Browse Prior Art Database

High Density Contact Design

IP.com Disclosure Number: IPCOM000075055D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Gaensslen, FH: AUTHOR [+2]

Abstract

The standard design of a semiconductor contact hole is shown in Fig. 1. Contact is made between a metal line 1 and a diffusion 2 in a semi-conductor wafer. Neighboring metal lines 3 and 4 have to maintain whatever minimum separation is required from the metal covering the square hole 5 through an oxide 6, which is disposed between the diffusion and metallic lines 1, 3 and 4. This causes an unnecessarily wide separation between these metal lines elsewhere. Layout efficiency is low, therefore, because it is limited by minimum metal spacing in the contact area.

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High Density Contact Design

The standard design of a semiconductor contact hole is shown in Fig. 1. Contact is made between a metal line 1 and a diffusion 2 in a semi-conductor wafer. Neighboring metal lines 3 and 4 have to maintain whatever minimum separation is required from the metal covering the square hole 5 through an oxide 6, which is disposed between the diffusion and metallic lines 1, 3 and 4. This causes an unnecessarily wide separation between these metal lines elsewhere. Layout efficiency is low, therefore, because it is limited by minimum metal spacing in the contact area.

A much more effective contact hole design is shown in Fig. 2. It utilizes a rectangular hole 5 through an oxide 6 disposed perpendicularly to metal line 1 of minimum width. The active contact area and the alignment requirements in both cases are the same. Hole 5 through oxide 6 only has to maintain a proper margin from the boundary of diffusion 2. In this layout, lines 3, 4 can be run with minimum spacing everywhere which results in considerable savings of area. A comparison of Figs. 1 and 2 shows that in Fig. 1 the spacing between lines 3, 4 is
0.75 unit whereas in Fig. 2 the spacing between lines 3 and 4 is 0.6 unit. It should also be noted that the maximum width of diffusion 2 has been reduced from 0.5 unit to 0.4 unit.

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