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Modification of Interlevel Via Design to Lower Line Resistivity

IP.com Disclosure Number: IPCOM000038822D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Cronin, JE: AUTHOR [+2]

Abstract

A technique is described for lowering the resistance of metal lines used to connect semiconductor circuits without changing the material used to fabricate the metal lines. Fig. 1 shows the conventional method used for wiring circuits on a chip when two levels of metal are used. Metal level two (M2) is used to connect metal level one (M1) points A and C by bridging point B. By replacing metal-filled round via studs with metal-filled troughs, shown in Fig. 2, a lower resistance interconnect method can be achieved. The trough has a minimum via size in one dimension (Y) and is as long (X) as needed to connect A' and C' but may not intersect a bridge zone 10 with underpass line B'. The trough length X may not be less than 2X long when gap-fill techniques which grow from the surface up are used to fill a trench.

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Modification of Interlevel Via Design to Lower Line Resistivity

A technique is described for lowering the resistance of metal lines used to connect semiconductor circuits without changing the material used to fabricate the metal lines. Fig. 1 shows the conventional method used for wiring circuits on a chip when two levels of metal are used. Metal level two (M2) is used to connect metal level one (M1) points A and C by bridging point B. By replacing metal-filled round via studs with metal-filled troughs, shown in Fig. 2, a lower resistance interconnect method can be achieved. The trough has a minimum via size in one dimension (Y) and is as long (X) as needed to connect A' and C' but may not intersect a bridge zone 10 with underpass line B'. The trough length X may not be less than 2X long when gap-fill techniques which grow from the surface up are used to fill a trench. The minimum trench length rule does not apply when evaporation or sputtering methods are used to fill a trench with a conducting material because the material does not grow up from the bottom surface but is deposited on the surface. The equivalent resistance of the wiring method shown in Fig. 1 is a simple series resistance network, where RL = resistance / unit length, as shown in Fig. 3a. When a trench via is utilized, the metal lines become thicker and lower resistance results. The equivalent resistance network for the trough via method is shown in Fig. 3b, where RA = the resistance of the added...