3D NAND: Who Will Make It and When?

SK hynix 3D NAND Cross SectionThis 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

An Alternative Kind of Vertical 3D NAND String

Samsung's TCAT 3D NAND flashMy 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

3D NAND: Making a Vertical String

Toshiba's Original BiCS Diagram - IEDM 2007Let’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

What is a 3D NAND?

Applied Materials' Explanation of 3D NANDIn the prior post we discussed the need to go vertically into the body of the die, since NAND flash can not be scaled much farther in length and width on the die’s surface.  Toshiba invented a 3D NAND which has been adopted and refined by all flash makers.  The idea is simple: Rather than shrink the cell’s length and width, why not turn the NAND string so that it’s standing on its end?

This concept is illustrated by this post’s first graphic, which was provided by Applied Materials.  (Click on the graphic to see the whole thing at a larger size.)  A standard NAND string that normally runs longitudinally is turned on its end to become a vertical string.  Not only that, but it makes things easier if the string is split into two sections and Continue reading

Why Do We Need 3D NAND?

NAND Flash Capped Gate StructureA memory chip of a certain area costs about the same amount to produce, no matter how many bits it holds. Naturally, the more bits you can cram onto this chip, the cheaper the price per bit will be. Low cost is of the utmost importance in the world of memory.

Memory chip makers have shrunk the cost of a bit some nine orders of magnitude since the 1960s largely by shrinking the process, or “scaling” to increasingly tighter process geometries.

Flash has always been expected to reach a scaling limit. Over the past few generations technologists have developed Continue reading


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