Growth of epitaxial TiN films deposited on MgO(100) by reactive magnetron sputtering: The role of low-energy ion irradiation during deposition

• Published in: Journal of crystal growth Vol. 92; no. 3; pp. 639 - 656
• Main Authors: Hultman, L., Barnett, S.A., Sundgren, J.-E., Greene, J.E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.1988; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Crystal growth; Channeling; Magnetron; Electron diffraction; Epitaxy; Transition metal Compounds; Dislocation loop; Experimental study; Inorganic compound; Thin film; Dislocation density; Electron micrography; Titanium Nitrides; Transmission electron microscopy; Irradiation; Heteroepitaxy; Current density; Radiofrequency sputtering
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/0022-0248(88)90048-6

Plan-view and cross-sectional transmission electron microscopy have been used to investigate the role of low-energy ion irradiation in controlling the defect structure of epitaxial TiN(100). The films were deposited by reactive magnetron sputter deposition onto MgO(100) substrates at film growth temperatures T s between 550 and 850°C (0.26 to 0.35 of the melting point of TiN in K) and negative substrate biases V s between 0 and 500 V. Sputtering was carried out in pure N 2 atmospheres, the energy per N ion incident at the film surface was ∼ eV s 2 (N 2 + was the predominant ionic species), the incident ion to thermal-atom flux ratio for films grown with V s ≥100 V was ∼1.3, and the deposition rate was ∼1 monolayer s -1 (1.3 μm h −1). The primary defects observed in the films were dislocation loops on {111} planes. The number density n d of these loops decreased with increasing T s (e.g., for V s =0, n d ranged from 5×10 12 cm −2 at 550°C to 1.5×10 10 cm −2 at 850°C). However, n d also decreased rapidly with increasing V s at constant T s until a minimum defect density was attained at V s ∗(T s) after which n d incre ased again. Films grown at T s ≥750° C and V s=V s ∗ ≅ 300 V were essentially free of dislocation loops. On the other hand, films grown with T s <650° C and V s ≥400 V (i.e., V s > V s ∗ ) exhibited very high dislocation loop densities, ≥5×10 12 cm −2, together with the preci itation of N 2 gas bubbles. The net effect of ion irradiation on film microstructure depended upon a competition between the defect annihilation rate due to enhanced adatom mobilities during deposition and the collisionally-induced defect formation rate. The residual defect density was thus a function of both T s and V s . Under the proper growth conditions, ion irradiation led to a reduction in dislocation loop densities by more than 5 orders of magnitude. Cross-sectional micrographs of multilayer films grown as a function of V s at constant T s showed that n d increased or decreased (depending upon the direction of the change in V s ) abruptly and reversibly.