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Micron, Intel tout 3D NAND flash chips

Posted: 27 Mar 2015 ?? ?Print Version ?Bookmark and Share

Keywords:3D NAND? flash? SSD? TLC? MLC?

Micron and Intel follow Samsung's lead with ultra-dense 3D NAND flash chips, which they plan to market as chips and in solid-state drives. Micron already samples chip-level products that will ship by the end of the year. With this move, Samsung might be forces into wide sales of its chips.

Micron said it will pack 256Gbits into vertical NAND chips using two-bit per cell (aka MLC) technology and 384Gbits in three-bit per cell (TLC) versions. By contrast, Samsung has been shipping since July its 850 series SSDs using 86Gbit MLC and 128Gbit TLC chips using vertical NAND. Both Samsung and Micron/Intel are fielding chips that stack 32 silicon levels.

The 256Gbit versions are sampling "with select partners" now and the 384Gbit TLC design will be sampling later this spring, Intel and Micron said. The fab production line has already begun initial runs and both devicesMLC and TLCwill be in full production by the fourth quarter of 2015. Their separate SSD products will "be available within the next year."

The companies would not state costs but vowed to be aggressive with "disruptive" pricing. Micron will sell the chips targeting a wide swath of systems from data centre gear to smartphones.

3D NAND

The Micron/Intel chip can pack 3.5TB in an M2-sized flash card.

Micron claims its advance is due, in part, to its use of floating gate technology, which it said is used in the majority of flash chips. However, one analyst was sceptical.

"The only reference I had seen to a floating gate 3D NAND so far was an IEDM paper SK Hynix delivered in 2013," said Jim Handy, of Objective Analysts (Los Gatos, Calif.).

"I haven't been briefed about this part, but two things about the floating gate concern me," Handy said. "One is that it is probably pretty tricky to make. I have heard rumours that SK Hynix abandoned its scheme for this reason. The other is that Samsung's use of a charge trap helped it get to 3bit [per cell] faster, since charge traps use lower programming energy, reducing the stress on the tunnel oxide."

Micron said it has used floating gate technology widely and its relatively large cells help ensure reliability. It said wear dynamics of the new chips will be similar to today's 28nm planar chips.

Handy said he has not heard of Samsung shipping any 3D flash chips yet, only selling them as SSD cards. "This may be helping them, because you can hide a lot of issues behind an SSD controller that would be made obvious if you shipped bare parts," he said.

For some time, flash chipmakers have been moving into the business of selling SSD cards to reap greater profit margins, rather than sell chips to third parties who make cards. Samsung's decision initially to sell its 3D flash parts only in SSDs is a natural step in that evolution.

Nevertheless, the move raised issues about the terms on which OEMs of consumer products such as smartphones, hungry for maximum storage, could get the chips. Samsung suggested it was differentiating its Galaxy S6 phones announced at Mobile World Congress last month with a unique memory chip stack, which may have been included 3D NAND parts.

Intel and Micron said their dense parts will enable gum stick-sized SSDs with more than 3.5TB of storage and standard 2.5in SSDs with greater than 10TB. They declined to share the read/write specifications of the new chips but spoke through a press representative about their internal structure.

  • To deliver high read/write performance and I/O speeds, we have implemented several architecture changes and key features in our 3D NAND, including a 4-plane architecture which provides twice the addressable bytes as a 2-plane architecture, a fast 4K read mode, an improved ONFI 4 interface and advanced single-pass MLC programming.

Intel co-designed the 3D NAND parts with Micron. The two companies have a joint development programme for developing non-volatile memory technologies and continue to jointly invest in the IM Flash Technologies joint venture, which has a 300mm NVM Fab in Lehi, Utah.

- Rick Merritt
??EE Times





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