An investigation of high-k materials in metal-insulator-metal capacitor structures

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Hutchinson, Barry James
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University College Cork
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Metal insulator metal (MIM) capacitors are vital components of many devices such as communication band beamformers, medical, automotive, RF IC’s and memory applications. Current MIM capacitors technology utilises low dielectric constant (k) materials (k~3.9 - 7), these materials achieve the required electrical properties of high electric field breakdown strength and minimal leakage current. The low k value of the current materials presents a challenge to development of many new technologies and the integration of high-k materials in MIM capacitor structures is vital to overcome this. In this work we investigate the electrical properties of a hafnium silicate material system in MIM capacitors with sputtered aluminium electrodes. A conduction mechanism study was performed and an investigation of the dielectric reliability was carried out using the time dependent dielectric breakdown methodology. The material was determined to have excellent reliability characteristics. In addition, further samples of the above hafnium silicate capacitors were irradiated with total radiation dosages of 16 krad(Si) and 78 krad(Si). The electrical properties of both samples were characterised and their reliability characteristics were determined. The 16 krad(Si) sample was determined to have excellent radiation hardness and the 78 krad(Si) sample displayed a minor decrease in overall performance. Furthermore, we investigate the growth of hafnium silicate films by plasma assisted atomic layer deposition on metal electrodes and compare with a previous growth study which exhibited excellent electrical properties over a range of substrate materials. In this study the dielectric growth was influenced by the bottom electrode material. High resolution transmission electron microscopy (HRTEM) analysis and Raman spectroscopy indicate that the main crystalline phase is monoclinic HfO2 (k ~18). The scanning transmission electron microscopy (STEM) analysis reveals the presence of nanoparticles, located at the HfO2 grain boundaries. Based on energy-dispersive x-ray spectroscopy (EDX) analysis the nanoparticles are consistent with silicon oxide inclusions.
High-k , Reliability , TDDB , Gamma irradiated , ALD , Conduction mechanisms , MIM capacitor , Dielectric , Atomic layer deposition
Hutchinson, B. J. 2017. An investigation of high-k materials in metal-insulator-metal capacitor structures. PhD Thesis, University College Cork.