Influence of HfAlO composition on memory effects of metal-oxide-semiconductor capacitors with Al2O3/HfAlO/Al2O3 layers and Pd electrode

The different charge trapping materials HfO2, HfAlO and Al2O3 have been compared electrically in metal-oxide-semiconductor capacitors with fixed Al2O3 tunneling and blocking layers and Pd-electrode. The capacitance–voltage hysteresis window, memory window, and stress-time dependent flat-band voltage shift increase with increasing the relative content of HfO2 in the charge trapping layer under the same measurement conditions. After programming at + 17 V for 0.1 s and erasing at − 17 V for 0.1 s, successively, the resulting memory window increases from 0.4 V to 3.8 V with increasing the content of HfO2 from 0% (Al2O3) to 100% (HfO2). However, the charge retention of the capacitors gradually worsens in the sequence of Al2O3, HfAlO and HfO2, which accords with the leakage characteristics of the capacitors. Our results reveal that HfAlO (A:H = 1:1) is a more promising charge trapping material than HfO2 and Al2O3 for polysilicon–oxide–nitride–oxide–silicon type memory applications. This is attributed to enough charge storage capacity, high thermal stability and medium dielectric constant.

► Al2O3, HfAlO and HfO2 are compared as charge trapping layer of memory device. ► The memory window increases with the HfO2 content in the layers. ► The charge retention worsens in the sequence Al2O3, HfAlO and HfO2. ► The underlying mechanisms are discussed.