Ultra-thin Gate Oxides Prepared by Tensile-Stress and Direct-Current Superimposed with Alternating-Current Cathode Anodization
Date Issued
2009
Date
2009
Author(s)
Lee, Chia-Jui
Abstract
In advanced technology of semiconductor, MOS devices are scaled down to deep-submicrometer region. As a result, thickness of silicon oxide also scales down. Based on the International Technology Roadmap for Semiconductor (ITRS), the equivalent oxide thickness (EOT) should be scaled to 0.75 nm in 2012. It is too leaky for ultra-thin gate silicon oxide so high-k films are introduced to solve the problem. However, silicon dioxide is still of interest due to the existing problems in high-k gate dielectrics. In the thesis, we introduce an alternative way to directly grow SiO2 on silicon substrate, i.e., anodization. The advantage of anodization includes good control of the thickness of ultra-thin gate oxides as well as the process can be held at room temperature. In addition, we improve the quality of oxide by applying mechanical tensile stress on silicon wafer and giving direct current superimposed with alternating-current (DAC) during anodization. The electrical characteristics and reliability of different oxide thickness prepared by tilted cathode anodization system will be discussed. From the experimental results, we demonstrate the quality of gate oxides would be improved in electrical characteristics and reliability test by either tensile-stress or DAC. Finally, conclusions and some other suggestions for future work about this thesis were given.
Subjects
Anodization (ANO)
Metal-oxide-semiconductor (MOS)
Tensile-stress oxidation
Type
thesis
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