230 likes | 547 Views
Emerging Memory Technologies. Sudhanva Gurumurthi http://www.cs.virginia.edu/~gurumurthi. Solid State Drive (SSD). Hard Disk Drive (HDD). The Transistor. If the voltage applied at the gate > a threshold voltage , a conducting channel forms between the source and drain. Flash Memory.
E N D
Emerging Memory Technologies Sudhanva Gurumurthi http://www.cs.virginia.edu/~gurumurthi
Solid State Drive (SSD) Hard Disk Drive (HDD)
The Transistor If the voltage applied at the gate > a threshold voltage, a conducting channel forms between the source and drain
Flash Memory • Floating Gate Transistor (FGT) • Has a “floating gate” between the gate and the channel that issurrounded by SiO2 • Removing the voltage on the gate leaves the induced charges on the floating gate • Non-Volatility
Tunneling Quantum mechanics provides for wave-particle duality Image Source: http://www.bun.kyoto-u.ac.jp/~suchii/Bohr/tunnel.html
Flash Cell Wearout • Writing and erasing flash cells is bad! Write Erase - - - - - - - - - - - - - - - - - - - - - Floating-Gate Transistor State After Write State After Erase
Impact on Retention Time Charge trapping increases Stress Induced Leakage Current (SILC) Time to Leak Time to Leak - - - - - - - - - - - - - - Memory cell state at time ‘t’ Memory cell state after retention period
Boosting Flash EnduranceComputed for a Flash Cell Using Our Model
Magnetic Tunnel Junctions • If tunnel barrier is thin enough, electrons can tunnel from one ferromagnet to the other • Electrical resistance of the MTJ depends on the orientation of the fields on the two plates Image Source: Wikipedia
Data Representation in an MTJ Used in Magnetic RAM (MRAM) and Spin Transfer-Torque RAM (STT-RAM) Image Source: http://www.mdm.imm.cnr.it/SPAM3/background.html