Last Tuesday was the SEMI’s annual Strategic Materials Conference (SMC). The opening keynotes were given by Gary Patton, the CTO of GlobalFoundries, and Mark Thirsk, Managing Partner of Linx Consulting. This year it was held in the Computer History Museum (which always makes the commute interesting since you have to fight with a zillion people going to the Googleplex along the same road).
Gary made something explicit that I sort of half-knew. Prior to 90nm, pretty much all the advances in semiconductor process came from scaling. Then we were down to gate oxide just 3 atoms thick and we needed to switch to materials and other sorts of innovation: strained silicon, High K metal gate, FinFET and more.
As we innovated in materials we spread our attention all over the periodic table, from a dozen elements in the 1980s (H, B, N, O, F, Al, P, Cl, Ar ,As ,Sb, and most of all Si) to about 60, half the table. Who even knew what Hafnium was before it became important in high K dielectrics?
There will be lots of innovation needed in devices in the future (gate-all-round, carbon nanotubes, III-V devices…) but there is a more urgent problem that our interconnect is running into the wall. The interconnect itself is protected by so many liners and caps that there is very little actual interconnect left and so the resistance is too high. There is lots of innovation going on in this area:
One materials challenge is that supply is often very concentrated in just one or two suppliers. For instance, one thing that several people commented on during SMC was availability of neon (Ne). The price has gone up 10X. It turns out that it all comes from eastern Ukraine, which you can’t have failed to notice is not the most stable part of the world right now. Plus, semiconductor just doesn’t move the needle that much. When we switched to copper interconnect the non-specialsit copper suppliers rubbed their hands with glee, before they discovered that annual consumption might be the same as the electrical wiring of a large building.
Mark pointed out that one result of this is that there is a lot of M&A (and spinouts of specialty divisions) in the materials industry. It is also important to remember that almost 3/4 of all 300mm capacity is in Asia (as of 2015). As a result there are also a large number of new suppliers entering in Asia, especially in China with its desire to become more self-sufficient in semiconductor manufacturing and the surrounding ecosystems. China is investing $160B over 10 years, with loans to supply-chain participants growing in importance.
So near-term trends that Mark and Gary both pointed out for devices and, especially, interconnect:
- High-mobility channel InGaAs n-channel and Ge p-channel FinFETs
- CVD Co improves Cu wetting and extends Cu gap fill (cobalt is a thin conformal layer that repairs discontinuities)
- 5nm Ru:TaN liner followed by ECD copper (plated films have larger grain size)
But each of these conceals dozens of smaller innovations needed to make the simple-sounding one-sentence summary work in an high-volume fab. For example, cobalt in the metalization requires materials and chemicals from a number of different specialized suppliers:
- PVD targets
- CVD precursors
- Electro/electroless plating chemistries
- CMP slurries for Co
- Co recess processes – Dry/Wet chemistry approaches
- Co compatible cleans (wets)
In summary, here is a couple of decades of material innovation, and the future innovation that is being developed, summarized in a single diagram:
But looming ahead is perhaps the biggest barrier of all. We are atomic level deposition and processes. But atoms still don’t scale. That is something no amount of innovation is going to change.