Chapter 11FRAM Ferroelectric Memories:Basic Operations, Limitations,Innovations and Applications 1
11.1. Taxonomy of non-volatile memories
11.1.1. Present and future solutions
Currently, the microelectronics industry is facing new technological challenges to continue improving the performances of memory devices, namely access time, storage capacity, endurance, power consumption, data retention, etc. The main obstacle to overcome is the downsizing of the memory cell (or downscaling), which is necessary to embed an increasing number of devices on a silicon surface that is maintained substantially constant. This drastic size reduction of the elementary devices comes up against the physical limits of materials integrated into the memory cell.
In terms of taxonomy, the memories are first divided according to their ability to retain or not retain information without external power supply (see Figure 11.1). Besides volatile memories such as Dynamic Random Access Memory (DRAM) or Static RAM (SRAM), non-volatile technologies may be subdivided into two categories depending on the mechanism used to store binary data. Conventional technologies such as Electrically Programmable Read Only Memory (EPROM), Electrically Erasable PROM (EEPROM), and Flash represent a historical and progressive evolution of memory devices relying on charge storage in a polycrystalline silicon (or polysilicon) “floating gate”. Although relevant even today, these technologies require several innovations to meet ...