Abstract
The radiation response of HfO2 films on a silicon substrate under gamma rays is studied in this article. HfO2 films with the thickness of 12.8 and 4.3 nm are prepared on a p-type silicon substrate by using the atomic layer deposition method, and the HfO2/Si MOS structure is irradiated under gamma rays with the total dose of 1.2/2.5/4 Mrad. The generation, transportation, and trapping characteristics of radiation induced charges are studied by using electronic, physical, and chemical methods. First, radiation induced oxide and interface trapped charge densities are found to be up to 1012 cm−2, and oxygen vacancies in HfO2 and Hf–Si metallic bonds at the HfO2/Si interface are dominant defects in the HfO2/Si system. Second, the leakage current through HfO2 increases with the increase in the radiation total dose and the crystallinity also increases after a large total dose of irradiation. Third, the valence band offset between HfO2 and Si is found to decrease slightly after irradiation. From the results, we can see that HfO2 is radiation resistant from the aspect of charge trapping even under a very large total dose of radiation, but the radiation induced leakage current and crystal structure change in the HfO2 film cannot be ignored. This provides a reference for microelectronic devices working in the space environment.
Highlights
Microelectronic technology has been developing according to “Moore’s law” for the past few decades, and the feature size of transistors has been shrinking to micrometer, submicrometer, and deep and very deep sub-micrometer
Alternative materials with larger permittivity, which can be called high-k materials, have been proposed to replace SiO2 as the gate dielectric, such as HfO2, Al2O3, ZrO2, and La2O3.2,3 High-k gate dielectrics used in MOS devices should have large permittivity and have a large bandgap and band offset with a silicon substrate to inhibit the charge tunneling through the dielectric/silicon interface, and the dielectric/silicon interface must have high thermodynamic stability to avoid the formation of silicates at the interface and good performance in electrical properties with low interface trap density
III A, we have found that the crystallinity of the HfO2 film is enhanced after a large total dose of irradiation owing to the local heating mechanism of nanoparticles of radiation energy, which would cause the increase in the leakage current through the HfO2 film as the new crystal grain boundaries can act as the current transport channels
Summary
Microelectronic technology has been developing according to “Moore’s law” for the past few decades, and the feature size of transistors has been shrinking to micrometer, submicrometer, and deep and very deep sub-micrometer. The developing roadmap of the semiconductor industry issued by ITRS (International Technology Roadmap For Semiconductors) specifies the size of the transistors, especially the size reduction of complementary metal–oxide–semiconductor (CMOS) devices.. The advanced CMOS technology requires scaling down of the gate length, channel width, and gate thickness, and the traditional gate materials cannot be used anymore. SiO2, which is widely used as a gate material in traditional MOS devices, is not applicable in advanced MOS devices. The leakage current and static power consumption would increase dramatically when the thickness of SiO2 decreases to lower than 2 nm, which would seriously impact the properties of MOS devices. Alternative materials with larger permittivity, which can be called high-k materials, have been proposed to replace SiO2 as the gate dielectric, such as HfO2, Al2O3, ZrO2, and La2O3.2,3 High-k gate dielectrics used in MOS devices should have large permittivity and have a large bandgap and band offset with a silicon substrate to inhibit the charge tunneling through the dielectric/silicon interface, and the dielectric/silicon interface must have high thermodynamic stability to avoid the formation of silicates at the interface and good performance in electrical properties with low interface trap density
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