NAND flash overview

NAND flash rapidly changes in technology nodes and number of bits per cell, ever increasing the user capacity while constantly reducing the cost per bit.
The main differentiator of NAND flash is the number of bits per cell.

· SLC (single level cell) stores 1 bit per cell
· MLC (multiple level cell) stores 2 bits per cell
· TLC (triple level cell) stores 3 bits per cell
· QLC (quadrupel level cell) stores 4 bits per cell

The reliability and retention of each programmed level shrinks with each additional bit.
Swissbit continues to ship products with SLC, MLC and 3D NAND TLC technology.

3D NAND

3D NAND is the latest technology innovation to increase chip capacity and reduce cost without stretching the limits of lithography.
The high intergration was possible by turning from Floating Gate as a storage element to Charge Trap Layer. This allowes an easy vertical rotation of the bit lines and stacking of 64 and more layers.
The mainly utilized 3D NAND technology of Swissbit products is called BICS which indicates the approach to reduce the bit cost.

The new 3D NAND enables high density products at lower cost, but requires significantly higher error correction and sophisticated flash firmware management. Only few 3D NAND products are able to fully support an industrial temperature grade of -40°C to +85°C.
While lots of 3D NAND products are available in consumer quality, only few products are truely supporting industrial 3D NAND.
Swissbit X-75 and N-10m2/N-12m2 products are based on industrial temperature grade 3D NAND technology.

 

 

 

 

Technology comparison

The endurance of flash-based products is primarily defined by the maximum number of program / erase cycles of the flash components. SLC components normally allow 100,000 PE cycles per block while MLC is typically specified as 3,000 PE cycles. But also other factors like retention, long term availability, temperature range and cost per bit differ significantly with the technology, as can be seen from the table.

Swissbit Life Time Monitoring Tool (SBLTM)