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https://designers-guide.org/forum/YaBB.pl Modeling >> Semiconductor Devices >> Poly Resistor Current density/Power density Guidelines https://designers-guide.org/forum/YaBB.pl?num=1216814701 Message started by eppramod on Jul 23rd, 2008, 5:05am |
Title: Poly Resistor Current density/Power density Guidelines Post by eppramod on Jul 23rd, 2008, 5:05am Experts, Don't know if this topic was discussed here. I would like to know while sizing Poly resistors (silicided/or unsalicided) what should be the critical parameter W or L in terms of reliability? To be more specific i read somewhere that resistor degradation mechanism in lower technologies is more due to Joule (self) heating rather than Current induced EM (Jmax limits). So people fix min W for Current density (Jmax) limits and people may have to think min L for Power density reasons.Even very low Jmax values can raise the local temperature considerably? Please give your thoughts |
Title: Re: Poly Resistor Current density/Power density Guidelines Post by vivkr on Jul 23rd, 2008, 11:39pm Hi, The sheet resistance of poly is fixed and so is the max. current density. If you are trying to realize a particular value of resistance at a certain current density, then you only have the choice of varying W. L is automatically determined. Regards Vivek |
Title: Re: Poly Resistor Current density/Power density Guidelines Post by eppramod on Jul 24th, 2008, 10:52pm Hi Vivek, I understand that point the rho or Jmax values are fixed in a particular technology for poly resistors and you may fix mostly W(or L?) and Come up with a L (or W)for realising particular resistance. But this fixing W (or L?) minimum value can be (will be) determined by Jmax limits.But what i came across was this minimum W or L is now determined by Power density more than Current density. I wanted to know if this is true. Thanks for your response Pramod |
Title: Re: Poly Resistor Current density/Power density Guidelines Post by vivkr on Jul 24th, 2008, 10:55pm Hi Pramod, They are the same thing. Since sheet resistivity is a process constant, a fixed power density corresponds to a fixed current density. Regards Vivek |
Title: Re: Poly Resistor Current density/Power density Guidelines Post by wave on Dec 29th, 2008, 8:41pm I've actually found that for small Poly R's with high currents (several mA), I need to watch the # of contacts the layout tool puts on the end. A default of 2 contacts may be a large % of effective resistance AND not meet current density guidelines. ~WAVE 8-) |
Title: Re: Poly Resistor Current density/Power density Guidelines Post by Maks on Jan 23rd, 2009, 12:32pm wave wrote on Dec 29th, 2008, 8:41pm:
You may have to watch not only the number of the contacts, but their layout as well - the edge and especially corner contacts/vias in the contact/via array may carry much higher current than the average current... Maks ------------- |
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