TCAD Simulation And X-ray Radiation Effects Of Pt/Bi_3.15Nd_0.85Ti₃O₁₂/Pt Ferroelectric Capacitors

The effects of ionizing radiation on integrated circuit are traditionally a concernfor devices intended for the space use. The memories are the core of space devicesbecause of a mounts of data should be holded. Ferroelectric memory can meet thespecifications mentioned above due to robust radiation hardness and non-volatile.Ferroelectric-gate-field-effect-transistors （FeFET） have many advantages such ashigh-density integration, low power dissipation, non-destructive read out operationand simple structure. FeFET having long data retention were found. Since then,FeFET became a real candidate of practical nonvolatile memories. As large remanentpolarization, lead-free and fatigue-free ferroelectrics, neodymium （Nd） dopedBi_3.15Nd_0.85Ti₃O₁₂（BNT） is currently regarded as one of the more promising candidatematerial for FeFET. If FeFET were envisaged for space applications, it would beobviously necessary to characterize and understand their electrical behavior underhigh-energy radiations especially X-ray.1. BNT ferroelectric thin films with different dopants were grown onPt/Ti/SiO₂/Si（100） substrates by chemical solution deposition （CSD） and thencrystallized by rapid thermal annealing at700℃for3min.A single phase of thebis-muth-layered perovskite structure is observed with （00l） and （117） mixedorientations. Highly c-axis oriented neodymium-modified bismuth titanate BNT hadthe largest remanent polarization. The remanent polarization （2Pr） is15μC/cm²（5V）and leakage current is1×10-5A/cm²（5V）, which suggest that ferroelectric thin filmcan meet requirements of the device. To examine the material properties, the thinfilms were characterized by traditional X-ray diffraction （XRD） before radiation.2.6-circle diffractometer combined with a ferroelectric analyzer, which enabledin situ electrical measurements at BL14B beam lines of SSRF. The P-E of irradiationdeformed and P-E shift depended on the imprint of prior ferroelectric films. Theremnant polarization （2Pr） decreased14%after2.50×10⁶Gy X-ray irradiation. Thus2Prrecovered to95%of its pre-irradiation value at the maximum dose of4.57×10⁹Gy,which indicates that the BNT ferroelectric films have excellent resistance to ionizingradiation. Effects of X-ray irradiation combine with either bias voltage that reduce theinsulating properties of ferroelectric thin film and make it easy to be breakdown. Theleakage current increase to10-4A/cm2after with1.04×10⁷Gy irradiation. The cycles of fatigue are promoted after irradiation. The fatigue-induced damage can be removedby irradiation with5.49×10⁶Gy.3. The ferroelectric capacitance device structure was modeled. And remnantpolarization were simulated by changing the parameters of gate voltage andirradiation dose. The P–E loops of irradiation shift depended on the imprint of priorFeCAPs. By simulation, the greater ratio of the applied voltage while the smaller thechange of P–E loops instead. The P–E curve constantly shifted along the horizontalpositive direction of E and negative direction of P during irradiation. P–E presented adistortion in the tail. The effects of ionizing radiation are simulated by TCAD and thesimulation results agreed with experimental results well.