Selective wet etching of atomic layer deposited ferroelectric hafnium zirconium oxide and hafnium oxide thin films Available to Purchase

The cointegration of conventional CMOS with high-k hafnium oxide (HfO₂) as the gate dielectric and ferroelectric field effect transistors (FeFETs) with hafnium zirconium oxide (HZO) as the ferroelectric gate dielectric has attracted substantial interest owing to several pragmatic applications, viz., embedded nonvolatile memory, neuromorphic computation, content addressable memories, etc. Such a cointegration requires patterning on HfO₂ and HZO thin films. In this study, selective wet etching of HZO and HfO₂ has been investigated. The etch rates of amorphous as-deposited HfO₂ and HZO films on the silicon substrate and etch resistance of the annealed HfO₂ film (crystalline) in hydrofluoric solution (HF) have been examined. It is observed that upon depositing HZO film over annealed HfO₂ (A-HfO₂), the as-deposited HZO layer inherits the crystallinity from underneath A-HfO₂ and, thus, becomes impervious to HF solution. By incorporating silicon oxide (SiO₂) as a barrier layer between A-HfO₂ and HZO (Si/A-HfO₂/SiO₂/HZO), the replication of crystallinity from underlying A-HfO₂ is prevented. Therefore, the HZO film (amorphous) along with the SiO₂ barrier layer can be etched in HF solution, while underneath A-HfO₂ is still unaffected. These findings can be applied toward realizing a novel selective wet etching of HfO₂/HZO, which is crucial for the cointegration of FeFET and traditional CMOS.