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Flash Memory Summit: Limitless Layers of 3D NAND

The single most interesting thing I learned at the 2015 Flash Memory Summit was that 3D NAND doesn’t have a natural limit, after which some other memory type will need to be adopted.

For years SanDisk has been presenting a memory roadmap (this post’s graphic is one rendition) that anticipates a move to ReRAM after 3D NAND has run through its natural life, which was expected to be as little as three generations. This has been backed by the idea that a 3D NAND stack would only be able to reach a certain number of layers before it would encounter difficulties caused by the need to etch a high aspect ratio hole through an increasing number of layers.

The aspect ratio issue is not hard to understand: Let’s assume that the hole in a 24-layer stack has an aspect ratio of 40:1, then a 32-layer hole would have an aspect ratio of about 50:1, and a 64-layer stack would be something close to 100:1. Today’s technology starts to have trouble etching holes with an aspect ratio higher than 60:1.

These high aspect ratios were thought to be the limiting factor that would prevent 3D NAND from continuing for more than three generations. 3D NAND could only have as many layers as the aspect ratio could support.

On a panel that I moderated at this year’s Flash Memory Summit one panelist, Dr. Myoung Kwan Cho of SK hynix, explained that although there is a limit Continue reading “Flash Memory Summit: Limitless Layers of 3D NAND”

DRAM Prices Down, But Not So Bad

For the past ten months DRAM prices have been undergoing a steady slide. Is the market in a crisis? Not really!

Today’s low spot price of $4.30/GB puts us on a par with February 2013, a full two years ago (see chart). DRAM makers have done a lot to reduce their production costs since that time, so their margins this quarter will be much better than they were in the first quarter of 2013.

But we are still a very long way from the bottom of the last market downturn. In late 2012 spot prices reached a low of $2.52/GB, a full 41% lower than today’s lowest spot prices.

The Memory Guy models the production costs of leading memory chips, and DRAM manufacturing costs have been decreasing for the past several years at an average annual rate of about 30%. That means that costs today are about half of what they were two years ago, and one third of their level this time in 2012.

So even though today’s Continue reading “DRAM Prices Down, But Not So Bad”

Why NAND is So Difficult to Scale

NAND flash is the process leader in memory technology, and this puts it in a very challenging position: It must ramp to high volume production using techniques that have never been tried before.

The graphic for this post (click to enlarge), supplied by ASML, the semiconductor industry’s leading lithography tool supplier, illustrates the challenge of migrating from one process node to the next. Across the bottom, on the X-axis, are representative process nodes ranging from “2D-45”, or two-dimensional (planar) 45nm NAND, to “3D-5x”, or three-dimensional 5xnm NAND. Below these numbers are the year of volume production.

The vertical axis, labeled “Tolerance” represents the minimum Continue reading “Why NAND is So Difficult to Scale”

Did SK hynix Beat Samsung to the 8Gb LPDDR4?

Every so often something very strange happens that puzzles The Memory Guy. On December 29 (or Dec. 30 in Seoul) something odd occurred.

I received two e-mails, one from SK hynix at 3:55 PM Pacific Time, and one from Samsung exactly one hour later. Both were press releases.

The SK hynix release was titled: “SK Hynix Developed the World’s First Next Generation Mobile Memory LPDDR4”. It announced that the company is sampling its 20nm-class 8Gb LPDDR4 DRAM to customers.

The Samsung release was Continue reading “Did SK hynix Beat Samsung to the 8Gb LPDDR4?”

SIA: Memories Drive Record Semi Revenues

The SIA yesterday released the WSTS semiconductor sales data for September. Monthly revenues reached a record $27 billion driving third-quarter revenues to their own record of $81 billion. This was the seventh straight month of semiconductor growth, the first such run-up since 2010.

This quote, by SIA CEO Brian Toohey really caught The Memory Guy’s eye: “Sales of memory products have increased sharply compared to last year and continue to be a major driver of industry growth.”

A lot has been happening to drive this increase in memory revenues: The recent SK hynix fire increased DRAM prices, but Continue reading “SIA: Memories Drive Record Semi Revenues”

Hynix Recovery – Not so Soon?

During SK hynix’ October 29 earnings call the company further clarified the status of its Wuxi fab line that was hit by a fire on September 4. In brief, the company may miss its expected end-November date to recover to full operation.

Interestingly, although DRAM bit shipments declined by 2% because of the fire, revenues increased by 3% thanks to price increases caused by the resulting tight DRAM supply. This gave the company a revenue boost taking total semiconductor revenues from ₩3.93 trillion ($3.54B US) in the second quarter to ₩4.08 trillion ($3.66B US) in the third quarter. Not only was this revenue a record number for SK hynix, but margins also reached a record high.

All in all, it was a very good quarter, despite the fire, and perhaps because of it.

The company disclosed that restoration of the air ventilation system and the clean room have been Continue reading “Hynix Recovery – Not so Soon?”