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Two Phase, Offset Gate, CCD Structure with Two Self Aligned Ion Implants

IP.com Disclosure Number: IPCOM000049715D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Garbarino, PL: AUTHOR [+4]

Abstract

Offset gate charge-coupled devices (CCDs) may be fabricated r using either stepped oxides or ion implants to create storage and transfer regions under a single phase electrode. A variety of design/process considerations point to the ion-implant mode as the most desirable. This method, therefore, is normally employed in creating the two regions under the second set of phase electrodes of the two-phase offset gate structure.

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Two Phase, Offset Gate, CCD Structure with Two Self Aligned Ion Implants

Offset gate charge-coupled devices (CCDs) may be fabricated r using either stepped oxides or ion implants to create storage and transfer regions under a single phase electrode. A variety of design/process considerations point to the ion-implant mode as the most desirable. This method, therefore, is normally employed in creating the two regions under the second set of phase electrodes of the two-phase offset gate structure.

A problem arises in attempting to employ ion implantation in delineating regions at the first electrode level. The edge of the implanted region must be aligned to the edge of the electrode to a greater precision than is attainable in any kind of lithography if one is to avoid regions of carrier trapping that can seriously degrade CCD performance.

The disclosed method of attaining ion-implant delineated regions under the first set of electrodes is as follows. On a thin oxide film over the silicon substrate, a lift-off structure is produced (Fig. 1). The lift-off structure is any light (or electron beam) sensitive material which is not attacked by common photoresist solvents. The open area is then partially masked with photoresist, and the ion implant done through the oxide (Fig. 2). The photoresist is stripped and the conductive material deposited, with excess lifted off, to give the desired structures (Fig. 3). The electrode material may be evaporated silicon, metal silici...