Electrical, optical, structural and chemical properties of Al₂TiO₅ films for high-к gate dielectric applications

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• 作者：Suresh Addepalli^a ; ^b ; ^{suresh181083@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Lakshmi Ganapathi Kolla^b ; ^{klganapathi@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Uthanna Suda^a ; ^{uthanna@rediffmail.com" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Al2TiO5 thin films ; Magnetron sputtering ; Structure ; Dielectric constant ; Optical properties
• 刊名：Materials Science in Semiconductor Processing
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：57
• 期：Complete
• 页码：137-146
• 全文大小：1529 K

文摘

In search of alternate gate dielectrics for electronic applications, aluminum titanate (Al₂TiO₅) thin films were deposited at room temperature by DC reactive magnetron sputtering and characterized for their structural, chemical, optical and dielectric properties. To realize the potentiality of these films for gate dielectric applications, we investigated the influence of annealing temperature on these properties. From X-ray photoelectron spectroscopic studies, it has been observed in the as-deposited films that the presence of Al³⁺ and Ti⁴⁺ oxidation states which correspond to Al₂O₃ and TiO₂ respectively. After annealing at 400 °C in oxygen ambient, the binding energies of Al 2p, Ti 2p and O 1s were shifted by ~1 eV and it remains constant with further increase of annealing temperature from 400 to 800 °C. This indicates the formation of an intermediate compound of Al₂O₃ and TiO₂. The extracted Al, Ti and O ratio was 2:1:5 which confirms the formation of Al₂TiO₅. XRD studies indicate that the as-deposited films were amorphous. After annealing at 400 °C, a diffraction peak (200) corresponds to aluminum titanate (Al₂TiO₅) started appearing, and its intensity increases with increase of annealing temperature. Metal-Oxide-Semiconductor (MOS) capacitors were fabricated and characterized to estimate the dielectric properties of the films. The as-deposited films shows high dielectric constant (к=27.0 at 100 kHz) and high leakage current density values (J=0.33 A/cm² at 1 MV/cm), high oxide traps (5.5×10¹³ cm⁻²) and high interface state density (1.5×10¹³ cm⁻² eV⁻¹). After annealing the films show improved dielectric constant and leakage current density values. The films annealed at 600 °C in oxygen ambient show better dielectric constant (к=11.2 at 100 kHz) and leakage current density values (J=2.23×10⁻⁹ A/cm² at 1 MV/cm), low oxide traps (1.4×10¹² cm⁻²) and low interface state density (7.1×10¹¹ cm⁻² eV⁻¹) compared with the other films. This suggests that the optimum annealing temperature is required to achieve better device properties.