Effect of Rapid Thermal Annealing on the Properties of $\mathbf{Al}_{2}\mathbf{O}_{3}$ Films Grown on $\mathbf{SiC}$ via Plasma-Enhanced Atomic Layer Deposition

Silicon carbide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{SiC})$</tex> is currently a promising semiconductor material in the field of power devices due to its wide band gap, high thermal conductivity, and high breakdown field strength. However, the thermal oxidation method used to prepare the gate oxide layer on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}$</tex> results in a high defect density at the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}$</tex> MOS interface. To address this issue, an innovative approach is to use high-k materials instead of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiO}_{2}$</tex> as the gate dielectric layer for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}$</tex> MOS. In this study, AI <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${}_{2}\mathrm{O}_{3}$</tex> was chosen due to its large dielectric constant and wide energy band offset from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}. \text{Al}_{2}\mathrm{O}_{3}$</tex> films were fabricated on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}$</tex> epitaxial wafers by plasma-enhanced atomic layer deposition, with aluminum used as the metal electrode. The samples were also subjected to rapid thermal annealing under N2 atmosphere at different temperatures. Spectroscopic ellipsometry was used to measure the refractive index and extinction coefficient, and the optical bandgap was fitted to be 6.19 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{eV}$</tex>, meeting the requirements for gate dielectrics in power devices. Atomic force microscopy characterized the prepared films, showing low roughness. Electrical tests were conducted on different samples, with the breakdown voltage of the untreated samples reaching 32.4 V. After annealing at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$400^{{\circ}}\mathrm{C}$</tex>, the breakdown voltage increased, but it began to decrease as the temperature continued to rise. The flat-band voltage and effective oxide charge density <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{N}_{\text{eff}})$</tex> were obtained from C-V test curves. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{\text{eff}}$</tex> of the untreated samples reached <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$7.77\times 10^{12}\text{cm}^{-3}$</tex>, which varied after annealing, with the annealed samples at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$400^{\circ}\mathrm{C}$</tex> achieving the optimal level. In conclusion, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiC}/\text{Al}_{2}\mathrm{O}_{3}$</tex> MOS capacitors show great potential, and their electrical properties can be further optimized through annealing.