Micron Sees No Reliability Issues with 20nm HKMG NAND Flash Memory

Micron: HKMG Does Not Make NAND Flash More Expensive

by Anton Shilov
12/21/2011 | 11:00 PM

Micron Technology said that the 20nm NAND flash memory that it is going to produce together with Intel Corp. at the IMFT joint-venture will not be less reliable that currently available MLC NAND flash made using 25nm fabrication process. According to Micron, the potential reliability issues were partly tackled by the use of high-k metal gate (HKMG) technology. Despite the fact that HKMG is a relatively expensive tech, Micron does not consider it too expensive.


Every new generation of multi-level cell (MLC) NAND flash memory produced using thinner process technology is traditionally somewhat less reliable than memory produced using older fabrication process. Apparently, HKMG - manufacturing technology used to produce pretty expensive devices like microprocessors or graphics chips - is one of the ways to improve reliability of 20nm NAND flash. Generally speaking, HKMG may not be a luxury, but rather a necessity for the next-generation of flash.

"We think [HKMG] is the right answer. [...] Do we see any long-term issues associated with the reliability of the device? Absolutely not! We think that this is the right way to scale from 25nm to 20nm. And we probably got few tricks up our sleeves to move on beyond that," said Ronald Foster, chief financial officer at Micron, during conference call with financial analysts.

Earlier this month Intel and Micron announced the world's first 20nm, 128Gb, MLC NAND flash device. The new 20nm monolithic 128Gb device is the first in the industry to enable 1Tb of data storage in a fingertip-size package by using just eight die. The 128Gb device meets the high-speed ONFI 3.0 specification to achieve speeds of 333MT/s, providing customers with a more cost-effective solid-state storage solution for tablets, smartphones and high-capacity solid-state drives (SSDs).

The companies also revealed that the key to their success with 20nm process technology is due to an innovative new cell structure that enables more aggressive cell scaling than conventional architectures. Their 20nm NAND uses a planar cell structure - the first in the industry - to overcome the inherent difficulties that accompany advanced process technology, enabling performance and reliability on par with the previous generation. The planar cell structure successfully breaks the scaling constraints of the standard NAND floating gate cell by integrating the first HKMG stack on NAND production.

When asked about the additional manufacturing costs that the high-k metal gate tech inevitably brings, the CFO of Micron said that

"There is nothing significant about the high-k metal gate as a new technology node that puts it completely out of proportion for what you would typically see moving from one technology to another to the other. HKMG is not an abnormal increment relatively for cost incurred that way," added Mr. Foster.