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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> Metal layers in layout https://designers-guide.org/forum/YaBB.pl?num=1298973596 Message started by saam on Mar 1st, 2011, 1:59am |
Title: Metal layers in layout Post by saam on Mar 1st, 2011, 1:59am Can anyone tell me ..why top metal layers in layout having high resistance compare to lower,,is there any analysis for this?? ThankU saam |
Title: Re: Metal layers in layout Post by raja.cedt on Mar 1st, 2011, 6:43am no top metals are always have less res because of its thickness and this is the reason why inductors have been made with top layers. Thanks. |
Title: Re: Metal layers in layout Post by Alexandar on Mar 1st, 2011, 8:05am Not always true Raja. Some processes have copper at the bottom and alu and the top. |
Title: Re: Metal layers in layout Post by saam on Mar 2nd, 2011, 7:56pm Thank U for reply But can u elaborate more, means in terms of analysis like using sheet resistance or resistance formula. also can u give me any materials,books or any links regarding how to use metal layers in layout Thanku saam |
Title: Re: Metal layers in layout Post by loose-electron on Mar 3rd, 2011, 8:58am Metal layer thickness, metal used, oxide thickness between layers, are all able to be defined and selected by whoever defines and creates the foundry process. Commonly used conventions are: - Top layer is often thicker metal. - Oxides are thick between layers (lower C coupling) However, its all unique to the foundry process you are on. |
Title: Re: Metal layers in layout Post by love_analog on Mar 3rd, 2011, 10:58am Alexander, Why would anyone flip the metal layers. The whole point of putting copper was to increase EM reliability. I would think the top layer metals would always carry more current since they are carrying it from the pads. |
Title: Re: Metal layers in layout Post by Alexandar on Mar 4th, 2011, 5:01am love_analog wrote on Mar 3rd, 2011, 10:58am:
Circuits that benefit from a thinner stack use copper at the bottom as copper can be thinner in height. |
Title: Re: Metal layers in layout Post by saam on Mar 6th, 2011, 1:39am ThankU for replies.. can anyone provide materials, books or any links regarding metal routing in analog layout. waiting saam |
Title: Re: Metal layers in layout Post by saam on Mar 6th, 2011, 8:46pm Can anyone tel me ..Why top metal layer (M8) has low resistance compare to bottom (M1) ??? ThankU saam |
Title: Re: Metal layers in layout Post by ACWWong on Mar 7th, 2011, 4:42am Maybe its thicker or of a different material. Check your process manual for data. For formulae on resitivity just google it. For methods of layout, Alan Hasting's book Art of Analog Layout is good. |
Title: Re: Metal layers in layout Post by saam on Mar 8th, 2011, 9:30pm Thank You ACWWong...i wl |
Title: Re: Metal layers in layout Post by rfmagic on Mar 9th, 2011, 6:22am Hi saam, As most of the guys have mentioned, the first thing you have to do is to find out the process paremeters of your foundry. Then you can start estimating the zero order parasitics of the layout i.e. comulative sheet resistance, cumulative capacitance of the traces and inductance of the metal layers. this can help you get started. I have created a simple spreadsheet a long time ago that does these simple calculations and you may find it useful. Enjoy. |
Title: Re: Metal layers in layout Post by loose-electron on Mar 10th, 2011, 10:48am love_analog wrote on Mar 3rd, 2011, 10:58am:
Increase EM reliability? Total news to me, and I was involved with the Cu CMP process at the time. Copper got added to drop the R down, to get faster RC time constants to allow higher clocking rates. Jerry |
Title: Re: Metal layers in layout Post by loose-electron on Mar 10th, 2011, 10:52am saam wrote on Mar 6th, 2011, 8:46pm:
Unique to process as others have stated, but commonly its because they make the top layer thicker. If its all copper CMP layers, you have very good control over the characteristics of the layer thickness. The PDR's are fussy so that you can avoid cupping/dishing issues, when doing the CMP planarization of the layers. |
Title: Re: Metal layers in layout Post by saam on Mar 20th, 2011, 10:40pm Thank you for all...:) for such a great discussion |
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