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Atomic scale engineering of HfO2–based dielectrics for future DRAM applications

  • Modern dielectrics in combination with appropriate metal electrodes have a great potential to solve many difficulties associated with continuing miniaturization process in the microelectronic industry. One significant branch of microelectronics incorporates dynamic random access memory (DRAM) market. The DRAM devices scaled for over 35 years starting from 4 kb density to several Gb nowadays. The scaling process led to the dielectric material thickness reduction, resulting in higher leakage current density, and as a consequence higher power consumption. As a possible solution for this problem, alternative dielectric materials with improved electrical and material science parameters were intensively studied by many research groups. The higher dielectric constant allows the use of physically thicker layers with high capacitance but strongly reduced leakage current density. This work focused on deposition and characterization of thin insulating layers. The material engineering process was based on Si cleanroom compatible HfO2 thin filmsModern dielectrics in combination with appropriate metal electrodes have a great potential to solve many difficulties associated with continuing miniaturization process in the microelectronic industry. One significant branch of microelectronics incorporates dynamic random access memory (DRAM) market. The DRAM devices scaled for over 35 years starting from 4 kb density to several Gb nowadays. The scaling process led to the dielectric material thickness reduction, resulting in higher leakage current density, and as a consequence higher power consumption. As a possible solution for this problem, alternative dielectric materials with improved electrical and material science parameters were intensively studied by many research groups. The higher dielectric constant allows the use of physically thicker layers with high capacitance but strongly reduced leakage current density. This work focused on deposition and characterization of thin insulating layers. The material engineering process was based on Si cleanroom compatible HfO2 thin films deposited on TiN metal electrodes. A combined materials science and dielectric characterization study showed that Ba added HfO2 (BaHfO3) films and Ti added BaHfO3 (BaHf0.5Ti0.5O3) layers are promising candidates for future generation of state of the art DRAMs. In especial a strong increase of the dielectric permittivity k was achieved for thin films of cubic BaHfO3 (k~38) and BaHf0.5Ti0.5O3 (k~90) with respect to monoclinic HfO2 (k~19). Meanwhile the CET values scaled down to 1 nm for BaHfO3 and ~0.8 nm for BaHf0.5Ti0.5O3 with respect to HfO2 (CET=1.5 nm). The Hf4+ ions substitution in BaHfO3 by Ti4+ ions led to a significant decrease of thermal budget from 900°C for BaHfO3 to 700°C for BaHf0.5Ti0.5O3. Future studies need to focus on the use of appropriate metal electrodes (high work function) and on film deposition process (homogeneity) for better current leakage control.show moreshow less

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Author: Piotr T. Dudek
URN:urn:nbn:de:kobv:co1-opus-22775
URL:http://opus.kobv.de/btu/volltexte/2011/2277/
Document Type:Doctoral thesis
Language:English
Year of publication:2011
Tag:Atomic Scale Engineering; Dielectrics; HfO2-based materials; High-k materials; XPS
Number of pages:106
Faculty/Chair:Fakultät 1 MINT - Mathematik, Informatik, Physik, Elektro- und Informationstechnik / FG Angewandte Physik und Halbleiterspektroskopie
Institution name at the time of publication:Fakultät für Mathematik, Naturwissenschaften und Informatik (eBTU) / LS Angewandte Physik / Sensorik
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