Fin-shaped MONOS flash memory cells are ‘world first’

Believed to be the first of its kind, split-gate metal-oxide nitride oxide silicon (SG-MONOS) flash memory cells employing fin-shaped transistors have been developed by Renesas Electronics. The cells are for use in microcontrollers with on-chip flash memory; they have a circuit line width of 16 to 14nm or finer.

SG-MONOS technology is reliable for use in automotive applications. The company already produces 40nm MCUs using this technology, and 28nm MCUs are under development. The successful development shows promising scalability of the SG-MONOS technology to 16 or 14nm process nodes and beyond.

Advances in automotive automation, such as advanced driver assistance systems (ADAS), and the smart society connected via the IoT have created demand for more advanced MCUs fabricated using finer process technology. At the 16 or 14nm logic process, Fin FETs (field effect transistors), i.e. transistors with a finned structure, are commonly used to improve performance and reduce power consumption to overcome the scaling limit of conventional planar transistors.

However, a fin structure for embedded flash memory can become a big challenge depending on the structure of the flash memory. Charge trap flash memory has superior charge retention characteristics, compared with floating gate memory, and a proven track record in automotive MCUs requiring a high level of reliability.The memory functional material is formed on the surface of the silicon substrate, making them comparatively easy to be extended into a three-dimensional fin structure, says the company. (In contrast, floating-gate flash memory cells have a complex structure, making them difficult to integrate it into a fin structure.)

Another advantage of SG-MONOS over the floating-gate structure, is that the memory cell structure is maintained after replacing the dummy polysilicon gate electrode with the metal gate electrode (the process used to manufacture advanced logic CMOS devices with high dielectric gate insulators and metal gate electrodes).

Renesas claims to be the first to develop a fin-structure SG-MONOS flash memory with highly scalability, for use in high-performance and highly reliable MCUs of 16 or 14nm process nodes and beyond.

It will announce details of the newly developed embedded flash memory technology at International Electron Device Meeting 2016 (IEDM 2016), held in San Francisco.


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