Semiconductor Memories ECE423 Xiang Yu 12.16.06
RAM vs. ROM <ul><li>Volatile </li></ul><ul><li>RAM (random access) </li></ul><ul><ul><li>SRAM (static) </li></ul></ul><ul>...
SRAM & DRAM <ul><li>SRAM </li></ul><ul><ul><li>Pros </li></ul></ul><ul><ul><ul><li>Extremely Fast </li></ul></ul></ul><ul>...
Flash Memory <ul><li>Pros </li></ul><ul><li>Non-volatile </li></ul><ul><li>Portability </li></ul><ul><li>High Density </li...
Focus For Improvement <ul><li>Non-volatility </li></ul><ul><li>Portability </li></ul><ul><li>Small Area </li></ul><ul><li>...
FRAM <ul><li>FeRAM (Ferroelectric RAM) </li></ul><ul><ul><li>Uses ferroelectric characteristics of the capacitor </li></ul...
MRAM <ul><li>Magnetoresistive RAM </li></ul><ul><ul><li>Uses properties of magnetism and the development of the MTJ </li><...
PRAM <ul><li>Phase-change RAM, PCM, C-RAM (chalcogenide RAM) </li></ul><ul><ul><li>Uses the special property of chalcogeni...
Comparisons <ul><li>Overall View </li></ul>5 ns 5 ns 20 ns 10 μ s 10 ns 2 ns Write Time > 10 12 > 10 15 > 10 12 10 5 > 10 ...
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Semiconductor Memories (Yu xiang).ppt

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Semiconductor Memories (Yu xiang).ppt

