Nanoscale and Spatial Variations Investigation of Etch Damage in Integrated Ferroelectric Capacitor Side Wall by Piezoresponse Force Microscopy

Abstract

The nanoscale and spatial variations etch damage in the typical integrated process ferroelectric capacitors (TIP-FeCAPs) and the innovated integrated process ferroelectric capacitors (IIP-FeCAPs) side wall is investigated by three-dimensional piezoresponse force microscopy (PFM). The topography of the IIP-FeCAP displays explicit and smooth profile with uniform compact columnar grains microstructure in the side wall, while the TIP-FeCAP side wall displays a coarse profile with irregular shape and two non-uniform grain size layers, and the desquamation of top electrode and some residue can be observed clearly. The three-dimensional nanoscale and spatial variations domain images in the IIP-FeCAP side wall exhibit that the side wall is the perfect ferroelectrics. The fine and clear nanoscale domain images, easily switched by an external voltage, similar dielectric constant and effective d à 33 values to the thin film indicate that the etch damage is minimized. The discrete domains that cannot be reversed by the external voltage, the lower effective d à 33 values and dielectric constants indicate that the nonferroelectric layers or grains, which are induced by the physical and chemical damage, exist in the TIP-FeCAP side wall. The investigating results also indicate that the degradation of electric properties in the etched ferroelectric thin film is owing to the presence of the nonferroelectric layer not the domain-wall pinning.

Leakage Current and Dielectric Properties of Integrated Ferroelectric Capacitor Etched in Non-Crystalline Phase

“…It is well documented that, for a given ferroelectric material, the electrical and reliability properties are strongly influenced by the integrated process, especially for the etching process [3,4]. Hence, to establish an integrated process being compatible with CMOS technique and without etching damage is important for ferroelectric capacitors applications, an innovated process has been attempted and ferroelectric properties of the capacitor were described formerly [2,[5][6][7], but other reliability properties are not investigated, such as leakage current, dielectric and time dependent dielectric breakdown etc. The leakage current is a sensitive diagnostic tool for monitoring material parameters, such as fatigue, retention, aging, power consumption, reliability and time dependent dielectric breakdown [8].…”