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Trench-Based Memory Cell Storage Node Dielectric Protection During Reactive Ion Etch of a Trench Bottom

IP.com Disclosure Number: IPCOM000061587D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Kenney, D: AUTHOR [+3]

Abstract

This article describes a technique for maintaining total trench sidewall dielectric integrity, while reactive ion etching (RIE) a trench bottom to split and isolate adjacent three-dimensional storage nodes, in a trench-based memory cell storage structure. Removal of a nitride film layer on the bottom of a trench is required to allow for growth of a thick oxide in its place which will isolate storage nodes on opposite faces of a trench. The nitride oxidation mask left behind after a selective RIE is also employed as the storage node dielectric sidewall film and must not be degraded by the etch process. RIE is a directional etch process used for removing films on horizontal surfaces, e.g., a trench bottom. The process is rather severe (i.e.

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Trench-Based Memory Cell Storage Node Dielectric Protection During Reactive Ion Etch of a Trench Bottom

This article describes a technique for maintaining total trench sidewall dielectric integrity, while reactive ion etching (RIE) a trench bottom to split and isolate adjacent three-dimensional storage nodes, in a trench-based memory cell storage structure. Removal of a nitride film layer on the bottom of a trench is required to allow for growth of a thick oxide in its place which will isolate storage nodes on opposite faces of a trench. The nitride oxidation mask left behind after a selective RIE is also employed as the storage node dielectric sidewall film and must not be degraded by the etch process. RIE is a directional etch process used for removing films on horizontal surfaces, e.g., a trench bottom. The process is rather severe (i.e., energetic), such that thin dielectric sidewalls, which may have slight variations in slope away from vertical, may be partially etched during a RIE of the trench bottom. Fig. 1a shows a typical example of a trench 10 with a vertical sidewall 11 and a slightly sloped sidewall 12. A layer of silicon nitride 13 is deposited on all surfaces, i.e., top, bottom and side walls of the trench. Fig. 1b shows the same trench 10 after RIE and oxidation of the exposed silicon on the trench bottom to form a semi-recessed oxidation structure 14. The silicon nitride film 13 is eroded on the straight sidewall 11 due to the RIE, and is over-oxidized during the growth of SiO2 14 on the...