Browse Prior Art Database

Post Diffusion Insulation

IP.com Disclosure Number: IPCOM000036784D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 86K

Publishing Venue

IBM

Related People

Kenney, DM: AUTHOR

Abstract

For dense random-access memories (DRAMs) utilizing trench storage nodes, a method is shown for processing the trench isolation after the high temperature processing is completed to eliminate crystal dislocations at isolation oxide intersections. The process may also be use in non-array applications.

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Post Diffusion Insulation

For dense random-access memories (DRAMs) utilizing trench storage nodes, a method is shown for processing the trench isolation after the high temperature processing is completed to eliminate crystal dislocations at isolation oxide intersections. The process may also be use in non-array applications.

Crystal dislocations are generated in association with isolation/ storage trench pattern intersections due to stress at temperatures above 850oC. By forming trench isolation after the high temperature (>850oC) processing is completed, oxide isolation intersections are eliminated. The process follows:

1) After removing cell isolation patterns from the current mask, a new mask level is created consisting of only the cell isolation pattern. Processing is done in the normal manner through diffusion self-aligned silicide (salicide) formation, and since no isolation/ storage trench intersection patterns exist to this point in the process, dislocations are avoided. It should be noted that the absence of cell isolation trench patterns causes normally separate bit-line diffusion regions to be connected together in strings parallel to word lines.

2) After printing and developing the new mask in photoresist on a wafer, the cell isolation windows will expose the unwanted salicide pdiffusion connections between the normally separate bit-line diffusion regions, as shown in the top view of the figure.

3) Reactive ion etch (RIE) the exposed salicide diffused...