Experts At The Table: Retrofitting Older Process Nodes

First of two parts: Addressing power issues; 3D stacking effects and re-use; economic vs. technology decisions; new competition from startup foundries.

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By Ed Sperling
Low-Power Engineering sat down with Walter Ng, vice president of the IP ecosystem at GlobalFoundries; Vishal Kapoor, vice president of marketing for SoC realization at Cadence; Naveed Sherwani, CEO of Open-Silicon; John Heinlein, vice president of marketing at ARM; and Jeff Lukanc, director of engineering at IDT. What follows are excerpts of that conversation, which was held in front of a live audience at the Global Technology Conference in Santa Clara, Calif.

LPE: What is the definition of a mainstream process node these days and why are older nodes so important?
Heinlein: We’re thinking of mainstream as 55nm and older. That’s where a lot of the high volume is. Even though it’s sexy to talk about the leading edge, last year about 75% of ARM’s royalties came from cores that were developed in 2006 and earlier. About 3 million of the 6 million cores we shipped were ARM 7.
Ng: From a manufacturing standpoint, the volumes are at 65nm. From that node it’s moving from 55nm and 40nm, but that’s still the bulk of the industry. A lot of companies are doing some very cool things that are very relevant today at those nodes. Even with some of the biggest companies, a lot of the volume is at 65nm. It’s what pays the bills. If you have 200mm capacity, those fabs are completely depreciated.

LPE: How about for the tools? Does the mainstream part of the market really pay the bills?
Kapoor: From an EDA perspective, 65nm pays the bills as much as 28nm and 20nm.

LPE: Is everything still following Moore’s Law? If a company is designing at 65nm, does it necessarily move to the next node?
Sherwani: We look at everything from networking to consumer applications. Some customers need the latest technology. But there are others who are at 0.18 (microns) and thinking about 0.13, and maybe they don’t to go there. The velocity of that move is segment-specific.
Lukanc: The mainstream for production is 0.13, but a lot of the new designs are ramping to 65nm. We’re looking at older technology and combining new things through integration. There may be a call management IC with a 30-volt option at 0.13 or 0.18, which allows the unique combination of analog and digital management on one chip. We can re-use some of the older technologies.

LPE: There’s a lot of investment in older processes these days. Why?
Sherwani: I visited about 10 fabs in China and I was surprised that none of them had 65nm processes. Most didn’t even have 90nm processes.
Ng: If you look at what’s driving a lot of technology today, it’s the consumer market. And that’s very cost-conscious. If you can’t take advantage of the latest technology, then you look at where your given application makes sense. Cost is very much a factor that customers consider at each process node. And for us, we have to find ways to keep investments in fabs relevant to our customers. We have a big focus on high voltage and power management. We have to find ways to add value on top of baseline logic, which is a commodity at this point.
Heinlein: If you look at smart phones, everyone is always focused on the processor and the high-end chip. But alongside those are the power management controllers and display drivers and RF/mixed signal. Another area for derivative value-added processes that Walter (Ng) mentioned is low leakage. When you get to 65nm leakage is a problem. There are ultra-low leakage variants and high-voltage variants coming out at the high end and the low end, so people can put those into applications that can run on a coin-cell battery for 10 years. To complement that there are ultra-dense libraries that bring the cost and the leakage down and which are suited very well to these kinds of applications.

LPE: If you develop a chip at 180nm and the process changes to low leakage or low power, does it yield the same?
Ng: The strategy in developing these new processes or modules on top of derivatives is to preserve the investment that was made earlier. It takes advantage of the proven solutions that are already there. When we originally developed those processes, at that time they were leading-edge processes. As you get much more volume using those processes, the manufacturing window becomes quite tight. You could probably tighten up the bit cells. But it’s a business tradeoff whether you re-invest in that or not. The yields are just as good.