  1. 1. Semiconductor Memories ECE423 Xiang Yu 12.16.06
  2. 2. RAM vs. ROM <ul><li>Volatile </li></ul><ul><li>RAM (random access) </li></ul><ul><ul><li>SRAM (static) </li></ul></ul><ul><ul><ul><li>Synchronous </li></ul></ul></ul><ul><ul><ul><li>Asynchronous </li></ul></ul></ul><ul><ul><li>DRAM (dynamic) </li></ul></ul><ul><ul><ul><li>FPM DRAM </li></ul></ul></ul><ul><ul><ul><li>EDO DRAM </li></ul></ul></ul><ul><ul><ul><li>SDRAM </li></ul></ul></ul><ul><ul><ul><li>DDR SDRAM </li></ul></ul></ul><ul><ul><ul><li>DDR2 SDRAM </li></ul></ul></ul><ul><ul><ul><li>Etc.. </li></ul></ul></ul><ul><li>Non-volatile </li></ul><ul><li>ROM (read only) </li></ul><ul><ul><li>System/Video BIOS </li></ul></ul><ul><li>PROM </li></ul><ul><ul><li>OTP with fuses/anti-fuses </li></ul></ul><ul><li>EPROM </li></ul><ul><ul><li>UV light for erasure </li></ul></ul><ul><li>EEPROM </li></ul><ul><ul><li>Reprogrammable with software and hardware </li></ul></ul><ul><ul><li> Flash Memory </li></ul></ul>
  3. 3. SRAM & DRAM <ul><li>SRAM </li></ul><ul><ul><li>Pros </li></ul></ul><ul><ul><ul><li>Extremely Fast </li></ul></ul></ul><ul><ul><ul><li>No refresh cycle </li></ul></ul></ul><ul><ul><li>Cons </li></ul></ul><ul><ul><ul><li>Large area - 6T/bit </li></ul></ul></ul><ul><ul><ul><li>Expensive </li></ul></ul></ul><ul><ul><li>Applications </li></ul></ul><ul><ul><ul><li>Memory caches L1 & L2 </li></ul></ul></ul><ul><li>DRAM </li></ul><ul><ul><li>Pros </li></ul></ul><ul><ul><ul><li>Cheaper </li></ul></ul></ul><ul><ul><ul><li>Higher density - 1T/bit </li></ul></ul></ul><ul><ul><li>Cons </li></ul></ul><ul><ul><ul><li>Slower in speed </li></ul></ul></ul><ul><ul><ul><li>Needs refresh cycle </li></ul></ul></ul><ul><ul><li>Applications </li></ul></ul><ul><ul><ul><li>Computer memory </li></ul></ul></ul>
  4. 4. Flash Memory <ul><li>Pros </li></ul><ul><li>Non-volatile </li></ul><ul><li>Portability </li></ul><ul><li>High Density </li></ul><ul><ul><li>Floating gate transistor </li></ul></ul><ul><ul><ul><li>CG and FG </li></ul></ul></ul><ul><ul><ul><li>MLC technology </li></ul></ul></ul><ul><li>High Isolation </li></ul><ul><li>Cons </li></ul><ul><li>Oxide layers near min. limit </li></ul><ul><li>High voltage required </li></ul><ul><li>Slow WRITE cycle </li></ul><ul><li>Capacitance Coupling </li></ul><ul><li>Limited Use </li></ul>
  5. 5. Focus For Improvement <ul><li>Non-volatility </li></ul><ul><li>Portability </li></ul><ul><li>Small Area </li></ul><ul><li>High Density </li></ul><ul><li>Faster WRITE/ERASE cycles </li></ul><ul><li>Lower Power </li></ul><ul><li>Lower Costs </li></ul><ul><li>Longevity </li></ul>
  6. 6. FRAM <ul><li>FeRAM (Ferroelectric RAM) </li></ul><ul><ul><li>Uses ferroelectric characteristics of the capacitor </li></ul></ul><ul><ul><ul><li>lead (Pb) zirconate (Zr) titanate (Ti) - PZT </li></ul></ul></ul><ul><li>Pros </li></ul><ul><li>Non-volatile </li></ul><ul><li>Small size </li></ul><ul><li>Fast WRITE cycles </li></ul><ul><li>Cons </li></ul><ul><li>A potential WRITE after each READ </li></ul><ul><li>Longevity </li></ul><ul><li>Polarization degradation </li></ul><ul><li>Requires high temperatures </li></ul><ul><li>Want higher densities </li></ul>
  7. 7. MRAM <ul><li>Magnetoresistive RAM </li></ul><ul><ul><li>Uses properties of magnetism and the development of the MTJ </li></ul></ul><ul><ul><li>Uses STT technology (Spin Torque Transfer) </li></ul></ul><ul><li>Pros </li></ul><ul><li>Non-volatile </li></ul><ul><li>Small size </li></ul><ul><li>Fast WRITE cycles </li></ul><ul><li>Longevity </li></ul><ul><li>Cons </li></ul><ul><li>Requires high temperatures </li></ul><ul><li>Want higher densities </li></ul>
  8. 8. PRAM <ul><li>Phase-change RAM, PCM, C-RAM (chalcogenide RAM) </li></ul><ul><ul><li>Uses the special property of chalcogenide alloy </li></ul></ul><ul><ul><ul><li>Germanium (Ge), antimony (Sb) and tellurium (Te) – GST </li></ul></ul></ul><ul><ul><ul><li>Switches between amorphous (0) and crystallized (1) states with heat from current </li></ul></ul></ul><ul><li>Pros </li></ul><ul><li>Non-volatile </li></ul><ul><li>Small size </li></ul><ul><li>High density </li></ul><ul><li>Fast switching times </li></ul><ul><li>Cons </li></ul><ul><li>Requires high current (heat) </li></ul><ul><li>Longevity </li></ul>
  9. 9. Comparisons <ul><li>Overall View </li></ul>5 ns 5 ns 20 ns 10 μ s 10 ns 2 ns Write Time > 10 12 > 10 15 > 10 12 10 5 > 10 15 > 10 15 Write cycles No No No No ms No Refresh 1T1R 1TCMTJ 1T1C 1T 1T1C 6T Cell Size 10ns Yes MRAM 10ns 10ns 70ns 10 ns 2 ns Read Time Yes Yes Yes No No Non-volatile PRAM FRAM Flash DRAM SRAM Parameters

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