occur as a
part of the micro level transfer if desired. The setup
operations for the AGV are to ensure that its receiving
port is empty and to drive to the transfer position in
front of the designated equipment.
The transfer proceeds in the following steps:
1. The host sends a Transfer Job Create message to
each transfer partner.
2. The partners each accept the transfer job.
3. The equipment both have the needed available
resources so the transfer job immediately. Thus,
Transfer Job Started messages are sent to the host
by each.
4. Each partner in turn completes its setup activities
for the atomic transfer, sends a “Committed To
Transfer” event to the host, and then sends an
HOReady message to its transfer partner (via the
host).
5. Each partner sends the “Atomic Transfer Started”
event to the host as soon as it determines that it has
both sent and received an HOReady message for
this handoff.
SEMI E32-0997 © SEMI 1994, 199739
6. The AGV (as primary transfer partner) begins the
transfer.
7. The AGV performs the transfer. Notice that no
HOCommand messages are needed since this is a
passive transfer.
8. The AGV sends an HOVerify message to the
equipment via the host.
9. The equipment ensures that the cassette is no
longer sensed in its port and then sends an
HOVerify Response message (via the host) to the
AGV, followed by an “Atomic Transfer Complete”
event to the host.
10. Upon receipt of the HOVerify Response message,
the AGV sends an “Atomic Transfer Complete”
event to the host.
11. Each partner completes its RESTORE operations
and then sends a Transfer Job Complete message to
the host.
The transfer is now complete. The host may now direct
the AGV to deliver the cassette to a new destination.
A1-4.2 Active Transfer/Exchange of Cassettes — This
example addresses the situation where the factory
control system needs to remove a processed lot from an
equipment and immediately replace it with an
unprocessed lot. The assumptions are that the
processing of the lot on the equipment is nearing
completion and that the AGV has already acquired the
unprocessed lot that will next be placed on the
equipment. Direct micro level communications exist
between the AGV and the equipment. This will be an
interactive transfer.
The setup operations for the equipment are opening the
port door, driving the cassette indexer to the home
position, and checking for the presence of the proper
cassette. AGV setup is movement to the transfer
location for that equipment. During the transfer, the
equipment acts as the primary transfer partner, and will
unclamp/clamp the cassette (clamps hold the cassette in
the proper position). The AGV will interact with the
equipment as the secondary transfer partner.
The transfer proceeds as follows:
1. The host sends Transfer Job Create requests to the
equipment and to the AGV. The timing is chosen
so that the time required for the AGV to travel to
the equipment is approximately equal to the time
left to complete processing of the lot to be
transferred. The Transfer Job Create message to
each contains two atomic transfers, the first dealing
with the removal of the processed cassette from the
equipment and the second dealing with the loading
of the unprocessed cassette onto the equipment.
2. The AGV accepts the transfer job and begins the
first atomic transfer immediately, sending a
Transfer Job Started message to the host. Setup
begins — the AGV begins traveling toward its
transfer partner. The equipment accepts the transfer
job and retains it for later execution.
3. When processing completes on the lot, the
equipment begins the transfer job. It sends a
Transfer Job Started message to the host and
begins its setup operations for the first atomic
transfer.
4. The AGV completes its setup activity and sends a
“Committed To Transfer” event to the host. It also
sends a HOReady message to the equipment.
5. The equipment completes its setup, then sends a
“Committed to Transfer” event to the host and an
HOReady message to the AGV.
6. Since the AGV had previously declared itself
ready, the equipment sends an Atomic Transfer
Started event to the host and starts the transfer.
7. The equipment begins by sending an HOCommand
that results in the AGV reaching out and grasping
the cassette.
8. Upon receiving the Command Complete message
from the AGV, the equipment unclamps the
cassette, allowing its removal.
9. The equipment sends an HOCommand that results
in the AGV removing the cassette from the
equipment. The material sent and material received
events are sent to the host by the respective
partners.
10. When the equipment receives the Command
Complete message from the AGV, it considers the
transfer to be complete. It sends the HOVerify
message to the AGV.
11. The AGV sends the HOVerify Response message
to the equipment.
12. Each of the transfer partners now determines that
another atomic transfer is required in order to
complete the transfer job.
13. Each transfer partner now transitions to the second
atomic transfer. They each send “Atomic Transfer
Complete” events.