LPE: What happens to the tools and the IP that was developed?
Heinlein: For the most part it all works. If you think about 180nm, nobody cared about leakage because it wasn’t an issue. Now, when people look at 180nm, they do care about leakage and power management. So we’re putting that back into 180nm.
Kapoor: The innovation at the leading nodes is going to drive benefits at the older nodes. You drive it back in terms of products, but you also drive it back in terms of design techniques. We developed a 28nm PHY, and we were challenged to do it differently because it’s for a leading node. Today we’re applying what we’ve learned back to 40nm and 65nm.
Lukanc: The best tools are developed at the leading nodes, but you may want to characterize older libraries for low power and power management.

LPE: If you improve an existing technology at an older node, can you charge more for it?
Lukanc: Yes. In general, what we’re offering is value-added solutions. In some cases we offer value-added solutions that are low power.

LPE: Will it be essential for older processes to be updated when we get into stacked die as a way of decreasing the overall power budgets and physical effects?
Sherwani: The answer is different for each area. There is no single, simple answer to that.
Kapoor: For a long time our industry has looked at the technology piece rather than the economics. The answer is, it depends. Can you get more value out of an older node? Yes. The economics will drive the longevity of nodes and what you can get out of them. But we cannot talk about the value of older nodes unless we invest in the newer ones.
Lukanc: If you have an existing product, you can look at the option of integrating oscillators or an EEPROM or something else on top of it to reduce the system cost. There are lot of things you can do in a package to reduce the overall cost, but you have to look at the total system cost. You may be offering a smaller footprint to the customer, but they may not be getting value out of that.
Heinlein: If you look at mixed signal and RF design at the leading-edge nodes, it’s really tough to get the transistor variation to be complementary to the analog. There’s a point at which it’s too hard, and in that case a heterogeneous 3D package makes sense.
Kapoor: With 3D ICs there’s a technical capability about whether you can marry different die. But you also have to look at it from a system capability. When you look at tablets, where the SoCs are talking in very high bandwidth to memory, that makes sense. The technology by itself won’t be an answer. You need to find out where it makes sense to use it.

LPE: Is investment in older process nodes an arms race that favors the big foundries?
Sherwani: The specialty foundries being built in places like China have nothing to do with companies like GlobalFoundries and TSMC. They will ship a lot of silicon. Over the next 10 years a lot of the analog silicon will be shipping out of China using all older nodes.
Kapoor: Those boutique fabs are certainly making investments in areas in which they specialize.
Ng: You have to continue to make fabs relevant and to drive a good margin. A big impetus for us in developing modules on top of our processes is that you do get the second- and third-tier foundries coming in and taking the floor out of the base logic price. That’s difficult for us to compete with. So we’re looking at where to add value and how to win a good percentage of market share. We have our investments in 200mm. We will continue to invest there.
Heinlein: We definitely see lots of specialty processes at the smaller players. We work with them and enable them. But once it gets to a certain point in the market they we work with the big players.

LPE: Will it become a battle of who has the deepest pockets?
Sherwani: The good thing about older nodes is that the investment needed is miniscule compared with the tens of billions of dollars at advanced nodes. A lot more players can be relevant at older nodes. At 14nm I don’t think there will be more than three or four players.
Ng: The incremental investment to bring up these value-added modules is nothing compared to the investment at the leading edge. The other side is that the equipment manufacturers are a leading component of the cost at the leading edge. At the mature nodes, you’re not buying a lot of new, expensive tooling.
Lukanc: That happens on the product development side, as well. To do a 100 million-gate design requires a certain amount of tools and people and mask costs. At the older technologies mask costs are quite cheap. And if you’re re-using technology and adding to it, you can keep NRE low so return on investment is quite high. You need to take advantage of mainstream older nodes as well as more aggressive nodes.
Ng: And most times our relationship with most of the leading-edge companies span multiple nodes.
Kapoor: At 14nm there are 5 or 10 customers. As a foundry, you have to worry about how you’re going to get the rest of the industry in. The economics even for the companies that can afford it aren’t that great. So you’re going to see continued innovation even at the older nodes.
Ng: A major part of the foundries’ concern is up and down the supply chain. It’s not just the fabs. It’s the tools, the support for IP providers, and packaging solutions. That’s a challenge we have to address as an industry.