FRAM

Before the 1950’s, ferromagnetic cores were the only type of
random-access, nonvolatile memories available. A core memory is a regular
array of tiny magnetic cores that can be magnetized in one of two opposite
directions, making it possible to store binary data in the form of a magnetic
field. The success of the core memory was due to a simple architecture that
resulted in a relatively dense array of cells. This approach was emulated in the
semiconductor memories of today (DRAM’s, EEPROM’s, and FRAM’s).
Ferromagnetic cores, however, were too bulky and expensive compared to the
smaller, low-power semiconductor memories. In place of ferromagnetic cores
ferroelectric memories are a good substitute. The term “ferroelectric’ indicates
the similarity, despite the lack of iron in the materials themselves.
Ferroelectric memory exhibit short programming time, low power
consumption and nonvolatile memory, making highly suitable for application
like contact less smart card, digital cameras which demanding many memory
write operations. In other word FRAM has the feature of both RAM and ROM.
A ferroelectric memory technology consists of a complementry metal-oxidesemiconductor
(CMOS) technology with added layers on top for ferroelectric
capacitors. A ferroelectric memory cell has at least one ferroelectric capacitor
to store the binary data, and one or two transistors that provide access to the
capacitor or amplify its content for a read operation.
A ferroelectric capacitor is different from a regular capacitor in that it
substitutes the dielectric with a ferroelectric material (lead zirconate titanate
(PZT) is a common material used)-when an electric field is applied and the
charges displace from their original position spontaneous polarization occurs
and displacement becomes evident in the crystal structure of the material.