A Highly Integrated NAND Flash Chip
SK Hynix has developed a one-terabit (Tb) quadruple level cell (QLC) chip based on 96-layer 4D NAND technology. The high-integration product with a larger data storage capacity signals the initiation of SK Hynix’s full-scale NAND memory business.
SK Hynix announced on May 9 that it supplied samples of the new product to solid state drive (SSD) controller manufacturers. The product can be defined as a combination between existing 96-layer charge trap flash (CTF) 4D NAND and the company’s QLC design technique.
QLC is to store four-bit data in a NAND cell, the minimum unit of data storage. NAND flashes are divided into SLC for one-bit storage per cell, MLC for two-bit storage per cell, TLC for three-bit storage per cell and QLC for four-bit storage per cell. In other words, QLC’s data storage capacity is four times that of SLC of the same area.
QLC allows a higher degree of integration at the same area and, as such, high-capacity products can be realized in a cost-saving manner. However, it is hard to make because it requires a very high level of cell integration in a chip as small as a nail. One Tb QLC requires 274.8 billion integrated cells. SK Hynix succeeded in stacking the chips in 96 layers this time.
In addition, SK Hynix applied a four-plane structure by utilizing the merit of 4D NAND, that is, a small plane. The plane is an assembly of cells independently operating within a single cell and their peripheral circuits. The new product of SK Hynix simultaneously processes 64 KB data with four planes whereas existing products simultaneously process 32 KB data with two planes.
Silicon Motion CEO Wallace Kou said that the engineering sample of SK Hynix sufficiently satisfies the reliability and performance required for SSDs for general consumers. Silicon Motion is a Taiwanese company developing and selling SSD controllers and NAND storage devices.
SK Hynix is planning to develop QLC software algorithms and controllers based on the new product in order to come up with solution products soon. Market research firm IDC recently reported that the ratio of QLC in the global NAND flash market is expected to rise from 3 percent to 22 percent from this year to 2023.