Chapter 3 - Size Effect of Ferroelectric and High Permittivity Thin Films

Abstract

This chapter discusses the size effects of ferroelectric and high permittivity thin films. Ferroelectric and dielectric property degradation with decreasing film thickness is the most critical issue in scaling these properties down to the nanometer-size range. In particular, property degradation of polycrystalline film is of greatest concern to devices such as ferroelectric random access memories (FeRAM) and film capacitors for decreasing the operating voltage and increasing the capacitance, respectively. The chapter introduces previous data and recent progress on the ‘size effect’ and discusses the recent results on polycrystalline films. Capacitors play an important role in many key devices such as gate dielectrics in field effect transistors (FET), dynamic random access memories (DRAM). To progress these devices, thin films of materials with high dielectric constant are required to achieve the necessary large capacitance. These materials have also been investigated as capacitance materials for DRAM devices. However, thin film research into materials with dielectric constants higher than 200 has found little commercial application in films of this thickness.