付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第23905号 / 工博第4992号 / 新制||工||1779(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 白石 誠司, 准教授 小林 圭 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Neste trabalho foram fabricados e caracterizados capacitores MOS com camada dielétrica de oxinitreto de silício de diferentes composição química, depositada pela técnica de PECVD a baixa temperatura, com o intuito de estudar suas propriedades dielétricas e de interface visando à aplicação deste material em dispositivos MOS e de filme fino. Os capacitores foram fabricados sobre lâminas de silício do tipo p que passaram pelo processo de limpeza química inicial, seguida da deposição da camada dielétrica, fotogravação, metalização e sinterização. Os filmes de SiOxNy, utilizados como camada dielétrica, foram depositados pela técnica de PECVD à temperatura de 320ºC variando os fluxos dos gases precursores de forma a obter filmes com diferentes composições químicas. Os capacitores MOS foram caracterizados por medidas de capacitância e corrente em função da tensão, de onde foram extraídas a densidade de estados de interface, a densidade de carga efetiva, constante dielétrica e campo elétrico de ruptura dos filmes. Os resultados mostraram uma variação linear da constante dielétrica do filme em função da concentração de nitrogênio, indo do valor de 3,9, correspondente ao dióxido de silício estequiométrico (SiO2) à 7,2 correspondente ao nitreto de silício estequiométrico (Si3N4). Também observamos que o nitrogênio é uma barreira eficiente à difusão de impurezas através do dielétrico. Porém, notamos uma grande dispersão de duas ordens de grandeza nos valores da carga efetiva (Nss) e de densidade de estados de interface (Dit). Por outro lado, controlando algumas variáveis de forma a manter constante o valor de Nss ( ~1012 cm-2), observamos uma variação de Dit em função da concentração de nitrogênio no filme, esta variação porém é pequena comparada com a dispersão de duas ordens de grandeza observada, que atribuímos assim a fatores externos. O menor valor obtido de Dit foi de 4,55.1010 eV-1.cm-2, que é ótimo para um filme obtido por PECVD, sem nenhum tratamento térmico e melhor que os reportados na literatura para dielétricos obtidos por técnicas que utilizam altas temperaturas (LPCVD-800ºC e oxinitretação térmica – 1100ºC). Assim, podemos concluir que a técnica de PECVD é promissora para a obtenção de dielétricos a baixas temperaturas. / In this work, MOS capacitors with different chemical composition silicon oxynitride insulating layer, deposited by PECVD technique at low temperature were fabricated and characterized, in order to study its dielectric and interface properties, seeking its aplication as insulating layer in MOS and thin films devices. The MOS capacitors were fabricated onto p-silicion wafers previously cleaned by a standard process, followed by the insulating layer deposition, photolitography, metalization and sinterization. The SiOxNy insulating layer was deposited by the PECVD technique at 320ºC changing the precursor gases flows to obtain films with different chemical compositions. The MOS capacitors were characterized by capacitance and current vs. voltage measurements, from where the interface state density (Dit), the effective charge density (Nss), the dielectric constant (k) and the film electrical breakdown field (Ebd) were extracted. The results showed a dielectric constant varying linearly as a function of the films nitrogen concentration, going from a value of 3.9, corresponding to stoichiometric silicon dioxide (SiO2) to a value of 7.2, corresponding to stoichiometric silicon nitride film (Si3N4). We also observed that nitrogen is an efficient diffusion barrier against contaminants. However, a large dispersion, about two orders of magnitude, in the effective charge and in the interface state density was observed. On the other hand, controlling some variables so as to keep the Nss value constant (~1012 cm-2) we observed a Dit variation as a function of the film nitrogen concentration, this variation is small when compared with the observed dispersion of two orders of magnitude, thus attributed to external factors. The smallest obtained Dit was 4.55.1010 eV-1.cm-2, which is unexpected for a PECVD film without any anealing process and is better than the values reported in the literature for dielectrics obtained at high temperatures techniques (as LPCVD – 800ºC and thermal oxynitridation – 1100ºC). Therefore, we can conclude that the PECVD technique is promising for obtaining low temperature dielectrics.

