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

To: THE WATSONYOUTH who wrote (75966)	10/19/1999 1:40:00 AM
From: Paul Engel	Respond to of 1571644

TWY - Re: "Could you explain how much of the density advantage is lost and how the DAMASCENE process would add further complexity over a different local interconnect approach?" First of all, an additional dielectric film must be deposited. Second, that film must then be planarized - a CMP step is required. When doing the photolithography to expose the dilectric film for trench etching, you now have a layer misregistration tolerance that is larger than would be had contacts been done directly at the poly/gate level. Also, Contact sizes can no longer be MINIMUM geometry (0.25 micron for 0.25 micron process, etc.) - but somewhat larger - to allow for the tungsten to deposit "completely" into the Damascene Interconnect Contact. Consequently, the DAMASCENE trench has to be WIDER than the minimum CONTACT size - hence WIDER than the process minimum that COULD HAVE been used at the GATE level WITHOUT a Damascene process. Contacts (DUAL DAMASCENE) must be registered THROUGH the trenches, adding yet another misregistration tolerance- also FURTHER INCREASING the MINIMUM PITCH between adjacent Damascene trenches. Tungsten (or other refractory meta) must be deposited not only into the contacts, but also "uniformly" through the Damascene trenches. Paul