A growing percentage of analog and mixed-signal ICs are being manufactured at foundries such as GLOBALFOUNDRIES.
When it comes to commentary about the semiconductor industry, we live in a big D (digital), little A (analog) world, with leading-edge digital garnering most of the attention. While analog and mixed-signal ICs account for about 15 percent of the chip industry’s revenues — $48 billion in 2016 — there is scant written about how they are manufactured. A principal reason is that, until recently, most analog parts were made on older technologies.
But that is changing.
Jim Feldhan, president of Semico Research (Phoenix), said mixed-signal chips are adding more digital content, which results in bigger chips, leading to using more advanced process technologies to keep chip size under control. “We used to talk about Big A, little D, but now there is a lot more digital circuitry being added,” he said.
The integration of analog and digital functions also leads to using 300mm wafers to control costs. “That encourages more foundry usage,” Feldhan said, adding that few analog IC companies can afford to build 300mm fabs.
Companies such as Texas Instruments have moved to 300mm manufacturing for high-volume analog parts, but very few analog companies have the capital to construct and fill a 300mm fab, he added.
The financial picture is changing in other ways as well. Analog companies once enjoyed enviable gross margins, Feldhan said, but increased competition has reduced average selling prices (ASPs) sharply over the last five years, from an analog ASP of 46 cents in 2011 to an average of 36 cents last year, according to Semico Research. That 25 percent drop in ASPs has caused more analog companies to put their investments into product development, and less into expensive capacity expansions.
“The analog companies are running into the same issues that the digital IC companies have been facing. Their margins are pretty tight, and so it is inevitable that they focus on product development and turn more to foundries,” Feldhan said.
GF has responded to these trends in two major ways: expanding analog and mixed-signal capacity, and accelerating its technology roadmap. The company’s 300mm fab in Chengdu, China, Fab 11, will add capacity for 180nm and 130nm production, as well as the 22nm fully depleted SOI (22FDX®) offering that is expected to see widespread mixed-signal usage. A 300mm fab in Singapore, Fab 7, has room for additional production of 130nm, 55nm, and upcoming 40nm analog/mixed-signal processes.
Mike Arkin, deputy director for Analog/Power Product Line at GF, said, “We see a need for more capacity. We expect to be growing substantially in the next three to five years, and when we look at our projections, the time is coming when we are going to need even more capacity. The expansion in China will allow GF to continue growing its analog and power business” for the 130nm BCDLite® and 180nm BCDLite offerings.
Arkin said many analog and mixed-signal IDMs are going fab-lite or fabless.
They are “looking for alternatives to continue their roadmaps without investing so much. Individual companies can’t stay on the treadmill like a foundry can, so we see more IDMs coming to us, reaching out, driving our roadmap and talking to us about designing into the GF processes.”
Also, more startups are targeting power management. “There are startups with brilliant ideas that no one has done. In some cases they come out of a university background and are looking for help on the process side,” Arkin said.
And, established companies that haven’t had a presence in power are designing solutions. “The companies that haven’t had a power presence need foundries, not just good mixed-signal processes today but an active roadmap to the future as well,” he said.
Adding Options and New Nodes
GF offers both a bipolar-CMOS-DMOS (BCD) process, which features deep-trench isolation and support for higher voltages as well as a lower cost, lower voltage BCDLite. (BCDLite is a patented process technology that is available only from GF).
The BCDLite process is more cost effective due to a less-complicated isolation structure, and is rated for lower voltages than traditional BCD. While BCD has a buried N layer and deep trench isolation, BCDLite uses a Triple Well isolation scheme as a cost reduction for customers which don’t need a high level of isolation.
Arkin said some companies could safely use a BCDLite process and reduce costs, compared with the BCD process.
“Many customers that use BCD are risk averse. They could use BCDLite, which operates up to 30 to 40 volts compared with 85V for BCD, and still have a robust design. For example, wireless charging could take advantage of BCDLite for consumer-oriented applications. Other industrial customers are thinking of using the automotive-grade BCD processes for assurance in high-temperature environments. There is not a hard line,” Arkin said.
BCDLite is a consumer-oriented process, but Arkin said “with automotive driving new applications customers are finding that they can take their consumer-use designs to the BCD automotive process (Grades 1 and 0) for an automotive version of their designs. This is analogous to the way traditional CMOS logic processes have been qualified and marketed for Automotive Gr1 applications.”
Expanding the Process Roadmap
Since 2010, GF has shipped a cumulative 2.3 million wafers of BCDLite. It is a “solid No. 2” in the analog foundry business, according to Arkin.
“GF is actively rolling out sub-100nm BCDLite this year,” Arkin said. “We are investing in bringing our analog and power expertise to even smaller nodes that complement our existing CMOS technologies.”
There is an array of other advances coming as well (see chart of process options), with SRAM and non-volatile memory options being offered at the 130nm BCD and BCDLite node, as well as high-voltage and ultra-high-voltage (UHV, up to 700 V) 180nm offerings.
Fewer Chips for Smaller Form Factors
Feldhan said as system companies seek to reduce the form factors of their phones and other consumer products, they are working with their IC suppliers to integrate more digital cores into their power-management products. “By putting fewer chips on the system board, that reduces the amount of reflow soldering required during assembly,” he added.
Arkin said governments around the world increasingly have been requiring less energy usage. “Things are moving faster than ten years ago, when power was flat. A watershed moment came in 2007 when the Energy Star® 4.0 added 80 PLUS® requirements for computers. That’s when the power management market began to change more to efficiency and technical differentiation, from just cost, cost, cost.”
The Future of BCDLite
“As BCDLite is incorporated into smaller process geometries, it becomes particularly interesting for battery-powered handheld devices, such as smart phones, smart watches, glucose monitors, and many others.”
To reduce the form factor of these systems, Arkin said the IC vendors are “working to integrate devices in new and interesting ways, adding features to the socket. Most of that feature enablement is adding digital functions on top of the analog or power.”
A next node BCDLite process, he said, is “ideal” for systems running on lithium-ion batteries. Since the analog functions in most cases don’t scale as strongly as digital, vendors adding digital functions on top of analog or power capabilities must deal with cost versus die size challenges. “When they are horizontally adding digital, they have to think about how much can they pack on a single die and still be cost effective,” Arkin said.
A major analog and mixed signal customer with strong digital design expertise has solutions which support the Force Touch interface, which offers a more complex or richer way for users to interact with the touch screen. But that comes at a premium, more tightly coupling increasing digital content with the analog functions.
With Force Touch and other “sensor sensitive” features, Arkin said “A next node BCDLite process would support more processing capability co-located with analog functions. GF is working on such a process in order to extend the sensor-sensitive capabilities even more.”
Automotive is another rapidly evolving market. Mark Granger, a vice president in GF’s automotive group, said BCD and BCDLite are figuring into new automotive applications. “Power management increasingly plays a very important role in EVs (electric vehicles) being able to provide the highest efficiency as they turn the battery charge into propulsion. There are a lot of places where that technology can be used for very efficient power delivery systems.”