Effect of ZrO₂ Seed Layer in Hf_0.5Zr_0.5O₂ Ferroelectric Device Fabricated by PEALD

FeRAM (Ferroelectric Random Access Memory) is one of the next-generation memories and has a non-volatile characteristic through the electrical polarization of a ferroelectric. Therefore, research is being conducted as a memory to replace DRAM (Dynamic Random Access Memory), which has a problem of information volatility.<br/>Among the HfO₂-based ferroelectrics, HfO₂ doped with Zr exhibits ferroelectricity in a wide composition range. The best ferroelectricity is measured when the doping concentration is about 50%. Recently, it has been reported that the ferroelectric properties of Hf_xZr_1-xO₂ (HZO) films are increased by forming a ZrO₂ seed layer.<br/>In this research, an Hf_0.5Zr_0.5O₂ ferroelectric layer was formed using PE-ALD (Plasma Enhanced Atomic Layer Deposition). A metal-ferroelectric-metal (MFM) type capacitor was fabricated using TiN with a thickness of 50nm as the Top and Bottom electrodes. First, to analyze the characteristics of the HZO ferroelectric layer according to various lamination methods, the total number of ALD cycles was fixed at 120 cycles, and the HfO₂-ZrO₂ super cycles were set to 4 types: 5cycle-5cycle, 10cycle-10cycle, 20cycle-20cycle, and 60cycle-60cycle. After setting to, each super cycle was repeated 12, 6, 3, and 1 time to form a ferroelectric layer. Second, to investigate the characteristics according to the heat treatment temperature, the specimens in which the ferroelectric layer was deposited using PE-ALD were heat-treated at 450/550/650°C for 30 seconds in a N₂ atmosphere using RTA (Rapid Thermal Annealing). Finally, four types of MFM capacitors were fabricated without or with the Top/Bottom/Top and Bottom seed layers. Electrical characteristics were analyzed using Keithley 4200A-SCS, and the properties of endurance, I-E curve, and Hysteresis curve were compared. In addition, the crystallinity and component ratio of the ferroelectric thin films were analyzed through XRD, XPS, and TEM.