Real-time control of AlN incorporation in epitaxial Hf sub(1-x)Al sub(x)N using high-flux, low-energy (10-40eV) ion bombardment during reactive magnetron sputter deposition from a Hf0.7Al0.3 alloy target

• Published in: Acta materialia 2011-01, Vol.59 (2), p.421-428
• Main Authors: Howe, B M, Sammann, E, Wen, J G, Spila, T, Greene, JE, Hultman, L, Petrov, I
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum nitride; Deposition; Epitaxy; Ion bombardment; Magnetron sputtering; Multilayers; Real time; Switching
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2010.08.023

The AlN incorporation probability in single crystal Hf sub(1-x)Al sub(x)N (0 0 1) layers is controllably adjusted between similar to 0% and 100% by varying the ion energy (E i) incident at the growing film over a narrow range, 10-40eV. The layers are grown on MgO(0 0 1) at 450 degree C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a Hf0.7Al0.3 alloy target in a 5%-N2/Ar atmosphere at a total pressure of 20mTorr (2.67Pa). The ion to metal flux ratio incident at the growing film is constant at 8. Epitaxial film compositions vary from x =0.30 with E i =10eV, to 0.27 with E i =20eV, 0.17 with E i =30eV, and less than or equal to 0.002 with E i greater than or equal to 40eV. Thus, the AlN incorporation probability decreases by greater than two orders of magnitude. This extraordinary range in real-time manipulation of film chemistry during deposition is due to the efficient resputtering of deposited Al atoms (27 amu) by Ar+ ions (40 amu) neutralized and backscattered from heavy Hf atoms (178.5 amu) in the film. This provides a new reaction pathway to synthesize, at high deposition rates, compositionally complex heterostructures, multilayers, and superlattices with abrupt interfaces from a single alloy target by controllably switching E i. For multilayer and superlattice structures, the choice of E i value determines the layer composition and the switching periods control the individual layer thickness.