Vacancy-type defects in TiN/ZrO2/TiN capacitors probed by monoenergetic positron beams

•The microstructures of TiN/ZrO2/TiN capacitors were characterized.•Vacancies in ZrO2 were identified as a Zr-vacancy coupled with oxygen vacancies.•Cation vacancies play an important role in the defect formation of ZrO2.•Leakage current mechanism is discussed in terms of point defects in ZrO2. TiN/ZrO2/TiN capacitors were fabricated by using a physical vapor deposition technique, and their microstructures were characterized using X-ray diffraction, a scanning transmission electron microscope, energy-dispersive X-ray spectroscopy, and monoenergetic positron beams. After the deposition of a 10-nm-thick ZrO2 layer on the top TiN layer, a defect-rich interlayer was formed in the ZrO2 layer. After post-deposition annealing at 550°C, the width of the interlayer expanded toward the center of the ZrO2 layer. The major vacancy-type defects in the ZrO2 layer were determined to be a Zr-vacancy coupled with oxygen vacancies. After annealing, the size of the vacancies increased, and it was close to the open spaces in amorphous high-k materials. The presence of such vacancy-type defects in the ZrO2 layer suggests that not only oxygen vacancies but also cation vacancies play an important role in the defect formation of the ZrO2 layer and affect its electrical properties. The introduction of the interlayer and defect-rich region was suppressed by annealing with the top TiN layer. The leakage current mechanism of the capacitor is discussed in terms of vacancy-type defects in the ZrO2 layer.