Growth, dielectric properties, and memory device applications of ZrO2 thin films

Abstract In the advancement of complementary metal-oxide-semiconductor device technology, SiO 2 was used as an outstanding dielectric and has dominated the microelectronics industry for the last few decades. However, with the recent size downscaling, ultrathin SiO 2 is no longer suitable. ZrO 2 has been introduced as a high- k dielectric to replace SiO 2 . This paper reviews recent progress of ZrO 2 thin films as dielectric layers for volatile dynamic random access memory (DRAM) applications and as a gate dielectric for CMOS devices. Materials and electrical properties of ZrO 2 films obtained by different deposition methods are compared. The effects of different top and bottom electrodes, and different doping elements, on ZrO 2 dielectric properties are described. Applications discussed include the use of ZrO 2 in Ge and SiGe nanocrystal-embedded nonvolatile flash memory devices. ZrO 2 films as charge trapping layers in SOZOS (poly-Si/SiO 2 /ZrO 2 /SiO 2 /Si) and TAZOS (TaN/Al 2 O 3 /ZrO 2 /SiO 2 /Si) based nonvolatile flash memory stacks, and bipolar, unipolar, and nonpolar ZrO 2 -based resistive switching memory devices are also briefly discussed. The impact of electrode materials, metal nanocrystals, metal implantation, metal doping, metal layers, and oxide ion conductor buffer layer on resistive switching properties and switching parameters of emerging ZrO 2 -based resistive switching memory devices for high speed, low power, nanoscale, nonvolatile memory devices are briefly reviewed. A roadmap of the applications of ZrO 2 thin film in future low power, nanoscale microelectronic device applications is realized from this review.