Emerging memories

Learn how emerging memories such as MRAM, PCM (phase-change memory), ReRAM and FeRAM store data through multiple-choice questions.

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Emerging memories: key points

To overcome the limits of DRAM and flash memory, memories based on many new principles are being developed. Most are non-volatile and store information not as charge but as differences in resistance or polarization direction.

MRAM uses the magnetization direction of a magnetic tunnel junction, PCM the resistance difference between crystalline and amorphous phases, ReRAM conductive paths in an oxide, and FeRAM the polarization of a ferroelectric. Learn to tell these principles and features apart.

All Emerging memories questions (50)

  1. Which correctly describes how MRAM stores data?
  2. Which correctly describes how phase-change memory (PCM) stores data?
  3. Which property does FeRAM (ferroelectric memory) use to store information?
  4. Which correctly describes how ReRAM (resistive memory) stores data?
  5. How is information written in STT-MRAM?
  6. Which correctly describes the position of 'storage-class memory'?
  7. Compared with flash memory, which is a general advantage of MRAM?
  8. Which ferroelectric material, compatible with CMOS processes, has recently attracted attention for FeRAM and ferroelectric transistors (FeFETs)?
  9. In phase-change memory (PCM), how is a cell put into the high-resistance amorphous state (reset)?
  10. What is the main application expected for in-memory computing using resistive memories and similar devices?
  11. Which correctly describes reading in capacitor-type FeRAM?
  12. Which material is widely used as the tunnel barrier in MRAM magnetic tunnel junctions (MTJs) and gives a large tunnel magnetoresistance ratio?
  13. In ReRAM, what is the initialization step called in which a relatively high voltage is first applied to form a conductive filament?
  14. Which is a characteristic of SOT-MRAM?
  15. Which is one reason MRAM is attracting attention as embedded non-volatile memory for microcontrollers and similar chips?
  16. In MRAM, what problem tends to arise if the storage element (MTJ) is made too small?
  17. Why have MTJs with magnetization perpendicular to the film plane (perpendicular MTJs) become mainstream in recent STT-MRAM?
  18. In a cross-point memory with resistive elements placed at the intersections of row and column lines, which element is placed in series with the storage element to prevent current from sneaking through unselected cells?
  19. Which is a characteristic of a FeFET, which uses a ferroelectric as the gate insulator?
  20. In phase-change memory (PCM), what is the phenomenon in which the resistance of the amorphous state gradually increases over time?
  21. How is data read from MRAM?
  22. What kind of material is GST, the typical recording material for phase-change memory?
  23. Which is an example of a material researched and used as the switching layer of ReRAM?
  24. Which correctly describes how using non-volatile memory for caches and registers is expected to save system power?
  25. Which is a typical application in which FeRAM has been used?
  26. In which process of a logic LSI is the MRAM storage element (MTJ) generally built?
  27. Which phenomenon becomes a problem when phase-change memory is scaled, in which heat from writing reaches a neighboring cell and changes its state?
  28. What design challenge arises from the probabilistic nature of writing in STT-MRAM?
  29. What challenge results from the large variation in resistance of ReRAM cells?
  30. In general, which memory has the fewest possible rewrite cycles?
  31. Which of the following is non-volatile memory that retains data after power is removed?
  32. What does the "M" in MRAM stand for?
  33. Which correctly describes the idea of "universal memory" that many emerging memory efforts have aimed for?
  34. What does the "Fe" in FeRAM stand for?
  35. What is the structure called that stores one bit in MRAM, consisting of two magnetic layers sandwiching a thin insulating layer?
  36. Which correctly describes the tunnel magnetoresistance (TMR) ratio of an MTJ?
  37. In an MTJ, how do the resistances compare when the magnetizations of the two magnetic layers are parallel versus antiparallel?
  38. Which correctly describes the roles of the two magnetic layers in an MTJ?
  39. In phase-change memory (PCM), how is a cell heated to put it into the low-resistance crystalline state (set)?
  40. On the hysteresis loop (polarization versus electric field) of a ferroelectric, what is the polarization that remains when the field returns to zero called?
  41. Which external environmental factor requires care when using MRAM?
  42. Why are MRAM and FeRAM sometimes used in high-radiation environments such as space equipment?
  43. Which storage-class memory technology, jointly developed by Intel and Micron, was sold under the product name "Optane"?
  44. In phase-change memory (PCM), how can multiple bits be stored in one cell (multi-level storage)?
  45. Which memory changes resistance by having metal ions such as silver or copper move through a solid electrolyte to form or break a conductive path?
  46. What is the difference between "bipolar" and "unipolar" operation of ReRAM?
  47. In cross-point memories such as PCM, which chalcogenide device, placed in series with the storage element as a selector, suddenly conducts above a certain voltage?
  48. Why must the read current be limited in STT-MRAM?
  49. Which device uses the fact that the tunneling current through a thin ferroelectric layer depends on the direction of its polarization?
  50. Which effect, being studied to reduce MRAM write energy, changes the magnetic anisotropy of a magnetic layer with a voltage?

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