( ESNUG 363 Item 12 ) -------------------------------------------- [01/25/01]
Subject: ( ESNUG 361 #1 ) Thad Follows Up On His 2 PKS TSMC Tape-Outs
> I'm a chip designer but my sidebar task here at Geocast is to also be the
> methodology guy, too. I set up our PKS flow here and we recently did two
> 200 Kgate tape-outs to test the PKS flow with our in-house custom standard
> cell library. We used MOSIS TSMC 0.18 and TSMC's CyberShuttle service.
>
> - Thad McCracken
> Geocast Networks Systems, Inc. Beaverton, OR
From: Thad McCracken <thad@geocast.com>
Hi John,
I don't often see people sending you followups on chips they've taped out,
so I'm not sure if this is something you'll be interested in. Nevertheless,
I thought I'd send it and let you decide:)
We got our chip back about a month ago and have had enough time to really
wring it out by now.
Functionally the chip came up w/ no problems (which shouldn't be a huge
surprise given that most of the logic was second generation). We were
able to fault grade the chip (to 99.78% - hooray for full-scan and BIST)
and get functional vectors passing very quickly w/no problem.
Perhaps more interesting, however, is the correlation between the speed at
which the die ran and pre-tapeout analysis of the same. We obviously wanted
to make sure we were very close here as we get ready to produce larger chips
using the same PKS flow and TSMC 0.18 process.
As mentioned in my previous write-up, our original timing target for this
chip was 160Mhz, and post-route timing came in 160 ps off this target, or
156Mhz. We expected the chip to run at this frequency for the following
operating conditions (those at which we characterize our cell library):
- typical process
- 1.62V
- 110 deg C
We duplicated these conditions to the extent possible in the lab, and
found the chip to run up to 163 Mhz given the following:
- 1.62V (measured at perimeter of die)
- 48 deg C (measured on surface of die)
Characterization of the ring-oscillator on the die and comparison of the
results to spice sims put the die within measurable limits of typical
process. Spice sims for this same ring-oscillator for speed vs. temp (at
1.62 V), and subsequent linear-fit of that data was used to extrapolate an
expected frequency of operation given a die temp of 110 deg C. That
frequency was 151 Mhz.
So our silicon appears to run within ~3% of the expected frequency, given
the same operating conditions (and extrapolation where they couldn't be
duplicated or measured).
Obviously we were really happy w/ these results, and feel very good about
our tool flow and cell library going forward. Our experiences with TSMC
were very good as well.
- Thad McCracken
Geocast Networks Systems, Inc. Beaverton, OR
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