20-nm threshold breached ST starts IC manufacturing with new 18-nm FD-SOI process and ePCM

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18 instead of 40 nanometers, phase-change memory instead of flash: The new FD-SOI production process promises faster, more energy-efficient chips, while the non-volatile ePCM memory helps reduce the footprint of the ICs. ST plans to deliver the first STM32 microcontrollers based on the new process to selected customers in the second half of the year 2024.

STMicroelectronics (ST) is expanding its semiconductor manufacturing to include an advanced CMOS manufacturing process based on 18-nm FD-SOI technology (Fully Depleted Silicon On Insulator) with embedded phase change memory (ePCM, Embedded Phase Change Memory). "For ST, this is a very important step," Remi El-Ouazzane, President of the Microcontrollers, Digital ICs and RF Products Group, emphasized the significance of the announcement during the press conference. The European chip manufacturer developed the new process technology together with the South Korean contract manufacturer Samsung Foundry. ST had already announced microcontrollers based on FD-SOI and ePCM in 2019 and manufactured a 16-Mbit ePCM array in a 28-nm process.

FD-SOI is a very interesting CMOS process technology where a very thin, depleted silicon layer – forming the transistor's channel – is separated from the underlying silicon substrate by another thin, insulating oxide layer. This technique, known as "buried oxide" or BOX for short, prevents electrons from flowing out of the channel into the substrate. The buried oxide layer also reduces the parasitic capacitance between source and drain, which in turn allows for higher switching speeds and thus higher performance. Additional advantages include improved electrostatic properties of the transistors, as well as lower noise and higher gain (up to +15 dB) compared to bulk CMOS technologies.

Thanks to the inherently power-saving FD-SOI technology, it's possible to precisely adjust (bias) the operating point of the integrated transistors to achieve a balance between computing power and energy efficiency that suits the application. According to El-Ouazzane, this allows for a "leap in computing power and energy efficiency for embedded processing applications." At the same time, the use of ePCM enables better utilization of the chip area, "meaning more memory and a higher degree of integration of analog and digital peripherals."

Advantages of the technology

In the press conference, El-Ouazzane and Ricardo De Sa Earp, Executive Vice President of the General-Purpose Microcontroller SubGroup and the Microcontrollers, Digital ICs and RF Products Group, provide some details. Accordingly, 18-nm FD-SOI with ePCM significantly improves the key performance indicators compared to the 40-nm technology currently used by ST for embedded non-volatile memory (eNVM): The ratio of computing power to power consumption (performance-to-power) is more than 50 percent better, the 2.5 times higher density of non-volatile memory (NVM) allows for larger on-chip memory, and the same area can integrate three times more digital peripherals like AI and graphic accelerators and advanced security features. Furthermore, the 18-nm FD-SOI technology improves the noise figure by 3 dB, allowing wireless MCUs to excel with higher radio performance.

Especially for use in an industrial environment, it is important that the components can be operated at 3 V, for instance, to supply analog functions such as power management, reset systems, clock sources, and digital/analog converters. “It is the only technology under 20 nm that supports this capability,” says De Sa Earp. In automotive applications, the FD-SOI technology has already distinguished itself with robust high-temperature operation, extensive insensitivity to radiation, and secure data storage capabilities. The manager is confident that the 18-nm process technology will also function extremely reliably.

Advantages for developers and customers of STM32 microcontrollers

El-Ouazzane explains that ST has already provided its customers with FD-SOI and PCM technologies for automotive and aerospace applications. “Now we are taking the next step to make the benefits of these technologies accessible to developers of industrial applications, starting with our next-generation STM32 microcontrollers.” These “next-generation” components will be shipped to selected customers from the second half of 2024, with volume production scheduled for the second half of 2025.

The new 18-nm technology enables the production of a new class of powerful, energy-saving, and wireless MCUs, explains De Sa Earp. This would also include new ultra-low-power devices. The larger possible memory sizes would support the growing need for edge AI processing, multi-protocol RF stacks, over-the-air updates, and advanced security features. "The high performance and large memory sizes give developers the opportunity to use highly integrated and more cost-effective microcontrollers in their designs instead of microprocessors."

De Sa Earp hints, "The first microcontroller based on this technology will be based on the most advanced Arm Cortex-M core." This core offers more enhanced computing power for machine learning and digital signal processing applications. It also includes fast and flexible external memory interfaces, advanced graphic capabilities, and numerous analog and digital peripheral units. "Moreover, it features the advanced, certified security functions that have already been introduced in ST's latest MCUs." (me)