Large Ferroelectric Polarization of TiN/Hf₀․₅Zr₀․₅0₂ Capacitors Due to Stress-Induced Crystallization at Low Thermal Budget

We report on atomic layer deposited Hf₀․₅Zr₀․₅0₂ (HZO)-based capacitors which exhibit excellent ferroelectric (FE) characteristics featuring a large switching polarization (45 μC/cm²) and a low FE saturation voltage (~1.5V) as extracted from pulse write/read measurements. The large FE polarization in HZO is achieved by the formation of a non-centrosymmetric orthorhombic phase, which is enabled by the TiN top electrode (TE) having a thickness of at least 90nm. The TiN films are deposited at room temperature and annealed at 400 ⁰C in an inert environment for at least 1 min in a rapid thermal annealing system. The room-temperature deposited TiN TE acts as a tensile stressor on the HZO film during the annealing process. The stress-inducing TiN TE is shown to inhibit the formation of the monoclinic phase during HZO crystallization, forming an orthorhombic phase that generates a large FE polarization, even at low process temperatures.