Lower electrodes for Pb(Zr,Ti)O3 (PZT) used in ferroelectric random access memories must have good electrical conductivity and must interact as little as possible with the PZT film. We have evaluated a number of bottom electrodes for use with PZT films deposited by ion beam sputter deposition These electrodes include Pt, Pt/Ti, RuO2, ReOP3, and C0Si2/Si3N4, all on SiO2/Si; and TiN and Pt on MgO. Films were studied by XTEM, Auger depth profiling, X-ray microanalysis, and XRD. Important issues for platinum include: a) microstructure (porous for magnetron sputtered Pt); b) rapid lead diffusion through porous Pt; c) adhesion (improved by raising deposition temperature or by adding a titanium layer); and d) hillock formation (related to compressive stress in platinum). RuO2 has good conductivity and has no apparent interfacial layer with PZT. Each of the remaining substrates has drawbacks: CoSi2 forms a surface oxide; ReO3 has poor phase stability; TiN oxidizes and loses conductivity.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Control and Systems Engineering
- Ceramics and Composites
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry