Browse Prior Art Database

Method of Contacting Conductors Through Contact Holes

IP.com Disclosure Number: IPCOM000034557D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Koblinger, O: AUTHOR [+2]

Abstract

If a contact hole H to an underlying electrically conductive layer, a conductor L1, is etched in a semiconductor process, as shown in Fig. 1A, this conductor usually serves as an etch stop. This works only if contact hole H rests on conductor L1 without protruding from its edge. Otherwise, etching continues beyond that edge and neighboring structures are damaged. To avoid this, conductor L1 should overlap contact hole H such that if the contact hole and conductor are misaligned, the contact hole does not touch the conductor edge. The required overlap a (alignment tolerance) corresponds to the permissible misalignment (not considering dimensional tolerances of the contact hole and the conductor for simplicity). The structure of Fig. 1A has the disadvantage that conductor L1 is widened at the position of contact hole H.

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Method of Contacting Conductors Through Contact Holes

If a contact hole H to an underlying electrically conductive layer, a conductor L1, is etched in a semiconductor process, as shown in Fig. 1A, this conductor usually serves as an etch stop. This works only if contact hole H rests on conductor L1 without protruding from its edge. Otherwise, etching continues beyond that edge and neighboring structures are damaged. To avoid this, conductor L1 should overlap contact hole H such that if the contact hole and conductor are misaligned, the contact hole does not touch the conductor edge. The required overlap a (alignment tolerance) corresponds to the permissible misalignment (not considering dimensional tolerances of the contact hole and the conductor for simplicity). The structure of Fig. 1A has the disadvantage that conductor L1 is widened at the position of contact hole H. As a result, the adjacent conductor L2 has to be arranged at a greater distance than would be necessary without contact hole H. It is assumed that b is the smallest dimension that can be photolithographically handled. The widened portion in the contact region increases distance d1 of the conductors from b to a + b. This disadvantage can be avoided (Fig. 1B) by using in lieu of the etch stop conductor L1, an additional electrically conductive layer S which contacts conductor L1 but which is defined by another photolithographic mask. The spacing of this etch stop S from the neighboring conductor L2...