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Magic Mailing List |
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From: Jeff Sondeen (sondeen AT ISI DOT EDU) Date: Fri Sep 05 2003 - 17:04:52 EDT
D.Jeff Dionne writes: > If an export to CIF, import, extract and conversion to spice works ok, > would one therefore still have to consider the capacitances wrong (or > the results inconclusive) because only one of the wells are generated > into the CIF file? here's an example of the problem with cap extraction, if M2 is over M1 is over Pwell, and M1 shields M2 from pwell, then the cap on M2 will be the area(M2-M1) + fringe(M2-M1). if instead they are over substrate, then M2 cap will also include area(M2-sub) and/or fringe(M2-sub). this is because of one or both those M2-sub cap shieldings don't work with substrate (last time i checked, but that was years ago). > > > the .cifcheck techfiles use the (very slow) cif checking rules to > > check for this, but the solution to any problems it shows is to draw > > the wells. so just draw them! > > > > i think the original question also wondered about the risk that layout > > conforming to old rules would have if fabbed nowadays after rules have > > changed. the answer to that is, it depends, but it's quite possible > > that results will be fatal (0 yield) with no recourse (since rules > > were violated). it's even possible that the current techfiles > > (getting dated now) aren't up-to-date... i hope to check them soon. > > That's concerning. Is SCNA.80.tech27 useful, or should we consider > things that pass DRC with it still suspect? > well i don't know of any problems with any techfiles (other than usage complications covered in the README and/or CHANGELOG) , but sometimes the rules (ie. mosis web page) change and i don't hear about it until a user sees a descrepancy. i used to routinely check for changes to the mosis web page, but turned that off when i got too many "false changes" (just format changes). looking at the Mosis web page, http://www.mosis.org/Technical/Designrules/scmos/scmos-main.html i can see that the rules HAVE changed: MOSIS Scalable CMOS (SCMOS) Design Rules (Revision 8.0) Updated: April 25, 2003 so any techfiles released before then (ie. all of them) could be impacted. until i can release new techfiles, you're going to have to open that page and check (ie. draw min width/space magic examples) and see if the rule is right. you could also just grep the DRC rule descriptions in the techfile and compare the rules. you need tounderstand the compromise that magic makes between the simple and alternate contact to active an poly (discussed in the README and/or CHANGELOG). (eg. rules 5.2 and 5.2.b). /jeff
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