Preparation of SiNx passivation films for PZT ferroelectric capacitors at low substrate temperatures by catalytic CVD

The feasibility of SiNx films prepared by catalytic chemical vapor depositi on (Cat-CVD) at low substrate temperatures was studied for passivation of f erroelectric non-volatile random access memories (FRAMs). First, the influe nce of exposure to active NH3 gas generated by the heated catalyzer on ferr oelectric Pb(Zr0.52T0.48)O-3 (PZT) capacitors was examined. Second, SiNx fi lms were prepared by Cat-CVD at low substrate temperature, at which the fer roelectricity of PZT is not degraded. The ferroelectric degradation of PZT capacitors due to exposure to active NH3 gas strongly depended on the sampl e temperature and the ambient. However, no degradation occurred when keepin g the sample temperature below 200 degreesC at an ambient of 1.3 Pa by cont rolling the heat flow from the catalyzer. By adjusting the flow rate ratio of SiH4/NH3, the refractive index of SiNx films measured by ellipsometry wa s controlled to be 2.0 for various substrate temperatures. The dense SiNx f ilms, which were resistive to oxidation in air exposure, were prepared at 2 00 degreesC at an ambient of 1.3 Pa. The ferroelectric PZT capacitors were not degraded during SiNx film deposition using the Cat-CVD method. The resu lts appeared to demonstrate the feasibility of application of Cat-CVD films to passivation of ferroelectric devices. (C) 2001 Elsevier Science B.V. Al l lights reserved.