Application of fluorinated SiO2 interlayer dielectrics for ferroelectric memory

Abstract

Fluorine-doped silicon oxide (SiOF) as interlayer dielectric (ILD) was deposited over PZT capacitors by electron cyclotron resonance (ECR) chemical vapor deposition using SiF4 and N2O gases. In the conventional deposition of SiO2 ILD layer using hydrogen-contained source gases, the properties of ferroelectric capacitors are known to be degraded during the formation of SiO2 layer. In this study, we examined the degradation of electrical properties of SiOF-deposited PZT capacitors. The remnant polarization and leakage currents were not degraded after the deposition of SiOF. We observed that the fluorine atoms were not diffused into the metal electrode in both cases of the SiOF deposited PZT capacitors and post-deposition annealed capacitors. The SiOF films deposited in the high CF4 flow rate exhibited rough columnar structure on the metal electrodes. We can successfully deposit SiOF in a smooth morphology by introducing TiO2buffer layer or using the novel deposition method of changing the SiF4 flow rate, namely two-layer-deposition method.