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Bipolar Random-Access Memory/Read-Only Memory Cell

IP.com Disclosure Number: IPCOM000060953D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Bergeron, DL: AUTHOR

Abstract

A bipolar cell is described that achieves both random-access memory (RAM) and read-only memory (ROM) functions by fabricating the load diodes with different characteristics. The exponential load diodes D1 and D2 (Fig. 1) are fabricated (see preceding article) with different characteristics by successive block MASK operations. The RAM and ROM functions can be achieved without an increase in cell size or additional wiring channels. The exponential load diodes have similar but not identical characteristics, as shown in Fig. 2. The table summarizes all the observed characteristics of two diodes fabricated by two different argon ion implant energies. These diodes, when operating in the .5 ua to 1 ma range, have similar characteristics, but at low currents there is a 60 mv offset between V1 and V2 at 10 na.

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Bipolar Random-Access Memory/Read-Only Memory Cell

A bipolar cell is described that achieves both random-access memory (RAM) and read-only memory (ROM) functions by fabricating the load diodes with different characteristics. The exponential load diodes D1 and D2 (Fig. 1) are fabricated (see preceding article) with different characteristics by successive block MASK operations. The RAM and ROM functions can be achieved without an increase in cell size or additional wiring channels. The exponential load diodes have similar but not identical characteristics, as shown in Fig. 2. The table summarizes all the observed characteristics of two diodes fabricated by two different argon ion implant energies. These diodes, when operating in the .5 ua to 1 ma range, have similar characteristics, but at low currents there is a 60 mv offset between V1 and V2 at 10 na. The differences in diode characteristics enable the cell to operate as a conventional exponential load cell in the .5 ua to 1 ma region. By lowering the cell standby current Icell to a value less than either diode saturation current (Icell < IsD1 or IsD2) and then raising the cell current to Icell, the diode with the higher saturation current (e.g., IsD2 > IsD1) will provide base current to the cross-coupled transistor T1. In this example, where IsD2 > IsD1, T1 will turn on first and the memory cell will be in a preselected state. This allows the cell to act as a ROM. The information is encoded by selectively fabric...