Ferroelectric Random Access Memory (FRAM)

Introduction

• Speaker: Bishnu Bantu
• Topic: Ferroelectric random access memory (FRAM)
• Overview: FRAM is a type of random access memory with a ferroelectric capacitor.
• Also known as FRAM or FeRAM
• Similar in construction and functionality to DRAM and Flash ROM

History

• Proposed by Dudley Alan Buck at MIT in 1952
• Development mainly by Ramtron, a fabless semiconductor company
• Large production lines by Fujitsu
• Collaboration: Ramtron, Texas Instruments, IBM, using 180 nm process

Structure of FRAM

• Similar to DRAM but uses ferroelectric material instead of dielectric
• Composed of word line, bit line, transistor, and ferroelectric capacitor
• Operations: read, write, store

Ferroelectric Materials

• Crystalline structure with a central atom
• Atoms have two energy states based on their position
• Common materials: Barium Titanate, Lead Zirconate Titanate
• Atoms move with electric field application, determining the state of the material
• Two polarization states: up and down
• Operates on a hysteresis loop
• Not containing ferrous material, name similarity to magnetic hysteresis curve
• Switched by electric fields, unaffected by magnetic fields

Operation

Read Cycle

• Similar to DRAM
• Bit line voltage compared to a reference
• Involves placing voltages on word lines and bit lines
• Destructive read process, requiring cell rewriting
• Voltage proportional to capacitance ratio
• Sense amplifiers used

Write Cycle

• Uses similar principles to read operation
• Control circuitry applies field across ferroelectric capacitor
• Non-volatile: retains data without power
• Charge does not leak away

Comparison to Other Memories

• Fast as SRAM
• Low power consumption
• Takes more area, higher cost
• Non-volatile
• Low densities, more real estate
• Applications in automotive, computing, advanced metering, gaming, etc.

Advantages and Drawbacks

Advantages

• Non-volatility
• Low power consumption
• High endurance

Drawbacks

• Low densities
• High cost

Applications

• Automotive: shift-by-wire, navigation control
• Computing: SSDs, network routers
• Advanced metering
• Gaming
• POS systems
• Motion control and process controls
• Various memory uses

Conclusion

• FRAM offers many advantages with some compromises needed
• Performance can be improved by:
  • Increasing storage density (stacking, 3D implementation)
  • Improving manufacturing processes
  • Size reduction

References

• Further information available from listed references