Preparation and evaluation of SrBi2Ta2O9 thin films prepared by originally developed sol-gel method

Ferroelectric thin film memory has been proposed as new nonvolatile memory. Ferroelectric SrBi₂Ta₂O₉ (SBT) thin films have fatigue-free characteristics and high potential for low-voltage operation. We have prepared SBT films using an originally developed sol-gel method and investigated crystallization mechanism. Role of Bi is the most important factor to determined ferroelectric properties. Excess Bi lowered crystallization temperature, but it deposited at triple point after crystallization and deteriorated process resistance for high-density semiconductor memories. We have prepared new SBT thin films with only 5% excess Bi by originally developed sol-gel method. Moreover, recently we have investigated original methods for lower-temperature and thinner-film formation. For lowering crystallization temperature, we used hydrolyzed sol-gel solution and developed new process. For thinner-film formation, we used excimer laser annealing and succeeded to prepare very thin SBT films, 60-nm thickness, with good ferroelectricity and low leakage current. Our SBT films have many advantages for ferroelectric memories