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Lithographic Method for Defining Edge Angles

IP.com Disclosure Number: IPCOM000045844D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Greschner, J: AUTHOR [+4]

Abstract

A multilayer resist structure is used in a reactive ion etch process. This process is used for layers in which edges with accurately defined edge angles are to he reproducibly fabricated.

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Lithographic Method for Defining Edge Angles

A multilayer resist structure is used in a reactive ion etch process. This process is used for layers in which edges with accurately defined edge angles are to he reproducibly fabricated.

On layer 1 to be etched, consisting, for example, of Nb, a thick resist 3 (approx 2 Mum) is deposited and, if necessary, prebaked. To resist layer 3, a very thin barrier layer 4 of, for example, nitride, is applied which is covered by a thin resist layer 5 (0.3 to 0.6 Mum). The pattern to be etched is defined in the thin resist layer 5 by lithographic means and transmitted to barrier layer 4 in a first etch step, preferably by reactive ion etching (RIE).

The pattern thus defined in the thin layer 4 is used as an etch mask for the thick resist layer 3 in a second RIE step. The process parameters (applied RF power, pressure, gas) of this step are chosen so that an overcut profile is generated whose slope angle Beta is accurately defined and homogeneous across the whole wafer being processed. In an O(2) RIE process, a pressure range of 5 to 25 mTorr has proved suitable for obtaining the desired homogeneous and straight edge boundaries in Nb; overetching must be limited to less than 20 percent.

Layers 1 and 2 are then etched in a third RIE step, with the thick resist acting as an etch mask; the slope angle of resist layer 3 is thus translated into the slope angle of the edge formed in layer 1 according to the ratio of the etch rates of re...