SRAM and flash memory

In 3D NAND, what is the structure called in which the edge of the stack is shaped into steps so that each layer's word line can be connected?

  1. AStaircase structure
  2. BDamascene structure
  3. CTrench structure
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Answer: A. Staircase structure

In 3D NAND, tens to hundreds of conductive layers acting as word lines are stacked, and each must be individually contacted. The edge of the array is therefore etched into steps, exposing the top of each layer so contacts can land on it. More layers make the staircase harder to form and require more area.

  • A. Correct. It is a stepped structure for connecting to each layer.
  • B. Damascene is a process of filling trenches with metal to form wiring.
  • C. A trench is a groove in the substrate, not a structure for connecting to each layer.
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More SRAM and flash memory questions

  1. In 3D NAND, what is the main advantage of placing peripheral circuits such as sense amplifiers beneath the memory array (CMOS under Array and similar)?
  2. Which correctly describes the structure of a typical six-transistor SRAM cell?
  3. Compared with NOR flash, which is a characteristic of NAND flash memory?
  4. In flash memory, what is the scheme that stores 3 bits of information in one memory cell called?
  5. Which correctly describes how data is written to and erased from flash memory?