Mn2B thin film deposition is explored because of the predicted promise of Mn2B as directional conductor for interconnects in integrated circuits. MnxB thin films, 40–80 nm thick, are deposited on Al2O3(0001), Al2O3(112¯0), and Al2O3(11¯02) substrates by combined d.c. and r.f. cosputtering from Mn and B targets, respectively. Energy dispersive spectroscopy analyses indicate that the Mn content decreases with increasing deposition temperature Ts = 600–800 °C, which is attributed to Mn evaporation from the substrate and growing film. Raising Ts from 600–700 °C also results in an increase in crystalline quality and surface roughness, while a further increase to Ts = 800 °C causes dewetting that results in discontinuous films. MnxB films on Al2O3(0001) and Al2O3(112¯0) form polycrystalline microstructures with random grain orientations, while Al2O3(11¯02) substrates facilitate epitaxial Mn2B(100) growth with Mn2B(100) || Al2O3(11¯02) and Mn2B010 || Al2O31¯101, as determined by x-ray diffraction methods. However, the epitaxial Mn2B(100) matrix contains MnB or Mn impurity phase grains for films with B-rich or Mn-rich compositions, respectively. The room temperature resistivity ρ of polycrystalline MnxB films decreases from 153 to 70 μΩ cm with increasing x = 1.3–5.6 and is further reduced for epitaxial Mn2B(100)/Al2O3(11¯02) films with measured ρ = 44 and 107 μΩ cm for x = 2.9 and 1.7, respectively. These values are affected by electron scattering at residual impurity grains such that the Mn2B bulk resistivity along the high-conductivity 001-direction is likely considerably smaller and may be competitive for the envisioned interconnect application.
Rahman et al. (Wed,) studied this question.