Study On Ferroelectric Hafnium Oxide Thin Films

Since its first use as a high-k gate dielectric layer in the Penryn chip of Intel Company in 2007,HfO₂ has been widely adopted as the industry standard gate dielectric thin film for advanced metal-oxide-semiconductor field effect transistors?MOSFET?.Many studies on high-k gate dielectrics have indicated their high compatibility with CMOS technology.The first report of ferroelectricity in doped HfO₂in 2011 triggered interest in the application of these thin films to ferroelectric memories,which may overcome the scaling problem of presently used commercial lead zirconate titanate?PZT?and barium titanate?BTO?ferroelectric memories?FERAM?.HfO₂ based ferroelectric capacitors can also use CMOS compatible TiN electrode materials.These prominent characteristics make HfO₂-based FERAM a promising candidate for future nonvolatile memories.However,so far there are still two main endurance problems that impede the application of HfO₂ based ferroelectric memory devices.One is the breakdown phenomenon during extensive cycling.The second problem is the fatigue phenomenon.The remanent polarization of HfO₂ ferroelectric thin films decays rapidly after 10⁵ to10⁶ cycles,which reduces the read-write window gradually,finally causing the device to fail.To address the above problems,in this paper,we do study on yttrium doped ferroelectric hafnium oxide thin films.We discuss the physical mechanism behind the fatigue phenomenon systematically and explore the possibility of application in radiation working condition.In the second chapter,we introduce the experiment method and the mechanism of fatigue phenomenon in ferroelectric hafnium oxide thin films.We also propose the domain pinning mechanism caused by carrier injection.In the third and fourth chapter,we introduce the characteristics of ferroelectric HfO₂ based memories in the radiation working condition.We firstly prove its stability in the gamma ray and proton radiation environment,which provide the possibility for this material as the aerospace level memory material.