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Small Area High Epsilon Capacitor in a Dynamic Memory Cell

IP.com Disclosure Number: IPCOM000085844D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Briska, M: AUTHOR [+2]

Abstract

The capacitor in a dynamic memory cell takes up a great part of the total cell area. When the insulator thickness is invariant, the area of the capacitor is determined by the magnitude of the electric charge required. This magnitude of the charge (signal) depends on the amplifier sensitivity.

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Small Area High Epsilon Capacitor in a Dynamic Memory Cell

The capacitor in a dynamic memory cell takes up a great part of the total cell area. When the insulator thickness is invariant, the area of the capacitor is determined by the magnitude of the electric charge required. This magnitude of the charge (signal) depends on the amplifier sensitivity.

In order to achieve the same capacity at a smaller capacitor area, the dielectric constant epsilon of the insulating material - generally SiO(2) - has to be increased. To this end a core of a high epsilon material consisting of titanate or titan zirconate compounds is formed within the SiO(2) layer. To produce such a core, the metals (Ti, Zr, Ba, Sr, etc.) forming the high epsilon compounds are introduced into the SiO layer preferably by ion implantation. This allows simple masking by using a photoresist mask. In addition, contamination is extremely low. The implanted metals are then thermally oxidized to form a mixture of metal oxides and SiO(2). During oxidation and the subsequent annealing process a crystallization of the oxides takes place, resulting in the high epsilon core being formed within the SiO(2).

A typical distribution of the core material in the Si0 layer is shown in the figure. Some compounds for achieving high epsilon values are for example, (BaSr)TiO(3), epsilon = 1800; BaTiO(3)/)MgZrO(3) 100:15, epsilon = 2030; BaTiO(3)/ SrZrO(3) 100 : 15, epsilon = 7430 (ratios in parts by weight). The epsilon val...