Micron and Intel Introduce 3-bit-per-cell NAND Technology

When Solid-State Disks were first introduced to consumers, many people didn’t quite know the differences between the various flash chips, and their technologies. Since then, though, information has been abundant, and it’s probably rare that anyone interested in an SSD hasn’t heard of SLC and MLC, or know their differences. But, prepare to add a third type, “3-bit-per-cell MLC”.

To understand what makes 3BPC MLC interesting, it’s important to first understand the basics of how NAND and its cells work. SLC, or “single-level” cells are 1-bit, which means two things. First, there are two possible logic states, and second, the resulting chip has equal bit density to the chip being used (typically, 16 Gbit, or 32 Gbit in really high-end situations). These are also the reasons SLC is so much faster than MLC. Because there are only two possible voltage states per cell, the access time is faster, and for the same reason, SLC has a longer lifespan.

MLC, or “multi-level” cell, increases the bit-density to 2-bit, meaning that we move from two possible states to four, but also a larger possible overall density (which is why MLC-based SSDs are far larger and far less expensive over SLC). But for the opposite reasons that SLC lasts much longer than MLC, the extra possible states per cell for MLC means far more writes, and ultimately, a shorter lifespan.

3BPC MLC takes things one step further, and increases the cells to 3-bits, which means larger possible densities, but an even shorter lifespan and also another performance hit. The reason is because that with 3BPC, there are eight possible states, and each would take a little bit longer to trigger.

So what’s this mean to you? 3-bit-per-cell is not for SSDs, but rather things like flash media (thumb drives, camera cards, media players), where density and physical size is more important than performance. On a related note, I have to vote for this as being one of the coolest-looking die shots I’ve seen in a while, or at least one of the most colorful.

Designed and manufactured by IM Flash Technologies (IMFT), their NAND flash joint venture, the new 3bpc NAND technology produces the industry’s smallest and most cost-effective 32-gigabit (Gb) chip that is currently available on the market. The 32Gb 3bpc NAND chip is 126mm². Micron is currently sampling and will be in mass production in the fourth quarter 2009. With the companies’ continuing to focus on the next process shrink, 3bpc NAND technology is an important piece of their product strategy and is an effective approach in serving key market segments.