The breakthrough includes back-end-of-line (BEOL) integration of TiN/HfO2:Si/TiN ferroelectric capacitors as small as 0.16 µm², and solder reflow compatibility for the first time for this type of memory.
The results were reported in a paper, “16kbit HfO2:Si-based 1T-1C FeRAM Arrays Demonstrating High Performance Operation and Solder Reflow Compatibility”, at this year's IEDM conference.
“This ultralow-power, fast, high-endurance, CMOS-compatible BEOL FeRAM memory uses a new HfO2-based ferroelectric material that also is more environmentally friendly than PZT,” said Laurent Grenouillet, an author of the paper. “This demonstration will pave the way toward embedded non-volatile memories at more advanced technology nodes.”
The highly versatile technology is expected to be interesting for embedded applications such as Internet of Things (IoT) devices and wearables.
Since ferroelectricity was first discovered in HfO2-based films a decade ago, much of the ferroelectric memory research that has been published has focused on the materials themselves or on large-area, single-device performance.
In the CEA-Leti work, the team observed zero bit failure at the array level, with the memory window fully open down to 2.5 V programming voltage, and ultrafast switching speed down to four nanoseconds. Array-level endurance was also said to be promising at up to 10 million cycles, as was array-level data retention at 125 °C for 104s (three hours).
“HfO2-based ferroelectric capacitors change the paradigm of FeRAM,” Grenouillet added. “Unlike PZT-based ferroelectric memories, HfO2-based FeRAM are fully CMOS compatible, and scalable to advanced nodes, in part because HfO2-based ferroelectric films are very thin, typically 10nm thick. They are also lead-free, which is less detrimental to the environment.”
The work was supported by the EU’s 3eFERRO Consortium project that was designed to produce new ferroelectric material Hf(Zr)O2 that makes FeRAM a competitive NVM candidate for IoT applications.