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Proceedings Paper

An LOD with improved breakdown voltage in full-frame CCD devices
Author(s): Edmund K. Banghart; Eric G. Stevens; Hung Q. Doan; John P. Shepherd; Eric J. Meisenzahl
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Paper Abstract

In full-frame image sensors, lateral overflow drain (LOD) structures are typically formed along the vertical CCD shift registers to provide a means for preventing charge blooming in the imager pixels. In a conventional LOD structure, the n-type LOD implant is made through the thin gate dielectric stack in the device active area and adjacent to the thick field oxidation that isolates the vertical CCD columns of the imager. In this paper, a novel LOD structure is described in which the n-type LOD impurities are placed directly under the field oxidation and are, therefore, electrically isolated from the gate electrodes. By reducing the electrical fields that cause breakdown at the silicon surface, this new structure permits a larger amount of n-type impurities to be implanted for the purpose of increasing the LOD conductivity. As a consequence of the improved conductance, the LOD width can be significantly reduced, enabling the design of higher resolution imaging arrays without sacrificing charge capacity in the pixels. Numerical simulations with MEDICI of the LOD leakage current are presented that identify the breakdown mechanism, while three-dimensional solutions to Poisson's equation are used to determine the charge capacity as a function of pixel dimension.

Paper Details

Date Published: 23 February 2005
PDF: 14 pages
Proc. SPIE 5678, Digital Photography, (23 February 2005); doi: 10.1117/12.594402
Show Author Affiliations
Edmund K. Banghart, Eastman Kodak Co. (United States)
Eric G. Stevens, Eastman Kodak Co. (United States)
Hung Q. Doan, Eastman Kodak Co. (United States)
John P. Shepherd, Eastman Kodak Co. (United States)
Eric J. Meisenzahl, Eastman Kodak Co. (United States)

Published in SPIE Proceedings Vol. 5678:
Digital Photography
Nitin Sampat; Jeffrey M. DiCarlo; Ricardo J. Motta, Editor(s)

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