pubs.cmpnet.com
Semiconductor Business News, c 1998, CMP Media Inc.
June 1, 1998
Battle to install digital
bus lines heats up in fabs
By Jack Robertson
WASHINGTON -- The growing complexities of operating new
generations of wafer fabs are forcing major changes in how the equipment is
linked together.
Digital bus lines are now regarded as almost essential for upcoming
300-mm wafer production fabs. The extensive use of automated handling
systems will require a vast number of I/O data points and will far surpass
what conventional single-tool wiring can handle, pointed out John Dunn,
marketing vice president for MKS Instruments Inc., a Santa Clara,
Calif.-based maker of tool gauges and valves.
The number of I/O ports on new 200-mm wafer fabs is also skyrocketing.
A new cluster tool may have more than a thousand I/O data points, he
noted. "A digital bus line is the only feasible way to connect within the
cluster as well as interconnect clusters and other parts of the production
line," Dunn said.
As a result, a fierce marketing battle is developing among the suppliers of
digital bus lines to interconnect cluster tools and eventually entire fab
production lines.
Unable to agree on a single bus-line standard, Sematech and
Semiconductor Equipment & Materials International (SEMI) so far have
blessed three different schemes, leaving it up to the marketplace to pick the
eventual winner. The three bus line vendors fighting it out now are
DeviceNet, a spinoff from Rockwell International Automation Corp.;
Echelon Corp.'s LonWorks; and Honeywell Automation Smart Distributed
System (SDS). Suppliers of at least three more bus lines are trying to get
Sematech's okay to enter the fight.
Bus line connections are quickly replacing individual wiring of tools within a
fab, said MKS Instruments' Dunn. He estimated that bus-line use on
semiconductor production equipment is growing at the rate of 49%
annually. "As chip makers go to smaller and smaller line geometries and add
more cluster tools, they need the much higher OEE [overall equipment
effectiveness] that digital bus lines bring," Dunn said.
The effectiveness of bus-line-equipped tools is now reaching 38% for the
new quarter-micron processes, Dunn said, which is up dramatically from an
OEE of less than 20% for conventional tool sets. The goal of bus-line
systems is to reach a 60% OEE for 0.15-micron feature-size processing.
One important role for the new digital bus lines is to provide the diagnostic
feedback on tool operation for troubleshooting, said Dave Heller, product
manager for Rockwell Automation's DeviceNet unit in Milwaukee, Wis. If a
tool goes down now, the entire fab is usually shut down until the problem is
diagnosed and corrected. Since the average cost of downtime on a fab line
ranges from $20,000 to $40,000 per hour, any lengthy shutdown to correct
a tool problem can be devastating, he noted.
Bus lines can also monitor performance continually on any tool on the line.
Operators usually can prevent a shutdown because they can detect a
problem coming and take corrective action before it occurs. If a tool does
shut down, data collected on its earlier runs can help operators speedily
diagnose the problem and get the tool up and running quickly, according to
Heller.
More often than not, it's a glitch in the software, not the tool, that's causing a
problem. "We have found that in more than 70% of the time, the shutdown
problem can be traced to the software," the Rockwell Automation official
said. The bus lines can also help out a lot by ensuring that software is
always running correctly and by instantly detecting any software problem
that pops up.
Bus lines also permit a "hot swap" of a new tool to replace a malfunctioning
tool on the line. This job can be done so that little or no downtime results on
the line. With conventional lines using individual wiring to link tools, it can
often take days to make such a switch, Heller added.
But even with such advantages, switching to digital buses won't happen
without plenty of missionary work. "A lot of education needs to take place
within the industry about semiconductor equipment automated controllers,"
commented Phil Naughton, new construction engineering project manager
for Motorola Inc.'s Semiconductor Products Sector in Austin, Tex. "They
can save money for everybody."
Motorola is both a LonWorks supplier and a user. It makes some of the
components used in the control nodes and already is using the format in at
least five of its global manufacturing sites. The big chip maker is using
LonWorks technology - which is not limited to the chip industry but is
designed for most industrial applications - to control a variety of
applications in its fabs. These include controlling equipment and process
controls, ventilation, and fire alarms.
Motorola wants to see more chip production equipment designed to work
in LonWorks-equipped fabs. "We have taken the position that if you want
to sell equipment like chillers to us, then you are going to have to develop
products using this type of automated controls," pointed out Naughton.
In the race to install digital buses, Echelon, in Palo Alto, Calif., had the
largest number of installations as of last year with 190 LonWorks systems
running. DeviceNet was in second place with 122 systems, according to a
study by MKS Instruments.
MKS, which has switched entirely to DeviceNet for its tools, estimated that
by 2002 the number of installed Rockwell buses will surpass those of
LonWorks. It estimated that DeviceNet will have 903 installed systems by
that year, with LonWorks selling 648, and Honeywell's SDS hitting 275
systems. According to MKS, 85% of all chip production-tool vendors have
picked the DeviceNet digital bus.
Several years ago, Rockwell made DeviceNet an open standard to
encourage its widespread use. DeviceNet is also being used as a bus line in
a vast array of different manufacturing operations in addition to the
semiconductor industry. "Our return is selling Rockwell Automation tools in
other factory applications," said one official at Rockwell, which doesn't have
a large presence in the semiconductor equipment field.
Considering the higher yields that chip makers can obtain using the digital
bus, the bus and node controllers are very low in cost. A typical node
controller can cost as little as $200. "It is a fantastic investment," said Dave
Ittner, Rockwell Automation chip industry product specialist in Milwaukee,
"with the cost of the bus line being only a small consideration." --Additional
reporting by Will Wade
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