The electrical properties of MIS capacitors with ALN gate dielectrics

We report on the characteristics of metal–insulator–semiconductor (MIS) capacitors with aluminum nitride (AlN) as the dielectric material. Using reactive magnetron sputtering, we deposited layers of AlN on 1–10 Ω cm p-type (1 0 0) silicon wafers. The deposition rates were investigated as a function of sputter pressure, power, gas composition, and substrate temperature. On films deposited over a range of sputter parameters, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) were performed indicating that optimal deposition conditions for best crystal quality and stoichiometry were a total pressure between 4 and 10 mT, a gas mixture of 85% nitrogen and 15% argon, and a substrate temperature ≈200°C. The films had a weak microcrystalline structure with the c-axis preferentially orientated parallel to the substrate normal. MIS capacitors were fabricated on silicon substrates with Ti/Au contacts. Current–voltage (IV) and capacitance–voltage (CV) measurements revealed breakdown fields of 4–12 MV/cm. Depending on the thickness, leakage current densities were between 10−10 and 10−3 A/cm2 at 1 V reverse bias, the interface charge density was ≤1013 cm2, and flat band voltages were from −10 to 2 V. The dielectric permittivity was between 4 and 11 for thick layers (≥100 Å) and decreased to values between 2 and 6 for thicknesses below 100 Å.