Ultrahigh-temperature microwave annealing of Al⁺- And P ⁺-implanted 4H-SiC

In this work, an ultrafast solid-state microwave annealing has been performed, in the temperature range of 1700-2120 °C on Al⁺- and P^--implanted 4H-SiC. The solid-state microwave system used in this study is capable of raising the SiC sample temperatures to extremely high values, at heating rates of ∼600 °C/s. The samples were annealed for 5-60 s in a pure nitrogen ambient. Atomic force microscopy performed on the annealed samples indicated a smooth surface with a rms roughness of 1.4 nm for 5 × 5 μm² scans even for microwave annealing at 2050 °C for 30 s. Auger sputter profiling revealed a <7 nm thick surface layer composed primarily of silicon, oxygen, and nitrogen for the samples annealed in N₂, at annealing temperatures up to 2100 °C. X-ray photoelectron spectroscopy revealed that this surface layer is mainly composed of silicon oxide and silicon nitride. Secondary ion mass spectrometry depth profiling confirmed almost no dopant in diffusion after microwave annealing at 2100 °C for 15 s. However, a sublimation of ∼100 nm of the surface SiC layer was observed for 15 s annealing at 2100 °C. Rutherford backscattering spectra revealed a lattice damage-free SiC material after microwave annealing at 2050 °C for 15 s, with scattering yields near the virgin SiC material. Van der Pauw-Hall measurements have revealed sheet resistance values as low as 2.4 kΩ/□ for Al⁺-implanted material annealed at 2100 °C for 15 s and 14 Ω/□ for the P⁺-implanted material annealed at 1950 °C for 30 s. The highest electron and hole mobilities measured in this work were 100 and 6.8 cm²/V s, respectively, for the P⁺- and Al⁺-implanted. materials.