Browse Prior Art Database

NVRAM Cell with a Buried Layer as a Select Node

IP.com Disclosure Number: IPCOM000109197D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 3 page(s) / 112K

Publishing Venue

IBM

Related People

Acovic, A: AUTHOR [+3]

Abstract

Disclosed is a NVRAM cell with a buried layer as a select node, which enables the use of the Fowler-Nordheim (FN) tunneling mechanism as program/erase tools without disturbance.

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NVRAM Cell with a Buried Layer as a Select Node

       Disclosed is a NVRAM cell with a buried layer as a select
node, which enables the use of the Fowler-Nordheim (FN) tunneling
mechanism as program/erase tools without disturbance.

      Using the Fowler-Nordheim tunneling instead of channel hot
carrier injection as programming mechanism for NVRAM cells can reduce
power consumption and enhance the performance.  However, in an array
of stacked-gate NVRAM, using FN tunneling to program one cell will
always disturb adjacent cells.  As a result, either all the cells
under the selected word line are programmed or the cells sharing the
source/drain with the selected cell are also programmed.

      Disclosed is a NVRAM cell with a buried layer, which serves as
a select node, underneath the conducting channel of the cell (Fig.
1a).  Changing the voltage on the buried layer will modulate the
threshold voltage which allows a specific cell to be selected and
programmed by FN tunneling without disturbing adjacent cells (Fig.
1b).  The operating conditions are illustrated in Table 1.  As shown
in Fig. 1, isolation oxide under S/D and n substrate for NFET are
needed to separate p well in each cell if p buried layer is used for
NFET.  Alternatively, if a n buried layer is used for NFET, the cell
structure will be quite similar with the one with buried injector
connected to an external voltage.  However, the operating conditions
listed in Table 2 differ.  The same c...