September 27, 2002
EDA, Manufacturing in Shotgun Wedding
By Gale Morrison - Electronic News |
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EDA, Manufacturing in Shotgun Wedding
At the annual BACUS gathering on Monday of all
those involved in photomask fabrication and
use, the trade association Semiconductor Equipment
and Materials International (SEMI) plans to
get the party started by releasing version 1.0
of a new database interchange format, a would-be
successor to GDS-II Stream Format.
It's a complicated engineering debate. The long
and short of it is, in the coming age of multimillion-dollar
mask sets, the chip data cannot be put at risk
by having it in a format that makes it unwieldy.
This reality is forcing EDA and their design-engineering
customers to sit down and hash it out with fab
engineers and all of their photomask and lithography
suppliers, because all of them take part in
either creating that data, or in using it.
Everybody who touches mask data has been grappling
with the explosion in file sizes. A complex
0.13-micron design can easily take 50Gbytes
of data. Semiconductor makers usually FTP these
files, which design engineering calls "the tape
out." The files are in GDS -II Stream format,
as they have been since the 1970s.
But at 50Gbytes, an FTP with a dedicated T1
line can take hours and often has to be done
in batches, says Roger Sturgeon, who helped
write GDS-II in the '70s while at Calma, the
proto- Cadence. Sturgeon later co-founded Transcription
Enterprises, which is now a subsidiary of Numerical
Technologies Inc. Transcription's CATS so-called
fracturing tool processes nearly every chip
design that's made into a mask. In other words,
every chip design that actually gets fabbed.
There is quite a bit of anxiety in breaking
up that million-dollar mask data set just so
it can FTP to Taipei, Taiwan, successfully before
the fracturing step. SEMI formed the IC Design/Photomask
Data Path Task Force last year to study this.
Tom Grebinski is the group's chairman; he works
for Micronic Laser Systems, which supplies the
$20 million mask writers. Micronic and Applied
Materials' Etec subsidiary compete fiercely
in this market. Mask writers live and die on
the integrity of the mask data set.
Mentor Graphics, which is the largest EDA tool
supplier in the backend of IC design with its
Calibre product, has been central to the task
force. Calibre group VP Joe Sawicki is overseeing
this effort, including Mentor's donation of
version 3 of its standard layout format, which
is used by every foundry. Calibre competes with
Synopsys' Hercules and Venus tools, and Cadence's
Virtuoso. All three will need to accommodate
the new format, which some are calling NSF,
but which Mentor pointedly says does not yet
have a name.
Interestingly, Mentor has also developed a fracturing
tool to compete with Numerical's CATS tool.
Backend design consultant Pallab Chatterjee
demonstrated it at the Design Automation Conference
(DAC) in New Orleans earlier this year. It's
this fact that continues to fuel rumors that
Cadence is buying Numerical and thus owning
the so-called polygon pushing and fracturing
flow, Both companies deny that there are talks
of a merger.
Not to be forgotten in this debate is the fact
that mask data sets have gotten so large because
of the adoption of mask engineering techniques
like phase shifting and optical proximity correction.
These have allowed chip manufacturers to keep
using their 193-nanometer laser lithography
systems, and put off the purchase of 157nm systems
to the 65nm node. At that time, when device
feature sizes should be almost one-third of
the width of the laser etching them, the data
size will probably be even that much greater.
