Hf- and Zr-based alkaline earth perovskite dielectrics for memory applications

We investigate a group of Hf- and Zr-based dielectrics crystallizing in the cubic perovskite structure for memory applications. The dielectrics are deposited in the form of thin layers (<30nm) onto TiN substrates using molecular beam deposition. Prepared layers are characterized with respect to their dielectric constant, crystallization temperature as well as some aspects of leakage current flowing across group-II hafnates and zirconates. We show that dielectric constants of about 40 can be achieved for BaHfO"3, BaZrO"3, and SrHfO"3 on TiN substrates. On an example of BaHf"1"-"xTi"xO"3, we demonstrate that a significant gain in the dielectric constant and capacitance density can be achieved by partial substitution of Hf atoms by Ti in BaHfO"3. This process leads also to a reduction of the crystallization temperature of the layers.