Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!ucla-cs!zen!ucbvax!CS.UCLA.EDU!sdk From: sdk@CS.UCLA.EDU (Scott D Kalter) Newsgroups: comp.lsi Subject: Crystal and Spice difficulties Message-ID: <8708272347.AA05760@oahu.cs.ucla.edu> Date: Thu, 27-Aug-87 19:47:57 EDT Article-I.D.: oahu.8708272347.AA05760 Posted: Thu Aug 27 19:47:57 1987 Date-Received: Sat, 29-Aug-87 14:12:27 EDT Sender: usenet@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 54 We are having some difficulties with our simulation tools and would appreciate any advice we can get. Crystal: It seems that the node resistance values that Magic extracts can be grossly incorrect. The algorithm it uses (finding a rectangle from the area and perimeter of the layer) is very bad with long thin rectangles through which the signals travel across the thin side. For example: == <- Poly == -------X==X------- | |X==X| | |Pdiff|X==X|Pdiff| | |X==X| | | Con-|X==X| Con-| | tact|X==X| tact| | |X==X| | -------X==X------- ^ ^ Pdiffusion Magic will extract the resistance of the thin layer of Pdiffusion as if the signal was flowing from top to bottom rather than from left to right. So, if this diffusion was 1 lambda wide by 10 lambda tall then the extracted resistance would be 10 times the sheet resistance of pdiffusion rather than 0.1 times the sheet resistance. This is an estimate that is 100 times larger than we want. Crystal uses these resistance estimates in its algorithm for finding the critical path of a circuit. Not only do the critical paths end up having extremely pessimistic delays but it seems questionable whether it has found the critical path at all. We would like to know whether anyone has found a way to deal with this problem. Hand-extraction seems like a particularly tedious and error-prone solution, especially on very large circuits. Spice: We are interested in what spice level 2 parameters people are using for the fabrication through MOSIS service. Why are you using those particular parameters and where did you get them? Thanks for your help, Scott Kalter Jae Cho