14. Each transfer partner now begins the new setup
phase. The AGV determines that it has already
reached the transfer point and has the unprocessed
cassette to be transferred. The equipment
determines that the port is now empty, and that the
door is open. This setup time was saved.
SEMI E32-0997 © SEMI 1994, 1997 40
15. The second atomic transfer now proceeds in a
similar fashion through steps 4–12 above. That
done, since there are no further moves required, the
restore stage begins, including “Atomic Transfer
Complete” events to the host.
16. Once restore operations are complete, each sends a
Transfer Job Complete message to the host. The
transfer is now complete.
A1-4.3 Sequential Moves — In this example, the
factory control system desires to move a cassette from
equipment “A” to equipment “B” using a fixed robot
stationed within reach of the two. Each piece of
equipment has a static port and will act as passive
transfer partners in all cases. The robot will act as the
primary partner for all transfers. The host system must
do the high-level planning of this move, determining
that the lot to be transferred will be ready to go, that the
robot is available, and that the receiving equipment is
available to receive the cassette.
To accomplish the transfer, two atomic moves are
required. First, the robot picks up the cassette at “A.”
Second, the robot deposits the cassette on “B.” The
gripper on the robot is considered its port in this case,
since that is the point at which ownership of the cassette
changes.
Since the step–by–step transfer details are similar to the
first two examples, they will be omitted. However, a
higher-level sequence will be given.
1. The host will send Transfer Job Create messages to
“A,” “B,” and the robot. The robot will be given
two sequential atomic moves to perform, the
equipment one each. Note that the Transfer Job
Create request to “B” could be delayed, if desired,
until the completion of the first atomic move.
2. The first atomic transfer is performed: the robot
removes the cassette from “A.” Note that no
HOCommands are issued, since the secondary
partner is passive.
3. The second atomic transfer is performed: the robot
places the cassette on “B.”
4. Both “A,” “B,” and the robot deliver Transfer Job
Complete messages to the host.
The transfer is complete.
An intelligent robot control system could combine the
two atomic moves discussed above into a single robot
program, achieving a more efficient transfer (e.g., no
redundant movement during the transfer). In such a
case, both “A” and “B” would need to be ready for
transfer before the robot program was executed. The
only limitation is that this combination would have to
match the model and messaging discussed above.
A1-4.4 Linked Lithography — The final example is
one where the micro level of material movement might
be used without the macro level messaging described in
this document. The linked lithography system described
below is not patterned after any existing system and
may not be the optimal implementation for such a
system.
For this example, the challenge is to transfer wafers
from a typical track system (following the coat/bake
process) into a stepper for imaging, and then back to the
track system for the develop process. In this example,
the stepper acts as a slave to the track system, accepting
wafers as they are given. The non–transfer-related
communications will not be discussed.
In the wafer transfer process, the track takes on the
macro level duties of the host. It is responsible for
informing the stepper that a wafer is to be transferred,
which wafer, and by what path and mechanism. It will
initiate the transfer in a method analogous to the
Transfer Job Create request. There is no transfer agent
in this case. Either equipment might act as the primary
transfer partner — it is irrelevant to this example.
The stepper and track will then exchange the normal
micro communications. First, the HOReady messages
will be sent. Next, the track will issue HOCommands to
cause the wafer to be physically transferred. Finally, the
HOVerify message transaction would occur.
Meaningful events would be reported to the host as
appropriate.
An alternative would be to design the system such that
the track system tells the stepper system, in effect, “I'll
be sending a series of wafers to you.” Since the
HOReady message contains sufficient information to
describe the transfer (assuming a specific transfer
recipe is not required), no specifics about the individual
transfers need be exchanged until the HOReady is sent.
In such a scheme, the stepper would take the HOReady
message as description of the specific transfer and
respond with an HOReady to match.
A1-4.5 Non–Compliant Transfer Partner — There will
be situations where only one of the transfer partners is
compliant with this standard. It is reasonable to use this
transfer methodology in some such cases, especially
those involving passive transfer. The host would be
responsible for emulating a compliant transfer partner
on behalf of the non–compliant partner (for the benefit
of the compliant partner). Examples of non–compliant
transfer partners might include a WIP rack, a human
transfer agent, an older process equipment, or any
material handling systems that support other protocols.