Heteroepitaxial growth of TaN on MgO(001) and TiN(001)/Si(001) by pulsed laser deposition
- PDF / 913,169 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 102 Downloads / 222 Views
Heteroepitaxial growth of TaN on MgO(001) and TiN(001)/Si(001) by pulsed laser deposition
H. Y. CHEUNG, K.H. WONG Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, People’s Republic of China. ABSTRACT Epitaxial TaN(001) films have been successfully grown on MgO(001) single crystal and TiN(001) buffered Si(001) substrates by pulsed laser deposition method. Crystalline TaN layers of about 100 nm thick were deposited under a base pressure of 5 x 10-6 Torr and at substrate temperatures ranging from 500oC to 700oC. X-ray diffraction results suggested that stoichiometric TaN films with cube-on-cube TaN||MgO heteroepitaxy are obtained in this temperature range. Plan-view and cross-sectional electron microscopy analysis revealed excellent structural quality and sharp interface boundary. TaN films grown on TiN(001) buffered Si(001), however, showed a mixture of TaNx (with x ≤ 1) components. Although the (001)-orientated TaN is always present prominently, the nitrogen deficient TaNx components are often co-existed in the films and show up as a broad peak in the X-ray diffraction profile. Stoichiometric and single phase TaN(001) films can only be obtained in a narrow temperature window at around 550oC and heteroepitaxial relation TaN||TiN||Si has been demonstrated. INTRODUCTION Thin films of the transition metal nitrides, such as TiN, TaN, and WN, have been extensively studied in recent years [1-2]. These refractory nitrides are useful materials with numerous industrial applications ranging from protective coatings for cutting tools to electronic devices [3]. Their low electrical resistivity, exceptional mechanical properties and chemical inertness make them excellent diffusion barriers and metallization materials in silicon technology. Among these nitrides, TaN has been identified as a very good diffusion barrier between Cu and Si and has been used in the Cu interconnect structures for ultra large scale integration (ULSI) circuits. [4] However, TaN has a defective structure [5] and deviations from stoichiometry are common. Indeed, nitrogen-contained tantalum films often consist of a variety of Ta-N phases including the NaCl-type TaN and hexagonal Ta2N. TaN has a higher melting point, Tm, at 3087oC and formation enthalpy, ∆H = -120 KJ/mol as compared with those of Ta2N (Tm = 2050oC, ∆H = -98 KJ/mol). Pure TaN phase is therefore expected to be thermally more stable than Ta2N at elevated temperature. It is highly desirable to fabricate stoichiometric cubic TaN for enhanced diffusion barrier performance and resistance to oxidation. Several methods have been reported for the preparation of TaN films, such as reactive sputtering [6-7], magnetron sputtering [8], triode sputtering [9], and ion beam assisted deposition (IBAD) [10-11]. Recently epitaxial TaN films grown on single crystal MgO substrate has been demonstrated [12]. The purpose of the present study is to focus on the low temperature growth of epitaxial cubic TaN films on Si by PLD method. Althou
Data Loading...
