We have a guest contribution today from Israel Beinglass, the CTO of MonolithIC 3D Inc. Israel discusses about TSVs. 

Have you read some of the recent TSV headlines?

1. January 31, 2012 - CEA-Leti launched a major new platform, Open 3D, that provides industrial and academic partners with a global offer of mature 3D packaging technologies for their advanced semiconductor products and research projects.

2. March 7, 2012 - Semiconductor fab equipment supplier Applied Materials Inc. (AMAT) opened the new Centre of Excellence in Advanced Packaging at Singapore's Science Park II with its partner in the endeavor, the Institute of Microelectronics (IME)

3. March 26, 2012 - PRNewswire - Semiconductor design/manufacturing software supplier Synopsys Inc. (Nasdaq: SNPS) is combining several products into a 3D-IC initiative for semiconductor designers moving to stacked-die silicon systems in 3D packaging.

It is amazing that after so many years of development and efforts and great presentations we are still not in a full production and still basic R&D as well as EDA still in infancy.

Most people in the Industry consider Merlin Smith and Emanuel Stern of IBM the inventors of TSV based on their patent “Methods of Making Thru-Connections in Semiconductor Wafers” filed on December 28, 1964 and granted on September 26, 1967, as shown below patent  number 3,343,256

In April 12, 2007 IBM announced a breakthrough new 3D technology:
Armonk, NY - 12 Apr, 2007: IBM (NYSE: IBM) today announced a breakthrough chip-stacking technology in a manufacturing environment that paves the way for three-dimensional chips that will extend Moore’s Law beyond its expected limits. The technology – called “through-silicon vias” - allows different chip components to be packaged much closer together for faster, smaller, and lower-power systems… IBM is already running chips using the through-silicon via technology in its manufacturing line and will begin making sample chips using this method available to customers in the second half of 2007, with production in 2008.

Figure 2 is taken from Ignatowski’s presentation made shortly after IBM’s TSV announcement. This type of argument where chip stacking is compared to 2 chips side by side has become the corner stone of the TSV story (http://www.sematech.org/meetings/archives/3d/8334/pres/Ignatowski.pdf).

Already at that point (2007) it was clear to IBM that there were many issues with the technology that needed to be resolved.  Figure 3 shows the IBM slide discussing some of the problems for implementing TSV for mass production.

During the years following and through to today there have been many attempts to bring the technology to the mass production. All have been without real success. 
The professional literature is full of beautiful road maps showing how TSV is going to change the industry with “more than Moore” as the next scaling methodology. 
Figure 4 is the Advanced Packaging road map for Texas Instruments which is typical of most companies Packaging/TSV road maps.

There are several issues that are facing the industry when trying to implement TSV technology: (not in any specific order)
Process issues:

• Via etching and filling are extremely slow since the dimensions are very different from the “normal” dimensions the industry uses (single/multiple digit microns for depth and diameter vs. nanometers, plus aspect ratios>5)
• Via, first, middle or last which way to go? Each affects the whole process logistics in differing ways
  
• How to integrate wafers from different sources Logic from IDM and/or foundry and memory from a memory Fab
  
• Wafer thinning, how to handle fully processed wafer 20-80 micron thick including bonding and de-bonding. Rumors are that both Applied Materials and TEL are developing this kind of a tool
  
• Wafer-to-wafer (W2W) or die-to-wafer (D2W) bonding: each  have processing challenges
  
• Singulation of the final product
• Substrate (carrier)for TSV

Design and EDA:

•  Design rules are currently not compatible with TSV
  
•  Who is responsible for the “system” design if there are several sources for product to be integrated?
  
• EDA is way, way behind
  
• Thermal simulation and heat removal issues

Back end issues:

• Foundries/IDM vs. OSAT, who is doing what and who picks up yield loss
  
• Final test
• Reliability
• The major foundries have no memory knowledge or how to integrate the memory on top of logic

Cost:

            - Currently the cost associated with implementing TSV is at least for now higher than other solutions. This is hampering the motivation to develop and implement the TSV technology.

Also the CapEx to implement TSV needs to be addressed, Figure 5 is a table put together by ASE that shows the readiness of the various equipment needed to run a typical TSV process.

One of the key issues that some people are neglecting right now is the fact that we do have an interim solution to the problem. It may- probably not be the best solution and perhaps not the most elegant one but it does work. These are the variety of packaging techniques using chip on chip with wire bonding, and assortment solutions (PoP etc).

The following are some of the comments made by industry experts over the last few months.

TSMC
Doug Yu’s keynote address at the 3D Architectures for Semiconductor Integration and Packaging Conference in December, he noted that TSMC intends to provide full 2.5F and 3D service including chip design and fabrication, stacking and packaging. Yu, who is senior director of integrated interconnect and packaging, R&D at TSMC, outlined the key technologies that offer the best path to commercializing 3D integration technologies, with the implication that TSMC is well positioned to provide them all.

(http://www.infoneedle.com/posting/100745?snc=20641)

“TSV is much more complex and challenging than ever before,” noted Yu. “There’s a new ballgame and a small window.” He said a conventional collaboration infrastructure is becoming harder. Integration must be simplified to reduce handling and an investment beyond conventional back-end (in other words, middle-end-of-line tools and processes) is required. In short, Yu said a full spectrum of expertise is needed that includes manufacturing excellence, capacity and customer relationships where there is no competition with the customer 


Hynix
Nick Kim VP of Packaging  announced that for Hynix, production of 3D devices is no longer a matter of if but when and how (http://www.infoneedle.com/posting/100669?snc=20641)

Kim provided a detailed cost breakdown illustrating why 3D TSV stacks are more expensive (1.3x more) than wire bond stacks to manufacture. Overall, TSVs alone add 25% to the manufacturing cost because there is additional cost at each step:  

•  Design: net die area decreases due to TSV array. 
•  Fab: increased process steps due to TSVG formation, and capex for TSV equipment. 
•  Packaging: Bumping, stacking, low yield and CapEx for backside processing equipment such as temporary bond and de-bond. 
  
