lithography - The Memory Guy Blog

Why are NAND Flash Fabs so Huge?

Many readers have probably wondered why NAND flash fabs are so enormous. Although DRAM fabs used to be the largest, running around 60,000 wafers per month, NAND flash fabs now put that number to shame, running anywhere from 100,000-300,000 wafers per month. Why are they so huge?

The reason is that you need to run that many wafers to reach the optimum equipment balance. The equipment must be balanced or some of it will be sitting idle, and with some tools costing $50 million (immersion scanners) you want to minimize their idle time to the smallest possible number. I am sure that this is a tough problem, although I have never had to solve it myself.

The most important reason that so much attention is focused on this is that the cost of the wafer depends on the efficiency of the fab. If you built a $13 billion NAND flash fab that produced 90,000 wafers per month instead of 100,000 wafers per month, then the amount of investment per wafer would be 10% higher. That can make a significant difference to Continue reading “Why are NAND Flash Fabs so Huge?”

How Samsung Will Improve 3D NAND Costs

One of the most intriguing revelations during the Flash Memory Summit two weeks ago was Samsung’s new approach to stairstep etch in 3D NAND. This was one of numerous innovations the company’s EVP of Flash Products & Technologies, Kye Hyun (KH) Kyung, shared during Samsung’s Tuesday Morning keynote presentation.

The Memory Guy would point readers to the pdf of Samsung’s presentation on the Flash Memory Summit website, but it isn’t there, and it’s unlikely to ever be posted there. Samsung seems to have a policy that prohibits sharing such presentations.

Although I was unable to get a copy of the drawing that the keynoter used, I have tried to re-create it using, of all things, Excel! The result is the graphic for this blog post. The only thing I was unable to easily recreate was the different colors representing the layers of the 3D NAND. You’ll need to use your imagination and envision layers of two colors, with all the surfaces exposed on the top being the same color, but at different layers of a 64-layer structure.

Today’s common approach to 3D NAND’s stairstep is to etch a simple step pattern in one dimension, which I illustrated in an early 3D NAND blog post four years ago. This is a challenging Continue reading “How Samsung Will Improve 3D NAND Costs”

What’s This Nano-Imprint Litho that Toshiba and SK hynix are Co-Developing?

Last week Toshiba and SK hynix announced an agreement to jointly develop Nano Imprint Lithography (NIL), building on a memorandum of understanding (MOU) that two companies signed in December last year. Development efforts will begin this April and practical adoption is expected to start in 2017. The collaboration is expected to reduce risk and accelerate commercialization of this technology.

NIL is expected to produce next-generation lithography at high throughput rates more economically than established lithography tools. It is should compete against Extreme Ultraviolet (EUV) lithography, an alternative technology whose use has been delayed by numerous technical challenges. EUV, a euphemism for X-Rays, cannot use transmissive optics like glass lenses, so a completely new reflective imaging technology has had to be developed to support its use. The advantage of EUV is that the light wavelength is only 13nm, which is an order of magnitude smaller than the 193nm light currently used to produce leading-edge chips, allowing it to print significantly smaller features.

Unlike today’s lithography, which uses a purely photographic process, NIL mechanically stamps a pattern into the photoresist in a similar manner to the sealing wax stamp shown in the photo (courtesy of BackToZero, a wax stamp maker). The stamp is produced using Continue reading “What’s This Nano-Imprint Litho that Toshiba and SK hynix are Co-Developing?”

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”

3D NAND’s Impact on the Equipment Market

A very unusual side effect of the move to 3D NAND will be the impact on the equipment market. 3D NAND takes the pressure off of lithographic steps and focuses more attention on deposition and etch. The reason for going to 3D is that it provides a path to higher density memories without requiring lithographic shrinks.

This sounds like bad news for stepper makers like ASML, Canon, and Nikon while it should be a boon to deposition and etch equipment makers like Applied Materials, Tokyo Electron, and Lam Research.

In its summer 2013 V-NAND announcement, Samsung explained that it would be Continue reading “3D NAND’s Impact on the Equipment Market”

Applied’s Take on 3D NAND

Early this month I was invited to participate in Applied Materials’ (AMAT) Analyst Day. The sessions were rich in data covering the markets that would profit the company over the next few years.

Naturally, The Memory Guy fixated on those presentations that dealt with memory. When it came to the upcoming transition to 3D NAND, AMAT had a lot to say.

A later post will explain what 3D NAND actually is. Suffice it to say that today’s approach to making NAND flash has nearly reached its limit, and the approach that manufacturers plan to use in the future involves making NAND strings that stand on their ends. This has phenomenal implications on Continue reading “Applied’s Take on 3D NAND”