Bipolar Random-Access Memory/Read-Only Memory Cell
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
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.