• Test: Probe and final package test time is increased because of the need to test at each layer as well as final. 
  
• Hynix 3D roadmap: volume TSV production will officially start after 2013:
  
• DRAM on Logic for mobile applications in a known good stacked die (KGSD) driven by form factor and power, are in development in 2012 with low production expected early 2013 ramping to volume late 2014. 
  
• DRAM on interposer in a 2.5D configuration for graphics applications, driven by bandwidth and capacity is in development in 2012 with low production expected by the end of the year and ramping to HVM early in 2014. 
  
• 3D DRAM on substrate for high performance computing (HPC) driven by bandwidth and capacity is in development in 2012, with low production expected early 2013, ramping to volume late 2014. 
  

In terms of supply chain management, Kim sees Hynix favoring the open ecosystem where logic and memory prepared with/for TSV from foundries and IDMs going to OSATs for assembly.

Overall it looks almost like a nightmare to implement TSV in a manufacturing facility. Even if all the processes steps will be taken care of, the logistics and co-ordination with different Fabs and OSAT are definitely no fun!!!

It looks like when we sum all the issues regarding the TSV methodology for achieving 3D, the approach of monolithic 3D suggested by MonolithIC 3D could resolve many of these issues and offer a far greater cost/performance gain from going 3D. Most of these advantages were already discussed in previous blogs and are part of the company web site,

Just few items that I would like to highlight:

•  Practically no limit on the amount of vias between the different chips in the stack.
  
• No deep TSV – nanometers, not microns!
  
•  All done within the IDM or the foundry – better yield control & ramp, and no pointing fingers.

Please comment and let’s get a discussion going.

We have a guest contribution from Zvi Or-Bach, the President and CEO of MonolithIC 3D Inc. Zvi discusses NVIDIA's presentation at the International Trade Partner Conference (ITPC) forum last November.

Recently I read a very uncommon report title: "NVIDIA deeply unhappy with TSMC, claims 20nm essentially worthless". Quoting directly: “One of the unspoken rules of customer-foundry relations is that you virtually never see the former speak poorly of the latter. Only when things have seriously hit the fan do partners like AMD or NVIDIA admit to manufacturing problems... That’s why we were surprised - and our source testified to being stunned - that Nvidia gave the following presentation at the International Trade Partner Conference (ITPC) forum last November”

The only explanation I can come up with is that NVIDIA is in a panic. And according to Andy Grove’s “Only the Paranoid Survive” I believe NVIDIA will overcome the challenge, and at the later part of this blog we will present our view for an action plan. But first let’s try to understand what the issue is about.

It all starts with the diminishing return of dimensional scaling. This time it is about costs. Dimensional scaling requires continual improvements in lithography capability, and is primarily driven by the rapidly escalating cost of lithography, as illustrated by the following chart:

Now that the cost of lithography dominates the cost of Fabs and accordingly the cost of a finished wafer, the cost reduction associated with getting more dies per wafer (scaling) becomes neutralized by the higher cost of wafers. This was recently articulated in View Point in EE Times by Dr. Handel Jones and illustrated by the following chart.

Furthermore, pure foundry leader TSMC publicly showed the issue as seen in the following chart

And accordingly the following charts from NVIDIA present the same trend in a very clear way:

Moreover, another chart by NVIDIA shows the higher cost of wafers eating away at the benefits of dimensional scaling:

But this is clearly not TSMC’s fault. So why: "NVIDIA deeply unhappy with TSMC, claims 20nm essentially worthless"? And why would NVIDIA care? If the price will stop going down they should be happy to be able to charge more as long as their competitors need to do the same. And it is hard to believe AMD would see different curves from TSMC??

But careful review of the bullet slide above and the bullet slide below might reveal NVIDIA’s underlying  concerns.

Both slides indicate real concerns and reflect some form of panic.

It seems to me that the key words are “Virtual IDM”, which are the only highlighted words of the second bullet slide but do appear also in the first one.
“When business ($) gets in the way, apply “First principle”, the principle of one company, one virtual IDM company”. I was not aware of this “First principle”. I thought our first principle is open competition, and individual companies are supposed to work as such and not as one company I believe we have some laws - Antitrust - against acting as one company instead of individual company.
Yet, NVIDIA does have one strong IDM competitor - Intel. Could it be that Intel’s costs are different??

I don't know but it does remind me of a previous blog I wrote: Required Change in EDA Vendors’ Role and Reward vs. Scaling Yield. In that blog we tried to understand the implication of dimensional scaling on yield, and more specifically on the systematic yield losses which are design related. The following chart was presented then

In that blog we suggested that an IDM would have a significant advantage over the “partnership” of Fabless-Fab-EDA.

Looking again on the cost related chart one can clearly see NVIDIA pointing to the importance of yield. But I believe they should not blame just TSMC as it would seem to me that the EDA part is just as important.
NVIDIA, TSMC and the other fabless companies and partners (EDA, etc.) should strategically consider the issues associated with dimension scaling, which seem to strongly benefit the IDMs. Such strategic evaluation should include a serious look into the better alternative to dimensional scaling - the monolithic 3D, or as we call it, scaling Up!!!