Preparation And Properties Of Metal / Antiferroelectric Pzt Thin Films / Alumina / Silicon Structure Of The Antiferroelectric Memory

Ferroelectric random access memories (FRAM) have attracted considerable attentions in past years for the advantages of low power consumption, fast writing/reading speed, and cell size scalability for high-density memories, among which the metal/ferroelectric/ insulator/semiconductor field-effect transistor (FeFET) shows excellent characteristics of non-destructive readout and integrating compatibility with standard CMOS process. However, the data retention, which is one of most important issues for memory commercialization, is still poor for this kind of memory due to some material inefficiencies, such as the formation of high-density interface traps and charge injection into the ferroelectric film, which increases the leakage current to eliminate the depolarization field.The ultra-thin Al2O3 layer is found to be used as a tunnel switch for polarization reversal in antiferroelectric PZT/Al2O3 stacking layers, where Al2O3 layer is conductive during domain switching but restores to a high insular after the completion of polarization reversal. Al2O3 layer is highly conductive under the field to complete antiferroelectric (AF)-ferroelectric (FE) transition. As the external field is removed, the Al2O3 layer restores its previous insulation to impede FE-AF transition. Therefore, the high-field ferroelectric phase is maintained in the AF/Al2O3 bilayer. Meantime, a large depolarization field is generated across Al2O3. The direction of the depolarization field can be changed with the polarization reversal of the high-field ferroelectric phase, which is useful to modulate the electron potential of the carriers within the conductive channel of the underlying silicon with the structure of AF-FET to realize a large on/off switching current ratio. The depolarization field in AF-FET is far smaller than that in FRAM, which efficiently improves the ultimate data retention of the memory.In this paper, Au/Pb(Zr0.96Ti0.04)O3/Al2O3/n-Si field-effect transistors were prepared. A large memory window of 10 V was achieved under the writing voltage of 19 V and the high/low capacitance ratio is over 8:1. Consequent retention measurement shows the better performance of the transistor than the traditional FeFET for the memory application.