Less Copper Means More Silicon at Varian
New Meaning to an Old Adage
“Replacing copper with silicon” is a catch phrase that has
proved popular with the engineering community in recent years. The phrase
refers to the use of (silicon) networking technology to reduce the proliferation
of (copper) wiring in many electronic products and solutions. At Varian
Thin Film Systems, however, the expression takes on an additional interpretation.
Located in the heart of California’s Silicon
Valley, Varian produces state-of-the-art semiconductor production
equipment. This equipment is used by companies to turn raw silicon
“wafers” into the integrated circuits—popularly
called “chips”—that populate our modern world.
One such product, the M2i, is a complete, multichamber vapor deposition
system, used to deposit conductive thin films (e.g., aluminum) on
silicon at a rate of up to 54 wafers/hour. The M2i is also a significant
upgrade of an earlier system, an upgrade that is yielding dramatic
benefits both to Varian and its customers. And has quite literally
created an improved semiconductor production tool by discarding
several hundred pounds of redundant copper. |
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No Downside to This Upgrade
Boris Relja, product manager for the M2i, recalls a principal goal of
the system upgrade: “We were determined to move about a thousand
discrete I/O control points off their dedicated wires, and on to a single,
twisted-pair communication network. The resulting reduction in wire would
provide dramatic improvements, not only in wiring cost and weight, but
also in installation and maintenance ease.” As many as six control
electronics cabinets are located up to 15 meters from the five vacuum-isolated
modules and robotic transfer unit that comprise the heart of the M2i,
so it is easy to imagine the potential cost savings.
To provide the functionality, flexibility, and reliability demanded
by their upgrade goals, Varian engineers turned to LonWorks technology,
an off-the-shelf control network solution. Using it, they developed a
variety of small “node control” boards, for 32-bit input,
32-bit output, 16-bit input/output, motor control, servo interface, VME
and Q-Bus gateways. Each board is a derivative of a common design, based
on the use of a single Neuron Chip. This chip incorporates three 8-bit
microprocessors and much of the program memory, communication, and I/O
interface circuitry necessary to implement various control functions.
Both peer-to-peer and master-slave communications are used among the nodes,
the latter being necessary to retain compatibility with an older computer
interface standard.
| Depending on system configuration, an M2i can include
as many as 60 such nodes. “All the nodes are self-installing,”
notes Relja, “requiring no separate configuration tool,”
just one of many maintenance features designed to reduce down time,
thus increasing the availability of a system that can range in price
from two to three and a half million dollars.
The Results Are In
From its first delivery in August, 1994, the new M2i has more than
lived up to its designers’ expectations. An astonishing 350
kilograms (770 pounds) of cables and connectors were eliminated.
Location and repair of component errors, which often took one to
two weeks, is now less than a day’s task. Installation at
customer premises, formerly a twelve week chore, is now half that.
Further, reductions in manufacturing, configuration, and test times
allow Varian to produce the new systems more quickly; they have
a hundred installations planned by the end of 1996. Customers love
the product improvement. And Boris Relja no longer worries about
the price of copper. |
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| A Multifunctional Cable
Even the network communication cable in the M2i deserves comment,
as it also contributes directly to the remarkable maintainability
of the system. Constructed with industry standard 10BaseT cable
(RJ45 connectors), it uses two conductors to carry LonWorks transmissions
at 1.25 Mbits/s (using standard Echelon transceivers), and additional
wires to propagate a 24 volt “connection health” signal.
In the System Status Interface chassis (main cabinet), where the
twisted-pair line is electrically terminated, an LED indicates end-to-end
connectivity, or an immediate warning of an improper installation.
Despite the fact that the network shares cable trays with RF and
high voltage DC power cables, communication is flawless. And the
measured traffic load has yet to exceed 20% of system bandwidth. |
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