The following is excerpted from an Objective Analysis Alert sent to our clients on March 26: On March 25 SanDisk and Toshiba announced sampling of their 3D NAND flash technology, a 128Gb (gigabit) 48-layer second-generation product based on the BiCS technology that the companies pioneered in 2007. Pilot production will begin in the second half of 2015 with meaningful production targeted for 2016. This release was issued at the same time that Intel and Micron were briefing the press and analysts for their March 26 announcement of their own 3D NAND offering (pictured), which is currently sampling with select customers, and is to enter full production by year-end. The Micron-Intel chip is a 32-layer 256Gb device, which the companies proudly point out is the densest flash chip in the industry.
Similarities and Differences
These two joint ventures (Intel-Micron and SanDisk-Toshiba) are taking very different Continue reading
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
This series has looked at 3D NAND technology in a good deal of technical depth. The last question to be answered centers around the players and the timing of the technology. A lot has been said about the technology and its necessity. Will everyone be making 3D NAND? When will this big transition occur?
This post will provide an update as of its publication (13 December 2013) to show each company’s current status, to the best of The Memory Guy’s understanding. Readers may want to refer back to the earlier posts in this series, as well as to a June 2013 Nikkei TechON article that gives a good review of the 3D NAND alternatives that have been presented at various technical conferences.
Let’s start with Samsung, the largest producer of NAND flash today. Just prior to Memcon 2013 last Continue reading
In a word: No.
(Before I get too far into this allow me to admit that The Memory Guy doesn’t understand quantum physics, so I will be presenting this only to the depth that I understand it. There will be no band-gap diagrams or equations to wrestle with.)
Both 3D NAND and planar NAND use Fowler Nordheim Tunneling (FN) to both program and erase. This differs from NOR flash which programs bits using Continue reading
One of the thornier problems in making 3D NAND is the job of connecting the peripheral logic (the row decoders) to all of those control gates that are on layers buried somewhere within the bit array. Remember that the control gates are the conductive sheets of polysilicon or tantalum nitride at various depths in the chip.
The problem boils down to this: You can’t run connections from each layer up or down the side of the chip to get to the CMOS circuits below. Instead you have to create a terrace structure to expose and connect to each layer.
These connections are made by etching a stair-step pattern into the layers and sinking Continue reading
My prior 3D NAND post explained how Toshiba’s BiCS cell works, using a silicon nitride charge trap to substitute for a floating gate. This post will look at an alternative technology used by Samsung and Hynix which is illustrated in the first graphic, a diagram Samsung presented at a technical conference. This cell also uses a charge trap.
Let The Memory Guy warn you, if the process in my prior post seemed tricky, this one promises to put that one to shame!
Part of this stems from the use of a different kind of NAND bit cell. You can shrink flash cells smaller if you use a high-k gate dielectric (one with a high dielectric constant “k”) since it Continue reading
Let’s look at how one form of 3D NAND is manufactured. For this post we will explore the original design suggested by Toshiba at the IEEE’s International Electron Device Meeting (IEDM) in 2007. It’s shown in the first graphic of this post. (Click on any of the graphics for a better view.)
Toshiba calls this technology “BiCS” for “Bit Cost Scaling.” The technique doesn’t scale the process the way the world of semiconductors has always done to date – it scales the cost without shrinking the length and width of the memory cell. It accomplishes this by going vertically, as is shown in this post’s first graphic.
This takes a special effort. This is where the real Continue reading
In August 2013 Samsung announced its V-NAND, the first production 3D NAND, kicking off a big change in the way that NAND flash will be manufactured. This new technology raises a number of important questions:
- What exactly is a 3D NAND?
- Why does the industry need to go to a 3D topology?
- How the heck do they make such a product?
To answer these questions I assembled a series of articles posted as weekly segments on The Memory Guy blog during the fourth quarter of 2013. The different sections are listed below, with hot links to each section.
- Why Do We Need 3D NAND?
- What Is a 3D NAND?
- Making a Vertical NAND String
- An Alternative Kind of Vertical 3D NAND String
- How Do You Access the Control Gates?
- Benefits of Charge Traps over Floating Gates
- How Do You Erase and Program 3D NAND?
- 3D NAND’s Impact on the Equipment Market
- Who Will Make It and When?
Each of these is a topic that is complex enough to warrant its own post, so for the nine Fridays I published a post to explain each one in depth. I hope you find it engaging and informative.
The companies introduced their new “1y” processing node that, according to SanDisk, produces 19nm x 19.5nm cell, versus the earlier “19nm” process (or “1x”) that used a 19nm x 26nm cell.
The graphic for this post (click to enlarge) was presented during SanDisk’s May 5th Analyst Day and compares the 24nm process to the 19 x 26nm process, moving to the 19 x 19nm process, and eventually to “1z” which neither company is yet revealing. After the 1z process SanDisk believes Continue reading
Every so often I run into someone who asks about the discrepancy between various analysts’ NAND market share rankings and SanDisk’s shipments. After all, SanDisk is a leading producer of flash memory and has captive manufacture through its joint venture with Toshiba. Yet, most market share rankings leave SanDisk out.
What’s going on here?
Owing to a long-standing convention SanDisk’s NAND chips aren’t counted since they are sold as “Systems” (with a controller.) The World Semiconductor Trade Statistics (WSTS) set that rule up, and most analysts Continue reading