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▲ [18p-E202-10] Thickness Dependence on Crystalline Quality and Residual Stresses of AlN Films Deposited by Pulsed DC Reactive Sputtering
Keywords:AlN, Sputtering, Thickness
AlN is expected to be one of candidate materials as a substrate for AlGaN based UV-LED owing to its wide band gap energy, and low lattice mismatch with AlGaN. Previously, the authors reported the polarity inversion of AlN layer grown on a nitride a-plane sapphire substrate[1] using pulsed DC reactive sputtering by varying the oxygen partial pressures (PO2) [2]. AlN films sputtered at low PO2 of 5.0×10-10-5.6×102 Pa (at Ptotal of 105 Pa) had nitrogen (−c)-polarity. The best crystalline quality for nitrogen (−c)-polar AlN film was achieved at PO2 of 5.0×100 Pa. Aluminum (+c)-polar AlN was grown at the high PO2 of 9.4×103 Pa. However, the AlN film sputtered at the high PO2 had high residual tensile stress of 17 GPa along the c-axis and compressive stress of 10 GPa along the a-axis. AlN film sputtered at the high PO2 also had a polycrystalline at the top part of AlN film. The purpose of this research is to investigate the thickness dependence of crystalline quality and residual stresses of AlN films deposited by pulsed DC reactive sputtering.
AlN films were sputtered on a nitride a-plane sapphire substrate at 823 K and 600 W of pulsed DC power with a frequency of 100 kHz and duty ratio of 60%. The oxygen partial pressure (PO2) was kept at 9.4×103 Pa in the Ar-50 vol%N2 mixture gases. The total pressure (Ptotal) was kept at 0.6 Pa. The thickness of AlN films were varied at 200, 300, and 1300 nm. The AlN film with two layer structures was also fabricated with a first 200 nm-thick AlN sputtered at PO2 of 9.4×103 Pa following by 1100 nm-thick AlN sputtered at PO2 of 5.0×100 Pa simultaneously to maintain crystalline part until the AlN film reach the thickness of 1300 nm.
References
1) H. Fukuyama, et al.: J. Appl. Phys. 107 (2010) 043502-1- 043502-7.
2) M. Noorprajuda, et al.: Abstracts of 12th International Conference on Nitride Semiconductors, Strasbourg, (2017), A 1.49.
AlN films were sputtered on a nitride a-plane sapphire substrate at 823 K and 600 W of pulsed DC power with a frequency of 100 kHz and duty ratio of 60%. The oxygen partial pressure (PO2) was kept at 9.4×103 Pa in the Ar-50 vol%N2 mixture gases. The total pressure (Ptotal) was kept at 0.6 Pa. The thickness of AlN films were varied at 200, 300, and 1300 nm. The AlN film with two layer structures was also fabricated with a first 200 nm-thick AlN sputtered at PO2 of 9.4×103 Pa following by 1100 nm-thick AlN sputtered at PO2 of 5.0×100 Pa simultaneously to maintain crystalline part until the AlN film reach the thickness of 1300 nm.
References
1) H. Fukuyama, et al.: J. Appl. Phys. 107 (2010) 043502-1- 043502-7.
2) M. Noorprajuda, et al.: Abstracts of 12th International Conference on Nitride Semiconductors, Strasbourg, (2017), A 1.49.