Browse Prior Art Database

Irradiation Technique for Making Single Electrode Charge Coupled Storage Cell

IP.com Disclosure Number: IPCOM000077454D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Bhatia, HS: AUTHOR [+4]

Abstract

The storage cell of Fig. 1 is suitable for high-density array memory applications by providing a single-gate region having two different thresholds. The channel region of field-effect transistor (FET) 1 is provided by the gate region having the higher threshold, while capacitor 2 is provided by the gate region having the lower threshold voltage.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 64% of the total text.

Page 1 of 2

Irradiation Technique for Making Single Electrode Charge Coupled Storage Cell

The storage cell of Fig. 1 is suitable for high-density array memory applications by providing a single-gate region having two different thresholds. The channel region of field-effect transistor (FET) 1 is provided by the gate region having the higher threshold, while capacitor 2 is provided by the gate region having the lower threshold voltage.

A simplified structure for attaining the double-threshold single-gate region is shown in Fig. 2. The structure is produced by a modification of a standard FET process wherein N substrate 3 is provided with thick oxide layer 4, P+ diffusion 5, thin oxide region 6 and electrode 7. After electrode 7 is formed, a positive voltage is applied and the V2 region of thin oxide 6 is irradiated with an electron beam or with x-ray. The radiation energy causes hole-electron pairs to be generated in the thin oxide. Because of the gate potential and high mobility of the electrons in the thin oxide, the electrons are swept out by the positive gate voltage. The resulting relatively immobile positive charge in the V2 region of the thin oxide creates a permanent negative image charge in the underlying surface of substrate 3. The negative image charge produces a higher threshold voltage in the V2 region than in the V1 region.

In operation, the word line is normally biased negatively to a value exceeding the low threshold of region V1 but not exceeding the higher th...