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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: Charles R who wrote (75839)	10/18/1999 2:27:00 AM
From: Paul Engel	Read Replies (2) \| Respond to of 1571423

Chuckles - Re: "My understanding is this is tight pitched metal that is used mostly for cache and datapath to increase the routing density but not used for global routing (I have heard it being counted like 1/2 layer metal)." Not quite. A Local Interconnect layer has nothing but thermal oxide protecting the polysilicon/CoSi gates and diffusions, and requires contacts to be etched in these features - thereby exposing the bulk silicon to contamination without phosphorus-doped dielectrics to help getter the contamination. Further, the metals used for the Interconnect layer generally have to have high meltingpoints and refractory metals are generally used - such as Tungsten - which itself is extremely difficult to process and has its own peculiar problems of adhesion, etching, etc. Paul

To: Charles R who wrote (75839)	10/18/1999 2:14:00 PM
From: Yousef	Read Replies (1) \| Respond to of 1571423

Chuckles, Re: "My understanding is this is tight pitched metal that is used mostly for cache and datapath to increase the routing density but not used for global routing (I have heard it being counted like 1/2 layer metal)." Well, there are two types of "local interconnect" (LI) ... One way is to just enlarge the contact (between Metal 1 and Poly). This allows a Poly to Source/Drain connection. The disadvantage is that now there are two different contact sizes present at etch. The other method is like a metal layer where a dielectric is deposited and patterned followed by conductor deposition and polish/etch. This approach is much more complicated, but allows the LI to cross over poly lines. The LI metal is usually thin and narrow so resistance is high ... This is why it is only used for "short runs". Make It So, Yousef