Abstract
About 20 Å of hafnium were deposited on silicon substrates using the electron beam evaporation technique. Two types of samples were investigated. In one type, the substrate was kept at the ambient temperature. After the deposition, the substrate temperature was increased to 100, 200, and 300∘C. In the other type, the substrate temperature was held fixed at some value during the deposition. For this type, the substrate temperatures used were 100, 200, 300, 400, 500, 550, and 600∘C. The samples were characterized in situ by the technique of X-ray photoelectron spectroscopy. No trace of elemental hafnium is observed in the deposited overlayer. Also, there is no evidence of any chemical reactivity between the overlayer and the silicon substrate over the temperature range used. The hafnium overlayer shows a mixture of the dioxide and the suboxide. The ratio of the suboxide to dioxide is observed to be more in the first type of samples. The spectral data indicate that hafnium has a strong affinity for oxygen. The overlayer gets completely oxidized to form HfO2 at substrate temperature around 300∘C for the first type of samples and at substrate temperature greater than 550∘C for the second type.
Highlights
In the semiconductor industry, the success of metal-oxidesemiconductor structures depends largely on the “near perfect” SiO2/Si interface
As the MOS devices are scaled down to the 65 nm technology mode, the thickness of the gate dielectric needs to be less than 2 nm [1, 2]
We have studied the formation of hafnium dioxide and hafnium suboxide as a function of the substrate temperature
Summary
The success of metal-oxidesemiconductor structures depends largely on the “near perfect” SiO2/Si interface. As the MOS devices are scaled down to the 65 nm technology mode (physical gate length equal to 45 nm), the thickness of the gate dielectric needs to be less than 2 nm [1, 2] In this regime, the major concerns are related to dramatic increase in direct tunneling leakage current and reliability issues associated with the SiO2 films [3]. The formation of the suboxide depends on the substrate temperature and the depositing conditions. No systematic investigation on the formation of hafnium suboxide and hafnium dioxide as a function of depositing conditions has been carried out. In this investigation, we have studied the formation of hafnium dioxide and hafnium suboxide as a function of the substrate temperature. The formation of the dioxide and the suboxide indicates that hafnium has a strong affinity for oxygen
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