In the spring of 2012, STMicroelectronics announced the company would be manufacturing ST-Ericsson’s next-generation (and very successful) NovaThor ARM-based smartphone/tablet processors using 28nm FD-SOI process technology. With first samples coming out this fall, ASN talks to Jean-Marc Chery, Executive Vice President, General Manager Digital Sector, Chief Technology & Manufacturing Officer, STMicroelectronics about the manufacturing process and the expected results.
Advanced Substrate News (ASN): You taped out ST-Ericsson’s 28nm FD-SOI NovaThor in the beginning of September. Did that go as you expected?
Jean-Marc Chery, STMicroelectronics (JMC): 28nm FD-SOI is a pretty exciting technology, allowing better design optimization (for higher speed and power efficiency) than traditional bulk technologies, still reusing most of manufacturing bricks of planar 28nm LP technology and the same design flow and methodology.
Adoption of 28nm FD-SOI for ST-Ericsson’s NovaThor has not introduced any major difficulty in its design, and the FD-SOI version has been taped out shortly after the Low-Power bulk version. Of course special care has been dedicated to further optimize power, exploiting FD-SOI exceptional flexibility and low-power capabilities.
On the manufacturing side, FD-SOI does not introduce additional complexity: on the contrary, process steps are reduced and thus cycle time.
ASN: Can you talk about the results you expect to see or have seen in the chip? Is there anything about it, or perhaps about the ARM core in particular, that makes it particularly well-suited to FD-SOI? Is there anything about the transistor back-biasing capability (which enables significant performance enhancements and power optimization) in the design that makes it challenging to manufacture?
JMC: The wide supply range (ranging from 1.2V down to 0.6V) with excellent performance, and extended back-biasing capability (allowing dynamic modulation of the transistor threshold voltage) offered by 28nm FD-SOI technology have allowed us to exploit the ARM implementation to offer an improved maximum frequency and reach an overall power reduction for the various operating modes of the SoC.
About back biasing, this is a standard feature of FD-SOI technology with no particular challenges for manufacturing. Of course, its dynamic usage to optimize operating points for power (or speed) requires an appropriate device architecture to fully benefit from it.
ASN: In the press, STMicroelectronics has indicated that the 28nm FD-SOI has better power and performance than the industry’s first-gen bulk 22nm FinFETs. Would you say that your choice of FD-SOI puts you in a position of strength, in that you’ll have the mobile industry’s leading technology for 28nm and a choice of mature technologies at 14nm?
JMC: 28nm FD-SOI technology is a unique offer in the SOC industry, allowing the introduction of a fully-depleted technology with a low-cost solution and in a timely manner.
28nm FD-SOI is a planar technology derived from 28nm LP bulk technology, with the same design rules and allowing direct layout reuse (or simplified porting) of basic building blocks and IPs, benefiting from inheriting their maturity level. Also on the manufacturing side, 28nm FD-SOI technology uses the same equipment as Low Power bulk CMOS in a simplified process flow. In ST/Crolles facility we are reaching yield levels comparable to 28nm LP bulk ones, proving that FD-SOI process does not introduce major yield detractors.
A smooth library and IP migration flow coupled with rapid availability for manufacturing is driving the success of this 28nm technology.
Looking at the technology roadmap, the same incremental step for the 14nm node is under development and is on track.
ASN: The plan was to start production in your fab in Crolles, then shift to GlobalFoundries for high-volume production in 2013 — is this still the schedule? From a manufacturing standpoint, what does it take to get a fab ready for FD-SOI production (does it take much longer than a typical bulk scaling transition)? Are there any special tools or other preparations needed?
JMC: For manufacturing, 28nm FD-SOI technology uses the same toolset as for 28nm LP bulk. Process development is complete, and ST/Crolles fab is now working to bring yield at production levels and complete the qualification of the technology, as done for any other.
Phase-in of the technology at GlobalFoundries is planned to start Q1 2013, with process qualified and with production level yield foreseen for Q4 2013.
ASN: Let’s talk about the Crolles fab for a minute. Although it may be considered small compared to the big pure-play foundries, some aspects you share with the big foundries – like a large mix of product and advanced automation, right?
JMC: Crolles’ technology mix encompasses Advanced CMOS 28/40 nm, Imaging Sensors, embedded Non Volatile Memories starting at 55nm for Microcontroller and Analog on CMOS 110nm. This mix optimizes very well the accumulated assets we have invested in this Fab toward 4500 wafers week capacity over the next two years.
ASN: How do you see the impact of STMicroelectronics’s decision on the industry? Do you expect others to follow? Will other companies be able to leverage your technology at your foundry partners?
JMC: We would like very much for others to follow us. Through GlobalFoundries, ST is making its FD-SOI technology available to anyone in the microelectronics industry. The ST wide set of silicon-proven 28nm foundation libraries and IPs, encompassing not only basic libraries (std-cells, srams, I/Os) but also complex AMS IPs, is also available to be licensed to those customers aiming for quick access to the technology.