3D-IC: Two for one

Zvi Or-Bach, President & CEO of MonolithIC 3D Inc. blogs about upcoming events related to 3D ICs.

This coming October there are two IEEE Conferences discussing 3D IC, both are within an easy drive from Silicon Valley.

The first one is the IEEE International Conference on 3D System Integration (3D IC), October 2-4, 2013 in San Francisco, and just following in the second week of October is the S3S Conference on October 7-10 in Monterey. The IEEE S3S Conference was enhanced this year to include the 3D IC track and accordingly got the new name S3S (SOI-3D-Subthreshold). It does indicate the growing importance and interest in 3D IC technology.

This year is special in that both of these conferences will contain presentations on the two aspects of 3D IC technologies. The first one is 3D IC by the use of Through -Silicon-Via which some call -“parallel” 3D and the second one is the monolithic 3D-IC which some call “sequential.”

This is very important progress for the second type of 3D IC technology. I clearly remember back in early 2010 attending another local IEEE 3D IC Conference: 3D Interconnect: Shaping Future Technology. An IBM technologist started his presentation titled “Through Silicon Via (TSV) for 3D integration” with an apology for the redundancy in his presentation title, stating that if it 3D integration it must be TSV!

 Yes, we have made quite a lot of progress since then. This year one of the major semiconductor research organization – CEA Leti – has placed monolithic 3D on its near term road-map, and was followed shortly after by a Samsung announcement of mass production of monolithic 3D non volatile memories – 3D NAND.

We are now learning to accept that 3D IC has two sides, which in fact complement each other. In hoping not to over-simplify- I would say that main function of the TSV type of 3D ICs is to overcome the limitation of PCB interconnect as well being manifest by the well known Hybrid Memory Cube consortium, bridging the gap between DRAM memories being built by the memory vendors and the processors being build by the processor vendors. At the recent VLSI Conference Dr. Jack Sun, CTO of TSMC present the 1000x gap which is been open between  on chip interconnect and the off chip interconnect. This clearly explain why TSMC is putting so much effort on TSV technology – see following figure:

System level interconnect gaps

System level interconnect gaps

On the other hand, monolithic 3D’s function is to enable the continuation of Moore’s Law and to overcome the escalating on-chip interconnect gap. Quoting Robert Gilmore, Qualcomm VP of Engineering, from his invited paper at the recent VLSI conference: As performance mismatch between devices and interconnects increases, designs have become interconnect limited. Monolithic 3D (M3D) is an emerging integration technology that is poised to reduce the gap significantly between device and interconnect delays to extend the semiconductor roadmap beyond the 2D scaling trajectory predicted by Moore’s Law…” In IITC11 (IEEE Interconnect Conference 2011) Dr. Kim presented a detailed work on the effect of the TSV size for 3D IC of 4 layers vs. 2D. The result showed that for TSV of 0.1µm – which is the case in monolithic 3D – the 3D device wire length (power and performance) were equivalent of scaling by two process nodes! The work also showed that for TSV of 5.0µm – resulted with no improvement at all (today conventional TSV are striving to reach the 5.0µm size) – see the following chart:

Cross comparison of various 2D and 3D technologies. Dashed lines are wirelengths of 2D ICs. #dies: 4.

Cross comparison of various 2D and 3D technologies. Dashed lines are wirelengths of 2D ICs. #dies: 4.

So as monolithic 3D is becoming an important part of the 3D IC space, we are most honored to have a role in these coming IEEE conferences. It will start on October 2nd in SF when we will present a Tutorial that is open for all conference attendees. In this Monolithic 3DIC Tutorial we plan to present more than 10 powerful advantages being opened up by the new dimension for integrated circuits. Some of those are well known and some probably were not presented before. These new capabilities that are about to open up would very important in various market and applications.

In the following S3S conference we are scheduled on October 8, to provide the 3D Plenary Talk for the 3D IC track of the S3S conference. The Plenary Talk will present three independent paths for monolithic 3D using the same materials, fab equipment and well established semiconductor processes for monolithic 3D IC. These three paths could be used independently or be mixed providing multiple options for tailoring differently by different entities.

Clearly 3D IC technologies are growing in importance and this coming October brings golden opportunities to get a ‘two for one’ and catch up and learn the latest and greatest in TSV and monolithic 3D technologies — looking forward to see you there.


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One thought on “3D-IC: Two for one

  1. Leonard Schaper

    The gap between on and off-chip wiring capability is not new. See, for example, the 1984 paper by me and Wulf Knausenberger: “Interconnection Costs of Various Substrates – The Myth of Cheap Wire,” IEEE Trans. on Comp., Hybrids, and Manuf. Tech., Sep. 1984. This gap was the motivation for the development of high density Multichip Modules, now morphed into System in Package, as well as for 3D stacking. I believe the general rule we developed 30 years ago is still valid today: wire cost per unit length is approximately the same for many technologies, thus minimizing the total length of wire in a system will produce the lowest cost system.

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