This week both the Toshiba-Western Digital team and Samsung disclosed details of their 64-layer 3D NAND designs at the IEEE’s International Solid-State Circuits Conference (ISSCC). The Memory Guy thought that it would be interesting to compare these two companies’ 64-layer chips against each other and against the one that Micron presented at last year’s ISSCC.
Allow me to point out that it’s no easy feat to get to 64 layers. Not only must the process build all 64 layers (or actually pairs of layers plus some additional ones for control) across the entire 300mm wafer with high uniformity and no defects, but then holes must be etched through varying materials from the top to the bottom with absolutely parallel sides at aspect ratios of about 60:1, that is, the hole is 60 times as deep as it is wide. After this the fab must deposit uniform layers of material onto the sides of these skinny holes without any variation in thickness.
None of these processes have ever been used to build any other semiconductor — it’s all brand new. This is what makes 3D NAND so challenging, and it’s why the technology is already 3 years behind its original schedule.
It’s not easy to tell from the conference papers whether or not Continue reading
In a letter to shareholders released today, Toshiba finally clarified its plans for restructuring the company. Since January 18 there have been numerous rumors that Toshiba planned to spin its memory business off or sell it outright. Today’s letter indicates that this hasn’t been decided yet. In fact, other than to call a late March shareholder vote and to reveal a restructuring, the letter discloses extraordinarily little.
In a nutshell Toshiba has decided to isolate the memory business (including the SSD business but not the HDD and image sensor businesses) into a separate wholly-owned subsidiary. There was no mention of either the recently-shrinking Discrete business or the System LSI business, which has been in a steady decline for the past decade. Click on this post’s graphic to see how each of the company’s semiconductor businesses has been doing.
The intent appears to be to groom the subsidiary to be spun off or sold, but this has not been expressly stated. Instead Toshiba simply states that: “The Company is still considering various structures with a view to an injection of third-party capital.”
The letter reiterates Toshiba’s prior position that the memory business Continue reading
On its way out the door the Obama Administration put together a proposed response to China’s plans to invest $150 billion in the semiconductor market over the next five years. It seems that US semiconductor industry views China’s investment as a threat to its position in the market.
Last week the President’s Council of Advisors on Science and Technology (PCAST) delivered a 25-page Report to the President entitled: “Ensuring Long-Term U.S. Leadership in Semiconductors.”
You might ask: “Who is PCAST?” The organization states its mission in this paragraph: “The President’s Council of Advisors on Science and Technology (PCAST) is an advisory group of the Nation’s leading scientists and engineers, appointed by the President to augment the science and technology advice available to him from inside the White House and from cabinet departments and other Federal agencies. PCAST is consulted about, and often makes policy recommendations concerning, the full range of issues where understandings from the domains of science, technology, and innovation bear potentially on the policy choices before the President.”
PCAST has a small Semiconductors Working Group whose elite members include Continue reading
Since I am the Memory Guy I hate learning that I missed something new and cool in the world of memories, but somehow I was unaware of last week’s Memsys conference in Washington DC until a participant notified me on Saturday that his paper: “Reverse Engineering of DRAMs: Row Hammer with Crosshair,” had been given the the best paper award.
Upon looking at the Memsys website it looks like a very intriguing academic conference. about sixty papers were presented in eight interesting sessions:
- Issues in High Performance Computing
- Nonvolatile Main Memories and DRAM Caches, Parts I & II
- Hybrid Memory Cube and Alternative DRAM Channels
- Thinking Outside the Box
- Improving the DRAM Device Architecture
- Issues and Interconnects for 2.5D and 3D Packaging
- Some Amazingly Cool Physical Experiments
in addition to a few apparently-fascinating keynotes.
Fortunately, all of the papers are Continue reading
The Memory Guy has been getting calls lately asking how to tell that a shortage is developing. My answer is always the same: It’s hard to tell.
One indicator is that spot prices which were below contract prices rise above contract prices. This doesn’t happen for all components or densities of DRAM or NAND flash at the same time. Some of these transitions are temporary as well. It takes patience to see if it was a momentary change or if it was the onset of a shortage.
DRAM spot prices have generally been below contract prices since August 2014, but this month they raised above contract prices. NAND flash spot prices also fell below contract prices in mid-2014 but today NAND’s spot price remains lower than contract prices.
Lead times represent another indicator. If the lead time for a number of components increases then those chips are moving into a shortage. Lead times have recently been rising for both NAND flash and DRAM.
A third indication occurs when suppliers start to Continue reading
The answer really depends upon who you ask. An article in the Financial Express quoted Samsung as saying that it would have a minimal impact, and that full-scale operations should resume in a few days. The article also said that Samsung estimated that the wafer loss would be below 10,000 wafers.
Assuming that the entire loss consisted of Samsung’s most advanced 48-layer 256Gb 3D NAND a 10,000-wafer loss would be less than 1% of total industry gigabyte shipments.
Korea Times quoted an anonymous fund manager who said: “The one-time incident will cost Samsung up to 20 billion won, which is very minimal. It won’t make heavy impact on Samsung’s chip business and the entire industry.”
Beleaguered Toshiba finally unveiled its restructuring plan on Friday. The plan aims to return the company to profitability and growth through management accountability.
A lot of the presentation focused on the memory business, a shining star of the Toshiba conglomerate, which has so far included appliances, nuclear power plants, and medical electronics.
Toshiba has big plans for its Semiconductor & Storage Products Company, calling it “A pillar of income with Memories as a core business”. The company plans to enhance its NAND flash cost competitiveness by accelerating development of BiCS (Toshiba’s 3D NAND technology) and by expanding its SSD business. There are three parts to this effort:
- Grow 3D NAND production capacity
- Speed up 3D NAND development
- Increase SSD development resources
This post’s graphic is an Continue reading
At the IEEE’s IEDM conference last week Belgian research consortium imec showed an improved “gate first” 3D NAND that replaced the conventional polysilicon channel with InGaAs, Indium Gallium Arsenide, a III-V material. This new technique opens the door to higher layer counts in 3D NAND, allowing denser parts to be made in support of further cost reductions.
For those unfamiliar with the term, the “gate first” approach is the foundation of Toshiba’s BiCS NAND, and presumably Micron’s floating gate 3D NAND.
imec explains that “Replacing poly-Si as a channel material is necessary, as it is not suitable for long-term scaling.” Further they report that on-state current (ION) and transconductance (gm) of the III-V channel was better than that of polysilicon devices, without any programming, erase, or endurance degradation. The device’s characteristics are shown in this post’s graphic.
The consortium reports that the current through the Continue reading
Objective Analysis has just introduced a new report that you might want to consider: A Close Look At The Micron/Intel 3D XPoint Memory.
The report covers the Intel-Micron 3D XPoint memory and includes Intel’s new Optane support products that are based on this technology. The report explains the technology and its special manufacturing challenges. It includes details of how 3D XPoint memory will be used, and provides an analysis of the benefits of its persistent nature.
Forecasts project how the market will develop and include optimistic and pessimistic forecast scenarios. Particular attention has been paid to its impact upon the DRAM, SSD, and other markets. Finally, the report analyzes different end-market segments to predict how this technology will impact each of them.
The Memory Guy, report author Jim Handy, will present the report’s findings during the Pre-Conference Primer of the Storage Network Industry Association (SNIA) Storage Developer Conference (SDC) this Sunday, September 20, at 2:00 PM, In Santa Clara, CA.
This breakthrough report is based on Continue reading
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