Browse Prior Art Database

MIS Digital Capacitor by Electron Beam Irradiation

IP.com Disclosure Number: IPCOM000087353D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Kurylo, A: AUTHOR [+3]

Abstract

Multivalued capacitors are produced by the electron-beam irradiation of metal-insulator-silicon (MIS) capacitors.

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 90% of the total text.

Page 1 of 2

MIS Digital Capacitor by Electron Beam Irradiation

Multivalued capacitors are produced by the electron-beam irradiation of metal-insulator-silicon (MIS) capacitors.

When an MIS capacitor is irradiated by electrons, positive fixed charge is generated in the insulator which causes the capacitance-voltage (C-V) curve to shift toward a more negative voltage. The voltage at which the maximum capacitance occurs (accumulation region) is also shifted leftward. The heavier the accumulated electron dosage, the larger the negative voltage shift.

As shown in Figure 1, an MIS (metal 1, insulator 2, semiconductor 3) capacitor is exposed to a weaker electron dosage on one half of the area (designated A1) and a stronger electron dosage on the other half (designated A2). The fixed charge in the insulator under the two areas will be different, and is shown qualitatively in Fig. 1.

The corresponding C-V curve (using a Ptype substrate as an example) will have a step (Fig. 2). This step structure results from the fact that the capacitor under A1 reaches accumulation at a smaller negative voltage than under A2. Therefore, the device has two well defined capacitance values: One region corresponds to the step extending from V1 to V2, and the other region corresponds to the maximum from V3 to V4. By applying a proper negative voltage, one can select any one of the two capacitance values.

By the same principle, multistep C-V curves can be achieved to give capacitors with more than two val...