Influences of oxygen source and substrate temperature on the unusual growth mechanism of atomic layer deposited magnesium oxide using bis(cyclopentadienyl)magnesium precursor

This research reports on the atomic layer deposition (ALD) mechanism of MgO thin film using bis(cyclopentadienyl) magnesium [Mg(Cp)(2)] as the Mg-precursor and O-3 or H2O as an oxygen source. The different growth temperature effects of growth behaviour for the two types of oxygen sources were carefully evaluated. Insufficient H2O purging time caused the Mg-hydrides to remain in the deposited MgO thin film, which may cause inhibited growth on the bare-Si substrate. For the case of O-3-based ALD, such an adverse reaction was not observed. However, it showed a complicated temperature-dependent growth behaviour, and an abnormal 'overgrowth' zone around 290 degrees C was found when the growth temperature was varied from 140 degrees C to 390 degrees C. The carbonate intermediates and OH- reactive sites involving the growth mechanism with Cp-ring rupture were suggested. This mechanism was supported by the subsequent chemical and physical properties analysis, correlating the electrical characteristics using the planar metal-insulator-metal capacitors [metal layer was titanium nitride (TiN)], with the substrate temperature varying from 230 degrees C to 390 degrees C. The MgO deposited at 290 degrees C, where oligomerisation may happen between ligands after the Cp-ring rupture, caused the void formation, low density, and a relatively high-impurity level. The post-deposition and post-metallisation annealing conditions were examined for the optimal leakage current and dielectric constant of the MgO film. MgO and TiN showed local epitaxial growth due to the close lattice match. This finding suggested the possible use of the in situ crystallised MgO as a crystallisation seed layer for ultrathin (

Automated summary

This research investigates the atomic layer deposition mechanism of MgO thin film using different oxygen sources, revealing the effects of oxygen source type and growth temperature on film growth behavior. An abnormal 'overgrowth' behavior was observed in O-3-based ALD, while Mg-hydrides affected growth when insufficient H2O purging time was provided. The study also suggests a mechanism involving carbonate intermediates and Cp-ring rupture for growth.