HfO2, the prevalent high-k gate dielectric for advanced CMOS transistors, can turn into ferroelectric after introducing appropriate doping and annealing procedure [J. Muller et al IEDM 2013]. This is a breakthrough for making ferroelectric-gate field-effect transistors (FeFETs), because unlike conventional perovskite ferroelectrics, such as PZT and SBT, HfO2 is completely compatible with CMOS processing, and possesses a large coercive field with a much smaller dielectric constant. The latter feature makes possible for a thin HfO2-based ferroelectric (<5 nm) to realize the same memory window as 200 nm of perovskites, and thus overcomes the fundamental road block of down scaling with the conventional perovskite ferroelectrics.
HfO2 Ferroelectrics (after Boscke et al Appl. Phys. Lett. 99, 102903 (2011))
In collaboration with Prof. Q. F. Xia’s group at University of Massachusetts, Amherst, we are optimizing Aluminum doped HfO2 for the application of Ferroelectric Flash and DRAM. Promising Ferroelectricity has been realized even in the preliminary trials.
Meanwhile, a Verilog-A model has been developed for DRAM and Flash chip design for HfO2 based FeFETs.