Neste trabalho foram fabricados e caracterizados capacitores MOS com camada dielétrica de oxinitreto de silício de diferentes composição química, depositada pela técnica de PECVD a baixa temperatura, com o intuito de estudar suas propriedades dielétricas e de interface visando à aplicação deste material em dispositivos MOS e de filme fino. Os capacitores foram fabricados sobre lâminas de silício do tipo p que passaram pelo processo de limpeza química inicial, seguida da deposição da camada dielétrica, fotogravação, metalização e sinterização. Os filmes de SiOxNy, utilizados como camada dielétrica, foram depositados pela técnica de PECVD à temperatura de 320ºC variando os fluxos dos gases precursores de forma a obter filmes com diferentes composições químicas. Os capacitores MOS foram caracterizados por medidas de capacitância e corrente em função da tensão, de onde foram extraídas a densidade de estados de interface, a densidade de carga efetiva, constante dielétrica e campo elétrico de ruptura dos filmes. Os resultados mostraram uma variação linear da constante dielétrica do filme em função da concentração de nitrogênio, indo do valor de 3,9, correspondente ao dióxido de silício estequiométrico (SiO2) à 7,2 correspondente ao nitreto de silício estequiométrico (Si3N4). Também observamos que o nitrogênio é uma barreira eficiente à difusão de impurezas através do dielétrico. Porém, notamos uma grande dispersão de duas ordens de grandeza nos valores da carga efetiva (Nss) e de densidade de estados de interface (Dit). Por outro lado, controlando algumas variáveis de forma a manter constante o valor de Nss ( ~1012 cm-2), observamos uma variação de Dit em função da concentração de nitrogênio no filme, esta variação porém é pequena comparada com a dispersão de duas ordens de grandeza observada, que atribuímos assim a fatores externos. O menor valor obtido de Dit foi de 4,55.1010 eV-1.cm-2, que é ótimo para um filme obtido por PECVD, sem nenhum tratamento térmico e melhor que os reportados na literatura para dielétricos obtidos por técnicas que utilizam altas temperaturas (LPCVD-800ºC e oxinitretação térmica – 1100ºC). Assim, podemos concluir que a técnica de PECVD é promissora para a obtenção de dielétricos a baixas temperaturas. / In this work, MOS capacitors with different chemical composition silicon oxynitride insulating layer, deposited by PECVD technique at low temperature were fabricated and characterized, in order to study its dielectric and interface properties, seeking its aplication as insulating layer in MOS and thin films devices. The MOS capacitors were fabricated onto p-silicion wafers previously cleaned by a standard process, followed by the insulating layer deposition, photolitography, metalization and sinterization. The SiOxNy insulating layer was deposited by the PECVD technique at 320ºC changing the precursor gases flows to obtain films with different chemical compositions. The MOS capacitors were characterized by capacitance and current vs. voltage measurements, from where the interface state density (Dit), the effective charge density (Nss), the dielectric constant (k) and the film electrical breakdown field (Ebd) were extracted. The results showed a dielectric constant varying linearly as a function of the films nitrogen concentration, going from a value of 3.9, corresponding to stoichiometric silicon dioxide (SiO2) to a value of 7.2, corresponding to stoichiometric silicon nitride film (Si3N4). We also observed that nitrogen is an efficient diffusion barrier against contaminants. However, a large dispersion, about two orders of magnitude, in the effective charge and in the interface state density was observed. On the other hand, controlling some variables so as to keep the Nss value constant (~1012 cm-2) we observed a Dit variation as a function of the film nitrogen concentration, this variation is small when compared with the observed dispersion of two orders of magnitude, thus attributed to external factors. The smallest obtained Dit was 4.55.1010 eV-1.cm-2, which is unexpected for a PECVD film without any anealing process and is better than the values reported in the literature for dielectrics obtained at high temperatures techniques (as LPCVD – 800ºC and thermal oxynitridation – 1100ºC). Therefore, we can conclude that the PECVD technique is promising for obtaining low temperature dielectrics.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21110号 / 工博第4474号 / 新制||工||1695(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 藤田 静雄, 教授 白石 誠司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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A new high-k dielectric material, i.e., zirconium-doped tantalum oxide (Zr-doped TaOx), in the form of a sputter-deposited thin film with a thickness range of 5-100 nm, has been studied. Important applications of this new dielectric material include the gate dielectric layer for the next generation metal-oxide-semiconductor field effect transistor (MOSFET). Due to the aggressive device scaling in ultra-large-scale integrated circuitry (ULSI), the ultra-thin conventional gate oxide (SiO2) is unacceptable for many practical reasons. By replacing the SiO2 layer with a high dielectric constant material (high-k), many of the problems can be solved. In this study, a novel high-k dielectric thin film, i.e., TaOx doped with Zr, was deposited and studied. The film’s electrical, chemical, and structural properties were investigated experimentally. The Zr dopant concentration and the thermal treatment condition were studied with respect to gas composition, pressure, temperature, and annealing time. Interface layer formation and properties were studied with or without an inserted thin tantalum nitride (TaNx) layer. The gate electrode material influence on the dielectric properties was also investigated. Four types of gate materials, i.e., aluminum (Al), molybdenum (Mo), molybdenum nitride (MoN), and tungsten nitride (WN), were used in this study. The films were analyzed with ESCA, XRD, SIMS, and TEM. Films were made into MOS capacitors and characterized using I-V and C-V curves. Many promising results were obtained using this kind of high-k film. It is potentially applicable to future MOS devices.

A new high-k dielectric material, i.e., zirconium-doped tantalum oxide (Zr-doped TaOx), in the form of a sputter-deposited thin film with a thickness range of 5-100 nm, has been studied. Important applications of this new dielectric material include the gate dielectric layer for the next generation metal-oxide-semiconductor field effect transistor (MOSFET). Due to the aggressive device scaling in ultra-large-scale integrated circuitry (ULSI), the ultra-thin conventional gate oxide (SiO2) is unacceptable for many practical reasons. By replacing the SiO2 layer with a high dielectric constant material (high-k), many of the problems can be solved. In this study, a novel high-k dielectric thin film, i.e., TaOx doped with Zr, was deposited and studied. The film’s electrical, chemical, and structural properties were investigated experimentally. The Zr dopant concentration and the thermal treatment condition were studied with respect to gas composition, pressure, temperature, and annealing time. Interface layer formation and properties were studied with or without an inserted thin tantalum nitride (TaNx) layer. The gate electrode material influence on the dielectric properties was also investigated. Four types of gate materials, i.e., aluminum (Al), molybdenum (Mo), molybdenum nitride (MoN), and tungsten nitride (WN), were used in this study. The films were analyzed with ESCA, XRD, SIMS, and TEM. Films were made into MOS capacitors and characterized using I-V and C-V curves. Many promising results were obtained using this kind of high-k film. It is potentially applicable to future MOS devices.