( ESNUG 377 Item 11 ) ------------------------------------------- [09/19/01]
Subject: ( ESNUG 375 #3 ) Have Raphael; Switch To Raphael NES (Quickcap)?
> I am a design kit developer for the IBM SIGE RF/Analog design kits.
>
> I am interested in purchasing Raphael NES (Quickcap). My group currently
> has one copy of Raphael. I know that Quickcap is most often used as a
> 'golden' capacitance extraction tool when comparing parasitic extraction
> tool capacitance accuracy. I currently use Raphael as our 'golden' 3D
> extractor, but am thinking of replacing it with Quickcap. I believe there
> are many reasons for this switch. Here are just a couple:
>
> - Quickcap offers full chip extraction for critical nets.
> - Quickcap is a full chip extraction tool.
> - Raphael works well for test structures, but for large structures the
> run times are not reasonable.
> - Raphael is more accurate than Quickcap for capacitance but the run
> times are long.
>
> Is it worth switching to Quickcap knowing that Quickcap is $78 K and I
> already have Raphael in house?
>
> - Grant Riley
> IBM
From: "Rajiv Mathur" <rajiv.mathur@intel.com>
Hi, John,
It depends on what you do with Raphael now. If you use it for developing
and characterizing your own capacitance models, then QuickCap is not a
replacement for that. If you are wondering if the models in a vendor tool,
say StarRC, are accurate for a fullchip net, then you can use QuickCap on
that net and compare with StarRC. You cannot do full chip net extraction
with Raphael.
For model development application, Raphael is fine unless you are running
large 3D test structures (still much smaller than a full chip net). If
Raphael is choking on these, QuickCap can be used on these structures.
However remember that QuickCap data comes with an uncertainty value and
model generation based on these extractions can be rather complex (harder
to get smoothly varying behavior.)
Regarding accuracy, it is not true that Raphael is more accurate than
QuickCap. For simple 2D cross-sections, Raphael gets an accurate result
fast, however it rapidly declines in performance as the structures become
complex, while QuickCap performance degrades only slightly with increasing
strucuture complexity. In fact for some 3D crossover structures, Raphael
gives very inaccurate results if you use the default grid, so watch out.
Always make sure that your answers do not change too much as you add more
grid points to your Raphael run.
- Rajiv Mathur
Intel Corp.
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