Nichrome Resistors in Programmable Read Only Memory Integrated Circuits

Computer designers whose-goals required rapid programming of semiconductor read only memories have utilized large quantities of PROMS (programmable read only memories). The most popular of these types of integrated circuit is programmed by raising the resistance of a nichrome resistor above a threshold value required to change the PROM output logic level. A study was made to determine the mechanisms associated with the problems of (1) hard to program resistors, (2) changes in output logic levels for resistors not programmed, and (3) resistors whose resistance drops after programming and causes a change in output level for the bit it reresents (reappearing bit or growback).