| |
This week, at the 2022 International Electron Devices Meeting (IEEE IEDM 2022), imec, a world-leading research and innovation hub in nanoelectronics and digital technologies, demonstrates a lanthanum-doped hafnium-zirconate (La:HZO)-based ferroelectric capacitor with high endurance (1011 cycles), high final remnant polarization (2PR = 30µC/cm2 at 1.8MV/cm) and reduced wake-up. Researchers obtained this unique combination of properties by interfacial oxide engineering of the ferroelectric capacitor material stack. This high-performance, scalable, CMOS-compatible ferroelectric capacitor technology will be crucial for enabling FeRAM-based embedded and standalone memory applications.
FeRAM is a class of non-volatile memories with the potential to be used as an embedded memory or as a storage class memory (SCM), as such filling the gap between fast DRAM (~10ns access time) and highly dense NAND Flash. FeRAM has a DRAM-like 1-transistor-1-capacitor (1T1C) cell architecture, in which the capacitor’s dielectric is replaced with a ferroelectric material to achieve non-volatility. This ferroelectric material can be in two different polarization states (+P and -P) that can be reversed with an external electric field. For several years, much attention has gone to HZO as a ferroelectric since it is compatible with CMOS processing and scalable below 10nm.
Several characteristics come into play to qualify as an embedded or standalone SCM. Ideally, the capacitor of the FeRAM memory cell has a high endurance (>1012 switching cycles) in combination with a remnant polarization 2PR of 30-40µC/cm2 during the entire lifetime. So far, such a combination has never been reported because the capacitors suffer from either a prolonged wake-up (small 2PR in the beginning) or fast fatigue (rapidly degrading 2PR).
“By interfacial oxide engineering, adding both a 1nm TiO2 seed layer and 2nm Nb2O5 cap layer to the La:HZO layer, we achieved for the first time high endurance (1011 cycles) in combination with a final 2PR as high as ~30µC/cm2 (at an applied electric field of 1.8MV/cm) and good initial 2PR,” explains Jan Van Houdt, program director of ferroelectrics and fellow at imec. “Following an initial understanding, contact with the Nb2O5 capping facilitates the transition to the desired orthorhombic phase of HZO (i.e., the ferroelectric phase) by injecting oxygen into the HZO layer, while the TiO2 layer favors the preferred (002) grain orientation further resulting in a higher initial 2PR.” Alternatively, using a different precursor for depositing the HZO layer, a record-high 2PR of 66.5µC/cm2 at 3MV/cm was obtained, though with an endurance of 106 cycles.
“Now we have a high-performance, scalable, and CMOS-compatible ferroelectric capacitor technology that will bring us to the next exciting phase, i.e., moving from planar to 3D FeRAM capacitor structures leveraging atomic layer deposition (ALD) processes,” adds Jan Van Houdt. “This will increase the density needed to bring FeRAM memories to the market as a new embedded or standalone memory.”
About imec
Imec (imec-int.com) is a world-leading research and innovation center in nanoelectronics and digital technologies. Imec leverages its state-of-the-art R&D infrastructure and its team of more than 5,000 employees and top researchers, for R&D in advanced semiconductor and system scaling, silicon photonics, artificial intelligence, beyond 5G communications and sensing technologies, and in application domains such as health and life sciences, mobility, industry 4.0, agrofood, smart cities, sustainable energy, education, … Imec unites world-industry leaders across the semiconductor value chain, Flanders-based and international tech, pharma, medical and ICT companies, start-ups, and academia and knowledge centers. Imec is headquartered in Leuven (Belgium), and has research sites across Belgium, in the Netherlands and the USA, and offices in China, India, Taiwan and Japan. In 2021, imec's revenue (P&L) totaled 732 million euro.
Imec is a registered trademark for the activities of imec International (IMEC International, a legal entity set up under Belgian law as a “stichting van openbaar nut”), imec Belgium (IMEC vzw supported by the Flemish Government), imec the Netherlands (Stichting IMEC Nederland), imec Taiwan (IMEC Taiwan Co.), imec China (IMEC Microelectronics (Shanghai) Co. Ltd.), imec India (IMEC India Private Limited), imec San Francisco (IMEC Inc.) and imec Florida (IMEC USA Nanoelectronics Design Center Inc.).
|
jade.liu[.]imec.be 
